Accelerated phosphatidylcholine turnover in macrophages promotes adipose tissue inflammation in obesity

Abstract

White adipose tissue (WAT) inflammation contributes to the development of insulin resistance in obesity. While the role of adipose tissue macrophage (ATM) pro-inflammatory signalling in the development of insulin resistance has been established, it is less clear how WAT inflammation is initiated. Here, we show that ATMs from obese mice and humans exhibit markers of increased de novo phosphatidylcholine (PC) biosynthesis rate. Macrophage-specific knockout of phosphocholine-cytidylyltransferase A (CCT), the rate-limiting enzyme of de novo PC biosynthesis pathway, alleviated obesity-induced WAT inflammation and insulin resistance. Mechanistically, CCT-deficient macrophages showed reduced ER stress and inflammation in response to palmitate. Surprisingly, this was not due to lower exogenous palmitate incorporation into cellular PCs. Instead, CCT-null macrophages had lower PC turnover, leading to elevated membrane polyunsaturated fatty acids that negated the pro-inflammatory effects of palmitate. Our results reveal a link between obesity-associated increase in PC synthesis, accelerated PC turnover and pro-inflammatory activation of ATMs.