RESUMEN
Introduction: Naringenin, a peroxisome proliferator-activated receptor (PPAR) activator found in citrus fruits, upregulates markers of thermogenesis and insulin sensitivity in human adipose tissue. Our pharmacokinetics clinical trial demonstrated that naringenin is safe and bioavailable, and our case report showed that naringenin causes weight loss and improves insulin sensitivity. PPARs form heterodimers with retinoic-X-receptors (RXRs) at promoter elements of target genes. Retinoic acid is an RXR ligand metabolized from dietary carotenoids. The carotenoid ß-carotene reduces adiposity and insulin resistance in clinical trials. Our goal was to examine if carotenoids strengthen the beneficial effects of naringenin on human adipocyte metabolism. Methods: Human preadipocytes from donors with obesity were differentiated in culture and treated with 8µM naringenin + 2µM ß-carotene (NRBC) for seven days. Candidate genes involved in thermogenesis and glucose metabolism were measured as well as hormone-stimulated lipolysis. Results: We found that ß-carotene acts synergistically with naringenin to boost UCP1 and glucose metabolism genes including GLUT4 and adiponectin, compared to naringenin alone. Protein levels of PPARα, PPARγ and PPARγ-coactivator-1α, key modulators of thermogenesis and insulin sensitivity, were also upregulated after treatment with NRBC. Transcriptome sequencing was conducted and the bioinformatics analyses of the data revealed that NRBC induced enzymes for several non-UCP1 pathways for energy expenditure including triglyceride cycling, creatine kinases, and Peptidase M20 Domain Containing 1 (PM20D1). A comprehensive analysis of changes in receptor expression showed that NRBC upregulated eight receptors that have been linked to lipolysis or thermogenesis including the ß1-adrenergic receptor and the parathyroid hormone receptor. NRBC increased levels of triglyceride lipases and agonist-stimulated lipolysis in adipocytes. We observed that expression of RXRγ, an isoform of unknown function, was induced ten-fold after treatment with NRBC. We show that RXRγ is a coactivator bound to the immunoprecipitated PPARγ protein complex from white and beige human adipocytes. Discussion: There is a need for obesity treatments that can be administered long-term without side effects. NRBC increases the abundance and lipolytic response of multiple receptors for hormones released after exercise and cold exposure. Lipolysis provides the fuel for thermogenesis, and these observations suggest that NRBC has therapeutic potential.
Asunto(s)
Adipocitos Blancos , Resistencia a la Insulina , Humanos , Adipocitos Blancos/metabolismo , beta Caroteno/farmacología , beta Caroteno/metabolismo , Lipólisis , PPAR gamma/metabolismo , Obesidad/metabolismo , Fenotipo , Hormonas , Triglicéridos , GlucosaRESUMEN
The beneficial effects of sodium butyrate (NaB) and sodium propionate (NaP) on fatty acid oxidation (FAO) genes and production of proinflammatory cytokines related to nonalcoholic fatty liver disease (NAFLD) were evaluated using HepG2 human liver hepatocellular carcinoma cells exposed to palmitate/oleate or lipopolysaccharides (LPSs) as a model. The results showed that NaP or NaB was able to promote FAO, regulate lipolysis, and reduce reactive oxygen species production by significantly increasing the mRNA expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), peroxisome proliferator-activated receptor alpha (PPARα), adipose triglyceride lipase (ATGL), carnitine palmitoyltransferase 1 alpha (CPT1α), fibroblast growth factor 21 (FGF21), and uncoupling protein 2 (UCP2) in HepG2 cells. Together, NaP and NaB may produce greater effects by increasing CPT1α, PPARα, and UCP2 mRNA expression in LPS-treated HepG2 cells and by increasing CPT1α and ATGL mRNA expression in palmitate-/oleate-treated HepG2 cells. Only NaP treatment significantly increased FGF21 mRNA expression in palmitate-/oleate-treated HepG2 cells. The enzyme-linked immunosorbent assay results revealed that only pretreatment with LPSs and not palmitate/oleate significantly increased tumor necrosis factor alpha (TNF-α) expression in HepG2 cells. NaP alone or in combination with NaB significantly decreased TNF-α expression in LPS-induced HepG2 cells. The expression of interleukin-8 in both models showed no significant differences in all treatments. NaP and NaB show potential for in vivo studies on NAFLD.
