Novel intriguing strategies attenuating to sarcopenia

Novel drug targets and molecular mechanisms for sarcopenia based on systems biology

Sarcopenia is a major public health concern among older adults, leading to disabilities, falls, fractures, and mortality. This study aimed to elucidate the pathophysiological mechanisms of sarcopenia and identify potential therapeutic targets using systems biology approaches. RNA-seq data from muscle biopsies of 24 sarcopenic and 29 healthy individuals from a previous cohort were analysed. Differential expression, gene set enrichment, gene co-expression network, and topology analyses were conducted to identify target genes implicated in sarcopenia pathogenesis, resulting in the selection of 6 hub genes (PDHX, AGL, SEMA6C, CASQ1, MYORG, and CCDC69). A drug repurposing approach was then employed to identify new pharmacological treatment options for sarcopenia (clofibric-acid, troglitazone, withaferin-a, palbociclib, MG-132, bortezomib). Finally, validation experiments in muscle cell line (C2C12) revealed MG-132 and troglitazone as promising candidates for sarcopenia treatment. Our approach, based on systems biology and drug repositioning, provides insight into the molecular mechanisms of sarcopenia and offers potential new treatment options using existing drugs.

Cognitive Dysfunction and Exercise: From Epigenetic to Genetic Molecular Mechanisms

Maintaining good health is crucial, and exercise plays a vital role in achieving this goal. It offers a range of positive benefits for cognitive function, regardless of age. However, as our population ages and life expectancy increases, cognitive impairment has become a prevalent issue, often coexisting with age-related neurodegenerative conditions. This can result in devastating consequences such as memory loss, difficulty speaking, and confusion, greatly hindering one's ability to lead an ordinary life. In addition, the decrease in mental capacity has a significant effect on an individual's physical and emotional well-being, greatly reducing their overall level of contentment and causing a significant financial burden for communities. While most current approaches aim to slow the decline of cognition, exercise offers a non-pharmacological, safe, and accessible solution. Its effects on cognition are intricate and involve changes in the brain's neural plasticity, mitochondrial stability, and energy metabolism. Moreover, exercise triggers the release of cytokines, playing a significant role in the body-brain connection and its impact on cognition. Additionally, exercise can influence gene expression through epigenetic mechanisms, leading to lasting improvements in brain function and behavior. Herein, we summarized various genetic and epigenetic mechanisms that can be modulated by exercise in cognitive dysfunction.

Effects of soy milk ingestion immediately after resistance training on muscular-related biomarkers in older men: a randomized controlled trial

We evaluated the effects of soy milk ingestion on changes in body composition, strength, power, and muscular-related biomarkers following 12 weeks of resistance training in older men. Thirty healthy older men (age = 65.63 ± 3.16 years; body mass = 62.63 ± 3.86 kg) were randomly assigned to one of two groups: soy milk + resistance training (SR) or placebo + resistance training (PR). Participants in the SR group received 240 ml of vanilla-flavoured non-dairy soy milk immediately after every training session and at the same time on non-training days. Differences in muscle mass, upper limb body strength (UBS), lower limb aerobic power (LAP), activin A, and GDF15 were significantly greater in the SR group vs. the PR group (P < 0.05). Both intervention groups experienced a significant (p < 0.05) reduction in body mass (PR = -3.9 kg; SR = -3.2 kg), body fat % (PR = -0.8%; SR = -1.2%), activin A (PR = -5.1 pg/ml; SR = -12.8 pg/ml), GDF15 (PR = -8.1 pg/ml; SR = -14.7 pg/ml), TGFβ1 (PR = -0.43 pg/ml; SR = -0.41 pg/ml), and increase in muscle mass (PR = 0.81 kg; SR = 2.5 kg), UBS (PR = 3.4 kg; SR = 6.7 kg), lower limb body strength (PR = 2.8 kg; SR = 5.2 kg), upper limb aerobic power (PR = 34.3 W; SR = 38.6 W), LAP (PR = 23.2 W; SR = 45.2 W), BDNF (PR = 8.3 ng/ml; SR = 12.7 ng/ml), and irisin (PR = 1.5 ng/ml; SR = 2.9 ng/ml) compared to baseline. The ingestion of soy milk during 12 weeks of resistance training augmented lean mass, strength, and power, and altered serum concentrations of skeletal muscle regulatory markers in older men.

