The Rosmarinus Bioactive Compound Carnosic Acid Is a Novel PPAR Antagonist That Inhibits the Browning of White Adipocytes.

Thermogenic brown and brite adipocytes convert chemical energy from nutrients into heat. Therapeutics that regulate brown adipocyte recruitment and activity represent interesting strategies to control fat mass such as in obesity or cachexia. The peroxisome proliferator-activated receptor (PPAR) family plays key roles in the maintenance of adipose tissue and in the regulation of thermogenic activity. Activation of these receptors induce browning of white adipocyte. The purpose of this work was to characterize the role of carnosic acid (CA), a compound used in traditional medicine, in the control of brown/brite adipocyte formation and function. We used human multipotent adipose-derived stem (hMADS) cells differentiated into white or brite adipocytes. The expression of key marker genes was determined using RT-qPCR and western blotting. We show here that CA inhibits the browning of white adipocytes and favors decreased gene expression of thermogenic markers. CA treatment does not affect ß-adrenergic response. Importantly, the effects of CA are fully reversible. We used transactivation assays to show that CA has a PPARα/γ antagonistic action. Our data pinpoint CA as a drug able to control PPAR activity through an antagonistic effect. These observations shed some light on the development of natural PPAR antagonists and their potential effects on thermogenic response.

Impact of dietary ω3 polyunsaturated fatty acid supplementation on brown and brite adipocyte function.

The recent characterization of functional brown adipose tissue in adult humans has opened new perspectives for regulation of energy expenditure with respect to obesity and diabetes. Furthermore, dietary recommendations have taken into account the insufficient dietary intake of ω3 PUFAs and the concomitant excessive intake of ω6 PUFA associated with the occurrence of overweight/obesity. We aimed to study whether ω3 PUFAs could play a role in the recruitment and function of energy-dissipating brown/brite adipocytes. We show that ω3 PUFA supplementation has a beneficial effect on the thermogenic function of adipocytes. In vivo, a low dietary ω6:ω3 ratio improved the thermogenic response of brown and white adipose tissues to ß3-adrenergic stimulation. This effect was recapitulated in vitro by PUFA treatment of hMADS adipocytes. We pinpointed the ω6-derived eicosanoid prostaglandin (PG)F2α as the molecular origin because the effects were mimicked with a specific PGF2α receptor agonist. PGF2α level in hMADS adipocytes was reduced in response to ω3 PUFA supplementation. The recruitment of thermogenic adipocytes is influenced by the local quantity of individual oxylipins, which is controlled by the ω6:ω3 ratio of available lipids. In human nutrition, energy homeostasis may thus benefit from the implementation of a more balanced dietary ω6:ω3 ratio.

Control of adipogenesis by oxylipins, GPCRs and PPARs.

Oxylipins are bioactive metabolites derived from the oxygenation of ω3 and ω6 polyunsaturated fatty acids, triggered essentially by cyclooxygenase and lipoxygenase activities. Oxylipins are involved in the development and function of adipose tissue and their productions are strictly related to diet quality and quantity. Oxylipins signal via cell surface membrane (G Protein-coupled receptors) and nuclear receptors (peroxisome proliferator-activated receptors), two pathways playing a pivotal role in adipocyte biology. In this review, we made an attempt to cover the available knowledge about synthesis and molecular function of oxylipins known to modulate adipogenesis, adipocyte function and phenotype conversion, with a focus on their interaction with peroxisome proliferator-activated nuclear receptor family.

IP-receptor and PPARs trigger the conversion of human white to brite adipocyte induced by carbaprostacyclin.

