[Effect of rhein treatment on first-phase insulin secretory function in db/db mice]

The aim of the present study is to investigate the effect of rhein treatment on the first-phase insulin secretory function in db/db mice.

Twenty 4-week-old male db/db mice were randomized to treatment with rhein (120 mg x kg(-1), n = 10) and placebo respectively (1% natrium cellulose solution, n = 10) by gavage for 8 weeks respectively. Ten age-matched non-diabetic male littermates db/m mice treated with placebo were studied as non-diabetic control. Body weight and fasting blood glucose level were measured before and after medication. The islets were isolated after 8 weeks' gavage. Islet perifusion system was set up, and all columns were perfused in parallel at a flow rate of 0.5 mL x min(-1) with KRB (2.8 mmol L(-1) glucose) at 37 degrees C. After 60-min static incubation with KRB (2.8 mmol x L(-1) glucose), the islets were stimulated in the continuous presence of a high concentration of 16.7 mmol x L(-1) glucose. Samples were collected every 20-second until 2-min, every 1-min until 5-min, thereafter every 5-min until 30-min. Samples were immediately stocked at -80 degrees C until further analysis.

Compared with the db/db control group, the fasting glucose concentration was significantly decreased in the rhein treatment group. The first-phase insulin secretory function was impaired significantly in db/db mice, while the first-phase insulin secretory peak was obvious in the rhein treatment mice.

Rhein treatment significantly improved glucose tolerance, restored the first-phase insulin secretion and protected the islets function.