Modulation of Neuroendocrine and Immunological Biomarkers Following Rehabilitation in Sarcopenic Patients

This study aimed to investigate if rehabilitation could down-regulated sarcopenia-associated inflammation by modulating the crosstalk between the neuroendocrine and immune systems, with the aim of ameliorating quality of life of sarcopenic subjects. A total of 60 sarcopenic patients (49 females and 11 males; median age 74.5, interquartile range 71–79), undergoing a personalized rehabilitation program, have been recruited and subjected to: (1) functional and physical evaluation (Short Physical Performance Battery (SPPB), Barthel Index and Tinetti Test); (2) pro-inflammatory IL-1β, TNF-α, IL-6, IL-18, and anti-inflammatory IL-10 cytokines plasmatic level measures; and (3) norepinephrine, epinephrine, dopamine, and serotonin neurotransmitter level evaluation at time of enrollment (T0) and once rehabilitation was concluded (1 month, T1). Rehabilitation combined a balance and strength training program with two daily sessions that were fine-tuned and personalized according to the ability of the patient. The results showed a significant increase at T1 in the plasmatic levels of IL-10 (p = 0.018) and of norepinephrine (p = 0.016)), whereas the concentration of IL-18 was significantly reduced (p = 0.012). Notably, changes in norepinephrine were positively correlated with clinical improvements (Tinetti and Barthel scores, p ≤ 0.0001; SPPB scores, p = 0.0002). These results show that efficient rehabilitation induces a reduction of inflammation, suggesting that this effect could be mediated by a modulation of the neuro-immune axis that results in an increase of norepinephrine.

Ursolic acid and SARS-CoV-2 infection: a new horizon and perspective

SARS-CoV-2 (severe acute respiratory syndrome coronavirus type 2) has been identified as the source of a world coronavirus pandemic in 2019. Covid-19 is considered a main respiratory disease-causing viral pneumonia and, in severe cases, leads to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Although, extrapulmonary manifestations of Covid-19 like neurological, cardiovascular, and gastrointestinal have been confirmed. Exaggerated immune response and release of a high amount of pro-inflammatory cytokines may progress, causing a cytokine storm. Consequently, direct and indirect effects of SARS-CoV-2 infection can evolve into systemic complications due to the progression of hyper inflammation, oxidative stress and dysregulation of the renin-angiotensin system (RAS). Therefore, anti-inflammatory and antioxidant agents could be efficient in alleviating these disorders. Ursolic acid has anti-inflammatory, antioxidant, and antiviral effects; it reduces the release of pro-inflammatory cytokines, improves anti-inflammatory cytokines, and inhibits the production of reactive oxygen species (ROS). In virtue of its anti-inflammatory and antioxidant effects, ursolic acid may minimize SARS-CoV-2 infection-induced complications. Also, by regulating RAS and inflammatory signaling pathways, ursolic acid might effectively reduce the development of ALI in ARDS in Covid-19. In this state, this perspective discusses how ursolic acid can mitigate hyper inflammation and oxidative stress in Covid-19.

The effect of resistance and endurance training with ursolic acid on atrophy-related biomarkers in muscle tissue of diabetic male rats induced by streptozotocin and a high-fat diet

In this study, the effect of resistance and endurance training with/without ursolic acid supplementation was evaluated to identify atrophy-related biomarkers in elderly rats induced by diabetes and a high-fat diet (HFD) based on in silico analysis algorithms and pharmaceutical methods. The visualizer software found differential gene expression levels in skeletal muscle atrophy via computed hub gene network parameters. Also, the impact of ursolic acid, as a potent inducer of the Trp53 protein in ameliorating decreased muscle mass, was analyzed in diabetic rats. Fifty-six-old male Wistar rats were randomly assigned into seven groups, including healthy control (Control), diabetic control (DM), Ursolic acid supplementation (UA), resistance training (RT), endurance training (ET), resistance training+ Ursolic acid supplementation (RT + U), and endurance training in combination with Ursolic acid supplementation (ET + U). Exercise intervention included 8 weeks of resistance or endurance training programs. Biomedical informatic outputs determined the P53 signaling pathway as a remarkable causative factor in the pathomechanism of atrophy. In addition, the results demonstrated that exercise and supplementation of UA impeded the interactions among p53/ATF4/p21. Moreover, ET and ursolic acid had a synergetic effect on the signaling pathway of p53/ATF4/p21 and probably could inhibit the aging process and modulate the p53/ATF4/p21 molecular pathway. The interaction between UA and endurance exercise significantly modified the activity of the p53/ATF4/p21 signaling pathway. Based on in silico studies, the p53/ATF4/p21 pathway plays an essential role in aging, and the inhibition of this pathway would be beneficial in decelerating the aging process. PRACTICAL APPLICATIONS: Ursolic acid (UA) is a natural pentacyclic triterpenoid carboxylic acid found in apples (a major compound of apple wax) and other fruits; it is known to improve skeletal muscle function and reduce the muscular atrophy pathways. We indicated that p53/ATF4/p21 signaling is an essential factor in aging, and the suppression of this pathway could be beneficial in the deceleration of the aging process. Therefore, this work would shed light on understanding the effect of exercise and nutrition interventions on preventing atrophy markers of skeletal muscle in diabetic rats. Further studies are needed to seek the precise mechanism of the synergism between UA and exercise in ameliorating atrophy markers.

