Prolonged Calorie Restriction Downregulates Skeletal Muscle mTORC1 Signaling Independent of Dietary Protein Intake and Associated microRNA Expression

Short-term (5-10 days) calorie restriction (CR) downregulates muscle protein synthesis, with consumption of a high protein-based diet attenuating this decline. Benefit of increase protein intake is believed to be due to maintenance of amino acid-mediated anabolic signaling through the mechanistic target of rapamycin complex 1 (mTORC1), however, there is limited evidence to support this contention. The purpose of this investigation was to determine the effects of prolonged CR and high protein diets on skeletal muscle mTORC1 signaling and expression of associated microRNA (miR). Twelve-week old male Sprague Dawley rats consumed ad libitum (AL) or calorie restricted (CR; 40%) adequate (10%, AIN-93M) or high (32%) protein milk-based diets for 16 weeks. Body composition was determined using dual energy X-ray absorptiometry and muscle protein content was calculated from muscle homogenate protein concentrations expressed relative to fat-free mass to estimate protein content. Western blot and RT-qPCR were used to determine mTORC1 signaling and mRNA and miR expression in fasted mixed gastrocnemius. Independent of dietary protein intake, muscle protein content was 38% lower (P < 0.05) in CR compared to AL. Phosphorylation and total Akt, mTOR, rpS6, and p70S6K were lower (P < 0.05) in CR vs. AL, and total rpS6 was associated with muscle protein content (r = 0.64, r² = 0.36). Skeletal muscle miR expression was not altered by either energy or protein intake. This study provides evidence that chronic CR attenuates muscle protein content by downregulating mTORC1 signaling. This response is independent of skeletal muscle miR and dietary protein.

Impact and Lessons From the Lifestyle Interventions and Independence for Elders (LIFE) Clinical Trials of Physical Activity to Prevent Mobility Disability

BACKGROUND

Walking independently is basic to human functioning. The Lifestyle Interventions and Independence for Elders (LIFE) studies were developed to assess whether initiating physical activity could prevent major mobility disability (MMD) in sedentary older adults.

METHODS

We review the development and selected findings of the LIFE studies from 2000 through 2019, including the planning phase, the LIFE-Pilot Study, and the LIFE Study.

RESULTS

The planning phase and the LIFE-Pilot provided key information for the successful implementation of the LIFE Study. The LIFE Study, involving 1635 participants randomized at eight sites throughout the United States, showed that compared with health education, the physical activity program reduced the risk of the primary outcome of MMD (inability to walk 400 m: hazard ratio = 0.82; 95% confidence interval = 0.69-0.98; P = .03), and that the intervention was cost-effective. There were no significant effects on cognitive outcomes, cardiovascular events, or serious fall injuries. In addition, the LIFE studies provided relevant findings on a broad range of other outcomes, including health, frailty, behavioral outcomes, biomarkers, and imaging. To date, the LIFE studies have generated a legacy of 109 peer-reviewed publications, 19 ancillary studies, and 38 independently funded grants and clinical trials, and advanced the development of 59 early career scientists. Data and biological samples of the LIFE Study are now publicly available from a repository sponsored by the National Institute on Aging (https://agingresearchbiobank.nia.nih.gov).

CONCLUSIONS

The LIFE studies generated a wealth of important scientific findings and accelerated research in geriatrics and gerontology, benefiting the research community, trainees, clinicians, policy makers, and the general public. J Am Geriatr Soc 68:872-881, 2020.

Muscle Power Is an Independent Determinant of Pain and Quality of Life in Knee Osteoarthritis

OBJECTIVE

This study examined the relationships between leg muscle strength, power, and perceived disease severity in subjects with knee osteoarthritis (OA) in order to determine whether dynamic leg extensor muscle power would be associated with pain and quality of life in knee OA.

METHODS

Baseline data on 190 subjects with knee OA (mean ± SD age 60.2 ± 10.4 years, body mass index 32.7 ± 7.2 kg/m(2) ) were obtained from a randomized controlled trial. Knee pain was measured using the Western Ontario and McMaster Universities Osteoarthritis Index, and health-related quality of life was assessed using the Short Form 36 (SF-36). One-repetition maximum (1RM) strength was assessed using the bilateral leg press, and peak muscle power was measured during 5 maximum voluntary velocity repetitions at 40% and 70% of 1RM.

RESULTS

In univariate analysis, greater muscle power was significantly associated with pain (r = -0.17, P < 0.02) and also significantly and positively associated with SF-36 physical component summary (PCS) scores (r = 0.16, P < 0.05). After adjustment for multiple covariates, muscle power was a significant independent predictor of pain (P ≤ 0.05) and PCS scores (P ≤ 0.04). However, muscle strength was not an independent determinant of pain or quality of life (P ≥ 0.06).

