Intestinal microbiota and obesity

Metabolic Syndrome: A Narrative Review from the Oxidative Stress to the Management of Related Diseases

Metabolic syndrome (MS) is a growing disorder affecting thousands of people worldwide, especially in industrialised countries, increasing mortality. Oxidative stress, hyperglycaemia, insulin resistance, inflammation, dysbiosis, abdominal obesity, atherogenic dyslipidaemia and hypertension are important factors linked to MS clusters of different pathologies, such as diabesity, cardiovascular diseases and neurological disorders. All biochemical changes observed in MS, such as dysregulation in the glucose and lipid metabolism, immune response, endothelial cell function and intestinal microbiota, promote pathological bridges between metabolic syndrome, diabesity and cardiovascular and neurodegenerative disorders. This review aims to summarise metabolic syndrome's involvement in diabesity and highlight the link between MS and cardiovascular and neurological diseases. A better understanding of MS could promote a novel strategic approach to reduce MS comorbidities.

The Muscle-Gut-Brain Axis and Psychiatric Illness

The microbiota-gut-brain axis (MGBA) has been the subject of much research over the past decade, offering an exciting new paradigm for the treatment of psychiatric disorders. In this review, the MGBA is extended to include skeletal muscle and the potential role of an expanded "muscle-gut-brain axis" (MuGBA) in conditions such as anxiety and depression is discussed. There is evidence, from both preclinical and human studies, of bidirectional links between the gut microbiome and skeletal muscle function and structure. The therapeutic role of exercise in reducing depressive and anxiety symptoms is widely recognised, and the potential role of the gut microbiota-skeletal muscle link is discussed within this context. Potential pathways of communication involved in the MuGBA including the tryptophan-kynurenine pathway, intestinal permeability, immune modulation, and bacterial metabolites such as short-chain-fatty-acids are explored.

Gut-brain axis through the lens of gut microbiota and their relationships with Alzheimer's disease pathology: Review and recommendations

Alzheimer's disease (AD) is a neurodegenerative disorder that affects millions of people worldwide. Growing evidence suggests that the gut microbiome (GM) plays a pivotal role in the pathogenesis of AD through the microbiota-gut-brain axis (MGB). Alterations in GM composition and diversity have been observed in both animal models and in human patients with AD. GM dysbiosis has been implicated in increased intestinal permeability, blood-brain barrier (BBB) impairment, neuroinflammation and the development of hallmarks of AD. Further elucidation of the role of GM in AD could pave way for the development of holistic predictive methods for determining AD risk and progression of disease. Furthermore, accumulating evidence suggests that GM modulation could alleviate adverse symptoms of AD or serve as a preventive measure. In addition, increasing evidence shows that Type 2 Diabetes Mellitus (T2DM) is often comorbid with AD, with common GM alterations and inflammatory response, which could chart the development of GM-related treatment interventions for both diseases. We conclude by exploring the therapeutic potential of GM in alleviating symptoms of AD and in reducing risk. Furthermore, we also propose future directions in AD research, namely fecal microbiota transplantation (FMT) and precision medicine.

Lactic acid bacteria: prominent player in the fight against human pathogens

INTRODUCTION

The human microbiome is a unique repository of diverse bacteria. Over 1000 microbial species reside in the human gut, which predominantly influences the host's internal environment and plays a significant role in host health. Lactic acid bacteria have long been employed for multiple purposes, ranging from food to medicines. Lactobacilli, which are often used in commercial food fermentation, have improved to the point that they might be helpful in medical applications.

AREAS COVERED

This review summarises various clinical and experimental evidence on efficacy of lactobacilli in treating a wide range of infections. Both laboratory based and clinical studies have been discussed.

EXPERT OPINION

Lactobacilli are widely accepted as safe biological treatments and host immune modulators (GRAS- Generally regarded as safe) by the US Food and Drug Administration and Qualified Presumption of Safety. Understanding the molecular mechanisms of lactobacilli in the treatment and pathogenicity of bacterial infections can help with the prediction and development of innovative therapeutics aimed at pathogens which have gained resistance to antimicrobials. To formulate effective lactobacilli based therapy significant research on the effectiveness of different lactobacilli strains and its association with demographic distribution is required. Also, the side effects of such therapy needs to be evaluated.

SGLT-2 inhibitors and GLP-1 receptor agonists in metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic condition that affects nearly one billion people globally, characterized by triacylglycerol accumulation in the liver as a consequence of metabolic abnormalities (obesity and impaired glucose regulation). Low-grade inflammation, oxidative stress, mitochondrial dysfunction, and dysbiosis in gut microbiota are involved in the etiology of MAFLD, and both cardiovascular events and hepatic complications are the long-term consequences. In the absence of approved therapies for this condition, sodium-glucose cotransporter 2 inhibitors (SGLT-2 Is) and glucagon-like peptide 1 receptor agonists (GLP-1 RAs) have the specific advantage of lowering body weight and providing cardiovascular benefits. Here, we discuss potential roles for SGLT-2 Is and GLP-1 RAs in the prevention and treatment of intrahepatic triacylglycerol accumulation and associated inflammation and/or fibrosis.

Probiotic Supplements: Their Strategies in the Therapeutic and Prophylactic of Human Life-Threatening Diseases

Chronic diseases and viral infections have threatened human life over the ages and constitute the main reason for increasing death globally. The rising burden of these diseases extends to negatively affecting the economy and trading globally, as well as daily life, which requires inexpensive, novel, and safe therapeutics. Therefore, scientists have paid close attention to probiotics as safe remedies to combat these morbidities owing to their health benefits and biotherapeutic effects. Probiotics have been broadly adopted as functional foods, nutraceuticals, and food supplements to improve human health and prevent some morbidity. Intriguingly, recent research indicates that probiotics are a promising solution for treating and prophylactic against certain dangerous diseases. Probiotics could also be associated with their essential role in animating the immune system to fight COVID-19 infection. This comprehensive review concentrates on the newest literature on probiotics and their metabolism in treating life-threatening diseases, including immune disorders, pathogens, inflammatory and allergic diseases, cancer, cardiovascular disease, gastrointestinal dysfunctions, and COVID-19 infection. The recent information in this report will particularly furnish a platform for emerging novel probiotics-based therapeutics as cheap and safe, encouraging researchers and stakeholders to develop innovative treatments based on probiotics to prevent and treat chronic and viral diseases.

