[Show abstract][Hide abstract] ABSTRACT: Environmental contaminants are suspected to be involved in the epidemic incidence of metabolic disorders, food ingestion being a primarily route of exposure. We hypothesized that life-long consumption of a high-fat diet that contains low doses of pollutants will aggravate metabolic disorders induced by obesity itself. Mice were challenged from preconception throughout life with a high-fat diet containing pollutants commonly present in food (2,3,7,8-tetrachlorodibenzo-p-dioxin, polychlorinated biphenyl 153, diethylhexyl phthalate, and bisphenol A), added at low doses in the tolerable daily intake range. We measured several blood parameters, glucose and insulin tolerance, hepatic lipid accumulation, and gene expression in adult mice. Pollutant-exposed mice exhibited significant sex-dependent metabolic disorders in the absence of toxicity and weight gain. In males, pollutants increased the expression of hepatic genes (from 36 to 88%) encoding proteins related to cholesterol biosynthesis and decreased (40%) hepatic total cholesterol levels. In females, there was a marked deterioration of glucose tolerance, which may be related to the 2-fold induction of estrogen sulfotransferase and reduced expression of estrogen receptor α (25%) and estrogen target genes (>34%). Because of the very low doses of pollutants used in the mixture, these findings may have strong implications in terms of understanding the potential role of environmental contaminants in food in the development of metabolic diseases.-Naville, D., Pinteur, C., Vega, N., Menade, Y., Vigier, M., Le Bourdais, A., Labaronne, E., Debard, C., Luquain-Costaz, C., Bégeot, M., Vidal, H., Le Magueresse-Battistoni, B. Low-dose food contaminants trigger sex-specific, hepatic metabolic changes in the progeny of obese mice.
[Show abstract][Hide abstract] ABSTRACT: Différentes données de la littérature étayent l’hypothèse d’un rôle des polluants environnementaux considérés comme perturbateurs endocriniens dans l’épidémie d’obésité et de ses complications métaboliques. Notre projet vise à évaluer l’impact d’une exposition chronique à un mélange de polluants présents dans l’alimentation à doses faibles, sur une population à risque de syndrome métabolique (descendants F1) en raison de l’obésité maternelle.Matériels et méthodesDes souris C57Bl6/J sont nourries avec un régime obésogène contenant ou non un mélange de polluants persistants (dioxine, PCB153) et non-persistants (Bisphénol-A, DEHP) à la Dose Journalière Admissible (DJA) pour l’homme, 5 semaines avant accouplement, pendant la gestation et la lactation, et jusqu’à 12 semaines dans la descendance F1 (appelée respectivement ObDJA et Ob0).Les paramètres suivis incluent la prise pondérale, la glycémie, les niveaux plasmatiques d’insuline, de leptine et d’adiponectine, et les tests de tolérance au glucose et de sensibilité à l’insuline. Le patron d’expression de gènes candidats a été étudié par qPCR dans le tissu adipeux sous-cutané des descendants F1 entre 3 (sevrage) et 12 semaines d’âge dans les deux sexes.RésultatsChez les femelles ObDJA, une augmentation de l’insulinémie au sevrage et une diminution de la tolérance au glucose à 12 semaines d’âge est observée, témoignant d’une insulino-résistance. Chez les mâles ObDJA, une insulino-résistance s’installe dès 7 semaines alors que l’adiponectine sérique est augmentée. Chez les femelles ObDJA une forte stimulation des niveaux d’expression de FABP4 et d’IL6 est observée dans le tissu adipeux sous-cutané. Les résultats pour FABP4 sont confirmés par Western-blot. Chez les mâles ObDJA, d’autres cibles ont été identifiées incluant PPARgamma (diminution) et TNFalpha (stimulation).Conclusion
La présence d’un mélange de polluants faiblement dosés dans l’alimentation obésogène de la mère induit chez la F1 des altérations métaboliques et des modifications d’expression génique qui varient selon l’âge et le sexe.
