Postnatal diet-induced obesity in rats upregulates systemic and adipose tissue glucocorticoid metabolism during development and in adulthood: its relationship with the metabolic syndrome

Early overnutrition results in early-onset arcuate leptin resistance and increased sensitivity to high-fat diet

Childhood obesity increases the risk of adult obesity and diabetes, suggesting that early overnutrition permanently programs altered energy and glucose homeostasis. In the present studies, we used a mouse model to investigate whether early overnutrition increases susceptibility to obesity and insulin resistance in response to a high-fat diet (HFD). Litters from Swiss Webster dams were culled to three [chronic postnatal overnutrition (CPO)] or 10 (control) pups and then weaned onto standard chow at postnatal day (P) 23. At 6 wk of age, a subset of mice was placed on HFD, and glucose and insulin tolerance were examined at 16-17 wk of age. Leptin sensitivity was determined by hypothalamic phosphorylated signal transducer and activator of transcription-3 immunoreactivity at P16 and adulthood after ip leptin. CPO mice exhibited accelerated body weight gain and hyperleptinemia during the preweaning period but only a slightly heavier body weight and normal glucose tolerance in adulthood on standard chow diet. Importantly, CPO mice exhibited significant leptin resistance in the arcuate nucleus, demonstrated by reduced activation of phospho-signal transducer and activator of transcription-3, as early as P16 and throughout life, despite normalized leptin levels. In response to HFD, CPO but not control mice displayed insulin resistance in response to an insulin tolerance test. In conclusion, CPO mice exhibited early and persistent leptin resistance in the arcuate nucleus and, in response to HFD, rapid development of obesity and insulin resistance. These studies suggest that early overnutrition can permanently alter energy homeostasis and significantly increase susceptibility to obesity and insulin resistance.

Postnatal early overfeeding induces hypothalamic higher SOCS3 expression and lower STAT3 activity in adult rats

Postnatal early overnutrition (EO) is a risk factor for future obesity and metabolic disorders. Rats raised in small litters (SLs) develop overweight, hyperphagia, hyperleptinemia, hyperinsulinemia and hypertension when adults. As obesity is related to hyperleptinemia, leptin resistance and metabolic syndrome, we aimed to investigate body composition, plasma hormone levels, glucose tolerance and the leptin signaling pathway in hypothalamus from early overfed animals at weaning and adulthood. To induce postnatal EO, we reduced litter size to three pups/litter (SL), and the groups with normal litter size (10 pups/litter) were used as control. Rats had free access to standard diet and water postweaning. Body weight and food intake were monitored daily, and offspring were killed at 21 (weaning) and 180 days old (adulthood). Postnatal EO group had higher body weight and total and visceral fat mass at both periods. Lean mass and serum high-density lipoprotein cholesterol (HDL-C) were higher at 21 days and lower at 180 days. Small litter rats presented higher levels of globulins at both periods, while albumin levels were higher at weaning and lower at adulthood. There was higher leptin, insulin and glucose serum concentrations at 21 days old, while no glucose intolerance was observed in adulthood. Leptin signaling pathway was unaffected at weaning. However, postnatal EO induced lower JAK2 and p-STAT3, and higher SOCS3 expression in adult animals, indicating central leptin resistance in adulthood. In conclusion, postnatal EO induces obesity, higher total and visceral fat mass, lower HDL-C and central leptin resistance in adult life.

Prenatal programming of metabolic syndrome in the common marmoset is associated with increased expression of 11beta-hydroxysteroid dehydrogenase type 1

OBJECTIVE

Recent studies in humans and animal models of obesity have shown increased adipose tissue activity of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which amplifies local tissue glucocorticoid concentrations. The reasons for this 11beta-HSD1 dysregulation are unknown. Here, we tested whether 11beta-HSD1 expression, like the metabolic syndrome, is "programmed" by prenatal environmental events in a nonhuman primate model, the common marmoset monkey.

RESEARCH DESIGN AND METHODS

We used a "fetal programming" paradigm where brief antenatal exposure to glucocorticoids leads to the metabolic syndrome in the offspring. Pregnant marmosets were given the synthetic glucocorticoid dexamethasone orally for 1 week in either early or late gestation, or they were given vehicle. Tissue 11beta-HSD1 and glucocorticoid receptor mRNA expression were examined in the offspring at 4 and 24 months of age.

RESULTS

Prenatal dexamethasone administration, selectively during late gestation, resulted in early and persistent elevations in 11beta-HSD1 mRNA expression and activity in the liver, pancreas, and subcutaneous-but not visceral-fat. The increase in 11beta-HSD1 occurred before animals developed obesity or overt features of the metabolic syndrome. In contrast to rodents, in utero dexamethasone exposure did not alter glucocorticoid receptor expression in metabolic tissues in marmosets.

CONCLUSIONS

These data suggest that long-term upregulation of 11beta-HSD1 in metabolically active tissues may follow prenatal "stress" hormone exposure and indicates a novel mechanism for fetal origins of adult obesity and the metabolic syndrome.

