Fishing in the stream of diabetes: from measuring insulin to the control of fetal organogenesis

Pathways linking the early environment to long-term health and lifespan

The intrauterine environment is a major contributor to normal physiological growth and development of an individual. Disturbances at this critical time can affect the long-term health of the offspring. Low birth weight individuals have strong correlations with increased susceptibility to type 2 diabetes and cardiovascular disease in later-life. These observations led to the Thrifty Phenotype Hypothesis which suggested that these associations arose because of the response of a growing fetus to a suboptimal environment such as poor nutrition. Animal models have shown that environmentally induced intrauterine growth restriction increases the risk of a variety of diseases later in life. These detrimental features are also observed in high birth weight offspring from mothers who were obese or consumed a high fat diet during gestation. Recent advances in our understanding of the mechanisms underlying this phenomenon have elucidated several potential candidates for the long-term effects of the early environment on the function and metabolism of a cell. These include: (1) Epigenetic alterations (e.g. DNA methylation and histone modifications), which regulate specific gene expression and can be influenced by the environment, both during gestation and early postnatal life and (2) Oxidative stress that changes the balance between reactive oxygen species generation (e.g. through mitochondrial dysfunction) and antioxidant defense capacity. This has permanent effects on cellular ageing such as regulation of telomere length. Further understanding of these processes will help in the development of therapeutic strategies to increase healthspan and reduced the burden of age-associated diseases.

Taurine supplementation restored the changes in pancreatic islet mitochondria in the fetal protein-malnourished rat

Intra-uterine growth retardation has been linked to the development of type 2 diabetes in later life. Mitochondrial changes have been suggested as a link between fetal malnutrition and adult insulin resistance. Taurine has been implicated in this process. We investigated whether protein malnutrition in early life alters mitochondria of the pancreatic islets in adulthood, and whether taurine supplementation restores these changes. Male offspring of rats fed a control diet, a low-protein diet or a low-protein diet supplemented with taurine during pregnancy and lactation were weaned onto the control diet. In each group, at 20 weeks of age, intravenous glucose tolerance tests, euglycaemic–hyperinsulinaemic clamp studies, morphometric analysis of the pancreatic islets and ultra-structural analysis of the mitochondria of the β-cells were performed. The expressions of cytochrome c oxidase (COX) I and mitochondrial respiratory chain complex II were also measured. Fetal protein-malnourished rats showed decreased pancreatic islet mass and reduced insulin-secretory responses to a glucose load. These rats also showed reduced mitochondrial DNA-encoded COX I gene expression in the islets. Electron microscopic examination showed abnormal mitochondrial shapes in the β-cells of fetal protein-malnourished rats. Taurine supplementation to the low-protein diet restored all these changes. Our findings indicate that a maternal protein-restriction diet causes long-lasting mitochondrial changes that may contribute to the development of type 2 diabetes later in life. The lack of taurine may be a key causative factor for these dysfunctional mitochondrial changes.

Non-catch-up growth in intrauterine growth-retarded rats showed glucose intolerance and increased expression of PDX-1 mRNA

BACKGROUND

  Children born with intrauterine growth retardation (IUGR) show long-term complications like non-catch-up growth and type 2 diabetes. We hypothesize that the duration of malnutrition influences the growth and pancreatic development in IUGR. The pancreatic duodenal homeobox-1 (PDX-1) expression might also be different because it links glucose metabolism to the regulation of insulin gene transcription in the pancreas.

METHODS

  We made an IUGR rat model with a low-protein diet (8% casein) during gestational periods. Catch-up rats (CU) were given normal lab chow immediately after birth. Non-catch-up rats (NCU) were given normal lab chow after lactation periods. PDX-1 mRNA level, islet areas and intravenous glucose tolerance test (IVGTT) were assessed in each group and compared with control rats (C) at the 16th week.

RESULTS

  The weight and length of CU and C rats were not different after 3 weeks, while NCU rats were smaller than C and CU rats (P < 0.05). In IVGTT, the 20-min and 50-min glucose level and area under the curve for glucose were increased in NCU rats compared with those values in C and CU rats (P < 0.05). The islet area of NCU rats was smaller than that of C and CU rats (P < 0.05). In contrast, PDX-1 mRNA levels of NCU rats were higher than those of C rats (P < 0.05). CU rats showed normal glucose response in IVGTT with increased islet number and size.

CONCLUSIONS

  IUGR rats that failed to undergo catch-up growth might be prone to abnormal glucose tolerance, decreased islet size, and increased PDX-1 mRNA levels in early adult life.

Energetic basis of correlation between catch-up growth, health maintenance, and aging

Catch-up growth, referring to infants with low birth weight reaching or exceeding normal body weight later in life, is negatively correlated to adult health outcome and life span. Life history theories have suggested that there exist trade-offs between early development and later health maintenance, but detailed mechanisms and the currency of the trade-off are unclear. In this paper, we present a general theoretical model for quantitatively elucidating the trade-off between growth rate and health maintenance in mammals from an energetic viewpoint. Based on the fundamental principles of energy conservation and organisms' energy budgets, our model analyzes the allocation of metabolic energy to growth and health maintenance in different sets of prenatal and postnatal environments. Our model also implies a relationship between growth rate and the general process of aging. Life-span predictions are supported by quantitative and qualitative empirical observations and offer theoretical frameworks for future experimental designs and data analyses.

Leptin-independent programming of adult body weight and adiposity in mice

Low birth weight and rapid postnatal weight gain are independent and additive risk factors for the subsequent development of metabolic disease. Despite an abundance of evidence for these associations, mechanistic data are lacking. The hormone leptin has received significant interest as a potential programming factor, because differences in the profile of leptin in early life have been associated with altered susceptibility to obesity. Whether leptin alone is a critical factor for programming obesity has, until now, remained unclear. Using the leptin-deficient ob/ob mouse, we show that low birth weight followed by rapid catch-up growth during lactation (recuperated offspring) leads to a persistent increase in body weight in adult life, both in wild-type and ob/ob animals. Furthermore, recuperated offspring are hyperphagic and epididymal fat pad weights are significantly increased, reflecting greater adiposity. These results show definitively that factors other than leptin are crucial in the programming of energy homeostasis in this model and are powerful enough to alter adiposity in a genetically obese strain.

Maternal malnutrition programs pancreatic islet mitochondrial dysfunction in the adult offspring

Accumulating evidence has shown that maternal malnutrition increases the risk of metabolic disease in the progeny. We previously reported that prenatal exposure to a low-protein diet (LP) leads to mitochondrial dysfunction in pancreatic islets from adult rodent offspring that could relate physiological and cellular alterations due to early diet. We aim to determine whether mitochondrial dysfunction could be a common consequence of prenatal nutritional unbalances. Pregnant Wistar rats received either a global food restriction (GFR), consisting in the reduction by 50% of the normal daily food intake, or a high-fat diet (HF) throughout gestation. GFR or HF diet during pregnancy leads to a lack of increase in insulin release and ATP content in response to glucose stimulation in islets from 3-month-old male and female offspring. These similar consequences originated from impairment in either glucose sensing or glucose metabolism, depending on the type of early malnutrition and on the sex of the progeny. Indeed, the glucose transport across β-cell membrane seemed compromised in female HF offspring, since GLUT-2 gene was markedly underexpressed. Additionally, for each progeny, consequences downstream the entry of glucose were also apparent. Expression of genes involved in glycolysis, TCA cycle and oxidative phosphorylations was altered in GFR and HF rats in a sex- and diet-dependent manner. Moreover, prenatal malnutrition affected the regulators of mitochondrial biogenesis, namely, PPAR coactivator 1 alpha (PGC-1α), since its expression was higher in islets from GFR rats. In conclusion, programming of mitochondrial dysfunction is a consequence of maternal malnutrition, which may predispose to glucose intolerance in the adult offspring.

