Nutritional status reshapes gut microbiota composition in adolescent Afghan refugees in Peshawar, Pakistan

Although the human gut microbiome, and its role in health and disease, have been extensively studied in different populations, a comprehensive assessment of gut microbiome composition has not been performed in vulnerable refugee populations. In this study, we hypothesized that overall nutritional status, as indicated by serum micronutrients concentrations, is an important driver of variations in gut microbiome composition. Therefore, gut-microbiome diversity and associated demographic, health and nutritional factors were assessed in adolescent Afghan refugees (n=206). Blood and faecal samples were collected and analysed for nutrition status markers and 16S rRNA gene amplicon-based community profiling, respectively. Bioinformatics and statistical analysis were performed using SPSS, QIIME and R. Overall, 56 distinct phyla, 117 families and 252 genera were identified in the faecal samples. Bacterial diversity (alpha and beta diversity) and the Firmicutes:Bacteroidetes (F/B) ratio were significantly higher in the 15 to 19 year old age group (cf. the 10-14 age group) but were lower in the underweight and vitamin D deficient groups. Furthermore, LEfSe analysis identified significant differences in the relative abundance of bacterial genera based on age, BMI and micronutrient (vitamins and minerals) status. These results were further scrutinised by correlation analysis which confirmed that age, BMI and micronutrient status show significant correlations with F/B ratio and the relative abundance of specific bacterial taxa. Collectively, our study provides the first indication of how the gut-microbiota profile of adolescent Afghan refugees is associated with a range of nutrition-status factors. These findings can thus provide a basis for translational microbiota research aimed at improving the health of such understudied and vulnerable populations.