Maternal tissue blood flow and oxygen saturation in pre-eclampsia and intrauterine growth restriction.

OBJECTIVE: To investigate the hypothesis that impaired maternal tissue perfusion occurs in pre-eclampsia and intrauterine growth restriction (IUGR) and this correlates with maternal tissue oxygenation. STUDY DESIGN: Strain gauge plethysmography was used to compare maternal calf blood flow during the third trimester in 16 women with pre-eclampsia, 6 women with IUGR and 16 normal pregnant controls. A Mediaid iPOX pulse oximeter was used to measure maternal tissue oxygenation in the three groups and these were compared with tissue blood flow. RESULTS: Maternal tissue blood flow was significantly reduced in pre-eclampsia compared to the two other groups (p=0.003). Blood flow was significantly reduced in pre-eclampsia compared to IUGR (p=0.03). However there was no difference in blood flow between normal pregnancy and IUGR groups (p=0.76). No significant difference was noted in maternal tissue oxygenation between the normal pregnancy, pre-eclampsia and IUGR groups (mean±S.E.M. [97.13±0.4, 96.69±0.33, 97.83±0.47 respectively], p=0.26). No correlation was noted between blood flow and tissue oxygenation in the three groups of women. CONCLUSION: We have demonstrated that reduced maternal resting tissue blood flow present in women with pre-eclampsia is not seen in women with IUGR and the reduction in blood flow in pre-eclampsia is not associated with changes in maternal tissue oxygenation.

Placental angiogenin inhibitor (ribonuclease inhibitor), a novel gene in pre-eclampsia.

There is convincing evidence that imbalance between angiogenic and anti-angiogenic factors play an important role in the pathophysiology of pre-eclampsia. Angiogenin, a member of the RNase A super family, is a potent inducer of angiogenesis and serum levels are shown to be elevated in pre-eclampsia. We hypothesize that placental expression of angiogenin inhibitor which binds and blocks the activity of angiogenin is altered in pre-eclampsia and may play a role in its pathophysiology. Placental expression of angiogenin inhibitor was measured in term placentae of 15 women with preeclampsia and 16 normal pregnant controls. The women were matched for age, parity and gestational age. Placental tissue was collected immediately after delivery and stored at -80°C until studied. Angiogenin inhibitor gene expression was measured using real-time quantitative polymerase chain reaction (rt-QPCR). The results were standardized using the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as reference gene. The mRNA expression of angiogenin inhibitor gene was significantly increased in preeclamptic placentae compared to normal pregnant controls [0.44 (0.174-1.048) versus 0.091 (0.029-0.301), median and interquatile range, p=0.027 for pre-eclampsia and normal controls respectively]. There was no correlation between angiogenin inhibitor gene expression and maternal age, blood pressure, platelet count, gestation age, birth weight of the baby in pre-eclampsia and normal pregnancy. This study showed that placental expression of the angiogenin inhibitor gene is significantly increased in pre-eclampsia and may play a role in its pathophysiology.

PP011. Increased placental expression of angiogenin inhibitor (Ribonuclease inhibitor), a novel gene in pre-eclampsia.

INTRODUCTION: There is convincing evidence that imbalance between angiogenic and anti-angiogenic factors play an important role in the pathophysiology of pre-eclampsia. Increased expression of soluble fms-like tyrosine kinase-1 (sFlt1), along with decreased placental growth factor (PlGF) and vascular endothelial growth factor (VEGF) appear to play a key role in the abnormal placentation and vascular dysfunction of pre-eclampsia. Angiogenin is a potent inducer of angiogenesis and serum levels are elevated in pre-eclampsia. Angiogenin Inhibitor (also called placental Ribonuclease inhibitor) is a potent antagonist of both angiogenic and ribonucloetic activities of angiogenin. We demonstrate that placental expression of angiogenin inhibitor is altered in pre-eclampsia and may play a role in its pathophysiology. OBJECTIVES: The aim of the study was to assess the expression of angiogenin inhibitor in healthy normotensive and pre-eclamptic placentas. METHODS: Placental expression of angiogenin inhibitor was measured in term placentae of 14 pre-eclamptic women and 16 normal pregnant controls. The women were matched for age, gestation and parity. Placental tissue was collected immediately after delivery and stored at -80°C. The angiogenin inhibitor gene expression was measured using real-time quantitative polymerase chain reaction (rt-QPCR). The results were standardized using the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) reference gene. RESULTS: mRNA expression of angiogenin inhibitor gene was significantly increased in pre-eclamptic placentae (p=0.027) compared to normal pregnant controls; 0.44 (0.174-1.048) versus 0.091 (0.029-0.301), median and interquartile range, for pre-eclampsia and normal controls, respectively. CONCLUSION: Placenta expression of angiogenin inhibitor gene is significantly increased in pre-eclampsia and may play a role in its pathophysiology. This finding may directly correlate with the reported ability of angiogenin inhibitor to protect from oxidative stress by its reactivity as an oxygen species scavenger.

