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Text of Aging

  • 1. Theories of Aging Brought to you by

2. Objectives This presentation will describe aging from both a biological/physiological and a psychosocial perspective. Biological/physiological theories will be presented in two main categories, program theories and error theories. Psychosocial theories will be discussed in two main categories, full-life theories and mature-life theories. 3. Ponce De Leon In Search of the Fountain of Youth 4. Is There a Fountain of Youth? 5. Is There a Fountain of Youth? 6. What is Aging? The gradual and spontaneous changes that occur in maturation from infant to young adult. These changes create a normal physiologic decline seen in middle and late adulthood. Changes during puberty Graying of hair 7. Senescence The process by which a cell looses its ability to divide, grow, and function. This loss of function ultimately ends in death. A degenerative process, only. Has no positive features. 8. Normal vs. Healthy Aging Normal Aging Diseases & impairments of elderly People age differently Diabetes may be a common disease of adulthood, but is not experienced by all aging adults. Healthy Aging Minimize and preserve function Influenced by lifestyle choices One may have a healthy life until senescence makes life impossible. 9. Life Expectancy Some Factors Influencing Your Life Expectancy Heredity Disease Processes Medical Treatment Lifestyle Choices Nutrition 10. Theories of Aging The link between genes and lifespan is unquestioned. The simple observation that some species live longer than others -- humans longer than dogs, tortoises longer than mice -- is one convincing piece of evidence. The National Institute on Aging 11. Theories of Aging All aging begins with genetics Aging changes the biochemical and physiological processes in the body Cell and molecular biologists examine and propose theories to explain the aging process What causes aging? How can you influence aging prolong life? 12. The Two Main Aging Theory Categories Programmed Theories Aging has a biological timetable or internal biological clock. Error Theories Aging is a result of internal or external assaults that damage cells or organs so they can no longer function properly. Many theories are a combination of programmed and error theories. 13. Programmed vs. Error Theories Programmed Theories Programmed Senescence Theory Endocrine Theory Immunology Theory Error Theories Wear and Tear Theory Rate-of-Living Theory Cross-linking Theory Free Radical Theory Error CatastropheTheory Somatic Mutation Theory 14. Programmed Theories Programmed Senescence Theory Endocrine Theory Immunology Theory 15. Programmed Senescence Theory The result of sequential switching off or on of specific genes. Example Hayflicks Limits Fibroblasts removed from umbilical cord & cultured Fibroblasts divide and repeated until ~ 50 divisions Will not divide past this point 16. Telomeric Theory This is an extension of the Hayflick Limit. Telomeres are specialized DNA sequences at the end of chromosomes. They shorten with each cell division. When the telomeres become too short, the cell enters the senescence stage. In the normal process of DNA replication, the end of the chromosome is not copied exactly, which leaves an unreplicated gap. 17. Telomeric Theory The enzyme, telomerase, fills the gap by attaching bases to the end of the chromosomes. As long as the cells have enough telomerase to do the job, they keep the telomeres long enough to prevent any important information from being lost as they go through each replication. With time, telomerase levels decrease. With decreasing telomerase levels, the telomeres become shorter and shorter. 18. Telomeric Theory Shortened telomeres are found in: Atherosclerosis Heart disease Hepatitis Cirrhosis 19. Telomeric Theory and Cancer 90% of cancer cells have been found to possess telomerase. Telomerase prevents the telomere from shortening. This allows the cancer cells to reproduce, resulting in tumor growth. Research areas Measuring telomerase may help detect cancer. Stopping telomerase may fight cancer by causing death of cancer cells. Telomerase may be used to help with wound healing or the immune response. 20. Endocrine Theory Biological clocks act through hormones to control the pace of aging. Hormones effects growth, metabolism, temperature, inflammation and stress. Examples- Menopause Decreased level of estrogen & progesterone Hot flashes, insomnia 21. Immunologic Theory A programmed decline in the immune system leads to an increased vulnerability to disease, aging and death Example- Decreased T cells (helper cells) in adults Increased diseases in older adults Increased autoimmune diseases in adults 22. Error Theories Wear and Tear Theory Error Free Radical Theory Rate-of-Living Theory CatastropheTheory Cross-linking Theory Somatic Mutation Theory 23. Wear and Tear Theory Years of damage to cells, tissues and organs eventually wears them out, killing both them and the body Example- 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. 