Lactobacillus rhamnosus GG protects against non-alcoholic fatty liver disease in mice

Probiotics modulate gut microbiota and improve insulin sensitivity in DIO mice

Obesity and type 2 diabetes are characterized by subclinical inflammatory process. Changes in composition or modulation of the gut microbiota may play an important role in the obesity-associated inflammatory process. In the current study, we evaluated the effects of probiotics (Lactobacillus rhamnosus, L. acidophilus and Bifidobacterium bifidumi) on gut microbiota, changes in permeability, and insulin sensitivity and signaling in high-fat diet and control animals. More importantly, we investigated the effects of these gut modulations on hypothalamic control of food intake, and insulin and leptin signaling. Swiss mice were submitted to a high-fat diet (HFD) with probiotics or pair-feeding for 5 weeks. Metagenome analyses were performed on DNA samples from mouse feces. Blood was drawn to determine levels of glucose, insulin, LPS, cytokines and GLP-1. Liver, muscle, ileum and hypothalamus tissue proteins were analyzed by Western blotting and real-time polymerase chain reaction. In addition, liver and adipose tissues were analyzed using histology and immunohistochemistry. The HFD induced huge alterations in gut microbiota accompanied by increased intestinal permeability, LPS translocation and systemic low-grade inflammation, resulting in decreased glucose tolerance and hyperphagic behavior. All these obesity-related features were reversed by changes in the gut microbiota profile induced by probiotics. Probiotics also induced an improvement in hypothalamic insulin and leptin resistance. Our data demonstrate that the intestinal microbiome is a key modulator of inflammatory and metabolic pathways in both peripheral and central tissues. These findings shed light on probiotics as an important tool to prevent and treat patients with obesity and insulin resistance.

A casein hydrolysate based formulation attenuates obesity and associated non-alcoholic fatty liver disease and atherosclerosis in LDLr-/-.Leiden mice

Background

Obesity frequently associates with the development of non-alcoholic fatty liver disease (NAFLD) and atherosclerosis. Chronic inflammation in white adipose tissue (WAT) seems to be an important driver of these manifestations.

Objective

This study investigated a combination of an extensively hydrolyzed casein (eHC), docosahexaenoic acid (DHA), arachidonic acid (ARA), and Lactobacillus Rhamnosus GG (LGG) (together referred to as nutritional ingredients, NI) on the development of obesity, metabolic risk factors, WAT inflammation, NAFLD and atherosclerosis in high-fat diet-fed LDLr-/-.Leiden mice, a model that mimics disease development in humans.

Methods

LDLr-/-.Leiden male mice (n = 15/group) received a high-fat diet (HFD, 45 Kcal%) for 21 weeks with or without the NI (23.7% eHC, 0.083% DHA, 0.166% ARA; all w/w and 1x10⁹ CFU LGG gavage 3 times/week). HFD and HFD+NI diets were isocaloric. A low fat diet (LFD, 10 Kcal%) was used for reference. Body weight, food intake and metabolic risk factors were assessed over time. At week 21, tissues were analyzed for WAT inflammation (crown-like structures), NAFLD and atherosclerosis. Effects of the individual NI components were explored in a follow-up experiment (n = 7/group).

Results

When compared to HFD control, treatment with the NI strongly reduced body weight to levels of the LFD group, and significantly lowered (P<0.01) plasma insulin, cholesterol, triglycerides, leptin and serum amyloid A (P<0.01). NI also reduced WAT mass and inflammation. Strikingly, NI treatment significantly reduced macrovesicular steatosis, lobular inflammation and liver collagen (P<0.05), and attenuated atherosclerosis development (P<0.01). Of the individual components, the effects of eHC were most pronounced but could not explain the entire effects of the NI formulation.

Conclusions

A combination of eHC, ARA, DHA and LGG attenuates obesity and associated cardiometabolic diseases (NAFLD, atherosclerosis) in LDLr-/-.Leiden mice. The observed reduction of inflammation in adipose tissue and in the liver provides a rationale for these comprehensive health effects.

A synbiotic composed of Lactobacillus fermentum CECT5716 and FOS prevents the development of fatty acid liver and glycemic alterations in rats fed a high fructose diet associated with changes in the microbiota

We investigated the effect of a high fructose diet (HFD) on Sprague Dawley rats and the impact of a synbiotic composed of Lactobacillus fermentum CECT5716 and fructooligosaccharides. Feeding the HFD for 5 weeks resulted in liver steatosis and insulin resistance but not obesity. These changes were associated with increased production of short-chain fatty acids and increased Bacteroidetes in feces, with an augmented Bacteroidetes/Firmicutes ratio, among other changes in the microbiota. In addition, barrier function was weakened, with increased LPS plasma levels. These data are consistent with increased fructose availability in the distal gut due to saturation of absorptive mechanisms, leading to dysbiosis, endotoxemia, hepatic steatosis, and insulin resistance. Treatment with the synbiotic prevented some of the pathological effects, so that treated rats did not develop steatosis or systemic inflammation, while dysbiosis and barrier function were greatly ameliorated. In addition, the synbiotic had hypolipidemic effects. The synbiotic composed by L. fermentum CECT5716 and fructooligosaccharides has beneficial effects in a model of metabolic syndrome induced by a HFD, suggesting it might be clinically useful in this type of condition, particularly considering that high fructose intake has been related to metabolic syndrome in humans.

Microbial Impact on Host Metabolism: Opportunities for Novel Treatments of Nutritional Disorders?

Malnutrition is the cause of major public health concerns worldwide. On the one hand, obesity and associated pathologies (also known as the metabolic syndrome) affect more than 10% of the world population. Such pathologies might arise from an elevated inflammatory tone. We have discovered that the inflammatory properties of high-fat diets were linked to the translocation of lipopolysaccharide (LPS). We proposed a mechanism associating the gut microbiota with the onset of insulin resistance and low-grade inflammation, a phenomenon that we called “metabolic endotoxemia.” We and others have shown that bacteria as well as host-derived immune-related elements control microbial communities and eventually contribute to the phenotype observed during diet-induced obesity, diabetes, and metabolic inflammation. On the other hand, undernutrition is one of the leading causes of death in children. A diet poor in energy and/or nutrients causes incomplete development of the gut microbiota and may profoundly affect energy absorption, initiating stunted growth, edema, and diarrhea. In this review, we discuss how changes in microbiota composition are associated with obesity and undernutrition. We also highlight that opposite consequences exist in terms of energy absorption from the diet (obesity versus undernutrition), but interestingly the two situations share similar defects in term of diversity, functionality, and inflammatory potential.

