Periconceptional undernutrition of ewes impairs glucose tolerance in their adult offspring

Birth weight, growth indices, and seminal parameters in male offspring are resilient features to maternal pre-conceptional dietary manipulation in sheep

Gestational diet manipulation can lead to inadequate fetal nutrient supply resulting in low birth weight, limited postnatal growth, and consequently, reduced reproductive performance in the progeny. However, effects of short-term maternal pre-conceptional dietary manipulation on postnatal growth and reproductive parameters of male offspring in large animals remains unexplored. To determine these consequences, female crossbred (Polypay x Dorset) sheep were allocated to three groups (n = 33/group) of dietary manipulation for 21 days prior to mating under the following conditions: (1) control at 100 % of maintenance energy requirements (40 Kcal of metabolizable energy/kg body weight [BW]), (2) undernutrition (UN) at 50 % of Control intake, and (3) overnutrition (ON) at 200 % of maintenance energy. Singleton ram lambs (UN:9; C:12; ON:6) were monitored from birth until 8 months of age, including birth weight, weekly weights, weight gain, body mass index (BMI), and circulating testosterone. After weaning, monthly scrotal circumference and subcutaneous fat depth were measured. Semen morphology and motility were evaluated at 7 and 8 months of age. Birth weight, weight gain, and BMI at birth and weaning were not significantly different among nutritional treatments. None of the pre-conceptional diets affected body weight change from weaning until 36 weeks of age, BMI, fat depth, or scrotal circumference across the experiment. A sustained rise in plasma testosterone concentrations was detected when ram lambs were, on average, 82 days old and 37 kg. Both testosterone concentrations and scrotal circumference were positively correlated to body weight regardless of treatment group. In addition, seminal parameters did not differ among treatments, but a transient increase in plasma testosterone at 18 weeks of age was observed in ON ram lambs compared to control rams. In conclusion, birth weight, growth indices, and seminal parameters in singleton rams are resilient features in the progeny upon maternal pre-conceptional dietary manipulation in sheep.

Effect of glucose infusion on glucose and insulin metabolism in early- and mid-lactation ewes and goats fed diets differing in starch and highly digestible fiber concentration

This study aimed to test possible metabolic differences between ewes and goats in response to an intravenous glucose infusion. Thirty-six animals, 18 mature Sarda dairy ewes and 18 mature Saanen goats (from 15 to 150 ± 11 d in milk [DIM], mean ± SD; body weight: 49.8 ± 6.8 kg for ewes, 60.6 ± 7.3 kg for goats) were compared simultaneously. In early lactation, both species received the same high-starch diet (HS: 20.4% starch, 35.4% neutral detergent fiber [NDF], on dry matter [DM] basis), whereas from 92 ± 11 DIM both species were randomly allocated to 2 dietary treatments: HS (20.0% starch, 36.7% NDF, on DM basis) and low-starch (LS: 7.8% starch, 48.8% NDF, on DM basis) diets. At 50 and 150 ± 11 DIM, ewes and goats were challenged with an intravenous glucose tolerance test and peripheral concentrations of glucose and insulin were determined 15 min before and 5, 10, 15, 30, 45, 90, and 180 min after glucose infusion. In early lactation, baseline plasma glucose and insulin concentrations tended to be higher in ewes than in goats (glucose: 55.8 vs. 42.9 ± 7.3 mg/dL; insulin: 0.13 vs. 0.05 ± 0.04 µg/L). After glucose infusion, glucose and insulin concentrations were higher in ewes than in goats (278.6 vs. 247.6 ± 13.1 mg/dL; 0.82 vs. 0.46 ± 0.12 µg/L). In mid-lactation, the dietary treatment (HS vs. LS) did not affect glucose and insulin metabolism. Baseline plasma glucose was numerically highest in ewes, while baseline insulin was higher in ewes than in goats (0.39 vs. 0.12 ± 0.099 µg/L). After glucose infusion, glucose concentration did not differ between ewes and goats, while insulin concentration was highest in ewes. Compared with goats, ewes showed in both periods a higher peak insulin, insulin increment, linear insulin area under the curve, insulin resistance index, and lower insulin sensitivity indices. In conclusion, despite the limitations associated with the use of intravenous glucose tolerance test to assess glucose regulation mechanisms, this study indicated large species differences in both early and mid-lactation and a more evident anabolic status in the ewes compared with the goats.

Developmental Programming, Evolution, and Animal Welfare: A Case for Evolutionary Veterinary Science

The conditions animals experience during the early developmental stages of their lives can have critical ongoing effects on their future health, welfare, and proper development. In this paper we draw on evolutionary theory to improve our understanding of the processes of developmental programming, particularly Predictive Adaptive Responses (PAR) that serve to match offspring phenotype with predicted future environmental conditions. When these predictions fail, a mismatch occurs between offspring phenotype and the environment, which can have long-lasting health and welfare effects. Examples include metabolic diseases resulting from maternal nutrition and behavioral changes from maternal stress. An understanding of these processes and their evolutionary origins will help in identifying and providing appropriate developmental conditions to optimize offspring welfare. This serves as an example of the benefits of using evolutionary thinking within veterinary science and we suggest that in the same way that evolutionary medicine has helped our understanding of human health, the implementation of evolutionary veterinary science (EvoVetSci) could be a useful way forward for research in animal health and welfare.

Short Communication: Maternal undernutrition during peri-conceptional period affects whole genome ovine muscle methylation in adult offspring

Experimental and epidemiological studies suggest that maternal nutritional status during early pregnancy, including the period around the time of conception, may induce long-lasting epigenetic changes in the offspring. However, this remains largely unexplored in livestock. Therefore, the objective of this study was to evaluate if modification of the maternal diet of sheep (CTR: control; UND: 50% undernutrition) during the peri-conceptional period (42 days in total: -14/+28 from mating), would impact CpG methylation in muscle tissue (Longissimus dorsi) of adult offspring (11.5 months old). Reduced Representation Bisulfite Sequencing (RRBS), identified 262 (Edge-R, FDR<0.05) and 686 (Logistic Regression, FDR <0.001) differentially methylated regions (DMRs) between the UND and CTR groups. Gene ontology (GO) analysis identified genes related to development, functions of the muscular system and steroid hormone receptor activity within the DMRs. The data reported here show that nutritional stress during early pregnancy leads to epigenetic modifications in the muscle of the resulting offspring, with possible implications for cardiac dysfunction, muscle physiology and meat production.

Gestation Food Restriction and Refeeding Compensate Maternal Energy Status and Alleviate Metabolic Consequences in Juvenile Offspring in a Rabbit Model

Nutritional status during gestation can influence mother and offspring metabolism. Undernutrition in pregnancy affects women in both western and developing countries, and it is associated with a high prevalence of chronic diseases in later life. The present work was conducted in the rabbit model, as a longitudinal study, to examine the effect of food restriction during early and mid-gestation, and re-feeding ad libitum until the end of pregnancy on metabolic status and body reserves of mother and, its association with development and metabolism of fetuses and female offspring to the juvenile stage. Little changes in live body weight (LBW), compensatory feed intake, similar body reserves, and metabolism were observed in dams. Placenta biometry and efficiency were slightly affected, but fetal BW and phenotype were not modified. However, hyperinsulinemia, insulin resistance, and hypertriglyceridemia were demonstrated in pre-term fetuses. In the juvenile period, these changes were not evidenced, and a similar pattern of growth and serum metabolic parameters in offspring of food-restricted mothers were found, except in serum aminotransferases levels, which increased. These were associated with higher liver fibrosis. Maternal food restriction in the early and mid-pregnancy followed by re-feeding in our rabbit model established a compensatory energy status in dams and alleviated potential long-term consequences in growth and metabolism in the offspring, even if fetal metabolism was altered.

