title: Myocellular triacylglycerol breakdown in females but not in males during exercise.
abstract: The resting content and use of myocellular triacylglycerol (MCTG) during 90 min of submaximal exercise [60% of peak oxygen uptake (VO(2 peak))] were studied in 21 eumenorrheic female and 21 male subjects at different training levels [untrained (UT), moderately trained (MT), and endurance trained (END)]. Males and females were matched according to their VO(2 peak) expressed relative to lean body mass, physical activity level, and training history. All subjects ingested the same controlled diet for 8 days, and all females were tested in the midfollicular phase of the menstrual cycle. Resting MCTG, measured with the muscle biopsy technique, averaged 48.4 +/- 4.2, 48.5 +/- 8.4, and 52.2 +/- 5.8 mmol/kg dry wt in UT, MT, and END females, respectively, and 34.1 +/- 4.9, 31.6 +/- 3.3, and 38.4 +/- 3.0 mmol/kg dry wt in UT, MT, and END males, respectively (P < 0.001, females vs. males in all groups). Exercise decreased MCTG content in the female subjects by an average of 25%, regardless of training status, whereas in the male groups MCTG content was unaffected by exercise. The arterial plasma insulin concentration was higher (P < 0.05) and the arterial plasma epinephrine concentration was lower (P < 0.05) in the females than in the males at rest and during exercise. MCTG use was correlated to the resting concentration of MCTG (P < 0.001). We conclude that resting content and use of MCTG during exercise are related to gender and furthermore are independent of training status.
authors.affiliation: Department of Human Physiology, Copenhagen Muscle Research Centre, University of Copenhagen, DK-2100 Copenhagen, Denmark.
authors.forename: Charlotte H
authors.initials: CH
authors.lastname: Steffensen
authors.forename: Carsten
authors.initials: C
authors.lastname: Roepstorff
authors.forename: Marianne
authors.initials: M
authors.lastname: Madsen
authors.forename: Bente
authors.initials: B
authors.lastname: Kiens
mesh_terms: D000328:Adult; D001158:Arteries; D001706:Biopsy; D001823:Body Composition; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D002149:Energy Intake; D004837:Epinephrine / Q000097:blood; D004958:Estradiol / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D005498:Follicular Phase; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption; D010807:Physical Endurance; D010809:Physical Fitness; D011374:Progesterone / Q000097:blood; D011659:Pulmonary Gas Exchange; D012727:Sex Characteristics; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D007328:Insulin; D014280:Triglycerides; D011374:Progesterone; D004958:Estradiol; D009638:Norepinephrine; D004837:Epinephrine