RESUMEN
Brown adipose tissue (BAT) activation is an emerging target for obesity treatments due to its thermogenic properties stemming from its ability to shuttle energy through uncoupling protein 1 (Ucp1). Recent rodent studies show how BAT and white adipose tissue (WAT) activity can be modulated to increase the expression of thermogenic proteins. Consequently, these alterations enable organisms to endure cold-temperatures and elevate energy expenditure, thereby promoting weight loss. In humans, BAT is less abundant in obese subjects and impacts of thermogenesis are less pronounced, bringing into question whether energy expending properties of BAT seen in rodents can be translated to human models. Our review will discuss pharmacological, hormonal, bioactive, sex-specific and environmental activators and inhibitors of BAT to determine the potential for BAT to act as a therapeutic strategy. We aim to address the feasibility of utilizing BAT modulators for weight reduction in obese individuals, as recent studies suggest that BAT's contributions to energy expenditure along with Ucp1-dependent and -independent pathways may or may not rectify energy imbalance characteristic of obesity.
Asunto(s)
Tejido Adiposo Pardo , Metabolismo Energético , Obesidad , Tejido Adiposo Pardo/metabolismo , Humanos , Obesidad/metabolismo , Obesidad/tratamiento farmacológico , Animales , Termogénesis , Proteína Desacopladora 1/metabolismo , Fármacos Antiobesidad/farmacología , Fármacos Antiobesidad/uso terapéuticoRESUMEN
Adipose tissue was once known as a reservoir for energy storage but is now considered a crucial organ for hormone and energy flux with important effects on health and disease. Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone secreted from the small intestinal K cells, responsible for augmenting insulin release, and has gained attention for its independent and amicable effects with glucagon-like peptide 1 (GLP-1), another incretin hormone secreted from the small intestinal L cells. The GIP receptor (GIPR) is found in whole adipose tissue, whereas the GLP-1 receptor (GLP-1R) is not, and some studies suggest that GIPR action lowers body weight and plays a role in lipolysis, glucose/lipid uptake/disposal, adipose tissue blood flow, lipid oxidation, and free-fatty acid (FFA) re-esterification, which may or may not be influenced by other hormones such as insulin. This review summarizes the research on the effects of GIP in adipose tissue (distinct depots of white and brown) using cellular, rodent, and human models. In doing so, we explore the mechanisms of GIPR-based medications for treating metabolic disorders, such as type 2 diabetes and obesity, and how GIPR agonism and antagonism contribute to improvements in metabolic health outcomes, potentially through actions in adipose tissues.
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Tejido Adiposo , Polipéptido Inhibidor Gástrico , Receptores de la Hormona Gastrointestinal , Humanos , Polipéptido Inhibidor Gástrico/metabolismo , Animales , Tejido Adiposo/metabolismo , Receptores de la Hormona Gastrointestinal/metabolismo , Glucosa/metabolismo , Lipólisis , Obesidad/metabolismoRESUMEN
Proteins activate small intestinal calcium sensing receptor (CaSR) and/or peptide transporter 1 (PepT1) to increase hormone secretion1-8, but the effect of small intestinal protein sensing and the mechanistic potential of CaSR and/or PepT1 in feeding and glucose regulation remain inconclusive. Here we show that, in male rats, CaSR in the upper small intestine is required for casein infusion to increase glucose tolerance and GLP1 and GIP secretion, which was also dependent on PepT1 (ref. 9). PepT1, but not CaSR, is required for casein infusion to lower feeding. Upper small intestine casein sensing fails to regulate feeding, but not glucose tolerance, in high-fat-fed rats with decreased PepT1 but increased CaSR expression. In the ileum, a CaSR-dependent but PepT1-independent pathway is required for casein infusion to lower feeding and increase glucose tolerance in chow-fed rats, in parallel with increased PYY and GLP1 release, respectively. High fat decreases ileal CaSR expression and disrupts casein sensing on feeding but not on glucose control, suggesting an ileal CaSR-independent, glucose-regulatory pathway. In summary, we discover small intestinal CaSR- and PepT1-dependent and -independent protein sensing mechanisms that regulate gut hormone release, feeding and glucose tolerance. Our findings highlight the potential of targeting small intestinal CaSR and/or PepT1 to regulate feeding and glucose tolerance.
