Cholesterol levels measurement

Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. 

With investigations of phytochemicals and functional foods, the outcome measure is generally going to be a biomarker of disease, such as serum cholesterol level as a marker of heart disease risk, or indicators of bone turnover as markers of osteoporosis risk. Alternatively, markers of exposure may also indicate the benefit from a functional food by demonstrating bioavailability, such as increased serum levels of vitamins or carotenoids. Some components will be measurable in both ways. For instance, effects of a folic acid-fortified food could be measured via decrease in plasma homocysteine levels, or increase in red blood cell folate. 

Probucol, another di-r-butyl phenol, is an anti-atherosclerotic agent that can suppress the oxidation of low-density lipoprotein (LDL) in addition to lowering cholesterol levels. The antioxidant activity of probucol was measured, using EPR, with oxidation of methyl linoleate that was encapsulated in liposomal membranes or dissolved in hexane. Probucol suppressed ffee-radical-mediated oxidation. Its antioxidant activity was 17-fold less than that of tocopherol. This difference was less in liposomes than in hexane solution. Probucol suppressed the oxidation of LDL as efficiently as tocopherol. This work implies that physical factors as well as chemical reactivity are important in determining overall lipid peroxidation inhibition activity (Gotoh et al., 1992). 

Often you need to carry forward data to a specific time point due to holes or sparseness of data. The previous example on determining baseline cholesterol level provides an excellent context for this problem. Assume that you have several cholesterol readings of HDL, LDL, and triglycerides for patients before they take an experimental pill designed to reduce cholesterol levels. For each cholesterol parameter, you want the last observation carried forward so long as the measures occur within a five-day window before the pill is taken. Here are some sample data that illustrate the problem ... 

Sometimes it is not possible to measure the direct effect of the drug. Endpoints or surrogate biomarkers are used to monitor the pharmacodynamics and pharmacokinetics of the drug. These markers may be changes in blood pressure, cholesterol level, concentrations of certain enzymes, proteins, blood glucose levels, and similar factors (see Table 6.2 for serum tumor markers and Appendix 7 for general biomarkers). 

Indicate which type of measurement scale (nominal, ordinal, interval, or ratio) is usually used for the following characteristics time, mass, library holdings, gender, type of heart attack, cholesterol level as measured by a clinical chemical laboratory, cholesterol level as reported by a doctor to a patient, pipet volume, and leaves on a plant. 

Serum cholesterol elevation Clinically relevant increases in serum cholesterol were recorded in venlafaxine-treated patients in placebo-controlled trials. Consider measurement of serum cholesterol levels during long-term treatment. 

The most common kind of data that we see is continuous data. Examples include cholesterol level, exercise duration, blood pressure, FEVj and so on. Each of these quantities is based on a continuum of potential values. In some cases, of course, our measurement technique may only enable us to record to the nearest whole number (blood pressure for example), but that does not alter the basic fact that the underlying scale is continuous. 

Lipoprotein disorders are detected by measuring lipids in serum after a 10-hour fast. Risk of heart disease increases with concentrations of the atherogenic lipoproteins, is inversely related to levels of HDL, and is modified by other risk factors (Table 35-1). Evidence from clinical trials suggests that LDL cholesterol levels of 60 mg/dL may be optimal for patients with coronary disease. Ideally, triglycerides should be below 120 mg/dL. Differentiation of the disorders requires identification of the lipoproteins involved (Table 35-2). Diagnosis of a primary disorder usually requires further clinical and genetic data as well as ruling out secondary hyperlipidemias (Table 35-3). 

Cholesterol is commonly associated with cardiovascular disease and its routine measurement is used to measure its potential health risk. High blood serum cholesterol levels are often correlated with excessive plaque deposits in the arteries, a condition known as atherosclerosis... 

Standard lipid screening to obtain a cholesterol profile for the risk of cardiovascular disease routinely reports total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. Cholesterol values are reported in milligrams per deciliter of blood (mg/dL). Different organizations have made recommendations for normal cholesterol levels, but these must be interpreted carefully, as they are contingent on other risk conditions. For example, the recommendations for smokers or those with a family history of heart disease will be lower for someone without these conditions. The National Center for Cholesterol Education (NCEP) endorsed by the American Heart Association believes that LDL is the primary cholesterol component to determine therapy. LDL cholesterol accounts for 60—70% of blood serum cholesterol. An LDL less than 160 mg/dL is recommended for individuals with no more than one risk factor and less than 100 mg/dL for individuals with coronary heart disease. NCEP classifies HDL, which comprises between 20% and 30% of blood cholesterol, below 40 mg/dL as low. Triglycerides are an indirect measure of VLDL cholesterol. The NCEP considers a normal triglyceride level as less than 150 mg/dL. 