Deleterious Metabolic Effects of High Fructose Intake: The Preventive Effect of Lactobacillus kefiri Administration

Modern lifestyle and diets have been associated with metabolic disorders and an imbalance in the normal gut microbiota. Probiotics are widely known for their health beneficial properties targeting the gut microbial ecosystem. The aim of our study was to evaluate the preventive effect of Lactobacillus kefiri (L. kefiri) administration in a fructose-rich diet (FRD) mice model. Mice were provided with tap water or fructose-added (20% w/v) drinking water supplemented or not with L. kefiri. Results showed that probiotic administration prevented weight gain and epidydimal adipose tissue (EAT) expansion, with partial reversion of the adipocyte hypertrophy developed by FRD. Moreover, the probiotic prevented the increase of plasma triglycerides and leptin, together with the liver triglyceride content. Leptin adipocyte secretion was also improved by L. kefiri, being able to respond to an insulin stimulus. Glucose intolerance was partially prevented by L. kefiri treatment (GTT) and local inflammation (TNFα; IL1β; IL6 and INFγ) was completely inhibited in EAT. L. kefiri supplementation generated an impact on gut microbiota composition, changing Bacteroidetes and Firmicutes profiles. Overall, our results indicate that the administration of probiotics prevents the deleterious effects of FRD intake and should therefore be promoted to improve metabolic disorders.

Oxidative Stress as a Critical Factor in Nonalcoholic Fatty Liver Disease Pathogenesis

SIGNIFICANCE

Nonalcoholic fatty liver disease (NAFLD), characterized by liver triacylglycerol build-up, has been growing in the global world in concert with the raised prevalence of cardiometabolic disorders, including obesity, diabetes, and hyperlipemia. Redox imbalance has been suggested to be highly relevant to NAFLD pathogenesis. Recent Advances: As a major health problem, NAFLD progresses to the more severe nonalcoholic steatohepatitis (NASH) condition and predisposes susceptible individuals to liver and cardiovascular disease. Although NAFLD represents the predominant cause of chronic liver disorders, the mechanisms of its development and progression remain incompletely understood, even if various scientific groups ascribed them to the occurrence of insulin resistance, dyslipidemia, inflammation, and apoptosis. Nevertheless, oxidative stress (OxS) more and more appears as the most important pathological event during NAFLD development and the hallmark between simple steatosis and NASH manifestation.

CRITICAL ISSUES

The purpose of this article is to summarize recent developments in the understanding of NAFLD, essentially focusing on OxS as a major pathogenetic mechanism. Various attempts to translate reactive oxygen species (ROS) scavenging by antioxidants into experimental and clinical studies have yielded mostly encouraging results.

FUTURE DIRECTIONS

Although augmented concentrations of ROS and faulty antioxidant defense have been associated to NAFLD and related complications, mechanisms of action and proofs of principle should be highlighted to support the causative role of OxS and to translate its concept into the clinic. Antioxid. Redox Signal. 26, 519-541.

Nonalcoholic Fatty Liver Disease, the Gut Microbiome, and Diet

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder in the world, yet the pathogenesis of the disease is not well elucidated. Due to the close anatomic and functional association between the intestinal lumen and the liver through the portal system, it is speculated that the gut microbiome may play a pivotal role in the pathogenesis of NAFLD. Furthermore, diet, which can modulate the gut microbiome and several metabolic pathways involved in NAFLD development, shows a potential tripartite relation between the gut, diet, and the liver. In this review, we summarize the current evidence that supports the association between NAFLD, the gut microbiome, and the role of diet.

Nutritional Approaches to Achieve Weight Loss in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) can range in spectrum from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH), which is characterized by lipotoxicity, hepatocellular ballooning, and inflammation and can progress to cirrhosis. Weight loss is the cornerstone treatment for NAFLD and NASH. Various randomized controlled trials have shown that weight loss of ≥5-10% leads to significant improvements in hepatic steatosis. Diets high in sodium and fructose have been implicated in the pathogenesis of NAFLD. Although some clinical studies suggest that an isocaloric high-fructose diet does not worsen NAFLD, these clinical studies are often short in duration. More recently, the Dietary Approaches to Stop Hypertension diet, a sodium-restricted diet, has been associated with less prevalence of NAFLD and has been shown to improve NAFLD. In addition, the Mediterranean diet has been promising in improving hepatic steatosis, and a larger randomized controlled trial is currently enrolling subjects. For those who are unable to pursue weight loss through dietary approaches, bariatric surgery has been shown to improve hepatic steatosis and steatohepatitis. This method has been variable in improving hepatic fibrosis. In conclusion, weight loss is crucial to the improvement of NAFLD and NASH, and patients should attempt various diets in an attempt to achieve weight loss.

Fructose and NAFLD: The Multifaceted Aspects of Fructose Metabolism

Among various factors, such as an unhealthy diet or a sedentarity lifestyle, excessive fructose consumption is known to favor nonalcoholic fatty liver disease (NAFLD), as fructose is both a substrate and an inducer of hepatic de novo lipogenesis. The present review presents some well-established mechanisms and new clues to better understand the pathophysiology of fructose-induced NAFLD. Beyond its lipogenic effect, fructose intake is also at the onset of hepatic inflammation and cellular stress, such as oxidative and endoplasmic stress, that are key factors contributing to the progression of simple steatosis to nonalcoholic steatohepatitis (NASH). Beyond its hepatic effects, this carbohydrate may exert direct and indirect effects at the peripheral level. Excessive fructose consumption is associated, for example, with the release by the liver of several key mediators leading to alterations in the communication between the liver and the gut, muscles, and adipose tissue and to disease aggravation. These multifaceted aspects of fructose properties are in part specific to fructose, but are also shared in part with sucrose and glucose present in energy–dense beverages and foods. All these aspects must be taken into account in the development of new therapeutic strategies and thereby to better prevent NAFLD.