Asunto(s)
Hormonas Gastrointestinales , Receptores Sensibles al Calcio , Animales , Masculino , Ratas , Caseínas/metabolismo , Hormonas Gastrointestinales/metabolismo , Glucosa/metabolismo , Intestino Delgado/metabolismo , Receptores Sensibles al Calcio/metabolismoRESUMEN
Metabolic diseases, such as obesity, type 2 diabetes mellitus (T2DM), cardiovascular disease, and liver disease, have become increasingly prevalent around the world. As an alternative to bariatric surgery, glucagon-like peptide 1 (GLP-1) receptor agonists have been at the forefront of weight loss medication to combat these metabolic complications. Recently, there has been an exciting rapid emergence of new weight loss medications that combine GLP-1 receptor (GLP-1R) agonists with other gut- and pancreatic-derived hormones, such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon (GCG) receptor agonists. Dual-agonist (GLP-1/GIP and GLP-1/GCG) and tri-agonist (GLP-1/GIP/GCG) administration generally result in greater weight loss, reduction of blood sugar and lipid levels, restoration of tissue function, and improvement in whole-body substrate metabolism compared to when GLP-1R agonists are used alone. The aim of this review is to summarize the recent literature of both preclinical and clinical studies on how these emerging gut-peptide therapies further improve weight loss and metabolic health outcomes for various metabolic diseases.
Asunto(s)
Fármacos Antiobesidad , Diabetes Mellitus Tipo 2 , Humanos , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Péptido 1 Similar al Glucagón/metabolismo , Polipéptido Inhibidor Gástrico/fisiología , Pérdida de Peso , Fármacos Antiobesidad/uso terapéutico , Páncreas/metabolismo , Receptor del Péptido 1 Similar al Glucagón/agonistasRESUMEN
SCOPE: Obesity and insulin resistance (IR) are associated with epigenetic changes of gene expression. However, the relationship between micronutrients, epigenetic regulation of gene expression, and IR during development of diet-induced obesity has yet to be defined. Our objective is to describe the effect of micronutrient addition to diets on IR and its related genes during obesity development. METHODS AND RESULTS: Male C57BL/6J mice are fed a high-fat (HFD) or low-fat (LFD) diets with or without a multi-vitamin mineral mix (MVM) addition containing vitamins A, B1, B6, B12, and Zn, and Se for 9 weeks. Compared to LFD mice, HFD mice have higher body weight, IR, fasting glucose, insulin, C-peptide, leptin, and hepatic triglyceride concentrations, and dysregulated gene expression in liver, muscle, pancreas, and fat tissues (p < 0.05). The addition of MVM reduces these HFD-induced effects. HFD downregulates 27 genes associated with insulin regulation and adipose tissue function across all tissues by an average of 47% and upregulates five genes by 230% (p < 0.001). Adding MVM downregulates five genes and upregulates one in HFD-fed mice. Both HFD and MVM alter one-carbon metabolites. CONCLUSION: Addition of micronutrients to the HFD decreases IR and modifies associated gene expression in obese and lean mice.
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Resistencia a la Insulina , Masculino , Animales , Ratones , Resistencia a la Insulina/fisiología , Dieta Alta en Grasa/efectos adversos , Micronutrientes/farmacología , Epigénesis Genética , Ratones Endogámicos C57BL , Obesidad/genética , Obesidad/metabolismo , Insulina/metabolismo , Genes ReguladoresRESUMEN
Branched chain fatty acids (BCFAs) are mainly saturated fatty acids with a methyl branch on the penultimate or antepenultimate carbon atom. While BCFAs are endogenously produced via the catabolism of branched chain amino acids, the primary exogenous source of BCFAs in the human body is via the diet, including dairy products. Recently, BCFAs have been identified as having a potentially protective role in the etiology of cardiometabolic disorders although current literature is limited. We aimed to investigate the longitudinal associations of circulating BCFAs across four serum pools with insulin sensitivity, beta cell function, and glucose concentrations in the PROMISE Cohort. Estimates of insulin sensitivity were assessed using Matsuda's insulin sensitivity index (ISI) and the homeostasis model assessment of insulin sensitivity (HOMA2). Estimates of beta cell function were determined using the insulinogenic index divided by HOMA insulin resistance and the insulin secretion-sensitivity index-2 (ISSI-2). Baseline serum samples were analyzed for BCFAs using gas-chromatography flame ionization detection. Longitudinal associations were determined using generalized estimating equations. In the free fatty acid (FFA) pool, iso15:0 and anteiso15:0 were positively associated with logHOMA2 (iso15:0 logHOMA2-%S: ß = 6.86, 95% CI: [1.64, 12.36], p < 0.05, anteiso15:0 logHOMA2-%S: ß = 6.36, 95% CI: [0.63, 12.42], p < 0.05) while anteiso14:0 was inversely associated with measures of insulin sensitivity (iso14:0 logHOMA2-%S: ß = -2.35, 95% CI: [-4.26, -0.40], p < 0.05, logISI: ß = -2.30, 95% CI: [-4.32, -0.23], p < 0.05, anteiso14:0 logHOMA2-%S: ß = -4.72, 95% CI: [-7.81, -1.52], p < 0.05, logISI: ß = -6.13, 95% CI: [-9.49, -2.66], p < 0.01). Associations in other pools were less consistent. We identified the potential importance of specific BCFAs, specifically iso14:0, anteiso14:0, iso15:0, anteiso15:0, in cardiometabolic phenotypes underlying type 2 diabetes.