Administration of human leptin differentially affects parameters of cortisol secretion in socially housed female rhesus monkeys

Chronic exposure to psychosocial stress may lead to a dysregulation of the limbic-hypothalamic-pituitary-adrenal axis that results in a number of adverse health outcomes. The fat-derived hormone leptin has been indicated as a potential key component to maintaining homeostasis by enhancing glucocorticoid negative feedback. Using an established model of nonhuman primate social stress, notably social subordination, this study examined the effects of continuous leptin administration on cortisol secretion in female rhesus monkeys. The 20 subjects were maintained in stable five-member social groups with established dominance hierarchies. All females were ovariectomized but received estradiol throughout the study to maintain serum concentrations at early follicular phase levels. Three parameters of cortisol secretion were examined in dominant and subordinate females during control and leptin-treatment conditions: diurnal cortisol secretion; response to a dexamethasone suppression test; and response to a brief separation from their social group. We hypothesized that leptin supplementation would attenuate the hypercortisolemia characteristic of subordinate females. During baseline conditions, subordinate female rhesus monkeys had significantly lower levels of serum leptin compared with more dominant monkeys and were less sensitive to glucocorticoid negative feedback. Exogenous administration of leptin improved glucocorticoid negative feedback in subordinate females and decreased morning cortisol in all animals. However, there were no status differences in response to a social separation test and diurnal rhythm in cortisol during baseline conditions. However, leptin administration did not attenuate the increase in cortisol in response to a social separation. The data presented in this study demonstrate that leptin can attenuate several parameters of cortisol secretion in female rhesus monkeys and thus may play a role in the response of the adrenal glands to socio-environmental stimuli.

Diet-induced obesity alters behavior as well as serum levels of corticosterone in F344 rats

Obesity is an increasing socio-economic health problem. Diet-induced obese (DIO) rodents are widely used as a model of obesity in humans. However, there is no comprehensive data about the behavioral phenotype of DIO rodents. Therefore, the aim of the present study was to determine whether a high-fat-diet changes behavioral patterns of DIO Fischer 344 (F344) rats in comparison with lean littermates. The behavioral tests (homecage, holeboard, social interaction, and hotplate) were performed in 28 normal-weight and 28 male DIO F344 rats (mean age: 16 weeks) and revealed a significantly higher level of anxiety- and aggression-related parameters in obese rats, whereas their pain threshold was significantly lower. Fitting to a different behavioral response, basal corticosterone levels (measured by RIA) of obese animals were significantly elevated (16.0ng/ml vs. 12.5ng/ml; p<0.01). We conclude that obese rats differ in various aspects from their lean littermates. The altered behavioral characteristics displayed by DIO F344 rats have to be considered in further experiments involving DIO rodents.

Neonatal overfeeding alters adult anxiety and stress responsiveness

The neonatal nutritional environment is critical for programming the systems regulating body weight, and an inappropriate nutritional environment in early life can lead to overweight or obesity later on. In this study we demonstrate that changes to the neonatal nutritional environment, induced by changing the litter size in which the animal is raised, can alter not only body weight into adulthood, but also anxiety behaviours and stress responsiveness. These effects appear to be somewhat sex-dependent, affecting female rats more strongly than males. Thus, Wistar rats raised in small litters, where they have greater access to their mothers' milk, weigh more in adulthood than those raised in large litters. Females from these small litters show enhanced exploratory behaviour and reduced anxiety in the elevated plus maze, entering the open arms more often. They also display enhanced central responses to restraint stress including greater activation of the paraventricular nucleus of the hypothalamus and paraventricular nucleus of the thalamus, possibly indicating that the changes we see are related to enhanced arousal. Thus, while neonatal litter size affects long-term body weight regulation, it can also alter long-term activity, anxiety and stress responsiveness, and the degree to which it does so appears to be sex-dependent.

Hypothalamic proopiomelanocortin promoter methylation becomes altered by early overfeeding: an epigenetic model of obesity and the metabolic syndrome

Pre- and neonatal overfeeding programmes a permanent obesity disposition and accompanying diabetic and cardiovascular disorders, by unknown mechanisms. We proposed that early overfeeding may alter DNA methylation patterns of hypothalamic promoter regions of genes critically involved in the lifelong regulation of food intake and body weight. We induced neonatal overfeeding by rearing Wistar rats in small litters (SL) and thereafter mapped the DNA methylation status of CpG dinucleotides of gene promoters from hypothalamic tissue, using bisulfite sequencing. Neonatal overfeeding led to rapid early weight gain, resulting in a metabolic syndrome phenotype, i.e. obesity, hyperleptinaemia, hyperglycaemia, hyperinsulinaemia, and an increased insulin/glucose ratio. Accompanying, without group difference to controls, the promoter of the main orexigenic neurohormone, neuropeptide Y, was methylated at low levels (i.e. < 5%). In contrast, in SL rats the hypothalamic gene promoter of the main anorexigenic neurohormone, proopiomelanocortin (POMC), showed hypermethylation (P < 0.05) of CpG dinucleotides within the two Sp1-related binding sequences (Sp1, NF-kappaB) which are essential for the mediation of leptin and insulin effects on POMC expression. Consequently, POMC expression lacked upregulation, despite hyperleptinaemia and hyperinsulinaemia. Accordingly, the extent of DNA methylation within Sp1-related binding sequences was inversely correlated to the quotients of POMC expression/leptin (P = 0.02) and POMC expression/insulin (P < 0.001), indicating functionality of acquired epigenomic alterations. These data for the first time demonstrate a nutritionally acquired alteration of the methylation pattern and, consequently, the regulatory 'set point' of a gene promoter that is critical for body weight regulation. Our findings reveal overfeeding as an epigenetic risk factor of obesity programming and consecutive diabetic and cardiovascular disorders and diseases, in terms of the metabolic syndrome.

