RNA Sequencing Exposes Adaptive and Immune Responses to Intrauterine Growth Restriction in Fetal Sheep Islets

Association of Fetal Catecholamines With Neonatal Hypoglycemia

Importance

Perinatal stress and fetal growth restriction increase the risk of neonatal hypoglycemia. The underlying pathomechanism is poorly understood. In a sheep model, elevated catecholamine concentrations were found to suppress intrauterine insulin secretion, followed by hyperresponsive insulin secretion once the adrenergic stimulus subsided.

Objective

To determine whether neonates with risk factors for hypoglycemia have higher catecholamine concentrations in umbilical cord blood (UCB) and/or amniotic fluid (AF) and whether catecholamines are correlated with postnatal glycemia.

Design, Setting, and Participants

In a prospective cohort study of 328 neonates at a tertiary perinatal center from September 2020 through May 2022 in which AF and UCB were collected immediately during and after delivery, catecholamines and metanephrines were analyzed using liquid chromatography with tandem mass spectrometry. Participants received postnatal blood glucose (BG) screenings.

Exposure

Risk factor for neonatal hypoglycemia.

Main Outcomes and Measures

Comparison of catecholamine and metanephrine concentrations between at-risk neonates and control participants, and correlation of concentrations of catecholamines and metanephrines with the number and severity of postnatal hypoglycemic episodes.

Results

In this study of 328 neonates (234 in the risk group: median [IQR] gestational age, 270 [261-277] days; and 94 in the control group: median [IQR] gestational age, 273 [270-278] days), growth-restricted neonates showed increased UCB median (IQR) concentrations of norepinephrine (21.10 [9.15-42.33] vs 10.88 [5.78-18.03] nmol/L; P < .001), metanephrine (0.37 [0.13-1.36] vs 0.12 [0.08-0.28] nmol/L; P < .001), and 3-methoxytyramine (0.149 [0.098-0.208] vs 0.091 [0.063-0.149] nmol/L; P = .001). Neonates with perinatal stress had increased UCB median (IQR) concentrations of norepinephrine (22.55 [8.99-131.66] vs 10.88 [5.78-18.03] nmol/L; P = .001), normetanephrine (1.75 [1.16-4.93] vs 1.25 [0.86-2.56] nmol/L; P = .004), and 3-methoxytyramine (0.120 [0.085-0.228] vs 0.091 [0.063-0.149] nmol/L; P = .008) (P < .0083 was considered statistically significant). Concentrations of UCB norepinephrine, metanephrine, and 3-methoxytyramine were negatively correlated with AF C-peptide concentration (rs = -0.212, P = .005; rs = -0.182, P = .016; and rs = -0.183, P = .016, respectively [P < .017 was considered statistically significant]). Concentrations of UCB norepinephrine, metanephrine, and 3-methoxytyramine were positively correlated with the number of hypoglycemic episodes (BG concentration of 30-45 mg/dL) (rs = 0.146, P = .01; rs = 0.151, P = .009; and rs = 0.180, P = .002, respectively). Concentrations of UCB metanephrine and 3-methoxytyramine were negatively correlated with the lowest measured BG concentration (rs = -0.149, P = .01; and rs = -0.153, P = .008, respectively).

Conclusions and Relevance

Neonates at risk for hypoglycemia displayed increased catecholamine and metanephrine concentrations that were correlated with postnatal hypoglycemic episodes and lower BG levels; these results are consistent with findings in a sheep model that fetal catecholamines are associated with neonatal β-cell physiology and that perinatal stress or growth restriction is associated with subsequent neonatal hyperinsulinemic hypoglycemia. Improving the pathomechanistic understanding of neonatal hypoglycemia may help to guide management of newborns at risk for hypoglycemia.

Effects of foetal size, sex and developmental stage on adaptive transcriptional responses of skeletal muscle to intrauterine growth restriction in pigs

Intrauterine growth restriction (IUGR) occurs both in humans and domestic species. It has a particularly high incidence in pigs, and is a leading cause of neonatal morbidity and mortality as well as impaired postnatal growth. A key feature of IUGR is impaired muscle development, resulting in decreased meat quality. Understanding the developmental origins of IUGR, particularly at the molecular level, is important for developing effective strategies to mitigate its economic impact on the pig industry and animal welfare. The aim of this study was to characterise transcriptional profiles in the muscle of growth restricted pig foetuses at different gestational days (GD; gestational length ~ 115 days), focusing on selected genes (related to development, tissue injury and metabolism) that were previously identified as dysregulated in muscle of GD90 fetuses. Muscle samples were collected from the lightest foetus (L) and the sex-matched foetus with weight closest to the litter average (AW) from each of 22 Landrace x Large White litters corresponding to GD45 (n = 6), GD60 (n = 8) or GD90 (n = 8), followed by analyses, using RT-PCR and protein immunohistochemistry, of selected gene targets. Expression of the developmental genes, MYOD, RET and ACTN3 were markedly lower, whereas MSTN expression was higher, in the muscle of L relative to AW littermates beginning on GD45. Levels of all tissue injury-associated transcripts analysed (F5, PLG, KNG1, SELL, CCL16) were increased in L muscle on GD60 and, most prominently, on GD90. Among genes involved in metabolic regulation, KLB was expressed at higher levels in L than AW littermates beginning on GD60, whereas both IGFBP1 and AHSG were higher in L littermates on GD90 but only in males. Furthermore, the expression of genes specifically involved in lipid, hexose sugar or iron metabolism increased or, in the case of UCP3, decreased in L littermates on GD60 (UCP3, APOB, ALDOB) or GD90 (PNPLA3, TF), albeit in the case of ALDOB this only involved females. In conclusion, marked dysregulation of genes with critical roles in development in L foetuses can be observed from GD45, whereas for a majority of transcripts associated with tissue injury and metabolism differences between L and AW foetuses were apparent by GD60 or only at GD90, thus identifying different developmental windows for different types of adaptive responses to IUGR in the muscle of porcine foetuses.

