Project description:<p>The HTN-IR Study, funded by NHLBI, was designed to explore genetic contributions to hypertension and glucose homeostasis traits among Hispanics using a family-based design. The baseline examination of the cohort included the euglycemic hyperinsulinemic clamp test from which the two key phenotypes were obtained: insulin sensitivity (M) and metabolic clearance rate of insulin (MCRI). Genome-wide genotyping was obtained under separate funding by NIDDK as a part of the GUARDIAN (Genetics Underlying Diabetes in Hispanics) Consortium. </p>
Project description:To explore genes that could be responsible to insulin in insulin resistance states (IR), we generated the IR mice models (mice after 6 weeks of high-fat feeding).
Project description:Insulin resistance is accompanied by chronic hyperinsulinemia and is associated with type 2 diabetes and other metabolic syndromes in a substantial portion of the population. The risk factors and features of insulin resistance have been thoroughly described but its mechanistic triggers are still under study. Here we consider a condensate model for insulin receptor (IR) function in normal conditions and when dysregulated in chronic hyperinsulinemia-induced insulin resistance. We find that IR is incorporated into liquid-like condensates at the plasma membrane, in the cytoplasm and in the nucleus of liver cells, and provide evidence for insulin-dependent IR function in condensates. Insulin stimulation promotes further incorporation of IR into these dynamic condensates in insulin sensitive cells, which form and dissolve on short, sub-minute time-scales. In contrast, insulin stimulation does not promote further incorporation of IR into condensates in insulin resistant cells, where IR molecules within condensates exhibit less dynamic behavior. Metformin treatment of insulin resistant cells rescues IR condensate dynamics and insulin responsiveness. Insulin resistant cells experience high levels of oxidative stress, which causes reduced condensate dynamics, and treatment of these cells with metformin reduces ROS levels and returns condensates to their normal dynamic behavior. The condensate model we propose can account for features of normal and dysregulated insulin response and has implications for improved therapeutic approaches to insulin resistance.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes