Expression of insulin-like growth factors I and II in conceptuses from normal and diabetic mice

Immunolocalization of insulin-like growth factors and their receptors in the diabetic mouse oviduct and uterine tissues during the preimplantation period

The aim of the present study was to analyze the immunolocalization of insulin-like growth factor (IGF)-1 and IGF-2 and their receptors in the oviduct and uterus of control and diabetic mice. Sexually mature female ICR mice aged 6-8 weeks were rendered diabetic by streptozotocin (200 mg/kg, administered intraperitoneally). Oviductal and uterine tissues were obtained from the superovulated control and diabetic mice at 48, 72 and 96 h post-human chorionic gonadotropin (hCG) treatment. Localization of IGF-1, IGF-2, IGF-1R and IGF-2R was determined by immunohistochemistry and a semi-quantitative scoring of immunolabelling was performed using a standardized 5-point system. The immunohistochemical scorings for both IGF-1 and IGF-1R were significantly decreased in the oviducts of diabetic mice at 96 h post-hCG treatment. The scores for IGF-2 were significantly increased in the oviducts of diabetic mice at 48 and 72 h post-hCG treatment, and for IGF-2R at 72 h post-hCG treatment. However, there was no significant difference in the scores of IGFs and their receptors in the uterus of control and diabetic mice. In conclusion, the oviductal immunolabelling for IGFs and their receptors was significantly altered by maternal diabetes, which may be of importance in the pathogenesis of preimplantation diabetic embryopathy.

Aortic intima-media thickness and lipid profile in macrosomic newborns

Macrosomia is associated with alterations in lipoprotein composition and concentration at birth. Exposure to diabetes in utero has been established as a significant risk factor for some of the components of metabolic syndrome. The aim of this study was to investigate the effect of macrosomia on lipid metabolism, aortic intima-media thickness (aIMT) and subsequent atherogenic risk in newborn infants. Aortic intima-media thickness was measured in 40 macrosomic neonates of diabetic mothers (group A), 30 macrosomic neonates of healthy mothers (group B) and 30 healthy neonates (group C). Lipid profile was determined in all infants and their mothers. Mean aIMT was significantly higher in macrosomic neonates of diabetic and healthy mothers (0.56+/-0.06 and 0.49+/-0.03 mm respectively) than in controls (0.39+/-0.03 mm). Weight-adjusted aIMT in macrosomic neonates of diabetic mothers (0.129+/-0.013 mm/kg) was significantly higher than in groups B and C (0.114+/-0.008 and 0.113+/-0.011 mm/kg respectively). There were significant alterations of total serum, high-density lipoprotein (HDL), very low-density lipoprotein (VLDL) cholesterols and triglyceride levels in the macrosomic neonates of diabetic mothers compared with controls. Macrosomia was associated with increased lipid concentrations. Macrosomic neonates of diabetic mothers have significantly higher aIMT with lipid alterations. This may play a role in the pathogenesis of atherosclerosis in adult life.

Serum insulin-like growth factor-I (IGF-I) IGF binding protein-3 (IGFBP-3) and leptin levels are related to abdominal aortic intima-media thickness in macrosomic newborns

OBJECTIVE

Exposure to diabetes in utero has been established as a significant risk factor for some of the components of metabolic syndrome, and was associated with increased levels of maternal, placental, and fetal insulin-like growth factors and leptin. The atherogenic effects of leptin and insulin-like growth factor-I (IGF-I) have been extensively described. The present study was therefore designed to investigate relationships between abdominal aortic intima-media thickness (aIMT), serum IGF-I, IGF binding protein-3 (IGFBP-3) and leptin levels in macrosomic newborns.

DESIGN

Neonates whose birth weights exceed 90th percentile for gestational age and gender are termed macrosomic. Abdominal aortic intima-media thickness was measured in 30 macrosomic neonates of diabetic mothers (group A), 30 macrosomic neonates of healthy mothers (group B) and 30 healthy neonates (group C). Serum IGF-I, IGFBP-3 and leptin levels were determined in all infants and their mothers. Stepwise logistic regression analysis was used to determine independent risk factors for aortic intima-media thickness.

