Lipoprotein (a) as an independent risk factor for myocardial infarction in patients with common hypercholesterolaemia

Quo vadis haemapheresis. Current developments in haemapheresis

The techniques of haemapheresis originated in the development of centrifugal devices separating cells from plasma and later on plasma from cells. Subsequently membrane filtration was developed allowing for plasma-cell separation. The unspecificity of therapeutic plasma exchange led to the development of secondary plasma separation technologies being specific, semi-selective or selective such as adsorption, filtration or precipitation. In contrast on-line differential separation of cells is still under development. Whereas erythrocytapheresis, granulocytapheresis, lymphocytapheresis and stem cell apheresis are technically advanced, monocytapheresis may need further improvement. Also, indications such as erythrocytapheresis for the treatment of polycythaemia vera or photopheresis though being clinically effective and of considerable importance for an appropriate disease control are to some extent under debate as being either too costly or without sufficient understanding of the mechanism. Other forms of cell therapy are under development. Rheohaemapheresis as the most advanced technology of extracorporeal haemorheotherapy is a rapidly developing approach contributing to the treatment of microcirculatory diseases and tissue repair. Whereas the control of a considerable number of (auto-) antibody mediated diseases is beyond discussion, the indication of apheresis therapy for immune complex mediated diseases is quite often still under debate. Detoxification for artificial liver support advanced considerably during the last years, whereas conclusions on the efficacy of septicaemia treatment are debatable indeed. LDL-apheresis initiated in 1981 as immune apheresis is well established since 24 years, other semi-selective or unspecific procedures, allowing for the elimination of LDL-cholesterol among other plasma components are also being used. Correspondingly Lp(a) apheresis is available as a specific, highly efficient elimination procedure superior to techniques which also eliminate Lp(a). Quality control systems, more economical technologies as for instance by increasing automation, influencing the over-interpretation of evidence based medicine especially in patients with rare diseases without treatment alternative, more insight into the need of controlled clinical trials or alternatively improved diagnostic procedures are among others tools ways to expand the application of haemapheresis so far applied in cardiology, dermatology, haematology, immunology, nephrology, neurology, ophthalmology, otology, paediatrics, rheumatology, surgery and transfusion medicine.

International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Standardization Project for the Measurement of Lipoprotein(a). Phase 2: selection and properties of a proposed secondary reference material for lipoprotein(a)

The International Federation of Clinical Chemistry and Laboratory Medicine Working Group for the Standardization of Lipoprotein(a) Assays has initiated a project to select a secondary reference material for lipoprotein(a) that can standardize the measurement of this lipoprotein. Most of the analytical problems with lipoprotein(a) assays are due to apolipoprotein(a) kringle 4 type 2 reactive antibodies and values being expressed in mg/l mass units rather than as nmol/l of apolipoprotein(a) particles. In Phase 2, four manufactured materials were compared for analytical performance, commutability properties and method harmonization in 27 lipoprotein(a) test systems. Results of precision and linearity testing were comparable for all materials whereas testing for the harmonization effect resulted in an among-assay coefficient of variation for corrected lipoprotein(a) values of between 11% and 22%. The material that gave maximum harmonization achieved a variation of < 8% for 18 immunonephelometric and immunoturbidimetric assay systems. It can be hypothesized that this residual variation in part takes into account the inaccuracy of lipoprotein(a) measurement due to apolipoprotein(a) size polymorphism. On the basis of acceptable analytical performance, maximal harmonization effect and documented stability, a lyophilized material has been selected as the common calibrator for lipoprotein(a) to be used in a value transfer procedure by diagnostic companies.

