1
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Nygaard RH, Lauritzen ES, Sikjær T, Højskov CS, Rejnmark L, Møller HJ. Unmeasurable low vitamin D levels caused by a novel, homozygote loss-of-function variant in the group-specific component gene. Eur J Endocrinol 2024; 190:K53-K56. [PMID: 38788201 DOI: 10.1093/ejendo/lvae061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 04/12/2024] [Accepted: 05/23/2024] [Indexed: 05/26/2024]
Abstract
A 29-year-old female, born to consanguineous parents, was found with unmeasurable levels of vitamin D (<10 nmol/L) after routine biochemical screening during her first pregnancy. She did not respond to either oral or intramuscular vitamin D supplementation and was an otherwise healthy young woman, with no signs of rickets, osteomalacia, osteoporosis, or secondary hyperparathyroidism. Western blot analysis revealed total lack of vitamin D binding protein, and next generation sequencing confirmed a novel, pathogenic homozygote loss-of-function mutation in exon 13 of the group-specific component gene, that encodes the poly A tail for vitamin D binding protein. She was therefore diagnosed with hereditary DBP deficiency, and vitamin D supplementation was diminished to life-long regular vitamin D supplementation (25 μg per day). This case is extremely interesting, as it expands our knowledge of vitamin D physiology and supports the free hormone hypothesis, given that the patient was asymptomatic despite no measurable levels of vitamin D.
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Affiliation(s)
- Rie Harboe Nygaard
- Department of Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Esben Stistrup Lauritzen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Internal Medicine, Horsens Regional Hospital, 8700 Horsens, Denmark
| | - Tanja Sikjær
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Internal Medicine, Horsens Regional Hospital, 8700 Horsens, Denmark
| | | | - Lars Rejnmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Holger Jon Møller
- Department of Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark
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2
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Al Masseri Z, Alqahtani M, Almoshawer E, Alkuraya FS. Vitamin D-binding protein deficiency: an underrecognized Mendelian disorder of vitamin D metabolism. Hum Genet 2024; 143:101-105. [PMID: 38265561 DOI: 10.1007/s00439-023-02632-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 12/18/2023] [Indexed: 01/25/2024]
Abstract
Vitamin D-binding protein (VDBP) deficiency is a recently discovered apparently benign biochemical disorder that can masquerade as treatment-resistant vitamin D deficiency and is likely underrecognized. We present the case of a child with persistently low 25OH vitamin D levels despite replacement therapy. Exome sequencing revealed a novel homozygous nonsense variant in the GC gene, leading to undetectable levels of VDBP. Interestingly, exome sequencing also revealed a homozygous loss-of-function variant in ZNF142, which likely explains the additional clinical features of recurrent febrile convulsions and global developmental delay. Our findings corroborate the two previously reported patients with autosomal recessive VDBP deficiency caused by biallelic GC variants and emphasize the importance of measuring VDBP levels in cases of apparent vitamin D deficiency that is treatment-resistant. We also urge caution in concluding "atypical" presentations without careful investigation of a potential dual molecular diagnosis.
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Affiliation(s)
- Zainab Al Masseri
- Department of Pediatric, Medical Genetics Unit, Qatif Central Hospital, Eastern Health Cluster, Ministry of Health, Riyadh, Saudi Arabia.
