Research on OGTT and HbAlc levels in patients with newly diagnosed type 2 diabetes mellitus and prediabetes / 中华老年医学杂志

ABSTRACT

Objective To explore different features and influencing factors of 75 g oral glucose tolerance test (OGTT) and glycated hemoglobin Ale (HbAlc) levels in subjects with newly diagnosed diabetes and prediabetes of natural history of type 2 diabetes. Methods All subjects were classified by OGTT into four groups (1) normal glucose test (NGT), 31 subjects at age of (48. 4±15. 3) yrs (29-75 years old); (2) impaired fasting glucose (IFG), 33 subjects at age of (50. 8±9. 8) yrs (38-72years old) ; (3) impaired glucose tolerance test (IGT), 34 subjects at age of (54. 5±11.4) yrs (33-74years old), (4) T2DM, 117 subjects at age of (54.3 ± 14.1) yrs (29-75 years old). Glucose metabolism was evaluated by results of OGTT and HbAlc levels. The insulin secretion function and insulin resistance (IR) were evaluated by HOMA-β, △I30/△G330, area under curve of insulin (AUCINS)and HOMA-IR respectively. Results (1) Significant changes of HbAlc values among groups were as following order T2DM(7. 41%)>IGT(5. 85%)>NGT(5.21%) (P<0. 01). HOMA-β value in T2DM, IGT and IFG decreased by 53. 1% (P<0. 01), 29.3% (P<0. 01) and 23.4% (P<0. 05)respectively as compared with NGT group. HOMA-IR value in diabetes group was 1.66-fold of NGT (P<0.01), 1. 29-fold of IFG (P<0.001) and 1.44-fold of IGT (P<0.05). (2) Only 3 h blood glucose concentration (BG) in 75 g OGTT was independently and positively correlated with HbAlc level (r=0. 71, P<0. 01). △I30/△G330 ratio was independently and negatively correlated with both 1 h and 2 h BG of OGTT (P<0.01). AUCins was positively correlated with only 3 h BG of OGTT (P<0.01). HOMA-β was independently and negatively correlated with all OGTT results except 2 h BG(P<0.01). HOMA-IR was an independently and negatively correlative factor of all OGTT results (P<0. 01 or P<0. 05). TG level was independently and positively correlated to only fasting BG (P<0. 05), and waist circumference value had an independent and positive relationship with only 1/2h BG (P<0. 01). Independently correlative factors of OGTT changes included △I30/△G330, AUCINS,HOMA-β, HOMA-IR and circumference values. Only 3 h BG was probably an independent contributor to HbAlc variation. Conclusions There are obvious HbAlc differences among T2DM,IGT and NGT patients. When HbAlc values are over 8%, no significant changes of glucose and insulin levels at 75 g glucose load test are found among subjects.