No preview · Article · Mar 2012 · Diabetes & Metabolism
[Show abstract][Hide abstract] ABSTRACT: CD36 is a ubiquitous membrane glycoprotein that binds long-chain fatty acids. The presence of a functional CD36 is required for the induction of satiety by a lipid load and its role as a lipid receptor driving cellular signal has recently been demonstrated. Our project aimed to further explore the role of intestinal CD36 in the regulation of food intake. Duodenal infusions of vehicle or sulfo-N-succinimidyl-oleate (SSO) was performed prior to acute infusions of saline or Intralipid (IL) in mice. Infusion of minute quantities of IL induced a decrease in food intake (FI) compared to saline. Infusion of SSO had the same effect but no additive inhibitory effect was observed in presence of IL. No IL- or SSO-mediated satiety occurred in CD36-null mice. To determine whether the CD36-mediated hypophagic effect of lipids was maintained in animals fed a satietogen diet, mice were subjected to a High-Protein diet (HPD). Concomitantly with the satiety effect, a rise in intestinal CD36 gene expression was observed. No satiety effect occurred in CD36-null mice. HPD-fed WT mice showed a diminished FI compared to control mice, after saline duodenal infusion. But there was no further decrease after lipid infusion. The lipid-induced decrease in FI observed on control mice was accompanied by a rise in jejunal oleylethanolamide (OEA). Its level was higher in HPD-fed mice than in controls after saline infusion and was not changed by lipids. Overall, we demonstrate that lipid binding to intestinal CD36 is sufficient to produce a satiety effect. Moreover, it could participate in the satiety effect induced by HPD. Intestine can modulate FI by several mechanisms including an increase in OEA production and CD36 gene expression. Furthermore, intestine of mice adapted to HPD have a diminished capacity to modulate their food intake in response to dietary lipids.
[Show abstract][Hide abstract] ABSTRACT: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related substances are ubiquitous environmental pollutants that exert adverse effects on reproductive processes. In testis, Leydig cells which produce testosterone are under hormonal and local control exerted by cytokines including TNFα. Using mouse Leydig primary cell cultures as a model, we studied the effects of TCDD on the steroidogenic outcome of Leydig cells and the gene expression levels of Ccl5 and Cxcl4, previously shown to be target genes of TCDD in testis. We found that TCDD did not alter the steroidogenic outcome of Leydig cells but that it up-regulated Cxcl4 gene expression levels. TCDD also impacted Ccl5 gene expression when cells had been co-treated with TNFα. TCDD action probably initiated with binding to the aryl hydrocarbon receptor (AhR) present on Leydig cells. TCDD regulated the gene expression levels of AhR (transient down-regulation) and its repressor AhRR and Cyp1b1 (up-regulation). The trophic human chorionic gonadotropin (hCG) hormone did not impact AhR, its repressor AhRR or Cyp1b1 but it opposed the TCDD-enhanced AhRR mRNA levels. Conversely, TNFα stimulated AhR gene expression levels. Collectively, it is suggested that the impact of TCDD on expression of target genes in Leydig cells may operate under the complex network of hormones and cytokines.
No preview · Article · Dec 2011 · Toxicology Letters
[Show abstract][Hide abstract] ABSTRACT: The hypothalamic melanocortin system--the melanocortin receptor of type 4 (MC4R) and its ligands: α-melanin-stimulating hormone (α-MSH, agonist, inducing hypophagia), and agouti-related protein (AgRP, antagonist, inducing hyperphagia)--is considered to play a central role in the control of food intake. We tested its implication in the mediation of the hunger-curbing effects of protein-enriched diets (PED) in mice. Whereas there was a 20% decrease in food intake in mice fed on the PED, compared to mice fed on an isocaloric starch-enriched diet, there was a paradoxical decrease in expression of the hypothalamic proopiomelanocortin gene, precursor of α-MSH, and increase in expression of the gene encoding AgRP. The hypophagia effect of PED took place in mice with invalidation of either MC4R or POMC, and was even strengthened in mice with ablation of the AgRP-expressing neurons. These data strongly suggest that the hypothalamic melanocortin system does not mediate the hunger-curbing effects induced by changes in the macronutrient composition of food. Rather, the role of this system might be to defend the body against the variations in food intake generated by the nutritional environment.
