Comparison of methodological approaches to human gut microbiota changes in response to metabolic and bariatric surgery: A systematic review

Recompensation in MASLD-related cirrhosis via metabolic bariatric surgery

The prognosis of patients with decompensated cirrhosis is poor, with significantly increased liver-related mortality rates. With the rising tide of decompensated cirrhosis associated with metabolic dysfunction-associated steatotic liver disease (MASLD), the role of metabolic bariatric surgery (MBS) in achieving hepatic recompensation is garnering increasing attention. However, the complexity of preoperative assessment, the risk of postoperative disease recurrence, and the potential for patients to experience surgical complications of the MBS present challenges. In this opinion article we analyze the potential of MBS to induce recompensation in MASLD-related cirrhosis, discuss the mechanisms by which MBS may affect recompensation, and compare the characteristics of different MBS procedures; we highlight the therapeutic potential of MBS in MASLD-related cirrhosis recompensation and advocate for research in this complex area.

Higher Prevalence of the Periodontal Pathogen Selenomonas noxia among Pediatric and Adult Patients May Be Associated with Overweight and Obesity

New evidence has suggested that oral and gut microflora may have significant impacts on the predisposition, development, and stability of obesity in adults over time-although less is known about this phenomenon in children. Compared with healthy-weight controls, overweight and obese adult patients are now known to harbor specific pathogens, such as Selenomonas noxia (S. noxia), that are capable of digesting normally non-digestible cellulose and fibers that significantly increase caloric extraction from normal dietary intake. To evaluate this phenomenon, clinical saliva samples (N = 122) from subjects with a normal BMI (18-25) and a BMI over 25 (overweight, obese) from an existing biorepository were screened using qPCR. The prevalence of S. noxia in samples from normal-BMI participants were lower (21.4%) than in overweight-BMI (25-29; 46.1%) and obese-BMI (30 and above; 36.8%) samples-a strong, positive correlation that was not significantly affected by age or race and ethnicity. These data strongly suggest that S. noxia may be intricately associated with overweight and obesity among patients, and more research will be needed to determine the positive and negative feedback mechanisms that may be responsible for these observations as well as the interventions needed to remove or reduce the potential effects of this oral pathogen.

A specific gut microbiota signature is associated with an enhanced GLP-1 and GLP-2 secretion and improved metabolic control in patients with type 2 diabetes after metabolic Roux-en-Y gastric bypass

Objective

To determine changes in incretins, systemic inflammation, intestinal permeability and microbiome modifications 12 months after metabolic RYGB (mRYGB) in patients with type 2 diabetes (T2D) and their relationship with metabolic improvement.

Materials and methods

Prospective single-center non-randomized controlled study, including patients with class II-III obesity and T2D undergoing mRYGB. At baseline and one year after surgery we performed body composition measurements, biochemical analysis, a meal tolerance test (MTT) and lipid test (LT) with determination of the area under the curve (AUC) for insulin, C-peptide, GLP-1, GLP-2, and fasting determinations of succinate, zonulin, IL-6 and study of gut microbiota.

Results

Thirteen patients aged 52.6 ± 6.5 years, BMI 39.3 ± 1.4 kg/m2, HbA1c 7.62 ± 1.5% were evaluated. After mRYGB, zonulin decreased and an increase in AUC after MTT was observed for GLP-1 (pre 9371 ± 5973 vs post 15788 ± 8021 pM, P<0.05), GLP-2 (pre 732 ± 182 vs post 1190 ± 447 ng/ml, P<0.001) and C- peptide, as well as after LT. Species belonging to Streptococaceae, Akkermansiacea, Rickenellaceae, Sutterellaceae, Enterobacteriaceae, Oscillospiraceae, Veillonellaceae, Enterobacterales_uc, and Fusobacteriaceae families increased after intervention and correlated positively with AUC of GLP-1 and GLP-2, and negatively with glucose, HbA1c, triglycerides and adiposity markers. Clostridium perfringens and Roseburia sp. 40_7 behaved similarly. In contrast, some species belonging to Lachnospiraceae, Erysipelotricaceae, and Rumnicocaceae families decreased and showed opposite correlations. Higher initial C-peptide was the only predictor for T2D remission, which was achieved in 69% of patients.

Conclusions

Patients with obesity and T2D submitted to mRYGB show an enhanced incretin response, a reduced gut permeability and a metabolic improvement, associated with a specific microbiota signature.

