Ghrelin regulates adiposity in white adipose tissue and UCP1 mRNA expression in brown adipose tissue in mice

To examine the involvement of ghrelin in obesity, we investigated the effects of treatment with peripherally administered ghrelin on food intake, adiposity, and expression of uncoupling protein (UCP) mRNA in brown (BAT) and white (WAT) adipose tissue in mice. Acute bolus administration of ghrelin at a dose of 120 nmol/kg increased cumulative food intake over 4 and 24 h as compared to controls (p<0.05 for each), whereas 12 nmol/kg/day ghrelin showed no remarkable effect (p>0.1). Chronic repeated treatment with 12 nmol/kg/day ghrelin for 7 days increased body weight and adiposity assessed by the weight of adipose tissue, triglyceride content in WAT (p<0.05 for each versus control). In addition, the same treatment decreased and increased mRNA expression of BAT UCP1 and WAT UCP2, respectively (p<0.05 for each). In conclusion, ghrelin can regulate body weight, adiposity and UCPs mRNA expression in mice. The present results provide evidence for a new regulatory loop involving ghrelin and UCP, and add novel insights into the regulatory mechanisms of obesity.     

Perilipin overexpression in white adipose tissue induces a brown fat-like phenotype

Background

Perilipin A (PeriA) exclusively locates on adipocyte lipid droplets and is essential for lipid storage and lipolysis. Previously, we reported that adipocyte specific overexpression of PeriA caused resistance to diet-induced obesity and resulted in improved insulin sensitivity. In order to better understand the biological basis for this observed phenotype, we performed additional studies in this transgenic mouse model.

Methodology and Principal Findings

When compared to control animals, whole body energy expenditure was increased in the transgenic mice. Subsequently, we performed DNA microarray analysis and real-time PCR on white adipose tissue. Consistent with the metabolic chamber data, we observed increased expression of genes associated with fatty acid β-oxidation and heat production, and a decrease in the genes associated with lipid synthesis. Gene expression of Pgc1a, a regulator of fatty acid oxidation and Ucp1, a brown adipocyte specific protein, was increased in the white adipose tissue of the transgenic mice. This observation was subsequently verified by both Western blotting and histological examination. Expression of RIP140, a regulator of white adipocyte differentiation, and the lipid droplet protein FSP27 was decreased in the transgenic mice. Importantly, FSP27 has been shown to control gene expression of these crucial metabolic regulators. Overexpression of PeriA in 3T3-L1 adipocytes also reduced FSP27 expression and diminished lipid droplet size.

Conclusions

These findings demonstrate that overexpression of PeriA in white adipocytes reduces lipid droplet size by decreasing FSP27 expression and thereby inducing a brown adipose tissue-like phenotype. Our data suggest that modulation of lipid droplet proteins in white adipocytes is a potential therapeutic strategy for the treatment of obesity and its related disorders.     

Regulation of UCP1, UCP2, and UCP3 mRNA expression in brown adipose tissue, white adipose tissue, and skeletal muscle in rats by estrogen

The effects of ovariectomy (OVX) and estrogen substitution on body weight, body composition, food intake, weight gain, and expression of uncoupling proteins (UCPs) in brown adipose tissue (BAT), white adipose tissue (WAT), and skeletal muscle were studied in four groups of rats: (1) Sham-operated rats (N = 8), (2) ovariectomized rats (OVX - E) (N = 8), (3) estrogen-treated OVX rats (OVX + E) (N = 8), and (4) OVX rats on energy restriction (OVX - E + D) (N = 8). OVX was associated with an increase in food intake and body weight gain during a 5-week study period compared to sham-operated rats. The estrogen-substituted rats had a significantly lower food intake and weight gain during the 5 weeks compared to the sham-operated group. However, we also included a nontreated OVX group that was allowed to eat only enough chow to match the weight gain of the sham-operated group. To match the weight gain in the two groups, the OVX group had to consume 16% less chow than the sham-operated group. In BAT, the UCP1 expression was significantly lower in estrogen-deficient rats compared to either intact rats or estrogen-substituted rats, whereas UCP2 and UCP3 mRNA expression was similar in BAT from all four groups. In WAT, both estrogen-deficient groups had significantly lower UCP2 mRNA expression compared to the control rats and estrogen-treated rats; In contrast, the UCP3 mRNA expression in WAT was similar in all four groups. Finally, in skeletal muscle the OVX group on mild energy restriction had reduced UCP3 mRNA expression compared to control, OVX, and estrogen-treated rats. In contrast, the UCP2 mRNA expression in skeletal muscle was similar in all four groups. Thus, the findings that estrogen deficiency is followed by reduced UCP1 expression in BAT and reduced UCP2 expression in WAT in association with weight gain probably caused by a decrease in energy expenditure might indicate that UCPs play a role for the estrogen-mediated changes in body weight and energy expenditure.     

