theories of aging, programmed and error theories
- 2. AGEING Ageing is a lifelong process of growing up and growing old. Begins at conception and ends with death. Chronological Aging is the number of years a person has lived so far. Biological aging is that aging occurs as you gradually accumulate damage to various cells and tissues in the body. Psychological Aging involves changes in memory, learning, intelligence, personality, and coping. Social Aging refers to changes in roles and relationships as individual age.
- 3. Theories of Ageing Each theory of aging attempts to provide a framework to understand aging from different perspectives. Biologic theories of aging aims to explain why the physical changes of aging occur. There are two primary categories of aging; these include: • Programmed theories - Programmed theories believe that aging is a normal process, just as puberty is a normal developmental process. • Error theories - Error theories believe that aging is not something which is programmed to occur, but rather aging is due to a series of "accidents."
- 4. Theories of Ageing Some general theories of aging related to nutrition aspects are: Neuroendocrine and hormonal theory Free radical theory Calorie restriction theory Immunological theory Wear and Tear theory Clinker theory
- 5. Free Radical Theory of Ageing Given by Denham Harman in 1950s. He studied that- lifespan is an inverse function of metabolic rate which in turn is proportional to oxygen -------- consumption He proposed that: cells continuously produce free radicals by normal metabolism and oxidation of organic compound these free radicals damage cellular components (membrane) and macromolecules (DNA, lipid, protein) accumulation of these damage over time period cause aging. Free radical structure
- 6. In 1972s, Denham Harman modified his theory- About 95% energy of a cell is produce in mitochondria. 97-99% of oxygen is used in energy formation and 1-3% utilized in reactive oxygen species formation. Theory states that: Reactive oxygen species (ROS) are produce in mitochondria during ETC cycle cause damage to macromolecules (lipid, protein, DNA) of mitochondria and nucleus leading to aging. Contd……. Mitochondrial Free Radical theory
- 7. Criticism of free radical theory: Main criticism- all free radicals are responsible for damage biomolecules which must be major reason for cell aging which is not true because: Many reactive oxygen species participate in signaling pathway. Many free radicals kill and inject harmful bacteria. Many free radicals are co-factor of enzyme and protein derivatives. Contd…………..
- 8. Calorie Restriction Theory Calorie restriction defined as reduction of energy intake without malnutrition. This theory of ageing is proposed by David Sinclair (2005)- considered that CR is not a simple and has passive effect. CR diet total amount of food is reduced but major nutrients, minerals and vitamins required for health are maintained. Gradual lose weight until maximal efficiency retards aging. Experimental mammalian models of CR reduce calorie intake by 40% throughout lifespan of animal.
- 9. • Results: CR proved to be beneficial at various level of functions and involving a number of molecules, cellular and systematic changes. • Calorie restriction diet influences both aging rate and disease susceptibility. Limitation: Some studies revealed that calorie restriction affects immunity and slow the DNA repair capacity Contd….
- 10. Neuroendocrine and hormonal theory Neuroendocrine cells are chemical messengers of the endocrine system, passing signals from one neuron to the next, and from a neuron to a target cell across a synapse. This theory is proposed by Vladimir Dilman Theory states that “The effectiveness of the body's homeostatic adjustments declines with aging—leading to the failure of adaptive mechanisms, aging, and death. Also called as aging clock theory and the pacemaker theory
- 11. Contd…… This theory view the functional decline in neurons and their associated hormones as central to aging. Give the major role- neuroendocrine system in physiology. This is an attractive theory of aging and neuroendocrine disease In humans, aging is associated with decreased production of hormones, amino acids, peptides, monoamines, and enzymes.
- 12. Contd…… According to this theory, ageing is mediated in brain. Dilman based his theory on past studies of hypothyroidism- a disease that mimics mature aging He proposed that the hypothalamic, pituitary and adrenal axis is the master timekeeper for the organism and primary regulate aging process.
- 13. Contd…… Criticism: Critics of the neuroendocrine theories point out that the master timekeeper of aging – the neuroendocrine system – lacks universality. Many organisms that age (e.g., higher vertebrates) have no complex neuroendocrine system. It can also be argued that the changes in the neuroendocrine system are expected and occur in all tissues.
- 14. • Proposed by Walford • This theory asserted that the process of human aging involves a highly complex series of processes which are suspected to be largely controlled by the immune system. • Basis: As humans age, they experience changes to almost all physiological functions, including those related to the immune system. • Theory explain rate of aging is controlled by the immune system which declines. Immunological theory
- 15. • It is based on two major observations: 1. The immune system weakens over time, making an aging person more susceptible to disease, increase in autoimmune disease and allergies. 2. Over time, cells involved in immune function are less self-regulatory, resulting in cells being misidentified as foreign material and being attacked by the immune system’s own defenses. • Example: rheumatoid arthritis (RA) and lupus. Contd…….
- 16. Limitations: Its difficult to defend the immune system’s role as the primary time keeper in biology of all organisms. Contd…….
- 17. Wear and Tear theory Proposed by Dr. August Weismann. This theory asserts that the effects of aging by progressive damage to cells and body systems over time. This may be referred to as simple deterioration theory or fundamental limitation theory. Long term damage to cells, tissues and organs eventually wear them out, killing both them and the body. Ex: wearing out of the skeletal system such as in osteoarthritis. Wear and tear can be viewed as a result of aging and not the cause of it. With age, body’s mechanism to repair the damage caused by wer and tear get reduced.
- 18. Contd……….. Criticism: Cells are well-equipped to repair damage. Humans and other organisms grows stronger from youth to maturity. Organisms vary widely in lifespan rather than all following the same pattern.
- 19. Clinker theory • This theory combines the somatic mutation, free radical and cross links in DNA • Due to metabolism process, potentially harmful substances get accumulate in the body over the years • These substances cause damage to body organs such as muscles, heart, nerves and brain • One substance that has been identified is LIPOFUSCIN.
- 20. Contd………. • Lipofuscin is a mixture of chemical waste products from normal cellular activities which becomes concentrated in the cells of the body e.g. heart and brain • High lipofusin concentrations make cells appear darker in colour- age pigment • Accumulation of glucose has been implicated in causing them to stick together