Insulin resistance and pre-eclampsia: a role for tumor necrosis factor-alpha?

Insulin resistance occurs in pre-eclampsia, but the cause is unknown. Furthermore, it is uncertain whether women destined to develop pre-eclampsia have a pre-existing insulin resistance or whether it is acquired with the development of the disease. We carried out this study to test the hypotheses that the increase in insulin resistance associated with pre-eclampsia is related to higher levels of tumor necrosis factor (TNF)-alpha, and that the increase in insulin resistance precedes the clinical onset of the disease. Fasting plasma samples were obtained from ten women who subsequently developed pre-eclampsia and ten normal pregnant controls at 16, 20, 24, 28, 32 and 36 weeks' gestation to measure circulating levels of insulin, glucose and TNF-alpha. Fasting insulin resistance index (FIRI) was calculated from insulin and glucose concentrations. In the normal controls, fasting insulin and TNF-alpha levels, and FIRI increased with gestation, and these were significantly greater than baseline values from 24, 28 and 28 weeks, respectively. In the group of women who developed pre-eclampsia, plasma levels of insulin and the FIRI were significantly higher than baseline from 20 and 24 weeks, respectively, but both were significantly higher than in the control group at 32 and 36 weeks. The increase in TNF-alpha in the pre-eclampsia group was significantly greater than in normal pregnant controls (p < 0.001). However, there was no significant association between TNF-alpha levels and FIRI in either normal pregnancy or pregnancies developing pre-eclampsia. These data suggest that insulin resistance in pre-eclampsia precedes the clinical onset of the disease, but that it is not related to elevated levels of TNF-alpha.

Impaired retrograde transmission of vasodilatory signals via the endothelium in pre-eclampsia: a cause of reduced tissue blood flow?

There is evidence that tissue blood flow is regulated by retrograde transmission of signals initiated at capillary and post-capillary sites, and transmitted via the endothelium to modulate pre-capillary resistance. We have used pre-eclampsia as a model to test the hypothesis that normal endothelium is required to enable adjustment of blood flow to match tissue requirements. Integrity of the endothelial pathway was assessed by measuring calf blood flow at increasing venous pressures, using an established small cumulative-step venous-congestion plethysmography protocol in ten women with pre-eclampsia, 17 normal pregnant controls and ten non-pregnant women. Endothelial cell activation was assessed by measuring plasma levels of the cell adhesion molecules, intercellular cell-adhesion molecule-1 (ICAM-1), vascular cell-adhesion molecule-1 (VCAM-1) and E-selectin. Baseline calf blood flow was significantly lower in pre-eclampsia than in the other two groups (P<0.0001; ANOVA). In the pre-eclampsia group, there was a fall in blood flow as venous congestion pressure was raised (P<0.0001; ANOVA). No such change was observed in the other two groups. A significant inverse correlation was observed between the reduction in blood flow in pre-eclampsia and the levels of E-selectin (r=-0.92, P=0.0002), VCAM-1 (r=-0.93, P=0.0008) and ICAM-1 (r=-0.86, P=0.001). The differences between the pre-eclamptic women and the other two groups support the notion that the failure to sustain blood flow during a cumulative pressure step protocol in the pre-eclamptic group might be influenced by interference with the retrograde transmission of signals via the endothelium in these patients.

Evidence of impaired microvascular function in pre-eclampsia: a non-invasive study.