Dousing the flame: reviewing the mechanisms of inflammatory programming during stress-induced intrauterine growth restriction and the potential for ω-3 polyunsaturated fatty acid intervention

Intrauterine growth restriction (IUGR) arises when maternal stressors coincide with peak placental development, leading to placental insufficiency. When the expanding nutrient demands of the growing fetus subsequently exceed the capacity of the stunted placenta, fetal hypoxemia and hypoglycemia result. Poor fetal nutrient status stimulates greater release of inflammatory cytokines and catecholamines, which in turn lead to thrifty growth and metabolic programming that benefits fetal survival but is maladaptive after birth. Specifically, some IUGR fetal tissues develop enriched expression of inflammatory cytokine receptors and other signaling cascade components, which increases inflammatory sensitivity even when circulating inflammatory cytokines are no longer elevated after birth. Recent evidence indicates that greater inflammatory tone contributes to deficits in skeletal muscle growth and metabolism that are characteristic of IUGR offspring. These deficits underlie the metabolic dysfunction that markedly increases risk for metabolic diseases in IUGR-born individuals. The same programming mechanisms yield reduced metabolic efficiency, poor body composition, and inferior carcass quality in IUGR-born livestock. The ω-3 polyunsaturated fatty acids (PUFA) are diet-derived nutraceuticals with anti-inflammatory effects that have been used to improve conditions of chronic systemic inflammation, including intrauterine stress. In this review, we highlight the role of sustained systemic inflammation in the development of IUGR pathologies. We then discuss the potential for ω-3 PUFA supplementation to improve inflammation-mediated growth and metabolic deficits in IUGR offspring, along with potential barriers that must be considered when developing a supplementation strategy.

Prenatal Oxygen and Glucose Therapy Normalizes Insulin Secretion and Action in Growth Restricted Fetal Sheep

Placental insufficiency (PI) lowers fetal oxygen and glucose concentrations, which disrupts glucose-insulin homeostasis and promotes fetal growth restriction (FGR). To date, prenatal treatments for FGR have not attempted to correct the oxygen and glucose supply simultaneously. Therefore, we investigated whether a five-day correction of oxygen and glucose concentrations in PI-FGR fetuses would normalize insulin secretion and glucose metabolism. Experiments were performed in near-term FGR fetal sheep with maternal hyperthermia-induced PI. Fetal arterial oxygen tension was increased to normal levels by increasing the maternal inspired oxygen fraction and glucose was infused into FGR fetuses (FGR-OG). FGR-OG fetuses were compared to maternal air insufflated, saline-infused fetuses (FGR-AS) and control fetuses. Prior to treatment, FGR fetuses were hypoxemic and hypoglycemic and had reduced glucose-stimulated insulin secretion (GSIS). During treatment, oxygen, glucose, and insulin concentrations increased, and norepinephrine concentrations decreased in FGR-OG fetuses, whereas FGR-AS fetuses were unaffected. On treatment day 4, glucose fluxes were measured with euglycemic and hyperinsulinemic-euglycemic clamps. During both clamps, rates of glucose utilization and production were greater in FGR-AS than FGR-OG fetuses, while glucose fluxes in FGR-OG fetuses were not different than control rates. After five-days of treatment, GSIS increased in FGR-OG fetuses to control levels and their ex vivo islet GSIS was greater than FGR-AS islets. Despite normalization in fetal characteristics, GSIS, and glucose fluxes, FGR-OG and FGR-AS fetuses weighed less than controls. These findings show that sustained, simultaneous correction of oxygen and glucose normalized GSIS and whole-body glucose fluxes in PI-FGR fetuses after the onset of FGR.

KLB dysregulation mediates disrupted muscle development in intrauterine growth restriction

Abstract

Intrauterine growth restriction (IUGR) is a leading cause of neonatal morbidity and mortality in humans and domestic animals. Developmental adaptations of skeletal muscle in IUGR lead to increased risk of premature muscle loss and metabolic disease in later life. Here, we identified β‐Klotho (KLB), a fibroblast growth factor 21 (FGF21) co‐receptor, as a novel regulator of muscle development in IUGR. Using the pig as a naturally‐occurring disease model, we performed transcriptome‐wide profiling of fetal muscle (day 90 of pregnancy) from IUGR and normal‐weight (NW) littermates. We found that, alongside large‐scale transcriptional changes comprising multiple developmental, tissue injury and metabolic gene pathways, KLB was increased in IUGR muscle. Moreover, FGF21 concentrations were increased in plasma in IUGR fetuses. Using cultures of fetal muscle progenitor cells (MPCs), we showed reduced myogenic capacity of IUGR compared to NW muscle in vitro, as evidenced by differences in fusion indices and myogenic transcript levels, as well as mechanistic target of rapamycin (mTOR) activity. Moreover, transfection of MPCs with KLB small interfering RNA promoted myogenesis and mTOR activation, whereas treatment with FGF21 had opposite and dose‐dependent effects in porcine and also in human fetal MPCs. In conclusion, our results identify KLB as a novel and potentially critical mediator of impaired muscle development in IUGR, through conserved mechanisms in pigs and humans. Our data shed new light onto the pathogenesis of IUGR, a significant cause of lifelong ill‐health in humans and animals.

Key points

Intrauterine growth restriction (IUGR) is associated with large‐scale transcriptional changes in developmental, tissue injury and metabolic gene pathways in fetal skeletal muscle.

Levels of the fibroblast growth factor 21 (FGF21) co‐receptor, β‐Klotho (KLB) are increased in IUGR fetal muscle, and FGF21 concentrations are increased in IUGR fetal plasma.