Asunto(s)
Enfermedad del Hígado Graso no Alcohólico , Humanos , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Ácido Butírico/farmacología , Células Hep G2 , Ácido Oléico , Factor de Necrosis Tumoral alfa/genética , Factor de Necrosis Tumoral alfa/metabolismo , PPAR alfa/genética , PPAR alfa/metabolismo , Lipopolisacáridos , Estrés Oxidativo , ARN Mensajero/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismoRESUMEN
A glucose-lowering medication that acts by a different mechanism than metformin, or other approved diabetes medications, can supplement monotherapies when patients fail to meet blood glucose goals. We examined the actions underlying the effects of an insulin sensitizer, tolimidone (MLR-1023) and investigated its effects on body weight. Diet-induced obesity (CD1/ICR) and type 2 diabetes (db/db) mouse models were used to study the effect of MLR-1023 on metabolic outcomes and to explore its synergy with menthol. We also examined the efficacy of MLR-1023 alone in a clinical trial (NCT02317796), as well as in combination with menthol in human adipocytes. MLR-1023 produced weight loss in humans in four weeks, and in mice fed a high-fat diet it reduced weight gain and fat mass without affecting food intake. In human adipocytes from obese donors, the upregulation of Uncoupling Protein 1, Glucose (UCP)1, adiponectin, Glucose Transporter Type 4 (GLUT4), Adipose Triglyceride Lipase (ATGL), Carnitine palmitoyltransferase 1 beta (CPT1ß), and Transient Receptor Potential Melastin (TRPM8) mRNA expression suggested the induction of thermogenesis. The TRPM8 agonist, menthol, potentiated the effect of MLR-1023 on the upregulation of genes for energy expenditure and insulin sensitivity in human adipocytes, and reduced fasting blood glucose in mice. The amplification of the thermogenic program by MLR-1023 and menthol in the absence of adrenergic activation will likely be well-tolerated, and bears investigation in a clinical trial.
RESUMEN
OBJECTIVE: Cav3.2, a T-type low voltage-activated calcium channel widely expressed throughout the central nervous system, plays a vital role in neuronal excitability and various physiological functions. However, the effects of Cav3.2 on energy homeostasis remain unclear. Here, we examined the role of Cav3.2 expressed by hypothalamic GABAergic neurons in the regulation of food intake and body weight in mice and explored the underlying mechanisms. METHODS: Male congenital Cana1h (the gene coding for Cav3.2) global knockout (Cav3.2KO) mice and their wild type (WT) littermates were first used for metabolic phenotyping studies. By using the CRISPR-Cas9 technique, Cav3.2 was selectively deleted from GABAergic neurons in the arcuate nucleus of the hypothalamus (ARH) by specifically overexpressing Cas9 protein and Cav3.2-targeting sgRNAs in ARH Vgat (VgatARH) neurons. These male mutants (Cav3.2KO-VgatARH) were used to determine whether Cav3.2 expressed by VgatARH neurons is required for the proper regulation of energy balance. Subsequently, we used an electrophysiological patch-clamp recording in ex vivo brain slices to explore the impact of Cav3.2KO on the cellular excitability of VgatARH neurons. RESULTS: Male Cav3.2KO mice had significantly lower food intake than their WT littermate controls when fed with either a normal chow diet (NCD) or a high-fat diet (HFD). This hypophagia phenotype was associated with increased energy expenditure and decreased fat mass, lean mass, and total body weight. Selective deletion of Cav3.2 in VgatARH neurons resulted in similar feeding inhibition and lean phenotype without changing energy expenditure. These data provides an intrinsic mechanism to support the previous finding on ARH non-AgRP GABA neurons in regulating diet-induced obesity. Lastly, we found that naringenin extract, a predominant flavanone found in various fruits and herbs and known to act on Cav3.2, decreased the firing activity of VgatARH neurons and reduced food intake and body weight. These naringenin-induced inhibitions were fully blocked in Cav3.2KO-VgatARH mice. CONCLUSION: Our results identified Cav3.2 expressed by VgatARH neurons as an essential intrinsic modulator for food intake and energy homeostasis, which is a potential therapeutic target in the treatment of obesity.
