Gastric Bypass Surgery Restores Meal Stimulation of the Anorexigenic Gut Hormones, Peptide Yy and Glucagon-Like Peptide-1 Independently of Caloric Restriction

Sarah Evans, MD, Zehra Pamuklar, MD, Jonathan Rosko, RN, Patrick Mahaney, RD, Ning Jiang, MD, Chan Park, MD, Alfonso Torquati, MD. Duke University, Department of Surgery

INTRODUCTION – This study investigated the effects of gastric bypass surgery (GBS) on the postprandial levels of anorexigenic gut hormones. Our primary hypotheses were that obese individuals with type 2 diabetes mellitus (T2DM) lack significant postprandial stimulation of polypeptide YY (PYY), and glucagon-like peptide-1 (GLP-1) and this response is restored after GBS independently of caloric restriction.

METHODS AND PROCEDURES – PYY and GLP-1 were measured in the fasting state and at different time points after a standardized liquid meal in two matched groups of obese subjects with T2DM treated only with oral hypoglycemic medications. The meal stimulation test was performed before and after (12 ± 4 days ) the two study interventions: Group 1 (n=10) – Gastric Bypass Surgery (GBS); Group 2 Control (n=10) – Caloric restriction by liquid diet matching post–GBS diet.

RESULTS – The two groups were successfully matched for sex (3M/7F in both cohorts), age (Control = 46.3 ± 6.5 years, GBS = 49.6 ± 11.1 years), and preoperative BMI (Control = 44 ± 8.9, GBS =45.6 ± 7.6). The magnitude of post-intervention change in BMI was similar in the two groups (-2.9 in GBS and -2.4 in Controls). However, excess weight loss was significantly higher (P<0.01) in the GBS group (14.2%) than in the Control group (7.2%).
As shown in the Figure, patients following GBS had a significantly (P=0.01) increased postprandial plasma levels of PYY and GLP-1 favoring enhanced satiety than obese controls with matched caloric restriction.

CONCLUSIONS – At baseline, the entire obese cohort in our study had a blunted postprandial PYY and GLP-1 response, which may reflect a functional deficiency state. However, following GBS there is a significant restoration of the postprandial stimulation of PYY and GLP-1 that is clearly independent from caloric restriction. The phenomenon of ‘bariatric surgery-induced anorexia’ may be potentially linked to the increased postprandial levels of PYY, and GLP-1 observed after GBS.