KLB mediates a reduction in muscle development through inhibition of mechanistic target of rapamycin signalling.

These effects of KLB on muscle cells are conserved in pig and human, suggesting a vital role of this protein in the regulation of muscle development and function in mammals.

Going Up Inflame: Reviewing the Underexplored Role of Inflammatory Programming in Stress-Induced Intrauterine Growth Restricted Livestock

The impact of intrauterine growth restriction (IUGR) on health in humans is well-recognized. It is the second leading cause of perinatal mortality worldwide, and it is associated with deficits in metabolism and muscle growth that increase lifelong risk for hypertension, obesity, hyperlipidemia, and type 2 diabetes. Comparatively, the barrier that IUGR imposes on livestock production is less recognized by the industry. Meat animals born with low birthweight due to IUGR are beset with greater early death loss, inefficient growth, and reduced carcass merit. These animals exhibit poor feed-to-gain ratios, less lean mass, and greater fat deposition, which increase production costs and decrease value. Ultimately, this reduces the amount of meat produced by each animal and threatens the economic sustainability of livestock industries. Intrauterine growth restriction is most commonly the result of fetal programming responses to placental insufficiency, but the exact mechanisms by which this occurs are not well-understood. In uncompromised pregnancies, inflammatory cytokines are produced at modest rates by placental and fetal tissues and play an important role in fetal development. However, unfavorable intrauterine conditions can cause cytokine activity to be excessive during critical windows of fetal development. Our recent evidence indicates that this impacts developmental programming of muscle growth and metabolism and contributes to the IUGR phenotype. In this review, we outline the role of inflammatory cytokine activity in the development of normal and IUGR phenotypes. We also highlight the contributions of sheep and other animal models in identifying mechanisms for IUGR pathologies.

Dietary rumen-protected L-arginine or N-carbamylglutamate attenuated fetal hepatic inflammation in undernourished ewes suffering from intrauterine growth restriction

This study aimed to explore whether dietary rumen-protected L-arginine (RP-Arg) or N-carbamylglutamate (NCG) supplementation to feed-restricted pregnant ewes counteracts fetal hepatic inflammation and innate immune dysfunction associated with intrauterine growth retardation (IUGR) in ovine fetuses. On d 35 of pregnancy, twin-bearing Hu ewes (n = 32) were randomly assigned to 4 treatment groups (8 ewes and 16 fetuses per group) and fed diets containing 100% of the NRC requirements (CON), 50% of the NRC requirements (RES), RES + RP-Arg (20 g/d) (RESA), or RES + NCG (5 g/d) (RESN). At 08:00 on d 110 of gestation, fetal blood and liver tissue samples were collected. The levels of triglyceride, free fatty acid, cholesterol and β-hydroxybutyrate in the fetal blood of RESA and RESN groups were lower (P < 0.05) than those of the RES group, but were higher (P < 0.05) than those of the CON group. The interleukin (IL)-6 and IL-1 levels in fetal blood and liver tissue as well as the myeloid differentiation primary response 88 (MyD88), transforming growth factor β (TGFβ), and nuclear factor kappa B (NF-κB) mRNA levels in the fetal liver were decreased (P < 0.05) by the NCG or RP-Arg supplementation compared to the RES treatment. Similarly, the toll-like receptor (TLR)-4, MyD88, TGFβ, and p-c-Jun N-terminal kinase (JNK) protein levels in the fetal liver were reduced (P < 0.05) in the NCG and RP-Arg -supplemented groups compared to the RES group. These results showed that dietary supplementation of RP-Arg or NCG to underfed pregnant ewes could protect against IUGR fetal hepatic inflammation via improving lipid metabolism, down-regulating the TLR-4 and the inflammatory JNK and NF-κB signaling pathways, and decreasing cytokine production in ovine fetal blood and liver tissue.

Sexually dimorphic changes in the endocrine pancreas and skeletal muscle in young adulthood following intra-amniotic IGF-I treatment of growth-restricted fetal sheep

Fetal growth restriction (FGR) is associated with decreased insulin secretory capacity and decreased insulin sensitivity in muscle in adulthood. We investigated whether intra-amniotic IGF-I treatment in late gestation mitigated the adverse effects of FGR on the endocrine pancreas and skeletal muscle at 18 mo of age. Singleton-bearing ewes underwent uterine artery embolization between 103 and 107 days of gestational age, followed by 5 once-weekly intra-amniotic injections of 360-µg IGF-I (FGRI) or saline (FGRS) and were compared with an unmanipulated control group (CON). We measured offspring pancreatic endocrine cell mass and pancreatic and skeletal muscle mRNA expression at 18 mo of age (n = 7-9/sex/group). Total α-cell mass was increased ∼225% in FGRI males versus CON and FGRS males, whereas β-cell mass was not different between groups of either sex. Pancreatic mitochondria-related mRNA expression was increased in FGRS females versus CON (NRF1, MTATP6, UCP2), and FGRS males versus CON (TFAM, NRF1, UCP2) but was largely unchanged in FGRI males versus CON. In skeletal muscle, mitochondria-related mRNA expression was decreased in FGRS females versus CON (PPARGC1A, TFAM, NRF1, UCP2, MTATP6), FGRS males versus CON (NRF1 and UCP2), and FGRI females versus CON (TFAM and UCP2), with only MTATP6 expression decreased in FGRI males versus CON. Although the window during which IGF-I treatment was delivered was limited to the final 5 wk of gestation, IGF-I therapy of FGR altered the endocrine pancreas and skeletal muscle in a sex-specific manner in young adulthood.NEW & NOTEWORTHY Fetal growth restriction (FGR) is associated with compromised metabolic function throughout adulthood. Here, we explored the long-term effects of fetal IGF-I therapy on the adult pancreas and skeletal muscle. This is the first study demonstrating that IGF-I therapy of FGR has sex-specific long-term effects at both the tissue and molecular level on metabolically active tissues in adult sheep.

