The role of intestinal bacteria overgrowth in obesity-related nonalcoholic fatty liver disease. Nutrients. 2014;6:5583-5599. [PMID: 25479248 DOI: 10.3390/nu6125583]

Differential Effect of Sucrose and Fructose in Combination with a High Fat Diet on Intestinal Microbiota and Kidney Oxidative Stress

There is controversial information about the adverse effect of sucrose (S) or fructose (F) in the development of obesity. Thus, the purpose of the study was to evaluate the effect of S or F in a high fat diet (HF) on gut microbiota and renal oxidative stress. Rats were fed for four months with either high-fat + sucrose (HFS) or high-fat + fructose (HFF) or a control diet (C). Half of the HFS or HFF groups were maintained with the same diet and the other half were switched to the consumption of C. HFS and HFF groups increased 51% and 19% body weight, respectively, compared with the C group. Body fat mass, metabolic inflexibility, glucose intolerance, lipopolysaccharide (LPS), insulin, renal reactive oxygen species (ROS), malondialdehyde (MDA), Nadphox, and Srebp-1 were significantly higher and antioxidant enzymes and lean body mass were significantly lower in the HFS group with respect to the HF-F group. Change in the consumption of HFS or HFF to a C diet ameliorated the insulin and glucose intolerance. The type of carbohydrate differentially modified the microbiota composition, however, both groups significantly decreased C. eutactus with respect to the C group. Thus, metabolic alterations with the HFS diet had a more detrimental effect than HFF.

Altered Gut Microbiota Composition and Immune Response in Experimental Steatohepatitis Mouse Models

BACKGROUND

Although several types of diet have been used in experimental steatohepatitis models, comparison of gut microbiota and immunological alterations in the gut among diets has not yet been performed.

AIM

We attempted to clarify the difference in the gut environment between mice administrated several experimental diets.

METHODS

Male wild-type mice were fed a high-fat (HF) diet, a choline-deficient amino acid-defined (CDAA) diet, and a methionine-choline-deficient (MCD) diet for 8 weeks. We compared the severity of steatohepatitis, the composition of gut microbiota, and the intestinal expression of interleukin (IL)-17, an immune modulator.

RESULTS

Steatohepatitis was most severe in the mice fed the CDAA diet, followed by the MCD diet, and the HF diet. Analysis of gut microbiota showed that the composition of the Firmicutes phylum differed markedly at order level between the mice fed the CDAA and HF diet. The CDAA diet increased the abundance of Clostridiales, while the HF diet increased that of lactate-producing bacteria. In addition, the CDAA diet decreased the abundance of lactate-producing bacteria and antiinflammatory bacterium Parabacteroides goldsteinii in the phylum Bacteroidetes. In CDAA-fed mice, IL-17 levels were increased in ileum as well as portal vein. In addition, the CDAA diet also elevated hepatic expression of chemokines, downstream targets of IL-17.

CONCLUSIONS

The composition of gut microbiota and IL-17 expression varied considerably between mice administrated different experimental diets to induce steatohepatitis.

Metabonomics Research Progress on Liver Diseases

Metabolomics as the new omics technique develops after genomics, transcriptomics, and proteomics and has rapid development at present. Liver diseases are worldwide public health problems. In China, chronic hepatitis B and its secondary diseases are the common liver diseases. They can be diagnosed by the combination of history, virology, liver function, and medical imaging. However, some patients seldom have relevant physical examination, so the diagnosis may be delayed. Many other liver diseases, such as drug-induced liver injury (DILI), alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD), and autoimmune liver diseases, still do not have definite diagnostic markers; the diagnosis consists of history, medical imaging, and the relevant score. As a result, the clinical work becomes very complex. So it has broad prospects to explore the specific and sensitive biomarkers of liver diseases with metabolomics. In this paper, there are several summaries which are related to the current research progress and application of metabolomics on biomarkers of liver diseases.

Toxins, Toxicity, and Endotoxemia: A Historical and Clinical Perspective for Chiropractors

OBJECTIVE

The purpose of this commentary is to review the notion of toxicity in the context of chiropractic practice.

