Adipocyte-specific IGF1R knockout activates the β-catenin/apelin axis to combat diet-induced obesity in male mice.

Abstract

AIMS: Obesity, driven by complex genetic and environmental interactions, remains a global health crisis with limited therapeutic options. The insulin-like growth factor 1 receptor (IGF1R) plays dual roles in metabolism and growth, but its tissue-specific functions in adipose biology are controversial. This study investigates how adipose-specific IGF1R knockout impacts systemic metabolism under high-fat diet (HFD) stress and explores the underlying mechanisms. METHODS: Adipose-specific IGF1R knockout mice (AdIGF1RKO) were generated by crossing Igf1rfl/fl mice with Adipoq-Cre transgenics. Mice were fed a normal chow diet (NCD) or HFD for 20 weeks. Metabolic phenotyping included glucose/insulin tolerance tests, body composition analysis and serum profiling. RNA-seq, Western blot and quantitative real-time reverse transcriptase PCR were used to identify molecular pathways. In vitro studies with stromal vascular fraction (SVF) cells validated β-catenin/apelin interactions. RESULTS: AdIGF1RKO male mice exhibited reduced adipose mass under NCD and resisted HFD-induced obesity, showing attenuated hepatic lipid deposition and improved glucose metabolism. Mechanistically, IGF1R knockout enhanced INSR and Akt phosphorylation, driving GSK3β-β-catenin activation and apelin upregulation. Apelin activated AMPK, suppressing lipogenesis and enhancing fatty acid oxidation. Notably, β-catenin's role shifted from inhibiting adipogenesis in precursors to promoting metabolic adaptation in mature adipocytes. CONCLUSION: We unveil a β-catenin/apelin-driven endocrine axis that reprograms energy metabolism under obesogenic stress. Therapeutically, targeting adipose IGF1R or apelin signalling could combat obesity while avoiding systemic toxicity. Limitations include unresolved β-catenin/Apln transcriptional mechanisms, APJ function and tissue-specific AMPK effects. Our findings redefine IGF1R's metabolic role and propose novel strategies for obesity-related disorders.