White, Thomas A.

Abstract Dynamic measures of resilience—the ability to resist and recover from a challenge—may be informative of the rate of aging before overt manifestations such as chronic disease, disability, and frailty. From this perspective mid-life resilience may predict longevity and late-life health. To test this hypothesis, we developed simple, reproducible, clinically relevant challenges, and outcome measures of physical resilience that revealed differences between and within age groups of genetically heterogeneous mice, and then examined associations between mid-life resilience and both lifespan and late-life measures of physiological function. We demonstrate that time to recovery from isoflurane anesthesia and weight change following a regimen of chemotherapy significantly differed among young, middle-aged, and older mice, and were more variable in older mice. Females that recovered faster than the median time from anesthesia (more resilient) at 12 months of age lived 8% longer than their counterparts, while more resilient males in mid-life exhibited better cardiac (fractional shortening and left ventricular volumes) and metabolic (glucose tolerance) function at 24 months of age. Moreover, female mice with less than the median weight loss at Day 3 of the cisplatin challenge lived 8% longer than those that lost more weight. In contrast, females who had more weight loss between Days 15 and 20 were relatively protected against early death. These data suggest that measures of physical resilience in mid-life may provide information about individual differences in aging, lifespan, and key parameters of late-life health.

Abstract Obesity-related type II diabetes (diabesity) has increased global morbidity and mortality dramatically. Previously, the ancient drug salicylate demonstrated promise for the treatment of type II diabetes, but its clinical use was precluded due to high dose requirements. In this study, we present a nitroalkene derivative of salicylate, 5-(2-nitroethenyl)salicylic acid (SANA), a molecule with unprecedented beneficial effects in diet-induced obesity (DIO). SANA reduces DIO, liver steatosis and insulin resistance at doses up to 40 times lower than salicylate. Mechanistically, SANA stimulated mitochondrial respiration and increased creatine-dependent energy expenditure in adipose tissue. Indeed, depletion of creatine resulted in the loss of SANA action. Moreover, we found that SANA binds to creatine kinases CKMT1/2, and downregulation CKMT1 interferes with the effect of SANA in vivo. Together, these data demonstrate that SANA is a first-in-class activator of creatine-dependent energy expenditure and thermogenesis in adipose tissue and emerges as a candidate for the treatment of diabesity.

We propose the beneficial effects of exercise are in part mediated through the prevention and elimination of senescent cells. Exercise counters multiple forms of age-related molecular damage that initiate the senescence program and activates immune cells responsible for senescent cell clearance. Preclinical and clinical evidence for exercise as a senescence-targeting therapy and areas needing further investigation are discussed.

