Insulin-like growth factor binding protein (IGFBP-1) involvement in intrauterine growth retardation: study on IGFBP-1 overexpressing transgenic mice

In humans, intrauterine growth retardation is correlated to high levels of serum IGF binding protein-1 (IGFBP-1). This present study analyzes in vivo the impact of circulating IGFBP-1 on body growth associated to bone mineralization and carbohydrate resources. Transgenic mice used in this work overexpressed human IGFBP-1 in liver from embryonic day (E)14.5, concomitantly to the appearance of ossification centers, through to adulthood. Growth retardation was observed as early as E17.5 in homozygous (HM) mice being 20% smaller at birth (postnatal d 1). Anatomical analysis of the skeletons by alizarin red and alcian blue staining showed that the mice exhibited pleiotropic defects of several skeletal units. Some bones were small and dysmorphic. Our results showed reduced mineralization in the posterior area of the skull (delayed suture closure), as well as in the appendicular and axial skeleton. Heterozygous crossings showed a loss of HM animals. Moreover, IGFBP-1 overexpression contributed to decreased fetal hepatic glycogen and neonate blood glucose levels which constitute the main reservoir of carbohydrate resources for neonates. Thus, this reduced carbohydrate pool contributed to perinatal mortality. Maternal IGFBP-1 expression was also clearly associated with neonate growth retardation (newborn weights from HM mothers were 20% smaller than newborns from NT mothers) and reduced fetal carbohydrate resources. In conclusion, antenatal growth retardation and delayed mineralization in transgenic mice are related to overexpressed fetal and maternal circulating human IGFBP-1. Similar perturbations could be observed in human intrauterine growth retardation suggesting the IGF/IGFBP system is involved in fetal growth, biomineralization, and energetic status in humans.     

The effect of maternal IGF-I on fetal and placental growth in mice

Insulin-like growth factor-I (IGF-I) is a polypeptide that mediates growth-promoting actions of GH and has insulin-like activity. Increase in the levels of IGF-I in the maternal and fetal circulation during pregnancy and the identification of the specific receptors for IGF-I in a variety of fetal tissues suggest that IGF-I may play a significant role in the regulation of fetal growth. The present study was undertaken to determine the significance of maternal IGF-I on fetal and placental growth by administering the specific antiserum for IGF-I to pregnant mice. The antiserum was produced by repeatedly injecting recombinant IGF-I into rabbits. The antiserum obtained showed 30% binding to 125I-IGF-I at a dilution of 1:240,000, and crossreactivity with IGF-II was 0.012%. In the first set of experiments, pregnant mice were given a daily dose of 50 microliters of the original antiserum (E-1) or normal rabbit serum (C-1) into the peritoneal cavity between Day 3 and 10. In the second set of experiments, antiserum (E-2) or normal rabbit serum (C-2) was administered between Day 11 and 18. On Day 18, all mice were killed, blood was collected for measurement of levels of IGF-I by RIA, and the weights of fetuses and placentas in individual mice were recorded. The maternal levels of IGF-I in group E-1 and E-2 were extremely low compared to those in group C-1 and C-2. The number of fetuses and rate of abortion among each group were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elevating maternal insulin-like growth factor-I in mice and rats alters the pattern of fetal growth by removing maternal constraint.

Fetal growth is normally constrained by maternal factors. This constraint is demonstrated by the usual inverse linear relationship between litter size and mean fetal weight. Cross-breeding experiments between mice of lines selected for high or low plasma insulin-like growth factor (IGF-I) levels suggested that elevations in maternal IGF-I abolish (P less than 0.01) this constraining effect and reverse the usual positive relationship between fetal and placental size in late gestation. This was confirmed by treating mice and rats throughout pregnancy with IGF-I. In normal mice and in low IGF-I line mice treatment with IGF-I (10 micrograms 8-hourly s.c. from day 1 to 19 of pregnancy) abolished maternal constraint whereas 0.9% (w/v) NaCl treatment did not. In Wistar rats osmotic pumps were implanted to deliver IGF-I (1 microgram/g body weight per day), bovine GH (bGH; 0.6 microgram/g body weight per day) or saline from day 1 to 19 of pregnancy. IGF-I therapy but not bGH or saline abolished (P less than 0.01) maternal constraint and altered (P less than 0.01) the relationship between placental and fetal weight. When high or low IGF-I line mice embroys were transplanted into a normal line of mice, the expected negative relationship (P less than 0.05) between mean fetal weight and litter size was maintained. However, the embryos of the high line were heavier (P less than 0.05) than those from the low line irrespective of fetal number, suggesting a direct role for IGF-I in the regulation of fetal growth.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phosphorylated insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) inhibits while non-phosphorylated IGFBP-1 stimulates IGF-I-induced amino acid uptake by cultured trophoblast cells.

