New insights into circulating FABP4: Interaction with cytokeratin 1 on endothelial cell membranes.

Fatty acid-binding protein 4 (FABP4) is an adipose tissue-secreted adipokine that is involved in the regulation of energetic metabolism and inflammation. Increased levels of circulating FABP4 have been detected in individuals with cardiovascular risk factors. Recent studies have demonstrated that FABP4 has a direct effect on peripheral tissues, specifically promoting vascular dysfunction; however, its mechanism of action is unknown. The objective of this work was to assess the specific interactions between exogenous FABP4 and the plasma membranes of endothelial cells. Immunofluorescence assays showed that exogenous FABP4 localized along the plasma membranes of human umbilical vein endothelial cells (HUVECs), interacting specifically with plasma membrane proteins. Anti-FABP4 immunoblotting revealed two covalent protein complexes containing FABP4 and its putative receptor; these complexes were approximately 108 kDa and 77 kDa in size. Proteomics and mass spectrometry experiments revealed that cytokeratin 1 (CK1) was the FABP4-binding protein. An anti-CK1 immunoblot confirmed the presence of CK1. FABP4-CK1 complexes were also detected in HAECs, HCASMCs, HepG2 cells and THP-1 cells. Pharmacological FABP4 inhibition by BMS309403 results in a slight decrease in the formation of these complexes, indicating that fatty acids may play a role in FABP4 functionality. In addition, we demonstrated that exogenous FABP4 crosses the plasma membrane to enter the cytoplasm and nucleus in HUVECs. These findings indicate that exogenous FABP4 interacts with plasma membrane proteins, specifically CK1. These data contribute to our current knowledge regarding the mechanism of action of circulating FABP4.

Survivin/BIRC5 as a novel molecular effector at the crossroads of glucose metabolism and radioresistance in head and neck squamous cell carcinoma.

BACKGROUND: Metabolic reprogramming and abnormal glucose metabolism are hallmarks of head and neck squamous cell carcinoma (HNSCC). Certain oncogenes can promote cancer-related metabolic changes, but understanding their crosstalk in HNSCC biology and treatment is essential for identifying predictive biomarkers and developing target therapies. METHODS: We assessed the value of survivin/BIRC5 as a radioresistance factor potentially modulated by glucose for predicting therapeutic sensitivity and prognosis of HNSCC in a cohort of 32 patients. Additionally, we conducted in vitro experiments to explore the role of survivin/BIRC5 in glucose metabolism concerning radiation response. RESULTS: Tumoral BIRC5 expression is associated with serum glucose and predicts locoregional disease-free survival and lower BIRC5 mRNA levels are associated with better outcomes. Upregulation of BIRC5 by radiation depends on glucose levels and provokes a pro-tumoral and radioresistant phenotype in surviving cells. CONCLUSIONS: Survivin/BIRC5 might be independently associated with the risk of recurrence in patients with HNSCC.

Phosphorylation regulates the subcellular location and activity of the snail transcriptional repressor.

The Snail gene product is a transcriptional repressor of E-cadherin expression and an inducer of the epithelial-to-mesenchymal transition in several epithelial tumor cell lines. This report presents data indicating that Snail function is controlled by its intracellular location. The cytosolic distribution of Snail depended on export from the nucleus by a CRM1-dependent mechanism, and a nuclear export sequence (NES) was located in the regulatory domain of this protein. Export of Snail was controlled by phosphorylation of a Ser-rich sequence adjacent to this NES. Modification of this sequence released the restriction created by the zinc finger domain and allowed nuclear export of the protein. The phosphorylation and subcellular distribution of Snail are controlled by cell attachment to the extracellular matrix. Suspended cells presented higher levels of phosphorylated Snail and an augmented extranuclear localization with respect to cells attached to the plate. These findings show the existence in tumor cells of an effective and fine-tuning nontranscriptional mechanism of regulation of Snail activity dependent on the extracellular environment.

Circulating PCSK9 in patients with type 2 diabetes and related metabolic disorders.