Asunto(s)
Canales de Calcio Tipo T/metabolismo , Neuronas GABAérgicas/metabolismo , Obesidad/metabolismo , Animales , Ratones , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
Triple negative breast cancer (TNBC) is an aggressive and highly metastatic breast cancer subtype with limited treatment options. Obesity and insulin resistance are associated with a worse prognosis in those with TNBC. Moringa oleifera (moringa) is a tropical edible plant used for both food and medicinal purposes and found to have anti-obesity and anti-cancer effects in vitro and in preclinical models. The anti-cancer effects of moringa seed extract alone and in combination with chemotherapy were evaluated in immunocompromised female mice with diet-induced obesity bearing MDA-MB-231-derived xenograft tumors. Moringa supplementation protected against high-fat diet- and chemotherapy-induced increases in fasting glucose and improved insulin sensitivity. Moringa supplementation alone did not attenuate tumor growth relative to chemotherapy alone, and in combination worsened tumor progression. Moringa supplementation alone reduced angiogenesis, but this effect was abrogated in combination with chemotherapy. Moringa supplementation may be an effective strategy to improve metabolic health in mice with obesity and TNBC and reduce angiogenesis in tumors, but may have a negative interaction when used as a concurrent complementary therapy. Caution should be taken when considering the consumption of moringa seed extracts while receiving chemotherapy for breast cancer treatment. Further investigations of alternative timings of moringa therapy are warranted.
Asunto(s)
Neoplasias Mamarias Experimentales/tratamiento farmacológico , Moringa oleifera/química , Obesidad/tratamiento farmacológico , Extractos Vegetales/farmacología , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Animales , Antineoplásicos/efectos adversos , Antineoplásicos/farmacología , Línea Celular Tumoral , Dieta Alta en Grasa/efectos adversos , Suplementos Dietéticos , Progresión de la Enfermedad , Femenino , Humanos , Resistencia a la Insulina , Neoplasias Mamarias Experimentales/metabolismo , Ratones , Obesidad/metabolismo , Semillas/química , Neoplasias de la Mama Triple Negativas/metabolismo , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Our studies in primary human adipocytes show that naringenin, a citrus flavonoid, increases oxygen consumption rate and gene expression of uncoupling protein 1 (UCP1), glucose transporter type 4, and carnitine palmitoyltransferase 1ß (CPT1ß). We investigated the safety of naringenin, its effects on metabolic rate, and blood glucose and insulin responses in a single female subject with diabetes. The subject ingested 150 mg naringenin from an extract of whole oranges standardized to 28% naringenin three times/day for 8 weeks, and maintained her usual food intake. Body weight, resting metabolic rate, respiratory quotient, and blood chemistry panel including glucose, insulin, and safety markers were measured at baseline and after 8 weeks. Adverse events were evaluated every 2 weeks. We also examined the involvement of peroxisome proliferator-activated receptor α (PPARα), peroxisome proliferator-activated receptor γ (PPARγ), protein kinase A (PKA), and protein kinase G (PKG) in the response of human adipocytes to naringenin treatment. Compared to baseline, the body weight decreased by 2.3 kg. The metabolic rate peaked at 3.5% above baseline at 1 h, but there was no change in the respiratory quotient. Compared to baseline, insulin decreased by 18%, but the change in glucose was not clinically significant. Other blood safety markers were within their reference ranges, and there were no adverse events. UCP1 and CPT1ß mRNA expression was reduced by inhibitors of PPARα and PPARγ, but there was no effect of PKA or PKG inhibition. We conclude that naringenin supplementation is safe in humans, reduces body weight and insulin resistance, and increases metabolic rate by PPARα and PPARγ activation. The effects of naringenin on energy expenditure and insulin sensitivity warrant investigation in a randomized controlled clinical trial.
