Max LAFONTAN | Université Paul Sabatier de Toulouse (original) (raw)
Papers by Max LAFONTAN
Annals of the New York Academy of Sciences, May 1, 1998
European journal of pharmacology, Apr 1, 1995
Acute exposure of isolated adipocytes to isoproterenol induces the desensitization of lipolytic r... more Acute exposure of isolated adipocytes to isoproterenol induces the desensitization of lipolytic responses to norepinephrine and selective /31-, /32-and /33-adrenoceptor agonists, as well as the adrenocorticotropic hormone 1-24 fragment (ACTH). Forskolin and 8-bromo-cAMP responses are also desensitized. When lipolysis was measured in the presence of OPC 3911 {N-cyclohexyl-N-2-hydroxyethyl-4(6-(1,2-dihydro-2-oxoquinolyloxy))butyramide}, a specific inhibitor of the cAMP phosphodiesterase of adipocytes, the desensitization of all lipolytic agents-except the /32-adrenoceptor agonist-was abolished. Isoproterenol induced a similar loss (35%) of both membrane/31-and/32-adrenoceptors and an uncoupling of/3t-adrenoceptors, but did not modify the weak coupling of control /32-adrenoceptors. These data suggest that isoproterenol induced (i) an activation of the cAMP phosphodiesterase, which is solely responsible for the desensitization of norepinephrine response as well as/31-and/33-adrenoceptor mediated responses and (ii) an additional desensitization of the sole/32-adrenergic signaling system which suggests a subtype-selective pattern of regulating processes.
Journal of Physiology and Biochemistry, Feb 12, 2015
The mechanisms underlying the relationships between nutritional status and immunity remain to be ... more The mechanisms underlying the relationships between nutritional status and immunity remain to be fully characterized. The present study was undertaken to analyze by flow cytometry, in the context of dietinduced obesity, the status of immune cells in subcutaneous, and epididymal fat depots in wild-type and immunodeficient Rag2−/− mice submitted to nutritional challenge, i.e., 48-h fasting and 1-week refeeding. In parallel, the responsiveness of mature adipocytes and immune cells in bone marrow, lymph node, and liver were also analyzed. The results show that fasting in obese wild-type mice induces a prominent lipolysis in epididymal AT and immunosuppression restricted to both subcutaneous and epididymal AT, characterized by reduced number of CD4+ T and B lymphocytes and M1/M2 macrophages associated with reduced leptin and increased FGF21 expression in mature adipocytes. One-week refeeding was sufficient to reverse the fasting-induced effects. Obese immunodeficient mice under nutritional challenge exhibited no changes in adipocyte leptin expression and no marked trafficking of AT macrophages or NK cells, while the fasted-induced upregulation of FGF21 expression was maintained as well as the lipolytic responses. The present results demonstrate that, in a context of dietinduced obesity, fasting-induced immunosuppression is restricted to fat depots in immunocompetent mice. Lack of adipocyte leptin regulation and fasting-induced immunosuppression in obese immunodeficient mice strongly suggests that lymphocytes are involved in the modulation of adipocyte leptin expression on one hand and on the other that leptin is involved in the immune changes in AT according to nutritional status.
Journal of Lipid Research, Feb 1, 1999
The sympathetic nervous system controls lipolysis in fat by activation of four adrenergic recepto... more The sympathetic nervous system controls lipolysis in fat by activation of four adrenergic receptors:  1,  2,  3, and ␣ 2. During pregnancy, maternal metabolism presents anabolic and catabolic phases, characterized by modifications of fat responsiveness to catecholamines. The contributions of the four adrenergic receptors to adipocyte responsiveness during pregnancy have never been studied. Our aim was to evaluate the influence of pregnancy on adrenergic receptor-mediated lipolysis in rabbit white adipocytes. Functional studies were performed using subtypeselective and non-selective adrenergic receptor agonists. Overall adrenergic responsiveness was measured with the physiological agonist epinephrine. Non-adrenergic agents were used to evaluate different steps of the lipolytic cascade. The ␣ 2-and  1/  2-adrenergic receptor numbers were determined with selective radioligands. Non-adrenergic agents revealed that pregnancy induced an intracytoplasmic modification of the lipolytic cascade in inguinal but not in retroperitoneal adipocytes. Pregnancy induced an increase in  1-and specially  3-mediated lipolysis. The amounts of adipocyte  1/  2-and ␣ 2-adrenergic receptors were increased in pregnant rabbits. Epinephrine effects revealed an increased contribution of ␣ 2-adrenergic receptor-mediated antilipolysis in adipocytes from pregnant rabbits. These results indicate that pregnancy regulates adipocyte responsiveness to catecholamines mainly via the ␣ 2-and  3-adrenergic pathways. Pregnancy induces an intracytoplasmic modification of the lipolytic cascade, probably via hormone-sensitive lipase, with differences according to fat location.-Bousquet-Mélou, A
American Journal of Physiology-regulatory Integrative and Comparative Physiology, Jul 1, 1994
The beta-adrenoceptor subtypes involved in the control of lipolysis in white fat cells of rat, do... more The beta-adrenoceptor subtypes involved in the control of lipolysis in white fat cells of rat, dog, marmoset (Callithrix jacchus), baboon (Papio papio), macaque (Macaca fascicularis), and human were compared. In all species [3H]CGP-12177 binding (up to 3 nM) indicated the existence of a homogeneous population of binding sites in fat cell membranes, and competition studies showed that beta 1- and beta 2-adrenoceptors were present. Selective beta 1 or beta 2-adrenoceptor agonists induced lipolysis. The efficiencies of isoproterenol and norepinephrine were similar. The use of selective beta 3-adrenoceptor agonists revealed that BRL-37344 and CL-316243 were full agonists, whereas CGP-12177 and SR-58611A were partial agonists in rat and dog white fat cells. beta 3-Agonists partially stimulated lipolysis in the marmoset, while CGP-12177 was weakly active in the baboon. In macaque and human fat cells, beta 3-agonists were ineffective. The lipolytic effect of norepinephrine involves beta 1-and/or beta 2-adrenoceptors in baboon, macaque, and human. The baboon and macaque constitute valuable models for studying the beta-adrenergic control of lipolysis.
