Remission of Type 2 Diabetes after Gastric Bypass and Banding: Mechanisms and 2 Year Outcomes

Dimitrios J. Pournaras, MRCS; Alan Osborne, MRCS; Simon C. Hawkins, MRCS; Royce P. Vincent, MSc; David Mahon, MD, FRCS; Paul Ewings, PhD; Mohammad A. Ghatei, PhD; Stephen R. Bloom, FRCP, DSc; Richard Welbourn, MD, FRCS; Carel W. le Roux, MRCP, PhD

Disclosures

Annals of Surgery. 2010;252(6):966-971. 

In This Article

Abstract and Introduction

Abstract

Objective: To investigate the rate of type 2 diabetes remission after gastric bypass and banding and establish the mechanism leading to remission of type 2 diabetes after bariatric surgery.
Summary Background Data: Glycemic control in type 2 diabetic patients is improved after bariatric surgery.
Methods: In study 1, 34 obese type 2 diabetic patients undergoing either gastric bypass or gastric banding were followed up for 36 months. Remission of diabetes was defined as patients not requiring hypoglycemic medication, fasting glucose below 7 mmol/L, 2 hour glucose after oral glucose tolerance test below 11.1 mmol/L, and glycated haemoglobin (HbA1c) <6%. In study 2, 41 obese type 2 diabetic patients undergoing either bypass, banding, or very low calorie diet were followed up for 42 days. Insulin resistance (HOMA-IR), insulin production, and glucagon-like peptide 1 (GLP-1) responses after a standard meal were measured.
Results: In study 1, HbA1c as a marker of glycemic control improved by 2.9% after gastric bypass and 1.9% after gastric banding at latest follow-up (P < 0.001 for both groups). Despite similar weight loss, 72% (16/22) of bypass and 17% (2/12) of banding patients (P = 0.001) fulfilled the definition of remission at latest follow-up. In study 2, within days, only bypass patients had improved insulin resistance, insulin production, and GLP-1 responses (all P < 0.05).
Conclusions: With gastric bypass, type 2 diabetes can be improved and even rapidly put into a state of remission irrespective of weight loss. Improved insulin resistance within the first week after surgery remains unexplained, but increased insulin production in the first week after surgery may be explained by the enhanced postprandial GLP-1 responses.

Introduction

Type 2 diabetes mellitus is exponentially increasing because of the current epidemic of obesity. Both these lethal conditions threaten to overwhelm healthcare resources.[1] The most effective treatment for both type 2 diabetes and obesity is metabolic surgery.[2,3] The 2 most commonly performed metabolic surgery operations are the Roux-en-Y gastric bypass described in 1967 and laparoscopic gastric banding described in 1993.[4] The vast improvement in glycemic control and the concept of remission of type 2 diabetes after metabolic surgery has been established, but the underlying mechanism remains unclear.[3,5]

A meta-analysis reported improved glycemic control and remission of type 2 diabetes in 83.8% of patients following gastric bypass and 47.8% following gastric banding.[3,6,7] However, data comparing the 2 operations in the same center are limited, and definitions of remission are inconsistent between studies. The likely reasons for this include strong surgeon, patient or cultural preference for one procedure over another. This may explain the lack of published randomized controlled studies comparing different types of operations.

The improved glycemic control after gastric banding depends on weight loss, but after gastric bypass surgery this improvement occurs before weight loss. Two mechanisms have been proposed to explain this rapid normalization of glucose control after gastric bypass. The first suggests that exclusion of the duodenum and proximal jejunum may reduce insulin resistance.[8,9] The second involves exaggerated responses from the distal small bowel to nutrients. In the latter hypothesis, gut hormones produced in the distal small bowel such as glucagon-like peptide 1 (GLP-1) may act as incretins stimulating the beta cells in the pancreas to restore normal first phase insulin responses.[10]

We aimed to investigate the improved glycemic control and rate of remission of type 2 diabetes after gastric bypass and gastric banding in a homogeneous population, using the same method for assessment after each operation. Moreover, to explore potential mechanisms, we measured changes in insulin resistance and insulin production in the first week after surgery to test the hypothesis that GLP-1 contributes to the improved glycemic control.

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