Small Intestinal Bacterial Overgrowth Is Associated with Non-Alcoholic Fatty Liver Disease

Small Intestinal Bacterial Overgrowth (SIBO) and Twelve Groups of Related Diseases-Current State of Knowledge

The human gut microbiota creates a complex microbial ecosystem, characterized by its high population density, wide diversity, and complex interactions. Any imbalance of the intestinal microbiome, whether qualitative or quantitative, may have serious consequences for human health, including small intestinal bacterial overgrowth (SIBO). SIBO is defined as an increase in the number of bacteria (103-105 CFU/mL), an alteration in the bacterial composition, or both in the small intestine. The PubMed, Science Direct, Web of Science, EMBASE, and Medline databases were searched for studies on SIBO and related diseases. These diseases were divided into 12 groups: (1) gastrointestinal disorders; (2) autoimmune disease; (3) cardiovascular system disease; (4) metabolic disease; (5) endocrine disorders; (6) nephrological disorders; (7) dermatological diseases; (8) neurological diseases (9); developmental disorders; (10) mental disorders; (11) genetic diseases; and (12) gastrointestinal cancer. The purpose of this comprehensive review is to present the current state of knowledge on the relationships between SIBO and these 12 disease groups, taking into account risk factors and the causal context. This review fills the evidence gap on SIBO and presents a biological-medical approach to the problem, clearly showing the groups and diseases having a proven relationship with SIBO, as well as indicating groups within which research should continue to be expanded.

Blood Endotoxin Levels as Biomarker of Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Growing evidence supports a role of gut-derived metabolites in nonalcoholic fatty liver disease (NAFLD), but the relation of endotoxin levels with gut permeability and NAFLD stage remains unclear. This systematic review with meta-analysis aims to provide further insights.

METHODS

PubMed, Embase, and Cochrane Library were searched for studies published until January 2022 assessing blood endotoxins in patients with NAFLD. Meta-analyses and univariate/multivariate meta-regression, as well as correlation analyses, were performed for endotoxin values and potential relationships to disease stage, age, sex, parameters of systemic inflammation, and metabolic syndrome, as well as liver function and histology.

RESULTS

Forty-three studies were included, of which 34 were used for meta-analyses. Blood endotoxin levels were higher in patients with simple steatosis vs liver-healthy controls (standardized mean difference, 0.86; 95% confidence interval, 0.62-1.11) as well as in patients with nonalcoholic steatohepatitis vs patients with nonalcoholic fatty liver/non-nonalcoholic steatohepatitis (standardized mean difference, 0.81; 95% confidence interval, 0.27-1.35; P = .0078). Consistently, higher endotoxin levels were observed in patients with more advanced histopathological gradings of liver steatosis and fibrosis. An increase of blood endotoxin levels was partially attributed to a body mass index rise in patients with NAFLD compared with controls. Nevertheless, significant increases of blood endotoxin levels in NAFLD retained after compensation for differences in body mass index, metabolic condition, or liver enzymes. Increases in blood endotoxin levels were associated with increases in C-reactive protein concentrations, and in most cases, paralleled a rise in markers for intestinal permeability.

CONCLUSION

Our results support blood endotoxin levels as relevant diagnostic biomarker for NAFLD, both for disease detection as well as staging during disease progression, and might serve as surrogate marker of enhanced intestinal permeability in NAFLD. Registration number in Prospero: CRD42022311166.

Ability of lactulose breath test results to accurately identify colorectal polyps through the measurement of small intestine bacterial overgrowth

BACKGROUND

While colorectal polyps are not cancerous, some types of polyps, known as adenomas, can develop into colorectal cancer over time. Polyps can often be found and removed by colonoscopy; however, this is an invasive and expensive test. Thus, there is a need for new methods of screening patients at high risk of developing polyps.

AIM

To identify a potential association between colorectal polyps and small intestine bacteria overgrowth (SIBO) or other relevant factors in a patient cohort with lactulose breath test (LBT) results.

METHODS

A total of 382 patients who had received an LBT were classified into polyp and non-polyp groups that were confirmed by colonoscopy and pathology. SIBO was diagnosed by measuring LBT-derived hydrogen (H) and methane (M) levels according to 2017 North American Consensus recommendations. Logistic regression was used to assess the ability of LBT to predict colorectal polyps. Intestinal barrier function damage (IBFD) was determined by blood assays.

RESULTS

H and M levels revealed that the prevalence of SIBO was significantly higher in the polyp group than in the non-polyp group (41% vs 23%, P < 0.01; 71% vs 59%, P < 0.05, respectively). Within 90 min of lactulose ingestion, the peak H values in the adenomatous and inflammatory/hyperplastic polyp patients were significantly higher than those in the non-polyp group (P < 0.01, and P = 0.03, respectively). In 227 patients with SIBO defined by combining H and M values, the rate of IBFD determined by blood lipopolysaccharide levels was significantly higher among patients with polyps than those without (15% vs 5%, P < 0.05). In regression analysis with age and gender adjustment, colorectal polyps were most accurately predicted with models using M peak values or combined H and M values limited by North American Consensus recommendations for SIBO. These models had a sensitivity of ≥ 0.67, a specificity of ≥ 0.64, and an accuracy of ≥ 0.66.

CONCLUSION

The current study made key associations among colorectal polyps, SIBO, and IBFD and demonstrated that LBT has moderate potential as an alternative noninvasive screening tool for colorectal polyps.

The Role of Small Intestinal Bacterial Overgrowth in Obesity and Its Related Diseases

Obesity has become a major public health problem worldwide and its occurrence is increasing globally. Obesity has also been shown to be involved in the occurrence and development of many diseases and pathological conditions, such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus (T2DM), insulin resistance (IR). In recent years, gut microbiota has received extensive attention as an important regulatory part involved in host diseases and health status. A growing body of evidence suggests that gut microbiota dysbiosis has a significant adverse effect on the host. Small intestinal bacterial overgrowth (SIBO), a type of intestinal microbial dysbiosis, has been gradually revealed to be associated with obesity and its related diseases. The presence of SIBO may lead to the destruction of intestinal barrier integrity, increased intestinal permeability, increased endotoxin levels, activation of inflammatory responses, and translocation of bacteria from the colon to the small intestine. However, the causal relationship between SIBO and obesity and the specific mechanisms have not been well elucidated. This review discusses the cross-talk between SIBO and obesity and its related diseases, and expounds its potential mechanisms and interventions, which may help to discover new therapeutic targets for obesity and its related diseases and develop treatment options.

Association between Gut Dysbiosis and the Occurrence of SIBO, LIBO, SIFO and IMO

Gut microbiota is the aggregate of all microorganisms in the human digestive system. There are 1014 CFU/mL of such microorganisms in the human body, including bacteria, viruses, fungi, archaea and protozoa. The Firmicutes and Bacteroidetes bacteria phyla comprise 90% of the human gut microbiota. The microbiota support the healthy functioning of the human body by helping with digestion (mainly via short-chain fatty acids and amino acids) and producing short-chain fatty acids. In addition, it exhibits many physiological functions, such as forming the intestinal epithelium, intestinal integrity maintenance, the production of vitamins, and protection against pathogens. An altered composition or the number of microorganisms, known as dysbiosis, disrupts the body's homeostasis and can lead to the development of inflammatory bowel disease, irritable bowel syndrome, and metabolic diseases such as diabetes, obesity and allergies. Several types of disruptions to the gut microbiota have been identified: SIBO (Small Intestinal Bacterial Overgrowth), LIBO (Large Intestinal Bacterial Overgrowth), SIFO (Small Intestinal Fungal Overgrowth), and IMO (Intestinal Methanogen Overgrowth). General gastrointestinal problems such as abdominal pain, bloating, gas, diarrhoea and constipation are the main symptoms of dysbiosis. They lead to malabsorption, nutrient deficiencies, anaemia and hypoproteinaemia. Increased lipopolysaccharide (LPS) permeability, stimulating the inflammatory response and resulting in chronic inflammation, has been identified as the leading cause of microbial overgrowth in the gut. The subject literature is extensive but of limited quality. Despite the recent interest in the gut microbiome and its disorders, more clinical research is needed to determine the pathophysiology, effective treatments, and prevention of small and large intestinal microbiota overgrowth. This review was designed to provide an overview of the available literature on intestinal microbial dysbiosis (SIBO, LIBO, SIFO and IMO) and to determine whether it represents a real threat to human health.