Apolipoprotein B independently predicts progression of very-low-level albuminuria in insulin-dependent diabetes mellitus

The purpose of the study was to examine the contribution of alterations in lipoprotein metabolism to the progression of very-low-level albuminuria in insulin-dependent diabetes mellitus (IDDM). We measured serum concentrations of lipids, lipoproteins, and apolipoproteins in 53 normoalbuminuric diabetic patients without overt hypertension, whom we restudied after 10 years. Albuminuria was measured as the urinary albumin to creatinine ratio (UA/UC) in repeated early-morning samples. Over 10 years, UA/UC increased significantly (P < .001), and five patients (9.4%) progressed to microalbuminuria. The increase in albuminuria was significantly and positively related to the baseline serum concentrations of total cholesterol (P < .05), low-density lipoprotein (LDL) cholesterol (P = .05), non-high-density lipoprotein (HDL) cholesterol (P < .05), and apolipoprotein (apo) B (P < .001), but no significant associations were found with triglycerides, HDL cholesterol, apo A-1, or lipoprotein(a) [Lp(a)]. The relative risk of developing microalbuminuria for a serum apo B concentration more than 1.1 g/L was 3.8 (95% confidence interval [CI], 1.9 to 7.7). In multiple linear regression analysis, serum apo B (P < .05) and glycated hemoglobin ([HbA] P < .05) at baseline were significant independent predictors of the increase in albuminuria, with no significant associations found for sex, smoking, duration of diabetes, mean arterial blood pressure (BP), or family history of cardiovascular disease and hypertension; the regression model predicted 42% of the variation in UA/UC at 10 years. The findings suggest that an abnormality in the metabolism of apo B may be independently associated with progression of very-low-level albuminuria and possibly with the development of early nephropathy in IDDM patients.

Lipids, lipoproteins, antioxidants and glomerular and tubular dysfunction in type 1 diabetes

We aimed to examine the relationship of serum lipids, lipoproteins, apolipoproteins and antioxidants with renal dysfunction as measured by urinary excretion of albumin and of retinol binding protein (RBP) in insulin-dependent diabetes mellitus (IDDM). We studied 121 patients with IDDM. Glomerular function was assessed as the urinary albumin/creatinine ratio (UA/UC), and tubular function as the urinary retinol-binding protein/creatinine ratio (UR/UC), both measured in three early morning spot urine samples. The mean (range) UA/UC was 1.95 mg/mmol (0.3-476.5) and UR/UC was 17.5 micrograms/mmol (1.0-1853.8). 17% of the patients had a UA/UC > 3 mg/mmol and 33% had a UR/UC > 20 micrograms/mmol. Significant positive correlations were observed between both UA/UC and UR/UC and the following: serum total cholesterol (P < 0.005); triglycerides (P < 0.001); apolipoproteins A-I (P < 0.05), A-II (P < 0.02) and B (P < 0.002); glycated haemoglobin (P < 0.002). No significant associations were found with serum vitamin E, beta-carotene or total antioxidant activity. In multiple regression, only UA/UC was independently associated with serum apo B and cholesterol concentrations. In conclusion, in IDDM glomerular dysfunction, as measured by UA/UC, is associated with elevated serum cholesterol, triglycerides, apo B, apo A-I and apo A-II, but not with HDL cholesterol or antioxidant status. Tubular dysfunction tends to occur with increasing albuminuria, but it is not independently associated with serum lipid, lipoprotein, apolipoprotein or antioxidant levels.

Hydrocephalus, mineralizing angiopathy, hypercholesterolemia, and hyperlipoprotein (a)

A boy born at 34 weeks gestation with initially normal development presented with acute hydrocephalus at 22 months. Subsequently his development has been slow and complicated clinically by epilepsy. Upon extensive investigation, he has been found to have extremely elevated lipoprotein(a) levels, hypercholesterolemia (familial), and lesions of the cortex and meninges. Radiologic studies have disclosed a mineralizing angiopathy.

Elevated serum lipoprotein(a) is a risk factor for clinical recurrence after coronary balloon angioplasty

BACKGROUND

Elevated lipoprotein (Lp) (a) concentrations are associated with coronary artery disease and myocardial infarction. Lp(a) is structurally related to proteins involved in lipid transport, fibrinolysis, coagulation, and cellular mitogenesis and is known to have important physiological interactions with the coagulation and fibrinolytic systems. Because these processes may be important to arterial healing after balloon injury, we hypothesized that elevated Lp(a) concentrations may be associated with recurrence of symptoms and restenosis after balloon angioplasty.

