Insulin-Like Growth Factor-1 and Resistance Exercise in Community Dwelling Old Adults

Mechanisms Underlying the Rarity of Skeletal Muscle Cancers

Skeletal muscle (SKM), despite comprising ~40% of body mass, rarely manifests cancer. This review explores the mechanisms that help to explain this rarity, including unique SKM architecture and function, which prohibits the development of new cancer as well as negates potential metastasis to SKM. SKM also presents a unique immune environment that may magnify the anti-tumorigenic effect. Moreover, the SKM microenvironment manifests characteristics such as decreased extracellular matrix stiffness and altered lactic acid, pH, and oxygen levels that may interfere with tumor development. SKM also secretes anti-tumorigenic myokines and other molecules. Collectively, these mechanisms help account for the rarity of SKM cancer.

Insulin-like growth factor-I biocompartmentalization across blood, interstitial fluid and muscle, before and after 3 months of chronic resistance exercise

This investigation examined the influence of 12-week ballistic resistance training programs on the IGF-I system in circulation, interstitial fluid, and skeletal muscle, at rest and in response to acute exercise. Seventeen college-aged subjects (11 women/6 men; 21.7 ± 3.7 yr) completed an acute ballistic exercise bout before and after the training program. Blood samples were collected pre-, mid-, and postexercise and analyzed for serum total IGF-I, free IGF-I, and IGF binding proteins (IGFBPs) 1-4. Dialysate and interstitial free IGF-I were analyzed in vastus lateralis (VL) interstitial fluid collected pre- and postexercise via microdialysis. Pre- and postexercise VL muscle biopsies were analyzed for IGF-I protein expression, IGF-I receptor phosphorylation (p-IGF-IR), and AKT phosphorylation (p-AKT). Following training, basal serum IGF-I, free IGF-I, IGFBP-2, and IGFBP-3 decreased whereas IGFBP-1 and IGFBP-4 increased. Training reduced basal dialysate and interstitial free IGF-I but had no effect on basal skeletal muscle IGF-I, p-IGF-IR, or p-AKT. Acute exercise elicited transient changes in IGF-I system concentrations and downstream anabolic signaling both pre- and posttraining; training did not affect this acute exercise response. Posttraining, acute exercise-induced changes in dialysate/interstitial free IGF-I were strongly correlated with the changes in intramuscular IGF-I expression, p-IGF-IR, and p-AKT. The divergent influence of resistance training on circulating/interstitial and skeletal muscle IGF-I demonstrates the importance of concurrent, multiple biocompartment analysis when examining the IGF-I system. As training elicited muscle hypertrophy, these findings indicate that IGF-I's anabolic effects on skeletal muscle are mediated by local, rather than systemic mechanisms.NEW & NOTEWORTHY In the first investigation to assess resistance training's effects on the IGF-I system in serum, interstitial fluid, and skeletal muscle, training decreased basal circulating and interstitial IGF-I but did not alter basal intramuscular IGF-I protein activity. Posttraining, acute exercise-induced interstitial IGF-I increases were strongly correlated with intramuscular IGF-I expression and signaling. These findings highlight the importance of multibiocompartment measurement when analyzing IGF-I and suggest that IGF-I's role in hypertrophic adaptations is locally mediated.

Effect of regular resistance training on memory in older adults: A systematic review

The purpose of this study was to evaluate the effect of regular resistance training on memory in older adults.

METHODS

Eight databases (PubMed, Cochrane Library, EMBASE, Web of Science, SinoMed, China National Knowledge Infrastructure (CNKI), China Science and Technology Periodical Database (VIP) and Wanfang) were searched from their inception to March 24, 2021. The data included in the study were analysed according to the Cochrane handbook using Review Manager 5.3 software.

RESULTS

Eighteen eligible randomized controlled trials (RCTs) with a total of 1365 older adults were identified that met the inclusion criteria for the systematic review. Compared with no specific exercise or a low intensity exercise control, regular resistance training significantly improved working memory (standardized mean difference (SMD): 0.27, 95% confidence interval (CI): 0.11, 0.42, P < 0.001), immediate memory (SMD: 0.27, 95% CI: 0.01, 0.54, P = 0.04), and short-term memory (SMD: 0.68, 95% CI: 0.23,1.14, P = 0.003) but had no significant impact on verbal memory (SMD: 0.15, 95% CI: -0.40, 0.71, P = 0.59) or delayed memory (SMD: 0.01, 95% CI: -0.39, 0.42, P = 0.18).

