New insights into vitamin D regulation: is there a role for alkaline phosphatase?

• Published in: Journal of endocrinological investigation Vol. 44; no. 9; pp. 1891 - 1896
• Main Authors: Bellastella, G., Scappaticcio, L., Longo, M., Carotenuto, R., Carbone, C., Caruso, P., Maio, A., Paglionico, V. A., Vietri, M. T., Maiorino, M. I., Esposito, K.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.09.2021; Springer Nature B.V
• Subjects: 25-Hydroxyvitamin D; Adolescent; Adult; Aged; Alanine; Alanine transaminase; Alkaline phosphatase; Alkaline Phosphatase - metabolism; Animals; Aspartate aminotransferase; Bilirubin; Bone and Bones - enzymology; Endocrinology; Humans; Hydroxylase; Hydroxylation; Internal Medicine; Liver; Liver Function Tests; Male; Medicine; Medicine & Public Health; Metabolic Diseases; Middle Aged; Original; Original Article; Phosphatase; Rabbits; Retrospective Studies; Vitamin D; Vitamin D - metabolism; Vitamin D Deficiency - epidemiology; Vitamin D Deficiency - metabolism; Vitamin deficiency; Young Adult; γ-Glutamyltransferase; Alkaline phosphatase; Vitamin D; 25-Hydroxylase; CYP2R1; 25-Hydroxyvitamin D
• ISSN: 1720-8386; 0391-4097; 1720-8386
• DOI: 10.1007/s40618-021-01503-w

Purpose The diagnosis of vitamin D deficiency is based on the determination of total plasma 25-hydroxyvitamin D (25-OHD) concentrations, but the regulation of vitamin D 25-hydroxylation is not a major consideration and very little information is available on this activity. To check what factors could interfere with the activity of vitamin D-25-hydroxylase and thus alter the 25-OHD concentrations, we looked for potential correlations between 25-OHD and results of liver function tests in healthy adults. Methods This single-centre study was retrospective and consisted of evaluating the correlations between 25-OHD and the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), and bone alkaline phosphatase (BALP) in 349 healthy subjects aged from 18 to 65 years. In particular, in Group 1 ( n  = 119), we looked for correlations between 25OHD and all liver function tests and in Group 2 ( n  = 230) the correlation between 25OHD and BALP. Results In Group 1, we found no correlation between 25OHD and AST ( r  =  − 0.03; p  = 0.8), ALT ( r  =  − 0.02; p  = 0.91), GGT (r =  − 0.08; p = 0.68), direct bilirubin ( r  =  − 0.02; p  = 0.89), indirect bilirubin ( r  =  − 0.24; p  = 0.21), and total bilirubin ( r  =  − 0.24; p  = 0.21) but one between 25OHD and ALP ( r  =  − 0.2; p  = 0.007); in Group 2, we found a significant negative correlation between 25-OHD and BALP ( r  =  − 0.2; p  = 0.0008). Conclusions The correlations that we found suggest that ALP and BALP might be involved in the regulation of vitamin D-25-hydroxylase activity, but further studies are mandatory to confirm our assumptions.