Sarcopenia of aging and its metabolic impact

Low Muscle Mass and Depressed Mood in Korean Adolescents: a Cross-Sectional Analysis of the Fourth and Fifth Korea National Health and Nutrition Examination Surveys

BACKGROUND

Muscle mass and muscle function are related to depressed mood in studies of adults. Like adults, Korean students are highly likely to suffer from decreased muscle mass due to social conditions. In this study, we evaluated the muscle mass status of Korean adolescents and assess the effect of muscle on depressive mood.

METHODS

A total of 1,233 adolescent boys and girls participants from the Korea National Health and Nutrition Examination Survey were enrolled in our study. Participants underwent dual-energy X-ray absorptiometry for assessment of appendicular muscle mass and completed questionnaires regarding depressed mood, stress, suicidal ideations, and attempts.

RESULTS

There was no difference in depressive mood according to muscle mass among boys (P = 0.634); girls with decreased muscle mass had a greater tendency for depressed mood compared to girls with optimal muscle mass (P = 0.023). After adjusting for age, waist circumference-to-height ratio, smoking status, alcohol consumption, frequency of physical activity, self-reported obesity, weight-loss efforts, and monthly household income, girls with low muscle mass (LMM) were 2.60 times more at risk of developing depression than girls with normal muscle mass (95% confidence interval [CI], 1.05-6.49; P = 0.040). This trend was similar for girls with LMM with obesity (95% CI, 1.00-11.97; P = 0.049).

CONCLUSION

Adolescent girls who have insufficient muscle mass are more likely to report depressed mood than girls who have ideal muscle mass. Interventions for maintaining proper muscle mass are required.

Independent Association Between Cardio-Ankle Vascular Index and Sarcopenia in Older U.K. Adults

OBJECTIVES

To investigate the correlation between sarcopenia and arterial stiffness in Caucasians, centering on the relationship between skeletal mass index (SMI) and the cardio-ankle vascular index (CAVI) to assess the use of CAVI in predicting sarcopenia.

DESIGN CROSS-SECTIONAL SETTING

United Kingdom.

PARTICIPANTS

UK adults aged 45 years and over (N = 366, n = 177 male, n = 189 female).

MEASUREMENTS

Bioimpedance analysis was used to derive SMI. CAVI score was calculated using a vascular screening system. Handgrip strength was measured using a standard dynamometer.

RESULTS

Average CAVI was significantly correlated with SMI (correlation coefficient (r) = -0.285, p < .001), with higher correlation in women (r = -0.416, p < .001) than men (r = -0.214, p = .01). CAVI had the highest correlation with SMI from appendicular muscle (fat-free mass in men, r = -0.253, p = .002; predicted muscle mass in women, r = -0.436, p < .001). There was a significant difference in average CAVI between groups, with participants who were not sarcopenic having lower CAVI (8.98) than those who were sarcopenic (9.80) (p < .001, t-test). Linear regression was performed using SMI as the dependent variable. After adjustment for age, average CAVI was a significant predictor of SMI in women (beta = -0.332, p < .001) but not men.

CONCLUSION

Indices of sarcopenia are independently associated with a higher CAVI, with greater correlation in women than men. The CAVI can be used to assess overall vascular compliance and may be a useful operator-independent tool that can be used to measure sarcopenia and its cardiovascular implications in older adults. J Am Geriatr Soc 67:317-322, 2019.

Lactate Promotes Myoblast Differentiation and Myotube Hypertrophy via a Pathway Involving MyoD In Vitro and Enhances Muscle Regeneration In Vivo

Lactate is a metabolic substrate mainly produced in muscles, especially during exercise. Recently, it was reported that lactate affects myoblast differentiation; however, the obtained results are inconsistent and the in vivo effect of lactate remains unclear. Our study thus aimed to evaluate the effects of lactate on myogenic differentiation and its underlying mechanism. The differentiation of C2C12 murine myogenic cells was accelerated in the presence of lactate and, consequently, myotube hypertrophy was achieved. Gene expression analysis of myogenic regulatory factors showed significantly increased myogenic determination protein (MyoD) gene expression in lactate-treated cells compared with that in untreated ones. Moreover, lactate enhanced gene and protein expression of myosin heavy chain (MHC). In particular, lactate increased gene expression of specific MHC isotypes, MHCIIb and IId/x, in a dose-dependent manner. Using a reporter assay, we showed that lactate increased promoter activity of the MHCIIb gene and that a MyoD binding site in the promoter region was necessary for the lactate-induced increase in activity. Finally, peritoneal injection of lactate in mice resulted in enhanced regeneration and fiber hypertrophy in glycerol-induced regenerating muscles. In conclusion, physiologically high lactate concentrations modulated muscle differentiation by regulating MyoD-associated networks, thereby enhancing MHC expression and myotube hypertrophy in vitro and, potentially, in vivo.

Financial impact of sarcopenia or low muscle mass - A short review

BACKGROUND & AIMS

Low muscle mass is associated with increased falls, medical complications, length of hospital stay and loss of independence. An increasing number of studies has also shown the association between sarcopenia and health care expenditure. The following narrative review summarizes the current evidence on the economic relevance of low muscle mass (MM) or sarcopenia.

METHODS

An extensive search of the literature in Medline identified twelve studies in English, which evaluated direct and indirect health care expenditure in patients with low muscle mass or sarcopenia (low MM and strength or mobility).

RESULTS

Three studies analysed the cost of age-related loss of MM or strength in large surveys of the general, older population. Six retrospective analyses evaluated perioperative medical costs related to low MM in primarily older patients from different medical areas. One prospective study presented hospital costs related to sarcopenia in patients with gastric cancer. Two studies presented data from general hospital patients. Despite the difference in diagnostic criteria, study population and statistical design, low MM and sarcopenia were consistently identified as predictors of increased health care expenditure in community, perioperative and general hospital settings.

CONCLUSIONS

Low MM and sarcopenia are prevalent and associated with significantly higher health care costs. Considering the demographic change, which will lead to an increasing number of patients with sarcopenia, every effort should be made to identify and treat patients with sarcopenia. The use of a unified definition and diagnostic criteria would allow a better comparison of data.

Developing sarcopenia criteria and cutoffs for an older Caucasian cohort - a strictly biometrical approach

Background

The aim of this strictly statistical approach was to provide a figure discrimination in a homogeneous cohort that is based on a main component, which includes disability, physical performance, and autonomy parameters.

Methods

We used data of 939 community-dwelling men aged ≥70 years, living in the area of Erlangen-Nürnberg, Germany. Briefly, we conducted a scaled principal component analysis based on criteria related to "physical function", "disability", "weakness", and "autonomy" to identify men who are likely to have sarcopenia as per the recognized sarcopenia criteria. Next, we applied fast-and-frugal decision trees, logistic regression, and classification and regression decision trees to classify men with and without sarcopenia, applying the 5% prevalence rate identified for this cohort by recent studies.

Results

In summary, the best fast-and-frugal decision trees included gait velocity, handgrip strength, and two skeletal muscle mass indices (SMI) - appendicular skeletal muscle mass (ASMM)/body mass index (BMI) and ASMM/height². Briefly, men below the cutoff point of 1.012 m/s for gait velocity were directly classified as sarcopenic. Faster men with a handgrip strength of >34.5 kg were excluded from further screening, while their weaker peers were assessed for SMI. Firstly, an ASMM/BMI-based exclusion criterion of >0.886 indicates no sarcopenia; while in men with a lower BMI-based SMI, an ASMM/height² of <7.25 kg/m² indicates sarcopenia. Of importance, about 72% of the participants can be classified without an SMI assessment.

