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

Effects of 12 Weeks of Daily Melatonin Administration on Inflammatory Markers and Adipose Tissue Mass of Rats under Hypoestrogenism

Background and Objectives: The hormonal state of hypoestrogenism is associated with the accumulation of white adipose tissue, which can induce an increase in pro-inflammatory markers, leading to progressive health complications. Melatonin can act on adipose tissue mass, promoting its reduction and influencing inflammation, reducing IL-6 and releasing IL-10, pro- and anti-inflammatory markers, respectively. However, the role of melatonin regarding such parameters under the context of hypoestrogenism remains unknown. The aim of this study was to determine the effect of 12 weeks of hypoestrogenism and melatonin on white adipose tissue mass and circulating levels of IL-6, IL-10, TGF-β-1, and leukotriene C4 (LTC4). Materials and Methods: The animals (Wistar rats with sixteen weeks of age at the beginning of the experiment) under hypoestrogenism were submitted to the surgical technique of bilateral ovariectomy. The animals received melatonin (10 mg·kg-1) or vehicles by orogastric gavage every day for 12 weeks and administration occurred systematically 1 h after the beginning of the dark period. White adipose tissue (perigonadal, peritoneal, and subcutaneous) was collected for mass recording, while blood was collected for the serum determination of IL-6, IL-10, TGF-β-1, and LTC4. Results: Hypoestrogenism increased the perigonadal and subcutaneous mass and IL-6 levels. Melatonin kept hypoestrogenic animals in physiological conditions similar to the control group and increased thymus tissue mass. Conclusions: Hypoestrogenism appears to have a negative impact on white adipose tissue mass and IL-6 and although melatonin commonly exerts a significant effect in preventing these changes, this study did not have a sufficiently negative impact caused by hypoestrogenism for melatonin to promote certain benefits.

Melatonin Alleviates Ovariectomy-Induced Cardiovascular Inflammation in Sedentary or Exercised Rats by Upregulating SIRT1

We aimed to evaluate the impact of hormone replacement, melatonin, or exercise alone or their combination on oxidative damage and functional status of heart, brain, and aorta of ovariectomized (OVX) rats and to determine whether the signaling pathway is dependent on sirtuin-1 (SIRT1). Ovariectomized Sprague Dawley rats were orally given either a hormone replacement therapy (1 mg/kg/day,17β estradiol; HRT) or melatonin (4 mg/kg/day) or HRT + melatonin treatments or tap water, while each group was further divided into sedentary and exercise (30 min/5 days/week) groups. After the heart rate measurements and memory tests were performed, trunk blood was collected at the end of the 10th week to determine metabolic parameters in serum samples. Tissue samples of abdominal aorta, heart, and brain were taken for biochemical measurements and histopathological evaluation. Heart rates and memory performances of the OVX rats were not changed significantly by none of the applications. Melatonin treatment or its co-administration with HRT upregulated the expressions of IL-10 and SIRT1, reduced the expressions of IL-6 and TNF-α, and reduced DNA damage in the hearts and thoracic aortae of non-exercised rats. Co-administration of melatonin and HRT to exercised OVX rats reduced inflammatory response and upregulated SIRT1 expression in the aortic and cardiac tissues. The present study suggests that melatonin treatment, either alone or in combination with exercise and/or HRT, upregulates SIRT1 expression and alleviates oxidative injury and inflammation in the hearts and aortas of OVX rats. Melatonin should be considered in alleviating cardiovascular disease risk in postmenopausal women.

Effect of 12-wk Training in Ovariectomised Rats on PGC-1α, NRF-1 and Energy Substrates

Metabolic diseases are associated with hypoestrogenism owing to their lower energy expenditure and consequent imbalance. Physical training promotes energy expenditure through PGC-1α and NRF-1, which are muscle proteins of the oxidative metabolism. However, the influence of physical training on protein expression in individuals with hypoestrogenism remains uncertain. Thus, the aim of this study is to determine the effect of 12 weeks of moderate-intensity swimming training on the muscle expression of PGC-1α, NRF-1, glycogen and triglyceride in ovariectomised rats. OVX and OVX+TR rats were subjected to ovariectomy. The trained animals swam for 30 minutes, 5 days/week, at 80% of the critical load intensity. Soleus was collected to quantify PGC-1α and NRF-1 expressions, while gastrocnemius and gluteus maximus were collected to measure glycogen and triglyceride. Blood glucose was also evaluated. Whereas ovariectomy decreased PGC-1α expression (p<0.05) without altering NRF-1 (p=0.48), physical training increased PGC-1α (p<0.01) and NRF-1 (p<0.05). Ovariectomy reduced glycogen (p<0.05) and triglyceride (p<0.05), whereas physical training increased glycogen (p<0.05) but did not change triglyceride (p=0.06). Ovariectomy increased blood glucose (p<0.01), while physical training reduced it (p<0.01). In summary, 12 weeks of individualized and moderate-intensity training were capable of preventing muscle metabolic consequences caused by ovariectomy.

