Impact of maternal dietary fat supplementation during gestation upon skeletal muscle in neonatal pigs.

BACKGROUND: Maternal diet during pregnancy can modulate skeletal muscle development of the offspring. Previous studies in pigs have indicated that a fat supplemented diet during pregnancy can improve piglet outcome, however, this is in contrast to human studies suggesting adverse effects of saturated fats during pregnancy. This study aimed to investigate the impact of a fat supplemented (palm oil) "high fat" diet on skeletal muscle development in a porcine model. Histological and metabolic features of the biceps femoris muscle obtained from 7-day-old piglets born to sows assigned to either a commercial (C, n = 7) or to an isocaloric fat supplementation diet ("high fat" HF, n = 7) during pregnancy were assessed. RESULTS: Offspring exposed to a maternal HF diet demonstrated enhanced muscular development, reflected by an increase in fractional growth rate, rise in myofibre cross-sectional area, increased storage of glycogen and reduction in lipid staining of myofibres. Although both groups had similar intramuscular protein and triglyceride concentrations, the offspring born to HF mothers had a higher proportion of arachidonic acid (C20:4n6) and a reduction in α-linolenic acid (C18:3n3) compared to C group offspring. The HF group muscle also exhibited a higher ratio of C20:3n6 to C20:4n6 and total n-6 to n-3 in conjunction with up-regulation of genes associated with free fatty acid uptake and biogenesis. CONCLUSION: In conclusion, a HF gestational diet accelerates the maturation of offspring biceps femoris muscle, reflected in increased glycolytic metabolism and fibre cross sectional area, differences accompanied with a potential resetting of myofibre nutrient uptake.

An exploration of student experiences of using biology podcasts in nursing training.

BACKGROUND: Students regard biological science as one of the most difficult components of the nursing curriculum. However, a good understanding of this area is essential for effective nursing practice. The aim of this study was to explore nursing students' perceptions of the usefulness of supplementary biology podcasts for their learning. METHODS: Biological science podcasts (n=9) were made available to first-year nursing students (n=189) as supplementary learning tools. On completion of their first year, students were asked to complete a survey which investigated the frequency of their podcast use, reasons for use and their perception of the usefulness of podcasts as a learning tool. 153 of these students participated in the survey study (80.9%). Two focus groups were conducted with students (n=6) to gain a detailed understanding of student experiences of the usefulness of the podcasts for their learning. RESULTS: Survey data demonstrated that most students (71%) accessed at least one podcast. The majority of students who reported accessing podcasts agreed that they were useful as learning tools (83%), revision aids (83%) and that they helped promote understanding of course materials (72%). Focus group participants discussed how they found podcasts especially useful in terms of revision. Students valued being able to repeatedly access the lecture materials, and appreciated having access to podcasts from a range of lecturers. Focus group members discussed the benefits of live recordings, in terms of valuing the information gleaned from questions asked during the lecture sessions, although there were concerns about the level of background noise in live recordings. Lack of awareness of the availability of podcasts was an issue raised by participants in both the survey component and the focus groups and this negatively impacted on podcast use. CONCLUSIONS: Nursing students found the availability of biology podcasts helpful for their learning. Successful implementation of these tools to support learning requires teaching staff to understand and promote the importance of these tools.

Using Audience Response Technology to provide formative feedback on pharmacology performance for non-medical prescribing students--a preliminary evaluation.

