Lipids

Which of the plasma lipoproteins is best described as follows: synthesized in the intestinal mucosa, contains a high concentration of triacylglycerol, and is responsible for the transport of dietary lipids in the circulation? A) Chylomicrons B) High-density lipoprotein C) Intermediate-density lipoprotein D) Low-density lipoprotein E) Very-low-density lipoprotein

A) Chylomicrons Explanation: Chylomicrons are triacylglycerol-rich lipoproteins synthesized in the intestinal mucosa using fat from the diet and secreted into lymph.

In amniotic fluid, the procedure used to determine fetal lung maturity is: A) lecithin/sphingomyelin ratio B) creatinine C) measurement of absorbance at 450nm D) alpha fetoprotein

A) lecithin/sphingomyelin ratio The historical method to evaluate fetal lung maturity is the lecithin\sphingomyelin (L/S) ratio. Measurement of pulmonary surfactant is done to evaluate fetal lung maturity. Lecithin is the major component of the lung surfactant. Sphingomyelin, a non-lung phospholipid, has no role in the surfactant system. It serves as a control for the increase in lecithin that occurs around the 34th-36 week of gestation. Other amniotic fluid evaluations include measurement of creatinine for fetal age; alpha-fetoprotein for neural tube disorder and bilirubin (absorbance at 450nm) for fetal distress. [Bishop 2018, p600]

In familial hypercholesterolemia, the hallmark finding is an elevation of: A) low density lipoproteins B) chylomicrons C) high density lipoproteins D) apolipoprotein A1

A) low density lipoproteins Familial hypercholesterolemia is a genetic condition characterized by elevated serum cholesterol levels. In homozygotes and heterozygotes, the elevated cholesterol is associated with an increased LDL level. The lack or deficiency of the LDL receptors prevents the metabolism of LDL cholesterol, resulting in an increased LDL level. [Bishop 2018, p323]

If the LDL-cholesterol is to be calculated by the Friedwald formula, what are the 2 measurements that need to be carried out by the same chemical procedure? A) total cholesterol and HDL-cholesterol B) total cholesterol and triglyceride C) triglyceride and chylomicrons D) apolipoprotein A and apolipoprotein B

A) total cholesterol and HDL-cholesterol In the indirect measurement of LDL using the Friedewald equation, values are needed for the total cholesterol, HDL cholesterol and triglyceride. Because Of LDL and HDL are measured based on their cholesterol content, it is necessary to determine the total cholesterol and HDL cholesterol using the same cholesterol procedure following the precipitation stepped in the HDL method. [Tietz 2015, P409]

Blood was collected in the serum separator tube on a patient who has been fasting since midnight. The time of collection was 7 AM. Laboratory tests which should be reelected is: A) triglycerides B) iron C) LD D) sodium

A) triglycerides Triglycerides are affected by recent ingestion (less than eight hours) of food. Fasting overnight 410-14 hours is the optimal time for fasting around which to standardize blood collections, including lipids. Iron is subject to circadian rhythm is best analyze on a specimen drawn in the morning, however a specific time with fasting is not as critical. LD and sodium are not affected by recent ingestion of food. [Tietz 2015, p 84]

A lipemic serum separated and frozen at -20°C for assay at a later date. One week later, prior to performing an assay for triglycerides, the specimen should be: A) warmed to 37°C and mixed thoroughly B) warmed to 15°C and centrifuged C) transferred to a glycerated test tube D) discarded and a new specimen obtained

A) warmed to 37°C and mixed thoroughly Frozen samples should be allowed to thaw slowly at room temperature or in a 37°C water bath and should then be mixed thoroughly before analysis. [Kaplan 2003, p78]

The formation and secretion of (A) chylomicrons by an intestinal cell and (B) very-low-density lipoproteins by a hepatic cell. (C, chylomicrons; E, endothelium; G, Golgi apparatus; N, nucleus; RER, rough endoplasmic reticulum; SD, space of Disse, containing blood plasma; SER, smooth endoplasmic reticulum; VLDL, very-low-density lipoprotein.) Apolipoprotein B, synthesized in the RER, is incorporated into particles with triacylglycerol, cholesterol, and phospholipids in the SER.

