Apo Phenotypes Research Articles

Apo(a) isoforms do not predict risk for coronary heart disease in a Gulf Arab population.

It is well recognized that blood lipoprotein A [Lp(a)] levels constitute an important risk factor for atherosclerotic vascular disease. In some populations, mainly Caucasian, Lp(a) levels and coronary heart disease (CHD) risk are determined by the pattern of apolipoprotein a [apo(a)] polymorphism. It is currently unclear if these observations apply to other populations and ethnic groups. The aim of the current study is to determine to what extent known apo(a) polymorphisms associate with development of CHD in a Kuwaiti Arab population. Serum Lp(a) levels were measured by enzyme-linked immunosorbent assay and apo(a) isoforms determined by a high-resolution sodium dodecyl sulphate/agarose gel electrophoresis with immunoblotting in two groups of Kuwaiti subjects: healthy controls (n = 140) and subjects with CHD (n = 140). Blood lipids and anthropometric parameters were also determined in these subjects by standard methods. Serum Lp(a) levels were greater in those with CHD than in those in the healthy group (P < 0.001). There was no consistent trend in the pattern of serum Lp(a) levels found with specific apo(a) isoforms in either group of subjects. There was, therefore, no simple relationship between the isoform pattern (and number of kringle-IV repeats) and serum Lp(a) concentration, unlike in certain other populations. Additionally, almost identical proportions of subjects in either group had single-banded (homozygous, approximately 70%), double-banded (heterozygous, approximately 23%) and no-band (null, approximately 7%) phenotypes. The distribution of the five identified isoforms (F, S1, S2, S3 and S4) also was almost identical for both groups of subjects, whether homozygous or heterozygous, and whether classified into fast-moving (F, S1 and S2) or slow-moving (S3 and S4) isoforms. We conclude that the frequency and pattern of distribution of apo(a) phenotypes did not differ significantly between healthy control Kuwaiti Arab subjects and those with CHD. It is thus unlikely that an individual's apo(a) phenotype can predict both serum Lp(a) level and risk for CHD, irrespective of race and/or ethnic grouping.

Apolipoprotein E isoform polymorphisms are not associated with insulin resistance: the Framingham Offspring Study.

Insulin resistance and the apolipoprotein (apo) allele e4 have both been associated with coronary heart disease (CHD). We examined the relationship between insulin resistance and apo(e) polymorphisms among participants in the Framingham Offspring Study. During 1991-1995, subjects underwent a clinical examination and an oral glucose tolerance test with measurement of fasting and 2-h glucose, insulin levels, and fasting lipid levels. We measured insulin resistance using the homeostasis model, in which insulin resistance (HOMA-IR) = fasting insulin x glucose/22.5. Apo(e) isoforms and phenotypes were determined in 1983-1987 using isoelectric focusing of plasma VLDL. Of the 2,120 subjects with complete HOMA-IR and apo(e) data, 204 with type 2 diabetes were excluded. The remainder were classified with features of the insulin resistance syndrome including impaired glucose tolerance (1997 American Diabetes Association criteria), hypertension (criteria from the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure [6th report]), obesity (BMI >85th percentile), high waist-to-hip ratio (>85th percentile), and high triglyceride and low HDL levels (NCEP-2 criteria). We analyzed data with contingency tables and age- and sex-adjusted logistic regression models. Among the 1,916 subjects, the mean age was 55 (range 28-83 years) and 51% were women. Median HOMA-IR was 6.4 (interquartile range 5.2-8.2), and allele frequencies were 7.8, 79.9, and 12.4% for apo(e) alleles e2, e3, and e4, respectively There were no differences in proportions of apo(e) isoforms or alleles across increasing quintiles of HOMA-IR. A less dramatic increase in proportions occurred with elevated triglycerides associated with increasing HOMA-IR among those with apo(e) isoforms 2/2 and 2/3 compared with the others (P < or = 0.01 for interaction). Otherwise, apo(e) did not substantially modify associations between insulin resistance and features of the insulin resistance syndrome. There is no association between apo(e) polymorphisms and insulin resistance. These appear to represent 2 completely independent risk factors for CHD.

