Lipid Disorders — MCQs
A person is diagnosed with familial type IIa hyperlipoproteinemia. What is the basic defect in this type of hyperlipoproteinemia?
Which apolipoprotein is the primary structural component of LpA-I particles?
Which of the following is not the criteria for diagnosis of Metabolic syndrome?
Which of the following enzymes is not targeted by hypolipidemic drugs?
Which lipoprotein is involved in reverse cholesterol transport?
What is the drug with the highest efficacy to increase plasma HDL?
Which of the following represents a desired lipid parameter for cardiovascular risk control in hypertension?
All of the following are true about nephrotic syndrome except?
HMG-CoA reductase is inhibited by:
Vitamin B12 deficiency can give rise to all of the following, except which of the following?
Lipid Disorders Indian Medical PG Practice Questions and MCQs
Question 1: 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 2: Which apolipoprotein is the primary structural component of LpA-I particles?
- A. Apo B-48
- B. Apo A-I (Correct Answer)
- C. Apo A-II
- D. Apo B-100
Explanation: ***Apo A-I*** - **Apolipoprotein A-I (Apo A-I)** is the main structural and functional protein of **high-density lipoprotein (HDL)**. - It plays a crucial role in **reverse cholesterol transport**, facilitating the removal of excess cholesterol from peripheral tissues back to the liver. *Apo B-48* - **Apo B-48** is found exclusively in **chylomicrons**, which are responsible for transporting dietary lipids from the intestines. - It is synthesized in the **intestine** and is critical for the assembly and secretion of chylomicrons. *Apo A-II* - **Apo A-II** is another apolipoprotein found in HDL particles, but it is not the primary structural component. - While present, it is less abundant than Apo A-I and its precise role is still being researched, though it may influence **HDL metabolism**. *Apo B-100* - **Apo B-100** is the primary structural protein of **low-density lipoprotein (LDL)** and very-low-density lipoprotein (VLDL). - It is essential for the binding of LDL to the **LDL receptor**, mediating the uptake of cholesterol into cells.
Question 3: Which of the following is not the criteria for diagnosis of Metabolic syndrome?
- A. High LDL (Correct Answer)
- B. Hyperiglyceridemia
- C. Hypertension
- D. Central obesity
Explanation: ***High LDL*** - While **high LDL (low-density lipoprotein)** is a risk factor for cardiovascular disease [1], it is **not** one of the specific diagnostic criteria for metabolic syndrome. - The criteria for metabolic syndrome focus on a cluster of metabolic abnormalities associated with insulin resistance. *Hypertriglyceridemia* - **Elevated triglycerides** (typically ≥ 150 mg/dL or on drug treatment for elevated triglycerides) is one of the key diagnostic criteria for metabolic syndrome. - It reflects impaired lipid metabolism often associated with insulin resistance [2]. *Hypertension* - **Elevated blood pressure** (systolic ≥ 130 mmHg or diastolic ≥ 85 mmHg, or on antihypertensive drug treatment) is a core component of metabolic syndrome. - Hypertension in this context is often linked to underlying insulin resistance. *Central obesity* - **Increased waist circumference** (varying by ethnicity and sex, e.g., >102 cm in men and >88 cm in women for adults of European descent) is a primary criterion for metabolic syndrome. - It is a strong indicator of visceral fat accumulation, which is closely linked to insulin resistance [3].
Question 4: Which of the following enzymes is not targeted by hypolipidemic drugs?
- A. HMG Co A reductase
- B. Lipoprotein lipase
- C. Acyl CoA, cholesterol acyl transferase 1
- D. Peripheral decarboxylase (Correct Answer)
Explanation: ***Peripheral decarboxylase*** - **Peripheral decarboxylase** (also known as DOPA decarboxylase) is involved in the synthesis of dopamine from L-DOPA and is a target for drugs used in **Parkinson's disease**, not hypolipidemic drugs. - Its inhibition by drugs like **carbidopa** or **benserazide** prevents the peripheral conversion of L-DOPA to dopamine, increasing L-DOPA availability for the brain. *HMG Co A reductase* - **HMG-CoA reductase** is the rate-limiting enzyme in cholesterol biosynthesis and is the primary target for **statins** (e.g., atorvastatin, simvastatin). - Statins effectively lower **LDL cholesterol** by inhibiting this enzyme, reducing endogenous cholesterol production. *Lipoprotein lipase* - **Lipoprotein lipase (LPL)** activity can be enhanced by certain hypolipidemic drugs, such as **fibrates**, which activate **PPAR-α**. - Increased LPL activity leads to enhanced hydrolysis of **triglycerides** from VLDL and chylomicrons, reducing triglyceride levels in plasma. *Acyl CoA, cholesterol acyl transferase 1* - **Acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors** were developed as potential hypolipidemic agents to prevent cholesterol esterification and absorption. - While not widely used clinically due to efficacy and side effect profiles, **ACAT1** is involved in cholesterol esterification in the intestine and liver, making it a target for reducing cholesterol absorption.
