| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Aortic permeability to LDL as a predictor of aortic cholesterol accumulation in cholesterol-fed rabbits Nielsen, L. B., B. G. Nordestgaard, et al. (1992), Arterioscler Thromb 12(12): 1402-9. Abstract: The aim of this study was to investigate the possibility that the permeability characteristics of the arterial wall are related to the development of atherosclerosis. The in vivo regional variation of aortic permeability to iodinated human low density lipoprotein (LDL) in normal rabbits was compared with the regional variation in aortic cholesterol accumulation in cholesterol-fed rabbits. Aortas were divided into the aortic arch, thoracic aorta, and abdominal aorta, and each of these three parts was further subdivided into four segments of similar size. The permeability to LDL was 40 +/- 7 nl.cm-2.hr-1 (mean +/- SEM, n = 11) in the most proximal segment of the aortic arch and decreased throughout the length of the aorta to 3 +/- 1 nl.cm-2.hr-1 in the most caudal segment of the abdominal aorta. In such normal rabbits the aortic cholesterol content was similar in all 12 arterial segments at 0.08 +/- 0.005 mumol/cm2 (mean +/- SEM, n = 3 x 12). Aortic cholesterol accumulation was determined in other rabbits with an average plasma cholesterol level of 32 +/- 1 mmol/l for 96 days; the cholesterol content in the most proximal segment of the aortic arch was 2.7 +/- 0.5 mumol/cm2 (mean +/- SEM, n = 11) and decreased with increasing distance from the heart to 0.17 +/- 0.03 mumol/cm2 in the most caudal segment of the abdominal aorta. Linear regression analysis showed a close positive association between the permeability to LDL of a given aortic segment and the cholesterol accumulation in that same aortic segment after cholesterol feeding (r2 = 0.96, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS) |
| Aortic plaque size and endometrial response in cholesterol-fed rabbits treated with estrogen plus continuous or sequential progestin Brehme, U., B. Bruck, et al. (1999), Arterioscler Thromb Vasc Biol 19(8): 1930-7. Abstract: ERT is associated with a reduced incidence of coronary risk and cardiac events in postmenopausal women, but increases the risk of endometrial hyperplasia and carcinoma. Combined estrogen and progestin therapy protects the endometrium; however, its effects on heart disease risk factors are not completely known. In our study, 56 ovariectomized New Zealand White rabbits in 7 groups received a 0.5% cholesterol diet for 12 weeks. Controls were not treated with hormones. All other animals received (per kilogram body weight per week) intramuscular injections of either 0.3 mg estrogen (estradiol valerate) alone, 8.3 mg progestin (hydroxyprogesterone caproate) alone, estrogen and progestin continuously in 3 different dosages (0.3 and 8.3 mg; 1 and 8.3 mg; or 1 and 2.8 mg; estrogen and progestin, respectively), or 1 mg estrogen with 25 mg progestin sequentially in 2-week cycles. Eight non-ovariectomized animals served as further controls for endometrial analysis. Morphometric analysis of plaque size in the aortic arch showed that estrogen monotherapy, and the 3 combined therapies with 1 mg estrogen, significantly reduced intimal thickening (P<0.05). The application of progestin alone had no effect on plaque size. The endometrium was enlarged by 3-fold after estrogen treatment, and was decreased by half after progestin treatment, compared with control uteri (P<0.05). In all groups with combined hormone regimens, endometrial size was not significantly different from control uteri. However, these uteri showed more inflammatory reactions, especially when higher doses of hormones were given. In this animal model, doses of progestin that are able to successfully reduce the proliferative effect of estrogen on endometrium do not diminish the desirable antiatherosclerotic properties of estrogen. |
| APF/CBP, an anionic polypeptide in bile and gallstones that may regulate calcium salt and cholesterol precipitation from bile Ostrow, J. D. (1992), Hepatology 16(6): 1493-6. |
