Endometrial carcinoma stage I--comparison of two different treatment regimes--evaluation of risk factors and its influence on prognosis; suggested step by step treatment protocol

Two hundred twenty-four patients with stage I endometrial carcinoma were treated between the years 1964 and 1978. One hundred and fifteen patients were classified as clinical stage Ia (51.3%) and 109 patients as clinical state Ib (48.7%). For stage Ia the standard treatment protocol was total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH + BSO). In stage Ib disease, preoperative irradiation was performed followed by TAH + BSO after an interval of 4 to 6 weeks. Postoperative irradiation to the pelvis and vaginal vault was given when extrauterine spread was found and in cases of myometrial penetration beyond the inner one-third of the myometrium. At evaluation in May 1983, the rate of disease recurrence in stage Ia was 20% and in stage Ib 9.1%. Five-year survival in stage Ia was 77.3% and 72.4% in stage Ib. Preoperative irradiation was found justified for G3 disregarding the clinical stage, therefore the approach of routine preoperative irradiation in stage Ib is not recommended. The uterine cavity depth was found to be an inaccurate prognostic parameter. According to the data collected in our material the histological grade and myometrial invasion are much better prognostic parameter and should be taken into consideration while planning the treatment regime.

Coffee, tea, and plasma cholesterol: the Jerusalem Lipid Research Clinic prevalence study

The association of intake of coffee and tea, assessed by 24 hour dietary recall, with plasma cholesterol and its lipoprotein fractions was studied in a sample of 1007 men and 589 women aged 35-64 resident in Jerusalem. These cross sectional data showed a significant linear association (p less than 0.001) between consumption of coffee in men and plasma cholesterol and low density lipoprotein cholesterol concentrations. Men who drank five cups of coffee or more had plasma cholesterol concentrations about 0.5 mmol/l (20 mg/100 ml) higher than non-drinkers after controlling for age, ethnicity, body mass, education, season of year, smoking, tea drinking, and dietary intake of fat and carbohydrates. In women adjusted mean plasma cholesterol concentration was 0.34 mmol/l (13 mg/100 ml) higher in coffee drinkers grouped together (p less than 0.01). The test for a linear trend was not significant. The association in both sexes was largely with the low density lipoprotein cholesterol fraction. High density lipoprotein cholesterol concentrations were somewhat increased in women who drank coffee (p less than 0.01 for a linear trend) but not in men. Tea drinking was not associated with unadjusted plasma cholesterol concentrations in either sex. Male tea drinkers, but not female, had slightly higher adjusted plasma cholesterol concentrations than non-drinkers (0.15 mmol/l (6 mg/100 ml), p = 0.04). No dose response relation was evident. In this population, characterised by a low intake of saturated fatty acids and relatively low mean plasma cholesterol concentrations, coffee drinking may be a determinant of low density lipoprotein cholesterol concentrations.

Coronary heart disease risk factors among religious groupings in a Jewish population sample in Jerusalem

The hypothesis that plasma lipids, blood pressure, smoking and dietary intake differed according to degree of religiosity was examined in a sample of Jewish residents of Jerusalem. Religiosity was classified according to the subject's self-ranking of his perceived degree of religiosity. Prevalence of smoking, and plasma levels of cholesterol, triglycerides, and low-density lipoprotein cholesterol were higher in secular participants than in the orthodox group. No differences in blood pressure and in high-density lipoprotein cholesterol were observed. Secular subjects consumed more total fat, more saturated fatty acids and less carbohydrate than religious subjects. These differences in nutrient intake among the religious groups reflected differences in their food selection, notably consumption of dairy products. These findings of parallel differences in plasma lipids and in dietary intake are consistent with the differing incidence of myocardial infarction in the religious groups which has been shown in the Israeli population.

