Selective increases of bifidobacteria in gut microflora improve high-fat-diet-induced diabetes in mice through a mechanism associated with endotoxaemia

Gut microbiota, enteroendocrine functions and metabolism

The gut microbiota affects host metabolism through a number of physiological processes. Emerging evidence suggests that gut microbes interact with the host through several pathways involving enteroendocrine cells (e.g. L cells). The activation of specific G protein coupled receptors expressed on L cells (e.g. GPR41, GPR43, GPR119 and TGR5) triggers the secretion of glucagon-like peptides (GLP-1 and GLP-2) and PYY. These gut peptides are known to control energy homeostasis, glucose metabolism, gut barrier function and metabolic inflammation. Here, we explore how crosstalk between the ligands produced by the gut microbiota (short chain fatty acids, or SCFAs), or produced by the host but influenced by gut microbes (endocannabinoids and bile acids), impact host physiology.

Harnessing the beneficial properties of adipogenic microbes for improving human health

Obesity is associated with numerous metabolic comorbidities. Weight loss is an effective measure for alleviating many of these metabolic abnormalities. However, considering the limited success of most medical weight-management approaches in producing a sustained weight loss, approaches that improve obesity-related metabolic abnormalities independent of weight loss would be extremely attractive and of practical benefit. Metabolically healthy obesity supports the notion that a better metabolic profile is possible despite obesity. Moreover, adequate expansion of adipose tissue appears to confer protection from obesity-induced metabolic comorbidities. To this end, the 10th Stock conference examined new approaches to improve metabolic comorbidities independent of weight loss. In particular, human adenovirus 36 (Ad36) and specific gut microbes were examined for their potential to influence lipid and glucose homeostasis in animals and humans. While these microbes possess some undesirable properties, research has identified attributes of adenovirus Ad36 and gut microbes that may be selectively harnessed to improve metabolic profile without the obligatory weight loss. Furthermore, identifying the host signalling pathways that these microbes recruit to improve the metabolic profile may offer new templates and targets, which may facilitate the development of novel treatment strategies for obesity-related metabolic conditions.

Cometabolism of microbes and host: implications for drug metabolism and drug-induced toxicity

The recognition of the gut microbial-mammalian metabolic axis and its implications in human metabolic disease opens a new window to understanding the contribution of the gut microbiome to drug metabolism and drug-induced toxicity. The integrative omics approaches, including pharmacometabonomics and metagenomics, have demonstrated great promise for characterizing xenobiotic interventions that are associated with wide variation in efficacy or toxicity in humans, as well as for predicting individual response and susceptibility to toxicity.

Insight into the prebiotic concept: lessons from an exploratory, double blind intervention study with inulin-type fructans in obese women

OBJECTIVE

To highlight the contribution of the gut microbiota to the modulation of host metabolism by dietary inulin-type fructans (ITF prebiotics) in obese women.

METHODS

A double blind, placebo controlled, intervention study was performed with 30 obese women treated with ITF prebiotics (inulin/oligofructose 50/50 mix; n=15) or placebo (maltodextrin; n=15) for 3 months (16 g/day). Blood, faeces and urine sampling, oral glucose tolerance test, homeostasis model assessment and impedancemetry were performed before and after treatment. The gut microbial composition in faeces was analysed by phylogenetic microarray and qPCR analysis of 16S rDNA. Plasma and urine metabolic profiles were analysed by 1H-NMR spectroscopy.

RESULTS

Treatment with ITF prebiotics, but not the placebo, led to an increase in Bifidobacterium and Faecalibacterium prausnitzii; both bacteria negatively correlated with serum lipopolysaccharide levels. ITF prebiotics also decreased Bacteroides intestinalis, Bacteroides vulgatus and Propionibacterium, an effect associated with a slight decrease in fat mass and with plasma lactate and phosphatidylcholine levels. No clear treatment clustering could be detected for gut microbial analysis or plasma and urine metabolomic profile analyses. However, ITF prebiotics led to subtle changes in the gut microbiota that may importantly impact on several key metabolites implicated in obesity and/or diabetes.

CONCLUSIONS

ITF prebiotics selectively changed the gut microbiota composition in obese women, leading to modest changes in host metabolism, as suggested by the correlation between some bacterial species and metabolic endotoxaemia or metabolomic signatures.

The role of diet in triggering human inflammatory disorders in the modern age

Previously uncommon human inflammatory disorders are emerging with alarming frequency, possibly triggered by environmental factors introduced through Westernization. This review highlights how Western diets heighten the inflammatory state promoting development of disease. Evidence that this can occur directly or indirectly through perturbations of host-microbe interactions are reviewed.

The Effect of High-Fat Diet-Induced Pathophysiological Changes in the Gut on Obesity: What Should be the Ideal Treatment?

Obesity is a metabolic disorder and fundamental cause of other fatal diseases including atherosclerosis and cancer. One of the main factor that contributes to the development of obesity is high-fat (HF) consumption. Lipid ingestion will initiate from the gut feedback mechanisms to regulate glucose and lipid metabolisms. But these lipid-sensing pathways are impaired in HF-induced insulin resistance, resulting in hyperglycemia. Besides that, duodenal lipid activates mucosal mast cells, leading to the disruption of the intestinal tight junction. Lipopolysaccharide that is co-transited with dietary fat postprandially, promotes the release of cytokines and the development of metabolic syndrome. HF-diet also alters microbiota composition and enhances fat storage. Although gut is protected by immune system and contains high level of antioxidants, obesity developed presumably when this protective mechanism is compromised by the presence of excessive fat. Several therapeutic approaches targeting different pathways have been proposed. There may be no one single most effective treatment, but all aimed to prevent obesity. This review will elaborate on the physiological and molecular changes in the gut that lead to obesity, and will provide a summary of potential treatments to manage these pathophysiological changes.

Effect of multispecies probiotic supplements on metabolic profiles, hs-CRP, and oxidative stress in patients with type 2 diabetes

BACKGROUND

We are aware of no study that has indicated the effects of daily consumption of multispecies probiotic supplements on metabolic profiles, high-sensitivity C-reactive protein (hs-CRP), and oxidative stress in diabetic patients.

OBJECTIVE

This study was designed to determine the effects of multispecies probiotic supplements on metabolic profiles, hs-CRP, and oxidative stress in diabetic patients.

METHODS

This randomized double-blind placebo-controlled clinical trial was performed on 54 diabetic patients aged 35-70 years. Subjects were randomly assigned to take either a multispecies probiotic supplement (n = 27) or placebo (n = 27) for 8 weeks. The multispecies probiotic supplement consisted of 7 viable and freeze-dried strains: Lactobacillus acidophilus (2 × 10(9) CFU), L. casei (7 × 10(9) CFU), L. rhamnosus (1.5 × 10(9) CFU), L. bulgaricus (2 × 10(8) CFU), Bifidobacterium breve (2 × 10(10) CFU), B. longum (7 × 10(9) CFU), Streptococcus thermophilus (1.5 × 10(9) CFU), and 100 mg fructo-oligosaccharide. Fasting blood samples were taken at baseline and after intervention to measure metabolic profiles, hs-CRP, and biomarkers of oxidative stress including plasma total antioxidant capacity and total glutathione (GSH).