Maternal protein restriction during pregnancy and lactation in rats imprints long-term reduction in hepatic lipid content selectively in the male offspring

Maternal protein restriction during pregnancy and lactation reduces whole body lipid stores and alters lipid homeostasis in the adult offspring. Lipid homeostasis in the body is regulated, in part, by the liver via the metabolic processes of synthesis and utilization of lipids. The present study tested the hypothesis that maternal protein restriction will imprint changes in hepatic lipid metabolism and thereby alter the hepatic lipid content of the adult offspring. Pregnant rats were fed purified diets containing 19% protein (control group) or 8% protein (low-protein group) throughout pregnancy and lactation. On day 28, pups from both groups were weaned onto regular laboratory chow. On days 65 and 150, male and female pups from each litter in both groups were killed and blood and liver collected. Maternal protein restriction was found to reduce birth weight and produce long-term reduction in the body weight of the offspring. On day 65, liver triglyceride content was decreased by 40% in the male offspring that were fed a low-protein diet. The reduction in liver triglyceride content persisted until day 150, at which time it was accompanied by decreases in hepatic cholesterol content. No such changes were observed in the female offspring. To determine if the alterations in liver lipid content resulted in compensatory changes in liver carbohydrate stores, hepatic glycogen content was measured in male offspring. Hepatic glycogen content was similar between the 2 groups on days 65 and 150. In conclusion, the present study in rats showed that maternal protein restriction during pregnancy and lactation imprints long-term changes in hepatic lipid content selectively in the male offspring.

Early life nutrition and metabolic programming

Research investigating the early programming of adult metabolic disease has in recent years provided much mechanistic insight into how the early environment impacts on long-term health. It includes studies addressing the roles of intrauterine nutrient availability, which is determined by maternal nutrition, maternal exposure to oxygen, toxic events, and infection; the placental interface; and also the early postnatal environment. This review will explore the epidemiological evidence for programming of metabolic disease and provide an overview of the various studies using animals to model metabolic phenotypic outcome. It will also discuss evidence for the proposed molecular mechanisms and the potential for intervention.

Hyperlipidic hypercholesterolemic diet in prepubertal rabbits affects gene expression in the embryo, restricts fetal growth and increases offspring susceptibility to obesity

Maternal hypercholesterolemia has been shown to lead to fetal intra-uterine growth retardation (IUGR) in rabbits. The effects of a long term maternal hyperlipidemic and hypercholesterolemic diet on embryo, fetal and post-natal development, have not been addressed so far. Rabbit does were fed either a hypercholesterolemic (0.2%) hyperlipidic (8%) (HH) or a control (C) diet from 10 weeks of age. Sixteen does (N = 8 HH and N = 8 C) were euthanized at 18 weeks to assess the effect of the diet on dams before mating. Embryos from 18 females (N = 9 HH and N = 9 C) were collected from the oviducts at the 16-20 cell stage (embryonic genome activation stage) for gene expression analysis (micro array and quantitative RT-PCR). Thirty females (N = 16 HH and N = 14 C) were mated naturally and fetal growth was monitored by ultrasound. Six of them (N = 4 HH and N = 2 C) were euthanized at D28 of gestation to collect fetuses and placentas. Finally, the remaining 24 does delivered at term and litters were cross fostered and equilibrated in number to create 4 groups according to the biological dam and the foster dam (C-C, C-HH, HH-C, HH-HH). Growth was monitored until weaning. A subset of 26 offspring from the 4 groups was fed the control diet until 25 weeks of age and then fed the HH diet for three weeks. All does had similar growth rates and bodyweight. Transcriptomic analyses evidenced an overexpression of Adipophilin in HH embryos at the stage of embryonic genome activation. This was confirmed by quantitative RT-PCR. During pregnancy, IUGR was observed from D9 by ultrasound and subsequently, fetal weight at 28 days, birthweight and fat deposition in newborn offspring were significantly decreased in HH (P < 0.05). After weaning, there was no significant difference for weight between HH-HH and HH-C offspring and both groups became significantly heavier (P < 0.0001) than C-C and C-HH offspring. During the 3 weeks when offspring were fed the HH diet, the differences in feed intake were no longer significant between groups but the differences in body weight remained. At post-mortem, offspring from HH does had significantly more abdominal and inter-scapular fat than offspring from C does (P < 0.05). These data illustrate the importance of maternal nutrition before and during gestation in the establishment and control of the growth trajectory of the conceptus and in the onset of disease in adult life.

Poor maternal nutrition leads to alterations in oxidative stress, antioxidant defense capacity, and markers of fibrosis in rat islets: potential underlying mechanisms for development of the diabetic phenotype in later life

Low birth weight is associated with glucose intolerance, insulin resistance, and type 2 diabetes (T2D) in later life. Good evidence indicates that the environment plays an important role in this relationship. However, the mechanisms underlying these relationships are defined poorly. Islets are particularly susceptible to oxidative stress, and this condition combined with fibrosis is thought to be instrumental in T2D pathogenesis. Here we use our maternal low-protein (LP) rat model to determine the effect of early diet on oxidative stress and fibrosis in pancreatic islets of male offspring at 3 and 15 mo of age. Islet xanthine oxidase (XO) expression was increased in 15-mo LP offspring, which suggests increased oxidative-stress. Manganese superoxide-dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), and heme oxygenase-1 (HO-1) (antioxidant enzymes) were reduced significantly in LP offspring, which indicated impairment of oxidative defense. Expression of fibrosis markers collagen I and collagen III also increased in 15-mo LP offspring. Angiotensin II receptor type I (AT(II)R(1)), induced by hyperglycemia and oxidative-stress, was significantly up-regulated in 15-mo LP offspring. Lipid peroxidation was also increased in 15-mo LP animals. We conclude that maternal protein restriction causes age-associated increased oxidative stress, impairment of oxidative defense, and fibrosis. These findings provide mechanisms by which suboptimal early nutrition can lead to T2D development later in life.

Elevated insulin sensitivity in low-protein offspring rats is prevented by a high-fat diet and is associated with visceral fat

This study tests the hypothesis that a high-fat postnatal diet increases fat mass and reduces improved insulin sensitivity (IS) found in the low-protein model of maternal undernutrition. Offspring from Wistar dams fed either a 20% (control (CON)) or 8% (low protein (LP)) protein diet during gestation and lactation were randomly assigned to a control (con) or cafeteria (caf) diet at weaning (21 days) until 3 months of age at which point IS was measured (hyperinsulinemic-euglycemic clamp). Fat mass, growth, energy intake (EI) and expenditure (EE), fuel utilization, insulin secretion, and leptin and adiponectin levels were measured to identify a possible role in any changes in IS. IS was increased in LP-con in comparison to CON-con animals. Cafeteria feeding prevented this increase in LP animals but had no effect in CON animals (insulin-stimulated glucose infusion rates (GIRs; mg/min/kg); CON-con: 13.9 +/- 1.0, CON caf: 12.1 +/- 2.1, LP-con: 25.4 +/- 2.0, LP-caf: 13.7 +/- 3.7, P < 0.05). CON-caf animals had similar percent epididymal white adipose tissue (%EWAT; CON-con: 1.71 +/- 0.09 vs. CON-caf: 1.66 +/- 0.08) and adiponectin (microg/ml: CON-con: 4.61 +/- 0.34 vs. CON-caf: 3.67 +/- 0.18) except hyperinsulinemia and relative hyperleptinemia in comparison to CON-con. Differently, LP-caf animals had increased %EWAT (LP-con: 1.11 +/- 0.06 vs. LP-caf: 1.44 +/- 0.08, P < 0.05) and adiponectin (microg/ml: LP-con: 5.38 +/- 0.39 vs. LP-caf: 3.75 +/- 0.35, P < 0.05) but did not show cafeteria-induced hyperinsulinemia or relative hyperleptinemia. An increased propensity to store visceral fat in LP animals may prevent the elevated IS in LP offspring.

