Amino acid metabolism and regulatory effects in aging

Essential amino acids and branched-chain amino acids are associated with skeletal muscle and inflammatory parameters in older age

Aging is associated with a decline in muscle mass and function, increasing the risk of adverse health outcomes. Amino acid profiling has emerged as a potential tool for assessing skeletal muscle health. This study examines the associations between fasting plasma amino acids, muscle function, and inflammation in healthy older and young adults. Data from 131 participants (101 older adults, 71.5±4.9 years; 30 young adults, 25.5±3.9 years) were analyzed. Skeletal muscle mass was assessed using bioimpedance analysis, and hand grip strength was measured with a dynamometer. Plasma amino acids, kynurenine, and inflammatory markers (CRP, IL-6) were quantified using ultraperformance liquid chromatography with tandem mass spectrometry and commercial immunosorbent assays, respectively. Older adults exhibited lower levels of glutamic acid, isoleucine, leucine, phenylalanine, kynurenine, and kynurenine-to-tryptophan (KYN:TRP) ratio compared to younger individuals (all p<0.05). In older adults, branched-chain and essential amino acids correlated positively with skeletal muscle index (SMI) and hand grip strength, whereas in young adults, only glutamic acid, proline, and KYN:TRP showed positive associations with SMI (all p<0.05). CRP and IL-6 were associated with several amino acids in older adults but not in younger individuals. These findings suggest that age-related shifts in amino acid profiles may reflect underlying changes in muscle metabolism and function, highlighting their potential as early indicators of muscle decline.

Serine metabolism in aging and age-related diseases

Non-essential amino acids are often overlooked in biomedical research; however, they are crucial components of organismal metabolism. One such metabolite that is integral to physiological function is serine. Serine acts as a pivotal link connecting glycolysis with one-carbon and lipid metabolism, as well as with pyruvate and glutathione syntheses. Interestingly, increasing evidence suggests that serine metabolism may impact the aging process, and supplementation with serine may confer benefits in safeguarding against aging and age-related disorders. This review synthesizes recent insights into the regulation of serine metabolism during aging and its potential to promote healthy lifespan and mitigate a spectrum of age-related diseases.

Study on the Effect of Bee Venom and Its Main Component Melittin in Delaying Skin Aging in Mice

Bee venom (BV) and its main compound melittin (MLT) have antioxidant, anti-inflammatory, and anti-aging activities; however, very little research has been conducted on their effects on skin aging. In this study, a mouse skin aging model induced by D-galactose was constructed via subcutaneous injection into the scruff of the neck, and different doses of BV and MLT were used as interventions. The anti-aging effects and mechanisms of BV and MLT were explored by detecting the skin morphology and structure, and anti-aging-related factors and performing non-targeted metabolomics of mice. BV and MLT improved dermal and epidermal thickness, boosted the collagen fiber content, increased hydroxyproline and hyaluronic acid levels, and enhanced transcript-level expression of IL-10, Col1a1, and Col3a1, while decreasing that of IL-1β. Metabolomic analysis showed that BV and MLT regulated the levels of some metabolites (compared to those in the skin aging control). BV effectively alleviated skin aging by regulating the pentose phosphate pathway, and pathways associated with carbon, galactose, and β-alanine metabolism, whereas MLT regulated pathways related to lipid metabolism, cholesterol metabolism, and atherosclerosis. This study highlights the potential applicability of BV and MLT in skin aging treatments and cosmetic products.

Association of Protein Intake with Sarcopenia and Related Indicators Among Korean Older Adults: A Systematic Review and Meta-Analysis

OBJECTIVES

Due to variations in the standards for optimal protein intake and conflicting results across studies for Korean older adults, this study aimed to quantitatively integrate existing research on the association of protein intake with sarcopenia and related indicators in Koreans aged 65 and older through meta-analysis.

METHODS

A total of 23 studies were selected according to the study selection criteria (PICOS). Sixteen cross-sectional studies, 5 randomized controlled trials (RCTs), and 2 non-RCTs were included in the review, with 9 out of 23 studies included in the meta-analysis. We used fixed-effects models and performed subgroup and sensitivity analyses.

RESULTS

A meta-analysis found that the risk of sarcopenia was significantly higher in the <0.8 g/kg/day protein intake group compared to the 0.8-1.2 g/kg/day and ≥1.2 g/kg/day groups, with odds ratios (ORs) of 1.25 (95% confidence interval (CI), 1.10 to 1.42; I2 = 55%) and 1.79 (95% CI, 1.53 to 2.10; I2 = 71%), respectively. For low hand grip strength (HGS), the risk was higher in the <0.8 g/kg/day group compared to the 0.8-1.2 g/kg/day or ≥1.2 g/kg/day groups (OR 1.31; 95% CI, 1.03 to 1.65; I2 = 28%). No significant associations were found with other sarcopenia indicators, such as skeletal muscle mass, short physical performance battery score, balance test, gait speed, and timed up-and-go test.

CONCLUSIONS

Lower protein intake is associated with a higher risk of sarcopenia and low HGS in Korean older adults. To establish protein intake recommendations for the prevention and management of sarcopenia in this population, further well-designed RCTs incorporating both protein supplementation and resistance training are necessary.

Aging insights from heterochronic parabiosis models

Heterochronic parabiosis consists of surgically connecting the circulatory systems of a young and an old animal. This technique serves as a model to study circulating factors that accelerate aging in young organisms exposed to old blood or induce rejuvenation in old organisms exposed to young blood. Despite the promising results, the exact cellular and molecular mechanisms remain unclear, so this study aims to explore and elucidate them in more detail.

Towards Healthy Longevity: Comprehensive Insights from Molecular Targets and Biomarkers to Biological Clocks

Aging is a complex and time-dependent decline in physiological function that affects most organisms, leading to increased risk of age-related diseases. Investigating the molecular underpinnings of aging is crucial to identify geroprotectors, precisely quantify biological age, and propose healthy longevity approaches. This review explores pathways that are currently being investigated as intervention targets and aging biomarkers spanning molecular, cellular, and systemic dimensions. Interventions that target these hallmarks may ameliorate the aging process, with some progressing to clinical trials. Biomarkers of these hallmarks are used to estimate biological aging and risk of aging-associated disease. Utilizing aging biomarkers, biological aging clocks can be constructed that predict a state of abnormal aging, age-related diseases, and increased mortality. Biological age estimation can therefore provide the basis for a fine-grained risk stratification by predicting all-cause mortality well ahead of the onset of specific diseases, thus offering a window for intervention. Yet, despite technological advancements, challenges persist due to individual variability and the dynamic nature of these biomarkers. Addressing this requires longitudinal studies for robust biomarker identification. Overall, utilizing the hallmarks of aging to discover new drug targets and develop new biomarkers opens new frontiers in medicine. Prospects involve multi-omics integration, machine learning, and personalized approaches for targeted interventions, promising a healthier aging population.

Nutrient intake and risk of multimorbidity: a prospective cohort study of 25,389 women

BACKGROUND

Multimorbidity is becoming an increasingly serious public health challenge in the aging population. The impact of nutrients on multimorbidity remains to be determined and was explored using data from a UK cohort study.

METHOD

Our research analysis is mainly based on the data collected by the United Kingdom Women's Cohort Study (UKWCS), which recruited 35,372 women aged 35-69 years at baseline (1995 to 1998), aiming to explore potential associations between diet and chronic diseases. Daily intakes of energy and nutrients were estimated using a validated 217-item food frequency questionnaire at recruitment. Multimorbidity was assessed using the Charlson comorbidity index (CCI) through electronic linkages to Hospital Episode Statistics up to March 2019. Cox's proportional hazards models were used to estimate associations between daily intakes of nutrients and risk of multimorbidity. Those associations were also analyzed in multinomial logistic regression as a sensitivity analysis. In addition, a stratified analysis was conducted with age 60 as the cutoff point.