Probiotics and Disease: A Comprehensive Summary-Part 3, Cardiometabolic Disease and Fatigue Syndromes

This article series provides a literature review of the disease-specific probiotic strains, associated with cardiometabolic diseases and fatigue syndromes, studied in published clinical trials in humans and animals. This is not an exhaustive review. The table design allows for quick access to supportive data and will be helpful as a guide for both researchers and clinicians. The goal of the probiotics and disease series is to provide clinically useful tools. The first article (part 1) focused on mental health and neurological conditions and the second article (part 2) explored cultured and fermented foods that are commonly available in the United States. This third article (part 3) explores the relationship between bacterial strains and 2 of the most prevalent diseases we have in modern society: cardiometabolic disease and fatigue syndromes. Future articles will review conditions related to respiratory, ear, nose, and throat infections and infectious diseases; autoimmunity and dermatological conditions; cancer; and gastrointestinal and genitourinary, followed by an article focused on probiotic supplements. This literature review is specific to disease condition, probiotic classification, and individual strain.

Precision medicine in alcoholic and nonalcoholic fatty liver disease via modulating the gut microbiota

Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) represent a major health burden in industrialized countries. Although alcohol abuse and nutrition play a central role in disease pathogenesis, preclinical models support a contribution of the gut microbiota to ALD and NAFLD. This review describes changes in the intestinal microbiota compositions related to ALD and NAFLD. Findings from in vitro, animal, and human studies are used to explain how intestinal pathology contributes to disease progression. This review summarizes the effects of untargeted microbiome modifications using antibiotics and probiotics on liver disease in animals and humans. While both affect humoral inflammation, regression of advanced liver disease or mortality has not been demonstrated. This review further describes products secreted by Lactobacillus- and microbiota-derived metabolites, such as fatty acids and antioxidants, that could be used for precision medicine in the treatment of liver disease. A better understanding of host-microbial interactions is allowing discovery of novel therapeutic targets in the gut microbiota, enabling new treatment options that restore the intestinal ecosystem precisely and influence liver disease. The modulation options of the gut microbiota and precision medicine employing the gut microbiota presented in this review have excellent prospects to improve treatment of liver disease.

Lactobacillus plantarum HAC01 regulates gut microbiota and adipose tissue accumulation in a diet-induced obesity murine model

The functional features of Lactobacillus plantarum HAC01 (HAC01), isolated from fermented Korean kimchi, were studied with regard to the fat mass, immunometabolic biomarkers and dysbiosis in a diet-induced obesity (DIO) murine model. L. rhamnosus GG (LGG) served as reference strain and a PBS-treated group as control. The administration of L. plantarum HAC01 resulted in reduction of the mesenteric adipose depot, the conjunctive tissue closely associated with the gastrointestinal tract, where lipid oxidative gene expression was upregulated compared to the control group. Metagenome analysis of intestinal microbiota showed that both strains HAC01 and LGG influenced specific bacterial families such as the Lachnospiraceae and Ruminococcaceae rather than the phyla Firmicutes and Bacteroidetes as a whole. The relative abundance of the Lachnospiraceae (phylum Firmicutes) was significantly higher in both LAB-treated groups than in the control. Comparing the impact of the two Lactobacillus strains on microbial composition in the gut also suggests strain-specific effects. The study emphasises the need for deeper studies into functional specificity of a probiotic organism at the strain level. Alleviation of obesity-associated dysbiosis by modulation of the gut microbiota appears to be associated with "indicator" bacterial taxa such as the family Lachnospiraceae. This may provide further insight into mechanisms basic to the mode of probiotic action against obesity and associated dysbiosis.

Altered Fecal Microbiota Correlates with Liver Biochemistry in Nonobese Patients with Non-alcoholic Fatty Liver Disease

Increasing evidence suggests a role of intestinal dysbiosis in obesity and non-alcoholic fatty liver disease (NAFLD). But it remains unknown in nonobese NAFLD. This prospective, cross-sectional study sought to characterize differences in fecal microbiota between nonobese adult individuals with and without NAFLD and their potential association with metabolic markers of disease progression. A total of 126 nonobese subjects were enrolled: 43 NAFLD and 83 healthy controls (HC). The microbial community was profiled by denaturing gradient gel electrophoresis and examined by 454 pyrosequencing of the 16S ribosomal RNA V3 region. Lower diversity and a phylum-level change in the fecal microbiome were found in NAFLD. Compared with HC, patients had 20% more phylum Bacteroidetes (p = 0.005) and 24% less Firmicutes (p = 0.002). Within Firmicutes, four families and their 8 genera, which were short-chain fatty acids-producing and 7α-dehydroxylating bacteria, were significantly decreased. Moreover, Gram-negative (G-) bacteria were prevalent in NAFLD (p = 0.008). Furthermore, a significant correlation with metabolic markers was revealed for disturbed microbiota in NAFLD. This novel study indicated that intestinal dysbiosis was associated with nonobese NAFLD and might increase the risk of NAFLD progression.

Prosteatotic and Protective Components in a Unique Model of Fatty Liver: Gut Microbiota and Suppressed Complement System

Goose can develop severe hepatic steatosis without overt injury, thus it may serve as a unique model for uncovering how steatosis-related injury is prevented. To identify the markedly prosteatotic and protective mechanisms, we performed an integrated analysis of liver transcriptomes and gut microbial metagenomes using samples collected from overfed and normally-fed geese at different time points. The results indicated that the fatty liver transcriptome, initially featuring a ‘metabolism’ pathway, was later joined by ‘cell growth and death’ and ‘immune diseases’ pathways. Gut microbiota played a synergistic role in the liver response as microbial and hepatic genes affected by overfeeding shared multiple pathways. Remarkably, the complement system, an inflammatory component, was comprehensively suppressed in fatty liver, which was partially due to increased blood lactic acid from enriched Lactobacillus. Data from in vitro studies suggested that lactic acid suppressed TNFα via the HNF1α/C5 pathway. In conclusion, gut microbes and their hosts respond to excess energy influx as an organic whole, severe steatosis and related tolerance of goose liver may be partially attributable to gut microbiotic products and suppressed complement system, and lactic acid from gut microbiota participates in the suppression of hepatic TNFα/inflammation through the HNF1α/C5 pathway.

Metabolic aspects of adult patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease and it encompasses a spectrum from simple steatosis to steatohepatitis, fibrosis, or cirrhosis. The mechanisms involved in the occurrence of NAFLD and its progression are probably due to a metabolic profile expressed within the context of a genetic predisposition and is associated with a higher energy intake. The metabolic syndrome (MS) is a cluster of metabolic alterations associated with an increased risk for the development of cardiovascular diseases and diabetes. NAFLD patients have more than one feature of the MS, and now they are considered the hepatic components of the MS. Several scientific advances in understanding the association between NAFLD and MS have identified insulin resistance (IR) as the key aspect in the pathophysiology of both diseases. In the multi parallel hits theory of NAFLD pathogenesis, IR was described to be central in the predisposition of hepatocytes to be susceptible to other multiple pathogenetic factors. The recent knowledge gained from these advances can be applied clinically in the prevention and management of NAFLD and its associated metabolic changes. The present review analyses the current literature and highlights the new evidence on the metabolic aspects in the adult patients with NAFLD.