Enteral nutrition modulation with n-3 PUFAs directs microbiome and lipid metabolism in mice

Nutritional support using exclusive enteral nutrition (EEN) has been studied as primary therapy for the management of liver diseases, Crohn’s disease, and cancers. EEN can also increase the number of beneficial microbiotas in the gut, improve bile acid and lipid metabolism, and decrease the number of harmful dietary micro-particles, possibly by influencing disease occurrence and increasing immunity. This study investigated the effects of EEN-n-3 polyunsaturated fatty acids (3PUFAs) (EEN-3PUFAs) on the gut microbiome, intestinal barrier, and lipid or bile acid metabolism in mice. Metagenomic sequencing technology was used to analyze the effects of EEN-3PUFAs on the composition of gut microbiome signatures. The contents of short-chain fatty acids (SCFAs) and bile acids in the feces and liver of the mice were assayed by gas chromatography and ultra-high-pressure liquid chromatography/high-resolution tandem mass spectrometry, respectively. The levels of lipopolysaccharide (LPS) and D-lactic acid in the blood were used to assess intestinal permeability. The results indicated that EEN-3PUFAs could improve the composition of gut microbiome signatures and increase the abundance of Barnesiella and Lactobacillus (genus), Porphyromonadaceae, and Bacteroidia (species), and Bacteroidetes (phylum) after EEN-3PUFAs initiation. In addition, EEN-3PUFAs induced the formation of SCFAs (mainly including acetic acid, propionic acid, and butyric acid) and increased the intestinal wall compared to the control group. In conclusion, EEN-3PUFAs modulate the alterations in gut microbiome signatures, enhanced intestinal barrier, and regulated the fatty acid composition and lipid metabolism shifts and the putative mechanisms underlying these effects.

Ginsenoside Rk3 Ameliorates Obesity-Induced Colitis by Regulating of Intestinal Flora and the TLR4/NF-κB Signaling Pathway in C57BL/6 Mice

Obesity-induced colonic inflammation-stimulated colitis is one of the main causes of colorectal cancer. Dietary phytochemicals are considered to be an effective strategy for relieving obesity-induced inflammatory diseases such as diabetes and colitis. Ginsenoside Rk3 (Rk3) is the main bioactive component of ginseng. Our previous study has demonstrated that Rk3 can effectively alleviate obesity-induced type 2 diabetes, but whether it plays a beneficial role in obesity-induced colitis remains poorly understood. Here, we found that Rk3 intervention repaired the intestinal barrier dysfunction by increasing the expression of the tight junction proteins (zonula occludens-1, claudin, and occludin), and reduced colonic inflammatory cytokine levels, oxidative stress, and macrophage infiltration in high-fat diet-induced mice. Importantly, Rk3 effectively ameliorated the metabolic dysbiosis of intestinal flora with significantly decreased Firmicute/Bacteroidete ratios and suppressed the inflammatory cascade by inhibiting the TLR4/NF-κB signaling pathway. Taken together, our findings indicate that Rk3 can be used as a potential natural anti-inflammatory agent to reduce chronic obesity-induced colitis.

Antiobesity and antidiabetic effects of the dairy bacterium Propionibacterium freudenreichii MJ2 in high-fat diet-induced obese mice by modulating lipid metabolism

Obesity can cause chronic metabolic disorders such as type 2 diabetes, hyperlipidemia, and nonalcoholic fatty liver diseases. The aim of this study was to investigate the antiobesity and antidiabetic effects of the dairy bacterium P. freudenreichii MJ2 isolated from raw milk using 3T3-L1 cells and high-fat diet (HFD)-induced obese mice. Lipid accumulation and the expression levels of genes related to lipid metabolism, such as preadipocytic gene (Pref-1), adipogenic genes (PPARγ and C/EBPα), and lipogenic genes (FAS, SCD-1, and ACC), significantly decreased in heat-killed P. freudenreichii MJ2 (hkMJ2)-treated adipocytes. Live P. freudenreichii MJ2 (MJ2), hkMJ2, and Lactobacillus plantarum (LP) decreased body weight gain in HFD-induced obese mice compared with the model group. The liver and epididymal white adipose tissue weights in the MJ2-, hkMJ2- and LP-treated groups were significantly lower than those in the model group. The expression levels of genes and proteins related to adipogenesis and lipogenesis significantly decreased and lipolysis (HSL and ATGL) increased in the MJ2-, hkMJ2-, and LP-treated groups. The expression levels of genes related to fatty acid β-oxidation (CPT-1α and ACOX1) increased in the MJ2-, hkMJ2-, and LP-treated groups. In addition, blood glucose and fasting insulin levels in the MJ2- and hkMJ2-treated groups decreased compared with those in the model group. P. freudenreichii MJ2 ameliorate insulin resistance by obesity. In conclusion, both MJ2 and hkMJ2 alleviate obesity and metabolic syndrome.

The protective effects of melatonin on survival, immune response, digestive enzymes activities and intestinal microbiota diversity in Chinese mitten crab (Eriocheir sinensis) exposed to glyphosate

Glyphosate is one of the most widely used pesticides, which can cause toxicity to aquatic animals. In this study, the survival rate, immune response, digestive enzyme activities, and the intestinal microbiota diversity of Chinese mitten crab (Eriocheir sinensis) were evaluated after 14 days of exposure to glyphosate (48.945 mg/L from 50% 96 h LC50 value) and melatonin feeding (80 mg/kg). The results showed that MT significantly improved the survival rate, antibacterial capacity of E. sinensis (P < 0.05). After exposure to glyphosate, the expression of Hsp60, Hsp70 and Hsp90 in cranial ganglia and thoracic ganglia was decreased significantly, but MT significantly raised the expression of these proteins (P < 0.05). Glyphosate significantly decreased lipase activity compared with the control group (P < 0.05), while melatonin significantly increased the lipase, amylase and trypsin activities (P < 0.05). Melatonin significantly increased the Chao1 and Shannon index and the relative abundance of Proteobacteria and Bacteroidetes (P < 0.05). This study shows that melatonin has a protective effect on the glyphosate exposed E. sinensis.

Microbiota Transplant in the Treatment of Obesity and Diabetes: Current and Future Perspectives

A wealth of evidence has revealed the critical role of the gut microbiota in health and disease. Many chronic diseases have been associated with gut microbiota imbalance in its composition, diversity and functional capacity. Several types of interventions have been shown to correct microbiota imbalance and restore the beneficial metabolic outcomes of a normal microbiota. Among them, fecal microbiota transplantation (FMT) is an emergent, promising technology employed to improve clinical outcomes of various pathological conditions through modifications in the gut microbiota composition. FMT has been used successfully as a treatment option in recurrent Clostridium difficile infection, a condition characterized by severe gut microbiota dysbiosis. However, the potential usage of FMT in other microbiota-associated conditions different from C. difficile such as metabolic syndrome or obesity that are also marked by gut dysbiosis is still under investigation. Furthermore, the contribution of the gut microbiota as a cause or consequence in metabolic disease is still largely debated. This review provides critical information on the methodological approaches of FMT and its technological innovation in clinical applications. This review sheds light on the current findings and gaps in our understanding of how FMT can be used as a future biotherapeutic to restore microbial homeostasis in amelioration of obesity and diabetes.

Gut microbiota and diabetes: From correlation to causality and mechanism

In this review, we summarize the recent microbiome studies related to diabetes disease and discuss the key findings that show the early emerging potential causal roles for diabetes. On a global scale, diabetes causes a significant negative impact to the health status of human populations. This review covers type 1 diabetes and type 2 diabetes. We examine promising studies which lead to a better understanding of the potential mechanism of microbiota in diabetes diseases. It appears that the human oral and gut microbiota are deeply interdigitated with diabetes. It is that simple. Recent studies of the human microbiome are capturing the attention of scientists and healthcare practitioners worldwide by focusing on the interplay of gut microbiome and diabetes. These studies focus on the role and the potential impact of intestinal microflora in diabetes. We paint a clear picture of how strongly microbes are linked and associated, both positively and negatively, with the fundamental and essential parts of diabetes in humans. The microflora seems to have an endless capacity to impact and transform diabetes. We conclude that there is clear and growing evidence of a close relationship between the microbiota and diabetes and this is worthy of future investments and research efforts.

