Bile synthesis and enterohepatic circulation

Which of the following is not involved in the pathway of bile salt production in the liver?

• Chenodeoxycholic acid

• 7⍺-hydroxylase

• Cholehydroxylic acid

• Glycine

Answer explanation

True or false? 7⍺-hydroxylase can be inhibited by bile salts or increased Vit C.

• True

• False

Answer explanation

7⍺-hydroxylase can be inhibited by bile acids or decreased Vit C.

Which of the following is false in the regulation of bile acid synthesis?

• Bile acids bind to farnesoid X-receptor

• Retinoid X-receptor activates farnesoid X-receptor

• Farnesoid and retinoid X-receptors inhibit the transcription of 7⍺-hydroxylase

• 7⍺-hydroxylase can be activated by cholestyramine

Answer explanation

Bile acids bind to FXR which activates RXR > inhibit transcription of 7⍺-H > reduction in processing of cholesterol and bile salt synthesis

7⍺-H is an ideal drug target to control plasma cholesterol levels > activated by drugs like statins and cholestyramine

About 95% of bile salts are reabsorbed into blood and recirculated into liver bile. Where are these secondary bile salts reabsorbed?

Which of the following is not involved in bile pigment production?

• Macrophage

• Heme oxygenase

• Biliverdin reductase

• Stercobilin

Answer explanation

Haem component is separated from RBC when digested by macrophages

Heme oxygenase converts heme to biliverdin

Biliverdin reductase converts biliverdin to unconjugated bilirubin

Bilirubin is conjugated with glucoronic acid to form conjugated bilirubin

Stercobilin and urobilin are metabolised from conjugated bilirubin to be excreted mainly as faeces (a small amount of urobilin is recycled in the liver/processed into urine).

Is unconjugated bilirubin soluble in water?

• Yes

• No

What binds to unconjugated bilirubin to transport it to the liver?

In which section of the intestines is conjugated bilirubin secreted into?

• Mid-duodenum

• Terminal duodenum

• Start of ileum

• Caecum

What gives urine its colourlessness?

• Urobilin

• Stercobilin

• Urobilinogen

• Bilirubin

Which liver function markers indicates an intrahepatic cause of jaundice? (select two)

• AST

• ALT

• ALP

• GGT

Answer explanation

ALT and AST = inTrahepatic, raised during hepatocellular damage

ALP = Posthepatic, raised in biliary cholestasis

GGT = posthepatic but can also be raised significantly in alcoholic ingestion

*for AST and ALT, ALT is more specific to liver damage

AST/ALT > 2 : specific to alcoholic hepatitis

AST/ALT = 1 : associated with tissue ischaemia

AST/ALT < 1 : non-alcoholic hepatocellular damage