Synthesis of Deuterium-Labeled Vitamin D Metabolites as Internal Standards for LC-MS Analysis

Blood levels of the vitamin D₃ (D₃) metabolites 25-hydroxyvitamin D₃ (25(OH)D₃), 24R,25-dihydroxyvitamin D₃, and 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) are recognized indicators for the diagnosis of bone metabolism-related diseases, D₃ deficiency-related diseases, and hypercalcemia, and are generally measured by liquid-chromatography tandem mass spectrometry (LC-MS/MS) using an isotope dilution method. However, other D₃ metabolites, such as 20-hydroxyvitamin D₃ and lactone D₃, also show interesting biological activities and stable isotope-labeled derivatives are required for LC-MS/MS analysis of their concentrations in serum. Here, we describe a versatile synthesis of deuterium-labeled D₃ metabolites using A-ring synthons containing three deuterium atoms. Deuterium-labeled 25(OH)D₃ (2), 25(OH)D₃-23,26-lactone (6), and 1,25(OH)₂D₃-23,26-lactone (7) were synthesized, and successfully applied as internal standards for the measurement of these compounds in pooled human serum. This is the first quantification of 1,25(OH)₂D₃-23,26-lactone (7) in human serum.     

Maximum Phonation Time is a Useful Assessment for Older Adults Requiring Long-term Care/support

Objective: The maximum phonation time (MPT) is used to assess simple respiratory functions and can be performed anywhere without special instruments. We investigated the association between MPT and respiration, considering the future utilization of simple respiratory assessments during home-based physical therapy. Method: This cross-sectional study included 140 older adults enrolled in Japanese long-term care insurance (77 men, 63 women; mean age, 77.9±8.0 years). The participants performed the MPT, followed by spirometry. We analyzed the MPT of the three age groups, relative reliability of the MPT values, and the association between MPT and respiratory function. Results: We found that the MPT of older men requiring long-term care or support was related to age. The intraclass correlation coefficient of MPT was >0.8 for all groups. Only forced vital capacity was associated with MPT in the partial correlation and multiple regression analyses. Conclusion: MPT could be an alternative assessment of respiratory function in home-based physical therapy for older adults requiring long-term care or support.