4 Theories of Aging - Volker PDF

One Perspective of Aging Loss of Homeostasis A breakdown in maintenance of specific molecular structures and pathways This breakdown is the inevitable consequence of the evolved anatomy and physiology of an organism Some are unique to the specific cellular and tissue context of a specific organ Some...

One Perspective of Aging Loss of Homeostasis A breakdown in maintenance of specific molecular structures and pathways This breakdown is the inevitable consequence of the evolved anatomy and physiology of an organism Some are unique to the specific cellular and tissue context of a specific organ Some are due to the overall organ system being stressed Geriatric Review Syllabus 10h Edition – Biology Chapter 29 March 2024 Volker Theories of Aging 1 Evolutionary theories Impact of natural selection on the reproductive fitness of a species Two main types – Mutation accumulation Aging viewed as a non-adaptive trait Late-acting genes accumulate – Antagonistic Pleiotropy A single gene controls or influences multiple traits Genes that effect early fitness are harmful in later years Example: Hyperlipidemia 29 March 2024 Volker Theories of Aging 2 Target Theory of Genetic Damage Damage to our genes from a variety of sources such as radiation or any number of damaging agents (chemicals) causes an alteration in structure and signaling for repair molecules Accumulation of “hits” to the genome Evidence: radiation shortens lifespan due to DNA damage 29 March 2024 Volker Theories of Aging 3 Mitochondrial Damage Damage to mitochondria reduces energy available for metabolism and cellular resilience Overall deleterious results: – Less energy production – More free radical formation – Reduced control of cellular processes – Accumulation of damaged harmful molecules 29 March 2024 Volker Theories of Aging 4 Free Radical Theory Reactive Oxygen Species (ROS) are extremely reactive and unstable and are produced in mitochondria, in oxidative enzymes, in the endoplasmic reticulum, and phagocytes Highly reactive oxygen-derived free radicals damage protein, lipid, and DNA, leading to altered structure and functional capacity Mitochondria particularly susceptible (in this way, similar to Mitochondrial Damage Theory) 29 March 2024 Volker Theories of Aging 5 Telomere Theory Telomeres shorten with each successive mitosis Cellular replicative senescence is triggered when cells acquire critically short telomeres 29 March 2024 Volker Theories of Aging 6 Transposable Element Activation Some individual genes or even portions of chromosomes can be transposed to other locations on its own or other chromosomes May interfere with gene expression This is cumulative over time 29 March 2024 Volker Theories of Aging 7 Epigenetic Theory Gene regulation can vary with age as DNA is methylated or chromatin-bound Some needed genetic expression may be blunted, or harmful expression may be accelerated “Kill Switch” 29 March 2024 Volker Theories of Aging 8 Error Catastrophe Theory Damage is not to the genes themselves but to the RNA and proteins that read the genes and carry out their instructions Damaged transcription can produce abnormal proteins (including the transcription proteins themselves) 29 March 2024 Volker Theories of Aging 9 Accumulation Theories “Clinker Theory” Accumulation of cellular and extracellular components with altered structures that compromise cellular function Detritus like lipofuscin accumulates and no one picks up the trash 29 March 2024 Volker Theories of Aging 10 Energetics Theories “The faster the metabolism, the shorter the life” Higher metabolism required higher oxygen consumption and thus greater exposure to reactive oxygenating species 29 March 2024 Volker Theories of Aging 11 Endocrine Theory With aging, secretion of many hormones change Circadian cycles of certain hormones become irregular – Growth hormone – Sex steroid hormones 29 March 2024 Volker Theories of Aging 12 Immune Theory In response to an age-related decline in acquired immunity, the innate immune system becomes activated resulting in over vigorous expression of cytokines and inflammatory substances 29 March 2024 Volker Theories of Aging 13 Stem Cell Theory Adult stem cells in the brain, bone marrow, and circulation maintain homeostasis by replenishing depleted reserves As time passes precursor cells become depleted by phenotypic drift, injury, illness, environmental challenges Result is lesser ability to replace cells lost to death or damage 29 March 2024 Volker Theories of Aging 14 What Now? Regardless of how the aging process happens, the way your patient handles the changes that come with aging is perhaps the most influential factor in defining the impact on their health Attitude plays a role in several ways, how well your patient lives, but may also play a significant role in how long they may live Successful aging can be thought of as maintaining good health, good functionality, good cognition, and remaining socially engaged 29 March 2024 Volker Theories of Aging 15 Remember Mentation Mobility Medication What Matters Most 29 March 2024 Volker Theories of Aging 16 Social / Friendships Extends your healthspan Recovery times Immunity Mental Health – Reduces anxiety – Protects against mental decline – Adapted from Mayo Clinic on Healthy Aging 2013 29 March 2024 Volker Theories of Aging 17 Spirituality Over 50% of older adults report frequent attendance at religious events or practices Death of friends, nearing own death prompt thoughts and questions about afterlife Legacy; what will I leave after I’m gone Invite your chaplains and clergy in I encourage you to explore your own spirituality, get comfortable relating to your patients in this way 29 March 2024 Volker Theories of Aging 18 Challenge Your Patients to “Use it or Lose it” Social support Religion and Spirituality Work your brain (especially learning activities) Work your body Eat well, but not too much Avoid drugs, tobacco, excessive alcohol Small changes add up This is pretty good advice for you and me, too! 29 March 2024 Volker Theories of Aging 19