CONCLUSION

Muscle power is an independent determinant of pain and quality of life in knee OA. Compared to strength, muscle power may be a more clinically important measure of muscle function within this population. New trials to systematically examine the impact of muscle power training interventions on disease severity in knee OA are particularly warranted.

Effect of Structured, Moderate Exercise on Kidney Function Decline in Sedentary Older Adults: An Ancillary Analysis of the LIFE Study Randomized Clinical Trial

Importance

Observational evidence suggests that higher physical activity is associated with slower kidney function decline; however, to our knowledge, no large trial has evaluated whether activity and exercise can ameliorate kidney function decline in older adults.

Objective

To evaluate whether a moderate-intensity exercise intervention can affect the rate of estimated glomerular filtration rate per cystatin C (eGFRCysC) change in older adults.

Design, Setting, and Participants

This ancillary analysis of the Lifestyle Interventions and Independence For Elders randomized clinical trial enrolled 1199 community-dwelling, sedentary adults aged 70 to 89 years with mobility limitations and available blood specimens. The original trial was conducted across 8 academic centers in the US from February 2010 through December 2013. Data for this study were analyzed from March 29, 2021, to February 28, 2022.

Interventions

Structured, 2-year, partially supervised, moderate-intensity physical activity and exercise (strength, flexibility) intervention compared with a health education control intervention with 2-year follow-up. Physical activity was measured by step count and minutes of moderate-intensity activity using accelerometers.

Main Outcomes and Measures

The primary outcome was change in eGFRCysC. Rapid eGFRCysC decline was defined by the high tertile threshold of 6.7%/y.

Results

Among the 1199 participants in the analysis, the mean (SD) age was 78.9 (5.2) years, and 800 (66.7%) were women. At baseline, the 2 groups were well balanced by age, comorbidity, and baseline eGFRCysC. The physical activity and exercise intervention resulted in statistically significantly lower decline in eGFRCysC over 2 years compared with the health education arm (mean difference, 0.96 mL/min/1.73 m2; 95% CI, 0.02-1.91 mL/min/1.73 m2) and lower odds of rapid eGFRCysC decline (odds ratio, 0.79; 95% CI, 0.65-0.97).

Conclusions and Relevance

Results of this ancillary analysis of a randomized clinical trial showed that when compared with health education, a physical activity and exercise intervention slowed the rate of decline in eGFRCysC among community-dwelling sedentary older adults. Clinicians should consider targeted recommendation of physical activity and moderate-intensity exercise for older adults as a treatment to slow decline in eGFRCysC.

Trial Registration

ClinicalTrials.gov Identifier: NCT01072500.

What is a Clinically Meaningful Improvement in Leg-Extensor Power for Mobility-limited Older Adults?

BACKGROUND

Muscle power is a key predictor of physical function in older adults; however, clinically meaningful improvements in leg-extensor muscle power have yet to be identified. The purpose of this study is to establish the minimal clinically important improvement (MCII) and substantial improvement (SI) for leg-extensor power and muscle contraction velocity in mobility-limited older adults.

METHODS

Data were extracted from three randomized trials of leg-extensor muscle power training interventions (3- to 6-month duration). Measurements of leg-extensor power and velocity were obtained using dynamic bilateral leg press at 40% and 70% of the one-repetition maximum. Anchor-based MCIIs were calculated using selected items extracted from the Late Life Function and Disability Instrument. Standard error of measurement and effect size methods were used to calculate the distribution-based MCII.

RESULTS

Data from 164 participants (mean age: 76.6 ± 5.6 years; Short Physical Performance Battery score: 7.8 ± 1.3) were used in this analysis. The respective MCII and SI estimates for 40% leg-extensor power were 18.3 (9%) and 30.5 (15%) W, and 23.1 (10%) and 41.6 (18%) W for 70% leg-extensor power. The respective MCII and SI estimates for 40% average velocity were 0.03(7%) and 0.08(18%) m/s, and 0.02(6%) and 0.05(15%) m/s for 70% average velocity.

CONCLUSIONS

This is the first study to establish a clinically meaningful improvement of leg-extensor power (9%-10%) and velocity (6%-7%) in mobility-limited older adults. These findings should be used to aid in the design and interpretation of clinical trials and interventions that target improvements in muscle power in this high-risk population.

Effects of exercise training in the elderly: impact of progressive- resistance training on skeletal muscle and whole-body protein metabolism

The declines in functional capacity and muscle function with advancing age are well-documented. In addition, it appears that the age-related changes in body composition have profound effects on functional capacity and nutrient requirements. The overwhelming evidence presented in the present review suggests that the loss of muscle strength and function observed with advancing age is reversible even in the frail elderly. Along with the profound functional improvement in older individuals in response to progressive-resistance training, several studies have reported increases in resting energy expenditure and increased requirements for dietary protein. Exercise programmes designed to improve muscle strength be recommended for older individuals as an effective countermeasure to the sarcopenia of old age.

