Resistance exercise induces region-specific adaptations in anterior pituitary gland structure and function in rats

Resistance exercise stress: theoretical mechanisms for growth hormone processing and release from the anterior pituitary somatotroph

Heavy resistance exercise (HRE) is the most effective method for inducing muscular hypertrophy and stimulating anabolic hormones, including growth hormone, into the blood. In this review, we explore possible mechanisms within the GH secretory pathway of the pituitary somatotroph, which are likely to modulate the flow of hormone synthesis and packaging as it is processed prior to exocytosis. Special emphasis is placed on the secretory granule and its possible role as a signaling hub. We also review data that summarize how HRE affects the quality and quantity of the secreted hormone. Finally, these pathway mechanisms are considered in the context of heterogeneity of the somatotroph population in the anterior pituitary.

Control of Protein and Energy Metabolism in the Pituitary Gland in Response to Three-Week Running Training in Adult Male Mice

It is assumed that crosstalk of central and peripheral tissues plays a role in the adaptive response to physical activity and exercise. Here, we wanted to study the effects of training and genetic predisposition in a marathon mouse model on mRNA expression in the pituitary gland. Therefore, we used a mouse model developed by phenotype selection for superior running performance (DUhTP) and non-inbred control mice (DUC). Both mouse lines underwent treadmill training for three weeks or were kept in a sedentary condition. In all groups, total RNA was isolated from the pituitary gland and sequenced. Molecular pathway analysis was performed by ingenuity pathway analysis (IPA). Training induced differential expression of 637 genes (DEGs) in DUC but only 50 DEGs in DUhTP mice. Genetic selection for enhanced running performance strongly affected gene expression in the pituitary gland and identified 1732 DEGs in sedentary DUC versus DUhTP mice. Training appeared to have an even stronger effect on gene expression in both lines and comparatively revealed 3828 DEGs in the pituitary gland. From the list of DEGs in all experimental groups, candidate genes were extracted by comparison with published genomic regions with significant effects on training responses in mice. Bioinformatic modeling revealed induction and coordinated expression of the pathways for ribosome synthesis and oxidative phosphorylation in DUC mice. By contrast, DUhTP mice were resistant to the positive effects of three-week training on protein and energy metabolism in the pituitary gland.

Bioactive growth hormone in humans: Controversies, complexities and concepts

OBJECTIVE

To revisit a finding, first described in 1978, which documented existence of a pituitary growth factor that escaped detection by immunoassay, but which was active in the established rat tibia GH bioassay.

METHODS

We present a narrative review of the evolution of growth hormone complexity, and its bio-detectability, from a historical perspective.

RESULTS

In humans under the age of 60, physical training (i.e. aerobic endurance and resistance training) are stressors which preferentially stimulate release of bioactive GH (bGH) into the blood. Neuroanatomical studies indicate a) that nerve fibers directly innervate the human anterior pituitary and b) that hind limb muscle afferents, in both humans and rats, also modulate plasma bGH. In the pituitary gland itself, molecular variants of GH, somatotroph heterogeneity and cell plasticity all appear to play a role in regulation of this growth factor.

CONCLUSION

This review considers more recent findings on this often forgotten/neglected subject. Comparison testing of a) human plasma samples, b) sub-populations of separated rat pituitary somatotrophs or c) purified human pituitary peptides by GH bioassay vs immunoassay consistently yield conflicting results.

The Behavioral Biology of Teams: Multidisciplinary Contributions to Social Dynamics in Isolated, Confined, and Extreme Environments

Teams in isolated, confined, and extreme (ICE) environments face many risks to behavioral health, social dynamics, and team performance. Complex long-duration ICE operational settings such as spaceflight and military deployments are largely closed systems with tightly coupled components, often operating as autonomous microsocieties within isolated ecosystems. As such, all components of the system are presumed to interact and can positively or negatively influence team dynamics through direct or indirect pathways. However, modern team science frameworks rarely consider inputs to the team system from outside the social and behavioral sciences and rarely incorporate biological factors despite the brain and associated neurobiological systems as the nexus of input from the environment and necessary substrate for emergent team dynamics and performance. Here, we provide a high-level overview of several key neurobiological systems relevant to social dynamics. We then describe several key components of ICE systems that can interact with and on neurobiological systems as individual-level inputs influencing social dynamics over the team life cycle-specifically food and nutrition, exercise and physical activity, sleep/wake/work rhythms, and habitat design and layout. Finally, we identify opportunities and strategic considerations for multidisciplinary research and development. Our overarching goal is to encourage multidisciplinary expansion of team science through (1) prospective horizontal integration of variables outside the current bounds of team science as significant inputs to closed ICE team systems and (2) bidirectional vertical integration of biology as the necessary inputs and mediators of individual and team behavioral health and performance. Prospective efforts to account for the behavioral biology of teams in ICE settings through an integrated organizational neuroscience approach will enable the field of team science to better understand and support teams who work, live, serve, and explore in extreme environments.