Postprandial metabolism of apolipoprotein B-48- and B-100-containing particles in type 2 diabetes mellitus: relations to angiographically verified severity of coronary artery disease

The aim of the present cross-sectional angiographic study was to examine if there is a relationship between the severity of CAD and postprandial lipemia in patients with type 2 diabetes mellitus. Special emphasis was directed to determining the contribution of apolipoprotein B-48 (apoB-48)-containing and B-100 (apoB-100)-containing triglyceride-rich particles to the magnitude of postprandial lipemia and degree of CAD. The role of apolipoprotein E (apoE) phenotype as a modulator of postprandial lipemia was also evaluated. The severity of CAD was determined by a quantitative coronary angiography and the subjects were classified into two groups based on the presence (severe CAD) or absence (mild CAD) of at least 50% stenosis in a major coronary vessel. The study population consisted of 43 subjects (31 men and 12 women) with fair glycemic control and comparable fasting lipids and body mass index. Postprandial responses of TG, apoB-48 and apoB-100 in lipoprotein subfractions (chylomicrons, VLDL1, VLDL2 and IDL) were determined after a fat load. Type 2 diabetic patients exhibited the classical dyslipidemia of the insulin resistance syndrome and delayed clearance of both hepatic and intestinal particles. Fasting or postprandial lipid or lipoprotein measurements, including apoB-48 and apoB-100 concentrations, did not differ between the groups. The presence or absence of apoE-4 allele did not significantly influence postprandial lipemia. The severity of the most significant coronary stenosis in angiography correlated with plasma and with chylomicron area under curve (AUC) for TG ( n=27) and chylomicron AUC for apoB-48 ( n=20). The strongest correlate of maximal stenosis was area under incremental curve (AUIC) for apoB-100 in IDL fraction ( r=0.548, P=0.012, n=20). In conclusion, postprandial apoB-48 and apoB-100 metabolism in triglyceride rich lipoproteins is distorted in type 2 diabetic patients, even in those with only mild CAD. The data suggest that postprandial change in small remnant particle numbers may contribute to the severity of CAD in type 2 diabetes.

Apolipoprotein E polymorphism in non-insulin-dependent diabetics of Mumbai, India and its effect on plasma lipids and lipoproteins

The role of apolipoproteinE (apoE) phenotypes in modulating the plasma lipid and lipoprotein levels was studied in a group of NIDDM patients and healthy individuals residing in Mumbai. The apoE phenotype frequencies were similar in the diabetic and healthy persons. The elevations in the lipid/lipoprotein levels were higher in diabetic subjects (53.3%) than in the controls (8%), showing the frequency of increase to be highest in the apoE4/4 group of diabetics, followed by apoE4/3 and apoE3/2 groups. In the controls as well, a similar trend was observed in different groups, indicating that the susceptibility to changes in lipid concentrations differs among apoE phenotypes. The apoE3/3 bearing individuals in both the categories showed close to normal lipid levels, suggesting it to be the wild type. The occurrence of apoE4 allele was higher than the apoE2 allele in diabetic individuals. Diabetic subjects with the apoE4 allele showed hypercholesterolemia, while those with apoE2 showed the presence of hypertriglyceridemia. One of the striking features of our work is a significant relationship between apoE4/3 phenotype in NIDDM persons and elevated levels of plasma triglyceride, thus suggesting a delayed catabolism of VLDL relative to production. In conclusion, the work suggests that the apoE2 and apoE4 alleles are associated with elevations in lipid levels and these changes are more pronounced in the diabetic individuals in whom most of the lipid levels were higher, indicating a gene–environment/disease interaction.

Apolipoprotein E polymorphism in alagille syndrome and progressive familial intrahepatic cholestasis.

The aim of the study was to assess the apolipoprotein E polymorphism (apoE) in two familial cholestatic diseases-Alagille syndrome (AS) and progressive familial intrahepatic cholestasis (PFIC)-and to estimate its association with gallstone formation, cholesterol levels, and response to UDCA treatment. We investigated 16 children with AS age 8.8 +/- 5.7 years (mean +/- SD) and 18 children with PFIC age 6.3 +/- 4.6 years. The frequency of the epsilon-2 allele in AS and PFIC was higher and the frequency of the epsilon-3 allele was lower than in controls. Gallstones were diagnosed in nine children with PFIC and different apoE phenotypes. No association between phenotype and cholesterol levels or response to UDCA therapy was observed in the patients studied. In conclusion, the allele epsilon-2 is overrepresented in AS and PFIC, similar to primary biliary cirrhosis, although this does not seem to contribute to different cholesterol levels, gallstones, and response to UDCA therapy.

