It is increasingly recognized that there is a connection between diet, intestinal microbiota, intestinal barrier function and the low-grade inflammation that characterizes the progression from obesity to metabolic disturbances, making dietary strategies to modulate the intestinal environment relevant. In this context, the ability of some Gram-positive anaerobic bacteria to produce the short-chain fatty acid butyrate is interesting. A lower abundance of butyrate-producing bacteria has been associated with metabolic risk in humans, and recent studies suggest that butyrate might have an anti-inflammatory potential that can alleviate obesity-related metabolic complications, possibly due to its ability to enhance the intestinal barrier function. Here, we review and discuss the potential of butyrate as an anti-inflammatory mediator in metabolic diseases, and the potential for dietary interventions increasing the intestinal availability of butyrate.

Background:Gut microbial gene richness and specific bacterial species are associated with metabolic risk markers in humans, but the impact of host physiology and dietary habits on the link between the gut microbiota and metabolic markers remain unclear. The objective of this study was to identify gut metagenomic markers associated with estimates of insulin resistance, lipid metabolism and inflammation in obesity, and to explore whether the associations between metagenomic and metabolic markers persisted after adjustment for body fat, age and habitual dietary intake.Methods:Faecal DNA from 53 women with obesity was analysed through quantitative metagenomic sequencing and analysis, and a systematic search was performed for bacterial genes associated with estimates of insulin resistance, inflammation and lipid metabolism. Subsequently, the correlations between metagenomic species and metabolic markers were tested by linear regression models, with and without covariate adjustment.Results:One hundred and fourteen metagenomic species correlated with metabolic markers (P<0.001) including Akkermansia muciniphila, Bilophila wadsworthia, Bifidobacterium longum and Faecalibacterium prausnitzii, but also species not previously associated with metabolic markers including Bacteroides faecis and Dorea longicatena. The majority of the identified correlations between bacterial species and metabolic markers persisted after adjustment for differences in body fat, age and dietary macronutrient composition; however, the negative correlation with insulin resistance observed for B. longum and F. prausnitzii appeared to be modified by the intake of dietary fibre and fat, respectively.Conclusions:This study shows that several gut bacterial species are linked to metabolic risk markers in obesity, also after adjustment for potential confounders, such as long-term diet composition. The study supports the use of gut metagenomic markers for metabolic disease prediction and warrants further investigation of causality.

Individuals with high P/B lost more body weight and body fat compared to individuals with low P/B, confirming that individuals with a high P/B are more susceptible to weight loss on a diet rich in fiber.

Aims/hypothesis The immune-mediated elimination of pancreatic beta cells in type 1 diabetes involves release of cytotoxic cytokines such as IL-1β and IFNγ, which induce beta cell death in vitro by mechanisms that are both dependent and independent of nitric oxide (NO). Nuclear factor kappa B (NFκB) is a critical signalling molecule in inflammation and is required for expression of the gene encoding inducible NO synthase (iNOS) and of proapoptotic genes. NFκB has recently been shown to associate with chromatin-modifying enzymes histone acetyltransferases and histone deacetylases (HDAC), and positive effects of HDAC inhibition have been obtained in several inflammatory diseases. Thus, the aim of this study was to investigate whether HDAC inhibition protects beta cells against cytokine-induced toxicity. Materials and methods The beta cell line, INS-1, or intact rat islets were precultured with HDAC inhibitors suberoylanilide hydroxamic acid or trichostatin A in the absence or presence of IL-1β and IFNγ. Effects on insulin secretion and NO formation were measured by ELISA and Griess reagent, respectively. iNOS levels and NFκB activity were measured by immunoblotting and by immunoblotting combined with electrophoretic mobility shift assay, respectively. Viability was analysed by 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl-tetrazolium bromide and apoptosis by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay and histone-DNA complex ELISA. Results HDAC inhibition reduced cytokine-mediated decrease in insulin secretion and increase in iNOS levels, NO formation and apoptosis. IL-1β induced a bi-phasic phosphorylation of inhibitor protein kappa Bα (IκBα) with the 2nd peak being sensitive to HDAC inhibition. No effect was seen on IκBα degradation and NFκB DNA binding. Conclusions/interpretation HDAC inhibition prevents cytokine-induced beta cell apoptosis and impaired beta cell function associated with a downregulation of NFκB transactivating activity.

Mutations in the gene encoding the melanocortin 4 receptor (MC4R) are associated with the most common monogenic form of obesity. We examined 750 Danish men with juvenile-onset obesity (body mass index 33.3 +/- 2.4 kg/m(2)) and 706 control subjects (body mass index 21.4 +/- 2.1 kg/m(2)) for mutations in MC4R. A total of 14 different mutations were identified of which two, Ala219Val and Leu325Phe, were novel variants. The variant receptor, Leu325Phe, was unable to bind [Nle4,d-Phe7]-alphaMSH, whereas the Ala219Val variant showed a significantly impaired melanotan II induction of cAMP, compared with the wild-type receptor. The remaining 11 mutations have previously been reported, but selected MC4R variants were further characterized in vitro in the present study. A previously identified nonsense mutation, Tyr35stop, had a relatively high allele frequency (0.6%), suggesting a possible founder effect in the Danish population. This study shows a carrier frequency of 2.5% of pathogenic mutations in the MC4R gene in a population-based study of obese men. Thus, variation in this gene is the most common known specific genetic cause of obesity among Scandinavian men.