Introduction
Age is a process of decay in an organism's function and structure in which molecular and cellular modifications have several effects on the individual over a lifetime. Due to epigenetic and genetic interactions and based on hereditary, stochastic, and environmental factors, molecular errors accumulate, leading to the aging process. Physiological functions are affected due to aging, which can be termed as damage accumulation in molecules, tissues, and cells over a lifetime. All this decreases the capacity of an organism to maintain balance during stress and processes higher risk for many diseases such as cardiovascular disorders, cancer, and neurodegenerative disorders. Aging is a multifactorial process that occurs due to environmental and genetic factors. The genotype among the individuals determines the lifespan variation.
What Is the Aging of a Cell?
An important factor in the process of aging is an increase in the mortality and incidence rates of non-cancerous and cancerous diseases, along with atrophy and tissue degeneration caused by a decrease in stem cell function.
Cells are constantly exposed to an environment that leads to cell damage. This contributes to alteration in the function that is characterized by aging.
There are certain genes in which mutations occur that reduce the rate of damage accumulation.
What Are the Genetic Factors in Aging?
Various genetic factors are involved in aging. Determination of lifespan is done by certain genotypes (gene combinations). Single gene alterations have resulted in remarkable changes. Repair efficacy is reduced due to the mutations in DNA (deoxyribonucleic acid), which further lead to deviation in the stem cell function.
Below are the listed genetic factors:
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Genes regulate the organism's structure and function.
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Alleles increase the reproductive capacity
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Mutations that involve physical characteristics.
What Are the Special Genetic Factors That Determine Length of the Life?
Changes associated with aging are programmed as per the current concept of biological aging. The occurrence of old age in humans or an increase in an individual's lifespan is a complex process that includes factors of environment and genetics.
Species-specific genotype determines the life span of an organism, as different organisms have different lifespans.
Age-related hereditary disorders caused by mutations of certain genes are also identified, which leads to establishing the function of specific genotypes in an individual's life.
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Environmental Factors:
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Stress.
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Pesticides.
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Genotypic Factors:
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Mitochondrial and genomic DNA.
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Stochastic Factors:
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Genetic and epigenetic alterations can decrease the stem cell function.
What Are Progerias?
Progerias are characterized by aging prematurely. Symptoms shown by progerias are as follows:
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Atherosclerosis (fats or cholesterol build up in the arteries, leading to blockage of blood vessels).
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Grey hair.
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Increased cancer risk.
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Hyperkeratosis (skin thickening on its outer layer by excessive deposition of keratin).
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Ulcers.
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Atrophy (wasting of a tissue).
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Senile dementia (decrease in memory power).
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Hyperlipidemia (increase in the levels of cholesterol).
What Are the Aging Syndromes?
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Werner Syndrome:
Werner syndrome is characterized by a genetic mutation of a gene involved in DNA repair and replication. Until puberty, there is a normal development in an individual suffering from Werner syndrome. Gonadal atrophy and absence of growth spurt of puberty resulting in short stature are the major symptoms. Loss of hair, premature greying of hair, and skin atrophy appear more prominently.
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Hutchinson Gilford Progeria Syndrome:
It is a rare syndrome as compared with other aging syndromes. Aging in early childhood with decreased expectancy of life is a major symptom. Individuals suffering from this syndrome do not live beyond adolescence. It is caused due to the substitution of a single base in the genes.
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Bloom Syndrome:
It is a rare hereditary disease in which the patient exhibits tiny blood vessels, short stature, facial photosensitivity, and is highly susceptible to tumors. Mutations of the gene BLM encoding a protein of DNA helicases are associated with the syndrome.
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Rothmund Thomson Syndrome:
It is an autosomal recessive disease that occurs in early life. The patient presents with short stature, rashes on the face, less hair on the scalp, absence or decreased eyelashes or eyebrows, abnormalities in the skeletal formations, premature aging, and osteosarcoma. All the presenting clinical features are indications of genetic heterogeneity. There are two subsites of this disease: Type 1, which is characterized by juvenile cataracts and poikiloderma, and Type 2, which is characterized by congenital bone defects, increased susceptibility of osteosarcoma in childhood, poikiloderma, and skin cancer.
What Is the Association or Linkage of Genetic Variants to Longevity and Aging?
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As genetic factors modulate the aging process, the lifespan of individuals is added with increased resistance to dangerous disorders, paving the way for death. Survival can be influenced by those following a balanced lifestyle and nutrition by showing longevity. Extreme longevity is influenced by genetic factors such as aging-associated polymorphisms.
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Growth hormones trigger cell growth and survival of the cells.
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The association of single nucleotide polymorphisms with longevity was reported recently in the gene FOX03A.
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Many variations of genes related to age-related diseases, such as APOE and PCDH11X gene variation, are linked to Alzheimer's disease.
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Homozygous APOE allele individuals have longer lifespans, which can be a risk for coronary disease.
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Longevity of lifespan can be linked with the adequate immune response of an individual.
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It was reported that certain genes like HSPA1A-AA and HSPA1B- AA were associated with decreased survival in women, and haplotype female carriers survived longer.
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Reactive oxygen species show extreme linkage to aging as a part of damaging the DNA mechanisms. Free radical detoxification includes protein mutations, which show their effects on aging and lifespan.
Conclusion
Aging is described as a complex process in which functions of cells and tissues are integrated until the process of senescence. The highest lifespan difference between individuals of the same species indicates that the aging process is affected by the accumulation of errors that alter repair systems and compromise the function of stem cells. Changes can occur due to many mechanisms influenced by genes, stochastic factors, and environmental factors. Alteration associated with age can also depend on epigenetic alterations such as hypermethylation or hypermethylation. Hence, it can be concluded that the aging process is not mediated by one gene or a particular mechanism.