RESULTS

Among the 25,389 participants, 7,799 subjects (30.7%) were confirmed with multimorbidity over a median follow-up of 22 years. Compared with the lowest quintile, the highest quintile of daily intakes of energy and protein were associated with 8% and 12% increased risk of multimorbidity respectively (HR 1.08 (95% CI 1.01, 1.16), p-linearity = 0.022 for energy; 1.12 (1.04, 1.21), p-linearity = 0.003 for protein). Higher quintiles of daily intakes of vitamin C and iron had a slightly lowered risk of multimorbidity, compared to the lowest quintile. A significantly higher risk of multimorbidity was found to be linearly associated with higher intake quintiles of vitamin B12 and vitamin D (p-linearity = 0.001 and 0.002, respectively) in Cox models, which became insignificant in multinomial logistic regression. There was some evidence of effect modification by age in intakes of iron and vitamin B1 associated with the risk of multimorbidity (p-interaction = 0.006 and 0.025, respectively).

CONCLUSIONS

Our findings highlight a link between nutrient intake and multimorbidity risk. However, there is uncertainty in our results, and more research is needed before definite conclusions can be reached.

Multi-Omic, Histopathologic, and Clinicopathologic Effects of Once-Weekly Oral Rapamycin in a Naturally Occurring Feline Model of Hypertrophic Cardiomyopathy: A Pilot Study

Hypertrophic cardiomyopathy (HCM) remains the single most common cardiomyopathy in cats, with a staggering prevalence as high as 15%. To date, little to no direct therapeutical intervention for HCM exists for veterinary patients. A previous study aimed to evaluate the effects of delayed-release (DR) rapamycin dosing in a client-owned population of subclinical, non-obstructive, HCM-affected cats and reported that the drug was well tolerated and resulted in beneficial LV remodeling. However, the precise effects of rapamycin in the hypertrophied myocardium remain unknown. Using a feline research colony with naturally occurring hereditary HCM (n = 9), we embarked on the first-ever pilot study to examine the tissue-, urine-, and plasma-level proteomic and tissue-level transcriptomic effects of an intermittent low dose (0.15 mg/kg) and high dose (0.30 mg/kg) of DR oral rapamycin once weekly. Rapamycin remained safe and well tolerated in cats receiving both doses for eight weeks. Following repeated weekly dosing, transcriptomic differences between the low- and high-dose groups support dose-responsive suppressive effects on myocardial hypertrophy and stimulatory effects on autophagy. Differences in the myocardial proteome between treated and control cats suggest potential anti-coagulant/-thrombotic, cellular remodeling, and metabolic effects of the drug. The results of this study closely recapitulate what is observed in the human literature, and the use of rapamycin in the clinical setting as the first therapeutic agent with disease-modifying effects on HCM remains promising. The results of this study establish the need for future validation efforts that investigate the fine-scale relationship between rapamycin treatment and the most compelling gene expression and protein abundance differences reported here.

Current Nutritional and Pharmacological Approaches for Attenuating Sarcopenia

Sarcopenia is characterized by a gradual slowing of movement due to loss of muscle mass and quality, decreased power and strength, increased risk of injury from falls, and often weakness. This review will focus on recent research trends in nutritional and pharmacological approaches to controlling sarcopenia. Because nutritional studies in humans are fairly limited, this paper includes many results from nutritional studies in mammals. The combination of resistance training with supplements containing amino acids is the gold standard for preventing sarcopenia. Amino acid (HMB) supplementation alone has no significant effect on muscle strength or muscle mass in sarcopenia, but the combination of HMB and exercise (whole body vibration stimulation) is likely to be effective. Tea catechins, soy isoflavones, and ursolic acid are interesting candidates for reducing sarcopenia, but both more detailed basic research on this treatment and clinical studies in humans are needed. Vitamin D supplementation has been shown not to improve sarcopenia in elderly individuals who are not vitamin D-deficient. Myostatin inhibitory drugs have been tried in many neuromuscular diseases, but increases in muscle mass and strength are less likely to be expected. Validation of myostatin inhibitory antibodies in patients with sarcopenia has been positive, but excessive expectations are not warranted.

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.

Identification of Novel Biomarkers in Late Preterm Neonates with Respiratory Distress Syndrome (RDS) Using Urinary Metabolomic Analysis

Urine metabolomics is gaining traction as a means of identifying metabolic signatures associated with health and disease states. Thirty-one (31) late preterm (LP) neonates admitted to the neonatal intensive care unit (NICU) and 23 age-matched healthy LPs admitted to the maternity ward of a tertiary hospital were included in the study. Proton nuclear magnetic resonance (¹H NMR) spectroscopy was employed for urine metabolomic analysis on the 1st and 3rd days of life of the neonates. The data were analyzed using univariate and multivariate statistical analysis. A unique metabolic pattern of enhanced metabolites was identified in the NICU-admitted LPs from the 1st day of life. Metabolic profiles were distinct in LPs presenting with respiratory distress syndrome (RDS). The discrepancies likely reflect differences in the gut microbiota, either due to variations in nutrient intake or as a result of medical interventions, such as the administration of antibiotics and other medications. Altered metabolites could potentially serve as biomarkers for identifying critically ill LP neonates or those at high risk for adverse outcomes later in life, including metabolic risks. The discovery of novel biomarkers may uncover potential targets for drug discovery and optimal periods for effective intervention, offering a personalized approach.

Sarcopenia: Molecular regulatory network for loss of muscle mass and function

Skeletal muscle is the foundation of human function and plays a key role in producing exercise, bone protection, and energy metabolism. Sarcopenia is a systemic disease, which is characterized by degenerative changes in skeletal muscle mass, strength, and function. Therefore, sarcopenia often causes weakness, prolonged hospitalization, falls and other adverse consequences that reduce the quality of life, and even lead to death. In recent years, sarcopenia has become the focus of in-depth research. Researchers have suggested some molecular mechanisms for sarcopenia according to different muscle physiology. These mechanisms cover neuromuscular junction lesion, imbalance of protein synthesis and breakdown, satellite cells dysfunction, etc. We summarize the latest research progress on the molecular mechanism of sarcopenia in this review in order to provide new ideas for future researchers to find valuable therapeutic targets and develop relevant prevention strategies.

Protein and Energy Supplements for the Elderly

The proportion of elderly individuals is rising globally, and data have shown that as high as 8% of the elderly community suffer from malnutrition. Protein energy malnutrition has shown to elevate morbidity and mortality risk in the elderly; therefore, protein and energy supplement are needed for the elderly populations to create healthy conditions. This chapter describes about general structure of protein, protein turnover, amino acid metabolism including metabolism in the elderly, protein change in aging, supplementation of amino acid as well as vitamin and mineral for the elderly. The discussion in this section aims to provide a general description of protein, amino acids, changes in amino acid metabolism in the elderly, and the benefits of supplementing amino acids as well as vitamins and minerals for the elderly.

Metabolite Changes during the Transition from Hyperthyroidism to Euthyroidism in Patients with Graves' Disease

BACKGRUOUND

An excess of thyroid hormones in Graves' disease (GD) has profound effects on systemic energy metabolism that are currently partially understood. In this study, we aimed to provide a comprehensive understanding of the metabolite changes that occur when patients with GD transition from hyperthyroidism to euthyroidism with methimazole treatment.