RESULTS

Between-group comparisons of fasting plasma glucose (FPG) revealed that consumption of probiotic supplements prevented a rise in FPG (+28.8 ± 8.5 for placebo vs. +1.6 ± 6 mg/dl for probiotic group, p = 0.01). Although a significant within-group increase in serum insulin and low-density lipoprotein cholesterol levels was found in both the probiotic group and the placebo group, the changes were similar between the two groups. We observed a significant increase in HOMA-IR (homeostasis model of assessment-insulin resistance) in both the probiotic group (p = 0.02) and the placebo group (p = 0.001); however, the increase in the placebo group was significantly higher than that in the probiotic group (+2.38 vs. +0.78, p = 0.03). Mean changes in serum hs-CRP were significantly different between the two groups (-777.57 for the probiotic group vs. +878.72 ng/ml for the placebo group, p = 0.02). Probiotic supplementation led to a significant increase in plasma GSH levels compared to placebo (240.63 vs. -33.46 µmol/l, p = 0.03).

CONCLUSION

In conclusion, multispecies probiotic supplementation, compared with placebo, for 8 weeks in diabetic patients prevented a rise in FPG and resulted in a decrease in serum hs-CRP and an increase in plasma total GSH.

Effects of probiotics in patients with diabetes mellitus type 2: study protocol for a randomized, double-blind, placebo-controlled trial

BACKGROUND

Low grade chronic inflammation is observed in patients with type 2 diabetes mellitus (T2DM). Endotoxin derived from gut bacteria may act as a potent inflammatory stimulant. Probiotics, which are believed to contain health promoting live microorganisms, may influence circulating endotoxin levels. Ingestion of live probiotic cultures may alter gut microbiota in a beneficial manner to reduce inflammation; no information is available whether or not they do so in patients with T2DM. Therefore, the aim of this study is to characterize the beneficial effects of probiotics on circulating endotoxin levels and other biomarkers related to systemic low-grade inflammation in patients with T2DM.

METHODS

One hundred and twenty consenting adult Saudi T2DM patients (naïve or newly diagnosed and without co-morbidities) will be enrolled in this clinical trial and randomized to receive daily placebo or probiotics (Ecologic®Barrier) for 26 weeks in a double-blind manner. Inflammatory and metabolic markers will be measured and fecal samples analyzed. Measurements/samples will be obtained at baseline and after 4, 8, 12/13 and 26 weeks of treatment.

DISCUSSION

It is expected that the probiotic product will induce beneficial changes in gut microbiota, reduce the systemic inflammatory state through altering systemic endotoxin levels and, as such, reduce the systemic inflammatory response observed in T2DM subjects.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01765517.

Effects of probiotics in patients with diabetes mellitus type 2: study protocol for a randomized, double-blind, placebo-controlled trial

Background

Low grade chronic inflammation is observed in patients with type 2 diabetes mellitus (T2DM). Endotoxin derived from gut bacteria may act as a potent inflammatory stimulant. Probiotics, which are believed to contain health promoting live microorganisms, may influence circulating endotoxin levels. Ingestion of live probiotic cultures may alter gut microbiota in a beneficial manner to reduce inflammation; no information is available whether or not they do so in patients with T2DM. Therefore, the aim of this study is to characterize the beneficial effects of probiotics on circulating endotoxin levels and other biomarkers related to systemic low-grade inflammation in patients with T2DM.

Methods

One hundred and twenty consenting adult Saudi T2DM patients (naïve or newly diagnosed and without co-morbidities) will be enrolled in this clinical trial and randomized to receive daily placebo or probiotics (Ecologic®Barrier) for 26 weeks in a double-blind manner. Inflammatory and metabolic markers will be measured and fecal samples analyzed. Measurements/samples will be obtained at baseline and after 4, 8, 12/13 and 26 weeks of treatment.

Discussion

It is expected that the probiotic product will induce beneficial changes in gut microbiota, reduce the systemic inflammatory state through altering systemic endotoxin levels and, as such, reduce the systemic inflammatory response observed in T2DM subjects.

Trial registration

ClinicalTrials.gov Identifier: NCT01765517

Metabolic endotoxemia directly increases the proliferation of adipocyte precursors at the onset of metabolic diseases through a CD14-dependent mechanism

Metabolic endotoxemia triggers inflammation, targets cells from the stroma-vascular fraction of adipose depots, and metabolic disease. To identify these cells we here infused mice with lipopolysaccharides and showed by FACS analyses and BrdU staining that the number of small subcutaneous adipocytes, preadipocytes and macrophages increased in wild type but not in CD14-knockout (KO) mice. This mechanism was direct since in CD14KO mice grafted subcutaneously and simultaneously with fat pads from CD14KO and wild-type mice the concentration of cytokine mRNA was increased in the wild-type fat pad only. Conversely, the mRNA concentration of genes involved in glucose and lipid metabolism and the number of large adipocytes was reduced. Eventually, a pretreatment with LPS enhanced HFD-induced metabolic diseases. Altogether, these results show that metabolic endotoxemia increases the proliferation of preadipocytes through a CD14-dependent mechanism directly, without recruiting CD14-positive cells from non-adipose depot origin. This mechanism could precede the onset of metabolic diseases.

Holobiont nutrition: considering the role of the gastrointestinal microbiota in the health benefits of whole grains

Intake of whole grains and other food products high in dietary fiber have long been linked to the prevention of chronic diseases associated with inflammation. A contribution of the gastrointestinal microbiota to these effects has been suggested, but little is known on how whole grains interact with gut bacteria. We have recently published the first human trial that made use of next-generation sequencing to determine the effect of whole grains (whole grain barley, brown rice or a mixture of the two) on fecal microbiota structure and tested for associations between the gut microbiota and blood markers of inflammation, glucose and lipid metabolism. Our study revealed that whole grains impacted gut microbial ecology by increasing microbial diversity and inducing compositional alterations, some of which are considered to have beneficial effects on the host. Interestingly, whole grains, and in particular the combination of whole grain barley and brown rice, caused a reduction in plasma interleukin-6 (IL-6), which was linked to compositional features of the gut microbiota. Therefore, the study provided evidence that a short-term increased intake of whole grains led to compositional alterations of the gut microbiota that coincided with improvements in systemic inflammation. In this addendum, we summarize the findings of the study and provide a perspective on the importance of regarding humans as holobionts when considering the health effects of dietary strategies.

Roux-en-Y gastric bypass surgery in rats alters gut microbiota profile along the intestine

Roux-en-Y gastric bypass (RYGB) surgery might modify the gut microbiota composition differently in the three distinct anatomical sections of the small intestine compared to sham surgery. We showed that RYGB induced changes in the microbiota of the alimentary limb and the common channel resembling those seen after prebiotic treatment or weight loss by dieting. These changes may be associated with altered production of intestinal hormones known to control energy balance. Postsurgical modulation of gut microbiota may significantly contribute to the beneficial metabolic effects of RYGB surgery.

Influence of gut microbiota on subclinical inflammation and insulin resistance

Obesity is the main condition that is correlated with the appearance of insulin resistance, which is the major link among its comorbidities, such as type 2 diabetes, nonalcoholic fatty liver disease, cardiovascular and neurodegenerative diseases, and several types of cancer. Obesity affects a large number of individuals worldwide; it degrades human health and quality of life. Here, we review the role of the gut microbiota in the pathophysiology of obesity and type 2 diabetes, which is promoted by a bacterial diversity shift mediated by overnutrition. Whole bacteria, their products, and metabolites undergo increased translocation through the gut epithelium to the circulation due to degraded tight junctions and the consequent increase in intestinal permeability that culminates in inflammation and insulin resistance. Several strategies focusing on modulation of the gut microbiota (antibiotics, probiotics, and prebiotics) are being experimentally employed in metabolic derangement in order to reduce intestinal permeability, increase the production of short chain fatty acids and anorectic gut hormones, and promote insulin sensitivity to counteract the inflammatory status and insulin resistance found in obese individuals.

