Apple consumption is associated with a distinctive microbiota, proteomics and metabolomics profile in the gut of Dawley Sprague rats fed a high-fat diet.
Garcia-Mazcorro JF, Pedreschi R, Yuan J, Kawas JR, Chew B, Dowd SE, Noratto G
PLoS One. 2019. doi: 10.1371/journal.pone.0212586
COMMENT: Apple compounds have shown beneficial effects associated with gut microbiota in mice, however, the effect of apple supplementation on health and the gut microbiota is not well understood. In this study the fecal microbiota of rats supplemented with freeze dried apple was examined using 16S marker sequencing targeting the V4 region in MiSeq (Illumina).
The aim of this study was to investigate the effect of apple supplementation on the fecal microbiota of rats exposed to a high-fat (HF) and a low-fat (LF) diet, and to determine how microbiota changes can be related to changes in relevant gut biomarkers and metabolites.
There was a statistically lower concentration of lipopolysaccharides (LPS) in blood of HF apple-supplemented subjects compared to controls in the HF group (…). No difference was found between the LF groups with and without supplementation groups whose LPS levels were lower than HF.
In the HF group, results showed that apple supplementation was associated with lower glucose levels (...), plasma LDL oxidation (...), leptin (...); insulin (...); and MCP-1 (..). Apple supplementation did not influence these biomarkers in LF groups. Overall, these results indicate that apple intake may lessen plasma biomarkers associated with disorders tied to obesity.
LEfSe revealed differences in relative proportions of multiple taxa between the HF and the LF groups.
The ratio Clostridiales:Bacteroidaceae was higher in apple-supplemented rats (median: 1.0) compared to controls (median: 0.6), and this difference was statistically stronger (P = 0.003) compared to the difference in Firmicutes:Bacteroidetes ratios. Overall, this supports the results at the phylum level and suggest that apple supplementation increases some members of Clostridiales and lowers some members of Bacteroidaceae in the presence of HF diet.
the abundance of Actinobacteria was increased in apple-supplemented rats (~0.45%) compared to controls (~0.29%, P = 0.025)
The number of observed “species” (i.e. OTUs at 97% similarity) revealed an interesting pattern of variation among the four treatment groups. First, overall HF rats had a relatively higher number of OTU types (940, range: 802–1090) compared to LF rats (865, range: 778–980) (P = 0.0097, Fig 5A) at the same rarefaction depth. Interestingly, apple supplementation was associated with relatively higher and lower numbers of OTU types in the HF and the LF groups, respectively.
The analysis of unweighted UniFrac distances revealed a clear and strong separation of bacterial communities based on diet (HF vs LF) and less strongly on Treatment (HF and LF with and without apple supplementation)
This study shows that apple supplementation for six weeks has a measurable impact on the abundance of specific fecal bacterial groups in vivo, particularly in the presence of a high-fat diet. This change in composition was accompanied by a change in whole communities, biochemical and inflammatory biomarkers in plasma, fecal and host proteins in colon mucosa, as well as fecal metabolites other than SCFAs, which remained similar.
There are a number of pitfalls that are important to discuss in order to guide future investigations on the effect of apple supplementation on the gut microbiota and overall health. Such as, the variation in nutritional content among different apple cultivars, the administration of specific bioactive compounds (as opposed to the whole fruit) and the effect in vitro and in vivo.