Conclusion

The present approach that applied recognized sarcopenia criteria and was based on a predominately functional understanding of sarcopenia provided a simple and feasible decision rule for sarcopenia discrimination. In summary, we consider our approach as a strictly biometrical contribution within the development of sarcopenia screening methods. However, our tool needs to be further evaluated to validate its appropriateness to discriminate sarcopenia in this relevant cohort.

Associations between high-risk alcohol consumption and sarcopenia among postmenopausal women

OBJECTIVE

Sarcopenia is an age-related process, leading to cardio-metabolic diseases and disabilities. High-risk drinking is also closely related to diabetes, hypertension, and dyslipidemia, which are modifiable risk factors for sarcopenia. In the present study, we aimed to investigate the association between alcohol-drinking patterns and sarcopenia in Korean postmenopausal women.

METHODS

Data from 2,373 postmenopausal women were analyzed from the 2008 to 2011 Korean National Health and Nutrition Examination Survey. We defined sarcopenia as two standard deviations below the sex-specific means of the appendicular skeletal muscle/weight (percentage) values of a young reference group. Participants were categorized into three groups according to alcohol-drinking patterns, as assessed by the Alcohol Use Disorders Identification Test questionnaire. The odds ratios and 95% confidence intervals for sarcopenia were calculated using multiple logistic regression analyses.

RESULTS

In total, 8.2% of Korean postmenopausal women met criteria for sarcopenia. The prevalence of sarcopenia increased from low-risk to high-risk alcohol-drinking groups as follows: 7.6, 11.0, and 22.7%, respectively. Compared with the low-risk group, the odds ratio (95% confidence interval) for the high-risk group was 4.29 (1.87-9.82) after adjusting for age, body mass index, systolic blood pressure, total cholesterol, fasting blood glucose, household income, education level, daily calorie intake, current smoking and regular exercise, and household food security status CONCLUSIONS:: High-risk alcohol drinking was associated with a higher risk of sarcopenia in postmenopausal Korean women.

Clinical usefulness of psoas muscle thickness for the diagnosis of sarcopenia in patients with liver cirrhosis

Background/Aims

The most widely used method for diagnosing sarcopenia is the skeletal muscle index (SMI). Several studies have suggested that psoas muscle thickness per height (PMTH) is also effective for detecting sarcopenia and predicting prognosis in patients with cirrhosis. The aim of this study was to evaluate the optimal cutoff values of PMTH for detecting sarcopenia in cirrhotic patients.

Methods

All cirrhotic patients who underwent abdominal computed tomography (CT) scan including L3 and umbilical levels for measuring SMI and transverse psoas muscle thickness, respectively, were included. Two definitions of sarcopenia were used: (1) sex-specific cutoffs of SMI (≤52.4 cm² /m² in men and ≤38.5 cm² /m² in women) for SMI-sarcopenia and (2) cutoff of PMTH (<16.8 mm/m) for PMTH-sarcopenia.

Results

Six hundred fifty-three patients were included. The average age was 53.6 ± 10.2 years, and 499 patients (76.4%) were men. PMTH correlated well with SMI in both men and women (P<0.001). Two hundred forty-one (36.9%) patients met the criteria for SMI-sarcopenia. The best PMTH cutoff values for predicting SMI-sarcopenia were 17.3 mm/m in men and 10.4 mm/m in women, and these were defined as sex-specific cutoffs of PMTH (SsPMTH). The previously published cutoff of PMTH was defined as sex-nonspecific cutoff of PMTH (SnPMTH). Two hundred thirty (35.2%) patients were diagnosed with SsPMTH-sarcopenia, and 280 (44.4%) patients were diagnosed with SnPMTH-sarcopenia. On a multivariate Cox regression analysis, SsPMTH-sarcopenia (hazard ratio [HR], 1.944; 95% confidence interval [CI], 1.144–3.304; P=0.014) was significantly associated with mortality, while SnPMTH-sarcopenia was not (HR, 1.446; 95% CI, 0.861–2.431; P=0.164).

Conclusions

PMTH was well correlated with SMI in cirrhotic patients. SsPMTH-sarcopenia was an independent predictor of mortality in these patients and more accurately predicted mortality compared to SnPMTH-sarcopenia.

Characterization of Ageing- and Diet-Related Swine Models of Sarcopenia and Sarcopenic Obesity

Sarcopenia and sarcopenic obesity are currently considered major global threats for health and well-being. However, there is a lack of adequate preclinical models for their study. The present trial evaluated the suitability of aged swine by determining changes in adiposity, fatty acids composition, antioxidant status and lipid peroxidation, development of metabolic disturbances and structural changes in tissues and organs. Iberian sows with clinical evidence of aging-related sarcopenia were fed a standard diet fulfilling their maintenance requirements or an obesogenic diet for 100 days. Aging and sarcopenia were related to increased lipid accumulation and cellular dysfunction at both adipose tissue and non-adipose ectopic tissues (liver and pancreas). Obesity concomitant to sarcopenia aggravates the condition by increasing visceral adiposity and causing dyslipidemia, insulin resistance and lipotoxicity in non-adipose tissues. These results support that the Iberian swine model represents certain features of sarcopenia and sarcopenic obesity in humans, paving the way for future research on physiopathology of these conditions and possible therapeutic targets.

Myoblast mitochondrial respiration is decreased in chronic binge alcohol administered simian immunodeficiency virus-infected antiretroviral-treated rhesus macaques

Work from our group demonstrated that chronic binge alcohol (CBA)-induces mitochondrial gene dysregulation at end-stage disease of simian immunodeficiency virus (SIV) infection in antiretroviral therapy (ART) naïve rhesus macaques. Alterations in gene expression can disrupt mitochondrial homeostasis and in turn contribute to the risk of metabolic comorbidities characterized by loss of skeletal muscle (SKM) functional mass that are associated with CBA, human immunodeficiency virus (HIV) infection, and prolonged ART. The aim of this study was to examine the interaction of CBA and ART on SKM fiber oxidative capacity and myoblast mitochondrial respiration in asymptomatic SIV-infected macaques. SKM biopsies were obtained and myoblasts isolated at baseline and 11 months post-SIV infection from CBA/SIV/ART+ and from sucrose (SUC)-treated SIV-infected (SUC/SIV/ART+) macaques. CBA and ART decreased succinate dehydrogenase (SDH) activity in type 1 and type 2b fibers as determined by immunohistochemistry. Myoblasts isolated from CBA/SIV/ART+ macaques showed decreased maximal oxygen consumption rate (OCR) compared to myoblasts from control macaques. Maximal OCR was significantly increased in control myoblasts following incubation with formoterol, a beta adrenergic agonist, and this was associated with increased PGC-1α expression and mtDNA quantity. Additionally, formoterol treatment of myoblasts isolated from CBA/SIV/ART+ macaques partially restored maximal OCR to levels not significantly different from control. These results show that CBA in combination with ART impairs myoblast mitochondrial homeostasis in SIV-infected macaques. Moreover, our findings suggest that adrenergic agonists can potentially ameliorate mitochondrial dysfunction. Future studies will elucidate whether physical exercise in HIV patients with alcohol use disorder can improve mitochondrial health.