Effects of synbiotic food consumption on metabolic status of diabetic patients: a double-blind randomized cross-over controlled clinical trial

BACKGROUND & AIMS

We are aware of no study indicating the effects of synbiotic food consumption on metabolic profiles, inflammation and oxidative stress among diabetic patients. The aim of the current study was to investigate the effects of synbiotic food consumption on metabolic profiles, hs-CRP and biomarkers of oxidative stress in diabetic patients.

METHODS

This randomized double-blinded cross-over controlled clinical trial was performed among 62 diabetic patients aged 35-70 y. After a 2-wk run-in period, subjects were randomly assigned to consume either a synbiotic (n = 62) or control food (n = 62) for 6 weeks. A 3-week washout period was applied following which subjects were crossed over to the alternate treatment arm for an additional 6 weeks. The synbiotic food consisted of a probiotic viable and heat-resistant Lactobacillus sporogenes (1 × 10(7) CFU), 0.04 g inulin (HPX) as prebiotic with 0.38 g isomalt, 0.36 g sorbitol and 0.05 g stevia as sweetener per 1 g. Control food (the same substance without probiotic bacteria and prebiotic inulin) was packed in identical 9-gram packages. Patients were asked to consume the synbiotic and control foods three times a day. Fasting blood samples were taken at baseline and after a 6-wk intervention to measure metabolic profiles, hs-CRP and biomarkers of oxidative stress.

RESULTS

Consumption of a synbiotic food, compared to the control, resulted in a significant decrease in serum insulin levels (changes from baseline: -1.75 ± 0.60 vs. +0.95 ± 1.09 μIU/mL, P = 0.03). Although we failed to find a significant effect of synbiotic food consumption on total- and LDL-cholesterol levels and HOMA-IR, the effects on FPG (22.3 vs. 4.2 mg/dL, P = 0.09), serum triglycerides (45.9 vs. 20.6 mg/dL, P = 0.08) and HDL-cholesterol levels (3.1 vs. -2 mg/dL, P = 0.06) tended to be significant. A significant reduction in serum hs-CRP levels (-1057.86 ± 283.74 vs. 95.40 ± 385.38 ng/mL, P = 0.01) was found following the consumption of synbiotic food compared with the control group. Supplementation with the synbiotic food led to a significant increase in plasma total GSH (319.98 vs. 19.73 μmol/L, P < 0.001) and serum uric acid levels (+0.7 vs. -0.1 mg/dL, P = 0.04) compared to the control food. No significant effect of the synbiotic food was observed on plasma TAC levels.

CONCLUSIONS

In conclusion, consumption of a synbiotic food for 6 weeks among diabetic patients had significant effects on serum insulin, hs-CRP, uric acid and plasma total GSH levels.

CLINICAL TRIAL REGISTRATION NUMBER

www.irct.ir: IRCT201201195623N1.

Contribution of the 7β-hydroxysteroid dehydrogenase from Ruminococcus gnavus N53 to ursodeoxycholic acid formation in the human colon

Bile acid composition in the colon is determined by bile acid flow in the intestines, the population of bile acid-converting bacteria, and the properties of the responsible bacterial enzymes. Ursodeoxycholic acid (UDCA) is regarded as a chemopreventive beneficial bile acid due to its low hydrophobicity. However, it is a minor constituent of human bile acids. Here, we characterized an UDCA-producing bacterium, N53, isolated from human feces. 16S rDNA sequence analysis identified this isolate as Ruminococcus gnavus, a novel UDCA-producer. The forward reaction that produces UDCA from 7-oxo-lithocholic acid was observed to have a growth-dependent conversion rate of 90-100% after culture in GAM broth containing 1 mM 7-oxo-lithocholic acid, while the reverse reaction was undetectable. The gene encoding 7β-hydroxysteroid dehydrogenase (7β-HSDH), which facilitates the UDCA-producing reaction, was cloned and overexpressed in Escherichia coli. Characterization of the purified 7β-HSDH revealed that the kcat/Km value was about 55-fold higher for the forward reaction than for the reverse reaction, indicating that the enzyme favors the UDCA-producing reaction. As R. gnavus is a common, core bacterium of the human gut microbiota, these results suggest that this bacterium plays a pivotal role in UDCA formation in the colon.

Relationship among intestinal flora, high-fat diets, and hyperlipidemia

In recent years, research has found close associations among intestinal flora, high-fat diets, and hyperlipidemia. Intestinal flora may regulate blood lipids by producing cholesterol oxidase, inhibiting the activity of liver lipase, regulating the distribution of cholesterol in the blood and liver, and affecting biliary enterohepatic circulation. High-fat diets and hyperlipidemia can influence the composition of intestinal flora by reducing intestinal nutrient source, changing redox state, and destroying the microenvironment in which intestinal flora survive. Molecular mechanisms by which intestinal flora regulates lipid metabolism include directly regulating fat storage genes of the host (inhibiting the activity of fasting-induced adipose factor gene, enhancing the expression of sterol regulatory element binding protein-1 and carbohydrate response element binding protein, and reducing the activity of AMP-activated protein kinase) and modulating the activity of lipopolysaccharide to change the body's chronic low inflammation state. Prevention of hyperlipidemia by regulating the intestinal flora or prevention and treatment of related diseases by adjusting the diet and reducing blood fat to change the composition of intestinal flora are becoming research hotspots.

Cross-talk between Akkermansia muciniphila and intestinal epithelium controls diet-induced obesity

Obesity and type 2 diabetes are characterized by altered gut microbiota, inflammation, and gut barrier disruption. Microbial composition and the mechanisms of interaction with the host that affect gut barrier function during obesity and type 2 diabetes have not been elucidated. We recently isolated Akkermansia muciniphila, which is a mucin-degrading bacterium that resides in the mucus layer. The presence of this bacterium inversely correlates with body weight in rodents and humans. However, the precise physiological roles played by this bacterium during obesity and metabolic disorders are unknown. This study demonstrated that the abundance of A. muciniphila decreased in obese and type 2 diabetic mice. We also observed that prebiotic feeding normalized A. muciniphila abundance, which correlated with an improved metabolic profile. In addition, we demonstrated that A. muciniphila treatment reversed high-fat diet-induced metabolic disorders, including fat-mass gain, metabolic endotoxemia, adipose tissue inflammation, and insulin resistance. A. muciniphila administration increased the intestinal levels of endocannabinoids that control inflammation, the gut barrier, and gut peptide secretion. Finally, we demonstrated that all these effects required viable A. muciniphila because treatment with heat-killed cells did not improve the metabolic profile or the mucus layer thickness. In summary, this study provides substantial insight into the intricate mechanisms of bacterial (i.e., A. muciniphila) regulation of the cross-talk between the host and gut microbiota. These results also provide a rationale for the development of a treatment that uses this human mucus colonizer for the prevention or treatment of obesity and its associated metabolic disorders.

Effect of acute and chronic red wine consumption on lipopolysaccharide concentrations

BACKGROUND

Chronic red wine (RW) consumption has been associated with decreased cardiovascular disease risk, mainly attributed to an improvement in lipid profile. RW intake is also able to change the composition of gut microbiota. High fat intake has recently been reported to increase metabolic endotoxemia. The gut microbiota has been proposed as the main resource of plasma lipopolysaccharides (LPSs) in metabolic endotoxemia.

OBJECTIVE

We analyzed the effect on LPS concentrations of chronic RW consumption and acute RW intake in relation to high fat intake in middle-aged men.

DESIGN

For the chronic study, 10 middle-aged male volunteers were randomly assigned in a crossover trial, and after a washout period, all subjects received RW, dealcoholized red wine (DRW), or gin for 20 d. Serum endotoxin and LPS-binding protein (LBP) concentrations were determined after the washout period and after each of the treatments, and changes in fecal microbiota were quantified. For the acute study, 5 adult men underwent a fat overload or a fat overload together with the consumption of RW, DRW, or gin. Baseline and postprandial serum LPS and LBP concentrations and postprandial chylomicron LPS concentrations were measured.