METHODS

Eighteen patients (mean age, 38.6±14.7 years; 66.7% female) with newly diagnosed or relapsed GD attending the endocrinology outpatient clinics in a single institution were recruited between January 2019 and July 2020. All subjects were treated with methimazole to achieve euthyroidism. We explored metabolomics by performing liquid chromatography-mass spectrometry analysis of plasma samples of these patients and then performed multivariate statistical analysis of the metabolomics data.

RESULTS

Two hundred metabolites were measured before and after 12 weeks of methimazole treatment in patients with GD. The levels of 61 metabolites, including palmitic acid (C16:0) and oleic acid (C18:1), were elevated in methimazole-naïve patients with GD, and these levels were decreased by methimazole treatment. The levels of another 15 metabolites, including glycine and creatinine, were increased after recovery of euthyroidism upon methimazole treatment in patients with GD. Pathway analysis of metabolomics data showed that hyperthyroidism was closely related to aminoacyl-transfer ribonucleic acid biosynthesis and branched-chain amino acid biosynthesis pathways.

CONCLUSION

In this study, significant variations of plasma metabolomic patterns that occur during the transition from hyperthyroidism to euthyroidism were detected in patients with GD via untargeted metabolomics analysis.

The amino acid content in the daily diet of seniors negatively correlates with the degree of platelet aggregation in a sex- and agonist-specific manner

Aging is a significant risk factor for the development of thrombotic diseases, dependent on blood platelet reactivity. However, the risk of thrombosis also appears to be significantly modulated by dietary nutrient content.

The aim of the current study was to assess the relationship between the amount of amino acids present in the daily diet (not supplemented) and the reactivity of blood platelets to arachidonate, collagen and ADP in 246 women and men aged 60–65 years.

Platelet reactivity was tested using whole blood impedance aggregometry. Amino acid intake was assessed with a 24-hour Recall Questionnaire and calculated with Dieta 5.0 software.

Older subjects receiving higher amounts of all essential amino acids with their daily diet exhibit significantly lower platelet responsiveness to AA-, COL- and ADP in a sex-specific manner: dietary amino acid content was more closely associated with AA- and, to some extent, ADP-induced platelet reactivity in women, and with COL-induced platelet aggregability in men. Therefore, dietary amino acid content may be a novel factor responsible for attenuating platelet reactivity in a sex- and agonist-specific manner.

Prospective Association Between Plasma Amino Acids And Multimorbidity In Older Adults

BACKGROUND

Some amino acids have been associated with aging-related disorders and risk of physical impairment. The aim of this study was to assess the association between plasma concentrations of nine amino acids, including branched-chain and aromatic amino acids, and multimorbidity.

METHODS

This research uses longitudinal data from the Seniors-ENRICA 2 study, a population-based cohort from Spain which comprises non-institutionalized adults older than 65. Blood samples were extracted at baseline and after a follow-up period of two years for a total of 1488 subjects. Participants' information was linked with electronic health records. Chronic diseases were grouped into a list of 60 mutually exclusive conditions. A quantitative measure of multimorbidity, weighting morbidities by their regression coefficients on physical functioning, was employed and ranged from 0 to 100. Generalized estimating equation models were used to explore the relationship between plasma amino acids and multimorbidity, adjusting for sociodemographics, socioeconomic status and lifestyle behaviors.

RESULTS

The mean age of participants at baseline was 73.6 (SD = 4.2) years, 49.6% were women. Higher concentrations of glutamine [coef. per mmol/l (95% confidence interval = 10.1 (3.7, 16.6)], isoleucine [50.3 (21.7, 78.9)] and valine [15.5 (3.1, 28.0)] were significantly associated with higher multimorbidity scores, after adjusting for potential confounders. Body mass index could have influenced the relationship between isoleucine and multimorbidity (p = 0.016).

CONCLUSIONS

Amino acids could play a role in regulating aging-related diseases. Glutamine and branched-chain amino acids as isoleucine and valine are prospectively associated and could serve as risk markers for multimorbidity in older adults.

Evenness of Dietary Protein Intake Is Positively Associated with Lean Mass and Strength in Healthy Women

Background:

Evenness of protein intake is associated with increased lean mass, but its relationship with muscle strength and performance is uncertain.

Objectives:

We determined the association of evenness of protein intake with lean mass, muscle strength and endurance, and functional ability.

Design:

This was a cross-sectional study.

Setting:

Data were collected at a research university in the upper midwestern United States.

Participants:

One hundred ninety-two healthy women, aged 18 to 79 years, mean ± SEM 41.9 ± 1.3, completed the study.

Measurements:

Dietary intake was assessed using 3-day food diaries verified with food frequency questionnaires. To assess evenness of protein intake, the day was divided into 3 periods: waking to 11:30, 11:31 to 16:30, and after 16:30. Lean mass was measured with dual energy X-ray absorptiometry. Lower-body muscle strength and endurance were determined using isokinetic dynamometry. Upper-body muscle strength was maximal handgrip strength. Functional ability was assessed using 6-m gait speed and 30-second chair stand tests. Accelerometry measured physical activity.

Results:

Intakes of 25 g or more of protein at 1 or more of the 3 periods was positively associated with lean mass (β ± S.E.; 1.067 ± 0.273 kg, P < .001) and upper-body (3.274 ± 0.737 kg, P < .001) and lower-body strength (22.858 ± 7.918 Nm, P = .004) when controlling for age, body mass index, physical activity, and energy and protein intakes. Consuming at least 0.24 g/kg/period for those under 60 years and 0.4 g/kg/period for those 60 years and older was related to lean mass (0.754 ± 0.244 kg, P = .002), upper-body strength (2.451 ± 0.658 kg, P < .001), and lower-body endurance (184.852 ± 77.185 J, P = .018), controlling for the same variables.

Conclusions:

Evenness of protein intake is related to lean mass, muscle strength, and muscular endurance in women. Spreading protein intake throughout the day maximizes the anabolic response to dietary protein, benefiting muscle mass and performance.

Can supplemental protein to low-protein containing meals superimpose on resistance-training muscle adaptations in older adults? A randomized clinical trial

PURPOSE

To evaluate the effects of supplementing protein to the low-protein containing meals on selected parameters of muscle mass, strength, and functional capacity in older individuals undergoing resistance training.

METHODS

Thirty-one male and female older individuals (60 to 80 years) were randomized into either a whey protein/WP (n = 15, 20 g at breakfast + 20 g at dinner) or placebo-maltodextrin/PL (n = 16, 20 g at breakfast + 20 g at dinner) group. Both groups underwent a supervised, progressive resistance training (2×/week) program for 12 weeks. Maximal isometric voluntary contraction (MIVC) of knee extensors, muscle thickness (MT) of knee extensors and elbow flexors, rectus femoris muscle quality (MQ), body composition (as measured by DXA) and functional capacity [as measured by 30-s sit-to-stand (30ss) and timed-up-and-go tests (TUG)] were evaluated at baseline and after the 12-week intervention.

