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PubMed1976

Studies on human serum high-density lipoproteins. Self-association of human serum apolipoprotein A-II in aqueous solutions.

Some of the solution properties of pure preparations of human serum high-density apolipoprotein A-II were studied by sedimentation equilibrium ultracentrifugation, conducted at different apoprotein concentrations and at several speeds. The concentration dependence of the apparent weight average molecular weight indicated that apolipoprotein A-II, when dissolved in 0.02 MEDTA (pH 8.6), undergoes self-association. Over a protein concentration range between 0.8 and 1.5 mg/ml, the self-association could best be described by a monomer-dimer-trimer step association, although indefinite self-association could not be ruled out. The equilibrium constants obtained were sufficient to describe the system over the concentration range investigated.

Binding Sites↗
PubMed1977

The measurement of apolipoprotein A-I and A-II levels in men and women by immunoassay.

To study apolipoprotein A-II, a simple, precise, and accurate immunodiffusion assay was developed and applied in a population sample of industrial employees. Apolipoprotein A-II (A-II) did not increase with age in men (r = -0.20, n = 172), but showed a slight increase with age in women (0.1 mg/dl per yr, r = 0.20, n = 188). A-II correlated significantly with apolipoprotein A-I (A-I) (r = 0.71) and high density lipoprotein (HDL) cholesterol (men, r = 0.64; women, r = 0.49). The A-I/A-II ratio was significantly related to HDL cholesterol (men, r = 0.29; women, r = 0.44). Women on no medication (n = 92) had A-II levels similar to men (34+/-5 and 33+/-5 mg/dl, mean+/-SD, respectively), whereas women on oral contraceptives or estrogens had significantly higher levels (39+/-6 mg/dl, n = 75, P < 0.01). The plasma A-I/A-II weight ratio was 3.6+/-0.4 for men and 3.8+/-0.5 for women. In the d = 1.10-1.21 subfraction, both males and females had similar A-I, A-II, and HDL cholesterol levels (men: mean, 97, 27, and 32 mg/dl, respectively; women: mean, 104, 28, and 36 mg/dl, respectively). Women had approximately twice the amount of A-I, A-II, and HDL cholesterol than men in the d = 1.063-1.10 fraction (men: mean, 10, 2, and 10 mg/dl, respectively; women: mean, 24, 4, and 19 mg/dl, respectively). The A-I/A-II weight ratio in the d = 1.063-1.10 fraction (men, 5.1+/-0.7; women, 6.1+/-1.3) was significantly greater (P < 0.01) than that in the d = 1.10-1.21 fraction (men, 3.7+/-0.2; women, 3.8+/-0.2). Furthermore, the weight ratio of cholesterol to total apoprotein A in the d = 1.063-1.10 fraction (men, 0.75+/-0.09; women, 0.67+/-0.05) was significantly higher (P < 0.01) than that found in the d = 1.10-1.21 fraction (men, 0.26+/-0.04, women, 0.28+/-0.05). Thus, the compositions of HDL hydrated density subclasses are significantly different from each other. These results suggest that the differences in HDL between men and women are due primarily to differences in the relative proportions of HDL subclasses rather than to the intrinsic differences in HDL structure.

Adult↗
PubMed1975

Radioimmunoassay of human high density lipoprotein apo-protein A-1.

A double antibody radioimmunoassay technique was developed for the measurement of apolipoprotein A-I, the major apoprotein of human high density lipoproteins. Apolipoprotein A-I was prepared from human delipidated high density lipoprotein (d equal to 1.085-1.210) by gel filtration and ion-exchange chromatography. Purified apolipoprotein A-I antibodies were obtained by means of apolipoprotein A-I immunoadsorbent. Apolipoprotein A-I was radiolabeled with 125-I by the iodine monochloride technique. 65-80% of 125 I-labeled apolipoprotein A-I could be bound by the different apolipoprotein A-I antibodies, and more than 95% of the 125-I-labeled apolipoprotein A-I was displaced by unlabeled apolipoprotein A-I. The immunoassay was found to be sensitive for the detection of about 10 ng of apolipoprotein A-I in the incubation mixture, and accurate with a variability of only 3-5% (S.E.M.). This technique enables the quantitation of apolipoprotein A-I in whole plasma or high density lipoprotein without the need of delipidation. The quantitation of apolipoprotein A-I in high density lipoprotein was found similar to that obtained by gel filtration technique. The displacement capacity of the different lipoproteins and apoproteins in comparison to unlabeled apolipoprotein A-I was: very low density lipoprotein, 1.8%; low density lipoprotein, 2.6%; high density lipoprotein, 68%; apolipoprotein B, non-detectable; apolipoprotein C, 0.5%; and apolipoprotein A-II, 4%. The distribution of immunoassayable apolipoprotein A-I among the different plasma lipoproteins was as follows: smaller than 1% in very low density lipoprotein and low density lipoprotein; 50% in high density lipoprotein, and 50% in lipoprotein fraction of density greater than 1.21 g/ml. The amount of apolipoprotein A-I in the latter fraction was found to be related to the number of centrifugations.