Early postnatal overfeeding induces early chronic renal dysfunction in adult male rats

Low birth weight is associated with an increased risk of hypertension and renal dysfunction at adulthood. Such an association has been shown to involve a reduction of nephron endowment and to be enhanced by accelerated postnatal growth in humans. However, while low-birth-weight infants often undergo catch-up growth, little is known about the long-term vascular and renal effects of accelerated postnatal growth. We surimposed early postnatal overfeeding (OF; reduction of litter size during the suckling period) to appropriate-birth-weight (NBW+OF) and intrauterine growth restriction (IUGR; IUGR+OF) pups, obtained after a maternal gestational low-protein diet. Blood pressure (systolic blood pressure; SBP) and renal function (glomerular filtration rate; GFR) were measured in young and aging offspring. Glomerulosclerosis and nephron number were determined in aging offspring (22 mo). Nephron number was reduced in both IUGR and IUGR+OF male offspring (by 24 and 26%). GFR was reduced by 40% in 12-mo-old IUGR+OF male offspring, and both NBW+OF and IUGR+OF aging male offspring had sustained hypertension (+25 mmHg) and glomerulosclerosis, while SBP and renal function were unaffected in IUGR aging offspring. Female offspring were unaffected. In conclusion, in this experimental model, early postnatal OF in the neonatal period has major long-lasting effects. Such effects are gender dependent. Reduced nephron number alone, associated with IUGR, may not be sufficient to induce long-lasting physiological alterations, and early postnatal OF acts as a "second hit." Early postnatal OF is a suitable model with which to study the long-term effects of postnatal growth in the pathogenesis of vascular disorders and renal disease.

Endocrine disrupters as obesogens

The recent dramatic rise in obesity rates is an alarming global health trend that consumes an ever increasing portion of health care budgets in Western countries. The root cause of obesity is thought to be a prolonged positive energy balance. Hence, the major focus of preventative programs for obesity has been to target overeating and inadequate physical exercise. Recent research implicates environmental risk factors, including nutrient quality, stress, fetal environment and pharmaceutical or chemical exposure as relevant contributing influences. Evidence points to endocrine disrupting chemicals that interfere with the body's adipose tissue biology, endocrine hormone systems or central hypothalamic-pituitary-adrenal axis as suspects in derailing the homeostatic mechanisms important to weight control. This review highlights recent advances in our understanding of the molecular targets and mechanisms of action for these compounds and areas of future research needed to evaluate the significance of their contribution to obesity.

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

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

Postnatal early overnutrition changes the leptin signalling pathway in the hypothalamic-pituitary-thyroid axis of young and adult rats

Postnatal early overnutrition (EO) is a risk factor for obesity in adult life. Rats raised in a small litter can develop hyperinsulinaemia, hyperphagia, hyperleptinaemia and hypertension as adults. Since leptin regulates the hypothalamic-pituitary-thyroid axis and the metabolism of thyroid hormones, we studied the leptin signalling pathway in pituitary and thyroid glands of the postnatal EO model. To induce EO, at the third day of lactation the litter size was reduced to three pups per litter (SL group). In control litters (NL group), the litter size was adjusted to 10 pups per litter. Body weight and food intake were monitored. Rat offspring were killed at 21 (weaning) and 180 days old (adulthood). Plasma thyroid hormones, thyroid-stimulating hormone (TSH) and leptin were measured by radioimmunoassay. Proteins of the leptin signalling pathway were analysed by Western blotting. Body weight of offspring in the SL group was higher from the seventh day of lactation (+33%, P < 0.05) until 180 days old (+18%, P < 0.05). Offspring in the SL group showed higher visceral fat mass at 21 and 180 days old (+176 and +52%, respectively, P < 0.05), but plasma leptin was higher only at 21 days (+88%, P < 0.05). The SL offspring showed higher plasma TSH, 3,5,3'-triiodothronine (T(3)) and thyroxine (T(4)) at 21 days (+60, +91 and +68%, respectively, P < 0.05), while the opposite was observed at 180 days regarding thyroid hormones (T(3), -10%; and T(4), -30%, P < 0.05), with no difference in TSH levels. In hypothalamus, no change was observed in the leptin signalling pathway at 21 days. However, lower janus thyrosine kinase 2 (JAK2) and phosphorilated-signal transducer and activator of transcription-3 (p-STAT3) content were detected in adulthood. In pituitary, the SL group presented higher leptin receptors (Ob-R), JAK2 and p-STAT3 content at 21 days and lower JAK2 and STAT3 content at 180 days old. In contrast, in thyroid, the Ob-R expression was lower in young SL rats, while the adult SL group presented higher Ob-R and JAK2 content. We showed that postnatal EO induces short- and long-term effects upon the hypothalamic-pituitary-thyroid axis. These changes may help to explain future development of metabolic and endocrine dysfunctions, such as metabolic syndrome and hypothyroidism.

Early undernutrition leads to long-lasting reductions in body weight and adiposity whereas increased intake increases cardiac fibrosis in male rats

Previous studies suggest that both overfeeding and undernutrition during development increase the risk of obesity and hypertension in adulthood. In this study, we examined both short- (24 d) and long- (16 wk) term effects of early postnatal over- and underfeeding in rats on body weight, body composition, plasma hormones, adiposity markers, and hypothalamic neuropeptide Y content. Cardiovascular changes were also examined by measuring blood pressure and cardiac fibrosis. Rats raised in litters of 3, 12, or 18 pups per mother were used to model early onset overfeeding, control, and underfeeding, respectively. At 24 d of age, pups raised in small litters (SL) were 10% heavier than pups from normal litters, accompanied by increased organ mass and fat mass, elevated plasma leptin, corticosterone, and uncoupling protein-1 mRNA in brown adipose tissue. On the other hand, pups raised in large litters were 17% lighter with no significant changes in plasma leptin. Overfeeding during the first 3 wk of life led to increased plasma leptin concentration in adulthood, whereas underfed rats remained significantly lighter throughout the study, with no evidence of catch-up growth. Rats raised in SL were more susceptible to developing cardiac fibrosis with a 22% increase in collagen deposition compared with control rats at 16 wk of age (P < 0.05). This was independent of any changes in blood pressure. This study demonstrates that nutritional changes early in postnatal development can have long-lasting effects on body weight, adiposity, and some mediators involved in energy homeostasis and can also lead to structural changes in the heart in adulthood. This highlights the importance of identifying potential early life risk factors involved in the modulation of childhood nutrition.

Hormonal programming in perinatal life: leptin and beyond

Central nervous system leptin resistance as a possible cause of obesity and associated diseases is a ‘hot topic’ in nutrition research. Simultaneously, a new field in biomedical sciences has evolved during the past years.

