Lipid and apolipoprotein changes after orthotopic liver transplantation for end-stage liver diseases.

Orthotopic liver transplantation was performed in 37 patients with different endstage liver diseases. Changes in lipid and apolipoprotein concentrations were followed daily from day 1 to 20 after surgery and regularly thereafter until 12 months. When the acute effects of surgery had cleared away, there was a sharp drop in HDL-C, apo A-I and A-II from day 1 to 5, a stabilization at their lowest values from day 5 to 15 and then a progressive rise. Contrasting with this drop, triglycerides, apo B, C-II and C-III increased from day 1 to 5 with variable concentrations thereafter. Apo SAA considerably increased early after surgery and remained significantly higher than normal in most patients after 12 months. All other parameters returned to normal from 3 to 6 months after transplant. The mechanism leading to these lipid and apolipoprotein changes are discussed with respect to the distant effect of infusions, re-alimentation, immunosuppressive therapy and lipoprotein metabolism. The apolipoprotein concentrations appear very useful indicators of functional liver recovery.

Receptor-dependent and -independent catabolism of low-density lipoprotein in a kindred with familial hypobetalipoproteinemia.

Three affected members of a kindred with asymptomatic hypobetalipoproteinemia (HBL) were injected intravenously with 125I-labeled native low-density lipoproteins (LDL) and 131I-labeled cyclohexanedione (CHD)-treated LDL. Plasma and urine radioactivity data were collected for 15 days at regular intervals. A compartmental model using the SAAM program was built to fit simultaneously 125I and 131I plasma radioactivity decay and urine excretion data. This model allows precise calculation of the kinetic parameters of both receptor-independent (NR) and receptor-dependent (R) pathways. Compared with normal subjects, HBL patients show a 90% increased fractional catabolic rate (FCR) of LDL by both routes, more marked for the R pathway (215% increase), and an approximately 50% reduced production rate (PR). Structural analysis did not show significant abnormalities of apolipoprotein (apo) B in HBL patients compared with normal. These data suggest that the very reduced, LDL-apo B plasma levels result from a combination of two processes: (1) an increased activity of all catabolic routes, and (2) a reduced "synthesis" rate. The latter may result from a decreased conversion of very-low-density lipoprotein (VLDL) to LDL secondary to an increased direct removal of large VLDL, suggested by apo C-II and C-III turnover studies previously reported.

Alterations in lipoprotein density classes in infantile visceral leishmaniasis: presence of apolipoprotein SAA.

This study describes the alterations in the plasma lipoproteins from nine young Tunisian children with active visceral Leishmaniasis. The plasma lipid profile from affected patients was characterized by a marked hypertriglyceridaemia associated with reduced levels of total and high density lipoprotein (HDL)-cholesterol and a significant increase in the plasma ratio of unesterified to total cholesterol. Quantitative determination of plasma apolipoproteins revealed significantly decreased levels of all measured apolipoproteins, especially of apolipoproteins A-I and A-II, with the exception of apolipoprotein E, the levels of which were markedly increased. Moreover, at least two isoforms of the apolipoprotein serum amyloid A (SAA), an acute phase protein, were detected in all patients' plasma using two-dimensional electrophoresis. Immunochemical evidence was presented that apolipoproteins E and SAA, although both primarily associated with apolipoprotein A- (A-I and A-II) as well as with apolipoprotein B-containing lipoproteins, could occur as LP-E and LP-SAA subspecies, devoid of apolipoproteins A and B. However, it should be pointed out that LP-SAA particles were found in HDL2 from only two patients whereas the abnormal LP-E particles were detected in LDL and HDL2 from all investigated patients. The polydispersity and heterogeneity of patients' HDL3 were assessed by electron microscopy. It was further suggested that the profound changes in the lipoprotein metabolism of these young patients may be due to the increased hepatic synthesis of apolipoprotein SAA and/or to their altered immune function during active visceral Leishmaniasis.

In vivo metabolism of apolipoproteins A-IV and A-I associated with high density lipoprotein in normolipidemic subjects.

