Bruno Fève

Molecular Cloning of a Major mRNA Species in Murine 3T3 Adipocyte Lineage DIFFERENTIATION-DEPENDENT EXPRESSION, REGULATION, AND IDENTIFICATION AS SEMICARBAZIDE-SENSITIVE AMINE OXIDASE

In an effort to identify novel mRNAs modulated during the course of adipose conversion, we have used a simplified differential display technique and have isolated a cDNA encoding an amine oxidase tremendously expressed in the adipocyte, the semicarbazide-sensitive amine oxidase (SSAO). The predicted amino acid sequence (765 amino acids) is likely to be the homologue of the human placental amine oxidase and of the partially known sequence of the rat adipocyte membrane amine oxidase. SSAO mRNAs are present in several tissues, but strikingly, the highest levels of gene expression are found in adipose tissue and aorta. Enzyme transcript levels are barely detectable in preadipocytes but are induced several hundred-fold during the adipocyte differentiation of 3T3-L1 or 3T3-F442A cells and of rat precursor primary cultures. These changes in transcript levels parallel a sharp increase in SSAO enzyme activity. The biochemical properties of the SSAO present in 3T3-L1 or 3T3-F442A adipocytes closely resemble the features of the SSAO activity previously described in white and brown adipose tissues. Interestingly, SSAO mRNA levels and enzyme activity drop in response to effectors of the cAMP pathway and to the cytokine tumor necrosis factor-α, indicating that two major signaling molecules of adipose tissue development and metabolism can control SSAO function. Moreover, the expression of SSAO transcripts and activity are clearly down-regulated in white adipose tissue from obese Zücker rats. Because of its known stimulatory effect on glucose transport, its biochemical properties and its pattern of expression and regulation, SSAO could play an important role in the regulation of adipocyte homeostasis.

Semicarbazide-sensitive amine oxidase activation promotes adipose conversion of 3T3-L1 cells.

Semicarbazide-sensitive amine oxidase (SSAO) is an amine oxidase related to the copper-containing amine oxidase family. The tissular form of SSAO is located at the plasma membrane, and is mainly expressed in vascular smooth muscle cells and adipocytes. Recent studies have suggested that SSAO could activate glucose transport in fat cells. In the present work, we investigated the potential role of a chronic SSAO activation on adipocyte maturation of the 3T3-L1 pre-adipose cell line. Exposure of post-confluent 3T3-L1 pre-adipocytes to methylamine, a physiological substrate of SSAO, promoted adipocyte differentiation in a time- and dose-dependent manner. This effect could be related to SSAO activation, since it was antagonized in the presence of the SSAO inhibitor semicarbazide, but not in the presence of the monoamine oxidase inhibitor pargyline. In addition, methylamine-induced adipocyte maturation was mimicked by 3T3-L1 cell treatment with other SSAO substrates. Finally, the large reversion of methylamine action by catalase indicated that hydrogen peroxide generated by SSAO was involved, at least in part, in the modulation of adipocyte maturation. Taken together, our results suggest that SSAO may contribute to the control of adipose tissue development.

Plasma NOV/CCN3 levels are closely associated with obesity in patients with metabolic disorders.

Objective Evidence points to a founder of the multifunctional CCN family, NOV/CCN3, as a circulating molecule involved in cardiac development, vascular homeostasis and inflammation. No data are available on the relationship between plasma NOV/CCN3 levels and cardiovascular risk factors in humans. This study investigated the possible relationship between plasma NOV levels and cardiovascular risk factors in humans. Methods NOV levels were measured in the plasma from 594 adults with a hyperlipidemia history and/or with lipid-lowering therapy and/or a body mass index (BMI) >30 kg/m2. Correlations were measured between NOV plasma levels and various parameters, including BMI, fat mass, and plasma triglycerides, cholesterol, glucose, and C-reactive protein. NOV expression was also evaluated in adipose tissue from obese patients and rodents and in primary cultures of adipocytes and macrophages. Results After full multivariate adjustment, we detected a strong positive correlation between plasma NOV and BMI (r = 0.36 p<0.0001) and fat mass (r = 0.33 p<0.0005). According to quintiles, this relationship appeared to be linear. NOV levels were also positively correlated with C-reactive protein but not with total cholesterol, LDL-C or blood glucose. In patients with drastic weight loss induced by Roux-en-Y bariatric surgery, circulating NOV levels decreased by 28% (p<0.02) and 48% (p<0.0001) after 3 and 6 months, respectively, following surgery. In adipose tissue from obese patients, and in human primary cultures NOV protein was detected in adipocytes and macrophages. In mice fed a high fat diet NOV plasma levels and its expression in adipose tissue were also significantly increased compared to controls fed a standard diet. Conclusion Our results strongly suggest that in obese humans and mice plasma NOV levels positively correlated with NOV expression in adipose tissue, and support a possible contribution of NOV to obesity-related inflammation.

