Hypertension and impaired renal function accompany juvenile obesity: the effect of prenatal diet

Gender differences in the renal changes induced by a prolonged high-fat diet in rats with altered renal development

The mechanisms involved in renal dysfunction induced by high-fat diet (HFD) in subjects with altered renal development (ARDev) are understudied. The objective of this study is to examine whether there are sex-dependent differences in the mechanisms involved in the hypertension and deterioration of renal function in SD rats with prolonged HFD and ARDev. The role of angiotensin II (Ang II) in the arterial pressure (AP) increments, the renal hemodynamic sensitivity to Ang II, glomerular damage and changes in fat abdominal volume, plasma adipokine levels, renal NADPHp67phox expression, and renal infiltration of immune cells were examined. Hypertension and deterioration of renal function were enhanced (P < 0.05) in both sexes of rats with HFD and ARDev. The decrease (P < 0.05) of AP elicited by candesartan in hypertensive rats was similar to that induced by the simultaneous administration of candesartan and apocynin. The greater (P < 0.05) renal vasoconstriction induced by Ang II in both sexes of rats with HFD and ARDev was accompanied by an enhanced (P < 0.05) infiltration of CD-3 cells and macrophages in the renal cortex and renal medulla. The increments (P < 0.05) in the renal expression of NADPHp67phox and glomeruloesclerosis were greater (P < 0.05) in males than in females with HFD and ARDev. Our results suggest that the hypertension and deterioration of renal function induced by HFD in rats with ARDev are Ang II-dependent and mediated by increments in oxidative stress and immune system activation. Sex-dependent increments in oxidative stress and glomerular damage may contribute to the deterioration of renal function in these rats.

Adaptive responses to maternal nutrient restriction alter placental transport in ewes

INTRODUCTION

Maternal nutrient partitioning, uteroplacental blood flow, transporter activity, and fetoplacental metabolism mediate nutrient delivery to the fetus. Inadequate availability or delivery of nutrients results in intrauterine growth restriction (IUGR), a leading cause of neonatal morbidity and mortality. Maternal nutrient restriction can result in IUGR, but only in an unforeseeable subset of individuals.

METHODS

To elucidate potential mechanisms regulating fetal nutrient availability, singleton sheep pregnancies were generated by embryo transfer. Pregnant ewes received either a 50% NRC (NR; n = 24) or 100% NRC (n = 7) diet from gestational Day 35 until necropsy on Day 125. Maternal weight did not correlate with fetal weight; therefore, the six heaviest (NR Non-IUGR) and five lightest (NR IUGR) fetuses from nutrient-restricted ewes, and seven 100% NRC fetuses, were compared to investigate differences in nutrient availability.

RESULTS

Insulin, multiple amino acids, and their metabolites, were reduced in fetal circulation of NR IUGR compared to NR Non-IUGR and 100% NRC pregnancies. In contrast, glucose in fetal fluids was not different between groups. There was a nearly two-fold reduction in placentome volume and fetal/maternal interface length in NR IUGR compared to NR Non-IUGR and 100% NRC pregnancies. Changes in amino acid concentrations were associated with altered expression of cationic (SLC7A2, SLC7A6, and SLC7A7) and large neutral (SLC38A2) amino acid transporters in placentomes.

DISCUSSION

Results establish a novel approach to study placental adaptation to maternal undernutrition in sheep and support the hypothesis that amino acids and polyamines are critical mediators of placental and fetal growth in sheep.

Differential impacts of late gestational over-and undernutrition on adipose tissue traits and associated visceral obesity risk upon exposure to a postnatal high-fat diet in adolescent sheep

We hypothesized that late gestation malnutrition differentially affects expandability of adipose tissues to predispose for early postnatal visceral adiposity. Twin-lambs born to dams fed HIGH (150%/110% of required energy/protein, respectively), NORM (100% of requirements) or LOW (50% of NORM) diets during the last trimester were used. Postnatally, lambs were raised on moderate (CONV) or high-carbohydrate-high-fat (HCHF) diets. Adipose tissues were sampled at autopsy at 6 months of age (~puberty) to characterize cellularity, adipocyte cross-sectional area and gene expression patterns. HIGH and LOW compared to NORM lambs had reduced intrinsic (under CONV diet) cellularity in subcutaneous and mesenteric (particularly LOW), and reduced obesity-induced (under HCHF diet) hyperplasia in subcutaneous, mesenteric and perirenal (particularly HIGH) adipose tissues. This corresponded with more pronounced HCHF diet-induced hypertrophy in mesenteric (particularly LOW), perirenal (particularly HIGH) and subcutaneous (particularly HIGH) adipose tissues, and tissue-specific reductions in mRNA expressions for lipid metabolism, angiogenesis and adipose development. Gene expression for inflammation and lipid metabolism markers were increased and decreased, respectively, in HCHF lambs (HCHF lambs became obese) in all tissues. Both prenatal over- and undernutrition predisposed for abdominal adiposity and extreme perirenal hypertrophy due to reduced intrinsic (observed under CONV diet) cellularity and impaired ability of subcutaneous, mesenteric and perirenal adipose tissues to expand by hyperplasia rather than hypertrophy on an obesogenic (HCHF) diet.

Sex-dependent differences in the adverse renal changes induced by an early in life exposure to a high-fat diet

This study examines whether the intake of a high-fat diet very early in life leads to changes in arterial pressure and renal function and evaluates whether the mechanisms involved in these changes are sex-dependent. Experiments were performed in male and female Sprague-Dawley rats fed a normal or high-fat diet from weaning to 4 mo of age. This exposure to a high-fat diet lead to an angiotensin II-dependent elevation in arterial pressure and to significant increments in fat abdominal volume and plasma leptin that were similar in both sexes. In addition, the angiotensin II-induced increment in renal vascular resistance was greater ( P < 0.05) in male (106 ± 14%) and female (97 ± 15%) rats fed a high-fat diet than in rats fed a normal-fat diet (51 ± 8%). However, the high-fat intake during early life induced increments in albuminuria, interleukin-6, and infiltration of CD3 lymphocytes in the renal parenchyma that were greater ( P < 0.05) in male than in female rats. Other sex-dependent differences in response to high-fat intake were that adiponectin levels only decreased in females (21%, P < 0.05), and renal NF-κB expression only increased in males (31%, P < 0.05). In summary, the early exposure to a high-fat diet leads to angiotensin II-dependent arterial pressure elevations and to increments in abdominal fat and in the renal sensitivity to angiotensin II that are similar in both sexes. However, the mechanisms involved in the renal changes associated with early exposure to a high-fat diet are different in males and females.

