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OBJECTIVE: Picalm (phosphatidylinositol-binding clathrin assembly protein), a ubiquitously expressed clathrin-adapter protein, is a well-known susceptibility gene for Alzheimer's disease, but its role in white adipose tissue (WAT) function has not yet been studied. Transcriptome analysis revealed differential expression of Picalm in WAT of diabetes-prone and diabetes-resistant mice, hence we aimed to investigate the potential link between Picalm expression and glucose homeostasis, obesity-related metabolic phenotypes, and its specific role in insulin-regulated GLUT4 trafficking in adipocytes. METHODS: Picalm expression and epigenetic regulation by microRNAs (miRNAs) and DNA methylation were analyzed in WAT of diabetes-resistant (DR) and diabetes-prone (DP) female New Zealand Obese (NZO) mice and in male NZO after time-restricted feeding (TRF) and alternate-day fasting (ADF). PICALM expression in human WAT was evaluated in a cross-sectional cohort and assessed before and after weight loss induced by bariatric surgery. siRNA-mediated knockdown of Picalm in 3T3-L1-adipocytes was performed to elucidate functional outcomes on GLUT4-translocation as well as insulin signaling and adipogenesis. RESULTS: Picalm expression in WAT was significantly lower in DR compared to DP NZO female mice, as well as in insulin-sensitive vs. resistant NZO males, and was also reduced in NZO males following TRF and ADF. Four miRNAs (let-7c, miR-30c, miR-335, miR-344) were identified as potential mediators of diabetes susceptibility-related differences in Picalm expression, while 11 miRNAs (including miR-23a, miR-29b, and miR-101a) were implicated in TRF and ADF effects. Human PICALM expression in adipose tissue was lower in individuals without obesity vs. with obesity and associated with weight-loss outcomes post-bariatric surgery. siRNA-mediated knockdown of Picalm in mature 3T3-L1-adipocytes resulted in amplified insulin-stimulated translocation of the endogenous glucose transporter GLUT4 to the plasma membrane and increased phosphorylation of Akt and Tbc1d4. Moreover, depleting Picalm before and during 3T3-L1 differentiation significantly suppressed adipogenesis, suggesting that Picalm may have distinct roles in the biology of pre- and mature adipocytes. CONCLUSIONS: Picalm is a novel regulator of GLUT4-translocation in WAT, with its expression modulated by both genetic predisposition to diabetes and dietary interventions. These findings suggest a potential role for Picalm in improving glucose homeostasis and highlight its relevance as a therapeutic target for metabolic disorders.
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BACKGROUND: The ability of skeletal muscle to respond adequately to changes in nutrient availability, known as metabolic flexibility, is essential for the maintenance of metabolic health and loss of flexibility contributes to the development of diabetes and obesity. The tumour suppressor protein, p53, has been linked to the control of energy metabolism. We assessed its role in the acute control of nutrient allocation in skeletal muscle in the context of limited nutrient availability. METHODS: A mouse model with inducible deletion of the p53-encoding gene, Trp53, in skeletal muscle was generated using the Cre-loxP-system. A detailed analysis of nutrient metabolism in mice with control and knockout genotypes was performed under ad libitum fed and fasting conditions and in exercised mice. RESULTS: Acute deletion of p53 in myofibres of mice activated catabolic nutrient usage pathways even under ad libitum fed conditions, resulting in significantly increased overall energy expenditure (+10.6%; P = 0.0385) and a severe nutrient deficit in muscle characterized by depleted intramuscular glucose and glycogen levels (-62,0%; P < 0.0001 and -52.7%; P < 0.0001, respectively). This was accompanied by changes in marker gene expression patterns of circadian rhythmicity and hyperactivity (+57.4%; P = 0.0068). These metabolic changes occurred acutely, within 2-3 days after deletion of Trp53 was initiated, suggesting a rapid adaptive response to loss of p53, which resulted in a transient increase in lactate release to the circulation (+46.6%; P = 0.0115) from non-exercised muscle as a result of elevated carbohydrate mobilization. Conversely, an impairment of proteostasis and amino acid metabolism was observed in knockout mice during fasting. During endurance exercise testing, mice with acute, muscle-specific Trp53 inactivation displayed an early exhaustion phenotype with a premature shift in fuel usage and reductions in multiple performance parameters, including a significantly reduced running time and distance (-13.8%; P = 0.049 and -22.2%; P = 0.0384, respectively). CONCLUSIONS: These findings suggest that efficient nutrient conservation is a key element of normal metabolic homeostasis that is sustained by p53. The homeostatic state in metabolic tissues is actively maintained to coordinate efficient energy conservation and metabolic flexibility towards nutrient stress. The acute deletion of Trp53 unlocks mechanisms that suppress the activity of nutrient catabolic pathways, causing substantial loss of intramuscular energy stores, which contributes to a fasting-like state in muscle tissue. Altogether, these findings uncover a novel function of p53 in the short-term regulation of nutrient metabolism in skeletal muscle and show that p53 serves to maintain metabolic homeostasis and efficient energy conservation.
