RESUMO
BACKGROUND: Angiotensinogen (AGT) is an essential component in the renin-angiotensin system. AGT has highly conserved sequences in the loop and ß-sheet regions among species; however, their functions have not been studied. METHODS: Adeno-associated viral vector (AAV) serotype 2/8 encoding mouse AGT with mutations of conserved sequences in the loop (AAV.loop-Mut), ß-sheet (AAV.ßsheet-Mut), or both regions (AAV.loop/ßsheet-Mut) was injected into male hepatocyte-specific AGT-deficient (hepAGT-/-) mice in an LDL (low-density lipoprotein) receptor-deficient background. AAV containing mouse wild-type AGT (AAV.mAGT) or a null vector (AAV.null) were used as controls. Two weeks after AAV administration, all mice were fed a western diet for 12 weeks. To determine how AGT secretion is regulated in hepatocytes, AAVs containing the above mutations were transducted into HepG2 cells. RESULTS: In hepAGT-/- mice infected with AAV.loop-Mut or ßsheet-Mut, plasma AGT concentrations, systolic blood pressure, and atherosclerosis were comparable to those in AAV.mAGT-infected mice. Interestingly, plasma AGT concentrations, systolic blood pressure, and atherosclerotic lesion size in hepAGT-/- mice infected with AAV.loop/ßsheet-Mut were not different from mice infected with AAV.null. In contrast, hepatic Agt mRNA abundance was elevated to a comparable magnitude as AAV.mAGT-infected mice. Immunostaining showed that AGT protein was accumulated in hepatocytes of mice infected with AAV.loop/ßsheet-Mut or HepG2 cells transducted with AAV.loop/ßsheet-Mut. Accumulated AGT was not located in the endoplasmic reticulum. CONCLUSIONS: The conserved sequences in either the loop or ß-sheet region individually have no effect on AGT regulation, but the conserved sequences in both regions synergistically contribute to the secretion of AGT from hepatocytes.
Assuntos
Angiotensinogênio , Animais , Camundongos , Angiotensinogênio/sangue , Angiotensinogênio/química , Angiotensinogênio/genética , Angiotensinogênio/metabolismo , Sequência Conservada , Sequência de Aminoácidos , Masculino , Feminino , Hepatócitos/metabolismo , Conformação Proteica em Folha beta , Aterosclerose/metabolismo , Aterosclerose/patologia , Retículo Endoplasmático/metabolismo , Glicosilação , Fígado/citologia , Fígado/metabolismo , Sistema Renina-AngiotensinaRESUMO
Obesity is associated with alterations in hepatic lipid metabolism. We previously identified the prorenin receptor (PRR) as a potential contributor to liver steatosis. Therefore, we aimed to determine the relative contribution of PRR and its soluble form, sPRR, to lipid homeostasis. PRR-floxed male mice were treated with an adeno-associated virus with thyroxine-binding globulin promoter-driven Cre to delete PRR in the liver [liver PRR knockout (KO) mice]. Hepatic PRR deletion did not change the body weight but increased liver weights. The deletion of PRR in the liver decreased peroxisome proliferator-activated receptor gamma (PPARγ) and triglyceride levels, but liver PRR KO mice exhibited higher plasma cholesterol levels and lower hepatic low-density lipoprotein receptor (LDLR) and Sortilin 1 (SORT1) proteins than control (CTL) mice. Surprisingly, hepatic PRR deletion elevated hepatic cholesterol, and up-regulated hepatic sterol regulatory element-binding protein 2 (SREBP2) and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA-R) genes. In addition, the plasma levels of sPRR were significantly higher in liver PRR KO mice than in controls. In vitro studies in HepG2 cells demonstrated that sPRR treatment upregulated SREBP2, suggesting that sPRR could contribute to hepatic cholesterol biosynthesis. Interestingly, PRR, total cleaved and noncleaved sPRR contents, furin, and Site-1 protease (S1P) were elevated in the adipose tissue of liver PRR KO mice, suggesting that adipose tissue could contribute to the circulating pool of sPRR. Overall, this work supports previous works and opens a new area of investigation concerning the function of sPRR in lipid metabolism and adipose tissue-liver cross talk.NEW & NOTEWORTHY Hepatic PRR and its soluble form, sPRR, contribute to triglyceride and cholesterol homeostasis and hepatic inflammation. Deletion of hepatic PRR decreased triglyceride levels through a PRR-PPARγ-dependent mechanism but increased hepatic cholesterol synthesis through sPRR-medicated upregulation of SREBP-2. Our study highlighted a new paradigm of cross talk between the liver and the adipose tissue involving cholesterol and sPRR.
