Muscle 8 Flashcards
How much muscle mass is lost from 20-80?
50%
How does muscle change with age?
Increase in fat mass and non muscle fat free mass
What happens to protein balance with age?
Protein breakdown exceeds synthesis-negative protein balance
What is sarcopenia and where is it noticeable?
- Loss of skeletal muscle mass, strength and power with aging and inactivity
- Most notable in weight bearing lower limb and trunk muscle groups
What fibre type does sarcopenia affect?
Type II myofibre atrophy, myofibre type grouping and fibre necrosis
What happens to the food response with age?
Reduced anabolic food response - blunted increase in protein synthesis with food intake
What happens to basal blood glucose levels in ICU patients?
Increased - hyperglycaemic - impairs other cellular processes
How much muscle mass lost in 10 days in ICU and what impact does multi-organ failure have?
20%
Muscle mass exacerbated and more rapid
When did patients in ICU have reduced muscle quality and what did this consist of?
Day 7
Infiltration of non-muscle cell types and macrophages - inflammation and muscle breakdown
What % of functional capacity do ICU patients recover?
70%
What did exercise do for ICU patients?
Stand after 11 days instead of 15
What does LPS (lipopolysaccharide) cause?
Translocation of NFB to nucleus - pro inflammatory cytokines released
What does LPS do to protein synthesis?
No change in protein breakdown markers but 40-50% reduction in protein synthesis
What is the initial effect of LPS?
Stops animals eating
What effect does LPS have on glucose levels and body mass?
- LPS reduced circulating blood glucose - stimulates glucose uptake to tissues
- LPS admin leads to reduced body mass - within 24 hours reduced muscle mass by 25%
What does a tumour cause?
- Secretes inflammatory factors - apoptosis
- Alters protein, fat, CHO and aa metabolism across the body
- Increased protein breakdown and aa oxidation
- Decreased protein synthesis and amino acid transport
What happens with amino acids if there is increased protein breakdown?
Increased release (alanine and glutamine)
Why is glutamine important for tumours?
Glutamine released from skeletal muscle is rapidly taken up by the tumour - can be converted to serine and shunted into carbon metabolism to increase growth of cells
How do tumour cells get energy?
Increase glucose output from liver
What happens to IGF-1 and myostatin levels in cancer?
Reduced IGF-1: decreased protein synthesis
Myostain: increases and supresses protein synthesis
What does FOXO do?
Increased transcription of MAFBX and MURF1 (E3 ligases) - regulate protein breakdown
What reduction in muscle mass does cancer cachexia lead to?
15-25%
What does Atrogin1/MAFBX do?
Tags proteins for breakdown, and directly regulates protein synthesis by reducing capacity of protein synthetic machinery
What is eLF3-f important for?
Binds to mTOR to start translation and protein synthesis
