Leukocyte low density lipoprotein receptor (LDL-R) does not contribute to LDL clearance in vivo: bone marrow transplantation studies in the mouse

The targeted disruption of the low density lipoprotein (LDL) receptor gene in mice results in accumulation of plasma LDL cholesterol and in predisposition to diet-induced aortic atherosclerosis. Although the liver is the central organ for receptor mediated clearance of LDL, the in vivo role of other organs and tissues in LDL catabolism has not been directly studied. Since bone marrow-derived cells such as blood leukocytes and tissue macrophages express LDL receptors and contribute a large mass to the body, we designed bone marrow transplantation (BMT) experiments to reconstitute LDL receptor null mice [LDL-R(-/-)] with marrow obtained from LDL-R wild-type mice [LDL-R(+/+)] and evaluate the effects on parameters of plasma lipid metabolism. Although reconstitution of the transplanted mice with donor bone marrow cells was complete, no differences in plasma lipid levels and lipoprotein distribution were found between groups, irrespective of the diet used, and turnover studies using 125I-labeled LDL showed that LDL receptor expression by leukocytes and macrophages does not significantly contribute to plasma LDL clearance. The complementary experiment of transplanting LDL-R(-/-) marrow into C57BL/6 recipients [LDL-R(-/-)-->LDL(+/+)], performed to evaluate the role of leukocyte LDL-R in normocholesterolemic condition, also produced no effects on plasma lipid parameters. LDL binding studies using macrophages isolated from transplanted mice showed a lack of LDL-R expression. Thus, despite their large number and wide distribution, bone marrow-derived cells do not significantly influence receptor-mediated clearance of plasma LDL.     

Delayed low density lipoprotein (LDL) catabolism despite a functional intact LDL-apolipoprotein B particle and LDL-receptor in a subject with clinical homozygous familial hypercholesterolemia

We identified a 38-yr-old male patient with the clinical expression of homozygous familial hypercholesterolemia presenting as severe coronary artery disease, tendon and skin xanthomas, arcus lipoides, and joint pain. The genetic trait seems to be autosomal recessive. Interestingly, serum concentrations of cholesterol responded well to diet and statins. We had no evidence of an abnormal low density lipoprotein (LDL)-apolipoprotein B (apoB) particle, which was isolated from the patient using the U937 proliferation assay as a functional test of the LDL-binding capacity. The apoB 3500 and apoB 3531 defects were ruled out by PCR. In addition, we found no evidence for a defect within the LDL-receptor by skin fibroblast analysis, linkage analysis, single-strand conformational polymorphism and Southern blot screening across the entire LDL-receptor gene. The in vivo kinetics of radioiodinated LDL-apoB were evaluated in the proband and three normal controls, subsequently. The LDL-apoB isolated from the patient showed a normal catabolism, confirming an intact LDL particle. In contrast the fractional catabolic rate (d-1) of autologous LDL in the subject and the normal controls revealed a remarkable delayed catabolism of the patient's LDL (0.15 vs. 0.33-0.43 d-1). In addition, the elevation of LDL-cholesterol in the patient resulted from an increased production rate with 22.8 mg/kg per day vs. 12.7-15.7 mg/kg per day. These data indicate that there is another catabolic defect beyond the apoB and LDL-receptor gene causing familial hypercholesterolemia.     

Receptors of the low density lipoprotein (LDL) receptor family in man. Multiple functions of the large family members via interaction with complex ligands

The LDL receptor family members are endocytic receptors composed of repeated protein modules, including clusters of ligand binding LDL receptor class A (LA) repeats. The large (approximately 600 kDa) members LRP and megalin bind numerous structurally unrelated and often complex ligands at different combinations of sites. LRP is expressed in a wide but restricted set of cell types including hepatocytes, macrophages, smooth muscle cells, and neurons of the CNS. Megalin is expressed in various epithelia including proximal kidney tubules, intestine, and ependymal cells. The two receptors share a multitude of ligands, and their function in vivo is therefore to a large extent determined by their expression pattern. For example, both receptors can endocytose lipoproteins, but this function appears mainly relevant for LRP. In addition, LRP helps regulating urokinase receptor expression on the cell surface via ligand-mediated internalization followed by return of the naked urokinase receptor to the cell surface. Both receptors also have specialist functions. LRP is specific for binding of alpha2-macroglobulin-proteinase complexes and provides clearance of the complexes and of peptides, e.g. cytokines, associated with the complex. Megalin has important functions in vitamin B12 homeostasis since it specifically mediates uptake of the vitamin B12-transcobalamin complex and helps building a storage pool for the vitamin in the kidneys. Moreover, megalin binds cubilin, the recently identified receptor for B12-intrinsic factor complex, thus providing a mechanism for uptake of dietary vitamin B12. Finally, megalin specifically mediates uptake of apolipoprotein J/clusterin, a binding protein for the Abeta peptide implicated in Alzheimer's disease. The binding of multiple complex ligands that belong to distinct physiological systems provides a challenge in future studies aiming at elucidating the role of LRP and megalin in disease mechanisms.     

