Distinct Roles of DRP1 in Conventional and Alternative Mitophagy in Obesity Cardiomyopathy.

RATIONALE: Obesity induces cardiomyopathy characterized by hypertrophy and diastolic dysfunction. Whereas mitophagy mediated through an Atg7-dependent mechanism serves as an essential mechanism to maintain mitochondrial quality during the initial development of obesity cardiomyopathy, Rab9-dependent alternative mitophagy takes over the role during the chronic phase. Although it has been postulated that DRP1 (dynamin-related protein 1)-mediated mitochondrial fission and consequent separation of the damaged portions of mitochondria are essential for mitophagy, the involvement of DRP1 in mitophagy remains controversial.

OBJECTIVE: We investigated whether endogenous DRP1 is essential in mediating the 2 forms of mitophagy during high-fat diet (HFD)-induced obesity cardiomyopathy and, if so, what the underlying mechanisms are.

METHODS AND RESULTS: Mice were fed either a normal diet or an HFD (60 kcal %fat). Mitophagy, evaluated with Mito-Keima, was increased after 3 weeks of HFD consumption. The induction of mitophagy by HFD consumption was completely abolished in tamoxifen-inducible cardiac-specific Drp1 knockout ( Drp1 MCM) mouse hearts, in which both diastolic and systolic dysfunction were exacerbated. The increase in LC3-dependent general autophagy and colocalization between LC3 and mitochondrial proteins was abolished in Drp1 MCM mice. Activation of alternative mitophagy was also completely abolished in Drp1 MCM mice during the chronic phase of HFD consumption. DRP1 was phosphorylated at Ser616, localized at the mitochondria-associated membranes, and associated with Rab9 and Fis1 only during the chronic, but not acute, phase of HFD consumption.

CONCLUSIONS: DRP1 is an essential factor in mitochondrial quality control during obesity cardiomyopathy that controls multiple forms of mitophagy. Although DRP1 regulates conventional mitophagy through a mitochondria-associated membrane-independent mechanism during the acute phase, it acts as a component of the mitophagy machinery at the mitochondria-associated membranes in alternative mitophagy during the chronic phase of HFD consumption.