Evaluación piloto de la reducción de niveles séricos de productos de glicación avanzada (AGEs) sobre la electrofisiología de la visión, en pacientes con diabetes mellitus tipo 2 / Pilot evaluation of the serum levels reduction of advanced glication products (AGEs) on the vision electrophysiology in type 2 diabetic patients

BACKGROUND: Diabetic vascular complications are associated with elevated concentrations of advanced glycation end-products (AGEs). These substances can be originated endogenously by hyperglycaemia and oxidative stress, but also by dietary intake. There is indirect evidence suggesting that these complications can be prevented by lowering AGEs levels by dietary or pharmacological interventions, however its clinical benefits are still not clear enough because this would require long periods of treatment. Specific neuro-ophthalmologic tests like Multifocal Electroretinogram (MFERG) and visual evoked potentials (VEP) can detect retinal and myelinic nerve early changes, and thus could represent good methods to study the results of certain interventions in shorter lapses. The aim of this preliminary study was to evaluate the effects of a pharmacological intervention designed to lower AGEs levels, on these variables. PATIENTS AND METHODS: We included 7 patients with type 2 diabetes (DM2), with more than 5 and less than 10 years of disease, without clinically evident micro and macrovascular disease, without renal failure, hypothyroidism nor vitamin B12 deficiency, whose AGEs dietary intake was moderately elevated or high (according to dietary recalls). Upon admission, a clinical evaluation, urine and blood samples were obtained for routine labs, plus ultrasensitive C Reactive Protein (usCRP) as an inflammatory marker, and carboxymethyl-lysine (CML) as representative of AGEs. Then a complete ophthalmologic evaluation was performed, including fundus, MFERG and VEP. After the initial evaluation, placebo capsules were prescribed (12 daily capsules, 4 with each main meal) during 3 months, repeating the same initial evaluation at completion of this period. Then the active treatment followed, with capsules containing cholestyramine (4 capsules containing 500 mg each, totaling 6 g per day). Patients were cited each month, to register adverse events and repeating the same evaluation after this second 3 months period. RESULTS: The sample was composed of 2 male patients, mean age was 55.1 ± 3.8 years, and diabetes was managed with metformin plus other oral agents or o insulin (4 cases). In addition, 4 patients received lipid lowering and 4 antihypertensive drugs. Metabolic control and lipid levels were variable (ranges of HbA1c 6.2-8.4%, LDL cholesterol 45-141 mg/dL, triglycerides 70-220 mg/dL). AGEs levels represented by CML were highly variable (median 31.7, range min-max 3.4-58.9 ug/uL). Basal usCRP was also variable (median 405.9, range min-max 265.6-490.7 mg/L). The treatment was well tolerated, except for mild constipation associated with cholestiramine intake. No significant changes in electroretinography or evoked potentials were observed when comparing the initial placebo period with cholestyramine treatment. A significant increase in triglyceride levels and decrease of vitamin D levels after cholestyramine treatment was observed. No changes were detected in serum concentrations of CML, usCRP or glycemic control, after treatment. The latter variables were not correlated with neurophthalmologic studies. DISCUSSION: In this preliminary study we did not observe changes in MFERG nor VEP after 6 g/day cholestyramine treatment, which did not induce lowering of CML levels. This could be attributed to the many limitations of a pilot study, such as a small sample size, short duration of treatment, reduced doses. However this design allowed to evaluate the patients´ tolerance to the drug and rule out adverse effects, in order to plan further studies using the necessary doses to obtain lowering of AGEs

Serum Fluorescent Advanced Glycation End (F-AGE) products in gestational diabetes patients

ABSTRACT Objectives Advanced glycation end products (AGEs) are involved in the pathogenesis and complications of diabetes mellitus (DM). Gestational DM (GDM) is characterized by increased glycemia and oxidative stress, which are factors associated with high serum AGE concentrations. The aim of this study was to evaluate the utility of a serum fluorescence AGE (F-AGE) method as a screening tool for gestational diabetes. Subjects and methods Serum samples from 225 GDM patients and 217 healthy pregnant women (healthy controls) were diluted 50-fold in phosphate-buffered saline, and the AGEs were estimated by fluorometric analysis (λEx 350 nm/ λEm 440 nm). Results No significant (P > 0.05) differences in AGE concentrations, expressed in Arbitrary Units (UA/mL × 104), were observed in the women with GDM or in the healthy controls. Furthermore, F-AGE concentrations did not change significantly during the pregnancy (12-32 weeks of gestation). Only the GDM group had a positive correlation (r = 0.421; P < 0.001) between F-AGEs and serum creatinine concentrations. Conclusion It was not possible to distinguish women with gestational diabetes from the healthy controls on the basis of serum F-AGE concentrations.

