Systematic review on intervention with prebiotics/probiotics in patients with obesity-related nonalcoholic fatty liver disease

Regular Consumption of Black Tea Kombucha Modulates the Gut Microbiota in Individuals with and Without Obesity

BACKGROUND

Kombucha, a fermented beverage obtained from a Symbiotic Culture of Bacteria and Yeast (SCOBY), has shown potential in modulating gut microbiota, although no clinical trials have been done.

OBJECTIVE

We aimed to evaluate the effects of regular black tea kombucha consumption on intestinal health in individuals with and without obesity.

METHODS

A pre-post clinical intervention study was conducted lasting eight weeks. Forty-six participants were allocated into two groups: normal weight + black tea kombucha (n=23); and obese + black tea kombucha (n=23). Blood, urine, and stool samples were collected at baseline (T0) and after 8 weeks of intervention (T8).

RESULTS

A total of 145 phenolic compounds were identified in the kombucha, primarily flavonoids (81%) and phenolic acids (19%). Kombucha favored commensal bacteria such as Bacteroidota and Akkermanciaceae, especially in the obese group. Subdoligranulum, a butyrate producer, also increased in the obese group after kombucha consumption (p=0.031). Obesity-associated genera Ruminococcus and Dorea were elevated in the obese group at baseline (p<0.05) and reduced after kombucha consumption, becoming similar to the normal weight group (Ruminococcus: obese T8 x normal weight T8: p=0.27; Dorea: obese T8 x normal weight T0: p=0.57; obese T8 x normal weight T8: p=0.32). Fungal diversity increased, with a greater abundance of Saccharomyces in both groups and reductions in Exophiala and Rhodotorula, particularly in the obese group. Pichia and Dekkera, key microorganisms in kombucha, were identified as biomarkers after the intervention.

CONCLUSIONS

Regular kombucha consumption positively influenced gut microbiota in both normal and obese groups, with more pronounced effects in the obese group, suggesting that it may be especially beneficial for those individuals.

REGISTRATION ID AND URL

This study is registered on the Brazilian Clinical Trial Registry - ReBEC (UTN code U1111-1263-9550); available at .

CLINICAL TRIAL STATEMENT

This study was conducted according to the guidelines established in the Declaration of Helsinki and the procedures were approved by the National Research Ethics Committee - CONEP/Brazil (registration no. 3.948.033). Written informed consent was obtained from all subjects. This study is registered on the Brazilian Clinical Trial Registry (ReBEC), available at (UTN code U1111-1263-9550).

The Role of Gut Microbiota Modification in Nonalcoholic Fatty Liver Disease Treatment Strategies

One of the most common chronic liver diseases is nonalcoholic fatty liver disease (NAFLD), which affects many people around the world. Gut microbiota (GM) dysbiosis seems to be an influential factor in the pathophysiology of NAFLD because changes in GM lead to fundamental changes in host metabolism. Therefore, the study of the effect of dysbiosis on the pathogenicity of NAFLD is important. European clinical guidelines state that the best advice for people with NAFLD is to lose weight and improve their lifestyle, but only 40% of people can achieve this goal. Accordingly, it is necessary to provide new treatment approaches for prevention and treatment. In addition to dietary interventions and lifestyle modifications, GM modification-based therapies are of interest. These therapies include probiotics, synbiotics, fecal microbiota transplantation (FMT), and next-generation probiotics. All of these treatments have had promising results in animal studies, and it can be imagined that acceptable results will be obtained in human studies as well. However, further investigations are required to generalize the outcomes of animal studies to humans.

Deciphering the Gut–Liver Axis: A Comprehensive Scientific Review of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has emerged as a significant global health issue. The condition is closely linked to metabolic dysfunctions such as obesity and type 2 diabetes. The gut–liver axis, a bidirectional communication pathway between the liver and the gut, plays a crucial role in the pathogenesis of NAFLD. This review delves into the mechanisms underlying the gut–liver axis, exploring the influence of gut microbiota, intestinal permeability, and inflammatory pathways. This review also explores the potential therapeutic strategies centered on modulating gut microbiota such as fecal microbiota transplantation; phage therapy; and the use of specific probiotics, prebiotics, and postbiotics in managing NAFLD. By understanding these interactions, we can better comprehend the development and advancement of NAFLD and identify potential therapeutic targets.

IFN-β Overexpressing Adipose-Derived Mesenchymal Stem Cells Mitigate Alcohol-Induced Liver Damage and Gut Permeability

Alcoholic liver disease (ALD) is a form of hepatic inflammation. ALD is mediated by gut leakiness. This study evaluates the anti-inflammatory effects of ASCs overexpressing interferon-beta (ASC-IFN-β) on binge alcohol-induced liver injury and intestinal permeability. In vitro, ASCs were transfected with a non-viral vector carrying the human IFN-β gene, which promoted hepatocyte growth factor (HGF) secretion in the cells. To assess the potential effects of ASC-IFN-β, C57BL/6 mice were treated with three oral doses of binge alcohol and were administered intraperitoneal injections of ASC-IFN-β. Mice treated with binge alcohol and administered ASC-IFN-β showed reduced liver injury and inflammation compared to those administered a control ASC. Analysis of intestinal tissue from ethanol-treated mice administered ASC-IFN-β also indicated decreased inflammation. Additionally, fecal albumin, blood endotoxin, and bacterial colony levels were reduced, indicating less gut leakiness in the binge alcohol-exposed mice. Treatment with HGF, but not IFN-β or TRAIL, mitigated the ethanol-induced down-regulation of cell death and permeability in Caco-2 cells. These results demonstrate that ASCs transfected with a non-viral vector to induce IFN-β overexpression have protective effects against binge alcohol-mediated liver injury and gut leakiness via HGF.

Probiotic-Reduced Inflammaging in Older Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

The disparity between increased lifespan and healthy aging, marked by prevalent "inflammaging", highlights the global challenge in care of older persons. This study explored the anti-inflammatory effects of Lactiplantibacillus plantarum HEAL9 (LpHEAL9), alone or combined with berries, on older volunteers with chronic low-grade inflammation (LGI). It was a randomized, double-blind, placebo-controlled trial, with a total of 66 volunteers (> 70 years old), randomly assigned, and equally distributed, to placebo, LpHEAL9 or LpHEAL9 + Berries group. After a 2-week run-in period, participants underwent a 4-week dietary intervention. Intake of LpHEAL9 showed a trend towards reduction in serum CRP but without reaching statistical significance. However, LpHEAL9 significantly decreased fecal calprotectin levels compared to placebo. LpHEAL9+Berries did not show any effect on inflammation. Both probiotic groups showed a trend in improving cognitive function albeit not reaching statistical significance. Our findings suggest that the probiotic strain L. plantarum HEAL9 has a modest impact on LGI in a healthy older population (ClinicalTrials.gov ID: NCT02342496).

