Skeletal muscle protein metabolism in the elderly: Interventions to counteract the 'anabolic resistance' of ageing

Meals containing equivalent total protein from foods providing complete, complementary, or incomplete essential amino acid profiles do not differentially affect 24-hour skeletal muscle protein synthesis in healthy, middle-aged women

BACKGROUND

Dietary protein quality can be assessed by skeletal muscle protein synthesis (MPS) stimulation. Limited knowledge exists on how consuming isonitrogenous meals with varied protein qualities affect postprandial and 24-h MPS.

OBJECTIVE

We assessed the effects of protein quality and complementary proteins on MPS. We hypothesized that meals containing a moderate amount of high-quality, complete protein would stimulate postprandial and 24-h MPS. Meals with two complementary, plant-based incomplete proteins would stimulate MPS less, and meals with plant-based incomplete proteins at each meal, but complementary over 24 h would not stimulate MPS.

DESIGN

This quasi-experimental study included a randomized, crossover design to assess protein quality and a non-randomized low-protein control. We measured postprandial and 24-h MPS responses of healthy middle-aged women (n=9, age 56±4 y), to three dietary conditions: isonitrogenous meals containing 23 g protein/meal from i) complete protein (lean beef); ii) two incomplete, but complementary protein sources (navy/black beans and whole wheat bread); and iii) single incomplete protein sources (black beans or whole wheat bread at a meal), but providing a complete amino acid profile over 24 h. In the low-protein group women (n=8, 54 ± 5 y) consumed a single breakfast meal containing 5 g of protein. Venous blood and vastus lateralis samples were obtained during primed, constant infusions of L-[ring-13C6] phenylalanine to measure mixed muscle fractional synthetic rates (FSR).

RESULTS

Meals with complete, complementary, or incomplete proteins did not differentially influence FSR responses after breakfast (p=0.90) or 24 h (p=0.38). At breakfast, the complete (p=0.030) and complementary (p=0.031) protein meals, but not the incomplete protein meal (p=0.38), had greater FSR responses, compared to the low-protein control meal.

CONCLUSIONS

Isonitrogenous meals containing a moderate serving of total protein from foods providing complete, complementary, or incomplete essential amino acid profiles do not differentially stimulate muscle protein synthesis after a meal and daily.

CLINICAL TRIALS REGISTRY

This clinical trial was registered at clinicaltrials.gov as NCT03816579. URL:; https://www.

CLINICALTRIALS

gov/ct2/show/NCT03816579?term=NCT03816579&draw=2&rank=1.

Vascular Impairment, Muscle Atrophy, and Cognitive Decline: Critical Age-Related Conditions

The triad of vascular impairment, muscle atrophy, and cognitive decline represents critical age-related conditions that significantly impact health. Vascular impairment disrupts blood flow, precipitating the muscle mass reduction seen in sarcopenia and the decline in neuronal function characteristic of neurodegeneration. Our limited understanding of the intricate relationships within this triad hinders accurate diagnosis and effective treatment strategies. This review analyzes the interrelated mechanisms that contribute to these conditions, with a specific focus on oxidative stress, chronic inflammation, and impaired nutrient delivery. The aim is to understand the common pathways involved and to suggest comprehensive therapeutic approaches. Vascular dysfunctions hinder the circulation of blood and the transportation of nutrients, resulting in sarcopenia characterized by muscle atrophy and weakness. Vascular dysfunction and sarcopenia have a negative impact on physical function and quality of life. Neurodegenerative diseases exhibit comparable pathophysiological mechanisms that affect cognitive and motor functions. Preventive and therapeutic approaches encompass lifestyle adjustments, addressing oxidative stress, inflammation, and integrated therapies that focus on improving vascular and muscular well-being. Better understanding of these links can refine therapeutic strategies and yield better patient outcomes. This study emphasizes the complex interplay between vascular dysfunction, muscle degeneration, and cognitive decline, highlighting the necessity for multidisciplinary treatment approaches. Advances in this domain promise improved diagnostic accuracy, more effective therapeutic options, and enhanced preventive measures, all contributing to a higher quality of life for the elderly population.

'Exerkines': A Comprehensive Term for the Factors Produced in Response to Exercise

Regular exercise and physical activity are now considered lifestyle factors with positive effects on human health. Physical activity reduces disease burden, protects against the onset of pathologies, and improves the clinical course of disease. Unlike pharmacological therapies, the effects mediated by exercise are not limited to a specific target organ but act in multiple biological systems simultaneously. Despite the substantial health benefits of physical training, the precise molecular signaling processes that lead to structural and functional tissue adaptation remain largely unknown. Only recently, several bioactive molecules have been discovered that are produced following physical exercise. These molecules are collectively called "exerkines". Exerkines are released from various tissues in response to exercise, and play a crucial role in mediating the beneficial effects of exercise on the body. Major discoveries involving exerkines highlight their diverse functions and health implications, particularly in metabolic regulation, neuroprotection, and muscle adaptation. These molecules, including peptides, nucleic acids, lipids, and microRNAs, act through paracrine, endocrine, and autocrine pathways to exert their effects on various organs and tissues. Exerkines represent a complex network of signaling molecules that mediate the multiple benefits of exercise. Their roles in metabolic regulation, neuroprotection, and muscle adaptation highlight the importance of physical activity in maintaining health and preventing disease.

Nutritional Considerations During Major Weight Loss Therapy: Focus on Optimal Protein and a Low-Carbohydrate Dietary Pattern

PURPOSE OF REVIEW

Considering the high prevalence of obesity and related metabolic impairments in the population, the unique role nutrition has in weight loss, reversing metabolic disorders, and maintaining health cannot be overstated. Normal weight and well-being are compatible with varying dietary patterns, but for the last half century there has been a strong emphasis on low-fat, low-saturated fat, high-carbohydrate based approaches. Whereas low-fat dietary patterns can be effective for a subset of individuals, we now have a population where the vast majority of adults have excess adiposity and some degree of metabolic impairment. We are also entering a new era with greater access to bariatric surgery and approval of anti-obesity medications (glucagon-like peptide-1 analogues) that produce substantial weight loss for many people, but there are concerns about disproportionate loss of lean mass and nutritional deficiencies.

RECENT FINDINGS

No matter the approach used to achieve major weight loss, careful attention to nutritional considerations is necessary. Here, we examine the recent findings regarding the importance of adequate protein to maintain lean mass, the rationale and evidence supporting low-carbohydrate and ketogenic dietary patterns, and the potential benefits of including exercise training in the context of major weight loss. While losing and sustaining weight loss has proven challenging, we are optimistic that application of emerging nutrition science, particularly personalized well-formulated low-carbohydrate dietary patterns that contain adequate protein (1.2 to 2.0 g per kilogram reference weight) and achieve the beneficial metabolic state of euketonemia (circulating ketones 0.5 to 5 mM), is a promising path for many individuals with excess adiposity.

Efficacy of Protein and Essential Amino Acid Supplementation in Lower Limb Surgeries: A Systematic Review and Meta-Analysis

This study aimed to examine the efficacy and safety of protein and/or essential amino acid (EAA) supplementation in all lower limb surgeries using systematic reviews and meta-analysis of randomized controlled trials (RCTs). We included RCTs that assessed the efficacy of protein and/or EAA supplementation in lower limb surgeries. On June 2, 2023, we searched EMBASE, MEDLINE, the Cochrane Central Register of Controlled Trials, the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. The primary outcomes were mobility, patient-reported outcomes (PRO), and acute kidney injury (AKI). The secondary outcomes were exercise capacity, muscle strength, muscle mass, and all adverse events. We performed meta-analyses using the random-effects model. We assessed the risk of bias using the Cochrane risk-of-bias tool and the certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation approach. We included 12 RCTs (622 patients). These studies included four on hip fracture surgery, three on total hip arthroplasty, and five on total knee arthroplasty. Protein and/or EAA supplementation may slightly improve PRO (standard mean difference 0.51, 95% confidence interval (CI): 0.22 to 0.80, low certainty of evidence). Nevertheless, it may not improve mobility (mean difference 0.07 m/s, 95% CI: -0.01 to 0.16, low certainty of evidence). No adverse events including AKI were reported. Muscle strength may have increased (standard mean difference 0.31, 95% CI: 0.02 to 0.61, very low certainty of evidence). However, exercise capacity (mean difference 5.43 m, 95% CI: -35.59 to 46.45, very low certainty of evidence) and muscle mass (standard mean difference -0.08, 95% CI: -0.49 to 0.33, very low certainty of evidence) were not improved. While protein and/or EAA supplementation in lower limb surgeries may improve PRO, it is unlikely to affect mobility. Despite this, the medical team and patients might still consider protein and/or EAA supplementation a useful option.

Diet and physical exercise in elderly people with obesity: The state of the art

Obesity is a disease that is assuming pandemic proportions in recent decades. With the advancement of medicine and increased access to care, average survival has increased, resulting in a larger number of elderly people. As a result, the amount of elderly people living with obesity is increasing, and the morbidity and impact of obesity on ageing implies severe limitations for these people. The link between obesity and ageing is not only epidemiological, but also strictly pathophysiological. Obesity accelerates the ageing process and ageing is characterised by pathophysiological mechanisms shared by obesity itself. Some examples of alterations shared by ageing and obesity are metabolic changes, sarcopenia and reduced functional capacity related to both loss of muscle strength and reduced cardiorespiratory fitness, as well as a general reduction in the perception of quality of life. The specific ability to antagonize these mechanisms through non-pharmacological treatment based on nutrition and exercise has always been one of the focal points of the international literature. Therefore, this review provides the state of the art on scientific knowledge regarding the main effects of an adequate nutritional plan and an individualised exercise prescription on the general health of elderly with obesity. In particular, this paper addresses the effect of nutrition and physical exercise on pathophysiological changes peculiar of ageing and obesity, providing also the scientific rational for nutritional and exercise prescription in the population.

