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OBJECTIVE: Recombinant adeno-associated virus (rAAV) vectors are powerful tools for the sustained expression of proteins in vivo and have been successfully used for mechanistic studies in mice. A major challenge associated with this method is to obtain tissue specificity and high expression levels without need of local virus administration. METHODS: To achieve this goal for brown adipose tissue (BAT), we developed a rAAV vector for intravenous bolus injection, which includes an expression cassette comprising an uncoupling protein-1 enhancer-promoter for transcription in brown adipocytes and miR122 target sequences for suppression of expression in the liver, combined with packaging in serotype Rec2 capsid protein. To test tissue specificity, we used a version of this vector expressing Cre recombinase to transduce mice with floxed alleles to knock out MLXIPL (ChREBP) or tdTomato-Cre reporter mice. RESULTS: We demonstrated efficient Cre-dependent recombination in interscapular BAT and variable effects in minor BAT depots, but little or no efficacy in white adipose tissues, liver and other organs. Direct overexpression of glucose transporter SLC2A1 (GLUT1) using the rAAV vector in wild type mice resulted in increased glucose uptake and glucose-dependent gene expression in BAT, indicating usefulness of this vector to increase the function even of abundant proteins. CONCLUSION: Taken together, we describe a novel brown adipocyte-specific rAAV method to express proteins for loss-of-function and gain-of-function metabolic studies. The approach will enable researchers to access brown fat swiftly, reduce animal breeding time and costs, as well as enable the creation of new transgenic mouse models combining multiple transgenes.
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BACKGROUND: Lipids, including phospholipids and bile acids, exert various signaling effects and are thought to contribute to the development of coronary artery disease (CAD). Here, we aimed to compare lipidomic and bile acid profiles in the blood of patients with and without CAD stratified by sex. METHODS: From 2015 to 2022, 3,012 patients who underwent coronary angiography were recruited in the INTERCATH cohort. From the overall cohort, subgroups were defined using patient characteristics such as CAD vs. no CAD, 1st vs. 3rd tertile of LDL-c, and female vs. male sex. Hereafter, a matching algorithm based on age, BMI, hypertension status, diabetes mellitus status, smoking status, the Mediterranean diet score, and the intake of statins, triglycerides, HDL-c and hs-CRP in a 1:1 ratio was implemented. Lipidomic analyses of stored blood samples using the Lipidyzer platform (SCIEX) and bile acid analysis using liquid chromatography with tandem mass spectrometry (LCâMS/MS) were carried out. RESULTS: A total of 177 matched individuals were analyzed; the median ages were 73.5 years (25th and 75th percentile: 64.1, 78.2) and 71.9 years (65.7, 77.2) for females and males with CAD, respectively, and 67.6 years (58.3, 75.3) and 69.2 years (59.8, 76.8) for females and males without CAD, respectively. Further baseline characteristics, including cardiovascular risk factors, were balanced between the groups. Women with CAD had decreased levels of phosphatidylcholine and diacylglycerol, while no differences in bile acid profiles were detected in comparison to those of female patients without CAD. In contrast, in male patients with CAD, decreased concentrations of the secondary bile acid species glycolithocholic and lithocholic acid, as well as altered levels of specific lipids, were detected compared to those in males without CAD. Notably, male patients with low LDL-c and CAD had significantly greater concentrations of various phospholipid species, particularly plasmalogens, compared to those in high LDL-c subgroup. CONCLUSIONS: We present hypothesis-generating data on sex-specific lipidomic patterns and bile acid profiles in CAD patients. The data suggest that altered lipid and bile acid composition might contribute to CAD development and/or progression, helping to understand the different disease trajectories of CAD in women and men. REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT04936438 , Unique identifier: NCT04936438.
