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The main aim of the present study was to investigate the effects of dietarytrans-10,cis-12-conjugated linoleic acid (t10c12-CLA) on intestinal microbiota composition and SCFA production. C57BL/6 mice (n8 per group) were fed a standard diet either supplemented witht10c12-CLA (0·5 %, w/w) (intervention) or with no supplementation (control), daily for 8 weeks. Metabolic markers (serum glucose, leptin, insulin and TAG, and liver TAG) were assessed by ELISA commercial kits, tissue long-chain fatty acids and caecal SCFA by GC, and microbial composition by 16S rRNA pyrosequencing. Dietaryt10c12-CLA significantly decreased visceral fat mass (Pt10c12-CLA intake. Caecal acetate, propionate and isobutyrate concentrations were higher (Pt10c12-CLA-supplemented group than in the control group. The analysis of the microbiota composition following 8 weeks oft10c12-CLA supplementation revealed lower proportions of Firmicutes (P= 0·003) and higher proportions of Bacteroidetes (P= 0·027) compared with no supplementation. Furthermore,t10c12-CLA supplementation for 8 weeks significantly altered the gut microbiota composition, harbouring higher proportions of Bacteroidetes, including Porphyromonadaceae bacteria previously linked with negative effects on lipid metabolism and induction of hepatic steatosis. These results indicate that the mechanism of dietaryt10c12-CLA on lipid metabolism in mice may be, at least, partially mediated by alterations in gut microbiota composition and functionality.

The human intestinal microbiota evolves from an immature and unstable ecosystem during infancy into a more complex and stable ecosystem in adulthood. Diet is one of the main factors contributing to the composition and diversity of the human intestinal microbiota. From birth, breast milk offers the best nutritional regime for maturation of the gut, whereas the introduction of solid food selects the most adapted bacteria, converging towards an adult-like microbiota. The gut microbiota plays an important role in host health, influencing the maturation of the immune system and regulating energy metabolism. Moreover, it has become evident that the microbiota can affect brain function and behaviour. On this bidirectional communication between intestine and the central nervous system (CNS), the so called gut-brain axis, the gut influences brain development and biochemistry, whereas the brain affects gastrointestinal function. In this context, probiotics and prebiotics have been used as dietary strategies aimed at improving host health by modulating the gut ecosystem and, consequently, affecting host stress-responses, behaviour and cognition. Industrial relevance Dietary manipulation represents a strategy to preserve a healthy gastrointestinal microbial community and contribute to the well being of the host. Several food products containing probiotics and prebiotics have been developed for specific age groups such as infants and elderly, aiming to enhance the host's immune system and to prevent gastrointestinal diseases. This review presents recent strong evidence suggesting that the use of dietary approaches such as probiotics, prebiotics and diets enriched with fatty acids or proteins not only modulate the microbiota but may also impact on brain function, affecting stress-responses, behaviour and cognition. This new field of research may lead to market opportunities with the development of new dietary strategies targeting the gut–brain axis for enhanced mental health.

Obesity is associated with a number of serious health consequences, including type 2 diabetes, cardiovascular disease and a variety of cancers among others and has been repeatedly shown to be associated with a higher risk of mortality. The relatively recent discovery that the composition and metabolic activity of the gut microbiota may affect the risk of developing obesity and related disorders has led to an explosion of interest in this distinct research field. A corollary of these findings would suggest that modulation of gut microbial populations can have beneficial effects with respect to controlling obesity. In this addendum, we summarize our recent data, showing that therapeutic manipulation of the microbiota using different antimicrobial strategies may be a useful approach for the management of obesity and metabolic conditions. In addition, we will explore some of the mechanisms that may contribute to microbiota-induced susceptibility to obesity and metabolic diseases.

peer-reviewed The aim of this study was to investigate if dietary administration of γ-aminobutyric acid (GABA)-producing Lactobacillus brevis DPC 6108 and pure GABA exert protective effects against the development of diabetes in streptozotocin (STZ)-induced diabetic Sprague Dawley rats. In a first experiment, healthy rats were divided in 3 groups (n=10/group) receiving placebo, 2.6 mg/kg body weight (bw) pure GABA or L. brevis DPC 6108 (~109microorganisms). In a second experiment, rats (n=15/group) were randomised to five groups and four of these received an injection of STZ to induce type 1 diabetes. Diabetic and non-diabetic controls received placebo [4% (w/v) yeast extract in dH2O], while the other three diabetic groups received one of the following dietary supplements: 2.6 mg/kg bw GABA (low GABA), 200 mg/kg bw GABA (high GABA) or ~109 L. brevis DPC 6108. L. brevis DPC 6108 supplementation was associated with increased serum insulin levels (P0.05), compared with non-diabetic controls while all other diabetic groups displayed reduced diversity (P

