Association of the inflammatory state in active juvenile rheumatoid arthritis with hypo-high-density lipoproteinemia and reduced lipoprotein-associated platelet-activating factor acetylhydrolase activity.
OBJECTIVE: To investigate the relationship between the quantitative and qualitative abnormalities of apolipoprotein B (Apo B)- and Apo A-I-containing lipoproteins and between lipoprotein-associated platelet-activating factor acetylhydrolase (PAF-AH) activity in patients with juvenile rheumatoid arthritis (JRA) as a function of the inflammatory state. METHODS: Twenty-six JRA patients and 22 age- and sex-matched control subjects with normal lipid levels participated in the study. Fourteen patients had active disease, and 12 had inactive disease. Plasma lipoproteins were fractionated by gradient ultracentrifugation into 9 subfractions, and their chemical composition and mass were determined. The PAF-AH activity associated with lipoprotein subfractions and the activity in plasma were also measured. RESULTS: Patients with active JRA had significantly lower plasma total cholesterol and high-density lipoprotein (HDL) cholesterol levels as compared with controls, due to the decrease in the mass of both the HDL2 and HDL3 subfractions. Patients with active JRA also had higher plasma triglyceride levels, mainly due to the higher triglyceride content of the very low-density lipoprotein plus the intermediate-density lipoprotein subfraction. The plasma PAF-AH activity in patients with active JRA was lower than that in controls, mainly due to the decrease in PAF-AH activity associated with the intermediate and dense low-density lipoprotein subclasses. The lipid abnormalities and the reduction in plasma PAF-AH activity were significantly correlated with plasma C-reactive protein levels and were not observed in patients with inactive JRA. CONCLUSION: This is the first study to show that patients with active JRA exhibit low levels of HDL2 and HDL3 and are deficient in plasma PAF-AH activity. These alterations suggest that active JRA is associated with partial loss of the antiinflammatory activity of plasma Apo B- and Apo A-I-containing lipoproteins. (+info)
Molecular dynamics on a model for nascent high-density lipoprotein: role of salt bridges.
The results of an all-atom molecular dynamics simulation on a discoidal complex made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and a synthetic alpha-helical 18-mer peptide with an apolipoprotein-like charge distribution are presented. The system consists of 12 acetyl-18A-amide (Ac-18A-NH2) (. J. Biol. Chem. 260:10248-10255) molecules and 20 molecules of POPC in a bilayer, 10 in each leaflet, solvated in a sphere of water for a total of 28,522 atoms. The peptide molecules are oriented with their long axes normal to the bilayer (the "picket fence" orientation). This system is analogous to complexes formed in nascent high-density lipoprotein and to Ac-18A-NH2/phospholipid complexes observed experimentally. The simulation extended over 700 ps, with the last 493 ps used for analysis. The symmetry of this system allows for averaging over different helices to improve sampling, while maintaining explicit all-atom representation of all peptides. The complex is stable on the simulated time scale. Several possible salt bridges between and within helices were studied. A few salt bridge formations and disruptions were observed. Salt bridges provide specificity in interhelical interactions. (+info)
Apolipoprotein A-I of hyperlipidemia atherosclerosis prone (LAP) quail: cDNA sequence and tissue expression.
Apolipoprotein A-I (apo A-I) has an important role in the transport of cholesterol. This study describes the complete nucleotide and deduced amino acid sequence for apo A-I of LAP quail. A full length apo A-I cDNA clone for hyperlipidemia atherosclerosis prone (LAP) quail was isolated from a lambda gt10 liver cDNA library. The DNA sequence of LAP apo A-I cDNA was similar to that of normal Japanese quail. The deduced amino acid sequence of LAP apo A-I was hence identical to that of normal Japanese quail. LAP apo A-I mRNA is about 1.4 kilobases in length and expressed in a variety of tissues including small intestine, liver, lung, breast muscle, testis, and heart. Although the tissue distribution of apo A-I was similar between strains, LAP quail expressed more apo A-I mRNA than normal Japanese quail in all tissues examined. This tendency was pronounced with the small intestine. Although the concentration of serum apo A-I did not correlate with the tissue expression of mRNA, the observation may suggest that the increased apo A-I expression in LAP strain had some relevance to the susceptibility of this strain to the experimental atherosclerosis. (+info)
Multiple dysfunctions of two apolipoprotein A-I variants, apoA-I(R160L)Oslo and apoA-I(P165R), that are associated with hypoalphalipoproteinemia in heterozygous carriers.
