Growth Of Muscle Mass Research Articles

The clinical significance of body composition and anthropometric evaluation in athletes

Body composition and anthropometric assessment provide the sports physician with useful information on the health state of the athlete and with some necessary elements to plan specific training loads in the most appropriate way. In practice, the chemical composition of an athlete’s body (especially those who carry out 1–2 daily workouts) is always in a physiologic condition that we can define as “dynamic” (concentration of electrolytes, hydration state and relationship between intra-and extra-cellular water, stages of growth of muscle mass and/or reduction of fat mass, etc.), with the exception of few times of year, such as the short resting break before resuming training. As a consequence, a real “baseline” (or “stationary”) physiological state, allowing to detect the parameters of body composition under the same conditions several times during the year, is only rarely achieved. In this paper, we wanted to review the most interesting parameters and methods for the evaluation of athletes’ body composition, and underline their potential applications, possible advantages, theoretical and practical limitations.

Effects of Different Levels of Protein Intake and Physical Training on Growth and Nutritional Status of Young Rats

This study aimed to investigate the effects of physical training, and different levels of protein intake in the diet, on the growth and nutritional status of growing rats. Newly-weaned Wistar rats (n=48) were distributed into six experimental groups; three of them were subjected to physical swim training (1 h per day, 5 d per week, for 4 wk, after 2 wk of familiarization) and the other three were considered as controls (non-trained). Each pair of groups, trained and non-trained, received diets with a different level of protein in their composition: 14%, 21% or 28%. The animals were euthanized at the end of the training period and the following analyses were performed: proteoglycan synthesis as a biomarker of bone and cartilage growth, IGF-I (insulin-like growth factor-I) assay as a biomarker of growth and nutritional status, total RNA and protein concentration and protein synthesis measured in vivo using a large-dose phenylalanine method. As a main finding, increased dietary protein, combined with physical training, was able to improve neither tissue protein synthesis nor muscle growth. In addition, cartilage and bone growth seem to be deteriorated by the lower and the higher levels of protein intake. Our data allow us to conclude that protein enhancement in the diet, combined with physical exercise, does not stimulate tissue protein synthesis or muscle mass growth. Furthermore, physical training, combined with low protein intake, was not favorable to bone development in growing animals.

POINT: IGF IS THE MAJOR PHYSIOLOGICAL REGULATOR OF MUSCLE MASS

The insulin-like growth factors (IGFs)-I and -II are homologous peptides that are structurally related to insulin. However, IGFs retain the C-peptide, enabling binding to their main signaling receptor, the IGF type 1 receptor (IGF1R). IGF-II, however, can also bind to and signal via the A isoform of

Effects of vitamin B 1 (thiamine) deficiency in lake trout (Salvelinus namaycush) alevins at hatching stage

The objectives of this study were to examine the relationship between thiamine concentrations in unfertilized eggs and yolksac individuals of lake trout (Salvelinus namaycush), along with any associated histopathological changes in the tissues of alevins at the hatching stage. We address these questions in a lake trout population from different spawning grounds of Lake Michigan (North and South), known for compromised survival due to early mortality syndrome (EMS). However, a dichotomous forage base of lake trout spawning stocks, with a dietary thiaminase-rich alewife in the North, and dietary low-thiaminase round goby in the South, provides the basis for the assumption that different diets may lead to differences in severity of EMS between different stocks. Lake trout eggs of 18 females were collected and fertilized individually with the sperm of several males. The eggs, eyed embryos and newly-hatched alevins were sampled to examine thiamine utilization during embryogenesis. Progenies of females with low (< 0.73 nmol/g) and high (> 0.85 nmol/g) levels of thiamine were chosen for histological studies. The obtained results showed that total thiamine levels in the body and yolk of eyed embryos and alevins at hatching were influenced by thiamine levels of unfertilized eggs and it decreased during embryogenesis (to 51% in eyed embryos and 28% in newly-hatched alevins in comparison to unfertilized eggs). The survival of lake trout until hatching stage does not correlate with the thiamine level, however it was affected by collection site and was significantly higher in fish from the South site (Julian's Reef). At the hatching stage, no pathological changes were observed in the brain, olfactory lobe, retina or liver in embryos regardless of thiamine concentrations in unfertilized eggs. It has been concluded that an enhanced thiamine requirement for the fast muscle mass growth near the swim-up stage is responsible for overt and histopathological signs of EMS. Current study confirms earlier findings that lake trout suffering from EMS can be successfully treated by immersion in thiamine solution as late as at the swim-up stage.

