Exercise training effects on skeletal muscle plasticity and IGF-1 receptors in frail elders

Myokine, a key cytokine for physical exercise to alleviate sarcopenic obesity

Skeletal muscle has a robust endocrine function as a powerful organ and can secrete and release cytokines or polypeptides known as myokines. These myokines have significant regulatory effects on signal transduction in skeletal muscle and the metabolism of peripheral tissues and organs and exert biological effects via autocrine, paracrine, or endocrine forms. Obesity and aging cause myokine secretion dysregulation, and hastening sarcopenic obesity (SO) development. Exercise is currently an excellent intervention and prevention method for SO. Meanwhile, exercise impacts many organs and tissues. These organs and tissues will produce various myokines in response to movement and metabolism throughout the body to govern muscle differentiation, growth, and remodeling. According to accumulating data, exercise can increase the release of myokines from diverse tissues into the blood and postpone the SO onset and progression by influencing protein metabolism, inflammation, mitochondrial quality control, and other mechanisms.

MicroRNA profiling of different exercise interventions for alleviating skeletal muscle atrophy in naturally aging rats

BACKGROUND

Exercise is an affordable and practical strategy to alleviate several detrimental outcomes from the aging process, including sarcopenia. The elucidation of molecular mechanisms to alleviate sarcopenia is one of the most important steps towards understanding human aging. Although microRNAs (miRNAs) regulate muscle growth, regeneration and aging, the potential role of exercise-mediated miRNAs during the prevention and rehabilitation of skeletal muscle atrophy upon exercise interventions remains unclear.

METHODS

A miRNA profile by miRNA sequencing for gastrocnemius muscle of a 24-month-old aged male rat model mimicking the naturally aging process was established through screening the differentially expressed miRNAs (DEMs) for alleviating aging-induced skeletal muscle atrophy upon optimal exercise intervention. The screened miRNAs and hub genes, as well as biomarkers with the most significantly enriched pathways, were validated by quantitative real-time polymerase chain reaction and western blotting.

RESULTS

The sarcopenia index (SI) value and cross-sectional area (CSA) of rats from the old control (OC) group significantly decreased when compared with the youth control (YC) group (P < 0.001, P < 0.01), whereas an increased SI value and an enlarged CSA of rats from the old-aerobic exercise (OE), old-resistance exercise (OR) and old-mixed exercise (OM) groups were determined (P < 0.01, P < 0.001, P < 0.05; P < 0.01, P < 0.01, P < 0.05). Our results demonstrate that 764 known miRNAs, 201 novel miRNAs and 505 miRNA-mRNA interaction networks were identified to be related to aging-induced muscular atrophy. Among them, 13 miRNAs were differentially expressed (P < 0.05 and log₂ |fold change| > 1) between the YC group and the OC group. Compared with the OC group, 7, 2 and 11 miRNAs were differentially expressed in the OE, OR and OM groups after exercise interventions, respectively. Meanwhile, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the identified DEMs were primarily related to apoptosis, autophagy and the NF-κB/MuRF1 signalling pathways (P < 0.05). Meanwhile, four DEMs (miR-7a-1-3p, miR-135a-5p, miR-151-5p and miR-196b-5p), six hub genes (Ar, Igf1, Hif1a, Bdnf, Fak and Nras) and several biomarkers (LC3, Beclin1, p62, Bax, Bcl-2 and NF-κB/MuRF1) with the most significantly enriched pathways were confirmed, which may play a key role in muscular atrophy during the aging process.

CONCLUSIONS

These findings are closely correlated with the progression of sarcopenia and could act as potential biomarkers for the diagnosis and interventional monitoring of aging-induced skeletal muscle atrophy.