Brite adipocytes recently discovered in humans are of considerable importance in energy expenditure by converting energy excess into heat. This property could be useful in the treatment of obesity, and nutritional aspects are relevant to this important issue. Using hMADS cells as a human cell model which undergoes a white to a brite adipocyte conversion, we had shown previously that arachidonic acid, the major metabolite of the essential nutrient Ω6-linoleic acid, plays a major role in this process. Its metabolites PGE2 and PGF2 alpha inhibit this process via a calcium-dependent pathway, whereas in contrast carbaprostacyclin (cPGI2), a stable analog of prostacyclin, activates white to brite adipocyte conversion. Herein, we show that cPGI2 generates via its cognate cell-surface receptor IP-R, a cyclic AMP-signaling pathway involving PKA activity which in turn induces the expression of UCP1. In addition, cPGI2 activates the pathway of nuclear receptors of the PPAR family, i.e. PPARα and PPARγ, which act separately from IP-R to up-regulate the expression of key genes involved in the function of brite adipocytes. Thus dual pathways are playing in concert for the occurrence of a browning process of human white adipocytes. These results make prostacyclin analogs as a new class of interesting molecules to treat obesity and associated diseases.

The ω6-fatty acid, arachidonic acid, regulates the conversion of white to brite adipocyte through a prostaglandin/calcium mediated pathway.

OBJECTIVE: Brite adipocytes are inducible energy-dissipating cells expressing UCP1 which appear within white adipose tissue of healthy adult individuals. Recruitment of these cells represents a potential strategy to fight obesity and associated diseases. METHODS/RESULTS: Using human Multipotent Adipose-Derived Stem cells, able to convert into brite adipocytes, we show that arachidonic acid strongly inhibits brite adipocyte formation via a cyclooxygenase pathway leading to secretion of PGE2 and PGF2α. Both prostaglandins induce an oscillatory Ca(++) signaling coupled to ERK pathway and trigger a decrease in UCP1 expression and in oxygen consumption without altering mitochondriogenesis. In mice fed a standard diet supplemented with ω6 arachidonic acid, PGF2α and PGE2 amounts are increased in subcutaneous white adipose tissue and associated with a decrease in the recruitment of brite adipocytes. CONCLUSION: Our results suggest that dietary excess of ω6 polyunsaturated fatty acids present in Western diets, may also favor obesity by preventing the "browning" process to take place.

Oxytocin reverses ovariectomy-induced osteopenia and body fat gain.

Osteoporosis and overweight/obesity constitute major worldwide public health burdens that are associated with aging. A high proportion of women develop osteoporosis and increased intraabdominal adiposity after menopause. which leads to bone fractures and metabolic disorders. There is no efficient treatment without major side effects for these 2 diseases. We previously showed that the administration of oxytocin (OT) normalizes ovariectomy-induced osteopenia and bone marrow adiposity in mice. Ovariectomized mice, used as an animal model mimicking menopause, were treated with OT or vehicle. Trabecular bone parameters and fat mass were analyzed using micro-computed tomography. Herein, we show that this effect on trabecular bone parameters was mediated through the restoration of osteoblast/osteoclast cross talk via the receptor activator of nuclear factor-κB ligand /osteoprotegerin axis. Moreover, the daily administration of OT normalized body weight and intraabdominal fat depots in ovariectomized mice. Intraabdominal fat mass is more sensitive to OT that sc fat depots, and this inhibitory effect is mediated through inhibition of adipocyte precursor's differentiation with a tendency to lower adipocyte size. OT treatment did not affect food intake, locomotors activity, or energy expenditure, but it did promote a shift in fuel utilization favoring lipid oxidation. In addition, the decrease in fat mass resulted from the inhibition of the adipose precursor's differentiation. Thus, OT constitutes an effective strategy for targeting osteopenia, overweight, and fat mass redistribution without any detrimental effects in a mouse model mimicking the menopause.

MicroRNA-26 family is required for human adipogenesis and drives characteristics of brown adipocytes.