The Gut Mucosal Firewall and Functional Medicine

The evidence is strong: Protection and restoration of the intestinal firewall is of primary importance in many patients suffering from a wide range of chronic diseases. The functional medicine approach to evaluation and treatment of problems associated with compromised integrity of the intestinal firewall represents a successful application of the systems biology approach to the management of chronic disease.

Gut Endotoxin Leading to a Decline IN Gonadal function (GELDING) - a novel theory for the development of late onset hypogonadism in obese men

Obesity is an increasing public health problem, with two-thirds of the adult population in many Western countries now being either overweight or obese. Male obesity is associated with late onset hypogonadism, a condition characterised by decreased serum testosterone, sperm quality plus diminished fertility and quality of life. In this paper we propose a novel theory underlying the development of obesity related hypogonadism- the GELDING theory (Gut Endotoxin Leading to a Decline IN Gonadal function). Several observational studies have previously reported an association between obesity related hypogonadism (low testosterone) and systemic inflammation. However, for the first time we postulate that the trans-mucosal passage of bacterial lipopolysaccharide (LPS) from the gut lumen into the circulation is a key inflammatory trigger underlying male hypogonadism. Obesity and a high fat/high calorie diet are both reported to result in changes to gut bacteria and intestinal wall permeability, leading to the passage of bacterial endotoxin (lipopolysaccharide- LPS) from within the gut lumen into the circulation (metabolic endotoxaemia), where it initiates systemic inflammation. Endotoxin is known to reduce testosterone production by the testis, both by direct inhibition of Leydig cell steroidogenic pathways and indirectly by reducing pituitary LH drive, thereby also leading to a decline in sperm production. In this paper we also highlight the novel evolutionary benefits of the GELDING theory. Testosterone is known to be a powerful immune-suppressive, decreasing a man's ability to fight infection. Therefore we postulate that the male reproductive axis has evolved the capacity to lower testosterone production during times of infection and resulting endotoxin exposure, decreasing the immunosuppressive influence of testosterone, in turn enhancing the ability to fight infection. While this response is adaptive in times of sepsis, it becomes maladaptive in the setting of "non-infectious" obesity related metabolic endotoxaemia.

Invited review: Role of bacterial endotoxins in the etiopathogenesis of periparturient diseases of transition dairy cows

The dairy industry continues to suffer severe economic losses due to the increased disease incidence cows experience during the transition period. It has long been the classical view that the major contributing factor to the development of these periparturient diseases is the considerable increase in nutritional demands for milk production. This classical view, however, fails to account for the substantial correlation between both metabolic and infectious diseases and the detrimental effects that can occur with the provision of high-energy diets to support these nutritional demands. Currently, increasing evidence implicates bacterial endotoxins in the etiopathology of most periparturient diseases. Bacterial endotoxins are components of the outer cell wall of gram-negative and gram-positive bacteria that are highly immunostimulatory and can trigger proinflammatory immune responses. The ability of endotoxins to translocate from the mucosal tissues, including the gastrointestinal tract, mammary gland, and uterus, into the systemic circulation has been observed. Once they have entered the circulation, endotoxins potentially contribute to disease either directly, through eliciting an inflammatory response, or indirectly through other factors such as the overreaction of the natural protective mechanisms of the host. Although the evidence implicating a role of endotoxins in the pathogenesis of transition diseases continues to grow, our current knowledge of the host response to mucosal endotoxin exposure and pathogenic mechanisms remain largely unknown. Developing our understanding of the connection between endotoxemia and dairy cattle disease holds significant potential for the future development of preventative measures that could benefit the productivity of the dairy industry as well as animal welfare.

The Pathogenesis of Nonalcoholic Fatty Liver Disease: Interplay between Diet, Gut Microbiota, and Genetic Background

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world, and it comprises a spectrum of hepatic abnormalities from simple hepatic steatosis to steatohepatitis, fibrosis, cirrhosis, and liver cancer. While the pathogenesis of NAFLD remains incompletely understood, a multihit model has been proposed that accommodates causal factors from a variety of sources, including intestinal and adipose proinflammatory stimuli acting on the liver simultaneously. Prior cellular and molecular studies of patient and animal models have characterized several common pathogenic mechanisms of NAFLD, including proinflammation cytokines, lipotoxicity, oxidative stress, and endoplasmic reticulum stress. In recent years, gut microbiota has gained much attention, and dysbiosis is recognized as a crucial factor in NAFLD. Moreover, several genetic variants have been identified through genome-wide association studies, particularly rs738409 (Ile748Met) in PNPLA3 and rs58542926 (Glu167Lys) in TM6SF2, which are critical risk alleles of the disease. Although a high-fat diet and inactive lifestyles are typical risk factors for NAFLD, the interplay between diet, gut microbiota, and genetic background is believed to be more important in the development and progression of NAFLD. This review summarizes the common pathogenic mechanisms, the gut microbiota relevant mechanisms, and the major genetic variants leading to NAFLD and its progression.

Diet, Microbiota, Obesity, and NAFLD: A Dangerous Quartet

Recently, the importance of the gut-liver-adipose tissue axis has become evident. Nonalcoholic fatty liver disease (NAFLD) is the hepatic disease of a systemic metabolic disorder that radiates from energy-surplus induced adiposopathy. The gut microbiota has tremendous influences in our whole-body metabolism, and is crucial for our well-being and health. Microorganisms precede humans in more than 400 million years and our guest flora evolved with us in order to help us face aggressor microorganisms, to help us maximize the energy that can be extracted from nutrients, and to produce essential nutrients/vitamins that we are not equipped to produce. However, our gut microbiota can be disturbed, dysbiota, and become itself a source of stress and injury. Dysbiota may adversely impact metabolism and immune responses favoring obesity and obesity-related disorders such as insulin resistance/diabetes mellitus and NAFLD. In this review, we will summarize the latest evidence of the role of microbiota/dysbiota in diet-induced obesity and NAFLD, as well as the potential therapeutic role of targeting the microbiota in this set.

