Increased glycine-amidated hyocholic acid correlates to improved early weight loss after sleeve gastrectomy

Increase in bile acids after sleeve gastrectomy improves metabolism by activating GPBAR1 to increase cAMP in mice with nonalcoholic fatty liver disease

BACKGROUND

Bile acids (BAs) concentration can affect metabolic improvement caused by bariatric surgery and BA concentrations increase in patients after sleeve gastrectomy (SG). Here, how BAs after SG affect metabolism in nonalcoholic fatty liver disease (NAFLD) was studied.

METHODS

Mice were given high-fat diet (HFD) to induce NAFLD and received SG surgery. Hepatic and fecal BA concentrations in mice were detected by liquid chromatography-tandem mass spectrometry method. BA-related genes were detected by quantitative real-time polymerase chain reaction. G protein BA receptor 1 (GPBAR1) expression was identified using western blot analysis. NAFLD mice after SG received GPBAR1 inhibitor Triamterene. The weight of mice and mice liver was detected. Mouse liver tissue was observed by hematoxylin-eosin and Oil Red O staining. Triglyceride (TG), nonesterified fatty acid (NEFA), and cyclic adenosine monophosphate (cAMP) levels in mouse liver tissue were analyzed by metabolic assay and enzyme-linked immune sorbent assay.

RESULTS

SG boosted increase in hepatic total/conjugated BAs and related genes and GPBAR1 expression, and attenuated increase in fecal total BAs/muricholic acid in HFD-induced mice and increased fecal taurine-BAs in HFD-induced mice. Triamterene (72 mg/kg) reversed the inhibitory role of SG in HFD-induced increase of body weight, lipid accumulation, inflammatory cell infiltration, and increase of hepatic weight and TG/NEFA content, and counteracted the positive role of SG in HFD-induced increase of hepatic cAMP concentration in mice.

CONCLUSIONS

BAs improve metabolism via activating GPBAR1 to increase cAMP in NAFLD mice after SG.

Impact of intestinal microenvironments in obesity and bariatric surgery on shaping macrophages

Obesity is associated with alterations in tissue composition, systemic cellular metabolism, and low-grade chronic inflammation. Macrophages are heterogenous innate immune cells ubiquitously localized throughout the body and are key components of tissue homeostasis, inflammation, wound healing, and various disease states. Macrophages are highly plastic and can switch their phenotypic polarization and change function in response to their local environments. Here, we discuss how obesity alters the intestinal microenvironment and potential key factors that can influence intestinal macrophages as well as macrophages in other organs, including adipose tissue and hematopoietic organs. As bariatric surgery can induce metabolic adaptation systemically, we discuss the potential mechanisms through which bariatric surgery reshapes macrophages in obesity.

Metabolomic signatures after bariatric surgery - a systematic review

Metabolomics emerged as an important tool to gain insights on how the body responds to therapeutic interventions. Bariatric surgery is the most effective treatment for severe obesity and obesity-related co-morbidities. Our aim was to conduct a systematic review of the available data on metabolomics profiles that characterize patients submitted to different bariatric surgery procedures, which could be useful to predict clinical outcomes including weight loss and type 2 diabetes remission. For that, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - PRISMA guidelines were followed. Data from forty-seven original study reports addressing metabolomics profiles induced by bariatric surgery that met eligibility criteria were compiled and summarized. Amino acids, lipids, energy-related and gut microbiota-related were the metabolite classes most influenced by bariatric surgery. Among these, higher pre-operative levels of specific lipids including phospholipids, long-chain fatty acids and bile acids were associated with post-operative T2D remission. As conclusion, metabolite profiling could become a useful tool to predict long term response to different bariatric surgery procedures, allowing more personalized interventions and improved healthcare resources allocation.