Leptin improves intestinal flora dysfunction in mice with high-fat diet-induced obesity

OBJECTIVE

This study investigated the effects of leptin on intestinal flora and inflammation in mice with high-fat diet (HFD)-induced obesity.

METHODS

Mice were fed an HFD for 8 weeks; some were concurrently administered oral leptin for 4 weeks. Pathological changes in adipose tissue were detected using hematoxylin-eosin staining; endotoxin content in adipose tissue was measured by enzyme-linked immunosorbent assay. Intestinal flora were characterized by 16S bacterial rDNA sequencing. Levels of Toll-like receptor 4 (TLR4), nuclear factor-κB inhibitor α (IκB-α), and phosphorylated c-Jun N-terminal kinase (p-JNK) were detected by western blotting.

RESULTS

Mice in the HFD group exhibited weight gain, elevated endotoxin content, and adipocyte hypertrophy, compared with the non-obese control group. Moreover, abundance of bacteria in the Bacteroides genus and community diversity were both reduced in the HFD group; reductions also were observed at corresponding phylum, class, and order levels. Levels of TLR4, IκB-α, and p-JNK were also elevated in the HFD group. Compared with the model group, leptin administration reduced the weight gain and endotoxin content, while increasing Bacteroides abundance and community diversity; it also reduced the levels of TLR4, IκB-α, and p-JNK.

CONCLUSION

Leptin administration improved intestinal flora dysfunction and inflammation in mice with HFD-induced obesity.

Gut Microbiota, Its Role in Induction of Alzheimer's Disease Pathology, and Possible Therapeutic Interventions: Special Focus on Anthocyanins

The human gut is a safe environment for several microbes that are symbiotic and important for the wellbeing of human health. However, studies on gut microbiota in different animals have suggested that changes in the composition and structure of these microbes may promote gut inflammation by releasing inflammatory cytokines and lipopolysaccharides, gut-wall leakage, and may affect systemic inflammatory and immune mechanisms that are important for the normal functioning of the body. There are many factors that aid in the gut’s dysbiosis and neuroinflammation, including high stress levels, lack of sleep, fatty and processed foods, and the prolonged use of antibiotics. These neurotoxic mechanisms of dysbiosis may increase susceptibility to Alzheimer’s disease (AD) and other neurodegenerative conditions. Therefore, studies have recently been conducted to tackle AD-like conditions by specifically targeting gut microbes that need further elucidation. It was suggested that gut dyshomeostasis may be regulated by using available options, including the use of flavonoids such as anthocyanins, and restriction of the use of high-fatty-acid-containing food. In this review, we summarize the gut microbiota, factors promoting it, and possible therapeutic interventions especially focused on the therapeutic potential of natural dietary polyflavonoid anthocyanins. Our study strongly suggests that gut dysbiosis and systemic inflammation are critically involved in the development of neurodegenerative disorders, and the natural intake of these flavonoids may provide new therapeutic opportunities for preclinical or clinical studies.

Changes in Intestinal Microbiota Are Associated with Islet Function in a Mouse Model of Dietary Vitamin A Deficiency

AIMS

The underlying mechanisms involved in Vitamin A- (VA-) related changes in glucose metabolic disorders remain unclear. Recent evidence suggests that intestinal microbiota is closely linked to the metabolic syndrome. Here, we explored whether and how intestinal microbiota affects glucose homeostasis in VA-deficient diet-fed mice.

METHODS

Six-week-old male C57BL/6 mice were randomly placed on either a VA-sufficient (VAS) or VA-deficient (VAD) diet for 10 weeks. Subsequently, a subclass of the VAD diet-fed mice was switched to a VA-deficient rescued (VADR) diet for an additional 8 weeks. The glucose metabolic phenotypes of the mice were assessed using glucose tolerance tests and immunohistochemistry staining. Changes in intestinal microbiota were assessed using 16S gene sequencing. The intestinal morphology, intestinal permeability, and inflammatory response activation signaling pathway were assessed using histological staining, western blots, quantitative-PCR, and enzyme-linked immunosorbent assays.

RESULTS

VAD diet-fed mice displayed reduction of tissue VA levels, increased area under the curve (AUC) of glucose challenge, reduced glucose-stimulated insulin secretion, and loss of β cell mass. Redundancy analysis showed intestinal microbiota diversity was significantly associated with AUC of glucose challenge and β cell mass. Redundancy analysis showed intestinal microbiota diversity was significantly associated with AUC of glucose challenge and κB signaling pathway activation. Reintroduction of dietary VA to VAD diet-fed mice restored tissue VA levels, endocrine hormone profiles, and inflammatory response, which are similar to those observed following VAS-controlled changes in intestinal microbiota.

CONCLUSIONS

We found intestinal microbiota effect islet function via controlling intestinal inflammatory phenotype in VAD diet-fed mice. Intestinal microbiota influences could be considered as an additional mechanism for the effect of endocrine function in a VAD diet-driven mouse model.

Changes in Intestinal Microbiota of Type 2 Diabetes in Mice in Response to Dietary Supplementation With Instant Tea or Matcha

OBJECTIVE

Gut microbiota plays a key role in metabolism and health in diabetes patients with gastrointestinal microbiota dysbiosis. Thus, regulating the ecological balance of gut microbiota may provide a pathway toward improvement for these patients. Our previous study showed that functional ingredients in tea may inhibit cornstarch digestion in vitro.

METHODS

A cornstarch-tea diet was developed, and in this study we investigated the effects of such a diet on blood glucose and gut microbiota in diabetic mice.

RESULTS

Diabetes resulted in significant weight loss, hyperphagia and hyperglycemia. 16S rDNA sequencing revealed that in diabetes there is significantly increased Bacteroidaceae, Helicobacteraceae, Ruminococcaceae, Enterobacteriaceae, Rikenellaceae and Saccharibacteria_genera_incertae_sedis, and significantly decreased Lactobacillaceae, Prevotellaceae, Coriobacteriaceae, Verrucomicrobiaceae and Bifidobacteriaceae. The cornstarch‒tea diet resulted in a trend toward reduced blood glucose, with particularly increased levels of Coriobacteriaceae, Lactobacillaceae, Prevotellaceae and Bifidobacteriaceae, and decreased Bacteroidaceae, Ruminococcaceae, Helicobacteraceae and Enterobacteriaceae.

CONCLUSIONS

Instant tea and matcha supplementation had beneficial effects on regulation of blood glucose and gut microbiota, reversing the changes in microbiota caused by alloxan injection. The cornstarch‒tea regulation pathway is involved in bacterium group regulation rather than single-species regulation, which suggests that cornstarch combined with tea may be used as a functional food supplement for diabetes patients.

