Beneficial effects of oligopeptides from marine salmon skin in a rat model of type 2 diabetes.

OBJECTIVE: This study aimed at investigating whether treatment with oligopeptides from marine salmon skin (OMSS) could modulate type 2 diabetes mellitus (T2DM)-related hyperglycemia and ß-cell apoptosis in rats induced by high fat diet and low doses of streptozotocin and its therapeutic mechanisms. METHODS: Groups of T2DM rats were treated with OMSS or bovine serum albumin (3.0 g/kg/d) for 4 wk and their blood samples, together with those of normal control rats, were collected before and 4 wk after treatment. The levels of fasting blood glucose (FBG) and insulin, serum superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH), tumor necrosis factor-alpha (TNFα), and interferon-gamma (IFNγ) in rats were determined. The islet cell apoptosis and Fas/FasL expression were detected by TUNEL and immunohistochemistry. RESULTS: In comparison with control rats, higher levels of FBG and frequency of apoptotic islet cells were detected in the bovine serum albumin group of diabetic rats, accompanied by higher levels of Fas expression in the pancreatic islets, serum TNFα, IFNγ, and MDA, but lower levels of SOD and GSH. However, the levels of FBG and frequency of apoptotic islet cells were significantly reduced in OMSS-treated rats. Lower levels of Fas expression were observed in the pancreatic islets of OMSS-treated rats. Significantly reduced levels of serum TNFα, IFNγ, and MDA, but increased levels of SOD and GSH, were detected in OMSS-treated rats. CONCLUSIONS: Treatment with OMSS significantly reduced FBG in diabetic rats. This antidiabetic activity may be mediated by down-regulating T2DM-related oxidative stress and inflammation, protecting the pancreatic ß-cells from apoptosis.