Inflamação renal, alterações metabólicas e oxidativas após 6 semanas de dieta de cafeteria em ratos / Renal inflammatory and oxidative and metabolic changes after 6 weeks of cafeteria diet in rats

Resumo Introdução: A obesidade é uma doença em que a inflamação está inteiramente envolvida e pode causar insuficiência renal. Objetivo: Avaliar a influência da exposição a curto prazo de uma dieta de cafeteria sobre a inflamação no tecido renal e a formação de produtos de glicação avançada (AGEs) no plasma de rato. Métodos: Ratos Wistar machos (10 semanas de idade, pesando 350 g) foram designados para receber dieta de ração comercial (C; n = 8 animais/grupo, 5% de energia a partir de gordura) ou dieta de cafeteria (CAF-D, n = 8 animais/grupo: 29% de energia de gordura) e de sacarose em água (300 g/L) de beber durante 6 semanas. Resultados: Índice de adiposidade em seis semanas foi maior no grupo CAF-D em comparação com C. O mesmo comportamento foi observado para os níveis plasmáticos de glicose, triglicerídeos, leptina, insulina e AGEs. A expressão do gene de IL-6 e TNF-α em tecido renal foi maior no grupo D-CAF e nenhuma diferença significativa no tecido adiposo. Não houve aumento destas citocinas no plasma ou rim. Houve uma diminuição significativa de adiponectina no grupo CAF-D. Conclusão: A exposição a curto prazo da CAF-D reflete alterações no metabolismo, aumento dos níveis plasmáticos de AGEs, o que pode refletir o aumento expressão de citocinas inflamatórias no rim.

Abstract Introduction: Obesity is a disease in which inflammation is directly involved and can lead to impaired renal function. Objective: To evaluate the influence of short term exposure to cafeteria diet on kidney tissue inflammation and advanced glycation end products (AGEs) in the rat plasma. Methods: Male Wistar rats (10 weeks of age, weighing 350 g) were assigned to receive commercial chow diet (C; n = 8 animals/group, 5% of energy from fat) or cafeteria diet (CAF-D, n = 8 animals/group: 29% energy fat) and sucrose in drinking water (300 g/L) for 6 weeks. Results: adiposity index at six weeks was higher in CAF-D group compared to C. The same behavior was observed for plasma levels of glucose, triglycerides, leptin, insulin and AGEs. The gene expression of IL-6 and TNF-α in renal tissue was higher in CAF-D group and no significant difference in adipose tissue. There was no increase of these cytokines in plasma and kidney or histologically. There was a significant decrease of adiponectin in the CAF-D group. Conclusion: The short exposure CAF-D reflects changes in metabolism, increased plasma levels of AGEs, which may reflect the increased expression of inflammatory cytokines in the kidney.

Glicosilación no enzimática de proteínas: su rol en las complicaciones crónicas de la diabetes y el envejecimiento / No-enzymatic glycosylation of proteins: role in aging and in the chronic complications of diabetes

En los últimos 15 años la glicosilación no enzimática de las proteínas ha pasado de ser un fenómeno de importancia bromatológica, a tener relevancia en procesos tales como el envejecimiento y las complicaciones crónicas que desarrollan los pacientes diabéticos. El enfoque inicial se centró en los productos de glicosilación temprana de proteínas o productos de Amadori; más recientemente se ha resaltado la formación de los productos de glicosilación avanzada de proteínas como uno de los factores causales de las alteraciones diabéticas y la senilidad. Se han diseñado fármacos que interfieren con las vías de formación de estos productos de glicosilación no enzimática, los cuales tendrían un importante potencial terapéutico en el control de la aparición de las complicaciones crónicas en la diabetes. La determinación en el laboratorio de los productos de glicosilación de proteínas es una herramienta muy útil para el pronóstico de la calidad de vida de un individuo, ya sea normal o diabético, y para el seguimiento del control metabólico a mediano y largo plazo en los pacientes diabéticos