Novel Insights into the Pathogenesis of Spinal Sarcopenia and Related Therapeutic Approaches: A Narrative Review

Spinal sarcopenia is a complex and multifactorial disorder associated with a loss of strength, increased frailty, and increased risks of fractures and falls. In addition, spinal sarcopenia has been associated with lumbar spine disorders and osteoporosis, which renders making decisions on treatment modalities difficult. Patients with spinal sarcopenia typically exhibit lower cumulative survival, a higher risk of in-hospital complications, prolonged hospital stays, higher postoperative costs, and higher rates of blood transfusion after thoracolumbar spine surgery. Several studies have focused on the relationships between spinal sarcopenia, appendicular muscle mass, and bone-related problems-such as osteoporotic fractures and low bone mineral density-and malnutrition and vitamin D deficiency. Although several techniques are available for measuring sarcopenia, each of them has its advantages and shortcomings. For treating spinal sarcopenia, nutrition, physical therapy, and medication have been proven to be effective; regenerative therapeutic options seem to be promising owing to their repair and regeneration potential. Therefore, in this narrative review, we summarize the characteristics, detection methodologies, and treatment options for spinal sarcopenia, as well as its role in spinal disorders.

Body Composition and Biochemical Markers of Nutrition in Non-dialysis-Dependent Chronic Kidney Disease Patients

The aim of this study was to examine the body composition in stages 3b to 5 of chronic kidney disease. There were 149 patients included in the study, with the mean age of 65.5 ± 16.5 years, body mass index (BMI) of 29.4 ± 5.6 kg/m², and estimated glomerular filtration rate (eGFR) of 23.2 ± 9.3/min/1.73m². They remained with dialysis. Body composition was measured using bioimpedance spectroscopy, and handgrip strength was measured with a hydraulic dynamometer. The main biochemical markers assessed consisted of serum protein, albumin, prealbumin, high-sensitivity C-reactive protein (hsCRP), and interleukin (IL)-6 content. We found that 39% of patients were overweight and 41% were obese. Obesity was more prevalent in stage 3b of chronic kidney disease than in stages 4-5 in women and in patients older than 60 years of age. Thirty-eight percent of the study population were sarcopenic, of whom 20% presented a sarcopenic obesity phenotype. There were significant associations between lean tissue index (LTI) and serum prealbumin content and handgrip strength. Fat tissue index (FTI) was associated and hsCRP, serum protein, body mass index (BMI), waist-hip ratio, and waist-to-height ratio. There were inverse associations between FTI-LTI and LTI-age. We conclude that the prevalence of obesity in non-dialysis-dependent patients with chronic kidney disease is higher than that in the general population. Earlier stages of chronic kidney disease are associated with a higher prevalence of obesity.

Effect of dietary fish oil intake on ubiquitin ligase expression during muscle atrophy induced by sciatic nerve denervation in mice

Dietary fish oil intake improves muscle atrophy in several atrophy models however the effect on denervation-induced muscle atrophy is not clear. Thus, the aim of this study was to investigate the effects of dietary fish oil intake on muscle atrophy and the expression of muscle atrophy markers induced by sciatic nerve denervation in mice. We performed histological and quantitative mRNA expression analysis of muscle atrophy markers in mice fed with fish oil with sciatic nerve denervation. Histological analysis indicated that dietary fish oil intake slightly prevented the decrease of muscle fiber diameter induced by denervation treatment. In addition, dietary fish oil intake suppressed the MuRF1 (tripartite motif-containing 63) expression up-regulated by denervation treatment, and this was due to decreased tumor necrosis factor-alpha (TNF-α) production in skeletal muscle. We concluded that dietary fish oil intake suppressed MuRF1 expression by decreasing TNF-α production during muscle atrophy induced by sciatic nerve denervation in mice.

Effect of Duration of Dietary Rapeseed and Soybean Oil Feeding on Physical Characteristics, Fatty Acid Profile, and Oxidative Stability of Pig Backfat

This study compared the effect of two vegetable oils and their feeding duration on pig backfat quality. The experiment was conducted with 60 DanBred pigs that were fed a diet supplemented (40 g/kg) with rapeseed or soybean oil for 2, 4 or 6 weeks before slaughter at 152 d of age. The supplementation of both vegetable oils in the diets for 6 weeks negatively changed backfat consistency. The pigs fed soybean oil for 4 (17.64%) and 6 weeks (18.52%) before slaughter showed an increase in backfat linoleic acid content (p = 0.002), whereas, in contrast to the other groups, rapeseed oil in the diet for 6 weeks (2.38%) increased α-linolenic acid content (p = 0.039). The content of PUFAs (p = 0.024) and n-6 PUFAs (p = 0.003) was increased by adding soybean oil to the diet for 4 and 6 weeks. The ratio of n-6/n-3 PUFAs was decreased (p = 0.040) by supplementing rapeseed oil for 4 and 6 weeks. The oil feeding duration decreased (p < 0.001) the atherogenic and thrombogenic indices. The lipid oxidative stability of backfat stored for 3 and 5 days increased (p < 0.001) in pigs fed dietary vegetable oils for 6 weeks prior to slaughter. In conclusion, the feeding of rapeseed oil for 4 weeks before slaughter is sufficient for improving the FA profile without negative effect on the consistency of the backfat.

