RESUMO
UNLABELLED: Major causes of lipid accumulation in liver are increased import or synthesis or decreased catabolism of fatty acids. The latter is caused by dysfunction of cellular organelles controlling energy homeostasis, i.e., mitochondria. Peroxisomes also appear to be an important organelle in lipid metabolism of hepatocytes, but little is known about their role in the development of non-alcoholic fatty liver disease (NAFLD). To investigate the role of peroxisomes alongside mitochondria in excessive hepatic lipid accumulation, we used leptin-resistant db/db mice on C57BLKS background, a mouse model that develops hyperphagia-induced diabetes with obesity and NAFLD. Proteome and gene expression analyses along with lipid analyses in the liver revealed differential expression of genes related to lipid metabolism and ß-oxidation, whereas genes for peroxisomal proteins were predominantly regulated. CONCLUSION: Our investigations show that in fatty liver disease in combination with obesity and diabetes, the hepatocyte-protecting organelle peroxisome is altered. Hence, peroxisomes might indicate a stage of pre-NAFLD, play a role in the early development of NAFLD and appear to be a potential target for treatment and prevention of NAFLD.
Assuntos
Metabolismo dos Lipídeos , Fígado/metabolismo , Hepatopatia Gordurosa não Alcoólica/metabolismo , Peroxissomos/fisiologia , Animais , Expressão Gênica , Metabolismo dos Lipídeos/genética , Fígado/patologia , Masculino , Redes e Vias Metabólicas/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Camundongos Transgênicos , Proteínas Mitocondriais/metabolismo , Hepatopatia Gordurosa não Alcoólica/genética , Hepatopatia Gordurosa não Alcoólica/patologia , Obesidade/genética , Obesidade/metabolismo , Obesidade/patologia , Peroxissomos/metabolismoRESUMO
BACKGROUND: Maturity onset diabetes of the young (MODY) is an autosomal dominant form of non-insulin-dependent diabetes mellitus caused by mutations in at least 13 different genes. The hepatocyte nuclear factor (HNF)-1α gene is affected in the most common form (HNF1A-MODY [MODY3]). CASE PRESENTATION: We describe the co-inheritance of a novel heterozygous missense mutation c.1761C > G (p.Pro588Ala) with a novel complex deletion insertion mutation (c.1765_1766delinsGCCCGfs86*) in the HNF-1α gene among affected members of one family. Both mutations were present in the affected patients and neither was present in unaffected family members. The family had not only inheritance of MODY but also increased susceptibility to type 2 diabetes. Therefore one family member had classical type 2 diabetes including metabolic syndrome aggravated by a genetic predisposition in the form of HNF1A-MODY. CONCLUSION: The presence of common type 2 diabetes features should not detract from the possibility of MODY in patients with a striking autosomal-dominant family history.
Assuntos
Diabetes Mellitus Tipo 2/genética , Fator 1-alfa Nuclear de Hepatócito/genética , Mutação INDEL , Mutação de Sentido Incorreto , Adulto , Feminino , Predisposição Genética para Doença , Heterozigoto , Humanos , Masculino , Linhagem , Fenótipo , Análise de Sequência de DNA/métodosRESUMO
The polycystic ovary syndrome (PCOS) is a complex endocrine-metabolic disorder consisting of reproductive disturbances associated with all aspects of the metabolic syndrome and genetic components in the pathology of this complex disease is very likely. Accordingly, variations in single genes might affect specific features of PCOS and thereby help to define different subgroups. SREBP-1 or LXRα have been shown to be genetically linked to lipid metabolism or insulin sensitivity. As these are two major aspects of the PCOS phenotype, we evaluated both genes in a cohort of 153 PCOS patients. Analyses of both genes revealed in SREBF-1, i.e. SREBP-1a and SREBP-1c, not any variation and in the LXRα gene no novel sequence variations. Common variants of LXRα (rs2279238:G; all:0.8658; PCOS:0.8627; controls: 0.8686 or A: all:0.13412; PCOS:0.1373; controls:0.1314; (OR (95% CI) 0.9508 (0.4226-2.1385); rs11039155: G: all:0.8767; PCOS:0.8663; controls:0.8857 and A all:0.1233; PCOS:0.1337; controls:0.1143; (OR (95% CI) 0.8383 (0.3618-1.9371)) were also not directly associated to PCOS. Combined analyses of both polymorphism revealed that there was no difference of distribution between the groups. In contrast, analyses of the impact of these polymorphisms on metabolic parameters of the syndrome indicated significant differences related to genotypes. The data indicated that rs11039155 increases metabolic risk, whereas rs2279238 has a protective effect on the overall metabolic risk. The investigation of the PCOS group presented indicates that the combined analyses of variations in putative candidate genes allowed a genotype-phenotype correlation for metabolic features.