Conjugated C-6 hydroxylated bile acids in serum relate to human metabolic health and gut Clostridia species

Knowledge about in vivo effects of human circulating C-6 hydroxylated bile acids (BAs), also called muricholic acids, is sparse. It is unsettled if the gut microbiome might contribute to their biosynthesis. Here, we measured a range of serum BAs and related them to markers of human metabolic health and the gut microbiome. We examined 283 non-obese and obese Danish adults from the MetaHit study. Fasting concentrations of serum BAs were quantified using ultra-performance liquid chromatography-tandem mass-spectrometry. The gut microbiome was characterized with shotgun metagenomic sequencing and genome-scale metabolic modeling. We find that tauro- and glycohyocholic acid correlated inversely with body mass index (P = 4.1e-03, P = 1.9e-05, respectively), waist circumference (P = 0.017, P = 1.1e-04, respectively), body fat percentage (P = 2.5e-03, P = 2.3e-06, respectively), insulin resistance (P = 0.051, P = 4.6e-4, respectively), fasting concentrations of triglycerides (P = 0.06, P = 9.2e-4, respectively) and leptin (P = 0.067, P = 9.2e-4). Tauro- and glycohyocholic acids, and tauro-a-muricholic acid were directly linked with a distinct gut microbial community primarily composed of Clostridia species (P = 0.037, P = 0.013, P = 0.027, respectively). We conclude that serum conjugated C-6-hydroxylated BAs associate with measures of human metabolic health and gut communities of Clostridia species. The findings merit preclinical interventions and human feasibility studies to explore the therapeutic potential of these BAs in obesity and type 2 diabetes.

Significance of intestinal microbiota in implementing metabolic effects of bariatric surgery

Bariatric surgery is among successful methods of obesity treatment, with effects going beyond weight reduction alone, but rather involving improved glucose tolerance, along with control or remission of the type 2 diabetes mellitus. The precise mechanisms causing metabolic effects of bariatric surgery are not fully elucidated, even though substantial evidence suggest that they include changes in the gut microbiota, bile acid homeostasis, and the close interactions of these factors. Intestinal microflora is directly involved in the energy metabolism of a host human. Obesity and type 2 diabetes mellitus are associated with certain changes in the species composition and diversity of intestinal microflora, which are considered important factors in the development and progression of these ailments. Bariatric surgery leads to significant and persistent changes in the composition of the intestinal microbiota, often bringing it closer to the characteristics of the microbiota of an average person with a normal weight. An important role in implementing the metabolic effects of bariatric surgery, primarily in the improvement of glucose metabolism, belongs to postoperative changes in homeostasis of bile acids. These changes imply close metabolism. Moreover, changes in the bile acid metabolism after bariatric surgery affect the microbiota of the host. Further study of these relationships would clarify the mechanisms underlying metabolic surgery, make it more predictable, targeted and controlled, as well as open new therapeutic targets in the treatment of obesity and associated conditions.

Downregulation of CTRP-3 by Weight Loss In Vivo and by Bile Acids and Incretins in Adipocytes In Vitro

The adipokine CTRP-3 (C1q/TNF-related protein-3) exerts anti-inflammatory and anti-diabetic effects. Its regulation in obesity and during weight loss is unknown. Serum and adipose tissue (AT) samples were obtained from patients (n = 179) undergoing bariatric surgery (BS). Moreover, patients (n = 131) participating in a low-calorie diet (LCD) program were studied. CTRP 3 levels were quantified by ELISA and mRNA expression was analyzed in AT and in 3T3-L1 adipocytes treated with bile acids and incretins. There was a persistent downregulation of CTRP-3 serum levels during weight loss. CTRP-3 expression was higher in subcutaneous than in visceral AT and serum levels of CTRP-3 were positively related to AT expression levels. A rapid decrease of circulating CTRP-3 was observed immediately upon BS, suggesting weight loss-independent regulatory mechanisms. Adipocytes CTRP-3 expression was inhibited by primary bile acid species and GLP 1. Adipocyte-specific CTRP-3 deficiency increased bile acid receptor expression. Circulating CTRP-3 levels are downregulated during weight loss, with a considerable decline occurring immediately upon BS. Mechanisms dependent and independent of weight loss cause the post-surgical decline of CTRP-3. The data strongly argue for regulatory interrelations of CTRP-3 with bile acids and incretin system.