After the addition of carbohydrate residues in G, they are released from the cell by reverse pinocytosis. Chylomicrons pass into the lymphatic system. VLDL are secreted into the space of Disse and then into the hepatic sinusoids through fenestrae in the endothelial lining.

A 41-year-old woman had the following laboratory results 6 hours after eating: Triglycerides: 280mg/dL Cholesterol: 140mg/dL Which of the following is the best interpretation of these results? A) Both results are normal and not affected by the recent meal B) Triglycerides are elevated, which may be attributed to the recent meal C) Both results are elevated, indicating a metabolic problem in a fasting state D) Cholesterol results are below normal, indicating a metabolic problem

B

Sodium determination by indirect ion selective electrode is falsely decreased by: A) elevated chloride levels B) elevated lipid levels C) decreased protein levels D D) decreased albumin levels

B

The subcellular site of the breakdown of long-chain fatty acids to acetyl-CoA via β-oxidation is: A) The cytosol B) The matrix of the mitochondria C) The endoplasmic reticulum D) The mitochondrial intermembrane space E) The Golgi apparatus

B

A nine month old boy from Israel has gradually lost the ability to set up, and develop seizures. He has an increased amount of the phospholipid called GM2-ganglioside in his neurons, and he lacks the enzyme hexosaminidase A in his leukocytes. These findings suggest: A) Niemann-Pick disease B) Tay-Sachs disease C) phenylketonuria D) Hurler syndrome

B) Tay-Sachs disease Tay-Sachs disease is a rare inherited disorder characterized by the near-total deficiency of the enzyme N-acetyl-beta-hexosaminidase A. The enzyme is responsible for the hydrolysis of the beta (one, four)-glycosidic bond between N-acetylgalactosamine and galactose in GM2 ganglioside. Niemann-Pick disease and hurler syndrome or lysosomal disorders as is Tay-Sachs. Phenylketonuria results from an absent enzyme, but is an inborn error of metabolism. [Burtis 2001, p931-932]

A 35-year-old man with severe hypercholesterolemia has a family history of deaths at a young age from heart disease and stroke. Which of the following genes is likely to be defective? A) Apolipoprotein E B) The LDL receptor C) Lipoprotein lipase D) PCSK9 E) LCAT

B) The LDL receptor Explanation: If the LDL receptor is defective, LDL is not cleared from the blood, causing severe hypercholesterolemia.

As part of a hyperlipidemia screening program, the following results were obtained on a 25-year-old woman 6 hours after eating: triglycerides: 260 mg/dL (2.86 mmol/L) cholesterol: 120 mg/dL (3.12 mmol/L) Which of the following is the best interpretation of these results? A) both results are normal, and not affected by the recent meal B) cholesterol is normal, but triglycerides are elevated, which may be attributed to the recent meal C) both results are elevated, indicating a metabolic problem in addition to the nonfasting state D) both results are below normal despite the recent meal, indicating a metabolic problem

B) cholesterol is normal, but triglycerides are elevated, which may be attributed to the recent meal A high-fat diet increases the serum concentrations of triglycerides. Fasting overnight for 10 - 14 hours is the optimal time for fasting around which to standardize blood collections, including lipids. [Tietz 2015, p 84]

The function of the major lipid components of the very low-density lipoproteins (VLDL) is to transport: A) cholesterol from peripheral cells to the liver B) cholesterol and phospholipids to peripheral cells C) exogenous triglycerides D) endogenous triglycerides

D) endogenous triglycerides In the endogenous pathway for lipid metabolism hepatocytes can synthesize triglycerides from carbohydrates and fatty acids. The triglycerides are packaged in VLDL, and ultimately delivered to the circulation that form. Exogenous triglycerides are transported primarily by chylomicrons. HDL transports cholesterol from peripheral cells to the liver. LDL transports cholesterol and phospholipids to peripheral cells. [Bishop 2018, p313]

True/False Nascent HDL particles are synthesized by the intestine and the liver.

