Reduction of cardiovascular morbidity and mortality in type 2 diabetes. A rational approach to hypoglycemic therapy

Ginsenoside-Rb1 Improved Diabetic Cardiomyopathy through Regulating Calcium Signaling by Alleviating Protein O-GlcNAcylation

Ginsenoside-Rb1 (Rb1), a major active component of ginseng, has many benefits for cardiovascular disease and diabetes mellitus (DM), but the effect and mechanism on diabetic cardiomyopathy are not clear. In the present study, we found that Rb1-feeding significantly improved cardiac dysfunction and abnormal cardiomyocytes calcium signaling caused by diabetes. This improved calcium signaling was because Rb1 reduced Ca²⁺ leakage caused by overactivated ryanodine receptor 2 (RyR2) and increased Ca²⁺ uptake by sarcoplasmic reticulum Ca²⁺-ATPase 2a (SERCA 2a). Furthermore, we found that Rb1 not only enhanced energy metabolism like metformin and eliminated O-GlcNAcylation of calcium handling proteins to regulate calcium signaling but also directly inhibited RyR2 activity to regulate calcium signaling. The present study indicated that as a health supplement or drug, Rb1 was a relatively effective auxiliary therapeutic substance for diabetic cardiomyopathy.

Association of Diet Alone, Insulin, Sulfonylureas, Metformin, and Thiazolidinediones with the Severity of Coronary Artery Disease in Patients with Diabetes Mellitus

Coronary angiography was performed in 152 men and 163 women with diabetes mellitus, mean age 55 +/- 8 years, because of chest pain. Of 67 patients with 3-vessel or 4-vessel coronary artery disease (CAD), 17 (25%) were treated with diet alone, 29 (43%) with insulin, 18 (27%) with sulfonylureas, 12 (18%) with metformin, and 6 (9%) with thiazolidinediones. Of 76 patients with 2-vessel CAD, 20 (26%) were treated with diet alone, 36 (47%) with insulin, 21 (28%) with sulfonylureas, 21 (28%) with metformin, and 11 (14%) with thiazolidinediones. Of 40 patients with 1-vessel CAD, 15 (38%) were treated with diet alone, 11 (28%) with insulin, 8 (20%) with sulfonylureas, 12 (30%) with metformin, and 4 (10%) with thiazolidinediones. Of 132 patients with 0-vessel CAD, 18 (14%) were treated with diet alone, 21 (16%) with insulin, 7 (5%) with sulfonylureas, 75 (56%) with metformin, and 35 (26%) with thiazolidinediones. Cochran-Armitage trend tests were used to examine whether the use of treatment significantly increases or decreases as the number of arteries with CAD increases (P = 0.036 for diet alone; P < 0.0001 for insulin, for sulfonylureas, and for metformin; P = 0.002 for thiazolidinediones).

Role of aldose reductase and oxidative damage in diabetes and the consequent potential for therapeutic options

Aldose reductase (AR) is widely expressed aldehyde-metabolizing enzyme. The reduction of glucose by the AR-catalyzed polyol pathway has been linked to the development of secondary diabetic complications. Although treatment with AR inhibitors has been shown to prevent tissue injury in animal models of diabetes, the clinical efficacy of these drugs remains to be established. Recent studies suggest that glucose may be an incidental substrate of AR, which appears to be more adept in catalyzing the reduction of a wide range of aldehydes generated from lipid peroxidation. Moreover, inhibition of the enzyme has been shown to increase inflammation-induced vascular oxidative stress and prevent myocardial protection associated with the late phase of ischemic preconditioning. On the basis of these studies, several investigators have ascribed an important antioxidant role to the enzyme. Additionally, ongoing work indicates that AR is a critical component of intracellular signaling, and inhibition of the enzyme prevents high glucose-, cytokine-, or growth factor-induced activation of protein kinase C and nuclear factor-kappa-binding protein. Thus, treatment with AR inhibitors prevents vascular smooth muscle cell growth and endothelial cell apoptosis in culture and inflammation and restenosis in vivo. Additional studies indicate that the antioxidant and signaling roles of AR are interlinked and that AR regulates protein kinase C and nuclear factor-kappaB via redox-sensitive mechanisms. These data underscore the need for reevaluating anti-AR interventions for the treatment of diabetic complications. Potentially, the development of newer drugs that selectively inhibit AR-mediated glucose metabolism and signaling, without affecting aldehyde detoxification, may be useful in preventing inflammation associated with the development of diabetic complications, particularly micro- and macrovascular diseases.

Insulin Response to Oral Glucose Loading and Coronary Artery Disease in Nondiabetics

Hyperinsulinemia is related to coronary artery disease (CAD), as an indication of decreased insulin sensitivity. Although there are many studies showing the relation between fasting insulin levels and insulin resistance, there are fewer studies on postprandial insulin levels. The aim of the present study was to investigate the relationship between postprandial insulin levels and CAD and its extent in our patients. For this purpose, oral glucose tolerance testing was performed in 222 patients with no known diabetes and who were scheduled to undergo diagnostic coronary angiography. The patients were first separated into two groups, one group (group I) having an insulin response within reference values to oral glucose loading, and the other group (group II) with a higher than normal insulin response. The presence and extent of CAD in the two groups were compared. While 65% of the patients in group 1 had CAD, this rate increased to 79% in group 2 patients (P = 0.02). The mean vessel scores were 0.92 +/- 0.78 in group 1 and 1.67 +/- 0.99 (P < 0.0001) in group 2 patients. The stenosis scores were 2.192 +/- 2.077 in group 1 and 5.588 +/- 3.519 (P < 0.001) in group 2, while the extent scores were 1.230 +/- 1.292 in group 1 and 2.729 +/- 1.847 in group 2 (P < 0.0001). The differences between the two groups were significant. Postprandial insulin values were positively correlated with CAD (P = 0.001, r = 0.214), vessel scores (P < 0.0001, r = 0.326), stenosis scores (P < 0.0001, r = 0.261), and extent scores (P < 0.0001, r = 0.419). Logistic regression analysis revealed hyperinsulinemia increased CAD independent from the other risk factors (OR = 5.742, CI 95%: 1.809-18.227, P = 0.003).