24-25-dihydroxyvitamin-d2 and 1-25-dihydroxyergocalciferol

Interactions between calcium and vitamin D may have implications for the regulation of serum 25-hydroxyvitamin D [25(OH)D] and its catabolism and, consequently, the vitamin D dietary requirement.. We investigated whether different calcium intakes influenced serum 25(OH)D and indexes of vitamin D activation and catabolism during winter and in the context of both adequate and inadequate vitamin D intakes.. A 15-wk winter-based, randomized, placebo-controlled, double-blind vitamin D₃ intervention (20 μg/d) study was carried out in free-living men and women aged ≥50 y (n = 125) who were stratified according to calcium intakes [moderate-low (<700 mg/d) or high (>1000 mg/d) intake]. The serum 25(OH)D concentration was the primary outcome, and serum calcium, parathyroid hormone (PTH), 1,25-dihydroxyvitamin D [1,25(OH)₂D], 24,25-dihydroxyvitamin D [24,25(OH)₂D], the ratio of 24,25(OH)₂D to 25(OH)D, vitamin D-binding protein, and free 25(OH)D were exploratory outcomes.. A repeated-measures ANOVA showed there was no significant (P = 0.2) time × vitamin D treatment × calcium intake grouping interaction effect on the mean serum 25(OH)D concentration over the 15-wk intervention period. Serum 25(OH)D concentrations increased (P ≤ 0.005) and decreased (P ≤ 0.002) in vitamin D₃ and placebo groups, respectively, and were of similar magnitudes in subjects with calcium intakes <700 mg/d (and even <550 mg/d) compared with >1000 mg/d. The response of serum PTH, 1,25(OH)₂D, 24,25(OH)₂D, the ratio of 24,25(OH)₂D to 25(OH)D, and free 25(OH)D significantly differed in vitamin D₃ and placebo groups but not by calcium intake grouping.. We found no evidence of a vitamin D sparing effect of high calcium intake, which has been referred to by some authors as "vitamin D economy." Thus, recent dietary vitamin D requirement estimates will cover the vitamin D needs of even those individuals who have inadequate calcium intakes.

Topics: 24,25-Dihydroxyvitamin D 3; 25-Hydroxyvitamin D 2; Aged; Aged, 80 and over; Aging; Calcifediol; Calcitriol; Calcium; Calcium, Dietary; Cholecalciferol; Dietary Supplements; Double-Blind Method; Ergocalciferols; Female; Humans; Ireland; Male; Middle Aged; Nutritional Requirements; Seasons; Vitamin D Deficiency

Serum levels of vitamin D metabolites were determined in 11 patients treated for cystic acne with a four-month course of isotretinoin (Roaccutane). The levels were measured before treatment and after two months of medication. We found a significant fall in the level of 1,25-dihydroxyvitamin D (p less than 0.01) and a significant increase in the molar ratio of 24, 25-dihydroxyvitamin D to 25-hydroxyvitamin D (p less than 0.05). No significant changes were found for the vitamin D metabolites 25-hydroxyvitamin D or 24,25-dihydroxy-vitamin D, for serum calcium, phosphorus, alkaline phosphatase or parathyroid hormone. Our data indicate early changes in the metabolism of vitamin D in patients on retinoid treatment.

Topics: Acne Vulgaris; Adolescent; Adult; Calcifediol; Calcium; Ergocalciferols; Female; Humans; Isotretinoin; Male; Middle Aged; Time Factors