Study of hemolysis interference with a peak rate nephelometric assay of lipoprotein(a)

Lipoprotein(a) [Lp(a)] is considered an independent risk factor in atherosclerosis and thrombosis. Its measurement in clinical laboratories necessitates the use of reliable methods and a strict control of preanalytical conditions. We studied here the potential interference of hemolysis on a peak rate nephelometric method. Serum samples were spiked with up to 500 μmol/L hemoglobin (Hb), and Lp(a) was measured with a Beckman Array 360 analyzer. Hb supplementation induced a significant decrease of Lp(a) values: −15% and −25% (p < 0.01) for Hb concentrations 200 and 500 μmol/L, respectively. Similar results were obtained when Hb addition was done before and after the manual step of sample predilution (1/5, v/v) in PEG-containing buffer. No significant difference of Hb interference was noticed according to apo(a) phenotypes. Our results indicate that hemolysis may significantly alter Lp(a) values obtained with this method, probably because of the low-dilution rate of samples. Even if this interference is of limited extent, it should be taken into account when interpretating results close to decisional values used for risk assessment. © 2000 John Wiley & Sons, Inc. Lab Robotics and Automation 12:23–26, 2000

Apolipoprotein E Polymorphism in IgA Nephropathy

Background/Aim: To clarify the role of the apolipoprotein E (Apo E) phenotype in IgA nephropathy, we investigated its relationship with histological damage and clinical factors. Methods: The subjects were 104 consecutive patients (41 men and 63 women) with IgA nephropathy. The Apo E phenotype was identified by plasma isoelectric focusing and immunoblotting, and the frequencies of Apo E alleles were calculated. Results: The frequencies of the phenotypes and the alleles were as follows: 2/2 = 0, 2/3 = 0.086, 3/3 = 0.654, 2/4 = 0.010, 4/3 = 0.211, 4/4 = 0.010, 3/5 = 0.029, Ε2 = 0.048, Ε3 = 0.817, Ε4 = 0.120, and others = 0.015. There were no significant differences between the IgA nephropathy patients and healthy individuals in the frequencies of Apo E phenotypes and the alleles. However, the Apo E2 phenotype was significantly more common among patients with severe histological damage than in those with mild damage. The serum triglyceride levels were significantly elevated, and the Apo E2 phenotype was significantly more prevalent in patients with severe histological damage as compared with those with mild damage. Conclusion: The Apo E2 phenotype appears to be associated with the severity of histological damage in IgA nephropathy.

The effect of aggressive and moderate lowering of LDL-cholesterol and low dose anticoagulation on plasma lipids, apolipoproteins and lipoprotein families in post coronary artery bypass graft trial

The reported results (The Post Coronary Artery Bypass Graft Trial Investigators. The effect of aggressive lowering of low-density lipoprotein cholesterol levels and low-dose anticoagulation on obstructive changes in saphenous-vein coronary-artery bypass grafts. New Engl J Med 1997;336:153–162) of the Post Coronary Artery Bypass Graft (Post CABG) trial have shown that aggressive lowering was more effective than moderate lowering of low density lipoprotein (LDL) cholesterol in reducing the progression of atherosclerosis in saphenous-vein grafts (27 vs. 39%; P<0.001); low dose warfarin had no effect on the progression of atherosclerosis. The present report describes the effect of long-term (an average of 4.3 years) aggressive treatment with high (40–80 mg/day) and moderate treatment with low (2.5–5 mg/day) doses of lovastatin on lipids, apolipoproteins (apo) and apoA- and apoB-containing lipoprotein families. To achieve the target LDL-cholesterol levels (60–85 mg/dl for aggressive group and 134–140 mg/dl for moderate group), cholestyramine (8 g/day) was given to 25% of subjects on aggressive and 5% of subjects on moderate treatment. Although with both treatment strategies there were significant decreases ( P<0.001) in the levels of total cholesterol, LDL-cholesterol, apoB, LDL-apoB and cholesterol-rich Lp-B family, percent changes in the levels of these variables were greater in the aggressive- than in the moderate-treatment groups. These treatments had only marginal effects in increasing the levels of high density lipoprotein cholesterol, apoA-I and Lp-A-I and Lp-A-I:A-II families. The long-term aggressive treatment exerted no effect on the concentrations of triglycerides, apoC-III, apoC-III in VLDL+LDL and triglyceride-rich Lp-B c families. Neither treatment affected the levels of Lp(a). The potentially modifying influence of warfarin and apoE phenotypes on lovastatin-induced changes in lipoprotein variables was found to be of little significance. It is likely that the beneficial effect of lovastatin in reducing the progression of atherosclerosis in grafts is mediated through its specific lowering effect on cholesterol-rich Lp-B particles.

