Intra-individual variability of long-chain fatty acids (C12-C24) in plasma and red blood cells.

Long-chain fatty acids (LCFA) play key roles in mammalian cells as sources of energy, structural components and signaling molecules. Given their importance in numerous physiological processes, the roles of LCFAs in health and disease have been extensively investigated. In the majority of studies, correlations are established using a single measurement in plasma or red blood cells (RBCs). Although a few studies have reported on reproducibility of individual fatty acid measurements, the comprehensive analysis of intra-individual LCFA variability has not been performed. Therefore, our goal was to determine intra-individual variability for the 22 most abundant LCFAs in both plasma and RBC samples collected from healthy individuals on a regular diet after overnight fasting. The measurements of LCFAs in RBCs were consistent throughout the course of study reflecting long-term nutritional status. In contrast, the results in plasma showed considerable LCFA intra-individual variability, even between fatty acids of the same type. Plasma intra-individual variability for omega-3 alpha-linolenic and eicosapentaenoic acids in some participants were >40% whereas the variability of docosahexaenoic acid was consistently <12.8%. Omega-6 linoleic and arachidonic acids also showed low variability in plasma. The results suggest that some LCFAs have less variability and would be more reliable as biomarkers. Reliability of biomarkers can have a profound impact on the research outcomes. Intra-individual variability of LCFAs should be taken into consideration in designing, conducting and interpreting results of clinical studies.

Bone resorption in syndromes of the Ras/MAPK pathway.

Disorders of the Ras/mitogen-activated protein kinase (MAPK) pathway have an overlapping skeletal phenotype (e.g. scoliosis, osteopenia). The Ras proteins regulate cell proliferation and differentiation and neurofibromatosis type 1 (NF1) individuals have osteoclast hyperactivity and increased bone resorption as measured by urine pyridinium crosslinks [pyridinoline (Pyd) and deoxypyridinoline (Dpd)]. Pyd and Dpd are hydroxylysine-derived crosslinks of collagen found in bone and cartilage and excreted in the urine. Dpd is most abundant in bone. The aim of this study was to evaluate if other syndromes of the Ras/MAPK pathway have increased bone resorption, which may impact the skeletal phenotype. Participants were individuals with Noonan syndrome (n = 14), Costello syndrome (n = 21), and cardiofaciocutaneous (CFC) syndrome (n = 14). Pyridinium crosslinks from two consecutive first morning urines were extracted after acid hydrolysis and analyzed by high performance liquid chromatography. Three separate analyses of covariance were performed to compare Pyd, Dpd, and Dpd/Pyd ratio of each group to controls after controlling for age. Data were compared to 99 healthy controls. The Dpd and the Dpd/Pyd ratio were elevated (p < 0.0001) in all three conditions compared to controls suggesting that collagen degradation was predominantly from bone. The data suggest that the Ras/MAPK signal transduction pathway is important in bone homeostasis.

Performance characteristics of a point of care C-reactive protein assay.

BACKGROUND: C-reactive protein (CRP) is a non-specific marker of inflammation that can be used for atherosclerotic risk assessment. This application requires increased precision at low CRP concentrations compared to traditional assays. METHODS: The Micros CRP analyzer (ABX Diagnostics) is a small bench top device. Its limit of detection, limit of quantitation, linearity and imprecision were assessed. Method comparison studies were performed using samples both inside and outside the reference interval. Anticoagulant effects and the prozone effect were also evaluated. RESULTS: The limit of detection was 0.1 mg/l. The method was linear from 2 to 60 and 0.3 to 60 mg/l using systematic error limits of 10% and 20%, respectively. The total imprecision was <8% for CRP concentrations from 0.7 to 9.1 mg/l. A prozone effect was seen at CRP concentrations >500 mg/l. Using samples from 120 apparently healthy adults, the Micros CRP method demonstrated excellent concordance with the BN II high sensitivity CRP (hs-CRP) method. The Micros CRP method compared well with a nephelometric method using samples with elevated CRP concentrations. CONCLUSIONS: The Micros CRP method is adequate for atherosclerotic risk prediction in clinical practice but does not have adequate accuracy at CRP concentrations <2 mg/l for epidemiological studies.