Assuntos
Receptores Nucleares Órfãos/genética , Síndrome do Ovário Policístico/genética , Proteína de Ligação a Elemento Regulador de Esterol 1/genética , Adulto , Glicemia , Índice de Massa Corporal , Estudos de Casos e Controles , Feminino , Frequência do Gene , Estudos de Associação Genética , Variação Genética , Humanos , Insulina/sangue , Desequilíbrio de Ligação , Receptores X do Fígado , Síndrome do Ovário Policístico/sangue , Síndrome do Ovário Policístico/fisiopatologia , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA , Adulto JovemRESUMO
The metabolic syndrome is usually associated with insulin resistance and visceral fat distribution, which appear to play a direct role in the development of clinical criteria of metabolic syndrome, like elevation of arterial blood pressure and dyslipidemia. In this review, the authors will first introduce the concept, that insulin resistance and increased visceral adipose tissue are also regularly associated with an abnormal or ectopic accumulation of lipids in nonadipocytes, like steatosis hepatis. Then, they will provide some evidence that epicardial fat can be associated with insulin resistance in a similar fashion as visceral intraabdominal fat. Furthermore, epicardial fat might directly affect the vessels and function of the heart. Accordingly, ectopic accumulation of fat within cardiac muscle cells can impair their function and possibly be related to heart failure. These new relations between obesity, fat distribution and cardiac function might help to identify and treat individuals at risk earlier and more appropriately.
Assuntos
Tecido Adiposo/fisiopatologia , Coristoma/fisiopatologia , Coração/fisiopatologia , Modelos Cardiovasculares , Obesidade/fisiopatologia , HumanosRESUMO
The Lufthansa Prevention Study (LUPS) study is a prospective observation of a healthy worker cohort to identify early changes in metabolism leading to the Metabolic Syndrome (MetS) and to analyze their relation to behavioral factors like nutrition, physical activity, psychological status, and to underlying genetic conditions. The LUPS study recruited a sample of 1.962 non-diabetic healthy adults between 25-60 years, employed at a flight base of Lufthansa Technik GmbH in Hamburg, Germany. Baseline assessments included anthropometric measures, blood and urine samples and medical history. Psychosocial variables, dietary habits and life-style risk factors were assessed via self-reported questionnaires.In this report we describe the study design and present baseline parameters including the prevalence of the MetS using different classification criteria. The MetS was present in 20% of male and 12% of female subjects according to the 'Harmonizing the metabolic syndrome' definition. The prevalence varies between 2.6% in male and 2.3% in female subjects up to 48% in male and 41% in female subjects according to different classification criteria of MetS.In conclusion, this first cross-sectional view on the LUPS data confirms the expectation that this cohort is rather healthy and thus provides the opportunity to analyze early changes associated with the development of the MetS. The LUPS study is registered as a clinical trial NCT01313156.
Assuntos
Depressão/diagnóstico , Dislipidemias/diagnóstico , Resistência à Insulina , Síndrome Metabólica/diagnóstico , Obesidade Abdominal/diagnóstico , Adulto , Glicemia/metabolismo , Estudos Transversais , Depressão/epidemiologia , Dislipidemias/epidemiologia , Dislipidemias/metabolismo , Diagnóstico Precoce , Feminino , Alemanha/epidemiologia , Inquéritos Epidemiológicos , Humanos , Estilo de Vida , Masculino , Síndrome Metabólica/epidemiologia , Síndrome Metabólica/metabolismo , Pessoa de Meia-Idade , Obesidade Abdominal/epidemiologia , Obesidade Abdominal/metabolismo , Estudos Prospectivos , Projetos de Pesquisa , Fatores de RiscoRESUMO
Offspring of type 2 diabetes (T2D) patients have increased risk to develop diabetes, due to inherited genetic susceptibility that directly interferes with the individual adaption to environmental conditions. We characterise T2D offspring (OSP) to identify metabolic risk markers for early disease prediction. Plasma of metabolically healthy OSP individuals (n = 43) was investigated after an oral lipid tolerance test (oLTT) by an untargeted mass spectrometric approach for holistic metabolome analyses. Two subgroups of OSP probands can be separated by oLTT, although not differing in general clinical parameters. Analyses of the plasma metabolome revealed mainly medium-chain acylcarnitines and very long-chain fatty acids with differential abundance in the subgroups. The study presented indicates that metabolically healthy OSP of T2D patients differ upon metabolic challenging in serum metabolite composition, especially medium-chain acylcarnitines. The difference suggest that postprandial lipid induced glucose intolerance (LGIT) may serve as a further valuable marker for early diabetes prediction.