The effects of phosphorylated insulin-like growth factor-binding protein (pIGFBP-1) and non-phosphorylated (npIGFBP-1) IGFBP-1 on amino acid uptake induced by IGF-I were studied using cultured trophoblast cells. Trophoblast cells obtained from term pregnancy were incubated with indicated concentrations of pIGFBP-1 or npIGFBP-1 for 24 h and further incubated with 10 nM IGF-I for 3 h. Cells were then incubated with 3H-alpha-amino isobutyric acid (3H-AIB) for 30 min. Both pIGFBP-1 and npIGFBP-1 alone had no effect on 3H-AIB uptake; however, pIGFBP-1 inhibited IGF-I-stimulated 3H-AIB uptake with an ED50 of 0.26 nM while npIGFBP-1 potentiated 3H-AIB uptake with an ED50 of 0.27 nM. Maternal IGF-I promotes fetal growth by stimulating nutrient transport in the placenta. As shown in this study, pIGFBP-1 inhibits while npIGFBP-1 stimulates this IGF-I action in the placenta. Thus, it is suggested that IGFBP-1 phosphoisoforms are also involved in fetal growth by modulating IGF-I action in the placenta.     

Serum levels of adiponectin and IGFBP-1 in short children born small for gestational age

OBJECTIVE: The aim of this study was to quantify serum adiponectin concentrations in short children born small for gestational age (SGA) compared with those in children born appropriate for gestational age (AGA), and to assess the relationship between the serum levels of adiponectin and insulin-like growth factor binding protein-1 (IGFBP-1) known as a predictor of the development of type 2 diabetes mellitus and cardiovascular disease. SUBJECTS AND METHODS: Sixteen prepubertal short children born SGA and 20 short children born AGA, matched for age, body mass index, height, pubertal status, gestational age, bone age and midparental height, were included in the study. The serum levels of adiponectin, IGFBP-1, insulin and insulin-like growth factor-I (IGF-I) were measured in the fasting state. RESULTS: The levels of serum adiponectin were significantly lower in the SGA than in AGA children (10.5 +/- 4.2 vs. 13.9 +/- 5.1 micro g/ml, P < 0.05). The levels of serum IGFBP-1, insulin and IGF-I were all similar in both groups. Overall, there was a significant positive correlation between adiponectin and IGFBP-1 (r = 0.40, P < 0.05). CONCLUSIONS: Our results suggest that hypoadiponectinaemia in short SGA children without catch-up growth may reflect insulin resistance and imply a higher risk of developing type 2 diabetes mellitus. Additionally, adiponectin may be a more sensitive indicator for latent insulin resistance than IGFBP-1 in short SGA children.     

Hepatocyte growth factor stimulates trophoblast invasion: a potential mechanism for abnormal placentation in preeclampsia

Hepatocyte growth factor (HGF) is a cytokine that is produced in the placental villous core and acts in a paracrine manner on trophoblasts that express the HGF receptor Met. Because HGF stimulates the invasion of many epithelial cell types, villous core HGF could regulate placental trophoblast invasion. As preeclampsia is characterized by inadequate trophoblast invasion, we investigated the hypothesis that decreased placental HGF production is a mechanism for inadequate trophoblast invasion in this disease. Placental villous explant HGF production over 24 h was 25% lower in patients with preeclampsia (n = 5; 7.29 +/- 0.8 ng/mL) than in normal patients (n = 5; 9.76 +/- 0.5 ng/mL; P < 0.05). The human first trimester trophoblast cell line (ED27) used in subsequent invasion studies was found to express c-met messenger ribonucleic acid by RT-PCR and Met protein by Western analysis, and underwent phosphorylation of tyrosine residues on Met with HGF exposure. A Boyden chamber invasion assay using collagen type I showed that HGF caused a specific dose-response increase in trophoblast invasion first seen at 10 ng/mL (2.2-fold increase; P < 0.05). The stimulation of trophoblast invasion by HGF may in part be due to the 2-fold induction of 92-kDa collagenase as determined by zymogram analysis of the trophoblast-conditioned medium. These studies suggest that HGF has an important role in placental trophoblast invasion through the activation of Met and the subsequent induction of 92-kDa collagenase in these cells. In addition, decreased placental production of HGF in preeclampsia provides a potential mechanism for the lack of trophoblast invasion that is seen in this pregnancy disorder.     

