Anthocyanin increases adiponectin secretion and protects against 1 diabetes - related endothelial dysfunction

14 Adiponectin is an adipose tissue-secreted adipokine with beneficial effects on the 15 cardiovascular system. In this study, we evaluated a potential role for adiponectin in the 16 protective effects of anthocyanin on diabetes-related endothelial dysfunction. We treated 17 db/db mice on a normal diet with anthocyanin C3G (2 g/kg diet) for 8 weeks. 18 Endothelium-dependent and independent relaxation of the aorta was then evaluated. 19 Adiponectin expression and secretion were also measured. C3G treatment restores 20 endotheliumdependent relaxation of the aorta in db/db mice, whereas diabetic mice treated 21 with an anti-adiponectin antibody do not respond. C3G treatment induces adiponectin 22 expression and secretion in cultured 3T3 adipocytes through transcription factor forkhead box 23 O1 (Foxo1). Silencing Foxo1 expression prevented C3G-stimulated induction of adiponectin 24 expression. In contrast, overexpression of Foxo1-ADA promoted adiponectin expression in 25 adipocytes. C3G activates Foxo1 by increasing its deacetylation via silent mating type 26 information regulation 2 homolog 1 (Sirt1). Furthermore, purified anthocyanin 27 supplementation significantly improved flow-mediated dilation (FMD) and increased serum 28 adiponectin concentrations in patients with type 2 diabetes. Changes in adiponectin 29 concentrations positively correlated with FMD in the anthocyanin group. Mechanistically, 30 adiponectin activates cAMP/PKA/eNOS signaling pathways in HAECs, increasing 31 endothelial nitric oxide (NO) bioavailability. These results demonstrate that adipocyte-derived 32 adiponectin is required for anthocyanin C3G-mediated improvement of endothelial function 33 in diabetes. 34 35