The kinetics of apolipoprotein A-IV associated with high density lipoproteins (HDL) of plasma from fasting human subjects was followed for 15 days in five healthy normolipidemic volunteers. Purified apoA-IV and apoA-I were radioiodinated, respectively, with 125I and 131I, incubated in vitro with normal HDL, isolated at density 1.250 g/ml, and finally reinjected intravenously as HDL-125I-labeled apoA-IV and HDL-131I-labeled apoA-I. Blood samples were withdrawn at regular intervals for 15 days, and 24-h urine samples were collected. More than 93% (93.5 +/- 0.9%) of apoA-IV was recovered in apoA-I-containing lipoprotein particles after affinity chromatography on an anti-apoA-I column and 69.7 +/- 4.8% was bound to apoA-II in apoA-I:A-II particles separated on an anti-apoA-II column. 125I-labeled apoA-IV showed a much faster decay than 131I-labeled apoA-I for the first 5 days and thereafter the curves became parallel. Urinary/plasma ratios (U/P) for the 125I-labeled parallel. Urinary/plasma ratios (U/P) for the 125I-labeled apoA-IV were much higher than those for 131I-labeled apoA-I for the first days, but the U/P curves became parallel for the last 7 days, suggesting heterogeneity of apoA-IV metabolism. A heterogeneous multicompartmental model was constructed to describe the metabolism of lipoprotein particles containing apoA-IV and apoA-I and to calculate the kinetic parameters, fitting simultaneously all plasma and urine data for both tracers.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo effect of simvastatin on lipoprotein cholesteryl ester metabolism in normocholesterolemic volunteers.

A kinetic study on lipoprotein cholesteryl ester metabolism was carried out in 4 normolipidemic volunteers before and after treatment with simvastatin. They received LDL labelled with 3H-cholesteryl linoleate. A lipoprotein cholesteryl ester model was developed that fit the radioactivity in LDL, HDL and VLDL cholesteryl ester during 24 hours following injection. Before treatment, the model is consistent with previously reported data. Moreover our results suggest that, in normal fasting subjects, the efflux of plasma cholesteryl ester is almost exclusively derived from LDL. Administration of drug decreased LDL cholesteryl ester concentration by 35%. After treatment, the rate constant concerning LDL catabolism was increased by 25% and the model required the existence of a direct removal of VLDL cholesteryl ester (40% of total VLDL turnover). Our results suggest that the reduction in the LDL cholesteryl ester concentration induced by treatment with simvastatin is due to an increase in the uptake of LDL and LDL precursors (VLDL, VLDL remnants) by LDL receptors.

Apolipoprotein C-II and C-III metabolism in a kindred of familial hypobetalipoproteinemia.

Three affected members of a kindred with asymptomatic hypobetalipoproteinemia (HBL) showed low levels of triglycerides, low-density lipoprotein (LDL)-cholesterol, and apolipoproteins (apo) B, C-II, and C-III. Turnover of iodine-labeled apo C-II and apo C-III associated in vitro to plasma lipoproteins was studied after intravenous injection. Radioactivity in plasma and lipoproteins (95% recovered in high-density lipoprotein [HDL] density range) and in 24-hour urine samples was observed for 16 days. A parallelism of the slowest slopes of plasma decay curves was observed between apo C-II and apo C-III, indicating a partial common catabolic route. Urine/plasma radioactivity ratio (U/P) varied with time, suggesting heterogeneity of metabolic pathways. A new compartmental model using the SAAM program was built, not only fitting simultaneously plasma and urine data, but also taking into account the partial common metabolism of lipoprotein particles (LP) containing apo C-II and apo C-III. The low apo C-II and C-III plasma concentrations observed in HBL compared with normal resulted from both an increased catabolism and a reduced synthesis, these changes being more marked for apo C-III. The modifications in the rate constants of the different pathways calculated from the new model are in favor of an increased direct removal of particles following the fast pathway, likely in the very-low-density lipoprotein (VLDL) density range.

Plasma lipids, lipoproteins and apolipoproteins in two kindreds of hypobetalipoproteinemia.