Show Me What You Have Inside-The Complex Interplay between SIBO and Multiple Medical Conditions-A Systematic Review

The microbiota, as a complex of microorganisms in a particular ecosystem, is part of the wider term-microbiome, which is defined as the set of all genetic content in the microbial community. Imbalanced gut microbiota has a great impact on the homeostasis of the organism. Dysbiosis, as a disturbance in bacterial balance, might trigger or exacerbate the course of different pathologies. Small intestinal bacterial overgrowth (SIBO) is a disorder characterized by differences in quantity, quality, and location of the small intestine microbiota. SIBO underlies symptoms associated with functional gastrointestinal disorders (FGD) as well as may alter the presentation of chronic diseases such as heart failure, diabetes, etc. In recent years there has been growing interest in the influence of SIBO and its impact on the whole human body as well as individual systems. Therefore, we aimed to investigate the co-existence of SIBO with different medical conditions. The PubMed database was searched up to July 2022 and we found 580 original studies; inclusion and exclusion criteria let us identify 112 eligible articles, which are quoted in this paper. The present SIBO diagnostic methods could be divided into two groups-invasive, the gold standard-small intestine aspirate culture, and non-invasive, breath tests (BT). Over the years scientists have explored SIBO and its associations with other diseases. Its role has been confirmed not only in gastroenterology but also in cardiology, endocrinology, neurology, rheumatology, and nephrology. Antibiotic therapy could reduce SIBO occurrence resulting not only in the relief of FGD symptoms but also manifestations of comorbid diseases. Although more research is needed, the link between SIBO and other diseases is an important pathway for scientists to follow.

The Prevalence of Small Intestinal Bacterial Overgrowth in Patients with Non-Alcoholic Liver Diseases: NAFLD, NASH, Fibrosis, Cirrhosis-A Systematic Review, Meta-Analysis and Meta-Regression

Bacterial overgrowth in the small intestine (SIBO) is a pathological growth of the intestinal microbiota in the small intestine that causes clinical symptoms and can lead to digestive and absorption disorders. There is increasing evidence that people with NAFLD have a distinct gut microflora profile as well metabolome changes compared to people without NAFLD. Thorough analysis of observational and RCT studies in the current databases (EMBASE, Web of Science, PubMed, Cinahl, Clinical Trials) was conducted from 3 November 2021 to 21 June 2022. The following inclusion criteria were applied: confirmed NAFLD, NASH, LIVER FIBROSIS, CIRRHOSIS due to steatosis; diagnostic methods of liver diseases—biopsy, elastography, transabdominal ultrasound; nonalcoholic fatty liver disease activity score; confirmed SIBO; diagnostic methods of SIBO−breath tests (hydrogen test; methane test and mix test; duodenal and jejunal aspiration before any type of intervention; adults above 18yo; number of participants ≥20; full articles. We excluded review articles, populations with HBV/HCV infection and alcohol etiology and interventions that may affect NAFLD or SIBO treatment. The quality of each study methodology was classified by means of the Cochrane Collaboration’s tool (RCT) and Newcastle—Ottawa Quality Assessment Scale adapted for cross-sectional, cohort and case-control studies. The random effects meta-analysis of outcomes for which ≥2 studies contributed data was conducted. The I2 index to measure heterogeneity and the χ2 test of homogeneity (statistically significant heterogeneity p < 0.05) were applied. For categorical outcome, the pooled event rate (effect size) was calculated. This systematic review was reported according to PRISMA reporting guidelines. We initially identified 6643 studies, from which 18 studies were included in final meta-analysis. The total number of patients was 1263. Accepted SIBO diagnostic methods were both available breath tests (n-total = 15) and aspirate culture (n-total = 3). We found that among patients with non-alcoholic liver diseases, the random overall event rate of SIBO was 0.350 (95% CI, 0.244−0.472), p = 0.017. The subgroup analysis regarding a type of diagnosis revealed that the lowest ER was among patients who developed simultaneously NAFLD, NASH and fibrosis: 0.197 (95% CI, 0.054−0.510) as compared to other annotated subgroups. The highest prevalence of SIBO was observed in the NASH subgroup: 0.411 (95% CI, 0.219−0.634). There were no statistically significant differences in the prevalence of SIBO in different subgroups (p = 0.854). Statistically significant heterogeneity between studies was estimated (I2 = 86.17%, p = 0.00). Egger’s test did not indicate a publication bias (df = 16, p = 0.885). A meta-regression using a random-effects model revealed that higher percentage of males in the population with liver diseases is a predisposing factor toward SIBO (Q = 4.11, df = 1, p = 0.0426 with coefficient = 0.0195, SE = 0.0096, Z = 2.03). We showed that the prevalence of SIBO in patients with chronic non-alcoholic liver diseases can be as high as 35%, and it increases with the percentage of men in the population. The prevalence of SIBO does not differ significantly depending on the type of chronic liver disease. Despite the high heterogeneity and moderate and low quality of included studies, our meta-analysis suggests the existence of a problem of SIBO in the population of patients with non-alcoholic liver diseases, and the presence of SIBO, in turn, determines the therapeutic treatment of such type of patients, which indicates the need for further research in this area. The study protocol was registered with the international Prospective Register of Systematic Reviews (PROSPERO ID: CRD42022341473).

Utility of Human Relevant Preclinical Animal Models in Navigating NAFLD to MAFLD Paradigm

Fatty liver disease is an emerging contributor to disease burden worldwide. The past decades of work established the heterogeneous nature of non-alcoholic fatty liver disease (NAFLD) etiology and systemic contributions to the pathogenesis of the disease. This called for the proposal of a redefinition in 2020 to that of metabolic dysfunction-associated fatty liver disease (MAFLD) to better reflect the current understanding of the disease. To date, several clinical cohort studies comparing NAFLD and MAFLD hint at the relevancy of the new nomenclature in enriching for patients with more severe hepatic injury and extrahepatic comorbidities. However, the underlying systemic pathogenesis is still not fully understood. Preclinical animal models have been imperative in elucidating key biological mechanisms in various contexts, including intrahepatic disease progression, interorgan crosstalk and systemic dysregulation. Furthermore, they are integral in developing novel therapeutics against MAFLD. However, substantial contextual variabilities exist across different models due to the lack of standardization in several aspects. As such, it is crucial to understand the strengths and weaknesses of existing models to better align them to the human condition. In this review, we consolidate the implications arising from the change in nomenclature and summarize MAFLD pathogenesis. Subsequently, we provide an updated evaluation of existing MAFLD preclinical models in alignment with the new definitions and perspectives to improve their translational relevance.

The contribution of the gut-liver axis to the immune signaling pathway of NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the liver manifestation of metabolic syndrome and is the most common chronic liver disease in the world. The pathogenesis of NAFLD has not been fully clarified; it involves metabolic disturbances, inflammation, oxidative stress, and various forms of cell death. The “intestinal-liver axis” theory, developed in recent years, holds that there is a certain relationship between liver disease and the intestinal tract, and changes in intestinal flora are closely involved in the development of NAFLD. Many studies have found that the intestinal flora regulates the pathogenesis of NAFLD by affecting energy metabolism, inducing endotoxemia, producing endogenous ethanol, and regulating bile acid and choline metabolism. In this review, we highlighted the updated discoveries in intestinal flora dysregulation and their link to the pathogenesis mechanism of NAFLD and summarized potential treatments of NAFLD related to the gut microbiome.

The impact of proton pump inhibitors in liver diseases and the effects on the liver

In this systematic and comprehensive overview, we aimed to evaluate the impact of proton pump inhibitors (PPIs) on chronic liver diseases, especially on cirrhosis. A manual and comprehensive search of the PubMed database was conducted to obtain relevant literatures. PPIs altered the composition and function of the intestinal microflora and might lead to small intestinal bacterial overgrowth and bacterial translocation, which were associated with adverse effects in liver diseases. They might increase the risk of hepatic encephalopathy, spontaneous bacterial peritonitis, infections, and are related to an increased mortality in cirrhosis. PPIs might lead to an increased risk of hepatocellular carcinoma, although the mechanism is unknown, and the results are controversial. PPIs also had an impact on the direct-acting antiviral regimen in patients with chronic hepatitis C. They were associated with an increased risk of liver abscess and increased mortality. Additionally, PPIs might lead to metabolic risk events, such as liver steatosis and weight gain. PPIs are associated with several adverse outcomes in liver diseases. Cautious use of PPIs is recommended and clinicians should be aware of the indications for their use in patients with liver diseases.

Highly Sensitive and Selective Detection of Hydrogen Using Pd-Coated SnO2 Nanorod Arrays for Breath-Analyzer Applications

We report a breath hydrogen analyzer based on Pd-coated SnO₂ nanorods (Pd-SnO₂ NRs) sensor integrated into a miniaturized gas chromatography (GC) column. The device can measure a wide range of hydrogen (1–100 ppm), within 100 s, using a small volume of human breath (1 mL) without pre-concentration. Especially, the mini-GC integrated with Pd-SnO₂ NRs can detect 1 ppm of H₂, as a lower detection limit, at a low operating temperature of 152 °C. Furthermore, when the breath hydrogen analyzer was exposed to a mixture of interfering gases, such as carbon dioxide, nitrogen, methane, and acetone, it was found to be capable of selectively detecting only H₂. We found that the Pd-SnO₂ NRs were superior to other semiconducting metal oxides that lack selectivity in H₂ detection. Our study reveals that the Pd-SnO₂ NRs integrated into the mini-GC device can be utilized in breath hydrogen analyzers to rapidly and accurately detect hydrogen due to its high selectivity and sensitivity.