Sex differences in single muscle fiber power in older adults

PURPOSE

This study was conducted to determine whether differences in power at the single muscle fiber level contribute to sex differences in whole muscle power production in the elderly.

METHODS

A total of 16 sedentary older persons (10 women, 6 men), mean age 72 yr, had percutaneous needle biopsy of musculus vastus lateralis. Chemically skinned single muscle fibers were activated with Ca for maximal isometric force measurement (Po). The slack test was performed to determine maximal unloaded shortening velocity (Vo). Force-velocity and power curves were generated via a series of isotonic contractions, allowing measurement of peak power and specific power. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine myosin heavy chain composition of single muscle fibers. Whole muscle strength, velocity, and power were measured for knee extension and double leg press.

RESULTS

Men had greater whole muscle strength, power, and velocity compared with women. Studied were 274 type I and 33 type IIa single fibers. No significant sex differences were found for fiber size, Po, specific force, Vo, power, or specific power in type I or IIa fibers.

CONCLUSIONS

Single muscle fiber quality in older women is equivalent to that in older men and can not explain the differences seen in whole muscle strength, power, or function.

Effect of Structured Physical Activity on Overall Burden and Transitions Between States of Major Mobility Disability in Older Persons: Secondary Analysis of a Randomized Trial

BACKGROUND

The total time a patient is disabled likely has a greater influence on his or her quality of life than the initial occurrence of disability alone.

OBJECTIVE

To compare the effect of a long-term, structured physical activity program with that of a health education intervention on the proportion of patient assessments indicating major mobility disability (MMD) (that is, MMD burden) and on the risk for transitions into and out of MMD.

DESIGN

Single-blinded, parallel-group, randomized trial. (ClinicalTrials.gov: NCT01072500).

SETTING

8 U.S. centers between February 2010 and December 2013.

PARTICIPANTS

1635 sedentary persons, aged 70 to 89 years, who had functional limitations but could walk 400 m.

INTERVENTION

Physical activity (n = 818) and health education (n = 817).

MEASUREMENTS

MMD, defined as the inability to walk 400 m, was assessed every 6 months for up to 3.5 years.

RESULTS

During a median follow-up of 2.7 years, the proportion of assessments showing MMD was substantially lower in the physical activity (0.13 [95% CI, 0.11 to 0.15]) than the health education (0.17 [CI, 0.15 to 0.19]) group, yielding a risk ratio of 0.75 (CI, 0.64 to 0.89). In a multistate model, the hazard ratios for comparisons of physical activity with health education were 0.87 (CI, 0.73 to 1.03) for the transition from no MMD to MMD; 0.52 (CI, 0.10 to 2.67) for no MMD to death; 1.33 (CI, 0.99 to 1.77) for MMD to no MMD; and 1.92 (CI, 1.15 to 3.20) for MMD to death.

LIMITATION

The intention-to-treat principle was maintained for MMD burden and first transition out of no MMD, but not for subsequent transitions.

CONCLUSION

A structured physical activity program reduced the MMD burden for an extended period, in part through enhanced recovery after the onset of disability and diminished risk for subsequent disability episodes.

PRIMARY FUNDING SOURCE

National Institute on Aging, National Institutes of Health.

Device-Measured Physical Activity As a Predictor of Disability in Mobility-Limited Older Adults

OBJECTIVES

To examine associations between objectively measured physical activity (PA) and incidence of major mobility disability (MMD) and persistent MMD (PMMD) in older adults in the Lifestyle Interventions and Independence for Elders (LIFE) Study.

DESIGN

Prospective cohort of individuals aged 65 and older undergoing structured PA intervention or health education.

SETTING

The LIFE Study was a multicenter (eight sites) randomized controlled trial designed to compare the efficacy of a long-term structured PA intervention with that of a health education (HE) program in reducing the incidence of MMD in mobility-limited older adults.

PARTICIPANTS

LIFE Study participants (n = 1,590) had a mean age±standard deviation of 78.9 ± 5.2, low levels of PA, and measured mobility-relevant functional impairment at baseline.

MEASUREMENTS

Activity data were collected using hip-worn 7-day accelerometers at baseline and 6, 12, and 24 months after randomization to test for associations with incident MMD and PMMD (≥2 consecutive instances of MMD).

RESULTS

At baseline, every 30 minutes spent being sedentary (<100 accelerometry counts per minute) was associated with higher rate of subsequent MMD (10%) and PMMD (11%) events. Every 500 steps taken was associated with lower rate of MMD (15%) and PMMD (18%). Similar associations were observed when fitting accelerometry-based PA as a time-dependent variable.