Asunto(s)
Metabolismo Basal/efectos de los fármacos , Flavanonas/administración & dosificación , Resistencia a la Insulina , Extractos Vegetales/administración & dosificación , Glucemia/metabolismo , Carnitina O-Palmitoiltransferasa/genética , Carnitina O-Palmitoiltransferasa/metabolismo , Citrus sinensis/química , Suplementos Dietéticos/análisis , Femenino , Humanos , Insulina/metabolismo , Persona de Mediana Edad , PPAR alfa/genética , PPAR alfa/metabolismo , PPAR gamma/genética , PPAR gamma/metabolismo , Proteína Desacopladora 1/genética , Proteína Desacopladora 1/metabolismoRESUMEN
AIMS: To evaluate the safety and pharmacokinetics of naringenin in healthy adults consuming whole-orange (Citrus sinensis) extract. METHODS AND METHODS: In a single-ascending-dose randomized crossover trial, 18 adults ingested doses of 150 mg (NAR150), 300 mg (NAR300), 600 mg (NAR600) and 900 mg (NAR900) naringenin or placebo. Each dose or placebo was followed by a wash-out period of at least 1 week. Blood safety markers were evaluated pre-dose and 24 hours post-dose. Adverse events (AEs) were recorded. Serum naringenin concentrations were measured before and over 24 hours following ingestion of placebo, NAR150 and NAR600. Four- and 24-hour serum measurements were obtained after placebo, NAR300 and NAR900 ingestion. Data were analysed using a mixed-effects linear model. RESULTS: There were no relevant AEs or changes in blood safety markers following ingestion of any of the naringenin doses. The pharmacokinetic variables were: maximal concentration: 15.76 ± 7.88 µM (NAR150) and 48.45 ± 7.88 µM (NAR600); time to peak: 3.17 ± 0.74 hours (NAR150) and 2.41 ± 0.74 hours (NAR600); area under the 24-hour concentration-time curve: 67.61 ± 24.36 µM × h (NAR150) and 199.05 ± 24.36 µM × h (NAR600); and apparent oral clearance: 10.21 ± 2.34 L/h (NAR150) and 13.70 ± 2.34 L/h (NAR600). Naringenin half-life was 3.0 hours (NAR150) and 2.65 hours (NAR600). After NAR300 ingestion, serum concentrations were 10.67 ± 5.74 µM (4 hours) and 0.35 ± 0.30 µM (24 hours). After NAR900 ingestion, serum concentrations were 43.11 ± 5.26 µM (4 hours) and 0.24 ± 0.30 µM (24 hours). CONCLUSIONS: Ingestion of 150 to 900 mg doses of naringenin is safe in healthy adults, and serum concentrations are proportional to the dose administered. Since naringenin (8 µM) is effective in primary human adipocytes, ingestion of 300 mg naringenin twice/d will likely elicit a physiological effect.