Deleterious effects of high-fat diet on perinatal and postweaning periods in adult rat offspring

BACKGROUND & AIMS

Pre- and postnatal environmental changes can reset the developmental path during intrauterine development leading to obesity and cardiovascular and metabolic disorders later in life. The effects of high-fat diets on body mass, fat mass, the plasma level of glucose, insulin and leptin, as well as the insulin/glucose ratio and cardiovascular parameters in adult rat offspring were studied.

METHODS

Pregnant Wistar rats in a standard chow group (SC) or high-fat chow group (HFC), at weaning their SC and HFC offspring were randomly divided into two postnatal groups: fed on SC or HFC. With euthanasia at 6-month-old, three-way ANOVA there were three-factor interactions among gender, perinatal diet and postweaning diet to body mass (BM), BP, left ventricle (LV) thickness, carbohydrate metabolism, plasma corticosterone concentrations and leptin/fat mass/adipocyte size pattern.

RESULTS

HFC/SC and SC/HFC offspring of both genders had high BM and BP, which were increased in HFC/HFC offspring. There was hyperinsulinism, hyperleptinemia, as well as high insulin/glucose ratio and high plasma corticosterone concentrations mainly in HFC/HFC offspring with adipocytes and LV hypertrophy.

CONCLUSIONS

Postweaning HFC was deleterious to the health of adult offspring from dams fed HFC during pregnancy and then during the first half of lactation period. HFC administrated in both periods shows supplementary effects, elevating BP with consequent LV hypertrophy, altering carbohydrate metabolism, plasma corticosterone concentrations and disturbing leptin/fat mass/adipocyte size pattern.

Hypothalamic neuropeptide expression of juvenile and middle-aged rats after early postnatal food restriction

Rats subjected to early postnatal food restriction (FR) show persistent changes in energy balance. The hypothalamus plays a major role in the regulation of energy balance. Therefore, we hypothesized that early postnatal food restriction induces developmental programming of hypothalamic gene expression of neuropeptides involved in this regulation. In the hypothalamus of juvenile and middle-aged rats that were raised in control (10 pups) or FR litters (20 pups), gene expression was investigated for neuropeptide Y (NPY), agouti-related protein (AgRP), proopiomelanocortin (POMC), and cocaine- and amphetamine-regulated transcript (CART) in the arcuate nucleus (ARC); CRH and TRH in the paraventricular nucleus; and melanin-concentrating hormone (MCH) and orexin in the lateral hypothalamic area. Early postnatal FR acutely and persistently reduced body size. Juvenile FR rats had significantly reduced CART gene expression and increased MCH expression. In middle-aged FR rats, POMC and CART mRNA levels were significantly reduced. The ratio between expression of the ARC orexigenic peptides (NPY and AgRP) and anorexigenic peptides (POMC and CART) was increased in juvenile, but not in middle-aged, FR rats. These results suggest that in neonatal rats, FR already triggers the ARC, and to a lesser extent the lateral hypothalamic area, but not the paraventricular nucleus, to increase expression of orexigenic relative to anorexigenic peptides. In addition, with enduring small body size and normalized hypothalamic gene expression, the adult FR rats appeared to have accepted this smaller body size as normal. This suggests that the body weight set-point was differently programmed in animals with early postnatal FR.

Postnatal programming of glucocorticoid metabolism in rats modulates high-fat diet-induced regulation of visceral adipose tissue glucocorticoid exposure and sensitivity and adiponectin and proinflammatory adipokines gene expression in adulthood

OBJECTIVE

Alterations of the perinatal environment, which lead to increased prevalence of the metabolic syndrome in adulthood, program an upregulation of systemic and/or adipose tissue glucocorticoid metabolism (11 beta-hydroxysteroid dehydrogenase type 1 [11 beta-HSD-1]-induced corticosterone reactivation). We hypothesized that postnatal programming could modulate high-fat diet-induced adipose tissue dysregulation in adulthood.

RESEARCH DESIGN AND METHODS

We compared the effects of chronic (since weaning) high- or low-fat diet in postnatally normofed (control) or overfed (programmed) rats.

RESULTS

Postnatal programming accentuated high-fat diet-induced overweight, insulin resistance, glucose intolerance, and decrease in circulating and epididymal adipose tissue adiponectin. Neither manipulation altered liver function. Postnatal programming or high-fat diet increased systemic corticosterone production, which was not further modified when both manipulations were associated. Postnatal programming suppressed high-fat diet-induced decrease in mesenteric adipose tissue (MAT) glucocorticoid sensitivity and triggered high-fat diet-induced increase in MAT glucocorticoid exposure, subsequent to enhanced MAT 11 beta-HSD-1 gene expression. MAT tumor necrosis factor (TNF)-alpha, TNF-receptor 1, interleukin (IL)-6, resistin, and plasminogen activator inhibitor-1 mRNAs were not changed by high-fat feeding in control rats and showed a large increase in programmed animals, with this effect further enhanced by high-fat diet for TNF-alpha and IL-6.

CONCLUSIONS

Our data show for the first time that postnatal manipulation programs high-fat diet-induced upregulation of MAT glucocorticoid exposure, sensitivity, and inflammatory status and therefore reveal the pivotal role of the environment during the perinatal period on the development of diet-induced adipose tissue dysregulation in adulthood. They also urge the need for clinical trials with specific 11 beta-HSD-1 inhibitors.

