L30: Nutritional Status and Utilization

Question 1

Which molecules are allosteric effectors? What are their signals and affects?

Answer 1

Question 2

Which molecules are inducers of covalent modifications (aka phosphorylations)? Signals and affects?

Answer 2

Question 3

What molecules are regulators of gene expression? Signals? Affects?

Answer 3

Question 4

Fuel preferences / energy needs of RBCs, muscles, brain, adipose and liver

Answer 4

• RBCs: glucose, anerobic metabolism - Non-cardiac muscle: glucose-anaerobic/aerobic, FFAs - Cardiac muscle: glucose aerobically only, FFAs - Brain: glucose aerobically, ketone bodies after serious period of starvation - Adipose: glucose, TAG – FAs - Liver: FAs, glucose, AAs and lactate

Question 5

Describe metabolism of glucose, AAs and FAs in well-fed state

Answer 5

Question 6

In what cells does insulin have a function? What response?

Answer 6

• Muscle: uptake of glucose, production of glycogen - Liver: production of glycogen, production of TAG - Adipose: uptake of glucose

Question 7

Objectives of well-fed state?

Answer 7

• Glucose stored directly in liver and muscles. Excess glucose converted into VLDL for storage in adipose - AAs used for protein synthesis, excess converted into glucose or FAs by liver - TAGs present in chylomicrons are broken down for energy by most cells of body

Question 8

Objectives of early fast?

Answer 8

• Overall: nutrients stored in well-fed are mobilized - Glucose released into circulation from glycogen stores in liver. Muscle uses endogenous glycogen - FAs and glycerol released from adipose for consumption by muscle cells - Ketone bodies produced from FAs by liver - AAs from breakdown of protein released by muscle. Liver converts to glucose and ketone bodies - Urea cycle enzymes induced

Question 9

Describe metabolism of early fast.

Answer 9

Question 10

In what cells does glucagon have a function? What response?

Answer 10

• Liver: stimulates degradation of glycogen, stimulates gluconeogenesis from AA sources, stimulates energy production from AA sources - Adipose: stimulates lipolysis

Question 11

Role of urea cycle during early fast?

Answer 11

• AAs are broken down from muscle and enter the liver to take part in gluconeogenesis or production of ketone bodies/ATP. - To cope with ammonia generation, urea cycle is induced during this period to rid body of this

Question 12

Describe transition from early to late fast

Answer 12

• Occurs after several days of fasting - Glycogen stores become exhausted and brain uses ketone bodies (generated primarily by liver, also minorly by kidney) to reduce glucose consumption - BMR drops

Question 13

Describe problems associated with refeeding and causes of refeeding syndrome. Consider what starvation leads to? How to refeed?

Answer 13

• Starvation: 1.) leads to degradation of digestive enzymes, 2.) depletes intracellular phosphate pools and 3.) depletes potassium stores - Problems: 1.) digestion is impaired and feeding leads to diarrhea and dehydration, 2.) glycolysis starting soaks up phosphate from serum leading to life-threatening hypophosphatemia and 3.) sudden insulin release (insulin moves K into cells) lowers serum potassium further - Watch electrolytes (esp. phosphate and K)

Question 14

Why obese pts can experience starvation?

Answer 14

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Question 15

Metabolic changes that occur during exercise?

Answer 15

• Muscles powered by FAs and glucose - Glycogen depletes more rapidly than fat deposits - After 1 hour of exercise, 50% of glycogen is spent - After 2 hours of exercise, glycogen is depleted and energy comes from FA oxidation