Animals↗
PubMed2026

Proteomic Profiling of Pulmonary Function and Cardiovascular Disease Risk in the Atherosclerosis Risk in Communities Study.

BACKGROUND: Pulmonary function is linked to cardiovascular disease risk; however, the underlying mechanisms remain unclear. We aimed to identify protein biomarkers associated with pulmonary function and examine their impact on incident chronic obstructive pulmonary disease, coronary heart disease, heart failure, and all-cause mortality. METHODS: Data from White and Black Americans in the Atherosclerosis Risk in Communities study (visit 2: N=11&#x2009;354, mean age=57 years; visit 5: N=3517, mean age=75 years), a prospective cohort, were analyzed. Linear regression assessed associations between protein levels and pulmonary function measures, including forced expiratory volume in 1 second and forced vital capacity. The impact of the identified proteins on incident chronic obstructive pulmonary disease, coronary heart disease, heart failure, and mortality was estimated using logistic regression and Cox proportional hazards models. Pathway enrichment and Mendelian randomization explored underlying biological functions and causal effects. RESULTS: Of 4766 proteins analyzed, 364 were cross-sectionally associated with forced expiratory volume in 1 second (and forced vital capacity (false discovery rate<0.05). Ninety-four and 270 proteins had concordant positive and negative effects, respectively. Five pathways related to pulmonary and cardiac function were enriched. Of the 364 proteins, 112 were linked to all 4 outcomes, where 86 were associated with increased risk (odds ratio/hazard ratio [OR/HR], 1.05-1.42) and 26 with reduced risk (OR/HR, 0.69-0.96). Six proteins (STAT3 [signal transducer and activator of transcription 3], MIC-1 [growth differentiation factor 15], apoA-II [apolipoprotein A-II], TPST1 [protein-tyrosine sulfotransferase 1], integrin a1b1 [integrin alpha-I: beta-1 complex], and BLC [C-X-C motif chemokine 13]) showed potential inverse causal effects on with forced expiratory volume in 1 second and forced vital capacity, and integrin a1b1 demonstrated consistent inverse associations with chronic obstructive pulmonary disease, coronary heart disease, and heart failure risks. CONCLUSIONS: Proteins associated with pulmonary function may influence CVD risk. Six proteins, including integrin a1b1, represent promising targets for future interventions.

Aged↗
PubMed1976

Determination of apolipoprotein A and its constitutive A-I and A-II polypeptides by separate electroimmunoassays.

Electroimmunoassays ("rocket" electrophoresis) are described for human serum apolipoprotein A and its constitutive A-I and A-II polypeptides. Purified lipoprotein A, A-I, and A-II were used to prepare monospecific antisera and to standardize assays. These specific, rapid (5-8 h), precise (the within-and between-assay coefficients of variations are 5 and 7%, respectively), and accurate (by gravimetry) assays are applicable to measurement of these polypeptides in whole serum and in various density classes of lipoproteins. Comparable results are obtained with intact and delipidized lipoproteins. Results correlated well with those obtained by radial immunodiffusion or radioimmunoassay. However, the present procedure is more rapid than the former and simpler than the latter immunoassay. Concentrations of A-I and A-II in the serum of normal men and women were similar (143 +/- 24 and 146 +/- 78 mg/dl, respectively, for A-I and 78 +/- 17 and 83 +/- 25 mg/dl for A-II). Subjects with type lla, llb, and IV hyperlipoproteinemias had similar concentrations of both polypeptides, while patients with type I disease, lecithin:cholesterol acyltransferase deficiency and LP-A deficiency had lowest concentrations of A-I (0.3-30 mg/dl) and A-II (11-20 mg/dl). The molar ratio of A-I/A-II in the serum and high-density lipoproteins was close to unity.

