Uptake of dietary milk miRNAs by adult humans: a validation study

Abstract

Breast milk is replete with nutritional content as well as nucleic acids including microRNAs (miRNAs). In a recent report, adult humans who drank bovine milk appeared to have increased circulating levels of miRNAs miR-29b-3p and miR-200c-3p. Since these miRNAs are homologous between human and cow, these results could be explained by xeno-miRNA influx, endogenous miRNA regulation, or both. More data were needed to validate the results and explore for additional milk-related alterations in circulating miRNAs. Samples from the published study were obtained, and 223 small RNA features were profiled with a custom OpenArray, followed by individual quantitative PCR assays for selected miRNAs. Additionally, small RNA sequencing (RNA-seq) data obtained from plasma samples of the same project were analyzed to find human and uniquely bovine miRNAs. OpenArray revealed no significantly altered miRNA signals after milk ingestion, and this was confirmed by qPCR. Plasma sequencing data contained no miR-29b or miR-200c reads and no intake-consistent mapping of uniquely bovine miRNAs. In conclusion, the results do not support transfer of dietary xenomiRs into the circulation of adult humans.

Toward the promise of microRNAs – Enhancing reproducibility and rigor in microRNA research

“…101,102 Finally, positive results from a milk intake study involving humans 103 could not be validated. 104 Exciting and new concepts in the microRNA oeuvre must be supported by rigorous data. When dealing with very low RNA concentrations, one must be on the outlook for laboratory contaminants, nonspecific amplification, sequencing bias, and effects of analysis pipelines, among others, that are more parsimonious explanations for the presence of foreign RNA than hypothetical uptake pathways.…”

Survey of 800+ data sets from human tissue and body fluid reveals xenomiRs are likely artifacts

“…A number of groups have searched for plant xenomiRs in human body fluids but have been unable to find these sequences at any substantial level (Snow et al 2013;Witwer et al 2013). Similarly, other groups were unable to detect dietary xenomiRs when conducting controlled feeding studies in humans, mice, bees, and other insects (Dickinson et al 2013;Witwer et al 2013;Auerbach et al 2016). Further, one independent research group investigated the xenomiR composition of sRNA-seq data from amphioxus animals, generated by the team of the original Zhang et al (2012) publication.…”

Non-Coding RNA Roles in Ruminant Mammary Gland Development and Lactation

“…However, other studies have not succeeded to validate the hypothesis that milk miRNAs exert physiological regulatory functions after transferring to offspring [126][127][128][129]. For instance, Auerbach et al [129] observed that drinking bovine milk increased circulating levels of miRNAs (miR-29b-3p and miR-200c-3p) but found no evidence that they significantly altered miRNA signals after milk ingestion. These authors concluded that milk miRNAs likely serve as a source of nutrition but not as post-transcriptional regulators in recipients.…”