Plasma lipids and apolipoproteins were quantified in two kindreds of hypobetalipoproteinemia. All affected members were asymptomatic but showed a decrease of 75% in apolipoprotein B and of 69% in LDL-cholesterol. There were no major changes in apo A-I and A-II but all affected family members had reduced levels of apo C-II (by 58%) and C-III (by 59%) without significant decrease in apo C-I and no specific decrease of apo C-III1. Apolipoprotein E is decreased in SDS-PAGE. The plasma level and phenotype of Lp(a) are not affected by HBL, suggesting that a catabolic rather than a synthetic mechanism is responsible for the disease. As shown by density gradient ultracentrifugation, HDL2 particles that contain essentially apolipoprotein A-I, cholesterol and phospholipids represent in affected subjects the major part of HDL. Due to the net reduction of apolipoprotein B-containing particles (VLDL and LDL) as acceptors of lipids in HBL, there is an accumulation of large particles rich in cholesteryl esters.

Characterization of anti-apolipoprotein A-I monoclonal antibodies and their use in the measurement of apolipoprotein A-I by a two-site enzyme immunoassay.

Six monoclonal antibodies raised against pure apo A-I or high density lipoprotein were characterized for epitope specificity by enzyme and radioimmunoassays, immunodiffusion and affinity chromatography. The six antibodies were classified into three groups according to the region of apo A-I they reacted with. The antibody VI10H, from group II, appeared to recognize a region fully exposed on native HDL-apo A-I, whereas group I comprised antibodies specific for a partially masked region. Group III comprised only one antibody. Use of the non-ionic detergent Tween 20 in the immunoassays permitted antibodies from the three groups to react with their respective epitope on native HDL-apo A-I. An antibody from group I (V4F) was chosen as the first antibody and VI10H, the antibody showing the highest affinity, was chosen for the anti-A-I-peroxidase conjugate in a two-site enzyme immunoassay.

Effect of simvastatin on receptor-dependent low density lipoprotein catabolism in normocholesterolemic human volunteers.

Simvastatin, an inhibitor of HMG-CoA reductase was given to 7 normolipidemic healthy volunteers for 1 month at a dose of 20 mg/day. Measurements of turnover of low density lipoprotein apolipoprotein B (LDL-apo B) were determined before and after drug treatment using intravenous injection of 125I-labeled LDL and 131I-labeled cyclohexanedione-treated LDL to quantify the receptor pathway. In addition to a 13% increase in HDL cholesterol and apolipoprotein A-I concentrations, plasma cholesterol was reduced by 20%, LDL-cholesterol by 32%, and apolipoprotein B by 23%. Assuming a heterogeneous pool of LDL, the new model presented in the companion paper was built to calculate the contribution of the receptor-dependent and the receptor-independent pathways and the corresponding fractional catabolic rates. Simvastatin did not modify constantly the synthetic rate of LDL-apo B but increased the fractional catabolic rate of the receptor-dependent pathway and the contribution of this pathway in the catabolism. The fall in LDL plasma levels observed in normocholesterolemic subjects can be then entirely explained by an enhanced fractional removal of LDL from the circulation by the receptor route.

Kinetics of a heterogeneous population of particles in low density lipoprotein apolipoprotein B.

This paper examines the kinetics of low density lipoprotein (LDL) metabolism following the in vivo injection of native and chemically-modified lipoproteins in an attempt to assess the relative importance of receptor-dependent and receptor-independent catabolic pathways. The shape of the urinary/plasma ratio curve suggested heterogeneity of the LDL-apolipoprotein B pool and excluded homogeneity. This heterogeneity required the building of a more complex model that allowed the simultaneous fitting of plasma and urinary data. This new model permits the precise quantification of both receptor and non-receptor pathways.

Plasma lipoproteins in infantile visceral leishmaniasis: deficiency of apolipoproteins A-I and A-II.

This study describes the plasma lipoprotein system of young children with visceral Leishmaniasis (Kala-azar disease). In addition to the presence of amastigote forms in the sternal aspirates of bone marrow, the patients exhibited fever, anemia, hepatosplenomegaly, various degrees of pancytopenia and a slight liver cytolysis. Patients had normal total cholesterol levels and increased triglyceride levels in the plasma. The concentrations of HDL and LDL were 30% and 50% of these reported for normolipemic subjects, respectively. In contrast, there was a three-fold increase in the concentration of VLDL. The ratio of free to total cholesterol was high; this was further substantiated by electron microscopy of HDL showing the presence of disc-like particles. Quantitative determination of apolipoproteins revealed a three- and seven-fold decrease of apolipoproteins (Apo) A-I and A-II, respectively, whereas Apo B levels were within the normal range. The presence of LP-A-II particles was demonstrated by two-dimensional immunoelectrophoresis in most of the patients' plasma during the acute phase of disease.

