Combined effects of curcumin and vitamin C to protect endothelial dysfunction in the iris tissue of STZ-induced diabetic rats.

This study was aimed to evaluate the combined effect of curcumin with vitamin C supplementation on hyperglycemic and dyslipidemia conditions and endothelial cell dysfunction induced in diabetic rats. Wistar Furth rats were used and divided into four groups: control (single injection of 0.9% sterile saline), STZ (streptozotocin, Sigma, 55 mg/kg.BW, i.v.), STZ-vitC (1 g/l ascorbic acid mixed in drinking water), STZ-cur (daily oral treatment of 300 mg/kg.BW curcumin; Cayman Chemical Co., USA), and STZ-cur+vitC (1 g/l ascorbic acid mixed in drinking water and oral treatment of 300 mg/kg.BW curcumin). On 8th week after STZ-injection, the microcirculation in the iris tissue was observed using intravital fluorescence videomicroscopy, and also leukocyte adhesion in the venule was examined for each group. Blood glucose (BG), lipid profiles, glycosylated hemoglobin (HbA1c) were measured in blood samples collected at the end of each experiment. The contents of liver malondialdehyde (MDA) were also quantified for each group. Feeding curcumin (STZ-cur) could decrease BG, HbA1c, dyslipidemia, and MDA significantly, compared to STZ. In cases of feedings curcumin with vitamin C, these results were more effective in all aspects, including leukocyte adhesion. In conclusion, curcumin might increase the effect of vitamin C in protecting the function of endothelial cells through its anti-oxidant with hypoglycemic and hypolipidemic actions.