Circulating follistatin displays a day-night rhythm and is associated with muscle mass and circulating leptin levels in healthy, young humans

Very short sleep duration reveals a proteomic fingerprint that is selectively associated with incident diabetes mellitus but not with incident coronary heart disease: a cohort study

BACKGROUND

The molecular pathways linking short and long sleep duration with incident diabetes mellitus (iDM) and incident coronary heart disease (iCHD) are not known. We aimed to identify circulating protein patterns associated with sleep duration and test their impact on incident cardiometabolic disease.

METHODS

We assessed sleep duration and measured 78 plasma proteins among 3336 participants aged 46-68 years, free from DM and CHD at baseline, and identified cases of iDM and iCHD using national registers. Incident events occurring in the first 3 years of follow-up were excluded from analyses. Tenfold cross-fit partialing-out lasso logistic regression adjusted for age and sex was used to identify proteins that significantly predicted sleep duration quintiles when compared with the referent quintile 3 (Q3). Predictive proteins were weighted and combined into proteomic scores (PS) for sleep duration Q1, Q2, Q4, and Q5. Combinations of PS were included in a linear regression model to identify the best predictors of habitual sleep duration. Cox proportional hazards regression models with sleep duration quintiles and sleep-predictive PS as the main exposures were related to iDM and iCHD after adjustment for known covariates.

RESULTS

Sixteen unique proteomic markers, predominantly reflecting inflammation and apoptosis, predicted sleep duration quintiles. The combination of PSQ1 and PSQ5 best predicted sleep duration. Mean follow-up times for iDM (n = 522) and iCHD (n = 411) were 21.8 and 22.4 years, respectively. Compared with sleep duration Q3, all sleep duration quintiles were positively and significantly associated with iDM. Only sleep duration Q1 was positively and significantly associated with iCHD. Inclusion of PSQ1 and PSQ5 abrogated the association between sleep duration Q1 and iDM. Moreover, PSQ1 was significantly associated with iDM (HR = 1.27, 95% CI: 1.06-1.53). PSQ1 and PSQ5 were not associated with iCHD and did not markedly attenuate the association between sleep duration Q1 with iCHD.

CONCLUSIONS

We here identify plasma proteomic fingerprints of sleep duration and suggest that PSQ1 could explain the association between very short sleep duration and incident DM.

The effects of resistance training on myostatin and follistatin in adults: A systematic review and meta-analysis

INTRODUCTION AND AIM

Myostatin and follistatin are the main hormones for regulating muscle mass, and previous research suggests they are modulated by resistance training. We therefore performed a systematic review and meta-analysis to investigate the impact of resistance training on circulating myostatin and follistatin in adults.

METHODS

A search was conducted in PubMed and Web of science from inception until October 2022 to identify original studies investigating the effects of resistance training compared with controls that did not exercise. Standardized mean differences and 95% confidence intervals (CIs) were calculated using random effects models.

RESULTS

A total 26 randomized studies, including 36 interventions, and involving 768 participants (aged ∼18 to 82 years), were included in the meta-analysis. Resistance training effectively decreased myostatin [-1.31 (95% CI -1.74 to -0.88, p=0.001, 26 studies] and increased follistatin [2.04 (95% CI: 1.51 to 2.52), p=0.001, 14 studies]. Subgroup analyses revealed a significant decrease in myostatin and increase in follistatin regardless of age.

CONCLUSION

Resistance training in adults is effective for reducing myostatin and increasing follistatin which may contribute to the beneficial effects of resistance training on muscle mass and metabolic outcomes.

Postprandial secretion of follistatin after gastric bypass surgery and sleeve gastrectomy