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Ácidos e Sais Biliares , Doença da Artéria Coronariana , Lipidômica , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ácidos e Sais Biliares/sangue , HDL-Colesterol/sangue , LDL-Colesterol/sangue , Doença da Artéria Coronariana/sangue , Caracteres Sexuais , Fatores Sexuais , Espectrometria de Massas em Tandem , Triglicerídeos/sangue , Estudos de CoortesRESUMO
Macrophages are functionally heterogeneous cells essential for apoptotic cell clearance. Apoptotic cells are defined by homogeneous characteristics, ignoring their original cell lineage identity. We found that in an interleukin-4 (IL-4)-enriched environment, the sensing of apoptotic neutrophils by macrophages triggered their tissue remodeling signature. Engulfment of apoptotic hepatocytes promoted a tolerogenic phenotype, whereas phagocytosis of T cells had little effect on IL-4-induced gene expression. In a mouse model of parasite-induced pathology, the transfer of macrophages conditioned with IL-4 and apoptotic neutrophils promoted parasitic egg clearance. Knockout of phagocytic receptors required for the uptake of apoptotic neutrophils and partially T cells, but not hepatocytes, exacerbated helminth infection. These findings suggest that the identity of apoptotic cells may contribute to the development of distinct IL-4-driven immune programs in macrophages.
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Apoptose , Interleucina-4 , Macrófagos , Fagocitose , Esquistossomose mansoni , Animais , Camundongos , Apoptose/imunologia , Hepatócitos/imunologia , Interleucina-4/genética , Interleucina-4/metabolismo , Macrófagos/imunologia , Camundongos Knockout , Neutrófilos/imunologia , Fagocitose/imunologia , Esquistossomose mansoni/genética , Esquistossomose mansoni/imunologia , Modelos Animais de DoençasRESUMO
Introduction: During thermogenesis, adipose tissue (AT) becomes more active and enhances oxidative metabolism. The promotion of this process in white AT (WAT) is called "browning" and, together with the brown AT (BAT) activation, is considered as a promising approach to counteract obesity and metabolic diseases. Transient receptor potential cation channel, subfamily M, member 2 (TRPM2), is an ion channel that allows extracellular Ca2+ influx into the cytosol, and is gated by adenosine diphosphate ribose (ADPR), produced from NAD+ degradation. The aim of this study was to investigate the relevance of TRPM2 in the regulation of energy metabolism in BAT, WAT, and liver during thermogenesis. Methods: Wild type (WT) and Trpm2-/- mice were exposed to 6°C and BAT, WAT and liver were collected to evaluate mRNA, protein levels and ADPR content. Furthermore, O2 consumption, CO2 production and energy expenditure were measured in these mice upon thermogenic stimulation. Finally, the effect of the pharmacological inhibition of TRPM2 was assessed in primary adipocytes, evaluating the response upon stimulation with the ß-adrenergic receptor agonist CL316,243. Results: Trpm2-/- mice displayed lower expression of browning markers in AT and lower energy expenditure in response to thermogenic stimulus, compared to WT animals. Trpm2 gene overexpression was observed in WAT, BAT and liver upon cold exposure. In addition, ADPR levels and mono/poly-ADPR hydrolases expression were higher in mice exposed to cold, compared to control mice, likely mediating ADPR generation. Discussion: Our data indicate TRPM2 as a fundamental player in BAT activation and WAT browning. TRPM2 agonists may represent new pharmacological strategies to fight obesity.
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Canais de Cátion TRPM , Camundongos , Animais , Canais de Cátion TRPM/genética , Canais de Cátion TRPM/metabolismo , Tecido Adiposo Marrom/metabolismo , Tecido Adiposo Branco/metabolismo , Obesidade/genética , Obesidade/metabolismo , Termogênese/genéticaRESUMO
Dietary polyunsaturated fatty acids (PUFA) are increasingly recognized for their health benefits, whereas a high production of endogenous fatty acids - a process called de novo lipogenesis (DNL) - is closely linked to metabolic diseases. Determinants of PUFA incorporation into complex lipids are insufficiently understood and may influence the onset and progression of metabolic diseases. Here we show that fatty acid synthase (FASN), the key enzyme of DNL, critically determines the use of dietary PUFA in mice and humans. Moreover, the combination of FASN inhibition and PUFA-supplementation decreases liver triacylglycerols (TAG) in mice fed with high-fat diet. Mechanistically, FASN inhibition causes higher PUFA uptake via the lysophosphatidylcholine transporter MFSD2A, and a diacylglycerol O-acyltransferase 2 (DGAT2)-dependent incorporation of PUFA into TAG. Overall, the outcome of PUFA supplementation may depend on the degree of endogenous DNL and combining PUFA supplementation and FASN inhibition might be a promising approach to target metabolic disease.
