T lymphocyte depletion ameliorates age-related metabolic impairments in mice.

Both glucose tolerance and adaptive immune function exhibit significant age-related alterations. The influence of the immune system on obesity-associated glucose intolerance is well characterized; however, whether the immune system contributes to age-related glucose intolerance is not as well understood. Here, we report that advancing age results in an increase in T cell infiltration in the epididymal white adipose tissue (eWAT), liver, and skeletal muscle. Subtype analyses show that both CD4+, CD8+ T cells are greater with advancing age in each of these tissues and that aging results in a blunted CD4 to CD8 ratio. Anti-CD3 F(ab')2 fragments depleted CD4+ and CD8+ cells in eWAT, CD4+ cells only in the liver, and did not deplete quadriceps T cells. In old mice, T cells producing both interferon-γ and tumor necrosis factor-α are accumulated in the eWAT and liver, and a greater proportion of skeletal muscle T cells produced interferon-γ. Aging resulted in increased proportion and numbers of T regulatory cells in eWAT, but not in the liver or muscle. Aging also resulted in greater numbers of eWAT and quadriceps CD206- macrophages and eWAT, liver and quadriceps B cells; neither cell type was altered by anti-CD3 treatment. Anti-CD3 treatment improved glucose tolerance in old mice and was accompanied by improved signaling related to liver and skeletal muscle insulin utilization and decreased gluconeogenesis-related gene expression in the liver. Our findings indicate a critical role of the adaptive immune system in the age-related metabolic dysfunction.