Bile Acids; Absorption and Digestion of Fats Flashcards
What are the biological functions of bile acids?
Bile acid synthesis provides a mechanism for cholesterol excretion. They also produce emulsification to stabilize the oil-water interface so the oils will not aggregate into larger participles.
Their detergent-like actions are necessary within the intestinal track for uptake of hydrophobic nutrients.
What is the nature of enterohepatic circulation of bile acids?
- Bile salts secreted into the intestine are reabsorbed and reused.
- Mixture of bile acids and bile salts absorbed are transported from the intestinal mucosal cells into the portal blood and are returned to the liver parenchymal cells.
- The liver then converts both primary and secondary bile acids into bile salts by reconjugation with glycine or taurine and re-secretes them into the bile
What is cholesterol-7-alpha-hydroxylase?
It converts Cholesterol to Cholic Acid.
Cholic Acid will inhibit it and Cholesterol activates it
What happens when the carboxyl group of Cholic acid is conjugated with glycine or Taurine?
It becomes a bile salt
What does Intestinal Flora do to Bile Salts?
Bacteria in the intestine remove glycine and taurine from bile salts, causing them to revert back to unconjugated bile acids.
What is Cholestyramin?
It is a bile acid sequestrant. It is positively-charged and binds bile acids in the gut, preventing reabsorption and ultimately promoting their excretion.
When do use Cholestyramin?
You use it in the treatment of hypercholesterolemia, because the removal of bile acids relieves the inhibition on bile acid synthesis in the liver, and ultimately diverts additional cholesterol into that pathway.
What does Dietary fiber do?
Binds bile acids/bile salts and increases their excretion
What causes Cholesterol stone disease?
Caused by a decrease of bile salts in the bile. Results from
- Extensive reabsorption of bile acids/bile salts from the intestine
- Obstruction of the biliary tract, interrupting enterohepatic circulation
- Severe hepatic dysfunction, leading to decreased synthesis of bile salts
What do Fibrates do?
Used to reduce serum triglycerides and increases HDL levels. They activate lipoprotein lipase and are used in combination with statin therapy. They tend to increase cholesterol content in the bile and increase the risk for gallstone disease
What do lipases do?
Play a role in lipid digestion. They are also important digestive enzymes in individuals who have pancreatic insufficiency (cystic fibrosis).
How are Triacylglycerols degraded?
Esterase (pancreatic lipase) removes fatty acids.
How are Cholesterol esters degraded?
By Pancreatic cholesterol ester hydrolase. This activity is greatly increased in the presence of bile salts
How are phospholipids degraded?
Pancreatic phospholipase