Consumption of lily bulb modulates fecal ratios of firmicutes and bacteroidetes phyla in rats fed a high-fat diet

It has been recently suggested a high ratio of fecal Firmicutes and reduction in the Bacteroidetes in obese animals. This study investigated the effect of dietary lily bulb (LB) on fecal Firmicutes and Bacteroidetes in rats fed a high-fat (HF) diet. In experiment 1, rats were fed an HF diet with or without 7% raw (R) or steamed (S) LB. In experiment 2, rats were fed the HF diet with or without 7% RLB, 0.9% ethanol extract of LB, or 6.1% ethanol extract residue of LB. In experiment 1, fecal Firmicutes was reduced and Bacteroidetes was increased in both the RLB and SLB groups. In experiment 2, the fecal Firmicutes/Bacteroidetes ratio was not affected by the ethanol extract or ethanol extract residue of LB. These results suggest that LB in its entirety modulates colonic microflora, regardless of heat treatment.

Protective effects of Lactobacillus rhamnosus GG against dyslipidemia in high-fat diet-induced obese mice

Recent reports suggest that gut microbiota can be a major determinant of dyslipidemia and non-alcoholic fatty liver disease (NAFLD) and its modulation by treating probiotics is a valid strategy to exert a protective effect. In this study, high-fat diet (HFD)-fed mice were orally administrated with Lactobacillus rhamnosus GG (LGG) for 13 weeks. Significant reductions in the weights of the liver, mesenteric and subcutaneous adipose tissues were observed in LGG-treated HFD-fed mice compared to LGG-non-treated controls. The serum levels of triglyceride and cholesterol were also significantly reduced in LGG-treated mice. Gut microbial composition analysis showed that shifts in the diversity of dominant gut bacteria were caused by HFD and restored by LGG treatment. A remarkable decrease of hepatic fat content was also observed in LGG-treated mice, accompanied by downregulated expressions of lipogenic and pro-inflammatory genes in the liver. LGG-treated mice had lower expression levels of genes involved in cholesterol synthesis, but conversely, higher expression levels of cholesterol efflux-related genes compared to LGG-non-treated controls. The cholesterol-lowering effect of LGG was also found to be mediated by suppression of FXR and FGF15 signaling, resulting in the upregulation of hepatic CYP7A1. Our findings confirm a therapeutic potential of probiotics for ameliorating dyslipidemia and NAFLD.

Comparative experimental investigation on the efficacy of mono- and multiprobiotic strains in non-alcoholic fatty liver disease prevention

Background

To investigate the efficacy of different probiotic strains, their combinations and forms (alive or lyophilized) in nonalcoholic fatty liver disease (NAFLD) prevention.

Methods

In this study, 70 rats have been used divided into 7 groups of 10 animals in each: I – intact rats, II-VII – rats with monosodium glutamate (MSG)-induced NAFLD. Rats with NAFLD were untreated (group II, MSG-obesity group) and treated with probiotics (groups III–VII). In order to develop NAFLD, newborn rats of groups II–VII were injected with a solution of monosodium glutamate (MSG) (4 mg/g) subcutaneously (s.c.) at 2nd,4th, 6th, 8th,10th postnatal day. The groups III–V received lyophilized monoprobiotics B. animalis VKL, B. animalis VKB, L.casei IMVB-7280, respectively. The group VI received 2.5 ml/kg of an aqueous solution of a mixture of the three probiotic strains (2:1:1 Lactobacillus casei IMVB-7280, Bifidobacterium animalis VKL, Bifidobacterium animalis VKB) at a dose of 50 mg/kg (5 × 10⁹ CFU/kg) (g) (intragastrically). The group VII was treated with multiprobiotic “Symbiter” containing biomass of 14 alive probiotic strains (Lactobacillus + Lactococcus (6 × 10¹⁰ CFU/g), Bifidobacterium (1 × 10¹⁰/g), Propionibacterium (3 × 10¹⁰/g), Acetobacter (1 × 10⁶/g)) at a dose of 140 mg/kg (1.4 × 10¹⁰ CFU/kg). The treatment with probiotics was started at the age of 1 month. There were 3 courses of treatment, each included 2-week administration and 2-week break. All parameters were measured in 4-month aged rats.

Results

Introduction of MSG during the neonatal period leads to the NAFLD development in the 4-months old rats. For steatosis degree there was no significant difference between MSG-obesity group and lyophilized monocomponent probiotics groups (III–V). The highest manifestation of steatosis was observed for B. animalis VKL group (2.0 ± 0.25) as compared to B. animalis VKB (1.70 ± 0.21) and L. casei IMVB-7280 (1.80 ± 0.20). The steatosis score changes between all monoprobiotics groups (III–V) were insignificant. Administration from birth of both alive (VII) and lyophilized (VI) probiotic mixture lead to a significant decrease by 69.5 % (p < 0.001) and 43.5 % (p < 0.025) of steatosis score respectively as compared to the MSG-obesity group (2.3 ± 0.21 %). For both alive and lyophilized probiotic mixtures, reduction of lobular inflammation was observed. These histological data were confirmed by the significant decrease of total lipids and triglycerides content in the liver approximately by 22–25 % in groups treated with probiotic mixtures (VI, VII) compared to the MSG-obesity group.

Conclusion

We established failure of NAFLD prevention with lyophilized monoprobiotic strains and the efficacy of probiotic mixture with the preference of alive probiotic strains.

Probiotics in prevention and treatment of obesity: a critical view

The worldwide prevalence of obesity more than doubled between 1980 and 2014. The obesity pandemic is tightly linked to an increase in energy availability, sedentariness and greater control of ambient temperature that have paralleled the socioeconomic development of the past decades. The most frequent cause which leads to the obesity development is a dysbalance between energy intake and energy expenditure. The gut microbiota as an environmental factor which influence whole-body metabolism by affecting energy balance but also inflammation and gut barrier function, integrate peripheral and central food intake regulatory signals and thereby increase body weight. Probiotics have physiologic functions that contribute to the health of gut microbiota, can affect food intake and appetite, body weight and composition and metabolic functions through gastrointestinal pathways and modulation of the gut bacterial community.