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Growth differentiation factor 15 (GDF15) is a mitochondrial stress-induced cytokine that modulates energy balance in an endocrine manner. However, the importance of its brainstem-restricted receptor GDNF family receptor alpha-like (GFRAL) to mediate endocrine GDF15 signaling to the brain upon mitochondrial dysfunction is still unknown. Using a mouse model with muscle-specific mitochondrial dysfunction, we here show that GFRAL is required for activation of systemic energy metabolism via daytime-restricted anorexia but not responsible for muscle wasting. We further find that muscle mitochondrial stress response involves a GFRAL-dependent induction of hypothalamic corticotropin-releasing hormone, without elevated corticosterone levels. Finally, we identify that GFRAL signaling governs an anxiety-like behavior in male mice with muscle mitochondrial dysfunction, with females showing a less robust GFRAL-dependent anxiety-like phenotype. Together, we here provide novel evidence of a mitochondrial stress-induced muscle-brain crosstalk via the GDF15-GFRAL axis to modulate food intake and anxiogenic behavior.
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Factor 15 de Diferenciación de Crecimiento , Obesidad , Femenino , Masculino , Humanos , Factor 15 de Diferenciación de Crecimiento/genética , Factor 15 de Diferenciación de Crecimiento/metabolismo , Factor 15 de Diferenciación de Crecimiento/farmacología , Receptores del Factor Neurotrófico Derivado de la Línea Celular Glial/metabolismo , Obesidad/metabolismo , Hormona Liberadora de Corticotropina , Corticosterona , Factor Neurotrófico Derivado de la Línea Celular Glial , Ingestión de Alimentos/genética , AnsiedadRESUMEN
Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in the liver. Various mechanisms such as an increased uptake in fatty acids or de novo synthesis contribute to the development of steatosis and progression to more severe stages. Furthermore, it has been shown that impaired lipophagy, the degradation of lipids by autophagic processes, contributes to NAFLD. Through an unbiased lipidome analysis of mouse livers in a genetic model of impaired lipophagy, we aimed to determine the resulting alterations in the lipidome. Observed changes overlap with those of the human disease. Overall, the entire lipid content and in particular the triacylglycerol concentration increased under conditions of impaired lipophagy. In addition, we detected a reduction in long-chain polyunsaturated fatty acids (PUFAs) and an increased ratio of n-6 PUFAs to n-3 PUFAs, which was due to the depletion of n-3 PUFAs. Although the abundance of major phospholipid classes was reduced, the ratio of phosphatidylcholines to phosphatidylethanolamines was not affected. In conclusion, this study demonstrates that impaired lipophagy contributes to the pathology of NAFLD and is associated with an altered lipid profile. However, the lipid pattern does not appear to be specific for lipophagic alterations, as it resembles mainly that described in relation to fatty liver disease.
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Ácidos Grasos Omega-3 , Enfermedad del Hígado Graso no Alcohólico , Animales , Autofagia , Ácidos Grasos/metabolismo , Ácidos Grasos Omega-3/metabolismo , Humanos , Metabolismo de los Lípidos , Hígado/metabolismo , Ratones , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Fosfatidilcolinas/metabolismo , Fosfolípidos/metabolismo , Triglicéridos/metabolismoRESUMEN
The intake of high-fat diets (HFDs) containing large amounts of saturated long-chain fatty acids leads to obesity, oxidative stress, inflammation, and insulin resistance. The trace element selenium, as a crucial part of antioxidative selenoproteins, can protect against the development of diet-induced insulin resistance in white adipose tissue (WAT) by increasing glutathione peroxidase 3 (GPx3) and insulin receptor (IR) expression. Whether selenite (Se) can attenuate insulin resistance in established lipotoxic and obese conditions is unclear. We confirm that GPX3 mRNA expression in adipose tissue correlates with BMI in humans. Cultivating 3T3-L1 pre-adipocytes in palmitate-containing medium followed by Se treatment attenuates insulin resistance with enhanced GPx3 and IR expression and adipocyte differentiation. However, feeding obese mice a selenium-enriched high-fat diet (SRHFD) only resulted in a modest increase in overall selenoprotein gene expression in WAT in mice with unaltered body weight development, glucose tolerance, and insulin resistance. While Se supplementation improved adipocyte morphology, it did not alter WAT insulin sensitivity. However, mice fed a SRHFD exhibited increased insulin content in the pancreas. Overall, while selenite protects against palmitate-induced insulin resistance in vitro, obesity impedes the effect of selenite on insulin action and adipose tissue metabolism in vivo.
