Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/00048622510.1159/000486225 © 2018 The Author(s).© 2018 Published The Author(s) by S. Karger AG, Basel Published online: online: January January 08, 08, 2018 2018 www.karger.com/cpbPublished by S. Karger AG, Basel 88 and Biochemistry www.karger.com/cpb Yi et al.: NPY Receptors in Metabolic Diseases Accepted: October 17, 2017

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A Promising Therapeutic Target for Metabolic Diseases: Y Receptors in Humans

Min Yia,b,c Hekai Lia,b,c Zhiye Wua,b,c Jianyun Yana,b,c Qicai Liua,b,c Caiwen Oua,b,c Minsheng Chena,b,c aDepartment of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University; Laboratory of Heart Center, Zhujiang Hospital, Southern Medical University; bGuangdong Provincial Biomedical Engineering Technology Research Center for Cardiovascular Disease; cSino-Japanese Cooperation Platform for Translational Research in Heart Failure, Guangzhou, P. R. China

Key Words • Neuropeptide Y receptors • G-protein-coupled receptors (GPCRs) • Metabolic diseases

Abstract Human neuropeptide Y (hNPY) is one of the most widely expressed neurotransmitters in the human central and peripheral nervous systems. It consists of 36 highly conserved amino acid residues, and was first isolated from the porcine hypothalamus in 1982. While it is the most recently discovered member of the family (which includes neuropeptide Y, gut-derived hormone YY, and pancreatic polypeptide), NPY is the most abundant peptide found in the mammalian brain. In order to exert particular functions, NPY needs to bind to the NPY to activate specific signaling pathways. NPY receptors belong to the class A or rhodopsin-like G-protein coupled receptor (GPCR) family and signal via cell-surface receptors. By binding to GPCRs, NPY plays a crucial role in various biological processes, including cortical excitability, stress response, food intake, circadian rhythms, and cardiovascular function. Abnormal regulation of NPY is involved in the development of a wide range of diseases, including , hypertension, atherosclerosis, epilepsy, metabolic disorders, and many cancers. Thus far, five receptors have been cloned from mammals (Y1, Y2, Y4, Y5, and y6), but only four of these (hY1, hY2, hY4, and hY5) are functional in humans. In this review, we summarize the structural characteristics of human NPY receptors and their role in metabolic diseases. © 2018 The Author(s) Published by S. Karger AG, Basel

Introduction

Neuropeptide Y is widely expressed in the human central and peripheral nervous sys- tem. This is a highly conserved 36-amino acid peptide which was first isolated from porcine Minsheng Chen Laboratory of Heart Center, Zhujiang hospital, Southern Medical University, andhypothalamus Caiwen Ou in 1982 [1]. ThereNo.1023,Shatai are three Nan members Road, Guangzhou of the (China); pancreatic Tel.+8613825199222, polypeptide +8618902309513, family, E-Mail [email protected], [email protected] Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 89 Yi et al.: NPY Receptors in Metabolic Diseases

- namely the neuropeptide Y, the gut-derived hormone peptide YY (PYY) and pancreatic poly- peptide (PP). Endogenous ligands (usually NPY, PYY and PP) and their C-terminal segments, monomerespecially proteinsthose with and parent belong residues to the class 3-36 A and or rhodopsin-like 13-36 [2, 3] activate G-protein Y receptors coupled receptorsvia bind ing and triggering a conformational change of the Y0 receptors (Table 1). NPY receptors are

(GPCRs) [4]. After binding to the ligands, the Gi or G subunit of the heterotrimeric G protein- complex is released2+ and and K in+ turn leads to the inhibition of adenylate cyclase, which prevents tothe the conversion Gi or G0 of ATP to the second signaling molecule, cAMP [4]. Finally, cAMP levels are re duced and the Ca channels are modulated [5]. Generally, NPY receptors are coupled- subunit. In rabbit smooth muscle cells, it has also been reported that Y2 and Y4- receptors could bind to the Gq protein and+ promote2+ the production of inositol 1, 4,5-triphos phate (IP3) by activating phospholipase C-β (PLC) [6]. In rat arcuate neurons, it was report- ed that NPY receptors could regulate K and Ca channels, and G protein-coupled inwardly Tablerectifying 1. potassium channels (Fig. 1) [4]. In addition to the seven membrane-confined he

The Characteristics of NPY Receptors In Humans The characteristics of NPY receptors in humans NPY receptor Y1 [140] NPY receptor Y2 [141] NPY receptor Y4 [142] NPY receptor Y5 [143] Amino acids 384 381 375 445-455

Expression Periphery, Brain, hippocampus, thalamus, Brain, gastrointestinal tract, Hypothalamus, hippocampus hypothalamus, hypothalamus pancreas, prostate hippocampus, neocortex, thalamus

Sequence of pNPY YPSKPDNPGEDAPAEDLARYYSALRHYINLITRQRY ligand hPYY YPIKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY structure hPP APLEPVYPGDNATPEQMAQYAADLRRYINMLTRPRY

Agonists NPY (endogenous NPY (endogenous agonist); NPY PP; NPY (endogenous agonist, NPY (endogenous agonist); agonist, non-subtype fragment 13-36(selective); 2- non-subtype selective); PYY; BWX-46 (selective NPY5 selective); PYY Thiouridine 5'triphosphate; PYY; PYY 3- GR-231,118 (mixed NPY1 agonist); PYY 36 fragment antagonist / NPY4 agonist)

Antagonists 1.Peptide: BVD-10 BIIE-0246 [5, 37, 144, 145], JNJ UR-AK49 CGP-71683, FMS-586 [6],L- (selective NPY1 5207787 ,SF 11 152,804,Lu AA-33810 [7],MK- antagonist), GR-231,118 0557 [8], NTNCB [9], (mixed NPY1 antagonist Velneperit / NPY4 agonist) 2.Non-peptide: BIBO- 3304,BIBP-3226,PD- 160,170

Location Chr 4: 163.32 – 163.34 Chr 4: 155.21 – 155.22 Mb Chr 10: 46.46 – 46.47 Mb Chr 4: 163.34 – 163.35 Mb Mb

Function vasoconstriction, Memory, circadian rhythm, Feeding, circadian ingestion, Food intake, epilepsy, circadian anxiolysis, food intake, angiogenesis, epilepsy, secretion, bone energy homeostasis, colonic rhythm heart rate, anxiety formation transit

Molecular NPY receptor /GPCR/Signal transduction function protein binding; PYY/ protein binding; PYY/PP receptor PP receptor PYY/PP receptor PP receptor calcium channel regulation

Biological GPCR/AC-inhibiting GPCR/cell surface receptor /AC- GPCR/cell surface GPCR/cell surface receptor/ process GPCR/cell surface inhibiting GPCR/dopamine secretion/ receptor/neuropeptide neuropeptide signaling receptor/ neuropeptide neuropeptide signaling pathways signaling pathways pathway signaling pathways positive regulation of cytosolic calcium blood circulation positive regulation of acute locomotory behavior ion concentration/peptide secretion feeding behavior inflammatory response/cell regulation of and circadian sleep/wake cycle, non- digestion and smooth muscle multicellular organism REM sleep/ smooth muscle contraction/ proliferation/ERK1 and ERK2 growth/blood pressure cell-substrate adhesion cascade outflow tract negative regulation of neurological negative regulation of morphogenesis system process/synaptic glutamate secretion/apoptotic blood circulation transmission/excitatory postsynaptic process/synaptic transmission, feeding behavior potential/ secretion/ feeding GABAergic/acute inflammatory glucose metabolic behavior/cAMP biosynthetic response to antigenic stimulus process process/synaptic transmission, generation of ovulation cycle sensory perception of glutamatergic rhythm pain sensory perception of pain eating/feeding behavior locomotory/feeding behavior outflow tract morphogenesis outflow tract morphogenesis aging cardiac left ventricle morphogenesis cardiac left ventricle behavioral fear response morphogenesis nitric oxide mediated signal chemical synaptic transmission transduction aging chemical synaptic transmission

Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 90 Yi et al.: NPY Receptors in Metabolic Diseases

lices, the heptahelical GPCRs have four extracellular and four intracellular segments, which- could be labeled as ec1-ec4 and ic1-ic4, respectively. The ec1 is an extracellular N-terminus and the ic4 is a intracellular C-terminus which cloud anchor onto the membrane by palmi toylation. The other six segments form three extracellular loops I-III and intracellular loops I-III was formed by the ec2-ec4 and ic1-ic3 segments, respectively. In extracellular regions, a disulfide bond between ec2 and ec3 segments is formed by two highly conserved cysteine (Cys) residues. This disulfide bond is a general feature of class A GPCRs and has been related to the stability of these receptors [7, 8]. The extracellular parts of the receptor can also be modified by glycosylation. In the intracellular regions, the C terminal tail, namely the ic4 ansegment, elementary and the complex ic2 segment coupled form to Y tworeceptors G protein [9]. binding sites. These two helices interact with signal transduction protein GTPases and bind to G proteins which consequently form

Thus far, seven different Y receptors (Y1-Y8) have been reportedcontemporary in vertebrates sequence [10- 14], of which five (Y1, Y2, Y4, Y5, and y6) are cloned from mammalsthe and Y receptorsfour (hY1, could hY2, behY4 and hY5) are proven functional in humans [15]. According to alignment (current UniProtein sequences aligned in clustalO program), intestine.classified In humansinto two， families, the Y1-Y4-Y6-Y8 (Y5) and the Y2-Y7 families; the first family is strongly expressed in neural tissue, and the second in visceral organs, especially kidney receptor and the Y5 receptor is slightly better aligned with the Y1 (23%) than with threethe Y2 somatostatin (22%); Y1 and receptors Y2 align [16]at 29%, Y1 and Y4 at 51%, Y4 and Y5 at 24%. The Y2 receptor.is akin to neurokinin /tachykinin GPCRs, both receptors, two receptors and , and could be phylogenetically more recent than the Y1

Fig. 1. - The molecular mechanisms and signaling pathways of GPCRs. In a resting state, the three subunits of GPCRs are complexed and bound to GDP. GPCRs change conformation and undergo activation by bind ingFig to special1 ligands, and can then function as a guanine nucleotide exchange factor (GEF). Once activated,- the Gβγ complex (formed by close binding between the β and γ subunits) is released from the Gα subunit and exchanges bound GDP for GTP. Then, the Gα subunit, and the bound GTP, separates from the Gβγ com plex and acts as an intracellular signaling molecule, or target protein, hinging on the top of its α subunit- (Gαs, Gαi/o, Gαq/11, Gα12/13). The free Gβγ complex can function as a messenger molecule by interacting pathway.with ion gating channels, or other types of transducer, such as cAMP. Generally, there are two essential sig naling pathways involving the GPCRs: the cAMP signaling pathway and the phosphatidylinositol signaling Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 91 Yi et al.: NPY Receptors in Metabolic Diseases

In the human central and peripheral nervous system, neuropeptide Y receptors are encoded by different genes and show distinct tissue distributions, as well as intracellular signaling pathways; this suggests that they function in a variety of physiological processes. Different Y receptors mediate different processes and diseases， such as food intake [17], obesity, hypertension, atherosclerosis, epilepsy, metabolic disorders, fracture healing [18] and many cancers [19-26]. By binding to different receptors receptorsNPY and plays hY5 various receptors roles can in human biological processes, and sometimes can even function quite receptors differently. For receptors instance, it has been reported that the down regulation of hY1 actingreduce Yfeeding receptors effect, has whereas demonstrated the increased clear expressiontherapeutic of potential hY2 in treating and hY4 obesity and can exert anorexigenic effects [27]. Selectively stimulating or blocking the differentially metabolic disorders [28, 29]. For example, the administration of NPY in the rat central nervous system induces hyperphagia, as well as a reduction in energy expenditure and the activation of lipogenic enzymes in the liver and adipose tissues, processes which are closely withassociated metabolic with diseases. obesity and metabolic disorders [16]. Herein, we summarize the structural characteristics of human NPY receptors (hY1, hY2, hY4 and hY5) and their relationships

The characteristics of human NPY receptors

Over recent years, there has been much research carried out on the genes encoding NPY receptors, particularly using a variety of gene-targeting techniques. Many of these investigations have involved the generation of NPY knockout mice; the deletion of genes encoding NPY receptors was used to determine their roles in physiological functions such as energyNeuropeptide metabolism Y andreceptor the regulation Y1 of food intake.

