Lynne Clarke

Influence of Restricted Maternal Nutrition in Early to Mid Gestation on Placental and Fetal Development at Term in Sheep

We investigated the influence of restricted maternal nutrition between 28 and 77 d of gestation on placental weight and appearance, and on fetal weight and conformation. Single-bearing ewes were fed either twice [i.e. controls (n = 19)] or half [i.e. nutrient-restricted (n = 28)] their energy requirements from 28 to 77 d of gestation, after which all ewes were fed to fully meet the energy requirements for maintenance and pregnancy. Close to term (145 ± 1 d) placental weight was higher in the nutrient-restricted group [nutrient-restricted, 416.3 ± 12.6 g; controls, 347.4 ± 17.6 g (p < 0.01)], as was the abundance of everted placentomes. There was no significant difference in total fetal weight, or weights of individual organs between groups, but crown-rump length was significantly greater in lambs born to nutrient-restricted ewes [nutrient-restricted, 50.4 ± 0.4 cm; controls, 48.2 ± 0.6, cm (p < 0.01)]. Fetal to placental weight ratio was lower in the nutrient-restricted group [nutrient-restricted, 9.51 ± 0.23; controls, 10.81 ± 0.39 (p < 0.01)]. A stronger relationship between the total weight of the fetal component of the placental and fetal weight was observed in controls (r2 = 0.50) than in nutrient-restricted ewes (r2 = 0.18). In conclusion, maternal nutrient restriction over the period of rapid placental growth results in a larger placenta and altered placental to fetal weight ratio if ewes are subsequently fed to requirements for the remainder of gestation.

Porcine models for the metabolic syndrome, digestive and bone disorders: a general overview

The aim of this review article is to provide an overview of the role of pigs as a biomedical model for humans. The usefulness and limitations of porcine models have been discussed in terms of metabolic, cardiovascular, digestive and bone diseases in humans. Domestic pigs and minipigs are the main categories of pigs used as biomedical models. One drawback of minipigs is that they are in short supply and expensive compared with domestic pigs, which in contrast cost more to house, feed and medicate. Different porcine breeds show different responses to the induction of specific diseases. For example, ossabaw minipigs provide a better model than Yucatan for the metabolic syndrome as they exhibit obesity, insulin resistance and hypertension, all of which are absent in the Yucatan. Similar metabolic/physiological differences exist between domestic breeds (e.g. Meishan v. Pietrain). The modern commercial (e.g. Large White) domestic pig has been the preferred model for developmental programming due to the 2- to 3-fold variation in body weight among littermates providing a natural form of foetal growth retardation not observed in ancient (e.g. Meishan) domestic breeds. Pigs have been increasingly used to study chronic ischaemia, therapeutic angiogenesis, hypertrophic cardiomyopathy and abdominal aortic aneurysm as their coronary anatomy and physiology are similar to humans. Type 1 and II diabetes can be induced in swine using dietary regimes and/or administration of streptozotocin. Pigs are a good and extensively used model for specific nutritional studies as their protein and lipid metabolism is comparable with humans, although pigs are not as sensitive to protein restriction as rodents. Neonatal and weanling pigs have been used to examine the pathophysiology and prevention/treatment of microbial-associated diseases and immune system disorders. A porcine model mimicking various degrees of prematurity in infants receiving total parenteral nutrition has been established to investigate gut development, amino acid metabolism and non-alcoholic fatty liver disease. Endoscopic therapeutic methods for upper gastrointestinal tract bleeding are being developed. Bone remodelling cycle in pigs is histologically more similar to humans than that of rats or mice, and is used to examine the relationship between menopause and osteoporosis. Work has also been conducted on dental implants in pigs to consider loading; however with caution as porcine bone remodels slightly faster than human bone. We conclude that pigs are a valuable translational model to bridge the gap between classical rodent models and humans in developing new therapies to aid human health.

Maternal nutrition in early-mid gestation and placental size in sheep

We investigated the influence of restricted maternal nutrition between 30 and 80 d gestation on placental growth. Singleton-bearing ewes were fed on either 0.6 (i.e. nutrient restricted) times their energy requirements of 2.25 times this amount (i.e. controls) up to 80 d gestation, when their placentas and fetuses were sampled and analysed. Nutrient-restricted ewes lost body condition score but not body weight and had lower plasma thyroid hormone concentrations than controls, but there were no differences in plasma glucose, non-esterified fatty acids or 3-hydroxybutyrate concentrations between groups. There was no effect of maternal nutrient restriction on fetal weight, conformation or organ weight with the exception of brain weight which was lower nutrient-restricted ewes. Nutrient restriction had no effect on total placental weight, or proportion of inverted placentomes, but was associated with an increased abundance of small placentomes and decreased weight of the fetal but not maternal components of the placenta. Fetal cotyledons form nutrient-restricted ewes also had a lower DNA but higher haemoglobin concentration than those sampled from controls. The plasma concentration of triiodothyronine in umbilical cord plasma was also increased in fetuses from nutrient-restricted ewes. In conclusion, maternal nutrient restriction during early-mid gestation is associated with a smaller placenta.