The interaction between gut microbiome and bone health

PURPOSE OF REVIEW

This review critically examines interconnected health domains like gut microbiome, bone health, interleukins, chronic periodontitis, and coronavirus disease 2019 (COVID-19), offering insights into fundamental mechanisms and clinical implications, contributing significantly to healthcare and biomedical research.

RECENT FINDINGS

This review explores the relationship between gut microbiome and bone health, a growing area of study. It provides insights into skeletal integrity and potential therapeutic avenues. The review also examines interleukins, chronic periodontitis, and COVID-19, highlighting the complexity of viral susceptibility and immune responses. It highlights the importance of understanding genetic predispositions and immune dynamics in the context of disease outcomes. The review emphasizes experimental evidence and therapeutic strategies, aligning with evidence-based medicine and personalized interventions. This approach offers actionable insights for healthcare practitioners and researchers, paving the way for targeted therapeutic approaches and improved patient outcomes.

SUMMARY

The implications of these findings for clinical practice and research underscore the importance of a multidisciplinary approach to healthcare that considers the complex interactions between genetics, immune responses, oral health, and systemic diseases. By leveraging advances in biomedical research, clinicians can optimize patient care and improve health outcomes across diverse patient populations.

Multifunctional role of oral bacteria in the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver disorders of varying severity, ultimately leading to fibrosis. This spectrum primarily consists of NAFL and non-alcoholic steatohepatitis. The pathogenesis of NAFLD is closely associated with disturbances in the gut microbiota and impairment of the intestinal barrier. Non-gut commensal flora, particularly bacteria, play a pivotal role in the progression of NAFLD. Notably, Porphyromonas gingivalis, a principal bacterium involved in periodontitis, is known to facilitate lipid accumulation, augment immune responses, and induce insulin resistance, thereby exacerbating fibrosis in cases of periodontitis-associated NAFLD. The influence of oral microbiota on NAFLD via the "oral-gut-liver" axis is gaining recognition, offering a novel perspective for NAFLD management through microbial imbalance correction. This review endeavors to encapsulate the intricate roles of oral bacteria in NAFLD and explore underlying mechanisms, emphasizing microbial control strategies as a viable therapeutic avenue for NAFLD.

Can modulation of gut microbiota affect anthropometric indices in patients with non-alcoholic fatty liver disease? An umbrella meta-analysis of randomized controlled trials

Background and aim

Modulating the gut microbiota population by administration of probiotics, prebiotics, and synbiotics has shown to have a variety of health benefits in different populations, particularly those with metabolic disorders. Although the promising effects of these compounds have been observed in the management of patients with non-alcoholic fatty liver disease (NAFLD), the exact effects and the mechanisms of action are yet to be understood. In the present study, we aimed to evaluate how gut microbiota modulation affects anthropometric indices of NAFLD patients to achieve a comprehensive summary of current evidence-based knowledge.

Methods

Two researchers independently searched international databases, including PubMed, Scopus, and Web of Science, from inception to June 2023. Meta-analysis studies that evaluated the effects of probiotics, prebiotics, and synbiotics on patients with NAFLD were entered into our umbrella review. The data regarding anthropometric indices, including body mass index, weight, waist circumference (WC), and waist-to-hip ratio (WHR), were extracted by the investigators. The authors used random effect model for conducting the meta-analysis. Subgroup analysis and sensitivity analysis were also performed.

Results

A total number of 13 studies were finally included in our study. Based on the final results, BMI was significantly decreased in NAFLD patients by modulation of gut microbiota [effect size (ES): -0.18, 05% CI: -0.25, -0.11, P<0.001]; however, no significant alteration was observed in weight and WC (ES: -1.72, 05% CI: -3.48, 0.03, P=0.055, and ES: -0.24, 05% CI: -0.75, 0.26, P=0.353, respectively). The results of subgroup analysis showed probiotics had the most substantial effect on decreasing BMI (ES: -0.77, 95% CI: -1.16, -0.38, P<0.001) followed by prebiotics (ES: -0.51, 95% CI: -0.76, -0.27, P<0.001) and synbiotics (ES: -0.12, 95% CI: -0.20, -0.04, P=0.001).

Conclusion

In conclusion, the present umbrella meta-analysis showed that although modulation of gut microbiota by administration of probiotics, prebiotics, and synbiotics had promising effects on BMI, no significant change was observed in the WC and weight of the patients. No sufficient data were available for other anthropometric indices including waist-to-hip ratio and waist-to-height ratio and future meta-analyses should be done in this regard.

Gut microbiota in MAFLD: therapeutic and diagnostic implications

Metabolic dysfunction-associated fatty liver disease (MAFLD), formerly known as nonalcoholic fatty liver disease, is becoming a significant contributor to chronic liver disease globally, surpassing other etiologies, such as viral hepatitis. Prevention and early treatment strategies to curb its growing prevalence are urgently required. Recent evidence suggests that targeting the gut microbiota may help treat and alleviate disease progression in patients with MAFLD. This review aims to explore the complex relationship between MAFLD and the gut microbiota in relation to disease pathogenesis. Additionally, it delves into the therapeutic strategies targeting the gut microbiota, such as diet, exercise, antibiotics, probiotics, synbiotics, glucagon-like peptide-1 receptor agonists, and fecal microbiota transplantation, and discusses novel biomarkers, such as microbiota-derived testing and liquid biopsy, for their diagnostic and staging potential. Overall, the review emphasizes the urgent need for preventive and therapeutic strategies to address the devastating consequences of MAFLD at both individual and societal levels and recognizes that further exploration of the gut microbiota may open avenues for managing MAFLD effectively in the future.

Probiotic consumption and hepatic steatosis: results from the NHANES 2011-2016 and Mendelian randomization study

Background

Recent research showed that probiotics treatment may reduce insulin resistance, regulate lipid metabolism, raise liver enzyme levels, and ameliorate inflammation in individuals with metabolic associated fatty liver disease (MAFLD). However, the possible effects of probiotic use on the progression of hepatic steatosis (HS) have not been identified. The purpose of this study was to investigate this in a large population database.

Methods

The cross-sectional research was conducted among adults with complete data on probiotic yogurt consumption and HS in the 2011-2016 National Health and Nutrition Examination Survey (NHANES). Probiotic yogurt consumption was assessed using a dietary supplement questionnaire, while HS was evaluated with HS index (HSI). To explore their relationship, weighted univariate regression analysis, subgroup analysis, and interaction analysis were conducted. To evaluate the causal association between yogurt consumption and NAFLD, mendelian randomization analysis (MR) were performed. A restricted cubic spline (RCS) was used to analyze the relationship curve between the leves of yogurt consumption and hepatic steatosis.

