Serum cholesterol and lipid peroxidation are decreased by melatonin in diet‐induced hypercholesterolemic rats

Abstract

The purpose of this study was to investigate the effect of melatonin, at pharmacological doses, on serum lipids of rats fed with a hypercholesterolemic diet. Therefore, different groups of animals were fed with either the regular Sanders Chow diet or a diet enriched in cholesterol. Moreover, animals were treated with or without melatonin in the drinking water for 3 months. We show that melatonin treatment did not affect the levels of cholesterol or triglycerides in rats fed with a regular diet. However, the increase in total cholesterol and low‐density lipoprotein (LDL)‐cholesterol induced by a cholesterol‐enriched diet was reduced significantly by melatonin administration. On the other hand, melatonin administration prevented the decrease in high‐density lipoprotein (HDL)‐cholesterol induced by the same diet. No differences in the levels of very low‐density lipoprotein (VLDL)‐cholesterol and triglycerides were found. We also found that melatonin administration slightly decreased serum uric, bilirubin and increased serum glucose levels. Other biochemical parameters, including total proteins, creatinine, urea, phosphorus, calcium, glutamic oxalacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), Γ‐glutamyltranspeptidase (Γ‐GT), acetyl cholinesterase (AcCho), and alkaline phosphatase (ALP) were not modified by melatonin treatment. Finally, lipid peroxidation (LPO) was studied in membranes of liver, brain, spleen, and heart as an index of membrane oxidative damage. Results show that hypercholesterolemic diet did not modify the LPO status in any of the tissues studied. However, chronic melatonin administration significantly decreased LPO. Results confirm that melatonin participates in the regulation of cholesterol metabolism and in the prevention of oxidative damage to membranes.

Effect of melatonin on biochemical variables of the blood in dairy cows

“…Changes observed in this study in the cholesterol levels of melatonin-treated cows are at variance with the data published previously. In studies on rats fed a diet high in cholesterol, melatonin lowered the level of this metabolite, while it did not cause any changes in rats fed a normal diet (Mori et al, 1989;Hoys et al, 2000). However, in the present experiment the pineal gland hormone caused an increase in the level of this variable, which seems advantageous from the aspect of interest of our study.…”

“…For this reason melatonin may affect -directly or indirectly -the metabolism of a given organism (Vanecek, 1998;Maćkowiak et al, 1999a, b). The advantageous effects of melatonin on carbohydrate-lipid metabolism (Maćkowiak et al, 1999a, b;Hoys et al, 2000) as well as on the endocrine status (Maćkowiak et al, 1999a;Esquifino et al, 1999;Fabiś et al, 2002) have already been demonstrated.…”

The effects of different doses of melatonin on lipid peroxidation in diet-induced hypercholesterolemic rats

“…Lipid peroxidation is a basically degenerative reaction and its products such as TBARS are toxic to cells (24)(25)(26). As mentioned above, melatonin has been shown to be highly effective in protecting against oxidative damage caused by several factors such as aging, ischemia-reperfusion, toxins and hypercholesterolemia (17,(27)(28)(29)(30). The present data also indicate the oxidant activity of ethanol on lipids.…”

“…Melatonin is a highly potent endogenous radical scavenger protecting the biomolecules against oxidative modifi cation (15). Melatonin administration has been shown to have no signifi cant effect on plasma lipids and lipoproteins in rats on normal diet but diminishes the effects of high-cholesterol diet on lipid parameters (14,17). The protective action of melatonin was manifested only following the induction of cholesterolemia in rats (16).…”

“…As a result of lipid peroxidation, several non-radical products are formed, including malondialdehyde (MDA) and other reactive aldehydes. Melatonin, its precursors, as well as its breakdown products have been shown to prevent the oxidation of lipids (17) Because of all these hypolipidemic and antioxidative effects, this pineal indole has been used in many experimental studies as a vehicle in different ways and in different doses. It is suggested to be a physiological antioxidant by experimental data (12)(13)(14)(15)(16).…”