Project description:Eccentric exercise (ECC) can result in ultra-structural and histological damage to skeletal muscle. The damage incurred following ECC is typically followed by a subsequent regenerative and adaptive response. The specific mechanisms that drive this response, particularly in human muscle, are not well understood. The objective of this study was to characterize the early molecular response in skeletal muscle following ECC in humans. We used an Agilent whole human genome microarray to assess global gene expression in male subjects (N=35) at 3 hours post-100 eccentric contractions of the knee extensors. ANCOVA (age and BMI covariates) was used to compare mRNA expression between the ECC and non-exercised (CON) legs of each subject. Novel transcripts from IPA identified networks were confirmed with quantitative real-time (qRT)-PCR. qRT-PCR analysis of 3 of these transcripts (IkBα, TNFRSF1A and ICAM-1) confirmed changes observed in the microarray analysis. 35 male subjects performed an eccentric exercise protocol consisting of 100 maximal eccentric contrations of the knee extensors. 3 hours after the completion of the exercise regimen, a muscle biopsy was taken from the vastus lateralis of both legs. The non-exercised leg served as the control. Gene expresssion was analyzed using an ANCOVA, with covariates for age and BMI.
Project description:Full title: Eccentric exercise activates novel transcriptional regulation of hypertrophic signaling pathways not affected by hormone changes. Unaccustomed eccentric exercise damages muscle tissue stimulating mechanisms of recovery and remodeling that may be affected by cellular protection by the sex hormone 17β-estradiol (E2). Using cDNA microarrays, we screened for differences in mRNA expression caused by E2 and eccentric exercise. After randomly assignment to 8 days of either placebo (CON) or E2 (EXP), eighteen men performed 150 single-leg eccentric contractions. Muscle biopsies were collected at baseline (BL), following supplementation (PS), +3 hours (3H) and +48 hours (48H) after exercise. Serum E2 concentrations increased significantly with supplementation (P < 0.001) but did not affect microarray results. Exercise led to early transcriptional changes in striated muscle activator of Rho signaling (STARS), Rho family GTPase 3 (RND3), mitogen activated protein kinase (MAPK) regulation and the downstream transcription factor FOS. Targeted RT-PCR analysis identified concurrent induction of negative regulators of calcineurin signaling RCAN (P < 0.001) and HMOX1 (P = 0.009). Protein contents were elevated for RND3 at 3H (P = 0.02) and FOS at 48H (P < 0.05). These findings indicate that early RhoA and NFAT signaling and regulation are altered following exercise for muscle remodeling and repair, but are not affected by E2.
Project description:Eccentric exercise (ECC) can result in ultra-structural and histological damage to skeletal muscle. The damage incurred following ECC is typically followed by a subsequent regenerative and adaptive response. The specific mechanisms that drive this response, particularly in human muscle, are not well understood. The objective of this study was to characterize the early molecular response in skeletal muscle following ECC in humans. We used an Agilent whole human genome microarray to assess global gene expression in male subjects (N=35) at 3 hours post-100 eccentric contractions of the knee extensors. ANCOVA (age and BMI covariates) was used to compare mRNA expression between the ECC and non-exercised (CON) legs of each subject. Novel transcripts from IPA identified networks were confirmed with quantitative real-time (qRT)-PCR. qRT-PCR analysis of 3 of these transcripts (IkBα, TNFRSF1A and ICAM-1) confirmed changes observed in the microarray analysis.
Project description:To further understand molecular mechanisms underlying skeletal muscle hypertrophy, expression profiles of translationally and transcriptionally regulated genes were characterized following an acute bout of maximally activated eccentric contractions. Experiments demonstrated that translational mechanisms contribute to acute gene expression changes following high resistance contractions with two candidate mRNAs, basic fibroblast growth factor (bFGF) and elongation factor-1 alpha (EF1alpha), targeted to the heavier polysomal fractions after a bout of contractions. Gene profiling was performed using Affymetrix Rat U34A GeneChips with either total RNA or polysomal RNA at one and six hours following contractions. There were 18 genes that changed expression at one hour and 70 genes that were different (60 genes increased:10 genes decreased)at six hours after contractions. The model from this profiling suggests that following high resistance contractions skeletal muscle shares a common growth profile with proliferating cells exposed to serum. This cluster of genes can be classified as "growth" genes and is commonly associated with progression of the cell cycle. However, a unique aspect was that there was induction of a cluster of tumour suppressor or antigrowth genes. We propose that this cluster of "antigrowth" genes is induced by the stress of contractile activity and may act to maintain skeletal muscle in the differentiated state. From the profiling results, further experiments determined that p53 levels increased in skeletal muscle at 6 h following contractions. This novel finding of p53 induction following exercise also demonstrates the power of expression profiling for identification of novel pathways involved in the response to muscle contraction. Keywords: other
Project description:Desmin is a cytoskeletal protein in muscle involved in integrating cellular space and transmitting forces. In this study we sought to determine the combinatory effects of desmin deletion, aging and eccentric exercise on skeletal muscle at the transcriptional level across many pathways of muscle physiology. RNA was isolated from the TA muscle of mice of two genotypes (wildtype (WT) and desmin knockout (KO)) and two ages (7-9 weeks (Adult) and 12-14 months (Aged)). TA muscles were subjected to a bout of 50 eccentric contractions 12 hours prior to RNA isolation. Numbers per group are as follows: WT_Adult (5), WT_Aged (5), KO_Adult (5), KO_Aged (4).
