Exercise, programmed cell death and exhaustion of cardiomyocyte proliferation in aging zebrafish

The zebrafish heart harbors a thermogenic beige fat depot analog of human epicardial adipose tissue

Epicardial adipose tissue (eAT) is a metabolically active fat depot that has been associated with a wide array of cardiac homeostatic functions and cardiometabolic diseases. A full understanding of its diverse physiological and pathological roles is hindered by the dearth of animal models. Here, we show, in the heart of an ectothermic teleost, the zebrafish, the existence of a fat depot localized underneath the epicardium, originating from the epicardium and exhibiting the molecular signature of beige adipocytes. Moreover, a subset of adipocytes within this cardiac fat tissue exhibits primitive thermogenic potential. Transcriptomic profiling and cross-species analysis revealed elevated glycolytic and cardiac homeostatic gene expression with downregulated obesity and inflammatory hallmarks in the teleost eAT compared to that of lean aged humans. Our findings unveil epicardium-derived beige fat in the heart of an ectotherm considered to possess solely white adipocytes for energy storage and identify pathways that may underlie age-driven remodeling of human eAT.

Rejuvenation of the Aging Heart: Molecular Determinants and Applications

In Canada and worldwide, the elderly population (i.e., individuals >65 years of age) is increasing disproportionately relative to the total population. This is expected to have a substantial impact on the healthcare system, as increased aged is associated with a greater incidence of chronic non-communicable diseases. Within the elderly population cardiovascular disease is a leading cause of death, therefore developing therapies which can prevent or slow disease progression in this demography is highly desirable. Historically aging research has focused on the development of anti-aging therapies which are implemented early in life and slow the age-dependent decline in cell and organ function. However, accumulating evidence supports that late-in-life therapies can also benefit the aged cardiovascular system by limiting the age-dependent functional decline. Moreover, recent studies have also demonstrated that rejuvenation (i.e. reverting cellular function to that of a younger phenotype) of the already aged cardiovascular system is possible, opening new avenues to develop therapies for older individuals. In this review, we first provide an overview of the functional changes that occur in the cardiomyocyte with aging and how this contributes to the age-dependent decline in heart function. We then discuss the various anti-aging/rejuvenation strategies that have been pursued to improve the function of the aged cardiomyocyte, with a focus on therapies implemented late in life. These strategies include 1) established systemic approaches (caloric restriction, exercise), 2) pharmacological approaches (mTOR, AMPK, SIRT1, and autophagy targeting molecules), and 3) emerging rejuvenation approaches (partial reprogramming, parabiosis/modulation of circulating factors, targeting endogenous stem cell populations, and senotherapeutics). Collectively, these studies demonstrate the exciting potential and limitations of current rejuvenation strategies and highlight future areas of investigation which will contribute to the development of rejuvenation therapies for the aged heart.

Adult zebrafish as advanced models of human disease

Modelling adult diseases to understand their aetiology and progression, and to develop new therapies, is a major challenge for medical biology. We are excited by new efforts in the zebrafish community to develop models of adult diseases that range from cancer to heart, infectious and age-related diseases, and those that relate to toxicology and complex social behaviours. Here, we discuss some of the advances in the field of zebrafish models of adult disease, and where we see opportunities and challenges ahead.

Exercise intervention mitigates zebrafish age-related sarcopenia via alleviating mitochondrial dysfunction

Sarcopenia is a common disorder that leads to a progressive decrease in skeletal muscle function in elderly people. Exercise effectively prevents or delays the onset and progression of sarcopenia. However, the molecular mechanisms underlying how exercise intervention improves skeletal muscle atrophy remain unclear. In this study, we found that 21-month-old zebrafish had a decreased swimming ability, reduced muscle fibre cross-sectional area, unbalanced protein synthesis, and degradation, increased oxidative stress, and mitochondrial dysfunction, which suggests zebrafish are a valuable model for sarcopenia. Eight weeks of exercise intervention attenuated these pathological changes in sarcopenia zebrafish. Moreover, the effects of exercise on mitochondrial dysfunction were associated with the activation of the AMPK/SIRT1/PGC-1α axis and 15-PGDH downregulation. Our results reveal potential therapeutic targets and indicators to treat age-related sarcopenia using exercise intervention.

Age-Associated Different Transcriptome Profiling in Zebrafish and Rats: an Insight into the Diversity of Vertebrate Aging

Most mammals, including humans, show obvious aging phenotypes, for example, loss of tissue plasticity and sarcopenia. In this regard, fish can be attractive models to study senescence because of their unique aging characteristics. The lifespan of fish varies widely, and several species can live for over 200 years. Moreover, some fish show anti-aging features and indeterminate growth throughout their life. Therefore, exploring the aging mechanism in fish could provide new insights into vertebrate aging. To this end, we conducted RNA sequencing (RNA-seq) assays for various organs and growth stages of zebrafish and compared the data with previously published RNA-seq data of rats. Age-associated differentially expressed genes (DEGs) for all zebrafish tissue samples reveal the upregulation of circadian genes and downregulation of hmgb3a. On one hand, a comparative analysis of DEG profiles associated with aging between zebrafish and rats identifies upregulation of circadian genes and downregulation of collagen genes as conserved transcriptome changes. On the other hand, in zebrafish, upregulation of autophagy-related genes in muscles and AP-1 transcription factor genes in various tissues is observed, which may imply fish-specific anti-aging characteristics. Consistent with our knowledge of mammalian aging, DEG profiles related to tissue senescence are observed in rats. We also detect age-associated downregulation of muscle homeostasis and differentiation-related genes in zebrafish gills, indicating a fish-specific senescence phenotype. Our results indicate both common and different aging profiles between fish and mammals, which could be used for future translational research.

Drosophila exercise, an emerging model bridging the fields of exercise and aging in human

Exercise is one of the most effective treatments for the diseases of aging. In recent years, a growing number of researchers have used Drosophila melanogaster to study the broad benefits of regular exercise in aging individuals. With the widespread use of Drosophila exercise models and the upgrading of the Drosophila exercise apparatus, we should carefully examine the differential contribution of regular exercise in the aging process to facilitate more detailed quantitative measurements and assessment of the exercise phenotype. In this paper, we review some of the resources available for Drosophila exercise models. The focus is on the impact of regular exercise or exercise adaptation in the aging process in Drosophila and highlights the great potential and current challenges faced by this model in the field of anti-aging research.

Disease Models & Mechanisms helps move heart failure to heart success

Heart failure affects ∼64 million people worldwide, resulting in high morbidity, mortality and societal cost. Current treatment strategies are primarily geared at slowing the progression to an advanced disease state, but do not reverse or cure heart failure. A more comprehensive understanding of the underlying biology and development of preclinical models of this heterogeneous group of disorders will improve diagnosis and treatment. Here, we summarise recent preclinical and translational research in this area published in Disease Models & Mechanisms. We also discuss how our Journal is propelling this field forward by launching a Special Issue and ongoing subject collection, ‘Moving Heart Failure to Heart Success: Mechanisms, Regeneration & Therapy’.