Abstract:

Objective: To observe the protective effect of rutin from buckwheat flowers and leaves (RBFL)on the vascular injury induced by high glucose stimulation,and to explore the possible mechanism.Methods: Eight rats were randomly selected from forty-five SD rats and used as control group,the last were used to induce the type Ⅰ diabetes mellitus model with STZ (60 mg·kg^-1,i.p.). The successful model rats were divided into model group (n=10),low dose (45 mg·kg^-1)of RBFL group,moderate dose (90 mg·kg^-1)of RBFL group and high dose (180 mg·kg^-1)of RBFLgroup (n=8). The rats in RBFL groups were gavaged the corresponding doses of RBFL once a day for 8 weeks;the rats in control group and model group were gavaged the same volume saline. The general condition was observed after 8 weeks;the blood glucose and body weight were recorded;the vessel relaxant rates of thoracic aortas induced by acetylcholine (Ach)(10^-9-10^-5 mol·L^-1)and sodium nitroprusside (SNP)(10^-10-10^-5 mol·L^-1)of the rats in various groups were detected;the serum reactive oxygen species (ROS)level,nitric oxide (NO)level,and superoxide dismutase (SOD),glutathione peroxidase (GSH-Px)and total nitric oxide synthase (tNOS)activities of the rats in various groups were detected. The thoracic aortas were separated rapidly from the normal rats and divided into normal glucose group (11 mmol·L^-1 glucose),high glucose(HG)group (44 mmol·L^-1 glucose),low RBFL(0.2 mg·L^-1)group,moderate RBFL(0.4 mg·L^-1)group,high RBFL(0.8 mg·L^-1)group,HG+ NG-nitro-L-arginine methyl ester (L-NAME)group,HG+L-NAME +RBFL group,HG+methylene blue (MB)group,and HG+MB +RBFL group. The vessel relaxant rates of thoracic aortas of the rats in various groups induced by Ach and SNP were detected;the SOD and NOS activities in thoracic aortas of the rats in normal group,HG group and RBFL group were detected.Results: Compared with control group,the body weights of the rats in model group were decreased and the blood glucose was increased (P<0.01);compared with model group,the body weights of the rats in RBFL group were increased and the blood glucose was decreased (P<0.05 or P<0.01);compared with control group,the vessel relaxant rate induced by Ach in model group was decreased (P<0.05 or P<0.01);compared with model group,the vessel relaxant rates induced by Ach in RBFL groups were increased (P<0.05 or P<0.01)and the effect was cancelled by L-NAME and MB,while the SNP-induced vessel relaxant rates had no changes (P>0.05). Compared with control group,the level of serum ROS in model group was increased(P<0.01);the NO level,the SOD and NOS activities were decreased(P<0.01).Compared with model group,the level of serum ROS in high RBFL group was decreased;the NO level,the activities of SOD and tNOS were increased (P<0.01),but the serum GSH-Px activity had no changes (P>0.05). Compared with normal glucose group,the vessel relaxant rate induced by Ach in HG group was decreased (P<0.01);compared with HG group,the vessel relaxant rates induced by Ach in RBFL groups were increased (P<0.05 or P<0.01)and the effect was cancelled by L-NAME and MB,while the SNP-induced vessel relaxant rate had no changes (P>0.05).Compared with normal glucose group,the SOD and NOS activities in HG group were decreased (P<0.01);compared with HG group,the activities of SOD and tNOS in high RBFL group were increased (P<0.01). Conclusion: RBFL could improve the endothelium-dependent vasorelaxation in high glucose injury of the rats and the mechanism may be related to enhancing the SOD activity,reducing the ROS generation and promoting the NO synthesis of endothelium cells.

Key words: rutin from buckwheat flowers and leaves, high glucose vascular injury, oxidative stress, endothelium, nitric oxide, vasorelaxation