Muscle and Bone Mass Loss in the Elderly Population: Advances in diagnosis and treatment

Aging is the result of different functional changes leading to a substantial reduction of all human capabilities. A variety of anatomical and physiological changes occur with advancing age. These changes are more evident in the elderly population. There are various methods to measure muscle and bone mass loss, but the dual X-ray absorptiometry (DXA) is considered one of the most efficient. The elderly population (65 years and older) has been increasing throughout the years. Loss of muscle mass (sarcopenia) and loss bone mass (osteopenia or osteoporosis) with advancing age, when untreated, represent a major public health problem for the elderly population and may result in loss of independence in later life. Untreated age-related sarcopenia and osteopenia/osteoporosis increase the risk for falls and fractures, making older individuals more susceptible to the development of mobility limitations or severe disabilities that ultimately affect their capacity for independence. In this review, we will discuss the muscle and bone mass loss in the elderly population and advances in diagnosis and treatment.

The Role of Inflammation in Age-Related Sarcopenia

Many physiological changes occur with aging. These changes often, directly or indirectly, result in a deterioration of the quality of life and even in a shortening of life expectancy. Besides increased levels of reactive oxygen species, DNA damage and cell apoptosis, another important factor affecting the aging process involves a systemic chronic low-grade inflammation. This condition has already been shown to be interrelated with several (sub)clinical conditions, such as insulin resistance, atherosclerosis and Alzheimer's disease. Recent evidence, however, shows that chronic low-grade inflammation also contributes to the loss of muscle mass, strength and functionality, referred to as sarcopenia, as it affects both muscle protein breakdown and synthesis through several signaling pathways. Classic interventions to counteract age-related muscle wasting mainly focus on resistance training and/or protein supplementation to overcome the anabolic inflexibility from which elderly suffer. Although the elderly benefit from these classic interventions, the therapeutic potential of anti-inflammatory strategies is of great interest, as these might add up to/support the anabolic effect of resistance exercise and/or protein supplementation. In this review, the molecular interaction between inflammation, anabolic sensitivity and muscle protein metabolism in sarcopenic elderly will be addressed.

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.

Quality evaluation of low fat bologna-type meat product with a nutritional profile designed for the elderly

The objective of this work was to evaluate the quality of a bologna-type meat product designed for the elderly. Treatments were: control, without addition of cranberries (C), prunes (P), pecan nuts (N) or flaxseed (F); NP, with 5% N+5% P; FC, with 5% F+5% C; NC, with 5% N+5% C; FP, with 5% F+5% P. These formulations resulted in a product with high protein, low SFA and high antioxidant activity. Treatments with pecan nuts had higher MUFA while those with flaxseed had higher polyunsaturated fatty acids (PUFA). Treatments with pecan nuts and flaxseed had higher PUFA/SFA ratios, but only those with flaxseed had very low n6/n3 ratios when compared to the control. Although treatments showed acceptable scores (>5.4), they were lower than the control. A combination of these non-traditional ingredients could be used to develop a meat product for older adults to provide a better nutritional profile with acceptable sensory properties.

Towards ageing well: Use it or lose it: Exercise, epigenetics and cognition

More and more people are living into the 90s or becoming centenarians. But, the gift of increased ‘age span’ seldom equates with an improved ‘health-span’. Governments across the world are expressing concern about the epidemic of chronic disease, and have responded by initiating policies that make prevention, reduction and treatment of chronic disease, a public health priority. But understanding, how to age long and well, with the avoidance of chronic disease and later life complex disease morbidity is challenging. While inherited genes have an undoubted role to play in the chance of maintaining good health or conversely a predilection to developing disease and chronic ill health, there is increasing evidence that behavioural and environmental life-style choices may contribute up to 50% of the variability of human lifespan. Physical exercise is readily available to everyone, and is a simple cheap and effective form of life-style intervention. Exercise appears to help maintain good health and to reduce the risk of developing chronic disease and ill health. Evidence suggests that physical activity improves well-being across many health domains through out life, continues to offer important health benefits in older age groups and tracks with a ‘healthy ageing’ profile. Although many of the molecular pathways remain to be fully identified, here we discuss how physical activity and exercise is understood to produce changes in the human epigenome, which have the potential to enhance cognitive and psychological health, improve muscular fitness, and lead to better ageing with improved quality of life in older age.

[Common therapeutic approaches of sarcopenia in the elderly and uremic myopathy]

The gradual loss of weight and function of muscle in patients with chronic kidney disease as in the elderly impacts the quality of life. Early management should help slow the functional limitation. Physical activity is the first therapy to propose that ensures stability of muscle mass and improved function. Resistance training programs have proven effective but are not yet widely available in nephrology units. The nutritional management should not be forgotten because there is a resistance to anabolism and protein intake should be involved in physical activity program. Associated treatments should not be neglected: vitamin D, anti-inflammatory, androgens. Some are still under evaluation. Therapeutic option, tomorrow, could be anti-myostatin antibodies and glitazones.

