Diet and Gut Microbiota Interaction-Derived Metabolites and Intrahepatic Immune Response in NAFLD Development and Treatment

Role of Gut Microbial Metabolites in the Pathogenesis of Primary Liver Cancers

Hepatobiliary malignancies, which include hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), are the sixth most common cancers and the third leading cause of cancer-related death worldwide. Hepatic carcinogenesis is highly stimulated by chronic inflammation, defined as fibrosis deposition, and an aberrant imbalance between liver necrosis and nodular regeneration. In this context, the gut-liver axis and gut microbiota have demonstrated a critical role in the pathogenesis of HCC, as dysbiosis and altered intestinal permeability promote bacterial translocation, leading to chronic liver inflammation and tumorigenesis through several pathways. A few data exist on the role of the gut microbiota or bacteria resident in the biliary tract in the pathogenesis of CCA, and some microbial metabolites, such as choline and bile acids, seem to show an association. In this review, we analyze the impact of the gut microbiota and its metabolites on HCC and CCA development and the role of gut dysbiosis as a biomarker of hepatobiliary cancer risk and of response during anti-tumor therapy. We also discuss the future application of gut microbiota in hepatobiliary cancer management.

Gut microbiota and metabolite interface-mediated hepatic inflammation

Immunologic and metabolic signals regulated by gut microbiota and relevant metabolites mediate bidirectional interaction between the gut and liver. Gut microbiota dysbiosis, due to diet, lifestyle, bile acids, and genetic and environmental factors, can advance the progression of chronic liver disease. Commensal gut bacteria have both pro- and anti-inflammatory effects depending on their species and relative abundance in the intestine. Components and metabolites derived from gut microbiota-diet interaction can regulate hepatic innate and adaptive immune cells, as well as liver parenchymal cells, significantly impacting liver inflammation. In this mini review, recent findings of specific bacterial species and metabolites with functions in regulating liver inflammation are first reviewed. In addition, socioeconomic and environmental factors, hormones, and genetics that shape the profile of gut microbiota and microbial metabolites and components with the function of priming or dampening liver inflammation are discussed. Finally, current clinical trials evaluating the factors that manipulate gut microbiota to treat liver inflammation and chronic liver disease are reviewed. Overall, the discussion of microbial and metabolic mediators contributing to liver inflammation will help direct our future studies on liver disease.

Prevalence of nonalcoholic fatty liver disease and the related risk factors among healthy adults: A cross-sectional study in Chongqing, China

Background

Epidemiological characteristics of nonalcoholic fatty liver disease (NAFLD) in Chongqing, a west-central city of China, remain unclear. The objective of this study was to investigate the prevalence of NAFLD and the related risk factors among healthy adults for physical examination in Chongqing.

Methods

A total of 110,626 subjects were enrolled in the present study. Each of the participants underwent physical examination, laboratory measurements, and abdominal ultrasonography. The chi-square test was employed to compare differences in the NAFLD prevalence, and logistic regression analysis was used to estimate the odds ratio for risk factors of NAFLD.

Results

The prevalence of NAFLD in individuals in the population of Chongqing was 28.5%, and the prevalence in men (38.1%) was significantly higher than that in women (13.6%) (OR = 2.44; 95% CI: 2.31-2.58). NAFLD was more common in men aged 51-60 years and women over 60 years. Approximately 79.1% of the people with obesity and 52.1% of the people with central obesity had NAFLD. The prevalence of NAFLD in people with hypertension and cholelithiasis was 48.9 and 38.4%, respectively. Logistic regression showed that gender, age, body max index (BMI), central obesity, hypertension, impaired fasting glucose/diabetes mellitus (DM), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), hyperuricemia (HUA), alanine transaminase (ALT), and cholelithiasis were independently associated with the presence of NAFLD.

Conclusion

The prevalence of NAFLD among healthy adults in Chongqing was high. To improve the prevention and management of NAFLD, special attention should be paid to the factors associated with the presence of NAFLD, including higher BMI, higher waist circumference, higher blood glucose, hypertension, hypertriglyceridemia, hyperuricemia, cholelithiasis, and elevated ALT.

Precision Nutrition in NAFLD: Effects of a High-Fiber Intervention on the Serum Metabolome of NAFD Patients-A Pilot Study

Non-alcoholic fatty liver disease (NAFLD) is associated with dysfunction of the intestinal microbiota and its metabolites. We aimed to assess whether replacing bread with high-fiber buns beneficially changes the metabolome in NAFLD patients. This study involved 27 adult patients with NAFLD validated by FibroScan^® (CAP ≥ 234 dB/m). Patients were asked to replace their existing bread for two meals with high-fiber buns. In this way, the patients ate two rolls every day for 2 months. The following parameters were analysed (at the beginning and after 2 months): the anthropometric data (BIA), eating habits (24 h food recalls), gut barrier markers (lipopolysaccharide S and liposaccharide binding protein (LPS, LBP)), serum short-chain fatty acids (SCFAs) and branched chain fatty acids (BCFAs) by GC/MS chromatography, as well as serum metabolites (by ¹H NMR spectroscopy). After 2 months of high-fiber roll consumption, the reduction of liver steatosis was observed (change Fibroscan CAP values from 309-277 dB/m). In serum propionate, acetate, isovaleric, and 2-methylbutyric decrease was observed. Proline, choline and one unknown molecule had higher relative concentration in serum at endpoint. A fiber-targeted dietary approach may be helpful in the treatment of patients with NAFLD, by changing the serum microbiota metabolome.

