Obesity Alters the Microbial Community Profile in Korean Adolescents

Abstract

Obesity is an increasing public health concern worldwide. According to the latest Organization for Economic Co-operation and Development (OECD) report (2014), the incidence of child obesity in Korea has exceeded the OECD average. To better understand and control this condition, the present study examined the composition of the gut microbial community in normal and obese adolescents. Fecal samples were collected from 67 obese (body mass index [BMI] ≥ 30 kg/m2, or ≥ 99th BMI percentile) and 67 normal (BMI < 25 kg/m2 or < 85th BMI percentile) Korean adolescents aged 13-16 years and subjected to 16S rRNA gene sequencing. Analysis of bacterial composition according to taxonomic rank (genus, family, and phylum) revealed marked differences in the Bacteroides and Prevotella populations in normal and obese samples (p < 0.005) at the genus and family levels; however, there was no difference in the Firmicutes-to-Bacteroidetes (F/B) ratio between normal and obese adolescents samples at the phylum level (F/B normal = 0.50 ± 0.53; F/B obese = 0.56 ± 0.86; p = 0.384). Statistical analysis revealed a significant association between the compositions of several bacterial taxa and child obesity. Among these, Bacteroides and Prevotella showed the most significant association with BMI (p < 0.0001 and 0.0001, respectively). We also found that the composition of Bacteroides was negatively associated with triglycerides (TG), total cholesterol, and high-sensitive C-reactive protein (hs-crp) (p = 0.0049, 0.0023, and 0.0038, respectively) levels, whereas that of Prevotella was positively associated with TG and hs-crp levels (p = 0.0394 and 0.0150, respectively). We then applied the association rule mining algorithm to generate "rules" to identify the association between the populations of multiple bacterial taxa and obesity; these rules were able to discriminate obese from normal states. Therefore, the present study describes a systemic approach to identify the association between bacterial populations in the gut and childhood obesity.

Fig 1. Average composition of the microbiota in fecal samples from normal and obese adolescents according to taxonomic rank.

The innermost ring of the donut plots for both normal and obese individuals shows the composition at the phylum level, whereas the middle and outermost rings show the composition at the family and genus levels, respectively. There was a marked difference in the average proportions of Bacteroides and Prevotella between normal and obese samples at the genus level. This trend persisted at the family level. However, there were no significant differences in the Bacteroidetes, Firmicutes, and Proteobacteria populations in samples from normal and obese adolescents at the phylum level. All microbiota representing > 1% (mean value) composition are shown.

Fig 2. Mann-Whitney U test result showing differentially abundant microbiota in obese and normal adolescents.

A. Genus level and B. Family level.

Fig 3. Mann-Whitney U test results at the phylum level.

A. Box plots showing similar abundance of the Bacteroidetes, Firmicutes, and Proteobacteria populations in normal and obese adolescents. B. The Firmicutes-to-Bacteroidetes ratio in the gut of normal and obese adolescents. There was no significant difference in F/B ratio between normal and obese adolescents.