Question 5: Which lipoprotein is involved in reverse cholesterol transport?
- A. LDL
- B. HDL (Correct Answer)
- C. VLDL
- D. Chylomicrons
Explanation: ***HDL*** - **High-density lipoprotein (HDL)** is responsible for **reverse cholesterol transport**, which involves picking up excess cholesterol from peripheral tissues. - This cholesterol is then transported back to the liver for excretion or recycling, hence HDL is often referred to as "good cholesterol." *LDL* - **Low-density lipoprotein (LDL)** primarily transports **cholesterol from the liver to peripheral tissues**, contributing to plaque formation in arteries. - It is often called "bad cholesterol" because high levels are associated with an increased risk of **atherosclerosis** and cardiovascular disease. *VLDL* - **Very-low-density lipoprotein (VLDL)** is synthesized in the liver and primarily transports **endogenous triglycerides** to peripheral tissues. - As triglycerides are removed, VLDL is converted into **intermediate-density lipoprotein (IDL)** and eventually to LDL. *Chylomicrons* - **Chylomicrons** are formed in the small intestine and are responsible for transporting **exogenous (dietary) triglycerides** and cholesterol absorbed from the gut to various tissues. - They are the largest and least dense lipoproteins, appearing after a fatty meal.
Question 6: What is the drug with the highest efficacy to increase plasma HDL?
- A. Ezetimibe (Zetia)
- B. Gemfibrozil (Lopid)
- C. Rosuvastatin (Crestor)
- D. Nicotinic acid (Niacin) (Correct Answer)
Explanation: ***Nicotinic acid (Niacin)*** - Niacin has the **highest efficacy** among lipid-lowering drugs in increasing **plasma HDL cholesterol** levels, often by 15-35%. - It works by reducing the **hepatic synthesis of VLDL** (and thus LDL) as well as increasing the half-life of HDL. *Ezetimibe (Zetia)* - Ezetimibe primarily acts by inhibiting the **absorption of cholesterol** from the intestine. - While it lowers LDL cholesterol, its effect on **increasing HDL** is modest at best, typically in the single digits. *Gemfibrozil (Lopid)* - Gemfibrozil is a **fibrate** that is best known for significantly lowering **triglycerides** and increasing HDL cholesterol modestly. - Its effects on HDL are generally **less robust** than those of niacin, usually in the range of 10-20%. *Rosuvastatin (Crestor)* - Rosuvastatin is a **statin**, which primarily works by inhibiting **HMG-CoA reductase**, leading to a significant reduction in LDL cholesterol. - While statins can cause a small increase in HDL, typically about 5-10%, this effect is **not its primary mechanism** of benefit nor its greatest strength compared to niacin.
Question 7: Which of the following represents a desired lipid parameter for cardiovascular risk control in hypertension?
- A. LDL / cholesterol > 10 mg%
- B. HDL < 30 mg%
- C. HDL / cholesterol ratio < 3.5
- D. Cholesterol/HDL < 3.5 (Correct Answer)
Explanation: Cholesterol/HDL < 3.5 [1] - A total cholesterol-to-HDL ratio of less than 3.5 is considered optimal for cardiovascular risk reduction. - This ratio indicates a favorable balance, where the proportion of 'good' HDL cholesterol is relatively high compared to total cholesterol. LDL / cholesterol > 10 mg% - This option is unclear and likely misphrased, as LDL cholesterol is typically measured independently, not as a ratio to total cholesterol in this manner [1]. - Desired LDL levels are typically much lower than 100 mg/dL for high-risk individuals, and a ratio of LDL to total cholesterol greater than 0.1 (or 10%) is generally observed, but not a specific target for reduction [1]. HDL < 30 mg% - An HDL level less than 40 mg/dL (or 30 mg% for some contexts) is considered low and undesirable, as high HDL is protective against cardiovascular disease [1]. - This value would indicate increased cardiovascular risk, contrary to a desired parameter. HDL / cholesterol ratio < 3.5 - This ratio, as stated, is the inverse of the commonly used and desirable total cholesterol-to-HDL ratio. - If the HDL/cholesterol ratio were less than 3.5, it would imply a relatively low HDL compared to total cholesterol, which is an undesirable cardiovascular risk factor [1].