Les abonnements sont mis en service dans un délai maximum de quatre semaines après réception de l... more Les abonnements sont mis en service dans un délai maximum de quatre semaines après réception de la commande et du règlement. Ils partent du premier numéro de l'année. Les réclamations pour les numéros non reçus doivent parvenir dans un délai maximum de six mois. Les numéros séparés de l'année et volumes antérieurs (jusqu'à épuisement du stock) peuvent être commandés à la même adresse.
HAL (Le Centre pour la Communication Scientifique Directe), 1995
The lipolysis in adipose tissue is controlled by the hormone-sensitive lipase activity which is d... more The lipolysis in adipose tissue is controlled by the hormone-sensitive lipase activity which is dependent on the intracellular cAMP level. In human adipose tissue, cAMP level is increased by catecholamines (through beta-adrenoceptor stimulation) or decreased by insulin, catecholamine (through alpha 2-adrenoceptor stimulation), neuropeptide Y, prostaglandins and adenosine. The mobilization of lipids from adipose tissue is an adaptative mechanism in response to starvation or hypocaloric diet, which involves reduction of the antilipolytic effect of insulin and the increase of catecholamine sensitivity. The regulatory pathways of lipolysis and their adaptation to caloric reduction are not defective in obesity state. Pharmacological approaches proposed for the activation of lipolysis are limited; they mainly consist either to stimulate the fat cell beta-adrenoceptors (beta-sympathomimetic drugs) or to indirectly activate the sympathetic nervous system (ephedrine and its derivatives, methylxanthines, alpha 2-antagonists). However, the side effects elicited by these drugs frequently limit their clinical use.
![Research paper thumbnail of Identification of human platelet a2-adrenoceptors with a new antagonist [3H]-RX821002, a 2-methoxy derivative of idazoxan](https://attachments.academia-assets.com/112107453/thumbnails/1.jpg)
](British Journal of Pharmacology, Aug 1, 1990
The binding of a new a2-adrenoceptor antagonist, [3H]-RX821002 (2-(2-methoxy-1,4-benzodioxan-2-yl... more The binding of a new a2-adrenoceptor antagonist, [3H]-RX821002 (2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline), was investigated in human platelet membranes and compared with [3H]-yohimbine binding parameters. 2 Analysis of kinetic data revealed association and dissociation time courses consistent with a simple bimolecular reaction. Saturation isotherms showed that [3H]-RX821002 labelled a higher total number of a2-binding sites (224 + 31 vs 168 + 24 fmol mg ' protein) than [3H]-yohimbine and with higher affinity (Kd: 0.92 + 0.06 vs 1.51 + 0.08 nM). Moreover [3H]-RX821002 exhibited a lower percentage of nonspecific binding. 3 The difference in total binding is due to a better labelling of the a2-adrenoceptors in the low affinity state by [3H]-RX821002 since the labelled receptors number in high affinity state was identical with the two radioligands. 4 [3H]-RX821002 binding displayed a specificity similar to that obtained with [3H]-yohimbine. The potency of various compounds acting on adrenoceptors was: yohimbine > oxymetazoline > UK14304 > (-)-adrenaline > prazosin > (+)-adrenaline > isoprenaline. This order of potency is classical for an a2A-adrenoceptor. 5 RX821002 is a more potent x2-adrenoceptor antagonist than yohimbine on adrenaline-induced platelet aggregation. 6 These results indicate that [3H]-RX821002 is a suitable ligand for the identification of human platelet a2-adrenoceptors. ' Author for correspondence. yohimbine binding was unsuccessful (Saulnier Blache et al., 1989). We describe here experiments concerning the efficacy of RX821002 in inhibiting adrenaline-induced platelet aggregation. We also compared the binding characteristics of [3H]-RX821002 and [3H]-yohimbine to human platelet a2-adrenoceptors and demonstrated that this new radioligand displayed all the characteristics for labelling a2A-adrenoceptors. Methods Platelet membrane preparqtion and binding procedure Blood was taken by antecubital venopuncture from six healthy male volunteers aged from 25 to 35 years. The platelet membranes were prepared as follows: 20-30ml of blood was
![Research paper thumbnail of [3H]RX821002: a new tool for the identification of α2A-adrenoceptors](https://attachments.academia-assets.com/112107452/thumbnails/1.jpg)
](European Journal of Pharmacology, Aug 1, 1989
The human adenocarcinoma cell-hne HT29 was used as a model to investigate the binding properties ... more The human adenocarcinoma cell-hne HT29 was used as a model to investigate the binding properties of a new antagonist radioligand of the imidazoline series, [3H]RX821002. All aspects of [3H]RX821002 binding conclusively prove that this radioligand is a valuable tool for labelling a2A-adrenoceptors. [3H]RX821002 binding was very rapid and reversible. Computer-assisted analysis of kinetic data revealed association and dissociation time courses consistent with a simple bimolecular reaction. Saturation isotherms indicated that [3H]RX821002 labeled with high affinity a single population of non-interacting sites displaying a K D of 1.7 + 0.1 nM. Adrenoceptor agonists and antagonists inhibited [3H]RX821002 and [3H]yohimbine binding with a strictly similar rank order of potency which is characteristic of a2~,-adrenoceptors. The binding parameters of [SH]RX821002 were compared with those of other commercially available I3H]antagonists, [3H]yohimbine and [3H]idazoxan. Analysis of the saturation isotherms for the three radioligands showed that (1) [3H]RX821002 was the radioligand exhibiting the lower percentage of non-specific binding and the better affinity, (2) the Bm~ of [3H]RX821002 was significantly higher than that of [3H]yohimbine. The difference in B,,,~ was not due to better labelling of one of the two affinity states of the receptor but was greatly reduced in glycylglycine buffer, suggesting that, in Tris-Mg 2+ buffer, [3H]yohimbine does not label the entire a2-adrenoceptor population.
