1. Lipids & Lipoproteins
Part 2
Lecture 13

2. Lipid and Lipoprotein Population Distributions
Serum lipoprotein concentrations differ between adult men and women,
Primarily as a result of differences in sex hormone levels,
Women having, on average, higher HDL cholesterol levels and lower total cholesterol and triglyceride levels than men.
The difference in total cholesterol, however, disappears after menopause as estrogen decreases

3. Diagnosis of Lipid Disorders
Diseases associated with abnormal lipid concentrations can be caused:
directly by genetic abnormalities or through environmental/lifestyle imbalances,
or they can develop secondarily, as a consequence of other diseases.
Generally defined by the clinical characteristics of patients and the results of laboratory tests
Many, but not all, lipid disorders, regardless of etiology, are associated with coronary heart disease (CHD), or arteriosclerosis.
Secondarily diseases: Pregnancy, Diabetes mellitus, infection, liver disease

4. Arteriosclerosis
Deposition of lipids, mainly, esterified cholesterol in artery walls = fatty streaks
Small damage to walls - macrophages & platelets move in to repair
LDL brings cholesterol for new cell membranes
LDL can also be taken up by macrophages = foam cells
Accumulation of foam cells deposit in artery walls = fatty streaks
Fatty streaks can develop over time into plaques which can partially block or occlude blood flow.
Arteriosclerosis is a general term describing any hardening (and loss of elasticity) of medium or large arteries
Therefore, atherosclerosis is a form of arteriosclerosis.

5. Arteriosclerosis
Increased LDL and decreased HDL associated with increased plaque formation
1% decrease in LDL drops CHD risk 2%
Treatment to reduce LDL below 100 mg/dL is effective in the stabilization and sometimes regression of plaques

6. Peripheral vascular disease (PVD)
When plaque develops in arteries of the arms or legs
Coronary artery disease (CAD)
when it develops in the heart
Cerebrovascular disease (CVD)
when it develops in the vessels of the brain

7. Adult Reference Ranges For Lipids
ANALYTE
REFERENCE RANGE
Total cholesterol
mg/dL
HDL cholesterol
40-75 mg/dL
LDL cholesterol
mg/dL
Triglyceride
mg/dL

8. Urine excretion of albumin is increased

10. Cardiac enzyme CK and CK isoenzyme and LD and LD isoenzyme would be useful.
Fasting total cholesterol, triglycerides, and HDL and LDL cholesterol could also be performed, but the values should be interpreted with caution because the patient is under stress and may have suffered a MI.
The fasting lipids should be repeated after he has been released from the hospital. If he had a MI, it will be approximately 6 weeks before the values represent true levels.

11. With a total cholesterol level of approximately 280 mg/dL and normal triglycerides and HDL cholesterol, his LDL cholesterol is estimated to be >190 mg/dL, which is extremely elevated.
His physician presumably would have started him on a Step II diet prior to leaving the hospital, based on the in-hospital values.
If the 6- to 8-week values do not show significant improvement, the physician would probably start him on medication.
The patient has a family history of CHD, and, presumably, the patient has now been diagnosed with CHD. Therefore, the goal would be to reduce LDL cholesterol values to <100 mg/dL.
Step 2 diet (30% of calories or less as total fat, less than 7% saturated fat, and less than 200 mg cholesterol per day) 

12. Dyslipidemias Dyslipidemia is a disorder of lipoprotein metabolism.
Include both the overproduction and deficiency of lipoproteins.
Dyslipidemia can manifest as the elevation of plasma cholesterol, triglycerides, or both.
It can also be manifested by:
the elevation of LDL cholesterol
and the decrease of HDL cholesterol in the blood.

13. Dyslipidemias Disease states are generally caused by:
malfunction in synthesis,
transport,
or catabolism of lipoproteins
Dyslipidemias can be subdivided into two major categories
Hyperlipoproteinemia
Hypercholesterolemia
Hypertriglyceridemia
Combined hyperlipoproteinemia
Hyolipoproteinemia

14. Hypercholesterolemia
Familial hypercholesterolemia (FH)
Homozygotes rare 1/million
Total cholesterol mg/dl
Heart attack as early as teenage years
Heterozygotes
cholesterols mg/dl
Heart attacks years

15. Hypercholesterolemia
Familial hypercholesterolemia (FH)
Primarily LDL elevations
Synthesis is normal but decrease or lack LDL receptors
Therefore LDL builds-up in serum
Since cells cannot acquire from LDL increase internal synthesis

