High intensity exercise increases expression of matrix metalloproteinases in fast skeletal muscle fibres

Effects of resistance training on matrix metalloproteinase-2 activity and biomechanical and physical properties of bone in ovariectomized and intact rats

The purpose of this study was to investigate the influence of resistance training on the activity of matrix metalloproteinase (MMP)-2 and bone biomechanical properties in ovariectomized and intact rats. Forty-eight female rats were divided into two distinct groups, ovariectomized (OVX) and intact (Int), which were subdivided into three similar subgroups: sedentary, acute exercise and chronic exercise. Rats performed a resistance training for 12 weeks in which animals climbed a vertical ladder of 1.1 m with weights attached to their tails. Sessions were performed with an interval of 3, 4-9 and 8-12 days scaled dynamic movements of climbing. Biomechanical and physical analyses were performed using a universal testing machine, and MMP-2 activity analysis by zymography. Bone density (BD), mineral density (MD), maximum load and fracture load was reduced in sedentary and acute exercise OVX groups compared with the sedentary intact group (P<0.05); in contrast, chronically trained groups (OVX and Int) showed a significant increase in BD, MD and fracture load compared with all the other groups. MMP-2 activity in chronically trained groups also showed a significant increase, while the sedentary OVX group showed a decrease in MMP-2 activity compared with the intact sedentary group (P<0.05). Our results suggest that the resistance training proposed in our work was efficient in reverting the deleterious effects of ovariectomy on bone tissue, and also produced modeling effects in intact rats. On the other hand, ovariectomy reduced the activity of MMP-2 and produced deleterious effects on bone tissue, mimicking menopause intrinsically.

Microscopical evaluation of extracellular matrix and its relation to the palatopharyngeal muscle in obstructive sleep apnea

Obstructive sleep apnea hypopnea syndrome (SAHS) is a complex disease of the upper respiratory airways. SAHS physiopathology is multifactorial in which airway compliance is a very important component. To evaluate the tissue changes in the palatopharyngeal muscle by morphometric, histochemical, immunohistochemical, and stereological quantification, with special attention to extracellular matrix associated with this muscle at the structural and ultrastructural levels. Thirty patients with SAHS were divided into groups of 10 according to disease severity: mild, moderate, and severe SAHS. In addition, the control group consisted of 10 patients. Fragments of palatopharyngeal muscle removed from patients with SAHS and tonsillectomies from patients in the control group were histopathologically submitted to light microscopy and transmission electron microscopy. Histopathological evaluations by light and transmission electron microscopes showed differences in analyzed groups, such as reduction of the muscle fiber diameter in patients with SAHS, taking disease severity into consideration. In contrast, stereological analysis showed a gradual increase of the collagen and elastic system fibers relative frequencies, proportionally to SAHS seriousness. MMP-2 and MMP-9 immunostaining also showed an increased reaction in the muscle fiber cytoplasm and endomisium during SAHS progression. The ultrastructural analysis showed that palatopharyngeal muscle fibers presented cytoplasmic residual corpuscles, a sign of early cell aging. In conclusion, the increase of tissue compliance in individuals with SAHS can be, in addition to other factors, consequence of diminished contractile activity of the muscle fibers, which exhibited clear signs of early senescence. Moreover, extracellular matrix components changes may contribute to muscle myopathy during SAHS progression.

Increased iNOS, MMP-2, and HSP-72 in skeletal muscle following high-intensity exercise training

Skeletal muscle adapts to exercise by an upregulation of cellular defenses, such as inducible nitric oxide synthase (iNOS) and matrix metalloproteinase type 2 (MMP-2) and heat shock protein type-72 (HSP-72). The aims of the study were to examine iNOS, MMP-2, and HSP-72 mRNA and protein expression after high-intensity exercise training and to examine whether the expression levels are fiber type dependent. Young Wistar rats were assigned to either 2 or 4 weeks of a high-intensity (32 m/min) running exercise for 40 minutes 5 day per week. A non-running group served as a control. Western blotting and reverse transcriptase-polymerase chain reaction of muscle mRNA and protein levels were assessed in the medial gastrocnemius, quadriceps, soleus, crural, and sternal head of diaphragm muscles. High-intensity exercise training for 4 weeks but not for 2 weeks resulted in a significant increase in both RNA and protein levels of iNOS, MMP-2, and HSP-72 in all muscles examined except the sternal head of diaphragm. High-intensity exercise training is required to promote the expression of iNOS, MMP-2, and HSP-72 in hind limb muscles regardless their muscle fiber type, whereas in the diaphragm the changes are fiber-type dependent.

