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

Etiology of the Neonatal Hypoglycemias

To provide a more appropriate foundation for dealing with the problem of hypoglycemia in newborn infants, this article focuses on the mechanisms which underlie the various forms of neonatal hypoglycemia and discusses their implications for newborn care. Evidence indicates that all of the major forms of neonatal hypoglycemia are the result of hyperinsulinism due to dysregulation of pancreatic islet insulin secretion. Based on these observations, the authors propose that routine measurement of B-hydroxybutyrate should be considered an essential part of glucose monitoring in newborn infants.

Neonatal hypoglycaemia

Low blood concentrations of glucose (hypoglycaemia) soon after birth are common because of the delayed metabolic transition from maternal to endogenous neonatal sources of glucose. Because glucose is the main energy source for the brain, severe hypoglycaemia can cause neuroglycopenia (inadequate supply of glucose to the brain) and, if severe, permanent brain injury. Routine screening of infants at risk and treatment when hypoglycaemia is detected are therefore widely recommended. Robust evidence to support most aspects of management is lacking, however, including the appropriate threshold for diagnosis and optimal monitoring. Treatment is usually initially more feeding, with buccal dextrose gel, followed by intravenous dextrose. In infants at risk, developmental outcomes after mild hypoglycaemia seem to be worse than in those who do not develop hypoglycaemia, but the reasons for these observations are uncertain. Here, the current understanding of the pathophysiology of neonatal hypoglycaemia and recent evidence regarding its diagnosis, management, and outcomes are reviewed. Recommendations are made for further research priorities.

Factors associated with neonatal hyperinsulinemic hypoglycemia, a case-control study

OBJECTIVES

We aimed to identify perinatal risk factors associated with hyperinsulinemic hypoglycemia in neonates. Secondary objectives included an examination of clinical and biochemical characteristics at the time of diagnosis and an exploration of the duration of diazoxide therapy.

METHODS

A case-control study was conducted, involving individual chart reviews of inborn infants diagnosed with hyperinsulinemic hypoglycemia (the HH group) between 2014 and 2021. These cases were paired with controls (the non-HH group) belonging to the same gestational age (GA) strata who did not exhibit HH or only had transient postnatal hypoglycemia.

RESULTS

A total of 52 infants with HH were matched with corresponding controls. The mean GA in the HH group was 34.4 ± 3.1 weeks. Notably, the HH group exhibited lower mean minimum plasma glucose (PG) levels and required higher glucose infusion rates in comparison to the non-HH group (26.5 ± 15.6 vs. 49.1 ± 37.7 mg/dL and 12.9 ± 3.8 vs. 5.7 ± 2.1 mg/kg/min, respectively; p<0.001 for both). After adjusting for potential confounding factors, only two variables, fetal growth restriction (FGR) and neonatal sepsis, demonstrated significant associations with HH (adjusted odds ratio [95 % confidence interval]: 8.1 [2.1-31.0], p=0.002 and 6.3 [1.9-21.4], p=0.003, respectively). The median duration of diazoxide therapy for the HH group was 4 months.

CONCLUSIONS

FGR and neonatal sepsis emerged as notable risk factors for HH. These infants exhibited lower PG levels and necessitated higher glucose infusion rates compared to their non-HH counterparts. Importantly, a substantial proportion of the HH group received diazoxide therapy, with a median treatment duration of 4 months.

Elevated Norepinephrine Stimulates Adipocyte Hyperplasia in Ovine Fetuses With Placental Insufficiency and IUGR

Prevailing hypoxemia and hypoglycemia in near-term fetuses with placental insufficiency-induced intrauterine growth restriction (IUGR) chronically increases norepinephrine concentrations, which lower adrenergic sensitivity and lipid mobilization postnatally, indicating a predisposition for adiposity. To determine adrenergic-induced responses, we examined the perirenal adipose tissue transcriptome from IUGR fetuses with or without hypercatecholaminemia. IUGR was induced in sheep with maternal hyperthermia, and hypercatecholaminemia in IUGR was prevented with bilateral adrenal demedullation. Adipose tissue was collected from sham-operated control (CON) and IUGR fetuses and adrenal-demedullated control (CAD) and IUGR (IAD) fetuses. Norepinephrine concentrations were lower in IAD fetuses than in IUGR fetuses despite both being hypoxemic and hypoglycemic. In IUGR fetuses, perirenal adipose tissue mass relative to body mass was greater compared with the CON, adrenal-demedullated control, and IAD groups. Transcriptomic analysis identified 581 differentially expressed genes (DEGs) in CON vs IUGR adipose tissue and 193 DEGs in IUGR vs IAD adipose tissue. Integrated functional analysis of these 2 comparisons showed enrichment for proliferator-activated receptor signaling and metabolic pathways and identified adrenergic responsive genes. Within the adrenergic-regulated DEGs, we identified transcripts that regulate adipocyte proliferation and differentiation: adipogenesis regulatory factor, C/CCAAT/enhancer binding protein α, and sterol carrier protein 2. DEGs associated with the metabolic pathway included pyruvate dehydrogenase kinase 4, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4, IGF-binding proteins (IGFBP-5 and IGFBP-7). Sex-specific expression differences were also found for adipogenesis regulatory factor, pyruvate dehydrogenase kinase 4, IGFBP5, and IGFBP7. These findings indicate that sustained adrenergic stimulation during IUGR leads to adipocyte hyperplasia with alterations in metabolism, proliferation, and preadipocyte differentiation pathways.

Effects of Intrauterine Growth Restriction (IUGR) on Growth and Body Composition Compared to Constitutionally Small Infants

(1) Intrauterine growth restriction (IUGR) is associated with multiple morbidities including growth restriction and impaired neurodevelopment. Small for gestational age (SGA) is defined as a birth weight <10th percentile, regardless of the etiology. The term is commonly used as a proxy for IUGR, but it may represent a healthy constitutionally small infant. Differentiating between IUGR and constitutionally small infants is essential for the nutritional management. (2) Infants born at <37 weeks of gestation between 2017 and 2022, who underwent body composition measurement (FFM: fat-free mass; FM: fat mass) at term-equivalent age, were included in this study. Infants with IUGR and constitutionally small infants (SGA) were compared to infants appropriate for gestational age (AGA). (3) A total of 300 infants (AGA: n = 249; IUGR: n = 40; SGA: n = 11) were analyzed. FFM (p < 0.001) and weight growth velocity (p = 0.022) were significantly lower in IUGR compared to AGA infants, but equal in SGA and AGA infants. FM was not significantly different between all groups. (4) The FFM Z-score was significantly lower in IUGR compared to AGA infants (p = 0.017). Being born constitutionally small compared to AGA had no impact on growth and body composition. These data showed that early aggressive nutritional management is essential in IUGR infants to avoid impaired growth and loss of FFM.