Leptin selectively reduces white adipose tissue in mice via a UCP1-dependent mechanism in brown adipose tissue

We tested the hypothesis that leptin, in addition to reducing body fat by restraining food intake, reduces body fat through a peripheral mechanism requiring uncoupling protein 1 (UCP1). Leptin was administered to wild-type (WT) mice and mice with a targeted disruption of the UCP1 gene (UCP1 deficient), while vehicle-injected control animals of each genotype were pair-fed to each leptin-treated group. Leptin reduced the size of white adipose tissue (WAT) depots in WT mice but not in UCP1-deficient animals. This was accompanied by a threefold increase in the amount of UCP1 protein and mRNA in the brown adipose tissue (BAT) of WT mice. Leptin also increased UCP2 mRNA in WAT of both WT and UCP1-deficient mice but increased UCP2 and UCP3 mRNA only in BAT from UCP1-deficient mice. These results indicate that leptin reduces WAT through a peripheral mechanism requiring the presence of UCP1, with little or no involvement of UCP2 or UCP3.     

Feeding scallop shell powder induces the expression of uncoupling protein 1 (UCP1) in white adipose tissue of rats

Previously we found that the organic components in scallop shell promote lipolysis in differentiated 3T3-L1 and C3H10T1/2 adipocyte cells, and that incorporating scallop shell powder into the diet of rats reduced the amount of white adipose tissue. In this study, we used RT-PCR to investigate the effect of ingesting scallop shell powder on the gene expression profile of uncoupling proteins (UCPs) regulating energy metabolism in rats.Feeding of scallop shell powder increased mRNA levels of UCP1 and UCP2 in white adipose tissue. By contrast, scallop shell powder had no effect on the expression of UCP1 in brown adipose tissue, although the expression level of UCP2 mRNA decreased significantly. These results suggest that feeding scallop shell powder increases gene expression of UCP1 that may regulate energy metabolism in white adipose tissue, resulting in the observed reduction in weight of white adipose tissue.     

Central leptin regulates the UCP1 and ob genes in brown and white adipose tissue via different beta-adrenoceptor subtypes

The three known subtypes of beta-adrenoreceptors (beta(1)-AR, beta(2)-AR, and beta(3)-AR) are differentially expressed in brown and white adipose tissue and mediate peripheral responses to central modulation of sympathetic outflow by leptin. To assess the relative roles of the beta-AR subtypes in mediating leptin's effects on adipocyte gene expression, mice with a targeted disruption of the beta(3)-adrenoreceptor gene (beta(3)-AR KO) were treated with vehicle or the beta(1)/beta(2)-AR selective antagonist, propranolol (20 microgram/g body weight/day) prior to intracerebroventricular (ICV) injections of leptin (0.1 microgram/g body weight/day). Leptin produced a 3-fold increase in UCP1 mRNA in brown adipose tissue of wild type (FVB/NJ) and beta(3)-AR KO mice. The response was unaltered by propranolol in wild type mice, but was completely blocked by this antagonist in beta(3)-AR KO mice. In contrast, ICV leptin had no effect on leptin mRNA in either epididymal or retroperitoneal white adipose tissue (WAT) from beta(3)-AR KOs. Moreover, propranolol did not block the ability of exogenous leptin to reduce leptin mRNA in either WAT depot site of wild type mice. These results demonstrate that the beta(3)-AR is required for leptin-mediated regulation of ob mRNA expression in WAT, but is interchangeable with the beta(1)/beta(2)-ARs in mediating leptin's effect on UCP1 mRNA expression in brown adipose tissue.     