Small dense low density lipoprotein has increased affinity for LDL receptor-independent cell surface binding sites: a potential mechanism for increased atherogenicity

Small dense low density lipoprotein (LDL) particles have altered apolipoprotein (apo) B conformation and lowered affinity for the LDL receptor (J. Biol. Chem. 1994. 269: 511-519). Herein, we examine the interaction of small dense LDL with cell LDL receptor-independent binding sites. Compared to normal LDL, at low LDL cell media concentrations (<10 microg/ml), small dense LDL had decreased specific binding to the LDL receptor on normal fibroblasts at 4 degrees C, but a 2-fold increased binding to LDL receptor-independent cell sites. At higher LDL concentration (100 microg/ ml), LDL receptor-independent binding of small dense LDL was 4.5-fold that of normal LDL in normal fibroblasts, but greater (2- to 14- fold) in LDL receptor-negative fibroblasts. In LDL receptor-negative fibroblasts at 37 degrees C, small dense LDL had higher (3-fold) cell association than normal size LDL but no effective LDL degradation. At high LDL concentrations (> or =100 microg/ml), LDL binding to normal or LDL receptor-negative fibroblasts was not affected by several anti-apoB monoclonal antibodies or by cell pretreatment with proteases, chondroitinase, or neuraminidase. In contrast, pretreating normal and receptor-negative fibroblasts with heparinase and heparitinase decreased LDL cell binding by 35% and 50%, respectively. Similarly, preincubation of receptor-negative fibroblasts with sodium chlorate, an inhibitor of proteoglycan sulfation, decreased LDL binding by about 45%. We hypothesize that small dense LDL might be more atherogenic than normal size LDL due to decreased hepatic clearance by the LDL receptor, and enhanced anchoring to LDL receptor-independent binding sites in extrahepatic tissues (e.g., the arterial wall), a process mediated, in part, by cell surface proteoglycans.     

Precipitation procedures used to isolate high density lipoprotein with particular reference to effects on apo A-I-only particles and lipoprotein(a)

Analysis of high density lipoprotein (HDL) isolated from serum without major hypertriglyceridaemia and by five different precipitation methods showed that there were no significant differences in total cholesterol and triglyceride concentrations in the HDL supernatants prepared by the different methods but that free cholesterol, phospholipid, apolipoprotein (apo) A-I and HDL particles containing apo A-I but not apo A-II (LpAI) concentrations were significantly lower for heparin-manganese chloride method 2 (final manganese chloride concentration 92 mmol/l) compared with the other methods. Modest differences in HDL cholesterol, apo A-I and LpAI were observed between heparin-manganese chloride method 1 (final magnesium concentration 46 mmol/l) and the dextran sulphate, phosphotungstate and polyethylene glycol 6000 methods. Lipoprotein(a) (Lp(a)) and apo B were undetectable in the HDL supernatants, indicating that apo B-containing lipoproteins including Lp(a) were essentially completely removed by all the precipitation procedures.     

Cellular uptake of saposin (SAP) precursor and lysosomal delivery by the low density lipoprotein receptor-related protein (LRP)

Sphingolipid activator proteins SAP-A, -B, -C and -D (also called saposins) are generated by proteolytic processing from a 73 kDa precursor and function as obligatory activators of lysosomal enzymes involved in glycosphingolipid metabolism. Although the SAP precursor can be recognized by the mannose-6-phosphate (M-6-P) receptor and shuttled directly from the secretory pathway to the lysosome, a substantial fraction of newly synthesized precursor is secreted from the cell where it may participate in sphingolipid transport and signaling events. Re-uptake of the secreted precursor is mediated by high-affinity cell surface receptors that are apparently distinct from the M-6-P receptor. We found that the low density lipoprotein receptor-related protein (LRP), a multifunctional endocytic receptor that is expressed on most cells, can mediate cellular uptake and lysosomal delivery of SAP precursor. Additional in vivo experiments in mice revealed that the mannose receptor system on macrophages also participates in precursor internalization. We conclude that SAP precursor gains entry into cells by at least three independent receptor mechanisms including the M-6-P receptor, the mannose receptor and LRP.     

