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Cardiorespiratory fitness and mitochondrial oxidative capacity are associated with reduced walking speed in older adults, but their impact on walking speed in older adults with diabetes has not been clearly defined. We examined differences in cardiorespiratory fitness and skeletal muscle mitochondrial oxidative capacity between older adults with and without diabetes, as well as determined their relative contribution to slower walking speed in older adults with diabetes. Participants with diabetes (n = 159) had lower cardiorespiratory fitness and mitochondrial respiration in permeabilized fiber bundles compared with those without diabetes (n = 717), following adjustments for covariates including BMI, chronic comorbid health conditions, and physical activity. Four-meter and 400-m walking speeds were slower in those with diabetes. Mitochondrial oxidative capacity alone or combined with cardiorespiratory fitness mediated ∼20-70% of the difference in walking speed between older adults with and without diabetes. Additional adjustments for BMI and comorbidities further explained the group differences in walking speed. Cardiorespiratory fitness and skeletal muscle mitochondrial oxidative capacity contribute to slower walking speeds in older adults with diabetes.

BACKGROUND: Phenotypic frailty syndrome identifies older adults at greater risk for adverse health outcomes. Despite the critical role of mitochondria in maintaining cellular function, including energy production, the associations between muscle mitochondrial energetics and frailty have not been widely explored in a large, well-phenotyped, older population. METHODS: The Study of Muscle, Mobility and Aging (SOMMA) assessed muscle energetics in older adults (N = 879, mean age = 76.3 years, 59.2% women). 31Phosporous magnetic resonance spectroscopy measured maximal production of adenosine triphosphate (ATPmax) in vivo, while ex vivo high-resolution respirometry of permeabilized muscle fibers from the vastus lateralis measured maximal oxygen consumption supported by fatty acids and complex I- and II-linked carbohydrates (e.g., Max OXPHOSCI+CII). Five frailty criteria, shrinking, weakness, exhaustion, slowness, and low activity, were used to classify participants as robust (0, N = 397), intermediate (1-2, N = 410), or frail (≥ 3, N = 66). We estimated the proportional odds ratio (POR) for greater frailty, adjusted for multiple potential confounders. RESULTS: One-SD decrements of most respirometry measures (e.g., Max OXPHOSCI+CII, adjusted POR = 1.5, 95%CI [1.2,1.8], p = 0.0001) were significantly associated with greater frailty classification. The associations of ATPmax with frailty were weaker than those between Max OXPHOSCI+CII and frailty. Muscle energetics was most strongly associated with slowness and low physical activity components. CONCLUSIONS: Our data suggest that deficits in muscle mitochondrial energetics may be a biological driver of frailty in older adults. On the other hand, we did observe differential relationships between measures of muscle mitochondrial energetics and the individual components of frailty.

Social stress experienced in childhood is associated with adverse health later in life. Mitochondrial function has been implicated as a mechanism for how stressful life events get under the skin to influence physical well-being. Using data from the Study of Muscle, Mobility, and Aging (n = 879, 59% women), linear models examined whether adverse childhood events (i.e., physical abuse) were associated with two measures of skeletal muscle mitochondrial energetics in older adults: (i) maximal adenosine triphosphate production (ATPmax) and (ii) maximal state 3 respiration (Max OXPHOS). Forty-five percent of the sample reported experiencing one or more adverse childhood events. After adjustment, each additional event was associated with -0.08 SD (95% confidence interval = -0.13, -0.02) lower ATPmax. No association was observed with Max OXPHOS. Adverse childhood events are associated with lower ATP production in later life. Findings indicate that mitochondrial function may be a mechanism for understanding how early social stress influences health in later life.