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Current attempts to prevent and manage type 2 diabetes have been moderately effective, and a better understanding of the molecular roots of this complex disease is important to develop more successful and precise treatment options. Recently, we initiated the collective diabetes cross, where four mouse inbred strains differing in their diabetes susceptibility were crossed with the obese and diabetes-prone NZO strain and identified the quantitative trait loci (QTL) Nidd13/NZO, a genomic region on chromosome 13 that correlates with hyperglycemia in NZO allele carriers compared to B6 controls. Subsequent analysis of the critical region, harboring 644 genes, included expression studies in pancreatic islets of congenic Nidd13/NZO mice, integration of single-cell data from parental NZO and B6 islets as well as haplotype analysis. Finally, of the five genes (Acot12, S100z, Ankrd55, Rnf180, and Iqgap2) within the polymorphic haplotype block that are differently expressed in islets of B6 compared to NZO mice, we identified the calcium-binding protein S100z gene to affect islet cell proliferation as well as apoptosis when overexpressed in MIN6 cells. In summary, we define S100z as the most striking gene to be causal for the diabetes QTL Nidd13/NZO by affecting ß-cell proliferation and apoptosis. Thus, S100z is an entirely novel diabetes gene regulating islet cell function.
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Diabetes Mellitus Tipo 2 , Hiperglucemia , Animales , Diabetes Mellitus Tipo 2/genética , Genotipo , Hiperglucemia/genética , Ratones , Ratones Endogámicos C57BL , Ratones Obesos , Sitios de Carácter CuantitativoRESUMEN
OBJECTIVE: Insulin regulates mitochondrial function, thereby propagating an efficient metabolism. Conversely, diabetes and insulin resistance are linked to mitochondrial dysfunction with a decreased expression of the mitochondrial chaperone HSP60. The aim of this investigation was to determine the effect of a reduced HSP60 expression on the development of obesity and insulin resistance. METHODS: Control and heterozygous whole-body HSP60 knockout (Hsp60+/-) mice were fed a high-fat diet (HFD, 60% calories from fat) for 16 weeks and subjected to extensive metabolic phenotyping. To understand the effect of HSP60 on white adipose tissue, microarray analysis of gonadal WAT was performed, ex vivo experiments were performed, and a lentiviral knockdown of HSP60 in 3T3-L1 cells was conducted to gain detailed insights into the effect of reduced HSP60 levels on adipocyte homeostasis. RESULTS: Male Hsp60+/- mice exhibited lower body weight with lower fat mass. These mice exhibited improved insulin sensitivity compared to control, as assessed by Matsuda Index and HOMA-IR. Accordingly, insulin levels were significantly reduced in Hsp60+/- mice in a glucose tolerance test. However, Hsp60+/- mice exhibited an altered adipose tissue metabolism with elevated insulin-independent glucose uptake, adipocyte hyperplasia in the presence of mitochondrial dysfunction, altered autophagy, and local insulin resistance. CONCLUSIONS: We discovered that the reduction of HSP60 in mice predominantly affects adipose tissue homeostasis, leading to beneficial alterations in body weight, body composition, and adipocyte morphology, albeit exhibiting local insulin resistance.
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Tejido Adiposo Blanco/metabolismo , Chaperonina 60/metabolismo , Proteínas Mitocondriales/metabolismo , Obesidad/metabolismo , Células 3T3-L1 , Animales , Células Cultivadas , Chaperonina 60/deficiencia , Dieta Alta en Grasa/efectos adversos , Metabolismo Energético , Homeostasis , Resistencia a la Insulina , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas Mitocondriales/deficienciaRESUMEN
BACKGROUND: Hepatic steatosis is a common chronic liver disease that can progress into more severe stages of NAFLD or promote the development of life-threatening secondary diseases for some of those affected. These include the liver itself (nonalcoholic steatohepatitis or NASH; fibrosis and cirrhosis, and hepatocellular carcinoma) or other organs such as the vessels and the heart (cardiovascular disease) or the islets of Langerhans (type 2 diabetes). In addition to elevated caloric intake and a sedentary lifestyle, genetic and epigenetic predisposition contribute to the development of NAFLD and the secondary diseases. SCOPE OF REVIEW: We present data from genome-wide association studies (GWAS) and functional studies in rodents which describe polymorphisms identified in genes relevant for the disease as well as changes caused by altered DNA methylation and gene regulation via specific miRNAs. The review also provides information on the current status of the use of genetic and epigenetic factors as risk markers. MAJOR CONCLUSION: With our overview we provide an insight into the genetic and epigenetic landscape of NAFLD and argue about the applicability of currently defined risk scores for risk stratification and conclude that further efforts are needed to make the scores more usable and meaningful.