Asunto(s)
Flavanonas/administración & dosificación , Flavanonas/farmacocinética , Administración Oral , Adulto , Área Bajo la Curva , Citrus/química , Estudios Cruzados , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Femenino , Flavanonas/efectos adversos , Semivida , Humanos , Masculino , Tasa de Depuración Metabólica , Persona de Mediana Edad , Extractos Vegetales/química , Adulto JovenRESUMEN
OBJECTIVE: Naringenin, a citrus flavonoid, prevents diet-induced weight gain and improves glucose and lipid metabolism in rodents. There is evidence that naringenin activates brown fat and increases energy expenditure in mice, but little is known about its effects in humans. The goal of this study was to examine the effects of naringenin on energy expenditure in adipose tissue. METHODS: Human white adipocyte cultures (hADSC) and abdominal subcutaneous adipose tissue (pWAT) were treated with naringenin for 7 to 14 days. Expression (quantitative real-time polymerase chain reaction, immunoblotting) of candidate genes involved in thermogenesis and glucose metabolism was measured. Oxygen consumption rate was measured in hADSC using a Seahorse flux analyzer. RESULTS: In hADSC, naringenin increased expression of the genes associated with thermogenesis and fat oxidation, including uncoupling protein 1 and adipose triglyceride lipase, and key factors associated with insulin sensitivity, including glucose transporter type 4, adiponectin, and carbohydrate-responsive element-binding protein (P < 0.01). Similar responses were observed in pWAT. Basal, ATP-linked, maximal and reserve oxygen consumption rate increased in the naringenin-treated hADSC (P < 0.01). CONCLUSIONS: Naringenin increases energy expenditure in hADSC and stimulates expression of key enzymes involved in thermogenesis and insulin sensitivity in hADSC and pWAT. Naringenin may promote conversion of human white adipose tissue to a brown/beige phenotype.
Asunto(s)
Tejido Adiposo Blanco/metabolismo , Flavanonas/uso terapéutico , Obesidad/tratamiento farmacológico , Termogénesis/efectos de los fármacos , Animales , Flavanonas/farmacología , Expresión Génica , Humanos , Masculino , RatonesRESUMEN
For many years, obesity was believed to be a condition of overeating that could be resolved through counseling and short-term drug treatment. Obesity was not recognized as a chronic disease until 1985 by the scientific community, and 2013 by the medical community. Pharmacotherapy for obesity has advanced remarkably since the first class of drugs, amphetamines, were approved for short-term use. Most amphetamines were removed from the obesity market due to adverse events and potential for addiction, and it became apparent that obesity pharmacotherapies were needed that could safely be administered over the long term. This review of central nervous system (CNS) acting anti-obesity drugs evaluates current therapies such as phentermine/topiramate, which act through multiple neurotransmitter pathways to reduce appetite. In the synergistic mechanism of bupropion/naltrexone, naltrexone blocks the feed-back inhibitory circuit of bupropion to give greater weight loss. Lorcaserin, a selective agonist of a serotonin receptor that regulates food intake, and the glucagon-like-peptide-1 (GLP-1) receptor agonist liraglutide are reviewed. Future drugs include tesofensine, a potent triple reuptake inhibitor in Phase III trials for obesity, and semaglutide, an oral GLP-1 analog approved for diabetes and currently in trials for obesity. Another potential new pharmacotherapy, setmelanotide, is a melanocortin-4 receptor agonist, which is still in an early stage of development. As our understanding of the communication between the CNS, gut, adipose tissue, and other organs evolves, it is anticipated that obesity drug development will move toward new centrally acting combinations and then to drugs acting on peripheral target tissues.
