Alterations of Gut Microbiota After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy in Sprague-Dawley Rats

Postoperative delayed gastric emptying: may gut microbiota play a role?

Postoperative delayed gastric emptying is a prevalent complication following surgical procedures, imposing heavy physical and financial burdens on patients. However, current treatment options remain suboptimal. In recent years, an increasing number of studies have highlighted that the gut microbiota and its metabolites are closely associated with postoperative complications. Various factors can disrupt the gut microbiome after surgery. This review discusses the potential mechanisms by which the gut microbiota and their metabolites may contribute to the pathogenesis of postoperative delayed gastric emptying. However, the current knowledge base is limited in terms of fully understanding the exact mechanisms involved. It is therefore evident that further research is required to fully elucidate the role of the gut microbiome in postoperative delayed gastric emptying, with the aim of uncovering new possibilities for preventive measures and therapeutic treatments.

Effects of single-anastomosis duodenal-ileal bypass with sleeve gastrectomy on gut microbiota and glucose metabolism in rats with type 2 diabetes

Background

Bariatric and metabolic surgery often leads to significant changes in gut microbiota composition, indicating that changes in gut microbiota after bariatric and metabolic surgery might play a role in ameliorating type 2 diabetes (T2D). However, the effects of single-anastomosis duodenal-ileal bypass with sleeve gastrectomy (SADI-S) on gut microbiota in T2D remain unclear.

Objectives

To investigate the effects of SADI-S on gut microbiota and glucose metabolism in T2D rats.

Methods

Nineteen T2D rats were randomly divided into the SADI-S group (n = 10) and the sham operation with pair-feeding group (sham-PF, n = 9). Fecal samples were collected to analyze the gut microbiota composition with 16S ribosomal DNA gene sequencing. The fasting blood glucose and glycated hemoglobin were measured to evaluate the effects of SADI-S on glucose metabolism.

Results

The Chao and ACE index results indicated the richness of the gut microbial community. The ACE and Chao index values were significantly lower in the SADI-S group than in the sham-PF group, indicating that indicating that species richness was significantly lower in the SADI-S group than in the sham-PF group (p < 0.05). Shannon and Simpson indices were used to estimate the species diversity of the gut microbiota. Compared with the sham-PF group, the SADI-S group showed significantly lower Shannon index and higher Simpson index values, indicating that the species diversity was significantly lower in the SADI-S group than in the sham-PF group (p < 0.05). At the genus level, SADI-S significantly changed the abundances of 33 bacteria, including the increased anti-inflammatory bacteria (Akkermansia and Bifidobacterium) and decreased pro-inflammatory bacteria (Bacteroides). SADI-S significantly decreased the fasting blood glucose and glycated hemoglobin levels. The blood glucose level of rats was positively correlated with the relative abundances of 12 bacteria, including Bacteroides, and negatively correlated with the relative abundances of seven bacteria, including Bifidobacterium.

Conclusion

SADI-S significantly altered the gut microbiota composition of T2D rats, including the increased anti-inflammatory bacteria (Akkermansia and Bifidobacterium) and decreased pro-inflammatory bacteria (Bacteroides). The blood glucose level of rats was positively correlated with the abundances of 12 bacteria, including Bacteroides, but negatively correlated with the relative abundance of 7 bacteria, including Bifidobacterium. These alternations in gut microbiota may be the mechanism through which SADI-S improved T2D. More studies should be performed in the future to validate these effects.

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

Changes in HLA-B27 Transgenic Rat Fecal Microbiota Following Tofacitinib Treatment and Ileocecal Resection Surgery: Implications for Crohn's Disease Management

The therapeutic management of Crohn's disease (CD), a chronic relapsing-remitting inflammatory bowel disease (IBD), is highly challenging. Surgical resection is sometimes a necessary procedure even though it is often associated with postoperative recurrences (PORs). Tofacitinib, an orally active small molecule Janus kinase inhibitor, is an anti-inflammatory drug meant to limit PORs in CD. Whereas bidirectional interactions between the gut microbiota and the relevant IBD drug are crucial, little is known about the impact of tofacitinib on the gut microbiota. The HLA-B27 transgenic rat is a good preclinical model used in IBD research, including for PORs after ileocecal resection (ICR). In the present study, we used shotgun metagenomics to first delineate the baseline composition and determinants of the fecal microbiome of HLA-B27 rats and then to evaluate the distinct impact of either tofacitinib treatment, ileocecal resection or the cumulative effect of both interventions on the gut microbiota in these HLA-B27 rats. The results confirmed that the microbiome of the HLA-B27 rats was fairly different from their wild-type littermates. We demonstrated here that oral treatment with tofacitinib does not affect the gut microbial composition of HLA-B27 rats. Of note, we showed that ICR induced an intense loss of bacterial diversity together with dramatic changes in taxa relative abundances. However, the oral treatment with tofacitinib neither modified the alpha-diversity nor exacerbated significant modifications in bacterial taxa induced by ICR. Collectively, these preclinical data are rather favorable for the use of tofacitinib in combination with ICR to address Crohn's disease management when considering microbiota.

Single-anastomosis duodeno-ileal bypass with sleeve gastrectomy improves lipid and glucose homeostasis in ob/ob mice

OBJECTIVE

The objective of this study was to compare the general and metabolic impact of single-anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) with Roux-en-Y gastric bypass (RYGB) in an obese (ob/ob) mouse model.

METHODS

10-week-old male ob/ob mice underwent either SADI-S, RYGB, or laparotomy surgery (Sham group). General and metabolic parameters were assessed during a 5-week period thereafter.

RESULTS

SADI-S induced a deeper weight loss ([mean ± SEM] -41.2% ± 3.3%) than RYGB (-5.6% ± 3.5%, p < 0.001) compared with the Sham group (+6.3% ± 1.0%, p < 0.05). A significant food restriction was observed after SADI-S only (-31%, 117.4 ± 10.3 g vs. 170.2 ± 5.2 g of food at day 35 in Sham group mice, p < 0.001). Random-fed glycemia and glucose tolerance were more improved after SADI-S than RYGB. SADI-S decreased plasma cholesterol concentration by 60% (0.49 ± 0.04 g/L vs. 1.40 ± 0.10 g/L in the Sham group at day 35, p < 0.01), significantly more than RYGB (1.04 ± 0.14 g/L, p = 0.018). Plasma sitosterol/cholesterol and campesterol/cholesterol ratios were decreased after SADI-S, suggesting a reduced intestinal cholesterol absorption. SADI-S increased exogenous plasma cholesterol-D7 clearance and fecal elimination, also indicating an increased plasma cholesterol excretion. Studying a pair-fed group demonstrated that calorie restriction alone did not explain the beneficial impact of SADI-S.

CONCLUSIONS

SADI-S is associated with a greater improvement in lipid and glucose homeostasis than RYGB in ob/ob mice.

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.

Dietary Fat Modulation of Gut Microbiota and Impact on Regulatory Pathways Controlling Food Intake

Obesity is a multifactorial disease that continues to increase in prevalence worldwide. Emerging evidence has shown that the development of obesity may be influenced by taxonomic shifts in gut microbiota in response to the consumption of dietary fats. Further, these alterations in gut microbiota have been shown to promote important changes in satiation signals including gut hormones (leptin, ghrelin, GLP-1, peptide YY and CCK) and orexigenic and anorexigenic neuropeptides (AgRP, NPY, POMC, CART) that influence hyperphagia and therefore obesity. In this review, we highlight mechanisms by which gut microbiota can influence these satiation signals both locally in the gastrointestinal tract and via microbiota-gut-brain communication. Then, we describe the effects of dietary interventions and associated changes in gut microbiota on satiety signals through microbiota-dependent mechanisms. Lastly, we present microbiota optimizing therapies including prebiotics, probiotics, synbiotics and weight loss surgery that can help restore beneficial gut microbiota by enhancing satiety signals to reduce hyperphagia and subsequent obesity. Overall, a better understanding of the mechanisms by which dietary fats induce taxonomical shifts in gut microbiota and their impact on satiation signaling pathways will help develop more targeted therapeutic interventions in delaying the onset of obesity and in furthering its treatment.

