Skeletal muscle enzymes as predictors of 24-h energy metabolism in reduced-obese persons.
BACKGROUND
Little is known about the effects of weight loss on the relation between skeletal muscle enzymes and energy metabolism.


OBJECTIVE
This study was performed retrospectively to investigate the relation between skeletal muscle enzymes and 24-h energy metabolism in obese persons before and after weight loss.


METHODS
Ten women and 9 men [with body mass indexes (in kg/m(2)) > 30] underwent a 15-wk weight-loss program (-700 kcal/d). Body weight and composition, 24-h energy metabolism (whole-body indirect calorimetry), and maximal activities of phosphofructokinase (EC 2.7.1.11), creatine kinase (CK; EC 2.7.3.2), citrate synthase (CS; EC 4.1.3.7), 3-hydroxyacyl-CoA dehydrogenase (HADH; EC 1.1.1.35), and cytochrome-c oxidase (COX; EC 1.9.3.1) were determined from biopsy samples of the vastus lateralis taken before and after weight loss.


RESULTS
Before weight loss, fat-free mass (FFM) was the only predictor of 24-h energy expenditure (R(2) = 0.70, P < 0.001), whereas the cumulative variance in sleeping metabolic rate explained by FFM and fat mass (FM) was 83% (P < 0.001). After weight loss, CS (r = 0.45, P = 0.05) and COX (r = 0.65, P < 0.01) were significantly associated with 24-h energy expenditure, whereas CK (r = 0.53, P < 0.05), CS (r = 0.45, P < 0.05), COX (r = 0.64, P < 0.01), and HADH (r = 0.45, P = 0.05) were all significant correlates of sleeping metabolic rate. After weight loss, FFM, FM, and COX explained 84% (P < 0.01) of the variance in 24-h energy expenditure, whereas FFM, FM, and CK all contributed to the cumulative variance in sleeping metabolic rate explained by this model (R(2) = 0.82, P < 0.05).


CONCLUSIONS
Maximal activities of key skeletal muscle enzymes contribute to the variability in 24-h energy metabolism in reduced-obese persons.
Doucet
Eric
E
School of Human Kinetics, University of Ottawa, Ontario, Canada. edoucet@uottawa.ca
Tremblay
Angelo
A
Simoneau
Jean-Aimé
JA
Joanisse
Denis R
DR
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000032:analysis / Q000502:physiology; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D002950:Citrate (si)-Synthase / Q000032:analysis / Q000502:physiology; D003402:Creatine Kinase / Q000032:analysis / Q000502:physiology; D003576:Electron Transport Complex IV / Q000032:analysis / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D009765:Obesity / Q000378:metabolism*; D025221:Phosphofructokinases / Q000032:analysis / Q000502:physiology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013997:Time Factors; D015431:Weight Loss / Q000502:physiology
D015415:Biomarkers; D015094:3-Hydroxyacyl CoA Dehydrogenases; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase; D025221:Phosphofructokinases; D003402:Creatine Kinase