Adipose tissue gene expression profiling reveals distinct molecular pathways that define visceral adiposity in offspring of maternal protein-restricted rats

Visceral adipose tissue and leptin increase colonic epithelial tight junction permeability via a RhoA-ROCK-dependent pathway

Proinflammatory cytokines produced by immune cells play a central role in the increased intestinal epithelial permeability during inflammation. Expansion of visceral adipose tissue (VAT) is currently considered a consequence of intestinal inflammation. Whether VAT per se plays a role in early modifications of intestinal barrier remains unknown. The aim of this study was to demonstrate the direct role of adipocytes in regulating paracellular permeability of colonic epithelial cells (CECs). We show in adult rats born with intrauterine growth retardation, a model of VAT hypertrophy, and in rats with VAT graft on the colon, that colonic permeability was increased without any inflammation. This effect was associated with altered expression of tight junction (TJ) proteins occludin and ZO-1. In coculture experiments, adipocytes decreased transepithelial resistance (TER) of Caco-2 CECs and induced a disorganization of ZO-1 on TJs. Intraperitoneal administration of leptin to lean rats increased colonic epithelial permeability and altered ZO-1 expression and organization. Treatment of HT29-19A CECs with leptin, but not adiponectin, dose-dependently decreased TER and altered TJ and F-actin cytoskeleton organization through a RhoA-ROCK-dependent pathway. Our data show that adipocytes and leptin directly alter TJ function in CECs and suggest that VAT could impair colonic epithelial barrier.

Nutritional manipulations in the perinatal period program adipose tissue in offspring

Epidemiological studies demonstrated initially that maternal undernutrition results in low birth weight with increased risk for long-lasting energy balance disorders. Maternal obesity and diabetes associated with high birth weight, excessive nutrition in neonates, and rapid catchup growth also increase the risk of adult-onset obesity. As stated by the Developmental Origin of Health and Disease concept, nutrient supply perturbations in the fetus or neonate result in long-term programming of individual body weight set point. Adipose tissue is a key fuel storage unit involved mainly in the maintenance of energy homeostasis. Studies in numerous animal models have demonstrated that the adipose tissue is the focus of developmental programming events in a sex- and depot-specific manner. In rodents, adipose tissue development is particularly active during the perinatal period, especially during the last week of gestation and during early postnatal life. In contrast to rodents, this process essentially takes place before birth in bigger mammals. Despite these different developmental time windows, altricial and precocial species share several mechanisms of adipose tissue programming. Offspring from malnourished dams present adipose tissue with a series of alterations: impaired glucose uptake, insulin and leptin resistance, low-grade inflammation, modified sympathetic activity with reduced noradrenergic innervations, and thermogenesis. These modifications reprogram adipose tissue metabolism by changing fat distribution and composition and by enhancing adipogenesis, predisposing the offspring to fat accumulation. Subtle adipose tissue circadian rhythm changes are also observed. Inappropriate hormone levels, modified tissue sensitivity (especially glucocorticoid system), and epigenetic mechanisms are key factors for adipose tissue programming during the perinatal period.

Nutritional potential of metabolic remodelling of white adipose tissue

PURPOSE OF REVIEW

Recent findings in animals suggest that diet-related factors can programme adipose tissue features in early life and remodel white adipose tissue (WAT) towards a brown adipose tissue (BAT)-like phenotype in adulthood, while impacting on body fat content and susceptibility to obesity. The purpose of this review is to address the significance of these results and their applicability in humans.

RECENT FINDINGS

Nutritional conditions in the perinatal period influence sympathetic innervation to WAT and WAT cellularity in rodents. Leptin intake during the suckling period prevents obesity and other metabolic alterations in later life in rats through mechanisms that include increased sensitivity of adipose tissues to leptin. Recent data support the thermogenic functionality of inducible brown-like cells in rodent WAT and functional thermogenic beige adipogenesis from human progenitor cells. Diet-related factors and exercise can promote BAT activation and/or WAT-to-BAT remodelling (WAT browning) in animals.

SUMMARY

Animal studies suggest that adipose tissue health and whole body adiposity might be influenced by early life nutrition and lifestyle factors in adulthood impacting energy metabolism in adipose tissues. For this knowledge to be translated to humans, biomarkers allowing early detection of the programming status of the individual and technologies allowing measuring of the thermogenic activity of adipose tissue depots in vivo are required.

Nutritional mismatch in postnatal life of low birth weight rat offspring leads to increased phosphorylation of hepatic eukaryotic initiation factor 2 α in adulthood

OBJECTIVE

Epidemiological studies have established that low birth weight offspring, when faced with a nutritional mismatch in postnatal life, have an increased risk of developing the metabolic syndrome. Our laboratory and others have demonstrated that maternal protein restriction (MPR) leads to high cholesterol and insulin resistance in the offspring due to impaired liver function, though the underlying molecular mechanisms remain elusive. Recent in vitro studies have associated decreased phosphorylation of Akt1 (Serine 473), a marker of insulin sensitivity, with increased phosphorylation of eukaryotic initiation factor (eIF)-2α (Serine 51), a key regulator of protein translation attenuation. The main aim of the study was to determine whether nutritional mismatch in MPR offspring leads to elevated phospho-eIF2α (Ser51) levels in the liver.

MATERIALS/METHODS

To investigate if this occurs long-term in MPR offspring, pregnant Wistar rats were fed a control (20%) protein diet (control) or a low (8%) protein diet during pregnancy and postnatal life (LP1), or during pregnancy and lactation (LP2).

RESULTS

At postnatal day 130, LP2 offspring exhibited increases in hepatic phosphorylation of eIF2α (Ser51) concomitant with decreases in the phosphorylation of Akt1 (Ser473), while LP1 offspring exhibited the converse relationship. Interestingly, in embryonic day 19 livers derived from control or MPR pregnancy, no changes in eIF2α (Ser51) or Ak1 (Ser473) phosphorylation were observed.

CONCLUSION

Collectively, our data provide robust evidence that phosphorylation of eIF2α (Ser51) is inversely correlated with phosphorylated Akt1 (Ser473) in vivo. Moreover, this study demonstrates that this inverse relationship is adversely influenced in these MPR offspring by a mismatch in the postnatal nutritional environment.

Prenatal low-protein and postnatal high-fat diets induce rapid adipose tissue growth by inducing Igf2 expression in Sprague Dawley rat offspring

Maternal low-protein diets result in lower birth weight followed by accelerated catch-up growth that is accompanied by the development of obesity and glucose intolerance in later life. Whether postnatal high-fat (HF) diets further contribute to the development of obesity and insulin resistance in offspring by affecting adipose tissue metabolism and DNA methylation is currently unknown. Obese-prone Sprague-Dawley rats were fed 8% low protein (LP) or 20% normal protein diets for 3 wk prior to conception and throughout pregnancy and lactation to investigate whether prenatal LP and postnatal HF diets affect the rate of adipose tissue growth, insulin-like growth factor 2 (Igf2) expression, and DNA methylation in male offspring. At weaning, the offspring were fed 10% normal fat or 45% HF diets for 12 wk. The adipose tissue growth rate was increased (up to 26-fold) by the LP prenatal and HF postnatal diets. Adipose tissue Igf2 mRNAs and DNA methylation were increased by the LP prenatal and HF postnatal diets. The LP prenatal and HF postnatal diet increased the number of small adipocytes in adipose tissue and decreased insulin sensitivity. These findings suggest that prenatal LP and postnatal HF intake result in adipose tissue catch-up growth through alterations in the expression of the Igf2 gene and DNA methylation within adipocytes. These alterations in adiposity are accompanied by an increased risk of development of type 2 diabetes.