Angiotensin II stimulates receptor-mediated uptake of LDL by bovine adrenal cortical cells in primary culture

Bovine adrenal cells were isolated from the subcapsular region of the gland to obtain cultures enriched in cells of the zona glomerulosa. The cells kept in primary cultures were shown to respond to angiotensin II and adrenocorticorticotropin (ACTH) by a significant increase in aldosterone production. These primary adrenal cultures were used to study the effect of angiotensin II on LDL metabolism. Addition of angiotensin II for 48 h to the culture medium resulted in a 200-300% increase in LDL metabolism, and the lowest effective concentration was 10(-8) -10(-9) M. The angiotensin II effect became evident after 12-16 h of incubation. To compare the metabolism of the 125I-labeled protein moiety to that of cholesteryl ester of LDL, the lipoprotein was labeled also with cholesteryl linoleyl ether, a nonhydrolyzable analog of cholesteryl ester. Under basal conditions and in the presence of angiotensin II or ACTH the ratio of [3H]cholesteryl linoleyl ether to 125I indicate some preferential uptake of the cholesteryl ester moiety. Stimulation of specific LDL binding at 4 degrees C and LDL metabolism at 37 degrees C by 10(-7) M angiotensin II occurred at all concentrations of LDL studied. Linearization of the kinetic data showed that angiotensin II increased the LDL receptor number significantly but not the affinity of the LDL receptor for its ligand. The present findings indicate that in analogy to ACTH, angiotensin II can influence receptor-mediated uptake of LDL by adrenal cortical cells. It remains to be shown whether the angiotensin II effect on LDL metabolism is limited to adrenal cells or will affect other cells which express the angiotensin II receptor.

Variability of plasma lipids and lipoproteins: the Jerusalem Lipid Research Clinic Study

We examined the variability of lipid and lipoprotein concentrations in plasma from a population sample from the Jerusalem Lipid Research Clinic study. Coefficients of variation of about 8% for plasma cholesterol, 11% to 15% for low- and high-density-lipoprotein cholesterol, and about 30% for triglyceride were reported, both for 17-year-olds and adults examined twice, with a median period of two months between measurements. Stability was similar in a subsample of adults who had an additional measurement a median of 28 months later. Within-assay analytical variation (CV) was 1.9-2.0% for cholesterol, 1.5-2.3% for triglyceride, and 4.5% for high-density-lipoprotein cholesterol. Between-assay variation was 3-5% for cholesterol and triglyceride and 10% for high-density-lipoprotein cholesterol. The lower stability of the lipoprotein fractions of cholesterol than of total cholesterol emphasizes the need for repeated measurements of these fractions for more accurate characterization of subjects, especially those with extreme values, both for clinical use and for predicting outcome in follow-up studies.

Variability of plasma lipids and lipoproteins: the Jerusalem Lipid Research Clinic Study

We examined the variability of lipid and lipoprotein concentrations in plasma from a population sample from the Jerusalem Lipid Research Clinic study. Coefficients of variation of about 8% for plasma cholesterol, 11% to 15% for low- and high-density-lipoprotein cholesterol, and about 30% for triglyceride were reported, both for 17-year-olds and adults examined twice, with a median period of two months between measurements. Stability was similar in a subsample of adults who had an additional measurement a median of 28 months later. Within-assay analytical variation (CV) was 1.9-2.0% for cholesterol, 1.5-2.3% for triglyceride, and 4.5% for high-density-lipoprotein cholesterol. Between-assay variation was 3-5% for cholesterol and triglyceride and 10% for high-density-lipoprotein cholesterol. The lower stability of the lipoprotein fractions of cholesterol than of total cholesterol emphasizes the need for repeated measurements of these fractions for more accurate characterization of subjects, especially those with extreme values, both for clinical use and for predicting outcome in follow-up studies.

Defective metabolism of hypertriglyceridemic low density lipoprotein in cultured human skin fibroblasts. Normalization with bezafibrate therapy