Sprint training interacts with body mass to affect hepatic insulin-like growth factor expression in female green anoles (Anolis carolinensis)

Locomotor performance is a key predictor of fitness in many animal species. As such, locomotion integrates the output of a number of morphological, physiological, and molecular levels of organization, yet relatively little is known regarding the major molecular pathways that bolster locomotor performance. One potentially relevant pathway is the insulin and insulin-like signaling (IIS) network, a significant regulator of physiological processes such as reproduction, growth, and metabolism. Two primary hormones of this network, insulin-like growth factor 1 (IGF1) and insulin-like growth factor 2 (IGF2) are important mediators of these processes and, consequently, of life-history strategies. We sprint-trained green anole (Anolis carolinensis) females to test the responsiveness of IGF1 and IGF2 hepatic gene expression to exercise training. We also tested how sprint training would affect glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and eukaryotic elongation factor 2 (EEF2). The former is a crucial enzyme for glycolytic function in a cell, and the latter is necessary for protein synthesis. Resistance exercise forces animals to increase investment of resources towards skeletal muscle growth. Because IGF1 and IGF2 are important hormones for growth, and GAPDH and EEF2 are crucial for proper cellular function, we hypothesized that these four genes would be affected by sprint training. We found that sprint training affects IGF and EEF2 expression, such that larger sprint-trained lizards express hepatic IGF1, IGF2, and EEF2 to a lesser extent than similarly sized untrained lizards. These results demonstrate that the IIS, and pathways connected to it, can react in a size-dependent manner and are implicated in the exercise response in reptiles.

Plasma tumor necrosis factor-α is associated with sarcopenia in elderly individuals residing in agricultural and pastoral areas of Xinjiang, China

Background

Inflammatory reactions play a significant role in the occurrence and development of sarcopenia. Determining the association between specific cytokines and sarcopenia may reveal the disease’s pathophysiological mechanism(s). Accordingly, the present study aimed to investigate the association between sarcopenia and inflammatory cytokines among the elderly natural population in agricultural and pastoral areas of Xinjiang.

Methods

We conducted a cross-sectional epidemiological survey of the community-dwelling older people using a multi-stage random sampling method in Mulei County in northern Xinjiang and Luopu County in southern Xinjiang from September 2017 to May 2018. Of the 2,100 participants, the statistical analyses included 1,838 participants with complete data. Comparisons of living habits, disease status, biochemical indexes, and levels of interleukin (IL)-4, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α in sarcopenia and non-sarcopenia participants were made in this study.

Results

Our study revealed no significant differences (i.e., P > 0.05) in sex, age, ethnicity, smoking and drinking habits, serum renal function, total cholesterol, and diabetes in the elderly between the sarcopenia and non-sarcopenia groups in Xinjiang. However, triglyceride levels (P = 0.004), hypertension (P = 0.019), and abdominal obesity (P < 0.001) in the sarcopenia group were significantly higher than those in the non-sarcopenia group. Moreover, the levels of IL-10 (P < 0.001), IL-4 (P < 0.001), and TNF-α (P < 0.001) in the sarcopenia group were higher than those in the non-sarcopenia group after adjusting for sex, age, hypertension, blood lipid concentration, and obesity. Furthermore, after adjusting for sex, age, hypertension, obesity, and IL-10, IL-4, and IL-6 levels, an increased TNF-α level was also significantly associated with sarcopenia.

Conclusion

The results of the present study suggest that an increased plasma level of TNF-α is significantly associated with sarcopenia among elderly individuals residing in Xinjiang’s agricultural and pastoral areas. Further study is still needed to determine the physiological role of “immune aging” in the pathogenesis of sarcopenia.

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.

Plasma microRNA-320a as a Potential Biomarker of Physiological Changes during Training in Professional Volleyball Players