Biochemical and Biophysical Research Communications, Jul 1, 2009
The primary inflammatory events occurring in the adipose tissue (AT) during high fat diet (HFD)-i... more The primary inflammatory events occurring in the adipose tissue (AT) during high fat diet (HFD)-induced obesity are poorly defined. The present study was undertaken to characterize, in wild-type(+/+) and lymphocyte deficient RAG2(-/-) mice under HFD, the changes in AT immune cells by flow cytometry analyses. In (+/+) mice, early accumulation of AT B-cells was observed, followed by increased AT T-cell numbers and finally by the appearance of insulin resistance and AT macrophage accumulation. Lack of lymphocytes in the RAG2(-/-) mice did not affect the onset of obesity and the state of insulin resistance. However, a striking accumulation of AT NK cells and activated macrophages was detected. The present study demonstrates that AT is the site of an unexpected dynamic in innate and adaptive cells during diet-induced obesity and insulin resistance. Moreover it appears that early AT lymphocyte infiltration could be considered a protective process to temper adipose tissue inflammation.
Background: Gluteofemoral adipose tissue areas are known to be poorly metabolically reactive. Mec... more Background: Gluteofemoral adipose tissue areas are known to be poorly metabolically reactive. Mechanical massage has previously been reported to show morphological and functional impact on this tissue. The present study was carried out to delve more deeply into the mechanistic considerations regarding the incidence of a mechanical massage technique on gene expression profile and β-adrenergic-mediated lipid mobilization in female femoral adipose tissue. Methods: Twelve premenopausal healthy women were included and received 12 sessions of calibrated mechanical massage (Endermologie®). Total RNA was extracted from femoral adipose tissue biopsies for gene expression studies. Microdialysis was carried out in the femoral adipose tissue in order to assess lipolytic responsiveness (via glycerol determination) and changes in local blood flow following perfusion of a lipolytic agent, isoproterenol. Evaluations were performed before and after the 6-week experimental period. Results: Mechanical...
Journal of Biological Chemistry, 1994
EXPERIMENTAL PROCEDURES Animals Male Wistar rats weighing 100-200 g were used for primary culture... more EXPERIMENTAL PROCEDURES Animals Male Wistar rats weighing 100-200 g were used for primary cultures. They were housed under a controlled photoperiod (12 h light-darkness) at constant temperature (20-22 " 0. They were fed ad libitum and had free access to water. They were killed by cervical dislocation. Cell Cultures Primary Culture of Rut Preadipocytes-Subcutaneous fat pads were removed aseptically. Stroma-vascular cells for primary culture were removed by collagenase digestion and separated from adipocytes and remaining tissues by flotation and sedimentation procedures as described previously (10). Cells were cultured at an inoculation density of The abbreviations used are: M A P , mitogen-activated protein; DMEM, Dulbecco's modified Eagle's medium; DAPI, 4',6-diamino-2phenylindole.2HCl. 30254 This is an Open Access article under the CC BY license.
Journal of Lipid Research, 1983
Adrenergic control of human fat cell lipolysis is mediated by two kinds of receptor sites that ar... more Adrenergic control of human fat cell lipolysis is mediated by two kinds of receptor sites that are simultaneously stimulated by physiological amines. To establish a correlation between the binding characteristics of the receptor and biological functions, the ability of physiological amines to stimulate or inhibit isolated fat cell lipolysis in vitro was compared to the beta- and alpha 2-adrenoceptor properties of the same fat cell batch. The beta-selective antagonist (-)[3H]dihydroalprenolol ([3H]DHA) and the alpha 2-selective antagonists [3H]yohimbine ([3H]YOH) and [3H]rauwolscine ([3H]RAU) were used to identify and characterize the two receptor sites. Binding of each ligand was rapid, saturable, and specific. The results demonstrate 1) the weaker lipolytic effect of epinephrine compared with norepinephrine. This can be explained by the equipotency of the amines at the beta 1-sites and the higher affinity of epinephrine for alpha 2-adrenergic receptors. 2) The preponderance of alpha 2-adrenergic receptor sites labeled by [3H]YOH (Bmax, 586 +/- 95 fmol/mg protein; KD, 2.7 +/- 0.2 nM) or [3H]RAU (Bmax, 580 +/- 100 fmol/mg protein; KD, 3.7 +/- 0.1 nM). These two ligands can be successfully used to label alpha 2-adrenergic receptor sites. 3) The beta 1-adrenergic receptor population labeled by [3H]DHA(Bmax, 234 +/- 37 fmol/mg protein; KD, 1.8 +/- 0.4 nM), although a third as numerous as the alpha 2-adrenergic population, is responsible for the lipolytic effect of physiological amines and is weakly counteracted by simultaneous alpha 2-adrenergic receptor stimulation under our experimental conditions. It is concluded that, in human fat cells, the characterization of beta 1- and alpha 2-adrenergic receptors by saturation studies or kinetic analysis to determine affinity (KD) and maximal number of binding sites (Bmax) is not sufficient for an accurate characterization of the functional adrenergic receptors involved in the observed biological effect.