Mucosal bacterial dysbiosis in patients with nodular lymphoid hyperplasia in the terminal ileum

BACKGROUND

Nodular lymphoid hyperplasia (NLH) in the small intestine is a rare benign lesion characterized by multiple small nodules on the intestinal surface. Patients with terminal ileal NLH may experience long-term abdominal pain, diarrhea, and abdominal distension, among other symptoms. Supplementation with probiotics could mitigate these symptoms. NLH is linked to the immune system, and it may result from accumulation of plasma-cell precursors due to a maturational defect during the development of B lymphocytes. The intestinal microbiome plays an essential role in the immune system. Thus, we speculate that the gut flora plays a key role in terminal ileal NLH.

AIM

To explore the correlation between intestinal flora and terminal ileal NLH.

METHODS

We collected mucosal biopsy samples that were obtained via colonoscopy from 15 patients with terminal ileal NLH (the test group) and 15 normal subjects (the control group). We subsequently performed 16S-rRNA gene amplicon sequencing of these samples, and the results were evaluated using alpha diversity, beta diversity and microbial composition analyses. The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States was used to predict the metabolic pathways and orthologous groups according to the Kyoto Encyclopedia of Genes and Genomes database.

RESULTS

Compared with the control group, the terminal ileal NLH group showed an increased alpha diversity (P < 0.05). The overall intestinal microbiota in the NLH group was significantly different from that of the control group (P < 0.05), implying that there was the dysbiosis in the terminal ileal NLH patients. The relative abundance of phylum Bacteroidetes was significantly lower in the NLH group, while that of Patescibacteria and Campilobacterota was significantly higher. The genus Bacteroides was the dominant gut microbiota in both groups, but its abundance was significantly lower in the test group than it was in the control group. Conversely, the relative abundances of Haemophilus, Streptococcus, Pseudomonas, Actinomyces, TM7X, Fusobacterium nucleatum, Parvimonas, Granulicatella, Helicobacter, and the [Eubacterium] nodatum group were significantly higher in the test group than they were in the control group. In addition, several altered metabolic pathways, orthologous groups, and modules were found. For example, the Peptidoglycan biosynthesis and Aminoacyl tRNA biosynthesis were both increased in the test group.

CONCLUSION

Maintaining the microbial balance and supplementing targeted protective bacteria could improve symptoms and potentially reduce the risk of lymphoma transformation in patients with terminal ileal NLH.

Effects of Proton Pump Inhibitors on the Small Bowel and Stool Microbiomes

BACKGROUND

Proton pump inhibitor (PPI) use is extremely common. PPIs have been suggested to affect the gut microbiome, and increase risks of Clostridium difficile infection and small intestinal bacterial overgrowth (SIBO). However, existing data are based on stool analyses and PPIs act on the foregut.

AIMS

To compare the duodenal and stool microbiomes in PPI and non-PPI users.

METHODS

Consecutive subjects presenting for upper endoscopy without colonoscopy were recruited. Current antibiotic users were excluded. Subjects taking PPI were age- and gender-matched 1:2 to non-PPI controls. Subjects completed medical history questionnaires, and duodenal aspirates were collected using a validated protected catheter. A subset also provided stool samples. Duodenal and stool microbiomes were analyzed by 16S rRNA sequencing.

RESULTS

The duodenal microbiome exhibited no phylum-level differences between PPI (N = 59) and non-PPI subjects (N = 118), but demonstrated significantly higher relative abundances of families Campylobacteraceae (3.13-fold, FDR P value < 0.01) and Bifidobacteriaceae (2.9-fold, FDR P value < 0.01), and lower relative abundance of Clostridiaceae (88.24-fold, FDR P value < 0.0001), in PPI subjects. SIBO rates were not significantly different between groups, whether defined by culture (> 10³ CFU/ml) or 16S sequencing, nor between subjects taking different PPIs. The stool microbiome exhibited significantly higher abundance of family Streptococcaceae (2.14-fold, P = 0.003), and lower Clostridiaceae (2.60-fold, FDR P value = 8.61E-13), in PPI (N = 22) versus non-PPI (N = 47) subjects.

CONCLUSIONS

These findings suggest that PPI use is not associated with higher rates of SIBO. Relative abundance of Clostridiaceae was reduced in both the duodenal and stool microbiomes, and Streptococcaceae was increased in stool. The clinical implications of these findings are unknown.

Association of small intestinal bacterial overgrowth with nonalcoholic fatty liver disease in children: A meta-analysis

It has been suggested that small intestinal bacterial overgrowth (SIBO) could cause nonalcoholic fatty liver disease (NAFLD), but this association was not examined in children by meta-analysis. This meta-analysis aimed to determine the association between SIBO and NAFLD in children. The electronic databases PubMed, Embase, and Cochrane Library were searched for studies published before April 22, 2021. The outcome was the association between SIBO and NAFLD. Three studies and 205 children were included. All three studies reported the association between SIBO and NAFLD. Children with SIBO were more likely to have NAFLD (odds ratio = 5.27, 95% confidence interval (CI): 1.66-16.68, P<0.001; I2 = 63.5%, Pheterogeneity = 0.065). When directly pooling the reported relative risks (RR) from two studies, children with NAFLD had an over 2-fold increased relative risk of developing SIBO (RR = 2.17, 05%CI: 1.66-2.82, P<0.001; I2 = 0.0%, Pheterogeneity = 0.837). This meta-analysis reports a possible association between SIBO and NAFLD in children.

Short-Bowel Syndrome: Epidemiology, Hospitalization Trends, In-Hospital Mortality, and Healthcare Utilization

INTRODUCTION

Short-bowel syndrome (SBS) is a common cause of chronic intestinal failure and is associated with increased morbidity, mortality, poor quality of life, and an increased burden on healthcare costs.

METHODS

We used the US Nationwide Inpatient Sample database from 2005 to 2014. We identified adult SBS hospitalizations by using a combination of International Classification of Diseases, Ninth Revision, Clinical Modification codes. We studied the demographics of the patients with SBS and analyzed the trends in the number of hospitalizations, in-hospital mortality, and healthcare costs. We also identified the risk factors associated with in-hospital mortality.

RESULTS

A total of 53,040 SBS hospitalizations were identified. We found that SBS-related hospitalizations increased by 55% between 2005 (N = 4037) and 2014 (N = 6265). During this period, the in-hospital mortality decreased from 40 per 1000 to 29 per 1000 hospitalizations, resulting in an overall reduction of 27%. Higher mortality was noted in SBS patients with sepsis (6.7%), liver dysfunction (6.2%), severe malnutrition (6.0%), and metastatic cancer (5.4%). The overall mean length of stay (LOS) for SBS-related hospitalizations was 14.7 days, with a mean hospital cost of $34,130. We noted a steady decrease in the LOS, whereas the cost of care remained relatively stable.

CONCLUSIONS

The national burden of SBS-related hospitalizations continues to rise, and the mortality associated with SBS has substantially decreased. Older SBS patients with sepsis, liver dysfunction, severe malnutrition, and metastatic cancer had the highest risk of mortality. Healthcare utilization in SBS remains high. healthcare utilization; hospitalization trend; mortality; research and diseases; short-bowel syndrome.

A review of non-alcoholic fatty liver disease in non-obese and lean individuals

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of hepatic disorders. It represents a wide range of chronic liver diseases in patients with no history of significant alcohol consumption, starting with simple steatosis and progressing towards non-alcoholic steatohepatitis, cirrhosis, and ultimately hepatocellular carcinoma. NAFLD is usually associated with type 2 diabetes mellitus, dyslipidemia, metabolic syndrome, and obesity. This disease has mostly been studied in obese individuals; however, it has been widely reported and studied among the lean/non-obese population in recent years. The pathogenesis of NAFLD in non-obese patients is associated with various genetic predispositions, particularly a patatin-like phospholipase domain-containing protein 3 G allele polymorphism, which results in the accumulation of triglyceride in the liver and resistance to insulin. Additionally, dietary factors such as high fructose consumption seem to play a substantial role in the pathology of non-obese NAFLD. Although there is not enough evidence on the treatment of NAFLD in non-obese patients, the standard approach is to advise altering one's lifestyle in order to diminish visceral adiposity. Dietary modification, weight loss, and increased physical activity are highly recommended. We aimed to review and summarize the existing information on the prevalence, pathogenesis, genetic predispositions, diagnosis, and treatment of NAFLD in non-obese patients according to the latest literature.

