ABSTRACT
Recent studies have shown that adipose tissue is an immunological organ. While inflammation in energy-storing white adipose tissues has been the focus of intense research, the regulatory mechanisms of inflammation in heat-producing brown adipose tissues remain largely unknown. We previously identified apoptosis signal-regulating kinase 1 (ASK1) as a critical regulator of brown adipocyte maturation; the PKA-ASK1-p38 axis facilitates uncoupling protein 1 (UCP1) induction cell-autonomously. Here, we show that ASK1 suppresses an innate immune pathway and contributes to maintenance of brown adipocytes. We report a novel chemical pull-down method for endogenous kinases using analog sensitive kinase allele (ASKA) technology and identify an ASK1 interactor in brown adipocytes, receptor-interacting serine/threonine-protein kinase 2 (RIPK2). ASK1 disrupts the RIPK2 signaling complex and inhibits the NOD-RIPK2 pathway to downregulate the production of inflammatory cytokines. As a potential biological significance, an in vitro model for intercellular regulation suggests that ASK1 facilitates the expression of UCP1 through the suppression of inflammatory cytokine production. In parallel to our previous report on the PKA-ASK1-p38 axis, our work raises the possibility of an auxiliary role of ASK1 in brown adipocyte maintenance through neutralizing the thermogenesis-suppressive effect of the NOD-RIPK2 pathway.
Subject(s)
Adipocytes, Brown/metabolism , MAP Kinase Kinase Kinase 5/pharmacology , Nod Signaling Adaptor Proteins/drug effects , Receptor-Interacting Protein Serine-Threonine Kinase 2/drug effects , Adipocytes, Brown/drug effects , Adipocytes, White/metabolism , Animals , Cytokines/analysis , HEK293 Cells , Humans , Inflammation/drug therapy , Mice , Receptor-Interacting Protein Serine-Threonine Kinase 2/metabolism , Signal Transduction/drug effects , Uncoupling Protein 1/drug effectsABSTRACT
Sesamol found in sesame oil has been shown to ameliorate obesity by regulating lipid metabolism. However, its effects on energy expenditure and the underlying molecular mechanism have not been clearly elucidated. In this study, we show that sesamol increased the uncoupling protein 1 (Ucp1) expression in adipocytes. The administration of sesamol in high-fat diet (HFD)-fed mice prevented weight gain and improved metabolic derangements. The three-week sesamol treatment of HFD-fed mice, when the body weights were not different between the sesamol and control groups, increased energy expenditure, suggesting that an induced energy expenditure is a primary contributing factor for sesamol's anti-obese effects. Consistently, sesamol induced the expression of energy-dissipating thermogenic genes, including Ucp1, in white adipose tissues. The microarray analysis showed that sesamol dramatically increased the Nrf2 target genes such as Hmox1 and Atf3 in adipocytes. Moreover, 76% (60/79 genes) of the sesamol-induced genes were also regulated by tert-butylhydroquinone (tBHQ), a known Nrf2 activator. We further verified that sesamol directly activated the Nrf2-mediated transcription. In addition, the Hmox1 and Ucp1 induction by sesamol was compromised in Nrf2-deleted cells, indicating the necessity of Nrf2 in the sesamol-mediated Ucp1 induction. Together, these findings demonstrate the effects of sesamol in inducing Ucp1 and in increasing energy expenditure, further highlighting the use of the Nrf2 activation in stimulating thermogenic adipocytes and in increasing energy expenditure in obesity and its related metabolic diseases.
Subject(s)
Adipose Tissue, White/metabolism , Benzodioxoles/pharmacology , Energy Metabolism/drug effects , Obesity/metabolism , Phenols/pharmacology , Uncoupling Protein 1/drug effects , Adipocytes/drug effects , Animals , Cell Culture Techniques , Diet, High-Fat/adverse effects , Disease Models, Animal , Mice , Mice, Obese , Weight Gain/drug effectsABSTRACT
BACKGROUND: The role of exendin-4 in brown adipose tissue (BAT) activation was not very clear. This study is to verify the role of BAT involved in renal benefits of exendin-4 in diabetes mellitus (DM). METHODS: In vivo, C57BL/6 mice were randomly divided into nondiabetic (control) and diabetic groups (DM). The diabetic mice were randomized into a control group (DM-Con), BAT-excision group (DM+Exc), exendin-4-treated group (DM+E4), and BAT-excision plus exendin-4-treated group (DM+Exc+E4). The weight, blood glucose and lipids, 24 h urine albumin and 8-OH-dG, and renal fibrosis were analyzed. In vitro, we investigated the role of exendin-4 in the differentiation process of 3T3-L1 and brown preadipocytes and its effect on the rat mesangial cells induced by oleate. RESULTS: The expressions of UCP-1, PGC-1α, ATGL, and CD36 in BAT of DM mice were all downregulated, which could be upregulated by exendin-4 treatment with significant effects on ATGL and CD36. BAT-excision exacerbated high blood glucose (BG) with no significant effect on the serum lipid level. Exendin-4 significantly lowered the level of serum triglycerides (TG) and low-density lipoprotein- (LDL-) c, 24 h urine albumin, and 8-OH-dG; improved renal fibrosis and lipid accumulation; and activated renal AMP-activated protein kinase (AMPK) in diabetic mice regardless of BAT excision. In vitro, there was no significant effect of exendin-4 on brown or white adipogenesis. However, exendin-4 could improve lipid accumulation and myofibroblast-like phenotype transition of mesangial cells induced by oleate via activating the AMPK pathway. CONCLUSIONS: Exendin-4 could decrease the renal lipid deposit and improve diabetic nephropathy via activating the renal AMPK pathway independent of BAT activation.