Asunto(s)
Enfermedades Cardiovasculares , Diabetes Mellitus Tipo 2 , Resistencia a la Insulina , Células Secretoras de Insulina , Humanos , Resistencia a la Insulina/fisiología , Diabetes Mellitus Tipo 2/metabolismo , Células Secretoras de Insulina/metabolismo , Ácidos Grasos/metabolismo , Enfermedades Cardiovasculares/metabolismo , InsulinaRESUMEN
CONTEXT: Despite advances in treatments for cardiometabolic disorders such as type 2 diabetes mellitus and obesity, the increasing frequency of these conditions is of major clinical and public health concern. Therefore, primary prevention including diet and lifestyle approaches continues to play a key role in risk reduction. Meta-analyses of prospective cohort studies have documented inverse associations of dairy consumption with the incidence of different cardiometabolic disorders. Dairy is the largest dietary contributor of branched chain fatty acids (BCFAs), which have been suggested to not only serve as biomarkers of dairy consumption but may also have bioactive properties contributing to reducing the risk of cardiometabolic outcomes. To date, however, the literature on this topic has not been systematically reviewed. OBJECTIVE: The aim here was to report the results of a systematic review of the association of BCFAs with cardiometabolic disorders in humans. DATA SOURCES: Search terms were developed and run through the Ovid MEDLINE, Ovid Embase, and the Cochrane Library databases. DATA EXTRACTION: Articles were selected on the basis of prespecified inclusion criteria and assessed for risk of bias by independent reviewers. RESULTS: Four studies (n = 2 cross sectional; n = 1 randomized feeding trial and n = 1 pre-post study) were identified. Two studies reported significant inverse associations between serum BCFAs and insulin resistance, triglycerides and/or body mass index. One study identified an inverse association between adipose tissue monomethyl BCFAs and skeletal muscle insulin resistance. In contrast, the randomized feeding trial reported no significant differences to stool BCFA concentrations or body mass index in obese participants following assignment to fruit-vegetable or whole-grain diet groups compared with a refined-grain control group. CONCLUSIONS: Current evidence suggests beneficial associations of circulating BCFAs with cardiometabolic risk phenotypes, although data in human participants are limited, indicating that additional research is required. PROSPERO REGISTRATION NO: CRD42021224975.
Asunto(s)
Enfermedades Cardiovasculares , Diabetes Mellitus Tipo 2 , Resistencia a la Insulina , Humanos , Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/prevención & control , Estudios Prospectivos , Estudios Transversales , Obesidad/epidemiología , Obesidad/prevención & control , Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/prevención & control , Ácidos Grasos , Ensayos Clínicos Controlados Aleatorios como AsuntoRESUMEN
Although the physiological role of glucagon receptor signaling in the liver is well defined, the impact of glucagon receptor (Gcgr) signaling on white adipose tissue (WAT) continues to be debated. Although numerous studies propose that glucagon stimulates WAT lipolysis, we lack evidence that physiological concentrations of glucagon regulate WAT lipolysis. In turn, we performed studies in both wild-type and WAT Gcgr knockout mice to determine if glucagon regulates lipolysis at WAT in the mouse. We assessed the effects of fasting and acute exogenous glucagon administration in wild-type C57BL/6J and GcgrAdipocyte+/+ versus GcgrAdipocyte-/- mice. Using an ex vivo lipolysis protocol, we further examined the direct effects of glucagon on physiologically (fasted) and pharmacologically stimulated lipolysis. We found that adipocyte Gcgr expression did not affect fasting-induced lipolysis or hepatic lipid accumulation in lean or diet-induced obese (DIO) mice. Acute glucagon administration did not affect serum nonesterified fatty acids (NEFA), leptin, or adiponectin concentration, but did increase serum glucose and FGF21, regardless of genotype. Glucagon did not affect ex vivo lipolysis in explants from either GcgrAdipocyte+/+ or GcgrAdipocyte-/- mice. Gcgr expression did not affect fasting-induced or isoproterenol-stimulated lipolysis from WAT explants. Moreover, glucagon receptor signaling at WAT did not affect body weight or glucose homeostasis in lean or DIO mice. Our studies have established that physiological levels of glucagon do not regulate WAT lipolysis, either directly or indirectly. Given that glucagon receptor agonism can improve dyslipidemia and decrease hepatic lipid accumulation, it is critical to understand the tissue-specific effects of glucagon receptor action. Unlike the crucial role of hepatic glucagon receptor signaling in maintaining glucose and lipid homeostasis, we observed no metabolic consequence of WAT glucagon receptor deletion.NEW & NOTEWORTHY It has been postulated that glucagon stimulates lipolysis and fatty acid release from white adipose tissue. We observed no metabolic effects of eliminating or activating glucagon receptor signaling at white adipose tissue.
