Black soybean seed coat extract ameliorates hyperglycemia and insulin sensitivity via the activation of AMP-activated protein kinase in diabetic mice.

Black soybean seed coat has abundant levels of polyphenols such as anthocyanins (cyanidin 3-glucoside; C3G) and procyanidins (PCs). This study found that dietary black soybean seed coat extract (BE) ameliorates hyperglycemia and insulin sensitivity via the activation of AMP-activated protein kinase (AMPK) in type 2 diabetic mice. Dietary BE significantly reduced blood glucose levels and enhanced insulin sensitivity. AMPK was activated in the skeletal muscle and liver of diabetic mice fed BE. This activation was accompanied by the up-regulation of glucose transporter 4 in skeletal muscle and the down-regulation of gluconeogenesis in the liver. These changes resulted in improved hyperglycemia and insulin sensitivity in type 2 diabetic mice. In vitro studies using L6 myotubes showed that C3G and PCs significantly induced AMPK activation and enhanced glucose uptake into the cells.