Administration of insulin-like growth factor-I, but not growth hormone, increases maternal weight gain in late pregnancy without affecting fetal or placental growth.

During late pregnancy in the rat, circulating levels of insulin-like growth factor-I (IGF-I) and some IGF-binding proteins (IGFBP) decline. The aim of the present study was to determine the relationship of GH to circulating IGF and IGFBP in the late-pregnant rat and to examine the effects on maternal, fetal and placental growth of preventing the decline in serum IGF and IGFBP concentrations. During the first 9 days of pregnancy, IGF-I concentrations increased from 340 to 500 micrograms/l. Recombinant human (rh) GH at 2.4 mg/kg per day and rhIGF-I at 1.4 mg/kg per day were infused into pregnant rats via osmotic mini pumps during the second half of pregnancy. After pump implantation on day 11 of pregnancy, only IGF-I infusion significantly increased circulating IGF-I. A maximum IGF-I concentration of 907 micrograms/l was measured on day 14 during treatment with IGF-I, after which the serum concentration decreased to 510 micrograms/l by day 20 of pregnancy. The serum IGFBPs were examined using a Western ligand blot technique. Infusion of neither GH nor IGF-I returned the IGFBPs to non-pregnant levels. Administration of IGF-I slightly increased IGFBP-3 and a smaller 32 kDa IGFBP at days 17 and 20 of pregnancy. Neither fetal nor placental weight was significantly different between treatment groups. However, administration of IGF-I significantly increased maternal weight gain during the 10-day treatment period.(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of the IGF axis in IGFBP-1 and IGF-I induced renal enlargement in Snell dwarf mice

Insulin-like growth factor (IGF) binding protein-1 (IGFBP-1) is generally believed to inhibit IGF action in the circulation. In contrast, IGFBP-1 has been reported to interact with cell surfaces and enhance IGF-I action locally in some tissues. Renal IGFBP-1 levels are found elevated in various conditions characterized by renal growth (e.g. diabetes mellitus, hypokalemia). To test whether IGFBP-1 is a renotropic factor, IGFBP-1 was administered alone or in combination with IGF-I to Snell dwarf mice, an in vivo model without compensatory feedback effects on growth hormone (GH) secretion. In three control groups of Snell dwarf mice, placebo, GH or IGF-I was administered. Compared with placebo, kidney weight increased in all treated groups, however, with different effects on kidney morphology. Administration of IGF-I, alone or in combination with IGFBP-1, tended to increase glomerular volume, while no changes were seen in the other groups. Administration of IGFBP-1 or IGFBP-1+IGF-I both caused dilatation of the thin limbs of Henle's loop, while GH or IGF-I administration had no visible effect. Furthermore, IGF-I administration resulted in an increased mean number of nuclei per cortical area and renal weight, whereas GH, IGF-I+IGFBP-1 or IGFBP-1 caused a decreased renal nuclei number. In situ hybridization and immunohistochemistry showed specific changes of the renal IGF system expression patterns in the different groups. Particularly, IGFBP-1 administration resulted in extensive changes in the mRNA expression of the renal IGF system, whereas the other administration regimen resulted in less prominent modifications. In contrast, administration of IGFBP-1 and IGFBP-1+IGF-I resulted in identical changes in the protein expression of the renal IGF system. Our results indicate that IGFBP-1, alone or in combination with IGF-I, demonstrated effects on the renal tubular system that differ from the effects of IGF-I.     

Prolonged hypoxia induced by the reduction of maternal uterine blood flow alters insulin-like growth factor-binding protein-1 (IGFBP-1) and IGFBP-2 gene expression in the ovine fetus.

