Metabolic surgery: shifting the focus from glycaemia and weight to end-organ health

Weight loss, bariatric surgery, and novel antidiabetic drugs effects on diabetic retinopathy: a review

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a leading cause of visual impairment, and the increasing prevalence of diabetes and obesity will impact rates of visual impairment moving forward. Our review aims to synthesize the current body of evidence regarding the impact of lifestyle interventions, such as weight loss, bariatric surgery, and novel antidiabetic drugs, on DR.

RECENT FINDINGS

Literature review revealed insufficient evidence regarding the impact of weight loss on DR. Preoperative DR patients undergoing bariatric surgery were found to have similar short-term chances of improvement or worsening DR. Progression of DR with glucagon-like peptide 1 receptor agonists treatments appears unrelated to specific drugs and was also observed with traditional antidiabetic medications.

SUMMARY

Rapidly correcting HbA1c levels (≥2%) can paradoxically lead to early worsening DR. Patients considering weight loss, bariatric surgery, and novel antidiabetic drugs should be aware of the potential for DR progression, but they should not be discouraged, as achieving glycemic control is essential for reducing long-term morbidity and mortality from other diabetes-related complications. It is advisable to conduct a baseline retinal examination before treatment and continue monitoring during therapy. Further research is needed to understand the long-term effects of these treatments on DR.

Lipid metabolic reprogramming mediated by circulating Nrg4 alleviates metabolic dysfunction-associated steatotic liver disease during the early recovery phase after sleeve gastrectomy

BACKGROUND

The metabolic benefits of bariatric surgery that contribute to the alleviation of metabolic dysfunction-associated steatotic liver disease (MASLD) have been reported. However, the processes and mechanisms underlying the contribution of lipid metabolic reprogramming after bariatric surgery to attenuating MASLD remain elusive.

METHODS

A case-control study was designed to evaluate the impact of three of the most common adipokines (Nrg4, leptin, and adiponectin) on hepatic steatosis in the early recovery phase following sleeve gastrectomy (SG). A series of rodent and cell line experiments were subsequently used to determine the role and mechanism of secreted adipokines following SG in the alleviation of MASLD.

RESULTS

In morbidly obese patients, an increase in circulating Nrg4 levels is associated with the alleviation of hepatic steatosis in the early recovery phase following SG before remarkable weight loss. The temporal parameters of the mice confirmed that an increase in circulating Nrg4 levels was initially stimulated by SG and contributed to the beneficial effect of SG on hepatic lipid deposition. Moreover, this occurred early following bariatric surgery. Mechanistically, gain- and loss-of-function studies in mice or cell lines revealed that circulating Nrg4 activates ErbB4, which could positively regulate fatty acid oxidation in hepatocytes to reduce intracellular lipid deposition.

CONCLUSIONS

This study demonstrated that the rapid effect of SG on hepatic lipid metabolic reprogramming mediated by circulating Nrg4 alleviates MASLD.

New mechanistic insights of anti-obesity by sleeve gastrectomy-altered gut microbiota and lipid metabolism

Background

The obesity epidemic has been on the rise due to changes in living standards and lifestyles. To combat this issue, sleeve gastrectomy (SG) has emerged as a prominent bariatric surgery technique, offering substantial weight reduction. Nevertheless, the mechanisms that underlie SG-related bodyweight loss are not fully understood.

Methods

In this study, we conducted a collection of preoperative and 3-month postoperative serum and fecal samples from patients who underwent laparoscopic SG at the First Affiliated Hospital of Shandong First Medical University (Jinan, China). Here, we took an unbiased approach of multi-omics to investigate the role of SG-altered gut microbiota in anti-obesity of these patients. Non-target metabolome sequencing was performed using the fecal and serum samples.

Results

Our data show that SG markedly increased microbiota diversity and Rikenellaceae, Alistipes, Parabacteroides, Bactreoidales, and Enterobacteraies robustly increased. These compositional changes were positively correlated with lipid metabolites, including sphingolipids, glycerophospholipids, and unsaturated fatty acids. Increases of Rikenellaceae, Alistipes, and Parabacteroide were reversely correlated with body mass index (BMI).

