Fawzi Kadi

The effects of heavy resistance training and detraining on satellite cells in human skeletal muscles

The aim of this study was to investigate the modulation of satellite cell content and myonuclear number following 30 and 90 days of resistance training and 3, 10, 30, 60 and 90 days of detraining. Muscle biopsies were obtained from the vastus lateralis of 15 young men (mean age: 24 years; range: 20–32 years). Satellite cells and myonuclei were studied on muscle cross‐sections stained with a monoclonal antibody against CD56 and counterstained with Mayers haematoxylin. Cell cycle markers CyclinD1 and p21 mRNA levels were determined by Northern blotting. Satellite cell content increased by 19% (P= 0.02) at 30 days and by 31% (P= 0.0003) at 90 days of training. Compared to pre‐training values, the number of satellite cells remained significantly elevated at 3, 10 and 60 days but not at 90 days of detraining. The two cell cycle markers CyclinD1 and p21 mRNA significantly increased at 30 days of training. At 90 days of training, p21 was still elevated whereas CyclinD1 returned to pre‐training values. In the detraining period, p21 and CyclinD1 levels were similar to the pre‐training values. There were no significant alterations in the number of myonuclei following the training and the detraining periods. The fibre area controlled by each myonucleus gradually increased throughout the training period and returned to pre‐training values during detraining. In conclusion, these results demonstrate the high plasticity of satellite cells in response to training and detraining stimuli and clearly show that moderate changes in the size of skeletal muscle fibres can be achieved without the addition of new myonuclei.

Creatine supplementation augments the increase in satellite cell and myonuclei number in human skeletal muscle induced by strength training

The present study investigated the influence of creatine and protein supplementation on satellite cell frequency and number of myonuclei in human skeletal muscle during 16 weeks of heavy‐resistance training. In a double‐blinded design 32 healthy, male subjects (19–26 years) were assigned to strength training (STR) while receiving a timed intake of creatine (STR‐CRE) (n= 9), protein (STR‐PRO) (n= 8) or placebo (STR‐CON) (n= 8), or serving as a non‐training control group (CON) (n= 7). Supplementation was given daily (STR‐CRE: 6–24 g creatine monohydrate, STR‐PRO: 20 g protein, STR‐CON: placebo). Furthermore, timed protein/placebo intake were administered at all training sessions. Muscle biopsies were obtained at week 0, 4, 8 (week 8 not CON) and 16 of resistance training (3 days per week). Satellite cells were identified by immunohistochemistry. Muscle mean fibre (MFA) area was determined after histochemical analysis. All training regimes were found to increase the proportion of satellite cells, but significantly greater enhancements were observed with creatine supplementation at week 4 (compared to STR‐CON) and at week 8 (compared to STR‐PRO and STR‐CON) (P < 0.01–0.05). At week 16, satellite cell number was no longer elevated in STR‐CRE, while it remained elevated in STR‐PRO and STR‐CON. Furthermore, creatine supplementation resulted in an increased number of myonuclei per fibre and increases of 14–17% in MFA at week 4, 8 and 16 (P < 0.01). In contrast, STR‐PRO showed increase in MFA only in the later (16 week, +8%) and STR‐CON only in the early (week 4, +14%) phases of training, respectively (P < 0.05). In STR‐CRE a positive relationship was found between the percentage increases in MFA and myonuclei from baseline to week 16, respectively (r= 0.67, P < 0.05). No changes were observed in the control group (CON). In conclusion, the present study demonstrates for the first time that creatine supplementation in combination with strength training amplifies the training‐induced increase in satellite cell number and myonuclei concentration in human skeletal muscle fibres, thereby allowing an enhanced muscle fibre growth in response to strength training.

Satellite cells and myonuclei in young and elderly women and men

The overall aim of this study was to assess the effects of aging on the satellite cell population. Muscle biopsies were taken from the tibialis anterior muscle of healthy, moderately active young (age range, 20–32 years; n = 31) and elderly (age range, 70–83 years; n = 27) women and men with comparable physical activity pattern. Satellite cells and myonuclei were visualized using a monoclonal antibody against neural cell adhesion molecule and counterstained with Mayers hematoxylin. An average of 211 (range, 192–241) muscle fibers were examined for each individual. Compared with the young women and men, the elderly subjects had a significantly lower (P < 0.011) number of satellite cells per muscle fiber but a significantly higher (P < 0.004) number of myonuclei per muscle fiber. The number of satellite cells relative to the total number of nuclei [satellite cells/(myonuclei + satellite cells)] was significantly lower in the elderly than in the young women and men. These results imply that a reduction in the satellite cell population occurs as a result of increasing age in healthy men and women. Muscle Nerve 29: 120–127, 2004