Insulin-like growth factors (IGF-I and IGF-II) are potent mitogenic and differentiating peptides which are synthesized by many fetal tissues. In the circulation and tissue fluids, IGFs are bound to binding proteins (BPs) which not only function as carrier proteins, but also inhibit or modulate the biological actions of IGFs. We have previously shown that prolonged hypoxia in the ovine fetus induced by the reduction of maternal uterine blood flow for 24 h causes a reduction in the DNA synthesis rate in selected fetal tissues. To determine if this effect is due to alterations in the local synthesis of tissue IGFs and their binding proteins or to changes in systemic concentrations of IGFs and IGFBPs, we have investigated the abundance of mRNAs encoding IGFs and IGFBPs in selected tissues and changes in plasma IGFs and IGFBPs. Ovine fetuses (115-120 days gestation; n = 6) underwent 24 h of hypoxia by the reduction of maternal uterine blood flow (RUBF). Controls (n = 6) underwent the same surgical procedure without RUBF. Serial plasma samples were collected before, during, and after the experiment, and tissues were collected at the end of 24 h. Mean plasma IGF-I and IGF-II concentrations tended to be lower in hypoxic fetuses than in controls during the course of hypoxia, but these differences were not statistically significant. Tissue mRNA levels for IGF-I and IGF-II in lung, muscle, thymus, and kidney were similar in control and hypoxic fetuses after 24 h of hypoxia. The relative abundance of liver IGF-I and IGF-II mRNAs was lower in hypoxic fetuses, but only IGF-I mRNA levels were significantly different from the control values (P < 0.05). Compared to control fetuses, IGFBP-1 mRNA levels in the liver of hypoxic fetuses were increased 3- to 7-fold, and IGFBP-1 mRNA expression was induced in kidneys of some hypoxic fetuses (two of six). In addition, IGFBP-2 mRNA levels were decreased in the liver (50%) and kidney (30%) of hypoxic fetuses. The increase in liver IGFBP-1 mRNA abundance and the decrease in liver and kidney IGFBP-2 mRNA abundance were accompanied by an increase in IGFBP-1 levels and a decrease in IGFBP-2 levels in fetal plasma. No changes were observed in either plasma levels or tissue mRNA abundance for IGFBP-3. Analysis of the time course of changes in plasma revealed that the changes in IGFBP-1 and IGFBP-2 occurred within 4 h of hypoxia.(ABSTRACT TRUNCATED AT 400 WORDS)     

Administration of human insulin-like growth factor-binding protein-1 increases circulating levels of growth hormone in mice

GH is the major regulator of circulating IGF-I, which, in return, controls pituitary GH secretion by negative feedback. IGF-binding protein-1 (IGFBP-1) is believed to modify this feedback through its effects on free IGF-I. In the present study we investigated the potential influence of IGFBP-1 on GH secretion in the absence or presence of a GH receptor antagonist (GHRA) that specifically blocks peripheral GH action. We administered human (h) IGFBP-1 and GHRA to mice alone or in combination for 2 or 7 d. GHRA was administered in a dose previously shown to block GH action without an effect on circulating GH or IGF-I levels. hIGFBP-1 administration increased stimulated circulating GH levels and serum total IGF-I and IGFBP-3 levels. Coadministration of GHRA abolished the hIGFBP-1-induced increase in serum IGF-I and IGFBP-3 levels, whereas stimulated GH levels remained increased. Free IGF-I levels in serum were unchanged in all treatment groups. In conclusion, GH serum levels increased in response to hIGFBP-1 administration, even in the setting of normal IGF-I levels. This finding suggests a direct involvement of IGFBP-1 in GH secretion.     

Systemic administration of insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4) increases bone formation parameters in mice by increasing IGF bioavailability via an IGFBP-4 protease-dependent mechanism

Insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4) is a potent inhibitor of IGF actions in vitro. However, we found that systemic administration of IGFBP-4 at pharmacological doses caused a significant increase in bone formation parameters in mice by a mechanism that may involve increased IGF bioavailability via proteolysis of IGFBP-4. To evaluate the hypothesis that proteolysis of IGFBP-4 is essential for the stimulatory effects of systemically administered IGFBP-4, we produced wild-type, protease-resistant, and IGFBP-4 proteolytic fragments and evaluated their effects using biochemical markers. Protease-resistant IGFBP-4 was more potent than wild-type IGFBP-4 in inhibiting IGF-I-induced mouse osteoblast cell proliferation in vitro and in inhibiting IGF-I-induced increase in alkaline phosphatase (ALP) activity in bone extract after local administration in vivo. Systemic administration of wild-type IGFBP-4, but not protease-resistant IGFBP-4, increased serum osteocalcin, serum ALP, and ALP in skeletal extracts in a dose-dependent manner, with a maximal effect of 40% (P < 0.05) at 1.25 nmol/mouse. Systemic administration of wild-type, but not protease-resistant, IGFBP-4 increased free IGF-I levels in serum in normal mice. IGF-I, but not wild-type IGFBP-4, increased bone formation parameters in IGF-I-deficient mice. This study demonstrates that systemic administration of IGFBP-4 increases bone formation parameters in mice by increasing IGF bioavailability in the circulation via an IGFBP-4 protease-dependent mechanism.     