BACKGROUND: The use of anonymous audience response technology (ART) to actively engage students in classroom learning has been evaluated positively across multiple settings. To date, however, there has been no empirical evaluation of the use of individualised ART handsets and formative feedback of ART scores. The present study investigates student perceptions of such a system and the relationship between formative feedback results and exam performance. METHODS: Four successive cohorts of Non-Medical Prescribing students (n=107) had access to the individualised ART system and three of these groups (n=72) completed a questionnaire about their perceptions of using ART. Semi-structured interviews were carried out with a purposive sample of seven students who achieved a range of scores on the formative feedback. Using data from all four cohorts of students, the relationship between mean ART scores and summative pharmacology exam score was examined using a non-parametric correlation. RESULTS: Questionnaire and interview data suggested that the use of ART enhanced the classroom environment, motivated students and promoted learning. Questionnaire data demonstrated that students found the formative feedback helpful for identifying their learning needs (95.6%), guiding their independent study (86.8%), and as a revision tool (88.3%). Interviewees particularly valued the objectivity of the individualised feedback which helped them to self-manage their learning. Interviewees' initial anxiety about revealing their level of pharmacology knowledge to the lecturer and to themselves reduced over time as students focused on the learning benefits associated with the feedback.A significant positive correlation was found between students' formative feedback scores and their summative pharmacology exam scores (Spearman's rho = 0.71, N=107, p<.01). CONCLUSIONS: Despite initial anxiety about the use of individualised ART units, students rated the helpfulness of the individualised handsets and personalised formative feedback highly. The significant correlation between ART response scores and student exam scores suggests that formative feedback can provide students with a useful reference point in terms of their level of exam-readiness.

Audience response technology: engaging and empowering non-medical prescribing students in pharmacology learning.

BACKGROUND: Non-medical prescribing (NMP) is a six month course for nurses and certain allied health professionals. It is critical that these students develop a good understanding of pharmacology; however, many students are mature learners with little or no formal biological science knowledge and struggle with the pharmacology component. The implications for patient safety are profound, therefore we encourage students not just to memorise enough pharmacology to pass the exam but to be able to integrate it into clinical practice. Audience response technology (ART), such as the KeePad system (KS) has been shown to promote an active approach to learning and provide instant formative feedback. The aim of this project, therefore, was to incorporate and evaluate the use the KS in promoting pharmacology understanding in NMP students. METHODS: Questions were incorporated into eight pharmacology lectures, comprising a mix of basic and clinical pharmacology, using TurningPoint software. Student (n = 33) responses to questions were recorded using the KS software and the percentage of students getting the question incorrect and correct was made immediately available in the lecture in graphical form. Survey data collected from these students investigated student perceptions on the use of the system generally and specifically as a learning tool. More in depth discussion of the usefulness of the KS was derived from a focus group comprising 5 students. RESULTS: 100% of students enjoyed using the KS and felt it promoted their understanding of key concepts; 92% stated that it helped identify their learning needs and 87% agreed that the technology was useful in promoting integration of concepts. The most prevalent theme within feedback was that of identifying their own learning needs. Analysis of data from the focus group generated similar themes, with the addition of improving teaching. Repeated questioning produced a significant increase (p < 0.05) in student knowledge of specific pharmacological concepts. CONCLUSIONS: The use of ART enhanced non-medical prescribing students' experience of pharmacology teaching. Student perceptions were that this system increased their ability to identify learning needs and promoted understanding and integration of concepts. Students also reported that the technology aided exam revision and reduced associated anxiety.

Influence of porcine genotype on the abundance of thyroid hormones and leptin in sow milk and its impact on growth, metabolism and expression of key adipose tissue genes in offspring.

Neonatal mortality is greater in commercial porcine genotypes, compared with the ancient Meishan breed that rapidly lay down adipose tissue; this may be related to hormones, such as triiodothyronine (T(3)) or leptin. Leptin is present in maternal milk; however, the extent to which this supply provides the neonate with leptin is unknown, but may play a role in growth and development. We investigated whether thyroid hormones and leptin concentrations in maternal milk differed between genotypes; and whether this influenced piglet concentrations or expression of genes involved in adipose tissue regulation. Eight Meishan and six commercial sows were entered into the study and milk samples from the day of parturition to day 4 postpartum was taken daily. The median birth weight piglet in each litter had a daily venous blood sample taken and was euthanised on day 4. Gene expressions of IGF-I, IGF-binding protein 3 (IGFBP-3), peroxisome proliferators activated receptor (PPAR)gamma and glucocorticoid receptor (GR) were measured in adipose tissue using real-time PCR. T(3) was increased in Meishan milk, but not in piglet plasma. Milk thyroxine was similar between breeds but commercial piglet levels were significantly higher. Leptin was higher in commercial sow milk throughout the study. Milk leptin was strongly correlated to plasma leptin during the first postnatal days and also to organ and body weight in Meishan piglets that also had significantly higher expression of GR, but not IGF-I, IGFBP-3 or PPARgamma. In conclusion, we have found a significant disparity in the provision of thyroid hormones in Meishan and commercial sow's milk. These changes are not always translated to plasma concentrations of hormone in the piglet. Leptin appears to have a stronger role in growth and development in the Meishan genotype compared with commercial; along with the increased GR expression, this may also represent a potential mechanism behind the rapid accumulation of adipose tissue in Meishan piglets.

