Metabolic surgery in diabetes
Bariatric surgery: Prevalence, predictors, and mechanisms of diabetes remission
This paper describes the potential mechanisms by which bariatric surgery, in particular Roux-en-Y gastric bypass surgery, leads to diabetes remission.
| Summary points |
- Currently available evidence suggests that Roux-en-Y gastric bypass (RYGB) surgery is the most effective treatment for achieving remission in diabetes.
- Potential mechanisms for diabetes remission following RYGB surgery include involvement of enterohepatic pathways, central pathways controlling energy balance, and the gut microbiota.
- Enterohepatic pathways, such as the fibroblast growth factor (FGF) 19 – cholesterol 7 alpha-hydroxylate 1 (CYP7A1) bile acid pathway, may be involved in diabetes remission following RYGB surgery. This may be via secretion of bile acids from the gallbladder into the now empty duodenum, giving ‘digestate-free’ bile acids, which may be more bioactive, with more potent stimulation of FGF 19 and potentially also of glucagon-like peptide 1 (GLP-1) production.
- Changes in the microbiome have been reported to occur following RYGB surgery, with metagenomic sequencing before and 3 months after RYGB revealing changes in the bacteria species composition of the gut microbiome.
- Currently available data suggest that weight loss following RYGB is unlikely to be a major contributing factor to diabetes remission.
- A simple mathematic tool, the DiaRem score, has been developed for predicting the probability that RYGB will result in diabetes remission in a patient.
- While current understanding of diabetes remission remains incomplete, it is encouraging that RYGB surgery leads to remission in the majority of patients.
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Argyropoulos G. Curr Diab Rep 2015; 15: 15. doi: 10.1007/s11892-015-0590-9
Role of the gut on glucose homeostasis: Lesson learned from metabolic surgery
This review summarizes findings from relevant randomized controlled trials investigating the impact of bariatric surgery on metabolic outcomes, and examines the role of the small intestine in driving such effects.
| Summary points |
- Randomized controlled trials support the use of bariatric surgery, particularly Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion (BPD), for the treatment of type 2 diabetes mellitus, independent of baseline body mass index.
- The three major surgical procedures are RYBG (stomach remnant 30mL), BPD (stomach remnant 400mL) and sleeve gastrectomy (stomach remnant 100mL). Sleeve gastrectomy does not bypass the intestine, whereas in RYGB, the duodenum and first portion of the jejunum is bypassed, and in BPD, the duodenum, entire jejunum and the first portion of the ileum are excluded from food transit.
- RYGB has been shown to be associated with increased insulin secretion and reduced hepatic glucose production, whereas BPD is associated with reduced insulin secretion, due to rapid normalization of insulin sensitivity.
- Regulation of blood glucose concentration is achieved via a number of mechanisms, many of which involve the small intestine, including gastric emptying, glucose absorption and insulin secretion.
- Proposed mechanisms by which bariatric surgery influences the role of the small intestine in glucose regulation include changes in gastric emptying, alterations in glucose absorption and nutrient sensing, incretin-mediated effects, ghrelin-associated changes, and changes in the gut microbiota.
- The small intestine plays a primary role in glucose homeostasis - the jejunum senses nutrients and regulates glucose production, and the entire small intestine secretes both glucagon-like peptide-1 and glucose-dependent insulinotropic peptide, thereby enhancing insulin secretion. Manipulation of these regions in bariatric surgery has a substantial impact on these glucose-regulating actions.
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Kamvissi-Lorenz V et al. Curr Atheroscler Rep 2017; 19: 9. doi: 10.1007/s11883-017-0642-5
Evidence base for bariatric surgery
This chapter reviews the most common bariatric surgical procedures, with a focus on weight loss and remission of comorbidities, including type 2 diabetes mellitus.
| Summary points |
- In addition to treating obesity, bariatric surgery has been shown to reduce metabolic complications of obesity, such as type 2 diabetes mellitus (T2DM).
- There are many different bariatric procedures, associated with different levels of risk and differing efficacy. These include laparoscopic adjustable gastric banding, laparoscopic Roux-en-Y gastric bypass (LRYGB), gastroplasties, laparoscopic sleeve gastrectomy (LSG), laparoscopic mini-gastric bypass, and laparoscopic biliopancreatic diversion and duodenal switch surgery (BDP-DS).
- Of these surgery types, those that evoke metabolic changes in addition to weight loss due to reduced intake, are preferred in the treatment of diabetes. These include LRYGB, LSG, and BPD-DS.
- Elucidating the mechanisms involved in weight loss following bariatric surgery is an ongoing process, and it is now understood that to successfully treat obesity, a multidisciplinary approach is needed.
- Evidence for the role of bariatric surgery in the management of morbidly obese patients with T2DM comes primarily from meta-analyses and cohort studies, but recently, two randomized controlled trials (the STAMPEDE trial from the USA and a single center study in Italy) have provided level I evidence for the role of bariatric surgery in the treatment of T2DM.
- In 2010, the International Diabetes Federation Taskforce on Epidemiology and Prevention of Diabetes established guidelines for the role of bariatric surgery in patients with T2DM, recommending bariatric surgery in patients with a body mass index (BMI) ≥35 kg/m2, and in patients with a BMI of 30–35 kg/m2 with poorly controlled diabetes despite appropriate lifestyle changes and pharmacotherapy.
- Surgery is not the answer for all patients, but should be considered as an option by those involved in the care of obese and diabetic patients.
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Leuratti L, Khwaja HA, Kerrigan DD. In: Obesity, bariatric and metabolic surgery: A practical guide. Edited by Agrawal S. Springer International Publishing, 2015. doi: 10.1007/978-3-319-04343-2_7