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Epigénesis Genética , Predisposición Genética a la Enfermedad , Enfermedad del Hígado Graso no Alcohólico/genética , Animales , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patología , Metilación de ADN , Diabetes Mellitus Tipo 2/genética , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Estudio de Asociación del Genoma Completo , Humanos , Cirrosis Hepática/diagnóstico , Cirrosis Hepática/genética , Cirrosis Hepática/patología , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patología , MicroARNs/metabolismo , Enfermedad del Hígado Graso no Alcohólico/complicaciones , Enfermedad del Hígado Graso no Alcohólico/diagnóstico , Enfermedad del Hígado Graso no Alcohólico/patología , Polimorfismo de Nucleótido Simple , Factores de Riesgo , Índice de Severidad de la EnfermedadRESUMEN
Overnutrition contributes to insulin resistance, obesity and metabolic stress, initiating a loss of functional beta-cells and diabetes development. Whether these damaging effects are amplified in advanced age is barely investigated. Therefore, New Zealand Obese (NZO) mice, a well-established model for the investigation of human obesity-associated type 2 diabetes, were fed a metabolically challenging diet with a high-fat, carbohydrate restricted period followed by a carbohydrate intervention in young as well as advanced age. Interestingly, while young NZO mice developed massive hyperglycemia in response to carbohydrate feeding, leading to beta-cell dysfunction and cell death, aged counterparts compensated the increased insulin demand by persistent beta-cell function and beta-cell mass expansion. Beta-cell loss in young NZO islets was linked to increased expression of thioredoxin-interacting protein (TXNIP), presumably initiating an apoptosis-signaling cascade via caspase-3 activation. In contrast, islets of aged NZOs exhibited a sustained redox balance without changes in TXNIP expression, associated with higher proliferative potential by cell cycle activation. These findings support the relevance of a maintained proliferative potential and redox homeostasis for preserving islet functionality under metabolic stress, with the peculiarity that this adaptive response emerged with advanced age in diabetes-prone NZO mice.
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Proteínas Portadoras , Diabetes Mellitus Tipo 2 , Células Secretoras de Insulina , Tiorredoxinas , Animales , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Ciclo Celular , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Homeostasis , Células Secretoras de Insulina/metabolismo , Ratones , Ratones Obesos , Oxidación-Reducción , Estrés Fisiológico , Tiorredoxinas/genética , Tiorredoxinas/metabolismoRESUMEN
OBJECTIVE: Altered gene expression contributes to the development of type 2 diabetes (T2D); thus, the analysis of differentially expressed genes between diabetes-susceptible and diabetes-resistant mouse models is an important tool for the determination of candidate genes that participate in the pathology. Based on RNA-seq and array data comparing pancreatic gene expression of diabetes-prone New Zealand Obese (NZO) mice and diabetes-resistant B6.V-ob/ob (B6-ob/ob) mice, the gap junction protein beta 4 (Gjb4) was identified as a putative novel T2D candidate gene. METHODS: Gjb4 was overexpressed in primary islet cells derived from C57BL/6 (B6) mice and INS-1 cells via adenoviral-mediated infection. The proliferation rate of cells was assessed by BrdU incorporation, and insulin secretion was measured under low (2.8 mM) and high (20 mM) glucose concentration. INS-1 cell apoptosis rate was determined by Western blotting assessing cleaved caspase 3 levels. RESULTS: Overexpression of Gjb4 in primary islet cells significantly inhibited the proliferation by 47%, reduced insulin secretion of primary islets (46%) and INS-1 cells (51%), and enhanced the rate of apoptosis by 63% in INS-1 cells. Moreover, an altered expression of the miR-341-3p contributes to the Gjb4 expression difference between diabetes-prone and diabetes-resistant mice. CONCLUSIONS: The gap junction protein Gjb4 is highly expressed in islets of diabetes-prone NZO mice and may play a role in the development of T2D by altering islet cell function, inducing apoptosis and inhibiting proliferation.
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Conexinas/metabolismo , Secreción de Insulina/genética , Islotes Pancreáticos/metabolismo , Animales , Proliferación Celular/fisiología , Conexinas/genética , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/fisiopatología , Expresión Génica , Glucosa/metabolismo , Prueba de Tolerancia a la Glucosa , Insulina/metabolismo , Secreción de Insulina/fisiología , Células Secretoras de Insulina/fisiología , Islotes Pancreáticos/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Obesos , Obesidad/metabolismo , Páncreas/metabolismoRESUMEN
BACKGROUND & AIMS: Currently, only a few genetic variants explain the heritability of fatty liver disease. Quantitative trait loci (QTL) analysis of mouse strains has identified the susceptibility locus Ltg/NZO (liver triglycerides from New Zealand obese [NZO] alleles) on chromosome 18 as associating with increased hepatic triglycerides. Herein, we aimed to identify genomic variants responsible for this association. METHODS: Recombinant congenic mice carrying 5.3 Mbp of Ltg/NZO were fed a high-fat diet and characterized for liver fat. Bioinformatic analysis, mRNA profiles and electrophoretic mobility shift assays were performed to identify genes responsible for the Ltg/NZO phenotype. Candidate genes were manipulated in vivo by injecting specific microRNAs into C57BL/6 mice. Pulldown coupled with mass spectrometry-based proteomics and immunoprecipitation were performed to identify interaction partners of IFGGA2. RESULTS: Through positional cloning, we identified 2 immunity-related GTPases (Ifgga2, Ifgga4) that prevent hepatic lipid storage. Expression of both murine genes and the human orthologue IRGM was significantly lower in fatty livers. Accordingly, liver-specific suppression of either Ifgga2 or Ifgga4 led to a 3-4-fold greater increase in hepatic fat content. In the liver of low-fat diet-fed mice, IFGGA2 localized to endosomes/lysosomes, while on a high-fat diet it associated with lipid droplets. Pulldown experiments and proteomics identified the lipase ATGL as a binding partner of IFGGA2 which was confirmed by co-immunoprecipitation. Both proteins partially co-localized with the autophagic marker LC3B. Ifgga2 suppression in hepatocytes reduced the amount of LC3B-II, whereas overexpression of Ifgga2 increased the association of LC3B with lipid droplets and decreased triglyceride storage. CONCLUSION: IFGGA2 interacts with ATGL and protects against hepatic steatosis, most likely by enhancing the binding of LC3B to lipid droplets. LAY SUMMARY: The genetic basis of non-alcoholic fatty liver disease remains incompletely defined. Herein, we identified members of the immunity-related GTPase family in mice and humans that act as regulators of hepatic fat accumulation, with links to autophagy. Overexpression of the gene Ifgga2 was shown to reduce hepatic lipid storage and could be a therapeutic target for the treatment of fatty liver disease.