Daily injection of the β2 adrenergic agonist clenbuterol improved poor muscle growth and body composition in lambs following heat stress-induced intrauterine growth restriction

Background: Intrauterine growth restriction (IUGR) is associated with reduced β2 adrenergic sensitivity, which contributes to poor postnatal muscle growth. The objective of this study was to determine if stimulating β2 adrenergic activity postnatal would rescue deficits in muscle growth, body composition, and indicators of metabolic homeostasis in IUGR offspring. Methods: Time-mated ewes were housed at 40°C from day 40 to 95 of gestation to produce IUGR lambs. From birth, IUGR lambs received daily IM injections of 0.8 μg/kg clenbuterol HCl (IUGR+CLEN; n = 11) or saline placebo (IUGR; n = 12). Placebo-injected controls (n = 13) were born to pair-fed thermoneutral ewes. Biometrics were assessed weekly and body composition was estimated by ultrasound and bioelectrical impedance analysis (BIA). Lambs were necropsied at 60 days of age. Results: Bodyweights were lighter (p ≤ 0.05) for IUGR and IUGR+CLEN lambs than for controls at birth, day 30, and day 60. Average daily gain was less (p ≤ 0.05) for IUGR lambs than controls and was intermediate for IUGR+CLEN lambs. At day 58, BIA-estimated whole-body fat-free mass and ultrasound-estimated loin eye area were less (p ≤ 0.05) for IUGR but not IUGR+CLEN lambs than for controls. At necropsy, loin eye area and flexor digitorum superficialis muscles were smaller (p ≤ 0.05) for IUGR but not IUGR+CLEN lambs than for controls. Longissimus dorsi protein content was less (p ≤ 0.05) and fat-to-protein ratio was greater (p ≤ 0.05) for IUGR but not IUGR+CLEN lambs than for controls. Semitendinosus from IUGR lambs had less (p ≤ 0.05) β2 adrenoreceptor content, fewer (p ≤ 0.05) proliferating myoblasts, tended to have fewer (p = 0.08) differentiated myoblasts, and had smaller (p ≤ 0.05) muscle fibers than controls. Proliferating myoblasts and fiber size were recovered (p ≤ 0.05) in IUGR+CLEN lambs compared to IUGR lambs, but β2 adrenoreceptor content and differentiated myoblasts were not recovered. Semitendinosus lipid droplets were smaller (p ≤ 0.05) in size for IUGR lambs than for controls and were further reduced (p ≤ 0.05) in size for IUGR+CLEN lambs. Conclusion: These findings show that clenbuterol improved IUGR deficits in muscle growth and some metabolic parameters even without recovering the deficit in β2 adrenoreceptor content. We conclude that IUGR muscle remained responsive to β2 adrenergic stimulation postnatal, which may be a strategic target for improving muscle growth and body composition in IUGR-born offspring.

Sexual dimorphic gene expression profile of perirenal adipose tissue in ovine fetuses with growth restriction

Worldwide, fetal growth restriction (FGR) affects 7%-10% of pregnancies, or roughly 20.5 million infants, each year. FGR increases not only neonatal mortality and morbidity but also the risk of obesity in later life. Currently, the molecular mechanisms by which FGR "programs" an obese phenotype are not well understood. Studies demonstrate that FGR females are more prone to obesity compared to males; however, the molecular mechanisms that lead to the sexually dimorphic programming of FGR are not known. Thus, we hypothesized that FGR leads to the sexually dimorphic programming of preadipocytes and reduces their ability to differentiate into mature adipocytes. To test the hypothesis, we utilized a maternal hyperthermia-induced placental insufficiency to restrict fetal growth in sheep. We collected perirenal adipose tissue from near-term (∼140 days gestation) male and female FGR and normal-weight fetal lambs (N = 4 to 5 in each group), examined the preadipocytes' differentiation potential, and identified differential mRNA transcript expression in perirenal adipose tissue. Male FGR fetuses have a lower cellular density (nuclei number/unit area) compared to control male fetuses. However, no difference was observed in female FGR fetuses compared to control female fetuses. In addition, the ability of preadipocytes to differentiate into mature adipocytes with fat accumulation was impaired in male FGR fetuses, but this was not observed in female FGR fetuses. Finally, we examined the genes and pathways involved in the sexually dimorphic programming of obesity by FGR. On enrichment of differentially expressed genes in males compared to females, the Thermogenesis KEGG Pathway was downregulated, and the Metabolic and Steroid Biosynthesis KEGG pathways were upregulated. On enrichment of differentially expressed genes in male FGR compared to male control, the Steroid Biosynthesis KEGG Pathway was downregulated, and the PPAR Signaling KEGG pathway was upregulated. No pathways were altered in females in response to growth restriction in perirenal adipose tissue. Thus, the present study demonstrates a sexually dimorphic program in response to growth restriction in sheep fetal perirenal adipose tissue.

Delayed-Onset Transient Hyperinsulinism in Infants with Very Low and Extremely Low Birth Weights: A Cohort Study

We describe 16 infants born preterm with birth weights <1500 g and transient hyperinsulinism. The onset of hyperinsulinism was delayed and often coincident with clinical stabilization. We hypothesize that postnatal stress caused by prematurity and associated problems may contribute to development of delayed-onset transient hyperinsulinism.

Seasonal and temporal variation in the placenta during melatonin supplementation in a bovine compromised pregnancy model

Compromised pregnancies result in a poorly functioning placenta restricting the amount of oxygen and nutrient supply to the fetus resulting in intrauterine growth restriction (IUGR). Supplementing dietary melatonin during a compromised pregnancy increased uteroplacental blood flow and prevented IUGR in a seasonal-dependent manner. The objectives were to evaluate seasonal melatonin-mediated changes in temporal alterations of the bovine placental vascularity and transcript abundance of clock genes, angiogenic factors, and nutrient sensing genes in 54 underfed pregnant Brangus heifers (Fall, n = 29; Summer, n = 25). At day 160 of gestation, heifers were assigned to treatments consisting of adequately fed (ADQ-CON; 100% NRC; n = 13), nutrient restricted (RES-CON; 60% NRC; n = 13), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL, n = 13; RES-MEL, n = 15). The animals were fed daily at 0900 hours until day 240 where Cesarean sections were performed in the morning (0500 hours) or afternoon (1300 hours) for placentome collections. In both seasons, we observed a temporal alteration of the core clock genes in the cotyledonary tissue in a season-dependent manner. In the fall, ARNTL, CLOCK, NR1D1, and RORA transcript abundance were decreased (P ≤ 0.05) in the afternoon compared to the morning; whereas in the summer, ARNTL, PER2, and RORA expression were increased (P ≤ 0.05) in the afternoon. Interestingly, in both seasons, there was a concomitant temporal increase (P ≤ 0.05) of cotyledonary blood vessel perfusion and caruncular melatonin receptor 1A transcript abundance. Melatonin supplementation did not alter the melatonin receptor 1A transcript abundance (P > 0.05), however, in the summer, melatonin supplementation increased cotyledonary VEGFA, CRY1, and RORA (P ≤ 0.05) transcript abundance. In addition, during the summer the placentomes from underfed dams had increased average capillary size and HIF1α transcript abundance compared to those adequately fed (P ≤ 0.05). In conclusion, these data indicate increased cotyledonary blood vessel size and blood distribution after feeding to better facilitate nutrient transport. Interestingly, the maternal nutritional plane appears to play a crucial role in regulating the bovine placental circadian clock. Based on these findings, the regulation of angiogenic factors and clock genes in the bovine placenta appears to be an underlying mechanism of the therapeutic effect of dietary melatonin supplementation in the summer.

The Role of Early Pregnancy Maternal pGCD59 Levels in Predicting Neonatal Hypoglycemia-Subanalysis of the DALI Study

CONTEXT

Neonatal hypoglycaemia (NH) is the most common metabolic problem in infants born of mothers with gestational diabetes. Plasma glycated CD59 (pGCD59) is an emerging biomarker that has shown potential in identifying women at risk of developing gestational diabetes. The aim of this study was to assess the association between early maternal levels of pGCD59 and NH.

OBJECTIVE

The aim of this study was to assess the association between early pregnancy maternal levels of plasma glycated CD59 (pGCD59) and neonatal hypoglycemia (NH).