1,24,25-Trihydroxyergocalciferol was isolated from bovine kidney homogenates incubated with 1,25-dihydroxyergocalciferol and from chick kidney homogenates incubated with 24,25-dihydroxyergocalciferol. The identity was established by ultraviolet absorbance, sensitivity to periodate, nuclear magnetic resonance, and mass spectrometry. The new metabolite had an affinity equal to 1,24,25-trihydroxycholecalciferol for the bovine-thymus and chick-intestinal 1,25-dihydroxyvitamin D receptor and had an affinity twice that of 1,24,25-trihydroxycholecalciferol for the rat-intestinal receptor. It was 3- and 6-fold less competitive than either 1,25-dihydroxycholecalciferol or 1,24,25-trihydroxycholecalciferol, respectively, for the rat plasma vitamin D transport protein. 1,24,25-Trihydroxyergocalciferol was at least 10-fold less active than 1,25-dihydroxycholecalciferol, 1,25-dihydroxyergocalciferol, and 1,24,25-trihydroxycholecalciferol at stimulating intestinal-calcium transport and was also relatively ineffective at stimulating bone-calcium resorption in rats. Moreover, in rats, [3H]1,24,25-trihydroxyergocalciferol was cleared from plasma approximately 40% faster than [3H]1,24,25-trihydroxycholecalciferol. These data suggest that C-24 hydroxylation of 1,25-dihydroxyergocalciferol represents a significant in vivo deactivation step, whereas equivalent deactivation of 1,25-dihydroxycholecalciferol seems to involve metabolic steps subsequent to C-24 hydroxylation (C-24 ketonization). C-24 ketonization of 1,25-trihydroxyergocalciferol would not be anticipated due to the presence of the 24(S)-methyl group. These results reveal further dissimilarities between ergocalciferol and cholecalciferol metabolism in mammals and suggest a mechanism for the lesser tendency of ergocalciferol to cause hypercalcemia relative to cholecalciferol.

Topics: Animals; Binding, Competitive; Biological Transport; Bone and Bones; Calcium; Cattle; Chickens; Ergocalciferols; Hydroxylation; Intestinal Mucosa; Intestines; Kidney; Kinetics; Male; Rats; Receptors, Calcitriol; Receptors, Steroid; Thymus Gland; Vitamin D-Binding Protein

The serum concentrations of 25-hydroxycholecalciferol (25OHD3), 25-hydroxyergocalciferol (25OHD2), 24,25-dihydroxyvitamin D (24,25(OH)2D), and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured in 10 normal subjects every 2 months for 1 year. Parallel seasonal variations were found in serum 25-hydroxycholecalciferol and 24,25-dihydroxyvitamin D reaching maximum values in June. Moreover, a highly significant correlation between changes in these two metabolites was observed (r = 0.89, P less than 0.001). On the other hand, the mean serum 1,25-dihydroxyvitamin D concentration remained constant throughout the year. Our data add further evidence to the tight regulatory mechanism of serum 1,25-dihydroxyvitamin D and the lack of regulatory mechanism of serum 24,25-dihydroxyvitamin D.

Topics: 25-Hydroxyvitamin D 2; Adult; Calcifediol; Ergocalciferols; Female; Humans; Longitudinal Studies; Male; Reference Values; Seasons; Vitamin D

Topics: 25-Hydroxyvitamin D 2; Animals; Dihydroxycholecalciferols; Dogs; Ergocalciferols; Female; Homeostasis; Hydroxycholecalciferols; Liver

Topics: 25-Hydroxyvitamin D 2; Adult; Calcium; Ergocalciferols; Humans; Hydroxycholecalciferols; Kidney Failure, Chronic; Radioligand Assay; Renal Dialysis

The authors report on a new case of severe hypercalcaemia induced by prolonged oral treatment with high doses of vitamin D2. (6 mg/day for 9 months). Blood calcium level did not return to normal until 6 months after the drug was discontinued. The plasma concentration of 25 (OH) D was more than three times the normal value and remained very high throughout the observation period. The plasma concentration of 24, 25 (OH)2 D was slightly raised during treatment but became normal after 15 days, while that of 1,25 (OH)2 D, the active form of vitamin D, remained normal throughout, suggesting that the pathogenesis of vitamin D-induced hypercalcaemia is probably complex.

Topics: 25-Hydroxyvitamin D 2; Aged; Ergocalciferols; Female; Humans; Hypercalcemia; Vitamin D