Exposure to maternal obesity alters gene expression in the preimplantation ovine conceptus

Background

Embryonic and fetal exposure to maternal obesity causes several maladaptive morphological and epigenetic changes in exposed offspring. The timing of these events is unclear, but changes can be observed even after a short exposure to maternal obesity around the time of conception. The hypothesis of this work is that maternal obesity influences the ovine preimplantation conceptus early in pregnancy, and this exposure will affect gene expression in embryonic and extraembryonic tissues.

Results

Obese and lean ewe groups were established by overfeeding or normal feeding, respectively. Ewes were then bred to genetically similar rams. Conceptuses were collected at day 14 of gestation. Morphological assessments were made, conceptuses were sexed by genomic PCR analysis, and samples underwent RNA-sequencing analysis. While no obvious morphological differences existed between conceptuses, differentially expressed genes (≥ 2-fold; ≥ 0.2 RPKM; ≤ 0.05 FDR) were detected based on maternal obesity exposure (n = 21). Also, differential effects of maternal obesity were noted on each conceptus sex (n = 347). A large portion of differentially expressed genes were associated with embryogenesis and placental development.

Conclusions

Findings reveal that the preimplantation ovine conceptus genome responds to maternal obesity in a sex-dependent manner. The sexual dimorphism in response to the maternal environment coupled with changes in placental gene expression may explain aberrations in phenotype observed in offspring derived from obese females.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5120-0) contains supplementary material, which is available to authorized users.

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.

Proteomic Analysis of One-carbon Metabolism-related Marker in Liver of Rat Offspring

Maternal food intake has a significant effect on the fetal environment, and an inadequate maternal diet may result in intrauterine growth restriction. Intrauterine growth restriction newborn rat pups nursed by normal diet-fed dams exhibited rapid catch-up growth, which plays a critical role in the risk for metabolic and cardiovascular disease in later life. Specifically, one-carbon metabolism in the liver plays a critical role in placental and fetal growth. Impaired functioning of one-carbon metabolism is associated with increased homocysteine levels. In this study, we applied a comprehensive proteomic approach to identify differential expression of proteins related to one-carbon metabolism in the livers of rat offspring as an effect of maternal food restriction during gestation. Data are available via ProteomeXchange with identifier PXD002578. We determined that betaine-homocysteine S-methyltransferase 1, methylenetetrahydrofolate dehydrogenase 1, and ATP synthase subunit beta mitochondrial (ATP5B) expression levels were significantly reduced in the livers of rat offspring exposed to maternal food restriction during gestation compared with in the offspring of rats fed a normal diet (p < 0.05). Moreover, the expression levels of betaine-homocysteine S-methyltransferase 1, methylenetetrahydrofolate dehydrogenase 1, and ATP synthase subunit beta mitochondrial were negatively correlated with serum homocysteine concentration in male offspring exposed to maternal food restriction during gestation and normal diet during lactation. However, in female offspring only expression levels of methylenetetrahydrofolate dehydrogenase 1 were negatively correlated with homocysteine concentration. This study shows that maternal food restriction during late gestation and normal diet during lactation lead to increased homocysteine concentration through disturbance of one-carbon metabolism in the livers of male offspring. This suggests that male offspring have an increased gender-specific susceptibility to disease in later life through fetal programming.

Suboptimal maternal nutrition during early fetal kidney development specifically promotes renal lipid accumulation following juvenile obesity in the offspring

Reduced maternal food intake between early-to-mid gestation results in tissue-specific adaptations in the offspring following juvenile-onset obesity that are indicative of insulin resistance. The aim of the present study was to establish the extent to which renal ectopic lipid accumulation, as opposed to other markers of renal stress, such as iron deposition and apoptosis, is enhanced in obese offspring born to mothers nutrient restricted (NR) throughout early fetal kidney development. Pregnant sheep were fed either 100% (control) or NR (i.e. fed 50% of their total metabolisable energy requirement from 30-80 days gestation and 100% at all other times). At weaning, offspring were made obese and, at approximately 1 year, kidneys were sampled. Triglyceride content, HIF-1α gene expression and the protein abundance of the outer-membrane transporter voltage-dependent anion-selective channel protein (VDAC)-I on the kidney cortex were increased in obese offspring born to NR mothers compared with those born to controls, which exhibited increased iron accumulation within the tubular epithelial cells and increased gene expression of the death receptor Fas. In conclusion, suboptimal maternal nutrition coincident with early fetal kidney development results in enhanced renal lipid deposition following juvenile obesity and could accelerate the onset of the adverse metabolic, rather than cardiovascular, symptoms accompanying the metabolic syndrome.

Sex differences in metabolic and adipose tissue responses to juvenile-onset obesity in sheep

Sex is a major factor determining adipose tissue distribution and the subsequent adverse effects of obesity-related disease including type 2 diabetes. The role of gender on juvenile obesity and the accompanying metabolic and inflammatory responses is not well established. Using an ovine model of juvenile onset obesity induced by reduced physical activity, we examined the effect of gender on metabolic, circulatory, and related inflammatory and energy-sensing profiles of the major adipose tissue depots. Despite a similar increase in fat mass with obesity between genders, males demonstrated a higher storage capacity of lipids within perirenal-abdominal adipocytes and exhibited raised insulin. In contrast, obese females became hypercortisolemic, a response that was positively correlated with central fat mass. Analysis of gene expression in perirenal-abdominal adipose tissue demonstrated the stimulation of inflammatory markers in males, but not females, with obesity. Obese females displayed increased expression of genes involved in the glucocorticoid axis and energy sensing in perirenal-abdominal, but not omental, adipose tissue, indicating a depot-specific mechanism that may be protective from the adverse effects of metabolic dysfunction and inflammation. In conclusion, young males are at a greater risk than females to the onset of comorbidities associated with juvenile-onset obesity. These sex-specific differences in cortisol and adipose tissue could explain the earlier onset of the metabolic-related diseases in males compared with females after obesity.

