Therapeutic effects of berberine in impaired glucose tolerance rats and its influence on insulin secretion

AIM: To explore the anti-diabetic effects of berberine and its influence on insulin secretion. METHODS: Impaired glucose tolerance rats induced by iv injection of streptozotocin 30 mg/kg were treated with berberine 187.5 and 562.5 mg/kg while fed with high fat laboratory chow. After rats were treated for 4 weeks, oral glucose tolerance was determined, and for 8 weeks, the fasting blood glucose, insulin, lipid series were determined. In insulin secretion experiments, berberine 93.75, 187.5, and 562.5 mg/kg was administered orally to BALB/c mice at a bolus. The murine serum was collected 2 h after the berberine administration for insulin determination. Insulin released from HIT-T15 cells and pancreatic islets incubated with berberine 1-100 micromol/L for 12 h was determined. RESULTS: The levels of fasting blood glucose (7.4+/-1.5 or 7.3+/-1.3 vs 9.3+/-1.3 mmol/L), triglycerides (0.61+/-0.22 or 0.63+/-0.17 vs 1.8+/-0.7 mmol/L), total cholesterol (1.8+/-0.3 or 1.9+/-0.3 vs 2.2+/-0.2 mmol/L), free fatty acid (456+/-93 or 460+/-72 vs 550+/-113 micromol/L) and apolipoprotein B (0.37+/-0.02 or 0.42+/-0.05 vs 0.46+/-0.04 g/L) were reduced greatly in berberine-treated groups at doses of 187.5 and 562.5 mg/g/d, respectively as compared with those in control group (P<0.05 or P<0.01), whereas high density lipoprotein-cholesterol (1.5+/-0.3 or 1.4+/-0.3 vs 1.1+/-0.1 g/L), apolipoprotein AI (0.80+/-0.08 or 0.87+/-0.08 vs 0.71+/-0.06 g/L) were significantly increased (P<0.05 or P<0.01), and oral glucose tolerance was improved. In vitro experiment showed that berberine 1-10 micromol/L facilitated insulin secretion of HIT-T15 cells and murine pancreatic islets in a dose-dependent manner. Meanwhile murine serum insulin level (27.5+/-2.7 or 29+/-4 or 29+/-4 vs 24.3+/-2.8 pIU/L) was undoubtedly promoted and blood glucose (4.52+/-0.31 or 4.45+/-0.29 or 4.30+/-0.19 vs 4.87+/-0.21 mmol/L) was reduced after berberine administration at doses of 93.75, 187.5, and 562.5 mg/kg, respectively in the BALB/c mice. CONCLUSION: Berberine possesses anti-diabetic effects, which is related to the property of stimulating insulin secretion and modulating lipids.