RESULTS

Knee extensor MIVC (WP ∆ = 11.9 ± 11.4% and PL ∆ = 12.9 ± 9.9%) was significantly increased over time, with no between-group differences (all p < 0.05 for main effect of time). Upper- and lower-limb MT were significantly increased over time, with no effect of supplementation (WP: ∆ = 7.0 ± 7.3%, PL: ∆ = 9.5 ± 10.3%; and WP: ∆ = 4.5 ± 5.8%, PL: ∆ = 14.7 ± 28.9%, respectively; all p = 0.001 for main effect of time, respectively). Total and upper-limb lean mass were significantly increased, irrespective of the dietary intervention (WP: ∆ = 0.2 ± 6.3%, PL: ∆ = 1.8 ± 2.9%; and WP: ∆ = 0.10 ± 0.03%, PL: ∆ = 0.15 ± 0.02%, respectively; all p < 0.05 for main effect of time). Main effects of time (all p < 0.05) were also found for 30SS and TUG (fast and usual speeds) (WP: ∆ = 18.2 ± 34.4%, PL: ∆ = 10.4 ± 16.9%; WP: ∆ = 5.4 ± 6.7%, PL: ∆ = 0.7 ± 6.0% and WP: ∆ = 3.3 ± 6.1%, PL: ∆ = 2.3 ± 5.2%, respectively).

CONCLUSION

Supplementing additional whey protein to the lowest-protein containing meals (i.e., ~20 g at breakfast and ~20 g at dinner, daily) did not further augment resistance training-induced neuromuscular adaptations (i.e. muscle strength and mass) in healthy older individuals.

Serum and Fecal Amino Acid Profiles in Cats with Chronic Kidney Disease

The purpose of the study was to quantify serum and fecal amino acids (AA) in cats with chronic kidney disease (CKD) and compare to healthy cats. Thirty-five cats with International Renal Interest Society Stage 1–4 CKD and 16 healthy mature adult and senior client-owned cats were included in this prospective cross-sectional study. Sera were analyzed for 25 AA concentrations using an ion exchange chromatography AA analyzer with post column ninhydrin derivatization. Voided fecal samples were analyzed for 22 AA concentrations using liquid chromatography with tandem mass spectrometry. CKD cats had lower serum concentrations of phenylalanine (mean difference ± standard error of the mean: 12.7 ± 4.3 µM; p = 0.03), threonine (29.6 ± 9.2 µM; p = 0.03), tryptophan (18.4 ± 5.4 µM; p = 0.005), serine (29.8 ± 12.6 µM; p = 0.03), and tyrosine (11.6 ± 3.8 µM; p = 0.01) and higher serum concentrations of aspartic acid (4.7 ± 2.0 µM; p = 0.01), β-alanine (3.4 ± 1.2 µM; p = 0.01), citrulline (5.7 ± 1.6 µM; p = 0.01), and taurine (109.9 ± 29.6 µM; p = 0.01) when compared to healthy cats. Fecal AA concentrations did not differ between healthy cats and CKD cats. 3-Methylhistidine-to-creatinine did not differ between healthy cats with and without muscle loss. Cats with CKD IRIS Stages 1–4 have a deranged serum amino acid profile compared to healthy cats.

Activated Protein C Strengthens Cardiac Tolerance to Ischemic Insults in Aging

BACKGROUND

APC (activated protein C) is a plasma serine protease with anticoagulant and anti-inflammatory activities. EPCR (Endothelial protein C receptor) is associated with APC's activity and mediates its downstream signaling events. APC exerts cardioprotective effects during ischemia and reperfusion (I/R). This study aims to characterize the role of the APC-EPCR axis in ischemic insults in aging.

METHODS

Young (3-4 months) and aged (24-26 months) wild-type C57BL/6J mice, as well as EPCR point mutation (EPCR^R84A/R84A) knockin C57BL/6J mice incapable of interaction with APC and its wild type of littermate C57BL/6J mice, were subjected to I/R. Wild-type APC, signaling-selective APC-2Cys, or anticoagulant-selective APC-E170A were administrated before reperfusion.

RESULTS

The results demonstrated that cardiac I/R reduces APC activity, and the APC activity was impaired in the aged versus young hearts possibly attributable to the declined EPCR level with aging. Serum EPCR measurement showed that I/R triggered the shedding of membrane EPCR into circulation, while administration of APC attenuated the I/R-induced EPCR shedding in both young and aged hearts. Subsequent echocardiography showed that APC and APC-2Cys but not APC-E170A ameliorated cardiac dysfunction during I/R in both young and aged mice. Importantly, APC elevated the resistance of the aged heart to ischemic insults through stabilizing EPCR. However, all these cardioprotective effects of APC were blunted in the EPCR^R84A/R84A mice versus its wild-type littermates. The ex vivo working heart and metabolomics results demonstrated that AMPK (AMP-activated protein kinase) mediates acute adaptive response while AKT (protein kinase B) is involved in chronic metabolic programming in the hearts with APC treatment.

CONCLUSIONS

I/R stress causes shedding of the membrane EPCR in the heart, and administration of APC prevents I/R-induced cardiac EPCR shedding that is critical for limiting cardiac damage in aging.

Interactive effects of aging and aerobic capacity on energy metabolism-related metabolites of serum, skeletal muscle, and white adipose tissue

Aerobic capacity is a strong predictor of longevity. With aging, aerobic capacity decreases concomitantly with changes in whole body metabolism leading to increased disease risk. To address the role of aerobic capacity, aging, and their interaction on metabolism, we utilized rat models selectively bred for low and high intrinsic aerobic capacity (LCRs/HCRs) and compared the metabolomics of serum, muscle, and white adipose tissue (WAT) at two time points: Young rats were sacrificed at 9 months of age, and old rats were sacrificed at 21 months of age. Targeted and semi-quantitative metabolomics analysis was performed on the ultra-pressure liquid chromatography tandem mass spectrometry (UPLC-MS) platform. The effects of aerobic capacity, aging, and their interaction were studied via regression analysis. Our results showed that high aerobic capacity is associated with an accumulation of isovalerylcarnitine in muscle and serum at rest, which is likely due to more efficient leucine catabolism in muscle. With aging, several amino acids were downregulated in muscle, indicating more efficient amino acid metabolism, whereas in WAT less efficient amino acid metabolism and decreased mitochondrial β-oxidation were observed. Our results further revealed that high aerobic capacity and aging interactively affect lipid metabolism in muscle and WAT, possibly combating unfavorable aging-related changes in whole body metabolism. Our results highlight the significant role of WAT metabolism for healthy aging.

Haematological and metabolic profiles associated with age and sex in giant kokopu (Galaxias argenteus) (Gmelin 1789) broodstock

This study characterized selected peripheral blood (PB) haematological parameters, liver, serum and muscle metabolic features in 3- and 5-year-old male and female giant kokopu (Galaxias argenteus) broodstock reared indoor at 16°C. Sex and age did not affect PB total cell count and haematocrit values. Nonetheless, higher erythrocytes in 5-year-old fish, elevated thrombocyte and lymphocyte counts in 3-year-old fish indicate age-specific cellular regulation. Higher thrombocyte counts in female fish suggest sex-specific regulation. At a metabolic level, liver abundance for long chain saturated fatty acids (FAs) was higher in males, whereas females had elevated levels of polyunsaturated FAs. Essential and non-essential amino acids (AAs) in liver and serum were also elevated in females compared to males. These findings suggest differential allocation of FAs and AAs to reflect requirements for gonadal, development and provisioning. Similarly, age significantly resulted in higher liver and serum abundances of some non-essential AAs in 3-year-olds compared to 5-year-old fish, suggesting higher metabolism in younger fish. Overall, results enhance our understanding of sex- and age-based differences in fish haematology, muscle, liver, and serum metabolite profiles in healthy G. argenteus. Future studies should carefully consider potential age- and sex-specific differences in metabolic responses.

Plasma Amino Acids and Risk of Impaired Lower-Extremity Function and Role of Dietary Intake: A Nested Case-Control Study in Older Adults

INTRODUCTION

Amino acids are key elements in the regulation of the aging process which entails a progressive loss of muscle mass. The health effects of plasma amino acids can be influenced by dietary intake. This study assessed the prospective association between amino acid species and impaired lower-extremity function (ILEF) in older adults, exploring the role of diet on this association.

