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Clinical Chemistry 2 > 2 Lipids and Cardiac Marker > Flashcards

2 Lipids and Cardiac Marker Flashcards

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1
Q

What is a lipid?

A

Marcomolecule composed of fatty acid monomers,
Water insoluble
But soluble in nonpolar solvents (acetone, ether, chloroform, or benzene).

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2
Q

What are the functions of lipids?

A
  1. Energy storage
  2. Protection and insulation
  3. Tissue structure (cell membranes)
  4. Compound synthesis (like carbs and steroid hormones).
  5. Transport of fat soluble vitamins (Vit A, D, E, and K need fat)
  6. Provide essential fatty acids.
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3
Q

What are the major form of lipids?

A
  1. Cholesterols (steroid alcohol containing 4 rings and a single C-H side chain tail).
  2. Triglycerides (3 fatty acids covalently linked to glycerol backbone)
  3. Phospholipids (phosphate head + glycerol + 2 fatty acids)
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4
Q

What are fatty acids?

A

Linear chain of C-H bonds that terminate with a carboxyl group (R-COOH)

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5
Q

How are phospholipids amphipathic?

A

Phospholipids are amphipathic as they have a:

Non-polar tail (Hydrophobic) - fatty acid chain
Polar Head (Hydrophilic) - phosphate group

amphipathic
ADJECTIVE
biochemistry
(of a molecule, especially a protein) having both hydrophilic and hydrophobic parts.

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6
Q

What does it mean when a fat is said to be saturated?

A

No double bonds in hydrocarbon chain –> saturated w/ hydrogen.

Free rotation around carbon bonds.
Weak van der wahl’s forces
Melting point increased, as chain length is increased.
Tends to be solid/waxy at room temperature (e.g. butter)
Harder for body to process.

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7
Q

What does it mean for a lipid to be unsaturated?

A

Unsaturated:

  1. Double bonds in hydrocarbon chain.
  2. No rotation around C=C bonds.
  3. Difficult for H and C molecules to get close enough for van der wahl’s forces.
  4. end to be liquid at room temp.

Can be one C=C bond (double bond) or several. Name based on location of the first double bond.

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8
Q

What is the result of the ‘Cis’ configuration of unsaturated fats and what is the result to the molecule?

A

Cis Configuration:

  1. Both hydrogen atoms on the same side of the C=C double bond –> results in a bend in the molecular structure.
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9
Q

What is the ‘Trans’ configuration for fat (i.e. Trans fat)?

A

Trans fat:

  1. Both hydrogen atoms of the C=C double bond are on opposite sides –> NO BEND in molecular structure.
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10
Q

Are ‘Trans’ fat commonly found in nature and what is the concern regarding them?

A

Trans fat:
1. Not commonly found in nature, but can be created by industry.
2. Increases risk of coronary heart disease (CHD).
Public health measures to reduce trans fat in food supply.

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11
Q

What are Lipoproteins?

A

Hydrophobic core of triglycerides and cholesterol surrounded by a monolayer of phospholipids with apolipoproteins attached –> forms a water soluble complex.

That enables transport of lipids through the bloodstream for storage, energy and hormone manf.

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12
Q

What are apolipoproteins?

A

Apolipoproteins are found on the surface of lipoproteins –> FUNCTONAL PART.

Maintain structural integrity of lipoproteins and act as activators for enzymes that modify lipoprotein particles.

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13
Q

What are the different types of lipoproteins from the least dense to the greatest?

A
  1. Chylomicrons (largest and least dense)
  2. VLDL, Very-low-density lipoproteins
  3. LDL, Low-density lipoproteins
  4. HDL, High-density lipoproteins
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14
Q

What does a chylomicron do?

A
  1. Carries dietary cholesterol to the liver. It is formed during lipid absorption in the intestine.
  2. Delivers dietary triglycerides to adipose tissue and muscle.
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15
Q

What can account for turbidity or milky appearance of blood samples after a patient has had a meal?

A

High levels of chylomicrons.

They float to the top when stored at 4C and form a creamy layer when present in high quantities.

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16
Q

What do Very-low-density (VLDL) lipoproteins do? Where are they made?

A

Carry triglycerides from the liver to peripheral tissue for energy and fat storage. They are rich in triglycerides.

Made in the liver.

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17
Q

What happens if triglycerides are removed from VLDL lipoproteins?

A

Becomes a LDL.

18
Q

What does a Low-density lipoprotein (LDL) do?

A

Transports cholesterol to tissues for cell membranes and hormone synthesis.

Considered “bad” cholesterol.

19
Q

What does a High-density lipoprotein (HDL) do? Where is it made?

A

Removes excess cholesterol from peripheral cells and takes it back to the liver where it gets EXCRETE or RECYCLED.

“Good cholesterol”.

Synthesized in the liver and intestine.

20
Q

How do you calculate LDL-C? and when is it valid to use?

A

To determine LDL you can use the Friedewald Formula:

LDL = Total Chol. - HDL - (Trig. x 0.46)

Valid when there is no chylomicronemia and if triglycerides are < 4.6 mmol/L

Trig. = Triglycerides
Total Chol = Total cholesterol.

21
Q

What is Lipolysis?

A

The break down of fat for energy if carbs are not available.

Uses lipases (enzymes) secreted by the pancreas into the SI to breakdown triglycerides.