Apoproteins↗
PubMed1977

Quantitative determination of human apolipoprotein D by electroimmunoassay and radial immunodiffusion.

1. An electroimmunoassay and a radial immunodiffusion procedure are described for the quantitative determination of human serum apolipoprotein D. Purified apolipoprotein D and antisera to both lipoprotein D and apolipoprotein D were used to standardize the assays. The assays are applicable to measurement of apolipoprotein D in serum and density classes. The electroimmunoassay is more sensitive (50 ng apolipoprotein D quantitatively detectable), rapid (time required for completion of assay is 5 h) and precise (the within- and between-assay coefficients of variation are 4 and 7%, respectively) than radial immunodiffusion. However, comparable results were obtained by both methods (r = 0.85). 2. Serum apolipoprotein D levels of normal subjects and hyperlipoproteinemic phenotypes IIa, IIb, III, IV and V were in the same range (10 to 12 mg/dl). In contrast, patients with hyperchylomicronemia (type I) had decreased apolipoprotein D levels (5 mg/dl; P less than 0.001). The apolipoprotein D in serum of normolipidemic subjects was detectable in all density classes but measurable only in HDL2 (21%), HDL3 (43%) and VHDL (36%). 3. Rocket electrophoresis is also a valuable tool for assessing the structural relationships among apolipoproteins or their constituent polypeptides. Interaction between serum and a mixture of antibodies to A-I, A-II and apolipoprotein D resulted in the formation of separate lipoprotein A and lipoprotein D rockets indicating that apolipoprotein D is not a constituent polypeptide of apolipoprotein A. This observation confirms the existence of lipoproteins A and D as separate lipoprotein families.

Apolipoproteins↗
PubMed1977

Evolution of lipoproteins deduced from protein sequence data.

1. Human serum apolipoprotein A-I contains a prominent 11-residue sequence periodicity. 2. Similar 11-residue segments occur in the other sequenced human apolipoproteins, C-I, C-III, and A-II. 3. Computer analyses of the sequences support the hypothesis that they evolved from a common ancestor. 4. An evolutionary history of these proteins is proposed. 5. The estimated rate of change of these proteins indicates that all four types will be found throughout the vertebrates and that related proteins will also be found in invertebrates.

Amino Acid Sequence↗
PubMed1978

Serum high-density lipoproteins in peripheral vascular disease.

High-density lipoprotein (H.D.L.) cholesterol has been measured by the 'Autoanalyzer', and apolipoproteins A-I, A-II, and B by an immunochemical method, in 100 patients with peripheral vascular disease (P.V.D.) and in 93 age and sex matched controls with an approximately similar prevalence of hyperlipidaemia. The patients with P.V.D. had significantly lower levels of the H.D.L. apolipoproteins (especially of apo A-I) than the controls. Further analysis of the data showed low H.D.L. levels to be related to the presence (but not to the severity) of the arterial disease and to be independent of concurrent hyperlipidaemia and smoking habits. The changes in H.D.L. apoproteins were not so clearly reflected by H.D.L.-cholesterol measurements in the same patients, possibly because of methodological reasons. It is therefore suggested that studies relating serum-H.D.L. to arterial disease may be more informative if both the lipid and protein portions of these lipoproteins are measured.

Apolipoproteins↗
PubMed1975

Plasma lipoprotein abnormalities in a case of primary high-density lipoprotein (HDL) deficiency.

