Insulin resistance, inflammation, and the prediabetic state

Type 2 diabetes is associated with a marked increase in the incidence of coronary artery disease (CAD); however, the correlation between glycemia and CAD in patients with type 2 diabetes is only modestly positive. This relatively weak association between glycemia and CAD in subjects with diabetes may be caused by the existence of an atherogenic prediabetic state. In the San Antonio Heart Study, subjects who start with normal glucose tolerance and later develop type 2 diabetes have increased triglyceride levels, increased systolic blood pressure, and decreased levels of high-density lipoprotein cholesterol before the onset of type 2 diabetes. The basis for these atherogenic prediabetic changes may be related to insulin resistance rather than reduced insulin secretion. Recently, interest has focused on a possible role of fibrinolysis and increased subclinical inflammation, as determined by high-sensitivity C-reactive protein (CRP) levels. The Insulin Resistance Atherosclerosis Study found that insulin resistance, as determined by a frequently sampled glucose tolerance test, is significantly related to higher CRP levels, higher fibrinogen, and higher plasminogen activator inhibitor–1 (PAI-1) levels. The investigators also have shown that high PAI-1 and CRP levels are predictors of the development of type 2 diabetes. In addition, the Womenʹs Health Study has shown that high CRP levels predict type 2 diabetes. Insulin-sensitizing interventions have been demonstrated to reduce these nontraditional risk factors. Rosiglitazone, an agent with insulin-sensitizing properties, decreases PAI-1 and CRP levels. Some of the adverse cardiovascular effects seen in patients with type 2 diabetes may be reversed by insulin-sensitizing agents.