Overweight, hypertension and renal dysfunction in adulthood of neonatally overfed rats

Accelerated growth in early infancy has been associated with later cardiovascular and metabolic diseases. We investigated the influence of overnutrition during neonatal periods on the development of renal pathophysiological changes in adult offspring rats. Three or 10 male pups per mother were assigned to either the small litter (SL) or normal litter (NL) control groups during the first 21 days of life. The effects of early postnatal overnutrition on body weight, blood pressure and renal changes were determined at 3 and 6 months. Pups in the SL group weighed more than controls between 7 days and 6 months of age (P<.05). In the SL group, serum creatinine levels were higher at 3 and 6 months (P<.05), and at 6 months, blood pressure levels were higher than those of the controls (P<.05). The number of ED-1 positive macrophages in renal cortex and glomerulosclerosis index increased in the SL group at 3 and 6 months (P<.05). Additionally, cortical apoptotic cells increased in the SL group at 6 months (P<.05). Immunoblotting and immunohistochemistry showed that matrix metalloproteinase (MMP)-9 protein expressions decreased and tissue inhibitor of MMP-1, tumor necrosis factor-α, osteopontin and adiponectin expressions increased in the SL group at 3 months (P<.05). However, at 6 months, MMP-9 expression was elevated, and osteopontin expression remained elevated in the SL group (P<.05). Early postnatal overfeeding can lead to lasting overweight, hypertension and renal dysfunction and place a greater burden on the kidney.

Nutrition, epigenetics, and metabolic syndrome

SIGNIFICANCE

Epidemiological and animal studies have demonstrated a close link between maternal nutrition and chronic metabolic disease in children and adults. Compelling experimental results also indicate that adverse effects of intrauterine growth restriction on offspring can be carried forward to subsequent generations through covalent modifications of DNA and core histones.

RECENT ADVANCES

DNA methylation is catalyzed by S-adenosylmethionine-dependent DNA methyltransferases. Methylation, demethylation, acetylation, and deacetylation of histone proteins are performed by histone methyltransferase, histone demethylase, histone acetyltransferase, and histone deacetyltransferase, respectively. Histone activities are also influenced by phosphorylation, ubiquitination, ADP-ribosylation, sumoylation, and glycosylation. Metabolism of amino acids (glycine, histidine, methionine, and serine) and vitamins (B6, B12, and folate) plays a key role in provision of methyl donors for DNA and protein methylation.

CRITICAL ISSUES

Disruption of epigenetic mechanisms can result in oxidative stress, obesity, insulin resistance, diabetes, and vascular dysfunction in animals and humans. Despite a recognized role for epigenetics in fetal programming of metabolic syndrome, research on therapies is still in its infancy. Possible interventions include: 1) inhibition of DNA methylation, histone deacetylation, and microRNA expression; 2) targeting epigenetically disturbed metabolic pathways; and 3) dietary supplementation with functional amino acids, vitamins, and phytochemicals.

FUTURE DIRECTIONS

Much work is needed with animal models to understand the basic mechanisms responsible for the roles of specific nutrients in fetal and neonatal programming. Such new knowledge is crucial to design effective therapeutic strategies for preventing and treating metabolic abnormalities in offspring born to mothers with a previous experience of malnutrition.

The early programming of metabolic health: is epigenetic setting the missing link?

Adult health is dependent, in part, on maternal nutrition and growth during early life, which may independently affect insulin sensitivity, body composition, and overall energy homeostasis. Since the publication of the "thrifty phenotype hypothesis" by Hales and Barker (Diabetologia 1992;35:595-601), animal experiments have focused on establishing the mechanisms involved, which include changes in fetal cortisol, insulin, and leptin secretion or sensitivity. Intrauterine growth retardation can be induced by either prolonged modest changes in maternal diet or by more severe changes in uterine blood supply near to term. These contrasting challenges result in different amounts of cellular stress in the offspring. In addition, shifts in the transcriptional activity of DNA may produce sustained metabolic adaptations. Within tissues and organs that control metabolic homeostasis (eg, hypothalamus, adipose tissue, stomach, skeletal muscle, and heart), a range of phenotypes can be induced by sustained changes in maternal diet via modulation of genes that control DNA methylation and by histone acetylation, which suggests epigenetic programming. We now need to understand how changes in maternal diet affect DNA and how they are conserved on exposure to oxidative stress. A main challenge will be to establish how the dietary environment interacts with the programmed phenotype to trigger the development of metabolic disease. This may aid in the establishment of nutrigenomic strategies to prevent the metabolic syndrome.

Programming research: where are we and where do we go from here?

Convincing evidence has accumulated to show that both pre- and postnatal nutrition preprogram long-term health, well-being, and performance until adulthood and old age. There is a very large potential in the application of this knowledge to promote public health. One of the prerequisites for translational application is to strengthen the scientific evidence. More extensive knowledge is needed (eg, on effect sizes of early life programming in contemporary populations, on specific nutritional exposures, on sensitive time periods in early life, on precise underlying mechanisms, and on potential effect differences in subgroups characterized by, eg, genetic predisposition or sex). Future programming research should aim at filling the existing gaps in scientific knowledge, consider the entire lifespan, address socioeconomic issues, and foster innovation. Research should aim at results suitable for translational application (eg, by leading to health-promoting policies and evidence-based dietary recommendations in the perinatal period). International collaboration and a close research partnership of academia, industry, and small and medium enterprises may strengthen research and innovative potential enhancing the likelihood of translational application. The scientific know-how and methodology available today allow us to take major steps forward in the near future; hence, research on nutritional programming deserves high priority.

Protein-energy malnutrition during early gestation in sheep blunts fetal renal vascular and nephron development and compromises adult renal function

Non-technical summary

A poor diet during pregnancy has been linked to long-term health outcomes for the baby, such as an increased risk of diseases of the heart and kidney. We show in an experimental model that recreates a poor diet during pregnancy, i.e. a diet low in protein with adequate energy, that kidney development in the baby is affected in such a way as to reduce the potential for new blood vessels to form. This results in a greater number of important, functional kidney cells spontaneously dying. Later in life, these effects in the kidney manifest as permanently reduced kidney function, especially if the baby subsequently becomes overweight as an adult. The research reinforces advice to pregnant mothers about the importance of eating a nutritionally balanced diet during pregnancy.

Abstract

A nutritionally poor maternal diet can reduce nephron endowment and pre-empt premature expression of markers for chronic renal disease in the offspring. A mechanistic pathway from variation in maternal diet through altered fetal renal development to compromised adult kidney structure and function with adult-onset obesity has not been described. We show that maternal protein-energy malnutrition in sheep blunts nephrogenic potential in the 0.44 gestation (65 days gestation, term ∼147 days) fetus by increasing apoptosis and decreasing angiogenesis in the nephrogenic zone, effects that were more marked in male fetuses. As adults, the low-protein-exposed sheep had reduced glomerular number and microvascular rarefaction in their kidneys compensated for, respectively, by glomerular hypertrophy and increased angiogenic support. In this study, the long-term mild anatomical deficits in the kidney would have remained asymptomatic in the lean state, but when superimposed on the broad metabolic challenge that obesity represents then microalbuminuria and blunted bilateral renal function revealed a long-term physiological compromise, that is only predicted to worsen with age. In conclusion, maternal protein-energy malnutrition specifically impacts fetal kidney vascular development and prevents full functionality of the adult kidney being achieved; these residual deficits are predicted to significantly increase the expected incidence of chronic kidney disease in prenatally undernourished individuals especially when coupled with a Western obesogenic environment.

