Eat to Regulate Your Genes?

Stephen L. Talbott

From In Context #28 (Fall, 2012) | View article as PDF

As you may have learned in biology class, a protein-coding gene is a segment of DNA that can be “transcribed” into messenger RNA, which then is (or may be) “translated” into protein. The entire process is broadly known as “gene expression.” However, one of the hottest fields of research in molecular biology over the past decade or two has to do with DNA regions that produce a wide assortment of non-protein-coding RNAs. These noncoding RNAs perform a wide range of regulatory functions in the cell. And one of the most important classes of these regulatory molecules consists of what are called “microRNAs,” or miRNAs. Their manifold functions primarily have to do with the regulation of gene expression, and their activities are interwoven with almost every aspect of an organism. Likewise their malfunctioning: the presence of the wrong miRNA in the wrong place at the wrong time contributes to many diseases, including cancers.

It has long been regarded as impossible for an miRNA ingested in an animal’s food to function as an miRNA in that animal. Avoiding degradation, getting from the digestive tract into the bloodstream, and moving from the bloodstream into tissues and organs — these seemed to be insurmountable barriers. But researchers have now brought the startling and wholly unexpected news that animals, including mammals, can assimilate in functional form at least some of the miRNAs they ingest from food. For example, plant-derived miRNAs have been identified in the blood serum and tissues of mice. One of these miRNAs was found to regulate gene expression in such a way as to affect levels of low-density lipoproteins in the mice. That same plant-derived miRNA is present “at a relatively high level” in human serum. The researchers (Zhang et al. 2012) conclude that “plant miRNAs in food can regulate the expression of target genes in mammals.”

Commenting on the implications of this research, another team of biologists write: “For decades there have been debates on the safety of transgenic [genetically engineered] food with regards to human health and the environment. This profound discovery by Zhang et al. should make decision takers more cautious when considering the issues that may arise from the consumption of transgenic crops.” (Jiang et al. 2012)

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References

Jiang, Mengxi, Xiaolin Sang and Zhi Hong (2012). “Beyond Nutrients: Food-Derived microRNAs Provide Cross-Kingdom Regulation,” Bioessays vol. 34, pp. 280-4.

Zhang, Lin, Dongxia Hou, Xi Chen et al. (2012). “Exogenous Plant MIR168a Specifically Targets Mammalian LD-LRAP1: Evidence of Cross-Kingdom Regulation by micro RNA,” Cell Research vol. 22, pp. 107-26.