Preweaning growth hormone treatment ameliorates adipose tissue insulin resistance and inflammation in adult male offspring following maternal undernutrition

It is well established that early-life nutritional alterations lead to increased risk of obesity and metabolic disorders in adult life. Although it is clear that obesity gives rise to chronic low-grade inflammation, there is little evidence regarding the role of inflammation in the adipose tissue of undernourished (UN) offspring. GH reduces fat mass and has antiinflammatory properties. The present study examined the effect of maternal UN on adipose inflammation in adult offspring and whether GH treatment during a critical period of developmental plasticity could ameliorate metabolic dysfunction associated with a poor start to life. Sprague Dawley rats were assigned to chow (C) or UN (50% ad libitum; UN) diet throughout gestation. Male C and UN pups received saline (control saline [CS]/UN) or GH (2.5 μg/g/d; control growth hormone [CGH]/undernourished growth hormone [UNGH]) from days 3-21. Postweaning males were further randomized and fed either chow or high-fat diet until day 160. An ex vivo glucose uptake assay demonstrated adipose tissue from UN offspring displayed attenuated insulin-stimulated glucose uptake compared with CS, CGH, and UNGH. This was associated with increased insulin receptor, glucose transporter 4, and insulin receptor substrate 1 gene expression. Furthermore, UN demonstrated enhanced TNFα and IL-1β secretion from adipose explants and stromal vascular fraction cultures accompanied by increased adipose tissue gene expression of several key proinflammatory genes and markers of macrophage infiltration. Overall, UN offspring displayed a more potent immunophenotype, which correlated with decreased insulin sensitivity. Preweaning GH treatment negates these detrimental effects, indicating the potential for reversing metabolic dysfunction in UN adult offspring.

Maternal protein restriction leads to enhanced hepatic gluconeogenic gene expression in adult male rat offspring due to impaired expression of the liver X receptor

Epidemiological studies demonstrate that the link between impaired fetal development and glucose intolerance in later life is exacerbated by postnatal catch-up growth. Maternal protein restriction (MPR) during pregnancy and lactation in the rat has been previously demonstrated to lead to impaired glucose tolerance in adulthood, however the effects of protein restoration during weaning on glucose homeostasis are largely unknown. Recent in vitro studies have identified that the liver X receptor α (LXRα) maintains glucose homeostasis by inhibiting critical genes involved in gluconeogenesis including G6pase (G6pc), 11β-Hsd1 (Hsd11b1) and Pepck (Pck1). Therefore, we hypothesized that MPR with postnatal catch-up growth would impair LXRα in vivo, which in turn would lead to augmented gluconeogenic LXRα-target gene expression and glucose intolerance. To examine this hypothesis, pregnant Wistar rats were fed a control (20%) protein diet (C) or a low (8%) protein diet during pregnancy and switched to a control diet at birth (LP). At 4 months, the LP offspring had impaired glucose tolerance. In addition, LP offspring had decreased LXRα expression, while hepatic expression of 11β-HSD1 and G6Pase was significantly higher. This was concomitant with decreased binding of LXRα to the putative LXRE on 11β-Hsd1 and G6pase. Finally, we demonstrated that the acetylation of histone H3 (K9,14) surrounding the transcriptional start site of hepatic Lxrα (Nr1h3) was decreased in LP offspring, suggesting MPR-induced epigenetic silencing of the Lxrα promoter. In summary, our study demonstrates for the first time the important role of LXRα in mediating enhanced hepatic gluconeogenic gene expression and consequent glucose intolerance in adult MPR offspring.

Foetal life protein restriction in male mink (Neovison vison) kits lowers post-weaning protein oxidation and the relative abundance of hepatic fructose-1,6-bisphosphatase mRNA

Foetal life malnutrition has been studied intensively in a number of animal models. Results show that especially foetal life protein malnutrition can lead to metabolic changes later in life. This might be of particular importance for strict carnivores, for example, cat and mink (Neovison vison) because of their higher protein requirement than in other domestic mammals. This study aimed to investigate the effects of low protein provision during foetal life to male mink kits on their protein metabolism during the early post-weaning period of rapid growth and to investigate whether foetal life protein deficiency affects the response to adequate or deficient protein provision post weaning. Further, we intended to study whether the changes in the gene expression of key enzymes in foetal hepatic tissue caused by maternal protein deficiency were manifested post-weaning. A total of 32 male mink kits born to mothers fed either a low-protein diet (LP), that is, 14% of metabolizable energy (ME) from protein (foetal low - FL), n = 16, or an adequate-protein (AP) diet, that is, 29% of ME from protein (foetal adequate - FA), n = 16) in the last 16.3 ± 1.8 days of pregnancy were used. The FL offspring had lower birth weight and lower relative abundance of fructose-1,6-bisphosphatase (Fru-1,6-P2ase) and pyruvate kinase mRNA in foetal hepatic tissue than FA kits. The mothers were fed a diet containing adequate protein until weaning. At weaning (7 weeks of age), half of the kits from each foetal treatment group were fed an AP diet (32% of ME from protein; n = 8 FA and 8 FL) and the other half were fed a LP diet (18% of ME from protein; n = 8 FA and 8 FL) until 9.5 weeks of age, yielding four treatment groups (i.e. FA-AP, FA-LP, FL-AP and FL-LP). Low protein provision in foetal life lowered the protein oxidation post-weaning compared with the controls (P = 0.006), indicating metabolic flexibility and a better ability to conserve protein. This could not, however, be supported by changes in liver mass because of foetal life experience. A lower relative abundance of Fru-1,6-P2ase mRNA was observed (P < 0.05), being lower in 9.5-week-old FL than in FA kits. It can be concluded that foetal life protein restriction leads to changes in post-weaning protein metabolism through lower protein oxidation of male mink kits.

Epigenetic basis for fetal origins of age-related disease

The current concept of fetal origins of adult diseases describes in utero programming, or adaptation to a spectrum of adverse environmental conditions that ultimately leads to increased susceptibility to age-related diseases (e.g., type 2 diabetes and cardiovascular disease) later in life. Although the precise mechanism of this biological memory remains unclear, mounting evidence suggests an epigenetic basis. The increased susceptibility to chronic disease and involvement of multiple organ systems that is observed is analogous to the decline in resistance to disease that is typical of normal aging. Although the cumulative environment over the course of a lifetime can induce increasing epigenetic dysregulation, we propose that adverse events that occur during early development can induce significant additional dysregulation of the epigenome. Here, we describe the current evidence for fetal origins of adult disease and the associated role of epigenetic dysregulation. In addition, we present a new perspective on the induction of epigenetic alterations in utero, which subsequently lead to an aging phenotype marked by increased susceptibility to age-related diseases.