METHODS

This is a case-control design comprising 43 incident cases of ILEF and 85 age- and sex-matched controls. Plasma concentrations of 20 amino acid species were measured at baseline using liquid chromatography-tandem mass spectrometry, and incident cases of ILEF were measured after 2 years by means of the Short Physical Performance Battery. Conditional logistic regression models were used to assess longitudinal relationships.

RESULTS

After adjusting for potential confounders, higher levels of tryptophan were associated with a decreased 2-year risk of ILEF (OR per 1-SD increase = 0.64, 95% CI = [0.42, 0.97]), while glutamine and total essential amino acids were linked to higher ILEF risk (OR = 1.57, 95% CI = [1.01, 2.45]; OR = 1.89, 95% CI = [1.18, 3.03], respectively). Those with a lower adherence to a Mediterranean diet, a higher BMI, a higher consumption of red meat, and a lower consumption of nuts and legumes had an increased risk of ILEF associated with higher levels of essential amino acids.

DISCUSSION/CONCLUSION

Some amino acid species could serve as risk markers for physical function decline in older adults, and healthy diet might attenuate the excess risk of ILEF linked to essential amino acids.

Comprehensive Metabolomics Study in Children With Graves' Disease

OBJECTIVE

Graves' disease (GD) related hyperthyroidism (HT) has profound effects on metabolic activity and metabolism of macromolecules affecting energy homeostasis. In this study, we aimed to get a comprehensive understanding of the metabolic changes and their clinical relevance in GD children.

METHODS

We investigated serum substances from 30 newly diagnosed GD children and 30 age- and gender-matched healthy controls. We explored the metabolomics using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) analysis, and then analyzed the metabolomic data via multivariate statistical analysis.

RESULTS

By untargeted metabolomic analysis, a total of 730 metabolites were identified in all participants, among which 48 differential metabolites between GD and control groups were filtered out, including amino acids, dipeptides, lipids, purines, etc. Among these metabolites, 33 were detected with higher levels, while 15 with lower levels in GD group compared to controls. Pathway analysis showed that HT had a significant impact on aminoacyl-transfer ribonucleic acid (tRNA) biosynthesis, several amino acids metabolism, purine metabolism, and pyrimidine metabolism.

CONCLUSION

In this study, via untargeted metabolomics analysis, significant variations of serum metabolomic patterns were detected in GD children.

The Association between Major Dietary Pattern and Low Muscle Mass in Korean Middle-Aged and Elderly Populations: Based on the Korea National Health and Nutrition Examination Survey

Reduced skeletal muscle mass in older populations is independently associated with functional impairment and disability, resulting in increased risk of mortality and various comorbidities. This study aimed to examine the association between major dietary pattern and low muscle mass among Korean middle-aged and elderly populations. A total of 8136 participants aged ≥50 years were included from a cross-sectional study based on the 2008–2011 Korea National Health and Nutrition Examination Survey. The following four distinct dietary patterns were derived using factor analysis: “Condiment, vegetables, and meats”; “wheat flour, bread, fruits, milk, and dairy products”; “white rice, fish, and seaweeds”; and “whole grain, bean products, and kimchi”. A higher “white rice, fish, and seaweeds” pattern score was associated with a lower prevalence of low muscle mass in both men and women, whereas a higher “condiment, vegetables, and meats” pattern score was associated with a higher prevalence of low muscle mass in men. A dietary pattern based on white rice, fish, and seaweeds can be helpful in protecting against loss of skeletal muscle mass in Korean middle-aged and elderly populations. Future research is paramount to confirm the causal association between dietary pattern and the risk of low muscle mass.

Associations between dietary patterns and physical fitness among Chinese elderly

OBJECTIVE

To explore the relationship between dietary patterns and physical fitness among older Chinese (≥60 years) individuals.

DESIGN

Cross-sectional survey. Dietary data were collected by a simplified semi-quantitative FFQ. The 30-s Chair Stand test (30sCST), 30-s Arm Curl test (30sACT), 8-foot Time Up-and-Go test (8fTUAGT) and 6-min Walking test (6mWT) were used to assess physical fitness. Dietary patterns were obtained by factor analysis. The association between dietary patterns and physical fitness was explored by multiple logistic regression.

SETTING

Six communities (villages) of three districts in Liaocheng City (Shandong Province, China).

PARTICIPANTS

A total of 596 residents were recruited from April to May 2017.

RESULTS

Among 556 residents who were finally enrolled, 196 were men (35 %) and 360 were women (65 %). Three dietary patterns were identified: 'Western', 'Vegetarian' and 'Modern'. The 30sACT revealed that men in the fourth quartile of the Western pattern were less likely to be classified in the 'high-level' group, but men in the fourth quartile of the Vegetarian pattern were classified in the high-level group. The 6mWT revealed that men in the fourth quartile of the Modern pattern were classified in the high-level group. These associations were independent of confounding factors.

CONCLUSIONS

Adherence to the Vegetarian pattern and Modern pattern may be protective factors for maintaining good physical fitness in older Chinese individuals. The Western pattern may lead to poor physical fitness in this population.

Dietary Selenium Intakes and Musculoskeletal Function in Very Old Adults: Analysis of the Newcastle 85+ Study

Background: Selenium is a trace element essential for health. Severe selenium deficiencies are associated with poor musculoskeletal (MSK) function. However, the effects of moderate deficiency on MSK function, especially in older adults, is unclear. Objectives: To determine the associations between selenium intake and MSK function in very old adults. Methods: Selenium intake at baseline and, hand-grip strength (HGS) and timed-up-and-go (TUG) at four phases over 5 years, were available in 791 participants in the Newcastle 85+ Study, a community-based, longitudinal cohort of ≥85 year old individuals. We investigated relationships between selenium intake and HGS and TUG in cross-sectional analyses at baseline using multivariate analyses and, prospectively using linear mixed models to explore HGS and TUG changes over 5 years in association with baseline selenium intake. Results: At baseline, 53% of participants had selenium intakes that were classified as low. These individuals had 2.80 kg lower HGS and were 2.30 s slower performing the TUG, cross-sectionally. In multivariate, baseline analyses, selenium intake had no significant impact on HGS or TUG. Selenium intake had no significant effect on MSK function, prospectively. Conclusion: Low selenium intake is common among very old adults and, in cross-sectional analyses, is associated with poorer MSK function.

Protein Requirements during Hypocaloric Nutrition for the Older Patient With Critical Illness and Obesity: An Approach to Clinical Practice

Current guidelines recommend a hypocaloric, high protein nutrition regimen for patients with obesity and critical illness. The impact of advancing age presents with unique challenges in which a greater protein intake is required to overcome the anabolic resistance associated with aging in the face of presumed decreased renal function. The primary objective of this review is to provide an overview of the impact of obesity and advancing age on protein requirements for patients with critical illness and review the scientific evidence supporting the rationale for hypocaloric, high protein nutrition for this subpopulation, as well as provide some practical suggestions for their clinical management.