Assuntos
Homeostase/genética , Metabolismo dos Lipídeos/genética , Receptores de Superfície Celular/fisiologia , Tecido Adiposo/metabolismo , Animais , Fígado Gorduroso/genética , Fígado Gorduroso/metabolismo , Fígado Gorduroso/patologia , Células Hep G2 , Humanos , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Camundongos Knockout , Obesidade/genética , Obesidade/metabolismo , Obesidade/patologia , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiologia , Receptores de Superfície Celular/química , Receptores de Superfície Celular/genética , Solubilidade , Triglicerídeos/metabolismo , Receptor de Pró-ReninaRESUMO
BACKGROUND: Developing an understanding of the biochemistry of aging in both sexes is critical for managing disease throughout the lifespan. Lipidomic associations with age and sex have been reported, but prior studies are limited by measurements in serum rather than plasma or by participants taking lipid-lowering medications. METHODS: Our study included lipidomic data from 980 participants aged 18-87 years old from the Genetics of Lipid-Lowering Drugs and Diet Network (GOLDN). Participants were off lipid-lowering medications for at least 4 weeks, and signal intensities of 413 known lipid species were measured in plasma. We examined linear age and sex associations with signal intensity of (a) 413 lipid species; (b) 6 lipid classes (glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, fatty acids, and acylcarnitines); and (c) 15 lipid subclasses; as well as with the particle sizes of three lipoproteins. RESULTS: Significant age associations were identified in 4 classes, 11 subclasses, 147 species, and particle size of one lipoprotein while significant sex differences were identified in 5 classes, 12 subclasses, 248 species, and particle sizes of two lipoproteins. For many lipid species (n = 97), age-related associations were significantly different between males and females. Age*sex interaction effects were most prevalent among phosphatidylcholines, sphingomyelins, and triglycerides. CONCLUSION: We identified several lipid species, subclasses, and classes that differ by age and sex; these lipid phenotypes may serve as useful biomarkers for lipid changes and associated cardiovascular risk with aging in the future. Future studies of age-related changes throughout the adult lifespan of both sexes are warranted. TRIAL REGISTRATION: ClinicalTrials.gov NCT00083369 ; May 21, 2004.
Assuntos
Lipidômica , Lipídeos/sangue , Caracteres Sexuais , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Lipídeos/classificação , Lipoproteínas/química , Masculino , Pessoa de Meia-Idade , Tamanho da Partícula , Adulto JovemRESUMO
Sitosterolemia is a lipid disorder characterized by the accumulation of dietary xenosterols in plasma and tissues caused by mutations in either ABCG5 or ABCG8. ABCG5 ABCG8 encodes a pair of ABC half transporters that form a heterodimer (G5G8), which then traffics to the surface of hepatocytes and enterocytes and promotes the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. We review the literature from the initial description of the disease, the discovery of its genetic basis, current therapy, and what has been learned from animal, cellular, and molecular investigations of the transporter in the twenty years since its discovery. The genomic era has revealed that there are far more carriers of loss of function mutations and likely pathogenic variants of ABCG5 ABCG8 than previously thought. The impact of these variants on G5G8 structure and activity are largely unknown. We propose a classification system for ABCG5 ABCG8 mutants based on previously published systems for diseases caused by defects in ABC transporters. This system establishes a framework for the comprehensive analysis of disease-associated variants and their impact on G5G8 structure-function.