CONCLUSION

Accelerometry-based PA levels were strongly associated with MMD and PMMD events in older adults with limited mobility. These results support the importance of daily PA and lower amounts of sedentary time levels in this population and suggest that accelerometry may be a useful tool for assessing risk of mobility disability.

Systemic vascular function is associated with muscular power in older adults

Age-associated loss of muscular strength and muscular power is a critical determinant of loss of physical function and progression to disability in older adults. In this study, we examined the association of systemic vascular function and measures of muscle strength and power in older adults. Measures of vascular endothelial function included brachial artery flow-mediated dilation (FMD) and the pulse wave amplitude reactive hyperemia index (PWA-RHI). Augmentation index (AIx) was taken as a measure of systemic vascular function related to arterial stiffness and wave reflection. Measures of muscular strength included one repetition maximum (1RM) for a bilateral leg press. Peak muscular power was measured during 5 repetitions performed as fast as possible for bilateral leg press at 40% 1RM. Muscular power was associated with brachial FMD (r = 0.43, P < 0.05), PWA-RHI (r = 0.42, P < 0.05), and AIx (r = -0.54, P < 0.05). Muscular strength was not associated with any measure of vascular function. In conclusion, systemic vascular function is associated with lower-limb muscular power but not muscular strength in older adults. Whether loss of muscular power with aging contributes to systemic vascular deconditioning or vascular dysfunction contributes to decrements in muscular power remains to be determined.

Vitamin D receptor protein is associated with interleukin-6 in human skeletal muscle

Vitamin D is associated with skeletal muscle physiology and function and may play a role in intramuscular inflammation, possibly via the vitamin D receptor (VDR). We conducted two studies to examine (1) whether serum 25-hydroxyvitamin D (25OHD) and/or intramuscular VDR protein concentrations are associated with intramuscular interleukin-6 (IL-6) and/or tumor necrosis factor-α (TNFα); and (2) whether 16-week supplementation with vitamin D3 alters intramuscular IL-6 and/or TNFα. Potential-related signaling pathways were also examined. Muscle biopsies of 30 older, mobility-limited adults were obtained at baseline. A subset of 12 women were supplemented with either 4,000 IU/day of vitamin D3 (N = 5) or placebo (N = 7), and biopsies were repeated at 16 weeks. Serum 25OHD was measured, and intramuscular VDR, IL-6, and TNFα gene expressions and protein concentrations were analyzed. Baseline serum 25OHD was not associated with intramuscular IL-6 or TNFα gene expression or protein concentration. Baseline intramuscular VDR protein concentration, adjusted for baseline serum 25OHD, was positively associated with intramuscular IL-6 gene expression (n = 28; p = 0.04), but negatively associated with intramuscular IL-6 protein (n = 18; p = 0.03). Neither intramuscular IL-6 nor TNFα gene expression was different between placebo (n = 7) or vitamin D3 supplementation groups (n = 5) after 16 weeks (p = 0.57, p = 0.11, respectively). These data suggest that VDR is a better predictor than serum 25OHD concentration of intramuscular IL-6 gene and protein expressions. A similar relationship was not observed for TNFα expression. Further, supplementation with 4,000 IU vitamin D3 per day does not appear to affect intramuscular IL-6 or TNFα gene expression after 16 weeks.

Metabolites Associated With Circulating Interleukin-6 in Older Adults

Background

Circulating levels of the pro-inflammatory cytokine interleukin-6 (IL-6) levels are elevated in older adults, but mechanisms are unclear. In the current study, we used an untargeted metabolomic approach to develop an improved understanding about mechanisms related to circulating IL-6 in older adults.

Methods

Serum IL-6 values were log-transformed to normalize its distribution. Multivariable-adjusted linear regression was used to examine the association between 324 serum metabolites with log IL-6. Backward elimination linear regression was used to develop a metabolite predictor set representative of log IL-6.

Results

Thirty-six metabolites were significantly associated (p < 0.05 and q < 0.30) with log IL-6 in 73 older adults (average age, 78 years). Metabolites related to tryptophan metabolism (kynurenine, 3-indoxyl sulfate, indoleacetate, indolepropionate, C-glycosyltryptophan), infectious burden (C-glycosyltryptophan, N6-carbamoylthreonyladenosine, 1-methylurate, N-formylmethionine, N1-methyladenosine, 3-indoxyl sulfate, bilirubin (E,E), indoleacetate, γ-CEHC, N-acetylneuraminate), aryl hydrocarbon receptor activation and cytochrome P450 (CYP) 1A expression (kynurenine, 3-indoxyl sulfate, indoleacetate, N6-carbamoylthreonyladenosine, bilirubin, 1-methylurate) were positively associated, whereas metabolites related to CYP-mediated ω-oxidation (adipate, 8-hydroxyoctanoate, azelate, sebacate, undecanedioate, γ-CEHC), and peroxisome proliferator activated receptor-alpha (PPAR-α) activation (13 + 9-HODE, bilirubin, 5-oxoproline, cholesterol, glycerate, uridine) were negatively associated with log IL-6. The use of backward elimination regression identified tyrosine, cysteine, uridine, bilirubin, N-formylmethionine, indoleacetate, and 3-indoxyl sulfate to collectively explain 51% of the variance inherent in log IL-6.