The impact of bariatric surgery on colorectal cancer risk

Obesity is considered a risk factor for different types of cancer, including colorectal cancer (CRC). Bariatric surgery has been associated with improvements in obesity-related co-morbidities and reductions in overall cancer risk. However, given the contradictory outcomes of several cohort studies, the impact of bariatric surgery on CRC risk appears controversial. Furthermore, measurement of CRC biomarkers following Roux-en-Y gastric bypass (RYGB) has revealed hyperproliferation and increased pro-inflammatory gene expression in the rectal mucosa. The proposed mechanisms leading to increased CRC risk are alterations of the gut microbiota and exposure of the colorectum to high concentrations of bile acids, both of which are caused by RYGB-induced anatomical rearrangements. Studies in animals and humans have highlighted the similarities between RYGB-induced microbial profiles and the gut microbiota documented in CRC. Microbial alterations common to post-RYGB cases and CRC include the enrichment of pro-inflammatory microbes and reduction in butyrate-producing bacteria. Lower concentrations of butyrate following RYGB may also contribute to an increased risk of CRC, given the anti-inflammatory and anticarcinogenic properties of this molecule. Laparoscopic sleeve gastrectomy appears to have a more moderate impact than RYGB; however, relatively few animal and human studies have investigated its effects on CRC risk. Moreover, evidence regarding the impact of anastomosis gastric bypass on one is even more limited. Therefore, further studies are required to establish whether the potential increase in CRC risk is restricted to RYGB or may also be associated with other bariatric procedures.

Bariatric Surgery as Treatment Strategy of Obesity in Saudi People: Effects of Gut Microbiota

Obesity prevalence is rising globally, as are the number of chronic disorders connected with obesity, such as diabetes, non-alcoholic fatty liver disease, dyslipidemia, and hypertension. Bariatric surgery is also becoming more common, and it remains the most effective and long-term treatment for obesity. This study will assess the influence of Laparoscopic Sleeve Gastrectomy (LSG) on gut microbiota in people with obesity before and after surgery. The findings shed new light on the changes in gut microbiota in Saudi people with obesity following LSG. In conclusion, LSG may improve the metabolic profile, resulting in decreased fat mass and increased lean mass, as well as improving the microbial composition balance in the gastrointestinal tract, but this is still not equivalent to normal weight microbiology. A range of factors, including patient characteristics, geographic dispersion, type of operation, technique, and nutritional and caloric restriction, could explain differences in abundance between studies. This information could point to a novel and, most likely, tailored strategy in obesity therapy, which could eventually be incorporated into health evaluations and monitoring in preventive health care or clinical medicine.

Effects of bariatric surgery on drug pharmacokinetics-Preclinical studies

With the rising worldwide obesity rates, bariatric surgeries are increasing. Although the surgery offers an effective treatment option for weight loss, the procedure causes dramatic physiological and metabolic changes. Animal models in rodents provide a valuable tool for studying the systemic effects of the surgery. Since the surgery may significantly influence the pharmacokinetic properties of medications, animal studies should provide essential insight into mechanisms underlying changes in how the body handles the drug. This review summarizes research work in rodents regarding the impact of standard bariatric procedures on pharmacokinetics. A qualitative literature search was conducted via PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE. Studies that examined bariatric surgery's effects on drug pharmacokinetics in rodent models were included. Clinical studies and studies not involving drug interventions were excluded. A total of 15 studies were identified and assessed in this review. These studies demonstrate the possible impact of bariatric surgery on drug absorption, distribution, metabolism, excretion, and potential mechanisms. Pharmacokinetic changes exhibited in the limited pre-clinical studies highlight a need for further investigation to fully understand the impact and mechanism of bariatric surgery on drug responses.

THE INTESTINAL MICROBIOME IN PATIENTS UNDERGOING BARIATRIC SURGERY: A SYSTEMATIC REVIEW

BACKGROUND

Dysbiosis of the gut microbiota is frequently found in cases of obesity and related metabolic diseases, such as type 2 diabetes mellitus. The composition of the microbiota in diabetics is similar to that of obese people, thereby causing increased energy uptake efficiency in the large intestine of obese people, maintenance of a systemic inflammatory state, and increased insulin resistance. Bariatric surgery seems to entail an improvement in gut dysbiosis, leading to an increased diversity of the gut microbiota.

AIMS

This study aimed to present a literature review on obesity-associated gut dysbiosis and its status post-bariatric surgery.

METHODS

A systematic review of primary studies was conducted in PubMed, SciELO, BIREME, LILACS, Embase, ScienceDirect, and Scopus databases using DeCS (Health Science Descriptors) with the terms "obesity," "intestinal dysbiosis," "bariatric surgery," and "microbiota."

RESULTS

We analyzed 28 articles that had clinical studies or literature reviews as their main characteristics, of which 82% (n=23) corresponded to retrospective studies. The sample size of the studies ranged from 9 to 257 participants and/or fecal samples. The epidemiological profile showed a higher prevalence of obesity in females, ranging from 24.4 to 35.1%, with a mean age of around 25-40 years. There was a variation regarding the type of bariatric surgery, migrating between the Roux-en-Y bypass, adjustable gastric banding, and vertical gastrectomy. Of the 28 studies, 6 of them evaluated the gut microbiota of obese patients undergoing bariatric surgery and their relationship with type 2 diabetes mellitus/glucose metabolism/insulin resistance.

CONCLUSIONS

The intestinal microbiota is an important influencer in the regulation of the digestive tract, and obese individuals with comorbidities (diabetes mellitus, hypercholesterolemia, and metabolic syndrome) present important alterations, with an unbalance normal state, generating dysbiosis and the proliferation of bacterial species that favor the appearance of new diseases. Patients who undergo bariatric surgery present an improvement in the intestinal microbiota imbalance as well as reversibility of their comorbidities, increasing their life expectancy.

Synbiotic Supplementation Modulates Gut Microbiota, Regulates β-Catenin Expression and Prevents Weight Gain in ob/ob Mice: Preliminary Findings

Background: Obesity is one of the main health problems in the world today, and dysbiosis seems to be one of the factors involved. The aim of this study was to examine the impact of synbiotic supplementation on obesity and the microbiota in ob/ob mice. Twenty animals were divided into four groups: obese treated (OT), obese control (OC), lean treated (LT) and lean control (LC). All animals received a standard diet for 8 weeks. The treated groups received a synbiotic (Simbioflora-Invictus Farmanutrição Ltd., Sao Paulo, Brazil) in water, while the nontreated groups received only water. After 8 weeks, all animals were sacrificed, and gut tissue and stool samples were collected for mRNA isolation and microbiota analysis, respectively. β-Catenin, occludin, cadherin and zonulin in the gut tissue were analyzed via RT-qPCR. Microbiome DNA was extracted from stool samples and sequenced using an Ion PGM Torrent platform. Results: Synbiotic supplementation reduced body weight gain in the OT group compared with the OC group (p = 0.0398) and was associated with an increase in Enterobacteriaceae (p = 0.005) and a decrease in Cyanobacteria (p = 0.047), Clostridiaceae (p = 0.026), Turicibacterales (p = 0.005) and Coprococcus (p = 0.047). On the other hand, a significant reduction in Sutterella (p = 0.009) and Turicibacter (p = 0.005) bacteria was observed in the LT group compared to the LC group. Alpha and beta diversities were different among all treated groups. β-Catenin gene expression was significantly decreased in the gut tissue of the OT group (p ≤ 0.0001) compared to the other groups. No changes were observed in occludin, cadherin or zonulin gene expression in the gut tissue. Conclusions: Synbiotic supplementation prevents excessive weight gain, modulates the gut microbiota, and reduces β-catenin expression in ob/ob mice.

Potential associations between alterations in gut microbiome and obesity-related traits after the bariatric surgery

AIM

This study aimed to examine the effects of both obesity and bariatric surgery on gut microbiome, dietary intake, as well as metabolic and inflammatory parameters.

METHODS

All participants (15 with morbid obesity who had bariatric surgery, 8 with morbid obesity and 11 non-obese) were followed-up for a 6-month period with the interviews at baseline (M0), at the end of 3 (M3) and 6 months (M6). Dietary assessment was done, and blood and faecal samples were collected.

RESULTS

Dietary energy and nutrient intakes as well as serum levels glucose, total cholesterol, LDL-cholesterol, and hs-CRP levels decreased by surgery (p<0.05, for each). Participants with morbid obesity had higher levels of Firmicutes and lower levels of Bacteroidetes at M0 compared to non-obese participants. The abundances of Bacteroidetes increased (p=0.02) while Firmicutes decreased (p>0.05) by the surgery, leading a significant decrease in Firmicutes/Bacteroidetes ratio (p=0.01). At sub-phylum level, the abundances of Lactobacillus and Bifidobacterium decreased while Akkermansia increased by the surgery (p<0.01, for each). Although participants who are morbidly obese had a distinct profile according to ß-diversity indices at M0, it became similar with the profile of non-obese participants (p>0.05) at M3 and M6. Similarly, α-diversity indices were lower in subjects with morbid obesity at M0, but became similar to levels in non-obese controls at M6.