Assuntos
Biomarcadores/metabolismo , Glicemia/metabolismo , Carnitina/análogos & derivados , Diabetes Mellitus Tipo 2/complicações , Intolerância à Glucose/diagnóstico , Lipídeos/efeitos adversos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Adolescente , Adulto , Idoso , Carnitina/metabolismo , Estudos de Casos e Controles , Cromatografia Líquida , Diabetes Mellitus Tipo 2/fisiopatologia , Feminino , Intolerância à Glucose/etiologia , Intolerância à Glucose/metabolismo , Teste de Tolerância a Glucose , Humanos , Masculino , Espectrometria de Massas , Metaboloma , Pessoa de Meia-Idade , Adulto JovemRESUMO
The transcription factor sterol regulatory element binding protein (SREBP)-1c plays a pivotal role in lipid metabolism. In this report we identified the main phosphorylation sites of MAPK-families, i.e. p38 stress-activated MAPK (p38), ERK-MAPK (ERK) or c-JUN N-terminal protein kinases (JNK) in SREBP-1c. The major phosphorylation sites of p38, i.e. serine 39 and threonine 402, are identical to those we recently identified in the splice-variant SREBP-1a. In contrast, ERK and JNK phosphorylate SREBP-1c at two major sites, i.e. threonine 81 and serine 93, instead of one site in SREBP-1a. Functional analyses of the biological outcome in the human liver cell line HepG2 reveals SREBP-1c phosphorylation dependent alteration in lipid metabolism and secretion pattern of lipid transporting proteins, e.g. ApoE or ApoA1. These results suggest that phosphorylation of SREBP-1c by different MAPKs interferes with lipid metabolism and the secretory activity of liver cells.
Assuntos
MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Hepatócitos/citologia , Hepatócitos/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Metabolismo dos Lipídeos , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Sítios de Ligação , Ácidos Graxos/metabolismo , Células Hep G2 , Humanos , Fosforilação , Proteína de Ligação a Elemento Regulador de Esterol 1/química , Especificidade por SubstratoRESUMO
Cellular compartmentalization of central metabolic pathways as lipid metabolism to mitochondria and peroxisomes enables high efficient control processes. The basis to understand mitochondrial or peroxisomal function is exactly to determine proteins physically present. For proteomic investigations of mouse liver organelles, we developed 2-DE reference maps covering the range pH 4-9, available under ( www.diabesityprot.org ). MALDI-TOF-MS/MS analyses identified a total of 799 (mitochondria) and 681 (peroxisome) protein spots resembling 323 and 293 unique proteins, respectively. Direct comparison of mitochondrial and peroxisomal proteins indicated an approximate overlap of 2/3 of identified proteins. Gene Ontologies (GO) of the identified proteins in respect to physical presence confirmed functional specifications within the organelles. The 2-DE organelle reference maps will aid to point out functional differences and similarities. Our observations suggest that for functional analyses metabolic alterations focusing on one organelle are not sufficient and parallel comparison of both organelles is to be preferred.
Assuntos
Fígado/química , Mitocôndrias/química , Peroxissomos/química , Proteoma/análise , Animais , Western Blotting , Eletroforese em Gel Bidimensional , Concentração de Íons de Hidrogênio , Processamento de Imagem Assistida por Computador , Focalização Isoelétrica , Camundongos , Camundongos Endogâmicos C57BL , Anotação de Sequência Molecular , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Espectrometria de Massas em TandemRESUMO
BACKGROUND: Congenital generalized lipodystrophy (CGL) or Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare genetic syndrome characterized by the absence of adipose tissue. As CGL is thought to be related to malfunctions in adipocyte development, genes involved in the mechanisms of adipocyte biology and maintenance or differentiation of adipocytes, especially transcription factors are candidates. Several genes (BSCL1-4) were found to be associated to the syndrome but not all CGL patients carry mutations in these genes. METHODS AND RESULTS: In a patient with CGL and insulin resistance we investigated the known candidate genes but the patient did not carry a relevant mutation. Analyses of the insulin activated signal transduction pathways in isolated fibroblasts of the patient revealed a postreceptor defect altering expression of the immediate early gene c-fos. Sequence analyses revealed a novel homozygous point mutation (c.-439, TâA) in the patients' c-fos promoter. The point mutation was located upstream of the well characterized promoter elements in a region with no homology to any known cis-elements. The identified mutation was not detected in a total of n=319 non lipodystrophic probands. In vitro analyses revealed that the mutation facilitates the formation of a novel and specific protein/DNA complex. Using mass spectrometry we identified the proteins of this novel complex. Cellular investigations demonstrate that the wild type c-fos promoter can reconstitute the signaling defect in the patient, excluding further upstream signaling alterations, and vice versa the investigations with the c-fos promoter containing the identified mutation generally reduce basal and inducible c-fos transcription activity. As a consequence of the identified point mutation gene expression including c-Fos targeted genes is significantly altered, shown exemplified in cells of the patient. CONCLUSION: The immediate-early gene c-fos is one essential transcription factor to initiate adipocyte differentiation. According to the role of c-fos in adipocyte differentiation our findings of a mutation that initiates a repression mechanism at c-fos promoter features the hypothesis that diminished c-fos expression might play a role in CGL by interfering with adipocyte development.