Question 8: All of the following are true about nephrotic syndrome except?
- A. Hypoalbuminemia
- B. Proteinuria >3.5 g/day
- C. Increased risk of infection
- D. Decreased serum triglycerides (Correct Answer)
Explanation: ***Decreased serum triglycerides*** - Nephrotic syndrome is characterized by **hyperlipidemia**, including **elevated total cholesterol** and **triglycerides**, due to increased hepatic synthesis of lipoproteins and decreased catabolism [1]. - This is a direct consequence of the body's attempt to compensate for low oncotic pressure and is a major diagnostic feature. *Hypoalbuminemia* - This is a **hallmark characteristic** of nephrotic syndrome, resulting from the significant loss of albumin in the urine [1]. - A low serum albumin level (typically <3.0 g/dL) contributes to **edema** due to decreased plasma oncotic pressure [1]. *Proteinuria >3.5 g/day* - This is the **defining diagnostic criterion** for nephrotic syndrome, indicating massive protein excretion through damaged glomerular capillaries [1]. - The protein loss is specifically defined as >3.5 grams per 1.73 m² of body surface area per day. *Increased risk of infection* - Patients with nephrotic syndrome are prone to infections, particularly **bacterial infections** like spontaneous bacterial peritonitis [1]. - This increased risk is due to the urinary loss of **immunoglobulins** (especially IgG), complement factors, and impaired cellular immunity [1].
Question 9: HMG-CoA reductase is inhibited by:
- A. Lovastatin (Correct Answer)
- B. Gemfibrozil
- C. Nicotinic acid
- D. Clofibrate
Explanation: ***Lovastatin*** - **Lovastatin** is part of the statin class of drugs, which are potent competitive inhibitors of **HMG-CoA reductase**. - By inhibiting this enzyme, statins reduce the synthesis of **mevalonate**, a precursor to **cholesterol**, thereby lowering LDL-cholesterol levels. *Gemfibrozil* - **Gemfibrozil** is a **fibrate**, a class of drugs that primarily act by activating **peroxisome proliferator-activated receptor alpha (PPAR-α)**. - Its main effect is to decrease **triglyceride** levels and increase **HDL cholesterol**, not directly inhibit HMG-CoA reductase. *Clofibrate* - **Clofibrate** is also a **fibrate** and operates similarly to gemfibrozil by activating **PPAR-α**. - It primarily reduces **triglycerides** and has a modest effect on increasing HDL, but does not inhibit HMG-CoA reductase. *Nicotinic acid* - **Nicotinic acid** (niacin or vitamin B3) reduces hepatic synthesis of **VLDL** and inhibits the release of **fatty acids** from adipose tissue. - This leads to a decrease in **LDL cholesterol** and triglycerides, and an increase in **HDL cholesterol**, but it does not directly inhibit HMG-CoA reductase.
Question 10: Vitamin B12 deficiency can give rise to all of the following, except which of the following?
- A. Optic atrophy
- B. Peripheral neuropathy
- C. Myopathy (Correct Answer)
- D. Myelopathy.
Explanation: ***Myopathy*** - **Myopathy**, or muscle disease, is not a direct consequence of **Vitamin B12 deficiency**. - **Vitamin B12 deficiency** primarily affects neurological and hematological systems due to its role in myelin synthesis and DNA production. [1] *Myelopathy* - **Myelopathy**, specifically subacute combined degeneration of the spinal cord, is a classic neurological complication of **Vitamin B12 deficiency**. - This involves demyelination of the posterior and lateral columns, leading to symptoms like **ataxia** and **sensory deficits**. *Optic atrophy* - **Optic atrophy** or **toxic amblyopia** can occur in severe cases of **Vitamin B12 deficiency**. - This damage to the **optic nerve** results in progressive vision loss. *Peripheral neuropathy* - **Peripheral neuropathy**, characterized by symptoms like **paresthesias**, numbness, and weakness, is a common neurological manifestation of **Vitamin B12 deficiency**. - It results from **demyelination** and axonal degeneration of peripheral nerves.
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