Lecture 13 - metabolic integration part 2

Question 1

What are the characteristics of the fed state?

Answer 1

• high blood glucose
• insulin secreted from the pancreas
• glucose uptake and glycogen formation promoted in the liver and muscle
• excess AA can be catabolized in the liver (BCAA go to muscle and promote protein synth)
• glutamine carries nitrogen to the liver from every tissue in the body that is catabolizing AAs (urea is produced thus preventing alkalosis)
• lipid uptake into adipose tissue

Question 2

What is the composition of urea and NH4+ in the fed state?

Answer 2

90% urea and 10% NH4+

Question 3

How long does the fed state last?

Answer 3

0-2 hours after eating

Question 4

What are some characteristics of the post-absorptive state?

Answer 4

• gut is empty of food
• blood glucose maintained by glucagon, which increases hepatic glycogen breakdown to glucose
• some protein catabolism occurs (muscles secrete more alanine which goes to the liver glucose alanine cycle)
• liver secretes glucose (necessary to maintain glucose for RBC and brain)
• blood glucose supports krebs cycle in all tissues
• fat not yet used as a major source of energy

Question 5

What is the composition of urea in the post-absorptive state?

Answer 5

still mainly urea

Question 6

When does the post-absorptive state occur?

Answer 6

3-18 hours after eating

Question 7

What are some characteristics of the fasted state?

Answer 7

• glycogen pools are empty
• corticosteroids secreted from adrenal glands promote more protein catabolism
• glucogenic AAs are used to make glucose int he liver
• RBCs and brain still require glucose for energy
• blood glucose supports the krebs cycle in all tissues
• alanine and glutamine carry nitrogen
• glucose alanine cycle active
• fat starts to be used for energy
• muscles start breaking down

Question 8

What is the urea and NH4+ composition in the fasted state?

Answer 8

urea decreases
NH4+ increases

Question 9

What are some characteristics of the starvation state?

Answer 9

• body switches primarily to fat usage for energy
• glucagon and catecholamines regulate adipose tissue lipolysis
• fat is predominantly ketogenic (only glycerol backbone is glucogenic)
• tissue metabolism adapts to spare protein loss
• liver produces ketones, which promotes a slight acidosis
• still have to maintain krebs cycle with some protein catabolism
• glutamine carries nitrogen directly to kidney (allows HCO3- to be used to buffer against acidic ketone bodies)
• glucose alanine cycle active
• long term starvation leads to marasmus

Question 10

What is the composition of urea and NH4+ in the starvation state?

Answer 10

10% urea
90% NH4+

Question 11

What is happening in each organ during the fed state?

Answer 11

muscle - protein synthesis BCAA replenish glycogen reserve
liver - clears blood glucose (for glycogen or TAG production); urea cycle active
adipose - TAG synthesis (long term energy storage)
primary hormones - insulin

Question 12

What is happening in each organ during the post-absorptive state?

Answer 12

muscle - glycogen breakdown protein catabolism
liver - glycogen breakdown urea cycle active
aidpose - nothing
primary hormone - glucagon

Question 13

What is happening in each organ during the fasted state?

Answer 13

muscle - protein catabolism
liver - liver produces and secretes glucose via gluconeogenesis, urea cycle activity reduced
adipose - TAG start to become lipolysed (releasing free FA and glycerol)
primary hormone - corticosteroids (glucagon as well)

Question 14

What is happening in each organ during the starvation state?

Answer 14

muscle - muscle protects its protein (still some protein catabolism happening to support blood glucose but not a lot)
liver - ketone production, glycerol backbone of TAG used to make glucose, urea cycle is minimally active
adipose - TAg lipolysis
primary hormones - catecholamines (glucagon as well)