GPR88 is a critical regulator of feeding and body composition in mice

GPR88 is an orphan G-protein-coupled receptor with predominant expression in reward-related areas in the brain. While the lack of GPR88 has been demonstrated to induce behavioral deficits, the potential function of the receptor in the control of food intake and energy balance remains unexplored. In this work, the role of GPR88 in energy homeostasis was investigated in Gpr88 ^-/- mice fed either standard chow or high fat diet (HFD). Gpr88 ^-/- mice showed significantly reduced adiposity accompanied with suppressed spontaneous food intake, particularly pronounced under HFD treatment. While energy expenditure was likewise lower in Gpr88 ^-/- mice, body weight gain remained unchanged. Furthermore, deregulation in glucose tolerance and insulin responsiveness in response to HFD was attenuated in Gpr88 ^-/- mice. On the molecular level, distinct changes in the hypothalamic mRNA levels of cocaine-and amphetamine-regulated transcript (Cartpt), a neuropeptide involved in the control of feeding and reward, were observed in Gpr88 ^-/- mice. In addition, GPR88 deficiency was associated with altered expressions of the anorectic Pomc and the orexigenic Npy in the arcuate nucleus, especially under HFD condition. Together, our results indicate that GPR88 signalling is not only important for reward processes, but also plays a role in the central regulatory circuits for energy homeostasis.