Exam 25: Lipid Transport

Routine blood studies on an infant show turbid plasma with markedly elevated levels of triacylglycerol.A sample of plasma that has been left in the refrigerator overnight has cream-colored material floating on top.The underlying plasma is clear.Which type of hyperlipoproteinemia is most likely present in this infant?

Excess cholesterol needs to be transported to the liver because it cannot be metabolized in most extrahepatic tissues.This "reverse" transport of cholesterol requires a lipoprotein that is not required for other routes of cholesterol transport.This lipoprotein is:

A 5-year-old boy develops severe stomach pain after eating a big piece of fatty cheesecake.The serum amylase level is found to be mildly elevated.The plasma triglyceride level is 1200 mg/dL, and the total cholesterol level is 220 mg/dL.The parents mention that the child does not like fatty foods at all, but this was the first time he tasted cheesecake.Which apolipoprotein might be deficient in this patient to account for his fat intolerance?

A 33-year-old man is found to have tendon xanthomas.When questioned about his lifestyle, he says that he exercises regularly, eats balanced meals, and is not in any physical distress.A blood analysis reveals a plasma total cholesterol level of 350 mg/dL and a triglyceride level of 70 mg/dL.He is treated with cholestyramine and a statin and sent for further analysis.His hyperlipidemia is best classified as:

On physical examination, you notice that a patient has tendon xanthomas.A blood analysis reveals a total cholesterol level of 350 mg/dL, which results mainly from raised levels of LDL, and normal levels of triglyceride.What other investigation would be helpful in this patient?

Cholestyramine can be used for the treatment of hypercholesterolemia, either alone or in combination with a statin.Which enzyme is most immediately affected by cholestyramine treatment?

You culture fibroblasts from a patient in the laboratory.In order to up-regulate the LDL receptors in these cells, you should:

Statins are the most important type of cholesterol-lowering drug, and they lower specifically LDL rather than HDL cholesterol.How do the statins lower LDL cholesterol?

Hypercholesterolemic patients taking 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) produce less cholesterol from endogenous synthesis.Lower intracellular cholesterol levels induce which of the following regulatory changes?