Autophagy acts as a brake on obesity-related fibrosis by controlling purine nucleoside signalling

A hallmark of obesity is a pathological expansion of white adipose tissue (WAT), accompanied by marked tissue dysfunction and fibrosis. Autophagy promotes adipocyte differentiation and lipid homeostasis, but its role in obese adipocytes and adipose tissue dysfunction remains incompletely understood. Using a mouse model, we demonstrate that autophagy is a key tissue-specific regulator of WAT remodelling in diet-induced obesity. Importantly, loss of adipocyte autophagy substantially exacerbates pericellular fibrosis in visceral WAT. Change in WAT architecture correlates with increased infiltration of macrophages with tissue-reparative, fibrotic features. We uncover that autophagy restrains purine nucleoside metabolism in obese adipocytes. This ultimately leads to a reduced release of the purine catabolites xanthine and hypoxanthine. Purines signal cell-extrinsically for fibrosis by driving macrophage polarisation towards a tissue reparative phenotype. Our findings in mice reveal a novel role for adipocyte autophagy in regulating tissue purine nucleoside metabolism, thereby limiting obesity-associated fibrosis and maintaining the functional integrity of visceral WAT. Purine signals may serve as a critical balance checkpoint and therapeutic target in fibrotic diseases Overall design: Gonadal white adipose tissue was isolated from lean C57BL/6J mice, mechanically and enzymatically digested. For primary cell culture, the stromal vascular fraction was enriched for CD11b+ cells with CD11b MicroBeads (Miltenyi Biotec) according to manufacturers' instructions after red blood cell lysis. 350,000 cells were seeded in 24-well plates in RPMI containing 10 % FBS and 1 % P/S and incubated overnight to allow macrophages to attach. The following day, macrophages were enriched by washing the wells with room temperature PBS and treated with experimental conditions. Macrophages were cultured in RPMI containing 10 % FBS and 1 % P/S and 50 ng/ml M-CSF and treated with 100 µM of either hypoxanthine or xanthine over 72 hours. RNA was extracted using RNeasy Plus Micro Kit (Qiagen) and gene expression profiling analysis was performed on RNA-seq macrophage data.