Assuntos
Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Colesterol/metabolismo , Hipercolesterolemia , Enteropatias , Erros Inatos do Metabolismo Lipídico , Lipoproteínas , Mutação , Fitosteróis/efeitos adversos , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/história , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/história , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Animais , Enterócitos/metabolismo , Enterócitos/patologia , Hepatócitos/metabolismo , Hepatócitos/patologia , História do Século XXI , Humanos , Hipercolesterolemia/genética , Hipercolesterolemia/história , Hipercolesterolemia/metabolismo , Hipercolesterolemia/patologia , Enteropatias/genética , Enteropatias/história , Enteropatias/metabolismo , Enteropatias/patologia , Erros Inatos do Metabolismo Lipídico/genética , Erros Inatos do Metabolismo Lipídico/história , Erros Inatos do Metabolismo Lipídico/metabolismo , Erros Inatos do Metabolismo Lipídico/patologia , Lipoproteínas/genética , Lipoproteínas/história , Lipoproteínas/metabolismo , Fitosteróis/genética , Fitosteróis/história , Fitosteróis/metabolismoRESUMO
OBJECTIVE: Determine the impact of CETP (cholesteryl ester transfer protein) on the route of cholesterol elimination in mice. Approach and Results: We adapted our protocol for biliary cholesterol secretion with published methods for measuring transintestinal cholesterol elimination. Bile was diverted and biliary lipid secretion maintained by infusion of bile acid. The proximal small bowel was perfused with bile acid micelles. In high-fat, high-cholesterol-fed mice, the presence of a CETP transgene increased biliary cholesterol secretion at the expense of transintestinal cholesterol elimination. The increase in biliary cholesterol secretion was not associated with increases in hepatic SR-BI (scavenger receptor BI) or ABCG5 (ATP-binding cassette G5) ABCG8. The decline in intestinal cholesterol secretion was associated with an increase in intestinal Niemann-Pick disease, type C1, gene-like 1 mRNA. Finally, we followed the delivery of HDL (high-density lipoprotein) or LDL (low-density lipoprotein) cholesteryl esters (CE) from plasma to bile and intestinal perfusates. HDL-CE favored the biliary pathway. Following high-fat feeding, the presence of CETP directed HDL-CE away from the bile and towards the intestine. The presence of CETP increased LDL-CE delivery to bile, whereas the appearance of LDL-CE in intestinal perfusate was near the lower limit of detection. CONCLUSIONS: Biliary and intestinal cholesterol secretion can be simultaneously measured in mice and used as a model to examine factors that alter cholesterol elimination. Plasma factors, such as CETP, alter the route of cholesterol elimination from the body. Intestinal and biliary cholesterol secretion rates are independent of transhepatic or transintestinal delivery of HDL-CE, whereas LDL-CE was eliminated almost exclusively in the hepatobiliary pathway.
Assuntos
Ácidos e Sais Biliares/metabolismo , Proteínas de Transferência de Ésteres de Colesterol/metabolismo , Motilidade Gastrointestinal/fisiologia , Hipercolesterolemia/metabolismo , Receptores Depuradores Classe B/metabolismo , Análise de Variância , Animais , Bile/metabolismo , Modelos Animais de Doenças , Feminino , Humanos , Immunoblotting , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Distribuição Aleatória , Reação em Cadeia da Polimerase em Tempo Real/métodosRESUMO
The ABCG5/G8 heterodimer is the primary neutral sterol transporter in hepatobiliary and transintestinal cholesterol excretion. Inactivating mutations on either the ABCG5 or ABCG8 subunit cause Sitosterolemia, a rare genetic disorder. In 2016, a crystal structure of human ABCG5/G8 in an apo state showed the first structural information on ATP-binding cassette (ABC) sterol transporters and revealed several structural features that were observed for the first time. Over the past decade, several missense variants of ABCG5/G8 have been associated with non-Sitosterolemia lipid phenotypes. In this review, we summarize recent pathophysiological and structural findings of ABCG5/G8, interpret the structure-function relationship in disease-causing variants and describe the available evidence that allows us to build a mechanistic view of ABCG5/G8-mediated sterol transport.
Assuntos
Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/química , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/química , Sistema Biliar/metabolismo , Colesterol/metabolismo , Lipoproteínas/química , Fígado/metabolismo , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/biossíntese , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/biossíntese , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Animais , Catálise , Homeostase , Humanos , Hipercolesterolemia/metabolismo , Enteropatias/metabolismo , Erros Inatos do Metabolismo Lipídico/metabolismo , Lipoproteínas/biossíntese , Lipoproteínas/metabolismo , Fitosteróis/efeitos adversos , Fitosteróis/metabolismoRESUMO
The elucidation of the molecular basis of the rare disease, sitosterolemia, has revolutionized our mechanistic understanding of how dietary sterols are excreted and how cholesterol is eliminated from the body. Two proteins, ABCG5 and ABCG8, encoded by the sitosterolemia locus, work as obligate dimers to pump sterols out of hepatocytes and enterocytes. ABCG5/ABCG8 are key in regulating whole-body sterol trafficking, by eliminating sterols via the biliary tree as well as the intestinal tract. Importantly, these transporters keep xenosterols from accumulating in the body. The sitosterolemia locus has been genetically associated with lipid levels and downstream atherosclerotic disease, as well as formation of gallstones and the risk of gallbladder cancer. While polymorphic variants raise or lower the risks of these phenotypes, loss of function of this locus leads to more dramatic phenotypes, such as premature atherosclerosis, platelet dysfunction, and thrombocytopenia, and, perhaps, increased endocrine disruption and liver dysfunction. Whether small amounts of xenosterol exposure over a lifetime cause pathology in normal humans with polymorphic variants at the sitosterolemia locus remains largely unexplored. The purpose of this review will be to summarize the current state of knowledge, but also highlight key conceptual and mechanistic issues that remain to be explored.
