Resistance exercise training modulates acute gene expression during human skeletal muscle hypertrophy.

We sought to determine whether acute resistance exercise (RE)-induced gene expression is modified by RE training. We studied the expression patterns of a select group of genes following an acute bout of RE in naïve and hypertrophying muscle. Thirteen untrained subjects underwent supervised RE training for 12 wk of the nondominant arm and performed an acute bout of RE 1 wk after the last bout of the training program (training+acute). The dominant arm was either unexercised (control) or subjected to the same acute exercise bout as the trained arm (acute RE). Following training, men (14.8 ± 2.8%; P < 0.05) and women (12.6 ± 2.4%; P < 0.05) underwent muscle hypertrophy with increases in dynamic strength in the trained arm (48.2 ± 5.4% and 72.1 ± 9.1%, respectively; P < 0.01). RE training resulted in attenuated anabolic signaling as reflected by a reduction in rpS6 phosphorylation following acute RE. Changes in mRNA levels of genes involved in hypertrophic growth, protein degradation, angiogenesis, and metabolism commonly expressed in both men and women was determined 4 h following acute RE. We show that RE training can modify acute RE-induced gene expression in a divergent and gene-specific manner even in genes belonging to the same ontology. Changes in gene expression following acute RE are multidimensional, and may not necessarily reflect the actual adaptive response taking place during the training process. Thus RE training can selectively modify the acute response to RE, thereby challenging the use of gene expression as a marker of exercise-induced adaptations.

Anti-inflammatory cytokine profile in early human tendon repair.

PURPOSE: The aim of this study was to assess inflammation and the presence and relative levels of cytokines, which may be involved in regulating early human Achilles tendon healing. METHODS: Nine patients with acute Achilles tendon rupture were included, operated on and post-operatively immobilized. Two weeks post-operatively, microdialysis of the peritendinous interstitial compartment was performed in the healing and intact contralateral Achilles tendons. Quantification of tumour necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-1ß, IL-6, IL-8, IL-10, IL-12p70 and IL-17A was accomplished using a cytometric bead array. Prostaglandin (PG) E2 levels were measured by enzyme immunoassay. RESULTS: None of the patients displayed detectable PGE2 levels. Pro-inflammatory cytokines were below detection levels (IFNγ, IL-12, and IL-17) or did not differ between injured and control tendons (IL-1ß and TNF). Notably, IL-6, IL-8 and IL-10 concentrations in the healing Achilles tendon were significantly elevated: 13-fold (p = 0.009), 28-fold (p = 0.02), and 3.7-fold (p = 0.03), respectively. CONCLUSION: At 2 weeks post-human Achilles tendon rupture, healing is characterized by a resolving inflammatory phase and up-regulation of IL-6, IL-8 and IL-10. The absence of inflammation suggests that at this time point, these cytokines may be associated with anti-inflammatory and regenerative effects on the tendon healing process.

Effect of birth size and proportionality on BMI and skinfold thickness in early adolescence: prospective birth cohort study.

OBJECTIVES: To assess the effect of birth weight, length and ponderal index at birth on body mass index (BMI) and skinfold thickness in early adolescence. SUBJECTS/METHODS: Population-based, prospective birth cohort study in Pelotas, Brazil. Out of 5249 cohort members, 87.5% were traced at 11 years of age. Birth weight, length and ponderal index (birth weight/birth length(3) x 100) -- treated as continuous variable and divided into fourths -- were the exposure variables. BMI at 11 years, triceps and subscapular skinfolds were the outcomes. Confounders included sex, gestational age, parity, maternal schooling, family income, maternal smoking during pregnancy and maternal BMI. RESULTS: All three exposure variables were significantly associated with BMI in early adolescence, but the strongest effect was observed for birth weight. Each unit (Z-score) increase in birth weight was associated with 0.46 kg m(-2) increase in BMI at 11 years. The equivalent coefficients for ponderal index and birth length were 0.22 and 0.21 kg m(-2), respectively. High birth weight, length and ponderal index were also associated with increased values for triceps and subscapular skinfolds at 11 years, and with increased prevalence of obesity. CONCLUSIONS: Of the three birth exposures studied, birth weight presented the strongest effect on anthropometry in early adolescence. Ponderal index, a proportionality indicator associated with infant mortality, hospitalizations and anthropometry in infancy, was also associated with anthropometry in early adolescence, but its predictive value for the latter is lower than that of birthweight alone. All three birth size indicators studied presented poor predictability of the later risk of obesity.

Intracellular signaling specificity in skeletal muscle in response to different modes of exercise.

The aim of this study was to understand better the specific signaling events resulting from different modes of exercise. Three different exercise protocols were employed based on their well-characterized, long-term training effects on either muscle hypertrophy or endurance phenotypes. Rats were subjected to a single bout of either a high-frequency electrical stimulation, a low-frequency electrical stimulation, or a running exercise protocol. Postexercise intracellular signaling was analyzed in the tibialis anterior and soleus muscles at 0, 3, and 6 h. A prolonged increase in p70(S6k) and a transient increase in protein kinase B phosphorylation were only observed in response to a growth-inducing stimulus (e.g., tibialis anterior in high-frequency electrical stimulation). In contrast, extracellular regulated kinase and 38-kDa stress-activated protein kinase were activated in response to all forms of exercise at 0 h, but only extracellular regulated kinase phosphorylation was found significantly elevated at 6 h after running exercise. These results demonstrate that different exercise protocols resulted in the selective activation of specific intracellular signaling pathways, which may determine the specific adaptations induced by different forms of exercise.