Disruption of Gpr45 causes reduced hypothalamic POMC expression and obesity
Jing Cui, … , Tian Xu, Xiaohui Wu
Jing Cui, … , Tian Xu, Xiaohui Wu
Published August 8, 2016
Citation Information: J Clin Invest. 2016;126(9):3192-3206. https://doi.org/10.1172/JCI85676.
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Disruption of Gpr45 causes reduced hypothalamic POMC expression and obesity

Abstract

A rise in the occurrence of obesity has driven exploration of its underlying genetic basis and potential targets for intervention. GWAS studies have identified obesity susceptibility pathways involving several neuropeptides that control energy homeostasis, suggesting that variations in the genes that regulate food intake and energy expenditure may contribute to obesity. In this study, we identified 5 additional obesity loci, including a neuronal orphan GPCR called Gpr45, in a forward genetic screen of mutant mice generated by piggyBac insertional mutagenesis. Disruption of Gpr45 led to increased adiposity at the time of weaning and increases in body mass, fat content, glucose intolerance, and hepatic steatosis with advancing age. Mice with disruptions in Gpr45 also displayed a reduction in expression of the metabolic regulator POMC and less energy expenditure prior to the onset of obesity. Mechanistically, we determined that GPR45 regulates POMC expression via the JAK/STAT pathway in a cell-autonomous manner. Consistent with this finding, intraventricular administration of melanotan-2, an analog of the POMC derivative α-MSH, suppressed adult obesity in Gpr45 mutants. These results reveal that GPR45 is a regulator of POMC signaling and energy expenditure, which suggests that it may be a potential intervention target to combat obesity.

Authors

Jing Cui, Yi Ding, Shu Chen, Xiaoqiang Zhu, Yichen Wu, Mingliang Zhang, Yaxin Zhao, Tong-Ruei R. Li, Ling V. Sun, Shimin Zhao, Yuan Zhuang, Weiping Jia, Lei Xue, Min Han, Tian Xu, Xiaohui Wu

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Figure 6

Disruption of Gpr45 decreases hypothalamic POMC expression and spontaneous firing rate of POMC neurons.

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Disruption of Gpr45 decreases hypothalamic POMC expression and spontaneo...
(A) Results of RT-PCR analysis showing the presence of Gpr45 mRNA in neuronal tissues and the testes of adult mice. (B) Real-time RT-PCR analysis revealed decreased Pomc, but similar expression of other hypothalamic neuropeptides in P14 mice (n ≥ 4 for each genotype). Expression of Gapdh serves as the internal control to calculate relative expression levels. (C) Western blots show decreased POMC levels in hypothalami of P14 mice (n = 3 for each genotype). A quantitative comparison is listed below. Expression of GAPDH serves as the internal control to calculate relative expression levels. (D) Bar graphs showing significantly reduced Gpr45 and Pomc expression in primary hypothalamic cells from the mutants. Summarized real-time RT-PCR results from 3 independent wells are shown, with Gapdh serving as the internal control. (E) Knockdown of Gpr45 in primary hypothalamic cells caused down regulation of Pomc. Real-time RT-PCR data were collected with the same procedure in (D), except for the use of 5 wells in each group. (F) Representative recordings of resting membrane potential from wild-type (n = 16 from 6 mice) and PB1/PB1 (n = 14 from 3 mice) animals. (G and H) Statistics for resting membrane potential (G) and spontaneous firing rate (H) in these recordings. All data are shown as the mean ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001 by Student’s t test.