Assuntos
Genes fos/genética , Lipodistrofia Generalizada Congênita/genética , Mutação Puntual , Adipócitos/citologia , Adipócitos/fisiologia , Adulto , Diferenciação Celular , Feminino , Expressão Gênica , Genes Precoces , Genes fos/fisiologia , HumanosRESUMO
The transcription factor sterol regulatory element binding protein (SREBP)-1a plays a pivotal role in lipid metabolism. Using the SREBP-1a expressing human hepatoma cell line HepG2 we have shown previously that human SREBP-1a is phosphorylated at serine 117 by ERK-mitogen-activated protein kinases (MAPK). Using a combination of cell biology and protein chemistry approach we show that SREBP-1a is also target of other MAPK-families, i.e. c-JUN N-terminal protein kinases (JNK) or p38 stress activated MAP kinases. Serine 117 is also the major phosphorylation site in SREBP-1a for JNK. In contrast to that the major phosphorylation sites of p38 MAPK family are serine 63 and threonine 426. Functional analyses reveal that phosphorylation of SREBP-1a does not alter protein/DNA interaction. The identified phosphorylation sites are specific for both kinase families also in cellular context. To provide direct evidence that phosphorylation of SREBP-1a is a regulatory principle of biological and clinical relevance, we generated transgenic mice expressing mature transcriptionally active N-terminal domain of human SREBP-1a variant lacking all identified phosphorylaton sites designed as alb-SREBP-1aΔP and wild type SREBP-1a designed as alb-SREBP-1a liver specific under control of the albumin promoter and a liver specific enhancer. In contrast to alb-SREBP-1a mice the phosphorylation-deficient mice develop no enlarged fatty livers under normocaloric conditions. Phenotypical examination reveales a massive accumulation of adipose tissue in alb-SREBP-1a but not in the phosphorylation deficient alb-SREBP-1aΔP mice. Moreover, preventing phosphorylation of SREBP-1a protects mice also from dyslipidemia. In conclusion, phosphorylation of SREBP-1a by ERK, JNK and p38 MAPK-families resembles a biological principle and plays a significant role, in vivo.
Assuntos
Fígado Gorduroso/metabolismo , Obesidade Abdominal/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Animais , Sítios de Ligação , DNA/química , Fígado Gorduroso/enzimologia , Células Hep G2 , Humanos , MAP Quinase Quinase 4/metabolismo , Sistema de Sinalização das MAP Quinases , Camundongos , Camundongos Transgênicos , Fenótipo , Fosforilação , Ligação Proteica , Proteína de Ligação a Elemento Regulador de Esterol 1/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
The pathogenesis of fatty liver is not understood in detail, but lipid overflow as well as de novo lipogenesis (DNL) seem to be the key points of hepatocyte accumulation of lipids. One key transcription factor in DNL is sterol regulatory element-binding protein (SREBP)-1c. We generated mice with liver-specific over-expression of mature human SREBP-1c under control of the albumin promoter and a liver-specific enhancer (alb-SREBP-1c) to analyze systemic perturbations caused by this distinct alteration. SREBP-1c targets specific genes and causes key enzymes in DNL and lipid metabolism to be up-regulated. The alb-SREBP-1c mice developed hepatic lipid accumulation featuring a fatty liver by the age of 24 weeks under normocaloric nutrition. On a molecular level, clinical parameters and lipid-profiles varied according to the fatty liver phenotype. The desaturation index was increased compared to wild type mice. In liver, fatty acids (FA) were increased by 50% (p<0.01) and lipid composition was shifted to mono unsaturated FA, whereas lipid profile in adipose tissue or serum was not altered. Serum analyses revealed a â¼2-fold (p<0.01) increase in triglycerides and free fatty acids, and a â¼3-fold (p<0.01) increase in insulin levels, indicating insulin resistance; however, no significant cytokine profile alterations have been determined. Interestingly and unexpectedly, mice also developed adipositas with considerably increased visceral adipose tissue, although calorie intake was not different compared to control mice. In conclusion, the alb-SREBP-1c mouse model allowed the elucidation of the systemic impact of SREBP-1c as a central regulator of lipid metabolism in vivo and also demonstrated that the liver is a more active player in metabolic diseases such as visceral obesity and insulin resistance.
