Dyslipidemias and Atherosclerosis — MCQs

10 questions

A patient with tendon xanthomas, Increased LDL and cholesterol. What is the most probable diagnosis?

Which among the following is the false statement regarding statins?

A person is diagnosed with familial type IIa hyperlipoproteinemia. What is the basic defect in this type of hyperlipoproteinemia?

Which of the following is not true about atherosclerosis?

What is the primary role of cholesterol in low-density lipoprotein (LDL) metabolism?

Atorvastatin is used as an anti-dyslipidemic drug. These drugs inhibit their target enzyme by:-

Which gene defect causes familial hypercholesterolemia?

A person switches from a high-fat diet to a low-fat diet with a compensatory increase in carbohydrates to maintain the same caloric intake. Which lipoprotein is likely to increase?

Consider the following statements with reference to 'trans fatty acids' : 1. They are geometrical isomers of cis-unsaturated fatty acids. 2. Though atherogenic, being unsaturated they are less so than saturated fatty acids. 3. It takes years for trans fatty acids to be flushed from the body. 4. They lower both LDL cholesterol and HDL cholesterol in the body. Which of the statements given above are correct ?

Q10Easy

Which organ does not utilise ketone bodies?

Dyslipidemias and Atherosclerosis Indian Medical PG Practice Questions and MCQs

Question 1: A patient with tendon xanthomas, Increased LDL and cholesterol. What is the most probable diagnosis?

A. Type II Hyperlipoproteinemia (Correct Answer)
B. Type III Hyperlipoproteinemia
C. Abetalipoproteinemia
D. Type I Hyperlipoproteinemia
E. Type IV Hyperlipoproteinemia

Explanation: ***Type II Hyperlipoproteinemia*** - This type is characterized by significantly **elevated LDL and total cholesterol** due to a defect in LDL receptor function or APOB-100. - **Tendon xanthomas** are a classic physical finding in Type II hyperlipoproteinemia, specifically in familial hypercholesterolemia. *Type III Hyperlipoproteinemia* - This condition involves increased levels of **chylomicron remnants** and **VLDL remnants (IDL)**, leading to elevated cholesterol and triglycerides. - While xanthomas can occur (e.g., **palmar xanthomas**), tendon xanthomas are less typical, and the primary lipid abnormality isn't isolated LDL elevation. *Abetalipoproteinemia* - This is a rare autosomal recessive disorder resulting in the **absence of LDL, VLDL, and chylomicrons** in the blood. - Patients present with **fat malabsorption**, neurologic symptoms, and generally have very low or undetectable cholesterol and triglyceride levels, which is contrary to the clinical presentation. *Type I Hyperlipoproteinemia* - This disorder is characterized by a deficiency of **lipoprotein lipase (LPL)** or its cofactor, APO C-II, leading to extremely high levels of **chylomicrons** and **triglycerides**. - While eruptive xanthomas can be seen, **tendon xanthomas** are not a feature, and the primary abnormality is hypertriglyceridemia, not elevated LDL. *Type IV Hyperlipoproteinemia* - This condition is characterized by **elevated VLDL** and **triglycerides** with normal or slightly elevated LDL. - Xanthomas are generally not a feature, and the primary abnormality is hypertriglyceridemia rather than hypercholesterolemia with elevated LDL.

Question 2: Which among the following is the false statement regarding statins?

A. These drugs should not be stopped even in severe conditions like injury, surgery etc.
B. Although HMG-CoA reductase inhibitors substantially reduce the risk of cardiovascular events, there is mild increase in lipoprotein a (Lpa) levels.
C. With the long term use, there is slight increase in the incidence of type 2 diabetes mellitus.
D. They can be given with verapamil and other enzyme inhibitors (Correct Answer)

Explanation: ***They can be given with verapamil and other enzyme inhibitors*** - This statement is **FALSE** and is the correct answer because **verapamil** (a moderate CYP3A4 inhibitor) and other potent CYP3A4 inhibitors like **clarithromycin** or **azole antifungals** can significantly increase statin concentrations, raising the risk of adverse effects like **myopathy** and **rhabdomyolysis**. - **Co-administration** of statins with these inhibitors generally requires careful dose adjustments or avoidance, as they increase the systemic exposure to most statins (especially **simvastatin**, **atorvastatin**, and **lovastatin**). *These drugs should not be stopped even in severe conditions like injury, surgery etc.* - This statement could be considered false in certain contexts, as statins **can be temporarily held** in acute, severe conditions like sepsis, major trauma, or complex surgery, especially if there's a concern for **acute kidney injury** or **rhabdomyolysis** [1]. - However, in most routine surgical situations, statins are typically continued due to their cardiovascular protective effects. *Although HMG-CoA reductase inhibitors substantially reduce the risk of cardiovascular events, there is mild increase in lipoprotein a (Lpa) levels.* - This statement is **TRUE**. Statins are associated with a **modest increase in Lp(a) levels** (approximately 10-20%), which has been consistently demonstrated in clinical studies [2]. - While statins effectively lower **LDL cholesterol**, Lp(a) levels are largely **genetically determined** and may paradoxically increase with statin therapy, though this effect is generally considered clinically insignificant compared to the overall cardiovascular benefits [2]. *With the long term use, there is slight increase in the incidence of type 2 diabetes mellitus.* - This statement is **TRUE**. Long-term statin use is associated with a **small but statistically significant increase** in the risk of developing **type 2 diabetes mellitus** (approximately 9-12% increased risk), particularly in individuals with pre-existing risk factors like **metabolic syndrome**. - This risk, however, is generally **outweighed by the cardiovascular benefits** of statin therapy in at-risk patients, making it an acceptable trade-off.