Understanding the Long-Lasting Effects of Fetal Nutrient Restriction versus Exposure to an Obesogenic Diet on Islet-Cell Mass and Function

Early life represents a window of phenotypic plasticity. Thus, exposure of the developing fetus to a compromised nutritional environment can have long term consequences for their health. Indeed, undernutrition or maternal intake of an obesogenic diet during pregnancy leads to a heightened risk of type 2 diabetes (T2D) and obesity in her offspring in adult life. Given that abnormalities in beta-cell function are crucial in delineating the risk of T2D, studies have investigated the impact of these exposures on islet morphology and beta-cell function in the offspring in a bid to understand why they are more at risk of T2D. Interestingly, despite the contrasting maternal metabolic phenotype and, therefore, intrauterine environment associated with undernutrition versus high-fat feeding, there are a number of similarities in the genes/biological pathways that are disrupted in offspring islets leading to changes in function. Looking to the future, it will be important to define the exact mechanisms involved in mediating changes in the gene expression landscape in islet cells to determine whether the road to T2D development is the same or different in those exposed to different ends of the nutritional spectrum.

Pancreatic Islets Exhibit Dysregulated Adaptation of Insulin Secretion after Chronic Epinephrine Exposure

Chronic adrenergic stimulation is the dominant factor in impairment of the β-cell function. Sustained adrenergic exposure generates dysregulated insulin secretion in fetal sheep. Similar results have been shown in Min6 under the elevated epinephrine condition, but impairments after adrenergic removal are still unknown and a high rate of proliferation in Min6 has been ignored. Therefore, we incubated primary rats' islets with half maximal inhibitory concentrations of epinephrine for three days, then determined their insulin secretion responsiveness and related signals two days after removal of adrenaline via radioimmunoassay and qPCR. Insulin secretion was not different between the exposure group (1.07 ± 0.04 ng/islet/h) and control (1.23 ± 0.17 ng/islet/h), but total islet insulin content after treatment (5.46 ± 0.87 ng/islet/h) was higher than control (3.17 ± 0.22 ng/islet/h, p < 0.05), and the fractional insulin release was 36% (p < 0.05) lower after the treatment. Meanwhile, the mRNA expression of Gαs, Gαz and Gβ1-2 decreased by 42.8% 19.4% and 24.8%, respectively (p < 0.05). Uncoupling protein 2 (Ucp2), sulphonylurea receptor 1 (Sur1) and superoxide dismutase 2 (Sod2) were significantly reduced (38.5%, 23.8% and 53.8%, p < 0.05). Chronic adrenergic exposure could impair insulin responsiveness in primary pancreatic islets. Decreased G proteins and Sur1 expression affect the regulation of insulin secretion. In conclusion, the sustained under-expression of Ucp2 and Sod2 may further change the function of β-cell, which helps to understand the long-term adrenergic adaptation of pancreatic β-cell.

Augmented glucose production is not contingent on high catecholamines in fetal sheep with IUGR

Fetuses with intrauterine growth restriction (IUGR) have high concentrations of catecholamines, which lowers the insulin secretion and glucose uptake. Here, we studied the effect of hypercatecholaminemia on glucose metabolism in sheep fetuses with placental insufficiency-induced IUGR. Norepinephrine concentrations are elevated throughout late gestation in IUGR fetuses but not in IUGR fetuses with a bilateral adrenal demedullation (IAD) at 0.65 of gestation. Euglycemic (EC) and hyperinsulinemic-euglycemic (HEC) clamps were performed in control, intact-IUGR, and IAD fetuses at 0.87 of gestation. Compared to controls, basal oxygen, glucose, and insulin concentrations were lower in IUGR groups. Norepinephrine concentrations were five-fold higher in IUGR fetuses than in IAD fetuses. During the EC, rates of glucose entry (GER, umbilical + exogenous), glucose utilization (GUR), and glucose oxidation (GOR) were greater in IUGR groups than in controls. In IUGR and IAD fetuses with euglycemia and euinsulinemia, glucose production rates (GPR) remained elevated. During the HEC, GER and GOR were not different among groups. In IUGR and IAD fetuses, GURs were 40% greater than in controls, which paralleled the sustained GPR despite hyperinsulinemia. Glucose-stimulated insulin concentrations were augmented in IAD fetuses compared to IUGR fetuses. Fetal weights were not different between IUGR groups but were less than controls. Regardless of norepinephrine concentrations, IUGR fetuses not only develop greater peripheral insulin sensitivity for glucose utilization but also develop hepatic insulin resistance because GPR was maintained and unaffected by euglycemia or hyperinsulinemia. These findings show that adaptation in glucose metabolism of IUGR fetuses are independent of catecholamines, which implicate that hypoxemia and hypoglycemia cause the metabolic responses.

Postnatal growth retardation is associated with deteriorated intestinal mucosal barrier function using a porcine model

Individuals with postnatal growth retardation (PGR) are prone to developing chronic diseases. Abnormal development in small intestine is casually implicated in impaired growth. However, the exact mechanism is still implausible. In this present study, PGR piglets (aged 42 days) were employed as a good model to analyze developmental changes in intestinal mucosal barrier function. Our data demonstrated that PGR piglets exhibited impaired jejunal and ileal epithelial villous morphology and permeability, accompanied by decreased cell proliferation ability and increased apoptosis rate. In addition, the expression of tight junction proteins (ZO-1, claudin 1, and occludin) and E-cadherin was markedly inhibited by PGR. The expression of P-glycoprotein was significantly reduced in PGR piglets, as well as decreased activity of lysozyme. Moreover, the mRNA abundance and content of inflammatory cytokines were significantly increased in the intestinal mucosa and plasma of PGR piglets, respectively. PGR also contributed to lower level of sIgA, and higher level of CD68-positive rate, β-defensins, and protein expression involved p38 MAPK/NF-κB pathway. Furthermore, PGR altered the intestinal microbial community such as decreased genus Alloprevotella and Oscillospira abundances, and led to lower microbial-derived butyrate production, which may be potential targets for treatment. Collectively, our findings indicated that the intestinal mucosal barrier function of PGR piglets could develop the nutritional intervention strategies in prevention and treatment of the intestinal mucosal barrier dysfunction in piglets and humans.