Maternal nutrient restriction during late gestation and early postnatal growth in sheep differentially reset the control of energy metabolism in the gastric mucosa

Fetal growth restriction followed by accelerated postnatal growth contributes to impaired metabolic function in adulthood. The extent to which these outcomes may be mediated centrally within the hypothalamus, as opposed to in the periphery within the digestive tract, remains unknown. In a sheep model, we achieved intrauterine growth restriction experimentally by maternal nutrient restriction (R) that involved a 40% reduction in food intake through late gestation. R offspring were then either reared singly to accelerate postnatal growth (RA) or as twins and compared with controls also reared singly. From weaning, all offspring were maintained indoors until adulthood. A reduced litter size accelerated postnatal growth for only the first month of lactation. Independently from postnatal weight gain and later fat mass, R animals developed insulin resistance as adults. However, restricted accelerated offspring compared with both the control accelerated and restricted restricted offspring ate less and had higher fasting plasma leptin as adults, an adaptation which was accompanied by changes in energy sensing and cell proliferation within the abomasum. Additionally, although fetal restriction down-regulated gene expression of mammalian target of rapamycin and carnitine palmitoyltransferase 1-dependent pathways in the abomasum, RA offspring compensated for this by exhibiting greater activity of AMP-activated kinase-dependent pathways. This study demonstrates a role for perinatal nutrition in the peripheral control of food intake and in energy sensing in the gastric mucosal and emphasizes the importance of diet in early life in regulating energy metabolism during adulthood.

The conflicting effects of maternal nutrient restriction and early-life obesity on renal health

Epidemiological and animal studies have demonstrated that early-life nutrition alters the metabolic responses and generates structural changes in complex tissues, such as the kidneys, which may lead to a reduction in the offspring lifespan. Independently, obesity induces a spontaneous low-grade chronic inflammatory response by modulating several of the major metabolic pathways that ultimately compromise long-term renal health. However, the combined effects of maternal nutrition and early-life obesity in the development of renal diseases are far from conclusive. Previous results, using the ovine model, demonstrated that the combination of a reduction in fetal nutrition and juvenile obesity induced a series of adaptations associated with severe metabolic syndrome in the heart and adipose tissue. Surprisingly, exposure to an obesogenic environment in the kidney of those offspring produced an apparent reduction in glomerulosclerosis in relation to age- and weight-matched controls. However, this reduction in cellular apoptosis was accompanied by a rise in glomerular filtration rate and blood pressure of equal intensity when compared with obese controls. The intention of this review is to explain the adaptive responses observed in this model, based on insights into the mechanism of renal fetal programming, and their potential interactions with some of the metabolic changes produced by obesity.

Suboptimal maternal nutrition, during early fetal liver development, promotes lipid accumulation in the liver of obese offspring

Maternal nutrition during the period of early organ development can modulate the offspring's ability to metabolise excess fat as young adults when exposed to an obesogenic environment. This study examined the hypothesis that exposing offspring to nutrient restriction coincident with early hepatogenesis would result in endocrine and metabolic adaptations that subsequently lead to increased ectopic lipid accumulation within the liver. Pregnant sheep were fed either 50 or 100% of total metabolisable energy requirements from 30 to 80 days gestation and 100% thereafter. At weaning, offspring were made obese, and at ∼1 year of age livers were sampled. Lipid infiltration and molecular indices of gluconeogenesis, lipid metabolism and mitochondrial function were measured. Although hepatic triglyceride accumulation was not affected by obesity per se, it was nearly doubled in obese offspring born to nutrient-restricted mothers. This adaptation was accompanied by elevated gene expression for peroxisome proliferator-activated receptor γ (PPARG) and its co-activator PGC1α, which may be indicative of changes in the rate of hepatic fatty acid oxidation. In contrast, maternal diet had no influence on the stimulatory effect of obesity on gene expression for a range of proteins involved in glucose metabolism and energy balance including glucokinase, glucocorticoid receptors and uncoupling protein 2. Similarly, although gene expressions for the insulin and IGF1 receptors were suppressed by obesity they were not influenced by the prenatal nutritional environment. In conclusion, excess hepatic lipid accumulation with juvenile obesity is promoted by suboptimal nutrition coincident with early development of the fetal liver.

Metabolic imprinting, programming and epigenetics – a review of present priorities and future opportunities

Metabolic programming and metabolic imprinting describe early life events, which impact upon on later physiological outcomes. Despite the increasing numbers of papers and studies, the distinction between metabolic programming and metabolic imprinting remains confusing. The former can be defined as a dynamic process whose effects are dependent upon a critical window(s) while the latter can be more strictly associated with imprinting at the genomic level. The clinical end points associated with these phenomena can sometimes be mechanistically explicable in terms of gene expression mediated by epigenetics. The predictivity of outcomes depends on determining if there is causality or association in the context of both early dietary exposure and future health parameters. The use of biomarkers is a key aspect of determining the predictability of later outcome, and the strengths of particular types of biomarkers need to be determined. It has become clear that several important health endpoints are impacted upon by metabolic programming/imprinting. These include the link between perinatal nutrition, nutritional epigenetics and programming at an early developmental stage and its link to a range of future health risks such as CVD and diabetes. In some cases, the evidence base remains patchy and associative, while in others, a more direct causality between early nutrition and later health is clear. In addition, it is also essential to acknowledge the communication to consumers, industry, health care providers, policy-making bodies as well as to the scientific community. In this way, both programming and, eventually, reprogramming can become effective tools to improve health through dietary intervention at specific developmental points.

Mechanisms involved in the developmental programming of adulthood disease

There are many instances in life when the environment plays a critical role in the health outcomes of an individual, yet none more so than those experienced in fetal and neonatal life. One of the most detrimental environmental problems encountered during this critical growth period are changes in nutrition to the growing fetus and newborn. Disturbances in the supply of nutrients and oxygen to the fetus can not only lead to adverse fetal growth patterns, but they have also been associated with the development of features of metabolic syndrome in adult life. This fetal response has been termed developmental programming or the developmental origins of health and disease. The present review focuses on the epidemiological studies that identified this association and the importance that animal models have played in studying this concept. We also address the potential mechanisms that may underpin the developmental programming of future disease. It also highlights (i) how developmental plasticity, although beneficial for short-term survival, can subsequently programme glucose intolerance and insulin resistance in adult life by eliciting changes in key organ structures and the epigenome, and (ii) how aberrant mitochondrial function can potentially lead to the development of Type 2 diabetes and other features of metabolic syndrome.

