Vitamin D insufficiency in neonatal hypoxic-ischemic encephalopathy

Abstract

Background: Vitamin D has neuroprotective and immunomodulatory properties, and deficiency is associated with worse stroke outcomes. Little is known about effects of hypoxia-ischemia or hypothermia treatment on vitamin D status in neonates with hypoxic-ischemic encephalopathy (HIE). We hypothesized vitamin D metabolism would be dysregulated in neonatal HIE altering specific cytokines involved in Th17 activation, which might be mitigated by hypothermia.

Methods: We analyzed short-term relationships between 25(OH) and 1,25(OH)₂ vitamin D, vitamin D binding protein, and cytokines related to Th17 function in serum samples from a multicenter randomized controlled trial of hypothermia 33 ^°C for 48 h after HIE birth vs. normothermia in 50 infants with moderate to severe HIE.

Results: Insufficiency of 25(OH) vitamin D was observed after birth in 70% of infants, with further decline over the first 72 h, regardless of treatment. 25(OH) vitamin D positively correlated with anti-inflammatory cytokine IL-17E in all HIE infants. However, Th17 cytokine suppressor IL-27 was significantly increased by hypothermia, negating the IL-27 correlation with vitamin D observed in normothermic HIE infants.

Conclusion: Serum 25(OH) vitamin D insufficiency is present in the majority of term HIE neonates and is related to lower circulating anti-inflammatory IL-17E. Hypothermia does not mitigate vitamin D deficiency in HIE.

Figure 1

Circulating 25(OH)D at enrollment after HI injury (n=46). (1a) Box plots of median, 25^th & 75^th IQR, and ranges of serum 25(OH)D by race in HIE infants (n= 27 Caucasian, 16 African American, 3 other race; * p=0.001 vs Caucasian). (1b) Incidence of sufficiency (≥30 ng/ml, green), low-sufficiency (20–30 ng/ml, yellow), insufficiency (12–20 ng/ml, orange) and deficiency (<12 ng/ml, red) of 25(OH)D. (1c) Median (± 95%CI) serum 25(OH)D levels over 72 hours in HIE patients that either maintained serum 25(OH)D levels during the study period (n=17, blue) or had declining serum 25(OH)D (n=17, green) at 48–72 hours compared to enrollment (*, p=0.002).

Figure 2

Circulating vitamin D binding proteins by hypothermia (blue) and normothermia (red) treatment. (2a) Median serum albumin over time (n=50, * p<0.01, **p<0.001); (2b) Serum DBP versus 25(OH)D concentrations at 0–12h after enrollment (n=33, rho=0.503, p=0.003); (2c) Median serum DBP over time by hypothermia and normothermia treatment. (*p<0.05).

Figure 3

Anti-inflammatory cytokines IL-17E and IL-27 in HIE neonates. (3a) 25(OH)D at 48 hours correlates with IL-17E at 72 hours after enrollment (rho=0.555, p=0.001). (3b) Median IL-27 (± 95% CI, pg/ml) over time in hypothermia (blue) and normothermia (red) treatment groups. (*p<0.05, mixed model post-hoc analysis). (3c) IL-27 at 36 hours positively correlates with 25(OH)D in normothermic infants (n=11, rho=0.809, p=0.003). (3d) IL-27 at 36 hours does not correlate with 25(OH)D in hypothermic infants (n=14, rho= −0.442, p=0.114).

Figure 4

Phosphorous is significantly higher 3–9h after birth in infants who do not survive (orange) the neonatal period compared to survivors (green). (4a) Circulating median phosphorous (± 95%CI, * indicates p<0.05) over 72 hours after HI birth. (4b) Enrollment pH negatively correlates with phosphorous (rho= −0.477, p=0.003).