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Hígado Graso/genética , Proteínas de Unión al GTP/genética , Regulación de la Expresión Génica , Hepatocitos/metabolismo , Lipasa/genética , Metabolismo de los Lípidos/genética , Proteínas Asociadas a Microtúbulos/genética , Animales , Autofagia , Modelos Animales de Enfermedad , Hígado Graso/metabolismo , Hígado Graso/patología , Femenino , GTP Fosfohidrolasas/genética , GTP Fosfohidrolasas/metabolismo , Proteínas de Unión al GTP/biosíntesis , Células Hep G2 , Hepatocitos/patología , Humanos , Lipasa/biosíntesis , Lipasa/metabolismo , Hígado/metabolismo , Hígado/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas Asociadas a Microtúbulos/biosíntesis , Fenotipo , ARN/genéticaRESUMEN
Eps15-homology domain containing protein 2 (EHD2) is a dynamin-related ATPase located at the neck of caveolae, but its physiological function has remained unclear. Here, we found that global genetic ablation of EHD2 in mice leads to increased lipid droplet size in fat tissue. This organismic phenotype was paralleled at the cellular level by increased fatty acid uptake via a caveolae- and CD36-dependent pathway that also involves dynamin. Concomitantly, elevated numbers of detached caveolae were found in brown and white adipose tissue lacking EHD2, and increased caveolar mobility in mouse embryonic fibroblasts. EHD2 expression itself was down-regulated in the visceral fat of two obese mouse models and obese patients. Our data suggest that EHD2 controls a cell-autonomous, caveolae-dependent fatty acid uptake pathway and imply that low EHD2 expression levels are linked to obesity.
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Proteínas Portadoras/metabolismo , Caveolas/metabolismo , Ácidos Grasos/metabolismo , Animales , Transporte Biológico , Membrana Celular/metabolismo , Células HeLa , Humanos , Gotas Lipídicas/metabolismo , Metabolismo de los Lípidos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
In a subset of patients, non-alcoholic fatty liver disease (NAFLD) is complicated by cell death and inflammation resulting in non-alcoholic steatohepatitis (NASH), which may progress to fibrosis and subsequent organ failure. Apart from cytokines, prostaglandins, in particular prostaglandin E2 (PGE2), play a pivotal role during inflammatory processes. Expression of the key enzymes of PGE2 synthesis, cyclooxygenase 2 and microsomal PGE synthase 1 (mPGES-1), was increased in human NASH livers in comparison to controls and correlated with the NASH activity score. Both enzymes were also induced in NASH-diet-fed wild-type mice, resulting in an increase in hepatic PGE2 concentration that was completely abrogated in mPGES-1-deficient mice. PGE2 is known to inhibit TNF-α synthesis in macrophages. A strong infiltration of monocyte-derived macrophages was observed in NASH-diet-fed mice, which was accompanied with an increase in hepatic TNF-α expression. Due to the impaired PGE2 production, TNF-α expression increased much more in livers of mPGES-1-deficient mice or in the peritoneal macrophages of these mice. The increased levels of TNF-α resulted in an enhanced IL-1ß production, primarily in hepatocytes, and augmented hepatocyte apoptosis. In conclusion, attenuation of PGE2 production by mPGES-1 ablation enhanced the TNF-α-triggered inflammatory response and hepatocyte apoptosis in diet-induced NASH.