Maternal parity and its effect on adipose tissue deposition and endocrine sensitivity in the postnatal sheep

Maternal parity influences size at birth, postnatal growth and body composition with firstborn infants being more likely to be smaller with increased fat mass, suggesting that adiposity is set in early life. The precise effect of parity on fat mass and its endocrine sensitivity remains unclear and was, therefore, investigated in the present study. We utilised an established sheep model in which perirenal-abdominal fat mass (the major fat depot in the neonatal sheep) increases approximately 10-fold over the first month of life and focussed on the impact of parity on glucocorticoid sensitivity and adipokine expression in the adipocyte. Twin-bearing sheep of similar body weight and adiposity that consumed identical diets were utilised, and maternal blood samples were taken at 130 days of gestation. One offspring from each twin pair was sampled at 1 day of age, coincident with the time of maximal recruitment of uncoupling protein 1 (UCP1), whilst its sibling was sampled at 1 month, when UCP1 had disappeared. Plasma leptin was lower in nulliparous mothers than in multiparous mothers, and offspring of nulliparous mothers possessed more adipose tissue with increased mRNA abundance of leptin, glucocorticoid receptor and UCP2, adaptations that persisted up to 1 month of age when gene expression for interleukin-6 and adiponectin was also raised. The increase in fat mass associated with firstborn status is therefore accompanied by a resetting of the leptin and glucocorticoid axis within the adipocyte. Our findings emphasise the importance of parity in determining adipose tissue development and that firstborn offspring have an increased capacity for adipogenesis which may be critical in determining later adiposity.

Influence of prenatal nutrition and obesity on tissue specific fat mass and obesity-associated (FTO) gene expression

The recent discovery of an association between body composition, energy intake and the fat mass and obesity-associated (FTO) gene represents a promising new therapeutic target in obesity prevention. In a well, pre-established large animal model, we investigated the regulation ofFTOgene expression under conditions either leading to obesity or increased risk of obesity related disorders: i) a sedentary ‘Western’ lifestyle and ii) prenatal exposure to nutrient restriction. Pregnant sheep were either fed to fully meet their nutritional requirements throughout gestation or 50% of this amount from early-to-mid gestation. Following weaning, offspring were either made obese through exposure to a sedentary obesogenic environment or remained lean. A significant positive relationship between placentalFTOgene expression and fetal weight was found at 110 days gestation. In both the newborn and adult offspring, the hypothalamus was the major site ofFTOgene expression. HypothalamicFTOgene expression was upregulated by obesity and was further increased by prenatal nutrient restriction. Importantly, we found a strong negative relationship between the hypothalamicFTOgene expression and food intake in lean animals only that may imply FTO as a novel controller of energy intake. In contrast,FTOgene expression in the heart was downregulated in obese offspring born to nutrient restricted mothers. In addition,FTOgene expression was unaffected by obesity or prenatal diet in insulin-dependent tissues, where it changed with age possibly reflecting adaptations in cellular energetic activity. These findings extend information gained from human epidemiology and provide new insights into the regulation ofin vivoenergy metabolism to prevent obesity.

Adult-onset obesity reveals prenatal programming of glucose-insulin sensitivity in male sheep nutrient restricted during late gestation

BACKGROUND

Obesity invokes a range of metabolic disturbances, but the transition from a poor to excessive nutritional environment may exacerbate adult metabolic dysfunction. The current study investigated global maternal nutrient restriction during early or late gestation on glucose tolerance and insulin sensitivity in the adult offspring when lean and obese.

METHODS/PRINCIPAL FINDINGS

Pregnant sheep received adequate (1.0M; CE, n = 6) or energy restricted (0.7M) diet during early (1-65 days; LEE, n = 6) or late (65-128 days; LEL, n = 7) gestation (term approximately 147 days). Subsequent offspring remained on pasture until 1.5 years when all received glucose and insulin tolerance tests (GTT & ITT) and body composition determination by dual energy x-ray absorptiometry (DXA). All animals were then exposed to an obesogenic environment for 6-7 months and all protocols repeated. Prenatal dietary treatment had no effect on birth weight or on metabolic endpoints when animals were 'lean' (1.5 years). Obesity revealed generalised metabolic 'inflexibility' and insulin resistance; characterised by blunted excursions of plasma NEFA and increased insulin(AUC) (from 133 to 341 [s.e.d. 26] ng.ml(-1).120 mins) during a GTT, respectively. For LEL vs. CE, the peak in plasma insulin when obese was greater (7.8 vs. 4.7 [s.e.d. 1.1] ng.ml(-1)) and was exacerbated by offspring sex (i.e. 9.8 vs. 4.4 [s.e.d. 1.16] ng.ml(-1); LEL male vs. CE male, respectively). Acquisition of obesity also significantly influenced the plasma lipid and protein profile to suggest, overall, greater net lipogenesis and reduced protein metabolism.

CONCLUSIONS

This study indicates generalised metabolic dysfunction with adult-onset obesity which also exacerbates and 'reveals' programming of glucose-insulin sensitivity in male offspring prenatally exposed to maternal undernutrition during late gestation. Taken together, the data suggest that metabolic function appears little compromised in young prenatally 'programmed' animals so long as weight is adequately controlled. Nutritional excess in adulthood exacerbates any programmed phenotype, indicating greater vigilance over weight control is required for those individuals exposed to nutritional thrift during gestation.

Maternal nutrient restriction during early fetal kidney development attenuates the renal innate inflammatory response in obese young adult offspring

Obesity is an independent risk factor for developing chronic kidney disease. Toll-like receptor 4 (TLR4), interleukin (IL)-18, and uncoupling protein 2 (UCP2) are important components of the innate immune system mediating inflammatory renal damage. Early to midgestation maternal nutrient restriction appears to protect the kidney from the deleterious effects of early onset obesity, although the mechanisms remain unclear. We examined the combined effects of gestational maternal nutrient restriction during early fetal kidney development and early onset obesity on the renal innate immune response in offspring. Pregnant sheep were randomly assigned to a normal (control, 100%) or nutrient-restricted (NR, 50%) diet from days 30 to 80 gestation and 100% thereafter. Offspring were killed humanely at 7 days or, following rearing in an obesogenic environment, at 1 yr of age, and renal tissues were collected. IL-18 and TLR4 expression were strongly correlated irrespective of intervention. Seven-day NR offspring had significantly lower relative renal mass and IL-18 mRNA expression. At 1 yr of age, obesity resulted in increased mRNA abundance of TLR4, IL-18, and UCP2, coupled with tubular atrophy and greater immunohistological staining of glomerular IL-6 and medullary tumor necrosis factor (TNF)-alpha. NR obese offspring had a marked reduction of TLR4 abundance and renal IL-6 staining. In conclusion, maternal nutrient restriction during early fetal kidney development attenuates the effects of early onset obesity-related nephropathy, in part, through the downregulation of the innate inflammatory response. A better understanding of maternal nutrition and the in utero nutritional environment may offer therapeutic strategies aimed at reducing the burden of later kidney disease.