Critical variables regulating age-related anabolic responses to protein nutrition in skeletal muscle

Protein nutrition is critical for the maintenance of skeletal muscle mass across the lifecourse and for the growth of muscle in response to resistance exercise - both acting via the stimulation of protein synthesis. The transient anabolic response to protein feeding may vary in magnitude and duration, depending on, e.g., timing, dose, amino acid composition and delivery mode, which are in turn influenced by physical activity and age. This review aims to: (i) summarise the fundamental metabolic responses of muscle to protein feeding, (ii) discuss key variables regulating muscle anabolic responses to protein feeding, and (iii) explore how these variables can be optimised for muscle anabolism in response to physical activity and ageing.

Nutritional Management and Physical Activity in the Treatment of Sarcopenic Obesity: A Review of the Literature

BACKGROUND

The prevalence of sarcopenic obesity among adults aged ≥65 years is increasing worldwide. It is a condition that describes the concomitant presence of sarcopenia and obesity, but it appears to be associated with greater increases in the risks for disability, morbidity, and mortality than the two conditions combined. The current review aims to summarize the available literature data on the effectiveness of lifestyle modification for the management of this high-risk geriatric syndrome.

METHODS

We conducted a comprehensive search across multiple databases, including PubMed, Scopus, Web of Science, and Cochrane Library, for publications published from January 1950 to June 2024.

RESULTS

The detection of early preventive and therapeutic approaches to combat sarcopenic obesity is essential for healthy aging. There is ample evidence that suggests that poor dietary habits and physical inactivity are the main reasons for the development of sarcopenic obesity and should thus be the main targets for intervention. In the absence of effective pharmacological interventions, the best effect on sarcopenic obesity is achieved by combination with proper dietary intervention and regular physical activity according to the individual's health condition.

CONCLUSIONS

Further research is needed to discover the most effective strategy for the prevention and treatment of sarcopenic obesity, as well as potential pharmacological options to improve muscle mass and function in older populations with physical restrictions.

Plant Protein Blend Ingestion Stimulates Postexercise Myofibrillar Protein Synthesis Rates Equivalently to Whey in Resistance-Trained Adults

PURPOSE

Whey protein ingestion is typically considered an optimal dietary strategy to maximize myofibrillar protein synthesis (MyoPS) after resistance exercise. Although single-source plant protein ingestion is typically less effective, at least partly, due to less favorable amino acid profiles, this could theoretically be overcome by blending plant-based proteins with complementary amino acid profiles. We compared the postexercise MyoPS response after the ingestion of a novel plant-derived protein blend with an isonitrogenous bolus of whey protein.

METHODS

Ten healthy, resistance-trained, young adults (male/female: 8/2; age: 26 ± 6 yr; BMI: 24 ± 3 kg·m -2 ) received a primed continuous infusion of L-[ ring - 2 H 5 ]-phenylalanine and completed a bout of bilateral leg resistance exercise before ingesting 32 g protein from whey (WHEY) or a plant protein blend (BLEND; 39.5% pea, 39.5% brown rice, 21.0% canola) in a randomized, double-blind crossover fashion. Blood and muscle samples were collected at rest, and 2 and 4 h after exercise and protein ingestion, to assess plasma amino acid concentrations, and postabsorptive and postexercise MyoPS rates.

RESULTS

Plasma essential amino acid availability over the 4 h postprandial postexercise period was ~44% higher in WHEY compared with BLEND ( P = 0.04). From equivalent postabsorptive values (WHEY, 0.042 ± 0.020%·h -1 ; BLEND, 0.043 ± 0.015%·h -1 ) MyoPS rates increased after exercise and protein ingestion (time effect; P < 0.001) over a 0- to 2-h period (WHEY, 0.085 ± 0.037%·h -1 ; BLEND, 0.080 ± 0.037%·h -1 ) and 2- to 4-h period (WHEY, 0.085 ± 0.036%·h -1 ; BLEND, 0.086 ± 0.034%·h -1 ), with no differences between conditions during either period or throughout the entire (0-4 h) postprandial period (time-condition interactions; all P > 0.05).

CONCLUSIONS

Ingestion of a novel plant-based protein blend stimulates postexercise MyoPS to an equivalent extent as whey protein, demonstrating the utility of plant protein blends to optimize postexercise skeletal muscle reconditioning.

Accelerated aging of skeletal muscle and the immune system in patients with chronic liver disease

Patients with chronic liver disease (CLD) often present with significant frailty, sarcopenia, and impaired immune function. However, the mechanisms driving the development of these age-related phenotypes are not fully understood. To determine whether accelerated biological aging may play a role in CLD, epigenetic, transcriptomic, and phenotypic assessments were performed on the skeletal muscle tissue and immune cells of CLD patients and age-matched healthy controls. Accelerated biological aging of the skeletal muscle tissue of CLD patients was detected, as evidenced by an increase in epigenetic age compared with chronological age (mean +2.2 ± 4.8 years compared with healthy controls at -3.0 ± 3.2 years, p = 0.0001). Considering disease etiology, age acceleration was significantly greater in both the alcohol-related (ArLD) (p = 0.01) and nonalcoholic fatty liver disease (NAFLD) (p = 0.0026) subgroups than in the healthy control subgroup, with no age acceleration observed in the immune-mediated subgroup or healthy control subgroup (p = 0.3). The skeletal muscle transcriptome was also enriched for genes associated with cellular senescence. Similarly, blood cell epigenetic age was significantly greater than that in control individuals, as calculated using the PhenoAge (p < 0.0001), DunedinPACE (p < 0.0001), or Hannum (p = 0.01) epigenetic clocks, with no difference using the Horvath clock. Analysis of the IMM-Age score indicated a prematurely aged immune phenotype in CLD patients that was 2-fold greater than that observed in age-matched healthy controls (p < 0.0001). These findings suggested that accelerated cellular aging may contribute to a phenotype associated with advanced age in CLD patients. Therefore, therapeutic interventions to reduce biological aging in CLD patients may improve health outcomes.

The effects of whey, pea, and collagen protein supplementation beyond the recommended dietary allowance on integrated myofibrillar protein synthetic rates in older males: a randomized controlled trial

BACKGROUND

Skeletal muscle mass is determined predominantly by feeding-induced and activity-induced fluctuations in muscle protein synthesis (MPS). Older individuals display a diminished MPS response to protein ingestion, referred to as age-related anabolic resistance, which contributes to the progression of age-related muscle loss known as sarcopenia.

OBJECTIVES

We aimed to determine the impact of consuming higher-quality compared with lower-quality protein supplements above the recommended dietary allowance (RDA) on integrated MPS rates. We hypothesized that increasing total protein intake above the RDA, regardless of the source, would support higher integrated rates of myofibrillar protein synthesis.

METHODS

Thirty-one healthy older males (72 ± 4 y) consumed a controlled diet with protein intake set at the RDA: control phase (days 1-7). In a double-blind, randomized controlled fashion, participants were assigned to consume an additional 50 g (2 × 25g) of whey (n = 10), pea (n = 11), or collagen (n = 10) protein each day (25 g at breakfast and lunch) during the supplemental phase (days 8-15). Deuterated water ingestion and muscle biopsies assessed integrated MPS and acute anabolic signaling. Postprandial blood samples were collected to determine feeding-induced aminoacidemia.

RESULTS

Integrated MPS was increased during supplemental with whey (1.59 ± 0.11 %/d; P < 0.001) and pea (1.59 ± 0.14 %/d; P < 0.001) when compared with RDA (1.46 ± 0.09 %/d for the whey group; 1.46 ± 0.10 %/d for the pea group); however, it remained unchanged with collagen. Supplemental protein was sufficient to overcome anabolic signaling deficits (mTORC1 and rpS6), corroborating the greater postprandial aminoacidemia.

CONCLUSIONS

Our findings demonstrate that supplemental protein provided at breakfast and lunch over the current RDA enhanced anabolic signaling and integrated MPS in older males; however, the source of additional protein may be an important consideration in overcoming age-related anabolic resistance. This trial was registered clinicaltrials.gov as NCT04026607.

Protein Intake and Physical Activity Levels as Determinants of Sarcopenia Risk in Community-Dwelling Older Adults

Community screening for sarcopenia is complex, with barriers including access to specialized equipment and trained staff to conduct body composition, strength and function assessment. In the current study, self-reported dietary protein intake and physical activity (PA) in adults ≥65 years was assessed relative to sarcopenia risk, as determined by body composition, strength and physical function assessments, consistent with the European Working Group on Sarcopenia in Older People (EWGSOP) definition. Of those screened (n = 632), 92 participants (77% female) were assessed as being at high risk of developing sarcopenia on the basis of dietary protein intake ≤1 g∙kg-1∙day-1 [0.9 (0.7-0.9) g∙kg-1∙day-1] and moderate intensity physical activity <150 min.week-1. A further 31 participants (65% female) were defined as being at low risk, with both protein intake [1.2 (1.1-1.5) g∙kg-1∙day-1] and PA greater than the cut-off values. High-risk participants had reduced % lean mass [53.5 (7.8)% versus 54.8 (6.1)%, p < 0.001] and impaired strength and physical function. Notably, high-risk females exhibited greater deficits in lean mass and strength, with minimal differences between groups for males. In community-dwelling older adults, self-reported low protein intake and low weekly PA is associated with heightened risk for sarcopenia, particularly in older women. Future research should determine whether early intervention in older adults with low protein intake and PA attenuates functional decline.

