Duality of Tocopherol Isoforms and Novel Associations with Vitamins Involved in One-Carbon Metabolism: Results from an Elderly Sample of the LifeLines Cohort Study.

Whether the affinity of serum vitamin E with total lipids hampers the appropriate assessment of its association with age-related risk factors has not been investigated in epidemiological studies. We aimed to compare linear regression-derived coefficients of the association of non-indexed and total lipids-indexed vitamin E isoforms with clinical and laboratory characteristics pertaining to the lipid, metabolic syndrome, and one-carbon metabolism biological domains. We studied 1429 elderly subjects (non-vitamin supplement users, 60-75 years old, with low and high socioeconomic status) from the population-based LifeLines Cohort and Biobank Study.

Measurement of plasma vitamin K1 (phylloquinone) and K2 (menaquinones-4 and -7) using HPLC-tandem mass spectrometry.

Background: Given the growing interest in the health benefits of vitamin K, there is great need for development of new high-throughput methods for quantitative determination of vitamin K in plasma. We describe a simple and rapid method for measurement of plasma vitamin K1 (phylloquinone [PK]) and K2 (menaquinones [MK]-4 and -7). Furthermore, we investigated the association of fasting plasma vitamin K with functional vitamin K insufficiency in renal transplant recipients (RTR).

Performance of plasma free metanephrines measured by liquid chromatography-tandem mass spectrometry in the diagnosis of pheochromocytoma.

Background: Plasma free metanephrines have proved a highly sensitive biochemical test for the diagnosis of pheochromocytoma. We have developed and validated a simple, LC-MS/MS method to determine plasma metanephrines and compared the diagnostic efficacy of the method with an enzyme immunoassay procedure in 151 patients, 38 with histologically confirmed pheochromocytoma.

Methods: Off-line solid phase extraction in a 96-well plate format was used to isolate metanephrines from 100-microL of plasma, followed by rapid separation with hydrophilic interaction chromatography.

Plasma free metanephrine measurement using automated online solid-phase extraction HPLC tandem mass spectrometry.

Background: Quantification of plasma free metanephrine (MN) and normetanephrine (NMN) is considered to be the most accurate test for the clinical chemical diagnosis of pheochromocytoma and follow-up of pheochromocytoma patients. Current methods involve laborious, time-consuming, offline sample preparation, coupled with relatively nonspecific detection. Our aim was to develop a rapid, sensitive, and highly selective automated method for plasma free MNs in the nanomole per liter range.

Angiotensin administration stimulates renal 11 beta-hydroxysteroid dehydrogenase activity in healthy men.

Background: We examined whether acute administration of angiotensin modulates the activity of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD), the intracellular enzyme catalyzing the interconversion between the hormonally active cortisol and inactive cortisone.

Methods: Twenty-one male healthy subjects were examined after 1 week of a low- and high-salt diet (50 and 200 mmol/day, respectively). Separate infusions of angiotensin I (Ang I) and II (Ang II) were administered, both at rates of 4 and 8 ng/kg/min.