Conclusions

These data suggest roles for tryptophan metabolism, infectious burden, activation of host defense, and detoxification through CYP1A-mediated pathways in mechanisms related to elevated inflammation, whereas CYP-mediated ω-oxidation and PPAR-α activation may be related to decreased inflammation in older adults.

Long-term exercise in older adults: 4-year outcomes of music-based multitask training

Prospective controlled evidence supporting the efficacy of long-term exercise to prevent physical decline and reduce falls in old age is lacking. The present study aimed to assess the effects of long-term music-based multitask exercise (i.e., Jaques-Dalcroze eurhythmics) on physical function and fall risk in older adults. A 3-year follow-up extension of a 1-year randomized controlled trial (NCT01107288) was conducted in Geneva (Switzerland), in which 134 community-dwellers aged ≥65 years at increased risk of falls received a 6-month music-based multitask exercise program. Four years following original trial enrolment, 52 subjects (baseline mean ± SD age, 75 ± 8 years) who (i) have maintained exercise program participation through the 4-year follow-up visit ("long-term intervention group", n = 23) or (ii) have discontinued participation following original trial completion ("control group", n = 29) were studied. They were reassessed in a blind fashion, using the same procedures as at baseline. At 4 years, linear mixed-effects models showed significant gait (gait speed, P = 0.006) and balance (one-legged stance time, P = 0.015) improvements in the long-term intervention group, compared with the control group. Also, long-term intervention subjects did better on Timed Up & Go, Five-Times-Sit-to-Stand and handgrip strength tests, than controls (P < 0.05, for all comparisons). Furthermore, the exercise program reduced the risk of falling (relative risk, 0.69; 95% confidence interval, 0.5-0.9; P = 0.008). These findings suggest that long-term maintenance of a music-based multitask exercise program is a promising strategy to prevent age-related physical decline in older adults. They also highlight the efficacy of sustained long-term adherence to exercise for falls prevention.

Effects of physical and cognitive training on gait speed and cognition in older adults: A randomized controlled trial

Gait speed is a measure of health and functioning. Physical and cognitive determinants of gait are amenable to interventions, but best practices remain unclear. We investigated the effects of a 12-month physical and cognitive training (PTCT) on gait speed, dual-task cost in gait speed, and executive functions (EFs) compared with physical training (PT) (ISRCTN52388040). Community-dwelling older adults, who did not meet physical activity recommendations, were recruited (n = 314). PT included supervised walking/balance (once weekly) and resistance/balance training (once weekly), home exercises (2-3 times weekly), and moderate aerobic activity 150 min/week in bouts of >10 min. PTCT included the PT and computer training (CT) on EFs 15-20 min, 3-4 times weekly. The primary outcome was gait speed. Secondary outcomes were 6-min walking distance, dual-task cost in gait speed, and EF (Stroop and Trail Making B-A). The trial was completed by 93% of the participants (age 74.5 [SD3.8] years; 60% women). Mean adherence to supervised sessions was 59%-72% in PT and 62%-77% in PTCT. Home exercises and CT were performed on average 1.9 times/week. Weekly minutes spent in aerobic activities were 188 (median 169) in PT and 207 (median 180) in PTCT. No significant interactions were observed for gait speed (PTCT-PT, 0.02; 95%CI -0.03, 0.08), walking distance (-3.8; -16.9, 9.3) or dual-task cost (-0.22; -1.74, 1.30). Stroop improvement was greater after PTCT than PT (-6.9; -13.0, -0.8). Complementing physical training with EFs training is not essential for promotion of gait speed. For EF's, complementing physical training with targeted cognitive training provides additional benefit.

Gait Speed and Mobility Disability: Revisiting Meaningful Levels in Diverse Clinical Populations

OBJECTIVES

To investigate the heterogeneity of clinically meaningful levels of gait speed relative to self-reported mobility disability (SR-MD).

DESIGN

Five longitudinal studies with older adults in different health states (onset of acute event, presence of chronic condition, sedentary, community living) were used to explore the relationship between gait speed and SR-MD.