A deeper insight into the mechanisms responsible for athlete performance that may serve as specific and detailed training indicators is still desired, because conventionally used biomarkers provide limited information about the adaptive processes that occur during exercise. The objective of our study was to assess insulin-like growth factor 1 receptors (IGF1R) gene expression and evaluate plasma concentration of selected microRNAs (miRNAs) during a 10-week training period (sampling times: week 1, 4, 7, and 10) in a group of 12 professional female volleyball players. Circulating miRNAs (miR-223, miR-320a, and miR-486) with established concentration in plasma and documented association with the IGF1 signaling pathway, which is involved in muscle development and recovery, were tested. The levels of analyzed miRNAs, tested by one-way ANOVA, were significantly different between four training periods during a 10-week training cycle (miR-223 p < 0.0001, miR-320a p = 0.00021, miR-486 p = 0.0037, respectively). The levels of IGF1R also appeared to be different (p = 0.00092), and their expression showed a trend to increase between the first and third periods. In the fourth period, the expression decreased, although it was higher compared with the baseline. Correlations between concentration levels of miR-223 and miR-320a (rs = 0.54, p < 0.001), as well as between miR-320a and miR-486 (rs = 0.73, p < 0.001) were also found. In the fourth period, a negative correlation between miR-223 plasma level and leucocyte IGF1R expression was found (rs = -0.63, p = 0.028). Multiple linear regression analysis showed that miR-320a (p = 0.024) and creatine kinase (p = 0.028) had the greatest impact on the expression levels of the IGF1R gene. Future studies are required to define whether these miRNAs, especially miR-320a, as well as IGF1R expression could be useful biomarkers of physiological changes during exercise and to discover their detailed biological roles in mode-specific exercise training adaptations of professional athletes.

The Role of Osteokines in Sarcopenia: Therapeutic Directions and Application Prospects

Sarcopenia is an age-related disease in which muscle mass, strength and function may decline with age or can be secondary to cachexia or malnutrition and can lead to weakness, falls and even death. With the increase in life expectancy, sarcopenia has become a major threat to the health of the elderly. Currently, our understanding of bone-muscle interactions is not limited to their mechanical coupling. Bone and muscle have been identified as secretory endocrine organs, and their interaction may affect the function of each. Both muscle-derived factors and osteokines can play a role in regulating muscle and bone metabolism via autocrine, paracrine and endocrine mechanisms. Herein, we comprehensively summarize the latest research progress on the effects of the osteokines FGF-23, IGF-1, RANKL and osteocalcin on muscle to explore whether these cytokines can be utilized to treat and prevent sarcopenia.

The Systemic Effects of Exercise on Regulators of Muscle and Bone in Girls and Women

PURPOSE

To assess the systemic effects of an acute bout of moderate-intensity exercise on factors that are known to regulate muscle and bone growth in prepubertal girls and women.

METHODS

A total of 12 prepubertal girls (8-10 y) and 12 women (20-30 y) cycled at 60% maximal oxygen uptake for 1 hour followed by 1 hour recovery. Blood samples were collected at rest, mid-exercise, end of exercise, mid-recovery, and end of recovery. Plasma was analyzed for interleukin-6, chemokine ligand 1, fibroblast growth factor-2, total insulin growth factor-1 (IGF-1), and free IGF-1 using enzyme-linked immunosorbent assays assays.

RESULTS

Both groups had similar concentrations of systemic factors at baseline with the exception of free IGF-1, which was higher in girls (P = .001). Interleukin-6 response was lower in girls versus women (P = .04), with a difference of +105.1% at end of exercise (P < .001), +113.5% at mid-recovery (P = .001), and +93.2% at end of recovery (P = .02). Girls and women exhibited significant declines in chemokine ligand 1, fibroblast growth factor-2, and total IGF-1 during recovery.

CONCLUSION

Compared with women, an acute bout of moderate-intensity exercise in girls elicits a lower inflammatory response, suggesting that other mechanisms may be more important for driving the anabolic effects of exercise on muscle and bone in girls.

Association of sarcopenia and muscle mass with both peripheral neuropathy and nerve function in patients with type 2 diabetes

AIM

This study aimed to investigate the association of sarcopenia and muscle mass with both peripheral neuropathy and nerve function in type 2 diabetes mellitus.

METHODS

A total of 1794 patients (937 men and 857 women) with type 2 diabetes, with a mean age of 60.22 years, were enrolled for a cross-sectional study; of these, 183 patients were enrolled for a follow-up study with a median follow-up of 2.7 years. All participants underwent nerve conduction studies and muscle mass index (ASM/HT²) measurements. The composite Z scores for the sensory nerve conduction velocity (SCV) and the motor nerve conduction velocity (MCV) were calculated. The changes in ASM/HT², SCV, and MCV were calculated from the measurements nearly 2 years apart and classified into three groups: a decrease in ASM/HT² of >3%, a minor change within ±3%, and an increase in ASM/HT² of >3%.