[Show abstract][Hide abstract] ABSTRACT: Objectif
Cette étude tente de mettre en évidence, l’impact d’hormones et neuromédiateurs contrôlant la prise alimentaire dans la régulation de l’expression de l’AGRP et des récepteurs aux mélanocortines dans la surrénale (MC2-R et MC4-R) et l’hypothalamus (MC4-R). Une corrélation des résultats est établie avec les tissus surrénalien et hypothalamique de souris maintenues sous régime hypercalorique qui modifie les taux circulants de ces hormones.
Matériels et méthodes
Les lignées murines surrénaliennes ATC7-L et hypothalamique GT1-7 sont traitées pendant 24 h par la leptine, insuline et AGRP (10-7 M), ACTH, dexaméthasone et NDPα-MSH (10-8 M) et la forskoline (10-5 M). Les souris C57BL-6J sont rendues obèses par un régime hypercalorique (36 % lipides, 19,8 % protéines) pendant 16 semaines. L’hypothalamus et les surrénales prélevés sont analysés. L’expression de l’ARN codant pour l’AGRP est analysée par RT-PCR, celles des récepteurs aux mélanocortines par Western Blot et la production d’AGRP ou de corticostérone dans le milieu de culture est mesurée par EIA.
L’insuline, la leptine et la dexaméthasone augmentent la quantité d’AGRP produite par les cellules ATC7-L et GT1-7, mais ne modifient pas l’expression des ARNm codant l’AGRP. Les quantités de MC2-R et MC4R sont respectivement diminuées par la leptine et augmentées par l’AGRP dans la lignée surrénalienne, mais MC4-R est augmenté par la leptine et l’insuline dans la lignée hypothalamique. Par contre, NDP-MSH ou la forskoline diminuent MC4-R dans la surrénale et l’augmentent dans l’hypothalamus.
In vivo, l’expression de l’AGRP chez les souris obèses augmente dans les deux tissus, accompagnée d’une diminution de MC4-R et MC2-R dans la surrénale et l’augmentation de MC4-R dans l’hypothalamus.
L’expression des récepteurs aux mélanocortines, régulée de manière opposée dans les deux tissus qui expriment le plus l’AGRP, par des hormones qui contrôlent la prise alimentaire, suggère l’existence d’un lien entre le statut métabolique et l’activation du système mélanocortinergique dans la surrénale, comme dans l’hypothalamus.
No preview · Article · Mar 2011 · Diabetes & Metabolism
[Show abstract][Hide abstract] ABSTRACT: To study the consequences of maternal obesity during gestation and suckling periods on metabolic features and expression of genes belonging to the melanocortinergic system, we developed Diet-Induced-Obesity (DIO) in mice fed high-fat-diet (HFD). After weaning, F1-descendants were fed the same diet than dams up to 16 weeks or received a 2-week standard chow at several time points. From birth, F1-DIO displayed higher body weight than F1-control. Hyperinsulinemia, hypertriglyceridemia, hyperleptinemia were detected from P10 and fasting hyperglycaemia from 2 week-post-weaning. From late gestation to 16-week-post-weaning the expression of MC4-R gene and/or the POMC/AgRP ratio was increased, suggesting an activation of this pathway to compensate the deleterious effects of HFD. Standard chow replacement at weaning normalized metabolic status but a partial recovery was obtained for later changes. Concomitant variations in the expression of the melanocortinergic genes were observed. Therefore, early nutritional intervention could override the impact of maternal and postnatal over-nutrition.
No preview · Article · May 2010 · Molecular and Cellular Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Familial glucocorticoid deficiency (FGD) is an autosomal recessive disorder resulting from resistance to the action of ACTH on the adrenal cortex. Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia and/or overwhelming infection. Mutations of the ACTH receptor (MC2R) and the melanocortin 2 receptor accessory protein (MRAP), FGD types 1 and 2 respectively, account for approximately 45% of cases.
A locus on chromosome 8 has previously been linked to the disease in three families, but no underlying gene defect has to date been identified.
The study design comprised single-nucleotide polymorphism genotyping and mutation detection.