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Inflamación/patología , Hígado/patología , Microsomas/enzimología , Enfermedad del Hígado Graso no Alcohólico/enzimología , Enfermedad del Hígado Graso no Alcohólico/patología , Prostaglandina-E Sintasas/metabolismo , Animales , Apoptosis , Dinoprostona/biosíntesis , Modelos Animales de Enfermedad , Retroalimentación Fisiológica , Hepatocitos/metabolismo , Humanos , Interleucina-1beta/metabolismo , Macrófagos Peritoneales/metabolismo , Ratones Endogámicos C57BL , Modelos Biológicos , Factor de Necrosis Tumoral alfa/metabolismo , Regulación hacia ArribaRESUMEN
While the impact of dietary cholesterol on the progression of atherosclerosis has probably been overestimated, increasing evidence suggests that dietary cholesterol might favor the transition from blunt steatosis to non-alcoholic steatohepatitis (NASH), especially in combination with high fat diets. It is poorly understood how cholesterol alone or in combination with other dietary lipid components contributes to the development of lipotoxicity. The current study demonstrated that liver damage caused by dietary cholesterol in mice was strongly enhanced by a high fat diet containing soybean oil-derived ω6-poly-unsaturated fatty acids (ω6-PUFA), but not by a lard-based high fat diet containing mainly saturated fatty acids. In contrast to the lard-based diet the soybean oil-based diet augmented cholesterol accumulation in hepatocytes, presumably by impairing cholesterol-eliminating pathways. The soybean oil-based diet enhanced cholesterol-induced mitochondrial damage and amplified the ensuing oxidative stress, probably by peroxidation of poly-unsaturated fatty acids. This resulted in hepatocyte death, recruitment of inflammatory cells, and fibrosis, and caused a transition from steatosis to NASH, doubling the NASH activity score. Thus, the recommendation to reduce cholesterol intake, in particular in diets rich in ω6-PUFA, although not necessary to reduce the risk of atherosclerosis, might be sensible for patients suffering from non-alcoholic fatty liver disease.
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Colesterol en la Dieta , Ácidos Grasos Omega-6/toxicidad , Hígado/efectos de los fármacos , Enfermedad del Hígado Graso no Alcohólico/inducido químicamente , Aceite de Soja/toxicidad , Animales , Muerte Celular/efectos de los fármacos , Modelos Animales de Enfermedad , Peroxidación de Lípido/efectos de los fármacos , Hígado/metabolismo , Hígado/patología , Masculino , Ratones Endogámicos C57BL , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Mitocondrias Hepáticas/patología , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Enfermedad del Hígado Graso no Alcohólico/patología , Estrés Oxidativo/efectos de los fármacosRESUMEN
Remodeling of the extracellular matrix is a key component of the metabolic adaptations of adipose tissue in response to dietary and physiological challenges. Disruption of its integrity is a well-known aspect of adipose tissue dysfunction, for instance, during aging and obesity. Adipocyte regeneration from a tissue-resident pool of mesenchymal stem cells is part of normal tissue homeostasis. Among the pathophysiological consequences of adipogenic stem cell aging, characteristic changes in the secretory phenotype, which includes matrix-modifying proteins, have been described. Here, we show that the expression of the matricellular protein periostin, a component of the extracellular matrix produced and secreted by adipose tissue-resident interstitial cells, is markedly decreased in aged brown and white adipose tissue depots. Using a mouse model, we demonstrate that the adaptation of adipose tissue to adrenergic stimulation and high-fat diet feeding is impaired in animals with systemic ablation of the gene encoding for periostin. Our data suggest that loss of periostin attenuates lipid metabolism in adipose tissue, thus recapitulating one aspect of age-related metabolic dysfunction. In human white adipose tissue, periostin expression showed an unexpected positive correlation with age of study participants. This correlation, however, was no longer evident after adjusting for BMI or plasma lipid and liver function biomarkers. These findings taken together suggest that age-related alterations of the adipose tissue extracellular matrix may contribute to the development of metabolic disease by negatively affecting nutrient homeostasis.
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Tejido Adiposo/metabolismo , Tejido Adiposo/patología , Envejecimiento/metabolismo , Moléculas de Adhesión Celular/deficiencia , Moléculas de Adhesión Celular/genética , Eliminación de Gen , Metabolismo de los Lípidos , Tejido Adiposo/efectos de los fármacos , Adrenérgicos/farmacología , Adulto , Anciano , Anciano de 80 o más Años , Animales , Tamaño Corporal/efectos de los fármacos , Moléculas de Adhesión Celular/metabolismo , Frío , Dieta Alta en Grasa , Activación Enzimática/efectos de los fármacos , Conducta Alimentaria , Femenino , Humanos , Metabolismo de los Lípidos/efectos de los fármacos , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , Obesidad/patología , Tamaño de los Órganos/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Esterol Esterasa/metabolismo , Termogénesis/efectos de los fármacos , Adulto JovenRESUMEN
To explore the genetic determinants of obesity and Type 2 diabetes (T2D), the German Center for Diabetes Research (DZD) conducted crossbreedings of the obese and diabetes-prone New Zealand Obese mouse strain with four different lean strains (B6, DBA, C3H, 129P2) that vary in their susceptibility to develop T2D. Genome-wide linkage analyses localized more than 290 quantitative trait loci (QTL) for obesity, 190 QTL for diabetes-related traits and 100 QTL for plasma metabolites in the outcross populations. A computational framework was developed that allowed to refine critical regions and to nominate a small number of candidate genes by integrating reciprocal haplotype mapping and transcriptome data. The efficiency of the complex procedure was demonstrated for one obesity QTL. The genomic interval of 35 Mb with 502 annotated candidate genes was narrowed down to six candidates. Accordingly, congenic mice retained the obesity phenotype owing to an interval that contains three of the six candidate genes. Among these the phospholipase PLA2G4A exhibited an elevated expression in adipose tissue of obese human subjects and is therefore a critical regulator of the obesity locus. Together, our broad and complex approach demonstrates that combined- and comparative-cross analysis exhibits improved mapping resolution and represents a valid tool for the identification of disease genes.
