Interleukin-2 improves insulin sensitivity through hypothalamic sympathetic activation in obese mice

Area of Science:

• Immunology
• Neuroscience
• Metabolic Diseases

Background:

• Interleukin-2 (IL-2) differentially regulates T cell subsets: low doses promote regulatory T cells (Tregs), while high doses activate cytotoxic cells.
• High-dose IL-2 is explored for cancer immunotherapy, but low-dose IL-2's potential in inflammatory diseases like obesity and insulin resistance is investigated.
• Obesity and insulin resistance are characterized by low-grade chronic inflammation.

Purpose of the Study:

• To investigate the therapeutic potential of low-dose IL-2 in treating obesity and insulin resistance.
• To elucidate the mechanisms by which low-dose IL-2 improves insulin sensitivity in inflammatory conditions.

Main Methods:

• Systemic and central administration of low-dose IL-2 in high-fat diet-fed obese mice.
• Assessment of T cell populations (Tregs, Th1 cells), inflammatory cytokine expression, and insulin sensitivity.
• Investigation of the sympathetic nervous system's role and hypothalamic microgliosis following IL-2 administration.
• Sympathetic denervation of gonadal white adipose tissue (gWAT) to assess its impact on IL-2 effects.

Main Results:

• Systemic low-dose IL-2 increased Treg cells and reduced gWAT inflammation, improving insulin sensitivity.
• Central IL-2 administration enhanced insulin sensitivity via sympathetic nervous system activation.
• Central IL-2 modulated immune cell populations, decreased pro-inflammatory cytokines (IFNγ, IL-1β, IL-6, IL-8), and increased Tregs and Tgfβ in gWAT.
• Hypothalamic microgliosis and pro-opiomelanocortin neuron activation were observed with central IL-2.
• Sympathetic denervation reversed IL-2-induced improvements in insulin sensitivity and immune cell profiles.

Conclusions:

• Low-dose IL-2 administration improves insulin sensitivity in obese mice.
• IL-2 exerts its beneficial effects through direct action on CD4+ T cells and indirectly via a neuro-immune axis involving hypothalamic microgliosis.
• The findings highlight a novel therapeutic strategy using low-dose IL-2 for metabolic and inflammatory disorders.