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.

Polyphenol-rich extract of pomegranate peel alleviates tissue inflammation and hypercholesterolaemia in high-fat diet-induced obese mice: potential implication of the gut microbiota.

Pomegranate extracts have been used for centuries in traditional medicine to confer health benefits in a number of inflammatory diseases, microbial infections and cancer. Peel fruit are rich in polyphenols that exhibit antioxidant and anti-inflammatory capacities in vitro. Recent studies strongly suggest that the gut microbiota is an environmental factor to be taken into account when assessing the risk factors related to obesity. The aim of the present study was to test the prebiotic potency of a pomegranate peel extract (PPE) rich in polyphenols in a nutritional model of obesity associated with hypercholesterolaemia and inflammatory disorders. Balb/c mice were fed either a control diet or a high-fat (HF) diet with or without PPE (6 mg/d per mouse) over a period of 4 weeks. Interestingly, PPE supplementation increased caecal content weight and caecal pool of bifidobacteria. It did not significantly modify body weight gain, glycaemia, glucose tolerance and inflammatory markers measured in the serum. However, it reduced the serum level of cholesterol (total and LDL) induced by HF feeding. Furthermore, it counteracted the HF-induced expression of inflammatory markers both in the colon and the visceral adipose tissue. Together, these findings support that pomegranate constitutes a promising food in the control of atherogenic and inflammatory disorders associated with diet-induced obesity. Knowing the poor bioavailability of pomegranate polyphenols, its bifidogenic effect observed after PPE consumption suggests the involvement of the gut microbiota in the management of host metabolism by polyphenolic compounds present in pomegranate.

Restoring specific lactobacilli levels decreases inflammation and muscle atrophy markers in an acute leukemia mouse model.

The gut microbiota has recently been proposed as a novel component in the regulation of host homeostasis and immunity. We have assessed for the first time the role of the gut microbiota in a mouse model of leukemia (transplantation of BaF3 cells containing ectopic expression of Bcr-Abl), characterized at the final stage by a loss of fat mass, muscle atrophy, anorexia and inflammation. The gut microbial 16S rDNA analysis, using PCR-Denaturating Gradient Gel Electrophoresis and quantitative PCR, reveals a dysbiosis and a selective modulation of Lactobacillus spp. (decrease of L. reuteri and L. johnsonii/gasseri in favor of L. murinus/animalis) in the BaF3 mice compared to the controls. The restoration of Lactobacillus species by oral supplementation with L. reuteri 100-23 and L. gasseri 311476 reduced the expression of atrophy markers (Atrogin-1, MuRF1, LC3, Cathepsin L) in the gastrocnemius and in the tibialis, a phenomenon correlated with a decrease of inflammatory cytokines (interleukin-6, monocyte chemoattractant protein-1, interleukin-4, granulocyte colony-stimulating factor, quantified by multiplex immuno-assay). These positive effects are strain- and/or species-specific since L. acidophilus NCFM supplementation does not impact on muscle atrophy markers and systemic inflammation. Altogether, these results suggest that the gut microbiota could constitute a novel therapeutic target in the management of leukemia-associated inflammation and related disorders in the muscle.

Dietary modulation of clostridial cluster XIVa gut bacteria (Roseburia spp.) by chitin-glucan fiber improves host metabolic alterations induced by high-fat diet in mice.

Recent studies have provided new evidence that alterations in the composition of the gut microbiota--known as dysbiosis--participate in the development of obesity. The aim of the present study was to investigate the ability of chitin-glucan (CG) from a fungal source to modulate both the gut microbiota and glucose and lipid metabolism in high-fat (HF) diet-induced obese mice. Supplementation of the HF diet with fungal CG (10% w/w) induced caecal enlargement with prominent changes in gut microbiota: it restored the number of bacteria from clostridial cluster XIVa including Roseburia spp., which were decreased due to HF feeding. Furthermore, CG treatment significantly decreased HF-induced body weight gain, fat mass development, fasting hyperglycemia, glucose intolerance, hepatic triglyceride accumulation and hypercholesterolemia, independently of the caloric intake. All those parameters were negatively correlated with specific bacteria of clostridial cluster XIVa, i.e., Roseburia spp. (Pearson's correlations analysis). In contrast to prebiotics that more specifically target the bifidobacteria species, CG effects on obesity appear to be independent of the incretin glucagon-like peptide 1 (GLP-1) production, since portal GLP-1 and proglucagon (its precursor) expression were not modified by the dietary intervention. In conclusion, our findings support the view that chronic consumption of CG has potential beneficial effects with respect to the development of obesity and associated metabolic diabetes and hepatic steatosis, through a mechanism related to the restoration of the composition and/or the activity of gut bacteria, namely, bacteria from clostridial cluster XIVa.

