Abstract
Parathyroid glands contain the vitamin D receptor (VDR) and 25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) and 24-hydroxylase (CYP24A1), which catalyze the production and degradation of 1,25-dihydroxyvitamin D [1,25(OH)2D], respectively. Previous studies have shown that the serum level of intact parathyroid hormone (iPTH) increases with age. We hypothesized that the expression of CYP27B1 or VDR in parathyroid glands decreases with age, which might account for the increased serum levels of iPTH due to decreased suppression of parathyroid hormone (PTH) secretion by 1,25(OH)2D in older people. To test this hypothesis, we examined relative expression levels of VDR, CYP27B1, CYP24A1, and PTH in specimens from parathyroid glands unintentionally removed during thyroidectomy for 70 patients varying in age from 10 to 70 years. The results showed that there was an inverse correlation between age and VDR, CYP27B1, and CYP24A1 expression (p < 0.05). A significant positive correlation between PTH expression levels and age was also observed (p < 0.05). These data indicate that older age is associated with decreased levels of VDR, CYP27B1, and CYP24A1 and increased levels of PTH in human parathyroid glands.
Highlights
Vitamin D is hydroxylated by 25-hydroxylase in the liver to 25-hydroxyvitamin D [25(OH)D] that is subsequently hydroxylated by 25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) in the kidney to 1,25-dihydroxyvitamin D [1,25(OH)2D]. e latter is the active hormone that plays an important role in maintaining blood calcium and phosphorus levels and skeletal mineralization. 1,25(OH)2D is catabolized to 1,24,25(OH)3D by vitamin D-24-hydroxylase (CYP24A1) in target cells
We examined the expression levels, vitamin D receptor (VDR), CYP27B1, CYP24A1, and parathyroid hormone (PTH) in human parathyroid glands in 70 patients undergoing thyroidectomy varying in age from 10 to 70 years
To determine whether the expression of VDR, CYP27B1, CYP24A1, and PTH in human parathyroid glands is associated with age, we examined expression levels of VDR, CYP27B1, CYP24A1, or PTH-positive cells in parathyroid glands obtained from 70 patients with different ages using
Summary
Vitamin D is hydroxylated by 25-hydroxylase in the liver to 25-hydroxyvitamin D [25(OH)D] that is subsequently hydroxylated by 25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) in the kidney to 1,25-dihydroxyvitamin D [1,25(OH)2D]. e latter is the active hormone that plays an important role in maintaining blood calcium and phosphorus levels and skeletal mineralization. 1,25(OH)2D is catabolized to 1,24,25(OH)3D by vitamin D-24-hydroxylase (CYP24A1) in target cells. Previous studies have shown that the expression of VDR decreases with age in cultured skeletal myocytes [9], human muscle tissue [10], rat intestine [11, 12], bone [11], and mammary glands [13]. It is unknown whether the expression of VDR, CYP27B1, or CYP24A1 is altered in parathyroid glands in older people. To address this question, we examined the expression levels, VDR, CYP27B1, CYP24A1, and PTH in human parathyroid glands in 70 patients undergoing thyroidectomy varying in age from 10 to 70 years
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