Journal of Lipid Research, 1993
Five adrenoceptor subtypes are involved in the adrenergic regulation of white and brown fat cell ... more Five adrenoceptor subtypes are involved in the adrenergic regulation of white and brown fat cell function. The effects on CAMP production and CAMP-related cellular responses are mediated through the control of adenylyl cyclase activity by the stimulatory betal-, beta2-, and beta3-adrenergic receptors and the inhibitory alphaz-adrenoceptors. Activation of alphal-adrenoceptors stimulates phosphoinositidase C activity leading to inositol 1,4,5-triphosphate and diacylglycerol formation with a consequent mobilization of intracellular CaZ+ stores and protein kinase C activation which trigger cell responsiveness. The balance between the various adrenoceptor subtypes is the point of regulation that determines the final effect of physiological amines on adipocytes in vitro and in vivo. Large speciesspecific differences exist in brown and white fat cell adrenoceptor distribution and in their relative importance in the control of the fat cell. Functional beta3-adrenoceptors coexist with betal-and betaz-adrenoceptors in a number of fat cells; they are weakly active in guinea pig, primate, and human fat cells. Physiological hormones and transmitters operate, in fact, through differential recruitment of all these multiple alpha-and beta-adrenoceptors on the basis of their relative affinity for the different subtypes. The affinity of the beta3-adrenoceptor for catecholamines is less than that of the classical betal-and betaz-adrenoceptors. Conversely, epinephrine and norepinephrine have a higher affinity for the alphaz-adrenoceptors than for betal-, 2-, or 3-adrenoceptors. Antagonistic actions exist between alpha2-and betaadrenoceptor-mediated effects in white fat cells while positive cooperation has been revealed between alphal-and betaadrenoceptors in brown fat cells. Homologous down-regulation of betal-and betaz-adrenoceptors is observed after administration of physiological amines and beta-agonists. Conversely, beta3-and alphaz-adrenoceptors are much more resistant to agonist-induced desensitization and down-regulation. Heterologous regulation of beta-adrenoceptors was reported with glucocorticoids while sex-steroid hormones were shown to regulate alphaz-adrenoceptor expression (androgens) and to alter adenylyl cyclase activity (estrogens).-Lafontan, M., and M. Berlan. Fat cell adrenergic receptors and the control of white and brown fat cell function.
Journal of Lipid Research, 1996
Ps-Adrenoceptors are involved in the control of catecholamine-induced lipolysis in rodent adipose... more Ps-Adrenoceptors are involved in the control of catecholamine-induced lipolysis in rodent adipose tissues. The expression and function of human Ps-adrenoceptors were investigated in subcutaneous white adipocytes of young healthy women. In these cells, Ps-adrenoceptor mRNAs rep resent 20% of total amount of P-adrenoceptor transcripts and less than half of PI-adrenoceptor transcripts. Among psagonists known to stimulate Ps-adrenoceptor-mediated lipolysis in rodent fat cells, only CGP12177 was able to mediate such activity in human fat cells. In in vitro lipolysis experiments and in situ microdialysis studies, CGP12177 had a 4 to 5-times lower lipolytic efficacy than isoprenaline, a nonselective badrenoceptor agonist. CGP121774nduced lipolysis was antagonized in vitro by bupranolol, a p-adrenergic antagonist potent on rodent Ps-adrenoceptors but not by nadolol, a PIand Peadrenoceptor antagonist. The in vitro blockade of isoprenaline-stimulated lipolysis by nadolol showed that the agonist acted solely via PIand P2-adrenoceptors. Isoprenaline and CGP12177 were able to increase the nutritive blood flow suggesting an interaction of these molecules with receptors present in adipose tissue vessels. I In conclusion, Psadrenoceptors are expressed in human subcutaneous white adipocytes but do not significantly contribute to isoprenalineinduced lipolysis.-Tavernier, G.
Journal of Applied Physiology, 2000
The goal of the study was to examine whether lipid mobilization from adipose tissue undergoes cha... more The goal of the study was to examine whether lipid mobilization from adipose tissue undergoes changes during repeated bouts of prolonged aerobic exercise. Microdialysis of the subcutaneous adipose tissue was used for the assessment of lipolysis; glycerol concentration was measured in the dialysate leaving the adipose tissue. Seven male subjects performed two repeated bouts of 60-min exercise at 50% of their maximal aerobic power, separated by a 60-min recovery period. The exercise-induced increases in extracellular glycerol concentrations in adipose tissue and in plasma glycerol concentrations were significantly higher during the second exercise bout compared with the first ( P < 0.05). The responses of plasma nonesterified fatty acids and plasma epinephrine were higher during the second exercise bout, whereas the response of norepinephrine was unchanged and that of growth hormone lower. Plasma insulin levels were lower during the second exercise bout. The results suggest that ad...
American Journal of Physiology-Cell Physiology, 1994
Adipose precursor cells from male hamsters were exposed to testosterone in primary culture. The e... more Adipose precursor cells from male hamsters were exposed to testosterone in primary culture. The effect of the sex steroid on alpha 2-adrenoceptor (AR) expression was studied. Testosterone enhanced alpha 2-AR expression during adipose conversion to an identical extent to that determined in vivo without modification of the differentiation state as estimated by glycerol-3-phosphate dehydrogenase activity. The expression of preadipocyte alha 2-ARs from female hamster was also submitted to the testosterone control. The upregulating effect was androgen specific, since only testosterone and dihydrotestosterone were efficient in inducing an increase of alpha 2-AR density, whereas estradiol, dexamethasone, progesterone, and androstenedione were without any action. To conclude, androgens act directly on fat cells by upregulating alpha 2-AR expression. The effects are not mediated by aromatization into estrogens and probably involve androgen receptor interactions.
Aktuelle Ernährungsmedizin, 2004
Biochemical Journal, 1993
The inhibition of insulin-stimulated glucose transport by isoprenaline, a mixed beta-adrenergic-r... more The inhibition of insulin-stimulated glucose transport by isoprenaline, a mixed beta-adrenergic-receptor (AR) agonist, is well documented in rat adipocytes. Since it has been described that rat adipocytes possess not only beta 1- and beta 2- but also beta 3-ARs, the influence of various subtype-selective beta-AR agonists and antagonists on 2-deoxyglucose (2-DG) transport was assessed in order to characterize the beta-AR subtype involved in the adrenergic counter-regulation of the insulin effect. The stimulation of 2-DG transport by insulin was counteracted, in a dose-dependent manner, by all the beta-AR agonists tested, and the magnitude of the inhibition followed the rank order: BRL 37344 > isoprenaline = noradrenaline >> dobutamine = procaterol. The same rank order of potency was obtained for lipolysis activation. This is not in accordance with the pharmacological definition of a beta 1- or a beta 2-adrenergic effect, but agrees with the pharmacological pattern of a beta ...