New insights into intestinal failure-associated liver disease in adults: A comprehensive review of the literature

Intestinal failure-associated liver disease (IFALD) remains one of the most common and serious complications of parenteral nutrition (PN), causing a wide spectrum of hepatic manifestations from steatosis and mild cholestasis to portal hypertension and end-stage liver failure. The prevalence of IFALD depends on the diagnostic criteria and ranges from 4.3% to 65%. Moreover, many factors are shown to contribute to its development, including nutrient deficiencies, toxicity of PN, infections, and alterations of bile acid metabolism and gut microbiota. Prevention and management of IFALD aim at ameliorating or eliminating the risk factors associated with IFALD. The use of PN formulations with a lower ratio omega-6-to-omega-3 polyunsaturated fatty acids, cycle PN, optimization of enteral stimulation and prevention and early treatment of infections constitute the main therapeutic targets. However, failure of improvement and severe IFALD with end-stage liver failure should be considered as the indications of intestinal transplantation. The aim of this review is to provide an update of the epidemiology, pathophysiology, and diagnosis of IFALD in the adult population as well as to present a clinical approach of the therapeutic strategies of IFALD and present novel therapeutic targets.

Gut microbiota mediated molecular events and therapy in liver diseases

Gut microbiota is a community of microorganisms that reside in the gastrointestinal tract. An increasing number of studies has demonstrated that the gut-liver axis plays a critical role in liver homeostasis. Dysbiosis of gut microbiota can cause liver diseases, including nonalcoholic fatty liver disease and alcoholic liver disease. Preclinical and clinical investigations have substantiated that the metabolites and other molecules derived from gut microbiota and diet interaction function as mediators to cause liver fibrosis, cirrhosis, and final cancer. This effect has been demonstrated to be associated with dysregulation of intrahepatic immunity and liver metabolism. Targeting these findings have led to the development of novel preventive and therapeutic strategies. Here, we review the cellular and molecular mechanisms underlying gut microbiota-mediated impact on liver disease. We also summarize the advancement of gut microbiota-based therapeutic strategies in the control of liver diseases.

Using intestinal flora to distinguish non-alcoholic steatohepatitis from non-alcoholic fatty liver

Objective

To explore specific flora in mouse models of non-alcoholic steatohepatitis (NASH) to improve NASH diagnostic protocols.

Methods

Sixty mice were divided into normal diet (ND, 20 mice) and high-fat/high-sugar diet (HFSD) groups (40 mice). After 8 weeks of feeding, 10 mice in the ND group and 20 mice in the HFSD group were sacrificed to create the short-term ND and non-alcoholic fatty liver (NAFL) groups, respectively. After 16 weeks of feeding, the remaining mice were sacrificed to create the long-term ND and NASH groups, respectively. We then examined fecal flora, serum biochemical indices, and lipopolysaccharide and tumor necrosis factor-α levels and analyzed liver tissue.

Results

The relative abundance of Lactobacillus, Desulfovibrio, Ruminiclostridium 9, and Turicibacter differed between NASH and NAFL mice, and the areas under the receiver operating characteristic curve of the four genera for diagnosing NASH were 0.705, 0.734, 0.737, and 0.937. The non-alcoholic fatty liver disease activity score was positively correlated with the relative abundance of Desulfovibrio (r = 0.353), Ruminiclostridium 9 (r = 0.431), and Turicibacter (r = 0.688).

Conclusions

The relative abundance of Lactobacillus, Desulfovibrio, Ruminiclostridium, and Turicibacter may help distinguish NASH from NAFL.

Chinese herbal medicine for the treatment of small intestinal bacterial overgrowth (SIBO): A protocol for systematic review and meta-analysis

BACKGROUND

Chinese medicine has a unique theory and the Chinese herbal medicine treatment is based on the integral concepts and syndrome differentiation of the Traditional Chinese Medicine system. Although antibiotics remain the mainstay of SIBO treatment, various alternative or adjunctive therapies are available, including prokinetic agents, dietary interventions, probiotics, and herbal combinations. There is accumulating evidence demonstrating the antimicrobial properties of a growing number of herbs including garlic, black cumin, cloves, cinnamon, thyme, all-spices, bay leaves, mustard, and rosemary. This has prompted an interest in herbal therapy for the treatment of SIBO. Currently, there is no systematic review focusing on efficacy of CHM in the treatment of SIBO with PCOS, so our meta-analysis aims to comprehensively explore it. Meanwhile we will provide high-quality evidence to help patients, clinicians as well as health policymakers select better treatment strategy of PCOS.

METHODS

We will search the following sources without restrictions for date, language, or publication status: PubMed, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL) Cochrane Library, EMBASE and China National Knowledge Infrastructure. We will apply a combination of Medical Subject Heading (MeSH) and free-text terms incorporating database-specific controlled vocabularies and text words to implement search strategies. We will also search the ongoing trials registered in the World Health Organization's International Clinical Trials Registry Platform. Besides, the previous relevant reviews conducted on CHM for SIBO and reference lists of included studies will also be searched.

RESULTS

This study will provide a reliable basis for the treatment of SIBO with CHM.

CONCLUSIONS

The findings will be an available reference to evaluate the efficacy and safety of CHM in the treatment of SIBO.

REGISTRATION NUMBER

INPLASY202080004.

PERIPHERAL BLOOD ENDOTOXIN LEVELS ARE NOT ASSOCIATED WITH SMALL INTESTINAL BACTERIAL OVERGROWTH IN NONALCOHOLIC FATTY LIVER DISEASE WITHOUT CIRRHOSIS

ABSTRACT BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is one of the most common forms of chronic liver disease worldwide. Approximately 20% of individuals with NAFLD develop nonalcoholic steatohepatitis (NASH), which is associated with increased risk of cirrhosis, portal hypertension, and hepatocellular carcinoma. Intestinal microflora, including small intestinal bacterial overgrowth (SIBO), appear to play an important role in the pathogenesis of the disease, as demonstrated in several clinical and experimental studies, by altering intestinal permeability and allowing bacterial endotoxins to enter the circulation. OBJECTIVE: To determine the relationship between SIBO and endotoxin serum levels with clinical, laboratory, and histopathological aspects of NAFLD and the relationship between SIBO and endotoxin serum levels before and after antibiotic therapy. METHODS: Adult patients with a histological diagnosis of NAFLD, without cirrhosis were included. A comprehensive biochemistry panel, lactulose breath test (for diagnosis of SIBO), and serum endotoxin measurement (chromogenic LAL assay) were performed. SIBO was treated with metronidazole 250 mg q8h for 10 days and refractory cases were given ciprofloxacin 500 mg q12h for 10 days. RESULTS: Overall, 42 patients with a histopathological diagnosis of NAFLD were examined. The prevalence of SIBO was 26.2%. Comparison of demographic and biochemical parameters between patients with SIBO and those without SIBO revealed no statistically significant differences, except for use of proton pump inhibitors, which was significantly more frequent in patients with positive breath testing. The presence of SIBO was also associated with greater severity of hepatocellular ballooning on liver biopsy. Although the sample, as a whole, have elevated circulating endotoxin levels, we found no significant differences in this parameter between the groups with and without SIBO. Endotoxin values before and after antibiotic treatment did not differ, even on paired analysis, suggesting absence of any relationship between these factors. Serum endotoxin levels were inversely correlated with HDL levels, and directly correlated with triglyceride levels. CONCLUSION: Serum endotoxin levels did not differ between patients with and without SIBO, nor did these levels change after antibacterial therapy, virtually ruling out the possibility that elevated endotoxinemia in non-cirrhotic patients with NAFLD is associated with SIBO. Presence of SIBO was associated with greater severity of ballooning degeneration on liver biopsy, but not with a significantly higher prevalence of NASH. Additional studies are needed to evaluate the reproducibility and importance of this finding in patients with NAFLD and SIBO.

Characteristics of intestinal bacteria with fatty liver diseases and cirrhosis

Non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD) are significant health burdens worldwide with a substantial rise in prevalence. Both can progress to liver cirrhosis. Recent studies have shown that the gut microbiome was associated with NAFLD/AFLD development and progression. The present review focuses on the characteristics of bacteria in NAFLD, AFLD and liver cirrhosis. The similarities and differences of intestinal bacteria are discussed. This study reviews the existing literatures on the microbiota, fatty liver disease, and liver cirrhosis based on Pubmed database. The study showed NAFLD was characterized by increased amounts of Lachnospiraceae from the phylum Firmicutes and Roseburia from the Lachnospiraceae family, and the proportion of Enterobacteria and Proteobacteria was increased after alcohol intake. Reduced Bacteroidetes was observed in cirrhosis. Microbiota can improve or aggravate the above liver diseases through several mechanisms, like increasing liver lipid metabolism, increasing alcohol production, increasing intestinal permeability, bacterial translocation, intestinal bacterial overgrowth, enteric dysbiosis, and impairing bile secretion. Different hepatic diseases owned different intestinal bacterial characters. Microbiota can improve or aggravate three kinds of liver diseases through several mechanisms. However, the depletion of these bacteria is needed to verify their role in liver disease.

