Effect of simvastatin on apoprotein B—containing lipoproteins in patients with diabetic nephropathy

Background: Diabetic patients with nephropathy usually have a more atherogenic lipoprotein profile than those without nephropathy, which may be associated with the substantially higher incidence of coronary heart disease (CHD) in this population. Simvastatin has been shown to significantly reduce the incidence of CHD events in diabetic patients.Objective: The purpose of this study was to evaluate the effect of simvastatin (10 mg/d) on atherogenic apoprotein (apo) B—containing lipoproteins in type 2 diabetic patients with nephropathy.Methods: Diabetic patients with nephropathy and a group of healthy control subjects matched for age, sex, and body weight were enrolled. Diabetic patients were administered simvastatin 10 mg/d for 6 months. Apo B—containing lipoproteins were sequentially separated by ultracentrifugation to yield very low-density lipoprotein (VLDL) (density <1.006 g/mL), intermediate-density lipoprotein (IDL) (1.006-1.019 g/mL), light low-density lipoprotein (LDL) (1.019-1.044 g/mL), and dense LDL (1.044-1.063 g/mL) fractions. Apo B in lipoproteins was measured by a sensitive enzyme-linked immunosorbent assay at baseline and after 6 months of simvastatin treatment.Results: A total of 18 patients with diabetic nephropathy and 36 matched controls were enrolled. The diabetic patients had significantly higher levels (P < 0.01) of total cholesterol, LDL cholesterol, triglycerides, and apo B compared with age- and weight-matched control subjects at baseline. The diabetic patients also had significantly higher levels (P < 0.05) of cholesterol and apo B in the VLDL, light LDL, and dense LDL fractions. Treatment with simvastatin for 6 months significantly reduced plasma total cholesterol by 21%, LDL cholesterol by 30%, and apo B by 25% (P < 0.001), but did not affect urinary albumin excretion. Simvastatin significantly decreased both triglyceride and cholesterol levels in VLDL by 18% (P < 0.05), and cholesterol and apo B in IDL by 22% (P < 0.05) and 26% (P < 0.01). Simvastatin decreased both the light and dense LDL subfractions to a similar extent, reducing cholesterol and apo B in light LDL by 27% (P < 0.001) and in dense LDL by 28% (P < 0.01) and 18% (P < 0.05), respectively. The light LDL/dense LDL ratio for apo B and for cholesterol were not altered by simvastatin therapy.Conclusions: The results of this study suggest that simvastatin may reduce levels of atherogenic apo B—containing lipoproteins and small dense LDL in diabetic patients with nephropathy.     

The atherogenic index of plasma is increased by hormonal contraception

Abstract

Background/Aims. Oral contraceptives are known to induce secondary dyslipidemia. The aim of this study was to determine if hormonal contraceptives affect the new atherogenic index of plasma (AIP) = log[triglycerides (TG)/high-density lipoprotein cholesterol (HDL-C)] together with the total cholesterol/HDL-C (TC/HDL-C) and the apolipoprotein B/apolipoprotein A1 (apoB/apoA1) ratios. Design and methods. This study included 43 healthy women. Blood lipids, apoA1, apoB and the high-sensitivity C-reactive protein (hsCRP) concentration were examined before the start of hormonal contraception and after 3, 6 and 9 months of its regular use. AIP, the apoB/apoA1 ratio and the TC/HDL-C ratio were calculated. Results. After 9 months of continued hormonal contraception, we found significantly increased levels of TC, HDL-C, low-density lipoprotein cholesterol (LDL-C), TG, apoA1 and apoB (p < 0.05 for all analytes). The TC/HDL-C and apoB/apoA1 ratios remained unchanged; however, the AIP and the hsCRP concentration increased significantly (p < 0.005 and p < 0.006). LDL-C increased slightly over the first three examinations (0, 3, 6 months), and the rest of the indices increased over the first two examinations (0, 3 months) and maintained stable values through the fourth examination (9 months). Conclusions. The increased AIP and hs-CRP concentration after 9 months of hormonal contraception demonstrate that contraceptive-induced dyslipidemia has a proatherogenic nature, even when the TC/HDL-C and the apoB/apoA1 ratios are unchanged.     