Crosstalk between nonalcoholic fatty liver disease and cardiometabolic syndrome

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition characterized by fat accumulation combined with low-grade inflammation in the liver. A large body of clinical and experimental data shows that increased flux of free fatty acids from increased visceral adipose tissue and de novo lipogenesis can lead to NAFLD and insulin resistance. Thus, individuals with obesity, insulin resistance, and dyslipidaemia are at the greatest risk of developing NAFLD. Conversely, NAFLD is a phenotype of cardiometabolic syndrome. Notably, researchers have discovered a close association between NAFLD and impaired glucose metabolism and focused on the role of NAFLD in the development of type 2 diabetes. Moreover, recent studies provide substantial evidence for an association between NAFLD and atherosclerosis and cardiometabolic disorders. Even if NAFLD can progress into severe liver disorders including nonalcoholic steatohepatitis (NASH) and cirrhosis, the majority of subjects with NAFLD die from cardiovascular disease eventually. In this review, we propose a potential pathological link between NAFLD/NASH and cardiometabolic syndrome. The potential factors that can play a pivotal role in this link, such as inflammation, insulin resistance, alteration in lipid metabolism, oxidative stress, genetic predisposition, and gut microbiota are discussed.

Effects of deoxynivalenol-feed contamination on circulating LPS in pigs

Low concentration of LPS can be detected in healthy mammals without triggering systemic inflammation. Here we analysed the influence of the mycotoxin deoxynivalenol (DON) on very low LPS concentrations and the role of DON in the physiology of pigs challenged with high artificial LPS dosage mimicking septic shock. Pigs were fed for 29 d with DON-contaminated (4.59 mg/kg feed) or control feed. Samples of control animals showed 6.6 ± 13.5 pg/ml LPS in portal and 3.1 ± 7.6 pg/ml LPS in jugular serum samples. In the DON fed group, 3.4 ± 7.2 pg/ml and 0.6 ± 0.8 pg/ml were detected. The differences were statistically not significant, indicating that DON is not a trigger for enhanced LPS transfer into the blood circulation. Next, pigs were challenged with 7.5 µg LPS/kg body mass via portal or jugular route. The application route did not significantly influence the LPS concentration. We expected higher circulating LPS concentrations in the presence of DON due to the additional stress of liver metabolism and reduced liver capacity to remove LPS from circulation. This scenario is supported by tendency. In summary, we found that DON is unlikely to influence LPS transfer in the gut; DON likely reduces the capacity for LPS removal in septic shock conditions.

Effects of the Brown Seaweed Laminaria japonica Supplementation on Serum Concentrations of IgG, Triglycerides, and Cholesterol, and Intestinal Microbiota Composition in Rats

The intestinal microbial communities play critical roles in various aspects of body function of the host. Prebiotics, such as dietary fiber, can affect health of the host by altering the composition of intestinal microbiota. Although brown seaweed Laminaria japonica is rich in dietary fiber, studies on its prebiotic potential are quite rare. In this study, basal diet (control), basal diet supplemented with dried L. japonica (DLJ), heat-treated dried L. japonica (HLJ), or heated dried L. japonica with added fructooligosaccharide (FHLJ) was fed to rats for 16 weeks. Serum concentrations of IgG, triglyceride, and cholesterol were measured. In addition, the intestinal microbiota composition was analyzed by high-throughput sequencing of 16S rRNA gene. As compared to the control group, DLJ, HLJ, and FHLJ groups showed significantly higher serum IgG concentration, but had lower weight gain and serum triglyceride concentration. Moreover, DLJ, HLJ, and FHLJ groups showed lower Fimicutes to Bacteroidetes ratio when compared with the control group. As compared with the control group, obesity-associated bacterial genera (Allobaculum, Turicibacter, Coprobacillus, Mollicute, and Oscilibacter), and the genera with pathogenic potentials (Mollicute, Bacteroides, Clostridium, Escherichia, and Prevotella) decreased while leanness-associated genera (Alistipes, Bacteroides, and Prevotella), and lactic acid bacterial genera (Subdoligranulum, Streptococcus, Lactobacillus, Enterococcus, and Bifidobacterium) increased in all treatment groups. On the contrary, butyric acid producing genera including Subdoligranulum, Roseburia, Eubacterium, Butyrivibrio, and Anaerotruncus increased significantly only in FHLJ group. The overall results support multiple prebiotic effects of seaweed L. japonica on rats as determined by body weight reduction, enhanced immune response, and desirable changes in intestinal microbiota composition, suggesting the great potential of L. japonica as an effective prebiotic for promotion of host metabolism and reduction of obesity in humans.

Starch Structure Influences Its Digestibility: A Review

Twenty-five years ago, it was found that a significant fraction of the starch present in foods is not digested in the small intestine and continues to the large intestine, where it is fermented by the microbiota; this fraction was named resistant starch (RS). It was also reported that there is a fraction of starch that is slowly digested, sustaining a release of glucose in the small intestine. Later, health benefits were found to be associated with the consumption of this fraction, called slowly digestible starch (SDS). The authors declare both fractions to be "nutraceutical starch." An overview of the structure of both fractions (RS and SDS), as well as their nutraceutical characteristics, is presented with the objective of suggesting methods and processes that will increase both fractions in starchy foods and prevent diseases that are associated with the consumption of glycemic carbohydrates.

Impact of dietary fat on gut microbiota and low-grade systemic inflammation: mechanisms and clinical implications on obesity

Dietary fat strongly affects human health by modulating gut microbiota composition and low-grade systemic inflammation. High-fat diets have been implicated in reduced gut microbiota richness, increased Firmicutes to Bacteroidetes ratio, and several changes at family, genus and species levels. Saturated (SFA), monounsaturated (MUFA), polyunsaturated (PUFA) and conjugated linolenic fatty acids share important pathways of immune system activation/inhibition with gut microbes, modulating obesogenic and proinflammatory profiles. Mechanisms that link dietary fat, gut microbiota and obesity are mediated by increased intestinal permeability, systemic endotoxemia, and the activity of the endocannabinoid system. Although the probiotic therapy could be a complementary strategy to improve gut microbiota composition, it did not show permanent effects to treat fat-induced dysbiosis. Based upon evidence to date, we believe that high-fat diets and SFA consumption should be avoided, and MUFA and omega-3 PUFA intake should be encouraged in order to regulate gut microbiota and inflammation, promoting body weight/fat control.

Significance of Microbiota in Obesity and Metabolic Diseases and the Modulatory Potential by Medicinal Plant and Food Ingredients

Metabolic syndrome is a cluster of three or more metabolic disorders including insulin resistance, obesity, and hyperlipidemia. Obesity has become the epidemic of the twenty-first century with more than 1.6 billion overweight adults. Due to the strong connection between obesity and type 2 diabetes, obesity has received wide attention with subsequent coining of the term "diabesity." Recent studies have identified unique contributions of the immensely diverse gut microbiota in the pathogenesis of obesity and diabetes. Several mechanisms have been proposed including altered glucose and fatty acid metabolism, hepatic fatty acid storage, and modulation of glucagon-like peptide (GLP)-1. Importantly, the relationship between unhealthy diet and a modified gut microbiota composition observed in diabetic or obese subjects has been recognized. Similarly, the role of diet rich in polyphenols and plant polysaccharides in modulating gut bacteria and its impact on diabetes and obesity have been the subject of investigation by several research groups. Gut microbiota are also responsible for the extensive metabolism of polyphenols thus modulating their biological activities. The aim of this review is to shed light on the composition of gut microbes, their health importance and how they can contribute to diseases as well as their modulation by polyphenols and polysaccharides to control obesity and diabetes. In addition, the role of microbiota in improving the oral bioavailability of polyphenols and hence in shaping their antidiabetic and antiobesity activities will be discussed.