Increased expression of decorin during the regeneration stage of mdx mouse

Satellite cells exist in postnatal muscle tissue and constitute the main source of muscle precursor cells for growth and repair. These cells carry out important roles for skeletal muscle formation postnatally during growth of muscle mass as well as damage-induced regenerative processes. Muscle regeneration supports muscle function in aging and has a role in the functional impairment caused by progressive neuromuscular diseases. Major substances controlling this process are growth factors and extracellular matrix. Myostatin, a member of TGF-beta family, was mainly expressed in muscle tissue. Decorin, a member of the small leucine-rich proteoglycan gene family, is composed of a core protein and a dermatan/chondroitin sulfate chain. Recent studies have shown that decorin enhanced the proliferation and differentiation of myogenic cells by suppressing myostatin activity. Thus, decorin appears to be a new molecule in the myostatin signaling pathway and a promising target for treatment of progressive neuromuscular diseases. Therefore, in this study, we examined the localization of decorin as well as myostatin in a muscular dystrophy model in mdx mice and B10 Scott Snells mice as a control to elucidate the differences between decorin and myostatin messages as well as protein distribution. This study revealed increased expression of decorin protein as well as mRNA at the regenerative stage of mdx mice compared to early stages, while only weak expression of decorin was detected in the control mice. Our study contributes to identifying the relationship between decorin and myostatin as well as the development of a therapeutic strategy for progressive neuromuscular diseases.

Evaluation of physiological measures for correcting variation in urinary output: Implications for assessing environmental chemical exposure in children

Urinary contaminant concentrations are commonly adjusted by creatinine to account for the variability in urinary output. This approach may not be optimal among children due to developmental growth of muscle mass and the associated increase in creatinine formation. An alternative approach is to measure the specific gravity of the urine sample, which reflects the solute concentration of the urine. We compare the appropriateness of urinary creatinine and urinary-specific gravity as factors for correcting morning and evening spot urine samples collected from 23 children (3-11 years) for a total of 41 days in four different seasons. Two linear mixed-effects models were fit using age, sex, season, and sample collection time (morning/evening) as predictors with specific gravity and creatinine as dependent variables. Specific gravity was significantly associated with the sample collection time (P<0.001) with morning samples higher than evening samples. Creatinine was significantly associated with season (P<0.05), sample collection time (P<0.0001), and age (P<0.0001). Creatinine levels were higher during the summer compared to the other seasons, higher in the morning compared to the evening, and higher with increases in children's age. Normalizing the children's spot urine samples using creatinine would introduce bias to the data analysis. Whereas using specific gravity to correct for variable urinary output would be more robust. In addition, measuring specific gravity is relatively easy, does not require the use of chemicals, and the results are available instantaneously.

Inhibition of fish myostatin activity by recombinant fish follistatin and myostatin prodomain: Potential implications for enhancing muscle growth in farmed fish