| | - Mashael Alqahtani
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Eman Almoshawer
- Department of Dermatology, Qatif Central Hospital, Eastern Health Cluster, Ministry of Health, Riyadh, Saudi Arabia
| | - Fowzan S Alkuraya
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
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3
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Albiñana C, Zhu Z, Borbye-Lorenzen N, Boelt SG, Cohen AS, Skogstrand K, Wray NR, Revez JA, Privé F, Petersen LV, Bulik CM, Plana-Ripoll O, Musliner KL, Agerbo E, Børglum AD, Hougaard DM, Nordentoft M, Werge T, Mortensen PB, Vilhjálmsson BJ, McGrath JJ. Genetic correlates of vitamin D-binding protein and 25-hydroxyvitamin D in neonatal dried blood spots. Nat Commun 2023; 14:852. [PMID: 36792583 PMCID: PMC9932173 DOI: 10.1038/s41467-023-36392-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 01/30/2023] [Indexed: 02/17/2023] Open
Abstract
The vitamin D binding protein (DBP), encoded by the group-specific component (GC) gene, is a component of the vitamin D system. In a genome-wide association study of DBP concentration in 65,589 neonates we identify 26 independent loci, 17 of which are in or close to the GC gene, with fine-mapping identifying 2 missense variants on chromosomes 12 and 17 (within SH2B3 and GSDMA, respectively). When adjusted for GC haplotypes, we find 15 independent loci distributed over 10 chromosomes. Mendelian randomization analyses identify a unidirectional effect of higher DBP concentration and (a) higher 25-hydroxyvitamin D concentration, and (b) a reduced risk of multiple sclerosis and rheumatoid arthritis. A phenome-wide association study confirms that higher DBP concentration is associated with a reduced risk of vitamin D deficiency. Our findings provide valuable insights into the influence of DBP on vitamin D status and a range of health outcomes.
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Affiliation(s)
- Clara Albiñana
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
| | - Zhihong Zhu
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
| | - Nis Borbye-Lorenzen
- Center for Neonatal Screening, Department of Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Sanne Grundvad Boelt
- Center for Neonatal Screening, Department of Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
- Clinical Mass Spectrometry, Statens Serum Institut, Artillerivej 5, DK-2300, Copenhagen S, Denmark
| | - Arieh S Cohen
- Testcenter Denmark, Statens Serum Institut, Artillerivej 5, DK-2300, Copenhagen S, Denmark
| | - Kristin Skogstrand
- Center for Neonatal Screening, Department of Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Naomi R Wray
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
- Queensland Brain Institute, University of Queensland, Brisbane, QLD, Australia
| | - Joana A Revez
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Florian Privé
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
| | - Liselotte V Petersen
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
| | - Cynthia M Bulik
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Oleguer Plana-Ripoll
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
- Department of Clinical Epidemiology, Aarhus University and Aarhus University Hospital, 8200, Aarhus N, Denmark
| | - Katherine L Musliner
- Department of Affective Disorders, Aarhus University and Aarhus University Hospital-Psychiatry, Aarhus, Denmark
| | - Esben Agerbo
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- CIRRAU - Centre for Integrated Register-based Research, Aarhus University, Aarhus, Denmark
| | - Anders D Børglum
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- Center for Genomics and Personalized Medicine, Aarhus University, Aarhus, Denmark
- Department of Biomedicine and the iSEQ Center, Aarhus University, Aarhus, Denmark
| | - David M Hougaard
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- Department for Congenital Disorders, Statens Serum Institut, 2300, Copenhagen S, Denmark
| | - Merete Nordentoft
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- Mental Health Services in the Capital Region of Denmark, Mental Health Center Copenhagen, University of Copenhagen, 2100, Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, 2200, Copenhagen N, Denmark
| | - Thomas Werge
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- Institute of Biological Psychiatry, Mental Health Services, Copenhagen University Hospital, Copenhagen N, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
- Lundbeck Center for Geogenetics, GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Preben Bo Mortensen
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- CIRRAU - Centre for Integrated Register-based Research, Aarhus University, Aarhus, Denmark
| | - Bjarni J Vilhjálmsson
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, 8210, Aarhus V, Denmark
- Bioinformatics Research Centre, Aarhus University, 8000, Aarhus C, Denmark
| | - John J McGrath
- National Centre for Register-Based Research, Aarhus University, 8210, Aarhus V, Denmark.
- Queensland Brain Institute, University of Queensland, Brisbane, QLD, Australia.
- Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Brisbane, QLD, 4076, Australia.