Immune dysfunction in developmental programming of type 2 diabetes mellitus

Intrauterine growth restriction (IUGR) is a common complication of pregnancy and increases the risk of the offspring developing type 2 diabetes mellitus (T2DM) later in life. Alterations in the immune system are implicated in the pathogenesis of IUGR-induced T2DM. The development of the fetal immune system is a delicate balance as it must remain tolerant of maternal antigens whilst also preparing for the post-birth environment. In addition, the fetal immune system is susceptible to an altered intrauterine milieu caused by maternal and placental inflammatory mediators or secondary to nutrient and oxygen deprivation. Pancreatic-resident macrophages populate the pancreas during fetal development, and their phenotype is dynamic through the neonatal period. Furthermore, macrophages in the islets are instrumental in islet development as they influence β-cell proliferation and islet neogenesis. In addition, cytokines, derived from β-cells and macrophages, are important to islet homeostasis in the fetus and adult and, when perturbed, can cause islet dysfunction. Several activated immune pathways have been identified in the islets of people who experienced IUGR, with alternations in the levels of IL-1β and IL-4 as well as changes in TGFβ signalling. Leptin levels are also altered. Immunomodulation has shown therapeutic benefit in T2DM and might be particularly useful in IUGR-induced T2DM.

Sustained maternal inflammation during the early third-trimester yields intrauterine growth restriction, impaired skeletal muscle glucose metabolism, and diminished β-cell function in fetal sheep1,2

Maternal inflammation causes fetal intrauterine growth restriction (IUGR), but its impact on fetal metabolism is not known. Thus, our objective was to determine the impact of sustained maternal inflammation in late gestation on fetal inflammation, skeletal muscle glucose metabolism, and insulin secretion. Pregnant ewes were injected every third day from the 100th to 112th day of gestation (term = 150 d) with saline (controls) or lipopolysaccharide (LPS) to induce maternal inflammation and IUGR (MI-IUGR). Fetal femoral blood vessels were catheterized on day 118 to assess β-cell function on day 123, hindlimb glucose metabolic rates on day 124, and daily blood parameters from days 120 to 125. Fetal muscle was isolated on day 125 to assess ex vivo glucose metabolism. Injection of LPS increased (P < 0.05) rectal temperatures, circulating white blood cells, and plasma tumor necrosis factor α (TNFα) concentrations in MI-IUGR ewes. Maternal leukocytes remained elevated (P < 0.05) and TNFα tended to remain elevated (P < 0.10) compared with controls almost 2 wk after the final LPS injection. Total white blood cells, monocytes, granulocytes, and TNFα were also greater (P < 0.05) in MI-IUGR fetuses than controls over this period. MI-IUGR fetuses had reduced (P < 0.05) blood O2 partial pressures and greater (P < 0.05) maternofetal O2 gradients, but blood glucose and maternofetal glucose gradients did not differ from controls. Basal and glucose-stimulated insulin secretion were reduced (P < 0.05) by 32% and 42%, respectively, in MI-IUGR fetuses. In vivo hindlimb glucose oxidation did not differ between groups under resting conditions but was 47% less (P < 0.05) in MI-IUGR fetuses than controls during hyperinsulinemia. Hindlimb glucose utilization did not differ between fetal groups. At day 125, MI-IUGR fetuses were 22% lighter (P < 0.05) than controls and tended to have greater (P < 0.10) brain/BW ratios. Ex vivo skeletal muscle glucose oxidation did not differ between groups in basal media but was less (P < 0.05) for MI-IUGR fetuses in insulin-spiked media. Glucose uptake rates and phosphorylated-to-total Akt ratios were less (P < 0.05) in muscle from MI-IUGR fetuses than controls regardless of media. We conclude that maternal inflammation leads to fetal inflammation, reduced β-cell function, and impaired skeletal muscle glucose metabolism that persists after maternal inflammation ceases. Moreover, fetal inflammation may represent a target for improving metabolic dysfunction in IUGR fetuses.

Label-Free Proteomics of the Fetal Pancreas Identifies Deficits in the Peroxisome in Rats with Intrauterine Growth Restriction

Aim

The objective of the present study was to identify differentially expressed proteins (DEPs) in the pancreas of a fetus with intrauterine growth restriction (IUGR) and to investigate the molecular mechanisms leading to adulthood diabetes in IUGR.

Methods

The IUGR rat model was induced by maternal protein malnutrition. The fetal pancreas was collected at embryonic day 20 (E20). Protein was extracted, pooled, and subjected to label-free quantitative proteomic analysis. Bioinformatics analysis (GO and IPA) was performed to define the pathways and networks associated with DEPs. LC-MS results were confirmed by western blotting and/or quantitative PCR (q-PCR). The principal parameters of oxidative stress-superoxide dismutase (Sod) were determined in blood samples of fetal rats.