Hepatic n-3 polyunsaturated fatty acid depletion promotes steatosis and insulin resistance in mice: genomic analysis of cellular targets.

Patients with non-alcoholic fatty liver disease are characterised by a decreased n-3/n-6 polyunsaturated fatty acid (PUFA) ratio in hepatic phospholipids. The metabolic consequences of n-3 PUFA depletion in the liver are poorly understood. We have reproduced a drastic drop in n-3 PUFA among hepatic phospholipids by feeding C57Bl/6J mice for 3 months with an n-3 PUFA depleted diet (DEF) versus a control diet (CT), which only differed in the PUFA content. DEF mice exhibited hepatic insulin resistance (assessed by euglycemic-hyperinsulinemic clamp) and steatosis that was associated with a decrease in fatty acid oxidation and occurred despite a higher capacity for triglyceride secretion. Microarray and qPCR analysis of the liver tissue revealed higher expression of all the enzymes involved in lipogenesis in DEF mice compared to CT mice, as well as increased expression and activation of sterol regulatory element binding protein-1c (SREBP-1c). Our data suggest that the activation of the liver X receptor pathway is involved in the overexpression of SREBP-1c, and this phenomenon cannot be attributed to insulin or to endoplasmic reticulum stress responses. In conclusion, n-3 PUFA depletion in liver phospholipids leads to activation of SREBP-1c and lipogenesis, which contributes to hepatic steatosis.

Prebiotic effects of wheat arabinoxylan related to the increase in bifidobacteria, Roseburia and Bacteroides/Prevotella in diet-induced obese mice.

BACKGROUND: Alterations in the composition of gut microbiota--known as dysbiosis--has been proposed to contribute to the development of obesity, thereby supporting the potential interest of nutrients targeting the gut with beneficial effect for host adiposity. We test the ability of a specific concentrate of water-extractable high molecular weight arabinoxylans (AX) from wheat to modulate both the gut microbiota and lipid metabolism in high-fat (HF) diet-induced obese mice. METHODOLOGY/PRINCIPAL FINDINGS: Mice were fed either a control diet (CT) or a HF diet, or a HF diet supplemented with AX (10% w/w) during 4 weeks. AX supplementation restored the number of bacteria that were decreased upon HF feeding, i.e. Bacteroides-Prevotella spp. and Roseburia spp. Importantly, AX treatment markedly increased caecal bifidobacteria content, in particular Bifidobacterium animalis lactis. This effect was accompanied by improvement of gut barrier function and by a lower circulating inflammatory marker. Interestingly, rumenic acid (C18:2 c9,t11) was increased in white adipose tissue due to AX treatment, suggesting the influence of gut bacterial metabolism on host tissue. In parallel, AX treatment decreased adipocyte size and HF diet-induced expression of genes mediating differentiation, fatty acid uptake, fatty acid oxidation and inflammation, and decreased a key lipogenic enzyme activity in the subcutaneous adipose tissue. Furthermore, AX treatment significantly decreased HF-induced adiposity, body weight gain, serum and hepatic cholesterol accumulation and insulin resistance. Correlation analysis reveals that Roseburia spp. and Bacteroides/Prevotella levels inversely correlate with these host metabolic parameters. CONCLUSIONS/SIGNIFICANCE: Supplementation of a concentrate of water-extractable high molecular weight AX in the diet counteracted HF-induced gut dysbiosis together with an improvement of obesity and lipid-lowering effects. We postulate that hypocholesterolemic, anti-inflammatory and anti-obesity effects are related to changes in gut microbiota. These data support a role for wheat AX as interesting nutrients with prebiotic properties related to obesity prevention.