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4
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Viloria K, Nasteska D, Ast J, Hasib A, Cuozzo F, Heising S, Briant LJB, Hewison M, Hodson DJ. GC-Globulin/Vitamin D-Binding Protein Is Required for Pancreatic α-Cell Adaptation to Metabolic Stress. Diabetes 2023; 72:275-289. [PMID: 36445949 DOI: 10.2337/db22-0326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 11/14/2022] [Indexed: 12/02/2022]
Abstract
GC-globulin (GC), or vitamin D-binding protein, is a multifunctional protein involved in the transport of circulating vitamin 25(OH)D and fatty acids, as well as actin scavenging. In the pancreatic islets, the gene encoding GC, GC/Gc, is highly localized to glucagon-secreting α-cells. Despite this, the role of GC in α-cell function is poorly understood. We previously showed that GC is essential for α-cell morphology, electrical activity, and glucagon secretion. We now show that loss of GC exacerbates α-cell failure during metabolic stress. High-fat diet-fed GC-/- mice have basal hyperglucagonemia, which is associated with decreased α-cell size, impaired glucagon secretion and Ca2+ fluxes, and changes in glucose-dependent F-actin remodelling. Impairments in glucagon secretion can be rescued using exogenous GC to replenish α-cell GC levels, increase glucagon granule area, and restore the F-actin cytoskeleton. Lastly, GC levels decrease in α-cells of donors with type 2 diabetes, which is associated with changes in α-cell mass, morphology, and glucagon expression. Together, these data demonstrate an important role for GC in α-cell adaptation to metabolic stress.
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Affiliation(s)
- Katrina Viloria
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Daniela Nasteska
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Julia Ast
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Annie Hasib
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Federica Cuozzo
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Silke Heising
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Linford J B Briant
- Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Radcliffe Department of Medicine, University of Oxford, Oxford, U.K
| | - Martin Hewison
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
- Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Radcliffe Department of Medicine, University of Oxford, Oxford, U.K
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5
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Narinx N, David K, Walravens J, Vermeersch P, Claessens F, Fiers T, Lapauw B, Antonio L, Vanderschueren D. Role of sex hormone-binding globulin in the free hormone hypothesis and the relevance of free testosterone in androgen physiology. Cell Mol Life Sci 2022; 79:543. [PMID: 36205798 DOI: 10.1007/s00018-022-04562-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 08/12/2022] [Accepted: 09/17/2022] [Indexed: 11/03/2022]
Abstract
According to the free hormone hypothesis, biological activity of a certain hormone is best reflected by free rather than total hormone concentrations. A crucial element in this theory is the presence of binding proteins, which function as gatekeepers for steroid action. For testosterone, tissue exposure is governed by a delicate equilibrium between free and total testosterone which is determined through interaction with the binding proteins sex hormone-binding globulin and albumin. Ageing, genetics and various pathological conditions influence this equilibrium, hereby possibly modulating hormonal exposure to the target tissues. Despite ongoing controversy on the subject, strong evidence from recent in vitro, in vivo and human experiments emphasizes the relevance of free testosterone. Currently, however, clinical possibilities for free hormone diagnostics are limited. Direct immunoassays are inaccurate, while gold standard liquid chromatography with tandem mass spectrometry (LC-MS/MS) coupled equilibrium dialysis is not available for clinical routine. Calculation models for free testosterone, despite intrinsic limitations, provide a suitable alternative, of which the Vermeulen calculator is currently the preferred method. Calculated free testosterone is indeed associated with bone health, frailty and other clinical endpoints. Moreover, the added value of free testosterone in the clinical diagnosis of male hypogonadism is clearly evident. In suspected hypogonadal men in whom borderline low total testosterone and/or altered sex hormone-binding globulin levels are detected, the determination of free testosterone avoids under- and overdiagnosis, facilitating adequate prescription of hormonal replacement therapy. As such, free testosterone should be integrated as a standard biochemical parameter, on top of total testosterone, in the diagnostic workflow of male hypogonadism.