Understanding the variation in exercise responses to guide personalized physical activity prescriptions

Understanding the factors that contribute to exercise response variation is the first step in achieving the goal of developing personalized exercise prescriptions. This review discusses the key molecular and other mechanistic factors, both extrinsic and intrinsic, that influence exercise responses and health outcomes. Extrinsic characteristics include the timing and dose of exercise, circadian rhythms, sleep habits, dietary interactions, and medication use, whereas intrinsic factors such as sex, age, hormonal status, race/ethnicity, and genetics are also integral. The molecular transducers of exercise (i.e., genomic/epigenomic, proteomic/post-translational, transcriptomic, metabolic/metabolomic, and lipidomic elements) are considered with respect to variability in physiological and health outcomes. Finally, this review highlights the current challenges that impede our ability to develop effective personalized exercise prescriptions. The Molecular Transducers of Physical Activity Consortium (MoTrPAC) aims to fill significant gaps in the understanding of exercise response variability, yet further investigations are needed to address additional health outcomes across all populations.

Aging as a Consequence of the Adaptation-Maladaptation Dilemma

In aging, the organism is unable to counteract certain harmful influences over its lifetime which leads to progressive dysfunction and eventually death, thus delineating aging as one failed process of adaptation to a set of aging stimuli. A central problem in understanding aging is hence to explain why the organism cannot adapt to these aging stimuli. The adaptation-maladaptation theory of aging proposes that in aging adaptation processes such as adaptive transcription, epigenetic remodeling, and metabolic plasticity drive dysfunction themselves over time (maladaptation) and thereby cause aging-related disorders such as cancer and metabolic dysregulation. The central dilemma of aging is thus that the set of adaptation mechanisms that the body uses to deal with internal and external stressors acts as a stressor itself and cannot be effectively counteracted. The only available option for the organism to decrease maladaptation may be a program to progressively reduce the output of adaptive cascades (e.g., via genomic methylation) which then leads to reduced physiological adaptation capacity and syndromes like frailty, immunosenescence, and cognitive decline. The adaptation-maladaptation dilemma of aging entails that certain biological mechanisms can simultaneously protect against aging as well as drive aging. The key to longevity may lie in uncoupling adaptation from maladaptation.

YTHDF2 governs muscle size through a targeted modulation of proteostasis

The regulation of proteostasis is fundamental for maintenance of muscle mass and function. Activation of the TGF-β pathway drives wasting and premature aging by favoring the proteasomal degradation of structural muscle proteins. Yet, how this critical post-translational mechanism is kept in check to preserve muscle health remains unclear. Here, we reveal the molecular link between the post-transcriptional regulation of m6A-modified mRNA and the modulation of SMAD-dependent TGF-β signaling. We show that the m6A-binding protein YTHDF2 is essential to determining postnatal muscle size. Indeed, muscle-specific genetic deletion of YTHDF2 impairs skeletal muscle growth and abrogates the response to hypertrophic stimuli. We report that YTHDF2 controls the mRNA stability of the ubiquitin ligase ASB2 with consequences on anti-growth gene program activation through SMAD3. Our study identifies a post-transcriptional to post-translational mechanism for the coordination of gene expression in muscle.

Utility of growth differentiation factor-15 as a predictor of cardiovascular surgery outcomes: Current research and future directions

In a world increasingly confronted by cardiovascular diseases (CVDs) and an aging population, accurate risk assessment prior to cardiac surgery is critical. Although effective, traditional risk calculators such as the Japan SCORE, Society of Thoracic Surgeons score, and EuroSCORE II may not completely capture contemporary risks, particularly due to emerging factors such as frailty and sarcopenia. These calculators often focus on regional and ethnic specificity and rely heavily on evaluations based on age and underlying diseases. Growth differentiation factor-15 (GDF-15) is a stress-responsive cytokine that has been identified as a potential biomarker for sarcopenia and a tool for future cardiac risk assessment. Preoperative plasma GDF-15 levels have been associated with preoperative, intraoperative, and postoperative factors and short- and long-term mortality rates in patients undergoing cardiac surgery. Increased plasma GDF-15 levels have prognostic significance, having been correlated with the use of cardiopulmonary bypass during surgery, amount of bleeding, postoperative acute kidney injury, and intensive care unit stay duration. Notably, the inclusion of preoperative levels of GDF-15 in risk stratification models enhances their predictive value, especially when compared with those of the N-terminal prohormone of brain natriuretic peptide, which does not lead to reclassification. Thus, this review examines traditional risk assessments for cardiac surgery and the role of the novel biomarker GDF-15. This study acknowledges that the relationship between patient outcomes and elevated GDF-15 levels is not limited to CVDs or cardiac surgery but can be associated with variable diseases, including diabetes and cancer. Moreover, the normal range of GDF-15 is not well defined. Given its promise for improving patient care and outcomes in cardiovascular surgery, future research should explore the potential of GDF-15 as a biomarker for postoperative outcomes and target therapeutic intervention.

Cross-sectional association of skeletal muscle mass and strength with dietary habits and physical activity among first-year university students in Japan: Results from the KEIJI-U study

OBJECTIVE

Recently, the high prevalence of young Japanese individuals who are underweight has received attention because of the potential risk for sarcopenia. The aim of this study was to examine the prevalence and characteristics of sarcopenia in Japanese youth.

METHODS

In this cross-sectional study, we measured skeletal muscle mass using a multifrequency bioelectrical impedance analysis device and handgrip strength (HGS) and administered questionnaires on dietary habits and physical activity in 1264 first-year university students ages 18 to 20 y (838 men and 426 women). Sarcopenia was confirmed based on the presence of both low skeletal muscle mass and weak muscle strength.

RESULTS

In all, 145 men (17%) and 69 women (16%) were diagnosed as underweight. Sarcopenia was diagnosed in 8 men (1%) and 5 women (1%). There was a significantly higher prevalence of low skeletal muscle mass index (SMI) and/or weak HGS in underweight individuals than in those in other body mass index (BMI) ranges. The multivariate analyses indicated that SMI and HGS were significantly associated with BMI in both sexes. Furthermore, after adjusting for BMI, both SMI and HGS were significantly associated with physical activity in men, and SMI was significantly associated with energy intake in women.

CONCLUSIONS

First-year university students showed a high incidence of being underweight with low SMI and/or weak HGS, but the prevalence of sarcopenia was low in both sexes. There may be sex differences in factors related to muscle mass and strength, but further research is needed to clarify this.

Probiotic BC30 Improves Amino Acid Absorption from Plant Protein Concentrate in Older Women

Weizmannia coagulans GBI-30, 6086 (BC30) has previously been shown to increase protein digestion in an in vitro model of the stomach and small intestine and amino acid appearance in healthy men and women after ingestion of milk protein concentrate. The impact of ingesting BC30 with other protein sources or in other demographics is largely unknown. The purpose of this study was to examine the impact of adding BC30 to a 20-g dose of a blend of rice and pea protein on postprandial changes in blood amino acids concentrations in healthy, older women. Healthy, older females (n = 30, 58.5 ± 5.2 years, 165.4 ± 6.8 cm, 65.6 ± 8.8 kg, 23.7 ± 3.2 kg/m2) completed two separate 14-day supplementation protocols separated by a 3-week washout period. Participants were instructed to ingest a 20-g protein dose of a blend of rice and pea protein concentrates (ProDiem Plant Protein Solutions, Kerry) with (PPCBC30) or without (PPC) the addition of 1 × 109 CFU BC30 (Kerry). Body composition and demographics were assessed upon arrival to the laboratory. Upon ingestion of their final assigned supplemental dose, blood samples were taken at 0 (baseline), 30-, 60-, 90-, 120-, 180-, and 240-min post-consumption and analyzed for amino acid concentrations. Alanine (p = 0.018), tryptophan (p = 0.003), cysteine (p = 0.041), essential amino acids (p = 0.050), and total amino acids (p = 0.039) all exhibited significantly (p ≤ 0.05) greater AUC with PPCBC30 when compared to PPC. In addition, tryptophan (p = 0.003), cysteine (p = 0.021), essential amino acids (p = 0.049), and total amino acids (p = 0.035) displayed significantly greater (p ≤ 0.05) concentration maximum (CMax) values in PPCBC30 when compared to PPC. Finally, time to reach CMax (TMax) was similar between conditions with 80% of all measured amino acids and amino acid combinations achieving CMax at a similar time (~ 60 min). Only phenylalanine TMax was found to be different (p = 0.01) between the two conditions with PPC displaying a greater proportion of TMax values after 30 min. Following qualitative (non-inferential) assessment, 88% of all measured outcomes achieved a higher AUC with PPCBC30 and 100% of all outcomes achieved a higher CMax with PPCBC30. In concert with previous findings in a younger mixed gender cohort with milk protein, the addition of BC30 to a daily 20-g dose of plant protein concentrate in healthy older women improved AUC and CMax values in several individual amino acids and amino acid combinations. Retrospectively registered on April 6, 2022, at ClinicalTrials.gov as NCT05313178.