Adipokine profile in glucocorticoid-treated patients: baseline plasma leptin level predicts occurrence of lipodystrophy

Glucocorticoid therapy may result in adipose tissue redistribution of unknown pathophysiology.

Paradoxical resistance to high-fat diet-induced obesity and altered macrophage polarization in mineralocorticoid receptor-overexpressing mice

The mineralocorticoid receptor (MR) exerts proadipogenic and antithermogenic effects in vitro, yet its in vivo metabolic impact remains elusive. Wild type (WT) and transgenic (Tg) mice overexpressing human MR were subjected to standard chow (SC) or high-fat diet (HFD) for 16 wk. Tg mice had a lower body weight gain than WT animals and exhibited a relative resistance to HFD-induced obesity. This was associated with a decrease in fat mass, an increased population of smaller adipocytes, and an improved glucose tolerance compared with WT animals. Quantitative RT-PCR studies revealed decreased expression of PPARγ2, a master adipogenic gene, and of glucocorticoid receptor and 11β-hydroxysteroid dehydrogenase type 1, consistent with an impaired local glucocorticoid signaling in adipose tissues (AT). This paradoxical resistance to HFD-induced obesity was not related to an adipogenesis defect since differentiation capacity of Tg preadipocytes isolated from stroma-vascular fractions was unaltered, suggesting that other nonadipocyte factors might compromise AT development. Although AT macrophage infiltration was not different between genotypes, Tg mice exhibited a distinct macrophage polarization, as revealed by FACS analysis and CD11c/CD206 expression studies. We further demonstrated that Tg macrophage-conditioned medium partially impaired preadipocyte differentiation. Therefore, we propose that modification of M1/M2 polarization of hMR-overexpressing macrophages could account in part for the metabolic phenotype of Tg mice. Collectively, our results provide evidence that MR exerts a pivotal immunometabolic role by controlling adipocyte differentiation processes directly but also indirectly through macrophage polarization regulation. Our findings should be taken into account for the pharmacological treatment of metabolic disorders.

From the conceptual basis to the discovery of leptin.

Two years ago, the Lasker Award was shared by Douglas Coleman and Jeffrey Friedman for their discovery of leptin, a hormone that exerts a key role in the central regulation of appetite and body weight. Douglas Coleman is recognized as the researcher who raised the hypothesis and predicted that a circulating satiety factor was lacking in the ob/ob mouse, and predicted that this factor acted at the hypothalamic level to modulate food intake. After three decades, in an attempt to identify the genes that were mutated in the ob/ob mouse, Jeffrey Friedman found that the ob gene encodes a protein hormone that reverses obesity and other abnormalities of this genetic rodent model of obesity. This discovery was a landmark event in physiology, and revolutionized our understanding of energy homeostasis. This short review aims to summarize the main steps that lead to the identification of leptin, the product of the ob gene.

Glycogen synthase kinase-3β genetic polymorphisms and insomnia in depressed patients: A prospective study

BACKGROUND 80-90% of patients with Major Depressive Episode (MDE) experience insomnia and up-to 50% severe insomnia. Glycogen Synthase Kinase-3β (GSK3B) is involved both in mood regulation and circadian rhythm. Since GSK3B polymorphisms could affect protein levels or functionality, we investigated the association of GSK3B polymorphisms with insomnia in a sample of depressed patients treated with antidepressants. METHODS In this 6-month prospective real-world treatment study in psychiatric settings (METADAP), 492 Caucasian patients requiring a new antidepressant treatment were included and genotyped for five GSK3B Single Nucleotide Polymorphisms (SNPs) (rs6808874, rs6782799, rs2319398, rs13321783, rs334558). Insomnia and MDE severity were rated using the Hamilton Depression Rating Scale (HDRS). Bi- and multivariate analyses were performed to assess the association between GSK3B SNPs and insomnia (main objective). We also assessed their association with MDE severity and HDRS response/remission after antidepressant treatment. RESULTS At baseline severe insomnia was associated with the GSK3B rs334558 minor allele (C+) [OR=1.81, CI95%(1.17-2.80), p=0.008]. GSK3B rs334558 C+ had greater insomnia improvement after 6 months of antidepressant treatment (p=0.007, β=0.17, t=2.736). No association was found between GSK3B SNPs and MDE baseline severity or 6-month response/remission. CONCLUSION GSK3B rs334558 was associated with insomnia but not with MDE severity in depressed patients. Targeting GSK3B in patients with MDE and a severe insomnia could be a way to improve their symptoms with greater efficiency. And it should be further studied whether the GSK3B-insomnia association may fit into the larger picture of mood disorders.

