One-Hour Postload Plasma Glucose Levels, a Predictor of Additional Risk for Diabetes: Prevalence, Mechanisms, and Associated Cardiovascular and Metabolic Risk Factors in Hispanics

Objective: The aim of this study was to determine the prevalence of and the mechanisms by which elevated glucose concentrations at 1-h after a glucose load, conferred increased risk for type 2 diabetes mellitus (T2DM). The study was conducted in subjects with glucose abnormalities (impaired fasting glucose [IFG], and impaired glucose tolerance [IGT]), as well as in normal fasting-normal tolerant subjects (NFG-NGT). Method: One-hour plasma glucose concentrations were measured as part of 0- to180-min oral glucose tolerance test (OGTT) performed in an unselected sample of 490 Latino-Hispanics. A cutoff of 154mg/dL at 1-h during the OGTT was employed, because higher glucose levels define subjects at increased risk for T2DM. Surrogate markers of insulin sensitivity and release, and glucose and insulin time courses were measured. Obesity, cardiovascular risk factors, and presence of metabolic syndrome were also assessed. Results: One-hour plasma glucose concentrations above the cutoff (>= 155mg/dL) were found in 8.3% of NFG-NGT, 43% of IFG, 65% of IGT, and in 90% of IFG+IGT, and were associated with greater postload hyperglycemia (AUCG) and hyperinsulinemia (AUCI), and with reductions in indices of beta-cell function (Delta I0-30/Delta G(0-30), and Delta I0-180/Delta G(0-180)), insulin sensitivity [Matsuda index, homeostasis model assessment of insulin resistance (HOMA-IR)], and disposition index (Delta I0-30/Delta(0-30) G divided by HOMA-I), markers of increased risk of T2DM. In addition, those with >= 155mg/dL were older, more obese, had higher blood pressure, and higher prevalence of metabolic syndrome. These clinical and metabolic changes were characteristic of subjects with 1-h plasma glucose concentrations >= 155 mg/dL, irrespectively of whether they were classified as NFG-NGT, IFG, or IGT. Conclusions: One-hour postload plasma glucose levels >= 155mg/dL identified a subgroup of subjects, which by current guidelines are classified as NFG-NGT, IFG, or IGT, but that are at a higher risk that their average group risk. Recognition and management of these subjects may reduce incidence of diabetes and cardiovascular events.