Plasma antioxidant enzymes and oxidized lipoproteins in hypercholesterolemic rabbits.

Silva EL, Moriel P, Chang YH, Abdalla DS.

Department of Clinical and Toxicological Analyses, Faculdade de Ciencias Farmaceuticas, Universidade de Sao Paulo, Brasil.

The activities of superoxide dismutase (SOD, EC 1.15.1.1), glutathione peroxidase (GPx, EC 1.11.1.9) and the levels of alpha-tocopherol and oxidized lipoproteins were investigated in the plasma of New Zealand rabbits either before or after cholesterol-diet induced hypercholesterolemia. Plasma SOD activity increased while GPx activity decreased after 60 days of cholesterol feeding. However, in the cholesterol-fed rabbits the release of superoxide dismutase fraction C from vasculature by heparin was lower than that in control rabbits. The levels of triglyceride hydroperoxides increased in low density and high density lipoproteins after feeding rabbits with the cholesterol-rich diet during 60 days. Also, a trend for increasing cholesteryl ester hydroperoxides was observed in beta-very low density and high density lipoproteins. An increase in alpha-tocopherol concentration (microM) was observed in very low density and low density lipoprotein fractions, but after normalization of these results to the cholesterol content of lipoprotein particles only the alpha-tocopherol content of low density lipoprotein remained higher after 60 days of cholesterol feeding. The data suggest that low glutathione peroxidase and superoxide dismutase fraction C activities may facilitate intravascular lipoprotein oxidation by oxidant species generated by the endothelium or blood cells.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7549968&dopt=Abstract cholesterol




[Relationship between cholesterol levels and depression in the elderly]

[Article in Italian]

Cadeddu G, Fioravanti P, Antonicelli R, Gasparrini PM, Gaetti R.

Divisione di Medicina Geriatrica, Ospedale Geriatrico INRCA, Ancona.

The aim of our study is to evaluate the possible association between lower plasma cholesterol and depression in the elderly. 140 subjects over 65 years old of both sexes were enrolled, of which 60 were affected by depression (DSM-III-R and Hamilton test) and 80 composed a control group homogeneous for sex and age with the previous one. Plasma cholesterol, HLD-cholesterol (HDL-C), LDL-cholesterol (LDL-C) and triglycerides were measured. A statistically significant difference between cholesterol and LDL-C (p < 0.001) was noted in the total group, in both males and females. Such modifications were independent of sex. In the group with lower cholesterol (cut-off < = 160 mg/dl) a prevalence of depression three times greater than subjects with higher cholesterol was found. In conclusion, the authors recommended a prudent use of lipid-lowering medications in the elderly because of its uncertain benefits.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7566558&dopt=Abstract cholesterol




The effect of fasting status on the determination of low-density and high-density lipoprotein cholesterol.

Wilder LB, Bachorik PS, Finney CA, Moy TF, Becker DM.

Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

PURPOSE: To determine the effect of a self-selected meal on concentrations of low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) in a screening setting and to determine the effect of using nonfasting values to classify individuals according to National Cholesterol Education Program guidelines. SUBJECTS AND METHODS: Study subjects were 115 employees who had previously participated in worksite total cholesterol screening, selected by stratified random sampling for sex and total cholesterol levels. Total cholesterol, triglycerides, HDL-C, and estimated LDL-C were determined before subjects ate a self-selected breakfast and 3 and 5 hours after eating it. RESULTS: LDL-C values determined 3 and 5 hours following breakfast were approximately 7% and 2.5% lower, respectively, than fasting values. Use of 3-hour and 5-hour LDL-C determinations to classify individuals with elevated fasting levels (> or = 3.36 mmol/L) resulted in false-negative rates of 20% and 14%, respectively. Three- and 5-hour HDL-C values were approximately 4% and 1.5% lower, respectively, than fasting levels. Use of 3-hour HDL-C values to classify individuals with low fasting levels (< 0.91 mmol/L) resulted in no false-negatives, whereas 1 of 7 individuals with low fasting HDL-C was misclassified when 5-hour values were used. CONCLUSIONS: These results support the 1993 National Cholesterol Education Program guidelines that LDL-C levels should be determined only in fasting persons, and that nonfasting HDL-C values may be acceptable for screening purposes.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7573092&dopt=Abstract cholesterol




Expression of the human oxytocin receptor in baculovirus-infected insect cells: high-affinity binding is induced by a cholesterol-cyclodextrin complex.

