Role of the Gut Microbiome in Nonalcoholic Fatty Liver Disease

The nerve cells in gastrointestinal cancers: from molecular mechanisms to clinical intervention

Gastrointestinal (GI) cancer is a formidable malignancy with significant morbidity and mortality rates. Recent studies have shed light on the complex interplay between the nervous system and the GI system, influencing various aspects of GI tumorigenesis, such as the malignance of cancer cells, the conformation of tumor microenvironment (TME), and the resistance to chemotherapies. The discussion in this review first focused on exploring the intricate details of the biological function of the nervous system in the development of the GI tract and the progression of tumors within it. Meanwhile, the cancer cell-originated feedback regulation on the nervous system is revealed to play a crucial role in the growth and development of nerve cells within tumor tissues. This interaction is vital for understanding the complex relationship between the nervous system and GI oncogenesis. Additionally, the study identified various components within the TME that possess a significant influence on the occurrence and progression of GI cancer, including microbiota, immune cells, and fibroblasts. Moreover, we highlighted the transformation relationship between non-neuronal cells and neuronal cells during GI cancer progression, inspiring the development of strategies for nervous system-guided anti-tumor drugs. By further elucidating the deep mechanism of various neuroregulatory signals and neuronal intervention, we underlined the potential of these targeted drugs translating into effective therapies for GI cancer treatment. In summary, this review provides an overview of the mechanisms of neuromodulation and explores potential therapeutic opportunities, providing insights into the understanding and management of GI cancers.

The protective effect of selenoprotein M on non-alcoholic fatty liver disease: the role of the AMPKα1-MFN2 pathway and Parkin mitophagy

Non-alcoholic fatty liver disease (NAFLD) is related to a dysregulation of mitophagy, a process that is not fully understood. Parkin-related mitophagy can sustain mitochondrial homeostasis and hepatocyte viability. Herein, we report that selenoprotein M (SELENOM) plays a central role in maintaining mitophagy in high-fat diet (HFD)-mediated NAFLD. We show that SELENOM was significantly downregulated in the liver of HFD-fed mice. SELENOM deletion aggravated HFD-mediated hepatic steatosis, inflammation, and fibrosis; accompanied by enhanced fatty acid oxidation and oxidative stress in the liver. Molecular analyses show that lipotoxicity was related to increased mitochondrial apoptosis as evidenced by enhanced mitochondrial ROS production, and attenuation of mitochondrial potential in the liver of HFD-fed SELENOM-/- mice. Additionally, SELENOM deletion reduced mitophagy and aggravated hepatic injury in NAFLD. Mechanistically, SELENOM overexpression activated Parkin-mediated mitophagy to reduce mitochondrial apoptosis and remove HFD-damaged mitochondria. We further found that SELENOM regulates Parkin expression via the AMPKα1-MFN2 pathway; blockade of AMPKα1 prevented SELENOM activation of Parkin-mediated mitophagy. Our work identified SELENOM downregulation as a possible explanation for the defective mitophagy in NAFLD. Thus, targeting SELENOM may be potential new therapeutic modalities for NAFLD treatment.

Effects of Chronic Intermittent Hypoxia and Chronic Sleep Fragmentation on Gut Microbiome, Serum Metabolome, Liver and Adipose Tissue Morphology

Chronic intermittent hypoxia (CIH) and chronic sleep fragmentation (CSF) are two cardinal pathological features of obstructive sleep apnea (OSA). Dietary obesity is a crucial risk intermediator for OSA and metabolic disorders. Gut microbiota affect hepatic and adipose tissue morphology under conditions of CIH or CSF through downstream metabolites. However, the exact relationship is unclear. Herein, chow and high-fat diet (HFD)-fed mice were subjected to CIH or CSF for 10 weeks each and compared to normoxia (NM) or normal sleep (NS) controls. 16S rRNA amplicon sequencing, untargeted liquid chromatography-tandem mass spectrometry, and histological assessment of liver and adipose tissues were used to investigate the correlations between the microbiome, metabolome, and lipid metabolism under CIH or CSF condition. Our results demonstrated that CIH and CSF regulate the abundance of intestinal microbes (such as Akkermansia mucinphila, Clostridium spp., Lactococcus spp., and Bifidobacterium spp.) and functional metabolites, such as tryptophan, free fatty acids, branched amino acids, and bile acids, which influence adipose tissue and hepatic lipid metabolism, and the level of lipid deposition in tissues and peripheral blood. In conclusion, CIH and CSF adversely affect fecal microbiota composition and function, and host metabolism; these findings provide new insight into the independent and synergistic effects of CIH, CSF, and HFD on lipid disorders.