Subject(s)
Adipose Tissue, Brown/drug effects , Blood Glucose/drug effects , Diabetes Mellitus, Type 2/metabolism , Diabetic Nephropathies/metabolism , Exenatide/pharmacology , Incretins/pharmacology , Kidney/drug effects , 3T3-L1 Cells , 8-Hydroxy-2'-Deoxyguanosine/urine , Adenylate Kinase/metabolism , Adipocytes, Brown/drug effects , Adipocytes, Brown/metabolism , Adipogenesis/drug effects , Adipose Tissue, Brown/metabolism , Adipose Tissue, Brown/surgery , Albuminuria , Animals , Blood Glucose/metabolism , Blotting, Western , Body Weight/drug effects , CD36 Antigens/drug effects , CD36 Antigens/genetics , Cholesterol, HDL/drug effects , Cholesterol, HDL/metabolism , Cholesterol, LDL/drug effects , Cholesterol, LDL/metabolism , Diabetes Mellitus, Type 2/complications , Diabetic Nephropathies/etiology , Diabetic Nephropathies/pathology , Disease Models, Animal , Fibrosis , Gene Expression/drug effects , Kidney/pathology , Lipase/drug effects , Lipase/genetics , Mesangial Cells/drug effects , Mesangial Cells/metabolism , Mesangial Cells/pathology , Mice , Mice, Inbred C57BL , Myofibroblasts/metabolism , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/drug effects , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics , Random Allocation , Rats , Real-Time Polymerase Chain Reaction , Triglycerides/metabolism , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/geneticsABSTRACT
The angiotensin II (ANG II)-ANG II type 1 receptor (AT1R) axis is a key player in the pathophysiology of obesity. Angiotensin-converting enzyme 2 (ACE2) counteracts the ANG II/AT1R axis via converting ANG II to angiotensin 1-7 (Ang 1-7), which is known to have an anti-obesity effect. In this study, we hypothesized that ACE2 exerts a strong anti-obesity effect by increasing Ang 1-7 levels. We injected intraperitoneally recombinant human ACE2 (rhACE2, 2.0 mg·kg-1·day-1) for 28 days to high-fat diet (HFD)-induced obesity mice. rhACE2 treatment decreased body weight and improved glucose metabolism. Furthermore, rhACE2 increased oxygen consumption and upregulated thermogenesis in HFD-fed mice. In the rhACE2 treatment group, brown adipose tissue (BAT) mass increased, accompanied with ameliorated insulin signaling and increased protein levels of uncoupling protein-1 (UCP-1) and PRD1-BF1-RIZ1 homologous domain containing 16. Importantly, subcutaneous white adipose tissue (sWAT) mass decreased, concomitant with browning, which was established by the increase of UCP-1 expression. The browning is the result of increased H3K27 acetylation via the downregulation of histone deacetylase 3 and increased H3K9 acetylation via upregulation of GCN5 and P300/CBP-associated factor. These results suggest that rhACE2 exerts anti-obesity effects by stimulating BAT and inducing browning in sWAT. ACE2 and the Ang 1-7 axis represent a potential therapeutic approach to prevent the development of obesity.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Angiotensin I/drug effects , Body Weight/drug effects , Obesity/metabolism , Peptide Fragments/drug effects , Peptidyl-Dipeptidase A/pharmacology , Thermogenesis/drug effects , Acetylation/drug effects , Adipose Tissue, Brown/metabolism , Adipose Tissue, White/metabolism , Angiotensin I/metabolism , Angiotensin-Converting Enzyme 2 , Animals , Diet, High-Fat , Down-Regulation , Histone Code/drug effects , Histone Deacetylases/drug effects , Histone Deacetylases/metabolism , Humans , Insulin/metabolism , Male , Mice , Mice, Inbred C57BL , Peptide Fragments/metabolism , Recombinant Proteins , Subcutaneous Fat/drug effects , Subcutaneous Fat/metabolism , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolism , p300-CBP Transcription Factors/drug effects , p300-CBP Transcription Factors/metabolismABSTRACT
We recently reported that membrane potential (ΔΨ) primarily determines the relationship of complex II-supported respiration by isolated skeletal muscle mitochondria to ADP concentrations. We observed that O2 flux peaked at low ADP concentration ([ADP]) (high ΔΨ) before declining at higher [ADP] (low ΔΨ). The decline resulted from oxaloacetate (OAA) accumulation and inhibition of succinate dehydrogenase. This prompted us to question the effect of incremental [ADP] on respiration in interscapular brown adipose tissue (IBAT) mitochondria, wherein ΔΨ is intrinsically low because of uncoupling protein 1 (UCP1). We found that succinate-energized IBAT mitochondria, even in the absence of ADP, accumulate OAA and manifest limited respiration, similar to muscle mitochondria at high [ADP]. This could be prevented by guanosine 5'-diphosphate inhibition of UCP1. NAD+ cycling with NADH requires complex I electron flow and is needed to form OAA. Therefore, to assess the role of electron transit, we perturbed flow using a small molecule, N1-(3-acetamidophenyl)-N2-(2-(4-methyl-2-(p-tolyl)thiazol-5-yl)ethyl)oxalamide. We observed decreased OAA, increased NADH/NAD+, and increased succinate-supported mitochondrial respiration under conditions of low ΔΨ (IBAT) but not high ΔΨ (heart). In summary, complex II-energized respiration in IBAT mitochondria is tempered by complex I-derived OAA in a manner dependent on UCP1. These dynamics depend on electron transit in complex I.-Fink, B. D., Yu, L., Sivitz, W. I. Modulation of complex II-energized respiration in muscle, heart, and brown adipose mitochondria by oxaloacetate and complex I electron flow.