Asunto(s)
Fármacos Antiobesidad/uso terapéutico , Fármacos del Sistema Nervioso Central/uso terapéutico , Obesidad/tratamiento farmacológico , Animales , Fármacos Antiobesidad/efectos adversos , Fármacos Antiobesidad/farmacología , Regulación del Apetito , Fármacos del Sistema Nervioso Central/efectos adversos , Fármacos del Sistema Nervioso Central/farmacología , Humanos , Pérdida de Peso/efectos de los fármacosRESUMEN
OBJECTIVE: This study evaluated the effect of lorcaserin 10 mg twice daily (LOR BID), or with phentermine 15 mg once daily (LOR BID + PHEN QD) and 15 mg twice daily (LOR BID + PHEN BID), in conjunction with energy restriction on food cravings. METHODS: Two hundred and thirty-five patients without diabetes but with obesity or overweight and ≥ 1 comorbidity received LOR BID, LOR BID + PHEN QD, or LOR BID + PHEN BID for 12 weeks in a randomized double-blind study. The Food Craving Inventory (FCI) and the Control of Eating Questionnaire (COEQ) were administered over 12 weeks. RESULTS: The FCI total score and the subscale scores reduced from baseline in all groups. The least squares means (95% confidence intervals) for the total scores were -0.65 (-0.75 to -0.55), -0.75 (-0.84 to -0.65), and -0.84 (-0.95 to -0.74) in the LOR BID, LOR BID + PHEN QD, and LOR BID + PHEN BID groups, respectively. Cravings assessed by COEQ reduced from baseline in all groups. In general, the combination treatments were more effective than lorcaserin alone. At week 12, except for fruit juice and dairy products, general and specific cravings reduced in LOR BID + PHEN BID compared with LOR BID (P < 0.05). CONCLUSIONS: Lorcaserin in combination with phentermine improves control of food cravings during short-term energy restriction.
Asunto(s)
Benzazepinas/uso terapéutico , Ansia/efectos de los fármacos , Obesidad/tratamiento farmacológico , Sobrepeso/tratamiento farmacológico , Fentermina/uso terapéutico , Adolescente , Adulto , Fármacos Antiobesidad/farmacología , Fármacos Antiobesidad/uso terapéutico , Benzazepinas/farmacología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Fentermina/farmacología , Adulto JovenRESUMEN
Rodent studies suggest that the antiobesity effects of fucoxanthin relate to activation of brown fat and conversion of white adipocytes to the brown phenotype. To evaluate the browning effect in human adipocytes, we investigated the genes involved in browning and measured the oxygen consumption rate (OCR). Data were analyzed by one way ANOVA. Relative to control, fucoxanthinol (1 µM, 0.1 µM, 0.01 µM, 1 nM, 0.1 nM), the metabolite present in human plasma, stimulated lipolysis acutely (mean ± SEM: 4.2 ± 0.8, 3.1 ± 0.6, 4.1 ± 0.9, 3.8 ± 0.7, 3.8 ± 0.7, respectively, p < 0.01). There was no effect on OCR or the mRNA expression of UCP1, CPT-1ß, and GLUT4, the genes associated with browning of adipose tissue, when human adipocytes were treated with fucoxanthin or fucoxanthinol. -mRNA expression of PGC-1α, PPARα, PPARγ, PDK4, FAS, and the lipolytic enzymes was not significantly altered by fucoxanthinol treatment (p > 0.05). Thus, in human adipocytes, fucoxanthin and its metabolite do not stimulate conversion of white adipocytes to the brown phenotype.
Asunto(s)
Xantófilas/metabolismo , beta Caroteno/análogos & derivados , Adipocitos/efectos de los fármacos , Adipocitos/metabolismo , Tejido Adiposo Pardo/citología , Tejido Adiposo Pardo/efectos de los fármacos , Tejido Adiposo Pardo/metabolismo , Transportador de Glucosa de Tipo 4/genética , Transportador de Glucosa de Tipo 4/metabolismo , Humanos , Lipólisis/efectos de los fármacos , PPAR gamma/genética , PPAR gamma/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/genética , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Proteína Desacopladora 1/genética , Proteína Desacopladora 1/metabolismo , Xantófilas/farmacología , beta Caroteno/metabolismo , beta Caroteno/farmacologíaRESUMEN
The purpose of this study was to determine whether pyruvate dehydrogenase kinase (PDK)4 was expressed in adipocytes and whether PDK4 expression was hormonally regulated in fat cells. Both Northern blot and Western blot analyses were conducted on samples isolated from 3T3-L1 adipocytes after various treatments with prolactin (PRL), growth hormone (GH), and/or insulin. Transfection of PDK4 promoter reporter constructs was performed. In addition, glucose uptake measurements were conducted. Our studies demonstrate that PRL and porcine GH can induce the expression of PDK4 in 3T3-L1 adipocytes. Our studies also show that insulin pretreatment can attenuate the ability of these hormones to induce PDK4 mRNA expression. In addition, we identified a hormone-responsive region in the murine PDK4 promoter and characterized a STAT5 binding site in this region that mediates the PRL (sheep) and GH (porcine) induction in PDK4 expression in 3T3-L1 adipocytes. PDK4 is a STAT5A target gene. PRL is a potent inducer of PDK4 protein levels, results in an inhibition of insulin-stimulated glucose transport in fat cells, and likely contributes to PRL-induced insulin resistance.