Intrauterine growth restriction in a rodent model and developmental programming of the metabolic syndrome: a critical appraisal of the experimental evidence

Research on intrauterine growth restriction (IUGR) and subsequent development of obesity, type 2 diabetes and the metabolic syndrome is rapidly expanding, and potential implications for primary prevention are considerable. We have critically appraised one of the experimental animal models frequently used as mimic of human fetal growth restriction, which involves bilateral ligation of the uterine artery in rats (Lig). Our experimental study showed that Lig performed on day 17 of pregnancy neither leads to IUGR nor to neonatal catch-up growth, an important pathogenetic co-factor in humans. Meta-analysis of the literature revealed domination by studies in which Lig pups with IUGR were actively selected. Accordingly, publication bias is evident (p=0.007). Altered placental perfusion--the main cause of IUGR in humans in Western countries--neither led to IUGR nor to neonatal catch-up growth in Lig offspring, i.e., to none of the etiological factors of the human 'small baby syndrome'. Appropriate and reproducible rodent models of IUGR through decreased placental flow remain to be established to uncover the pathophysiological basis of the 'small baby syndrome'. This may lead to new strategies of primary prevention of diabetes, obesity, and the metabolic syndrome.

Microcirculation in obesity: an unexplored domain

Obesity is traditionally linked to diabetes and cardiovascular diseases. Very recent experimental, clinical and epidemiological, sometimes provocative, data challenge this automaticity by showing that not the amount but the distribution of fat is the important determinant. Moderate abdominal fat accumulation may thus be more harmful than even consequent overweight. In view of the worldwide burden of obesity, factors leading to it in children and young adults must urgently be identified. Since obesity is a very complex cardiometabolic situation, this will require to focus investigations on uncomplicated obese subjects and adequate animal models. The recent discovery of intergenerational transmissions of obesity risk factors and also the key role played by gestational and perinatal events (epigenetic factors) give rise to completely new concepts and research avenues. Considering the potential close relationship between microcirculation and tissue metabolism, demonstrations of structural and/or functional abnormalities in microvascular physiology very early in life of subjects at risk for obesity might provide a solid basis for further investigations of such links. Microcirculation(arterioles, capillaries and venules) is conceivably a key compartment determining over one or several decades the translation of genetic and epigenetic factors into fat accumulation. Available animal models should serve to answer this cardinal question.

Energy intake and resting energy expenditure in adult male rats after early postnatal food restriction

Both in man and in animal models, changes in food intake and body composition in later life have been reported after alterations in perinatal nutrition. Therefore, we hypothesised that early postnatal undernutrition in the rat induces permanent changes in energy balance. Food restriction (FR) during lactation was achieved by enlarging litter size to twenty pups, whereas control animals were raised in litters containing ten pups. Energy intake and resting energy expenditure were determined in adult males. Early postnatal FR resulted in acute growth restriction followed by incomplete catch-up in body weight, body length and BMI. At the age of 12 months, middle-aged FR males had significantly lower absolute resting energy expenditure (200 v. 216 kJ/24 h, P = 0.009), absolute energy intake (281 v. 310 kJ/24 h, P = 0.001) and energy intake adjusted for BMI (284 v. 305 kJ/24 h, P = 0.016) than controls, whereas resting energy expenditure adjusted for BMI did not differ significantly between the groups (204 v. 211 kJ/24 h, P = 0.156). The amount of energy remaining for other functions was lower in FR males (80 v. 94 kJ/24 h, P = 0.044). Comparable data were obtained at the age of 6 months. These results indicate that in rats energy balance can be programmed by early nutrition. A low early postnatal food intake appears to programme these animals for a low energy intake and to remain slender in adult life.

Could preference for palatable foods in neonatally handled rats alter metabolic patterns in adult life?

Previous studies indicate that, in adulthood, neonatally handled rats consume more sweet food than nonhandled rats. The aim of the present study was to assess the effects of the chronic exposure to a palatable diet (chocolate) in adult neonatally handled rats. We measured the consumption of foods (standard lab chow and chocolate), body weight gain, abdominal fat deposition, and levels of plasma lipids, glucose, insulin, and corticosterone in adult neonatally handled (10 min/d, first 10 d of life) and nonhandled rats. We found an increased intake of chocolate in handled rats, but this consumption decreased over time. Handled male animals exhibited higher body weight, higher caloric efficiency, and lower triglyceride levels. Nonhandled females that were exposed long-term to the highly caloric diet had increased abdominal fat deposition compared with handled females. Overall female rats had increased abdominal fat deposition, higher total cholesterol and glucose levels, and lower insulin in comparison with males. Interestingly, chocolate consumption diminished the weight of the adrenal glands in both handled and nonhandled animals. These findings suggest that neonatal handling induces a particular metabolic pattern that is sex specific.

Effects of early postnatal hypernutrition on nephron number and long-term renal function and structure in rats

Various antenatal events impair nephrogenesis in humans as well as in several animal models. The consecutive low nephron endowment may contribute to an increased risk for cardiovascular and renal diseases in adulthood. However, little knowledge is available on the influence of the postnatal environment, especially nutrition, on nephrogenesis. Moreover, the consequences of early postnatal nutrition in late adulthood are not clear. We used a model of early postnatal overfeeding (OF) induced by reduction of litter size (3 pups/litter) in rats. Systolic blood pressure (SBP; plethysmography), glomerular filtration rate (clearance of creatinine), glomerular number and volume, and glomerulosclerosis were evaluated in 22-mo-old aging offspring. Early postnatal OF was associated with increased weight gain during the suckling period (+40%, P < 0.01) and a 20% increase in glomerular number (P < 0.05). However, an increase in SBP at 12 mo by an average of 18 mmHg and an increase in proteinuria (2.6-fold) and glomerulosclerosis at 22 mo of age were observed in OF male offspring compared with controls. In conclusion, early postnatal OF in the rat enhances postnatal nephrogenesis, but elevated blood pressure and glomerulosclerosis are still observed in male adults. Factors other than glomerular number reduction are likely to contribute to the arterial hypertension induced by early postnatal OF.

