Regulation of fuel selection during endurance exercise

Question 1

What enzyme does carbohydrate oxidation rely on, and is considered the ‘gatekeeper’ of oxidative metabolism?

Answer 1

Pyruvate dehydrogenase (PDH)

Question 2

How is PDH activated?

Answer 2

Dehydrogenation

Question 3

What is the main relationship between carb and fat oxidation?

Answer 3

It is all about acetyl-CoA

Question 4

What are the factors which stimulate the actions of hormones involved in lipolysis?

Answer 4

Increased epinephrine
Increased Ca2+

Question 5

What enzyme produces fatty acyl CoA?

Answer 5

fatty acyl CoA synthase

Question 6

What decreases fat oxidation at higher intensities?

Answer 6

• Decreased plasma FA availability
• Decreased IMTG lipolyis,
• Decreased mitochondrial fat uptake

Question 7

How is PDH regulated?

Answer 7

PDH is under covalent control. It exists in an inactive form at rest and transitions to an active form via Ca2+ during exercise. The influence of Ca2+ (and pyruvate) keeps appropriate amount of PDH in active form, despite increases in acetyl-CoA that would normally inactivate the enzyme at rest.

Question 8

What protein facilitates the influx of glucose into cells and increases glucose delivery?

Answer 8

GLUT4

Question 9

At roughly what intensity (% VO2 max) does fuel use shift to carbohydrate and less reliance on fat?

Answer 9

> 70% VO2 max

Question 10

What is beta-HAD?

Answer 10

An extremely important enzyme involved in beta-oxidation