A 53-year-old patient with primary HDL-deficiency is reported. About 2% of the normal concentration of alpha1 HDL was present in his plasma. The alpha1-high-density-lipoproteins separated into two fast-moving components in polyacrylamide gel electrophoresis. The Apo HDL contained both the main apolipoproteins, Apo A-I and Apo A-II, but in disproportionally reduced amounts, the concentration of Apo A-I being reduced about 360-fold, and that of Apo A-II about 14-fold. Concomitantly, the amount of the Apo C polypeptides in the HDL-fractions was decreased to about 5.5% and the activity of the enzyme lecithin cholesterol acyltransferase (EC 2.3.1.4.3) in plasma was found to be only 40% of normal. Apoprotein D was present in the LDL in association with Apo B, forming an abnormal, fast-moving LDL-complex. Apo A-I and Apo A-II were both of normal size as determined by SDS-PAGE, and reduction with thiols resulted in the shift of the M.W. of Apo A-II from 17,000 daltons to about 8,500 daltons. Both proteins were found in the same position as their normal counterparts in analytical isoelectric focusing. The most likely explanation for the multiple lipoprotein abnormalities seems to be that a defect in the regulation or structure of Apo A-I is the basis of the HDL-deficeincy.

Blood Protein Electrophoresis↗
PubMed1975

A critical evaluation of the proposal that serum apolipoproteins are the major constituents of the human erythrocyte membrane.

1. The EDTA and Triton X-100 extracts of human erythrocyte ghosts gave no precipitin lines in double diffusion analyses with antibodies to either lipoprotein A, lipoprotein B, lipoprotein C, lipoprotein D, Lp(a) lipoprotein or arginine-rich apolipoprotein of normal human serum (for nomenclature for serum lipoprotein families and apolipoptoteins, see Alaupovic, P., Kostner, G., Lee, D. M., McConathy, W.J. and Magnani, HN. (1972) Expo. Annu. Biochem. Med. 31, 145-160 and Alaupovic, P., Lee, D.M. and McConathy, W.J., (1972) Biochim. Biophys. Acta 260, 689-707.) These membrane preparations also reacted negatively with commercially available antisera to alpha- and beta-lipoproteins. 2. The normal serum very low density, low density and high density lipoproteins formed no precipitin lines with antibodies to either intact or EDTA-extracted ghosts. 3. The serum apolipoproteins and their constitutive polypeptides (A-I, A-II, B, C-I, C-II, C-III, D and arginine-rich apolipoprotein) reacted negatively with antibodies to intact or EDTA-extracted ghosts. The EDTA and Triton X-100 extracts of erythrocyte ghosts gave no reaction with monospecific antibodies to serum apolipoproteins and their constitutive polypeptides. 4. Ghosts dissolved 2% sodium dodecyl sulfate gave positive immunoprecipitin lines with antisera to alpha- and beta-lipoproteins. However, the sodium dodecyl sulfate solution in concentrations greater than 0.1% also formed precipitin lines with antisera to the same lipoproteins. 5. These results do not support the suggestion (Langdon, R.G. (1974) Biochim. Biophys. Acta 342, 213-228) that serum apolipoptoteins are integral protein constituents of human erythrocyte ghosts. The immunoprecipitin lines observed in the latter study might have been due to the presence of trace amounts of serum lipoproteins loosely attached to the cellular surfaces or, more probably, resulted from nonspecific interactions between the proteins and the sodium dodecyl sulfate used as the solubilizing agent

Apoproteins↗
PubMed1976

Studies on the isolation and partial characterization of apolipoprotein D and lipoprotein D of human plasma.

This report describes further studies on the characterization of apolipoprotein D (ApoD), a recently recognized human plasma apolipoprotein, and presents results on the isolation and distribution of its lipoprotein form, lipoprotein D (LP-D). ApoD, isolated by a procedure combining hydroxylapatite and Sephadex G-100 column chromatography, migrated on 7% polyacrylamide gel as a single band with a mobility intermediate between those of A-II and C-II polypeptides. On double diffusion and immunoelectrophoresis, ApoD reacted only with antiserum to ApoD. It was characterized by the presence of all common amino acids including half-cystine. The amino terminal acid was blocked. Carbohydrate analysis demonstrated that ApoD is a glycoprotein with glucose, mannose, galactose, glucosamine, and sialic acid accounting for 18% of the dry weight of ApoD. The estimated molecular weight of ApoD IS 22 100. ApoD occurs in the serum as a lipoprotein which was isolated from high density lipoproteins3 by two different chromatographic procedures. In the first procedure, high density lipoproteins3 were treated with neuraminidase and chromatographed on concanavlin A. The retained fraction containing LP-D was purified by hydroxylapatite column chromatography. Alternatively, LP-D was isolated by a procedure combining chromatography of high density lipoproteins3 or whole serum on an immunosorber containing antibodies to ApoD, and hydroxylapatite column chromatography. LP-D displayed a single, symmetrical boundary in the analytical ultracentrifuge and a single band on 7% polyacrylamide gel electrophoresis. When injected into rabbits it produced antisera that reacted only with ApoD. On immunoelectrophoresis LP-D had a mobility different from that of lipoprotein A (LP-A). A direct immunological comparison of LP-D and LP-A showed a reaction of nonidentity. LP-D consists of 65-75% protein and 25-35% lipid. The lipid moiety contains cholesterol, cholesterol ester, triglyceride, and phospholipid. The phospholipid. composition is characterized by a relative high content of lysolecithin and sphingomyelin and a relatively low content of lecithin. We have concluded from these studies that ApoD is a unique apolipoprotein that exists in the form of a distinct lipoprotein family with a macromolecular distribution extending from very low density lipoproteins into very high density lipoproteins, but with a maximum concentration in high density lipoproteins3 and a minimum concentration in high density lipoproteins.