RESULTS

The ASM/HT² of men was positively associated with the composite Z scores of MCV and SCV, and sarcopenia highly correlated with DPN after adjusting for confounding factors. The optimal cutoff point for ASM/HT² that indicated DPN was 7.09 kg/m². Furthermore, increases in ASM/HT² independently predicted a greater benefit of MCV and SCV increment outcomes, whereas a minor change in ASM/HT² only significantly associated with lower benefit in terms of SCV increment. However, this phenomenon was not observed in women.

CONCLUSIONS

Sarcopenia and DPN exhibited a close association. The increased muscle mass improved the partial MCVs and SCVs. However, a sex-related discrepancy was observed in this phenomenon.

Effects of Traditional and Pyramidal Resistance Training Systems on Muscular Strength, Muscle Mass, and Hormonal Responses in Older Women: A Randomized Crossover Trial

Ribeiro, AS, Schoenfeld, BJ, Fleck, SJ, Pina, FLC, Nascimento, MA, and Cyrino, ES. Effects of traditional and pyramidal resistance training systems on muscular strength, muscle mass, and hormonal responses in older women: a randomized crossover trial. J Strength Cond Res 31(7): 1888-1896, 2017-The purpose of this study was to investigate the effect of resistance training (RT) performed in a pyramid (PR) versus a traditional (TD) system on muscular strength, muscle mass, and hormonal responses in older women. Twenty-five older women (67.6 ± 5.1 years, 65.9 ± 11.1 kg, 154.7 ± 5.8 cm, and 27.5 ± 4.5 kg·m) performed both a TD and PR system RT program in a balanced crossover design. The TD program consisted of 3 sets of 8-12 repetition maximum (RM) with a constant load for the 3 sets, whereas the PR system consisted of 3 sets of 12/10/8-RM with incrementally higher loads for each set. Training was performed in 2 phases of 8 weeks each, with a 12-week washout between the 8-week phases. One repetition maximum (1RM) tests were used as measures of muscular strength. Dual X-ray absorptiometry was used to estimate skeletal muscle mass. Testosterone and IGF-1 concentrations were determined preintervention and postintervention after 12 hours fasting. Significant (p ≤ 0.05) increases were observed in both groups for muscular strength in the 1RM chest press (TD = 12.4% and effect size [ES] = 0.86 vs. PR = 11.5% and ES = 0.74), knee extension (TD = 12.5% and ES = 0.61 vs. PR = 11.8% and ES = 0.62), preacher curl (TD = 10.9% and ES = 0.63 vs. PR = 8.6% and ES = 0.54), and for skeletal muscle mass (TD = 3.6% and ES = 0.32 vs. PR = 2.4% and ES = 0.24) with no differences between groups. There were no significant (p > 0.05) main effects for IGF-1 and testosterone. The results suggest that the PR and TD systems performed are similarly effective for promoting positive adaptations in muscular strength and hypertrophy in older women.

Functionally Diverse NK-Like T Cells Are Effectors and Predictors of Successful Aging

The fundamental challenge of aging and long-term survivorship is maintenance of functional independence and compression of morbidity despite a life history of disease. Inasmuch as immunity is a determinant of individual health and fitness, unraveling novel mechanisms of immune homeostasis in late life is of paramount interest. Comparative studies of young and old persons have documented age-related atrophy of the thymus, the contraction of diversity of the T cell receptor (TCR) repertoire, and the intrinsic inefficiency of classical TCR signaling in aged T cells. However, the elderly have highly heterogeneous health phenotypes. Studies of defined populations of persons aged 75 and older have led to the recognition of successful aging, a distinct physiologic construct characterized by high physical and cognitive functioning without measurable disability. Significantly, successful agers have a unique T cell repertoire; namely, the dominance of highly oligoclonal αβT cells expressing a diverse array of receptors normally expressed by NK cells. Despite their properties of cell senescence, these unusual NK-like T cells are functionally active effectors that do not require engagement of their clonotypic TCR. Thus, NK-like T cells represent a beneficial remodeling of the immune repertoire with advancing age, consistent with the concept of immune plasticity. Significantly, certain subsets are predictors of physical/cognitive performance among older adults. Further understanding of the roles of these NK-like T cells to host defense, and how they integrate with other physiologic domains of function are new frontiers for investigation in Aging Biology. Such pursuits will require a research paradigm shift from the usual young-versus-old comparison to the analysis of defined elderly populations. These endeavors may also pave way to age-appropriate, group-targeted immune interventions for the growing elderly population.