ApoA-I(R160L)Oslo and apoA-I(P165R) are naturally occurring apolipoprotein (apo) A-I variants that are associated with low HDL-cholesterol in heterozygous carriers. We characterized the capacity of these variants to bind lipid, to activate lecithin:cholesterol acyltransferase (LCAT), and to promote efflux of biosynthetic cholesterol from porcine aortic smooth muscle cells (SMCs) or exogenous cholesterol from lipid-loaded mouse peritoneal macrophages. During cholate dialysis, normal apoA-I and both variants associated completely with dipalmitoylphosphatidylcholine (DPPC) and formed rLpA-I of identical size. However, both apoA-I(P165R) and apoA-I(R160L)Oslo showed a reduced capacity to clear a turbid emulsion of dimyristoylphosphatidylcholine (DMPC). Compared to normal apoA-I, the LCAT-cofactor activity of apoA-I(P165R) and apoA-I(R160L)Oslo as defined by the ratio of Vmax to appKm was reduced significantly by 62% and 29%, respectively (here and throughout the text, the apparent Km is given as Michaelis-Menten kinetics do not take particle binding into account and therefore would result in errors with an interfacial enzyme such as LCAT; Vmax estimates are not affected by this error). ApoA-I/DPPC complexes induced biphasic cholesterol efflux from SMCs with a fast and a slow efflux component. Compared to rLpA-I reconstituted with wild type apoA-I, rLpA-I with apoA-I(P165R) or apoA-I(R160L)Oslo were significantly less effective in promoting cholesterol efflux from SMCs in incubations of 10 min duration but equally effective in incubations of 6 h duration. Lipid-free apoA-I did not induce efflux of biosynthetic cholesterol from SMCs but induced hydrolysis of cholesteryl esters and cholesterol efflux from acetyl-LDL-loaded mouse peritoneal macrophages. In the lipid-free form, both apoA-I variants promoted normal cholesterol efflux from murine peritoneal macrophages. We conclude that amino acid residues arginine 160 and proline 165 of apoA-I contribute to the formation of a domain that is very important for initial lipid binding and contributes to LCAT-activation and promotion of initial cholesterol efflux but not to the stabilization of preformed rLpA-I. (+info)
Apolipoprotein A-I charge and conformation regulate the clearance of reconstituted high density lipoprotein in vivo.
While low apolipoprotein A-I (apoA-I) levels are primarily associated with increased high density lipoprotein (HDL) fractional catabolic rate (FCR), the factors that regulate the clearance of HDL from the plasma are unclear. In this study, the effect of lipid composition of reconstituted HDL particles (LpA-I) on their rate of clearance from rabbit plasma has been investigated. Sonicated LpA-I containing 1 to 2 molecules of purified human apoA-I and 5 to 120 molecules of palmitoyl-oleoyl phosphatidylcholine (POPC) exhibit similar charge and plasma FCR to that for lipid free apoA-I, 2.8 pools/day. Inclusion of 1 molecule of apoA-II to an LpA-I complex increases the FCR to 3.5 pools/day, a value similar to that observed for exchanged-labeled HDL3. In contrast, addition of 40 molecules of triglyceride, diglyceride, or cholesteryl ester to a sonicated LpA-I containing 120 moles of POPC and 2 molecules of apoA-I increases the negative charge of the particle and reduces the FCR to 1.8 pools/day. Discoidal LpA-I are the most positively charged lipoprotein particles and also have the fastest clearance rates, 4.5 pools/day. Immunochemical characterization of the different LpA-I particles shows that the exposure of an epitope at residues 98 to 121 of the apoA-I molecule is associated with an increased negative particle charge and a slower clearance from the plasma. We conclude that the charge and conformation of apoA-I are sensitive to the lipid composition of LpA-I and play a central role in regulating the clearance of these lipoproteins from plasma. conformation regulate the clearance of reconstituted high density lipoprotein in vivo. (+info)
ApoA1 reduces free cholesterol accumulation in atherosclerotic lesions of ApoE-deficient mice transplanted with ApoE-expressing macrophages.