Association between urea trajectory and protein dose in critically ill adults: a secondary exploratory analysis of the effort protein trial (RE-EFFORT)

BACKGROUND

Delivering higher doses of protein to mechanically ventilated critically ill patients did not improve patient outcomes and may have caused harm. Longitudinal urea measurements could provide additional information about the treatment effect of higher protein doses. We hypothesised that higher urea values over time could explain the potential harmful treatment effects of higher doses of protein.

METHODS

We conducted a reanalysis of a randomised controlled trial of higher protein doses in critical illness (EFFORT Protein). We applied Bayesian joint models to estimate the strength of association of urea with 30-day survival and understand the treatment effect of higher protein doses.

RESULTS

Of the 1301 patients included in EFFORT Protein, 1277 were included in this analysis. There were 344 deaths at 30 days post-randomisation. By day 6, median urea was 2.1 mmol/L higher in the high protein group (95% CI 1.1-3.2), increasing to 3.0 mmol/L (95% CI 1.3-4.7) by day 12. A twofold rise in urea was associated with an increased risk of death at 30 days (hazard ratio 1.34, 95% credible interval 1.21-1.48), following adjustment of baseline characteristics including age, illness severity, renal replacement therapy, and presence of AKI. This association persisted over the duration of 30-day follow-up and in models adjusting for evolution of organ failure over time.

CONCLUSIONS

The increased risk of death in patients randomised to a higher protein dose in the EFFORT Protein trial was estimated to be mediated by increased urea cycle activity, of which serum urea is a biological signature. Serum urea should be taken into consideration when initiating and continuing protein delivery in critically ill patients.

CLINICALTRIALS

gov Identifier: NCT03160547 (2017-05-17).

Post-intensive care syndrome follow-up system after hospital discharge: a narrative review

BACKGROUND

Post-intensive care syndrome (PICS) is the long-lasting impairment of physical functions, cognitive functions, and mental health after intensive care. Although a long-term follow-up is essential for the successful management of PICS, few reviews have summarized evidence for the efficacy and management of the PICS follow-up system.

MAIN TEXT

The PICS follow-up system includes a PICS follow-up clinic, home visitations, telephone or mail follow-ups, and telemedicine. The first PICS follow-up clinic was established in the U.K. in 1993 and its use spread thereafter. There are currently no consistent findings on the efficacy of PICS follow-up clinics. Under recent evidence and recommendations, attendance at a PICS follow-up clinic needs to start within three months after hospital discharge. A multidisciplinary team approach is important for the treatment of PICS from various aspects of impairments, including the nutritional status. We classified face-to-face and telephone-based assessments for a PICS follow-up from recent recommendations. Recent findings on medications, rehabilitation, and nutrition for the treatment of PICS were summarized.

CONCLUSIONS

This narrative review aimed to summarize the PICS follow-up system after hospital discharge and provide a comprehensive approach for the prevention and treatment of PICS.

Environmental Enrichment Improves Motor Function and Muscle Transcriptome of Aged Mice

Aging results in the progressive decline of muscle strength. Interventions to maintain muscle strength may mitigate the age-related loss of physical function, thus maximizing health span. The work on environmental enrichment (EE), an experimental paradigm recapitulating aspects of an active lifestyle, has revealed EE-induced metabolic benefits mediated by a brain-fat axis across the lifespan of mice. EE initiated at 18-month of age shows a trend toward an increased mean lifespan. While previous work described EE's influences on the aging dynamics of several central-peripheral processes, its influence on muscle remained understudied. Here, the impact of EE is investigated on motor function, neuromuscular physiology, and the skeletal muscle transcriptome. EE is initiated in 20-month-old mice for a five-month period. EE mice exhibit greater relative lean mass that is associated with improved mobility and hindlimb grip strength. Transcriptomic profiling of muscle tissue reveals an EE-associated enrichment of gene expression within several metabolic pathways related to oxidative phosphorylation and the TCA cycle. Many mitochondrial-related genes-several of which participate in the electron transport chain-are upregulated. Stress-responsive signaling pathways are downregulated because of EE. The results suggest that EE improves motor function-possibly through preservation of mitochondrial function-even late in life.

Zebrafish as an Emerging Model for Sarcopenia: Considerations, Current Insights, and Future Directions

Sarcopenia poses a significant challenge to public health and can severely impact the quality of life of aging populations. Despite extensive efforts to study muscle degeneration using traditional animal models, there is still a lack of effective diagnostic tools, precise biomarkers, and treatments for sarcopenia. Zebrafish models have emerged as powerful tools in biomedical research, providing unique insights into age-related muscle disorders like sarcopenia. The advantages of using zebrafish models include their rapid growth outside of the embryo, optical transparency during early developmental stages, high reproductive potential, ease of husbandry, compact size, and genetic tractability. By deepening our understanding of the molecular processes underlying sarcopenia, we may develop novel diagnostic tools and effective treatments that can improve the lives of aging individuals affected by this condition. This review aims to explore the unique advantages of zebrafish as a model for sarcopenia research, highlight recent breakthroughs, outline potential avenues for future investigations, and emphasize the distinctive contributions that zebrafish models offer. Our research endeavors to contribute significantly to address the urgent need for practical solutions to reduce the impact of sarcopenia on aging populations, ultimately striving to enhance the quality of life for individuals affected by this condition.

Publication trends in nutrition research for sarcopenic obesity: A 20-year bibliometric analysis

BACKGROUND

We used bibliometric methods to evaluate publications on the role of nutrition in sarcopenic obesity and analyzed the current situation and developmental trends over the past 2 decades.

METHODS

Publications from 2002 to 2022 related to the role of nutrition in sarcopenic obesity were extracted from the Web of Science Core Collection database. CiteSpace, VOSviewer, and the Bibliometrix R package were applied to build relevant network diagrams.

RESULTS

One thousand ninety-four articles from 64 countries were included. The annual number of publications in this field has shown an intense growth trend. The University of Alberta, Yonsei University, and Korea University are the major research institutions. Clinical Nutrition has published the most papers on the role of nutrition in sarcopenic obesity, and the American Journal of Clinical Nutrition is the most co-cited journal. A total of 5834 authors conducted the relevant studies. Yves Boirie has published the most papers in this field, and AJ Cruz-Jentoft is the most co-cited author.

CONCLUSION

This is the first bibliometric study of the role of nutrition in sarcopenic obesity. This study systematically summarizes the research hotspots and development directions in this field, and provides a reference for scholars studying the role of nutrition in sarcopenic obesity.

Current Research on Vitamin D Supplementation against Sarcopenia: A Review of Clinical Trials

Vitamin D plays an important role in skeletal muscle function and metabolism. The aim of this review was A) to discuss the clinical evidence of vitamin D supplementation either alone or combined with other strategies in the prevention of sarcopenia in non-sarcopenic individuals and B) to critically discuss the clinical evidence on the effect of vitamin D combined with other strategies on muscle strength, mass and function in sarcopenic individuals without vitamin D deficiency. Sparse clinical data on non-sarcopenic individuals indicate that vitamin D alone has a subtle beneficial effect on knee extensor strength at doses 880-1600 IU/day without improving handgrip strength or muscle mass. When co-administered with other supplements such as protein, mixed effects appear to prevent the decline of muscle mass, possibly delaying the onset of sarcopenia in non-sarcopenic individuals, at doses of 800-1,000 IU/day over 6-12 weeks. In sarcopenic individuals, vitamin D 100-1,000 IU/day co-supplementation with protein results in increased handgrip strength between 9.8-40.5%. However, there is no strong clinical evidence that vitamin D dosage correlates with changes in muscle strength or mass. Potential sources of discrepancy among studies are discussed. Future studies with appropriate experimental design are essential to dissect the net effect of vitamin D on sarcopenia.

Sarcopenia and malignancies: epidemiology, clinical classification and implications

Sarcopenia is a progressive systemic skeletal muscle disorder characterized by a pathological decline in muscle strength, quantity, and quality, which frequently affects the elderly population. The majority of cancer patients are of advanced age. Patients may already have sarcopenia prior to cancer development, and those with cancer are prone to developing sarcopenia due to hypercatabolism, inflammation, reduced physical fitness, anorexia, adverse effects, and stress associated with anticancer therapy. Based on the timing, sarcopenia in patients with cancer can be categorized into three: pre-existing sarcopenia before the onset of cancer, sarcopenia related to cancer, and sarcopenia related to cancer treatment. Sarcopenia not only changes the body composition of patients with cancer but also increases the incidence of postoperative complications, reduces therapeutic efficacy, impairs quality of life, and results in shortened survival. Different therapeutic strategies are required to match the cancer status and physical condition of patients with different etiologies and stages of sarcopenia. Here, we present a comprehensive review of the epidemiology and diagnosis of sarcopenia in patients with cancer, elucidate the complex interactions between cancer and sarcopenia, and provide evidence-based strategies for sarcopenia management in these patients.

