High-density lipoproteins measurement

Cholesterol is biosynthesized in the liver trans ported throughout the body to be used in a va riety of ways and returned to the liver where it serves as the biosynthetic precursor to other steroids But cholesterol is a lipid and isn t soluble in water How can it move through the blood if it doesn t dis solve in if The answer is that it doesn t dissolve but IS instead carried through the blood and tissues as part of a lipoprotein (lipid + protein = lipoprotein) The proteins that carry cholesterol from the liver are called low density lipoproteins or LDLs those that return it to the liver are the high-density lipoproteins or HDLs If too much cholesterol is being transported by LDL or too little by HDL the extra cholesterol builds up on the walls of the arteries caus mg atherosclerosis A thorough physical examination nowadays measures not only total cholesterol con centration but also the distribution between LDL and HDL cholesterol An elevated level of LDL cholesterol IS a risk factor for heart disease LDL cholesterol is bad cholesterol HDLs on the other hand remove excess cholesterol and are protective HDL cholesterol IS good cholesterol... 

K38. Kronenberg, F., Lobenstanz, E.-M., Konig, P., Utermann, G., and Dieplinger, H., Effect of sample storage on the measurement of lipoprotein(a), apolipoproteins B and A-IV, total and high density lipoprotein cholesterol and triglycerides. J. Lipid Res. 35, 1318-11328 (1994). 

Whole plasma can also be fractionated into specific lipoprotein size classes to further resolve the underlying biochemistry and metabolism of tissues that deliver these lipids to blood and selectively remove them. Thus, TrueMass analysis can be used to measure the lipid profiles of very-low-density lipoprotein, quantify the lipid pathways responsible for metabolic changes in the liver and measure profiles of high-density lipoprotein to quantify the flux of lipids in reverse cholesterol transport. 

The effects of coenzyme Q10 on coronary artery disease and chronic stable angina are modest but appear promising. A theoretical basis for such benefit could be metabolic protection of the ischemic myocardium. Double-blind, placebo-controlled trials have demonstrated that coenzyme Q10 supplementation improved a number of clinical measures in patients with a history of acute myocardial infarction (AMI). Improvements have been observed in lipoprotein a, high-density lipoprotein cholesterol, exercise tolerance, and time to development of ischemic changes on the electrocardiogram during stress tests. In addition, very small reductions in cardiac deaths and rate of reinfarction in patients with previous AMI have been reported (absolute risk reduction 1.5%). 

In vivo studies were also conducted by several researchers. Anraku et al. (2009) examined the antioxidant effects of water-soluble chitosan in normal subjects by measuring the reduction of indices of oxidative stress. Treatment with chitosan for 4weeks produced a significant decrease in levels of plasma glucose and the atherogenic index, and led to an increase in high-density lipoprotein cholesterol (HDL-C). Chitosan treatment also lowered the ratio of oxidized to reduced albumin and increased total plasma antioxidant activity. Further, Anraku et al. (2011) proved the antioxidant effects of high MW chitosan in normal volunteers, and the obtained results were consistent with previous results observed by Anraku et al. (2009). 

Clinical findings may include hypertrophied muscles, acne, oily skin, hirsutism in females, gynecomastia in males, and needle punctures. Edema and jaundice may develop in heavy users. Common laboratory abnormalities include elevated hemoglobin and hematocrit measurements, elevated low-density lipoprotein cholesterol and depressed high-density lipoprotein cholesterol levels. Liver function test results may be elevated, and luteinizing hormone levels are usually depressed. 

A better indication of a person s riidi of heart disease comes from a measurement of blood lipoprotein levels. Lipoproteins arc romfdex mol ecules with both lipid and protein parts that transport lipids through the body. They can be divided into four types ucconbiig to density as shown in 6tble 27.4. People with a high serum level high-density lipoproteins 4 HDL s) seem to have a decreased risk of heart disease. Asa rule of thumb, u person s risk drops about for each increase of 5 mg/dl.. in HDL con-... 

R203 Ng, R.H., Sparks, K.M. and Statland, B.E. (1991). Direct measurement of high-density lipoprotein cholesterol by the Reflotron assay with no manual precipitation step. Clin. Chem. 37, 435-437. 

Baycol was indicated as an adjunct to diet to reduce elevated total-cholesterol, low-density lipoprotein cholesterol (LDL-C), apo B, and triglycerides (TG) and to increase high-density lipoprotein cholesterol (HDL-C) levels in patients with primary hypercholesterolemia and mixed dyslipidemia (Fredrickson types Ila and Ilb) when the response to dietary restriction of saturated fat and cholesterol and other nonpharmacological measures alone had been inadequate. Therapy with lipid altering drugs should bea component of multiple risk factor intervention in those patients at significantly high risk for atherosclerotic vascular disease due to hypercholesterolemia. 

Harris N, Galpchian V, Rifai N. Three routine methods for measuring high-density lipoprotein cholesterol compared with the Reference Method. 

Hubbard RS, Hirany SV, Devaraj S, Martin L, Parupia J, Jialal I. Evaluation of a rapid homogeneous method for direct measurement of high-density lipoprotein cholesterol. Am J Clin Pathol 1998 110 495-502. 

McMillan TA, Warnick GR. Interlaboratory proficiency survey of cholesterol and high-density lipoprotein cholesterol measurement. Clin Chem 1988 34 1629-32. 

Sugiuchi H, Uji Y, Okabe H, Me T, Uekama K, Kayahara N, Miyauchi K. Direct measurement of high-density lipoprotein cholesterol in serum with polyethylene glycol-modified enzymes and sulfated alpha-cyclodextrin. Clin Chem 1995 41 717-23. 

The assay used by Pattnaik et al. (1978) to isolate the cholesteryl ester transfer protein in human plasma measured the transfer of 3H-labeled cholesteryl ester from low density to high density lipoprotein. The transfer reaction was terminated by adding MnC and centrifuging to sediment the low density lipoprotein. A heparin, MnCl2 precipitation step may also be used however, in the presence of a phosphate buffer, heparin is not necessary for precipitation of low density lipoprotein. Routine assays were found to be reproducible to within 10%. The increase in high density lipoprotein radioactivity is linear with time until about 25% of the initial low density lipoprotein radioactivity is transferred. The lipoproteins may also be separated by ultracentrifugation. When these two methods were compared, the results agreed within 10%. The precipitation technique is much faster (less than 15 min compared with 18 hr) and simpler. 

Fig. 6. A summary of important ABC transporters acting on sterols and phospholipids. In many cases, the ABC transporters are requited for the movement of lipids across membranes and insert them into extramembranous acceptors. The known physiological acceptors are indicated, as determined by biochemical measurements. When not known, the acceptors are designated Unk. The transporters Pdrl Ip, Auslp, Yorlp, and PdrSp are found in yeast. ABCA3 is found primarily in alveolar type 2 cells of the lung in which lamellar bodies are pulmonary surfactant storage organelles. ABCA4 is found in rod and cone cells of the eye. CHOL, cholesterol Ret-PE, retinylidene-PE HDL, high-density lipoprotein Apo A1, apolipoprotein A1 SIT, sitosterol.

This enzyme may be measured in studies of organophosphate-induced neurotoxicities. More recently, its cardioprotective role in association with high-density lipoprotein has received some attention. Paraoxanase has also been used as marker of hepatotoxicity (Gil et al. 1994 Hernandez et al. 1997 Ferre et al. 2002). 

Reed, R. G. 1997. In searchof the ideal measure of high-density lipoprotein. Clinical Chemistry 43 1809-1810. 

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