Gender discrimination in the influence of hyperglycemia and hyperosmolarity on rat aortic tissue responses to insulin

Ginsenoside Rb1 Reduces Hyper-Vasoconstriction Induced by High Glucose and Endothelial Dysfunction in Rat Aorta

Acute hyperglycemia induces oxidative damage and inflammation, leading to vascular dysfunction. Ginsenoside Rb1 (Rb1) is a major component of red ginseng with anti-diabetic, anti-oxidant and anti-inflammatory properties. Here, we investigated the beneficial effects and the underlying mechanisms of Rb1 on hypercontraction induced by high glucose (HG) and endothelial dysfunction (ED). The isometric tension of aortic rings was measured by myography. The rings were treated with NG-nitro-L-arginine methyl ester (L-NAME) to induce chemical destruction of the endothelium, and Rb1 was added after HG induction. The agonist-induced vasoconstriction was significantly higher in the aortic rings treated with L-NAME + HG50 than in those treated with HG50 or L-NAME (p = 0.011) alone. Rb1 significantly reduced the hypercontraction in the aortic rings treated with L-NAME + HG50 (p = 0.004). The ATP-sensitive K+ channel (KATP) blocker glibenclamide tended to increase the Rb1-associated reduction in the agonist-induced vasoconstriction in the rings treated with L-NAME + HG50. The effect of Rb1 in the aortic rings treated with L-NAME + HG50 resulted from a decrease in extracellular Ca2+ influx through the receptor-operated Ca2+ channel (ROCC, 10-6-10-4 M CaCl2, p < 0.001; 10-3-2.5 × 10-3 M CaCl2, p = 0.001) and the voltage-gated Ca2+ channel (VGCC, 10-6 M CaCl2, p = 0.003; 10-5-10-2 M CaCl2, p < 0.001), whereas Rb1 did not interfere with Ca2+ release from the sarcoplasmic reticulum. In conclusion, we found that Rb1 reduced hyper-vasoconstriction induced by HG and ED by inhibiting the ROCC and the VGCC, and possibly by activating the KATP in rat aorta. This study provides further evidence that Rb1 could be developed as a therapeutic target for ED in diabetes.

Zinc protects against diabetes-induced pathogenic changes in the aorta: roles of metallothionein and nuclear factor (erythroid-derived 2)-like 2

Background

Cardiovascular diseases remain a leading cause of the mortality world-wide, which is related to several risks, including the life style change and the increased diabetes prevalence. The present study was to explore the preventive effect of zinc on the pathogenic changes in the aorta.

Methods

A genetic type 1 diabetic OVE26 mouse model was used with/without zinc supplementation for 3 months. To determine gender difference either for pathogenic changes in the aorta of diabetic mice or for zinc protective effects on diabetes-induced pathogenic changes, both males and females were investigated in parallel by histopathological and immunohistochemical examinations, in combination of real-time PCR assay.

Results

Diabetes induced significant increases in aortic oxidative damage, inflammation, and remodeling (increased fibrosis and wall thickness) without significant difference between genders. Zinc treatment of these diabetic mice for three months completely prevented the above pathogenic changes in the aorta, and also significantly up-regulated the expression and function of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a pivotal regulator of anti-oxidative mechanism, and the expression of metallothionein (MT), a potent antioxidant. There was gender difference for the protective effect of zinc against diabetes-induced pathogenic changes and the up-regulated levels of Nrf2 and MT in the aorta.

Conclusions

These results suggest that zinc supplementation provides a significant protection against diabetes-induced pathogenic changes in the aorta without gender difference in the type 1 diabetic mouse model. The aortic protection by zinc against diabetes-induced pathogenic changes is associated with the up-regulation of both MT and Nrf2 expression.