Rita van Bree

C-peptide, insulin-like growth factors I and II, and insulin-like growth factor binding protein-1 in umbilical cord serum: Correlations with birth weight

OBJECTIVE Our purpose was to determine the correlation between birth weight and hormones or growth factors believed to be involved in fetal growth: insulin, insulin-like growth factors I and II, and insulin-like growth factor binding protein-1. STUDY DESIGN Five hundred thirty-eight cord serum samples were analyzed for insulin-like growth factor-I, insulin-like growth factor-II, C-peptide, and insulin-like growth factor binding protein-1 by immunoassay. Samples included all gestational ages in the third trimester and a large range of birth weights. RESULTS Cord serum insulin-like growth factor-I concentrations increased until 39 weeks (+84% from 28 to 29 weeks), followed by a 21% decline at 41 weeks. Insulin-like growth factor-I levels were decreased by 40% in small-for-gestational-age (< 10th percentile) newborns and were increased by 28% in large-for-gestational-age (> 90th percentile) newborns in the absence of diabetes. Insulin-like growth factor-I levels were best correlated with birth weight (R = 0.48, p < 0.001). Cord serum insulin-like growth factor-II concentrations were sixfold to tenfold higher than those of insulin-like growth factor-I and were 8% to 10% (p < 0.001) higher in large-for-gestational-age than in average-weight and small-for-gestational-age newborns. Cord serum C-peptide concentrations were 28% and 34% higher in large-for-gestational-age than in average-for-gestational-age and small-for-gestational-age newborns, respectively. Insulin-like growth factor binding protein-1 levels were increased in preterm average-for-gestational-age and in term small-for-gestational-age newborns compared with term average-for-gestational-age newborns and showed a negative correlation with birth weight (R = -0.43, n = 131, p < 0.001). Insulin-like growth factor binding protein-1 was not correlated with C-peptide concentrations. CONCLUSIONS Insulin-like growth factors I and II and insulin are all related to fetal growth and weight gain, and insulin-like growth factor-I correlates best with birth weight. Insulin is mainly related to fetal overgrowth (macrosomia). Insulin-like growth factor binding protein-1 may be a growth inhibitor in the fetus.

Decreased osteoblast activity in spontaneously diabetic rats: in vivo studies on the pathogenesis

Diabetes in both humans and rats is accompanied by low bone formation, which is presumably caused by serum-borne factors. To explore its pathogenesis, we carried out experiments in diabetic and nondiabetic BB rats, using plasma osteocalcin concentrations (OC) as a marker for osteoblast activity. In nondiabetic rats, the iv infusion of glucose (30%, 4 d) did not change OC; sc insulin infusion (4 U/d, 14 d) reduced OC by 27% (p<0.01). In diabetic rats, OC were decreased from the first day of glycosuria (71±5% of paired controls), declining exponentially to 24±3% after 5 wk. Insulin infusion (1,2, and 3 U/d, 14 d) produced gradual restoration of OC. OC were better correlated with insulin-like growth factor-I (IGF-I) than with insulin levels in these experiments. OC were dramatically increased 4 d after adrenalectomy (ADX) in all diabetic rats (73±8 vs 22±4 μg/L before ADX;p<0.001), but not if corticosterone was administered. Ligand blotting of IGF binding proteins showed a marked decrease in two bands (44–49 and 32–35 kDa) 10–14 d after diabetes onset; the density of these bands was increased, but not normalized after ADX. Thus, decreased osteoblast activity is present from the onset of diabetes, is dependent on endogenous corticosterone, and cannot be reproduced by hyperglycemia in nondiabetic rats.

Cholesterol‐independent endothelial dysfunction in virgin and pregnant rats fed a diet high in saturated fat

1 Western diets high in saturated fat are associated with an increased incidence of cardiovascular diseases. In this study we have evaluated vascular endothelial function and oxidative stress in virgin rats fed a normal (VC) or high in saturated fat diet (VHF) (20% lard and corn oil w/w) from weaning until adulthood, and throughout subsequent pregnancy (PC and PHF, respectively). 2 The saturated fat diet was associated with enhanced noradrenaline sensitivity in small mesenteric arteries from VHF rats (VHF vs. VC, P < 0.05) and blunted endothelium‐dependent relaxation in VHF and PHF rats (VHF vs. VC, P < 0.001; PHF vs. PC, P < 0.05). Endothelial dysfunction was attributable to a reduced nitric oxide component of relaxation in VHF rats, and blunted prostacyclin and endothelium‐derived hyperpolarizing factor components in PHF rats. 3 Other than plasma cholesterol, which was reduced in VHF and PHF rats, plasma lipids were normal. Fasting plasma insulin and glucose concentrations were raised in VHF rats (P < 0.05) and the plasma marker of oxidative stress, 8‐iso PGF2α, was increased in PHF animals (P < 0.01). 4 These findings suggest that endothelial dysfunction induced by a saturated fat diet is cholesterol independent and likely to be of different mechanistic origin in virgin and pregnant rats.

