title: Associations of serum vitamin D concentrations with obstetric glucose metabolism in a subset of the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study cohort.
abstract: OBJECTIVE
  To assess associations between maternal serum vitamin D concentration and glucose metabolism in a cohort of pregnant women living in an Australian subtropical environment.
  
  
  METHODS
  Cross-sectional assessment of 25-hydroxy vitamin D concentrations in 399 Hyperglycemia and Adverse Pregnancy Outcome ancillary study participants, treated at an obstetric teaching hospital in Brisbane, Australia. All patients underwent a blinded 75-g oral glucose tolerance test at 24-32 (target 28) weeks' gestation.
  
  
  RESULTS
  The mean (± standard deviation) fasting plasma glucose was 4.5 ± 0.4 mmol/l. Mean (± standard deviation) serum 25-hydroxy vitamin D was 132.5 ± 44.0 nmol/l. A difference of one standard deviation in maternal 25-hydroxy vitamin D was inversely related to fasting glucose (fasting glucose lower by 0.047 mmol/l, P=0.012) when assessed with multiple linear regression after adjusting for confounders. Maternal 25-hydroxy vitamin D correlated with β-cell function as estimated by the log-transformed homeostasis model assessment-β-cell function equation (r=0.131, P=0.009), but not with the homeostasis model assessment of insulin resistance.
  
  
  CONCLUSIONS
  An association between mid-gestational 25-hydroxy vitamin D and fasting glucose was confirmed in a largely normoglycaemic and vitamin D-replete pregnant population. The correlation between 25-hydroxy vitamin D and β-cell function suggests that vitamin D may influence glucose metabolism through this mechanism. Intervention studies are required to determine causality and the role of vitamin D replacement in deficient individuals.
authors.affiliation: Department of Internal Medicine, Royal Brisbane and Women's Hospital, Herston, Qld, Australia. donald.mcleod@gmail.com
authors.forename: D S A
authors.initials: DS
authors.lastname: McLeod
authors.forename: J V
authors.initials: JV
authors.lastname: Warner
authors.forename: M
authors.initials: M
authors.lastname: Henman
authors.forename: D
authors.initials: D
authors.lastname: Cowley
authors.forename: K
authors.initials: K
authors.lastname: Gibbons
authors.forename: H D
authors.initials: HD
authors.lastname: McIntyre
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D016640:Diabetes, Gestational / Q000097:blood / Q000209:etiology; D005215:Fasting / Q000097:blood; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D006943:Hyperglycemia / Q000209:etiology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000209:etiology*; D011256:Pregnancy Outcome; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications*
chemical_list: D001786:Blood Glucose; D014807:Vitamin D; C104450:25-hydroxyvitamin D