Results

A total of 7,891 participants were included in the study represented 146.7 million non-institutionalized residents of the United States, of whom 4,322 (54.77%) were diagnosed with HS. Multivariable logistic regression showed probiotic yogurt consumption had significantly inverse relationship for HS (OR = 0.84, 95% CI: 0.72-0.97, p = 0.02) after adjusting for all covariates. Once more, the independent relationship between probiotic yogurt consumption and HS was verified by subgroup analysis and interaction analysis. The MR analysis results indicate that there is no causal relationship between yogurt consumption and NAFLD. The RCS model demonstrated a robust J-shaped link between yogurt consumption and HS, revealing a significant decrease in risk within the lower range of yogurt consumption, which attained the lowest risk close to 0.4 cup.

Conclusion

According to the NHANES data, the consumption of probiotics and yogurt has a beneficial effect on HS, whereas the MR results indicated it was not related to NAFLD. The RCS analysis indicates a J-shaped relationship between yogurt consumption and HS, which may account for the inconsistency in the results. Based on these findings, we recommend that adults take half a cup of yogurt daily.

Potential Complementary Effect of Zinc and Alkalihalobacillus clausii on Gut Health and Immunity: A Narrative Review

A balanced microbiota-microorganisms that live in the gut-is crucial in the early years of a child's life, while dysbiosis-altered microbiota-has been linked to the development of various diseases. Probiotics, such as Alkalihalobacillus clausii, are commonly used to restore the balance of gut microbiota and have shown additional antimicrobial and immunomodulatory properties. Intake of micronutrients can affect the structure and function of the gut barrier and of the microbiota by having multiple effects on cellular metabolism (e.g., immunomodulation, gene expression, and support structure proteins). An inadequate zinc intake increases the risk of deficiency and associated immune dysfunctions; it is responsible for an increased risk of developing gastrointestinal diseases, respiratory infections, and stunting. Paediatric zinc deficiency is a public health concern in many countries, especially in low-income areas. Currently, zinc supplementation is used to treat childhood diarrhoea. This review examines how combining A. clausii and zinc could improve dysbiosis, gut health, and immunity. It suggests that this combination could be used to prevent and treat infectious diseases and diarrhoea in children up to adolescence.

Ferrostatin-1 improves prognosis and regulates gut microbiota of steatotic liver transplantation recipients in rats

Aims: To investigate the effects of Ferrostatin-1 (Fer-1) on improving the prognosis of liver transplant recipients with steatotic liver grafts and regulating gut microbiota in rats. Methods: We obtained steatotic liver grafts and established a liver transplantation model. Recipients were divided into sham, liver transplantation and Fer-1 treatment groups, which were assessed 1 and 7 days after surgery (n = 6). Results & conclusion: Fer-1 promotes recovery of the histological structure and function of steatotic liver grafts and the intestinal tract, and improves inflammatory responses of recipients following liver transplantation. Fer-1 reduces gut microbiota pathogenicity, and lowers iron absorption and improves fat metabolism of recipients, thereby protecting steatotic liver grafts.

Composition of gut microbiota and non-alcoholic fatty liver disease: A systematic review and meta-analysis

The present systematic review and meta-analysis aimed to summarize the associations between gut microbiota composition and non-alcoholic fatty liver disease. To compare the differences between individuals with or without NAFLD, the standardized mean difference and 95% confidence interval were computed for each α-diversity index and relative abundance of gut microbes. The β-diversity indices were summarized in a qualitative manner. A total of 54 studies with 8894 participants were included. Overall, patients with NAFLD had moderate reduction in α-diversity indices including Shannon (SMD = -0.36, 95% CI = [-0.53, -0.19], p < 0.001) and Chao 1 (SMD = -0.42, 95% CI = [-0.68, -0.17], p = 0.001), but no significant differences were found for Simpson, observed species, phylogenetic diversity, richness, abundance-based coverage estimator, and evenness (p ranged from 0.081 to 0.953). Over 75% of the included studies reported significant differences in β-diversity. Although there was substantial interstudy heterogeneity, especially for analyses at the phylum, class, and family levels, the majority of the included studies showed alterations in the depletion of anti-inflammatory microbes (i.e., Ruminococcaceae and Coprococcus) and the enrichment of proinflammatory microbes (i.e., Fusobacterium and Escherichia) in patients with NAFLD. Perturbations in gut microbiota were associated with NAFLD, commonly reflected by a reduction in beneficial species and an increase in the pathogenic species.

Deciphering the role of gut metabolites in non-alcoholic fatty liver disease

Perturbations in microbial abundance or diversity in the intestinal lumen leads to intestinal inflammation and disruption of intestinal membrane which eventually facilitates the translocation of microbial metabolites or whole microbes to the liver and other organs through portal vein. This process of translocation finally leads to multitude of health disorders. In this review, we are going to focus on the mechanisms by which gut metabolites like SCFAs, tryptophan (Trp) metabolites, bile acids (BAs), ethanol, and choline can either cause the development/progression of non-alcoholic fatty liver disease (NAFLD) or serves as a therapeutic treatment for the disease. Alterations in some metabolites like SCFAs, Trp metabolites, etc., can serve as biomarker molecules whereas presence of specific metabolites like ethanol definitely leads to disease progression. Thus, proper understanding of these mechanisms will subsequently help in designing of microbiome-based therapeutic approaches. Furthermore, we have also focussed on the role of dysbiosis on the mucosal immune system. In addition, we would also compile up the microbiome-based clinical trials which are currently undergoing for the treatment of NAFLD and non-alcoholic steatohepatitis (NASH). It has been observed that the use of microbiome-based approaches like prebiotics, probiotics, symbiotics, etc., can act as a beneficial treatment option but more research needs to be done to know how to manipulate the composition of gut microbes.

Role of immune responses for development of NAFLD-associated liver cancer and prospects for therapeutic modulation

The liver is the central metabolic organ of the body regulating energy and lipid metabolism and at the same time has potent immunological functions. Overwhelming the metabolic capacity of the liver by obesity and sedentary lifestyle leads to hepatic lipid accumulation, chronic necro-inflammation, enhanced mitochondrial/ER-stress and development of non-alcoholic fatty liver disease (NAFLD), with its pathologic form nonalcoholic steatohepatitis (NASH). Based on knowledge on pathophysiological mechanisms, specifically targeting metabolic diseases to prevent or slow down progression of NAFLD to liver cancer will become possible. Genetic/environmental factors contribute to development of NASH and liver cancer progression. The complex pathophysiology of NAFLD-NASH is reflected by environmental factors, particularly the gut microbiome and its metabolic products. NAFLD-associated HCC occurs in most of the cases in the context of a chronically inflamed liver and cirrhosis. Recognition of environmental alarmins or metabolites derived from the gut microbiota and the metabolically injured liver create a strong inflammatory milieu supported by innate and adaptive immunity. Several recent studies indicate that the chronic hepatic microenvironment of steatosis induces auto-aggressive CD8+CXCR6+PD1+ T cells secreting TNF and upregulating FasL to eliminate parenchymal and non-parenchymal cells in an antigen independent manner. This promotes chronic liver damage and a pro-tumorigenic environment. CD8+CXCR6+PD1+ T cells possess an exhausted, hyperactivated, resident phenotype and trigger NASH to HCC transition, and might be responsible for a less efficient treatment response to immune-check-point inhibitors - in particular atezolizumab/bevacizumab. Here, we provide an overview of NASH-related inflammation/pathogenesis focusing on new discoveries on the role of T cells in NASH-immunopathology and therapy response. This review discusses preventive measures to halt disease progression to liver cancer and therapeutic strategies to manage NASH-HCC patients.