Gimpl G, Klein U, Reilander H, Fahrenholz F.

Max-Planck-Institut fur Biophysik, Frankfurt, Germany.

We have expressed a c-myc epitope-tagged human oxytocin receptor in the baculovirus/Sf9 cell system. The receptor was identified by SDS-PAGE and subsequent immunoblot as a approximately 50 kDa protein which decreased to about 44 kDa upon treatment with tunicamycin. Binding studies showed that the human oxytocin receptor was expressed in a low-affinity state (Kd = 215 nM; Bmax = 1.66 pmol/mg). After addition of cholesterol in the form of a soluble cholesterol-methyl-beta-cyclodextrin complex to the membranes, we obtained part of the human oxytocin receptor in its high-affinity state for oxytocin (Kd = 0.96 nM and Bmax = 318 fmol/mg of protein). In subsequent studies, we added the cholesterol-methyl-beta-cyclodextrin complex to the Sf9 cell culture medium at various times post infection. Binding analysis showed that this results in a more than 3-fold further increase in functional receptor binding sites of high-affinity state (Bmax = 1.08 pmol/mg). The cholesterol effect was dose-dependent, with an EC50 of about 50 microM cholesterol. Due to these findings, we determined the cholesterol and phospholipid content in purified Sf9 plasma membranes. The untreated naturally cholesterol auxotroph insect cells grown in medium with 2% fetal calf serum had a molar cholesterol/phospholipid ratio of about 0.04, which is approximately 20-fold lower than normally found in plasma membranes of higher eukaryotic cells. The high-affinity binding of the oxytocin receptor increased in parallel with the cholesterol levels present in the corresponding plasma membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

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Differences in the phenotypic characteristics of subjects with familial defective apolipoprotein B-100 and familial hypercholesterolemia.

Miserez AR, Keller U.

Department of Research, University Hospital, Basel, Switzerland.

Familial defective apolipoprotein B-100 (FDB) is a recently identified autosomal-dominantly inherited disorder caused by a point mutation in the apolipoprotein (apo) B gene. To determine whether the phenotypic characteristics in FDB subjects are similar to those in subjects with familial hypercholesterolemia (FH), 76 kindreds fulfilling the clinical criteria for heterozygous FH/FDB were characterized using molecular biological techniques. Allele-specific polymerase chain reaction (PCR) at the apoB locus was used for diagnosis or exclusion of FDB. PCR-based methods for detection of two point mutations (V408M and P664L) at the LDL receptor (LDLR) locus, cosegregation analysis using eight restriction fragment length polymorphisms (RFLPs) at the LDLR locus, or the exclusion of FDB confirmed the clinical diagnosis of FH. Three kindreds were not included because of a missing cosegregation between a particular haplotype and the FH phenotype. We predicted that a similar number of kindreds would be detected in the two groups, assuming comparable prevalences of the diseases in our population and similar phenotypic characteristics. However, only nine kindreds were identified with the FDB mutation compared with 64 kindreds with FH (P < .0001). From these 73 kindreds, 28 FDB heterozygotes and 129 FH heterozygotes were compared using multivariate analysis. There were no differences between these two groups with respect to age, sex, and apoE genotype distribution, lipoprotein(a) concentrations, body mass index, blood pressure, and smoking habits. However, FDB subjects demonstrated significantly lower concentrations of total cholesterol (8.1 versus 10.2 mmol/L, P < .001), LDL cholesterol (6.3 versus 8.2 mmol/L, P < .001), and triglycerides (1.3 versus 1.8 mmol/L, P = .025) and higher concentrations of HDL cholesterol (1.4 versus 1.2 mmol/L, P = .015) than subjects with FH. In contrast to FH, female FDB subjects tended to have higher concentrations of total cholesterol (8.9 versus 7.5 mmol/L, P = .032) and LDL cholesterol (7.1 versus 5.7 mmol/L, P = .026) than FDB males. The same results regarding total and LDL cholesterol and sex differences were observed when individual data of 238 FDB and 415 FH subjects from the literature were compared. In addition, FDB subjects showed much larger total cholesterol fluctuations than FH subjects (median of intraindividual coefficients of variation: FDB, 14.5%; FH, 5.3%; P < .001). In summary, these results demonstrate that FDB subjects tend to have a milder form of hyperlipoproteinemia than FH subjects and that only a part of the subjects with FDB fulfill the established criteria for identifying FH.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7583549&dopt=Abstract cholesterol




