Inhibition of Mitochondrial Fission Improves Mitochondrial Respiratory Capacity in Primary Myotubes Derived from Obese Humans

Abstract

Obesity induces mitochondrial fragmentation in skeletal muscle causing reduced mitochondrial respiratory capacity, which has been linked with the development of insulin resistance and type 2 diabetes. Recent evidence suggests that excessive mitochondrial fission is the culprit behind the mitochondrial fragmentation in skeletal muscle from obese humans. The purpose of this study was to determine if inhibiting mitochondrial fission in human skeletal muscle cells derived from severely obese individuals reduces mitochondrial fragmentation and improves mitochondrial respiratory capacity. Human skeletal muscle cells were isolated from muscle biopsies obtained from severely obese, insulin‐resistant subjects (n=6, BMI = 47.3 ± 2.8 kg/m2, HOMA‐IR = 3.4 ± 0.4), pooled and differentiated into myotubes. On day 6 of differentiation, myotubes were treated with either mitochondrial fission inhibitor Mdivi‐1 (20μM) or DMSO for 12 hrs. Mitochondrial respiratory capacity was measured using Seahorse XFp Analyzer. Live cells were stained with MitoTracker, and mitochondrial morphology was examined by confocal microscopy. Mitochondrial fission, fusion, and OXPHOS protein expressions were assessed by immunoblot. All experiments were repeated on three different occasions. Preliminary data indicate that mitochondrial fission protein dynamin related protein (Drp1) was reduced (20.9%, P = 0.093), with no changes in mitochondrial content or mitochondrial fusion proteins. Inhibiting mitochondrial fission resulted in a reduction of mitochondrial networks (9.7%) while increasing mitochondrial branch length (14.7%). Reserved mitochondrial respiratory capacity, as measured by the mitochondrial spare capacity, was significantly increased (31.4%, P < 0.05) with Mdivi‐1 treatment. These results demonstrate that inhibition of mitochondrial fission improves mitochondrial morphology and respiratory capacity in skeletal muscle from obese humans, suggesting mitochondrial fission may be a novel therapeutic target for treating metabolic disorders that are typically linked to mitochondrial dysfunction.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.