Postprandial apolipoprotein B100 and B48 metabolism in familial combined hyperlipidaemia before and after reduction of fasting plasma triglycerides*

Abstract Hepatic VLDL overproduction in familial combined hyperlipidaemia (FCH) may delay the clearance of atherogenic apolipoprotein (apo) B containing particles. We investigated if normalization of fasting plasma triglycerides (TG) by hypolipidaemic treatment results in improved metabolism of apo B48 and apo B100 in six male subjects with FCH and compared them to six normolipidaemic controls. The FCH patients were studied before (TG, 5·2±1·2 mmoll^-1; mean ± SEM) and after therapy (TG, 2·1±0·3 mmoll^-1) with either simvastatin (n= 4) or combined therapy with gemfibrozil (n= 2). The post-prandial changes of apo B100 and apo B48 were studied after a single oral fat meal (24h; 50 gram fatm^-2). Changes in triglyceride rich particles (TRP; d < 1·006 gml^-1) and remnant fractions (REM; d: 1·006–1·019g ml^-1) of apo B were quantitated by scanning silverstained SDS-PAGE (4–15%). Apo B48 in fasting TRP in untreated and treated FCH was 15% and 14% of total apo B, and 6% in controls (P < 0·05). In controls, postprandial B48 increased maximally at 4h by 81% in TRP and by 137% in REM compared to baseline. In treated FCH, the post-prandial apo B48 pattern normalized in TRP compared to the untreated state. Postprandial apo B100 in controls decreased in TRP and REM by 33% and 18% (P < 0·05). In untreated and treated FCH, postprandial apo B100 remained unchanged vs. baseline in TRP and in REM suggesting hypersecretion of VLDL. The elimination of B100—assessed as area under the curve—in TRP (32·5±3·6 au.h; mean±SEM) and REM fractions (33·2±3·1 au.h), improved significantly after treatment (21·0±2·8 and 20·4±3·3 au.h, respectively). The apo B48 clearance in TRP fractions was improved after treatment (4·3±1·4 au.h vs. 2·9±1·2 au.h; P= 0·06), but not in REM fractions (2·8±1·0 au.h vs. 1·8±0·5 au.h; NS). In conclusion, in FCH subjects with apo B100 hypersecretion and increased fasting plasma apo B48 levels, reduction of fasting plasma TG improved, but did not normalize, TRP apo B48 and B100 metabolism. However, therapy normalized postprandial apo B100 remnant metabolism. Impaired postprandial apo B metabolism may be instrumental in the development of premature atherosclerosis in FCH subjects.     

Serum histidine-rich glycoprotein during pregnancy and hormone treatment

The concentration of serum histidine-rich glycoprotein (HRG) was determined by radial immunodiffusion during weeks 27–42 of pregnancy in 110 pregnant women. HRG was also measured in serum from 11 lactating women 6 weeks post partum, from 11 women taking oral contraceptives, and from four women having progestin-releasing subcutaneous capsules used for contraception. The concentration of serum HRG decreased during the last trimester of pregnancy reaching a nadir at the 36–37th week (HRG 49± 14 g/1, mean± SD). Thereafter serum HRG increased slightly towards term. In pregnancies complicated by hypertension the concentration of HRG was lower than in normal pregnancies at 32 weeks of pregnancy, but in other pathological pregnancies the values fell within the normal range. By 6 weeks postpartum normal non-pregnant HRG levels had been reached (107±13 g/1). The concentration of serum HRG was significantly lower in oral contraceptive users (74± 22 g/1) than in controls (109± 25 g/1, P<0.005). Low dose progestin treatment had no effect on serum HRG. The results show that serum HRG decreases during pregnancy and with oral contraceptive treatment and suggest that oestrogens are responsible for this increase.     

