Characterization of the gut microbiota in Chinese children with overweight and obesity using 16S rRNA gene sequencing

BACKGROUND: Childhood obesity constitutes a worldwide health problem, and the gut microbiota play extremely important roles in obesity. Herein, we aimed to characterize the gut microbiota in children of normal weight, overweight, and obesity. METHODS: Thirty children of normal weight, 35 who were overweight, and 35 with obesity were enrolled from Nanjing, China. We isolated DNA from fecal samples, and employed 16S rRNA gene sequencing to explore the diversity and composition of gut microbiota. RESULTS: The operational taxonomic unit (OTU) numbers exhibited a reduction in the gut microbiota abundance with the increase in the body weight. Alpha diversity analysis revealed a sharp decrease in the mean microbial abundance among the three groups (Chao1: F = 5.478, P = 0.006; observed species: F = 7.271, P = 0.001; PD whole tree: F = 8.735, P < 0.001). Beta diversity analysis indicated notable differences in the gut microbial composition between children of normal weight and obesity. However, overweight children had little difference in gut microbiota compared to either children of normal weight or obesity. At the genus level, Oscillospira decreased among the three groups (χ(2) = 10.062, P = 0.001), and Sutterella increased (F = 4.052, P = 0.020). There were many remarkably increased species of gut bacteria in the comparison among three groups, 31 in the normal weight group, 32 in the obese group, and only three species of bacteria were identified in the overweight group. These significantly increased species of gut bacteria may have a close relationship with the progression of obesity. CONCLUSIONS: The abundance of species decreased significantly as the BMI increased. Although the gut microbial composition between children of normal weight and obesity was notably different, due to the changing ratio of some microbial communities, gut microbiota in overweight children showed similarities to that of children with normal weight and obesity.