0169 Paraoxonase 1 activity, in the fructose-fed rats, in the presence and in the absence of an antioxidant treatment with alpha-lipoic acid

Abstract

Paraoxonase 1 (PON1) is an esterase synthesized by the liver and secreted into the plasma, where it is associated with high density lipoproteins (HDL). Its role is to protect LDL and HDL from oxidation, thus preventing atherosclerosis. A decreased level of plasma PON1 activities has been found in diabetes mellitus, cardiovascular disorders and chronic liver diseases; but, it can also be influenced by diet and life-style. The purpose of this study was to assess the PON1 activities in the insulin-resistant rats fed with a fructose-enriched diet, in the presence and in the absence of an antioxidant treatment with alpha-lipoic acid (AL). 48 male Sprague-Dawley rats were randomized into two series: rats fed for 3 months with standard chow (Control) or with standard chow supplemented with fructose (60%). In each series, a group of rats was treated intraperitoneally during 14 days/month with NaCl 0.9% and another group with 50 mg/kg/day AL. At the end of the 3 months, we assessed: 1) peripheral tissue resistance to insulin (HOMA-IR) and plasma lipid profile, 2) paraoxonase, arylesterase and lactonase activities of PON1, 3) plasma homocysteine (Hcy) level and 4) hepatic transaminase activities: aspartate-aminotransferase and alanine-aminotransferase. The fructose intake increased peripheral tissue resistance to insulin (HOMA-IR) and plasma lipoprotein level, less the HDL. Also, transaminase and PON1 activities, especially arylesterase and lactonase activities, and the plasma Hcy level were significantly (p>0.05) enhanced in the fructose group. The AL discontinuous treatment associated with the fructose-enriched diet improved the tissue sensitivity to insulin and decreased the plasma lipoprotein levels. Moreover, the AL treatment restored PON1 and transaminase activities, without influencing the Hcy concentration. A decrease in plasma transaminase activities was noted even when AL was associated with standard diet. In our experimental conditions, the fructose intake induced an increase in plasma transaminase and PON1 activities in association with a Hyperhomocysteinemia. The AL treatment restored the enzymes’ activities and had a hepatoprotective effect, but without influence on Hcy level.