DISCUSSION

The belief that body toxicity is the cause of disease has been promoted for thousands of years. Prior to the emergence of the chiropractic profession, the medical profession embraced the notion that the body becomes "toxic," requiring detoxification interventions or surgery. The legacy of body toxicity within the chiropractic approach to patient care began with Daniel David Palmer. Today, some sectors within the medical and chiropractic professions continue to embrace the concept of body toxicity and the related need to engage in detoxifying treatments. The most common areas of focus for detoxification are the intestines and liver; however, the nature of the toxicity in these organs has yet to be defined or measured. In contrast, diet-induced systemic bacterial endotoxemia is a measureable state that is known to be promoted by a diet rich in sugar, flour, and refined oil. This suggests that bacterial endotoxin may be a candidate toxin to consider in the clinical context, as many common conditions, such as obesity, metabolic syndrome, diabetes, interstitial cystitis, depression, and migraine headache, are known to be promoted by endotoxemia.

CONCLUSION

A diet rich in refined sugar, flour, and oils may induce proinflammatory changes within intestinal microbiota that lead to systemic, low-grade endotoxemia, which is a common variety of "toxicity" that is measurable and worthy of research consideration. Introducing a diet to reduce endotoxemia, rather than attempting to target a specific organ, appears to be a rational clinical approach for addressing the issue of toxicity.

Preserved Gut Microbial Diversity Accompanies Upregulation of TGR5 and Hepatobiliary Transporters in Bile Acid-Treated Animals Receiving Parenteral Nutrition

BACKGROUND

Parenteral nutrition (PN) is a lifesaving therapy but is associated with gut atrophy and cholestasis. While bile acids (BAs) can modulate intestinal growth via gut receptors, the gut microbiome likely influences gut proliferation and inflammation. BAs also regulate the bile salt export pump (BSEP) involved in cholestasis. We hypothesized that the BA receptor agonist oleanolic acid (OA) regulates gut TGR5 receptor and modulates gut microbiota to prevent PN-associated injury.

MATERIALS AND METHODS

Neonatal piglets were randomized to approximately 2 weeks of isocaloric enteral nutrition (EN), PN, or PN + enteral OA. Serum alanine aminotransferase, bilirubin, BAs, hepatic BSEP, gut TGR5, gut, liver morphology, and fecal microbiome utilizing 16S rRNA sequencing were evaluated. Kruskal-Wallis test, pairwise Mann-Whitney U test, and multilevel logistic regression analysis were performed.

RESULTS

PN support resulted in gut atrophy substantially prevented by OA. The median (interquartile range) for villous/crypt ratio was as follows: EN, 3.37 (2.82-3.80); PN, 1.73 (1.54-2.27); and OA, 2.89 (2.17-3.34; P = .006). Pairwise comparisons yielded P = .002 (EN vs PN), P = .180 (EN vs OA), P = .026 (PN vs OA). OA upregulated TGR5 and BSEP without significant improvement in serum bilirubin ( P = .095). A decreased microbial diversity and shift toward proinflammatory phylum Bacteroidetes were seen with PN, which was prevented by OA.

CONCLUSIONS

OA prevented PN-associated gut mucosal injury, Bacterioides expansion, and the decreased microbial diversity noted with PN. This study demonstrates a novel relationship among PN-associated gut dysfunction, BA treatment, and gut microbial changes.

Gut-liver axis: An important target for prevention and treatment of liver diseases

The human intestine harbors a complex and diverse community of microbes that promote metabolism and digestion in their symbiotic relationship with the host. Liver diseases have long been associated with qualitative (dysbiotic) and quantitative (overgrowth) changes in the intestinal microbiota. Extrinsic factors, such as diet and alcohol, contribute to intestinal microbiota dysbiosis. Dysbiosis results in intestinal inflammation, intestinal barrier breakdown, and translocation of microbial products in animal models, further aggravating hepatic injury and inflammation. Microbial metabolites produced in a dysbiotic intestinal environment and host factors are equally important in the pathogenesis of liver diseases. In the current review, we discuss the progress in understanding the role of gut-liver axis dysfunction in the progression of non-alcoholic fatty liver disease, alcoholic liver disease and cirrhosis, and the potential application value of the restoration of intestinal homeostasis in the prevention and treatment of liver diseases.