Identification of a common low density lipoprotein receptor mutation (C163Y) in the west of Scotland

BACKGROUND: The pathological processes by which Helicobacter pylori infection leads to the development of gastroduodenal disease are still incompletely understood. Oxygen-derived free radicals are important mediators of inflammation and potential carcinogens. Furthermore, dietary studies have suggested that antioxidant vitamins may protect against gastric cancer. OBJECTIVE: To determine plasma free radical activity and antioxidant vitamin levels in dyspeptic patients and to correlate the results with H. pylori infection and tobacco smoking. SUBJECTS: Forty-three patients undergoing routine endoscopy for investigation of dyspepsia. METHODS: Plasma free radical activity was determined by measurement of thiobarbituric acid-reactive substances (TBARS). Plasma samples were also assayed for the antioxidant vitamins A, C and E. Gastroduodenal biopsies were obtained from all patients for histological examination. RESULTS: Plasma TBARS levels were significantly higher in H. pylori positive versus negative subjects (P < 0.03), smokers versus non-smokers (P < 0.04) and males versus females (P < 0.01). Multiple regression analysis revealed that after correcting for male sex and smoking there was no significant association between plasma free radical activity and H. pylori infection. Smokers had significantly lower levels of plasma vitamin C than non-smokers (P< 0.05); no differences were seen in vitamin A and E levels. Gender and H. pylori infection did not significantly affect plasma antioxidant vitamin levels. Gastroduodenal disease was present in all of the smokers compared with 67% of the non-smokers (P < 0.05); 69% of the smokers were H. pylori positive versus 53% of the non-smokers. CONCLUSIONS: Tobacco smoking and male sex, both recognized risk factors for gastroduodenal disease, appear to be the major determinants of increased plasma free radical activity in dyspeptic subjects, rather than H. pylori infection. The reason for the higher prevalence of H. pylori infection and gastroduodenal disease in dyspeptic smokers is unclear but may relate to weakened antioxidant defences.     

Lipoprotein receptors in acute myelogenous leukemia: failure to detect increased low-density lipoprotein (LDL) receptor numbers in cell membranes despite increased cellular LDL degradation

The high-affinity degradation of low-density lipoprotein (LDL) is enhanced 3- to 100-fold in leukemic blood cells from patients with acute myelogenous leukemia (AML), suggesting an increased cellular LDL receptor expression. There are, however, inconsistencies regarding the published properties of LDL receptor regulation in AML cells, and previous data on this are indirect. In the present study the aim was to determine whether the LDL receptor number is increased in AML cells. The LDL receptor number was assayed by ligand blot with rabbit 125I-labeled beta-very-low-density lipoprotein (beta-VLDL) of transferred, SDS-polyacrylamide-gel-electrophoresis-separated AML cell membranes. Samples from 10 patients, six with AML, one with chronic myelogenous leukemia in blast crisis, and three with acute lymphoblastic leukemia, were investigated. The LDL receptor expression was strongly suppressed in all samples to levels lower than that of normal mononuclear cells. This was despite the fact that cells from one patient with AML of M4 subtype had a 50- to 100-fold higher 125I labeled LDL degradation compared with normal cells. Immunoblots with antibodies against gp330/megalin and the LDL-receptor-related protein (LRP) and ligand blot using 125I-labeled 39-kd receptor-associated protein (RAP) could not detect gp330/megalin or VLDL receptors. The LRP was abundant in AML samples of M4 and M5b subtype, as determined from both RAP ligand blot and immunoblot using an LRP-specific antibody. It is concluded that LDL receptors are suppressed in AML cells. It is possible that the high degradation of 125I-labeled LDL present in type M4 and M5 AML cells may involve another lipoprotein receptor.     

