Dyslipidemia Overview Quiz

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Questions and Answers

What is the most common type of dyslipidemia?

Hyperlipidemia (correct)

Hypercholesterolemia

Hypolipidemia

Hypocholesterolemia

Which condition is characterized by low levels of lipoproteins?

Hypolipoproteinemia (correct)

Hyperglyceridemia

Hyperlipoproteinemia

Hypertriglyceridemia

What is one factor that can raise HDL levels?

High-fat diet

Exercise (correct)

Smoking

Sedentary lifestyle

Which genetic disorder is most commonly associated with familial lipoprotein lipase deficiency?

Chylomicron syndrome Signup and view all the answers

Which of the following is an example of a condition that can lead to hypolipidemia?

Abetalipoproteinemia Signup and view all the answers

What makes primary hyperlipidemias different from other types?

Single or multiple gene mutations Signup and view all the answers

What condition is indicated by a serum cholesterol level greater than $240$ mg/dl?

Dyslipidemia indicators Signup and view all the answers

Which lipoprotein is primarily involved in transferring cholesterol to tissues?

LDL Signup and view all the answers

What happens to oxidized LDL cholesterol when its levels become high?

It is taken up by macrophages and forms foam cells. Signup and view all the answers

Which apolipoproteins primarily make up HDL?

Apo A-I and apo A-II Signup and view all the answers

What is the primary role of lecithin:cholesterol acyltransferase (LCAT) in relation to HDL?

It esterifies cholesterol taken up by HDL. Signup and view all the answers

What is one of the main functions of HDL particles?

To supply apolipoprotein C-II and apolipoprotein E. Signup and view all the answers

How does HDL participate in cholesterol homeostasis?

Through reverse cholesterol transport to the liver and steroidogenic cells. Signup and view all the answers

What defines the two subclasses of HDL, HDL2 and HDL3?

Their lipid content and density differences. Signup and view all the answers

What is the contribution of high-density lipoproteins (HDL) to cardiovascular health?

They help decrease the risk of coronary artery disease. Signup and view all the answers

What type of cholesterol is returned to the liver by HDL after uptake from peripheral tissues?

Cholesteryl esters Signup and view all the answers

What condition is associated with a severe elevation of plasma triglycerides and characteristic lipid stigmata?

Chylomicron syndrome Signup and view all the answers

Which phenotype does Familial hypercholesterolemia typically show?

Type II Signup and view all the answers

What is a common manifestation of heterozygous Familial hypercholesterolemia in men?

Accelerated atherosclerosis Signup and view all the answers

What genetic inheritance pattern does Familial hypercholesterolemia follow?

Codominant Signup and view all the answers

What distinctive feature of retinal vessels indicates lipidemia in patients?

Milky appearance Signup and view all the answers

At what age do plasma LDL levels typically start to be elevated in individuals with Familial hypercholesterolemia?

At birth Signup and view all the answers

What common clinical finding is associated with xanthoma due to hypercholesterolemia?

Tendon xanthomata Signup and view all the answers

Which group of individuals shows a higher prevalence of Familial hypercholesterolemia?

Afrikaners and French Canadians Signup and view all the answers

What is a common presentation of patients with Type III hyperlipoproteinaemia?

Xanthomas and vascular disease Signup and view all the answers

Which condition is NOT a known factor that can increase VLDL levels?

Hypertension Signup and view all the answers

What are the expected plasma concentrations of cholesterol and triglycerides in Type III hyperlipoproteinaemia?

Around 9–10 mmol/L Signup and view all the answers

In cases of secondary hyperlipidaemia, what is a common lifestyle-related cause for elevated triglycerides?

High intake of refined carbohydrates Signup and view all the answers

Which of the following disorders is associated with elevated LDL cholesterol?

Nephrotic syndrome Signup and view all the answers

Which drug category is NOT known to cause elevated triglyceride levels?

Beta blockers (not carvedilol) Signup and view all the answers

What pathognomonic sign is associated with Type III hyperlipoproteinaemia?

Palmar xanthomata Signup and view all the answers

Which of the following treatments is contraindicated during pregnancy and lactation?

Statins Signup and view all the answers

What genetic mutation leads to Tangier disease?

Nonsense mutation within exon 12 of the ABCA1 gene Signup and view all the answers

Which of the following is a major clinical sign of Tangier disease?

Peripheral neuropathy Signup and view all the answers

What is the effect of the ABCA1 gene mutation in Tangier disease?

Inability to transport cholesterol out of cells Signup and view all the answers

What is a common biochemical lab finding in patients with Tangier disease?

Low serum total cholesterol Signup and view all the answers

Why do individuals with Tangier disease experience accumulation of cholesterol in the tonsils?

