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The active vitamin D, 1, 25-dihydroxyvitamin D (1, 25 (OH)_2D), expresses its function mediated through vitamin D receptor (VDR). The VDR gene is comprised of 11 exons that together with intervening introns span approximately 75 kilobases. The noncoding 5' end of the gene includes exons 1 A, 1 B, and 1C. Eight additional exons (exons 2〜9) encode the structural portion of the VDR gene product. This article reviews our contribution on pathophysiologic analysis of vitamin D-dependent rickets type II (VDDRII), the role of vitamin D (D) on phosphate metabolism, and the association of D with osteoporosis. 1) VDDR II consists of a spectrum of VDR defects is characterized by the early onset of severe rickets and associated alopecia. This can be attributed to mutations in the VDR gene. Massive doses of D analogues and calcium supplementation is usually required for the treatment, however the responses to therapy sometimes show heterogeneity. 2) Inorganic phosphate (Pi) homeostasis is maintained mainly by the regulation of sodium-dependent phosphate (Na/Pi) transporters in the renal proximal tubules. Three nonhomologous Na/Pi transporters (types I, II and III) have been identified in the renal cortex of various species. Type II Na/Pi transporters play a major role in the regulation of renal Pi reabsorption by dietary Pi and a variety of hormones including 1, 25 (OH)_2D. 3) The polymorphism at the translation initiation codon of the human VDR gene affects the bone mineral density in the lumbar spine and the extent of D-dependent transcriptional activation on 24-hydroxylase gene. These results were confirmed by various studies using different ethnic populations. From these studies, it is concluded that D and VDR system is important for bone health through the human life.

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As a step of obtaining actual status of vitamin B_6 (B_6) intake, the B_6 intakes determined by duplicate meal method were compared with the values calculated from dietary records and also the B_6 nutritional status was studied in 19 healthy female students aged 22〜30 years. Furthermore, cooking loss was estimated as difference of both the intakes. The B_6 vitamers (pyridoxamine 5'-phosphate, pyridoxamine, pyridoxal 5'-phosphate, pyridoxal, pyridoxine 5'-phosphate, pyridoxine and pyridoxine 5'-β-glucoside) in duplicate meals were measured separately by HPLC. At the same time, the B_6 intakes were calculated from diet records for three sequential days and the total amount of B_6 in serum was measured. The relationship of the B_6 intakes and the serum B_6 levels were studied. The mean intake of B_6 in duplicate meals was 0.91±0.25 mg/day (mean±sd) and that calculated from dietary records was 1.12±0.25 mg/day (mean±sd), and the former was equivalent to 83.4% of the latter. The mean intake of pyridoxine 5'-β-glucoside was 15.8% of total B_6 intake, and a significant correlation was observed between both the intakes. The main dietary sources of B_6 commonly used were vegetables, fishes and meats. A significant correlation was found between the intake of B_6 (mg/g protein) by duplicate meals and the total B_6 concentration in serum.

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