METHODS

This is an observational study of pregnant women with a prepregnancy body mass index (BMI) greater than or equal to 29 screened for eligibility to participate in the Vitamin D and Lifestyle Intervention for Gestational Diabetes (DALI) trial. This analysis included 399 pregnancies. Levels of pGCD59 were measured in fasting maternal samples taken at the time of a 75-g, 2-hour oral glucose tolerance test performed in early pregnancy (< 20 weeks). NH, the study outcome, was defined as a heel-prick capillary glucose level of less than 2.6 mmol/L within 48 hours of delivery.

RESULTS

We identified 30 infants with NH. Maternal levels of pGCD59 in early pregnancy were positively associated with the prevalence of NH (one-way analysis of variance, P < .001). The odds of NH were higher in infants from mothers in tertile 3 of pGCD59 levels compared to those from mothers in tertile 1 (odds ratio [OR]: 2.41; 95% CI, 1.03-5.63). However, this was attenuated when adjusted for maternal BMI (OR: 2.28; 95% CI, 0.96-5.43). The cross-validated area under the curve (AUC) was 0.64 (95% CI, 0.54-0.74), and adjusted for maternal BMI, age, and ethnicity, the AUC was 0.70 (95% CI, 0.56-0.78).

CONCLUSION

Although pGCD59 levels in early pregnancy in women with BMI greater than or equal to 29 are associated with NH, our results indicate that this biomarker by itself is only a fair predictor of NH.

Prenatal transcript levels and metabolomics analyses reveal metabolic changes associated with intrauterine growth restriction and sex

The metabolic changes associated with intrauterine growth restriction (IUGR) particularly affect the liver, which is a central metabolic organ and contributes significantly to the provision of energy and specific nutrients and metabolites. Therefore, our aim was to decipher and elucidate the molecular pathways of developmental processes mediated by miRNAs and mRNAs, as well as the metabolome in fetal liver tissue in IUGR compared to appropriate for gestational age groups (AGA). Discordant siblings representing the extremes in fetal weight at day 63 post conception (dpc) were selected from F2 fetuses of a cross of German Landrace and Pietrain. Most of the changes in the liver of IUGR at midgestation involved various lipid metabolic pathways, both on transcript and metabolite levels, especially in the category of sphingolipids and phospholipids. Differentially expressed miRNAs, such as miR-34a, and their differentially expressed mRNA targets were identified. Sex-specific phenomena were observed at both the transcript and metabolite levels, particularly in male. This suggests that sex-specific adaptations in the metabolic system occur in the liver during midgestation (63 dpc). Our multi-omics network analysis reveals interactions and changes in the metabolic system associated with IUGR and identified an important biosignature that differs between IUGR and AGA piglets.

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.

Hyperinsulinemic hypoglycemia in growth restricted convalescent preterm neonates: clinical characteristics and impediments to early diagnosis

OBJECTIVES

Describe clinical characteristics, course, and risk factors for hyper-insulinemic hypoglycemia (HIH) in preterm infants and identify impediments to early diagnosis.

METHODS

Electronic records of infant-mother dyads were used to describe clinical characteristics, lab parameters, and course of HIH.

RESULTS

All eight patients (gestational ages 26w0d-29w3d) had intrauterine growth restriction (IUGR) due to placental insufficiency, (4/8) were small for gestational age. All maintained normal glucose levels with glucose infusion during the first 48 h six of eight patients had cholestasis despite being on parenteral nutrition for short time (average 17 days). Four of eight patients were treated with diazoxide (average 22 days). Four of eight patients who recovered spontaneously (average 49 days after diagnosis) responded to continuous feeds and hydrocortisone for other clinical indications.

CONCLUSIONS

In IUGR preterms, HIH is asymptomatic, may be prolonged, requiring diazoxide treatment. Transient cholestasis is seen in majority of patients. Euglycemia should be demonstrated on bolus gavage feeds, off glucocorticoids before discontinuing blood glucose monitoring.

Tissue-specific responses that constrain glucose oxidation and increase lactate production with the severity of hypoxemia in fetal sheep

Fetal hypoxemia decreases insulin and increases cortisol and norepinephrine concentrations and may restrict growth by decreasing glucose utilization and altering substrate oxidation. Specifically, we hypothesized that hypoxemia would decrease fetal glucose oxidation and increase lactate and pyruvate production. We tested this by measuring whole body glucose oxidation and lactate production, and molecular pathways in liver, muscle, adipose, and pancreas tissues of fetuses exposed to maternal hypoxemia for 9 days (HOX) compared with control fetal sheep (CON) in late gestation. Fetuses with more severe hypoxemia had lower whole body glucose oxidation rates, and HOX fetuses had increased lactate production from glucose. In muscle and adipose tissue, expression of the glucose transporter GLUT4 was decreased. In muscle, pyruvate kinase (PKM) and lactate dehydrogenase B (LDHB) expression was decreased. In adipose tissue, LDHA and lactate transporter (MCT1) expression was increased. In liver, there was decreased gene expression of PKLR and MPC2 and phosphorylation of PDH, and increased LDHA gene and LDH protein abundance. LDH activity, however, was decreased only in HOX skeletal muscle. There were no differences in basal insulin signaling across tissues, nor differences in pancreatic tissue insulin content, β-cell area, or genes regulating β-cell function. Collectively, these results demonstrate coordinated metabolic responses across tissues in the hypoxemic fetus that limit glucose oxidation and increase lactate and pyruvate production. These responses may be mediated by hypoxemia-induced endocrine responses including increased norepinephrine and cortisol, which inhibit pancreatic insulin secretion resulting in lower insulin concentrations and decreased stimulation of glucose utilization.NEW & NOTEWORTHY Hypoxemia lowered fetal glucose oxidation rates, based on severity of hypoxemia, and increased lactate production. This was supported by tissue-specific metabolic responses that may result from increased norepinephrine and cortisol concentrations, which decrease pancreatic insulin secretion and insulin concentrations and decrease glucose utilization. This highlights the vulnerability of metabolic pathways in the fetus and demonstrates that constrained glucose oxidation may represent an early event in response to sustained hypoxemia and fetal growth restriction.

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.

The Price of Surviving on Adrenaline: Developmental Programming Responses to Chronic Fetal Hypercatecholaminemia Contribute to Poor Muscle Growth Capacity and Metabolic Dysfunction in IUGR-Born Offspring

Maternofetal stress induces fetal programming that restricts skeletal muscle growth capacity and metabolic function, resulting in intrauterine growth restriction (IUGR) of the fetus. This thrifty phenotype aids fetal survival but also yields reduced muscle mass and metabolic dysfunction after birth. Consequently, IUGR-born individuals are at greater lifelong risk for metabolic disorders that reduce quality of life. In livestock, IUGR-born animals exhibit poor growth efficiency and body composition, making these animals more costly and less valuable. Specifically, IUGR-associated programming causes a greater propensity for fat deposition and a reduced capacity for muscle accretion. This, combined with metabolic inefficiency, means that these animals produce less lean meat from greater feed input, require more time on feed to reach market weight, and produce carcasses that are of less quality. Despite the health and economic implications of IUGR pathologies in humans and food animals, knowledge regarding their specific underlying mechanisms is lacking. However, recent data indicate that adaptive programing of adrenergic sensitivity in multiple tissues is a contributing factor in a number of IUGR pathologies including reduced muscle mass, peripheral insulin resistance, and impaired glucose metabolism. This review highlights the findings that support the role for adrenergic programming and how it relates to the lifelong consequences of IUGR, as well as how dysfunctional adrenergic signaling pathways might be effective targets for improving outcomes in IUGR-born offspring.

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.