The gut microbiota is a complex ecosystem consisting of a diverse population of prokaryotes that has a symbiotic relationship with its host; thus it plays a vital role for the host's health. Our understanding of the effect of the gut microbiome in health and disease has grown substantially over the past 2 decades, mostly because of recent advances in sequencing and other high-throughput technologies. Given its high metabolic potential, close proximity to the intestinal mucosa, and interaction with the immune system, it is not surprising that the gut microbiome is an important partaker in human health. Evidence to the importance of the gut microbiome in human health and disease is the growing number of conditions now linked to changes in the resident gut microbiota, including recurrent Clostridium difficile infections, inflammatory bowel disease, irritable bowel syndrome, colorectal cancer, allergies, neurological diseases, and metabolic diseases. Research into this field of the association of the gut microbiome with health and disease continues to expand at a rapid pace as we come to accept the gut microbiome as our "second genome." Targeting the gut microbiome to restore/modulate its composition with the use of antibiotics, probiotics, prebiotics, and even fecal microbiota transplantation is considered a promising future strategy for the development of new solutions in the treatment of various diseases associated with an imbalance in microbiota composition and functioning.

Background: We previously showed that microbial metabolism in the gut influences the composition of bioactive fatty acids in host adipose tissue. Objective: This study compared the effect of dietary supplementation for 8 wk with human-derived Bifidobacterium breve strains on fat distribution and composition and the composition of the gut microbiota in mice. Methods: C57BL/6 mice (n = 8 per group) received B. breve DPC 6330 or B. breve NCIMB 702258 (10 9 microorganisms) daily for 8 wk or no supplement (controls). Tissue fatty acid composition was assessed by gas-liquid chromatography while 16S rRNA pyrosequencing was used to investigate microbiota composition. Results: Visceral fat mass and brain stearic acid, arachidonic acid, and DHA were higher in mice supplemented with B. breve NCIMB 702258 than in mice in the other 2 groups (P , 0.05). In addition, both B. breve DPC 6330 and B. breve NCIMB 702258 supplementation resulted in higher propionate concentrations in the cecum than did no supplementation (P , 0.05). Compositional sequencing of the gut microbiota showed a tendency for greater proportions of Clostridiaceae (25%, 12%, and 18%; P = 0.08) and lower proportions of Eubacteriaceae (3%, 12%, and 13%; P = 0.06) in mice supplemented with B. breve DPC 6330 than in mice supplemented with B. breve NCIMB 702258 and unsupplemented controls, respectively. Conclusion: The response of fatty acid metabolism to administration of bifidobacteria is strain-dependent, and strain-strain differences are important factors that influence modulation of the gut microbial community by ingested microorganisms. Am J Clin Nutr 2012;95:1278‐87.

Background and Aims Increased efficiency of energy harvest, due to alterations in the gut microbiota (increased Firmicutes and decreased Bacteroidetes ), has been implicated in obesity in mice and humans. However, a causal relationship is unproven and contributory variables include diet, genetics and age. Therefore, we explored the effect of a high-fat (HF) diet and genetically determined obesity ( ob/ob ) for changes in microbiota and energy harvesting capacity over time. Methods Seven-week-old male ob/ob mice were fed a low-fat diet and wild-type mice were fed either a low-fat diet or a HF-diet for 8 weeks (n=8/group). They were assessed at 7, 11 and 15 weeks of age for: fat and lean body mass (by NMR); faecal and caecal short-chain fatty acids (SCFA, by gas chromatography); faecal energy content (by bomb calorimetry) and microbial composition (by metagenomic pyrosequencing). Results A progressive increase in Firmicutes was confirmed in both HF-fed and ob/ob mice reaching statistical significance in the former, but this phylum was unchanged over time in the lean controls. Reductions in Bacteroidetes were also found in ob/ob mice. However, changes in the microbiota were dissociated from markers of energy harvest. Thus, although the faecal energy in the ob/ob mice was significantly decreased at 7 weeks, and caecal SCFA increased, these did not persist and faecal acetate diminished over time in both ob/ob and HF-fed mice, but not in lean controls. Furthermore, the proportion of the major phyla did not correlate with energy harvest markers. Conclusion The relationship between the microbial composition and energy harvesting capacity is more complex than previously considered. While compositional changes in the faecal microbiota were confirmed, this was primarily a feature of high-fat feeding rather than genetically induced obesity. In addition, changes in the proportions of the major phyla were unrelated to markers of energy harvest which changed over time. The possibility of microbial adaptation to diet and time should be considered in future studies.