SETTING

Lifestyle Interventions and Independence for Elders Pilot (LIFE-P), LIFE, Trial of Angiotensin-Converting Enzyme Inhibition and Novel Cardiovascular Risk Factors (TRAIN), Baltimore Hip Fracture Study (BHS2), Invecchiare in Chianti (InCHIANTI).

PARTICIPANTS

Individuals aged 65 and older (N=3,540): sedentary, community dwelling (LIFE-P/LIFE), with hip fracture (BHS2), random population-based sample (InCHIANTI), high cardiovascular risk (TRAIN).

MEASUREMENTS

Usual-pace gait speed across 3 to 4 m and SR-MD, defined as inability to walk approximately 1 block or climb 1 flight of stairs.

RESULTS

The mean gait speed of participants without SR-MD was greater than 1.0 m/s in InCHIANTI and TRAIN, 0.79 m/s in LIFE-P/LIFE, and 0.46 m/sec in BHS2. Of individuals with SR-MD, mean gait speed was 0.08 m/s slower in LIFE-P/LIFE, 0.19 m/s slower in TRAIN, 0.22 m/s slower in BHS2, and 0.36 m/s slower in InCHIANTI. The optimal gait speed cutpoint for minimizing SR-MD misclassification rates ranged from 0.3 m/s in BHS2 to 1.0 m/s in TRAIN. In longitudinal analyses, development of SR-MD was dependent on initial gait speed and change in gait speed (p<.001).

CONCLUSION

The relationship between absolute levels of gait speed and SR-MD may be context specific, and there may be variations between populations. Across diverse clinical populations, clinical interpretations of how change in usual pace gait speed relates to development of SR-MD depend on where on the gait speed continuum change occurs.

Predictors of Change in Physical Function in Older Adults in Response to Long-Term, Structured Physical Activity: The LIFE Study

OBJECTIVES

To evaluate the extent of variability in functional responses in participants in the Lifestyle Interventions and Independence for Elders (LIFE) study and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability.

DESIGN

Secondary analysis.

SETTING

Multicenter institutions.

PARTICIPANTS

A volunteer sample (N=1635) of sedentary men and women aged 70 to 89 years who were able to walk 400m but had physical limitations, defined as a Short Physical Performance Battery (SPPB) score of ≤9.

INTERVENTIONS

Moderate-intensity physical activity (n=818) consisting of aerobic, resistance, and flexibility exercises performed both center-based (2times/wk) and home-based (3-4times/wk) sessions or health education program (n=817) consisting of weekly to monthly workshops covering relevant health information.

MAIN OUTCOME MEASURES

Physical function (gait speed over 400m) and lower extremity function (SPPB score) assessed at baseline and 6, 12, and 24 months.

RESULTS

Greater baseline physical function (gait speed, SPPB score) was negatively associated with change in gait speed (regression coefficient β=-.185; P<.001) and change in SPPB score (β=-.365; P<.001), whereas higher number of steps per day measured by accelerometry was positively associated with change in gait speed (β=.035; P<.001) and change in SPPB score (β=.525; P<.001). Other baseline factors associated with positive change in gait speed and/or SPPB score include younger age (P<.001), lower body mass index (P<.001), and higher self-reported physical activity (P=.002).

CONCLUSIONS

Several demographic and physical activity-related factors were associated with the extent of change in functional outcomes in participants in the LIFE study. These factors should be considered when designing interventions for improving physical function in older adults with limited mobility.

The AMPK-related kinase SNARK regulates muscle mass and myocyte survival

The maintenance of skeletal muscle mass is critical for sustaining health; however, the mechanisms responsible for muscle loss with aging and chronic diseases, such as diabetes and obesity, are poorly understood. We found that expression of a member of the AMPK-related kinase family, the SNF1-AMPK-related kinase (SNARK, also known as NUAK2), increased with muscle cell differentiation. SNARK expression increased in skeletal muscles from young mice exposed to metabolic stress and in muscles from healthy older human subjects. The regulation of SNARK expression in muscle with differentiation and physiological stress suggests that SNARK may function in the maintenance of muscle mass. Consistent with this hypothesis, decreased endogenous SNARK expression (using siRNA) in cultured muscle cells resulted in increased apoptosis and decreased cell survival under conditions of metabolic stress. Likewise, muscle-specific transgenic animals expressing a SNARK dominant-negative inactive mutant (SDN) had increased myonuclear apoptosis and activation of apoptotic mediators in muscle. Moreover, animals expressing SDN had severe, age-accelerated muscle atrophy and increased adiposity, consistent with sarcopenic obesity. Reduced SNARK activity, in vivo and in vitro, caused downregulation of the Rho kinase signaling pathway, a key mediator of cell survival. These findings reveal a critical role for SNARK in myocyte survival and the maintenance of muscle mass with age.

