Abstract
GPR75 has emerged as a therapeutic target for obesity following the discovery of a causal relationship between GPR75 variants and reduced body mass index in humans. Herein, we examined whether GPR75 is dispensable for normal feeding, body growth, and reproduction using newly generated Gpr75 knockout (KO) rats fed normal chow. Gpr75 was highly expressed in the brain, including several hypothalamic nuclei, in rats of both sexes. Gpr75 KO male and female rats exhibited significantly lower food intake, reduced feeding duration during the dark phase, and lower body weight (BW) than wild-type rats. Importantly, Gpr75 KO did not affect reproduction in either sex, including puberty onset, pulsatile luteinizing hormone secretion, or litter size. We also examined the effects of Gpr75 KO on hyperphagia, obesity, hyperglycemia, and hyperinsulinemia in male rats on a high-fat diet (HFD). HFD-fed Gpr75 KO male rats exhibited significantly lower food intake, BW, and fat accumulation than wild-type rats and were normoglycemic and normoinsulinemic. Notably, hypothalamic Ccl5 (encoding C-C motif chemokine ligand 5 [CCL5]) expression was significantly higher in Gpr75 KO male rats than in wild-type rats, suggesting that Gpr75 KO may prevent HFD-induced hyperphagia via central CCL5 signaling in rats. Thus, GPR75 signaling, although dispensable for reproduction, contributes to feeding and body growth in rats on normal chow and is involved in HFD-induced hyperphagia, obesity, hyperglycemia, and hyperinsulinemia development. Therefore, GPR75 antagonism may offer a potential therapeutic approach to control feeding and BW and prevent obesity and insulin resistance without affecting reproduction in humans.