Cholesterol content of circulating immune complexes in patients with coronary stenosis and subjects without evidence of atherosclerosis.

Lecomte E, Herbeth B, Clerc G, Khalife K, Siest G, Artur Y.

Laboratoire du Centre de Medecine Preventive, Vandoeuvre-ies-Nancy, France.

The biological variation factors for cholesterol in circulating immune complexes (CIC-cholesterol) were studied in 941 unselected supposedly healthy volunteers, ages 4 to 78 years. We found a complex effect of age, including the existence of two peaks of CIC-cholesterol, one in males between 11 and 14 years and in females between 11 and 30 years, and in both sexes another peak between 41 and 60 years, and in both sexes a decrease between 31 and 40 years. By use of multiple regression analysis and after adjustment for age, CIC-cholesterol was positively related to plasma cholesterol concentration and leukocyte count, values being lower in females than in males and among subjects taking anti-inflammatory drugs. In addition, CIC-cholesterol was measured in 76 coronary angiography patients and in 100 supposedly healthy controls, ages 30 to 77 years. We noticed a significant increase (P < or = 0.05) of CIC-cholesterol when patients were affected by coronary stenosis between 20% and 50% (71.8 +/- 52.5 mumol/L vs 46.2 +/- 45.9 mumol/L in controls), but this was less pronounced in those with > 50% of obstruction (58.9 +/- 54.3 mumol/L); however, serum total cholesterol was not modified or even surprisingly slightly decreased in the coronary angiography individuals. Nevertheless, an important overlap of values in controls and patients makes questionable the usefulness of this variable in clinical practice.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7586529&dopt=Abstract cholesterol




Evidence for a cholesterol-lowering gene in a French-Canadian kindred with familial hypercholesterolemia.

Sass C, Giroux LM, Ma Y, Roy M, Lavigne J, Lussier-Cacan S, Davignon J, Minnich A.

Hyperlipidemia and Atherosclerosis Research Group, Clinical Research Institute of Montreal, Quebec, Canada.

We describe a four-generation kindred with familial hypercholesterolemia (FH) in which two of the eight heterozygotes for a 5-kb deletion (exons 2 and 3) in the low density lipoprotein (LDL) receptor gene were found to have normal LDL-cholesterol levels. In our search for a gene responsible for the cholesterol-lowering effect in this family, we have studied variation in the genes encoding the LDL receptor, apolipoprotein (apo) B, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, apoAI-CIII-AIV, and lipoprotein lipase. The analysis showed that it was unlikely that variation in any of these genes was responsible for the cholesterol-lowering effect. Expression of the LDL receptor, as assessed in vitro with measurements of activity and mRNA levels, was similar in normo and hyperlipidemic subjects carrying the deletion. Analysis of the apo E isoforms revealed that most of the e2 allele carriers in this family, including the two normolipidemic 5-kb deletion carriers, were found to have LDL-cholesterol levels substantially lower than subjects with the other apo E isoforms. Thus, this kindred provides evidence for the existence of a gene or genes, including the apo e2 allele, with profound effects on LDL-cholesterol levels.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7607649&dopt=Abstract cholesterol




Effects of interactions of apolipoprotein A-II with apolipoproteins A-I or A-IV on [3H]cholesterol efflux and uptake in cell culture.

Stein O, Dabach Y, Hollander G, Ben-Naim M, Oette K, Stein Y.

Department of Experimental Medicine and Cancer Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel.