Differential effects of leptin on thermoregulation and uncoupling protein abundance in the neonatal lamb.

As the role of leptin in energy balance in neonate is unknown, we investigated the effect of acute (2 h) and chronic (7 days) administration of leptin (100 microg/day) on thermoregulation and mitochondrial protein abundance in adipose tissue. The concentration of uncoupling protein (UCP)1 and voltage-dependent anion channel (VDAC) located on the inner and outer mitochondrial membranes, respectively, were measured. Administration of leptin prevented the normal decline in colonic temperature over the first few hours and days after birth. It subsequently accelerated the loss of both mRNA and protein for UCP1 but had no effect on VDAC abundance. At seven days of age, colonic temperature was correlated strongly with both mRNA abundance and thermogenic potential of UCP1 in leptin-treated but not control lambs, indicating more effective use of UCP1 for heat production following leptin administration. Leptin had no effect on weight gain or adipose tissue deposition; at one day of age only, leptin mRNA was correlated positively with adipose tissue weight. In conclusion, leptin administration to neonatal lambs improves thermoregulation and promotes the loss of UCP1 in brown adipose tissue.

Nutrient availability, the microbiome, and intestinal transport during pregnancy.

Adequate adaptation of the gastrointestinal tract is important during pregnancy to ensure that the increased metabolic demands by the developing fetus are met. These include changes in surface area mediated by villus hypertrophy and enhanced functional capacity of individual nutrient receptors, including those transporting glucose, fructose, leucine, and calcium. These processes are regulated either by the enhanced nutrient demand or are facilitated by changes in the secretion of pregnancy hormones. Our review also covers recent research into the microbiome, and how pregnancy could lead to microbial adaptations, which are beneficial to the mother, yet are also similar to those seen in the metabolic syndrome. The potential role of diet in modulating the microbiome during pregnancy, as well as the potential for the intestinal microbiota to induce pregnancy complications, are examined. Gaps in the current literature are highlighted, including those where only historical evidence is available, and we suggest areas that should be a priority for further research. In summary, although a significant degree of adaptation has been described, there are both well-established processes and more recent discoveries, such as changes within the maternal microbiome, that pose new questions as to how the gastrointestinal tract effectively adapts to pregnancy, especially in conjunction with maternal obesity.

UCP1 is present in porcine adipose tissue and is responsive to postnatal leptin.

Intrauterine growth restriction (IUGR) may be accompanied by inadequate thermoregulation, especially in piglets that are not considered to possess any brown adipose tissue (BAT) and are thus entirely dependent on shivering thermogenesis in order to maintain body temperature after birth. Leptin can stimulate heat production by promoting non-shivering thermogenesis in BAT, but whether this response occurs in piglets is unknown. Newborn female piglets that were characterised as showing IUGR (mean birth weight of approximately 0.98 kg) were therefore administered injections of either saline or leptin once a day for the first 5 days of neonatal life. The dose of leptin was 0.5 mg/kg, which is sufficient to increase plasma leptin by approximately tenfold and on the day of birth induced a rapid increase in body temperature to values similar to those of normal-sized 'control' piglets (mean birth weight of ∼1.47 kg). Perirenal adipose tissue was then sampled from all offspring at 21 days of age and the presence of the BAT-specific uncoupling protein 1 (UCP1) was determined by immunohistochemistry and immunoblotting. UCP1 was clearly detectable in all samples analysed and its abundance was significantly reduced in the IUGR piglets that had received saline compared with controls, but was raised to the same amount as in controls in those IUGR females given leptin. There were no differences in gene expression between primary markers of brown and white adipose tissues between groups. In conclusion, piglets possess BAT that when stimulated exogenously by leptin can promote increased body temperature.

