Glucose effectiveness and its components in relation to body mass index.

Abstract

Obesity is known to induce a deterioration of insulin sensitivity (SI ), one of the insulin-dependent components of glucose tolerance. However, few studies investigated whether obesity affects also the insulin-independent component, that is glucose effectiveness (SG ). This cross-sectional study aimed to analyse SG and its components in different body mass index (BMI) categories. Three groups of subjects spanning different BMI (kgm-2 ) categories underwent a 3-h frequently sampled intravenous glucose tolerance test: Lean (LE; 18.5≤BMI<25, n=73), Overweight (OW; 25≤BMI<30, n=90), and Obese (OB; BMI≥30, n=41). OB has been further divided into two subgroups, namely Obese I (OB-I; 30≤BMI<35, n=27) and Morbidly Obese (OB-M; BMI≥35, n=14). Minimal model analysis provided SG and its components at zero (GEZI) and at basal (BIE) insulin. Values for SG were 1.98±1.30×10-2 ·min-1 in all subjects grouped and 2.38±1.23, 1.84±0.82, 1.59±0.61 10-2 ·min-1 in LE, OW and OB, respectively. In all subjects grouped, a significant inverse linear correlation was found between the log-transformed values of SG and BMI (r=-0.3, P<0.0001). SG was significantly reduced in OW and OB with respect to LE (P<0.001) but no significant difference was detected between OB and OW (P=0.35) and between OB-I and OB-M (P=0.25). Similar results were found for GEZI. BIE was not significantly different among NW, OW and OB (P=0.11) and between OB-I and OB-M (P≥0.07). SG and its major component GEZI deteriorate in overweight individuals compared to those in the normal BMI range, without further deterioration when BMI increases above 30kgm-2 .