CONCLUSION

This study confirmed that bariatric surgery has substantial impacts on gut microbiome composition and diversity, as well as anthropometrical measurements and biochemical parameters, which were associated with the alterations in dietary intake patterns. This article is protected by copyright. All rights reserved.

The Genus Parabacteroides Is a Potential Contributor to the Beneficial Effects of Truncal Vagotomy-Related Bariatric Surgery

PURPOSE

Evidences about the gut microbiota role in weight loss after bariatric surgery (BS) are growing. The objective of this study was to observe the changes of gut microbiota after sleeve gastrectomy (SG) and SG plus truncal vagotomy (SG-TV) and identify specific microbes that may contribute to the improvement of obesity after surgeries.

MATERIALS AND METHODS

Forty high-fat diet-induced obesity (DIO) mice were randomized to SG, SG-TV, or sham operation (SH) groups. Body weight (BW) and fast blood glucose (FBG) were measured before and 1, 2, 4, 8, and 12 weeks post-operatively. Fecal samples were collected before and at post-operative week 12 and profiled using 16S rRNA relative and absolute quantitative sequencing.

RESULTS

After the surgery, the SG and SG-TV surgeries significantly reduce BW and FBG levels compared with SH, and the SG-TV achieved better effects than SG. A decreasing trend in alpha diversity of gut microbiota and significant changes in taxonomic composition were observed after surgeries. Then, we identified a set of microbes and pathways significantly different in abundance after BS. The genus Parabacteroides and one pathway (polyketide sugar unit biosynthesis) increased in SG-TV group specially, which was also negatively correlated with BW and FBG.

CONCLUSION

SG and SG-TV indeed achieve effects of weight loss, but TV could enhance the efficacy of SG. The identified different microbes and pathways, like Parabacteroides, polyketide sugar unit biosynthesis, may partly mediate the beneficial effects of BS, and thus possibly contribute to the development of novel bacteria-based therapeutic approaches.

Functional changes of the gastric bypass microbiota reactivate thermogenic adipose tissue and systemic glucose control via intestinal FXR-TGR5 crosstalk in diet-induced obesity

BACKGROUND

Bariatric surgery remains the most effective therapy for adiposity reduction and remission of type 2 diabetes. Although different bariatric procedures associate with pronounced shifts in the gut microbiota, their functional role in the regulation of energetic and metabolic benefits achieved with the surgery are not clear.

METHODS

To evaluate the causal as well as the inherent therapeutic character of the surgery-altered gut microbiome in improved energy and metabolic control in diet-induced obesity, an antibiotic cocktail was used to eliminate the gut microbiota in diet-induced obese rats after gastric bypass surgery, and gastric bypass-shaped gut microbiota was transplanted into obese littermates. Thorough metabolic profiling was combined with omics technologies on samples collected from cecum and plasma to identify adaptions in gut microbiota-host signaling, which control improved energy balance and metabolic profile after surgery.

RESULTS

In this study, we first demonstrate that depletion of the gut microbiota largely reversed the beneficial effects of gastric bypass surgery on negative energy balance and improved glucolipid metabolism. Further, we show that the gastric bypass-shaped gut microbiota reduces adiposity in diet-induced obese recipients by re-activating energy expenditure from metabolic active brown adipose tissue. These beneficial effects were linked to improved glucose homeostasis, lipid control, and improved fatty liver disease. Mechanistically, these effects were triggered by modulation of taurine metabolism by the gastric bypass gut microbiota, fostering an increased abundance of intestinal and circulating taurine-conjugated bile acid species. In turn, these bile acids activated gut-restricted FXR and systemic TGR5 signaling to stimulate adaptive thermogenesis.

CONCLUSION

Our results establish the role of the gut microbiome in the weight loss and metabolic success of gastric bypass surgery. We here identify a signaling cascade that entails altered bile acid receptor signaling resulting from a collective, hitherto undescribed change in the metabolic activity of a cluster of bacteria, thereby readjusting energy imbalance and metabolic disease in the obese host. These findings strengthen the rationale for microbiota-targeted strategies to improve and refine current therapies of obesity and metabolic syndrome. Video Abstract Bariatric Surgery (i.e. RYGB) or the repeated fecal microbiota transfer (FMT) from RYGB donors into DIO (diet-induced obesity) animals induces shifts in the intestinal microbiome, an effect that can be impaired by oral application of antibiotics (ABx). Our current study shows that RYGB-dependent alterations in the intestinal microbiome result in an increase in the luminal and systemic pool of Taurine-conjugated Bile acids (TCBAs) by various cellular mechanisms acting in the intestine and the liver. TCBAs induce signaling via two different receptors, farnesoid X receptor (FXR, specifically in the intestines) and the G-protein-coupled bile acid receptor TGR5 (systemically), finally resulting in metabolic improvement and advanced weight management. BSH, bile salt hydrolase; BAT brown adipose tissue.

Roux-en-Y gastric bypass and sleeve gastrectomy induce substantial and persistent changes in microbial communities and metabolic pathways

Bariatric surgery induces significant microbial and metabolomic changes, however, links between microbial and metabolic pathways have not been fully elucidated. The objective of this study was to conduct a comprehensive investigation of the microbial, metabolomic, and inflammatory changes that occur following Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). A prospective clinical trial was conducted with participants undergoing RYGB, SG, and non-operative controls (CTRL). Clinical parameters, blood samples, and fecal samples were collected pre-intervention and at 3 and 9 months. A multi-omics approach was used to perform integrated microbial-metabolomic analysis to identify functional pathways in which weight loss and metabolic changes occur after surgery. RYGB led to profound microbial changes over time that included reductions in alpha-diversity, increased Proteobacteria and Verrucomicrobiota, decreased Firmicutes, and numerous changes at the genera level. These changes were associated with a reduction in inflammation and significant weight loss. A reduction in Romboutsia genera correlated strongly with weight loss and integrated microbial-metabolomic analysis revealed the importance of Romboutsia. Its obliteration correlated with improved weight loss and insulin resistance, possibly through decreases in glycerophospholipids. In contrast, SG was associated with no changes in alpha-diversity, and only a small number of changes in microbial genera. A cluster of Firmicutes genera including Butyriciccocus, Eubacterium ventriosum, and Monoglobus was decreased, which correlated with decreased weight, insulin resistance, and systemic inflammation. This work represents comprehensive analyses of microbial-metabolomic changes that occur following bariatric surgery and identifies several pathways that are associated with beneficial metabolic effects of surgery.

Metformin Exerts Anti-inflammatory and Mucus Barrier Protective Effects by Enriching Akkermansia muciniphila in Mice With Ulcerative Colitis

The present study aimed to determine if metformin exerts anti-inflammatory and mucus-protective effects via the gut microbiota. Metformin has extensive benefits including anti-inflammatory effects. Previous studies showed that metformin changed the gut microbiota composition and increases the number of goblet cells. Intestinal dysbiosis and goblet cell depletion are important features of ulcerative colitis (UC). The underlying mechanism and whether metformin can improve the mucus barrier in UC remain unclear. Metformin (400 mg/kg/day) was administered to mice with dextran sulfate sodium (DSS)-induced UC for 2 wk to investigate the effects of metformin on the intestinal mucus barrier. The gut microbiota was depleted, using antibiotics, to explore its role in the mucus-protecting effects of metformin. Akkermansia muciniphila (A. muciniphila), which was enriched in metformin-treated mice, was administered to mice to investigate the effects of the bacteria on UC and the mucus barrier. Metformin attenuated DSS-induced UC in mice, as evidenced by the alleviation of diarrhea, hematochezia, and the decrease in body weight. The expression of mucin2, a prominent mucus barrier protein, was increased in the metformin-treated group compared to the DSS-treated group. Furthermore, fecal 16S rRNA analysis showed that metformin treatment changed the gut microbiota composition by increasing the relative abundance of Lactobacillus and Akkermansia species while decreasing Erysipelatoclostridium at the genus level. Antibiotic treatment partly abolished the anti-inflammatory and mucus-protecting effects of metformin. Administration of A. muciniphila alleviated the colonic inflammation and mucus barrier disruption. Metformin alleviated DSS-induced UC in mice and protected against cell damage via affecting the gut microbiota, thereby providing a new mechanism for the therapeutic effect of metformin in patients with UC. This study also provides evidence that A. muciniphila as a probiotic has potential benefits for UC.