The metabolism of hypertriglyceridemic low density lipoprotein (HTG-LDL) was investigated in upregulated cultured human skin fibroblasts. Low density lipoprotein (LDL) was isolated by zonal centrifugation from the plasma of seven HTG subjects, before and 2 wk after the initiation of bezafibrate (BZ) therapy. HTG-LDL is a cholesterol-poor, triglyceride-rich lipoprotein of smaller diameter than BZ-LDL or normal LDL (N-LDL). Binding, cell association, and proteolytic degradation of HTG-LDL were compared with that of BZ-LDL and N-LDL and were found to be significantly lower by a paired t test analysis (P less than 0.001). After 6 h preincubation with unlabeled HTG-LDL, the incorporation of [14C]acetate to sterols was significantly higher than with BZ-LDL or N-LDL (577 +/- 43.7; 330 +/- 41.5; 262 +/- 47, mean +/- SE, picomoles sterols per milligram cell protein per 2 h, respectively; P less than 0.001 by paired t test). To determine the effectiveness of HTG-LDL and BZ-LDL on the down-regulation of LDL receptor activity, up-regulated cells were incubated for 48 h with HTG-LDL and BZ-LDL. LDL receptor activity was significantly higher after preincubation with HTG-LDL compared with BZ-LDL, and the rates of sterol synthesis were similarly increased. These results demonstrate that HTG-LDL does not down-regulate the LDL receptor activity as efficiently as BZ-LDL and that its cholesterol content is not enough to adequately suppress cellular sterol synthesis. Significant correlation between LDL composition and cholesterol synthesis by cultured cells was found with all LDL preparations over a wide range of cholesteryl ester to protein ratio (0.8-2.2). This correlation indicates that the compositional and structural abnormalities of HTG-LDL, and especially the low cholesterol content of the lipoprotein, alter LDL metabolism and cellular cholesterol formation.

Putative role of cholesteryl ester transfer protein in removal of cholesteryl ester from vascular interstitium, studied in a model system in cell culture

A model system to study the putative role of cholesteryl ester transfer protein in the egress of interstitial cholesteryl ester is described. Confluent cultures of bovine aortic smooth muscle cells were labeled for 24 h with [3H]cholesteryl linoleyl ether and [14C]cholesteryl linoleate by incubation with bovine milk lipoprotein lipase. This method of labeling results in the transfer of cholesteryl linoleyl ether and cholesteryl ester to three compartments: a trypsin-releasable, trypsin-resistant and catabolic compartment (Stein, O., Halperin, G., Leitersdorf, E., Olivecrona, T. and Stein, Y. (1984) Biochim. Biophys. Acta 795, 47-59). The efflux of labeled cholesteryl linoleyl ether and cholesteryl ester from the extracellular and cell-surface related compartments into a serum-free culture medium containing 1% bovine serum albumin was studied during 24 h of postincubation. The efflux was expressed as a percentage of pulse value, i.e., radioactivity retained by the cell culture at the end of the labeling period. The efflux of [3H]cholesteryl linoleyl ether, [14C]cholesteryl ester and 14C-labeled free cholesterol (formed by cellular hydrolysis of cholesterol ester) into the culture medium with 1% bovine serum albumin was about 5% of the pulse value. Addition of human lipoprotein-deficient serum resulted in a 3-10-fold increase in the efflux of [3H]cholesteryl linoleyl ether and [14C]cholesteryl ester, but did not change markedly the efflux of 14C-labeled free cholesterol. Rat lipoprotein-deficient serum which does not contain cholesteryl ester transfer protein did not increase the efflux of [3H]cholesteryl linoleyl ether or [14C]cholesteryl ester. The rate of cholesteryl ester efflux in the presence of human lipoprotein-deficient serum was linear for about 6 h and increased further up to 24 h. Addition of Intralipid to medium containing human lipoprotein-deficient serum further enhanced the efflux of [3H]cholesteryl linoleyl ether and, to a lesser extent, that of cholesteryl ester. A similar effect was observed also by addition of rat VLDL to medium containing human lipoprotein-deficient serum. Inhibition of cholesteryl linoleyl ether and cholesteryl ester efflux and marked enhancement of free cholesterol efflux occurred when rat HDL was added to medium containing human lipoprotein-deficient serum, while human HDL was only slightly inhibitory. The results obtained with human lipoprotein-deficient serum were reproduced with partially purified cholesteryl ester transfer protein. Using the partially purified cholesteryl ester transfer protein, the efflux of cholesteryl linoleate was compared to that of cholesteryl oleate and was found to be the same.

