BBA - Molecular Basis of Disease 1865 (2019) 678–687 Contents lists available at ScienceDirect BBA - Molecular Basis of Disease journal homepage: www.elsevier.com/locate/bbadis Hepatic hexokinase domain containing 1 (HKDC1) improves whole body T glucose tolerance and insulin sensitivity in pregnant mice Md. Wasim Khana, Medha Priyadarshinia, Jose Cordoba-Chacona, Thomas C. Beckerb, ⁎ Brian T. Laydena,c, a Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Illinois at Chicago, IL, USA b Duke Molecular Physiology Institute, Department of Internal Medicine, Duke University Medical Center, Durham, NC, USA c Jesse Brown Veterans Affairs Medical Center, Chicago, IL, USA ARTICLE INFO ABSTRACT Keywords: Hexokinase domain containing 1, a recently discovered putative fifth hexokinase, is hypothesized to play key Gestational diabetes roles in glucose metabolism. Specifically, during pregnancy in a recent genome wide association study (GWAS), Hexokinase a strong correlation between HKDC1 and 2-h plasma glucose in pregnant women from different ethnic back- Insulin resistance grounds was shown. Our earlier work also reported diminished glucose tolerance during pregnancy in our whole body HKDC1 heterozygous mice. Therefore, we hypothesized that HKDC1 plays important roles in gestational metabolism, and designed this study to assess the role of hepatic HKDC1 in whole body glucose utilization and insulin action during pregnancy. We overexpressed human HKDC1 in mouse liver by injecting a human HKDC1 adenoviral construct; whereas, for the liver-specific HKDC1 knockout model, we used AAV-Cre constructs inour HKDC1fl/fl mice. Both groups of mice were subjected to metabolic testing before and during pregnancy on gestation day 17–18. Our results indicate that hepatic HKDC1 overexpression during pregnancy leads to im- proved whole-body glucose tolerance and enhanced hepatic and peripheral insulin sensitivity while hepatic HKDC1 knockout results in diminished glucose tolerance. Further, we observed reduced gluconeogenesis with hepatic HKDC1 overexpression while HKDC1 knockout led to increased gluconeogenesis. These changes were associated with significantly enhanced ketone body production in HKDC1 overexpressing mice, indicating that these mice shift their metabolic needs from glucose reliance to greater fat oxidation and ketone utilization during fasting. Taken together, our results indicate that hepatic HKDC1 contributes to whole body glucose disposal, insulin sensitivity, and aspects of nutrient balance during pregnancy. 1. Introduction conditions is important. Overall, insulin controls glucose homeostasis by lowering plasma glucose by increasing cellular uptake and inhibiting Pregnancy brings forth significant metabolic reprogramming that hepatic glucose production. In contrast, reduced insulin action pro- induces a number of metabolic changes to ensure that the nutrient re- motes lipolysis, fatty acid oxidation and gluconeogenesis. A balance quirements of the mother and fetus are met [1–3]. These adaptations between insulin production by the pancreas and its subsequent action change radically over the period of pregnancy depending on the ana- on maternal muscle, liver and fat tissues mediates the regulation of bolic or catabolic demand [1–3]. The overall focus of the maternal gestational glucose levels with unique differences from this balance in metabolic response is focused on conserving and storing nutrients to the non-pregnant state [6]. sustain the demands of continuous supply of nutrients to the fetus even Early pregnancy is characterized by heightened insulin sensitivity during periods of food unavailability to preserve fetal development and that leads to maternal lipid accumulation; whereas, later stages of maternal survival [4,5]. Understanding these shifts of nutrients is in- pregnancy show increased resistance to insulin with increased mobili- tegral to the health of the mother and developing fetus. zation of the stored lipid depots [2,3,7–15]. In early gestation, pro- Glucose is the major source of energy and macromolecular building gressive accumulation of maternal adipose tissue lipids is due to en- blocks during pregnancy, and thus, understanding its regulation and hanced food intake, extrahepatic tissue lipoprotein lipase (LPL) activity, flux during pregnancy under physiological and pathophysiological and adipose tissue lipogenesis [16]. During the later stages of ⁎ Corresponding author at: Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Illinois at Chicago, IL, USA. E-mail address: [email protected] (B.T. Layden). https://doi.org/10.1016/j.bbadis.2018.11.022 Received 20 September 2018; Received in revised form 19 November 2018; Accepted 26 November 2018 Available online 10 