Case 3: Hypercholesterolemia
A 36-year-old man was found to have hypercholesterolemia. A dietary evaluation indicated that he was consuming about 600 mg/day of cholesterol. His plasma concentration on two separate occasions was approximately 330 mg/dl. Ultracentrifugal analysis revealed that the cholesterol elevation was due to an increase in plasma LDL. He was treated with a cholesterol-free vegetarian diet for 3 months, but his plasma cholesterol level decreased to only 300 mg/dl. Subsequently he was treated with colestipol-HCl, bile acid-binding resin that is not absorbed. The resin binds bile acids, causing increased amounts to be excreted in the feces. This treatment lowered the fasting plasma cholesterol concentration to 250 mg/dl.
Discuss this case by applying the cholesterol absorption, transport and metabolic pathways and answer the following questions:
1. How is dietary cholesterol absorbed?
2. How is it possible for a patient to continue to have high plasma cholesterol after being on a cholesterol-free diet for 3 months?
3. What connection is there between bile acids and cholesterol?
4. How does a bile acid-binding resin (fiber) lower the plasma cholesterol concentration?
5. Would you combine this drug with statins? If yes what is the benefit?
Case 4: Obesity
A 19-year-old woman sought medical help because she was 30 kg
Overweight. Most of her excess weight was in the form of adipose
Tissue. A medical history revealed that her diet was extremely poor.
Much of her caloric intake was carbohydrate-candy. Cookies. Cake.
Soft drinks and beer; her dietary fat intake was actually quite moderate.
BIOCHEMICAL QUESTIONS
1. How is it possible to form excess amounts of triglyceride in the body if a diet contains predominantly carbohydrate?
2. How does acetyl CoA generated inside the mitochondria reach the cytoplasm for use by the fatty acid biosynthetic pathway?
3. Why is bicarbonate required for fatty acid synthesis?
4. How are sulfhydryl groups involved in the action of fatty acid synthase?
5. How might the carbohydrate ingested by this patient supply the NADPH needed for fatty acid biosynthesis?
