Current Knowledge of Vitamin D Metabolism and Function

Transcription

1 Current Knowledge of Vitamin D Metabolism and Function Glenville Jones, Ph.D Craine Professor & ead, Department of Biochemistry, Professor, Department of Medicine Queen's University, Kingston, ON, Canada gj1@queensu.ca

2 RECENT ADVANCES IN VITAMIN D RESEARC EPIDEMIOLOGICAL STUDIES OF VITAMIN D DEFICIENCY - SUGGEST ASSOCIATION TO MANY DISEASE STATES VDR GENE EXPRESSION STUDIES - SUGGEST # OF VIT D-DEPENDENT GENES = CLONING OF TE 1α-YDROXYLASE (CYP27B1) - WIDESPREAD DISTRIBUTION NOT JUST KIDNEY

3 Vitamin D Metabolism & Function Objectives: Review current knowledge of Vitamin D Metabolism - New information about the cytochrome P450s involved - Concept of extra-renal 1α-hydroxylase Review the classical and non-classical roles of Vitamin D - Importance of calcitriol in VDR-mediated gene expression Implications of vitamin D renaissance for physicians - Serum 25-O-D assay as a Biomarker for vitamin D status - Vitamin D Deficiency may underlie several major diseases - Vitamin D Supplementation

4 Metabolism of Vitamin D 3 C 3 C3 C 3 C3 C3 C3 C 2 CYP27A1 CYP2R1 Liver O O O O Vitamin D 3 25-O-D 3 C 2 CYP27B1 Kidney O C 2 1α,25-(O) 2 D 3 Calcitriol O Similar pathway exists for vitamin D 2

5 Metabolism of Vitamin D 3 C 3 C3 C 3 C3 C 2 CYP27A1 CYP2R1 CYP3A4 C 2 O O O Vitamin D 3 25-O-D 3

6 Perfused Liver reveals two 25-ydroxylases Suda et al. (1977) Vitamin D: Biochemical, Chemical and Clinical Aspects Related to Calcium Metabolism

7 CYP2R1 LIVER MICROSOMAL VITAMIN D 25-YDROXYLASE SUBSTRATES INCLUDE VITAMINS D 3 & D 2 & ANTICANCER PRODRUGS (eg 1α-O-D 2 ) MUTATION IN hcyp2r1 AT L99P CAUSES RICKETS WORKS AT NANOMOLAR SUBSTRATE & PROBABLY TE PYSIOLOGICALLY RELEVANT VIT.D-25-YDROXYLASE SGC (TORONTO) CRYSTALLISED A FUNCTIONAL UMAN CYP2R1 WIT VITAMIN D 3 IN ACTIVE SITE

8 25-ydroxylation of 1a-O-D 2 by Mouse cyp2r1 1a-O-D 2 1a,25-(O) 2 D 2

9 1α-O-D 2 in CYP2R1 11α-O-D 2 1α,25-(O) 2 D 2 From : Strushkevich N, Usanov SA, Plotnikov AN, Jones G, Park -W (2008) Structural Analysis of CYP2R1 in complex with vitamin D 3. J Mol Biol 380:

10 Perfused Liver reveals two 25-ydroxylases CYP2R1 CYP27A1 CYP3A4 Suda et al. (1977) Vitamin D: Biochemical, Chemical and Clinical Aspects Related to Calcium Metabolism

11 Metabolism of Vitamin D 3 C 3 C3 C 3 C3 C3 C3 C 2 CYP27A1 CYP2R1 Liver O O O O Vitamin D 3 25-O-D 3 C 2 CYP27B1 Kidney O C 2 1α,25-(O) 2 D 3 Calcitriol O Similar pathway exists for vitamin D 2

12 CYP27B1 KIDNEY MITOCONDRIAL 1α-YDROXYLASE SUBSTRATES INCLUDE 25-O-D 3 & 25-O-D 2 MUTATIONS IN hcyp27b1 CAUSE VDDR-RICKETS TYPE 1 PROBES & ANTIBODIES REVEAL PRESENCE OF CYP27B1 IN EXTRA-RENAL TISSUES eg SKIN, MONOCYTE REGULATION DIFFERENT IN DIFFERENT TISSUES: A) KIDNEY CYP27B1 PT & FGF-23; Ca & PO 4 B) EXTRA-RENAL CYP27B1 -- CYTOKINES

13 ? Janssens W et al (2009) Am J Respir Crit Care Med 179:630-6.

