Metabolic syndrome: therapeutic considerations

The metabolic syndrome is a constellation of metabolic risk factors for atherosclerotic cardiovascular disease (ASCVD) occurring in one individual. There are five cardiovascular risk factors that accompany the metabolic syndrome: atherogenic dyslipidemia [elevated apolipoprotein B (apo B), elevated triglyceride, small low-density lipoprotein (LDL) particles, and low high-density lipoprotein (HDL)cholesterol], elevated blood pressure, elevated glucose, a prothrombotic state, and a proinflammatory state. The likelihood of an individual developing metabolic syndrome is enhance by underlying risk factors, notably, obesity, insulin resistance, lack of physical activity, advancing age, and hormonal factors (e.g., androgens and corticosteroids). Besides being at higher risk for ASCVD, persons with the metabolic syndrome are at increased risk for type 2 diabetes. Persons with the metabolic syndrome deserve management in the clinical setting to reduce the risk for both ASCVD and type 2 diabetes. The two major therapeutic strategies for treatment of affected persons are modification of the underlying risk factors and separate drug treatment of the particular metabolic risk factors when appropriate. First-line therapy for underlying risk factors is therapeutic lifestyle changes, i.e., weight loss in obese persons, increased physical activity, and anti-atherogenic diet. These changes will improve all of the metabolic risk factors. Whether use of drugs to reduce insulin resistance is effective, safe, and cost-effective before the onset of diabetes awaits the results of more clinical research. Turning to individual risk components, for atherogenic dyslipidemia, drug therapies that promote lowering of apo B and raise HDL cholesterol will be needed for higher risk patients. Treatment of categorical hypertension with drugs has become standard practice. When hyperglycemia reaches the diabetic level, glucose-lowering agents will become necessary when dietary control is no longer effective, and reduction of a prothrombotic state with low-dose aspirin may be indicated in higher-risk patients.

Surface expression of collagen receptor Fc receptor-gamma/glycoprotein VI is enhanced on platelets in type 2 diabetes and mediates release of CD40 ligand and activation of endothelial cells

Diabetes is associated with an enhanced collagen-mediated platelet activation that contributes significantly to thromboischemic complications. In this study, the platelet collagen receptor glycoprotein VI (GPVI) was studied in 385 patients with type 2 diabetes. Surface expression of the platelet Fc receptor that forms a functional complex with GPVI was significantly increased in patients with diabetes compared with those without diabetes (P = 0.02). Fc receptor expression correlated with GPVI expression and was found to be independently associated with diabetes (r = 0.529, P < 0.001). Stimulation of GPVI through a specific anti-GPVI monoclonal antibody significantly enhanced surface expression of CD40L (P = 0.006). Because CD40L is a potent platelet-derived cytokine that is involved in thrombosis and atherosclerosis, we evaluated the effect of GPVI-mediated release of CD40L on activation of endothelial cells. Coincubation of GPVI-stimulated platelets resulted in substantial enhanced endothelial surface expression of CD62P, alphavbeta3, and intercellular adhesion molecule 1 (P < 0.05) and secretion of monocyte chemoattractant protein 1 of cultured human umbilical vein endothelial cells (P < 0.01). These results suggest that the function of collagen receptor GPVI is altered in type 2 diabetes and may play an important role in atherothrombotic complications. Inhibition of GPVI may be a promising pharmacological target in the treatment of high-risk diabetic patients.