Adipose tissue contains thermogenic adipocytes (i.e., brown and brite/beige) that oxidize nutrients at exceptionally high rates via nonshivering thermogenesis. Its recent discovery in adult humans has opened up new avenues to fight obesity and related disorders such as diabetes. Here, we identified miR-26a and -26b as key regulators of human white and brite adipocyte differentiation. Both microRNAs are upregulated in early adipogenesis, and their inhibition prevented lipid accumulation while their overexpression accelerated it. Intriguingly, miR-26a significantly induced pathways related to energy dissipation, shifted mitochondrial morphology toward that seen in brown adipocytes, and promoted uncoupled respiration by markedly increasing the hallmark protein of brown fat, uncoupling protein 1. By combining in silico target prediction, transcriptomics, and an RNA interference screen, we identified the sheddase ADAM metallopeptidase domain 17 (ADAM17) as a direct target of miR-26 that mediated the observed effects on white and brite adipogenesis. These results point to a novel, critical role for the miR-26 family and its downstream effector ADAM17 in human adipocyte differentiation by promoting characteristics of energy-dissipating thermogenic adipocytes.

Chondrogenic potential of stem cells derived from adipose tissue: a powerful pharmacological tool.

Chondrogenesis has been widely investigated in vitro using bone marrow-derived mesenchymal stromal cells (BM-MSCs) or primary chondrocytes. However, their use raises some issues partially circumvented by the availability of Adipose tissue-derived MSCs. Herein; we characterized the chondrogenic potential of human Multipotent Adipose-Derived Stem (hMADS) cells, and their potential use as pharmacological tool. hMADS cells are able to synthesize matrix proteins including COMP, Aggrecan and type II Collagen. Furthermore, hMADS cells express BMP receptors in a similar manner to BM-MSC, and BMP6 treatment of differentiated cells prevents expression of the hypertrophic marker type X Collagen. We tested whether IL-1ß and nicotine could impact chondrocyte differentiation. As expected, IL-1ß induced ADAMTS-4 gene expression and modulated negatively chondrogenesis while these effects were reverted in the presence of the IL-1 receptor antagonist. Nicotine, at concentrations similar to those observed in blood of smokers, exhibited a dose dependent increase of Aggrecan expression, suggesting an unexpected protective effect of the drug under these conditions. Therefore, hMADS cells represent a valuable tool for the analysis of in vitro chondrocyte differentiation and to screen for potentially interesting pharmacological drugs.

Omega-6 polyunsaturated fatty acids and the early origins of obesity.

PURPOSE OF REVIEW: The incidence of obesity and its related metabolic disorders has increased significantly over the past 3 decades, culminating in the current global epidemic of metabolic disease and leading to the search for contributing factors. Exposure of the developing foetus/neonate to a typical Western diet increases their risk of obesity and metabolic disorders throughout the life-course, creating an intergenerational cycle of metabolic disease. In Western countries, this epidemic of metabolic disease has coincided with a marked increase in the intake of omega-6 polyunsaturated fatty acids (omega-6 PUFA), leading to suggestions that the two may be causally related. RECENT FINDINGS: Recent studies have emphasized the proadipogenic properties of the omega-6 PUFA, and provided evidence that rodents fed on diets with omega-6 PUFA contents similar to the typical US diet (6-8% energy) have an increased fat mass. Importantly, recent studies have shown that perinatal exposure to a high omega-6 PUFA diet results in a progressive accumulation of body fat across generations. SUMMARY: This review highlights the recent evidence supporting the role of the omega-6 PUFA in the early life origins of obesity and metabolic disease, the need for more clinical studies and the potential need for health agencies to re-evaluate current recommendations to further increase omega-6 PUFA intakes.

Activation of protein kinase A and exchange protein directly activated by cAMP promotes adipocyte differentiation of human mesenchymal stem cells.