Conclusion

In conclusion, our findings provide evidence that SG induces significant alterations in the abundances of Rikenellaceae, Alistipes, Parabacteroides, and Bacteroidales, as well as changes in lipid metabolism-related metabolites. Importantly, these changes were found to be closely linked to the alleviation of obesity. On the basis of these findings, we have identified a number of microbiotas that could be potential targets for treatment of obesity.

Type 2 diabetes and metabolic surgery guidelines and recommendations should urgently be unified

Metabolic surgery has been studied in the last decades as an effective and safe treatment for type 2 diabetes (T2D), and randomized controlled trials generally found surgery superior when compared with medical treatment. In 2016, the DSS-II Joint Statement recognized the importance of metabolic surgery in the treatment of T2D and urged clinicians to discuss, recommend, or at least consider this procedure for their patients. Diabetes societies also cogitate metabolic surgery as an option for T2D patients in their guidelines. However, there are some differences in recommendations that could lead a careful reader to some confusion. This was potentialized in a recent document published by the same DSS-II group concerning prioritization for surgery after the COVID-19 pandemic, in which the criteria suggested for an expedited recommendation that is not exactly evidence-based, and collided substantially with several clinical guidelines worldwide, especially with regard to secondary prevention of cardiovascular disease. A more harmonious discussion and unified guidelines between clinicians and surgeons are needed in order to provide the same message for those who read different articles.

Metabolic Surgery: Weight Loss, Diabetes, and Beyond

The alarming rise in the worldwide prevalence of obesity is paralleled by an increasing burden of type 2 diabetes mellitus. Metabolic surgery is the most effective means of obtaining substantial and durable weight loss in individuals with obesity. Randomized trials have recently shown the superiority of surgery over medical treatment alone in achieving improved glycemic control, as well as a reduction in cardiovascular risk factors. The mechanisms seem to extend beyond the magnitude of weight loss alone and include improvements in incretin profiles, insulin secretion, and insulin sensitivity. Moreover, observational data suggest that the reduction in cardiovascular risk factors translates to better patient outcomes. This review describes commonly used metabolic surgical procedures and their current indications and summarizes the evidence related to weight loss and glycemic outcomes. It further examines their potential effects on cardiovascular outcomes and mortality and discusses future perspectives.

Metabolic surgery for the treatment of type 2 diabetes in patients with BMI lower than 35 kg/m2 : Why caution is still needed

Bariatric surgery has shifted from being a risky procedure to an evidence-based one, with proven benefits on all-cause mortality, cardiovascular disease, cancer, and diabetes control. The procedure has an overall positive result on type 2 diabetes mellitus (T2DM), with a substantial number of patients achieving disease remission. This has resulted in several studies assessing possible weight-independent effects of bariatric surgery on glycemic improvement, in addition to recommendation of the procedure to patients with class 1 obesity and T2DM, for whom the procedure was classically not indicated, and adoption of a new term, "metabolic surgery," to highlight the overall metabolic benefit of the procedure beyond weight loss. Recently, the Diabetes Surgery Summit (DSS) has included metabolic surgery in its T2DM treatment algorithm. Although the discussion brought by this consensus is highly relevant, the recommendation of metabolic surgery for patients with uncontrolled T2DM and a body mass index of 30 to 35 kg/m² still lacks enough evidence. This article provides an overall view of the metabolic benefits of bariatric/metabolic surgery in patients with class 1 obesity, compares the procedure against clinical treatment, and presents our rationale for defending caution on recommending the procedure to less obese individuals.