Annals of the New York Academy of Sciences, May 1, 1998
European journal of pharmacology, Apr 1, 1995
Acute exposure of isolated adipocytes to isoproterenol induces the desensitization of lipolytic r... more Acute exposure of isolated adipocytes to isoproterenol induces the desensitization of lipolytic responses to norepinephrine and selective /31-, /32-and /33-adrenoceptor agonists, as well as the adrenocorticotropic hormone 1-24 fragment (ACTH). Forskolin and 8-bromo-cAMP responses are also desensitized. When lipolysis was measured in the presence of OPC 3911 {N-cyclohexyl-N-2-hydroxyethyl-4(6-(1,2-dihydro-2-oxoquinolyloxy))butyramide}, a specific inhibitor of the cAMP phosphodiesterase of adipocytes, the desensitization of all lipolytic agents-except the /32-adrenoceptor agonist-was abolished. Isoproterenol induced a similar loss (35%) of both membrane/31-and/32-adrenoceptors and an uncoupling of/3t-adrenoceptors, but did not modify the weak coupling of control /32-adrenoceptors. These data suggest that isoproterenol induced (i) an activation of the cAMP phosphodiesterase, which is solely responsible for the desensitization of norepinephrine response as well as/31-and/33-adrenoceptor mediated responses and (ii) an additional desensitization of the sole/32-adrenergic signaling system which suggests a subtype-selective pattern of regulating processes.
Journal of Physiology and Biochemistry, Feb 12, 2015
The mechanisms underlying the relationships between nutritional status and immunity remain to be ... more The mechanisms underlying the relationships between nutritional status and immunity remain to be fully characterized. The present study was undertaken to analyze by flow cytometry, in the context of dietinduced obesity, the status of immune cells in subcutaneous, and epididymal fat depots in wild-type and immunodeficient Rag2−/− mice submitted to nutritional challenge, i.e., 48-h fasting and 1-week refeeding. In parallel, the responsiveness of mature adipocytes and immune cells in bone marrow, lymph node, and liver were also analyzed. The results show that fasting in obese wild-type mice induces a prominent lipolysis in epididymal AT and immunosuppression restricted to both subcutaneous and epididymal AT, characterized by reduced number of CD4+ T and B lymphocytes and M1/M2 macrophages associated with reduced leptin and increased FGF21 expression in mature adipocytes. One-week refeeding was sufficient to reverse the fasting-induced effects. Obese immunodeficient mice under nutritional challenge exhibited no changes in adipocyte leptin expression and no marked trafficking of AT macrophages or NK cells, while the fasted-induced upregulation of FGF21 expression was maintained as well as the lipolytic responses. The present results demonstrate that, in a context of dietinduced obesity, fasting-induced immunosuppression is restricted to fat depots in immunocompetent mice. Lack of adipocyte leptin regulation and fasting-induced immunosuppression in obese immunodeficient mice strongly suggests that lymphocytes are involved in the modulation of adipocyte leptin expression on one hand and on the other that leptin is involved in the immune changes in AT according to nutritional status.
Journal of Lipid Research, Feb 1, 1999
The sympathetic nervous system controls lipolysis in fat by activation of four adrenergic recepto... more The sympathetic nervous system controls lipolysis in fat by activation of four adrenergic receptors:  1,  2,  3, and ␣ 2. During pregnancy, maternal metabolism presents anabolic and catabolic phases, characterized by modifications of fat responsiveness to catecholamines. The contributions of the four adrenergic receptors to adipocyte responsiveness during pregnancy have never been studied. Our aim was to evaluate the influence of pregnancy on adrenergic receptor-mediated lipolysis in rabbit white adipocytes. Functional studies were performed using subtypeselective and non-selective adrenergic receptor agonists. Overall adrenergic responsiveness was measured with the physiological agonist epinephrine. Non-adrenergic agents were used to evaluate different steps of the lipolytic cascade. The ␣ 2-and  1/  2-adrenergic receptor numbers were determined with selective radioligands. Non-adrenergic agents revealed that pregnancy induced an intracytoplasmic modification of the lipolytic cascade in inguinal but not in retroperitoneal adipocytes. Pregnancy induced an increase in  1-and specially  3-mediated lipolysis. The amounts of adipocyte  1/  2-and ␣ 2-adrenergic receptors were increased in pregnant rabbits. Epinephrine effects revealed an increased contribution of ␣ 2-adrenergic receptor-mediated antilipolysis in adipocytes from pregnant rabbits. These results indicate that pregnancy regulates adipocyte responsiveness to catecholamines mainly via the ␣ 2-and  3-adrenergic pathways. Pregnancy induces an intracytoplasmic modification of the lipolytic cascade, probably via hormone-sensitive lipase, with differences according to fat location.-Bousquet-Mélou, A
American Journal of Physiology-regulatory Integrative and Comparative Physiology, Jul 1, 1994
The beta-adrenoceptor subtypes involved in the control of lipolysis in white fat cells of rat, do... more The beta-adrenoceptor subtypes involved in the control of lipolysis in white fat cells of rat, dog, marmoset (Callithrix jacchus), baboon (Papio papio), macaque (Macaca fascicularis), and human were compared. In all species [3H]CGP-12177 binding (up to 3 nM) indicated the existence of a homogeneous population of binding sites in fat cell membranes, and competition studies showed that beta 1- and beta 2-adrenoceptors were present. Selective beta 1 or beta 2-adrenoceptor agonists induced lipolysis. The efficiencies of isoproterenol and norepinephrine were similar. The use of selective beta 3-adrenoceptor agonists revealed that BRL-37344 and CL-316243 were full agonists, whereas CGP-12177 and SR-58611A were partial agonists in rat and dog white fat cells. beta 3-Agonists partially stimulated lipolysis in the marmoset, while CGP-12177 was weakly active in the baboon. In macaque and human fat cells, beta 3-agonists were ineffective. The lipolytic effect of norepinephrine involves beta 1-and/or beta 2-adrenoceptors in baboon, macaque, and human. The baboon and macaque constitute valuable models for studying the beta-adrenergic control of lipolysis.