Effect of maternal nutrient restriction on expression of glucose transporters (SLC2A4 and SLC2A1) and insulin signaling in skeletal muscle of SGA and Non-SGA sheep fetuses

Maternal nutrient restriction (NR) causes small for gestational age (SGA) offspring, which are at higher risk for accelerated postnatal growth and developing insulin resistance in adulthood. Skeletal muscle is essential for whole-body glucose metabolism, as 80% of insulin-mediated glucose uptake occurs in this tissue. Maternal NR can alter fetal skeletal muscle mass, expression of glucose transporters, insulin signaling, and myofiber type composition. It also leads to accumulation of intramuscular triglycerides (IMTG), which correlates to insulin resistance. Using a 50% NR treatment from gestational day (GD) 35 to GD 135 in sheep, we routinely observe a spectral phenotype of fetal weights within the NR group. Thus, we classified those fetuses into NR(Non-SGA; n = 11) and NR(SGA; n = 11). The control group (n = 12) received 100% of nutrient requirements throughout pregnancy. At GD 135, fetal plasma and gastrocnemius and soleus muscles were collected. In fetal plasma, total insulin was lower in NR(SGA) fetuses compared NR(Non-SGA) and control fetuses (P < 0.01), whereas total IGF-1 was lower in NR(SGA) fetuses compared with control fetuses (P < 0.05). Within gastrocnemius, protein expression of insulin receptor (INSRB; P < 0.05) and the glucose transporters, solute carrier family 2 member 1 and solute carrier family 2 member 4, was higher (P < 0.05) in NR(SGA) fetuses compared with NR(Non-SGA) fetuses; IGF-1 receptor protein was increased (P < 0.01) in NR(SGA) fetuses compared with control fetuses, and a lower (P < 0.01) proportion of type I myofibers (insulin sensitive and oxidative) was observed in SGA fetuses. For gastrocnemius muscle, the expression of lipoprotein lipase (LPL) messenger RNA (mRNA) was upregulated (P < 0.05) in both NR(SGA) and NR(Non-SGA) fetuses compared with control fetuses, whereas carnitine palmitoyltransferase 1B (CPT1B) mRNA was higher (P < 0.05) in NR(Non-SGA) fetuses compared with control fetuses, but there were no differences (P > 0.05) for protein levels of LPL or CPT1B. Within soleus, there were no differences (P > 0.05) for any characteristic except for the proportion of type I myofibers, which was lower (P < 0.05) in NR(SGA) fetuses compared with control fetuses. Accumulation of IMTG did not differ (P > 0.05) in gastrocnemius or soleus muscles. Collectively, the results indicate molecular differences between SGA and Non-SGA fetuses for most characteristics, suggesting that maternal NR induces a spectral phenotype for the metabolic programming of those fetuses.

Effects of maternal periconceptional undernutrition in sheep on offspring glucose-insulin axis function into adulthood

Maternal periconceptional undernutrition (PCUN) affected fetal pancreatic maturation in late gestation lambs and impaired glucose tolerance in 10-month-old sheep. To examine the importance of the timing of maternal undernutrition around conception, a further cohort was born to PCUN ewes [undernourished for 61 d before conception (PreC), 30 d after conception (PostC), or 61 d before until 30 d after conception (PrePostC)], or normally fed ewes (Control) (n = 15-20/group). We compared glucose tolerance, insulin secretion, and sensitivity at 36 months of age. We also examined protein expression of insulin signalling proteins in muscle from these animals and in muscle from a fetal cohort (132 d of gestation; n = 7-10/group). Adult PostC and PrePostC sheep had higher glucose area under the curve than Controls (P = 0.07 and P = 0.02, respectively), whereas PreC sheep were similar to Controls (P = 0.97). PostC and PrePostC had reduced first-phase insulin secretion compared with Control (P = 0.03 and P = 0.02, respectively). PreC was similar to Control (P = 0.12). Skeletal muscle SLC2A4 protein expression in PostC and PrePostC was increased 19%-58% in fetuses (P = 0.004), but decreased 39%-43% in adult sheep (P = 0.003) compared with Controls. Consistent with this, protein kinase C zeta (PKCζ) protein expression tended to be increased in fetal (P = 0.09) and reduced in adult (P = 0.07) offspring of all PCUN ewes compared with Controls. Maternal PCUN alters several aspects of offspring glucose homeostasis into adulthood. These findings suggest that maternal periconceptional nutrition has a lasting impact on metabolic homeostasis of the offspring.

Prenatal exposure to different diets influences programming of glucose and insulin metabolism in dairy ewes

Nutrition in fetal and postnatal life can influence the development of several biological systems, with permanent effects in adult life. The aim of this work was to investigate in dairy sheep whether diets rich in starch or fiber during intrauterine life (75 d before lambing) and postnatal life (from weaning to first pregnancy; growth phase) program glucose and insulin metabolism in the female offspring during their first pregnancy. Starting from intrauterine life, 20 nulliparous Sarda ewes were exposed to 4 dietary regimens (n = 5 per group) based on different dietary carbohydrates during their intrauterine life and their subsequent growth phase: (1) the fiber (FI) diet during both intrauterine and growth life, (2) the starch (ST) diet during both intrauterine and growth life, (3) the FI diet in intrauterine life followed by the ST diet in the growth phase, and (4) the ST diet in intrauterine life followed by the FI diet in the growth phase. After the end of the growth phase, all growing ewes were fed the same diet and naturally mated. When ewes were pregnant, on average at 124 ± 2 d of gestation they were challenged with an intravenous glucose tolerance test, and peripheral concentrations of glucose and insulin were determined. Basal insulin concentrations were higher in ewes exposed to the ST diet (0.97 μg/L) than in ewes exposed to the FI diet (0.52 μg/L) in intrauterine life. After glucose infusion, glucose and insulin concentrations were not affected by intrauterine diet. Insulin resistance, determined by the homeostasis model assessment, was affected by the intrauterine × growth phases interaction. Insulin sensitivity, assessed by the quantitative insulin check index, was lower in ewes exposed to the ST diet than in those exposed to the FI diet in intrauterine life (ST = 0.28; FI = 0.30). Diet in growth life had no effect on glucose and insulin metabolism. In conclusion, starchy diets offered during intrauterine life but not during postnatal life increased basal insulin level and lowered insulin sensitivity during the first pregnancy. Nutritional strategies of metabolic programming should consider that exposure to starchy diets in late fetal life might favor the programming of dietary nutrient partitioning toward organs with high requirements, such as the gravid uterus or the mammary gland.

Developmental programming of insulin resistance: are androgens the culprits?

Insulin resistance is a common feature of many metabolic disorders. The dramatic rise in the incidence of insulin resistance over the past decade has enhanced focus on its developmental origins. Since various developmental insults ranging from maternal disease, stress, over/undernutrition, and exposure to environmental chemicals can all program the development of insulin resistance, common mechanisms may be involved. This review discusses the possibility that increases in maternal androgens associated with these various insults are key mediators in programming insulin resistance. Additionally, the intermediaries through which androgens misprogram tissue insulin sensitivity, such as changes in inflammatory, oxidative, and lipotoxic states, epigenetic, gut microbiome and insulin, as well as data gaps to be filled are also discussed.