CONCLUSIONS

Regular resistance training has a positive beneficial effect on working memory, immediate memory and short-term memory in older adults. However, due to the limitations of the included studies, these findings should be interpreted cautiously.

Links Between Testosterone, Oestrogen, and the Growth Hormone/Insulin-Like Growth Factor Axis and Resistance Exercise Muscle Adaptations

Maintenance of skeletal muscle mass throughout the life course is key for the regulation of health, with physical activity a critical component of this, in part, due to its influence upon key hormones such as testosterone, estrogen, growth hormone (GH), and insulin-like growth factor (IGF). Despite the importance of these hormones for the regulation of skeletal muscle mass in response to different types of exercise, their interaction with the processes controlling muscle mass remain unclear. This review presents evidence on the importance of these hormones in the regulation of skeletal muscle mass and their responses, and involvement in muscle adaptation to resistance exercise. Highlighting the key role testosterone plays as a primary anabolic hormone in muscle adaptation following exercise training, through its interaction with anabolic signaling pathways and other hormones via the androgen receptor (AR), this review also describes the potential importance of fluctuations in other hormones such as GH and IGF-1 in concert with dietary amino acid availability; and the role of estrogen, under the influence of the menstrual cycle and menopause, being especially important in adaptive exercise responses in women. Finally, the downstream mechanisms by which these hormones impact regulation of muscle protein turnover (synthesis and breakdown), and thus muscle mass are discussed. Advances in our understanding of hormones that impact protein turnover throughout life offers great relevance, not just for athletes, but also for the general and clinical populations alike.

Resistance training effect on serum insulin-like growth factor 1 in the serum: a meta-analysis

BACKGROUND

The resistance exercise has drawn considerable attention to the level of insulin-like growth factor 1 in the serum. However, the relationship between resistance exercise and the level of insulin-like growth factor 1 in the serum is conflicting. This meta-analysis was performed to evaluate this relationship.

METHODS

A systematic literature search up to May 2020 was performed and 22 studies were detected with 680 subjects. They reported relationships between resistance exercise and the level of insulin-like growth factor 1 in the serum. Odds ratio (OR) with 95% confidence intervals (CIs) was calculated comparing the resistance exercise and the level of insulin-like growth factor 1 in the serum using the continuous method with a random or fixed-effect model.

RESULTS

Significantly higher insulin-like growth factor 1 was observed in subjects performing resistance training for less than 16 weeks (OR, 4.03; 95% CI, 2.49-5.57, p<.001); subjects performing resistance training for more than 16 weeks (OR, 11.55; 95% CI, 6.58-16.52, p<.001); subjects older than 60 years (OR, 11.88; 95% CI, 9.84-13.93, p<.001); females (OR, 3.87; 95% CI, 2.26-5.49, p<.001) and males (OR, 16.82; 95% CI, 7.29-26.35, p<.001). However, significantly lower insulin-like growth factor 1 was observed in subjects younger than 60 years (OR, -4.80; 95% CI, -7.74 to -1.86, p=.001).

CONCLUSIONS

However, the resistance exercise significantly increases insulin-like growth factor 1 in subjects older than 60 years, both males and females, and subjects performing resistance exercise for all any period. Surprisingly, resistance exercise significantly decreases insulin-like growth factor 1 in subjects younger than 60 years. This relationship forces us to recommend the resistance exercise to improve insulin-like growth factor 1 in serum.

