Adipocyte FMO3-derived TMAO induces WAT dysfunction and metabolic disorders by promoting inflammasome activation in ageing.

Trimethylamine N-oxide (TMAO) contributes to cardio-metabolic diseases, with hepatic flavin-containing monooxygenase 3 (FMO3) recognized as its primary source. Here we demonstrate that elevated adipocyte FMO3 and its derived TMAO trigger white adipose tissue (WAT) dysfunction and its related metabolic disorders in ageing. In adipocytes, ageing or p53 activation upregulates FMO3 and TMAO levels. Adipocyte-specific ablation of FMO3 attenuates TMAO accumulation in WAT and circulation, leading to enhanced glucose metabolism and energy and lipid homeostasis in ageing and obese mice. These improvements are associated with reduced senescence, fibrosis and inflammation in WAT. Proteomics analysis identified TMAO-interacting proteins involved in inflammasome activation in adipocytes and macrophages. Mechanistically, TMAO binds to the central inflammasome adaptor protein ASC, promoting caspase-1 activation and interleukin-1β production. Our findings uncover a pivotal role for adipocyte FMO3 in modulating TMAO production and WAT dysfunction by promoting inflammasome activation in ageing via an autocrine and paracrine manner.