Effects of ovariectomy and resistance training on MMP-2 activity in skeletal muscle

Matrix metallopeptidases (MMPs) are crucial to the maintenance of healthy tissue. The aim of this study was to investigate MMP-2 activity in gastrocnemius, soleus, tibialis anterior (TA), and extensor digitorium longus (EDL) muscle after resistance training in ovariectomized rats. Wistar adult female rats were grouped into 7 groups (n = 10 per group): sedentary (Sed-Intact); ovariectomized sedentary (Sed-Ovx); pseudo-ovariectomized sedentary (Sed-Pseudo); acute exercise (AcuteEx-Intact); ovariectomized acute exercise (AcuteEx-Ovx); strength trained (ChronicEx-Intact); and ovariectomized strength trained (ChronicEx-Ovx). A 12-week resistance training period, during which the animals climbed a 1.1-m vertical ladder with weights secured to their tails, was used. The sessions were performed once every 3 days, with 4-9 climbs and 8-12 dynamic movements per climb. The MMP-2 activity was analyzed by zymography. There was higher MMP-2 activity in soleus muscle in the ChronicEx-Intact and ChronicEx-Ovx groups, and lower MMP-2 activity in the AcuteEx-Ovx group, compared with the Sed-Intact group (p < or =0.05). The Sed-Ovx and ChronicEx-Ovx groups presented lower MMP-2 activity than the Sed-Intact group in TA. There was higher MMP-2 activity in AcuteEx-Intact and the AcuteEx-Ovx compared with the Sed-Intact and Sed-Ovx in TA, respectively (p < or = 0.05). In TA and EDL, training increased MMP-2 activity in the Sed-Intact group. No statistically significant alterations were observed for gastrocnemius muscle. Strength training increases MMP-2 activity in soleus, TA, and EDL muscle, which may be important for muscle remodeling. Ovariectomy downregulates MMP-2 in TA and EDL, which may compromise muscle function.

Regulation of extracellular matrix compounds involved in angiogenic processes in short- and long-track elite runners

Exercise induces alterations of the extracellular matrix (ECM), e.g. by an increased release of endostatin or by regulation of matrix metalloproteases (MMP)-2/-9, and cathepsin L. To investigate the influence of training status on exercise-induced ECM-processing of angiogenic molecules, alterations of endostatin-, MMP-2, and MMP-9 plasma concentrations during incremental running step tests in male elite short-track (n=6) and male elite long-track runners (n=7) were studied. Three blood samples (pre-exercise, 0, and 1 h post-exercise) were taken from each subject at each running test. In both groups, the basal endostatin plasma concentration was significantly decreased at the second running test, i.e. after the training season. Exercise-related acute alterations of the parameters were also observed only during the second test. In the long-track group, there was a significant increase in endostatin at 0 h and of MMP-2 at 1 h post-exercise. In the short-track group, only MMP-9 was significantly increased at 0 h post-exercise. Cathepsin L was increased at 0 h post-exercise. In conclusion, regular exercise performance decreases the basal endostatin plasma concentration, facilitates ECM-processing of angiogenic molecules by regular performance, and seems to be dependent on the kind of training.

