ABSTRACT
Background and objective: Antioxidants may be useful in preventing vascular diseases. Among the antioxidant agents, tetrahydrocurcumin (THC) has not yet been examined in regard to its effectiveness in ameliorating cerebral blood flow impairment in diabetes. The objective of this study is to examine the long-term effect of THC supplementation on the cerebral microcirculation in diabetes, using streptozotocin (STZ)-induced diabetic rats. Methods: Diabetes was induced in male Wistar Furth rats by a single intravenous injection of STZ (55 mg/kg BW). The rats were divided into control and diabetic groups either with or without THC supplementation. THC was supplemented at a dose of 100mg/kg BW for 24 weeks. The cerebral microcirculation was directly observed using fluorescence video microscopy. The regional cerebral blood flow (rCBF) was continuously measured using laser Doppler flowmetry. Leukocyte adhesion to endothelium was evaluated in cerebral post-capillary venules by counting the number of adherent cells labeled with rhodamine 6G. Results: Compared to non-diabetic rats, the diabetic rats demonstrated a significant reduction of the rCBF while leukocyte adhesion was significantly increased. In STZ rats with THC supplementation, the rCBF was significantly greater, whereas the leukocyte adhesion was significantly less than that in the STZ rats with no THC supplementation. Conclusion: Long-term supplementation of THC can markedly prevent cerebral blood-flow reduction as induced by diabetes.
ABSTRACT
Background: Many clinical reports have indicated that ascorbic acid (vitamin C) improves vasodilatory impairments in patients with diabetes mellitus, but there is very little in vivo evidence to demonstrate its effectiveness on the brain. Objective: To investigate long-term effects of oral vitamin C administration on the cerebral microvascular vasodilation in diabetes, using streptozotocin (STZ)-induced diabetic rats. Materials and methods: Diabetes was induced in male Wistar Furth rats by a single intravenous injection of STZ (55 mg/kg b.w). Ascorbic acid (vitamin C) was administered in drinking water (1g/l). The rats were divided into control and diabetic groups with or without administration of vitamin C. The cerebral microcirculation was observed at different times (12, 24 and 36 weeks) after vitamin C supplementation, using fluorescence videomicroscopy. Responses of cerebral arterioles to acetylcholine (ACh), adenosine-5 diphosphate (ADP) and nitroglycerine (NTG) were studied by measuring diameters of cerebral arterioles before and after topical application on the cortical surface. Results: The vasodilatory responses of cerebral arterioles to ACh and ADP were significantly decreased in diabetic rats, compared with non-diabetic (control) rats. The response to NTG was not altered in diabetic rats, indicating that the vasodilatory impairment involves at the endothelium. The impaired endothelium-dependent vasodilation was prevented by long-term vitamin C administration. Conclusion: Long-term oral vitamin C administration might be of clinical relevance in improving cerebral microvascular vasodilatory impairment in diabetes.