Regional Differences in the Association between Dietary Patterns and Muscle Strength in Korean Older Adults: Data from the Korea National Health and Nutrition Examination Survey 2014-2016

Objectives: Adequate nutrition is an important factor to prevent sarcopenia in older adults. The purpose of this study was to identify the regional differences in the association between dietary pattern and muscle strength in older Korean adults. Methods: This study was based on data from the Korea National Health and Nutrition Examination Survey (KNHANES) in 2014–2016. Muscle strength was measured by grip strength, and dietary patterns were derived by a cluster analysis using the k-means algorithm. Multiple logistic regression analyses were applied to determine the associations between factors (dietary patterns and residential areas) and grip strength. Results: Most participants in the rural area group (50.4%) had the Cluster Three dietary pattern (diet dominant in white rice and kimchi), while most people in the urban area group (43.8%) and the metropolitan area group (53.2%) had the Cluster One dietary pattern (diet dominant in fruits and fish). Those having poor hand grip strength represented 25.8% of the total in rural, 20.6% in urban, and 17.9% in metropolitan (p = 0.009) areas. Upon adjustment for socio-demographic characteristics, health behaviors, and co-morbidity, the odds ratio of Cluster Two (diet dominant in meat) was 1.601 (95%, CI: 1.001–2.563, p = 0.050) compared to the Cluster Three dietary pattern, but there was no significant difference in residence. Conclusions: Muscle strength in the elderly was more related to dietary pattern than was residence. Education and support for conveying the importance of protein intake in the elderly are required to motivate adequate nutrition. In addition, these actions should lead to prevention of muscle weakness and further prevent frailty.

The Urinary Metabolome of Healthy Newborns

The knowledge of normal metabolite values for neonates is key to establishing robust cut-off values to diagnose diseases, to predict the occurrence of new diseases, to monitor a neonate's metabolism, or to assess their general health status. For full term-newborns, many reference biochemical values are available for blood, serum, plasma and cerebrospinal fluid. However, there is a surprising lack of information about normal urine concentration values for a large number of important metabolites in neonates. In the present work, we used targeted tandem mass spectrometry (MS/MS)-based metabolomic assays to identify and quantify 136 metabolites of biomedical interest in the urine from 48 healthy, full-term term neonates, collected in the first 24 h of life. In addition to this experimental study, we performed a literature review (covering the past eight years and over 500 papers) to update the references values in the Human Metabolome Database/Urine Metabolome Database (HMDB/UMDB). Notably, 86 of the experimentally measured urinary metabolites are being reported in neonates/infants for the first time and another 20 metabolites are being reported in human urine for the first time ever. Sex differences were found for 15 metabolites. The literature review allowed us to identify another 78 urinary metabolites with concentration data. As a result, reference concentration values and ranges for 378 neonatal urinary metabolites are now publicly accessible via the HMDB.

Menopause-Associated Lipid Metabolic Disorders and Foods Beneficial for Postmenopausal Women

Menopause is clinically diagnosed as a condition when a woman has not menstruated for one year. During the menopausal transition period, there is an emergence of various lipid metabolic disorders due to hormonal changes, such as decreased levels of estrogens and increased levels of circulating androgens; these may lead to the development of metabolic syndromes including cardiovascular diseases and type 2 diabetes. Dysregulation of lipid metabolism affects the body fat mass, fat-free mass, fatty acid metabolism, and various aspects of energy metabolism, such as basal metabolic ratio, adiposity, and obesity. Moreover, menopause is also associated with alterations in the levels of various lipids circulating in the blood, such as lipoproteins, apolipoproteins, low-density lipoproteins (LDLs), high-density lipoproteins (HDL) and triacylglycerol (TG). Alterations in lipid metabolism and excessive adipose tissue play a key role in the synthesis of excess fatty acids, adipocytokines, proinflammatory cytokines, and reactive oxygen species, which cause lipid peroxidation and result in the development of insulin resistance, abdominal adiposity, and dyslipidemia. This review discusses dietary recommendations and beneficial compounds, such as vitamin D, omega-3 fatty acids, antioxidants, phytochemicals—and their food sources—to aid the management of abnormal lipid metabolism in postmenopausal women.

The Role of Nutrition in Attenuating Age-Related Skeletal Muscle Atrophy

The elderly population is increasing rapidly worldwide, and we are faced with the significant challenge for maintaining or improving physical activity, independence, and quality of life. Sarcopenia, the age-related decline of skeletal muscle mass, is characterized by loss of muscle quantity and quality resulting to a gradual slowing of movement, a decrease in strength and power, elevated risk of fall-related injury, and often frailty. Supplemental, hormonal, and pharmacological approaches have been attempted to attenuate sarcopenia but these have not achieved outstanding results. In this review, we summarize the current knowledge of nutrition-based therapies for counteracting sarcopenia.

Dietary strategies for mitigating osteosarcopenia in older adults: a narrative review

The synchronic loss of bone mineral density and decrease in muscle mass, strength, and function defines the scenario of osteosarcopenia, which is associated with an increased risk of falls and fractures in older adults. An important role in preventing muscle and bone loss is played by nutritional factors, in particular the intake of proteins, calcium, magnesium and vitamin D. This review summarizes the available literature concerning the influence of protein intake and supplementation (vitamin D, Ca, Mg, branched-chain amino acids) on the decline of musculoskeletal integrity in healthy older adults. Furthermore, in this paper, we attempted to give some suggestions to build up adequate nutritional and dietary strategies against the age-related loss of muscle and bone mass.

1H NMR-based metabolomics revealed the protective effects of Guilingji on the testicular dysfunction of aging rats

ETHNOPHARMACOLOGICAL RELEVANCE

Guilingji (GLJ), a famous and classical traditional Chinese medicine (TCM) prescription, has been used to extend the lifespan and improve the life qualities of the elderly for hundreds of years in China.

AIM OF THE STUDY

We aimed to explore the protective effects of GLJ on the testicular dysfunction of aging rats, as well as the regulating effects of GLJ on the metabolic disturbance and metabolite changes in natural aging rats.

MATERIALS AND METHODS

Forty 23-month-old rats were divided randomly into four groups, including the old control group and three groups of GLJ treatment at 37.5, 75, and 150 mg/kg doses, respectively. Additionally, 10 four-month rats were included as the youth control group. Testicular dysfunction was first evaluated by measuring the changes in the wet weights of the testicles, concentration of serum testosterone (T), and morphologic changes of the testis. Subsequently, an ¹H NMR-based metabolomics approach coupled with multivariate analysis, including partial least squares discriminant analysis (PLS-DA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) was applied to monitor the metabolite changes.

RESULTS

Compared with the old control group, the wet weights of the testicles and T concentration were significantly increased, while the morphologic abnormality of testicular tissues was improved by a 4-week treatment course with GLJ. Furthermore, compared with the old control group, the urinary levels of alanine, pantothenate, phenylalanine, β-hydroxybutyrate and pyruvate were significantly decreased after a 4-week treatment course with GLJ. Additionally, we found that amino acid metabolism and pyruvate metabolism were significantly involved in the regulatory effect of GLJ.

CONCLUSIONS

The current findings provided, for the first time, sound evidence of the protective effects of GLJ on testicular dysfunction from both biochemical and metabolomics perspectives. The mechanisms of GLJ could be related to regulating amino acid metabolism and pyruvate metabolism. The current study lays an important foundation for further research and for the broad clinical application of GLJ.