The study was conducted at secondary and tertiary referral centers.
Eighty probands from families referred for investigation of the genetic cause of FGD participated in the study.
There were no interventions.
Analysis by single-nucleotide polymorphism array of the genotype of one individual with FGD previously linked to chromosome 8 revealed a large region of homozygosity encompassing the steroidogenic acute regulatory protein gene, STAR. We identified homozygous STAR mutations in this patient and his affected siblings. Screening of our total FGD patient cohort revealed homozygous STAR mutations in a further nine individuals from four other families.
Mutations in STAR usually cause lipoid congenital adrenal hyperplasia, a disorder characterized by both gonadal and adrenal steroid deficiency. Our results demonstrate that certain mutations in STAR (R192C and the previously reported R188C) can present with a phenotype indistinguishable from that seen in FGD.
No preview · Article · Sep 2009 · The Journal of Clinical Endocrinology and Metabolism
[Show abstract][Hide abstract] ABSTRACT: Adrenocortical cells of several species have been reported to express significant levels of Agouti-related protein (Agrp) as well as melanocortin 4-receptor (MC4-R). In this study, we used the mouse tumoral adrenal cell line ATC7- L that secretes corticosterone in basal conditions with a 2- fold increase in response to ACTH treatment. We reported that these cells expressed functional MC4-R. They also expressed Agrp mRNA and secreted immunoreactive Agrp in the culture medium. Long-term treatment of ATC7-L with (Nle4,D-Phe7)-alpha MSH (NDP-alpha MSH) or forskolin as well as Agrp strongly reduced MC4-R level by more than 30%. On the contrary, leptin treatment did not modify this level although it significantly reduced MC2-R level. These results could be correlated to some data obtained in vivo on adrenal glands removed from diet-induced obese mice exhibiting a hyperleptinemia, where the level of both MC2-R and MC4-R appeared to be reduced as Agrp mRNA expression level was increased compared to Control mice. All these data would suggest the existence of a link between the metabolic status and the activation of the adrenal melanocortinergic system.
No preview · Article · Feb 2009 · Journal of endocrinological investigation
[Show abstract][Hide abstract] ABSTRACT: The melanocortinergic system consisting of the melanocortin receptors (MC3-R, MC4-R) and their ligands α-MSH (agonist) and AGRP (antagonist) is a major regulator of food intake and energy homeostasis. It appears from in vivo studies using peripheral or central administration that this system is highly regulated by several circulating hormones and nutrients. These data have been confirmed by studies performed ex vivo on hypothalamic slices or explants as well as by using primary cultured isolated neurons or cell lines from hypothalamic origin. Some studies have been performed in rodents using modified diets by caloric restriction or by caloric excess as lipid enriched diets. These diets induced gradual metabolic disorders depending on the length of the diet administration. Consequently, several alterations in the expression of the different components of the melanocortinergic system are observed in order to counterbalance the metabolic defects.
No preview · Article · Feb 2009 · Cahiers de Nutrition et de Diététique
[Show abstract][Hide abstract] ABSTRACT: The objectives of this study were to identify potential alterations in gene expression of melanocortin-4 receptor (MC4-R), proopiomelanocortin (POMC), and Agouti-related protein (AgRP) in mouse hypothalamus under a chronic peripheral infusion of leptin or at early (8 weeks) and advanced (16 weeks) phases of diet-induced obesity. Control or diet-induced obesity mice (8 or 16 weeks of high-fat diet) were either treated or not treated with leptin. Metabolic features were analyzed and expression of the genes of interest was measured by quantitative reverse transcriptase-PCR (RT-qPCR) and western blot. We reported that in control mice, but not in obese mice, leptin infusion induced an increase in POMC mRNA level as well as in MC4-R mRNA level suggesting that leptin could act directly and/or through alpha-melanocyte-stimulating hormone (alpha-MSH). This hypothesis was reinforced after in vitro studies, using the mouse hypothalamic GT1-7 cell line, since both leptin and Norleucine(4), D-Phenylalanine(7)-alpha-MSH (NDP-alpha-MSH) treatments increased MC4-R expression. After 8 weeks of high-fat diet, nondiabetic obese mice became resistant to the central action of leptin and their hypothalamic content of POMC and AgRP mRNA were decreased without modification of MC4-R mRNA level. After 16 weeks of high-fat diet, mice exhibited more severe metabolic disorders with type 2 diabetes. Moreover, hypothalamic expression of MC4-R was highly increased. In conclusion, several alterations of the melanocortin system were found in obese mice that are probably consecutive to their central resistance to leptin. Moreover, when the metabolic status is highly degraded (with all characteristics of a type 2 diabetes), other regulatory mechanisms (independent of leptin) can also take place.