Assuntos
Adiposidade , Fígado Gorduroso/genética , Gordura Intra-Abdominal/patologia , Fígado/metabolismo , Fígado/patologia , Proteína de Ligação a Elemento Regulador de Esterol 1/genética , Transcrição Gênica , Acetiltransferases/metabolismo , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Adiposidade/efeitos dos fármacos , Animais , Composição Corporal/efeitos dos fármacos , Citocinas/sangue , Citocinas/metabolismo , Elongases de Ácidos Graxos , Ácidos Graxos/metabolismo , Fígado Gorduroso/sangue , Fígado Gorduroso/patologia , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Insulina/farmacologia , Resistência à Insulina , Gordura Intra-Abdominal/efeitos dos fármacos , Gordura Intra-Abdominal/metabolismo , Lipogênese/efeitos dos fármacos , Lipogênese/genética , Fígado/efeitos dos fármacos , Fígado/enzimologia , Masculino , Camundongos , Camundongos Transgênicos , Tamanho do Órgão/efeitos dos fármacos , Especificidade de Órgãos/efeitos dos fármacos , Fenótipo , Estrutura Terciária de Proteína , Estearoil-CoA Dessaturase/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/química , Transcrição Gênica/efeitos dos fármacosRESUMO
Patients with polycystic ovary syndrome (PCOS) suffer, in addition to reproductive disturbances, from symptoms of the metabolic syndrome like insulin resistance, elevated coronary risk and visceral obesity. Genes with confirmed associations to the metabolic syndrome are also candidate genes for a relationship to metabolic parameters of the PCOS syndrome. The study presented indicates that genetic variants of the transcription factors LXRα or PPARγ and the PON-1 or the IGF-2 cluster are associated with altered metabolic phenotypes in PCOS patients. Next to this the absolute cytokine levels and the relation of certain cytokines to IL2, IL12 or INFγ are depending on the genotype. These observations support the hypothesis that various genetic variants in metabolic relevant genes might not only alter the metabolic characteristics within a cohort of PCOS patients but might also influence the cytokine level and the overall pattern of secreted cytokines.
Assuntos
Biomarcadores/metabolismo , Variação Genética , Inflamação/genética , Síndrome do Ovário Policístico/genética , Síndrome do Ovário Policístico/metabolismo , Adulto , Biomarcadores/sangue , Estudos de Coortes , Citocinas/sangue , Citocinas/genética , Feminino , Genótipo , Humanos , Inflamação/sangue , Síndrome do Ovário Policístico/sangue , Fatores de RiscoRESUMO
OBJECTIVE: Increased lipid accumulation in cells and tissues is a key phenomenon in the development of obesity, insulin resistance, and atherosclerosis. In the regulation of lipid content of cells and tissues the SREBPs play a dominant role as transcription factors. METHODS: Since growth hormone (GH) affects lipid metabolism and function of fat as well as liver cells, we have investigated the role of SREBP-1a, SREBP-1c and SREBP-2 in the gene regulatory action of GH in the human liver cell line HepG2 and primary mouse hepatocytes. RESULTS: These experiments showed that SREBP-1a couples the stimulatory effect of GH on cholesterol regulated genes, e.g. LDL receptor gene, via sterol sensitive binding cis-element (sre-1). This effect was not depending on RNA expression, but related to phosphorylation of SREBP-1a protein. The result was supported by experiments with the mutant variant SREBP-1a S117A, which is not phosphorylated by Erk-MAP kinases. To analyse a possible role of GH-induced SREBP-1a phosphorylation in cellular physiology we investigated an expression profile of genes coding for central players in lipid transport or lipid metabolism as well as for transcription factors by real time PCR in primary mouse hepatocytes and human hepatoma cell line stably overexpressing the mature form of SREBP-1a or mutated form. CONCLUSION: These experiments emphasize the role SREBP-1a and its phosphorylation for gene regulatory effects of GH.