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Ácidos Graxos Ômega-3 , Doenças Metabólicas , Camundongos , Humanos , Animais , Lipogênese , Ácidos Graxos Ômega-3/farmacologia , Ácidos Graxos Ômega-3/metabolismo , Ácidos Graxos Insaturados , Triglicerídeos/metabolismo , Ácidos Graxos , Dieta Hiperlipídica/efeitos adversosRESUMO
Adenine nucleotides (AN) are ubiquitous metabolites that regulate cellular energy metabolism and modulate cell communication and inflammation. To understand how disturbances in AN balance arise and affect cellular function, robust quantification techniques for these metabolites are crucial. However, due to their hydrophilicity, simultaneous quantification of AN across various biological samples has been challenging. Here we present a hydrophilic interaction high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) based method for the quantification of 26 adenosine nucleotides and precursors as well as metabolic products of nicotinamide adenine dinucleotide (NAD) in plasma, liver, and adipose tissue samples as well as cell culture supernatants and cells. Method validation was performed with regard to linearity, accuracy, precision, matrix effects, and carryover. Finally, analysis of cell culture supernatants derived from intestinal organoids and RAW 264.7 cells illustrates that the here described method is a reliable and easy-to-use tool to quantify AN and opens up new avenues to understand the role of AN generation and breakdown for cellular functions.
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NAD , Nucleotídeos , NAD/metabolismo , Nucleotídeos/metabolismo , Espectrometria de Massas em Tandem/métodos , Adenosina , Cromatografia Líquida/métodos , Nucleotídeos de AdeninaRESUMO
Omnivorous animals, including mice and humans, tend to prefer energy-dense nutrients rich in fat over plant-based diets, especially for short periods of time, but the health consequences of this short-term consumption of energy-dense nutrients are unclear. Here, we show that short-term reiterative switching to 'feast diets', mimicking our social eating behavior, breaches the potential buffering effect of the intestinal microbiota and reorganizes the immunological architecture of mucosa-associated lymphoid tissues. The first dietary switch was sufficient to induce transient mucosal immune depression and suppress systemic immunity, leading to higher susceptibility to Salmonella enterica serovar Typhimurium and Listeria monocytogenes infections. The ability to respond to antigenic challenges with a model antigen was also impaired. These observations could be explained by a reduction of CD4+ T cell metabolic fitness and cytokine production due to impaired mTOR activity in response to reduced microbial provision of fiber metabolites. Reintroducing dietary fiber rewired T cell metabolism and restored mucosal and systemic CD4+ T cell functions and immunity. Finally, dietary intervention with human volunteers confirmed the effect of short-term dietary switches on human CD4+ T cell functionality. Therefore, short-term nutritional changes cause a transient depression of mucosal and systemic immunity, creating a window of opportunity for pathogenic infection.
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Mucosa , Salmonella typhimurium , Humanos , Camundongos , Animais , Linfócitos T , Imunidade nas MucosasRESUMO
Nonalcoholic fatty liver disease (NAFLD) is the most common liver pathology worldwide. In mice and humans, NAFLD progression is characterized by the appearance of TREM2-expressing macrophages in the liver. However, their mechanistic contributions to disease progression have not been completely elucidated. Here, we show that TREM2+ macrophages prevent the generation of a pro-inflammatory response elicited by LPS-laden lipoproteins in vitro. Further, Trem2 expression regulates bone-marrow-derived macrophages (BMDMs) and Kupffer cell capacity to phagocyte apoptotic cells in vitro, which is dependent on CD14 activation. In line with this, loss of Trem2 resulted in an increased pro-inflammatory response, which ultimately aggravated liver fibrosis in murine models of NAFLD. Similarly, in a human NAFLD cohort, plasma levels of TREM2 were increased and hepatic TREM2 expression was correlated with higher levels of liver triglycerides and the acquisition of a fibrotic gene signature. Altogether, our results suggest that TREM2+ macrophages have a protective function during the progression of NAFLD, as they are involved in the processing of pro-inflammatory lipoproteins and phagocytosis of apoptotic cells and, thereby, are critical contributors for the re-establishment of liver homeostasis.
