<scp>CRTC1</scp> deficiency, specifically in melanocortin‐4 receptor‐expressing cells, induces hyperphagia, obesity, and insulin resistance

Melanocortin-4 receptor (MC4R) is a critical regulator of appetite and energy expenditure in rodents and humans. MC4R deficiency causes hyperphagia, reduced energy expenditure, and impaired glucose metabolism. Ligand binding to MC4R activates adenylyl cyclase, resulting in increased levels of intracellular cyclic adenosine monophosphate (cAMP), a secondary messenger that regulates several cellular processes. Cyclic adenosine monophosphate responsive element-binding protein-1-regulated transcription coactivator-1 (CRTC1) is a cytoplasmic coactivator that translocates to the nucleus in response to cAMP and is reportedly involved in obesity. However, the precise mechanism through which CRTC1 regulates energy metabolism remains unknown. Additionally, there are no reports linking CRTC1 and MC4R, although both CRTC1 and MC4R are known to be involved in obesity. Here, we demonstrate that mice lacking CRTC1, specifically in MC4R cells, are sensitive to high-fat diet (HFD)-induced obesity and exhibit hyperphagia and increased body weight gain. Moreover, the loss of CRTC1 in MC4R cells impairs glucose metabolism. MC4R-expressing cell-specific CRTC1 knockout mice did not show changes in body weight gain, food intake, or glucose metabolism when fed a normal-chow diet. Thus, CRTC1 expression in MC4R cells is required for metabolic adaptation to HFD with respect to appetite regulation. Our results revealed an important protective role of CRTC1 in MC4R cells against dietary adaptation.