Subject(s)
Mitochondria, Muscle/drug effects , Mitochondria/metabolism , Respiration/drug effects , Succinate Dehydrogenase/pharmacology , Adenosine Diphosphate/metabolism , Adipose Tissue, Brown/drug effects , Adipose Tissue, Brown/metabolism , Adiposity/drug effects , Adiposity/physiology , Animals , Electron Transport Complex I/metabolism , Male , Mice, Inbred C57BL , Mitochondria/drug effects , Mitochondria, Muscle/metabolism , Myocardium/metabolism , Obesity/metabolism , Oxygen Consumption/drug effects , Succinate Dehydrogenase/metabolism , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
CB1 receptor (CB1R) antagonism improves the deleterious effects of a high-fat diet (HFD) by reducing body fat mass and adipocyte cell size. Previous studies demonstrated that the beneficial effects of the CB1R antagonist rimonabant (RIM) in white adipose tissue (WAT) are partially due to an increase of mitochondria numbers and upregulation thermogenesis markers, suggesting an induction of WAT beiging. However, the molecular mechanism by which CB1R antagonism induces weight loss and WAT beiging is unclear. In this study, we probed for genes associated with beiging and explored longitudinal molecular mechanisms by which the beiging process occurs. HFD dogs received either RIM (HFD+RIM) or placebo (PL) (HFD+PL) for 16 wk. Several genes involved in beiging were increased in HFD+RIM compared with pre-fat, HFD, and HFD+PL. We evaluated lipolysis and its regulators including natriuretic peptide (NP) and its receptors (NPRs), ß-1 and ß-3 adrenergic receptor (ß1R, ß3R) genes. These genes were increased in WAT depots, accompanied by an increase in lipolysis in HFD+RIM. In addition, RIM decreased markers of inflammation and increased adiponectin receptors in WAT. We observed a small but significant increase in UCP1; therefore, we evaluated the newly discovered UCP1-independent thermogenesis pathway. We confirmed that SERCA2b and RYR2, the two key genes involved in this pathway, were upregulated in the WAT. Our data suggest that the upregulation of NPRs, ß-1R and ß-3R, lipolysis, and SERCA2b and RYR2 may be one of the mechanisms by which RIM promotes beiging and overall the improvement of metabolic homeostasis induced by RIM.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Adipose Tissue/drug effects , Diet, High-Fat/adverse effects , Receptor, Cannabinoid, CB1/antagonists & inhibitors , Receptors, Atrial Natriuretic Factor/drug effects , Uncoupling Protein 1/drug effects , Animals , Dogs , Gene Expression/drug effects , Inflammation/pathology , Inflammation/prevention & control , Insulin Resistance , Male , Organelle Biogenesis , Receptors, Adrenergic, beta/drug effects , Receptors, Adrenergic, beta/metabolism , Rimonabant/pharmacology , Thermogenesis/drug effects , Thermogenesis/genetics , Weight Loss/drug effectsABSTRACT
OBJECTIVE: To investigate the effects of genipin on promoting brown adipose tissue activation and white adipose tissue browning. METHODS: The male C57BL/6J mice were divided into three groups: normal control group, genipin group and cold-stimulus group.Genipin group were treated consecutively with genipin at a dose of 15 mg/kg once a day for 9 days, normal control group were treated with the saline.The mice with cold-stimulus were exposed to 4â environment for 5 days.Daily food amount and body weight were measured.Morphological changes were observed in the subscapular region, inguinal region and epididymis around the adipose tissue.The expression of uncoupling protein 1 (UCP1) was determined by real-time PCR and Western blot respectively. RESULTS: The wet weight of white fat in genipin-treated mice was decreased by 16% , and 28% in that of cold-stimulus mice, compared with the normal control group (Pï¼0.05).After treatments of genipin and cold-stimulus, the color of white adipose tissues was darker, and the size of lipid droplets in adipocytes was smaller, whereas the number was increased.Compared with the normal control group, UCP1 expression was increased obviously in fat tissues, including the subcutaneous and visceral white adipose tissues, and brown adipose tissue after treated with genipin and cold-stimulus (Pï¼0.05). CONCLUSION: Genipin promoted activation of brown adipose tissue and browning of white adipose tissue by upregulating UCP1 expression, which could contribute to the loss of body weight against obesity.