| Apical sorting of bovine enteropeptidase does not involve detergent-resistant association with sphingolipid-cholesterol rafts Zheng, X., D. Lu, et al. (1999), J Biol Chem 274(3): 1596-605. Abstract: Enteropeptidase is a heterodimeric type II membrane protein of the brush border of duodenal enterocytes. In this location, enteropeptidase cleaves and activates trypsinogen, thereby initiating the activation of other intestinal digestive enzymes. Recombinant bovine enteropeptidase was sorted directly to the apical surface of polarized Madin-Darby canine kidney cells. Replacement of the cytoplasmic and signal anchor domains with a cleavable signal peptide (mutant proenteropeptidase lacking the amino-terminal signal anchor domain (dSA-BEK)) caused apical secretion. The additional amino-terminal deletion of a mucin-like domain (HL-BEK) resulted in secretion both apically and basolaterally. Further deletion of the noncatalytic heavy chain (L-BEK) resulted in apical secretion. Thus enteropeptidase appears to have at least three distinct sorting signals as follows: the light chain (L-BEK) directs apical sorting, addition of most of the heavy chain (HL-BEK) inhibits apical sorting, and addition of the mucin-like domain (dSA-BEK) restores apical sorting. Inhibition of N-linked glycosylation with tunicamycin or disruption of microtubules with colchicine caused L-BEK to be secreted equally into apical and basolateral compartments, whereas brefeldin A caused basolateral secretion of L-BEK. Full-length BEK was not found in detergent-resistant raft domains of Madin-Darby canine kidney cells or baby hamster kidney cells. These results suggest apical sorting of enteropeptidase depends on N-linked glycosylation of the serine protease domain and an amino-terminal segment that includes an O-glycosylated mucin-like domain and three potential N-glycosylation sites. In contrast to many apically targeted proteins, enteropeptidase does not form detergent-resistant associations with sphingolipid-cholesterol rafts. |
| Apo A-I promoter polymorphism influences basal HDL-cholesterol and its response to pravastatin therapy Lahoz, C., R. Pena, et al. (2003), Atherosclerosis 168(2): 289-95. Abstract: Statins decrease cardiovascular morbidity and mortality, essentially, by reducing LDL-cholesterol levels and, additionally, by increasing HDL-cholesterol concentrations. Environmental and genetic factors are known to affect LDL-C response to statins but less is known regarding HDL-C. We have evaluated the lipid and lipoprotein response to 20 mg/day of pravastatin for 16 weeks in relation to the G/A polymorphism in the promoter region of the apo A-I gene in 397 hypercholesterolaemic subjects followed-up on an out-patient basis. In the study population, 61.7% were homozygous for the G allele and 36% were heterozygous. The A allele carriers had an HDL-C 6.5% higher than the G allele homozygotes (P=0.021 in univariate analysis; P=0.009 in multivariate analysis). However, on segregation by gender and smoking status the effect was significant only in non-smoking males. The A allele carriers did not increase their HDL-C concentrations after treatment (-0.3, 95%CI -3.3 to 2.7%) while G allele homozygotes had a 4.9% increase (95%CI 2.5-7.3%). Differences in the response between both groups were significant before (P=0.008) and after adjustment for confounding variables such as age and baseline HDL-C concentration (P=0.046). We conclude that the G/A polymorphism of the apo A-I promoter region affects not only baseline HDL-C concentrations but also its response to pravastatin treatment. |
| Apo AI/ABCA1-dependent and HDL3-mediated lipid efflux from compositionally distinct cholesterol-based microdomains Drobnik, W., H. Borsukova, et al. (2002), Traffic 3(4): 268-78. Abstract: We have investigated whether a raft heterogeneity exists in human monocyte-derived macrophages and fibroblasts and whether these microdomains are modulated by lipid efflux. Triton X-100 (Triton) or Lubrol WX (Lubrol) detergent-resistant membranes from cholesterol-loaded monocytes were associated with the following findings: (i) Lubrol-DRM contained most of the cellular cholesterol and at least 75% of Triton-detergent-resistant membranes. (ii) 'Lubrol rafts', defined by their solubility in Triton but insolubility in Lubrol, were enriched in unsaturated phosphatidylcholine and showed a lower cholesterol to choline-phospholipid ratio compared to Triton rafts. (iii) CD14 and CD55 were recovered in Triton- and Lubrol-detergent-resistant membranes, whereas CD11b was found exclusively in Triton DRM. ABCA1 implicated in apo AI-mediated lipid efflux and CDC42 were partially localized in Lubrol- but not in Triton-detergent-resistant membranes. (iv) Apo AI preferentially depleted cholesterol and choline-phospholipids from Lubrol rafts, whereas HDL3 additionally decreased the cholesterol content of Triton rafts. In fibroblasts, neither ABCA1 nor CDC42 was found in Lubrol rafts, and both apo AI and HDL3 reduced the lipid content in Lubrol- as well as in Triton-detergent-resistant membranes. In summary, we provide evidence for the existence of compositionally distinct membrane microdomains in human cells and their modulation by apo AI/ABCA1-dependent and HDL3-mediated lipid efflux. |