Asunto(s)
Glucagón , Receptores de Glucagón , Adiponectina/metabolismo , Tejido Adiposo/metabolismo , Tejido Adiposo Blanco/metabolismo , Animales , Ácidos Grasos no Esterificados/metabolismo , Glucagón/metabolismo , Glucosa/metabolismo , Isoproterenol , Leptina/metabolismo , Lipólisis , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Obesos , Receptores de Glucagón/genética , Receptores de Glucagón/metabolismoRESUMEN
The incretin hormone glucose-dependent insulinotropic polypeptide (GIP) augments glucose-dependent insulin secretion through its receptor expressed on islet ß-cells. GIP also acts on adipose tissue; yet paradoxically, both enhanced and reduced GIP receptor (GIPR) signaling reduce adipose tissue mass and attenuate weight gain in response to nutrient excess. Moreover, the precise cellular localization of GIPR expression within white adipose tissue (WAT) remains uncertain. We used mouse genetics to target Gipr expression within adipocytes. Surprisingly, targeting Cre expression to adipocytes using the adiponectin (Adipoq) promoter did not produce meaningful reduction of WAT Gipr expression in Adipoq-Cre:Giprflx/flx mice. In contrast, adenoviral expression of Cre under the control of the cytomegalovirus promoter, or transgenic expression of Cre using nonadipocyte-selective promoters (Ap2/Fabp4 and Ubc) markedly attenuated WAT Gipr expression. Analysis of single-nucleus RNA-sequencing, adipose tissue data sets localized Gipr/GIPR expression predominantly to pericytes and mesothelial cells rather than to adipocytes. Together, these observations reveal that adipocytes are not the major GIPR+ cell type within WAT-findings with mechanistic implications for understanding how GIP and GIP-based co-agonists control adipose tissue biology.
Asunto(s)
Receptores de la Hormona Gastrointestinal , Tejido Adiposo Blanco/metabolismo , Animales , Polipéptido Inhibidor Gástrico/metabolismo , Glucosa , Ratones , Receptores de la Hormona Gastrointestinal/genética , Receptores de la Hormona Gastrointestinal/metabolismoRESUMEN
Glucocorticoids (GCs) are hormones that aid the body under stress by regulating glucose and free fatty acids. GCs maintain energy homeostasis in multiple tissues, including those in the liver and skeletal muscle, white adipose tissue (WAT), and brown adipose tissue (BAT). WAT stores energy as triglycerides, while BAT uses fatty acids for heat generation. The multiple genomic and non-genomic pathways in GC signaling vary with exposure duration, location (adipose tissue depot), and species. Genomic effects occur directly through the cytosolic GC receptor (GR), regulating the expression of proteins related to lipid metabolism, such as ATGL and HSL. Non-genomic effects act through mechanisms often independent of the cytosolic GR and happen shortly after GC exposure. Studying the effects of GCs on adipose tissue breakdown and generation (lipolysis and adipogenesis) leads to insights for treatment of adipose-related diseases, such as obesity, coronary disease, and cancer, but has led to controversy among researchers, largely due to the complexity of the process. This paper reviews the recent literature on the genomic and non-genomic effects of GCs on WAT and BAT lipolysis and proposes research to address the many gaps in knowledge related to GC activity and its effects on disease.
Asunto(s)
Tejido Adiposo Pardo/metabolismo , Tejido Adiposo Blanco/metabolismo , Genómica , Glucocorticoides , Lipogénesis , Lipólisis , Animales , Glucocorticoides/genética , Glucocorticoides/metabolismo , HumanosRESUMEN
OBJECTIVE: Glucose-dependent insulinotropic polypeptide (GIP) and Glucagon-like peptide-1 (GLP-1) are incretin hormones that exert overlapping yet distinct actions on islet ß-cells. We recently observed that GIP, but not GLP-1, upregulated islet expression of Transcription Factor 7 (TCF7), a gene expressed in immune cells and associated with the risk of developing type 1 diabetes. TCF7 has also been associated with glucose homeostasis control in the liver. Herein we studied the relative metabolic importance of TCF7 expression in hepatocytes vs. islet ß-cells in mice. METHODS: Tcf7 expression was selectively inactivated in adult mouse hepatocytes using adenoviral Cre expression and targeted in ß-cells using two different lines of insulin promoter-Cre mice. Glucose homeostasis, plasma insulin and triglyceride responses, islet histology, hepatic and islet gene expression, and body weight gain were evaluated in mice fed regular chow or high fat diets. Tcf7 expression within pancreatic islets and immune cells was evaluated using published single cell RNA-seq (scRNA-seq) data, and in islet RNA from immunodeficient Rag2-/-Il2rg-/- mice. RESULTS: Reduction of hepatocyte Tcf7 expression did not impair glucose homeostasis, lipid tolerance or hepatic gene expression profiles linked to control of metabolic or immune pathways. Similarly, oral and intraperitoneal glucose tolerance, plasma insulin responses, islet histology, body weight gain, and insulin tolerance were not different in mice with targeted recombination of Tcf7 in insulin-positive ß-cells. Surprisingly, islet Tcf7 mRNA transcripts were not reduced in total islet RNA containing endocrine and associated non-endocrine cell types from Tcf7ßcell-/- mice, despite Cre-mediated recombination of islet genomic DNA. Furthermore, glucose tolerance was normal in whole body Tcf7-/- mice. Analysis of scRNA-seq datasets localized pancreatic Tcf7 expression to islet progenitors during development, and immune cells, but not within differentiated islet ß-cells or endocrine lineages within mature islets. Moreover, the expression of Tcf7 was extremely low in islet RNA from Rag2-/-Il2rg-/- mice and, consistent with expression within immune cells, Tcf7 was highly correlated with levels of Cd3g mRNA transcripts in RNA from wild type mouse islets. CONCLUSIONS: These findings demonstrate that Tcf7 expression is not a critical determinant of glucose homeostasis in mice. Moreover, the detection of Tcf7 expression within islet mRNA is attributable to the expression of Tcf7 RNA in islet-associated murine immune cells, and not in islet ß-cells.