Les abonnements sont mis en service dans un délai maximum de quatre semaines après réception de l... more Les abonnements sont mis en service dans un délai maximum de quatre semaines après réception de la commande et du règlement. Ils partent du premier numéro de l'année. Les réclamations pour les numéros non reçus doivent parvenir dans un délai maximum de six mois. Les numéros séparés de l'année et volumes antérieurs (jusqu'à épuisement du stock) peuvent être commandés à la même adresse.
HAL (Le Centre pour la Communication Scientifique Directe), 1995
The lipolysis in adipose tissue is controlled by the hormone-sensitive lipase activity which is d... more The lipolysis in adipose tissue is controlled by the hormone-sensitive lipase activity which is dependent on the intracellular cAMP level. In human adipose tissue, cAMP level is increased by catecholamines (through beta-adrenoceptor stimulation) or decreased by insulin, catecholamine (through alpha 2-adrenoceptor stimulation), neuropeptide Y, prostaglandins and adenosine. The mobilization of lipids from adipose tissue is an adaptative mechanism in response to starvation or hypocaloric diet, which involves reduction of the antilipolytic effect of insulin and the increase of catecholamine sensitivity. The regulatory pathways of lipolysis and their adaptation to caloric reduction are not defective in obesity state. Pharmacological approaches proposed for the activation of lipolysis are limited; they mainly consist either to stimulate the fat cell beta-adrenoceptors (beta-sympathomimetic drugs) or to indirectly activate the sympathetic nervous system (ephedrine and its derivatives, methylxanthines, alpha 2-antagonists). However, the side effects elicited by these drugs frequently limit their clinical use.
British Journal of Pharmacology, Aug 1, 1990
The binding of a new a2-adrenoceptor antagonist, [3H]-RX821002 (2-(2-methoxy-1,4-benzodioxan-2-yl... more The binding of a new a2-adrenoceptor antagonist, [3H]-RX821002 (2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline), was investigated in human platelet membranes and compared with [3H]-yohimbine binding parameters. 2 Analysis of kinetic data revealed association and dissociation time courses consistent with a simple bimolecular reaction. Saturation isotherms showed that [3H]-RX821002 labelled a higher total number of a2-binding sites (224 + 31 vs 168 + 24 fmol mg ' protein) than [3H]-yohimbine and with higher affinity (Kd: 0.92 + 0.06 vs 1.51 + 0.08 nM). Moreover [3H]-RX821002 exhibited a lower percentage of nonspecific binding. 3 The difference in total binding is due to a better labelling of the a2-adrenoceptors in the low affinity state by [3H]-RX821002 since the labelled receptors number in high affinity state was identical with the two radioligands. 4 [3H]-RX821002 binding displayed a specificity similar to that obtained with [3H]-yohimbine. The potency of various compounds acting on adrenoceptors was: yohimbine > oxymetazoline > UK14304 > (-)-adrenaline > prazosin > (+)-adrenaline > isoprenaline. This order of potency is classical for an a2A-adrenoceptor. 5 RX821002 is a more potent x2-adrenoceptor antagonist than yohimbine on adrenaline-induced platelet aggregation. 6 These results indicate that [3H]-RX821002 is a suitable ligand for the identification of human platelet a2-adrenoceptors. ' Author for correspondence. yohimbine binding was unsuccessful (Saulnier Blache et al., 1989). We describe here experiments concerning the efficacy of RX821002 in inhibiting adrenaline-induced platelet aggregation. We also compared the binding characteristics of [3H]-RX821002 and [3H]-yohimbine to human platelet a2-adrenoceptors and demonstrated that this new radioligand displayed all the characteristics for labelling a2A-adrenoceptors. Methods Platelet membrane preparqtion and binding procedure Blood was taken by antecubital venopuncture from six healthy male volunteers aged from 25 to 35 years. The platelet membranes were prepared as follows: 20-30ml of blood was
European Journal of Pharmacology, Aug 1, 1989
The human adenocarcinoma cell-hne HT29 was used as a model to investigate the binding properties ... more The human adenocarcinoma cell-hne HT29 was used as a model to investigate the binding properties of a new antagonist radioligand of the imidazoline series, [3H]RX821002. All aspects of [3H]RX821002 binding conclusively prove that this radioligand is a valuable tool for labelling a2A-adrenoceptors. [3H]RX821002 binding was very rapid and reversible. Computer-assisted analysis of kinetic data revealed association and dissociation time courses consistent with a simple bimolecular reaction. Saturation isotherms indicated that [3H]RX821002 labeled with high affinity a single population of non-interacting sites displaying a K D of 1.7 + 0.1 nM. Adrenoceptor agonists and antagonists inhibited [3H]RX821002 and [3H]yohimbine binding with a strictly similar rank order of potency which is characteristic of a2~,-adrenoceptors. The binding parameters of [SH]RX821002 were compared with those of other commercially available I3H]antagonists, [3H]yohimbine and [3H]idazoxan. Analysis of the saturation isotherms for the three radioligands showed that (1) [3H]RX821002 was the radioligand exhibiting the lower percentage of non-specific binding and the better affinity, (2) the Bm~ of [3H]RX821002 was significantly higher than that of [3H]yohimbine. The difference in B,,,~ was not due to better labelling of one of the two affinity states of the receptor but was greatly reduced in glycylglycine buffer, suggesting that, in Tris-Mg 2+ buffer, [3H]yohimbine does not label the entire a2-adrenoceptor population.