Pregnancy in Mice Lacking the Vitamin D Receptor: Normal Maternal Skeletal Response, But Fetal Hypomineralization Rescued by Maternal Calcium Supplementation

Fetal mineralization appears to be driven by the pregnancy-induced stimulation of intestinal Ca absorption. We thus hypothesized that mineralization would be impaired in fetuses of mice that lack the vitamin D receptor (VDR). Here we report on the maternal response to pregnancy, and the fetal mineralization, in mice with a homozygous disruption of the VDR gene (VDR −/−) mated with wild-type (wt) males. We found that VDR −/− mice show mild hypocalcemia, clear rickets and osteomalacia on bone histomorphometry, lower cortical bone density on quantitative tomography, and reduced concentrations of calbindin-D9k (CaBP-D9k) in duodenal mucosa and kidney. The skeletal response to pregnancy was comparable in wt and VDR −/− mice; duodenal CaBP-D9k concentrations increased during pregnancy in VDR −/− as in wt mice, but remained 40% lower than in wt mice. We confirmed our hypothesis that mineralization is defective in d18.5 VDR+/ − fetuses of VDR −/− mice, both by whole-body Ca determination and histomorphometric evaluation; the number of osteoclastic cells in bone was increased. The fetuses were hypercalcemic and had a 5-fold increase in circulating 1,25(OH)2D3. We then studied pregnancies in VDR −/− females, mated with wt males, fed a high Ca/P/lactose rescue diet during pregnancy. The rescue diet normalized the mineralization, the number of osteoclastic cells, and plasma Ca and 1,25(OH)2D3 concentrations in the fetuses. We interpret the data as evidence that, to ensure normal fetal mineralization, the maternal VDR-dependent intestinal Ca absorption can be substituted by passive Ca absorption entrained by a higher Ca intake. Alternatively or additionally, elevated 1,25(OH)2D3in utero may disturb bone development.

Vitamin D Deficiency in Guinea Pigs: Exacerbation of Bone Phenotype During Pregnancy and Disturbed Fetal Mineralization, with Recovery by 1,25(OH)2D3 Infusion or Dietary Calcium-Phosphate Supplementation

Vitamin D (D) deficiency during human pregnancy appears to disturb fetal growth and mineralization, but fetal development is normal in D-deficient rats and vitamin D receptor gene-ablated mice. We used the guinea pig model to investigate maternal and fetal effects of D deficiency. Pregnant (Pr) and nonpregnant (NPr) animals were fed a D-replete (+D) or D-deficient diet (?D) for 8 weeks. We further studied whether the effects of a ?D diet are reversed by continuous 1,25(OH)2D3 infusion (?D+1,25) and/or by a lactose-, Ca- and P-enriched D-deficient diet (?D+Ca/P). Bone analyses included histomorphometry of the proximal tibiae, dual-energy X-ray absorptiometry (DXA), and quantitative computed tomography (QCT) of the femora. Depletion of 25(OH)D3 and 1,25(OH)2D3 levels and the D-deficiency syndrome were more severe in pregnant animals. Indeed, Pr/?D but not NPr/?D guinea pigs were hypophosphatemic, and showed robust increases in growth plate width and osteoid surface and thickness; in addition, bone mineral density on DXA was lower in Pr/?D animals only, which was exclusively in cortical bone on QCT. Bone phenotype was partly normalized in Pr/?D+1,25 and Pr/?D+Ca/P animals. Compared with +D fetuses, ?D fetuses had very low or undetectable 25(OH)D3 and 1,25(OH)2D3, were hypercalcemic and hypophosphatemic, and had lower osteocalcin levels. In addition, body weight and total body bone mineral content were 10–15% lower; histomorphometry showed hypertrophic chondrocyte zone expansion and hyperosteoidosis. 1,25(OH)2D3 levels were restored in ?D+1,25 fetuses, and the phenotype was partially corrected. Similarly, the fetal +D phenotype was rescued in large part in ?D+Ca/P fetuses, despite undetectable circulating 25(OH)D3 and 1,25(OH)2D3. We conclude that pregnancy markedly exacerbates D deficiency, and that augmenting Ca and P intake overrides the deleterious effects of D deficiency on fetal development.

