8 - frailty Flashcards
sarcopenia
loss of muscle mass, strength and quality
aging is a … process
heterogenous
how many hallmarks of aging
9
genomic instability
hallmark of aging
DNA damage accumulation
exogenous or endogenous cause
creates lesions
telomere attrition
shortening of telomeres
telomeres are required for normal cell divison
epigenetic alterations
changes in DNA methylation
changes in histone modification
loss of protestasis
proteins become unstable and unfolded
causes aggregation
deregulated nutrient sensing
caused by genetic polymorphisms
growth factors e.g. IGF-1
targets = FOXO/mTOR
mitochondrial dysfunction
destabilisation of ETC
cellular senescence
stable arrest of cell cycle
stem cell exhaustion
types of stem cell:
- haematopoietic
- mesenchymal
- satellite
- intestinal epithelial
altered intracellular communication
neuroendocrine dysfunction
inflammaging
immunosenescence
programmes theory of aging
deteriation is inevitable over time
- programmed longevity
- endocrine theory
- immunological theory
programmed longevity
sequential switching on and off of switches over time causes deteroiration
damage and error theory consists of 5 parts
wear and tear rate of living cross-linking proteins free radicals somatic DNA damage
rate of living theory
greater metabolism = shorter life span
free radicals theory
cause oxidative damage to macromolecular cell components
what does ELISA stand for
enzyme-linked immunosoribent assay
what is ELISA
plate based assay technique
what does elisa used for
detecting and quantifying peptides, proteins, antibodies and hormones
rt-pcr stands for
reverse transcriptase polymerase chain reaction
rt-pcr steps
- convert RNA population to cDNA by reverse transcription
2. amplify cDNA by PCR
why is rt-pcr useful
allows more detailed study of original RNA species even if they are expressed in low abundance
uses of rt-pcr
detection of expressed genes
examination of transcript variants
generation of cDNA templates for cloning and sequencing
one step rt-pcr
single tube combines cDNA synthesis and PCR otgether reduces variation reduces contamination quicker
two step rt-pcr
cDNA synthesis and PCR in separate tubes and reaction s
used for detecting multiple genes in the same sample
can reach optimum reaction conditions
longer workflow
less contamination
how do you test for different genes in the same sample with rt-pcr
2 step method
make different specific primers for each time you run PCR
define senescence
loss of a cell’s power to divide and grow
main mechanism of senescence
telomere shortening
why do telomeres shorten
linear DNA is not completely replicated every mitosis
DNA damage response
when telomeres reach a critically short length
they become dysfunctional
hayflick limit
when a cell has reached its maximum amount of times it can divide
why are cancer and stem cells immortal
their DNA doesnt shorten
no hayflick limit
they express telomerase
telomerase
adds telomere back on when lost
effect of DNA damage/telomere malfunction
premature senescence
benefit of senescence
helps prevent tumours
cons of senescence
causes ageing
age-releated diseases
prevents tissues reparing well
accumulation of senescence
negatively affects tissue structure and fucntion leading to frailty
Senescence associated secretory phenotype
secreted factors by senescing cells
e..g proinflammatory cytokines, chemokines, proteases, growth factors
immunosenescence
gradual deterioration of the immune system with age
immunosenescence cellular effects
defects in haematopoietic stem cells
defects in peripheral lymphocyte migration, maturation and function
overall effects of immunosenescence
increased infection , cancer and autoimmune disease
why does immunosenescence cause decreased adaptive immune resposne
causes decreased antigen presentation
thymic involution
immunosenescence causes decrease in thymuc tissue mass
leads to loss of naive t cells
inflammaging
chronic inflammation associated with age
chronic inflammatory cytokine production
process of inflammaging
irritation causes cell membrane damage
causes arachidonic acid to be cut into leukotrienes and prostaglandins
inflammatory leukotrienes cause free radical damage
effect of free radicals produced by inflammaging
cause elastase and collagenase to affect skin and destruct skin structure
role of inflammaging in cancer
reduces immune response to new antigens
direct ELISA
target antigen bound to bottom of well
complementary primary labelled antibody added
antibody binds to antigen
enzyme label catalyses colour change reaction
advantages of direct elisa
cross-reactivity of secondary antibody eliminated
not max reactivity as antibody is labelled
indirect elisa
antigen bound to bottom
primary antibody added and binds to antigen
well washed to remove any non-bound antibodies
secondary enzyme-linked antibody added
- complementary to constant region of primary antibdy
enzyme label causes colour chnage
advantages of inirect elisa
maximum immuno-reactivity of primary antibody as it isnt labelled
sandwich elisa
antibody bound to bottom of well target antigen added and binds well washed - removes non-bound antigen secondary enzyme-labelled antibody added colour change measured