The human Y1(hY1) receptor was first discovered and cloned by Herzog et al. [30] by analyzing and characterizing a number of peptide fragments. The Y1 receptor is composed of 384 amino acids and its native agonists are NPY and PYY. The Y1 receptor can be activatedcow. by NPY in an endogenous and non-subtype selective way (Table 1) and shares over 92% sequence identity with that of its orthologues such as mouse, rat, pig, guinea pig, and Generally, the homologies among human Y receptor subtypes are very low. The hY1 andIn situhY4 receptors share the highest sequence similarities which are thought of as belongings to the same gene family, while hY2 and hY5 each belongs to an autonomous one [13]. hybridization and immunohistochemistry have been used to reveal the distribution of the Y1 receptor and its binding sites. The Y1 receptor was predominantly expressed in the periphery, hypothalamus, hippocampus, neocortex and thalamus (Table 1). In rats, Y1 receptor mRNA expression was detected in pancreatic β cells [31], in the colon [32] and in the visceral adipose tissues [33]. In humans, the Y1 receptor is expressed in the colonic epithelium and mucosal nerve, in the heart, adrenal gland, kidney as well as the placenta [34]. In the human central nervous system, Y1 receptor mRNA was moderately expressed in the caudate nucleus, amygdaloid nuclei, putamen and arcuate nucleus (ARC) and the nucleus accumben [35]. As in human and the rat brain, discrepancy once exists regarding the existence and distribution of Y1 receptors in the telencephalon, in particular the striatum and cerebral cortex. Unlike earlier findings, the binding sites and mRNA of Y1 receptors are expressed abundantly in the human frontal cortex and, suggest that the human brain contains a mixture of Y1 and Y2 receptor subtypes [36]. There is also an important concern in terms of large and considerablepreferential inactivation Y1 receptors of inhuman human Y1 cortex sites post were mortem detected [37]. [38]. It appearsThe reason that could Y1 receptors be that exist as a low affinity agonist conformation in postmortem samples of frontal cortex though the titers of Y1 receptor across brain areas depend to a varying degree on the post mortem interval prior to tissue homogenization or freezing [38]. The binding sites of Y1 receptor Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 92 Yi et al.: NPY Receptors in Metabolic Diseases

were sensitive to post-mortem delay whereas Y1 mRNA expression levels were not found to vary significantly within the post-mortem interval range examined in another study [37]. Thus, the Y1 sites in any tissue are much more prone to be inactivated by a variety of agents than that of Y2 receptors. Previous studies have shown that the Y1 receptor is involved in the regulation of hyperphagia, vasoconstriction of vascular smooth muscles, proliferation of neuronal precursors, as well as potentiating noradrenaline-evoked vasoconstriction post-junctional and decreasing ethanol tolerance [39, 40]. Furthermore, the hY1 receptor is highly expressed in human primary breast cancer and Ewing’s sarcoma, suggesting that this receptor represents an important diagnostic and therapeutic target for these types of cancer [41, 42]. The most prominent and significant effects of the Y1 receptor is the regulation of energy homeostasis and the induction of food intake; these effects often require involvement of the Y5 receptor [43]. However, the knockout of either Y1 or Y5 receptors can induce late onset obesity, while Y5 receptor knockout also induces hyperphagia; this suggests that both Y1 andNeuropeptide Y5 act in combination Y receptor Y2 in the mediation of food intake.

The hY2 receptor consists of 381 amino acids and its preferred agonists are NPY and PYY. This receptor couples to NPY and PYY with high affinity, although its affinity for PP is relatively lower [4]. The hY2 receptor is mainly localized presynaptically and is predominantly expressed in central neuronal tissue, such as the brain, hippocampus, thalamus,kidney hypothalamus cortical slices and and some white parts as of well the asperipheral brown adipocyte nervous system tissue. (Table The Y2 1). receptor Studies ishave abundantly also reported distributed the detection in rodent of and hY2 lagomorph in blood kidney vessels, cortex spleen, and liver, also gastrointestinaldetected in dog kidneytract, .

[44] In presynaptic neurons, hY2 is abundantly distributed and acts as a regulator in the release of neurotransmitters [3, 45].The hY2 receptors also share over 92% sequence similarity with that of its orthologues such as mouse, rat, pig, guinea pig, and cow. Though been localized close to the Y1 and Y5 gene cluster on chromosome 4q31-32, the Y2 receptor turns out to be quite different from the Y1 receptor which shows only approximately 30% total amino acid sequence similarity with that of Y1 receptor [46, 47]. Pharmacologically, the most important feature of the Y2 receptor is its role in the regulation of feeding, circadian ingestion, energy homeostasis, colonic transit and bone formation (Table 1) [48]. In central presynaptic neurons, the overexpression of Y2 receptors prevents the release of neurotransmitters [49] such as NPY and glutamate, suggesting that Y2 receptor act as a potential therapeutic target for epilepsy [50]. In addition, Y2 receptors also exert anorexigenic effects in humans since elevating the postprandial secretion of the Y2 receptor agonist, PYY (3-36), may act via Y2 receptor in the arcuate nucleus to prevent feeding through a gut-hypothalamic signaling system [51]. In overweight and obese humans, the expression of PYY (3-36) is additive and co-administration of Y2 receptor agonists and GLP-1 receptor agonists may be a useful treatment strategy for obesity [52]. Meanwhile, the Y2 receptor is also related to fear conditioning and fear extinction [53], angiogenesis and restoration of ischemic skeletal muscles [54], as well as ethanol-induced behavioral sensitization [55]. In central nervous system tumors, such as neuroblastoma and glioblastoma, the Y2 receptor is upregulated and acts as an inducer for tumor growth and vascularization [56-58]. In metabolic disorders, Y2 receptors are related to the promotion of adipocyte proliferation and differentiation, as well as the regeneration of adipose tissue nervescapillaries, is increased all of which and could the Y2 result receptors in abdominal are upregulated obesity and in metabolica glucocorticoid-dependent syndrome. Under cold or aggressive conditions, the production of NPY from the abdominal fat sympathetic manner. This response leads to the accumulation of abdominal fat [59]. Peripheral-specific Y2 receptor knockdown experiments revealed a protective effect in mice against high-fat diet- induced obesity. Research aiming to investigate the relationship between the peripheral Y2 receptors and high-fat diet-induced obesity further showed that the individual knockdown of peripheral Y2 receptors can prevent diet-induced obesity. Interestingly, the effects of Y2 Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 93 Yi et al.: NPY Receptors in Metabolic Diseases

non-neuronal tissues with the central nervous system. receptors are site-specific, and distinctive functions have been identified when comparing Y4

The Y4 receptor was first cloned by homology cloning techniques [60]. This is the only subtype of the family which shows preferential affinity to PP, but can also be activated by PYY and NPY to some extent. In humans, the gene encoding the Y4 receptor is located in chromosome 10q11.2 and shows low levels of conservation with the other receptors. andY4 shares the least sequence identity (less than 86%) with that of its orthologues when compared to other Y receptor subtypes. The Y4 receptor is composed of 375 amino acids is thus far found in the gastrointestinal tract [61, 62], central nervous system such as the circadianhippocampus ingestion and hypothalamus, and energy homeostasis pancreas, prostate [68] and and colonic in human muscle epidermis contraction [60, 62-65].[69]. The Studies have shown that the Y4 receptor is involved in the regulation of feeding [66, 67], thushuman regulating Y4 receptor energy also playshomeostasis a critical and role emotional in the regulation behavior of foodin combination intake and reproductivewith the Y2 functions [70]. Peripherally, the Y4 receptor can be activated by circulating PP and NPY, receptor [66, 71]. In the postrema region, this receptor is activated by PP and transmits anorexigenic signals from the peripheral circulation to the hypothalamus by regulating the vago-vagal reflex arc [66, 72]. In the arcuate of the hypothalamus, the Y4 receptors directly regulate the pancreatic polypeptide-mediated reduction of food intake by activating anorexigenic α-Melanocyte-stimulating hormone (α-MSH) signaling. Specific-knockout of the hypothalamus Y4 receptor conditionally eliminates polypeptide-mediated ARC c-Fos activation and prevents the PP-induced increase in (POMC) mRNA expression. Collectively, these findings suggest that the Y4 receptor is a potential therapeutic targetNeuropeptide for the prevention Y receptor of obesity Y5 [66].

Research was carried out to test the existence of an additional Y receptor subtype, which was pharmacologically similar to the Y1 receptor, but had the ability to regulate NPY-induced feeding independently of the Y1 receptors. Eventually, the Y5 receptor was isolated and cloned from rat hypothalamic cDNA [34, 73, 74]. The Y5 receptor encoding gene is located on human chromosome 4(4q31) and overlaps with Y1 although Y5 is transcribed in the opposite direction. Pharmacologically, the Y5 receptor shows equal affinities to hNPY, hPYY and hPP. Structurally, the hY5 receptor mainly exists in two forms with similar pharmacological characteristics [75]: a long isoform consisting of 455 amino acids, and a shorter (splice variant) form consisting of 445 amino acids. When compared to other members of the Y receptor family, the third intracellular loop (ICL3) of the Y5 receptors, which consists of 140 amino acids, is much larger, while the C-terminus is much shorter. The Y5 receptor is well conserved, shares more than 85% sequence similarity with its orthologues, and is predominantly expressed in the central nervous system, including the thalamus, temporal cortex, hypothalamus and amygdala [76]. One of the alternative promoters and 5’ exons of the Y1 gene is located within the coding sequence of the Y5 gene, suggesting the potential butexistence are are of transcribed partially coordinated in opposite transcriptional directions regulation between these two genes. Structurally, the genes encoding Y1 and Y5 receptors share a common promoter region, duplication event , on human chromosome 4q31-q32 [77]. The similarity of these two Y receptor genes suggest that they arise from the same gene . Reverse transcription of the same gene sequence indicates that either one transcriptional activation of the two genes will exert influence on the expression levels of the other. In agreement with this, recent studies showed that the Y5 receptor can regulate energy homeostasis [43], anticonvulsant effects [78] and anxiety [79], and that these effects occur in combination in with the Y1 receptors. Since it is known that the Y1 and Y5 receptors are both involved in modulating food intake and energy homeostasis [80, 81], the coordinated expression of their genes may be critical in regulating NPY activity [77]. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 94 Yi et al.: NPY Receptors in Metabolic Diseases

The Y5 receptors were detected in a brain region related to memory processing and canceremotion cell regulation, line via an indicating extracellular their signal-regulated potential involvement kinase pathway in mood and control by inhibiting [74]. In the a manner similar to the Y1 receptors,In situ the Y5 receptor promotes cell growth in a human breast production of cAMP [82]. hybridization and immunohistochemicalsupporting staining has also shown that Y5 mRNA is apparently upregulated in areas of the central nervous system which are thought to regulate the action of food intake and feeding, thus a role for the Y5 receptorsThe role ofin NPYfeeding receptors and food in metabolic intake [74, diseases 83].

