Table 2 Contradicting evidence of cross-kingdom communication by diet/plant-derived miRNAs
From: MicroRNAs from plants to animals, do they define a new messenger for communication?
Year | Contents | miRNAs involved | Source origin | miRNA levels | Refuting points | Detection methods | Conclusion | Reference |
|---|---|---|---|---|---|---|---|---|
2013 | Little or no plant miRNAs or miR168a were detected in blood or liver of mice fed with rice-containing diets. | miR168a | Rice | Unmeasurable | The observed changes in LDL levels might be due to the release of endogenous cholesterol stores in response to negligible dietary cholesterol intake in mice fed with only rice. | HTS, RT-qPCR, ELISA | Dietary exposure to miR168a did not affect plasma LDL levels. Plasma LDL changes reported by Zhang resulted from nutritional imbalances between test and control groups rather than an RNAi-mediated effect of consuming miR168a in rice. | [154] |
2013 | Plant miRNAs were not detectable in the plasma from healthy human subjects after intake of a western diet containing fruits. | miR156a miR159a miR169a | Plant material | Undetectable | Low measurable uptake | RT-qPCR | Horizontal delivery of miRNAs via oral ingestion of a typical diet was neither a frequent nor a prevalent event across multiple recipient animal organisms. | [158] |
| Â | Negligible expression of miR21 in plasma or organ tissue in miR21 knockout mice after oral diets replete with endogenous miR21. | miR21 | Animal lard diet replete with miR21 | Undetectable in plasma; less than one copy per cell in the liver, lungs, kidneys and stomach. | Â | Â | Â | Â |
Negligible expression of miR156a, miR159a and miR169a in plasma or organs in mice after diets replete with these miRNAs. | miR156a miR159a miR169a | Vegetarian diets replete with these miRNAs | miR156a: far less than one copy of miRNA per cell in liver, lungs, kidneys and stomach; miR159a and miR169a: undetectable in either plasma and/or organs. | |||||
| Â | Negligible expression of plant-derived miRNAs in recipient honey bee tissues. | miR156a miR159a miR169a | plant-derived miRNA | Only miR156a but not miR159a or miR169a, was detected in abdominal tissue derived from nurses and foragers, but again at exceptionally low levels. | ||||
2012 | Predominant monocot miR168 sequence was present as a result of contamination from a non-plant source. | miR168a | Plant | Not available | Contamination | HTS, NB | The observed plant miRNAs in animal sRNA datasets could originate in the process of sequencing, and accumulation of plant miRNAs via dietary exposure was not universal in animals. | [155] |
2014 | Cross-contamination during library preparation was a source of exogenous RNAs. | miR168a miR156a miR167a | Plant | Not available | Contamination | HTS | Variable amounts of plant miRNAs were found in publicly available sRNA-seq data sets of human tissues. | [156] |
2014 | Failed to observe a postprandial increase in the brassica-specific miR824 or miR167a in broccoli sprouts feeding study. | miR167a miR824 | Broccoli sprouts | Below detection limit | Low measurable uptake | RT-qPCR | Skeptical of the bioavailability and biologic activity of plant-borne miRNAs | [157] |
2013 | Nonhuman primates failed to uptake dietary plant miRNAs. | miR156 miR160 miR166 miR167 miR168 miR172 | Fruit | Not available | The concentrations were too low to be specific and reliable. | RT-qPCR, droplet digital PCR | The level of miRNAs was too low to be true and/or amplification was non-specific. | [159] |
2018 | Corn miRNA was extensively degraded in the GI tract and that the uptake into circulation and tissues was minimal. | miR156a miR164a miR167a | Corn | No corn miRNAs could be detected in whole blood, fecal or liver of animals. | Significant degradation of corn miRNAs occurred during digestion. | Â | No evidence of increased levels of corn miRNAs in whole blood or tissues after supplementation of corn miRNAs in the diet was observed in a mouse model. | [160] |