Toll-like receptor 4 and myeloid differentiation factor 88 are required for gastric bypass-induced metabolic effects

Background:

Toll-like receptor 4 (TLR4) has been suggested as one of the forefront cross-communicators between the intestinal bacteria and the host to regulate inflammatory signals and energy homeostasis. High-fat diet–induced inflammation is mediated by changes in gut microbiota and requires a functional TLR-4, the deficiency of which renders mice resistant to diet-induced obesity and its associated metabolic dysfunction. Furthermore, gut microbiota was suggested to play a key role in the beneficial effects of Roux-en-Y gastric bypass (RYGB), a commonly performed bariatric procedure.

Objectives:

To explore whether TLR4, myeloid differentiation factor 8 (MyD88; 1 of its key downstream signaling regulators) and gut microbiota play an integrative role in RYGB-induced metabolic outcomes.

Setting:

Animal-based study.

Method:

We performed RYGB in TLR4 and MyD88 knock-out (KO) mice and used fecal microbiota transplant (FMT) from RYGB-operated animals to these genetic mouse models to address our questions.

Results:

We demonstrate that RYGB reduces TLR4 expression explicitly in the small and large intestine of C57Blc/6J mice. We also show that TLR4 KO mice have an attenuated glucoregulatory response to RYGB. In addition, we reveal that MyD88 KO mice fail to respond to all RYGB-induced metabolic effects. Finally, fecal microbiota transplant from RYGB-operated mice into TLR4 KO and MyD88 KO naïve recipients fails to induce a metabolic phenotype similar to that of the donors, as it does in wild-type recipients.

Conclusion:

TLR4 and MyD88 are required for RYGB-induced metabolic response that is likely mediated by gut microbiome.

Metabolic surgery in China: present and future

Obesity and its related complications comprise a serious public health problem worldwide, and obesity is increasing in China. Metabolic surgery is a new type of treatment with unique advantages in weight loss and obesity-related metabolic complications. The pathogenesis of obesity is complex and not yet fully understood. Here, we review the current efficacy and safety of metabolic surgery, as well as recent progress in mechanistic studies and surgical procedures in China. The exciting and rapid advances in this field provide new opportunities for patients with obesity and strike a balance between long-term effectiveness and safety.

Changes in the Gut Microbiota Following Bariatric Surgery Are Associated with Increased Alcohol Intake in a Female Rat Model

AIMS

We aimed to investigate if differences in gut microbiota diversity and composition are associated with post-operative alcohol intake following bariatric surgery in a rat model.

METHODS

Twenty-four female rats were randomized to three treatment groups: sham surgery, vertical sleeve gastrectomy (VSG) or Roux-en-Y gastric bypass (RYGB). Stool was collected pre- and post-operatively and 16S rRNA gene amplification and sequencing was performed. Analysis focused on correlating microbial diversity, type of surgery and alcohol (EtOH) intake.

RESULTS

Pre-operative stools samples on regular diet showed similar taxonomic composition and Shannon diversity among the three treatment groups. There was a significant decrease in Shannon diversity and a change in taxonomic composition of the gut microbiota after rats was fed high fat diet. Post-operatively, the RYGB group showed significantly lower taxonomic diversity than the VSG and sham groups, while the VSG and sham groups diversity were not significantly different. Taxonomic composition and function prediction based on PICRUSt analysis showed the RYGB group to be distinct from the VSG and sham groups. Shannon diversity was found to be negatively associated with EtOH intake.

CONCLUSIONS

Changes in the taxonomic profile of the gut microbiota following bariatric surgery, particularly RYGB, are associated with increased EtOH intake and may contribute to increased alcohol use disorder risk through the gut-brain-microbiome axis.

Projection of Gut Microbiome Pre- and Post-Bariatric Surgery To Predict Surgery Outcome

Bariatric surgery is often the preferred method to resolve obesity and diabetes, with ∼800,000 cases worldwide yearly and high outcome variability. The ability to predict the long-term body mass index (BMI) change following surgery has important implications for individuals and the health care system in general. Given the tight connection between eating habits, sugar consumption, BMI, and the gut microbiome, we tested whether the microbiome before any treatment is associated with different treatment outcomes, as well as other intakes (high-density lipoproteins [HDL], triglycerides, etc.). A projection of the gut microbiome composition of obese (sampled before and after bariatric surgery) and lean patients into principal components was performed, and the relation between this projection and surgery outcome was studied. The projection revealed three different microbiome profiles belonging to lean, obese, and obese individuals who underwent bariatric surgery, with the postsurgery microbiome more different from the lean microbiome than the obese microbiome. The same projection allowed for a prediction of BMI loss following bariatric surgery, using only the presurgery microbiome. The microbial changes following surgery were an increase in the relative abundance of Proteobacteria and Fusobacteria and a decrease in Firmicutes. The gut microbiome can be decomposed into main components depicting the patient's development and predicting in advance the outcome. Those may be translated into the better clinical management of obese individuals planning to undergo metabolic surgery.

IMPORTANCE BMI and diabetes can affect the gut microbiome composition. Bariatric surgery has large variabilities in the outcome. The microbiome was previously shown to be a good predictor for multiple diseases. We analyzed here the gut microbiome before and after bariatric surgery and showed the following. (i) The microbiome before surgery can be used to predict surgery outcomes. (ii) The postsurgery microbiome drifts further away from the lean microbiome than the microbiome of the presurgery obese patients. These results can lead to a microbiome-based presurgery decision whether to perform surgery.

Visualizing the Growth and Division of Rat Gut Bacteria by D-Amino Acid-Based in vivo Labeling and FISH Staining

Rat is a widely used mammalian model for gut microbiota research. However, due to the difficulties of individual in vitro culture of many of the gut bacteria, much information about the microbial behaviors in the rat gut remains largely unknown. Here, to characterize the in situ growth and division of rat gut bacteria, we apply a chemical strategy that integrates the use of sequential tagging with D-amino acid-based metabolic probes (STAMP) with fluorescence in situ hybridization (FISH) to rat gut microbiota. Following sequential gavages of two different fluorescent D-amino acid probes to rats, the resulting dually labeled gut bacteria provides chronological information of their in situ cell wall synthesis. After taxonomical labeling with FISH probes, most of which are newly designed in this study, we successfully identify the growth patterns of 15 bacterial species, including two that have not been cultured separately in the laboratory. Furthermore, using our labeling protocol, we record Butyrivibrio fibrisolvens cells growing at different growth stages of a complete cell division cycle, which offers a new scope for understanding basic microbial activities in the gut of mammalian hosts.

Alterations of Serum Uric Acid Level and Gut Microbiota After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy in a Hyperuricemic Rat Model

Background

The objective of this study was to observe alterations of serum uric acid (SUA) level and gut microbiota after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery in a hyperuricemic rat model.

Method

We performed Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery in a hyperuricemic rat model. Serum uric acid (UA), xanthine oxidase (XO) activity, IL-6, TNF-α and lipopolysaccharide (LPS) level changes, and 16S rDNA of gut microbiota were analyzed.

Results

After the surgery, the RYGB and SG procedures significantly reduced body weight, serum UA, IL-6, TNF-α and LPS levels, and XO activity. In addition, the RYGB and SG procedures altered the diversity and taxonomic composition of the gut microbiota. Compared with Sham group, RYGB and SG procedures were enriched in the abundance of phylum Verrucomicrobia and species Akkermansia muciniphila, while the species Escherichia coli was reduced.

Discussion

We here concluded that bariatric surgery-induced weight loss and resolution of inflammatory remarkers as well as changes of gut microbiota may be responsible for the reduced XO activity and SUA level. To have a better understanding of the underlying mechanism of UA metabolism following bariatric surgery, further research is needed.

Biliary Jejunostomy Might Improve Glucose in Type 2 Diabetes Patients

PURPOSES

Biliopancreatic diversion could improve type 2 diabetes mellitus. Our aim was to investigate the effects of biliary jejunostomy on the improvement of glucose.

MATERIALS AND METHODS

Twenty-seven type 2 diabetes patients underwent biliary jejunostomy between January 2013 and January 2018 in our hospital and were followed up. Demographic data, operation details, body weight, food intake, effects on diabetes control, and biomedical parameters were collected and analyzed.

