Analytes and Metabolites Associated with Muscle Quality in Young, Healthy Adults

Serum metabolome and gut microbiome alterations are associated with low handgrip strength in older adults

Handgrip strength (HGS), which represents global muscle strength, is a powerful indicator of disability and mortality in older adults; it is also used for the diagnosis of possible- or probable- sarcopenia and physical frailty. This study aimed to explore the metabolic mechanisms and potential biomarkers associated with declining HGS among older adults. We recruited 15 age- and environment-matched inpatients (age, 77-90 years) with low or normal HGS. Liquid chromatography-mass spectrometry (LC-MS) and 16S ribosomal DNA (rDNA) gene sequencing were performed to analyze the metabolome of serum and stool samples and the gut microbiome composition of stool samples. Spearman's correlation analysis was used to identify the potential serum and fecal metabolites associated with HGS. We assessed the levels of serum and fecal metabolites belonging to the class of cinnamic acids and derivatives and reported that the levels of carboxylic acids and their derivatives decreased in the low-HGS group. Serum levels of microbial metabolites, including cinnamoylglycine, 4-methoxycinnamic acid, and (e)-3,4,5-trimethoxycinnamic acid, were positively correlated with HGS. We found that gut microbial α-diversity was significantly higher in the low-HGS group, whereas higher β-diversity was observed in the normal group. The relative abundances of the genera Parabacteroides and Intestinibacter increased significantly in the low-HGS group and were negatively correlated with the serum levels of cinnamoylglycine. The identified metabolites whose levels were markedly altered, and intestinal flora associated with these metabolites suggest the potential metabolic underpinnings for HGS and provide a basis for the further identification of biomarkers of muscle strength decline in older adults.

Evaluating variations in metabolic profiles during the dry period related to the time of hyperketonemia onset in dairy cows

Hyperketonemia (HYK) in early lactation can have a different impact on health and productivity depending on the timing of HYK onset. While specific metabolites measured during the dry period may serve as biomarkers of HYK, the correlations between metabolites represent a challenge for the use of metabolic profiles dataset, and little has been explored on HYK. This exploratory cohort study aimed a) to characterize the correlations among metabolites measured during the late dry period in dairy cows, and b) to identify biomarkers in the late dry period associated with the onset of HYK at the first (wk1) and second (wk2) week of lactation. Individual blood samples from 440 Holstein dairy cows were collected at 21 ± 3 days before expected parturition. From each sample, 36 different metabolites were measured in serum and plasma. Hyperketonemia was diagnosed in wk1 and wk2 of lactation based on the blood concentration of beta-hydroxybutyrate (BHB > 1.2 mmol/L). Principal component analysis (PCA) was performed to reduce metabolites to a smaller number of uncorrelated components. Multivariable logistic regression models were applied to assess the associations between principal components (PC) and HYK at wk1 only (HYK+ wk1), wk2 only (HYK+ wk2), or both weeks (HYK+ wk1-2). The incidence of HYK was 16.2% in the first week, 13.0% in the second week, and 21.2% within the first two weeks of lactation. The results of PCA highlighted 10 PCs from which two were associated with HYK+ wk1 as compared with cows without HYK during the first two weeks of lactation (non-HYK); the PC a2 led by bilirubin and non-esterified fatty acids (OR = 1.29; 95%CI: 1.02-1.68), and the PC a5 led by alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) (OR = 2.77; 95%CI: 1.61-4.97). There was no evidence of an association between any PC and HYK+ wk2 (vs. non-HYK cows). Cows with elevated PC a5 (led by ALP and GGT) in the dry period were 3.18 times more likely to be HYK+ wk1 than HYK+ wk2 (OR: 3.18, 95%CI: 1.34-8.73; P = 0.013). Overall, the main hypothesis generated by our exploratory study suggests that cows with biomarkers of liver dysfunction (ALP, GGT, bilirubin) assessed by PCA at 3 weeks before calving are more likely to develop HYK during the first week of lactation compared to the second week. In addition, results suggest that cows with HYK in both of the first two weeks of lactation had an overall metabolic disbalance during the onset of the late dry period, which based on PCs, encompass biomarkers related to glucogenic and ketogenic metabolic pathways as well as liver dysfunction and fatty liver. Further research is needed to determine the underlying mechanisms associated with the different adaptations between cows that develop HYK during the first and second week of lactation.

