Effect of physiological concentration of phloridzin on normal and diabetic human erythrocytes under oxidative stress

Type 2 diabetes mellitus (T2DM) is the most prevalent metabolic disease affecting people all over the world. Recent studies hypothesize that oxidative stress, present inT2DM, plays a crucial role in suppression of insulin biosynthesis and in progression of insulin resistance (1); therefore an evaluation of the potential usefulness of dietary antioxidants in treatment for T2DM is required. Several in vitro studies on human erythrocytes (RBCs) show the antioxidant property of some polyphenols but in very high and far to in vivo reachable concentrations. OBJECTIVES: evaluate the potential antioxidant effect of phloridzin (PRZ), a polyphenol present in apple (2), at in vivo-liked concentration, on RBCs membrane fluidity and on some membrane and cytosolic glycohydrolases activities indicated as a very sensitive markers of RBCs oxidative stress (3). MATERIALS AND METHODS: RBCs (from health subjects and T2DM patients), preincubated with 1M of phloridzin, then stressed by a Xanthine/Xanthine oxidase system for 1 hour; were analysed for: a) membrane fluorescence anisotropy; b) cytosolic O-GlcNAcase and Hexosaminidase (Hex) activities; c) ß-D-glucuronidase (GCR) and Hex activities in plasma membrane. RESULTS: a) decrease of membrane fluidity and an increment of membrane GCR activity in T2DM patients. b) no appreciable effect of PRZ on enzyme activities nor in membrane fluidity. CONCLUSIONS: We don’t find, at in vivo concentration, the protective effect of PRZ against oxidative stress reported in previously studies in-vitro (2). Possible synergistic in vitro effects with other polyphenols and/or their derivative metabolites at physiological levels will be focused in further studies.