Comparative long-term effectiveness and safety of primary bariatric surgeries in treating type 2 diabetes mellitus in adults: a protocol for systematic review and network meta-analysis of randomised controlled trials

INTRODUCTION

Bariatric surgeries are effective in treating obesity related comorbidities, including type 2 diabetes mellitus. More robust evidence is needed to facilitate choice of procedure. In this systemic review, we aim to investigate the comparative long-term effectiveness in inducing remission of type 2 diabetes, halting diabetic complications, reducing mortality and the safety of conventional and emerging bariatric surgeries.

METHODS AND ANALYSIS

Databases including Cochrane Central Register, EMBASE, MEDLINE and clinical trial registries will be searched for randomised controlled trials with at least 3 years of follow-up, including direct and/or indirect evidence regarding primary bariatric surgeries in overweight or obese adults with type 2 diabetes mellitus, from inception of each database to 2019, with no language or publication type limits imposed. Dual selection of studies, data extraction and risk of bias assessments will be performed. Primary outcomes include full diabetes remission, composite outcome of full or partial diabetes remission and adverse event profiles. Secondary outcomes include anthropometric measurements, cardiovascular risk factor burden, medication burden, diabetic complications and all-cause mortality. Given sufficient homogeneity, network meta-analyses will be performed in a random-effects model based on the Bayesian framework, while assessing for consistency between direct and indirect estimates. Heterogeneities of studies will be explored through meta-regression analysis, and robustness of findings will be checked by sensitivity analysis, and an alternative method under a frequentist framework. All statistical analysis and graphical presentations will be conducted by R software V.3.3.3 (The R Project for Statistical Computing). The overall quality of the evidence will be assessed using the Grading of Recommendations, Assessment, Development and Evaluation criteria for each outcome.

ETHICS AND DISSEMINATION

Ethics approval is not required as individual patient data will not be included. This review will be subject for publication in a peer reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42018110775.

Effect of bariatric surgery on diabetic nephropathy in obese type 2 diabetes patients in a retrospective 2-year study: A local pilot

PURPOSE

To determine the effects of bariatric surgery on albuminuria in obese patients with type 2 diabetes mellitus.

METHODS

Retrospective analyses of clinical records of obese patients with type 2 diabetes mellitus who had either micro- or macroalbuminuria and had undergone various bariatric surgery were retrieved from a local hospital database. Their clinical data from follow-up appointments including albuminuria were analysed.

RESULTS

Of the 46 subjects with type 2 diabetes mellitus, 15 subjects had diabetic nephropathy and had pre- and post-bariatric surgery urine albumin-to-creatinine ratio or urine protein-to-creatinine ratio data available for analysis; 13 out of the 15 subjects (86.7%) showed improvement of urine albumin-to-creatinine ratio or urine protein-to-creatinine ratio after surgery; 2 showed equivocal results; 9 of 13 subjects (69.2%) showed remission of diabetic nephropathy; 7 of these 9 patients had microalbuminuria before surgery, 2 had macroalbuminuria before surgery. There were significant improvements to glycosylated haemoglobin, fasting plasma glucose, blood pressure and body weight post surgery. The usage of insulin and oral medications dropped significantly post surgery for all subjects.

CONCLUSION

This study shows that bariatric surgery significantly improves diabetic nephropathy in obese type 2 diabetes mellitus subjects. The results suggest that in our local type 2 diabetes mellitus patients, it is possible not only to improve metabolic parameters, but also to reverse what may be considered established microvascular complications by means of bariatric surgery.

Preoperative weight loss with glucagon-like peptide-1 receptor agonist treatment predicts greater weight loss achieved by the combination of medical weight management and bariatric surgery in patients with type 2 diabetes: A longitudinal analysis