| apo B gene knockout in mice results in embryonic lethality in homozygotes and neural tube defects, male infertility, and reduced HDL cholesterol ester and apo A-I transport rates in heterozygotes Huang, L. S., E. Voyiaziakis, et al. (1995), J Clin Invest 96(5): 2152-61. Abstract: apo B is a structural constituent of several classes of lipoprotein particles, including chylomicrons, VLDL, and LDL. To better understand the role of apo B in the body, we have used gene targeting in embryonic stem cells to create a null apo B allele in the mouse. Homozygous apo B deficiency led to embryonic lethality, with resorption of all embryos by gestational day 9. Heterozygotes showed an increased tendency to intrauterine death with some fetuses having incomplete neural tube closure and some live-born heterozygotes developing hydrocephalus. The majority of male heterozygotes were sterile, although the genitourinary system and sperm were grossly normal. Viable heterozygotes had normal triglycerides, but total, LDL, and HDL cholesterol levels were decreased by 37, 37, and 39%, respectively. Hepatic and intestinal apo B mRNA levels were decreased in heterozygotes, presumably contributing to the decreased LDL levels through decreased synthesis of apo B-containing lipoproteins. Kinetic studies indicated that heterozygotes had decreased transport rates of HDL cholesterol ester and apo A-I. As liver and intestinal apo A-I mRNA levels were unchanged, the mechanism for decreased apo A-I transport must be posttranscriptional. Heterozygotes also had normal cholesterol absorption and a normal response of the plasma lipoprotein pattern to chronic consumption of a high fat, high cholesterol, Western-type diet. In summary, we report a mouse model for apo B deficiency with several phenotypic features that were unexpected based on clinical studies of apo B-deficient humans, such as embryonic lethality in homozygotes and neural tube closure defects, male infertility, and a major defect in HDL production in heterozygotes. This model presents an opportunity to study the mechanisms underlying these phenotypic changes. |
| ApoA1 reduces free cholesterol accumulation in atherosclerotic lesions of ApoE-deficient mice transplanted with ApoE-expressing macrophages Boisvert, W. A., A. S. Black, et al. (1999), Arterioscler Thromb Vasc Biol 19(3): 525-30. Abstract: Along with apolipoprotein (apo) E, which promotes cholesterol efflux from foam cells, apoA1-containing high density lipoprotein (HDL) is thought to facilitate the transport of cholesterol from lesions. This role for apoA1 was tested in vivo by lethally irradiating apoE-deficient and apoE- plus apoA1-deficient mice and reconstituting them with bone marrow cells isolated from wild-type (WT) mice. ApoE, but not apoA1, was synthesized by the transplanted bone marrow-derived cells. Therefore, this transplantation procedure generated apoE-deficient animals with atherosclerotic lesions that contained both apoE and apoA1 (E/A1 mice) and apoE-deficient animals with lesions that contained apoE but no apoA1 (E/A1o mice). As shown previously, the transplanted WT macrophage-derived apoE dramatically lowered the plasma hypercholesterolemia in both groups. On feeding with an atherogenic diet after transplantation, plasma cholesterol levels were raised in both groups of mice, but the levels in the E/A1 mice at 20 weeks were 2- to 3-fold higher than in E/A1o mice. Immunohistochemical staining verified that apoE was abundant in lesions of both groups, whereas apoA1 was detected in the lesions of E/A1 mice only. Despite a 2- to 3-fold lower total plasma cholesterol in the E/A1o mice, the free cholesterol recovered from isolated aortas was approximately 60% higher and the mean lesion area in serial sections of the aortic valves 45% larger. Therefore, apoA1 reduces free cholesterol accumulation in vivo in atherosclerotic lesions. |
