Within White Adipose Tissue Research Articles

Glucocorticoids and regulation of brown adipose tissue in humans – physiological and pathophysiological considerations

This review discusses the effects of glucocorticoids (GCs) on brown adipose tissue (BAT) in the context of obesity prevention and therapy. Due to the unique expression of the uncoupling protein 1 (UCP1), BAT is capable of non-shivering thermogenesis, also defined as a metabolic heat production, related to increased metabolic rate. All processes that contribute to an increase in activity and/or quantity of BAT are able to upturn metabolism, and thus enable the above therapeutic goals to be achieved. GCs may stimulate BAT differentiation and proliferation. In the case of differentiation, the opposite effect of GCs has been also described. Within white adipose tissue (WAT) GCs inhibit the formation of so called beige adipocytes that are functionally and morphologically similar to the adipocytes from BAT. The activity of GCs with concomitant inhibition of WAT browning is mediated by the induction of microRNA-27b (MIR27B) expression. GCs are responsible for the decline in BAT activity as the body ages. Depriving the body of an enzyme responsible for local reduction of cortisone into an active GC-cortisol in BAT (11ß-hydroxysteroid dehydrogenase type 1; 11ß-HSD1) prevents the reduction of BAT activity. The effects of high doses of GCs on BAT generally depend on the exposure time. Prolonged elevation in GCs level decreases BAT activity. During adrenergic stimulation the effect of GCs on BAT is ambiguous, because both decrease and increase in activity has been described. A full understanding of the GCs impact on brown remodeling in WAT may reveal a discovery of a novel preventive and therapeutic strategies for obesity and possibly other metabolic disorders.

Nanoparticles encapsulated with resveratrol induce browning of white adipocytes

Functional brown adipose tissue, including classical brown adipocytes and brown‐like or beige adipocytes, which develop within white adipose tissue (WAT) in response to various stimuli, has emerged as novel targets for obesity treatment and prevention. Through browning process, beige adipocytes are induced to express UCP‐1 and become capable of thermogenesis. Identifying nutritional strategies that increase UCP‐1 and induce browning within white adipocytes is key to unlocking browning potential. Resveratrol (Res) is a well‐known polyphenol found in the skins of grapes and other fruits such as berries with anti‐inflammatory, antioxidant, and anti‐carcinogenic properties. Nanotechnology has shown great promise in encapsulating polyphenols, such as Res, to increase their solubility and stability, consequently, bioactivities. In this study, Res encapsulated in biocompatible and biodegradable lipid nanoparticles (Nano‐Res) or liposomes (Lipo‐Res), along with free Res (Res) and their respective controls (Nano‐Void or Lipo‐Void respectively) were tested at three doses (5, 10, 20 μM) in 3T3‐L1 mouse pre‐adipocytes in a 7‐day differentiation process. At the end of differentiation, the cells were subjected to thermogenic activation by isoproterenol (ISO), a β‐adrenergic receptor agonist, or the control for 6 hours. Cytotoxicity of the treatments and mRNA expression of UCP‐1, brown (PPARγ, PGC1α, PRDM16, and Cidea), beige (CD137 and Tmem26), and white marker genes (IGFBP3), as well as mitochondria related genes (Cox4a, Uqrch, Nrf, and Tfam) were measured. We report that none of the treatments showed signs of cytotoxicity at 24‐hrs and minimal toxicity at 72‐hrs. Lipo‐Res and Nano‐Res significantly induced dose‐dependent increase of UCP‐1 mRNA expression under ISO stimulated conditions compared to the controls (p<0.05). At the low dose of 5 μM Lipo‐Res significantly stimulated UCP‐1 to a higher level than free Res (p<0.05). Under both basal (non‐ISO stimulated) and ISO stimulated conditions, both Lipo‐Res and Nano‐Res dose‐dependently decreased WAT marker IGFBP3 mRNA (p<0.05) while simultaneously increasing mRNA of beige marker CD137 and brown markers PRDM16 (p<0.05). Interestingly, Lipo‐Res significantly increased Cidea expression in ISO‐stimulated conditions (p<0.05); however, Nano‐Res (and Nano‐Void) decreased Cidea expression (p<0.05). Other beige markers and mitochondrial structural genes were increased by encapsulated Res, but did not reach significance compared to the controls. Taken together, our results demonstrate that nanoencapsulation enhances Res's bioactivities in inducing browning of white adipocytes. Our results point towards promising nutritional strategies for obesity treatment and prevention.Support or Funding InformationThe work has been supported by NIH 1R15AT008733 award.