We examined the relationship between weight changes after preoperative glucagon-like peptide-1 receptor agonist (GLP-1RA) treatment and weight changes from the start of medical weight management (MWM) until 12 months after bariatric surgery in patients with type 2 diabetes in a retrospective cohort study. A total of 45 patients (64.4% women, median [interquartile range] age 49 [45-60] years) were included. The median (interquartile range) weight loss from start of MWM until 12 months post-surgery was 17.9% (13.0%-29.3%). GLP-1RA treatment during MWM resulted in 5.0% (1.9%-7.7%) weight loss. Weight loss during GLP-1RA treatment predicted weight loss from the start of MWM until 12 months post-surgery, but not postoperative weight loss after adjustment. The proportion of weight loss from start of MWM to 12 months post-surgery attributed to GLP-1RA treatment was negatively associated with that attributed to surgery, after adjustment. In conclusion, weight change after GLP-1RA treatment predicted the weight loss achieved by a combination of MWM and bariatric surgery, but not weight loss induced by surgery only. Failure to lose weight after GLP-1RA treatment should not be considered a barrier to undergoing bariatric surgery.

Is there a Reason Why Obese Patients Choose Either Conservative Treatment or Surgery?

BACKGROUND

The effects of bariatric surgery on excess weight loss (EWL) and comorbidities are proven. Still, a significant number of patients prefer conservative therapy (ConsP).

OBJECTIVES

The goal of this study was to examine why ConsP and patients awaiting bariatric surgery (SurgP) choose which therapy, and to define the differences in their expectations.

SETTING

Prospective study, 1 university hospital, 1 general hospital, Germany.

METHODS

ConsP and SurgP were asked to complete a questionnaire. Statistical analysis including all patients and a BMI-matched cohort was performed using the chi-square and Wilcoxon rank-sum test.

RESULTS

Overall, 151 patients participated in this study (50 ConsP, 101 SurgP, 69.4% females). The mean age was 41.1 years (SD ± 12.2 years). ConsP had a significant lower body mass index (BMI, 44.7 kg/m² vs. 49.3 kg/m², p < 0.01). The educational level was significantly higher in ConsP. SurgP suffered significantly more often from depression (21.6% vs. 36.6%, p = 0.02) and joint pain (45.1% vs. 68.7%, p = 0.02). ConsP completed significantly more diets that were supervised by physicians or considered well-structured (56.3% vs. 31.0%, p = 0.04). SurgP considered their chosen therapy a last resort significantly more often (p < 0.01). A BMI-matched analysis between ConsP and SurgP revealed no significant differences in the prevalence of comorbidities but showed that fear of surgery plays a major role in the decision-making processes of obese patients.

CONCLUSION

A higher BMI and a greater prevalence of comorbidities had driven patients to seek a more radical solution for their obesity, i.e., surgery. The BMI-matched analysis suggests that fear of surgery is a relevant factor in why obese patients do not decide to undergo bariatric surgery lightly.

Mechanisms underpinning remission of albuminuria following bariatric surgery

PURPOSE OF REVIEW

Albuminuria is a biomarker of renal injury commonly used to monitor progression of diabetic kidney disease. The appearance of excess albumin in the urine reflects alterations in the structure and permeability of the glomerular filtration barrier. The present article summarizes the clinical evidence base for remission of albuminuria after bariatric surgery. It furthermore focuses on how beneficial impacts on glomerular podocyte structure and function may explain this phenomenon.

RECENT FINDINGS

A coherent clinical evidence base is emerging demonstrating remission of albuminuria following bariatric surgery in patients with obesity and diabetes. The impaired metabolic milieu in diabetic kidney disease drives podocyte dedifferentiation and death through glucotoxic, lipotoxic proinflammatory, and pressure-related stress. Improvements in these parameters after surgery correlate with improvements in albuminuria and preclinical studies provide mechanistic data that support the existence of cause-effect relationship.

SUMMARY

The benefits of bariatric surgery extend beyond weight loss in diabetes to encompass beneficial effects on diabetic renal injury. Attenuation of the toxic metabolic milieu that the podocyte is exposed to postbariatric surgery suggests that the restitution of podocyte health is a key cellular event underpinning remission of albuminuria.

The Effect of Bariatric Surgery on Diabetic Retinopathy: Good, Bad, or Both?