The Effect of Exercise on Glucoregulatory Hormones: A Countermeasure to Human Aging: Insights from a Comprehensive Review of the Literature

Hormones are secreted in a circadian rhythm, but also follow larger-scale timetables, such as monthly (hormones of the menstrual cycle), seasonal (i.e., winter, summer), and, ultimately, lifespan-related patterns. Several contexts modulate their secretion, such as genetics, lifestyle, environment, diet, and exercise. They play significant roles in human physiology, influencing growth of muscle, bone, and regulating metabolism. Exercise training alters hormone secretion, depending on the frequency, duration, intensity, and mode of training which has an impact on the magnitude of the secretion. However, there remains ambiguity over the effects of exercise training on certain hormones such as glucoregulatory hormones in aging adults. With advancing age, there are many alterations with the endocrine system, which may ultimately alter human physiology. Some recent studies have reported an anti-aging effect of exercise training on the endocrine system and especially cortisol, growth hormone and insulin. As such, this review examines the effects of endurance, interval, resistance and combined training on hormones (i.e., at rest and after) exercise in older individuals. We summarize the influence of age on glucoregulatory hormones, the influence of exercise training, and where possible, examine masters' athletes' endocrinological profile.

Effects of Acute Aerobic and Resistance Exercise on Cognitive Function and Salivary Cortisol Responses

This study aimed to determine the comparative effectiveness of aerobic vs. resistance exercise on cognitive function. In addition, salivary cortisol responses, as an indicator of arousal-related neuroendocrine responses, were assessed as a potential mechanism underlying the effects of these 2 modes of acute exercise on cognition. Forty-two young adults were recruited and performed the Stroop task after 1 session of aerobic exercise, resistance exercise, and a sedentary condition performed on separate days. Saliva samples were collected at baseline and immediately and 30 min after treatment conditions. Acute exercise, regardless of exercise modality, improved multiple aspects of cognitive function as reflected by the Stroop task. Cortisol responses were higher after both modes of acute exercise compared with the sedentary condition and were higher at baseline and 30 min afterward compared with immediately after treatment conditions. These findings suggest that acute exercise of moderate intensity facilitates cognitive function, and, although salivary cortisol is influenced by acute exercise, levels were not related to improvements in cognition.

Nutmeg Extract Increases Skeletal Muscle Mass in Aging Rats Partly via IGF1-AKT-mTOR Pathway and Inhibition of Autophagy

The sarcopenic phenotype is characterized by a reduction of muscle mass, a shift in fiber-type distribution, and reduced satellite cell regeneration. Sarcopenia is still a major challenge to healthy aging. Traditional Indonesian societies in Sulawesi island have been using nutmeg for maintaining health condition during aging. Interestingly, nutmeg has been known to stimulate peroxisome proliferator activated receptors γ (PPARγ) which may contribute to myogenesis process in cardiac muscle. There is limited information about the role of nutmeg extract into physiological health benefit during aging especially myogenesis process in skeletal muscle. In the present study, we want to explore the potential effect of nutmeg in preserving skeletal muscle mass of aging rats. Aging rats, 80 weeks old, were divided into two groups (control and nutmeg). Nutmeg extract was administered for 12 weeks by gavaging. After treatment, rats were anaesthesized, then soleus and gastrocnemius muscles were collected, weighted, frozen using liquid nitrogen, and stored at -80°C until use. We observed phenomenon that nutmeg increased a little but significant food consumption on week 12, but significant decrease in body weight on weeks 10 and 12 unexpectedly increased significantly in soleus muscle weight (p<0.05). Nutmeg extract increased significantly gene expression of myogenic differentiation (MyoD), paired box 7 (Pax7), myogenin, myosin heavy chain I (MHC I), and insulin-like growth factor I (p<0.01) in soleus muscle. Furthermore, nutmeg increased serine/threonine kinase (AKT) protein levels and activation of mammalian target of rapamycin (mTOR), inhibited autophagy activity, and stimulated or at least preserved muscle mass during aging. Taken together, nutmeg extract may increase muscle mass or prevent decrease of muscle wasting in soleus muscle by partly stimulating myogenesis, regeneration process, and preserving muscle mass via IGF-AKT-mTOR pathway leading to inhibition of autophagy activity during aging. This finding may reveal the potential nutmeg benefits as alternative supplement for preserving skeletal muscle mass and preventing sarcopenia in elderly.

