title: Gene expression responses over 24 h to lengthening and shortening contractions in human muscle: major changes in CSRP3, MUSTN1, SIX1, and FBXO32.
abstract: Resistance training using lengthening (eccentric) contractions induces greater increases in muscle size than shortening (concentric) contractions, but the underlying molecular mechanisms are not clear. Using temporal expression profiling, we compared changes in gene expression within 24 h of an acute bout of each type of contractions conducted simultaneously in the quadriceps of different legs. Five healthy young men performed shortening contractions with one leg while the contralateral leg performed lengthening contractions. Biopsies were taken from both legs before exercise and 3, 6, and 24 h afterwards, in the fed state. Expression profiling (n = 3) was performed using a custom-made Affymetrix MuscleChip containing probe sets of approximately 3,300 known genes and expressed sequence tags expressed in skeletal muscle. We identified 51 transcripts differentially regulated between the two exercise modes. Using unsupervised hierarchical clustering, we identified four distinct clusters, three of which corresponded to unique functional categories (protein synthesis, stress response/early growth, and sarcolemmal structure). Using quantitative RT-PCR (n = 5), we verified expression changes (lengthening/shortening) in SIX1 (3 h, -1.9-fold, P < 0.001), CSRP3 (6 h, 2.9-fold, P < 0.05), and MUSTN1 (24 h, 4.3-fold, P < 0.05). We examined whether FBXO32/atrogin-1/MAFbx, a known regulator of protein breakdown and of muscle atrophy was differentially expressed: the gene was downregulated after lengthening contractions (3 h, 2.7-fold, P < 0.05; 6 h, 3.3-fold, P < 0.05; 24 h, 2.3-fold, P < 0.05). The results suggested that lengthening and shortening contractions activated distinct molecular pathways as early as 3 h postexercise. The molecular differences might contribute to mechanisms underlying the physiological adaptations seen with training using the two modes of exercise.
authors.affiliation: Center for Genetic Medicine Research, Children's National Medical Center, Washington, District of Columbia 20010, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Kostek
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Chen
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Cuthbertson
authors.forename: Rongye
authors.initials: R
authors.lastname: Shi
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Fedele
authors.forename: Karyn A
authors.initials: KA
authors.lastname: Esser
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rennie
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D015444:Exercise; D020869:Gene Expression Profiling / Q000379:methods*; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D060588:LIM Domain Proteins; D009119:Muscle Contraction; D009124:Muscle Proteins / Q000096:biosynthesis / Q000235:genetics*; D009132:Muscles / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044843:SKP Cullin F-Box Protein Ligases / Q000096:biosynthesis / Q000235:genetics*; D013997:Time Factors
chemical_list: D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; C523782:MUSTN1 protein, human; D009124:Muscle Proteins; D009687:Nuclear Proteins; C099236:SIX1 protein, human; C090114:cysteine and glycine-rich protein 3; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases