Adipocytes

Question 1

What is the relative abundance of adipose tissue?

Answer 1

Men: 15-20% of body weight in normal-weight men
Women: 20-25% of body weight in normal-weight women

Question 2

How does white adipose tissue store fatty acids (as triglycerides)?

Question 3

How does white adipose tissue release fatty acids (as triglycerides)?

Question 4

How does neuronal signaling impact storage/release of fatty acids

Answer 4

• Adjacent neurons release norepinephrine (NE)
• extracellular NE signals an increase in intracellular cAMP
• cAMP activates a lipase within the adipocytes
• Free fatty acids and glycerol are liberated from triglycerides
• Free fatty acids and glycerol diffuse into adjacent capillaries
• Free fatty acids bind albumin for transport
• glycerol is often taken back up by the liver

Question 5

How does hormonal signaling impact storage/release of fatty acids?

Answer 5

Insulin: Inhibit lipase keeping the triglycerides from breaking down
Glucagon and Growth Hormone: Promotes the release of free fatty acid

Question 6

How does white adipose tissue release hormones to regulate the energy status of the animal?

Answer 6

Adiponectin: moderate energy metabolism
Resistin: glucose homeostasis; impedes insulin activity
Leptin: monitors energy status and satiety

Question 7

What are the structural and functional differences between white and brown adipocytes?

Answer 7

Brown: multilocular, many mitochondria, ‘non-shivering’ thermogenesis
White: unilocular, a repository for energy storage, endocrine signaling (energy balance)

Question 8

What is the function of thermogenin in brown adipocytes (excess energy ~ heat)

Answer 8

supplies heat by allowing the dissipation of the proton gradient without ATP synthesis