Radioimmunological determination of apparent free cortisol concentration: Some physiological and clinical applications

The measurement of free cortisol would be preferable with respect to the total hormone content, since it yields more reliable information about the plasma levels of the biologically active steroid.The methods so far described for the measurement of free cortisol in plasma use radiolabelled cortisol for determination of the steroid free fraction, and are generally unsuitable for routine use.We have developed a new method for the determination of the apparent free plasma cortisol concentration by means of direct radioimmunological measurement of dialyzed cortisol. This method is characterized by a sufficient degree of reproducibility and high sensitivity.Apparent free cortisol concentration in 40 control subjects of both sexes (blood drawn at 8 a.m.) was 9.00 ± 4.6 ng/ml. The mean value of free cortisol concentration in blood samples drawn at 11--12 p.m. from 21 of these subjects was highly significantly different (2.3 ± 1.6 ng/ml, p < 0.001). In addition, in 13 of these subjects circadian variation of the apparent free cortisol concentration showed a pattern similar to that of total cortisol concentration. The mean free cortisol concentration found in a group of women during normal pregnancy was significant higher than in non-pregnant women.Patients with renal insufficiency do not show a significant difference in free cortisol plasma levels, whereas higher values were found in hepatic cyrrhosis.     

A truncated species of apolipoprotein B (B67) in a kindred with familial hypobetalipoproteinemia.

We describe a kindred in which the proband and 6 of his 12 children have hypobetalipoproteinemia. The plasma lipoproteins of the affected subjects contained a unique species of apolipoprotein (apo) B, apo B67, in addition to the normal species, apo B100 and apo B48. The size of apo B67 and immunochemical studies with a panel of apo B-specific antibodies indicated that apo B67 was a truncated species of apo B that contained approximately the amino-terminal 3,000-3,100 amino acids of apo B100. Sequencing of genomic apo B clones revealed that affected family members were heterozygous for a mutant apo B allele containing a single nucleotide deletion in exon 26 (cDNA nucleotide 9327). This frameshift mutation is predicted to result in the synthesis of a truncated apo B containing 3,040 amino acids. Apo B67 is present in low levels in the plasma but is easily detectable within the very low density lipoprotein and low density lipoprotein fractions. Examination of the proband's immediate family revealed seven normolipidemic subjects and seven subjects with hypobetalipoproteinemia. In the affected subjects, the mean total and low density lipoprotein cholesterol levels were 120 and 42 mg/dl, respectively. A significantly higher mean high density lipoprotein cholesterol level was found in the affected subjects (75 vs. 55 mg/dl). We hypothesize that the elevated high density lipoprotein cholesterol levels in subjects heterozygous for the apo B67 mutation may be metabolically linked to the low levels of apo B-containing lipoproteins in their plasma.     

Development and application of a simple radioimmunoassay for urinary aldosterone

A simple, economical and direct assay was developed to measure aldosterone in urine, using aldosterone antibody of high specificity and gamma labelled ligand. The assay allows the direct measurement of aldosterone in 100 μl aliquots of urine after acid hydrolysis. It does not require preliminary solvent extraction and purification steps and hence a large number of samples in a single batch can be assayed simultaneously. An excellent correlation was obtained between the results of the direct assay and the levels measured after extraction and paper chromatography (Y = 0.97X + 0.89, r = 0.99, p< 0.001) or after extraction alone (Y = 0.98X + 1.75, r = 0.99, p< 0.001). The coefficients of variation for inter-assay and intra-assay determinations of samples from normal and high urine pools were 4.2–6.5% and 5.6–9.8%, respectively. Total urinary aldosterone excretion in 21 normal subjects on unrestricted sodium diet ranged from 3.8–20.2 μg/24 h (10.5–55.0 nmol/24h) with a mean of 12.5 ± 4.6 (SD) μg/24 h (34.7 ± 12.8 (SD) nmol/24 h).     

Radioimmunoassay of Group II pepsinogen in human serum

A new radioimmunoassay (RIA) using a double antibody method for human Group II pepsinogens in serum was developed. (1) Sensitivity of this assay system was of the order of 1 μg per l of serum and optimal assay range was 10 to 50 μg per 1; (2) no effect of interference of human serum was detected and there was no cross-reaction with human Group I pepsinogens within the optimal assay range; (3) satisfactory results were obtained for both within- and between-assay reproducibility (coefficient of variation was 3.9% and 3.7–15.3%, respectively); (4) the mean (± SEM) serum Pg II level in healthy donors was 15.9 ± 0.7 μg/l for males and 12.8 ± 1.3 μg/l for females; the difference between males and females was statistically significant (p< 0.05); (5) the mean serum Pg II level in 10 patients with total gastrectomy was 1.2 ± 0.05 μg/l. These results suggest that most of Pg II in human serum is derived from the gastroduodenal system.     