Impact of Sleeve Gastrectomy on Fecal Microbiota in Individuals with Morbid Obesity

BACKGROUND

The intestinal microbiota plays an important role in the etiology of obesity. Sleeve gastrectomy (SG) is a frequently performed and effective therapy for morbid obesity.

OBJECTIVE

To investigate the effect of sleeve gastrectomy on the fecal microbiota of individuals with morbid obesity and to examine whether shifts in microbiota composition are associated with markers of inflammation and intestinal barrier function.

METHODS

Fecal and blood samples of healthy individuals (n = 27) and morbidly obese individuals pre-SG (n = 24), and at 2 months (n = 13) and 6 months post-SG (n = 9) were collected. The 16SrRNA gene was sequenced to assess microbiota composition. Fecal calprotectin, plasma inflammatory markers and intestinal permeability markers (multi-sugar test) were determined.

RESULTS

Fecal microbiota composition between morbidly obese and lean individuals was significantly different. The fecal microbiota composition changed significantly 2 and 6 months post-SG (p = 0.008) compared to pre-SG but not towards a more lean profile. The post-SG microbiota profile was characterized by an increase in facultative anaerobic bacteria, characteristic for the upper gastrointestinal tract. No correlations were found between inflammatory markers, intestinal permeability and microbial profile changes.

CONCLUSIONS

Fecal microbiota composition in morbidly obese individuals changed significantly following SG. This change might be explained by functional changes induced by the SG procedure.

Comparison between metabolic-associated fatty liver disease and nonalcoholic fatty liver disease: From nomenclature to clinical outcomes

As a result of the obesity epidemic, Nonalcoholic fatty liver disease (NAFLD) and its complications have increased among millions of people. Consequently, a group of experts recommended changing the term NAFLD to an inclusive terminology more reflective of the underlying pathogenesis; metabolic-associated fatty liver disease (MAFLD). This new term of MAFLD has its own disease epidemiology and clinical outcomes prompting efforts in studying its differences from NAFLD. This article discusses the rationale behind the nomenclature change, the main differences, and its clinical implications.

The changes in cognitive function following bariatric surgery considering the function of gut microbiome

Background

There is a correlation between gut microbiota and cognitive function. The mechanisms and pathways explain why the incidence of Alzheimer's disease in subjects undergoing bariatric surgery is lower than in other people with obesity.

Methods

In this review article, we aim to discuss the association of obesity, cognitive impairment, and physiological changes after bariatric surgery.

Results

Bariatric surgery has a series of physiological benefits which may lead to an improvement in cognitive functions in individuals who are prone to later developing Alzheimer's disease. Also, taxonomical change in the gut microbiome profile provides a healthy condition for living with better levels of cognition without neuropathological damages in older ages.

Conclusion

It can be concluded that there is a possible correlation between cognitive dysfunction and increased risk of cognitive dysfunction in people with a BMI higher than 40 kg/m2. Bariatric surgery may increase neurotransmitters and improve the gut bacteria, leading to a significant reduction in the risk of Alzheimer's disease.

Fecal Metabolome and Bacterial Composition in Severe Obesity: Impact of Diet and Bariatric Surgery

The aim of this study was to monitor the impact of a preoperative low-calorie diet and bariatric surgery on the bacterial gut microbiota composition and functionality in severe obesity and to compare sleeve gastrectomy (SG) versus Roux-en-Y gastric bypass (RYGB). The study also aimed to incorporate big data analysis for the omics results and machine learning by a Lasso-based analysis to detect the potential markers for excess weight loss. Forty patients who underwent bariatric surgery were recruited (14 underwent SG, and 26 underwent RYGB). Each participant contributed 4 fecal samples (baseline, post-diet, 1 month after surgery and 3 months after surgery). The bacterial composition was determined by 16S rDNA massive sequencing using MiSeq (Illumina). Metabolic signatures associated to fecal concentrations of short-chain fatty acids, amino acids, biogenic amines, gamma-aminobutyric acid and ammonium were determined by gas and liquid chromatography. Orange 3 software was employed to correlate the variables, and a Lasso analysis was employed to predict the weight loss at the baseline samples. A correlation between Bacillota (formerly Firmicutes) abundance and excess weight was observed only for the highest body mass indexes. The low-calorie diet had little impact on composition and targeted metabolic activity. RYGB had a deeper impact on bacterial composition and putrefactive metabolism than SG, although the excess weight loss was comparable in the two groups. Significantly higher ammonium concentrations were detected in the feces of the RYGB group. We detected individual signatures of composition and functionality, rather than a gut microbiota characteristic of severe obesity, with opposing tendencies for almost all measured variables in the two surgical approaches. The gut microbiota of the baseline samples was not useful for predicting excess weight loss after the bariatric process.