Fetal Sex Does Not Impact Placental Blood Flow or Placental Amino Acid Transfer in Late Gestation Pregnant Sheep With or Without Placental Insufficiency

Pregnant sheep have been used to model complications of human pregnancies including placental insufficiency and intrauterine growth restriction. Some of the hallmarks of placental insufficiency are slower uterine and umbilical blood flow rates, impaired placental transport of oxygen and amino acids, and lower fetal arterial concentrations of anabolic growth factors. An impact of fetal sex on these outcomes has not been identified in either human or sheep pregnancies. This is likely because most studies measuring these outcomes have used small numbers of subjects or animals. We undertook a secondary analysis of previously published data generated by our laboratory in late-gestation (gestational age of 133 ± 0 days gestational age) control sheep (n = 29 male fetuses; n = 26 female fetuses; n = 3 sex not recorded) and sheep exposed to elevated ambient temperatures to cause experimental placental insufficiency (n = 23 male fetuses; n = 17 female fetuses; n = 1 sex not recorded). The primary goal was to determine how fetal sex modifies the effect of the experimental insult on outcomes related to placental blood flow, amino acid and oxygen transport, and fetal hormones. Of the 112 outcomes measured, we only found an interaction between fetal sex and experimental insult for the uterine uptake rates of isoleucine, phenylalanine, and arginine. Additionally, most outcomes measured did not show a difference based on fetal sex when adjusting for the impact of placental insufficiency. Exceptions included fetal norepinephrine and cortisol concentrations, which were higher in female compared to male fetuses. For the parameters measured in the current analysis, the impact of fetal sex was not widespread.

Macrosomia and fetal growth restriction: evidence for similar extrauterine metabolic risks but with differences in pathophysiology

PURPOSE

To investigate and compare the causes of macrosomia and FGR fetuses, their ultrasound characteristics and the importance of their similar metabolic profile in intrauterine and extrauterine life.

MATERIALS AND METHODS

We searched Pubmed/Google Scholar database up until 15 December 2020 using keywords. Out of the 70 matching results we selected 50 most representative and matching papers.

RESULTS

We found similar causes and metabolic profiles and in both conditions offspring are at increased risk of developing metabolic and cardiovascular diseases in the extrauterine life.

CONCLUSION

Despite similarities of the maternal factors and fetal metabolic profile it is still unknown which of them has worse metabolic status during intrauterine and extrauterine life.

Assessment of fetal cardiac diastolic function of gestational diabetes mellitus using dual-gate Doppler

Gestational Diabetes Mellitus (GDM), as a common complication of pregnancy, has an increasing trend globally. GDM leads to maternal complications and fetal complications. Fetal cardiac diastolic dysfunction is strongly associated with GDM. This study aims to assess the ventricular diastolic function of fetuses exposed to GDM by looking into the diagnostic parameters using both conventional method and Dual-gate Doppler method (DD). And to investigate the potential of DD method in early detection of fetal cardiac diastolic dysfunction.56 women diagnosed with GDM and 55 non-GDM pregnant women were enrolled in their 24 to 30 weeks of gestation. Conventional method and DD method were applied to measure mitral and tricuspid inflow velocities E-waves, A-waves on pulsed-wave Doppler, and mitral and tricuspid annular velocities e'-waves, a'-waves on Tissue Doppler imaging. E/A, e'/a' and E/e' ratio was calculated. The difference between GDM and control groups was statistically tested and analysed using one-sample Kolmogorov-Smirnov test, Student t test, Mann-Whitney U test and Kruskal-Wallis test and Bland-Altman plot analysis.Intraobserver intraclass correlation coefficients of E/A, e'/a', and E/e' value of both mitral and tricuspid valve are all greater than 0.80, while interobserver intraclass correlation coefficients are between 0.71 and 0.88. Right (6.35 vs 6.79; P = .001) ventricular function showed significantly lower E/e' ratios in the GDM group compared with control fetuses by conventional method. Both left (6.16 vs 6.59; P = .036) and right (6.28 vs 6.75; P = .01) ventricular function showed significantly lower E/e' ratios in the GDM group compared with control fetuses by DD method.Exposure to high level of maternal blood glucose leads to impaired diastolic function in the fetuses. Fetal right ventricular function is a potential key point to study to enable an early detection for fetal diastolic dysfunction since the alteration and damage are more likely to happen in right ventricular. Measurement of E/e' ratio using DD method is considered as a promising method in fetal cardiac diastolic function assessment. Well or poorly control of the GDM does not have significant influence on the fetal diastolic function thus an early detection of GDM and GDM induced fetal cardiac dysfunction is necessary.

Gestational diabetes: Implications for fetal growth, intervention timing, and treatment options

Maternal gestational diabetes mellitus (GDM) is one of the most common medical complications of pregnancy, which can adversely affect the short- and long-term health of mothers and newborns. In recent years, several studies have revealed the early impact of maternal hyperglycemia on fetal growth trajectory and birth weight abnormalities in GDM-exposed pregnancies. However, an intense debate continues regarding the mode and optimal timing of diagnosis and treatment of this condition. The purpose of this review is to provide a brief overview of the understanding of GDM and its implications for fetal growth, addressing the modulatory role of medical nutrition therapy and available pharmacological antidiabetic agents (i.e. insulin, metformin, and glyburide), and to identify gaps in current knowledge toward which future research should be directed.

Strategies to improve neurodevelopmental outcomes in babies at risk of neonatal hypoglycaemia

Neonatal hypoglycaemia is associated with adverse development, particularly visual-motor and executive function impairment, in childhood. As neonatal hypoglycaemia is common and frequently asymptomatic in at-risk babies-ie, those born preterm, small or large for gestational age, or to mothers with diabetes, it is recommended that these babies are screened for hypoglycaemia in the first 1-2 days after birth with frequent blood glucose measurements. Neonatal hypoglycaemia can be prevented and treated with buccal dextrose gel, and it is also common to treat babies with hypoglycaemia with infant formula and intravenous dextrose. However, it is uncertain if screening, prophylaxis, or treatment improves long-term outcomes of babies at risk of neonatal hypoglycaemia. This narrative review assesses the latest evidence for screening, prophylaxis, and treatment of neonates at risk of hypoglycaemia to improve long-term neurodevelopmental outcomes.

Perinatal Nutritional and Metabolic Pathways: Early Origins of Chronic Lung Diseases

Lung development is not completed at birth, but expands beyond infancy, rendering the lung highly susceptible to injury. Exposure to various influences during a critical window of organ growth can interfere with the finely-tuned process of development and induce pathological processes with aberrant alveolarization and long-term structural and functional sequelae. This concept of developmental origins of chronic disease has been coined as perinatal programming. Some adverse perinatal factors, including prematurity along with respiratory support, are well-recognized to induce bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease that is characterized by arrest of alveolar and microvascular formation as well as lung matrix remodeling. While the pathogenesis of various experimental models focus on oxygen toxicity, mechanical ventilation and inflammation, the role of nutrition before and after birth remain poorly investigated. There is accumulating clinical and experimental evidence that intrauterine growth restriction (IUGR) as a consequence of limited nutritive supply due to placental insufficiency or maternal malnutrition is a major risk factor for BPD and impaired lung function later in life. In contrast, a surplus of nutrition with perinatal maternal obesity, accelerated postnatal weight gain and early childhood obesity is associated with wheezing and adverse clinical course of chronic lung diseases, such as asthma. While the link between perinatal nutrition and lung health has been described, the underlying mechanisms remain poorly understood. There are initial data showing that inflammatory and nutrient sensing processes are involved in programming of alveolarization, pulmonary angiogenesis, and composition of extracellular matrix. Here, we provide a comprehensive overview of the current knowledge regarding the impact of perinatal metabolism and nutrition on the lung and beyond the cardiopulmonary system as well as possible mechanisms determining the individual susceptibility to CLD early in life. We aim to emphasize the importance of unraveling the mechanisms of perinatal metabolic programming to develop novel preventive and therapeutic avenues.