Human muscle protein synthesis and breakdown during and after exercise

Skeletal muscle demonstrates extraordinary mutability in its responses to exercise of different modes, intensity, and duration, which must involve alterations of muscle protein turnover, both acutely and chronically. Here, we bring together information on the alterations in the rates of synthesis and degradation of human muscle protein by different types of exercise and the influences of nutrition, age, and sexual dimorphism. Where possible, we summarize the likely changes in activity of signaling proteins associated with control of protein turnover. Exercise of both the resistance and nonresistance types appears to depress muscle protein synthesis (MPS), whereas muscle protein breakdown (MPB) probably remains unchanged during exercise. However, both MPS and MPB are elevated after exercise in the fasted state, when net muscle protein balance remains negative. Positive net balance is achieved only when amino acid availability is increased, thereby raising MPS markedly. However, postexercise-increased amino acid availability is less important for inhibiting MPB than insulin, the secretion of which is stimulated most by glucose availability, without itself stimulating MPS. Exercise training appears to increase basal muscle protein turnover, with differential responses of the myofibrillar and mitochondrial protein fractions to acute exercise in the trained state. Aging reduces the responses of myofibrillar protein and anabolic signaling to resistance exercise. There appear to be few, if any, differences in the response of young women and young men to acute exercise, although there are indications that, in older women, the responses may be blunted more than in older men.

Differential MMP-2 and MMP-9 activity and collagen distribution in skeletal muscle from pacu (Piaractus mesopotamicus) during juvenile and adult growth phases

Here, we evaluated collagen distribution and matrix metalloproteinases (MMPs) MMP-2 and MMP-9 activities in skeletal muscle of pacu (Piaractus mesopotamicus) during juvenile and adult growth phases. Muscle samples from juvenile and adult fishes were processed by histochemistry for collagen system fibers and for gelatin-zymography for MMP-2 and MMP-9 activities analysis. Picrosirius staining revealed a myosept, endomysium, and perimysium-like structures in both growth phases and muscle types, with increased areas of collagen fibers in adults, mainly in red muscle. Reticulin staining showed that reticular fibers in the endomysium-like structure were thinner and discontinuous in the red muscle fibers. The zymography revealed clear bands of the pro- MMP-9, active- MMP-9, intermediate- MMP-2, and active- MMP-2 forms in red and white muscle in both growth phases. MMP-2 activity was more intense in juvenile than adult muscle fibers. Comparing the red and white muscle types, MMP-2 activity was significantly higher in red muscle in adult phase only. The activity of MMP-9 forms was similar in juvenile red and white muscles and in the adult red muscle, without any activity in adult white muscle. In conclusion, our results show that, in pacu, the higher activities of MMP-2 and -9 are associated with the rapid muscle growth in juvenile age and in adult fish, these activities are related with a different red and white muscle physiology. This study may contribute to the understanding muscle growth mechanisms and may also contribute to analyse red and the white muscle parameters of firmness and softness, respectively, of the commercial product.

Endurance exercise activates matrix metalloproteinases in human skeletal muscle

In the present study, the effect of exercise training on the expression and activity of matrix metalloproteinases (MMPs) in the human skeletal muscle was investigated. Ten subjects exercised one leg for 45 min with restricted blood flow and then exercised the other leg at the same absolute workload with unrestricted blood flow. The exercises were conducted four times per week for 5 wk. Biopsies were taken from the vastus lateralis muscles of both legs at rest before the training period, after 10 days and 5 wk of training, and 2 h after the first exercise bout for analysis of MMP and tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA, enzyme activity, and protein expression. Levels of MMP-2, MMP-14, and TIMP-1 mRNA in muscle tissue increased after 10 days of training regardless of blood flow condition. MMP-2 mRNA level in laser-dissected myofibers and MMP-2 activity in whole muscle increased with training. The level of MMP-9 mRNA and activity increased after the first bout of exercise. Although MMP-9 mRNA levels appeared to be very low, the activity of MMP-9 after a single bout of exercise was similar to that of MMP-2 after 10 days of exercise. MMP-2 and MMP-9 protein was both present throughout the extracellular matrix of the muscle, both around fibers and capillaries, but MMP-2 was also present within the skeletal muscle fibers. These results show that MMPs are activated in skeletal muscle in nonpathological conditions such as voluntary exercise. The expression and time pattern indicate differences between the MMPs in regards of production sites as well as in the regulating mechanism.