Effects of preterm birth induced with or without exogenous glucocorticoids on the ovine glucose-insulin axis

Antenatal exogenous glucocorticoids (ANG) are standard management for women at risk of preterm birth but are reputed to impair glucose tolerance in preterm offspring. We compared lambs born preterm (137 days gestation) following labour induced with exogenous glucocorticoids (G-Prem, glucocorticoid-induced preterm group), or with a progesterone synthesis inhibitor (NG-Prem, non-glucocorticoid-induced preterm group), with term-born lambs (Term; 149 days). We assessed glucose tolerance, insulin secretion and sensitivity at 4 and 10 months n = 11-14/group) and pancreatic and hepatic gene and protein expression at 4 weeks post-term (4 weeks; n = 6/group) and 12 months (12 months; n = 12-13/group). NG-Prem had higher plasma glucose concentrations than G-Prem, but not Term, at 4 months (Mean[SEM] mM: NG-Prem = 4.1[0.1]; G-Prem = 3.4[0.1]; Term = 3.7[0.1]; p = 0.003) and 10 months (NG-Prem = 3.9[0.1]; G-Prem = 3.5[0.1]; Term = 3.7[0.1]; p = 0.01). Insulin sensitivity decreased from 4 to 10 months, in NG-Prem but not in Term (Mean[SEM] µmol·ml-1·kg-1·min-1·ng-1, 4 vs. 10 months: NG-Prem = 18.7[2.5] vs. 9.5[1.5], p < 0.01; Term: 12.1[2.8] vs. 10.4[1.5], p = 0.44). At 12 months, β-cell mass in NG-Prem was reduced by 30% vs. G-Prem (p < 0.01) and 75% vs. Term (p < 0.01) and was accompanied by an increased β-cell apoptosis: proliferation ratio at 12 months. At 12 months, pancreatic glucokinase, igf2 and insulin mRNA levels were reduced 21%-71% in NG-Prem vs. G-Prem and 42%-80% vs. Term. Hepatic glut2 mRNA levels in NG-Prem were 250% of those in G-Prem and Term. Thus, induction of preterm birth without exogenous glucocorticoids more adversely affected pancreas and liver than induction with exogenous glucocorticoids. These findings do not support that ANG lead to long-term adverse metabolic effects, but support an effect of preterm birth itself.

Epigenetic regulation of POMC; implications for nutritional programming, obesity and metabolic disease

Proopiomelanocortin (POMC) is a key mediator of satiety. Epigenetic marks such as DNA methylation may modulate POMC expression and provide a biological link between early life exposures and later phenotype. Animal studies suggest epigenetic marks at POMC are influenced by maternal energy excess and restriction, prenatal stress and Triclosan exposure. Postnatal factors including energy excess, folate, vitamin A, conjugated linoleic acid and leptin may also affect POMC methylation. Recent human studies suggest POMC DNA methylation is influenced by maternal nutrition in early pregnancy and associated with childhood and adult obesity. Studies in children propose a link between POMC DNA methylation and elevated lipids and insulin, independent of body habitus. This review brings together evidence from animal and human studies and suggests that POMC is sensitive to nutritional programming and is associated with a wide range of weight-related and metabolic outcomes.

Redox disequilibrium vis-a-vis inflammatory cascade mediation of lymphocyte dysfunction, apoptosis, cytokine expression and activation of NF-κB in subclinical diabetic goats

Molecular basis of diabetes induced oxidative stress and immune dysfunction have not been reported in animal science. The present study envisages same in subclinical diabetic (SCD) goats (6) diagnosed on biochemical and histopathological basis in reference to non-diabetic (NSCD) goats (6). Oxidative stress indices were analyzed by manual methods. The concentration of reduced glutathione (GSH) and the activity of superoxide dismutase (SOD) was significantly lower in SCD goats than in NSCD goats; whereas the lipid peroxide (LPO) was higher in SCD. Catalase (CAT) activity was nonsignificantly lower in SCD goats than NSCD goats. SCD goats had significantly lower lymphocyte stimulation index by cell culture and higher apoptotic cell percentage by flow cytometry than NSCD goats. The concentration of the transforming growth factor beta 1 (TGF-β1) by ELISA was significantly higher in SCD goats than in NSCD. The expressions of tumour necrosis factor alpha (TNF-α) and interleukin 8 (IL 8) by RT-PCR were higher in SCD goats than in non-diabetic ones. Expression of transcription factor (NF-κB) by western blot was significantly higher in SCD goats than NSCD goats. Fall of antioxidants (GSH, SOD, catalase) and rise of oxidants (LPO) suggest oxidative stress. Decrease of immune cell function, rise of inflammatory cytokines and transcription factors suggest immune dysfunction. Hence it was concluded that SCD induced oxidative stress and impairment of immunity in goats, which was most likely associated with depletion of antioxidants, increase of oxidants and inflammatory mediators. NF-κB, most likely have played a mediatory role in coordinating these intricate responses.

Early-Stage Translational Research in Perinatal Medicine

BACKGROUND

Pre-clinical research, which encompasses studies in animals and in the laboratory, has made significant contributions to the improvement of neonatal outcomes.

METHODS

Here, we describe examples of how pre-clinical research can be the starting point on the journey to the development of new interventions to improve neonatal care and outcomes and discuss recent progress in ensuring methodological and ethical rigour in pre-clinical research involving animal models.

RESULTS

Studies in pregnant sheep led to the serendipitous discovery that preterm lambs born after exogenous corticosteroid exposure were able to aerate their lungs. Subsequent clinical trials confirmed that antenatal corticosteroids given to women at risk of preterm delivery substantially reduce mortality and morbidity in babies born preterm. Animal research also contributed to discoveries in the mechanism of brain injury after hypoxic ischaemic encephalopathy, leading to the use of therapeutic hypothermia as an effective treatment. However, animals are sentient creatures and there are significant ethical concerns with their use in studies to benefit human health. Mandated institutional animal research ethics committees ensure adherence to ethical requirements. To provide high-quality data which can be translated into clinical research, pre-clinical research needs to follow rigorous standards of study design and reporting. The ARRIVE guidelines provide guidance for pre-clinical research similar to that provided in the CONSORT guidelines for clinical trials and are gaining acceptance among researchers and journal editors.

CONCLUSION

Improved scientific rigour in the use of animal research will increase the likelihood that pre-clinical research will continue to translate into improved neonatal outcomes.

Impact of prematurity for pancreatic islet and beta-cell development

As increasing numbers of babies born preterm survive into adulthood, it is becoming clear that, in addition to the well-described risks of neurodevelopmental sequelae, there also are increased risks for non-communicable diseases, including diabetes. Epidemiological studies indicate that risks are increased even for birth at late preterm and early term gestations and for both type 1 and type 2 diabetes. Thus, factors related to preterm birth likely affect development of the fetal and neonatal beta-cell in addition to effects on peripheral insulin sensitivity. These factors could operate prior to preterm birth and be related to the underlying cause of preterm birth, to the event of being born preterm itself, to the postnatal care of the preterm neonate or to a combination of these exposures. Experimental evidence indicates that factors may be operating during all these critical periods to contribute to altered development of beta-cell mass in those born preterm. Greater understanding of how these factors impact upon development of the pancreas may lead to interventions or management approaches that mitigate the increased risk of later diabetes.

Epigenetic changes of hepatic glucocorticoid receptor in sheep male offspring undernourished in utero

The aim of this study was to characterise the effects of maternal undernutrition during gestation on hepatic gluconeogenic enzyme gene expression and to determine whether such effects are mediated through epigenetic changes in the glucocorticoid receptor (GR). Pregnant ewes were fed a 50% nutrient-restricted diet from Day 0 to 30 (R1) or from Day 31 to 100 of gestation (R2) or a 100% diet throughout gestation (Control). After parturition lambs were fed to appetite. At 10 months of age offspring were euthanised and livers were removed. Maternal undernutrition did not affect offspring bodyweight at birth or at 10 months of age. However, liver weight of males of the R2 group was lower (P<0.05) in relation to other groups. A significant (P<0.05) hypomethylation of the hepatic GR promoter was revealed in males of the R2 group and a tendency towards the same in the R1 group, along with increased (P<0.001) GR gene expression in both restricted groups. A significant increase (P<0.05) in hepatic phosphoenolpyruvate carboxykinase (PEPCK) gene expression was found in male lambs of both undernourished groups, accompanied by increased (P<0.01) protein levels, while no differences were detected for glucose-6-phosphatase (G6Pase) mRNA abundance and protein levels. In female lambs, no differences between groups were observed for any parameter studied. These data represent potential mechanisms by which insults in early life may lead to persistent physiological changes in the offspring.

Impacts of prenatal nutrition on animal production and performance: a focus on growth and metabolic and endocrine function in sheep

The concept of foetal programming (FP) originated from human epidemiological studies, where foetal life nutrition was linked to health and disease status later in life. Since the proposal of this phenomenon, it has been evaluated in various animal models to gain further insights into the mechanisms underlying the foetal origins of health and disease in humans. In FP research, the sheep has been quite extensively used as a model for humans. In this paper we will review findings mainly from our Copenhagen sheep model, on the implications of late gestation malnutrition for growth, development, and metabolic and endocrine functions later in life, and discuss how these implications may depend on the diet fed to the animal in early postnatal life. Our results have indicated that negative implications of foetal malnutrition, both as a result of overnutrition and, particularly, late gestation undernutrition, can impair a wide range of endocrine functions regulating growth and presumably also reproductive traits. These implications are not readily observable early in postnatal life, but are increasingly manifested as the animal approaches adulthood. No intervention or cure is known that can reverse this programming in postnatal life. Our findings suggest that close to normal growth and slaughter results can be obtained at least until puberty in animals which have undergone adverse programming in foetal life, but manifestation of programming effects becomes increasingly evident in adult animals. Due to the risk of transfer of the adverse programming effects to future generations, it is therefore recommended that animals that are suspected to have undergone adverse FP are not used for reproduction. Unfortunately, no reliable biomarkers have as yet been identified that allow accurate identification of adversely programmed offspring at birth, except for very low or high birth weights, and, in pigs, characteristic changes in head shape (dolphin head). Future efforts should be therefore dedicated to identify reliable biomarkers and evaluate their effectiveness for alleviation/reversal of the adverse programming in postnatal life. Our sheep studies have shown that the adverse impacts of an extreme, high-fat diet in early postnatal life, but not prenatal undernutrition, can be largely reversed by dietary correction later in life. Thus, birth (at term) appears to be a critical set point for permanent programming in animals born precocial, such as sheep. Appropriate attention to the nutrition of the late pregnant dam should therefore be a priority in animal production systems.

Review: Is rapid fat accumulation in early life associated with adverse later health outcomes?

This review discusses ways in which the maternal environment and placental function affect the birth weight and adult health outcomes of offspring. These maternal and placental factors have varying and sometimes opposing effects on birth weight, resulting in infants that are born small for gestational age (SGA), large for gestational age (LGA) or preterm. However, all these alterations in weight have similar effects on adult health, increasing the risk of obesity and its associated cardiovascular and metabolic disorders. While birth weight has been used as a marker for risk of adverse adult health, we propose that a common feature of all these scenarios - early accumulation of excess body fat - may be a better marker than birth weight alone. Furthermore, altered neonatal fat accumulation may be more closely related to the mechanism by which maternal environment and placental adaptation mediate effects on adult health. We suggest that more research should be focussed on early fat accretion, factors that promote fat accretion and if it can be avoided, and whether it would be beneficial to try to reduce fat accumulation in early life.

Neonatal milk supplementation in lambs has persistent effects on growth and metabolic function that differ by sex and gestational age

The perinatal environment has a major influence on long-term health and disease risk. Preterm birth alters early-life environment and is associated with altered metabolic function in adulthood. Whether preterm birthper seor the early nutritional interventions used to support growth in preterm infants underpins this association is unknown. Lambs born preterm, following dexamethasone induction of labour, or spontaneously at term were randomised to receive nutrient supplementation, analogous to the milk fortifier used clinically or water as a control for the first 2 weeks after birth. Thereafter, nutrition was not different between groups. Growth was monitored, and the glucose–insulin axis function was assessed in juvenile (4 months) and adult life (14 months). Early nutrition influenced adult metabolic function and body composition to a greater extent than preterm birth. In supplemented females, arginine-stimulated insulin secretion was increased in preterm but reduced in term-born juveniles compared with controls (repeated-measures ANOVAP<0·01). In supplemented preterm males, adult weight, ponderal index (PI) and fasting insulin concentrations were elevated compared with preterm controls (weight, 75 (sem3)v. 69 (sem2) kg; PI, 48·0 (sem2·1)v. 43·7 (sem1·7) kg/m3; fasting insulin, 0·19 (sem0·02)v. 0·10 (sem0·02) ng/ml). Conversely, supplemented term-born males had reduced adult weight, PI and fasting insulin concentrations compared with term-born controls (weight, 64 (sem2)v. 70 (sem2) kg; PI, 44·4 (sem1·8)v. 48·2 (sem1·7) kg/m3; fasting insulin, 0·09 (sem0·02)v. 0·14 (sem0·02) ng/ml; all group×supplement interactionsP<0·05). Adult metabolic health may reflect both gestational age at birth and early nutrition. Human studies are urgently needed to investigate the adult sex-specific health implications of neonatal nutritional strategies.

Brief neonatal nutritional supplementation has sex-specific effects on glucose tolerance and insulin regulating genes in juvenile lambs

BACKGROUND

The nutritional plane and composition during fetal life can impact upon growth and epigenetic regulation of genes affecting pancreatic β-cell development and function. However, it is not clear whether β-cell development can be altered by nutritional factors or growth rate after birth. We therefore investigated the effect of neonatal nutritional supplements on growth, glucose tolerance, and pancreatic development in lambs.

METHODS

Newborn lambs were randomized to daily nutritional supplements, calculated to increase macronutrient intake to a similar degree as human breast milk fortifier, or an equivalent volume of water, for 2 wk while continuing to suckle ewe milk. Intravenous glucose tolerance test (IVGTT) was performed at 4 mo of age, and pancreata collected for molecular analysis.

RESULTS

Supplemented lambs had slower weight gain than controls. In supplemented lambs, insulin response to IVGTT was increased in males but decreased in females, compared to same sex controls, and was unrelated to growth rate. mRNA expression of key genes in β-cell development showed sexually dimorphic effects. Epigenetic change occurred in the promotor region of PDX1 gene with decreased suppression and increased activation marks in supplemented lambs of both sexes.

CONCLUSION

Nutritional interventions in early life have long-term, sex-specific effects on pancreatic function.

Placental restriction in multi-fetal pregnancies increases spontaneous ambulatory activity during daylight hours in young adult female sheep

Intrauterine growth restriction (IUGR) has adverse effects on metabolic health and early life, whereas physical activity is protective against later development of metabolic disease. Relationships between birth weight and physical activity in humans, and effects of IUGR on voluntary activity in rodents, are mixed and few studies have measured physical activity in a free-ranging environment. We hypothesized that induced restriction of placental growth and function (PR) in sheep would decrease spontaneous ambulatory activity (SAA) in free-ranging adolescent and young adult progeny from multi-fetal pregnancies. To test this hypothesis, we used Global Positioning System watches to continuously record SAA between 1800 and 1200 h the following day, twice during a 16-day recording period, in progeny of control (CON, n=5 males, 9 females) and PR pregnancies (n=9 males, 10 females) as adolescents (30 weeks) and as young adults (43 weeks). PR reduced size at birth overall, but not in survivors included in SAA studies. In adolescents, SAA did not differ between treatments and females were more active than males overall and during the day (each P<0.001). In adults, daytime SAA was greater in PR than CON females (P=0.020), with a similar trend in males (P=0.053) and was greater in females than males (P=0.016). Adult SAA was negatively correlated with birth weight in females only. Contrary to our hypothesis, restricted placental function and small size at birth did not reduce progeny SAA. The mechanisms for increased daytime SAA in adult female PR and low birth weight sheep require further investigation.