The impact of diet during early life and its contribution to later disease: critical checkpoints in development and their long-term consequences for metabolic health

Changes in maternal diet at different stages of reproduction can have pronounced influences on the health and well-being of the resulting offspring, especially following exposure to an obesogenic environment. The mechanisms mediating adaptations in development of the embryo, placenta, fetus and newborn include changes in the maternal metabolic environment. These changes include reductions in a range of maternal counter-regulatory hormones such as cortisol, leptin and insulin. In the sheep, for example, targeted maternal nutrient restriction coincident with the period of maximal placental growth has pronounced effects on the development of the kidney and adipose tissue. As a consequence, the response of these tissues varies greatly following adolescent-onset obesity and ultimately results in these offspring exhibiting all the symptoms of the metabolic syndrome earlier in young adult life. Leptin administration to the offspring after birth can have some long-term differential effects, although much higher amounts are required to cause a response in small compared with large animal models. At the same time, the responsiveness of the offspring is gender dependent, which may relate to the differences in leptin sensitivity around the time of birth. Increasing maternal food intake during pregnancy, either globally or of individual nutrients, has little positive impact on birth weight but does impact on liver development. The challenge now is to establish which components of the maternal diet can be sustainably modified in order to optimise the maternal endocrine environment through pregnancy, thus ensuring feto–placental growth is appropriate in relation to an individual's gender and body composition.

Adipose tissue inflammation: developmental ontogeny and consequences of gestational nutrient restriction in offspring

Increasing adiposity predisposes to the development of the metabolic syndrome, in part, through adipose tissue dysregulation and inflammation. In addition, offspring nutrient-restricted (NR) in utero can exhibit an increased risk of early-onset insulin resistance and obesity, although the mechanisms remain unclear. We aimed to: 1) define adipose tissue ontogeny of key proinflammatory and endoplasmic reticulum stress gene expression from late fetal to early adult life and 2) examine the impact on these genes in gestational nutrient restriction. Pregnant sheep were fed 100% (control) or 50% (NR) of their nutritional requirements between early to mid (28-80 d, term approximately 147 d) or late (110-147 d) gestation. In control offspring, toll-like receptor 4 (TLR4), and the macrophage marker CD68, peaked at 30 d of life before declining. IL-18 peaked at 6 months of age, whereas the endoplasmic reticulum chaperone glucose-regulated protein 78 peaked at birth and subsequently declined through postnatal life. TLR4 and CD68 positively correlated with relative adipose tissue mass and with each other. Early to midgestational NR offspring had decreased abundance of IL-18 at 6 months of age. In late gestational NR offspring, CD68 was significantly lower at birth, a pattern that reversed in juvenile offspring, coupled with increased TLR4 abundance. In conclusion, the in utero nutritional environment can alter the adipose tissue inflammatory profile in offspring. This may contribute to the increased risk of insulin resistance or obesity, dependent on the timing of nutrient restriction. Establishing the optimal maternal diet during pregnancy could reduce the burden of later adult disease in the offspring.

Impact of early onset obesity and hypertension on the unfolded protein response in renal tissues of juvenile sheep

Childhood obesity has reached epidemic proportions. Obesity is an independent risk factor for the development of end-stage renal disease. Endoplasmic reticulum stress and subsequent activation of the unfolded protein response (UPR) are implicated in the development of adipose tissue dysregulation and type 2 diabetes mellitus in obesity. The present study explored the impact of adolescent-onset obesity on the UPR after obesity-related hypertension and nephropathy, using an ovine model in which obesity was induced by increased food intake and reduced activity. Obese young adults had a higher mean arterial pressure (lean, 89.6+/-1.7 mm Hg versus obese, 101+/-3.0 mm Hg; P<0.01) and greater sensitivity to low physiological doses of angiotensin II. Obesity increased the glomerular area and was associated with activation of the UPR in renal cells with a greater abundance of glucose-regulated protein 78, C/EBP homologous protein, Bax, phosphorylated c-Jun amino-terminal kinase, and activating transcription factor 6 (all P<0.05). In addition, there was a marked upregulation of proinflammatory genes, most notably those involved in macrophage signaling. Reactive oxygen species production and handling were also perturbed in obese adults. Renal endoplasmic reticulum stress was positively correlated with macrophage content (r=0.83; P<0.001), phosphorylated c-Jun amino-terminal kinase (r=0.73; P<0.01), and adiposity (r=0.71; P<0.01). In conclusion, adolescent-onset, obesity-related renal endoplasmic reticulum stress was associated with activation of the UPR, apoptosis, and inflammation, potentially increasing the associated renal damage observed in young adults. The UPR may prove to be a useful therapeutic target for the treatment and prevention of obesity-related nephropathy and associated hypertension, thereby reducing the burden of end-stage renal disease.

Early determinants of cardiovascular disease: the role of early diet in later blood pressure control

It is now widely accepted that a gross change in the maternal diet during pregnancy results in offspring with raised blood pressure. More recently, results from human intervention studies and a range of animal experiments have questioned this concept. It thus appears that, when blood pressure is measured directly or by telemetry, the extent to which blood pressure is raised is largely dependent on the magnitude of the postnatal catch-up growth. In addition, such effects can be lost when appropriate corrections are made for current body weight. Consequently, offspring born to nutritionally manipulated mothers can actually have a lower blood pressure than control group offspring. At the same time, studies of the offspring born to contemporary women in developed countries show very little, if any, effect of changes in maternal diet on blood pressure in the offspring when assessed during childhood. In small animal studies, at least, the cardiovascular outcomes linked to small size at birth can differ between the sexes, which may be related in part to differences in kidney function between males and females. With respect to large animal studies, significant effects on blood pressure are less apparent and may relate to the much slower onset of hypertension. The challenge is to use our increased knowledge of the critical windows in early development to optimize later health. One clear priority is the prevention of excess adiposity and to determine how epigenetic mechanisms may provide novel strategies in this regard.