December 2018 0925-4439/ © 2018 Elsevier B.V. All rights reserved. Md. W. Khan et al. BBA - Molecular Basis of Disease 1865 (2019) 678–687 pregnancy, insulin resistance is characterized by reduced maternal 2.2. Adenovirus construction glucose utilization, increased lipolysis and increased levels of hepatic glucose production [7–15]. In late gestation, there is increasing insulin Adenovirus containing the human HKDC1 cDNA was generated as resistance contributing to maternal hypertriglyceridemia and also de- previously described [21]. In brief, fragment containing the 2750 bp creased fat synthesis accompanied by enhanced adipose tissue lipolytic ORF of HKDC1 (RC221178 plasmid, Origene, Rockville, MD, USA), was activity, which depletes maternal fat depots [7–15,17–19]. Ad- cloned into the pShuttle-CMV adenoviral vector (Agilent, Santa Clara, ditionally, in late gestation, the maternal-fetal glucose transfer results CA, USA). The resulting HKDC1 adenoviral shuttles were then linear- in a lowering of the maternal glucose set point especially during fasting ized and transformed into BJ5183-AD1 cells (Agilent) producing re- and/or starvation which further activates maternal gluconeogenesis combinant clones which were isolated and digested. Recombinant [4,5]. HKDC1 adenoviruses were produced by transfecting HEK293 cells Recently, in a genome-wide association (GWA) study that focused (Clontech, Mountainview, CA, USA) with PacI-digested recombinant on human gestational glucose metabolism, we discovered that HKDC1 plasmid DNA and FuGene36. After transfection was complete, the viral (hexokinase domain containing 1), a novel fifth hexokinase, is asso- lysate was collected and further amplified in HEK293 cells. Infected ciated with glucose tolerance in pregnant mothers at 24–28 weeks of cells were collected and lysed by two freeze/thaw cycles in 2 mL freeze/ gestation [20], through polymorphisms in regulatory variants [21]. thaw buffer (10 mM Tris/HCl, pH 8.0, 1 mM MgCl2). The virus wasthen These data suggest that HKDC1 may play a specific role during preg- purified by ultracentrifugation using a CsCl gradient. Purified viruswas nancy [20–24]. HKDC1, based on sequence, was suggested to be a novel de-salted using a 7 k MWCO column (Thermo Scientific, Waltham, MA, hexokinase, and has since been shown to have hexokinase activity [21]. USA) and equilibrated with freeze/thaw buffer, after which glycerol The primary function of a hexokinase is to phosphorylate and thus trap was added to a final concentration of 10%. Viruses were titrated by glucose in the cell for further processing [25]. Previously, the hex- measuring OD260 (1 OD260 = 1.1 Å ~ 1012 virions mL-1) and by okinase (HK) family was comprised of four known members, each plaque assay in HEK293 cells. having distinct expression patterns and enzyme activities [25,26]. HK 1–3 have a high enzymatic activity in phosphorylating glucose (re- 2.3. Mice presented by low Km values) and are responsible for glucose metabo- lism and energy production. In contrast, HK 4, known as glucokinase All mouse studies were approved by the IACUC of the University of (GCK), has a high Km value and is considered the glucose sensor of the Illinois at Chicago and performed in accordance with the Guide for the body due to its expression being restricted to tissues that participate in Care and Use of Laboratory Animals. Animals were housed in a tem- whole-body glucose sensing (pancreas and liver) [27]. These four HKs perature (22–24 °C) and humidity-controlled specific pathogen-free have been thought to be the only HKs in humans to mediate this pivotal barrier facility with 12-h light/12-h dark cycle (lights on at 06:00 h). step of glucose metabolism, until the discovery of HKDC1. Our data, Mice were fed a standard laboratory rodent chow diet (Envigo 7912, and others, have now confirmed that HKDC1 is a 5th hexokinase; Madison WI, USA). however, its enzymatic properties have yet to be fully reported [20,21,28]. 2.3.1. Adult-onset human HKDC1 overexpression model (aHepHKDC1-OE) Studies conducted in our laboratory, thus far, have shown that 10–12 weeks old male and female C57Bl/6J (The Jackson HKDC1 is broadly expressed [28]. Using the first developed HKDC1 Laboratory) mice were mated and female mice were assessed for plug mouse model, we found that complete loss of HKDC1 function is em- formation the next day and their body weights were followed for bryonic lethal, similar to other HKs [29,30]. Further studies using 10 days to ensure they were pregnant. 10-day pregnant females were HKDC1 heterozygous knockout mice showed normal insulin produc- injected in the lateral tail vein with 100 μL saline containing 1 × 109 tion, insulin sensitivity, gluconeogenesis and glucose