Postprandial serum endotoxin in healthy humans is modulated by dietary fat in a randomized, controlled, cross-over study

Background

High-fat diets may contribute to metabolic disease via postprandial changes in serum endotoxin and inflammation. It is unclear how dietary fat composition may alter these parameters. We hypothesized that a meal rich in n-3 (ω3) fatty acids would reduce endotoxemia and associated inflammation but a saturated or n-6 (ω6) fatty acid-rich meal would increase postprandial serum endotoxin concentrations and systemic inflammation in healthy adults.

Methods

Healthy adults (n = 20; mean age 25 ± 3.2 S.D. years) were enrolled in this single-blind, randomized, cross-over study. Participants were randomized to treatment and reported to the laboratory, after an overnight fast, on four occasions separated by at least one week. Participants were blinded to treatment meal and consumed one of four isoenergetic meals that provided: 1) 20 % fat (control; olive oil) or 35 % fat provided from 2) n-3 (ω3) (DHA = 500 mg; fish oil); 3) n-6 (ω6) (7.4 g; grapeseed oil) or 4) saturated fat (16 g; coconut oil). Baseline and postprandial blood samples were collected. Primary outcome was defined as the effect of treatment meal on postprandial endotoxemia. Serum was analyzed for metabolites, inflammatory markers, and endotoxin. Data from all 20 participants were analyzed using repeated-measures ANCOVA.

Results

Participant serum endotoxin concentration was increased during the postprandial period after the consumption of the saturated fat meal but decreased after the n-3 meal (p < 0.05). The n-6 meal did not effect a different outcome in participant postprandial serum endotoxin concentration from that of the control meal (p > 0.05). There was no treatment meal effect on participant postprandial serum biomarkers of inflammation. Postprandial serum triacylglycerols were significantly elevated following the n-6 meal compared to the n-3 meal. Non-esterified fatty acids were significantly increased after consumption of the saturated fat meal compared to other treatment meals.

Conclusions

Meal fatty acid composition modulates postprandial serum endotoxin concentration in healthy adults. However, postprandial endotoxin was not associated with systemic inflammation in vivo.

Trial registration

This study was retrospectively registered at clinicaltrials.gov as NCT02521779 on July 28, 2015.

Stress hormone release is a key component of the metabolic response to lipopolysaccharide: studies in hypopituitary and healthy subjects

OBJECTIVE

Acute and chronic inflammatory and metabolic responses are generated by lipopolysaccharide (LPS) during acute illness and in the pathogenesis of the metabolic syndrome, type 2 diabetes and cardiovascular disease, but whether these responses depend on intact pituitary release of hormones are not clearly identified. We compared the metabolic effects of LPS in hypopituitary patients (HPs) (in the absence of growth hormone (GH) and ACTH responses) and healthy control subjects (CTR) (with normal pituitary hormone responses).

DESIGN

Single-blind randomized.

METHODS

We compared the effects of LPS on glucose, protein and lipid metabolism in eight HP and eight matched CTR twice during 4-h basal and 2-h hyperinsulinemic-euglycemic clamp conditions with muscle and fat biopsies in each period during infusion with saline or LPS.

RESULTS

LPS increased cortisol and GH levels in CTR but not in HP. Also, it increased whole-body palmitate fluxes (3-fold) and decreased palmitate-specific activity (SA) 40-50% in CTR, but not in HP. G(0)/G(1) Switch Gene 2 (G0S2 - an inhibitor of lipolysis) adipose tissue (AT) mRNA was decreased in CTR. Although LPS increased phenylalanine fluxes significantly more in CTR, there was no difference in glucose metabolism between groups and intramyocellular insulin signaling was unaltered in both groups.

CONCLUSIONS

LPS increased indices of lipolysis and amino acid/protein fluxes significantly more in CTR compared with HP and decreased adipocyte G0S2 mRNA only in CTR. Thus, in humans intact pituitary function and appropriate cortisol and GH release are crucial components of the metabolic response to LPS.

Characterization of microbiome in bronchoalveolar lavage fluid of patients with lung cancer comparing with benign mass like lesions

OBJECTIVES

Disruption in the stability of respiratory microbiota is known to be associated with many chronic respiratory diseases. However, only few studies have examined microbiomes in lung cancer. Therefore, we characterized and compared the microbiomes of patients with lung cancer and those with benign mass-like lesions.

MATERIALS AND METHODS

Bronchoalveolar fluid was collected prospectively to evaluate lung masses in patients who had undergone bronchoscopies from May to September 2015. Twenty-eight patients (20 male, 8 female) were enrolled: 20 diagnosed with lung cancer and 8 diagnosed with benign diseases. Samples were analysed by 16S rRNA-based next-generation sequencing.

RESULTS

The participants' mean age was 64±11years. Bacterial operational taxonomic units were classified into 26 phyla, 44 classes, 81 orders, 153 families, 288 genera, and 797 species. The relative abundance of two phyla (Firmicutes and TM7) was significantly increased in patients with lung cancer (p=0.037 and 0.035, respectively). Furthermore, two genera (Veillonella and Megasphaera) were relatively more abundant in lung cancer patients (p=0.003 and 0.022, respectively). The area under the curve of a combination of these two genera used to predict lung cancer was 0.888 (sensitivity=95.0%, specificity=75.0% and sensitivity=70.0%, specificity=100.0%; p=0.002).

CONCLUSION

The results indicate that differences exist in the bacterial communities of patients with lung cancer and those with benign mass-like lesions. The genera Veillonella and Megasphaera showed the potential to serve as biomarkers to predict lung cancer. Thus, the lung microbiota may change the environment in patients with lung cancer.

Gut Microbiota: A Contributing Factor to Obesity

Obesity, a global epidemic of the modern era, is a risk factor for cardiovascular diseases (CVD) and diabetes. The pervasiveness of obesity and overweight in both developed as well as developing populations is on the rise and placing a huge burden on health and economic resources. Consequently, research to control this emerging epidemic is of utmost importance. Recently, host interactions with their resident gut microbiota (GM) have been reported to be involved in the pathogenesis of many metabolic diseases, including obesity, diabetes, and CVD. Around 10(14) microorganisms reside within the lower human intestine and many of these 10(14) microorganisms have developed mutualistic or commensal associations with the host and actively involved in many physiological processes of the host. However, dysbiosis (altered gut microbial composition) with other predisposing genetic and environmental factors, may contribute to host metabolic disorders resulting in many ailments. Therefore, delineating the role of GM as a contributing factor to obesity is the main objective of this review. Obesity research, as a field is expanding rapidly due to major advances in nutrigenomics, metabolomics, RNA silencing, epigenetics, and other disciplines that may result in the emergence of new technologies and methods to better interpret causal relationships between microbiota and obesity.

