Early effects of gastric banding (LGB) and of biliopancreatic diversion (BPD) on insulin sensitivity and on glucose and insulin response after OGTT.

BACKGROUND: Bariatric surgery improves glucose metabolism.
METHODS: To assess the direct role of surgery (i.e., independently of significant weight loss) on insulin sensitivity (homeostasis model assessment (HOMA) insulin resistance (IR) and oral glucose insulin sensitivity (OGIS)), on glucose and insulin response (area under the curve (AUC) blood glucose (BG) and AUC insulin (Ins)) to oral glucose tolerance test (OGTT), and on glucose tolerance, 11 subjects underwent OGTT (75 g, p.o.) before and 5 days after laparoscopic gastric banding (LGB; no change of initial body mass index (BMI), 46.7 +/- 2.21 kg/m(2)), and ten subjects underwent OGTT before and 7 days after biliopancreatic diversion (BPD; BMI decreased from 54.5 +/- 3.75 to 52.1 +/- 4.03 kg/m(2)). As controls, we considered OGTT performed twice over a 30-45-day period in two groups of subjects [BMI 43.0 +/- 0.41 (n = 13, matched with LGB subjects for BMI) and 48.2 +/- 0.49 kg/m(2) (n = 14, matched with BPD subjects for BMI), respectively] with stable weight (+/-1.5 kg); a further control group was made of 11 subjects with a spontaneous weight loss similar to BPD subjects (BMI from 55.5 +/- 1.27 to 52.2 +/- 1.35 kg/m(2)).
RESULTS: Fasting BG and OGIS improved in BPD subjects and in subjects with spontaneous weight loss, not in LGB subjects or in weight-stable controls; HOMA-IR, AUC BG, and AUC Ins only decreased in BPD subjects. Glucose tolerance was not affected in a different way in the various groups of subjects.
CONCLUSIONS: These data indicate an early effect of BPD different from LGB on insulin sensitivity and on glucose and on insulin response to OGTT, mostly independent of weight loss.