And now to the quiz Humans get cholesterol from the diet or

And now to the quiz: Humans get cholesterol from the diet or they synthesize it from Acetyl CoA. An adult on a low cholesterol diet synthesizes around 600 mg cholesterol per day. This amount drops dramatically if the person transitions to a red-meat diet. Give a mechanistic explanation for this observation! The amount of HMG-CoA reductase can increase substantially in patients treated with statins. What might be the reason for this side effect? Why do you think some doctors suggest that patients treated with statins also take a coenzyme Q supplement? Why is a drug that prevent reuptake of bile acids often taken together with statins? How many moles of ATP are needed to synthesize one mole of lanosterol (precursor to cholesterol)? Which diet do you think make a person more prone to generate ketone bodies; a \"no-carb diet\" or a \"no-carb diet\" supplemented with glucogenic amino acids such as aspartate and valine? Justify very briefly.

Solution

humans get cholesterol from diet and also from acetyl CoA condensation to HMG CoA. body absorbs cholesterol from the meats. The key enzyme of cholesterol synthesis is hydroxymethylglutaryl-CoA (HMG-CoA) reductase and the key protein of cholesterol uptake is the low density lipoprotein (LDL) receptor. Both HMG-CoA reductase and the LDL receptor are subjected to feedback inhibition by cholesterol. This control mechanism makes sure that when cell membranes contain enough cholesterol no more is either synthesised by the cell or taken up from the circulation. The Nobel Prize winners Michael Brown and Joseph Goldstein have established the molecular mechanism for feedback inhibition by using HMG CoA.

statins block HMG CoA and help in cholesterol management and CVDs. So elevated blood reductase levels are due ot the blocked enzyme present in the blood stream. as there is no cholesterol available the body senses this and will activate mavalonate pathway and this inturn the enzymes in the pathway and statins bind to the HMG CoA.

Coenzyme Q10 is essential for antioxidant activity and also for the muscle cell activity. Statins have side effects on reducing the Q10 levela in the bodies and leads to muscle aches. So the supplement is recommended.

Bile acid sequestrants also given in the statin therapy to reduce the availability of some components of bile so that the bile reabsorption of fast in the gut is prevented. \\