Gut microbiota disturbances and protein-energy wasting in chronic kidney disease: a narrative review

Protein-energy wasting (PEW) is common in patients with chronic kidney disease (CKD) and is associated with increased morbidity and mortality, and lower quality of life. It is a complex syndrome, in which inflammation and retention of uremic toxins are two main factors. Causes of inflammation and uremic toxin retention in CKD are multiple; however, gut dysbiosis plays an important role, serving as a link between those entities and PEW. Besides, there are several pathways by which microbiota may influence PEW, e.g., through effects on appetite mediated by microbiota-derived proteins and hormonal changes, or by impacting skeletal muscle via a gut-muscle axis. Hence, microbiota disturbances may influence PEW independently of its relationship with local and systemic inflammation. A better understanding of the complex interrelationships between microbiota and the host may help to explain how changes in the gut affect distant organs and systems of the body and could potentially lead to the development of new strategies targeting the microbiota to improve nutrition and clinical outcomes in CKD patients. In this review, we describe possible interactions of gut microbiota with nutrient metabolism, energy balance, hunger/satiety signals and muscle depletion, all of which are strongly related to PEW in CKD patients.

Plasma high-resolution metabolomic phenotyping of lean mass in a United States adult cohort

BACKGROUND

Rapid loss of lean mass during catabolic states is associated with impaired convalescence and increased mortality rates. An understanding of metabolic pathways related to lean mass is needed to enable future interventions designed to combat malnutrition. This study assessed the plasma metabolome in relation to lean mass in clinically stable working adults in a US cohort.

METHODS

This cross-sectional study included 180 adults (mean ± SD, aged 49.7 ± 10.0 years; body mass index, 27.3 ± 5.5 kg/m² ; 64% female [n=116]). Fasting plasma was analyzed using high-resolution metabolomics (HRM) via liquid chromatography/mass spectrometry. Lean mass was assessed by dual-energy x-ray absorptiometry and expressed as lean mass index (LMI, lean mass kg/height m² ). Multiple linear regression, metabolic pathway enrichment, and module analyses were used to characterize systemic metabolism associated with LMI.

RESULTS

Of 5360 metabolites used in analyses, 593 were related to LMI, either upregulated or downregulated (P < .05). These were enriched within 11 metabolic pathways, including branched-chain amino acid degradation, metabolism of alanine and aspartate and other amino acids, butyrate, purines, and niacin metabolism. Module analysis revealed central associations between LMI and L-glutamate, L-leucine/L-isoleucine, L-valine, L-phenylalanine, L-methionine, and L-aspartate, among other validated metabolites.

CONCLUSION

These novel plasma HRM data demonstrate the wide-reaching associations of lean mass with systemic metabolism in a single snapshot. Such data may inform targeted nutrition support interventions designed to mitigate loss of lean mass and promote regaining skeletal muscle mass and function after illness or injury.

Effects of Aerobic Exercise Training on Systemic Biomarkers and Cognition in Late Middle-Aged Adults at Risk for Alzheimer's Disease

Increasing evidence indicates that physical activity and exercise training may delay or prevent the onset of Alzheimer's disease (AD). However, systemic biomarkers that can measure exercise effects on brain function and that link to relevant metabolic responses are lacking. To begin to address this issue, we utilized blood samples of 23 asymptomatic late middle-aged adults, with familial and genetic risk for AD (mean age 65 years old, 50% female) who underwent 26 weeks of supervised treadmill training. Systemic biomarkers implicated in learning and memory, including the myokine Cathepsin B (CTSB), brain-derived neurotrophic factor (BDNF), and klotho, as well as metabolomics were evaluated. Here we show that aerobic exercise training increases plasma CTSB and that changes in CTSB, but not BDNF or klotho, correlate with cognitive performance. BDNF levels decreased with exercise training. Klotho levels were unchanged by training, but closely associated with change in VO2peak. Metabolomic analysis revealed increased levels of polyunsaturated free fatty acids (PUFAs), reductions in ceramides, sphingo- and phospholipids, as well as changes in gut microbiome metabolites and redox homeostasis, with exercise. Multiple metabolites (~30%) correlated with changes in BDNF, but not CSTB or klotho. The positive association between CTSB and cognition, and the modulation of lipid metabolites implicated in dementia, support the beneficial effects of exercise training on brain function. Overall, our analyses indicate metabolic regulation of exercise-induced plasma BDNF changes and provide evidence that CTSB is a marker of cognitive changes in late middle-aged adults at risk for dementia.