advantages of sandwich elisa
allows concentration of unknown substances to be measured
most common one
characteristics of apoptosis process
chromatin condensation
nuclear fragmentation
blebbing and cell shrinkage
release of apoptotic bodies
extrinsic apoptosis pathway
Fas binds to death receptor transautophosphrylation of RTK death inducing complex formed activation of caspase-8 activation of effector caspases e.g. caspase-3 apoptosis
intrinsic apoptosis pathway
intracellular damage/ no growth factor Bad not phosphorylated Bcl-2 inihibited mitochondrial dysfunction release of cytochrome-c into cytosol caspase-9 activated effector caspases activated - eg caspase-3 apoptosis
Bad protein in presence of trophic factor
Bad gets phosphorylated
binds to Bcl-2
no apoptosis
process of necrosis
cell swells chromatin digested organelle membranes disrupted cells lyse and spill contetns hydrolytic enzymes damage neighbouring cells inflammation
cause of auto-phagy
response to cell starvation and stress or if organelles wear out
source of energy for cell
autophagy in cellular homeostasis
digestion of intracellular components
degradation products transloacted to cytoplasm
microautophagy
invagination of lysosomal membrane
sequesters proteins and degrades
macroautophagy steps
isolation membrane
vesicle elongates to form phagophore
autophagosome formation - double membrane
LC3 allows binding to lysosome
autolysosome forms
contents broken down by acid proteases/hydrolytic enzymes
defects in autophagy
prevent cells from clearing unwanted proteins/microbes
allow disease manifestation
principal mechanism for protein catabolism
ubiquitin proteasome pathway
role of E1-activating enzyme
binds to Ub
primes Ub
adds ATP
role of E2-conjugating enzyme
binds to Ub and replaces E1
escorts Ub to E3 enzyme
role of E3-ubiquitin ligase enzyme
acts as a platform fro E2-Ub complex to bind to targeted protein
Ub is then transferred to protein
type I skeletal muscle fibres
slow twitch fibres red aerobic respiration slow-contracting low myosin ATPase activity
type IIa skeletal muscle fibres
fast oxidative fibres red aerobic respiration fast-contracting higher myosin ATPase activity
type llb skeletal muscle fibres
fast glycolytic fibres white fast-contracting anaerobic respiration lower capactiy for ATP production sparser capillary network less sustainable
what triggers contraction of cardiac muscle
calcium induced calcium release
triggers opening of ryanodine receptor
characteristics of cardiac muscle
involuntary
striated - intercalated disks
cardiomyocyte
heart muscle cell
diseases of cardiac muscle
caused by restriction to blood supply
angina
myocardial infarction
t-tubules in cardiac muscle
bigger/wider than skeletal muscle
transmit action potentials to cells core
regulate Ca2+ conc in excitation-contraction coupling
angina
obstruction to coronary arteries
reduces blood flow to heart
heart cant contract properly
chest pain
PI3/Akt pathway until PIP3 is activated
signal binds to RTK
receptor dimerisation and transautophosphorylation
PI3 recruited via SH2 domain
PIP2 converted to PIP3
PI3/Akt pathway once PIP3 is activated
PIP3 recruits Akt and PDK-1 via their PH domains
PIP3 binds to Akt
Akt phosphorylated by MTORC2 and PDK-1
Akt downstream affects
3 downstream effects of phosphorylated Akt
1 - activation of Rheb by inactivation of TSC2
MTORC1 activated - growth
2 - activation of AIP (apoptosis inhibiting) by inactivating Bad - cell survival
3 - inactivation of FOXO (T. factor) which prevents transcription of atrogenes in myofibres (prevents autophagy)
3 overall effects of PIP2/Akt pahway
activation of MTORC1 - cell growth
inhibition of apoptosis - cell survival
inhibition of autophagy
PI3-Kinase
converts PIP2 to PIP3
mTOR
mammalian target of rapamycin
mTOR involevd in
cell growth, proliferation
regulation of mTOR
growth factors, insulin, glucose
inactivated TSC2
activated Rheb
activated MTORC1
mTOR pathway in presence of growth factor
Akt causes inactivation of TSC2 activation of Rheb (Rheb-GTP) activae mTOR cell growth
mTOR in absence of growth factor
TSC2 active acts as a GAP to Rheb Rheb-GDP (inactive) inactive mTOR no cell growth
myostatin
protein produced and released by myocytes that inhibits myogenesis
myogenesis
determines muscle fibre number in development and muscle size in adults
increased myostatin
decreased muscle mass
effect of myostatin on Akt
inhibits Akt
inhibition of protein synthesis
myofibirl degradation
muscle atrophy
inhibition of myostatin as a therapuetic
for sarcopenia (prevent muscle wasting)
IGF-1
insulin like growth factor
produced in liver
stimualted by growth hormone
binds to RTK
IGF-1 pathway
IGF-1 binds to RTK receptor dimerisation and transautophosphorylation activation of PI3-K via SH domain PIP2 to PIP3 Akt recruited mTOR pathway initiated protein synthesis etc
effects of IGF-1
protein synthesis
inhibition of proteolysis
stimulates nutrient uptake
IRS-1
signalling adaptor protein
has a PH domain
binds to RTKs
IRS-1 pathway
ligand binds to RTKs
transautophosphorytion
IRS-1 binds via PH domain
recruits docking proteins bind via SH2 domains
e.g. grb2 and PI3-K
Activates downstream pathways e.g. MAPK and PI3-K/Akt