Isolation of Immune Cells from Adipose Tissue for Flow Cytometry.

Beige and brown adipocytes are thermogenic cells essential for maintaining metabolic homeostasis within white adipose tissue (WAT) and brown adipose tissue (BAT), respectively. Emerging studies indicate that various immune cell types such as alternatively activated macrophages (AAMacs), eosinophils, and group 2 innate lymphoid cells (ILC2s) critically regulate beige and/or brown adipocyte development and activation to protect against obesity and maintain core body temperature. These findings suggest that studies of beige and brown adipose tissue may benefit from traditional immunologic approaches such as flow cytometry of immune cells residing within WAT and BAT. The purpose of this article is to describe an efficient method to isolate immune cells from numerous adipose tissue samples in parallel. The composition, phenotype, and activation state of cells isolated with this protocol may then be assessed by multiple methods including but not limited to flow cytometry. As an example, this article briefly describes a method to identify AAMacs, eosinophils, and ILC2s in adipose tissues.

MiR-125b affects mitochondrial biogenesis and impairs brite adipocyte formation and function.

ObjectiveIn rodents and humans, besides brown adipose tissue (BAT), islands of thermogenic adipocytes, termed “brite” (brown-in-white) or beige adipocytes, emerge within white adipose tissue (WAT) after cold exposure or β3-adrenoceptor stimulation, which may protect from obesity and associated diseases. microRNAs are novel modulators of adipose tissue development and function. The purpose of this work was to characterize the role of microRNAs in the control of brite adipocyte formation.Methods/ResultsUsing human multipotent adipose derived stem cells, we identified miR-125b-5p as downregulated upon brite adipocyte formation. In humans and rodents, miR-125b-5p expression was lower in BAT than in WAT. In vitro, overexpression and knockdown of miR-125b-5p decreased and increased mitochondrial biogenesis, respectively. In vivo, miR-125b-5p levels were downregulated in subcutaneous WAT and interscapular BAT upon β3-adrenergic receptor stimulation. Injections of an miR-125b-5p mimic and LNA inhibitor directly into WAT inhibited and increased β3-adrenoceptor-mediated induction of UCP1, respectively, and mitochondrial brite adipocyte marker expression and mitochondriogenesis.ConclusionCollectively, our results demonstrate that miR-125b-5p plays an important role in the repression of brite adipocyte function by modulating oxygen consumption and mitochondrial gene expression.

Cold-Induced Browning Dynamically Alters the Expression Profiles of Inflammatory Adipokines with Tissue Specificity in Mice

Cold exposure or β3-adrenoceptor agonist treatment induces the adipose tissues remodeling, relevant for beige adipogenesis within white adipose tissue (WAT). It remains unclear whether this process influences inflammatory adipokines expression in adipose tissues. We determine the temporal profile of cold or β3-adrenoceptor agonist (CL316,243)-induced changes in the expression of inflammatory adipokines in adipose tissues in mice or primary mice adipocytes. Male C57BL/6J mice at eight weeks old were exposed to 4 °C for 1–5 days. Interscapular brown adipose tissue (iBAT), inguinal subcutaneous WAT (sWAT) and epididymal WAT (eWAT) were harvested for gene and protein expression analysis. In addition, cultured primary mice brown adipocyte (BA) and white adipocyte (WA) treated with or without CL316,243 were harvested for gene expression analysis. The inflammatory adipokines expressed significantly higher in WAT than BAT at baseline. They were rapidly changed in iBAT, while down-regulated in sWAT and up-regulated in eWAT during the cold acclimation. Upon CL316,243 treatment, detected inflammatory adipokines except Leptin were transiently increased in both BA and WA. Our in vivo and in vitro data demonstrate that the browning process alters the inflammatory adipokines expression in adipose tissues, which is acutely responded to in iBAT, dynamically decreased in sWAT whilst increased in eWAT for compensation.