NIR light-responsive bacteria with live bio-glue coatings for precise colonization in the gut

Recombinant bacterial colonization plays an indispensable role in disease prevention, alleviation, and treatment. Successful application mainly depends on whether bacteria can efficiently spatiotemporally colonize the host gut. However, a primary limitation of existing methods is the lack of precise spatiotemporal regulation, resulting in uncontrolled methods that are less effective. Herein, we design upconversion microgels (UCMs) to convert near-infrared light (NIR) into blue light to activate recombinant light-responsive bacteria (Lresb) in vivo, where autocrine "functional cellular glues" made of adhesive proteins assist Lresb inefficiently colonizing the gut. The programmable engineering platform is further developed for the controlled and effective colonization of Escherichia coli Nissle 1917 (EcN) in the gut. The colonizing bacteria effectively alleviate DSS-induced colitis in mice. We anticipate that this approach could facilitate the clinical application of engineered microbial therapeutics to accurately and effectively regulate host health.

The Role of Gut Microbiota in Duodenal-Jejunal Bypass Surgery-Induced Improvement of Hepatic Steatosis in HFD-Fed Rats

Bariatric surgery including duodenal-jejunal bypass surgery (DJB) improves insulin sensitivity and reduces obesity-associated inflammation. However, the underlying mechanism for such an improvement is still incompletely understood. Our objective was to investigate the role of the gut microbiota in DJB-associated improvement of hepatic steatosis in high fat diet (HFD)-fed rats. To study this, hepatic steatosis was induced in male adult Sprague-Dawley rats by feeding them with a 60% HFD. At 8 weeks after HFD feeding, the rats were subjected to either DJB or sham operation. HFD was resumed 1 week after the surgery for 3 more weeks. In additional groups of animals, feces were collected from HFD-DJB rats at 2 weeks after DJB. These feces were then transplanted to HFD-fed rats without DJB at 8 weeks after HFD feeding. Hepatic steatosis and fecal microbiota were analyzed at 4 weeks after surgery or fecal transplantation. Our results showed that DJB alleviated hepatic steatosis in HFD-fed rats. Fecal microbiota analysis showed that HFD-fed and standard diet-fed rats clustered differently. DJB induced substantial compositional changes in the gut microbiota. The fecal microbiota of HFD-fed rats received fecal transplant from DJB rats overlapped with that of HFD-DJB rats. Treatment of rats with HFD-induced liver lesions by fecal transplant from DJB-operated HFD-fed rats also attenuated hepatic steatosis. Thus, alterations in the gut microbiota after DJB surgery are sufficient to attenuate hepatic steatosis in HFD-fed rats. Targeting the gut microbiota could be a promising approach for preventing or treating human NAFLD.

Effects of Diet-Modulated Autologous Fecal Microbiota Transplantation on Weight Regain

BACKGROUND & AIMS

We evaluated the efficacy and safety of diet-modulated autologous fecal microbiota transplantation (aFMT) for treatment of weight regain after the weight-loss phase.

METHODS

In the DIRECT PLUS (Dietary Intervention Randomized Controlled Trial Polyphenols-Unprocessed) weight-loss trial (May 2017 through July 2018), abdominally obese or dyslipidemic participants in Israel were randomly assigned to healthy dietary guidelines, Mediterranean diet, and green-Mediterranean diet weight-loss groups. All groups received free gym membership and physical activity guidelines. Both isocaloric Mediterranean groups consumed 28 g/d walnuts (+440 mg/d polyphenols provided). The green-Mediterranean dieters also consumed green tea (3-4 cups/d) and a Wolffia globosa (Mankai strain, 100 g/d) green shake (+800 mg/d polyphenols provided). After 6 months (weight-loss phase), 90 eligible participants (mean age, 52 years; mean weight loss, 8.3 kg) provided a fecal sample that was processed into aFMT by frozen, opaque, and odorless capsules. The participants were then randomly assigned to groups that received 100 capsules containing their own fecal microbiota or placebo until month 14. The primary outcome was regain of the lost weight over the expected weight-regain phase (months 6-14). Secondary outcomes were gastrointestinal symptoms, waist circumference, glycemic status, and changes in the gut microbiome, as measured by metagenomic sequencing and 16s ribosomal RNA. We validated the results in a parallel in vivo study of mice specifically fed with Mankai compared with control chow diet.

RESULTS

Of the 90 participants in the aFMT trial, 96% ingested at least 80 of 100 oral aFMT or placebo frozen capsules during the transplantation period. No aFMT-related adverse events or symptoms were observed. For the primary outcome, although no significant differences in weight regain were observed among the participants in the different lifestyle interventions during months 6-14 (aFMT, 30.4% vs placebo, 40.6%; P = .28), aFMT significantly attenuated weight regain in the green-Mediterranean group (aFMT, 17.1%, vs placebo, 50%; P = .02), but not in the dietary guidelines (P = .57) or Mediterranean diet (P = .64) groups (P for the interaction = .03). Accordingly, aFMT attenuated waist circumference gain (aFMT, 1.89 cm vs placebo, 5.05 cm; P = .01) and insulin rebound (aFMT, -1.46 ± 3.6 μIU/mL vs placebo, 1.64 ± 4.7 μIU/mL; P = .04) in the green-Mediterranean group but not in the dietary guidelines or Mediterranean diet (P for the interaction = .04 and .03, respectively). The green-Mediterranean diet was the only intervention to induce a significant change in microbiome composition during the weight-loss phase, and to prompt preservation of weight-loss-associated specific bacteria and microbial metabolic pathways (mainly microbial sugar transport) after the aFMT. In mice, Mankai-modulated aFMT in the weight-loss phase compared with control diet aFMT, significantly prevented weight regain and resulted in better glucose tolerance during a high-fat diet-induced regain phase (all, P < .05).