Sarcopenia in cancer survivors is associated with increased cardiovascular disease risk

PURPOSE

The aim of this study was to assess the association between sarcopenia and cardiovascular disease (CVD) risk in cancer survivors.

METHODS

We analyzed a consecutive series of 683 cancer survivors from the Korean National Health and Nutritional Exam Survey (2008-2011 years). Sarcopenia was defined as the appendicular skeletal muscle mass divided by weight (Kg) < 1 standard deviation below the sex-specific healthy population aged 20-39 years. CVD risks were assessed using the Framingham Risk Score (FRS), which were divided by tertile. Predictors of higher shift of FRS tertile by sex were calculated by stratified ordinal logistic regression analyses.

RESULTS

Proportions of sarcopenia were 24.2% in males and 22.5% in females. Sarcopenic survivors were more likely to have a higher body mass index, waist circumference, blood pressure and fasting glucose level, and a lower high-density lipoprotein compared to those without sarcopenia. Sarcopenia was associated with a higher shift of FRS tertile (common odds ratio, 2.67; 95% confidence interval, 1.18-6.52, P < 0.001) in males. However, this association was not significant in female survivors.

CONCLUSIONS

Sarcopenia was associated with an increased CVD risk in Korean male cancer survivors. Interventions to prevent sarcopenia may be necessary to improve cardiovascular burden in cancer survivors.

The association between muscle mass deficits and arterial stiffness in middle-aged men

BACKGROUND AND AIMS

Early diagnosis of arteriosclerosis is fundamental for the prevention of cardiovascular morbidity and mortality. The current study was performed to identify major predictors of arteriosclerosis and to assess the association between arterial stiffness as measured by cardio-ankle vascular index (CAVI) and muscle mass deficit (MMD) estimated by bioelectrical impedance analysis (BIA) in middle-aged men.

METHODS AND RESULTS

Data were gathered from 3356 middle-aged men who visited a health promotion center. CAVI was measured as an index of arterial stiffness. Body composition analysis was performed using BIA. MMD was positively associated with CAVI in the regression model. The odds ratios for high-CAVI (≥9.0) rose with MMD grade in a dose-dependent manner after adjusting for age, lifestyle factors and current medication use. The estimated mean CAVI rose as MMD grade increased (P for trend >0.001).

CONCLUSIONS

MMD estimated from BIA was positively associated with arterial stiffness in middle-aged men. These findings show a close interaction between low muscle mass and cardiovascular risk.

Association between muscle function and body composition, vitamin D status, and blood glucose in postmenopausal women with type 2 diabetes

AIMS

The aim of this study was to examine the association between muscle function, and body composition, vitamin D status, and blood glucose in post-menopausal women with type 2 diabetes (T2D).

METHODS

Forty post-menopausal women (62.48±7.67years; 154.6±5.11cm; 73.93±15.43kg; 31.13±5.82 BMI kg/m²) with a diagnosis of T2D participated in this cross-sectional study. The patients performed fasting blood sample exams, anthropometrics assessments, body composition, and clinical exams. Subjects performed physical tests including handgrip, timed up and go, 30-s chair stand, arm curl, and sit-to-stand. The correlation between the parameters of physical tests, age, body composition, vitamin D, and blood glucose was assessed by Pearson correlation.

RESULTS

The results showed there were significant correlations between blood glucose and relative strength (R=-0.398, p=0.011), arm curl test (R=-0.367 and p=0.020), and hip flexion (R=0.427, p=0.006).

CONCLUSIONS

These findings are important because they highlight the importance of resistance training in individuals with T2D and the relationship with a fat increase during a dicrease process. Furthermore, the concentration of serum glucose might be associated with decreases in muscle strength and muscle function in older adults. Thus, T2D patients should be involved with strength training to improve the strength and the muscle hypertrophy.

Association of sarcopenic obesity predicted by anthropometric measurements and 24-y all-cause mortality in elderly men: The Kuakini Honolulu Heart Program

OBJECTIVE

The aim of this study was to investigate the association between anthropometric measurements of sarcopenic obesity and all-cause mortality.

METHODS

The study included 2309 Japanese-American men ages 71 to 93 y. Mortality data were available for up to 24 y of follow-up. Sarcopenic obesity defined by three patterns of obesity indexes (body mass index [BMI], percent body fat [%BF] and waist circumference [WC]) and skeletal muscle index estimated by anthropometric measurements.

RESULTS

Of the 2309 participants, 2210 deaths were reported during the mean follow-up period of 11.7 y. Risk for death was significantly increased with sarcopenia after adjusting for baseline age, lifestyle variables, hypertension, diabetes, and cognitive scores (hazard ratio [HR], 1.26; 95% confidence interval [CI], 1.15-1.38). Risk for death was significantly decreased with obesity using WC and %BF to define obesity, but not BMI. Risk for death also was significantly increased in the sarcopenia group compared with the optimal group, regardless of which pattern of obesity indexes (BMI, %BF, and WC) was used. Risk for death was significantly increased in sarcopenic obesity defined by WC (HR, 1.19; 95% CI, 1.02-1.38), borderline in the BMI-defined group, and not significant in the %BF-defined group.

CONCLUSION

All-cause mortality was increased in men with sarcopenic obesity defined by WC, but not BMI and %BF. Sarcopenia was a stronger predictor of all-cause mortality in this cohort >70 y of age. These results suggest that anthropometric definitions for sarcopenia and sarcopenic obesity are clinically useful as a predictor of all-cause mortality.

Irisin prevents and restores bone loss and muscle atrophy in hind-limb suspended mice

We previously showed that Irisin, a myokine released from skeletal muscle after physical exercise, plays a central role in the control of bone mass. Here we report that treatment with recombinant Irisin prevented bone loss in hind-limb suspended mice when administered during suspension (preventive protocol) and induced recovery of bone mass when mice were injected after bone loss due to a suspension period of 4 weeks (curative protocol). MicroCT analysis of femurs showed that r-Irisin preserved both cortical and trabecular bone mineral density, and prevented a dramatic decrease of the trabecular bone volume fraction. Moreover, r-Irisin protected against muscle mass decline in the hind-limb suspended mice, and maintained the fiber cross-sectional area. Notably, the decrease of myosin type II expression in unloaded mice was completely prevented by r-Irisin administration. Our data reveal for the first time that Irisin retrieves disuse‐induced bone loss and muscle atrophy. These findings may lead to development of an Irisin-based therapy for elderly immobile osteoporotic and physically disable patients, and might represent a countermeasure for astronauts subjected to microgravity-induced bone and muscle losses.

Cardiometabolic risk factors in type 2 diabetes with high fat and low muscle mass: At baseline and in response to exercise

OBJECTIVE

To examine the interplay between high fat and low muscle mass on cardiometabolic risk factors at baseline and in response to exercise in type 2 diabetes.

METHODS

Using baseline percent body fat and skeletal muscle mass index, 248 participants were divided into high fat versus low fat and low muscle versus high muscle. Linear mixed models were used to examine the main effects of fat mass and muscle mass and their interaction on baseline cardiometabolic risk factors and changes in risk factors in response to 6-month exercise training.

RESULTS

At baseline, there was a fat mass by muscle mass interaction effect on hemoglobin A_1c (HbA_1c ; P = 0.009), suggesting that low muscle was associated with elevated HbA_1c in those with high fat but not low fat. Significant interactions between baseline fat mass and muscle mass on the exercise-induced changes in visceral adipose tissue, insulin resistance, and triglyceride concentration indicated that low muscle attenuated the exercise responses in participants with high fat at baseline (all P < 0.05).

