Impaired exercise-induced mitochondrial biogenesis in the obese Zucker rat, despite PGC-1α induction, is due to compromised mitochondrial translation elongation

Abstract

Previously, we demonstrated that high-volume resistance exercise stimulates mitochondrial protein synthesis (a measure of mitochondrial biogenesis) in lean but not obese Zucker rats. Here, we examined factors involved in regulating mitochondrial biogenesis in the same animals. PGC-1α was 45% higher following exercise in obese but not lean animals compared with sedentary counterparts. Interestingly, exercised animals demonstrated greater PPARδ protein in both lean (47%) and obese (>200%) animals. AMPK phosphorylation (300%) and CPT-I protein (30%) were elevated by exercise in lean animals only, indicating improved substrate availability/flux. These findings suggest that, despite PGC-1α induction, obese animals were resistant to exercise-induced synthesis of new mitochondrial and oxidative protein. Previously, we reported that most anabolic processes are upregulated in these same obese animals regardless of exercise, so the purpose of this study was to assess specific factors associated with the mitochondrial genome as possible culprits for impaired mitochondrial biogenesis. Exercise resulted in higher mRNA contents of mitochondrial transcription factor A (∼50% in each phenotype) and mitochondrial translation initiation factor 2 (31 and 47% in lean and obese, respectively). However, mitochondrial translation elongation factor-Tu mRNA was higher following exercise in lean animals only (40%), suggesting aberrant regulation of mitochondrial translation elongation as a possible culprit in impaired mitochondrial biogenesis following exercise with obesity.

Diet‐induced obesity alters anabolic signalling in mice at the onset of skeletal muscle regeneration

“…, , Greene et al . ). Briefly, tissue was homogenized in Mueller buffer, and protein concentration was measured using the Qubit 2.0 ® fluorometer (Invitrogen, Carlsbad, CA, USA).…”

Differential effects of leucine supplementation in young and aged mice at the onset of skeletal muscle regeneration

“…The Ponceau-stained membranes were digitally scanned. The 45-kDa actin bands were quantified by densitometry and used as a protein loading correction factor for each lane as previously described (Brown et al, 2015; Greene et al, 2014; Washington et al, 2011). …”

The Akt/mTOR pathway: Data comparing young and aged mice with leucine supplementation at the onset of skeletal muscle regeneration

“…Western blot analysis was performed as previously described [1], [4], [5]. Equal amounts of protein were loaded into 8-12% SDS-PAGE gels, subjected to electrophoresis, and transferred to a PVDF membrane.…”

“…The Ponceau-stained membranes were digitally scanned. The 45-kDa actin bands were quantified by densitometry and used as a protein loading correction factor for each lane as previously described [4], [5], [6].…”

“…RNA was extracted with Trizol reagent (Life Technologies, Grand Island, NY, USA) and reverse transcribed to cDNA as previously described [1], [4], [5], [7]. Real-time PCR was performed and results were analyzed using the StepOne Real-Time PCR detection system (Applied Biosystems, Foster City, CA).…”