RESULTS

There were no significant differences in the change in LPS or LBP concentrations between chronic RW, DRW, and gin consumption. Bifidobacterium and Prevotella amounts were significantly increased by RW and correlated negatively with LPS concentrations. There were no differences in postprandial serum LPS, LBP, or chylomicron LPS concentrations between acute RW, DRW, or gin intake together with a fatty meal.

CONCLUSION

Chronic RW consumption increases Bifidobacterium and Prevotella amounts, which may have beneficial effects by leading to lower LPS concentrations. This trial was registered at controlled-trials.com as ISRCTN88720134.

Oligofructose supplementation (10%) during pregnancy and lactation does not change the inflammatory effect of concurrent trans fatty acid ingestion on 21-day-old offspring

Background

Previously, we demonstrated that trans fatty acid ingestion during pregnancy and lactation caused a pro-inflammatory effect on the newborn. The opposite effect was described for gestational prebiotic intake. In the present study, we examined whether supplementation of the diet of the dams with 10% of oligofructose with or without hydrogenated vegetable fat during pregnancy and lactation affected the pro-inflammatory status on the pups at age 21 days.

Methods

On the first day of pregnancy, rats were divided into four groups, each of which received one of four diets: a control diet (C group), a control diet supplemented with 10% oligofructose (CF group), a diet enriched with hydrogenated vegetable fat containing trans fatty acids (T group) or a diet enriched with hydrogenated vegetable fat containing trans fatty acids supplemented with 10% oligofructose (TF group). The pups were weighed at birth and at 7, 14 and 21 days of life and were euthanized on post-natal day 21. The serum glucose, insulin and adiponectin concentrations were analyzed. The IL-6, IL-10 and TNF-α contents of the retroperitoneal white adipose tissue, liver, soleus and extensor digital longus muscles were analyzed by ELISA. The results are presented as the means ± standard error of the mean. Statistical significance was assessed using two-way ANOVA, followed by Tukey's test and considered significant at p < 0.05

Results

The body weights of the 21-day old pups in the CF and TF groups were significant lower than those of the C (27% and 21%) and T (25% and 19%, respectively) groups. The serum levels of adiponectin in the CF, T and TF groups were lower than in the C group (41%; 34% and 31%, respectively). In the retroperitoneal adipose tissue, the IL-6 content was increased in TF group relative to the C and CF groups (74% for both), and the TNF-α content was higher in the T and TF groups than in the C group (62% and 98%, respectively). In the liver, the TNF-α (56% and 104%) and IL-10 (52% and 73%) contents were increased in the CF group relative to the C and TF groups.

Conclusions

Supplementation of the diet of the dams with 10% of oligofructose during pregnancy and lactation, independent of supplementation with hydrogenated vegetable fat, adversely affected the development of the offspring and contributed to development of a pro-inflammatory status in the pups on postnatal day 21.

Gut microbiota and obesity: lessons from the microbiome

The distal gut harbours microbial communities that outnumber our own eukaryotic cells. The contribution of the gut microbiota to the development of several diseases (e.g. obesity, type 2 diabetes, steatosis, cardiovascular diseases and inflammatory bowel diseases) is becoming clear, although the causality remains to be proven in humans. Global changes in the gut microbiota have been observed by a number of culture-dependent and culture-independent methods, and while the latter have mostly included 16S ribosomal RNA gene analyses, more recent studies have utilized DNA sequencing of whole-microbial communities. Altogether, these high-throughput methods have facilitated the identification of novel candidate bacteria and, most importantly, metabolic functions that might be associated with obesity and type 2 diabetes. This review discusses the association between specific taxa and obesity, together with the techniques that are used to characterize the gut microbiota in the context of obesity and type 2 diabetes. Recent results are discussed in the framework of the interactions between gut microbiota and host metabolism.

Oral administration of Lactobacillus reuteri GMNL-263 improves insulin resistance and ameliorates hepatic steatosis in high fructose-fed rats

BACKGROUND

Type 2 diabetes mellitus (DM), characterized by peripheral insulin resistance, is the most common form of diabetes. Probiotics are live micro-organisms that, when administered in adequate amounts, confer delaying effect on DM development. In this study, the effects Lactobacillus reuteri GMNL-263 (Lr263), a new probiotic strain developed by our laboratory, on insulin resistance and the development of hepatic steatosis in high-fructose fed rats were explored. Furthermore, the relevant regulatory pathways involved were also investigated.

METHOD

Male Sprague-Dawley rats were fed a high-fructose diet with or without Lr263 administration for 14 weeks. The composition of fecal microbiota, oral glucose tolerance, glycated haemoglobin, insulin, leptin, C-peptide, and incretins were measured. The markers of liver injury, serum and hepatic lipids profile, activity of hepatic antioxidant enzyme, and proinflammatory cytokines in adipose tissue were investigated. Additionally, the expression of hepatic lipogenic genes and insulin signaling related genes in adipose tissue were also studied. Liver sections were examined for hepatic steatosis using hematoxylin-eosin staining.

RESULTS

The levels of serum glucose, insulin, leptin, C-peptide, glycated hemoglobin, GLP-1, liver injury markers, lipid profile in serum and liver were significantly increased in high-fructose-fed rats. However, after Lr263 administration, the elevation of these parameters was significantly suppressed. Feeding of Lr263 reversed the decreased number of bifidobacterium species and lactobacillus species and increased number of clostridium species induced by high fructose treatment. The decreased activities of hepatic antioxidant enzymes in HFD rats were dramatically reversed by Lr263 treatment. Concentrations of IL-6 and TNF-α in adipose tissue which were elevated in high fructose treatment were markedly decreased after Lr263 feeding. Decreased levels of PPAR-γ and GLUT4 mRNA after high fructose treatment were significantly enhanced by Lr263 administration. Lr263 consumption normalized the increased lipogenic gene (Srebp-1c, FAS, and Elvol6) expressions stimulated by high fructose. Administration of Lr263 significantly ameliorated hepatic steatosis observed in high fructose treated rats.

CONCLUSION

Our study provided evidences clarifying the effectiveness of Lr263 on reducing insulin resistance as well as hepatic steatosis formation in high-fructose-fed rats and suggested that Lr263 may be a promising therapeutic agent in treating type 2 diabetes.

Effects of indigestible carbohydrates in barley on glucose metabolism, appetite and voluntary food intake over 16 h in healthy adults

Background

Recent knowledge in animals suggests that gut microbial metabolism may affect host metabolism, including appetite regulating hormones. The aim of the present study was to evaluate the potential effects of a whole grain barley kernel product, rich in intrinsic indigestible carbohydrates (dietary fibre and resistant starch), on markers of metabolism and appetite regulation in healthy subjects.

Methods

Boiled barley kernels (BK) or white wheat bread (WWB; reference) were provided as late evening meals to 19 young adults in random order using a cross-over design. During subsequent ad libitum standardized breakfast and lunch meals (10.5-16 h), blood was collected for analysis of glucose, plasma insulin, adiponectin, ghrelin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), serum free fatty acids (FFA) and interleukin (IL)-6. In addition, appetite sensations, voluntary energy intake and breath H₂ were determined.