Asunto(s)
Adipocitos/fisiología , Hormona de Crecimiento Humana/farmacología , Prolactina/farmacología , Proteínas Quinasas/genética , Factor de Transcripción STAT5/fisiología , Células 3T3 , Adipocitos/efectos de los fármacos , Animales , Núcleo Celular/enzimología , Citosol/enzimología , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Genes Reporteros , Ratones , Plásmidos , Regiones Promotoras Genéticas , TransfecciónRESUMEN
Cold exposure induces brown adipocytes in retroperitoneal fat (RP) of adult A/J mice but not in C57BL/6J (B6) mice. In contrast, induction of the mitochondrial uncoupling protein 1 gene (Ucp1) in interscapular brown adipose tissue (iBAT) shows no strain dependence. We now show that unlike iBAT, in which Ucp1 was expressed in the fetus and continued throughout life, in RP, Ucp1 was transiently expressed between 10 and 30 days of age and then disappeared. Similar to the lack of genetic variation in the expression of Ucp1 in iBAT during cold induction of adult mice, no genetic variation in Ucp1 expression in iBAT was detected during development. In contrast, UCP1-positive multilocular adipocytes, together with corresponding increases in Ucp1 expression, appeared in RP at 10 days of age in A/J and B6 mice, but with much higher expression in A/J mice. At 20 days of age, brown adipocytes represent the major adipocyte present in RP of A/J mice. The disappearance of brown adipocytes by 30 days of age suggested that tissue remodeling occurred in RP. Genetic variability in Ucp1 expression could not be explained by variation in the expression of selective transcription factors and signaling molecules of adipogenesis. In summary, the existence of genetic variability between A/J and B6 mice during the development of brown adipocyte expression in RP, but not in iBAT, suggests that developmental mechanisms for the brown adipocyte differentiation program are different in these adipose tissues.
Asunto(s)
Adipocitos/fisiología , Tejido Adiposo Pardo/fisiología , Tejido Adiposo/fisiología , Variación Genética , Tejido Adiposo/anatomía & histología , Tejido Adiposo Pardo/anatomía & histología , Animales , Peso Corporal , Frío , Femenino , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos A , ARN/genética , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Growth hormone (GH) diminishes adipose tissue mass in vivo and prolactin (PRL) can also modulate adipocyte metabolism. Both GH and PRL are potent activators of STAT5 and exert a variety of effects on adipocyte gene expression. In this study, we have demonstrated that GH and PRL increase the mRNA of acyl CoA oxidase in 3T3-L1 adipocytes. We also identified seven putative STAT elements in the murine AOX promoter. We observed that GH modulates protein binding to the majority of these promoter elements. However, GH induced very potent binding to -1841 to -1825 of the murine AOX promoter. EMSA supershift analysis revealed that this site was specifically bound by STAT5A, but not by STAT1 or STAT3. Taken together, these data strongly suggest that GH directly induces the expression of AOX in adipocytes through STAT5A binding to the -1841 to -1825 site within the AOX promoter. Our observations are consistent with other studies that demonstrate that STAT5 activators modulate fatty acid oxidation.