Reference values for apolipoproteins A-I and B in healthy subjects, by age.

We determined reference values of apolipoproteins A-I (apo A-I) and B (apo B) in serum from a population of 448 healthy subjects (265 men and 183 women, ages 18 to 61 years) by a kinetic immunonephelometric procedure. Frequency distributions of apo A-I were normal, whereas those of apo B were not and yielded asymmetrical curves. Thus, reference intervals for apo A-I were determined as mean +/- 2SD (1.08-1.89 g/L), but a nonparametric method was used for determining reference intervals for apo B (0.60-1.94 g/L). Apo B concentrations were significantly higher (P less than 0.001) in men than in women (0.63-2.01 g/L, mean 1.21 g/L; and 0.54-1.91 g/L, mean 1.08 g/L, respectively). No significant differences for apo A-I between men and women were observed. Concentrations of both proteins increased with age, but apo B increased more than apo A-I. We conclude that not only sex but also the age of the subjects must be considered in interpreting laboratory results for apolipoproteins.     

Serum pepsinogen: correlation of techniques and analysis of levels found in different diseases of the stomach and duodenum

Serum pepsinogen levels (SPL) were determined in 86 men and 52 women by the method of Uete et al. which employs the protein of the patients serum as the substrate. The 138 individuals were divided into 8 groups according to clinical diagnosis of stomach and duodenal diseases. Mean SPL ± S.D. (μg of tyrosine/ml of serum/24 h of incubation) were obtained for the following groups: Group I, patients without gastroenterological disease (n = 43; 108.8 ± 31.3); Group II, active duodenal ulcer (n = 29; 172 ± 59.8); Group III, healed duodenal ulcer (n = 28; 171.5 ± 71.8); Group IV, gastric ulcer (n = 13; 151.8 ± 60.1); Group V, pyloric ulcer (n = 5; 147.5 ± 42.4); Group VI, atrophic gastritis (n = 9; 125.8 ± 57.8); Group VII, superficial gastritis (n = 6; 115.8 ± 47.5); and Group VIII, gastrectomies (n = 5; 78.7 ± 35.8). No significant statistical difference was observed between the SPL of Groups II and HI or between the gastric and duodenal ulcer groups. However, when mean SPL of Group I (normal controls) was compared with those of duodenal ulcer (Active + healed) and gastric ulcer, marked differences (p < 0.001 and < 0.01, respectively) were detected. The method of Uete et al. was compared with that described by Anson and Mirsky which uses denatured hemoglobin as substrate. Concomitant determinations of SPL in 43 of the above patients gave a correlation coefficient (r) equal to 0.670.     

Apolipoprotein(B) identifies dyslipidemic phenotypes associated with cardiovascular risk in normocholesterolemic type 2 diabetic patients.

OBJECTIVE: Apolipoprotein(B) [apo(B)] reflects the total mass of atherogenic particles (VLDL, IDL, and LDL), and its increase is associated with cardiovascular disease independently of LDL cholesterol (LDLc) levels. Apo(B) determination has been recently standardized, but attention to regional reference limits is advisable. Our aim was to analyze the frequency of dyslipidemic phenotypes, including those dependent on increased apo(B) in normocholesterolemic type 2 diabetic patients. RESEARCH DESIGN AND METHODS: A total of 100 consecutively seen type 2 diabetic patients (63 men, 37 women; aged 59 +/- 11 years) were included, after excluding those on lipid-lowering therapy. Apo(B) cutoff (1.1 g/l) was obtained from a group of normolipidemic (47 men, 21 women) control subjects, and LDLc, triglycerides, and HDL cholesterol (HDLc) cutoff points were those from the National Cholesterol Education Program guidelines. LDLc levels were obtained by ultracentrifugation if triglyceride levels were > 3.45 mmol/l; otherwise, they were calculated (Friedwald). Apo(B) levels were measured by immunoturbidimetry. RESULTS: Normocholesterolemia (LDLc < 4.13 mmol/l) appeared in 75 of the 100 patients, of whom 55 were normo- and 20 hypertriglyceridemic. Hyperapolipoprotein(B) [hyperapo(B)] was the most frequent lipid disorder, present in 34 (45%) of the normocholesterolemic patients (22 normo- and 12 hypertriglyceridemic). Low HDLc levels were more prevalent (53%) in patients with hyperapo(B) than in the rest (24%). CONCLUSIONS: Hyperapo(B) was found in almost half of the normocholesterolemic type 2 diabetic patients and was frequently associated with low HDLc levels and hypertriglyceridemia. Thus, given its independent association with cardiovascular disease and that it identifies high-risk phenotypes in normocholesterolemic diabetic patients apo(B) should be used to evaluate the lipidic pattern of these patients.     