Conflicting evidence has accumulated with years regarding the putative negative effect of apolipoprotein A-II on apo A-I mediated cholesterol efflux. In this study, this question was reexamined and in addition to the interaction of apo A-II with apo A-I, its possible effect on apo E and apo A-IV was investigated as well. Free cholesterol (FC) donors were the main components of atheroma, namely, mouse peritoneal macrophages (MP), bovine aortic smooth muscle (SMC) and fibroblasts labeled with [3H]FC. Acceptors of FC were dioleoylphosphatidylcholine (DOPC) liposomes containing apo A-I, rh-apo A-IV or rh-apo E alone or together with apo A-II. When [3H]FC labeled MP were incubated for 2 or 4 h with equimolar concentrations of apo A-I, A-II, A-IV or E, the lowest [3H]cholesterol efflux occurred with apo A-II. Exposure of [3H]FC MP to liposomes containing apo A-I/A-II at 1:2 M/M (keeping the total protein concentration at 50 micrograms/ml), resulted in a lower [3H]FC efflux as compared to apo A-I alone. However, when apo A-I or apo A-IV protein concentration was kept constant and supplemented with apo A-II, a lower [3H]FC efflux was found only at 1:3 M/M of apo A-I/A-II. Apo A-II added to apo E had no effect on FC efflux. With aortic SMC and fibroblasts, no inhibitory effect of addition of apo A-II to apo A-I or apo A-IV on cholesterol efflux was seen at apo A-I/A-II of 1:1 or 1:2 M/M. The uptake of macrophage derived [3H]FC by SMC or HepG2 cells was studied using the serum-free efflux media, containing PC liposomes + apolipoproteins, from 3H-labeled macrophages. The cellular uptake of [3H]FC was higher when apo A-II had been added to apo A-I or apo A-IV than when the apolipoproteins were added alone. In conclusion, apo A-II was found to be less effective in cholesterol efflux and to interfere with the action of A-I only when the cholesterol donors were macrophages and when the relative amount of apo A-I to apo A-II was low. This was not the case when SMC or fibroblasts served as cholesterol donors. In the presence of apo A-II, enhanced [3H]cholesterol delivery to cells was seen which could contribute to the proatherogenic activity of apo A-II.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7619858&dopt=Abstract cholesterol




Dietary polyunsaturated fat modifies low-density lipoproteins and reduces atherosclerosis of nonhuman primates with high and low diet responsiveness.

Rudel LL, Johnson FL, Sawyer JK, Wilson MS, Parks JS.

Department of Comparative Medicine, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157, USA.

We tested the hypothesis that an increased content of n-6 polyunsaturated fatty acids (principally linoleic acid) in an atherogenic diet of nonhuman primates would decrease atherosclerosis by modifying the composition and decreasing the concentration of plasma low-density lipoprotein (LDL). A species readily susceptible to diet-induced atherosclerosis (cynomolgus monkey) was compared with a less-susceptible species (African green monkey) with dietary cholesterol concentration and saturated or polyunsaturated fat (40% of energy) as variables. In both species, cholesterol concentrations in whole plasma, LDL, and high-density lipoprotein (HDL) were 20-30% lower when polyunsaturated fat was fed, whereas dietary cholesterol increased LDL cholesterol three- to fourfold. LDL was enriched in cholesteryl oleate when saturated fat and cholesterol were fed. Dietary linoleic acid prevented cholesteryl oleate enrichment and promoted cholesteryl linoleate accumulation in LDL. At the same plasma cholesterol concentration, cynomolgus monkeys had higher LDL cholesterol and lower HDL-cholesterol concentrations than did African green monkeys. LDL particle size was significantly (P < 0.001) larger in the group of cynomolgus monkeys fed polyunsaturated fat but tended to be smaller in African green monkeys fed polyunsaturated fat. Dietary polyunsaturated fat protected against coronary artery atherosclerosis in both species. Thus, LDL particle size, per se, was not atherogenic; instead, coronary artery atherosclerosis and cholesteryl oleate enrichment of LDL were more highly correlated. This outcome suggests that information about LDL composition may be more important for understanding the pathogenesis of atherosclerosis than previously suspected.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7625361&dopt=Abstract cholesterol