ESPE Abstracts

Background: Animal studies suggest a role of vitamin D in fetal lung development although not studied in preterm animals.

Objective and hypotheses: We tested the hypothesis that vitamin D depletion does not aggravate respiratory insufficiency in preterm rat offspring. Furthermore, the effects of vitamin D depletion on growth and lung surfactant were investigated.

Method: Female Sprague-Dawley rats were randomly assigned low vitamin D (VD_L) or control diet before mating and followed with serum 25-hydroxyvitamin D (s-25(OH)D) determinations. After cesarean section at gestational day 19 (E19) or 22 (E22), placental weight, birth weight, crown-rump-length (CRL), oxygenation (SaO₂) at 30 min and foster-mother reared survival time were recorded. Lungs from the euthanized pups were analyzed for phospholipid concentration, surfactant mRNA and expression of the vitamin D receptor (VDR).

Results: S-25(OH)D was lower in the VD_L group before mating (43 vs 64 nmol/L, P=0.009) and at cesarean section (12 vs 30 nmol/L, P<0.0001). Compared to the controls, E19 VD_L pups had lower birth weight (2.13 vs. 2.29 g, P<0.001), lung weight (0.09 vs 0.10 g, P=0.002), lung/birth weight ratio (0.042 vs 0.044, P=0.011), SaO₂ (54% vs 69%, P=0.002) as well as reduced survival time (0.50 vs 1.25h, P<0.0001). At E22, no such differences were observed, but VD_L pups had lower CRL (4.0 vs 4.5 cm, P<0.0001). A trend towards lower VDR expression was seen in VD_L at E19 (P=0.068), but not at E22, where the expression was significantly lower in both dietary groups compared to E19. The phospholipid concentration and the surfactant mRNA expression did not differ between the groups.

Conclusion: Vitamin D depletion led to lower oxygenation and reduced survival time in the preterm offspring, associated with reduced lung weight and birth weight, but not with changes in phospholipids or surfactant. The role of vitamin D in respiratory insufficiency in human preterm neonates should be studied further.