Question 3: A person is diagnosed with familial type IIa hyperlipoproteinemia. What is the basic defect in this type of hyperlipoproteinemia?

A. Lipoprotein lipase deficiency
B. Defective LDL receptor (Correct Answer)
C. Abnormal activity of Apo E
D. Overproduction of LDL

Explanation: ***Defective LDL receptor*** - **Familial hypercholesterolemia** (Type IIa hyperlipoproteinemia) is characterized by high levels of **LDL cholesterol** due to a genetic defect in the **LDL receptor** gene. - This defective receptor leads to impaired clearance of LDL particles from the bloodstream, resulting in their accumulation. *Lipoprotein lipase deficiency* - This defect is associated with **Type I hyperlipoproteinemia**, which is characterized by elevated **chylomicrons** and **triglycerides**, not primarily LDL cholesterol. - **Lipoprotein lipase (LPL)** is essential for the hydrolysis of triglycerides in chylomicrons and VLDL. *Abnormal activity of Apo E* - Variants of **Apolipoprotein E (Apo E)**, particularly Apo E2, are associated with **Type III hyperlipoproteinemia** (familial dysbetalipoproteinemia). - This condition involves increased levels of **chylomicron remnants** and **VLDL remnants** (IDL), not primarily isolated LDL elevation. *Overproduction of LDL* - While increased **LDL production** can contribute to elevated LDL levels, the primary genetic defect in familial type IIa hyperlipoproteinemia is strictly related to the impaired **clearance** of LDL due to a defective **LDL receptor**, rather than solely overproduction. - Many secondary causes of hypercholesterolemia can involve LDL overproduction, but Type IIa is specifically linked to the receptor defect.

Question 4: Which of the following is not true about atherosclerosis?

A. Deposition of lipids on vessels
B. It is an inflammatory response to endothelial injury
C. Always involves small arterioles (Correct Answer)
D. Necrosis of Vessels

Explanation: ***Does not involve small arterioles*** - Atherosclerosis predominantly affects **large and medium-sized arteries** [1], especially the **aorta**, coronary, and carotid arteries. - Small arterioles are generally not involved; instead, they are more affected in conditions like **hyaline arteriolosclerosis** [2]. *Deposition of lipids on vessels* - This option is true; atherosclerosis involves **accumulation of lipids** in the arterial wall [3][4], including cholesterol. - The buildup of lipids leads to **plaque formation** [3], causing narrowing and potential occlusion of the artery. *It is an inflammatory response to endothelial injury* - This statement is accurate; atherosclerosis is driven by **endothelial injury**, leading to an inflammatory response [3]. - Events such as **oxidation of LDL** and recruitment of inflammatory cells play crucial roles in the pathogenesis. *Necrosis of Vessels* - This option is misleading; while atherosclerosis can lead to ischemia and cell death, it is not primarily characterized by **necrosis of vessels** itself. - Rather, it results from **luminal narrowing** and plaque rupture, not direct tissue necrosis in the arterial wall. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 507-508. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 498-499. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Cardiovascular Disease, pp. 268-270. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 504-505.

Question 5: What is the primary role of cholesterol in low-density lipoprotein (LDL) metabolism?

A. Cholesterol binds to receptors on cell membranes.
B. Excess cholesterol in cells reduces the number of LDL receptors. (Correct Answer)
C. Cholesterol regulates the activity of enzymes involved in cholesterol metabolism.
D. Cholesterol in LDL is primarily involved in transporting cholesterol to tissues.