Results

A total of 57 DEPs (27 upregulated, 30 downregulated) were identified with a 1.5-fold change threshold and a p value ≤ 0.05 between the IUGR and the control pancreas. Bioinformatics analysis revealed that these proteins play important roles in peroxisome biogenesis and fission, fatty acid beta-oxidation (FAO), mitotic cell cycle, and histone modification. The peroxin Pex14 was downregulated in the IUGR pancreas as confirmed by western blotting and q-PCR. Pmp70, a peroxisomal membrane protein involved in the transport of fatty acids, was upregulated. Hsd17b4 and Acox1/2, which catalyze different steps of peroxisomal FAO, were dysregulated. Sod plasma concentrations in the IUGR fetus were higher than those in the control, suggesting partial compensation for oxidative stress. Multiple DEPs were related to the regulation of the cell cycle, including reduced Cdk1, Mcm2, and Brd4. The histone acetylation regulators Hdac1/2 were downregulated, whereas Sirt1/3 and acetylated H3K56 were increased in the IUGR fetal pancreas.

Conclusion

The present study identified DEPs in the fetal pancreas of IUGR rats by proteomic analysis. Downregulation of pancreas peroxins and dysregulation of enzymes involved in peroxisomal FAO may impair the biogenesis and function of the peroxisome and may underlie the development of T2 diabetes mellitus in adult IUGR rats. Disorders of cell cycle regulators may induce cell division arrest and lead to smaller islets. The present data provide new insight into the role of the peroxisome in the development of the pancreas and may be valuable in furthering our understanding of the pathogenesis of IUGR-induced diabetes.

Alterations to DNA structure as a cause of expression modifications of selected genes of known intrauterine-growth-restriction-association shared by chosen species - a review

The review aimed at searching for DNA structure markers of epigenetic modifications leading to intrauterine growth restriction (IUGR) in three livestock species, mouse and human. IUGR affects mammals by harming their wellbeing and the profitability of breeding enterprises. Of the livestock species, we chose cow, pig and sheep owing to there being many reports on the epigenetics of IUGR. IUGR investigations in human and mouse are particularly numerous, as we are interested in our own wellbeing and the mouse is a model species. We decided to focus on five genes (Igf2r, Igf2, H19, Peg3 and Mest) of known IUGR association, reported in all of those species. Despite the abundance of papers on IUGR, naturally occurring mutations responsible for epigenetic modifications have been described only in human and cow. The effect of induced DNA structural modifications upon epigenetics has been described in mouse and pig. One paper regarding mouse was chosen from among those describing DNA modifications performed to obtain parthenogenetic progeny. Papers regarding pig parthenogenetic progeny described the epigenetics of genes involved in foetal development, with no interference with the genome structure. No reports on DNA modifications altering IUGR epigenetics in sheep were found. Only environmental effects were studied and we could not conclude from the experiment designs whether the gene setup could affect the expression of involved genes, as different populations were not included or not specified within particular experiments. Apparently, DNA markers of IUGR epigenetics exist. It has been reported that the small number of them, occurring naturally, may result from neglecting existing evidence of such selection or health status forecasting markers.

Osteoprotegerin promotes islet β cell proliferation in intrauterine growth retardation rats through the PI3K/AKT/FoxO1 pathway

Osteoprotegerin (OPG) is a critical factor involved in bone metabolism. The level of OPG is increased in the serum of diabetic patients; however, there is no consensus in prior studies on the role of OPG in regulating the function of islet β cells. A rat model of intrauterine growth retardation (IUGR) was established in the present study to investigate whether OPG could enhance the proliferation of β cells; and an in vitro culture model of rat islet β cell line INS-1 was used, to confirm the effect of OPG supplementation and reveal the possible mechanism. The results showed that endogenous OPG expression was reduced and normal proliferation of β cells was impaired in the IUGR islets. Exogenous supplement of OPG restored β cell proliferation to an extent in the IUGR rats, possibly associated with regulation of the PI3K/AKT/FoxO1 signalling, as evidenced by the changes of protein expression in the pathway. Furthermore, treating rat islet INS-1 cells with a PI3K inhibitor, LY294002, blunted the effects of OPG supplement in promoting cell cycle and suppressing cell apoptosis. Taken together, the present work demonstrated that OPG supplementation could improve the proliferation of islet β cells in IUGR, and the PI3K/AKT/FoxO1 pathway is involved in the underlying mechanism.

Oxidative Stress, Intrauterine Growth Restriction, and Developmental Programming of Type 2 Diabetes

Intrauterine growth restriction (IUGR) leads to reduced birth weight and the development of metabolic diseases such as Type 2 diabetes in adulthood. Mitochondria dysfunction and oxidative stress are commonly found in key tissues (pancreatic islets, liver, and skeletal muscle) of IUGR individuals. In this review, we explore the role of oxidative stress in IUGR-associated diabetes etiology.

Chronic Adrenergic Signaling Causes Abnormal RNA Expression of Proliferative Genes in Fetal Sheep Islets

Intrauterine growth restriction (IUGR) increases the risk of developing diabetes in later life, which indicates developmental programming of islets. IUGR fetuses with placental insufficiency develop hypoxemia, elevating epinephrine and norepinephrine (NE) concentrations throughout late gestation. To isolate the programming effects of chronically elevated catecholamines, NE was continuously infused into normally grown sheep fetuses for 7 days. High plasma NE concentrations suppress insulin, but after the NE infusion was terminated, persistent hypersecretion of insulin occurred. Our objective was to identify differential gene expression with RNA sequencing (RNAseq) in fetal islets after chronic adrenergic stimulation. After determining the NE-regulated genes, we identified the subset of differentially expressed genes that were common to both islets from NE fetuses and fetuses with IUGR to delineate the adrenergic-induced transcriptional responses. A portion of these genes were investigated in mouse insulinoma (Min6) cells chronically treated with epinephrine to better approximate the β-cell response. In islets from NE fetuses, RNAseq identified 321 differentially expressed genes that were overenriched for metabolic and hormone processes, and the subset of 96 differentially expressed genes common to IUGR islets were overenriched for protein digestion, vitamin metabolism, and cell replication pathways. Thirty-eight of the 96 NE-regulated IUGR genes changed similarly between models with functional enrichment for proliferation. In Min6 cells, chronic epinephrine stimulation slowed proliferation and augmented insulin secretion after treatment. These data establish molecular mechanisms underlying persistent adrenergic stimulation in hyperfunctional fetal islets and identify a subset of genes dysregulated by catecholamines in IUGR islets that may represent programming of β-cell proliferation capacity.