Reduced glucose-stimulated insulin secretion following a 1-wk IGF-1 infusion in late gestation fetal sheep is due to an intrinsic islet defect

Insulin and insulin-like growth factor-1 (IGF-1) are fetal hormones critical to establishing normal fetal growth. Experimentally elevated IGF-1 concentrations during late gestation increase fetal weight but lower fetal plasma insulin concentrations. We therefore hypothesized that infusion of an IGF-1 analog for 1 wk into late gestation fetal sheep would attenuate fetal glucose-stimulated insulin secretion (GSIS) and insulin secretion in islets isolated from these fetuses. Late gestation fetal sheep received infusions with IGF-1 LR3 (IGF-1, n = 8), an analog of IGF-1 with low affinity for the IGF binding proteins and high affinity for the IGF-1 receptor, or vehicle control (CON, n = 9). Fetal GSIS was measured with a hyperglycemic clamp (IGF-1, n = 8; CON, n = 7). Fetal islets were isolated, and insulin secretion was assayed in static incubations (IGF-1, n = 8; CON, n = 7). Plasma insulin and glucose concentrations in IGF-1 fetuses were lower compared with CON (P = 0.0135 and P = 0.0012, respectively). During the GSIS study, IGF-1 fetuses had lower insulin secretion compared with CON (P = 0.0453). In vitro, glucose-stimulated insulin secretion remained lower in islets isolated from IGF-1 fetuses (P = 0.0447). In summary, IGF-1 LR3 infusion for 1 wk into fetal sheep lowers insulin concentrations and reduces fetal GSIS. Impaired insulin secretion persists in isolated fetal islets indicating an intrinsic islet defect in insulin release when exposed to IGF-1 LR3 infusion for 1 wk. We speculate this alteration in the insulin/IGF-1 axis contributes to the long-term reduction in β-cell function in neonates born with elevated IGF-1 concentrations following pregnancies complicated by diabetes or other conditions associated with fetal overgrowth.NEW & NOTEWORTHY After a 1-wk infusion of IGF-1 LR3, late gestation fetal sheep had lower plasma insulin and glucose concentrations, reduced fetal glucose-stimulated insulin secretion, and decreased fractional insulin secretion from isolated fetal islets without differences in pancreatic insulin content.

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.

Maternofetal inflammation induced for 2 wk in late gestation reduced birth weight and impaired neonatal growth and skeletal muscle glucose metabolism in lambs

Intrauterine stress impairs growth and metabolism in the fetus and offspring. We recently found that sustained maternofetal inflammation resulted in intrauterine growth-restricted (MI-IUGR) fetuses with asymmetric body composition, impaired muscle glucose metabolism, and β-cell dysfunction near term. These fetuses also exhibited heightened inflammatory tone, which we postulated was a fetal programming mechanism for the IUGR phenotype. Thus, the objective of this study was to determine whether poor growth and metabolism persisted in MI-IUGR lambs after birth. Polypay ewes received serial lipopolysaccharide or saline injections in the first 2 wk of the third trimester of pregnancy to produce MI-IUGR (n = 13) and control (n = 12) lambs, respectively. Lambs were catheterized at 25 d of age. β-Cell function was assessed at 29 d, hindlimb glucose metabolism at 30 d, and daily blood parameters from day 26 to 31. Glucose metabolism was also assessed in flexor digitorum superficialis (FDS) muscle isolated at necropsy on day 31. Asymmetric body composition persisted in MI-IUGR neonates, as these lambs were lighter (P < 0.05) than controls at birth and 31 d, but body and cannon bone lengths did not differ at either age. FDS muscles from MI-IUGR lambs were smaller (P < 0.05) and exhibited reduced (P < 0.05) glucose oxidation and Akt phosphorylation but similar glucose uptake compared with controls when incubated in basal or insulin-spiked media. Similarly, hindlimb glucose oxidation was reduced (P < 0.05) in MI-IUGR lambs under basal and hyperinsulinemic conditions, but hindlimb glucose utilization did not differ from controls. Circulating urea nitrogen and cholesterol were reduced (P < 0.05), and triglycerides, high-density lipoprotein cholesterol, and glucose-to-insulin ratios were increased (P < 0.05) in MI-IUGR lambs. Glucose and insulin concentrations did not differ between groups during basal or hyperglycemic conditions. Although circulating monocyte and granulocyte concentrations were greater (P < 0.05) in MI-IUGR lambs, plasma tumor necrosis factor α (TNFα) was reduced (P < 0.05). FDS muscle contained greater (P < 0.05) TNF receptor 1 (TNFR1) and IκBα protein content. These findings indicate that maternofetal inflammation in late pregnancy results in fetal programming that impairs growth capacity, muscle glucose oxidation, and lipid homeostasis in offspring. Inflammatory indicators measured in this study appear to reflect heightened cytokine sensitivity in muscle and compensatory systemic responses to it.

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.

Prolonged transitional neonatal hypoglycaemia: characterisation of a clinical syndrome

BACKGROUND

We performed a case-control study to characterise infants with "prolonged transitional hypoglycaemia".

METHODS

Cases were born ≥36 weeks' gestation; had ≥1 hypoglycaemic episode <72 h and ≥72 h; received ongoing treatment for hypoglycaemia ≥72 h; and were without congenital disorders or acute illness. Cases were compared to controls born ≥36 weeks' with brief transitional hypoglycaemia, resolving <72 h.

RESULTS

39/471 infants screened met case definition: 71.8% were male, 61.5% were small-for-gestational-age (SGA), and most were admitted <6 h. Compared to controls (N = 75), key risk factors for prolonged transitional hypoglycaemia were SGA (OR = 6.4, 95%CI 2.7-15.1), severe/recurrent hypoglycaemia <24 h (OR = 16.7, 95%CI 4.5-16.1), intravenous glucose bolus <24 h (OR = 26.6, 95%CI 9.4-75.1) and maximum glucose delivery rate <48 h of ≥8 mg/kg/min (OR = 25.5, 95%CI 7.7-84.1).

CONCLUSIONS

Infants with prolonged transitional hypoglycaemia are predominantly male, SGA and have early severe/recurrent hypoglycaemia requiring glucose boluses and high glucose delivery rates in the first 24-48 h.

Early-life exposure to alcohol and the risk of alcohol-induced liver disease in adulthood

Alcohol consumption remains prevalent among pregnant and nursing mothers despite the well-documented adverse effects this may have on the offspring. Moderate-to-high levels of alcohol consumption in pregnancy result in fetal alcohol syndrome (FAS) disorders, with brain defects being chief among the abnormalities. Recent findings indicate that while light-to-moderate levels may not cause FAS, it may contribute to epigenetic changes that make the offspring prone to adverse health outcomes including metabolic disorders and an increased propensity in the adolescent-onset of drinking alcohol. On the one hand, prenatal alcohol exposure (PAE) causes epigenetic changes that affect lipid and glucose transcript regulating genes resulting in metabolic abnormalities. On the other hand, it can program offspring for increased alcohol intake, enhance its palatability, and increase acceptance of alcohol's flavor through associative learning, making alcohol a plausible second hit for the development of alcohol-induced liver disease. Adolescent drinking results in alcohol dependence and abuse in adulthood. Adolescent drinking results in alcohol dependence and abuse in adulthood. Alterations on the opioid system, particularly, the mu-opioid system, has been implicated in the mechanism that induces increased alcohol consumption and acceptance. This review proposes a mechanism that links PAE to the development of alcoholism and eventually to alcoholic liver disease (ALD), which results from prolonged alcohol consumption. While PAE may not lead to ALD development in childhood, there are chances that it may lead to ALD in adulthood.