Follistatin is secreted from the liver and may regulate muscle growth and insulin sensitivity. Protein intake stimulates follistatin secretion, which may be mediated by increased glucagon in the context of low insulin concentrations. We investigated circulating follistatin after mixed-meals in two cohorts of patients who were part of previously published studies and had undergone bariatric surgery with either simultaneous assessment of amino acid absorption or administration of the GLP-1 receptor antagonist exendin-(9-39), which increased glucagon concentrations and impaired insulin secretion. Study 1 comprised obese matched subjects with previous Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) surgery and unoperated controls who underwent 6-hour mixed-meal tests with intravenous and oral tracers including intrinsically labelled caseinate in the meal. Study 2 comprised obese subjects with previous RYGB who underwent two 5-hour mixed-meal tests with concomitant exendin-(9-39) or saline infusion. In study 1, the secretion of follistatin as well as the amino acid absorption was accelerated after RYGB compared with SG and controls, but the glucagon-to-C-peptide ratios did not differ between the groups. In study 2, exendin-(9-39) administration increased postprandial glucagon concentrations and lowered insulin secretion, whereas the concentration of follistatin was unchanged. In conclusion, postprandial follistatin secretion is accelerated in patients after RYGB which might be explained by an accelerated protein absorption rate rather than the glucagon-to-insulin ratio.

Activins, follistatins and inhibins in postmenopausal osteoporosis: A proof of concept, case-control study

BACKGROUND

Bone metabolism has been proposed to be affected by the activins-follistatins-inhibins (AFI) hormonal system. We aimed to evaluate AFI in patients with osteoporosis and osteopenia compared with postmenopausal and premenopausal controls.

METHODS

In this case-control study, circulating levels of the AFI system were evaluated, individually and jointly, between postmenopausal women with osteoporosis (BMD T-score ≤-2.5; n = 25) or osteopenia (BMD T-score >-2.5 and ≤-1; n = 25) and postmenopausal women with normal BMD (T-score >-1.0; n = 25) or premenopausal women with normal BMD (Z-score >-1.0; n = 25), with and without adjustment for potential confounders.

RESULTS

In the sum of participants, AFI molecules and their ratios followed an opposite pattern of correlations for age and BMI vs. BMD. In unadjusted models, FSTL3 concentrations were higher, whereas activin B, inhibin A and inhibin B and the ratios of activin B/follistatin and activin B/FSTL3 were lower in the three postmenopausal groups compared with the premenopausal group. Activin A/follistatin and activin AB/follistatin ratios were lower in the osteoporosis group than the other three groups. After adjustment for BMI and age, inhibin B (p = 0.005), and the ratios of activin A/follistatin (p = 0.009), activin B/follistatin (p = 0.040) and activin AB/follistatin (p = 0.003) were lower in the osteoporotic group compared with the other groups. In fully adjusted logistic regression analysis log(inhibin B) (p = 0.041), log(activinA/follistatin) (p = 0.014), log(activinB/follistatin) (p = 0.025) and log(activinAB/follistatin) (p = 0.021), but not FSTL3, remained independently associated with the presence of osteoporosis.

CONCLUSIONS

Lower inhibin B and higher ratios of activins A, B, and AB to follistatin are associated with lumbar spine BMD and the presence of osteoporosis independently from age or BMI.

In patients with anorexia nervosa, myokine levels are altered but are not associated with bone mineral density loss and bone turnover alteration

Objectives

The two-fold aim of this study was: (i) to determine the effects of undernutrition on the myokines in patients with restrictive anorexia nervosa (AN) and (ii) to examine the potential link between myokines and bone parameters.

Methods

In this study, 42 young women with restrictive AN and 42 age-matched controls (CON) (mean age, 18.5 ± 4.2 years and 18.6 ± 4.2 years, respectively) were enrolled. aBMD and body composition were determined with DXA. Resting energy expenditure (REEm), a marker of energy status, was indirectly assessed by calorimetry. Bone turnover markers and myokines (follistatin, myostatin and irisin) were concomitantly evaluated.

Results

AN patients presented low aBMD at all bone sites. REEm, bone formation markers, myostatin and IGF-1 were significantly lower, whereas the bone resorption marker and follistatin were higher in AN compared with controls. No difference was observed between groups for irisin levels. When the whole population was studied, among myokines, only myostatin was positively correlated with aBMD at all bone sites. However, multiple regression analyses showed that in the AN group, the independent variables for aBMD were principally amenorrhoea duration, lean tissue mass (LTM) and procollagen type I N-terminal propeptide (PINP). For CON, the independent variables for aBMD were principally LTM, age and PINP. Whatever the group analysed, none of the myokines appeared as explicative independent variables of aBMD.

