Type 2 diabetics have increased levels of oxidative stress. This results in specific modifications to proteins and is linked to health complications such as cardiovascular disease( Reference Rabbani, Chittari and Bodmer 1 ). Dietary strategies for alleviating these complications are being pursued as alternatives or supplementary to pharmaceutical interventions. Berries from the genus Vaccinium such as bilberry are enriched in anthocyanins, polyphenolics recognized for their ability to provide and activate cellular antioxidant protection( Reference Zafra-Stone, Yasmin and Bagchi 2 ). This pilot study investigated whether three weeks supplementation with a concentrated bilberry extract would alter oxidised protein markers in the blood plasma of overweight/obese type 2 diabetics compared to pre-supplementation samples.
The volunteer subjects in this study were overweight/obese males (BMI>25) with type 2 diabetes controlling their diabetes by diet alone (n=11). All subjects provided informed written consent before inclusion in the study which was approved by the NOSREC. Volunteers were given 1.4 g a day of Mirtoselect® Indena S.p.A. (standardized bilberry extract, 36% (w/w) anthocyanins), formulated in gelatin capsules. Three different oxidised protein markers were measured in plasma samples: protein-pyrroles, protein-nitrotyrosine (3-NT) and oxidised LDL. Protein-pyrroles were determined using a slot-blot after labelling the pyrroles with biotin tagged Ehrlich's Reagent( Reference Campbell, Rucklidge and Reid 3 ). Protein-3-NT was determined by immunoblotting. Plasma levels of oxidised LDL were determined using Mercodia Oxidized LDL ELISA from Mercodia AB (Sweden).
1NT-BSA, nitrated bovine serum albumin standard (Sigma-Aldrich, UK), *p⩽0.05 post-supplementation values vs. pre-supplementation values using t-test paired 2 samples for mean.
In conclusion three weeks of taking capsules containing concentrated standardised bilberry extract resulted in a significant reduction in three sensitive markers of oxidative stress in the plasma of overweight/obese type 2 diabetics. This gives support for the use of such dietary supplements to reduce diabetes associated oxidative stress. However, one limitation to this study is a lack of a control group taking suitable placebo capsules for a direct comparison of the effects of the bilberry extract. We intend following up this pilot study with a larger cohort of volunteers including such a control group.
This work was funded by the Scottish Government Rural and Environment Science and Analytical Services (RESAS).