Oral 24-week probiotics supplementation did not decrease cardiovascular risk markers in patients with biopsy proven NASH: A double-blind placebo-controlled randomized study

INTRODUCTION AND OBJECTIVES

Cardiovascular disease (CVD) is the major cause of death in non-alcoholic fatty liver disease (NAFLD), a clinical condition without any approved pharmacological therapy. Probiotics are often indicated for the disease, but their results are controversial in part due to the poor quality of studies. Thus, we investigated the impact of 24-week probiotics supplementation on cardiovascular risk (CVR) in biopsy-proven non-alcoholic steatohepatitis (NASH) patients.

PATIENTS AND METHODS

Double-blind, placebo-controlled, single-center study (NCT03467282), adult NASH, randomized for 24 weeks daily sachets of probiotic mix (10⁹CFU of Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus paracasei and Bifidobacterium lactis) or placebo. Clinical scores (atherogenic indexes, atherosclerotic cardiovascular disease-ASCVD and systematic coronary risk evaluation-SCORE), biochemistry, miR-122, miR-33a, plasminogen activator inhibitor-1 (PAI-1), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), were determined before and after the intervention.

RESULTS

Forty-six patients were enrolled (23 received probiotics and 23 placebo), with a mean age of 51.7 years, most of them females and whites. Clinical and demographic features were similar between the groups at the baseline. The Median NAFLD activity score was 4.13 in both groups. Fibrosis was mild in most patients (15.2% and 65.2% F0 and F1, respectively). Treatment did not promote any clinically significant changes in body mass index or laboratory, including lipid and glucose profile. High CVR patients through atherogenic indexes decreased from baseline in both groups, as well as PAI-1 and miR-122 levels, although there was no difference between probiotics and placebo.

CONCLUSIONS

A 24-week probiotic mix administration was not superior to placebo in reducing CVR markers in patients with NASH.

Targeting keystone species helps restore the dysbiosis of butyrate-producing bacteria in nonalcoholic fatty liver disease

The dysbiosis of the gut microbiome is one of the pathogenic factors of nonalcoholic fatty liver disease (NAFLD) and also affects the treatment and intervention of NAFLD. Among gut microbiomes, keystone species that regulate the integrity and stability of an ecological community have become the potential intervention targets for NAFLD. Here, we collected stool samples from 22 patients with nonalcoholic steatohepatitis (NASH), 25 obese patients, and 16 healthy individuals from New York for 16S rRNA gene sequencing. An algorithm was implemented to identify keystone species based on causal inference theories and dynamic intervention simulation. External validation was performed in an independent cohort from California. Eight keystone species in the gut of NAFLD, represented by Porphyromonas loveana, Alistipes indistinctus, and Dialister pneumosintes, were identified, which could efficiently restore the microbial composition of the NAFLD toward a normal gut microbiome with 92.3% recovery. These keystone species regulate intestinal amino acid metabolism and acid-base environment to promote the growth of the butyrate-producing Lachnospiraceae and Ruminococcaceae species that are significantly reduced in NAFLD patients. Our findings demonstrate the importance of keystone species in restoring the microbial composition toward a normal gut microbiome, suggesting a novel potential microbial treatment for NAFLD.

The intestinal microbiome associated with lipid metabolism and obesity in humans and animals

Intestinal microbiota is considered to play an integral role in maintaining health of host by modulating several physiological functions including nutrition, metabolism and immunity. Accumulated data from human and animal studies indicate that intestinal microbes can affect lipid metabolism in host through various direct and indirect biological mechanisms. These mechanisms include the production of various signalling molecules by the intestinal microbiome, which exert a strong effect on lipid metabolism, bile secretion in the liver, reverse transport of cholesterol and energy expenditure and insulin sensitivity in peripheral tissues. This review discusses the findings of recent studies suggesting an emerging role of intestinal microbiota and its metabolites in regulating lipid metabolism and the association of intestinal microbiota with obesity. Additionally, we discuss the controversies and challenges in this research area. However, intestinal micro-organisms are also affected by some external factors, which in turn influence the regulation of microbial lipid metabolism. Therefore, we also discuss the effects of probiotics, prebiotics, diet structure, exercise and other factors on intestinal microbiological changes and lipid metabolism regulation.

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.

Health Effects of Probiotics on Nonalcoholic Fatty Liver in the Life Cycle Based on Data Analysis

Objective

To observe the effect of intestinal probiotics in the treatment of nonalcoholic fatty liver disease (NAFLD) and the effect on liver function and inflammatory factors.

Methods

34 healthy rats were selected for the study and divided into 10 rats in the control group, 12 rats in the model group, and 12 rats in the treatment group according to the random number table method. The control group was given behavioral and lifestyle interventions, and the treatment group was given Bifidobacterium minus Black enteric capsules 5 g/(kg-d) by strong feeding method on the basis of the control group. The fatty liver index (FLI), liver ultrasound examination results, liver function, and inflammatory factor levels were compared among the three groups. After 8 weeks of treatment, there were statistically significant differences between the FLI values and liver ultrasound results of the three groups, and the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), triacylglycerol (TG), and total cholesterol (TC) levels of the observation group were lower than those of the control group and the model group. The levels of serum high molecular weight lipocalin (HMW-APN) and interleukin 22 (IL-22) in the observation group were higher than those in the control group, and the levels of tumor necrosis factor-α (TNF-α) were lower than those in the control and model groups, and the differences were statistically significant (P < 0.05).

Conclusion

Intestinal probiotics can improve the clinical efficacy of patients with NAFLD, improve liver function, and alleviate the inflammatory response, in order to provide a theoretical basis for the clinical treatment of patients with NAFLD.

A water soluble extract of radish greens ameliorates high fat diet-induced obesity in mice and inhibits adipogenesis in preadipocytes

Radish (Raphanus sativus L.) is a rich source of nutrients and its greens have reported functionalities. This study aimed to investigate the effects of a water-soluble extract from radish greens (WERG) on adipogenesis in 3T3-L1 adipocytes and high-fat diet-induced obesity in model mice. We also quantified the phytochemical composition of WERG such as glucoraphenin and ferulic acid. These findings show that treatment with 100 μg mL^-1 WERG reduced lipid accumulation in 3T3-L1 adipocytes, whereas in mice, the administration of 100 mg kg^-1 WERG reduced weight gain and hepatic lipid accumulation and improved the levels of serum lipid biomarkers. Furthermore, WERG treatment improved intestinal permeability and suppressed the activities of harmful intestinal enzymes in feces, thus improving gut health. It also inhibited metabolic endotoxemia and inflammatory marker levels in serum. Moreover, WERG reduced the expression of lipid-metabolism-related proteins in the liver and white adipose tissue. Collectively, these results indicate that WERG may potentiate the anti-obesity effect by improving gut health and regulating lipid metabolism.

Effect of Probiotics on Liver Enzymes in Patients With Non-alcoholic Fatty Liver Disease: An Umbrella of Systematic Review and Meta-Analysis

Non-alcoholic fatty liver disease (NAFLD) has become prevalent in recent decades, especially in developed countries; yet the approaches for preventing and treating NAFLD are not clear. This study aimed to summarize meta-analyses of randomized controlled trials that examined the effects of probiotics on NAFLD. We systematically searched PubMed, Scopus, Embase, Web of Science, and Cochrane Central Library databases up to August 2021. All Meta-analysis studies assessing the effect of probiotics on liver function tests [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and Gamma-glutamyl transferase (GGT)] were included. Meta-analysis was conducted using a random-effects model. Sensitivity and subgroup analyses were also performed. The umbrella study covered ten eligible studies involving 5,162 individuals. Beneficial effects of probiotics supplementation were revealed on ALT (ES = −10.54 IU/L; 95% CI: −12.70, −8.39; p < 0.001; I² = 60.9%, p = 0.006), AST (ES = −10.19 IU/L, 95%CI: −13.08, −7.29, p < 0.001; I² = 79.8%, p < 0.001), and GGT (ES = −5.88 IU/L, 95% CI: −7.09, −4.67, p = 0.009; I² = 0.0%, p = 0.591) levels. Probiotics have ameliorating effects on ALT, AST, and GGT levels in patients with NAFLD. Overall, Probiotics could be recommended as an adjuvant therapeutic method for the management of NAFLD.

Targeting Gut Microbiota With Natural Polysaccharides: Effective Interventions Against High-Fat Diet-Induced Metabolic Diseases

Unhealthy diet, in particular high-fat diet (HFD) intake, can cause the development of several metabolic disorders, including obesity, hyperlipidemia, type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), and metabolic syndrome (MetS). These popular metabolic diseases reduce the quality of life, and induce premature death worldwide. Evidence is accumulating that the gut microbiota is inextricably associated with HFD-induced metabolic disorders, and dietary intervention of gut microbiota is an effective therapeutic strategy for these metabolic dysfunctions. Polysaccharides are polymeric carbohydrate macromolecules and sources of fermentable dietary fiber that exhibit biological activities in the prevention and treatment of HFD-induced metabolic diseases. Of note, natural polysaccharides are among the most potent modulators of the gut microbiota composition. However, the prebiotics-like effects of polysaccharides in treating HFD-induced metabolic diseases remain elusive. In this review, we introduce the critical role of gut microbiota human health and HFD-induced metabolic disorders. Importantly, we review current knowledge about the role of natural polysaccharides in improving HFD-induced metabolic diseases by regulating gut microbiota.

Human microbiome and metabolic health: An overview of systematic reviews

To summarize the microbiome's role in metabolic disorders (insulin resistance, hyperglycemia, type 2 diabetes, obesity, hyperlipidemia, hypertension, nonalcoholic fatty liver disease [NAFLD], and metabolic syndrome), systematic reviews on observational or interventional studies (prebiotics/probiotics/synbiotics/transplant) were searched in MEDLINE and Embase until September 2020. The 87 selected systematic reviews included 57 meta-analyses. Methodological quality (AMSTAR2) was moderate in 62%, 12% low, and 26% critically low. Observational studies on obesity (10 reviews) reported less gut bacterial diversity with higher Fusobacterium, Lactobacillus reuteri, Bacteroides fragilis, and Staphylococcus aureus, whereas lower Methanobrevibacter, Lactobacillus plantarum, Akkermansia muciniphila, and Bifidobacterium animalis compared with nonobese. For diabetes (n = 1), the same was found for Fusobacterium and A. muciniphila, whereas higher Ruminococcus and lower Faecalibacterium, Roseburia, Bacteroides vulgatus, and several Bifidobacterium spp. For NAFLD (n = 2), lower Firmicutes, Rikenellaceae, Ruminococcaceae, whereas higher Escherichia and Lactobacillus were detected. Discriminating bacteria overlapped between metabolic disorders, those with high abundance being often involved in inflammation, whereas those with low abundance being used as probiotics. Meta-analyses (n = 54) on interventional studies reported 522 associations: 54% was statistically significant with intermediate effect size and moderate between-study heterogeneity. Meta-evidence was highest for probiotics and lowest for fecal transplant. Future avenues include better methodological quality/comparability, testing functional differences, new intervention strategies, and considerating other body habitats and kingdoms.

NASH and the Gut Microbiome: Implications for New Therapies

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Probiotic and prebiotic interventions for non-alcoholic fatty liver disease: a systematic review and network meta-analysis

Many studies have associated altered intestinal bacterial communities and non-alcoholic fatty liver disease, but the putative effects are inconclusive. The purpose of this network meta-analysis (NMA) was to evaluate the effects of probiotics, prebiotics, and synbiotics on non-alcoholic fatty liver disease through randomised intervention trials. Literature searches were performed until March 2020. For each outcome, a random NMA was performed, the surface under the cumulative ranking curve (SUCRA) was determined. A total of 22 randomised trials comparing prebiotic, probiotic, and synbiotic treatments included 1301 participants. Considering all seven results (aspartate aminotransferase, alanine aminotransferase, body mass index, weight, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol) together, the highest SUCRA values are probiotics (94%), synbiotics (61%) and prebiotics (56%), respectively. NMA results provide evidence that probiotics, prebiotics, and synbiotics can alleviate non-alcoholic fatty liver disease. However, due to the lack of high-quality randomised trials, this research also has some limitations.