Biochemical and Biophysical Research Communications, Jul 1, 2009
The primary inflammatory events occurring in the adipose tissue (AT) during high fat diet (HFD)-i... more The primary inflammatory events occurring in the adipose tissue (AT) during high fat diet (HFD)-induced obesity are poorly defined. The present study was undertaken to characterize, in wild-type(+/+) and lymphocyte deficient RAG2(-/-) mice under HFD, the changes in AT immune cells by flow cytometry analyses. In (+/+) mice, early accumulation of AT B-cells was observed, followed by increased AT T-cell numbers and finally by the appearance of insulin resistance and AT macrophage accumulation. Lack of lymphocytes in the RAG2(-/-) mice did not affect the onset of obesity and the state of insulin resistance. However, a striking accumulation of AT NK cells and activated macrophages was detected. The present study demonstrates that AT is the site of an unexpected dynamic in innate and adaptive cells during diet-induced obesity and insulin resistance. Moreover it appears that early AT lymphocyte infiltration could be considered a protective process to temper adipose tissue inflammation.
Background: Gluteofemoral adipose tissue areas are known to be poorly metabolically reactive. Mec... more Background: Gluteofemoral adipose tissue areas are known to be poorly metabolically reactive. Mechanical massage has previously been reported to show morphological and functional impact on this tissue. The present study was carried out to delve more deeply into the mechanistic considerations regarding the incidence of a mechanical massage technique on gene expression profile and β-adrenergic-mediated lipid mobilization in female femoral adipose tissue. Methods: Twelve premenopausal healthy women were included and received 12 sessions of calibrated mechanical massage (Endermologie®). Total RNA was extracted from femoral adipose tissue biopsies for gene expression studies. Microdialysis was carried out in the femoral adipose tissue in order to assess lipolytic responsiveness (via glycerol determination) and changes in local blood flow following perfusion of a lipolytic agent, isoproterenol. Evaluations were performed before and after the 6-week experimental period. Results: Mechanical...
Journal of Biological Chemistry, 1994
EXPERIMENTAL PROCEDURES Animals Male Wistar rats weighing 100-200 g were used for primary culture... more EXPERIMENTAL PROCEDURES Animals Male Wistar rats weighing 100-200 g were used for primary cultures. They were housed under a controlled photoperiod (12 h light-darkness) at constant temperature (20-22 " 0. They were fed ad libitum and had free access to water. They were killed by cervical dislocation. Cell Cultures Primary Culture of Rut Preadipocytes-Subcutaneous fat pads were removed aseptically. Stroma-vascular cells for primary culture were removed by collagenase digestion and separated from adipocytes and remaining tissues by flotation and sedimentation procedures as described previously (10). Cells were cultured at an inoculation density of The abbreviations used are: M A P , mitogen-activated protein; DMEM, Dulbecco's modified Eagle's medium; DAPI, 4',6-diamino-2phenylindole.2HCl. 30254 This is an Open Access article under the CC BY license.
Journal of Lipid Research, 1983
Adrenergic control of human fat cell lipolysis is mediated by two kinds of receptor sites that ar... more Adrenergic control of human fat cell lipolysis is mediated by two kinds of receptor sites that are simultaneously stimulated by physiological amines. To establish a correlation between the binding characteristics of the receptor and biological functions, the ability of physiological amines to stimulate or inhibit isolated fat cell lipolysis in vitro was compared to the beta- and alpha 2-adrenoceptor properties of the same fat cell batch. The beta-selective antagonist (-)[3H]dihydroalprenolol ([3H]DHA) and the alpha 2-selective antagonists [3H]yohimbine ([3H]YOH) and [3H]rauwolscine ([3H]RAU) were used to identify and characterize the two receptor sites. Binding of each ligand was rapid, saturable, and specific. The results demonstrate 1) the weaker lipolytic effect of epinephrine compared with norepinephrine. This can be explained by the equipotency of the amines at the beta 1-sites and the higher affinity of epinephrine for alpha 2-adrenergic receptors. 2) The preponderance of alpha 2-adrenergic receptor sites labeled by [3H]YOH (Bmax, 586 +/- 95 fmol/mg protein; KD, 2.7 +/- 0.2 nM) or [3H]RAU (Bmax, 580 +/- 100 fmol/mg protein; KD, 3.7 +/- 0.1 nM). These two ligands can be successfully used to label alpha 2-adrenergic receptor sites. 3) The beta 1-adrenergic receptor population labeled by [3H]DHA(Bmax, 234 +/- 37 fmol/mg protein; KD, 1.8 +/- 0.4 nM), although a third as numerous as the alpha 2-adrenergic population, is responsible for the lipolytic effect of physiological amines and is weakly counteracted by simultaneous alpha 2-adrenergic receptor stimulation under our experimental conditions. It is concluded that, in human fat cells, the characterization of beta 1- and alpha 2-adrenergic receptors by saturation studies or kinetic analysis to determine affinity (KD) and maximal number of binding sites (Bmax) is not sufficient for an accurate characterization of the functional adrenergic receptors involved in the observed biological effect.
