James P. White

Aerobic exercise is a disease-modifying intervention in multiple sclerosis (MS) that ameliorates several progressive neurological symptoms in people with MS. Here we show that the exercise hormone irisin mediates neuroprotective effects of exercise in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. We demonstrate that voluntary free-wheel running exercise protects against inflammation-induced neurodegeneration in EAE, but these neuroprotective effects are abrogated in mice lacking Fndc5 /irisin. Peripheral delivery of irisin increases irisin plasma levels and reduces both clinical symptoms and neuronal loss in EAE. Although peripheral irisin does not alter peripheral and central immune responses in EAE, it induces a direct neuroprotective gene programme in spinal cord neurons and preserves synapses and mitochondrial activity, probably through direct binding to motor neurons. Taken together, these findings suggest that irisin induction in response to exercise confers direct neuroprotective effects in an inflammation-driven neurodegenerative condition, making it an attractive therapeutic candidate for MS.

Sarcopenia and the age-related decline in muscular strength and regenerative capacity contribute directly to loss of autonomy, greater risk for hospitalization and healthcare utilization. One contributing cellular phenotype associated with skeletal muscle aging is a loss in the function and number of resident muscle stem cells (MuSCs) or satellite cells. MuSC activation leads to dramatic changes in cellular architecture and metabolic reprogramming, including both mitochondrial biogenesis and increased glycolysis. Despite these changes to increase energy production, high energy demands may not be fully met during periods of MuSC activation. Here we used in vitro and in vivo approaches in mice to demonstrate the function of glutaminase for age-related changes in MuSC function. By combining fluorescence-activated cell sorting (FACS) isolation with metabolomics and stable isotope tracing, we show an age-related decline in reductive (counterclockwise) flux of glutamine through the tricarboxylic acid (TCA) cycle, a pathway by which MuSCs build cellular fatty acid stores as necessary biomass for MuSC function.

Caloric restriction (CR) slows biological aging and prolongs healthy lifespan in model organisms. Findings from the CALERIE randomized, controlled trial of long-term CR in healthy, nonobese humans broadly supports a similar pattern of effects in humans. To expand our understanding of the molecular pathways and biological processes underpinning CR effects in humans, we generated a series of genomic datasets from stored biospecimens collected from n = 218 participants during the trial. These data constitute a genomic data resource for a randomized controlled trial of an intervention targeting the biology of aging. Datasets include whole-genome single-nucleotide polymorphism genotypes, and three-timepoint-longitudinal DNA methylation, mRNA and small RNA datasets generated from blood, skeletal muscle and adipose tissue samples (total sample n = 2,327). The CALERIE Genomic Data Resource described in this article is available from the Aging Research Biobank. This multi-tissue, multi-omics, longitudinal data resource has great potential to advance translational geroscience. ClinicalTrials.gov registration: NCT00427193.

Heterochronic parabiosis (HPB) is known for its functional rejuvenation effects across several mouse tissues. However, its impact on biological age and long-term health is unknown. Here we performed extended (3-month) HPB, followed by a 2-month detachment period of anastomosed pairs. Old detached mice exhibited improved physiological parameters and lived longer than control isochronic mice. HPB drastically reduced the epigenetic age of blood and liver based on several clock models using two independent platforms. Remarkably, this rejuvenation effect persisted even after 2 months of detachment. Transcriptomic and epigenomic profiles of anastomosed mice showed an intermediate phenotype between old and young, suggesting a global multi-omic rejuvenation effect. In addition, old HPB mice showed gene expression changes opposite to aging but akin to several lifespan-extending interventions. Altogether, we reveal that long-term HPB results in lasting epigenetic and transcriptome remodeling, culminating in the extension of lifespan and healthspan.

Pathologies associated with sarcopenia include decline in muscular strength, lean mass and regenerative capacity. Despite the substantial impact on quality of life, no pharmacological therapeutics are available to counteract the age-associated decline in functional capacity and/or, resilience. Evidence suggests immune-secreted cytokines can improve muscle regeneration, a strategy which we leverage in this study by rescuing the age-related deficiency in Meteorin-like through several in vivo add-back models. Notably, the intramuscular, peptide injection of recombinant METRNL was sufficient to improve muscle regeneration in aging. Using ex vivo media exchange and in vivo TNF inhibition, we demonstrate a mechanism of METRNL action during regeneration, showing it counteracts a pro-fibrotic gene program by triggering TNFα-induced apoptosis of fibro/adipogenic progenitor cells. These findings demonstrate therapeutic applications for METRNL to improve aged muscle, and show Fibro/Adipogenic Progenitors are viable therapeutic targets to counteract age-related loss in muscle resilience.

SUMMARY: Heterochronic parabiosis (HPB) is known for its functional rejuvenation effects across several mouse tissues. However, its impact on the biological age of organisms and their long-term health remains unknown. Here, we performed extended (3-month) HPB, followed by a 2-month detachment period of anastomosed pairs. Old detached mice exhibited improved physiological parameters and lived longer than control isochronic mice. HPB drastically reduced the biological age of blood and liver based on epigenetic analyses across several clock models on two independent platforms; remarkably, this rejuvenation effect persisted even after 2 months of detachment. Transcriptomic and epigenomic profiles of anastomosed mice showed an intermediate phenotype between old and young, suggesting a comprehensive multi-omic rejuvenation effect. In addition, old HPB mice showed transcriptome changes opposite to aging, but akin to several lifespan-extending interventions. Altogether, we reveal that long-term HPB can decrease the biological age of mice, in part through long-lasting epigenetic and transcriptome remodeling, culminating in the extension of lifespan and healthspan.