Mechanisms behind the immediate effects of Roux-en-Y gastric bypass surgery on type 2 diabetes

Long-Term Weight Outcome After Bariatric Surgery in Patients with Melanocortin-4 Receptor Gene Variants: a Case-Control Study of 105 Patients

INTRODUCTION

Pathogenic heterozygous MC4R variants are associated with hyperphagia and variable degrees of obesity. Several research groups have reported short-term weight loss outcomes after bariatric surgery in a few patients with MC4R variants, but lack of longer-term data prevents evidence-based clinical decision-making.

MATERIALS AND METHODS

Bariatric surgery patients with heterozygous (likely) pathogenic MC4R variants, from three collaborating centers in the Netherlands, France, and the UK, were compared to matched controls (matched 2:1 for age, sex, preoperative BMI, surgical procedure, and diabetes mellitus, but without MC4R mutations). Weight loss and regain outcomes up to 6 years of follow-up were compared.

RESULTS

At 60 months of follow-up after RYGB, cases with MC4R variants showed weight regain with a mean of 12.8% (± 10.4 SD) total weight loss (TWL) from nadir, compared to 7.9% (± 10.5 SD) in the controls (p = 0.062). Among patients receiving SG, the cases with MC4R variants experienced inferior weight loss (22.6% TWL) during the first year of follow-up compared to the controls (29.9% TWL) (p = 0.010).

CONCLUSIONS

This multicenter study reveals inferior mid-term weight outcomes of cases with MC4R variants after SG, compared to RYGB. Since adequate weight loss outcomes were observed after RYGB, this procedure would appear to be an appropriate surgical approach for this group. However, the pattern of weight regain seen in cases with MC4R variants after both RYGB and SG highlights the need for pro-active lifelong management to prevent relapse, as well as careful expectation management.

Distal gastric mucosa ablation induces significant weight loss and improved glycemic control in type 2 diabetes Sprague-Dawley rat model

BACKGROUND

Excluding the foregut (distal stomach and duodenum) from food transit in RYGB normalizes glucose tolerance. Excluding/removing the duodenal mucosa partly improves glycemic control. So far, the effect of excluding/removing the gastric mucosa remains unknown.

OBJECTIVE

To observe the effect of removing the distal gastric mucosa on glucose tolerance.

METHOD

Thirty fatty Sprague-Dawley rats received low-dose streptozotocin (STZ) to induce type 2 diabetes (T2D), then randomly assigned to Roux-en-Y gastric bypass (RYGB, n = 8), distal gastric mucosa removal (DGMR, n = 8), duodenal-jejunal bypass (DJB, n = 8), and Sham (n = 6) groups. In the DGMR group, the distal third of the gastric mucosa was removed by thermal ablation using an electrocautery. Rats were followed for 8 weeks postoperatively. Preoperative oral glucose tolerance test (OGTT), insulin tolerance test (ITT), and mixed-meal tolerance test (MMTT) were repeated 3 and 6 weeks postoperatively. Changes in body weight, food intake, and fasting blood glucose were also recorded.

RESULTS

Gastrin AUC decreased significantly (p < 0.05) in the DGMR group after surgery. A significantly increased GLP-1 AUC was found in the RYGB, DGMR, and DJB groups at week 3 and only the RYGB group at week 6 postoperatively. The improved glucose tolerance in the RYGB group was significantly greater than the improved glucose tolerance in the DGMR and DJB groups. The improved glucose tolerance 3 and 6 weeks after surgery in the DGMR group was significantly greater than the improved glucose tolerance in the DJB group. Body weight decreased significantly in the RYGB, DGMR, and DJB groups postoperatively.

CONCLUSION

Removing the distal gastric mucosa induced significant weight loss and improved glycemic control in T2D SD rat model. Therefore, the gastric mucosa exclusion in RYGB may be key to the weight loss and diabetes remission, which perhaps warrants a new theory.