CONCLUSIONS

Autologous FMT, collected during the weight-loss phase and administrated in the regain phase, might preserve weight loss and glycemic control, and is associated with specific microbiome signatures. A high-polyphenols, green plant-based or Mankai diet better optimizes the microbiome for an aFMT procedure. ClinicalTrials.gov number, NCT03020186.

Obesity Worsens Gulf War Illness Symptom Persistence Pathology by Linking Altered Gut Microbiome Species to Long-Term Gastrointestinal, Hepatic, and Neuronal Inflammation in a Mouse Model

Persistence of Gulf War illness (GWI) pathology among deployed veterans is a clinical challenge even after almost three decades. Recent studies show a higher prevalence of obesity and metabolic disturbances among Gulf War veterans primarily due to the existence of post-traumatic stress disorder (PTSD), chronic fatigue, sedentary lifestyle, and consumption of a high-carbohydrate/high-fat diet. We test the hypothesis that obesity from a Western-style diet alters host gut microbial species and worsens gastrointestinal and neuroinflammatory symptom persistence. We used a 5 month Western diet feeding in mice that received prior Gulf War (GW) chemical exposure to mimic the home phase obese phenotype of the deployed GW veterans. The host microbial profile in the Western diet-fed GWI mice showed a significant decrease in butyrogenic and immune health-restoring bacteria. The altered microbiome was associated with increased levels of IL6 in the serum, Claudin-2, IL6, and IL1β in the distal intestine with concurrent inflammatory lesions in the liver and hyperinsulinemia. Microbial dysbiosis was also associated with frontal cortex levels of increased IL6 and IL1β, activated microglia, decreased levels of brain derived neurotrophic factor (BDNF), and higher accumulation of phosphorylated Tau, an indicator of neuroinflammation-led increased risk of cognitive deficiencies. Mechanistically, serum from Western diet-fed mice with GWI significantly increased microglial activation in transformed microglial cells, increased tyrosyl radicals, and secreted IL6. Collectively, the results suggest that an existing obese phenotype in GWI worsens persistent gastrointestinal and neuronal inflammation, which may contribute to poor outcomes in restoring cognitive function and resolving fatigue, leading to the deterioration of quality of life.

Epigallocatechin Gallate Protects Mice against Methionine-Choline-Deficient-Diet-Induced Nonalcoholic Steatohepatitis by Improving Gut Microbiota To Attenuate Hepatic Injury and Regulate Metabolism

Epigallocatechin gallate (EGCG) has been regarded as a protective bioactive polyphenol in green tea against nonalcoholic steatohepatitis (NASH), but the mechanism remains poorly deciphered. Herein, we assessed the role and mechanism of EGCG on gut microbiota and the metabolism in NASH development. Forty-eight male C57BL/6J mice were fed with either a methionine-choline-sufficient diet or a methionine-choline-deficient (MCD) diet with or without EGCG administration for 4 weeks. Liver injury, inflammation, lipid accumulation, and iron overload were examined. 16S ribosomal RNA sequencing was used to detect the fecal microbiome. In our research, we observed that EGCG notably improved MCD-diet-derived gut microbiota dysbiosis, as proved by a distinctively clustered separation from that of the MCD group and by the decrease of the Oxalobacter, Oscillibacter, Coprococcus_1, and Desulfovibrio genera and enrichment of norank_f__Bacteroidales_S24_7_group, Alloprevotella, and Bacteroides. Spearman-correlation heatmap analysis indicated that Bacteroides and Alloprevotella induced by EGCG were strongly negatively correlated with lipid accumulation. Functional enzymes of the gut microbiome were predicted by PICRUSt based on the operation classification unit. The results revealed that 1468 enzymes were involved in various metabolic pathways, and 371 enzymes showed distinct changes between untreated and EGCG-treated mice. Long-chain-fatty-acid-CoA ligase ACSBG played a distinct role in fatty acid metabolism and ferroptosis and was significantly negatively correlated with Bacteroides. Altogether, the salutary effect of EGCG on NASH might be via shifting gut flora and certain enzymes from genera. Our study thus takes a step toward NASH prevention and therapy.

Microbiome diurnal rhythmicity and its impact on host physiology and disease risk

Host-microbiome interactions constitute key determinants of host physiology, while their dysregulation is implicated in a wide range of human diseases. The microbiome undergoes diurnal variation in composition and function, and this in turn drives oscillations in host gene expression and functions. In this review, we discuss the newest developments in understanding circadian host-microbiome interplays, and how they may be relevant in health and disease contexts. We summarize the molecular mechanisms by which the microbiome influences host function in a diurnal manner, and inversely describe how the host orchestrates circadian rhythmicity of the microbiome. Furthermore, we highlight the future perspectives and challenges in studying this new and exciting facet of host-microbiome interactions. Finally, we illustrate how the elucidation of the microbiome chronobiology may pave the way for novel therapeutic approaches.