Family history of myocardial infarction as an independent risk factor for coronary heart disease

The hypothesis that a family history of heart attack before the age of 60 years is an independent risk factor for coronary heart disease was examined in a random sample of 1044 men aged 40-70. Data on personal and family history, smoking, weight, height, plasma lipid and lipoprotein concentrations, blood pressure, and resting and exercise electrocardiograms were collected according to the standard Lipid Research Clinics protocol. A history of heart attack in first degree relatives was ascertained by interviewing the participants. Evidence of coronary heart disease was found in 123 men (reported heart attack in 20, electrocardiographic findings of ischaemic heart disease at rest in 40, and electrocardiographic findings during heart rate limited exercise in 63). Subjects with coronary heart disease had considerably higher concentrations of total cholesterol, higher blood pressures, and lower concentrations of high density lipoprotein cholesterol than those without. Twenty nine per cent of the subjects with coronary heart disease reported a history of heart attack in a first degree relative before 60 years of age compared with 19% of those without. In a multivariate logistic model, the coefficients for age, cholesterol concentrations, and hypertension were all positive and statistically significant. The coefficient for HDL cholesterol concentration was negative and significant. A family history of heart attack showed a significant positive association, indicating a relation with coronary heart disease that is independent of the other variables in the model. The relation persisted in apparently asymptomatic patients with coronary heart disease.

Effects of smoking and physical activity on serum uric acid in a Jerusalem population sample

In 932 adult males and 531 adult females, we found large independent correlations of serum uric acid (SUA) with body mass and serum creatinine. In males, but not in females, SUA was lower in smokers than in non-smokers and in men who reported themselves to be physically active, compared to non-active men. After controlling for confounding variables by multiple regression analysis, we found that smoking remained a significant predictor of SUA in males (P = 0.003) but the effects of reported physical activity dropped to borderline significance (P = 0.056). In females, no significant relationship of SUA with reported physical activity was seen. These results, the first from an unselected free-living Israeli population, are generally in agreement with previously reported studies.

Verapamil enhances receptor-mediated endocytosis of low density lipoproteins by aortic cells in culture

Bovine aortic endothelial and smooth muscle cells (SMC) and human skin fibroblasts (HSF) were used to study the effect of verapamil on cellular interactions with human low density lipoprotein (LDL). Verapamil, 10 to 50 microM, increased 125I-LDL uptake and degradation by 70% to 200% in the various cells after 24 to 48 hours of incubation. The increase in the total amount of LDL endocytosed, labeled with 3H-cholesteryl linoleate (3H-CL), was comparable to that determined with 125I-LDL. In HSF and SMC, a delay in 125I-LDL degradation and hydrolysis of 3H-CL was seen in cells treated for 3 to 24 hours with verapamil. Pretreatment of HSF with 50 microM verapamil for 24 hours and incubation with 2 to 50 micrograms 125I-LDL protein/ml for 1 hour resulted in a 50% to 200% increase in heparin releasable and in a 40% to 130% increase in cellular 125I-LDL. Thus, the increase in 125I-LDL binding and uptake in verapamil-treated cells was apparently due to an increase in receptor number, rather than in receptor affinity. The effect of verapamil on LDL uptake and degradation was also seen in cells that were pretreated for 24 hours and incubated with 125I-LDL in the absence of verapamil. The effect of verapamil was not apparent in LDL receptor-negative cells. Cycloheximide blocked the verapamil effect. The Na+ channel blocker, tetrodotoxin x 10(-6) M, caused a 30% to 50% increase in the total amount of LDL endocytosed, but no delay in LDL degradation; amiloride 2 x 10(-3) M was not effective. If the presently described effect of verapamil also occurs in vivo, this might contribute to the reported beneficial effects of Ca++ channel blockers in experimental atherosclerosis by promoting transfer of LDL cholesteryl ester from the aortic interstitium to a catabolic compartment.

Metabolic fate of low density lipoprotein and high density lipoprotein labeled with an ether analogue of cholesteryl ester

Low density lipoprotein (LDL) metabolism by human skin fibroblasts was studied using LDL labeled with a nonhydrolyzable cholesteryl ether analogue, 3H-cholesteryl linoleyl ether (CLE). The 3H-CLE-LDL was taken up by the apo-B, E receptor mediated endocytosis similar to 125I-labeled LDL. This was shown by saturation kinetics of uptake with respect to 3H-CLE-LDL concentration and very low uptake of 3H-CLE-LDL by receptor negative cell strains. When injected (CE)-LDL were cleared at equal rates and about 30% of the injected LDL was recovered in the liver. Treatment with ethinyl estradiol resulted in a three-fold increase in 3H-CLE-LDL uptake by the liver. The liver is also the major site of uptake of 3H-CLE-high density lipoprotein (HDL) (40%-45% of the injected dose) but its uptake by the liver increased only by 20% with estradiol treatment. As 3H-CLE-HDL was cleared from the circulation at a somewhat faster rate than 125I-HDL it appeared that some dissociation in the tissue uptake of the protein and CE moieties occurs.

