Lipid Metabolism

Question 1

What is the anti-inflammatory cytokine?

Answer 1

IL-10

Question 2

What needs to happen to fat before any enzymes can effectively be broken down?

Answer 2

They must be emulsified in bile salts (it increases the surface area of the fats to be hit by enzymes)

Question 3

What are the three forms of consumed fat?

Answer 3

Triacylglycerol, phospholipids, and cholesterol ester

Question 4

What cuts triacylglerol? And where is it cut? What are products?

Answer 4

Pancreatic lipase cuts the fatty acids off at carbons 1 and 3 creating 2 fatty acids and 1 mono-acylglycerol

Question 5

What cuts the fatty acid off of monoacylglycerol?

Answer 5

PLA-2 (also from the pancreas) which cuts the number 2 fatty acid from the triacylglycerol. It stands for phospholipase A 2. (think of it as pancreatic lipase 2 for our purposes, as it cuts the fatty acid from the second carbon from triacylglycerol)

Question 6

What goes into chylomicrons?

Answer 6

Triglycerides (they were broken down by lipase’s into fatty acids and 2 monoacylgylcerol, but the intestinal epithelial cells re-esterify the glycerol to make TAG)

Question 7

Where do short and medium chain fatty acids go from the gut epithelial cells?

Answer 7

Portal blood

Question 8

What breaks cholesterol Esters?

Answer 8

cholesterol esterase. It frees a fatty acid and a cholesterol

Question 9

What breaks phospholipids and what do you get?

Answer 9

Phospholipase A2 cuts off the fatty acid from carbon three and you are left with Lysophospholipid.

Question 10

Where do chilomicrons go from the gut?

Answer 10

It leaves the gut epithelial cell and goes through side tube out of gut through lymphatic canniculi b/c you want the fats from the chylomicrons to be used as energy sources, so they bypass liver and go through thoracic duct.

Question 11

What is the major apoprotein of chilomicrons? What does it do?

Answer 11

ApoB-48 binds fat globs that had been taken up into the ER of epithelial cells and makes nascent chylomicrons.

Question 12

Talk a little bit about ApoB-48 genetics

Answer 12

It is on the same gene as ApoB-100 (which is for VLDL and takes fat from carbohydrates) and it has an early stop signal put in by INTESTINAL EPITHELIAL CELLS RNA EDITING capabilities. So the protein is shorter and works for making nascent chylomicrons

Question 13

What proteins do nascent chylomicrons need added?

Answer 13

ApoCII and ApoE and they get them from HDL

Question 14

What is HDL’s main function?

Answer 14

Maintain cholesterol and apoprotein homeostasis. It is from liver and donates ApoCII and ApoE to make mature chilomicrons. HDL also returns particles to the liver

Question 15

What happens if there was no HDL?

Answer 15

Chylomicrons wouldn’t mature and you would have high blood fat.

Question 16

How do muscle and adipose cells get fat from the chilomicrons?

Answer 16

Lipoprotein Lipase is an extracellular lipase in capillary beds of muscle and adipose cells which is ACTIVATED BY APOCII. It can then take fatty acids to make energy or make adipose tissue

Question 17

What happens as chylomicrons lose all their fats?

Answer 17

Gets smaller and more dense and eventually becomes a remnant which is taken up by the liver which snags it by the LDL receptor which interacts with ApoE. Components of the remnant can then be recycled into new VLDL particles

Question 18

How is VLDL synthesis different than chylomicrons?

Answer 18

TAG component is from a different source (its in the liver). So it uses ApoB100. Dumb card if you remembered ApoB100, but hey, i always forget this shit.

Question 19

As VLDL delivers fats to tissues, what happens?

Answer 19

It gets smaller and more dense. It becomes ILDL, then LDL. Then the receptors for ApoE take it back into the liver.

Question 20

List the proteins on chylomicrons we should know

Answer 20

ApoB48, ApoCII, ApoE. Note: REMNANTS HAVE NO ApoCII

Question 21

What are important proteins on VLDL?

Answer 21

ApoB100, ApoCII and ApoE. Note, LDL has only ApoB100

Question 22

Why is it that adipose cells can only store fatty acids as triacylglycerolin the fed state?

Answer 22

The glycerol 3-phosphate backbones can only be produced by glycolysis in the adipocyte.

Question 23

To what can the LDL receptor bind?

Answer 23

ApoB100 and ApoE