Sarcopenia associated with renal function in the patients with type 2 diabetes

AIMS

Studies have suggested that low muscle mass is associated with declining renal function in healthy populations, whether the association is relevant to patients with type 2 diabetes is not well understood. This study investigates the association between sarcopenia and estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratios (UACR) in the patients with type 2 diabetes.

METHODS

Two recruited groups consisted of 793 persons without diabetes (males/females=550/243) and 762 persons with type 2 diabetes (males/females=501/261).

RESULTS

The non-sarcopenia population demonstrated higher ASM/HT(2), GFR (P<0.001) and lower UACR (P＜0.05) than the sarcopenia population. In studied men, the association between ASM/HT(2) and eGFR was statistically significant in the group without diabetes (OR=0.580, P=0.020), a trend which persisted in women (OR=0.491, P=0.014). The association between ASM/HT(2) and UACR persisted in studied women of two groups (OR=0.269, P=0.005; OR=0.405, P=0.008, respectively). The highest quartile of ASM/HT(2) in the non-sarcopenia population exhibited a 3.753-fold risk of abnormal eGFR within the diabetes group (OR=3.753, P=0.020). The cutoff point of ASM/HT(2) to indicate abnormal renal function for population with non-sarcopenia was 6.32kg/m(2) in the group without diabetes and 6.31kg/m(2) in diabetes group.

CONCLUSIONS

Sarcopenia is associated with declining renal function, which induces lower eGFR and higher UACR. In the non-sarcopenia population, ASM/HT(2) presents as renal function risk factor, which perhaps associated with higher muscle mass to induce a greater underestimation for creatinine and urinary albumin.

Physical activity, body composition and general health status of physically active students of the University of the Third Age (U3A)

OBJECTIVE

To evaluate general health status of a group of older adults, physically active students of the University of the Third Age (U3A), based on results of biochemical analyses of blood, assessment of their physical activity (PA) level, body composition and cognitive function with respect to age and sex.

METHODS

A total of 104 students (85 women and 19 men, aged 63.7±6.6 y) of the U3A's located in the Upper Silesia region of Poland volunteered to participate in this study. A habitual PA level and body composition were objectively assessed by using ActiGraph GT1M and InBody 720, respectively. Serum lipid profile and glucose metabolism markers were measured for assessment of cardiovascular disease risk factors. Moreover, subjects' cognitive functions were tested.

RESULTS

Most of the study participants reached the daily step goal of 10,000 steps and thus fulfilled the ACSM recommendations for the quantity and quality of cardiorespiratory exercise. Highly negative correlations between the number of steps per day and body adiposity markers, serum insulin and HOMA-IR confirmed that vigorous physical activity at the recommended level was associated with better body composition and lower levels of risk markers of coronary heart disease and diabetes. Most of the U3A students were characterized by a favorable lipid profile, prevalence of normal blood pressure, low rates of HOMA-estimated insulin resistance and normal cognitive function.

CONCLUSION

Adherence to ACSM recommendations is associated with beneficial changes in risk factors related to cardiovascular disease.