Beneficial alterations in body composition, physical performance, oxidative stress, inflammatory markers, and adipocytokines induced by long-term high-intensity interval training in an aged rat model

Sarcopenia is associated with loss of muscle mass and function as well as oxidative stress, chronic low-grade inflammatory status, and adipocytokine dysfunction. It has been reported that sarcopenia can be attenuated by exercise training. The purpose of this study was to evaluate whether long-term high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) protocols could differentially modulate changes in body composition, physical performance, inflammatory parameters, and adipocytokines in fat tissues and serum, as well as oxidative parameters and insulin-like growth factor 1 (IGF-1) levels in skeletal muscle tissue of aged rats. Middle-aged (18-month-old) female Sprague Dawley rats (n = 36) were subjected to 8 months of MICT (26-m MICT) or HIIT (26-m HIIT) treadmill training (45 min, 5 times per week), and the results were compared with those of age-matched sedentary controls (26-m SED); 8-month-old (8-m SED) and 18-month-old (18-m SED) rats served as aging sedentary controls. Body composition parameters; physical performance; serum and skeletal muscle oxidative stress parameters; levels of IGF-1, a serum and fat tissue inflammatory marker; adipocytokine (leptin, adiponectin) levels; and plasma glucose and lipid metabolism-related parameters were analyzed among the five groups. The percent fat and body fat to lean mass ratio increased as a main effect with age, whereas 26-m HIIT but not 26-m MICT attenuated these alterations. The 26-m HIIT group showed a larger improvement in grip strength compared to that of 26-m MICT, with a similar increase in inclined plane performance, maximum running speed, and exhaustion over time as compared with the 26-m SED group. Notably, the 26-m HIIT group showed lower high-sensitivity C-reactive protein levels and higher IL-10 in serum compared with those of the 26-m SED and 26-m MICT groups. Both exercise protocols promoted increased skeletal muscle IGF-1 and decreased serum IGF-1 and adiponectin relative to those in the 26-m SED group, whereas only 26-m HIIT dampened the age-related decrease in plasma free fatty acids and increased serum leptin, along with providing lower fat tissue leptin as compared with that in the 26-m SED group. Moreover, the 26-m HIIT group showed lower serum and skeletal muscle malonylaldehyde and skeletal muscle 8-hydroxydeoxyguanosine (8-OHdG) levels than those in the 26-m MICT group, albeit similar decreases in serum and skeletal muscle 4-hydroxynonenal and serum 8-OHdG and increases in skeletal muscle superoxide dismutase 2 activity. In conclusion, HIIT initiated late in life exhibited greater beneficial effects in ameliorating aged-related elevations in oxidative stress and inflammation, as well as dysfunction of circulating adipocytokine levels, than a volume-matched MICT program. HIIT may therefore contribute to improvements in body composition and physical performance changes associated with aging.

Molecular Insights into Muscle Homeostasis, Atrophy and Wasting

Muscle homeostasis is guaranteed by a delicate balance between synthesis and degradation of cell proteins and its alteration leads to muscle wasting and diseases. In this review, we describe the major anabolic pathways that are involved in muscle growth and homeostasis and the proteolytic systems that are over-activated in muscle pathologies. Modulation of these pathways comprises an attractive target for drug intervention.

Biochemical Pathways of Sarcopenia and Their Modulation by Physical Exercise: A Narrative Review

Aging is a complex process characterized by progressive multisystem derangement predisposing individuals to increased risk of developing negative health outcomes. Sarcopenia is the age-related decline of muscle mass and function/strength and represents a highly prevalent correlate of aging. Several factors have been indicated to play a role in the onset and progression of sarcopenia; however, its pathophysiology is still unclear. Physical exercise is to date one of the few strategies able to improve muscle health in old age through multiple metabolic and transcriptional adaptations. Although the benefits of different exercise modalities on the function and structure of aged myocytes is acknowledged, the cellular and molecular mechanisms underlying such effects are not yet fully identified. Here, we briefly overview the current knowledge on the biochemical pathways associated with the onset and progression of sarcopenia. We subsequently describe the effects of exercise on relevant signaling pathways involved in sarcopenia pathophysiology.

