Ageing, Impairment & Disability (AID) Flashcards
What happens when you square the rectangle of survival?
- Fall in infant mortality, higher living standards, better public health, better sanitation + better diet.
Chronically disabling diseases that have steep relationship to age?
Stroke, AD, Parkinsons, Osteoarthritis.
what happens in the Ageing process?
- Impairment of function, which means there is a loss of adaptive responses to stress = growing risk of age related disease.
- There are no symptoms of ageing - no pain and nausea etc.
What is frailty?
- Physiological syndrome = decreased reserve and less resistance to stressors because of decline across lots of physiological systems. Causes vulnerability to adverse outcomes
- Physical frailty is the combination of weight loss, fatigue, impaired grip strength, diminished physical activity or slow gait.
what are the differences in Ageing vs. disease
- Disease needs identifying = can respond to treatment but ageing is not reversible. But ageing can be compensate able, so should not put all changes down to age.
- Delaying onset of disabling disease to later ages when intrinsic ageing has raised fatality by reducing adaptability the average duration of disability before death is shorter = spend longer time living and shorter time dying.
- Older you are when you become disabled = shorter dependency time before death. Disability in later life = postponement of age onset –> prevents suffering.
> Universal, Intrinsic, Progressive, Deleterious, Individual, Intrinsic or extrinsic
> Progressive but may be halted or reversed
> Deleterious but may be arrested or cured
What are Strehlers concepts for a true ageing process
- (ST)UPID
Universal, Progressive, Intrinsic, Deleterious - Need all 4 to be a proper ageing process.
Universal - identifiable in all members of species, affects people to different extent - e.g. collagen cross links and loss of calcium from the bones.
Progressive - changes progress with time like hair getting grey and losing muscle power.
Intrinsic - restricted to changes of endogenous origin. Skin in axilla, hair loss
Deleterious - eventually harmful to organism like loss of visual acuity + hearing
Health promotion, illness prevention, use technologies and find new technologies to postpone disability in old age.
What are the 3 theories of why we age?
- “Wear + tear”
- Adaptive evolutionary
- Non adaptive evolutionary
What are the 3 theories of why we age? - “Wear + tear”
- Organism is a machine that wears out - like elephants teeth/weddell seal.
- Not all animals age (e.g. Sea Anemone) - they have the ability to repair, e.g. germ line. We can repair whole organs e.g. Salamanders.
- Therefore cannot be the whole answer
What are the 3 theories of why we age? - Adaptive evolutionary
- Evolution + natural selection (Darwin Principles). Ageing can be selectively advantageous to species - prevents elderly and worn out animals competing
- Advantage is to the population and not individual and is rarely seen in natural populations. B/c of circular arrangement, old and worn out ones cannot compete.
What are the 3 theories of why we age? - Non adaptive evolutionary
• There are 2 theories within this: mutation accumulation and antagonistic pleiotrophic genes + disposable soma theory
What is MUTATION ACCOMODATION
Within the non-adaptive evolutionary theory?
- Less natural selection powers with age and the genes that are early expressed effect most of the population
- The genes that get expressed after reproduction = lost from evolutionary control
- Ageing is because of miscellaneous collection of late acting, deleterious genes
But there is no experimental support.
ANTAGONISTIC PLEIOTROPHIC GENES
Within the non adaptive evolutionary theory for ageing
There is an early good effect which is retained, and a bad late effect which contributes to ageing. Drosophilia studies support this.
The drosophilia experiments that support the non adaptive evolutionary theory for ageing within the antagonistic pleiotrophic genes - describe how?
- AA (abnormal abdomen) allele greatly increases early fecundity and pleiotrophically reduces longevity.
If breeding is prevented until later in life over 15 generations then lifespan is extended by a third. Short winged flying is reduced.
Describe the disposable soma theory?
- Development of non adaptive evolutionary views, this theory suggests that organisms are a machine that transfer free energy into progeny.
- Success is to ensure that genes survive in the most efficient way
- Disposable = produced with limited lifespan.
- The soma is not of a germ line
- Amount of energy that is used on up possibilities depends on ecological niche occupied by that organisms, which results in the species specific longevity. For some, fertility is priority. Others need to maintain soma for longer time period.
- Entropy increases [via 2nd law of thermodynamics] - i.e. we age and decay, resist this with defensive and repair processes. These protective mechanisms eventually fail. The rate of ageing is determined by investment of self-maintenance.
- = we are programmed to survive, not to age.
Processes through which we age?
- System level theories
- Cellular + molecular level theories
- Genetic theories
- Genomic stability
• Theories are based on total body systems
Neuroendocrine theory of ageing?
- There is a functional fall in neurones + associated hormones is central to ageing process and hypothalamic, pituitary and adrenal axis controls growth and development - so potentially ageing.
- Decreased pulsatile GH + GnRH in ageing rats
- Hypothesectomy + hormone replacement increases lifespan
- DECO / death hormone is proposed but never found.
Describe cellular + molecular theories of ageing
• Wear + tear
“Wear + tear, and rate of living”
- Some rates of ageing look like wear and tear. Higher basal metabolic rate and shorter lifespan. Accumulation of damage might be important.
Cellular + molecular theories of ageing
• X link formation
Biological molecules develop cross linkage / bonds over time - changes physical/chemical properties. Collagen cross links.
describe heat shock proteins involved in ageing?