16. Hypertriglyceridemia
Triglycerides
Borderline = mg/ dl
High mg/dl
Very High > 500 mg/dl
Familial hypertriglyceridemia
Genetic
Secondary hypertriglyceridemia
Hormonal imbalances
Imbalance between synthesis and clearance of VLDL
hormonal abnormalities associated with the pancreas, adrenal glands, and pituitary,

17. Hypertriglyceridemia
Generally caused by deficiency of LPL or LPL cofactor.
LPL hydrolyzes triglycerides in chylomicrons and VLDL
Deficiency prevents processing and clearing
Elevated even with fasting

18. Combined Hyperlipoproteinemia
Presence of elevated levels of serum total cholesterol and triglycerides
Genetic form of this condition
Familial combined hyperlipoproteinemia (FCH)
Type III hyperlipoproteinemia
an accumulation of cholesterol-rich VLDL and chylomicron remnants as a result of defective catabolism of those particles
Rare form of apo E, called apo E2/2

19. Hypolipoproteinemia Low levels of lipoproteins
Hypo alpha or hypobetalipoproteinemias
Hypobetalipoproteinemia
Associated with low LDL
Not associated with CHD

20. Hypolipoproteinemia Hypoalphalipoproteinemia Several genetic defects
decrease in circulating HDL (<40mg/dl) without hypertriglyceridemia
Premature CHD
An extreme form -Tangier Disease
may have HDL 1-2 mg/dl
People with Tangier disease have defective ABCA1 transporters

21. Hypolipoproteinemia Hypoalphalipoproteinemia
Acute transient hypoalphalipoproteinemia
Severe physiologic stress
Infection, surgery, generalized illness
Therefore samples taken during hospitalization interpret with caution
Return to normal after recovery

23. Yes, she has diabetes mellitus.
Eruptive xanthomas; triglycerides
Yes
Yes, she has diabetes mellitus.
Cessation of estrogen replacement therapy, with consideration of transdermal estrogen therapy, triglyceride- lowering diet and medication, hypoglycemic medication. Most acute risk is pancreatitis.

24. Lipid and Lipoprotein Analyses
Lipids and lipoproteins are important indicators of CHD risk,
This is the major reason for their measurement in research, as well as in clinical practice.
Diagnosis of dyslipidemia is dependent upon the measurement of:
1- Total cholesterol
2- Triglycerides
3- HDL cholesterol
4- and LDL cholesterol
Lipid Panel or profile

25. Cholesterol Enzymatic Method
Cholesterol esterase cleaves the fatty acid residue from cholesteryl esters,
Comprise about two thirds of circulating cholesterol,
Converting them to unesterified or free cholesterol.
The free cholesterol is reacted by cholesterol oxidase, producing hydrogen peroxide,
A common enzymatic color reaction using horseradish peroxidase to couple two colorless chemicals into a colored compound.
The intensity of the resulting color, proportional to the amount of cholesterol

26. Cholesterol Enzymatic Method

27. Triglyceride measurement
Several enzymatic reaction sequences are available for triglyceride measurement,
All including lipases to cleave fatty acids from the glycerol backbone.
The freed glycerol participates in any one of several enzymatic reactions.
The last reaction include:
conversion of NADH to NAD+
Or produce a colored product

28. Triglyceride measurement+

29. HDL Methods CDC reference method Three step process
Ultracentrifugation to remove VLDL
Heparin manganese precipitation to remove LDL activity
Then analysis
Two-step method with precipitation of non- HDL fractions (apo-B) then analysis on supernatant
Enzymatic cholesterol method on remaining
CDC = center for disease control and prevention
Apo B in VLDL and LDL is rich in positively charged amino acids,

30. LDL = Total Cholesterol – HDL – Trig/5
LDL Methods
Friedewald calculation
Determine total cholesterol, total triglycerides and HDL as before
VLDL is estimated as triglycerides/5
400 mg/dl is the upper limit for TG
LDL = Total Cholesterol – HDL – Trig/5
It assumes, first, that virtually all of the plasma TG is carried on VLDL, and second, that the TG:cholesterol ratio of VLDL is constant at about 5:1

31. Lipoprotein Methods Must separate fractions
Electrophoresis – agarose or polyacrylamide
Chromatographic
Precipitation
Ultracentrifugation
Immunochemical

32. Apolipoprotein Methods
Primarily a research method or specialty cardiac service center
Usually done by Immunoassay –
Turbidimetric
ELISA, RIA