Combined sprint and resistance training abrogates age differences in somatotropic hormones

The aim of this investigation was to compare serum growth hormone (GH), insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein-3 (IGFBP-3) in response to a combined sprint and resistance training (CSRT) program in young and middle-aged men.Thirty-eight healthy, moderately trained men participated in this study. Young and middle-aged men were randomly assigned to, a young training group (YT = 10, 21.4±1.2yrs) ora young control group (YC = 9, 21.6±1.8 yrs), a middle-aged training group (MAT = 10, 40.4±2.1 yrs) or a middle-aged control group (MAC = 9, 40.5±1.8 yrs). Participants performed the Wingate Anaerobic Test (WAnT) before and after a 13-week CSRT program (three sessions per week). Blood samples were collected at rest, after warm-up, immediately post-WAnT, and 10 min post-WAnT. CSRT induced increases in GH at rest and in response to the WAnT in YT and MAT (P<0.05). CSRT-induced increases were observed for IGF-1 and IGFBP-3 at rest in MAT only (P<0.05). Pre-training, GH, IGF-1 and IGFBP-3 were significantly higher at rest and in response to the WAnT in young participants as compared to their middle-aged counterparts (P<0.05). Post-training, YT and MAT had comparable basal GH (P>0.05). In response to the WAnT, amelioration of the age-effect was observed between YT and MAT for IGF-1 and IGF-1/IGFBP-3 ratio following CSRT (P>0.05). These data suggest that CSRT increases the activity of the GH/IGF-1 axis at rest and in response to the WAnT in young and middle-aged men. In addition, CSRT reduces the normal age-related decline of somatotropic hormones in middle-age men.

Assessed and Emerging Biomarkers in Stroke and Training-Mediated Stroke Recovery: State of the Art

Since the increasing update of the biomolecular scientific literature, biomarkers in stroke have reached an outstanding and remarkable revision in the very recent years. Besides the diagnostic and prognostic role of some inflammatory markers, many further molecules and biological factors have been added to the list, including tissue derived cytokines, growth factor-like molecules, hormones, and microRNAs. The literatures on brain derived growth factor and other neuroimmune mediators, bone-skeletal muscle biomarkers, cellular and immunity biomarkers, and the role of microRNAs in stroke recovery were reviewed. To date, biomarkers represent a possible challenge in the diagnostic and prognostic evaluation of stroke onset, pathogenesis, and recovery. Many molecules are still under investigation and may become promising and encouraging biomarkers. Experimental and clinical research should increase this list and promote new discoveries in this field, to improve stroke diagnosis and treatment.

High-intensity interval training (HIIT) increases insulin-like growth factor-I (IGF-I) in sedentary aging men but not masters' athletes: an observational study

INTRODUCTION

The aim of this investigation was to examine the impact high-intensity interval training (HIIT) on serum insulin-like growth factor-I (IGF-I) in active compared with sedentary aging men.

METHODS

22 lifetime sedentary (SED; 62 ± 2 years) and 17 masters' athletes (LEX; 60 ± 5 years) were recruited to the study. As HIIT requires preconditioning exercise in sedentary cohorts, the study required three assessment phases; enrollment (phase A), following preconditioning exercise (phase B), and post-HIIT (phase C). Serum IGF-I was determined by electrochemiluminescent immunoassay.

RESULTS

IGF-I was higher in LEX compared to SED at baseline (p = 0.007, Cohen's d = 0.91), and phase B (p = 0.083, Cohen's d = 0.59), with only a small difference at C (p = 0.291, Cohen's d = 0.35). SED experienced a small increase in IGF-I following preconditioning from 13.1 ± 4.7 to 14.2 ± 6.0 μg·dl^-1 (p = 0.376, Cohen's d = 0.22), followed by a larger increase post-HIIT (16.9 ± 4.4 μg·dl^-1), which was significantly elevated compared with baseline (p = 0.002, Cohen's d = 0.85), and post-preconditioning (p = 0.005, Cohen's d = 0.51). LEX experienced a trivial changes in IGF-I from A to B (18.2 ± 6.4 to 17.2 ± 3.7 μg·dl^-1 [p = 0.538, Cohen's d = 0.19]), and a small change post-HIIT (18.4 ± 4.1 μg·dl^-1 [p = 0.283, Cohen's d = 0.31]). Small increases were observed in fat-free mass in both groups following HIIT (p < 0.05, Cohen's d = 0.32-0.45).

CONCLUSIONS

In conclusion, HIIT with preconditioning exercise abrogates the age associated difference in IGF-I between SED and LEX, and induces small improvements in fat-free mass in both SED and LEX.