Assuntos
Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Esteróis/metabolismo , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/química , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/química , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Animais , HumanosRESUMO
BMAL1 is a core component of the transcription/translation machinery that regulates central and peripheral circadian rhythms that coordinate behavior and metabolism, respectively. Our objective was to determine the impact of BMAL1 in adipose alone or in combination with liver on metabolic phenotypes. Control, adipose-Bmal1 knockout (ABKO), and liver- and adipose-Bmal1 knockout (LABKO) female mice were placed in TSE System metabolic chambers for metabolic phenotyping. A second cohort of male mice was fed a control or diabetogenic diet, and body weight and composition, glucose tolerance, insulin sensitivity, and serum and hepatic lipids were measured. Both female ABKO and LABKO mice exhibited increased food consumption compared with control mice. ABKO mice also exhibited increased overall activity predominantly during the light phase compared with both control and LABKO mice and were protected from increased weight gain. When the male cohort was challenged with a diabetogenic diet, LABKO mice had increased body weight due to increased fat mass compared with control and ABKO mice. However, these mice did not present further impairments in glycemic control, adipose inflammation, or liver injury. LABKO mice had increased hepatic cholesterol and elevated expression of cholesterol synthesis and uptake genes. Our data indicate that deletion of this allele in adipose or in combination with liver alters feeding behavior and locomotor activity. However, obesity is exacerbated only with the combination of liver and adipose deletion.
Assuntos
Fatores de Transcrição ARNTL/metabolismo , Tecido Adiposo/metabolismo , Transtornos Cronobiológicos/etiologia , Transtornos Cronobiológicos/metabolismo , Fígado/metabolismo , Doenças Metabólicas/metabolismo , Animais , Ritmo Circadiano , Diabetes Mellitus Experimental/etiologia , Diabetes Mellitus Experimental/metabolismo , Dieta/efeitos adversos , Feminino , Masculino , Doenças Metabólicas/etiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos TransgênicosRESUMO
Previous studies suggest an interdependent relationship between liver and intestine for cholesterol elimination from the body. We hypothesized that a combination of ursodiol (Urso) and ezetimibe (EZ) could increase biliary secretion and reduce cholesterol reabsorption, respectively, to promote cholesterol excretion. Treatment with Urso increased hepatic ABCG5 ABCG8 (G5G8) protein and both biliary and fecal sterols in a dose-dependent manner. To determine whether the drug combination (Urso-EZ) further increased cholesterol excretion, mice were treated with Urso alone or in combination with two doses of EZ. EZ produced an additive and dose-dependent increase in fecal neutral sterol (FNS) elimination in the presence of Urso. Finally, we sequentially treated wide-type and G5G8-deficient mice with Urso and Urso-EZ to determine the extent to which these effects were G5G8 dependent. Although biliary and FNS were invariably lower in G5G8 KO mice, the relative increase in FNS following treatment with Urso alone or the Urso-EZ combination was not affected by genotype. In conclusion, Urso increases G5G8, biliary cholesterol secretion, and FNS and acts additively with EZ to promote fecal sterol excretion. However, the stimulatory effect of these agents was not G5G8 dependent.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Colesterol/metabolismo , Ezetimiba/farmacologia , Fezes/química , Lipoproteínas/metabolismo , Ácido Ursodesoxicólico/farmacologia , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/química , Transportadores de Cassetes de Ligação de ATP/deficiência , Transportadores de Cassetes de Ligação de ATP/genética , Animais , Ácidos e Sais Biliares/biossíntese , Sistema Biliar/efeitos dos fármacos , Sistema Biliar/metabolismo , Transporte Biológico/efeitos dos fármacos , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Feminino , Técnicas de Inativação de Genes , Mucosa Intestinal/metabolismo , Intestinos/efeitos dos fármacos , Lipoproteínas/química , Lipoproteínas/deficiência , Lipoproteínas/genética , Masculino , Camundongos , Multimerização Proteica , Estrutura Quaternária de ProteínaRESUMO
