Effect of a salmon diet on the distribution of plasma lipoproteins and apolipoproteins in normolipidemic adult men.

The effects of n-3 fatty acids on plasma lipids, lipoproteins and apoproteins have usually been studied in humans after feeding of purified fish oil. This study describes the effect of a natural diet, containing salmon as the source of n-3 fatty acids, on these parameters as compared to a diet very low in n-3 fatty acids. The subjects were nine normolipidemic, healthy males who were confined to a nutrition suite for 100 days. During the first 20 days of the study the participants were given a stabilization diet consisting of 55% carbohydrates, 15% protein, and 30% fat. The n-3 content of this diet was less than 1%, and it contained no 20- or 22-carbon n-3 fatty acids. After the stabilization period the men were split into two groups, one group continued on the stabilization diet while the other received the salmon diet that contained approximately 2.1 energy percent (En%) of calories from 20- and 22-carbon n-3 fatty acids. Both diets contained equal amounts of n-6 fatty acids. This regime continued for 40 days, then the two groups switched diets for the remainder of the study. Plasma triglycerides were lowered significantly (p less than 0.01) and high density lipoprotein cholesterol (HDL-C) was significantly elevated (p less than 0.01) after the men consumed the salmon diet for 40 days. The very low density lipoproteins (VLDL) were lowered, but the trend did not reach statistical significance during the intervention period.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial specific volume and preferential hydration of low density lipoprotein subfractions.

We have determined the partial specific volume (v-) for five low density lipoprotein (LDL) subfractions (n = 5-7) and evaluated preferential hydration (n = 2) for LDL subfraction 3 in normolipoproteinemic subjects in order to characterize these highly atherogenic components of the human plasma lipoprotein spectra. Values for v- at 1 g were determined by sixth place density measurements of the solvent and lipoprotein solutions and carbon, hydrogen and nitrogen (CHN) absolute mass of the lipoprotein concentrations. Mean values for v- were 0.9757 +/- 0.0019, 0.9701 +/- 0.0007, 0.9674 +/- 0.0016, 0.9616 +/- 0.0016 and 0.9550 +/- 0.0025 ml/g for subfractions 1, 2, 3, 4 and 5, respectively. However, molecular densities (sigma) obtained from rho (rho) = 1/v- for respective LDL subfractions were 1.0249, 1.0308, 1.0337, 1.0399 and 1.0471 g/ml, respectively. The preferential hydration of lipoprotein subfraction 3 (n = 2) in NaCl/H2O solutions was 2.9-4.8 wt percent, whereas values were much lower (0.3-0.6 wt percent) in NaCl/NaBr/H2O solvent system. Unhydrated densities for LDL subfraction 3 (n = 2) at 1 g (sixth-place density meter) were 1.0287 and 1.0269 g/ml, whereas at 200,000 X g (used in D2O flotation eta F degrees vs rho determinations) both values were 1.0308 g/ml, indicating that these similar LDL fractions have 23 and 53% higher compressibility than the solvent at 200,000 X g force. It was observed that the linearity of eta F degrees vs rho may not be valid for solvents NaCl/NaBr/H2O of density as high as 1.4744 g/ml. Thus, flotation velocity data using extreme salt concentrations (1.4744 g/ml and higher) may be viewed with caution.

Characterization of plasma lipids and lipoproteins in patients with beta 2-glycoprotein I (apolipoprotein H) deficiency.

The fasting plasma lipids, lipoproteins, and apolipoproteins were evaluated in 5 subjects with undetectable levels of the plasma protein beta 2-glycoprotein I (apolipoprotein H). Family studies confirmed an autosomal co-dominant inheritance pattern for the concentrations of apo H. The total lack of this protein is rare and less than 0.3% of clinic patients demonstrated levels undetectable by radial immunodiffusion. Plasma lipoprotein evaluation in these subjects with beta 2-glycoprotein I absence by analytical ultracentrifugation and compositional analysis demonstrated low concentrations of HDL2b and HDL3. More striking, however, was the lack of a consistent marked effect on the plasma lipoproteins as is found in other apolipoprotein deficiency states. We conclude that the lack of apolipoprotein H does not result in a significant perturbation of normal lipoprotein metabolism as reflected by analysis of fasting plasma lipoproteins. Further study is required to evaluate the role of this glycoprotein in the metabolism of triglyceride-rich lipoproteins.

Analytic ultracentrifuge calibration and determination of lipoprotein-specific refractive increments.

Accurate quantification of the major classes and subfractions of human serum lipoproteins is an important analytical need in the characterization and evaluation of therapy of lipid and lipoprotein abnormalities. For calibrating the analytic ultracentrifuge (AnUC), we routinely use a Beckman calibration wedge cell with parallel scribed lines 1 cm apart. Such a cell gives a rectangular pattern in the schlieren diagram, which determines magnification and also provides an area corresponding to an invariant refractive increment. We have independently validated this wedge calibration cell using a special boundary-forming cell in which 1.174% sucrose is overlayered with distilled water. Comparing wedge cell area with extrapolated zero time boundary area refractive increment gives agreement to within less than 1%, corresponding to a refractive increment error of +/- 0.00002 delta n. Complete calibration for AnUC analysis of lipoproteins also requires accurate determination of the specific refractive increments (SRI) of the major lipoprotein classes, namely low density lipoprotein (LDL) and high density lipoprotein (HDL). These are measured in the density in which they are analyzed, i.e., 1.061 g/ml for LDL and 1.200 g/ml for HDL. Five fresh serum samples were fractionated for total LDL and total HDL and their SRI determined. Total lipoprotein mass was determined using precise CHN elemental analysis and compositional analyses. The results yielded corrected SRI of 0.00142 and 0.00135 delta n/g/100 ml for LDL and HDL. Thus, our current values using 0.00154 and 0.00149 delta n/g/100 ml underestimate LDL and HDL by 9% and 11%. Corrections of all previous LDL and HDL AnUC data can be made using appropriate factors of 1.087 and 1.106.

