Selective ligation of uterine artery branches accelerates fetal growth in the rat

The Crowded Uterine Horn Mouse Model for Examining Postnatal Metabolic Consequences of Intrauterine Growth Restriction vs. Macrosomia in Siblings

Differential placental blood flow and nutrient transport can lead to both intrauterine growth restriction (IUGR) and macrosomia. Both conditions can lead to adult obesity and other conditions clustered as metabolic syndrome. We previously showed that pregnant hemi-ovariectomized mice have a crowded uterine horn, resulting in siblings whose birth weights differ by over 100% due to differential blood flow based on uterine position. We used this crowded uterus model to compare IUGR and macrosomic male mice and also identified IUGR males with rapid (IUGR-R) and low (IUGR-L) postweaning weight gain. At week 12 IUGR-R males were heavier than IUGR-L males and did not differ from macrosomic males. Rapid growth in IUGR-R males led to glucose intolerance compared to IUGR-L males and down-regulation of adipocyte signaling pathways for fat digestion and absorption and type II diabetes. Macrosomia led to increased fat mass and altered adipocyte size distribution compared to IUGR males, and down-regulation of signaling pathways for carbohydrate and fat digestion and absorption relative to IUGR-R. Clustering analysis of gonadal fat transcriptomes indicated more similarities than differences between IUGR-R and macrosomic males compared to IUGR-L males. Our findings suggest two pathways to adult metabolic disease: macrosomia and IUGR with rapid postweaning growth rate.

Intrauterine growth restriction in a rodent model and developmental programming of the metabolic syndrome: a critical appraisal of the experimental evidence

Research on intrauterine growth restriction (IUGR) and subsequent development of obesity, type 2 diabetes and the metabolic syndrome is rapidly expanding, and potential implications for primary prevention are considerable. We have critically appraised one of the experimental animal models frequently used as mimic of human fetal growth restriction, which involves bilateral ligation of the uterine artery in rats (Lig). Our experimental study showed that Lig performed on day 17 of pregnancy neither leads to IUGR nor to neonatal catch-up growth, an important pathogenetic co-factor in humans. Meta-analysis of the literature revealed domination by studies in which Lig pups with IUGR were actively selected. Accordingly, publication bias is evident (p=0.007). Altered placental perfusion--the main cause of IUGR in humans in Western countries--neither led to IUGR nor to neonatal catch-up growth in Lig offspring, i.e., to none of the etiological factors of the human 'small baby syndrome'. Appropriate and reproducible rodent models of IUGR through decreased placental flow remain to be established to uncover the pathophysiological basis of the 'small baby syndrome'. This may lead to new strategies of primary prevention of diabetes, obesity, and the metabolic syndrome.

Effect of uteroplacental insufficiency upon brain neuropeptide Y and corticotropin-releasing factor gene expression and concentrations

Various hypothalamic functions such as feeding behavior, energy expenditure, body weight gain, level of anxiety, and sexual maturation are mediated by a balance between the concentrations of neuropeptide Y (NPY) and corticotropin-releasing factor (CRF). To test the hypothesis that maternal uteroplacental insufficiency alters the offspring's brain NPY and/or CRF levels, we examined the effect of maternal uterine artery ligation with intrauterine growth restriction (IUGR) (p < 0.05) upon fetal (20 d) and postnatal (4, 14, and 21 d) brain NPY and CRF synthesis, concentrations, and regional distribution. An age-related increase in NPY (0.8 kb) and CRF (1.4 kb) mRNA levels with peak amounts at the 14-d postnatal age (p < 0.05) was observed. IUGR was associated with a 75% increase in fetal brain NPY mRNA levels (p < 0.05) with no change in NPY peptide, CRF mRNA and peptide amounts. Although the increase in NPY mRNA levels persisted postnatally (p < 0.05) at d 4 and 21, CRF mRNA amounts were 2.5-fold higher only in the 4-d IUGR (p < 0.05). Paralleling the mRNA changes, an age-related increase in RIA of NPY and CRF peptide concentrations was noted (p < 0.05). IUGR caused postnatal brain NPY and CRF peptide changes similar to corresponding mRNA levels (p < 0.05), despite normal postnatal circulating glucose, insulin, corticosterone, and leptin concentrations. The age-specific intergroup differences in the NPY and CRF peptide immunoreactivity appeared predominantly in the hypothalamic region. We conclude that maternal uteroplacental insufficiency causing IUGR leads to a pretranslational imbalance in the immediate (4 d) postnatal brain NPY and CRF peptide concentrations, thereby altering the developmental pattern. This alteration in NPY and CRF peptide concentrations, despite normalization of the metabolic milieu was associated with a persistent diminution in body weight. The IUGR-associated pretranslational increase in NPY and not CRF peptide levels at d 21, may herald changes in feeding behavior during the postsuckling phase.