Human mesenchymal stem cells are primary multipotent cells capable of differentiating into several cell types including adipocytes when cultured under defined in vitro conditions. In the present study we investigated the role of cAMP signaling and its downstream effectors, protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac) in adipocyte conversion of human mesenchymal stem cells derived from adipose tissue (hMADS). We show that cAMP signaling involving the simultaneous activation of both PKA- and Epac-dependent signaling is critical for this process even in the presence of the strong adipogenic inducers insulin, dexamethasone, and rosiglitazone, thereby clearly distinguishing the hMADS cells from murine preadipocytes cell lines, where rosiglitazone together with dexamethasone and insulin strongly promotes adipocyte differentiation. We further show that prostaglandin I(2) (PGI(2)) may fully substitute for the cAMP-elevating agent isobutylmethylxanthine (IBMX). Moreover, selective activation of Epac-dependent signaling promoted adipocyte differentiation when the Rho-associated kinase (ROCK) was inhibited. Unlike the case for murine preadipocytes cell lines, long-chain fatty acids, like arachidonic acid, did not promote adipocyte differentiation of hMADS cells in the absence of a PPARγ agonist. However, prolonged treatment with the synthetic PPARδ agonist L165041 promoted adipocyte differentiation of hMADS cells in the presence of IBMX. Taken together our results emphasize the need for cAMP signaling in concert with treatment with a PPARγ or PPARδ agonist to secure efficient adipocyte differentiation of human hMADS mesenchymal stem cells.

Cardiac natriuretic peptides act via p38 MAPK to induce the brown fat thermogenic program in mouse and human adipocytes.

The ability of mammals to resist body fat accumulation is linked to their ability to expand the number and activity of "brown adipocytes" within white fat depots. Activation of ß-adrenergic receptors (ß-ARs) can induce a functional "brown-like" adipocyte phenotype. As cardiac natriuretic peptides (NPs) and ß-AR agonists are similarly potent at stimulating lipolysis in human adipocytes, we investigated whether NPs could induce human and mouse adipocytes to acquire brown adipocyte features, including a capacity for thermogenic energy expenditure mediated by uncoupling protein 1 (UCP1). In human adipocytes, atrial NP (ANP) and ventricular NP (BNP) activated PPARγ coactivator-1α (PGC-1α) and UCP1 expression, induced mitochondriogenesis, and increased uncoupled and total respiration. At low concentrations, ANP and ß-AR agonists additively enhanced expression of brown fat and mitochondrial markers in a p38 MAPK-dependent manner. Mice exposed to cold temperatures had increased levels of circulating NPs as well as higher expression of NP signaling receptor and lower expression of the NP clearance receptor (Nprc) in brown adipose tissue (BAT) and white adipose tissue (WAT). NPR-C(-/-) mice had markedly smaller WAT and BAT depots but higher expression of thermogenic genes such as Ucp1. Infusion of BNP into mice robustly increased Ucp1 and Pgc-1α expression in WAT and BAT, with corresponding elevation of respiration and energy expenditure. These results suggest that NPs promote "browning" of white adipocytes to increase energy expenditure, defining the heart as a central regulator of adipose tissue biology.

Overproduction of angiotensinogen from adipose tissue induces adipose inflammation, glucose intolerance, and insulin resistance.

Although obesity is associated with overactivation of the white adipose tissue (WAT) renin-angiotensin system (RAS), a causal link between the latter and systemic insulin resistance is not established. We tested the hypothesis that overexpression of angiotensinogen (Agt) from WAT causes systemic insulin resistance via modulation of adipose inflammation. Glucose tolerance, systemic insulin sensitivity, and WAT inflammatory markers were analyzed in mice overexpressing Agt in the WAT (aP2-Agt mice). Proteomic studies and in vitro studies using 3T3-L1 adipocytes were performed to build a mechanistic framework. Male aP2-Agt mice exhibited glucose intolerance, insulin resistance, and lower insulin-stimulated glucose uptake by the skeletal muscle. The difference in glucose tolerance between genotypes was normalized by high-fat (HF) feeding, and was significantly improved by treatment with angiotensin-converting enzyme (ACE) inhibitor captopril. aP2-Agt mice also had higher monocyte chemotactic protein-1 (MCP-1) and lower interleukin-10 (IL-10) in the WAT, indicating adipose inflammation. Proteomic studies in WAT showed that they also had higher monoglyceride lipase (MGL) and glycerol-3-phosphate dehydrogenase levels. Treatment with angiotensin II (Ang II) increased MCP-1 and resistin secretion from adipocytes, which was prevented by cotreating with inhibitors of the nuclear factor-κB (NF-κB) pathway or nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In conclusion, we show for the first time that adipose RAS overactivation causes glucose intolerance and systemic insulin resistance. The mechanisms appear to be via reduced skeletal muscle glucose uptake, at least in part due to Ang II-induced, NADPH oxidase and NFκB-dependent increases in WAT inflammation.