Serum lipid and lipoprotein concentrations following exposure to ozone.

The effects of exposure to ozone (O3) on concentrations of serum lipids and lipoproteins were investigated. Male and female guinea pigs were exposed to O3 at 1 ppm for two weeks. Serum concentrations of cholesterol, triglycerides, low density (LDL) and very low density (VLDL) lipoproteins were elevated after O3 exposure, particularly in males. During O3 exposure the food intake per day decreased (for a constant body weight), suggesting that metabolic rate and possibly basal metabolic rate was lower. Lung wet weights increased during O3 exposure by 87% for males and 45% for females. When individual lung weight/body weight ratios were correlated with cholesterol and LDL values from the same animal, a high correlation is found for males (r = 0.81, P less than 0.05), suggesting that there may be a relationship between lipoprotein elevations and lung damage for males. Because elevated concentrations of lipids and lipoproteins in humans increase the risk of coronary heart disease (CHD), the lipoprotein results suggest that an epidemiological study of the incidence of CHD with metropolitan O3 levels may be warranted.

Sedimentation equilibrium of human low density lipoprotein subfractions.

The molecular weights of low density lipoprotein (LDL) subfractions were determined precisely by meniscus depletion sedimentation equilibrium. Equilibrium speeds ranged from 9743 to 5896 rpm. The average molecular weights of various LDL subfractions of Sf values 9.49, 7.94, 6.42, 5.17, and 3.71 determined by sedimentation equilibrium were 2.97 X 10(6) ; 3.13 X 10(6); 2.89 X 10(6); 2.45 X 10(6); and 2.61 X 10(6) daltons, respectively; and their respective densities were 1.0267, 1.0306, 1.0358, 1.0422, and 1.0492 g/ml. Minimal hydrated molecular weights for this fractions determined by flotation velocity at 37,020 rpm were 2.57 X 10(6); 2.37 X 10(6); 2.09 X 10(6); 1.94 X 10(6); and 1.81 X 10(6) daltons; whereas similar molecular weights determined at 52,640 rpm were 2.53 X 10(6); 2.27 X 10(6); 1.99 X 10(6); 1.86 X 10(6); and 1.74 X 10(6) daltons for the respective LDL subfractions. Higher molecular weights of fractions 2 and 5 compared to their adjacent fractions 1 and 4 by sedimentation equilibrium are of great interest. The calculated fractional ratio f/f O from sedimentation equilibrium and flotation velocity data ranges from 1.10 to 1.31, suggesting complexity and asymmetry of LDL subfraction molecules. There is also evidence that compressibility of LDL molecules may be different than that for the salt solution under high g-force. Assuming that redistributed LDL molecules at equilibrium under low g-force are spherical, it is possible that the shape of LDL molecules undergoing flotation velocity determinations may be distorted in high g-force conditions. Such distortion may be consistent with the high f/f O values obtained and may also be a basis for structural rearrangement and/or lipoprotein degradation with prolonged preparative ultracentrifugation at high g-force and pressure.

Automated microdensitometry and quantification of lipoproteins by agarose gel electrophoresis.

A major obstacle in the application of quantitative microelectrophoresis has been tedious manipulations and calculations. To overcome these difficulties, we have developed an automatic system for the microdensitometry and calculations as part of a quantitative agarose gel electrophoresis facility. Results are internally standardized by serum cholesterol and/or triglyceride measurements. The hardware consists of a densitometer, an analog to digital converter, a cathode ray tube terminal, a teleprinter, and a small computer. A program in 4K words allows sample coding, electrophoretic scan display, indexing, and systematic identification of each peak. Data are acquired from scans of electrophoretic patterns of serum alone or in combination with the 1.006 gm/ml VLDL top and/or bottom preparative lipoprotein fractions. As many as 30 scans can be stored in 4K words of memory and then sent via high-speed telephone line to a larger computer for remote processing. The analysis corrects for baseline drifts and pre-beta asymmetry and will properly identify and quantify the amount of VLDL, LDL, and HDL with corrections for "sinking pre-beta" and "floating beta" in LDL and VLDL, respectively. Results are given in milligrams per 100 milliliter as well as percentile rank and standard deviation score ranking of each lipoprotein class as compared to an appropriate normal reference population. The latter data are in a form more meaningful to the physician and patient and provide a quantitative dimension to lipoprotein phenotyping.

Lipid and lipoprotein measurements in a normal adult American population.

From a parent population of 774, a subpopulation of 160 normal adults ages 27-66 was randomly selected, 20 from each decade and sex. A detailed comparison was made by analytic ultracentrifugation and complete agarose gel electrophoresis on serum and the 1.006 g/ml top and bottom preparative ultracentrifuge lipoprotein fractions. The latter was internally standardized by total lipid and plasma total cholesterol and triglyceride determinations giving normal reference lipoprotein values. The reading procedure allowed the identification and quantification of floating beta and sinking pre-beta. In the subpopulation, there were two of the former and 13 of the latter. For large scale clinical application of such quantitative lipoprotein electrophoresis full automation of the microdensitometry and calculations will be required.