* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Principles of Skeletal Muscle Adaptation
Secreted frizzled-related protein 1 wikipedia , lookup
G protein–coupled receptor wikipedia , lookup
Histone acetylation and deacetylation wikipedia , lookup
Gene expression profiling wikipedia , lookup
Ancestral sequence reconstruction wikipedia , lookup
Magnesium transporter wikipedia , lookup
Protein (nutrient) wikipedia , lookup
Protein structure prediction wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Gene regulatory network wikipedia , lookup
Intrinsically disordered proteins wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Interactome wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
List of types of proteins wikipedia , lookup
Protein moonlighting wikipedia , lookup
Western blot wikipedia , lookup
Gene expression wikipedia , lookup
Principles of Skeletal Muscle Adaptation • • • • • • • • Brooks ch 19 p 401-420 Outline Myoplasticity Protein turnover Fiber Type Training adaptations Adaptations with inactivity, injury Age associated changes 1 Myoplasticity • Altered gene expression - resulting in an increase or decrease in amount of specific protein – tremendous potential to alter expression in sk ms – molecular basis for adaptations that occur due to exercise tx in sk ms proteins • 20%of sk ms is protein, balance is water, ions... – All types of protein can be regulated by altering gene expression • Fig 19-1 cascade of regulatory events - impacting gene expression 2 Myoplasticity cont. • myoplasticity - change either quantity (amount) or quality (type) of protein expressed • Eg. Responses to training • type IIb - hypertrophy (enlargement) - inc amount of protein in fiber – larger fast II b fiber • Another fiber - hypertrophy – also repress gene for fast II b myosin HC, turn on fast IIa myosin HC – not only enlarged, but change in contractile phenotype – larger, slower contracting fiber. 3 Protein turnover • Protein Turnover reflects 1/2 life of protein - time frame for existence – protein transcribed (DNA-mRNA) – translated then degraded • level of protein in cell governed by – synthesis / degeneration ratio – precise regulation of content through control of transcription rate – and/or degradation rate • capacity to regulate structural and functional properties of the ms – applies to both structural and contractile proteins and regulatory proteins – as well as enzymes involved in metabolism 4 Adaptation • Sk ms adaptation characterized by – – – – morphological biochemical molecular variables that alter the functional attributes of fibers in specific motor units • adaptations readily reversible when stimulus is diminished or removed • Fig 19-2 intracellular and extracellular influences - reg gene pool expression – stimuli of sufficient amount for sufficient time- overload – lead to changes in expression of specific proteins - specificity 5 Signals for Adaptation • Insufficient energy balance • nutrition can also influence endocrine system - insulin • endocrine system influence independent of nutrition – thyroid hormone – IGF-1 - insulin like growth factor 1 – mediates Growth Hormone effects • power developed by motor unit – load against which fibers contract – specific responses to demands • each result in acute changes in cellular environment – changes can lead to altered rates of protein synthesis and degradation – changes [ ] or activity of proteins 6 Hormonal Influences(cont) • IGF-1 - GH stimulates release from liver - 8-30 hours – also muscle mediated release • Autocrine/paracrine • MGH - mechanogrowth factor – Training inc IGF-1 mRNA expression • GH dependant and independant • Endurance Training – GH- no change at rest – Less dramatic rise during exercise • Unless training above lactate inflection • Resistance Training – Testosterone and GH - two primary hormones that affect adaptations – Inc secretion with training – Testosterone - augments GH release • Inc muscle force production - Nervous system influence 7 Phenotype • When protein structure of muscle is altered - phenotype change – outwardly observable characteristics of muscle – reflects underlying genes (genotype) and their regulation by several factors (exercise) – altered phenotypes - affect cellular environment as well • eg. Receptors, integrating centers, signal translocation factors and effectors - mechanisms not fully understood. 8 Muscle Fiber Types • Elite athletes - specialized fiber typing – sprinter II b, endurance I • Fig 19-3 - elite - ends of spectrum • genetics - strong influence on fiber type disposition • Training studies - alter biochemical and histological properties - not fiber type distinction - (myosin isoform) • evidence, however, that intermediate transitions can occur in MHC expression - not detected with conventional techniques 9 Endurance Adaptations • Occurs with large increase in recruitment frequency and modest inc in load – – – – minimal impact on X-sec area significant adaptations to metabolic Inc mitochondrial proteins HK inc, LDH dec(cytosol), inc mito • 2 fold inc in ox metabolism – degree of adaptation depends on pre training status, intensity and duration • Table 19-1 Succinate DH (Krebs) – response varies with fiber type involvement in training – inc max blood flow, capillary density, and potential for O2 extraction 10 Adaptations to Resistance Training • Increased recruitment frequency and load • Hypertrophy - inc X-sec area • Hyperplasia - inc cell number – major adaptation is with hypertropyhy inc max force generating capacity • Fig 17-28b - Force velocity after tx – move sub max load at higher velocity of shortening – enhanced power capacity • Fiber type specific adaptation – inc X-sec area of both type I and II – Fig 19-4 5-6 month longitudinal study – II - 33% , I - 27% increase 11 Resistance Training • Fastest MHC’s repressed , inc in expression of intermediate MHC isoforms II x - II a • mito volume and cap density reduced with resistance tx • Fig 19-5 - 25 % dec in mito protein • Fig 19-6 - cap density dec 13% • Adaptation with decreased activity • large reduction in recruitment frequency and /or load • reduction in ms and ms fiber X-sec area - dec in metabolic proteins • Fig 19-8 12 Injury and Regeneration • • • • • • • • • • Induced by a variety of insults trauma, ischemia, excessive stretch eccentric exercise, dennervation active lifestyle - continuous population of regenerating fibers two phases immediate - mechanical secondary - biochemical - several days Gender differences Table 19-2 - size and strength Table 19-3 - strength vs. X-sec area 13