Oxytocin and bone remodelling: relationships with neuropituitary hormones, bone status and body composition.

PURPOSE: There is growing evidence that oxytocin, which regulates appetite, plays a role in bone remodelling and improves osteoporosis. We previously showed a significant decrease in circulating oxytocin levels in postmenopausal osteoporotic women compared to healthy controls. However, factors involved in the pathophysiology of osteoporosis, such as estrogens and leptin, are known to regulate oxytocin secretion. Herein, we evaluated the relationships between oxytocin and other hormonal factors known to regulate bone remodeling and body composition in postmenopausal osteoporotic women, compared to healthy controls. METHODS: In 20 postmenopausal women with severe osteoporosis compared to 16 healthy controls, we measured serum levels of oxytocin, high sensitive estradiol, testosterone, FSH, LH, SHBG, TSH, osteocalcin, serum type I collagen carboxy-terminal telopeptide, leptin. Bone mineral density and body composition were also measured with DXA. RESULTS: Osteoporotic women had significantly lower oxytocin, leptin and LH serum levels and higher CTX and SHBG; all other biological parameters were similar in both groups. Fat mass and lean mass were significantly decreased in osteoporotic women. Oxytocin serum levels were significantly correlated to bone mineral density but not to any other measured parameter, including leptin, estradiol and age. In a logistic regression analysis, osteoporosis remained significantly correlated to oxytocin, regardless of age. CONCLUSIONS: Low oxytocin serum levels appeared to be associated with severe osteoporosis, independently of other factors associated with osteoporosis or known to regulate oxytocin serum levels, such as estradiol or leptin, reinforcing the concept that oxytocin may be involved in the pathophysiology of postmenopausal osteoporosis.

Differentiation of Human Adipose-Derived Stem Cells into "Brite" (Brown-in-White) Adipocytes.

It is well established now that adult humans possess active brown adipose tissue (BAT) which represents a potential pharmacological target to combat obesity and associated diseases. Moreover thermogenic brown-like adipocytes ("brite adipocytes") appear also in mouse white adipose tissue (WAT) upon ß3-adrenergic stimulation. We had previously shown that human multipotent adipose-derived stem cells (hMADS) are able to differentiate into cells which exhibit the key properties of human white adipocytes, and then to convert into functional brown adipocytes upon PPARγ activation. In light of a wealth of data indicating that thermogenic adipocytes from BAT and WAT have a distinct cellular origin, we have characterized at the molecular level UCP1 positive hMADS adipocytes from both sexes as brite adipocytes. Conversion of white to brown hMADS adipocytes is dependent on PPARγ activation with rosiglitazone as the most potent agonist and is inhibited by a PPARγ antagonist. In contrast to mouse cellular models, hMADS cells conversion into brown adipocytes is weakly induced by BMP7 treatment and not modulated by activation of the Hedgehog pathway. So far no primary or clonal precursor cells of human brown adipocytes have been obtained that can be used as a tool to develop therapeutic drugs and to gain further insights into the molecular mechanisms of brown adipogenesis in humans. Thus hMADS cells represent a suitable human cell model to delineate the formation and/or the uncoupling capacity of brown/brite adipocytes that could help to dissipate caloric excess intake among individuals.

Activin a plays a critical role in proliferation and differentiation of human adipose progenitors.