Conclusion

This study demonstrated that despite the altered myokine levels in patients with AN, their direct effect on aBMD loss and bone turnover alteration seems limited in comparison with other well-known disease-related factors such as oestrogen deprivation.

Follistatin secretion is enhanced by protein, but not glucose or fat ingestion, in obese persons independently of previous gastric bypass surgery

Follistatin is secreted from the liver and is involved in the regulation of muscle mass and insulin sensitivity via inhibition of activin A in humans. The secretion of follistatin seems to be stimulated by glucagon and inhibited by insulin, but only limited knowledge on the postprandial regulation of follistatin exists. Moreover, results on postoperative changes after Roux-en-Y gastric bypass (RYGB) are conflicting with reports of increased, unaltered, and lowered fasting concentrations of follistatin. In this study, we investigated postprandial follistatin and activin A concentrations after intake of isocaloric amounts of protein, fat, or glucose in subjects with obesity with and without previous RYGB to explore the regulation of follistatin by the individual macronutrients. Protein intake enhanced follistatin concentrations similarly in the two groups, whereas glucose and fat ingestion did not change postprandial follistatin concentrations. Concentrations of activin A were lower after protein intake compared with glucose intake in RYGB. Glucagon concentrations were also particularly enhanced by protein intake and tended to correlate with follistatin in RYGB. In conclusion, we demonstrated that protein intake, but not glucose or fat, is a strong stimulus for follistatin secretion in subjects with obesity and that this regulation is maintained after RYGB surgery.NEW & NOTEWORTHY Circulating follistatin and activin A were studied after intake of isocaloric protein, fat, or glucose drinks in subjects with obesity with and without previous Roux-en-Y gastric bypass (RYGB). Protein intake enhanced follistatin similarly in both groups, whereas glucose and fat ingestion did not change follistatin. Activin A was lower after protein compared with glucose in RYGB. The novel finding is that protein intake, but neither glucose nor fat, stimulates follistatin secretion independently of previous RYGB.

Sleep duration is associated with protein biomarkers for cardiometabolic health: A large-scale population study

Sleep problems and short sleep duration have been linked to adverse health effects, such as cardiovascular disease and diabetes, but the mechanisms are not fully understood. Finding biomarkers could explain mechanistic pathways and help in understanding relationships between sleep and cardiometabolic health. The aim was to assess if sleep duration and sleep quality affect the cardiometabolic-related protein profile. In total, 242 proteins related to cardiometabolic health were measured in 2,430 plasma samples (male:female ratio 1:1, aged 45-75 years) from the population-based EpiHealth cohort, using a proximity extension assay. The association of self-reported sleep duration and sleep quality with each of the 242 proteins (primary outcome) was assessed with linear regression modelling, adjusting for confounders, and corrected for multiple testing using the false discovery rate (5%). Potential effect modification of age and sex was also tested using an interaction term. We identified U-shaped associations between sleep duration and the plasma levels of the proteins follistatin (more prominent in younger individuals), matrix metallopeptidase 9 (men only), urokinase receptor, adrenomedullin and kidney injury molecule, all previously known to be related to cardiovascular risk. There was no relationship between sleep quality and any of the proteins, after adjustment for confounders. These results give new leads to investigate the potential mechanistic pathways between sleep and cardiometabolic health.

Circulating Follistatin and Activin A and Their Regulation by Insulin in Obesity and Type 2 Diabetes

BACKGROUND

Circulating follistatin (Fst) binds activin A and thereby regulates biological functions such as muscle growth and β-cell survival. However, Fst and activin A's implication in metabolic regulation is unclear.

OBJECTIVE

To investigate circulating Fst and activin A in obesity and type 2 diabetes (T2D) and determine their association with metabolic parameters. Further, to examine regulation of Fst and activin A by insulin and the influence of obesity and T2D hereon.

METHODS

Plasma Fst and activin A levels were analyzed in obese T2D patients (N = 10) closely matched to glucose-tolerant lean (N = 12) and obese (N = 10) individuals in the fasted state and following a 4-h hyperinsulinemic-euglycemic clamp (40 mU·m-2·min-1) combined with indirect calorimetry.