Mechanisms of developmental programming of the metabolic syndrome and related disorders

There is consistent epidemiological evidence linking low birth weight, preterm birth and adverse fetal growth to an elevated risk of the metabolic syndrome (obesity, raised blood pressure, raised serum triglycerides, lowered serum high-density lipoprotein cholesterol and impaired glucose tolerance or insulin resistance) and related disorders. This “fetal or developmental origins/programming of disease” concept is now well accepted but the “programming” mechanisms remain poorly understood. We reviewed the major evidence, implications and limitations of current hypotheses in interpreting developmental programming and discuss future research directions. Major current hypotheses to interpret developmental programming include: (1) thrifty phenotype; (2) postnatal accelerated or catch-up growth; (3) glucocorticoid effects; (4) epigenetic changes; (5) oxidative stress; (6) prenatal hypoxia; (7) placental dysfunction; and (8) reduced stem cell number. Some hypothetical mechanisms (2, 4 and 8) could be driven by other upstream “driver” mechanisms. There is a lack of animal studies addressing multiple mechanisms simultaneously and a lack of strong evidence linking clinical outcomes to biomarkers of the proposed programming mechanisms in humans. There are needs for (1) experimental studies addressing multiple hypothetical mechanisms simultaneously; and (2) prospective pregnancy cohort studies linking biomarkers of the proposed mechanisms to clinical outcomes or surrogate biomarker endpoints. A better understanding of the programming mechanisms is a prerequisite for developing early life interventions to arrest the increasing epidemic of the metabolic syndrome, type 2 diabetes and other related disorders.

Effect of late gestation low protein supply to mink (Mustela vison) dams on reproductive performance and metabolism of dam and offspring

Protein malnutrition in utero that induces permanent changes in metabolism has been investigated intensively in various animals in recent years, but to the best of our knowledge, not yet in the mink, a strict carnivore. In the present study, minks were fed either a low-protein (LP) diet, i.e., with a protein:fat:carbohydrate ratio of 14:51:35% of metabolisable energy (ME), or an adequate-protein diet (AP), i.e. 29:56:15% of ME, from when implantation was completed until parturition (17.9 +/- 3.6 days). Respiration and balance experiments were performed during both gestation and lactation. Plasma concentrations of leptin, IGF-1, and insulin were determined by radioimmunoassay; the relative abundances of glucose-6-phosphatase (G-6-Pase), fructose-1,6-bisphosphatase (Fru-1,6-P2ase), phosphoenol-pyruvate carboxykinase (PEPCK), and pyruvate kinase (PKM2) were determined in liver, and abundances of adiponectin and leptin in adipose tissue were determined by real-time quantitative PCR (q PCR). The protein supply only affected quantitative metabolism traits during the period of differentiated feeding. The dietary composition was reflected in the nitrogen metabolism and substrate oxidation, but no effects remained during lactation. The LP dams tended to have a smaller liver mass in relation to body weight than did AP dams (2.5% vs. 2.9%; p = 0.09), significantly less leptin mRNA (p < 0.05), and 30.6% fewer kits per mated female (p = 0.03). Furthermore, F1-generation kits exposed to protein restriction during foetal life (FLP1; 10.3 g) had a lower birth weight (p = 0.004) than did F1-generation kits exposed to adequate protein (FAP1; 11.3 g). Differences remained significant until 21 days of age (120.4 g vs. 127.6 g; p = 0.005). The FLP1 foetuses displayed a lower abundance of Fru-1,6-P2ase mRNA (p = 0.007) and of PKM2 mRNA (p = 0.002) than did FAP1 foetuses. Whether these changes during foetal life cause permanent changes in the glucose homeostasis of the offspring and result in the transmission of epigenetic phenotypic changes, as seen in the rat, needs further investigation.

Gestational and postnatal low protein diet alters insulin sensitivity in female rats

Nutrition during pregnancy and lactation can program an offspring's metabolism with regard to glucose and lipid homeostasis. A suboptimal environment during fetal, neonatal and infant development is associated with impaired glucose tolerance, type 2 diabetes and insulin resistance in later adult life. However, studies on the effects of a low protein diet imposed from the beginning of gestation until adulthood are scarce. This study's objective was to investigate the effects of a low protein diet imposed from the gestational period until 4 months of age on the parameters of glucose tolerance and insulin responsiveness in Wistar rats. The rats were divided into a low protein diet group and a control group and received a diet with either 7% or 25% protein, respectively. After birth, the rats received the same diet as their mothers, until 4 months of age. In the low protein diet group it was observed that: (i) the hepatic glycogen concentration and hepatic glycogen synthesis from glycerol were significantly greater than in the control group; (ii) the disposal of 2-deoxyglucose in soleum skeletal muscle slices was 29.8% higher than in the control group; (iii) there was both a higher glucose tolerance in the glucose tolerance test; and (iv) a higher insulin responsiveness in than in the control group. The results suggest that the low protein diet animals show higher glucose tolerance and insulin responsiveness relative to normally nourished rats. These findings were supported by the higher hepatic glycogen synthesis and the higher disposal of 2-deoxyglucose in soleum skeletal muscle found in the low protein diet rats.

Effects of early malnutrition on mental system, metabolic syndrome, immunity and the gastrointestinal tract

The notion of how malnutrition early in life affects ontogenesis has evolved considerably since the mid-1960s. Since then, there have been many studies on the effects of early malnutrition. Nutritional and metabolic exposure during critical periods in early human and animal development may have long-term programming effects in adulthood. This is supported by evidence from epidemiological studies, numerous animal models and clinical intervention trials. In this paper, we review the effects of early malnutrition on cognitive function, metabolic syndrome, immunity and the gastrointestinal tract, as well as possible underlying mechanisms, and consider diarrhoeal disease and poor cognitive function as examples for understanding the interrelation of the harmful effects caused by early malnutrition. Previous studies on early malnutrition have mainly concentrated on humans and rats. Therefore, the main aim of the present review was to give animal scientists a clear understanding of the harmful effects of early malnutrition on animal growth and animal production, and to help identify appropriate feeding techniques to prevent early malnutrition.

Maternal low-protein diet alters pancreatic islet mitochondrial function in a sex-specific manner in the adult rat

Mitochondrial dysfunction may be a long-term consequence of a poor nutritional environment during early life. Our aim was to investigate whether a maternal low-protein (LP) diet may program mitochondrial dysfunction in islets of adult progeny before glucose intolerance ensues. To address this, pregnant Wistar rats were fed isocaloric diets containing either 20% protein (control) or 8% protein (LP diet) throughout gestation. From birth, offspring received the control diet. The mitochondrial function was analyzed in islets of 3-mo-old offspring. Related to their basal insulin release, cultured islets from both male and female LP offspring presented a lower response to glucose challenge and a blunted ATP production compared with control offspring. The expression of malate dehydrogenase as well as the subunit 6 of the ATP synthase encoded by mitochondrial genome (mtDNA) was lower in these islets, reducing the capacity of ATP production through the Krebs cycle and oxidative phosphorylation. However, mtDNA content was unchanged in LP islets compared with control. Several consequences of protein restriction during fetal life were more marked in male offspring. Only LP males showed an increased reactive oxygen species production associated with a higher expression of mitochondrial subunits of the electron transport chain NADH-ubiquinone oxireductase subunit 4L, an overexpression of peroxisome proliferator-activated receptor-gamma and uncoupling protein-2, and a strongly reduced beta-cell mass. In conclusion, mitochondrial function is clearly altered in islets from LP adult offspring in a sex-specific manner. That may provide a cellular explanation for the earlier development of glucose intolerance in male than in female offspring of dams fed an LP diet.

