Objective This study aimed to elucidate the mechanism by which hypertrophic adipocytes regulate insulin signaling in cardiac myocytes. Methods Palmitate was used to induce hypertrophic 3T3‐L1 adipocytes. Exosomes were purified from normal control or hypertrophic 3T3‐L1 adipocyte‐associated conditioned medium. Exosome‐exposed neonatal rat ventricular myocytes were stimulated with insulin to investigate the effects of exosomes on insulin signaling. Small interfering RNA techniques were used to downregulate protein levels, and their efficiency was evaluated by Western blot. Results Hypertrophic adipocyte–derived exosomes highly expressed miR‐802‐5p. Insulin sensitivity of neonatal rat ventricular myocytes was negatively regulated by miR‐802‐5p. TargetScan and luciferase reporter assays revealed that heat shock protein 60 (HSP60) was a direct target of miR‐802‐5p. HSP60 silencing was found to induce insulin resistance and to mitigate the insulin‐sensitizing effects of adiponectin. In addition, HSP60 depletion significantly increased the expression levels of C/EBP‐homologous protein and enhanced oxidative stress, accompanied by the increases in the phosphorylation of JNK and IRS‐1 Ser307. Moreover, the effects of HSP60 knockdown on C/EBP‐homologous protein and oxidative stress were abolished by the inhibition of either miR‐802‐5p or endocytosis. Conclusions Hypertrophic adipocyte–derived exosomal miR‐802‐5p caused cardiac insulin resistance through downregulating HSP60. These findings provide a novel mechanism by which epicardial adipose tissue impairs cardiac function.
For the better understanding of insulin resistance (IR), the molecular biomarkers in IR white adipocytes and its potential mechanism, we downloaded two mRNA expression profiles from Gene Expression Omnibus (GEO). The white adipocyte samples in two databases were collected from the human omental adipose tissue of IR obese (IRO) subjects and insulin-sensitive obese (ISO) subjects, respectively. We identified 86 differentially expressed genes (DEGs) between the IRO and ISO subjects using limma package in R software. Gene Set Enrichment Analysis (GSEA) provided evidence that the most gene sets enriched in kidney mesenchyme development in the ISO subjects, as compared with the IRO subjects. The Gene Ontology (GO) analysis indicated that the most significantly enriched in cellular response to interferon-gamma. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the DEGs were most significantly enriched in cytokine-cytokine receptor interaction. Protein-Protein Interaction (PPI) network was performed with the STRING, and the top 10 hub genes were identified with the Cytohubba. CMap analysis found several small molecular compounds to reverse the altered DEGs, including dropropizine, aceclofenac, melatonin, and so on. Our outputs could empower the novel potential targets to treat omental white adipocyte insulin resistance, diabetes, and diabetes-related diseases.
Background : Epicardial adipose tissue (EAT) is implicated in insulin resistance, which has been recognized as a strongest predictor of the development of diabetic cardiomyopathy and subsequent heart failure. However, the underlying mechanism remains incompletely understood. Herein, we investigated the effect of hypertrophic adipocytes on cardiac insulin resistance. Methods : Palmitate was used to induce hypertrophic 3T3-L1 adipocytes. Exosomes were purified from normal control or hypertrophic 3T3-L1 adipocyte-associated conditioned medium. Exosome-exposed neonatal rat ventricular myocytes (NRVMs) were treated with insulin to investigate the effects of exosomes on insulin signaling. Insulin sensitivity was evaluated by measuring insulin-stimulated Akt phosphorylation and glucose uptake. SiRNA techniques were used to downregulate protein levels and its efficiency was evaluated by western blot.Results : Hypertrophic adipocyte-derived exosomes (h-Exo) induced insulin resistance in NRVMs. Furthermore, h-Exo high-expressed miR-802-5p. Insulin sensitivity of NRVMs was impaired by miR-802-5p mimic but improved by its inhibitor. TargetScan and luciferase reporter assays revealed that heat shock protein 60 (HSP60) was a direct target of miR-802-5p. Both h-Exo and miR-802-5p mimic could downregulate HSP60 protein levels. In addition, HSP60 silencing induced insulin resistance and mitigated the insulin-sensitizing effects of adiponectin. HSP60 depletion also significantly increased the expression levels of CHOP, a marker of the unfolded protein response (UPR), and enhanced oxidative stress, accompanied by the increased phosphorylation of JNK and IRS-1 Ser307. Inhibition of both miR-802-5p and endocytosis abolished the impacts of HSP60 knockdown on the UPR and oxidative stress. Conclusion : Hypertrophic adipocyte-derived exosomal miR-802-5p caused cardiac insulin resistance in NRVMs through downregulating HSP60. These findings provide a novel mechanism by which EAT impairs cardiac function.
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