Multi-Pharmacology of Berberine in Atherosclerosis and Metabolic Diseases: Potential Contribution of Gut Microbiota

Atherosclerosis (AS), especially atherosclerotic cardiovascular diseases (ASCVDs), and metabolic diseases (such as diabetes, obesity, dyslipidemia, and nonalcoholic fatty liver disease) are major public health issues worldwide that seriously threaten human health. Exploring effective natural product-based drugs is a promising strategy for the treatment of AS and metabolic diseases. Berberine (BBR), an important isoquinoline alkaloid found in various medicinal plants, has been shown to have multiple pharmacological effects and therapeutic applications. In view of its low bioavailability, increasing evidence indicates that the gut microbiota may serve as a target for the multifunctional effects of BBR. Under the pathological conditions of AS and metabolic diseases, BBR improves intestinal barrier function and reduces inflammation induced by gut microbiota-derived lipopolysaccharide (LPS). Moreover, BBR reverses or induces structural and compositional alterations in the gut microbiota and regulates gut microbe-dependent metabolites as well as related downstream pathways; this improves glucose and lipid metabolism and energy homeostasis. These findings at least partly explain the effect of BBR on AS and metabolic diseases. In this review, we elaborate on the research progress of BBR and its mechanisms of action in the treatment of AS and metabolic diseases from the perspective of gut microbiota, to reveal the potential contribution of gut microbiota to the multifunctional biological effects of BBR.

Beyond the Paradigm of Weight Loss in Non-Alcoholic Fatty Liver Disease: From Pathophysiology to Novel Dietary Approaches

Current treatment recommendations for non-alcoholic fatty liver disease (NAFLD) rely heavily on lifestyle interventions. The Mediterranean diet and physical activity, aiming at weight loss, have shown good results in achieving an improvement of this liver disease. However, concerns related to compliance and food accessibility limit the feasibility of this approach, and data on the long-term effects on liver-related outcomes are lacking. Insulin resistance is a central aspect in the pathophysiology of NAFLD; therefore, interventions aiming at the improvement of insulin sensitivity may be preferable. In this literature review, we provide a comprehensive summary of the available evidence on nutritional approaches in the management of NAFLD, involving low-calorie diets, isocaloric diets, and the novel schemes of intermittent fasting. In addition, we explore the harmful role of single nutrients on liver-specific key metabolic pathways, the role of gene susceptibility and microbiota, and behavioral aspects that may impact liver disease and are often underreported in clinical setting. At present, the high variability in terms of study populations and liver-specific outcomes within nutritional studies limits the generalizability of the results and highlights the urgent need of a tailored and standardized approach, as seen in regulatory trials in Non-Alcoholic Steatohepatitis (NASH).

Probiotics and Amelioration of Rheumatoid Arthritis: Significant Roles of Lactobacillus casei and Lactobacillus acidophilus

Rheumatoid arthritis is a chronic autoimmune disorder that can lead to disability conditions with swollen joints, pain, stiffness, cartilage degradation, and osteoporosis. Genetic, epigenetic, sex-specific factors, smoking, air pollution, food, oral hygiene, periodontitis, Prevotella, and imbalance in the gastrointestinal microbiota are possible sources of the initiation or progression of rheumatoid arthritis, although the detailed mechanisms still need to be elucidated. Probiotics containing Lactobacillus spp. are commonly used as alleviating agents or food supplements to manage diarrhea, dysentery, develop immunity, and maintain general health. The mechanism of action of Lactobacillus spp. against rheumatoid arthritis is still not clearly known to date. In this narrative review, we recapitulate the findings of recent studies to understand the overall pathogenesis of rheumatoid arthritis and the roles of probiotics, particularly L. casei or L. acidophilus, in the management of rheumatoid arthritis in clinical and preclinical studies.

Effects of pine pollen wall on gut microbiota and biomarkers in mice with dyslipidemia

Pinus yunnanensis pollen is rich in various physiological functions. However, whether the pine pollen wall (PW) plays a beneficial role in the body has not been studied. In this work, we have analyzed its effects on the metabolism and gut microbiota of mouse models of dyslipidemia. We found that the intake of pine PW prevents the liver pathologic changes and reduce the concentrations of TNF-α, IL-6, TC, and high-density lipoprotein cholesterol. Moreover, it can regulate bile acid and fat metabolism, SCFAs content, and the structure of the gut microbiota. According to the change of carbohydrate metabolites, we speculated that cellulose should be the main component to play the above beneficial role, and sporopollenin cannot be utilized in the intestine. Therefore, we consider this study of great significance as it gives a description of biological effects of the pine PW and paves the road to its use in health products.

Human Intestinal Barrier: Effects of Stressors, Diet, Prebiotics, and Probiotics

The objectives of this article are to understand the effects of stressors (nonsteroidal antiinflammatory drug, exercise, and pregnancy) and components in the diet, specifically prebiotics and probiotics, on intestinal barrier function. Stressors generally reduce barrier function, and these effects can be reversed by supplements such as zinc or glutamine that are among the substances that enhance the barrier. Other dietary factors in the diet that improve the barrier are vitamins A and D, tryptophan, cysteine, and fiber; by contrast, ethanol, fructose, and dietary emulsifiers increase permeability. Effects of prebiotics on barrier function are modest; on the other hand, probiotics exert direct and indirect antagonism of pathogens, and there are documented effects of diverse probiotic species, especially combination agents, on barrier function in vitro, in vivo in animal studies, and in human randomized controlled trials conducted in response to stress or disease. Clinical observations of benefits with combination probiotics in inflammatory diseases have simultaneously not appraised effects on intestinal permeability. In summary, probiotics and synbiotics enhance intestinal barrier function in response to stressor or disease states. Future studies should address the changes in barrier function and microbiota concomitant with assessment of clinical outcomes.

The Relationship between Prebiotic Supplementation and Anthropometric and Biochemical Parameters in Patients with NAFLD-A Systematic Review and Meta-Analysis of Randomized Controlled Trials

We aim to systematically review the efficacy of prebiotics in reducing anthropometric and biochemical parameters in individuals with non-alcoholic fatty liver disease (NAFLD). A systematic search using PubMed/MEDLINE, Embase, clinicaltrials.gov, Cinahl, and Web of Science of articles published up to 20 March 2020 was performed for randomized controlled trials enrolling >20 adult patients. Random-effect meta-analysis for metabolic outcomes in NAFLD patients was performed for anthropometric data in addition to liver enzyme, carbohydrate, and lipid parameters. We found six trials (comprising a total of 242 patients) with NAFLD, with subjects aged 38-52 years. The mean time of fiber administration varied between 10 and 12 weeks. The main fiber types were psyllium (seeds or powder), Ocimum basilicum (seeds), and high-performance inulin and oligofructose powder at doses of either 10 or 16 g per day. The control group received either maltodextrin (powder or capsules) or crushed wheat (powder). Patients on the diet with added fiber had improvements in body mass index (BMI) (standardized mean difference (SMD) = -0.494, 95% confidence interval (CI): -0.864 to -0.125, p = 0.009); alanine aminotransferase (ALT) (SMD = -0.667, 95% CI: -1.046 to -0.288, p = 0.001); aspartate aminotransferase (AST) (SMD = -0.466, 95% CI: -0.840 to -0.091, p = 0.015); fasting insulin (SMD = -0.705, 95% CI: -1.115 to -0.295, p = 0.001); and homeostasis model assessment for insulin resistance (HOMA-IR) (SMD = -0.619, 95% CI: -1.026 to -0.211, p = 0.003). Hence, the results show that fiber supplements result in favorable changes as reflected in the measurement of anthropometric, metabolic, and liver-related biomarkers, i.e., body mass index (BMI), homeostasis model assessment for insulin resistance (HOMA-IR), insulin, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). These effects suggest the potential benefits of fiber consumption for NAFLD populations. More prospective, controlled studies should be conducted to reveal specific details regarding the fiber type, dosage, and duration for optimal intervention.