CONCLUSIONS

High fat and low muscle may be synergistically associated with higher HbA_1c in type 2 diabetes. In participants with high fat mass, low muscle mass may attenuate exercise-induced improvements in some cardiometabolic risk factors.

The association between sleep duration and physical performance in Chinese community-dwelling elderly

Background

Physical performance is an important healthy factor in elder people. Good living habits, which include sleep, can maintain physical strength and physical performance. The aim of the present study was to conduct a cross-sectional study to determine the association between total sleep duration and physical performance.

Methods

Our study population comprised residents of the township central hospital in the suburban of Tianjin, China. We measured muscle strength, walk speed and balance function by grip, 4-m walk test and timed up and go test (TUGT). We divided sleep duration into four groups <7h, 7-8h, >8-9h, >9h.

Results

A total 898 participants had completed data (392 men and 506 women, mean age 67.71 years). In man, adjusted sleep duration was associated with lower grip in > 9 h group, the mean value (95% CI) was 0.429 (0.409, 0.448), and longer TUGT time was also associated with long sleep duration, 10.46s (9.97 s, 10.95 s). In women, adjusted slower 4-m walk speed present an inverse U-shaped relation with sleep duration, by 0.93 m/s (0.86 m/s, 0.98 m/s), 0.97 m/s (0.96 m/s, 1.00 m/s), 0.97 m/s (0.95 m/s, 0.99 m/s) and 0.92 m/s (0.89 m/s, 0.96 m/s); longer TUGT time were associated with long sleep duration (> 9 h), by 11.23 s (10.70 s, 11.77 s).

Conclusion

In Chinese community-dwelling elderly, lower muscle strength and lower balance function were associated with long sleep duration in men. Slower walk speed and lower balance function were associated with long sleep duration in women.

Gene-based genome-wide association study identified 19p13.3 for lean body mass

Lean body mass (LBM) is a complex trait for human health. To identify genomic loci underlying LBM, we performed a gene-based genome-wide association study of lean mass index (LMI) in 1000 unrelated Caucasian subjects, and replicated in 2283 unrelated Caucasians subjects. Gene-based association analyses highlighted the significant associations of three genes UQCR, TCF3 and MBD3 in one single locus 19p13.3 (discovery p = 6.10 × 10-5, 1.65 × 10-4 and 1.10 × 10-4; replication p = 2.21 × 10-3, 1.84 × 10-3 and 6.95 × 10-3; combined p = 2.26 × 10-6, 4.86 × 10-6 and 1.15 × 10-5, respectively). These results, together with the known functional relevance of the three genes to LMI, suggested that the 19p13.3 region containing UQCR, TCF3 and MBD3 genes was a novel locus underlying lean mass variation.

Exercise training in older adults, what effects on muscle oxygenation? A systematic review

AIM

To determine the effects of different modality of exercise training programs on muscle oxygenation in older adults.

METHODS

Relevant articles were searched in PubMed, Web of Science, Science Direct and Scopus, using the keywords: "Aged" AND "Muscle oxygenation" AND (Exercise OR "Exercise therapy" OR "Exercise Movement Techniques" OR Hydrotherapy), without limitation concerning the publication date. To be included in the full analysis, the study had to be a randomized controlled trial in which older adults participants (mean age: 65 years at least) were submitted to an exercise-training program and muscle oxygenation assessment.

RESULTS

The searches resulted in 1238 articles from which 7 met all the inclusion criteria. The trials involved 370 older adults (68.7±1.7years), healthy and with peripheral arterial disease. Studies included resistance and endurance exercises as well as walking sessions. Training sessions were 2-6 time per week, lasted 3-24 months and with different training intensity throughout studies. After a long-term resistance training, healthy older adults showed enhanced muscle oxygen extraction capacity, regulation of vessels and vascular endothelium function; endurance training is reported to improve microvascular blood flow and matching of oxygen delivery to oxygen utilization, muscle oxidative capacity and muscle saturation, and walking sessions results in better muscle oxygen availability and muscle oxygen extraction capacity in older adults with peripheral arterial disease.

CONCLUSIONS

This review supports the fact that depending on the clinical status of the participants and the modality, exercise training improves different aspects of the muscle oxygenation in older adults.

Involvement of Cbl-b-mediated macrophage inactivation in insulin resistance

Aging and overnutrition cause obesity in rodents and humans. It is well-known that obesity causes various diseases by producing insulin resistance (IR). Macrophages infiltrate the adipose tissue (AT) of obese individuals and cause chronic low-level inflammation associated with IR. Macrophage infiltration is regulated by the chemokines that are released from hypertrophied adipocytes and the immune cells in AT. Saturated fatty acids are recognized by toll-like receptor 4 (TLR4) and induce inflammatory responses in AT macrophages (ATMs). The inflammatory cytokines that are released from activated ATMs promote IR in peripheral organs, such as the liver, skeletal muscle and AT. Therefore, ATM activation is a therapeutic target for IR in obesity. The ubiquitin ligase Casitas b-lineage lymphoma-b (Cbl-b) appears to potently suppress macrophage migration and activation. Cbl-b is highly expressed in leukocytes and negatively regulates signals associated with migration and activation. Cbl-b deficiency enhances ATM accumulation and IR in aging- and diet-induced obese mice. Cbl-b inhibits migration-related signals and SFA-induced TLR4 signaling in ATMs. Thus, targeting Cbl-b may be a potential therapeutic strategy to reduce the IR induced by ATM activation. In this review, we summarize the regulatory functions of Cbl-b in ATMs.

Molecular signatures of age-associated chronic degeneration of shoulder muscles

Chronic muscle diseases are highly prevalent in the elderly causing severe mobility limitations, pain and frailty. The intrinsic molecular mechanisms are poorly understood due to multifactorial causes, slow progression with age and variations between individuals. Understanding the underlying molecular mechanisms could lead to new treatment options which are currently limited. Shoulder complaints are highly common in the elderly, and therefore, muscles of the shoulder's rotator cuff could be considered as a model for chronic age-associated muscle degeneration. Diseased shoulder muscles were characterized by muscle atrophy and fatty infiltration compared with unaffected shoulder muscles. We confirmed fatty infiltration using histochemical analysis. Additionally, fibrosis and loss of contractile myosin expression were found in diseased muscles. Most cellular features, including proliferation rate, apoptosis and cell senescence, remained unchanged and genome-wide molecular signatures were predominantly similar between diseased and intact muscles. However, we found down-regulation of a small subset of muscle function genes, and up-regulation of extracellular region genes. Myogenesis was defected in muscle cell culture from diseased muscles but was restored by elevating MyoD levels. We suggest that impaired muscle functionality in a specific environment of thickened extra-cellular matrix is crucial for the development of chronic age-associated muscle degeneration.

Combination of Recreational Soccer and Caloric Restricted Diet Reduces Markers of Protein Catabolism and Cardiovascular Risk in Patients with Type 2 Diabetes

BACKGROUND

Moderate calorie-restricted diets and exercise training prevent loss of lean mass and cardiovascular risk. Because adherence to routine exercise recommendation is generally poor, we utilized recreational soccer training as a novel therapeutic exercise intervention in type 2 diabetes (T2D) patients.

OBJECTIVE

We compared the effects of acute and chronic soccer training plus calorie-restricted diet on protein catabolism and cardiovascular risk markers in T2D.