ATP-binding cassette transporter D2 (D2) is an ABC half transporter that is thought to promote the transport of very long-chain fatty acyl-CoAs into peroxisomes. Both D2 and peroxisomes increase during adipogenesis. Although peroxisomes are essential to both catabolic and anabolic lipid metabolism, their function, and that of D2, in adipose tissues remain largely unknown. Here, we investigated the D2 localization and the proteome of D2-containing organelles, in adipose tissue. Centrifugation of mouse adipose homogenates generated a fraction enriched with D2, but deficient in peroxisome markers including catalase, PEX19, and ABCD3 (D3). Electron microscopic imaging of this fraction confirmed the presence of D2 protein on an organelle with a dense matrix and a diameter of â¼ 200 nm, the typical structure and size of a microperoxisome. D2 and PEX19 antibodies recognized distinct structures in mouse adipose. Immunoisolation of the D2-containing compartment confirmed the scarcity of PEX19 and proteomic profiling revealed the presence of proteins associated with peroxisome, endoplasmic reticulum (ER), and mitochondria. D2 is localized to a distinct class of peroxisomes that lack many peroxisome proteins, and may associate physically with mitochondria and the ER.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Tecido Adiposo/metabolismo , Peroxissomos/metabolismo , Subfamília D de Transportador de Cassetes de Ligação de ATP , Animais , Retículo Endoplasmático/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microscopia Eletrônica , Microscopia de Fluorescência , Mitocôndrias/metabolismo , Proteoma/metabolismo , Proteômica , Transdução de SinaisRESUMO
OBJECTIVE: Recent studies support a role for cholesterol in the development of obesity and nonalcoholic fatty liver disease. Mice lacking the ABCG5 ABCG8 (G5G8) sterol transporter have reduced biliary cholesterol secretion and are more susceptible to steatosis, hepatic insulin resistance, and loss of glycemic control when challenged with a high-fat diet. We hypothesized that accelerating G5G8-mediated biliary cholesterol secretion would correct these phenotypes in obese mice. APPROACH AND RESULTS: Obese (db/db) male and their lean littermates were administered a cocktail of control adenovirus or adenoviral vectors encoding ABCG5 and ABCG8 (AdG5G8). Three days after viral administration, measures of lipid and glucose homeostasis were determined, and tissues were collected for biochemical analyses. AdG5G8 increased biliary cholesterol and fecal sterol elimination. Fasting glucose and triglycerides declined, and glucose tolerance improved in obese mice expressing G5G8 compared with mice receiving control adenovirus. These changes were associated with a reduction in phosphorylated eukaryotic initiation factor 2α and c-Jun N-terminal kinase in liver, suggesting alleviation of endoplasmic reticulum stress. Phosphorylated insulin receptor and protein kinase B were increased, indicating restored hepatic insulin signaling. However, there was no reduction in hepatic triglycerides after the 3-day treatment period. CONCLUSIONS: Accelerating biliary cholesterol secretion restores glycemic control and reduces plasma triglycerides in obese db/db mice.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Bile/metabolismo , Glicemia/metabolismo , Colesterol/sangue , Terapia Genética , Hipertrigliceridemia/terapia , Obesidade/complicações , Triglicerídeos/sangue , Transportadores de Cassetes de Ligação de ATP/genética , Adenoviridae/genética , Animais , Biomarcadores/sangue , Modelos Animais de Doenças , Fator de Iniciação 2 em Eucariotos/metabolismo , Técnicas de Transferência de Genes , Predisposição Genética para Doença , Vetores Genéticos , Hipertrigliceridemia/sangue , Hipertrigliceridemia/etiologia , Hipertrigliceridemia/genética , Mucosa Intestinal/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Fígado/metabolismo , Masculino , Camundongos , Camundongos Obesos , Obesidade/sangue , Obesidade/genética , Fenótipo , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor de Insulina/metabolismo , Fatores de TempoRESUMO
Fenofibrate is a peroxisome proliferator-activated receptor (PPAR) α ligand that has been widely used as a lipid-lowering agent in the treatment of hypertriglyceridemia. ABCD2 (D2) is a peroxisomal long-chain acyl-CoA transporter that is highly induced by fenofibrate in the livers of mice. To determine whether D2 is a modifier of fibrate responses, wild-type and D2-deficient mice were treated with fenofibrate for 14 days. The absence of D2 altered expression of gene clusters associated with lipid metabolism, including PPARα signaling. Using 3T3-L1 adipocytes, which express high levels of D2, we confirmed that knockdown of D2 modified genomic responses to fibrate treatment. We next evaluated the impact of D2 on effects of fibrates in a mouse model of diet-induced obesity. Fenofibrate treatment opposed the development of obesity, hypertriglyceridemia, and insulin resistance. However, these effects were unaffected by D2 genotype. We concluded that D2 can modulate genomic responses to fibrates, but that these effects are not sufficiently robust to alter the effects of fibrates on diet-induced obesity phenotypes.