Metabolic liver disease in diabetes - From mechanisms to clinical trials

Non-alcoholic fatty liver disease (NAFLD) comprises fatty liver (steatosis), non-alcoholic steatohepatitis (NASH) and fibrosis/cirrhosis and may lead to end-stage liver failure or hepatocellular carcinoma. NAFLD is tightly associated with the most frequent metabolic disorders, such as obesity, metabolic syndrome, and type 2 diabetes mellitus (T2DM). Both multisystem diseases share several common mechanisms. Alterations of tissue communications include excessive lipid and later cytokine release by dysfunctional adipose tissue, intestinal dysbiosis and ectopic fat deposition in skeletal muscle. On the hepatocellular level, this leads to insulin resistance due to abnormal lipid handling and mitochondrial function. Over time, cellular oxidative stress and activation of inflammatory pathways, again supported by multiorgan crosstalk, determine NAFLD progression. Recent studies show that particularly the severe insulin resistant diabetes (SIRD) subgroup (cluster) associates with NAFLD and its accelerated progression and increases the risk of diabetes-related cardiovascular and kidney diseases, underpinning the critical role of insulin resistance. Consequently, lifestyle modification and certain drug classes used to treat T2DM have demonstrated effectiveness for treating NAFLD, but also some novel therapeutic concepts may be beneficial for both NAFLD and T2DM. This review addresses the bidirectional relationship between mechanisms underlying T2DM and NAFLD, the relevance of novel biomarkers for improving the diagnostic modalities and the identification of subgroups at specific risk of disease progression. Also, the role of metabolism-related drugs in NAFLD is discussed in light of the recent clinical trials. Finally, this review highlights some challenges to be addressed by future studies on NAFLD in the context of T2DM.

Anti-obesity effects of capsaicin and the underlying mechanisms: a review

Obesity and overweight have become serious health problems in the world and are linked to a variety of metabolic disorders. Phytochemicals with a weight-loss effect have been widely studied for the past few decades. Capsaicin is the major bioactive component in red chili peppers with many beneficial functions. Its anti-obesity effects have been evaluated extensively using different model systems, including cell models, animal models and human subjects. In this paper, anti-obesity effects of capsaicin are reviewed and the underlying mechanisms are characterized.

Liraglutide modulates gut microbiome and attenuates nonalcoholic fatty liver in db/db mice

AIMS

Liraglutide, a glucagon-like peptide-1(GLP-1) analog, is effective for the treatment of type II diabetes and nonalcoholic fatty liver disease (NAFLD). It was proved that gut microbiome plays a role in the development of NAFLD. This study aims to observe the therapeutic effect of liraglutide on nonalcoholic fatty liver (NAFL) in mice and effect on the gut microbial community.

MAIN METHODS

The db/db mice were used as the NAFL model, and lactulose was used as the positive control drug. Hepatic triglyceride, liver histopathology, and indices of glucolipid metabolism, including fasting blood glucose, fasting insulin, insulin resistance index and blood lipids were evaluated after treatment of liraglutide or lactulose for four weeks. The colonic microbiome of the mice was analyzed by 16S rRNA gene sequencing.

KEY FINDINGS

Liraglutide significantly reduced the hepatic triglyceride (TG) content, alanine aminotransferase (ALT) activity, fasting blood glucose, insulin resistance and serum low density lipoprotein (LDL) in the db/db mice. In terms of hepatic pathologies, hepatic steatosis was significantly improved after liraglutide treating. Microbiome analysis revealed that liraglutide significantly increased the abundance of Akkermansia, Romboutsia, norank_f_Bacteroidales_S24-7_group, and decreased the abundance of Klebsiella, Anaerotruncus, Bacteroides, Lachnospiraceae_UCG-001, Lachnospiraceae_NK4A136_group, Ruminiclostridium, uncultured_f__Ruminococcaceae, and Desulfovibrio.

SIGNIFICANCE

The results of the present study suggested that liraglutide had a certain therapeutic effect on fatty liver in db/db mice and had an impact on the composition of the intestinal microflora, especially some bacteria related to glucolipid metabolism and intestinal inflammation. Affecting gut microbiome might be a potential mechanism of liraglutide in treating NAFL.

Effects of probiotic and prebiotic supplementation on metabolic parameters, liver aminotransferases, and systemic inflammation in nonalcoholic fatty liver disease: A randomized clinical trial

This study aimed to evaluate the clinical efficacy of probiotic and prebiotic supplementation on the metabolic parameters, liver enzymes, and inflammation in patients with nonalcoholic fatty liver disease (NAFLD). In this study, patients with NAFLD were assigned to receive either probiotic capsule + placebo of prebiotic (probiotic group), oligofructose + placebo of probiotic (prebiotic group), or placebo of probiotic + placebo of prebiotic (control group) for 12 weeks. All participants followed a weight loss diet and physical activity recommendation during intervention. Anthropometric measurements decreased in all three groups, but there was no significant difference among groups. Probiotic supplementation was able to decrease triglyceride, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), and alkaline phosphatase compared to control group. The serum levels of triglyceride, total and low-density lipoprotein cholesterol, ALT, AST, and GGT differed significantly in prebiotic group in comparison to the placebo. High-sensitive C-reactive protein significantly decreased within all groups; however, there was no significant difference among groups after intervention. Probiotic and prebiotic may be beneficial in improving liver enzymes and lipid profile in patients with NAFLD.

Immune boosting functional foods and their mechanisms: A critical evaluation of probiotics and prebiotics

Comprehensive studies conducted on the link between the gut microbiome and immunity in recent decades have correspondingly led to ever increasing interests in functional foods, especially probiotics and prebiotics. Probiotics and prebiotics play crucial roles in managing the intestinal microbiota in order to improve host health, even though their influence on other body sites are being investigated. Different colonic bacteria metabolize dietary prebiotics to produce beneficial metabolites, especially short chain fatty acids (SCFAs) that improve luminal contents and intestinal performance, while positively affecting overall host physiology. Thus, this review provides a general perspective of the immune system, the gut immune system and its microbiota. The review also evaluates functional foods with critical but comprehensive perspectives into probiotics and prebiotics, their immune boosting and mechanisms of action. It is recommended that further mechanistic and translational studies are conducted to promote health, social life and also empower poverty-stricken communities.