Results

BK as evening meal increased plasma GLP-1 at fasting (P < 0.05) and during the experimental day (P < 0.01) compared with WWB. In addition the BK evening meal decreased fasting serum FFA (P < 0.05) and tended to decrease fasting serum IL-6 (P = 0.06). At lunch, preceded by BK evening meal, voluntary energy intake was decreased (P < 0.05) when compared to WWB evening meal. The BK evening meal decreased incremental blood glucose area (P < 0.01), promoted higher breath H₂ (P < 0.001), maintained adiponectin concentrations (P < 0.05) and reduced perceived hunger (P < 0.05) during 10.5-16 h after the meal.

Conclusions

The results indicate that the BK evening meal, facilitate glucose regulation, increase the release of GLP-1, reduce subsequent energy intake while at the same time decreasing hunger over 2 subsequent meals, and reduce fasting FFA the subsequent morning, possibly mediated through gut microbial fermentation of the indigestible carbohydrates.

Effects of a brown beans evening meal on metabolic risk markers and appetite regulating hormones at a subsequent standardized breakfast: a randomized cross-over study

BACKGROUND

Dietary prevention strategies are increasingly recognized as essential to combat the current epidemic of obesity and related metabolic disorders. The purpose of the present study was to evaluate the potential prebiotic effects of indigestible carbohydrates in Swedish brown beans (Phaseolus vulgaris var. nanus) in relation to cardiometabolic risk markers and appetite regulating hormones.

METHODS

Brown beans, or white wheat bread (WWB, reference product) were provided as evening meals to 16 healthy young adults in a randomised crossover design. Glucose, insulin, appetite regulatory hormones, GLP-1, GLP-2, appetite sensations, and markers of inflammation were measured at a following standardised breakfast, that is at 11 to 14 h post the evening meals. Additionally, colonic fermentation activity was estimated from measurement of plasma short chain fatty acids (SCFA, including also branched chain fatty acids) and breath hydrogen (H2) excretion.

RESULTS

An evening meal of brown beans, in comparison with WWB, lowered blood glucose (-15%, p<0.01)- and insulin (-16%, p<0.05) responses, increased satiety hormones (PYY 51%, p<0.001), suppressed hunger hormones (ghrelin -14%, p<0.05), and hunger sensations (-15%, p = 0.05), increased GLP-2 concentrations (8.4%, p<0.05) and suppressed inflammatory markers (IL-6 -35%, and IL-18 -8.3%, p<0.05) at a subsequent standardised breakfast. Breath H2 (141%, p<0.01), propionate (16%, p<0.05), and isobutyrate (18%, P<0.001) were significantly increased after brown beans compared to after WWB, indicating a higher colonic fermentative activity after brown beans.

CONCLUSIONS

An evening meal with brown beans beneficially affected important measures of cardiometabolic risk and appetite regulatory hormones, within a time frame of 11-14 h, in comparison to a WWB evening meal. Concentrations of plasma SCFA and H2 were increased, indicating involvement of colonic fermentation. Indigestible colonic substrates from brown beans may provide a preventive tool in relation to obesity and the metabolic syndrome.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01706042.

Gut microbiota and metabolic disorders: How prebiotic can work?

Experimental data in animals, but also observational studies in obese patients, suggest that the composition of the gut microbiota differs in obese v. lean individuals, in diabetic v. non-diabetic patients or in patients presenting other diseases associated with obesity or nutritional dysbalance, such as non-alcoholic steatohepatitis. In the present review, we will describe how changes in the gut microbiota composition and/or activity by dietary fibres with prebiotic properties, can modulate host gene expression and metabolism. We will evaluate their potential relevance in the management of obesity and related metabolic disturbances, in view of the experimental data and intervention studies published up to date.

Effect of Lactobacillus gasseri BNR17 on Overweight and Obese Adults: A Randomized, Double-Blind Clinical Trial

Background

Lactobacillus gasseri BNR17 is a type of probiotic strain isolated from human breast milk. A study was reported regarding the fact that BNR17 was an inhibitor of obesity and diabetic activities in the human body through previous animal experiments. This study was furthered to investigate the effect of BNR17, a probiotic strain isolated from human breast milk, on obese and overweight adults.

Methods

Sixty-two obese volunteers aged 19 to 60 with body mass index ≥ 23 kg/m² and fasting blood sugar ≥ 100 mg/dL participated in a placebo controlled, randomized, and double-blind trial. For 12 weeks, 57 participants were given either placebo or BNR17 and were tested by measuring body fat, body weight, various biochemical parameters, vital signs, and computed tomography at the start of the study and at weeks 4, 8, and 12. The subjects assumed usual daily activities without having to make behavioral or dietary modifications during the course of the study.

Results

At the 12th week, a slight reduction in body weight was noted in the BNR17 group, but there were no significant weight changes between groups. Decrease of waist and hip circumferences in the BNR17 group was more pronounced than those in the placebo group. The two groups had no special or severe adverse reactions.

Conclusion

Despite there being no change in behavior or diet, administration of only the supplement of BNR17 reduced weight and waist and hip circumference. However, there were no significant differences between the two groups. These findings warrant a subsequent longer-term prospective clinical investigation with a large population.

Implication of fermentable carbohydrates targeting the gut microbiota on conjugated linoleic acid production in high-fat-fed mice

In vitro experiments have shown that isolated human gut bacteria are able to metabolise PUFA into conjugated PUFA like conjugated linoleic acids (CLA). The hypothesis of the present paper was that high-fat (HF) diet feeding and supplementation with fermentable carbohydrates that have prebiotic properties modulate the in vivo production of CLA by the mouse gut microbiota. Mice were treated for 4 weeks as follows: control (CT) groups were fed a standard diet; HF groups were fed a HF diet rich in linoleic acid (18 : 2n-6); the third groups were fed with the HF diet supplemented with either inulin-type fructans (HF-ITF) or arabinoxylans (HF-Ax). HF diet feeding increased rumenic acid (cis-9,trans-11-18 : 2 CLA) content both in the caecal and liver tissues compared with the CT groups. ITF supplementation had no major effect compared with the HF diet whereas Ax supplementation increased further rumenic acid (cis-9,trans-11-18 : 2 CLA) in the caecal tissue. These differences between both prebiotics may be linked to the high fat-binding capacity of Ax that provides more substrates for bacterial metabolism and to differential modulation of the gut microbiota (specific increase in Roseburia spp. in HF-Ax v. HF). In conclusion, these experiments supply the proof of concept that the mouse gut microbiota produces CLA in vivo, with consequences on the level of CLA in the caecal and liver tissues. We postulate that the CLA-producing bacteria could be a mediator to consider in the metabolic effects of both HF diet feeding and prebiotic supplementation.

Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: Part II - contemporary contextual research

In recent years there has been a renewed interest concerning the ways in which the gastrointestinal tract – its functional integrity and microbial residents – might influence human mood (e.g. depression) and behavioral disorders. Once a hotbed of scientific interest in the early 20th century, this area lay dormant for decades, in part due to its association with the controversial term ‘autointoxication’. Here we review contemporary findings related to intestinal permeability, small intestinal bacterial overgrowth, lipopolysaccharide endotoxin (LPS) exposure, D-lactic acid, propionic acid, and discuss their relevance to microbiota and mental health. In addition, we include the context of modern dietary habits as they relate to depression, anxiety and their potential interaction with intestinal microbiota.

GPR43/FFA2: physiopathological relevance and therapeutic prospects

Research interest in free fatty acid-binding receptors has been growing during the past decade, with an aim to better understand the modulation of host physiology in response to nutrition. G-protein-coupled receptor 43 (GPR43), also called free fatty acid receptor 2 (FFA2/FFAR2), binds short-chain fatty acids (SCFAs) produced by the microbial fermentation of carbohydrates and has shown promising therapeutic potential. This review presents current knowledge regarding the pharmacological properties of GPR43 and addresses its functions in selected organs (adipose tissue, intestine and immune cells). Furthermore, the demonstration of GPR43 involvement in several pathological conditions such as obesity, inflammatory disease, and cancer suggests new fields of interest related to this receptor. Finally, GPR43 could be a key player in gut microbes-host crosstalk, although further research is needed to clearly evaluate its role in the management of host health by nutrients or treatments targeting the gut microbiota.

