Diurnal Variations of Human Circulating Cell-Free Micro-RNA

Abstract

A 24-hour light and dark cycle-dependent rhythmicity pervades physiological processes in virtually all living organisms including humans. These regular oscillations are caused by external cues to endogenous, independent biological time-keeping systems (clocks). The rhythm is reflected by gene expression that varies in a circadian and specific fashion in different organs and tissues and is regulated largely by dynamic epigenetic and post-transcriptional mechanisms. This leads to well-documented oscillations of specific electrolytes, hormones, metabolites, and plasma proteins in blood samples. An emerging, important class of gene regulators is short single-stranded RNA (micro-RNA, miRNA) that interferes post-transcriptionally with gene expression and thus may play a role in the circadian variation of gene expression. MiRNAs are promising biomarkers by virtue of their disease-specific tissue expression and because of their presence as stable entities in the circulation. However, no studies have addressed the putative circadian rhythmicity of circulating, cell-free miRNAs. This question is important both for using miRNAs as biological markers and for clues to miRNA function in the regulation of circadian gene expression. Here, we investigate 92 miRNAs in plasma samples from 24 young male, healthy volunteers repeatedly sampled 9 times during a 24-hour stay in a regulated environment. We demonstrate that a third (26/79) of the measurable plasma miRNAs (using RT-qPCR on a microfluidic system) exhibit a rhythmic behavior and are distributed in two main phase patterns. Some of these miRNAs weakly target known clock genes and many have strong targets in intracellular MAPK signaling pathways. These novel findings highlight the importance of considering bio-oscillations in miRNA biomarker studies and suggest the further study of a set of specific circulating miRNAs in the regulation and functioning of biological clocks.

Circulating, Cell-Free Micro-RNA Profiles Reflect Discordant Development of Dementia in Monozygotic Twins

“…For the qPCR, a Fluidigm BioMark microfluidic chip system (Fluidigm Corp. USA) allowing duplicate assays for 48 miRNAs in 96 samples in one operation was used. For more technical details please refer to [18]. …”

Alterations in Serum MicroRNA Profile During Hemodialysis - Potential Biological Implications

“…Diurnal variation for miRNAs levels should be considered. However, since samples were collected between morning-noon time and single session was not longer than four hours we can assume that our observation was an effect of hemodialysis and not a physiological change through the time, since diurnal variation occurs mainly between day and night and the change is not more than two-fold [35]. Another limitation arises from discrepancies in fold change between the screening and validation studies.…”

The plasma miR-122 basal levels respond to circulating catecholamines in rats

“…The diurnal variance of plasma miR-122 levels was reported with up to 2-fold difference between daytime peak and nocturnal sleep (Heegaard, et al 2016). Comparison of plasma miR-122 diurnal variations between healthy individuals and patients, may reveal the mechanistic aspect of some liver diseases.…”

“…While efforts were made to reduce the intra-individual variances, studies of plasma miR-122 as DILI biomarkers were reported recently in more negative tones in general, due to its release from hepatocytes in absence of overt cellular injuries (Church and Watkins 2017). Additionally, the diurnal variation of plasma miR-122 (Heegaard, et al 2016) is also a concern for its intraday variance, especially those during daytime. In an attempt to understand what contribute to the high variation of circulating miR-122 measurement, we utilized plasma-direct miRFLP assays (Xie, et al 2015, Zhu, et al 2017 and stress-trained rat models to explore the effects of stress and drugs on plasma miR-122 levels.…”