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These data indicate glucose-induced EndMT in vitro and in vivo is possibly mediated through TGFβ and regulated by miR-200b and p300.

Hyperglycemia-induced endothelial injury is a key pathogenetic factor in diabetic cardiomyopathy. Endothelial injury may lead to a phenotypic change (i.e., endothelial-to-mesenchymal transition [EndMT]), causing cardiac fibrosis. Epigenetic mechanisms, through specific microRNA, may regulate such a process. We investigated the mechanisms for such changes in cardiac microvascular endothelial cells and in the heart of genetically engineered mice with chemically induced diabetes. Cardiac tissues and isolated mouse heart endothelial cells (MHECs) from animals with or without endothelial-specific overexpression of miR-200b, with or without streptozotocin-induced diabetes, were examined at the mRNA and protein levels for endothelial and mesenchymal markers. Expression of miR-200b and its targets was quantified. Cardiac functions and structures were analyzed. In the hearts of wild-type diabetic mice, EndMT was observed, which was prevented in the miR-200b transgenic diabetic mice. Expression of specific markers such as vascular endothelial growth factor, zinc finger E-box–binding homeobox, transforming growth factor-β1, and p300 were increased in the hearts of diabetic mice and were prevented following miR-200b overexpression. MHECs showed similar changes. miR-200b overexpression also prevented diabetes-induced cardiac functional and structural changes. These data indicate that glucose-induced EndMT in vivo and in vitro in the hearts of diabetic mice is possibly mediated by miR-200b and p300.

Diabetic nephropathy (DN) is a frequent and severe complication of diabetes that is structurally characterized by glomerular basement membrane thickening, extracellular matrix accumulation, and destabilization of podocyte foot processes. MicroRNAs (miRNAs) are dysregulated in DN, but identification of the specific miRs involved remains incomplete. Here, we confirm that the peripheral blood from patients with diabetes and the kidneys of animals with type 1 or 2 diabetes have low levels of miR-23b compared with those of their nondiabetic counterparts. Furthermore, exposure to high glucose downregulated miR-23b in cultured kidney cells. In contrast, renal expression of Ras GTPase-activating protein SH3 domain-binding protein 2 (G3BP2), a putative miR-23b target, increased in DN. In vitro, overexpression of miR-23b decreased, and inhibition of miR-23b increased, G3BP2 expression levels. Bioinformatics analysis also revealed p53 binding sites in the miR-23b promoter; in vitro inhibition of p53 or the upstream p38 mitogen-activated protein kinase (p38MAPK) upregulated miR-23b expression in high-glucose conditions. In turn, inhibition of G3BP2 or overexpression of miR-23b downregulated p53 and p38MAPK expression in high-glucose conditions. In vivo, overexpression of miR23b or inhibition of p53 in db/db mice reversed hyperalbuminuria and kidney fibrosis, whereas miR-23b antagomir treatment promoted renal fibrosis and increased albuminuria in wild-type mice. These data suggest that hyperglycemia regulates pathogenic processes in DN through an miR-23b/G3BP2 feedback circuit involving p38MAPK and p53. In conclusion, these results reveal a role for miR-23b in DN and indicate a novel potential therapeutic target.

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