The clinical presentation of pre-eclampsia suggests that microvascular dysfunction may play a role in the maternal manifestations of the disease. Isovolumetric venous pressure ( P V(i)) is an index of microvascular function, reflecting local plasma colloid osmotic (oncotic) pressure, and is abnormal in clinical conditions with microvascular dysfunction. We hypothesized that, in pre-eclampsia, post-capillary margination of neutrophils would increase post-capillary resistance, and therefore P V(i). A small cumulative step strain-gauge plethysmography protocol was used to compare P V(i) in 18 women with pre-eclampsia, 16 normal pregnant women and 17 non-pregnant controls. Circulating levels of vascular cell-adhesion molecule-1 (VCAM-1), intercellular cell-adhesion molecule-1 (ICAM-1) and E-selectin, and neutrophil elastase, were measured to assess endothelial and neutrophil activation respectively. P V(i) was significantly greater in the pre-eclampsia group, relative to the normal pregnant and non-pregnant controls ( P <0.001, ANOVA, for both comparisons). P V(i) was significantly lower during normal pregnancy compared with the non-pregnant controls ( P =0.001). Plasma levels of neutrophil elastase, VCAM-1, ICAM-1 and E-selectin ( P =0.001) were significantly greater in the pre-eclamptics than the controls. Significant positive correlations were observed between P V(i) and neutrophil elastase ( r =0.71, P =0.001), VCAM-1 ( r =0.52, P =0.03), ICAM-1 ( r =0.67, P =0.002), E-selectin ( r =0.69, P =0.001), uric acid levels ( r =0.54, P =0.02) and haematocrit ( r =0.64, P =0.004) in pre-eclampsia. The relationship with the platelet count was negative ( r =-0.65, P =0.003). No significant correlations were observed between P V(i) and maternal age, gestational age, total protein, albumin, diastolic blood pressures, age, body mass index and infant birth mass in the normal pregnant and non-pregnant controls. These data suggest that microvascular dysfunction occurs in pre-eclampsia, and that it is related to alterations in endothelial cell and neutrophil activation.

The relationship between insulin and insulin-like growth factor binding protein-1 is modified by pre-eclampsia.

Insulin is the main negative regulator of insulin-like growth factor binding protein-1 (IGFBP-1) in the non-pregnant state. Although changes in insulin resistance and circulating level of IGFBP-1 occur in pre-eclampsia, little is known about the relationship between insulin and IGFBP-1 in pregnancies complicated by the disease. In this study, we have investigated whether the relationship between insulin and IGFBP-1 is modified by pre-eclampsia. Maternal levels of insulin and IGFBP-1 were measured, at 4-weekly intervals between 16 and 36 weeks' gestation, in plasma samples obtained from ten normal pregnant controls and ten women who developed pre-eclampsia. The controls were chosen to be similar in maternal age and booking body mass index to the pre-eclampsia group. Insulin levels increased in both the normal controls and the women who developed pre-eclampsia. The levels in pre-eclampsia were significantly greater than those in normal pregnancy at 32 and 36 weeks' gestation (p = 0.02 and 0.005, respectively). IGFBP-1 levels were unchanged in normal pregnancy and rose in pre-eclampsia. In normal pregnancy, insulin levels were inversely related to IGFBP-1 levels throughout. In women developing pre-eclampsia, the relationship between insulin and IGFBP-1 was negative at 16 weeks and positive from 24 weeks. These data suggest that whereas the inverse relationship between insulin and IGFBP-1 is maintained during normal pregnancy, this relationship is reversed in women who develop pre-eclampsia.

Does endothelial cell activation occur with intrauterine growth restriction?

It is possible that in fetal growth restriction without pre-eclampsia endothelial cell activation does not occur. This might be either because there is no release of 'factor X' or because of maternal resistance to its effects. To test this hypothesis, we took blood samples from 26 women with pre-eclampsia (without fetal growth restriction), 13 women with fetal growth restriction (without pre-eclampsia) and 24 normal pregnant controls, and measured the circulating levels of three markers of endothelial cell activation (soluble VCAM, ICAM and E-selectin) and three cytokines [tumour necrosis factor-a (TNF-alpha), interleukin-6 (IL-6) and -8 (IL-8)]. The levels of the markers of endothelial cell activation were raised in both pre-eclampsia and fetal growth restriction pregnancies compared with controls; however, the levels of TNF-alpha, IL-6 and IL-8 were significantly raised in pregnancies complicated by pre-eclampsia, but not in fetal growth restriction, compared with controls. These data show that endothelial cell activation is common to both pre-eclampsia and fetal growth restriction, but that the circulating levels of cytokines are elevated only in pre-eclampsia. Thus, it seems likely that endothelial cell activation is a consequence of a failure of trophoblast invasion and that a further step is required, possibly involving cytokine release, for the expression of the full clinical picture of pre-eclampsia.

A longitudinal study of biochemical markers of bone turnover during normal pregnancy and pregnancies complicated by pre-eclampsia.

