Blocking Fas signaling in adipose tissue ameliorates obesity-associated inflammation, insulin resistance, and hepatosteatosis

Abstract

Purpose: Adipose tissue inflammation is a crucial early stage of obesity-related metabolic dysfunction and insulin resistance. Adipocytes, and infiltrating immune cells in the adipose tissue, play significant roles in fostering the inflammatory milieu through Fas signaling. The Fas receptor (CD95) and its interaction with FasL induces apoptotic or non-apoptotic signals, activating inflammatory responses. In obesity, Fas is overexpressed in adipocytes and macrophages, triggering non-apoptotic pathways that release a range of cytokines which ultimately impairs insulin signaling and exacerbates inflammation. Methods: Pentameric Fas-targeting peptide (pFTP) was synthesized by dimethylsulfoxide-based peptide polymerization. The pFTP was characterized through several analytical techniques including matrix-assisted laser desorption/ionization-time of flight spectrometry. The efficacy of pFTP was validated using Jurkat cells, mature 3T3L-1 adipocytes, and mouse peritoneal macrophages. For effectiveness assessment, immunohistochemistry, hematoxylin and eosin staining, and terminal deoxynucleotidyl transferase dUTP nick-end labeling assay were conducted. Gene expression was evaluated by real-time PCR, protein expression by Western blotting, and pro-inflammatory cytokine analysis by enzyme-linked immunosorbent assay. Metabolic studies including glucose and insulin tolerance tests were also conducted. Results: Inhibiting Fas signaling in adipocytes and infiltrating adipose tissue macrophages using pFTP blocked the recruitment of adipose tissue macrophages, shifted macrophage polarization from M2 to M1, prevented adipocyte apoptosis, suppressed production of inflammatory cytokines, and alleviated insulin resistance. Treatment with pFTP successfully reversed inflammation, insulin resistance, and hepatic steatosis in a high-fat diet-induced obese mouse model. Conclusion: Inhibiting Fas-mediated inflammation in the adipose tissue is promising for addressing inflammation, insulin resistance, and hepatosteatosis associated with obesity.