Accelerometer Assessment of Physical Activity and Its Association with Physical Function in Older Adults Residing at Assisted Care Facilities

OBJECTIVES

To describe levels of physical activity among older adults residing at assisted care facilities and their association with physical function.

DESIGN

Cross-sectional analysis.

SETTING

Assisted care facilities within the greater Boston, MA area.

PARTICIPANTS

Older adults aged 65 years and older (N = 65).

MEASUREMENTS

Physical Activity Level (PAL) as defined by quartiles from accelerometry (counts and steps), Short Physical Performance Battery (SPPB) Score, gait speed, and handgrip strength.

RESULTS

Participants in the most active accelerometry quartile engaged in 25 minutes/week of moderate to vigorous physical activity (MVPA) and walked 2,150 steps/day. These individuals had an SPPB score, 400 meter walk speed, and handgrip strength that was 3.7-3.9 points, 0.3-0.4 meters/second, and 4.5-5.1 kg greater respectively, than individuals in the lowest activity quartile, who engaged in less than 5 min/wk of MVPA or took fewer than 460 steps/day.

CONCLUSION

Despite engaging in physical activity levels far below current recommendations (150 min/week of MVPA or > 7000 steps/day), the most active older adults in this study exhibited clinically significant differences in physical function relative to their less active peers. While the direction of causality cannot be determined from this cross-sectional study, these findings suggest a strong association between PAL and physical function among older adults residing in an assisted care facility.

Effect of Losartan and Fish Oil on Plasma IL-6 and Mobility in Older Persons. The ENRGISE Pilot Randomized Clinical Trial

BACKGROUND

Low-grade chronic inflammation, characterized by elevations in plasma Interleukin-6 (IL-6), is an independent risk factor of impaired mobility in older persons. Angiotensin receptor blockers and omega-3 polyunsaturated fatty acids (ω-3) may reduce IL-6 and may potentially improve physical function. To assess the main effects of the angiotensin receptor blocker losartan and ω-3 as fish oil on IL-6 and 400 m walking speed, we conducted the ENRGISE Pilot multicenter randomized clinical trial.

METHODS

The ENRGISE Pilot enrolled participants between April 2016 and June 2017, who participated for 12 months. Participants were aged ≥70 years with mobility impairment, had IL-6 between 2.5 and 30 pg/mL, and were able to walk 400 m at baseline. Participants were randomized in three strata 2 × 2 factorial to: (i) losartan 50-100 mg/d or placebo (n = 43), (ii) fish oil 1,400-2,800 mg/d or placebo (n = 180), and (iii) with both (n = 66).

RESULTS

Two hundred eighty-nine participants were randomized (mean age 78.3 years, 47.4% women, 17.0% black). There was no effect of losartan (difference of means = -0.065 ± 0.116 [SE], 95% confidence interval [CI]: -0.293-0.163, p = .58) or fish oil (-0.020 ± 0.077, 95% CI: -0.171-0.132, p = .80) on the log of IL-6. Similarly, there was no effect of losartan (-0.025 ± 0.026, 95% CI: -0.076-0.026, p = .34) or fish oil (0.010 ± 0.017, 95% CI: -0.025-0.044, p = .58) on walking speed (m/s).

CONCLUSIONS

These results do not support the use of these interventions to prevent mobility loss in older adults at risk of disability with low-grade chronic inflammation.

REGISTRATION

Clinicaltrials.gov NCT02676466.

Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with Exercise Training in Mobility-Limited Older Adults

BACKGROUND

Human aging is characterized by a chronic, low-grade inflammation suspected to contribute to reductions in skeletal muscle size, strength, and function. Inflammatory cytokines, such as interleukin-6 (IL-6), may play a role in the reduced skeletal muscle adaptive response seen in older individuals.

OBJECTIVES

To investigate relationships between circulating IL-6, skeletal muscle health and exercise adaptation in mobility-limited older adults.

DESIGN

Randomized controlled trial.

SETTING

Exercise laboratory on the Health Sciences campus of an urban university.

PARTICIPANTS

99 mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults.

INTERVENTION

6-month structured physical activity with or without a protein and vitamin D nutritional supplement.

MEASUREMENTS

Circulating IL-6, skeletal muscle size, composition (percent normal density muscle tissue), strength, power, and specific force (strength/CSA) as well as physical function (gait speed, stair climb time, SPPB-score) were measured pre- and post-intervention.

RESULTS

At baseline, Spearman's correlations demonstrated an inverse relationship (P<0.05) between circulating IL-6 and thigh muscle composition (r = -0.201), strength (r = -0.311), power (r = -0.210), and specific force (r = -0.248), and positive association between IL-6 and stair climb time (r = 0.256; P<0.05). Although the training program did not affect circulating IL-6 levels (P=0.69), reductions in IL-6 were associated with gait speed improvements (r = -0.487; P<0.05) in "higher" IL-6 individuals (>1.36 pg/ml). Moreover, baseline IL-6 was inversely associated (P<0.05) with gains in appendicular lean mass and improvements in SPPB score (r = -0.211 and -0.237, respectively).