Tetradecylthioacetic acid incorporated into very low density lipoprotein: changes in the fatty acid composition and reduced plasma lipids in cholesterol-fed hamsters

The mechanism behind the hypolipidemic effect of tetradecylthioacetic acid (CMTTD, a non-beta-oxidizable 3-thia fatty acid) was studied in hamsters fed a high cholesterol diet (2%), which resulted in hyperlipidemia. Treating hyperlipidemic hamsters with CMTTD resulted in a progressive hypocholesterolemic and hypotriacylglycerolemic effect. Decreased plasma cholesterol was followed by a 39% and 30% reduction in VLDL-cholesterol and LDL-cholesterol, respectively. In contrast, the HDL-cholesterol content was not affected, thus decreasing the VLDL-cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios. 3-Hydroxy-3-methylglutaryl- (HMG) CoA reductase activity and its mRNA level were unchanged after CMTTD administration. Also, the LDL receptor and LDL receptor-related protein (LRP-4) mRNAs were unchanged. The decrease in plasma triacylglycerol was accompanied by a 45% and 56% reduction in VLDL-triacylglycerol and LDL-triacylglycerol, respectively. The hypolipidemic effect of CMTTD was followed by a 1.4-fold increase in mitochondrial fatty acid oxidation and a 2.3-fold increase in peroxisomal fatty acid oxidation. CMTTD treatment led to an accumulation of dihomo-gamma-linolenic acid (20:3n-6) in liver, plasma, very low density lipoprotein, and heart. Noteworthy, CMTTD accumulated more in the heart, plasma, and VLDL particles compared to the liver, and in the VLDL particle alpha-linolenic acid (18:3n-3) decreased whereas eicosatetraenoic acid (20:4n-3) increased. In addition, linoleic acid (18:2n-6) and the total amount of polyunsaturated fatty acids decreased, the latter mainly due to a decrease in n-6 fatty acids. The present data show that CMTTD was detected in plasma and incorporated into VLDL, liver, and heart. The relative incorporation (mol%) of CMTTD was heart > VLDL > liver. In conclusion, CMTTD causes both a hypocholesterolemic and hypotriacylglycerolemic effect in hyperlipidemic hamsters.     

Racial differences in the distribution of a low density lipoprotein receptor-related protein (LRP) polymorphism and its association with serum lipoprotein, lipid and apolipoprotein levels

We recently demonstrated that granulocyte-macrophage colony-stimulating factor (GM-CSF) is an autocrine growth factor for human osteoblastic (hOB) cells. Since GM-CSF is a member of the heparin-binding factor family, we examined the interactions between GM-CSF and glycosaminoglycans (GAGs) present in the osteoblast microenvironment. Using a bioassay in which the mitogenic activity of recombinant human (rh) GM-CSF was measured after incubation in the presence of an hOB cell layer or extracellular matrix (ECM) produced by these cells, we showed that rhGM-CSF binds to GAG components present in the ECM and that the bound rhGM-CSF retains its ability to stimulate hOB cell proliferation. Heparan sulfate compounds on the hOB cell surface were also found to sequester GM-CSF. Moreover, treatment with sodium chlorate, an inhibitor of GAG sulfation, suppressed the mitogenic activity of rhGM-CSF on hOB cells. This inhibitory effect was rescued by a low dose of heparin. Heparin was also found to promote the effect of rhGM-CSF on hOB cell proliferation, allowing nonmitogenic high doses of rhGM-CSF to stimulate hOB cell growth. Western blot analysis showed that undersulfation of cellular GAGs by chlorate inhibited the increased tyrosine phosphorylation of proteins involved in GM-CSF signaling in cloned immortalized hOB cells. The data demonstrate that GM-CSF binds to proteoglycans on the hOB cell surface and in ECM produced by these cells and that the bound GM-CSF is biologically active. Furthermore, this study shows that cellular proteoglycans play an essential role in GM-CSF signaling and biological activity in hOBs.     

