Effect of melatonin on the maintenance of cholesterol homeostasis in the rat

Abstract

The effect of melatonin on cholesterol metabolism in the rat was investigated in the dietary and hypothyroid models of hypercholesterolemia. In normal and dietary hypercholesterolemia (induced by 1% cholesterol, 0.5% bile acid), melatonin treatment (12.5mg/kg i.p.) reduced total serum cholesterol concentration and total low density lipoprotein (VLDL+LDL) cholesterol. The protective action of melatonin was manifested only following the induction of cholesterolemia in such animals. Enhanced catabolism of cholesterol to bile acids is likely involved as shown by an increase in fecal bile acid excretion following melatonin treatment. Incorporation of 1-14C acetate into sterols was unaffected by melatonin treatment which suggests its lack of influence on sterol biosynthesis. In secondary hypercholesterolemia (hypothyroidism induced by 2-thiouracil), melatonin exerted a beneficial effect by increasing the HDL/total LDL cholesterol ratio. These findings suggest that the hypocholesterolemic effect of melatonin may work through the augmentation of endogenous cholesterol clearance mechanisms. This is accompanied by the lowering of the cholesterol fraction associated with low density lipoproteins.

Beneficial effects of melatonin on serum nitric oxide, homocysteine, and ADMA levels in fructose-fed rats

“…Melatonin is a hormone which is closely related to the regulation of insulin secretion and glucose/lipid metabolism. Melatonin showed positive impacts on metabolic syndrome due to its anti-hyperlipidemic effect and it is reported to reduce adiposity and body weight in animal studies (Chan & Tang, 1995;Srinivasan et al, 2013;Zanuto et al, 2013). Moreover, melatonin was showed to increase insulin sensitivity and glucose tolerance in rats fed with high fat or sucrose diets (Srinivasan et al, 2013).…”

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

“…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). Therefore, as the antioxidant system is a protector in situations like hypercholesterolemia, which can induce oxidative stress, melatonin seems to be an agent playing its metabolic role harder on the lipid side.…”

“…Exogenous melatonin has been shown to reduce the lipids. Plasma levels of LDL-C and TC were reduced by melatonin in hypercholesterolemic rats (13)(14)(15)(16).…”

“…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). In addition, a correlation between melatonin levels and blood antioxidant status has been suggested.…”

The effect of melatonin and/or complex vitamin B1,B6,B12 in modulating epinephrine-induced stress in male rats

“…The antihyperlipidimic actions of MT has been studied by many researchers. Chan and Tang (1995) stated that MT exerted a beneficial effect by increasing the HDL/total LDL cholesterol ratio accompanied by the lowering of the cholesterol fraction associated with low density lipoproteins in secondary hypercholesterolemia. Sener et al (2004) reported that the administration of MT caused significant increase in HDL-cholesterol with a clear significant drop in TGs, total cholesterol and LDL-cholesterol in the rats and mice fed hypercholesterolemic diet.…”