CONCLUSIONS

These findings implicate age-related increases in circulating IL-6 as an important contributor to declines in skeletal muscle strength, quality, function, and training-mediated adaptation. Given the pervasive nature of inflammation among older adults, novel therapeutic strategies to reduce IL-6 as a means of preserving skeletal muscle health are enticing.

The expression of neuregulin and erbB receptors in human skeletal muscle: effects of progressive resistance training

The neuregulin/erbB-signaling axis contributes to the development and growth of multiple mammalian tissues including skeletal muscle. In this study, we sought to characterize the native expression of this system in human skeletal muscle and test the hypothesis that a program of progressive resistance training (PRT) would regulate the expression of neuregulin (NRG) and its cognate receptors. Twelve healthy-male subjects underwent 8-weeks of lower-extremity PRT and muscle biopsies were performed at baseline and following 1- and 8-weeks of the intervention. PRT resulted in significant gains in skeletal muscle strength without appreciable changes in fiber size or myosin heavy chain (MHC) composition. At baseline, Western Blot analysis demonstrated expression of erbB2, erbB3 and erbB4 receptors and multiple NRG isoforms. Following 1- and 8-weeks of PRT, no changes erbB2, erbB4 or NRG expression were observed. ErbB3 expression, however, was significantly increased at both time points compared to baseline. Double labeling of muscle cross-sections revealed increased expression of erbB3 following PRT was not exclusive to fibers staining positive for MHC IIa. Thus, erbB2, erbB3, erbB4 and multiple NRG isoforms are natively expressed in human skeletal muscle. Following PRT, a significant increase in erbB3 was observed. The ability to detect basal expression and alterations in response to physiologic stimuli merit further studies examining the role of this system in skeletal muscle.

Cardiovascular Events in a Physical Activity Intervention Compared With a Successful Aging Intervention: The LIFE Study Randomized Trial

IMPORTANCE

Whether sustained physical activity prevents cardiovascular disease (CVD) events in older adults is uncertain.

OBJECTIVE

To test the hypothesis that cardiovascular morbidity and mortality would be reduced in participants in a long-term physical activity program.

DESIGN, SETTING, AND PARTICIPANTS

The Lifestyle Interventions and Independence for Elders (LIFE) study was a multicenter, randomized trial. Participants were recruited at 8 centers in the United States. We randomized 1635 sedentary men and women aged 70 to 89 years with a Short Physical Performance Battery (SPPB) score of 9 or less but able to walk 400 m.

INTERVENTIONS

The physcial activity (PA) intervention was a structured moderate-intensity program, predominantly walking 2 times per week on site for 2.6 years on average. The successful aging intervention consisted of weekly health education sessions for 6 months, then monthly.

MAIN OUTCOMES AND MEASURES

Total CVD events, including fatal and nonfatal myocardial infarction, angina, stroke, transient ischemic attack, and peripheral artery disease, were adjudicated by committee, and silent myocardial infarction was assessed by serial electrocardiograms. A limited outcome of myocardial infarction, stroke, and CVD death was also studied. Outcome assessors and adjudicators were blinded to intervention assignment.

RESULTS

The 1635 LIFE study participants were predominantly women (67%), with a mean (SD) age of 78.7 (5.2) years; 20% were African-American, 6% were Hispanic or other race or ethnic group, and 74% were non-Latino white. New CVD events occurred in 121 of 818 PA participants (14.8%) and 113 of 817 successful aging participants (13.8%) (HR, 1.10; 95% CI, 0.85-1.42). For the more focused combined outcome of myocardial infarction, stroke, or cardiovascular death, rates were 4.6% in PA and 4.5% in the successful aging group (HR, 1.05; 95% CI, 0.67-1.66). Among frailer participants with an SPPB score less than 8, total CVD rates were 14.2% in PA vs 17.7% in successful aging (HR, 0.76; 95% CI, 0.52-1.10), compared with 15.3% vs 10.5% among those with an SPPB score of 8 or 9 (HR, 1.59; 95% CI, 1.09-2.30) (P for interaction = .006). With the limited end point, the interaction was not significant (P = .59), with an HR of 0.94 (95% CI, 0.50-1.75) for an SPPB score less than 8 and an HR of 1.20 (95% CI, 0.62-2.34) for an SBBP score of 8 or 9.

CONCLUSIONS AND RELEVANCE

Among participants in the LIFE Study, an aerobically based, moderately intensive PA program was not associated with reduced cardiovascular events in spite of the intervention's previously documented ability to prevent mobility disability.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00116194.