The measurement of serum cholesterol is one of the most common tests performed in the clinical laboratory. Hypercholesterolemia (high blood cholesterol levels) can be the result of a variety of medical conditions. Among the conditions implicated are diabetes mellitus, atherosclerosis, and diseases of the endocrine system, liver, or kidney. High blood cholesterol levels do not point to a specific disease determination of cholesterol is used in conjunction with other clinical measurements mainly for confirmation of a particular diseased condition, rather than for diagnosis of a specific ailment. 

Serum, Cholesterol and Triglyceride Serum triglyceride and cholesterol levels were measured in rats fed Maillard browned proteins or control diets for l8 months. The results are given in Table VI. The feeding of Maillard browned egg albumin resulted in a significantly lower level of both cholesterol and triglycerides over animals fed the control egg albumin diet. Similar results of serum cholesterol values were observed by Gomyo (2 ). 

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. 

PBS and gently blotted to remove blood and tissue fluids, then suspended over the lip of a small (250 pi) microcentrifuge tube and punctured with a needle to allow the bile to drain into the tube. Store frozen until assay. There is usually enough material to measure lipid composition (bile acids, cholesterol, phospholipids) with standard colorimetric kits (<1 pi needed for each assay). In addition to biliary cholesterol levels, it is important to take note of bile salt concentrations, since these are the detergents which suspend dietary lipids in micelles and deliver them to the intestinal epithelium for absorption by enterocytes. Differences in bile salt concentration alone could lead to differences in cholesterol absorption. 

The proportions of delta 8-cholesterol and desmosterol in the serum rose while those of cholestanol, campesterol and sitosterol dropped, implying a decreased absorption of cholesterol and a compensatory increase in its synthesis. High basal precursor sterol proportions were predictive of a large decrement in titer of LDL cholesterol. It appeared that partial substitution of normal dietary lipid consumption with sitostanol was a safe and effective therapeutic measure for children with FH (Lees et al., 1977 Wang and Ng, 1999). The effect of a small amount of sitosterol, sitostanol and sitostanol esters dissolved in rapeseed oil on serum lipids and cholesterol metabolism in patients with primary hypercholesterolemia and various apolipoprotein E phenotypes on a rapeseed oil diet showed a diminution in TC and LDL-cholesterol levels in the serum (Gylling and Miettinen, 1994). 

There is a substantial interindividual variation in LDL cholesterol levels among patients with FH. Generally, LDL cholesterol levels are inversely related to the residual LDL receptor activity, as measured in the in vitro assay that uses skin fibroblasts. Patients with homozygous FH are classically divided into two groups based on the fibroblast LDL receptor activity. Patients with less than 2% activity, as the patient described in the case report, are classified as receptornegative. Patients with 2%-20% LDL receptor activity are classified as receptor-defective. The natural history of the disease is much more severe in receptor-negative patients, who, if left untreated, rarely survive beyond the second decade of fife. Receptor-defective patients, in contrast, have less-severe hypercholesterolemia and a more delayed onset of coronary artery disease and mortality. 

While low serum cholesterol levels have been observed in malnourished patients, largely as a result of decreased synthesis of lipoproteins in the liver, hypocholesterolemia occurs later in the course of malnutrition and is therefore not useful as a screening test. PEM usually results in low serum urea nitrogen (BUN), urinary urea, and total nitrogen. Estimation of 24-h urine creatinine excretion is also a valuable biochemical index of muscle mass (when there is no impairment in renal function). The urinary CHI is correlated to lean body mass and anthropometric measurements. In edematous patients, for whom the extracellular fluids contribute to body weight and spuriously high body mass index values, the decreased CHI values are especially useful in diagnosing malnutrition. 

Most men and women have had their blood pressure measured at one time or another. But, bearing in mind that without knowing it, many individuals have either pressure above optimal levels or frank hypertension, if you haven t had a test lately, call your doctor s office and schedule an appointment. While you re there, it would be a good idea to have your cholesterol levels checked as well. Elevated cholesterol counts are not only a major risk factor for heart attack and stroke, in and of themselves, but they also predispose a person to developing hypertension. 

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