OBJECTIVE: Growth of white adipose tissue takes place in normal development and in obesity. A pool of adipose progenitors is responsible for the formation of new adipocytes and for the potential of this tissue to expand in response to chronic energy overload. However, factors controlling self-renewal of human adipose progenitors are largely unknown. We investigated the expression profile and the role of activin A in this process. RESEARCH DESIGN AND METHODS: Expression of INHBA/activin A was investigated in three types of human adipose progenitors. We then analyzed at the molecular level the function of activin A during human adipogenesis. We finally investigated the status of activin A in adipose tissues of lean and obese subjects and analyzed macrophage-induced regulation of its expression. RESULTS: INHBA/activin A is expressed by adipose progenitors from various fat depots, and its expression dramatically decreases as progenitors differentiate into adipocytes. Activin A regulates the number of undifferentiated progenitors. Sustained activation or inhibition of the activin A pathway impairs or promotes, respectively, adipocyte differentiation via the C/EBPß-LAP and Smad2 pathway in an autocrine/paracrine manner. Activin A is expressed at higher levels in adipose tissue of obese patients compared with the expression levels in lean subjects. Indeed, activin A levels in adipose progenitors are dramatically increased by factors secreted by macrophages derived from obese adipose tissue. CONCLUSIONS: Altogether, our data show that activin A plays a significant role in human adipogenesis. We propose a model in which macrophages that are located in adipose tissue regulate adipose progenitor self-renewal through activin A.

A Western-like fat diet is sufficient to induce a gradual enhancement in fat mass over generations.

The prevalence of obesity has steadily increased over the last few decades. During this time, populations of industrialized countries have been exposed to diets rich in fat with a high content of linoleic acid and a low content of alpha-linolenic acid compared with recommended intake. To assess the contribution of dietary fatty acids, male and female mice fed a high-fat diet (35% energy as fat, linoleic acid:alpha-linolenic acid ratio of 28) were mated randomly and maintained after breeding on the same diet for successive generations. Offspring showed, over four generations, a gradual enhancement in fat mass due to combined hyperplasia and hypertrophy with no change in food intake. Transgenerational alterations in adipokine levels were accompanied by hyperinsulinemia. Gene expression analyses of the stromal vascular fraction of adipose tissue, over generations, revealed discrete and steady changes in certain important players, such as CSF3 and Nocturnin. Thus, under conditions of genome stability and with no change in the regimen over four generations, we show that a Western-like fat diet induces a gradual fat mass enhancement, in accordance with the increasing prevalence of obesity observed in humans.

microRNA miR-27b impairs human adipocyte differentiation and targets PPARgamma.

Obesity has emerged as a global health problem with more than 1.1 billion adults to be classified as overweight or obese, and is associated with type 2 diabetes, cardiovascular disease, and several cancers. Since obesity is characterized by an increased size and/or number of adipocytes, elucidating the molecular events governing adipogenesis is of utmost importance. Recent findings indicate that microRNAs (miRNAs) - small non-protein-coding RNAs that function as post-transcriptional gene regulators - are involved in the regulatory network of adipogenesis. Whereas only a single human miRNA is known so far to be functional in adipogenesis as pro-adipogenic, several mouse miRNAs have been identified very recently as adipogenic regulators, thereby stimulating demand for studying the functional role of miRNAs during adipogenesis in human. Here, we demonstrate that miR-27b abundance decreased during adipogenesis of human multipotent adipose-derived stem (hMADS) cells. Overexpression of miR-27b blunted induction of PPARgamma and C/EBPalpha, two key regulators of adipogenesis, during early onset of adipogenesis and repressed adipogenic marker gene expression and triglyceride accumulation at late stages. PPARgamma has a predicted and highly conserved binding site in its 3'UTR and was indeed confirmed to be a direct target of miR-27b. Thus, these results suggest that the anti-adipogenic effect of miR-27b in hMADS cells is due, at least in part, to suppression of PPARgamma.

Human multipotent adipose-derived stem cells differentiate into functional brown adipocytes.