RESULTS

As defined previously, 3 of 27 diabetes patients were "under control," 8 patients were "in remission," and 12 patients were "improved." The fasting glucose decreased from 9.7 ± 2.1 mmol/L before surgery to 7.9 ± 1.8 mmol/L 12 months after surgery (P = 0.001). The level of hemoglobin A1c in these patients was 9.1 ± 2.3% before surgery, and it decreased to 7.2 ± 1.3% 12 months after surgery (P < 0.001). There was no significant difference in the body weight index (P = 0.78) or food intake (P = 0.18) between the time prior to surgery and 12 months afterward. The average level of total bile acids increased significantly after surgery, from 6.7 ± 2.2 μmol/L before surgery to 8.6 ± 2.9 μmol/L 12 months after surgery (P < 0.001).

CONCLUSIONS

Fasting glucose in type 2 diabetes patients was improved after biliary jejunostomy. Increasing bile acids levels might play an important role in the remission of type 2 diabetes.

Roux-en-Y gastric bypass contributes to weight loss-independent improvement in hypothalamic inflammation and leptin sensitivity through gut-microglia-neuron-crosstalk

Objective

Hypothalamic inflammation and endoplasmic reticulum (ER) stress are extensively linked to leptin resistance and overnutrition-related diseases. Surgical intervention remains the most efficient long-term weight-loss strategy for morbid obesity, but mechanisms underlying sustained feeding suppression remain largely elusive. This study investigated whether Roux-en-Y gastric bypass (RYGB) interacts with obesity-associated hypothalamic inflammation to restore central leptin signaling as a mechanistic account for post-operative appetite suppression.

Methods

RYGB or sham surgery was performed in high-fat diet-induced obese Wistar rats. Sham-operated rats were fed ad libitum or by weight matching to RYGB via calorie restriction (CR) before hypothalamic leptin signaling, microglia reactivity, and the inflammatory pathways were examined to be under the control of gut microbiota-derived circulating signaling.

Results

RYGB, other than CR-induced adiposity reduction, ameliorates hypothalamic gliosis, inflammatory signaling, and ER stress, which are linked to enhanced hypothalamic leptin signaling and responsiveness. Mechanistically, we demonstrate that RYGB interferes with hypothalamic ER stress and toll-like receptor 4 (TLR4) signaling to restore the anorexigenic action of leptin, which most likely results from modulation of a circulating factor derived from the altered gut microbial environment upon RYGB surgery.

Conclusions

Our data demonstrate that RYGB interferes with hypothalamic TLR4 signaling to restore the anorexigenic action of leptin, which most likely results from modulation of a circulating factor derived from the post-surgical altered gut microbial environment.

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RYGB surgery-related weight loss independently restores hypothalamic leptin signaling and action in diet-induced obesity.

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RGYB modulates hypothalamic TLR4-mediated pro-inflammatory signaling and ER stress to restore leptin's anorexigenic action.

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Humoral factors contribute to modulated microglia-POMC neuron interaction, which appears specific to the RYGB procedure.

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Altering the gut microbiota environment by antibiotics deteriorates leptin's feeding suppressive action after RYGB.

Clostridium butyricum Alleviates Gut Microbiota Alteration-Induced Bone Loss after Bariatric Surgery by Promoting Bone Autophagy

Bariatric surgery is the most common and effective treatment of severe obesity; however, these bariatric procedures always result in detrimental effects on bone metabolism by underlying mechanisms. This study aims to investigate the skeletal response to bariatric surgery and to explore whether Clostridium butyricum alleviates gut microbiota alteration-induced bone loss after bariatric surgery. Consequently, male SD rats received Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery, respectively, followed by body weight recording. The bone loss after bariatric surgery was further determined by dual-energy X-ray absorptiometry (DXA), micro-CT measurement, histologic analyses, and Western blot. Besides, 16S rDNA gene sequencing was performed to determine the gut microbiota alteration after surgery, and intervention with fecal microbiota from RYGB donor was conducted in obese SD rats, followed by C. butyricum administration. Accordingly, rats in the RYGB and SG groups maintained sustained weight loss, and DXA and micro-CT measurement further demonstrated significant bone loss after bariatric surgery. Besides, histologic and Western blot analyses validated enhanced osteoclastogenesis and inhibited osteoblastogenesis and defective autophagy after surgery. The 16S rDNA gene sequencing suggested a significant alteration of gut microbiota composition in the RYGB group, and intervention with fecal microbiota from RYGB donor further determined that this kind of alteration contributed to the bone loss after RYGB. Meanwhile, C. butyricum might protect against this postoperative bone loss by promoting osteoblast autophagy. In summary, this study suggests novel mechanisms to clarify the skeletal response to bariatric surgery and provides a potential candidate for the treatment of bone disorder among bariatric patients. SIGNIFICANCE STATEMENT: The significance of this study is the discovery of obvious bone loss and defective autophagy after bariatric surgery. Besides, it is revealed that gut microbiota alterations could be the reason for impaired bone mass after bariatric surgery. Furthermore, Clostridium butyricum could alleviate the gut microbiota alteration-induced bone loss after bariatric surgery by promoting osteoblast autophagy.

Relationship between bariatric surgery outcomes and the preoperative gastrointestinal microbiota: a cohort study

BACKGROUND

The composition of the gastrointestinal microbiota is associated with obesity. We hypothesized that the gut microbiota influences the outcomes of bariatric surgery.

OBJECTIVES

We aimed to analyze using oral swabs and stool samples the microbiota of patients with morbid obesity who were undergoing laparoscopic sleeve gastrectomy (SG).

SETTING

A university hospital in Poland.

METHODS

This prospective cohort study was conducted between November 2018 and June 2019. Participants underwent SG or no surgery (controls). Results were then analyzed as a group 1 (surgical participants who achieved a percentage of excess weight loss [%EWL] >50%), group 2 (surgical participants who achieved a %EWL <50%), and group 3 (nonsurgical controls). %EWL was measured 6 months following surgery. Before surgery, oral swabs were obtained and stool samples were provided. The endpoint was the composition of the gut microbiota.

RESULTS

Group 1 comprised 19 participants, group 2 comprised 11 participants, and group 3 comprised 16 participants. No participants were lost to follow-up during the study. Participants in group 1 had an oral microbiota that was enriched in the phyla Proteobacteria, and Bacteroidetes. Their intestinal microbiota was enriched in the Proteobacteria. In contrast, the oral microbiota of group 2 was enriched in the Actinobacteria and the intestinal microbiota was enriched in the phyla Bacteroidetes and Firmicutes.

CONCLUSIONS

The compositions of the microbiota of the oral cavity and large intestine are related to the weight loss achieved following SG.

RYGB increases postprandial gastric nesfatin-1 and rapid relieves NAFLD via gastric nerve detachment

Background

Roux-en-Y gastric bypass (RYGB) could reduce nonalcoholic fatty liver disease (NAFLD) ahead of the weight-loss effects. But the detailed mechanisms remain unclear.

Material and methods

A high-fat diet (HFD) was fed to induce obesity. RYGB was then performed. Gastric nesfatin-1 was measured by enzyme-linked immunosorbent assay (ELISA) in portal vein and polymerase chain reaction (PCR) in gastric tissues. Modified surgeries including vagus-preserved bypass and vagectomy were performed and postprandial gastric nesfatin-1 were analyzed. The effects of nesfatin-1 on hepatocytes were studied by PCR and immunohistochemistry. Both intraperitoneal and intracerebroventricular injection (ICV) were performed to analyze the in vivo effects on liver lipid metabolism.

Results

Increased postprandial portal vein nesfatin-1 was observed in RYGB but not in control groups. This increase is mainly due to induction of gastric nesfatin-1. A modified RYGB in which the gastric vagus is preserved is conducted and, in this case, this nesfatin-1 induction effect is diminished. Mere vagectomy could also induce a similar nesfatin-1 increase pattern. The infusion of nesfatin-1 in the brain could inhibit the expression of gastric nesfatin-1, and the effects are diminished after gastric vagectomy. In vivo and in vitro nesfatin-1 stimulation in the liver resulted in improvements in lipid metabolism.

Conclusions

Severing the gastric vagus during RYGB could cut off the negative control from the central nervous system (CNS) and result in increased postprandial gastric nesfatin-1 post surgery, which in turn, improves NAFLD.