Chronic Fetal Leucine Infusion Does Not Potentiate Glucose-Stimulated Insulin Secretion or Affect Pancreatic Islet Development in Late-Gestation Growth-Restricted Fetal Sheep

BACKGROUND

Growth-restricted fetuses have attenuated glucose-stimulated insulin secretion (GSIS), smaller pancreatic islets, less pancreatic β-cells, and less pancreatic vascularization compared with normally growing fetuses. Infusion of leucine into normal late-gestation fetal sheep potentiates GSIS, as well as increases pancreatic islet size, the proportion of the pancreas and islet comprising β-cells, and pancreatic and islet vascularity. In addition, leucine stimulates hepatocyte growth factor (HGF ) mRNA expression in islet endothelial cells isolated from normal fetal sheep.

OBJECTIVE

We hypothesized that a 9-d leucine infusion would potentiate GSIS and increase pancreatic islet size, β-cells, and vascularity in intrauterine fetal growth restriction (IUGR) fetal sheep. We also hypothesized that leucine would stimulate HGF mRNA in islet endothelial cells isolated from IUGR fetal sheep.

METHODS

Late-gestation Columbia-Rambouillet IUGR fetal sheep (singleton or twin) underwent surgeries to place vascular sampling and infusion catheters. Fetuses were randomly allocated to receive a 9-d leucine infusion to achieve a 50-100% increase in leucine concentrations or a control saline infusion. GSIS was measured and pancreas tissue was processed for histologic analysis. Pancreatic islet endothelial cells were isolated from IUGR fetal sheep and incubated with supplemental leucine. Data were analyzed by mixed-models ANOVA; Student, Mann-Whitney, or a paired t test; or a test of equality of proportions.

RESULTS

Chronic leucine infusion in IUGR fetuses did not affect GSIS, islet size, the proportion of the pancreas comprising β-cells, or pancreatic or pancreatic islet vascularity. In isolated islet endothelial cells from IUGR fetuses, HGF mRNA expression was not affected by supplemental leucine.

CONCLUSIONS

IUGR fetal sheep islets are not responsive to a 9-d leucine infusion with respect to insulin secretion or any histologic features measured. This is in contrast to the response in normally growing fetuses. These results are important when considering nutritional strategies to prevent the adverse islet and β-cell consequences in IUGR fetuses.

[Analysis of metabolic pathways in intrauterine growth restriction]

Objective was to analyze metabolic pathways based on a study of the metabolomic profile of pregnant women with intrauterine growth restriction. The metabolic profile of pregnant women with fetal growth restriction has been analyzed using liquid chromatography-mass spectrometry. At the second stage pathways were identified using SMPDB and MetaboAnalyst databases to clarify the relationship between metabolites. Biological networks allow to determine the effect of proteins on the metabolic pathways involved in pathogenesis of IUGR and determine the epigenetic mechanisms of its formation.

Chronically elevated norepinephrine concentrations lower glucose uptake in fetal sheep

Fetal conditions associated with placental insufficiency and intrauterine growth restriction (IUGR) chronically elevate plasma norepinephrine (NE) concentrations. Our objective was to evaluate the effects of chronically elevated NE on insulin-stimulated glucose metabolism in normally grown, non-IUGR fetal sheep, which are independent of other IUGR-related reductions in nutrients and oxygen availability. After surgical placement of catheters, near-term fetuses received either a saline (control) or NE intravenous infusion with controlled euglycemia. In NE fetuses, plasma NE concentrations were 5.5-fold greater than controls, and fetal euglycemia was maintained with a maternal insulin infusion. Insulin secretion was blunted in NE fetuses during an intravenous glucose tolerance test. Weight-specific fluxes for glucose were measured during a euinsulinemic-euglycemic clamp (EEC) and a hyperinsulinemic-euglycemic clamp (HEC). Plasma glucose and insulin concentrations were not different between groups within each clamp, but insulin concentrations increased 10-fold between the EEC and the HEC. During the EEC, rates of glucose uptake (umbilical uptake + exogenous infusion) and glucose utilization were 47% and 35% lower (P < 0.05) in NE fetuses compared with controls. During the HEC, rates of glucose uptake were 28% lower (P < 0.05) in NE fetuses than controls. Glucose production was undetectable in either group, and glucose oxidation was unaffected by the NE infusion. These findings indicate that chronic exposure to high plasma NE concentrations lowers rates of net glucose uptake in the fetus without affecting glucose oxidation rates or initiating endogenous glucose production. Lower fetal glucose uptake was independent of insulin, which indicates insulin resistance as a consequence of chronically elevated NE.

Perinatal biomarkers implying 'Developmental Origins of Health and Disease' consequences in intrauterine growth restriction

The intrauterine-growth-restricted (IUGR) state, particularly the asymmetric one, has been associated with 'Developmental Origins of Health and Disease' (DOHaD) consequences later in life. Several environmental factors, acting during the phase of foetal developmental plasticity interact with genotypic variation, 'programme' tissue function and change the capacity of the organism to cope with its environment. They may be responsible for chronic illness risk in adulthood. Detection of possible future DOHaD consequences at a very early age, by applying relevant biomarkers, is of utmost importance. This review focuses on biomarkers possibly predicting consequences from bone, psychoneural system and lung. Although no concrete biomarker has been identified for bone disorders in adulthood, reduced brain-derived neurotrophic factor (BDNF) concentrations in cord blood and BDNF DNA methylation might predict schizophrenia and possibly depression, bipolar disorder and autism. High surfactant protein D (SP-D) concentrations in cord blood of IUGR foetuses/neonates could point to structural lung immaturity, resulting to asthma and chronic obstructive pulmonary disease in adult life.

Sex Differences Across the Lifespan: A Focus on Cardiometabolism

Women's health and sex differences research remain understudied. In 2016, to address the topic of sex differences, the Center for Women' s Health Research (CWHR) at the University of Colorado (cwhr@ucdenver.edu) held its inaugural National Conference, "Sex Differences Across the Lifespan: A Focus on Metabolism" and published a report summarizing the presentations. Two years later, in 2018, CWHR organized the 2nd National Conference. The research presentations and discussions from the 2018 conference also addressed sex differences across the lifespan with a focus on cardiometabolism and expanded the focus by including circadian physiology and effects of sleep on cardiometabolic health. Over 100 participants, including basic scientists, clinicians, policymakers, advocacy group leaders, and federal agency leadership participated. The meeting proceedings reveal that although exciting advances in the area of sex differences have taken place, significant questions and gaps remain about women's health and sex differences in critical areas of health. Identifying these gaps and the subsequent research that will result may lead to important breakthroughs.

Fetal ovine skeletal and cardiac muscle transcriptomics are differentially altered by increased maternal cortisol during gestation

We have previously found that in utero exposure to excess maternal cortisol (1 mg/kg/day) in late gestation increases the incidence of stillbirth during labor and produces fetal bradycardia at birth. In the interventricular septum, mitochondrial DNA (mt-DNA) was decreased, and transcriptomics and metabolomics were consistent with altered mitochondrial metabolism. The present study uses transcriptomics to model effects of increased maternal cortisol on fetal biceps femoris. Transcriptomic modeling revealed that pathways related to mitochondrial metabolism were downregulated, whereas pathways for regulation of reactive oxygen species and activation of the apoptotic cascade were upregulated. Mt-DNA and the protein levels of cytochrome C were significantly decreased in the biceps femoris. RT-PCR validation of the pathways confirmed a significant decrease in SLC2A4 mRNA levels and a significant increase in PDK4, TXNIP, ANGPTL4 mRNA levels, suggesting that insulin sensitivity of the biceps femoris muscle may be reduced in cortisol offspring. We also tested for changes in gene expression in diaphragm by rt-PCR. PDK4, TXNIP, and ANGPTL4 mRNA were also increased in the diaphragm, but SLC2A4, cytochrome C protein, and mt-DNA were unchanged. Comparison of the change in gene expression in biceps femoris to that in cardiac interventricular septum and left ventricle showed few common genes and little overlap in specific metabolic or signaling pathways, despite reduction in mt-DNA in both heart and biceps femoris. Our results suggest that glucocorticoid exposure alters expression of nuclear genes important to mitochondrial activity and oxidative stress in both cardiac and skeletal muscle tissues, but that these effects are tissue-specific.