Bioinformatics Analysis of Key Differentially Expressed Genes in Nonalcoholic Fatty Liver Disease Mice Models

Nonalcoholic fatty liver disease (NAFLD) is a global health problem characterized by excessive accumulation of fat in the liver without effect of other pathological factors including hepatitis infection and alcohol abuse. Current studies indicate that gene factors play important roles in the development of NAFLD. However, the molecular characteristics of differentially expressed genes (DEGs) and associated mechanisms with NAFLD have not been well elucidated. Using two microarray data associated with the gene expression profiling in liver tissues of NAFLD mice models, we identified and selected several common key DEGs that contributed to NAFLD. Based on bioinformatics analysis, we discovered that the DEGs were associated with a variety of biological processes, cellular components, and molecular functions and were also related to several significant pathways. Via pathway crosstalk analysis based on overlapping DEGs, we observed that the identified pathways could form large and complex crosstalk networks. Besides, large and complex protein interaction networks of DEGs were further constructed. In addition, many hub host factors with a high degree of connectivity were identified based on interaction networks. Furthermore, significant modules in interaction networks were found, and the DEGs in the identified modules were found to be enriched with distinct pathways. Taken together, these results suggest that the key DEGs, associated pathways, and modules contribute to the development of NAFLD and might be used as novel molecular targets for the treatment of NAFLD.

Serum levels of immunoglobulins in an adult population and their relationship with nonalcoholic fatty liver disease

OBJECTIVES

Few studies have reported the association between nonalcoholic fatty liver disease (NAFLD) and immunoglobulins. In this study, we aimed to investigate the relationship between serum immunoglobulin levels and NAFLD in a Chinese adult population.

METHODS

We performed a cross-sectional study including 11 261 Chinese adults. NAFLD was diagnosed based on the Chinese Guidelines for the diagnosis and treatment of fatty liver diseases and an alcohol intake of <70 g/week in women and <140 g/week in men, and serum immunoglobulin (Ig) levels were determined using immune nephelometry. Multiple logistic regression analysis was done to assess relationships between concentrations of serum immunoglobulins and NAFLD.

RESULTS

Of the 11 261 adults recruited from January 2010 to December 2015, the prevalence of NAFLD was 40.8% (n = 4598). The geometric mean levels of IgG, IgM, IgE and IgA were 1177.49 mg/dL (95% confidence interval [CI] 1173.07-1181.93), 93.56 mg/dL (95% CI 92.70-94.42), 30.70 IU/mL (95% CI 29.92-31.49) and 216.64 mg/dL (95% CI 214.95-218.34), respectively. Compared with the lowest quintile, the multivariable adjusted odds ratio (95% CI) of NAFLD for the highest quintile of IgG, IgM, IgE, and IgA were 0.78 (0.66-0.92), 0.71 (0.60-0.84), 0.98 (0.84-1.15) and 1.41 (1.21-1.66), respectively.

CONCLUSION

Increased IgA and decreased IgG and IgM levels are independently associated with NAFLD prevalence. Further research is needed to explore the causal association between serum immunoglobulins and NAFLD.

Sphingolipid metabolism in non-alcoholic fatty liver diseases

Non-alcoholic fatty liver disease (NAFLD) involves a panel of pathologies starting with hepatic steatosis and continuing to irreversible and serious conditions like steatohepatitis (NASH) and hepatocarcinoma. NAFLD is multifactorial in origin and corresponds to abnormal fat deposition in liver. Even if triglycerides are mostly associated with these pathologies, other lipid moieties seem to be involved in the development and severity of NAFLD. That is the case with sphingolipids and more particularly ceramides. In this review, we explore the relationship between NAFLD and sphingolipid metabolism. After providing an analysis of complex sphingolipid metabolism, we focus on the potential involvement of sphingolipids in the different pathologies associated with NAFLD. An unbalanced ratio between ceramides and terminal metabolic products in the liver and plasma promotes weight gain, inflammation, and insulin resistance. In the etiology of NAFLD, some sphingolipid species such as ceramides may be potential biomarkers for NAFLD. We review the clinical relevance of sphingolipids in liver diseases.

Human Gut Microbiota and Gastrointestinal Cancer

Human gut microbiota play an essential role in both healthy and diseased states of humans. In the past decade, the interactions between microorganisms and tumors have attracted much attention in the efforts to understand various features of the complex microbial communities, as well as the possible mechanisms through which the microbiota are involved in cancer prevention, carcinogenesis, and anti-cancer therapy. A large number of studies have indicated that microbial dysbiosis contributes to cancer susceptibility via multiple pathways. Further studies have suggested that the microbiota and their associated metabolites are not only closely related to carcinogenesis by inducing inflammation and immune dysregulation, which lead to genetic instability, but also interfere with the pharmacodynamics of anticancer agents. In this article, we mainly reviewed the influence of gut microbiota on cancers in the gastrointestinal (GI) tract (including esophageal, gastric, colorectal, liver, and pancreatic cancers) and the regulation of microbiota by diet, prebiotics, probiotics, synbiotics, antibiotics, or the Traditional Chinese Medicine. We also proposed some new strategies in the prevention and treatment of GI cancers that could be explored in the future. We hope that this review could provide a comprehensive overview of the studies on the interactions between the gut microbiota and GI cancers, which are likely to yield translational opportunities to reduce cancer morbidity and mortality by improving prevention, diagnosis, and treatment.

Isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics for the investigation of the effect of Hugan Qingzhi on non-alcoholic fatty liver disease in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Hugan Qingzhi tablet (HQT), a traditional Chinese medicine formula has been adopted for preventing and treating nonalcoholic fatty liver disease (NAFLD).

AIM

In order to explore the anti-NAFLD mechanisms of HQT, iTRAQ-based proteomic was employed to investigate the expression profiles of proteins in NAFLD rats induced by high-fat diet after HQT treatment.

MATERIALS AND METHODS

The NAFLD rat model was administrated with high-fat diet (HFD) for 12weeks. HQT was administrated in a daily basis to the HFD groups. Biochemical markers, liver histology, pro-inflammatory cytokines, and oxidative stress/antioxidant biomarkers were assayed to evaluate HQT effects in HFD-induced NAFLD rats. Furthermore, the combined strategy of iTRAQ labeling with strong cation exchange-non-liquid chromatography-tandem mass spectrometry (SCX-non-LC-MS/MS) analysis were employed to explore the mechanisms of HQT's protective effect against NAFLD in rats. Western blotting was performed to verify the proteomic results.

RESULTS

The histopathologic characteristics and biochemical data showed that HQT exhibited protective effects on HFD-induced NAFLD rats. After being analyzed by the combined strategy of iTRAQ with LC-MS/MS and subsequent investigation, we identified 275 differentially expressed proteins in the HFD group, compared to the control; 207 altered proteins in the HQT high dose + HFD group, compared to the HFD group; and 316 altered proteins in the HQT high dose + HFD group, compared to the control. Based on the Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway mapping, the conclusion has reached that several pathways including microbial metabolism in diverse environments, fatty acid metabolism, inflammatory response, oxidative stress, bile secretion, and peroxisome proliferator activated receptor (PPAR) signaling pathway were closely related to the effects of HQT in HFD-induced NAFLD in rats. Furthermore, several differentially expressed proteins, including phytanoyl-CoA 2-hydroxylase (PHYH), acyl-CoA synthetase 1 long chain (ACSL1), hemopexin, Alpha-1-acid glycoprotein (ORM1), fatty acid binding protein 4 (FABP4), soluble sulphotransferase 2a1 (Sult2a1), and argininosuccinate synthase 1 (ASS1) were verified by the western blotting analysis and these results were consistent with the data obtained from the proteomics analysis.

CONCLUSIONS

Our results not only confirm that Hugan Qingzhi exhibits a significant protective effect in HFD-induced NAFLD rats but also provide a better understanding for the treatments of NAFLD.

Human Gut Microbiota and Gastrointestinal Cancer

Human gut microbiota play an essential role in both healthy and diseased states of humans. In the past decade, the interactions between microorganisms and tumors have attracted much attention in the efforts to understand various features of the complex microbial communities, as well as the possible mechanisms through which the microbiota are involved in cancer prevention, carcinogenesis, and anti-cancer therapy. A large number of studies have indicated that microbial dysbiosis contributes to cancer susceptibility via multiple pathways. Further studies have suggested that the microbiota and their associated metabolites are not only closely related to carcinogenesis by inducing inflammation and immune dysregulation, which lead to genetic instability, but also interfere with the pharmacodynamics of anticancer agents. In this article, we mainly reviewed the influence of gut microbiota on cancers in the gastrointestinal (GI) tract (including esophageal, gastric, colorectal, liver, and pancreatic cancers) and the regulation of microbiota by diet, prebiotics, probiotics, synbiotics, antibiotics, or the Traditional Chinese Medicine. We also proposed some new strategies in the prevention and treatment of GI cancers that could be explored in the future. We hope that this review could provide a comprehensive overview of the studies on the interactions between the gut microbiota and GI cancers, which are likely to yield translational opportunities to reduce cancer morbidity and mortality by improving prevention, diagnosis, and treatment.

Influence of dietary macronutrients on liver fat accumulation and metabolism

The liver is a principal metabolic organ within the human body and has a major role in regulating carbohydrate, fat, and protein metabolism. With increasing rates of obesity, the prevalence of non-alcoholic fatty liver disease (NAFLD) is growing. It remains unclear why NAFLD, which is now defined as the hepatic manifestation of the metabolic syndrome, develops but lifestyle factors such as diet (ie, total calorie and specific nutrient intakes), appear to play a key role. Here we review the available observational and intervention studies that have investigated the influence of dietary macronutrients on liver fat content. Findings from observational studies are conflicting with some reporting that relative to healthy controls, patients with NAFLD consume diets higher in total fat/saturated fatty acids, whilst others find they consume diets higher in carbohydrates/sugars. From the limited number of intervention studies that have been undertaken, a consistent finding is a hypercaloric diet, regardless of whether the excess calories have been provided either as fat, sugar, or both, increases liver fat content. In contrast, a hypocaloric diet decreases liver fat content. Findings from both hyper- and hypo-caloric feeding studies provide some suggestion that macronutrient composition may also play a role in regulating liver fat content and this is supported by data from isocaloric feeding studies; fatty acid composition and/or carbohydrate content/type appear to influence whether there is accrual of liver fat or not. The mechanisms by which specific macronutrients, when consumed as part of an isocaloric diet, cause a change in liver fat remain to be fully elucidated.

