The significance of anthocyanins in the prevention and treatment of type 2 diabetes.

Anthocyanins are food compounds which belong to polyphenols and can mainly be found in dark fruits (e.g., blueberries, black currants, cranberries) and vegetables (e.g., red cabbage, radish, eggplant). The results of large research have shown that these compounds play an important role in the prevention of type 2 diabetes (T2D). In rodent studies and in studies with isolated omental adipocytes, it was observed that anthocyanins regulated the carbohydrate metabolism in the body due to the upregulation of GLUT4 (insulinregulated glucose transporter) translocation, increased activation of PPARγ (peroxisome proliferator-activated receptor-γ) in adipose tissue and skeletal muscles as well as increased secretion of adiponectin and leptin. Moreover, these compounds reduced the inflammation status in the body. Studies conducted on humans and experimental animals showed that anthocyanins decrease insulin resistance. This effect may be achieved by the upregulation of GLUT4 gene expression, activation of AMP-activated protein kinase and downregulation of retinol binding protein 4 (RBP4) expression. Anthocyanins also increased the uptake and utilization of glucose by tissues in streptozotocin-induced diabetic rats and mice, and they also protected pancreatic cells against necrosis induced by streptozotocin. Another mechanism that might explain the lower glucose level in the blood after a meal with anthocyanins compared to a meal without them is the inhibition of intestinal α-glucosidase and pancreatic α-amylase by these compounds. Moreover, anthocyanins improve insulin secretion, which can have a special meaning for people with T2D. The evidence from the presented studies suggests that foods rich in anthocyanins may be one of the diet elements supporting the prevention and treatment of T2D.