Developmental Programming, a Pathway to Disease

Accumulating evidence suggests that insults occurring during the perinatal period alter the developmental trajectory of the fetus/offspring leading to long-term detrimental outcomes that often culminate in adult pathologies. These perinatal insults include maternal/fetal disease states, nutritional deficits/excess, stress, lifestyle choices, exposure to environmental chemicals, and medical interventions. In addition to reviewing the various insults that contribute to developmental programming and the benefits of animal models in addressing underlying mechanisms, this review focuses on the commonalities in disease outcomes stemming from various insults, the convergence of mechanistic pathways via which various insults can lead to common outcomes, and identifies the knowledge gaps in the field and future directions.

Maternal protein restriction during gestation impairs female offspring pancreas development in the rat

A maternal low-protein (LP) diet programs fetal pancreatic islet β-cell development and function and predisposes offspring to metabolic dysfunction later in life. We hypothesized that maternal protein restriction during pregnancy differentially alters β- and α-cell populations in offspring by modifying islet ontogeny and function throughout life. We aimed to investigate the effect of an LP maternal diet on pancreatic islet morphology and cellular composition in female offspring on postnatal days (PNDs) 7, 14, 21, 36, and 110. Mothers were divided into 2 groups: during pregnancy, the control group (C) was fed a diet containing 20% casein, and the LP group was fed an isocaloric diet with 10% casein. Offspring pancreases were obtained at each PND and then processed. β and α cells were detected by immunohistochemistry, and cellular area and islet size were quantified. Islet cytoarchitecture and total area were similar in C and LP offspring at all ages studied. At the early ages (PNDs 7-21), the proportion of β cells was lower in LP than C offspring. The proportion of α cells was lower in LP than C offspring on PND 14 and higher on PND 21. The β/α-cell ratio was lower in LP compared with C offspring on PNDs 7 and 21 and higher on PND 36 (being similar on PNDs 14 and 110). We concluded that maternal protein restriction during pregnancy modifies offspring islet cell ontogeny by altering the proportions of islet sizes and by reducing the number of β cells postnatally, which may impact pancreatic function in adult life.

The early origins of obesity and insulin resistance: timing, programming and mechanisms

Maternal obesity is associated with an increased risk of developing gestational diabetes mellitus and it also results in an increased risk of giving birth to a large baby with increased fat mass. Furthermore, it is also contributes to an increased risk of obesity and insulin resistance in the offspring in childhood, adolescence and adult life. It has been proposed that exposure to maternal obesity may therefore result in an 'intergenerational cycle' of obesity and insulin resistance. There is significant interest in whether exposure to maternal obesity around the time of conception alone contributes directly to poor metabolic outcomes in the offspring and whether dieting in the obese mother before pregnancy or around the time of conception has metabolic benefits for the offspring. This review focusses on experimental and clinical studies that have investigated the specific impact of exposure to maternal obesity during the periconceptional period alone or extending beyond conception on adipogenesis, lipogenesis and on insulin signalling pathways in the fat, liver and muscle of the offspring. Findings from these studies highlight the need for a better evidence base for the development of dietary interventions in obese women before pregnancy and around the time of conception to maximize the metabolic benefits and minimize the metabolic costs for the next generation.

Impact of maternal undernutrition around the time of conception on factors regulating hepatic lipid metabolism and microRNAs in singleton and twin fetuses

We have investigated the effects of embryo number and maternal undernutrition imposed either around the time of conception or before implantation on hepatic lipid metabolism in the sheep fetus. We have demonstrated that periconceptional undernutrition and preimplantation undernutrition each resulted in decreased hepatic fatty acid β-oxidation regulators, PGC-1α (P < 0.05), PDK2 (P < 0.01), and PDK4 (P < 0.01) mRNA expression in singleton and twin fetuses at 135-138 days gestation. In singletons, there was also lower hepatic PDK4 (P < 0.01), CPT-1 (P < 0.01), and PKCζ (P < 0.01) protein abundance in the PCUN and PIUN groups and a lower protein abundance of PDPK-1 (P < 0.05) in the PCUN group. Interestingly, in twins, the hepatic protein abundance of p-AMPK (Ser(485)) (P < 0.01), p-PDPK-1 (Ser(41)) (P < 0.05), and PKCζ (P < 0.05) was higher in the PCUN and PIUN groups, and hepatic PDK4 (P < 0.001) and CPT-1 (P < 0.05) protein abundance was also higher in the PIUN twin fetus. We also found that the expression of a number of microRNAs was altered in response to PCUN or PIUN and that there is evidence that these changes may underlie the changes in the protein abundance of key regulators of hepatic fatty acid β-oxidation in the PCUN and PIUN groups. Therefore, embryo number and the timing of maternal undernutrition in early pregnancy have a differential impact on hepatic microRNA expression and on the factors that regulate hepatic fatty acid oxidation and lipid synthesis.

Prenatal origins of postnatal variation in growth, development and productivity of ruminants

This review provides an update on recent research into the effects of maternal nutrition on fetal biology and the growth, development and productivity of progeny in postnatal life of ruminant livestock. Evidence is summarised for effects on postnatal growth and body composition, feed intake and efficiency, carcass characteristics and meat quality, wool production, reproduction and lactation performance. In general, these demonstrated effects are not large in relation to the effects of postnatal nutrition and other environmental influences. The mechanisms underpinning the above production outcomes are briefly discussed in terms of systemic endocrine and metabolic responses, and cellular and molecular effects in skeletal muscle, bone, adipose tissue, wool follicles and brain of fetal, neonatal and adult progeny. Treatments observed to elicit tissue responses include maternal under- and overnutrition at various stages of pregnancy and placental insufficiency caused by increased litter size, chronic maternal heat stress and premating carunclectomy in sheep. The as yet meagre evidence for epigenetic mediation of intergenerational effects in ruminants is considered, as is the likelihood that other, more conventional explanations may suffice in some cases. Finally, evidence is summarised for the proposition that the placenta is not merely a passive conduit for nutrient transfer from dam to fetus, but plays an active role in buffering the effects of variations in maternal nutrition on fetal growth and development, and thence, postnatal outcomes.

Glucocorticoid-Induced Preterm Birth and Neonatal Hyperglycemia Alter Ovine β-Cell Development

Adults born preterm are at increased risk of impaired glucose tolerance and diabetes. Late gestation fetuses exposed to high blood glucose concentration also are at increased risk of impaired glucose tolerance as adults. Preterm babies commonly become hyperglycemic and are thus exposed to high blood glucose concentration at an equivalent stage of pancreatic maturation. It is not known whether preterm birth itself, or complications of prematurity, such as hyperglycemia, alter later pancreatic function. To distinguish these, we made singleton preterm lambs hyperglycemic (HYPER) for 12 days after birth with a dextrose infusion and compared them with vehicle-treated preterm and term controls and with HYPER lambs made normoglycemic with an insulin infusion. Preterm birth reduced β-cell mass, apparent by 4 weeks after term and persisting to adulthood (12 mo), and was associated with reduced insulin secretion at 4 months (juvenile) and reduced insulin mRNA expression in adulthood. Hyperglycemia in preterm lambs further down-regulated key pancreatic gene expression in adulthood. These findings indicate that reduced β-cell mass after preterm birth may be an important factor in increased risk of diabetes after preterm birth and may be exacerbated by postnatal hyperglycemia.