Effect of maternal cold exposure on brown adipose tissue and thermogenesis in the neonatal lamb.

1. This study examines the effect of chronic cold exposure during pregnancy, induced by winter shearing twin‐bearing ewes 4 weeks before predicted lambing date, on O2 consumption and CO2 production during non‐rapid‐eye‐movement (REM) sleep in lambs maintained for at least 1 h at warm (28‐18 degrees C) and cold (14‐5 degrees C) ambient temperatures at 1, 4, 14 and 30 days of age. This was combined with measurement of the thermogenic activity (GDP binding to uncoupling protein in mitochondrial preparations) of perirenal adipose tissue from lambs immediately after birth and at 33 days of age. 2. Lambs born from shorn (cold‐exposed) ewes were 15% heavier (P < 0.01) and possessed 21% (P < 0.01) more perirenal adipose tissue that contained 40% more protein and mitochondrial protein than unshorn (P < 0.05) controls. Total GDP binding in perirenal adipose tissue was 40% greater (P < 0.05) in lambs born from shorn ewes but there was no difference in lipid content of this tissue between the two groups. 3. At 1 day of age, lambs born from shorn ewes exhibited a 16% higher (P < 0.05) rate of O2 consumption (per kilogram bodyweight) at the warm temperature and a 40% greater metabolic response to the cold ambient temperature. All lambs born from shorn ewes responded to cold exposure without shivering (i.e. via non‐shivering thermogenesis) whilst shivering was measured in four out of seven lambs in the unshorn group. These differences had disappeared by 4 days of age as a result of a 25% increased (P < 0.01) rate of O2 consumption in the warm in lambs born from unshorn ewes and a 20% decrease (P < 0.05) in the response to the cold in lambs from shorn ewes. Shivering during cold exposure was measured in six out of nine lambs born from shorn ewes indicating a rapid alteration in thermoregulatory responses to cold during the first few days of life. 4. The levels of GDP binding and mitochondrial protein in perirenal adipose tissue fell by one‐third in both groups of lambs during the first 33 days of life whereas lipid content either increased or was unchanged. This indicated that brown adipose tissue (BAT) was developing the characteristics of white adipose tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

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°C) or cool (15°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.

Influence of relative size at birth on growth and glucose homeostasis in twin lambs during juvenile life

The effect of differences in size at birth on growth and glucose homeostasis between female twin lambs during juvenile life was examined. Twenty-six sets of twins were entered into the study, of which ten were used for organ sampling at birth and 16 were studied over the first year of life. Eleven sets were defined as being mismatched for birthweight as the weight difference between twins was >25%, with light lambs weighing 4.1 +/- 0.3 kg and heavy lambs weighing 5.1 +/- 0.1 kg. All remaining twins were matched in bodyweight, weighing 4.6 +/- 0.5 kg. During the rapid period of juvenile growth (i.e. one, three and six months of age) and following stabilization of bodyweight (i.e. 12 months of age) glucose tolerance tests were performed by intravenously injecting 0.8 mg kg(-1) bodyweight glucose. This was followed the next day with an insulin tolerance test, performed by intravenously injecting 0.08 units kg(-1) bodyweight insulin. At birth there were no differences in organ weight as a fraction of total bodyweight between matched and mismatched twins, but the ratio of liver to brain weight was lower in light compared with heavy twins. Light lambs remained lighter than their twins up to six months of age, and crown-rump length was also shorter. At one and three months of age there were no differences in basal plasma glucose concentrations between the groups, but glucose tolerance was greater in light compared with heavy lambs at one and six months of age. Insulin tolerance was greater in light compared with matched lambs at one and six months of age. In conclusion, it has been shown that size at birth of one twin in relation to its co-twin is one factor determining glucose regulation during postnatal life. This not only affects glucose and insulin tolerance but also growth over the first six months of age.

Delivery by Caesarean section, rather than vaginal delivery, promotes hepatic steatosis in piglets

There has been a marked increase in the number of babies born by elective CS (Caesarean section). Following CS, the lack of normal stimuli that occur at birth alters the thermogeneic response, but any effects on hepatic metabolism have not been identified. In the present study, we compared the effect of delivery on hepatic metabolism in piglets, born either by CS or VD (vaginal delivery) and fed by TPN (total parenteral nutrition), by measuring lipid metabolism and enzyme activity coupled with metabolomic and genomic approaches. Hepatic lipid in the CS piglets at 7 days post-partum was in excess of 5 mg/g of liver consistent with hepatic steatosis, whereas in the VD piglets the amount of lipid was markedly lower (3 mg/g of liver) and below the threshold for a diagnosis of steatosis. Metabolomic analysis indicated that CS resulted in higher hepatic glycerol and lower glycerol phosphate dehydrogenase activity, suggesting that CS causes a decrease in hepatic gluconeogenesis from glycerol. CS also resulted in altered cholesterol handling and gene expression, despite the same dietary intake for 7 days post-partum. Furthermore, the CS piglets had a lower expression of interferon-responsive genes, but a higher expression of markers of immature hepatocytes. In conclusion, the results suggest that VD promotes normal liver maturation and hepatic metabolism, thereby reducing the accumulation of hepatic lipid.