Explanation: ***Excess cholesterol in cells reduces the number of LDL receptors.*** - High intracellular **cholesterol levels** signal the cell to *downregulate* the production of **LDL receptors** via the **SREBP-2 pathway**. - This negative feedback mechanism prevents excessive accumulation of cholesterol within cells and maintains cellular **cholesterol homeostasis**. - This is the primary regulatory mechanism specifically related to **LDL receptor-mediated metabolism**. *Cholesterol binds to receptors on cell membranes.* - It is actually the **LDL particle**, specifically its **apolipoprotein B-100 (apoB-100)** component, that binds to the **LDL receptors** on cell membranes. - While cholesterol is the cargo within LDL, it does not directly bind to the receptors itself. *Cholesterol regulates the activity of enzymes involved in cholesterol metabolism.* - While **intracellular cholesterol levels** do regulate various enzymes (e.g., **HMG-CoA reductase** via SREBP-2, and **ACAT**), this describes cholesterol's broader role in **cholesterol synthesis regulation** rather than specifically in **LDL metabolism**. - The question asks specifically about cholesterol's role in **LDL metabolism**, which refers to the receptor-mediated pathway and its regulation. *Cholesterol in LDL is primarily involved in transporting cholesterol to tissues.* - This statement describes the *function of LDL itself*, which is to transport cholesterol to peripheral tissues. - However, the question asks for the **primary role of cholesterol *in* LDL metabolism**, referring to its regulatory effects on the LDL receptor pathway rather than its transport function.

Question 6: Atorvastatin is used as an anti-dyslipidemic drug. These drugs inhibit their target enzyme by:-

A. Noncompetitive inhibition
B. Competitive inhibition (Correct Answer)
C. Irreversible inhibition
D. Uncompetitive inhibition

Explanation: ***Competitive inhibition*** - Atorvastatin is a **statin**, which acts as a **competitive inhibitor** of **HMG-CoA reductase**, the rate-limiting enzyme in cholesterol synthesis. - It competes with the natural substrate, HMG-CoA, for binding to the **active site of the enzyme**, thereby reducing cholesterol production. *Uncompetitive* - **Uncompetitive inhibitors** bind only to the **enzyme-substrate complex**, not to the free enzyme. - This type of inhibition is characterized by a decrease in both **apparent Vmax** and **apparent Km**. *Noncompetitive inhibition* - **Noncompetitive inhibitors** bind to an allosteric site on the enzyme, distinct from the active site, and can bind to either the **free enzyme or the enzyme-substrate complex**. - This leads to a decrease in the **apparent Vmax** but does not affect Km. *Irreversible inhibition* - **Irreversible inhibitors** form a **strong covalent bond** with the enzyme, permanently inactivating it. - Statins do not form covalent bonds with HMG-CoA reductase; their inhibition is **reversible** upon drug discontinuation.

Question 7: Which gene defect causes familial hypercholesterolemia?

A. LDL Receptor (Correct Answer)
B. Apo E
C. Apo CII
D. Apo B48

Explanation: ***LDL Receptor*** - Familial hypercholesterolemia (FH) is primarily caused by mutations in the **LDL receptor (LDLR) gene**, which leads to impaired clearance of **low-density lipoprotein (LDL)** from the blood. - This defect results in significantly elevated levels of **LDL cholesterol** and an increased risk of premature cardiovascular disease. *Apo E* - Mutations in the **Apo E gene** are associated with **Type III hyperlipoproteinemia (dysbetalipoproteinemia)**, characterized by elevated **chylomicron remnants** and **VLDL remnants**. - This condition presents with xanthomas and premature atherosclerosis, but is distinct from the primary defect in FH. *Apo CII* - **Apo CII** is a cofactor for **lipoprotein lipase (LPL)**, an enzyme essential for the breakdown of **triglycerides** in chylomicrons and VLDL. - Deficiency in Apo CII or LPL causes **Type I hyperlipoproteinemia (familial chylomicronemia syndrome)**, leading to marked **hypertriglyceridemia**, not hypercholesterolemia. *Apo B48* - **Apo B48** is a structural component of **chylomicrons**, which are responsible for transporting dietary fats from the intestines. - It is not directly involved in the primary defect of **LDL clearing** that characterizes familial hypercholesterolemia.

Question 8: A person switches from a high-fat diet to a low-fat diet with a compensatory increase in carbohydrates to maintain the same caloric intake. Which lipoprotein is likely to increase?

A. Chylomicron
B. IDL
C. HDL
D. VLDL (Correct Answer)

Explanation: ***VLDL*** - A low-fat diet with increased **carbohydrates** can lead to increased hepatic synthesis of triglycerides, which are then packaged into **VLDL** particles for transport from the liver. This is because excess carbohydrates can be converted to fatty acids and then to triglycerides in the liver. - The liver's increased triglyceride production, driven by abundant **glucose** from carbohydrates, directly corresponds to a rise in **VLDL** secretion to export these lipids. *Chylomicron* - **Chylomicrons** primarily transport **dietary fats** (exogenous triglycerides) absorbed from the intestine. - Switching to a low-fat diet would typically lead to a *decrease* in chylomicron production, as less dietary fat is available for absorption. *IDL* - **IDL** (Intermediate-Density Lipoprotein) is a remnant of **VLDL** metabolism, formed after VLDL loses some triglycerides. - While VLDL may increase, leading to *more* IDL formation, IDL itself is not the primary component that *increases* directly due to high carbohydrate intake; rather, the precursor **VLDL** is directly affected. *HDL* - **HDL** (High-Density Lipoprotein) is involved in **reverse cholesterol transport**, picking up excess cholesterol from peripheral tissues and returning it to the liver. - High carbohydrate intake, especially refined carbohydrates, can sometimes lead to a *decrease* in HDL levels, not an increase.