Prenatal stress, glucocorticoids and the programming of adult disease

Numerous clinical studies associate an adverse prenatal environment with the development of cardio-metabolic disorders and neuroendocrine dysfunction, as well as an increased risk of psychiatric diseases in later life. Experimentally, prenatal exposure to stress or excess glucocorticoids in a variety of animal models can malprogram offspring physiology, resulting in a reduction in birth weight and subsequently increasing the likelihood of disorders of cardiovascular function, glucose homeostasis, hypothalamic–pituitary–adrenal (HPA) axis activity and anxiety-related behaviours in adulthood. During fetal development, placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) provides a barrier to maternal glucocorticoids. Reduced placental 11β-HSD2 in human pregnancy correlates with lower birth weight and higher blood pressure in later life. Similarly, in animal models, inhibition or knockout of placental 11β-HSD2 lowers offspring birth weight, in part by reducing glucose delivery to the developing fetus in late gestation. Molecular mechanisms thought to underlie the programming effects of early life stress and glucocorticoids include epigenetic changes in target chromatin, notably affecting tissue-specific expression of the intracellular glucocorticoid receptor (GR). As such, excess glucocorticoids in early life can permanently alter tissue glucocorticoid signalling, effects which may have short-term adaptive benefits but increase the risk of later disease.

Exposure of the pregnant rat to low protein diet causes impaired glucose homeostasis in the young adult offspring by different mechanisms in males and females

The understanding of the mechanisms by which gender dimorphisms are involved in the modulation of insulin sensitivity and glucose tolerance can be crucial to unravel the development of type 2 diabetes. Rats treated with a low protein diet (LP, 8% protein content) during pregnancy and lactation have a reduced beta-cell mass at birth and a reduced insulin secretion at weaning. In this study we examined the effect of LP diet on glucose homeostasis from birth to adulthood when offspring previously exposed to LP were subsequently switched to control diet (C, 20% protein content) at weaning. The LP group had a reduced body weight after weaning compared to the C-fed rats, although their food intake was not significantly different. Furthermore, LP males had a significant increase in visceral adiposity relative to their body weight (P < 0.05). Intraperitoneal glucose tolerance test (IGTT) showed that glucose clearance was unchanged until 130 days of age when LP-fed females showed elevated blood glucose compared to C, despite similar plasma insulin levels. Females also demonstrated a significant reduction in mean pancreatic islet number, individual islet size and beta cell mass. However, no differences in IGTT or islet morphometry were observed in LP males, although basal insulin levels were twofold higher. Akt phosphorylation in response to insulin was reduced in adipose and skeletal muscle of adult rats following exposure to LP diet in early life when compared to control-fed animals, but this was only apparent in males. Plasma testosterone levels were also reduced in males at 130 days age. These data suggest that the development of impaired glucose homeostasis in offspring of LP-fed rats is likely to occur by different mechanisms in males and females.

The timing of "catch-up growth" affects metabolism and appetite regulation in male rats born with intrauterine growth restriction

Epidemiological studies demonstrated a relationship between low birth weight mainly caused by intrauterine growth restriction (IUGR) and adult metabolic disorders. The concept of metabolic programming centers on the idea that nutritional and hormonal status during the key period of development determines the long-term control of energy balance by programming future feeding behavior and energy expenditure. The present study examined the consequence of early or late "catch-up growth" after IUGR on feeding behavior and metabolic cues of male offspring of rat dams exposed to protein restriction during gestation and/or lactation. Our results suggest that early catch-up growth may be favorable for fasting metabolic parameters at weaning, as no differences were observed on plasma leptin, triglyceride, glucose, and insulin levels compared with controls. In contrast, if pups remained malnourished until weaning, low insulin concentration was detected and was accompanied by hyperphagia associated with a large increase in hypothalamic NPY and AgRP mRNA expression. At adult age, on a regular chow diet, only the meal structure was modified by fetal programming. The two IUGR groups demonstrated a reduced meal duration that enhanced the speed of food ingestion and consequently increased the rest period associated to the satiety state without changes in the hypothalamic expression of appetite neuropeptides. Our findings demonstrate that in IUGR, regardless of postnatal growth magnitude, metabolic programming occurred in utero and was responsible for both feeding behavior alteration and postprandial higher insulin level in adults. Additionally, catch-up growth immediately after early malnutrition could be a key point for the programming of postprandial hyperleptinemia.

Early low protein diet aggravates unbalance between antioxidant enzymes leading to islet dysfunction

BACKGROUND

Islets from adult rat possess weak antioxidant defense leading to unbalance between superoxide dismutase (SOD) and hydrogen peroxide-inactivating enzymatic activities, catalase (CAT) and glutathione peroxidase (GPX) rending them susceptible to oxidative stress. We have shown that this vulnerability is influenced by maternal diet during gestation and lactation.

METHODOLOGY/PRINCIPAL FINDINGS

The present study investigated if low antioxidant activity in islets is already observed at birth and if maternal protein restriction influences the development of islet antioxidant defenses. Rats were fed a control diet (C group) or a low protein diet during gestation (LP) or until weaning (LPT), after which offspring received the control diet. We found that antioxidant enzymatic activities varied with age. At birth and after weaning, normal islets possessed an efficient GPX activity. However, the antioxidant capacity decreased thereafter increasing the potential vulnerability to oxidative stress. Maternal protein malnutrition changed the antioxidant enzymatic activities in islets of the progeny. At 3 months, SOD activity was increased in LP and LPT islets with no concomitant activation of CAT and GPX. This unbalance could lead to higher hydrogen peroxide production, which may concur to oxidative stress causing defective insulin gene expression due to modification of critical factors that modulate the insulin promoter. We found indeed that insulin mRNA level was reduced in both groups of malnourished offspring compared to controls. Analyzing the expression of such critical factors, we found that c-Myc expression was strongly increased in islets from both protein-restricted groups compared to controls.

CONCLUSION AND SIGNIFICANCE

Modification in antioxidant activity by maternal low protein diet could predispose to pancreatic islet dysfunction later in life and provide new insights to define a molecular mechanism responsible for intrauterine programming of endocrine pancreas.

Periconceptional undernutrition of ewes impairs glucose tolerance in their adult offspring

Maternal undernutrition throughout pregnancy can have long-term effects on the health of adult offspring. Undernutrition around the time of conception alters growth, metabolism, and endocrinology of the sheep fetus, but the impact on offspring after birth is largely unknown. We determined the effect of maternal periconceptional undernutrition in sheep on glucose tolerance in the offspring before and after puberty. Undernourished (UN) ewes were fed individually to maintain weight loss of 10-15% bodyweight from 61 d before until 30 d after mating. Offspring (24 UN, 30 control) underwent an i.v. glucose tolerance test at 4 and 10 mo of age. Glucose tolerance was similar in both groups at 4 mo. Insulin area under the curve increased by 33% between 4 and 10 mo (101 +/- 8 versus 154 +/- 12 ng x min x mL(-1), p < 0.0001). At 10 mo, UN offspring had a 10% greater glucose area under the curve than controls (809 +/- 22 versus 712 +/- 20 mM x min, p < 0.01), a reduced first phase insulin response (p = 0.003) which was particularly apparent in females and in singletons, and a decreased insulin:glucose ratio (p = 0.01). We conclude that maternal undernutrition around the time of conception results in impaired glucose tolerance in postpubertal offspring.