Involvement of gut microbial fermentation in the metabolic alterations occurring in n-3 polyunsaturated fatty acids-depleted mice.

BACKGROUND: Western diet is characterized by an insufficient n-3 polyunsaturated fatty acid (PUFA) consumption which is known to promote the pathogenesis of several diseases. We have previously observed that mice fed with a diet poor in n-3 PUFA for two generations exhibit hepatic steatosis together with a decrease in body weight. The gut microbiota contributes to the regulation of host energy metabolism, due to symbiotic relationship with fermentable nutrients provided in the diet. In this study, we have tested the hypothesis that perturbations of the gut microbiota contribute to the metabolic alterations occurring in mice fed a diet poor in n-3 PUFA for two generations (n-3/- mice). METHODS: C57Bl/6J mice fed with a control or an n-3 PUFA depleted diet for two generations were supplemented with prebiotic (inulin-type Fructooligosaccharides, FOS, 0.20 g/day/mice) during 24 days. RESULTS: n-3/-mice exhibited a marked drop in caecum weight, a decrease in lactobacilli and an increase in bifidobacteria in the caecal content as compared to control mice (n-3/+ mice). Dietary supplementation with FOS for 24 days was sufficient to increase caecal weight and bifidobacteria count in both n-3/+ and n-3/-mice. Moreover, FOS increased lactobacilli content in n-3/-mice, whereas it decreased their level in n-3/+ mice. Interestingly, FOS treatment promoted body weight gain in n-3/-mice by increasing energy efficiency. In addition, FOS treatment decreased fasting glycemia and lowered the higher expression of key factors involved in the fatty acid catabolism observed in the liver of n-3/-mice, without lessening steatosis. CONCLUSIONS: the changes in the gut microbiota composition induced by FOS are different depending on the type of diet. We show that FOS may promote lactobacilli and counteract the catabolic status induced by n-3 PUFA depletion in mice, thereby contributing to restore efficient fat storage.

Changes in intestinal bifidobacteria levels are associated with the inflammatory response in magnesium-deficient mice.

Magnesium (Mg) deficiency is a common nutritional disorder that is linked to an inflammatory state characterized by increased plasma acute phase protein and proinflammatory cytokine concentrations. Recent studies have shown that changes in the composition of gut microbiota composition participate in systemic inflammation. In this study, therefore, we assessed the potential role of gut microbiota in intestinal and systemic inflammation associated with Mg deficiency in mice. For this purpose, mice were fed a control or Mg-deficient diet (500 mg vs. 70 mg Mg/kg) for 4 or 21 d. Compared with the mice fed the control diet, mice fed the Mg-deficient diet for 4 d had a lower gut bifidobacteria content (-1.5 log), a 36-50% lower mRNA content of factors controlling gut barrier function in the ileum (zonula occludens-1, occludin, proglucagon), and a higher mRNA content (by approximately 2-fold) in the liver and/or intestine of tumor necrosis factor-alpha, interleukin-6, CCAAT/enhancer binding protein homologous protein, and activating transcription factor 4, reflecting inflammatory and cellular stress. In contrast, mice fed the Mg-deficient diet for 21 d had a higher cecal bifidobacteria content compared with the control group, a phenomenon accompanied by restoration of the intestinal barrier and the absence of inflammation. In conclusion, we show that Mg deficiency, independently of any other changes in nutrient intake, modulates the concentration of bifidobacteria in the gut, a phenomenon that may time-dependently affect inflammation and metabolic disorders in mice.

Gut microbiota fermentation of prebiotics increases satietogenic and incretin gut peptide production with consequences for appetite sensation and glucose response after a meal.

