Ydfors 2015 J Physiol

Ydfors M, Hughes MC, Laham R, Schlattner U, Norrbom J, Perry CG (2015) Modelling in vivo creatine/phosphocreatine in vitro reveal divergent adaptations in human muscle mitochondrial respiratory control by ADP after acute and chronic exercise. J Physiol [Epub ahead of print].

» PMID: 26631938

Ydfors M, Hughes MC, Laham R, Schlattner U, Norrbom J, Perry CG (2015) J Physiol

Abstract: Mitochondrial respiratory control by ADP (K_mapp) is viewed as a critical regulator of muscle energy homeostasis. However, acute exercise increases, decreases or has no effect on K_mapp in human muscle whereas chronic exercise surprisingly decreases sensitivity despite greater mitochondrial content. We hypothesized modelling in vivo mitochondrial creatine kinase (mtCK)-dependent phosphate shuttling conditions in vitro would reveal increased sensitivity (lower K_mapp) following acute and chronic exercise. K_mapp was determined in vitro with 20 mM Cr (+Cr), 0 mM Cr (-Cr) or 'in vivo exercising' 20 mM Cr/2.4 mM PCr (Cr:PCr) on vastus lateralis biopsies sampled from 11 males before, immediately Post and 3hr Post exercise on the 1^st, 5^th and 9^th sessions over 3 weeks. Dynamic responses to acute exercise occurred throughout training, whereby the 1^st session did not change K_mapp with in vivo Cr:PCr despite increases in -Cr. The 5^th session decreased sensitivity with Cr:PCr or +Cr despite no change in -Cr. Chronic exercise increased sensitivity +/- Cr in association with increased electron transport chain content (+33-62% Complexes I-V), supporting classic proposals linking increased sensitivity to oxidative capacity. However, in vivo Cr:PCr reveals a perplexing decreased sensitivity contrasting the increases seen +/- Cr. Functional responses occurred without changes in fibre type or proteins regulating mitochondrial-cytosolic energy exchange (mtCK, VDAC, ANT). Despite the dynamic responses seen with +/- Cr, modelling in vivo phosphate shuttling conditions in vitro reveals ADP sensitivity is unchanged following high intensity exercise and is decreased after training. These findings challenge our understanding of how exercise regulates skeletal muscle energy homeostasis.

• O2k-Network Lab: CA Toronto Perry CG

Labels: MiParea: Respiration, Exercise physiology;nutrition;life style

Organism: Human Tissue;cell: Skeletal muscle

HRR: Oxygraph-2k

Labels, 2016-01