BackgroundThe effects of aging on circadian patterns of behavior are insufficiently described. To address this, we characterized age-specific features of rest-activity rhythms (RAR) in community dwelling older adults both overall, and in relation, to sociodemographic characteristics.MethodsWe examined cross-sectional associations between RAR and age, sex, race, education, multimorbidity burden, financial, work, martial, health, and smoking status using assessments of older adults with wrist-worn free-living actigraphy data (N=820, Age=76.4 yrs, 58.2% women) participating in the Study of Muscle, Mobility and Aging (SOMMA). RAR parameters were determined by mapping an extension to the traditional cosine curve to activity data. Functional principal component analysis determined variables accounting for variance.ResultsAge was associated with several metrics of dampened RAR; women had stronger and more robust RAR vs. men (all P < 0.05). Total activity (56%) and time of activity (20%) accounted for most the RAR variance. Compared to the latest decile of acrophase, those in the earliest decile had higher average amplitude (P

BACKGROUND: Aging is associated with declines in circadian functions. The effects of aging on circadian patterns of behavior are insufficiently described. We characterized age-specific features of rest-activity rhythms (RAR) in community dwelling older adults, both overall, and in relation, to sociodemographic characteristics. METHODS: We analyzed baseline assessments of older adults with wrist-worn free-living wrist-worn actigraphy data (N=820, Age=76.4 yrs, 58.2% women) participating in the Study of Muscle, Mobility and Aging (SOMMA). We applied an extension to the traditional cosine curve to map RAR to activity data, calculating the parameters: rhythmic strength (amplitude); robustness (pseudo-F statistic); and timing of peak activity (acrophase). We also used function principal component analysis to determine 4 components describing underlying patterns of activity accounting for RAR variance. Linear models were used to examine associations between RAR and sociodemographic variables. RESULTS: Age was associated with several metrics of dampened RAR; women had stronger and more robust RAR metrics vs. men (all P < 0.05). Total activity (56%) and time of activity (20%) accounted for most the RAR variance. Compared to the latest decile of acrophase, those in the earliest decile had higher average amplitude (P

Cellular metabolism generates molecular damage affecting all levels of biological organization. Accumulation of this damage over time is thought to play a central role in the aging process, but damage manifests in diverse molecular forms complicating its assessment. Insufficient attention has been paid to date to the role of molecular damage in aging-related phenotypes, particularly in humans, in part because of the difficulty in measuring its various forms. Recently, omics approaches have been developed that begin to address this challenge, because they are able to assess a sizeable proportion of age-related damage at the level of small molecules, proteins, RNA, DNA, organelles and cells. This review describes the concept of molecular damage in aging and discusses its diverse aspects from theoretical models to experimental approaches. Measurement of multiple types of damage enables studies of the role of damage in human aging outcomes and lays a foundation for testing interventions to reduce the burden of molecular damage, opening new approaches to slowing aging and reducing its consequences.

Background How magnetic resonance (MR) derived thigh muscle volume and deuterated creatine dilution derived muscle mass (D3Cr muscle mass) differentially relate to strength, fitness, and other functions in older adults—and whether associations vary by sex—is not known. Methods Men (N  = 345) and women (N  = 482) aged ≥70 years from the Study of Muscle, Mobility, and Aging completed leg extension strength (1-repetition max) and cardiopulmonary exercise testing to assess fitness (VO2peak). Correlations and adjusted regression models stratified by sex were used to assess the association between muscle size measures, study outcomes, and sex interactions. Results D3Cr muscle mass and MR thigh muscle volume were correlated (men: r  = 0.62, women: r  = 0.51, p  < .001). Each standard deviation (SD) decrement in D3Cr muscle mass was associated with lower 1-repetition max strength (−14 kg men, −4 kg women, p  < .001 for both; p -interaction = .003) and lower VO2peak (−79 mL/min men, −30 mL/min women, p  < .001 for both, p -interaction:.016). Each SD decrement in MR thigh muscle volume was also associated with lower strength (−32 kg men, −20 kg women, p  < .001 for both; p -interaction = .139) and lower VO2peak (−217 mL/min men, −111 mL/min women, p  < .001 for both, p -interaction = .010). There were associations, though less consistent, between muscle size or mass with physical performance and function; associations varied by sex. Conclusions Less muscle—measured by either D3Cr muscle mass or MR thigh muscle volume—was associated with lower strength and fitness. Varied associations by sex and assessment method suggest consideration be given to which measurement to use in future studies. [ABSTRACT FROM AUTHOR]