Rates of myogenesis and myofiber numbers are reduced in late gestation IUGR fetal sheep

Intrauterine growth-restricted (IUGR) fetuses are born with reduced skeletal muscle mass. We hypothesized that reduced rates of myogenesis would contribute to fewer and smaller myofibers in IUGR fetal hindlimb muscle compared to the normally growing fetus. We tested this hypothesis in IUGR fetal sheep with progressive placental insufficiency produced by exposing pregnant ewes to elevated ambient temperatures from 38 to 116 days gestation (dGA; term = 147 dGA). Surgically catheterized control (CON, n = 8) and IUGR (n = 13) fetal sheep were injected with intravenous 5-bromo-2′-deoxyuridine (BrdU) prior to muscle collection (134 dGA). Rates of myogenesis, defined as the combined processes of myoblast proliferation, differentiation, and fusion into myofibers, were determined in biceps femoris (BF), tibialis anterior (TA), and flexor digitorum superficialis (FDS) muscles. Total myofiber number was determined for the entire cross-section of the FDS muscle. In IUGR fetuses, the number of BrdU+ myonuclei per myofiber cross-section was lower in BF, TA, and FDS (P < 0.05), total myonuclear number per myofiber cross-section was lower in BF and FDS (P < 0.05), and total myofiber number was lower in FDS (P < 0.005) compared to CON. mRNA expression levels of cyclins, cyclin-dependent protein kinases, and myogenic regulatory factors were lower (P < 0.05), and inhibitors of the cell cycle were higher (P < 0.05) in IUGR BF compared to CON. Markers of apoptosis were not different in IUGR BF muscle. These results show that in IUGR fetuses, reduced rates of myogenesis produce fewer numbers of myonuclei, which may limit hypertrophic myofiber growth. Fewer myofibers of smaller size contribute to smaller muscle mass in the IUGR fetus.

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.

Attenuation of sympathoadrenal function during delivery in the fetus of a diabetic mother

Objective: We compared the association between cord arterial catecholamine levels and fetal oxygenation in newborns of mothers with diabetes mellitus to those of nondiabetic pregnancies.Methods: Cord blood obtained at delivery in 25 term appropriate-for-gestational age newborns of women with diabetes and 27 nondiabetic controls were assayed for norepinephrine, epinephrine, insulin, glucose, and blood gases.Results: There was no statistical difference in parity, birth weight, gestational age, delivery mode, use of epidural analgesia, or frequency of low 1-min Apgar scores between the groups. The pO₂ and frequency of cord arterial pH < 7.20 were also similar. Diabetic pregnancies had somewhat higher fetal glucose and substantially higher insulin levels than controls. Regression analysis using cord arterial pH to reflect oxygenation revealed significant inverse relationships between cord artery pH and ln norepinephrine (Prob > F = .001) and ln epinephrine (Prob > F = .019) in controls. In newborns of women with diabetes, however, neither relationship was significant.Conclusion: The expected surge in catecholamines associated with diminished oxygenation was attenuated in fetuses of diabetic mothers. This suggests the possibility that fetal exposure to hyperglycemia or other metabolic derangements in pregnant diabetics might compromise the fetal ability to adapt to changes in oxygenation, and might thereby contribute to the risk of fetal death.

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Key points

Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity.

Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation.

Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing.

We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies.

IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.

Abstract

Placental insufficiency causes intrauterine growth restriction (IUGR) and disturbances in glucose homeostasis with associated β adrenergic receptor (ADRβ) desensitization. Our objectives were to measure insulin‐sensitive glucose metabolism in neonatal lambs with IUGR and to determine whether daily treatment with ADRβ2 agonist and ADRβ1/β3 antagonists for 1 month normalizes their glucose metabolism. Growth, glucose‐stimulated insulin secretion (GSIS) and glucose utilization rates (GURs) were measured in control lambs, IUGR lambs and IUGR lambs treated with adrenergic receptor modifiers: clenbuterol atenolol and SR59230A (IUGR‐AR). In IUGR lambs, islet insulin content and GSIS were less than in controls; however, insulin sensitivity and whole‐body GUR were not different from controls. Of importance, ADRβ2 stimulation with β1/β3 inhibition increases both insulin sensitivity and whole‐body glucose utilization in IUGR lambs. In IUGR and IUGR‐AR lambs, hindlimb GURs were greater but fractional glucose oxidation rates and ex vivo skeletal muscle glucose oxidation rates were lower than controls. Glucose transporter 4 (GLUT4) was lower in IUGR and IUGR‐AR skeletal muscle than in controls but GLUT1 was greater in IUGR‐AR. ADRβ2, insulin receptor, glycogen content and citrate synthase activity were similar among groups. In IUGR and IUGR‐AR lambs heart rates were greater, which was independent of cardiac ADRβ1 activation. We conclude that targeted ADRβ2 stimulation improved whole‐body insulin sensitivity but minimally affected defects in GSIS and skeletal muscle glucose oxidation. We show that risk factors for developing diabetes are independent of postnatal catch‐up growth in IUGR lambs as early as 1 month of age and are inherent to the islets and myocytes.

Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity.

Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation.

Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing.

We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies.

IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.

Postnatal Nutrient Repartitioning due to Adaptive Developmental Programming

Fetal stress induces developmental adaptations that result in intrauterine growth restriction (IUGR) and low birthweight. These adaptations reappropriate nutrients to the most essential tissues, which benefits fetal survival. The same adaptations are detrimental to growth efficiency and carcass value in livestock, however, because muscle is disproportionally targeted. IUGR adipocytes, liver tissues, and pancreatic β-cells also exhibit functional adaptations. Identifying mechanisms underlying adaptive changes is fundamental to improving outcomes and value in low birthweight livestock. The article outlines studies that have begun to identify stress-induced fetal adaptations affecting growth, metabolism, and differential nutrient utilization in IUGR-born animals.

Risk of hypertension following perinatal adversity: IUGR and prematurity

Consistent with the paradigm shifting observations of David Barker and colleagues that revealed a powerful relationship between decreased weight through 2 years of age and adult disease, intrauterine growth restriction (IUGR) and preterm birth are independent risk factors for the development of subsequent hypertension. Animal models have been indispensable in defining the mechanisms responsible for these associations and the potential targets for therapeutic intervention. Among the modifiable risk factors, micronutrient deficiency, physical immobility, exaggerated stress hormone exposure and deficient trophic hormone production are leading candidates for targeted therapies. With the strong inverse relationship seen between gestational age at delivery and the risk of hypertension in adulthood trumping all other major cardiovascular risk factors, improvements in neonatal care are required. Unfortunately, therapeutic breakthroughs have not kept pace with rapidly improving perinatal survival, and groundbreaking bench-to-bedside studies are urgently needed to mitigate and ultimately prevent the tsunami of prematurity-related adult cardiovascular disease that may be on the horizon. This review highlights our current understanding of the developmental origins of hypertension and draws attention to the importance of increasing the availability of lactation consultants, nutritionists, pharmacists and physical therapists as critical allies in the battle that IUGR or premature infants are waging not just for survival but also for their future cardiometabolic health.