Concomitant increases in myonuclear and satellite cell content in female trapezius muscle following strength training

Abstract A skeletal muscle fibre maintains its cytoplasmic volume by means of hundreds of myonuclei distributed along its entire length. Therefore it is hypothesised that changes in fibre size would involve modifications in myonuclear number. In this study, we have examined whether 10 weeks of strength training can induce changes in the number of myonuclei and satellite cells in female trapezius muscles. Biopsies were taken pre- and posttraining from the upper part of the descending trapezius muscle of nine subjects. Muscle samples were analysed for fibre area and myonuclear and satellite cell number using immunohistochemistry. There was a 36% increase in the cross-sectional area of muscle fibres. The hypertrophy of muscle fibres was accompanied by an approximately 70% increase in myonuclear number and a 46% increase in the number of satellite cells. Myonuclei number was positively correlated to satellite cell number indicating that a muscle with an increased concentration of myonuclei will contain a correspondingly higher number of satellite cells. The acquisition of additional myonuclei appears to be required to support the enlargement of multinucleated muscle cells following 10 weeks of strength training. Increased satellite cell content suggests that mitotic divisions of satellite cells produced daughter cells that became satellite cells.

Cellular adaptation of the trapezius muscle in strength-trained athletes

Abstract The aim of this study was to elucidate the cellular events that occur in the trapezius muscle following several years of strength training. In muscle biopsies from ten elite power lifters (PL) and six control subjects (C), several parameters were studied: cross-sectional area of muscle fibres, myosin heavy chain composition (MHC) and capillary supply [capillaries around fibres (CAF) and CAF/fibre area]. A method was also developed for counting the number of myonuclei and satellite cell nuclei. The proportion of fibres expressing MHC IIA, the cross-sectional area of each fibre type and the number of myonuclei, satellite cells and fibres expressing markers for early myogenesis were significantly higher in PL than in C (P<0.05). A significant correlation between the myonuclear number and the cross-sectional area was observed. Since myonuclei in mature muscle fibres are not able to divide, we suggest that the incorporation of satellite cell nuclei into muscle fibres resulted in the maintenance of a constant nuclear to cytoplasmic ratio. The presence of small diameter fibres expressing markers for early myogenesis indicates the formation of new muscle fibres.

Neuromuscular fatigue and recovery in elite female soccer : effects of active recovery

PURPOSE To investigate the time course of recovery from neuromuscular fatigue and some biochemical changes between two female soccer matches separated by an active or passive recovery regime. METHODS Countermovement jump (CMJ), sprint performance, maximal isokinetic knee flexion and extension, creatine kinase (CK), urea, uric acid, and perceived muscle soreness were measured in 17 elite female soccer players before, immediately after, 5, 21, 45, 51, and 69 h after a first match, and immediately after a second match. Eight players performed active recovery (submaximal cycling at 60% of HRpeak and low-intensity resistance training at < 50% 1RM) 22 and 46 h after the first match. RESULTS In response to the first match, a significant decrease in sprint performance (-3.0 +/- 0.5%), CMJ (-4.4 +/- 0.8%), peak torque in knee extension (-7.1 +/- 1.9%) and flexion (-9.4 +/- 1.8%), and an increase in CK (+ 152 +/- 28%), urea (15 +/- 2), uric acid (+ 11 +/- 2%), and muscle soreness occurred. Sprint ability was first to return to baseline (5 h) followed by urea and uric acid (21 h), isokinetic knee extension (27 h) and flexion (51 h), CK, and muscle soreness (69 h), whereas CMJ was still reduced at the beginning of the second match. There were no significant differences in the recovery pattern between the active and passive recovery groups. The magnitude of the neuromuscular and biochemical changes after the second match was similar to that observed after the first match. CONCLUSION The present study reveals differences in the recovery pattern of the various neuromuscular and biochemical parameters in response to a female soccer match. The active recovery had no effects on the recovery pattern of the four neuromuscular and three biochemical parameters.