Roux-en-Y Gastric Bypass Surgery Has Early Differential Effects on Bile Acids and the Levels of Complement Component 3 and Acylation-Stimulating Protein

BACKGROUND

Bile acids have been implicated in the mechanism by which Roux-en-Y gastric bypass (RYGB) can induce remission of type 2 diabetes (T2D). Our goal was to identify circulating proteins whose levels changed after RYGB when dysglycemic parameters normalized.

MATERIALS AND METHODS

This was a retrospective study of 26 participants who underwent RYGB. Blood proteins were identified using two-dimensional electrophoresis and mass spectroscopy. Complement proteins were measured using immunoassays and bile acids measured using ultra-high-performance liquid chromatography and mass spectroscopy.

RESULTS

A total of 7/452 blood proteins were found to change 2 days after RYGB. Complement component 3 (C3) was selected because of its regulation by bile acids and the glucoregulatory function of its proteolytically processed product C3adesArg or acylation-stimulating protein (ASP). The median (inter-quartile range/IQR) C3 level was 47.4 (34.5, 65.9) mg/dL before surgery decreasing to 40.9 (13.4, 64.1) mg/dL within 2 days after surgery (p = 0.0292). The median (IQR) ASP level increased from 2.8 (0.9, 7.3) nM before surgery to 8.0 (5.3, 14.1) nM within 2 days after surgery (p = 0.0016). ASP levels increased in 14/17 (82%) with T2D remission and in 6/6 with normoglycemia but decreased in 3/3 with persistent T2D. Of ten bile acids measured, the levels of ursodeoxycholic acid (UDCA) were significantly decreased after RYGB and the levels of taurodeoxycholic acid (TDCA) were significantly decreased with T2D remission.

CONCLUSIONS

These data further support an association of C3 with glucose metabolism and implicate bile acids and ASP in the early remittive effects of RYGB on T2D.

A retrospective case control study identifies peripheral blood mononuclear cell albumin RNA expression as a biomarker for non-alcoholic fatty liver disease

PURPOSE

Non-alcoholic fatty liver disease (NAFLD) improves after bariatric surgery. The aim of this study was to determine whether peripheral blood mononuclear cell albumin gene expression was related to NAFLD and whether albumin (ALB) and alpha fetoprotein (AFP) expression could be detected in whole blood and visceral adipose tissue.

METHODS

Using a retrospective case control study design, RNA isolated from peripheral blood mononuclear cells from patients prior to undergoing bariatric surgery was used for pooled microarray analysis. Quantitative polymerase chain reaction (QPCR) was used to analyze whole blood and visceral adipose tissue. Liver histology was obtained via intra-operative biopsy and clinical data extracted from the electronic health record.

RESULTS

The albumin (ALB) gene was the second most up-regulated found in microarray analysis of peripheral blood mononuclear cell RNA from patients with hepatic lobular inflammation versus normal liver histology. Transcript levels of ALB were significantly different across those with normal (n = 50), steatosis (n = 50), lobular inflammation (n = 50), and peri-sinusoidal fibrosis (n = 50) liver histologies, with lobular inflammation 3.9 times higher than those with normal histology (p < 0.017). Albumin expression levels decreased in 11/13 patients in paired samples obtained prior to and at 1 year after Roux-en-Y gastric bypass surgery. ALB expression could be detected in 23 visceral adipose tissue samples obtained intra-operatively and in 18/19 available paired whole blood samples. No significant correlation was found between ALB expression in visceral adipose tissue and whole blood RNA samples. Alpha fetoprotein expression as a marker of early hepatocytic differentiation was detected in 17/17 available VAT RNA samples, but in only 2/17 whole blood RNA samples.

CONCLUSION

Albumin RNA expression from blood cells may serve as a biomarker of NAFLD. Albumin and alpha fetoprotein appear to be ubiquitously expressed in visceral adipose tissue in patients with extreme obesity.