Sample preparation optimization in fecal metabolic profiling

Metabolomic analysis of feces can provide useful insight on the metabolic status, the health/disease state of the human/animal and the symbiosis with the gut microbiome. As a result, recently there is increased interest on the application of holistic analysis of feces for biomarker discovery. For metabolomics applications, the sample preparation process used prior to the analysis of fecal samples is of high importance, as it greatly affects the obtained metabolic profile, especially since feces, as matrix are diversifying in their physicochemical characteristics and molecular content. However there is still little information in the literature and lack of a universal approach on sample treatment for fecal metabolic profiling. The scope of the present work was to study the conditions for sample preparation of rat feces with the ultimate goal of the acquisition of comprehensive metabolic profiles either untargeted by NMR spectroscopy and GC-MS or targeted by HILIC-MS/MS. A fecal sample pooled from male and female Wistar rats was extracted under various conditions by modifying the pH value, the nature of the organic solvent and the sample weight to solvent volume ratio. It was found that the 1/2 (w_f/v_s) ratio provided the highest number of metabolites under neutral and basic conditions in both untargeted profiling techniques. Concerning LC-MS profiles, neutral acetonitrile and propanol provided higher signals and wide metabolite coverage, though extraction efficiency is metabolite dependent.

Sepsis in preterm infants causes alterations in mucosal gene expression and microbiota profiles compared to non-septic twins

Sepsis is a life-threatening condition in preterm infants. Neonatal microbiota plays a pivotal role in the immune system maturation. Changes in gut microbiota have been associated to inflammatory disorders; however, a link with sepsis in the neonatal period has not yet been established. We aimed to analyze gut microbiota and mucosal gene expression using non-invasively obtained samples to provide with an integrative perspective of host-microbe interactions in neonatal sepsis. For this purpose, a prospective observational case-control study was conducted in septic preterm dizygotic twins and their non-septic twin controls. Fecal samples were used for both microbiota analysis and host genome-wide expression using exfoliated intestinal cells. Gene expression of exfoliated intestinal cells in septic preterm showed an induction of inflammatory and oxidative stress pathways in the gut and pro-oxidant profile that caused dysbiosis in the gut microbiota with predominance of Enterobacteria and reduction of Bacteroides and Bifidobacterium spp.in fecal samples, leading to a global reduction of beneficial anaerobic bacteria. Sepsis in preterm infants induced low-grade inflammation and oxidative stress in the gut mucosa, and also changes in the gut microbiota. This study highlights the role of inflammation and oxidative stress in neonatal sepsis on gut microbial profiles.

The Intestinal Microbiota in Metabolic Disease

Gut bacteria exert beneficial and harmful effects in metabolic diseases as deduced from the comparison of germfree and conventional mice and from fecal transplantation studies. Compositional microbial changes in diseased subjects have been linked to adiposity, type 2 diabetes and dyslipidemia. Promotion of an increased expression of intestinal nutrient transporters or a modified lipid and bile acid metabolism by the intestinal microbiota could result in an increased nutrient absorption by the host. The degradation of dietary fiber and the subsequent fermentation of monosaccharides to short-chain fatty acids (SCFA) is one of the most controversially discussed mechanisms of how gut bacteria impact host physiology. Fibers reduce the energy density of the diet, and the resulting SCFA promote intestinal gluconeogenesis, incretin formation and subsequently satiety. However, SCFA also deliver energy to the host and support liponeogenesis. Thus far, there is little knowledge on bacterial species that promote or prevent metabolic disease. Clostridium ramosum and Enterococcus cloacae were demonstrated to promote obesity in gnotobiotic mouse models, whereas bifidobacteria and Akkermansia muciniphila were associated with favorable phenotypes in conventional mice, especially when oligofructose was fed. How diet modulates the gut microbiota towards a beneficial or harmful composition needs further research. Gnotobiotic animals are a valuable tool to elucidate mechanisms underlying diet–host–microbe interactions.

Gut Microbiota and Metabolic Endotoxemia in Young Obese Mexican Subjects

BACKGROUND

The gut microbiota plays an important role in human metabolism; previous studies suggest that the imbalance can cause a metabolic endotoxemia that may be linked to weight gain and insulin resistance. The purpose of this study was to investigate the relationship between the gut microbiota composition, the lipopolysaccharide levels and the metabolic profile in obese and normal-weight young subjects.

METHODS

We studied 32 obese (BMI ≥ 30 kg/m2) and 32 normal-weight subjects (BMI = 18.5-24.9 kg/m2), aged 18-25 years. Quantification of intestinal bacteria was performed by real-time PCR. Endotoxin units were determined with the test QCL-1000, and biochemical profile was performed under a standard protocol of Spinreact.

RESULTS

Obese individuals had a BMI of 34.5 (32.9-36.45) kg/m2, increased triglycerides (123 vs. 70 mg/dl), total cholesterol (168 vs. 142 mg/dl), and LDL-cholesterol (114 vs. 96.5 mg/dl). In obese subjects body temperature was higher than in normal-weight subjects. We found a greater number of Clostridum leptum and Lactobacillus (p < 0.001) and lower numbers of Prevotella and Escherichia coli (p < 0.001) in the obese group. A decrease of E. coli was associated with an increased risk of lipopolysaccharide levels ranging from 1 to 1.3 EU/ml. A positive correlation was found between serum lipopolysaccharides and BMI (r = 0.46, p = 0.008), triglyceride levels (r = 0.44, p = 0.011) as well as waist circumference (r = 0.34, p = 0.040), being more evident in young obese females.

CONCLUSION

Subclinical metabolic endotoxemia determined by serum concentration of lipopolysaccharides was related to the smallest amount of E. coli, high triglyceride levels, and central adiposity in obese young persons.

Does the buck stop with the bugs?: an overview of microbial dysbiosis in rheumatoid arthritis

The human body is an environmental niche which is home to diverse co-habiting microbes collectively referred as the human microbiome. Recent years have seen the in-depth characterization of the human microbiome and associations with diseases. Linking of the composition or number of the human microbiota with diseases and traits date back to the original work of Elie Metchnikoff. Recent advances in genomic technologies have opened up finer details and dynamics of this new science with higher precision. Microbe-rheumatoid arthritis connection, largely related to the gut and oral microbiomes, has showed up as a result - apart from several other earlier, well-studied candidate autoimmune diseases. Although evidence favouring roles of specific microbial species, including Porphyromonas, Prevotella and Leptotricha, has become clearer, mechanistic insights still continue to be enigmatic. Manipulating the microbes by traditional dietary modifications, probiotics, and antibiotics and by currently employed disease-modifying agents seems to modulate the disease process and its progression. In the present review, we appraise the existing information as well as the gaps in knowledge in this challenging field. We also discuss the future directions for potential clinical applications, including prevention and management of rheumatoid arthritis using microbial modifications.

Comparison of the gut microbiota composition between obese and non-obese individuals in a Japanese population, as analyzed by terminal restriction fragment length polymorphism and next-generation sequencing

BACKGROUND

Obesity has become one of the most serious social problems in developed countries, including Japan. The relationship between the gut microbiota and obesity has recently attracted the attention of many researchers. Although the gut microbiota was long thought to contribute to obesity, the exact association remains largely unknown. We examined the human gut microbiota composition in a Japanese population in order to determine its relationship to obesity.