BACKGROUND: PCSK9 is a pivotal molecule in the regulation of lipid metabolism. Previous studies have suggested that PCSK9 expression and its function in LDL receptor regulation could be altered in the context of diabetes. The aim was to assess PCSK9 plasma levels in patients with type 2 diabetes (T2DM) and other related metabolic disorders as well as its relation to the metabolomic profile generated by nuclear magnetic resonance (NMR) and glucose homeostasis. METHODS: There were recruited a total of 457 patients suffering from T2DM and other metabolic disorders (metabolic syndrome (MetS), obesity and atherogenic dyslipidaemia (AD) and other disorders). Anamnesis, anthropometry and physical examinations were conducted, and vascular and abdominal adiposity imaging were carried out. Biochemical studies were performed to determine PCSK9 plasma levels 6 weeks after lipid lowering drug wash-out in treated patients. A complete metabolomic lipid profile was also generated by NMR. The rs505151 and rs11591147 genetic variants of PCSK9 gene were identified in patients. RESULTS: The results showed that PCSK9 levels are increased in patients with T2DM and MetS (14% and 13%; p<0.005, respectively). Circulating PCSK9 levels were correlated with an atherogenic lipid profile and with insulin resistance parameters. PCSK9 levels were also positively associated with AD, as defined by lipoprotein particle number and size. The rs11591147 genetic variant resulted in lower levels of circulating PCSK9 and LDL cholesterol (LDL-C). CONCLUSIONS: PCSK9 plasma levels are increased in T2DM and MetS patients and are associated with LDL-C and other parameters of AD and glucose metabolism.

Impact of epidermal fatty acid binding protein on 2D-NMR-assessed atherogenic dyslipidemia and related disorders.

BACKGROUND: The role of circulating FABP5 on metabolic alterations is under active evaluation. On the other hand, FABP5 SNPs (rs454550 and rs79370435) seem to modulate its effect. OBJECTIVES: Our aim was to examine the role of circulating FABP5 levels and its main SNPs in atherogenic dyslipidemia (AD) assessed by 2D-Nuclear Magnetic Resonance (NMR) and related metabolic and inflammation markers. We hypothesized that circulating FABP5 may be a biomarker for metabolic risk. METHODS: We studied 459 subjects admitted to the metabolism unit because of lipid metabolism disturbances and/or associated disorders. After a 6-week lipid-lowering drug wash-out period, anamnesis and physical examination were performed. Carotid intime-media thickness (cIMT) was measured by ultrasound. FABP5, FABP4, lipids, metabolic proteins, and enzymes were determined by biochemical methods. The lipid profile was assessed by NMR. The rs454550 and rs79370435 FABP5 gene variants were also determined. RESULTS: The FABP5 plasma levels were positively correlated with adiposity, glucose metabolism, and lipolysis parameters and were associated with AD, as assessed by NMR. There was a significant positive correlation between hsCRP and FABP5. The presence of type 2 diabetes, obesity, metabolic syndrome, or AD was associated with higher FABP5 plasma levels (P < .005). The FABP5 concentrations, but not those of FABP4, were higher in patients with carotid plaques. FABP5 was a main determinant of plaque presence according to logistic regression analysis. The rare rs454550 allele was hyper-represented in nonobese subjects (P = .011). CONCLUSIONS: FABP5 is a biomarker of adiposity-associated metabolic derangements that include AD thus underscoring the concomitant presence of inflammation. FABP5 is associated with increased subclinical atherosclerosis.

[Interaction of FABP4 with plasma membrane proteins of endothelial cells]. / Interacción de FABP4 con proteínas de membrana de células endoteliales.

INTRODUCTION: Fatty acid binding protein (FABP4) is an adipose tissue-secreted adipokine implicated in the regulation of the energetic metabolism and inflammation. High levels of circulating FABP4 have been described in people with obesity, atherogenic dyslipidemia, diabetes and metabolic syndrome. Recent studies have demonstrated that FABP4 could have a direct effect on peripheral tissues and, specifically, on vascular function. It is still unknown how the interaction between FABP4 and the endothelial cells is produced to prompt these effects on vascular function. The objective of this work is studying the interaction between FABP4 and the plasma membrane proteins of endothelial cells. METHODOLOGY: HUVEC cells were incubated with and without FABP4 (100 ng/ml) for 5 minutes. Immunolocalization of FABP4 was studied by confocal microscopy. The results showed that FABP4 colocalizates with CD31, a membrane protein marker. A strategy which combines 6XHistidine-tag FABP4 (FABP4-His), incubations with or without FABP4-His (100 ng/ml), formaldehyde cross-linking, cellular membrane protein extraction and western blot, was designed to study the FABP4 interactions with membrane proteins of HUVECs. RESULTS: The results showed different western blot profiles depending of the incubation with or without FABP4-His. The immunoblot revelead three covalent protein complexes of about 108, 77 and 33 kDa containing FAPB4 and its putative receptor. DISCUSSION: The existence of a specific binding protein complex able to bind FABP4 to endothelial cells is supported by these results. The obtained results will permit us advance in the molecular knowledge of FABP4 effects as well as use this protein and its receptor as therapeutic target to prevent cardiovascular.

