RESUMO
Only a few studies have explored relationships between thiamine intake and function, and a few studies have examined the effects of supplements on various clinical or biochemical outcomes. None of these studies, however, makes a useful contribution to understanding requirements in healthy populations. The requirement of thiamine relates to energy and carbohydrate intake. Clinical signs of deficiency have been observed at intakes below 0.5 mg/day, which corresponds to 0.05 mg/MJ. In other studies, thiamine excretion in the urine and normalisation of enzyme activity were normalised at intakes of 0.07-0.08 mg/MJ. The lower limit of intake thus estimates at 0.05 mg/MJ. It has not been possible to set a safe upper intake level for thiamine due to a lack of data. Studies on pregnant and lactating women indicate a higher requirement as assessed by biochemical parameters. A few studies indicate that thiamine utilisation is impaired among elderly subjects.
RESUMO
Only a few studies have explored relationships between riboflavin intake and function and a few studies have examined the effects of supplements on various clinical or biochemical outcomes. None of these studies, however, make a useful contribution to understanding requirements in healthy populations. Thus, there is no strong evidence to change the recommendations. The requirement for riboflavin is estimated based on the relationship between intake and biochemical indices of riboflavin status, including urinary excretion and enzyme activities.
RESUMO
Quantification of the specific folate vitamers to estimate total folate in foods is not standardized. A collaborative study, including eight European laboratories, was conducted in order to determine the repeatability and reproducibility of the method for folate quantification in foods using the plant-origin γ-glutamyl hydrolase as part of the extraction procedure. The seven food samples analyzed represent the food groups; fruits, vegetables, dairy products, legumes, offal, fish, and fortified infant formula. The homogenization step was included, and six folate vitamers were analyzed using LC-MS/MS. Total folate content, expressed as folic acid equivalent, was 17-490 µg/100 g in all samples. Horwitz ratio values were within the acceptable range (0.60-1.94), except for fish. The results for fortified infant formula, a certified reference material (NIST 1869), confirmed the trueness of the method. The collaborative study is part of a standardization project within the Nordic Committee on Food Analysis (NMKL).
Assuntos
Fracionamento Químico/métodos , Ácido Fólico/análise , Análise de Alimentos/métodos , Espectrometria de Massas em Tandem/métodos , Animais , Cromatografia Líquida/métodos , Cromatografia Líquida/normas , Laticínios/análise , Grão Comestível/química , Produtos Pesqueiros/análise , Análise de Alimentos/normas , Alimentos Fortificados/análise , Frutas/química , Humanos , Lactente , Fórmulas Infantis/análise , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem/normas , Verduras/químicaRESUMO
PURPOSE: IL2 inducible T-cell kinase (ITK) promoter CpG sites are hypomethylated in melanomas compared with nevi. The expression of ITK in melanomas, however, has not been established and requires elucidation. EXPERIMENTAL DESIGN: An ITK-specific monoclonal antibody was used to probe sections from deidentified, formalin-fixed paraffin-embedded tumor blocks or cell line arrays and ITK was visualized by IHC. Levels of ITK protein differed among melanoma cell lines and representative lines were transduced with four different lentiviral constructs that each contained an shRNA designed to knockdown ITK mRNA levels. The effects of the selective ITK inhibitor BI 10N on cell lines and mouse models were also determined. RESULTS: ITK protein expression increased with nevus to metastatic melanoma progression. In melanoma cell lines, genetic or pharmacologic inhibition of ITK decreased proliferation and migration and increased the percentage of cells in the G0-G1 phase. Treatment of melanoma-bearing mice with BI 10N reduced growth of ITK-expressing xenografts or established autochthonous (Tyr-Cre/Pten(null)/Braf(V600E)) melanomas. CONCLUSIONS: We conclude that ITK, formerly considered an immune cell-specific protein, is aberrantly expressed in melanoma and promotes tumor development and progression. Our finding that ITK is aberrantly expressed in most metastatic melanomas suggests that inhibitors of ITK may be efficacious for melanoma treatment. The efficacy of a small-molecule ITK inhibitor in the Tyr-Cre/Pten(null)/Braf(V600E) mouse melanoma model supports this possibility.
Assuntos
Melanoma/enzimologia , Proteínas Tirosina Quinases/biossíntese , Neoplasias Cutâneas/enzimologia , Animais , Antineoplásicos/farmacologia , Western Blotting , Linhagem Celular Tumoral , Modelos Animais de Doenças , Eletroforese em Gel Bidimensional , Técnicas de Silenciamento de Genes , Humanos , Processamento de Imagem Assistida por Computador , Imuno-Histoquímica , Melanoma/patologia , Camundongos , Análise de Sequência com Séries de Oligonucleotídeos , Inibidores de Proteínas Quinases/farmacologia , Proteínas Tirosina Quinases/antagonistas & inibidores , Neoplasias Cutâneas/patologia , Análise Serial de Tecidos , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Tetrahydrofolate is the parent molecule of the folate coenzymes required for one carbon metabolism. Together with other unsubstituted folates such as dihydrofolate and folic acid, tetrahydrofolate represents the third pool of dietary folates following 5-methyltetrahydrofolate and formyl folates. Low intake of dietary folates and poor folate status are common problems in many countries. There is a critical need for reliable methods to determine folate in foods to accurately estimate folate intakes in populations. However, current values for folates in foods in databanks are often underestimated due to the high instability of several folate forms, especially tetrahydrofolate. The present review highlights the occurrence of unsubstituted folates in foods and their oxidation mechanisms and chemical behavior as well as interconversion reaction between tetrahydrofolate and 5,10-methylenetetrahydrofolate. The review shows also the important role of antioxidants in protecting folates during analysis and describes strategies to stabilize unsubstituted folates throughout all steps of the analytical procedure.
