Measurement of 25-OH-vitamin D in human serum using liquid chromatography tandem-mass spectrometry with comparison to radioimmunoassay and automated immunoassay.

The plasma 25-OH vitamin D concentration is a reliable biomarker for vitamin D status but assay's variability makes adequate monitoring of vitamin D status difficult. We employed isotope-dilution liquid chromatography (LC) tandem-mass spectrometry (MS/MS) for the measurement of both 25-OH vitamin D3 and 25-OH vitamin D2 in human serum. Hexadeuterium labelled 25-OH vitamin D3 internal standard (IS) was added to calibrators (prepared in phosphate-buffered saline with 60 g/L albumin), controls or patient sera and 25-OH vitamin D metabolites were released from vitamin D binding protein by adding sodium hydroxide prior to protein precipitation by acetonitrile/methanol (9:1, v/v).

Plasma citrulline measurement using UPLC tandem mass-spectrometry to determine small intestinal enterocyte pathology.

Citrulline is a nonessential free amino acid, detectable in various biological fluids such as plasma, urine and cerebrospinal fluid. The plasma citrulline concentration is increasingly considered to be a reliable biomarker of enterocyte function. Current analysis usually involves lengthy HPLC separations as a part of classical amino acid profiling, or mass spectrometry usually in combination with derivatization.

Freeze-thaw and matrix effects in direct high-density lipoprotein cholesterol methods.

Background: There is frequent discussion on the susceptibility of direct high-density lipoprotein cholesterol (HDL-C) methods to matrix effects. In Vitro Diagnostics manufacturers recognize this issue and regularly improve their HDL-C reagent formulations in subsequent generations.

Methods: The 3rd generation direct HDL-C assay from Roche was investigated for matrix effects in comparison to the former generation, a Beckman direct HDL-C method and a conventional phosphotungstate (PTA)/Mg(2+) precipitation method.

LPS-induced release of IL-1 beta, IL-1Ra, IL-6, and TNF-alpha in whole blood from patients with familial hypercholesterolemia: no effect of cholesterol-lowering treatment.

Proinflammatory cytokines, such as interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha), are suggested to have an important role in the process of atherosclerosis. Patients with heterozygous familial hypercholesterolemia (FH) have a marked elevation in the plasma level of low-density lipoproteins (LDL), and they show early development of atherosclerosis. The aim of the present study was to test with a whole blood culture system if hyperlipoproteinemia is associated with increased cytokine production capacity in these patients and if treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors influences this production capacity of blood cells, at both the protein and mRNA levels.

Apolipoprotein-E-deficient mice exhibit an increased susceptibility to disseminated candidiasis.

The effect of hyperlipoproteinemia on systemic candidiasis was investigated by assessing the susceptibility of hyperlipoproteinemic, apolipoprotein E (ApoE)-deficient (ApoE -/-) mice to a systemic Candida albicans infection. The absence of ApoE in these mice resulted in an eightfold increase in plasma lipoprotein concentrations in the very low-density lipoprotein (VLDL) fraction, as compared with levels seen in ApoE +/+ mice. Mortality due to candidemia was significantly higher (86%) in ApoE -/- mice than in ApoE+/+ mice (52%), and in platings of homogenized kidney material on fungal culture medium, ApoE -/- mice yielded significantly higher levels of C.

Assessment of risk factors for coronary heart disease in vascular medicine: long-term experience and a personal view from the laboratory.

Physicians should be properly informed of the clinical chemistry diagnostic potential for the diagnosis and classification of hyper- and dyslipidemias by laboratory determinations of lipids, lipoproteins, and apolipoproteins. New analytes are regularly found to be relevant for screening and risk estimation for coronary artery disease in vascular medicine. These analytes can be distinguished between parameters working on the long-term or working acutely.

Laboratory-based assessment of plasma lipids and lipoproteins for the classification of familial hypercholesterolemic and hypertriglyceridemic states.

