Abstract
Gut microbiota play a key role in the development of metabolic disorders. Defining and correlating structural shifts in gut microbial assemblages with conditions related to metabolic syndrome have, however, been proven difficult. Results from 16S genomic DNA and 16S ribosomal RNA analyses of fecal samples may differ widely, leading to controversial information on the whole microbial community and metabolically active microbiota. Using a C57BL/6J murine model, we compared data from 16S genomic DNA and ribosomal RNA of the fecal microbiota. The study included three groups of experimental animals comprising two groups with high fat diet induced obesity (DIO) while a third group (control) received a low fat diet. One of the DIO groups was treated with the probiotic Lactobacillus rhamnosus GG (LGG). Compared to the data obtained by DNA analysis, a significantly higher abundance of OTUs was accounted for by RNA analysis. Moreover, rRNA based analysis showed a modulation of the active gut microbial population in the DIO group receiving LGG, thus reflecting a change in the induced obesity status of the host. As one of the most widely studied probiotics the functionality of LGG has been linked to the alleviation of metabolic syndrome, and, in some cases, to an impact on the microbiome. Yet, it appears that no study has reported thus far on modulation of the active microbiota by LGG treatment. It is postulated that the resulting impact on calorie consumption affects weight gain concomitantly with modulation of the functional structure of the gut microbial population. Using the 16S rRNA based approach therefore decisively increased the precision of gut microbiota metagenome analysis.
Highlights
Application of novel techniques such as those based on culturomics has revealed a hitherto unexpected complexity of the human gut microbiome; numerous microbial taxonomic units have only recently been detected, bringing the estimated number of microbial species to more than 1500 at present (Lagier et al, 2016; Utzschneider et al, 2016)
Compared to the high fat diet (HFD) phosphate buffered saline (PBS)-treated group, weight gain was significantly lower in the probiotic Lactobacillus rhamnosus GG (LGG) treatment group (HFD+LGG) (Figure 1A) while a minor reduction in calorie uptake was detected in the HFD+LGG group
Both the liver and epididymal adipose tissue (EAT) weight was significantly lower in the low fat diet (LFD) group, while only the EAT weight was significantly reduced in the HFD+LGG group (Figure 1B)
Summary
Application of novel techniques such as those based on culturomics has revealed a hitherto unexpected complexity of the human gut microbiome; numerous microbial taxonomic units have only recently been detected, bringing the estimated number of microbial species to more than 1500 at present (Lagier et al, 2016; Utzschneider et al, 2016). While shifts or alterations in the autochthonous microbial population of people suffering from metabolic diseases have been reported frequently (Turnbaugh et al, 2006; Cani et al, 2008; Raoult, 2008; Armougom et al, 2009; Cani and Delzenne, 2009; Larsen et al, 2010; Zhang et al, 2013; Kasai et al, 2015; Ussar et al, 2015), this issue has, remained controversial, since an overwhelming part of the data has been acquired by microbial genomic DNA- and not ribosomal RNAbased gut microbiota analysis The latter technology may reflect more reliably the metabolically active microbial communities more precisely (Baldrian et al, 2012; Pérez-Cobas et al, 2013). This study was conducted to compare DNA vs. RNA approaches for gut microbiota analysis in a C57BL/6J mouse model by modifying the gut ecosystem system with a specific high fat diet (control: low fat diet) and by the administration of the probiotic strain Lactobacillus rhamnosus GG (LGG)
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