Developmental origins of obesity: programmed adipogenesis

The metabolic syndrome epidemic, including a marked increase in the prevalence of obesity and gestational diabetes mellitus (GDM) among pregnant women, represents a significant public health problem. There is increasing recognition that the risk of adult obesity is clearly influenced by prenatal and infant environmental exposures, particularly nutrition. This tenet is the fundamental basis of developmental programming. Low birth weight, together with infant catch-up growth, is associated with a significant risk of adult obesity. Exposure to maternal obesity, with or without GDM, or having a high birth weight also represents an increased risk for childhood and adult obesity. Animal models have replicated human epidemiologic findings and elucidated potential programming mechanisms that include altered organ development, cellular signaling responses, and epigenetic modifications. Prenatal care has made great strides in optimizing maternal, fetal, and neonatal health, and now has the opportunity to begin interventions which prevent or reduce childhood/adult obesity. Guidelines that integrate optimal pregnancy nutrition and weight gain, management of GDM, and newborn feeding strategies with long-term consequences on adult obesity, remain to be elucidated.

Association between body weight at weaning and remodeling in the subcutaneous adipose tissue of obese adult mice with undernourishment in utero

Rapid growth in infancy considerably increases the risk of obesity and metabolic disorders in adulthood especially among neonates born small. To investigate the mechanism involved, we developed an animal model of undernourishment in utero by maternal caloric restriction, in which the Z scores of body weight at weaning (19.5 days) positively correlated with parameters of obesity, metabolic disorders, and remodeling of subcutaneous adipose tissue, such as numbers of macrophages in adipose tissue, the ratio of inflammatory M1 to anti-inflammatory M2 macrophages, estimated by gene expression of specific antigens, and the relative ratio of small adipocytes less than 30 μm in diameter, on a high-fat diet at 17 weeks of age. To our knowledge, this is the first report of a possible connection between infantile body weight and adipose tissue remodeling in obesity after undernourishment in utero.

Early metabolic defects in dexamethasone-exposed and undernourished intrauterine growth restricted rats

Poor fetal growth, also known as intrauterine growth restriction (IUGR), is a worldwide health concern. IUGR is commonly associated with both an increased risk in perinatal mortality and a higher prevalence of developing chronic metabolic diseases later in life. Obesity, type 2 diabetes or metabolic syndrome could result from noxious “metabolic programming.” In order to better understand early alterations involved in metabolic programming, we modeled IUGR rat pups through either prenatal exposure to synthetic glucocorticoid (dams infused with dexamethasone 100 µg/kg/day, DEX) or prenatal undernutrition (dams feeding restricted to 30% of ad libitum intake, UN). Physiological (glucose and insulin tolerance), morphometric (automated tissue image analysis) and transcriptomic (quantitative PCR) approaches were combined during early life of these IUGR pups with a special focus on their endocrine pancreas and adipose tissue development. In the absence of catch-up growth before weaning, DEX and UN IUGR pups both presented basal hyperglycaemia, decreased glucose tolerance, and pancreatic islet atrophy. Other early metabolic defects were model-specific: DEX pups presented decreased insulin sensitivity whereas UN pups exhibited lowered glucose-induced insulin secretion and more marked alterations in gene expression of pancreatic islet and adipose tissue development regulators. In conclusion, these results show that before any catch-up growth, IUGR rats present early physiologic, morphologic and transcriptomic defects, which can be considered as initial mechanistic basis of metabolic programming.

In utero programming of later adiposity: the role of fetal growth restriction

Intrauterine growth restriction (IUGR) is strongly associated with obesity in adult life. The mechanisms contributing to the onset of IUGR-associated adult obesity have been studied in animal models and humans, where changes in fetal adipose tissue development, hormone levels and epigenome have been identified as principal areas of alteration leading to later life obesity. Following an adverse in utero development, IUGR fetuses display increased lipogenic and adipogenic capacity in adipocytes, hypoleptinemia, altered glucocorticoid signalling, and chromatin remodelling, which subsequently all contribute to an increased later life obesity risk. Data suggest that many of these changes result from an enhanced activity of the adipose master transcription factor regulator, peroxisome proliferator-activated receptor-γ (PPARγ) and its coregulators, increased lipogenic fatty acid synthase (FAS) expression and activity, and upregulation of glycolysis in fetal adipose tissue. Increased expression of fetal hypothalamic neuropeptide Y (NPY), altered hypothalamic leptin receptor expression and partitioning, reduced adipose noradrenergic sympathetic innervations, enhanced adipose glucocorticoid action, and modifications in methylation status in the promoter of hepatic and adipose adipogenic and lipogenic genes in the fetus also contribute to obesity following IUGR. Therefore, interventions that inhibit these fetal developmental changes will be beneficial for modulation of adult body fat accumulation.

Metabolic programming of insulin action and secretion

Type 2 diabetes (T2D), also known as non-insulin dependent diabetes mellitus, arises as a consequence of peripheral insulin resistance in combination with an inability of pancreatic islet β-cells to secrete adequate amounts of insulin. It is widely recognized that the current environment (e.g. an unhealthy diet and sedentary lifestyle) contributes to this process. In recent years, however, the role of the early environment, particularly nutrition, has emerged as an important factor capable of influencing health and disease risk of an individual, including risk of T2D. The impact of early environment on glucose metabolism has been extensively studied. Compelling evidence from epidemiological studies and animal models suggests that early nutrition can affect insulin action as a mediator of glucose homeostasis in peripheral tissues and as an important regulator of appetite and body weight. The early environment can also affect β-cell mass and function, and hence insulin secretion. The molecular mechanisms underlying the relationship between a suboptimal early environment and impaired insulin action and secretion is thought to include epigenetic modifications of the foetal genome, oxidative stress and mitochondrial dysfunction.

Azuki bean polyphenols intake during lactation upregulate AMPK in male rat offspring exposed to fetal malnutrition

OBJECTIVE

Fetal malnutrition is an early-life inducer of dyslipidemia and glucose intolerance. The aim of this study was to examine whether maternal azuki bean (Vigna angularis) polyphenol (AP) intake during lactation affects the adenosine monophosphate-activated protein kinase (AMPK) pathway and lipid metabolism in offspring exposed to fetal malnutrition.

METHODS

Pregnant Wistar rats were divided into three groups: a control diet offered during gestation and lactation (CC), a low-protein diet during gestation and a control diet during lactation (LPC); and a low-protein diet during gestation and a 1.0% AP-containing control diet during lactation (LPAP). Male pups were randomly selected for the study; half the pups were sacrificed at 3 wk of age and the other half were fed a standard diet and sacrificed at 23 wk. Hepatic triacylglycerol levels, phosphorylation levels of AMPK and acetyl-coenzyme A carboxylase (ACC), and mRNA levels of sterol regulatory element-binding protein-1c (SREBP-1c) were evaluated.

