Liu et al. Cell Discovery (2020) 6:19 Cell Discovery https://doi.org/10.1038/s41421-020-0152-4 www.nature.com/celldisc

CORRESPONDENCE Open Access The Asprosin–OLFR734 module regulates appetitive behaviors Yang Liu1, Aijun Long1,LiqunChen1, Liangjie Jia1 and Yiguo Wang 1

Dear Editor, first hour after fasting and at night (dark phase). As a Organisms need to maintain the balance between result, the accumulated amount of food intake of − − energy intake and expenditure for healthy survival. For Olfr734 / mice is much less than WT mice (Fig. 1b). , eating is the most common process to fuel the Under ad lib-feeding conditions, the accumulated food − − body, and ingestive behaviors are well controlled by the intake is comparable between fed WT and Olfr734 / − − neural system in response to peripheral signals, such as mice, although Olfr734 / mice ate slightly less at the nutrients and hormones1. In the arcuate nucleus (ARC) of very beginning of the test than WT mice (Supplementary the , Agouti-related -expressing Fig. S1a, b). In addition, the body weights of WT and − − (AgRP) neurons are activated by energy deficit to promote Olfr734 / mice are similar under fed or fasted conditions appetitive behaviors2. By contrast, (Supplementary Fig. S1c). Together, these results indicate (POMC) neurons sense when energy levels are sufficient that OLFR734 promotes fasting-induced food intake in and inhibit food intake2. , such as mice. Y (NPY), , and -like peptide-1 AgRP neurons in the ARC of the hypothalamus are (GLP-1), and circulating nutrients deliver signals to these activated by energy deficit to promote feeding behaviors2. neurons3. Olfaction also plays an important role in reg- To investigate whether OLFR734 can mediate the acti- 1 fi fi

1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; ulating appetitive behavior . The hypothalamus can vation of AgRP neurons, we rst identi ed the expression receive olfactory inputs from olfactory sensory neurons of Olfr734 in AgRP neurons. Olfr734 is expressed in AgRP and the olfactory bulb (OB) to coordinate food appre- neurons, as evaluated by fluorescence in situ hybridization ciation and selection4. (Fig. 1c). The expression of Fos in the AgRP neurons and Asprosin, which is cleaved from fibrillin 1, is a fasting- the proportion of cells positive for Fos (a marker of − − induced secreted by adipose tissue5. Circulating neuronal activation) are much lower in Olfr734 / mice Asprosin binds to the OLFR734 in the than in WT mice (Fig. 1d, e). In addition, Asprosin to promote hepatic via the cAMP- administration enhanced Fos staining in AgRP neurons − − PKA-signaling pathway5,6. It is also reported that Aspro- from WT mice but not Olfr734 / mice (Fig. 1d, e). sin can cross the blood–brain barrier to activate AgRP Together, these results show that OLFR734, as a receptor neurons to stimulate appetite7. However, it is still of Asprosin, promotes AgRP neuronal activity. unknown whether OLRF734, as an olfactory receptor and Since olfaction also plays an important role in reg- a receptor of Asprosin, mediates appetitive behaviors. ulating appetitive behavior, we investigated whether the To determine whether OLFR734 regulates appetitive Asprosin–OLFR734 module affects olfactory perfor- behaviors, we compared the food intake between wildtype mance. Olfactory performance is enhanced by fasting − − (WT) mice and Olfr734 / mice. OLFR734 deficiency and reduced by feeding in rodents and humans8.Since significantly decreased the food intake in overnight-fasted Asprosin is enhanced during fasting and OLFR734 is also mice compared with WT mice (Fig. 1a), especially in the highly expressed in olfactory epithelium and OB, we used aburiedfoodtest9 to investigate whether Asprosin affects mouse olfaction via OLFR734. Plasma Asprosin − − Correspondence: Yiguo Wang ([email protected]) was enhanced to a similar extent in WT and Olfr734 / 1MOE Key Laboratory of Bioinformatics, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China mice after fasting, while OLFR734 expression was not These authors contributed equally: Yang Liu, Aijun Long