Maternal protein restriction affects postnatal growth and the expression of key proteins involved in lifespan regulation in mice

We previously reported that maternal protein restriction in rodents influenced the rate of growth in early life and ultimately affected longevity. Low birth weight caused by maternal protein restriction followed by catch-up growth (recuperated animals) was associated with shortened lifespan whereas protein restriction and slow growth during lactation (postnatal low protein: PLP animals) increased lifespan. We aim to explore the mechanistic basis by which these differences arise. Here we investigated effects of maternal diet on organ growth, metabolic parameters and the expression of insulin/IGF1 signalling proteins and Sirt1 in muscle of male mice at weaning. PLP mice which experienced protein restriction during lactation had lower fasting glucose (P = 0.038) and insulin levels (P = 0.046) suggesting improved insulin sensitivity. PLP mice had higher relative weights (adjusted by body weight) of brain (P = 0.0002) and thymus (P = 0.031) compared to controls suggesting that enhanced functional capacity of these two tissues is beneficial to longevity. They also had increased expression of insulin receptor substrate 1 (P = 0.021) and protein kinase C zeta (P = 0.046). Recuperated animals expressed decreased levels of many insulin signalling proteins including PI3 kinase subunits p85alpha (P = 0.018), p110beta (P = 0.048) and protein kinase C zeta (P = 0.006) which may predispose these animals to insulin resistance. Sirt1 protein expression was reduced in recuperated offspring. These observations suggest that maternal protein restriction can affect major metabolic pathways implicated in regulation of lifespan at a young age which may explain the impact of maternal diet on longevity.

Nutritional models of type 2 diabetes mellitus

In order to better understand the events which precede and precipitate the onset of type 2 diabetes (T2DM) several nutritional animal models have been developed. These models are generated by manipulating the diet of either the animal itself or its mother during her pregnancy and, in comparison to traditional genetic and knock out models, have the advantage that they more accurately reflect the aetiology of human T2DM. This chapter will discuss some of the most widely used nutritional models of T2DM: Diet-induced obesity (DIO) in adult rodents, and studies of prenatal and postnatal nutrition in offspring of mothers fed a low-protein diet or overnourished during pregnancy. Several common mechanisms have been identified through which these nutritional manipulations can lead to metabolic disease, including pancreatic beta-cell dysfunction, impaired insulin signalling in skeletal muscle and the excess accumulation of visceral adipose tissue and consequent deposition of non-esterified fatty acids in peripheral tissues resulting in peripheral insulin resistance. The following chapter will discuss each of these nutritional models, their application and relationship to human aetiology, and will highlight the important insights these models have provided into the pathogenesis of T2DM.

Postnatal nutrition alters body composition in adult offspring exposed to maternal protein restriction

The insulin-like growth factor (IGF) system is altered with intra-uterine growth retardation and in adult metabolic disease. The aim of the present study was to observe effects of continued protein restriction on the IGF-I system and body composition in offspring of mothers fed a low-protein (LP) diet. Offspring from Wistar dams fed either a 20 % (CON) or 8 % (LP) protein diet during gestation and lactation were studied at birth, 10 d, weaning and at 12 weeks after maintenance on either the 8 % (lp) or 20 % (con) protein diet from weaning. LP offspring had reduced weaning weights (P < 0·05) and reduced serum insulin (P < 0·005). Serum IGF-I (P < 0·001) and acid-labile subunit (ALS) (P < 0·0001) were reduced at 10 and 21 d. Hepatic expression of IGF-I (P < 0·05) and ALS (P < 0·005) were reduced at 10 and 21 d. IGF binding protein (IGFBP)-1 hepatic expression was elevated at 10 d (P < 0·001) but not at 21 d. Adult LP-con offspring had reduced body weight (P < 0·05), lean (P < 0·0001) and bone (P < 0·0001) but not fat (P = 0·6) mass with no persistent effects on IGF-I, ALS and IGFBP-1.Postnatal lp feeding reduced lean mass (P < 0·0001) and bone mass (P < 0·0001) in CON and LP animals. Percentage fat (LP P = 0·04; CON P = 0·6) and IGFBP-1 (LP P = 0·01; CON P = 0·2) were increased in LP-lp but not CON-lp offspring. This suggests that postnatal nutrition is important in the effects of maternal protein restriction on adult body composition and that IGFBP-1 may be involved.

Post-weaning protein malnutrition in the rat produces short and long term metabolic impairment, in contrast to earlier and later periods

Malnutrition during gestation and lactation modifies metabolic strategies and leads to metabolic disease in adult life. Studies in human populations suggest that malnutrition during infancy may also induce long term metabolic disorders.

The present study investigated if post-weaning and a late period of development might be sensitive for long term metabolic impairment. Hereto male Wistar rats were malnourished with a low protein diet (6%), during gestation and lactation (MGL), from weaning to 55 days (MPW) or during adulthood from 90 to 120 days (MA). Control rats (C) were fed with a regular diet (23% protein). We determine plasma concentrations of insulin, glucagon, triacylglycerols (TAG), free fatty acids (FFA), and liver glycogen after a Glucose Tolerance Test (GTT).

Independent of the age of onset, malnutrition induced low body weight. Early and post-weaning malnutrition produced impaired glucose tolerance and low values of TAG, also in MPW induced low values of insulin and glucagon. At 90 days, after balanced diet rehabilitation, the MGL group showed a similar glucose tolerance test as the controls but display low values of insulin, while the MPW group exhibited high levels of glucose and TAG, and low values of insulin, glucagon, FFA and hepatic glycogen. At 180 days, after balanced rehabilitation only MPW rats showed metabolic alterations. Malnutrition during adult life (MA) did not produce metabolic disturbances. Surprisingly the results uncover the post-weaning stage as a vulnerable period to malnutrition that induces long lasting metabolic alterations and deficiency in pancreatic function.

Impaired beta-cell function and inadequate compensatory increases in beta-cell mass after intrauterine growth restriction in sheep

Poor growth before birth increases the risk of non-insulin-dependent diabetes mellitus (NIDDM) and impairs insulin secretion relative to sensitivity. We investigated the effects of intrauterine growth restriction in sheep on insulin secretion, beta-cell mass, and function from before birth to young adulthood and its molecular basis. Pancreas was collected from control and placentally restricted sheep as fetuses (d 143 gestation), lambs (aged 42 d), and young adults (aged 556 d), following independent measures of in vivo insulin secretion and sensitivity. beta-Cells and islets were counted after immunohistochemical staining for insulin. In lambs, gene expression was measured by RT-PCR and expressed relative to 18S. beta-Cell mass correlated positively with fetal weight but negatively with birth weight in adult males. Glucose-stimulated insulin disposition and beta-cell function correlated negatively with fetal weight but positively with birth weight in adult males. Placental restriction increased pancreatic expression of IGF-II and IGF-I but decreased that of voltage-gated calcium channel, alpha1D subunit (CACNA1D) in lambs. In male lambs, pancreatic IGF-II and insulin receptor expression correlated strongly and positively with beta-cell mass and CACNA1D expression with glucose-stimulated insulin disposition. Restricted growth before birth in the sheep does not impair insulin secretion, relative to sensitivity, before birth or in young offspring. IGF-II and insulin receptor are implicated as key molecular regulators of beta-cell mass compensation, whereas impaired expression of the voltage-gated calcium channel may underlie impaired beta-cell function after intrauterine growth restriction. With aging, the insulin secretory capacity of the beta-cell is impaired in males, and their increases in beta-cell mass are inadequate to maintain adequate insulin secretion relative to sensitivity.

Are nutrition-induced epigenetic changes the link between socioeconomic pathology and cardiovascular diseases?