RESULTS

Significant decreases in body weights and hepatic triacylglycerol levels were found in the LPAP compared with the LPC group. Plasma adiponectin levels in the LPAP group were higher than those in the LPC group. AMPK phosphorylation was upregulated in the livers and skeletal muscles in young and adult LPAP compared with LPC rats. ACC phosphorylation was upregulated in skeletal muscles of LPAP rats. SREBP-1c mRNA expression was decreased in the livers of LPAP rats.

CONCLUSION

Our results suggest that maternal AP intake during lactation upregulates AMPK phosphorylation not only in young but also in adult offspring exposed to fetal malnutrition and may lead to decreased hepatic lipid accumulation by ACC phosphorylation and downregulation of SREBP-1c expression.

MicroRNA-130b and microRNA-374b mediate the effect of maternal dietary protein on offspring lipid metabolism in Meishan pigs

To investigate whether the effect of maternal dietary protein on offspring lipid metabolism is mediated by microRNA (miRNA), fourteen Meishan sows were fed either low-protein (LP, half of standard protein (SP) level, n 7) or SP (n 7) diets throughout gestation and lactation periods. PPAR-γ and CCAAT/enhancer-binding protein-β (C/EBP-β) protein expression was evaluated. The expression of miRNA predicted to directly target PPAR-γ and C/EBP-β in the subcutaneous fat of offspring at weaning age was determined, and the functions of these potential miRNA were verified. The results showed that piglet body weight and back fat thickness were significantly decreased in the LP group compared with the SP group (P< 0·05). The protein level of PPAR-γ was significantly decreased and C/EBP-β protein expression was also decreased, though not significantly (P= 0·056), in the subcutaneous fat of the LP group. Furthermore, miRNA expression analysis showed that miR-130b, targeting the PPAR-γ 3′-untranslated region (UTR), and miR-374b, targeting the C/EBP-β 3′-UTR, were significantly increased in the LP group compared with the SP group; other candidate regulatory miRNA were expressed similarly in both groups. Dual luciferase activity assay results indicated that miR-130b directly recognised and bound to the 3′-UTR of PPAR-γ and thereby suppressed PPAR-γ gene expression. Similar results were found for miR-374b and the 3′-UTR of C/EBP-β. The present study showed that miR-130b and miR-374b are involved in the effect of maternal dietary protein on offspring lipid metabolism in pigs. These results shed new light on our understanding of the maternal effect on offspring lipid deposition.

Coordinated Regulation of PPARγ Expression and Activity through Control of Chromatin Structure in Adipogenesis and Obesity

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) is required for differentiation and function of mature adipocytes. Its expression is induced during adipogenesis where it plays a key role in establishing the transcriptome of terminally differentiated white fat cells. Here, we review findings indicating that PPARγ expression and activity are intricately regulated through control of chromatin structure. Hierarchical and combinatorial activation of transcription factors, noncoding RNAs, and chromatin remodelers allows for temporally controlled expression of PPARγ and its target genes through sequential chromatin remodelling. In obesity, these regulatory pathways may be altered and lead to modified PPARγ activity.

Fructose consumption during pregnancy and lactation induces fatty liver and glucose intolerance in rats

Nutritional insults during pregnancy and lactation are health risks for mother and offspring. Both fructose (FR) and low-protein (LP) diets are linked to hepatic steatosis and insulin resistance in nonpregnant animals. We hypothesized that dietary FR or LP intake during pregnancy may exacerbate the already compromised glucose homeostasis to induce gestational diabetes and fatty liver. Therefore, we investigated and compared the effects of LP or FR intake on hepatic steatosis and insulin resistance in unmated controls (CTs) and pregnant and lactating rats. Sprague-Dawley rats were fed a CT, or a 63% FR, or an 8% LP diet. Glucose tolerance test at day 17 of the study revealed greater (P < .05) blood glucose at 10 (75.6 mg/dL vs 64.0 ± 4.8 mg/dL) minutes and 20 (72.4 mg/dL vs 58.6 ± 4.0 mg/dL) minutes after glucose dose and greater area under the curve (4302.3 mg∙dL(-1)∙min(-1) vs 3763.4 ± 263.6 mg∙dL(-1)∙min(-1)) for FR-fed dams compared with CT-fed dams. The rats were euthanized at 21 days postpartum. Both the FR- and LP-fed dams had enlarged (P < .05) livers (9.3%, 7.1% body weight vs 4.8% ± 0.2% body weight) and elevated (P < .05) liver triacylglycerol (216.0, 130.0 mg/g vs 19.9 ± 12.6 mg/g liver weight) compared with CT-fed dams. Fructose induced fatty liver and glucose intolerance in pregnant and lactating rats, but not unmated CT rats. The data demonstrate a unique physiological status response to diet resulting in the development of gestational diabetes coupled with hepatic steatosis in FR-fed dams, which is more severe than an LP diet.

Transcriptional response of skeletal muscle to a low-protein gestation diet in porcine offspring accumulates in growth- and cell cycle-regulating pathways

Inadequate maternal protein supply during gestation represents an environmental factor that affects physiological signaling pathways with long-term consequences for growth, function, and structure of various tissues. Hypothesizing that the offspring's transcriptome is persistently altered by maternal diets, we used a porcine model to monitor the longitudinal expression changes in muscle to identify pathways relevant to fetal initiation of postnatal growth and development. German Landrace gilts were fed isoenergetic gestational diets containing 6.5% (LP) or 12.1% protein. The longissimus dorsi samples were collected from offspring at 94 days postconception (dpc) and 1, 28, and 188 days postnatum (dpn) for expression profiling. At 94 dpc, 1 dpn, and 28 dpn relatively few transcripts (<130) showed an altered abundance between the dietary groups. In fact, at 94 dpc genes of G2/M checkpoint regulation and mitotic roles of Polo-like kinases showed lowered transcript abundance in LP. At 188 dpn 677 transcripts were altered including those related to oxidative phosphorylation, citrate cycle, fatty acid metabolism (higher abundance in LP) and cell cycle regulation (lower abundance in LP). Correspondingly, transcriptional alterations during pre and postnatal development differed considerably among dietary groups, particularly for genes related to cell cycle regulation (G1/S and G2/M checkpoint regulation; cyclines), growth factor signaling (GH, IGF1, mTOR, RAN, VEGF, INSR), lipid metabolism, energy metabolism, and nucleic acid metabolism. In skeletal muscle, fetal programming related to maternal LP diets disturbed gene expression in growth-related pathways into adulthood. Diet-dependent gene expression may hamper proper development, thereby affecting signaling pathways related to energy utilization.