Myostatin (MSTN) is a negative regulator of skeletal muscle mass and has a potential application in aquaculture. Inactivation of MSTN results in significant muscle mass growth, a phenomenon known as “double muscling”. As part of our efforts to define ways in order to lower MSTN in fish, leading to enhanced muscle growth, we report here on the expression and purification of two potential binding proteins to fish MSTN: MSTN prodomain and follistatin (FST), both cloned from the marine fish, gilthead sea bream, Sparus aurata. MSTN prodomain was expressed in Escherichia coli, refolded and purified using anion-exchange chromatography. FST was stably expressed in CHO-K1 cells and partially purified from conditioned medium by affinity chromatography on Ni-NTA column. Secreted FST is glycosylated as evidenced from the reduction in its apparent molecular weight following treatment with Peptide N-glycosidase F seen on SDS-PAGE. Both MSTN prodomain and FST inhibited the biological activity of purified, cleaved and activated recombinant S. aurata MSTN in a dose-dependent manner, using the mammalian CAGA reporter gene assay. These results demonstrate that the inhibitory effect of MSTN prodomain and FST on MSTN activity, probably through binding, is conserved in fish. Moreover, these results offer an approach for lowering bioactive MSTN and thereby enhance muscle growth in fish important for aquaculture.

Hormonal Aspects of the Muscle-Bone Unit

Osteoporotic fractures are the result of low density and especially inferior bone quality (microarchitecture) caused by both internal (genes, hormones) and external (life style) influences. Bone mechanosensors are extremely important for the overall integrity of the skeleton, because in response to mechanical load they activate its modeling, resulting in an increase in bone density and strength. The largest physiological loads are caused by muscle contractions. Bone mass in adult men has a closer relationship to muscle mass than is case in women. The sexual differences in the relationship between bone and muscle mass are also apparent in children. Based on the mechanostatic theory, the muscle-bone unit has been defined as a functional system whose components are under the common control of the hormones of the somatotropin-IGF-I axis, sexual steroids, certain adipose tissue hormones and vitamin D. The osteogenic effects of somatotropin-IGF-I system are based on the stimulation of bone formation, as well as increase in muscle mass. Moreover, somatotropin decreases the bone mechanostat threshold and reinforces the effect of physical stress on bone formation. The system, via the muscle-bone unit, plays a significant role in the development of the childhood skeleton as well as in its stability during adulthood. The muscle and bone are also the targets of androgens, which increase bone formation and the growth of muscle mass in men and women, independently of IGF-I. The role of further above-mentioned hormones in regulation of this unified functional complex is also discussed.

Clinicochemical follow-up of broiler rearing — A five-week study

Commercial broilers were raised in a 5-week period and a detailed clinicochemical follow-up was carried out, to characterise a flock selected for one-sided muscle mass production. Blood samples were drawn at the ages of 1 day, 1, 2, 3, 4 and 5 weeks, and plasma enzyme activities, metabolite and ion concentrations were determined. Early increases were found for all plasma nitrogenous compounds (total protein, albumin, creatinine and urate). Triglyceride showed a posthatch peak with a significant effect of age. Plasma total cholesterol was characterised by a marked post-hatch concentration peak, while during the first week its concentration decreased markedly. Plasma AST showed an increase during the rearing, while a one-magnitude increment was found for creatine kinase activity during the study. The main results of the study outlined a typical precocial bird (post-hatch triglyceride peak; decreasing cholesterol and early peaking plasma protein and urate concentrations) with very quick skeletal muscle mass growth (increasing creatine kinase and AST activities, slight hyperkalaemia).

Last Word on Point:Counterpoint: Satellite cell addition is/is not obligatory for skeletal muscle hypertrophy

To the Editor : The authors of the Point:Counterpoint debate ([1][1], [2][2]) collectively thank our colleagues for their thoughtful responses to the topic “Satellite cell addition is/is not obligatory for skeletal muscle hypertrophy.” While the goal of our initial position piece and rebuttal

Point:Counterpoint: Satellite cell addition is/is not obligatory for skeletal muscle hypertrophy

Myofiber size is dynamically regulated, increasing and decreasing depending on muscle use. Hypertrophy is defined by increases in myofiber cross-sectional area and mass as well as myofibrillar protein content. Myofibers contain many hundreds of nuclei, each of which has a nuclear domain. A nuclear

Intraspecific variation in testis size of small mammals: implications for muscle mass