Physical resilience, defined as the ability to resist and respond to challenges and return to homeostasis, has been postulated to be a determinant of healthspan and lifespan. To test this premise, we have begun to optimize a standardized, clinically relevant battery of resilience challenges, including anesthesia and cisplatin chemotherapy, and recovery outcome measures in younger (2–3 month) and older (26–29 month) mice. We have also started to test whether interventions shown to increase murine lifespan‐acarbose, rapamycin, and 17a‐estradiol‐impact the resilience of older mice. Our preliminary data demonstrate that younger mice (n = 10) have faster dorsal to sternal recumbence recovery time compared to older mice (n = 8) (39 ± 1 sec vs. 67 ± 6 sec, p < 0.001) following a 5‐minute 4% isoflurane anesthesia challenge. In response to a 5‐day cisplatin (2 mg/kg/day) challenge, both younger (n=5) and older (n=4) mice lost a significant percent of their baseline body weight (younger mice −10.6 ± 0.8% and older mice −13.2 ± 2.1%, p = 0.26), however, older mice failed to regain body weight 11 days after the challenge (younger mice −0.9 ± 0.8% and older mice −9.8 ± 0.8%, p < 0.01). Changes in body weight in younger and older mice were largely attributable to the loss/regain of fat mass. Interestingly, 8 weeks of either acarbose (1,000 ppm) or 17α‐estradiol (14.4 ppm) administration to older female mice improved body weight recovery after the cisplatin challenge, while rapamycin (14 ppm) had no appreciable effect. Our preliminary results demonstrate that younger mice, as expected, have greater resilience than older mice to clinically relevant physical challenges. The age at which physical resilience starts to decline requires further investigation. Our early observations suggest interventions that extend health‐ and lifespan may impact resilience in older mice. Ultimately, a standardized battery of resilience challenges may provide a new framework for testing and translating interventions that target the fundamental biology of aging. Support or Funding Information This work was supported by grant AG52958 from the National Institutes of Health. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Adipocytes accumulate within and around skeletal muscle with advancing age. Adipose progenitor cells, preadipocytes, are prone to cellular senescence, a state of stable growth arrest associated with the secretion of cytokines, chemokines and matrix remodeling proteins, collectively referred to as the senescence‐associated secretory phenotype (SASP). Considerable evidence implicates the SASP in age‐related tissue inflammation and degeneration; however, its impact on skeletal muscle is poorly understood. Herein, we examined the effects of conditioned media (CM) collected from healthy human (control CM) and senescent by irradiation (senescent CM) preadipocytes on human skeletal muscle cells (SkMCs). Compared to control CM, senescent CM had more than 10‐fold higher concentrations of IL‐6, IL‐1β, IL‐8, PAI‐1, MCP‐1 and TNFα as quantified by a multiplexed antibody‐based assay. Senescent CM increased expression of IL‐6 (5‐fold), IL‐1α (1.6‐fold), IL‐1β (3.5‐fold), MCP‐1 (2.5‐fold), PAI‐1 (1.7‐fold) and MMP‐3 (3‐fold) in differentiated SkMCs relative to control CM as measured by qPCR (all p < 0.05). Senescent CM increased proliferation of undifferentiated SKMCs by 20%; however, inhibited differentiation relative to control CM per the fusion index. Preliminary data further suggest senescent CM compromises insulin‐ and IGF‐1‐mediated activation of Akt. Collectively, our data suggest that the SASP of senescent preadipocytes may drive inflammation in SkMCs and compromise their differentiation and, potentially, response to metabolic an anabolic stimuli. These effects may contribute to age‐related changes in skeletal muscle health and regeneration. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Inflammation is a hallmark of aging and a likely contributor to skeletal muscle loss ( sarcopenia ). We investigated whether the inflammatory phenotype of differentiated primary skeletal muscle‐derived cells (SkMDCs) from a 17‐year‐old (young) differed from that of a 68‐year‐old (older) donor. Under basal conditions, expression of genes encoding pro‐inflammatory cytokines was in fact lower in older compared to younger SkMDCs. However, in response to lipopolysaccharide (LPS), these factors were more highly upregulated in older cells. Specifically, in young compared to older SkMDCs, interleukin‐6 (IL‐6) increased 3‐ vs. 9‐fold, tumor necrosis factor‐alpha (TNF‐alpha) increased 11‐ vs. 80‐fold, and IL‐1alpha increased 14‐ vs. 21‐fold (all differences were p < 0.01). Given adipose tissue is a primary source of pro‐inflammatory stimuli and infiltrates skeletal muscle with age, we hypothesized that secreted factors from senescent preadipocytes drive a similar molecular phenotype to LPS. Exposure of SkMDCs to conditioned medium from senescent‐preadipocytes increased expression IL‐6 and TNF‐alpha in young and even more so in older cells (both p < 0.05). Thus, there are inherent differences in the molecular inflammatory phenotype and its response between young and older SkMDCs. These data also suggest that the age‐related accumulation of senescent preadipocytes may contribute to sarcopenia.

Infiltration of fat cells into skeletal muscle is a hallmark of aging that has been associated with insulin resistance and the pathogenesis of type 2 diabetes mellitus (T2DM). The mechanisms by which fat cells affect the health and metabolic state of skeletal muscle are poorly understood. Given the evidence for cross‐talk between these tissues and the secretory phenotype of senescent preadipocytes, we first utilized real time‐PCR to examine the expression of inflammatory cytokines in primary human skeletal muscle‐derived cells (SkMDCs) in response to conditioned medium (CM) from either control human preadipocytes (Normal CM) or from human preadipocytes driven to senescence by irradiation (Senescent CM). Exposure of SkMDCs to either Normal CM or Senescent CM for 24 hours significantly increased their expression of IL‐6 (5.1±1.7‐and 14.1±4.7‐fold, respectively), TNFα (1.3±0.2‐and 2.1±0.67‐fold, respectively) and MCP‐1 (2.9±1.1‐and 6.8±2.3‐fold, respectively). Next, we investigated the effects of CM on insulin signaling in SkMDCs via Western blot analysis. Exposure of SKMDCs to preadipocyte CM significantly blunted insulin‐stimulated phosphorylation of its downstream effectors, including Akt (14–24%, p<0.05). Finally, we examined the effects of CM on the proliferative capacity of undifferentiated SkMDCs. Senescent CM inhibited SkMDC proliferation by more than 30% (p < 0.05). In conclusion, factors secreted by preadipocytes, and in particular, senescent preadipocytes, negatively impact the inflammatory and metabolic phenotype and the proliferative capacity of skeletal muscle cells. Elucidation of the biologic materials that are secreted from fat cells and mediate these effects may lead to novel therapeutic strategies for the treatment of age‐related conditions, including T2DM. The authors acknowledge the support of Mayo Clinic and a generous gift from Robert and Arlene Kogod.

