title: Muscle protein synthesis and gene expression during recovery from aerobic exercise in the fasted and fed states.
abstract: The purpose of this investigation was to assess mixed-muscle fractional synthesis rate (FSR) and the expression of genes involved in skeletal muscle remodeling after aerobic exercise in the fasted and fed states. Eight recreationally active males (25 ± 1 yr; Vo(2 max): 52 ± 2 ml·kg(-1)·min(-1)) performed 60-min of cycle ergometry at 72 ± 1% Vo(2 max) on two occasions in a counter-balanced design. Subjects ingested a noncaloric placebo (EX-FAST) or a beverage containing (per kg body wt): 5 kcal, 0.83 g carbohydrate, 0.37 g protein, and 0.03 g fat (EX-FED) immediately and 1 h after exercise. FSR was assessed at rest and following exercise with the use of a l-[ring (2)H(5)]-phenylalanine infusion combined with muscle biopsies at 2 and 6 h postexercise. mRNA expression was assessed at 2 and 6 h postexercise via real-time RT-PCR. FSR was higher (P < 0.05) after exercise in both EX-FAST (0.112 ± 0.010%·h(-1)) and EX-FED (0.129 ± 0.014%·h(-1)) compared with rest (0.071 ± 0.005%·h(-1)). Feeding attenuated the mRNA expression (P < 0.05) of proteolytic factors MuRF-1 (6 h) and calpain-2 (2 and 6 h) postexercise but did not alter FOXO3A, calpain-1, caspase3, or myostatin mRNA expression compared with EX-FAST. Myogenic regulatory factor (MRF4) mRNA was also attenuated (P < 0.05) at 2 and 6 h postexercise in EX-FED compared with EX-FAST. These data demonstrate that a nonexhaustive bout of aerobic exercise stimulates skeletal muscle FSR in the fasted state and that feeding does not measurably enhance FSR between 2 and 6 h after aerobic exercise. Additionally, postexercise nutrient intake attenuates the expression of factors involved in the ubiquitin-proteosome and Ca(2+)-dependent protein degradation pathways. These data provide insight into the role of feeding on muscle protein metabolism during recovery from aerobic exercise.
authors: Human Performance Laboratory, Ball State Univ., Muncie, IN 47306, USA. mharber@bsu.edu
authors: Matthew P
authors: MP
authors: Harber
authors: Adam R
authors: AR
authors: Konopka
authors: Bozena
authors: B
authors: Jemiolo
authors: Scott W
authors: SW
authors: Trappe
authors: Todd A
authors: TA
authors: Trappe
authors: Paul T
authors: PT
authors: Reidy
mesh_terms: D000328:Adult; D001628:Beverages; D001706:Biopsy; D001786:Blood Glucose / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D004435:Eating; D015444:Exercise; D005215:Fasting; D005227:Fatty Acids / Q000097:blood; D005786:Gene Expression Regulation; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood; D008297:Male; D009119:Muscle Contraction; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000235:genetics; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D010649:Phenylalanine / Q000008:administration & dosage / Q000031:analogs & derivatives; D012333:RNA, Messenger / Q000378:metabolism; D020127:Recovery of Function; D013997:Time Factors; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D005227:Fatty Acids; D007328:Insulin; D009124:Muscle Proteins; D012333:RNA, Messenger; D010649:Phenylalanine; D006003:Glycogen