Portulaca oleracea extract increases lecithin:cholesterol acyltransferase and paraoxonase 1 activities and enhances reverse cholesterol transport in streptozotocin-induced diabetic rat

Background: Plant extracts are generally assumed to be more acceptable and less hazardous than synthetic compounds and could be alternative antidiabetic treatments. Portula caoleracea has been used as one of the traditional edible and medicinal plant in Algeria to treat diabetes. The aim of the present study was to determine the effects of lyophilized aqueous extract of Portulaca oleracea on high-density lipoproteins composition, paraoxonase (PON1) and lecithin:cholesterol acyltransferase (LCAT) activities in streptozotocin-induced diabetic rat. Methods: Diabetes was induced intraperitonially by a single injection of streptozotocin (STZ) (60mg/kg bw). Twelve diabetic rats, weighing 263±5g, were divided into two groups fed a casein diet supplemented or not with Portulaca oleracea extract (1g/kg bw), for 4 weeks. Results: At d28, in Portulaca oleracea treated vs untreated diabetic group, glycemia, serum total cholesterol (TC), triacylglycerols (TG) and phospholipids (PL) concentrations were decreased significantly (p<0.05). The hypolipidemic effect induced by Portulaca oleracea extract was due to the reduction of total cholesterol (TC) in LDL-HDL₁ (-51%) and C-HDL₃ (-21%). Portulaca oleracea treatment improved PON1 and LCAT activities by 48%. HDL3-UC (acyl group acceptor) and -PL (enzyme substrate) were diminished respectively by 47% and 82%, whereas HDL₂-CE concentrations (product of LCAT reaction) were increased by 44%. Moreover, HDL-C levels were found to be positively correlated with PON1 activity (r=0.96, p<0.05). Serum, LDL-HDL₁, HDL₂ and HDL₃ TBARS levels were respectively, 2.9-, 2.6-, 2.4- and 2.8-fold lower in Portulaca oleracea treated than untreated diabetic groups. Conclusion: These findings reflect the potential antihyperglycemic and hypolipidemic of Portulaca oleracea extract, in STZ-induced diabetic rat. Moreover, Portulaca oleracea extract restores PON1 and ameliorates the reverse cholesterol transport (RCT) by enhancing LCAT activity, therefore could prevent many diabetic complications by reducing dyslipidemia and oxidative damage.

Key words: Rats, Streptozotocin, Portulaca oleracea, Cholesterol, PON1, LCAT, apo A-I, lipoprotein peroxidation.