Long-Term Outcomes of Three Types of Bariatric Surgery on Obesity and Type 2 Diabetes Control and Remission

BACKGROUND

Different bariatric surgeries have demonstrated different effectiveness for weight loss and glucose control in obese persons with diabetes, over a short follow-up time. The aim of this study was to compare weight loss, glucose control, and diabetes remission in individuals with type 2 diabetes, after three types of bariatric surgery: gastric banding (GB), sleeve gastrectomy (SG), and Roux-en-Y gastric bypass (RYGB), with 5 years follow-up.

METHODS

A retrospective study was conducted on bariatric surgeries performed during 2002-2011 in a large nationwide healthcare organization.

RESULTS

Of 2190 patients, 64.8 % were women. The operations performed were 1027 GB, 1023 SG, and 140 RYGB. Mean BMI ± SD at baseline, 1 year postoperatively, and 5 years postoperatively were 43.5 ± 6.18, 37.1 ± 6.35, and 35.5 ± 6.48 for GB; 43.6 ± 6.42, 34.4 ± 6.08, and 35.3 ± 6.7 for SG; and 42.8 ± 5.81, 32.8 ± 4.9, and 34.1 ± 5.09 for RYGB. Mean HbA1c ± SD at baseline, 1 year postoperatively, and 5 years postoperatively were 7.6 + 1.58, 6.5 + 1.22, and 6.8 + 1.48 for GB; 7.7 + 1.63, 6.4 + 1.18, and 6.7 + 1.57 for SG; and 8.0 + 1.78, 6.3 + 0.98, and 7.04 + 1.42 for RYGB. At 1 year follow-up, 53.2 % had achieved remission; at 5 years, 54.4 %. Remission rates at 5 years were similar for the three surgeries. Five-year remission was inversely associated with baseline HbA1c and with treatment with insulin at baseline and positively associated with BMI.

CONCLUSIONS

For all three surgeries, diabetes remission was higher than the baseline after 5 years; mean BMI and HbA1c decreased considerably during the first year postoperatively and remained lower than basal values throughout follow-up. Early improvements were greatest for RYGB, though the advantage over the other operations diminished with time.

The Mechanism of Metabolic Surgery: Gastric Center Hypothesis

BACKGROUND

There is growing evidence that bariatric surgery can lead to remission of metabolic syndrome. But the mechanism by which bariatric surgery alleviates metabolic syndrome is unclear.

MATERIALS AND METHODS

Several present hypotheses which include decreased caloric intake following the surgeries, foregut and hindgut hypothesis, bile acid and bacterial flora changes, and proposed gastric center hypothesis were discussed.

RESULTS

None of the currently available hypotheses is solely capable to lead to a reasonable explanation regarding improvement of metabolic syndrome by various bariatric surgical procedures. Proposed gastric center hypothesis could give a better explanation of the mechanism.

CONCLUSIONS

All the present bariatric surgeries are involved in changes of the stomach. There could be some particular cells on the stomach, which could secrete unknown special hormones, and then lead to control the metabolic process.

The gut in the brain: the effects of bariatric surgery on alcohol consumption

Obesity represents a major medical and public health problem worldwide. Efforts have been made to develop novel treatments, and among them bariatric surgery is used as an effective treatment to achieve significant, long-term weight loss and alleviate medical problems related to obesity. Alcohol use disorder (AUD) is also a leading cause of morbidity and mortality worldwide. Recent clinical studies have revealed a concern for bariatric surgery patients developing an increased risk for alcohol consumption, and for AUD. A better understanding of the relationship between bariatric surgery and potential later development of AUD is important, given the critical need of identifying patients at high risk for AUD. This paper reviews current clinical and basic science research and discusses potential underlying mechanisms. Special emphasis in this review is given to recent work suggesting that, alterations in alcohol metabolism/pharmacokinetics resulting from bariatric surgery are unlikely to be the primary or at least the only explanation for increased alcohol use and development of AUD, as changes in brain reward processing are also likely to play an important role. Additional studies are needed to clarify the potential role and mechanisms of how bariatric surgery may increase alcohol use and lead to AUD development.

