title: Skeletal muscle mitochondrial function is associated with longitudinal growth velocity in children and adolescents.
abstract: BACKGROUND
  Periods of rapid growth require an increase in energy use and substrate formation. Mitochondrial function contributes to each of these and therefore may play a role in longitudinal growth.
  
  
  METHODS
  Twenty-nine children and adolescents of ages 8-15 yr were enrolled in a comprehensive longitudinal assessment of glucose homeostasis and mitochondrial function. Fasting laboratory studies and an estimate of mitochondrial function (as assessed by the time to recovery of phosphocreatine (PCr) concentration after submaximal quadriceps extension/flexion exercise using (31)P magnetic resonance spectroscopy) were obtained at baseline and annually for 2 yr.
  
  
  RESULTS
  Data were complete for 23 subjects. Subjects were 11.3 ± 1.9 (sd) yr old at the beginning of the study; 61% were male. Average annualized growth velocity at 1 yr for boys was 7.1 ± 1.5 cm/yr and for girls 6.5 ± 1.7 cm/yr. More rapid recovery of PCr concentration, suggestive of greater skeletal muscle oxidative phosphorylation capacity at baseline, was associated with faster growth velocity in the subsequent year (r(2) = 0.29; P = 0.008). In multivariate modeling, baseline mitochondrial function remained significantly and independently associated with growth (R(2) for model = 0.51; P = 0.05 for effect of phosphocreatine recovery time constant), controlling for age, gender, Tanner stage, body mass index Z-score, and height Z-score.
  
  
  CONCLUSIONS
  We report a novel association between time to recovery of PCr concentration after submaximal exercise and faster annual linear growth in healthy children. Future studies are needed to determine the physiological mechanisms and clinical consequences of this observation.
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, LON 207, Boston, Massachusetts 02114, USA.
authors.forename: Shana E
authors.initials: SE
authors.lastname: McCormack
authors.forename: Meaghan A
authors.initials: MA
authors.lastname: McCarthy
authors.forename: Loredana
authors.initials: L
authors.lastname: Farilla
authors.forename: Mirko I
authors.initials: MI
authors.lastname: Hrovat
authors.forename: David M
authors.initials: DM
authors.lastname: Systrom
authors.forename: Steven K
authors.initials: SK
authors.lastname: Grinspoon
authors.forename: Amy
authors.initials: A
authors.lastname: Fleischman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000293:Adolescent; D000375:Aging / Q000502:physiology; D001786:Blood Glucose; D015992:Body Mass Index; D002648:Child; D015331:Cohort Studies; D002149:Energy Intake / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005260:Female; D005951:Glucose Tolerance Test; D012739:Gonadal Steroid Hormones / Q000097:blood; D006128:Growth / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D007333:Insulin Resistance; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008931:Mitochondria, Muscle / Q000502:physiology*; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000502:physiology*; D010725:Phosphocreatine / Q000097:blood; D011627:Puberty / Q000502:physiology; D012727:Sex Characteristics
chemical_list: D001786:Blood Glucose; D012739:Gonadal Steroid Hormones; D010725:Phosphocreatine; D007334:Insulin-Like Growth Factor I; D000255:Adenosine Triphosphate