Effects of anabolic steroids on the muscle cells of strength-trained athletes

PURPOSE Athletes who use anabolic steroids get larger and stronger muscles. How this is reflected at the level of the muscle fibers has not yet been established and was the topic of this investigation. METHODS Muscle biopsies were obtained from the trapezius muscles of high-level power lifters who have reported the use of anabolic steroids in high doses for several years and from high-level power lifters who have never used these drugs. Enzyme-immunohistochemical investigation was performed to assess muscle fiber types, fiber area, myonuclear number, frequency of satellite cells, and fibers expressing developmental protein isoforms. RESULTS The overall muscle fiber composition was the same in both groups. The mean area for each fiber type in the reported steroid users was larger than that in the nonsteroid users (P < 0.05). The number of myonuclei and the proportion of central nuclei were also significantly higher in the reported steroid users (P < 0.05). Likewise, the frequency of fibers expressing developmental protein isoforms was significantly higher in the reported steroid users group (P < 0.05). CONCLUSION Intake of anabolic steroids and strength-training induce an increase in muscle size by both hypertrophy and the formation of new muscle fibers. We propose that activation of satellite cells is a key process and is enhanced by the steroid use. The incorporation of the satellite cells into preexisting fibers to maintain a constant nuclear to cytoplasmic ratio seems to be a fundamental mechanism for muscle fiber growth. Although all the subjects in this study have the same level of performance, the possibility of genetic differences between the two groups cannot be completely excluded.

Effects of endurance training on satellite cell frequency in skeletal muscle of old men.

We investigated the effects of endurance training on satellite cells, which are a major component of the regenerative capacity of muscles. Muscle biopsies were obtained from the vastus lateralis of 11 men aged between 70 and 80 years who trained for 14 weeks (work load corresponding to 65–95% of peak oxygen consumption, V̇O2 peak). Satellite cells were identified by immunohistochemistry. There was a significant increase in satellite cell number. Additionally, V̇O2 peak, citrate synthase activity, and the area of type IIA fibers were significantly increased. Fiber type distribution and the myonuclear number were not significantly affected. The enhancement of satellite cell frequency and fiber area indicate that endurance training is an efficient strategy to improve muscle function in the elderly. Muscle Nerve 28: 87–92, 2003

The expression of androgen receptors in human neck and limb muscles: effects of training and self-administration of androgenic-anabolic steroids.

Abstract The purpose of this study was to investigate the immunohistochemical expression of androgen receptors (AR) in human vastus lateralis and trapezius muscles and to determine whether long-term strength training and self-administration of androgenic-anabolic steroids are accompanied by changes in AR content. Biopsy samples were taken from eight high-level power-lifters (P), nine high-level power-lifters who used anabolic steroids (PAS) and six untrained subjects (U). Myonuclei and AR were visualised in cross-sections stained with the monoclonal antibody against AR and 4’,6-diamidino-2-phenylindole. The proportion of AR-containing myonuclei per fibre cross-section was higher in the trapezius than in the vastus lateralis (P<0.05). In the trapezius, the proportion of AR-containing myonuclei was higher in P compared to U and in PAS compared to both P and U (P<0.05). On the contrary, in the vastus lateralis, there were no differences in AR content between the three groups. Myonuclear number in both muscles was higher in P compared to U and in PAS compared to both P and U (P<0.05). In conclusion, AR content differs greatly between human neck and limb muscles. Moreover, the regulation of AR-containing myonuclei following training and self-administration of androgenic-anabolic steroids is muscle dependent.

Effects of combined lower body endurance and upper body resistance training on the satellite cell pool in elderly subjects

To distinguish the respective potential of endurance and resistance training to increase the satellite cell pool, we investigated the effects of 14 weeks of concurrent lower body endurance and upper body resistance training (3 sessions/week) on vastus lateralis (VLat) and deltoid (Del) muscles of 10 active elderly men. NCAM+ satellite cells and myonuclear number were assessed in VLat and Del. After 14 weeks of training the NCAM+ satellite cell pool increased similarly (+38%) in both muscles, mainly in type II muscle fibers (P < 0.05). There was no significant change in myonuclear number or myonuclear domain in either muscle. Combining resistance training in the upper limbs with endurance training in the lower limbs is an efficient strategy to enhance the satellite cell pool in upper and lower body muscles in elderly subjects. Our results provide a practical reference for the determination of optimal exercise protocols to improve muscle function and regeneration in the elderly. Muscle Nerve, 2008