True

True/False Nephrotic syndrome is a classic cause of excessive VLDL production

True

Which low-density-lipoprotein (LDL)-c level exceeds the cutoff for coronary heart disease (CHD) high risk? A) 168mg/dL B) 154mg/dL C) 126mg/dL D) 105mg/dL

A

Which of the following will be elevated in the bloodstream about 2 hours after eating a high-fat meal? A) Chylomicrons B) High-density lipoprotein C) Ketone bodies D) Nonesterified fatty acids E) Very-low-density lipoprotein

A) Chylomicrons Explanation: Chylomicrons are synthesized in the intestine and secreted into lymph after a fat meal.

A fasting serum sample from an asymptomatic 43-year-old woman is examined visually chemically with the following results: Initial appearance of serum: Milky Appearance of serum after overnight refrigeration: Creamy layer over turbid serum Triglyceride level: 2000 mg/dL Cholesterol level: 550 mg/dL This sample contains predominantly: A) chylomicrons, alone B) chylomicrons and very low-density lipoproteins (VLDL) C) very low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) D) hi-density lipoproteins (HDL)

B) chylomicrons and very low-density lipoproteins (VLDL) Mixed hyperlipoproteinemia or type V hyperlipoproteinemia occurs primarily in adulthood is characterized by markedly elevated triglycerides, elevated very low-density lipoproteins (VLDL) and chylomicrons. Because of the markedly increased triglyceride level, the specimen integrity is milky, and overnight refrigeration shows a creamy layer over turbid serum due to the chylomicrons and triglycerides. [Tietz 2015, p402]

The substance that is measured to estimate the serum concentration of triglycerides by most methods is: A) phospholipids B) glycerol C) fatty acids D) pre-beta lipoprotein

B) glycerol There are several enzymatic methods for measuring serum triglyceride. The first step of the coupled reactions involves the hydrolysis of triglyceride by lipase to produce glycerol and fatty acids. Glycerol is a reactant in one of the two enzymatic sequences for the final measurement of triglycerides. Fatty acids are not easily measured. Pre-betalipoprotein is the source of a large portion of endogenous triglycerides but is not produced in enzymatic methods triglyceride analysis. Phospholipids are separate from triglycerides although similar. They contain two esterified fatty acids in a phospholipid group such as choline on the glycerol molecule. Thus, they are more complex than triglycerides and not a byproduct of enzymatic hydrolysis with lipase. [Bishop 2018, p328]

Which of the following methods for quantitation of high-density lipoprotein is most suited for clinical laboratory? A) Gomori procedure B) homogenous C) column chromatography D) agarose gel electrophoresis

B) homogenous The high-volume HDL method is homogenous or direct. This method uses antibodies or complexing agents such as cyclodextrins to mask or consume non--HDL cholesterol lipids do not require a separation step. The indirect (2-3 step) method required separate pretreatment and centrifugation to remove interference and non-HDL cholesterol lipids. The Gomori procedure has been used with acid phosphatase or uric acid but is more currently associated with tri-chrome histological staining of muscle tissue. Column chromatography is a purification step prior to separation by ultra centrifugation, a research method for lipoprotein separation. Gross gel electrophoresis has been used historically for separation of lipoproteins including HDL but is tedious, laborious and not use routinely. [Tietz 2015. p 408]

Which of the following with the results would be expected to be falsely elevated on a serum specimen from a NON-fasting patient? A) cholesterol B) triglyceride C) HDL D) LDL

B) triglyceride food intake can cause a transient increase in the triglyceride level by 50%. The LDL and HDL levels may be decreased depending on the fat content of the meal. Total cholesterol does not usually change significantly after a meal. [Bishop 2018, p327]