| APOA5 gene polymorphism modulates levels of triglyceride, HDL cholesterol and FERHDL but is not a risk factor for coronary artery disease Lee, K. W., A. F. Ayyobi, et al. (2004), Atherosclerosis 176(1): 165-72. Abstract: Variation in the APOA5 gene has been shown to be associated with triglyceride levels in several independent population studies. It was our objective to determine if a relationship existed between selected genotypes or haplotypes of the APOA5 gene and findings on selective coronary angiography (SCA) in an independent cohort. The Vancouver SCA Cohort consists of individuals referred for angiography between 1993 and 1995. DNA was extracted from 537 patients and analyzed for the -1131T>C and the c.56C>G polymorphisms which define three common haplotypes of the APOA5 gene. Plasma triglycerides and the fractional esterification rate in apoB-depleted lipoproteins (FER(HDL)), an index of high-density lipoprotein (HDL) composition, were significantly higher (P = 0.01 and P = 0.001, respectively), and HDL cholesterol (HDL-C) was significantly lower (P = 0.03) in Caucasians with genotypes containing the minor allele of the -1131T>C polymorphism compared to the homozygotes for the major allele. However, there was no relationship between the c.56C>G polymorphism of the APOA5 gene and any of the measured lipid and lipoprotein parameters. Subjects homozygous for the common haplotype APOA5*1 had decreased triglyceride levels and FER(HDL) (P = 0.04 and P < 0.001, respectively) and increased HDL-C levels (P = 0.01) compared to subjects with all other haplogenotypes. Multivariate linear regression analysis indicated that the -1131T>C polymorphism remained an independent predictor of triglyceride, HDL-C, and FER(HDL) following adjustment of several variables including age, gender, body mass index, diabetes, lipid lowering and beta-blocker medication. The APOA5*1/*1 haplogenotype remained an independent predictor of HDL-C and FER(HDL) following adjustment of the same variables. The relationship between APOA5 genotype or haplogenotype and FER(HDL) remained significant even after the addition of both HDL-C and triglyceride to the model. However, there was no association between APOA5 gene polymorphisms or haplotypes and coronary artery disease as determined by angiography. |
| ApoAI deficiency results in marked reductions in plasma cholesterol but no alterations in amyloid-beta pathology in a mouse model of Alzheimer's disease-like cerebral amyloidosis Fagan, A. M., E. Christopher, et al. (2004), Am J Pathol 165(4): 1413-22. Abstract: Epidemiological studies suggest links between cholesterol metabolism and Alzheimer's disease (AD), with hypercholesterolemia associated with increased AD risk, and use of cholesterol-lowering drugs associated with decreased risk. Animal models using cholesterol-modifying dietary or pharmacological interventions demonstrate similar findings. Proposed mechanisms include effects of cholesterol on the metabolism of amyloid-beta (Abeta), the protein that deposits in AD brain. To investigate the effect of genetic alterations in plasma cholesterol on Abeta pathology, we crossed the PDAPP transgenic mouse model of AD-like cerebral amyloidosis to apolipoprotein AI-null mice that have markedly reduced plasma cholesterol levels due to a virtual absence of high density lipoproteins, the primary lipoprotein in mice. Interestingly and in contrast to models using non-physiological high fat diets or cholesterol-lowering drugs to modify plasma cholesterol, we observed no differences in Abeta pathology in PDAPP mice of the various apoAI genotypes despite robust differences in plasma cholesterol levels between the groups. Absence of apoAI also resulted in reductions in brain but not cerebrospinal fluid cholesterol, but had no effect on brain apolipoprotein E levels. These and other data suggest that it is perhaps the level of brain apolipoprotein E, not cholesterol per se, that plays a primary role in brain Abeta metabolism. |