RESULTS

Mean aortic intima-media thickness was significantly higher in groups A and B (0.489+/-0.015,0.466+/-0.019 mm, respectively) than in controls (0.375+/-0.024 mm, p<0.0001). Weight-adjusted aortic intima-media thickness was significantly higher in-group A than in groups B (p=0.004) and C (p=0.048). Serum leptin concentration in-group B (37.4+/-10.7 ng/ml) was significantly greater than in-group C (23.5+/-7.1 ng/ml, p<0.0001), but significantly lower than in-group A (46.6+/-14.1 ng/ml, p<0.0001). Serum IGF-I levels of the infants were significantly lower in-group C (113.2+/-33.1 ng/ml) than in groups A and B (205.2+/-60.1 and 179.3+/-55.1 ng/ml respectively, p<0.0001). Serum IGF-I, IGFBP-3 and leptin levels of the infants were positively correlated with mean (p<0.0001) and weight-adjusted aortic intima-media thickness measurements (p=0.003, p=0.006 and p=0.001, respectively).

CONCLUSIONS

Macrosomic neonates of diabetic mothers have significantly increased aortic intima-media thickness with higher serum IGF-I, IGFBP-3 and leptin concentrations than those of controls. It might be speculated that these changes may exaggerate the atherosclerotic process later in life.

Macrosomic newborns of diabetic mothers are associated with increased aortic intima-media thickness and lipid concentrations

BACKGROUND/AIMS

Exposure to diabetes in utero has been established as a significant risk factor for some of components of metabolic syndrome. A few studies have examined relationship between the metabolic syndrome and echocardiographic left ventricular (LV) mass. We aimed to investigate relationship between abdominal aortic intima-media thickness (aIMT), LV mass and lipid profile in macrosomic newborns.

METHODS

Abdominal aIMT was measured in 30 macrosomic neonates of diabetic mothers (group A), 30 macrosomic neonates of healthy mothers (group B) and 30 healthy neonates (group C). Lipid profile and LV mass were determined.

RESULT

Mean aIMT was significantly higher in groups A and B (0.489 +/- 0.015, 0.466 +/- 0.019 mm, respectively) than in controls (0.375 +/- 0.024 mm). Weight-adjusted aIMT in group A was significantly higher than in groups B and C. Macrosomia was associated with increased lipid concentrations. Both LV mass indexed for BSA (body surface area) and birth weight measurements were significantly increased in group A compared with control.

CONCLUSIONS

Macrosomic neonates of diabetic mothers have significant aIMT and LV mass indexed for BSA and birth weight with lipid alterations. It might play a role in the pathogenesis of atherosclerosis in adult life.

Altered nephrogenesis due to maternal diabetes is associated with increased expression of IGF-II/mannose-6-phosphate receptor in the fetal kidney

We have recently demonstrated that the exposure to hyperglycemia in utero impairs nephrogenesis in rat fetuses (Amri K et al., Diabetes 48:2240-2245, 1999). Diabetic pregnancy is commonly associated with alterations in the IGF system in fetal tissues. It has also been shown that both IGF-I and IGF-II are produced within developing metanephros and promote renal organogenesis. Therefore, we investigated the effect of maternal diabetes on IGFs and their receptors in developing fetal rat kidney. Diabetes was induced in pregnant rats by a single injection of streptozotocin on day 0 of gestation. We measured the amounts of IGF and their receptors, both proteins and mRNAs, in the metanephroi of fetuses issued from diabetic subjects and in age-matched fetuses from control subjects (14-20 days of gestation). IGF-II was produced throughout fetal nephrogenesis, whereas IGF-I protein was not detected, suggesting a critical role of IGF-II in kidney development. Fetal exposure to maternal diabetes caused no change in IGF production in the early stages of nephrogenesis. Similarly, the amounts of IGF-I receptor and insulin receptor were not altered. By contrast, there was an increase in production of IGF-II/mannose-6-phosphate receptor throughout nephrogenesis. Because this receptor plays an essential role in regulating the action of IGF-II, the altered nephrogenesis in fetuses exposed to maternal diabetes may be linked to a decrease in IGF-II bioavailability.