Suggested involvement of ketone bodies in the pathogenesis of the metabolic syndrome

Untreated brain mitochondria are strong producers of H2O2. High peroxide production (in the presence of glutamate and pyruvate) is strictly succinate-dependent. Importantly, it is inhibited by the ketone body acetoacetate (AcAc) starting at 10 μM (maximal effect at 0.5mM). Butyrate derives from the fermentation of prebiotics, is present physiologically in the colon and is a strong producer of AcAc: indeed butyrate induces in the colon the transcription of mitochondrial 3-hydroxy-3-methyl glutarylCoA (HMGCoA) synthase, a key enzyme in ketone body synthesis. Obesity and insulin resistance were shown to be dependent on increased permeability of the colon epithelium to bacterial lipopolysaccharide (LPS); the process is evident particularly upon ingestion of lipids (a peroxidative event, inhibited by vitamin E) and is likely sensitive to AcAc. The oxidation of butyrate and the production of AcAc in the colon appear to be inhibited by high luminal sulphides and high NH3, a situation that presumably facilitates LPS permeation (on the contrary beta-hydroxy-butyrate oxidation is not inhibited). It is proposed that these damaging events may be opposed by the delivery of ketone bodies directly to the colon.

Gut bacterial microbiota and obesity

Although probiotics and antibiotics have been used for decades as growth promoters in animals, attention has only recently been drawn to the association between the gut microbiota composition, its manipulation, and obesity. Studies in mice have associated the phylum Firmicutes with obesity and the phylum Bacteroidetes with weight loss. Proposed mechanisms linking the microbiota to fat content and weight include differential effects of bacteria on the efficiency of energy extraction from the diet, and changes in host metabolism of absorbed calories. The independent effect of the microbiota on fat accumulation has been demonstrated in mice, where transplantation of microbiota from obese mice or mice fed western diets to lean or germ-free mice produced fat accumulation among recipients. The microbiota can be manipulated by prebiotics, probiotics, and antibiotics. Probiotics affect the microbiota directly by modulating its bacterial content, and indirectly through bacteriocins produced by the probiotic bacteria. Interestingly, certain probiotics are associated with weight gain both in animals and in humans. The effects are dependent on the probiotic strain, the host, and specific host characteristics, such as age and baseline nutritional status. Attention has recently been drawn to the association between antibiotic use and weight gain in children and adults. We herein review the studies describing the associations between the microbiota composition, its manipulation, and obesity.

A mixture of trans-galactooligosaccharides reduces markers of metabolic syndrome and modulates the fecal microbiota and immune function of overweight adults

Metabolic syndrome is a set of disorders that increases the risk of developing cardiovascular disease. The gut microbiota is altered toward a less beneficial composition in overweight adults and this change can be accompanied by inflammation. Prebiotics such as galactooligosaccharides can positively modify the gut microbiota and immune system; some may also reduce blood lipids. We assessed the effect of a galactooligosaccharide mixture [Bi2muno (B-GOS)] on markers of metabolic syndrome, gut microbiota, and immune function in 45 overweight adults with ≥3 risk factors associated with metabolic syndrome in a double-blind, randomized, placebo (maltodextrin)-controlled, crossover study (with a 4-wk wash-out period between interventions). Whole blood, saliva, feces, and anthropometric measurements were taken at the beginning, wk 6, and end of each 12-wk intervention period. Predominant groups of fecal bacteria were quantified and full blood count, markers of inflammation and lipid metabolism, insulin, and glucose were measured. B-GOS increased the number of fecal bifidobacteria at the expense of less desirable groups of bacteria. Increases in fecal secretory IgA and decreases in fecal calprotectin, plasma C-reactive protein, insulin, total cholesterol (TC), TG, and the TC:HDL cholesterol ratio were also observed. Administration of B-GOS to overweight adults resulted in positive effects on the composition of the gut microbiota, the immune response, and insulin, TC, and TG concentrations. B-GOS may be a useful candidate for the enhancement of gastrointestinal health, immune function, and the reduction of metabolic syndrome risk factors in overweight adults.

Dietary supplementation with Agaricus blazei murill extract prevents diet-induced obesity and insulin resistance in rats

OBJECTIVE

Dietary supplement may potentially help to fight obesity and other metabolic disorders such as insulin-resistance and low-grade inflammation. The present study aimed to test whether supplementation with Agaricus blazei murill (ABM) extract could have an effect on diet-induced obesity in rats.

DESIGN AND METHODS

Wistar rats were fed with control diet (CD) or high-fat diet (HF) and either with or without supplemented ABM for 20 weeks.

RESULTS

HF diet-induced body weight gain and increased fat mass compared to CD. In addition HF-fed rats developed hyperleptinemia and insulinemia as well as insulin resistance and glucose intolerance. In HF-fed rats, visceral adipose tissue also expressed biomarkers of inflammation. ABM supplementation in HF rats had a protective effect against body weight gain and all study related disorders. This was not due to decreased food intake which remained significantly higher in HF rats whether supplemented with ABM or not compared to control. There was also no change in gut microbiota composition in HF supplemented with ABM. Interestingly, ABM supplementation induced an increase in both energy expenditure and locomotor activity which could partially explain its protective effect against diet-induced obesity. In addition a decrease in pancreatic lipase activity is also observed in jejunum of ABM-treated rats suggesting a decrease in lipid absorption.

CONCLUSIONS

Taken together these data highlight a role for ABM to prevent body weight gain and related disorders in peripheral targets independently of effect in food intake in central nervous system.

Association of plasma endotoxin, inflammatory cytokines and risk of colorectal adenomas

Background

Recent studies suggest that bacterial endotoxins may be associated with various chronic diseases, including colorectal adenomas and cancer. Given the evidence linking inflammation and colorectal cancer, we sought to determine if plasma endotoxin concentrations are associated with indicators of systemic or local inflammation and colorectal adenomas.

Methods

This cross-sectional study consisted of participants who underwent screening colonoscopies and included adenoma cases (n=138) and non-adenoma controls (n=324). Plasma concentrations of endotoxin were measured with Limulus Amebocyte Lysate (LAL) assay. We quantified concentrations of inflammatory cytokines, interleukin-4 (IL-4), IL-6, IL-8, IL-10, IL-12, tumor necrosis factor-alpha (TNF-α), and interferon-γ (IFN-γ) in plasma by ELISA and mRNA expression levels in rectal mucosal biopsies by quantitative RT-PCR. Interleukin-17 was evaluated only in the rectal mucosa.

Results

Compared to subjects with low plasma endotoxin concentrations, those with higher concentrations were more likely to have adenomas (OR 1.4, 95% CI 1.0-2.1). Among subjects with adenomas, those with villous histology were more likely to have higher endotoxin concentrations (5.4 vs. 4.1EU/mL, p=0.05) and lower plasma IFN-γ (0 vs. 1.64 pg/mL, p=0.02) compared to those with only tubular adenomas. Cases showed a trend of having higher plasma TNF-α levels than controls (p=0.06), but none of the other plasma or rectal mucosal cytokine levels differed between cases and controls. Elevated mucosal IL-12 levels were associated with having multiple adenomas (p=0.04). Higher concentrations of plasma endotoxin predicted increased plasma IL-12 levels (OR 1.5, 95% CI 1.0-2.2) and rectal mucosal IL-12 (OR 1.9, 95% CI 1.0-3.7) and IL-17 gene expression (OR 2.2, 95% CI 1.0-4.6).

