Adaptive thermogenesis in beige adipocytes is essential for maintaining energy homeostasis and preventing obesity. Emerging evidence suggests that human visceral adipose tissue harbors adipocytes with beige-like thermogenic features, enabling analysis of thermogenic gene regulation in humans. Isocitrate dehydrogenase 3A (IDH3A) is a rate-limiting enzyme of the tricarboxylic acid cycle, yet its function in adipocytes remains poorly defined. In this study, we examined IDH3A expression in human visceral adipose tissue and generated adipocyte-specific IDH3A knockout mice to investigate its role in beige adipocyte thermogenesis and metabolic regulation. IDH3A expression in human visceral fat was inversely associated with adiposity and adverse metabolic traits. Moreover, IDH3A expression was induced in human and mouse adipocytes following thermogenic stimulation. Adipocyte-specific IDH3A deletion in mice impaired beige fat thermogenic capacity, led to cold intolerance, and exacerbated diet-induced metabolic dysfunction. Mechanistically, IDH3A deficiency increased DNA methylation at the Bckdha promoter, resulting in the repression of this key branched-chain amino acid (BCAA) catabolic gene and impaired BCAA catabolism. Notably, restoring BCKDHA in IDH3A-deficient adipocytes rescued respiration and thermogenic function. Together, in addition to its canonical enzymatic role, our findings identify IDH3A as a critical regulator of BCAA catabolism that facilitates adaptive thermogenesis under metabolic stress conditions. Article Highlights IDH3A expression in human visceral fat exhibits a negative correlation with metabolic dysfunction indicators. IDH3A is induced during thermogenic activation, yet its role in adipose tissue is not well characterized. Adipocyte-specific deletion of IDH3A impairs adaptive thermogenesis and metabolic homeostasis by disrupting BCKDHA-mediated BCAA catabolism. Overexpression of BCKDHA restores the thermogenic program in IDH3A-deficient beige adipocytes.
Lu et al. (Mon,) studied this question.