14 CYP27B1 KIDNEY MITOCONDRIAL 1α-YDROXYLASE SUBSTRATES INCLUDE 25-O-D 3 & 25-O-D 2 MUTATIONS IN hcyp27b1 CAUSE VDDR-RICKETS TYPE 1 PROBES & ANTIBODIES REVEAL PRESENCE OF CYP27B1 IN EXTRA-RENAL TISSUES eg SKIN, MONOCYTE REGULATION DIFFERENT IN DIFFERENT TISSUES: A) KIDNEY CYP27B1 PT & FGF-23; Ca & PO 4 B) EXTRA-RENAL CYP27B1 -- CYTOKINES

15 Plasma Calcium omeostasis Thyroid

16 CENTRAL ROLE OF FGF23 IN POSPATE & VITAMIN D OMEOSTASIS FGF23 24,25-(O) 2 D 3 + CYP24A1 AUSSLER, M U. ARIZONA, 2009 Roles of FGF23 1) Increase PO 4 excretion 2) Decrease CYP27B1 3) Increase CYP24A1 & NET INCREASE IN D CATABOLISM

17 CYP24A1 MITOCONDRIAL 25-O-D 24-YDROXYLASE IN KIDNEY AND ALL TARGET CELLS SUBSTRATES INCLUDE 25-O-D 3 & 1α,25-(O) 2 D 3 & CYP24 IS A MULTICATALYTIC ENZYME INDUCED BY 1α,25-(O) 2 D 3 & FGF-23 IN TARGET CELLS CYP24A1 KNOCKOUT MOUSE SOWS 50% LETALITY MAJOR ROLE IS CATABOLIC AND EXISTS TO ATTENUATE ACTION OF CALCITRIOL INSIDE TARGET CELLS

18 C 3 C 3 C 2 Metabolism of Vitamin D C 3 C 3 O C 3 C 3 BILE COO O Vitamin D 3 O CYP27A1 CYP2J3 CYP2R1 CYP3A4 Liver O C 2 CYP24 O 1a,24,25-(O) 3 D 3 O C 2 O Calcitroic Acid C 3 C 3 C 3 C 3 O O O O C 2 O C 2 O 25-O-D 3 1a,25-(O) 2 D 3 CYP24 C 3 C 3 C 2 24,25-(O) 2 D 3 CYP27B1 Kidney O O O C 3 C 3 C 2 O O O CYP24 O C 3 C 3 C 2 1a,23,25-(O) 3 D 3 1a,25-(O) 2 D 3-26,23- lactone Prosser and Jones (2004) Trends in Biochemical Sciences 29: O O? O O

19 CYP24 IS INDUCED BY ITS SUBSTRATE 1a,25-(O) 2 D hydroxylase CYP24 Calcitroic Acid Transcriptional up-regulation Kidney Liver CYP24 mrna β-actin mrna

20 [ 3 ] as 1a,25-(O) 2 D 3 (CPM) [ 3 ]1a,25-(O) 2 D 3 in Blood of Wild type and Cyp24-XO Mice CYP CYP24-XO-Blood Wild type Time (hours) Masuda et al Endocrinology, 2005

21 Blood Vessel Vitamin D Target Cell RXR/VDR Nucleus RNA Polymerase 1a,25-(O) 2 D 3 VDRE Vitamin D-dependent gene DBP VDR Calcitroic Acid CYP24