The prevalence of cardiovascular diseases (CVD) and diabetes mellitus type 2 (DM 2) is decreasing in developed countries despite the increase in the percentage of subjects with obesity and other well-recognized cardiovascular risk factors. In contrast, the recent transition of the economic model experienced by developing countries, characterized by the adoption of a Western lifestyle, that we have named "socioeconomic pathology," has led to an increase in the burden of CVD. It has been demonstrated that conventional cardiovascular risk factors in developed and developing countries are the same. Why then does the population of developing countries currently have a higher incidence of CVD than that of developed countries if they share the same risk factors? We have proposed the existence of a higher susceptibility to the development of systemic inflammation at low levels of abdominal obesity in the population of developing countries and the consequent endothelial dysfunction, insulin resistance, DM 2, and CVD. In contrast, an important percentage of obese people living in developed countries have a healthy phenotype and low risk of developing CVD and DM 2. Human epidemiologic studies and experimental dietary interventions in animal models have provided considerable evidence to suggest that nutritional imbalance and metabolic disturbances early in life may later have a persistent effect on an adult's health that may even be transmitted to the next generations. Epigenetic changes dependent on nutrition could be key in this evolutionary health behavior, acting as a buffering system, permitting the adaptation to environmental conditions by silencing or increasing the expression of certain genes.

Early life growth and hemostatic factors: the Barry Caerphilly Growth study

Associations between early life growth trajectories and a range of adult (aged approximately 25 years) hemostatic factors were assessed in the Barry Caerphilly Growth study (N = 517) in South Wales, 1974-1999. Associations of birth weight, birth length, and weight and height velocities during three periods ("immediate": 0-<5 months, "infant": 5 months-<1 year 9 months, and "childhood": 1 year 9 months-5 years) with adult levels of hemostatic factors were assessed. Birth weight was inversely associated with fibrinogen (beta per 1-unit change in z score = -0.08, 95% confidence interval (CI): -0.15, -0.02). Immediate weight velocity was inversely associated with factor VII (beta = -1.88, 95% CI: -3.84, 0.09), factor VIII (beta = -2.58, 95% CI: -4.07, -0.45), and von Willebrand factor antigen (beta = -4.07, 95% CI: -7.25, -0.89). Birth length was inversely associated with fibrinogen (beta = -0.07, 95% CI: -0.14, -0.01). Evidence was weaker for an inverse association of immediate height velocity with factor VIII (beta = -2.16, 95% CI: -4.62, 0.29) and von Willebrand factor antigen (beta = -2.85, 95% CI: -6.52, 0.81). Childhood height velocity was positively associated with D-dimer (ratio of geometric means = 1.11, 95% CI: 1.01, 1.23). Results support the view that the immediate postnatal period may be particularly important, possibly through impaired liver development and/or infection in early life, in determining cardiovascular disease risk.

Prenatal origins of adult disease

PURPOSE OF REVIEW

Human epidemiological and animal studies show that many chronic adult conditions have their antecedents in compromised fetal and early postnatal development. Developmental programming is defined as the response by the developing mammalian organism to a specific challenge during a critical time window that alters the trajectory of development with resulting persistent effects on phenotype. Mammals pass more biological milestones before birth than any other time in their lives. Each individual's phenotype is influenced by the developmental environment as much as their genes. A better understanding is required of gene-environment interactions leading to adult disease.

RECENT FINDINGS

During development, there are critical periods of vulnerability to suboptimal conditions when programming may permanently modify disease susceptibility. Programming involves structural changes in important organs; altered cell number, imbalance in distribution of different cell types within the organ, and altered blood supply or receptor numbers. Compensatory efforts by the fetus may carry a price. Effects of programming may pass across generations by mechanisms that do not necessarily involve structural gene changes. Programming often has different effects in males and females.

SUMMARY

Developmental programming shows that epigenetic factors play major roles in development of phenotype and predisposition to disease in later life.

Early life programming of obesity and metabolic disease

It is becoming increasingly apparent that conditions experienced in early life play an important role in the long-term health of individuals. Alterations in development due to impaired, excessive or imbalanced growth, both in utero and during critical periods of relative plasticity beyond birth, can lead to the permanent programming of physiological systems. The regulation of energy balance is one area that is receiving particular attention, as rates of obesity and associated metabolic and cardiovascular disease continue to rise. Over recent decades, much progress has been made toward understanding the way in which metabolic tissues and physiological systems develop, and the impact of early life events and nutrition on these processes. It is apparent within human populations that some individuals are better able to maintain an appropriate body weight in the face of an obesogenic environment. Animal models have been widely used for the investigation of differential susceptibility to diet-induced obesity (DIO) and impaired energy balance regulation, and are shedding light on key pathways that may be involved. Alterations in pathways mediating energy homeostasis, outlined below, are likely candidates for programming effects following disturbed growth in early life.

Telomere length assessment: biomarker of chronic oxidative stress?

Telomeres are nucleoprotein structures, located at the ends of chromosomes and are subject to shortening at each cycle of cell division. They prevent chromosomal ends from being recognized as double strand breaks and protect them from end to end fusion and degradation. Telomeres consist of stretches of repetitive DNA with a high G-C content and are reported to be highly sensitive to damage induced by oxidative stress. The resulting DNA strand breaks can be formed either directly or as an intermediate step during the repair of oxidative bases. In contrast to the majority of genomic DNA, there is evidence that telomeric DNA is deficient in the repair of single strand breaks. Since chronic oxidative stress plays a major role in the pathophysiology of several chronic inflammatory diseases, it is hypothesized that telomere length is reducing at a faster rate during oxidative stress. Therefore, assessment of telomere length might be a useful biomarker of disease progression. In this review several features of telomere length regulation, their relation with oxidative stress, and the potential application of measurement of telomere length as biomarker of chronic oxidative stress, will be discussed.

The associations between birthweight and adult markers of liver damage and function

Evidence suggesting an effect of fetal growth on liver development and function stems from both animal and human studies. The association of birthweight with adult markers of liver damage and function was examined in a random sample of 2101 British women aged 60-79 years. Age-adjusted natural logged levels of alanine aminotransferase (ALT) and gamma glutamyltransferase (GGT) decreased linearly across increasing thirds of birthweight. Alkaline phosphatase (ALP) levels were higher in women of the lowest third of the birthweight distribution compared with other women. No evidence was found for associations of birthweight with aspartate aminotransferase (AST), total bilirubin and albumin. After full adjustment for social class, physical activity, smoking and alcohol consumption, an increase in one standard deviation of birthweight (691 g) was associated with a 2% ([95% CI 0%, 4%], P = 0.021) decrease in the geometric mean of ALT, a 4% decrease in GGT ([95% CI 1%, 6%], P = 0.008) and a 2% decrease in ALP ([95% CI 0%, 3%], P = 0.001). Associations of birthweight with ALT and GGT, but not with ALP, were attenuated when adjusting for components of the metabolic syndrome. These findings suggest that factors affecting intrauterine growth may increase the propensity for adult liver damage. The attenuation of associations with adjustment for components of the metabolic syndrome is in line with non-alcoholic fatty liver disease, indicated by elevated ALT and GGT, being the hepatic manifestation of the metabolic syndrome, and of the influence of perinatal factors on this syndrome.

Intrauterine programming of the endocrine pancreas

Epidemiological studies have revealed strong relationships between poor foetal growth and subsequent development of the metabolic syndrome. Persisting effects of early malnutrition become translated into pathology, thereby determine chronic risk for developing glucose intolerance and diabetes. These epidemiological observations identify the phenomena of foetal programming without explaining the underlying mechanisms that establish the causal link. Animal models have been established and studies have demonstrated that reduction in the availability of nutrients during foetal development programs the endocrine pancreas and insulin-sensitive tissues. Whatever the type of foetal malnutrition, whether there are not enough calories or protein in food or after placental deficiency, malnourished pups are born with a defect in their beta-cell population that will never completely recover, and insulin-sensitive tissues will be definitively altered. Despite the similar endpoint, different cellular and physiological mechanisms are proposed. Hormones operative during foetal life like insulin itself, insulin-like growth factors and glucocorticoids, as well as specific molecules like taurine, or islet vascularization were implicated as possible factors amplifying the defect. The molecular mechanisms responsible for intrauterine programming of the beta cells are still elusive, but two hypotheses recently emerged: the first one implies programming of mitochondria and the second, epigenetic regulation.