Asunto(s)
Glucemia/metabolismo , Factor Nuclear 1-alfa del Hepatocito/metabolismo , Hepatocitos/metabolismo , Homeostasis/genética , Células Secretoras de Insulina/metabolismo , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Animales , Células Cultivadas , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Dieta Alta en Grasa/efectos adversos , Modelos Animales de Enfermedad , Femenino , Expresión Génica , Factor Nuclear 1-alfa del Hepatocito/genética , Insulina/sangre , Insulina/genética , Subunidad gamma Común de Receptores de Interleucina/genética , Subunidad gamma Común de Receptores de Interleucina/metabolismo , Linfocitos/metabolismo , Masculino , Ratones , Ratones Noqueados , Enfermedad del Hígado Graso no Alcohólico/genética , Triglicéridos/sangre , Aumento de Peso/genéticaRESUMEN
Postprandial triglycerides (TGs) are elevated in people with type 2 diabetes (T2D). Glucose-lowering agents, such as glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors, also reduce postprandial TG excursion. Although the glucose-lowering mechanisms of DPP-4 have been extensively studied, how the reduction of DPP-4 activity improves lipid tolerance remains unclear. Here, we demonstrate that gut-selective and systemic inhibition of DPP-4 activity reduces postprandial TG excursion in young mice. Genetic inactivation of Dpp4 simultaneously within endothelial cells and hematopoietic cells using Tie2-Cre reduced intestinal lipoprotein secretion under regular chow diet conditions. Bone marrow transplantation revealed a key role for hematopoietic cells in modulation of lipid responses arising from genetic reduction of DPP-4 activity. Unexpectedly, deletion of Dpp4 in enterocytes increased TG excursion in high-fat diet-fed (HFD-fed) mice. Moreover, chemical reduction of DPP-4 activity and increased levels of GLP-1 were uncoupled from TG excursion in older or HFD-fed mice, yet lipid tolerance remained improved in older Dpp4-/- and Dpp4EC-/- mice. Taken together, this study defines roles for specific DPP-4 compartments, age, and diet as modifiers of DPP-4 activity linked to control of gut lipid metabolism.
Asunto(s)
Dipeptidil Peptidasa 4/metabolismo , Enterocitos/enzimología , Triglicéridos/metabolismo , Animales , Trasplante de Médula Ósea , Dieta Alta en Grasa/efectos adversos , Dipeptidil Peptidasa 4/sangre , Dipeptidil Peptidasa 4/genética , Dipeptidil Peptidasa 4/aislamiento & purificación , Inhibidores de la Dipeptidil-Peptidasa IV/farmacología , Péptido 1 Similar al Glucagón/sangre , Células Madre Hematopoyéticas/enzimología , Mucosa Intestinal/enzimología , Mucosa Intestinal/metabolismo , Metabolismo de los Lípidos/efectos de los fármacos , Metabolismo de los Lípidos/fisiología , Masculino , Ratones Endogámicos C57BL , Ratones Mutantes , Ratones Transgénicos , Periodo Posprandial/efectos de los fármacos , Periodo Posprandial/fisiología , Fosfato de Sitagliptina/farmacologíaRESUMEN
Proglucagon-derived peptides (PGDPs) and related gut hormones exemplified by glucose-dependent insulinotropic polypeptide (GIP) regulate energy disposal and storage through actions on metabolically sensitive organs, including adipose tissue. The actions of glucagon, glucagon-like peptide (GLP)-1, GLP-2, GIP, and their rate-limiting enzyme dipeptidyl peptidase-4, include direct and indirect regulation of islet hormone secretion, food intake, body weight, all contributing to control of white and brown adipose tissue activity. Moreover, agents mimicking actions of these peptides are in use for the therapy of metabolic disorders with disordered energy homeostasis such as diabetes, obesity, and intestinal failure. Here we highlight current concepts and mechanisms for direct and indirect actions of these peptides on adipose tissue depots. The available data highlight the importance of indirect peptide actions for control of adipose tissue biology, consistent with the very low level of endogenous peptide receptor expression within white and brown adipose tissue depots. Finally, we discuss limitations and challenges for the interpretation of available experimental observations, coupled to identification of enduring concepts supported by more robust evidence.
