Dietary supplementation of A-type procyanidins from litchi pericarp improves glucose homeostasis by modulating mTOR signaling and oxidative stress in diabetic ICR mice

This study evaluated the protective role of litchi pericarp oligomeric procyanidins (LPOPC) and synbiotics (Bifidobacterium Bb-12 and xylo-oligosaccharide) against high fat and streptozotocin (STZ)-induced diabetes. LPOPC or synbiotics have no effect on blood glucose in normal mice. Treatments with LPOPC for 12 weeks significantly reduced blood glucose, FFA, endotoxin, GHbA1c and improved glucose homeostasis, lipid metabolism and insulin level. LPOPC also attenuated hyperglycemia-induced oxidative stress in serum, liver. In addition, administration of LPOPC remarkably reversed the increase of mTOR and p66(shc) in liver, skeletal muscle and white adipose tissue (WAT). LPOPC dramatically increased glucose uptake and glycolysis in liver, skeletal muscle and WAT, while inhibiting gluconeogenesis and lipogenesis in liver and improving heat generation in brown adipose tissue (BAT). Furthermore, synbiotics strengthened the improving effect of LPOPC. These findings demonstrated that LPOPC and synbiotics may regulate glucose disposal in peripheral target tissues through p66(shc)-mTOR signaling pathway.