Background Frailty can occur in older adults without disability or multimorbidity. Current methods focus on the most frail, but poorly discriminate among those "not frail." Methods The Study of Muscle, Mobility, and Aging (SOMMA) included 879 adults aged 70 years and older without mobility disability. We operationalized frailty domains using: peak oxygen consumption (endurance), digit symbol substitution test (speed), leg power (strength), perceived fatigability, D3 creatine dilution (sarcopenia), and accelerometry (sedentary behavior) to construct a frailty score of 0–12 summing tertiles (0–2) of each component. We used linear or logistic regression with and without adjustment for confounders to examine associations with age, reported, and performance function. Results The SOMMA frailty score distribution was broad and strongly associated with age (r  = 0.33, p  < .0001). Each point was associated with a 30%–50% higher odds of having reported difficulty with activities of daily living or mobility. After grouping the total score (0–3, 4–7, and 8–12) those in the highest group were 9–31 times more likely to have functional limitation, and at least 8 times more likely to have poorer function after full adjustment. Higher scores identified those less likely to report ease of walking or higher physical activity. Peak oxygen consumption, leg power, fatigability, and digit symbol score contributed most to these associations. Conclusions The SOMMA frailty score characterizes frailty as a continuum from frail to vigorous with assessments that are amenable to change. Associations with age and function suggest utility for distinguishing a wide range of vigor and vulnerability in relatively well-functioning older adults. [ABSTRACT FROM AUTHOR]

Background The Study of Muscle, Mobility and Aging (SOMMA) aims to understand the biological basis of many facets of human aging, with a focus on mobility decline, by creating a unique platform of data, tissues, and images. Methods The multidisciplinary SOMMA team includes 2 clinical centers (University of Pittsburgh and Wake Forest University), a biorepository (Translational Research Institute at Advent Health), and the San Francisco Coordinating Center (California Pacific Medical Center Research Institute). Enrollees were age ≥70 years, able to walk ≥0.6 m/s (4 m); able to complete 400 m walk, free of life-threatening disease, and had no contraindications to magnetic resonance or tissue collection. Participants are followed with 6-month phone contacts and annual in-person exams. At baseline, SOMMA collected biospecimens (muscle and adipose tissue, blood, urine, fecal samples); a variety of questionnaires; physical and cognitive assessments; whole-body imaging (magnetic resonance and computed tomography); accelerometry; and cardiopulmonary exercise testing. Primary outcomes include change in walking speed, change in fitness, and objective mobility disability (able to walk 400 m in 15 minutes and change in 400 m speed). Incident events, including hospitalizations, cancer diagnoses, fractures, and mortality are collected and centrally adjudicated by study physicians. Results SOMMA exceeded its goals by enrolling 879 participants, despite being slowed by the COVID-19 pandemic: 59.2% women; mean age 76.3 ± 5.0 years (range 70–94); mean walking speed 1.04 ± 0.20 m/s; 15.8% identify as other than Non-Hispanic White. Over 97% had data for key measurements. Conclusions SOMMA will provide the foundation for discoveries in the biology of human aging and mobility. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial energetics are an important property of aging muscle, as generation of energy is pivotal to the execution of muscle contraction. However, its association with functional outcomes, including leg power and cardiorespiratory fitness is largely understudied.Methods: In the Study of Muscle, Mobility, and Aging (SOMMA), we collected vastus lateralis biopsies from older adults (n=879,70-94 years,59.2% women). Maximal state 3 respiration (Max OXPHOS) was assessed in permeabilized fiber bundles by high-resolution respirometry. Capacity for maximal adenosine triphosphate production (ATPmax) was measured in vivo by 31P magnetic resonance spectroscopy. Leg extension power was measured with a Keiser press system, and VO2 peak was determined using a standardized cardiopulmonary exercise test. Gender-stratified multivariate linear regression models were adjusted for age, race, technician/site, adiposity, and physical activity with beta-coefficients expressed per 1 SD increment in the independent variable.Results: Max OXPHOS was associated with leg power for both women (β=0.12Watts/kg,p<0.001) and men (β=0.11Watts/kg,p<0.050). ATPmax was associated with leg power for men (β=0.09Watts/kg p<0.05) but was not significant for women (β=0.03Watts/kg,p=0.11). Max OXPHOS and ATPmax were associated with VO2 peak in women and men (Max OXPHOS, βwomen=1.03mL/kg/min, βmen=1.32 mL/kg/min; ATPmax βwomen=0.87mL/kg/min, βmen=1.50mL/kg/min;all p<0.001).Conclusions: Higher muscle mitochondrial energetics measures were associated with both better cardiorespiratory fitness and greater leg power in older adults. Muscle mitochondrial energetics explained a greater degree of variance in VO2 peak compared to leg power. [ABSTRACT FROM AUTHOR]