Postmenopausal effects of resistance training on muscle damage and mitochondria

The purpose of this study was to measure the effects of a 12-month progressive resistance training intervention on muscle morphology and strength gains in postmenopausal women. Skeletal muscle biopsies were obtained from the vastus lateralis of 5 independent community-dwelling women (mean age: 75.6 ± 4.28 years; mean height: 163 ± 5.34 cm; mean weight: 72 ± 17.5 kg) before 6 months and 12 months after progressive resistance training. Muscle strength (1 repetition maximum) was measured at the same time points. After 6 months of training, morphological analysis revealed evidence of increased proteolysis and tissue repair, and rudimentary fiber development. The percent of Z-bands with mild Z-band disruption increased from 43.9% at baseline to 66.7% after 6 months of training (p < 0.01). Mitochondrial volume also increased (percent of mitochondria = 0.86% at baseline, 1.19% at 6 months, and 1.04% at 12 months, p < 0.05), and there was a shift to larger sized mitochondria. The training did not result in statistically significant increases in muscle leg strength (p < 0.18). It appears that mild Z-band disruption acts as a precursor for increased protein synthesis and stimulates an increase in mitochondrial mass. Therefore, although a progressive resistance training program in this population did not increase muscle strength, it did demonstrate clinical applications that lend support to the importance of resistance training in older adults.

Chronic resistance training activates autophagy and reduces apoptosis of muscle cells by modulating IGF-1 and its receptors, Akt/mTOR and Akt/FOXO3a signaling in aged rats

Resistance exercise training (RET) remains the most effective treatment for the loss of muscle mass and strength in elderly people. However, the underlying cellular and molecular mechanisms are not well understood. Recent evidence suggests that autophagic signaling is altered in aged skeletal muscles. This study aimed to investigate if RET affects IGF-1 and its receptors, the Akt/mTOR, and Akt/FOXO3a signaling pathways and regulates autophagy and apoptosis in the gastrocnemius muscles of 18-20 month old rats. The results showed that 9 weeks of RET prevented the loss of muscle mass and improved muscle strength, accompanied by reduced LC3-II/LC3-I ratio, reduced p62 protein levels, and increased levels of autophagy regulatory proteins, including Beclin 1, Atg5/12, Atg7, and the lysosomal enzyme cathepsin L. RET also reduced cytochrome c level in the cytosol but increased its level in mitochondrial fraction, and inhibited cleaved caspase 3 production and apoptosis. Furthermore, RET upregulated the expression of IGF-1 and its receptors but downregulated the phosphorylation of Akt and mTOR. In addition, RET upregulated the expression of total AMPK, phosphorylated AMPK, and FOXO3a. Taken together, these results suggest that the benefits of RET are associated with increased autophagy activity and reduced apoptosis of muscle cells by modulating IGF-1 and its receptors, the Akt/mTOR and Akt/FOXO3a signaling pathways in aged skeletal muscles.

IGF-1 Increases with Hyperbaric Oxygen Therapy and Promotes Wound Healing in Diabetic Foot Ulcers

Objectives. To investigate insulin-like growth factor I (IGF-1) levels in response to hyperbaric oxygen therapy (HBOT) for diabetic foot ulcers and to determine whether IGF-1 is a predictive indicator of wound healing in patients with diabetic foot ulcers. Design and Methods. We treated 48 consecutive patients with diabetic foot ulcers with HBOT. Alterations of IGF-1 levels in patients whose wound healed with HBOT were compared with those in patients who did not benefit from HBOT. Results. There was no significant difference in initial IGF-1 levels between the two groups (P = 0.399). The mean IGF-1 level increased with HBOT (P < 0.05). In the healed group, the mean IGF-1 increase and the final values were significantly higher (P < 0.05). In the nonhealed group, the mean IGF-1 increase was minus and the final values were not significantly different (P < 0.05). The increase in IGF-1 level with HBOT was significantly higher in the healed group (P < 0.001). Conclusions. IGF-1 increased significantly in the healed group. We believe that HBOT is effective in the treatment of diabetic foot ulcers, with an elevation of IGF-1. This alteration seems to be a predictive factor for wound healing in diabetic foot ulcers treated with HBOT.