[Show abstract][Hide abstract] ABSTRACT: The aldo-keto reductase 1B7 (AKR1B7) encodes an aldose-reductase that has been reported as a detoxification enzyme until now. We have demonstrated that AKR1B7 is differently expressed in various mouse white adipose tissues depending on their location. Its expression is associated with a higher ratio of preadipocytes vs. adipocytes. The cells that express AKR1B7 did not contain lipid droplets, and the expression level of akr1b7 was very low in mature adipocytes. We have defined the role of AKR1B7 in adipogenesis using either primary cultures of adipose stromal cells (containing adipocyte precursors) or the 3T3-L1 cell line. Under the same differentiation conditions, adipose stromal cells from tissues that expressed AKR1B7 had a decreased capacity to accumulate lipids compared with those that did not express it. Moreover, the overexpression of sense or antisense AKR1B7 in 3T3-L1 preadipocytes inhibited or accelerated, respectively, their rate of differentiation into adipocytes. In vivo experiments demonstrated that AKR1B7-encoding mRNA expression decreased in adipose tissues from mice where obesity was induced by a high-fat diet. All these results attributed for the first time a novel role to AKR1B7, which is the inhibition of adipogenesis in some adipose tissues.
[Show abstract][Hide abstract] ABSTRACT: The levels of Agouti-related protein (AgRP) mRNA in the adrenal are second only to those in the hypothalamus, raising questions regarding its target binding sites and its specific role in adrenal steroidogenesis. We and others demonstrated the presence of a population of melanocortin receptor-4 (MC4R) positively coupled to steroidogenesis in adrenal cells. Moreover, AgRP inhibited both the acute and long-term steroidogenic responses of these cells to NDP-alphaMSH through its antagonistic properties towards MC4R. Although AgRP had no antagonistic properties towards the MC2R and did not modify the acute steroidogenic response to ACTH, it exerted a biphasic sustained inhibitory effect on the long-term response to ACTH through an undefined alternate mechanism. Since adrenal cells release a relatively large amount of AgRP, this protein likely exerts a local paracrine/autocrine control on adrenal steroidogenesis.
No preview · Article · Mar 2007 · Molecular and Cellular Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Obesity results from disturbances of tightly regulated interactions between the nervous, endocrine, and metabolic systems that can be caused by external factors, such as viral infections. A mouse model of obesity induced by brain infection with a morbillivirus, canine distemper virus, allowed us to identify obesity-related genes. Using a subtractive library for the hypothalamus, the main brain structure regulating energy homeostasis, we identified a new gene on mouse chromosome 19 which we named upregulated obese product (Urop) 11 and, which has no homology with any known mRNA. A step-by-step molecular approach allowed us to isolate the full-length mRNA, predict the protein sequence, and identify consensus sites. Urop11 was mainly detected in the hypothalamus and adipocytes, and was dramatically upregulated in these central and peripheral structures in obese mice. Urop11 was also expressed in human neural and lymphoid samples and its expression seemed to be regulated by the state of lymphocyte activation. Interestingly, Urop11 expression was strongly upregulated both in vivo in mouse hypothalamus and in vitro in mouse neural cell lines, after leptin treatment. Taken together, our data show that Urop11 is a target of leptin, the satiety factor produced by adipocytes, in physiological and pathological conditions, including obesity. This new gene can be considered a key molecule in the hypothalamic integration pathway and demonstrates the importance of Urop11 as a target of leptin action.
Preview · Article · Mar 2007 · Journal of Molecular Endocrinology