A single bout of prior resistance exercise attenuates muscle atrophy and declines in myofibrillar protein synthesis during bed-rest in older men

Impairments in myofibrillar protein synthesis (MyoPS) during bed rest accelerate skeletal muscle loss in older adults, increasing the risk of adverse secondary health outcomes. We investigated the effect of prior resistance exercise (RE) on MyoPS and muscle morphology during a disuse event in 10 healthy older men (65-80 years). Participants completed a single bout of unilateral leg RE the evening prior to 5 days of in-patient bed-rest. Quadriceps cross-sectional area (CSA) was determined prior to and following bed-rest. Serial muscle biopsies and dual stable isotope tracers were used to determine rates of integrated MyoPS (iMyoPS) over a 7 day habitual 'free-living' phase and the bed-rest phase, and rates of acute postabsorptive and postprandial MyoPS (aMyoPS) at the end of bed rest. Quadriceps CSA at 40%, 60% and 80% of muscle length significantly decreased in exercised (EX) and non-exercised control (CTL) legs with bed-rest. The decline in quadriceps CSA at 40% and 60% of muscle length was attenuated in EX compared with CTL. During bed-rest, iMyoPS rates decreased from habitual values in CTL, but not EX, and were significantly different between legs. Postprandial aMyoPS rates increased above postabsorptive values in EX only. The change in iMyoPS over bed-rest correlated with the change in quadriceps CSA in CTL, but not EX. A single bout of RE attenuated the decline in iMyoPS rates and quadriceps atrophy with 5 days of bed-rest in older men. Further work is required to understand the functional and clinical implications of prior RE in older patient populations. KEY POINTS: Age-related skeletal muscle deterioration, linked to numerous adverse health outcomes, is driven by impairments in muscle protein synthesis that are accelerated during periods of disuse. Resistance exercise can stimulate muscle protein synthesis over several days of recovery and therefore could counteract impairments in this process that occur in the early phase of disuse. In the present study, we demonstrate that the decline in myofibrillar protein synthesis and muscle atrophy over 5 days of bed-rest in older men was attenuated by a single bout of unilateral resistance exercise performed the evening prior to bed-rest. These findings suggest that concise resistance exercise intervention holds the potential to support muscle mass retention in older individuals during short-term disuse, with implications for delaying sarcopenia progression in ageing populations.

Nutritional Value of Yogurt as a Protein Source: Digestibility/Absorbability and Effects on Skeletal Muscle

Yogurt is a traditional fermented food that is accepted worldwide for its high palatability and various health values. The milk protein contained in yogurt exhibits different physical and biological properties from those of non-fermented milk protein due to the fermentation and manufacturing processes. These differences are suggested to affect the time it takes to digest and absorb milk protein, which in turn will influence the blood levels of amino acids and/or hormones, such as insulin, and thereby, the rate of skeletal muscle protein synthesis via the activation of intracellular signaling, such as the mTORC1 pathway. In addition, based on the relationship between gut microbiota and skeletal muscle conditions, yogurt, including lactic acid bacteria and its metabolites, has been evaluated for its role as a protein source. However, the substantial value of yogurt as a protein source and the additional health benefits on skeletal muscle are not fully understood. The purpose of this review is to summarize the research to date on the digestion and absorption characteristics of yogurt protein, its effect on skeletal muscle, and the contribution of lactic acid bacterial fermentation to these effects.

Diet Is Associated with Frailty in Lung Cancer: A Possible Role of Gut Microbiota

This study investigated the associations between diet and frailty in lung cancer patients and the potential role of the gut microbiota involved. We assessed dietary intake and frailty status in 231 lung cancer patients by 3-day, 24-h dietary recalls and Fried frailty criteria, respectively, and collected 50 fecal samples for next-generation sequencing. A total of 75 (32.5%) patients were frail, which might be related to significantly lower intake of energy, protein, carbohydrate, dietary fiber, niacin, leucine, some minerals, and a poorer dietary quality as indicated by the Chinese Healthy Eating Index (p < 0.05). Among these, carbohydrate (OR = 0.98; 95% CI 0.96-0.99; p = 0.010), calcium (OR = 0.99; 95% CI 0.99-1.00; p = 0.025), and selenium (OR = 1.03; 95% CI 1.00-1.06; p = 0.022) were all significantly associated with frailty. A multivariate logistic regression analysis showed that the mean risk of frailty was 0.94 times lower (95% CI 0.90-0.99; p = 0.009) among participants with higher CHEI scores. Additionally, the frail patients demonstrated significantly lower gut microbiota β diversity (p = 0.001) and higher relative abundance of Actinobacteriota (p = 0.033). Frailty in lung cancer patients might be associated with insufficient nutrients intake and a poor dietary quality through gut microbiota regulation.

A focus on leucine in the nutritional regulation of human skeletal muscle metabolism in ageing, exercise and unloading states

Muscle protein synthesis (MPS) and muscle protein breakdown (MPB) are influenced through dietary protein intake and physical (in)activity, which it follows, regulate skeletal muscle (SKM) mass across the lifespan. Following consumption of dietary protein, the bio-availability of essential amino acids (EAA), and primarily leucine (LEU), drive a transient increase in MPS with an ensuing refractory period before the next MPS stimulation is possible (due to the "muscle full" state). At the same time, MPB is periodically constrained via reflex insulin actions. Layering exercise on top of protein intake increases the sensitivity of SKM to EAA, therefore extending the muscle full set-point (∼48 h), to permit long-term remodelling (e.g., hypertrophy). In contrast, ageing and physical inactivity are associated with a premature muscle full set-point in response to dietary protein/EAA and contractile activity. Of all the EAA, LEU is the most potent stimulator of the mechanistic target of rapamycin complex 1 (mTORC1)-signalling pathway, with the phosphorylation of mTORC1 substrates increasing ∼3-fold more than with all other EAA. Furthermore, maximal MPS stimulation is also achieved following low doses of LEU-enriched protein/EAA, negating the need for larger protein doses. As a result, LEU supplementation has been of long term interest to maximise muscle anabolism and subsequent net protein accretion, especially when in tandem with resistance exercise. This review highlights current knowledge vis-à-vis the anabolic effects of LEU supplementation in isolation, and in enriched protein/EAA sources (i.e., EAA and/or protein sources with added LEU), in the context of ageing, exercise and unloading states.

Blazing a trail for the clinical use of rapamycin as a geroprotecTOR

Treatment with rapamycin, an inhibitor of the mechanistic Target Of Rapamycin Complex One (mTORC1) protein kinase, has been repeatedly demonstrated to extend lifespan and prevent or delay age-related diseases in diverse model systems. Concerns over the risk of potentially serious side effects in humans, including immunosuppression and metabolic disruptions, have cautiously limited the translation of rapamycin and its analogs as a treatment for aging associated conditions. During the last decade, we and others have developed a working model that suggests that while inhibition of mTORC1 promotes healthy aging, many of the negative side effects of rapamycin are associated with "off-target" inhibition of a second mTOR complex, mTORC2. Differences in the kinetics and molecular mechanisms by which rapamycin inhibits mTORC1 and mTORC2 suggest that a therapeutic window for rapamycin could be exploited using intermittent dosing schedules or alternative rapalogs that may enable more selective inhibition of mTORC1. However, the optimal dosing schedules and the long-term efficacy of such interventions in humans are unknown. Here, we highlight ongoing or upcoming clinical trials that will address outstanding questions regarding the safety, pharmacokinetics, pharmacodynamics, and efficacy of rapamycin and rapalogs on several clinically oriented outcomes. Results from these early phase studies will help guide the design of phase 3 clinical trials to determine whether rapamycin can be used safely to inhibit mTORC1 for the treatment and prevention of age-related diseases in humans.

Anabolic Resistance in the Pathogenesis of Sarcopenia in the Elderly: Role of Nutrition and Exercise in Young and Old People

The development of sarcopenia in the elderly is associated with many potential factors and/or processes that impair the renovation and maintenance of skeletal muscle mass and strength as ageing progresses. Among them, a defect by skeletal muscle to respond to anabolic stimuli is to be considered. Common anabolic stimuli/signals in skeletal muscle are hormones (insulin, growth hormones, IGF-1, androgens, and β-agonists such epinephrine), substrates (amino acids such as protein precursors on top, but also glucose and fat, as source of energy), metabolites (such as β-agonists and HMB), various biochemical/intracellular mediators), physical exercise, neurogenic and immune-modulating factors, etc. Each of them may exhibit a reduced effect upon skeletal muscle in ageing. In this article, we overview the role of anabolic signals on muscle metabolism, as well as currently available evidence of resistance, at the skeletal muscle level, to anabolic factors, from both in vitro and in vivo studies. Some indications on how to augment the effects of anabolic signals on skeletal muscle are provided.

Aging, adaptation and maladaptation

Aging is accompanied by a dysregulation of adaptive processes. On the one hand, physiological adaptation mechanisms such as learning and memory, immune system plasticity and exercise-dependent muscle remodeling are blunted. On the other hand, several maladaptive processes increase with age including cancer, pathological cardiovascular remodeling and metabolic dysregulation. With increasing age the quotient of beneficial adaptation (Ab) to harmful adaptation (Ah), Ab/Ah, decreases. The adaptation-maladaptation framework of aging entails that there are age-related pathological phenotypes that are the result of activation of physiological adaptation mechanisms (e.g., maladaptation as a result of misdirection of adaptive cascades and molecular damage incurred by adaptation processes) and their occurrence over time might, to some degree, be inevitable. Aging might hence result from the organism's inability to solve the adaptation-maladaptation dilemma. The present work explores the concept of counteracting aging through adaptation and proposes that interventions such as exercise, environmental enrichment and dietary restriction work in counteracting aging because they increase the ratio Ab/Ah by both raising Ab (e.g., by inducing metaplasticity in cells, meaning they raise the adaptability of cells to future stimuli) and decreasing Ah (e.g., through desensitizing certain potentially harmful adaptive mechanisms). Molecules whose aging-related expression changes can explain aspects of dysfunctional adaptation such as CREB and certain immediate early genes are examined and it is delineated how a better understanding of the dynamical organization of adaptation cascades could elucidate the seemingly complex role of adaptation in driving aging as well as protecting against it.