Subject(s)
Adipose Tissue, Brown , Adipose Tissue, White , Cholagogues and Choleretics , Iridoids , Uncoupling Protein 1 , Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Animals , Cholagogues and Choleretics/pharmacology , Iridoids/pharmacology , Male , Mice , Mice, Inbred C57BL , Obesity/drug therapy , Uncoupling Protein 1/drug effects , Up-RegulationABSTRACT
BACKGROUND The uncoupling protein 1 (UCP1) gene has a role in mitochondrial energy expenditure in brown adipose tissue. This study aimed to investigate the effects of berberine, a benzylisoquinoline alkaloid used in traditional Chinese medicine, on energy expenditure, expression of the UCP1 gene, the cell stress protein inositol-requiring enzyme 1α (IRE1α), apoptosis genes, and macrophage phenotype (M1 and M2) in white and brown adipose tissue in an obese mouse model fed a high-fat diet. MATERIAL AND METHODS Four-week-old C57BL/6J male mice (n=20) were divided into a high-fat diet group, a normal diet group, a group treated with berberine at 100 mg/kg/d in 0.9% normal saline, and a non-treated group. Whole-body fat mass, blood glucose, insulin resistance, and oxygen expenditure during physical activity were measured. After 16 weeks, the mice were euthanized for examination of liver and adipose tissue. The expression of pro-inflammatory cytokines, apoptosis genes, thermogenic genes (including UCP1), and IRE1α, were investigated using immunohistochemistry, Western blot, and quantitative reverse transcription polymerase chain reaction (qRT-PCR), in white and brown adipose tissue. Magnetic cell sorting harvested M1 and M2 macrophages in adipose tissue. Clodronate liposomes were used to inhibit macrophage recruitment. RESULTS Berberine treatment in mice fed a high-fat diet increased energy metabolism, glucose tolerance, and expression of UCP1, and reduced expression of pro-inflammatory cytokines, macrophage recruitment, and resulted in M2 macrophage polarization in white adipose tissue. Polarized M2 macrophages showed reduced expression of apoptotic genes and IRE1α. CONCLUSIONS Berberine improved metabolic function in a mouse model fed a high-fat diet.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Berberine/pharmacology , Adipose Tissue/drug effects , Animals , China , Diet, High-Fat , Endoribonucleases/drug effects , Energy Metabolism/drug effects , Inflammation/metabolism , Macrophage Activation/drug effects , Macrophages/drug effects , Macrophages/metabolism , Male , Medicine, Chinese Traditional , Mice , Mice, Inbred C57BL , Obesity/metabolism , Protein Serine-Threonine Kinases/drug effects , Uncoupling Protein 1/drug effectsABSTRACT
Capsaicin, the major active constituent of chilli, is an agonist on transient receptor potential vanilloid channel 1 (TRPV1). TRPV1 is present on many metabolically active tissues, making it a potentially relevant target for metabolic interventions. Insulin resistance and obesity, being the major components of metabolic syndrome, increase the risk for the development of cardiovascular disease, type 2 diabetes, and non-alcoholic fatty liver disease. In vitro and pre-clinical studies have established the effectiveness of low-dose dietary capsaicin in attenuating metabolic disorders. These responses of capsaicin are mediated through activation of TRPV1, which can then modulate processes such as browning of adipocytes, and activation of metabolic modulators including AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor α (PPARα), uncoupling protein 1 (UCP1), and glucagon-like peptide 1 (GLP-1). Modulation of these pathways by capsaicin can increase fat oxidation, improve insulin sensitivity, decrease body fat, and improve heart and liver function. Identifying suitable ways of administering capsaicin at an effective dose would warrant its clinical use through the activation of TRPV1. This review highlights the mechanistic options to improve metabolic syndrome with capsaicin.
Subject(s)
Capsaicin , Metabolic Syndrome , AMP-Activated Protein Kinases/drug effects , AMP-Activated Protein Kinases/metabolism , Adipocytes/drug effects , Adipose Tissue/drug effects , Animals , Capsaicin/administration & dosage , Capsaicin/chemistry , Capsaicin/pharmacology , Diabetes Mellitus, Type 2 , Diet , Glucagon-Like Peptide 1/drug effects , Glucagon-Like Peptide 1/metabolism , Humans , Insulin Resistance , Metabolic Syndrome/prevention & control , Non-alcoholic Fatty Liver Disease , Obesity , Oxidation-Reduction , PPAR alpha/drug effects , PPAR alpha/metabolism , TRPV Cation Channels/agonists , TRPV Cation Channels/drug effects , TRPV Cation Channels/physiology , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
OBJECTIVE: The mitochondrial uncoupling agent 2,4-dinitrophenol (DNP), historically used as a treatment for obesity, is known to cross the blood-brain-barrier, but its effects on central neural circuits controlling body weight are largely unknown. As hypothalamic melanocortin neuropeptide Y/agouti-related protein (NPY/AgRP) and pro-opiomelanocortin (POMC) neurons represent key central regulators of food intake and energy expenditure we investigated the effects of DNP on these neurons, food intake and energy expenditure. METHOD: C57BL/6 and melanocortin-4 receptor (MC4R) knock-out mice were administered DNP intracerebroventricularly (ICV) and the metabolic changes were characterized. The specific role of NPY and POMC neurons and the ionic mechanisms mediating the effects of uncoupling were examined with in vitro electrophysiology performed on NPY hrGFP or POMC eGFP mice. RESULTS: Here we show DNP-induced differential effects on melanocortin neurons including inhibiting orexigenic NPY and activating anorexigenic POMC neurons through independent ionic mechanisms coupled to mitochondrial function, consistent with an anorexigenic central effect. Central administration of DNP induced weight-loss, increased BAT thermogenesis and browning of white adipose tissue, and decreased food intake, effects that were absent in MC4R knock-out mice and blocked by the MC4R antagonist, AgRP. CONCLUSION: These data show a novel central anti-obesity mechanism of action of DNP and highlight the potential for selective melanocortin mitochondrial uncoupling to target metabolic disorders.