Measurement of serum apolipoprotein B by radioimmunoassay

Abstract. A sensitive and specific double antibody radioimmunoassay for the major apolipoprotein (apo B) of human serum very low density lipoprotein (VLDL) and low density lipoprotein (LDL) is described. Using anti-LDL and anti-apo B antibodies the immunoreactivity of LDL and apo B were compared. Human LDL and its isolated apo B were not immunologically identical when each antiserum was used with its homologous label; a population of antibodies was selected which reacted with antigenic sites unique to the antigen itself as well as to those which were common to the closely related protein. When the heterologous label was used with either antiserum, a population of antibodies directed against antigenic sites shared by the LDL and apo B molecules was selected.
Apo B in sera samples can be measured using either anti-LDL or anti-apo B antibodies provided that intact LDL was used for preparation of the iodinated tracer and standard. Serum apo B levels in healthy normolipi-daemic males and females were 0.93 ±0.25 g/l (range 0.58–1.39) and 0.90 ± 0.15 g/l (range 0.58–1.12), respectively. The total cholesterol and apo B, and phos-pholipid and apo B concentrations for both males and females were significantly correlated (P<0.05). In another normolipidaemic population ( n = 52), total serum apo B values correlated positively with LDL cholesterol ( r= 0.92, P< 0.001).
Apo B was measured in sera from patients with abetalipoproteinaemia, familial hypercholesterolaemia and Tangiers disease. Apo B was not detected in the serum of subjects with abetalipoproteinaemia, while the apo B level in the familial hypercholesterolaemic subjects was significantly elevated (range 3.26–4.94 g/l) compared to normals (P<0.001). Serum apo B (0.80 g/l) of the subject with Tangier disease was within the normal range.     

Distribution of lecithin-cholesterol acyltransferase in normolipidemic and dyslipidemic plasma

Summary Plasma lecithin-cholesterol acyltransferase levels and cholesterol esterification rates have been reported to be different between normolipidemic and dyslipidemic subjects. Since apolipoprotein A-I is the presumed primary physiological activator of lecithin-cholesterol acyltransferase, the distribution of the enzyme among A-I-containing lipoprotein particles and A-I-free plasma in normolipidemic and dyslipidemic subjects was examined. A-I-containing lipoprotein particles with and without apolipoprotein A-II were isolated from plasma by immunoaffinity chromatography, and the lecithin-cholesterol acyltransferase mass in these particles and in the A-I-free plasma was quantified by radioimmunoassay. The plasma lecithin-cholesterol acyltransferase concentration was comparable between normolipidemic men (5.9±1.1 μg/ml,n=15) and women (5.8±1.1 μg/ml,n=19), with 71±8% located in particles without apolipoprotein A-II, 17.6±6% in particles containing A-II, and 12±6% in the A-I-free plasma. In patients with elevated cholesterol (n=12), triglyceride (n=10), and with renal failure (n=15) plasma levels of the enzyme were significantly higher (6.7±1.2, 6.9±1.3, and 6.6±1.3 μg/ml, respectively) (P<0.05). In all three patient groups, a higher proportion of the enzyme (27±12%, 33±12%, and 19±9%) was not apo A-I associated. This phenomenon was also observed in plasma samples after incubation at 37°C. Since the characteristics of lipoproteins differ between native and incubated plasma, and between normolipidemic and dyslipidemic plasma, the increased presence of lecithin-cholesterol acyltransferase in dyslipidemic apolipoprotein A-I-free plasma may be related to differences in lipoprotein composition, and may contribute in part to the reported differences in the plasma cholesterol esterification rate.     