Cord serum insulin-like growth factor binding protein-1 and -3: effect of maternal diabetes and relationships to fetal growth

OBJECTIVES: Insulin-like growth factor binding protein-1 and -3 (IGFBP-1 and -3) are the main insulin-like growth factor (IGF) carriers in fetal blood whose concentrations are regulated by hormonal factors such as insulin. IGFBPs may regulate fetal growth by altering the biological activity of IGF-I and IGF-II. We studied the effect of maternal diabetes on cord serum IGFBP-1 and IGFBP-3 levels, and the usability of IGFBP-1 and IGFBP-3 in the detection of birth weight variations. METHODS: Cord serum IGFBP-1 and IGFBP-3 concentrations were measured at birth by immunofluorometric assays in 67 pregnancies with type 1 diabetes and in 62 normal pregnancies. RESULTS: Concentrations of IGFBP-1 in cord serum were lower in diabetic pregnancies than in normal pregnancies (156 +/- 28 microg/l vs 266 +/- 29 microg/l, P = 0.007), whereas those of IGFBP-3 did not differ significantly (3327 +/- 158 microg/l vs 2982 +/- 105 microg/l, P = 0.076). IGFBP-1 correlated negatively and IGFBP-3 positively with birth weight z-score in diabetic pregnancies. The trend was similar in normal pregnancies. In multiple regression models, birth weight z-score was significantly associated with IGFBP-1 in diabetic and normal pregnancies, and with IGFBP-3 in diabetic pregnancies.CONCLUSION: Maternal diabetes is associated with suppressed levels of IGFBP-1 in cord serum, whereas those of IGFBP-3 do not change markedly. In diabetic pregnancies, both cord serum IGFBP-1 and IGFBP-3 correlate with fetal growth.     

A potential role for endothelin-1 in human placental growth: interactions with the insulin-like growth factor family of peptides.

Endothelin-1 (Et-1) stimulated DNA synthesis in placental fibroblasts in a dose-dependent manner, as measured by [3H]thymidine incorporation (ED50, 0.2-0.3 ng/mL). Insulin-like growth factor-I (IGF-I) interacted synergistically with Et-1 to potentiate the stimulation of DNA synthesis. Additionally, Et-1 stimulated the turnover of phosphoinositides in a time- and concentration-dependent manner (ED50, 1 ng/mL), as measured by a 2- to 3-fold increase in the total accumulation of [3H]inositol phosphates. This was accompanied by a 2- to 3-fold rise in intracellular calcium, as measured by fura-2 fluorescence. IGF-I, however, had no potentiating effect on Et-1-stimulated phosphoinositide turnover or increase in cytosolic Ca2+. The ability of Et-1 to stimulate the production of IGF-II and IGFBPs by placental fibroblasts was then studied. Western ligand blot analysis using an [125I]IGF-II probe revealed the presence of six major binding proteins corresponding to 42, 38, 35, 32, 31, and 24 kilodaltons. Et-1 (50 ng/mL) stimulated all binding fractions concordantly. This was accompanied by a similar increase in immunoreactive IGF-II secretion, as assessed by a specific RIA. No increase in immunoreactive IGF-I was observed. The ability of the placenta to produce Et-1 was examined by Northern blot analysis. Placentae at 14 and 17 weeks gestation expressed small amounts Et-1 mRNA, whereas significantly higher levels of mRNA were expressed at term. These data suggest that the human placenta produces Et-1 in a developmentally regulated manner that may act via paracrine and/or autocrine mechanisms to regulate placental growth.     