Subject(s)
2,4-Dinitrophenol/pharmacology , Neuropeptide Y/metabolism , Pro-Opiomelanocortin/metabolism , Adipose Tissue, Brown/metabolism , Animals , Body Weight/drug effects , Eating/drug effects , Energy Metabolism/drug effects , Male , Melanocortins/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Mitochondria/metabolism , Mitochondria/physiology , Neurons/drug effects , Obesity/metabolism , Receptor, Melanocortin, Type 4/metabolism , Receptors, Melanocortin/physiology , Thermogenesis/physiology , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/physiology , Weight LossABSTRACT
Human subcutaneous (SC) white adipose tissue (WAT) increases the expression of beige adipocyte genes in the winter. Studies in rodents suggest that a number of immune mediators are important in the beiging response. We studied the seasonal beiging response in SC WAT from lean humans. We measured the gene expression of various immune cell markers and performed multivariate analysis of the gene expression data to identify genes that predict UCP1. Interleukin (IL)-4 and, unexpectedly, the mast cell marker CPA3 predicted UCP1 gene expression. Therefore, we investigated the effects of mast cells on UCP1 induction by adipocytes. TIB64 mast cells responded to cold by releasing histamine and IL-4, and this medium stimulated UCP1 expression and lipolysis by 3T3-L1 adipocytes. Pharmacological block of mast cell degranulation potently inhibited histamine release by mast cells and inhibited adipocyte UCP1 mRNA induction by conditioned medium (CM). Consistently, the histamine receptor antagonist chlorpheniramine potently inhibited adipocyte UCP1 mRNA induction by mast cell CM. Together, these data show that mast cells sense colder temperatures, release factors that promote UCP1 expression, and are an important immune cell type in the beiging response of WAT.
Subject(s)
Adipocytes/metabolism , Adipose Tissue, Beige/metabolism , Adipose Tissue, White/metabolism , Mast Cells/metabolism , RNA, Messenger/metabolism , Seasons , Uncoupling Protein 1/genetics , 3T3-L1 Cells , Adipocytes/drug effects , Adult , Animals , Carboxypeptidases A/genetics , Cell Degranulation , Chlorpheniramine/pharmacology , Cold Temperature , Female , Gene Expression Regulation , Histamine/metabolism , Histamine H1 Antagonists/pharmacology , Humans , Interleukin-4/genetics , Interleukin-4/metabolism , Lipolysis , Male , Membrane Proteins/genetics , Mice , Multivariate Analysis , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics , RNA, Messenger/drug effects , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Subcutaneous Fat/metabolism , Thigh , Uncoupling Protein 1/drug effectsABSTRACT
OBJECTIVE: Browning of white adipose tissue (WAT) promotes increased energy expenditure through the action of uncoupling protein 1 (UCP1) and is an attractive target to promote weight loss in obesity. Lowering of mitochondrial membrane potential by UCP1 is uniquely beneficial in this context; in other tissues, reduced membrane potential promotes mitochondrial clearance via mitophagy. It is unknown how parkin-mediated mitophagy is regulated in beige adipocytes. METHODS: The relationship between parkin expression and WAT browning was investigated in 3T3-L1 adipocytes and parkin-deficient male C57BL/6 mice in response to pharmacological browning stimuli. RESULTS: Rosiglitazone treatment in 3T3-L1 adipocytes promoted mitochondrial biogenesis, UCP1 expression, and mitochondrial uncoupling. Parkin expression was decreased and reduced mitochondrial-associated parkin, and p62 indicated a reduction in mitophagy activity. Parkin overexpression prevented mitochondrial remodeling in response to rosiglitazone. In CL 316,243-treated wild-type mice, decreased parkin expression was observed in subcutaneous inguinal WAT, where UCP1 was strongly induced. CL 316,243 treatment weakly induced UCP1 expression in the gonadal depot, where parkin expression was unchanged. In contrast, parkin-deficient mice exhibited robust UCP1 expression in gonadal WAT following CL 316,243 treatment. CONCLUSIONS: WAT browning was associated with a decrease in parkin-mediated mitophagy, and parkin expression antagonized browning of WAT.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/physiopathology , Mitophagy/physiology , Ubiquitin-Protein Ligases/physiology , 3T3-L1 Cells , Adipocytes/physiology , Animals , Dioxoles/pharmacology , Down-Regulation , Energy Metabolism , Hypoglycemic Agents/pharmacology , Ion Channels/genetics , Male , Mice , Mice, Inbred C57BL , Mitochondria/drug effects , Obesity/metabolism , Rosiglitazone , Thiazolidinediones/pharmacology , Uncoupling Protein 1/drug effectsABSTRACT
Low-grade sustained inflammation links obesity to insulin resistance and nonalcoholic fatty liver disease (NAFLD). However, therapeutic approaches to improve systemic energy balance and chronic inflammation in obesity are limited. Pharmacological activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) alleviates obesity and insulin resistance in mice; however, Nrf2 inducers are not clinically available owing to safety concerns. Thus, we examined whether dietary glucoraphanin, a stable precursor of the Nrf2 inducer sulforaphane, ameliorates systemic energy balance, chronic inflammation, insulin resistance, and NAFLD in high-fat diet (HFD)-fed mice. Glucoraphanin supplementation attenuated weight gain, decreased hepatic steatosis, and improved glucose tolerance and insulin sensitivity in HFD-fed wild-type mice but not in HFD-fed Nrf2 knockout mice. Compared with vehicle-treated controls, glucoraphanin-treated HFD-fed mice had lower plasma lipopolysaccharide levels and decreased relative abundance of the gram-negative bacteria family Desulfovibrionaceae in their gut microbiomes. In HFD-fed mice, glucoraphanin increased energy expenditure and the protein expression of uncoupling protein 1 (Ucp1) in inguinal and epididymal adipose depots. Additionally, in this group, glucoraphanin attenuated hepatic lipogenic gene expression, lipid peroxidation, classically activated M1-like macrophage accumulation, and inflammatory signaling pathways. By promoting fat browning, limiting metabolic endotoxemia-related chronic inflammation, and modulating redox stress, glucoraphanin may mitigate obesity, insulin resistance, and NAFLD.