22
Q

Summarize the process that happens to fatty acids during lipolysis?

A

Fatty acids oxidized in mitochondria to acetyl CoA –> citric acid cycle –> ETC = energy!

Results in formation of ketone bodies.
(acetoacetic acid, acetone, and beta-hydroxybutyrate).

23
Q

What happens in lipogenesis in summary?

A

Lipogenesis:

Acetyl CoA from breakdown of carbs and fatty acids are used to form new fatty acids.

24
Q

What are sources of cholesterol?

A

Hepatic synthesis = 1000 mg / day

Dietary = 100-300 mg/day (animal & dairy products, saturated fatty acids, main factor in raising blood cholesterol).

25
Q

What type of blood sample is required for testing of lipids and cardiac markers?

A

Serum or Plasma
Non fasting sample is acceptable.
Fasting sample (min 8 hrs) when previous triglycerides are > 4.5 mmol/L

26
Q

What are the testing methods for lipids?

A

Enzymatic Testing Methods
Where a bacterial lipase is used as a substitute of the body’s own gastric lipases to mimic the body’s reaction.
Then a dye + peroxidase produces a colour that is measured with a spec (visible light).
Cholesterol at 500 nm
Triglycerides at 540 nm

27
Q

When is the friedewald formula value to use for calculating LDL cholesterol?

A

No chylomicronemia
Triglycerides are < 4.6 mmol/L

Note: accuracy decreases when fasting triglycerides are > 2.3 mmol/L

28
Q

What do you do with LDL calc when fasting triglycerides are > 4.6 mmol/L?

A

Cannot report results, unreliable.

29
Q

How do you calculate Non-HDL cholesterol?

A

Non-HDL Chl = Total Chl - HDL Chl.

30
Q

What are two analytes that can be tested for to assess risk of cardiovascular disease?

A
  1. CRP

2. Homocysteine

31
Q

What is troponin as a cardiac marker?

A

Troponin:
Contractile proteins that regulate cardiac muscle contracts. Three types studied: Troponin C, I and T. (TNC, TNI, and CTNC).
CTNI and CTNT, Most widely used as it is sensitive and specific for cardiac muscle.
TNC is also in skeletal muscle with same calcium binding role as in heart.

32
Q

How is troponin a better cardiac marker than previous markers used?

A

Troponin stays elevated longer than creatine kinase (does not differentiate between cardiac or smooth), myoglobin (heme protein found in the smooth, skeletal and cardiac muscle).

The other two markers Aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were very general to other damage in the body and not specific enough.

33
Q

What are some common measurements done for the troponin cardiac markers?

A
  1. Troponin T, High-sensitivity (HSTNT) –> improved assay method, 10x more sensitive than CTNI or CTNT assays, identifies myocardial necrosis.
  2. iSTAT for CTNI –> point of care (POCT), amperometric, two-site ELISA method.
34
Q

Congestive heart failure, mainly was diagnosed by signs and symptoms (edema, hypertension, shortness of breath, etc.) but now what biomarkers can be used to assist?

A

Congestive Heart Failure Markers:
1. PROBNP - gets enzymatically cleaved to produce B-type natriuretic peptide (BNP) and N-terminal fragment (NT-PROBNP)

  1. BNP and NT-PROBNP both are produced and released by heart during CHF (volume stretch).

Can assess severity of heart disease.
Differentiate with pulmonary disease.

35
Q

When are fecal fats analyzed in the lab?

A

Fecal fat is only analyzed when qualitative analysis is negative and patient has persistent symptoms of fat malabsorption.

Stain feces and examine microscopically.

36
Q

Why is lipase tested in the lab?

A

For detection of pancreatic disease. Lipases break down triglycerides.

Diagnosis of acute pancreatitis requires presence of 2 of the following 3 criteria:

  1. Abdominal pain, consistent with disease.
  2. Serum lipase > 3x normal upper limit.
  3. Characteristics finding from abdominal imaging.
37
Q

What is Steatorrhea?

A

Increased fat excretion in stool.

Malabsorptive disorder, pancreatic disease (cystic fibrosis), etc.

38
Q

How long is stool collected for Steatorrhea assessment?

A

Stool is collected for 72 hours.

Patients must have adequate fat intake for at least 2 days.

39
Q

What is the L/S ratio represent and why is it requested?

A

L/S ratio is Lecithin levels (phospholipid) expressed as a ratio against Sphingomyelin (phospholipid).

Lecithin is related to the synthesis of surfactant which helps prevent collapse of alveoli in the lungs and Sphingomyelin is a component in amniotic fluid.

When L/S ratio > 2 the baby can be born without concern for respiratory distress syndrome (except in complicated pregnancies); i.e. induction should be ok.
L/S < 1.5 indicates risk of RDS. Failure to excrete CO2. Acidosis.

40
Q

How is L/S ratio tested for?

A

Thin Layer Chromatography for L/S ratio. Gold standard for labs but slow to perform.

Fluorescence polarization –> TDxFLM by Abbott measures lipid membrane fluidity in amniotic fluid.

41
Q

What is the sample requirement for L/S measurement by Fluorescence polarization?

A

1 mL of amniotic fluid collected by amniocentesis.

Sent on ice.

Clinical Chemistry 2 (13 decks)

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