Cellular and Physiological Effects of Dietary Supplementation with β-Hydroxy-β-Methylbutyrate (HMB) and β-Alanine in Late Middle-Aged Mice

There is growing evidence that severe decline of skeletal muscle mass and function with age may be mitigated by exercise and dietary supplementation with protein and amino acid ingredient technologies. The purposes of this study were to examine the effects of the leucine catabolite, beta-hydroxy-beta-methylbutyrate (HMB), in C₂C₁₂ myoblasts and myotubes, and to investigate the effects of dietary supplementation with HMB, the amino acid β-alanine and the combination thereof, on muscle contractility in a preclinical model of pre-sarcopenia. In C₂C₁₂ myotubes, HMB enhanced sarcoplasmic reticulum (SR) calcium release beyond vehicle control in the presence of all SR agonists tested (KCl, P<0.01; caffeine, P = 0.03; ionomycin, P = 0.03). HMB also improved C₂C₁₂ myoblast viability (25 μM HMB, P = 0.03) and increased proliferation (25 μM HMB, P = 0.04; 125 μM HMB, P<0.01). Furthermore, an ex vivo muscle contractility study was performed on EDL and soleus muscle from 19 month old, male C57BL/6nTac mice. For 8 weeks, mice were fed control AIN-93M diet, diet with HMB, diet with β-alanine, or diet with HMB and β-alanine. In β-alanine fed mice, EDL muscle showed a 7% increase in maximum absolute force compared to the control diet (202 ± 3vs. 188± 5 mN, P = 0.02). At submaximal frequency of stimulation (20 Hz), EDL from mice fed HMB plus β-alanine showed an 11% increase in absolute force (88.6 ± 2.2 vs. 79.8 ± 2.4 mN, P = 0.025) and a 13% increase in specific force (12.2 ± 0.4 vs. 10.8 ± 0.4 N/cm², P = 0.021). Also in EDL muscle, β-alanine increased the rate of force development at all frequencies tested (P<0.025), while HMB reduced the time to reach peak contractile force (TTP), with a significant effect at 80 Hz (P = 0.0156). In soleus muscle, all experimental diets were associated with a decrease in TTP, compared to control diet. Our findings highlight beneficial effects of HMB and β-alanine supplementation on skeletal muscle function in aging mice.

Ratio of dietary ω-3 and ω-6 fatty acids-independent determinants of muscle mass-in hemodialysis patients with diabetes

OBJECTIVE

ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) are essential nutrients in the human diet and possibly affect muscle mass. We evaluated the association between the dietary ratios of ω-3 and ω-6 PUFAs and muscle mass, indicated as skeletal muscle mass (SMM) and appendicular skeletal muscle mass (ASM), in patients with diabetes undergoing hemodialysis (HD).

METHODS

In this cross-sectional study, data on 69 patients with diabetes who underwent standard HD therapy were analyzed. For estimating muscle mass, anthropometric and bioelectrical impedance analyses were conducted following dialysis. In addition, routine laboratory and 3-d dietary data were obtained. The adequate intake (AI) cut-off for ω-3 PUFAs was 1.6 g/d and 1.1 g/d for male and female patients, respectively.

RESULTS

The average age of the participants was 63.0 ± 10.4 y. The mean ratios of ω-3/ω-6 PUFA intake, ω-6/ω-3 PUFA intake, SMM, and ASM of the patients were 0.13 ± 0.07, 9.4 ± 6.4, 24.6 ± 5.4 kg, and 18.3 ± 4.6 kg, respectively. Patients who had AI of ω-3 PUFAs had significantly higher SMM and ASM than did their counterparts. Linear and stepwise multivariable adjustment analyses revealed that insulin resistance and the ω-6/ω-3 PUFA ratio were the independent deleterious determinants of ASM normalized to height in HD patients.

CONCLUSIONS

Patients with AI of ω-3 PUFAs had total-body SMM and ASM that were more appropriate. A higher dietary ratio of ω-6/ω-3 PUFAs was associated with reduced muscle mass in HD patients.

Clinical Screening Tools for Sarcopenia and Its Management

Sarcopenia, an age-related decline in muscle mass and function, is affecting the older population worldwide. Sarcopenia is associated with poor health outcomes, such as falls, disability, loss of independence, and mortality; however it is potentially treatable if recognized and intervened early. Over the last two decades, there has been significant expansion of research in this area. Currently there is international recognition of a need to identify the condition early for intervention and prevention of the disastrous consequences of sarcopenia if left untreated. There are currently various screening tools proposed. As yet, there is no consensus on the best tool. Effective interventions of sarcopenia include physical exercise and nutrition supplementation. This review paper examined the screening tools and interventions for sarcopenia.

Characterizing a distal muscle enhancer in the mouse Igf2 locus

Insulin-like growth factor-2 (IGF2) is highly expressed in skeletal muscle and was identified as a quantitative trait locus for muscle mass. Yet little is known about mechanisms of its regulation in muscle. Recently, a DNA segment found ∼100 kb from the Igf2 gene was identified as a possible muscle transcriptional control element. Here we have developed an in vivo reporter system to assess this putative enhancer by substituting nuclear (n) EGFP for Igf2 coding exons in a bacterial artificial chromosome containing the mouse Igf2 - H19 chromosomal locus. After stable transfection into a mesenchymal stem cell line, individual clones were converted to myoblasts and underwent progressive muscle-specific gene expression and myotube formation in differentiation medium. Transgenic mRNA and nuclear-targeted enhanced green fluorescent protein were produced coincident with endogenous Igf2 mRNA, but only in lines containing an intact distal conserved DNA element. Our results show that a 294 bp DNA fragment containing two E-boxes is a necessary and sufficient long-range enhancer for induction of Igf2 gene transcription during skeletal muscle differentiation and provides a robust experimental platform for its further functional dissection.