The Role of Probiotics on the Microbiota: Effect on Obesity

The microbiota and the human host maintain a symbiotic association. Nowadays, metagenomic analyses are providing valuable knowledge on the diversity and functionality of the gut microbiota. However, with regard to the definition of a "healthy microbiota" and the characterization of the dysbiosis linked to obesity, there is still not a clear answer. Despite this fact, attempts have been made to counteract obesity through probiotic supplementation. A literature search of experimental studies relevant to the topic was performed in PubMed database with the keywords "probiotic" and "obesity" and restricted to those with "Lactobacillus" or "Bifidobacterium" in the title. So far, evidence of an antiobesity effect of different lactobacilli and bifidobacteria has been mainly obtained from animal models of dietary-induced obesity. Using these experimental models, a substantial number of studies have reported reductions in weight gain and, in particular, fat tissue mass at different locations following administration of bacteria, as compared with controls. Antiatherogenic and anti-inflammatory effects-including regulation of expression of lipogenic and lipolytic genes in the liver, reduction in liver steatosis, improvement of blood lipid profile and glucose tolerance, decreased endotoxemia, and regulation of inflammatory pathways-are also reported in many of them. The number of human studies focused on probiotic administration for obesity management is still very scarce, and it is too soon to judge their potential efficacy, especially when considering the fact that the actions of probiotics are always strain specific and the individual response varies according to intrinsic factors, the overall composition of diet, and their interactions.

Dietary phytic acid prevents fatty liver by reducing expression of hepatic lipogenic enzymes and modulates gut microflora in rats fed a high-sucrose diet

OBJECTIVES

The aim of this study was to investigate the effect of phytic acid (PA) on fatty liver and gut microflora in rats fed a high-sucrose (HSC) diet.

METHODS

Three groups of rats were fed a high-starch (HSR) diet or an HSC diet with or without 1.02% sodium PA for 12 d. We evaluated hepatic weight, total lipids, and triacylglycerol (TG) levels, the activities and expression of hepatic lipogenic enzymes (glucose-6-phosphate dehydrogenase, malic enzyme 1, and fatty acid synthetase), and fecal microflora.

RESULTS

The HSC diet significantly increased hepatic total lipids and TG levels, and the activities and expression of the hepatic lipogenic enzymes compared with the HSR diet. These upregulations were clearly suppressed by dietary PA. Consumption of PA elevated the fecal ratio of Lactobacillus spp. and depressed the ratio of Clostridium cocoides, and suppressed the elevation in the ratio of C. leptum induced by the HSC diet.

CONCLUSION

This work showed that dietary PA ameliorates sucrose-induced fatty liver through reducing the expression of hepatic lipogenesis genes and modulates gut microflora in rats.

Dietary Lactobacillus rhamnosus GG Supplementation Improves the Mucosal Barrier Function in the Intestine of Weaned Piglets Challenged by Porcine Rotavirus

Lactobacillus rhamnosus GG (LGG) has been regarded as a safe probiotic strain. The aim of this study was to investigate whether dietary LGG supplementation could alleviate diarrhea via improving jejunal mucosal barrier function in the weaned piglets challenged by RV, and further analyze the potential roles for apoptosis of jejunal mucosal cells and intestinal microbiota. A total of 24 crossbred barrows weaned at 21 d of age were assigned randomly to 1 of 2 diets: the basal diet and LGG supplementing diet. On day 11, all pigs were orally infused RV or the sterile essential medium. RV infusion increased the diarrhea rate, increased the RV-Ab, NSP4 and IL-2 concentrations and the Bax mRNA levels of jejunal mucosa (P<0.05), decreased the villus height, villus height: crypt depth, the sIgA, IL-4 and mucin 1 concentrations and the ZO-1, occludin and Bcl-2 mRNA levels of jejunal mucosa (P<0.05), and affected the microbiota of ileum and cecum (P<0.05) in the weaned pigs. Dietary LGG supplementation increased the villus height and villus height: crypt depth, the sIgA, IL-4, mucin 1 and mucin 2 concentrations, and the ZO-1, occludin and Bcl-2 mRNA levels of the jejunal mucosa (P<0.05) reduced the Bax mRNA levels of the jejunal mucosa (P<0.05) in weaned pigs. Furthermore, dietary LGG supplementation alleviated the increase of diarrhea rate in the weaned pigs challenged by RV (P<0.05), and relieve the effect of RV infection on the villus height, crypt depth and the villus height: crypt depth of the jejunal mucosa (P<0.05), the NSP4, sIgA, IL-2, IL-4, mucin 1 and mucin 2 concentrations of jejunal mucosa (P<0.05), the ZO-1, occludin, Bax and Bcl-2 mRNA levels of the jejunal mucosa (P<0.05), and the microbiota of ileum and cecum (P<0.05) in the weaned pigs challenged by RV. These results suggest that supplementing LGG in diets alleviated the diarrhea of weaned piglets challenged by RV via inhibiting the virus multiplication and improving the jejunal mucosal barrier function, which was possibly due to the decreasing apoptosis of jejunal mucosal cells and the improvement of intestinal microbiota.

Gut microbiota and non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a common disorder with poorly understood pathogenesis. Beyond environmental and genetic factors, cumulative data support the causative role of gut microbiota in disease development and progression.

DATA SOURCE

We performed a PubMed literature search with the following key words: "non-alcoholic fatty liver disease", "non-alcoholic steatohepatitis", "fatty liver", "gut microbiota" and "microbiome", to review the data implicating gut microbiota in NAFLD development and progression.

RESULTS

Recent metagenomic studies revealed differences in the phylum and genus levels between patients with fatty liver and healthy controls. While bacteroidetes and firmicutes remain the dominant phyla among NAFLD patients, their proportional abundance and genera detection vary among different studies. New techniques indicate a correlation between the methanogenic archaeon (methanobrevibacter smithii) and obesity, while the bacterium akkermanshia municiphila protects against metabolic syndrome. Among NAFLD patients, small intestinal bacterial overgrowth detected by breath tests might induce gut microbiota and host interactions, facilitating disease development.

CONCLUSIONS

There is evidence that gut microbiota participates in NAFLD development through, among others, obesity induction, endogenous ethanol production, inflammatory response triggering and alterations in choline metabolism. Further studies with emerging techniques are needed to further elucidate the microbiome and host crosstalk in NAFLD pathogenesis.

