Rodrigo Bibiloni

Changes in gut microbiota control metabolic endotoxemia-induced inflammation in high-fat diet-induced obesity and diabetes in mice

OBJECTIVE—Diabetes and obesity are characterized by a low-grade inflammation whose molecular origin is unknown. We previously determined, first, that metabolic endotoxemia controls the inflammatory tone, body weight gain, and diabetes, and second, that high-fat feeding modulates gut microbiota and the plasma concentration of lipopolysaccharide (LPS), i.e., metabolic endotoxemia. Therefore, it remained to demonstrate whether changes in gut microbiota control the occurrence of metabolic diseases. RESEARCH DESIGN AND METHODS—We changed gut microbiota by means of antibiotic treatment to demonstrate, first, that changes in gut microbiota could be responsible for the control of metabolic endotoxemia, the low-grade inflammation, obesity, and type 2 diabetes and, second, to provide some mechanisms responsible for such effect. RESULTS—We found that changes of gut microbiota induced by an antibiotic treatment reduced metabolic endotoxemia and the cecal content of LPS in both high-fat–fed and ob/ob mice. This effect was correlated with reduced glucose intolerance, body weight gain, fat mass development, lower inflammation, oxidative stress, and macrophage infiltration marker mRNA expression in visceral adipose tissue. Importantly, high-fat feeding strongly increased intestinal permeability and reduced the expression of genes coding for proteins of the tight junctions. Furthermore, the absence of CD14 in ob/ob CD14−/− mutant mice mimicked the metabolic and inflammatory effects of antibiotics. CONCLUSIONS—This new finding demonstrates that changes in gut microbiota controls metabolic endotoxemia, inflammation, and associated disorders by a mechanism that could increase intestinal permeability. It would thus be useful to develop strategies for changing gut microbiota to control, intestinal permeability, metabolic endotoxemia, and associated disorders.

Gut microbiota modulation with norfloxacin and ampicillin enhances glucose tolerance in mice

Recent data suggest that the gut microbiota plays a significant role in fat accumulation. However, it is not clear whether gut microbiota is involved in the pathophysiology of type 2 diabetes. To assess this issue, we modulated gut microbiota via antibiotics administration in two different mouse models with insulin resistance. Results from dose‐determination studies showed that a combination of norfloxacin and ampicillin, at a dose of 1g/L, maximally suppressed the numbers of cecal aerobic and anaerobic bacteria in ob/ob mice. After a 2‐wk intervention with the antibiotic combination, both ob/ob and diet‐induced obese and insulin‐resistant mice showed a significant improvement in fasting glycemia and oral glucose tolerance. The improved glycemic control was independent of food intake or adiposity because pair‐fed ob/ob mice were as glucose intolerant as the control ob/ob mice. Reduced liver triglycerides and increased liver glycogen correlated with improved glucose tolerance in the treated mice. Concomitant reduction of plasma lipopolysaccharides and increase of adiponectin further supported the antidiabetic effects of the antibiotic treatment in ob/ob mice. In summary, modulation of gut microbiota ameliorated glucose tolerance of mice by altering the expression of hepatic and intestinal genes involved in inflammation and metabolism, and by changing the hormonal, inflammatory, and metabolic status of the host.—Membrez, M., Blancher, F., Jaquet, M., Bibiloni, R., Cani, P. D., Burcelin, R. G., Corthesy, I., Macé, K., Chou, C. J. Gut microbiota modulation with norfloxacin and ampicillin enhances glucose tolerance in mice. FASEB J. 22, 2416–2426 (2008)

Panorganismal gut microbiome-host metabolic crosstalk.

Coevolution shapes interorganismal crosstalk leading to profound and diverse cellular and metabolic changes as observed in gut dysbiosis in human diseases. Here, we modulated a simplified gut microbiota using pro-, pre-, and synbiotics to assess the depth of systemic metabolic exchanges in mice, using a multicompartmental modeling approach with metabolic signatures from 10 tissue/fluid compartments. The nutritionally induced microbial changes modulated host lipid, carbohydrate, and amino acid metabolism at a panorganismal scale. Galactosyl-oligosaccharides reduced lipogenesis, triacylglycerol incorporation into lipoproteins and triglyceride concentration in the liver and the kidney. Those changes were not correlated with decreased plasma lipoproteins that were specifically induced by L. rhamnosus supplementation. Additional alteration of transmethylation metabolic pathways (homocysteine-betaine) was observed in the liver and the pancreas following pre- and synbiotic microbial modulation, which may be of interest for control of glucose metabolism and insulin sensitivity. Probiotics also reduced hepatic glycogen and glutamine and adrenal ascorbate with inferred effects on energy homeostasis, antioxidation, and steroidogenesis. These studies show the breadth and the depth of gut microbiome modulations of host biochemistry and reveal that major mammalian metabolic processes are under symbiotic homeostatic control.