The Influence of Piglet Birth Weight on Physical and Behavioural Development in Early Life

The objective of this study was to determine whether body weight at birth influences the physical and behavioural development of the neonatal pig. Sixteen sows and their litters were randomly allocated into four treatment groups. From the normal distribution curve of their birth weight, piglets were sub-divided into three groups: (1) low (<10th percentile) (2) normal (10–90th percentile) and (3) high (>90th percentile).To assess behavioural development, each litter was exposed to a ball placed in the creep area for a period of 1,800 s, and evaluated once over a 3-day period starting on either 5, 7, 14 or 21 days of postnatal life. Their response to, and interaction with, an object was used to calculate a numerical index of piglet behavioural development. Teat order was calculated following observations during consecutive suckling on days 11, 13 and 15 of life, and dominance hierarchy was assessed on day 12, 14 and 16. Individual body weight was recorded on days 0, 5, 7, 14 and 21 of postnatal life. Statistical differences between groups were analysed using general linear model, analysis of variance. Regression analyses were used to determine relationships between physical and behavioural development with teat order and dominance. There was a significant (p < 0.001) relationship between birth weight, growth performance and behavioural development. Behavioural developmental index (BDI) significantly improved (p < 0.001) with age and was also influenced by the day on which the ball was introduced (p < 0.01). Body weight on day 1 of the test was significantly (p < 0.001) correlated to BDI and age at test. Piglets demonstrating compensatory growth were more dominant and exhibited an improved behavioural developmental score than their slower growing littermates. In conclusion, compromised growth in utero can have a detrimental effect on the physical and behavioural development of the neonate. Animals with an enhanced developmental index in conjunction with a higher dominance value exhibited a improved neonatal growth performance.

Effect of |[beta]|3-Adrenergic Agonist (Zeneca D7114) on Thermoregulation in Near-Term Lambs Delivered by Cesarean Section

We investigated the effect of a β3-adrenergic agonist, Zeneca D7114, on thermoregulation in near-term lambs delivered by cesarean section. Lambs were delivered into a cool ambient temperature of 15°C, and between 60 and 80 min of life were given an oral dose of Zeneca D7114 (10 mg·kg body weight-1) dissolved in 20 mL of milk, or milk alone. During the first 0.5 h of life colonic temperature decreased in all lambs, and then increased to plateau levels (39.6-40.4°C) after 120-150 min of life, in 19 out of 23 lambs studied. In the remaining lambs, colonic temperature failed to return to normothermic values, plateauing at 34.3°C. All control lambs were observed to shiver throughout the study, but after Zeneca D7114 treatment 7 out of 10 normothermic lambs stopped shivering, and plateau colonic temperature was 0.8°C higher. Hypothermic β3-agonist-treated lambs had significantly lower rates of heat production, breathing frequency, and plasma triiodothyronine and cortisol concentrations than normothermic lambs. The level of GDP binding and norepinephrine content of brown adipose tissue (BAT) sampled from hypothermic β3-agonist-treated lambs was significantly lower than in normothermic lambs. There was no difference in GDP binding in BAT between control and Zeneca D7114-treated groups, but the Hb content was higher in the latter group. It is concluded that administration of Zeneca D7114 to euthroid lambs enhances their ability to thermoregulate and restore colonic temperature without altering the thermogenic activity of BAT. This response may be mediated by increasing blood flow to BAT and/or an improvement in the animals thermal efficiency (i.e. decreased heat loss) due to a reduced reliance on shivering thermogenesis.

Fatty Acid Composition of the Maternal Diet During the First or the Second Half of Gestation Influences the Fatty Acid Composition of Sows’ Milk and Plasma, and Plasma of Their Piglets

Dietary supplements of olive oil (OO) or fish oil (FO) during the first (G1: day 1–60) or second half of gestation (G2: day 60 to term, day 115) were offered to pregnant sows. The proportion of fatty acids in milk and plasma were determined by gas chromatography. When supplements were given during G1, the proportions of oleic acid (OA) and arachidonic acid (AA) in the plasma were higher in the OO group than in the FO group, whereas docosahexaenoic acid (DHA) was higher in the latter group at day 56 of gestation. These differences in plasma DHA were still apparent at day 7 of lactation. Similarly, DHA was also higher in the colostrum and milk on days 3 and 21 of lactation and in the plasma of piglets from FO dams compared to the OO group, whereas AA was lower. When the FO supplement was given during G2, AA was lower and DHA higher in the plasma at day 105 of gestation and at day 7 of lactation compared with the OO group. Likewise, DHA was greater in FO than in OO animals during lactation in colostrum and in milk on days 3 and 21 of lactation, and in 3-day old suckling piglets plasma, whereas AA was lower in these animals. Thus, maternal adipose tissue plays an important role in the storage of dietary long-chain polyunsaturated fatty acids (LCPUFA) during G1. They are mobilized around parturition for milk synthesis, and an excess of dietary n-3 LCPUFA decreases the availability of AA in suckling newborns.