The population dynamics of bifidobacteria in human feces during raffinose administration were investigated at the species level by using fluorescence in situ hybridization (FISH) coupled with flow cytometry (FCM) analysis. Although double-staining FISH-FCM using both fluorescein isothiocyanate (FITC) and indodicarbocyanine (Cy5) as labeling dyes for fecal samples has been reported, the analysis was interfered with by strong autofluorescence at the FITC fluorescence region because of the presence of autofluorescence particles/debris in the fecal samples. We circumvented this problem by using only Cy5 fluorescent dye in the FISH-FCM analysis. Thirteen subjects received 2 g of raffinose twice a day for 4 weeks. Fecal samples were collected, and the bifidobacterial populations were monitored using the established FISH-FCM method. The results showed an increase in bifidobacteria from about 12.5% of total bacteria in the prefeeding period to about 28.7 and 37.2% after the 2-week and 4-week feeding periods, respectively. Bifidobacterium adolescentis , the Bifidobacterium catenulatum group, and Bifidobacterium longum were the major species, in that order, at the prefeeding period, and these bacteria were found to increase nearly in parallel during the raffinose administration. During the feeding periods, indigenous bifidobacterial populations became more diverse, such that minor species in human adults, such as Bifidobacterium breve , Bifidobacterium bifidum , Bifidobacterium dentium , and Bifidobacterium angulatum , proliferated. Four weeks after raffinose administration was stopped, the proportion of each major bifidobacterial species, as well as that of total bifidobacteria, returned to approximately the original values for the prefeeding period, whereas that of each minor species appeared to differ considerably from its original value. To the best of our knowledge, these results provide the first clear demonstration of the population dynamics of indigenous bifidobacteria at the species level in response to raffinose administration.

There is a growing appreciation that microbiota composition can significantly affect host health and play a role in disease onset and progression. This study assessed the impact of streptozotocin (STZ)-induced type-1-diabetes (T1D) on intestinal microbiota composition and diversity in Sprague–Dawley rats, compared with healthy controls over time. T1D was induced by injection of a single dose (60 mg STZ kg−1) of STZ, administered via the intraperitoneal cavity. Total DNA was isolated from faecal pellets at weeks 0 (pre-STZ injection), 1, 2 and 4 and from caecal content at week 5 from both healthy and T1D groups. High-throughput 16S rRNA sequencing was employed to investigate intestinal microbiota composition. The data revealed that although intestinal microbiota composition between the groups was similar at week 0, a dramatic impact of T1D development on the microbiota was apparent post-STZ injection and for up to 5 weeks. Most notably, T1D onset was associated with a shift in the Bacteroidetes : Firmicutes ratio (P

The aim of this study was to assess the impact of streptozotocin (STZ) induced type-1-diabetes (T1D) onset on intestinal microbiota composition in Sprague-Dawley rats compared with healthy control ...

Objective The gut microbiota is an environmental regulator of fat storage and adiposity. Whether the microbiota represents a realistic therapeutic target for improving metabolic health is unclear. This study explored two antimicrobial strategies for their impact on metabolic abnormalities in murine diet-induced obesity: oral vancomycin and a bacteriocin-producing probiotic ( Lactobacillus salivarius UCC118 Bac + ). Design Male (7-week-old) C57BL/J6 mice (9–10/group) were fed a low-fat (lean) or a high-fat diet for 20 weeks with/without vancomycin by gavage at 2 mg/day, or with L salivarius UCC118Bac + or the bacteriocin-negative derivative L salivarius UCC118Bac − (each at a dose of 1×10 9 cfu/day by gavage). Compositional analysis of the microbiota was by 16S rDNA amplicon pyrosequencing. Results Analysis of the gut microbiota showed that vancomycin treatment led to significant reductions in the proportions of Firmicutes and Bacteroidetes and a dramatic increase in Proteobacteria , with no change in Actinobacteria. Vancomycin-treated high-fat-fed mice gained less weight over the intervention period despite similar caloric intake, and had lower fasting blood glucose, plasma TNFα and triglyceride levels compared with diet-induced obese controls. The bacteriocin-producing probiotic had no significant impact on the proportions of Firmicutes but resulted in a relative increase in Bacteroidetes and Proteobacteria and a decrease in Actinobacteria compared with the non-bacteriocin-producing control. No improvement in metabolic profiles was observed in probiotic-fed diet-induced obese mice. Conclusion Both vancomycin and the bacteriocin-producing probiotic altered the gut microbiota in diet-induced obese mice, but in distinct ways. Only vancomycin treatment resulted in an improvement in the metabolic abnormalities associated with obesity thereby establishing that while the gut microbiota is a realistic therapeutic target, the specificity of the antimicrobial agent employed is critical.