Impact of periconceptional and preimplantation undernutrition on factors regulating myogenesis and protein synthesis in muscle of singleton and twin fetal sheep

In this study, we determined the effect of maternal undernutrition in the periconceptional (PCUN: ~80 days before to 6 days after conception) and preimplantation (PIUN: 0-6 days after conception) periods on the mRNA and protein abundance of key factors regulating myogenesis and protein synthesis, and on the relationship between the abundance of these factors and specific microRNA expression in the quadriceps muscle of singleton and twin fetal sheep at 135-138 days of gestation. PCUN and PIUN resulted in a decrease in the protein abundance of MYF5, a factor which determines the myogenic lineage, in singletons and twins. Interestingly, there was a concomitant increase in insulin-like growth factor-1 mRNA expression, a decrease in the protein abundance of the myogenic inhibitor, myostatin (MSTN), and an increase in the mRNA and protein abundance of the MSTN inhibitor, follistatin (FST), in the PCUN and PIUN groups in both singletons and twins. These promyogenic changes may compensate for the decrease in MYF5 protein abundance evoked by early embryonic undernutrition. PCUN and PIUN also increased the protein abundance of phosphorylated eukaryotic translation initiation factor binding protein 1 (EIF4EBP1; T70 and S65) in fetal muscle in singletons and twins. There was a significant inverse relationship between the expression of miR-30a-5p, miR-30d-5p, miR-27b-3p, miR106b-5p, and miR-376b and the protein abundance of mechanistic target of rapamycin (MTOR), FST, or MYF5 in singletons or twins. In particular, the expression of miR-30a-5p was increased and MYF5 protein abundance was decreased, in PCUN and PIUN twins supporting the conclusion that the impact of PCUN and PIUN is predominantly on the embryo.

Embryos, DOHaD and David Barker

The early embryo and periconceptional period is a window during which environmental factors may cause permanent change in the pattern and characteristics of development leading to risk of adult onset disease. This has now been demonstrated across small and large animal models and also in the human. Most evidence of periconceptional 'programming' has emerged from maternal nutritional models but also other in vivo and in vitro conditions including assisted reproductive treatments, show consistent outcomes. This short review first reports on the range of environmental in vivo and in vitro periconceptional models and resulting long-term outcomes. Second, it uses the rodent maternal low protein diet model restricted to the preimplantation period and considers the stepwise maternal-embryonic dialogue that comprises the induction of programming. This dialogue leads to cellular and epigenetic responses by the embryo, mainly identified in the extra-embryonic cell lineages, and underpins an apparently permanent change in the growth trajectory during pregnancy and associates with increased cardiometabolic and behavioural disease in adulthood. We recognize the important advice of David Barker some years ago to investigate the sensitivity of the early embryo to developmental programming, an insight for which we are grateful.

Developmental programming of hypothalamic neuronal circuits: impact on energy balance control

The prevalence of obesity in adults and children has increased globally at an alarming rate. Mounting evidence from both epidemiological studies and animal models indicates that adult obesity and associated metabolic disorders can be programmed by intrauterine and early postnatal environment- a phenomenon known as "fetal programming of adult disease." Data from nutritional intervention studies in animals including maternal under- and over-nutrition support the developmental origins of obesity and metabolic syndrome. The hypothalamic neuronal circuits located in the arcuate nucleus controlling appetite and energy expenditure are set early in life and are perturbed by maternal nutritional insults. In this review, we focus on the effects of maternal nutrition in programming permanent changes in these hypothalamic circuits, with experimental evidence from animal models of maternal under- and over-nutrition. We discuss the epigenetic modifications which regulate hypothalamic gene expression as potential molecular mechanisms linking maternal diet during pregnancy to the offspring's risk of obesity at a later age. Understanding these mechanisms in key metabolic genes may provide insights into the development of preventative intervention strategies.

Parental diet, pregnancy outcomes and offspring health: metabolic determinants in developing oocytes and embryos

The periconceptional period, embracing the terminal stages of oocyte growth and post-fertilisation development up to implantation, is sensitive to parental nutrition. Deficiencies or excesses in a range of macro- and micronutrients during this period can lead to impairments in fertility, fetal development and long-term offspring health. Obesity and genotype-related differences in regional adiposity are associated with impaired liver function and insulin resistance, and contribute to fatty acid-mediated impairments in sperm viability and oocyte and embryo quality, all of which are associated with endoplasmic reticulum stress and compromised fertility. Disturbances to maternal protein metabolism can elevate ammonium concentrations in reproductive tissues and disturb embryo and fetal development. Associated with this are disturbances to one-carbon metabolism, which can lead to epigenetic modifications to DNA and associated proteins in offspring that are both insulin resistant and hypertensive. Many enzymes involved in epigenetic gene regulation use metabolic cosubstrates (e.g. acetyl CoA and S-adenosyl methionine) to modify DNA and associated proteins, and so act as 'metabolic sensors' providing a link between parental nutritional status and gene regulation. Separate to their genomic contribution, spermatozoa can also influence embryo development via direct interactions with the egg and by seminal plasma components that act on oviductal and uterine tissues.

Periconceptional undernutrition in sheep leads to decreased locomotor activity in a natural environment

Maternal undernutrition during pregnancy increases offspring obesity and metabolic disease risk. We hypothesized that periconceptional undernutrition in sheep from 60 days before conception through to day 30 of gestation (UN) would decrease voluntary locomotor activity in adult offspring. Distance travelled was measured at 18 months of age for ∼48 h in the paddock. Data were analysed using multiple regression analysis, with explanatory variables including sex, nutrition group, birth weight, average time between GPS measurements and percentage of time during the measurement period spent in daylight. Mean (±s.e.) distance walked (m/h) was greater for control (CON) than UN animals, and greater for females than males [110.2 (6.5), CON females; 110.7 (6.3), CON males; 105.1 (5.3), UN females and 95.5 (5.8), UN males; P = 0.02 for nutrition group effect and for sex effect]. Periconceptional undernutrition may lead to a significant decrease in voluntary physical activity in adult offspring.

Optimum feeding and growth in preterm neonates

Approximately 10% of all babies worldwide are born preterm, and preterm birth is the leading cause of perinatal mortality in developed countries. Although preterm birth is associated with adverse short- and long-term health outcomes, it is not yet clear whether this relationship is causal. Rather, there is evidence that reduced foetal growth, preterm birth and the long-term health effects of both of these may all arise from a suboptimal intrauterine environment. Further, most infants born preterm also experience suboptimal postnatal growth, with potential adverse effects on long-term health and development. A number of interventions are used widely in the neonatal period to optimise postnatal growth and development. These commonly include supplementation with macronutrients and/or micronutrients, all of which have potential short-term risks and benefits for the preterm infant, whereas the long-term health consequences are largely unknown. Importantly, more rapid postnatal growth trajectory (and the interventions required to achieve this) may result in improved neurological outcomes at the expense of increased cardiovascular risk in later life.

