MiR‐133a Mitigates Mitophagy in Ins2+/‐ Diabetic Heart

Abstract

To test the hypothesis that inhibition of miR‐133a induces mitophagy in diabetic hearts and it is ameliorated by overexpression of miR‐133a, we used four in vivo groups: C57BL/6J, Akita (T1D), Akita+miR‐133a, and Akita+scramble; and four in vitro groups of HL1 cardiomyocytes: low (LG‐5mM), high (HG‐25mM) doses of D‐glucose, HG+miR‐133a, and HG+scramble; and determined mitoSOX generation, depolarization of damaged mitochondria (ΔΨ, by JC‐1), mitochondrial fission (by DRP1 and Parkin), autophagosome formation (by Beclin1, ATG14, ATG3, LC3B) and its lysosomal degradation (by RFP‐GFP‐LC3B) using qPCR, Western blotting, immunofluorescence, and transmission electron microscopy (TEM). Our results demonstrate that in HG cardiomyocytes, mitoSOX generation, depolarization of mt‐ΔΨ and DRP1 protein are elevated by 2.5±0.3, 1.44±0.08 and 1.94±0.29 folds, respectively, but ameliorated (mitoSOX:4.9±0.04, mt‐ΔΨ:2.11±0.08, and DRP1:0.85±0.17 fold down regulation) by overexpression of miR‐133a. The levels of Beclin1, ATG14, ATG3 and LC3B are increased in HG by 1.21±0.09, 1.46±0.24, 1.63±0.2, and 1.44±0.02 folds but mitigated by 1.47±0.08, 1.16±0.03, and 2.19±0.2, 1.54±0.02 folds respectively. The lysosomal degradation of autophagosome is elevated in HG by 4.51±0.9 fold but down regulated by 2.07±0.2 fold in miR‐133a overexpressing cardiomyocytes. DRP1 and Parkin proteins are up regulated by 1.94±0.01 and 1.99±0.37 folds in Akita but mitigated 2.5±0.02 and 2.25±0.43 folds by miR‐133a, respectively. TEM elicited increased mitophagy in Akita but restored in Akita+miR‐133a. We conclude that attenuation of miR‐133a increases mitoSOX, depolarizes mt‐ΔΨ and induces mitophagy, whereas overexpression of miR‐133a restores their levels and ameliorates mitophagy in diabetic hearts.