RESUMO
BACKGROUND: Beside the influence of nutritional habits and reduced physical activity, metabolic syndrome is associated with alterations in the structure of gut microbiota influencing the inflammatory immune responses. Gut microbiota and microbial metabolic activities are known to affect the lipid and glucose metabolism, satiety and chronic low-grade inflammation in the metabolic syndrome. The aim of the study was to identify genera or even species affecting host metabolism in obesity and type 2 diabetes beside the common used indicator: Firmicutes/ Bacteroidetes ratio. METHODS: Differences in gut microbiota were investigated in three groups of subjects over a four month intervention period: type 2 diabetics under GLP1-Agonist therapy, obese individuals without established insulin resistance, both receiving nutritional counseling concerning weight reduction, and a lean control group. Collection of fecal samples was accomplished at two time points, before treatment, and after four months of treatment. For identification of bacteria at species-level we used 454 high-throughput sequencing and fragment length polymorphism analysis based on IS-pro (Intergenic-Spacer-profiling). Five bacterial species, two bacterial genera, total bacterial abundance, and the Firmicutes/Bacteroidetes ratio were determined. RESULTS: Type 2 diabetics showed a higher Firmicutes/Bacteroidetes ratio even with an increase to the second time point (p=0.07). The abundance of B. thetaiotaomicron remained unaffected, whereas B. vulgatus significantly increased in type 2 diabetics (p=0.07) over the study period. Either Alistipes spp. showed an increase in type 2 diabetics between the time points (p=0.06). The abundance of F. prausnitzii (p=0.03) and A. muciniphila (p=0.03) also increased in type 2 diabetics over study period. In addition, the concentration of P. anaerobius (p=0.03) was significantly higher in type 2 diabetics after intervention compared to lean and obese controls. CONCLUSION: Our results clearly show a difference in the gut bacterial composition in type 2 diabetics compared to lean controls or obesity. Therefore, the ratio of Fimicutes/Bacteroidetes might only be an indicator, but a detailed view at species level is even more important in regard to distinction of their functions.
RESUMO
The human gut microbiota and microbial influences on lipid and glucose metabolism, satiety, and chronic low-grade inflammation are known to be involved in metabolic syndrome. Fermentation end products, especially short chain fatty acids, are believed to engage the epigenetic regulation of inflammatory reactions via FFARs (free fatty acid receptor) and other short chain fatty acid receptors. We studied a potential interaction of the microbiota with epigenetic regulation in obese and type 2 diabetes patients compared to a lean control group over a four month intervention period. Intervention comprised a GLP-1 agonist (glucagon-like peptide 1) for type 2 diabetics and nutritional counseling for both intervention groups. Microbiota was analyzed for abundance, butyryl-CoA:acetate CoA-transferase gene and for diversity by polymerase chain reaction and 454 high-throughput sequencing. Epigenetic methylation of the promoter region of FFAR3 and LINE1 (long interspersed nuclear element 1) was analyzed using bisulfite conversion and pyrosequencing. The diversity of the microbiota as well as the abundance of Faecalibacterium prausnitzii were significantly lower in obese and type 2 diabetic patients compared to lean individuals. Results from Clostridium cluster IV and Clostridium cluster XIVa showed a decreasing trend in type 2 diabetics in comparison to the butyryl-CoA:acetate CoA-transferase gene and according to melt curve analysis. During intervention no significant changes were observed in either intervention group. The analysis of five CpGs in the promoter region of FFAR3 showed a significant lower methylation in obese and type 2 diabetics with an increase in obese patients over the intervention period. These results disclosed a significant correlation between a higher body mass index and lower methylation of FFAR3. LINE-1, a marker of global methylation, indicated no significant differences between the three groups or the time points, although methylation of type 2 diabetics tended to increase over time. Our results provide evidence that a different composition of gut microbiota in obesity and type 2 diabetes affect the epigenetic regulation of genes. Interactions between the microbiota and epigenetic regulation may involve not only short chain fatty acids binding to FFARs. Therefore dietary interventions influencing microbial composition may be considered as an option in the engagement against metabolic syndrome.