Question 9: Consider the following statements with reference to 'trans fatty acids' : 1. They are geometrical isomers of cis-unsaturated fatty acids. 2. Though atherogenic, being unsaturated they are less so than saturated fatty acids. 3. It takes years for trans fatty acids to be flushed from the body. 4. They lower both LDL cholesterol and HDL cholesterol in the body. Which of the statements given above are correct ?

A. 1 and 3 only
B. 2, 3 and 4
C. 1 only (Correct Answer)
D. 1, 3 and 4

Explanation: ***1 only*** - **Statement 1 is CORRECT**: Trans fatty acids are **geometrical isomers of cis-unsaturated fatty acids**, differing in the spatial arrangement of hydrogen atoms around the carbon-carbon double bond. This structural difference gives them physical and biological properties more similar to saturated fats. - **Statement 2 is INCORRECT**: Trans fatty acids are **MORE atherogenic** than saturated fatty acids, not less. They raise LDL cholesterol and lower HDL cholesterol more significantly than saturated fats. - **Statement 3 is INCORRECT**: Trans fatty acids are metabolized and eliminated from the body within **days to weeks**, not years. Long-term cardiovascular damage results from chronic dietary exposure, not slow elimination kinetics. - **Statement 4 is INCORRECT**: Trans fatty acids **raise LDL cholesterol** ("bad" cholesterol) and **lower HDL cholesterol** ("good" cholesterol). They do not lower both as stated. *1 and 3 only* - Statement 1 is correct, but statement 3 is **incorrect**. The body processes and eliminates trans fatty acids relatively quickly (days to weeks), not years. The detrimental cardiovascular effects accumulate due to chronic dietary exposure, not slow metabolism of individual molecules. *2, 3 and 4* - All three statements are **incorrect**. Statement 2 is wrong because trans fats are **more atherogenic** than saturated fats. Statement 3 is wrong because trans fats are metabolized within weeks, not years. Statement 4 is wrong because trans fats **raise LDL** (not lower it) while lowering HDL. *1, 3 and 4* - Only statement 1 is correct. Statement 3 is **incorrect** as trans fatty acids are metabolized within weeks, not years. Statement 4 is **incorrect** because trans fatty acids **increase LDL cholesterol** and **decrease HDL cholesterol** - they do not lower both.

Question 10: Which organ does not utilise ketone bodies?

A. Liver (Correct Answer)
B. Brain
C. Skeletal muscles
D. Cardiac muscles

Explanation: **Explanation** The correct answer is **A. Liver**. **1. Why the Liver cannot utilize Ketone Bodies:** The liver is the primary site for **ketogenesis** (the synthesis of ketone bodies), but it cannot utilize them for energy. This is because the liver lacks the essential enzyme **Thiophorase** (also known as Succinyl-CoA:3-ketoacid CoA transferase). In extrahepatic tissues, Thiophorase converts Acetoacetate into Acetoacetyl-CoA by transferring a CoA group from Succinyl-CoA. Without this enzyme, the liver cannot activate ketone bodies to enter the TCA cycle, preventing a "futile cycle" where the liver would consume the fuel it is supposed to export to the rest of the body. **2. Why the other options are incorrect:** * **B. Brain:** During prolonged fasting or starvation, the brain adapts to use ketone bodies (specifically 3-hydroxybutyrate and acetoacetate) as its primary energy source, reducing its dependence on glucose. * **C & D. Skeletal and Cardiac Muscles:** These tissues possess high levels of Thiophorase. In the early stages of fasting, muscles are the primary consumers of ketone bodies to spare glucose for the brain. **High-Yield NEET-PG Pearls:** * **Rate-limiting enzyme of Ketogenesis:** HMG-CoA Synthase (Mitochondrial). * **Ketone bodies include:** Acetone (non-metabolizable, excreted in breath), Acetoacetate, and β-Hydroxybutyrate. * **Site of Ketogenesis:** Mitochondria of hepatocytes. * **Key Enzyme for Utilization:** Thiophorase (absent in Liver). * **Clinical Sign:** "Fruity odor" of breath in Diabetic Ketoacidosis (DKA) is due to the excretion of Acetone.

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