Intraspecific variation in testis size is usually interpreted in the context of sperm competition, yet an unconsidered consequence of increased testis size may be an increase in the production of testosterone, which can affect the growth of muscle mass. After muscle mass is corrected for body size, male small mammals have more muscle mass than females, which suggests that it may be a sexually selected trait. An enhanced musculature may have fitness consequences with respect to male mate-searching activities and male–male competition for access to females. We tested the prediction that males with large testes have more muscle mass (measured as lean dry mass) by examining testis size and body composition in three species of small mammals (bushy-tailed wood rat (Neotoma cinerea), deer mouse (Peromyscus maniculatus), and red-backed vole (Clethrionomys gapperi)) from the Kananaskis Valley, Alberta. In all three species, males with relatively large testes had relatively more lean dry mass than males with relatively small testes. This suggests that a secondary consequence of relatively large testes may be a relative increase in muscle mass. Further research should investigate alternative effects of intraspecific variation in testis size on individual fitness within wild populations to gain further insight into sexual selection.

Regulation of myofibrillar protein turnover during maturation in normal and undernourished rat pups.

The study tested the hypothesis that a higher rate of myofibrillar than sarcoplasmic protein synthesis is responsible for the rapid postdifferentiation accumulation of myofibrils and that an inadequate nutrient intake will compromise primarily myofibrillar protein synthesis. Myofibrillar (total and individual) and sarcoplasmic protein synthesis, accretion, and degradation rates were measured in vivo in well-nourished (C) rat pups at 6, 15, and 28 days of age and compared at 6 and 15 days of age with pups undernourished (UN) from birth. In 6-day-old C pups, a higher myofibrillar than sarcoplasmic protein synthesis rate accounted for the greater deposition of myofibrillar than sarcoplasmic proteins. The fractional synthesis rates of both protein compartments decreased with age, but to a greater degree for myofibrillar proteins (-54 vs. -42%). These decreases in synthesis rates were partially offset by reductions in degradation rates, and from 15 days, myofibrillar and sarcoplasmic proteins were deposited in constant proportion to one another. Undernutrition reduced both myofibrillar and sarcoplasmic protein synthesis rates, and the effect was greater at 6 (-25%) than 15 days (-15%). Decreases in their respective degradation rates minimized the effect of undernutrition on sarcoplasmic protein accretion from 4 to 8 days and on myofibrillar proteins from 13 to 17 days. Although these adaptations in protein turnover reduced overall growth of muscle mass, they mitigated the effects of undernutrition on the normal maturational changes in myofibrillar protein concentration.

Growth equations for skeletal muscle derived from the cytonuclear ratio and growth constraining supplementary functions

AbstractFor purely hypertrophic muscle it is postulated that the growth rate in number of nuclei is proportional to the cytoplasmic mass per nucleus multiplied by a growth constraining supplementary function. Growth constraint depends on the distance from any one of the limit number of nuclei, the limit muscle mass or the limit cytoplasmic mass per nucleus. Furthermore, theory and evidence are presented for a power (allometric) relationship between total number of nuclei (n) and muscle mass (m) given by the equation n = gmh. Evidence points to two clusters of values for h, one in the vicinity of h = 2/3 and the other h = 1/2. Both may depend on a linear relationship between number of nuclei inside muscle fibre and fibre cross-sectional area. The difference between the two situations can be derived from basic assumptions on either local or systemic diffusion mediated control of the number or division of satellite cell nuclei, leading directly to values of h either equal to 2/3 or V2. For likely values of h and suitable choices of growth constraints, almost all well known growth functions in the literature are derived as potentially applicable to total number of nuclei, or muscle mass or their ratio. Muscle mass growth will show a sigmoidal form for h = 1. This explains sigmoidal growth in body mass as it is mostly dominated by muscle mass. A possible linear growth phase before maturity is explicable from the cessation of either length (h = 1) or nuclear (h = 0) growth in muscle fibres, while cytoplasmic growth continues to maturity. Furthermore, two rat examples indicate that whole body protein growth can be described by the equations derived for muscle mass growth.