Analysis of protein posttranslational modifications using DIGE-based proteomics.

Difference gel electrophoresis (DIGE) is most often used to assess relative changes in the expression levels of individual proteins in multiple complex samples, and this information is valuable in making inferences about relative protein activity. However, a protein's activity is not solely dependent upon its expression level. A change in activity may also be influenced by myriad posttranslational modifications (PTMs), including palmitoylation, ubiquitination, oxidation, and phosphorylation. In this chapter, we describe the use of DIGE to determine specific PTMs by introducing specific labels or changes in pI and/or molecular weight.

Analysis of proteins using DIGE and MALDI mass spectrometry.

Difference gel electrophoresis (DIGE) is a common technique for characterizing differential protein expression in quantitative proteomics. Usually a combination of enzymatic digestion and peptide analysis by mass spectrometry is used to identify differentially expressed proteins following separation and statistical analysis by DIGE. In this chapter, methods for gel spot picking, enzymatic digestion, and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) for protein identification of DIGE-analyzed proteins are discussed. Two examples are given: first, a specific protein is used to test the sensitivity of the 2D DIGE/MALDI MS combination for protein quantification and identification, and second, several proteins with and without the labels typically used in DIGE are identified to demonstrate that these labels do not alter MS-based protein identification. Technical variations of protein gel spot preparation, in-gel digestion, and mass spectral protein identification are discussed.

Diabetes mellitus in patients with Alzheimer's disease: clinical description and correlation with the APOE genotype in a sample population from the province of Antioquia, Colombia.

INTRODUCTION: Alzheimer's disease is a multifactorial disease affecting approximately twenty million people worldwide. Numerous variables are associated with increased risk of developing this severe neurological disorder. Among the risk factors, diabetes mellitus, and the ε4 isoform of the APOE gene have been amply demonstrated as increasing the risk of developing this disease. OBJECTIVE: To determine if a correlation exists between APOE genotype, diabetes mellitus and Alzheimer's disease. MATERIALS AND METHODS: Clinical studies were carried out by surveying the clinical histories in a group of patients in the province of Antioquia, Colombia. Forty-three Alzheimer's patients were compared with 43 control subjects, paired by age and gender. Commercially available methods were used to determine whether the patients had diabetes, and restriction enzyme-based genotyping was used to determine the APOE genotypes. RESULTS: The most common non-neurological comorbidities were: arterial hypertension, acute myocardial infarction, chronic obstructive pulmonary disease and hypothyroidism. From the many variables investigated, two were conclusive: (1) the presence of Alzheimer's disease was higher in patients with diabetes mellitus, and (2) no correlation between late-onset sporadic Alzheimer's disease and APOE was found in the target population. CONCLUSIONS: To detect any association with the APOE genotype, a study involving much a larger population samples must be undertaken.

Diabetes mellitus in patients withAlzheimer´s disease: clinical descriptionand correlation with the APOEgenotype in a sample population from the province of Antioquia, Colombia / Diabetes mellitus en pacientes con enfermedad de Alzheimer: descripción clínica y correlación con el genotipo APOE en una muestra de población del departamento de Antioquia, Colombia

Introduction. Alzheimer´s disease is a multifactorial disease affecting approximately twenty million people worldwide. Numerous variables are associated with increased risk of developing this severe neurological disorder. Among the risk factors, diabetes mellitus, and the ε4 isoform of the APOE gene have been amply demonstrated as increasing the risk of developing this disease. Objective. To determine if a correlation exists between APOE genotype, diabetes mellitus and Alzheimer´s disease. Materials and methods. Clinical studies were carried out by surveying the clinical histories in a group of patients in the province of Antioquia, Colombia. Forty-three Alzheimer´s patients were compared with 43 control subjects, paired by age and gender. Commercially available methods were used to determine whether the patients had diabetes, and restriction enzyme-based genotyping was used to determine the APOE genotypes. Results. The most common non-neurological comorbidities were: arterial hypertension, acute myocardial infarction, chronic obstructive pulmonary disease and hypothyroidism. From the many variables investigated, two were conclusive: (1) the presence of Alzheimer´s disease was higher in patients with diabetes mellitus, and (2) no correlation between late-onset sporadic Alzheimer´s disease and APOE was found in the target population. Conclusions. To detect any association with the APOE genotype, a study involving much a larger population samples must be undertaken.

Introducción. La enfermedad de Alzheimer es compleja y afecta, aproximadamente, a 20 millones de personas en todo el mundo. Muchas variables parecen aumentar el riesgo de desarrollar esta alteración neurológica. Entre los factores de riesgo, se ha demostrado ampliamente que la diabetes mellitus y la isoforma ε4 del gen APOE tienen incidencia positiva en el desarrollo de la enfermedad. Se reporta un estudio en el cual se investigó la posible correlación entre APOE, diabetes mellitus y la enfermedad de Alzheimer, en un grupo específico de pacientes del departamento de Antioquia, Colombia. Objetivo. Determinar si existe una correlación entre APOE, diabetes mellitus y la enfermedad de Alzheimer, en un grupo de pacientes de Antioquia, Colombia. Materiales y métodos. Se buscaron y analizaron las historias clínicas de los pacientes con diagnóstico de enfermedad de Alzheimer. Se seleccionaron aquellos que cumplían los criterios de inclusión. Se utilizaron métodos comercialmente disponibles para confirmar la presencia de diabetes mellitus. La genotipificación de APOE se hizo con un método basado en la PCR y la digestión con enzimas de restricción, en muestras de todos los participantes en el estudio. Resultados. En este estudio se analizan 43 casos de enfermedad de Alzheimer y 43 individuos sanos controles, pareados por edad y sexo. Las enfermedades concomitantes no neurológicas más comunes fueron: hipertensión arterial, infarto agudo del miocardio, enfermedad pulmonar obstructiva crónica e hipotiroidismo. Conclusiones. De las diferentes variables investigadas, dos arrojaron resultados concluyentes: i) la presencia de la enfermedad de Alzheimer es más frecuente en pacientes con diabetes mellitus, y 2) no se encontró correlación entre la enfermedad de Alzheimer de inicio tardío esporádico y el genotipo de APOE. Es importante indicar que debe llevarse a cabo un estudio con un tamaño de población mayor, para determinar cualquier posible correlación o inferencia con el genotipo de APOE.