Glucocorticoids, metabolism and metabolic diseases

Since the discovery of the beneficial effects of adrenocortical extracts for treating adrenal insufficiency more than 80 years ago, glucocorticoids (GC) and their cognate, intracellular receptor, the glucocorticoid receptor (GR) have been characterized as critical components of the delicate hormonal control system that determines energy homeostasis in mammals. Whereas physiological levels of GCs are required for proper metabolic control, excessive GC action has been tied to a variety of pandemic metabolic diseases, such as type II diabetes and obesity. Highlighted by its importance for human health, the investigation of molecular mechanisms of GC/GR action has become a major focus in biomedical research. In particular, the understanding of tissue-specific functions of the GC-GR pathway has been proven to be of substantial value for the identification of novel therapeutic options in the treatment of severe metabolic disorders. Therefore, this review focuses on the role of the GC-GR axis for metabolic homeostasis and dysregulation, emphasizing tissue-specific functions of GCs in the control of energy metabolism.

Excess weight gain during the early postnatal period is associated with permanent reprogramming of brown adipose tissue adaptive thermogenesis

Excess weight gain during the early postnatal period increases the risk of persistent obesity into adulthood and impacts on the subsequent risk for metabolic and cardiovascular diseases. The current study investigated the long-term effect of early excess weight gain, through reduced nursing litter size, on body weight regulation and its relation to brown adipose tissue (BAT) thermogenesis. Animals raised in a small litter (SL, three pups per litter) were compared with those raised in a normal litter size (NL, eight pups per litter). BAT from young adult NL and SL rats, maintained under either ambient or cold conditions, were used for gene expression, morphological, and functional analysis. Compared with NL, SL rats showed excess weight gain, and adult SL animals had a reduced thermogenic capacity as displayed by lower levels of uncoupling protein 1 (UCP1). When exposed to cold, BAT from SL rats was less active and demonstrated reduced responsiveness to cold. Furthermore, reduction in transcript abundance of several lipid lipases and transcriptional regulators was observed in SL rats either at ambient temperature or under cold conditions. Finally, the expression of sympathetic beta 3-adrenergic receptor and the response to the sympathetic receptor agonist isoproterenol were decreased in SL rats. Overall, these observations provide the first evidence that postnatal excess weight gain results in abnormalities in BAT thermogenesis and sympathetic outflow, which likely increases susceptibility to obesity in adulthood.

Fetal growth restriction and postnatal development

The interaction between genetic constitution and in utero environment determines fetal growth and development and influences the susceptibility to certain disorders in adulthood. Data from both animal and human studies indicate that prenatal and early postnatal malnutrition can program the hypothalamus-pituitary-adrenal axis (HPA axis), altering neuroendocrine response to stressors throughout lifetime. Impaired uteroplacental perfusion results in fetal growth restriction (FGR). In FGR there is evidence of chronic hypoxemia and alterations in metabolic, endocrine, and hematological parameters, compatible with starvation. Furthermore, FGR is associated with increased perinatal mortality and in the survivors there is increased susceptibility to diabetes and cardiovascular disease in adulthood. There is evidence that early postnatal growth acceleration, which would normally be considered desirable, may exacerbate metabolic dysfunction in later life.

Insulin resistance of hypothalamic arcuate neurons in neonatally overfed rats

Rats exposed to early postnatal overfeeding by rearing in small litters become hyperphagic, hyperleptinemic, and hyperinsulinemic throughout later life. Medial arcuate neurons are involved in body weight regulation. They were tested in brain slices of control and small-litter rats concerning differences in responses to insulin. Insulin induced suppression of firing in controls, whereas in small-litter rats inhibition was significantly reduced and activation increased. This could be observed in juvenile as well as adult rats. A gamma-aminobutyric acid type A receptor antagonist did not change the responses. Thus, negative feedback to the satiety signal insulin on medial arcuate neurons is reduced in neonatally overfed small-litter rats. This can be regarded as insulin resistance, which is induced during early development and persists in later life.

Increased 11β-hydroxysteroid dehydrogenase type-1 and hexose-6-phosphate dehydrogenase in liver and adipose tissue of rat offspring exposed to alcohol in utero

Rat offspring prenatally exposed to alcohol display features of metabolic syndrome characterized by a low birth weight, catch-up growth, dyslipidemia, and insulin-resistant diabetes with increased gluconeogenesis, during adult life. Gluconeogenesis is partly regulated by cyclic AMP- and glucocorticoid-dependent mechanisms. Glucocorticoid action at the receptor level depends on its circulating concentrations and is amplified at the prereceptor level by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which regenerates active glucocorticoids from inactive forms. To determine whether 11β-HSD1 is dysregulated in this rat model, we examined the expression and enzyme activity of 11β-HSD1 and its regulator enzyme hexose-6-phosphate dehydrogenase (H6PD) in the liver of postnatal day 7 (neonatal) and 3-mo-old (adult) rat offspring prenatally exposed to alcohol. Measurements of 11β-HSD1 and H6PD were also performed in the omental fat of adult rat offspring. In both neonatal and adult rats, prenatal alcohol exposure resulted in increased tissue corticosterone concentrations, increased expression, and oxoreductase activity of 11β-HSD1, and a parallel increase of H6PD expression. The data suggest that due to both transcriptional and posttranscriptional dysregulations, rats exposed to alcohol early in life have increased 11β-HSD1 activity, which may explain insulin-resistant diabetes in these animals later in life.

To catch up or not to catch up: is this the question? Lessons from animal models

PURPOSE OF REVIEW

Low birth weight and accelerated postnatal catch-up growth during early life are independent risk factors for adult disease, including diabetes, obesity, and cardiovascular disease. As they are intimately linked, it is difficult to determine the independent contributions of birth weight and catch-up growth per se. This review focuses on evidence derived from animal models of disease, in which it is possible to dissect more clearly the independent roles of intrauterine growth retardation, low birth weight, and catch-up growth in mediating disease risk.

