Relevance of beta-cell function for improved glycemic control after gastric bypass surgery

Background: Residual beta-cell function and gastrointestinal hormones have been suggested as relevant determinants of improved glycemic control ensuing Roux-en-Y gastric bypass (RYGB). The objective of this study was to compare the glycemic control up to 24 months after RYGB in C-peptide negative morbidly obese (MO) type 1 diabetes mellitus (T1 DM) women (n = 7) and C-peptide positive (>.6 ng/mL) MO women with type 2 diabetes mellitus (T2 DM, n = 7) on basal-bolus insulin therapy. The glucagon-like peptide 1 (GLP-1) and glucagon response to a mixed meal challenge were also compared between groups. Methods: Percent excess weight loss (%EWL), HbA(1c), and daily insulin dose (DID) after RYGB were compared between groups. The GLP-1 and glucagon response (area under the curve 0-120 minutes) after a mixed meal at last follow-up visit were also compared. Results: At 24-months, marked %EWL was observed in women with T1 DM and women with T2 DM (mean standard error, 82.6% +/- 11.3% and 87.4% +/- 30.5%, respectively; P = .722]. In women with T1 DM, HbA(1c) (4 months, P < .05) and DID improved transiently (P < .05, up to 8 months) but were comparable to baseline thereafter (HbA(1c): baseline, 8.3 +/- 1.2 and 24 months, 8.2 +/- .9, P = 1.00; DID: baseline, .61 +/- .17 and 24 months .62 +/- .12 IU/kg/d, P = 1.00]. In contrast, in MO women with T2 DM, HbA(1c) decreased significantly throughout follow up, with 2 patients presenting diabetes remission and all but one an HbA(1c) < 7% at 24 months. The GLP-1 response was comparable between groups (P = .612), and was not accompanied by suppression of the glucagon response to meal intake. Conclusions: In the absence of residual beta-cell, RYGB results in no significant benefit on glycemic control, despite a marked response of GLP-1 to meal intake. (C) 2014 American Society for Metabolic and Bariatric Surgery. All rights reserved.