Caffeine reduces 11β-hydroxysteroid dehydrogenase type 2 expression in human trophoblast cells through the adenosine A(2B) receptor

Maternal caffeine consumption is associated with reduced fetal growth, but the underlying molecular mechanisms are unknown. Since there is evidence that decreased placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) is linked to fetal growth restriction, we hypothesized that caffeine may inhibit fetal growth partly through down regulating placental 11β-HSD2. As a first step in examining this hypothesis, we studied the effects of caffeine on placental 11β-HSD2 activity and expression using our established primary human trophoblast cells as an in vitro model system. Given that maternal serum concentrations of paraxanthine (the primary metabolite of caffeine) were greater in women who gave birth to small-for-gestational age infants than to appropriately grown infants, we also studied the effects of paraxanthine. Our main findings were: (1) both caffeine and paraxanthine decreased placental 11β-HSD2 activity, protein and mRNA in a concentration-dependent manner; (2) this inhibitory effect was mediated by the adenosine A(2B) receptor, since siRNA-mediated knockdown of this receptor prevented caffeine- and paraxanthine-induced inhibition of placental 11β-HSD2; and (3) forskolin (an activator of adenyl cyclase and a known stimulator of 11β-HSD2) abrogated the inhibitory effects of both caffeine and paraxanthine, which provides evidence for a functional link between exposure to caffeine and paraxanthine, decreased intracellular levels of cAMP and reduced placental 11β-HSD2. Taken together, these findings reveal that placental 11β-HSD2 is a novel molecular target through which caffeine may adversely affect fetal growth. They also uncover a previously unappreciated role for the adenosine A(2B) receptor signaling in regulating placental 11β-HSD2, and consequently fetal development.

Molecular mechanisms underlying the fetal programming of adult disease

Adverse events in utero can be critical in determining quality of life and overall health. It is estimated that up to 50 % of metabolic syndrome diseases can be linked to an adverse fetal environment. However, the mechanisms linking impaired fetal development to these adult diseases remain elusive. This review uncovers some of the molecular mechanisms underlying how normal physiology may be impaired in fetal and postnatal life due to maternal insults in pregnancy. By understanding the mechanisms, which include epigenetic, transcriptional, endoplasmic reticulum (ER) stress, and reactive oxygen species (ROS), we also highlight how intervention in fetal and neonatal life may be able to prevent these diseases long-term.

A low protein diet during pregnancy provokes a lasting shift of hepatic expression of genes related to cell cycle throughout ontogenesis in a porcine model

Background

In rodent models and in humans the impact of gestational diets on the offspring's phenotype was shown experimentally and epidemiologically. Adverse environmental conditions during fetal development provoke an intrauterine adaptive response termed 'fetal programming', which may lead to both persistently biased responsiveness to extrinsic factors and permanent consequences for the organismal phenotype. This leads to the hypothesis that the offspring's transcriptome exhibits short-term and long-term changes, depending on the maternal diet. In order to contribute to a comprehensive inventory of genes and functional networks that are targets of nutritional programming initiated during fetal life, we applied whole-genome microarrays for expression profiling in a longitudinal experimental design covering prenatal, perinatal, juvenile, and adult ontogenetic stages in a porcine model. Pregnant sows were fed either a gestational low protein diet (LP, 6% CP) or an adequate protein diet (AP, 12% CP). All offspring was nursed by foster sows receiving standard diets. After weaning, all offspring was fed standard diets ad libitum.

Results

Analyses of the hepatic gene expression of the offspring at prenatal (94 dies post conceptionem, dpc) and postnatal stages (1, 28, 188 dies post natum, dpn) included comparisons between dietary groups within stages as well as comparisons between ontogenetic stages within diets to separate diet-specific transcriptional changes and maturation processes. We observed differential expression of genes related to lipid metabolism (e.g. Fatty acid metabolism, Biosynthesis of steroids, Synthesis and degradation of ketone bodies, FA elongation in mitochondria, Bile acid synthesis) and cell cycle regulation (e.g. Mitotic roles of PLK, G1/S checkpoint regulation, G2/M DNA damage checkpoint regulation). Notably, at stage 1 dpn no regulation of a distinct pathway was found in LP offspring.

Conclusions

The transcriptomic modulations point to persistent functional demand on the liver towards cell proliferation in the LP group but not in the AP group at identical nutritional conditions during postnatal life due to divergent 'programming' of the genome. Together with the observation that the offspring of both groups did not differ in body weight but in body composition and fat content, the data indicate that the activity of various genes led to diverse partitioning of nutrients among peripheral and visceral organs and tissues.

Endocrine pancreas development: effects of metabolic and intergenerational programming caused by a protein-restricted diet

Experimental studies have demonstrated an association between low birth weight and the later development of type 2 diabetes. This association could be a result of the programming process that affects pancreatic beta-cell development due to poor fetal nutrition. This mechanism may not be limited to the first generation. In rodents, endocrine cells of the pancreas are derived from cells of the endodermal dorsal and ventral anlage that migrate and gather in clusters in a process termed isletogenesis. Islet development occurs relatively late in gestation, and islets undergo substantial remodeling immediately after birth under the regulation of a transcription factor network. Furthermore, the offspring of mice fed a protein-restricted diet exhibit a reduced pancreatic beta-cell mass at birth, lower vascularization, increased apoptosis rate, and changes in glucose metabolism in later life. Although the mechanisms underlying these relationships are unclear, it has been hypothesized that in utero nutritional conditions affect epigenetic patterns of gene transcription that persist throughout life and subsequent generations. We aimed to review the process of the formation of the endocrine pancreas in rodents, the consequences of a protein-restricted diet on offspring, and the transgenerational effects of this insult on the incidence of type 2 diabetes.

Is the adipose tissue a key target of developmental programming of adult adiposity by maternal undernutrition?

Epidemiological studies have shown that maternal undernutrition during pregnancy (MU) leads to intrauterine growth retardation and low birth weight, and may predispose individuals to the development of metabolic syndrome symptoms later in life such as overweight. Some clues from a model of prenatal maternal 70% food-restricted diet throughout gestation in pregnant female rats (FR30) suggest that the white adipose tissue (WAT) is a key target of MU fetal programming. Under standard diet, although showing a lean phenotype, adult FR30 male rats were predisposed to adiposity exhibiting higher serum leptin and corticosterone concentration, two hormones actively involved in WAT regulation. Although FR30 procedure does not worsen the metabolic syndrome features induced by HF diet, FR30HF rats gained more weight and showed hyperleptinemia suggesting increased adiposity. WAT FR30 adult rats revealed marked changes in transcript levels of several genes. In particular, leptin and Ob-Rb, many peptide precursors and receptors, factors involved in lipogenesis and glucocorticoid sensitivity mRNA expression levels as well as mechanisms involved in leptin sensitivity, were modified in FR30 offspring in depot-specific and diet-specific manners. These modifications might predispose for altered fat accumulation in adult male rat offspring.