RESULTS

Circulating Fst was ~30% higher in patients with T2D compared with both lean and obese nondiabetic individuals (P < .001), while plasma activin A was unaltered. In the total cohort, fasting plasma Fst correlated positively with fasting plasma glucose, serum insulin and C-peptide levels, homeostasis model assessment of insulin resistance, and hepatic and adipose tissue insulin resistance after adjusting for age, gender and group (all r > 0.47; P < .05). However, in the individual groups these correlations only achieved significance in patients with T2D (not plasma glucose). Acute hyperinsulinemia at euglycemia reduced circulating Fst by ~30% (P < .001) and this response was intact in patients with T2D. Insulin inhibited FST expression in human hepatocytes after 2 h and even further after 48 h.

CONCLUSIONS

Elevated circulating Fst, but not activin A, is strongly associated with measures of insulin resistance in patients with T2D. However, the ability of insulin to suppress circulating Fst is preserved in T2D.

Targeted Analysis of Three Hormonal Systems Identifies Molecules Associated with the Presence and Severity of NAFLD

AIMS

To investigate circulating levels and liver gene expression of 3 hormonal pathways associated with obesity, insulin resistance, and inflammation to identify leads towards potential diagnostic markers and therapeutic targets in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

We compared circulating levels of (1) proglucagon-derived hormones (glucagon-like peptide [GLP]-1, GLP-2, glicentin, oxyntomodulin, glucagon, major proglucagon fragment [MPGF]), (2) follistatins-activins (follistatin-like [FSTL]3, activin B), (3) IGF axis (insulin-like growth factor [IGF]-1, total and intact IGF binding protein [IGFBP]-3 and IGFBP-4, and pregnancy-associated plasma protein [PAPP]-A) in 2 studies: (1) 18 individuals with early stage NAFLD versus 14 controls (study 1; early NAFLD study) and in (2) 31 individuals with biopsy proven NAFLD (15 with simple steatosis [SS] and 16 with nonalcoholic steatohepatitis [NASH]), vs 50 controls (24 lean and 26 obese) (study 2). Liver gene expression was assessed in 22 subjects (12 controls, 5 NASH, 5 NASH-related cirrhosis).

RESULTS

Patients in early stages of NAFLD demonstrate higher fasting MPGF and lower incremental increase of glicentin during oral glucose tolerance test than controls. In more advanced stages, FSTL3 levels are higher in NASH than simple steatosis and, within NAFLD patients, in those with more severe lobular and portal inflammation. The IGF-1/intact IGFBP-3 ratio is lower in patients with liver fibrosis. Genes encoding follistatin, activin A, activin B, and the IGF-1 receptor are higher in NASH.

CONCLUSION

MPGF and glicentin may be involved in early stages of NAFLD, whereas FSTL3 and IGF-1/intact IGFBP3 in the progression to NASH and liver fibrosis respectively, suggesting potential as diagnostic markers or therapeutic targets.

Physiology of Activins/Follistatins: Associations With Metabolic and Anthropometric Variables and Response to Exercise

CONTEXT

Clinical trials are evaluating the efficacy of inhibitors of the myostatin pathway in neuromuscular and metabolic diseases. Activins and follistatins are major regulators of the myostatin pathway, but their physiology in relation to metabolic and anthropometric variables and in response to exercise remains to be fully elucidated in humans.

OBJECTIVE

We investigated whether concentrations of circulating activin A, activin B, follistatin, and follistatin-like 3 (FSTL3) are associated with anthropometric and metabolic variables and whether they are affected by exercise.

DESIGN

Activin A, activin B, follistatin, and FSTL3 were measured in (1) 80 subjects divided according to age (young vs old) and fitness status (active vs sedentary) before and after exercise at 70% maximal oxygen consumption (VO2max), followed by 90% of VO2max until exhaustion; and (2) 23 subjects [9 healthy and 14 with metabolic syndrome (MetS)] who completed four sessions: no exercise, high-intensity interval exercise, continuous moderate-intensity exercise, and resistance exercise for up to 45 minutes.