UCP1-independent thermogenesis in white adipose tissue of cold-acclimated Ucp1-/- mice

Apart from UCP1-based nonshivering thermogenesis in brown adipocytes, the identity of thermogenic mechanisms that can be activated to reduce a positive energy balance is largely unknown. To identify potentially useful mechanisms, we have analyzed physiological and molecular mechanisms that enable mice, genetically deficient in UCP1 and sensitive to acute exposure to the cold at 4 degrees C, to adapt to long term exposure at 4 degrees C. UCP1-deficient mice that can adapt to the cold have increased oxygen consumption and show increased oxidation of both fat and glucose as indicated from serum metabolite levels and liver glycogen content. Enhanced energy metabolism in inguinal fat was also indicated by increased oxygen consumption and fat oxidation in tissue suspensions and increased AMP kinase activity in dissected tissues. Analysis of gene expression in skeletal muscle showed surprisingly little change between cold-adapted Ucp1+/+ and Ucp1-/- mice, whereas in inguinal fat a robust induction occurred for type 2 deiodinase, sarcoendoplasmic reticulum Ca2+-ATPase, mitochondrial glycerol 3-phosphate dehydrogenase, PGC1alpha, CoxII, and mitochondrial DNA content. Western blot analysis showed an induction of total phospholamban and its phosphorylated form in inguinal fat and other white fat depots, but no induction was apparent in muscle. We conclude that alternative thermogenic mechanisms, based in part upon the enhanced capacity for ion and substrate cycling associated with brown adipocytes in white fat depots, are induced in UCP1-deficient mice by gradual cold adaptation.     

Chronic REM-sleep deprivation of rats elevates metabolic rate and increases UCP1 gene expression in brown adipose tissue

A cluster of unique pathologies progressively develops during chronic total- or rapid eye movement-sleep deprivation (REM-SD) of rats. Two prominent and readily observed symptoms are hyperphagia and decline in body weight. For body weight to be lost despite a severalfold increase in food consumption suggests that SD elevates metabolism as the subject enters a state of negative energy balance. To test the hypothesis that mediation of this hypermetabolism involves increased gene expression of uncoupling protein-1 (UCP1), which dissipates the thermodynamic energy of the mitochondrial proton-motive force as heat instead of ATP formation in brown adipose tissue (BAT), we 1) established the time course and magnitude of change in metabolism by measuring oxygen consumption, 2) estimated change in UCP1 gene expression in BAT by RT-PCR and Western blot, and 3) assayed serum leptin because of its role in regulating energy balance and food intake. REM-SD of male Sprague-Dawley rats was enforced for 20 days with the platform (flowerpot) method, wherein muscle atonia during REM sleep causes contact with surrounding water and awakens it. By day 20, rats more than doubled food consumption while losing approximately 11% of body weight; metabolism rose to 166% of baseline with substantial increases in UCP1 mRNA and immunoreactive UCP1 over controls; serum leptin decreased and remained suppressed. The decline in leptin is consistent with the hyperphagic response, and we conclude that one of the mediators of elevated metabolism during prolonged REM-SD is increased gene expression of UCP1 in BAT.     