| ApoA-I lipidation in primary mouse hepatocytes. Separate controls for phospholipid and cholesterol transfers Zheng, H., R. S. Kiss, et al. (2005), J Biol Chem 280(22): 21612-21. Abstract: The liver is the major site of both apolipoprotein A-I (apoA-I) synthesis and ATP-binding cassette transporter A1 (ABCA1) expression. Here, we compare the lipidation with cholesterol and phospholipid of newly synthesized human apoA-I (hapoA-I) using adenoviral vector-mediated endogenous expression or exogenously added hapoA-I in wild type and ABCA1-null hepatocytes. Hepatocytes were labeled with 3Hcholesterol (delivered with LDL or methyl-beta-cyclodextrin), 3Hmevalonate, or 3Hcholine. ABCA1 deficiency decreased apoA-I phospholipidation by 80%, but acquisition of de novo synthesized and exogenous cholesterol only decreased by 40-60%. The transfer of de novo synthesized cholesterol to apoA-I was decreased at all time points, but that of exogenously delivered cholesterol was independent of ABCA1 activity at the early time points. Progesterone does not affect apoA-I synthesis or its lipidation but inhibited the early phase of apoA-I cholesterol lipidation in both wild type and ABCA1-null hepatocytes. Fast protein liquid chromatography analysis of medium lipoproteins confirmed that with ABCA1 deficiency, the proportion of secreted high density lipoprotein-associated apoA-I and cholesterol decreased by about 50%. The very low density lipoprotein (VLDL)/LDL size fraction also contained a significant level of cholesterol in ABCA1 deficiency, consistent with the result of immunoprecipitations showing the presence of lipoproteins with both apoA-I and murine apoB. ApoA-I lipidation with newly synthesized cholesterol in ABCA1-null hepatocytes was significantly decreased by brefeldin A and monensin. In conclusion, we demonstrate that: (i) whereas most hepatic phospholipidation of apoA-I is mediated by ABCA1, acquisition of cholesterol depends on active transfer from intracellular compartments by ABCA1-dependent and -independent pathways, both sensitive to progesterone and (ii) there is separate regulation of phospholipid and cholesterol lipidation of apoA-I in hepatocytes. |
| ApoA-IHelsinki (Lys107-->0) associated with reduced HDL cholesterol and LpA-I:A-II deficiency Tilly-Kiesi, M., Q. Zhang, et al. (1995), Arterioscler Thromb Vasc Biol 15(9): 1294-306. Abstract: A Finnish kindred with premature coronary heart disease and decreased HDL cholesterol levels was identified as having an apoA-I variant, apoA-I (Lys107-->0), caused by a 3-bp deletion of nucleotides 1396 through 1398 in exon 4 of the apoA-I gene. These subjects (n = 10) were heterozygous for this mutation. The mean serum HDL cholesterol concentration (26.7 +/- 9.7 mg/dL) of affected family members was 36%, lower than that of unaffected family members (P <.05). Mean serum apoA-I and apoA-II concentrations in heterozygotes were reduced by 18% and 22%, respectively, compared with normal family members (P <.05). In heterozygotes the mean concentration of lipoprotein containing both apoA-I and apoA-II (LpA-I:A-II) was 31% lower than in those with normal apoA-I (P <.001), while the mean level of lipoproteins containing apoA-I without apoA-II was similar in the two groups. HDL density-gradient ultracentrifugation showed a lack of HDL2 and small dense HDL3 in heterozygotes compared with unaffected family members. The HDL particle size distribution, as analyzed by nondenaturing gradient gel electrophoresis of heterozygotes, revealed one major peak at 8.0 to 9.7 nm, a minor peak at 7.8 to 8.5 nm, and an absence of HDL2b and HDL2a peaks. These latter peaks were observed in unaffected family members. Serum levels of LDL cholesterol, triglycerides, VLDL, IDL, and LDL subclasses were similar in the two groups. However, in heterozygotes the cholesterol-to-triglyceride ratios in VLDL2, LDL1, LDL3, HDL2b, HDL2a, and HDL3a were 8% to 54% lower than in unaffected family members (P <.05). Cholesteryl ester transfer protein activity in heterozygotes was reduced by 25% compared with unaffected family members (P <.05), while the plasma lecithin:cholesterol acyltransferase (LCAT) activity did not differ between heterozygotes and unaffected family members. The ability of isolated variant apoA-I to serve as a cofactor for LCAT in vitro did not differ from that of normal apoA-I. Our data are consistent with the concept that a low HDL cholesterol level in subjects heterozygous for the apoA-IHelsinki mutation (Lys107-->0) having normal LCAT activity is a consequence of decreased concentration of LpA-I:A-II particles and of a smaller size and reduced cholesterol content of HDL particles. |