Along with apolipoprotein (apo) E, which promotes cholesterol efflux from foam cells, apoA1-containing high density lipoprotein (HDL) is thought to facilitate the transport of cholesterol from lesions. This role for apoA1 was tested in vivo by lethally irradiating apoE-deficient and apoE- plus apoA1-deficient mice and reconstituting them with bone marrow cells isolated from wild-type (WT) mice. ApoE, but not apoA1, was synthesized by the transplanted bone marrow-derived cells. Therefore, this transplantation procedure generated apoE-deficient animals with atherosclerotic lesions that contained both apoE and apoA1 (E/A1 mice) and apoE-deficient animals with lesions that contained apoE but no apoA1 (E/A1o mice). As shown previously, the transplanted WT macrophage-derived apoE dramatically lowered the plasma hypercholesterolemia in both groups. On feeding with an atherogenic diet after transplantation, plasma cholesterol levels were raised in both groups of mice, but the levels in the E/A1 mice at 20 weeks were 2- to 3-fold higher than in E/A1o mice. Immunohistochemical staining verified that apoE was abundant in lesions of both groups, whereas apoA1 was detected in the lesions of E/A1 mice only. Despite a 2- to 3-fold lower total plasma cholesterol in the E/A1o mice, the free cholesterol recovered from isolated aortas was approximately 60% higher and the mean lesion area in serial sections of the aortic valves 45% larger. Therefore, apoA1 reduces free cholesterol accumulation in vivo in atherosclerotic lesions. (+info)
Targeted mutation of plasma phospholipid transfer protein gene markedly reduces high-density lipoprotein levels.
It has been proposed that the plasma phospholipid transfer protein (PLTP) facilitates the transfer of phospholipids and cholesterol from triglyceride-rich lipoproteins (TRL) into high-density lipoproteins (HDL). To evaluate the in vivo role of PLTP in lipoprotein metabolism, we used homologous recombination in embryonic stem cells and produced mice with no PLTP gene expression. Analysis of plasma of F2 homozygous PLTP-/- mice showed complete loss of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, and partial loss of free cholesterol transfer activities. Moreover, the in vivo transfer of [3H]phosphatidylcholine ether from very-low-density proteins (VLDL) to HDL was abolished in PLTP-/- mice. On a chow diet, PLTP-/- mice showed marked decreases in HDL phospholipid (60%), cholesterol (65%), and apo AI (85%), but no significant change in non-HDL lipid or apo B levels, compared with wild-type littermates. On a high-fat diet, HDL levels were similarly decreased, but there was also an increase in VLDL and LDL phospholipids (210%), free cholesterol (60%), and cholesteryl ester (40%) without change in apo B levels, suggesting accumulation of surface components of TRL. Vesicular lipoproteins were shown by negative-stain electron microscopy of the free cholesterol- and phospholipid-enriched IDL/LDL fraction. Thus, PLTP is the major factor facilitating transfer of VLDL phospholipid into HDL. Reduced plasma PLTP activity causes markedly decreased HDL lipid and apoprotein, demonstrating the importance of transfer of surface components of TRL in the maintenance of HDL levels. Vesicular lipoproteins accumulating in PLTP-/- mice on a high-fat diet could influence the development of atherosclerosis. (+info)
Effect of moderate improvement in metabolic control on magnesium and lipid concentrations in patients with type 1 diabetes.
OBJECTIVE: To evaluate the effect of clinically obtainable improvements in metabolic control in patients with type 1 diabetes on biochemical cardiovascular risk factors. RESEARCH DESIGN AND METHODS: Blood and 24-h urinary samples were obtained from 49 patients with type 1 diabetes before and after a run-in period and after 3 months of intervention, with frequent adjustment of insulin dosage according to measured blood glucose concentrations. RESULTS: The intervention caused a mean insulin dosage increment of 10%, a 20% decrease in fasting plasma glucose concentration, a 10% decrease in albumin corrected serum fructosamine, and a somewhat lesser decrease in HbAlc.A 14% decrease in the renal excretion of magnesium (Mg) was observed, but without a change in average serum Mg concentration. Serum HDL cholesterol increased 4%, and serum triglycerides decreased 10% as an average. Looking at individual patients, the decrease in serum triglycerides correlated with both the change in serum total Mg concentration and with the increase in insulin dosage. Using the change in serum total Mg concentration and in insulin dosage as independent variables in a multiple regression analysis, the coefficient of correlation with the decrease in serum triglycerides was 0.52. CONCLUSIONS: Moderate but clinically obtainable improvement of metabolic control in patients with type 1 diabetes seems to reduce the loss of Mg, increase serum HDL cholesterol, and decrease serum triglycerides. The decrease in serum triglycerides was associated with the change in serum total Mg concentration. These reductions in Mg loss and serum triglycerides might reduce the risk of developing cardiovascular disease in patients with type 1 diabetes. (+info)