Asunto(s)
Tejido Adiposo/metabolismo , Dipeptidil Peptidasa 4/metabolismo , Polipéptido Inhibidor Gástrico/metabolismo , Glucosa/metabolismo , Proglucagón/metabolismo , Animales , Humanos , Proglucagón/químicaRESUMEN
Adipokines secreted from white adipose tissue play a role in metabolic crosstalk and homeostasis, whereas the brown adipose secretome is less explored. We performed high-sensitivity mass-spectrometry-based proteomics on the cell media of human adipocytes derived from the supraclavicular brown adipose and from the subcutaneous white adipose depots of adult humans. We identified 471 potentially secreted proteins covering interesting categories such as hormones, growth factors, extracellular matrix proteins, and proteins of the complement system, which were differentially regulated between brown and white adipocytes. A total of 101 proteins were exclusively quantified in brown adipocytes, and among these was ependymin-related protein 1 (EPDR1). EPDR1 was detected in human plasma, and functional studies suggested a role for EPDR1 in thermogenic determination during adipogenesis. In conclusion, we report substantial differences between the secretomes of brown and white human adipocytes and identify novel candidate batokines that can be important regulators of human metabolism.
Asunto(s)
Adipocitos Marrones/metabolismo , Adipocitos Blancos/metabolismo , Tejido Adiposo Pardo/metabolismo , Proteínas de Neoplasias/sangre , Proteómica/métodos , Adulto , Anciano , Animales , Estudios de Cohortes , Femenino , Técnicas de Silenciamiento del Gen , Bocio/sangre , Bocio/patología , Bocio/cirugía , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , Proteínas de Neoplasias/genética , Proteínas del Tejido Nervioso , Vías Secretoras/genética , Transducción de Señal/genética , Transfección , Adulto JovenRESUMEN
OBJECTIVE: Glucose-dependent insulinotropic polypeptide (GIP) is secreted from the gut in response to nutrient ingestion and promotes meal-dependent insulin secretion and lipid metabolism. Loss or attenuation of GIP receptor (GIPR) action leads to resistance to diet-induced obesity through incompletely understood mechanisms. The GIPR is expressed in white adipose tissue; however, its putative role in brown adipose tissue (BAT) has not been explored. METHODS: We investigated the role of the GIPR in BAT cells in vitro and in BAT-specific (GiprBAT-/-) knockout mice with selective elimination of the Gipr within the Myf5+ expression domain. We analyzed body weight, adiposity, glucose homeostasis, insulin and lipid tolerance, energy expenditure, food intake, body temperature, and iBAT oxygen consumption ex vivo. High-fat diet (HFD)-fed GiprBAT-/- mice were studied at room temperature (21 °C), 4 °C, and 30 °C ambient temperatures. RESULTS: The mouse Gipr gene is expressed in BAT, and GIP directly increased Il6 mRNA and IL-6 secretion in BAT cells. Additionally, levels of thermogenic, lipid and inflammation mRNA transcripts were altered in BAT cells transfected with Gipr siRNA. Body weight gain, energy expenditure, and glucose and insulin tolerance were normal in HFD-fed GiprBAT-/- mice housed at room temperature. However, GiprBAT-/- mice exhibited higher body temperatures during an acute cold challenge and a lower respiratory exchange ratio and impaired lipid tolerance at 21 °C. In contrast, body weight was lower and iBAT oxygen consumption was higher in HFD-fed mice housed at 4 °C but not at 30 °C. CONCLUSIONS: The BAT GIPR is linked to the control of metabolic gene expression, fuel utilization, and oxygen consumption. However, the selective loss of the GIPR within BAT is insufficient to recapitulate the findings of decreased weight gain and resistance to obesity arising in experimental models with systemic disruption of GIP action.