DESIGN, SETTING AND SUBJECTS

Fifty-one T2D patients (61.1±6.4 years, 29 females: 22 males) were randomly allocated to the soccer+diet-group (SDG) or to the diet-group (DG). The 40-min soccer sessions were held 3 times per week for 12 weeks.

RESULTS

Nineteen participants attended 100% of scheduled soccer sessions, and none suffered any injuries. The SDG group showed higher levels of growth hormone (GH), free fatty acids and ammonia compared with DG. After 12 weeks, insulin-like growth factor binding protein (IGFPB)-3 and glucose levels were lower in SDG, whereas insulin-like growth factor (IGF)-1/ IGFBP-3 ratio increased in both groups. After the last training session, an increase in IGF-1/IGFBP-3 and attenuation in ammonia levels were suggestive of lower muscle protein catabolism.

CONCLUSIONS

Recreational soccer training was popular and safe, and was associated with decreased plasma glucose and IGFBP-3 levels, decreased ammoniagenesis, and increased lipolytic activity and IGF-1/IGFBP-3 ratio, all indicative of attenuated catabolism.

Favorable effects of skeletal muscle on bone are distinguished according to gender and skeletal sites

Objectives

The aim of this study was to investigate associations between skeletal muscle mass and bone mineral density according to gender and skeletal sites.

Methods

Using the data from Korean National Health and Nutrition Examination Survey (KNHANES IV) 2009, a total of 711 males and 847 females over 65 years of age were evaluated. Bone mineral density (BMD) and body composition were assessed using dual-energy X-ray absorptiometry.

Results

Relative appendicular skeletal muscle (RASM) was positively related with the femur BMD with a stronger relationship in males (r = 0.207, p < 0.001) than in females (r = 0.095, p < 0.05). However, lumbar spine BMDs in both males and females did not show any significant associations with the RASM value. In the logistic regression for osteoporosis expressed as a decrease of risk per increase of RASM by 1 standard deviation (SD) of the same sex healthy reference group, the age- and BMI-adjusted odds ratio (OR) for osteoporosis was 0.42 (95% CI 0.12–0.76) in the femur neck and 0.24 (95% CI 0.07–0.76) in the total hip for males. Among females, the age- and BMI-adjusted OR for osteoporosis was 0.65 (95% CI 0.33–1.00), which showed importance only in the total hip.

Conclusions

Higher RASM was significantly associated with lower risk for osteoporosis and the areas at the femur neck and total hip appeared to more likely be affected positively by muscle. Moreover, because males showed faster muscle loss with aging than females, the bones of males may be more prone to favorable effects of muscle.

Dynapenia and Metabolic Health in Obese and Nonobese Adults Aged 70 Years and Older: The LIFE Study

OBJECTIVE

The purpose of this study was to examine the relationship between dynapenia and metabolic risk factors in obese and nonobese older adults.

METHODS

A total of 1453 men and women (age ≥70 years) from the Lifestyle Interventions and Independence for Elders (LIFE) Study were categorized as (1) nondynapenic/nonobese (NDYN-NO), (2) dynapenic/nonobese (DYN-NO), (3) nondynapenic/obese (NDYN-O), or (4) dynapenic/obese (DYN-O), based on muscle strength (Foundation for the National Institute of Health criteria) and body mass index. Dependent variables were blood lipids, fasting glucose, blood pressure, presence of at least 3 metabolic syndrome (MetS) criteria, and other chronic conditions.

RESULTS

A significantly higher likelihood of having abdominal obesity criteria in NDYN-NO compared with DYN-NO groups (55.6 vs 45.1%, P ≤ .01) was observed. Waist circumference also was significantly higher in obese groups (DYN-O = 114.0 ± 12.9 and NDYN-O = 111.2 ± 13.1) than in nonobese (NDYN-NO = 93.1 ± 10.7 and DYN-NO = 92.2 ± 11.2, P ≤ .01); and higher in NDYN-O compared with DYN-O (P = .008). Additionally, NDYN-O demonstrated higher diastolic blood pressure compared with DYN-O (70.9 ± 10.1 vs 67.7 ± 9.7, P ≤ .001). No significant differences were found across dynapenia and obesity status for all other metabolic components (P > .05). The odds of having MetS or its individual components were similar in obese and nonobese, combined or not with dynapenia (nonsignificant odds ratio [95% confidence interval]).

CONCLUSION

Nonobese dynapenic older adults had fewer metabolic disease risk factors than nonobese and nondynapenic older adults. Moreover, among obese older adults, dynapenia was associated with lower risk of meeting MetS criteria for waist circumference and diastolic blood pressure. Additionally, the presence of dynapenia did not increase cardiometabolic disease risk in either obese or nonobese older adults.

Circular RNAs in monkey muscle: age-dependent changes

Circular RNAs (circRNAs) have been identified in numerous species, including human, mouse, nematode, and coelacanth. They are believed to function as regulators of gene expression at least in part by sponging microRNAs. Here, we describe the identification of circRNAs in monkey (Rhesus macaque) skeletal muscle. RNA sequencing analysis was employed to identify and annotate ∼12,000 circRNAs, including numerous circular intronic RNAs (ciRNAs), from skeletal muscle of monkeys of a range of ages. Reverse transcription followed by real-time quantitative (q)PCR analysis verified the presence of these circRNAs, including the existence of several highly abundant circRNAs, and the differential abundance of a subset of circRNAs as a function of age. Taken together, our study has documented systematically circRNAs expressed in skeletal muscle and has identified circRNAs differentially abundant with advancing muscle age. We propose that some of these circRNAs might influence muscle function.

Mitochondrial Dynamics Is Linked to Longevity and Protects from End-Organ Injury: The Emerging Role of Sirtuin 3

SIGNIFICANCE

Mitochondrial integrity is instrumental in protecting against damage associated with aging and a variety of chronic disease conditions. Mitochondrial silent information regulator 3 (Sirt3) plays pivotal roles in maintaining mitochondrial homeostasis by regulating different aspects of the organelle processes.

RECENT ADVANCES

Mitochondria are highly dynamic organelles that constantly fuse and divide to maintain normal cell function, and perturbation in mitochondrial dynamics is responsible for mitochondrial dysfunction. Improved knowledge of mitochondrial physiology has disclosed the pleiotropic role of Sirt3 in mitochondria and shows how alterations in protein expression and/or activity may have an important impact on aging-associated organ dysfunction.

CRITICAL ISSUES

This review describes updated experimental evidence on the role of mitochondrial dysfunction during aging and renal diseases and highlights the emerging role of Sirt3 as a crucial regulator of mitochondrial dynamics.

FUTURE DIRECTIONS

Strategies that activate Sirt3 may offer attractive therapies to achieve healthy longevity and preserve functional integrity of multiple organs. Antioxid. Redox Signal. 25, 185-199.

