Associations between insulin resistance and three B-vitamins in European adolescents: the HELENA study / Asociaciones entre la resistencia a la insulina y tres vitaminas del grupo B en adolescentes europeos: el estudio HELENA

Objective: To assess whether adolescents with high body mass index (BMI), or fat mass index (FMI), in combination with insulin resistance (assessed with the Homeostatic Model Assessment [HOMA] index), had also lower blood vitamin B6, folate and vitamin B12 concentrations. Methods and materials: Six hundred and fifteen adolescents from the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study, with data on B-vitamins (both intakes and status), and BMI, FMI, HOMA, were selected. Intakes were assessed by two non-consecutive 24-h recalls. B-vitamins biomarkers were measured by chromatography and immunoassay. Analysis of covariance was applied to elucidate the differences in B-vitamins between combinations of groups defined according to the median of the z-scores of markers of body composition and insulin sensitivity. Results: When considering energy intakes and education of the mother in the model, in females, vitamin B6 intakes were higher in the high BMI/ high HOMA group than in the high BMI-low HOMA group. Similarly, vitamin B6 intakes were higher in the high FMI/high HOMA group than in the low FMI/low HOMA group. Plasma vitamin B12 was significantly lower in males in the high FMI/high HOMA group than in the low FMI/low HOMA group, keeping also significant their trends throughout the groups, a fact that can be observed also for females (p < 0.05). Conclusion: Adolescents with combined higher adiposity and higher HOMA insulin sensitivity showed lower vitamin B12 plasma concentrations. These differences do not seem to be explained by dietary vitamin B12 intake (AU)

Objetivo: evaluar si los adolescentes con mayor índice de masa corporal (IMC), o de masa grasa (IMG), en combinación con la resistencia a la insulina (medida con el Modelo de Valoración Homeostática [índice HOMA]), ingieren y tienen valores más bajos de vitamina B6, folato y vitamina B12. Métodos y materiales: seiscientos quince adolescentes participantes en el estudio Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA), con valores de ingesta y concentraciones de las vitaminas B6, folato y B12, e IMC, IMG y HOMA, fueron seleccionados. Las ingestas se midieron mediante dos recuerdos de 24 horas no consecutivos. Los biomarcadores de las vitaminas fueron obtenidos mediante cromatografía e inmunoensayo. Se aplicó el análisis de la covarianza para evaluar las diferencias entre las vitaminas (ingesta y concentraciones) entre las combinaciones de los grupos definidos según las medianas de los valores z de los marcadores de la composición corporal y de la sensibilidad a la insulina. Resultados: considerando la ingesta energética y la educación de la madre en el modelo en chicas, las ingestas de vitamin B6 fueron mayores en el grupo de mayor IMC/mayor HOMA que en el grupo mayor IMC/menor HOMA. Del mismo modo, el grupo constituido por mayor IMG/mayor HOMA presentó mayores ingestas de esta vitamina que el grupo formado por la combinación entre menor IMG/menor HOMA. La vitamina B12 plasmática en chicos fue significativamente menor en el grupo formado por mayor IMG/mayor HOMA que en el grupo menor IMG/menor HOMA, manteniendo también la tendencia significativa en los grupos, lo que también se puede observar en las chicas (p < 0.05). Conclusiones: los adolescentes con mayor adiposidad en combinación con una mayor sensibilidad a la insulina mostraron menores valores de vitamina B12 plasmática. Estas diferencias no parecen estar explicadas por diferencias en la ingesta de vitamina B12 (AU)

Multi-walled carbon nanotubes as solid-phase extraction adsorbents for the speciation of cobalamins in seafoods by liquid chromatography.

Multi-walled carbon nanotubes (MWCNTs) were evaluated as potential adsorbents for miniaturized solid-phase extraction coupled to liquid chromatography. The adsorption capacity of this sorbent was applied to assess the speciation of four cobalamins representing the various forms of vitamin B(12). The preconcentration on the MWCNTs was based on the retention of analytes by introducing the sample online into the mini-column system. Dimethyl sulfoxide was used to elute the retained vitamins for liquid chromatographic analysis. The experimental conditions of the continuous flow device, which affect the enrichment procedure, such as the type and amount of nanotubes, the volume, pH and flow rate of the sample solution, and the eluent and its volume, were optimized. For detection purposes, a diode array device was used and good resolution was obtained with a mobile-phase acetonitrile-phosphate buffer and gradient elution. Specificity was demonstrated by the retention characteristics and UV spectra and by comparing the peak purity index with commercial standards. Linearity, precision, recovery, and sensitivity were satisfactory. Detection limits ranged from 0.35 to 30 ng mL(-1). The method was successfully applied to the determination of cobalamins in seafoods, which were extracted from the sample with a buffer solution using an ultrasonic probe. The reliability of the procedure was checked by analyzing a certified reference material.

Microbial production of vitamin B12.

One of the most alluring and fascinating molecules in the world of science and medicine is vitamin B12 (cobalamin), which was originally discovered as the anti pernicious anemia factor and whose enigmatic complex structure is matched only by the beguiling chemistry that it mediates. The biosynthesis of this essential nutrient is intricate, involved and, remarkably, confined to certain members of the prokaryotic world, seemingly never have to have made the eukaryotic transition. In humans, the vitamin is required in trace amounts (approximately 1 microg/day) to assist the actions of only two enzymes, methionine synthase and (R)-methylmalonyl-CoA mutase; yet commercially more than 10 t of B12 are produced each year from a number of bacterial species. The rich scientific history of vitamin B12 research, its biological functions and the pathways employed by bacteria for its de novo synthesis are described. Current strategies for the improvement of vitamin B12 production using modern biotechnological techniques are outlined.