Asunto(s)
Tejido Adiposo Pardo/metabolismo , Receptores de la Hormona Gastrointestinal/metabolismo , Animales , Línea Celular , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
OBJECTIVE: Administration of glucagon (GCG) or GCG-containing co-agonists reduces body weight and increases energy expenditure. These actions appear to be transduced by multiple direct and indirect GCG receptor (GCGR)-dependent mechanisms. Although the canonical GCGR is expressed in brown adipose tissue (BAT) the importance of BAT GCGR activity for the physiological control of body weight, or the response to GCG agonism, has not been defined. METHODS: We studied the mechanisms linking GCG action to acute increases in oxygen consumption using wildtype (WT), Ucp1-/- and Fgf21-/- mice. The importance of basal GCGR expression within the Myf5+ domain for control of body weight, adiposity, glucose and lipid metabolism, food intake, and energy expenditure was examined in GcgrBAT-/- mice housed at room temperature or 4 °C, fed a regular chow diet (RCD) or after a prolonged exposure to high fat diet (HFD). RESULTS: Acute GCG administration induced lipolysis and increased the expression of thermogenic genes in BAT cells, whereas knockdown of Gcgr reduced expression of genes related to thermogenesis. GCG increased energy expenditure (measured by oxygen consumption) both in vivo in WT mice and ex vivo in BAT and liver explants. GCG also increased acute energy expenditure in Ucp1-/- mice, but these actions were partially blunted in Ffg21-/- mice. However, acute GCG administration also robustly increased oxygen consumption in GcgrBAT-/- mice. Moreover, body weight, glycemia, lipid metabolism, body temperature, food intake, activity, energy expenditure and adipose tissue gene expression profiles were normal in GcgrBAT-/- mice, either on RCD or HFD, whether studied at room temperature, or chronically housed at 4 °C. CONCLUSIONS: Exogenous GCG increases oxygen consumption in mice, also evident both in liver and BAT explants ex vivo, through UCP1-independent, FGF21-dependent pathways. Nevertheless, GCGR signaling within BAT is not physiologically essential for control of body weight, whole body energy expenditure, glucose homeostasis, or the adaptive metabolic response to cold or prolonged exposure to an energy dense diet.
Asunto(s)
Tejido Adiposo Pardo/metabolismo , Metabolismo Energético , Homeostasis , Receptores de Glucagón/metabolismo , Animales , Frío , Masculino , Ratones , Ratones NoqueadosRESUMEN
OBJECTIVE: Fibroblast Activation Protein (FAP), an enzyme structurally related to dipeptidyl peptidase-4 (DPP-4), has garnered interest as a potential metabolic drug target due to its ability to cleave and inactivate FGF-21 as well as other peptide substrates. Here we investigated the metabolic importance of FAP for control of body weight and glucose homeostasis in regular chow-fed and high fat diet-fed mice. METHODS: FAP enzyme activity was transiently attenuated using a highly-specific inhibitor CPD60 and permanently ablated by genetic inactivation of the mouse Fap gene. We also assessed the FAP-dependence of CPD60 and talabostat (Val-boroPro), a chemical inhibitor reportedly targeting both FAP and dipeptidyl peptidase-4 RESULTS: CPD60 robustly inhibited plasma FAP activity with no effect on DPP-4 activity. Fap gene disruption was confirmed by assessment of genomic DNA, and loss of FAP enzyme activity in plasma and tissues. CPD60 did not improve lipid tolerance but modestly improved acute oral and intraperitoneal glucose tolerance in a FAP-dependent manner. Genetic inactivation of Fap did not improve glucose or lipid tolerance nor confer resistance to weight gain in male or female Fap-/- mice fed regular chow or high-fat diets. Moreover, talabostat markedly improved glucose homeostasis in a FAP- and FGF-21-independent, DPP-4 dependent manner. CONCLUSION: Although pharmacological FAP inhibition improves glucose tolerance, the absence of a metabolic phenotype in Fap-/-mice suggest that endogenous FAP is dispensable for the regulation of murine glucose homeostasis and body weight. These findings highlight the importance of characterizing the specificity and actions of FAP inhibitors in different species and raise important questions about the feasibility of mouse models for targeting FAP as a treatment for diabetes and related metabolic disorders.
Asunto(s)
Dipeptidil Peptidasa 4/metabolismo , Gelatinasas/metabolismo , Glucosa/metabolismo , Proteínas de la Membrana/metabolismo , Serina Endopeptidasas/metabolismo , Animales , Glucemia/metabolismo , Peso Corporal/fisiología , Diabetes Mellitus/tratamiento farmacológico , Dieta Alta en Grasa , Dipeptidil Peptidasa 4/sangre , Inhibidores de la Dipeptidil-Peptidasa IV/administración & dosificación , Endopeptidasas , Femenino , Factores de Crecimiento de Fibroblastos/metabolismo , Gelatinasas/fisiología , Péptido 1 Similar al Glucagón/sangre , Homeostasis/fisiología , Insulina/metabolismo , Masculino , Proteínas de la Membrana/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Serina Endopeptidasas/fisiología , Aumento de PesoRESUMEN
Dipeptidyl peptidase-4 (DPP-4) controls glucose homeostasis through enzymatic termination of incretin action. We report that plasma DPP-4 activity correlates with body weight and fat mass, but not glucose control, in mice. Genetic disruption of adipocyte Dpp4 expression reduced plasma DPP-4 activity in older mice but did not perturb incretin levels or glucose homeostasis. Knockdown of hepatocyte Dpp4 completely abrogated the obesity-associated increase in plasma DPP-4 activity, reduced liver cytokine expression, and partially attenuated inflammation in adipose tissue without changes in incretin levels or glucose homeostasis. In contrast, circulating levels of soluble DPP4 (sDPP4) were dissociated from inflammation in mice with endothelial-selective or global genetic inactivation of Dpp4. Remarkably, inhibition of DPP-4 enzymatic activity upregulated circulating levels of sDPP4 originating from endothelial or hematopoietic cells without inducing systemic or localized inflammation. Collectively, these findings reveal unexpected complexity in regulation of soluble versus enzymatic DPP-4 and control of inflammation and glucose homeostasis.