Previous studies have demonstrated that the NPY family plays important roles in various physiological functions by binding to different types of NPY receptors. Activation or inhibition of NPY receptors could change the levels of some neurotransmitters which may, in turn, cause alterations in some physiological processes. Gene knockout studies have revealed various roles for the NPY receptors. For example, a series of investigations has reported that the NPY receptor may play a significant role in several diseases, particularly in terms of metabolism diseases such as diabetes, obesity, hypertension, and dyslipidemia. In this article,The relationship we summarize between the NPY potential receptors role and of NPY dyslipidemia receptors in metabolic syndrome.

The elevation of hepatic very-low-density lipoprotein (VLDL)-triglyceride (TG) secretion leads to the occurrence of atherosclerotic dyslipidemia, which is closely related to diabetes, obesity and metabolic syndrome [84, 85]. A previous study reported that increased NPY in the neural circuits can result in dyslipidemia, independent of an increased total energy increment and visceral adipose accumulation. In paraventricular nucleus, long-term over-expression of NPY contributes to the establishment of adipose tissue resistance partly through Y5 receptor [86]. A single injection of NPY into the third lateral ventricle can directly increase VLDL-TG secretion by one-fold in the liver of lean and fasted rats, a mechanism mediated predominantly by the central nervous system Y1 receptor [87, 88]. Studies conducted by Bruinstroop reported that the hypothalamic arcuate nucleus, along with hepatic sympathetic innervation, are essential factors in maintaining the secretion of VLDL-TG during fasting. In addition, the stimulatory effect of VLDL-TG secretion, caused by the intracerebroventricular injection of NPY, requires the involvement of hepatic sympathetic innervation [89]. The increased secretion of hepatic VLDL-TG resulting from intracerebroventricular NPY injection is independent of lipolysis, suggesting a liver-selective effect upon lipid metabolism. Collectively, these findings indicate that the sympathetic nervous system is essential to the stimulatory effect of increased NPY in fasted rat in maintaining hepatic VLDL-TG secretion [89]. Consist with this investigation, other studies [87-89] have shown that central nervous system NPY stimulates hepatic VLDL-TG secretion independent of changes in plasma free fatty acid levels. In the central nervous system, increased levels of NPY promotes the effect of sympathetic intervention in the liver, thus regulating key regulatory proteins to coordinate thea multi-stage Y1 receptor response and the andsympathetic promote pathway.liver phospholipid remodeling and VLDL maturation, finally resulting in the increased secretion of hepatic VLDL [90]. This effect is mediated by

The process of adipose accumulation consists of the proliferation and differentiation of adipocyte precursor cells, which are specialized in the accumulation of lipid. The differentiation of adipocytes is regulated by the coordinated expression of various transcription factors, of which peroxisome proliferator-activated receptor 2 (PPAR-2γ) is the most common type [91]. Numerous investigations have shown that NPY promotes and modulates the formation of adipose tissue. Previous studies have demonstrated that the increased local expression of byNPY Kuo in visceralet al. reported adipose that tissue these can processes promote the were proliferation mediated viaof pre-adipocytes the Y2 receptor and [59]. induce A more the accumulation of adipose tissue via Y1 receptor activation [33]. However, a study conducted recent study reported that in adipocyte precursor cells, the exogenous dipeptidyl peptidase- Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 95 Yi et al.: NPY Receptors in Metabolic Diseases

IV (DPP-IV) inhibitor, vildagliptin, could prevent the formation of adipose and lipid accumulation stimulated by DPP-IV. The immunoneutralization of NPY, or inhibition of the Y2 receptor, can prevent this process, suggesting that DPPIV could promote the formation of adipose tissue by the cleavage of NPY and activation of the Y2 and Y5 receptors [92]. The Y5 receptor agonist-induced accumulation of lipid can be inhibited by protein kinase C (PKC) and PLC inhibitors. In addition, activation of the Y2 receptor can stimulate lipid accumulation via the protein kinase A, mitogen-activated protein kinases (MAPK) and phosphoinositide 3-kinase (PI3K) signaling pathways [92]. The DPPIV inhibitor, vildagliptin, suppressed the expression of PPAR-γ and the accumulation of lipid, with no effect upon lipolysis, indicating that this process has no effect on the storage of triglycerides inside the lipid droplets of adipose tissue. These results showed that the combined regulation of DPP-IV and NPY upon lipid metabolism can attenuate the deposition of adipose tissue [93]. liverCollectively, and exert potent this roles data supportin metabolic the disorders. fact that NPY neurons, and the Y1 receptor, are increasingly regarded to have an important role in the modulation of lipid metabolism in the The relationship between NPY receptors and obesity

Obesity, as a major risk factor for type 2 diabetes mellitus, heart disease, obstructive sleep apnea, and certain types of tumors and osteoarthritis, has become a worldwide epidemic as a result of social changes and improvements in living standards. These diseases are caused by long-term energy metabolism disequilibrium, together with an imbalance between energy intake and energy expenditure. Studies have revealed that NPY is a major regulator in balancing energy metabolism [26, 94, 95] and resists excessive loss of fat by lipolysis in calorie‐restricted mice indicating a trait potential for the life‐extending effect of calorie restriction [95]. The NPY receptors, as is reported, can regulate energy balance and body weight in a cooperative manner. For instance, in mice featuring either single or multiple Y receptor deletion (including Y1, Y2, and Y4), the long-term overexpression of hypothalamic NPY can result in a significant increase in food intake, fat accumulation, insulin levels and body weight. However, the combined deletions of Y1, Y2 or Y4 receptors can also prevent NPY-induced hyperinsulinemia [92]. The Y2 receptor encoding gene is abundantly expressed in the central nervous system, especially in the hypothalamus, which is recognized as a crucial regulator of appetite. Knockout of the Y2 receptor can lead to increased weight gain and accumulation of adipose tissue. The ligand for Y2 receptor, PYY, is released in a postprandial from L cells in the distal part of the intestine in proportion to the amount of ingested food [96]. Peripherally, the administration of PYY can reduce the amount of ingested food and thus, the extent of weight gain. However, in Y2 receptor knockout mice, this effect does not exist [51]. The postprandial level of circulating PYY is relatively higher in obese subjects than that in lean subjects [97], which indicates that PYY gene variants can change the expression of circulating PYY. A number of research studies have investigated the relationship between variations in the gene encoding for the Y2 receptor and obesity. In fact, in a population-based study, which enrolled 5, 965 subjects, the PYY common allele Arg72 variant was shown to be related to type 2 diabetes and excessive weight gain [98]. In Pima Indians (a population genetically affected by obesity), severe obesity was found to be linked to mutations in both the Y2 receptors and the PYY gene [99]. These data indicated that the PYY-Y2 receptor signaling pathway may be involved in the regulation of body weight via a gender-specific mechanism. Consistent with this result, another study, which enrolled 1, 800 North American, 1, 030 Polish and 240 geneticScandinavian variants participants, have no relationship showed that with genetic obesity. mutations Body mass in the index 5’ region and waist-to-hip of Y2 receptors ratio were closely related to obesity [100]. However, in early onset obesity, PYY and Y2 receptors were significantly lower in 421 white homozygous-carrying males with Y2 receptors Ile195 (rs1047214) [101], whereas directly opposite results were obtained for 479 homozygous- carrying Swedish males [102]. A further study enrolled 5, 971 white Danish subjects and reported that the common variants rs6857530, rs12649641, and rs2342676, located in the Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 96 Yi et al.: NPY Receptors in Metabolic Diseases

which should 5’ region of Y2 receptors were related to obesity [103]. However, since existing data have arisen from different regions and ethnic groups, further studies are required feature larger sample sizes and be based upon a multi-center approach. Over recent years, the Y1 and Y5 receptors have attracted increasing pharmacological attention as potent anti-obesity targets. Numerous NPY knockout, and NPY receptor deficient models, have demonstrated that these two receptor subtypes play a pivotal role in the regulation of body weight, food intake and fat accumulation. However, since there are various neural signaling pathways involved in maintaining the homeostasis of food intake and energy balance, few antagonists have been identified and tested in clinical trials. These factors mean that the identification of ligands with higher selectivity and affinity is very important for the future. The Y1 signaling pathway is essential to the process of insulin resistance and obesity in the hematopoietic system of diet-induced obese mice; moreover, this effect was specific to the Y1 receptor and did not involve the Y2 receptor [104]. The elevation of NPY by chronic intracerebroventricular NPY injection was also shown to induce obese-like secretion changes of hormone and metabolism parameters in normal rats [28]. Centrally, the chronical activation of NPY Y1, Y2 or Y5 receptors in mice can modulate the balance of energy metabolism and food intake. Over a duration of 6 days, the administration causeof NPY, transient Y1 or Y5 reductions agonists inresulted weight in [105]. significant increases of body weight, adiposity, and respiratory quotient in C57Bl/6 mice. In contrast, selective activation of the Y2 receptor can

The mRNAs for Y1, Y2, and Y5 receptor are detectable in human adipose tissue, indicating that NPY plays a significant role in this region. A clinical study [106] investigated the expression of Y1 receptor mRNA in visceral adipose of obese subjects and showed that circulating Y1 receptor mRNA levels were much higher than that in participants of normal weight; however this phenomenon was not evident in subcutaneous adipose. In visceral adipose tissue, Y1 receptor mRNA level was positively correlated with body mass index, waist and hip circumferences as well as body weight. These data suggest that elevated NPY circulating levels are related to obesity in visceral adipose tissue. These results are consistent with previous findings that the inhibition of Y1 receptor expression, or Y1 receptors deficiency, can reduce body weight in mice. However, the molecular mechanisms and NPY-Y1 receptor signaling pathway involved in this phenomenon remain unclear. In rats, NPY regulates the proliferation of pre-adipocytes by extracellular regulated protein kinases signaling [33], and specific Y1 receptor antagonists can inhibit lipolysis [107]. Collectively, these data indicate that the expression of Y1 receptor in visceral adipose tissue is associated with the development of obesity and the formation of adipose tissue. The molecular factors underlying this mechanism now needs to be investigated in future research studies. Moreover, since the genes encoding Y receptors vary across different ethnic populations, and because genetic variants of Y receptors could exert different functions and may play roles in different physiological processes, it is necessary to conduct further researchThe relationshipstudies to elucidate between the NPY specific receptors effects and ofdiabetes different Y receptors in different regions.

