Methodological approaches to the study of the determinants of somatic mitochondrial heteroplasmy in the elderly

Abstract

The article substantiates the algorithm and methodology of the study aimed at search and analysis of the determinants of somatic mitochondrial heteroplasmy in the elderly people. Aging is considered as a process that has developed in the process of evolution, characterized by a decrease in all basic biological functions and accompanied by a gradual degradation of organs, tissues and systems of the body, a classification of the main hypotheses and theories of aging is given. The need to develop diagnostic criteria and markers to differentiate the concept of «healthy aging» from diseases of the elderly is noted. Separately, the authors analyze the role of mitochondria in the development of age-related changes associated with the development of neurodegeneration and muscular dystrophy. It has been noted that the development of senile changes is to some extent associated with the main function of mitochondria, namely the oxidation of nutrients and the production of ATP molecules, a universal energy source for most biological processes in cells. For the mitochondrial genome, a driving mechanism has been proposed to explain how mitochondrial somatic mutations can lead to certain aging phenotypes — neurodegeneration and muscular dystrophy. To establish the relationship between mitochondrial somatic deletions and age-related changes, an algorithm and methodology have been developed based on a comprehensive study of the determinants of somatic mitochondrial heteroplasmy in a cohort of elderly people. It is planned to analyze the dynamics of mitochondrial somatic mutations in muscle tissues (biopsies) for 450 elderly volunteers. The authors propose an original approach to the determination of mtDNA heteroplasmy and the detection of de-novo mutations, including the enrichment of mitochondrial fractions and the purification of mtDNA from muscle tissues, as well as a method for quantifying mtDNA copy number to normalize the amount of genomic material in the samples. The resulting material will be used to prepare libraries for sequencing on NGS platforms. Subsequently, the data after bioinformatic analysis will be compared with the results of neurological and psychological studies, including an assessment of the level of cognitive processes, the presence of asthenic disorders, and an assessment of the patient’s rehabilitation potential. It is assumed that this psychoneurological block will allow us to further distinguish at least three groups among volunteers, namely: persons with normal aging (healthy aging), patients with a weakening of mental and physical abilities associated with neurodegenerative or with vascular pathologies. In order to search for informative markers in the immune system that allow differentiating «healthy aging» from diseases of the elderly, it is proposed to perform a correlation analysis between the assessment of immune and cytokine status and the data of clinical and bioinformatic studies.