Improvement in nonalcoholic fatty liver disease through bariatric surgery

Content available: Author Interview and Audio Recording.

The impact of dietary, surgical, and pharmacological interventions on gut microbiota in individuals with diabetes mellitus: A systematic review

AIMS

To conduct a systematic review assessing the association between dietary, surgical, and pharmacological interventions and changes in the gut microbiota of individuals with diabetes.

METHODS

The MEDLINE, EMBASE, and Cochrane Library databases were searched focusing on the effects of dietary, bariatric surgery, and pharmacological interventions on gut microbiota in adults with diabetes. Studies were classified based on qualitative changes using a simple vote-counting method, evaluating reduction, no effect, or an increase in the gut microbiota outcomes.

RESULTS

6,004 studies were retained to review their titles and abstracts. A total of 149 full-text articles were reassessed, of which 49 were included in the final analysis. This review indicates that dietary, surgical, and pharmacological interventions increase or decrease bacterial populations from more than 60 families, genera, or species. In general, the interventions led to an increase in the bacterial population from phylum Firmicutes, mainly Lactobacillus species, compared to the gram-negative bacterial population from phylum Bacteroidetes.

CONCLUSIONS

The results of the included studies suggest that interventions aimed at reducing species related to uncontrolled diabetes and increasing species related to the healthy gut are potential adjuvants in treating diabetes; however, well-conducted interventional studies targeting gut microbiota are necessary.

The Implication of Gastric Microbiome in the Treatment of Gastric Cancer

Simple Summary

Gastric cancer (GC) represents the fifth most common cancer worldwide. Recent developments in PCR and metagenomics clarify that the stomach contains a powerful microbiota. Conventional treatments for GC that include surgery, chemotherapy, and radiotherapy are not very effective. That’s why new therapeutic strategies are needed. The intestinal microbiota is involved in oncogenesis and cancer prevention, and the effectiveness of chemotherapy. Recent studies have shown that certain bacteria may enhance the effect of some traditional antineoplastic drugs and immunotherapies.

Abstract

Gastric cancer (GC) is one of the most common and deadly malignancies worldwide. Helicobacter pylori have been documented as a risk factor for GC. The development of sequencing technology has broadened the knowledge of the gastric microbiome, which is essential in maintaining homeostasis. Recent studies have demonstrated the involvement of the gastric microbiome in the development of GC. Therefore, the elucidation of the mechanism by which the gastric microbiome contributes to the development and progression of GC may improve GC’s prevention, diagnosis, and treatment. In this review, we discuss the current knowledge about changes in gastric microbial composition in GC patients, their role in carcinogenesis, the possible therapeutic role of the gastric microbiome, and its implications for current GC therapy.

Intestinal barrier disorders and metabolic endotoxemia in obesity: Current knowledge

The World Health Organization reports that the prevalent problem of excessive weight and obesity currently affects about 1.9 billion people worldwide and is the fifth most common death factor among patients. In view of the growing number of patients with obesity, attention is drawn to the insufficient effectiveness of behavioral treatment methods. In addition to genetic and environmental factors leading to the consumption of excess energy in the diet and the accumulation of adipose tissue, attention is paid to the role of intestinal microbiota in maintaining a normal body weight. Dysbiosis – a disorder in the composition of the gut microbiota – is mentioned as one of the contributing factors to the development of metabolic diseases, including obesity, type 2 diabetes, and cardiovascular disorders. The human gastrointestinal tract is colonized largely by a group of Gram-negative bacteria that are indicated to be a source of lipopolysaccharide (LPS), associated with inducing systemic inflammation and endotoxemia. Research suggests that disturbances in the gut microbiota, leading to damage to the intestinal barrier and an increase in circulating LPS, are implicated in obesity and other metabolic disorders. Plasma LPS and lipopolysaccharide-binding protein (LBP) levels have been shown to be elevated in individuals with excess body weight. Bariatric surgery has become a popular treatment option, leading to stable weight loss and an improvement in obesity-related conditions. The aim of this study was to characterize the factors that promote the induction of metabolic endotoxemia and its associated health consequences, along with the presentation of their changes after bariatric surgery.

