IL-1RA administration exerts diet-dependent metabolic effects on adipose tissue function and lipid handling in male mice.

Interleukin-1 (IL-1) signaling is a key mediator of metabolic inflammation, yet its tissue-specific contribution to obesity-associated dysfunction remains incompletely understood. Here, we investigated the effects of pharmacological IL-1 receptor antagonism on systemic metabolism, adipose tissue dysfunction, and hepatic lipid handling under distinct nutritional conditions. Male mice fed a normal diet (ND) or high-fat diet (HFD) were treated subcutaneously with the IL-1 receptor antagonist (IL-1RA) anakinra for three weeks. IL-1RA did not significantly affect body weight or global adiposity; however, under ND conditions, it reduced fat mass and circulating leptin levels and increased the adiponectin/leptin ratio, indicating improved adipose endocrine function. In adipose tissue, IL-1RA partially restored Acaca expression and selectively modulated extracellular matrix remodeling genes, including Mmp9, without broadly suppressing inflammatory markers. In the liver, triglyceride content was altered in a diet-dependent manner without changes in the expression of key metabolic genes (Fasn, Acaca, Ppara), suggesting that IL-1 blockade does not directly reprogram intrinsic hepatic lipid metabolism. Consistent with this, analyses in complementary models, including leptin-deficient mice, showed that Il1rn expression is regulated by local inflammatory and endocrine cues rather than adiposity per se. Together, these findings identify IL-1 signaling as a context-dependent modulator of adipose tissue function and systemic lipid handling. The dissociation between adipose tissue responses and hepatic triglyceride accumulation highlights the tissue-specific effects of IL-1 receptor antagonism and underscores the need for direct metabolic flux studies to define the mechanisms underlying these effects.