Assessment of the role of FGF15 in mediating the metabolic outcomes of murine Vertical Sleeve Gastrectomy (VSG)

Vertical sleeve gastrectomy (VSG) is the best current therapy for remission of obesity and its co-morbidities. It is understood to alter the enterohepatic circulation of bile acids in vivo. Fibroblast growth factor 19 (FGF19) in human and its murine orthologue Fgf15 plays a pivotal role in this bile acid driven enterohepatic signaling. The present study evaluated the metabolic outcomes of VSG in Fgf15 deficient mice. 6-8 weeks old male wildtype mice (WT) and Fgf15 deficient mice (KO) were fed a high fat diet (HFD) for 8 weeks. At 8th week of diet, both WT and KO mice were randomly distributed to VSG or sham surgery. Post-surgery, mice were observed for 8 weeks while fed a HFD and then euthanized to collect tissues for experimental analysis. Fgf15 deficient (KO) mice lost weight post VSG, but glucose tolerance in KO mice did not improve post VSG compared to WT mice. Enteroids derived from WT and KO mice proliferated with bile acid exposure in vitro. Post VSG both WT and KO mice had similarly altered bile acid enterohepatic flux, however Fgf15 deficient mice post VSG had increased hepatic accumulation of free and esterified cholesterol leading to lipotoxicity related ER stress, inflammasome activation, and increased Fgf21 expression. Intact Fgf15 mediated enterohepatic bile acid signaling, but not changes in bile acid flux, appear to be important for the metabolic improvements post-murine bariatric surgery. These novel data introduce a potential point of distinction between bile acids acting as ligands compared to their canonical downstream signaling pathways.

Gut microbiota in human metabolic health and disease

Observational findings achieved during the past two decades suggest that the intestinal microbiota may contribute to the metabolic health of the human host and, when aberrant, to the pathogenesis of various common metabolic disorders including obesity, type 2 diabetes, non-alcoholic liver disease, cardio-metabolic diseases and malnutrition. However, to gain a mechanistic understanding of how the gut microbiota affects host metabolism, research is moving from descriptive microbiota census analyses to cause-and-effect studies. Joint analyses of high-throughput human multi-omics data, including metagenomics and metabolomics data, together with measures of host physiology and mechanistic experiments in humans, animals and cells hold potential as initial steps in the identification of potential molecular mechanisms behind reported associations. In this Review, we discuss the current knowledge on how gut microbiota and derived microbial compounds may link to metabolism of the healthy host or to the pathogenesis of common metabolic diseases. We highlight examples of microbiota-targeted interventions aiming to optimize metabolic health, and we provide perspectives for future basic and translational investigations within the nascent and promising research field.

Effects of laparoscopic sleeve gastrectomy on concentration and composition of bile acids in an Asian population with morbid obesity

Background:

Bile acids (BAs) are traditionally associated with lipid absorption and phase II detoxification by forming various BA conjugates. Recently, it has been discovered that BAs also regulate glucose metabolism, and the increase in BAs in patients following bariatric surgery may contribute to the post-surgery improvement in insulin resistance (IR). However, while Roux-en-Y gastric bypass can increase BA concentrations post-surgery, this may not be the case after laparoscopic sleeve gastrectomy (LSG). We hypothesized that the profiling of BAs that include the conjugated BA species could detect post-surgery BA changes after LSG. To test our hypothesis, we performed comprehensive profiling of BAs in Asian individuals with morbid obesity at baseline, and at 6 months following LSG.

Methods:

Fourteen subjects scheduled for LSG were recruited. Anthropometric measurements, oral glucose tolerance test, and biochemistry tests were performed at baseline and at 6 months after LSG. BAs were profiled using liquid chromatography–mass spectrometry.

