title: High vitamin D status before conception, but not during pregnancy, is inversely associated with maternal gestational diabetes mellitus in guinea pigs.
abstract: BACKGROUND
  Whether there is a dose-dependent effect of maternal dietary cholecalciferol during pregnancy on maternal glucose tolerance is unknown. In addition, circulating osteocalcin is increased by 1,25-dihydroxyvitamin D [1,25(OH)2D] and may improve glucose homeostasis.
  
  
  OBJECTIVE
  This study was designed to test whether dietary cholecalciferol during pregnancy dose-dependently affects maternal glucose tolerance and maternal and neonatal glucose concentrations in relation to plasma osteocalcin and body composition.
  
  
  METHODS
  Female guinea pigs (n = 45; 4 mo old) were randomly assigned to 5 doses of cholecalciferol (0, 0.25, 0.5, 1, or 2 IU/g diet) fed from mating to delivery. Plasma vitamin D metabolites, minerals, and osteocalcin, and blood glucose were measured before mating, at midgestation (day 42), and at day 2 postpartum in sows and in 2-d-old pups. At day 50 of pregnancy (early third trimester), a 3-h oral-glucose-tolerance test (OGTT) (2 g/kg) was conducted. Body composition was measured before mating and at day 2 postpartum in sows and in pups.
  
  
  RESULTS
  A positive dose-response to dietary cholecalciferol was observed for change in maternal plasma 25-hydroxyvitamin D [25(OH)D] through pregnancy (P < 0.0001), with 1,25(OH)2D increasing by 198% in the 1-IU/g group by midgestation vs. a reduction of 43.6% in the 0-IU/g group (P = 0.05). Twenty-four (54.5%) sows had gestational diabetes mellitus (GDM) on the basis of nonfed glucose and 39 (88.6%) had GDM on the basis of 2-h OGTT glucose concentrations. There were no group differences in maternal OGTT or changes in glucose, minerals, osteocalcin concentrations, and body composition. Pre-mating 25(OH)D was inversely related to 3-h area under the curve for blood glucose from the OGTT (r = -0.31, P = 0.05). In guinea pig pups, although both 25(OH)D (P < 0.0001) and 1,25(OH)2D (P < 0.0001) followed a dose-response to maternal diet, glucose, osteocalcin, minerals, and body composition were not altered.
  
  
  CONCLUSIONS
  Dietary vitamin D intake during pregnancy in guinea pigs does not affect the already high rate of GDM, whereas higher prepregnancy vitamin D status appears to be protective.
authors.affiliation: School of Dietetics and Human Nutrition, McGill University, Ste-Anne-de-Bellevue, Canada;
authors.forename: Negar
authors.initials: N
authors.lastname: Tabatabaei
authors.affiliation: Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, Canada; and.
authors.forename: Celia J
authors.initials: CJ
authors.lastname: Rodd
authors.affiliation: Faculty of Medicine, Faculty of Dentistry, Calcium Research Laboratory, McGill University, Montreal, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Kremer
authors.affiliation: School of Dietetics and Human Nutrition, McGill University, Ste-Anne-de-Bellevue, Canada; hope.weiler@mcgill.ca.
authors.forename: Hope A
authors.initials: HA
authors.lastname: Weiler
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition / Q000187:drug effects; D002118:Calcium / Q000097:blood; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000097:blood*; D016640:Diabetes, Gestational / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005951:Glucose Tolerance Test; D006168:Guinea Pigs; D039382:Maternal Nutritional Physiological Phenomena; D015675:Osteocalcin / Q000097:blood; D011247:Pregnancy; D012098:Reproduction / Q000187:drug effects
chemical_list: D001786:Blood Glucose; D015675:Osteocalcin; D002762:Cholecalciferol; D002118:Calcium
keywords: Vitamin D; dose-response; gestational diabetes; guinea pig; pregnancy