Inositol phosphoglycan putative insulin mediator in human amniotic fluid

Placenta and maternal endothelium during preeclampsia: Disruption of the glycocalyx explains increased inositol phosphoglycans and angiogenic factors in maternal blood

The etiology of the pregnancy syndrome preeclampsia is still unclear, while most hypotheses center on the placenta as the major contributor of the syndrome. Especially changes of the placental metabolism, including the use of glucose to produce energy, are important features. As an example, inositol phosphoglycan P-type molecules, second messengers involved in the glucose metabolism of all cells, can be retrieved from maternal urine of preeclamptic women, even before the onset of clinical symptoms. Alterations in the placental metabolism may subsequently lead to negative effects on the plasma membrane of the placental syncytiotrophoblast. This in turn may have deleterious effects on the glycocalyx of this layer and a disruption of this layer in all types of preeclampsia. The interruption of the glycocalyx in preeclampsia may result in changes of inositol phosphoglycan P-type signaling pathways and the release of these molecules as well as the release of soluble receptors such as sFlt-1 and sEndoglin. The release of placental factors later affects the maternal endothelium and disrupts the endothelial glycocalyx as well. This in turn may pave the way for edema, endothelial dysfunction, coagulation, all typical symptoms of preeclampsia.

Inositol and antioxidant supplementation: Safety and efficacy in pregnancy

Pregnancies complicated by diabetes have largely increased in number over the last 50 years. Pregnancy is characterized by a physiologic increase in insulin resistance, which, associated with increased oxidative stress and inflammations, could induce alterations of glucose metabolism and diabetes. If not optimally controlled, these conditions have a negative impact on maternal and foetal outcomes. To date, one can resort only to diet and lifestyle to treat obesity and insulin resistance during pregnancy, and insulin remains the only therapeutic option to manage diabetes during pregnancy. However, in the last years, in a variety of experimental models, inositol and antioxidants supplementation have shown insulin-sensitizing, anti-inflammatory, and antioxidant properties, which could be mediated by some possible complementary mechanism of action. Different isomers and multiple combinations of these compounds are presently available: Aim of the present review article is to examine the existing evidence in order to clarify and/or define the effects of different inositol- and antioxidant-based supplements during pregnancy complicated by insulin resistance and/or by diabetes. This could help the clinician's evaluation and choice of the appropriate supplementation regimen.

The association of second trimester biomarkers in amniotic fluid and fetal outcome

Objective: To identify the level of amniotic fluid lactate (AFL), placental growth factor (PLGF), and vascular endothelial growth factor (VEGF) at second trimester amniocentesis, and to compare levels in normal pregnancies with pregnancies ending in a miscarriage, an intrauterine growth restricted fetus (IUGR) or decreased fetal movements. Study design: A prospective cohort study. Amniotic fluid was consecutively collected at amniocentesis in 106 pregnancies. Fetal wellbeing at delivery was evaluated from medical files and compared with the levels of AFL, VEGF, and PLGF at the time of amniocentesis. Results: The median level of AFL was 6.9 mmol/l, VEGF 0.088 pg/ml, and PLGF 0.208 pg/ml. The median levels of AFL in pregnancies ended in miscarriage were significantly higher (10.7 mmol/l) compared to those with a live new-born (6.9 mmol/L, p = .02). The levels of VEGF (p = .2) and PLGF (p = .7) were not affected. In pregnancies with an IUGR, the median level of AFL was higher compared to those with normal fetal growth (p = .003). No differences VEGF (p = .5), but significant lower PLGF were found in IUGR pregnancies (p = .03). Conclusions: Pregnancies ending in a miscarriage or with IUGR had significantly higher median values of AFL but lower values of PLGF in the amniotic fluid at the time of second trimester amniocentesis compared to normal pregnancies.

Second trimester amniotic fluid myo-inositol concentrations in women later developing gestational diabetes mellitus or pregnancy-induced hypertension

OBJECTIVE

To evaluate myo-inositol concentrations in amniotic fluid in women later developing gestational diabetes and hypertension.

METHODS

A retrospective study was carried out with three groups of amniotic fluid samples (15-18 gestational weeks): 30 gestational hypertension pregnancies, 30 gestational diabetes pregnancies, and 30 normal pregnancy.

RESULTS

A significant difference was observed in myo-inositol concentrations between the median gestational diabetes values (124.0 µmol/L, IQR 90.0-162.5) and the control group values (79.0 µmol/L, IQR 62.0-107.5), but also with gestational hypertension median values (79.0 µmol/L, IQR 67.75-92.0) (p < 0.001).

CONCLUSIONS

This study has shown that myo-inositol concentrations in amniotic fluid increased significantly in women later developing gestational diabetes compared to the control group.

Endometrial secretions: creating a stimulatory microenvironment within the human early placenta and implications for the aetiopathogenesis of preeclampsia

Endometrial glands represent an important source of nutrients for the conceptus during the first trimester. Their secretions are enriched with carbohydrates, and glycogen accumulates within the syncytiotrophoblast of the placenta. It has been assumed that fetal and placental metabolism follow adult pathways, although it is now appreciated that early development occurs in a low-oxygen environment. In past decades, a novel family of putative insulin mediators, inositol phosphoglycans (IPGs), was discovered. These molecules act as allosteric activators and/or inhibitors of enzymes and transduction proteins involved in the control of cell signalling and metabolic pathways, and determine the specificity of responses after activation of the insulin receptor. One member, IPG P-type, activates pyruvate dehydrogenase phosphatase (PDH-Pase), glycogen synthase phosphatase, and glycerol-3-phosphate acyltransferase. Activation of key phosphatases play a major role in the regulation of glucose disposal by oxidative metabolism via PDH, and the non-oxidative storage by glycogen synthesis, both pathways classically known to be regulated by insulin. High concentrations of IPG P-type in amniotic fluid suggest a role in the regulation of carbohydrate metabolism in the fetal-placental unit. Glycogen accumulation in the syncytiotrophoblast also occurs in preeclamptic pregnancies, and is consistently associated with higher placental levels of IPG P-type. Here, we explore the relationship between nutrients provided by the endometrial glands during early pregnancy, IPG P-type and fetal metabolic requirements. We also discuss whether a disconnect between the placental/fetal metabolic state and oxygen tension could lead to a preeclamptic-type syndrome via leakage of Warburg/IPG mediators into the maternal circulation.

