Our previous studies have demonstrated that stable microRNAs (miRNAs) in mammalian serum and plasma are actively secreted from tissues and cells and can serve as a novel class of biomarkers for diseases, and act as signaling molecules in intercellular communication. Here, we report the surprising finding that exogenous plant miRNAs are present in the sera and tissues of various animals and that these exogenous plant miRNAs are primarily acquired orally, through food intake. MIR168a is abundant in rice and is one of the most highly enriched exogenous plant miRNAs in the sera of Chinese subjects. Functional studies in vitro and in vivo demonstrated that MIR168a could bind to the human/mouse low-density lipoprotein receptor adapter protein 1 (LDLRAP1) mRNA, inhibit LDLRAP1 expression in liver, and consequently decrease LDL removal from mouse plasma. These findings demonstrate that exogenous plant miRNAs in food can regulate the expression of target genes in mammals.

Abbreviations: FDR, false discovery rate; miRNA, microRNA; NAFLD, nonalcoholic fatty liver disease; qRT-PCR, quantitative reverse transcription polymerase chain reaction; SAM, signifi cance analysis of microarray; STZ, streptozotocin.

BackgroundOleic acid (OA) stimulates vascular smooth muscle cell (VSMC) proliferation and migration. The precise mechanism is still unclear. We sought to investigate the effects of peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1 alpha (PGC-1α) on OA-induced VSMC proliferation and migration.Principal FindingsOleate and palmitate, the most abundant monounsaturated fatty acid and saturated fatty acid in plasma, respectively, differently affect the mRNA and protein levels of PGC-1α in VSMCs. OA treatment resulted in a reduction of PGC-1α expression, which may be responsible for the increase in VSMC proliferation and migration caused by this fatty acid. In fact, overexpression of PGC-1α prevented OA-induced VSMC proliferation and migration while suppression of PGC-1α by siRNA enhanced the effects of OA. In contrast, palmitic acid (PA) treatment led to opposite effects. This saturated fatty acid induced PGC-1α expression and prevented OA-induced VSMC proliferation and migration. Mechanistic study demonstrated that the effects of PGC-1α on VSMC proliferation and migration result from its capacity to prevent ERK phosphorylation.ConclusionsOA and PA regulate PGC-1α expression in VSMCs differentially. OA stimulates VSMC proliferation and migration via suppression of PGC-1α expression while PA reverses the effects of OA by inducing PGC-1α expression. Upregulation of PGC-1α in VSMCs provides a potential novel strategy in preventing atherosclerosis.

In the initial published version of this article, an error was made during the assembly of Figure 5B. Figure 5B is a representative image of western blots, which shows that rice-derived MIR168a can down-regulate LDLRAP1 expression in mouse liver and that the injection of antiMIR168a rescued the expression of LDLRAP1. After the initial publishing of this article, it has been brought to our attention that the image of the internal control in previous Figure 5B showing the western blot results of α-tubulin, actually duplicated the images in other parts of the paper (specifically, the left two lanes of the α-tubulin western data in previous Figure 5B duplicated the α-tubulin image of Figure 3C, while the right two lanes duplicated the α-tubulin image of Figure S3D). This error in previous Figure 5B was inadvertently introduced during the assembly of figure panels for this paper.Moreover, after a careful re-examination of the figure legend, we also found that the figure legend of previous Figure 5 was not precise. The corrected figure and its legend are provided below. The detailed results of all the western blot experiments analyzing liver samples of individual mice from different groups (chow diet, rice, rice + anti-ncRNA, rice + anti-MIR168a) are also available for interested readers at our website: http://mcube.nju.edu. cn/mir168a_regulates_ldlrap1.html This correction of Figure 5 and its legend does not affect the description of the results in the paper or the conclusions of our paper. We would like to thank the reader who brought the error of Figure 5B to our attention. We also deeply apologize for any inconvenience that may have been caused by our error.

It is known that endogenous levels of the incretin hormone glucagon-like peptide 1 (GLP1) can be enhanced by various secretagogues, but the mechanism underlying GLP1 secretion is still not fully understood. We assessed the possible effect of uncoupling protein 2 (UCP2) on GLP1 secretion in mouse intestinal tract and NCI-H716 cells, a wellcharacterized human enteroendocrine L cell model. Localization of UCP2 and GLP1 in the gastrointestinal tract was assessed by immunofluorescence staining. Ucp2 mRNA levels in gut were analyzed by quantitative RT-PCR. Human NCI-H716 cells were transiently transfected with siRNAs targeting UCP2. The plasma and ileum tissue levels of GLP1 (7-36) amide were measured using an ELISA kit. UCP2 was primarily expressed in the mucosal layer and colocalized with GLP1 in gastrointestinal mucosa. L cells secreting GLP1 also expressed UCP2. After glucose administration, UCP2-deficient mice showed increased glucose-induced GLP1 secretion compared with wild-type littermates. GLP1 secretion increased after NCI-H716 cells were transfected with siRNAs targeting UCP2. UCP2 was markedly upregulated in ileum tissue from ob/ob mice, and GLP1 secretion decreased compared with normal mice. Furthermore, GLP1 secretion increased after administration of genipin by oral gavage. Taken together, these results reveal an inhibitory role of UCP2 in glucose-induced GLP1 secretion.