Association between small intestinal bacterial overgrowth and beta-cell function of type 2 diabetes

Aims

Previous studies suggest that small intestinal bacterial overgrowth (SIBO) is associated with type 2 diabetes. However, few studies have evaluated the association between SIBO and beta-cell function in type 2 diabetes. The aim of this study was to evaluate whether beta-cell function was associated with SIBO.

Materials and methods

One hundred four patients with type 2 diabetes were included in this study. Based on the presence of SIBO, the patients were divided into SIBO-positive and SIBO-negative groups. Oral glucose tolerance tests were performed. Insulin sensitivity was measured using 1/homeostasis model assessment of insulin resistance (1/HOMA-IR) and the insulin sensitivity index (ISIM). Insulin release was calculated by HOMA-β, early-phase insulin secretion index InsAUC₃₀/GluAUC₃₀, and total-phase insulin secretion index InsAUC₁₂₀/GluAUC₁₂₀.

Results

Compared with the SIBO-negative group, patients in the SIBO-positive group showed a higher glucose level at 120 minutes, HbA1c, 1/HOMA-IR, and ISIM and a lower HOMA-β level, early-phase InsAUC₃₀/GluAUC₃₀, and total-phase InsAUC₁₂₀/GluAUC₁₂₀. Multiple linear regression analysis showed that body mass index, glucose at 0 minutes, and SIBO were independently associated with the early-phase and total-phase insulin secretion.

Conclusion

SIBO may be involved in lower levels of insulin release and worse glycemic control.

The duodenal microbiome is altered in small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) is highly prevalent and is associated with numerous gastrointestinal disorders, but the microbes involved remain poorly defined. Moreover, existing studies of microbiome alterations in SIBO have utilized stool samples, which are not representative of the entire gastrointestinal tract. Therefore, we aimed to determine and compare the duodenal microbiome composition in SIBO and non-SIBO subjects, using duodenal aspirates from subjects undergoing standard-of-care esophagogastroduodenoscopy without colon preparation. Using the recently-redefined cutoff for SIBO of >103 colony forming units per milliliter (CFU/mL), 42 SIBO and 98 non-SIBO subjects were identified. Duodenal samples from SIBO subjects had 4x103-fold higher counts than non-SIBO subjects when plated on MacConkey agar (P<0.0001), and 3.8-fold higher counts when plated on blood agar (P<0.0001). Twenty subjects had also undergone lactulose hydrogen breath tests (LHBTs), of whom 7/20 had SIBO. At the 90-minute timepoint, 4/7 SIBO subjects had positive LHBTs (rise in hydrogen (H2) ≥ 20 ppm above baseline), as compared to 2/13 non-SIBO subjects. 16S ribosomal RNA (rRNA) sequencing revealed that SIBO subjects had 4.31-fold higher relative abundance of Proteobacteria (FDR P<0.0001) and 1.64-fold lower Firmicutes (P<0.0003) than non-SIBO subjects. This increased relative abundance of Proteobacteria correlated with decreased α-diversity in SIBO subjects (Spearman R = 0.4866, P<0.0001) Specific increases in class Gammaproteobacteria correlated with the area-under-the-curve for H2 for 0-90 mins during LHBT (R = 0.630, P = 0.002). Increases in Gammaproteobacteria resulted primarily from higher relative abundances of the family Enterobacteriaceae (FDR P<0.0001), which correlated with the symptom of bloating (Spearman R = 0.185, 2-tailed P = 0.028). Increases in family Aeromonadaceae correlated with urgency with bowel movement (Spearman R = 0.186, 2-tailed P = 0.028). These results validate the >103 CFU/mL cutoff for the definition of SIBO, and also reveal specific overgrowth of Proteobacteria in SIBO vs. non-SIBO subjects, coupled with an altered Proteobacterial profile that correlates with symptom severity. Future research may elucidate host-microbiome interactions underlying these symptoms in SIBO patients.

The Influence of Small Intestinal Bacterial Overgrowth in Digestive and Extra-Intestinal Disorders

Small intestinal bacterial overgrowth (SIBO) is a condition hallmarked by an increase in the concentration of colonic-type bacteria in the small bowel. Watery diarrhea, bloating, abdominal pain and distension are the most common clinical manifestations. Additionally, malnutrition and vitamin (B12, D, A, and E) as well as minerals (iron and calcium) deficiency may be present. SIBO may mask or worsen the history of some diseases (celiac disease, irritable bowel disease), may be more common in some extra-intestinal disorders (scleroderma, obesity), or could even represent a pathogenetic link with some diseases, in which a perturbation of intestinal microbiota may be involved. On these bases, we performed a review to explore the multiple links between SIBO and digestive and extra-intestinal diseases.

Obesity and Risk of Small Intestine Bacterial Overgrowth: A Systematic Review and Meta-Analysis

BACKGROUND/OBJECTIVES

Recent studies have proposed that obesity may be associated with a higher risk of small intestine bacterial overgrowth (SIBO) although the results were inconsistent. The microbiome has a known metabolic role; its impact on obesity in animal models generated the hypothesis of an association between a dysfunctional microbiome and obesity. We performed this systematic review and meta-analysis to elucidate this possible association by summarizing all available data.

METHODS

A literature search utilizing MEDLINE and EMBASE databases from inception until August 2019 was conducted. Eligible studies included either cohort studies or cross-sectional studies that consisted of two groups of participants, those with obesity and those without obesity, and compared the prevalence of SIBO between the groups. Adjusted odds ratios (OR) from each study were consolidated by the generic inverse variance method of DerSimonian and Laird.

RESULTS

A total of five studies with 515 patients fulfilled eligibility criteria and were included in this meta-analysis. The risk of SIBO among individuals with obesity was higher than in individuals without obesity but did not reach statistical significance with a pooled OR of 2.08 [95% confidence interval (CI) 0.82-5.31; p = 0.12; I² 84%]. Sensitivity analysis including only studies from Western countries increased the pooled OR to 3.41 and reached statistical significance (95% CI 1.21-9.59; p = 0.02; I² 62%).

CONCLUSIONS

This meta-analysis found that the risk of SIBO was about two times higher among individuals with obesity compared to individuals without obesity, although the result did not reach statistical significance. The risk increased to threefold and reached statistical significance when only studies from Western countries were included. These observations may suggest the role of obesity as a predisposing factor for SIBO although more studies are still needed to corroborate these preliminary results.

Small intestinal bacterial overgrowth and nonalcoholic fatty liver disease: a systematic review and meta-analysis

OBJECTIVES

Recent studies have suggested that small intestinal bacterial overgrowth (SIBO) could be a predisposing factor for nonalcoholic fatty liver disease (NAFLD) although the results were inconsistent. This systematic review and meta-analysis was conducted with the aim to summarize all available data.

METHODS

A comprehensive literature review was conducted utilizing MEDLINE and EMBASE databases through September 2018 to identify all studies that compared the risk of NAFLD among patients with SIBO versus those without SIBO. Effect estimates from each study were extracted and combined together using the random effect, generic inverse variance method of DerSimonian and Laird.

RESULTS

A total of 10 studies with 1093 participants fulfilled the eligibility criteria and were included in the meta-analysis. A significant association between NAFLD and SIBO was observed with the pooled odds ratio of 3.82 (95% confidence interval, 1.93-7.59; I 65%). Funnel plot is relatively symmetric and is not suggestive of the presence of publication bias.

CONCLUSION

A significant association between NAFLD and SIBO was observed in this meta-analysis.

ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth

Small intestinal bacterial overgrowth is defined as the presence of excessive numbers of bacteria in the small bowel, causing gastrointestinal symptoms. This guideline statement evaluates criteria for diagnosis, defines the optimal methods for diagnostic testing, and summarizes treatment options for small intestinal bacterial overgrowth. This guideline provides an evidence-based evaluation of the literature through the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) process. In instances where the available evidence was not appropriate for a formal GRADE recommendation, key concepts were developed using expert consensus.

Salidroside improves high-fat diet-induced non-alcoholic steatohepatitis by regulating the gut microbiota-bile acid-farnesoid X receptor axis

BACKGROUND

Our previous studies found that salidroside can effectively treat non-alcoholic steatohepatitis (NASH). Here, we discuss the mechanism of salidroside in the treatment of NASH with a focus on the gut microbiota-bile acid-farnesoid X receptor axis.