Metabolic effects of fluvastatin extended release 80 mg and atorvastatin 20 mg in patients with type 2 diabetes mellitus and low serum high-density lipoprotein cholesterol levels: a 4-month, prospective, open-label, randomized, blinded—end point (probe) trial

Background

Diabetic dyslipidemia is characterized by greater triglyceridation of all lipoproteins and low levels of plasma high-density lipoprotein cholesterol (HDL-C). In this condition, the serum level of low-density lipoprotein cholesterol (LDL-C) is only slightly elevated. The central role of decreased serum HDL-C level in diabetic cardiovascular disease has prompted the establishment of a target of ≥50 mg/dL in patients with diabetes mellitus (DM).

Objective

The aim of the study was to assess the effects of once-daily administration of fluvastatin extended release (XL) 80 mg or atorvastatin 20 mg on serum HDL-C levels in patients with type 2 DM and low levels of serum HDL-C.

Methods

This 4-month, prospective, open-label, randomized, blinded—end point (PROBE) trial was conducted at Endocrinology and Diabetology Service, L. Sacco-Polo University Hospital (Milan, Italy). Patients aged 45 to 71 years with type 2 DM receiving standard oral antidiabetic therapy, with serum HDL-C levels <50 mg/dL, and with moderately high serum levels of LDL-C and triglycerides (TG) were enrolled. After 1 month of lifestyle modification and dietary intervention, patients who were still showing a decreased HDL-C level were randomized, using a 1:1 ratio, to receive fluvastatin XL 80-mg tablets or atorvastatin 20-mg tablets, for 3 months. Lipoprotein metabolism was assessed by measuring serum levels of LDL-C, HDL-C, TG, apolipoprotein (apo) A-I (the lipoprotein that carries HDL), and apo B (the lipoprotein that binds very low-density lipoprotein cholesterol, intermediate-density lipoprotein, and LDL on a molar basis). Patients were assessed every 2 weeks for treatment compliance and subjective adverse events. Serum creatine phosphokinase and liver enzymes were assessed before the run-in period, at the start of the trial, and at 1 and 3 months during the study.

Results

One hundred patients were enrolled (50 patients per treatment group; fluvastatin XL group: 33 men, 17 women; mean [SD] age, 58 [12] years; atorvastatin group: 39 men, 11 women; mean [SD] age, 59 [11] years). In the fluvastatin group after 3 months of treatment, mean (SD) LDL-C decreased from 149 (33) to 95 (25) mg/dL (36%; P < 0.01), TG decreased from 437 (287) to 261 (164) mg/dL (40%; P < 0.01), and HDL-C increased from 41 (7) to 46 (10) mg/dL (12%; P < 0.05). In addition, apo A-I increased from 118 (18) to 124 (15) mg/dL (5%; P < 0.05) and apo B decreased from 139 (27) to 97 (19) mg/dL (30%; P < 0.05). In the atorvastatin group, LDL-C decreased from 141 (25) to 84 (23) mg/dL (40%; P < 0.01) and TG decreased from 411 (271) to 221 (87) mg/dL (46%; P < 0.01). Neither HDL-C (41 [7] vs 40 [6] mg/dL; 2%) nor apo A-I (117 [19] vs 114 [19] mg/dL; 3%) changed significantly. However, apo B decreased significantly, from 131 (20) to 92 (17) mg/dL (30%; P < 0.05). Mean changes in HDL-C (+5 [8] vs −1 [2] mg/dL; P < 0.01) and apo A-I (+6 [18] mg/dL vs −3 [21] mg/dL; P < 0.01) were significantly greater in the fluvastatin group than in the atorvastatin group, respectively. However, the decreases in LDL-C (54 [31] vs 57 [32] mg/ dL), TG (177 [219] vs 190 [65] mg/dL), and apo B (42 [26] vs 39 [14] mg/dL) were not significantly different between the fluvastatin and atorvastatin groups, respectively. No severe adverse events were reported.