Adverse Adipose Phenotype and Hyperinsulinemia in Gravid Mice Deficient in Placental Growth Factor

Pregnancy-induced metabolic changes are regulated by signals from an expanded adipose organ. Placental growth factor (PlGF), acting through vascular endothelial growth factor receptor-1, may be among those signals. There is a steep rise in circulating PlGF during normal pregnancy, which is repressed in gravidas who develop preeclampsia. PlGF-deficiency in mice impairs adipose vascularization and development. Here we studied young-adult PlGF-deficient (PlGF(-/-)) and wild-type mice on a high-fat diet in the nongravid state and at embryonic day (E) 13.5 or E18.5 of gestation. Litter size and weight were normal, but E18.5 placentas were smaller in PlGF(-/-) pregnancies. PlGF(-/-) mice showed altered intraadipose dynamics, with the following: 1) less blood vessels and fewer brown, uncoupling protein (UCP)-1-positive, adipocytes in white sc and perigonadal fat compartments and 2) white adipocyte hypertrophy. The mRNA expression of beta(3)-adrenergic receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha, and UCP-1 was decreased accordingly. Moreover, PlGF(-/-) mice showed hyperinsulinemia. Pregnancy-associated changes were largely comparable in PlGF(-/-) and wild-type dams. They included expanded sc fat compartments and adipocyte hypertrophy, whereas adipose expression of key angiogenesis/adipogenesis (vascular endothelial growth factor receptor-1, peroxisome proliferator-activated receptor-gamma(2)) and thermogenesis (beta(3)-adrenergic receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha, and UCP-1) genes was down-regulated; circulating insulin levels gradually increased during pregnancy. In conclusion, reduced adipose vascularization in PlGF(-/-) mice impairs adaptive thermogenesis in favor of energy storage, thereby promoting insulin resistance and hyperinsulinemia. Pregnancy adds to these changes by PlGF-independent mechanisms. Disturbed intraadipose dynamics is a novel mechanism to explain metabolic changes in late pregnancy in general and preeclamptic pregnancy in particular.

Adipokine profile and C-reactive protein in pregnancy: effects of glucose challenge response versus body mass index.

Objective: To test the hypothesis that gravidas who have an abnormal response to glucose loading have dysfunctional adipose tissue cells that produce more insulin resistance-inducing and proinflammatory adipokines but less insulin-sensitizing adipokines. Methods: We performed a nested case-control study within a larger sample of gravidas who had a glucose challenge test (GCT) at 24-29 weeks; we compared 73 cases with an abnormal GCT (>8.3 mM) and 146 controls with a strictly normal GCT (<7.2 mM) matched for body mass index (BMI) and height (mean diference between cases and controls: 0. 1 kg/mn2 and 1 cm, respectively). We measured plasma insulin, adipokines (leptin, adiponectin, resistin, tumor necrosis factor [TNF]-α, interleukin [IL]-6), soluble leptin receptor (sOb-R), the main leptin-binding protein, and C-reactive protein (CRP). Results: The cases showed a 48% increase in insulin concentrations and a 27% increase in TNF-α concentrations compared to the controls (both P < .0001), but leptin, sOb-R, IL-6, and adiponectin, as well as CRP, concentrations were comparable between cases and controls. In the whole group (n = 219), BMI was correlated with insulin, leptin, IL-6, and CRP, and inversely with sOb-R and adiponectin concentrations (all P < .0003). Conclusions: Plasma leptin, sOb-R, IL-6, and adiponectin, as well as CRP, are strongly related to BMI ingravidas at 24-29 weeks gestational age but not to the glucose loading response. However, TNF-α is higher in women with an abnormal GCT. Further studies should disclose the source of increased TNF-α in these women, and to assess whether TNF-α is causally related to glucose intolerance during pregnancy.