The Kidney-Gut-Muscle Axis in End-Stage Renal Disease is Similarly Represented in Older Adults

Decreased renal function, elevated circulating levels of urea, intestinal levels of urea-degrading bacteria, and gut-derived uremic metabolites are present in end-stage renal disease (ESRD), a cohort that has reduced muscle mass and physical function, and poor muscle composition. This phenotype, defined as the kidney–gut–muscle axis, is similarly represented in older adults that do not have ESRD. The purpose of this short communication is to illuminate these findings, and to propose a strategy that can positively impact the kidney–gut–muscle axis. For example, dietary fiber is fermented by intestinal bacteria, thereby producing the short-chain fatty acids (SCFAs) acetate, propionate, and butyrate, which affect each component of the kidney–gut–muscle axis. Accordingly, a high-fiber diet may be an important approach for improving the kidney–gut–muscle axis in ESRD and in older adults that do not have ESRD.

Physical activity, dietary calcium to magnesium intake and mortality in the National Health and Examination Survey 1999-2006 cohort

Calcium and magnesium affect muscle mass and function. Magnesium and calcium are also important for optimal vitamin D status. Vitamin D status modifies the associations between physical activity and risk of incident cardiovascular disease (CVD) and CVD mortality. However, no study examined whether levels of magnesium and calcium and the ratio of dietary calcium to magnesium (Ca:Mg) intake modify the relationship between physical activity and mortality. We included 20,295 National Health and Nutrition Examination Survey participants (1999-2006) aged >20 years with complete dietary, physical activity and mortality data (2,663 deaths). We assessed physical activity based on public health guidelines and sex-specific tertiles of MET-minutes/week. We used Cox proportional hazards models adjusted for potential confounding factors and stratified by the intakes of magnesium, calcium, Ca:Mg ratio. We found higher physical activity was significantly associated with reduced risk of total mortality and cause-specific mortality, regardless of Ca:Mg ratio, magnesium or calcium intake. In contrast, both moderate and high physical activity were significantly associated with substantially reduced risks of mortality due to cancer when magnesium intake was above the RDA level. We also found higher physical activity was significantly associated with a reduced risk of mortality due to cancer only when Ca:Mg ratios were between 1.7 and 2.6, although the interaction was not significant. Overall, dietary magnesium and, potentially, the Ca:Mg ratio modify the relationship between physical activity and cause-specific mortality. Further study is important to understand the modifying effects of the balance between calcium and magnesium intake on physical activity for chronic disease prevention.

Associations of Aerobic Fitness and Maximal Muscular Strength With Metabolites in Young Men

IMPORTANCE

High physical fitness is associated with a reduction in risk of cardiovascular diseases and death, but the underlying mechanisms are insufficiently understood.

OBJECTIVE

To determine how aerobic fitness and muscular strength are associated with serum metabolome measures.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included Finnish men receiving military refresher training from May 5, 2015, to November 28, 2015, representing partly overlapping groups of individuals with the lowest vs highest aerobic fitness and the lowest vs highest muscular strength. Data analyses were conducted from January 1, 2018, to May 31, 2019.

MAIN OUTCOMES AND MEASURES

The associations of aerobic fitness (determined with maximum oxygen consumption in milliliters per minute per kilogram, measured with maximal cycle ergometer test) and muscular strength (determined with a maximal strength test for lower extremities in kilograms) with 66 metabolome measures from fasting serum samples (nuclear magnetic resonance-based metabolomics) were analyzed.

RESULTS

Participants included 580 Finnish men (mean [SD] age, 26.1 [6.5] years). Including overlap between groups, there were 196 men in the lowest aerobic fitness group and 197 men in the highest aerobic fitness group as well as 196 men in the lowest muscular strength group and 197 men in the highest muscular strength group. Of 66 studied metabolome measures, 48 differed between high vs low aerobic fitness groups, including small very low-density lipoprotein (standardized median difference, -0.67; 95% CI, -0.83 to -0.49), large high-density lipoprotein (standardized median difference, 0.89; 95% CI, 0.69-1.15), total triglyceride levels (standardized median difference, -0.52; 95% CI, -0.65 to -0.34), isoleucine (standardized median difference, -0.37; 95% CI, -0.55 to -0.16), leucine (standardized median difference, -0.55; 95% CI, -0.72 to -0.34), phenylalanine (standardized median difference, -0.54; 95% CI, -0.71 to -0.32), glycerol (standardized median difference, -0.64; 95% CI, -0.81 to -0.48), and glycoprotein (standardized median difference, -0.78; 95% CI, -0.95 to -0.62) concentration, a high unsaturation degree of fatty acids (standardized median difference, 0.59; 95% CI, 0.42-0.81), and apolipoprotein B to apolipoprotein A1 ratio (standardized median difference, -0.88; 95% CI, -1.08 to -0.67). Adding aerobic fitness into the regression model after age, education, smoking, use of alcohol, and dietary factors accounted for more than an additional 5% of variation for 25 metabolome measures (R2 range, 5.01%-15.90% by measure). With these 2 criteria, maximal muscular strength was not associated with any metabolome measures. Aerobic fitness was associated with high large high-density lipoprotein particle concentration (R2, 14.97%; 95% CI, 10.65%-20.85%), low apolipoprotein B to apolipoprotein A1 ratio (R2, 14.49%; 95% CI, 10.58%-19.51%), and low glycoprotein concentration (R2, 15.90%; 95% CI, 11.22%-21.51%). Aerobic fitness was also associated with low very low-density lipoprotein, triglyceride, isoleucine, leucine, phenylalanine, glycerol, and glycoprotein concentrations and with a high unsaturation degree of fatty acids. Adjusting for recent physical activity influenced the results minimally. Adjusting for body fat percentage showed that some of the associations were mechanistically associated with body fat percentage.