Circulating PCSK9 in patients with type 2 diabetes and related metabolic disorders / Concentraciones circulantes de PCSK9 en población con diabetes tipo 2 y alteraciones metabólicas asociadas

Background: PCSK9 is a pivotal molecule in the regulation of lipid metabolism. Previous studies have suggested that PCSK9 expression and its function in LDL receptor regulation could be altered in the context of diabetes. The aim was to assess PCSK9 plasma levels in patients with type 2 diabetes (T2DM) and other related metabolic disorders as well as its relation to the metabolomic profile generated by nuclear magnetic resonance (NMR) and glucose homeostasis. Methods: There were recruited a total of 457 patients suffering from T2DM and other metabolic disorders (metabolic syndrome (MetS), obesity and atherogenic dyslipidaemia (AD) and other disorders). Anamnesis, anthropometry and physical examinations were conducted, and vascular and abdominal adiposity imaging were carried out. Biochemical studies were performed to determine PCSK9 plasma levels 6 weeks after lipid lowering drug wash-out in treated patients. A complete metabolomic lipid profile was also generated by NMR. The rs505151 and rs11591147 genetic variants of PCSK9 gene were identified in patients. Results: The results showed that PCSK9 levels are increased in patients with T2DM and MetS (14% and 13%;p < 0.005, respectively). Circulating PCSK9 levels were correlated with an atherogenic lipid profile and with insulin resistance parameters. PCSK9 levels were also positively associated with AD, as defined by lipoprotein particle number and size. The rs11591147 genetic variant resulted in lower levels of circulating PCSK9 and LDL cholesterol (LDL-C). Conclusions: PCSK9 plasma levels are increased in T2DM and MetS patients and are associated with LDL-C and other parameters of AD and glucose metabolism

Introducción: PCSK9 es una molécula clave en la regulación del metabolismo lipídico. Estudios previos sugieren que la expresión y función de PCSK9 entorno a la regulación del receptor LDL puede alterarse en la diabetes. El objetivo del estudio fue determinar los niveles circulantes de PCSK9 en pacientes con diabetes tipo 2 (DM) y otras enfermedades metabólicas y su relación con las lipoproteínas estudiadas mediante resonancia magnética nuclear (RMN) y la homeostasis de la glucosa. Métodos: Se estudiaron un total de 457 pacientes, afectos de DM y otras alteraciones metabólicas (síndrome metabólico [SMet], obesidad y dislipidemia aterogénica [DA] y otros). Se realizó anamnesis, antropometría, exploración física y estudio vascular de carótidas y adiposidad abdominal. Se realizó bioquímica incluyendo PCSK9 circulante (tras 6 semanas de lavado en pacientes con hipolipemiantes). Se estudió mediante RMN el perfil de lipoproteínas. Se determinaron las variantes genéticas rs505151 y rs11591147 del gen PCSK9. Resultados: Los niveles circulantes de PCSK9 están aumentados en pacientes con DM y SMet (14 y 13%; p<0.005, respectivamente). Los niveles circulantes de PCSK9 se correlacionaron de forma positiva con el perfil lipídico aterogénico y parámetros de resistencia insulínica. Los niveles circulantes de PCSK9 también se asociaron positivamente a DA, definida mediante el número y el tamaño de lipoproteínas analizado mediante RMN. Los portadores de la variante genética rs11591147 mostraron niveles inferiores de PCSK9 plasmática y cLDL. Conclusiones: Los niveles circulantes de PCSK9 están aumentados en pacientes con DM y SMet junto con parámetros de DA y metabolismo de la glucosa, más allá del cLDL

Interacción de FABP4 con proteínas de membrana de células endoteliales / Interaction of FABP4 with plasma membrane proteins of endothelial cells

