title: Uncarboxylated osteocalcin stimulates 25-hydroxy vitamin D production in Leydig cell line through a GPRC6a-dependent pathway.
abstract: Recent studies disclosed a cross talk between testis and bone. By the action of LH, Leydig cells are able to modulate bone metabolism through testosterone and insulin-like factor 3. Moreover, LH modulates the Leydig expression of CYP2R1, the key enzyme involved in vitamin D (Vit D) 25-hydroxylation. However, pathways regulating CYP2R1 expression have been poorly investigated. The cross talk from the bone to the testis of the vitamin D 25-hydroxylase CYP2R1 involves osteocalcin (OC), which is produced by the osteoblasts and stimulates the production of testosterone by the Leydig cells through its putative receptor GPRC6A, a cation-sensing G-protein-coupled receptor. The aim of this study was to investigate the possible action of OC on CYP2R1 expression and 25-hydroxy Vit D (25-OH Vit D) production in a mouse Leydig cell line (MA-10). After confirmation of the expression of GPRC6A by MA-10, we found that stimulation with either human chorionic gonadotropin or uncarboxylated-OC (ucOC) increases CYP2R1 protein expression in a dose-dependent manner and, in turn, increases the release of 25-OH Vit D in culture medium. This effect was abolished by receptor blockade with, respectively, anti-LH receptor and anti-GPRC6A antibodies. Moreover, both agonists converged to phosphorylation of Erk1/2 by a likely differential action on second messengers. Human chorionic gonadotropin induced slow "tonic" increase of intercellular calcium and accumulation of cAMP, whereas ucOC mainly induced phasic increase of cell calcium. Supporting these findings, we found that serum ucOC positively correlated with 25-OH Vit D levels in 40 overweight male patients and 21 controls. Altogether, our results suggest that OC contributes with LH to 25-OH Vit D production by Leydig cells.
authors.affiliation: Department of Medicine (L.D.T., A.F., C.F.), Centre for Human Reproduction Pathology, University of Padova, 35128 Padova, Italy; Laboratory of Protein Chemistry (V.D.F., S.T.), Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy; Department of Medicine (V.S., A.A.), Section of Diabetes and Metabolic Diseases, University of Padova, 35120 Padova, Italy; and Department of Molecular Medicine (M.F.) and Internal Medicine 3 (R.V.), Endocrine-Metabolic Laboratory, Department of Medicine, University of Padova, 35121 Padova, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: De Toni
authors.forename: Vincenzo
authors.initials: V
authors.lastname: De Filippis
authors.forename: Simone
authors.initials: S
authors.lastname: Tescari
authors.forename: Marco
authors.initials: M
authors.lastname: Ferigo
authors.forename: Alberto
authors.initials: A
authors.lastname: Ferlin
authors.forename: Valentina
authors.initials: V
authors.lastname: Scattolini
authors.forename: Angelo
authors.initials: A
authors.lastname: Avogaro
authors.forename: Roberto
authors.initials: R
authors.lastname: Vettor
authors.forename: Carlo
authors.initials: C
authors.lastname: Foresta
mesh_terms: D000328:Adult; D000818:Animals; D002245:Carbon Dioxide; D016022:Case-Control Studies; D002460:Cell Line; D053493:Cholestanetriol 26-Monooxygenase / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007985:Leydig Cells / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D053858:Metabolic Networks and Pathways / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood / Q000737:chemistry / Q000494:pharmacology*; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism
chemical_list: C515750:GPRC6A protein, mouse; D043562:Receptors, G-Protein-Coupled; D015675:Osteocalcin; D014807:Vitamin D; D002245:Carbon Dioxide; C041069:carboxyl radical; C104450:25-hydroxyvitamin D; C569548:Cyp2r1 protein, mouse; D053493:Cholestanetriol 26-Monooxygenase