The association of weight loss with changes in the gut microbiota diversity, composition, and intestinal permeability: a systematic review and meta-analysis

The gut microbiome may be a mediator between obesity and health outcomes. However, it is unclear how intentional weight loss changes the gut microbiota and intestinal permeability. We aimed to systematically review and quantify this association. We searched Medline, Embase, CINAHL, Cochrane databases, and trial registries until June 2020 (PROSPERO: CRD42020205292). We included trials of weight loss interventions (energy-restricted diets, pharmacotherapy, bariatric surgery) reporting on the microbiome. Two reviewers independently completed screening, extraction, and risk assessment with the ROBINS-I tool. Pooled standardized mean differences (SMDs) were obtained from random-effects meta-analyses. Forty-seven trials with 1,916 participants (81% female) and a median follow-up of 6 months (range: 2-24) were included. Based on imprecise evidence but with fairly consistent direction of effect, weight loss was associated with a statistically significant increase in α-diversity [SMD: 0.4 (95% CI: 0.2, 0.6], p < .0001, I² = 70%, n = 30 studies) and a statistically significant reduction in intestinal permeability [SMD: -0.7 (95% CI: -0.9, -0.4), p < .0001, I² = 83%, n = 17 studies]. Each kg of weight loss was associated with a 0.012 (95% CI: 0.0003, 0.024, p = .045) increase in α-diversity and a -0.017 (95% CI: -0.034, -0.001, p = .038) reduction in intestinal permeability. There was clear evidence of increases in the relative abundance of Akkermansia, but no clear evidence of changes in individual phyla, species, or fecal short-chain fatty acids. Restricting the analyses to the studies with lower risk of bias did not materially alter the estimates. Increasing weight loss is positively associated with increases in gut microbiota α-diversity and reductions in intestinal permeability.

Changes in the Composition of Oral and Intestinal Microbiota After Sleeve Gastrectomy and Roux-En-Y Gastric Bypass and Their Impact on Outcomes of Bariatric Surgery

Background

We aimed to assess the changes in composition of bacterial microbiota at two levels of the digestive tract: oral cavity and large intestine in patients 6 months after bariatric surgery.

Methods

This was a prospective cohort study including patients undergoing bariatric surgery. Before surgery and 6 months after the procedure, oral swabs were obtained and stool samples were provided. Our endpoint was the analysis of the differences in compositions of oral and fecal microbiota prior and after the surgical treatment of obesity.

Results

Bacteria from phylum Bacteroidetes seemed to increase in abundance in both the oral cavity and the large intestine 6 months after surgery among patients undergoing bariatric surgery. The subgroup analysis we conducted based on the volume of weight-loss revealed that patients achieving at least 50% of excess weight loss present similar results to the entire study group. Patients with less favorable outcomes presented an increase in the population of bacteria from phylum Fusobacteria and a decrease of phylum Firmicutes in oral cavity.

Conclusion

Intestinal microbiota among these patients underwent similar changes in composition to the rest of the study group. Bariatric surgery introduces a significant change in composition of oral and intestinal microbiota.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11695-022-05954-9.

Bariatric Surgery in NAFLD

Currently, there are no approved medications to treat patients with nonalcoholic steatohepatitis (NASH) with fibrosis or cirrhosis. Although the management goal in these patients is weight reduction by 7-10% with lifestyle modifications, only less than 10% of patients achieve this target at 1-year, and fewer maintain the weight loss at 5 years. Bariatric surgery is an option that may be considered in those who fail to lose weight by lifestyle changes. Bariatric surgery has been shown to improve liver histology including fibrosis secondary to NASH, in addition to other benefits including an improvement or resolution of type 2 diabetes mellitus, dyslipidemia, and hypertension, and a reduction of cardiovascular morbidity or mortality. There are no guidelines of bariatric surgery indications for the management of NASH. The purpose of this review is to critically appraise the current knowledge of the role of bariatric surgery and the potential mechanisms for its perceived benefits in the management of patients with NASH-related liver disease.