MiR-125b impairs brite adipocyte formation and function

Type 2 diabetes mellitus and the associated beta-cell failure is attributable up to 90% to weight gain and has increased in parallel with the epidemic of obesity. We are now aware that healthy adult humans possess active brown adipose tissue (BAT) presenting a high glucose uptake. Furthermore, in rodents and humans, islands of brown adipocytes, termed “brite” (brown-in-white), emerge within white adipose tissue (WAT) depots after cold or β3-adrenergic stimulation. Therefore, the identification of regulatory factors, which allows converting white to brite adipocytes, would be of great interest for the treatment of obesity related type 2 diabetes. microRNAs are a novel class of modulators of adipose tissue development and function. Using hMADS cells, we identified miR-125b as down-regulated upon this conversion. In human and rodent, miR-125b expression was down regulated in BAT compared to WAT. miR-125b mimic/inhibitor transfection in hMADS adipocytes impacts significantly basal and maximal mitochondrial oxygen consumption. We showed that after β3-adrenergic receptor stimulation in mice in vivo, miR-125b levels were down-regulated in subcutaneous (sc) WAT and in BAT. Finally, we found that injection of miR-125b mimic in scWAT inhibited, while of the inhibitor induced, brown adipocyte marker expression and mitochondriogenesis.

Cdkn1c Boosts the Development of Brown Adipose Tissue in a Murine Model of Silver Russell Syndrome.

The accurate diagnosis and clinical management of the growth restriction disorder Silver Russell Syndrome (SRS) has confounded researchers and clinicians for many years due to the myriad of genetic and epigenetic alterations reported in these patients and the lack of suitable animal models to test the contribution of specific gene alterations. Some genetic alterations suggest a role for increased dosage of the imprinted CYCLIN DEPENDENT KINASE INHIBITOR 1C (CDKN1C) gene, often mutated in IMAGe Syndrome and Beckwith-Wiedemann Syndrome (BWS). Cdkn1c encodes a potent negative regulator of fetal growth that also regulates placental development, consistent with a proposed role for CDKN1C in these complex childhood growth disorders. Here, we report that a mouse modelling the rare microduplications present in some SRS patients exhibited phenotypes including low birth weight with relative head sparing, neonatal hypoglycemia, absence of catch-up growth and significantly reduced adiposity as adults, all defining features of SRS. Further investigation revealed the presence of substantially more brown adipose tissue in very young mice, of both the classical or canonical type exemplified by interscapular-type brown fat depot in mice (iBAT) and a second type of non-classic BAT that develops postnatally within white adipose tissue (WAT), genetically attributable to a double dose of Cdkn1c in vivo and ex-vivo. Conversely, loss-of-function of Cdkn1c resulted in the complete developmental failure of the brown adipocyte lineage with a loss of markers of both brown adipose fate and function. We further show that Cdkn1c is required for post-transcriptional accumulation of the brown fat determinant PR domain containing 16 (PRDM16) and that CDKN1C and PRDM16 co-localise to the nucleus of rare label-retaining cell within iBAT. This study reveals a key requirement for Cdkn1c in the early development of the brown adipose lineages. Importantly, active BAT consumes high amounts of energy to generate body heat, providing a valid explanation for the persistence of thinness in our model and supporting a major role for elevated CDKN1C in SRS.

Emerging Complexities in Adipocyte Origins and Identity.

The global incidence of obesity and its comorbidities continues to rise along with a demand for novel therapeutic interventions. Brown adipose tissue (BAT) is attracting attention as a therapeutic target because of its presence in adult humans and high capacity to dissipate energy as heat, and thus burn excess calories, when stimulated. Another potential avenue for therapeutic intervention is to induce, within white adipose tissue (WAT), the formation of brown-like adipocytes called brite (brown-like-in-white) or beige adipocytes. However, understanding how to harness the potential of these thermogenic cells requires a deep understanding of their developmental origins and regulation. Recent cell-labeling and lineage-tracing experiments are beginning to shed light on this emerging area of adipocyte biology. We review here adipocyte development, giving particular attention to thermogenic adipocytes.

Cell-Autonomous Brown-Like Adipogenesis of Preadipocytes From Retinoblastoma Haploinsufficient Mice.

