Coronary vasomotor function is abnormal in first-degree relatives of patients with type 2 diabetes

Nondiabetic first-degree relatives of patients with type 2 diabetes are at increased risk of developing diabetes ( 1 ) and cardiovascular disease (CVD) ( 2 ). Endothelial dysfunction is regarded as an early step in the development of atherosclerosis ( 3 ). Abnormal peripheral endothelial dysfunction detected by flow-mediated, endothelium-dependent, forearm-mediated dilatation (FMD) has been reported in first-degree relatives ( 4 , 5 ). The abnormal FMD could not be explained by confounding variables including age, sex, ethnicity, obesity, lipids, blood pressure, glycemia, or insulin resistance ( 5 ). However, endothelial dysfunction detected in brachial arteries may not reflect the condition of the coronary vasculature, as brachial and coronary circulations differ in terms of the microvascular architecture, pattern of blood flow, their metabolic regulation, and the pathways that are activated to induce hyperemia ( 6 ). Coronary flow reserve measurement has been considered to be a useful physiologic index for coronary circulation ( 6 ). In this study, we report for the first time impaired coronary flow reserve in young nonobese normoglycemic first-degree relatives compared with healthy control subjects.