Session 6: Infant nutrition: future research developments in Europe EARNEST, the early nutrition programming project: EARly Nutrition programming - long-term Efficacy and Safety Trials and integrated epidemiological, genetic, animal, consumer and economic research

Increasing evidence from lifetime experimental studies in animals and observational and experimental studies in human subjects suggests that pre- and postnatal nutrition programme long-term health. However, key unanswered questions remain on the extent of early-life programming in contemporary European populations, relevant nutritional exposures, critical time periods, mechanisms and the effectiveness of interventions to prevent or reverse programming effects. The EARly Nutrition programming - long-term Efficacy and Safety Trials and integrated epidemiological, genetic, animal, consumer and economic research (EARNEST) consortium brings together a multi-disciplinary team of scientists from European research institutions in an integrated programme of work that includes experimental studies in human subjects, modern prospective observational studies and mechanistic animal work including physiological studies, cell-culture models and molecular techniques. Theme 1 tests early nutritional programming of disease in human subjects, measuring disease markers in childhood and early adulthood in nineteen randomised controlled trials of nutritional interventions in pregnancy and infancy. Theme 2 examines associations between early nutrition and later outcomes in large modern European population-based prospective studies, with detailed measures of diet in pregnancy and early life. Theme 3 uses animal, cellular and molecular techniques to study lifetime effects of early nutrition. Biomedical studies are complemented by studies of the social and economic importance of programming (themes 4 and 5), and themes encouraging integration, communication, training and wealth creation. The project aims to: help formulate policies on the composition and testing of infant foods; improve the nutritional value of infant formulas; identify interventions to prevent and reverse adverse early nutritional programming. In addition, it has the potential to develop new products through industrial partnerships, generate information on the social and economic cost of programming in Europe and help maintain Europe's lead in this critical area of research.

Programmed metabolic syndrome: prenatal undernutrition and postweaning overnutrition

Maternal nutrient restriction results in intrauterine growth restriction (IUGR) newborns that develop obesity despite normal postweaning diet. The epidemic of metabolic syndrome is attributed to programmed "thrifty phenotype" and exposure to Western diets. We hypothesized that programmed IUGR newborns would demonstrate greater susceptibility to obesity and metabolic abnormalities in response to high-fat diet. From day 10 to term gestation and lactation, control pregnant rats received ad libitum (AdLib) food, whereas study rats were 50% food restricted (FR). Cross-fostering techniques resulted in three offspring groups: control (AdLib/AdLib), FR during pregnancy (FR/AdLib), and FR during lactation (AdLib/FR). At 3 weeks, offspring were weaned to laboratory chow or high-fat calorie diet (9% vs. 17% calorie as fat). Body composition, appetite hormones, and glucose and lipid profiles were determined in 9-mo-old male and female offspring. High-fat diet had no effect on body weight of AdLib/AdLib, but significantly increased weights of FR/AdLib and AdLib/FR offspring. High-fat diet significantly increased body fat, reduced lean body mass, and accentuated plasma leptin but not ghrelin levels in both sexes in all groups. In males, high-fat diet caused a significant increase in glucose levels in all three groups with increased insulin levels in AdLib/AdLib and AdLib/FR, but not in FR/AdLib. In females, high-fat diet had no effect on glucose but significantly increased basal insulin among all three groups. High-fat diet caused hypertriglyceridemia in all three groups although only food-restricted females exhibited hypercholesterolemia. Sex and offspring phenotype-associated effects of high-fat diet indicate differing pathophysiologic mechanisms that require specific therapeutic approaches.

Programming of intermediate metabolism in young lambs affected by late gestational maternal undernourishment

Effects of moderate maternal undernourishment during late gestation on the intermediary metabolism and maturational changes in young lambs were investigated. 20 twin-bearing sheep, bred to two different rams, were randomly allocated the last 6 wk of gestation to either a NORM diet [barley, protein supplement, and silage ad libitum approximately 15 MJ metabolizable energy (ME)/day] or a LOW diet (50% of ME intake in NORM, offered exclusively as silage approximately 7 MJ ME/day). Post partum, ewes were fed to requirement. After weaning, lambs were fed concentrate and hay ad libitum. At 10 and 19 wk of age, lambs were subjected to an intravenous glucose tolerance test (IGTT) followed by 24 h of fasting. Heat energy (HE) was determined in a respiration chamber at 9 or 20 wk of age. LOW lambs had a lower birth weight and continued to be lighter throughout the experiment. Glucose tolerance did not differ between groups. However, 19-wk-old LOW lambs secreted less insulin during IGTT, released more NEFA, and tended to have lower leptin during fasting than NORM. Surprisingly, several metabolite and hormone responses during IGTT and fasting were greatly influenced by the paternal heritage. In conclusion, when lambs entered adolescence (19 wk) programming effects of late prenatal malnutrition on the glucose-insulin homeostasis and metabolism were manifested: LOW lambs had less insulin-secretory capacity, but this was apparently compensated for by increased target tissue sensitivity for insulin, and adipose lipolytic capacity increased during fasting. Thereby, glucose may be spared through increased lipid oxidation, but overall energetic efficiency is apparently deteriorated rather than improved.

Maternal protein restriction permanently programs adipocyte growth and development in adult male rat offspring

We previously demonstrated that maternal protein restriction (MPR) during pregnancy and lactation led to fetal growth restriction and development of increased visceral adiposity in adult male rat offspring. Here we studied the rate of proliferation and differentiation of adipocyte precursors (preadipocytes) in vitro to investigate whether MPR may permanently program adipocyte growth and development in adult male offspring. Preadipocytes were isolated from visceral adipose tissue of control and MPR offspring at 130 days of age, and cultured under standard conditions. The rate of proliferation was studied by [(3)H]-thymidine incorporation, and the rate of differentiation assessed with the use of biochemical and morphological markers. Although it did not affect the rate of differentiation, MPR increased the rate of preadipocyte proliferation by almost twofold. To ascertain if the increased proliferation was due to persisting in vivo influences or aberrations inherent in the precursor cells, we studied the rate of preadipocyte proliferation in subcultures. We found that the increased rate of proliferation of MPR preadipocytes persisted throughout the first two subcultures, indicative of an inherent abnormality. In addition, we examined the rate of preadipocyte proliferation under reduced serum conditions. We showed that MPR reduced the rate of preadipocyte proliferation to 56 and 35% of the control in the presence of 5 and 2.5% serum, respectively. Taken together, these results demonstrate that MPR permanently programs adipocyte growth and development such that adipocyte precursors derived from MPR offspring replicate excessively under standard culture conditions but exhibit markedly attenuated growth rate under reduced serum conditions.

The timing of nutrient restriction during rat pregnancy/lactation alters metabolic syndrome phenotype

OBJECTIVE

Modulation of growth of intrauterine growth restricted (IUGR) newborns causes either adult obesity or normalization of body weight and fat. We investigated the impact of rapid versus delayed catch-up growth of IUGR offspring on glucose and lipid profiles.

STUDY DESIGN

From 10 days to term gestation and through lactation, control pregnant rats received ad libitum food, whereas study rats were 50% food restricted. Cross-fostering techniques were used to examine effects of food restriction during pregnancy and/or lactation periods. Glucose and lipid profiles were determined in offspring at ages 1 day, 3 weeks, and 9 months.