Propriedades mecânicas do gastrocnêmio eletroestimulado pós-imobilização

INTRODUÇÃO: As propriedades mecânicas (PM) consistem num instrumento de aplicabilidade clínica para profissionais de saúde que atuam no sistema músculo-esquelético. OBJETIVOS: Avaliar dois protocolos de estimulação elétrica neuromuscular (NMES) na potencialização do restabelecimento das PM no complexo músculo-tendíneo após imobilização segmentar de ratas. MATERIAIS E MÉTODOS: Foram utilizados 50 animais distribuídos em: Controle (GC, n=10); Imobilizado (GI, n=10); Imobilizado e remobilizado livre (GIL, n=10), Imobilizado e NMES uma vez ao dia (GIE1, n=10) e Imobilizado e NMES duas vezes ao dia (GIE2, n=10). A imobilização foi realizada por 14 dias. O GIL foi liberado posteriormente por 10 dias. A NMES foi aplicada pós-imobilização por 10 dias, GIE1 aplicado pela manhã (10 minutos) e, GIE2 aplicado pela manhã e à tarde (totalizando 20 minutos). Posteriormente, o músculo gastrocnêmio foi submetido ao ensaio mecânico de tração sendo as PM de rigidez, resiliência, carga e o alongamento no limite máximo avaliadas. RESULTADOS: A imobilização reduziu os valores das propriedades de carga e rigidez (p<0,05). A NMES utilizada duas vezes ao dia determinou resultados menos satisfatórios das PM avaliadas que àqueles obtidos uma vez ao dia e no grupo remobilizado (p>0,05). CONCLUSÃO: O músculo gastrocnênio tornou-se estruturalmente mais organizado frente à aplicação unitária da NMES e na remobilização.

Passive leg movement enhances interstitial VEGF protein, endothelial cell proliferation, and eNOS mRNA content in human skeletal muscle

The present study used passive limb movement as an experimental model to study the effect of increased blood flow and passive stretch, without enhanced metabolic demand, in young healthy male subjects. The model used was 90 min of passive movement of the leg leading to a 2.8-fold increase ( P < 0.05) in blood flow without a significant enhancement in oxygen uptake. Muscle interstitial fluid was sampled with microdialysis technique and analyzed for vascular endothelial growth factor (VEGF) protein and for the effect on endothelial cell proliferation. Biopsies obtained from the musculus vastus lateralis were analyzed for mRNA content of VEGF, endothelial nitric oxide synthase (eNOS), and matrix metalloproteinase-2 (MMP-2). The passive leg movement caused an increase ( P < 0.05) in interstitial VEGF protein concentration above rest (73 ± 21 vs. 344 ± 83 pg/ml). Addition of muscle dialysate to cultured endothelial cells revealed that dialysate obtained during leg movement induced a 3.2-fold higher proliferation rate ( P < 0.05) than dialysate obtained at rest. Passive movement also enhanced ( P < 0.05) the eNOS mRNA level fourfold above resting levels. VEGF mRNA and MMP-2 mRNA levels were unaffected. The results show that a session of passive leg movement, elevating blood flow and causing passive stretch, augments the interstitial concentrations of VEGF, the proliferative effect of interstitial fluid, and eNOS mRNA content in muscle tissue. We propose that enhanced blood flow and passive stretch are positive physiological stimulators of factors associated with capillary growth in human muscle.

Aging alters gene expression of growth and remodeling factors in human skeletal muscle both at rest and in response to acute resistance exercise

