Effects of lipoic acid on glucose utilization, protein glycosylation and viscosity of high glucose-treated red blood cells

Abstract

UTILIZATION, PROTEIN GLYCOSYLATION AND VISCOSITY OF HIGH GLUCOSE-TREATED RED BLOOD CELLS Sushi1 K. Jain, Melissa Palmer, Yanyun Chen Department of Pediatrics, Louisiana State University Medical Center, Shreveport, LA 71130 USA Glycosylation of proteins can cause inactivation of enzymes and alterations in the structure and function of collagen and membranes. which may play a role in the long-term complications of diabetes and aging. Lipoic acid has been shown beneficial in reducing diabetic complications. such as. neuropathy. The present study was undertaken to test the hypothesis that lipoic acid increases glucose utilization and thereby reduces protein glycosylation and viscosity of red blood cells (RBC). RBC (15% hematocrit in PBS) were treated with high glucose levels (6-45 mM) with and without lipoic acid (5-200 LM) for 24 hrs in a shakine water bath at 3?‘C. Glucose was ‘determined using gl&ose oxidasel Glycosylated hemoglobin (HbAI) was determined using affinity chromatography to assess protein glycosylation. an: viscositv of washed RBC at tixed hematocrit was determined using computerized Brookfield viscometer. Lipoic acid treatment increased glucose utilization in high glucose (45 mM) exposed RBC by 75-120%. Over untreated fresh RBC, the increase in HbA, level in high glucose treated RBC was reduced by 22-40% in the presence of lipoic acid compared with high glucose alone. Treatment of RBC with high glucose increased viscosity of RBC. However. presence of lipoic acid in the medium significantly blocked increase in viscosity of high glucose-treated RBC. The level of glycated hemoglobin in blood has been considered to reflect the degree of glycation of other proteins that are freely exposed to circulating glucose. Using REX as a model. this study demonstrates that lipoic acid can reduce glycosylation of proteins and viscosity of cells exposed to high glucose. LIPID PEROXIDATION AND ANTIOXIDANT ENZYMES IN IMMUNE COMPLEX DISEASE G. Wbjcicka, A. Marciniak, D. G6my, R. CzabakGarbacz’, A. Korolczuk’, J. Beltowski Dept of Pathophysiologv, ‘Dept of Physiology, 2Dept of Pathomorphology, University of Medicine, Lublin, Poland The purpose of this study was to investigate lipid peroxidation and antioxidant mechanisms during early stage of immunisation and developed type III hypersensitivity. The male New Zeland rabbits (2.5 3 kg) were immunised by i.v. BSA. Four days after BSA administration malonyldialdehyde (MDA) level increased in plasma, renal cortex and renal medulla by 63%, 246% and 140% respectively, conjugated diens (CDs) increased in plasma, renal cortex and renal medulla by 76%, 122% and 63% respectively, lipid hydroperoxides (HPE) increased in plasma by 14%, in renal cortex by 11% and in renal medulla by 85%. Superoxide dismutase (SOD) activity in erythrocytes increased by 17%, blood glutathione peroxidase (Gpx) increased by 63% and total antioxidant status (TAS) decreased by 19%. Proteinuria was maximal 8 days after BSA administration. This day we observed 110% increase in MDA level in renal cortex and 271% increase in renal medulla. CDs increased by 60% in plasma, by 23% in renal cortex and by 40% in renal medulla. HPE in plasma was increased by 20% and in renal cortex by 100%. SOD and Gpx increased by 61% and 57% respectively whereas TAS decreased by 45%.