Introducción: Fatty acid-binding protein 4 (FABP4) es una adipocina secretada por el tejido adiposo implicada en la regulación del metabolismo energético y la inflamación. FABP4 circulante se asocia con obesidad, dislipidemia aterogénica y síndrome metabólico. Estudios recientes muestran una asociación entre FABP4 circulante y disfunción endotelial, aunque se desconoce cómo se produce esta. El objetivo de este trabajo es estudiar la interacción entre FABP4 con las proteínas de la membrana citoplasmática en células endoteliales. Metodología: Se incubaron células HUVEC con y sin FABP4 (100 ng/ml) durante 5 min. La inmunolocalización de FABP4 se estudió mediante microscopia confocal. Para estudiar las interacciones de FABP4 con las proteínas de membrana de las células HUVEC se diseñó una estrategia que combina incubaciones con o sin 6XHistidine-tag FABP4 (FABP4-His) (100 ng/ml), cross-linking con formaldehído, extracción de proteínas de membrana y western blot. Resultados: Los resultados muestran que FABP4 colocaliza con CD31, una proteína utilizada como marcador de membrana citoplasmática. Además se observan diferentes patrones de western blot en función de la incubación con o sin FABP4-His. El inmunoblot revela la existencia de 3 complejos proteicos de aproximadamente 108, 77 y 33 kDa formados por FABP4 exógena y su posible receptor/es. Discusión: Los resultados obtenidos apoyan la existencia de un complejo proteico capaz de unir FABP4 a las células endoteliales mediante una unión específica. Además, nos permiten avanzar en el conocimiento de los efectos moleculares de FABP4 y, en caso de confirmarse, podrían utilizarse como diana terapéutica para prevenir enfermedades cardiovasculares

Introduction: Fatty acid binding protein (FABP4) is an adipose tissue-secreted adipokine implicated in the regulation of the energetic metabolism and inflammation. High levels of circulating FABP4 have been described in people with obesity, atherogenic dyslipidemia, diabetes and metabolic syndrome. Recent studies have demonstrated that FABP4 could have a direct effect on peripheral tissues and, specifically, on vascular function. It is still unknown how the interaction between FABP4 and the endothelial cells is produced to prompt these effects on vascular function. The objective of this work is studying the interaction between FABP4 and the plasma membrane proteins of endothelial cells. Methodology: HUVEC cells were incubated with and without FABP4 (100 ng/ml) for 5 minutes. Immunolocalization of FABP4 was studied by confocal microscopy. The results showed that FABP4 colocalizates with CD31, a membrane protein marker. A strategy which combines 6XHistidine-tag FABP4 (FABP4-His), incubations with or without FABP4-His (100 ng/ml), formaldehyde cross-linking, cellular membrane protein extraction and western blot, was designed to study the FABP4 interactions with membrane proteins of HUVECs. Results: The results showed different western blot profiles depending of the incubation with or without FABP4-His. The immunoblot revelead three covalent protein complexes of about 108, 77 and 33 kDa containing FAPB4 and its putative receptor. Discussion: The existence of a specific binding protein complex able to bind FABP4 to endothelial cells is supported by these results. The obtained results will permit us advance in the molecular knowledge of FABP4 effects as well as use this protein and its receptor as therapeutic target to prevent cardiovascular

Snail induction of epithelial to mesenchymal transition in tumor cells is accompanied by MUC1 repression and ZEB1 expression.

E-cadherin protein plays a key role in the establishment and maintenance of adherent junctions. Recent evidence implicates the transcription factor Snail in the blockage of E-cadherin expression in fibroblasts and some epithelial tumor cells through direct binding to three E-boxes in the E-cadherin promoter. Transfection of Snail into epithelial cells leads to a more fibroblastic phenotype. Cells expressing Snail presented a scattered flattened phenotype with low intercellular contacts. Other epithelial markers like Cytokeratin 18 or MUC1 were also repressed. The effects of Snail on MUC1 transcription were mediated by two E-boxes present in the proximal promoter. Snail also induced expression of the mesenchymal markers fibronectin and LEF1 and the transcription repressor ZEB1. ZEB1 and Snail had a similar pattern of expression in epithelial cell lines, and both were induced by overexpression of ILK1, a kinase that causes the loss of E-cadherin and the acquisition of a fibroblastic phenotype. Snail overexpression in several cell lines raised ZEB1 RNA levels and increased the activity of ZEB1 promoter. ZEB1 could also repress E-cadherin and MUC1 promoters but less strongly than Snail. However, since ZEB1 expression persisted after Snail was down-regulated, ZEB1 may regulate epithelial genes in several tumor cell lines.