Inability to eliminate cholesterol from cells Signup and view all the answers

What role does ApoA1 play in cholesterol transport?

Facilitates the transport of cholesterol from cells Signup and view all the answers

What is the inheritance pattern of Tangier disease?

Autosomal recessive Signup and view all the answers

What can result from the accumulation of cholesterol in cells for individuals with Tangier disease?

Cell death or impaired function Signup and view all the answers

What is the primary function of triglycerides in plasma?

Furnishing energy for the cell Signup and view all the answers

Which lipid types are most prominent in plasma?

Triglycerides, cholesterol, and phospholipids Signup and view all the answers

How does dietary cholesterol affect blood levels?

It contributes 10% to 20% to blood levels Signup and view all the answers

What makes plasma lipoproteins unique in their structure?

They have a neutral lipid core surrounded by a shell of apolipoproteins Signup and view all the answers

Which event occurs after the absorption of triglycerides in the intestine?

Triglycerides are reconstituted into chylomicrons Signup and view all the answers

What role do lipoproteins play in lipid transport?

They provide a mechanism for transporting lipid contents to and from tissues Signup and view all the answers

Which of the following lipoproteins is indicative of high energy reserves?

Chylomicrons Signup and view all the answers

What is the relationship between elevated plasma lipid levels and health risks?

Elevated cholesterol levels are linked to the development of atherosclerosis Signup and view all the answers

Study Notes

Clinical Chemistry Case Studies

Plasma lipid study and case studies on familial hypercholesterolemia, abetalipoproteinemia, and Tangier disease are presented.

Lipids

Major plasma lipids include fatty acids, triglycerides, cholesterol and phospholipids.
Other lipid-soluble substances (e.g., steroid hormones) are present in smaller amounts.
Elevated plasma lipid concentrations, particularly cholesterol, are linked to atherosclerosis, a major cause of death worldwide.

Cholesterol

Cholesterol is a sterol derivative crucial for cell membranes, steroid hormones, and bile acids.
Cholesterol is largely endogenous and synthesized in the liver.
Diet influences blood cholesterol levels by 10-20%.
30-60% of dietary cholesterol is absorbed along with conjugated bile acids, phospholipids, fatty acids, and monoacylglycerides.

Triglycerides

Triglycerides are the most abundant dietary fat, comprising 95% of stored fat in adipose tissue.
Their primary function is to provide energy for cells.
In the intestines, triglycerides are hydrolyzed into fatty acids, glycerol, and monoglycerides with the help of lipases and bile acids.
After absorption, they are reconstituted into chylomicrons.
Triglycerides are also produced endogenously by the liver.

Plasma Lipoproteins

Plasma lipoproteins are spherical macromolecular complexes of lipids and specific proteins (apolipoproteins).
They consist of a neutral lipid core (triacylglycerol [TAG] and cholesteryl esters) surrounded by a shell of amphipathic phospholipids and unesterified cholesterol.
Lipoprotein particles constantly exchange lipids and apolipoproteins.
Lipoproteins maintain lipid solubility during transport and provide efficient mechanisms for lipid delivery to/from tissues.
In humans, lipoprotein transport is less perfect than in other animals, leading to gradual lipid deposition in tissues and vessels.
Lipoprotein particles include chylomicrons, very-low-density lipoproteins (VLDLs), intermediate-density lipoproteins (IDLs), low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs).
HDL particles are the smallest and densest.
Lipoproteins are characterized by size, density, composition and origin.

Classes and Characteristics of Major Lipoproteins

Key characteristics of major lipoprotein classes (e.g., size, major apolipoproteins, and density). Data on specific lipoprotein densities, size, major apolipoproteins, and density are given in a table.

Electrophoretic Mobility

Electrophoretic pattern of serum lipoproteins, illustrating the migration of different lipoproteins (e.g., chylomicrons, VLDL, LDL, HDL) in an electric field.

Chylomicrons (CM)

Large particles produced by the intestines, rich in triglycerides (90%), and low in protein (1%).
Less dense than water, causing them to float and contribute to "milky" plasma.
Hydrolyzed into triglycerides-poor CM remnants, incorporated by the liver (using apoE).

Very-Low-Density Lipoproteins (VLDL)

Triglyceride-rich (55%), endogenous (produced by the liver).
Contains cholesterol and phospholipids (25%) and protein (8%).
Lipoprotein lipase action converts VLDL into intermediate-density lipoprotein (IDL) remnants.
The resulting IDL remnants are either incorporated directly by the liver (using apoE) or converted to LDL by hepatic lipase.

