Muscle Memory

Sharples AP, Stewart CE, Seaborne RA. Does skeletal muscle have an ‘epi’-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise. Aging Cell. Does skeletal muscle have an ‘epi’-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise - Sharples - 2016 - Aging Cell - Wiley Online Library

Skeletal muscle mass, quality and adaptability are fundamental in promoting muscle performance, maintaining metabolic function and supporting longevity and healthspan. Skeletal muscle is programmable and can ‘remember’ early-life metabolic stimuli affecting its function in adult life. In this review, the authors pose the question as to whether skeletal muscle has an ‘epi’-memory? Following an initial encounter with an environmental stimulus, we discuss the underlying molecular and epigenetic mechanisms enabling skeletal muscle to adapt, should it re-encounter the stimulus in later life. We also define skeletal muscle memory and outline the scientific literature contributing to this field. Furthermore, we review the evidence for early-life nutrient stress and low birth weight in animals and human cohort studies, respectively, and discuss the underlying molecular mechanisms culminating in skeletal muscle dysfunction, metabolic disease and loss of skeletal muscle mass across the lifespan. We also summarize and discuss studies that isolate muscle stem cells from different environmental niches in vivo (physically active, diabetic, cachectic, aged) and how they reportedly remember this environment once isolated in vitro. Finally, we will outline the molecular and epigenetic mechanisms underlying skeletal muscle memory and review the epigenetic regulation of exercise-induced skeletal muscle adaptation, highlighting exercise interventions as suitable models to investigate skeletal muscle memory in humans. We believe that understanding the ‘epi’-memory of skeletal muscle will enable the next generation of targeted therapies to promote muscle growth and reduce muscle loss to enable healthy aging.
 
The Concept of Skeletal Muscle Memory: Evidence from Animal and Human Studies

Within the current paradigm of the myonuclear domain theory, it is postulated that a linear relationship exists between muscle fiber size and myonuclear content. The myonuclear domain is kept (relatively) constant by adding additional nuclei (supplied by muscle satellite cells) during muscle fiber hypertrophy and nuclear loss (by apoptosis) during muscle fiber atrophy.

However, data from recent animal studies suggest that myonuclei that are added to support muscle fiber hypertrophy are not lost within various muscle atrophy models. Such myonuclear permanence has been suggested to constitute a mechanism allowing the muscle fiber to (re)grow more efficiently during retraining, a phenomenon referred to as ‘muscle memory’.

The concept of ‘muscle memory by myonuclear permanence’ has mainly been based on data attained from rodent experimental models. Whether the postulated mechanism also holds true in humans remains largely ambiguous. Nevertheless, there are several studies in humans that provide evidence to potentially support or contradict (parts of) the muscle memory hypothesis.

The goal of the present review is to discuss the evidence for the existence of ‘muscle memory’ in both animal and human models of muscle fiber hypertrophy as well as atrophy. Furthermore, to provide additional insight in the potential presence of muscle memory by myonuclear permanence in humans, we present new data on previously performed exercise training studies. Finally, suggestions for future research are provided to establish whether muscle memory really exists in humans.

Snijders T, Aussieker T, Holwerda A, Parise G, van Loon LJC, Verdijk LB. The concept of skeletal muscle memory: evidence from animal and human studies. Acta Physiologica 2020;n/a. Error - Cookies Turned Off
 

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Potential Effects of Long-Term Abuse of Anabolic Androgen Steroids on Human Skeletal Muscle

BACKGROUND: We have previously evaluated muscle functions and morphology in power athletes of long term (5 to15 years) abuse of anabolic androgen steroids (AAS; Doped) and in clean power athletes (Clean), and observed significant improvements in both muscle morphology and muscle functions in Doped. To our knowledge, the effects of long term AAS abuse on human muscle protein profile have never been studied.

METHODS: The study examined further the muscle biopsies using a two-dimensional difference gel electrophoresis (2D DIGE) for proteomic screening and protein expression. Cellular localization/distribution of specific proteins identified by proteomic analysis was examined using immunohistochemistry (IHC).

RESULTS: Different protein profiles were observed between Doped and Clean, and a valid orthogonal projection of latent structure discriminant analysis model was built (N.=16, x=5, R2=0.88/Q2=0.84, P=0.0005), which separated Doped from Clean.

Liquid chromatography followed by tandem spectrometry identified 14 protein spots (representing nine different proteins) of significant difference in relative quantity (P<0.05), of which nine spots were down-regulated in Doped compared with Clean.

IHC revealed no significant alteration in cellular localization in phosphoglucomutase-1 and heat shock protein beta-1, but indeed in two reference proteins desmin and F-actin in Doped.

CONCLUSIONS: Long term abuse of AAS in combination with training is potentially associated with alterations in skeletal muscle protein profile and protein expression, and structural proteins rather than non-structural proteins are preferentially affected in cellular localization/distribution.

Yu JG, Isaksson A, Rova A, Tegner Y, Eriksson A, Malm C. Potential effects of long-term abuse of anabolic androgen steroids on human skeletal muscle. J Sports Med Phys Fitness 2020;60:1040-8. DOI: 10.23736/S0022-4707.20.10443-2 Potential effects of long-term abuse of anabolic androgen steroids on human skeletal muscle - The Journal of Sports Medicine and Physical Fitness 2020 July;60(7):1040-8 - Minerva Medica - Journals
 
[OA] Moberg M, Lindholm ME, Reitzner SM, Ekblom B, Sundberg C-J, Psilander N. Exercise Induces Different Molecular Responses in Trained and Untrained Human Muscle. Medicine & Science in Sports & Exercise 2020;52. Exercise Induces Different Molecular Responses in Trained... : Medicine & Science in Sports & Exercise

Introduction Human skeletal muscle is thought to have heightened sensitivity to exercise stimulus when it has been previously trained (i.e., it possesses “muscle memory”). We investigated whether basal and acute resistance exercise-induced gene expression and cell signaling events are influenced by previous strength training history.

Methods Accordingly, 19 training naïve women and men completed 10 wk of unilateral leg strength training, followed by 20 wk of detraining. Subsequently, an acute resistance exercise session was performed for both legs, with vastus lateralis biopsies taken at rest and 1 h after exercise in both legs (memory and control).

Results The phosphorylation of AMPKThr172 and eEF2Thr56 was higher in the memory leg than that in the control leg at both time points. The postexercise phosphorylation of 4E-BP1Thr46 and Ser65 was higher in the memory leg than that in the control leg. The memory leg had lower basal mRNA levels of total PGC1α and, unlike the control leg, exhibited increases in PGC1α-ex1a transcripts after exercise. In the genes related to myogenesis (SETD3, MYOD1, and MYOG), mRNA levels differed between the memory and the untrained leg; these effects were evident primarily in the male subjects. Expression of the novel gene SPRYD7 was lower in the memory leg at rest and decreased after exercise only in the control leg, but SPRYD7 protein levels were higher in the memory leg.

Conclusion In conclusion, several key regulatory genes and proteins involved in muscular adaptations to resistance exercise are influenced by previous training history. Although the relevance and mechanistic explanation for these findings need further investigation, they support the view of a molecular muscle memory in response to training.
 
first blast since 2018
5 weeks in down 4%bf and steady 235 after initially losing 7lbs.
leaner and fuller.
lifts up and size and vascularity there.
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