The purpose of this investigation was to compare expression of genes that function in inflammation and stress, cell structure and signaling, or remodeling and growth in skeletal muscle of young (32 +/- 7 yr, n = 15) and elderly (72 +/- 5 yr, n = 16) healthy subjects before and after a bout of resistance leg exercises. A real-time RT-PCR method was used to screen 100 transcripts in v. lateralis biopsies obtained before and 72 h postexercise. The screen identified 15 candidates for differential expression due to aging and/or exercise that were measured quantitatively. The median levels of four mRNAs (insulin-like growth factor-1 and its binding protein IGFBP5, ciliary neurotrophic factor, and the metallopeptidase MMP2) were significantly affected by aging and were greater (1.6- to 2.3-fold, P </= 0.05) in the young than elderly muscle at both time points. The median levels of three mRNAs were significantly (P </= 0.05) affected by exercise in the young. The metallopeptidase inhibitor TIMP1 and alpha-cardiac actin mRNAs increased 2-fold and 6.5-fold, respectively, and GDF8 (myostatin) mRNA decreased by 50%. However, elderly muscle did not display any significant changes in gene expression postexercise. Thus, aging muscle shows decreased levels at rest and an impaired response to exercise for a number of mRNAs for factors potentially involved in muscle growth and remodeling. Future studies must determine the functional importance of these gene expression changes to protein synthesis, satellite cell activity, and other processes that are directly involved in the mechanisms of muscle hypertrophy.

Effects of short-term vibration and hypoxia during high-intensity cycling exercise on circulating levels of angiogenic regulators in humans

This study aimed to investigate the biological response to hypoxia as a stimulus, as well as exercise- and vibration-induced shear stress, which is known to induce angiogenesis. Twelve male cyclists (27.8 ± 5.4 yr) participated in this study. Each subject completed four cycle training sessions under normal conditions (NC) without vibration, NC with vibration, normobaric hypoxic conditions (HC) without vibration, and HC with vibration. Each session lasted 90 min, and sessions were held at weekly intervals in a randomized order. Five blood samples (pretraining and 0 h post-, 0.5 h post-, 1 h post-, and 4 h posttraining) were taken from each subject at each training session. Hypoxia was induced by a normobaric hypoxic chamber with an altitude of 2,500 m. The mechanical forces (cycling with or without vibration) were induced by a cycling ergometer. The parameters VEGF, endostatin, and matrix metalloproteinases (MMPs) were analyzed using the ELISA method. VEGF showed a significant increase immediately after the exercise only with exogenously induced vibrations, as calculated with separate ANOVA analysis. Endostatin increased after training under all conditions. Western blot analysis was performed for the determination of endostatin corresponding to the 22-kDa cleavage product of collagen XVIII. This demonstrated elevated protein content for endostatin at 0 h postexercise. MMP-2 increased in three of the four training conditions. The exception was NC with vibration. MMP-9 reached its maximum level at 4 h postexercise. In conclusion, the results support the contention that mechanical stimuli differentially influence factors involved in the induction of angiogenesis. These findings may contribute to a broader understanding of angiogenesis.

Cathepsin D and MMP-9 activity increase following a high intensity exercise in hind limb muscles of young rats

The influence of an intensive exercise regime on cathepsin D and MMP-9 activity in hind limb muscles was investigated. We hypothesized that high-intensity exercise would increase the number of these proteins, indicating their involvement in the pathogenesis of exercise-induced muscle injury. Muscle fibers from the gastrocnemius and soleus were used from young (6-mo-old) female rats (n = 6) who completed 10 consecutive days of treadmill running at high intensity (34 m min(-1) gradually up to 40 min per day), compared with nonrunning, age and sex-matched rats (n = 6). After a high-intensity exercise regime, cathepsin D activity significantly increased in the gastrocnemius (from 6.6 x 10(-3) to 10.7 x 10(-3) or 61% nM tyrosine x mg-1 protein x min-1) and the soleus (from 5.9 x 10(-3) to 8.9 x 10(-3) or 66%). The activity level of mRNA MMP-9, expressed as ng mg(-1) protein, increased in both muscles subjected to intensity running. The results of this study suggest that high-intensity running results in an elevation in the activity of lysosomal enzymes involved in matrix protein degradation.