Higher avidity binding of apolipoprotein (E-AII) complex than of apolipoprotein E monomer to ?-amyloid

Apolipoprotein E (apoE) is believed to be closely involved in the pathogenesis of Alzheimer's disease (AD) because of its ability to bind to beta-amyloid (Abeta), the primary component of senile plaques. The presence of cystein residues in apoE2 and apoE3 allows these isoforms to form disulfide-linked complexes, such as apo(E-AII) complex and apo(AII-E-AII) complex. A 50-kDa complex [which corresponded to apo(E-AII)-Abeta, because it reacted with any of the three antibodies, anti-apoE, anti-apoAII, or anti-Abeta] was detected by immunoblot analysis in native cerebrospinal fluid (CSF) obtained from nondementia patients with the apoE phenotype E3/E3. However, a band considered to represent apoE-Abeta was not observed. The dissociation constant (Kd) values obtained for the specific binding of recombinant apoE2, apoE3, and apoE4 to Abeta(1-42) were 48.1 +/- 2.2 nM, 63.7 +/- 2.1 nM, and 75.9 +/- 1.8 nM, respectively. In contrast, the binding affinity of the partially purified apo(E3-AII) complex to Abeta(1-42) was very high, the Kd being 5.5 +/- 0.5 nM. No basic difference was observed between lipidated and nonlipidated apoE in terms of the characteristics of the binding of apoE isoforms to Abeta(1-42); however, lipidation reduced the binding capacity of each isoform in a dose-dependent manner. These findings seem consistent with the generally accepted idea that apoE4 is a risk factor for AD, insofar as only apoE4 is unable to form a complex with apoAII owing to its lack of a cystein residue. In addition, it is possible that apoE3 monomer (and possibly apoE2 monomer), like apoE4 but unlike apo(E-AII) complex, can act as a risk factor in the pathogenesis of AD.

Plasma lipoprotein (a) levels in children with minimal lesion nephrotic syndrome.

We studied the plasma lipoprotein (a)[Lp(a)] levels in 31 children with minimal lesion nephrotic syndrome (MLNS) in both stages of acute NS and remission. The mean Lp(a) levels in acute NS were significantly higher than those of the controls. The Lp(a) levels in remission were significantly lower than the Lp(a) levels in acute NS. In addition, the Lp(a) levels in remission were not significantly different from those of the controls. However, there were 5 patients whose Lp(a) levels remained higher than 30 mg/dl (the generally accepted limit for cardiovascular risk) after remission. Two of these 5 patients had Lp(a) levels greater than 40 mg/dl. In these patients apoprotein (a) [apo(a)] phenotypes were of lower molecular weight than those of the other 23 patients whose apo(a) phenotypes were examined. Additional episodes of relapse may put the patient with sustained elevated Lp(a) levels at significant risk for the development of cardiovascular disease in the long term.