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Fenofibrato/farmacologia , Obesidade/tratamento farmacológico , PPAR alfa/genética , PPAR alfa/metabolismo , Subfamília D de Transportador de Cassetes de Ligação de ATP , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Animais , Dieta/métodos , Modelos Animais de Doenças , Hipertrigliceridemia/tratamento farmacológico , Hipertrigliceridemia/genética , Resistência à Insulina/genética , Metabolismo dos Lipídeos/efeitos dos fármacos , Metabolismo dos Lipídeos/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/genética , Obesidade/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genéticaRESUMO
PURPOSE OF REVIEW: Selective lipid uptake (SLU) is known to be a major pathway of lipoprotein cholesterol metabolism in experimental animals and humans, but remains poorly understood. This review provides a brief overview of SLU mediated by the HDL receptor scavenger receptor B-type I (SR-BI), and highlights several surprising new findings related to the impact of SLU pathways in cholesterol homeostasis. RECENT FINDINGS: Under certain conditions, SR-BI-mediated SLU contributes to reverse cholesterol transport (RCT) independently of ABCG5/G8-mediated biliary cholesterol secretion, implying a novel trafficking mechanism. Hepatic SR-BI expression and RCT are decreased in diabetic mice. Farnesoid X receptor (FXR) and the microRNAs miR-185, miR-96 and miR-223 are emerging therapeutic targets for increasing SR-BI expression. SR-BI-independent selective cholesteryl ester uptake is a newly characterized pathway in macrophage foam cells. SUMMARY: New findings underscore the importance of SR-BI-mediated SLU in hepatic SLU and RCT, while indicating that further investigation is needed to define SLU pathways, including SR-BI-independent macrophage selective cholesteryl ester uptake. The intracellular trafficking of cholesterol in these pathways appears to be critical to their normal function and is a major subject of ongoing studies.
Assuntos
Ésteres do Colesterol/metabolismo , Fígado/metabolismo , Macrófagos/metabolismo , Receptores Depuradores Classe B/metabolismo , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Animais , Transporte Biológico Ativo/genética , Ésteres do Colesterol/genética , Diabetes Mellitus/genética , Diabetes Mellitus/metabolismo , Diabetes Mellitus/patologia , Humanos , Lipoproteínas/genética , Lipoproteínas/metabolismo , Fígado/patologia , Macrófagos/patologia , Camundongos , MicroRNAs/genética , MicroRNAs/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores Depuradores Classe B/genéticaRESUMO
BACKGROUND AND AIMS: Inflammatory cells within atherosclerotic lesions secrete proteolytic enzymes that contribute to lesion progression and destabilization, increasing the risk for an acute cardiovascular event. Elastase is a serine protease, secreted by macrophages and neutrophils, that may contribute to the development of unstable plaque. We previously reported interaction of endogenous protease-inhibitor proteins with high-density lipoprotein (HDL), including alpha-1-antitrypsin, an inhibitor of elastase. These findings support a potential role for HDL as a modulator of protease activity. In this study, we test the hypothesis that enhancement of HDL-associated elastase inhibitor activity is protective against atherosclerotic lesion progression. METHODS: We designed an HDL-targeting protease inhibitor (HTPI) that binds to HDL and confers elastase inhibitor activity. Lipoprotein binding and the impact of HTPI on atherosclerosis were examined using mouse models. Histology and immunofluorescence staining of aortic root sections were used to examine the impact of HTPI on lesion morphology and inflammatory features. RESULTS: HTPI is a small (1.6 kDa) peptide with an elastase inhibitor domain, a soluble linker, and an HDL-targeting domain. When incubated with human plasma ex vivo, HTPI predominantly binds to HDL. Intravenous administration of HTPI to mice resulted in its binding to plasma HDL and increased elastase inhibitor activity on isolated HDL. Accumulation of HTPI within plaque was observed after administration to Apoe-/- mice. To examine the effect of HTPI treatment on atherosclerosis, prevention and progression studies were performed using Ldlr-/- mice fed Western diet. In both study designs, HTPI-treated mice had reduced lipid deposition in plaque. CONCLUSIONS: These data support the hypothesis that HDL-associated anti-elastase activity can improve the atheroprotective potential of HDL and highlight the potential utility of HDL enrichment with anti-protease activity as an approach for stabilization of atherosclerotic lesions.