Introduction: Senescent cells with essentially irreversible loss of replicative potential accumulate in various tissues with aging. Cellular senescence is associated with a pro‐inflammatory senescence‐associated secretory phenotype which the Janus‐associated kinase (JAK) pathway plays a role in. We hypothesized that senescent preadipocytes contribute to age‐related dysfunction of healthy cells. Methods: Preadipocytes from lean subjects were X‐irradiated to induce senescence. We co‐cultured non‐senescent cells with senescent cells or cultured them in conditioned medium (CM) from senescent preadipocytes to test the inflammation, differentiation and insulin sensitivity. Macrophage migration in response to CM was assayed as well. Moreover, we treated old or obese mice with Ruxolitinib, a JAK1/2 inhibitor, to test the beneficial effect. Results: The adipogenesis of preadipocytes was impaired by exposure to senescent cells. Macrophage migration was greater in response to senescent preadipocytes. Inflammation was increased in both adipose tissue and preadipocytes exposed to CM from senescent cells. All these adverse effect could be partially rescued by JAK inhibitor. In addition, senescent preadipocytes inhibited insulin‐induced phosphor‐AKT in adipose tissue and HepG2 cells. Insulin‐induced glycogen synthesis was also inhibited in HepG2 cells. Two months of Ruxolitinib treatment reduced inflammation, reversed age‐related lipodystrophy and improved physical function in frail, 24 month old mice. It also improved insulin sensitivity in diet‐induced obese mice. Conclusion: Senescent preadipocytes contribute to age‐related impairment in adipogenesis, fat tissue inflammation, and insulin resistance. Grant Funding Source : supported by NIH AG13925 and Robert and Arlene Kogod Center on Aging in Mayo Clinic.

Nutrient excess and physical inactivity are primary drivers of numerous age‐related chronic diseases. A growing body of evidence has implicated cellular senescence, a process in which cells lose the ability to divide and concurrently damage neighboring cells by the factors they secrete, as an underlying mechanism of aging and its associated conditions. However, the impact of lifestyle choices on the age‐associated accumulation of senescent cells remains poorly understood. Thus, we examined the effects of a fast food diet (FFD) and a voluntary exercise intervention on multiple parameters of healthspan and cellular senescence using a transgenic mouse model that expresses green fluorescent protein (GFP) in p16 Ink4a ‐positive senescent cells. As expected, 12‐month old male mice that had received the FFD diet for 5 months demonstrated significantly greater gains in body weight and fat mass compared to mice fed a standard chow diet. Moreover, mice fed the FFD exhibited hyperinsulinemia, impaired glucose tolerance, reduced exercise capacity, and diastolic dysfunction. Impressively, providing an exercise wheel (26.9 ± 6.9 km/wk) in parallel with the FFD nullified the deleterious effects of the FFD on body weight and composition, whole‐body metabolism, physical performance and cardiac function. Strikingly, our data further suggest that exercise markedly lowers the number of cells in visceral fat depots that express GFP and stain positively for senescent‐associated β‐galactosidase; markers of senescence, that are highly abundant in sedentary mice fed the FFD. Correspondingly, FFD‐induced expression of senescence‐associated inflammatory factors was also diminished by the exercise intervention. Collectively, our data suggest that lifestyle choices may affect the abundance of senescence cells with advancing age, and exercise may partly mediate its salutary effects on multiple organ systems by preventing their accumulation and/or mediating their removal.

Abstract Cellular senescence has emerged as a significant and potentially tractable mechanism of aging and multiple aging‐related conditions. Biomarkers of senescent cell burden, including molecular signals in circulating immune cells and the abundance of circulating senescence‐related proteins, have been associated with chronological age and clinical parameters of biological age in humans. The extent to which senescence biomarkers are affected by interventions that enhance health and function has not yet been examined. Here, we report that a 12‐week structured exercise program drives significant improvements in several performance‐based and self‐reported measures of physical function in older adults. Impressively, the expression of key markers of the senescence program, including p16, p21, cGAS , and TNFα , were significantly lowered in CD3 + T cells in response to the intervention, as were the circulating concentrations of multiple senescence‐related proteins. Moreover, partial least squares discriminant analysis showed levels of senescence‐related proteins at baseline were predictive of changes in physical function in response to the exercise intervention. Our study provides first‐in‐human evidence that biomarkers of senescent cell burden are significantly lowered by a structured exercise program and predictive of the adaptive response to exercise.