Paternal low protein diet affects adult offspring cardiovascular and metabolic function in mice

Although the association between maternal periconceptional diet and adult offspring health is well characterised, our understanding of the impact of paternal nutrition at the time of conception on offspring phenotype remains poorly defined. Therefore, we determined the effect of a paternal preconception low protein diet (LPD) on adult offspring cardiovascular and metabolic health in mice. Male C57BL/6 mice were fed either normal protein diet (NPD; 18% casein) or LPD (9% casein) for 7 wk before mating. At birth, a reduced male-to-female ratio ( P = 0.03) and increased male offspring weight ( P = 0.009) were observed in litters from LPD compared with NPD stud males with no differences in mean litter size. LPD offspring were heavier than NPD offspring at 2 and 3 wk of age ( P < 0.02). However, no subsequent differences in body weight were observed. Adult male offspring derived from LPD studs developed relative hypotension (decreased by 9.2 mmHg) and elevated heart rate ( P < 0.05), whereas both male and female offspring displayed vascular dysfunction and impaired glucose tolerance relative to NPD offspring. At cull (24 wk), LPD males had elevated adiposity ( P = 0.04), reduced heart-to-body weight ratio ( P = 0.04), and elevated circulating TNF-α levels ( P = 0.015) compared with NPD males. Transcript expression in offspring heart and liver tissue was reduced for genes involved in calcium signaling ( Adcy, Plcb, Prkcb) and metabolism ( Fto) in LPD offspring ( P < 0.03). These novel data reveal the impact of suboptimal paternal nutrition on adult offspring cardiovascular and metabolic homeostasis, and provide some insight into the underlying regulatory mechanisms.

Impact of embryo number and maternal undernutrition around the time of conception on insulin signaling and gluconeogenic factors and microRNAs in the liver of fetal sheep

This study aimed to determine whether exposure of the oocyte and/or embryo to maternal undernutrition results in the later programming of insulin action in the liver and factors regulating gluconeogenesis. To do this, we collect livers from singleton and twin fetal sheep that were exposed to periconceptional (PCUN; -60 to 7 days) or preimplantation (PIUN; 0-7 days) undernutrition at 136-138 days of gestation (term = 150 days). The mRNA and protein abundance of insulin signaling and gluconeogenic factors were then quantified using qRT-PCR and Western blotting, respectively, and global microRNA expression was quantified using deep sequencing methodology. We found that hepatic PEPCK-C mRNA (P < 0.01) and protein abundance and the protein abundance of IRS-1 (P < 0.01), p110β (P < 0.05), PTEN (P < 0.05), CREB (P < 0.01), and pCREB (Ser(133); P < 0.05) were decreased in the PCUN and PIUN singletons. In contrast, hepatic protein abundance of IRS-1 (P < 0.01), p85 (P < 0.01), p110β (P < 0.001), PTEN (P < 0.01), Akt2 (P < 0.01), p-Akt (Ser(473); P < 0.01), and p-FOXO-1 (Thr24) (P < 0.01) was increased in twins. There was a decrease in PEPCK-C mRNA (P < 0.01) but, paradoxically, an increase in PEPCK-C protein (P < 0.001) in twins. Both PCUN and PIUN altered the hepatic expression of 23 specific microRNAs. We propose that the differential impact of maternal undernutrition in the presence of one or two embryos on mRNAs and proteins involved in the insulin signaling and gluconeogenesis is explained by changes in the expression of a suite of specific candidate microRNAs.

Periconception weight loss: common sense for mothers, but what about for babies?

Obesity in the childbearing population is increasingly common. Obesity is associated with increased risk for a number of maternal and neonatal pregnancy complications. Some of these complications, such as gestational diabetes, are risk factors for long-term disease in both mother and baby. While clinical practice guidelines advocate for healthy weight prior to pregnancy, there is not a clear directive for achieving healthy weight before conception. There are known benefits to even moderate weight loss prior to pregnancy, but there are potential adverse effects of restricted nutrition during the periconceptional period. Epidemiological and animal studies point to differences in offspring conceived during a time of maternal nutritional restriction. These include changes in hypothalamic-pituitary-adrenal axis function, body composition, glucose metabolism, and cardiovascular function. The periconceptional period is therefore believed to play an important role in programming offspring physiological function and is sensitive to nutritional insult. This review summarizes the evidence to date for offspring programming as a result of maternal periconception weight loss. Further research is needed in humans to clearly identify benefits and potential risks of losing weight in the months before conceiving. This may then inform us of clinical practice guidelines for optimal approaches to achieving a healthy weight before pregnancy.

Adverse prenatal environment and kidney development: implications for programing of adult disease

The 'developmental origins of health and disease' hypothesis suggests that many adult-onset diseases can be attributed to altered growth and development during early life. Perturbations during gestation can be detrimental and lead to an increased risk of developing renal, cardiovascular, metabolic, and neurocognitive dysfunction in adulthood. The kidney has emerged as being especially vulnerable to insult at almost any stage of development resulting in a reduction in nephron endowment. In both humans and animal models, a reduction in nephron endowment is strongly associated with an increased risk of hypertension. The focus of this review is twofold: i) to determine the importance of specific periods during development on long-term programing and ii) to examine the effects of maternal perturbations on the developing kidney and how this may program adult-onset disease. Recent evidence has suggested that insults occurring around the time of conception also have the capacity to influence long-term health. Although epigenetic mechanisms are implicated in mediating these outcomes, it is unclear as to how these may impact on kidney development. This presents exciting new challenges and areas for research.

Periconceptional undernutrition programs changes in insulin-signaling molecules and microRNAs in skeletal muscle in singleton and twin fetal sheep

Maternal undernutrition around the time of conception is associated with an increased risk of insulin resistance in adulthood. We determined the effect of maternal undernutrition in the periconceptional period (PCUN, i.e., 60 days prior to 6 days after conception) and the preimplantation period (PIUN, i.e., 0-6 days after conception) on mRNA expression and protein abundance of key insulin-signaling molecules as well as the global microRNA expression in quadriceps muscle of singleton and twin fetal sheep in late gestation. In singleton fetuses, exposure to PCUN resulted in lower protein abundance of PIK3CB (P < 0.01), PRKCZ (P < 0.05), and pPRKCZ (Thr410) (P < 0.05) in skeletal muscle compared to controls. In PIUN singletons, there was a higher protein abundance of IRS1 (P < 0.05), PDPK1 (P < 0.05), and SLC2A4 (P < 0.05) compared to controls. In twins, PCUN resulted in higher protein abundance of IRS1 (P < 0.05), AKT2 (P < 0.05), PDPK1 (P < 0.05), and PRKCZ (P < 0.001), while PIUN also resulted in higher protein abundance of IRS1 (P < 0.05), PRKCZ (P < 0.001), and SLC2A4 (P < 0.05) in fetal muscle compared to controls. There were specific patterns of the types and direction of changes in the expression of 22 microRNAs in skeletal muscle after exposure to PCUN or PIUN and clear differences in these patterns between singleton and twin pregnancies. These findings provide evidence that maternal undernutrition around the time of conception induces changes in the expression of microRNAs, which may play a role in altering the abundance of the key insulin-signaling molecules in skeletal muscle and in the association between PCUN undernutrition and insulin resistance in adult life.

Programming of glucose-insulin homoeostasis: long-term consequences of pre-natal versus early post-natal nutrition insults. Evidence from a sheep model

AIM

Exposure to adverse intra-uterine conditions can predispose for metabolic disorders later in life. By using a sheep model, we studied (i) how programming of glucose-insulin homoeostasis during late gestation is manifested later in life depending on the early post-natal dietary exposure and (ii) whether dietary alteration in obese individuals can prevent adverse outcomes of early life programming.

METHODS

During late gestation, twin-pregnant sheep were fed 100% (NORM) or 50% (LOW) of energy and protein requirements. After birth, offspring were exposed to a moderate (CONV) or high-carbohydrate-high-fat (HCHF) diet until around puberty. Offspring remaining thereafter (exclusively females) were fed a moderate diet until young adulthood.

RESULTS

LOW lambs had increased insulin secretory responses during intravenous glucose tolerance tests indicative of reduced insulin sensitivity. HCHF lambs were hypertriglyceridaemic, 75% had mild pancreatic collagen infiltration, and their acute insulin secretory response and insulin clearance during intravenous glucose and insulin tolerance tests, respectively, were reduced. However, NORM-HCHF in contrast to LOW-HCHF lambs had normal glucose tolerance, indicating that later health outcomes are highly influenced by pre-natal nutrition. Dietary alteration normalized glucose-insulin homoeostasis in adult HCHF females, whereas late-gestation undernutrition (LOW) permanently depressed insulin sensitivity.