24. Rate-of-Living Theory The greater an organisms basal metabolic rate, the shorter the life span. Free radicals or other metabolic by-products play a role in senesce. Example Animals with the most rapid metabolisms tend to have the shortest lifespans, i.e, birds have a shorter lifespan than humans. Studies examining the relationship between metabolic rates and longevity have produced inconsistent results, limiting the usefulness of this theory. 25. Cross-Linking Theory The accumulation of cross-linked proteins damages cells and tissue, slowing down bodily processes. Example Non-enzymatic glycosylation reactions occur when glucose molecules attach to proteins causing a chain of chemical reactions resulting in a structural change to the proteins. Loss of flexibility of connective tissue Microvascular changes in arteries 26. Free Radical Theory During aging, damage produced by free radicals cause cells and organs to stop functioning. A free radical is a molecule with an unpaired, highly reactive electron. One type of very reactive free radical is the oxygen free radical, which may be produced during metabolism or as a result of environmental pollution. Oxygen free radicals are formed in your cells, naturally, during the oxidation of food to water and carbon dioxide. 27. Free Radical Theory The free radical grabs a electron from any molecule it its vicinity. It does this because electrons like to exist in pairs. When it grabs an electron from another molecule, it damages the other molecule. 28. Free Radical Theory Some of the molecules that may be damaged by free radicals are fats, proteins, and DNA (both in the nucleus and in mitochondria). If membrane fats are attacked, then you get the breakdown of the cell membrane. If it is a red blood cell membrane, you get hemolysis. If proteins are attacked, you get the breakdown of proteins, which may result in the loss of biological function and the accumulation of catastrophic compounds. If DNA is attacked, you will get a mutation that may cause aging or cancer. 29. Free Radicals As the free radical (green) attacks the membrane it can release another type free radical (blue). 30. Damaged membrane The free radical (blue) attacks the DNA releasing another free radical (purple). mitochondrion 31. Free Radical Theory Free radicals do not go unchecked. The body has a multi-layed defense system that reacts and detoxifies the damaging radicals. Defenses include: Natural antioxidants in the body, such as bilirubin. Enzymes such as superoxide dismutase (SOD), catalase, & glutathione peroxidase. Dietary antioxidants such as beta carotene, and the vitamins C and E. 32. Free Radical Theory Under normal conditions, your natural defense mechanisms prevent most of the oxidative damage from occurring. The free radical theory of aging proposes that, little-by-little, small amounts of damage accumulate and contribute to deterioration of tissues and organs. 33. anti-oxidant molecule repaired membrane damaged DNA The anti-oxidant molecule destroys the damaging free radical. The membrane repairs itself, but the DNA remains damaged, impairing the cells function. In addition, the anti-oxidant molecule now has an unpaired electron and thus becomes a new radical. 34. Free Radical Theory For example, when Vitamin E scavenges free radicals, it becomes a free radical and may be more carcinogenic than the original free radical. This is the reason why taking high doses of vitamin E SUPPLEMENTS appears to INCREASE cancer risk in a person, not decrease cancer risk. 35. Free Radical Theory Not all free radicals cause damage. You use free radicals as part of your immunological response system. Macrophages engulf bacteria Free radical reactions produced inside the macrophage oxidize and kill bacteria. Question: Does it make any biological sense to try to eliminate all free radicals in your body by taking supplements? 36. Can This Stop Aging? 37. Can you delay or stop aging by taking vitamins and other free radical scavengers? There is no evidence-based proof that dietary supplements delay or stop aging. This is a big area of nutrition quackery. BEWARE! Remember, there is a lot of evidence-based proof that taking some supplements INCREASES cancer rate, for example lung cancer. Smokers who take beta-carotene supplements have higher lung cancer rates than smokers not taking these supplements. Therefore, the risk/benefit ratio is in favor of NOT taking SUPPLEMENTS to retard aging. 38. Catastrophe Theory Any damage to the enzyme systems that synthesize proteins in the body results in faulty protein synthesis. The faulty proteins continue to accumulate in the cell until they reach a level that damage