Assuntos
Aterosclerose , Modelos Animais de Doenças , Progressão da Doença , Lipoproteínas HDL , Animais , Aterosclerose/patologia , Aterosclerose/prevenção & controle , Aterosclerose/enzimologia , Aterosclerose/metabolismo , Aterosclerose/tratamento farmacológico , Lipoproteínas HDL/metabolismo , Humanos , Camundongos Endogâmicos C57BL , Camundongos , Camundongos Knockout para ApoE , Placa Aterosclerótica , Masculino , Elastase Pancreática/metabolismo , Aorta/patologia , Aorta/efeitos dos fármacos , Aorta/enzimologia , Aorta/metabolismo , Doenças da Aorta/prevenção & controle , Doenças da Aorta/patologia , Doenças da Aorta/enzimologia , Doenças da Aorta/metabolismo , Inibidores de Proteases/farmacologia , alfa 1-Antitripsina/farmacologia , alfa 1-Antitripsina/metabolismoRESUMO
Lysophosphatidic acid (LPA) is a bioactive lipid mediator. Concentrations of the major LPA species in mouse plasma decreased uniformly following administration of a potent selective inhibitor of the LPA-generating lysophospholipase D autotaxin, identifying an active mechanism for removal of LPA from the circulation. LPA, akylglycerol phosphate (AGP), sphingosine 1-phosphate (S1P), and a variety of structural mimetics of these lipids, including phosphatase-resistant phosphonate analogs of LPA, were rapidly eliminated (t1/2 < 30 s) from the circulation of mice following intravenous administration of a single bolus dose without significant metabolism in situ in the blood. These lipids accumulated in the liver. Elimination of intravenously administered LPA was blunted by ligation of the hepatic circulation, and â¼90% of LPA administered through the portal vein was accumulated by the isolated perfused mouse liver at first pass. At early times following intravenous administration, more LPA was associated with a nonparenchymal liver cell fraction than with hepatocytes. Primary cultures of nonparenchymal liver cells rapidly assimilated exogenously provided LPA. Our results identify hepatic uptake as an important determinant of the bioavailability of LPA and bioactive lysophospholipid mimetics and suggest a mechanism to explain changes in circulating LPA levels that have been associated with liver dysfunction in humans.
Assuntos
Metabolismo dos Lipídeos , Lisofosfolipídeos/sangue , Animais , Benzoxazóis/farmacologia , Células Cultivadas , Meia-Vida , Hepatócitos/metabolismo , Fígado/metabolismo , Lisofosfolipídeos/farmacocinética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Inibidores de Fosfodiesterase/farmacologia , Diester Fosfórico Hidrolases/metabolismo , Piperazinas/farmacologia , Espectrometria de Massas em Tandem , Distribuição TecidualRESUMO
ABCG5 and ABCG8 form a complex (G5G8) that opposes the absorption of plant sterols but is also expressed in liver where it promotes the excretion of cholesterol into bile. Hepatic G5G8 is transcriptionally regulated by a number of factors implicated in the development of insulin resistance and nonalcoholic fatty liver disease. Therefore, we hypothesized that G5G8 may influence the development of diet-induced obesity phenotypes independently of its role in opposing phytosterol absorption. G5G8 knock-out (KO) mice and their wild type (WT) littermates were challenged with a plant sterol-free low fat or high fat (HF) diet. Weight gain and the rise in fasting glucose were accelerated in G5G8 KO mice following HF feeding. HF-fed G5G8 KO mice had increased liver weight, hepatic lipids, and plasma alanine aminotransferase compared with WT controls. Consistent with the development of nonalcoholic fatty liver disease, macrophage infiltration, the number of TUNEL-positive cells, and the expression of proinflammatory cytokines were also increased in G5G8 KO mice. Hepatic lipid accumulation was associated with increased peroxisome proliferator activated receptor γ, CD36, and fatty acid uptake. Phosphorylation of eukaryotic translation initiation factor 2α (eiF2α) and expression of activating transcription factor 4 and tribbles 3 were elevated in HF-fed G5G8 KO mice, a pathway that links the unfolded protein response to the development of insulin resistance through inhibition of protein kinase B (Akt) phosphorylation. Phosphorylation of Akt and insulin receptor was reduced, whereas serine phosphorylation of insulin receptor substrate 1 was elevated.