METHODS AND RESULTS

We assessed 240 consecutive patients undergoing coronary balloon angioplasty with measurements of Lp(a), total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, apolipoprotein A-I, and apolipoprotein B-100 concentrations from fresh specimens. Patients were evaluated 4 to 6 months after angioplasty for clinical recurrence by repeat angiography if angina had returned or by maximal exercise treadmill testing with thallium imaging if patients remained asymptomatic. Ninety-seven patients (40%) had clinical recurrence; 143 (60%) did not. Patients with recurrence had significantly greater Lp(a) concentrations compared with those without (median, 29 versus 14; P < .0001). Each patient quintile stratified by increasing Lp(a) concentrations had incrementally greater recurrence rates ranging from 27% (lowest quintile) to 60% (highest quintile). By multivariate logistic regression analysis, Lp(a) concentration was the only predictor of recurrence (P < .0001). A subset of frozen, stored serum samples showed a significant decrease in measured Lp(a) concentration over time (mean, 605 days; P < .01).

CONCLUSIONS

An elevated Lp(a) concentration was a risk factor for clinical recurrence after percutaneous transluminal balloon coronary angioplasty. Other lipid levels or clinical characteristics were not significantly associated with recurrence. When serum was frozen and stored for a prolonged period, Lp(a) concentration decreased over time.

The effect of growth hormone replacement on serum lipids, lipoproteins, apolipoproteins and cholesterol precursors in adult growth hormone deficient patients

OBJECTIVE

Adult patients with growth hormone deficiency are thought to be at higher risk of mortality from cardiovascular disease. We therefore investigated the effect of recombinant human growth hormone (rhGH) replacement therapy on fasting serum concentrations of lipids, lipoproteins and cholesterol precursors in adult growth hormone deficient patients.

DESIGN

Double-blind placebo controlled trial. Patients were randomly allocated to placebo or rhGH replacement therapy (0.018 U/kg/day for 1 month followed by 0.036 U/kg/day for 1 month).

PATIENTS

Eighteen patients with severe growth hormone deficiency.

MEASUREMENTS

Fasting lipid, lipoprotein and cholesterol precursors (lathosterol and mevalonic acid) were measured at baseline and after 2 months.

RESULTS

In the rhGH treated group there was a significant fall in serum cholesterol (P < 0.01) (6.44 +/- 0.49 to 5.71 +/- 0.48 mmol/l), LDL cholesterol (P < 0.02) (4.29 +/- 0.49 to 3.62 +/- 0.44 mmol/l), LDL cholesterol/HDL cholesterol ratio (P < 0.02) (3.99 +/- 0.62 to 3.26 +/- 0.39), apolipoprotein B (P < 0.01 (1.30 +/- 0.11 to 1.15 +/- 0.11 g/l) and mevalonic acid (P < 0.05) (13.4 +/- 10.96 to 6.21 +/- 1.91 micrograms/l). There were no significant changes in triglycerides, HDL cholesterol, apolipoprotein A1, lipoprotein (a) or lathosterol concentrations. In the GH treated group the rise in serum insulin was inversely correlated with the fall in cholesterol (P < 0.05), LDL cholesterol (P < 0.01) and apolipoprotein B (P < 0.01). There were no significant changes in any of the measured variables in the placebo group.

CONCLUSION

We conclude that GH may be involved in the regulation of lipid and lipoprotein metabolism and that rhGH replacement therapy of adult GHD patients is associated with beneficial changes in lipid and lipoprotein profiles. The reduction in mevalonic acid is consistent with up-regulation of hepatic LDL receptors caused by GH and this may explain the fall in LDL cholesterol and apolipoprotein B concentrations.