Bariatric surgery, initially intended as a weight-loss procedure, is superior to standard lifestyle intervention and pharmacological therapy for type 2 diabetes in obese individuals. Intensive medical management of hyperglycemia is associated with improved microvascular outcomes. Whether or not the reduction in hyperglycemia observed after bariatric surgery translates to improved microvascular outcomes is yet to be determined. There is substantial heterogeneity in the data relating to the impact of bariatric surgery on diabetic retinopathy (DR), the most common microvascular complication of diabetes. This review aims to collate the recent data on retinal outcomes after bariatric surgery. This comprehensive evaluation revealed that the majority of DR cases remain stable after surgery. However, risk of progression of pre-existing DR and the development of new DR is not eliminated by surgery. Instances of regression of DR are also noted. Potential risk factors for deterioration include severity of DR at the time of surgery and the magnitude of glycated hemoglobin reduction. Concerns also exist over the detrimental effects of postprandial hypoglycemia after surgery. In vivo studies evaluating the chronology of DR development and the impact of bariatric surgery could provide clarity on the situation. For now, however, the effect of bariatric surgery on DR remains inconclusive.

Losing weight for a better health: Role for the gut microbiota

In recent years, there have been several reviews on gut microbiota, obesity and cardiometabolism summarizing interventions that may impact the gut microbiota and have beneficial effects on the host (some examples include [1–3]). In this review we discuss how the gut microbiota changes with weight loss (WL) interventions in relation to clinical and dietary parameters. We also evaluate available evidence on the heterogeneity of response to these interventions. Two important questions were generated in this regard: 1) Can response to an intervention be predicted? 2) Could pre-intervention modifications to the gut microbiota optimize WL and metabolic improvement? Finally, we have delineated some recommendations for future research, such as the importance of assessment of diet and other environmental exposures in WL intervention studies, and the need to shift to more integrative approaches of data analysis.

Cardiometabolic Profile Related to Body Adiposity Identifies Patients Eligible for Bariatric Surgery More Accurately than BMI

BACKGROUND

Eligibility criteria for bariatric surgery (BS) are based on BMI and the presence of major comorbidities. Our aim was to analyze the usefulness of body adiposity determination in establishing the indication for BS.

METHODS

In order to analyze the cardiometabolic risk according to eligibility criteria for BS, four groups were studied. Morbidly obese patients with BMI ≥ 40 kg/m(2) (n = 360), and obese subjects with BMI ≥ 35 kg/m(2) and at least one comorbidity (n = 431), represented two groups of patients meeting original NIH criteria for BS. A third group included two cohorts of patients with a high body fat (BF)% that do not meet the original NIH eligibility criteria for BS: patients with either a BMI <35 kg/m(2) or a BMI ≥ 35 kg/m(2) without comorbidities (n = 266, NEHF). Lean subjects by BMI were the reference group (n = 140). BMI, BF% and markers of insulin sensitivity, lipid profile, and cardiovascular risk were measured.

RESULTS

Individuals from the NEHF group exhibited increased HbA1c (P < 0.05) and decreased insulin sensitivity evidenced by a significant reduction in QUICKI (P < 0.001). Triglyceride concentrations were similarly increased (P < 0.05) in the three groups of obese patients. Uric acid concentrations were significantly elevated (P < 0.01) to a similar extent in the obese groups. Levels of the inflammatory marker CRP and hepatic enzymes were significantly increased in the three obese groups.

CONCLUSION

The present study provides evidence for the existence of an adverse cardiometabolic profile in subjects currently considered to be outside traditional NIH guidelines but exhibiting a highly increased adiposity. It is concluded that body composition analysis yields valuable information to be incorporated into indication criteria for BS and that adiposity may be an independent indicator for BS.

