Musculoskeletal Ageing: Osteoporosis, Osteoarthritis, and Sarcopenia Flashcards
What is functional reserve and how does it change with old age?
Ability to look after self
Decreases
What happens once the functional reserve threshold is reached?
Loss of independence
What is sarcopenia?
Loss of muscle mass, quality, strength
What is the impact of sarcopenia?
Decreases functional reserve - drives frailty, mortality
Does muscle strength or mass decline faster with age?
Strength
Is loss of muscle strength or mass the key risk factor for disability in old age?
Strength
Name a test of muscle strength
Grip strength
Which pathologies in ageing muscle underlie sarcopenia?
Decreased actin and myosin
Decreased mitos
Increased fat infiltration
Name the age-related risk factors for sarcopenia
Decreased anabolic hormones (e.g. IGF1, oestrogen, testosterone)
Anorexia of ageing
Increased catabolic stimuli (inflammatory cytokines)
Physical inactivity
Which is the biggest age-related risk factor for sarcopenia?
Physical inactivity
What is the effect of testosterone replacement therapy in old men?
Increased muscle mass and strength
What is the effect of oestrogen replacement therapy in old women?
Inconclusive
Why does anorexia of ageing occur?
Depression
Drug side effects
Which treatment can reverse sarcopenia?
Resistance training
Which pathway regulates muscle mass?
PI3k-Akt
Which pathway is upstream of the PI3k-Akt pathway?
Insulin/IIS signalling
What are the 2 pathways in PI3k-Akt signalling and their effects on muscle?
mTOR activation - increased protein synthesis - muscle growth
Myostatin causes PI3k inhibition - activates FOXO (transcription factor) - MuRF-1 expression - muscle breakdown
How do extreme periods of inactivity in the elderly affect muscles?
Decreased leg mass and strength
Decreased mTORC1 signalling
Increased MuRF-1 expression
Decreased protein synthesis
What is the evidence for a role of inflammation in sarcopenia?
COPD patients have increased MuRF-1 expression Sepsis patients (inactivity and pro-inflammatory state) have decreased strength
What is immunosenescence?
Decline in immune function with age - includes inflammageing
What is inflammageing?
Chronic inflammation with age
Which cell type produces IL-6?
Myocytes
Name a pro-inflammatory cytokine
IL-6
What is the effect of IL-6 on muscle?
Increases proteasomal activity - increases muscle breakdown
Induces insulin resistance - decreases Akt-mTOR activity
Which catabolic hormone is produced in the inflammatory response?
Cortisol
Which enzyme synthesises cortisol?
11β-HSD1
How do 11β-HSD1 levels change with age and what causes this?
Increase
Induced by TNFalpha and IL-6
What is the effect of TNF-alpha administration in mice?
Increased proteasome activity, PI3-Akt suppression - muscle loss
Name an anti-inflammatory cytokine
IL-10
How do the levels of IL-10 change with age?
Decrease
What is the effect of an IL-10 KO in mice?
Develop sarcopenia
How does the number of leukocytes change in frail older people?
Increases
How does neutrophil chemotactic ability change with age and what is the effect of this?
Decreases
Inefficient neutrophil migration - causes tissue damage - causes inflammageing
How can neutrophil chemotactic ability be restored in older people?
Pharmacological PI3K inhibition
What are the 3 main factors causing sarcopenia in old age?
PI3K-Akt signalling dysregulation
Inflammation
Physical inactivity
How does inflammageing affect cortisol production and what is the impact of this?
Increases - causes muscle breakdown
What are the direct and indirect effects of PI3K-Akt signalling dysregulation on sarcopenia?
Direct - decreased muscle synthesis, increased degradation
Indirect - via inflammageing
Is old age sarcopenia preventable?
Yes
Which is the best form of physical activity to prevented the age-related decline in muscle strength?
Strength training
Name 4 sarcopenia treatments
Exercise - best method
Hormone replacement - side effects
Vitamin D - mixed evidence
Myostatin antagonists - untested
In which distinct areas is there continuous remodelling of bone?
Bone metabolic units
Which cell type controls bone formation?
Osteoblasts
Which cell type controls bone reabsorption?
Osteoclasts
Why is a homeostatic balance required in bone?
Maintain bone mass and strength
How do the levels of osteoblasts and osteoclasts change over the life-course?
Bone growth up to ~30yrs old - osteoblasts>osteoclasts
Midlife plateau - osteoblasts=osteoclasts
Decline after peak - osteoclasts>osteoblasts
How does bone marrow fat change with ageing and what is the impact of this?
Increases
Favours differentation of mesenchymal stem cells (MSCs) to adipocytes - instead of osteoblasts - prevents bone growth
What causes the age-related decline in MSC proliferative capacity?
Telomere shortening
Accumulation of DNA damage
What is osteoporosis
Decline in bone mass and microarchitecture - less dense bone matrix
What is an implication of osteoporosis?
Increases fracture risk
What are the intrinsic (non-modifiable) osteoporosis risk factors?
Gender (post-menopausal women) Age Small body size Ethnicity (Caucasian/Asian) Family history - part hereditary
What was the effect on bone of older people with a later menopause or longer reproductive life in the NSHD?
Increased bone density
What are the modifiable osteoporosis risk factors?
Sex hormones (low oestrogen/testosterone)
Low dietary calcium and vitamin D
Inactivity
Smoking
Why does viamin D insufficiency worsen osteoporosis?
Vitamin D required for osteoblastogenesis
Which scanning type can be used to asses bone mass density?
DEXA scanning
What are the 3 main aims of osteoporosis treatments?
Inhibit osteoclasts
Increase osteoblast activity
Regulate bone marrow adipogenesis
Name 3 osteoporosis treatments
Bisphosphonates
Vitamin D
Denosumab
What is denosumab and how does it work?
Monoclonal antibody to RANKL
RANKL bound to RANK - on osteoclasts
Denosumab binding inhibits osteoclast activity
What is zoledronate and how does it work?
Bisphosphonate
Affects mTOR signalling - decreases DNA damage - extends MSC lifespan - preserves ability to proliferate and differentiate
What is osteoarthritis?
Breakdown of joint cartilage and underlying bone
What are the risk factors for osteoarthritis and which is the biggest?
Age - biggest
Obesity
Genetics
Previous joint injury
What are the 2 main mechanisms behind osteoarthritis?
Mechanical stress on joint
Inflammation