121 - Regulation of Energy Systems Flashcards
Components of daily energy expenditure 1 2 3 4
1) Sleeping metabolic rate + Arousal
2) Basal metabolic rate (when awake)
3) Thermic effect of food (heat released when food is digested)
4) Activity (variable amount of energy expenditure)
Measurements of energy expenditure 1 2 3 4 5
1) Doubly-labelled water
2) O2 consumption
3) Heart rate-based estimation of VO2
4) Activity monitors
5) Population-based algorithms
Doubly-labelled water
Label H and O in water, look at how quickly it is metabolised.
Very accurate, but difficult to do.
How can VO2 be estimated with measuring heart rate?
Linear relationship between the two.
Can be inaccurate, as factors other than VO2 can alter heart rate.
Determinants of energy expenditure 1 2 3 4 5
1) Adrenaline, thyroid hormones
2) Muscle mass and oxidative capacity
3) Exercise/physical activity levels
4) Non-exercise activity thermogenesis
5) Shivering thermogenesis
Effect of oxidative capacity on basal metabolism
More oxidative fibres in muscle (slow-twitch) associated with lower body mass. Might metabolise fat more effectively.
Non-exercise activity thermogenesis
Fidgeting, tapping, etc during day can expend energy.
Brown fat
Similar metabolic profile to muscle.
Present in low amounts in adults.
Uptakes glucose particularly in cold conditions.
Uncoupling protein
Uncouples e- transport chain with mitochondrial ATPase, making the process much more inefficient. Need to expend more energy to make the same amount of ATP, generating a lot of heat in the process.
Brown fat has high transcription levels of uncoupling protein, used by hibernating animals.
50% of current anti-obesity drugs target what?
CNS
Examples of hormones that inhibit hunger (short-term)
CCK, GLP-1, PYY (short-term)
Examples of hormones that inhibit hunger (long-term)
Leptin
Leptin and regulation of body mass
Released by adipose tissue.
As adiposity increases, leptin levels increase, which reduces drive to eat.
Effect of genetic leptin deficiency
Increase in adiposity.
Why can’t obesity be treated with leptin?
Leptin insensitivity arises