Black Adzuki Bean (Vigna angularis) Attenuates High-Fat Diet-Induced Colon Inflammation in Mice

Adzuki beans (Vigna angularis), one of the most important legume crops in East Asia, have been shown to possess potential antioxidant and anti-inflammatory effects in mice. Here, we investigated the effects of black adzuki bean (BAB) on colon inflammation triggered by high-fat diet (HD)-induced obesity in mice. We also isolated lipopolysaccharide (LPS)-stimulated peritoneal macrophages and assessed inflammation-related parameters. We found that BAB decreased the concentrations of LPS and various circulating proinflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in mice with HD-induced obesity. BAB also attenuated changes associated with HD-induced colon inflammation, such as increased expression of proinflammatory cytokines. Moreover, BAB inhibited induction of nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, and activation of nuclear factor-kappa B (NF-κB) in the colon. Furthermore, BAB upregulated colon mRNA expression of tight junction-associated proteins such as claudin-1 and Zo-1, as well as mucosal barrier defense promoting genes such as mucin (Muc) 1 and Muc3. BAB also reduced macrophage infiltration into adipose tissue in mice with HD-induced intestinal inflammation. In LPS-stimulated peritoneal macrophages, treatment with BAB significantly decreased TNF-α and NO production, NF-κB activation, and iNOS expression. Our findings indicate that BAB ameliorates HD-induced disorders such as obesity and colitis by improving mucosal barrier protection and reducing endotoxemia, as well as by inactivating NF-κB to decrease the production of proinflammatory cytokines.