Results:

At 6 months, subjects lost significant weight from 117.4±5.4 to 92.1±3.8 kg and demonstrated significant improvement in IR. HOMA-IR decreased from 6.2±0.7 to 2.0±0.2 and the Matsuda index increased from 1.9±0.3 to 3.3±0.3. We did not detect any significant post-operative change in the levels of total BAs (5237.1±1219.4 vs. 3631.7±457.9, p=0.181) or non-sulfated BAs after LSG. However, sulfated BA species increased significantly after LSG.

Conclusion:

Our study showed that the serum concentrations of sulfated BA species in morbidly obese Asian individuals increased significantly 6 months after LSG; the increase in sulfated BAs after LSG might contribute to the post-surgery improvement of metabolic health.

Targeting bile acid metabolism in obesity reduction: A systematic review and meta-analysis

A systematic review and meta-analysis was conducted of studies that address the association of bile acid (BA) with obesity and of studies on the effects of treatment in patients with obesity on BA metabolism, assessed from systemic BA, fibroblast growth factor 19 (FGF19), 7α-hydroxy-4-cholesten-3-one (C4) level, and faecal BA. We searched PubMed, Embase, and the Cochrane Library from inception to 1 August 2019 using the keywords obesity, obese, body mass index, and overweight with bile acid, FGF19, FXR, and TGR5. Two reviewers independently searched, selected, and assessed the quality of studies. Data were analysed using either fixed or random effect models with inverse variance weighting. Of 3771 articles, 33 papers were relevant for the association of BA with obesity of which 22 were included in the meta-analysis, and 50 papers were relevant for the effect of obesity interventions on BA of which 20 were included in the meta-analysis. Circulating fasting total BA was not associated with obesity. FGF19 was inversely and faecal BA excretion was positively associated with obesity. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) modulated BA metabolism, ie, increased BA and FGF19. Our results indicate that BA metabolism is altered in obesity. Certain bariatric surgeries including RYGB and SG modulate BA, whether these underlie the beneficial effect of the treatment should be investigated.

Childhood and Adolescent Obesity: A Review

Obesity is a complex condition that interweaves biological, developmental, environmental, behavioral, and genetic factors; it is a significant public health problem. The most common cause of obesity throughout childhood and adolescence is an inequity in energy balance; that is, excess caloric intake without appropriate caloric expenditure. Adiposity rebound (AR) in early childhood is a risk factor for obesity in adolescence and adulthood. The increasing prevalence of childhood and adolescent obesity is associated with a rise in comorbidities previously identified in the adult population, such as Type 2 Diabetes Mellitus, Hypertension, Non-alcoholic Fatty Liver disease (NAFLD), Obstructive Sleep Apnea (OSA), and Dyslipidemia. Due to the lack of a single treatment option to address obesity, clinicians have generally relied on counseling dietary changes and exercise. Due to psychosocial issues that may accompany adolescence regarding body habitus, this approach can have negative results. Teens can develop unhealthy eating habits that result in Bulimia Nervosa (BN), Binge- Eating Disorder (BED), or Night eating syndrome (NES). Others can develop Anorexia Nervosa (AN) as they attempt to restrict their diet and overshoot their goal of "being healthy." To date, lifestyle interventions have shown only modest effects on weight loss. Emerging findings from basic science as well as interventional drug trials utilizing GLP-1 agonists have demonstrated success in effective weight loss in obese adults, adolescents, and pediatric patients. However, there is limited data on the efficacy and safety of other weight-loss medications in children and adolescents. Nearly 6% of adolescents in the United States are severely obese and bariatric surgery as a treatment consideration will be discussed. In summary, this paper will overview the pathophysiology, clinical, and psychological implications, and treatment options available for obese pediatric and adolescent patients.

Study of changes of obesity-related inflammatory cytokines after laparoscopic sleeve gastrectomy

BACKGROUND

Chronic inflammation in adipose tissue may play a substantial role in the pathogenesis of obesity-related metabolic disorders. The present study aims to evaluate the changes in adipocytokines, bile acids, fibroblast growth factor 19 (FGF-19) and pro-inflammatory cytokines 6 months after laparoscopic sleeve gastrectomy (LSG).