Anthocyanins as inflammatory modulators and the role of the gut microbiota

The health benefits of consuming fruits that are rich in polyphenols, especially anthocyanins, have been the focus of recent in vitro and in vivo investigations. Thus, greater attention is being directed to the reduction of the inflammatory process associated with the intestinal microbiota and the mechanism underlying these effects because the microbiota has been closely associated with the metabolism of these compounds in the gastrointestinal tract. Further interest lies in the ability of these metabolites to modulate the growth of specific intestinal bacteria. Thus, this review examines studies involving the action of the anthocyanins that are present in many fruits and their effect in the modulating the inflammatory process associated with the interaction between the host and the gut microbiota. The findings of both in vitro and in vivo studies suggest a potential antiinflammatory effect of these compounds, which seem to inhibit activation of the signaling pathway mediated by the transcription factor NFκB. This effect is associated with modulation of a beneficial gut microbiota, particularly an increase in Bifidobacterium strains.

Relevant Aspects of Nutritional and Dietary Interventions in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the main cause of liver disease worldwide. NAFLD is linked to circumstances such as type 2 diabetes, insulin resistance, obesity, hyperlipidemia, and hypertension. Since the obesity figures and related comorbidities are increasing, NAFLD has turned into a liver problem that has become progressively more common. Currently, there is no effective drug therapy for NAFLD; therefore, interventions in lifestyles remain the first line of treatment. Bearing in mind that adherence rates to this type of treatment are poor, great efforts are currently focused on finding novel therapeutic agents for the prevention in the development of hepatic steatosis and its progression to nonalcoholic steatohepatitis and cirrhosis. This review presents a compilation of the scientific evidence found in the last years showing the results of interventions in lifestyle, diet, and behavioral therapies and research results in human, animal and cell models. Possible therapeutic agents ranging from supplementation with vitamins, amino acids, prebiotics, probiotics, symbiotics, polyunsaturated fatty acids and polyphenols to interventions with medicinal plants are analyzed.

Co-Administration of Cholesterol-Lowering Probiotics and Anthraquinone from Cassia obtusifolia L. Ameliorate Non-Alcoholic Fatty Liver

Non-alcoholic fatty liver disease (NAFLD) has become a common liver disease in recent decades. No effective treatment is currently available. Probiotics and natural functional food may be promising therapeutic approaches to this disease. The present study aims to investigate the efficiency of the anthraquinone from Cassia obtusifolia L. (AC) together with cholesterol-lowering probiotics (P) to improve high-fat diet (HFD)-induced NAFLD in rat models and elucidate the underlying mechanism. Cholesterol-lowering probiotics were screened out by MRS-cholesterol broth with ammonium ferric sulfate method. Male Sprague-Dawley rats were fed with HFD and subsequently administered with AC and/or P. Lipid metabolism parameters and fat synthesis related genes in rat liver, as well as the diversity of gut microbiota were evaluated. The results demonstrated that, compared with the NAFLD rat, the serum lipid levels of treated rats were reduced effectively. Besides, cholesterol 7α-hydroxylase (CYP7A1), low density lipoprotein receptor (LDL-R) and farnesoid X receptor (FXR) were up-regulated while the expression of 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMGCR) was reduced. The expression of peroxisome proliferator activated receptor (PPAR)-α protein was significantly increased while the expression of PPAR-γ and sterol regulatory element binding protein-1c (SREBP-1c) was down-regulated. In addition, compared with HFD group, in AC, P and AC+P group, the expression of intestinal tight-junction protein occludin and zonula occluden-1 (ZO-1) were up-regulated. Furthermore, altered gut microbiota diversity after the treatment of probiotics and AC were analysed. The combination of cholesterol-lowering probiotics and AC possesses a therapeutic effect on NAFLD in rats by up-regulating CYP7A1, LDL-R, FXR mRNA and PPAR-α protein produced in the process of fat metabolism while down-regulating the expression of HMGCR, PPAR-γ and SREBP-1c, and through normalizing the intestinal dysbiosis and improving the intestinal mucosal barrier function.

Mitochondrial dysfunction and tissue injury by alcohol, high fat, nonalcoholic substances and pathological conditions through post-translational protein modifications

Mitochondria are critically important in providing cellular energy ATP as well as their involvement in anti-oxidant defense, fat oxidation, intermediary metabolism and cell death processes. It is well-established that mitochondrial functions are suppressed when living cells or organisms are exposed to potentially toxic agents including alcohol, high fat diets, smoking and certain drugs or in many pathophysiological states through increased levels of oxidative/nitrative stress. Under elevated nitroxidative stress, cellular macromolecules proteins, DNA, and lipids can undergo different oxidative modifications, leading to disruption of their normal, sometimes critical, physiological functions. Recent reports also indicated that many mitochondrial proteins are modified via various post-translation modifications (PTMs) and primarily inactivated. Because of the recently-emerging information, in this review, we specifically focus on the mechanisms and roles of five major PTMs (namely oxidation, nitration, phosphorylation, acetylation, and adduct formation with lipid-peroxides, reactive metabolites, or advanced glycation end products) in experimental models of alcoholic and nonalcoholic fatty liver disease as well as acute hepatic injury caused by toxic compounds. We also highlight the role of the ethanol-inducible cytochrome P450-2E1 (CYP2E1) in some of these PTM changes. Finally, we discuss translational research opportunities with natural and/or synthetic anti-oxidants, which can prevent or delay the onset of mitochondrial dysfunction, fat accumulation and tissue injury.

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Hepatotoxic agents including alcohol and high fat elevate nitroxidative stress.

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Increased nitroxidative stress promotes post-translational protein modifications.

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Post-translational protein modifications of many proteins lead to their inactivation.

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Inactivation of mitochondrial proteins contributes to mitochondrial dysfunction.

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Mitochondrial dysfunction contributes to necrotic or apoptotic tissue injury.

Probiotics as Complementary Treatment for Metabolic Disorders

Over the past decade, growing evidence has established the gut microbiota as one of the most important determinants of metabolic disorders such as obesity and type 2 diabetes. Indeed, obesogenic diet can drastically alter bacterial populations (i.e., dysbiosis) leading to activation of pro-inflammatory mechanisms and metabolic endotoxemia, therefore promoting insulin resistance and cardiometabolic disorders. To counteract these deleterious effects, probiotic strains have been developed with the aim of reshaping the microbiome to improve gut health. In this review, we focus on benefits of widely used probiotics describing their potential mechanisms of action, especially their ability to decrease metabolic endotoxemia by restoring the disrupted intestinal mucosal barrier. We also discuss the perspective of using new bacterial strains such as butyrate-producing bacteria and the mucolytic Akkermansia muciniphila, as well as the use of prebiotics to enhance the functionality of probiotics. Finally, this review introduces the notion of genetically engineered bacterial strains specifically developed to deliver anti-inflammatory molecules to the gut.