Type 2 diabetes, in around 90% of cases is characterized by insulin resistance and defective islet beta cell function. Pre-diabetes is characterized by hyperinsulinemia, impaired glucose tolerance, as well as insulin resistance which is associated with the dysfunctional islet beta cells [108]. Previous studies demonstrated that in diabetes models, NPY exerts a profound role in the regulation of blood glucose homeostasis [26]. Insulin acts on NPY neurons and modulates the balance of energy regulation and the dysfunction of which may result in the development of metabolic diseases. Meanwhile, by changing the pain response and transduction of the orofacial sensory pathways, +diabetes neurons mellituswas observed influences both inthe type trigeminal 1 and 2 diabetes nerve function [109]. and affects inflammatory response via NPY and vascular endothelial growth factor since an increased percentage of NPY Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 97 Yi et al.: NPY Receptors in Metabolic Diseases

Pituitary adenylate cyclase activating polypeptide (PACAP), sensory fiber substance P (SP) and sympathetic neuropeptide Y (NPY) are co-transmitters in the process of neuronal signal transmission and both PACAP and SP have been shown to have an impact upon the insulin sensitivity of adipocytes [110]. With regards to NPY, studies have mainly focused upon the influence upon glucose metabolism in adipocytes. Notably, the activation of NPY receptors leads to the inhibition of adenylate cyclase in conjunction with a reduction of cyclic adenosine monophosphate levels or binding to other signal systems, such as calcium influx, which is modulated via the Y1 receptors in a preferential manner. Moreover, NPY acts as a potent therapeutic target for obesity and type 2 diabetes in that Y2 receptor inhibitors could prevent the progress of obesity and impair glucose tolerance; moreover the increased expression of NPY caused by chronic stress can cause hyperinsulinemia [59]. NPY also plays a significant role in the regulation of insulin sensitivity in 3T3-L1 adipocytes [111]. By transporting impaired GLUT4, NPY prohibits the uptake of glucose stimulated by insulin via the AKT signaling pathway. On the surface of 3T3-L1 adipocytes, the increase of GLUT4 was ameliorated and the phosphorylation of AKT mediated by insulin was prevented by NPY and this could result in the inhibition of glucose uptake. NPY impairs the phosphorylation of AKT through the Y1 receptor signaling pathway in a GLUT4-dependent manner, which thus leads to the inhibition of glucose uptake induced by insulin secretion [112]. The administration of an NPY Y1 receptor agonist reduced the translocation of GLUT4 induced by insulin secretion, suggesting a critical role of the Y1 receptor in the translocation of GLUT4. However, since the phosphorylation of AKT is independent of the insulin signaling pathway and glucose uptake, NPY could not completely inhibit the translocation of GLUT4 [113]; this study provided evidence that NPY impairs the insulin sensitivity of adipocytes and further suggested that the Y1 receptors could be a potential therapeutic target for type 2 diabetes [111]. These findings concurred with those arising from experiments using transgenic mice. For example, the secretion of insulin was elevated in the pancreatic islets of mice in which NPY had been deleted. NPY and the Y1 receptors are now recognized to play a physiological role in the progression of diabetes [114]. A reduction in pancreatic NPY leads to increased levels of insulin secretion from the islets to compensate for obesity-mediated insulin resistance, whereas endogenous NPY in the islet cells stimulate the secretion of pancreatic insulin. receptors.Taken together, these data prove that NPY can promote sensitivity to insulin in adipocytes, which therefore act as potential therapeutic targets for type 2 diabetes together with the Y1

It was found that circulating NPY levels are significantly elevated in both diabetic rats and patients [115]. NPY has a， critical impact upon the regulating secretory function of pancreatic α and β cells [116] as well as β cell differentiation both in mice and humans [117]. Under different circumstances NPY can exert opposite functions upon the secretion of and insulin. Moreover, NPY Y1 receptors are expressed on the surface of pancreatic islet cells and NPY autoantibody could be used as diagnostic indicator of Type 1 diabetes [118]. Mutation of NPY receptor type 2 may lead to type 2 diabetes [119]. NPY-induced transient ERK1/2 phosphorylation， can also promote the proliferation and replication of islet beta cells via the activation of extracellular signal-regulated kinase [116]. During the development of pancreas NPY expression is restricted from the progenitor populations and marks functionally immature β cells in fetal and neonatal mice and humans [120]. NPY- positive cells were detectable in the central and periphery regions of islet cells in diabetic rats, although in normal rats, NPY-positive cells were only found in the peripheral regions of islet cells. Among all pancreatic cell types, NPY is predominantly expressed in PP cells under normal conditions. However, in the presence of a high-fat diet, or under diabetic conditions (both type 1 and type 2), the localization of NPY expression in pancreatic cell types changes; NPY expression in PP cells is relatively lower while the number of NPY positive cells in the islets increases markedly [121]. The level of NPY expression is epigenetically downregulated during the maturation of βcells. In neonatal mouse, NPY expressingβcells are more replicative, and the knockdown of NPY gene could reduce replication ofβcells and enhances insulin secretion in response to high glucose. Those findings indicating that the expression Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 98 Yi et al.: NPY Receptors in Metabolic Diseases

of NPY may promote the replication of neonatal βcells and contributes to impaired glucose responsiveness. In diabetic mice and those fed with high-fat diet, the expression of NPY expression reemerges which may explain the impairedβcell maturity in diabetes. Taken together, NPY could regulateβcell differentiation and have potential applications on β cell supplementation for diabetes therapy [120]. NPY is widely expressed in the cardiovascular system [122] and is also known to play an essential role in the modulation and pathological process of diabetic cardiomyopathy besides food intake, body weight, energy homeostasis, peripheral vascular tone and various other conditions [123]. In the myocardium of the diabetic rat, the expression of NPY was shown to be different than other tissues and its receptors were up-regulated [124]. In the cardiovascular system, NPY is co-expressed and co-exists predominantly in the coronary arteries, endothelium [122] and cardiomyocytes innervated by sympathetic nerves together with other classic neurotransmitters such as sympathetic noradrenaline. NPY receptors, particularly the Y1 and Y2 receptors, have been demonstrated to play a fundamental role in the pathogenesis of myocardial hypertrophy in the rat [124]. Indeed, NPY Y1 receptor expression was elevated in rat myocardium leading to hypertrophy of the cardiac myocytes via reduced degradation and the increasedin vitro and synthesis in vivo of protein via PI3K/p70 signaling pathways [125]. Research has also revealed that activation of the Y2 receptor stimulates the process of angiogenesis, both . Some researchers believe that the levels of , and leptin resistance, changes in diabetic conditions, which in turn, affects the expression of NPY and its receptor distribution in the hypothalamus and peripheral autonomic nervous system. However, the exact mechanisms and interactions between leptin and NPY still remain unclear. An earlier study [126] investigated diabetic and non-diabetic patients and showed that the expression of neuropeptide in the serum and myocardium differed. Plasma NPY levels were significantly elevated in patients with type 2 diabetes when compared to non-diabetic patients, whereas in atrial tissue, NPY mRNA levels were lower in diabetic patients. In diabetic patients, myocardial Y2 and Y5 receptors were upregulated, andwhile vascular the apoptosis smooth andmuscle angiogenesis cells. The same hormone, phenomenon leptin was was downregulated. also shown to exist Furthermore, in animal the Y1 receptors appeared to be preferentially expressed in the nuclei of cardiomyocytes models of chronic hyperglycemia [124] and may occur because of the counter regulation response to reduced levels of NPY. However, whether these alterations in NPY and its receptors are associated with the initial etiology of disease in the myocardium requires furtherThe investigation. relationship between NPY receptors and hypertension

Over recent years, some researchers have begun to investigate the molecular and cellular mechanisms underlying human NPY-mediated gender-difference in the regulation of blood pressure.2+ -It was reported that long-term administration of NPY in the subcutaneous infusion could induce cardiac dysfunction and cardiac hypertrophy of which may be mediated by the Ca /CaM dependent CaN pathway and p38 mitogen-activated protein kinase (MAPK) signal pathway in rats [127]. The proliferation and migration of vascular smooth muscle cells plays Y5a vital receptors role in andpathophysiological in vascular tissues remodeling in vivo ofvia arteries Y5 receptor during [128]. hypertension Human inhypertension pregnancy. NPY could promote the proliferation and migration of vascular smooth muscle cells via Y1, previous studies have investigated correlations between catecholamine secretion and is heritable [129], and exhibits pleiotropic determination with autonomic activity. Some genetic variation in the adrenergic pathway, which controls catecholamine synthesis, and revealed new pathophysiological correlations between important adrenergic loci, blood pressure and catecholamine secretion [130]. NPY can regulate blood pressure, and the activation of adrenaline, by coupling to the NPY Y1 receptor. In transgenic rodents, over- expression of the NPY gene attenuated the elevation of blood pressure after central Nitric Oxide Synthase (NOS) inhibition administration; the injection of a selective Y1 receptor antagonist, BIBP3226, was shown to reverse this phenomenon centrally [131]. In mice, Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 99 Yi et al.: NPY Receptors in Metabolic Diseases

the specific deletion of the gene encoding NPY Y1 receptor results in changes in adrenergic activity, as well as enhanced biosynthesis and secretion of catecholamine [132]. Peripherally, hypertensiveNPY activates [131]. the NPY Y1 receptor receptor and modulates vasoconstrictor or vasopressor responses [133], while centrally, these effects may be the total opposite, and are usually anti-

