Insulin resistance in human preeclamptic placenta is mediated by serine phosphorylation of insulin receptor substrate-1 and -2.

CONTEXT: Preeclampsia is a severe complication of human pregnancy often associated with maternal risk factors. Insulin resistance represents a major risk for developing preeclampsia during pregnancy. OBJECTIVE: A putative second messenger of insulin, inositol phosphoglycan P type (P-IPG), was previously shown to be highly increased during active preeclampsia. Its association with insulin resistance was investigated. DESIGN AND SETTING: A cross-sectional study was carried out in a referral center. PATIENTS: Nine preeclamptic (PE) and 18 healthy women were recruited and matched for maternal age, body mass index, parity, and ethnicity in a 1:2 ratio. Placental specimens were collected immediately after delivery. INTERVENTION: Placental tissue was incubated with insulin and P-IPG production assessed. Insulin signaling proteins were subsequently studied by immunoblotting. RESULTS: P-IPG extracted from human term placentas upon incubation with insulin was found to be far lower in those with preeclampsia than controls (P < 0.001). Immunoblotting studies revealed serine phosphorylation of insulin receptor substrate-1 and -2 in PE placentas (P < 0.001) with downstream impairment of insulin signaling. The activation of the p85 regulatory subunit of phosphatidylinositol 3- kinase was markedly decreased in PE samples (P < 0.001). CONCLUSIONS: These findings highlight the importance of P-IPG in active preeclampsia and demonstrate a substantially different response to the insulin stimulus of human PE placentas. Acquired alterations in activation of proteins involved in insulin signaling may play a role in the complex pathogenesis of preeclampsia, probably as a consequence of the immunological dysfunction that occurs in this syndrome. These results seem to confirm an insulin-resistant state in PE placenta and shed a different light on its role in the pathogenesis of this disease with potential therapeutic implications.

Urinary inositol phosphoglycan P-type as a marker for prediction of preeclampsia and novel implications for the pathophysiology of this disorder.

OBJECTIVE: Hypertensive disorders represent the most common complications of human pregnancy with substantial impact on fetal and maternal outcomes. Inositol phosphoglycan P-type has recently been identified as a novel marker of preeclampsia, the most severe form of hypertension during pregnancy, with a significant increase in urinary excretion preceding the clinical diagnosis. METHODS: A prospective, longitudinal study was carried out to assess the potential of urinary levels of inositol phosphoglycan P-type as a screening test for preeclampsia. A specific ELISA-based test was used to assess urinary levels of P-IPG. RESULTS: Nine patients out of 93 women recruited (496 urinary samples were collected) went on to develop preeclampsia in a cohort of women with high-risk pregnancies. A cut-off value of urinary inositol phosphoglycan P-type was identified by ROC analysis providing a sensitivity and specificity for the current protocol of 88.9% and 62.7%, respectively. Twenty-three women with healthy pregnancies had sporadic episodes of increased excretion of inositol phosphoglycan P-type during pregnancy that consistently resolved back to normal baseline without development of preeclampsia. There was no correlation of urine levels of inositol phosphoglycan P-type and urine protein and patients with gestational hypertension had normal levels of urine inositol phosphoglycan P-type. CONCLUSIONS: These findings suggest that, given the rapid raise of P-IPG before the onset of the disease, multiple assessments may help at identifying women at risk of developing preeclampsia.

Release of inositol phosphoglycan P-type by the human placenta following insulin stimulus: a multiple comparison between preeclampsia, intrauterine growth restriction, and gestational hypertension.

OBJECTIVE: Abnormal metabolism of inositol phosphoglycan P-type (P-IPG) has been described in insulin-resistant states. Recently, a definite link between P-IPG and preeclampsia has been reported. P-IPG release after insulin stimulus has been described in the placental tissue of healthy women and a complete absence of P-IPG release has been found in preeclamptic samples, associated with disturbed insulin signaling. This study was undertaken to assess the release of this mediator in intrauterine growth restriction (IUGR) and hypertensive disorders other than preeclampsia. METHODS: Seven women with IUGR, seven with gestational hypertension, 11 with preeclampsia, and 12 controls were recruited for this study. Fresh placental membranes were prepared and incubated with human recombinant insulin. Bioactivity of P-IPG released after insulin stimulus was assessed using a specific bioassay. A multiple comparison between groups was carried out. The study population provided a statistical power of 0.94. RESULTS: P-IPG release was highest and lowest from healthy and preeclamptic samples, respectively (p < 0.01). Specimens from patients with IUGR and gestational hypertension released less P-IPG than did controls (p < 0.05). CONCLUSIONS: Abnormal release of P-IPG from placentas of IUGR and gestational hypertensive mothers seems to confirm an association between these disorders of human pregnancy and insulin resistance.