Uptake of rat plasma HDL subfractions labeled with [3H]cholesteryl linoleyl ether or with 125I by cultured rat hepatocytes and adrenal cells

Rat plasma low- and high-density lipoproteins were labeled with [3H]cholesteryl linoleyl ether and isolated by rate-zonal ultracentrifugation into apolipoprotein B-containing LDL, apolipoprotein E-containing HDL1 and apolipoprotein E-poor HDL2. These fractions were incubated with cultured rat hepatocytes and comparable amounts of all lipoproteins were taken up by the cells. Rat HDL was isolated at d 1.085-1.21 g/ml and apolipoprotein E-free HDL was prepared by heparin Sepharose chromatography. The original HDL and the apolipoprotein E-free HDL were labeled with 125I or with [3H]cholesteryl linoleyl ether and incubated with rat hepatocytes or adrenal cells in culture. The uptake of apolipoprotein E-free [3H]cholesterol linoleyl ether HDL by the cultured hepatocytes was 20-40% more than that of the original HDL. Comparison of uptake of cholesteryl ester moiety (represented by uptake of [3H]cholesteryl linoleyl ether) and of protein moiety (represented by metabolism of 125I-labeled protein) was carried out using both original and apolipoprotein E-free HDL. In experiments in which low concentrations of HDL were used, the ratio of 3H/125I exceeded 1.0. In cultured adrenal cells, the uptake of [3H]cholesteryl linoleyl ether-labeled HDL was stimulated 3-6-fold by 1 X 10(-7) M ACTH, while the uptake of 125I-labeled HDL increased about 2-fold. The ratio of 3H/125I representing cellular uptake was 2-3 and increased to 5 in ACTH-treated cells. The present results indicate that in cultured rat hepatocytes the uptake of homologous HDL does not depend on the presence of apolipoprotein E. Evidence was also presented for an uptake of cholesteryl ester independent of protein uptake in cultured rat adrenal cells and to a lesser extent in rat hepatocytes.

Modulation of lipoprotein lipase in the intact rat by cholera toxin--an irreversible agonist of cyclic AMP

Rats were injected intravenously with cholera toxin, a potent stimulator of adenylate cyclase, and lipoprotein lipase was determined in various organs and plasma. 16 h after cholera toxin injection, lipoprotein lipase activity increased 2-6-fold in heart, diaphragm and lung and decreased to one-third in adipose tissue. An increase in lipoprotein lipase activity was seen in the plasma and in the liver, as determined by antiserum to lipoprotein lipase. The increase in heart lipoprotein lipase was preceded by a rise in cyclic AMP and continued for 24 h when cyclic AMP returned to base-line levels. Both heparin-releasable and residual lipoprotein lipase increased in the heart, but to an unequal extent. The more pronounced rise in residual activity (up to 10-fold) could have contributed to an increase in the t1/2 of heart lipoprotein lipase from 1.5 to 2.6 h. The relatively lower increase in heparin-releasable lipoprotein lipase could have been due to a loss of the enzyme from this compartment into the circulation. The effect of cholera toxin on heart and adipose tissue lipoprotien lipase was observed in fasted, fed and super-fed animals and thus appears to be independent of the nutritional state of the animal. Since cholera toxin not only mimics hormonal stimulation, but causes an exaggerated response to hormones, it made studies on some aspects of regulation of both the functional and storage forms of lipoprotein lipase in the intact organism possible.