RESULTS

Food restriction during pregnancy produced hypoglycemic IUGR pups. Those permitted rapid catch-up growth demonstrated adult obesity with insulin resistance (hyperglycemia/hyperinsulinemia) and hypertriglyceridemia. Conversely, IUGR exhibiting delayed catch-up growth demonstrated normal adult body weight and insulin deficiency (hyperglycemia/hypoinsulinemia) and elevated cholesterol levels as compared with controls. However, these adult offspring had higher glucose though similar insulin levels as control offspring nursed by food restricted dam.

CONCLUSION

The timing and the rate of IUGR newborn catch-up growth causes markedly altered adult phenotypes. Although delayed newborn catch-up growth may be beneficial in the prevention of adult obesity, there may be significant adverse effects on pancreatic function.

Prenatal programming of skeletal development in the offspring: effects of maternal treatment with beta-hydroxy-beta-methylbutyrate (HMB) on femur properties in pigs at slaughter age

Alteration in fetal growth and development in response to prenatal environmental conditions such as nutrition has long-term or permanent effects during postnatal life. The aim of this study was to investigate effects of beta-hydroxy-beta-methylbutyrate (HMB) treatment of sows during the last 2 weeks of pregnancy on programming of skeletal development in the offspring. The study was performed on 141 pigs born by 12 sows of Polish Landrace breed. Two weeks before delivery, pregnant sows were divided into two groups. The first group consisted of control sows (N=6) that were treated with placebo. Sows that were orally treated with beta-hydroxy-beta-methylbutyrate (N=6) at the dosage of 0.05 g/kg of body weight per day belonged to the second group. Newborn piglets were weighed and subjected to blood collection for determination of serum levels of growth hormone (GH), insulin-like growth factor-1 (IGF-1), insulin, leptin, glucose and bone alkaline phosphatase (BAP) activity and lipid profile. At the age of 6 months, the piglets were slaughtered, their femur was isolated for analysis and assessment of lean meat content of carcasses was performed. The effects of maternal administration with HMB on skeletal properties in the offspring were evaluated in relation to bone mineral density and geometrical and mechanical properties. Maternal treatment with HMB increased serum levels of GH, IGF-1 and BAP activity in the newborns by 38.0%, 20.0% and 26.0%, respectively (P<0.01). HMB administration significantly increased volumetric bone mineral density of the trabecular and cortical bone of femur in the offspring at the age of 6 months (P<0.001). The weight of femur and geometrical parameters such as cross-sectional area, second moment of inertia, mean relative wall thickness and cortical index were significantly increased after HMB treatment (P<0.05). HMB induced higher values of maximum elastic strength and ultimate strength of femur (P<0.01). Furthermore, lean meat content of carcass was significantly increased in the females born by HMB-treated sows (P<0.05). The obtained results showed that maternal administration with HMB has positive long-term effects on bone tissue and improves volumetric bone mineral density, geometrical and mechanical properties of femur in the offspring. These effects were connected with increased level of GH and IGF-1 in the newborns indicating involvement of improved somatotrophic axis function in prenatal programming of skeletal development in pigs.

Prenatal and postnatal pathways to obesity: different underlying mechanisms, different metabolic outcomes

Obesity and type 2 diabetes are worldwide health issues. The present paper investigates prenatal and postnatal pathways to obesity, identifying different metabolic outcomes with different effects on insulin sensitivity and different underlying mechanisms involving key components of insulin receptor signaling pathways. Pregnant Wistar rats either were fed chow ad libitum or were undernourished throughout pregnancy, generating either control or intrauterine growth restricted (IUGR) offspring. Male offspring were fed either standard chow or a high-fat diet from weaning. At 260 d of age, whole-body insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp, and other metabolic parameters were measured. As expected, high-fat feeding caused diet-induced obesity (DIO) and insulin resistance. Importantly, the insulin sensitivity of IUGR offspring was similar to that of control offspring, despite fasting insulin hypersecretion and increased adiposity, irrespective of postnatal nutrition. Real-time PCR and Western blot analyses of key markers of insulin sensitivity and metabolic regulation showed that IUGR offspring had increased hepatic levels of atypical protein kinase C zeta (PKC zeta) and increased expression of fatty acid synthase mRNA. In contrast, DIO led to decreased expression of fatty acid synthase mRNA and hepatic steatosis. The decrease in hepatic PKC zeta with DIO may explain, at least in part, the insulin resistance. Our data suggest that the mechanisms of obesity induced by prenatal events are fundamentally different from those of obesity induced by postnatal high-fat nutrition. The origin of insulin hypersecretion in IUGR offspring may be independent of the mechanistic events that trigger the insulin resistance commonly observed in DIO.

Developmental programming of energy balance and the metabolic syndrome

The increasing prevalence of the metabolic syndrome in numerous populations throughout the world is currently of major concern, and presents a huge global health problem. The link between low birth weight and the subsequent development of obesity, disrupted glucose homeostasis and hypertension is now well established, and there is extensive evidence supporting these associations in both epidemiological and experimental studies. Alterations in the secretion of, and responses to, the circulating hormones insulin and leptin are likely candidates in terms of disease development. The aim of current research is to define how the central and peripheral pathways in which these signals exert their effects may be disrupted following poor early growth, and how this disruption contributes to the development of metabolic disease. The present review aims to outline the existing evidence whereby alterations in early growth may programme an individual to be at increased risk of the metabolic syndrome. The development of central appetite and expenditure circuits and of peripheral metabolic tissues, are likely to play a key role in the long-term regulation of energy balance.

Experimental IUGR and later diabetes

It is widely accepted that an association exists between the intrauterine environment in which a fetus grows and develops and the subsequent development of type 2 diabetes. Any disturbance in maternal ability to provide nutrients and oxygen to the fetus can lead to fetal intrauterine growth restriction (IUGR). Here we will review IUGR in rodent models, in which maternal metabolism has been experimentally manipulated to investigate the molecular basis of the relationship between IUGR and development of type 2 diabetes in later life, and the identification of the molecular derangements in specific metabolically - sensitive organs/tissues.

Blood pressure response to psychological stressors in adults after prenatal exposure to the Dutch famine

OBJECTIVE

There is increasing evidence that restricted prenatal growth is associated with exaggerated blood pressure responses to stress. We investigated the effect of maternal undernutrition on the adult offspring's stress response.

DESIGN

A historical cohort study.

METHODS

We performed continuous blood pressure and heart rate measurements during a battery of three 5-min physiological stress tests (Stroop test, mirror-drawing test and a public speech task) in 721 men and women, aged 58 years, born as term singletons in Amsterdam at about the time of the Dutch 1944-1945 famine.

RESULTS

During the stress tests, the systolic blood pressure (SBP) rose from baseline by 20 mmHg during the Stroop test, by 30 mmHg during the mirror-drawing test and by 47 mmHg during the public speech task. The SBP and diastolic blood pressure increase during stress was highest among individuals exposed to famine in early gestation compared with unexposed subjects (4 mmHg extra systolic increase, P = 0.04; 1 mmHg diastolic increase, P = 0.1, both adjusted for sex). Exposure during mid and late gestation was not associated with a stress-related increment of blood pressure (P adjusted for sex > 0.6). Correcting for confounders in a multivariable model did not attenuate the association between famine exposure in early gestation and the SBP increment. The heart rate increment was not related to famine exposure during any part of gestation.

CONCLUSION

We found a greater blood pressure increase during stress among individuals exposed to famine in early gestation. Increased stress responsiveness may underlie the known association between coronary heart disease and exposure to famine in early gestation.