OBJECTIVES: To test the hypothesis that the increased bone turnover observed in established pre-eclampsia is present earlier in pregnancy prior to the diagnosis of pre-eclampsia. DESIGN: A prospective longitudinal study. SETTING: Obstetric Unit at Chelsea and Westminster Hospital, London. POPULATION: Nine women who subsequently developed pre-eclampsia and 17 normal pregnant controls. METHODS: Maternal plasma levels of the cross-linked carboxyl terminal telopeptide of the type I collagen (ICTP), a marker of bone resorption, and of the carboxy-terminal propeptide of type I collagen (PICP), a marker of bone formation, were measured longitudinally in nine women who developed pre-eclampsia and 17 women with normal pregnancy. Serial blood samples were obtained at 16, 20, 24, 28, 32 and 36 weeks of gestation and the levels of ICTP and PICP were measured by radio-immunoassay. RESULTS: ICTP and PICP increased progressively in the normal pregnant and pre-eclampsia groups, but the rate of increase was significantly greater in the latter (P = 0.00002 and 0.0008, unpaired t test, for ICTP and PICP summary measures, respectively). In the pre-eclampsia group, positive correlation were observed between ICTP levels at 36 weeks of gestation and plasma uric acid (r = 0.9, P = 0.001) and degree of proteinuria (r = 0.78, P = 0.04). No correlation was observed between the two bone markers and other variables during normal pregnant group. CONCLUSION: These data show that biochemical markers of bone turnover are greater in pregnancies complicated by pre-eclampsia compared with normal pregnancy but only when the disease is clinically evident.

A longitudinal study of resting peripheral blood flow in normal pregnancy and pregnancies complicated by chronic hypertension and pre-eclampsia.

OBJECTIVES: To investigate the hypothesis that reduced resting tissue blood flow precedes the clinical onset of pre-eclampsia in women at risk of the disease. METHODS: We used venous occlusion plethysmography to compare resting calf muscle blood flow in 18 normal pregnant controls, 18 pregnant women with chronic hypertension, and 23 pregnant women at increased risk of developing pre-eclampsia. Calf blood flow was measured at 16, 20, 24, 28, 32 and 36 weeks of gestation. RESULTS: Blood flow increased with gestation in normal pregnancy (P = 0.004) and chronic hypertension (P = 0.006), but not in the 'at risk' women who did not develop pre-eclampsia (P = 0.36). In contrast, blood flow decreased significantly in eight out of the 23 women 'at risk', who developed pre-eclampsia (P < 0.00001, ANOVA). The decrease in flow preceded the clinical diagnosis of the pre-eclampsia by several weeks. Moreover, a significant inverse correlation was observed between resting blood flow and plasma uric acid concentrations (r = -0.86, P = 0.03) in the women that developed pre-eclampsia. CONCLUSIONS: We have shown that reduced resting blood flow precedes the clinical onset of pre-eclampsia independently of hypertension per se. These findings support the notion that impaired tissue blood flow may be involved at an early stage in the pathophysiology of the disease.

Biochemical markers of maternal bone turnover are elevated in pre-eclampsia.

OBJECTIVES: To investigate the hypothesis that bone turnover is reduced in pre-eclampsia compared with normal pregnancy. DESIGN: A prospective cross-sectional study. SETTING: Obstetric unit at the Chelsea and Westminster Hospital, London. METHODS: Third trimester maternal plasma levels of the cross-linked carboxyl-terminal telo-peptide of type I collagen (ICTP), (a marker of bone resorption) and the carboxyl terminal pro-peptide of type I pro-collagen (PICP), (a marker of bone formation) were compared in 25 women with pre-eclampsia and in 24 normal pregnant controls. The subjects were matched for maternal age, booking body mass index and gestational age. PICP and ICTP levels were measured by radio-immunoassay. RESULTS: ICTP and PICP levels were significantly increased in women with pre-eclampsia compared with the normal pregnant controls (P = 0.0001 and P = 0.004, for ICTP and PICP respectively, Wilcoxon signed ranked test). There was no significant correlation between either of the markers and booking body mass index, blood pressure, serum uric acid levels or platelet count. CONCLUSIONS: These data suggest that bone turnover is increased in established pre-eclampsia compared with normal pregnancy. Further studies are required to investigate whether this precedes the onset of the disease.

Resting peripheral blood flow in normal pregnancy and in pre-eclampsia.

Multiple organ dysfunction followed by end organ failure occurs in pre-eclampsia. While one would intuitively reason that one of the factors contributing to the end organ failure is poor nutritional blood flow, this has yet to be demonstrated. The aim of the present study was to determine whether changes in resting nutritional blood flow occur in pre-eclampsia. We used strain-gauge plethysmography to study calf blood flow in 19 women with pre-eclampsia, 13 normal pregnant women and 17 non-pregnant controls. We reasoned that, since the calf comprises mostly skeletal muscle, without anastomotic channels, blood flowing through this region would primarily reflect nutritive flow. Calf blood flow was significantly reduced in women with pre-eclampsia (1.95+/-0.9 ml.min(-1).100 ml(-1)) compared with normal pregnant (3.9+/-1.4 ml.min(-1).100 ml(-1)) and non-pregnant (3.8+/-1.0 ml.min(-1).100 ml(-1)) women (P=0.0004 and P=0.0005 respectively; ANOVA). Blood flow in pre-eclampsia was also correlated significantly with platelet count as an index of disease severity. In addition, there was a significant negative correlation between blood flow and systolic blood pressure (r=-0.69, P=0.004) in the women with pre-eclampsia. These findings support the hypothesis that nutritional blood flow is reduced in pre-eclampsia. We suggest that measurement of resting calf blood flow could give a non-invasive index of deterioration of nutritive blood flow to vital organs in pre-eclampsia.