Impact of exercise and leucine-enriched protein supplementation on physical function, body composition, and inflammation in pre-frail older adults: a quasi-experimental study

Background

Exercise and a protein-enriched diet are essential for muscle protein synthesis, cellular growth, mitochondrial function, and immune function. The U.S. Food and Nutrition Board's current guideline on recommended dietary allowance for protein in older adults is 0.8 g/kg per day, which may not be sufficient in vulnerable pre-frail older adults.

Aims

This study aimed to evaluate the impact of leucine-enriched protein supplementation with or without exercise over 3 months in pre-frail older adults who consumed ≤1 g/kg/day of protein on improving (i) physical function, (ii) body composition measures, and (iii) inflammatory biomarkers such as interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α).

Methods

A non-randomized cluster quasi-experimental study guided by the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist of 178 pre-frail older adults [112 control, 44 nutrition (Nu), and 22 in the nutrition with exercise (Nu+Ex) group] comparing the effect of Nu+Ex and Nu on physical function, body composition, and inflammation. At 0, 3, and 6 months, questionnaires on demographics, depression, perceived health, and cognition were administered. Physical function assessment (short physical performance battery [SPPB] test, gait speed, handgrip strength, 5× sit-to-stand [STS]) was conducted, and body composition analysis was performed using a bioelectrical impedance analysis machine. IL-6 and TNF-α were measured at 0 and 3 months.

Results

At 3 months, there were significant improvements in gait speed, 5× STS, SPPB scores, depression, perceived health, fat-free mass, and appendicular skeletal muscle mass indices in the Nu+Ex group. Both Nu+Ex and Nu groups had improvements in body cell mass and reductions in IL-6 and TNF-α. The improvements were not sustained after 6 months.

Conclusion

Our study results need to be validated in future longitudinal randomized studies with a larger sample size focusing on populations at risk.

Hesperidin Ameliorates Sarcopenia through the Regulation of Inflammaging and the AKT/mTOR/FoxO3a Signaling Pathway in 22-26-Month-Old Mice

Faced with a globally aging society, the maintenance of health and quality of life in older people is very important. The age-related loss of muscle mass and strength, known as sarcopenia, severely reduces quality of life and increases the risks of various diseases. In this study, we investigated the inhibitory effect of hesperidin (HES) on inflammaging, with the intention of evaluating its potential use as a treatment for sarcopenia. We studied 22-26-month-old mice, corresponding to humans aged ≥70 years, with aging-related sarcopenia, and young mice aged 3-6 months. The daily administration of HES for 8 weeks resulted in greater muscle mass and strength and increased the fiber size of the old mice. HES also restored the immune homeostasis that had been disrupted by aging, such as the imbalance in M1/M2 macrophage ratio. In addition, we found that HES ameliorated the sarcopenia by regulating AKT/mammalian target of rapamycin/forkhead box 3a signaling through an increase in insulin-like growth factor (IGF)-1 expression in the old mice. Therefore, HES represents a promising candidate inhibitor of sarcopenia in older people, and its effects are achieved through the maintenance of immune homeostasis.

Association of postprandial postexercise muscle protein synthesis rates with dietary leucine: A systematic review

BACKGROUND

Dietary protein ingestion augments post (resistance) exercise muscle protein synthesis (MPS) rates. It is thought that the dose of leucine ingested within the protein (leucine threshold hypothesis) and the subsequent plasma leucine variables (leucine trigger hypothesis; peak magnitude, rate of rise, and total availability) determine the magnitude of the postprandial postexercise MPS response.

METHODS

A quantitative systematic review was performed extracting data from studies that recruited healthy adults, applied a bout of resistance exercise, ingested a bolus of protein within an hour of exercise, and measured plasma leucine concentrations and MPS rates (delta change from basal).

RESULTS

Ingested leucine dose was associated with the magnitude of the MPS response in older, but not younger, adults over acute (0-2 h, r2  = 0.64, p = 0.02) and the entire postprandial (>2 h, r2  = 0.18, p = 0.01) period. However, no single plasma leucine variable possessed substantial predictive capacity over the magnitude of MPS rates in younger or older adults.

CONCLUSION

Our data provide support that leucine dose provides predictive capacity over postprandial postexercise MPS responses in older adults. However, no threshold in older adults and no plasma leucine variable was correlated with the magnitude of the postexercise anabolic response.

Impaired lower limb muscle mass, quality and function in end stage liver disease: A cross-sectional study

NEW FINDINGS

What is the central question of this study? To what extent does musculoskeletal impairment occur (i.e., muscle mass, quality and function) in patients with end stage liver disease (ESLD) by comparison to a healthy age/sex-matched control group? What is the main finding and its importance? Muscle mass, quality and function are impaired in patients with ESLD (compared to age/sex matched controls). Importantly, greater impairments were seen in lower limb compared to arm and trunk muscle groups. These findings may suggest that there should be greater consideration of muscle health in functionally relevant lower limb muscle groups.

ABSTRACT

Sarcopenia is associated with reduced quality of life and increased mortality in patients with end stage liver disease (ESLD). Historically, sarcopenia identification in ESLD utilised L3 skeletal muscle index (SMI). There are few data on muscle quality and function within lower limb muscle groups with high functional relevance. The aim of this prospective case-control study was to evaluate the quadriceps muscle in patients with ESLD. Muscle mass and quality were evaluated using MRI (quadriceps anatomical cross sectional area (ACSA), quadriceps volume index, L3 SMI, quadriceps intermuscular adipose tissue (IMAT)), mid-arm muscle circumference (MAMC) and ultrasonography (vastus lateralis (VL) thickness and quadriceps ACSA). Muscle strength/function was assessed by handgrip strength, peak quadriceps isokinetic torque and chair rise time. Thirty-nine patients with ESLD (55 years, 61% male, 48% alcoholic related liver disease (ArLD), 71% Child-Pugh B/C) and 18 age/sex-matched healthy control participants (HC) were studied. Quadriceps mass was significantly reduced in ESLD versus HC (-17%), but L3 SMI and MAMC were unchanged. Quadriceps IMAT percentage was increased in ESLD (+103%). Handgrip strength (-15%), peak isokinetic torque (-29%), and chair rise time (+56%) were impaired in ESLD. Ultrasound measures of VL thickness (r = 0.56, r = 0.57, r = 0.42) and quadriceps ACSA (r = 0.98, r = 0.86, r = 0.67) correlated to MRI quadriceps ACSA, quadriceps volume and L3 SMI, respectively. Quadriceps muscle mass, quality, and function were impaired in patients with ESLD, whereas conventional assessments of muscle (L3 SMI and MAMC) highlighted no differences between ESLD and HC. Full evaluation of lower limb muscle health is essential in ESLD in order to accurately assess sarcopenia and target future interventions.

Possible-sarcopenic screening with disturbed plasma amino acid profile in the elderly

BACKGROUND

The mass and strength of skeletal muscle decline with age, leading to its progressive dysfunction. High-throughput metabolite profiling provides the opportunity to reveal metabolic mechanisms and the identification of biomarkers. However, the role of amino acid metabolism in possible sarcopenia remains unclear.

OBJECTIVES

The aim of this study included exploring variations in plasma amino acid concentrations in elderly individuals who have possible sarcopenia and further attempting to characterize a distinctive plasma amino acid profile through targeted metabolomics.

METHODS

A cross-sectional, correlational research design was used for this study. Thirty possible-sarcopenic elderly participants were recruited (n = 30), as determined by the Asian Working Group for Sarcopenia (AWGS). Meanwhile, a reference group of non-sarcopenic (sex-, age-, and Appendicular Skeletal muscle Mass Index (ASMI)-matched non-sarcopenic controls, n = 36) individuals was included to compare the potential differences in metabolic fingerprint of the plasma amino acids associated with sarcopenia. Both groups were conducted the body composition analysis, physical function examination, and plasma amino acid-targeted metabolomics. The amino acids in plasma were measured using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS). Also, orthogonal partial least-squares-discriminant analysis (OPLS-DA) was applied to characterize the plasma amino acid profile.

RESULTS

With respect to Handgrip Strength (HGS), the Five-Repetition Chair Stand Test (CS-5), the Six-Minute Walking Test (6MWT), the arm curl, the 30 s-Chair Stand Test (CST), the 2-Minute Step Test (2MST), the Timed Up-and-Go Test (TUGT), there was a decline in skeletal muscle function in the possible-sarcopenic group compared to the non-sarcopenic group. The mean plasma concentrations of arginine, asparagine, phenylalanine, serine, lysine, glutamine, and threonine were significantly lower in the possible sarcopenia group, whereas cirulline, proline, serine, and glutamic acid concentrations were higher. According to the multi-analysis, glutamine, serine, lysine, threonine, and proline were determined as the potential markers that indicated possible sarcopenia.

CONCLUSIONS

The findings characterize significantly altered plasma amino acid metabolisms in the elderly with possible sarcopenia, which aids to screening people who are at a high risk of developing condition, and motivating to design new preventive and therapeutic approaches.