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Affiliation(s)
- N Narinx
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Herestraat 49, ON1bis box 902, 3000, Leuven, Belgium.,Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
| | - K David
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Herestraat 49, ON1bis box 902, 3000, Leuven, Belgium.,Department of Endocrinology, University Hospitals Leuven, Leuven, Belgium
| | - J Walravens
- Department of Internal Medicine and Pediatrics, Ghent University, Ghent, Belgium
| | - P Vermeersch
- Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
| | - F Claessens
- Laboratory of Molecular Endocrinology, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - T Fiers
- Department of Laboratory Medicine, Ghent University Hospital, Ghent, Belgium
| | - B Lapauw
- Department of Internal Medicine and Pediatrics, Ghent University, Ghent, Belgium.,Department of Endocrinology, Ghent University Hospital, Ghent, Belgium
| | - L Antonio
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Herestraat 49, ON1bis box 902, 3000, Leuven, Belgium.,Department of Endocrinology, University Hospitals Leuven, Leuven, Belgium
| | - D Vanderschueren
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Herestraat 49, ON1bis box 902, 3000, Leuven, Belgium. .,Department of Endocrinology, University Hospitals Leuven, Leuven, Belgium.
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6
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Moon RJ, Cooke LDF, D’Angelo S, Curtis EM, Titcombe P, Davies JH, Godfrey KM, Cleal JK, Lewis RM, Cooper C, Harvey NC. Maternal and Fetal Genetic Variation in Vitamin D Metabolism and Umbilical Cord Blood 25-Hydroxyvitamin D. J Clin Endocrinol Metab 2022; 107:e3403-e3410. [PMID: 35474389 PMCID: PMC9282354 DOI: 10.1210/clinem/dgac263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Indexed: 11/19/2022]
Abstract
CONTEXT Single nucleotide polymorphisms (SNPs) in vitamin D metabolism pathway genes are associated with circulating 25-hydroxyvitamin D (25(OH)D) in adults. Less is known about the relationships between mother and offspring SNPs and umbilical cord blood 25(OH)D. OBJECTIVE (1) To undertake a meta-analysis of the relationships of maternal and offspring SNPs in the vitamin D metabolism pathway and cord blood 25(OH)D in pregnant women including novel data; and (2) to examine these relationships in women who received antenatal cholecalciferol supplementation in a clinical trial. METHODS Novel data analysis from an observational mother-offspring cohort study (Southampton Women's Survey) and the MAVIDOS double-blind, randomized, placebo-controlled trial of 1000 IU/day cholecalciferol supplementation in pregnancy, and an electronic literature search of published studies in PubMed up to 31 July 2021. Studies reporting associations between rs12785878 (DHCR7), rs10741657 (CYP2R1), rs6013897 (CYP24A1), or rs2282679 (GC) and cord blood 25(OH)D. One published study was included in addition to the novel data analysis. Associations between both maternal and offspring SNPs at rs2282679 (GC) and rs12785878 (DHCR7), and cord blood 25(OH)D were identified. When maternal genotype was adjusted for offspring genotype, and vice versa, there was persisting evidence for associations with maternal rs12785878 (β [95% CI] 1.6 nmol/L [0.3, 2.8] per common allele), and offspring rs2282679 (β 3.1 nmol/L ]2.0, 4.4] per common allele). Maternal and offspring SNPs at rs1074657 and rs613897 were not associated with cord blood 25(OH)D. RESULT Associations between both maternal and offspring SNPs at rs2282679 (GC) and rs12785878 (DHCR7), and cord blood 25(OH)D were identified. When maternal genotype was adjusted for offspring genotype, and vice versa, there was persisting evidence for associations with maternal rs12785878 (β [95% CI] 1.6 nmol/L [0.3, 2.8] per common allele), and offspring rs2282679 (β 3.1 nmol/L ]2.0, 4.4] per common allele). Maternal and offspring SNPs at rs1074657 and rs613897 were not associated with cord blood 25(OH)D. CONCLUSION Common genetic variation in the vitamin D metabolism pathway is associated with umbilical cord blood 25(OH)D.