© The Author(s) 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a linktotheCreativeCommons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Liu et al. Cell Discovery (2020) 6:19 Page 2 of 3

Fig. 1 Asprosin improves olfactory performance and activates AgRP neurons via OLFR734. a, b Food intake curves (a) and cumulative food intake (b) from 0 to 24 h in WT and Olfr734−/− mice immediately after overnight fasting. n = 8 mice. c Fluorescence in situ hybridization showing the expression of Olfr734 and Agrp in the arcuate nucleus (ARC) of the hypothalamus from WT and Olfr734−/− mice. Scale bars, 50 μm. d, e Fos staining (d) and quantitation of Fos-positive cells (e) showing neuronal activation of AgRP neurons from WT and Olfr734−/− mice administered with GST (Asprosin−) or GST-Asprosin (Asprosin+). Scale bars, 50 μm. n = 5 mice. f Time taken to find hidden food pellets by WT and Olfr734−/− mice administered with GST (Asprosin−) or GST-Asprosin (Asprosin+). n = 9 mice. g Relative mRNA levels of Fos in olfactory bulb extracts from WT and Olfr734−/− mice administered with GST (Asprosin−) or GST-Asprosin (Asprosin+). n = 5 mice. h, i Fos staining (h) and quantitation of Fos-positive cells (i) showing neuronal activation of olfactory bulbs from WT and Olfr734−/− mice administered with GST (Asprosin−) or GST-Asprosin (Asprosin+). GL glomerular layer, MCL mitral cell layer, EPL external plexiform layer, GCL granule cell layer. Scale bars, 50 μm. n = 8 mice. Data are shown as mean ± sem. *P < 0.05, **P < 0.01, ***P < 0.001. affected by fasting (Supplementary Fig. S2a, b). In fasted decreased the food finding time (Fig. 1f–i). These results WT mice, the food finding time was about 50% of that in indicate that the Asprosin–OLFR734 axis mediates the fed WT mice (Supplementary Fig. S2c). The fasting- fasting-induced increase of olfactory performance. induced effect on food finding was much weaker in Olfactory sensitivity and discrimination are impaired − − Olfr734 / mice than WT (Supplementary Fig. S2c). in obese or diabetic rodents and humans10.Comparedto Considering the effect of OLFR734 on smell, we tested regular diet (RD)-fed mice, mice fed a high fat diet whether Asprosin has a similar effect by injecting (HFD) for 16 weeks had significantly higher levels of Asprosin into mice. Without food odor stimulus, plasma Asprosin (Supplementary Fig. S3a), a decreased − − Asprosin administration to satiated WT or Olfr734 / proportion of cells positive for Fos (Supplementary Fig. mice cannot induce any elevated Fos expression in the S3b, c) and lower expression of Fos (Supplementary Fig. OB (Supplementary Fig. S2d). With food odor stimulus, S3d) in the OB. The buried food test further revealed Asprosin administration in WT mice, but not in that HFD-fed mice took more time to find food pellets − − Olfr734 / mice, increased the expression of Fos in the than RD-fed mice (Supplementary Fig. S3e). These OB and the proportion of cells positive for Fos, and results indicate that HFD feeding impaired olfactory Liu et al. Cell Discovery (2020) 6:19 Page 3 of 3