Ursolic Acid--A Pentacyclic Triterpenoid with a Wide Spectrum of Pharmacological Activities

Ursolic acid (UA) is a natural terpene compound exhibiting many pharmaceutical properties. In this review the current state of knowledge about the health-promoting properties of this widespread, biologically active compound, as well as information about its occurrence and biosynthesis are presented. Particular attention has been paid to the application of ursolic acid as an anti-cancer agent; it is worth noticing that clinical tests suggesting the possibility of practical use of UA have already been conducted. Amongst other pharmacological properties of UA one can mention protective effect on lungs, kidneys, liver and brain, anti-inflammatory properties, anabolic effects on skeletal muscles and the ability to suppress bone density loss leading to osteoporosis. Ursolic acid also exhibits anti-microbial features against numerous strains of bacteria, HIV and HCV viruses and Plasmodium protozoa causing malaria.

Ratio of Dietary n-6/n-3 Polyunsaturated Fatty Acids Independently Related to Muscle Mass Decline in Hemodialysis Patients

Background

n-3 polyunsaturated fatty acids (PUFAs) might be useful nutritional strategy for treating patients with sarcopenia. We evaluated the effect of the intake of dietary n-3 PUFAs on the skeletal muscle mass (SMM), appendicular skeletal muscle mass (ASM), and its determinants in patients receiving standard hemodialysis (HD) treatment for the management of end stage renal disease.

Methods

In this cross-sectional study, data of 111 HD patients were analyzed. Anthropometric and bioelectrical impedance measurements used to estimate the muscle mass were performed the day of dialysis immediately after the dialysis session. Routine laboratory and 3-day dietary data were also collected. The cutoff value of adequate intake (AI) for both n-3 PUFAs and alpha-linolenic acid (ALA) was 1.6 g/day and 1.1 g/day for men and women, respectively.

Results

The mean age, mean dietary n-3 PUFAs intake, ALA intake, ratio of n-6/n-3 PUFAs intake, SMM, and ASM of patients were 61.4 ± 10.4 years, 2.0 ± 1.3 g/day, 1.5 ± 1.0 g/day, 9.5 ± 6.7 g/day, 23.9 ± 5.5 kg, and 17.5 ± 4.5 kg, respectively. A higher SMM and ASM significantly observed in patients who achieved an AI of n-3 PUFAs. Similar trends appeared to be observed among those patients who achieved the AI of ALA, but the difference was not significantly, except for ASM (P = 0.047). No relevant differences in demographics, laboratory and nutritional parameters were observed, regardless of whether the patients achieved an AI of n-3 PUFAs. Multivariate analysis showed that the BMI and equilibrated Kt/V were independent determinants of the muscle mass. Moreover, the ratio of n-6/n-3 PUFAs was an independent risk determinant of reduced ASM in HD patients.

Conclusion

Patients with an AI of n-3 PUFAs had better total-body SMM and ASM. A higher dietary ratio of n-6/n-3 PUFAs seemed to be associated with a reduced muscle mass in HD patients.

Living long and ageing well: is epigenomics the missing link between nature and nurture?

Human longevity is a complex trait and increasingly we understand that both genes and lifestyle interact in the longevity phenotype. Non-genetic factors, including diet, physical activity, health habits, and psychosocial factors contribute approximately 50% of the variability in human lifespan with another 25% explained by genetic differences. Family clusters of nonagenarian and centenarian siblings, who show both exceptional age-span and health-span, are likely to have inherited facilitatory gene groups, but also have nine decades of life experiences and behaviours which have interacted with their genetic profiles. Identification of their shared genes is just one small step in the link from genes to their physical and psychological profiles. Behavioural genomics is beginning to demonstrate links to biological mechanisms through regulation of gene expression, which directs the proteome and influences the personal phenotype. Epigenetics has been considered the missing link between nature and nurture. Although there is much that remains to be discovered, this article will discuss some of genetic and environmental factors which appear important in good quality longevity and link known epigenetic mechanisms to themes identified by nonagenarians themselves related to their longevity. Here we suggest that exceptional 90-year old siblings have adopted a range of behaviours and life-styles which have contributed to their ageing-well-phenotype and which link with important public health messages.

Peripheral arterial disease decreases muscle torque and functional walking capacity in elderly

OBJECTIVES

The aim of this study is to compare values of force-velocity and functional walking capacity in elderly patients with intermittent claudication with respect to the control group.

