Extracellular RNAs Are Associated With Insulin Resistance and Metabolic Phenotypes

Abstract

Objective: Insulin resistance (IR) is a hallmark of obesity and metabolic disease. Circulating extracellular RNAs (ex-RNAs), stable RNA molecules in plasma, may play a role in IR, though most studies on ex-RNAs in IR are small. We sought to characterize the relationship between ex-RNAs and metabolic phenotypes in a large community-based human cohort.

Research design and methods: We measured circulating plasma ex-RNAs in 2,317 participants without diabetes in the Framingham Heart Study (FHS) Offspring Cohort at cycle 8 and defined associations between ex-RNAs and IR (measured by circulating insulin level). We measured association between candidate ex-RNAs and markers of adiposity. Sensitivity analyses included individuals with diabetes. In a separate cohort of 90 overweight/obese youth, we measured selected ex-RNAs and metabolites. Biology of candidate microRNAs was investigated in silico.

Results: The mean age of FHS participants was 65.8 years (56% female), with average BMI 27.7 kg/m²; participants in the youth cohort had a mean age of 15.5 years (60% female), with mean BMI 33.8 kg/m². In age-, sex-, and BMI-adjusted models across 391 ex-RNAs in FHS, 18 ex-RNAs were associated with IR (of which 16 were microRNAs). miR-122 was associated with IR and regional adiposity in adults and IR in children (independent of metabolites). Pathway analysis revealed metabolic regulatory roles for miR-122, including regulation of IR pathways (AMPK, target of rapamycin signaling, and mitogen-activated protein kinase).

Conclusions: These results provide translational evidence in support of an important role of ex-RNAs as novel circulating factors implicated in IR.

Figure 1

Age, sex, and BMI-adjusted plasma abundance of miR-122 across quartiles of circulating insulin. Comparisons across all quartiles were statistically significant (after Bonferroni correction for type 1 error), except 1st vs. 2nd quartile and 2nd vs. 3rd quartile.

Figure 2

Visualization of selected miRNA targeting events on the insulin signaling pathway (from WikiPathways). The genes targeted by miRNA per pathway, as counted in Supplementary Table 3, are visualized in this figure for selected pathways. Pathway was imported into Cytoscape from WikiPathways, and ID mapping was performed to obtain Entrez Gene identifiers for each gene. An intermediate file from the Pathway Finder tool was parsed and imported into Cytoscape to supply the mappings between Entrez Gene and the selected set of miRNAs. A visual style was defined in Cytoscape to highlight any gene targeted by these miRNAs in preferential order: miR-122 (blue), miR-192 (red), and any of the other 14 possible miRNAs (gray). Other selected pathways from WikiPathways are shown in Supplementary Fig. 1.