CONCLUSIONS AND RELEVANCE

This study provides data on the association of high aerobic fitness with underlying oxidative lipid metabolism associated with a reduction in cardiometabolic risk. High maximal muscular strength is not similarly associated with these benefits.

Protein Supplements and Their Relation with Nutrition, Microbiota Composition and Health: Is More Protein Always Better for Sportspeople?

Sports nutrition products are developed and targeted mainly for athletes to improve their nutrient intake, performance, and muscle growth. The fastest growing consumer groups for these products are recreational sportspeople and lifestyle users. Although athletes may have elevated physiological protein requirements and they may benefit from dietary supplements, the evidence regarding the role of dietary protein and supplements in the nutrition of recreational sportspeople and sedentary populations is somewhat complex and contradictory. In high-protein diets, more undigested protein-derived constituents end up in the large intestine compared to moderate or low-protein diets, and hence, more bacterial amino acid metabolism takes place in the colon, having both positive and negative systemic and metabolic effects on the host. The aim of the present review is to summarize the impact of the high-protein products and diets on nutrition and health, in sportspeople and in sedentary consumers. We are opening the debate about the current protein intake recommendations, with an emphasis on evidence-based effects on intestinal microbiota and personalized guidelines regarding protein and amino acid supplementation in sportspeople and lifestyle consumers.

Gut Microbiota Contribute to Age-Related Changes in Skeletal Muscle Size, Composition, and Function: Biological Basis for a Gut-Muscle Axis

Skeletal muscle is a highly plastic tissue that plays a central role in human health and disease. Aging is associated with a decrease in muscle mass and function (sarcopenia) that is associated with a loss of independence and reduced quality of life. Gut microbiota, the bacteria, archaea, viruses, and eukaryotic microbes residing in the gastrointestinal tract are emerging as a potential contributor to age-associated muscle decline. Specifically, advancing age is characterized by a dysbiosis of gut microbiota that is associated with increased intestinal permeability, facilitating the passage of endotoxin and other microbial products (e.g., indoxyl sulfate) into the circulation. Upon entering the circulation, LPS and other microbial factors promote inflammatory signaling and skeletal muscle changes that are hallmarks of the aging muscle phenotype. This review will summarize existing literature suggesting cross-talk between gut microbiota and skeletal muscle health, with emphasis on the significance of this axis for mediating changes in aging skeletal muscle size, composition, and function.

Even mealtime distribution of protein intake is associated with greater muscle strength, but not with 3-y physical function decline, in free-living older adults: the Quebec longitudinal study on Nutrition as a Determinant of Successful Aging (NuAge study)

Background: Functional status declines with aging, thus impeding autonomy. Recently, a more even mealtime distribution of dietary protein was positively associated with muscle mass, but the relation of this distribution to physical performance remains unknown.Objective: We examined the relation between mealtime protein-intake distribution and physical performance and its 3-y decline in community-dwelling older adults.Design: Three-year follow-up data from 827 men and 914 women (67-84 y) in the longitudinal study on nutrition and aging [Quebec longitudinal study on Nutrition as a Determinant of Successful Aging (NuAge study); Quebec, Canada] were analyzed. Physical performance, which was measured yearly, was grouped into the following 2 functional composite scores: muscle strength (handgrip, arm, and leg) and mobility (timed-up-and-go, chair stand, and walking speed). Dietary data were collected in 2 sets of three 24-h food recalls at baseline and year 2. The individual mealtime protein distribution was calculated as the CV (i.e., SD divided by the mean) of grams of protein per meal. A mixed model analysis was used to examine trajectories of muscle strength and mobility across time by sex as conditioned by the protein distribution and adjusted for potential covariates.Results: Physical performance deteriorated over 3 y with muscle strength declining more than the mobility score in men (-1.51 ± 1.68 compared with -0.66 ± 2.81) and women (-1.35 ± 1.77 compared with -0.78 ± 2.63) (means ± SD, P < 0.001). More-evenly distributed protein intake, independent of the total quantity, was associated with a higher muscle-strength score in both sexes throughout follow-up. It was also associated with a greater mobility score, but only in men and only before adjustment for covariates. Strength and mobility rates of decline were not affected by protein-intake distribution in either sex.Conclusions: In addition to the previously observed association with lean mass, an even distribution of daily protein intake across meals is independently associated with greater muscle strength, but not with the mobility score, in older adults. A longer-term investigation of the role of protein intake and its distribution on physical performance is warranted, as are intervention studies, to support future recommendations.