ROS production in brown adipose tissue mitochondria: The question of UCP1-dependence

Whether active UCP1 can reduce ROS production in brown-fat mitochondria is presently not settled. The issue is of principal significance, as it can be seen as a proof- or disproof-of-principle concerning the ability of any protein to diminish ROS production through membrane depolarization. We therefore undertook a comprehensive investigation of the significance of UCP1 for ROS production, by comparing the ROS production in brown-fat mitochondria isolated from wildtype mice (that display membrane depolarization) or from UCP1(−/−) mice (with a high membrane potential). We tested the significance of UCP1 for glycerol-3-phosphate-supported ROS production by three methods (fluorescent dihydroethidium and the ESR probe PHH for superoxide, and fluorescent Amplex Red for hydrogen peroxide), and followed ROS production also with succinate, acyl-CoA or pyruvate as substrate. We studied the effects of the reverse electron flow inhibitor rotenone, the UCP1 activity inhibitor GDP, and the uncoupler FCCP. We also examined the effect of a physiologically induced increase in UCP1 amount. We noted GDP effects that were not UCP1-related. We conclude that only ROS production supported by exogenously added succinate was affected by the presence of active UCP1; ROS production supported by any other tested substrate (including endogenously generated succinate) was unaffected. This conclusion indicates that UCP1 is not involved in control of ROS production in brown-fat mitochondria. Extrapolation of these data to other tissues would imply that membrane depolarization may not necessarily decrease physiologically relevant ROS production. This article is a part of a Special Issue entitled: 18th European Bioenergetics Conference (Biochim. Biophys. Acta, Volume 1837, Issue 7, July 2014).     

Sema3A and neuropilin-1 expression and distribution in rat white adipose tissue

Semaphorins are cell surface and/or soluble signals that exert an inhibitory control on axon guidance. Sema3A, the vertebrate-secreted semaphorin, binds to neuropilin-1, which together with plexins constitutes the functional receptor. To verify whether Sema3A is produced by white adipocytes and, in that case, to detect its targets in white adipose tissue, we studied the cell production and tissue distribution of Sema3A and neuropilin-1 in rat retroperitoneal and epididymal adipose depots. Sema3A and neuropilin-1 were detected in these depots by Western blotting. The immunohistochemical results showed that Sema3A is produced in, and possibly secreted by, smooth muscle cells of arteries and white adipocytes. Accordingly, neuropilin-1 was found on perivascular and parenchymal nerves. Such a pattern of distribution is in line with a role for secreted Sema3A in the growth and plasticity of white adipose tissue nerves. Indeed, after fasting, when white adipocytes are believed to be overstimulated by noradrenaline and rearrangement of the parenchymal nerve supply may occur, adipocytic expression of Sema3A is reduced. Finally, the presence of neuropilin-1 in some white adipocytes raises the interesting possibility that Sema3A also exerts an autocrine-paracrine role on these cells.     

Tea catechins enhance the mRNA expression of uncoupling protein 1 in rat brown adipose tissue

The aim of the present study was to determine whether the antiobesity effects of tea catechins (TCs) are associated with the expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT). Male Sprague–Dawley rats were fed a high-fat (HF; 35% fat) diet for 5 weeks, then divided into four groups and fed an HF, HF with 0.5% TC (HFTC), normal-fat (NF; 5% fat) or NF with 0.5% TC (NFTC) diet for 8 weeks. At the end of the experimental period, perirenal and epididymal white adipose tissues (WATs) and interscapular BAT were isolated. The NFTC group had significantly lower perirenal WAT weights than the NF group (NF: 12.7±0.53 g; NFTC: 10.2±0.43 g; P<.01), but the HF and HFTC groups did not differ significantly. TC intake had no effects on epididymal WAT weights. The NFTC and HFTC groups had significantly lower BAT weights than the NF and HF groups, respectively. The NFTC group had significantly higher UCP1 mRNA levels in BAT than the NF group (NF: 0.35±0.02; NFTC: 0.60±0.11; P<.05), but the HF and HFTC groups did not differ significantly. Thus, TC intake in the context of the NF diet reduced perirenal WAT weight and up-regulated UCP1 mRNA expression in BAT. These results suggest that the suppressive effect of TC on body fat accumulation is associated with UCP1 expression in BAT.     