Expression of collagen and related growth factors in rat tendon and skeletal muscle in response to specific contraction types

Acute exercise induces collagen synthesis in both tendon and muscle, indicating an adaptive response in the connective tissue of the muscle-tendon unit. However, the mechanisms of this adaptation, potentially involving collagen-inducing growth factors (such as transforming growth factor-beta-1 (TGF-beta-1)), as well as enzymes related to collagen processing, are not clear. Furthermore, possible differential effects of specific contraction types on collagen regulation have not been investigated. Female Sprague-Dawley rats were subjected to 4 days of concentric, eccentric or isometric training (n = 7-9 per group) of the medial gastrocnemius, by stimulation of the sciatic nerve. RNA was extracted from medial gastrocnemius and Achilles tendon tissue 24 h after the last training bout, and mRNA levels for collagens I and III, TGF-beta-1, connective tissue growth factor (CTGF), lysyl oxidase (LOX), metalloproteinases (MMP-2 and -9) and their inhibitors (TIMP-1 and 2) were measured by Northern blotting and/or real-time PCR. In tendon, expression of TGF-beta-1 and collagens I and III (but not CTGF) increased in response to all types of training. Similarly, enzymes/factors involved in collagen processing were induced in tendon, especially LOX (up to 37-fold), which could indicate a loading-induced increase in cross-linking of tendon collagen. In skeletal muscle, a similar regulation of gene expression was observed, but in contrast to the tendon response, the effect of eccentric training was significantly greater than the effect of concentric training on the expression of several transcripts. In conclusion, the study supports an involvement of TGF-beta-1 in loading-induced collagen synthesis in the muscle-tendon unit and importantly, it indicates that muscle tissue is more sensitive than tendon to the specific mechanical stimulus.

Heart failure alters matrix metalloproteinase gene expression and activity in rat skeletal muscle

Heart failure is associated with a skeletal muscle myopathy with cellular and extracellular alterations. The hypothesis of this investigation is that extracellular changes may be associated with enhanced mRNA expression and activity of matrix metalloproteinases (MMP). We examined MMP mRNA expression and MMP activity in Soleus (SOL), extensor digitorum longus (EDL), and diaphragm (DIA) muscles of young Wistar rat with monocrotaline-induced heart failure. Rats injected with saline served as age-matched controls. MMP2 and MMP9 mRNA contents were determined by RT-PCR and MMP activity by electrophoresis in gelatin-containing polyacrylamide gels in the presence of SDS under non-reducing conditions. Heart failure increased MMP9 mRNA expression and activity in SOL, EDL and DIA and MMP2 mRNA expression in DIA. These results suggest that MMP changes may contribute to the skeletal muscle myopathy during heart failure.

Tissue inhibitor of metalloproteinase-2(TIMP-2)-deficient mice display motor deficits

The degradation of the extracellular matrix is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Matrix components of the basement membrane play critical roles in the development and maintenance of the neuromuscular junction (NMJ), yet almost nothing is known about the regulation of MMP and TIMP expression in either the pre- or postsynaptic compartments. Here, we demonstrate that TIMP-2 is expressed by both spinal motor neurons and skeletal muscle. To determine whether motor function is altered in the absence of TIMP-2, motor behavior was assessed using a battery of tests (e.g., RotaRod, balance beam, hindlimb extension, grip strength, loaded grid, and gait analysis). TIMP-2(-/-) mice fall off the RotaRod significantly faster than wild-type littermates. In addition, hindlimb extension is reduced and gait is both splayed and lengthened in TIMP-2(-/-) mice. Motor dysfunction is more pronounced during early postnatal development. A preliminary analysis revealed NMJ alterations in TIMP-2(-/-) mice. Juvenile TIMP-2(-/-) mice have increased nerve branching and acetylcholine receptor expression. Adult TIMP-2(-/-) endplates are enlarged and more complex. This suggests a role for TIMP-2 in NMJ sculpting during development. In contrast to the increased NMJ nerve branching, cerebellar Purkinje cells have decreased neurite outgrowth. Thus, the TIMP-2(-/-) motor phenotype is likely due to both peripheral and central defects. The tissue specificity of the nerve branching phenotype suggests the involvement of different MMPs and/or extracellular matrix molecules underlying the TIMP-2(-/-) motor phenotype.