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Fígado Gorduroso/metabolismo , Resistência à Insulina , Lipoproteínas/metabolismo , Complexos Multiproteicos/metabolismo , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Alanina Transaminase/genética , Alanina Transaminase/metabolismo , Animais , Antígenos CD36/genética , Antígenos CD36/metabolismo , Gorduras na Dieta/efeitos adversos , Gorduras na Dieta/farmacologia , Fator de Iniciação 2 em Eucariotos/genética , Fator de Iniciação 2 em Eucariotos/metabolismo , Fígado Gorduroso/genética , Fígado Gorduroso/patologia , Proteínas Substratos do Receptor de Insulina/genética , Proteínas Substratos do Receptor de Insulina/metabolismo , Lipoproteínas/genética , Camundongos , Camundongos Knockout , Complexos Multiproteicos/genética , Tamanho do Órgão/efeitos dos fármacos , Tamanho do Órgão/genética , PPAR gama/genética , PPAR gama/metabolismo , Fosforilação/efeitos dos fármacos , Fosforilação/genética , Fitosteróis/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Resposta a Proteínas não Dobradas/efeitos dos fármacos , Resposta a Proteínas não Dobradas/genéticaRESUMO
Background: Inflammatory cells within atherosclerotic lesions secrete various proteolytic enzymes that contribute to lesion progression and destabilization, increasing the risk for an acute cardiovascular event. The relative contributions of specific proteases to atherogenesis is not well understood. Elastase is a serine protease, secreted by macrophages and neutrophils, that may contribute to the development of unstable plaque. We have previously reported interaction of endogenous protease-inhibitor proteins with high-density lipoprotein (HDL), including alpha-1-antitrypsin, an inhibitor of elastase. These findings support a potential role for HDL as an endogenous modulator of protease activity. In this study, we test the hypothesis that enhancement of HDL-associated elastase inhibitor activity is protective against atherosclerotic lesion progression. Methods: We designed an HDL-targeting protease inhibitor (HTPI) that binds to HDL and confers elastase inhibitor activity. Lipoprotein binding and the impact of HTPI on atherosclerosis was examined using mouse models. Results: HTPI is a small (1.6 kDa) peptide with an elastase inhibitor domain, a soluble linker, and an HDL-targeting domain. When incubated with human plasma ex vivo , HTPI predominantly binds to HDL. Intravenous administration of HTPI to mice resulted in its binding to plasma HDL and increased elastase inhibitor activity on isolated HDL. Accumulation of HTPI within plaque was observed after systemic administration to Apoe -/- mice. To examine the effect of HTPI treatment on atherosclerosis, prevention and progression studies were performed using Ldlr -/- mice fed Western diet. In both study designs, HTPI-treated mice had reduced lipid deposition in plaque. Histology and immunofluorescence staining of aortic root sections were used to examine the impact of HTPI on lesion morphology and inflammatory features. Conclusions: These data support the hypothesis that HDL-associated anti-elastase activity can improve the atheroprotective potential of HDL and highlight the potential utility of HDL enrichment with anti-protease activity as an approach for stabilization of atherosclerotic lesions.
RESUMO
Background and Aims: Genome and epigenome wide association studies identified variants in carnitine palmitoyltransferase 1a (CPT1a) that associate with lipid traits. The goal of this study was to determine the impact by which liver-specific CPT1a deletion impacts hepatic lipid metabolism. Approach and Results: Six-to-eight-week old male and female liver-specific knockout (LKO) and littermate controls were placed on a low-fat or high-fat diet (HFD; 60% kcal fat) for 15 weeks. Mice were necropsied after a 16 hour fast, and tissues were collected for lipidomics, matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI), kinome analysis, RNA-sequencing, and protein expression by immunoblotting. Female LKO mice had increased serum alanine aminotransferase (ALT) levels which were associated with greater deposition of hepatic lipids, while male mice were not affected by CPT1a deletion relative to male control mice. Mice with CPT1a deletion had reductions in DHA-containing phospholipids at the expense of monounsaturated fatty acids (MUFA)-containing phospholipids in both whole liver and at the level of the lipid droplet (LD). Male and female LKO mice increased RNA levels of genes involved in LD lipolysis ( Plin2 , Cidec , G0S2 ) and in polyunsaturated fatty acid (PUFA) metabolism ( Elovl5, Fads1, Elovl2 ), while only female LKO mice increased genes involved in inflammation ( Ly6d, Mmp12, Cxcl2 ). Kinase profiling showed decreased protein kinase A (PKA) activity, which coincided with increased PLIN2, PLIN5, and G0S2 protein levels and decreased triglyceride hydrolysis in LKO mice. Conclusions: Liver-specific deletion of CPT1a promotes sexually dimorphic steatotic liver disease (SLD) in mice, and here we have identified new mechanisms by which females are protected from HFD-induced liver injury.