Relationship between pancreatic beta-cell function and body mass index and age in patients with newly diagnosed type 2 diabetes

Abstract

Objective To investigate relationship between insulin sensitivity and beta-cell function with body mass index (BMI) and age in patients with newly diagnosed type 2 diabetes mellitus (T2DM).Methods Totally, 304 patients with T2DM newly-diagnosed at admission to the first hospital affiliated to Nanjing Medical University, Jiangsu province, during 2006 to 2007 were recruited in the study. The patients were divided into three groups based on WHO criteria of obesity in Asia Pacific Region in 2003, 68 cases with normal weight ( 18. 5≤ BMI ＜ 23.0), 69 in overweight (23.0 ≤ BMI ＜ 25.0), and 167 in obesity (BMI≥25.0). Fasting serum glucose, glycesylated hemoglobin Alc (HbAlc) and lipids were measured for all the subjects, as well as oral glucose tolerance test (OGTr), C-peptide releasing tests and determination of serum insulin performed. Homeostasis model assessment of insulin resistance index (HOMA-IR), insulinogenic index (AI30/AG30) and modified beta-cell function index (MBCI) werecalculated to evaluate their insulin sensitivity and beta-cell function of the islets. All these parameters werecompared between the three groups and subgroups. Results HOMA-IR and MBCI were significantly higherin T2DM patients with obesity than those in the groups with normal weight and over-weight ( P < 0. 05 ).AI30/AG30 in obesity group was significantly higher than that in the group with normal weight (P <0. 05).Multiple linear regression analysis showed that BMI independently correlated with HOMA-IR ( P < O. 05 ).Sub-group analysis showed that △I30/△G30 and MBCI were significantly higher in those aged 60 years and over with obesity than those in the groups aged less than 60 years ( P ＜ 0. 05 ). Conclusions Non-obese patients with newly diagnosed T2DM have more severe impaired insulin secretion than that in obese ones,and their insulin resistance increases with BMI. Age has no significant correlation with pancreatic beta-cell function or insulin sensitivity. Key words: Diabetes mellitns,type 2; Body mass index; Insulin resistance; Pancreatic β cell function; Age factors