O15 NOV/CCN3 : une nouvelle adipokine impliquée dans l’homéostasie énergétique ?

Introduction La physiologie de l’obesite est complexe et encore mal connue. Caracteriser de nouvelles adipokines constitue un enjeu majeur dans la comprehension des mecanismes conduisant a cette pathologie. Nos resultats recents montrent que NOV est une nouvelle molecule produite par le tissu adipeux dont les concentrations plasmatiques chez l’homme sont correlees a l’IMC et a la masse grasse, et diminuent apres chirurgie bariatrique (Pakradouni et al, 2013). NOV est une proteine matricielle multifonctionnelle impliquee dans la cicatrisation, les pathologies fibrotiques, les processus inflammatoires et les cancers, mais son role dans le tissu adipeux et l’homeostasie energetique n’est pas connu. Notre objectif a ete d’explorer : in vitro les effets de NOV sur le profil inflammatoire et secretoire des adipocytes et in vivo dans des souris NOV -/-, l’impact de l’absence de ce gene sur le metabolisme glucido-lipique. Materiels et methodes Les effets de NOV in vitro ont ete etudies sur la lignee 3T3-L1 et in vivo sur des souris mâles NOV -/- et +/+ soumises a un regime normal ou hyper-lipidique. Resultats In vitro l’expression de NOV est regulee dans les adipocytes matures par le TNF-alpha et l’insuline. Surtout, NOV augmente significativement l’expression de plusieurs molecules pro-inflammatoires (IL6, CCL2 et CCL5) connues pour jouer un role dans la resistance a l’insuline et a l’inflammation associees a l’obesite. In vivo les premiers resultats montrent que l’absence de NOV retentit favorablement sur la prise de poids, le developpement du tissu adipeux et sur la tolerance au glucose des souris soumises a un regime hyperlipidique. D’autres resultats de ses effets sur le metabolisme energetique seront discutes. Conclusion L’ensemble de ces donnees suggere pour la premiere fois que NOV pourrait constituer une nouvelle adipokine jouant un role dans l’insulino-resistance et dans l’inflammation au cours de l’obesite.

Nouveaux mécanismes physiopathologiques du Syndrome Métabolique : implication des récepteurs nucléaires orphelins ?

Resume Cette revue fait le point sur un certain nombre de donnees recentes sur la biologie et la physiopathologie du syndrome metabolique (MetS) et l’implication des recepteurs nucleaires qui ont ete presentees en juin 2012 lors du dernier congres de l’ Endocrine Society , a Houston. Plusieurs etudes ont rapporte les effets benefiques de differents recepteurs nucleaires dits « orphelins », notamment SHP ( Small Heterodimeric Partner, NR0B2 ) et LXR ( Liver X Receptor, NR1H3 et NR1H2 ), sur diverses composantes du MetS. En utilisant un modele d’invalidation de SHP chez la souris, l’equipe de David Moore a demontre que SHP avait des effets « anti-diabetiques », ceci aux depens d’une steatose hepatique. Par ailleurs, cette equipe a egalement montre que le DLPC ( dilauroyl phosphatidylcholine ), un phospholipide non classique, avait une action anti-diabetique via LRH-1 ( Liver Receptor Homolog-1 , NR5A2 ), un partenaire moleculaire de SHP. De maniere tres interessante, Carolyn Cummins a presente des donnees sur les mecanismes impliques dans les effets metaboliques deleteres des glucocorticoides en se focalisant notamment sur LXR, a l’aide de modeles murins d’invalidation des isoformes α et β de LXR. Ces donnees nouvelles et originales permettent d’envisager, a plus long terme, l’utilisation de modulateurs selectifs de ces recepteurs dans la prise en charge des troubles metaboliques chez l’Homme.