The assembly of very-low-density lipoprotein (VLDL) in the liver. (Apo, apolipoprotein; ARF-1, ADP-ribosylation factor-1; FFA, free fatty acids; HDL, high-density lipoproteins; MTP, microsomal triacylglycerol transfer protein; PA, phosphatidic acid; PL, phospholipid; PLD, phospholipase D; TG, triacylglycerol.) The pathways indicated underlie the events depicted in Figure 25-2. Apo B-100 is synthesized on polyribosomes and is lipidated with PL by MTP as it enters the ER lumen. Any excess is degraded in proteasomes. TG derived from lipolysis of cytosolic lipid droplets followed by resynthesis is transferred into the ER lumen with the aid of MTP and interacts with apo B-100 forming VLDL2. Excess TG is recycled to the cytosolic lipid droplets. VLDL2 are translocated to the golgi in COPII vesicles where they fuse with TG-rich particles to form VLDL1. PA is produced by activation of PLD by ARF-1 and is incorporated into the TG-rich VLDL1 and/or VLDL2.

Both VLDL1 and VLDL2 may be secreted into the blood. Insulin inhibits VLDL secretion by inhibiting apo B-100 synthesis and the formation of VLDL1 from VLDL2.

The chemical composition of HDL - cholesterol corresponds to: Triglyceride Cholesterol Protein A) 60% 15% 10% B) 10% 45% 25% C) 5% 15% 50% D) 85% 5% 2%

C) 5% Triglyceride 15% Cholesterol 50%Protein High density lipoprotein (HDL) is the smallest and most dense of the lipoproteins. This is evidenced by its lipid content of 20% protein concentration of 50%. [Bishop 2018, P312]

Which one of the following statements concerning the biosynthesis of cholesterol is CORRECT? A) The rate-limiting step is the formation of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) by the enzyme HMG-CoA synthase. B) Synthesis occurs in the cytosol of the cell. C) All the carbon atoms in the cholesterol synthesized originate from acetyl-CoA. D) Squalene is the first cyclic intermediate in the pathway. E) The initial substrate is mevalonate.

C) All the carbon atoms in the cholesterol synthesized originate from acetyl-CoA. Explanation: Cholesterol is synthesized in the endoplasmic reticulum from acetyl CoA. The rate-limiting step is the formation of mevalonate from 3-hydroxy 3-methylglutaryl-CoA by HMG CoA reductase and lanosterol is the first cyclic intermediate.

Which type of lipoprotein transports the MAJORITY of cholesterol to cells for steroid hormone synthesis or cell membrane incorporation? A) Chylomicrons B) Very low density lipoproteins (VLDL) C) Low density lipoproteins (LDL) D) High density lipoproteins (HDL)

C) Low density lipoproteins (LDL) The majority of cholesterol (about 70%) is transported by LDL to the various cells in the body, and the rest is transported by HDL through reverse cholesterol transport for excretion purposes, ultimately through bile or bile salts. VLDL transports endogenous products, mostly lipids, whereas chylomicrons transport exogenous (dietary) products (lipids).

Which of the following statements about bile acids (or bile salts) is INCORRECT? A) Primary bile acids are synthesized in the liver from cholesterol. B) Bile acids are needed for the breakdown of fats by pancreatic lipase. C) Secondary bile acids are produced by modification of primary bile acids in the liver. D) Bile acids facilitate the absorption of the products of lipid digestion in the jejunum. E) Bile acids are recirculated between the liver and the small intestine in the enterohepatic circulation.

C) Secondary bile acids are produced by modification of primary bile acids in the liver. Explanation: Secondary bile acids are produced by the modification of primary bile acids in the intestine.

Which of the following diseases results from a familial absence of high density lipoprotein? A) Krabbe disease B) Gaucher disease C) Tangier disease D) Tay-Sachs disease

C) Tangier disease Tangier disease results from a defect in the catabolism of Apo A-I, an essential APOprotein for HDL. In homozygotes, the plasma level for HDL is practically zero. It is a rare autosomal disorder. The reduced HDL levels result from increased HDL catabolism. Other more common causes of hypoalphalipoproteinemia include LCAT deficiency and mutations of the APOA1 gene. [Tietz 2015, p404]

Turbidity and serum suggest elevation of: A) cholesterol B) total protein C) chylomicrons D) albumin