Molecular characterization of adipose tissue in the African elephant (Loxodonta africana).

Adipose tissue (AT) is a dynamic and flexible organ with regulatory roles in physiological functions including metabolism, reproduction and inflammation; secreted adipokines, including leptin, and fatty acids facilitate many of these roles. The African elephant (Loxodonta africana) is experiencing serious challenges to optimal reproduction in captivity. The physiological and molecular basis of this impaired fertility remains unknown. AT production of leptin is a crucial molecular link between nutritional status, adiposity and fertility in many species. We propose that leptin has a similar function in the African elephant. African elephant visceral and subcutaneous adipose tissue (AT) was obtained from both sexes and a range of ages including females with known pregnancy status. RNA was extracted and histological sections created and analyzed by microarray, PCR and immunohistochemistry respectively. Gas-chromatography was used to determine the fatty acid composition of AT. Microarray expression profiling was used to compare gene expression profiles of AT from pre-pubertal versus reproductively competent adult African elephants. This study demonstrates, for the first time, leptin mRNA and protein expression in African elephant AT. The derived protein sequence of the elephant leptin protein was exploited to determine its relationship within the class I helical cytokine superfamily, which indicates that elephant leptin is most closely related to the leptin orthologs of Oryctolagus cuniculus (European rabbit), Lepus oiostolus (woolly hare), and members of the Ochotonidae (Pika). Immunohistological analysis identified considerable leptin staining within the cytoplasm of adipocytes. Significant differences in fatty acid profiles between pregnant and non-pregnant animals were revealed, most notably a reduction in both linoleic and α linoleic acid in pregnant animals. This report forms the basis for future studies to address the effect of nutrient composition and body condition on reproduction in captive and wild elephants.

The health implications of birth by Caesarean section.

Since the first mention of fetal programming of adult health and disease, a plethora of programming events in early life has been suggested. These have included intrauterine and postnatal events, but limited attention has been given to the potential contribution of the birth process to normal physiology and long-term health. Over the last 30 years a growing number of studies have demonstrated that babies born at term by vaginal delivery (VD) have significantly different physiology at birth to those born by Caesarean section (CS), particularly when there has been no exposure to labour, i.e. pre-labour CS (PLCS). This literature is reviewed here and the processes involved in VD that might programme post-natal development are discussed. Some of the effects of CS are short term, but longer term problems are also apparent. We suggest that VD initiates important physiological trajectories and the absence of this stimulus in CS has implications for adult health. There are a number of factors that might plausibly contribute to this programming, one of which is the hormonal surge or "stress response" of VD. Given the increasing incidence of elective PLCS, an understanding of the effects of VD on normal development is crucial.

Reduced neonatal mortality in Meishan piglets: a role for hepatic fatty acids?

The Meishan pig breed exhibits increased prolificacy and reduced neonatal mortality compared to commercial breeds, such as the Large White, prompting breeders to introduce the Meishan genotype into commercial herds. Commercial piglets are highly susceptible to hypoglycemia, hypothermia, and death, potentially due to limited lipid stores and/or delayed hepatic metabolic ability. We therefore hypothesized that variation in hepatic development and lipid metabolism could contribute to the differences in neonatal mortality between breeds. Liver samples were obtained from piglets of each breed on days 0, 7, and 21 of postnatal age and subjected to molecular and biochemical analysis. At birth, both breeds exhibited similar hepatic glycogen contents, despite Meishan piglets having significantly lower body weight. The livers from newborn Meishan piglets exhibited increased C18∶1n9C and C20∶1n9 but lower C18∶0, C20∶4n6, and C22∶6n3 fatty acid content. Furthermore, by using an unsupervised machine learning approach, we detected an interaction between C18∶1n9C and glycogen content in newborn Meishan piglets. Bioinformatic analysis could identify unique age-based clusters from the lipid profiles in Meishan piglets that were not apparent in the commercial offspring. Examination of the fatty acid signature during the neonatal period provides novel insights into the body composition of Meishan piglets that may facilitate liver responses that prevent hypoglycaemia and reduce offspring mortality.