Bacteria-Derived Extracellular Vesicles in Urine as a Novel Biomarker for Gastric Cancer: Integration of Liquid Biopsy and Metagenome Analysis

Simple Summary

Gastric cancer shows an improved prognosis when diagnosed in its early stage. However, non-invasive diagnostic markers for gastric cancer known to date have poor clinical efficacies. Many studies have shown that gastric cancer patients have distinct microbial changes compared to normal subjects. In the present study, we performed metagenome analysis using body fluid samples (gastric juice, blood, and urine) to investigate the distinct microbial composition using bacteria-derived EVs from gastric cancer patients. We could build diagnostic prediction models for gastric cancer with the metagenomic data and analyzed the accuracy of models. Although further validation is required to apply these findings to real clinical practice yet, our study showed the possibility of gastric cancer diagnosis with the integration of liquid biopsy and metagenome analysis.

Abstract

Early detection is crucial for improving the prognosis of gastric cancer, but there are no non-invasive markers for the early diagnosis of gastric cancer in real clinical settings. Recently, bacteria-derived extracellular vesicles (EVs) emerged as new biomarker resources. We aimed to evaluate the microbial composition in gastric cancer using bacteria-derived EVs and to build a diagnostic prediction model for gastric cancer with the metagenome data. Stool, urine, and serum samples were prospectively collected from 453 subjects (gastric cancer, 181; control, 272). EV portions were extracted from the samples for metagenome analysis. Differences in microbial diversity and composition were analyzed with 16S rRNA gene profiling, using the next-generation sequencing method. Biomarkers were selected using logistic regression models based on relative abundances at the genus level. The microbial composition of healthy groups and gastric cancer patient groups was significantly different in all sample types. The compositional differences of various bacteria, based on relative abundances, were identified at the genus level. Among the diagnostic prediction models for gastric cancer, the urine-based model showed the highest performance when compared to that of stool or serum. We suggest that bacteria-derived EVs in urine can be used as novel metagenomic markers for the non-invasive diagnosis of gastric cancer by integrating the liquid biopsy method and metagenome analysis.

Immunosuppression and Clostridioides (Clostridium) difficile Infection Risk in Metabolic and Bariatric Surgery Patients

BACKGROUND

Immunosuppressant use increases risk of Clostridioides (Clostridium) difficile infection. To date, no studies have analyzed the relationship between immunosuppressant use and C difficile infections after metabolic and bariatric surgery (MBS).

METHODS

A retrospective analysis of the 2015-2018 MBSAQIP data was conducted. The MBSAQIP data include information from 854 affiliated practices in the US and Canada. Initial sample size was 760,076 MBS patients. After excluding participants due to missing variables (n = 188,106) and the use of surgical procedures other than Roux-en-Y gastric bypass and sleeve gastroplasty (n = 129,712), final analyses were performed on 442,258 participants. Logistic regression models generated the odds of C difficile infection developing post MBS, according to immunosuppressant status (positive or negative).

RESULTS

Unadjusted logistic regression analysis showed that patients using immunosuppressants were 95% more likely to have postoperative C difficile infection (odds ratio 1.945; 95% CI, 1.230 to 3.075; p < 0.001) vs MBS patients not taking immunosuppressants. After adjusting for age, sex, ethnicity, preoperative BMI, diabetes status, and surgical procedure type, the association remained unaffected (adjusted odds ratio 1.956; 95% CI, 1.236 to 3.095; p < 0.01). Patients who completed the laparoscopic Roux-en-Y gastric bypass procedure had more than double the odds of C difficile infection developing compared with those who completed the laparoscopic sleeve gastrectomy procedure (odds ratio 2.183; 95% CI, 1.842 to 2.587; p < 0.0001).

CONCLUSIONS

Our results using a population-based sample of MBS patients showed that those taking immunosuppressants have a significantly higher risk of developing Clostridioides (Clostridium) difficile infection postoperatively. These findings suggest that patients using immunosuppressants should be closely monitored both pre and post procedure.

Interactions of the microbiome with pharmacological and non-pharmacological approaches for the management of ageing-related musculoskeletal diseases

Despite major progress in the understanding of the pathophysiology and therapeutic options for common ageing-related musculoskeletal conditions (i.e. osteoporosis and associated fractures, sarcopenia and osteoarthritis), there is still a considerable proportion of patients who respond sub optimally to available treatments or experience adverse effects. Emerging microbiome research suggests that perturbations in microbial composition, functional and metabolic capacity (i.e. dysbiosis) are associated with intestinal and extra-intestinal disorders including musculoskeletal diseases. Besides its contributions to disease pathogenesis, the role of the microbiome is further extended to shaping individuals' responses to disease therapeutics (i.e. pharmacomicrobiomics). In this review, we focus on the reciprocal interactions between the microbiome and therapeutics for osteoporosis, sarcopenia and osteoarthritis. Specifically, we identify the effects of therapeutics on microbiome's configurations, functions and metabolic output, intestinal integrity and immune function, but also the effects of the microbiome on the metabolism of these therapeutics, which in turn, may influence their bioavailability, efficacy and side-effect profile contributing to variable treatment responses in clinical practice. We further discuss emerging strategies for microbiota manipulation as preventive or therapeutic (alone or complementary to available treatments) approaches for improving outcomes of musculoskeletal health and disease.