Asunto(s)
Acil-CoA Oxidasa/genética , Adipocitos/enzimología , Hormona del Crecimiento/farmacología , Factor de Transcripción STAT5/metabolismo , Células 3T3-L1 , Adipocitos/efectos de los fármacos , Animales , Ratones , Prolactina/farmacología , Regiones Promotoras Genéticas , ARN Mensajero/metabolismo , Elementos de Respuesta , Factor de Transcripción STAT1/metabolismo , Factor de Transcripción STAT3/metabolismoRESUMEN
Induction of brown adipocytes in white fat depots by adrenergic stimulation is a complex genetic trait in mice that affects the ability of the animal to regulate body weight. An 80-fold difference in expression of the mitochondrial uncoupling gene (Ucp1) at the mRNA and protein levels between A/J and C57BL/6J (B6) mice is controlled by allelic interactions among nine quantitative trait loci (QTLs) on eight chromosomes. Overlapping patterns of these QTLs also regulate expression levels of Pgc-1alpha, Pparalpha, and type 2 deiodinase. Independent validation that PPARalpha is associated with Ucp1 induction was obtained by treating mice with the PPARalpha agonist clofibrate, but not from the analysis of PPARalpha knockout mice. The most upstream sites of regulation for Ucp1 that differed between A/J and B6 were the phosphorylation of p38 mitogen-activated protein kinase and CREB and then followed by downstream changes in levels of mRNA for PPARgamma, PPARalpha, PGC-1alpha, and type 2 deiodinase. However, compared to Ucp1 expression, the two- to fourfold differences in the expression of these regulatory components are very modest. It is proposed that small variations in the levels of several transcriptional components of the Ucp1 enhanceosome interact synergistically to achieve large differences in Ucp1 expression.
Asunto(s)
Adipocitos/metabolismo , Tejido Adiposo Pardo/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Regulación de la Expresión Génica , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Tejido Adiposo/citología , Animales , Cromosomas , Clofibrato/farmacología , Frío , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Hipolipemiantes/farmacología , Yoduro Peroxidasa/genética , Yoduro Peroxidasa/metabolismo , Canales Iónicos , Ratones , Ratones Noqueados , Proteínas Mitocondriales , PPAR alfa/agonistas , PPAR alfa/genética , PPAR alfa/metabolismo , PPAR gamma/genética , PPAR gamma/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma , Sitios de Carácter Cuantitativo , ARN Mensajero/análisis , ARN Mensajero/metabolismo , Transactivadores/genética , Transactivadores/metabolismo , Factores de Transcripción , Transcripción Genética , Proteína Desacopladora 1 , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Yodotironina Deyodinasa Tipo IIRESUMEN
To identify novel regulatory factors controlling induction of the brown adipocyte-specific mitochondrial uncoupling protein (Ucp1) mRNA in the retroperitoneal white fat depot, we previously mapped quantitative trait loci (QTLs) that control this trait to chromosomes 2, 3, 8, and 19. Since the peroxisome proliferator activator receptor-gamma coactivator-1alpha (PGC-1alpha) regulates Ucp1 and other genes of energy metabolism, we have evaluated whether the QTLs controlling Ucp1 mRNA levels also modulate Pgc-1alpha mRNA levels by analysis of backcross progeny from the A/J and C57BL/6J strains of mice. The results indicate that a locus on chromosome 3 orchestrates expression of Pgc-1alpha and Ucp1 in retroperitoneal fat of mice fed a low-fat diet; however, the effect of this locus on Pgc-1alpha is lost, and a significant correlation between Ucp1 and Pgc-1alpha is severely reduced in mice fed a high-fat diet. An additional QTL located on chromosome 5 has also been identified for the selective regulation of Ucp1 mRNA levels. Similar to the effects of a high-fat diet on the chromosome 3 QTL, linkage of the chromosome 5 QTL is also lost in mice on a high-fat diet. Thus dietary fat has a profound influence on PGC-1alpha-regulated pathways controlling energy metabolism in white fat. The allelic variation observed in the regulation of Ucp1 and Pgc-1alpha expression in brown adipocytes of white fat but not interscapular brown fat suggests that fundamentally different regulatory mechanisms exist to control the thermogenic capacities of these tissues.