Oligonol, a low-molecular-weight polyphenol derived from lychee peel, attenuates diabetes-induced pancreatic damage by inhibiting inflammatory responses via oxidative stress-dependent mitogen-activated protein kinase/nuclear factor-kappa B signaling.

This study investigated the effects of oligonol, a low-molecular-polyphenol derived from lychee peel, against diabetes-induced pancreatic damage via oxidative stress-induced inflammation. Oligonol was orally administered at 10 or 20 mg/kg body weight/day for 10 days to streptozotocin-induced diabetic rats, and the rats were compared with nondiabetic and diabetic control rats. The diabetic rats showed loss of body weight and increased pancreatic weight, and the oral administration of oligonol attenuated these parameters. Moreover, the administration of oligonol caused a significant decrease in the serum glucose level and a significant increase in the serum and pancreatic insulin and C-peptide levels in the diabetic rats. Oligonol also significantly reduced the enhanced levels of reactive oxygen species and 2-thiobarbituric acid reactive substance, which are oxidative stress biomarkers, in the serum and pancreas. Oligonol treatment reduced the overexpression of phospho-p38, phospho-ERK1/2, phospho-inhibitor of nuclear factor-kappa B (NF-κB), NF-κBp65, and NF-κBp65-induced inflammatory protein such as cyclooxygenase-2, inducible nitric oxide synthase, tumor necrosis factor-α, and interleukin-6. Furthermore, oligonol treatment led to significantly attenuated histological damage in the pancreas. On the basis of these results, we conclude that a plausible mechanism of oligonol's antidiabetic action may be its antioxidative stress-related anti-inflammatory action.