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Endotoxemia , Glucosinolates/pharmacology , Imidoesters/pharmacology , Insulin Resistance , Liver/drug effects , Non-alcoholic Fatty Liver Disease/metabolism , Obesity/metabolism , Adipose Tissue, Brown/metabolism , Adipose Tissue, White/metabolism , Animals , Desulfovibrio , Diet, High-Fat , Energy Metabolism/drug effects , Gastrointestinal Microbiome/drug effects , Inflammation , Lipid Peroxidation/drug effects , Lipopolysaccharides/blood , Liver/metabolism , Macrophages/drug effects , Mice , Mice, Knockout , NF-E2-Related Factor 2/genetics , Oximes , Sulfoxides , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
Previous studies have shown that very low-dose infusions of leptin into the third or the fourth ventricle alone have little effect on energy balance, but simultaneous low-dose infusions cause rapid weight loss and increased phosphorylation of STAT3 (p-STAT3) in hypothalamic sites that express leptin receptors. Other studies show that injecting high doses of leptin into the fourth ventricle inhibits food intake and weight gain. Therefore, we tested whether fourth-ventricle leptin infusions that cause weight loss are associated with increased leptin signaling in the hypothalamus. In a dose response study 14-day infusions of increasing doses of leptin showed significant hypophagia, weight loss, and increased hypothalamic p-STAT3 in rats receiving at least 0.9 µg leptin/day. In a second study 0.6 µg leptin/day transiently inhibited food intake and reduced carcass fat, but had no significant effect on energy expenditure. In a final study, we identified the localization of STAT3 activation in the hypothalamus of rats receiving 0, 0.3, or 1.2 µg leptin/day. The high dose of leptin, which caused weight loss in the first experiment, increased p-STAT3 in the ventromedial, dorsomedial, and arcuate nuclei of the hypothalamus. The low dose that increased brown fat UCP1 but did not affect body composition in the first experiment had little effect on hypothalamic p-STAT3. We propose that hindbrain leptin increases the precision of control of energy balance by lowering the threshold for leptin signaling in the forebrain. Further studies are needed to directly test this hypothesis.
Subject(s)
Energy Metabolism/drug effects , Hypothalamus/drug effects , Leptin/pharmacology , STAT3 Transcription Factor/drug effects , Adipose Tissue, Brown/drug effects , Adipose Tissue, Brown/metabolism , Animals , Blotting, Western , Dose-Response Relationship, Drug , Fourth Ventricle , Hypothalamus/metabolism , Infusions, Intraventricular , Liver/drug effects , Liver/metabolism , Male , Mitogen-Activated Protein Kinase 1/drug effects , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/drug effects , Mitogen-Activated Protein Kinase 3/metabolism , Phosphatidylinositol 3-Kinase/drug effects , Phosphatidylinositol 3-Kinase/metabolism , Phosphatidylinositol 3-Kinases , Phosphoproteins/drug effects , Phosphoproteins/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 1/drug effects , Protein Tyrosine Phosphatase, Non-Receptor Type 1/metabolism , Rats , Rats, Sprague-Dawley , Rhombencephalon/drug effects , Rhombencephalon/metabolism , STAT3 Transcription Factor/metabolism , Suppressor of Cytokine Signaling 3 Protein/drug effects , Suppressor of Cytokine Signaling 3 Protein/metabolism , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
Activation of brown adipose tissue (BAT) and browning of white adipose tissue (WAT) present potential new therapies for obesity and type 2 diabetes. Here, we examined the effects of ß3-adrenergic stimulation on tissue-specific uptake and storage of free fatty acids (FFA) and its implications for whole body FFA metabolism in diet-induced obese rats using a multi-radiotracer technique. Male Wistar rats were high fat-fed for 12 wk and administered ß3-agonist CL316,243 (CL, 1 mg·kg-1·day-1) or saline via osmotic minipumps during the last 3 wk. The rats were then fasted and acutely infused with a tracer mixture ([14C]palmitate and the partially metabolized R-[3H]bromopalmitate) under anesthesia. CL infusion decreased body weight gain and fasting plasma glucose levels. While core body temperature was unaffected, infrared thermography showed an increase in tail heat dissipation following CL infusion. Interestingly, CL markedly increased both FFA storage and utilization in interscapular and perirenal BAT, whereas the flux of FFA to skeletal muscle was decreased. In this rat model of obesity, only sporadic populations of beige adipocytes were detected in the epididymal WAT depot of CL-infused rats, and there was no change in FFA uptake or utilization in WAT following CL infusion. In summary, ß3-agonism robustly increased FFA flux to BAT coupled with enhanced utilization. Increased BAT activation most likely drove the increased tail heat dissipation to maintain thermostasis. Our results emphasize the quantitative role of brown fat as the functional target of ß3-agonism in obesity.