The induction of the fibroblast extracellular senescence metabolome is a dynamic process

Cellular senescence is often associated with irreparable DNA double strand breaks (IrrDSBs) which accumulate with chronological age (IrrDSBsen). The removal of senescent cells ameliorates several age-related diseases in mice but the translation of these findings into a clinical setting would be aided by the characterisation of non-invasive biomarkers of senescent cells. Several serum metabolites are independent indicators of chronological age and some of these accumulate outside senescent fibroblasts independently of cell cycle arrest, repairable DNA breaks and cell size (the extracellular senescence metabolome, or ESM). The post-mitotic phase of senescence is dynamic, making the detection of senescent cells in vivo difficult. An unbiased metabolomic screen of the IrrDSBsen fibroblast ESM also showed differences in the times of initiation and maintenance of different metabolites but generally the ESM altered progressively over the 20 day study period unlike the reported transcriptional profiles. This more detailed analysis of IrrDSBsen identified several new ESM metabolites that are associated with chronological ageing. Targeted analysis of citrate confirmed the dynamic nature of this metabolite in two cell lines and revealed its independence from the senescence effector p16^INK4A. These data will aid our understanding of metabolic signatures of ageing and their relationship to cellular senescence and IrrDSBs.

Proteogenomic Analyses Revealed Favorable Metabolism Pattern Alterations in Rotifer Brachionus plicatilis Fed with Selenium-rich Chlorella

Organoselenium have garnered attention because of their potential to be used as ingredients in new anti-aging and antioxidation medicines and food. Rotifers are frequently used as a model organism for aging research. In this study, we used Se-enriched Chlorella (Se- Chlorella), a novel organoselenium compound, to feed Brachionus plicatilis to establish a rotifer model with a prolonged lifespan. The results showed that the antioxidative effect in Se-enriched rotifer was associated with an increase in guaiacol peroxidase (GPX) and catalase (CAT). The authors then performed the first proteogenomic analysis of rotifers to understand their possible metabolic mechanisms. With the de novo assembly of RNA-Seq reads as the reference, we mapped the proteomic output generated by iTRAQ-based mass spectrometry. We found that the differentially expressed proteins were primarily involved in antireactive oxygen species (ROS) and antilipid peroxidation (LPO), selenocompound metabolism, glycolysis, and amino acid metabolisms. Furthermore, the ROS level of rotifers was diminished after Se- Chlorella feeding, indicating that Se- Chlorella could help rotifers to enhance their amino acid metabolism and shift the energy generating metabolism from tricarboxylic acid cycle to glycolysis, which leads to reduced ROS production. This is the first report to demonstrate the anti-aging effect of Se- Chlorella on rotifers and to provide a possible mechanism for this activity. Thus, Se- Chlorella is a promising novel organoselenium compound with the potential to prolong human lifespans.

Oral Supplementation with Beta-Hydroxy-Beta-Methylbutyrate, Arginine, and Glutamine Improves Lean Body Mass in Healthy Older Adults

Oral intake of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine may ameliorate muscle loss by stimulating protein synthesis and decreasing protein degradation while simultaneously decreasing inflammation. Previous studies provide evidence for improvement in body composition with dietary supplementation of these ingredients among patients with muscle-wasting diseases. The objectives of this study were to examine the effects of this amino acid mixture on lean body mass, muscle volume, and physical function among healthy older adults. Thirty-one community-dwelling men and women, aged 65-89 years, were randomized to either two oral doses of the amino acid supplement (totaling 3 g HMB, 14 g arginine, 14 g glutamine) or placebo daily for six months. At baseline and month six, lean body mass was measured by air displacement plethysmography, dual-energy X-ray absorptiometry (DXA), and four-compartment model. Muscle volume of quadriceps was quantified by magnetic resonance imaging (MRI), and participants performed a battery of tests to assess physical function. As compared to the placebo group, the treatment group exhibited improvement in a timed stair climb (p =.016) as well as significant increases in lean body mass by all methods of assessment (p <.05). Regional analysis by DXA revealed increased arm lean mass in the supplement group only (p =.035). However, no change was observed in MRI-derived quadriceps volume. Dietary supplementation with HMB, arginine, and glutamine improved total body lean mass among a small sample of healthy older adults. Further research is indicated to elucidate mechanisms of action and to determine whether supplementation may benefit frail elders. Registered under ClinicalTrials.gov identifier no. NCT01057082.

Reduced muscular fatigue after a 12-week leucine-rich amino acid supplementation combined with moderate training in elderly: a randomised, placebo-controlled, double-blind trial

Background

Age-related muscle loss is characterised by a progressing decrease in muscle mass, strength and function. Besides resistance training and physical activity, appropriate nutrition that is rich in protein, especially branched-chain amino acids, is very important to support training effects and positively influence the protein synthesis to degradation ratio.

Aim

The purpose of this study was to evaluate the effect of a 12-week leucine-rich amino acid supplementation in combination with moderate training.

Methods

Forty-eight healthy subjects exercised for 30 min three times per week and received either a leucine-rich amino acid supplementation or a placebo. Before and after supplementation, volunteers performed an exhaustive eccentric exercise protocol. Maximal concentric strength, muscle soreness, creatine kinase (CK), type II collagen collagenase cleavage neoepitope (C2C), C propeptide of type II procollagen (CP2) and safety assessments were performed before exercise and after 3, 24, 48 and 72 hours.

Results

The supplementation with leucine resulted in reduced loss of strength at 0 and 3 hours after downhill walking compared with the placebo (p=0.0439). The reduction of C2C/CP2 ratio deflection was significantly increased (p=0.038) due to leucine compared with the placebo. The same tendency could be observed for the recovery phase. No significant supplement effects for muscle soreness and CK could be observed.

Conclusion

The principle findings show that leucine-rich amino acid supplementation can counteract the negative effects of eccentric exercise. The treatment resulted in a reduction of exercise-induced strength loss.

Nitrogen Balance and Protein Requirements for Critically Ill Older Patients

Critically ill older patients with sarcopenia experience greater morbidity and mortality than younger patients. It is anticipated that unabated protein catabolism would be detrimental for the critically ill older patient. Healthy older subjects experience a diminished response to protein supplementation when compared to their younger counterparts, but this anabolic resistance can be overcome by increasing protein intake. Preliminary evidence suggests that older patients may respond differently to protein intake than younger patients during critical illness as well. If sufficient protein intake is given, older patients can achieve a similar nitrogen accretion response as younger patients even during critical illness. However, there is concern among some clinicians that increasing protein intake in older patients during critical illness may lead to azotemia due to decreased renal functional reserve which may augment the propensity towards worsened renal function and worsened clinical outcomes. Current evidence regarding protein requirements, nitrogen balance, ureagenesis, and clinical outcomes during nutritional therapy for critically ill older patients is reviewed.

Dietary protein intake is associated with better physical function and muscle strength among elderly women

Dietary protein intake might be beneficial to physical function (PF) in the elderly. We examined the cross-sectional and prospective associations of protein intake of g/kg body weight (BW), fat mass (FM) and lean mass (LM) with PF in 554 women aged 65·3-71·6 years belonging to the Osteoporosis Risk Factor and Prevention Fracture Prevention Study. Participants filled a questionnaire on lifestyle factors and 3-d food record in 2002. Body composition was measured by dual-energy X-ray absorptiometry, and PF measures were performed at baseline and at 3-year follow-up. Sarcopaenia was defined using European Working Group on Sarcopenia in Older People criteria. At the baseline, women with higher protein intake (≥ 1·2 g/kg BW) had better performance in hand-grip strength/body mass (GS/BM) (P=0·001), knee extension/BM (P=0·003), one-leg stance (P=0·047), chair rise (P=0·043), squat (P=0·019), squat to the ground (P=0·001), faster walking speed for 10 m (P=0·005) and higher short physical performance battery score (P=0·004) compared with those with moderate and lower intakes (0·81-1·19 and ≤ 0·8 g/kg BW, respectively). In follow-up results, higher protein intake was associated with less decline in GS/BM, one-leg stance and tandem walk for 6 m over 3 years. Overall, results were no longer significant after controlling for FM. Associations were detected between protein intake and PF in non-sarcopaenic women but not in sarcopaenic women, except for change of GS (P=0·037). Further, FM but not LM was negatively associated with PF measures (P<0·050). This study suggests that higher protein intake and lower FM might be positively associated with PF in elderly women.