Maternal periconceptional and gestational low protein diet affects mouse offspring growth, cardiovascular and adipose phenotype at 1 year of age

Human and animal studies have revealed a strong association between periconceptional environmental factors, such as poor maternal diet, and an increased propensity for cardiovascular and metabolic disease in adult offspring. Previously, we reported cardiovascular and physiological effects of maternal low protein diet (LPD) fed during discrete periods of periconceptional development on 6-month-old mouse offspring. Here, we extend the analysis in 1 year aging offspring, evaluating mechanisms regulating growth and adiposity. Isocaloric LPD (9% casein) or normal protein diet (18% casein; NPD) was fed to female MF-1 mice either exclusively during oocyte maturation (for 3.5 days prior to mating; Egg-LPD, Egg-NPD, respectively), throughout gestation (LPD, NPD) or exclusively during preimplantation development (for 3.5 days post mating; Emb-LPD). LPD and Emb-LPD female offspring were significantly lighter and heavier than NPD females respectively for up to 52 weeks. Egg-LPD, LPD and Emb-LPD offspring displayed significantly elevated systolic blood pressure at 52 weeks compared to respective controls (Egg-NPD, NPD). LPD females had significantly reduced inguinal and retroperitoneal fat pad: body weight ratios compared to NPD females. Expression of the insulin receptor (Insr) and insulin-like growth factor I receptor (Igf1r) in retroperitoneal fat was significantly elevated in Emb-LPD females (P<0.05), whilst Emb-LPD males displayed significantly decreased expression of the mitochondrial uncoupling protein 1 (Ucp1) gene compared to NPD offspring. LPD females displayed significantly increased expression of Ucp1 in interscapular brown adipose tissue when compared to NPD offspring. Our results demonstrate that aging offspring body weight, cardiovascular and adiposity homeostasis can be programmed by maternal periconceptional nutrition. These adverse outcomes further exemplify the criticality of dietary behaviour around the time of conception on long-term offspring health.

Developmental programming of adult obesity and cardiovascular disease in rodents by maternal nutrition imbalance

Studies on fetal undernutrition have generated the hypothesis that fetal programming corresponds to an attempt of the fetus to adapt to adverse conditions encountered in utero. These adaptations would be beneficial if these conditions prevail later in life, but they become detrimental in the case of normal or plentiful nutrition and favor the appearance of the metabolic syndrome. In this article, the discussion is limited to the developmental programming of obesity and cardiovascular disorders caused by an early mismatched nutrition, particularly intrauterine growth retardation followed by postnatal catch-up growth. Selected data in humans are reviewed before evoking some mechanisms revealed or suggested by experiments in rodents. A variety of physiologic mechanisms are implicated in obesity programming, 2 of which are detailed. In some, but not all observations, hyperphagia resulting namely from perturbed development of the hypothalamic circuitry devoted to appetite regulation may contribute to obesity. Another contribution may be the developmental changes in the population of fat cell precursors in adipose tissue. Even if the link between obesity and cardiovascular disease is well established, alteration of blood pressure regulation may appear independently of obesity. A loss of diurnal variation in heart rate and blood pressure in adulthood has resulted from maternal undernutrition followed by postnatal overnutrition. Further research should clarify the effect of mismatched early nutrition on the development of brain centers regulating energy intake, energy expenditure, and circadian rhythms.

Developmental programming of the metabolic syndrome - critical windows for intervention

Metabolic disease results from a complex interaction of many factors, including genetic, physiological, behavioral and environmental influences. The recent rate at which these diseases have increased suggests that environmental and behavioral influences, rather than genetic causes, are fuelling the present epidemic. In this context, the developmental origins of health and disease hypothesis has highlighted the link between the periconceptual, fetal and early infant phases of life and the subsequent development of adult obesity and the metabolic syndrome. Although the mechanisms are yet to be fully elucidated, this programming was generally considered an irreversible change in developmental trajectory. Recent work in animal models suggests that developmental programming of metabolic disorders is potentially reversible by nutritional or targeted therapeutic interventions during the period of developmental plasticity. This review will discuss critical windows of developmental plasticity and possible avenues to ameliorate the development of postnatal metabolic disorders following an adverse early life environment.

Maternal prenatal undernutrition programs adipose tissue gene expression in adult male rat offspring under high-fat diet

Several studies have shown that maternal undernutrition leading to low birth weight predisposes offspring to the development of metabolic pathologies such as obesity. Using a model of prenatal maternal 70% food restriction diet (FR30) in rat, we evaluated whether postweaning high-fat (HF) diet would amplify the phenotype observed under standard diet. We investigated biological parameters as well as gene expression profile focusing on white adipose tissues (WAT) of adult offspring. FR30 procedure does not worsen the metabolic syndrome features induced by HF diet. However, FR30HF rats displayed catch-up growth to match the body weight of adult control HF animals, suggesting an increase of adiposity while showing hyperleptinemia and a blunted increase of corticosterone. Using quantitative RT-PCR array, we demonstrated that FR30HF rats exhibited leptin and Ob-Rb as well as many peptide precursor and receptor gene expression variations in WAT. We also showed that the expression of genes involved in adipogenesis was modified in FR30HF animals in a depot-specific manner. We observed an opposite variation of STAT3 phosphorylation levels, suggesting that leptin sensitivity is modified in WAT adult FR30 offspring. We demonstrated that 11β-HSD1, 11β-HSD2, GR, and MR genes are coexpressed in WAT and that FR30 procedure modifies gene expression levels, especially under HF diet. In particular, level variation of 11β-HSD2, whose protein expression was detected by Western blotting, may represent a novel mechanism that may affect WAT glucocorticoid sensitivity. Data suggest that maternal undernutrition differently programs the adult offspring WAT gene expression profile that may predispose for altered fat deposition.

Developmental programming of energy balance and its hypothalamic regulation

Developmental programming is an important physiological process that allows different phenotypes to originate from a single genotype. Through plasticity in early life, the developing organism can adopt a phenotype (within the limits of its genetic background) that is best suited to its expected environment. In humans, together with the relative irreversibility of the phenomenon, the low predictive value of the fetal environment for later conditions in affluent countries makes it a potential contributor to the obesity epidemic of recent decades. Here, we review the current evidence for developmental programming of energy balance. For a proper understanding of the subject, knowledge about energy balance is indispensable. Therefore, we first present an overview of the major hypothalamic routes through which energy balance is regulated and their ontogeny. With this background, we then turn to the available evidence for programming of energy balance by the early nutritional environment, in both man and rodent models. A wealth of studies suggest that energy balance can indeed be permanently affected by the early-life environment. However, the direction of the effects of programming appears to vary considerably, both between and within different animal models. Because of these inconsistencies, a comprehensive picture is still elusive. More standardization between studies seems essential to reach veritable conclusions about the role of developmental programming in adult energy balance and obesity.