Characterization of Apolipoprotein E-containing Lipoproteins in Cerebrospinal Fluid: Effect of Phenotype on the Distribution of Apolipoprotein E

Apolipoprotein (apo) E, one of the main apolipoproteins in the central nervous system, may play an important role in lipid metabolism; however, the details of its function are poorly understood. In this study, we characterized apoE-containing lipoproteins in cerebrospinal fluid (CSF) and examined the effect of apoE phenotype on the distribution of apoE among the lipoprotein fractions. CSF lipoproteins were fractionated by gel filtration and ultracentrifugation, and then characterized by electrophoresis, immunoblot, electron microscopy, and analysis of apoE, total cholesterol, and phospholipid concentrations. The ratio of sialylated to nonsialylated apoE was higher in CSF than in serum. However, the fundamental forms containing apoE homodimers or heterodimers [such as apo(E-AII) and apo(AII-E2-AII) complexes] were similar in CSF and serum. apoE-containing lipoproteins were fractionated at densities of <1.006, 1.063-1.125, and 1.125-1.21 kg/L. Neither apoE nor apoAI was detected in the fraction with a density range of 1.006-1.063 kg/L. The diameters of the lipoprotein particles with densities of <1.006, 1.063-1.125, and 1.125-1.21 kg/L were 16.7 +/- 3.1, 14.0 +/- 3.2, and 11.6 +/- 2.8 nm (mean +/- SD, n = 200), respectively. All of these lipoproteins exhibited a spherical structure. The distribution profile of apoE-containing lipoproteins was affected by the apoE phenotype. A relatively large amount of apoE-containing lipoproteins was isolated from the fraction with a density >1.125 kg/L obtained from CSF associated with apoE2 or apoE3. This tendency was more obvious in CSF associated with apoE2 than in CSF without apoE2. apoE-containing lipoproteins were predominantly observed in the fraction with a density of <1.006 kg/L obtained from CSF associated with apoE4. The lipoproteins in CSF have a unique composition that is different from that of the lipoproteins in plasma. However, the differences in diameter between the CSF fractions were not as large as for the serum fractions. Our data suggest that the apoE phenotype may affect the distribution profile of apoE-containing lipoproteins in the CSF. This would mean that the metabolism of apoE-containing lipoproteins depends on the apoE isoform present.

No relationship between serum lipoprotein(a) and albumin concentrations in patients with acute phase response.

The aim of this study was to investigate the relationship between lipoprotein(a) [Lp(a)] and albumin concentrations in the serum of patients with acute phase response (APR). We have compared the Lp(a) concentrations and apolipoprotein [apo(a)] phenotypes of 40 controls with those of 40 APR patients with normoalbuminaemia and 40 APR patients with hypoalbuminaemia. We have also compared concentrations of haptoglobin (Hp) and alpha 1-antitrypsin (AAT) containing a high sialic acid content, similar to Lp(a). The mean serum Lp(a) concentration (SD) of the 40 controls was 0.190 (0.142) g/L. The mean serum Lp(a) concentration was 0.358 (0.257) g/L (P < 0.001) in 80 APR patients. However, there was no difference in serum Lp(a) concentrations between the APR patients with hypoalbuminaemia [0.353 (0.268) g/L] and the APR patients with normoalbuminaemia [0.362 (0.249) g/L]. No significant difference was found in the distributions of apo(a) phenotypes between the controls, the APR patients with hypoalbuminaemia, and the APR patients with normoalbuminaemia (P = 0.183). In the APR patients, the serum concentrations of AAT and Hp were respectively 2.709 (0.822) g/L and 2.631 (1.340) g/L, whereas those of normal controls were respectively 1.422 (0.219) g/L (P < 0.001) and 0.956 (0.442) g/L (P < 0.001). In conclusion, the Lp(a) is one of the acute phase reactants whose synthesis concurrently increases with other APRs, especially those with a high sialic acid content. The increase of the serum Lp(a) concentrations in the APR patients is not related to serum albumin concentration.

Metabolic and anthropometric determinants of serum Lp(a) concentrations and Apo(a) polymorphism in a healthy Arab population.