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Affiliation(s)
- Rebecca J Moon
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
- Paediatric Endocrinology, Southampton Children’s Hospital, Southampton University Hospitals NHS Foundation Trust, Southampton,UK
| | - Laura D F Cooke
- The Institute of Developmental Sciences, Human Development and Health, Faculty of Medicine, University of Southampton, Southampton,UK
| | - Stefania D’Angelo
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
| | - Elizabeth M Curtis
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
| | - Philip Titcombe
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
| | - Justin H Davies
- Paediatric Endocrinology, Southampton Children’s Hospital, Southampton University Hospitals NHS Foundation Trust, Southampton,UK
| | - Keith M Godfrey
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
- NIHR Southampton Nutrition Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton,UK
| | - Jane K Cleal
- The Institute of Developmental Sciences, Human Development and Health, Faculty of Medicine, University of Southampton, Southampton,UK
| | - Rohan M Lewis
- The Institute of Developmental Sciences, Human Development and Health, Faculty of Medicine, University of Southampton, Southampton,UK
| | - Cyrus Cooper
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
- NIHR Southampton Nutrition Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton,UK
- National Institute for Health Research (NIHR) Musculoskeletal Biomedical Research Unit, University of Oxford, UK
| | - Nicholas C Harvey
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton,UK
- NIHR Southampton Nutrition Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton,UK
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7
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Banerjee RR, Spence T, Frank SJ, Pandian R, Hoofnagle AN, Argiropoulos B, Marcadier JL. Very Low Vitamin D in a Patient With a Novel Pathogenic Variant in the GC Gene That Encodes Vitamin D-Binding Protein. J Endocr Soc 2021; 5:bvab104. [PMID: 34589658 PMCID: PMC8362819 DOI: 10.1210/jendso/bvab104] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Indexed: 12/18/2022] Open
Abstract
Circulating plasma vitamin D metabolites are highly bound to vitamin D-binding protein
(DBP), also known as group-specific component or
Gc-globulin. DBP, encoded by the GC gene, is a member of the albumin
family of globular serum transport proteins. We previously described a homozygous
GC gene deletion in a patient with apparent severe vitamin D
deficiency, fragility fractures, and ankylosing spondylitis. Here, we report an unrelated
patient free of fractures or rheumatologic disease, but with very low 25-hydroxyvitamin D
and 1,25-hydroxyvitamin D, as well as undetectable DBP measured by liquid
chromatography–tandem mass spectrometry. A whole gene deletion was excluded by microarray,
and Sanger sequencing of GC revealed a homozygous pathogenic variant
affecting a canonical splice site (c0.702-1G > A). These findings indicate that loss of
function variants in GC that eliminate DBP, and severely reduced total
circulating vitamin D levels, do not necessarily result in significant metabolic bone
disease. Together with our previous report, these cases support the free-hormone
hypothesis, and suggest free vitamin D metabolites may serve as preferable indicators of
bone and mineral metabolism, particularly when clinical suspicion of DBP deficiency is
high.
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Affiliation(s)
- Ronadip R Banerjee
- Division of Endocrinology, Department of Medicine, University of Alabama at Birmingham School of Medicine, Birmingham, AL 35294, USA.,Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, AL 35233, USA
| | - Tara Spence
- Department of Genetics and Genomics, Alberta Precision Laboratories, Calgary, Alberta T3B 6A8, Canada
| | - Stuart J Frank
- Division of Endocrinology, Department of Medicine, University of Alabama at Birmingham School of Medicine, Birmingham, AL 35294, USA.,Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, AL 35233, USA
| | | | - Andrew N Hoofnagle
- Departments of Laboratory Medicine and Pathology, Kidney Research Institute, University of Washington, Seattle, WA 98195, USA
| | - Bob Argiropoulos
- Department of Genetics and Genomics, Alberta Precision Laboratories, Calgary, Alberta T3B 6A8, Canada
| | - Julien L Marcadier
- The University of Calgary, and the Division of Medical Genetics, Alberta Children's Hospitals, Calgary, Alberta T3B 6A8, Canada
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