en Biochemistry Biochemistry پژوهشي Research <div><strong>Introduction: </strong>The aim of this study was to investigate the effect of aerobic training and consumption of L-carnitine supplements on HMG-CoA reductase and low density lipoprotein receptor (LDL-R) in the liver of male Wistar rats toxicated by boldenone.<br> <strong>Materials and methods:</strong> In this clinical study, 30 male Wistar rats aged 12 weeks (weight 195&plusmn;7.94g) were randomly divided into five groups: control, no-treatment, boldenone (5mg per kg), L-carnitine and L-carnitine + training groups with six rat in each group. The moderate intensity endurance training program (50-55% of maximal oxygen consumption) performed for 6 weeks and 5 times a week. Injection once a week, on an appointed day, and in the quadriceps and hamstring was conducted in depth. After anesthesia, biopsy in aliquots was prepared. The HMG-CoA reductase and LDL-R expression in the samples was measured by Real-Time-PCR and the quantification of gene expression levels was calculated using the formula 2^{-&Delta;&Delta;ct} then analyzed by One-way ANOVA and post hoc Scheffe at P<0.05.<br> <strong>Results:</strong> The results showed that aerobic training and supplementation with L-carnitine had significant effects on HMG-CoA reductase and LDL-R in the liver of male Wistar rats intoxicated by boldenone (P=0.0001). The results showed that the expression of HMG-CoA reductase in training-L-carnitine group was significantly lower than the control group (P=0.0001). The expression of LDL-R in training-L-carnitine and L-carnitine group increased significantly compared to control group (P=0.0001).</div> <strong>Conclusion: </strong>According to the findings, it seems to the supplementation with L-carnitine alongwith regular aerobic training modulate the biosynthesis of cholesterol in liver tissue. Aerobic training, Boldenone, L-carnitine, HMG-CoA reductase, LDL receptor, Wistar rats 11 22 http://jbrms.medilam.ac.ir/browse.php?a_code=A-10-361-1&slc_lang=en&sid=1 Behnam Bagherzadeh Rahmani b.bagherzadeh@gmail.com 10031947532846003385 10031947532846003385 No Department of Exercise Physiology, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran Asieh Abbassi Daloii abbasi.daloii@gmail.com 10031947532846003386 10031947532846003386 Yes Department of Exercise Physiology, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran