Betaine–homocysteine methyltransferase promotes adipocyte commitment and insulin resistance via p38 MAPK/Smad signaling

Abstract Objective Betaine–homocysteine methyltransferase (Bhmt) belongs to the family of methyltransferases and is involved in the one‐carbon metabolic cycle, which is associated with the risk of diabetes and adiposity. This study aimed to explore whether Bhmt participated in the development of obesity or its associated diabetes, as well as the mechanism involved. Methods The expression levels of Bhmt were examined in stromal vascular fraction cells and mature adipocytes in obesity and nonobesity. Knockdown and overexpression of Bhmt in C3H10T1/2 cells were used to investigate Bhmt's function in adipogenesis. Bhmt's role in vivo was analyzed using an adenovirus‐expressing system and a high‐fat diet–induced obesity mouse model. Results Bhmt was highly expressed in stromal vascular fraction cells rather than mature adipocytes of adipose tissue and was upregulated in adipose tissue in obesity and C3H10T1/2‐commited preadipocytes. Overexpression of Bhmt promoted adipocyte commitment and differentiation in vitro and exacerbated adipose tissue expansion in vivo , with a concomitant increase in insulin resistance, whereas Bhmt silencing exhibited opposite effects. Mechanistically, Bhmt‐induced adipose expansion was mediated by stimulating the p38 MAPK/Smad pathway. Conclusions The findings of this study highlight the obesogenic and diabetogenic role of adipocytic Bhmt and propose Bhmt as a promising therapeutic target for obesity and obesity‐related diabetes.