GLP-1 and Amylin in the Treatment of Obesity

For decades, extensive research has aimed to clarify the role of pancreas and gut-derived peptide hormones in the regulation of glucose homeostasis and feeding behavior. Among these are the beta-cell hormone amylin and the intestinal L cell hormone glucagon-like peptide-1 (GLP-1). They exhibit distinct and yet several similar physiological actions including suppression of food intake, postprandial glucagon secretion, and gastric emptying-altogether lowering plasma glucose and body weight. These actions have been clinically exploited by the development of amylin and GLP-1 hormone analogs now used for treatment of diabetes and obesity. This review will outline the physiology and pharmacological potential of amylin and GLP-1, respectively, and focus on innovative peptide drug development leading to drugs acting on two or more distinct receptors, such as an amylin and GLP-1 peptide hybrid, potentially producing a more effective treatment strategy to combat the rapidly increasing global obesity.

Bariatric and metabolic surgery: a shift in eligibility and success criteria

The obesity epidemic, combined with the lack of available and effective treatments for morbid obesity, is a scientific and public health priority. Worldwide, bariatric and metabolic surgeries are increasingly being performed to effectively aid weight loss in patients with severe obesity, as well as because of the favourable metabolic effects of the procedures. The positive effects of bariatric surgery, especially with respect to improvements in type 2 diabetes mellitus, have expanded the eligibility criteria for metabolic surgery to patients with diabetes mellitus and a BMI of 30-35 kg/m(2). However, the limitations of BMI, both in the diagnosis and follow-up of patients, need to be considered, particularly for determining the actual adiposity and fat distribution of the patients following weight loss. Understanding the characteristics shared by bariatric and metabolic surgeries, as well as their differential aspects and outcomes, is required to enhance patient benefits and operative achievements. For a holistic approach that focuses on the multifactorial effects of bariatric and metabolic surgery to be possible, a paradigm shift that goes beyond the pure semantics is needed. Such a shift could lead to profound clinical implications for eligibility criteria and the definition of success of the surgical approach.

Cardiovascular benefits of bariatric surgery

The prevalence of obesity is increasing in the United States and worldwide, bringing with it an excess of morbidity and premature death. Obesity is strongly associated with both traditional cardiovascular risk factors as well as direct effects on hemodynamics and cardiovascular structure and function. In fact, cardiovascular disease is one of the major causes of morbidity and mortality in obese patients. Often, lifestyle and pharmacological weight-loss interventions are of limited efficacy in severely obese patients. Bariatric surgery has been shown to be a feasible option to achieve substantial and sustained weight loss in this group of patients. It is a safe procedure with low in-hospital and 30-day mortality rates even in groups that are considered higher risk for surgery (e.g., the elderly), especially if performed in high-volume centers. There is observational evidence that bariatric surgery in severely obese patients is associated with both a reduction of traditional cardiovascular risk factors as well as improvement in cardiac structure and function. Marked decreases in the levels of inflammatory and prothrombotic markers, as well as markers of subclinical atherosclerosis and endothelial dysfunction, are seen after bariatric surgery. This article summarizes the existing evidence regarding the cardiovascular benefits in patients following bariatric surgery.

The physiology underlying Roux-en-Y gastric bypass: a status report

Obesity and its related comorbidities can be detrimental for the affected individual and challenge public health systems worldwide. Currently, the only available treatment options leading to clinically significant and maintained body weight loss and reduction in obesity-related morbidity and mortality are based on surgical interventions. This review will focus on two main clinical effects of Roux-en-Y gastric bypass (RYGB), namely body weight loss and change in eating behavior. Animal experiments designed to understand the underlying physiological mechanisms of these post-gastric bypass effects will be discussed. Where appropriate, reference will also be made to vertical sleeve gastrectomy. While caloric malabsorption and mechanical restriction seem not to be major factors in this respect, alterations in gut hormone levels are invariably found after RYGB. However, their causal role in RYGB effects on eating and body weight has recently been challenged. Other potential factors contributing to the RYGB effects include increased bile acid concentrations and an altered composition of gut microbiota. RYGB is further associated with remarkable changes in preference for different dietary components, such as a decrease in the preference for high fat or sugar. It needs to be noted, however, that in many cases, the question about the necessity of these alterations for the success of bariatric surgery procedures remains unanswered.