No association between the low density lipoprotein receptor-related protein (LRP) gene and late-onset Alzheimer's disease in a community-based sample

It is now commonly known that possession of the epsilon4 allele of the apolipoprotein E (APOE) gene confers an increased risk for both familial and sporadic Alzheimer's disease (AD), in a dose-dependent way. Other genes that may play a role in AD, either through independent association with the disease or through modification of the existing APOE risk, have been reported with conflicting results. One such gene, the low density lipoprotein receptor-related protein (LRP) gene, was recently reported by two groups to be associated with AD, although the groups identified different risk-conferring alleles. Both studies were based on clinic-derived AD populations (one American, one French), and both reported only marginally significant results. We have genotyped a community-based AD and control population at this LRP polymorphism and find no association between the variants at that polymorphism and the occurrence of AD. Further, despite the biochemical relationship between LRP and the ApoE protein, we find no significant statistical interaction between the alleles at these loci.     

Treatment effects on serum lipoprotein lipids, apolipoproteins and low density lipoprotein particle size and relationships of lipoprotein variables to progression of coronary artery disease in the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT)

OBJECTIVES: To investigate the mechanisms by which bezafibrate retarded the progression of coronary lesions in the Bezafibrate Coronary Atherosclerosis Intervention Trial (BECAIT), we examined the relationships of on-trial lipoproteins and lipoprotein subfractions to the angiographic outcome measurements. BACKGROUND: BECAIT, the first double-blind, placebo-controlled, randomized serial angiographic trial of a fibrate compound, showed that progression of focal coronary atherosclerosis in young survivors of myocardial infarction could be retarded by bezafibrate treatment. METHODS: A total of 92 dyslipoproteinemic men who had survived a first myocardial infarction before the age of 45 years were randomly assigned to treatment for 5 years with bezafibrate (200 mg three times daily) or placebo; 81 patients underwent baseline and at least one post-treatment coronary angiography. RESULTS: In addition to the decrease in very low density lipoprotein (VLDL) cholesterol (-53%) and triglyceride (-46%) and plasma apolipoprotein (apo) B (-9%) levels, bezafibrate treatment resulted in a significant increase in high density lipoprotein-3 (HDL3) cholesterol (+9%) level and a shift in the low density lipoprotein (LDL) subclass distribution toward larger particle species (peak particle diameter +032 nm). The on-trial HDL3 cholesterol and plasma apo B concentrations were found to be independent predictors of the changes in mean minimum lumen diameter (r=-0.23, p < 0.05), and percent (%) stenosis (r = 0.30, p < 0.01), respectively. Decreases in small dense LDL and/or VLDL lipid concentrations were unrelated to disease progression. CONCLUSIONS: Our results suggest that the effect of bezafibrate on progression of focal coronary atherosclerosis could be at least partly attributed to a rise in HDL3 cholesterol and a decrease in the total number of apo B-containing lipoproteins.     

Native and modified (acetylated) low density lipoprotein-supported steroidogenesis by macaque granulosa cells collected before and after the ovulatory stimulus: correlation with fluorescent lipoprotein uptake

We recently reported that uptake of fluorescent-tagged low density lipoprotein (DiI-LDL) by macaque granulosa cells (GC) was greatly enhanced within 27 h of an ovulatory stimulus (hCG injection). The present study was designed to determine whether increased DiI-LDL uptake correlated with an increased capacity for LDL-supported steroidogenesis. We also tested whether modified [acetylated (ac)] LDL or high density lipoprotein (HDL), which are not ligands for the LDL receptor, supported progesterone (P) production. Beginning at menses, adult female rhesus macaques were treated with human (h) FSH and hLH for 9 days to promote development of multiple follicles. On day 10, monkeys were injected with hCG (1000 IU) or received no ovulatory stimulus. Large follicles were aspirated on day 10 (nonluteinized GC) or 27-34 h after hCG administration (luteinizing GC). GC (2 x 10(4)/0.2 ml) were cultured in Dulbecco's Modified Eagle's Medium-Ham's F-12 plus insulin, transferrin, H2SeO3, and aprotinin, with 0-100 micrograms hLDL, ac-hLDL, or hHDL. P concentrations in medium were determined by RIA. LDL (1-25 micrograms/ml) dose-dependently increased (up to 15-fold; P < 0.05) basal and hCG-stimulated P production by luteinized GC on days 1-8 of culture. However, LDL (25 micrograms/ml) did not alter basal P production by nonluteinized GC and increased (2-fold; P < 0.05) hCG-stimulated P secretion only on days 4-8. Basal and hCG-stimulated P production by luteinized GC were initially (days 1-2) increased (up to 2-fold; P < 0.05), but later (days 6-8) suppressed (P < 0.05) in a dose-dependent manner by 1-100 micrograms ac-LDL/ml. Ac-LDL did not alter basal or hCG-stimulated P production by nonluteinized GC. HDL (1-100 micrograms/ml) did not alter P production by either luteinized or nonluteinized GC. The number of viable luteinized GC on day 8 was reduced (30-50%; P < 0.05) after exposure to 10 micrograms ac-LDL/ml or more, whereas only the highest dose (100 micrograms/ml) of LDL or HDL reduced cell survival. Ac-LDL did not alter the survival of nonluteinized GC in culture. Flow cytometric analyses using fluorescent-tagged lipoproteins (DiI-LDL/DiI-ac-LDL) demonstrated the uptake of both native and ac-LDL by luteinized GC. Uptake of DiI-LDL was competitively suppressed in a dose-dependent manner by unlabeled LDL, but not by ac-LDL. In contrast, DiI-ac-LDL uptake was competitively inhibited by both ac-LDL and LDL.(ABSTRACT TRUNCATED AT 400 WORDS)     

