Bone Abstracts

Mutations in the PHEX gene cause X-linked familial hypophosphatemic rickets (XLH) with severe bone (osteomalacia) and tooth abnormalities being the distinguishing features of this disease. The PHEX mutations lead to an increase in ASARM peptides (acidic serine- and aspartate-rich motif) and osteopontin fragments which inhibit bone extracellular matrix mineralization. MEPE-derived ASARM has been shown to accumulate in tooth dentin of patients with XLH where it may impair dentin...

ASARM peptide (acidic, serine- and aspartate-rich motif) and osteopontin (OPN) fragments accumulate in X-linked hypophosphatemia patients and/or in the Hyp mouse model and, when phosphorylated, potently inhibit mineralization in osteoblast cultures. To investigate this inhibition, we modeled the binding to hydroxyapatite of the human OPN-ASARM peptide (DDSHQSDESHHSDESDEL) using RosettaSurface computational simulations. Peptide binding to hydroxyapatite atomic planes constructe...

Proprotein convertase PC5/6 (Pcsk5) is expressed in mouse bone and Pcsk5 epiblast-specific conditional knockout mice have a bone phenotype displaying small size, delayed ossification and additional thoracic segments and ribs. Some features are attributed to growth and developmental factor 11 (GDF11) – a known substrate for PC5/6 – while the delayed mineralization has yet to be explained. Osteopontin (OPN) is a bone matrix protein with roles in miner...

Fibroblast growth factor-23 (FGF23) is a major regulator of phosphate metabolism often elevated in genetic hypophosphataemic disorders and in chronic kidney disease–bone mineral disorder (CKD–BMD). Recent studies have identified relationships between FGF23 and vitamin D.Objectives: To determine the relationship between vitamin D and FGF23 metabolism in CKD.Method: We used randomized samples from patient...

Supported by Alexion & IDS)-->Low vitamin D serum levels have been associated with a considerable number of diseases and conditions and have attracted significant attention of the scientific community as well as of health authorities all over the world. However, discussions and controversies are ongoing about the reliability, significance and correct ranges of low vitamin D serum levels. A central goa...

Introduction and aim: Vitamin D plays an important role in bone growth. In children, low levels can cause rickets. In adults, low levels can lead to osteoporosis and fragility fractures. The aim of this survey was to get information about vitamin D levels in Lebanese population.Subjects and methods: Serum 25-hydroxy vitamin D level is considered to be the best indicator of vitamin D status. 13 000 subjects included in this study were coming for routine c...

Background: Vitamin D plays an important role in calcium and phosphate homeostasis. Circulating 25 hydroxyvitamin D [25(OH)D] is metabolised into its biologically active form 1,25-dihydroxyvitamin D [1,25-d(OH)D] by the actions of 1α hydroxylase, and into inactive 2metabolite 24,25-dihydroxyvitamin D [24,25-d(OH)D] by 24-hydroxylase. Recent studies suggest the production of 1,25-d(OH)D) from 25(OH)D is 24,25-d(OH)D dependent. Genetic mutations of CYP24A1 gene resulting in...

In Canada, and many other countries, a vitamin D supplement of 400 IU/day is recommended for breastfed infants and staple foods are fortified with vitamin D in accordance with public health policy for the primary prevention of rickets. Both vitamin D receptors and 1-alpha hydroxylase enzymes are expressed in human muscle, implicating vitamin D status and metabolism in growth and development. In a randomized dose response study of vitamin D supplementation (400, 800, 1200, or 1...

Vitamin D deficiency in pregnancy is common, and is linked to increased risk of adverse outcomes including preterm birth, preeclampsia, infection, gestational diabetes and asthma. Vitamin D possesses well-recognized immunomodulatory functions, and programming of the immune system during foetal development can influence asthma-related risk factors and health outcomes in later life. We hypothesized that influencing vitamin D status during pregnancy would impact the immune profil...

Objectives: Vitamin D intake at a dose 400 IU/d is recommended for breastfed infants and is considered as sufficient. Vitamin D status is connected with bone mass and fat mass. We aimed to assess, if 400 IU/d has the same efficiency and impact on body composition in infants with different vitamin D status at birth (<20 ng/ml vs ≧20 ng/ml).Methods: 148 breastfed infants were supplemented with 400 IU/d of cholecalciferol up to 6 months of age. S...