Whey Protein Supplementation with or without Vitamin D on Sarcopenia-Related Measures: A Systematic Review and Meta-Analysis

The effects of supplementation with whey protein alone or with vitamin D on sarcopenia-related outcomes in older adults are unclear. We aimed to assess the effect of whey protein supplementation alone or with vitamin D on lean mass (LM), strength, and function in older adults with or without sarcopenia or frailty. We searched PubMed, Web of Science, and SCOPUS databases. Randomized controlled trials (RCT) that investigated the effect of whey protein supplementation with or without vitamin D on sarcopenia outcomes in healthy and sarcopenic or frail older adults were included. Standardized mean differences (SMDs) were calculated for LM, muscle strength, and physical function data. The analysis showed that whey protein supplementation had no effect on LM and muscle strength; nevertheless, a significant improvement was found in physical function (SMD = 0.561; 95% confidence interval [CIs]: 0.256, 0.865, n = 33), particularly gait speed (GS). On the contrary, whey protein supplementation significantly improved LM (SMD = 0.982; 95% CI: 0.228, 1.736; n = 11), appendicular lean mass and physical function (SMD = 1.211; 95% CI: 0.588, 1.834; n = 16), and GS in sarcopenic/frail older adults. By contrast, co-supplementation with vitamin D enhanced LM gains (SMD =0.993; 95% CI: 0.112, 1.874; n = 11), muscle strength (SMD =2.005; 95% CI: 0.975, 3.035; n = 11), and physical function (SMD = 3.038; 95% CI: 2.196, 3.879; n = 18) significantly. Muscle strength and physical function improvements after whey protein supplementation plus vitamin D were observed without resistance exercise (RE) and short study duration subgroups. Moreover, the combination of whey protein and vitamin D with RE did not enhance the effect of RE. Whey protein supplementation improved LM and function in sarcopenic/frail older adults but had no positive effect in healthy older persons. By contrast, our meta-analysis showed that co-supplementation with whey protein and vitamin D is effective, particularly in healthy older adults, which is likely owing, we propose, to the correction of vitamin D insufficiency or deficiency. The trial was registered at https://inplasy.com as INPLASY202240167.

Age-related metabolite profiles and their relation to clinical outcomes in young adults, middle-aged individuals, and older people

Age is a significant risk factor for common noncommunicable diseases, yet the physiological alterations of aging are poorly understood. We were interested in metabolic patterns between cross-sectional cohorts of different age ranges with particular emphasis on waist circumference. We recruited three cohorts of healthy subjects with different age ranges (adolescents 18-25 years, adults 40-65 years, and older citizens 75-85 years) and stratified these based on waist circumference. Using targeted LC-MS/MS metabolite profiling, we analyzed 112 analytes in plasma (amino acids, acylcarnitines, and derivatives). We associated age-related alterations with various anthropometric and functional parameters such as insulin sensitivity and handgrip strength. Strongest age-dependent increases were found for fatty acid-derived acylcarnitines. Amino acid-derived acylcarnitines displayed increased associations with BMI and adiposity. Some essential amino acids changed in opposite directions, being lower at increased age and higher with increasing adiposity. τ-methylhistidine was elevated in older subjects, especially on an adiposity background, suggesting an increased protein turnover. Both aging and adiposity are associated with impaired insulin sensitivity. Skeletal muscle mass decreased with age and increased with adiposity. Profound differences in the metabolite signatures during healthy aging and elevated waist circumference/body weight were found. Opposite changes in skeletal muscle mass as well as possible differences in insulin signaling (relative insulin deficiency in older subjects versus hyperinsulinemia associated with adiposity), might be underlying origins for the observed metabolite signatures. We describe novel associations between metabolites and anthropometric factors during aging which underlines the complex interplay of aging, insulin resistance, and metabolic health.

Exercise and ageing impact the kynurenine/tryptophan pathway and acylcarnitine metabolite pools in skeletal muscle of older adults

Exercise-induced perturbation of skeletal muscle metabolites is a probable mediator of long-term health benefits in older adults. Although specific metabolites have been identified to be impacted by age, physical activity and exercise, the depth of coverage of the muscle metabolome is still limited. Here, we investigated resting and exercise-induced metabolite distribution in muscle from well-phenotyped older adults who were active or sedentary, and a group of active young adults. Percutaneous biopsies of the vastus lateralis were obtained before, immediately after and 3 h following a bout of endurance cycling. Metabolite profile in muscle biopsies was determined by tandem mass spectrometry. Mitochondrial energetics in permeabilized fibre bundles was assessed by high resolution respirometry and fibre type proportion was assessed by immunohistology. We found that metabolites of the kynurenine/tryptophan pathway were impacted by age and activity. Specifically, kynurenine was elevated in muscle from older adults, whereas downstream metabolites of kynurenine (kynurenic acid and NAD+ ) were elevated in muscle from active adults and associated with cardiorespiratory fitness and muscle oxidative capacity. Acylcarnitines, a potential marker of impaired metabolic health, were elevated in muscle from physically active participants. Surprisingly, despite baseline group difference, acute exercise-induced alterations in whole-body substrate utilization, as well as muscle acylcarnitines and ketone bodies, were remarkably similar between groups. Our data identified novel muscle metabolite signatures that associate with the healthy ageing phenotype provoked by physical activity and reveal that the metabolic responsiveness of muscle to acute endurance exercise is retained [NB]:AUTHOR: Please ensure that the appropriate material has been provide for Table S2, as well as for Figures S1 to S7, as also cited in the text with age regardless of activity levels. KEY POINTS: Kynurenine/tryptophan pathway metabolites were impacted by age and physical activity in human muscle, with kynurenine elevated in older muscle, whereas downstream products kynurenic acid and NAD+ were elevated in exercise-trained muscle regardless of age. Acylcarnitines, a marker of impaired metabolic health when heightened in circulation, were elevated in exercise-trained muscle of young and older adults, suggesting that muscle act as a metabolic sink to reduce the circulating acylcarnitines observed with unhealthy ageing. Despite the phenotypic differences, the exercise-induced response of various muscle metabolite pools, including acylcarnitine and ketone bodies, was similar amongst the groups, suggesting that older adults can achieve the metabolic benefits of exercise seen in young counterparts.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: Hype or Hope for Skeletal Muscle Anti-Frailty

Steadily rising population ageing is a global demographic trend due to the advancement of new treatments and technologies in the medical field. This trend also indicates an increasing prevalence of age-associated diseases, such as loss of muscle mass (sarcopenia), which tends to afflict the older population. The deterioration in muscle function can cause severe disability and seriously affects a patient's quality of life. Currently, there is no treatment to prevent and reverse age-related skeletal muscle ageing frailty. Existing interventions mainly slow down and control the signs and symptoms. Mesenchymal stem cell-derived extracellular vesicle (MSC-EV) therapy is a promising approach to attenuate age-related skeletal muscle ageing frailty. However, more studies, especially large-scale randomised clinical trials need to be done in order to determine the adequacy of MSC-EV therapy in treating age-related skeletal muscle ageing frailty. This review compiles the present knowledge of the causes and changes regarding skeletal muscle ageing frailty and the potential of MSC-EV transplantation as a regenerative therapy for age-related skeletal muscle ageing frailty and its clinical trials.

Efficacy and Safety of 6-Month High Dietary Protein Intake in Hospitalized Adults Aged 75 or Older at Nutritional Risk: An Exploratory, Randomized, Controlled Study

The aim of this study was to investigate the effects of increased dietary protein in daily-life settings in Japan for 6 months on the activities of daily living (ADL) in adults aged 75 or older at nutritional risk. The study was an open-label, exploratory, randomized controlled trial conducted at seven hospitals in Japan. The study participants were adults aged 75 or older who were hospitalized for treatable cancer, pneumonia, fractures, and/or urinary-tract infection at nutritional risk. The primary outcome was change in grip strength, skeletal muscle, and ADL indices (Barthel index, Lawton score). One hundred sixty-nine patients were randomly assigned to the intensive care (IC) or standard care (SC) group; the protein intake goals (g/kgw/day) were 1.5 for IC and 1.0 for SC. There was a significant improvement in grip strength only in the IC group (1.1 kg: 95% CI 0.1 to 2.1) (p = 0.02). While the skeletal muscle index and ADL indices were not significantly improved in either group, the improvement ratio tended to be greater in the IC group. There was no decrease in renal function in either group. Thus, intervention of increased dietary protein in daily-life settings for 6 months in adults aged 75 or older with treatable cancer, pneumonia, fractures, and/or urinary-tract infection and at nutritional risk may be effective in ameliorating loss of muscle strength.

Leucine Intake and Risk of Impaired Physical Function and Frailty in Older Adults

BACKGROUND

Leucine is suggested to play a central role in age-related physical decline, but the effect of dietary leucine intake on physical functioning is uncertain. We examined the prospective association between dietary leucine intake and impaired lower-extremity function (ILEF) and frailty in older adults.

METHODS

We used data from 2 956 adults aged ≥60 and older from the Seniors-ENRICA cohort. At baseline (2008-2010) and in 2012, dietary information was obtained with a validated computerized face-to-face diet history, from which energy-adjusted cumulative leucine intake per body weight was calculated. Participants were followed up through 2017 to assess incident ILEF, ascertained with the Short Physical Performance Battery, and incident frailty, according to the Fried phenotype criteria. Statistical analysis was performed with Cox models adjusted for the main potential confounders.

