**3. Endogenous function by plant and animal miRNAS**

In recent years, a series of research studies have provided important advances in plant molecular biology by discovering that plants can regulate the expression of some target genes [11, 24, 25]. The first example was discovered in the nematode *C. elegans* by studying the lin-4 gene in 1993, which transcribes for a small RNA complementary to some segments of the 3'untranslated region of an mRNA encoding the LIN-14

#### *Effect in Human Gene Regulation of Food-Derived Plant miRNAs DOI: http://dx.doi.org/10.5772/intechopen.106366*

protein, required for passage to the late larval stage [26]. However, up until 2000, it was reported that these small transcripts, due to their size, had gone unnoticed. But they were the perpetrators of gene silencing. Over time it has been evidenced that animals and plants produce a large amount of miRNAs [27]. In plants miRNAs generally participate in the process of growth, disease resistance, morphogenesis, leaf and fruit size, development of healthy plant characteristics, and the process of flowering regulation [6]. Some miRNA targets have been found to be involved in processes such as metabolism, transport, cell signaling, stress response [28]. In humans, it is estimated that approximately 60% of all protein-coding genes are miRNA targets, which could practically affect most physiological processes in the body [29]. The miRNAs are, therefore, important regulatory molecules of gene expression in different processes, such as neuronal development, differentiation, proliferation, and cell survival [2]. There is evidence that miRNAs offer potential targets for the diagnosis, prognosis, and treatment of a wide variety of diseases [21]. More importantly, miRNA profiles, especially in serum, plasma, and urine, have been reported to be closely related to various diseases and disease states, including cancer, diabetes, inflammation, infections, and tissue injury [8, 14, 30].