Gut Microbiota in Patients with Morbid Obesity Before and After Bariatric Surgery: a Ten-Year Review Study (2009-2019)

The changes in the composition and function of gut microbiota affect the metabolic functions (which are mediated by microbial effects) in patients with obesity, resulting in significant physiological regulation in these patients. Most of the studies emphasize that the Western-style diet (high fat and low vegetable consumption) leads to significant changes in the intestinal microbiome in individuals with metabolic syndrome. A deeper understanding of the profiles of gut microbes will contribute to the development of new therapeutic strategies for the management of metabolic syndrome and other metabolic diseases and related disorders. The aim of this review is to evaluate recent experimental evidence outlining the alterations of gut microbiota composition and function in recovery from bariatric surgical operations with an emphasis on sleeve gastrectomy and gastric bypass.

Whole Blueberry and Isolated Polyphenol-Rich Fractions Modulate Specific Gut Microbes in an In Vitro Colon Model and in a Pilot Study in Human Consumers

Blueberry (BB) consumption is linked to improved health. The bioconversion of the polyphenolic content of BB by fermentative bacteria in the large intestine may be a necessary step for the health benefits attributed to BB consumption. The identification of specific gut microbiota taxa that respond to BB consumption and that mediate the bioconversion of consumed polyphenolic compounds into bioactive forms is required to improve our understanding of how polyphenols impact human health. We tested the ability of polyphenol-rich fractions purified from whole BB-namely, anthocyanins/flavonol glycosides (ANTH/FLAV), proanthocyanidins (PACs), the sugar/acid fraction (S/A), and total polyphenols (TPP)-to modulate the fecal microbiota composition of healthy adults in an in vitro colon system. In a parallel pilot study, we tested the effect of consuming 38 g of freeze-dried BB powder per day for 6 weeks on the fecal microbiota of 17 women in two age groups (i.e., young and older). The BB ingredients had a distinct effect on the fecal microbiota composition in the artificial colon model. The ANTH/FLAV and PAC fractions were more effective in promoting microbiome alpha diversity compared to S/A and TPP, and these effects were attributed to differentially responsive taxa. Dietary enrichment with BB resulted in a moderate increase in the diversity of the microbiota of the older subjects but not in younger subjects, and certain health-relevant taxa were significantly associated with BB consumption. Alterations in the abundance of some gut bacteria correlated not only with BB consumption but also with increased antioxidant activity in blood. Collectively, these pilot data support the notion that BB consumption is associated with gut microbiota changes and health benefits.

Type 2 Diabetes Mellitus Associated with Obesity (Diabesity). The Central Role of Gut Microbiota and Its Translational Applications

Obesity is a condition of rising prevalence worldwide, with important socioeconomic implications, being considered as a growing public health concern. Frequently, obesity brings other complications in addition to itself—like Type 2 Diabetes Mellitus (T2DM)—sharing origin, risk factors and pathophysiological mechanisms. In this context, some authors have decided to include both conditions as a unique entity known as “diabesity”. In fact, understanding diabesity as a single disease is possible to maximise the benefits from therapies received in these patients. Gut microbiota plays a key role in individual’s health, and their alterations, either in its composition or derived products are related to a wide range of metabolic disorders like T2DM and obesity. The present work aims to collect the different changes reported in gut microbiota in patients with T2DM associated with obesity and their possible role in the onset, development, and establishment of the disease. Moreover, current research lines to modulate gut microbiota and the potential clinical translation derived from the knowledge of this system will also be reviewed, which may provide support for a better clinical management of such a complex condition.

Recent advances in the mechanisms underlying the beneficial effects of bariatric and metabolic surgery

Bariatric and metabolic surgery (BMS) is the most effective treatment for obesity, type 2 diabetes and co-morbidities, including nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. The beneficial effects of BMS are beyond the primary goal of gastric restriction and nutrients malabsorption. Roux-en-Y gastric bypass and vertical sleeve gastrectomy are the 2 most commonly performed procedures of BMS. Both surgeries lead to physiologic changes in gastrointestinal tract; subsequently alter bile acids pool and composition, gut microbial activities, gut hormones, and circulating exosomes; and ultimately contribute to the improved glycemic control, insulin sensitivity, lipid metabolism, energy expenditure, and weight loss. The mechanisms underlying the benefits of BMS likely involve the bile acid-signaling pathway mediated mainly by nuclear farnesoid X receptor and the membrane Takeda G protein-coupled receptor, bile acids-gut microbiota interaction, and exosomes. In this review, we focus on recent advances in potential mechanisms and aim to learn novel insights into the molecular mechanisms underlying metabolic disorders.

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.

Changes in Gut Microbiota Composition after Bariatric Surgery: a New Balance to Decode

BACKGROUND

Recently, the link between obesity and gut microbiota has become a focus for research. This study shed some light on the modification of postoperative gut microbial composition after bariatric surgery.

METHODS

A prospective longitudinal study on healthy lean subjects and patients who underwent bariatric surgery (Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy) was carried out. Anthropometric and metabolic data, smoking, food preferences data, and stool samples were collected from lean subjects and from obese patients before and 3 and 6 months after surgery (T0, T3, and T6, respectively).

RESULTS

We collected stool samples from 25 obese patients before surgery and 3 and 6 months thereafter and from 25 normal weight patients. After Roux-en-Y gastric bypass, Yokenella regensburgei (p < 0.05), Fusobacterium varium (p < 0.05), Veillonella dispar/atypica (p < 0.05), and Streptococcus australis/gordonii (p < 0.05) were transiently identified in the gut at T3. Roux-en-Y gastric bypass patients had a permanent increase in Akkermansia muciniphila (p < 0.05), which is associated with healthy metabolism, both at T3 and T6. There were no significant changes in gut microbiota in laparoscopic sleeve gastrectomy patients.

CONCLUSIONS

In our study, Roux-en-Y gastric bypass induced major microbial differences and greater weight loss compared with laparoscopic sleeve gastrectomy. Analyzing the microbiota composition, a proliferation of potential pathogens and the onset of beneficial bacteria was observed. The effects of these bacteria on human health are still far from clear. Understanding the mechanisms of action of these bacteria could be the keystone in developing new therapeutic strategies for obesity.

Alterations of Gut Microbiota After Biliopancreatic Diversion with Duodenal Switch in Wistar Rats

BACKGROUND

The biliopancreatic diversion with duodenal switch (BPD/DS) represents the most effective surgical procedure for the treatment of severe obesity and associated type 2 diabetes. The mechanisms whereby BPD/DS exerts its positive metabolic effects have however yet to be fully delineated. The objective of this study was to distinguish the effects of the two components of BPD/DS, namely the sleeve gastrectomy (SG) and the DS derivation, on gut microbiota, and to appraise whether changes in microbial composition are linked with surgery-induced metabolic benefits.

METHODS

BPD/DS, DS, and SG were performed in Wistar rats fed a standard chow diet. Body weight and energy intake were measured daily during 8 weeks post-surgery, at which time glucagon-like peptide 1 (GLP-1), peptide tyrosine tyrosine (PYY), insulin, and glucose were measured. Fecal samples were collected prior to surgery and at 2 and 8 weeks post-surgery. Intraluminal contents of the alimentary, biliopancreatic, and common limbs (resulting from BPD/DS) were taken from the proximal portion of each limb. Fecal and small intestinal limb samples were analyzed by 16S ribosomal RNA gene sequencing.

RESULTS

BPD/DS and DS led to lower digestible energy intake (P = 0.0007 and P = 0.0002, respectively), reduced weight gain (P < 0.0001) and body fat mass (P < 0.0001), improved glucose metabolism, and increased GLP-1 (P = 0.0437, SHAM versus DS) and PYY levels (P < 0.0001). These effects were associated with major alterations of both the fecal and small intestinal microbiota, as revealed by significant decrease in bacterial richness and diversity at 2 (P < 0.0001, Chao1 index; P < 0.0001, Shannon index) and 8 weeks (P = 0.0159, SHAM versus DS, Chao1 index; P = 0.0219, SHAM versus DS, P = 0.0472, SHAM versus BPD/DS, Shannon index) post-surgery in BPD/DS and DS, and increased proportions of Bifidobacteriales (a 60% increase in both groups) but reduced Clostridiales (a 50% decrease and a 90% decrease respectively), which were mostly accounted at the genus level by higher relative abundance of Bifidobacterium in both the fecal and intestinal limb samples, as well as reduced abundance of Peptostreptococcaceae and Clostridiaceae in the small intestine. Those effects were not seen in SG rats.

CONCLUSION

The metabolic benefits following BPD/DS are seemingly due to the DS component of the surgery. Furthermore, BPD/DS causes marked alterations in fecal and small intestinal microbiota resulting in reduced bacterial diversity and richness. Our data further suggest that increased abundance of Bifidobacterium and reduced level of two Clostridiales species in the gut microbiota might contribute to the positive metabolic outcomes of BPD/DS.