Blood lipoprotein(a) Lp(a) concentrations are an important risk factor for atherosclerosis. The basis for this atherogenic property of Lp(a) and the factors that influence its cross-population levels, however, remain poorly understood. To investigate the relationship between serum Lp(a) and metabolic and anthropometric parameters in a healthy Kuwaiti population. Cross-sectional study. 177 (72 male, 105 female) randomly recruited healthy Kuwait Arabs aged 17-60 y Metabolic parameters in serum: Lp(a), apo(a) phenotypes, lipids and lipoproteins, glucose and urate. Anthropometric parameters: body mass index (BMI) and waist:hip-ratio (WHR). The distribution of Lp(a) concentrations was positively skewed (median 153 mg/l, range 0-1086). Women had higher concentrations-(194, 0-1086) than men (117, 0-779), P = 0.069. Lp(a) and insulin concentrations were significantly higher when the men and women were obese. In all subjects, there were significant correlations between Lp(a) and BMI (r = 0.23), total cholesterol (TC) (r = 0.17) and LDL (r = 0.20). Lp(a) correlated only with glucose in men (r = 0.28). In women it correlated with age (r = 0.20), BMI (r = 0.30), BP (r = 0.20), TC (r = 0.20) and LDL (r = 0.26). Multivariate analyses confirmed BMI and low-density lipoprotein (LDL) as the significant determinants of serum Lp(a). On apo (a) phenotyping, 114 (67%), 51 (30%) and 6 (4%) had single, double and null phenotypes respectively. The isoforms and their corresponding kringle IV repeat numbers were: F (14 repeats in 3%, mean Lp(a) 497 mg/l); S1 (19 repeats in 14%, mean 245 mg/l); S2 (23 repeats in 16%, mean 264 mg/l); S3 (27 repeats in 35%, mean 236 mg/l); and S4 (35 repeats in 28%, mean 235 mg/l). The results from the Kuwaiti population studied suggest that: (1) serum Lp(a) concentrations and distribution are similar to the pattern in Caucasians and Asians but not African-Americans or Africans; (2) serum Lp(a) is variably influenced by BMI and LDL--the impact of either factor differs between the sexes; (3) there is a high frequency of the single-banded phenotype; (4) contrary to reports in some Caucasian and Asian populations, there is no simple relationship between kringle IV repeat numbers and plasma Lp(a) concentrations.

Is apolipoprotein(a) a susceptibility gene for Type I diabetes mellitus and related to long-term survival?

High lipoprotein(a) [Lp(a)] plasma concentrations are a genetically determined risk factor for atherosclerotic complications. In healthy subjects Lp(a) concentrations are mostly controlled by the apolipoprotein(a) [apo(a)] gene locus which determines a size polymorphism with more than 30 alleles. Subjects with low molecular weight apo(a) phenotypes on average have higher Lp(a) concentrations than those with high molecular weight apo(a) phenotypes. There are many opinions about whether and why Lp(a) is raised in patients with Type I diabetes (insulin-dependent) mellitus. We investigated Lp(a) plasma concentrations and apo(a) phenotypes in 327 patients with Type I diabetes mellitus (disease duration 1-61 years) and in 200 control subjects matched for age and sex. Patients with a disease duration of up to 15 years had significantly higher Lp(a) concentrations (24.3 +/- 34.0 mg/dl vs 16.7 +/- 22.6 mg/dl, p = 0.014) compared with control subjects. This increase can be explained by a considerably higher frequency of low molecular weight apo(a) phenotypes (38.9% vs 23.5%, p < 0.005). The frequency of low molecular weight apo(a) phenotypes decreased continuously with disease duration from 41.7% in those with disease duration of up to 5 years to 18.2% in those with the disease lasting more than 35 years. Our data show that an increase of Lp(a) in Type I diabetic patients can only be observed in groups with short diabetes duration and that this elevation is genetically determined. Therefore, the apo(a) gene, located at 6q26-27, might be a susceptibility gene for Type I diabetes mellitus which is supported by recently published studies reporting evidence for linkage of this region (6q27) with Type I diabetes mellitus. Furthermore, the decreasing frequency of low molecular weight apo(a) phenotypes with disease duration suggests a survivor effect.