Metabolic Characterization of Advanced Liver Fibrosis in HCV Patients as Studied by Serum 1H-NMR Spectroscopy

Several etiologies result in chronic liver diseases including chronic hepatitis C virus infection (HCV). Despite its high incidence and the severe economic and medical consequences, liver disease is still commonly overlooked due to the lack of efficient non-invasive diagnostic methods. While several techniques have been tested for the detection of fibrosis, the available biomarkers still present severe limitations that preclude their use in clinical diagnostics. Liver diseases have also been the subject of metabolomic analysis. Here, we demonstrate the suitability of ¹H NMR spectroscopy for characterizing the metabolism of liver fibrosis induced by HCV. Serum samples from HCV patients without fibrosis or with liver cirrhosis were analyzed by NMR spectroscopy and the results were submitted to multivariate and univariate statistical analysis. PLS-DA test was able to discriminate between advanced fibrotic and non-fibrotic patients and several metabolites were found to be up or downregulated in patients with cirrhosis. The suitability of the most significantly regulated metabolites was validated by ROC analysis. Our study reveals that choline, acetoacetate and low-density lipoproteins are the most informative biomarkers for predicting cirrhosis in HCV patients. Our results demonstrate that statistical analysis of ¹H-NMR spectra is able to distinguish between fibrotic and non-fibrotic patients suffering from HCV, representing a novel diagnostic application for NMR spectroscopy.

Nonalcoholic Fatty Liver Disease and the Gut Microbiome

Recent progress has allowed a more comprehensive study of the gut microbiota. Gut microbiota helps in health maintenance and gut dysbiosis associates with chronic metabolic diseases. Modulation of short-chain fatty acids and choline bioavailability, lipoprotein lipase induction, alteration of bile acid profile, endogenous alcohol production, or liver inflammation secondary to endotoxemia result from gut dysbiosis. Modulation of the gut microbiota by pre/probiotics gives promising results in animal, but needs to be evaluated in human before use in clinical practice. Gut microbiota adds complexity to the pathophysiology of nonalcoholic fatty liver disease but represents an opportunity to discover new therapeutic targets.

Pathogenesis of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease and a risk factor for cirrhosis and hepatocellular carcinoma. The pathological features of NASH include steatosis, hepatocyte injury, inflammation, and various degrees of fibrosis. Steatosis reflects disordered lipid metabolism. Insulin resistance and excessive fatty acid influx to the liver are two important contributing factors. Steatosis is also likely associated with lipotoxicity and cellular stresses such as oxidative stress and endoplasmic reticulum stress, which result in hepatocyte injury. Inflammation and fibrosis are frequently triggered by various signals such as proinflammatory cytokines and chemokines, released by injuried hepatocytes and activated Kupffer cells. Although much progress has been made, the pathogenesis of NASH is not fully elucidated. The purpose of this review is to discuss the current understanding of NASH pathogenesis, mainly focusing on factors contributing to steatosis, hepatocyte injury, inflammation, and fibrosis.

Microbiota Modulation With Synbiotic Decreases Liver Fibrosis in a High Fat Choline Deficient Diet Mice Model of Non-Alcoholic Steatohepatitis (NASH)

BACKGROUND

Gut microbiota may play a role in non-alcoholic steatohepatitis (NASH). Previous studies showed that prebiotics and probiotics might halt the progression of steatohepatitis.

AIM

To clarify the potential effect of Synbiotic 2000^®Forte (Synb) in preventing or ameliorating diet induced steatohepatitis, particularly in fibrosis progression and how this intervention correlates with gut microbiota composition and endotoxinemia.

METHODS

Twenty-seven C57BL/6 mice were divided into three groups: chow diet (CD, n = 7); high-fat choline deficient diet (HFCD, n = 10) and HFCD diet supplemented with Synbiotic 2000^®Forte (four probiotic strains and four prebiotics mixture) (HFCD + Synb, n = 10). At 6 and 18 weeks, blood samples (lipopolysaccharides assay - LPS), cecal feaces (gut microbiota) and liver tissue (histology) were collected for analysis.