Do Bariatric Surgeries Enhance Brown/Beige Adipose Tissue Thermogenesis?

Bariatric surgeries induce marked and durable weight loss in individuals with morbid obesity through powerful effects on both food intake and energy expenditure. While alterations in gut-brain communication are increasingly implicated in the improved eating behavior following bariatric surgeries, less is known about the mechanistic basis for energy expenditure changes. Brown adipose tissue (BAT) and beige adipose tissue (BeAT) have emerged as major regulators of whole-body energy metabolism in humans as well as in rodents due to their ability to convert the chemical energy in circulating glucose and fatty acids into heat. In this Review, we critically discuss the steadily growing evidence from preclinical and clinical studies suggesting that Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), the two most commonly performed bariatric surgeries, enhance BAT/BeAT thermogenesis. We address the documented mechanisms, highlight study limitations and finish by outlining unanswered questions in the subject. Further understanding how and to what extent bariatric surgeries enhance BAT/BeAT thermogenesis may not only aid in the development of improved obesity pharmacotherapies that safely and optimally target both sides of the energy balance equation, but also in the development of novel hyperglycemia and/or hyperlipidemia pharmacotherapies.

Enteric hyperoxaluria: role of microbiota and antibiotics

PURPOSE OF REVIEW

Enteric hyperoxaluria is commonly observed in malabsorptive conditions including Roux en Y gastric bypass (RYGB) and inflammatory bowel diseases (IBD). Its incidence is increasing secondary to an increased prevalence of both disorders. In this review, we summarize the evidence linking the gut microbiota to the risk of enteric hyperoxaluria.

RECENT FINDINGS

In enteric hyperoxaluria, fat malabsorption leads to increased binding of calcium to free fatty acids resulting in more soluble oxalate in the intestinal lumen. Bile acids and free fatty acids in the lumen also cause increased gut permeability allowing more passive absorption of oxalate. In recent years, there is more interest in the role of the gut microbiota in modulating urinary oxalate excretion in enteric hyperoxaluria, stemming from our knowledge that microbiota in the intestines can degrade oxalate. Oxalobacter formigenes reduced urinary oxalate in animal models of RYGB. The contribution of other oxalate-degrading organisms and the microbiota community to the pathophysiology of enteric hyperoxaluria are also currently under investigation.

SUMMARY

Gut microbiota might play a role in modulating the risk of enteric hyperoxaluria through oxalate degradation and bile acid metabolism. O. formigenes is a promising therapeutic target in this population; however, further studies in humans are needed to test its effectiveness.

The genus Sutterella is a potential contributor to glucose metabolism improvement after Roux-en-Y gastric bypass surgery in T2D

BACKGROUND

Alterations in gut microbiota have been associated with improvements in blood glucose due to bariatric surgery.

OBJECTIVES

Our aim is to identify specific gut microbiota that contribute to the remission of T2D after RYGB and SG.

METHODS

Rats fed a high-fat diet (HFD) were administered a low dose of streptozotocin as T2D models; next, their caecum content was collected 8 weeks after RYGB and SG. We also used case-control of gut microbial profiles of T2D patients and healthy people by collecting the mucosal-luminal interface from the ascending colon. Samples were profiled by 16S rRNA gene sequencing.

RESULTS

RYGB and SG reduced weight and improved glucose and insulin tolerance. Principal coordinate analysis showed that SG and, especially, RYGB cause changes in the composition of gut microbiota. We found that family Alcaligenaceae (genus Sutterella) was significantly decreased in the ascending colon of patients with T2D and increased after RYGB surgery in the caecum of T2D rats as shown by a linear discriminant analysis effect size (LEfSe) analysis, with no significant changes after SG. This result might benefit the improvement of glycometabolism.

CONCLUSIONS

RYGB can significantly reduce weight, improve glycometabolism and change the composition of the gut microbiota. Sutterella may have beneficial effects on glycometabolism in T2D patients after RYGB.

Bariatric Surgery in Obesity: Effects on Gut Microbiota and Micronutrient Status

Obesity is associated with reduced gut microbial diversity and a high rate of micronutrient deficiency. Bariatric surgery, the therapy of choice for severe obesity, produces sustained weight loss and improvements in obesity-related comorbidities. Also, it significantly alters the gut microbiota (GM) composition and function, which might have an important impact on the micronutrient status as GM is able to synthesize certain vitamins, such as riboflavin, folate, B12, or vitamin K2. However, recent data have reported that GM is not fully restored after bariatric surgery; therefore, manipulation of GM through probiotics represents a promising therapeutic approach in bariatric patients. In this review, we discuss the latest evidence concerning the relationship between obesity, GM and micronutrients, the impact of bariatric surgery on GM in relation with micronutrients equilibrium, and the importance of the probiotics' supplementation in obese patients submitted to surgical treatment.

Multiorgan Systems Study Reveals Igfbp7 as a Suppressor of Gluconeogenesis after Gastric Bypass Surgery

Roux-en-Y gastric bypass (RYGB) surgery reduces weight in obese patients. A marked decrease in blood glucose levels occurs before weight loss; however, key molecules that improve the glycemic profile remain largely unknown. Using a murine RYGB surgery model, we performed multiorgan proteomics and bioinformatics to monitor the proteins and molecular pathways that change in this early glycemic response. Multiplexed proteomic kinetics data analysis revealed that the Roux limb, biliopancreatic limb, liver, and pancreas each exhibited unique temporal and molecular responses to the RYGB surgery. In addition, protein-protein network analysis indicated that the changes to the microbial environment in the intestine may play a crucial role in the beneficial effects of RYGB surgery. Furthermore, insulin-like growth factor binding protein 7 (Igfbp7) was identified as an early induced protein in the Roux limb. Known secretory properties of Igfbp7 prompted us to further investigate its role as a remote organ regulator of glucose metabolism. Igfbp7 overexpression decreased blood glucose levels in diet-induced obese mice and attenuated gluconeogenic gene expression in the liver. Secreted Igfbp7 appeared to mediate these beneficial effects. These results demonstrate that organs responded differentially to RYGB surgery and indicate that Igfbp7 may play an important role in improving blood glucose levels.

Review of the management of diarrhea syndrome after a bariatric surgery

Obesity is a prevalent health problem in our population. Bariatric surgery is the indicated treatment for severe cases. It is very effective (together with an adequate lifestyle modification) but it is also associated with frequent adverse events. One of the most frequent and disturbing adverse event is diarrhea. Diarrhea after bariatric surgery may be secondary to multiple causes and the physiopathogenic mechanisms may depend on the type of surgery performed. The most frequent diarrhea mechanisms are dumping syndrome, vagotomy, short bowel syndrome, carbohydrate malabsorption, protein malabsorption, alterations of the microbiota, Clostridium difficile infection, bacterial overgrowth, bile salt malabsorption, pancreatic insufficiency, endocrinological disorders, addictive disorders, and other digestive disorders not necessarily related to surgery.

Mechanisms of Weight Loss After Sleeve Gastrectomy and Adjustable Gastric Banding: Far More Than Just Restriction

Obesity has reached global epidemic proportions in recent decades. Bariatric surgery is currently accepted as most effective in alleviating morbid obesity and related disorders. Sleeve gastrectomy (SG) and adjustable gastric banding (AGB) have gained popularity since the beginning of this century because of their efficacy, safety, and simplicity. SG, in particular, has emerged as the most popular bariatric procedure because of its simpler concept and shorter operative time compared with gastric bypass. Caloric restriction, however, cannot account for the sustained weight loss and improved glucose metabolism seen following SG and AGB. Other mechanisms, including changes in gastrointestinal hormone secretion, rearrangement of hypothalamic and vagal control, alteration in energy expenditure, and re-regulation of bile acid metabolism and the intestinal flora environment, are thought to contribute to the postoperative benefits. This review focuses on clinical and experimental literature addressing the potential mechanisms for SG and AGB procedures in human and animal models. Understanding such mechanisms can provide important insight into how current gastric restrictive procedures work and how future treatments of obesity, both surgical and nonsurgical, can be developed.

Gut Microbiota Dysbiosis in Human Obesity: Impact of Bariatric Surgery

PURPOSE OF REVIEW

In this review, we summarize what is currently described in terms of gut microbiota (GM) dysbiosis modification post-bariatric surgery (BS) and their link with BS-induced clinical improvement. We also discuss how the major inter-individual variability in terms of GM changes could impact the clinical improvements seen in patients.

