<i>Lespedeza homoloba</i> enhances the immunosuppressive milieu of adipose tissue and suppresses fasting blood glucose

Immune cells migrate to hypertrophied adipocytes and release proinflammatory cytokines, leading to adipocyte dysfunction and diabetes. Numerous species of <i>Lespedeza</i>, which are members of the plant family Fabaceae and distributed primarily in temperate Asia and North America, exhibit binding to peroxisome proliferator-activated receptor (PPAR) γ, a target nuclear receptor for treating diabetes. Therefore, the present study aimed to determine which species of <i>Lespedeza</i> plants exert an anti-inflammatory effect in adipose tissue and suppression of blood glucose increase through PPARγ ligand and radical scavenging activity. PPARγ binding and DPPH radical scavenging assays of <i>L. homoloba</i> (LH), <i>L. thunbergii</i> (LT), <i>L. maximowiczii</i> (LM) and <i>L. thunbergii</i> (LT) were performed. LH and LT showed significant ligand activity towards PPARγ and notable radical scavenging activity. LH exhibited a stronger DPPH radical scavenging activity than LT and thus was measured adiponectin secretion from 3T3-L1-derived adipocytes and IL-10 secretion from murine splenocytes. LH increased the adiponectin and the IL-10 secretions. In flow cytometric analysis, BALB/c male mice administered LH exhibited an increase in regulatory T cells (Tregs) and cytotoxic T lymphocyte-associated protein (CTLA)-4⁺ Tregs as well as a decrease in T helper (Th)17, Th17/Treg ratio and CD8⁺ and CD4⁺ T cells in subcutaneous adipose tissue. Conversely, in the spleen, LH decreased Tregs and increased Th17 cells, Th17/Treg ratio and CD4⁺ and CD8⁺ T cells. These findings indicated that LH activated immunoreaction in the spleen and Treg cells that migrate to subcutaneous adipose tissue may suppress inflammation. In fasting blood glucose and adiponectin assays, LH-exposed mice exhibited suppression of fasting glucose levels. Therefore, LH may prevent type 2 diabetes by suppressing adipose tissue inflammation.