Mechanisms behind the emergence of brown adipocyte-like (brite or beige) adipocytes within white adipose tissue (WAT) are of interest. Retinoblastoma protein gene (Rb) haploinsufficiency associates in mice with improved metabolic regulation linked to a greater capacity for fatty acid oxidation and thermogenesis in WAT. We aimed to explain a feasible mechanism of WAT-to-BAT remodeling in this model. Differentiated primary adipocytes and Sca1-positive preadipocytes derived from adipose depots of Rb(+/-) mice and wild-type siblings were compared. Primary white Rb(+/-) adipocytes displayed under basal conditions increased glucose uptake and an enhanced expression of brown adipocyte-related genes (Pparg, Ppargc1a, Ppargc1b, Prdm16, Cpt1b) but not of purported beige/brite transcriptional markers (Cd137, Tmem26, Tbx1, Slc27a1, Hoxc9, Shox2). Lack of induction of beige markers phenocopied results in WAT of adult Rb(+/-) mice. Flow cytometry analysis evidenced an increased number of preadipocytes in WAT depots of Rb(+/-) mice. Sca1(+) preadipocytes from WAT of Rb(+/-) mice displayed increased gene expression of several transcription factors common to the brown and beige adipogenic programs (Prdm16, Pparg, Ppargc1a) and of receptors of bone morphogenetic proteins (BMPs); however, among the recently proposed beige markers, only Tbx1 was upregulated. Adult Rb(+/-) mice had increased circulating levels of BMP7. These results indicate that preadipose cells resident in WAT depots of Rb(+/-) mice retain an increased capacity for brown-like adipogenesis that appears to be different from beige adipogenesis, and suggest that the contribution of these precursors to the Rb(+/-) adipose phenotype is driven, at least in part, by interaction with BMP7 pathways. J. Cell. Physiol. 231: 1941-1952, 2016. © 2016 Wiley Periodicals, Inc.

Curcumin promotes browning of white adipose tissue in a norepinephrine-dependent way

Brown adipose tissue converts energy from food into heat via the mitochondrial uncoupling protein UCP1, defending against cold. In some conditions, inducible 'brown-like' adipocytes, also known as beige adipocytes, can develop within white adipose tissue (WAT). These beige adipocytes have characteristics similar to classical brown adipocytes and thus can burn lipids to produce heat. In the current study, we demonstrated that curcumin (50 or 100 mg/kg/day) decreased bodyweight and fat mass without affecting food intake in mice. We further demonstrated that curcumin improves cold tolerance in mice. This effect was possibly mediated by the emergence of beige adipocytes and the increase of thermogenic gene expression and mitochondrial biogenesis in inguinal WAT. In addition, curcumin promotes β3AR gene expression in inguinal WAT and elevates the levels of plasma norepinephrine, a hormone that can induce WAT browning. Taken together, our data suggest that curcumin can potentially prevent obesity by inducing browning of inguinal WAT via the norepinephrine-β3AR pathway.

Prostaglandin profiling reveals a role for haematopoietic prostaglandin D synthase in adipose tissue macrophage polarisation in mice and humans.

Background/Objectives:Obesity has been associated with both changes in adipose tissue lipid metabolism and inflammation. A key class of lipid-derived signalling molecules involved in inflammation are the prostaglandins. In this study, we aimed to determine how obesity affects the levels of prostaglandins within white adipose tissue (WAT) and determine which cells within adipose tissue produce them. To avoid the effects of cellular stress on prostaglandin levels, we developed a multivariate statistical approach in which metabolite concentrations and transcriptomic data were integrated, allowing the assignment of metabolites to cell types.Subjects/Methods:Eicosanoids were measured by liquid chromatography-tandem mass spectrometry and mRNA levels using real-time PCR. Eicosanoid levels and transcriptomic data were combined using principal component analysis and hierarchical clustering in order to associate metabolites with cell types. Samples were obtained from C57Bl/6 mice aged 16 weeks. We studied the ob/ob genetically obese mouse model and diet-induced obesity model. We extended our results in mice to a cohort of morbidly obese humans undergoing bariatric surgery.Results:Using our modelling approach, we determined that prostglandin D2 (PGD2) in adipose tissue was predominantly produced in macrophages by the haematopoietic isoform of prostaglandin D synthase (H-Pgds). Analysis of sub-fractionated WAT confirmed that H-Pgds was expressed in adipose tissue macrophages (ATMs). Furthermore, H-Pgds expression in ATMs isolated from lean and obese mice was consistent with it affecting macrophage polarisation. Functionally, we demonstrated that H-PGDS-produced PGD2 polarised macrophages toward an M2, anti-inflammatory state. In line with a potential anti-inflammatory role, we found that H-PGDS expression in ATMs was positively correlated with both peripheral insulin and adipose tissue insulin sensitivity in humans.Conclusions:In this study, we have developed a method to determine the cellular source of metabolites within an organ and used it to identify a new role for PGD2 in the control of ATM polarisation.

Activation of natriuretic peptides and the sympathetic nervous system following Roux-en-Y gastric bypass is associated with gonadal adipose tissues browning.