Identification of morphological markers of sarcopenia at early stage of aging in skeletal muscle of mice

The gastrocnemius muscle (GM) of young (3months) and aged (12months) female wild-type C57/BL6 mice was examined by light and electron microscopy, looking for the presence of structural changes at early stage of the aging process. Morphometrical parameters including body and gastrocnemius weights, number and type of muscle fibers, cross section area (CSA), perimeter, and Feret's diameter of single muscle fiber, were measured. Moreover, lengths of the sarcomere, A-band, I-band, H-zone, and number and CSA of intermyofibrillar mitochondria (IFM), were also determined. The results provide evidence that 12month-old mice had significant changes on skeletal muscle structure, beginning with the reduction of gastrocnemius weight to body weight ratio, compatible with an early loss of skeletal muscle function and strength. Moreover, light microscopy revealed increased muscle fibers size, with a significant increase on their CSA, perimeter, and diameter of both type I and type II muscle fibers, and a reduction in the percentage of muscle area occupied by type II fibers. Enhanced connective tissue infiltrations, and the presence of centrally nucleated muscle fibers, were also found in aged mice. These changes may underlie an attempt to compensate the loss of muscle mass and muscle fibers number. Furthermore, electron microscopy discovered a significant age-dependent increase in the length of sarcomeres, I and H bands, and reduction on the overlapped actin/myosin length, supporting contractile force loss with age. Electron microscopy also showed an increased number and CSA of IFM with age, which may reveal more endurance at 12months of age. Together, mice at early stage of aging already show significant changes in gastrocnemius muscle morphology and ultrastructure that are suggestive of the onset of sarcopenia.

Environmental 24-hr Cycles Are Essential for Health

Circadian rhythms are deeply rooted in the biology of virtually all organisms. The pervasive use of artificial lighting in modern society disrupts circadian rhythms and can be detrimental to our health. To investigate the relationship between disrupting circadian rhythmicity and disease, we exposed mice to continuous light (LL) for 24 weeks and measured several major health parameters. Long-term neuronal recordings revealed that 24 weeks of LL reduced rhythmicity in the central circadian pacemaker of the suprachiasmatic nucleus (SCN) by 70%. Strikingly, LL exposure also reduced skeletal muscle function (forelimb grip strength, wire hanging duration, and grid hanging duration), caused trabecular bone deterioration, and induced a transient pro-inflammatory state. After the mice were returned to a standard light-dark cycle, the SCN neurons rapidly recovered their normal high-amplitude rhythm, and the aforementioned health parameters returned to normal. These findings strongly suggest that a disrupted circadian rhythm reversibly induces detrimental effects on multiple biological processes.

Targeting Cognitive Frailty: Clinical and Neurobiological Roadmap for a Single Complex Phenotype

Late-life cognitive disorders may be prevented by influencing age-related conditions such as frailty, characterized by decreased resistance to stressors and increased risk for adverse health outcomes. In the present review article, we examined clinical and epidemiological studies investigating the possible role of different frailty models in modulating the risk of Alzheimer's disease (AD), dementia, vascular dementia (VaD), mild cognitive impairment (MCI), and late-life cognitive impairment/decline that have been published over the past 3 years. Both deficit accumulation and physical frailty models were associated with late-life cognitive impairment/decline, incident dementia, AD, MCI, VaD, non-AD dementias, and AD pathology, proposing cognitive frailty as a new clinical construct with coexisting physical frailty and cognitive impairment in nondemented older subjects. Two subtypes of this new clinical condition have been recently proposed: "potentially reversible" cognitive frailty and "reversible" cognitive frailty. The physical factors should be physical prefrailty and frailty, while the cognitive impairment of potentially reversible cognitive frailty should be MCI (Clinical Dementia rating Scale = 0.5), while the cognitive impairment of reversible cognitive frailty should be pre-MCI Subjective Cognitive Decline (SCD), as recently proposed by the SCD Initiative Working Group. The mechanisms underlying the cognitive-frailty link are multifactorial and vascular, inflammatory, nutritional, and metabolic influences may be of major relevance. Considering both physical frailty and cognition as a single complex phenotype may be crucial in the prevention of dementia and its subtypes with secondary preventive trials on cognitive frail older subjects.

Contribution of Heritability and Epigenetic Factors to Skeletal Muscle Mass Variation in United Kingdom Twins

CONTEXT

Skeletal muscle mass (SMM) is one of the major components of human body composition, with deviations from normal values often leading to sarcopenia.

OBJECTIVE

Our major aim was to conduct a genome-wide DNA methylation study in an attempt to identify potential genomic regions associated with SMM.

DESIGN

This was a mixed cross-sectional and longitudinal study.

SETTING

Community-based study.

PARTICIPANTS

A total of 1550 middle-aged United Kingdom twins (monozygotic [MZ] and dizygotic [DZ]), 297 of which were repeatedly measured participated in the study.

MAIN OUTCOME MEASURE

Appendicular lean mass assessed using dual-energy X-ray absorptiometry technology, and methylated DNA immunoprecipitation sequencing DNA methylation profiling genome-wide were obtained from each individual.

RESULTS

Heritability estimate of SMM, with simultaneous adjustment for covariates obtained using variance decomposition analysis, was h(2) = 0.809 ± 0.050. After quality control and analysis of longitudinal stability, the DNA methylation data comprised of 723 029 genomic sites, with positive correlations between repeated measurements (Rrepeated = 0.114-0.905). Correlations between MZ and DZ twins were 0.51 and 0.38 at a genome-wide average, respectively, and clearly increased with Rrepeated. Testing for DNA methylation association with SMM in 50 discordant MZ twins revealed 36 081 nominally significant results, of which the top-ranked 134 signals (P < .01 and Rrepeated > 0.40) were subjected to replication in the sample of 1196 individuals. Seven SMM methylation association signals replicated at a false discovery rate less than 0.1, and these were located in or near genes DNAH12, CAND1, CYP4F29P, and ZFP64, which have previously been highlighted in muscle-related studies. Adjusting for age, smoking, and blood cell heterogeneity did not alter significance of these associations.

CONCLUSION

This epigenome-wide study, testing longitudinally stable methylation sites, discovered and replicated a number of associations between DNA methylation at CpG loci and SMM. Four replicated signals were related to genes with potential muscle functions, suggesting that the methylome of whole blood may be informative of SMM variation.

Associations of Low Muscle Mass and the Metabolic Syndrome in Caucasian and Asian Middle-aged and Older Adults

OBJECTIVE

Age-related declines in skeletal muscle mass may confer significant metabolic consequences for older adults. Associations of low muscle mass and metabolic syndrome (MetS) in Caucasians, and comparisons with associations observed in Asian populations, have not been reported. We examined associations of low muscle mass and metabolic syndrome (MetS) in Asian and Caucasian middle-aged and older men and women using criteria for low muscle mass.

DESIGN, SETTING AND PARTICIPANTS

Two population-based studies of Australian (Tasmanian Older Adult Cohort Study; TASOAC; N=1005) and Korean (Korean Sarcopenic Obesity Study; KSOS; N=376) community-dwelling adults, mean age 62 and 58 years, respectively.

MEASUREMENTS

Appendicular lean mass (aLM) determined by dual-energy X-ray absorptiometry and normalised to height squared (aLM/Ht2), weight (aLM/Wt) or body mass index (aLM/BMI). Participants in the lowest sex-specific 20% for aLM measures were defined as having low muscle mass. MetS was defined according to National Cholesterol Education Program Adult Treatment Panel III criteria.

RESULTS

Although Australians demonstrated generally unfavourable anthropometric and metabolic characteristics compared to Koreans, prevalence of MetS was similar (29.5% in Australians and 31.4% in Koreans, respectively). Low aLM/Ht2 was associated with significantly reduced likelihood of MetS in both Australians (OR: 0.30, 95% CI 0.19 - 0.46) and Koreans (OR: 0.31, 95% CI 0.16 - 0.62). Conversely, low aLM/BMI was associated with increased odds for MetS in Australians (OR: 1.78, 95% CI 1.12 - 2.84), but not Koreans (OR: 1.33, 95% CI = 0.67 - 2.64).