Validity of maternal reporting of breast feeding history and the association with blood lipids in 17 year olds in Jerusalem

The validity of mothers' reporting of the breast feeding history of their children more than 20 years after their birth was studied in a Jerusalem population. Among 74 study subjects, duration of breast feeding as ascertained from an interview was well correlated with that recorded in mother and child health clinic charts. Concordance was of similar magnitude in subgroups of ethnicity, mother's education, family size, and sex of child. Duration of breast feeding in 101 youngsters was inversely associated with plasma cholesterol in 17 year old girls, though not in boys, which was statistically significant on univariate analysis and of borderline significance on multivariable analysis. Among 17 year old boys, though not in girls, a statistically significant inverse association for plasma triglyceride was apparent on multivariable analysis. Reported breast feeding history derived from interview of mothers may be a useful instrument for study of possible long term effects of breast feeding in their adolescent or adult progeny.

Adolescent smokers and nonsmokers: profiles and their changing structure

The status of smoking among tenth-graders in Jerusalem high schools as part of a smoking prevention program was examined. Two consecutive cohorts of 792 and 771 subjects were given questionnaires on two occasions: at the onset of the study (fall 1980 for the first cohort and fall 1981 for the second), and either 2 years (first cohort) or 1 year (second cohort) later. Based on the theory that smoking relates to counterconformity entailing rebelliousness and conformity to a nonconformist peer culture, subjects were asked about their behaviors and cognitions concerning school, home, peers, drinking, and smoking. It was reasoned that no single variable can predict, let alone explain, the onset and continuation of smoking and that the various factors that relate to smoking and distinguish between smokers and nonsmokers (a) constitute a systematic and coherent syndrome of counterconformity variables, which (b) reinforce each other, and (c) that over time, smoking and counterconformity come to affect each other reciprocally. These hypotheses were supported by the data. Smokers were found to differ from nonsmokers in a number of ways that were all related to counterconformity. Truancy and an inability to resist peer pressure to smoke, manifestations of two aspects of this syndrome, were the best predictors of smoking for both sexes, both cohorts, and both measuring occasions. With time, personal rebelliousness tended to become a weaker predictor, while social interaction variables became relatively stronger. The intercorrelations among the nonsmokers who became smokers were the highest, as predicted. The nature of the syndrome, its changing structure, and implications for prevention are discussed.

Lipoprotein lipase mediated uptake of non-degradable ether analogues of phosphatidylcholine and cholesteryl ester by cultured cells

Lipoprotein lipase mediated transfer of cholesteryl ester and its ether analog, cholesteryl linoleyl ether, from unilamellar liposomes, prepared from a nonhydrolyzable ether analog of 1,2-diacyl-sn-glycero-3-phosphocholine (PC), 1,2-dioleyl ether-sn-glycero-3-phosphocholine (DOEPC), was studied in various cells in culture. It was found that lipoprotein lipase enhanced the uptake of cholesteryl linoleyl ether and of DOEPC. These findings provided a definitive proof that hydrolysis of liposomal PC is not needed for the lipoprotein lipase catalyzed transfer of cholesteryl linoleyl ether and cholesteryl ester to cells. The lipids transferred by lipoprotein lipase to cells were localized in three compartments, trypsin-releasable, resistant and metabolic; the latter was a chloroquine-sensitive pool as evidenced by inhibition of cholesteryl ester hydrolysis. Labeled PC and, to a lesser extent DOEPC, in the trypsin-releasable pool was able to return to the medium, while cholesteryl linoleyl ether and cholesteryl ester required cholesteryl ester transfer protein for release. The transfer of cholesteryl linoleyl ether and cholesteryl ester into a trypsin-resistant compartment did not require metabolic energy and occurred also in formaldehyde-fixed cells. Metabolic energy was needed for the translocation of cholesteryl linoleyl ether and cholesteryl ester into the lysosomal compartment, presumably by a process of endocytosis. The physiological relevance of the present findings is that as intravascular hydrolysis of triacylglycerol-rich lipoproteins is mediated by lipoprotein lipase attached to endothelial cells, the latter can provide a very extensive surface for removal and metabolism of phospholipids and cholesteryl ester by a mechanism mediated by lipoprotein lipase.