Conclusions

These findings suggest that interactions between elevated plasma endotoxin concentrations and inflammatory cytokines may be relevant to the development of colorectal adenomas.

Faecal levels of Bifidobacterium and Clostridium coccoides but not plasma lipopolysaccharide are inversely related to insulin and HOMA index in women

BACKGROUND & AIMS

The abundance of specific microbes might be associated with plasma lipopolysaccharide and insulin levels. The aims were to quantify the abundance of specific microbes and plasma LPS in females and assess their association with anthropometric, body composition and biochemical measurements.

METHODS

Seventeen lean (BMI 19-24.99 kg/m(2)) and fifteen obese females (BMI > 30 kg/m(2)) participated. Anthropometry, body composition, food intake and biochemical analyses were assessed. Bacterial groups in faeces were analysed by qPCR method.

RESULTS

Lactobacillus plantarum prevalence was higher (p = 0.005) and its counts tended to be higher in lean vs. obese group (p = 0.06). Bifidobacterium genus, Bifidobacterium longum, Clostridium coccoides and Clostridium leptum counts were higher in lean women (p < 0.05); prevalence and counts of Akkermansia muciniphila tended to be higher in lean group (p = 0.09, p = 0.06, respectively). Plasma LPS levels were similar between the study groups (p > 0.05). No association was found between LPS and bacterial levels or insulin. Bifidobacteria and C. coccoides counts were inversely associated with insulin and HOMA index.

CONCLUSIONS

Abundance of specific microbes is distinct between obese and lean women, but is not associated with LPS level. Bifidobacterial and C. coccoides levels are associated with insulin sensitivity. These bacterial groups may be capable of modulating insulin action.

Characterisation of gut microbiota in Ossabaw and Göttingen minipigs as models of obesity and metabolic syndrome

Background

Recent evidence suggests that the gut microbiota is an important contributing factor to obesity and obesity related metabolic disorders, known as the metabolic syndrome. The aim of this study was to characterise the intestinal microbiota in two pig models of obesity namely Göttingen minipigs and the Ossabaw minipigs.

Methods and Findings

The cecal, ileal and colonic microbiota from lean and obese Osabaw and Göttingen minipigs were investigated by Illumina-based sequencing and by high throughput qPCR, targeting the 16S rRNA gene in different phylogenetic groups of bacteria. The weight gain through the study was significant in obese Göttingen and Ossabaw minipigs. The lean Göttingen minipigs’ cecal microbiota contained significantly higher abundance of Firmicutes (P<0.006), Akkermensia (P<0.01) and Methanovibribacter (P<0.01) than obese Göttingen minipigs. The obese Göttingen cecum had higher abundances of the phyla Spirochaetes (P<0.03), Tenericutes (P<0.004), Verrucomicrobia (P<0.005) and the genus Bacteroides (P<0.001) compared to lean minipigs. The relative proportion of Clostridium cluster XIV was 7.6-fold higher in cecal microbiota of obese Göttingen minipigs as compared to lean. Obese Ossabaw minipigs had a higher abundance of Firmicutes in terminal ileum and lower abundance of Bacteroidetes in colon than lean Ossabaw minipigs (P<0.01). Obese Ossabaws had significantly lower abundances of the genera Prevotella and Lactobacillus and higher abundance of Clostridium in their colon than the lean Ossabaws. Overall, the Göttingen and Ossabaw minipigs displayed different microbial communities in response to diet-induced obesity in the different sections of their intestine.

Conclusion

Obesity-related changes in the composition of the gut microbiota were found in lean versus obese Göttingen and Ossabaw minipigs. In both pig models diet seems to be the defining factor that shapes the gut microbiota as observed by changes in different bacteria divisions between lean and obese minipigs.

ILSI Brazil International Workshop on Functional Foods: a narrative review of the scientific evidence in the area of carbohydrates, microbiome, and health

To stimulate discussion around the topic of ‘carbohydrates’ and health, the Brazilian branch of the International Life Sciences Institute held the 11th International Functional Foods Workshop (1–2 December 2011) in which consolidated knowledge and recent scientific advances specific to the relationship between carbohydrates and health were presented. As part of this meeting, several key points related to dietary fiber, glycemic response, fructose, and impacts on satiety, cognition, mood, and gut microbiota were realized: 1) there is a need for global harmonization of a science-based fiber definition; 2) low-glycemic index foods can be used to modulate the postprandial glycemic response and may affect diabetes and cardiovascular outcomes; 3) carbohydrate type may influence satiety and satiation; glycemic load and glycemic index show links to memory, mood, and concentration; 4) validated biomarkers are needed to demonstrate the known prebiotic effect of carbohydrates; 5) negative effects of fructose are not evident when human data are systematically reviewed; 6) new research indicates that diet strongly influences the microbiome; and 7) there is mounting evidence that the intestinal microbiota has the ability to impact the gut–brain axis. Overall, there is much promise for development of functional foods that impact the microbiome and other factors relevant to health, including glycemic response (glycemic index/glycemic load), satiety, mood, cognition, and weight management.

Nutrition, the gut microbiome and the metabolic syndrome

Metabolic syndrome is a lifestyle disease, determined by the interplay of genetic and environmental factors. Obesity is a significant risk factor for development of the metabolic syndrome, and the prevalence of obesity is increasing due to changes in lifestyle and diet. Recently, the gut microbiota has emerged as an important contributor to the development of obesity and metabolic disorders, through its interactions with environmental (e.g. diet) and genetic factors. Human and animal studies have shown that alterations in intestinal microbiota composition and shifts in the gut microbiome towards increased energy harvest are associated with an obese phenotype. However, the underlying mechanisms by which gut microbiota affects host metabolism still need to be defined. In this review we discuss the complexity surrounding the interactions between diet and the gut microbiota, and their connection to obesity. Furthermore, we review the literature on the effects of probiotics and prebiotics on the gut microbiota and host metabolism, focussing primarily on their anti-obesity potential.

Diabetes, obesity and gut microbiota

The gut microbiota composition has been associated with several hallmarks of metabolic syndrome (e.g., obesity, type 2 diabetes, cardiovascular diseases, and non-alcoholic steatohepatitis). Growing evidence suggests that gut microbes contribute to the onset of the low-grade inflammation characterising these metabolic disorders via mechanisms associated with gut barrier dysfunctions. Recently, enteroendocrine cells and the endocannabinoid system have been shown to control gut permeability and metabolic endotoxaemia. Moreover, targeted nutritional interventions using non-digestible carbohydrates with prebiotic properties have shown promising results in pre-clinical studies in this context, although human intervention studies warrant further investigations. Thus, in this review, we discuss putative mechanisms linking gut microbiota and type 2 diabetes. These data underline the advantage of investigating and changing the gut microbiota as a therapeutic target in the context of obesity and type 2 diabetes.

Lipotoxicity: effects of dietary saturated and transfatty acids

The ingestion of excessive amounts of saturated fatty acids (SFAs) and transfatty acids (TFAs) is considered to be a risk factor for cardiovascular diseases, insulin resistance, dyslipidemia, and obesity. The focus of this paper was to elucidate the influence of dietary SFA and TFA intake on the promotion of lipotoxicity to the liver and cardiovascular, endothelial, and gut microbiota systems, as well as on insulin resistance and endoplasmic reticulum stress. The saturated and transfatty acids favor a proinflammatory state leading to insulin resistance. These fatty acids can be involved in several inflammatory pathways, contributing to disease progression in chronic inflammation, autoimmunity, allergy, cancer, atherosclerosis, hypertension, and heart hypertrophy as well as other metabolic and degenerative diseases. As a consequence, lipotoxicity may occur in several target organs by direct effects, represented by inflammation pathways, and through indirect effects, including an important alteration in the gut microbiota associated with endotoxemia. Interactions between these pathways may perpetuate a feedback process that exacerbates an inflammatory state. The importance of lifestyle modification, including an improved diet, is recommended as a strategy for treatment of these diseases.