In contrast to the earlier contention, adult humans have been shown recently to possess active brown adipose tissue with a potential of being of metabolic significance. Up to now, brown fat precursor cells have not been available for human studies. We have shown previously that human multipotent adipose-derived stem (hMADS) cells exhibit a normal karyotype and high self-renewal ability; they are known to differentiate into cells that exhibit the key properties of human white adipocytes, that is, uncoupling protein two expression, insulin-stimulated glucose uptake, lipolysis in response to beta-agonists and atrial natriuretic peptide, and release of adiponectin and leptin. Herein, we show that, upon chronic exposure to a specific PPARgamma but not to a PPARbeta/delta or a PPARalpha agonist, hMADS cell-derived white adipocytes are able to switch to a brown phenotype by expressing both uncoupling protein one (UCP1) and CIDEA mRNA. This switch is accompanied by an increase in oxygen consumption and uncoupling. The expression of UCP1 protein is associated to stimulation of respiration by beta-AR agonists, including beta3-AR agonist. Thus, hMADS cells represent an invaluable cell model to screen for drugs stimulating the formation and/or the uncoupling capacity of human brown adipocytes that could help to dissipate excess caloric intake of individuals.

Contribution of adipose triglyceride lipase and hormone-sensitive lipase to lipolysis in hMADS adipocytes.

Lipolysis is the catabolic pathway by which triglycerides are hydrolyzed into fatty acids. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) have the capacity to hydrolyze in vitro the first ester bond of triglycerides, but their respective contributions to whole cell lipolysis in human adipocytes is unclear. Here, we have investigated the roles of HSL, ATGL, and its coactivator CGI-58 in basal and forskolin-stimulated lipolysis in a human white adipocyte model, the hMADS cells. The hMADS adipocytes express the various components of fatty acid metabolism and show lipolytic capacity similar to primary cultured adipocytes. We show that lipolysis and fatty acid esterification are tightly coupled except in conditions of stimulated lipolysis. Immunocytochemistry experiments revealed that acute forskolin treatment promotes HSL translocation from the cytosol to small lipid droplets and redistribution of ATGL from the cytosol and large lipid droplets to small lipid droplets, resulting in enriched colocalization of the two lipases. HSL or ATGL overexpression resulted in increased triglyceride-specific hydrolase capacity, but only ATGL overexpression increased whole cell lipolysis. HSL silencing had no effect on basal lipolysis and only partially reduced forskolin-stimulated lipolysis. Conversely, silencing of ATGL or CGI-58 significantly reduced basal lipolysis and essentially abolished forskolin-stimulated lipolysis. Altogether, these results suggest that ATGL/CGI-58 acts independently of HSL and precedes its action in the sequential hydrolysis of triglycerides in human hMADS adipocytes.

Deficiency of angiotensin type 2 receptor rescues obesity but not hypertension induced by overexpression of angiotensinogen in adipose tissue.

Increased angiotensinogen (AGT) production by white adipose tissue has been related to not only obesity but also hypertension. Several studies have highlighted the importance of the angiotensin II type 2 receptor (AT2) in the regulation of blood pressure and fat mass, but the relevance of this transporter in a physiopathological model of increased AGT production, as it occurs in obesity, has not yet been investigated. We used transgenic mice that display either a deletion of AT2 (AT2 KO), an overexpression of AGT (OVEX), or both compound mutants (KOVEX). Results demonstrated that adipocyte hypertrophy and increased lipogenic gene expression induced by adipose AGT overproduction was rescued by deletion of AT2. In line with AGT overexpression, KOVEX and OVEX mice have similar increased plasma AGT levels. However, KOVEX mice display a higher blood pressure than OVEX mice. In kidney, renin expression was clearly reduced in OVEX mice, and its expression was normalized in KOVEX mice. Taken together, we demonstrated that the loss of AT2 expression was sufficient to rescue obesity induced by adipose tissue AGT overexpression and confirmed the necessary role of AT2 for the onset of obesity in this model. Furthermore, despite a reduction of adipose mass in KOVEX, AT2 deficiency caused increased renin production, further worsening the hypertension caused by AGT overexpression.