Using genetics to inform new therapeutics for diabetes

The genetic architecture of diabetes has been extensively studied. Numerous genetic markers for diabetes have been reported. However, the translation of such knowledge into clinical interventions has been inadequate. Areas covered: We performed a literature search on various frontiers in diabetes treatment that could be improved using genetic information: (1) understanding the mechanisms of existing antidiabetic drugs, (2) repurposing existing drugs for the treatment of diabetes, (3) complementing clinical trial findings; (4) finding novel treatment approaches; (5) better estimation of the efficacy of metabolic surgery. Expert commentary: The translation of genetic information to clinical intervention requires further study, including the development of an appropriate genetic risk score algorithm for type 2 diabetes. Genomic studies provide empirical explanations for clinical trial findings. Moreover, the mechanisms of antidiabetic drugs should be thoroughly investigated to enable clinical trials and pharmacogenomics studies of these drugs. As metabolic surgery becomes more prevalent for the treatment of diabetes, genetic approaches may improve patient prioritization.

Obesity coverage gap: Consumers perceive low coverage for obesity treatments even when workplace wellness programs target BMI

OBJECTIVE

Evidence-based obesity treatments, such as bariatric surgery, are not considered essential health benefits under the Affordable Care Act. Employer-sponsored wellness programs with incentives based on biometric outcomes are allowed and often used despite mixed evidence regarding their effectiveness. This study examines consumers' perceptions of their coverage for obesity treatments and exposure to workplace wellness programs.

METHODS

A total of 7,378 participants completed an online survey during 2015-2016. Respondents answered questions regarding their health coverage for seven medical services and exposure to employer wellness programs that target weight or body mass index (BMI). Using χ² tests, associations between perceptions of exposure to employer wellness programs and coverage for medical services were examined. Differences between survey years were also assessed.

RESULTS

Most respondents reported they did not have health coverage for obesity treatments, but more of the respondents with employer wellness programs reported having coverage. Neither the perception of coverage for obesity treatments nor exposure to wellness programs increased between 2015 and 2016.

CONCLUSIONS

Even when consumers have exposure to employer wellness programs that target BMI, their health insurance often excludes obesity treatments. Given the clinical and cost-effectiveness of such treatments, reducing that coverage gap may mitigate obesity's individual- and population-level effects.

Genetics of Bariatric Surgery Outcomes

Outcomes after bariatric surgery can vary widely and seem to have a significant genetic component. Only a small number of candidate gene and genome-wide association studies have analyzed bariatric surgery outcomes. The role of bile acids in mediating the beneficial effects of bariatric surgery implicate genes regulated by the farnesoid X receptor transcription factor.

Improvements in glycemic control after gastric bypass occur despite persistent adipose tissue inflammation

OBJECTIVE

Type 2 diabetes commonly goes into remission following Roux-en-Y gastric bypass (RYGB). As the mechanisms remain incompletely understood, a reduction in adipose tissue inflammation may contribute to these metabolic improvements. Therefore, whether RYGB reduces adipose tissue inflammation compared with equivalent weight loss from an intensive lifestyle intervention was investigated.

METHODS

Sixteen people with obesity and type 2 diabetes were randomized to RYGB or lifestyle intervention. Fasting blood and subcutaneous abdominal adipose tissue were obtained before and after the loss of ∼7% of baseline weight. Adipose tissue inflammation was assessed by whole-tissue gene expression and flow cytometry-based quantification of tissue leukocytes.

RESULTS

At 7% weight loss, insulin and metformin use were reduced among the RYGB but not the Lifestyle cohort, while fasting glucose and insulin declined in both. Adipose tissue inflammation increased modestly after RYGB and to a similar extent following nonsurgical weight loss. In both groups, the number of neutrophils increased severalfold (P < 0.001), mRNA levels of the proinflammatory cytokine interleukin-1β increased (P = 0.037), and mRNA expression of the anti-inflammatory and insulin-sensitizing adipokine adiponectin decreased (P = 0.010).

CONCLUSIONS

A reduction in adipose tissue inflammation is not one of the acute weight loss-independent mechanisms through which RYGB exerts its antidiabetes effects.