Alterations in fecal Lactobacillus and Bifidobacterium species in type 2 diabetic patients in Southern China population

Background: The connection between gut microbiota and metabolism and its role in the pathogenesis of diabetes are increasingly recognized. The objective of this study was to quantitatively measure Bifidobacterium and Lactobacillus species, members of commensal bacteria found in human gut, in type 2 diabetic patients (T2D) patients from Southern China.

Methods: Fifty patients with T2D and thirty control individuals of similar body mass index (BMI) were recruited from Southern China. T2D and control subjects were confirmed with both oral glucose tolerance test (OGTT) and HbA_1c measurements. Bifidobacterium and Lactobacillus species in feces were measured by real-time quantitative PCR. Data were analyzed with STATA 11.0 statistical software.

Results: In comparison to control subjects T2D patients had significantly more total Lactobacillus (+18%), L. bugaricus (+13%), L. rhamnosum (+37%) and L. acidophilus (+48%) (P < 0.05). In contrast, T2D patients had less amounts of total Bifidobacteria (−7%) and B. adolescentis (−12%) (P < 0.05). Cluster analysis showed that gut microbiota pattern of T2D patients is characterized by greater numbers of L. rhamnosus and L. acidophillus, together with lesser numbers of B. adolescentis (P < 0.05).

Conclusion: The gut microflora in T2D patients is characterized by greater numbers of Lactobacillus and lesser numbers of Bifidobacterium species.

Effects of diet on gut microbiota profile and the implications for health and disease

Gut microbes are present in large concentrations on the human intestinal mucosal surface and play important roles in health and disease of the host. Numerous groups of gut microbes are associated with immunological and metabolic diseases and in maintaining health status of the host. Among these health- and disease-associated gut microbes, Bacteroides, Clostridium and Bifidobacterium appear regularly in the list. Scientific and clinical evidence available to date indicates that diet is a major driving factor for the establishment of the gut microbiome. Slow digestible carbohydrates (human milk glycan, inulin and fructooligosaccharide), insoluble complex carbohydrates and protein diets favor the growth of Bacteroides, Clostridium and Bifidobacterium. Fat on the other hand suppresses the number of Bacteroides, Clostridium and Bifidobacterium; whereas polyphenols in general suppress Bacteroides and Clodtridium but enhance the Bifodobacterium. The implication is that dietary habits could be a major determinant of health and disease susceptibility. Dietary strategies could be an effective means of potentially inducing changes in intestinal microbiota and are certainly achievable, thus facilitating correction of intestinal microbiome aberrations or imbalances to improve our health. Most of the physiological and functional interactions between individual dietary components and the concoction of foods in a meal and gut microbiota have not yet been well studied. A concerted effort is required to acquire better understanding of their interaction in order to rationally maintain our intestinal microbiome homeostasis and general health through dietary intervention.

Anti-obesity effect of Lactobacillus gasseri BNR17 in high-sucrose diet-induced obese mice

Previously, we reported that Lactobacillus gasseri BNR17 (BNR17), a probiotic strain isolated from human breast milk, inhibited increases in body weight and adipocyte tissue weight in high-sucrose diet-fed Sprague-Dawley (SD) rats and reduced glucose levels in type 2 diabetes mice. In the current study, we conducted further experiments to extend these observations and elucidate the mechanism involved. C57BL/6J mice received a normal diet, high-sucrose diet or high-sucrose diet containing L. gasseri BNR17 (10⁹ or 10¹⁰ CFU) for 10 weeks. The administration of L. gasseri BNR17 significantly reduced the body weight and white adipose tissue weight regardless of the dose administered. In BNR17-fed groups, mRNA levels of fatty acid oxidation-related genes (ACO, CPT1, PPARα, PPARδ) were significantly higher and those of fatty acid synthesis-related genes (SREBP-1c, ACC) were lower compared to the high-sucrose-diet group. The expression of GLUT4, main glucose transporter-4, was elevated in BNR17-fed groups. L. gasseri BNR17 also reduced the levels of leptin and insulin in serum. These results suggest that the anti-obesity actions of L. gasseri BNR17 can be attributed to elevated expression of fatty acid oxidation-related genes and reduced levels of leptin. Additionally, data suggested the anti-diabetes activity of L. gasseri BNR17 may be to due elevated GLUT4 and reduced insulin levels.

Changes in gut microbiota due to supplemented fatty acids in diet-induced obese mice

Consumption of a high-fat diet (HFD), which is associated with chronic 'low-grade' systemic inflammation, alters the gut microbiota (GM). The aim of the present study was to investigate the ability of an oleic acid-derived compound (S1) and a combination of n-3 fatty acids (EPA and DHA, S2) to modulate both body weight and the GM in HFD-induced obese mice. A total of eighty mice were fed either a control diet or a HFD, non-supplemented or supplemented with S1 or S2. At week 19, faeces were collected in order to analyse the GM. Group-specific primers for accurate quantification of several major bacterial groups from faecal samples were assayed using quantitative PCR. The HFD induced an increase in body weight, which was reduced by supplementation with S1. Furthermore, S1 supplementation markedly increased total bacterial density and restored the proportions of bacteria that were increased (i.e. clostridial cluster XIVa and Enterobacteriales) or decreased (i.e. Bifidobacterium spp.) during HFD feeding. S2 supplementation significantly increased the quantities of Firmicutes (especially the Lactobacillus group). Correlation analysis revealed that body weight correlated positively with the phylum Firmicutes and clostridial cluster XIVa, and negatively with the phylum Bacteroidetes. In conclusion, the consumption of a HFD induced changes in the faecal microbiota, which were associated with the appearance of an obese phenotype. Supplementation of the HFD with S1 counteracted HFD-induced gut dysbiosis, together with an improvement in body weight. These data support a role for certain fatty acids as interesting nutrients related to obesity prevention.

Does our food (environment) change our gut microbiome ('in-vironment'): a potential role for inflammatory bowel disease?

Human biology can only be fully assessed by combining an analysis of both the host and its surrounding environment. As a part of the environment, the human gastrointestinal tract hosts more than 100 trillion bacteria making up the gut microbiota. The human host provides a nutrient-rich environment while the microbiota provides indispensable functions that humans cannot exert themselves. Shifts in the bacterial makeup of the human gut microbiota have been associated with disorders such as inflammatory bowel disease (IBD), irritable bowel syndrome and obesity. However, since most bacteria inhabiting our gut are not cultivable to date, until recently little was known about their individual functions. Metagenomics, i.e. the analysis of the collective genomes present in a defined ecosystem, gives insight into these specific functions. The first extensive catalogue of the intestinal metagenome outnumbers the size of the human genome by a factor of 150. Recently, 3 distinct 'types' of gut composition within the human population have been highlighted. These so-called 'enterotypes' are characterized by the dominant genera (Bacteroides, Prevotella and Ruminococcus) and their co-occurring phylogenetic groups. In accordance with the previously described impact of nutritional behavior (diet, probiotics and prebiotics) on specific bacterial populations, an association has been observed between long-term dietary habits and enterotypes. This recent discovery, i.e. that belonging to one or the other enterotype might be modulated by the diet opens up new perspectives in the fields of IBD, nutrition and therapeutic strategies.