RECENT FINDINGS

The persisting increase in severe obesity prevalence has led to the subsequent burst in BS number. Indeed, it is to date the best treatment option to induce major and sustainable weight loss and metabolic improvement in these patients. During obesity, the gut microbiota displays distinctive features such as low microbial gene richness and compositional and functional alterations (termed dysbiosis) which have been associated with low-grade inflammation, increased body weight and fat mass, as well as type-2 diabetes. Interestingly, GM changes post-BS is currently being proposed as one the many mechanism explaining BS beneficial clinical outcomes. BS enables partial rescue of GM dysbiosis observed during obesity. Some of the GM characteristics modified post-BS (composition in terms of bacteria and functions) are linked to BS beneficial outcomes such as weight loss or metabolic improvements. Nevertheless, the changes in GM post-BS display major variability from one patient to the other. As such, further large sample size studies associated with GM transfer studies in animals are still needed to completely decipher the role of GM in the clinical improvements observed post-surgery.

Roux-Y Gastric Bypass and Sleeve Gastrectomy directly change gut microbiota composition independent of surgery type

Bariatric surgery in morbid obesity, either through sleeve gastrectomy (SG) or Roux-Y gastric bypass (RYGB), leads to sustainable weight loss, improvement of metabolic disorders and changes in intestinal microbiota. Yet, the relationship between changes in gut microbiota, weight loss and surgical procedure remains incompletely understood. We determined temporal changes in microbiota composition in 45 obese patients undergoing crash diet followed by SG (n = 22) or RYGB (n = 23). Intestinal microbiota composition was determined before intervention (baseline, S1), 2 weeks after crash diet (S2), and 1 week (S3), 3 months (S4) and 6 months (S5) after surgery. Relative to S1, the microbial diversity index declined at S2 and S3 (p < 0.05), and gradually returned to baseline levels at S5. Rikenellaceae relative abundance increased and Ruminococcaceae and Streptococcaceae abundance decreased at S2 (p < 0.05). At S3, Bifidobacteriaceae abundance decreased, whereas those of Streptococcaceae and Enterobacteriaceae increased (p < 0.05). Increased weight loss between S3-S5 was not associated with major changes in microbiota composition. No significant differences appeared between both surgical procedures. In conclusion, undergoing a crash diet and bariatric surgery were associated with an immediate but temporary decline in microbial diversity, with immediate and permanent changes in microbiota composition, independent of surgery type.

Microbial and metabolomic remodeling by a formula of Sichuan dark tea improves hyperlipidemia in apoE-deficient mice

Medicine-food homology is a long-standing concept in traditional Chinese medicine. YiNianKangBao (YNKB) tea is a medicine-food formulation based on Sichuan dark tea (Ya'an Tibetan tea), which is traditionally used for its lipid-lowering properties. In this study, we evaluated the effects of YNKB on dyslipidemia and investigated the mechanism underlying its correlation with gut microbiota and serum metabolite regulation. Wild-type mice were fed a normal diet as a control. Male ApoE-/- mice were randomly divided into three high-fat diet (HFD) groups, a model group, and two treated groups (100, 400 mg/kg/d for low, high-dose), and fed by gavage for 12 weeks. Serum lipid levels, composition of gut microbiota, and serum metabolites were then analyzed before treatment with YNKB. We extracted the ingredients of YNKB in boiled water for one hour. YNKB supplementation at a high dose of 400 mg/kg/day reduced bodyweight gains (relative epididymal fat pad and liver weight), and markedly attenuated serum lipid profiles and atherosclerosis index, with no significant differences present between the low-dose treatment and HFD groups. Gut microbiota and serum metabolic analysis indicated that significant differences were observed between normal, HFD, and YNKB treatment groups. These differences in gut microbiota exhibited strong correlations with dyslipidemia-related indexes and serum metabolite levels. Oral administration of high-dose YNKB also showed significant lipid-lowering activity against hyperlipidemia in apoE-deficient mice, which might be associated with composition alterations of the gut microbiota and changes in serum metabolite abundances. These findings highlight that YNKB as a medicine-food formulation derived from Sichuan dark tea could prevent dyslipidemia and improve the understanding of its mechanisms and the pharmacological rationale for preventive use.

Nutritional Modulation of Immune and Central Nervous System Homeostasis: The Role of Diet in Development of Neuroinflammation and Neurological Disease

The gut-microbiome-brain axis is now recognized as an essential part in the regulation of systemic metabolism and homeostasis. Accumulating evidence has demonstrated that dietary patterns can influence the development of metabolic alterations and inflammation through the effects of nutrients on a multitude of variables, including microbiome composition, release of microbial products, gastrointestinal signaling molecules, and neurotransmitters. These signaling molecules are, in turn, implicated in the regulation of the immune system, either promoting or inhibiting the production of pro-inflammatory cytokines and the expansion of specific leukocyte subpopulations, such as Th17 and Treg cells, which are relevant in the development of neuroinflammatory and neurodegenerative conditions. Metabolic diseases, like obesity and type 2 diabetes mellitus, are related to inadequate dietary patterns and promote variations in the aforementioned signaling pathways in patients with these conditions, which have been linked to alterations in neurological functions and mental health. Thus, maintenance of adequate dietary patterns should be an essential component of any strategy aiming to prevent neurological pathologies derived from systemic metabolic alterations. The present review summarizes current knowledge on the role of nutrition in the modulation of the immune system and its impact in the development of neuroinflammation and neurological disease.

Gut microbiota: a new path to treat obesity

Obesity is a multifactorial disease resulting in excessive accumulation of adipose tissue. Over the last decade, growing evidence has identified the gut microbiota as a potential factor in the pathophysiology of both obesity and the related metabolic disorders. The gut microbiota is known to protect gastrointestinal mucosa permeability and to regulate the fermentation and absorption of dietary polysaccharides, perhaps explaining its importance in the regulation of fat accumulation and the resultant obesity. The proposed mechanisms by which the gut microbiota could contribute to the pathogenesis of obesity and the related metabolic diseases include: (a) a high abundance of bacteria that ferment carbohydrates, leading to increased rates of short-chain fatty acid (SCFA) biosynthesis, providing an extra source of energy for the host, that is eventually stored as lipids or glucose; (b) increased intestinal permeability to bacterial lipopolysaccharides (LPS), resulting in elevated systemic LPS levels that aggravate low-grade inflammation and insulin resistance; (c) increased activity of the gut endocannabinoid system. Fecal transplantation studies in germ-free mice have provided crucial insights into the potential causative role of the gut microbiota in the development of obesity and obesity-related disorders. Diet +/- bariatric surgery have been reported to modulate the gut microbiota, leading to lean host phenotype body composition. This review aims to report clinical evidence for a link of the gut microbiota with human obesity and obesity-related diseases, to provide molecular insights into these associations, and to address the effect of diet and bariatric surgery on the gut microbiota, including colonic microbiota, as a potential mechanism for promoting weight loss.

Changes of gut microbiota between different weight reduction programs

BACKGROUND

Gut microbiota may induce obesity, diabetes, and metabolic syndrome. Different weight reduction programs may induce different changes in gut microbiota.

OBJECTIVES

To assess the changes in gut microbiota between obese adults who participated in 2 different weight reduction programs, the dietary counseling (DC) group and sleeve gastrectomy (SG) group, for 3 months.

SETTING

A University Hospital.

METHODS

Ten obese participants from each group were matched according to sex, age, and body mass index. Gut microbiota compositions were determined by metagenomics using next-generation sequencing before and after treatment. Anthropometric indices, metabolic factors, and gut microbiota were compared between and within groups.

RESULTS

After 3 months of treatment, compared with subjects in DC group, subjects in SG group experienced a greater reduction in body weight, body mass index, body fat, waist and hip circumference, diastolic blood pressure, hemoglobin, insulin, insulin resistance, glutamate pyruvate transaminase, blood urine nitrogen, and glycated hemoglobin (HbA1C). A total of 8, 17, and 46 species experienced significant abundance changes in DC, in SG, and between the 2 groups, respectively. Diversity of the gut flora increased in SG and between the 2 groups after treatment. The weight change over the course of the weight loss program was further adjusted and only 4 species, including Peptoniphilus lacrimalis 315 B, Selenomonas 4 sp., Prevotella 2 sp., and Pseudobutyrivibrio sp., were found to be significantly different between the 2 weight loss programs. These 4 species may be the different gut microbiota change between internal and surgical weight reduction programs.

CONCLUSIONS

There are significant differences not only in anthropometric indices and metabolic factors but also in gut microbiota change between the 2 programs.