Mchr1, short for melanin-concentrating hormone receptor 1, is a G-protein-coupled receptor. It has a crucial role in regulating appetite and energy homeostasis, with its ligand being melanin-concentrating hormone (MCH) secreted mainly by the hypothalamus. It is also involved in pathways related to emotion regulation and has potential importance in metabolism-related biological processes [1,3]. Genetic models, such as gene knockout mice, can be valuable for studying Mchr1's functions.

In Mchr1-deficient mice, osteoporosis occurs due to a reduction in cortical bone mass, with increased serum levels of c-telopeptide indicating high bone turnover osteoporosis. This reveals that Mchr1-signalling is involved in tonic stimulation of bone mass [2]. In systemic sclerosis (SSc), Mchr1 promotes the fibrotic response in normal human dermal fibroblasts (NHDF) through modulating profibrotic factors, intracellular cAMP levels, and PDGF-BB-induced signalling pathways, suggesting it plays a role in SSc pathogenesis and could be a therapeutic target [4].

In conclusion, Mchr1 is essential in regulating energy homeostasis and appetite. The Mchr1-KO mouse models have shown its importance in bone mass regulation, highlighting its significance in osteoporosis-related research. Additionally, its role in SSc-associated fibrosis provides potential therapeutic implications for this autoimmune disease.