performance in mice, and the increased plasma Asprosin Acknowledgements levels in HFD-fed mice was not sufficient to reverse the We appreciate the helpful work of Drs. Erwei Li, Haili Shan, and Cheng Zhan during the beginning of this study. This work was supported by grants from deteriorated olfaction. Consistent with this notion, the National Natural Science Foundation of China (31625014, 31830040, and administration of additional Asprosin increased the 91957206) and the Ministry of Science and Technology of the People’s proportion of Fos-positive cells and the expression of Republic of China (2016YFC1304803 and 2017YFA0503404). Fos fi ,anddecreasedthefood nding time in HFD-fed Author contributions mice (Supplementary Fig. S3a–e). Together, these Y.L., A.L., and Y.W. designed the study. Y.L., A.L., L.C., and L.J. performed the results demonstrate that Asprosin can enhance olfactory experiments. Y.L., A.L., and Y.W. wrote the paper. All authors reviewed and performance and partially rescue HFD-induced olfactory commented on the manuscript. impairment. Conflict of interest Previous studies showed that OLFR734 in the liver, as a The authors declare that they have no conflict of interest. receptor of Asprosin, promotes hepatic gluconeogenesis6. Here, we reported that OLFR734 in the nervous system, as Publisher’s note a receptor of Asprosin, stimulates appetitive behavior by Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. improving olfactory performance and activating AgRP −/− neurons. The decreased food intake in Olfr734 mice in Supplementary Information accompanies the paper at (https://doi.org/ the first hour after fasting (Fig. 1a) may reflect the 10.1038/s41421-020-0152-4). importance of olfaction in food seeking behavior. The OLFR734–Asprosin axis mediates two important fasting- Received: 3 February 2020 Accepted: 28 February 2020 related functions to help organisms to acquire more energy. Thus, it will bell interesting to determine how the two processes coordinate energy homeostasis though References crosstalk between peripheral organs and the central ner- 1. Schneider, J. E., Wise, J. D., Benton, N. A., Brozek, J. M. & Keen-Rhinehart, E. vous system. When do we eat? Ingestive behavior, survival, and reproductive success. Horm. fi Behav. 64,702–728 (2013). Our nding that Asprosin alone cannot activate neu- 2. Chen,Y.,Lin,Y.C.,Kuo,T.W.&Knight,Z.A.Sensorydetectionoffoodrapidly rons in the OB (Supplementary Fig. S2d) indicates that modulates arcuate feeding circuits. Cell 160,829–841 (2015). Asprosin itself is a potential amplifier, but not an inducer, 3. Thomas, M. A. & Xue, B. Mechanisms for AgRP neuron-mediated regulation of appetitive behaviors in rodents. Physiol. Behav. 190,34–42 (2018). of odor-stimulated signals. It is possible that Asprosin, as 4. Riera, C. E. et al. The sense of smell impacts metabolic health and . Cell an internal cue, and odorants, as external cues, coordinate Metab. 26,198–211 (2017). smell and food seeking behavior via OLFR734. Therefore, 5. Romere, C. et al. Asprosin, a fasting-induced glucogenic protein hormone. Cell – it is important to determine which odorants are 165,566 579 (2016). 10 6. Li, E. et al. OLFR734 mediates metabolism as a receptor of Asprosin. of OLFR734. Asprosin and other hormonal factors can Cell Metab. 30,319–328 (2019). improve HFD-induced olfactory impairment. However, it 7. Duerrschmid, C. et al. Asprosin is a centrally acting orexigenic hormone. Nat. Med. 23, 1444–1453 (2017). should be noted that Asprosin is a gluconeogenic hor- 8. Critchley, H. D. & Rolls, E. T. and satiety modify the responses of mone and activation of OLFR734 signaling may increase olfactory and visual neurons in the primate orbitofrontal cortex. J. Neurophy- the risk of hyperglycemia. In contrast, immunologic siol. 75,1673–1686 (1996). 9. Yang, M. & Crawley, J. N. Simple behavioral assessment of mouse olfaction. neutralization of Asprosin to relieve resistance and Curr. Protoc. Neurosci. Chapter 8, Unit 8, 24 (2009). obesity in mice may worsen olfaction under metabolic 10. Palouzier-Paulignan, B. et al. Olfaction under metabolic influences. Chem. stress. Senses 37, 769–797 (2012).