Conclusions

Fluvastatin XL 80 mg and atorvastatin 20 mg achieved mean serum LDL-C (≤ 100 mg/dL) and apo B target levels (≤ 100 mg/dL) in the majority of this population of patients with type 2 DM, but mean serum HDL-C level was increased significantly only with fluvastatin—16 patients (32%) in the fluvastatin group compared with none in the atorvastatin group achieved HDL-C levels ≥50 mg/dL. The increase in HDL-C in the fluvastatin-treated patients was associated with an increase in apo A-I, suggesting a potential pleiotropic and selective effect in patients with low HDL-C levels.     

Apolipoprotein E polymorphism in the Tunisian population: frequency and effect on lipid parameters

OBJECTIVES: We determined the frequencies of apolipoprotein E (apo E) gene alleles and examined the association between apo E polymorphism and lipid parameters in a sample of the Tunisian population. DESIGN AND METHODS: Apo E polymorphism was investigated using PCR, and plasma lipid parameters were measured in 122 men and 111 women aged 35 to 87 years. RESULTS: The allele frequencies were epsilon2: 7.3%, epsilon3: 84.6%, and epsilon4: 8.1%. Apo E polymorphism was associated with significant differences (P<0.001) in total cholesterol, apo B and LDL cholesterol in both men and women. epsilon2 carriers had the lowest mean total cholesterol, apo B and LDL-C concentrations, and subjects with the epsilon4 allele had the highest levels. Triglycerides levels increased with the epsilon4 allele, but this did not reach statistical significance. These results remained unchanged after adjustment for age, body mass index, sex, hypertension, diabetes and smoking. However, in obese subjects (BMI>30 kg/m2), TG concentrations were significantly lower in individuals homozygous for the epsilon3 allele compared to those with the alleles epsilon2 or epsilon4. CONCLUSION: In this sample of the Tunisian population, the distribution of apo E gene alleles is similar to that observed in Southern European populations with low prevalence of the epsilon4 allele. Variations in the apo E gene play a role in determining plasma lipid levels. These data also suggest that effects of apo E alleles on lipids levels are partly dependent on environmental variables such as BMI. These findings highlight the importance of the gene/environment interaction on the deleterious effect of obesity on cardiovascular risk factors.     

Hypoxanthine production by ischemic heart demonstrated by high pressure liquid chromatography of blood purine nucleosides and oxypurines

An isocratic high pressure liquid Chromatographic system was developed for the estimation of purine nucleosides and oxypurines in blood. Use was made of a reversed-phase column. Nucleotides derived from erythrocytes affected the separation; these compounds were removed with Al₂O₃. The recovery of the whole clean-up procedure exceeded 75%, and the lower detection limit of the assay for blood metabolites was 0.1 μmol/l. In 6 healthy volunteers, non-resting, the following blood concentrations (mean values ± S.D. in μmol/l) were observed: adenosine (< 0.1), inosine (0.2 ± 0.1), hypoxanthine (2.2 ± 1.3) and xanthine (0.2 ±0.1). In plasma and serum the total amount of these compounds was 1.9 and 5.4 times higher, respectively, presumably due to nucleotide breakdown during blood processing. The myocardial arterial-venous differences of blood purine nucleosides, oxypurines and lactate were subsequently measured in blood samples from 13 patients with angiographically documented ischemic heart disease, undergoing an atrial pacing stress test. No significant release of adenosine, inosine and xanthine by the heart was detectable in this study. The myocardial arterial-venous difference of lactate changed from 0.01 ± 0.03 mmol/1 (mean ± SEM) at rest, to ?0.10 ± 0.04 mmol/1 during pacing (p < 0.002). Relatively larger changes were observed for hypoxanthine: pacing increased the arterial-venous difference from ?0.01 ± 0.05 to ?0.51 ± 0.17 μmol/1 (p <0.02). We conclude that the high pressure liquid chromatographic assay of blood hypoxanthine is a useful tool in the diagnosis of ischemic heart disease.     