Inositol phosphoglycan P-type in healthy and preeclamptic pregnancies

An association between inositol phosphoglycan P-type (P-IPG) and preeclampsia has been demonstrated over recent years. This molecule can mediate many of the metabolic and growth promoting effects of insulin. Dysregulation of the mediator family is associated with insulin resistance. An increased concentration of P-IPG has been reported in preeclamptic placenta, although its precursor (GPI) was undetectable in those placental samples. Insulin administration, that induces P-IPG release in normal human placenta, was shown not to cause production/release of the mediator from preeclamptic placental tissue as a consequence of a disturbed insulin signalling. Amniotic fluid is enriched of this mediator, with further increase during preeclampsia. We have found that the fetus released increasing amounts of P-IPG in the urine between 13 and 18 weeks of gestation, reaching a plateau beyond 20 weeks. Cord blood of infants of preeclamptic mothers showed an increased content of soluble P-IPG compared to controls and to the mother.

Preeclampsia, insulin signalling and immunological dysfunction: a fetal, maternal or placental disorder?

An inappropriate glycogen accumulation in preeclamptic placentas was described as secondary to biochemical alterations. Insulin resistance is widely accepted to be associated with preeclampsia, although its basis remain unclear. A family of putative insulin mediators, namely inositol phosphoglycans, were described to exert many insulin-like effects on lipid and glucose metabolism. A definite association between the P-type mediator (P-IPG) and preeclampsia was reported, being increased in placenta, urine, amniotic fluid and cord blood from human preeclamptic pregnancies. A strong link exists between insulin resistance and inflammation. Clear features of insulin resistance and systemic inflammatory activation were described in preeclampsia. It may be a consequence of the immunological dysfunction that occurs in preeclampsia that is temporized during sperm exposure and co-habitation which confuses the maternal immune network to perceive 'danger'. The over-expression of P-IPG during preeclampsia may be a counter-regulatory mechanism to insulin resistance since these molecules mimic insulin action. Besides, the lipidic form of P-IPG was reported to be similar to endotoxins, and may represent the 'danger signa'. We propose here a novel working theory on insulin resistance and preeclampsia.

Urinary excretion of inositol phosphoglycan P-type in gestational diabetes mellitus

OBJECTIVE

The mechanisms underlying insulin resistance during normal pregnancy, and its further exacerbation in pregnancies complicated by gestational diabetes mellitus (GDM), are generally unknown. Inositolphosphoglycan P-type (P-IPG), a putative second messenger of insulin, correlates with the degree of insulin resistance in diabetic subjects. An increase during normal pregnancy, in maternal and fetal compartments, has recently been reported.

METHODS

A cross-sectional study was carried out in 48 women with GDM and 23 healthy pregnant women. Urinary levels of P-IPG were assessed spectrophotometrically by the activation of pyruvate dehydrogenase phosphatase in urinary specimens and correlated with clinical parameters.

RESULTS

Urinary excretion of P-IPG was higher in GDM than in control women (312.1 +/- 151.0 vs. 210.6 +/- 82.7 nmol NADH/min/mg creatinine, P < 0.01) with values increasing throughout pregnancy in control subjects (r2 = 0.34, P < 0.01). P-IPG correlated with blood glucose levels (r(2) = 0.39, P < 0.01 for postprandial glycaemia and r2 = 0.18 P < 0.01 for mean glycaemia) and birthweight in the diabetic group (r2 = 0.14, P < 0.01).

CONCLUSIONS

Increased P-IPG urinary excretion occurs in GDM and positively correlates with blood glucose levels. P-IPG may play a role in maternal glycaemic control and, possibly, fetal growth in GDM.

Inositol Phosphoglycan P-Type in Preeclampsia

A state of insulin resistance has been demonstrated in active preeclampsia, and women with clinical evidence of insulin resistance are at higher risk to develop this syndrome during pregnancy. Recently, inositol phosphoglycan P-type, a putative second messenger of insulin action, has been implicated in the pathophysiology of preeclampsia and is increased in the placenta, amniotic fluid, and maternal urine of preeclamptic women compared with normal pregnant women. We report here a case–control study to assess the potential of urinary levels of inositol phosphoglycan P-type as a screening test for preeclampsia. Twenty-seven preeclamptic women and 47 healthy pregnant women were recruited. A polyclonal antibody-based ELISA was developed to detect levels of inositol phosphoglycan P-type in urine. Its content in urinary specimens was found to be 30-fold higher in preeclamptic subjects than control subjects (329.1±21.8 versus 9.2±1.5; P <0.001), with a higher level in all of the preeclamptic cases. For 6 women who developed preeclampsia, >1 gestational date sample of urine was available, and retrospective analysis showed a significant time-related increase of the urinary level of inositol phosphoglycan P-type ≤7 weeks before clinical diagnosis of preeclampsia. Urinary level of inositol phosphoglycan P-type increased after diagnosis indicating a possible pathophysiological threshold level and steeply decreased after delivery.