The Species of Gut Bacteria Associated with Antitumor Immunity in Cancer Therapy

Both preclinical and clinical studies have demonstrated that the modulation of gut microbiota could be a promising strategy for enhancing antitumor immune responses and reducing resistance to immunotherapy in cancer. Various mechanisms, including activation of pattern recognition receptors, gut commensals-produced metabolites and antigen mimicry, have been revealed. Different gut microbiota modulation strategies have been raised, such as fecal microbiota transplantation, probiotics, and dietary selection. However, the identification of gut bacteria species that are either favorable or unfavorable for cancer therapy remains a major challenge. Herein, we summarized the findings related to gut microbiota species observed in the modulation of antitumor immunity. We also discussed the different mechanisms underlying different gut bacteria's functions and the potential applications of these bacteria to cancer immunotherapy in the future.

Communication in non-communicable diseases (NCDs) and role of immunomodulatory nutraceuticals in their management

Conveyance of pathogens between organisms causes communicable diseases. On the other hand, a non-communicable disease (NCD) was always thought to have no causative transmissible infective agents. Today, this clear distinction is increasingly getting blurred and NCDs are found to be associated with some transmissible components. The human microbiota carries a congregation of microbes, the majority and the most widely studied being bacteria in the gut. The adult human gut harbors ginormous inhabitant microbes, and the microbiome accommodates 150-fold more genes than the host genome. Microbial communities share a mutually beneficial relationship with the host, especially with respect to host physiology including digestion, immune responses, and metabolism. This review delineates the connection between environmental factors such as infections leading to gut dysbiosis and NCDs and explores the evidence regarding possible causal link between them. We also discuss the evidence regarding the value of appropriate therapeutic immunomodulatory nutritional interventions to reduce the development of such diseases. We behold such immunomodulatory effects have the potential to influence in various NCDs and restore homeostasis. We believe that the beginning of the era of microbiota-oriented personalized treatment modalities is not far away.

Identification of the Non-Alcoholic Fatty Liver Disease Molecular Subtypes Associated With Clinical and Immunological Features via Bioinformatics Methods

Background

Non-alcoholic fatty liver disease (NAFLD) is a manifestation of metabolic syndrome in the liver with varying severity. Heterogeneity in terms of molecules and immune cell infiltration drives NAFLD from one stage to the next. However, a precise molecular classification of NAFLD is still lacking, and the effects of complex clinical phenotypes on the efficacy of drugs are usually ignored.

Methods

We introduced multiple omics data to differentiate NAFLD subtypes via consensus clustering, and a weighted gene co-expression network analysis was used to identify eight co-expression modules. Further, eigengenes of eight modules were analyzed with regard to Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathways. Furthermore, the infiltration rates of 22 immune cell types were calculated with CIBERSORT and the ESTIMATE algorithm.

Results

In total, 111 NAFLD patients from three independent GEO datasets were divided into four molecular subtypes, and the corresponding clinical features and immune cell infiltration traits were determined. Based on high gene expression correlations, four molecular subtypes were further divided into eight co-expression modules. We also demonstrated a significant correlation between gene modules and clinical phenotypes. Moreover, we integrated phenotypic, immunologic, and genetic data to assess the potential for progression of different molecular subtypes. Furthermore, the efficacy of drugs against various NAFLD molecular subtypes was discussed to aid in individualized therapy.

Conclusion

Overall, this study could provide new insights into the underlying pathogenesis of and drug targets for NAFLD.

The Microbiota and It’s Correlation With Metabolites in the Gut of Mice With Nonalcoholic Fatty Liver Disease

In recent years, nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease in the world. As an important model animal, the characteristics of gut microbiota alteration in mice with NAFLD have been studied but the changes in metabolite abundance in NAFLD mice and how the gut microbiota affects these intestinal metabolites remain unclear. In this experiment, a mouse model for NAFLD was established by a high-fat diet. The use of 16S rDNA technology showed that while there were no significant changes in the alpha diversity in the cecum of NAFLD mice, the beta diversity changed significantly. The abundance of Blautia, Unidentified-Lachnospiraceae, Romboutsia, Faecalibaculum, and Ileibacterium increased significantly in NAFLD mice, while Allobaculum and Enterorhabdus decreased significantly. Amino acids, lipids, bile acids and nucleotide metabolites were among the 167 significantly different metabolites selected. The metabolic pathways of amino acids, SFAs, and bile acids were significantly enhanced, while the metabolic pathways of PUFAs, vitamins, and nucleotides were significantly inhibited. Through correlation and MIMOSA2 analysis, it is suggested that gut microbiota does not affect the changes of lipids and bile acids but can reduce thiamine, pyridoxine, and promote L-phenylalanine and tyramine production. The findings of this study will help us to better understand the relationship between gut microbiota and metabolites in NAFLD.

Overview of the Importance of Biotics in Gut Barrier Integrity

Increased gut permeability is suggested to be involved in the pathogenesis of a growing number of disorders. The altered intestinal barrier and the subsequent translocation of bacteria or bacterial products into the internal milieu of the human body induce the inflammatory state. Gut microbiota maintains intestinal epithelium integrity. Since dysbiosis contributes to increased gut permeability, the interventions that change the gut microbiota and correct dysbiosis are suggested to also restore intestinal barrier function. In this review, the current knowledge on the role of biotics (probiotics, prebiotics, synbiotics and postbiotics) in maintaining the intestinal barrier function is summarized. The potential outcome of the results from in vitro and animal studies is presented, and the need for further well-designed randomized clinical trials is highlighted. Moreover, we indicate the need to understand the mechanisms by which biotics regulate the function of the intestinal barrier. This review is concluded with the future direction and requirement of studies involving biotics and gut barrier.