Assuntos
Ácido Fólico/química , Análise de Alimentos , Animais , Ácido Fólico/metabolismo , Humanos , Estrutura Molecular , OxirreduçãoRESUMO
Malignant melanoma is characterized by a propensity for early lymphatic and hematogenous spread. The hypoxia-inducible factor (HIF) family of transcription factors is upregulated in melanoma by key oncogenic drivers. HIFs promote the activation of genes involved in cancer initiation, progression, and metastases. Hypoxia has been shown to enhance the invasiveness and metastatic potential of tumor cells by regulating the genes involved in the breakdown of the ECM as well as genes that control motility and adhesion of tumor cells. Using a Pten-deficient, Braf-mutant genetically engineered mouse model of melanoma, we demonstrated that inactivation of HIF1α or HIF2α abrogates metastasis without affecting primary tumor formation. HIF1α and HIF2α drive melanoma invasion and invadopodia formation through PDGFRα and focal adhesion kinase-mediated (FAK-mediated) activation of SRC and by coordinating ECM degradation via MT1-MMP and MMP2 expression. These results establish the importance of HIFs in melanoma progression and demonstrate that HIF1α and HIF2α activate independent transcriptional programs that promote metastasis by coordinately regulating cell invasion and ECM remodeling.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Regulação Neoplásica da Expressão Gênica , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Melanoma/metabolismo , Neoplasias Cutâneas/metabolismo , Animais , Linhagem Celular Tumoral , Matriz Extracelular/metabolismo , Proteína-Tirosina Quinases de Adesão Focal/metabolismo , Humanos , Hipóxia , Melanoma/patologia , Camundongos , Microscopia de Fluorescência , Mutação , Metástase Neoplásica , Oncogenes , PTEN Fosfo-Hidrolase/metabolismo , Proteínas Proto-Oncogênicas B-raf/metabolismo , RNA Interferente Pequeno/metabolismo , Neoplasias Cutâneas/patologiaRESUMO
Tumor hypoxia is associated with disease progression, resistance to conventional cancer therapies and poor prognosis. Hypoxia, by largely unknown mechanisms, leads to deregulated accumulation of and signaling via receptor tyrosine kinases (RTKs) that are critical for driving oncogenesis. Here, we show that hypoxia or loss of von Hippel-Lindau protein--the principal negative regulator of hypoxia-inducible factor (HIF)--prolongs the activation of epidermal growth factor receptor that is attributable to lengthened receptor half-life and retention in the endocytic pathway. The deceleration in endocytosis is due to the attenuation of Rab5-mediated early endosome fusion via HIF-dependent downregulation of a critical Rab5 effector, rabaptin-5, at the level of transcription. Primary kidney and breast tumors with strong hypoxic signatures show significantly lower expression of rabaptin-5 RNA and protein. These findings reveal a general role of the oxygen-sensing pathway in endocytosis and support a model in which tumor hypoxia or oncogenic activation of HIF prolongs RTK-mediated signaling by delaying endocytosis-mediated deactivation of receptors.
Assuntos
Endocitose , Oxigênio/metabolismo , Animais , Sequência de Bases , Linhagem Celular , Humanos , Hipóxia/metabolismo , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Receptores Proteína Tirosina Quinases/metabolismo , Homologia de Sequência do Ácido Nucleico , Transdução de Sinais , Proteínas de Transporte Vesicular/genética , Proteínas de Transporte Vesicular/fisiologia , Proteína Supressora de Tumor Von Hippel-Lindau/fisiologiaRESUMO
After decades of therapeutic nihilism in the treatment of advanced renal cell carcinoma, remarkable therapeutic strides have been made over the last few years. Early forays into molecularly targeted therapy for this difficult-to-treat disease were based around the inhibition of gene products of the hypoxia-inducible factor (HIF) transcription factor (i.e., VEGF). Recent data suggest that inhibition of mTOR results in clinical benefit in patients with poor prognostic features, and in preclinical models this therapeutic effect involves downregulation of HIF. Intriguingly, patients with nonclear cell histology appeared to obtain clinical benefit when treated with mTOR inhibitors. This review will highlight the mTOR pathway, its relevance to both clear cell and nonclear cell renal cell carcinoma, and its place in the host of quickly expanding treatment options.