METHODS

Stool samples from 23 non-obese subjects (body mass index [BMI] <20 kg/m(2)) and 33 obese subjects (BMI ≥25 kg/m(2)) were collected and DNA was extracted prior to colonoscopy. After terminal restriction fragment length polymorphism (T-RFLP) analysis, samples from 10 subjects (4 non-obese and 6 obese) were selected and subjected to next-generation sequencing for species-level analysis.

RESULTS

T-RFLP analysis showed significantly reduced numbers of Bacteroidetes and a higher Firmicutes to Bacteroidetes ratio in obese subjects compared with non-obese subjects. Bacterial diversity was significantly greater in obese subjects compared with non-obese subjects. Next-generation sequencing revealed that obese and non-obese subjects had different gut microbiota compositions and that certain bacterial species were significantly associated with each group (obese: Blautia hydrogenotorophica, Coprococcus catus, Eubacterium ventriosum, Ruminococcus bromii, Ruminococcus obeum; non-obese: Bacteroides faecichinchillae, Bacteroides thetaiotaomicron, Blautia wexlerae, Clostridium bolteae, Flavonifractor plautii).

CONCLUSION

Gut microbial properties differ between obese and non-obese subjects in Japan, suggesting that gut microbiota composition is related to obesity.

Oral supplementation with L-glutamine alters gut microbiota of obese and overweight adults: A pilot study

OBJECTIVE

The aim of this study was to determine whether oral supplementation with L-glutamine (GLN) modifies the gut microbiota composition in overweight and obese adults.

METHODS

Thirty-three overweight and obese adults, ages between 23 and 59 y and body mass index between 25.03 and 47.12 kg/m(2), were randomly assigned to receive either oral supplementation with 30 g of L-alanine (ALA group control) or 30 g of GLN (GLN group) daily for 14 d. We analyzed the gut microbiota composition with new-generation sequencing techniques and bioinformatics analysis.

RESULTS

After 14 d of supplementation, adults in the GLN group exhibited statistically significant differences in the Firmicutes and Actinobacteria phyla compared with those in the ALA group. The ratio of Firmicutes to Bacteroidetes, a good biomarker for obesity, decreased in the GLN group from 0.85 to 0.57, whereas it increased from 0.91 to 1.12 in the ALA group. At the genus level, Dialister, Dorea, Pseudobutyrivibrio, and Veillonella, belonging to the Firmicutes phylum, had statistically significant reduction.

CONCLUSION

Oral supplementation with GLN, for a short time, altered the composition of the gut microbiota in overweight and obese humans reducing the Firmicutes to Bacteroidetes ratio, which resembled weight loss programs already seen in the literature.

The immunomodulatory role of bile acids

Enzymatic oxidation of cholesterol generates numerous distinct bile acids which function both as detergents that facilitate the digestion and absorption of dietary lipids and as hormones that activate five distinct receptors. Activation of these receptors alters gene expression in multiple tissues, leading to changes not only in bile acid metabolism but also in glucose homeostasis, lipid and lipoprotein metabolism, energy expenditure, intestinal motility, bacterial growth, inflammation, and in the liver-gut axis. This review focuses on the present knowledge regarding the physiologic and pathologic role of bile acids and their immunomodulatory role, with particular attention to bacterial lipopolysaccharides (endotoxins) and bile acid and immunological disorders. The specific role that bile acids play in the regulation of innate immunity, various systemic inflammations, inflammatory bowel diseases, allergy, psoriasis, cholestasis, obesity, metabolic syndrome, alcoholic liver disease, and colon cancer will be reviewed.

[Roles of enteric microbial composition and metabolism in health and diseases]

A complex microbiota colonizes mucosal layers in different regions of the human gut. In the healthy state, the microbial communities provide nutrients and energy to the host via fermentation of non-digestible dietary components in the large intestine. In contrast, they can play roles in inflammation and infection, including gastrointestinal diseases and metabolic syndrome such as obesity. However, because of the complexity of the microbial community, the functional connections between the enteric microbiota and metabolism are less well understood. Nevertheless, major progress has been made in defining dominant bacterial species, community profiles, and systemic characteristics that produce stable microbiota beneficial to health, and in identifying their roles in enteric metabolism. Through studies in both mice and humans, we are recently in a better position to understand what effect the enteric microbiota has on the metabolism by improving energy yield from food and modulating dietary components. Achieving better knowledge of this information may provide insights into new possibilities that reconstitution of enteric microbiota via diet can provide the maintenance of healthy state and therapeutic/preventive strategies against metabolic syndrome such as obesity. This review focuses on enteric microbial composition and metabolism on healthy and diseased states.

Circadian disorganization alters intestinal microbiota

Intestinal dysbiosis and circadian rhythm disruption are associated with similar diseases including obesity, metabolic syndrome, and inflammatory bowel disease. Despite the overlap, the potential relationship between circadian disorganization and dysbiosis is unknown; thus, in the present study, a model of chronic circadian disruption was used to determine the impact on the intestinal microbiome. Male C57BL/6J mice underwent once weekly phase reversals of the light:dark cycle (i.e., circadian rhythm disrupted mice) to determine the impact of circadian rhythm disruption on the intestinal microbiome and were fed either standard chow or a high-fat, high-sugar diet to determine how diet influences circadian disruption-induced effects on the microbiome. Weekly phase reversals of the light:dark (LD) cycle did not alter the microbiome in mice fed standard chow; however, mice fed a high-fat, high-sugar diet in conjunction with phase shifts in the light:dark cycle had significantly altered microbiota. While it is yet to be established if some of the adverse effects associated with circadian disorganization in humans (e.g., shift workers, travelers moving across time zones, and in individuals with social jet lag) are mediated by dysbiosis, the current study demonstrates that circadian disorganization can impact the intestinal microbiota which may have implications for inflammatory diseases.

A rosemary extract rich in carnosic acid selectively modulates caecum microbiota and inhibits β-glucosidase activity, altering fiber and short chain fatty acids fecal excretion in lean and obese female rats

Background

Carnosic acid (CA) and rosemary extracts (RE) show body-weight, energy metabolism and inflammation regulatory properties in animal models but the mechanisms are not yet understood. Gut microbiota plays an important role in the host metabolism and inflammatory status and is modulated by the diet. The aim of this research was to investigate whether a RE enriched in CA affected caecum microbiota composition and activity in a rat model of genetic obesity.

Methods and Principal Findings

A RE (40% CA) was administered with the diet (0.5% w/w) to lean (fa/+) and obese (fa/fa) female Zucker rats for 64 days. Changes in the microbiota composition and β-glucosidase activity in the caecum and in the levels of macronutrients and short chain fatty acids (SCFA) in feces were examined. The RE increased the Blautia coccoides and Bacteroides/Prevotella groups and reduced the Lactobacillus/Leuconostoc/Pediococccus group in both types of animals. Clostridium leptum was significantly decreased and Bifidobacterium increased only in the lean rats. β-Glucosidase activity was significantly reduced and fecal fiber excretion increased in the two genotypes. The RE also increased the main SCFA excreted in the feces of the obese rats but decreased them in the lean rats reflecting important differences in the uptake and metabolism of these molecules between the two genotypes.