| ApoA-IV phenotype affects diet-induced plasma LDL cholesterol lowering Mata, P., J. M. Ordovas, et al. (1994), Arterioscler Thromb 14(6): 884-91. Abstract: The National Cholesterol Education Program (NCEP) recommends that dietary total fat, saturated fat, and cholesterol intake be reduced to < or = 30% of calories, < 10% of calories, and < 300 mg/d, respectively (step 1 diet), in the general population to reduce plasma low-density lipoprotein cholesterol (LDL-C) levels and heart disease risk. We examined the LDL-C-lowering response to such a diet (26% fat, 8% saturated fat, and 201 mg/d cholesterol) compared with an average American diet (39% fat, 15% saturated fat, and 435 mg cholesterol/d) in 153 subjects using diet periods of 4 through 24 weeks for each diet phase. The mean LDL-C reduction was 13% in men (n = 93) and 7% in postmenopausal women (n = 60). The effect of apolipoprotein (apo) A-IV phenotype on responsiveness was examined. LDL-C lowering in men was significantly (P <.005) less (7%) for 17 apoA-IV (1/2) subjects than for 76 apoA-IV (1/1) subjects (16%). In women, 7% lowering was observed in both 12 apoA-IV (1/2) subjects and 48 apoA-IV (1/1) subjects. ApoA-IV phenotype had a significant effect on plasma high-density lipoprotein cholesterol levels during both dietary periods; women carrying the apoA-IV-2 allele had higher levels than those homozygous for the apoA-IV-1 allele. The opposite was true for triglyceride levels, but only during the period when the subjects consumed the high-fat, high-cholesterol diet.(ABSTRACT TRUNCATED AT 250 WORDS) |
| APOE epsilon4 and low cholesterol as risks for depression in a biracial elderly community sample Blazer, D. G., B. B. Burchett, et al. (2002), Am J Geriatr Psychiatry 10(5): 515-20. Abstract: OBJECTIVE: The epsilon4 allele of apolipoprotein (APOE) is known to be associated with a number of adverse health outcomes, yet the association of the allele with depression has not been conclusively determined. The authors explored the hypothesis that the epsilon4 allele is a risk factor for depression among older persons with a low cholesterol level (a known risk factor for depression). METHODS: A biracial community sample of 2,550 older African Americans and Whites in North Carolina was genotyped for APOE, tested for cholesterol, and evaluated for depression at both baseline and 4-year follow-up. RESULTS: No relationship was found between the epsilon4 allele and depression or low cholesterol and depression in either cross-sectional or longitudinal analyses. The interaction of the epsilon4 allele and cholesterol was also not associated with depression in controlled analyses. Female gender, less education, being unmarried, and cognitive impairment were associated with depression in cross-sectional controlled analyses; only cognitive impairment was associated with depression in longitudinal analyses. CONCLUSION: Despite the association of the epsilon4 allele with a number of adverse health outcomes, as well as the association between depression and cholesterol in previous studies, no association was found between epsilon4 and low cholesterol or depression in cross-sectional and longitudinal analyses. The interaction of epsilon4 and cholesterol was not associated with depression. |
| ApoE genotype in relation to AD and cholesterol: a study of 2,326 Chinese adults Liu, H. C., C. J. Hong, et al. (1999), Neurology 53(5): 962-6. Abstract: OBJECTIVE: To calculate the frequencies of apolipoprotein E (apoE) alleles in a large Chinese community sample and to compare the serum cholesterol levels of epsilon2, epsilon3, and epsilon4 carriers. BACKGROUND: In comparison with Western populations, a lower frequency of the apoE epsilon4 allele among the Chinese has been proposed as one factor for the lower prevalence of AD found in Chinese populations, but there are insufficient Chinese data on epsilon4 frequency that are based on large community samples. In addition, although Western studies have repeatedly found a lower cholesterol level in epsilon2 carriers and a higher cholesterol level in epsilon4 carriers in comparison with epsilon3 homozygotes, two Chinese studies have yielded inconsistent findings between them. METHODS: During the incidence phase of an epidemiologic survey of several neurologic disorders in a Chinese community, the authors took blood samples from 2,326 participants to determine the apoE genotypes and to measure cholesterol levels. RESULTS: The allelic frequencies of epsilon2, epsilon3, and epsilon4 were 11.8%, 76.4%, and 11.8% among 17 AD patients, and 7.8%, 84.1%, and 8.1% for the entire sample. The mean cholesterol level of the epsilon2 carriers was significantly lower, and that of the epsilon4 carriers significantly higher, than that of the epsilon3 homozygotes. CONCLUSIONS: The obtained epsilon4 rate of 8.1% is lower than most of the Western findings, and this may account in part for the lower prevalence of AD found among the Chinese. The associations between the apoE genotype and serum cholesterol level are similar between Chinese and white populations. |