A whole-grain cereal-rich diet increases plasma betaine, and tends to decrease total and LDL-cholesterol compared with a refined-grain diet in healthy subjects

Epidemiological studies have repeatedly found that whole-grain (WG) cereal foods reduce the risk of several lifestyle-related diseases, though consistent clinical outcomes and mechanisms are elusive. To compare the effects of a WG-rich diet with a matched refined-grain (RG) diet on plasma biomarkers and bowel health parameters, seventeen healthy subjects (eleven females and six males) completed an exploratory cross-over study with a 2-week intervention diet based on either WG- or RG-based foods, separated by a washout of at least 5 weeks. Both diets were the same except for the use of WG (150 g/d) or RG foods. Subjects undertook a 4 h postprandial challenge on day 8 of each intervention diet. After 2 weeks, the WG diet tended to decrease plasma total and LDL-cholesterol (both P = 0·09), but did not change plasma HDL-cholesterol, fasting glucose, C-reactive protein or homocysteine compared with the RG diet. Plasma betaine and alkylresorcinol concentrations were elevated after 1 week of the WG diet (P = 0·01 and P < 0·0001, respectively). Clostridium leptum populations in faeces were increased after the WG diet, along with a trend for decreased faecal water pH (P = 0·096) and increased stool frequency (P < 0·0001) compared with the RG diet. A short controlled intervention trial with a variety of commercially available WG-based products tended to improve biomarkers of CVD compared with a RG diet. Changes in faecal microbiota related to increased fibre fermentation and increased plasma betaine concentrations point to both fibre and phytochemical components of WG being important in mediating any potential health effects.

Oral T4-like phage cocktail application to healthy adult volunteers from Bangladesh

The genomic diversity of 99 T4-like coliphages was investigated by sequencing an equimolar mixture with Illumina technology and screening them against different databases for horizontal gene transfer and undesired genes. A 9-phage cocktail was given to 15 healthy adults from Bangladesh at a dose of 3×10(9) and 3×10(7) plaque-forming units and placebo respectively. Phages were detected in 64% of the stool samples when subjects were treated with higher titer phage, compared to 30% and 28% with lower-titer phage and placebo, respectively. No Escherichia coli was present in initial stool samples, and no amplification of phage was observed. One percent of the administered oral phage was recovered from the feces. No adverse events were observed by self-report, clinical examination, or from laboratory tests for liver, kidney, and hematology function. No impact of oral phage was seen on the fecal microbiota composition with respect to bacterial 16S rRNA from stool.

Impact of coffee consumption on the gut microbiota: a human volunteer study.

The impact of a moderate consumption of an instant coffee on the general composition of the human intestinal bacterial population was assessed in this study. Sixteen (16) healthy adult volunteers consumed a daily dose of 3 cups of coffee during 3 weeks. Faecal samples were collected before and after the consumption of coffee, and the impact of the ingestion of the product on the intestinal bacteria as well as the quantification of specific bacterial groups was assessed using nucleic acid-based methods. Although faecal profiles of the dominant microbiota were not significantly affected after the consumption of the coffee (Dices similarity index=92%, n=16), the population of Bifidobacterium spp. increased after the 3-week test period (P=0.02). Moreover, in some subjects, there was a specific increase in the metabolic activity of Bifidobacterium spp. Our results show that the consumption of the coffee preparation resulting from water co-extraction of green and roasted coffee beans produce an increase in the metabolic activity and/or numbers of the Bifidobacterium spp. population, a bacterial group of reputed beneficial effects, without major impact on the dominant microbiota.

Safety analysis of a Russian phage cocktail: from MetaGenomic analysis to oral application in healthy human subjects

Phage therapy has a long tradition in Eastern Europe, where preparations are comprised of complex phage cocktails whose compositions have not been described. We investigated the composition of a phage cocktail from the Russian pharmaceutical company Microgen targeting Escherichia coli/Proteus infections. Electron microscopy identified six phage types, with numerically T7-like phages dominating over T4-like phages. A metagenomic approach using taxonomical classification, reference mapping and de novo assembly identified 18 distinct phage types, including 7 genera of Podoviridae, 2 established and 2 proposed genera of Myoviridae, and 2 genera of Siphoviridae. De novo assembly yielded 7 contigs greater than 30 kb, including a 147-kb Myovirus genome and a 42-kb genome of a potentially new phage. Bioinformatic analysis did not reveal undesired genes and a small human volunteer trial did not associate adverse effects with oral phage exposure.