Conclusions

Our results indicate that the consumption of a RE enriched in CA modifies microbiota composition and decreases β-glucosidase activity in the caecum of female Zucker rats while it increases fiber fecal elimination. These results may contribute to explain the body weight gain reducing effects of the RE. The mutated leptin receptor of the obese animals significantly affects the microbiota composition, the SCFA fecal excretion and the host response to the RE intake.

Non-alcoholic fatty liver disease, diet and gut microbiota

Non-alcoholic fatty liver disease (NAFLD) is a severe liver disease that is increasing in prevalence with the worldwide epidemic of obesity and its related insulin-resistance state. Evidence for the role of the gut microbiota in energy storage and the subsequent development of obesity and some of its related diseases is now well established. More recently, a new role of gut microbiota has emerged in NAFLD. The gut microbiota is involved in gut permeability, low-grade inflammation and immune balance, it modulates dietary choline metabolism, regulates bile acid metabolism and produces endogenous ethanol. All of these factors are molecular mechanisms by which the microbiota can induce NAFLD or its progression toward overt non-alcoholic steatohepatitis. Modification of the gut microbiota composition and/or its biochemical capacity by specific dietary or pharmacological interventions may advantageously affect host metabolism. Large-scale intervention trials, investigating the potential benefit of prebiotics and probiotics in improving cardiometabolic health in high-risk populations, are fervently awaited.

The role of gut microbiota in nutritional status

PURPOSE OF REVIEW

The objective of this review is to outline the contribution of the gut microbiota to nutritional status and to highlight the mechanisms by which this can occur.

RECENT FINDINGS

Historically, research linking intestinal bacteria with nutritional status focused on the degradation of indigestible food components by bacterial enzymes and metabolites. Of late, emerging evidence suggests an independent role of the gut microbiota in the regulation of glucose and energy homeostasis via complex interactions between microbially derived metabolites and specific target tissue cells. In addition, novel findings highlight specific microbial species involved in the production of a number of micronutrient components, which could potentially improve nutritional status in certain population groups, if available to the host at sufficiently abundant levels.

SUMMARY

New insights into the role of the gut microbiota and its holistic effects on the host are now emerging. High-throughput technologies allow for a greater insight into the role of the intestinal microbiota and the mechanisms by which it can contribute to overall nutritional status. Further, exploration of this evolving field of research will advance our understanding of how this complex ecosystem could advance the area of personalized nutrition in the future.

Docosahexaenoic acid, inflammation, and bacterial dysbiosis in relation to periodontal disease, inflammatory bowel disease, and the metabolic syndrome

Docosahexaenoic acid (DHA), a long-chain omega-3 polyunsaturated fatty acid, has been used to treat a range of different conditions, including periodontal disease (PD) and inflammatory bowel disease (IBD). That DHA helps with these oral and gastrointestinal diseases in which inflammation and bacterial dysbiosis play key roles, raises the question of whether DHA may assist in the prevention or treatment of other inflammatory conditions, such as the metabolic syndrome, which have also been linked with inflammation and alterations in normal host microbial populations. Here we review established and investigated associations between DHA, PD, and IBD. We conclude that by beneficially altering cytokine production and macrophage recruitment, the composition of intestinal microbiota and intestinal integrity, lipopolysaccharide- and adipose-induced inflammation, and insulin signaling, DHA may be a key tool in the prevention of metabolic syndrome.

Identification of Human Intestinal Microbiota of 92 Men by Data Mining for 5 Characteristics, i.e., Age, BMI, Smoking Habit, Cessation Period of Previous Smokers and Drinking Habit

The intestinal microbiota compositions of 92 men living in Japan were identified following consumption of identical meals for 3 days. Fecal samples were analyzed by terminal restriction fragment length polymorphism with 4 primer-restriction enzyme systems, and the 120 obtained operational taxonomic units (OTUs) were analyzed by Data mining software focusing on the following 5 characteristics, namely, age, body mass index, present smoking habit, cessation period of previous smokers and drinking habit, according to the answers of the subjects. After performing Data mining analyses with each characteristic, the details of the constructed Decision trees precisely identified the subjects or discriminated them into various suitable groups. Through the pathways to reach the groups, practical roles of the related OTUs and their quantities were clearly recognized. Compared with the other identification methods for OTUs such as bicluster analyses, correlation coefficients and principal component analyses, the clear difference of this Data mining technique was that it set aside most OTUs and emphasized only some closely related ones. For example for a selected characteristic, such as smoking habit, only 7 OTUs out of 120 were able to identify all smokers, and the remaining 113 OTUs were thought of as data noise for smoking. Data mining analyses were affirmed as an effective method of subject discrimination for various physiological constitutions. The species of bacteria that were closely related to heavy smokers, i.e., HaeIII-291, were also discussed.

Linking the gut microbiota to human health

The human gut is the natural environment for a diverse and dynamic microbial ecosystem, whose structure and functions are presently a major target of research in biomedicine. Experimental studies in germ-free animals performed some decades ago revealed the importance of these microbial communities for normal growth and development and for the maintenance of health in adult life. The host provides habitat and nutrition to the microbial communities and derives many benefits from its symbionts that contribute to metabolic, defensive and trophic functions. Development of novel gene sequencing technologies as well as availability of powerful bioinformatic analysis tools provide new insights into the composition and structure of the human gut microbiota. There is no clear definition of the characteristics of a normal 'healthy' gut microbiota in human subjects, but several disease states have been associated with changes in the composition of faecal and intestinal mucosal communities, including inflammatory bowel diseases, obesity and the metabolic syndrome. Probiotics and prebiotics are used to improve symbiosis between enteric microbiota and the host or restore states of dysbiosis.

Genetically obese mice do not show increased gut permeability or faecal bile acid hydrophobicity

Gut barrier dysfunction may lead to metabolic endotoxaemia and low-grade inflammation. Recent publications have demonstrated gut barrier dysfunction in obesity induced by a diet high in fat, and a pathogenetic role for luminal bile acids has been proposed. We aimed to investigate whether genetically obese mice develop increased gut permeability and alterations in luminal bile acids on a diet with a regular fat content. We used seven obese male ob/ob mice of C57BL/6J background and ten male wild-type (WT) mice of the same strain. Faeces were collected for bile acid analysis. Intestinal permeability was measured in an Ussing chamber upon euthanasia, using 4 kDa fluorescein isothiocyanate dextran, as per mille (‰, 1/1000) of translocated dextran. We analysed the liver expression of lipopolysaccharide-binding protein (LBP), as well as serum LBP (ELISA). Intestinal permeability was not affected by genetic obesity (jejunum: 0·234 (sem 0·04) ‰ for obese v. 0·225 (sem 0·03) ‰ for WT, P= 0·93; colon: 0·222 (sem 0·06) ‰ for obese v. 0·184 (sem 0·03) ‰ for WT, P= 0·86), nor was liver LBP expression (relative expression: 0·55 (sem 0·08) for obese v. 0·55 (sem 0·13) for WT, P= 0·70). Serum LBP was 2·5-fold higher in obese than in WT mice (P= 0·001). Obese mice had increased daily excretion of total bile acids, but their faecal bile acid hydrophobicity was unchanged. In conclusion, genetic obesity did not impair gut barrier function in mice on a regular chow diet, nor was faecal bile acid hydrophobicity affected.