Project description:Preclinical models of type 1 diabetes mellitus exhibit marked declines in skeletal muscle health including significant impairments in muscle repair. The present study investigated, for the first time, whether muscle repair was altered in young adults with uncomplicated type 1 diabetes (T1D) following damaging exercise.In this cohort study, eighteen physically-active young adults (M=22.1, SEM=0.9 years) with T1D (n, male/female=4/5; MHbA1c= 58, SEMHbA1c=5.9 mmol/mol) and without T1D (n, male/female=4/5) performed 300 unilateral eccentric contractions (90°s-1) of the knee extensors. Prior to exercise, at 48-hours and at 96-hours after exercise, participants gave a venous blood sample and vastus lateralis biopsy and performed a maximal voluntary isometric knee extension. Skeletal muscle extracellular matrix content, and satellite cell content/proliferation were assessed by immunofluorescence. Transmission electron microscopy was used to quantify ultrastructural damage.Maximal isometric strength was comparable between T1D and their sex-matched control group prior to exercise for both sexes. Immediately following damaging exercise, strength was decreased in both groups but there was a moderate effect size for lower strength during recovery in the T1D group at both 48-hours and 96-hours. Serum creatine kinase, an indicator of muscle damage, was moderately higher in T1D participants compared to controls at rest, and exhibited a small elevation 96-hours after exercise. Immunofluorescence analyses showed satellite cell content was lower at all timepoints in those with type 1 diabetes. T1D participants demonstrated a moderate delay in satellite cell proliferation (as assessed by Pax7+/Ki67+ nuclei counts) after exercise, reaching peak levels of proliferation 48-hours after control participants. Despite these differences, those with T1D did not exhibit greater ultrastructural muscle damage than controls as assessed by electron microscopy. Finally, a transcriptomic investigation of T1D muscle revealed several networks of dysregulated genes involving RNA translation as well as mitochondrial respiration function, providing potential explanations for previous observations of mitochondrial dysfunction in similar T1D cohorts. Our novel findings indicate that skeletal muscle from physically active, young adults with moderately controlled T1D may have a reduced ability to handle, and repair from, damaging exercise. While larger cohort studies are clearly needed, these results suggest that those with T1D may require longer recovery times following damaging exercise.
Project description:To further understand molecular mechanisms underlying skeletal muscle hypertrophy, expression profiles of translationally and transcriptionally regulated genes were characterized following an acute bout of maximally activated eccentric contractions. Experiments demonstrated that translational mechanisms contribute to acute gene expression changes following high resistance contractions with two candidate mRNAs, basic fibroblast growth factor (bFGF) and elongation factor-1 alpha (EF1alpha), targeted to the heavier polysomal fractions after a bout of contractions. Gene profiling was performed using Affymetrix Rat U34A GeneChips with either total RNA or polysomal RNA at one and six hours following contractions. There were 18 genes that changed expression at one hour and 70 genes that were different (60 genes increased:10 genes decreased)at six hours after contractions. The model from this profiling suggests that following high resistance contractions skeletal muscle shares a common growth profile with proliferating cells exposed to serum. This cluster of genes can be classified as 'growth' genes and is commonly associated with progression of the cell cycle. However, a unique aspect was that there was induction of a cluster of tumour suppressor or antigrowth genes. We propose that this cluster of 'antigrowth' genes is induced by the stress of contractile activity and may act to maintain skeletal muscle in the differentiated state. From the profiling results, further experiments determined that p53 levels increased in skeletal muscle at 6 h following contractions. This novel finding of p53 induction following exercise also demonstrates the power of expression profiling for identification of novel pathways involved in the response to muscle contraction.
Project description:Desmin is a cytoskeletal protein in muscle involved in integrating cellular space and transmitting forces. In this study we sought to determine the combinatory effects of desmin deletion, aging and eccentric exercise on skeletal muscle at the transcriptional level across many pathways of muscle physiology.
Project description:We examined global mRNA expression using cDNA microarrays in skeletal muscle of humans before, and 3h and 48h after 300 maximal eccentric contractions. Keywords: Time course Healthy, non-trained university-aged subjects performed 300 single leg maximal eccentric contractions. Skeletal muscle biopsies were taken from the vastus lateralis before, 3h and 48h after the exercise bout. Total RNA was extracted, amplified, reverse transcribed, and cDNA was analyzed on a custom made cDNA microarray. Four subjects were analyzed, and samples were not pooled between subjects (i.e. individual microarrays were used for baseline vs. 3H and baseline vs. 48h for EACH subject; repeated measures design).