Germ-free status and altered caecal subdominant microbiota are associated with a high susceptibility to cow's milk allergy in mice

Studies suggesting that the development of atopy is linked to gut microbiota composition are inconclusive on whether dysbiosis precedes or arises from allergic symptoms. Using a mouse model of cows milk allergy, we aimed at investigating the link between the intestinal microbiota, allergic sensitization, and the severity of symptoms. Germ-free and conventional mice were orally sensitized with whey proteins and cholera toxin, and then orally challenged with β-lactoglobulin (BLG). Allergic responses were monitored with clinical symptoms, plasma markers of sensitization, and the T-helper Th1/Th2/regulatory-T-cell balance. Microbiota compositions were analysed using denaturing gradient gel electrophoresis and culture methods. Germ-free mice were found to be more responsive than conventional mice to sensitization, displaying a greater reduction of rectal temperature upon challenge, higher levels of blood mouse mast cell protease-1 (mMCP-1) and BLG-specific immunoglobulin G1 (IgG1), and a systemic Th2-skewed response. This may be explained by a high susceptibility to release mMCP-1 even in the presence of low levels of IgE. Sensitization did not alter the microbiota composition. However, the absence of or low Staphylococcus colonization in the caecum was associated with high allergic manifestations. This work demonstrates that intestinal colonization protects against oral sensitization and allergic response. This is the first study to show a relationship between alterations within the subdominant microbiota and severity of food allergy.

A Whole-Grain–Rich Diet Reduces Urinary Excretion of Markers of Protein Catabolism and Gut Microbiota Metabolism in Healthy Men after One Week

Epidemiological studies consistently find that diets rich in whole-grain (WG) cereals lead to decreased risk of disease compared with refined grain (RG)-based diets. Aside from a greater amount of fiber and micronutrients, possible mechanisms for why WGs may be beneficial for health remain speculative. In an exploratory, randomized, researcher-blinded, crossover trial, we measured metabolic profile differences between healthy participants eating a diet based on WGs compared with a diet based on RGs. Seventeen healthy adult participants (11 female, 6 male) consumed a controlled diet based on either WG-rich or RG-rich foods for 2 wk, followed by the other diet after a 5-wk washout period. Both diets were the same except for the use of WG (150 g/d) or RG foods. The metabolic profiles of plasma, urine, and fecal water were measured using (1)H-nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry (plasma only). After 1 wk of intervention, the WG diet led to decreases in urinary excretion of metabolites related to protein catabolism (urea, methylguanadine), lipid (carnitine and acylcarnitines) and gut microbial (4-hydroxyphenylacetate, trimethylacetate, dimethylacetate) metabolism in men compared with the same time point during the RG intervention. There were no differences between the interventions after 2 wk. Urinary urea, carnitine, and acylcarnitine were lower at wk 1 of the WG intervention relative to the RG intervention in all participants. Fecal water short-chain fatty acids acetate and butyrate were relatively greater after the WG diet compared to the RG diet. Although based on a small population and for a short time period, these observations suggest that a WG diet may affect protein metabolism.

Tolerance, safety, and effect on the faecal microbiota of an enteral formula supplemented with pre- and probiotics in critically ill children.

Objectives: The aim of this study was to demonstrate the tolerance and safety of an enteral formula containing prebiotics/probiotics, and its effect on the faecal microbiota in critically ill children. Subjects and Methods: Ninety-four patients between 1 and 3 years old under mechanical ventilation requiring enteral feeding were randomised to receive either a test formula containing a synbiotic blend (composed of 2 probiotic strains [Lactobacillus paracasei NCC 2461 and Bifidobacterium longum NCC 3001], fructooligosaccharides [FOS], inulin, and Acacia gum), or a control formula. Patients remained in the intensive care unit for 7 days and were examined at day 14. Tolerance was assessed by overall caloric intake and time to reach caloric goal. Safety was assessed by abdominal distention, vomiting, and stool frequency. Microbiota was analysed by culture- and molecular-based methods. Results: Overall caloric intake and time to reach caloric goal were similar between groups (noninferiority was shown). Abdominal distention, vomiting, and stool frequency were not affected by the supplementation with pre- and probiotics. Faecal bifidobacteria were higher in the test group at the end of the study. A similar trend was observed for total lactobacilli. L paracasei NCC 2461 and B longum NCC 3001 were detected in 80.4% and 17% of the test group patients, respectively. Enterobacteria levels remained unchanged during hospitalisation in the control group but diminished in the test group. Conclusions: The enteral formula supplemented with synbiotics was well tolerated by children in intensive care units; it was safe and produced an increase in faecal bacterial groups of previously reported beneficial effects.