Depletion of Dietary microRNAs from Cow's Milk Causes an Increase of Purine Metabolites in Human Body Fluids and Mouse Livers

Abstract

BackgroundMicroRNAs (miRNAs) play essential roles in gene regulation. We have recently reported the ground‐breaking discovery that miRNAs are not exclusively derived from endogenous synthesis but can also be obtained from dietary sources such as cow's milk. Evidence suggests that milk consumption is inversely correlated with serum uric acid (UA) concentrations, and 19 miRNAs regulate 11 pathways in purine metabolism.HypothesisConsumption of a diet depleted of milk miRNAs causes changes in purine metabolism.MethodsIn a first screen, C57BL/6 mice were fed a diet depleted of miRNAs (encapsulated in exosomes) from age 3 to 7 weeks [denoted Exosome (E) Minus, E−], whereas controls were fed a miRNA‐sufficient diet (E+). Mouse liver metabolites were analyzed using non‐targeted LC/MS‐MS, and targeted enzymatic assays for purine metabolites. Subsequently, we assessed purine metabolites in urine and plasma from human dairy avoiders and dairy consumers. The statistical significance of differences was assessed by t‐test.ResultsPrincipal Components Analysis (PCA), a dendrogram performed with hierarchical clustering, Variable Important in Projection (VIP) scores, and a heat map analysis consistently suggested that concentrations of purine metabolites were higher in E− livers than in E+ livers, and that purine metabolites were affected by milk miRNA intake to a greater extent than any of the other metabolites that were identified (p<0.01; n=5). As for effect size, the concentrations of xanthine were 16.6 ± 3.3 μM and 10.1 ± 1.0 μM in E − and E+ livers, respectively (p<0.05). Likewise, the concentrations of plasma xanthine and urinary uric acid were 81.6% and 19.3% higher in human dairy avoiders compared with dairy consumers (n=6).ConclusionDietary depletion of milk miRNAs causes an increase in purine metabolites in mouse tissues and human body fluids.Future plansA reversed‐phased HPLC was developed to quantify eight purine metabolites in a comprehensive analysis of purine metabolism; gene expression analysis and purine feeding studies will be used to identify the step(s) in purine metabolism targeted by milk miRNAs.Support or Funding InformationNIFA/USDA 2015‐67017‐23181, NIH 1P20GM104320, Gerber Foundation, Egg Nutrition Center, USDA W‐3002, Hatch and NIH P30GM103335