Gastric Cancer Microbiome

Identifying a microbiome pattern in gastric cancer (GC) is hugely debatable due to the variation resulting from the diversity of the studied populations, clinical scenarios, and metagenomic approach. H. pylori remains the main microorganism impacting gastric carcinogenesis and seems necessary for the initial steps of the process. Nevertheless, an additional non-H. pylori microbiome pattern is also described, mainly at the final steps of the carcinogenesis. Unfortunately, most of the presented results are not reproducible, and there are no consensual candidates to share the H. pylori protagonists. Limitations to reach a consistent interpretation of metagenomic data include contamination along every step of the process, which might cause relevant misinterpretations. In addition, the functional consequences of an altered microbiome might be addressed. Aiming to minimize methodological bias and limitations due to small sample size and the lack of standardization of bioinformatics assessment and interpretation, we carried out a comprehensive analysis of the publicly available metagenomic data from various conditions relevant to gastric carcinogenesis. Mainly, instead of just analyzing the results of each available publication, a new approach was launched, allowing the comprehensive analysis of the total sample amount, aiming to produce a reliable interpretation due to using a significant number of samples, from different origins, in a standard protocol. Among the main results, Helicobacter and Prevotella figured in the "top 6" genera of every group. Helicobacter was the first one in chronic gastritis (CG), gastric cancer (GC), and adjacent (ADJ) groups, while Prevotella was the leader among healthy control (HC) samples. Groups of bacteria are differently abundant in each clinical situation, and bacterial metabolic pathways also diverge along the carcinogenesis cascade. This information may support future microbiome interventions aiming to face the carcinogenesis process and/or reduce GC risk.

Different Weight Loss Intervention Approaches Reveal a Lack of a Common Pattern of Gut Microbiota Changes

Options for treatment of obesity include dietary approaches and bariatric surgery. Previous studies have shown that weight loss interventions have an impact on gut microbiota. However, a pattern of gut microbiota changes associated with weight loss independently of the type of intervention has not been described yet. This study includes 61 individuals who followed different weight loss strategies in three different trials: 21 followed a hypocaloric Mediterranean diet (MedDiet), 18 followed a very-low-calorie ketogenic diet (VLCKD) and 22 patients underwent sleeve gastrectomy bariatric surgery (BS). Gut microbiota profile was assessed by next-generation sequencing. A common taxon that had significantly changed within the three weight loss interventions could not be find. At the family level, Clostiridiaceae significantly increased its abundance with MedDiet and VLCKD, whilst Porphyromonadacean and Rikenellaceae significantly increased with VLCKD and BS. At genus level, in VLCKD and BS, Parabacteroides and Alistipes significantly increased their abundance whilst Lactobacillus decreased. At the species level, BS and VLCKD produced an increase in Parabacteroidesdistasonis and a decrease in Eubactieriumventriosum and Lactobacillusrogosae, whilst Orodibactersplanchnicus increased its abundance after the BS and MedDiet. Predicted metagenome analysis suggested that most of the changes after VLCKD were focused on pathways related to biosynthesis and degradation/utilization/assimilation, while BS seems to decrease most of the biosynthesis pathways. MedDiet was enriched in several pathways related to fermentation to short-chain fatty acids. Our results show that weight loss is not associated with a specific pattern of gut microbiota changes independently of the strategy used. Indeed, gut microbiota changes according to type of weight loss intervention.

