chatgpt Flashcards
1
Q
What are the liver’s roles in lipid homeostasis?
A
- Synthesizes and secretes VLDL
- Major site for cholesterol and bile acid synthesis/secretion
- Major site for LDL uptake (40–60%)
- Uptake of chylomicron remnants, VLDL, IDL, LDL, and HDL cholesterol
2
Q
What happens after consuming a lipid-rich meal?
A
- Liver coordinates lipid digestion-absorption with enterohepatic circulation
- Exogenous lipid absorption predominates
- Chylomicrons drain into bloodstream at thoracic duct
- TGs are removed by LPL in adipose/muscle
- Remnants go to liver → cholesterol stored, repackaged, or excreted
3
Q
What happens during inter-digestive and post-prandial phases?
A
- Inter-digestive: Liver receives FA & glycerol from adipose
- Post-prandial: Liver synthesizes FA & phospholipids, excreted into bile with cholesterol to form micelles
4
Q
Describe enterohepatic circulation of bile acids.
A
- Synthesized in liver, stored in gallbladder
- Released into duodenum post-meal
- Reabsorbed mostly in ileum
- 95% reabsorbed; 5% excreted
- 80–90% reabsorbed bile acids are recycled by liver
- Conjugated with glycine/taurine → secreted again
5
Q
Which transport mechanisms are used for bile acid absorption?
A
- Jejunum/colon: passive diffusion (unconjugated)
- Ileum: active transport (conjugated via bile salt transporters)
6
Q
What is the composition of VLDL?
A
- Triacylglycerol (TAG), Phospholipids, Cholesterol, Cholesteryl esters (CE), Proteins (ApoB100)
7
Q
What happens to VLDL after secretion?
A
- Transported in blood
- Lipolysis via LPL → IDL → LDL
- LDL = ‘bad cholesterol’
8
Q
What is the role of ApoB100 and MTP in VLDL synthesis?
A
- ApoB100: structural protein
- MTP: mediates lipidation of ApoB100
- Without lipidation, ApoB100 is degraded (post-translational regulation)
9
Q
What determines ApoB100 degradation or VLDL assembly?
A
- Lipid-poor state: ApoB100 is degraded
- Lipid-rich state: VLDL is assembled and secreted
10
Q
How does VLDL synthesis differ in fed vs fasting states?
A
- Fasting: delivers endogenous lipids from adipose
- Feeding: incorporates dietary fats and DNL
11
Q
What are the TAG input sources for the liver?
A
- Fatty acid flux (adipose lipolysis)
- Dietary fat (chylomicron remnants)
- De novo lipogenesis (DNL)
12
Q
What are the TAG output pathways?
A
- VLDL synthesis and secretion
- Oxidation
13
Q
What leads to hepatic steatosis (fatty liver)?
A
- Imbalance between TAG input and output
- Impaired VLDL assembly/secretion
- Excess TAG stored in lipid droplets
14
Q
What happens when TAG input > output in liver?
A
- Homeostasis fails
- TAG accumulates
- Steatosis develops → fatty liver disease