Mutations in APOA-I and ABCA1 in Norwegians with low levels of HDL cholesterol

BackgroundEpidemiological studies have shown that low levels of plasma high density lipoprotein (HDL) cholesterol are associated with increased risk of ischemic heart disease (IHD), but it appears that genetic forms of low HDL cholesterol levels, as opposed to lifestyle-induced low levels of HDL cholesterol, do not result in increased risk of IHD. Therefore, the etiology of reduced levels of plasma HDL cholesterol may represent a factor that should be considered in risk stratification with respect to primary prevention. Genes encoding proteins involved in HDL metabolism, such as the ATP-binding cassette transporter A1 (ABCA1) and apolipoprotein (apo) A-I genes, are candidate genes for harboring mutations that lead to low HDL cholesterol levels.MethodsThe ABCA1 and apoA-I genes in 56 Norwegian patients, with a mean HDL cholesterol level of 0.53 (± 0.15) mmol/l, were subjected to DNA sequencing.ResultsSeveral mutations were identified in the ABCA1 gene, and two mutations were identified in the apoA-I gene. A total of 18 patients (32%) were carriers of mutations considered to be pathogenic. Their mean HDL cholesterol level was 0.45 (± 0.15) mmol/l compared to 0.57 (± 0.14) mmol/l in noncarriers (p < 0.005).ConclusionMutations in the genes encoding ABCA1 and apoA-I are common in Norwegians, with a markedly decreased HDL cholesterol level.     

Apolipoproteins and lipoprotein particles in moroccan patients with previous myocardial infarction

We investigated for the first time in the Moroccan population the relationship between lipoprotein particles and the progression of coronary atherosclerosis. Plasma lipid variables, including total cholesterol, triglycerides, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, apolipoproteins AI and B, Lp AI, Lp AI:AII, and Lp(a) were measured in 40 Moroccan adults who suffered a verified myocardial infarction before the age of 50 years. The results were compared with a healthy control group. Plasma total cholesterol, triglyceride, and Lp AI : AII levels of patients did not differ significantly from control subjects. Patients had lower plasma high-density lipoprotein-cholesterol (P<0.05), apo AI (P<0.05), and Lp AI (P<0.001 ) than control subjects, suggesting that the cholesterol reverse transport system is altered in patients with previous myocardial infarction. However, patients had higher plasma low-density lipoproteincholesterol (P<0.001), apo B (P<0.001), and Lp(a) (P<0.001). In all patients the best predictor of cardiovascular risk was the independent risk factor Lp(a) plasma level, and the Lp AI plasma level. In this study, the increased coronary atherosclerosis risk with elevated plasma levels of apo B and Lp(a), and with reduced Lp AI, was substantially modified by smoking habits, but not by family history of myocardial infarction.     

Serum lipids and apolipoproteins A-I, A-II and B in primary hypothyroidism before and during treatment

Serum lipids and apolipoproteins (apo) A-I, A-II, and B were measured in twenty-four patients with severe primary hypothyroidism (Thyrotropin above 40 mU/l), before and during 1-thyroxine treatment. Apo A-I, A-II, and B were assayed by immunonephelometry, using monospecific antisera. The serum levels of total cholesterol (TC), of low-density lipoprotein cholesterol (LDLc), and of the major LDL apoprotein, apo B, were markedly increased in the untreated hypothyroid patients compared to the values during therapy (TC: mean +/- SD, 8.87 +/- 2.9 v. 5.48 +/- 1.6 mmol/l; LDLc: 6.66 +/- 2.6 v. 3.78 +/- 1.4 mmol/l; apo B: 1.66 +/- 0.48 v. 1.14 +/- 0.37 g/l; P less than 0.00001 for all variables). High-density lipoprotein cholesterol (HDLc) was slightly higher before than during therapy (1.58 +/- 0.7 v. 1.31 +/- 0.4 mmol/l; P less than 0.05), while the main HDL apoprotein, apo A-I, was significantly elevated (1.49 +/- 0.42 v. 1.13 +/- 0.27 g/l; P less than 0.0002). The increase of the second major HDL apoprotein, apo A-II, was less pronounced (0.33 +/- 0.1 v. 0.30 +/- 0.08 g/l; P less than 0.022). The apo A-I to apo A-II ratio, which reflects the relative concentrations of the HDL subfractions HDL2 and HDL3, was significantly higher before than during treatment (P less than 0.0006). Serum triglyceride levels were moderately elevated in the untreated hypothyroid patients (1.34 +/- 0.6 v. 0.95 +/- 0.4 mmol/l; P less than 0.002). The small decrease in body weight during therapy did not correlate with the changes of the various lipid and apoprotein parameters.(ABSTRACT TRUNCATED AT 250 WORDS)