Amino Acids↗
PubMed1977

Isolation and characterization of an abnormal high density lipoprotein in Tangier Diesase.

The nature of the high density lipoproteins has been investigated in five patients homozygous for Tangier disease (familial high density lipoprotein deficiency). It has been established that Tangier high density lipoproteins, as isolated by ultracentrifugation, are morphologically heterogenous and contain several proteins (Apo B, albumin, and Apo A-II). An abnormal lipoprotein has been isolated from the d = 1.063-1.21 g/ml ultracentrifugal fraction by agarose-column chromatography which contains apoprotein A-II as the sole protein constituent. In negative-stain electron microscopy, these lipoproteins appeared as spherical particles 55-75 A in diameter. By a variety of criteria (immunochemical, polyacrylamide electrophoresis, amino acid composition, and fluorescence measurements), apoprotein A-I the major apoprotein of normal high density lipoproteins and the C apoproteins were absent from this lipoprotein. As demonstrated by (125)I very low density lipoprotein incubation experiments with Tangier plasma, C apoproteins did not associate with lipoproteins of d = 1.063-1.21 g/ml. Tangier apoprotein A-II, isolated to homogeneity by delipidation of the apoprotein A-II-containing lipoprotein or Sephadex G-200 guanidine-HCl chromatography of the d = 1.063-1.21 g/ml fraction, was indistinguishable from control apoprotein A-II with respect to amino acid composition and migration of tryptic peptides in urea-polyacrylamide electrophoresis. The ability of Tangier apoprotein A-II to bind phospholipid was demonstrated by in vitro reconstitution experiments and morphological and chemical analysis of lipid-protein complexes. It is concluded that normal high density lipoproteins, as defined by polypeptide composition and morphological appearance, are absent from Tangier plasma and that as a consequence, the impairment of C apoprotein metabolism contributes to the hypertriglyceridemia and fasting chylomicronemia observed in these patients.

Amino Acids↗
PubMed1977

The lipoprotein abnormality in Tangier disease: quantitation of A apoproteins.

In this study we have determined by radioimmunoassay and double immunoelectrophoresis the total quantities and distributions of A apoproteins in three adult patients affected with Tangier disease (hereditary alpha-lipoprotein deficiency). Compared with normal plasma, the total quantities of apoproteins A-I and A-II in Tangier plasma were determined to be less than 1% and 5-7%, respectively. In Tangier patients, approximately 90% of the apoprotein A-I sedimented when ultracentrifugations of plasma were carried out at density 1.21 g/ml KBr. By contrast, more than 95% of the apoprotein A-II floated under those conditions. In normal plasma, approximately 90% of both apoproteins A-I and A-II is found in the 1.063-1.21-g/ml KBr density fraction. These findings suggest that complete dissociation of A apoproteins occurs in Tangier plasma. This dissociation of apoproteins was confirmed by double immunoelectrophoresis with monospecific antisera. Immunochemical and electrophoretic experiments did not provide evidence for a structural abnormality of apoprotein A-I in these patients, The results taken together strongly suggest that normal high-density lipoproteins are absent from Tangier plasma.

Adult↗
PubMedDate not supplied

Lipid transport in the avian species. Part I. Isolation and characterization of apolipoproteins and major lipoprotein density classes of male turkey serum.