| ApoE-mediated cholesterol efflux from macrophages: separation of autocrine and paracrine effects Dove, D. E., M. F. Linton, et al. (2005), Am J Physiol Cell Physiol 288(3): C586-92. Abstract: Macrophages in the vessel wall secrete high levels of apolipoprotein E (apoE). Cholesterol efflux from macrophages to apoE has been shown to decrease foam cell formation and prevent atherosclerosis. An apoE molecule can mediate cholesterol efflux from the macrophage that originally secreted it (autocrine effect) or from surrounding macrophages (paracrine effect). Traditional methodologies have not been able to separate these serial effects. The novel methodology presented here was developed to separate autocrine and paracrine effects by using a simple mathematical model to interpret the effects of dilution on apoE-mediated cholesterol efflux. Our results show that, at very dilute concentrations, the paracrine effect of apoE is not evident and the autocrine effect becomes the dominant mediator of efflux. However, at saturating concentrations, paracrine apoE causes 80-90% of the apoE-mediated cholesterol efflux, whereas autocrine apoE is responsible for the remaining 10-20%. These results suggest that the relative importance of autocrine and paracrine apoE depends on the size of the local distribution volume, a factor not considered in previous in vitro studies of apoE function. Furthermore, autocrine effects of apoE could be critical in the prevention of foam cell formation in vivo. This novel methodology may be applicable to other types of mixed autocrine/paracrine systems, such as signal transduction systems. |
| Apolipoprotein A and high density lipoprotein cholesterol in childhood nephrotic syndrome Agbedana, E. O., G. O. Taylor, et al. (1990), East Afr Med J 67(4): 279-85. Abstract: Plasma triglyceride, apolipoprotein A, total and high density lipoprotein cholesterol levels were estimated in childhood nephrotic syndrome. The plasma lipid concentrations within the nephrotic group were variable with elevation of both triglyceride and cholesterol present in 60%, triglyceride alone in 10% and cholesterol alone in 30% respectively. The mean plasma triglyceride and total cholesterol levels were significantly elevated in the nephrotic children. The increase in plasma triglyceride seems unrelated to the serum cholesterol concentration. The high density lipoprotein cholesterol was significantly reduced, whereas the apolipoprotein A concentration was elevated, probably suggesting the presence of an Apolipoprotein A-rich high density lipoprotein in nephrotic children. |
| Apolipoprotein A-1 interaction with plasma membrane lipid rafts controls cholesterol export from macrophages Gaus, K., L. Kritharides, et al. (2004), Faseb J 18(3): 574-6. Abstract: Cholesterol efflux to apolipoprotein A-1 (apoA-1) from cholesterol-loaded macrophages is an important anti-atherosclerotic mechanism in reverse cholesterol transport. We recently provided kinetic evidence for two distinct pathways for cholesterol efflux to apoA-1 Gaus et al. (2001) Biochemistry 40, 9363. Cholesterol efflux from two membrane pools occurs sequentially with different kinetics; a small pool rapidly effluxed over the first hour, followed by progressive release from a major, slow efflux pool over several hours. In the present study, we propose that the rapid and slow cholesterol efflux pools represent cholesterol derived from lipid raft and nonraft domains of the plasma membrane, respectively. We provide direct evidence that apoA-1 binds to both lipid raft and nonraft domains of the macrophage plasma membrane. Conditions that selectively deplete plasma membrane lipid raft cholesterol, such as incorporation of 7-ketocholesterol or rapid exposure to cyclodextrins, block apoA-1 binding to these domains but also inhibit cholesterol efflux from the major, slow pool. We propose that cholesterol exported to apoA-1 from this major slow efflux pool derives from nonraft regions of the plasma membrane but that the interaction of apoA-1 with lipid rafts is necessary to stimulate this efflux. |