Sarcopenic Obesity and Metabolic Syndrome in Adult Caucasian Subjects

OBJECTIVES

Recently metabolic aspects linked to sarcopenic obesity (SO) were investigated. Extant studies involved especially older people from Asian or White-mixed American cohorts.

THE AIMS OF OUR STUDY WERE

to explore the prevalence of sarcopenia in Caucasian adult obese subjects using two different indices of sarcopenia, and to investigate the relationship among SO, metabolic syndrome (MS), inflammation, and serum albumin concentrations.

DESIGN

Cross- sectional study.

SUBJECTS/METHODS

The study was performed from 2011 to 2014 in a hospitalized care setting. Inclusion criteria were: age>18 and <65 years, BMI≥30 Kg/m2. Fat mass (FM) and fat-free mass (FFM) were assessed by DXA. Appendicular skeletal muscle mass (ASMM) was calculated. Sarcopenia was defined as ASMM/height2 or ASMM/weight <2SD than the sex-specific mean of a young population. The cutoffs were ASMM/h2<6.54 Kg/m2 for men and 4.82 Kg/m2 for women, and ASMM/weight<0.2827 for men and 0.2347 for women. ISI-Matsuda was calculated. MS was diagnosed (NCEP-ATPIII).

RESULTS

727 subjects (age: 45.72±13.56 years, BMI: 37.74±5.82 kg/m2) were enrolled. The prevalence of SO was 1.0% or 34.8% in men and 0.6% or 50.1% in women, using ASMM/height2 ratio or ASMM/weight. Subjects with SO based on ASMM/height2 were scarce, only data relying on ASMM/weight were considered. Subjects with SO had higher BMI, waist circumference, FM, and lower FFM and ASMM than nonsarcopenic obese individuals (all p<0.05). ISI-Matsuda was lower and hs-CRP levels were higher in subjects with SO (all p<0.05). MS was more prevalent in subjects with SO than nonsarcopenic obese subjects (47.6% vs 34.3%, p<0.001). ASMM/weight was decreased in subjects with MS (0.2522±0.0410 vs 0.2423±0.0352, p=0.001).

CONCLUSION

SO is associated with MS and low- grade inflammation in adult Caucasian subjects. Metabolic profile evaluation should be recommended in subjects with SO.

Dietary Protein Intake Is Protective Against Loss of Grip Strength Among Older Adults in the Framingham Offspring Cohort

BACKGROUND

Age-related decline in muscle strength is an important public health issue for older adults. Dietary protein has been associated with maintenance of muscle mass, yet its relation to muscle strength remains unclear.

METHODS

We determined the association of dietary protein (total, animal, and plant) intake, measured by food frequency questionnaire, with change in grip strength over 6 years in 1,746 men and women from the Framingham Offspring cohort.

RESULTS

Mean age at baseline was 58.7 years (range: 29-85), and mean total, animal, and plant protein intakes were 79, 57, and 22 g/d, respectively. Adjusted baseline mean grip strength did not differ across quartiles of energy-adjusted total, animal or protein intake. Greater protein intake, regardless of source, was associated with less decrease in grip strength (all p for trend ≤.05): participants in the lowest quartiles lost 0.17% to 0.27% per year while those in the highest quartiles gained 0.52% to 0.60% per year. In analyses stratified by age, participants aged 60 years or older (n = 646) had similar linear trends on loss of grip strength for total and animal (all p for trend <.03) but not plant protein, while the trends in participants younger than 60 years (n = 896) were not statistically significant.

CONCLUSIONS

Higher dietary intakes of total and animal protein were protective against loss of grip strength in community-dwelling adults aged 60 years and older. Increasing intake of protein from these sources may help maintain muscle strength and support prevention of mobility impairment in older adults.