Starvation/Integration - Dr. Groseclose

Question 1

Name the tissues of the body that are most dependent on glucose.

Answer 1

Brain, RBCs, and Muscle

Question 2

What are the “favored” substrates of skeletal muscle?…of heart?…brain?…RBC’s?

Answer 2

Muscle: Fatty acids, ketone bodies, and glucose

Brain: glucose and ketone bodies (Ex. acetone)

RBC: glucose

Question 3

What is the role of adipose tissue?

Answer 3

Stores triacylglycerols (by using Glucose to provide glycerol 3-phosphate) and releases Fatty acids and glycerol.

Question 4

Discuss the formation of ketone bodies: What are the reactions? How do they influence the metabolism of skeletal muscle? Which organ forms them, and where are they used?

Answer 4

Ketone bodies are created via decaboxylation of acetoacetone to create acetone. Condensation of two acetone molecules form acetoacetyl CoA, which is then converted to HMG CoA. HMG CoA is then split into acetyl CoA and Acetoacetate (ketone body).

Metabolism of ketone bodies occur in the liver but is used in the skeletal muscle.

Question 5

What are the advantages of fat (triglycerides) over glycogen as an energy-storage form?

Answer 5

They are more compact storage forms.

Question 6

Which two hormones are most important for the control of energy metabolism in the body? What are their predominant effects?

Answer 6

Insulin and Glucagon, Insulin increases [glycogen], [protein], and [fatty acids]. Glucagon decreases [glycogen], [protein], and [fatty acids].

Question 7

Which organs are responsive to insulin?

Answer 7

Muscle and adipose. Liver is not very responsive.

Question 8

Discuss the importance of renal gluconeogenesis.

Answer 8

Renal Gluconeogenesis spares the energy of urea synthesis and helps to correct acidosis.

Question 9

What is the single most important determinant of length of survival of starvation?

Answer 9

The ability/efficiency in the metabolism of Fat and Proteins (to a lesser extent)

Question 10

What is the hexosamine pathway? What is the enzyme that characterizes this pathway?

Answer 10

The Hexoxamine pathway converts Glucose to UDP-GlcNAc (UDP-N-acetylglucosamine), which depending on feast or famine, goes to glycosylation (feast) or is converted into protein (famine)

Glutamine:fructose 5:phosphate amitransferase (GFAT)

Question 11

What substance can be used as fuel but is NOT a stored fuel source?

Answer 11

Protein

Question 12

What organ is responsible for control of making fatty acids, ketone bodies and glucose?

Answer 12

Liver

Question 13

What two substances stimulates glucagon secretion?

Answer 13

Epinephrine and Cortisol (stress hormone)

Question 14

What substances via the hypothalamus affect feeding behavior?

Answer 14

Leptin (makes people eat more) and ghrelin

Question 15

What would you measure to determine nutrition status, biochemically?

Answer 15

UDP-N-acetylglucosamine (UDP-GlcNAc)

Question 16

What does the presence of inflammation tell you about the treatment of malnutrition?

Answer 16

Inflammation absent = treatable via nutritional resuscitation

Inflammation present = limited effectiveness of nutritional intervetion

Question 17

What are possible consequences of refeeding someone who has been malnourished too long?

Answer 17

tachycardia
tachypnea
delirium
vomiting
coma
death

Question 18

Why are ketone bodies good to be used “in a pinch” situation when there is no glucose?

Answer 18

They are water soluble, need no plasma carrier or insulin, and inhibits glucose metabolism.