INSULIN-SECRETION, CLEARANCE AND ACTION BEFORE AND AFTER GASTROPLASTYIN SEVERELY OBESE SUBJECTS

This study investigated the effects of a drastic weight reduction on i nsulin secretion rate (ISR), insulin metabolic clearance rate (MCR(I)) and insulin sensitivity (S-I) in severely obese subjects. A frequentl y sampled intravenous glucose tolerance test (FSIVGTT, 0.3 g/kg) was p erformed before and 8 +/- 1 months after a vertical ring gastroplasty in 12 overnight-fasted obese non-diabetic subjects; the results were c ompared to those obtained in 12 lean controls matched for age and sex. ISR was derived by deconvolution of plasma C-peptide levels; MCR(I) w as obtained by dividing the area under the curve (AUC(180 min) ) of IS R by the corresponding AUC of plasma insulin levels (IRI); the S-I and the glucose effectiveness index (S-G) were calculated by Bergman's mi nimal model. Before gastroplasty, obese subjects showed significantly higher ISR (P < 0.02), lower MCR(I) (P < 0.001), lower S-I (P < 0.001) but similar S-G when compared to lean controls. After gastroplasty (r eduction of body weight from 104.8 +/- 3.8 to 73.4 +/- 3.6 kg and of B MI from 37.9 +/- 0.8 to 26.5 +/- 0.9 kg/m(2); P < 0.001), ISR only dec reased from 53 125 +/- 7968 to 42 302 +/- 3716 pmol/180 min (not signi ficant) while AUC-IRI dramatically fell from 53 626 +/- 6378 to 21 111 +/- 2584 pmol.min/l; P < 0.001); consequently, MCR(I), markedly incre ased from 526 +/- 96 to 1257 +/- 150 ml/min/m(2); P < 0.01). S-I signi ficantly rose from 3.12 +/- 0.45 to 7.10 +/- 1.20 x 10(-4) l/mU/min (P < 0.005) while S-G remained unchanged. Except for ISR (still higher i n the obese subjects; P < 0.05), no significant differences in MCR(I), S-I or S-G were observed between lean controls and obese subjects aft er gastroplasty. In conclusion, in severely obese non-diabetic subject s, a considerable post-gastroplasty weight loss slightly reduces insul in secretion but markedly improves insulin clearance, the result being an almost complete correction of the peripheral hyperinsulinaemia tog ether with a near-normalization of the sensitivity to insulin.