Altered miRNA-4321 expression in maternal and foetal placenta of intrauterine growth restricted bovine foetuses

Intrauterine growth restriction (IUGR) is a serious pregnancy complication caused by placental insufficiency. We previously reported that truncation of MIMT1 gene exons 3 and 4 (MIMT1^Del) causes IUGR in cattle. Here we investigated miRNA expression in the foetal and maternal placenta tissues of MIMT1^Del/WT foetuses. Small RNA next generation sequencing and quantitative PCR revealed placental tissue-specific expression of the miR-4321, known to regulate many genes involved in early foetal development. This study also indicated that maternal and foetal components of the placenta respond differently to a deleterious conceptus mutation.

Adrenergic receptor stimulation suppresses oxidative metabolism in isolated rat islets and Min6 cells

Insulin secretion is stimulated by glucose metabolism and inhibited by catecholamines through adrenergic receptor stimulation. We determined whether catecholamines suppress oxidative metabolism in β-cells through adrenergic receptors. In Min6 cells and isolated rat islets, epinephrine decreased oxygen consumption rates compared to vehicle control or co-administration of epinephrine with α2-adrenergic receptor antagonist yohimbine. Epinephrine also decreased forskolin-stimulated oxygen consumption rates, indicating cAMP dependent and independent actions. Furthermore, glucose oxidation rates were decreased with epinephrine, independent of the exocytosis of insulin, which was blocked with yohimbine. We evaluated metabolic targets through proteomic analysis after 4 h epinephrine exposure that revealed 466 differentially expressed proteins that were significantly enriched for processes including oxidative metabolism, protein turnover, exocytosis, and cell proliferation. These results demonstrate that acute α2-adrenergic stimulation suppresses glucose oxidation in β-cells independent of nutrient availability and insulin exocytosis, while cAMP concentrations are elevated. Proteomics and immunoblots revealed changes in electron transport chain proteins that were correlated with lower metabolic reducing equivalents, intracellular ATP concentrations, and altered mitochondrial membrane potential implicating a new role for adrenergic control of mitochondrial function and ultimately insulin secretion.

Fetal undernutrition, placental insufficiency, and pancreatic β-cell development programming in utero

The prevalence of obesity and type 2 (T2D) diabetes is a major health concern in the United States and around the world. T2D is a complex disease characterized by pancreatic β-cell failure in association with obesity and insulin resistance in peripheral tissues. Although several genes associated with T2D have been identified, it is speculated that genetic variants account for only <10% of the risk for this disease. A strong body of data from both human epidemiological and animal studies shows that fetal nutrient factors in utero confer significant susceptibility to T2D. Numerous studies done in animals have shown that suboptimal maternal environment or placental insufficiency causes intrauterine growth restriction (IUGR) in the fetus, a critical factor known to predispose offspring to obesity and T2D, in part by causing permanent consequences in total functional β-cell mass. This review will focus on the potential contribution of the placenta in fetal programming of obesity and TD and its likely impact on pancreatic β-cell development and growth.

ASAS-SSR Triennnial Reproduction Symposium: Looking Back and Moving Forward-How Reproductive Physiology has Evolved: Fetal origins of impaired muscle growth and metabolic dysfunction: Lessons from the heat-stressed pregnant ewe

Intrauterine growth restriction (IUGR) is the second leading cause of perinatal mortality and predisposes offspring to metabolic disorders at all stages of life. Muscle-centric fetal adaptations reduce growth and yield metabolic parsimony, beneficial for IUGR fetal survival but detrimental to metabolic health after birth. Epidemiological studies have reported that IUGR-born children experience greater prevalence of insulin resistance and obesity, which progresses to diabetes, hypertension, and other metabolic disorders in adulthood that reduce quality of life. Similar adaptive programming in livestock results in decreased birth weights, reduced and inefficient growth, decreased carcass merit, and substantially greater mortality rates prior to maturation. High rates of glucose consumption and metabolic plasticity make skeletal muscle a primary target for nutrient-sparing adaptations in the IUGR fetus, but at the cost of its contribution to proper glucose homeostasis after birth. Identifying the mechanisms underlying IUGR pathophysiology is a fundamental step in developing treatments and interventions to improve outcomes in IUGR-born humans and livestock. In this review, we outline the current knowledge regarding the adaptive restriction of muscle growth and alteration of glucose metabolism that develops in response to progressively exacerbating intrauterine conditions. In addition, we discuss the evidence implicating developmental changes in β adrenergic and inflammatory systems as key mechanisms for dysregulation of these processes. Lastly, we highlight the utility and importance of sheep models in developing this knowledge.