CONCLUSION

Maintenance of glucose tolerance in sheep exposed to pre-natal undernutrition relied on pancreatic hypersecretion of insulin to compensate for reduced insulin sensitivity. A mismatching high-fat diet in early post-natal life interfered with this pancreatic hypersecretion resulting in reduced glucose tolerance. Early post-natal, but not late pre-natal, impacts on glucose-insulin homoeostasis could be reversed by dietary correction later in life.

Differential effects of exposure to maternal obesity or maternal weight loss during the periconceptional period in the sheep on insulin signalling molecules in skeletal muscle of the offspring at 4 months of age

Exposure to maternal obesity before and/or throughout pregnancy may increase the risk of obesity and insulin resistance in the offspring in childhood and adult life, therefore, resulting in its transmission into subsequent generations. We have previously shown that exposure to maternal obesity around the time of conception alone resulted in increased adiposity in female lambs. Changes in the abundance of insulin signalling molecules in skeletal muscle and adipose tissue precede the development of insulin resistance and type 2 diabetes. It is not clear, however, whether exposure to maternal obesity results in insulin resistance in her offspring as a consequence of the impact of increased adiposity on skeletal muscle or as a consequence of the programming of specific changes in the abundance of insulin signalling molecules in this tissue. We have used an embryo transfer model in the sheep to investigate the effects of exposure to either maternal obesity or to weight loss in normal and obese mothers preceding and for one week after conception on the expression and abundance of insulin signalling molecules in muscle in the offspring. We found that exposure to maternal obesity resulted in lower muscle GLUT-4 and Ser 9 phospho-GSK3α and higher muscle GSK3α abundance in lambs when compared to lambs conceived in normally nourished ewes. Exposure to maternal weight loss in normal or obese mothers, however, resulted in lower muscle IRS1, PI3K, p110β, aPKCζ, Thr 642 phospho-AS160 and GLUT-4 abundance in the offspring. In conclusion, maternal obesity or weight loss around conception have each programmed specific changes on subsets of molecules in the insulin signalling, glucose transport and glycogen synthesis pathways in offspring. There is a need for a stronger evidence base to ensure that weight loss regimes in obese women seeking to become pregnant minimize the metabolic costs for the next generation.

Maternal undernutrition programs tissue-specific epigenetic changes in the glucocorticoid receptor in adult offspring

Epidemiological data indicate that an adverse maternal environment during pregnancy predisposes offspring to metabolic syndrome with increased obesity, and type 2 diabetes. The mechanisms are still unclear although epigenetic modifications are implicated and the hypothalamus is a likely target. We hypothesized that maternal undernutrition (UN) around conception in sheep would lead to epigenetic changes in hypothalamic neurons regulating energy balance in the offspring, up to 5 years after the maternal insult. We found striking evidence of decreased glucocorticoid receptor (GR) promoter methylation, decreased histone lysine 27 trimethylation, and increased histone H3 lysine 9 acetylation in hypothalami from male and female adult offspring of UN mothers. These findings are entirely compatible with the increased GR mRNA and protein observed in the hypothalami. The increased GR predicted the decreased hypothalamic proopiomelanocortin expression and increased obesity that we observed in the 5-year-old adult males. The epigenetic and expression changes in GR were specific to the hypothalamus. Hippocampal GR mRNA and protein were decreased in UN offspring, whereas pituitary GR was altered in a sex-specific manner. In peripheral polymorphonuclear leukocytes there were no changes in GR methylation or protein, indicating that this epigenetic analysis did not predict changes in the brain. Overall, these results suggest that moderate changes in maternal nutrition, around the time of conception, signal life-long and tissue-specific epigenetic alterations in a key gene regulating energy balance in the hypothalamus.

Impact of embryo number and periconceptional undernutrition on factors regulating adipogenesis, lipogenesis, and metabolism in adipose tissue in the sheep fetus

Maternal undernutrition around the time of conception is associated with an increased risk of insulin resistance in adulthood. We hypothesized that maternal undernutrition during the periconceptional (PCUN: -60 to 7 days) and/or preimplantation (PIUN: 0-7 days) periods would result in a decrease in UCP1 expression and the abundance of insulin signaling molecules and an increase in the abundance of factors that regulate adipogenesis and lipogenesis in fetal perirenal adipose tissue (PAT) and that these effects would be different in singletons and twins. Maternal PCUN and PIUN resulted in a decrease in UCP1 expression in PAT, and PIUN resulted in higher circulating insulin concentrations, an increased abundance of pPKCζ and PDK4, and a decreased abundance of Akt1, phosphorylated mTOR, and PPARγ in PAT in singleton and twin fetuses. In singletons, there was also a decrease in the abundance of p110β in PAT in the PCUN and PIUN groups and an increase in total AMPKα in PAT in the PIUN group. In twins, however, there was an increase in the abundance of mTOR in the PCUN group and an increase in PDK2 and decrease in total AMPKα in the PIUN group. Thus exposure to periconceptional undernutrition programs changes in the thermogenic capacity and the insulin and fatty acid oxidation signaling pathway in visceral fat, and these effects are different in singletons and twins. These findings are important, as the thermogenic capacity of brown fat and the insulin sensitivity of visceral fat are important determinants of the risk of developing obesity and an insulin resistance phenotype in later life.

Nutritional programming of insulin resistance: causes and consequences

Strong evidence indicates that adverse prenatal and early postnatal environments have a significant long-term influence on risk factors that result in insulin resistance, type 2 diabetes (T2D), and cardiovascular disease later in life. Here we discuss current knowledge of how maternal and neonatal nutrition influence early growth and the long-term risk of developing insulin resistance in different organs and at the whole-body level. Accumulating evidence supports a role for epigenetic mechanisms underlying this nutritional programming, consisting of heritable changes that regulate gene expression which in turn shapes the phenotype across generations. Deciphering these molecular mechanisms in key tissues and discovering key biological markers may provide valuable insight towards the development of effective intervention strategies.

Differential effects of maternal obesity and weight loss in the periconceptional period on the epigenetic regulation of hepatic insulin-signaling pathways in the offspring

Our aim was to determine the effect of exposure to maternal obesity or to maternal weight loss around conception on the programming of hepatic insulin signaling in the offspring. We used an embryo transfer model in sheep to investigate the effects of exposure to either maternal obesity or to weight loss in normal and obese mothers preceding and for 1 wk after conception on the expression of hepatic insulin-signaling and gluconeogenic factors and key miRNAs involved in insulin signaling in the offspring. We found that exposure to maternal obesity resulted in increased hepatic miR-29b (P<0.05), miR-103 (P<0.01), and miR-107 (P<0.05) expression, a decrease in IR (P<0.05), phopsho-Akt (P<0.01), and phospho-FoxO1 (P<0.01) abundance, and a paradoxical decrease in 11βHSD1 (P<0.05), PEPCK-C (P<0.01), and PEPCK-M (P<0.05) expression in lambs. These changes were ablated by a period of moderate dietary restriction imposed during the periconceptional period. Maternal dietary restriction alone also resulted in decreased abundance of a separate subset of hepatic insulin-signaling molecules, namely, IRS1 (P<0.05), PDK1 (P<0.01), phospho-PDK1 (P<0.05), and aPKCζ (P<0.05) and in decreased PEPCK-C (P<0.01) and G6Pase (P<0.01) expression in the lamb. Our findings highlight the sensitivity of the epigenome to maternal nutrition around conception and the need for dietary interventions that maximize metabolic benefits and minimize metabolic costs for the next generation.