ObjectiveRoux-en-Y gastric bypass (RYGB) is an effective method of weight loss and remediation of type-2 diabetes; however, the mechanisms leading to these improvements are unclear. Additionally, adipocytes within white adipose tissue (WAT) depots can manifest characteristics of brown adipocytes. These ‘BRITE/beige’ adipocytes express uncoupling protein 1 (UCP1) and are associated with improvements in glucose homeostasis and protection from obesity. Interestingly, atrial and B-type natriuretic peptides (NPs) promote BRITE/beige adipocyte enrichment of WAT depots, an effect known as “browning.” Here, we investigate the effect of RYGB surgery on NP, NP receptors, and browning in the gonadal adipose tissues of female mice. We propose that such changes may lead to improvements in metabolic homeostasis commonly observed following RYGB.MethodsWild type, female, C57/Bl6 mice were fed a 60% fat diet ad libitum for six months. Mice were divided into three groups: Sham operated (SO), Roux-en-Y gastric bypass (RYGB), and Weight matched, sham operated (WM-SO). Mice were sacrificed six weeks following surgery and evaluated for differences in body weight, glucose homeostasis, adipocyte morphology, and adipose tissue gene expression.ResultsRYGB and calorie restriction induced similar weight loss and improved glucose metabolism without decreasing food intake. β3-adrenergic receptor expression increased in gonadal adipose tissue, in addition to Nppb (BNP), and NP receptors, Npr1, and Npr2. The ratio of Npr1:Npr3 and Npr2:Npr3 increased in RYGB, but not WM-SO groups. Ucp1 protein and mRNA, as well as additional markers of BRITE/beige adipose tissue and lipolytic genes increased in RYGB mice to a greater extent than calorie-restricted mice.ConclusionsUpregulation of Nppb, Npr1, Npr2, and β3-adrenergic receptors in gonadal adipose tissue following RYGB was associated with increased markers of browning. This browning of gonadal adipose tissue may underpin the positive effect of RYGB on metabolic parameters and may in part be mediated through upregulation of natriuretic peptides.

A possible crosstalk between cGMP pathway and Activin receptor-like kinase 7 (Alk7) in adipocytes

Background In last decades, obesity became a major health issue worldwide. Processes as well as molecules involved in fat mass regulation remain unresolved up to now. Brown adipose tissue (BAT) is an interesting target to fight obesity, especially since brown adipose tissue in adult humans was recently “rediscovered”. In addition, the occurrence of “brown-like” adipocytes within white adipose tissue (WAT) has also sparked an interest due to potential antiobese effect. Transforming growth factor-b (TGF-b) superfamily consists of structurally related but functionally diverse cytokines involved in regulation of adipogenesis. Activin receptor-like kinase-7 (Alk7), a member of the TGF-s family, is highly expressed in adipose tissue. However, its role in adipogenesis, thermogenesis and adipocyte function is not well known.

Role of PRDM16 in the activation of brown fat programming. Relevance to the development of obesity.

From a histological and functional point of view, two types of adipose tissue can be identified. As opposed to the mainly unilocular white adipocytes, brown adipocytes possess plenty of small multilocular lipid droplets and dissipate energy as heat. Moreover, two distinct types of brown adipose cells exist. In vivo fate mapping experiments of brown adipose tissue (BAT) precursors suggest that classical brown adipocytes and skeletal myoblasts originate from a common mesenchymal, myogenic factor 5 (Myf5)-positive precursor cell. In addition to the classical brown adipocytes, thermogenic brown-like adipocytes (brite/beige cells) may appear within white adipose tissue (WAT) depots, sharing many of the morphological and functional features of brown adipocytes, but arising from a Myf5-negative lineage. In humans, the conversion of white fat cells into brite adipocytes could be a strategy to increase energy expenditure. The zinc finger transcription factor Prdm16 controls the bidirectional fate decision between brown adipocytes and myoblasts. Prdm16 determines the brown fat-like programme and thermogenesis in both brown and white adipose tissues. Moreover, the expression of this transcriptional regulator is strongly correlated with beige cell-selective genes. From a therapeutical point of view, the potential of inducing BAT or the transdifferentiation of WAT into beige cells by enhancing Prdm16 expression, as well as the identification of mechanisms of Prdm16 function and regulation represent potentially exciting new approaches for treatment or prevention of obesity and related diseases.