Plasma leptin concentrations are increased in women with premenstrual syndrome.

Leptin is a metabolic regulator of the hypothalamic- pituitary-gonadal axis, and plays an important role in human reproduction. Its neuro-endocrine effects are mediated by interactions with receptors in the hypothalamus, where emotional drive is also controlled. We postulated that circulating leptin concentrations are increased in premenstrual syndrome (PMS), and that this may be associated with the psychological symptoms of the disease. We obtained fasting venous samples from 32 women with PMS and 28 women with asymptomatic menstrual cycles, matched for age, body mass index and menstrual cycle length. Leptin concentrations were measured by radioimmunoassay. Leptin concentrations increased significantly during the luteal phases of the menstrual cycles of the control and PMS groups as compared with the follicular phase, having excluded the 11 women with PMS and six controls found to be anovulatory on the basis of mid-luteal plasma progesterone concentrations from the analysis. A greater increase was observed in women with PMS than the controls (P: = 0.00006 and 0.003 respectively). Although leptin concentrations in the follicular and luteal phases were higher in PMS than the controls, the difference was only statistically significant between the follicular phases (P: = 0.001). There was no clear relationship between leptin and oestradiol or progesterone in this study. These findings suggest that leptin may play a role in the pathophysiology of the disease, and requires further evaluation.

A longitudinal study of maternal plasma insulin-like growth factor binding protein-1 concentrations during normal pregnancy and pregnancies complicated by pre-eclampsia.

Insulin-like growth factor binding protein-1 (IGFBP-1) is synthesized by the decidual stroma, and is thought to act locally to inhibit IGF activity and so limit trophoblast invasion. Cross-sectional studies have reported conflicting data on maternal circulating concentrations of IGFBP-1 in early pregnancy before the development of pre-eclampsia. A longitudinal study was performed in 10 women who went on to develop pre-eclampsia and a group of 12 normal pregnant controls, chosen to be similar for maternal age, booking body mass index (BMI) and gestational age. Maternal IGFBP-1 concentrations were measured in plasma obtained at 16, 20, 24, 28, 32 and 36 weeks. Plasma IGFBP-1 concentrations were unchanged over this period in normal pregnancy. In contrast, the concentrations in women who developed pre-eclampsia increased progressively. At 16, 20, and 24 weeks the concentrations were significantly lower compared to normal pregnancy, at 28 and 32 weeks, similar, but by 36 weeks the concentrations were significantly greater than the normal controls. The data show that circulating IGFBP-1 concentrations are lower in early pregnancy before the development of pre-eclampsia. Thus, it is suggested that IGFBP-1-induced inhibition of IGF activity is unlikely to be responsible for the impaired trophoblast invasion observed in pre-eclampsia.

Longitudinal analysis of maternal plasma leptin concentrations during normal pregnancy and pre-eclampsia.

Leptin concentrations have been found to be elevated in cross-sectional studies of established pre-eclampsia. Circulating concentrations of leptin were measured in a cross-sectional study to confirm these findings (19 women with pre-eclampsia and 13 normal pregnant controls) and in a longitudinal study to establish the timing of the increase in leptin concentrations (samples obtained at 16, 20, 24, 28, 32, 36 and 38 weeks gestation from eight women who went on to develop pre-eclampsia and seven normal pregnant controls). In the cross-sectional study, plasma leptin concentrations were significantly greater in women with pre-eclampsia than in normal controls (P: = 0.001). In the longitudinal study, it was found that circulating leptin concentrations rose gradually to 32 weeks and thereafter declined slightly in normals. The concentrations in women destined to develop pre-eclampsia were consistently higher from 20 weeks gestation (P: = 0.04-0.003) and, in contrast to the normal controls, rose markedly from 32 weeks as pre-eclampsia developed. This study confirms that plasma leptin concentrations are increased in established pre-eclampsia and reports for the first time that leptin concentrations are elevated before pre-eclampsia is clinically evident.