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Hepatopatia Gordurosa não Alcoólica , Humanos , Camundongos , Animais , Hepatopatia Gordurosa não Alcoólica/metabolismo , Cirrose Hepática/patologia , Macrófagos/metabolismo , Apoptose , Glicoproteínas de Membrana/genética , Receptores ImunológicosRESUMO
Brown adipose tissue (BAT) has emerged as an appealing therapeutic target for cardio metabolic diseases. BAT is a heat-producing organ and upon activation substantially lowers hyperlipidemia. In response to cold exposure, not only the uptake of lipids into BAT is increased but also the Cyp7b1-mediated synthesis of bile acids (BA) from cholesterol in the liver is triggered. In addition to their role for intestinal lipid digestion, BA act as endocrine signals that can activate thermogenesis in BAT. When exposed to cold temperatures, Cyp7b1 -/- mice have compromised BAT function along with reduced fecal bile acid levels. Here, we aim to evaluate the role of Cyp7b1 for BAT-dependent lipid clearance. Using metabolic studies with radioactive tracers, we show that in response to a cold stimulus, BAT-mediated clearance of fatty acids derived from triglyceride-rich lipoproteins (TRL), and their remnants are reduced in Cyp7b1 -/- mice. The impaired lipid uptake can be explained by reduced BAT lipoprotein lipase (LPL) levels and compromised organ activity in Cyp7b1 -/- mice, which may be linked to impaired insulin signaling. Overall, our findings reveal that alterations of systemic lipoprotein metabolism mediated by cold-activated BAT are dependent, at least in part, on CYP7Β1.
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Short Chain Fatty Acids (SCFAs) are produced by the gut microbiota and are present in varying concentrations in the intestinal lumen, in feces but also in the circulatory system. By interacting with different cell types in the body, they have a great impact on host metabolism and their exact quantification is indispensable. Here, we present a derivatization-free method for the gas chromatography mass spectrometry (GC-MS) based quantification of SCFAs in plasma, feces, cecum, liver and adipose tissue. SCFAs were extracted using ethanol and concentrated by alkaline vacuum centrifugation. To allow volatility for separation by GC, samples were acidified with succinic acid. Analytes were detected in selected ion monitoring (SIM) mode and quantified using deuterated internal standards and external calibration curves. Method validation rendered excellent linearity (R2 > 0.99 for most analytes), good recovery rates (95-117%), and good reproducibility (RSD: 1-4.5%). Matrix effects were ruled out in plasma, feces, cecum, liver and fat tissues where most abundant SCFAs were detected and accurately quantified. Finally, applicability of the method was assessed using samples derived from conventionally raised versus germ-free mice or mice treated with antibiotics. Altogether, a reliable, fast, derivatization-free GC-MS method for the quantification of SCFAs in different biological matrices was developed allowing for the study of the (patho)physiological role of SCFAs in metabolic health.
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Activation of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) upon cold stimulation leads to substantial increase in energy expenditure to defend body temperature. Increases in energy expenditure after a high-caloric food intake, termed diet-induced thermogenesis, are also attributed to BAT. These properties render BAT a potential target to combat diet-induced obesity. However, studies investigating the role of UCP1 to protect against diet-induced obesity are controversial and rely on the phenotyping of a single constitutive UCP1-knockout model. To address this issue, we generated a novel UCP1-knockout model by Cre-mediated deletion of exon 2 in the UCP1 gene. We studied the effect of constitutive UCP1 knockout on metabolism and the development of diet-induced obesity. UCP1 knockout and wild-type mice were housed at 30°C and fed a control diet for 4 wk followed by 8 wk of high-fat diet. Body weight and food intake were monitored continuously over the course of the study, and indirect calorimetry was used to determine energy expenditure during both feeding periods. Based on Western blot analysis, thermal imaging and noradrenaline test, we confirmed the lack of functional UCP1 in knockout mice. However, body weight gain, food intake, and energy expenditure were not affected by loss of UCP1 function during both feeding periods. We introduce a novel UCP1-KO mouse enabling the generation of conditional UCP1-knockout mice to scrutinize the contribution of UCP1 to energy metabolism in different cell types or life stages. Our results demonstrate that UCP1 does not protect against diet-induced obesity at thermoneutrality.NEW & NOTEWORTHY We provide evidence that the abundance of UCP1 does not influence energy metabolism at thermoneutrality studying a novel Cre-mediated UCP1-KO mouse model. This model will be a foundation for a better understanding of the contribution of UCP1 in different cell types or life stages to energy metabolism.