METHODS

A NASH mouse model was created by providing mice with a high-fat diet (HFD) for 14 weeks. Mice were randomly divided into the HFD group, HFD + salidroside treatment group, and HFD + obeticholic acid treatment group (n = 8 in each group) and were intragastrically administered corresponding drugs for 4 weeks. Hematoxylin-eosin staining was performed to evaluate the histopathological changes associated with the various treatments. In addition, liver triglyceride (TG) content, serum alanine aminotransferase (ALT) activity, serum inflammatory factors, gut microbiota diversity, and the bile acid profile were evaluated. Western blotting and RT-PCR were performed to detect the expressions of FXR and fibroblast growth factor 15 (FGF15).

RESULTS

The HFD group displayed obvious signs of hepatic steatosis. The liver TG, serum ALT, and IL-1a, IL-12, MCP-1, KC, MIP-1a, and MIP-1β were significantly higher in the HFD group than the control group (P < 0.01). Intestinal bacteria and bile acid profiles changed significantly in the HFD group (P < 0.05). Further, the expressions of FXR and FGF15 decreased significantly in the HFD group (P < 0.05). After treatment with salidroside, liver steatosis, TG content, and serum inflammatory factors significantly improved and HFD-induced intestinal bacteria, bile acid disorder, and FXR deficiency were significantly alleviated (P < 0.05).

CONCLUSION

Salidroside can improve NASH via the gut microbiota-bile acid-FXR axis.

Associations of Chronic Inflammation, Insulin Resistance, and Severe Obesity With Mortality, Myocardial Infarction, Cancer, and Chronic Pulmonary Disease

IMPORTANCE

Chronic inflammation and insulin resistance often accompany severe obesity, and all are associated with disease risk.

OBJECTIVE

To examine how the association of severe obesity with adverse outcomes may be modified by the presence of systemic inflammation and/or insulin resistance.

DESIGN, SETTING, AND PARTICIPANTS

This population-based, retrospective cohort study included all residents of Alberta, Canada, aged 18 years and older with at least 1 procedure to ascertain severe obesity and measures of C-reactive protein, fasting glucose, triglyceride, and high-density lipoprotein cholesterol levels. Participants were observed from April 2003 to March 2017, and data analysis was conducted from June 2018 to December 2018.

EXPOSURES

Severe obesity (body mass index ≥35 or ≥40 after January 1, 2017, as indicated with a procedure-fee modifier), chronic inflammation (all measures of C-reactive protein >10 mg/L), and a surrogate measure of insulin resistance.

MAIN OUTCOMES AND MEASURES

All-cause death, first acute myocardial infarction during follow-up, first cancer diagnosis during follow-up, and new chronic pulmonary disease.

RESULTS

Among 420 636 participants, the median age was 45 years (interquartile range, 34-56 years; range, 18-97 years), 157 799 (37.5%) were male, 185 782 (44.2%) had insulin resistance, 71 987 (17.1%) had severe obesity, and 10 770 (2.6%) had inflammation. In women with chronic inflammation, the presence of severe obesity was associated with a lower mortality risk (hazard ratio [HR], 0.75; 95% CI, 0.65-0.86), but there was no difference in risk in men with inflammation (HR, 0.89; 95% CI, 0.78-1.02). In contrast, the presence of severe obesity was associated with a higher mortality risk in men without inflammation (HR, 1.20; 95% CI, 1.13-1.26), but there was no difference in risk in women without inflammation (HR, 1.00; 95% CI, 0.95-1.06). For myocardial infarction, severe obesity was associated with increased risk in both women and men without inflammation (women: HR, 1.26; 95% CI, 1.17-1.36; men: HR, 1.35; 95% CI, 1.27-1.43) but not in women and men with inflammation (women: HR, 0.85; 95% CI, 0.67-1.07; men: HR, 0.90; 95% CI, 0.71-1.14). Severe obesity was associated with increased risk in women and men, irrespective of chronic inflammation, for new chronic pulmonary disease (women with inflammation: HR, 1.34; 95% CI, 1.23-1.46; women without inflammation: HR, 1.58; 95% CI, 1.54-1.62; men with inflammation: HR, 1.41; 95% CI, 1.29-1.54; men without inflammation: HR, 1.65; 95%, CI, 1.60-1.71) and cancer (women with inflammation: HR, 1.16; 95% CI, 1.03-1.30; women without inflammation, HR, 1.32; 95% CI, 1.28-1.36; men with inflammation: HR, 1.17; 95% CI, 1.04-1.32; men without inflammation: HR, 1.33; 95% CI, 1.28-1.39). Similar to chronic inflammation, severe obesity was not always associated with higher risk in participants with insulin resistance.

CONCLUSIONS AND RELEVANCE

The findings suggest that severe obesity with systemic inflammation is associated with a different prognosis than severe obesity without inflammation.

Role of Bile Acids in Dysbiosis and Treatment of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a major health threat around the world and is characterized by dysbiosis. Primary bile acids are synthesized in the liver and converted into secondary bile acids by gut microbiota. Recent studies support the role of bile acids in modulating dysbiosis and NAFLD, while the mechanisms are not well elucidated. Dysbiosis may alter the size and the composition of the bile acid pool, resulting in reduced signaling of bile acid receptors such as farnesoid X receptor (FXR) and Takeda G protein-coupled receptor 5 (TGR5). These receptors are essential in lipid and glucose metabolism, and impaired bile acid signaling may cause NAFLD. Bile acids also reciprocally regulate the gut microbiota directly via antibacterial activity and indirectly via FXR. Therefore, bile acid signaling is closely linked to dysbiosis and NAFLD. During the past decade, stimulation of bile acid receptors with their agonists has been extensively explored for the treatment of NAFLD in both animal models and clinical trials. Early evidence has suggested the potential of bile acid receptor agonists in NAFLD management, but their long-term safety and effectiveness need further clarification.

Lactulose Breath Testing Can Be a Positive Predictor Before Weight Gain in Participants with Obesity Submitted to Roux-en-Y Gastric Bypass

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is defined as the colonization of fermentative bacteria in the duodenum and jejunum. The alteration of digestive anatomy promoted by bariatric surgery may be a pre-disposing factor for SIBO. In this context, the prevalence of SIBO in participants undergoing bariatric surgery using Roux-en-Y gastric bypass (BGYR) was evaluated.

METHODS

Participants, both sexes, older than 18 years, were those who (a) had bariatric surgery by the BGYR technique at least 1 year before the data collection and (b) did not use antibiotics recently. The SIBO diagnosis was established through the hydrogen breath test (H₂BT), with intake of lactulose and serial collection of breath samples over 2 h. A test with ≥ 12-point elevation over the basal sample at 60 min after substrate intake was deemed positive.

RESULTS

A total of 18 participants (14 females (77.8%)) were enrolled with a mean age of 50.5 years (range, 23 to 79 years). The interval between surgery and data collection ranged from 5 to 20 years (mean, 11.2 years). The mean preoperative body mass index (BMI) was 44.6 kg/m² (range, 36.7-56.2 kg/m²). The H₂RT with lactulose was positive for SIBO in seven (six female) participants. The participants with negative test measured trough H₂BT with lactulose had a lower mean BMI of 28.69 kg/m², in comparison with the positive group, which presented a mean BMI of 33.04 kg/m² (p value = 0.041).

CONCLUSION

Our data point to a high prevalence of SIBO (38.8%) in patients undergoing BGYR with a value in accordance with the literature. Moreover, the differences in BMI between negative and positive groups by H₂BT with lactulose evidenced a weight gain relapse in participants with SIBO.

Intestinal Barrier Function-Non-alcoholic Fatty Liver Disease Interactions and Possible Role of Gut Microbiota

Non-alcoholic fatty liver disease (NAFLD) is a metabolic stress liver injury that is closely related to obesity, insulin resistance, type 2 diabetes, atherosclerosis, and metabolic syndrome. The pathological features are diffuse hepatic vesicular steatosis, including non-alcoholic steatohepatitis, liver fibrosis, and even liver cancer. A variety of pathological outcomes cause serious harm to human health. At present, an increasing number of researchers are investigating the pathogenesis of NAFLD from the perspective of changes in the function of the intestinal barrier. The physical, chemical, immunological, and microbiological barriers in the intestinal tract constitute the complete intestinal barrier, which plays an important defensive role against the invasion of harmful substances from the intestines. Protecting the function of the intestinal barrier is a new way to treat NAFLD and its related diseases. In this perspective, we summarized the current knowledge of the role of the intestinal barrier in NAFLD.