22 Vitamin D Endocrine & Intracrine System liver Vitamin D 3 CYP27A1 Nucleus kidney megalin/ cubulin Nucleus 25-O-D 3 1a,25-(O) 2 D 3 Calcitroic acid DBP Megalin/cubulin vitamin D-dependent genes RXR/VDR VDRE mrna extra-renal 1a-hydroxylating target cells Jones G (2008) Pharmacokinetics of Vitamin D Toxicity. Amer J Clin Nutr 88: 582S-586S. p21 cytokines calbindins vitamin D-dependent genes RXR/VDR VDRE mrna normal target cells p21 osteopontin calbindins

23 Vitamin D Metabolism & Function Objectives: Review current knowledge of Vitamin D Metabolism - New information about the cytochrome P450s involved - Concept of extra-renal 1α-hydroxylase Review the classical and non-classical roles of Vitamin D - Importance of calcitriol in VDR-mediated gene expression Implications of vitamin D renaissance for physicians - Serum 25-O-D assay as a Biomarker for vitamin D status - Vitamin D Deficiency may underlie several major diseases - Vitamin D Supplementation

24 Mechanism of Action of Vitamin D

25 olick M (2006) Mayo Clin Proc 81:

26 MCF-7 ERa(+) 49 Microarray Analysis of Calcitriol Treatment Breast Cancer Cells 19 Cell Cycle/Apoptosis 3 DNA Repair 6 Cell Adhesion 7 Growth/Immune Mod. 2 Steroid Receptors 2 Oncogenes 8 Others Rb2 TGFb2 RAB5A Integrin av Thioredoxin Red. CYP24 VDR 2 Cell Adhesion 5 Cell Cycle/Apoptosis MB231 ERa(-) 2 Growth/Immune Mod. 1 Steroid Receptors 1 Oncogene 3 Trans Factors/Kinases 16 3 Cell Adhesion 2 Cell Cycle/Apoptosis 5 Growth/Immune Mod Steroid Receptors 3 Kinases 4 Other Swami et al., (2003) Breast Cancer Res. Treat. 80: BRCA2 3 Cell Adhesion 2 Growth Factors 4 Metalloproteinases 1 Kinase 4 Other Gene Probes

27 Calcitriol blocks prostaglandin pathways

28

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30 Relative risk of Colon Cancer vs Serum 25-O-D KDOQI >30 ng/ml 50% Risk

31 Am J Clin Nutr 2007; 85: WOMEN FOLLOWED 5 YR Ca = 1400 mg/d VITAMIN D = 1100 IU/d BLOOD 25-O-D level Ca+D = nmol/l Ca ONLY = 71 nmol/l PLACEBO = 71 nmol/l

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33 environment TNF-a IL-1 APC (DC) MC-II CD80/86 IL-12 b MC-I IL-1 TNF-a IFN-g Free radical (O 2-, NO) CD40 CD40L CD4 TCR CD28/CTLA-4 Th1 IL-4 IL-10 CD8 TCR Fas FasL Mø Mø Th1 Th1 Th2 IFN-g Tc Tc genetic predispostion IL-2 C. Gysemans

34 25(O)D 3 1αOase Mon/Mf Antimicrobial response Chemotaxis Phagocytosis Cathelicidin Defensin beta4 Reactive oxigen species IL-12 IL-6 TNF-α IL-23 1αOase DC 25(O)D 3 IL-10 CCL22 CD40 MC II CD80/86 Ag target tissue 1,25(O) 2 D 3 TCR CD40L CD28 CD4+T IL-1 IL-6 TNF-a 1αOase Tc Mf IFN-g IL-2 Th1 Th1 Th1 Th2 Th2 Th2 IL-4 IL-5 IL-13 N IL-17 Th17 Th17 Treg Treg IL-10 TGF-b CANTAL MATIEU, U OF LEUVEN, 2009

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36 OLICK Vitamin D Deficiency-NEJM 357: (July )

37 Evidence of a role for 1,25-(O) 2 D in Skin C 3 C 3 O C 2 O O

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39 1,25-(O) 2 D & Renin-Angiotensin System 1,25(O) 2 D functions directly and negatively as a novel endocrine regulator of the renin-angiotensin system in vivo and in vitro 1,25(O) 2 D markedly suppresses renin transcription by VDR-mediated mechanism in cell cultures and animal models VDR-Knockout animal studies demonstrate the importance of maintaining normal serum levels of 1,25(O) 2 D for proper homeostasis of calcium, electrolytes, volume, and blood pressure VDR VDR -/- -/- VDR Li, Yan Chun, Kong, J, The Journal of Clinical Investigation, 2002, Vol. 110, No. 2