| Apolipoprotein A-1 of Japanese quail: cDNA sequence and modulation of tissue expression by cholesterol feeding Oku, H., T. Toda, et al. (1997), Biosci Biotechnol Biochem 61(2): 286-90. Abstract: Apolipoprotein (apo) A-1 cDNA was amplified by the reverse-transcriptase-polymerase chain reaction (RT-PCR). Primers were synthesized according to the nucleotide sequence of chicken apo A-1, and the identity of apo A-1 cDNA was confirmed by comparing with the N-terminal amino acid sequence. The open reading frame of apo A-1 cDNA consists of 795 nucleotides, and it is capable of coding a polypeptide of 264 amino acids. A comparison between quail and chicken apo A-1 revealed 94.5% homology in the nucleotide sequence and 91.7% homology in the amino acid sequence. There was a similar 11- or 22-amino acid repeat in quail apo A-1 as was the case for chicken apo A-1. Apo A-1 mRNA was evaluated to be 1.4 k in length and was expressed in various tissues of Japanese quail: the liver, small intestine, lung, kidney, heart, and muscle. A quantitative evaluation, however, revealed that the liver and small intestine were the major organs for apo A-1 synthesis, accounting for more than 90% of the total expression of apo A-1 mRNA. Besides apo A-1 mRNA (1.4 k in length), a transcript of 4.1 k was detected in all the tissues examined, with a magnitude ranging from 5 to 10% of the apo A-1 mRNA level. The effect of cholesterol level on the expression of apo A-1 mRNA was studied to address the physiological significance of apo A-1 in the liver, small intestine, and muscle. The level of cholesterol in the liver and breast muscle was increased by feeding with cholesterol and reached a saturation level at day 7. There was also a temporal rise of cholesterol level at day 7 in the small intestine. Dietary cholesterol increased the expression of apo A-1 mRNA two fold in both the liver and small intestine. This was not the case for breast muscle, in which the expression of apo A-1 mRNA was not modulated by the cholesterol level. |
| Apolipoprotein A-1 predicts coronary heart disease only at low concentrations of high-density lipoprotein cholesterol: an epidemiological study of Japanese-Americans Sharp, D. S., C. M. Burchfiel, et al. (2000), Int J Clin Lab Res 30(1): 39-48. Abstract: Conventional epidemiological and clinical studies of apolipoprotein A-1 and high-density lipoprotein-cholesterol have demonstrated, when examined jointly, that high-density lipoprotein is a better predictor of coronary heart disease. This strategy does not take into account known lipid metabolic relationships. A statistical approach that takes into account apolipoprotein A-1 being a constituent of the high-density lipoprotein particle is more appropriate. Among 1,177 Japanese-American men of the Honolulu Heart Program cohort free of disease at baseline (1980-1982), 182 new coronary heart disease cases developed over a 12-year follow-up period. After removing the linear relationship with high-density lipoprotein-cholesterol, a relative measure of apoliprotein A-1 concentration was derived. Based on joint conditions of "low" and "high" relative apoliprotein A-1 concentration and < or =40 and >40 mg/dl for the high-density lipoprotein-cholesterol distribution, four groupings were created. Among relative joint groupings of high/< or =40, low/< or =40, high/>40, and low/>40, respectively, the 12-year coronary heart disease incidence varied from 28.6, 18.2, 8.3, to 11.7 cases per 1,000 person-years. A test of statistical interaction was significant (P=0.028). Additional analyses revealed coronary heart disease cases were more likely among men with triglycerides > 190 mg/dl. Observed patterns of relationships among relative apoliprotein A-1 level, high-density lipoprotein cholesterol, and triglycerides with incident coronary heart disease are consistent with patterns noted in clinical, laboratory, and transgenic animal research more capable of elucidating mechanisms of disease causation. This epidemiological study suggests similar mechanisms may be operating at a population level, and may contribute to the public health burden of coronary heart disease. |