MECHANISMS IN ENDOCRINOLOGY: Exogenous insulin does not increase muscle protein synthesis rate when administered systemically: a systematic review

BACKGROUND

Though it is well appreciated that insulin plays an important role in the regulation of muscle protein metabolism, there is much discrepancy in the literature on the capacity of exogenous insulin administration to increase muscle protein synthesis rates in vivo in humans.

OBJECTIVE

To assess whether exogenous insulin administration increases muscle protein synthesis rates in young and older adults.

DESIGN

A systematic review of clinical trials was performed and the presence or absence of an increase in muscle protein synthesis rate was reported for each individual study arm. In a stepwise manner, multiple models were constructed that excluded study arms based on the following conditions: model 1, concurrent hyperaminoacidemia; model 2, insulin-induced hypoaminoacidemia; model 3, supraphysiological insulin concentrations; and model 4, older, more insulin resistant, subjects.

CONCLUSIONS

From the presented data in the current systematic review, we conclude that: i) exogenous insulin and amino acid administration effectively increase muscle protein synthesis, but this effect is attributed to the hyperaminoacidemia; ii) exogenous insulin administered systemically induces hypoaminoacidemia which obviates any insulin-stimulatory effect on muscle protein synthesis; iii) exogenous insulin resulting in supraphysiological insulin levels exceeding 50, 000  pmol/l may effectively augment muscle protein synthesis; iv) exogenous insulin may have a diminished effect on muscle protein synthesis in older adults due to age-related anabolic resistance; and v) exogenous insulin administered systemically does not increase muscle protein synthesis in healthy, young adults.

Effect of initiating enteral protein feeding on whole-body protein turnover in critically ill patients

BACKGROUND

Critically ill patients are susceptible to protein catabolism. Enteral feeding may ameliorate protein loss, but its effect is not well characterized in terms of protein kinetics.

OBJECTIVE

We established a method of quantifying the effect of enteral protein feeding on whole-body protein turnover and studied critically ill patients receiving early enteral nutrition.

DESIGN

In a proof-of-concept study, we established, in healthy subjects (n = 6), a method of measuring the effect of continuous enteral protein feeding on whole-body protein turnover by using ¹³C-phenylalanine (¹³C-Phe) intrinsically labeled casein by a nasogastric feeding tube and an intravenous ²H₅-Phe tracer. The protocol was applied to study critically ill patients (n = 10) during the initial hypocaloric-hyponitrogenous dose of enteral nutrition.

RESULTS

Patients were catabolic with a negative protein balance. The median splanchnic extraction fraction of hourly dietary Phe intake was 92% (range: 86-99%); that is, the availability of dietary Phe in arterial plasma was low. In patients with a stable parenteral amino acid supply (n = 7), the median net protein balance improved during enteral feeding from -8.6 to -5.8 μmol · kg body weight⁻¹ · h⁻¹ (P = 0.018).

CONCLUSIONS

Whole-body protein turnover and the contribution of dietary protein can be quantified in critically ill patients by using intravenous and enteral stable-isotope Phe tracers. The whole-body protein balance improved during early hypocaloric-hyponitrogenous enteral protein feeding in these patients.

Dietary protein intake in elderly women: association with muscle and bone mass

BACKGROUND

An inadequate food intake, mainly with regard to protein intake, seems to contribute to a reduction of skeletal muscle and bone mass in the elderly. This study was undertaken to evaluate differences in protein intake in women with or without sarcopenia and verify the intake level that is related to a better bone and muscle mass.

METHODS

Elderly women older than 65 years with sarcopenia (n = 35) and without sarcopenia (n = 165) participated in the study. Assessment of bone mineral density of the lumbar spine and femur was taken, body composition was evaluated by dual-energy x-ray absorptiometry, and an evaluation of protein intake was performed through 3-day dietary records.

RESULTS

Muscle, bone, and fat mass was significantly higher in women who had protein intake >1.2 g/kg/d. A lower intake of essential amino acids in women with sarcopenia was also observed. Protein and energy intake were significant predictors of muscle mass. The presence of osteoporosis was a predictor of muscle strength. In conclusion, the present study demonstrated that in elderly women, an adequate protein intake in terms of quality and quantity, without need of supplementation, could have a positive impact on bone mineral density, lean mass, and skeletal muscle mass.

The role of dietary protein and vitamin D in maintaining musculoskeletal health in postmenopausal women: a consensus statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO)

From 50 years of age, postmenopausal women are at an increased risk of developing sarcopenia and osteoporosis as a result of deterioration of musculoskeletal health. Both disorders increase the risk of falls and fractures. The risk of developing sarcopenia and osteoporosis may be attenuated through healthy lifestyle changes, which include adequate dietary protein, calcium and vitamin D intakes, and regular physical activity/exercise, besides hormone replacement therapy when appropriate. Protein intake and physical activity are the main anabolic stimuli for muscle protein synthesis. Exercise training leads to increased muscle mass and strength, and the combination of optimal protein intake and exercise produces a greater degree of muscle protein accretion than either intervention alone. Similarly, adequate dietary protein intake and resistance exercise are important contributors to the maintenance of bone strength. Vitamin D helps to maintain muscle mass and strength as well as bone health. These findings suggest that healthy lifestyle measures in women aged >50 years are essential to allow healthy ageing. The European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) recommends optimal dietary protein intake of 1.0-1.2g/kgbodyweight/d with at least 20-25g of high-quality protein at each main meal, with adequate vitamin D intake at 800IU/d to maintain serum 25-hydroxyvitamin D levels >50nmol/L as well as calcium intake of 1000mg/d, alongside regular physical activity/exercise 3-5 times/week combined with protein intake in close proximity to exercise, in postmenopausal women for prevention of age-related deterioration of musculoskeletal health.

Association of dairy intake with body composition and physical function in older community-dwelling women

Impaired muscle function has been demonstrated to be an important predictor of frailty and fracture in elderly people. The aim of this cross-sectional study was to evaluate the association of dairy intake with body composition and physical performance in 1,456 older women aged 70 to 85 years. Participants were assessed for dairy consumption (milk, yogurt, and cheese) by a validated food frequency questionnaire, body composition by dual-energy x-ray absorptiometry, and physical performance using hand-grip strength and Timed Up and Go tests. Data on falls in the previous 3 months were collected. Women were categorized according to tertiles of dairy intake: first tertile (≤1.5 servings/day), second tertile (1.5 to 2.2 servings/day), and third tertile (≥2.2 servings/day). Main outcomes were compared using analysis of covariance adjusting for confounding factors. Odds ratios for self-reported falls and risk of poor Timed Up and Go were obtained by using binary logistic regression. The mean age was 75.2±2.7 years and body mass index was 27.2±4.7. Compared with those in the first tertile of dairy intake, women in the third tertile had significantly greater whole body lean mass (34.4±0.3 vs 32.9±0.3 kg; P=0.001) and appendicular skeletal muscle mass (15.3±0.2 vs 14.5±0.2 kg; P=0.002), greater hand-grip strength (20.9±0.2 vs 20.0±0.2 kg; P=0.02), and 26% lower odds for a poor Timed Up and Go test (P=0.04); however, the difference in prevalence of falls in the previous 3 months was not statistically significant (10.3% vs 14.4%; P=0.08). Our results suggest an association of higher dairy intake with greater whole body lean mass and better physical performance in older women.