Abstract
Objective To investigate the effects of capsaicin (CAP) on coronary endothelium-dependent vasodilation in rats with type 2 diabetes mellitus (T2DM). Methods Sixty healthy male Sprague Dawley rats (120-140 g) were used in this study. Intraperitoneal injection of streptozotocin and high fat diet were used to establish T2DM in rats. Then all diabetic rats were randomly divided into diabetes mellitus (DM) group, CAP intervention (CAP) group and capsazepine intervention (CAPZ) group with 15 rats in each group. And 15 normal rats were selected as normal control (NC) group. Rats in CAP group and CAPZ group were injected intraperitoneal with CAP (1 mg·kg-1·d-1) or CAPZ (1.5 mg·kg-1·d-1), respectively. The same volume of saline was injected to rats in NC group and DM group. After 14 weeks, the levels of fasting plasma glucose (FPG), total cholesterol (TC), triglycerides (TG), nitric oxide (NO), endothelial nitric oxide synthase (eNOS), endothelin1 (ET-1) in serum were determined. Endothelium-dependent and endothelium-independent vasodilation were examined in isolated vascular ring by perfusion technique; coronary NO concentration were checked by nitrate reduction assay; levels of coronary transient receptor potential vanilloid 1 (TRPV1), eNOS and phospho-eNOS(p-eNOS) were tested by Western blotting. Paired t test and independent sample t test were used for statistical analysis. Results The coronary NO concentration, levels of TRPV1 and p-eNOS were significantly increased in CAP group compared with those in DM group [(105.7±3.9) vs (92.8±8.3) μmol/(mg·pro),(0.41±0.05) vs (0.30±0.05), (0.24 ± 0.03) vs (0.14 ± 0.04), t=-4.47,-2.80,-3.06, all P<0.05]. The endothelium-dependent relaxation induced by different concentrations of acetylcholine were significantly higher in CAP group than in DM group (t=10.42,-5.19,-13.38,-17.46,-20.94, respectively, all P<0.05). The levels of serum FPG, TC, TG and ET-1 were significantly lower in CAP group than those in DM group (t=-13.67,-16.41,-20.39,-42.29, respectively, all P<0.05). Conclusion Long-term CAP supplementation prevents the impairment of coronary endothelium-dependent vasodilation in T2DM. Key words: Diabetes mellitus, type 2; Capsaicin; Coronary artery; Vascular endothelial dilation; Transient receptor potential vanilloid 1
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