2000 WHRG Grant Program

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Symposia

eNOS Polymorphisms and Pre-eclampsia

Mark Lustberg
School of Medicine, University of Maryland, Baltimore

Background: Pre-eclampsia (or toxemia of pregnancy) is a syndrome characterized by hypertension, edema, and proteinuria (protein in the urine). Affecting 5% of pregnancies, pre-eclampsia is a public health problem with potential complications which include maternal morbidity and mortality, as well as fetal hypoxia and low birth weight. Identification of risk factors for pre-eclampsia and the complications of pre-eclampsia has the potential to reduce complications from this disease.

While risk factors such as maternal obesity and carrying multiple pregnancies have been associated with pre-eclampsia, the cause of pre-eclampsia remains unclear. Decreased nitric oxide (NO) production has been theorized to be a cause of pre-eclampsia. Recent evidence indicates that the Asp-variant of endothelial nitric oxide synthase (eNOS, the enzyme which produces nitric oxide) is associated with decreased NO production, leading to increased vascular reactivity, and predisposing to hypertension and heart attack (although some studies have provided conflicting evidence for these associations). Studies need to be conducted to consider the effect of the polymorphism in pregnant women, to assess an association with pre-eclampsia.

Hypothesis: The Asp-variant of a Glu298Asp substitution polymorohism in the endothelial nitric oxide synthase (eNOS) gene is a risk factor for pre-eclampsia and the complications of pre-eclampsia.

Specific Aims: 1)Purify DNA samples from banked blood samples, and genotype the purified DNA for the polymorphism by restriction endonuclease digest assay. 2)Compile a database on genotype information, and then analyze this data for the association of the polymorphism and pre-eclampsia and the association of the polymorphism and complications of pre-eclampsia (using infant birth weight and gestational age as measures of complications).

Research Design: This will be a nested case control study of blood samples banked from the prospective, ongoing PEPP study (Prenatal Exposures and Pre-eclampsia Prevention Study) at the Magee Women's Hospital at the University of Pittsburgh. 100 pre-eclamptic blood samples and ~100 control samples from uncomplicated pregnancies will be provided for this study.

Methods: A commercially available kit will be used to isolate DNA from the banked blood samples. Using PCR a fragment containing the polymorphism will be amplified up from the purified DNA. As the Glu298Asp substitution polymorphism creates an Mbol restriction site in the eNOS gene, restriction endonuclease digests will be used to distinguish the two variant alleles.

After compiling a database of genotype information, the association of the polymorphism and pre-eclampsia and the complications of pre-eclampsia will be evaluated. Logistic regression will be used to model the association of the polymorphism and pre-eclampsia, taking into account effects such as maternal age and obesity. In both controls and pre-eclamptic pregnancies, linear regression will be used to model the association of the polymorphism and infant birth weight/gestational age (indicators of the complications of pre-eclampsia), taking into account effects such as infant gender and maternal age.

Significance: If Asp-variant eNOS is associated with pre-eclampsia or its complications, this would be a finding of potentially important public health significance; possibly reducing complications from this disease by facilitating earlier interventions. Results from this study may also provide important insight into the etiology of pre-eclampsia, which is currently unclear.