A causal role for mitochondrial DNA (mtDNA) mutagenesis in mammalian aging is supported by recent studies demonstrating that the mtDNA mutator mouse, harboring a defect in the proofreading-exonuclease activity of mitochondrial polymerase gamma, exhibits accelerated aging phenotypes characteristic of human aging, systemic mitochondrial dysfunction, multisystem pathology, and reduced lifespan. Epidemiologic studies in humans have demonstrated that endurance training reduces the risk of chronic diseases and extends life expectancy. Whether endurance exercise can attenuate the cumulative systemic decline observed in aging remains elusive. Here we show that 5 mo of endurance exercise induced systemic mitochondrial biogenesis, prevented mtDNA depletion and mutations, increased mitochondrial oxidative capacity and respiratory chain assembly, restored mitochondrial morphology, and blunted pathological levels of apoptosis in multiple tissues of mtDNA mutator mice. These adaptations conferred complete phenotypic protection, reduced multisystem pathology, and prevented premature mortality in these mice. The systemic mitochondrial rejuvenation through endurance exercise promises to be an effective therapeutic approach to mitigating mitochondrial dysfunction in aging and related comorbidities.

Endurance exercise is known to induce metabolic adaptations in skeletal muscle via activation of the transcriptional co-activator peroxisome proliferator-activated receptor ␥ co-activator 1␣ (PGC-1␣). PGC-1␣ regulates mitochondrial biogenesis via regulating transcription of nuclear-encoded mitochondrial genes. Recently, PGC-1␣ has been shown to reside in mitochondria; however, the physiological consequences of mitochondrial PGC-1␣ remain unknown. We sought to delineate if an acute bout of endurance exercise can mediate an increase in mitochondrial PGC-1␣ content where it may co-activate mitochondrial transcription factor A to promote mtDNA transcription. C57Bl/6J mice (n ‫؍‬ 12/group; Ǩ ‫؍‬ () were randomly assigned to sedentary (SED), forced-endurance (END) exercise (15 m/min for 90 min), or forced endurance ؉3 h of recovery (END؉3h) group. The END group was sacrificed immediately after exercise, whereas the SED and END؉3h groups were euthanized 3 h after acute exercise. Acute exercise coordinately increased the mRNA expression of nuclear and mitochondrial DNAencoded mitochondrial transcripts. Nuclear and mitochondrial abundance of PGC-1␣ in END and END؉3h groups was significantly higher versus SED mice. In mitochondria, PGC-1␣ is in a complex with mitochondrial transcription factor A at mtDNA D-loop, and this interaction was positively modulated by exercise, similar to the increased binding of PGC-1␣ at the NRF-1 promoter. We conclude that in response to acute altered energy demands, PGC-1␣ re-localizes into nuclear and mitochondrial compartments where it functions as a transcriptional co-activator for both nuclear and mitochondrial DNA transcription factors. These results suggest that PGC-1␣ may dynamically facilitate nuclear-mitochondrial DNA cross-talk to promote net mitochondrial biogenesis.Physical inactivity is a major threat to public health worldwide. It is a primary modifiable risk factor for sarcopenia, cardiovascular diseases, type 2 diabetes, obesity, stroke, hypertension, and other chronic diseases including colon and breast cancer, end-stage renal disease, osteoporosis, osteoarthritis, and neuromuscular and neurometabolic disorders (1). Given the dire consequences associated with sedentary living, public health initiatives and therapeutic strategies that improve independent living and promote a physically active lifestyle are an international priority. Indeed, there is incontrovertible evidence from epidemiological studies and randomized trials that illustrate that regular physical activity and endurance exercise reduces the risk of chronic diseases and physical disability in later life and even extends lifespan (1, 2). The therapeutic effects of endurance exercise are associated with the maintenance of homeostatic energy metabolism via mitochondrial biogenesis in various tissues including skeletal muscle, heart, brain, adipose tissue, and liver (2-4). Endurance exercise-mediated enhancement of skeletal muscle mitochondrial content and oxidative capacity is a well established phenomenon in physio...

MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNA species involved in post-transcriptional gene regulation. In vitro studies have identified a small number of skeletal muscle-specific miRNAs which play a crucial role in myoblast proliferation and differentiation. In skeletal muscle, an acute bout of endurance exercise results in the up-regulation of transcriptional networks that regulate mitochondrial biogenesis, glucose and fatty acid metabolism, and skeletal muscle remodelling. The purpose of this study was to assess the expressional profile of targeted miRNA species following an acute bout of endurance exercise and to determine relationships with previously established endurance exercise responsive transcriptional networks. C57Bl/6J wild-type male mice (N = 7/group) were randomly assigned to either sedentary or forced-endurance exercise (treadmill run @ 15 m/min for 90 min) group. The endurance exercise group was sacrificed three hours following a single bout of exercise. The expression of miR- 181, 1, 133, 23, and 107, all of which have been predicted to regulate transcription factors and co-activators involved in the adaptive response to exercise, was measured in quadriceps femoris muscle. Endurance exercise significantly increased the expression of miR-181, miR-1, and miR-107 by 37%, 40%, and 56%, respectively, and reduced miR-23 expression by 84% (P≤0.05 for all), with no change in miR-133. Importantly, decreased expression of miRNA-23, a putative negative regulator of PGC-1α was consistent with increased expression of PGC-1α mRNA and protein along with several downstream targets of PGC-1α including ALAS, CS, and cytochrome c mRNA. PDK4 protein content remains unaltered despite an increase in its putative negative regulator, miR-107, and PDK4 mRNA expression. mRNA expression of miRNA processing machinery (Drosha, Dicer, and DGCR8) remained unchanged. We conclude that miRNA-mediated post-transcriptional regulation is potentially involved in the complex regulatory networks that govern skeletal muscle adaptation to endurance exercise in C57Bl/6J male mice.

Old age is associated with lower physical activity levels, suboptimal protein intake, and desensitization to anabolic stimuli, predisposing for age-related muscle loss (sarcopenia). Although resistance exercise (RE) and protein supplementation partially protect against sarcopenia under controlled conditions, the efficacy of home-based, unsupervised RE (HBRE) and multi-ingredient supplementation (MIS) is largely unknown. In this randomized, placebo-controlled and double-blind trial, we examined the effects of HBRE/MIS on muscle mass, strength, and function in free-living, older men. Thirty-two sedentary men underwent twelve weeks of home-based resistance band training (3 d/week), in combination with daily intake of a novel five-nutrient supplement (‘Muscle5’; M5, n = 16, 77.4 ± 2.8 y) containing whey, micellar casein, creatine, vitamin D, and omega-3 fatty acids, or an isocaloric/isonitrogenous placebo (PLA; n = 16, 74.4 ± 1.3 y), containing collagen and sunflower oil. Appendicular and total lean mass (ASM; +3%, TLM; +2%), lean mass to fat ratios (ASM/% body fat; +6%, TLM/% body fat; +5%), maximal strength (grip; +8%, leg press; +17%), and function (5-Times Sit-to-Stand time; −9%) were significantly improved in the M5 group following HBRE/MIS therapy (pre vs. post tests; p < 0.05). Fast-twitch muscle fiber cross-sectional areas of the quadriceps muscle were also significantly increased in the M5 group post intervention (Type IIa; +30.9%, Type IIx, +28.5%, p < 0.05). Sub-group analysis indicated even greater gains in total lean mass in sarcopenic individuals following HBRE/MIS therapy (TLM; +1.65 kg/+3.4%, p < 0.05). We conclude that the Muscle5 supplement is a safe, well-tolerated, and effective complement to low-intensity, home-based resistance exercise and improves lean mass, strength, and overall muscle quality in old age.

Biological aging is associated with progressive damage accumulation, loss of organ reserves, and systemic inflammation ('inflammaging'), which predispose for a wide spectrum of chronic diseases, including several types of cancer. In contrast, aerobic exercise training (AET) reduces inflammation, lowers all-cause mortality, and enhances both health and lifespan. In this study, we examined the benefits of early-onset, lifelong AET on predictors of health, inflammation, and cancer incidence in a naturally aging mouse model (C57BL/J6). Lifelong, voluntary wheel-running (O-AET; 26-month-old) prevented age-related declines in aerobic fitness and motor coordination vs. age-matched, sedentary controls (O-SED). AET also provided partial protection against sarcopenia, dynapenia, testicular atrophy, and overall organ pathology, hence augmenting the ‘physiologic reserve’ of lifelong runners. Systemic inflammation, as evidenced by a chronic elevation in 17 of 18 pro- and anti-inflammatory cytokines and chemokines (P < 0.05 O-SED vs. 2-month-old Y-CON), was potently mitigated by lifelong AET (P < 0.05 O-AET vs. O-SED), including master regulators of the cytokine cascade and cancer progression (IL-1β, TNF-α, and IL-6). In addition, circulating SPARC, previously known to be upregulated in metabolic disease, was elevated in old, sedentary mice, but was normalized to young control levels in lifelong runners. Remarkably, malignant tumours were also completely absent in the O-AET group, whereas they were present in the brain (pituitary), liver, spleen, and intestines of sedentary mice. Collectively, our results indicate that early-onset, lifelong running dampens inflammaging, protects against multiple cancer types, and extends healthspan of naturally-aged mice.