RESULTS

Both HCFD diet mice developed steatohepatitis with ballooning at 6 and 18 weeks, opposite to CD. Comparison of histological scores in HFCD and HFCD + Synb, at 6 and 18 weeks showed no significant difference regarding steatosis, inflammation, or ballooning. Evaluating fibrosis with Sirius Red, and degree of smooth-muscle cell activation, HFCD mice had significantly more fibrosis; addition of Synb significantly reduced fibrosis at 6 weeks and 18 weeks. Serum endotoxin levels were similarly increased in HFCD and HFCD + Synb at week 6; however at week 18 HFCD + Synb had significantly lower endotoxin levels than HFCD. Gut microbiota of HFCD vs CD, showed no significant differences regarding the phyla Firmicutes and Bacteroidetes, either at 6 or 18 weeks; Proteobacteria increased at 6 week (3.3) and 18 week (7.5), while the addition of Synb resulted in a decrease at week 18 (-3.90). Fusobacteria markedly increase at week 18 (10.0), but less so with the addition of Synb (5.2).

CONCLUSION

Synbiotic 2000^®Forte is able to modulate the mouse gut microbiota reducing the degree of fibrosis while simultaneously decreasing endotoxemia.

Macronutrient intakes in obese subjects with or without small intestinal bacterial overgrowth: an alimentary survey

OBJECTIVE

Obesity is a multifactorial disorder with a possible microbiota derangement in its pathogenesis. Moreover, in obese patients the likelihood of small intestinal bacterial overgrowth (SIBO) is greater than in controls, although few studies are currently available. This study investigates the prevalence of SIBO and the possible role of dietary macronutrients in obesity.

MATERIALS AND METHODS

Sixty obese patients and normal lean controls were enrolled for SIBO detection. Diagnosis of SIBO was performed by a glucose breath test. A 24-hour recall questionnaire was administered to investigate macronutrient daily intake between the two obese patient subgroups (with/without SIBO).

RESULTS

The presence of SIBO in obese and controls was respectively 23.3% and 6.6% (p = 0.02, OR = 4.26, 95% Confidence interval = 1.31-13.84). Obese patients with SIBO ingested more carbohydrates (252.75 ± 30.53 vs 201 ± 70.76 g/day, p = 0.01), more refined sugars (104.15 ± 28.69 vs 73.32 ± 44.93 g/day, p = 0.02) and less total and insoluble fibers (9.6 ± 1.97 vs 14.65 ± 8.80 g/day, p = 0.04 and 4.7 ± 1.11 vs 8.82 ± 5.80 g/day, p = 0.01, respectively). There were no significant differences in lipid and protein intake between the two groups.

CONCLUSIONS

SIBO is widespread in obese subjects. Carbohydrates might promote the development of SIBO in obesity and fibers provide a protective function. Our results suggest a close relationship between diet and SIBO in obesity, thus supporting a possible role for intestinal microbiota.

Gut Microbiota and Host Reaction in Liver Diseases

Although alcohol feeding produces evident intestinal microbial changes in animals, only some alcoholics show evident intestinal dysbiosis, a decrease in Bacteroidetes and an increase in Proteobacteria. Gut dysbiosis is related to intestinal hyperpermeability and endotoxemia in alcoholic patients. Alcoholics further exhibit reduced numbers of the beneficial Lactobacillus and Bifidobacterium. Large amounts of endotoxins translocated from the gut strongly activate Toll-like receptor 4 in the liver and play an important role in the progression of alcoholic liver disease (ALD), especially in severe alcoholic liver injury. Gut microbiota and bacterial endotoxins are further involved in some of the mechanisms of nonalcoholic fatty liver disease (NAFLD) and its progression to nonalcoholic steatohepatitis (NASH). There is experimental evidence that a high-fat diet causes characteristic dysbiosis of NAFLD, with a decrease in Bacteroidetes and increases in Firmicutes and Proteobacteria, and gut dysbiosis itself can induce hepatic steatosis and metabolic syndrome. Clinical data support the above dysbiosis, but the details are variable. Intestinal dysbiosis and endotoxemia greatly affect the cirrhotics in relation to major complications and prognosis. Metagenomic approaches to dysbiosis may be promising for the analysis of deranged host metabolism in NASH and cirrhosis. Management of dysbiosis may become a cornerstone for the future treatment of liver diseases.

