Sex-specific metabolic effects of Treg expansion in db/db mice.

Introduction: Type 2 diabetes mellitus (T2D) is characterized by chronic, low-grade inflammation and immune dysregulation, contributing to insulin resistance and metabolic complications. Regulatory T cells (Tregs) are key modulators of immune homeostasis, and their therapeutic expansion has shown promise in limiting inflammation. Here, we investigated whether Methods: Male and female db/db and db/+ mice received intraperitoneal injections of IL-2/anti-IL-2 (JES6-1) complexes for six weeks to induce endogenous Treg expansion. Body weight, blood glucose, and insulin levels were monitored to calculate HOMA-IR. Plasma inflammatory and anti-inflammatory mediators (CRP, adiponectin, IL-10, IL-13, CCL3) were quantified by bead-based immunoassays. Hepatic triglycerides and gene expression of Foxp3, F4/80, Pparγ, Il10 and Il13 were analyzed by biochemical assays, western blot, and RT-qPCR. Results: Treg expansion reduced weight gain in db/db mice independently of food intake. Female mice displayed lower HOMA-IR, decreased CRP, and increased adiponectin, IL-10, and IL-13 levels, whereas males showed limited improvement. Hepatic triglycerides and F4/80 expression were reduced after Treg expansion, with restored Foxp3 and elevated Il10/Il13 expression, indicating diminished hepatic inflammation. Conclusion: Endogenous Treg expansion exerts sex-specific metabolic and anti-inflammatory benefits in db/db T2D mice, with females showing greater improvements in insulin resistance, inflammation, and hepatic lipid metabolism. These findings support Treg-based immunomodulation as a potential therapeutic approach for T2D and emphasize the need for sex-specific considerations in future research.