Wu-Mei-Wan prevents high-fat diet-induced obesity by reducing white adipose tissue and enhancing brown adipose tissue function

BackgroundWu-Mei-Wan, a classic traditional Chinese herb medicine, is one of the most important formulations to treat digestive diseases from ancient times to the present. Our previous study showed that WMW treatment can prevent T2DM in db/db mice, which motivating the application of WMW on metabolic disorders.PurposeObesity and its comorbid diseases have increased dramatically and are now a worldwide health problem. There is still a lack of satisfactory treatment strategies for obesity. This work was designed to assess the effect and related mechanism of WMW on high fat diet (HFD)-induced obese mice model.MethodsObese mice were induced by HFD. Thetherapeutic effect of WMW were analyzed by examining body and adipose tissue weight, metabolic profile and energy expenditure. Adipose tissue phenotype was determined by histological staining and the mitochondrial content was examined by transmission electron microscopy (TEM). Immunohistochemical and immunofluorescence staining, RT-qPCR and Western blot analysis were used to evaluate expression of key molecules in adipose tissue.ResultsWMW treatment significantly protects HFD-induced obesity. Here we showed that WMW limits weight gain, improves metabolic profile and increases energy expenditure. WMW inhibits the hypertrophy and hyperplasia of white adipocytes, the mechanism involving the inhibition of TLR3/IL-6/JAK1/STAT3 pathway. In brown adipose tissue (BAT), WMW promotes thermogenicprogramme without affecting cell proliferation. The activated BMP7/ Smad1/5/9 pathway is considered to be one of the explanations for the effect of WMW on BAT.ConclusionOur results suggested that WMW can prevent obesity and its underlying mechanisms are associated with reducing white adipose tissue and enhancing brown adipose tissue function.     

Morphochemical study of brown adipose tissue during adrenal gland regeneration in the white rat

The interscapular brown adipose tissue in male, white Wistar rats in the 1,3,6,15,30, and 60th day of regeneration of adrenals after their enucleation weas investigated. The tissue slides were stained with H and E, with Masson's triple stain and with Sudan B. The activity of the following dehydrogenses was evaluated: Succinic dehydrogenase, delta 5,3 beta-hydroxysteroid dehydrogenase and the activity of the following enzymes; monoaminooxidase (MAO), Alkaline phosphatase (AlPh) and acid phosphatase (AcPh) was studied. Between the first ad 30th day of regeneration of adrenals morphochemical changes were observed; a great number of cells with eosinophylic cytoplasm appeared and with minute vacuols in their cytoplasm, the blood vessels became more numerous and enlarged and the activity of the enzymes tested was enhanced, instead sudanophilia was weaken and the reaction of corticosteriods significantly intensified. The changes observed may indicate on an enhanced hormonal activity. The brown adipose tissue may function as an endocrine gland which supports the regenerating adrenals of the white rat, enables survival and preservation of homeostasis during the insufficiency of the adrenal cortex after adrenal enucleation. The initiation of the endocrine activity of the brown adipose tissue in the course of regeneration of the adrenals proceeds probably without the direct participation of catecholamines originating from the adrenals.     

High-energy diets produce different effects on fatty acid synthesis in brown adipose tissue, white adipose tissue and liver in the rat

The influence of feeding rats a high-energy diet for 7 days on fatty acid synthesis in brown adipose tissue, white adipose tissue and liver of the rat was investigated. The incorporation of 3H2O and [U-14C]glucose into fatty acid was measured in vivo. The rats fed the high-energy diets had higher rates of fatty acid synthesis in white adipose tissue than the controls fed on chow, while fatty acid synthesis in brown adipose tissue and liver was either decreased or unchanged relative to that of controls fed on chow. After an oral load of [U-14C]glucose the incorporation of radioactivity into tissue fatty acid was several-fold higher in brown adipose tissue than in white adipose tissue in rats fed on chow. In rats fed the high-energy diets, incorporation of radioactivity into fatty acid in brown adipose tissue was decreased while that into white adipose tissue was either increased (Wistar rats) or unchanged (Lister rats).