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Skeletal Muscle Mitochondrial Density and Quality in Untrained and Endurance‐Trained Humans
Author(s) -
Gifford Jayson,
Garten Ryan,
Trinity Joel,
Layec Gwenael,
Richardson Russell
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.742.4
Subject(s) - respiration , mitochondrion , citrate synthase , skeletal muscle , respiratory system , endurance training , medicine , endocrinology , chemistry , biology , zoology , anatomy , biochemistry , enzyme
Endurance‐trained skeletal muscle typically exhibits greater peak respiratory capacity than untrained muscle. The purpose of this study was to determine the extent to which mitochondrial density and/or enhanced intrinsic, qualitative function account for this augmented respiratory capacity. State 2, complex I (CI) driven State 3 (State 3:CI ), complex II (CII)‐driven State 3( State 3:CII) and CI and CII‐driven State 3 (State 3:CI+CII) mitochondrial respiration were measured using permeabilized muscle fibers from the vastus lateralis of 10 untrained (VO 2max = 39±1 ml/kg/min) and 10 endurance‐trained (VO 2max = 59±1 ml/kg/min) males. Mitochondrial density was assessed via citrate synthase (CS) activity. Indeed, per mg of tissue, endurance trained muscle did exhibit significantly greater respiratory capacity ( Figure 1, P<0.05) and greater CS activity (0.57±0.03 vs. 0.33±0.02 U/mg; P <0.05). Nevertheless, as State 3:CI+CII was still elevated in the trained compared to the untrained when normalized by CS activity, the greater respiratory capacity exhibited by endurance‐trained muscle appears to be driven by qualitative enhancements in the mitochondria as well as augmented mitochondrial density ( Figure 2, P <0.05). Furthermore, a tight relationship between mitochondrial density and State 3:CI+CII was observed among untrained individuals, but not among trained individuals ( Figure 3). In conclusion, while peak respiration is tightly related to mitochondrial density in untrained muscle, the augmented peak respiration exhibited by trained muscle appears to be related to qualitative enhancements in the mitochondria as well as augmented density. As State 3:CI and State 3:CII per unit of CS were not different between groups, the qualitative enhancement in trained mitochondria may be related to increased capacity of Coenzyme Q to receive electrons from CI and CII simultaneously. Support or Funding Information This study was funded in part by grants from the NIH National Heart, Lung and Blood Institute (PO1 H1091830) and VA Merit grant E6910R.Mitochondrial respiration per mg of muscle in endurance‐trained and untrained muscle.Mitochondrial respiration per unit of CS activity in endurance‐trained and untrained muscle.Relationship between mitochondrial density, as measured by CS activity, and peak respiration ( State 3:CI+CII) in endurance‐trained and untrained muscle.