RESULTS

At baseline, follistatin and FSTL3 concentrations were positively associated with age, fat percentage, and body mass index (P < 0.001). Follistatin was positively associated with serum cholesterol (P = 0.005), low-density lipoprotein cholesterol (P = 0.01), triglycerides (P = 0.033), and blood pressure (P = 0.019), whereas activin A and activin B were higher in physically active participants (P = 0.056 and 0.029, respectively). All exercise types increased the levels of all hormones ∼10% to 21% (P = 0.034 for activin B, P < 0.001 for the others) independent of the presence of MetS.

CONCLUSION

Concentrations of circulating activins and follistatins are associated with metabolic parameters and increase after 45 minutes of exercise.

Regulation of the activins-follistatins-inhibins axis by energy status: Impact on reproductive function

BACKGROUND

We have previously demonstrated that the adipose tissue derived hormone leptin controls reproductive function by regulating the hypothalamic-pituitary-gonadal axis in response to energy deficiency. Here, we evaluate the activins-follistatins-inhibins (AFI) axis during acute (short-term fasting in healthy people) and chronic energy deficiency (women with hypothalamic amenorrhea due to strenuous exercise [HA]) and investigate their relation to leptin and reproductive function in healthy subjects and subjects with HA.

METHODS

The AFI axis was investigated in: a) A double-blinded study in healthy subjects having three randomly assigned admissions, each time for four days: in the isocaloric fed state, complete fasting with placebo treatment, complete fasting with leptin replacement, b) A case-control study comparing women with HA vs healthy controls, c) An open-label interventional study investigating leptin treatment in women with HA over a period of up to three months, d) A randomized interventional trial investigating leptin treatment vs placebo in women with HA for nine months.

RESULTS

The circulating levels of activin A, activin B, follistatin and follistatin-like 3 change robustly in response to acute and chronic energy deficiency. Leptin replacement in acute energy deprivation does not affect the levels of these hormones suggesting an independent regulation by these two hormonal pathways. In chronic energy deficiency, leptin replacement restores only activin B levels, which are in turn associated with an increase in the number of dominant follicles.

CONCLUSIONS

We demonstrate for the first time that the AFI axis is affected both by acute and chronic energy deficiency. Partial restoration of a component of the axis, i.e. activin B only, through leptin replacement is associated with improved reproductive function in women with HA.

Donor and recipient plasma follistatin levels are associated with acute GvHD in Blood and Marrow Transplant Clinical Trials Network 0402

Follistatin is an angiogenic factor elevated in the circulation after allogeneic hematopoietic cell transplantation (HCT). Elevations in follistatin plasma concentrations are associated with the onset of and poor survival after acute graft versus host disease (aGVHD). Using data from the Blood and Marrow Transplant Clinical Trials Network 0402 study (n=247), we sought to further quantify the longitudinal associations between plasma follistatin levels in transplant recipients, as well as baseline HCT donor follistatin levels, and allogeneic HCT outcomes. Higher recipient baseline follistatin levels were predictive of development of aGVHD (P=0.04). High donor follistatin levels were also associated with the incidence of aGVHD (P<0.01). Elevated follistatin levels on day 28 were associated with the onset of grade II–IV aGVHD prior to day 28, higher one-year non-relapse mortality, (NRM), and lower overall survival (OS). In multivariate analyses, individuals with follistatin levels >1088 pg/mL at day 28 had a four-fold increased risk for NRM (RR=4.3, 95% CI 1.9–9.9, P<0.01) and a nearly three-fold increased overall risk for mortality (RR=2.8, 95% CI 1.5–5.2, P<0.01). Given the multiple roles of follistatin in tissue inflammation and repair, and the confirmation that this biomarker is predictive of important HCT outcomes, the pathobiology of these relationships need further study.

Physiological parameters regulating circulating levels of the IGFBP-4/Stanniocalcin-2/PAPP-A axis

BACKGROUND

Insulin Growth Factor Binding Protein 4 (IGFBP-4), Stanniocalcin-2 (STC-2) and Pregnancy-Associated Plasma Protein-A (PAPP-A) have a well-documented involvement in several physiological functions in humans but predictors of their circulating levels remain largely unknown. We aimed to identify anthropometric and biochemical parameters associated with circulating levels of IGFBP-4/STC-2/PAPP-A axis (ISPa) cross-sectionally and to study their day-night variation and their regulation in response to mixed meal and exercise.