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Dieta Hiperlipídica/efeitos adversos , Obesidade/etiologia , Obesidade/metabolismo , Temperatura , Proteína Desacopladora 1/metabolismo , Tecido Adiposo Marrom/metabolismo , Animais , Calorimetria Indireta/métodos , Suscetibilidade a Doenças/metabolismo , Ingestão de Alimentos/genética , Metabolismo Energético/genética , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/genética , Termogênese/genética , Proteína Desacopladora 1/genética , Aumento de Peso/genéticaRESUMO
Ambient temperature is an important determinant of both the alternative bile acid synthesis pathway controlled by oxysterol 7-α hydroxylase (CYP7B1) and the progression of metabolic-associated fatty liver disease (MAFLD). Here, we investigated whether CYP7B1 is involved in the etiology of MAFLD under conditions of low and high energy expenditure. For this, Cyp7b1-/- and wild type (WT) mice were fed a choline-deficient high-fat diet and housed either at 30 °C (thermoneutrality) or at 22 °C (mild cold). To study disease phenotype and underlying mechanisms, plasma and organ samples were analyzed to determine metabolic parameters, immune cell infiltration by immunohistology and flow cytometry, lipid species including hydroxycholesterols, bile acids and structural lipids. In WT and Cyp7b1-/- mice, thermoneutral housing promoted MAFLD, an effect that was more pronounced in CYP7B1-deficient mice. In these mice, we found higher plasma alanine aminotransferase activity, hyperlipidemia, hepatic accumulation of potentially harmful lipid species, aggravated liver fibrosis, increased inflammation and immune cell infiltration. Bile acids and hydroxycholesterols did not correlate with aggravated MAFLD in Cyp7b1-/- mice housed at thermoneutrality. Notably, an up-regulation of lipoprotein receptors was detected at 22 °C but not at 30 °C in livers of Cyp7b1-/- mice, suggesting that accelerated metabolism of lipoproteins carrying lipotoxic molecules counteracts MAFLD progression.
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Família 7 do Citocromo P450/metabolismo , Fígado Gorduroso/enzimologia , Fígado Gorduroso/metabolismo , Esteroide Hidroxilases/metabolismo , Temperatura , Animais , Biomarcadores/metabolismo , Família 7 do Citocromo P450/deficiência , Inflamação/patologia , Metabolismo dos Lipídeos , Fígado/metabolismo , Fígado/patologia , Cirrose Hepática/metabolismo , Cirrose Hepática/patologia , Camundongos , Camundongos Knockout , Fenótipo , Receptores de Lipoproteínas/metabolismo , Baço/imunologia , Esteroide Hidroxilases/deficiência , Regulação para CimaRESUMO
The physiologic activation of thermogenic brown and white adipose tissues (BAT/WAT) by cold exposure triggers heat production by adaptive thermogenesis, a process known to ameliorate hyperlipidemia and protect from atherosclerosis. Mechanistically, it has been shown that thermogenic activation increases lipoprotein lipase (LPL)-dependent hydrolysis of triglyceride-rich lipoproteins (TRL) and accelerates the generation of cholesterol-enriched remnants and high-density lipoprotein (HDL), which promotes cholesterol flux from the periphery to the liver. HDL is also subjected to hydrolysis by endothelial lipase (EL) (encoded by LIPG). Genome-wide association studies have identified various variants of EL that are associated with altered HDL cholesterol levels. However, a potential role of EL in BAT-mediated HDL metabolism has not been investigated so far. In the present study, we show that in mice, cold-stimulated activation of thermogenic adipocytes induced expression of Lipg in BAT and inguinal WAT but that loss of Lipg did not affect gene expression of thermogenic markers. Furthermore, in both wild type (WT) and Lipg-deficient mice, activation of thermogenesis resulted in a decline of HDL cholesterol levels. However, cold-induced remodeling of the HDL lipid composition was different between WT and Lipg-deficient mice. Notably, radioactive tracer studies with double-labeled HDL indicated that cold-induced hepatic HDL cholesterol clearance was lower in Lipg-deficient mice. Moreover, this reduced clearance was associated with impaired macrophage-to-feces cholesterol transport. Overall, these data indicate that EL is a determinant of HDL lipid composition, cholesterol flux, and HDL turnover in conditions of high thermogenic activity.