Inhibition of rat liver retinyl palmitate hydrolase activity by ether analogs of cholesteryl esters and acylglycerides

In previous studies, retinyl palmitate hydrolase activity in rat liver was partly characterized and was found to correlate and to partially copurify with hydrolytic activities against cholesteryl oleate and triolein. The present studies were designed to further explore relationships between these three lipid ester hydrolase activities, by use of non-hydrolyzable ether analogs of cholesteryl esters and acylglycerides. Cholesteryl ether analogs were potent inhibitors of all three hydrolase activities with relative potencies for the series of ethers of: linoleyl greater than oleyl = palmitoyl greater than n-butyl = n-propyl greater than ethyl = methyl. Retinyl palmitate hydrolase activity was most strongly inactivated by this series of analogs, with 48-86% of the activity inhibited at cholesteryl ether levels of 1 microM. The acylglyceride ether analogs were much weaker inhibitors of the three hydrolase activities, with the triolein, diolein and dipalmitin analogs showing similar inhibitory potencies, greater than that of the monolein and monopalmitin analogs. The data demonstrate the potential usefulness of ether analogs of cholesteryl esters and acylglycerides for exploring some of the characteristics of lipid ester hydrolase activities.

Synthesis and secretion of triacylglycerol lipase by cultured rat hepatocytes

Rat hepatocytes isolated by collagenase perfusion were cultured for 48-72 h and examined for synthesis and secretion of hepatic triacylglycerol lipase activity. Low levels of enzyme activity found in the culture medium increased with time of incubation, and a 3-10-fold rise was encountered in the presence of optimal concentrations of heparin (5 U/ml). After interruption of enzyme synthesis by cycloheximide, plateauing of enzyme activity in the medium occurred, indicating that addition of heparin may not only stabilize but also enhance hepatic triacylglycerol lipase secretion. Synthesis and secretion of hepatic triacylglycerol lipase was not related to cell density, and enzyme secretion was encountered in subconfluent cultures. Release of enzyme activity into the medium was not sensitive to chlorpromazine, a lysosomal enzyme inhibitor, but was completely inhibited by treatment with tunicamycin, an inhibitor of glycosylation. As release of enzyme activity could be maintained for 12 h in the absence of serum, possible hormonal regulation was sought. Under the present experimental conditions, no modulation of hepatic triacylglycerol lipase was encountered by either gonadal or thyroid hormones. Addition of cyclic AMP to the culture medium resulted in a 30% decrease in enzyme activity. The dependence of hepatic triacylglycerol lipase secretion on the intactness of the Golgi apparatus and on vesicular transport was demonstrated by the treatment with monensin. The present results show that cultured rat hepatocytes provide a good model system by which the regulation of synthesis and secretion of hepatic triacylglycerol lipase can be studied.

Metabolism of liposomes prepared from a labelled ether analog of 1,2-dioleoyl-sn-glycero-3-phosphocholine in the rat

To synthesize the ether analog of 1,2-diacyl-sn-glycero-3-phosphocholine (PC), 1-O-cis-9'- octadecenyl -2-O-cis-9'-[9',10'(n)-3H] ocatadecenyl -sn-glycero-3- phosphocholine, we have adapted available methodology and have obtained a product of high specific activity and purity. The labelled dioleyl ether phosphatidylcholine ( DOEPC ) was used to prepare 250-350 A unilamellar liposomes, which contained also PC and free cholesterol. Following intravenous injection into rats, labelled PC was cleared from the plasma at a faster rate than DOEPC . The uptake of both labelled compounds by the liver increased up to 3 h, at which time there was about 40% of injected PC and 60% of DOEPC . The PC disappeared more rapidly than the DOEPC , so that 17 and 48% of injected label were present in the liver 24 h after injection of PC and DOEPC , respectively. Ten days after injection of DOEPC , about 10% of the label was still present in the liver. During the first 5 days after injection of DOEPC , 10% of radioactivity was found in the gastrointestinal tract and about 20% in the carcass; no increase in carcass radioactivity occurred during the loss of label from the liver. 24 and 48 h after injection of DOEPC , 40% of liver radioactivity was present in a neutral lipid, which on TLC comigrated with triacylglycerol. Since after alkaline hydrolysis this compound comigrated with diacylglycerol, it appears that the ether bond of DOEPC was not hydrolyzed, but after removal of phosphocholine, presumably by phospholipase C, the diether glycerol was reacylated . In experiments in vitro, the rate of exchange of labelled PC with red blood cell phospholipids exceeded that of DOEPC . Incubation of cultured hepatocytes with liposomes containing PC and/or DOEPC resulted in uptake of both phospholipids and metabolism of DOEPC to neutral lipids. The present findings indicate that DOEPC undergoes slow metabolism and can be eliminated from the body. These properties could prove advantageous for the use of DOEPC as a carrier of drugs and possibly as a carrier of free cholesterol in reverse cholesterol transport.