RECENT FINDINGS

Recent data from rats, mice and birds show that accelerated postnatal growth is a trigger for the development of adult disease and, ultimately, can affect longevity.

SUMMARY

Understanding the mechanisms and relative contribution of low birth weight and early postnatal catch-up growth to late onset of disease is critical to establish appropriate interventions to prevent or delay adult disease.

Insulin resistance induced by hydrocortisone is increased in patients with abdominal obesity

Glucocorticoids hypersensitivity may be involved in the development of abdominal obesity and insulin resistance. Eight normal weight and eight obese women received on two occasions a 3-h intravenous infusion of saline or hydrocortisone (HC) (1.5 microg x kg(-1) x min(-1)). Plasma cortisol, insulin, and glucose levels were measured every 30 min from time(-30) (min) (time(-30)) to time(240). Free fatty acids, adiponectin, and plasminogen activator inhibitor-1 (PAI-1) levels were measured at time(-30), time(180), and time(240). At time(240), subjects underwent an insulin tolerance test to obtain an index of insulin sensitivity (K(ITT)). Mean(30-240) cortisol level was similar in control and obese women after saline (74 +/- 16 vs. 75 +/- 20 microg/l) and HC (235 +/- 17 vs. 245 +/- 47 microg/l). The effect of HC on mean(180-240) insulin, mean(180-240) insulin resistance obtained by homeostasis model assessment (HOMA-IR), and K(ITT) was significant in obese (11.4 +/- 2.0 vs. 8.2 +/- 1.3 mU/l, P < 0.05; 2.37 +/- 0.5 vs. 1.64 +/- 0.3, P < 0.05; 2.81 +/- 0.9 vs. 3.32 +/- 1.02%/min, P < 0.05) but not in control women (3.9 +/- 0.6 vs. 2.8 +/- 0.5 mU/l; 0.78 +/- 0.1 vs. 0.49 +/- 0.1; 4.36 +/- 1.1 vs. 4.37 +/- 1.2%/min). In the whole population, the quantity of visceral fat, estimated by computerized tomography scan, was correlated with the increment of plasma insulin and HOMA-IR during HC infusion [Delta mean(30-240) insulin (r = 0.61, P < 0.05), Delta mean(30-240) HOMA-IR (r = 0.66, P < 0.01)]. The increase of PAI-1 between time(180) and time(240) after HC was higher in obese women (+25%) than in controls (+12%) (P < 0.05), whereas no differential effect between groups was observed for free fatty acids or adiponectin. A moderate hypercortisolism, equivalent to that induced by a mild stress, has more pronounced consequences on insulin sensitivity in abdominally obese women than in controls. These deleterious effects are correlated with the amount of visceral fat.

Mechanisms of Disease: regulation of glucocorticoid and receptor levels—impact on the metabolic syndrome

Glucocorticoids exert their effects in target tissues predominantly through their interaction with the glucocorticoid receptor, a member of the nuclear receptor superfamily of transcription factors. Over the years many studies have linked hormone responsiveness, both in vitro and in vivo, to the levels of both glucocorticoid and glucocorticoid receptor; furthermore, an impact of glucocorticoid receptor subcellular trafficking on hormone response has been revealed. This review will focus on the molecular mechanisms responsible for the regulation of glucocorticoid receptor trafficking and expression, and will highlight work that revealed selective physiological effects of altered glucocorticoid receptor expression. The role of alterations in glucocorticoid levels and glucocorticoid receptor function in the metabolic syndrome will also be discussed.

GABAA receptor antagonists prevent abnormalities in leptin, insulin and amylin actions on paraventricular hypothalamic neurons of overweight rats

The hypothalamic regulatory system of body weight which develops in rats during critical periods of early postnatal life seems to express plastic changes depending on nutrition at that time. Adult rats previously exposed to early postnatal overnutrition by raising them in small litters become persistently predisposed to overweight, hyperphagia and hyperleptinaemia. The hypothesis was raised that feeding-related peptides could be involved through altered effects on neuronal activity of the regulatory systems of such rats. This was studied on brain slices of small-litter rats and normal-weight controls between days 60 and 120 of life. Neurons of the medial parvocellular part of the paraventricular nucleus were significantly activated by the adiposity signals leptin, insulin and amylin in controls. This is a kind of negative feedback, because activation of these neurons is known to be followed in vivo by increased energy expenditure. GABAergic mechanisms seem to affect these neuronal responses because the activating effects of insulin and amylin were reduced in the presence of a GABA(A) receptor antagonist. In overweight small-litter rats, however, the neuronal responses to the adiposity signals were significantly changed; activating effects were reduced and inhibitory effects increased. By means of blockade of GABA(A) receptors, significant alterations in the neuronal responses to leptin, insulin and amylin in small-litter rats were prevented. Responses to the peptides were reversed and now resembled those of controls. In conclusion, changes in neuronal wiring with GABAergic interneurons seem to contribute to a persistently reduced negative feedback of adiposity signals in early postnatally overfed rats.

Effects of perinatal overfeeding on mechanisms controlling food intake and body weight homeostasis

The prevalence of overweight and obesity in most developed countries has markedly increased during the last several decades. In addition to genetic, hormonal and metabolic influences, epigenetic environmental factors, such as fetal and neonatal nutrition, play a key role in the development of obesity. Interestingly, becoming overweight during critical developmental periods of fetal and/or neonatal life has been shown to continue throughout juvenile life into adulthood. In spite of this evidence, the specific biological mechanisms underlying this fetal/neonatal programming are not perfectly understood. However, it is clear that circulating hormones, such as insulin, leptin and ghrelin, play a critical role in the development and programming of hypothalamic circuits regulating food intake and bodyweight homeostasis.

