Background: Glycosaminoglycan (GAG), a major component of the endothelial glycocalyx, is severely perturbed in diabetic vasculature leading to endothelial inflammation and vascular disease in diabetes. We tested the hypothesis that blueberry metabolites (BBM) ameliorate endothelial inflammation in diabetic endothelial cells (ECs) by restoring cell surface GAGs.
Methods: ECs isolated from healthy individuals [human aortic ECs (HAECs)] and diabetic patients (diabetic HAECs) were treated with ±BBM (benzoic acid-4-sulfate, hippuric acid, hydroxyhippuric acid, isovanillic acid-3-sulfate, and vanillic acid-4-sulfate at concentrations known to circulate in human plasma following blueberry consumption) for 3 days, and indices for endothelial inflammation were measured. To analyze GAGs, ECs were incubated with sulfate-free medium supplemented with [35S] Na2SO4 ± BBM. Total GAGs in ECs and medium were purified using DEAE-Sepharose column and were analyzed with high-pressure liquid chromatography coupled to an inline flow scintillation analyzer. Heparan sulfate/chondroitin sulfate ratio and disaccharide composition of GAGs from the medium were analyzed using DEAE-3SW column and Dionex CarboPac PA1 column, respectively.
Results: BBM suppressed diabetes-induced monocyte binding to ECs, and reduced the expression of inflammatory markers in diabetic HAECs. Diabetic HAECs displayed a decrease in [35S] sulfate incorporation into the cell surface GAGs indicating the dysregulation of sulfated GAGs. However, treatment with BBM restored the levels of GAGs in diabetic HAECs. The composition, heparan sulfate/chondroitin sulfate ratio, and disaccharide composition of GAGs from medium were similar among groups.
Conclusions: BBM restored cell surface GAGs and attenuated endothelial inflammation in diabetic HAECs. Blueberry might complement conventional therapies to improve vascular complications in diabetes.