Hypoglycemia in unmonitored full-term newborns-a surveillance study

Background and objectives

Hypoglycemia monitoring is not recommended for most full-term newborns. We wished to determine the incidence, presentation and case characteristics of hypoglycemia in low-risk newborns.

Methods

With the assistance of the Canadian Paediatric Surveillance Program, we conducted a national study of severe hypoglycemia in apparently low-risk full-term newborns. Paediatricians who reported a case were sent a detailed questionnaire and the data were analyzed.

Results

All 93 confirmed cases were singletons, 56% were first-borns and 65% were male. An 8% rate of First Nations cases was twofold the population rate. Maternal hypertension rate was 23%, fourfold the general pregnancy rate. Maternal obesity was double the general pregnancy rate at 23%. Concerning signs or feeding issues were noted in 98% at the time of diagnosis. Median time to diagnosis was 4.1 hours. Mean blood glucose at intravenous (IV) start was 1.4 ± 0.5 hours (SD). Seventy-eight per cent had at least one of four potential stress indicators and were more likely to have early diagnosis (P=0.03). Major signs were present in 20%. Those cases presented later and had lower glucose levels (median=0.8 mmol/L versus 1.6 mmol/L, [P<0.001). Twenty-five per cent of cases had birth weight less than the 10th centile. Neurodevelopmental concern was reported in 20%. Of the 13 cases which had brain magnetic resonance imaging, 11 were abnormal.

Conclusion

Hypoglycemia in unmonitored newborns is uncommon but is associated with significant morbidity. We provide a range of clues to help identify these newborns soon after birth. Widespread adoption of norm-based standards to identify small-for-gestational age infants is supported.

Postnatal undernutrition alters adult female mouse cardiac structure and function leading to limited exercise capacity

KEY POINTS

Impaired growth during fetal life can reprogramme heart development and increase the risk for long-term cardiovascular dysfunction. It is uncertain if the developmental window during which the heart is vulnerable to reprogramming as a result of inadequate nutrition extends into the postnatal period. We found that adult female mice that had been undernourished only from birth to 3 weeks of age had disproportionately smaller hearts compared to males, with thinner ventricle walls and more mononucleated cardiomyocytes. In females, but not males, cardiac diastolic function, and heart rate responsiveness to adrenergic stimulation were limited and maximal exercise capacity was compromised. These data suggest that the developmental window during which the heart is vulnerable to reprogramming by inadequacies in nutrient intake may extend into postnatal life and such individuals could be at increased risk for a cardiac event as a result of strenuous exercise.

ABSTRACT

Adults who experienced undernutrition during critical windows of development are at increased risk for cardiovascular disease. The contribution of cardiac function to this increased disease risk is uncertain. We evaluated the effect of a short episode of postnatal undernutrition on cardiovascular function in mice at the whole animal, organ, and cellular levels. Pups born to control mouse dams were suckled from birth to postnatal day (PN) 21 on dams fed either a control (20% protein) or a low protein (8% protein) isocaloric diet. After PN21 offspring were fed the same control diet until adulthood. At PN70 V ̇ O 2 , max was measured by treadmill test. At PN80 cardiac function was evaluated by echocardiography and Doppler analysis at rest and following β-adrenergic stimulation. Isolated cardiomyocyte nucleation and Ca²⁺ transients (with and without β-adrenergic stimulation) were measured at PN90. Female mice that were undernourished and then refed (PUN), unlike male mice, had disproportionately smaller hearts and their exercise capacity, cardiac diastolic function, and heart rate responsiveness to adrenergic stimulation were limited. A reduced left ventricular end diastolic volume, impaired early filling, and decreased stored energy at the beginning of diastole contributed to these impairments. Female PUN mice had more mononucleated cardiomyocytes; under resting conditions binucleated cells had a functional profile suggestive of increased basal adrenergic activation. Thus, a brief episode of early postnatal undernutrition in the mouse can produce persistent changes to cardiac structure and function that limit exercise/functional capacity and thereby increase the risk for the development of a wide variety of cardiovascular morbidities.

Prolonged amino acid infusion into intrauterine growth-restricted fetal sheep increases leucine oxidation rates

Overcoming impaired growth in an intrauterine growth-restricted (IUGR) fetus has potential to improve neonatal morbidity, long-term growth, and metabolic health outcomes. The extent to which fetal anabolic capacity persists as the IUGR condition progresses is not known. We subjected fetal sheep to chronic placental insufficiency and tested whether prolonged amino acid infusion would increase protein accretion in these IUGR fetuses. IUGR fetal sheep were infused for 10 days with either mixed amino acids providing ~2 g·kg^-1·day^-1 (IUGR-AA) or saline (IUGR-Sal) during late gestation. At the end of the infusion, fetal plasma leucine, isoleucine, lysine, methionine, and arginine concentrations were higher in the IUGR-AA than IUGR-Sal group ( P < 0.05). Fetal plasma glucose, oxygen, insulin, IGF-1, cortisol, and norepinephrine concentrations were similar between IUGR groups, but glucagon concentrations were fourfold higher in the IUGR-AA group ( P < 0.05). Net umbilical amino acid uptake rate did not differ between IUGR groups; thus the total amino acid delivery rate (net umbilical amino acid uptake + infusion rate) was higher in the IUGR-AA than IUGR-Sal group (30 ± 4 vs. 19 ± 1 μmol·kg^-1·min^-1, P < 0.05). Net umbilical glucose, lactate, and oxygen uptake rates were similar between IUGR groups. Fetal leucine oxidation rate, measured using a leucine tracer, was higher in the IUGR-AA than IUGR-Sal group (2.5 ± 0.3 vs. 1.7 ± 0.3 μmol·kg^-1·min^-1, P < 0.05). Fetal protein accretion rate was not statistically different between the IUGR groups (1.6 ± 0.4 and 0.8 ± 0.3 μmol·kg^-1·min^-1 in IUGR-AA and IUGR-Sal, respectively) due to variability in response to amino acids. Prolonged amino acid infusion into IUGR fetal sheep increased leucine oxidation rates with variable anabolic response.

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.

A 1 week IGF-1 infusion decreases arterial insulin concentrations but increases pancreatic insulin content and islet vascularity in fetal sheep

Fetal insulin is critical for regulation of growth. Insulin concentrations are partly determined by the amount of β-cells present and their insulin content. Insulin-like growth factor-1 (IGF-1) is a fetal anabolic growth factor which also impacts β-cell mass in models of β-cell injury and diabetes. The extent to which circulating concentrations of IGF-1 impact fetal β-cell mass and pancreatic insulin content is unknown. We hypothesized that an infusion of an IGF-1 analog for 1 week into the late gestation fetal sheep circulation would increase β-cell mass, pancreatic islet size, and pancreatic insulin content. After the 1-week infusion, pancreatic insulin concentrations were 80% higher than control fetuses (P < 0.05), but there were no differences in β-cell area, β-cell mass, or pancreatic vascularity. However, pancreatic islet vascularity was 15% higher in IGF-1 fetuses and pancreatic VEGFA, HGF, IGF1, and IGF2 mRNA expressions were 70-90% higher in IGF-1 fetuses compared to control fetuses (P < 0.05). Plasma oxygen, glucose, and insulin concentrations were 25%, 22%, and 84% lower in IGF-1 fetuses, respectively (P < 0.05). The previously described role for IGF-1 as a β-cell growth factor may be more relevant for local paracrine signaling in the pancreas compared to circulating endocrine signaling.

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.