Apolipoprotein E polymorphism and renal disease

Lipid abnormalities are frequently found in end-stage renal disease (ESRD), and abnormal lipid metabolism may contribute to the progression of renal disease. Previous investigators have reported that apolipoprotein E (apoE) has an important role in lipoprotein metabolism and that the process of lipoprotein catabolism varies according to the apoE phenotype. In addition, the relative frequency of the apoE alleles is different among the races. In this study, we investigated the allele frequency of apoE phenotypes and evaluated the impact of apoE polymorphism on lipid profile in Japanese patients with renal disease. ApoE phenotypes were determined using isoelectric focusing and Western blotting in 592 Japanese patients with renal disease [86 out of 107 patients with glomerulonephritis had proteinuria of not less than 0.25 g per 24 hr and 485 with ESRD; 448 were on hemodialysis (HD), and 37 were on continuous ambulatory peritoneal dialysis (CAPD)]. The allele frequency and apoE phenotype distribution were estimated by the gene-counting method. Serum lipid parameters related to lipid metabolism were measured after at least a 12-hour fast. The allele frequency of the three major apoE phenotypes (apoE2, apoE3, and apoE4) in 107 glomerulonephritis patients (epsilon 2; 0.037, epsilon 3; 0.860, epsilon 4; 0.103) was almost identical to that in the normal control population (epsilon 2; 0.036, epsilon 3; 0.848, epsilon 4; 0.115). However, 86 glomerulonephritis patients with proteinuria had higher allele frequency of apoE2 (epsilon 2; 0.052, P < 0.01) and apoE4 (epsilon 4; 0.140, P < 0.001) and lower allele frequency of apoE3 (epsilon 3; 0.808, P < 0.001) than the controls. Furthermore, ESRD patients had higher allele frequency of apoE2 (epsilon 2; 0.058, P < 0.01) and lower allele frequency of apoE4 (epsilon 4; 0.091, P < 0.05) than the controls. Higher prevalence of nephrotic syndrome was found in proteinuric glomerulonephritis patients with apoE2. The impact of apoE polymorphism on serum lipid profile in patients with glomerulonephritis, HD, and CAPD was different from that generally expected. The higher frequency of apoE2 in ESRD patients suggests that apoE2 is a possible genetic predisposition to ESRD in a Japanese population. The impact of apoE2 and apoE4 on lipid profile in patients with renal disease was unique and different from that in the normal population.

Serum lipoproteins and apolipoprotein E in infants with congenital hypothyroidism.

Hypothyroid adults have a high risk of atherosclerosis, secondary to increased levels of various cholesterol fractions, particularly low-density lipoprotein cholesterol (LDL-C). We investigated the existence of a correlation between thyroid hormone deficiency and serum lipoproteins and a possible effect of different apolipoprotein E (apoE) phenotypes on lipoprotein levels in 75 infants with hypothyroidism. Seventy-three of the 75 infants had congenital hypothyroidism. At the age of one month, prior to the initiation of thyroid hormone substitution therapy, thyroid-stimulating hormone (TSH), thyroid hormones and lipid profile parameters were determined. Subsequently, apoE phenotyping in all patients was performed by isoelectric focusing followed by immunoblotting. Significant negative correlations were identified between triiodothyronine (T3) and LDL-C and total cholesterol (TC) levels and between thyroxine (T4) and TC levels. There were no correlations between TSH and free (F)T4 and lipid profile parameters. Although infants carrying at least one E4 allele had higher LDL-C (as well as TC and triglyceride) levels than those carrying at least one E2 allele, these differences were not statistically significant. No significant differences in thyroid hormones were noted in E4 allele carriers in comparison with other patients. The observed lack of a significant correlation between thyroid hormones (except T3), apoE phenotypes and lipoprotein levels suggests that, early in infancy, other factors may play a more important role in determining lipoprotein levels.

Lipids, lipoproteins and apolipoprotein (a) isoforms in type 2 diabetic patients.