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Biomarcadores/análisis , Biología Computacional/métodos , Diabetes Mellitus Tipo 2/genética , Fosfolipasas A2 Grupo IV/genética , Obesidad/genética , Polimorfismo de Nucleótido Simple , Sitios de Carácter Cuantitativo , Tejido Adiposo/metabolismo , Tejido Adiposo/patología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Animales , Mapeo Cromosómico , Cruzamientos Genéticos , Diabetes Mellitus Tipo 2/complicaciones , Femenino , Ligamiento Genético , Humanos , Masculino , Ratones , Ratones Congénicos , Ratones Endogámicos C3H , Ratones Endogámicos DBA , Persona de Mediana Edad , Obesidad/complicaciones , Fenotipo , Porcinos , Adulto JovenRESUMEN
AIMS/HYPOTHESIS: Wingless-type (Wnt) inducible signalling pathway protein-1 (WISP1) has been recently identified as a proinflammatory adipokine. We examined whether WISP1 expression and circulating levels are altered in type 2 diabetes and whether WISP1 affects insulin signalling in muscle cells and hepatocytes. METHODS: Serum and visceral adipose tissue (VAT) biopsies, for analysis of circulating WISP1 levels by ELISA and WISP1 mRNA expression by real-time quantitative RT-PCR, were collected from normal-weight men (control group, n = 33) and obese men with (n = 46) and without type 2 diabetes (n = 56) undergoing surgery. Following incubation of primary human skeletal muscle cells (hSkMCs) and murine AML12 hepatocytes with WISP1 and insulin, insulin signalling was analysed by western blotting. The effect of WISP1 on insulin-stimulated glycogen synthesis and gluconeogenesis was investigated in hSkMCs and murine hepatocytes, respectively. RESULTS: Circulating WISP1 levels were higher in obese men (independent of diabetes status) than in normal-weight men (mean [95% CI]: 70.8 [55.2, 86.4] ng/l vs 42.6 [28.5, 56.6] ng/l, respectively; p < 0.05). VAT WISP1 expression was 1.9-fold higher in obese men vs normal-weight men (p < 0.05). Circulating WISP1 levels were positively associated with blood glucose in the OGTT and circulating haem oxygenase-1 and negatively associated with adiponectin levels. In hSkMCs and AML12 hepatocytes, recombinant WISP1 impaired insulin action by inhibiting phosphorylation of insulin receptor, Akt and its substrates glycogen synthase kinase 3ß, FOXO1 and p70S6 kinase, and inhibiting insulin-stimulated glycogen synthesis and suppression of gluconeogenic genes. CONCLUSIONS/INTERPRETATION: Circulating WISP1 levels and WISP1 expression in VAT are increased in obesity independent of glycaemic status. Furthermore, WISP1 impaired insulin signalling in muscle and liver cells.
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Proteínas CCN de Señalización Intercelular/metabolismo , Hepatocitos/metabolismo , Resistencia a la Insulina/fisiología , Fibras Musculares Esqueléticas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Animales , Glucemia/metabolismo , Proteínas CCN de Señalización Intercelular/sangre , Ensayo de Inmunoadsorción Enzimática , Humanos , Grasa Intraabdominal/metabolismo , Ratones , Fosforilación , Proteínas Proto-Oncogénicas/sangre , Receptor de Insulina/metabolismo , Transducción de SeñalRESUMEN
OBJECTIVE: Obesity and type 2 diabetes (T2D) arise from the interplay between genetic, epigenetic, and environmental factors. The aim of this study was to combine bioinformatics and functional studies to identify miRNAs that contribute to obesity and T2D. METHODS: A computational framework (miR-QTL-Scan) was applied by combining QTL, miRNA prediction, and transcriptomics in order to enhance the power for the discovery of miRNAs as regulative elements. Expression of several miRNAs was analyzed in human adipose tissue and blood cells and miR-31 was manipulated in a human fat cell line. RESULTS: In 17 partially overlapping QTL for obesity and T2D 170 miRNAs were identified. Four miRNAs (miR-15b, miR-30b, miR-31, miR-744) were recognized in gWAT (gonadal white adipose tissue) and six (miR-491, miR-455, miR-423-5p, miR-132-3p, miR-365-3p, miR-30b) in BAT (brown adipose tissue). To provide direct functional evidence for the achievement of the miR-QTL-Scan, miR-31 located in the obesity QTL Nob6 was experimentally analyzed. Its expression was higher in gWAT of obese and diabetic mice and humans than of lean controls. Accordingly, 10 potential target genes involved in insulin signaling and adipogenesis were suppressed. Manipulation of miR-31 in human SGBS adipocytes affected the expression of GLUT4, PPARγ, IRS1, and ACACA. In human peripheral blood mononuclear cells (PBMC) miR-15b levels were correlated to baseline blood glucose concentrations and might be an indicator for diabetes. CONCLUSION: Thus, miR-QTL-Scan allowed the identification of novel miRNAs relevant for obesity and T2D.
