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.
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.
To highlight the contribution of the gut microbiota to the modulation of host metabolism by dietary inulin-type fructans (ITF prebiotics) in obese women.
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.
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.
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.
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 almost equal to3-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.
Summary Background & aims : Inulin-type fructans (ITF) prebiotics promote changes in the composition and activity of the gut microbiota. The aim of this study was to determine variations on fecal ...short chain fatty acids (SCFA) concentration in obese women treated with ITF and to explore associations between Bifidobacterium species, SCFA and host biological markers of metabolism. Methods Samples were obtained in a randomized, double blind, parallel, placebo-controlled trial, with 30 obese women randomly assigned to groups that received either 16 g/day ITF ( n = 15) or maltodextrin ( n = 15) for 3 months. The qualitative and quantitative analysis of Bifidobacterium spp. was performed in feces by PCR-DGGE and q-PCR, and SCFA profile was analyzed by gas chromatography. Spearman correlation analysis was performed between the different variables analyzed. Results The species Bifidobacterium longum , Bifidobacterium pseudocatenulatum and Bifidobacterium adolescentis were significantly increased at the end of the treatment in the prebiotic group ( p < 0.01) with being B. longum negatively correlated with serum lipopolysaccharide (LPS) endotoxin ( p < 0.01). Total SCFA, acetate and propionate, that positively correlated with BMI, fasting insulinemia and homeostasis model assessment (HOMA) ( p < 0.05), were significantly lower in prebiotic than in placebo group after the treatment period. Conclusions ITF consumption selectively modulates Bifidobacterium spp. and decreases fecal SCFA concentration in obese women. ITF could lessen metabolic risk factors associated with higher fecal SCFA concentration in obese individuals.
Interactions between the diet and intestinal microbiota play a role in health and disease, including obesity and related metabolic complications. There is great interest to use dietary means to ...manipulate the microbiota to promote health. Currently, the impact of dietary change on the microbiota and the host metabolism is poorly predictable and highly individual. We propose that the responsiveness of the gut microbiota may depend on its composition, and associate with metabolic changes in the host.
Our study involved three independent cohorts of obese adults (n = 78) from Belgium, Finland, and Britain, participating in different dietary interventions aiming to improve metabolic health. We used a phylogenetic microarray for comprehensive fecal microbiota analysis at baseline and after the intervention. Blood cholesterol, insulin and inflammation markers were analyzed as indicators of host response. The data were divided into four training set - test set pairs; each intervention acted both as a part of a training set and as an independent test set. We used linear models to predict the responsiveness of the microbiota and the host, and logistic regression to predict responder vs. non-responder status, or increase vs. decrease of the health parameters.
Our models, based on the abundance of several, mainly Firmicute species at baseline, predicted the responsiveness of the microbiota (AUC = 0.77-1; predicted vs. observed correlation = 0.67-0.88). Many of the predictive taxa showed a non-linear relationship with the responsiveness. The microbiota response associated with the change in serum cholesterol levels with an AUC of 0.96, highlighting the involvement of the intestinal microbiota in metabolic health.
This proof-of-principle study introduces the first potential microbial biomarkers for dietary responsiveness in obese individuals with impaired metabolic health, and reveals the potential of microbiota signatures for personalized nutrition.
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.
Inulin-type fructans (ITF) are nondigestible/fermentable carbohydrates which are able -- through the modification of the gut microbiota -- to counteract high-fat (HF) diet-induced obesity, ...endotoxemia and related-metabolic alterations. However, their influence on adipose tissue metabolism has been poorly studied until now. The aim of this study was to assess the influence of ITF supplementation on adipose tissue metabolism, by focusing on a G protein-coupled receptor (GPR), GPR43, as a potential link between gut fermentation processes and white adipose tissue development. Male C57bl6/J mice were fed a standard diet or an HF diet without or with ITF (0.2 g/day per mouse) during 4 weeks. The HF diet induced an accumulation of large adipocytes, promoted peroxisome proliferator activated receptor gamma (PPARγ)-activated differentiation factors and led to a huge increase in GPR43 expression in the subcutaneous adipose tissue. All those effects were blunted by ITF treatment, which modulated the gut microbiota in favor of bifidobacteria at the expense of Roseburia spp. and of Clostridium cluster XIVa. The dietary modulation of GPR43 expression seems independent of endotoxemia, in view of data obtained in vivo (acute and chronic lipopolysaccharides treatment). In conclusion, ITF, which promote gut fermentation, paradoxically counteract GPR43 overexpression induced in the adipose tissue by an HF diet, a phenomenon that correlates with a beneficial effect on adiposity and with potential decrease in PPARγ-activated processes.
Scope
Recent data suggest that gut microbiota contributes to the regulation of host lipid metabolism. We report how fermentable dietary fructo‐oligosaccharides (FOS) control hepatic steatosis induced ...by n‐3 PUFA depletion, which leads to hepatic alterations similar to those observed in non‐alcoholic fatty liver disease patients.
Methods and results
C57Bl/6J mice fed an n‐3 PUFA‐depleted diet for 3 months were supplemented with FOS during the last 10 days of treatment. FOS‐treated mice exhibited higher caecal Bifidobacterium spp. and lower Roseburia spp. content. Microarray analysis of hepatic mRNA revealed that FOS supplementation reduced hepatic triglyceride accumulation through a proliferator‐activated receptor α‐stimulation of fatty acid oxidation and lessened cholesterol accumulation by inhibiting sterol regulatory element binding protein 2‐dependent cholesterol synthesis. Cultured precision‐cut liver slices confirmed the inhibition of fatty acid oxidation. FOS effects were related to a decreased hepatic micro‐RNA33 expression and to an increased colonic glucagon‐like peptide 1 production.
Conclusions
The changes in gut microbiota composition by n‐3 PUFA‐depletion and prebiotics modulate hepatic steatosis by changing gene expression in the liver, a phenomenon that could implicate micro‐RNA and gut‐derived hormones. Our data underline the advantage of targeting the gut microbiota by colonic nutrients in the management of liver disease.
GPR43 is a G-protein-coupled receptor that participates in adipocyte differentiation in mice and is over-expressed in adipose tissue of obese mice. The aim of this study was to investigate the ...implication of GPR43 in adipogenesis in humans and to determine the influence of obesity on its expression in human adipose tissue.
Preadipocytes were isolated from human omental adipose tissue and cultured during 13 days. One PPARγ agonist (troglitazone) and three GPR43 agonists (two physiological and one synthetic) were tested for their ability to induce differentiation. After 13 days, the three GPR43 agonists had no impact on aP2 expression, a marker of adipocyte differentiation, whereas troglitazone led to a huge over-expression of aP2 in these cells but tended to decrease GPR43 expression (p=0.06).GPR43 and inflammatory markers expression was also quantified in omental adipose tissue from lean and obese individuals. GPR43 expression in total adipose tissue was similar between obese patients and lean subjects and did not correlate with aP2 expression. In contrast, GPR43 expression positively correlated with TNFα mRNA.
Our results suggest the absence of relationship between GPR43 and adipocyte differentiation in humans, unlike what was observed in mice. Furthermore, GPR43 expression is not increased in adipose tissue from obese subjects but could be related to TNFα-related inflammatory processes.
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