The effects of the antihormones RU486 and tamoxifen on fetoplacental development and placental bed vascularisation in the rat: a model for intrauterine fetal growth retardation

OBJECTIVE

To examine the effect of administration of the antihormones RU486 and tamoxifen in early pregnancy during the period of maximal decidual development in the rat upon fetoplacental and placental bed development.

DESIGN

Case-control study in an experimental animal model.

SETTING

Academic department of obstetrics and gynaecology in a UK medical school.

ANIMALS

Small laboratory animal-the rat-exhibiting haemochorial placentation.

INTERVENTION

Administration of antiprogesterone or antioestrogen (RU486 and tamoxifen respectively) during early pregnancy.

MAIN OUTCOME MEASURES

Weight of the whole pregnancy implant, fetus, mesometrial decidua and placenta; incidence of intrauterine fetal death: and histological changes in the placental bed.

RESULTS

RU486 produced resorption of all implants when administered above a threshold dose, below which it had no effect upon subsequent fetoplacental development. Tamoxifen treatment on days 9 to 11 resulted in significant reduction of decidual weight (35.1% on day 12 of pregnancy, P < 0.001). This was associated with a higher rate of implants or fetuses weighing below the 10th centile (59.6% and 5.7% on day 12, P < 0.001; 42.9% and 7% on day 16, P < 0.001; 25.4% and 7.6% on day 20, P < 0.001 in treated and control animals, respectively). This was also associated with a higher rate of intrauterine fetal death (30.7% on day 16 compared with 4.5% in controls, P < 0.001; 47.8% on day 20 compared to 0.83% in controls, P < 0.001). Histologically, the placental bed of treated animals failed to develop a dilated uteroplacental artery although trophoblast cells migrated endovascularly to a level equivalent to untreated animals.

CONCLUSIONS

RU486 had an all or none dose-dependent effect on fetoplacental development, resulting in either abortion or normal development of pregnancy. Tamoxifen produced significant impairment of decidual development, which was associated with altered blood vessel transformation in the placental bed, impaired fetoplacental development and higher incidence of growth retarded fetuses and fetal death.

Altered hepatic gene expression of enzymes involved in energy metabolism in the growth-retarded fetal rat

Intrauterine growth retardation (IUGR) resulting from placental insufficiency is a common complication of pregnancy. Bilateral uterine artery ligation of the pregnant rat is a model which mimics intrauterine growth retardation in the human. IUGR rat fetuses have altered hepatic energy and redox states, with reduced fetal hepatic ATP/ADP ratio, increased cytosolic NAD+/NADH ratio, and decreased mitochondrial NAD+/NADH ratio. These critical changes in energy metabolism contribute to IUGR. The effects of these changes at the molecular level are largely unknown. To address these effects we compared hepatic mRNA populations of IUGR and normal fetuses and neonates using mRNA differential display, a polymerase chain reaction-based method for assaying transcriptional differences under various conditions. We isolated and sequenced 18 cDNA products whose mRNA levels were elevated in IUGR compared with normal fetal and neonatal liver. These analyses demonstrated that NADH-ubiquinone oxireductase subunit 4L mRNA (ND-4L) was significantly increased in liver of IUGR fetuses and neonates. This suggested that IUGR may be associated with altered expression of genes involved in the generation of ATP and NADH. Therefore, we measured mRNA levels of adenine-nucleotide translocator-2 (ANT-2), glucose-6-phosphate dehydrogenase (G6PD), mitochondrial malate dehydrogenase (MMD), ornithine transcarbamylase (OTC), and phosphofructokinase-2 (PFK-2) using a semiquantitative reverse transcriptase-polymerase chain reaction-based technique. In the IUGR fetus, ND-4L, ANT-2, G6PD, and MMD mRNA levels were significantly elevated; PFK-2 mRNA levels were unchanged, and OTC levels were decreased. In the IUGR newborn rat, mRNA levels of all 6 enzymes were increased suggesting that the metabolic state of the growth retarded newborn remains abnormal after birth. Uteroplacental insufficiency affects the immediate and long-term metabolic milieu of the growth retarded animal, and forces specific adjustments, including the expression of mRNA encoding enzymes involved with hepatic energy production.