Melatonin May Increase Anticancer Potential of Pleiotropic Drugs

Melatonin (N-acetyl-5-methoxytryptamine) is not only a pineal hormone, but also an ubiquitary molecule present in plants and part of our diet. Numerous preclinical and some clinical reports pointed to its multiple beneficial effects including oncostatic properties, and as such, it has become one of the most aspiring goals in cancer prevention/therapy. A link between cancer and inflammation and/or metabolic disorders has been well established and the therapy of these conditions with so-called pleiotropic drugs, which include non-steroidal anti-inflammatory drugs, statins and peroral antidiabetics, modulates a cancer risk too. Adjuvant therapy with melatonin may improve the oncostatic potential of these drugs. Results from preclinical studies are limited though support this hypothesis, which, however, remains to be verified by further research

Effect of a Short-Term and Long-Term Melatonin Administration on Mammary Carcinogenesis in Female Sprague-Dawley Rats Influenced by Repeated Psychoemotional Stress

The aim of this study was to evaluate the effect of melatonin (MEL) on N-methyl-N-nitrosourea (NMU)-induced mammary carcinogenesis in female Sprague-Dawley rats exposed to repeated psychoemotional stress - immobilization in boxes. NMU was applied intraperitoneally in two doses each of 50 mg/kg b.w. between 40 - 50 postnatal days. Melatonin was administered in drinking water at a concentration of 4 μg/ml daily from 15:00 h to 8:00 h. The application was initiated 5 days prior to the fi rst NMU dose and lasted 15 days, i.e. during the promotion phase of tumour development, or long-term until the end of the experiment (week 20). Immobilization (2 h per day) began on the third day after the second carcinogen application and lasted for 7 consecutive days. Short-term MEL administration to immobilized animals increased incidence by 22%, decreased tumour frequency per animal by 26% and reduced tumour volume gain (by 21%) when compared to the immobilized group without MEL application. Decreased frequency per animal by 28% and more than a 40% decrease in tumour volume gain and cumulative volume were the most pronounced changes in the animals drinking MEL until the end of the experiment. Long-term MEL administration reduced the number and size of mammary tumours more markedly than its short-term administration. Melatonin decreased certain attributes of mammary carcinogenesis in female rats influenced by psychoemotional stress

Chemoprevention of N-Methyl-N-Nitrosourea Induced Mammary Carcinogenesis with Raloxifene and Melatonin: Metabolic Changes in Female Rats

Abstract Chamilová M., P. Kubatka, K. Kalická, E. Adámeková, B. Bojková, I. Ahlers, E. Ahlersová: Chemoprevention of N-methyl-N-nitrosourea Induced Mammary Carcinogenesis with Raloxifene and Melatonin: Metabolic Changes in Female Rats. Acta Vet. Brno 2002, 71: 235-242. The aim of this work was to determine the selected parameters of carbohydrate and lipid metabolism in the mammary carcinogenesis induced with N-methyl-N-nitrosourea (NMU) in two doses, each by 50 mg/kg of body weight with a 7-day interval between them within the postnatal days 43 and 54 in female Sprague-Dawley rats. Chemoprevention started with the administration of melatonin (MEL, 4 µg/ml in water, from 15.00 h to 08.00 h) 12 days and raloxifene (RAL 5 mg/kg, 2 × weekly) 10 days before the application of NMU. Twenty-four weeks following the NMU administration the animals were killed, and the incidence, latency, frequency and volume of tumours were evaluated. The animals were divided into: tumour-bearing (TB) and non-tumourbearing (NTB) with the influence of RAL, MEL and their combination. While RAL and RAL plus MEL significantly decreased the incidence and frequency of tumours, the effect of isolated MEL was substantially lower. In the serum, an increase in the concentration of serum glucose in TB and also NTB animals was observed. In the liver of both the TB and NTB animals, the content of cholesterol (CH) and triacylglycerols (TG) decreased and the contents of phospholipids (PL) increased. RAL decreased the contents of CH and PL in the liver of NTB animals and increased the concentration of TG in both groups of animals. Administration of RAL to NTB animals decreased the concentrations of malondialdehyde (MDA) in the serum and thymus, in the bone marrow also in TB animals. MEL decreased the concentration of MDA in the bone marrow of TB animals. MEL increased the concentrations of serum glucose and glycogen content in the heart muscle of NTB animals. RAL plus MEL decreased the concentration of serum TG and PL and decreased the contents of CH and PL in the liver of TB as well as NTB animals. In the thymus and liver, combination of RAL+MEL decreased the MDA content compared with the RAL alone in NTB animals. The co-effect of two or more substances will be probably the optimal way in prevention of cancer. The co-effect of RAL and MEL shows to be a prospective way for influencing the mammary tumors. Breast cancer, female rats, raloxifene, melatonin, chemoprevention The hormonal therapy of the breast carcinoma is an inseparable part of the variety of therapeutic procedures. The substitution with estrogens has been considered for a long time as a dominant indication of therapy in postmenopausal women, and it has been recognized that approximately one third of women will have a benefit of this procedure. The use of estrogens protects these women against osteoporosis and decreases the cardiovascular risk, but on the other hand, increases the risk of breast and endometrium carcinom

Prolonged melatonin administration in 6-month-old Sprague-Dawley rats: metabolic alterations

The aim of this work was to evaluate the effect of prolonged melatonin administration on chosen metabolic and hormonal variables in male and female Sprague-Dawley rats. Melatonin was administered in tap water (4 μg/ml) daily from the 6th month of age. Rats were fed a standard type of diet ad libitum and were kept in a light regimen L:D - 12:12h. The experiment was terminated after 12 weeks of melatonin administration. Melatonin decreased body mass during the whole experiment in females and from the 42nd day of the experiment in males. Relative heart muscle weight in females and absolute/relative thymus weight in males were increased after melatonin administration. Melatonin decreased glycaemia, heart muscle glycogen concentration in females and liver glycogen concentration in both sexes. Serum insulin concentration in males was decreased; serum corticosterone concentration was increased in both males and females. Serum triacylglycerol and heart muscle cholesterol concentration in females were decreased, however in males serum and heart muscle cholesterol concentration was increased. Liver phospholipid concentration in females was decreased and heart muscle phospholipid concentration in males was increased. Melatonin increased malondialdehyde concentration in heart muscle in males and in liver in both sexes. Melatonin induced prominent sexdependent changes in both carbohydrate and lipid metabolism