11beta-hydroxysteroid dehydrogenase type 1 mRNA is increased in both visceral and subcutaneous adipose tissue of obese patients

OBJECTIVE

Data from rodents provide evidence for a causal role of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) in the development of obesity and its complications. In humans, 11beta-HSD-1 is increased in subcutaneous adipose tissue (SAT) of obese patients, and higher adipose 11beta-HSD-1 was associated with features of the metabolic syndrome. To date, there is no evidence for an increased expression of 11beta-HSD-1 in human visceral adipose tissue (VAT), although VAT is the major predictor for insulin resistance and the metabolic syndrome.

RESEARCH METHODS AND PROCEDURES

11beta-HSD-1 and hexose-6-phosphate dehydrogenase (the enzyme responsible for the synthesis of nicotinamide adenine dinucleotide phosphate, the cofactor required for 11beta-HSD-1 oxoreductase activity) mRNA levels were measured using real-time quantitative reverse transcriptase-polymerase chain reaction in abdominal SAT and VAT biopsies obtained from 10 normal-weight and 12 obese women. Adiponectin mRNA was used as an internal control.

RESULTS

11beta-HSD-1 mRNA concentrations were significantly increased in both SAT and VAT of obese patients (720% and 450% of controls, respectively; p < 0.05) and correlated with hexose-6-phosphate dehydrogenase mRNA levels. The level of VAT 11beta-HSD-1 mRNA correlated with anthropometric parameters: BMI (r = 0.41, p = 0.05), waist circumference (r = 0.44, p = 0.04), abdominal sagittal diameter (r = 0.51, p = 0.02), and percentage fat (r = 0.51, p = 0.02).

DISCUSSION

Our results demonstrate for the first time that 11beta-HSD-1 mRNA expression is increased in VAT from obese patients. They strengthen the importance of 11beta-HSD-1 in human obesity and its associated complications and suggest the need of clinical studies with specific 11beta-HSD-1 inhibitors.

[Corticotropic axis and chronic stress in abdominal obesity and metabolic syndrome]

Several indicators of corticotropic axis hyperactivity have been observed in common abdominal obesity, which is clinically similar to the obesity found in Cushing's syndrome. Corticotropic axis hyperactivity may be involved in the development and metabolic and cardiovascular complications of abdominal obesity. Several mechanisms may be responsible for this hormonal dysregulation: genetic, lifestyle, and nutritional factors, and chronic stress. We note the necessity of methodologically-impeccable clinical studies for an objective evaluation of the role of stress in obesity.

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

Increased glucocorticoid action and adipose tissue inflammation contribute to excess adiposity. These adaptations may be enhanced in offspring exposed to nutrient restriction (NR) in utero, thereby increasing their susceptibility to later obesity. We therefore determined the developmental ontogeny of glucocorticoid receptor (GR), 11β-hydroxysteroid dehydrogenase (11βHSD) types 1 and 2, and uncoupling protein (UCP)-2 mRNA in perirenal adipose tissue between late gestation and 6 mo after birth in the sheep, as well as the effect of maternal NR targeted between early to mid (28–80 days, term ∼147 days)- or late (110–147 days) gestation. GR and 11βHSD1 mRNA increased with fat mass and were all maximal within the 6-mo observation period. 11βHSD2 mRNA abundance demonstrated a converse decline, whereas UCP2 peaked at 30 days. GR and 11βHSD1 mRNA abundance were strongly correlated with total and relative perirenal adipose tissue weight, and UCP2 was strongly correlated with GR and 11βHSD1 mRNA. Early- to midgestational NR increased GR, 11βHSD1, and UCP2 mRNA, but decreased 11βHSD2 mRNA abundance, an adaptation reversed with late-gestational NR. We conclude that the continual rise in glucocorticoid action and fat mass after birth may underlie the development of later obesity. The magnitude of this adaptation is partly dependent on maternal food intake through pregnancy.

Obesity and type 2 diabetes do not alter splanchnic cortisol production in humans

CONTEXT

Cortisol is a potent regulator of carbohydrate, fat, and protein metabolism.

OBJECTIVE

The objective of the study was to determine whether obesity alone or in combination with type 2 diabetes increases splanchnic and/or leg cortisol production.

DESIGN

Splanchnic and leg cortisol production were measured using the hepatic and leg catheterization technique combined with infusion of D4-cortisol.

SETTING

The study was conducted in a General Clinical Research Center.

PARTICIPANTS

Nine lean nondiabetic, 10 obese nondiabetic, and 11 obese diabetic subjects were studied.

INTERVENTIONS

Diabetic volunteers were withdrawn from their glucose-lowering medications before study.

MAIN OUTCOME MEASURES

Rates of total body, splanchnic and leg cortisol, and D3-cortisol production were measured.

RESULTS

Rates of splanchnic cortisol production equaled or exceeded those occurring in extrasplanchnic tissues (e.g. the adrenals) in all three groups. However, because concurrent splanchnic cortisol uptake also occurred, net splanchnic cortisol release was minimal. Splanchnic cortisol production and splanchnic D3-cortisol production (an index of splanchnic 11beta-hydroxysteroid dehydrogenase type 1 activity) did not differ among the three groups. In addition, splanchnic cortisol production did not correlate with either visceral fat or endogenous glucose production. On the other hand, splanchnic cortisol uptake was greater in the obese diabetic than lean nondiabetic subjects (25 +/- 2.9 vs. 15.3 +/- 2.5 microg/min; P < 0.05). Splanchnic, but not leg, D3-cortisol production was correlated with total body D3-cortisol production (r = 0.70; P < 0.001).

CONCLUSIONS

Although large amounts of cortisol are produced within the splanchnic bed, implying high intrahepatic glucocorticoid concentrations, rates do not differ in lean and obese nondiabetic humans and are not influenced by the presence of type 2 diabetes mellitus. On the other hand, obesity but not diabetes increases splanchnic cortisol uptake.