NPY is highly expressed in the cardiovascular neural control center and co-localized with other excitatory neurotransmitters, such as norepinephrine or glutamate; research has shown that NPY is able to prevent the expression of these neurotransmitters [49, 134, 135]. These observations indicate that NPY modulates physiological effects by acting as a buffering neurotransmitter in the central nervous system. Consistent with this theory, a study conducted by Michalkiewicz et al. [136] found that NPY-enhanced signaling could alleviate chronic hypertension mediated by nitric oxide (NO) deficiency. The central Y1 receptor subtype could modulate the hypertensive effect caused by increased NPY signaling and may act as a potent antihypertensive target. Another study demonstrated that NPY is an effective vascular contractor and is co-transmitted with sympathetic norepinephrine. These effects were mediated mainly by the increasing activity and expression of Rho kinase in the vascular wall of the mesenteric artery, and by reducing the excessive production of NO in the mesenteric vascular wall, thus leading to the contraction of mesenteric arteries and portal hypertension [137]. system.The This nucleus is a medullaryof the solitary relay tract, nucleus located which in expressesthe dorsal Y1 medulla and Y2 of receptors the brainstem, and delivers is the main control center for cardiovascular and other autonomic functions in the central nervous cardiovascular and respiratory signals [138]. NPY is expressed abundantly in the brainstem (the nucleus of solitary tract, the area postrema, and the dorsomotor nucleus of the vagus), and peripheral sympathetic nerves play critical roles in the regulation of blood pressure. A microinjection of NPY into the nucleus of the solitary tract can induce a dose-dependent reduction in both blood pressure and heart rate, while the NOS inhibitor, via NPY receptor- mediated downstream signaling, can cause the enhancement of systemic arterial pressure and renal sympathetic nerve activity [139]. In the nucleus of the solitary tract, NPY regulates2+ signalingblood pressure system and [131]. exerts a depressor effect by activating two signaling pathways: the Y1 receptor-PKC-ERK-ribosomalHypertension in pregnancy protein is a disorder S6 kinase involved (RSK)-eNOS with the pathophysiological pathway and the remodeling Ca -eNOS of the vasculature. Neuropeptide Y has been proven to be a risk factor for the cardiovascular system and was found in increased levels in hypertensive pregnant patients [140]. In pregnant hypertensive rats, circulating levels of NPY are also elevated, and this was reported to be associated with the proliferation and migration2+ of vascular smooth muscle cells (VSMCs). In hypertensive pregnancies, the proliferation and migration of VSMCs changes via several signaling pathways, including MAPKs, Ca [141] and G-proteins [142]. By activation of the Y5 receptor, circulating NPY expression was increased and the proliferation of VSMCs was induced. Consequently, signal transducer andin activator vivo. In ofvitro transcription 3 (STAT3) and c-Fos signaling pathways were activated. These finding indicate that NPY predominantly exerts its effects upon VSMCs via the Y5 receptor , however, NPY mainly acts on VSMCs via both Y1 and Y5 receptors. Postsynaptic Y1 receptors modulate vasoconstriction and hypertension effects by enhancing norepinephrine-mediated contraction and VSMC proliferation [143]. Since the molecular mechanism of hypertension during pregnancy is betweenvery complicated, Y receptors. further research studies are needed in order to clarify the opposing effects of Y receptors in different tissues, as well as the co-regulated functions and inter-reactions Conclusion

In humans, NPY has been shown to bind to at least five different receptors: Y1, Y2, Y4, Y5, and y6. However, only four of these (hY1, hY2, hY4 and hY5) are functional in humans. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 100 Yi et al.: NPY Receptors in Metabolic Diseases

in vitro and in vivo Of note, NPY has been confirmed to interact with some other types of receptors, both , such as the sigma receptor. Over recent years, several new receptors have been discovered; these advances have occurred via the use of intracerebroventricular (ICV) and other technologies. However, the mechanisms and pathways mediating the various functions and processes carried out by NPY receptors in different organs and tissues still need to be clarified. It is possible that mechanisms other than coupling to G-proteins may be identified in future. Furthermore, the potential roles of NPY receptors in the process of the browning of white adipocyte tissue and metabolism disorders such as diabetes, obesity and hypertension also need to be elucidated; studies in this area may provide new insight into novel treatment options for these types of diseases. Further studies and efforts should moretherefore research aim toattention. discover high affinity and specific NPY receptors as potential therapeutic agents. In addition, the modification of NPY receptors for specific purposes should be given

Disclosure Statement

None.

Abbreviations

GTP (guanosine triphosphate); AC (adenylate cyclase); GEF (guanine nucleotide exchange factor); GDP (Guanosine diphosphate); ATP (Adenosine triphosphate); cAMP (Cyclic adenosine monophosphate); IP3 (inositol 1, 4,5-triphosphate); DAG (diacyl glycerol); PLCβ (phospholipase Cβ); PIP2 (phosphatidylinositol biphosphate); PKA (protein kinase A); PKB (protein kinase B); ERK1/2 (extracellular regulated protein kinases); EGR-1 (early growth response protein 1); CRE (cyclic adenosine monophosphate response element); NFAT-RE (nuclear factor of activated T-cells response element); SRF-RE (serum response factor response element); SRE (serum response element); RhoA (Ras homolog gene family member A) Acknowledgements

This study are supported by the National Natural Science Foundation of China (3147096) and the Provincial Natural Science Foundation of Guangdong Province (2014A030313327).

References

1 Tatemoto K, Carlquist M, Mutt V: Neuropeptide Y--a novel brain peptide with structural similarities to peptide YY and pancreatic polypeptide. Nature 1982;296:659-660. 2 Grandt D, Teyssen S, Schimiczek M, Reeve JR, Jr., Feth F, Rascher W, Hirche H, Singer MV, Layer P, Goebell H, et al.: Novel generation of hormone receptor specificity by amino terminal processing of peptide YY. Biochem Biophys Res Commun 1992;186:1299-1306. 3 Wahlestedt C, Yanaihara N, Hakanson R: Evidence for different pre-and post-junctional receptors for neuropeptide Y and related . Regul Pept 1986;13:307-318. 4 Michel MC, Beck-Sickinger A, Cox H, Doods HN, Herzog H, Larhammar D, Quirion R, Schwartz T, Westfall T: XVI. International Union of Pharmacology recommendations for the nomenclature of neuropeptide Y, peptide YY, and pancreatic polypeptide receptors. Pharmacol Rev 1998;50:143-150. 5 Cabrele C, Beck-Sickinger AG: Molecular characterization of the ligand-receptor interaction of the neuropeptide Y family. J Pept Sci 2000;6:97-122. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 101 Yi et al.: NPY Receptors in Metabolic Diseases

6 Misra S, Murthy KS, Zhou H, Grider JR: Coexpression of Y1, Y2, and Y4 receptors in smooth muscle coupled to distinct signaling pathways. J Pharmacol Exp Ther 2004;311:1154-1162. 7 Palczewski K, Kumasaka T, Hori T, Behnke CA, Motoshima H, Fox BA, Le Trong I, Teller DC, Okada T, Stenkamp RE, Yamamoto M, Miyano M: Crystal structure of rhodopsin: A G protein-coupled receptor. Science 2000;289:739-745. 8 Cherezov V, Rosenbaum DM, Hanson MA, Rasmussen SG, Thian FS, Kobilka TS, Choi HJ, Kuhn P, Weis WI, Kobilka BK, Stevens RC: High-resolution crystal structure of an engineered human beta2-adrenergic G protein-coupled receptor. Science 2007;318:1258-1265. 9 Estes AM, McAllen K, Parker MS, Sah R, Sweatman T, Park EA, Balasubramaniam A, Sallee FR, Walker MW, Parker SL: Maintenance of Y receptor dimers in epithelial cells depends on interaction with G-protein heterotrimers. Amino Acids 2011;40:371-380. 10 Tensen CP, Cox KJ, Burke JF, Leurs R, van der Schors RC, Geraerts WP, Vreugdenhil E, Heerikhuizen H: Molecular cloning and characterization of an invertebrate homologue of a neuropeptide Y receptor. Eur J Neurosci 1998;10:3409-3416. 11 Garczynski SF, Brown MR, Shen P, Murray TF, Crim JW: Characterization of a functional neuropeptide F receptor from Drosophila melanogaster. Peptides 2002;23:773-780. 12 Hill CA, Fox AN, Pitts RJ, Kent LB, Tan PL, Chrystal MA, Cravchik A, Collins FH, Robertson HM, Zwiebel LJ: G protein-coupled receptors in Anopheles gambiae. Science 2002;298:176-178. 151. 13 Larhammar D, Salaneck E: Molecular evolution of NPY receptor subtypes. 2004;38:141-

14 Sundstrom G, Larsson TA, Xu B, Heldin J, Larhammar D: Interactions of zebrafish peptide YYb with the neuropeptide Y-family receptors Y4, Y7, Y8a, and Y8b. Front Neurosci 2013;7:29. 15 Pedragosa-Badia X, Stichel J, Beck-Sickinger AG: Neuropeptide Y receptors: how to get subtype selectivity. Front Endocrinol (Lausanne) 2013;4:5. 16 Parker SL, Balasubramaniam A: Neuropeptide Y Y2 receptor in health and disease. Br J Pharmacol 2008;153:420-431. 17 Lang UE, Beglinger C, Schweinfurth N, Walter M, Borgwardt S: Nutritional aspects of depression. Cell Physiol Biochem 2015;37:1029-1043. 18 Tang P, Duan C, Wang Z, Wang C, Meng G, Lin K, Yang Q, Yuan Z: NPY and CGRP Inhibitor Influence on ERK Pathway and Macrophage Aggregation during Fracture Healing. Cell Physiol Biochem 2017;41:1457-1467. 19 Sainsbury A, Bergen HT, Boey D, Bamming D, Cooney GJ, Lin S, Couzens M, Stroth N, Lee NJ, Lindner D, Singewald N, Karl T, Duffy L, Enriquez R, Slack K, Sperk G, Herzog H: Y2Y4 receptor double knockout protects against obesity due to a high-fat diet or Y1 receptor deficiency in mice. Diabetes 2006;55:19-26. 20 Zhang L, Riepler SJ, Turner N, Enriquez RF, Lee IC, Baldock PA, Herzog H, Sainsbury A: Y2 and Y4 receptor signaling synergistically act on energy expenditure and physical activity. Am J Physiol Regul Integr Comp Physiol 2010;299:R1618-1628. 21 Antal-Zimanyi I, Bruce MA, Leboulluec KL, Iben LG, Mattson GK, McGovern RT, Hogan JB, Leahy CL, Flowers SC, Stanley JA, Ortiz AA, Poindexter GS: Pharmacological characterization and appetite suppressive properties of BMS-193885, a novel and selective neuropeptide Y(1) receptor antagonist. Eur J Pharmacol 2008;590:224-232. 22 Zhang L, Bijker MS, Herzog H: The neuropeptide Y system: pathophysiological and therapeutic implications in obesity and cancer. Pharmacol Ther 2011;131:91-113. 23 Li J, Tian Y, Wu A: Neuropeptide Y receptors: a promising target for cancer imaging and therapy. Regen Biomater 2015;2:215-219. 24 Crnkovic S, Egemnazarov B, Jain P, Seay U, Gattinger N, Marsh LM, Balint Z, Kovacs G, Ghanim B, Klepetko W, Schermuly RT, Weissmann N, Olschewski A, Kwapiszewska G: NPY/Y(1) receptor-mediated vasoconstrictory and proliferative effects in pulmonary hypertension. Br J Pharmacol 2014;171:3895- 3907. 25 Cassie N, Anderson RL, Wilson D, Pawsey A, Mercer JG, Barrett P: Body weight loss, effective satiation and absence of homeostatic neuropeptide compensation in male Sprague Dawley rats schedule fed a protein crosslinked diet. Appetite 2017;117:234-246. 26 Loh K, Zhang L, Brandon A, Wang Q, Begg D, Qi Y, Fu M, Kulkarni R, Teo J, Baldock P, Brüning JC, Cooney G, Neely G, Herzog H: Insulin controls food intake and energy balance via NPY neurons. Mol Metab 2017;6:574-584. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 102 Yi et al.: NPY Receptors in Metabolic Diseases