METHODS

This prospective study included 75 obese patients with body mass index >35 kg/m² who underwent LSG. All patients were recruited preoperatively and followed up post-operatively at 6 months, with laboratory assessment of their cytokines including adiponectin, leptin, resistin, bile acid, interleukin (IL)-6, IL-8, tumour necrosis factor-α, monocyte chemotactic protein-1, high-sensitivity C-reactive protein, plasminogen activator inhibitor-1, serum amyloid-A and FGF-19.

RESULTS

There were statistically highly significant changes regarding anthropometric parameters (weight, body mass index and waist-to-hip ratio), blood glucose and lipid profile as well as liver enzymes at 6 months post-sleeve gastrectomy. The present study showed that the levels of serum adiponectin and FGF-19 significantly increased at 6 months of follow-up after surgery (P < 0.001), while the levels of serum leptin, resistin, high-sensitivity C-reactive protein, plasminogen activator inhibitor-1 and serum amyloid-A significantly decreased at 6 months of follow-up after surgery (P < 0.001). There were no significant differences regarding serum bile acid, IL-6, IL-8, tumour necrosis factor-α and monocyte chemotactic protein-1.

CONCLUSION

Weight loss after LSG is associated with significant improvement of the adipokine levels towards anti-diabetic and anti-inflammatory profiles. Future studies should use a larger sample size and longer follow-up periods.

Role of Bile Acids in Bariatric Surgery

Bariatric surgery has been proved to be effective and sustainable in the long-term weight-loss and remission of metabolic disorders. However, the underlying mechanisms are still far from fully elucidated. After bariatric surgery, the gastrointestinal tract is manipulated, either anatomically or functionally, leading to changed bile acid metabolism. Accumulating evidence has shown that bile acids play a role in metabolic regulation as signaling molecules other than digestive juice. And most of the metabolism-beneficial effects are mediated through nuclear receptor FXR and membrane receptor TGR5, as well as reciprocal influence on gut microbiota. Bile diversion procedure is also performed on animals to recapitulate the benefits of bariatric surgery. It appears that bile acid alteration is an important component of bariatric surgery, and represents a promising target for the management of metabolic disorders.

Sleeve gastrectomy in obese Wistar rats improves diastolic function and promotes cardiac recovery independent of weight loss

BACKGROUND

Heart failure with preserved ejection fraction is the most common cause of heart failure and is characterized by impaired diastolic relaxation. Bariatric surgery significantly improves diastolic relaxation, but a mechanism beyond weight loss remains unknown.

OBJECTIVES

We tested the hypothesis that a sleeve gastrectomy (SG) will improve diastolic dysfunction independent of weight loss due to postoperative alterations in the enterocardiac axis.

SETTING

University research laboratory.

METHODS

Male Wistar rats were fed a high-fat diet (HFD) or low-fat diet (LFD) for 10 weeks and then divided into SG-HFD, pair-fed sham HFD, ad-lib sham HFD, or ad-lib sham LFD groups (n = 9-14 per group). At least 2 months postoperatively, cardiac function, meal tolerance, glucose tolerance, and cardiac gene expression were compared between groups.

RESULTS

Only the SG cohort showed significant improvements in postoperative diastolic relaxation (isovolumetric relaxation time pre-SG: 14.7 ± 2.3 msec, post-SG: 11.2 ± 1.8 msec, P < .001). SG significantly increased active glucagon-like peptide-1 (P = .03). Compared to pair-fed sham HFD rats, SG-HFD rats had significantly altered mRNA cardiac gene expression, including sarco/endoplasmic reticulum Ca2+-ATPase 2 a (SERCA2 a) (P < .001).

CONCLUSIONS

SG improves diastolic function independent of weight loss in a rat model of obesity with beneficial alterations in cardiac gene expression of multiple known targets related to cardiac failure, including SERCA2 a. These data support that a greater curve gastrectomy induces beneficial intracellular cardiac signaling for diastolic function mediated by the enterocardiac axis that is independent of weight loss. These findings could translate to offering metabolic surgery to patients with heart failure with preserved ejection fraction.