Effect of maternal nutrient restriction from early to midgestation on cardiac function and metabolism after adolescent-onset obesity

Maternal nutrient restriction (NR) from early to midgestation has marked effects on endocrine sensitivity and organ function of the resulting offspring. We hypothesized that early NR may reset the expression profile of genes central to myocardial energy metabolism, influencing ectopic lipid deposition and cardiac function in the obese adult offspring. NR offspring were exposed to an "obesogenic" environment, and their cardiac function and molecular indexes of myocardial energy metabolism were assessed to explore the hypothesis that an obese individual's risk of heart disease may be modified after maternal NR. Pregnant sheep were fed 100% (control) or 50% (NR) energy requirement from days 30 to 80 of gestation and 100% energy requirement thereafter. At weaning, offspring were exposed to an obesogenic environment or remained lean. At approximately 1 yr of age, the hemodynamic response of these offspring to hypotension, together with left ventricular expression profiles of fatty acid-binding protein 3 (FABP3), peroxisome proliferator-activated receptor-gamma (PPARgamma) and its coactivator (PGC)-1alpha, acetyl-CoA carboxylase (ACC), AMP-activated protein kinase (AMPK)-alpha(2), and voltage-dependent anion channel 1 (VDAC1), was determined. Obesity produced left ventricular hypertrophy in all animals, with increased ectopic (myocardial) lipid in NR offspring. Obesity per se significantly reduced myocardial transcript expression of PGC-1alpha, AMPKalpha(2), VDAC1, and ACC and increased expression of PPARgamma and FABP3. However, although NR animals were similarly obese, their transcript expression of ACC, PPARgamma, and FABP3 was similar to that of lean animals, indicating altered cardiac energy metabolism. Indeed, blunted tachycardia and an amplified inotropic response to hypotension characterized cardiac function in obese NR offspring. The results suggest that maternal NR during early organogenesis can precipitate an altered myocardial response to hypotension and increased myocardial lipid deposition in the adult offspring after adolescent-onset obesity, potentially rendering these individuals more at risk of early heart failure as they age.

Nutritional models of the developmental programming of adult health and disease

The ability to not only replicate but also extend the findings from both historical epidemiological studies and contemporary cohorts of the developmental programming of later disease are critical if the mechanisms by which early diet impacts on later disease are to be fully understood. To date, a plethora of models have been established, with the range including global changes in dietary input, imbalanced diets and diets deficient in single nutrients. Key factors in translating these findings to the human situation are the pronounced differences in the relative growth and development between large and small mammals from the time of conception through pregnancy, lactation and weaning. This disparity is reflected in the very different nutritional requirements between species and the substantial divergence between rodents and large animals in the ontogeny of many of the organ systems that are nutritionally regulated. For example, hypothalamic circuitry is much more developed in species with a long gestation and offspring are born with a mature hypothalamic-pituitary axis in sheep and man compared with mice and rats. Similarly, nephron number is established towards the end of gestation in large mammals compared with the lactational period in rats. These types of differences will impact on the ability of individual and combined nutritional interventions to reset developmental processes, and may be further compounded by the gender of a fetus. The challenge for future work in this exciting and dynamic area of research is to utilise these marked comparative differences to generate imaginative nutritional interventions in order to improve the viability, health and well-being of the offspring.

Maternal nutrient restriction between early and midgestation and its impact upon appetite regulation after juvenile obesity

The impact of maternal nutrient restriction during early-to-midgestation, a period coinciding with early fetal brain development, on appetite regulation and energy balance in the offspring after juvenile obesity was examined. Pregnant sheep were either fed to meet fully their nutritional requirements throughout gestation or 50% of this amount between 30 and 80 d gestation. After weaning, offspring were either made obese through exposure to a sedentary obesogenic environment or remained lean. Maternal nutrient restriction had no effect on birth weight or subsequent growth. At 1 wk of age, only, gene expression for neuropeptide Y in the hypothalamus was reduced in nutrient-restricted offspring. By 1 yr of age, all O animals had increased plasma leptin, nonesterified fatty acids, and insulin, with the latter effect amplified in NR offspring. Fasting plasma glucose, triglycerides, and cortisol were unaffected by obesity. The entrained reduction in physical activity that led to obesity persisted when all animals were maintained within individual pens. However, NRO offspring exhibited reduced daily food intake and were, therefore, no longer in positive "energy balance." This adaptation was accompanied by elevated hypothalamic gene expression for the melanocortin-4 and insulin receptors, AMP-activated kinase, and acetyl coenzyme A carboxylase alpha. In conclusion, nutrient restriction specifically targeted over the period of early fetal brain development contributes to a profoundly different adaptation in energy balance after juvenile obesity. The extent to which this adaptive response may benefit the offspring or result in an exacerbated risk of type 2 diabetes remains to be established.

Developmental origins of obesity: programming of food intake or physical activity?

Mans ability to capture, harness and store energy most efficiently as fat in adipose tissue has been an evolutionary success story for the majority of human existence. Only over the last 30-40 years has our remarkable metabolic efficiency been revealed as our energy balance increasingly favours storage without regular periods of depletion. Historical records show us that while the composition of our diet has changed markedly over this time, our overall energy intake has significantly reduced. The inevitable conclusion therefore is that habitual physical activity and thus energy expenditure has reduced by a greater extent. Recent studies have illustrated how the finely tuned long-term control of energy intake and of energy expenditure are both developmentally plastic and susceptible to environmentally-induced change that may persist with that individual throughout their adult life, invariably rendering them more susceptible to greater adipose tissue deposition. The central role that lean body mass has upon the 'gating' of energy sensing and the importance of regular physical activity for its potential to reduce the burden of a 'thrifty phenotype' will be briefly discussed in the present review.

Maternal nutrient restriction during pregnancy differentially alters the unfolded protein response in adipose and renal tissue of obese juvenile offspring

Maternal diet during pregnancy can program an offspring's risk of disease in later life. Obesity adversely alters renal and adipose tissue function, resulting in chronic kidney disease and insulin resistance, respectively, the latter associated with dysregulation of the unfolded protein response (UPR). In view of the current obesity epidemic, we explored the combined effects of in utero early- to midgestational nutrient restriction and postnatal obesity on the UPR in ovine juvenile offspring. Nutrient restriction was coincident with fetal kidney development but prior to exponential adipose tissue deposition. Nutrient restricted (NR) and normal diet (control) offspring were exposed to an obesogenic environment throughout adolescence, resulting in similar degrees of juvenile obesity. NR offspring showed enhanced adipose tissue dysregulation characterized by activation of the UPR, perturbed insulin signaling, and marked inflammation, as demonstrated by increased abundance of crownlike structures and proinflammatory genes. Conversely, in renal tissue NR offspring had marked attenuation of cellular stress and inflammation evident as reduced activation of the UPR, down-regulation of proinflammatory genes, and less histological damage. In conclusion, obesity-related activation of the UPR can be determined by the in utero nutritional environment, demonstrating organ-specific effects dependent on the developmental phase targeted within the fetus.