MATERIALS AND METHODS

The study involved 135 individuals: 85-peripheral arterial disease (PAD) group diagnosed with stage II chronic lower limb ischemia, according to Fontaine's classification, and 50-control group. The studies included an assessment of walking capacity using a six-minute walk test (6MWT) and measurement of force-velocity parameters (peak torque-PTQ, total work-TW, average power-AVGP) of the lower limbs obtained by means of a functional dynamometry under isokinetic conditions.

RESULTS

The peripheral arterial disease group is characterized by significantly lower values of force-velocity parameters compared to the control group (p<0.005). Walking capacity in this group is significantly reduced due to significant differences in the distance covered (p<0.0001), walking speed (p<0.01), and its intensity (p<0.01). Further, a positive correlation was found between the maximum distance specified in the six-minute walk test and lower limb muscle strength in the isokinetic test.

CONCLUSIONS

Mean values of all force-velocity parameters and walk distance were significantly higher in the control group than in the peripheral arterial disease group. In the PAD group, in both men and women, the value of the agonist/antagonist ratio of both lower limbs are lower in men and women comparing to the control group. A rehabilitation program for patients with intermittent claudication must consider exercises improving strength, exercise capacity, and endurance in patients with PAD.

Cachexia and sarcopenia: mechanisms and potential targets for intervention

Cachexia is a multi-organ syndrome associated with cancer and other chronic diseases, characterized by body weight loss, muscle and adipose tissue wasting and inflammation, being often associated with anorexia. Skeletal muscle tissue represents more than 40% of body weight and seems to be one of the main tissues involved in the wasting that occurs during cachexia. Sarcopenia is a degenerative loss of skeletal muscle mass, quality, and strength associated with healthy ageing. The molecular mechanisms behind cachexia and sarcopenia share some common trends. Muscle wasting is the result of a combination of an imbalance between synthetic and degradative protein pathways together with increased myocyte apoptosis and decreased regenerative capacity. Oxidative pathways are also altered in skeletal muscle during muscle wasting and this seems to be a consequence of mitochondrial abnormalities that include altered morphology and function, decreased ATP synthesis and uncoupling. The aim of the present review is to analyse common molecular pathways between cachexia and sarcopenia in order to put forward potential targets for intervention.

Sarcopenia: Monitoring, Molecular Mechanisms, and Physical Intervention

According to European Working Group on Sarcopenia in Older People (EWGSOP) sarcopenia includes both a loss of muscle strength and a decline in functional quality in addition to the loss of muscle protein mass. In order to develop strategies to prevent and treat sarcopenia, the risk factors and causes of sarcopenia must be identified. Age-related muscle loss is characterized by the contribution of multiple factors, and there is growing evidence for a prominent role of low-grade chronic inflammation in sarcopenia. The elderly who are less physically active are more likely to have lower skeletal muscle mass and strength and are at increased risk of developing sarcopenia. Resistance training added to aerobic exercise or high-intensity interval training promote numerous changes in skeletal muscle, many of which may help to prevent or reverse sarcopenia. In this review, we provided current information on definition and monitoring, molecular mechanisms, and physical intervention to counteract sarcopenia.

The TWEAK-Fn14 dyad is involved in age-associated pathological changes in skeletal muscle

Progressive loss of skeletal muscle mass and strength (sarcopenia) is a major clinical problem in the elderly. Recently, proinflammatory cytokine TWEAK and its receptor Fn14 were identified as key mediators of muscle wasting in various catabolic states. However, the role of the TWEAK-Fn14 pathway in pathological changes in skeletal muscle during aging remains unknown. In this study, we demonstrate that the levels of Fn14 are increased in skeletal muscle of 18-month old (aged) mice compared with adult mice. Genetic ablation of Fn14 significantly increased the levels of specific muscle proteins and blunted the age-associated fiber atrophy in mice. While gene expression of two prominent muscle-specific E3 ubiquitin ligases MAFBx and MuRF1 remained comparable, levels of ubiquitinated proteins and the expression of autophagy-related molecule Atg12 were significantly reduced in Fn14-knockout (KO) mice compared with wild-type mice during aging. Ablation of Fn14 significantly diminished the DNA-binding activity of transcription factor nuclear factor-kappa B (NF-κB), gene expression of various inflammatory molecules, and interstitial fibrosis in skeletal muscle of aged mice. Collectively, our study suggests that the TWEAK-Fn14 signaling axis contributes to age-associated muscle atrophy and fibrosis potentially through its local activation of proteolytic systems and inflammatory pathways.