C) chylomicrons Elevated levels of chylomicrons in serum or plasma will result in a turbid specimen. The large size of the chylomicrons will reflect the light, causing a turbid appearance. [Bishop 2018, p313]

Chylomicrons are present in which of the following dyslipidemias? A) familial hypercholesterolemia B) hypertriglyceridemia C) deficiency in lipoprotein lipase activity D) familial hypoalphalipoproteinemia

C) deficiency in lipoprotein lipase activity Lipoprotein lipase idolizes triglycerides and chylomicrons during normal lipid metabolism. Deficiency in lipoprotein lipase results in markedly increased serum chylomicrons and triglycerides. [Tietz, p402]

Premature atherosclerosis can occur when which of the following becomes elevated? A) chylomicrons B) prostaglandins C) low density lipoproteins D) high density lipoproteins

C) low density lipoproteins Atherosclerosis is characterized by thickening and hardening of the arterial walls by cholesterol plaques in the lining of the arteries. Elevated levels of cholesterol are associated with the development of the plaques. One of the roles of LDL is to transport cholesterol esters to the cell for metabolism. Elevated LDL levels are also associated with development of atherosclerosis. [Bishop 2018, p321]

Transportation of 60-75% of the plasma cholesterol is performed by: A) chylomicrons B) very low-density lipoproteins C) low-density lipoproteins D) high-density lipoproteins

C) low-density lipoproteins Low-density lipoprotein (LDL) transports about 70% of the total plasma cholesterol. HDL transports a smaller portion of the cholesterol through reverse-cholesterol transport from peripheral cells. Chylomicrons and VLDL transport triglycerides. [Tietz 2015, p400]

What is the good lipoprotein?

HDL

Which of the following is the formula for calculating absorbance given the percent transmittance (%T) of a solution? A) 1-log(%T) B) log(%T)/2 C) 2 X log(%T) D) 2 - log(%T)

D) 2 - log(%T) because the following relationship is true, A= light stopped and T= light passed through, A and T are inversely related. They are also logarithmically related, because the absorption of light is a logarithmic function. A= -log(I/Io) = log100% - log%T Log of 100% =2. [Bishop 2018, p104]

Which one of the following statements concerning chylomicrons is CORRECT? A) Chylomicrons are made inside intestinal cells and secreted into lymph, where they acquire apolipoproteins B and C. B) The core of chylomicrons contains triacylglycerol and phospholipids. C) The enzyme hormone-sensitive lipase acts on chylomicrons to release fatty acids from triacylglycerol when they are bound to the surface of endothelial cells in blood capillaries. D) Chylomicron remnants differ from chylomicrons in that they are smaller and contain a lower proportion of triacylglycerol and a higher proportion of cholesterol. E) Chylomicrons are taken up by the liver.

D) Chylomicron remnants differ from chylomicrons in that they are smaller and contain a lower proportion of triacylglycerol and a higher proportion of cholesterol. Explanation: Chylomicrons are metabolized by lipoprotein lipase when bound to the surface of endothelial cells. This process releases fatty acids from triacylglycerol which are then taken up by the tissues. The resulting smaller, cholesterol-enriched chylomicron remnant particles are released into the circulation and cleared by the liver.

High levels of which lipoprotein class are associated with decreased risk of accelerated atherosclerosis? A) chylomicrons B) VLDL C) LDL D) HDL

D) HDL High density lipoprotein (HDL) is the smallest and most dense lipoprotein. His role in lipid metabolism involves removing cholesterol from the peripheral cells and transporting it to the liver for further metabolism. Because of these actions, HDL is thought to be anti--atherogenic. Increased levels of LDL, VLDL, and chylomicrons are associated with atherosclerosis. [Tietz 2015, P401]

Which of the plasma lipoproteins is best described as follows: formed in the circulation by removal of triacylglycerol from very-low-density lipoprotein, contains apo B-100, delivers cholesterol to extrahepatic tissues? A) Chylomicrons B) High-density lipoprotein C) Intermediate-density lipoprotein D) Low-density lipoprotein E) Very-low-density lipoprotein

D) Low-density lipoprotein Explanation: Very low density lipoprotein secreted by the liver is converted to intermediate density lipoprotein and then to low density lipoprotein (LDL) by the action of lipases and the transfer of cholesterol and proteins from high density lipoprotein. LDL delivers cholesterol to extrahepatic tissues and is also cleared by the liver.