Subject(s)
Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Adrenergic beta-3 Receptor Agonists/pharmacology , Diet, High-Fat , Dioxoles/pharmacology , Fatty Acids, Nonesterified/metabolism , Obesity/metabolism , Adipose Tissue, Brown/metabolism , Adipose Tissue, Brown/pathology , Adipose Tissue, White/metabolism , Adipose Tissue, White/pathology , Animals , Blotting, Western , Carbon Radioisotopes , Immunohistochemistry , Male , Muscle, Skeletal/drug effects , Muscle, Skeletal/metabolism , Palmitates/metabolism , Rats , Rats, Wistar , Receptors, Adrenergic, beta-3 , Reverse Transcriptase Polymerase Chain Reaction , Thermography , Tritium , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
Cachexia represents a fatal energy-wasting syndrome in a large number of patients with cancer that mostly results in a pathological loss of skeletal muscle and adipose tissue. Here we show that tumor cell exposure and tumor growth in mice triggered a futile energy-wasting cycle in cultured white adipocytes and white adipose tissue (WAT), respectively. Although uncoupling protein 1 (Ucp1)-dependent thermogenesis was dispensable for tumor-induced body wasting, WAT from cachectic mice and tumor-cell-supernatant-treated adipocytes were consistently characterized by the simultaneous induction of both lipolytic and lipogenic pathways. Paradoxically, this was accompanied by an inactivated AMP-activated protein kinase (Ampk), which is normally activated in peripheral tissues during states of low cellular energy. Ampk inactivation correlated with its degradation and with upregulation of the Ampk-interacting protein Cidea. Therefore, we developed an Ampk-stabilizing peptide, ACIP, which was able to ameliorate WAT wasting in vitro and in vivo by shielding the Cidea-targeted interaction surface on Ampk. Thus, our data establish the Ucp1-independent remodeling of adipocyte lipid homeostasis as a key event in tumor-induced WAT wasting, and we propose the ACIP-dependent preservation of Ampk integrity in the WAT as a concept in future therapies for cachexia.
Subject(s)
AMP-Activated Protein Kinases/metabolism , Adipocytes, White/drug effects , Adipose Tissue, White/drug effects , Apoptosis Regulatory Proteins/drug effects , Cachexia/metabolism , Lipid Metabolism/drug effects , Neoplasms/metabolism , Peptide Fragments/pharmacology , AMP-Activated Protein Kinases/pharmacology , Adipocytes, White/metabolism , Adipose Tissue, White/metabolism , Animals , Apoptosis Regulatory Proteins/metabolism , Cachexia/etiology , Cells, Cultured , In Vitro Techniques , Lipogenesis/drug effects , Lipolysis/drug effects , Mice , Neoplasms/complications , Thermogenesis/drug effects , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
To better understand the role of irisin in humans, we examined the effects of irisin in human primary adipocytes and fresh human subcutaneous white adipose tissue (scWAT). Human primary adipocytes derived from 28 female donors' fresh scWAT were used to examine the effects of irisin on browning and mitochondrial respiration, and preadipocytes were used to examine the effects of irisin on adipogenesis and osteogenesis. Cultured fragments of scWAT and perirenal brown fat were used for investigating signal transduction pathways that mediate irisin's browning effect by Western blotting to detect phosphorylated forms of p38, ERK, and STAT3 as well as uncoupling protein 1 (UCP1). Individual responses to irisin in scWAT were correlated with basal expression levels of brown/beige genes. Irisin upregulated the expression of browning-associated genes and UCP1 protein in both cultured primary mature adipocytes and fresh adipose tissues. It also significantly increased thermogenesis at 5 nmol/l by elevating cellular energy metabolism (OCR and ECAR). Treating human scWAT with irisin increased UCP1 expression by activating the ERK and p38 MAPK signaling. Blocking either pathway with specific inhibitors abolished irisin-induced UCP1 upregulation. However, our results showed that UCP1 in human perirenal adipose tissue was insensitive to irisin. Basal levels of brown/beige and FNDC5 genes correlated positively with the browning response of scWAT to irisin. In addition, irisin significantly inhibited adipogenic differentiation but promoted osteogenic differentiation. We conclude that irisin promotes "browning" of mature white adipocytes by increasing cellular thermogenesis, whereas it inhibits adipogenesis and promotes osteogenesis during lineage-specific differentiation. Our findings provide a rationale for further exploring the therapeutic use of irisin in obesity and exercise-associated bone formation.
Subject(s)
Adipocytes, White/drug effects , Adipogenesis/drug effects , Cell Differentiation/drug effects , Fibronectins/pharmacology , Mitochondria/drug effects , Osteogenesis/drug effects , RNA, Messenger/drug effects , Thermogenesis/drug effects , Adipocytes, Brown/drug effects , Adipocytes, Brown/metabolism , Adipocytes, White/metabolism , Adipogenesis/genetics , Adolescent , Adult , Aged , Blotting, Western , Cell Respiration/drug effects , Cells, Cultured , Exercise , Extracellular Signal-Regulated MAP Kinases/drug effects , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Humans , Immunohistochemistry , Middle Aged , Mitochondria/metabolism , Obesity/metabolism , Osteoblasts/drug effects , Osteoblasts/metabolism , Osteogenesis/genetics , Phosphoproteins/drug effects , Phosphoproteins/metabolism , RNA, Messenger/metabolism , Real-Time Polymerase Chain Reaction , STAT3 Transcription Factor/drug effects , STAT3 Transcription Factor/metabolism , Signal Transduction , Subcutaneous Fat/cytology , Thermogenesis/genetics , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolism , Up-Regulation , Young Adult , p38 Mitogen-Activated Protein Kinases/drug effects , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
Adipose tissue PKA has roles in adipogenesis, lipolysis, and mitochondrial function. PKA transduces the cAMP signal downstream of G protein-coupled receptors, which are being explored for therapeutic manipulation to reduce obesity and improve metabolic health. This study aimed to determine the overall physiological consequences of PKA activation in adipose tissue. Mice expressing an activated PKA catalytic subunit in adipose tissue (Adipoq-caPKA mice) showed increased PKA activity in subcutaneous, epididymal, and mesenteric white adipose tissue (WAT) depots and brown adipose tissue (BAT) compared with controls. Adipoq-caPKA mice weaned onto a high-fat diet (HFD) or switched to the HFD at 26 wk of age were protected from diet-induced weight gain. Metabolic health was improved, with enhanced insulin sensitivity, glucose tolerance, and ß-cell function. Adipose tissue health was improved, with smaller adipocyte size and reduced macrophage engulfment of adipocytes. Using metabolic cages, we found that Adipoq-caPKA mice were shown to have increased energy expenditure, but no difference to littermate controls in physical activity or food consumption. Immunoblotting of adipose tissue showed increased expression of uncoupling protein-1 (UCP1) in BAT and dramatic UCP1 induction in subcutaneous WAT, but no induction in the visceral depots. Feeding a HFD increased PKA activity in epididymal WAT of wild-type mice compared with chow, but did not change PKA activity in subcutaneous WAT or BAT. This was associated with changes in PKA regulatory subunit expression. This study shows that adipose tissue PKA activity is sufficient to increase energy expenditure and indicates that PKA is a beneficial target in metabolic health.