27 Yulyaningsih E, Zhang L, Herzog H, Sainsbury A: NPY receptors as potential targets for anti-obesity drug development. Br J Pharmacol 2011;163:1170-1202. 28 Zarjevski N, Cusin I, Vettor R, Rohner-Jeanrenaud F, Jeanrenaud B: Chronic intracerebroventricular neuropeptide-Y administration to normal rats mimics hormonal and metabolic changes of obesity. Endocrinology 1993;133:1753-1758. 29 Lin EJ, Sainsbury A, Lee NJ, Boey D, Couzens M, Enriquez R, Slack K, Bland R, During MJ, Herzog H: Combined deletion of Y1, Y2, and Y4 receptors prevents hypothalamic neuropeptide Y overexpression- 5101. induced hyperinsulinemia despite persistence of hyperphagia and obesity. Endocrinology 2006;147:5094-

30 Herzog H, Hort YJ, Ball HJ, Hayes G, Shine J, Selbie LA: Cloned human neuropeptide Y receptor couples to two different second messenger systems. Proc Natl Acad Sci U S A 1992;89:5794-5798. 31 Morgan DG, Kulkarni RN, Hurley JD, Wang ZL, Wang RM, Ghatei MA, Karlsen AE, Bloom SR, Smith DM: Inhibition of glucose stimulated insulin secretion by neuropeptide Y is mediated via the Y1 receptor and inhibition of adenylyl cyclase in RIN 5AH rat insulinoma cells. Diabetologia 1998;41:1482-1491. 32 Goumain M, Voisin T, Lorinet AM, Laburthe M: Identification and distribution of mRNA encoding the Y1, Y2, Y4, and Y5 receptors for peptides of the PP-fold family in the rat intestine and colon. Biochem Biophys Res Commun 1998;247:52-56. 33 Yang K, Guan H, Arany E, Hill DJ, Cao X: Neuropeptide Y is produced in visceral adipose tissue and promotes proliferation of adipocyte precursor cells via the Y1 receptor. FASEB J 2008;22:2452-2464. 34 Wahlestedt C, Reis DJ: Neuropeptide Y-related peptides and their receptors--are the receptors potential therapeutic drug targets? Annu Rev Pharmacol Toxicol 1993;33:309-352. 35 Jacques D, Tong Y, Dumont Y, Shen SH, Quirion R: Expression of the neuropeptide Y Y1 receptor mRNA in the human brain: an in situ hybridization study. Neuroreport 1996;7:1053-1056. 36 Statnick MA, Schober DA, Mayne NG, Burnett JP, Gehlert DR: Analysis of NPY receptor subtypes in the human frontal cortex reveals abundant Y1 mRNA and binding sites. Peptides 1997;18:137-143. 37 Caberlotto L, Fuxe K, Sedvall G, Hurd YL: Localization of neuropeptide Y Y1 mRNA in the human brain: abundant expression in cerebral cortex and striatum. Eur J Neurosci 1997;9:1212-1225. 38 Statnick MA, Schober DA, Gehlert DR: Identification of multiple neuropeptide Y receptor subtypes in the human frontal cortex. Eur J Pharmacol 1997;332:299-305. 39 Bhisikar SM, Kokare DM, Nakhate KT, Chopde CT, Subhedar NK: Tolerance to ethanol sedation and withdrawal hyper-excitability is mediated via neuropeptide Y Y1 and Y5 receptors. Life Sci 2009;85:765- 772. 40 Arvidsson AK, Wraith A, Jonsson-Rylander AC, Larhammar D: Cloning of a neuropeptide Y/peptide YY receptor from the Atlantic cod: the Yb receptor. Regul Pept 1998;75-76:39-43. 41 Reubi JC, Gugger M, Waser B, Schaer JC: Y(1)-mediated effect of neuropeptide Y in cancer: breast carcinomas as targets. Cancer Res 2001;61:4636-4641. 42 Korner M, Waser B, Reubi JC: High expression of neuropeptide Y1 receptors in ewing sarcoma tumors. Clin Cancer Res 2008;14:5043-5049. 43 Nguyen AD, Mitchell NF, Lin S, Macia L, Yulyaningsih E, Baldock PA, Enriquez RF, Zhang L, Shi YC, Zolotukhin S, Herzog H, Sainsbury A: Y1 and Y5 receptors are both required for the regulation of food intake and energy homeostasis in mice. PLoS One 2012;7:e40191. 44 Rump LC, Riess M, Schwertfeger E, Michel MC, Bohmann C, Schollmeyer P: Prejunctional neuropeptide Y receptors in human kidney and atrium. J Cardiovasc Pharmacol 1997;29:656-661. 45 Potter EK, Mitchell L, McCloskey MJ, Tseng A, Goodman AE, Shine J, McCloskey DI: Pre- and postjunctional actions of neuropeptide Y and related peptides. Regul Pept 1989;25:167-177. 46 Gerald C, Walker MW, Vaysse PJ, He C, Branchek TA, Weinshank RL: Expression cloning and pharmacological characterization of a human hippocampal neuropeptide Y/peptide YY Y2 receptor subtype. J Biol Chem 1995;270:26758-26761. 47 Ammar DA, Eadie DM, Wong DJ, Ma YY, Kolakowski LF, Jr., Yang-Feng TL, Thompson DA: Characterization of the human type 2 neuropeptide Y receptor gene (NPY2R) and localization to the chromosome 4q region containing the type 1 neuropeptide Y receptor gene. Genomics 1996;38:392-398. 48 Baldock PA, Allison SJ, Lundberg P, Lee NJ, Slack K, Lin EJ, Enriquez RF, McDonald MM, Zhang L, During MJ, Little DG, Eisman JA, Gardiner EM, Yulyaningsih E, Lin S, Sainsbury A, Herzog H: Novel role of Y1 receptors in the coordinated regulation of bone and energy homeostasis. J Biol Chem 2007;282:19092-19102. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 103 Yi et al.: NPY Receptors in Metabolic Diseases

in vitro 49 Klapstein GJ, Colmers WF: On the sites of presynaptic inhibition by neuropeptide Y in rat hippocampus . Hippocampus 1993;3:103-111. 50 Vezzani A, Sperk G: Overexpression of NPY and Y2 receptors in epileptic brain tissue: an endogenous neuroprotective mechanism in temporal lobe epilepsy? Neuropeptides 2004;38:245-252. 51 Batterham RL, Cowley MA, Small CJ, Herzog H, Cohen MA, Dakin CL, Wren AM, Brynes AE, Low MJ, Ghatei MA, Cone RD, Bloom SR: Gut hormone PYY(3-36) physiologically inhibits food intake. Nature 2002;418:650-654. 52 Field BC, Wren AM, Peters V, Baynes KC, Martin NM, Patterson M, Alsaraf S, Amber V, Wynne K, Ghatei MA, Bloom SR: PYY3-36 and can be additive in their effect on food intake in overweight and obese humans. Diabetes 2010;59:1635-1639. 53 Verma D, Tasan RO, Herzog H, Sperk G: NPY controls fear conditioning and fear extinction by combined action on Y(1) and Y(2) receptors. Br J Pharmacol 2012;166:1461-1473. 54 Lee EW, Michalkiewicz M, Kitlinska J, Kalezic I, Switalska H, Yoo P, Sangkharat A, Ji H, Li L, Michalkiewicz T, Ljubisavljevic M, Johansson H, Grant DS, Zukowska Z: Neuropeptide Y induces ischemic angiogenesis and restores function of ischemic skeletal muscles. J Clin Invest 2003;111:1853-1862. 55 Hayes DM, Fee JR, McCown TJ, Knapp DJ, Breese GR, Cubero I, Carvajal F, Lerma-Cabrera JM, Navarro M, Thiele TE: Neuropeptide Y signaling modulates the expression of ethanol-induced behavioral sensitization in mice. Addict Biol 2012;17:338-350. 56 Lu C, Everhart L, Tilan J, Kuo L, Sun CC, Munivenkatappa RB, Jonsson-Rylander AC, Sun J, Kuan-Celarier A, Li L, Abe K, Zukowska Z, Toretsky JA, Kitlinska J: Neuropeptide Y and its Y2 receptor: potential targets in neuroblastoma therapy. Oncogene 2010;29:5630-5642. 57 Korner M, Reubi JC: Neuropeptide Y receptors in primary human brain tumors: overexpression in high- grade tumors. J Neuropathol Exp Neurol 2008;67:741-749. 58 Kitlinska J, Abe K, Kuo L, Pons J, Yu M, Li L, Tilan J, Everhart L, Lee EW, Zukowska Z, Toretsky JA: Differential effects of neuropeptide Y on the growth and vascularization of neural crest-derived tumors. Cancer Res 2005;65:1719-1728. 59 Kuo LE, Kitlinska JB, Tilan JU, Li L, Baker SB, Johnson MD, Lee EW, Burnett MS, Fricke ST, Kvetnansky R, Herzog H, Zukowska Z: Neuropeptide Y acts directly in the periphery on fat tissue and mediates stress- induced obesity and metabolic syndrome. Nat Med 2007;13:803-811. 60 Bard JA, Walker MW, Branchek TA, Weinshank RL: Cloning and functional expression of a human Y4 subtype receptor for pancreatic polypeptide, neuropeptide Y, and peptide YY. J Biol Chem 1995;270:26762- 26765. 61 Ferrier L, Segain JP, Bonnet C, Cherbut C, Lehur PA, Jarry A, Galmiche JP, Blottiere HM: Functional mapping of NPY/PYY receptors in rat and human gastro-intestinal tract. Peptides 2002;23:1765-1771. 62 Lundell I, Blomqvist AG, Berglund MM, Schober DA, Johnson D, Statnick MA, Gadski RA, Gehlert DR, Larhammar D: Cloning of a human receptor of the NPY receptor family with high affinity for pancreatic polypeptide and peptide YY. J Biol Chem 1995;270:29123-29128. 63 Bellmann-Sickert K, Elling CE, Madsen AN, Little PB, Lundgren K, Gerlach LO, Bergmann R, Holst B, Schwartz TW, Beck-Sickinger AG: Long-acting lipidated analogue of human pancreatic polypeptide is slowly released into circulation. J Med Chem 2011;54:2658-2667. 64 Lindner D, Stichel J, Beck-Sickinger AG: Molecular recognition of the NPY hormone family by their receptors. Nutrition 2008;24:907-917. 65 Dumont Y, Bastianetto S, Duranton A, Breton L, Quirion R: Immunohistochemical distribution of neuropeptide Y, peptide YY, pancreatic polypeptide-like immunoreactivity and their receptors in the epidermal skin of healthy women. Peptides 2015;70:7-16. 66 Lin S, Shi YC, Yulyaningsih E, Aljanova A, Zhang L, Macia L, Nguyen AD, Lin EJ, During MJ, Herzog H, Sainsbury A: Critical role of arcuate Y4 receptors and the melanocortin system in pancreatic polypeptide- induced reduction in food intake in mice. PLoS One 2009;4:e8488. 67 Sainsbury A, Shi YC, Zhang L, Aljanova A, Lin Z, Nguyen AD, Herzog H, Lin S: Y4 receptors and pancreatic polypeptide regulate food intake via hypothalamic orexin and brain-derived neurotropic factor dependent pathways. Neuropeptides 2010;44:261-268. 68 Edelsbrunner ME, Painsipp E, Herzog H, Holzer P: Evidence from knockout mice for distinct implications of neuropeptide-Y Y2 and Y4 receptors in the circadian control of locomotion, exploration, water and food intake. Neuropeptides 2009;43:491-497. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 104 Yi et al.: NPY Receptors in Metabolic Diseases

