Vitamin D Deficiency in Guinea Pigs: Exacerbation of Bone Phenotype During Pregnancy and Disturbed Fetal Mineralization, with Recovery by 1,25(OH)2D3 Infusion or Dietary Calcium-Phosphate Supplementation

Abstract

Vitamin D (D) deficiency during human pregnancy appears to disturb fetal growth and mineralization, but fetal development is normal in D-deficient rats and vitamin D receptor gene-ablated mice. We used the guinea pig model to investigate maternal and fetal effects of D deficiency. Pregnant (Pr) and nonpregnant (NPr) animals were fed a D-replete (+D) or D-deficient diet (-D) for 8 weeks. We further studied whether the effects of a -D diet are reversed by continuous 1,25(OH)2D3 infusion (-D+1,25) and/or by a lactose-, Ca- and P-enriched D-deficient diet (-D+Ca/P). Bone analyses included histomorphometry of the proximal tibiae, dual-energy X-ray absorptiometry (DXA), and quantitative computed tomography (QCT) of the femora. Depletion of 25(OH)D3 and 1,25(OH)2D3 levels and the D-deficiency syndrome were more severe in pregnant animals. Indeed, Pr/-D but not NPr/-D guinea pigs were hypophosphatemic, and showed robust increases in growth plate width and osteoid surface and thickness; in addition, bone mineral density on DXA was lower in Pr/-D animals only, which was exclusively in cortical bone on QCT. Bone phenotype was partly normalized in Pr/-D+1,25 and Pr/-D+Ca/P animals. Compared with +D fetuses, -D fetuses had very low or undetectable 25(OH)D3 and 1,25(OH)2D3, were hypercalcemic and hypophosphatemic, and had lower osteocalcin levels. In addition, body weight and total body bone mineral content were 10-15% lower; histomorphometry showed hypertrophic chondrocyte zone expansion and hyperosteoidosis. 1,25(OH)2D3 levels were restored in -D+1,25 fetuses, and the phenotype was partially corrected. Similarly, the fetal +D phenotype was rescued in large part in -D+Ca/P fetuses, despite undetectable circulating 25(OH)D3 and 1,25(OH)2D3. We conclude that pregnancy markedly exacerbates D deficiency, and that augmenting Ca and P intake overrides the deleterious effects of D deficiency on fetal development.

Season of birth is associated with anthropometric and neurocognitive outcomes during infancy and childhood in a general population birth cohort

“…The presence of vitamin D dampens proliferation, and induces cells to exit the cell cycle via differentiation and, in certain circumstances, induces apoptosis (DeLuca et al, 1990). Hypovitaminosis D (in the presence of normal calcium) in the pregnant guinea pig has been found to cause widened growth plates in the fetal long bones (Rummens et al, 2002), thus this feature may underlie the longer length of winter-spring born infants . The altered cognitive trajectory noted in this study may be as a consequence of the impact of low prenatal vitamin D on brain development.…”

Pregnancy in Mice Lacking the Vitamin D Receptor: Normal Maternal Skeletal Response, But Fetal Hypomineralization Rescued by Maternal Calcium Supplementation

“…The dry weight of the adult femora was obtained after dehydrating (in ethanol and diethylether for several days) and drying (24 h at 100°C) the bones. QCT of the adult femora was measured with a XCT Bone Scanner (Norland, Fort Atkinson, WI), as described (19). Trabecular bone density was measured in an inner area of 25% of the total cross-sectional area, at 0.75, 1.0 and 1.25 mm from the distal growth plate; the average value was calculated.…”

“…Histomorphometry of adult tibiae was performed as described previously for rat (20) and guinea pig tibiae (19,21), with adaptations for mouse bones. The undecalcified left proximal tibia was embedded in methylmethacrylate, and 4 mthick longitudinal sections were cut.…”

“…In TRAP-stained sections, we counted the TRAPpositive cells in the trabecular bone area, at magnification ϫ600. We also measured the area occupied by hypertrophic chondrocytes relative to the total chondrocyte area of the growth plate at magnification ϫ150, as described previously in guinea-pig fetuses (19) and in VDRϪ/Ϫ mice (8). Dynamic histomorphometry could not be performed in fetuses, because the calcein labeling pattern was indistinct.…”

Seasonal fluctuations in birth weight and neonatal limb length; does prenatal vitamin D influence neonatal size and shape?

“…For example, compared to control animals, the new born offspring of normocalcaemic rats deprived of vitamin D were significantly heavier and have subtle changes in the shape of the brain [39]. Of particular relevance to the association between winter and spring birth and longer limbs, recent studies in the guinea pig have linked low prenatal vitamin D and growth plate hypertrophy [40]. This experiment found expansion of the hypertrophic chondrocyte area and an increase in the osteoid surface and thickness in the growth plates of fetuses from vitamin D deplete (but normocalcaemic) guinea pigs.…”