Effect of Weight Loss by Diet or Gastric Bypass Surgery on Peptide YY3–36 Levels

Abstract

Objective-To examine the effect of an equivalent weight loss, by gastric bypass surgery (GBP) or by diet, on peptide YY ), ghrelin, and leptin levels and to determine the effect of diabetes status on PYY 3-36 levels.Summary Background Data-The increased PYY 3-36 levels after GBP may be involved in the magnitude and the sustainability of weight loss after surgery.Methods-Of the 30 morbidly obese women who participated in the study, 21 had type 2 diabetes mellitus, and were studied before and after equivalent weight loss of 10 kg by either GBP (n = 11) or by diet (n = 10).Results-PYY 3-36 levels were higher in obese diabetic as compared with nondiabetic individuals (64.1 ± 34.4 pg/mL vs. 39.9 ± 21.1 pg/mL; P < 0.05). PYY 3-36 levels increased markedly in response to oral glucose after GBP (peak: 72.3 ± 20.5 pg/mL-132.7 ± 49.7 pg/mL; P < 0.001; AUC 0-180 : 51.5 ± 23.3 pg/mL.min −1 -91.1 ± 32.2 pg/mL.min −1 P < 0.001), but not after diet (peak: 85.5 ± 51.9 pg/ mL-84.8 ± 41.13 pg/mL; P = NS; AUC 0-180 : 68.3 ± 38.5 pg/mL.min −1 -61.1 ± 42.2 pg/mL.min −1 P = NS). Fasting ghrelin levels increased after diet (425 ± 91 pg/mL-519 ± 105 pg/mL; P < 0.05), but did not change after GBP (506 ± 121 pg/mL-482 ± 196 pg/mL; P = NS).Conclusions-Diabetes status seems to be a determinant of PYY 3-36 levels. GBP, but not dietinduced weight loss, resulted in markedly increased glucose-stimulated PYY 3-36 levels. The increase in stimulated PYY 3-36 levels after GBP is likely a result of the surgery rather than a secondary outcome of weight loss. Changes in PYY 3-36 levels and ghrelin could contribute to the success of GBP in sustaining weight loss.Weight loss by diet is often of small magnitude and difficult to sustain over time. On the contrary, bariatric surgery, particularly Roux-en-Y gastric bypass (GBP), typically results in loss of 50% excess body weight within the first year, and the effect is often sustained at 10 years. The rapid and dramatic resolution of type 2 diabetes mellitus (T2DM) after GBP has led to the hypothesis that some of the metabolic effects of the surgery may be independent of weight loss1 -3 and may be related to the changes in incretins, gut hormones that stimulate insulin secretion.4 , 5 The mechanisms by which GBP suppresses appetite are not clear. The NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript marked increase in levels of 2 anorexigenic hormones, peptide YY (PYY),6 -10 and glucagonlike peptide 1 (GLP-1),4 , 7 could explain the increased satiety after GBP. A greater PYY release is associated with greater weight loss after GBP11 and weight regain has been shown with lower PYY levels in a rodent model.12 Previous reports on change in PYY levels after diet intervention are scarce, report only fasting levels, and are inconsistent. 13,14 The gastric hormone ghrelin may also be implicated in meal-to-meal regulation.15 Its levels increase in anticipation of a meal and decrease after feeding, suggesting a role in short-term meal-to-meal regulation. 16 Ghrelin levels vary a...

Roux-en-Y gastric bypass: effects on feeding behavior and underlying mechanisms

“…The gut hormone system has been extensively investigated in relation to the physiological changes induced by RYGBP (56). In particular, there is now a well-established body of research documenting markedly increased meal-stimulated peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) levels after RYGBP (57)(58)(59)(60)(61)(62)(63)(64)(65)(66). The enhanced gut hormone responses occur as early as one or two days after RYGBP independent of weight loss per se (67), thus implicating a process directly related to the procedure itself.…”

Bariatric surgery and obesity: influence on the incretins

“…[33][34][35] RYGBP surgical procedure involves the creation of a small gastric pouch (~30 ml) and a gastrojejunal anastomosis, resulting in the shunting of the larger part of the stomach, pylorus, duodenum and upper jejunum from ingested food. Gastric emptying of liquid is accelerated after RYGBP 33,36-38 and GLP-1 peak levels correlate positively with measures of gastric pouch emptying.…”

Metabolic surgery—principles and current concepts

“…Because of the ultradian rhythm of ghrelin release, the time points for ghrelin measurements seem to be very important, since fasting levels, early postprandial, and late postprandial levels differ a lot. In addition, the missing spike of ghrelin release before meals mentioned in the study by Cummings could not consistently be reproduced in other studies [55,56,[111][112][113][114]. A confounding issue in comparing studies is the patients' actual state of energy homeostasis, whether patients are in phases of weight loss (patients being in a catabolic state) vs. the phases of a steady-state after weight loss 1-2 years after bariatric surgery vs. "failures" without any weight loss or regaining weight.…”