Apolipoproteins C-II and C-III metabolism in hypertriglyceridemic patients. Effect of a drastic triglyceride reduction by combined diet restriction and fenofibrate administration.

Four hypertriglyceridemic patients, who had received an equilibrated high calorie diet and no lipid lowering drug for 1 month, were injected intravenously with 125I-apo C-II and 131I-apo C-III labeled homologous lipoproteins. Plasma and urine radioactivity, lipid and apolipoprotein levels were followed at regular intervals for 15 days. At the end of this first kinetic study the patients were advised to adhere for 1 month to a more restricted diet, limited in fat, and were given additionally 300 mg fenofibrate daily. After this treatment, a new kinetic study involving intravenous injection (similar to the first one) was performed. The protocols of both studies were identical. Treatment (diet plus drug) (1) reduced total cholesterol by 26 +/- 8%, triglycerides by 56 +/- 15%, apo C-II by 36 +/- 14%, and apo C-III by 48 +/- 10%; (2) modified the distribution of radioactivity between lipoproteins proportionally to the change in their mass ratio (decrease in VLDL and increase in HDL); (3) changed the kinetics of both apoproteins by rising the fractional removal rate, shortening residence time and decreasing the synthesis rate of both apolipoproteins C-II and C-III. The treatment was, however, unable to reduce the synthesis rate of apo C-III to normal, suggesting a major role of the apoprotein overproduction in the triggering of hypertriglyceridemia.

Modifications of plasma lipids, lipoproteins and apolipoproteins in advanced cancer patients treated with recombinant interleukin-2 and autologous lymphokine-activated killer cells.

Intravenous injection of recombinant interleukin-2 (r-Met-hu-IL-2(Ala-125] and LAK cells induced dramatic changes of lipoproteins in 12 patients with advanced cancer. After r-IL-2 injection (1) total cholesterol was reduced by 47% as a mean, LDL-cholesterol by 62%, HDL-cholesterol by 77%; (2) the triglyceride/cholesterol ratio was greatly increased (352%); (3) apolipoproteins B, A-I and A-II showed a mean reduction of 26%, 55% and 51%, respectively; and (4) very low density lipoproteins relatively increased, and HDL were separated into two definite fractions (I and II). LAK cell administration accentuated all the above effects and in most patients, HDL-fraction I almost completely disappeared. An action on hepatic synthesis of acute phase proteins is pointed out by the increase in C-reactive protein and apolipoprotein S concentrations contrasting with an unexpected reduction of fibrinogen. Surprisingly the drastic changes caused by treatment were quickly and completely reversible.

Non-competitive enzyme-linked immunosorbent assay for human apolipoprotein SAA or S.

Purified antibodies against human apolipoprotein S were used to measure apo S levels in human plasma by a sandwich ELISA technique. The method developed was highly sensitive and specific. A reliable calibration of a plasma standard was obtained by reassociating the purified protein with plasma HDL. A significant correlation (r = 0.69) was found between plasma apo S and CRP values. This correlation coefficient reached 0.97 when the plasma samples were selected according to additional clinical and laboratory criteria.

Proposed folding pattern for apolipoprotein A-II based on a structural analogy with uteroglobin.

The tertiary structure observed in the crystalline state for uteroglobin, a small steroid binding protein, is used as a template to build an approximated model for apolipoprotein A-II. The presence of four proline residues and four hydrophobic clusters located at similar positions in apolipoprotein A-II and uteroglobin is taken as the major source of stability in such tertiary structures. A brief description of plausible specific binding sites appearing on the model of apolipoprotein A-II is given. It is suggested that the internal cavity and the four surface pockets observed for uteroglobin and postulated for apolipoprotein A-II might be used to insure specific binding of triglycerides, phospholipids, or cholesterol.