Metabolic characteristics of subjects with normal glucose tolerance and 1-h hyperglycaemia

Abstract

Objective: Nondiabetic subjects with a 1-h plasma glucose >or= 11.1 mmol/l during an oral glucose tolerance test (OGTT) drew our attention to their somewhat confusing status and relative frequency among Chinese patients. The aim of this study was to clarify the metabolic characteristics of these subjects.

Design and patients: A total of 2549 Chinese subjects were included in this study. Based on results of OGTT, these subjects were classified into three groups: normal glucose tolerance (NGT), impaired glucose regulation (IGR) and diabetes mellitus (DM). Then, according to the level of 1-h plasma glucose, the NGT and IGR groups were subclassified, respectively, as: NGT without 1-h hyperglycaemia (NGTN), NGT with hyperglycaemia at 1 h (NGT1H), IGR without 1-h hyperglycaemia (IGRN), and IGR with hyperglycaemia at 1 h (IGR1H).

Results: After adjustments for age and gender, the insulinogenic index (IGI) of NGT1H and IGR1H was found to be lower than for those with NGTN and of IGRN, respectively (P < 0.05). No statistical differences, however, were found in oral glucose insulin sensitivity (OGIS) between either of the 1-h hyperglycaemic groups or of the corresponding NGTN or IGRN groups. Homeostasis model assessment for beta-cell function (HOMA-B) of NGT1H was lower than that of NGTN (P < 0.05), while IGRN and IGR1H showed no difference. No differences in homeostasis model assessment for insulin resistance (HOMA-IR) were found among NGTN, NGT1H, IGRN and IGR1H groups. The levels of triglycerides (TG) were not significantly different among NGT1H, IGRN and IGR1H, while TG in these groups were significantly higher than in NGTN (P < 0.05). LDL-C was significantly higher and HDL significantly lower in NGT1H than in all other groups (P < 0.05).The IGR group was also subclassified as: isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT) and combined glucose intolerance (CGI). The IGI of the NGT1H group was similar to the IGI that of combined glucose intolerance group but lower than those of IFG and IGT (P < 0.05).The OGIS of the NGT1H group was the highest among all groups (P < 0.05). HOMA-B of IGT and NGT1H were higher than that of IFG (P < 0.05). There was no difference among all groups in HOMA-IR. Plasma lipid levels were not significantly different between NGT1H and any other group.

Conclusions: Chinese NGT subjects with a 1-h plasma glucose >/= 11.1 mmol/l are characterized by metabolic abnormalities, which may be caused by the impairment of early insulin release rather than aggravated insulin resistance.