Journal of Lipid Research, 1993
Five adrenoceptor subtypes are involved in the adrenergic regulation of white and brown fat cell ... more Five adrenoceptor subtypes are involved in the adrenergic regulation of white and brown fat cell function. The effects on CAMP production and CAMP-related cellular responses are mediated through the control of adenylyl cyclase activity by the stimulatory betal-, beta2-, and beta3-adrenergic receptors and the inhibitory alphaz-adrenoceptors. Activation of alphal-adrenoceptors stimulates phosphoinositidase C activity leading to inositol 1,4,5-triphosphate and diacylglycerol formation with a consequent mobilization of intracellular CaZ+ stores and protein kinase C activation which trigger cell responsiveness. The balance between the various adrenoceptor subtypes is the point of regulation that determines the final effect of physiological amines on adipocytes in vitro and in vivo. Large speciesspecific differences exist in brown and white fat cell adrenoceptor distribution and in their relative importance in the control of the fat cell. Functional beta3-adrenoceptors coexist with betal-and betaz-adrenoceptors in a number of fat cells; they are weakly active in guinea pig, primate, and human fat cells. Physiological hormones and transmitters operate, in fact, through differential recruitment of all these multiple alpha-and beta-adrenoceptors on the basis of their relative affinity for the different subtypes. The affinity of the beta3-adrenoceptor for catecholamines is less than that of the classical betal-and betaz-adrenoceptors. Conversely, epinephrine and norepinephrine have a higher affinity for the alphaz-adrenoceptors than for betal-, 2-, or 3-adrenoceptors. Antagonistic actions exist between alpha2-and betaadrenoceptor-mediated effects in white fat cells while positive cooperation has been revealed between alphal-and betaadrenoceptors in brown fat cells. Homologous down-regulation of betal-and betaz-adrenoceptors is observed after administration of physiological amines and beta-agonists. Conversely, beta3-and alphaz-adrenoceptors are much more resistant to agonist-induced desensitization and down-regulation. Heterologous regulation of beta-adrenoceptors was reported with glucocorticoids while sex-steroid hormones were shown to regulate alphaz-adrenoceptor expression (androgens) and to alter adenylyl cyclase activity (estrogens).-Lafontan, M., and M. Berlan. Fat cell adrenergic receptors and the control of white and brown fat cell function.
Journal of Lipid Research, 1996
Ps-Adrenoceptors are involved in the control of catecholamine-induced lipolysis in rodent adipose... more Ps-Adrenoceptors are involved in the control of catecholamine-induced lipolysis in rodent adipose tissues. The expression and function of human Ps-adrenoceptors were investigated in subcutaneous white adipocytes of young healthy women. In these cells, Ps-adrenoceptor mRNAs rep resent 20% of total amount of P-adrenoceptor transcripts and less than half of PI-adrenoceptor transcripts. Among psagonists known to stimulate Ps-adrenoceptor-mediated lipolysis in rodent fat cells, only CGP12177 was able to mediate such activity in human fat cells. In in vitro lipolysis experiments and in situ microdialysis studies, CGP12177 had a 4 to 5-times lower lipolytic efficacy than isoprenaline, a nonselective badrenoceptor agonist. CGP121774nduced lipolysis was antagonized in vitro by bupranolol, a p-adrenergic antagonist potent on rodent Ps-adrenoceptors but not by nadolol, a PIand Peadrenoceptor antagonist. The in vitro blockade of isoprenaline-stimulated lipolysis by nadolol showed that the agonist acted solely via PIand P2-adrenoceptors. Isoprenaline and CGP12177 were able to increase the nutritive blood flow suggesting an interaction of these molecules with receptors present in adipose tissue vessels. I In conclusion, Psadrenoceptors are expressed in human subcutaneous white adipocytes but do not significantly contribute to isoprenalineinduced lipolysis.-Tavernier, G.
Journal of Applied Physiology, 2000
The goal of the study was to examine whether lipid mobilization from adipose tissue undergoes cha... more The goal of the study was to examine whether lipid mobilization from adipose tissue undergoes changes during repeated bouts of prolonged aerobic exercise. Microdialysis of the subcutaneous adipose tissue was used for the assessment of lipolysis; glycerol concentration was measured in the dialysate leaving the adipose tissue. Seven male subjects performed two repeated bouts of 60-min exercise at 50% of their maximal aerobic power, separated by a 60-min recovery period. The exercise-induced increases in extracellular glycerol concentrations in adipose tissue and in plasma glycerol concentrations were significantly higher during the second exercise bout compared with the first ( P < 0.05). The responses of plasma nonesterified fatty acids and plasma epinephrine were higher during the second exercise bout, whereas the response of norepinephrine was unchanged and that of growth hormone lower. Plasma insulin levels were lower during the second exercise bout. The results suggest that ad...
American Journal of Physiology-Cell Physiology, 1994
Adipose precursor cells from male hamsters were exposed to testosterone in primary culture. The e... more Adipose precursor cells from male hamsters were exposed to testosterone in primary culture. The effect of the sex steroid on alpha 2-adrenoceptor (AR) expression was studied. Testosterone enhanced alpha 2-AR expression during adipose conversion to an identical extent to that determined in vivo without modification of the differentiation state as estimated by glycerol-3-phosphate dehydrogenase activity. The expression of preadipocyte alha 2-ARs from female hamster was also submitted to the testosterone control. The upregulating effect was androgen specific, since only testosterone and dihydrotestosterone were efficient in inducing an increase of alpha 2-AR density, whereas estradiol, dexamethasone, progesterone, and androstenedione were without any action. To conclude, androgens act directly on fat cells by upregulating alpha 2-AR expression. The effects are not mediated by aromatization into estrogens and probably involve androgen receptor interactions.
Aktuelle Ernährungsmedizin, 2004
Biochemical Journal, 1993
The inhibition of insulin-stimulated glucose transport by isoprenaline, a mixed beta-adrenergic-r... more The inhibition of insulin-stimulated glucose transport by isoprenaline, a mixed beta-adrenergic-receptor (AR) agonist, is well documented in rat adipocytes. Since it has been described that rat adipocytes possess not only beta 1- and beta 2- but also beta 3-ARs, the influence of various subtype-selective beta-AR agonists and antagonists on 2-deoxyglucose (2-DG) transport was assessed in order to characterize the beta-AR subtype involved in the adrenergic counter-regulation of the insulin effect. The stimulation of 2-DG transport by insulin was counteracted, in a dose-dependent manner, by all the beta-AR agonists tested, and the magnitude of the inhibition followed the rank order: BRL 37344 > isoprenaline = noradrenaline >> dobutamine = procaterol. The same rank order of potency was obtained for lipolysis activation. This is not in accordance with the pharmacological definition of a beta 1- or a beta 2-adrenergic effect, but agrees with the pharmacological pattern of a beta ...