Which one of the following statements concerning fatty acid molecules is CORRECT? A) They consist of a carboxylic acid head group attached to a carbohydrate chain. B) They are called polyunsaturated when they contain one or more carbon-carbon double bonds. C) Their melting points increase with increasing unsaturation. D) They almost always have their double bonds in the cis configuration when they occur naturally. E) They occur in the body mainly in the form of free (nonesterified) fatty acids.

D) They almost always have their double bonds in the cis configuration when they occur naturally.

The most consistent analytical error involved in the routine determination of HDL-cholesterol is caused by: A) incomplete precipitation of LDL-cholesterol B) co-precipitation of HDL-and LDL-cholesterol C) inaccurate protein estimation of HDL-cholesterol D) a small concentration of apoB-containing lipoproteins after precipitation

D) a small concentration of apoB-containing lipoproteins after precipitation Serum HDL has been routinely measured indirectly by a two-step procedure. Precipitation of all of the non--HDL lipoproteins with a polyanion-divalent cation combination reagent and centrifugation to obtain the supernatant containing only HDL. The cholesterol bound to HDL is measured as HDL. One challenge regarding the method has been the selection of a precipitating reagent that would precipitate the apoB containing lipoproteins. Dextran sulfate with magnesium has proven to be very effective. [Tietz 2015, p409]

A one-year-old girl with hyperlipoproteinemia and lipoprotein lipase deficiency has the following lipid profile: Cholesterol: 300mg/dL (7.77mmol/L) LDL: Increased HDL: Increased Triglycerides: 1200mg/dL (13.56mmol/L) Chylomicrons: present A serum specimen from this patient that was refrigerated overnight would most likely be: A) clear B) cloudy C) creamy layer over cloudy serum D) creamy layer over clear serum

D) creamy layer over clear serum Lipid analysis using overnight refrigeration involves incubating the sample at 4°C overnight. The chylomicrons, present as a thick homogenous cream layer, may be observed floating at the plasma surface. This typifies familial hyperchylomicronemia due to deficiency in lipoprotein lipase activity. [Tietz 2015, P402]

Fatty acids are broken down by repeated removal of two carbon fragments as acetyl-CoA in the β-oxidation cycle, and synthesized by repeated condensation of acetyl-CoAs until a long-chain saturated fatty acid with an even number of carbons is formed. Since fatty acids need to be broken down when energy is short supply and synthesized when it is plentiful, there are important differences between the two processes which help cells to regulate them efficiently. Which one of the following statements concerning these differences is INCORRECT? A) Fatty acid breakdown takes place inside mitochondria, while synthesis occurs in the cytosol. B) Fatty acid breakdown uses NAD+ and produces NADH, while synthesis uses NADPH and produces NADP. C) Fatty acyl groups are activated for breakdown using CoA and for synthesis using acyl carrier protein. D) Transport across the mitochondrial membrane of fatty acyl groups is required for fatty acid breakdown, but not for synthesis. E) Glucagon promotes fatty acid synthesis and inhibits fatty acid breakdown.

E) Glucagon promotes fatty acid synthesis and inhibits fatty acid breakdown. Explanation: Glucagon is released when blood glucose levels are low. In this situation, fatty acids are broken down for energy and fatty acid synthesis is inhibited.

Which of the following will be elevated in the bloodstream about 4 hours after eating a high-fat meal? A) Low-density lipoprotein B) High-density lipoprotein C) Ketone bodies D) Nonesterified fatty acids E) Very-low-density lipoprotein

E) Very-low-density lipoprotein Explanation: Chylomicrons and their remnants are cleared from the circulation rapidly after a meal, and the secretion of very low density lipoprotein by the liver then increases. Ketone bodies and nonesterified fatty acids are elevated in the fasting state.

