期刊
JOURNAL OF STEROID BIOCHEMISTRY AND MOLECULAR BIOLOGY
卷 103, 期 3-5, 页码 631-634出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsbmb.2006.12.066
关键词
vitamin D; 25-hydroxyvitamin D; nutritional vitamin D status
资金
- NICHD NIH HHS [R01 HD043921, R01 HD047511] Funding Source: Medline
Circulating 25-hydroxyvitamin D [25(OH)D] is generally considered the means by which we define nutritional vitamin D status. There is much debate. however, with respect to what a healthy minimum level of circulation 25(OH)D should be. Recent data using various biomarkers such as intact parathyroid hormone (PTH), intestinal calcium absorption, and skeletal density measurements suggest this minimum level to be 80 nmol (32 ng/mL). Surprisingly, the relationship between circulating vitamin D-3 and its metabolic product-25(OH)D-3 has not been studied. We investigated this relationship in two separate populations: the first, individuals from Hawaii who received significant sun exposure; the second. subjects from a lactation study who received up to 6400 IU vitamin D-3/day for 6 months. Results (1) the relationship between circulating vitamin D-3 and 25(OH)D in both groups was not linear, but appeared saturable and controlled; (2) optimal nutritional vitamin D status appeared to occur when molar ratios of circulating vitamin D-3 and 25(OH)D exceeded 0.3; at this point, the V-max of the 25-hydroxylase appeared to be achieved. This was achieved when circulating 25(OH)D exceeded 100 nmol. We hypothesize that as humans live today, the 25-hydroxylase operates well below its V-max because of chronic substrate deficiency, namely vitamin D-3. When humans are sun (or dietary) replete, the vitamin D endocrine system will function in a fashion as do these other steroid synthetic pathways, not limited by substrate. Thus, the relationship between circulating vitamin D and 25(OH)D may represent what normal vitamin D status should be. (c) 2006 Elsevier Ltd. All rights reserved.
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