ABC | Volume 115, Nº1, July 2020

Original Article Derakhshanian et al. Quercetin improves glucocorticoid-induced dyslipidemia Arq Bras Cardiol. 2020; 115(1):102-108 This naturally occurring polyphenol compound is generally known for its antioxidant and anti-inflammatory properties and is reported to enhance the antioxidant defense system, and decrease the incidence of cardiovascular, neoplastic and inflammatory diseases. 7-9 Since the oxidant-antioxidant balance and inflammation status play an important role the etiology of many diseases, flavonoid compounds have been in the spotlight as natural preventive or therapeutic agents. 10,11 In addition, some previous studies reported the beneficial impact of quercetin on metabolic syndrome and lipid metabolism. 12,13 The aim of this study is to evaluate the effect of quercetin on lipid profile of rats treated with high-dose glucocorticoid. Materials and methods Animals A total of 32 Sprague-Dawley rats, aged 6-7 months, weighing 210±30 grams were obtained from the Razi Institute (Karaj, Iran). The animals were acclimatized to the standard laboratory conditions (temperature 20-25˚C, and a 12-h light/dark cycle) for 10 days before the beginning of the main experiment. Clean water and pelleted standard chow diet (Danbehparvar, Thran, Iran) were provided ad libitum . The experimental protocol was in accordance with the Principles of Laboratory Animal Care. 14 The sample size was calculated with 80% power, using a two-sided test at the 5% significance level and based on the effect size of 0.5. Chemicals Methylprednisolone sodium succinate (MP) was used as the glucocorticoid (SOLU-MEDROL, Pfizer Pharmaceuticals, NY, U.S.A) for generating GC-induced dyslipidemia. 15 Quercetin, with a purity of 95%, was obtained from Sigma-Aldrich Chemicals (St. Louis, MO, U.S.A) and the quercetin suspension was prepared by adding quercetin to 0.05% aqueous carboxymethyl cellulose (CMC) solution immediately before being administered by oral gavage. Experimental procedure Thirty-two animals were randomly distributed into four groups, using the block randomization scheme. Each experimental group contained eight rats, which were treated for six weeks. All groups were injected subcutaneously (s.c.) with MP (40 mg/kg body weight), except the control group, which received normal saline solution three days a week. Each of the three glucocorticoid-injected groups received one of the following treatments: CMC as placebo, 50 mg/kg quercetin or 150 mg/kg quercetin. All treatments were given three days a week per os . At the end of the study all animals were anesthetized with an intra-peritoneal (i.p.) injection of ketamine together with xylazine (50 mg/kg and 30 mg/kg respectively). 15,16 Blood samples were collected by cardiac puncture and were immediately centrifuged at 3000 rpm for 10 min for serum isolation and stored at -80˚C until analysis of the lipid profile. The rats were fasted for 12-14 hours and all blood samples were collected between 8 and 10 am. Commercially available enzymatic kits were used to measure the serum concentrations of total cholesterol (TC), high density lipoprotein (HDL), and triglycerides (TG) in duplicate tests (Pars Azmoon Co., Tehran, Iran) and Apo A and Apo B were measured by immunoturbidimetric methods (biorexfars LTD, Iran). Low-density lipoprotein (LDL) level was calculated using the Friedewald equation. 17 Animals were weighed at the beginning and end of the study. Statistical analysis All data were presented as mean ± standard deviation (SD) and analyzed by the Statistical Package for Social Sciences (version 23.0; SPSS Inc., Chicago, USA). The Kolmogorov‑Smirnov test was used to assess the normality of the data. Statistical differences between groups were evaluated using analysis of variance (one-way ANOVA) followed by Bonferroni post hoc test. Statistical significance was set at p < 0.05. Results Although the average body weight of rats was the same in all groups at the beginning of the experiment, after six weeks of intervention, all glucocorticoid-treated animals showed a significant weight reduction compared with their own initial weights and with their age-matched controls (Table 1). Following six weeks of methylprednisolone injection, the mean plasma cholesterol and triglyceride levels were drastically increased in glucocorticoid-treated animals compared with the control group. Both doses of quercetin (50 and150 mg/kg) improved the hypercholesterolemia and hypertriglyceridemia in comparison with the MP group, and the same trend was observed for LDL levels. In addition, the MP injection caused a moderate increase in HDL levels, which was not significantly changed following quercetin supplementation. However, the reduction in TC/HDL, TG/HDL and LDL/HDL ratios were statistically and clinically significant. Moreover, Apo B/A1 ratio decreased more than 20% following quercetin intake (Table 2; Figures 1-3). It seems that a higher dose of quercetin does not have a conspicuous superiority for cholesterol and apolipoprotein level improvement. However, a negative correlation was found between the quercetin dose and TG, as well as TC/HDL (-0.87 and -0.75 respectively). Discussion Our findings revealed that the administration of high‑dose glucocorticoid for 6 weeks drastically increased serum concentrations of total cholesterol, LDL and triglycerides. However, oral supplementation with two different doses of quercetin, as a naturally occurring flavone that was previously reported to be beneficial in metabolic syndrome, conspicuously reversed the undesirable effects of methylprednisolone. Different doses of quercetin were chosen, since the lower one can be provided by a quercetin-rich diet and the higher one might be taken as commercially available supplements. 18 Needless to say, the different metabolic rates of rats and humans were taken into account for dose determination. 19 The final results indicated that 150 mg/kg quercetin were not much more effective than 50 mg/kg to improve lipid profile, except 103