The National Institute on Aging (NIA)-sponsored Interventions Testing Program (ITP) has identified a number of dietary drug interventions that significantly extend life span, including rapamycin, acarbose, and 17-α estradiol. However, these drugs have diverse downstream targets, and their effects on age-associated organ-specific changes are unclear (Nadon NL, Strong R, Miller RA, Harrison DE. NIA Interventions Testing Program: investigating putative aging intervention agents in a genetically heterogeneous mouse model. EBioMedicine. 2017;21:3-4. doi:10.1016/j.ebiom.2016.11.038). Potential mechanisms by which these drugs extend life could be through their effect on inflammatory processes often noted in tissues of aging mice and humans. Our study focuses on the effects of three drugs in the ITP on inflammation in gonadal white adipose tissue (gWAT) of HET3 mice-including adiposity, adipose tissue macrophage (ATM) M1/M2 polarization, markers of cellular senescence, and endoplasmic reticulum stress. We found that rapamycin led to a 56% increase of CD45+ leukocytes in gWAT, where the majority of these are ATMs. Interestingly, rapamycin led to a 217% and 106% increase of M1 (CD45+CD64+CD206-) ATMs in females and males, respectively. Our data suggest rapamycin may achieve life-span extension in part through adipose tissue inflammation. Additionally, HET3 mice exhibit a spectrum of age-associated changes in the gWAT, but acarbose and 17-α estradiol do not strongly alter these phenotypes-suggesting that acarbose and 17- α estradiol may not influence life span through mechanisms involving adipose tissue inflammation. [ABSTRACT FROM AUTHOR]

Visceral adipose tissue (VAT) inflammation plays a central role in longevity and multiple age-related disorders. Cellular senescence (SEN) is a fundamental aging mechanism that contributes to age-related chronic inflammation and organ dysfunction, including VAT. Recent studies using heterochronic parabiosis models strongly suggested that circulating factors in young plasma alter the aging phenotypes of old animals. Our study investigated if young plasma rescued SEN phenotypes in the VAT of aging mice. With heterochronic parabiosis model using young (3 months) and old (18 months) mice, we found significant reduction in the levels of pro-inflammatory cytokines and altered adipokine profile that are protective of SEN in the VAT of old mice. These data are indicative of protection from SEN of aging VAT by young blood circulation. Old parabionts also exhibited diminished expression of cyclin-dependent kinase inhibitors (CDKi) genes p16 (Cdkn2a) and p21 (Cdkn1a/Cip1) in the VAT. In addition, when exposed to young serum condition in an ex vivo culture system, aging adipose tissue-derived stromovascular fraction cells produced significantly lower amounts of pro-inflammatory cytokines (MCP-1 and IL-6) compared to old condition. Expressions of p16 and p21 genes were also diminished in the old stromovascular fraction cells under young serum condition. Finally, in 3T3-preadipocytes culture system, we found reduced pro-inflammatory cytokines (Mcp-1 and Il-6) and diminished expression of cyclin-dependent kinase inhibitor genes in the presence of young serum compared to old serum. In summary, this study demonstrates that young milieu is capable of protecting aging adipose tissue from SEN and thereby inflammation. [ABSTRACT FROM AUTHOR]