Diurnal oscillations in human salivary microRNA and microbial transcription

We investigated daily oscillations in salivary miRNA and microbial RNA to explore relationships between these components of the gut-brain-axis and their implications in human health. Nine subjects provided 120 saliva samples at designated times, on repeated days. Samples were divided into three sets for exploration and cross-validation. Identification and quantification of host miRNA and microbial RNA was performed using next generation sequencing. Eleven miRNAs and 11 microbial RNAs demonstrated consistent diurnal oscillation across the first 2 sample sets and accurately predicted collection time in the hold-out set based on multivariate logistic regression modeling. Associations among five circadian miRNAs and four circadian microbial RNAs were observed. Overall design: Salivary miRNA and microbial taxon profiles of 120 human samples were generated by shotgun sequencing, using Illumina NextSeq 500.