BACKGROUND: We have previously shown that gut microbial fermentation of prebiotics promotes satiety and lowers hunger and energy intake in humans. In rodents, these effects are associated with an increase in plasma gut peptide concentrations, which are involved in appetite regulation and glucose homeostasis. OBJECTIVE: Our aim was to examine the effects of prebiotic supplementation on satiety and related hormones during a test meal for human volunteers by using a noninvasive micromethod for blood sampling to measure plasma gut peptide concentrations. DESIGN: This study was a randomized, double-blind, parallel, placebo-controlled trial. A total of 10 healthy adults (5 men and 5 women) were randomly assigned to groups that received either 16 g prebiotics/d or 16 g dextrin maltose/d for 2 wk. Meal tolerance tests were performed in the morning to measure the following: hydrogen breath test, satiety, glucose homeostasis, and related hormone response. RESULTS: We show that the prebiotic treatment increased breath-hydrogen excretion (a marker of gut microbiota fermentation) by approximately 3-fold and lowered hunger rates. Prebiotics increased plasma glucagon-like peptide 1 and peptide YY concentrations, whereas postprandial plasma glucose responses decreased after the standardized meal. The areas under the curve for plasma glucagon-like peptide 1 and breath-hydrogen excretion measured after the meal (0-60 min) were significantly correlated (r = 0.85, P = 0.007). The glucose response was inversely correlated with the breath-hydrogen excretion areas under the curve (0-180 min; r = -0.73, P = 0.02). CONCLUSION: Prebiotic supplementation was associated with an increase in plasma gut peptide concentrations (glucagon-like peptide 1 and peptide YY), which may contribute in part to changes in appetite sensation and glucose excursion responses after a meal in healthy subjects.

Coenzyme Q10 supplementation lowers hepatic oxidative stress and inflammation associated with diet-induced obesity in mice.

BACKGROUND: Diabetes and obesity are metabolic disorders induced by an excessive dietary intake of fat, usually related to inflammation and oxidative stress. AIMS: The aim of the study is to investigate the effect of the antioxidant coenzyme Q10 (CoQ10) on hepatic metabolic and inflammatory disorders associated with diet-induced obesity and glucose intolerance. METHODS: C57bl6/j mice were fed for 8 weeks, either a control diet (CT) or a high-fat diet plus 21% fructose in the drinking water (HFF). CoQ10 supplementation was performed in this later condition (HFFQ). RESULTS: HFF mice exhibit increased energy consumption, fat mass development, fasting glycaemia and insulinemia and impaired glucose tolerance. HFF treatment promoted the expression of genes involved in reactive oxygen species production (NADPH oxidase), inflammation (CRP, STAMP2) and metabolism (CPT1alpha) in the liver. CoQ10 supplementation decreased the global hepatic mRNA expression of inflammatory and metabolic stresses markers without changing obesity and tissue lipid peroxides compared to HFF mice. HFF diets paradoxically decreased TBARS (reflecting lipid peroxides) levels in liver, muscle and adipose tissue versus CT group, an effect related to vitamin E content of the diet. CONCLUSION: In conclusion, HFF model promotes glucose intolerance and obesity by a mechanism independent on the level of tissue peroxides. CoQ10 tends to decrease hepatic stress gene expression, independently of any modulation of lipid peroxidation, which is classically considered as its most relevant effect.

Critical role of Kupffer cells in the management of diet-induced diabetes and obesity.

The aim of this study was to investigate the role of Kupffer cell in glucose metabolism and hepatic insulin sensitivity in mice. Both phagocytic activity and secretory capacity of Kupffer cells were blunted 24h after GdCl3 administration. Glucose tolerance--evaluated following an oral glucose tolerance test (OGTT)--was higher in GdCl3-treated mice whereas fasting insulinemia and HOMA-IR index decreased. The improvement of glucose tolerance and hepatic insulin signalling pathway after inhibition of Kupffer cells was supported by a lower hepatic gluconeogenic enzyme expression and a higher phosphorylation of Akt upon insulin challenge. Moreover, fasting hyperglycemia, insulin resistance and impaired glucose tolerance--induced by high fat (HF) diet--were improved through chronic administration of GdCl3. Interestingly, the inhibition of Kupffer cell exerted antiobesity effects in HF-fed mice, and lowered hepatic steatosis. Therefore, strategies targeting Kupffer cell functions could be a promising approach to counteract obesity and related metabolic disorders.