- Produced @ time of cell stress. Disassemble damaged proteins and transport in new. Reduced production with age. Decreased ability to cope with stress = ageing.
What is the hayflick phenomena involved in ageing?
- The fibroblasts that are grown in culture do certain # of divisions and then stop, and there is more divisions from a younger source. This is repeated in other cell types, we have biological clock.
- HeLa cell line from Ca breast unlimited division.
Ageing genetic theories: Geronto genes, longevity assurance genes
- Genes are important - twin studies, long lived families, species specific longevity.
- Genes in drosophilia, yeast and nematodes have been seen that can shorten and lengthen life.
There can be a mutation in nematode that doubles 3/52 lifespan by increasing superoxide dismutase.
What can a mutation in nematode do in ageing?
- Doubles 3/52 lifespan by increasing superoxide dismutase.
Characteristic of telomerase
- Chromosome tail = repeated short DNA base sequence
- Stabilise chromosome during cell division, gets shorter with division.
- There is a critical length where divisions can no longer occur - which explains Hayflick phenomena. In germ cells + tumour cells telomerase is produced.
- Germ and tumour cells make telomerase.
characteristics of Mice + telomerase?
- Telomerase activity can change due to changes in comprehensive activity and telomere length in men, with biopsy proven low - risk prostate cancer
• Shown by 10 subjects + 25 age matched controlled. Comprehensive lifestyle changes like diet and activity can alter.
• Findings = telomere length increased from the base level in lifestyle intervention group but fell in control group!
• Telomerase activity fell more in control group than in the lifestyle group
What can telomerase length regulate?
- Can regulate ISG 15 expression in human cells
Genomic stability in ageing: error catastrophe
- Errors in transcription + translation = weird protein production, can be fixed by replacing protein. If the protein is important in DNA repair / protein synthesis might lead to a cascade and then cell death.
- Accumulation of such errors = ageing.
Somatic mutation + DNA repair - what occurs?
- Based on irradiation, shortens life of mice - somatic mutation is now considered not as important because the occurrence rate is too low and DNA repair is sufficient.
- However repair might fail in combo with other toxic agents, like UV and O2 radicals
- DNA repair is more efficient in humans than in mice + more efficient in germ cells! Declines with ageing, which is more seen in cancer
What is the free radical theory of ageing?
- Theory suggests that highly reactive chemical compounds come from enzymatic and non enzymatic reactions, which damage cellular DNA
- Lots of enzymes like super oxide dismutase, catalase, glutathione peroxidase + vitamin E, C, and carotene protect cells - this protection reduces with age.
Describe the mitochondrial theory of ageing?
- Ageing due to mitochondrial DNA damage and there is high exposure to O2 radicals - no protein coat to mitochondrial DNA. There is damage + mutation that increase with age. Genetic mitochondrial dysfunction syndromes mimic ageing.
Cell senescence characteristics?
- Senescent cells # rise with age + are at site of age related pathologies like OA and pancreatic dysfunction.
- Neurogenesis, haemopoesis, and pancreatic function decreases associated with p16 dependent senescence
- Altered gene expression, and upregulated of genes that control enzymes that degrade ECM, inflammatory cytokines and growth factor
- Disrupt normal tissue structure and function and stimulate the growth of premalignant cells.
Ageing changes - describe what happens
- Due to many changes, accumulation of DNA damage = central.
- The energy that is put into DNA repair and protection determines ageing rate.
- Within genetic specific genetic makeup seems to influence rate of ageing via ability to resist DNA damage and external factors can influence ageing rate.
- Calorie restriction can increase lifespan - also causes delayed puberty and increased infection in death prepuberty: okinawa diet.
- Moderate exercise can have + effect
Overcrowding has - effect
What are the functions of parathyroid hormone on bone?
- Stimulates bone resorption
What are the functions of parathyroid hormone on kidney?
- Increases calcium absorption
- Decreases phosphate, HCO3-, and Na+ reabsorption
- 1alpha hydroxylase enzyme
What is the action of vitamin D in calcium homeostasis?
- Increases ca2+ absorption in the gut
- This process needs CaBPs - synthesis is stimulated by vitamin D
- Synergises with PTH on bone
- Inhibits PTH synthesis
- Inhibits 1alpha hydroxylase
describe bones cells involved in tissue structure - osteoBLASTS
- Bone forming cells
- Secrete organic matric (osteoid)
- Bone mineralisation
describe bones cells involved in tissue structure - osteocytes
- May sense mechanical stresses and physiological conditions
- Signal to other cells
describe bones cells involved in tissue structure - osteoclasts
- Bone digesting cells, “diggers”
- Break down bone matrix releasing Ca and Pi into circulation
Describe the overview of bone remodelling
- Continuous cycle of resorption and formation of new bone
Balance between osteoblast and osteoclast activity
Describe the induction of osteoclast differentiation by RANK ligand + define RANK/L and OPG
- Osteoblast stimulates the differentiation of osteoclasts by the production of RANK ligand
- This activates the RANK receptor on the osteoblast precursor
- activation of nuclear kappa beta stimulates gene transcription and differentiation of osteoclasts
- OPG binding to RANK inhibits differentiation
RANK – Receptor Activator of Nuclear kappa beta.
RANKL – RANK ligand
OPG - osteoprotogenin