The role of gut microbiota in liver disease development and treatment

Liver cancer is the sixth most common cancer worldwide, and the third most common cause of cancer-related death. Hepatocellular carcinoma (HCC), which accounts for more than 90% of primary liver cancers, is an important public health problem. In addition to cirrhosis caused by hepatitis B viral (HBV) or hepatitis C viral (HCV) infection, non-alcoholic fatty liver disease (NAFLD) is becoming a major risk factor for liver cancer because of the prevalence of obesity. Non-alcoholic steatohepatitis (NASH) will likely become the leading indication for liver transplantation in the future. It is well recognized that gut microbiota is a key environmental factor in the pathogenesis of liver disease and cancer. The interplay between gut microbiota and liver disease has been investigated in animal and clinical studies. In this article, we summarize the roles of gut microbiota in the development of liver disease as well as gut microbiota-targeted therapies.

Small intestinal bacterial overgrowth and nonalcoholic fatty liver disease

The gut microbiota has recently been recognized as a major environmental factor in the pathophysiology of several human diseases. The anatomical and functional association existing between the gut and the liver provides the theoretical basis to assume that the liver is a major target for gut microbes. In the last decades, many studies have reported an altered composition of gut microbiota in patients with chronic liver diseases and liver cirrhosis, suggesting a progressively marked dysbiosis to be related to worsening of the liver disease. Modifications of microbiota result in alteration in providing signals through the intestine and bacterial products, as well as hormones produced in the bowel that affect metabolism at different levels including the liver. There is increasing evidence for a correlation between intestinal microbiota, bacterial translocation and hepatic steatosis. Intestinal microbiota affects nutrient absorption and energy homeostasis. Altered intestinal permeability may favor the passage of bacteria derived compounds into the systemic circulation, causing a systemic inflammatory state, characteristic of the metabolic syndrome. At present, an increasing number of studies indicate a close relationship between dysbiosis, defined as abnormal composition and the amount of intestinal bacteria (gut microbiota), intestinal permeability and some metabolic, inflammatory, degenerative and even psychiatric diseases. Microbiota pharmacological modulation seems to be a promising tool for a new therapeutic approach to non-alcoholic fatty liver disease and in prevention of cirrhosis.

The following study aims to briefly discuss the role of microbiota disorder (dysbiosis), and in particular small intestinal bacterial overgrowth (SIBO), in the pathogenesis of nonalcoholic fatty liver disease (NAFLD).

Gegen Qinlian Decoction Attenuates High-Fat Diet-Induced Steatohepatitis in Rats via Gut Microbiota

Gut microbiota play an important role in modulating energy contribution, metabolism, and inflammation, and disruption of the microbiome population is closely associated with chronic metabolic diseases, such as nonalcoholic fatty liver disease (NAFLD). Gegen Qinlian decoction (GGQLD), a well-known traditional Chinese herbal medicine (CHM), was previously found to regulate lipid metabolism and attenuate inflammation during NAFLD pathogenesis. However, the underlying mechanism of this process, as well as how the gut microbiome is involved, remains largely unknown. In this study, we investigated the effect of varying doses of GGQLD on the total amount and distribution of gut bacteria in rats fed a high-fat diet (HFD) for 8 weeks. Our analysis indicates that Oscillibacter and Ruminococcaceae_g_unclassified are the dominant families in the HFD group. Further, HFD-dependent differences at the phylum, class, and genus levels appear to lead to dysbiosis, characterized by an increase in the Firmicutes/Bacteroidetes ratio and a dramatic increase in the Oscillibacter genus compared to the control group. Treatment with GGQLD, especially the GGQLL dose, improved these HFD-induced changes in intestinal flora, leading to increased levels of Firmicutes, Clostridia, Lactobacillus, bacilli, and Erysipelotrichales that were similar to the controls. Taken together, our data highlight the efficacy of GGQLD in treating NAFLD and support its clinical use as a treatment for NAFLD/NASH patients.

Gut Microbiota's Relationship with Liver Disease and Role in Hepatoprotection by Dietary Natural Products and Probiotics

A variety of dietary natural products have shown hepatoprotective effects. Increasing evidence has also demonstrated that gut microorganisms play an important role in the hepatoprotection contributed by natural products. Gut dysbiosis could increase permeability of the gut barrier, resulting in translocated bacteria and leaked gut-derived products, which can reach the liver through the portal vein and might lead to increased oxidative stress and inflammation, thereby threatening liver health. Targeting gut microbiota modulation represents a promising strategy for hepatoprotection. Many natural products could protect the liver from various injuries or mitigate hepatic disorders by reverting gut dysbiosis, improving intestinal permeability, altering the primary bile acid, and inhibiting hepatic fatty acid accumulation. The mechanisms underlying their beneficial effects also include reducing oxidative stress, suppressing inflammation, attenuating fibrosis, and decreasing apoptosis. This review discusses the hepatoprotective effects of dietary natural products via modulating the gut microbiota, mainly focusing on the mechanisms of action.

Mechanistic and therapeutic advances in non-alcoholic fatty liver disease by targeting the gut microbiota

Non-alcoholic fatty liver disease (NAFLD) is one of the most common metabolic diseases currently in the context of obesity worldwide, which contains a spectrum of chronic liver diseases, including hepatic steatosis, non-alcoholic steatohepatitis and hepatic carcinoma. In addition to the classical "Two-hit" theory, NAFLD has been recognized as a typical gut microbiota-related disease because of the intricate role of gut microbiota in maintaining human health and disease formation. Moreover, gut microbiota is even regarded as a "metabolic organ" that play complementary roles to that of liver in many aspects. The mechanisms underlying gut microbiota-mediated development of NAFLD include modulation of host energy metabolism, insulin sensitivity, and bile acid and choline metabolism. As a result, gut microbiota have been emerging as a novel therapeutic target for NAFLD by manipulating it in various ways, including probiotics, prebiotics, synbiotics, antibiotics, fecal microbiota transplantation, and herbal components. In this review, we summarized the most recent advances in gut microbiota-mediated mechanisms, as well as gut microbiota-targeted therapies on NAFLD.

Proton pump inhibitors as risk factor for metabolic syndrome and hepatic steatosis in coeliac disease patients on gluten-free diet

BACKGROUND

Recent research has shown that patients with coeliac disease (CD) are at risk of developing metabolic syndrome (MS) and hepatic steatosis (HS) after commencing a gluten-free diet (GFD). This study aimed to evaluate the predictive factors for MS and HS in CD after 1 year of GFD.

METHODS

All consecutive newly diagnosed CD patients were enrolled. We prospectively collected data about BMI; waist circumference; blood pressure; cholesterol; triglycerides, glucose and insulin blood levels; insulin resistance (through the homeostatic model assessment HOMA-IR) and treatment with proton pump inhibitors (PPI). Diagnosis of MS was made in accordance with current guidelines and HS was diagnosed by ultrasonography. The prevalence of MS and HS was re-assessed after 1 year of GFD. A logistic regression analysis was performed to identify risk factors for MS and HS occurrence after 1 year of GFD.

RESULTS

Of 301 patients with newly diagnosed CD, 4.3% met criteria for diagnosis of MS and 25.9% presented with HS at the time of CD diagnosis; 99 subjects (32.8%) had long-term exposure to PPI during the study period. After 1 year, 72 (23.9%) patients had developed MS (4.3 vs 23.9%; p < 0.001, OR 6.9) and 112 (37.2%) had developed HS (25.9 vs 37.2%; p < 0.01, OR 1.69). At multivariate analysis, high BMI at diagnosis (OR 10.8; p < 0.001) and PPI exposure (OR 22.9; p < 0.001) were the only factors associated with the occurrence of MS; HOMA-IR (OR 9.7; p < 0.001) and PPI exposure (OR 9.2; p < 0.001) were the only factors associated with the occurrence of HS.

CONCLUSIONS

PPI exposure adds further risk of occurrence of MS and HS for patients with CD on GFD. The use of PPI in patients with CD on GFD should be limited to strict indications.

Gut microbiota, fatty liver disease, and hepatocellular carcinoma

Intestinal bacteria contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Recently developed microbial profiling techniques are beginning to shed light on the nature of the changes in the gut microbiota that accompany NAFLD and non-alcoholic steatohepatitis (NASH). In this review, we summarize the role of gut microbiota in the development of NAFLD, NASH, and hepatocellular carcinoma (HCC). We highlight the mechanisms by which gut microbiota contribute to NAFLD/NASH, including through alterations in gut epithelial permeability, choline metabolism, endogenous alcohol production, release of inflammatory cytokines, regulation of hepatic Toll-like receptor (TLR), and bile acid metabolism. In addition, we analyze possible mechanisms for enhanced hepatic carcinogenesis, including alterations in bile acid metabolism, release of inflammatory cytokines, and expression of TLR-4. Finally, we describe therapeutic approaches for NAFLD/NASH and preventive strategies for HCC involving modulation of the intestinal microbiota or affected host pathways. Although recent studies have provided useful information, large-scale prospective studies are required to better characterize the intestinal microbiota and metabolome, in order to demonstrate a causative role for changes in the gut microbiota in the etiology of NAFLD/NASH, to identify new therapeutic strategies for NAFLD/NASH, and to develop more effective methods of preventing HCC.