A microbial signature following bariatric surgery is robustly consistent across multiple cohorts

Bariatric surgery induces significant shifts in the gut microbiota which could potentially contribute to weight loss and metabolic benefits. The aim of this study was to characterize a microbial signature following Roux-en-Y Gastric bypass (RYGB) surgery using novel and existing gut microbiota sequence data. We generated 16S rRNA gene and metagenomic sequences from fecal samples from patients undergoing RYGB surgery (n = 61 for 16S rRNA gene and n = 135 for metagenomics) at pre-surgical baseline and one, six, and twelve-month post-surgery. We compared these data with three smaller publicly available 16S rRNA gene and one metagenomic datasets from patients who also underwent RYGB surgery. Linear mixed models and machine learning approaches were used to examine the presence of a common microbial signature across studies. Comparison of our new sequences with previous longitudinal studies revealed strikingly similar profiles in both fecal microbiota composition (r = 0.41 ± 0.10; p < .05) and metabolic pathways (r = 0.70 ± 0.05; p < .001) early after surgery across multiple datasets. Notably, Veillonella, Streptococcus, Gemella, Fusobacterium, Escherichia/Shigella, and Akkermansia increased after surgery, while Blautia decreased. Machine learning approaches revealed that the replicable gut microbiota signature associated with RYGB surgery could be used to discriminate pre- and post-surgical samples. Opportunistic pathogen abundance also increased post-surgery in a consistent manner across cohorts. Our study reveals a robust microbial signature involving many commensal and pathogenic taxa and metabolic pathways early after RYGB surgery across different studies and sites. Characterization of the effects of this robust microbial signature on outcomes of bariatric surgery could provide insights into the development of microbiome-based interventions for predicting or improving outcomes following surgery.

Efficacy of probiotics in patients with morbid obesity undergoing bariatric surgery: a systematic review and meta-analysis

Bariatric surgery is considered effective for morbid obesity, and probiotic supplementation might provide some benefits. We aimed to revise the evidence regarding probiotic supplementation in patients with morbid obesity undergoing bariatric surgery. MEDLINE, Embase, Web of Science, CENTRAL, and trial registers were searched up to April 1, 2020. We included randomized controlled trials and controlled clinical trials, and outcomes of interest were weight change, quality of life, gastrointestinal symptoms, and adverse events. All stages of the review were done by 2 authors independently and we followed Cochrane Handbook guidance. We screened 2541 references and included 5 studies. Probiotics may have minor to no effect regarding percentage excess weight loss (%EWL) at 6 weeks (mean difference [MD], .28; 95% CI, -9.53 to 10.09; 44 participants, 2 studies), 3 months (MD, 5.47; 95% CI, -3.22 to 14.17; 165 participants, 3 studies), 6 months (MD, .46; 95% CI, -8.14 to 9.07; 115 participants, 2 studies), and 12 months post surgery (MD, .35; 95% CI, -8.66 to 9.37; 123 participants, 2 studies). We observed short-term improvement in gastrointestinal symptoms. There was no important effect on quality of life and no meaningful adverse events. Because probiotic supplementation might provide some benefit with respect to weight loss, might alleviate some gastrointestinal symptoms, and is associated with minor or no adverse events, continuous supplementation might be worth considering in certain individuals. Our findings are based on the body of evidence of very low certainty, and further well-designed randomized controlled trials are required to elucidate the effect and strengthen the certainty in the estimates.

Gut Microbiota, Probiotics and Psychological States and Behaviors after Bariatric Surgery-A Systematic Review of Their Interrelation

The gastrointestinal (GI) microbiota plays an important role in health and disease, including brain function and behavior. Bariatric surgery (BS) has been reported to result in various changes in the GI microbiota, therefore demanding the investigation of the impact of GI microbiota on treatment success. The goal of this systematic review was to assess the effects of BS on the microbiota composition in humans and other vertebrates, whether probiotics influence postoperative health, and whether microbiota and psychological and behavioral factors interact. A search was conducted using PubMed and Web of Science to find relevant studies with respect to the GI microbiota and probiotics after BS, and later screened for psychological and behavioral parameters. Studies were classified into groups and subgroups to provide a clear overview of the outcomes. Microbiota changes were further assessed for whether they were specific to BS in humans through the comparison to sham operated controls in other vertebrate studies. Changes in alpha diversity appear not to be specific, whereas dissimilarity in overall microbial community structure, and increases in the abundance of the phylum Proteobacteria and Akkermansia spp. within the phylum Verrucomicrobia after surgery were observed in both human and other vertebrates studies and may be specific to BS in humans. Human probiotic studies differed regarding probiotic strains and dosages, however it appeared that probiotic interventions were not superior to a placebo for quality of life scores or weight loss after BS. The relationship between GI microbiota and psychological diseases in this context is unclear due to insufficient available data.