Lipoprotein reference concentrations

Only nine years after its discovery in plasma as an antigenic trait, a relationship was suggested between lipoprotein(a) and coronary heart disease (CHD) (B6, D2). Moreover, an interesting relationship between longevity and Lp(a) concentrations was reported by Berg (B10) The frequency of higher Lp(a) levels in very old persons (>83 years) was lower than in the reference population. The same observation was made by Knapp (K18) in black American men. This... 

A 64-year-old woman who had taken metformin for 3 years had a high-density lipoprotein concentration of 1.2 mmol/1, which fell to 0.26 mmol/1 when she took rosiglitazone. The HbAic fell from 10.1% to 7.9%. Fenofibrate was added and the HDL concentration fell further to 0.11 mmol/1. Triglycerides, 2.7 mmol/1 before treatment, increased to 4.7 mmol/1. Apolipoprotein A1 concentrations were low at 0.14 g/ 1 (reference range 1.1-2.05 g/1). On withdrawing both the rosiglitazone and the fenofibrate the HDL concentration rose to 0.95 mmol/1. 

Very-Low-Density Lipoproteins (VLDL) are less dense than chylomicrons. They contain more protein, although lipids (fatty acids, cholesterol and phospholipid, in that order) still make up 90 to 95 percent of their weight. Low-density lipoproteins (LDLs) are about 85 percent lipid by weight and contain more cholesterol than any other kind of lipid. VLDL and LDL contain large amounts of Apolipoprotein B. The VLDL and LDL are sometimes referred to as bad cholesterol because elevated serum concentrations of these lipoproteins correspond with a high incidence of artery disease (stroke and heart disease). The LDLs carry cholesterol and fatty acids to sites of cellular membrane synthesis. 

The most commonly used index of vitamin E nutritional status is the plasma concentration of a-tocopherol because it is transported in plasma lipoproteins, it is best expressed per mole of cholesterol or per milligram of total plasma lipids (Horwitt et al., 1972 Winbauer et al., 1999). The reference range is... 

In addition, in species with high concentrations of HDL-with apoE, it has been postulated that this lipoprotein class serves to transport excess cholesterol from peripheral cells to the liver for elimination from the body (Mahley et al, 1980). This transport process is referred to as the reverse cholesterol transport process (Glomset, 1968). In contrast, in species with high CETP activity, the excess cholesterol from the periphery is transferred from the typical non-apoE-containing HDL to the lower density lipoprotein classes (VLDL, IDL, and LDL) for clearance by the liver. 

Reference Lipid, Lipoprotein Cholesterol, and Apolipoprotein Concentrations... 

Plasma lipid and lipoprotein concentrations in male and female subjects are presented in Tables 26-7 through 26-10. These reference intervals have been developed using the Lipid Research CHnics (LRC) population. Although reference intervals for apo A-I and B-lOO from the Framingham Heart Study using the approved World Health Organiza-tion/Internationai Federation of Clinical Chemistry and Laboratory Medicine (IFCC) calibrators have been published,distributions of these two proteins that better reflect the North American population have only recently... 

Using this approach had several advantages. First, it established the same basis for accuracy that had been used in developing the relationships between lipid and lipoprotein concentration and CHD, and second, it provided a reference point by which the accuracy of existing or newly developed methods could be assessed. 

Fatty acids are transported between organs either as unesterified fatty acids complexed to serum albumin or in the form of triacylglycerols associated with lipoproteins. Triacylglycerols are hydrolyzed outside cells by lipoprotein lipase to yield free fatty acids (Chapter 19). The mechanism by which fatty acids enter cells remains poorly understood despite a number of studies performed with isolated cells from various tissues [4]. Kinetic evidence has been obtained for both a saturable and a non-saturable uptake of fatty acids. The saturable uptake predominates at nanomolar concentrations of fatty acids and is thought to be mediated, or assisted, by proteins. In contrast, the non-saturable uptake that is effective at higher concentrations of fatty acids has been attributed to passive diffusion of fatty acids across the membrane. Several suspected fatty acid transport proteins have been identified [5]. Although their specific functions in fatty acid uptake remain to be elucidated, these proteins may assist in the desorption of fatty acids from albumin and/or function in uptake coupled to the esterification of fatty acids with CoA, in a process referred to as vectorial acylation. 

Fig. 1. Hazard ratios, with 95% confidence intervals as floating absolute risks, as estimate of association between category of update mean HbAlc concentration and any end point or deaths related to diabetes and all cause mortality. Reference category (hazard ratio 1.0) is HbAlc <6% with log-linear scales, p-value reflects contribution of glycaemia to multivariate model. Data adjusted for age at diagnosis of diabetes, sex, ethnic group, smoking, presence of albuminuria, systolic blood pressure, high- and low-density lipoprotein cholesterol and triglycerides [2].

Apart from the hyperlipoproteinaemias that act as determinants of abnormal plasma lipoprotein concentrations, conditions with abnormally low concentrations of certain lipoproteins are also encountered and are generally referred to as the hypolipoproteinaemias. Tangier disease is one such condition that occurs as a rare inherited condition with autosomal recessive characteristics. The condition, a familial HDL deficiency, is characterized by cholesteryl ester accumulation in the reticuloendothelial system, which is similar in pattern to other lipid-storage diseases, such as gangliosidoses. Atheroma are substantially absent from the aorta and coronary vessels of such patients. The plasma cholesterol concentration is reduced and the triacylglycerol concentration is normal or increased in these cases. 

The total lipoprotein fraction (d<1.210) prepared from serum by the ultracentrifugation was analyzed in the same HPLC conditions as in Fig. 7. As presented in Fig. 8, well separated peaks corresponding to chylomicrons+VLDL, LDL, HDL2 and HDLj are observed by monitoring at A2gQ. The elution volume of each lipoprotein peak in Fig. 8 is consistent with that of the reference standards in Fig. 7. The concentration of total cholesterol, triglycerides and phospholipids in each ml of eluate are plotted in the same figure. For all lipoprotein classes, the peak position of protein is consistent with those of the three lipid components. 

The protective effect of terpinolene with reference to the lipoproteins of human blood and compared to that of the well-known antioxidative substances, such as a-tocopherol and P-carotene, was investigated. The oxidative modification of LDL, which was obtained from the blood of healthy volunteers, can be detected with the use of the increasing absorbance at 234 nm. An elongation of the time until rapid extinction (lag-phase) exhibits an antioxidative activity. The longer the lag-phase lasts, the better is the antioxidative capacity. Similar to other test systems with other EOs, the antioxidative capacity is dependent on the concentration. In that case a higher concentration of terpinolene means that the LDL particles are better loaded with terpinolene molecules. The result of this investigation proved that the protective and thus the antioxidative activity of terpinolene is only a bit weaker than that of the most common antioxidant a-tocopherol. 

For film analysis it is necessary to make reference runs in the same analytical cells under similar conditions, using solutions identical with those containing the lipoprotein concentrate, but free from lipoproteins. The following reference solutions are appropriate. 

In lipoprotein analysis of the continuum type we have made the approximation that a particular lipoprotein band, e. g., the Sf 0-12 lipoprotein band, can be considered as a discrete component and assigned a flotation rate, which is determined by the position on the x axis of the integral curve that divides the total concentration for that band in half. This position is referred to as the mid-area position. The flotation rates corresponding to such mid-area positions (by use of the Svedbeig identity) are used in applications of the Johnston-Ogston correction. 

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