Alterations of expression of developmentally important genes in preimplantation bovine embryos by in vitro culture conditions: implications for subsequent development

Recent advances in molecular technology and in vitro production of bovine embryos have enabled studies of gene transcription in preimplantation embryos. On the basis of knowledge of the sequence of the selected gene, various modifications of Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) technology have been employed. Several lines of evidence in mouse and cattle indicate that expression patterns of genes from in vitro-produced embryos are not necessarily representative of those of in vivo embryos. An important gene that has been found to be expressed by in vivo-derived bovine blastocysts, but not in their in vitro-produced counterparts, is the Connexin43 gene that is crucial for maintenance of compaction. The bovine leukemia inhibitory factor (bLIF) and LIF-receptor-beta (LR-beta) genes were expressed by in vitro-produced embryos, but not in their in vivo counterparts. The heat shock protein gene 70.1 (Hsp 70.1) was upregulated by blastocysts produced in vitro compared to in vivo embryos, while the glucose transporter-1 mRNA (Glut-1) was downregulated by morulae produced in vitro as compared to in vivo-derived morulae. Furthermore, mRNA expression levels of a set of "marker genes" were shown to be affected by the presence or absence of serum in the culture medium. Most embryos grown under serum-free conditions had higher mRNA abundances than those cultured in serum-enriched medium. It is hypothesized that persistent alterations of the normal gene expression patterns may be responsible for the large offspring syndrome that is observed in approximately one third of the calves resulting from the transfer of in vitro-produced embryos. A primary candidate for such deviations may be an altered methylation pattern that can either lead to silencing or induction of a specific gene. Messenger RNA phenotyping of genes essential in early development provides a useful tool to assess the normality of the produced embryos and a tool to optimize in vitro culture conditions for bovine embryos.

Maternal and fetal insulin-like growth factor system and embryonic survival during pregnancy in rats: interaction between dietary chromium and diabetes

Chromium (Cr) depletion may exacerbate hyperglycemia and negative outcomes of pregnancy in the streptozotocin (STZ) diabetic pregnant rat model through the regulation of the insulin-like growth factor (IGF) system. To test this hypothesis, 40 female rats, all fed a low Cr diet (i.e., 70 microgram Cr/kg diet ) from 21 d of age, were randomly assigned one of four treatments, applied on Day 1 of pregnancy, in a 2 x 2 factorial design: 1) very low Cr diet (40 microgram Cr/kg diet) + citrate buffer injection, 2) very low Cr diet + STZ injection (30 mg STZ/kg body wt in citrate buffer), 3) adequate Cr diet (2 mg Cr [from added CrK(SO4)2]/kg diet) + citrate buffer injectionand 4) adequate Cr diet + STZ injection. Blood and tissues were collected on Day 20 of pregnancy. Chromium depletion increased (P < 0.05) urinary hydroxyproline excretion, 22-kDa IGF binding protein (IGFBP) concentration and litter size but decreased (P < 0. 05) placental wt, percentage of protein per fetus, and fetal IGF-I and -II concentrations. Chromium had no effect (P > 0.10) on maternal hormones, 32-kDa IGFBP, glucose, or placental and fetal hydroxyproline concentrations. Diabetes decreased (P < 0.05) maternal wt gain, embryonic survival, litter size, mean pup wt and maternal insulin concentrations, increased (P < 0.05) maternal blood glucose, IGF-I concentrations and maternal hydroxyproline excretion but did not affect fetal concentrations of hormones, IGFBP, glucose or hydroxyproline. Interaction between chromium and diabetes tended (P < 0.10) to affect maternal IGF-II concentrations, but had no effect on other maternal or fetal variables. In conclusion, maternal chromium depletion did not exacerbate hyperglycemia or pregnancy outcome in STZ-induced diabetic rats, but may negatively affect fetal protein content by decreasing fetal IGF-II concentrations. Diabetes may negatively affect fetal growth through its effect on maternal glucose, insulin and IGF-I.

The role of growth factors in preimplantation development

It has become clear that the mammalian embryo participates in a complex dialogue with the maternal physiology. The language of the dialogue is growth factor signalling. The embryo expresses receptors for insulin, IGFs, GH, EGF and cytokines including LIF, and CSFs; whilst ligands are secreted by the supporting tissues of the oviduct and uterus, and in some cases, the embryo itself. In the preimplantation period when the embryo is travelling to the uterus and passing through its first differentiation, these ligands affect embryonic physiology, apparently in ways that optimise developmental potential and synchronise embryonic and maternal physiologies. It is not yet clear in most cases whether this is by autocrine, paracrine or endocrine mode. In the crucial peri-implantation phase the embryo is preparing to invade the maternal system for which extensive uterine remodelling is necessary. A model is proposed in which a cascade of growth factor activities, orchestrated by the ovarian steroid patterns, choreographs the biochemical players (ECM proteinases and their inhibitors) which initiate this activity.