CONCLUSION

Low aLM/BMI is associated with significantly increased likelihood of MetS in Australian adults, but not Koreans, suggesting potential differences in effects of low muscle mass relative to body mass on cardiometabolic health in Caucasian and Asian middle-aged and older adults. Low muscle mass relative to height is associated with reduced likelihood of MetS in both populations.

Low skeletal muscle mass is associated with non-alcoholic fatty liver disease in Korean adults: the Fifth Korea National Health and Nutrition Examination Survey

BACKGROUND

Sarcopenia and non-alcoholic fatty liver disease (NAFLD) share similar pathophysiological mechanisms, and the relationship between sarcopenia and NAFLD has been recently investigated. The study investigated whether low skeletal muscle mass is differentially associated with NAFLD by gender in Korean adults.

METHODS

We conducted a cross-sectional analysis of the data from the Fifth Korea National Health and Nutrition Examination Survey. The skeletal muscle index (SMI) was obtained by the appendicular skeletal muscle mass divided by the weight. NAFLD was defined as a fatty liver index (FLI) ≥60 in the absence of other chronic liver disease.

RESULTS

Among the included subjects, 18.3% (SE: 1.4%) in men and 7.0% (SE: 0.7%) in women were classified as having FLI-defined NAFLD. Most of the risk factors for FLI-defined NAFLD showed a significant negative correlation with the SMI in both genders. Multiple logistic regression analysis showed that low SMI was associated with FLI-defined NAFLD, independent of other metabolic and lifestyle parameters in both genders [males: odds ratio (OR)=1.35; 95% confidence interval (CI): 1.17-1.54; females: OR=1.36; 95% CI: 1.18-1.55]. The magnitude of the association between FLI-defined NAFLD and low SMI was higher in middle aged to elderly males (OR=1.50; 95% CI: 1.22-1.84) than in males less than 45 years of age (OR=1.25; 95% CI: 1.02-1.52) and in premenopausal females (OR=1.50; 95% CI: 1.12-2.03) than in postmenopausal females (OR=1.36; 95% CI: 1.20-1.54).

CONCLUSIONS

Low SMI is associated with the risk of FLI-defined NAFLD independent of other well-known metabolic risk factors in both genders. This association may differ according to age group or menopausal status. Further studies are warranted to confirm this relationship.

Optimizing Ligand Efficiency of Selective Androgen Receptor Modulators (SARMs)

A series of selective androgen receptor modulators (SARMs) containing the 1-(trifluoromethyl)benzyl alcohol core have been optimized for androgen receptor (AR) potency and drug-like properties. We have taken advantage of the lipophilic ligand efficiency (LLE) parameter as a guide to interpret the effect of structural changes on AR activity. Over the course of optimization efforts the LLE increased over 3 log units leading to a SARM 43 with nanomolar potency, good aqueous kinetic solubility (>700 μM), and high oral bioavailability in rats (83%).

Ultrasound-Derived Abdominal Muscle Thickness Better Detects Metabolic Syndrome Risk in Obese Patients than Skeletal Muscle Index Measured by Dual-Energy X-Ray Absorptiometry

Sarcopenia has never been diagnosed based on site-specific muscle loss, and little is known about the relationship between site-specific muscle loss and metabolic syndrome (MetS) risk factors. To this end, this cross-sectional study aimed to investigate the relationship between site-specific muscle size and MetS risk factors. Subjects were 38 obese men and women aged 40-82 years. Total body fat and lean body mass were assessed by whole-body dual-energy X-ray absorptiometry (DXA) scan. Muscle thickness (MTH) was measured using B-mode ultrasound scanning in six body regions. Subjects were classified into general obesity (GO) and sarcopenic obesity (SO) groups using the threshold values of one standard deviation below the sex-specific means of either MTH or skeletal muscle index (SMI) measured by DXA. MetS risk score was acquired by standardizing and summing the following continuously distributed variables: visceral fat area, mean blood pressure, HbA1c, and serum triglyceride / high density lipoprotein cholesterol, to obtain the Z-score. Multiple regression analysis revealed that the MetS risk score was independently associated with abdominal MTH in all subjects, but not with MTH in other muscle regions, including the thigh. Although HbA1c and the number of MetS risk factors in the SO group were significantly higher than those in the GO group, there were no significant differences between GO and SO groups as defined by SMI. Ultrasound-derived abdominal MTH would allow a better assessment of sarcopenia in obese patients and can be used as an alternative to the conventionally-used SMI measured by DXA.

The emerging role of skeletal muscle oxidative metabolism as a biological target and cellular regulator of cancer-induced muscle wasting

While skeletal muscle mass is an established primary outcome related to understanding cancer cachexia mechanisms, considerable gaps exist in our understanding of muscle biochemical and functional properties that have recognized roles in systemic health. Skeletal muscle quality is a classification beyond mass, and is aligned with muscle's metabolic capacity and substrate utilization flexibility. This supplies an additional role for the mitochondria in cancer-induced muscle wasting. While the historical assessment of mitochondria content and function during cancer-induced muscle loss was closely aligned with energy flux and wasting susceptibility, this understanding has expanded to link mitochondria dysfunction to cellular processes regulating myofiber wasting. The primary objective of this article is to highlight muscle mitochondria and oxidative metabolism as a biological target of cancer cachexia and also as a cellular regulator of cancer-induced muscle wasting. Initially, we examine the role of muscle metabolic phenotype and mitochondria content in cancer-induced wasting susceptibility. We then assess the evidence for cancer-induced regulation of skeletal muscle mitochondrial biogenesis, dynamics, mitophagy, and oxidative stress. In addition, we discuss environments associated with cancer cachexia that can impact the regulation of skeletal muscle oxidative metabolism. The article also examines the role of cytokine-mediated regulation of mitochondria function, followed by the potential role of cancer-induced hypogonadism. Lastly, a role for decreased muscle use in cancer-induced mitochondrial dysfunction is reviewed.

Muscle-specific 4E-BP1 signaling activation improves metabolic parameters during aging and obesity

Eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) is a key downstream effector of mTOR complex 1 (mTORC1) that represses cap-dependent mRNA translation initiation by sequestering the translation initiation factor eIF4E. Reduced mTORC1 signaling is associated with life span extension and improved metabolic homeostasis, yet the downstream targets that mediate these benefits are unclear. Here, we demonstrated that enhanced 4E-BP1 activity in mouse skeletal muscle protects against age- and diet-induced insulin resistance and metabolic rate decline. Transgenic animals displayed increased energy expenditure; altered adipose tissue distribution, including reduced white adipose accumulation and preserved brown adipose mass; and were protected from hepatic steatosis. Skeletal muscle-specific 4E-BP1 mediated metabolic protection directly through increased translation of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and enhanced respiratory function. Non-cell autonomous protection was through preservation of brown adipose tissue metabolism, which was increased in 4E-BP1 transgenic animals during normal aging and in a response to diet-induced type 2 diabetes. Adipose phenotypes may derive from enhanced skeletal muscle expression and secretion of the known myokine FGF21. Unlike skeletal muscle, enhanced adipose-specific 4E-BP1 activity was not protective but instead was deleterious in response to the same challenges. These findings indicate that regulation of 4E-BP1 in skeletal muscle may serve as an important conduit through which mTORC1 controls metabolism.