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Diabetes Mellitus Tipo 2/genética , MicroARNs/genética , Obesidad/genética , Sitios de Carácter Cuantitativo , Transcriptoma , Tejido Adiposo/metabolismo , Animales , Células Sanguíneas/metabolismo , Línea Celular , Diabetes Mellitus Tipo 2/metabolismo , Humanos , Ratones , Obesidad/metabolismoRESUMEN
AIMS/HYPOTHESIS: Low-protein diets are well known to improve glucose tolerance and increase energy expenditure. Increases in circulating fibroblast growth factor 21 (FGF21) have been implicated as a potential underlying mechanism. METHODS: We aimed to test whether low-protein diets in the context of a high-carbohydrate or high-fat regimen would also protect against type 2 diabetes in New Zealand Obese (NZO) mice used as a model of polygenetic obesity and type 2 diabetes. Mice were placed on high-fat diets that provided protein at control (16 kJ%; CON) or low (4 kJ%; low-protein/high-carbohydrate [LP/HC] or low-protein/high-fat [LP/HF]) levels. RESULTS: Protein restriction prevented the onset of hyperglycaemia and beta cell loss despite increased food intake and fat mass. The effect was seen only under conditions of a lower carbohydrate/fat ratio (LP/HF). When the carbohydrate/fat ratio was high (LP/HC), mice developed type 2 diabetes despite the robustly elevated hepatic FGF21 secretion and increased energy expenditure. CONCLUSION/INTERPRETATION: Prevention of type 2 diabetes through protein restriction, without lowering food intake and body fat mass, is compromised by high dietary carbohydrates. Increased FGF21 levels and elevated energy expenditure do not protect against hyperglycaemia and type 2 diabetes per se.
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Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Dieta con Restricción de Proteínas , Carbohidratos de la Dieta/metabolismo , Tejido Adiposo , Animales , Glucemia/metabolismo , Peso Corporal , Diabetes Mellitus Tipo 2/genética , Metabolismo Energético , Factores de Crecimiento de Fibroblastos/genética , Prueba de Tolerancia a la Glucosa , Insulina/metabolismo , Resistencia a la Insulina , Masculino , Ratones , Ratones Obesos , Ratones Transgénicos , Obesidad/metabolismoRESUMEN
AIMS/HYPOTHESIS: Obesity results from a constant and complex interplay between environmental stimuli and predisposing genes. Recently, we identified the IFN-activated gene Ifi202b as the most likely gene responsible for the obesity quantitative trait locus Nob3 (New Zealand Obese [NZO] obesity 3). The aim of this study was to evaluate the effects of Ifi202b on body weight and adipose tissue biology, and to clarify the functional role of its human orthologue IFI16. METHODS: The impact of Ifi202b and its human orthologue IFI16 on adipogenesis was investigated by modulating their respective expression in murine 3T3-L1 and human Simpson-Golabi-Behmel syndrome (SGBS) pre-adipocytes. Furthermore, transgenic mice overexpressing IFI202b were generated and characterised with respect to metabolic traits. In humans, expression levels of IFI16 in adipose tissue were correlated with several variables of adipocyte function. RESULTS: In mice, IFI202b overexpression caused obesity (Δ body weight at the age of 30 weeks: 10.2 ± 1.9 g vs wild-type mice) marked by hypertrophic fat mass expansion, increased expression of Zfp423 (encoding the transcription factor zinc finger protein [ZFP] 423) and white-selective genes (Tcf21, Tle3), and decreased expression of thermogenic genes (e.g. Cidea, Ucp1). Compared with their wild-type littermates, Ifi202b transgenic mice displayed lower body temperature, hepatosteatosis and systemic insulin resistance. Suppression of IFI202b/IFI16 in pre-adipocytes impaired adipocyte differentiation and triacylglycerol storage. Humans with high levels of IFI16 exhibited larger adipocytes, an enhanced inflammatory state and impaired insulin-stimulated glucose uptake in white adipose tissue. CONCLUSIONS/INTERPRETATION: Our findings reveal novel functions of Ifi202b and IFI16, demonstrating their role as obesity genes. These genes promote white adipogenesis and fat storage, thereby facilitating the development of obesity-associated insulin resistance.