In vitro metabolism of LDL labeled with a nondegradable cholesteryl ester analogue

Low density lipoprotein (LDL) metabolism by human skin fibroblasts was studied using LDL labeled in the neutral lipid fraction with a nonhydrolysable cholesteryl ester analogue 3H-cholesteryl linoleyl ether (3H-CLE-LDL). LDL uptake could be quantitated accurately using 3H-CLE-LDL, since the label accumulated intracellularly due to its resistance to hydrolysis. 3H-CLE-LDL was taken up via apo B,E receptor-mediated endocytosis in a manner similar to 125I-labeled LDL. This was demonstrated by similar rates of uptake of the two differently labeled LDL preparations, saturation kinetics of uptake with respect to 3H-CLE-LDL concentration, regulation of 3H-CLE-LDL uptake by procedures that up-regulate or down-regulate the number of apo B,E receptors, and negligible uptake of 3H-CLE-LDL by receptor-negative cell strains. The major difference between the handling of 125I-LDL and 3H-CLE-LDL was the finding that, while the amount of trypsin-releasable (surface) 3H-CLE increased progressively over a 24-hour experimental period, trypsin-releasable 125I-LDL reached a maximum within 30 minutes. After 24 hours of incubation, the 3H radioactivity released by brief trypsinization was three to four times higher than could be accounted for by 125I radioactivity released by a similar treatment. Possible reasons for this behavior are discussed.

Effect of weight loss in moderate obesity on plasma lipoprotein and apolipoprotein levels and on high density lipoprotein composition

Plasma lipids, lipoprotein and apolipoprotein levels were determined in seven women and seven men with moderate obesity before, during 7 weeks of continuous weight loss (10.4% to 9.6% of body weight, 1000 kCal/day diet), and after 3 months at a stable, reduced weight. Plasma triglyceride levels decreased by 30.4% in men and by 39.4% in women (p less than 0.0001) after 1 week of caloric restriction and remained at this level throughout the study period. The plasma cholesterol decreased by 19.0% in men (p less than 0.001) and by 10.9% in women (p less than 0.01) in the period of active weight loss, but returned to prediet values after stabilization at a leaner body mass. Similar changes were observed in LDL cholesterol levels. No change in high density lipoprotein (HDL) cholesterol levels occurred during active weight reduction, but after 3 months at a reduced weight, a significant increase in HDL cholesterol was evident, and the ratio of HDL cholesterol to plasma cholesterol increased over prediet values (p less than 0.001), women). Separation of HDL subpopulations by zonal ultracentrifugation before and after weight reduction revealed that HDL2 increased slightly in men and decreased slightly in women. In both genders, HDL3 tended to decrease after weight reduction. Plasma levels of apolipoprotein A-I decreased during active weight loss, but this was significant only in women (p less than 0.05). After 3 months of reduced weight, plasma apo A-I increased to prediet levels. No significant changes in plasma apo A-II or apo E were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Admixture analysis of plasma cholesterol levels in a Jewish population sample in Jerusalem

The frequency distribution of total plasma cholesterol levels (TC) in 17-year-old Jerusalem youngsters and their parents (n = 6,170) was examined for evidence of admixture of normal distributions. Probability plots indicated bimodality of age-adjusted TC in both sexes. Using a maximum likelihood procedure, two normal distributions fitted the age- and sex-adjusted data significantly better than 1, with 0.9% males and 1.2% females coming from a lower distribution 2-3 standard deviations below the major mode and 0.2% males and 1.1% females belonging to the higher distribution. These results suggest that single genes may determine high as well as low cholesterol levels, but are open to other interpretations, and thus require confirmation by segregation analysis. Jews originating from Europe showed the highest TC levels followed by those from Israel, Asia, and Africa. Adjustment of TC for ethnicity did not alter the above estimates. Analysis of bimodality within countries of origin showed greater separation of the distributions in Asian and Israeli origin groups than in European and North African groups, in whom there was less evidence for admixture.