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Thermoneutral conditions typical for standard human living environments result in brown adipose tissue (BAT) involution, characterized by decreased mitochondrial mass and increased lipid deposition. Low BAT activity is associated with poor metabolic health, and BAT reactivation may confer therapeutic potential. However, the molecular drivers of this BAT adaptive process in response to thermoneutrality remain enigmatic. Using metabolic and lipidomic approaches, we show that endogenous fatty acid synthesis, regulated by carbohydrate-response element-binding protein (ChREBP), is the central regulator of BAT involution. By transcriptional control of lipogenesis-related enzymes, ChREBP determines the abundance and composition of both storage and membrane lipids known to regulate organelle turnover and function. Notably, ChREBP deficiency and pharmacological inhibition of lipogenesis during thermoneutral adaptation preserved mitochondrial mass and thermogenic capacity of BAT independently of mitochondrial biogenesis. In conclusion, we establish lipogenesis as a potential therapeutic target to prevent loss of BAT thermogenic capacity as seen in adult humans.
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Tecido Adiposo Marrom/metabolismo , Ácidos Graxos/biossíntese , Animais , Humanos , CamundongosRESUMO
In response to cold exposure, thermogenic adipocytes internalize large amounts of fatty acids after lipoprotein lipase-mediated hydrolysis of triglyceride-rich lipoproteins (TRL) in the capillary lumen of brown adipose tissue (BAT) and white adipose tissue (WAT). Here, we show that in cold-exposed mice, vascular endothelial cells in adipose tissues endocytose substantial amounts of entire TRL particles. These lipoproteins subsequently follow the endosomal-lysosomal pathway, where they undergo lysosomal acid lipase (LAL)-mediated processing. Endothelial cell-specific LAL deficiency results in impaired thermogenic capacity as a consequence of reduced recruitment of brown and brite/beige adipocytes. Mechanistically, TRL processing by LAL induces proliferation of endothelial cells and adipocyte precursors via beta-oxidation-dependent production of reactive oxygen species, which in turn stimulates hypoxia-inducible factor-1α-dependent proliferative responses. In conclusion, this study demonstrates a physiological role for TRL particle uptake into BAT and WAT and establishes endothelial lipoprotein processing as an important determinant of adipose tissue remodeling during thermogenic adaptation.
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Tecido Adiposo Marrom/metabolismo , Tecido Adiposo Branco/metabolismo , Lipoproteínas/metabolismo , Lisossomos/metabolismo , Termogênese , Triglicerídeos/metabolismo , Adiponectina/genética , Adiponectina/metabolismo , Tecido Adiposo Marrom/patologia , Tecido Adiposo Branco/patologia , Animais , Antígenos CD36/metabolismo , Diferenciação Celular , Proliferação de Células , Temperatura Baixa , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Lipoproteínas/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Espécies Reativas de Oxigênio/metabolismo , Receptores de Lipoproteínas/genética , Receptores de Lipoproteínas/metabolismo , Esterol Esterase/deficiência , Esterol Esterase/genética , Esterol Esterase/metabolismo , Triglicerídeos/genéticaRESUMO
Dietary fibers are fermented by gut bacteria into the major short chain fatty acids (SCFAs) acetate, propionate, and butyrate. Generally, fiber-rich diets are believed to improve metabolic health. However, recent studies suggest that long-term supplementation with fibers causes changes in hepatic bile acid metabolism, hepatocyte damage, and hepatocellular cancer in dysbiotic mice. Alterations in hepatic bile acid metabolism have also been reported after cold-induced activation of brown adipose tissue. Here, we aim to investigate the effects of short-term dietary inulin supplementation on liver cholesterol and bile acid metabolism in control and cold housed specific pathogen free wild type (WT) mice. We found that short-term inulin feeding lowered plasma cholesterol levels and provoked cholestasis and mild liver damage in WT mice. Of note, inulin feeding caused marked perturbations in bile acid metabolism, which were aggravated by cold treatment. Our studies indicate that even relatively short periods of inulin consumption in mice with an intact gut microbiome have detrimental effects on liver metabolism and function.