Effects of muscular strength training and growth hormone (GH) supplementation on femoral bone tissue: analysis by Raman spectroscopy, dual-energy X-ray absorptiometry, and mechanical resistance

The aim of the present study was to verify the effects of muscular strength training and growth hormone (GH) supplementation on femoral bone tissue by Raman spectroscopy (Raman), dual-energy X-ray absorptiometry (DXA), and mechanical resistance (F-max) analysis. A total of 40 male Wistar animals, 60 days old, were used. The animals were distributed into four groups: control (C), control with GH (GHC), muscular strength training (T), and muscular strength training with GH (GHT). Blood samples were collected for the quantification of creatine kinase (CK-MB) and the femurs were removed for analysis by Raman, DXA, and F-max. A more pronounced increase in the bone mineral components was verified in the T group, for all the variables obtained by the Raman (calcium, phosphate, amide, and collagen). In addition, for animals submitted to GH supplementation, there was a reduction in the variable bone mineral density (BMD) obtained by the DXA (p < 0.05). Finally, the animals that received GH supplementation presented a higher F-max, but without statistical significance (p > 0.05). It was concluded that animals that received GH supplementation demonstrated a decrease in BMD. In addition, T alone was able to promote increased calcium, phosphate, amide, and collagen compounds in bone tissue.

Total training load may explain similar strength gains and muscle hypertrophy seen in aged rats submitted to resistance training and anabolic steroids

This study aimed to quantify training parameters and analyze the morphological response of aged muscles submitted to resistance training and anabolic steroids. Aged Wistar rats were divided into groups: C - initial control; CF - final control; CAS - control with anabolic steroid, RT - resistance training, and RTA - resistance training with anabolic steroid. Maximum carried load, absolute and relative loads increased significantly in RT and RTA. RTA demonstrated greater relative load than RT. Average total volume, total climbing volume, relative total volume, relative total climbing volume, and mean climbing volume were similar between groups RT and RTA. For soleus, CAS, RT, and RTA enlarged cross-sectional area of type I fibers and nuclear ratio. As for type II fibers, RTA was higher than C and CF. For plantaris, RT and RTA showed significant increases in myofibers type I compared to C and CF. For type II fibers, RTA showed a significant increase compared to C and CF. Regarding the nuclear ratio, RT and RTA showed a higher ratio than C, CF, and CAS. Our results demonstrated that both RT and RTA were not different among the analyzed morphological parameters. This fact can be explained by the absence of differences found in the training variables analyzed.

Effects of intermittent ladder-climbing exercise training on mitochondrial biogenesis and endoplasmic reticulum stress of the cardiac muscle in obese middle-aged rats

The aim of this study is to investigate the effects of intermittent ladder-climbing exercise training on mitochondrial biogenesis and ER stress of the cardiac muscle in high fat diet-induced obese middle-aged rats. We induced obesity over 6 weeks of period in 40 male Sprague-Dawley rats around 50 weeks old, and were randomly divided into four experimental groups: chow, HFD, exercise+HFD, and exercise+chow. The exercising groups underwent high-intensity intermittent training using a ladder-climbing and weight exercise 3 days/week for a total of 8 weeks. High-fat diet and concurrent exercise resulted in no significant reduction in body weight but caused a significant reduction in visceral fat weight (p<0.05). Expression of PPARδ increased in the exercise groups and was significantly increased in the high-fat diet+exercise group (p<0.05). Among the ER stress-related proteins, the expression levels of p-PERK and CHOP, related to cardiac muscle damage, were significantly higher in the cardiac muscle of the high-fat diet group (p<0.05), and were significantly reduced by intermittent ladder-climbing exercise training (p<0.05). Specifically, this reduction was greater when the rats underwent exercise after switching back to the chow diet with a reduced caloric intake. Collectively, these results suggest that the combination of intermittent ladder-climbing exercise training and a reduced caloric intake can decrease the levels of ER stress-related proteins that contribute to cardiac muscle damage in obesity and aging. However, additional validation is required to understand the effects of these changes on mitochondrial biogenesis during exercise.