RESULTS

During follow-up, we identified 515 incident cases of ILEF and 241 of frailty. Compared with participants in the lowest tertile of leucine intake (35.5-89.0 mg/kg/d), those in the highest tertile (107.4-372.5 mg/kg/d) had a lower risk of ILEF (fully adjusted hazard ratio [95% confidence interval]: 0.70 [0.53-0.93], p trend: .01) and of frailty (0.63 [0.41-0.96], p trend: .03]. A higher consumption of important sources of leucine in this population, including unprocessed beef, oily and white fish, and bread, were also associated with a lower risk of incident ILEF and frailty.

CONCLUSIONS

Higher leucine intake was associated with reduced risk of ILEF and frailty. Dietary leucine, obtained from foods rich in high-quality protein, could be a key nutrient to prevent age-related physical function decline in older adults.

Sarcopenia - Definition, Radiological Diagnosis, Clinical Significance

BACKGROUND

 Sarcopenia is an age-related syndrome characterized by a loss of muscle mass and strength. As a result, the independence of the elderly is reduced and the hospitalization rate and mortality increase. The onset of sarcopenia often begins in middle age due to an unbalanced diet or malnutrition in association with a lack of physical activity. This effect is intensified by concomitant diseases such as obesity or metabolic diseases including diabetes mellitus.

METHOD

 With effective preventative diagnostic procedures and specific therapeutic treatment of sarcopenia, the negative effects on the individual can be reduced and the negative impact on health as well as socioeconomic effects can be prevented. Various diagnostic options are available for this purpose. In addition to basic clinical methods such as measuring muscle strength, sarcopenia can also be detected using imaging techniques like dual X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI), and sonography. DXA, as a simple and cost-effective method, offers a low-dose option for assessing body composition. With cross-sectional imaging techniques such as CT and MRI, further diagnostic possibilities are available, including MR spectroscopy (MRS) for noninvasive molecular analysis of muscle tissue. CT can also be used in the context of examinations performed for other indications to acquire additional parameters of the skeletal muscles (opportunistic secondary use of CT data), such as abdominal muscle mass (total abdominal muscle area - TAMA) or the psoas as well as the pectoralis muscle index. The importance of sarcopenia is already well studied for patients with various tumor entities and also infections such as SARS-COV2.

RESULTS AND CONCLUSION

 Sarcopenia will become increasingly important, not least due to demographic changes in the population. In this review, the possibilities for the diagnosis of sarcopenia, the clinical significance, and therapeutic options are described. In particular, CT examinations, which are repeatedly performed on tumor patients, can be used for diagnostics. This opportunistic use can be supported by the use of artificial intelligence.

KEY POINTS

· Sarcopenia is an age-related syndrome with loss of muscle mass and strength.. · Early detection and therapy can prevent negative effects of sarcopenia.. · In addition to DEXA, cross-sectional imaging techniques (CT, MRI) are available for diagnostic purposes.. · The use of artificial intelligence (AI) offers further possibilities in sarcopenia diagnostics..

CITATION FORMAT

· Vogele D, Otto S, Sollmann N et al. Sarcopenia - Definition, Radiological Diagnosis, Clinical Significance. Fortschr Röntgenstr 2023; DOI: 10.1055/a-1990-0201.

Alternative dietary protein sources to support healthy and active skeletal muscle aging

To mitigate the age-related decline in skeletal muscle quantity and quality, and the associated negative health outcomes, it has been proposed that dietary protein recommendations for older adults should be increased alongside an active lifestyle and/or structured exercise training. Concomitantly, there are growing environmental concerns associated with the production of animal-based dietary protein sources. The question therefore arises as to where this dietary protein required for meeting the protein demands of the rapidly aging global population should (or could) be obtained. Various non-animal-derived protein sources possess favorable sustainability credentials, though much less is known (compared with animal-derived proteins) about their ability to influence muscle anabolism. It is also likely that the anabolic potential of various alternative protein sources varies markedly, with the majority of options remaining to be investigated. The purpose of this review was to thoroughly assess the current evidence base for the utility of alternative protein sources (plants, fungi, insects, algae, and lab-grown "meat") to support muscle anabolism in (active) older adults. The solid existing data portfolio requires considerable expansion to encompass the strategic evaluation of the various types of dietary protein sources. Such data will ultimately be necessary to support desirable alterations and refinements in nutritional guidelines to support healthy and active aging, while concomitantly securing a sustainable food future.

Oligonucleotide Therapeutics for Age-Related Musculoskeletal Disorders: Successes and Challenges

Age-related disorders of the musculoskeletal system including sarcopenia, osteoporosis and arthritis represent some of the most common chronic conditions worldwide, for which there remains a great clinical need to develop safer and more efficacious pharmacological treatments. Collectively, these conditions involve multiple tissues, including skeletal muscle, bone, articular cartilage and the synovium within the joint lining. In this review, we discuss the potential for oligonucleotide therapies to combat the unmet clinical need in musculoskeletal disorders by evaluating the successes of oligonucleotides to modify candidate pathological gene targets and cellular processes in relevant tissues and cells of the musculoskeletal system. Further, we discuss the challenges that remain for the clinical development of oligonucleotides therapies for musculoskeletal disorders and evaluate some of the current approaches to overcome these.

Association of Different Obesity Phenotypes with Sarcopenia in Han Chinese Middle-Aged and Elderly with Type 2 Diabetes Individuals

PURPOSE

To investigate the relationship between different obesity phenotypes and sarcopenia in hospitalized Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

This cross-sectional study included 385 men. Anthropometric measurements including applied the determination method of Dual-energy X-ray absorptiometry (DXA) determination of limb skeletal muscle mass index (ASMI) and blood samples were analyzed. The people were divided into four groups according to body mass index (BMI) (≥24kg/m²) and waist circumference (WC) (female ≥85cm, male ≥90cm). Group A (BMI and WC were normal), Group B (BMI was normal and high WC), Group C (high BMI and WC were normal), and Group D (BMI and WC were abnormal).

RESULTS

The prevalence rates of sarcopenia and abdominal obesity were 32.2% and 74.0%, respectively. The detection rate of lower ASMI decreased gradually from Group A to Group D(74.6% vs 68.3% vs 54.5% vs 51.6%, χ 2 =14.243, P=0.003). Logistic analysis showed that the risk of lower ASMI were decreased by 62.4% (95% CI: 0.149-0.950, P = 0.039) in Group C and 68.8% (95% CI: 0.165-0.593, P = 0.000) in Group D compared with Group A, respectively. The risk of lower ASMI were increased 4.153-fold (95% CI: 2.623-6.576, P = 0.000) in male. Male (OR = 4.065, 95% CI: 2.246-7.356, P = 0.000) and WC (OR = 1.053, 95% CI: 1.004-1.104, P = 0.033) were risk factors for lower ASMI, but the risk of lower ASMI was decreased by 32% (95% CI: 0.5744-0.804, P = 0.000) by elevated BMI in the overweight and obese group (Group C and Group D).

CONCLUSION

The prevalence of sarcopenia and abdominal obesity was elevated in han Chinese middle-aged and elderly patients with T2DM. Being overweight or obesity as defined by BMI protect against sarcopenia, while abdominal obesity increases the risk of sarcopenia.

The Influence of n-3PUFA Supplementation on Muscle Strength, Mass, and Function: A Systematic Review and Meta-Analysis

The effects of omega 3 polyunsaturated fatty acids (n-3PUFA) supplementation on skeletal muscle are currently unclear. The purpose of this systematic review was to synthesize all available evidence regarding the influence of n-3PUFA supplementation on muscle mass, strength, and function in healthy young and older adults. Four databases were searched (Medline, Embase, Cochrane CENTRAL, and SportDiscus). Predefined eligibility criteria were determined according to Population, Intervention, Comparator, Outcomes, and Study Design. Only peer-reviewed studies were included. The Cochrane RoB2 Tool and the NutriGrade approach were used to access risk of bias and certainty in evidence. Effect sizes were calculated using pre-post scores and analyzed using a three-level, random-effects meta-analysis. When sufficient studies were available, subanalyses were performed in the muscle mass, strength, and function outcomes according to participant's age (<60 or ≥60 years), supplementation dosage (<2 or ≥2 g/day), and training intervention ("resistance training" vs. "none or other"). Overall, 14 individual studies were included, total 1443 participants (913 females; 520 males) and 52 outcomes measures. Studies had high overall risk of bias and consideration of all NutriGrade elements resulted in a certainty assessment of moderate meta-evidence for all outcomes. n-3PUFA supplementation had no significant effect on muscle mass (standard mean difference [SMD] = 0.07 [95% CI: -0.02, 0.17], P = 0.11) and muscle function (SMD = 0.03 [95% CI: -0.09, 0.15], P = 0.58), but it showed a very small albeit significant positive effect on muscle strength (SMD = 0.12 [95% CI: 0.006, 0.24], P = 0.04) in participants when compared with placebo. Subgroup analyses showed that age, supplementation dose, or cosupplementation alongside resistance training did not influence these responses. In conclusion, our analyses indicated that n-3PUFA supplementation may lead to very small increases in muscle strength but did not impact muscle mass and function in healthy young and older adults. To our knowledge, this is the first review and meta-analysis investigating whether n-3PUFA supplementation can lead to increases in muscle strength, mass, and function in healthy adults. Registered protocol: doi.org/10.17605/OSF.IO/2FWQT.