Effectiveness and safety of laparoscopic Roux-en-Y gastric bypass for the treatment of type 2 diabetes mellitus

Gastric bypass may be conducted to aid in glycemic control in adults with type 2 diabetes mellitus (T2DM). The aim of the present study was to investigate the clinical results of diabetes remission and metabolic syndrome in individuals with T2DM after undergoing a gastric bypass. A total of 85 patients (39 men and 46 women) with T2DM underwent laparoscopic Roux-en-Y gastric bypass (LRYGB). Data regarding patient demographics, body mass index (BMI), co-morbidities and details of diabetes mellitus, including disease duration, remission, β-cell function, blood lipid levels and nutritive status were prospectively collected and analyzed. The mean duration from the onset of T2DM was 7.79±4.84 years (range, 1 month to 22 years). The preoperative mean BMI was 31.60±4.10 (range, 28.53–48.10 kg/m²), mean percentage of body fat was 36.35±9.12% (range, 18–56%), and the mean HbA1c was 8.32±2.13% (range, 7–15.9%). Five patients (5.9%) developed complications without mortality. T2DM and β-cell function were significantly improved from by month 6 after surgery (P<0.05). Improvements in central obesity, blood pressure (BP; systolic and diastolic) control, blood lipid levels were observed, without malnutrition or severe anemia. Therefore, the present results indicate that laparoscopic RYGBP is a safe and effective procedure for improving glycemic control, obesity, body fat percentage and BP in patients with T2DM and obesity.

Bile Acids, FXR, and Metabolic Effects of Bariatric Surgery

Overweight and obesity represent major risk factors for diabetes and related metabolic diseases. Obesity is associated with a chronic and progressive inflammatory response leading to the development of insulin resistance and type 2 diabetes (T2D) mellitus, although the precise mechanism mediating this inflammatory process remains poorly understood. The most effective intervention for the treatment of obesity, bariatric surgery, leads to glucose normalization and remission of T2D. Recent work in both clinical studies and animal models supports bile acids (BAs) as key mediators of these effects. BAs are involved in lipid and glucose homeostasis primarily via the farnesoid X receptor (FXR) transcription factor. BAs are also involved in regulating genes involved in inflammation, obesity, and lipid metabolism. Here, we review the novel role of BAs in bariatric surgery and the intersection between BAs and immune, obesity, weight loss, and lipid metabolism genes.

GLP-1: a mediator of the beneficial metabolic effects of bariatric surgery?

There has been increasing interest in the role that gut hormones may play in contributing to the physiological changes produced by certain bariatric procedures, such as Roux-en-Y gastric bypass and sleeve gastrectomy. Here, we review the evidence implicating one such gut hormone, glucagon-like peptide-1, as a mediator of the metabolic benefits of these two procedures.

Long-term effects of laparoscopic sleeve gastrectomy versus roux-en-Y gastric bypass for the treatment of Chinese type 2 diabetes mellitus patients with body mass index 28-35 kg/m(2)

Background

To compare long term effects of two bariatric procedures for Chinese type 2 diabetes mellitus (T2DM) patients with a body mass index (BMI) of 28-35 kg/m².

Methods

Sixty four T2DM patients with Glycated hemoglobin A1c (HbA1c) ≧ 7.0 % were randomly assigned to receive laparoscopic sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) procedure. Weight, percentage of excess weight loss (%EWL), BMI, waist circumference, HbA1c, fasting blood glucose (FBG), and C-peptide were measured. Serum lipid levels were also measured during three-year postoperative follow-up visits.

Results

Fifty five patients completed the 36-month follow-up. Both groups had similar baseline anthropometric and biochemical measures. At the end point, 22 patients (78.6 %) in SG group and 23 patients (85.2 %) in RYGB group achieved complete remission of diabetes mellitus with HbA1c < 6.0 % (P = 0.525) and without taking diabetic medications, and 25 patients in each group (89.3 % vs. 92.6 %) gained successful treatment of diabetes with HbA1c≦6.5 % (P = 0.100). Change in HbA1c, FBG and C peptide were comparable in the two groups. The RYGB group had significantly greater weight loss than the SG group [percentage of total weight loss (%TWL) of 31.0 % vs. 27.1 % (P = 0.049), %EWL of 92.3 % vs. 81.9 % (P = 0.003), and change in BMI of 11.0 vs. 9.1 kg/m²(P = 0.017), respectively]. Serum lipids in each group were also greatly improved.