The association of HincII/low density lipoprotein receptor (LDLR) restriction fragment length polymorphism (RFLP) with diabetes mellitus and its lipid phenotype with PCR gene amplification

The association of low density lipoprotein receptor (LDLR) gene HincII RFLP with diabetes mellitus and its lipid metabolism was studied in 196 Chinese with PCR gene amplification. 16 IDDM and 75 NIDDM were included. The most common genotype and allele frequencies of NIDDM were H2H2 (0.78) and H2 (0.89) respectively, and no significant differences were found in comparison with the normal control. The NIDDM with low LDL level (< 1.3 mmol/L) had less H2H2 type and H2 frequencies. Allele 1 (H1) was possibly related to the higher level of serum cholesterol, but allele 2 (H2) was quite the reverse. The phenotype of lipid metabolism was partially determined by the genotype. LDL, tc and tg level of NIDDM were significantly higher than the normal control (P < 0.001, 0.001, 0.05 respectively), indicating that NIDDM was accompanied by disturbance of lipid metabolism.     

Laboratory studies of antipredator behavior in the Mongolian gerbil (Meriones unguiculatus): factors affecting response attenuation with repeated presentations

A series of experiments was conducted to study the properties of the attenuation of responding to repeated presentation of overhead visual transients in the gerbil (Meriones unguiculatus). Results suggest that this attenuation consists of habituation to the repeated association of a potentially threatening sensory stimulus with an increasingly familiar spatial context. The results of these experiments further suggest that the likelihood of eliciting fleeing is a conjoint function of the degree of risk posed by an overhead sensory transient and the degree of safety that is to be gained by fleeing. Results are discussed in the context of the ecology of predator recognition and the structural organization of the rodent visual system.     

Low density lipoprotein receptor-negative mice expressing human apolipoprotein B-100 develop complex atherosclerotic lesions on a chow diet: no accentuation by apolipoprotein(a)

We have generated mice with markedly elevated plasma levels of human low density lipoprotein (LDL) and reduced plasma levels of high density lipoprotein. These mice have no functional LDL receptors [LDLR-/-] and express a human apolipoprotein B-100 (apoB) transgene [Tg(apoB+/+)] with or without an apo(a) transgene [Tg(apoa+/-)]. Twenty animals (10 males and 10 females) of each of the following four genotypes were maintained on a chow diet: (i) LDLR-/-, (ii) LDLR-/-;Tg(apoa+/-), (iii) LDLR-/-;Tg(apoB+/+), and (iv)LDLR-/-;Tg(apoB+/+);Tg(apo+/-). The mice were killed at 6 mo, and the percent area of the aortic intimal surface that stained positive for neutral lipid was quantified. Mean percent areas of lipid staining were not significantly different between the LDLR-/- and LDLR-/-;Tg(apoa+/-) mice (1.0 +/- 0.2% vs. 1.4 +/- 0.3%). However, the LDLR-/-;Tg(apoB+/+) mice had approximately 15-fold greater mean lesion area than the LDLR-/- mice. No significant difference was found in percent lesion area in the LDLR-/-;Tg(apoB+/+) mice whether or not they expressed apo(a) [18.5 +/- 2.5%, without lipoprotein(a), Lp(a), vs. 16.0 +/- 1.7%, with Lp(a)]. Histochemical analyses of the sections from the proximal aorta of LDLR-/-;Tg(apoB+/+) mice revealed large, complex, lipid-laden atherosclerotic lesions that stained intensely with human apoB-100 antibodies. In mice expressing Lp(a), large amounts of apo(a) protein colocalized with apoB-100 in the lesions. We conclude that LDLR-/-; Tg(apoB+/+) mice exhibit accelerated atherosclerosis on a chow diet and thus provide an excellent animal model in which to study atherosclerosis. We found no evidence that apo(a) increased atherosclerosis in this animal model.     