69 Moriya R, Fujikawa T, Ito J, Shirakura T, Hirose H, Suzuki J, Fukuroda T, Macneil DJ, Kanatani A: Pancreatic polypeptide enhances colonic muscle contraction and fecal output through neuropeptide Y Y4 receptor in mice. Eur J Pharmacol 2010;627:258-264. 70 Sainsbury A, Zhang L: Role of the arcuate nucleus of the hypothalamus in regulation of body weight during energy deficit. Mol Cell Endocrinol 2010;316:109-119. 71 Tasan RO, Lin S, Hetzenauer A, Singewald N, Herzog H, Sperk G: Increased novelty-induced motor activity and reduced depression-like behavior in neuropeptide Y (NPY)-Y4 receptor knockout mice. Neuroscience 2009;158:1717-1730. 72 Katsuura G, Asakawa A, Inui A: Roles of pancreatic polypeptide in regulation of food intake. Peptides 2002;23:323-329. 73 Hu Y, Bloomquist BT, Cornfield LJ, DeCarr LB, Flores-Riveros JR, Friedman L, Jiang P, Lewis-Higgins L, Sadlowski Y, Schaefer J, Velazquez N, McCaleb ML: Identification of a novel hypothalamic neuropeptide Y receptor associated with feeding behavior. J Biol Chem 1996;271:26315-26319. 74 Gerald C, Walker MW, Criscione L, Gustafson EL, Batzl-Hartmann C, Smith KE, Vaysse P, Durkin MM, Laz TM, Linemeyer DL, Schaffhauser AO, Whitebread S, Hofbauer KG, Taber RI, Branchek TA, Weinshank RL: A receptor subtype involved in neuropeptide-Y-induced food intake. Nature 1996;382:168-171. 75 Rodriguez M, Audinot V, Dromaint S, Macia C, Lamamy V, Beauverger P, Rique H, Imbert J, Nicolas JP, Boutin JA, Galizzi JP: Molecular identification of the long isoform of the human neuropeptide Y Y5 receptor and pharmacological comparison with the short Y5 receptor isoform. Biochem J 2003;369:667-673. 76 Durkin MM, Walker MW, Smith KE, Gustafson EL, Gerald C, Branchek TA: Expression of a novel neuropeptide Y receptor subtype involved in food intake: an in situ hybridization study of Y5 mRNA distribution in rat brain. Exp Neurol 2000;165:90-100. neuropeptide Y receptor subtypes Y1 and Y5 suggests coordinate transcriptional regulation. Genomics 77 Herzog H, Darby K, Ball H, Hort Y, Beck-Sickinger A, Shine J: Overlapping gene structure of the human

1997;41:315-319. 78 Benmaamar R, Richichi C, Gobbi M, Daniels AJ, Beck-Sickinger AG, Vezzani A: Neuropeptide Y Y5 receptors inhibit kindling acquisition in rats. Regul Pept 2005;125:79-83. 79 Morales-Medina JC, Dominguez-Lopez S, Gobbi G, Beck-Sickinger AG, Quirion R: The selective neuropeptide Y Y5 agonist [cPP(1-7),NPY(19-23),Ala31,Aib32,Gln34]hPP differently modulates emotional processes and body weight in the rat. Behav Brain Res 2012;233:298-304. 80 Brothers SP, Wahlestedt C: Therapeutic potential of neuropeptide Y (NPY) receptor ligands. EMBO Mol Med 2010;2:429-439. 81 Kalra SP, Kalra PS: NPY and cohorts in regulating appetite, obesity and metabolic syndrome: beneficial effects of gene therapy. Neuropeptides 2004;38:201-211. 82 Sheriff S, Ali M, Yahya A, Haider KH, Balasubramaniam A, Amlal H: Neuropeptide Y Y5 receptor promotes cell growth through extracellular signal-regulated kinase signaling and cyclic AMP inhibition in a human breast cancer cell line. Mol Cancer Res 2010;8:604-614. 83 Parker RM, Herzog H: Regional distribution of Y-receptor subtype mRNAs in rat brain. Eur J Neurosci 1999;11:1431-1448. 84 Ginsberg HN, Zhang YL, Hernandez-Ono A: Metabolic syndrome: focus on dyslipidemia. Obesity (Silver Spring) 2006;14:41S-49S. 85 Isomaa B, Almgren P, Tuomi T, Forsen B, Lahti K, Nissen M, Taskinen MR, Groop L: Cardiovascular morbidity and mortality associated with the metabolic syndrome. Diabetes Care 2001;24:683-689. 86 Long M, Zhou J, Li D, Zheng L, Xu Z, Zhou S: Long-Term Over-Expression of Neuropeptide Y in Hypothalamic Paraventricular Nucleus Contributes to Adipose Tissue Insulin Resistance Partly via the Y5 Receptor. PLoS One 2015;10:e0126714. 87 Rojas JM, Stafford JM, Saadat S, Printz RL, Beck-Sickinger AG, Niswender KD: Central nervous system neuropeptide Y signaling via the Y1 receptor partially dissociates feeding behavior from lipoprotein metabolism in lean rats. Am J Physiol Endocrinol Metab 2012;303:E1479-1488. 88 Stafford JM, Yu F, Printz R, Hasty AH, Swift LL, Niswender KD: Central nervous system neuropeptide Y signaling modulates VLDL triglyceride secretion. Diabetes 2008;57:1482-1490. 89 Bruinstroop E, Pei L, Ackermans MT, Foppen E, Borgers AJ, Kwakkel J, Alkemade A, Fliers E, Kalsbeek A: Hypothalamic neuropeptide Y (NPY) controls hepatic VLDL-triglyceride secretion in rats via the sympathetic nervous system. Diabetes 2012;61:1043-1050. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 105 Yi et al.: NPY Receptors in Metabolic Diseases

90 Rojas JM, Bruinstroop E, Printz RL, Alijagic-Boers A, Foppen E, Turney MK, George L, Beck-Sickinger phospholipid remodeling and very low-density lipoprotein triglyceride secretion via sympathetic AG, Kalsbeek A, Niswender KD: Central nervous system neuropeptide Y regulates mediators of hepatic

innervation. Mol Metab 2015;4:210-221. 91 Farmer SR: Regulation of PPARgamma activity during adipogenesis. Int J Obes (Lond) 2005;29:S13-16. 92 Rosmaninho-Salgado J, Cortez V, Estrada M, Santana MM, Goncalves A, Marques AP, Cavadas C: Intracellular mechanisms coupled to NPY Y2 and Y5 receptor activation and lipid accumulation in murine adipocytes. Neuropeptides 2012;46:359-366. 93 Rosmaninho-Salgado J, Marques AP, Estrada M, Santana M, Cortez V, Grouzmann E, Cavadas C: Dipeptidyl- peptidase-IV by cleaving neuropeptide Y induces lipid accumulation and PPAR-gamma expression. Peptides 2012;37:49-54. 94 Liu L, Wang G, Xiao Y, Shipp SL, Siegel PB, Cline MA, Gilbert ER: Peripheral neuropeptide Y differentially influences adipogenesis and lipolysis in chicks from lines selected for low or high body weight. Comp Biochem Physiol A Mol Integr Physiol 2017;213:1-10. 95 Park S, Komatsu T, Kim SE, Tanaka K, Hayashi H, Mori R, Shimokawa I: Neuropeptide Y resists excess loss of fat by lipolysis in calorie‐restricted mice: a trait potential for the life‐extending effect of calorie restriction. Aging Cell 2017;16:339-348. 96 Grandt D, Schimiczek M, Beglinger C, Layer P, Goebell H, Eysselein VE, Reeve JR, Jr.: Two molecular forms of peptide YY (PYY) are abundant in human blood: characterization of a radioimmunoassay recognizing PYY 1-36 and PYY 3-36 Regul Pept 1994;51:151-159. 97 Batterham RL, Cohen MA, Ellis SM, Le Roux CW, Withers DJ, Frost GS, Ghatei MA, Bloom SR: Inhibition of food intake in obese subjects by peptide YY3-36 N Engl J Med 2003;349:941-948. 98 Torekov SS, Larsen LH, Glumer C, Borch-Johnsen K, Jorgensen T, Holst JJ, Madsen OD, Hansen T, Pedersen O: Evidence of an association between the Arg72 allele of the peptide YY and increased risk of type 2 diabetes. Diabetes 2005;54:2261-2265. 99 Ma L, Tataranni PA, Hanson RL, Infante AM, Kobes S, Bogardus C, Baier LJ: Variations in peptide YY and Y2 receptor genes are associated with severe obesity in Pima Indian men. Diabetes 2005;54:1598-1602. 100 Weng HH, Bastian LA, Taylor DH, Jr., Moser BK, Ostbye T: Number of children associated with obesity in middle-aged women and men: results from the health and retirement study. J Womens Health (Larchmt) 2004;13:85-91. the peptide YY and neuropeptide Y2 receptor genes in relation to human obesity and obesity-related traits. 101 Hung CC, Pirie F, Luan J, Lank E, Motala A, Yeo GS, Keogh JM, Wareham NJ, O’Rahilly S, Farooqi IS: Studies of