Deficiency of C5L2 Increases Macrophage Infiltration and Alters Adipose Tissue Function in Mice

BackgroundObesity is considered as a systemic chronic low grade inflammation characterized by increased serum pro-inflammatory proteins and accumulation of macrophages within white adipose tissue (WAT) of obese patients. C5L2, a 7-transmembrane receptor, serves a dual function, binding the lipogenic hormone acylation stimulating protein (ASP), and C5a, involved in innate immunity.AimWe evaluated the impact of C5L2 on macrophage infiltration in WAT of wildtype (Ctl) and C5L2 knock-out (C5L2−/−) mice over 6, 12 and 24 weeks on a chow diet and moderate diet-induced obesity (DIO) conditions.ResultsIn Ctl mice, WAT C5L2 and C5a receptor mRNA increased (up to 10-fold) both over time and with DIO. By contrast, in C5L2−/−, there was no change in C5aR in WAT. C5L2−/− mice displayed higher macrophage content in WAT, varying by time, fat depot and diet, associated with altered systemic and WAT cytokine patterns compared to Ctl mice. However, in all cases, the M1 (pro-) vs M2 (anti-inflammatory) macrophage proportion was unchanged but C5L2−/− adipose tissue secretome appeared to be more chemoattractant. Moreover, C5L2−/− mice have increased food intake, increased WAT, and altered WAT lipid gene expression, which is reflected systemically. Furthermore, C5L2−/− mice have altered glucose/insulin metabolism, adiponectin and insulin signalling gene expression in WAT, which could contribute to development of insulin resistance.ConclusionDisruption of C5L2 increases macrophage presence in WAT, contributing to obesity-associated pathologies, and further supports a dual role of complement in WAT. Understanding this effect of the complement system pathway could contribute to targeting treatment of obesity and its comorbidities.

Brown-fat paucity due to impaired BMP signalling induces compensatory browning of white fat

SummaryMaintenance of body temperature is essential for survival of homeotherms. Brown adipose tissue (BAT) is a specialized fat tissue that is dedicated to thermoregulation1. Due to its remarkable capacity to dissipate stored energy and its demonstrated presence in adult humans2-5, BAT holds great promise for the treatment of obesity and metabolic syndrome1. Rodent data suggest the existence of two types of brown fat cells: the constitutive BAT (cBAT), which is of embryonic origin and anatomically located in the interscapular region of mice, and the recruitable BAT (rBAT) that resides within white adipose tissue (WAT)6 and skeletal muscle7, that has alternatively been called beige8, brite9, or inducible BAT10. Bone morphogenetic proteins (BMPs) regulate the formation and thermogenic activity of BAT10-12. We here provide evidence for a systemically active regulatory mechanism that serves to control whole body BAT-activity for thermoregulation and energy homeostasis. Genetic ablation of type 1A BMP-receptor (Bmpr1A) in brown adipogenic progenitor cells leads to a severe paucity of cBAT. This in turn increases sympathetic input to WAT, thereby promoting the formation of rBAT within white fat depots. This previously unknown compensatory mechanism, aimed at restoring total brown fat-mediated thermogenic capacity in the body, is sufficient to maintain normal temperature homeostasis and resistance to diet-induced obesity. These data suggest an important physiological cross-talk between the constitutive and recruitable brown fat cells. This sophisticated regulatory mechanism of body temperature may participate in the control of energy balance and metabolic disease.

Increased cGMP promotes healthy expansion and browning of white adipose tissue

With more than half a billion individuals affected worldwide, obesity has reached pandemic proportions. Development of "brown-like" or "brite" adipocytes within white adipose tissue (WAT) has potential antiobesity and insulin-sensitizing effects. We investigated the role of cyclic GMP (cGMP) signaling, focusing on cGMP-dependent protein kinase I (PKGI) in WAT. PKGI is expressed in murine WAT, primary adipocytes, and 3T3-L1. Treatment of adipocytes with cGMP resulted in increased adipogenesis, with a 54% increase in expression of peroxisome proliferator-activated receptor-γ. Lentiviral overexpression of PKGI further increased adipogenesis, whereas loss of PKGI significantly reduced adipogenic differentiation. In addition to adipogenic effects, PKGI had an antihypertrophic and anti-inflammatory effect via RhoA phosphorylation and reduction of proinflammatory adipokine expression. Moreover, PKGI induced a 4.3-fold increase in abundance of UCP-1 and the development of a brown-like thermogenic program in primary adipocytes. Notably, treatment of C57BL/6 mice with phosphodiesterase inhibitor sildenafil (12 mg/kg/d) for 7 d caused 4.6-fold increase in uncoupling protein-1 expression and promoted establishment of a brown fat cell-like phenotype ("browning") of WAT in vivo. Taken together, PKGI is a key regulator of cell size, adipokine secretion and browning of white fat depots and thus could be a valuable target in developing novel treatments for obesity.