Abstract

The most common aging-associated diseases are cardiovascular diseases which affect 40% of elderly people. Elderly people are prone to suffer aging-associated diseases which are not only related to health and medical cost but also to labor, household productivity and mortality cost. Aging is becoming a world problem and it is estimated that 21.8% of global population will be older than 65 years old in 2050; and for the first time in human history, there will be more elderly people than children. It is well accepted that the origin of aging-associated cardiovascular diseases is mitochondrial dysfunction. Mitochondria have their own genome (mtDNA) that is circular, double-stranded, and 16,569 bp long in humans. There are between 500 to 6000 mtDNA copies per cell which are tissue-specific. As a by-product of ATP production, reactive oxygen species (ROS) are generated which damage proteins, lipids, and mtDNA. ROS-mutated mtDNA co-existing with wild type mtDNA is called mtDNA heteroplasmy. The progressive increase in mtDNA heteroplasmy causes progressive mitochondrial dysfunction leading to a loss in their bioenergetic capacity, disruption in the balance of mitochondrial fusion and fission events (mitochondrial dynamics, MtDy) and decreased mitophagy. This failure in mitochondrial physiology leads to the accumulation of depolarized and ROS-generating mitochondria. Thus, besides attenuated ATP production, dysfunctional mitochondria interfere with proper cellular metabolism and signaling pathways in cardiac cells, contributing to the development of aging-associated cardiovascular diseases. In this context, there is a growing interest to enhance mitochondrial function by decreasing mtDNA heteroplasmy. Reduction in mtDNA heteroplasmy is associated with increased mitophagy, proper MtDy balance and mitochondrial biogenesis; and those processes can delay the onset or progression of cardiovascular diseases. This has led to the development of mitochondrial therapies based on the application of nutritional, pharmacological and genetic treatments. Those seeking to have a positive impact on mtDNA integrity, mitochondrial biogenesis, dynamics and mitophagy in old and sick hearts. This review covers the current knowledge of mitochondrial physiopathology in aging, how disruption of OXPHOS or mitochondrial life cycle alter mtDNA and cardiac cell function; and novel mitochondrial therapies to protect and rescue our heart from cardiovascular diseases.

Highlights

  • The world is aging at a very high speed and with it, the agingassociated diseases are going up

  • Cristae hold the Oxidative Phosphorylation (OXPHOS) system and considering the length of cristae and the electrodense nature of mitochondrial matrix seen by TEM, it is possible to suggest that cardiac mitochondria are fully packed with OXPHOS having a highly oxidative metabolism

  • Mitophagy is the cellular process to dismiss dysfunctional mitochondria and secure ATP demand for heart cells. As it was discussed before, many pathways and proteins are implicated in mitophagy which responds to different stimuli like reactive oxygen species (ROS), hypoxia and mitochondrial depolarization

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Summary

INTRODUCTION

The world is aging at a very high speed and with it, the agingassociated diseases are going up. Changes in MtDy regulate bioenergetics outputs including respiratory rate, mtDNA Heteroplasmy at the Core of Aging-Associated Heart Failure energy expenditure and ATP synthesis as well as apoptosis and the segregation and elimination of dysfunctional mitochondrial units by mitophagy (Bénard et al, 2007; Sheridan and Martin, 2010; Westermann, 2012). FUNDC1-OPA1 interaction is dismissed, mtDNA Heteroplasmy at the Core of Aging-Associated Heart Failure promoting DRP1 translocation to mitochondria for fission and a new association FUNDC1-DRP1 for mitophagy. This reveals the complexity and importance that MtDy and Mitophagy play for cellular physiology. This oxidative damage may be caused by hypoxia, linking the lack of oxygen to mtDNA replication (Pastukh et al, 2016)

MITOCHONDRIA IN CARDIAC CELLS
Predominant basal mitophagy pathway
CARDIAC MITOCHONDRIA IN AGING
PROPOSED MODEL OF CARDIAC AGING
Findings
MITOCHONDRIAL THERAPIES FOR A HEALTHY HEART
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