Supplementation of triple viable probiotics combined with dietary intervention is associated with gut microbial improvement in humans on a high-fat diet

Abstract

Numerous animal studies have demonstrated that oral probiotics may have a beneficial role in preventing obesity, inflammatory bowel disease and even colorectal cancer, which are all associated with a high-fat diet (HFD). However, the underlying beneficial effects of combined probiotic and dietary intervention on the gut microbiota of 'non-patient' individuals previously on an HFD have yet to be fully elucidated. In the present study, fecal samples were obtained from 36 volunteers on a high-fat diet and after dietary intervention for 4 months, and 16S rDNA sequencing was applied to identify how probiotics and dietary intervention had altered the composition of the microbiota. The results demonstrated that probiotics treatment and dietary intervention in combination raised the diversity of lumen microbes compared with their individual applications. A markedly separated distribution (β-diversity) was observed, confirming the difference in gut microbiota composition among the treatment groups. Bacterial taxonomic analysis demonstrated that the relative abundance of 30 species was altered among the groups following dietary intervention and/or probiotic supplementation. The majority of the species that exhibited a population increase belonged to two butyrate-producing families, Ruminococcaceae and Lachnospiraceae, whereas the species with reduced populations mainly belonged to the Bacteroidaceae family. Collectively, these results suggest that combined probiotic and dietary intervention is able to improve the gut microbiota composition of human subjects on an HFD.

Keywords: community population; dietary intervention; gut microbiota; high-fat diet; probiotics.

Figure 1.

Composition of experimental diet. Dietary fat of the HFD accounted for >40% of total energy, whereas that of the DI was <40%. Furthermore, no significant changes in the daily intake of dietary fiber in any of the groups occurred between day 0 and the end of the experiment (at month 4). HFD, high-fat diet; DI, dietary intervention with low-fat diet.

Figure 2.

Clustering of samples based on fecal microbiota communities. (A) Principal coordinates analysis of samples from the HFD, DI, HFD + Probiotic and DI + Probiotic groups. (B) Unweighted pairgroup method with arithmetic mean of samples from the HFD, DI, HFD + Probiotic and DI + probiotic groups. Probiotics included Bifidobacterium longum, Lactobacillus acidophilus and Enterococcus faecalis. PC1, PC2 and PC3, three eigenvalues calculated by distance matrix of fecal samples, represent the top three principal coordinate components explaining as much of the variability in the data as possible. HFD, high-fat diet; DI, dietary intervention with low-fat diet.

Figure 3.

Effect of dietary intervention and probiotic supplementation on the fecal microbiota composition at the phylum level. (A) Pie charts displaying the average relative abundance of stool phyla. (B) Bar graphs indicating the inter-individual variability of stool bacteria at the phylum level. HFD, high-fat diet; DI, dietary intervention with low-fat diet.

Figure 4.

Effect of dietary intervention and probiotic supplementation on the fecal microbiota composition at the species level. The relative abundance of altered species was visualized using a heatmap. Data are represented as row-scaled Z-scores. The black bars represent absent species. i and ii indicate species reduced and elevated in the DI, HFD + Probiotic and DI +Probiotic groups when respectively compared with the HFD group. Probiotics included Bifidobacterium longum, Lactobacillus acidophilus and Enterococcus faecalis. HFD, high-fat diet; DI, dietary intervention with low-fat diet.