Animal models for the study of the developmental origins of health and disease.

Human epidemiological studies have indicated that the risk of developing non-communicable diseases in later life may be related to exposures during the developmental period. Developmental life is a vulnerable period of the lifespan during which adverse environmental factors have the potential to disturb the processes of cell proliferation and differentiation or to alter patterns of epigenetic remodelling. Animal models have been instrumental in demonstrating the biological plausibility of the associations observed in human populations, providing proof of principle to the theory of the developmental origins of health and disease (DOHaD). A variety of large- and small-animal models have made important contributions to the field, providing strong evidence of a causal relationship between early-life exposures and metabolic risk factors in later life. Studies of animal models are continuing to contribute to improving the understanding of the mechanisms of the developmental origins of disease. All models have their advantages and disadvantages, and the model that is most appropriate for any particular study is hypotheses dependent. The present review aims to briefly summarise the contributions that animal models have made to the DOHaD field, before reviewing the strengths and weaknesses of these animal models. It is proposed that the integration of evidence from a variety of different models is required for the advancement of understanding within the field.

Early programming of adipose tissue function: a large-animal perspective.

The emerging role of adipose tissue as a dynamic endocrine organ with an extent of anatomical and physiological plasticity has generated numerous studies linking early-life events with long-term alterations in adipose tissue structure and function. Coupled with increasing rates of human obesity, which cannot be explained without some genetic component, the role of early programming of adipose tissue may provide an insight into potential mechanisms. The developmental origins of health and disease hypothesis investigates the potential association between a compromised fetal and postnatal environment and later disease, such as obesity and type 2 diabetes, in the offspring. A number of animal models have been developed to examine potential mechanisms that drive these physiological changes, including rodent and large-mammal models that provide mechanistic insights into the epidemiological findings. In utero challenges such as under- or over-provision of nutrients, placental insufficiency and glucocorticoid infusion, as well as postnatal nutritional challenges, can all result in the long-term programming of adipose tissue abundance and function. A range of hormones, enzymes, transcription factors and other metabolic signalling molecules have been implicated in adverse adipose tissue development, including leptin, glucocorticoids, members of the PPAR family, fatty acid-binding proteins and adipokines. The long-term structural and physiological consequences associated with these molecular and cellular changes are less well described. The experimental models, potential mechanisms and regulators of the early programming of adipose tissue in large mammalian species will be summarised in the present review.

Differential effects of thyroid hormone manipulation and beta adrenoceptor agonist administration on uncoupling protein mRNA abundance in adipose tissue and thermoregulation in neonatal pigs.

We have shown that there is significant disparity in the expression of uncoupling proteins (UCP) 2 and 3 between modern-commercial and ancient-Meishan porcine genotypes, commercial pigs also have higher plasma triiodothyronine (T(3)) in on the first day of life. T(3) and the sympathetic nervous system are both known to regulate UCPs in rodents and humans; their role in regulating these proteins in the pig is unknown. This study examined whether thyroid hormone manipulation or administration of a selective beta3 adrenoceptor agonist (ZD) influenced plasma hormones, colonic temperature and UCP expression in adipose tissue of two breeds of pig. To mimic the differences observed in thyroid hormone status, piglets from Meishan and commercial litters were randomly assigned to control (1 ml/kg water), T(3) (10 mg/kg) (Meishan only), methimazole (a commonly used antithyroid drug) (50 mg/kg) (commercial only) or ZD (10 mg/kg) oral administration for the first 4 days of postnatal life. Adipose tissue UCP2/3 mRNA abundance was measured on day 4 using PCR. T(3) administration raised plasma T(3) concentrations and increased colonic temperature on day 4. UCP3 mRNA abundance was higher in Meishan, than commercial piglets (p = 0.042) and was downregulated following T(3) administration (p = 0.014). Irrespective of genotype, ZD increased UCP2 mRNA abundance (Meishan p = 0.05, commercial p = 0.03). Expression of neither UCP2 nor 3 was related to colonic temperature, regardless of treatment. In conclusion, we have demonstrated a dissociation between thyroid hormones and the sympathetic nervous system in the regulation of UCPs in porcine adipose tissue. We have also suggested that expression of adipose tissue UCP2 and 3 are not related to body temperature in piglets.