Factors associated with sarcopenia in subjects aged 80 years and over

OBJECTIVE: To analyze whether sarcopenia is associated with sociodemographic factors and chronic noncommunicable diseases in adults aged 80 years and older. METHODS: The sample consisted of 120 adults aged 80 to 95 years (83.4±2.9 years) from the city of Presidente Prudente (São Paulo, Brazil), of which 76 were females (83.4±3.0 years) and 44 were males (83.4±2.6 years). The study sociodemographic and epidemiological factors were: age stratum, gender, marital status, education level, chronic noncommunicable diseases, ethnicity, and nutritional status. Body composition was determined by Dual-Energy X-Ray Absorptiometry and sarcopenia was identified by the appendicular lean mass ratio (upper limb lean mass + lower limb lean mass [kg]/height [m]2). The Chi-square test analyzed whether sarcopenia was associated with sociodemographic and epidemiological factors and binary logistic regression expressed the magnitude of the associations. The data were treated by the software Statistical Package for the Social Sciences (17.0) at a significance level of 5%. RESULTS: The factors associated with sarcopenia were gender, age, nutritional status, and osteopenia/osteoporosis. CONCLUSION: The factors gender, age, nutritional status, and osteopenia/osteoporosis are independently associated with sarcopenia in adults aged 80 years and older.

Genomics and metabolomics of muscular mass in a community-based sample of UK females

The contribution of specific molecular-genetic factors to muscle mass variation and sarcopenia remains largely unknown. To identify endogenous molecules and specific genetic factors associated with appendicular lean mass (APLM) in the general population, cross-sectional data from the TwinsUK Adult Twin Registry were used. Non-targeted mass spec-based metabolomic profiling was performed on plasma of 3953 females (mostly dizygotic and monozygotic twins). APLM was measured using dual-energy X-ray absorptiometry (DXA) and genotyping was genome-wide (GWAS). Specific metabolites were used as intermediate phenotypes in the identification of single-nucleotide polymorphisms associated with APLM using GWAS. In all, 162 metabolites were found significantly correlated with APLM, and explained 17.4% of its variation. However, the top three of them (unidentified substance X12063, urate, and mannose) explained 11.1% (P ≤ 9.25 × 10(-26)) so each was subjected to GWAS. Each metabolite showed highly significant (P ≤ 9.28 × 10(-46)) associations with genetic variants in the corresponding genomic regions. Mendelian randomization using these SNPs found no evidence for a direct causal effect of these metabolites on APLM. However, using a new software platform for bivariate analysis we showed that shared genetic factors contribute significantly (P ≤ 4.31 × 10(-43)) to variance in both the metabolites and APLM--independent of the effect of the associated SNPs. There are several metabolites, having a clear pattern of genetic inheritance, which are highly significantly associated with APLM and may provide a cheap and readily accessible biomarker of muscle mass. However, the mechanism by which the genetic factor influences muscle mass remains to be discovered.

Association between muscle mass and adipo-metabolic profile: a cross-sectional study in older subjects

Background

Sarcopenia, the decrease in muscle mass and function, may lead to various negative health outcomes in elderly. The association among sarcopenia with adiposity and metabolic markers has rarely been studied in the elderly population, with controversial results. The aim of this study is to evaluate this relationship in older subjects.

Methods

A cross-sectional study was conducted in 290 elderly patients, focusing on the possible association between muscle mass loss, assessed by relative skeletal muscle mass (RSMM), and an adipo-metabolic profile (AMP) defined by adiposity and metabolic biochemical markers. Measurements of body composition were assessed by dual energy X-ray absorptiometry. Biochemical parameters, such as albumin, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, total cholesterol, triglycerides, C-reactive protein, and homocysteine and its related markers (folate and vitamin B12) were measured. Using canonical correlation analysis and structural equation modeling, an individual score of AMP was created and correlated with RSMM.

Results

The AMP–RSMM correlation was equal to +0.642 (95% confidence interval, +0.512 to +0.773; P<0.001). Hence, a negative association between sarcopenia severity and adiposity/metabolic biochemical markers was highlighted.

Conclusion

This study contained a novel way to examine the relationship between the variables of interest based on a composite index of adiposity and metabolic conditions. Results shed light on the orientation and magnitude of adiposity and metabolic markers in preventing muscle mass loss. There might be a protective effect of adiposity, compatible with the “obesity paradox.”

Altered microRNA expression in bovine skeletal muscle with age

Age-dependent decline in skeletal muscle function leads to several inherited and acquired muscular disorders in elderly individuals. The levels of microRNAs (miRNAs) could be altered during muscle maintenance and repair. We therefore performed a comprehensive investigation for miRNAs from five different periods of bovine skeletal muscle development using next-generation small RNA sequencing. In total, 511 miRNAs, including one putatively novel miRNA, were identified. Thirty-six miRNAs were differentially expressed between prenatal and postnatal stages of muscle development including several myomiRs (miR-1, miR-206 and let-7 families). Compared with miRNA expression between different muscle tissues, 14 miRNAs were up-regulated and 22 miRNAs were down-regulated in the muscle of postnatal stage. In addition, a novel miRNA was predicted and submitted to the miRBase database as bta-mir-10020. A dual luciferase reporter assay was used to demonstrate that bta-mir-10020 directly targeted the 3'-UTR of the bovine ANGPT1 gene. The overexpression of bta-mir-10020 significantly decreased the DsRed fluorescence in the wild-type expression cassette compared to the mutant type. Using three computational approaches - miranda, pita and rnahybrid - these differentially expressed miRNAs were also predicted to target 3609 bovine genes. Disease and biological function analyses and the KEGG pathway analysis revealed that these targets were statistically enriched in functionality for muscle growth and disease. Our miRNA expression analysis findings from different states of muscle development and aging significantly expand the repertoire of bovine miRNAs now shown to be expressed in muscle and could contribute to further studies on growth and developmental disorders in this tissue type.

Appendicular skeletal muscle mass and insulin resistance in an elderly korean population: the korean social life, health and aging project-health examination cohort

BACKGROUND

Increasing evidence supports an association between age-related loss of muscle mass and insulin resistance. However, the association has not been fully investigated in the general population. Thus, we investigated the association between appendicular skeletal muscle mass (ASM) and insulin resistance in an elderly Korean population.

METHODS

This cross-sectional study included 158 men (mean age, 71.8) and 241 women (mean age, 70.6) from the Korean Social Life, Health and Aging Project, which started in 2011. In this study, ASM was measured by bioelectrical impedance analysis and was analyzed in three forms: ASM (kg), ASM/height(2) (kg/m(2)), and ASM/weight (%). The homeostasis model assessment of insulin resistance (HOMA-IR) was used as a measure of insulin resistance. The relationships between the ASM values and the HOMA-IR were investigated by multiple linear regression models.

RESULTS

The HOMA-IR was positively associated with ASM (β=0.43, P<0.0001) and ASM/height(2) (β=0.36, P<0.0001) when adjusted for sex and age. However, after additional adjustment for body weight, HOMA-IR was inversely associated with ASM (β=-0.43, P<0.001) and ASM/height(2) (β=-0.30, P=0.001). Adjustment for other potential confounders did not change these associations. Conversely, HOMA-IR was consistently and inversely associated with ASM/weight before and after adjustment for other potential confounders.

CONCLUSION

Our results support the idea that lower skeletal muscle mass is independently associated with insulin resistance in older adults. When evaluating sarcopenia or muscle-related conditions in older adults, their whole body sizes also need to be considered.