Conclusion

In this three-year study, SG had similar positive effects on diabetes and dyslipidemia compared to RYGB in Chinese T2DM patients with BMI of 28-35 kg/m². Longer term follow-ups and larger sample studies are needed to confirm these outcomes, however.

Five-year outcome of bariatric surgery in a patient with melanocortin-4 receptor mutation

Monogenic obesity is characterized by mutations in genes involved in the central regulation of food intake. Melanocortin-4 receptor (MC4R) mutations are the most frequent monogenic cause of severe early onset human obesity. Although bariatric surgery is the most effective therapy for idiopathic morbid obesity in adults, little is known about its effectiveness in patients with monogenic obesity syndromes. We report 5-year outcome of gastric bypass surgery in a young man with severe super-obesity associated with MC4R mutation. A 22-year-old man with a weight of 221.6 kg and body mass index of 76.7 kg m(-2) associated with a heterozygous MC4R mutation was referred to our centre for bariatric surgery. He underwent Roux-en-Y gastric bypass (RYGB) surgery and achieved weight loss of 76% of excess weight over a follow-up period of 58 months. Heterozygous MC4R mutations have been associated with dominantly inherited obesity in various ethnic groups, and non-surgical interventions are rarely effective in the long term. One previous report of bariatric surgery in a patient with complete MC4R deficiency reported poor weight loss after gastric banding. We speculate that patients with MC4R mutations achieve superior weight loss outcomes from procedures such as RYGB that produce neurohormonal changes rather than gastric restriction alone due to beneficial effects on appetite and satiety regulation.

Laparoscopic Roux-en-Y gastric bypass for nonobese type II diabetes mellitus in Asian patients

BACKGROUND

The beneficial role of laparoscopic Roux-en-Y gastric bypass (LRYGB) for type 2 diabetes mellitus (T2 DM) in morbidly obese patients has been established; however, there is scant evidence supporting its effectiveness in nonobese T2 DM Asian patients. The objective of this study was to evaluate the effect of LRYGB in nonobese T2 DM patients and elucidate the predictors of DM remission after one year follow-up.

METHODS

Between June 2009 and May 2011, twenty-nine nonobese (body mass index (BMI)<27 kg/m(2)) Asian patients with T2 DM who underwent LRYGB were enrolled. All patients were prospectively followed up for one year. Baseline demographic characteristics, diabetic status, and clinical and biochemical data were collected preoperatively and one year after LRYGB. DM remission was defined as those with hemoglobin A1 c (HbA1 c)<6.5% without oral hypoglycemic drugs (OHA)/insulin. Outcomes in the DM remission group were compared with the nonremission group and analyzed.

RESULTS

All clinical and biochemical parameters, except uric acid, were significantly improved. DM remission was achieved in eleven patients (37.9%) of whom five (45.5%) were male. Blood glucose, HbA1 c, c-peptide, homeostatic model assessment (HOMA-%B), and low density lipoprotein (LDL)-cholesterol were the significant variables in patients with DM remission; however, multiple logistic regression showed that only preoperative HOMA-%B (odds ratio (OR) = 1.13, 95% CI = 1.03-1.24) was a predictor for DM remission. Though no mortality was seen, the complication rate was 20.7%, of which 17.3% was related to marginal ulcers.

CONCLUSION

LRYGB resulted in significant clinical and biochemical improvements in nonobese Asian patients, with HOMA-%B indicating β-cell function as the main predictor of T2 DM remission. Appropriate patient selection with better β-cell function and evidence from long-term follow-up may justify this therapeutic approach.