Dietary supplementation with chitosan derived from mushrooms changes adipocytokine profile in diet-induced obese mice, a phenomenon linked to its lipid-lowering action.

Recent data reported that chitosan reduces high-fat (HF) diet-induced obesity in mice without describing the metabolic consequences of such an effect. The aim of this study was to investigate the capacity of chitosan derived from edible mushrooms to modify adipocytokine levels and to assess the relevance of this effect on the development of fat mass, and on glucose and lipid metabolism in obese mice. Mice were fed a HF diet or a HF diet supplemented with 5% fungal chitosan for ten weeks. HF-induced hypertriglyceridaemia, fasting hyperinsulinaemia and fat accumulation in liver, muscle and white adipose tissue (WAT) were reduced after chitosan treatment. The higher lipid content in the caecum following treatment with chitosan suggested that this dietary fiber reduced lipid absorption. We postulated that the lower triglyceridaemia observed upon chitosan treatment could also be the result of the lower FIAF (fasting-induced adipose factor) expression observed in visceral adipose tissue. IL-6, resistin and leptin levels decreased in the serum after chitosan supplementation. We conclude that fungal chitosan counteracts some inflammatory disorders and metabolic alterations occurring in diet-induced obese mice since it decreases feed efficiency, fat mass, adipocytokine secretion and ectopic fat deposition in the liver and the muscle.

Immunomodulatory properties of two wheat bran fractions - aleurone-enriched and crude fractions - in obese mice fed a high fat diet.

Several data suggest that fermentable dietary fibers could play a role in the control of obesity and associated metabolic disorders. In mice, dietary fructans, which are extensively fermented in caeco-colon by bifidobacteria, decrease fat mass development and modulate gastrointestinal peptides involved in the control of food intake (namely glucagon-like peptide (GLP)-1). The aim of this study was to compare the effect of two cereal bran fractions isolated from wheat - aleurone-enriched and crude fractions - in a nutritional model of obesity. In a first experiment, we confirmed that 2 weeks of treatment with a high fat (HF) diet is sufficient to exhibit glucose intolerance and to increase adiposity in mice. In the second experiment, mice were fed a HF or a HF diet enriched with 10% wheat bran fractions during 3 weeks. None of the wheat bran fractions modified body weight, adipose tissue mass, glucose or lipid homeostasis. Wheat bran fractions increased bifidobacteria and lactobacilli in the caecal content without any effect on caecal enlargement and on GLP-1 precursor expression in the colon. Furthermore, wheat bran fractions decreased circulating interleukin 6 (IL-6) and CD68 mRNA in the visceral adipose tissue, suggesting a decrease in recruited-tissue macrophages. We propose that specific and early immunomodulatory properties of cereal products with prebiotic properties, may occur in obese mice independently of extensive gut fermentation.

Intact satellite cells lead to remarkable protection against Smn gene defect in differentiated skeletal muscle.

Deletion of murine Smn exon 7, the most frequent mutation found in spinal muscular atrophy, has been directed to either both satellite cells, the muscle progenitor cells and fused myotubes, or fused myotubes only. When satellite cells were mutated, mutant mice develop severe myopathic process, progressive motor paralysis, and early death at 1 mo of age (severe mutant). Impaired muscle regeneration of severe mutants correlated with defect of myogenic precursor cells both in vitro and in vivo. In contrast, when satellite cells remained intact, mutant mice develop similar myopathic process but exhibit mild phenotype with median survival of 8 mo and motor performance similar to that of controls (mild mutant). High proportion of regenerating myofibers expressing SMN was observed in mild mutants compensating for progressive loss of mature myofibers within the first 6 mo of age. Then, in spite of normal contractile properties of myofibers, mild mutants develop reduction of muscle force and mass. Progressive decline of muscle regeneration process was no more able to counterbalance muscle degeneration leading to dramatic loss of myofibers. These data indicate that intact satellite cells remarkably improve the survival and motor performance of mutant mice suffering from chronic myopathy, and suggest a limited potential of satellite cells to regenerate skeletal muscle.