Maternal protein restriction elevates cholesterol in adult rat offspring due to repressive changes in histone modifications at the cholesterol 7alpha-hydroxylase promoter

Adverse events in utero, such as intrauterine growth restriction (IUGR), can permanently alter epigenetic mechanisms leading to the metabolic syndrome, which encompasses a variety of symptoms including augmented cholesterol. The major site for cholesterol homeostasis occurs via the actions of hepatic cholesterol 7α-hydroxylase (Cyp7a1), which catabolizes cholesterol to bile acids. To determine whether posttranslational histone modifications influence the long-term expression of Cyp7a1 in IUGR, we used a protein restriction model in rats. This diet during pregnancy and lactation led to IUGR offspring with decreased liver to body weight ratios, followed by increased circulating and hepatic cholesterol levels in both sexes at d 21 and exclusively in the male offspring at d 130. The augmented cholesterol was associated with decreases in the expression of Cyp7a1. Chromatin immunoprecipitation revealed that this was concomitant with diminished acetylation and enhanced methylation of histone H3 lysine 9 [K9,14], markers of chromatin silencing, surrounding the promoter region of Cyp7a1. These epigenetic modifications originate in part due to dietary-induced decreases in fetal hepatic Jmjd2a expression, a histone H3 [K9] demethylase. Collectively, these findings suggest that the augmented cholesterol observed in low-protein diet-derived offspring is due to permanent repressive posttranslational histone modifications at the promoter of Cyp7a1. Moreover, this is the first study to demonstrate that maternal undernutrition leads to long-term cholesterol dysregulation in the offspring via epigenetic mechanisms.

Oxygenomics in environmental stress

Environmental stressors such as chemicals and physical agents induce various oxidative stresses and affect human health. To elucidate their underlying mechanisms, etiology and risk, analyses of gene expression signatures in environmental stress-induced human diseases, including neuronal disorders, cancer and diabetes, are crucially important. Recent studies have clarified oxidative stress-induced signaling pathways in human and experimental animals. These pathways are classifiable into several categories: reactive oxygen species (ROS) metabolism and antioxidant defenses, p53 pathway signaling, nitric oxide (NO) signaling pathway, hypoxia signaling, transforming growth factor (TGF)-beta bone morphogenetic protein (BMP) signaling, tumor necrosis factor (TNF) ligand-receptor signaling, and mitochondrial function. This review describes the gene expression signatures through which environmental stressors induce oxidative stress and regulate signal transduction pathways in rodent and human tissues.

Keratinocyte growth factor promotes preadipocyte proliferation via an autocrine mechanism

Keratinocyte growth factor (KGF; also known as FGF-7) is a well-characterized paracrine growth factor for tissue growth and regeneration. However, its role in adipose tissue, which is known to undergo tremendous expansion in obesity, is virtually unknown. Given that we previously identified KGF as one of the up-regulated growth factors in adipose tissue of an early-life programmed rat model of visceral obesity, the present study was undertaken to examine the hypothesis that KGF promotes adipogenesis. Using 3T3-L1 and rat primary preadipocytes as in vitro model systems, we demonstrated that (1) KGF stimulated preadipocyte proliferation in a concentration-dependent manner with a maximal effect at 2.5 ng/ml (approximately 2-fold increase); (2) KGF mRNA was highly expressed in rat adipocytes and preadipocytes as well as 3T3-L1 cells; (3) treatment of preadipocytes with a neutralizing antibody against KGF and siRNA-mediated knockdown of KGF led to a 50% reduction in their proliferative capacity; (4) KGF activated the protein kinase Akt, and the PI3 kinase inhibitor LY294002 blocked KGF stimulation of preadipocyte proliferation; and (5) KGF did not promote differentiation of preadipocytes to mature adipocytes. Together, these results reveal adipocytes and their precursor cells as novel sites of KGF production. Importantly, they also demonstrate that KGF promotes preadipocyte proliferation by an autocrine mechanism that involves activation of the PI3K/Akt signaling pathway. Aberrant KGF expression may have consequences not only for normal adipose tissue growth but also for the pathogenesis of obesity.

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.

Maternal perinatal undernutrition programs a “brown-like” phenotype of gonadal white fat in male rat at weaning

Several studies indicate that maternal undernutrition sensitizes the offspring to the development of metabolic disorders, such as obesity. Using a model of perinatal maternal 50% food-restricted diet (FR50), we recently reported that rat neonates from undernourished mothers exhibit decreased leptin plasma levels associated with alterations of hypothalamic proopiomelanocortin system. The present study aimed at examining the consequences of FR50 on the brain-adipose axis in male rat neonates. Using quantitative RT-PCR array containing 84 obesity-related genes, we demonstrated that most of the genes involved in energy metabolism regulation are expressed in rat gonadal white adipose tissue (WAT) and are sensitive to maternal perinatal undernutrition (MPU). In contrast, hypothalamic gene expression was not substantially affected by MPU. Gene expression of uncoupling protein 1 (UCP1), a marker of brown adipocytes, showed an almost 400-fold stimulation in postnatal day 21 (PND21) FR50 animals, suggesting that their gonadal WAT possesses a brown-like phenotype. This was confirmed by histological and immunoshistochemical procedures, which demonstrated that PND21 FR50 gonadal adipocytes are multilocular, resembling those present in interscapular brown adipose tissue, and exhibit an overexpression of UCP1 and neuropeptide Y (NPY) at the protein level. Control animals contained almost exclusively “classical” unilocular white adipocytes that did not show high UCP1 and NPY labeling. After weaning, FR50 animals exhibited a transient hyperphagia that was associated with the disappearance of brown-like fat pads in PND30 WAT. Our results demonstrate that MPU delays the maturation of gonadal WAT during critical developmental time windows, suggesting that it could have long-term consequences on body weight regulation in the offspring.

BMP-3 promotes mesenchymal stem cell proliferation through the TGF-beta/activin signaling pathway

Adipogenesis plays a key role in the pathogenesis of obesity. It begins with the commitment of mesenchymal stem cells (MSCs) to the adipocyte lineage, followed by terminal differentiation of preadipocytes to mature adipocytes. A critical, but poorly understood, component of adipogenesis involves proliferation of MSCs and preadipocytes. The present study was undertaken to examine the hypothesis that bone morphogenetic protein-3 (BMP-3) promotes adipogenesis using C3H10T1/2 MSCs and 3T3-L1 preadipocytes as in vitro model systems. We demonstrated that although it did not promote the commitment of MSCs to the adipocyte lineage or the differentiation of preadipocytes to adipocytes, BMP-3-stimulated proliferation by threefold in both cell types. Owing to a lack of information on MSC proliferation, we then delineated the molecular mechanisms underlying BMP-3-stimulated MSC proliferation. We showed that BMP-3 activated the transforming growth factor-beta (TGF-beta)/activin but not ERK1/2, p38 MAPK, or JNK signaling pathways in C3H10T1/2 cells. Furthermore, the TGF-beta/activin receptor kinase inhibitor SB-431542 blocked BMP-3-stimulated proliferation. Importantly, siRNA-mediated knockdown of the key TGF-beta/activin signaling pathway components, ActRIIB, ALK4, or Smad2, abrogated the mitogenic effects of BMP-3 on MSCs. Together, these results demonstrate that BMP-3 stimulates MSC proliferation via the TGF-beta/activin signaling pathway, thus revealing a novel role for this divergent and poorly understood member of the TGF-beta superfamily in regulating MSC proliferation.

