Melatonin supplementation in rat ameliorates ovariectomy-induced oxidative stress.

OBJECTIVE: The present study aims to determine the potential of melatonin supplementation in ameliorating tissue oxidative stress, elevated serum corticosterone and hepatic and renal dysfunction. MATERIALS AND METHODS: Adult Wistar rats, either ovariectomized or sham-operated, served as experimental or control groups, respectively. Rats received either melatonin, estrogen, progesterone or a combination of melatonin and estrogen for a period of 15 days. Tissue oxidative stress, serum markers of hepatic and renal dysfunction and serum corticosterone level formed the parameters of assay in all groups at the end of the treatment schedule. RESULTS: Ovariectomized rats showed significant increases in levels of tissue lipid peroxidation, serum levels of glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, alkaline phosphatase, acid phosphatase and corticosterone and significant decrement in enzymatic and non-enzymatic antioxidant status. All parameters showed maximal reversal to control levels on supplementation with high-dose melatonin or estrogen + melatonin treatment. CONCLUSION: Melatonin supplementation proved better than estrogen replacement therapy, with the higher dose being more effective in preventing ovariectomy-induced increases in oxidative stress and serum levels of marker parameters of hepatic and renal dysfunction and corticosterone titer. Overall, melatonin supplementation therapy qualifies as a more potent and safe alternative to estrogen replacement therapy in alleviating postmenopausal increases in oxidative stress and hepatic and renal dysfunction.

Melatonin supplementation therapy as a potent alternative to ERT in ovariectomized rats.

AIM: To evaluate the efficacy of melatonin supplementation therapy as an alternative to estrogen replacement therapy in an ovariectomized rat model and to assess diabetogenic metabolic dysregulation caused by estrogen deficiency in postmenopausal individuals. METHODS: Ovariectomized adult Wistar rats were treated with either estrogen/progesterone, melatonin or a combination of estrogen and melatonin. Body weight gain, feed efficiency, serum glucose, insulin, glucose tolerance and insulin response, serum and tissue lipids, tissue glycogen contents and activities of glycogen phosphorylase and glucose-6-phosphatase were analyzed in all the experimental groups. RESULTS: Ovariectomized animals showed increased body weight gain, feed efficiency, fasting insulin resistance, greater area under curve for the glucose tolerance test, higher serum and tissue lipids and reduced glycogen content and insulin sensitivity. A low dose of melatonin was more efficient than estrogen in reversing all the ovariectomy-induced changes. The combination of estrogen + melatonin was found to be best in correcting glycemic dysregulation while high doses of melatonin could effectively regulate dyslipidemia. CONCLUSION: The present study provides strong evidence for melatonin supplementation therapy to be more potent and effective in comparison to estrogen replacement therapy due to its single-handed ability to revert all the ovariectomy-induced changes. No reported side-effect or long-term effect of melatonin, against the known effects of estrogen replacement therapy, make it more attractive as a candidate to treat postmenopausal symptoms.

Melatonin protects against alterations in hippocampal cholinergic system, trace metals and oxidative stress induced by gestational and lactational exposure to cadmium.

Dietary exposure to cadmium, even at lower doses, can lead to free radical induced neurotoxicity, neurobehavioral changes and alteration in neurotransmitters. Such changes are likely to be more pronounced in the developing brain due to incompleteness of blood brain barrier (BBB). Hippocampus being the seat of intelligence has a role in learning and cognitive behavior and any damage to hippocampus during developmental stage is likely to result in neurodegenerative changes in later life. To this end, fetal and neonatal exposure to cadmium was induced by exposing pregnant dams of Swiss albino strain throughout the period of gestation and following parturition up till 5th day post partum (pp) through drinking water (3ppm/animal/day). The neonates were sacrificed on day 6 pp and indices of oxidative stress, levels of trace elements and changes in cholinergic system were evaluated in the hippocampus. Increased lipid peroxidation, surge in reactive oxygen species (ROS), depressed antioxidant defense, increased accumulation of cadmium, differential alterations in trace elements and decreased activity of AChE were the features of cadmium toxicity. Simultaneous administration of melatonin to cadmium challenged animals offset these detrimental changes. The results suggest that melatonin co-administration can effectively protect against the adverse effects of cadmium on endogenous antioxidant status, changes in trace metal concentrations and compromised hippocampal cholinergic system.