From the Cover: Adiponectin supplementation in pregnant mice prevents the adverse effects of maternal obesity on placental function and fetal growth

Mothers with obesity or gestational diabetes mellitus have low circulating levels of adiponectin (ADN) and frequently deliver large babies with increased fat mass, who are susceptible to perinatal complications and to development of metabolic syndrome later in life. It is currently unknown if the inverse correlation between maternal ADN and fetal growth reflects a cause-and-effect relationship. We tested the hypothesis that ADN supplementation in obese pregnant dams improves maternal insulin sensitivity, restores normal placental insulin/mechanistic target of rapamycin complex 1 (mTORC1) signaling and nutrient transport, and prevents fetal overgrowth. Compared with dams on a control diet, female C57BL/6J mice fed an obesogenic diet before mating and throughout gestation had increased fasting serum leptin, insulin, and C-peptide, and reduced high-molecular-weight ADN at embryonic day (E) 18.5. Placental insulin and mTORC1 signaling was activated, peroxisome proliferator-activated receptor-α (PPARα) phosphorylation was reduced, placental transport of glucose and amino acids in vivo was increased, and fetal weights were 29% higher in obese dams. Maternal ADN infusion in obese dams from E14.5 to E18.5 normalized maternal insulin sensitivity, placental insulin/mTORC1 and PPARα signaling, nutrient transport, and fetal growth without affecting maternal fat mass. Using a mouse model with striking similarities to obese pregnant women, we demonstrate that ADN functions as an endocrine link between maternal adipose tissue and fetal growth by regulating placental function. Importantly, maternal ADN supplementation reversed the adverse effects of maternal obesity on placental function and fetal growth. Improving maternal ADN levels may serve as an effective intervention strategy to prevent fetal overgrowth caused by maternal obesity.Obesity and the metabolic syndrome are major risk factors for a wide array of diseases, including type 2 diabetes mellitus, cardiovascular disease, and cancer (1, 2). Compelling evidence shows that metabolic syndrome is caused, in part, by a suboptimal intrauterine environment (3). The strong association between maternal obesity during pregnancy and metabolic syndrome in childhood is of particular concern because almost two-thirds of American women now enter pregnancy either overweight or obese (4). Obesity during pregnancy therefore creates a vicious, detrimental cycle of intrauterine transmission of metabolic disease from the mother to her children (5). Intervention strategies involving lifestyle changes or antiobesity drugs remain largely unsuccessful, and it is therefore urgent to explore the possibility of intervening in utero to prevent the development of obesity and metabolic syndrome.Obesity in pregnant women is associated with activation of placental insulin and mechanistic target of rapamycin complex 1 (mTORC1) signaling, up-regulation of specific placental amino acid transporters, and fetal overgrowth (6, 7). In addition, circulating levels of adiponectin (ADN) are decreased in obese pregnant women (8, 9). The ADN protein is synthesized in adipose tissue and undergoes tightly regulated multimerization involving chaperone proteins, including disulfide-bond A oxidoreductase-like protein (DsbA-L), resulting in the assembly of oligomeric ADN proteins of different molecular weight (10). Multimerization into the high-molecular-weight (HMW) form increases the t_1/2 of ADN (11), and the insulin-sensitizing effect of ADN can largely be attributed to the HMW form (12). Low circulating levels of HMW ADN strongly predict the development of gestational diabetes mellitus (GDM) independent of maternal adiposity (13, 14).We recently reported that ADN, in contrast to its well-known insulin-sensitizing effects in skeletal muscle and liver, inhibits insulin and mTORC1 signaling and amino acid transport in cultured primary human trophoblast (PHT) cells (15) and in pregnant mice in vivo (16). This effect is mediated by activation of trophoblast peroxisome proliferator-activated receptor-α (PPARα) signaling and increased ceramide synthesis, resulting in inhibition of IRS-1 (17). Thus, low circulating ADN in maternal obesity may be causally linked to changes in placental function and increased fetal growth. These findings, together with the recent discovery of an orally active ADN receptor agonist (AdipoRon) (18), provide the rationale for exploring the possibility that maternal ADN supplementation may prevent the adverse fetal outcomes in maternal obesity.We recently established a mouse model of obesity in pregnancy, which shows extensive similarities to the human condition, including low maternal ADN and glucose intolerance, increased placental nutrient transport, and fetal overgrowth (19). In this study, we used this model to test the hypothesis that ADN supplementation in obese pregnant dams improves maternal insulin sensitivity, restores normal placental insulin signaling and nutrient transport, and prevents fetal overgrowth.