96 - Sex differences in HIF-related metabolic adaptation in cyanotic congenital heart defects

Children with cyanotic congenital heart defects (CHD) experience high rates of morbidity and mortality in infancy with heightened risk in females. Survival may be related to metabolic adaptation to hypoxia. Hypoxia-inducible factors (HIF) are key regulators of metabolic adaption, but the effects are largely unknown in infancy and have not been explored by sex.

Objective:

To study the hypothesis that activity of glycolysis is sex-dependent through altered HIF1α activation and differences in expression of targeted genes.

Design/Methods:

Plasma was obtained in the first month of life or prior to cardiopulmonary bypass and grouped by cyanotic CHD (O₂ saturation < 92%), non-cyanotic CHD, and controls (ages < 1 month). Unbiased global metabolic profiling was performed with UPLC-MS/MS (Metabolon, Inc). Statistical significance was estimated by Welch’s two-sample T-test and one-way ANOVA with p< 0.05. RNA-seq of whole blood was performed for differential expression of the genes targeted by HIF1α between cyanotic CHD and controls adjusted by sex.

Results:

The study included 27 cyanotic CHD, 11 non-cyanotic CHD, and 12 controls (52% females). Glutamine reductive carboxylation intermediate α-ketoglutaramate was 2 to 3-fold higher in cyanotic patients and controls compared to non-cyanotic patients (p< 0.01). Significantly altered levels of fatty acids and fatty acylcarnitines were observed in cyanotic patients and controls compared to non-cyanotic patients. Cyanotic and control females had a 3-fold increase in glycolysis intermediate 3-phosphoglycerate compared to non-cyanotic females (p< 0.01); no differences were observed in male counterparts. Cyanotic females had a 7-fold increase in TCA cycle intermediate isocitrate compared to cyanotic males (p=0.016); isocitrate levels were similar between non-cyanotic patients and controls as expected. Glucose transporter 1 (GLUT1) was significantly upregulated in cyanotic females compared to males (FC=1.5, p=0.008). Seven other HIF1α-targeted metabolic genes were also increased in cyanotic females but not significant. No differences in HIF1α or its targets were observed among controls.

Conclusion(s):

HIF1α was not constitutively expressed in neonatal chronic hypoxia. Our findings suggest neonates may adapt to chronic hypoxia through stimulation of reductive glutamine metabolism, an alternative source of citrate (TCA cycle), to support fatty acid synthesis and storage. Additionally, increased glycolysis in cyanotic females may be driven by GLUT1, a key regulator of glycolysis. Alternative metabolic pathways are likely utilized in neonatal chronic hypoxia and differ by sex.