Maternal nutritional programming of fetal adipose tissue development: long-term consequences for later obesity.

As obesity reaches epidemic levels in the United States there is an urgent need to understand the developmental pathways leading to this condition. Obesity increases the risk of hypertension and diabetes, symptoms of which are being seen with increased incidence in children. Adipocyte development begins in the fetus and, in contrast to all other tissues whose growth ceases in late juvenile life, it has the capacity for "unlimited" growth. In normal healthy individuals, the increase in fat mass with age is accompanied by a parallel increase in cortisol sensitivity, i.e., increased glucocorticoid receptor abundance and increased activity of the enzyme 11beta hydroxysteroid dehydrogenase type 1. Enhanced adipocyte sensitivity to cortisol is promoted in offspring born to mothers that were nutrient-restricted in utero in conjunction with increased peroxisome proliferator activated receptor alpha. This adaptation only appears to be associated with greater fat mass in the offspring when maternal nutrient restriction is confined to late gestation, coincident with the period of maximal fetal growth. In these offspring, increased fat mass is accompanied by glucose intolerance and insulin resistance, in conjunction with an adipose tissue specific reduction in glucose transporter 4 abundance. In conclusion, changes in maternal and, therefore, fetal nutrient supply at specific stages of gestation have the potential to substantially increase the risk of those offspring becoming obese in later life. The extent to which changes in dietary habits, both during pregnancy and in later life, may act to contribute to the current explosion in childhood and adult obesity remains a scientific and public health challenge to us all.

Ontogeny and nutritional programming of adiposity in sheep: potential role of glucocorticoid action and uncoupling protein-2.

Increased glucocorticoid action and adipose tissue inflammation contribute to excess adiposity. These adaptations may be enhanced in offspring exposed to nutrient restriction (NR) in utero, thereby increasing their susceptibility to later obesity. We therefore determined the developmental ontogeny of glucocorticoid receptor (GR), 11beta-hydroxysteroid dehydrogenase (11betaHSD) types 1 and 2, and uncoupling protein (UCP)-2 mRNA in perirenal adipose tissue between late gestation and 6 mo after birth in the sheep, as well as the effect of maternal NR targeted between early to mid (28-80 days, term approximately 147 days)- or late (110-147 days) gestation. GR and 11betaHSD1 mRNA increased with fat mass and were all maximal within the 6-mo observation period. 11betaHSD2 mRNA abundance demonstrated a converse decline, whereas UCP2 peaked at 30 days. GR and 11betaHSD1 mRNA abundance were strongly correlated with total and relative perirenal adipose tissue weight, and UCP2 was strongly correlated with GR and 11betaHSD1 mRNA. Early- to midgestational NR increased GR, 11betaHSD1, and UCP2 mRNA, but decreased 11betaHSD2 mRNA abundance, an adaptation reversed with late-gestational NR. We conclude that the continual rise in glucocorticoid action and fat mass after birth may underlie the development of later obesity. The magnitude of this adaptation is partly dependent on maternal food intake through pregnancy.

Influence of size at birth on the endocrine profiles and expression of uncoupling proteins in subcutaneous adipose tissue, lung, and muscle of neonatal pigs.