Patients with type 2 diabetes mellitus have a greater than normal risk of developing atherosclerotic vascular diseases. Higher than normal plasma concentrations of lipoprotein (a) [Lp(a)] have been associated with premature atherosclerosis in several studies. To determine the concentrations of lipids, lipoproteins, and Lp(a) in 107 type 2 diabetic patients, and the distribution of apolipoprotein (a) [apo(a)] phenotypes for this group, and to compare the results found with results for healthy subjects. Plasma concentrations of cholesterol, triglycerides, and apolipoprotein B in the diabetics were significantly higher than those in control subjects. Diabetic patients had slightly lower Lp(a) concentrations than did nondiabetic subjects, but these differences were not statistically significant. Distributions of Lp(a) concentrations both in type 2 diabetic patients and in control subjects were markedly skewed, the highest prevalences being of low values. Distributions of apo(a) phenotypes for patients with type 2 diabetes mellitus and controls were remarkably alike. Smaller isoforms were similarly prevalent for the two populations, as were the null, single-band and double-band apo(a) phenotypes.

Electrophoretic analysis of oxidative modification of apolipoprotein E in very low density lipoprotein from fresh human plasma.

Ferrous ion-induced oxidative modification of apoE in lipid peroxidation of human very low density lipoprotein (VLDL) and the role of the cysteinyl group, present in apoE3 but absent in apoE4, were examined. Fresh human VLDL was obtained from healthy volunteers with different apoE phenotypes as determined by isoelectric focusing (IEF). The VLDL was oxidized by incubating with FeSO4. The time course of the lipid peroxidation was determined by thiobarbituric acid (TBA) assay. The sequential oxidative modification of the apoE was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting with an anti-apoE antibody. To modify the cysteinyl group of apoE3, the VLDL from the apoE3/3 subject was pretreated with cysteamine before the TBA assay and electrophoresis. The ferrous ion-induced peroxidation of the VLDL was pH-dependent, with increased reactivity at acidic pH ranges. In the initial stage of the lipid peroxidation of the VLDL, aggregates were formed involving apoE dimers and apoB via disulfide bonds, followed by the intra- and intermolecular cross-linkings of apoE monomers. The VLDL with apoE3/4 showed a shorter lag time than the VLDL with apoE3/3 in the TBA assay, suggesting a lower antioxidative effect with apoE3/4. The apoE3/3 pretreated with cysteamine showed the patterns of apoE3/4 in IEF and SDS-PAGE with immunoblotting, but it did not show the shortened lag time in the TBA assay. This suggests that factors other than cysteinyl groups contribute to the reduced antioxidative activity of apoE4.

LP(a) concentrations and apo(a) phenotypes in patients with chronic renal failure

LP(a) concentrations and apo(a) phenotypes in patients with chronic renal failure

The low molecular weight apo(a) phenotype is an independent predictor for coronary artery disease in hemodialysis patients: a prospective follow-up.

Patients with end-stage renal disease treated by hemodialysis have a tremendous risk for cardiovascular complications that cannot be explained by traditional atherosclerosis risk factors. Lipoprotein(a) (Lp(a)), a risk factor for these complications in the general population, is significantly elevated in these patients. In this study, it was determined whether Lp(a) and/or the genetically determined apo(a) phenotype are risk predictors for the development of coronary artery disease in these patients. A cohort of 440 unselected hemodialysis patients were followed for a period of 5 yr independent of the cause of renal disease, duration of preceding treatment, and the preexistence of coronary artery disease at study entry. Coronary events defined as definite myocardial infarction, percutaneous transluminal coronary angioplasty, aortocoronary bypass, or a stenosis >50% in the coronary angiography were the main outcome measure. Sixty-six (15%) of the 440 patients suffered a coronary event during follow-up. In univariate analysis, patients with events were significantly older and showed a trend to lower HDL cholesterol concentrations, and higher apolipoprotein B and Lp(a) concentrations without reaching significance. Apo(a) phenotypes of low molecular weight, however, were significantly more frequent in patients with compared to those without events (43.9% versus 21.9%, P<0.001). The other lipids, lipoproteins, and apolipoproteins were similar in both groups. Multiple Cox proportional hazards regression analysis found age and the apo(a) phenotype to be the best predictors for coronary events during the observation period, independent of whether patients with a preexisting coronary artery disease or an age >65 yr at the study entry or both were excluded from the analysis. Diabetes mellitus was a risk factor only in presence of a low molecular weight apo(a) phenotype. The genetically determined apo(a) phenotype is a strong and independent predictor for coronary events in hemodialysis patients. Apo(a) phenotyping might be helpful to identify hemodialysis patients at high risk for coronary artery disease.