Treatment efficacy of a probiotic preparation for non-alcoholic steatohepatitis: A pilot trial

OBJECTIVE

To evaluate the therapeutic effect of a probiotic cocktail containing Lactobacilli, Bifidobacteria and Streptococcus thermophilus on non-alcoholic steatohepatitis (NASH).

METHODS

In this open-label trial, 75 patients with NASH fed a low-fat/low-calorie diet were randomly divided into the control group and experimental group, with the latter receiving the probiotic cocktail once daily for 12 weeks.

RESULTS

All patients were diagnosed with fatty liver by ultrasound examination and had elevated levels of γ-glutamyl transferase (GGT) and alanine aminotransferase (ALT), and slightly increased body mass index (BMI) and cholesterol levels. BMI and serum cholesterol were reduced by the low-fat/low-calorie diet but ALT was not. However, the short-term (12-week) treatment with the probiotic cocktail caused a significant (by >20%) reduction of serum ALT compared with controls, indicating mitigation of inflammation. Accordingly, liver stiffness was decreased in the probiotic-treated group compared with the control group (P < 0.05). Moreover, a more significant decrease in the BMI and serum cholesterol was observed in the probiotic-treated group compared with control (P < 0.05). However, the reduction of GGT as a steatosis marker was insignificant. The composition of stool microbiota in probiotic-treated patients demonstrated a shift towards a normal pattern for all bacterial species examined. No adverse events were observed in any patient during the trial.

CONCLUSION

Short-term treatment with the probiotic cocktail caused significant improvement of liver inflammation without adverse events and, thus, may represent a promising candidate therapeutic approach for NASH.

NAFLD, Helicobacter species and the intestinal microbiome

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. It is well-accepted that gut dysbiosis is associated with NAFLD, however, there is some conflicting evidence regarding the nature of these alterations. Infection with Helicobacter species, mainly H. pylori, has also been associated with increased NAFLD risk, however, some studies have failed to reproduce this finding. Further studies including large study samples and standardised procedures for microbiota analyses, H. pylori detection and NAFLD diagnostic criteria, are required. The mechanisms involving Helicobacter species and the intestinal microbiome in NAFLD pathogenesis appear to be part of the multiple-hit theory, in which increased intestinal permeability, inflammatory responses, altered choline, bile acids and carbohydrate metabolism, production of short-chain fatty acids, urea cycle and urea transport systems, altered maintenance of hepatic γδT-17 cells, insulin resistance, hormones secreted by the adipose tissue, metabolic hormones, bacterial metabolites and Helicobacter toxins, are all implicated.

The relationship between non-alcoholic fatty liver disease and small intestinal bacterial overgrowth among overweight and obese children and adolescents

BACKGROUND

The increasing rate of obesity and overweight among children has highlighted nonalcoholic fatty liver disease (NAFLD) as the most common cause of chronic pediatric liver diseases. There are many publications supporting the idea that gut microbiota is altered in NAFLD. The aim of this study was to evaluate the prevalence of NAFLD among overweight and obese children with and without small intestinal bacterial overgrowth (SIBO) compared to a control group and to assess if intestinal dysbiosis represents a risk factor for NAFLD.

METHODS

One hundred and twenty-five overweight and obese children aged 10-18 years and 120 controls matched for age and gender were enrolled. SIBO was assessed by glucose hydrogen breath test (GHBT) in all subjects. NAFLD was assessed in all children using abdominal imaging and laboratory findings.

RESULTS

Of 125 obese children enrolled, 47 (37.6%) presented intestinal dysbiosis and 78 (62.4%) were SIBO negative. Only four (3.3%) controls were SIBO positive. NAFLD was detected in 28/47 (59.5%) of the SIBO positive obese group, compared to 8/78 (10.2%) of the SIBO negative obese group (p<0.001) and 0/120 (0%) controls (p<0.001). Children from the SIBO positive obese group had higher rates of elevated aminotransferases levels: aspartate aminotransferases (ASAT) (53.1% vs. 6.4%; p<0.001) and alanine aminotransferase (ALAT) (59.5% vs. 7.6%; p<0.001), hypertension (23.4% vs. 5.1%; p=0.002) and metabolic syndrome (44.6% vs. 9%; p=0.002) compared to the SIBO negative obese group.

CONCLUSIONS

Obese children with SIBO have an increased risk for developing NAFLD. The relationship between intestinal dysbiosis and diet can influence the gut-liver axis.

Gut Microbiota and Nonalcoholic Fatty Liver Disease: Insights on Mechanisms and Therapy

The gut microbiota plays critical roles in development of obese-related metabolic diseases such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes(T2D), and insulin resistance(IR), highlighting the potential of gut microbiota-targeted therapies in these diseases. There are various ways that gut microbiota can be manipulated, including through use of probiotics, prebiotics, synbiotics, antibiotics, and some active components from herbal medicines. In this review, we review the main roles of gut microbiota in mediating the development of NAFLD, and the advances in gut microbiota-targeted therapies for NAFLD in both the experimental and clinical studies, as well as the conclusions on the prospect of gut microbiota-targeted therapies in the future.

Non-alcoholic Fatty Liver Disease in Lean Subjects: Characteristics and Implications

Non-alcoholic fatty liver disease (NAFLD) is commonly diagnosed in obese subjects; however, it is not rare among lean individuals. Given the absence of traditional risk factors, it tends to remain under-recognised. The metabolic profiles of lean NAFLD patients are frequently comparable to those of obese NAFLD patients. Though results from several studies have been mixed, it has been generally revealed that lean subjects with NAFLD have minor insulin resistance compared to that in obese NAFLD. Several genetic variants are associated with NAFLD without insulin resistance. Some data suggest that the prevalence of steatohepatitis and advanced fibrosis do not differ significantly between lean and obese NAFLD; however, the former tend to have less severe disease at presentation. The underlying pathophysiology of lean NAFLD may be quite different. Genetic predispositions, fructose- and cholesterol-rich diet, visceral adiposity and dyslipidaemia have potential roles in the pathogenic underpinnings. Lean NAFLD may pose a risk for metabolic disturbances, cardiovascular morbidity or overall mortality. Secondary causes of hepatic steatosis are also needed to be ruled out in lean subjects with NAFLD. The effectiveness of various treatment modalities, such as exercise and pharmacotherapy, on lean NAFLD is not known. Weight loss is expected to help lean NAFLD patients who have visceral obesity. Further investigation is needed for many aspects of lean NAFLD, including mechanistic pathogenesis, risk assessment, natural history and therapeutic approach.

Low-grade small intestinal bacterial overgrowth is common in patients with non-alcoholic steatohepatitis on quantitative jejunal aspirate culture

BACKGROUND

Though pathogenesis of non-alcoholic steatohepatitis (NASH) is unclear, association with small intestinal bacterial overgrowth [SIBO] and fecal dysbiosis is suggested. We evaluated SIBO in NASH using quantitative jejunal aspirate culture (conventional criteria: ≥ 10⁵ colony forming unit (CFU)/mL and newer cutoff ≥ 10³ CFU/mL) and glucose hydrogen breath test.

METHODS

Thirty-eight patients with NASH (age 37.5 years, range 20-54, 9, 24% female), diagnosed by ultrasonography, alanine aminotransferase >1.5 times normal and liver biopsy (in 27/38, 71%) and exclusion of other causes and 12 constipation-predominant irritable bowel syndrome as historical controls (age 39.5-y, 26-44; 3, 25% female) without fatty liver were studied.

RESULTS

Jejunal aspirates, obtained in 35/38 patients, were sterile in 14/35 (40%) and bacteria isolated in 21 (60%) (all aerobic, in one anaerobe also; Gram positive 5, negative 13, both 3). In contrast, bacteria (two Gram negative) were isolated in 3/12 (25%) controls (odds ratio 4.5, 95% CI 1.0-19.5; p = 0.04); colony counts were higher in NASH than controls (median 380 CFU/mL, 0-200,000 vs. 0 CFU/mL, 0-1000; p = 0.02). Gram negative bacteria tended to be commoner in NASH than controls (16/35 vs. 2/12; p = 0.07). Seven out of 35 (20%) patients with NASH (≥ 10⁵ CFU/mL in 5 and 2 other on glucose hydrogen breath test) and no control had SIBO (p = ns); low-grade SIBO (≥10³ CFU/mL) was commoner in NASH than controls (14/35, 40%, vs. 1/12, 8.3%; p = 0.04). There was no correlation between bacterial colony count and bacterial type and anthropometric and biochemical parameters.

CONCLUSION

Low-grade bacterial overgrowth, particularly with Gram negative bacteria, was commoner in NASH than controls.