(1) Lipoproteins from the serum of male turkeys maintained on a normal diet were separated by sequential preparative ultracentrifugation into VLDL (d less than 1.006 g/ml), LDL (d = 1.006-1.063 g/ml), HDL (d = 1.063-1.21 g/ml) and VHDL (d greater than 1.21 g/ml). Lipoprotein density classes were characterized by analytical ultracentrifugation, agarose electrophoresis, immunodiffusion and immunoelectrophoresis, and by quantitative determination of protein, lipids and individual phosphatides. (2) HDL were the major density class representing 75% of the total lipoprotein content, LDL accounted for approximately 20% and VLDL for only 3-5% of the total lipoproteins. (3) VLDL were characterized by a relatively low content of glyceride (34%). Cholesterol esters were the major lipid (38%) of LDL, and the phospholipids (26%) of HDL. Glycerides of all major density classes consisted of equal amounts of triglycerides and diglycerides. (4) Phosphatidylcholine was the major phosphatide in all density classes. The composition of phosphatides was very similar in the VLDL and LDL, but it was different in the HDL. The ratio of phosphatidylcholine/sphingomyelin was higher in HDL than in VLDL and LD. (5) Immunological and electrophoretic studies showed that all three major density classes consisted of two lipoprotein families designated, in analogy to the human serum lipoprotein system [1], as LP-A and LP-B. The exception was HDL3 (d = 1.125-1.21 g/ml) which contained only LP-A. (6) ApoB was insoluble in aqueous buffers but could be solubilized after reduction and carboxymethylation. No C- or N-terminal amino acids were released by the usual chemical methods. The carbohydrate moiety of ApoB contained mannose, galactose and galactosamine. (7) ApoA consisted of a non-identical polypeptides designated in analogy to the human polypeptides as A-I and A-II. A-I was the major ApoA polypeptide and had a molecular weight of about 27,000. This polypeptide contained no half cystine, and the aspartic acid as the N-terminal and alanine as the C-terminal amino acids. A-II had a molecular weight of about 10,000, contained no half cystine and had alanine as the C-terminal amino acid. A-II showed no N-terminal amino acid by either dansylation, dinitrophenylation or Edman's procedure. Neither A-I nor A-II contained neutral sugars or hexosamines. (8) Concentrations of polypetides analogous to human ApoC, ApoD and "arginine-rich" polypeptide, if present, were too low for their unequivocal chemical characterization.

Animals↗
PubMed1977

A new method for the fractionation of human plasma high density lipoprotein.

We have devised a new method for the fractionation of human plasma high density lipoprotein (HDL). The HDL was chromatographed on DEAE-agarose columns using a continuous gradient of 0.06--0.15 M NaCl. The elution pattern obtained showed three phases, each with differing peptide composition. Examination of the three subfraction showed that each contained both apoA-I and apo A-II, but in different proportions. Subfraction 1 contained no apo C-II or C-III-1 and only a trace of apo C-III-2, subfraction 2 contained apo C-II and C-III-1 but no C-III-2, while subfraction 3 contained considerable apo C-III-2 with only traces of apo C-II or C-III-1.

Apolipoproteins↗
PubMed1977

Analysis of rat serum apolipoproteins by isoelectric focusing. II. Studies on the low molecular weight subunits.

The low molecular weight proteins of rat apo HDL and apo VLDL have been isolated and analyzed by the technique of isoelectric focusing. Sephadex fractions from apo HDL (HS-3) and apo VLDL (VS-3) that contain these proteins reveal three major bands with apparent isoelectric points of pH 4.50, 4.67, and 4.74, as well as three minor bands at pH 4.43, 4.57, and 4.61. In addition, apo HDL has a major band at pI of 4.83. DEAE-Cellulose chromatography was used to prepare purified fractions of these components that were characterized by N-terminal analyses and molecular weight determinantions by SDS gel electrophoresis. The major low molecular weight components of apo HDL were focused on a slab gel and the bands were identified as A-II (pI 4.83), C-II (pI 4.74), C-III-0 (pI 4.67), and C-III-3 (pI 4.50). Neuraminidase treatment of apo HDL, followed by isoelectric focusing, suggested that the other bands, which have not previously been reported, may be additional forms of the C-III protein, differing only in their content of sialic acid.

Animals↗