Insulin-like growth factor-II regulates maternal hemodynamic adaptation to pregnancy in rats

The relationship between maternal plasma volume (PV) expansion and fetal growth is well established, but the underlying mechanisms remain unclear. Here, we examined the influence of maternal body weight and fetoplacental mass on gestational PV increment in the rat. Because IGF-I and IGF-II have growth-promoting and vasoactive properties, their relationship to PV expansion and fetoplacental growth was also studied. In normal rats, the gradual expansion of PV (+35% at day 22, i.e., term) was accompanied by a rise in circulating IGF-II (+45%) and a considerable drop in IGF-I (-73%). Increased maternal body weight induced by an obesogenic diet did not influence PV and circulating IGFs compared with rats on the standard diet. Combining the results from both diets, circulating IGF-II was the principal correlate of PV. A second experiment examined the effect of fetoplacental mass reduction by surgically removing half of the gestational sacs at day 16. This procedure reduced maternal PV and circulating IGF-II at term by 14% and 20%, respectively. We then investigated the effect of a constant infusion of IGF-II (1 mgxkg(-1)xday(-1)) from day 16, which raised circulating IGF-II by 38% and found increased PV (+19%) and a larger placental trophospongial area (+29%) at term. Our results indicate that the placenta, the primary source of IGF-II synthesis in pregnancy, drives PV expansion, and that IGF-II is among the regulatory factors of the gestational PV increment. Further studies should clarify whether IGF-II directly affects vascular function and/or indirectly promotes the secretion of placenta-derived vasoactive substances.

Oxidative stress after antenatal betamethasone: Acute downregulation of glutathione peroxidase-3

BACKGROUND Human and experimental data show that antenatal exposure to glucocorticoids (GC) temporarily reduces fetal well-being and impairs the fetal response to hypoxemia. AIMS We tested the hypothesis that antenatal betamethasone provokes transient oxidative stress, which may be triggered directly by the GC or indirectly by metabolic signals such as increased glucose and free fatty acid (FFA) concentrations. STUDY DESIGN Prospective (single center, 18 months) cohort study in newborns <34 weeks gestational age at birth. METHODS We studied 105 newborns and measured oxidative damage to lipids [malondialdehyde (MDA)] and proteins (protein carbonyls), as well as glutathione peroxidase-3 (GPx3), an important antioxidant enzyme, in umbilical vein (UV) plasma. In addition, we measured umbilical artery and UV blood gases, and metabolic indices (plasma glucose, FFA and insulin) in UV. RESULTS MDA but not protein carbonyl concentrations was inversely related to time elapsed since the first or last betamethasone administration (p=0.006); MDA remained elevated by 69-96% for at least 72 h after the last betamethasone. By contrast, GPx3 concentrations were repressed in newborns who received betamethasone < or =24h before birth. GPx3 and MDA concentrations were correlated (r=-0.38, p<0.001). Labor, GA, sex, size at birth, blood gases or metabolic indices did not explain the effects of betamethasone on MDA and GPx3. CONCLUSIONS Antenatal GC elicit a rapid suppression of the GPx3 antioxidant defense system which may contribute to a longer-lasting but also transient rise in lipid oxidative damage.

Transient catabolic state with reduced IGF-I after antenatal glucocorticoids.

Glucocorticoid (GC) administration before preterm birth reduces neonatal morbidity but may restrain growth. Here we explored the effect of antenatal GC on nutrient substrates [glucose, FFA, amino acids (AA)], and on IGF-I and IGF-binding protein-1 (IGFBP-1). We analyzed umbilical vein (UV) plasma obtained at birth from 91 preterm newborns that received one course of GC (last exposure 1–1358 h before birth) and 49 newborns that did not. We found that recent GC exposure (≤48 h) raised glucose, FFA, and AA concentrations, and the homeostasis model assessment of insulin resistance (HOMA-IR) index, but lowered IGF-I concentrations. The AA surge was greater in newborns with a birth weight z score <0 than in those with a z score >0. Although all AA were transiently increased, the increment was most robust for glutamine and alanine. Shorter duration since GC administration and lower IGF-I concentrations independently predicted AA levels. In conclusion, an antenatal course of GC elicited a transient catabolic state encompassing all nutrient substrates, and a temporary drop in IGF-I concentrations. These changes may explain the growth-inhibitory effects of repeated antenatal GC administration. Future research should clarify the role of IGF-I in the protein-catabolic response to GC.