Taurine and tea polyphenols combination ameliorate nonalcoholic steatohepatitis in rats

Background

Nonalcoholic steatohepatitis (NASH) is a progressive form of nonalcoholic fatty liver disease, for which there is currently no safe and effective drug for therapy. In this study, we explored the effects of taurine, tea polyphenols (TPs), or a combination thereof, on NASH rats.

Methods

Rats were divided into a normal group, a high-fat diet induced model group and a treatment group (including taurine, TPs, or taurine + TPs treatment for 8 weeks). Twelve weeks later, all rats were sacrificed, and serum transaminase, lipid and lipopolysaccharide levels and hepatic oxidative stress levels were determined. Histological changes were evaluated.

Results

In NASH rats, hepatocyte damage, lipid disturbance, oxidative stress and elevated lipopolysaccharide levels were confirmed. Taurine treatment alleviated hepatocyte damage and oxidative stress. TPs treatment improved lipid metabolism and increased hepatic antioxidant activity. The therapeutic effects of taurine + TPs treatment on hepatocyte damage, lipid disturbance, and oxidative stress were superior to those of taurine and TPs treatment, respectively. Taurine, TPs and their combination all decreased serum lipopolysaccharide levels in NASH rats, but the combination of the compounds caused these levels to decrease more significantly than taurine or TPs treatment alone.

Conclusion

Taurine combined with TPs treatment could relieve NASH by alleviating hepatocyte damage, decreasing oxidative stress and improving lipid metabolism and gut flora disturbance partly. Taurine and TPs combination may act as a new effective medicine for treating NASH patients.

Altered gut microbiome in a mouse model of Gulf War Illness causes neuroinflammation and intestinal injury via leaky gut and TLR4 activation

Many of the symptoms of Gulf War Illness (GWI) that include neurological abnormalities, neuroinflammation, chronic fatigue and gastrointestinal disturbances have been traced to Gulf War chemical exposure. Though the association and subsequent evidences are strong, the mechanisms that connect exposure to intestinal and neurological abnormalities remain unclear. Using an established rodent model of Gulf War Illness, we show that chemical exposure caused significant dysbiosis in the gut that included increased abundance of phylum Firmicutes and Tenericutes, and decreased abundance of Bacteroidetes. Several gram negative bacterial genera were enriched in the GWI-model that included Allobaculum sp. Altered microbiome caused significant decrease in tight junction protein Occludin with a concomitant increase in Claudin-2, a signature of a leaky gut. Resultant leaching of gut caused portal endotoxemia that led to upregulation of toll like receptor 4 (TLR4) activation in the small intestine and the brain. TLR4 knock out mice and mice that had gut decontamination showed significant decrease in tyrosine nitration and inflammatory mediators IL1β and MCP-1 in both the small intestine and frontal cortex. These events signified that gut dysbiosis with simultaneous leaky gut and systemic endotoxemia-induced TLR4 activation contributes to GW chemical-induced neuroinflammation and gastrointestinal disturbances.

Effects of symbiotic and vitamin E supplementation on blood pressure, nitric oxide and inflammatory factors in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has been suggested to be well correlated with altered blood pressure. This study was conducted to determine the effects of symbiotic and vitamin E supplementation on blood pressure and inflammatory indices of patients with NAFLD. This randomized, double-blind, placebo-controlled trial was performed among 60 NAFLD patients aged 25 to 64 years old. Participants were randomly divided into four groups to receive a 400 IU alpha-tocopherol and 2 × 10⁸ CFU/g symbiotic supplement for 8 weeks. The anthropometric parameters, systolic blood pressure (SBP) and diastolic blood pressure (DBP), serum malondialdehyde (MDA), nitric oxide (NO) and tumor necrosis factor α (TNFα) were assessed at baseline and after 8 weeks of intervention. After 8 weeks of intervention, combined symbiotic and alpha-tocopherol, symbiotic and alpha-tocopherol alone administration, compared with the placebo, resulted in significant decreases in SBP (-17.07±2.1, -16.07±3.56, -1.73±2.25 and -1.55±3.01 mmHg, P=0.01), serum MDA (-1.19±0.5, -0.12±0.65, 0.14 ± 0.64 and 0.16±0.34 nmol/mL, P<0.001), serum TNFα (-15.62±13.93, -9.24±7.12, -11.44 ± 15.47 and 3.01±1.71 pg/ml, P<0.001) concentrations. A significant decrease in serum AST (-11.36±4.52, -7.43±8.58, -5.93±6.61 and 2.5±5.75 μmol/L, P <0.001), ALT (-12.79±3.65, -3.66±6.81, -6.54±7.66 and 4.16±3.43 μmol/L, P <0.001) and ALP (-26.8±11.1, -4.56±9.22, -14.48±12.22 and 5.19±2.64 μmol/L, P <0.001) was seen. Variations in DBP and serum NO concentration were not significant. Alpha-tocopherol and symbiotic supplementation among patients with NAFLD resulted in decreased SBP, serum MDA, TNFα levels and enzymes liver; however, they did not affect DBP and serum NO concentration.