Divergent effects of resistance training and anabolic steroid on the postsynaptic region of different skeletal muscles of aged rats

This study aimed to analyze the effects of resistance training associated with testosterone administration in the neuromuscular junction (NMJ) postsynaptic region of different skeletal muscle types of aged rats. Wistar rats were divided into: SEI - 20-months-old control, SEF - 24-months-old control, T - 20-months-old with testosterone, S - 20-months-old resistance trained and ST - 20-months-old with resistance training associated with testosterone propionate. All groups were submitted to familiarization and maximum load carrying testing (MLCT). The MLCT was applied before and after the resistance training (RT) period. RT (6-8×/session with progressive loads of 50 to 100%, 3×/week and 120s interval) was performed in ladder climbing for 15weeks. The administration of testosterone propionate was performed 2×/week (10mg/kg/body weight). After euthanize, soleus and plantaris muscles were removed and prepared for histochemistry and cytofluorescence. T, S and ST significantly increased their maximum carrying load capacity compared to SEI and SEF (p<0.05). For soleus postsynaptic region, ST had lower total and stained area than SEF (p<0.05). For plantaris, the postsynaptic component of T was statistically larger than SEI (p<0.05). For soleus histochemistry, T, S and ST groups showed the same magnitude of type I myofibers hypertrophy, thus statistically different from SEI and SEF (p<0.05). The cross-sectional area of the type IIa myofibers of the ST was larger than SEF (p<0.05). The volume density of type I myofibers show to be lower in ST than SEI (p<0.05). As for type IIa myofibers, ST increased Vv [type IIa] compared to SEI and SEF (p<0.05). For plantaris, T significantly hypertrophied type I myofibers compared to SEI and SEF (p<0.05). S and ST demonstrated significant increases of type I myofibers compared to SEI and SEF (p<0.05). As for type IIx myofibers, both S and ST showed myofibers larger than SEI (p<0.05). However, only the ST had significant difference compared to SEF (p<0.05). In conclusion, both therapies, alone or combined, have little effect on the morphology of the NMJ postsynaptic region of distinct muscles. Moreover, the three therapies are potentially stimulating for strength gains and muscle hypertrophy.

Multi-modal exercise training and protein-pacing enhances physical performance adaptations independent of growth hormone and BDNF but may be dependent on IGF-1 in exercise-trained men

OBJECTIVE

Protein-pacing (P; 5-6meals/day @ 2.0g/kgBW/day) and multi-mode exercise (RISE; resistance, interval, stretching, endurance) training (PRISE) improves muscular endurance, strength, power and arterial health in exercise-trained women. The current study extends these findings by examining PRISE on fitness, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and brain-derived neurotrophic factor (BDNF) response, cardiometabolic health, and body composition in exercise-trained men.

DESIGN

Twenty active males (>4daysexercise/week) completed either: PRISE (n=11) or RISE (5-6meals/day @ 1.0g/kgBW/day; n=9) for 12weeks. Muscular strength (1-repetition maximum bench and leg press, 1-RM BP, and 1-RM LP), endurance (sit-ups, SU; push-ups, PU), power (squat jump, SJ, and bench throw, BT), flexibility (sit-and-reach, SR), aerobic performance (5km cycling time-trial, TT), GH, IGF-1, BDNF, augmentation index, (AIx), and body composition, were assessed at weeks 0 (pre) and 13 (post).

RESULTS

At baseline, no differences existed between groups except for GH (RISE, 230±13 vs. PRISE, 382±59pg/ml, p<0.05). The exercise intervention improved 1-RM, SJ, BT, PU, SU, SR, 5km-TT, GH, AIx, BP, and body composition in both groups (time, p<0.05). However, PRISE elicited greater improvements in 1-RM BP (21 vs. 10∆lbs), SJ (171 vs. 13∆W), 5km-TT (-37 vs. -11∆s), and sit-and-reach (5.3 vs. 1.2∆cm) over RISE alone (p<0.05) including increased IGF-1 (12%, p<0.05).

CONCLUSIONS

Exercise-trained men consuming a P diet combined with multi-component exercise training (PRISE) enhance muscular power, strength, aerobic performance, and flexibility which are not likely related to GH or BDNF but possibly to IGF-1 response.

A single bout of resistance exercise improves memory consolidation and increases the expression of synaptic proteins in the hippocampus