Which of the plasma lipoproteins is best described as follows: synthesized in the liver, contains a high concentration of triacylglycerol, and is mainly cleared from the circulation by adipose tissue and muscle? A) Chylomicrons B) High-density lipoprotein C) Intermediate-density lipoprotein D) Low-density lipoprotein E) Very-low-density lipoprotein

E) Very-low-density lipoprotein Explanation: VLDL is synthesized and secreted by the liver, and adipose tissue and muscle take up the fatty acids released by the action of lipoprotein lipase.

What are the expected lipid values in Cushing's syndrome?

Endogenous or exogenous glucocorticoid excess is associated with increased VLDL synthesis and secretion and hypertriglyceridemia Patients with Cushing's syndrome frequently have dyslipidemia especially characterized by hypertriglyceridemia and low HDL-C, although elevations in plasma levels of LDL-C can also be seen.

Which of the following lipoprotein disorders is characterized by an increase in chylomicrons in the development of xanthomas rather than atherosclerosis? A) abetalipoproteinemia B) Famililal dysbetalipoproteinemia C) Familial hypercholesterolemia D) Familial hypertriglyceridemia E) Familial hypobetalipoproteinemia F) Familial lipoprotein lipase deficiency G) Lecithin cholesterol acyl transferase (LCAT) deficiency H) Multiple lipoprotein type hyperlipidemia I) Tangier disease

F) Familial lipoprotein lipase deficiency In familial lipoprotein deficiency (type I lipoprotein pattern on electrophoresis), there is elevation of serum triglycerides with particular elevation of chylomicrons. Patients do not have an especially increased risk of atherosclerosis but do develop xanthomas. Abetalipoproteinemia (choice A) is a genetic absence of a boat protein, which leads to fat malabsorption and a complete absence of chylomicrons. There are neurologic abnormalities, and the patient's erythrocytes are deformed (acanthocytosis). Familial dysbetalipoproteinemia (type III pattern; choice B) is a defect in a boat protein that prevents remnant particles from binding to liver cells; patients are prone to both xanthomas and very early atherosclerosis. Both plasma cholesterol and triglycerides are elevated. Familial hypercholesterolemia (type IIa or IIb pattern; choice C) causes elevation of LDL (and sometimes VLDL) as a consequence of a defective LDL receptor. Familial hypertriglyceridemia (type IV or V patterns; choice D) causes elevated VLDL, xanthomas, and atherosclerosis by an unknown mechanism. Familial hypobetalipoproteinemia (choice E) is a decrease in (but not absence of) apoprotein B that is relatively benign clinically. Lecithin cholesterol acyl transferase deficiency (choice G) leads to an inability to ESTERIFY cholesterol associated with HDL. Is associated clinically with corneal opacities, hemolytic anemia, premature atherosclerosis, and renal failure. Multiple lipoprotein-type hyperlipidemia (type IIa, IIb, or IV pattern; choice H) is an elevation of LDL, possibly due to excess production of VLDL, associated with premature atherosclerosis. Tangier disease (choice I) is an absence of HDL with low serum cholesterol, orange tonsils (like a tangerine), and no atherosclerosis

When are triglycerides increased?

Increased in: Hypothyroidism, diabetes mellitus (diabetic dyslipidemia), nephrotic syndrome, chronic alcoholism (fatty liver), biliary tract obstruction, stress, familial lipoprotein lipase deficiency, familial dysbetalipoproteinemia, familial combined hyperlipidemia, obesity, the metabolic syndrome, viral hepatitis, cirrhosis, pancreatitis, chronic renal failure, gout, pregnancy, glycogen storage diseases types I, III, and VI, anorexia nervosa, dietary excess. Drugs: β-blockers, cholestyramine, corticosteroids, diazepam, diuretics, estrogens, oral contraceptives.

What are lipoproteins?

Lipoproteins are complexes of lipids and proteins that are essential for transport of cholesterol, triglycerides (TGs), and fat-soluble vitamins in the blood.