Isobaric Tags for Relative and Absolute Quantitation (iTRAQ)-Based Proteomic Analysis of Hugan Qingzhi and Its Protective Properties against Free Fatty Acid-Induced L02 Hepatocyte Injury

In previous research, Hugan Qingzhi, a traditional Chinese medicine, was shown to have protective effects against hepatic steatosis. However, its activity against non-alcoholic fatty liver disease (NAFLD) and the mechanisms by which it exerts its effects remain unknown. In the present study, the effects of Hugan Qingzhi on free fatty acid (FFA)-induced L02 cells were examined. The techniques of iTRAQ labeling, together with strong cation exchange-non-liquid chromatography–tandem mass spectrometry (SCX-non-LC-MS/MS) analysis and serum pharmacology, were used to evaluate the effects of Hugan Qingzhi-medicated serum on FFA-induced L02 hepatocyte injury. Results identified 355 differentially expressed proteins following FFA treatment, compared with a control group; 359 altered proteins in the Hugan Qingzhi high dose + FFA treatment group, compared with the FFA treatment group; and 365 altered proteins in the Hugan Qingzhi high dose + FFA treatment group, compared with the control group. Based on the Kyoto Encyclopedia of Gene and Genomes pathway enrichment analysis, it is concluded that several pathways including those of microbial metabolism in diverse environments, fatty acid metabolism, peroxisome proliferator activated receptor signaling, and mitogen-activated protein kinase signaling are closely associated with the effects of Hugan Qingzhi-medicated serum in FFA-induced L02 hepatocyte injury. Furthermore, several differentially expressed proteins, including heat shock protein 27 (HSP27), acetyl-CoA acetyltransferase 1, calnexin, and integrin-linked kinase, were validated by western blotting. A target-specific HSP27 siRNA was used to investigate further the function of HSP27, and it was found that HSP27 might have a key role in the observable effects of Hugan Qingzhi-medicated serum in FFA-induced L02 hepatocyte injury. The results not only confirmed that Hugan Qingzhi exhibits a significant protective effect in FFA-induced L02 hepatocyte injury, but also suggest insights into the mechanism of such protective effects.

An Intestinal Microbiota-Farnesoid X Receptor Axis Modulates Metabolic Disease

The gut microbiota is associated with metabolic diseases including obesity, insulin resistance, and nonalcoholic fatty liver disease, as shown by correlative studies and by transplant of microbiota from obese humans and mice into germ-free mice. Modification of the microbiota by treatment of high-fat diet (HFD)-fed mice with tempol or antibiotics resulted in decreased adverse metabolic phenotypes. This was owing to lower levels of the genera Lactobacillus and decreased bile salt hydrolase (BSH) activity. The decreased BSH resulted in increased levels of tauro-β-muricholic acid (MCA), a substrate of BSH and a potent farnesoid X receptor (FXR) antagonist. Mice lacking expression of FXR in the intestine were resistant to HFD-induced obesity, insulin resistance, and nonalcoholic fatty liver disease, thus confirming that intestinal FXR is involved in the potentiation of metabolic disease. A potent intestinal FXR antagonist, glycine-β-MCA (Gly-MCA), which is resistant to BSH, was developed, which, when administered to HFD-treated mice, mimics the effect of the altered microbiota on HFD-induced metabolic disease. Gly-MCA had similar effects on genetically obese leptin-deficient mice. The decrease in adverse metabolic phenotype by tempol, antibiotics, and Gly-MCA was caused by decreased serum ceramides. Mice lacking FXR in the intestine also have lower serum ceramide levels, and are resistant to HFD-induced metabolic disease, and this was reversed by injection of C16:0 ceramide. In mouse ileum, because of the presence of endogenous FXR agonists produced in the liver, FXR target genes involved in ceramide synthesis are activated and when Gly-MCA is administered they are repressed, which likely accounts for the decrease in serum ceramides. These studies show that ceramides produced in the ileum under control of FXR influence metabolic diseases.