Lactobacillus plantarum NCU116 improves liver function, oxidative stress and lipid metabolism in rats with high fat diet induced non-alcoholic fatty liver disease

The effect of Lactobacillus plantarum NCU116 on liver function, oxidative stress and lipid metabolism in rats with high fat diet induced non-alcoholic fatty liver disease (NAFLD) was studied. The rats were divided into four groups: the normal diet (ND) group; the high fat diet (HFD) group; and HFD plus L. plantarum NCU116 as two doses (NCU116-L, 10(8) CFU mL(-1); NCU116-H, 10(9) CFU mL(-1)) groups. Treatment of L. plantarum NCU116 for 5 weeks was found to restore liver function and oxidative stress in rats with NAFLD, and decrease the levels of fat accumulation in the liver. In addition, the bacterium significantly reduced endotoxin and proinflammatory cytokines, and regulated bacterial flora in the colon and the expression of lipid metabolism in the liver. These results suggest that possible underlying mechanisms for the beneficial effect of L. plantarum NCU116 on NAFLD may include two pathways of downregulating lipogenesis and upregulating lipolysis and fatty acid oxidation related gene expression.

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.

The Influence of the Gut Microbiome on Obesity, Metabolic Syndrome and Gastrointestinal Disease

There is a fine balance in the mutual relationship between the intestinal microbiota and its mammalian host. It is thought that disruptions in this fine balance contribute/account for the pathogenesis of many diseases. Recently, the significance of the relationship between gut microbiota and its mammalian host in the pathogenesis of obesity and the metabolic syndrome has been demonstrated. Emerging data has linked intestinal dysbiosis to several gastrointestinal diseases including inflammatory bowel disease, irritable bowel syndrome, nonalcoholic fatty liver disease, and gastrointestinal malignancy. This article is intended to review the role of gut microbiota maintenance/alterations of gut microbiota as a significant factor as a significant factor discriminating between health and common diseases. Based on current available data, the role of microbial manipulation in disease management remains to be further defined and a focus for further clinical investigation.

Gut Microbiota: Association with NAFLD and Metabolic Disturbances

Nonalcoholic fatty liver disease is the hepatic expression of metabolic syndrome, being frequently associated with obesity, insulin resistance, and dyslipidemia. Recent lines of evidence have demonstrated a role of gut microbiota in insulin resistance, obesity, and associated metabolic disturbances, raising the interest in its relationship with NAFLD pathogenesis. Therefore, intestinal microbiota has emerged as a potential factor involved in NAFLD, through different pathways, including its influence in energy storage, lipid and choline metabolism, ethanol production, immune balance, and inflammation. The main objective of this review is to address the pathogenic association of gut microbiota to NAFLD. This comprehension may allow the development of integrated strategies to modulate intestinal microbiota in order to treat NAFLD.

Role of diet on non-alcoholic fatty liver disease: An updated narrative review

The purpose of this article review is to update what is known about the role of diet on non-alcoholic fatty liver disease (NAFLD). NAFLD is the most common cause of chronic liver disease in the developed world and is considered to be a spectrum, ranging from fatty infiltration of the liver alone (steatosis), which may lead to fatty infiltration with inflammation known as non alcoholic steatohepatitis While the majority of individuals with risk factors like obesity and insulin resistance have steatosis, only few people may develop steatohepatitis. Current treatment relies on weight loss and exercise, although various insulin-sensitizing medications appear promising. Weight loss alone by dietary changes has been shown to lead to histological improvement in fatty liver making nutrition therapy to become a cornerstone of treatment for NAFLD. Supplementation of vitamin E, C and omega 3 fatty acids are under consideration with some conflicting data. Moreover, research has been showed that saturated fat, trans-fatty acid, carbohydrate, and simple sugars (fructose and sucrose) may play significant role in the intrahepatic fat accumulation. However, true associations with specific nutrients yet to be clarified.

Gut microbiome, gut function, and probiotics: Implications for health

New insights from a rapidly developing field of research have ushered in a new era of understanding of the complexity of host-microbe interactions within the human body. The paradigm shift from culturing to metagenomics has provided an insight into the complex diversity of the microbial species that we harbor, revealing the fact that we are in fact more microbes than human cells. The largest consortium of these microbes resides in the gut and is called the gut microbiota. This new science has expanded the ability to document shifts in microbial populations to an unparalleled degree. It is now understood that signals from the microbiota provide trophic, nutritional, metabolic, and protective effects for the development and maintenance of the host digestive, immune, and neuroendocrine system. Evidence linking changes in the gut microbiota to gastrointestinal and extraintestinal disorders like irritable bowel syndrome, inflammatory bowel disease, obesity, diabetes, and celiac disease have begun to emerge recently. Probiotics act through diverse mechanisms positively affecting the composition and/or function of the commensal microbiota and alter host immunological responses. Well-controlled intervention trials, systematic reviews, and meta-analysis provide convincing evidence for the benefit of probiotics in prevention and treatment of gastrointestinal as well as extraintestinal disorders.

Effect of Lactobacillus plantarum Strain K21 on High-Fat Diet-Fed Obese Mice

Recent studies have demonstrated beneficial effects of specific probiotics on alleviating obesity-related disorders. Here we aimed to identify probiotics with potential antiobesity activity among 88 lactic acid bacterial strains via in vitro screening assays, and a Lactobacillus plantarum strain K21 was found to harbor abilities required for hydrolyzing bile salt, reducing cholesterol, and inhibiting the accumulation of lipid in 3T3-L1 preadipocytes. Furthermore, effects of K21 on diet-induced obese (DIO) mice were examined. Male C57Bl/6J mice received a normal diet, high-fat diet (HFD), or HFD with K21 administration (10⁹ CFU in 0.2 mL PBS/day) for eight weeks. Supplementation of K21, but not placebo, appeared to alleviate body weight gain and epididymal fat mass accumulation, reduce plasma leptin levels, decrease cholesterol and triglyceride levels, and mitigate liver damage in DIO mice. Moreover, the hepatic expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) related to adipogenesis was significantly downregulated in DIO mice by K21 intervention. We also found that K21 supplementation strengthens intestinal permeability and modulates the amount of Lactobacillus spp., Bifidobacterium spp., and Clostridium perfringens in the cecal contents of DIO mice. In conclusion, our results suggest that dietary intake of K21 protects against the onset of HFD-induced obesity through multiple mechanisms of action.