The effectiveness of exercise interventions for the management of frailty: a systematic review

This systematic review examines the effectiveness of current exercise interventions for the management of frailty. Eight electronic databases were searched for randomized controlled trials that identified their participants as “frail” either in the title, abstract, and/or text and included exercise as an independent component of the intervention. Three of the 47 included studies utilized a validated definition of frailty to categorize participants. Emerging evidence suggests that exercise has a positive impact on some physical determinants and on all functional ability outcomes reported in this systematic review. Exercise programs that optimize the health of frail older adults seem to be different from those recommended for healthy older adults. There was a paucity of evidence to characterize the most beneficial exercise program for this population. However, multicomponent training interventions, of long duration (≥5 months), performed three times per week, for 30–45 minutes per session, generally had superior outcomes than other exercise programs. In conclusion, structured exercise training seems to have a positive impact on frail older adults and may be used for the management of frailty.

Increased fat mass, decreased myofiber size, and a shift to glycolytic muscle metabolism in adolescent male transgenic mice overexpressing IGFBP-2

To elucidate the functional role of insulin-like growth factor (IGF)-binding protein-2 (IGFBP-2) for in vivo skeletal muscle growth and function, skeletal muscle cellularity and metabolism, expression of signal molecules, and body growth and composition were studied in a transgenic mouse model overexpressing IGFBP-2. Postnatal growth rate of transgenic mice was reduced from day 21 of age by 6-8% compared with nontransgenic controls. At 10 wk of age body lean protein and moisture percentages were lower, whereas fat percentage was higher in IGFBP-2 transgenic mice. Muscle weights were reduced (-13% on day 30 of age, -14% on day 72), which resulted from slower growth of myofibers in size but not from decreases in myofiber number. The reduction in muscle mass was associated with lower total DNA, RNA, and protein contents as well as greater DNA/RNA and protein/RNA ratios. The percentage of proliferating (Ki-67-positive) nuclei within myofibers was reduced (3.4 vs. 5.8%) in 30-day-old transgenic mice. These changes were accompanied by slight reductions in specific p44/42 MAPK activity (-18% on day 72) and, surprisingly, by increased levels of phosphorylated Akt (Ser(473)) (+25% on day 30, +66% on day 72). The proportion of white glycolytic fibers (55.9 vs. 53.5%) and the activity of lactate dehydrogenase (+8%) were elevated in 72-day-old transgenic mice. Most of the differences observed between transgenic and nontransgenic mice were more pronounced in males. The results suggest that IGFBP-2 significantly inhibits postnatal skeletal myofiber growth by decreasing myogenic proliferation and protein accretion and enhances glycolytic muscle metabolism.

Osteoporosis, falls and exercise

Osteoporosis, a manifestation of bone atrophy that leads to great susceptibility to fractures, is a very important public health problem today because of its great morbidity, mortality and important economic repercussions. It is a problem that will tend to become more serious with the increase in the number of elderly persons. Bone mass is gained during adolescence, reaches a plateau during the third decade and remains stable until approximately age 50, after which a progressively gradual loss is observed. There is no real cure for osteoporosis, but a series of strategies can be used to reduce bone loss and improve bone mass. Osteoporosis has been considered a disease that accompanies the process of ageing; however, this fatalistic attitude should be discarded, as it is possible to correct and decrease the risk factors. Intervention strategies are based on three pillars: nutrition, physical activity and pharmacological agents. Physical activities and exercise programmes are important because they not only can counter the loss of bone mass but also improve neuromuscular capacity, maintaining and increasing strength and muscle mass, which can help to avoid falls and reduce their impact and consequences. The general principles that apply to any exercise programme also apply to preventing bone mass loss. They also can be applied to persons with osteoporosis. However, to understand the peculiarities of these programmes, the propensity for suffering fractures of these former groups should be kept in mind. Special care should be taken to avoid falls and injuries. Weight-bearing exercise and resistance training are recommended for the prevention programmes. Other activities such as tai-chi, dancing, gymnastic or callisthenic exercises can help to improve balance, gait and muscle coordination and diminish the risk of falling. These programmes should be complemented with postural education and a series of safety precautions.