Lifestyle and Dietary Interventions in the Management of Nonalcoholic Fatty Liver Disease

NAFLD is the leading cause of chronic liver disease in the Western world with an estimated prevalence of 20-30 %. Lifestyle interventions targeted at weight loss through dietary interventions and exercise are the most effective treatment, but only a minority of patients are able to achieve and sustain the necessary intervention targets. Weight loss of 3-5 % has been associated with a reduction of hepatic steatosis while weight loss of ≥5-7 % has correlated with resolution of NASH in some studies. Greater reductions in weight loss (≥10 %) may improve hepatic fibrosis. In the absence of weight loss, no specific diet has demonstrated superiority. Physical activity can improve hepatic steatosis and metabolic indices even without weight loss. Diet coupled with exercise can produce significant weight loss and may improve histologic components of the NAFLD activity score. While formal guidelines for diet and exercise in NAFLD are lacking, adherence to diet and exercise recommendations similar to those from the American Diabetes Association for diabetic care seems reasonable. Dietary supplementation with vitamin E in non-diabetics with biopsy-proven NASH has been shown to improve NAFLD activity score. The role for other macronutrients, micronutrients, antioxidants, and probiotics in the treatment of NAFLD remains limited.

Role of MicroRNAs in NAFLD/NASH

MicroRNAs (miRNAs) are highly conserved, small, 18-25 nucleotide, non-coding RNAs that regulate gene expression at the post-transcriptional level. Each miRNA can regulate hundreds of target genes, and vice versa each target gene can be regulated by numerous miRNAs, suggesting a very complex network and explaining how miRNAs play pivotal roles in fine-tuning essentially all biological processes in all cell types in the liver. Here, we summarize the current knowledge on the role of miRNAs in the pathogenesis and diagnosis of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) with an outlook to the broader aspects of metabolic syndrome. Furthermore, we discuss the role of miRNAs as potential biomarkers and therapeutic targets in NAFLD/NASH.

Antibiotic perturbation of the murine gut microbiome enhances the adiposity, insulin resistance, and liver disease associated with high-fat diet

Background

Obesity, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD) are serious health concerns, especially in Western populations. Antibiotic exposure and high-fat diet (HFD) are important and modifiable factors that may contribute to these diseases.

Methods

To investigate the relationship of antibiotic exposure with microbiome perturbations in a murine model of growth promotion, C57BL/6 mice received lifelong sub-therapeutic antibiotic treatment (STAT), or not (control), and were fed HFD starting at 13 weeks. To characterize microbiota changes caused by STAT, the V4 region of the 16S rRNA gene was examined from collected fecal samples and analyzed.

Results

In this model, which included HFD, STAT mice developed increased weight and fat mass compared to controls. Although results in males and females were not identical, insulin resistance and NAFLD were more severe in the STAT mice. Fecal microbiota from STAT mice were distinct from controls. Compared with controls, STAT exposure led to early conserved diet-independent microbiota changes indicative of an immature microbial community. Key taxa were identified as STAT-specific and several were found to be predictive of disease. Inferred network models showed topological shifts concurrent with growth promotion and suggest the presence of keystone species.

Conclusions

These studies form the basis for new models of type 2 diabetes and NAFLD that involve microbiome perturbation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0297-9) contains supplementary material, which is available to authorized users.

Association of maternal diabetes/glycosuria and pre-pregnancy body mass index with offspring indicators of non-alcoholic fatty liver disease

BACKGROUND

Little is known about early life determinants of non-alcoholic fatty liver disease (NAFLD). We examined associations of maternal pregnancy diabetes/glycosuria and pre-pregnancy body mass index (BMI) with offspring markers of NAFLD and liver pathology and examined mediation by birthweight and concurrent offspring adiposity.

METHODS

We used data from a UK prospective pregnancy cohort. Offspring underwent abdominal ultrasonography (USS) at mean age 17.8 years. Outcomes included USS-assessed fatty liver, estimated liver volume and shear velocity, a variant of elastography (a marker of liver fibrosis) (N = 1 215) and blood-based markers of liver pathology [alanine amino transferase, aspartate amino transferase, gamma- glutamyltransferase and haptoglobin] (N = 2 359).

RESULTS

2.1 % (N = 25) of participants had USS-assessed fatty liver [maternal diabetes/glycosuria (N = 7) and no diabetes/glycosuria (N = 18)]. Maternal diabetes/glycosuria was associated with greater odds of offspring USS fatty liver in confounder adjusted models [adjusted odds ratio (aOR) 6.74 (95 % confidence interval (CI) 2.47, 18.40)] and higher shear velocity [adjusted ratio of geometric mean (aRGM):1.10 (95 % CI 1.05, 1.15)]. These associations were not mediated by offspring birthweight or concurrent adiposity. Maternal diabetes/glycosuria was not associated with liver volume or blood-based outcomes. Greater maternal pre-pregnancy BMI was associated with greater odds of offspring USS fatty liver [aOR 2.72 (95 % CI: 1.20, 6.15)], higher liver volume [aRGM 1.03 (95 % CI 1.00, 1.07)] and shear velocity [aRGM1.03 (95 % CI: 1.01, 1.06)] in confounder adjusted models. These associations were largely mediated by offspring adiposity. Maternal pre-pregnancy BMI was not consistently associated with blood-based outcomes.

CONCLUSIONS

Results suggest that maternal pregnancy diabetes/glycosuria is associated with offspring NAFLD through mechanisms other than offspring's own adiposity.