METHODS

One hundred twenty two healthy individuals were evaluated cross-sectionally. Subgroups were subjected to standardized mixed meal ingestion in increasing quantities of 125mL or 250mL, or aerobic exercise for 30min, or day-night rhythm study. Main outcome measurements were circulating IGFBP-4 (total and intact), STC-2 and PAPP-A levels.

RESULTS

In multivariate models, the main predictors of serum total IGFBP-4 were PAPP-A and female gender. Intact IGFBP-4 was positively associated with serum creatinine. Height was inversely and female gender and % of total body fat were positively correlated with STC-2. PAPP-A decreased after ingesting both the 125mL (p=0.03) and 250mL quantities (p=0.001), while total IGFBP-4 was reduced after the 250mL quantity (p=0.001). Exercise increased STC-2 and PAPP-A levels (p<0.001 for both). Intact, and to a lesser extent total, IGFBP-4 displayed a cortisol-like day/night variation.

CONCLUSIONS

We report for the first time anthropometric and physiological modulators of ISPa serum levels in healthy humans.

Circulating irisin levels are lower in patients with either stable coronary artery disease (CAD) or myocardial infarction (MI) versus healthy controls, whereas follistatin and activin A levels are higher and can discriminate MI from CAD with similar to CK-MB accuracy

BACKGROUND

Several myokines are produced by cardiac muscle. We investigated changes in myokine levels at the time of acute myocardial infarction (MI) and following reperfusion in relation to controls.

METHODS

Patients with MI (MI Group, n=31) treated with percutaneous coronary intervention (PCI) were compared to patients with stable coronary artery disease (CAD) subjected to scheduled PCI (CAD Group, n=40) and controls with symptoms mimicking CAD without stenosis in angiography (Control Group, n=43). The number and degree of stenosis were recorded. Irisin, follistatin, follistatin-like 3, activin A and B, ALT, AST, CK and CK-MB were measured at baseline and 6 or 24h after the intervention.

RESULTS

MI and CAD patients had lower irisin than controls (p<0.001). MI patients had higher follistatin, activin A, CK, CK-MB and AST than CAD patients and controls (all p≤0.001). None of the myokines changed following reperfusion. Circulating irisin was associated with the degree of stenosis in all patients (p=0.05). Irisin was not inferior to CK-MB in predicting MI while folistatin and activin A could discriminate MI from CAD patients with similar to CK-MB accuracy. None of these myokines was altered following PCI in contrast to CK-MB.

CONCLUSIONS

Irisin levels are lower in MI and CAD implying that their production may depend on myocadial blood supply. Follistatin and activin A are higher in MI than in CAD suggesting increased release due to myocardial necrosis. They can predict MI with accuracy similar to CK-MB and their role in the diagnosis of MI remains to be confirmed by prospective large clinical studies.

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

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

Role of the Cytokine-like Hormone Leptin in Muscle-bone Crosstalk with Aging

The cytokine-like hormone leptin is a classic adipokine that is secreted by adipocytes, increases with weight gain, and decreases with weight loss. Additional studies have, however, shown that leptin is also produced by skeletal muscle, and leptin receptors are abundant in both skeletal muscle and bone-derived mesenchymal (stromal) stem cells. These findings suggest that leptin may play an important role in muscle-bone crosstalk. Leptin treatment in vitro increases the expression of myogenic genes in primary myoblasts, and leptin treatment in vivo increases the expression of microRNAs involved in myogenesis. Bone marrow adipogenesis is associated with low bone mass in humans and rodents, and leptin can reduce marrow adipogenesis centrally through its receptors in the hypothalamus as well as directly via its receptors in bone marrow stem cells. Yet, central leptin resistance can increase with age, and low circulating levels of leptin have been observed among the frail elderly. Thus, aging appears to significantly alter leptin-mediated crosstalk among various organs and tissues. Aging is associated with bone loss and muscle atrophy, contributing to frailty, postural instability, and the incidence of falls. Therapeutic interventions such as protein and amino acid supplementation that can increase muscle mass and muscle-derived leptin may have multiple benefits for the elderly that can potentially reduce the incidence of falls and fractures.