Asunto(s)
Dipeptidil Peptidasa 4/fisiología , Glucosa/metabolismo , Hepatocitos/metabolismo , Incretinas/metabolismo , Inflamación/inmunología , Obesidad/metabolismo , Células 3T3-L1 , Animales , Citocinas/metabolismo , Hepatocitos/citología , Ratones , Ratones Endogámicos C57BLRESUMEN
GPR119 was originally identified as an orphan ß-cell receptor; however, subsequent studies demonstrated that GPR119 also regulates ß-cell function indirectly through incretin hormone secretion. We assessed the importance of GPR119 for ß-cell function in Gpr119-/- mice and in newly generated Gpr119ßcell-/- mice. Gpr119-/- mice displayed normal body weight and glucose tolerance on a regular chow (RC) diet. After high-fat feeding, Gpr119-/- mice exhibited reduced fat mass, decreased levels of circulating adipokines, improved insulin sensitivity, and better glucose tolerance. Unexpectedly, oral and intraperitoneal glucose tolerance and the insulin response to glycemic challenge were not perturbed in Gpr119ßcell-/- mice on RC and high-fat diets. Moreover, islets from Gpr119-/- and Gpr119ßcell-/- mice exhibited normal insulin responses to glucose and ß-cell secretagogues. Furthermore, the selective GPR119 agonist AR231453 failed to directly enhance insulin secretion from perifused islets. In contrast, AR231453 increased plasma glucagon-like peptide 1 (GLP-1) and insulin levels and improved glucose tolerance in wild-type and Gpr119ßcell-/- mice. These findings demonstrate that ß-cell GPR119 expression is dispensable for the physiological control of insulin secretion and the pharmacological response to GPR119 agonism, findings that may inform the lack of robust efficacy in clinical programs assessing GPR119 agonists for the therapy of type 2 diabetes.
Asunto(s)
Glucemia/metabolismo , Diabetes Mellitus Experimental/metabolismo , Péptido 1 Similar al Glucagón/metabolismo , Resistencia a la Insulina , Células Secretoras de Insulina/metabolismo , Receptores Acoplados a Proteínas G/genética , Adipoquinas/metabolismo , Animales , Apoptosis , Dieta Alta en Grasa , Perfilación de la Expresión Génica , Glucagón/metabolismo , Péptido 1 Similar al Glucagón/efectos de los fármacos , Glucosa/metabolismo , Prueba de Tolerancia a la Glucosa , Incretinas/metabolismo , Insulina/metabolismo , Secreción de Insulina , Masculino , Ratones Noqueados , Oxadiazoles/farmacología , Pirimidinas/farmacología , Receptores Acoplados a Proteínas G/agonistasRESUMEN
Severe caloric restriction (CR), in a setting of regular physical exercise, may be a stress that sets the stage for adiposity rebound and insulin resistance when the food restriction and exercise stop. In this study, we examined the effect of mifepristone, a glucocorticoid (GC) receptor antagonist, on limiting adipose tissue mass gain and preserving whole body insulin sensitivity following the cessation of daily running and CR. We calorically restricted male Sprague-Dawley rats and provided access to voluntary running wheels for 3 wk followed by locking of the wheels and reintroduction to ad libitum feeding with or without mifepristone (80 mg·kg(-1)·day(-1)) for 1 wk. Cessation of daily running and CR increased HOMA-IR and visceral adipose mass as well as glucose and insulin area under the curve during an oral glucose tolerance test vs. pre-wheel lock exercised rats and sedentary rats (all P < 0.05). Insulin sensitivity and glucose tolerance were preserved and adipose tissue mass gain was attenuated by daily mifepristone treatment during the post-wheel lock period. These findings suggest that following regular exercise and CR there are GC-induced mechanisms that promote adipose tissue mass gain and impaired metabolic control in healthy organisms and that this phenomenon can be inhibited by the GC receptor antagonist mifepristone.