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Ácidos e Sais Biliares/metabolismo , Colesterol/metabolismo , Inulina/efeitos adversos , Fígado/efeitos dos fármacos , Animais , Ácidos e Sais Biliares/sangue , Bilirrubina/sangue , Doença Hepática Induzida por Substâncias e Drogas/etiologia , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Colesterol/análise , Colesterol/sangue , Suplementos Nutricionais , Ácidos Graxos Voláteis/metabolismo , Fezes/química , Abrigo para Animais , Inulina/administração & dosagem , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , TemperaturaRESUMO
Thermogenic adipocytes burn nutrients in order to produce heat. Upon activation, brown adipose tissue (BAT) clears vast amounts of lipids and glucose from the circulation and thus substantially lowers plasma lipid levels. As a consequence, BAT activation protects from the development of atherosclerosis. However, it is unclear if pharmacologic activation of BAT can be exploited therapeutically to reduce plaque burden in established atherosclerotic disease. Here we study the impact of thermogenic adipose tissues on plaque regression in a mouse model of atherosclerosis. Thermogenic adipocytes in atherosclerotic low-density lipoprotein (LDL) receptor (LDLR)-deficient mice were pharmacologically activated by dietary CL316,243 (CL) treatment for 4 weeks and the outcomes on metabolically active tissues, plasma lipids and atherosclerosis were analyzed. While the chronic activation of thermogenic adipocytes reduced adiposity, increased browning of white adipose tissue (WAT), altered liver gene expression, and reduced plasma triglyceride levels, atherosclerotic plaque burden remained unchanged. Our findings suggest that despite improving adiposity and plasma triglycerides, pharmacologic activation of thermogenic adipocytes is not able to reverse atherosclerosis in LDLR-deficient mice.
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Adipócitos/fisiologia , Placa Aterosclerótica/patologia , Temperatura , Adipócitos/efeitos dos fármacos , Animais , Dioxóis/farmacologia , Masculino , Camundongos , Camundongos Knockout , Placa Aterosclerótica/metabolismo , Receptores de LDL/genética , Receptores de LDL/metabolismo , Triglicerídeos/sangueRESUMO
The here described method can be used to estimate the uptake of orally provided cholesterol in mice. Briefly, mice are gavaged with radiolabeled cholesterol and 4 h later, organ distribution of the radiolabel is determined by liquid scintillation counting. The method has been applied successfully to determine dietary cholesterol handling of mice housed at different ambient temperatures.
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Microglia play a pivotal role in the maintenance of brain homeostasis but lose homeostatic function during neurodegenerative disorders. We identified a specific apolipoprotein E (APOE)-dependent molecular signature in microglia from models of amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and Alzheimer's disease (AD) and in microglia surrounding neuritic ß-amyloid (Aß)-plaques in the brains of people with AD. The APOE pathway mediated a switch from a homeostatic to a neurodegenerative microglia phenotype after phagocytosis of apoptotic neurons. TREM2 (triggering receptor expressed on myeloid cells 2) induced APOE signaling, and targeting the TREM2-APOE pathway restored the homeostatic signature of microglia in ALS and AD mouse models and prevented neuronal loss in an acute model of neurodegeneration. APOE-mediated neurodegenerative microglia had lost their tolerogenic function. Our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target that could aid in the restoration of homeostatic microglia.