Acute molecular mechanisms responsive to feeding and meal constitution in mesenteric adipose tissue

To identify the acute effects of feeding on mesenteric fat, we have performed a transcriptomic study in the mesenteric adipose tissue after low-fat (LF) and high-fat (HF) meal ingestion. After fasting, one group of mice was killed and the others were fed ad libitum with HF or LF meal, and killed 3 h after the ingestion. Serial analysis of gene expression (SAGE) was performed, generating approximately 150,000 tags/sample. The results were confirmed using quantitative real-time PCR (qRT-PCR). Transcripts involved in lipid biosynthesis were upregulated only by LF meal, whereas intracellular lipid catabolism was repressed by feeding. Apoptotic genes were downregulated, whereas antiapoptosis and proteolysis were upregulated by feeding. The expression levels of genes coding for adiponectin and ribosomal proteins were decreased by HF meal, as well as transcripts involved in mRNA processing, cytoskeleton, and extracellular matrix. Several other fat-responsive genes were identified, including diverse uncharacterized transcripts. These results revealed that mesenteric adipose tissue transcriptome was responsive to food intake and was affected differently according to meal constitution. The identification of uncharacterized transcripts regulated by LF and HF meals is a first step toward further understanding the early mechanisms of diet-induced obesity as well as discovering new therapeutic targets for obesity-related diseases.

Fetal origins of insulin resistance and the metabolic syndrome: a key role for adipose tissue?

For several years now, the epidemiological data have shown an inverse relationship between birth-weight and the development in later life of cardiovascular disease and metabolic disorders. The term "small for gestational age" (SGA) describes a neonate whose birth-weight is two standard deviations (SD) below the reference mean, corrected for gestational age and gender. SGA is associated with increased risks of developing hypertension, insulin resistance and type2 diabetes. However, the association with an atherogenic lipid profile is less clear. Nevertheless, all of the components of the metabolic syndrome are present. Yet, in spite of the large body of data in the literature, the biological mechanisms underlying this association are still unclear. To explain the association, various hypotheses have been proposed, pointing to the role of a detrimental fetal environment or genetic susceptibility, or interaction between the two, and to the particular dynamic changes in adiposity that occur during catch-up growth. However, not only quantitative, but also qualitative, abnormalities of adipose tissue have been observed, suggesting a critical role of this organ in the development of metabolic complications.

The p38 mitogen-activated protein kinase regulates 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) expression in human trophoblast cells through modulation of 11beta-HSD2 messenger ribonucleic acid stability

The placental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2; encoded by the HSD11B2 gene) has emerged as a key player in controlling fetal development, but its regulation is incompletely understood. Here we identified p38 MAPK as an important regulator of placental 11beta-HSD2. We showed that inhibition of p38 MAPK with the pharmacological inhibitor SB202190 led to an approximately 50% reduction in 11beta-HSD2 activity, protein, and mRNA in primary human placental trophoblast cells. Furthermore, the effect of SB202190 was confirmed by the use of two additional p38 inhibitors, SB203580 and SB220025. In addition, SB202190 decreased the half-life of 11beta-HSD2 mRNA without altering the HSD11B2 promoter activity, indicating that p38 MAPK regulates placental 11beta-HSD2 expression through modulation of 11beta-HSD2 mRNA stability. Importantly, small interfering RNA-mediated knockdown of p38alpha caused a 50% reduction in 11beta-HSD2 activity, suggesting that p38alpha is the primary p38 isoform involved. Taken together, these findings suggest a novel pathway controlling placental 11beta-HSD2 expression resulting from the activation of p38 MAPK. Given that p38alpha is abundantly expressed in the human placenta in which its function is largely unknown, our present study also reveals 11beta-HSD2 as an important target through which p38alpha may regulate human placental function and consequently fetal growth and development.

Forced catch-up growth after fetal protein restriction alters the adipose tissue gene expression program leading to obesity in adult mice

A mismatch between fetal and postnatal environment can permanently alter the body structure and physiology and therefore contribute later to obesity and related disorders, as revealed by epidemiological studies. Early programming of adipose tissue might be central in this observation. Moreover, adipose tissue secretes adipokines that provide a molecular link between obesity and its related disorders. Therefore, our aim was to investigate whether a protein restriction during fetal life, followed by catch-up growth could lead to obesity in 9-mo-old male mice and could alter the adipose tissue gene expression profile. Dams were fed a low-protein (LP) or an isocaloric control (C) diet during gestation. Postnatal catch-up growth was induced in LP offspring by feeding dams with control diet and by culling LP litters to four pups instead of eight in the C group. At weaning, male mice were fed by lab chow alone (C) or supplemented with a hypercaloric diet (HC), to induce obesity (C-C, C-HC, LP-C, and LP-HC groups). At 9 mo, LP offspring featured increased relative fat mass, hyperglycemia, hypercholesterolemia, and hyperleptinemia. Using a microarray designed to study the expression of 89 genes involved in adipose tissue differentiation/function, we demonstrated that the expression profile of several genes were dependent upon the maternal diet. Among the diverse genes showing altered expression, we could identify genes encoding several enzymes involved in lipid metabolism. These results indicated that offspring submitted to early mismatched nutrition exhibited alterations in adipose tissue gene expression that probably increases their susceptibility to overweight when challenged after weaning with a HC diet.

Gestational programming of offspring obesity/hypertension

The intrauterine milieu impacts fetal growth directly during gestation. It is now clear, however, that postnatal phenotype is also influenced by prenatal conditions. A variety of disorders in the adult have been linked to fetal size at birth; these include glucose intolerance, cardiovascular disease, and the subjects of this review, obesity and hypertension. We will review recent data regarding these associations and the pathophysiologic mechanisms underlying them in humans as well as in animal models.

Whole body magnetic resonance imaging of healthy newborn infants demonstrates increased central adiposity in Asian Indians

Abdominal adiposity and metabolic ill health in Asian Indians are a growing public health concern. Causal pathways are unknown. Preventive measures in adults have had limited success. The aim of this observational case-control study was to compare adipose tissue partitioning in 69 healthy full term Asian Indian and white European newborns born in Pune, India and London, UK, respectively. The main outcome measures were total and regional adipose tissue content measured by whole body magnetic resonance imaging. Although smaller in weight (95% CI for difference -0.757 to -0.385 kg, p < 0.001), head circumference (-2.15 to -0.9 cm, p < 0.001), and length (-2.9 to -1.1 cm p < 0.001), the Asian Indian neonates had significantly greater absolute adiposity in all three abdominal compartments, internal (visceral) (0.012-0.023 L, p < 0.001), deep s.c. (0.003-0.017 L, p = 0.006) and superficial s.c. (0.006-0.043 L, p = 0.011) and a significant reduction in nonabdominal superficial s.c. adipose tissue (-0.184 to -0.029 L, p = 0.008) in comparison to the white European babies despite similar whole body adipose tissue content (-0.175 to 0.034 L, p = 0.2). We conclude that differences in adipose tissue partitioning exist at birth. Investigative, screening, and preventive measures must involve maternal health, intrauterine life, and infancy.

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.