Laboratory-based coronary heart disease risk assessment classically involves measurement of lipids and lipoproteins. In this review, information is provided on the methods commonly used in laboratories for the diagnosis of hyperlipidemia, including aspects of precision and accuracy. The latter, when fulfilled, allows the use of uniform reference values.

Nomogram to diagnose familial combined hyperlipidemia on the basis of results of a 5-year follow-up study.

Background: Familial combined hyperlipidemia (FCH) is traditionally diagnosed by total plasma cholesterol and/or triglyceride levels above the 90th percentile adjusted for age and gender. In a recent study, we showed that the diagnosis of FCH on the basis of these diagnostic criteria was inconsistent in 26% of the subjects over a 5-year period. This result emphasizes the need for reevaluation of the diagnostic criteria for FCH.

Apolipoprotein C-III isofocusing in the diagnosis of genetic defects in O-glycan biosynthesis.

Background: Defects in the biosynthesis of N-glycans may be found by isoelectric focusing (IEF) of plasma transferrin. No test is available to demonstrate O-glycan biosynthesis defects.

Methods: We used isoforms of apolipoprotein C-III (apoC-III) as a marker for the biosynthesis of core 1 mucin type O-glycans.

Improved cardiovascular risk profile and renal function in renal transplant patients after randomized conversion from cyclosporine to tacrolimus.

Cyclosporine is considered to contribute to the high cardiovascular morbidity and mortality in patients after renal transplantation. Tacrolimus may be more favorable in this respect, but controlled data are scarce. In this prospective randomized study in 124 stable renal transplant patients, the effects of conversion from cyclosporine to tacrolimus on cardiovascular risk factors and renal function were investigated.

Neutrophil superoxide-anion generating capacity in chronic smoking: effect of long-term alpha-tocopherol therapy.

We investigated whether long-term alpha-tocopherol therapy in chronic smoking affects superoxide generating capacity of neutrophils ex vivo. To this purpose, we randomly assigned 128 male chronic smokers (37 +/- 21 pack years of smoking) to treatment with placebo (n = 64) or alpha-tocopherol (400 IU dL-a-tocopherol daily, n = 64). After two years of therapy, we measured phorbol 12-myristate 13-acetate-induced superoxide production of isolated neutrophils and of diluted whole blood by monitoring reduction of ferricytochrome c and luminol-enhanced peroxidase-catalyzed chemiluminescence.

Native LDL potentiate TNF alpha and IL-8 production by human mononuclear cells.

Native LDL (nLDL) increases expression of adhesion molecules on endothelial cells through induction of Ca(2+) mobilization. Ca(2+) mobilization is also involved in the induction of proinflammatory cytokines, important mediators involved in atherogenesis. The aim of the study was to evaluate the capacity of nLDL to affect spontaneous and lipopolysaccharide (LPS)-stimulated cytokine production.

Changes in the plasma lipid profile as a potential predictor of clinical outcome in dengue hemorrhagic fever.

In 50 consecutive children admitted to the intensive care unit with the clinical diagnosis of dengue hemorrhagic fever (DHF)/dengue shock syndrome (grade III or IV), 20 patients with mild DHF (grade I or II), and 20 healthy control patients, the plasma lipid profile was measured. Levels of total plasma cholesterol, high-density lipoprotein, and low-density lipoprotein were significantly decreased in patients with the severest cases, compared with patients with mild DHF and healthy controls. Changes in the plasma lipid profile differentiate between patients with different stages of DHF disease severity and could be used as a potential predictor for clinical outcome.

Diagnosis of familial combined hyperlipidemia based on lipid phenotype expression in 32 families: results of a 5-year follow-up study.

Familial combined hyperlipidemia (FCH) is characterized by a variable expression of hypercholesterolemia and/or hypertriglyceridemia. We evaluated the variability in lipid phenotype expression over a 5-year period and studied factors affecting the lipid phenotype expression. A total of 32 families (299 subjects) were studied in 1994 and in 1999.