Prognostic factors in low grade (WHO grade II) gliomas of the cerebral hemispheres: the role of surgery

OBJECTIVE: To assess the role of surgery on survival of patients with grade II gliomas of the cerebral hemispheres. METHODS: One hundred and thirty one low grade hemispheric gliomas surgically treated (biopsied patients excluded) between 1978 and 1989 were retrospectively reviewed. Thalamic, basal ganglia, callosal, or ventricular location were not considered. All tumours were World Health Organisation (WHO) grade II gliomas: 42 fibrillary and 11 gemistocytic astrocytomas, 49 oligodendrogliomas, and 29 oligoastrocytomas. Patients' ages ranged from 14 to 63 (mean 32.9, median 34) years, Karnofsky performance from 0.50 to 0.90 (mean 80.7, median 80), and postsurgical follow up of the living patients from 24 to 190 (mean 97.02, median 93) months. Postoperative external radiotherapy was performed in 49 cases. RESULTS: The overall survival probability at five years was 97.1%, at eight years 76.1%, and at 10 years 62.7% (median survival time 144 months). The impact on survival of the following variables was analysed: age (< 20, 21-40, and > 40 years), Karnofsky score (80-100, 70 < or = 70), histology, tumour extension (T1 < 3 cm, T2 3-5 cm, T3 > 5 cm maximum diameter), extent of surgical resection (S1 radical, S2 subtotal < 10% residual tumour, S3 partial-10%-50% residual tumour), and radiotherapy (either performed or not). A significant positive association with survival at univariate analysis was found for the age group < 20 years (P = 0.003), for total and subtotal surgical resections (S1 and S2; P < 0.001) and for the non-irradiated patients (P = 0.0049), whereas a shorter survival probability was noticed for gemistocytic astrocytomas (P < 0.001) and for tumour extension > 5 cm (T3; P = 0.0193). Karnofsky performance did not show any significant association with survival. The most relevant factor affecting survival at the multivariate analysis was the extent of surgical resection, which resulted as the only variable retaining a significant value (P = 0.001, risk factor = 2.20). CONCLUSIONS: The data strongly support the role of a surgical removal as extensive as possible in the treatment of these tumours.     

The Münster Heart Study (PROCAM): total mortality in middle-aged men is increased at low total and LDL cholesterol concentrations in smokers but not in nonsmokers

BACKGROUND: Some large epidemiological studies have shown an increase in mortality at low levels of total and LDL cholesterol. It has been speculated that low cholesterol levels may play a causative role in this association. To investigate this question, we analyzed all deaths occurring among middle-aged men in the Münster Heart Study (PROCAM), one of the largest prospective epidemiological studies of coronary heart disease risk markers in Europe. METHODS AND RESULTS: In the Münster Heart Study, 10,856 men aged 36 to 65 years at study entry (46.8+/-7.3 years [mean+/-SD]) were followed for 4 to 14 years (7.1+/-2.4 years). During this period, 313 deaths occurred--46 from myocardial infarction, 48 from suspected or definite sudden cardiac death, 14 from cerebrovascular disease, and 10 from other diseases of the circulatory system. There were 121 deaths from cancer and 33 deaths from violent causes (injuries in 16, suicide in 14, and homicide in 3 cases). Death in 29 cases occurred from other causes and was unexplained in 12 cases. Total cholesterol, LDL cholesterol, and the LDL/HDL ratio showed a J-shaped relationship with total mortality. At high total and LDL cholesterol concentrations, increased mortality was due to increased coronary deaths. At low total and LDL cholesterol concentrations, increased mortality was seen in smokers only and was explained by an increase in smoking-related cancer deaths. CONCLUSIONS: The increase in mortality at low levels of total and LDL cholesterol among middle-aged men in the Münster Heart Study is explained by an increase in smoking-related cancer deaths among smokers.