Endocrine Abstracts

Background - Adverse fetal nutritional supply results in programmed endothelial dysfunction and hypertension in offspring. Nitric Oxide Synthase (eNOS), Endothelin-1 (ET-1), and human Cationic Amino acid Transporter-1 (hCAT-1) are key players in endothelial function. We have shown that hCAT-1 is down-regulated in smaller neonates. One possible explanatory mechanism is DNA methylation, which reduces gene expression. In mice and rat models maternal diets with altered levels of methyl donors, lead to altered DNA methylation and phenotypic change in offspring. Another murine model demonstrated permanent stress response changes, via methylation of the hippocampal glucocorticoid receptors, in response to grooming.

Hypothesis - Endothelial function may be programmed such that low birth weight could be associated with permanent adverse expression of hCAT-1, ET-1 and eNOS, is detectable at birth and associated with promoter methylation density.

Objective - To use bisulphite sequencing to precisely assess the methylation patterns of hCAT-1, eNOS and ET-1 in human neonatal vascular endothelium, and correlate these with gene expression and auxology.

Methods - After ethical approval and informed written consent, umbilical cords were obtained from term elective caesarian sections, across a range of birth weights. Human umbilical vein endothelial cells were extracted and cultured. DNA was extracted prior to undertaking bisulphite sequencing of hCAT-1, ET-1 and eNOS. Measurements were taken of birth weight, length, occipito-frontal circumference and mid upper arm circumference.

Results - The distal enhancer and promoter of eNOS are variably methylated at low density. Despite variation in endothelial hCAT-1 expression between neonates, it is not significantly methylated, neither is that of ET-1.

Conclusions - This is the first study in humans to provide evidence that DNA methylation is involved in the mechanism of fetal programming, specifically that of endothelial dysfunction. This has important implications for adult vascular health.