40 LOWEST 25-O-D LOWEST 25-O-D

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42 1,25-(O) 2 D & Muscle Differentiation 100 Counts 13.8+/-6.2mm Mean +/- SD VDR -/- Muscle Fiber Diameter Counts /-4.4mm Mean +/- SD VDR +/ Protein Expression VDR -/- VDR +/+ Myf5 E2A Myogenin MyoD MRF4

43 Vitamin D Metabolism & Function Objectives: Review current knowledge of Vitamin D Metabolism - New information about the cytochrome P450s involved - Concept of extra-renal 1α-hydroxylase Review the classical and non-classical roles of Vitamin D - Importance of calcitriol in VDR-mediated gene expression Implications of vitamin D renaissance for physicians - Serum 25-O-D assay as a Biomarker for vitamin D status - Vitamin D Deficiency may underlie several major diseases - Vitamin D Supplementation

44 Prevention and treatment of vitamin D insufficiency and vitamin D deficiency in CKD patients.. SUGGESTED TRESOLD = 30 ng/ml or 75 nmol/l Deficiency Insufficiency Sufficiency Toxicity Vitamin D intoxication at 25-O-D >250 ng/ml K/DOQI Adapted from ollis Plasma 25-O-D ng/ml

45 at Latitude 59º N Deficiency Insufficiency Sufficiency (Jan-Mar) (Sep) 17.6 ng/ml 23.6 ng/ml

46 CORRECTION OF 25-O-D INSUFFICIENCY INCREASED UV EXPOSURE - OPPOSED BY DERMATOLOGISTS FOOD FORTIFICATION - MOST FOODS POOR IN VITAMIN D (except SALMON) - FORTIFICATION VARIES WIT STATE--- Dairy Products - MILK INTOLERANCE & DOSAGE ISSUES ORAL VITAMIN D SUPPLEMENTS - PRESCRIPTION-VIT. D 2 in US (Drisdol)- 50,000 IU/dose - OTC VITAMIN PILLS-CURRENT DRI IU/day - OTC DIETARY D 3 SUPPLEMENTS IN USE IU - NATIONAL ACADEMY OF SCIENCE- NEW DRI-FALL 2010

47 TAVERA-MENDOZA & WITE, Sci Am pp (Nov 2007)

48 Sources of Vitamin D Sun (April to October) Diet (Dairy &Fish)

49 Summary The Vitamin D Metabolic Machinery is series of CYPs operating in a well-integrated Endocrine-Intracrine system 1α,25-(O) 2 D has many varied classical and non-classical roles around the body Emergence of extra-renal 1α-hydroxylase emphasizes the value of serum 25-O-D assay as a tool to monitor vitamin D status Much interest in determining the underlying importance of vitamin D deficiency/insufficiency in various common diseases Vitamin D Supplementation should be considered

50 Reviews at Jones G, Strugnell S and DeLuca F (1998) Current understanding of the molecular actions of vitamin D. Physiological Reviews 78: Prosser DE & Jones G (2004) Enzymes involved in the activation and inactivation of vitamin D. Trends in Biochemical Sciences 29: Masuda S & Jones G (2006) The promise of vitamin D analogs in the treatment of hyperproliferative conditions. Molecular Cancer Therapeutics 5: Jones G (2007) Expanding role for vitamin D in chronic kidney disease. Seminars in Dialysis 20: Jones G, orst RL, Carter G, Makin LJ (2007). Contemporary Diagnosis and Treatment of Vitamin D-related Disorders. J Bone Mineral Res 22(Suppl. 2):V11-V15. Jones G (2008) Pharmacokinetics of Vitamin D Toxicity. Amer J Clin Nutr 88 (Suppl.): 582S-586S.