Controversies in the Mechanism of Total Parenteral Nutrition Induced Pathology

Over 30,000 patients are permanently dependent on Total Parenteral Nutrition (TPN) for survival with several folds higher requiring TPN for a prolonged duration. Unfortunately, it can cause potentially fatal complications. TPN infusion results in impairment of gut mucosal integrity, enhanced inflammation, increased cytokine expression and trans-mucosal bacterial permeation. It also causes endotoxin associated down regulation of bile acid transporters and Parenteral Nutrition Associated Liver Disease (PNALD), which includes steatosis, disrupted glucose metabolism, disrupted lipid metabolism, cholestasis and liver failure. Despite multiple theories, its etiology and pathophysiology remains elusive and is likely multifactorial. An important cause for TPN related pathologies appears to be a disruption in the normal enterohepatic circulation due to a lack of feeding during such therapy. This is further validated by the fact that in clinical settings, once cholestasis sets in, its reversal occurs when a patient is receiving a major portion of calories enterally. There are several other postulated mechanisms including gut bacterial permeation predisposing to endotoxin associated down regulation of bile acid transporters. An additional potential mechanism includes toxicity of the TPN solution itself, such as lipid mediated hepatic toxicity. Prematurity, leading to a poor development of bile acid regulating nuclear receptors and transporters has also been implicated as a causative factor. This review presents the current controversies and research into mechanisms of TPN associated injury.

Gut-liver axis, nutrition, and non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of diseases involving hepatic fat accumulation, inflammation with the potential progression to fibrosis and cirrhosis over time. NAFLD is often associated with obesity, insulin resistance, and diabetes. The interactions between the liver and the gut, the so-called "gut-liver axis", play a critical role in NAFLD onset and progression. Compelling evidence links the gut microbiome, intestinal barrier integrity, and NAFLD. The dietary factors may alter the gut microbiota and intestinal barrier function, favoring the occurrence of metabolic endotoxemia and low grade inflammation, thereby contributing to the development of obesity and obesity-associated fatty liver disease. Therapeutic manipulations with prebiotics and probiotics to modulate the gut microbiota and maintain intestinal barrier integrity are potential agents for NAFLD management. This review summarizes the current knowledge regarding the complex interplay between the gut microbiota, intestinal barrier, and dietary factors in NAFLD pathogenesis. The concepts addressed in this review have important clinical implications, although more work needs to be done to understand how dietary factors affect the gut barrier and microbiota, and to comprehend how microbe-derived components may interfere with the host's metabolism contributing to NAFLD development.

Alcoholic, Nonalcoholic, and Toxicant-Associated Steatohepatitis: Mechanistic Similarities and Differences

Hepatic steatosis and steatohepatitis are common histologic findings that can be caused by multiple etiologies. The three most frequent causes for steatosis/steatohepatitis are alcohol (alcoholic steatohepatitis, ASH), obesity/metabolic syndrome (nonalcoholic steatohepatitis, NASH), and environmental toxicants (toxicant-associated steatohepatitis, TASH). Hepatic steatosis is an early occurrence in all three forms of liver disease, and they often share common pathways to disease progression/severity. Disease progression is a result of both direct effects on the liver as well as indirect alterations in other organs/tissues such as intestine, adipose tissue, and the immune system. Although the three liver diseases (ASH, NASH, and TASH) share many common pathogenic mechanisms, they also exhibit distinct differences. Both shared and divergent mechanisms can be potential therapeutic targets. This review provides an overview of selected important mechanistic similarities and differences in ASH, NASH, and TASH.

A concise review of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and the incidence of which is rising rapidly due to the increasing epidemic of obesity in both adults and children. The initial accumulation of fat followed by subsequent inflammation is central to the development of liver damage, and is critically influenced by host factors including age, gender, presence of diabetes, genetic polymorphisms and more recently by the gut microbiome. An increasing body of data suggest that NAFLD is also an independent risk factor of cardiovascular disease, which remains the commonest cause of mortality in such patients. This review focusses on the pathogenesis of NAFLD, and the evolution of new approaches to the management and treatment of NAFLD.