Subject(s)
Adipose Tissue/metabolism , Cyclic AMP-Dependent Protein Kinases/pharmacology , Energy Metabolism/physiology , Uncoupling Protein 1/biosynthesis , Adiponectin/genetics , Adiponectin/metabolism , Adipose Tissue, Brown/metabolism , Adipose Tissue, White/metabolism , Adiposity , Animals , Cyclic AMP-Dependent Protein Kinases/genetics , Diet, High-Fat , Glucose Intolerance , Health Status , Insulin Resistance , Insulin-Secreting Cells/metabolism , Mice , Mice, Inbred C57BL , Uncoupling Protein 1/drug effects , Weight GainABSTRACT
Emergence of thermogenic adipocytes such as brown and beige adipocytes is critical for whole body energy metabolism. Promoting the emergence of these adipocytes, which increase energy expenditure, could be a viable strategy in treating obesity and its related diseases. However, little is known regarding the mechanisms that regulate the emergence of these adipocytes in obese adipose tissue. Here, we demonstrated that classically activated macrophages (M1 MÏ) suppress the induction of thermogenic adipocytes in obese adipose tissues of mice. Cold exposure significantly induced the expression levels of uncoupling protein-1 (UCP1), which is a mitochondrial protein unique in thermogenic adipocytes, in C57BL/6 mice fed a normal diet. However, UCP1 induction was significantly suppressed in adipose tissues of C57BL/6 mice fed a high-fat diet, into which M1 MÏ infiltrated. Depletion of M1 MÏ using clodronate liposomes eliminated the suppressive effect and markedly reduced the mRNA level of tumor necrosis factor-α (TNFα) in the adipose tissues. Importantly, consistent with the observed changes in the expression levels of marker genes for thermogenic adipocytes, combination treatment of clodronate liposome and cold exposure resulted in metabolic benefits such as lowered body weight and blood glucose level in obese mice. Moreover, intraperitoneal injection of recombinant TNFα protein suppressed UCP1 induction in lean adipose tissues of mice. Collectively, our data indicate that infiltrated M1 MÏ suppress the induction of thermogenic adipocytes in obese adipose tissues via TNFα. This report suggests that inflammation induced by infiltrated MÏ could cause not only insulin resistance but also reduction of energy expenditure in adipose tissues.
Subject(s)
Adipose Tissue/metabolism , Cell Differentiation/immunology , Insulin Resistance/immunology , Macrophages/immunology , Obesity/metabolism , RNA, Messenger/metabolism , Tumor Necrosis Factor-alpha/immunology , Uncoupling Protein 1/genetics , Adipocytes, Beige/drug effects , Adipocytes, Beige/metabolism , Adipocytes, Brown/drug effects , Adipocytes, Brown/metabolism , Adipose Tissue/drug effects , Adipose Tissue/immunology , Animals , Cell Differentiation/drug effects , Clodronic Acid/pharmacology , Cold Temperature , Diet, High-Fat , Energy Metabolism/immunology , Immunoblotting , Immunohistochemistry , Liposomes , Macrophages/drug effects , Male , Mice , Mice, Inbred C57BL , Mice, Obese , Obesity/immunology , RNA, Messenger/drug effects , Reverse Transcriptase Polymerase Chain Reaction , Thermogenesis , Tumor Necrosis Factor-alpha/drug effects , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/pharmacology , Uncoupling Protein 1/drug effects , Uncoupling Protein 1/metabolismABSTRACT
Accumulating evidence suggests that microRNAs (miRNAs) play an important role in regulating the pathways in adipose tissue that control processes such as adipogenesis, insulin resistance, and inflammation. Adipogenic differentiation of preadipocytes is a complex process regulated by various factors including miRNAs and cytokines. MiR-455 is a well-known miRNA that enhances adipogenesis. Uncoupling protein-1 (UCP-1), a heparinbinding growth factor, plays a negative role in adipogenesis. In this investigation, we demonstrate that UCP-1 is a target gene of miR-455 during adipogenic differentiation in 3T3-L1 preadipocytes. MiR-455 downregulates UCP-1 expression through interaction with a target site of miR-455 in the coding region of mouse UCP-1. The rare codons upstream of the target site regulate miR-455-induced translational knockdown of UCP-1, which provides more insight into the mechanism of adipogenic differentiation. Thus, these results suggest that the acceerative adipogenic effect of miR-455 in 3T3-L1 cells is due, at least in part, to suppression of UCP-1.