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Skeletal muscle mitochondrial respiration in AMPK α2 kinase‐dead mice
Author(s) -
Larsen S.,
Kristensen J. M.,
Stride N.,
Wojtaszewski J. F. P.,
Helge J. W.,
Dela F.
Publication year - 2012
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2011.02399.x
Subject(s) - citrate synthase , medicine , endocrinology , mitochondrion , respiration , skeletal muscle , respiratory system , ampk , oligomycin , ex vivo , chemistry , biology , biochemistry , atpase , kinase , protein kinase a , anatomy , enzyme , in vitro
Aim: To study whether the phenotypical characteristics (exercise intolerance; reduced spontaneous activity) of the AMPK α2 kinase‐dead ( KD ) mice can be explained by a reduced mitochondrial respiratory flux rates ( J O 2 ) in skeletal muscle. Secondly, the effect of the maturation process on J O 2 was studied. Methods: In tibialis anterior (almost exclusively type 2 fibres) muscle from young (12–17 weeks, n = 7) and mature (25–27 weeks, n = 12) KD and wild‐type ( WT ) (12–17 weeks, n = 9; 25–27 weeks, n = 11) littermates, J O 2 was quantified in permeabilized fibres ex vivo by respirometry, using a substrate‐uncoupler‐inhibitor‐titration ( SUIT ) protocol: malate, octanoyl carnitine, ADP and glutamate ( GMO 3 ), + succinate ( GMOS 3 ), + uncoupler ( U ) and inhibitor (rotenone) of complex I respiration. Citrate synthase ( CS ) activity was measured as an index of mitochondrial content. Results: Citrate synthase activity was highest in young WT animals and lower in KD animals compared with age‐matched WT . J O 2 per mg tissue was lower ( P < 0.05) in KD animals (state GMOS 3 ). No uncoupling effect was seen in any of the animals. Normalized oxygen flux ( J O 2 / CS ) revealed a uniform pattern across the SUIT protocol with no effect of KD . However, J O 2 / CS was higher [ GMO 3 , GMOS 3 , U and rotenone (only WT )] in the mature compared with the young mice – irrespective of the genotype ( P < 0.05). Conclusion: Exercise intolerance and reduced activity level seen in KD mice may be explained by reduced J O 2 in the maximally coupled respiratory state. Furthermore, an enhancement of oxidative phosphorylation capacity per mitochondrion is seen with the maturation process.