Differential effects of maternal nutrient restriction through pregnancy on kidney development and later blood pressure control in the resulting offspring

The mechanisms whereby maternal nutritional manipulation through pregnancy result in altered blood pressure in the offspring may include changes in fetal and newborn and adult renal prostaglandin (PG) synthesis, metabolism, and receptor expression. Since the postnatal effects of nutrient restriction on the renal PG synthesis and receptor system during nephrogenesis in conjunction with nephron numbers and blood pressure have not been evaluated in the rat, the present study examined the effect of reducing maternal food intake by 50% of ad libitum through pregnancy on young male rats. Six control-fed mothers and eight nutrient-restricted pregnant rats with single litter mates were used at each sampling time point, most of which occurred during nephrogenesis. Offspring of nutrient-restricted dams were lighter from birth to 3 days. This was accompanied by reduced PGE2, with smaller kidneys up to 14 days. Nutrient restriction also decreased mRNA expression of the PG synthesis enzyme, had little effect on the PG receptors, and increased mRNA expression of the degradation enzyme during nephrogenesis and the glucocorticoid receptor in the adult kidney. These mRNA changes were normally accompanied by similar changes in protein. Nephron number was also reduced from 7 days up to adulthood when blood pressure (measured by telemetry) did not increase as much as in control offspring during the dark, active period. In conclusion, maternal nutrient restriction suppressed renal PG concentrations in the offspring, and this was associated with suppressed kidney growth and development and decreased blood pressure.

Adverse renal consequences of obesity

Emerging evidence indicates that obesity, even in the absence of diabetes, contributes significantly to the development and progression of chronic kidney disease (CKD). Glomerular hyperfiltration/hypertrophy in response to the increased metabolic needs of obesity are postulated to lead to the development of glomerulosclerosis (GS) in a manner analogous to that in reduced renal mass states. Nevertheless, the individual risk for developing GS with obesity is very low. It is proposed that glomerular hyperfiltration/hypertrophy are per se not pathogenic in the absence of an enhanced glomerular blood pressure (BP) transmission, and the modest preglomerular vasodilation that is likely present in the large majority of obese individuals is not sufficient to result in such increased BP transmission. However, in the small subset of obese individuals who are also born with a substantially reduced nephron number, there is a greater risk of enhanced glomerular BP transmission due to the substantially greater preglomerular vasodilation. Of perhaps greater clinical importance, similar additive deleterious effects of obesity on BP transmission would be expected in individuals with reduced renal mass, either congenital or acquired, or with concurrent renal disease, leading to accelerated progression. Of note, a low birth weight may be a risk factor for not only reduced nephron numbers at birth, but also for obesity and hypertension, resulting in a clustering of risk factors for progressive GS. Therefore, even though the individual risk for developing obesity GS is low, the cumulative impact of obesity on the public health burden of CKD is likely to be large because of its huge prevalence.

Measurement of rest and activity in newborn lambs using actigraphy: studies in term and preterm lambs

The present study used actigraphy to monitor rest–activity cycles in lambs. We employed an Actiwatch Activity Monitor, which was secured on the lamb’s neck in 13 term lambs and six preterm lambs. Activity measurements began on the day of delivery and lasted for 7.3 ± 0.7 days. All lambs exhibited bouts of activity, lasting from ~2 to 60 min, separated by periods of inactivity of about equal duration. There was a progressive increase in the frequency and intensity of activity bouts with age, and a decrease in duration. In relation to postnatal age, preterm lambs had a significantly lower frequency and intensity of activity bouts compared with term lambs and significantly longer mean active bout duration. However, in relation to post-conceptual age, preterm animals were less active at birth, but thereafter the trajectory for activity development was steeper compared with the term lambs. These differences between term and preterm lambs may be due to several factors including differences in: (1) the lengths of time the two groups spent in utero and as neonates as a proportion of the perinatal period, which could influence the rate of muscle and bone growth; (2) prenatal and postnatal hormonal profiles; and (3) maternal care. We also found differences in postnatal motility in male and female lambs, with the trajectory of activity increasing in males at Days 4–5, which could be due, in part at least, to sex differences in both prenatal and postnatal hormonal profiles.

Ontogeny and nutritional programming of the hepatic growth hormone-insulin-like growth factor-prolactin axis in the sheep

The liver is an important metabolic and endocrine organ in the fetus, but the extent to which its hormone receptor sensitivity is developmentally regulated in early life is not fully established. Therefore, we examined developmental changes in mRNA abundance for the GH receptor (GHR) and prolactin receptor (PRLR) plus IGF-I and -II and their receptors. Fetal and postnatal sheep were sampled at either 80 or 140 d gestation, 1 or 30 d, or 6 months of age. The effect of maternal nutrient restriction between early gestation to midgestation (i.e. 28-80 d gestation, the time of early liver growth) on gene expression was also examined in the fetus and juvenile offspring. Gene expression for the GHR, PRLR, and IGF-I receptor increased through gestation peaking at birth, whereas IGF-I was maximal near to term. In contrast, IGF-II mRNA decreased between midgestation and late gestation to increase after birth, whereas IGF-II receptor remained unchanged. A substantial decline in mRNA abundance for GHR, PRLR, and IGF-I receptor then occurred up to 6 months. Maternal nutrient restriction reduced GHR and IGF-II receptor mRNA abundance in the fetus, but caused a precocious increase in the PRLR. Gene expression for IGF-I and -II were increased in juvenile offspring born to nutrient-restricted mothers. In conclusion, there are marked differences in the ontogeny and nutritional programming of specific hormones and their receptors involved in hepatic growth and development in the fetus. These could contribute to changes in liver function during adult life.

A fat chance of renal injury

Williams et al. demonstrate in sheep that juvenile obesity per se leads to renal pathology but that prenatal undernutrition effectively abolishes any renal pathology associated with juvenile obesity. These peculiar findings are quite opposite to what has been documented in many epidemiological and animal studies. They provoke questions about how adverse developmental conditions can either support or compromise adaptation to excess nutrient intake and low motor activity later in life.