Transcriptomic Analysis Reveals Novel Mechanisms Mediating Islet Dysfunction in the Intrauterine Growth-Restricted Rat

Intrauterine growth restriction (IUGR) increases the risk of type 2 diabetes developing in adulthood. In previous studies that used bilateral uterine artery ligation in a rat model of IUGR, age-associated decline in glucose homeostasis and islet function was revealed. To elucidate mechanisms contributing to IUGR pathogenesis, the islet transcriptome was sequenced from 2-week-old rats, when in vivo glucose tolerance is mildly impaired, and at 10 weeks of age, when rats are hyperglycemic and have reduced β-cell mass. RNA sequencing and functional annotation with Ingenuity Pathway Analysis revealed temporal changes in IUGR islets. For instance, gene expression involving amino acid metabolism was significantly reduced primarily at 2 weeks of age, but ion channel expression, specifically that involved in cell-volume regulation, was more disrupted in adult IUGR islets. Additionally, we observed alterations in the microenvironment of IUGR islets with extracellular matrix genes being significantly increased at 2 weeks of age and significantly decreased at 10 weeks. Specifically, hyaluronan synthase 2 expression and hyaluronan staining were increased in IUGR islets at 2 weeks of age (P < 0.05). Mesenchymal stromal cell-derived factors that have been shown to preserve islet allograft function, such as Anxa1, Cxcl12, and others, also were increased at 2 weeks and decreased in adult islets. Finally, comparisons of differentially expressed genes with those of type 2 diabetic human islets support a role for these pathways in human patients with diabetes. Together, these data point to new mechanisms in the pathogenesis of IUGR-mediated islet dysfunction in type 2 diabetes.

The impact of IUGR on pancreatic islet development and β-cell function

Placental insufficiency is a primary cause of intrauterine growth restriction (IUGR). IUGR increases the risk of developing type 2 diabetes mellitus (T2DM) throughout life, which indicates that insults from placental insufficiency impair β-cell development during the perinatal period because β-cells have a central role in the regulation of glucose tolerance. The severely IUGR fetal pancreas is characterized by smaller islets, less β-cells, and lower insulin secretion. Because of the important associations among impaired islet growth, β-cell dysfunction, impaired fetal growth, and the propensity for T2DM, significant progress has been made in understanding the pathophysiology of IUGR and programing events in the fetal endocrine pancreas. Animal models of IUGR replicate many of the observations in severe cases of human IUGR and allow us to refine our understanding of the pathophysiology of developmental and functional defects in islet from IUGR fetuses. Almost all models demonstrate a phenotype of progressive loss of β-cell mass and impaired β-cell function. This review will first provide evidence of impaired human islet development and β-cell function associated with IUGR and the impact on glucose homeostasis including the development of glucose intolerance and diabetes in adulthood. We then discuss evidence for the mechanisms regulating β-cell mass and insulin secretion in the IUGR fetus, including the role of hypoxia, catecholamines, nutrients, growth factors, and pancreatic vascularity. We focus on recent evidence from experimental interventions in established models of IUGR to understand better the pathophysiological mechanisms linking placental insufficiency with impaired islet development and β-cell function.

Fetal adaptations in insulin secretion result from high catecholamines during placental insufficiency

Placental insufficiency and intrauterine growth restriction (IUGR) of the fetus affects approximately 8% of all pregnancies and is associated with short- and long-term disturbances in metabolism. In pregnant sheep, experimental models with a small, defective placenta that restricts delivery of nutrients and oxygen to the fetus result in IUGR. Low blood oxygen concentrations increase fetal plasma catecholamine concentrations, which lower fetal insulin concentrations. All of these observations in sheep models with placental insufficiency are consistent with cases of human IUGR. We propose that sustained high catecholamine concentrations observed in the IUGR fetus produce developmental adaptations in pancreatic β-cells that impair fetal insulin secretion. Experimental evidence supporting this hypothesis shows that chronic elevation in circulating catecholamines in IUGR fetuses persistently inhibits insulin concentrations and secretion. Elevated catecholamines also allow for maintenance of a normal fetal basal metabolic rate despite low fetal insulin and glucose concentrations while suppressing fetal growth. Importantly, a compensatory augmentation in insulin secretion occurs following inhibition or cessation of catecholamine signalling in IUGR fetuses. This finding has been replicated in normally grown sheep fetuses following a 7-day noradrenaline (norepinephrine) infusion. Together, these programmed effects will potentially create an imbalance between insulin secretion and insulin-stimulated glucose utilization in the neonate which probably explains the transient hyperinsulinism and hypoglycaemia in some IUGR infants.

Enhanced insulin secretion and insulin sensitivity in young lambs with placental insufficiency-induced intrauterine growth restriction

Intrauterine growth restriction (IUGR) is associated with persistent metabolic complications, but information is limited for IUGR infants. We determined glucose-stimulated insulin secretion (GSIS) and insulin sensitivity in young lambs with placental insufficiency-induced IUGR. Lambs with hyperthermia-induced IUGR (n = 7) were compared with control lambs (n = 8). GSIS was measured at 8 ± 1 days of age, and at 15 ± 1 days, body weight-specific glucose utilization rates were measured with radiolabeled d-glucose during a hyperinsulinemic-euglycemic clamp (HEC). IUGR lambs weighed 23% less (P < 0.05) than controls at birth. Fasting plasma glucose and insulin concentrations were not different between IUGR and controls for either study. First-phase insulin secretion was enhanced 2.3-fold in IUGR lambs compared with controls. However, second-phase insulin concentrations, glucose-potentiated arginine-stimulated insulin secretion, and β-cell mass were not different, indicating that IUGR β-cells have an intrinsic enhancement in acute GSIS. Compared with controls, IUGR lambs had higher body weight-specific glucose utilization rates and greater insulin sensitivity at fasting (1.6-fold) and hyperinsulinemic periods (2.4-fold). Improved insulin sensitivity for glucose utilization was not due to differences in skeletal muscle insulin receptor and glucose transporters 1 and 4 concentrations. Plasma lactate concentrations during HEC were elevated in IUGR lambs compared with controls, but no differences were found for glycogen content or citrate synthase activity in liver and muscle. Greater insulin sensitivity for glucose utilization and enhanced acute GSIS in young lambs are predicted from fetal studies but may promote conditions that exaggerate glucose disposal and lead to episodes of hypoglycemia in IUGR infants.