Diabetes 2004;53:2461-2466. 102 Lavebratt C, Alpman A, Persson B, Arner P, Hoffstedt J: Common neuropeptide Y2 receptor gene variant is protective against obesity among Swedish men. Int J Obes (Lond) 2006;30:453-459. 103 Torekov SS, Larsen LH, Andersen G, Albrechtsen A, Glumer C, Borch-Johnsen K, Jorgensen T, Hansen T, Pedersen O: Variants in the 5’ region of the neuropeptide Y receptor Y2 gene (NPY2R) are associated with obesity in 5, 971 white subjects. Diabetologia 2006;49:2653-2658. 104 Macia L, Yulyaningsih E, Pangon L, Nguyen AD, Lin S, Shi YC, Zhang L, Bijker M, Grey S, Mackay F, Herzog H, Sainsbury A: Neuropeptide Y1 receptor in immune cells regulates inflammation and insulin resistance associated with diet-induced obesity. Diabetes 2012;61:3228-3238. 105 Henry M, Ghibaudi L, Gao J, Hwa JJ: Energy metabolic profile of mice after chronic activation of central NPY Y1, Y2, or Y5 receptors. Obes Res 2005;13:36-47. 106 Sitticharoon C, Chatree S, Churintaraphan M: Expressions of neuropeptide Y and Y1 receptor in subcutaneous and visceral fat tissues in normal weight and obese humans and their correlations with clinical parameters and peripheral metabolic factors. Regul Pept 2013;185:65-72. 107 Serradeil-Le Gal C, Lafontan M, Raufaste D, Marchand J, Pouzet B, Casellas P, Pascal M, Maffrand JP, Le Fur G: Characterization of NPY receptors controlling lipolysis and leptin secretion in human adipocytes. FEBS Lett 2000;475:150-156. 108 Faeh D, William J, Yerly P, Paccaud F, Bovet P: Diabetes and pre-diabetes are associated with cardiovascular risk factors and carotid/femoral intima-media thickness independently of markers of insulin resistance and adiposity. Cardiovasc Diabetol 2007;6:32. 109 Jeric M, Vukojevic K, Vuica A, Filipovic N: Diabetes mellitus influences the expression of NPY and VEGF in neurons of rat trigeminal ganglion. Neuropeptides 2017;62:57-64. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 106 Yi et al.: NPY Receptors in Metabolic Diseases

110 Karagiannides I, Torres D, Tseng YH, Bowe C, Carvalho E, Espinoza D, Pothoulakis C, Kokkotou E: Substance P as a novel anti-obesity target. Gastroenterology 2008;134:747-755. 111 Gericke MT, Schroder T, Kosacka J, Nowicki M, Kloting N, Spanel-Borowski K: Neuropeptide Y impairs insulin-stimulated translocation of glucose transporter 4 in 3T3-L1 adipocytes through the Y1 receptor. Mol Cell Endocrinol 2012;348:27-32. 112 Choi K, Kim YB: Molecular mechanism of insulin resistance in obesity and type 2 diabetes. Korean J Intern Med 2010;25:119-129. 113 Leney SE, Tavare JM: The molecular basis of insulin-stimulated glucose uptake: signalling, trafficking and potential drug targets. J Endocrinol 2009;203:1-18. 114 Imai Y, Patel HR, Hawkins EJ, Doliba NM, Matschinsky FM, Ahima RS: Insulin secretion is increased in pancreatic islets of neuropeptide Y-deficient mice. Endocrinology 2007;148:5716-5723. 115 Ilhan A, Rasul S, Dimitrov A, Handisurya A, Gartner W, Baumgartner-Parzer S, Wagner L, Kautzky-Willer A, Base W: Plasma neuropeptide Y levels differ in distinct diabetic conditions. Neuropeptides 2010;44:485- 489. 116 Cho YR, Kim CW: Neuropeptide Y promotes beta-cell replication via extracellular signal-regulated kinase activation. Biochem Biophys Res Commun 2004;314:773-780. 117 Rodnoi P, Rajkumar M, Moin ASM, Georgia SK, Butler AE, Dhawan S: Neuropeptide Y expression marks partially differentiated β cells in mice and humans. JCI Insight 2: 118 Hirai H, Miura J, Hu Y, Larsson H, Larsson K, Lernmark A, Ivarsson SA, Wu T, Kingman A, Tzioufas AG, Notkins AL: Selective screening of secretory vesicle-associated proteins for autoantigens in type 1 diabetes: VAMP2 and NPY are new minor autoantigens. Clin Immunol 2008;127:366-374. 119 Campbell CD, Lyon HN, Nemesh J, Drake JA, Tuomi T, Gaudet D, Zhu X, Cooper RS, Ardlie KG, Groop LC, Hirschhorn JN: Association studies of BMI and type 2 diabetes in the neuropeptide Y pathway: a possible role for NPY2R as a candidate gene for type 2 diabetes in men. Diabetes 2007;56:1460-1467. 120 Rodnoi P, Rajkumar M, Moin ASM, Georgia SK, Butler AE, Dhawan S: Neuropeptide Y expression marks partially differentiated beta cells in mice and humans. JCI Insight 2017;2: 121 Ruipan Z, Xiangzhi M, Li L, Ying Z, Mingliang Q, Peng J, Jingwei L, Zijun Z, Yan G: Differential expression and localization of neuropeptide Y peptide in pancreatic islet of diabetic and high fat fed rats. Peptides 2014;54:33-38. 122 Jonsson-Rylander AC, Nordlander M, Svindland A, Ilebekk A: Distribution of neuropeptide Y Y1 and Y2 receptors in the postmortem human heart. Peptides 2003;24:255-262. 123 Abe K, Kuo L, Zukowska Z: Neuropeptide Y is a mediator of chronic vascular and metabolic maladaptations to stress and hypernutrition. Exp Biol Med (Maywood) 2010;235:1179-1184. 124 Chottova Dvorakova M, Wiegand S, Pesta M, Slavikova J, Grau V, Reischig J, Kuncova J, Kummer W: Expression of neuropeptide Y and its receptors Y1 and Y2 in the rat heart and its supplying autonomic and spinal sensory ganglia in experimentally induced diabetes. Neuroscience 2008;151:1016-1028. 125 Protas L, Qu J, Robinson RB: Neuropeptide y: neurotransmitter or trophic factor in the heart? News Physiol Sci 2003;18:181-185. 126 Matyal R, Mahmood F, Robich M, Glazer H, Khabbaz K, Hess P, Bianchi C, Hagberg R, Hu SX, Sellke FW: Chronic type II diabetes mellitus leads to changes in neuropeptide Y receptor expression and distribution in human myocardial tissue. Eur J Pharmacol 2011;665:19-28. 127 Zhang R, Niu H, Kang X, Ban T, Hong H, Ai J: Long-Term Administration of Neuropeptide Y in the Subcutaneous Infusion Results in Cardiac Dysfunction and Hypertrophy in Rats. Cell Physiol Biochem 2015;37:94-104. 128 Zhang P, Qi YX, Yao QP, Chen XH, Wang GL, Shen BR, Han Y, Gao LZ, Jiang ZL: Neuropeptide Y Stimulates Proliferation and Migration of Vascular Smooth Muscle Cells from Pregnancy Hypertensive Rats via Y1 and Y5 Receptors. PLoS One 2015;10:e0131124. 129 O’Connor DT, Insel PA, Ziegler MG, Hook VY, Smith DW, Hamilton BA, Taylor PW, Parmer RJ: Heredity and the autonomic nervous system in human hypertension. Curr Hypertens Rep 2000;2:16-22. 130 Rao F, Zhang L, Wessel J, Zhang K, Wen G, Kennedy BP, Rana BK, Das M, Rodriguez-Flores JL, Smith DW, Cadman PE, Salem RM, Mahata SK, Schork NJ, Taupenot L, Ziegler MG, O’Connor DT: Tyrosine hydroxylase, in vivo the rate-limiting enzyme in catecholamine biosynthesis: discovery of common human genetic variants governing transcription, autonomic activity, and blood pressure . Circulation 2007;116:993-1006. Cellular Physiology Cell Physiol Biochem 2018;45:88-107 DOI: 10.1159/000486225 © 2018 The Author(s). Published by S. Karger AG, Basel and Biochemistry Published online: January 08, 2018 www.karger.com/cpb 107 Yi et al.: NPY Receptors in Metabolic Diseases

131 Cheng PW, Wu AT, Lu PJ, Yang YC, Ho WY, Lin HC, Hsiao M, Tseng CJ: Central hypotensive effects of neuropeptide Y are modulated by endothelial nitric oxide synthase after activation by ribosomal protein S6 kinase. Br J Pharmacol 2012;167:1148-1160. 132 Cavadas C, Cefai D, Rosmaninho-Salgado J, Vieira-Coelho MA, Moura E, Busso N, Pedrazzini T, Grand D, Rotman S, Waeber B, Aubert JF, Grouzmann E: Deletion of the neuropeptide Y (NPY) Y1 receptor gene reveals a regulatory role of NPY on catecholamine synthesis and secretion. Proc Natl Acad Sci U S A 2006;103:10497-10502. 133 Kennedy B, Shen GH, Ziegler MG: Neuropeptide Y-mediated pressor responses following high-frequency stimulation of the rat sympathetic nervous system. J Pharmacol Exp Ther 1997;281:291-296. 134 de Wardener HE: The hypothalamus and hypertension. Physiol Rev 2001;81:1599-1658. 135 Tsuda K, Tsuda S, Masuyama Y, Goldstein M: Norepinephrine release and neuropeptide Y in medulla oblongata of spontaneously hypertensive rats. Hypertension 1990;15:784-790. 136 Michalkiewicz M, Zhao G, Jia Z, Michalkiewicz T, Racadio MJ: Central neuropeptide Y signaling ameliorates N(omega)-nitro-L-arginine methyl ester hypertension in the rat through a Y1 receptor mechanism. Hypertension 2005;45:780-785. 137 Moleda L, Trebicka J, Dietrich P, Gabele E, Hellerbrand C, Straub RH, Sauerbruch T, Schoelmerich J, Wiest R: Amelioration of portal hypertension and the hyperdynamic circulatory syndrome in cirrhotic rats by neuropeptide Y via pronounced splanchnic vasoaction. Gut 2011;60:1122-1132. 138 Kask A, Harro J, von Horsten S, Redrobe JP, Dumont Y, Quirion R: The neurocircuitry and receptor subtypes mediating anxiolytic-like effects of neuropeptide Y. Neurosci Biobehav Rev 2002;26:259-283. 139 Tseng CJ, Liu HY, Lin HC, Ger LP, Tung CS, Yen MH: Cardiovascular effects of nitric oxide in the brain stem nuclei of rats. Hypertension 1996;27:36-42. 140 Jin L, Wang C: [Changes of plasma level of neuropeptide Y in patients with pregnancy induced hypertension]. Zhonghua Fu Chan Ke Za Zhi 2001;36:206-208. 141 Adamova Z, Ozkan S, Khalil RA: Vascular and cellular calcium in normal and hypertensive pregnancy. Curr Clin Pharmacol 2009;4:172-190. 142 Zhao YJ, Zou QY, Li Y, Li HH, Wu YM, Li XF, Wang K, Zheng J: Expression of G-protein subunit alpha-14 is increased in human placentas from preeclamptic pregnancies. J Histochem Cytochem 2014;62:347-354. 143 Movafagh S, Hobson JP, Spiegel S, Kleinman HK, Zukowska Z: Neuropeptide Y induces migration, proliferation, and tube formation of endothelial cells bimodally via Y1, Y2, and Y5 receptors. FASEB J 2006;20:1924-1926. 144 Hausman GJ, Barb CR, Dean RG: Patterns of gene expression in pig adipose tissue: insulin-like growth factor system proteins, neuropeptide Y (NPY), NPY receptors, neurotrophic factors and other secreted factors. Domest Anim Endocrinol 2008;35:24-34. 145 Balasubramaniam A: Clinical potentials of neuropeptide Y family of hormones. Am J Surg 2002;183:430- 434.