Frye, Robert L.

A paradoxical increase in mortality attributable to diabetes has occurred, particularly during the last decade, despite the overall decrease in mortality attributable to coronary artery disease in patients without diabetes. Insulin resistance with or without frank type 2 diabetes has emerged as a major determinant of accelerated coronary artery disease and its sequelae. The advent of insulin sensitizers enables clinicians to target treatment of insulin resistance, as well as hyperglycemia and dyslipidemia. The prevalence of diabetes in the United States is enormous and is increasing rapidly. Patients with diabetes respond less favorably to percutaneous coronary interventions and surgery compared with nondiabetic patients. These considerations led to the initiation of the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) trial. It is designed to determine whether treatment targeted to attenuate insulin resistance can arrest or retard progression of coronary artery disease compared with treatment targeted to the same level of glycemic control with an insulin-providing approach. It is designed also to determine whether early revascularization reduces mortality and morbidity in patients with type 2 diabetes whose cardiac symptoms are mild and stable. Despite challenges in study design and enrollment, intensive follow-up, and the long duration of follow-up planned, the questions being addressed are compelling and seem to merit the effort.

Background— Few studies have compared long-term status of bypass grafts between patients with and without diabetes, and uncertainty exists as to whether diabetes independently predicts poor clinical outcome after CABG. Methods and Results— Among 1526 patients in BARI who underwent CABG as initial revascularization, 99 of 292 (34%) with treated diabetes mellitus (TDM) (those on insulin or oral hypoglycemic agents) and 469 of 1234 (38%) without TDM had follow-up angiography. Angiograms with the longest interval from initial surgery and before any percutaneous graft intervention (mean 3.9 years) were reviewed. An average of 3.0 grafts were placed at initial CABG for patients with TDM (n=297; internal mammary artery [IMA], 33%) and 2.9 grafts for patients without TDM (n=1347; IMA, 34%). Patients with TDM were more likely than those without to have small (<1.5 mm) grafted distal vessels (29% versus 22%) and vessels of poor quality (9% versus 6%). On follow-up angiography, 89% of IMA grafts were free of stenoses ≥50% among patients with TDM versus 85% among patients without TDM ( P =0.23). For vein grafts, the corresponding percentages were 71% versus 75% ( P =0.40). After statistical adjustment, TDM was unrelated to having a graft stenosis ≥50% (adjusted odds ratio, 0.87; 95% CI, 0.58 to 1.32). Conclusions— Despite diabetic patients’ having smaller distal vessels and vessels judged to be of poorer quality, diabetes does not appear to adversely affect patency of IMA or vein grafts over an average of 4-year follow-up. Previously observed differences in survival between CABG-treated patients with and without diabetes may be largely a result of differential risk of mortality from noncardiac causes.

Background — CD4 T lymphocytes accumulate in unstable plaque. The direct and indirect involvement of these T cells in tissue injury and plaque instability is not understood. Methods and Results — Gene profiling identified perforin, CD161, and members of the killer-cell immunoglobulin-like receptors as being differentially expressed in CD4 + CD28 null T cells, a T-cell subset that preferentially infiltrates unstable plaque. Frequencies of CD161 + and perforin-expressing CD4 T cells in peripheral blood were significantly increased in patients with unstable angina (UA). CD161 appeared on CD4 + CD28 null T cells after stimulation, suggesting spontaneous activation of circulating CD4 T cells in UA. Perforin-expressing CD4 + T-cell clones from patients with UA exhibited cytotoxic activity against human umbilical vein endothelial cells (HUVECs) in redirected cytotoxicity assays after T-cell receptor triggering and also after stimulation of major histocompatibility complex class I–recognizing killer-cell immunoglobulin-like receptors. HUVEC cytolysis was dependent on granule exocytosis, as demonstrated by the paralyzing effect of pretreating CD4 + CD28 null T cells with strontium. Incubation of HUVECs with C-reactive protein (CRP) increased HUVEC lysis in a dose-dependent fashion. Conclusions — In patients with UA, CD4 T cells undergo a change in functional profile and acquire cytotoxic capability. Cytotoxic CD4 T cells effectively kill endothelial cells; CRP sensitizes endothelial cells to the cytotoxic process. We propose that T-cell–mediated endothelial cell injury is a novel pathway of tissue damage that contributes to plaque destabilization. The sensitizing effect of CRP suggests synergy between dysregulated T-cell function and acute phase proteins in acute coronary syndromes.