Over the past decade, several studies have indicated that chronic resistance exercise (i.e., strength training, weight lifting, etc.) is beneficial for brain health and cognitive function. However, little is known about the effects of a single bout of resistance exercise on brain function, particularly on memory consolidation. Therefore, the purpose of the present study is to examine the effects of a single bout of resistance exercise applied immediately after the training of fear conditioning on memory consolidation and on the expression of IGF-1 and synaptic proteins in the hippocampus. Male Wistar rats were familiarized with climbing a ladder without a load for 3 days and randomly assigned into control (CTL) and resistance exercise (RES) groups. The RES group was subjected to a single bout of resistance exercise applied immediately after fear conditioning training. Subsequently, the animals were tested for contextual (24 h) and tone (48 h) fear memory. Another group of animals were subjected to a single bout of resistance exercise and euthanized 24 h later for hippocampal analysis of IGF-1 and synaptic proteins (synapsin I, synaptophysin, and PSD-95). The exercised rats improved contextual but not tone fear memory. Hippocampal IGF-1 was not altered by resistance exercise. However, the levels of synapsin I, synaptophysin, and PSD-95 increased significantly in the RES group. The results suggested that a single bout of resistance exercise applied immediately after fear conditioning could improve contextual memory, probably through the activation of pre- and postsynaptic machinery required for memory consolidation. © 2016 Wiley Periodicals, Inc.

The effect of ladder-climbing exercise on atrophy/hypertrophy-related myokine expression in middle-aged male Wistar rats

We investigated the change in myokine expression related to hypertrophy (IL-4, IL-6, IL-10) and atrophy (TNF-α, NFκB, IL-1β) in middle-aged rats after resistance exercise with ladder climbing. 50- and 10-week-old male Wistar rats were randomly assigned to two groups: the sedentary and exercise groups. The exercise groups underwent a ladder-climbing exercise for 8 weeks. While the tibialis anterior muscle mass in the young group significantly increased after the ladder-climbing exercise, the middle-aged group did not show any changes after undergoing the same exercise. To understand the molecular mechanism causing this difference, we analyzed the change in hypertrophy- and atrophy-related myokine levels from the tibialis anterior muscle. After 8 weeks of ladder-climbing exercise, the IL-4 and IL-10 protein levels did not change. However, the IL-6 level significantly increased after exercise training, but the amount of increase in the young training group was higher than in the middle-aged training group. IL-1β and TNF-α as well as NFκB protein levels were significantly higher in the middle-aged group than in the young group. Except for TNF-α, exercise training did not affect IL-1β and NFκB protein levels. The TNF-α level significantly decreased in the middle-aged exercise training group. AMPK and PGC-1α levels also significantly increased after exercise training, but there was no difference between age-related groups. Therefore, 8-week high-intensity exercise training using ladder climbing downregulates the skeletal muscle production of myokine involved in atrophy and upregulates hypertrophic myokine. However, the extent of these responses was lower in the middle-aged than young group.

Acute resistance exercise stimulates sex-specific dimeric immunoreactive growth hormone responses

PURPOSE

We sought to determine if an acute heavy resistance exercise test (AHRET) would elicit sex-specific responses in circulating growth hormone (GH), with untreated serum and serum treated with a reducing agent to break disulfide-bindings between GH dimers.

METHODS

19 untrained participants (nine men and ten women) participated in an acute heavy resistance exercise test using the back squat. Blood samples were drawn before exercise (Pre), immediate post (IP), +15 min (+15), and +30 min (+30) afterwards. Serum samples were chemically reduced using glutathione (GSH). ELISAs were then used to compare immunoreactive GH concentrations in reduced (+GSH) and non-reduced (-GSH) samples. Data were analyzed using a three-way (2 sex × 2 treatment × 4 time) mixed methods ANOVA, with significance set at p ≤ 0.05.

RESULTS

GSH reduction resulted in increased immunoreactive GH concentrations when compared to non-reduced samples at Pre (1.68 ± 0.33 μg/L vs 1.25 ± 0.25 μg/L), IP (7.69 ± 1.08 μg/L vs 5.76 ± 0.80 μg/L), +15 min (4.39 ± 0.58 μg/L vs 3.24 ± 0.43 μg/L), and +30 min (2.35 ± 0.49 μg/L vs 1.45 ± 0.23 μg/L). Also, women demonstrated greater GH responses compared to men, and this was not affected by reduction.

CONCLUSIONS

Heavy resistance exercise increases immunoreactive GH dimer concentrations in men and women, with larger increases in women and more sustained response in men. The physiological significance of a sexually dimorphic GH response adds to the growing literature on aggregate GH and may be explained by differences in sex hormones and the structure of the GH cell network.

Alcohol consumption and hormonal alterations related to muscle hypertrophy: a review

Detrimental effects of acute and chronic alcohol (ethanol) consumption on human physiology are well documented in the literature. These adversely influence neural, metabolic, cardiovascular, and thermoregulatory functions. However, the side effects of ethanol consumption on hormonal fluctuations and subsequent related skeletal muscle alterations have received less attention and as such are not entirely understood. The focus of this review is to identify the side effects of ethanol consumption on the major hormones related to muscle metabolism and clarify how the hormonal profiles are altered by such consumption.