Hypo-activity induced skeletal muscle atrophy and potential nutritional interventions: A review

Periods of hypo-activity result in profound changes in skeletal muscle morphology and strength. This review primarily addresses the differential impact of de-training, bed-rest, limb immobilisation and unilateral lower limb suspension on muscle morphology, strength and fatigability. The degree of muscle atrophy differs depending on the hypo-activity model and the muscles in question, with the leg and postural muscles being the most susceptible to atrophy. Hypo-activity also results in the dramatic loss of strength that often surpasses the loss of muscle mass, and consequently, the nervous system and contractile properties adapt to adjust for this excessive loss of strength. In addition, the degree of muscle strength loss is different depending on the hypo-activity model, with immobilisation appearing to have a greater impact on strength than unloaded models. There is a step-wise difference in the magnitude of muscle loss so that, even after accounting for differential durations of interventions immobilisation ≥ unilateral lower limb suspension ≥ bed-rest ≥ de-training. Muscle fatigability varies between hypo-activity models but the results are equivocal and this may be due to task-specific adaptations. This review also addresses potential nutritional interventions for attenuating hypo-activity induced muscle atrophy and strength declines, in the absence of exercise. Essential amino acid supplementation stands as a strong candidate but other supplements are good contenders for attenuating hypo-activity induced atrophy and strength losses. Several potential nutritional supplements are highlighted that could be used to combat muscle atrophy but extensive research is needed to determine the most effective.

Insulin resistance: a risk marker for disease and disability in the older person

Clinical metabolic studies have demonstrated that insulin action declines progressively with age in humans. In addition to its close association with Type 2 diabetes, which reduces life expectancy in older people, age-related insulin resistance is implicated in pathogenesis of several highly prevalent disorders for which ageing is a major risk factor. These include atherosclerotic cardiovascular disease, dementia, frailty and cancer. Accordingly, insulin resistance may be viewed as biomarker of age-related ill health and reduced lifespan. The rapidly rising number of older people, coupled with a high prevalence of insulin resistance resulting from obesity and sedentary lifestyles, presents unprecedented public health and societal challenges. Studies of centenarians have shown that preserved whole-body sensitivity to insulin is associated with longevity. The mechanisms through which insulin action is associated with age-related diseases remain unclear. Changes in body composition, i.e. sarcopenia and excess adiposity, may be more potent than age per se. Moreover, the impact of insulin resistance has been difficult to disentangle from the clustering of vascular risk factors that co-segregate with the insulin resistance-hyperinsulinaemia complex. Potentially modifiable mediators of age-related changes in insulin sensitivity include alterations in adipocytokines, impaired skeletal myocyte mitochondrial function and brown fat activity. The hypothesis that improving or maintaining insulin sensitivity preserves health and extends lifespan merits further evaluation. Practical non-pharmacological interventions directed against age-related insulin resistance remain underdeveloped. Novel metabolically active pharmacological agents with theoretical implications for some age-related disorders are entering clinical trials. However, recent adverse experiences with the thiazolidinediones suggest the need for a cautious approach to the use of insulin sensitizing drugs in older people. This could be particularly important in the absence of diabetes where the risk to benefit analysis may be less favourable.

Defining Akt actions in muscle differentiation

Muscle development in childhood and muscle regeneration in adults are highly regulated processes that are necessary for reaching and maintaining optimal muscle mass and strength throughout life. Muscle repair after injury relies on stem cells, termed satellite cells, whose activity is controlled by complex signals mediated by cell-cell contact, by growth factors, and by hormones, which interact with genetic programs controlled by myogenic transcription factors. Insulin-like growth factors (IGFs) play key roles in muscle development and help coordinate muscle repair after injury, primarily by stimulating the phosphatidylinositol 3-kinase-Akt signaling pathway, and both in vitro and in vivo studies have shown that Akt kinase activity is critical for optimal muscle growth and regeneration. Here we find that of the two Akts expressed in muscle, Akt1 is essential for initiation of differentiation in culture and is required for normal myoblast motility, while Akt2 is dispensable. Although Akt2 deficiency did lead to diminished myotube maturation, as assessed by a decline in myofiber area and in fusion index, either Akt1 or Akt2 could restore these processes toward normal. Thus levels of Akt expression rather than distinct actions of individual Akt species are critical for normal myofiber development during the later stages of muscle differentiation.

Musculoskeletal frailty: a geriatric syndrome at the core of fracture occurrence in older age

A progressive decline in physiologic reserves inevitably occurs with ageing. Frailty results from reaching a threshold of decline across multiple organ systems. By consequence, frail elderly experience an excess vulnerability to stressors and are at high risk for functional deficits and comorbid disorders, possibly leading to institutionalization, hospitalization and death. The phenotype of frailty is referred to as the frailty syndrome and is widely recognized in geriatric medical practice. Although frailty affects both musculoskeletal and nonmusculoskeletal systems, sarcopenia, which is defined as age-related loss of muscle mass and strength, constitutes one of the main determinants of fracture risk in older age and one of the main components of the clinical frailty syndrome. As a result, operational definitions of frailty and therapeutic strategies in older patients tend to focus on the consequences of sarcopenia.

Sarcopenia: pharmacology of today and tomorrow

Sarcopenia remains largely undiagnosed and undertreated because of the lack of a universally accepted definition, effective ways to measure it, and identification of the outcomes that should guide treatment efficacy. An ever-growing number of clinicians and researchers along with funding and regulatory agencies have gradually recognized that sarcopenia is a human condition that requires both prevention and treatment. In this article, we review sarcopenia and its common and less known pharmacological treatments, attempt to define sarcopenia in its broader context, and present some new ideas for potential future treatment for this devastating condition.