Epidemiological studies suggest that infants of low birth weight show poor neonatal growth and increased susceptibility to adult diseases such as diabetes and lung disease. Uncoupling protein 2 and 3 (UCP2 and UCP3) have been implicated in the development of such diseases; pigs provide an ideal model to examine the influence of birth weight due to the natural variance in piglet weight within a litter. This study examined whether birth weight influences the expression of UCP2 and UCP3 in adipose tissue, skeletal muscle, and lung. Piglets from 11 litters were ranked according to birth weight and three from each litter assigned to small (SFD), normal (NFD), or large for dates (LFD) groups. Blood samples and morphometric measurements were taken over the first 14 days of life, and tissue samples were taken on day 7 or 14. Plasma hormone and metabolite concentrations and the expression of UCP2 and UCP3 mRNA in adipose tissue, skeletal muscle, and lung were measured. UCP2 and UCP3 expression in adipose tissue was lower in the SFD compared with the LFD group on day 7. UCP3 expression in skeletal muscle was higher than that of adipose tissue. Lung UCP2 and skeletal muscle UCP3 mRNA expression were unaffected by size at birth. Regression analysis indicated that UCP3 expression was differentially associated with IGF-1, leptin, and insulin. In conclusion, low birth weight is associated with tissue-specific effects on UCP expression. It remains to be established whether these subsequently contribute to pathological conditions such as diabetes.

Ambient temperature, maternal dexamethasone, and postnatal ontogeny of leptin in the neonatal lamb.

The influence of route of delivery, ambient temperature, maternal dexamethasone treatment, and postnatal age on plasma concentrations of leptin or leptin mRNA abundance in perirenal adipose tissue was examined from 6-h-old lambs, born vaginally or delivered by cesarean section into warm (30 degrees C) or cool (15 degrees C) ambient temperatures, and from cesarean section-delivered lambs whose mothers had been treated with dexamethasone beginning 2 d before parturition. The ontogeny of leptin during the first month of postnatal life was also examined. In lambs born into a cool ambient temperature, but not in those born to dexamethasone-treated mothers, leptin mRNA abundance decreased within 6 h of birth. Plasma concentrations of leptin decreased during the first 6 h of life, an adaptation delayed by cesarean section birth. After the first day of postnatal life, both plasma concentrations of leptin and its mRNA increased to peak at 7 d of age and were positively correlated with each other, as well as with whole-body and perirenal adipose tissue weights. A similar relationship was not observed after 7 d of age, as plasma leptin declined despite an increase in adipose tissue weight. In conclusion, route of delivery, ambient temperature, or maternal dexamethasone therefore delays the rate of leptin disappearance after birth. Concomitantly, leptin abundance was only associated with body and adipose tissue weights for 1 week after birth, which may be coincident with the onset of peak lactation and the time at which nutrient supply should no longer be limiting to the neonate.

Differential effects of fetal number and maternal nutrition in late gestation on prolactin receptor abundance and adipose tissue development in the neonatal lamb.

The present study examined the extent to which abundance of the prolactin receptor (PRLR) and a range of primary mitochondrial proteins are influenced by either maternal nutrition and/or fetal number in adipose tissue. Pregnant sheep were control fed [consuming 100% of total metabolizable energy (ME) requirements (taking into account requirements for both ewe maintenance and growth of the conceptus to produce a 4.5-kg lamb at term) for that stage of gestation] or were nutrient restricted (consuming 60% of total ME requirements). All ewes lambed normally at term and both perirenal adipose and hepatic tissues were sampled within 6 h of birth. Plasma membranes and mitochondria were prepared and analyzed using immunoblotting for abundance of PRLR and/or cytochrome c, voltage-dependent anion channel (VDAC), and uncoupling protein-1 (UCP1). Irrespective of maternal nutrition, abundance of specific isoforms of PRLR were significantly higher in adipose tissue sampled from twins compared with singletons and total UCP1 concentration per milligram of tissue was increased (p < 0.05). There was no effect of fetal number on PRLR abundance in the liver. Maternal nutrient restriction resulted in an increased abundance of both cytochrome c (p < 0.001) and VDAC in adipose tissue of twins but not singletons. This occurred despite maternal nutrition having no effect on either lamb body or adipose tissue weights, although both were lower (p < 0.05) in twins compared with singletons. In conclusion, fetal adipose tissue development is highly sensitive to nutritionally mediated changes in late gestation. An increase in fetal number results in greater PRLR abundance, which, in conjunction with a decrease in maternal nutrition, results in up-regulation of specific mitochondrial proteins.