Microbiota and nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH)

Genetic predisposition, the intestinal microbiota (IM) and environmental factors, such as sedentary lifestyle and inadequate diet, should be considered as critical factors for the development of nonalcoholic fatty liver disease (NAFLD). Recently, some studies have demonstrated an association between dysbiosis and NAFLD; however, the exact mechanisms that lead to intestinal membrane damage, bacterial translocation and inflammation are not well elucidated. Due to the relevance of this theme, the IM and its metabolites have received special attention in recent years in an attempt to better understand the mechanisms related to the prevention, physiopathology, and treatment of NAFLD. In this paper, we provide a review of the human IM and its role in diet, obesity, and the development/progression of NAFLD/NASH, as well as the use of prebiotics and probiotics in the modulation of IM.

Vital members in the gut microbiotas altered by two probiotic Bifidobacterium strains against liver damage in rats

Background

Probiotics are effective to rectify the imbalanced gut microbiota in the diseased cohorts. Two Bifidobacterium strains (LI09 and LI10) were found to alleviate D-galactosamine-induced liver damage (LD) in rats in our previous work. A series of bioinformatic and statistical analyses were performed to determine the vital bacteria in the gut microbiotas altered by the LI09 or LI10 in rats.

Results

Two groups of representative phylotypes could distinguish the gut microbiotas of LI09 or LI10 groups from the other groups. Among them, OTU170_Porphyromonadaceae acted as a gatekeeper in LI09 group, while OTU12_Bacteroides was determined with multiple correlations in the gut network of LI10 group. Multiple reduced OTUs associated with LC and increased OTUs associated with health were determined in LI09 or LI10 groups, among which, increased OTU51_Barnesiella and reduced OTU99_Barnesiella could be associated with the protective effects of both the two probiotics. The gut microbiotas in LI09, LI10 and positive control groups were clustered into three clusters, i.e., Cluster_1_Microbiota, Cluster_2_Microbiota and Cluster_3_Microbiota, by Partition Around Medoids clustering analysis. Cluster_2_Microbiota was determined at least dysbiotic status due to its greatest LD dysbiosis ratio, lowest levels of liver function variables and plasma cytokines compared with the two other clustered microbiotas, suggesting the treated rats in Cluster_2 were at better health status.

Conclusion

Our findings suggest that OTU170_Porphyromonadaceae and OTU12_Bacteroides are vital in the gut microbiotas altered by LI09 and LI10. Characteristics of the LD cohorts treated by LI09 or LI10 at different gut microbial colonization states could help monitor the cohorts’ health status.

[Gut microbiota-an important contributor to liver diseases]

Gut microbiota constitute a complicated but manifold ecosystem, in which specific symbiotic relationships are formed among various bacteria. To maintain a steady state, the gastrointestinal tract and the liver form a close anatomical and functional two-way, interconnected network through the portal circulation. "Gut-liver axis" plays a key role in the pathogenesis of liver diseases. Accumulating evidence indicates that gut microbiota can influence the liver pathophysiology directly or indirectly via a variety of signal pathways. In a pathological state where an ecological imbalance occurs at the compositional and functional levels, gut microbes would interact with the host immune system and other type of cells to cause liver steatosis, inflammation and fibrosis, which in turn give rise to the development of such liver diseases as alcoholic liver disease, nonalcoholic fatty liver disease, primary sclerosing cholangitis, and acute liver failure, to name a few. Studies have shown that microorganisms, such as prebiotics and probiotics, can improve the prognosis of certain diseases, which open a new era of treating liver diseases with bacteria. There are many unknowns and hidden values in the gut microbiome. To explore the pathophysiological mechanism of various complex diseases and develop scientific and effective clinical treatment strategies, efforts should be made to obtain insights into how certain intestinal microbiota participates in the occurrence and progression of liver diseases. As the connection between gut microbiota and liver diseases at both the acute and chronic phases was not elaborated in previously published review articles, herein we discuss the association between gut microbiota and both acute and chronic liver injury. The anatomical structure of the liver enables it to form a close network with the gut microbiota, which is an important mediator in the regulation of the hepatic physiological and pathological functions.

Supplementation of Inulin with Various Degree of Polymerization Ameliorates Liver Injury and Gut Microbiota Dysbiosis in High Fat-Fed Obese Mice

The chain length of fructan determines its different physiological effects. This study is to explore the effects of low-performance inulin [LPI, degree of polymerization (DP) ≤ 9] and high-performance inulin (HPI, DP ≥ 23) on obesity-associated liver injury of high-fat diet (HFD) feeding mice and its underlying mechanism. Eight weeks of supplementation of C57BL/6J mice with HPI, relative to LPI (p < 0.05), caused the more efficient improvement against the HFD-induced liver insulin resistance through activating IRS1/PI3K/Akt pathway and reduced protein expressions of inflammatory factors nuclear factor-kappaB (NF-κB) and interleukin-6 (IL-6) in the liver. HPI exhibited the more positive effects on liver steatosis by inhibiting acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and sterol regulatory element binding protein 1 (SREBP1) in comparison with LPI (p < 0.05). HPI also increased acetic acid, propionic acid, and butyric acid levels in the colon of HFD-fed mice (p < 0.05). Compared to LPI, HPI feeding of HFD-fed mice led to the more effective decrease in the Firmicutes abundance from 72.1% to 34.5%, but a more significant increase in the Bacteroidetes population from 19.8 to 57.1% at the phyla level, and increased the abundance of Barnesiella, Bacteroides, and Parabacteroides at the genus level (p < 0.05). Depending on DP, HPI exerts the more positive regulation on liver injury and gut microbiota dysfunction than LPI.

Intestinal microbiome and NAFLD: molecular insights and therapeutic perspectives

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of dysregulated lipid and glucose metabolism, which is often associated with obesity, dyslipidemia and insulin resistance. In view of the high morbidity and health risks of NAFLD, the lack of effective cure has drawn great attention. In recent years, a line of evidence has suggested a close linkage between the intestine and liver diseases such as NAFLD. We summarized the composition and characteristics of intestinal microbes and reviewed molecular insights into the intestinal microbiome in development and progression of NAFLD. Intestinal microbes mainly include bacteria, archaea, viruses and fungi, and the crosstalk between non-bacterial intestinal microbes and human liver diseases should be paid more attention. Intestinal microbiota imbalance may not only increase the intestinal permeability to gut microbes but also lead to liver exposure to harmful substances that promote hepatic lipogenesis and fibrosis. Furthermore, we focused on reviewing the latest "gut-liver axis"-targeting treatment, including the application of antibiotics, probiotics, prebiotics, synbiotics, farnesoid X receptor agonists, bile acid sequestrants, gut-derived hormones, adsorbents and fecal microbiota transplantation for NAFLD. In this review, we also discussed the potential mechanisms of "gut-liver axis" manipulation and efficacy of these therapeutic strategies for NAFLD treatment.