Low-Density Lipoproteins (LDL)

Make up 50% of total lipoproteins.
Does not cause plasma turbidity, even at high concentrations.
Primarily composed of esterified cholesterol (50%).
Peripheral tissues absorb LDL viaLDL receptors to meet cholesterol requirements (primary function).
Leftover LDL is removed by the liver via the LDL receptor.
Oxidized LDL and macrophages lead to foam cell formation and atherosclerosis.

High-Density Lipoproteins (HDL)

Primarily composed of protein (50%), mostly apoA-I and II.
Secreted by the liver and intestines as discoidal nascent HDL with low lipid content.
Subclasses include HDL2 and HDL3.
Low levels of apoA-1 are linked to coronary artery disease.
A cofactor for activation of lecithin-cholesterol acyltransferase (LCAT), which esterifies cholesterol for transport to the liver.
Crucial for reverse cholesterol transport.
HDL also performs other functions, including apolipoprotein supply and uptake of unesterified cholesterol.

Metabolism of HDL

A detailed illustration of metabolic pathway of HDL. Key proteins and enzymatic components involved are discussed (e.g., CETP, LCAT, ApoA-I, ApoE)

HDL Functions

Detailed functions of HDL including: apolipoprotein supply, uptake of unesterified cholesterol, esterification of cholesterol, and reverse cholesterol transport, as illustrated in the specific diagrams.

Dyslipidemias

A general medical condition indicative of abnormal blood lipid levels. Common types include hyperlipidemia (high lipid levels) and hypolipidemia (low lipid levels).
Specific types of hyperlipidemia discussed, including their causes, presentation, and diagnostic tests; e.g., familial hypercholesterolemia, familial hypertriglyceridemia, and type III hyperlipoproteinemia.

Primary Hyperlipidemias

Result from single or multiple gene mutations associated with production or clearance of LDL, HDL, and triglycerides. Risk factors (e.g., premature heart disease, family history, high serum cholesterol levels) that support diagnosis are included.

Fredrickson's Classification of Hyperlipidemias

A table classifying hyperlipidemias based on electrophoretic patterns and types, (e.g., type I, type IIa, type IIb, type III, type IV, type V).

Chylomicron Syndrome

Related to familial lipoprotein lipase deficiency affecting 1 in 1,000,000 people.
Symptoms, findings, diagnosis and relevant lipid profiles.

Familial Hypercholesterolemia

A codominant genetic disorder due to LDL receptor mutations affecting LDL removal via circulation.
Diagnosis, symptoms (e.g., high plasma LDL levels, xanthoma, corneal arcus) and clinical presentation.

Familial Hypertriglyceridemia

Exact metabolic defect is largely unclear but likely results from overproduction or impaired conversion of VLDL to LDL.
Increased risk of cardiovascular disease and acute pancreatitis (with plasma triglyceride levels above 10 mmol/L).
Presentation (symptoms, findings, diagnosis and relevant lipid profiles).

Type III Hyperlipoproteinemia

Characterized by reduced clearance of chylomicron and VLDL remnants.
Symptoms (including xanthomas, premature coronary and peripheral vascular disease and elevated lipid levels) are discussed.
Diagnosis often based on plasma lipoprotein electrophoretic patterns.

Secondary Dyslipidemia

Many secondary causes of hyperlipidemia (related to diet, drugs, or conditions). Examples discussed include specific drug or diet induced alterations (e.g., diuretics, cyclosporine, etc.) or specific diseases (e.g., biliary obstruction, nephrotic syndrome, diabetes).

Lipid Profile

A panel of blood tests used to screen for lipid abnormalities such as cholesterol and triglycerides. Common components and typical reference ranges.

Fasting Lipid Profile

A blood test performed after 12-14 hours of fasting to optimize accuracy and reliability.

Adult Reference Ranges for Lipids

A standard table of normal ranges for total cholesterol, HDL cholesterol, and LDL cholesterol in mmol/L.

Case Studies (Examples)

Specific case studies illustrating clinical presentation, diagnostic findings, and suspected diagnoses for each disorder (e.g., specific case examples for Abetalipoproteinemia and Tangier disease). Additional info about these particular conditions is included.

Clinical Biochemistry Case Study - Tangier Disease

Details about the historical insights into the discovery of Tangier disease by Dr. Donald Fredrickson.

Patient Findings and Explanation (Examples)

Detailed descriptions of patient symptoms, including relevant history of present illness, past medical history, family history, clinical examinations or results, and laboratory tests for each case study.
Explanation of the specific findings for each case study.

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Description

Test your knowledge on dyslipidemia, focusing on types, causes, and effects of lipid disorders. This quiz covers key concepts related to high-density lipoprotein (HDL) and its role in cardiovascular health. Explore questions about genetic disorders, conditions leading to hypolipidemia, and the functions of lipoproteins.