The Crosstalk between Melatonin and Sex Steroid Hormones

Melatonin, an indolamine mainly released from the pineal gland, is associated with many biological functions, namely, the modulation of circadian and seasonal rhythms, sleep inducer, regulator of energy metabolism, antioxidant, and anticarcinogenic. Although several pieces of evidence also recognize the influence of melatonin in the reproductive physiology, the crosstalk between melatonin and sex hormones is not clear. Here, we review the effects of sex differences in the circulating levels of melatonin and update the current knowledge on the link between sex hormones and melatonin. Furthermore, we explore the effects of melatonin on gonadal steroidogenesis and hormonal control in females. The literature review shows that despite the strong evidence that sex differences impact on the circadian profiles of melatonin, reports are still considerably ambiguous, and these differences may arise from several factors, like the use of contraceptive pills, hormonal status, and sleep deprivation. Furthermore, there has been an inconclusive debate about the characteristics of the reciprocal relationship between melatonin and reproductive hormones. In this regard, there is evidence for the role of melatonin in gonadal steroidogenesis brought about by research that shows that melatonin affects multiple transduction pathways that modulate Sertoli cell physiology and consequently spermatogenesis, and also estrogen and progesterone production. From the outcome of our research, it is possible to conclude that understanding the correlation between melatonin and reproductive hormones is crucial for the correction of several complications occurring during pregnancy, like preeclampsia, and for the control of climacteric symptoms.

Co-administering Melatonin With an Estradiol-Progesterone Menopausal Hormone Therapy Represses Mammary Cancer Development in a Mouse Model of HER2-Positive Breast Cancer

Melatonin has numerous anti-cancer properties reported to influence cancer initiation, promotion, and metastasis. With the need for effective hormone therapies (HT) to treat menopausal symptoms without increasing breast cancer risk, co-administration of nocturnal melatonin with a natural, low-dose HT was evaluated in mice that develop primary and metastatic mammary cancer. Individually, melatonin (MEL) and estradiol-progesterone therapy (EPT) did not significantly affect mammary cancer development through age 14 months, but, when combined, the melatonin-estradiol-progesterone therapy (MEPT) significantly repressed tumor formation. This repression was due to effects on tumor incidence, but not latency. These results demonstrate that melatonin and the HT cooperate to decrease the mammary cancer risk. Melatonin and EPT also cooperate to alter the balance of the progesterone receptor (PR) isoforms by significantly increasing PRA protein expression only in MEPT mammary glands. Melatonin significantly suppressed amphiregulin transcripts in MEL and MEPT mammary glands, suggesting that amphiregulin together with the higher PRA:PRB balance and other factors may contribute to reducing cancer development in MEPT mice. Melatonin supplementation influenced mammary morphology by increasing tertiary branching in the mouse mammary glands and differentiation in human mammary epithelial cell cultures. Uterine weight in the luteal phase was elevated after long-term exposure to EPT, but not to MEPT, indicating that melatonin supplementation may reduce estrogen-induced uterine stimulation. Melatonin supplementation significantly decreased the incidence of grossly-detected lung metastases in MEL mice, suggesting that melatonin delays the formation of metastatic lesions and/or decreases aggressiveness in this model of HER2⁺ breast cancer. Mammary tumor development was similar in EPT and MEPT mice until age 8.6 months, but after 8.6 months, only MEPT continued to suppress cancer development. These data suggest that melatonin supplementation has a negligible effect in young MEPT mice, but is required in older mice to inhibit tumor formation. Since melatonin binding was significantly decreased in older mammary glands, irrespective of treatment, melatonin supplementation may overcome reduced melatonin responsiveness in the aged MEPT mice. Since melatonin levels are known to decline near menopause, nocturnal melatonin supplementation may also be needed in aging women to cooperate with HT to decrease breast cancer risk.

Melatonin in perimenopausal and postmenopausal women: associations with mood, sleep, climacteric symptoms, and quality of life

OBJECTIVE

Melatonin synthesis and secretion are partly modulated by estrogen and progesterone. Changes in melatonin concentrations, possibly related to the menopausal transition, may be associated with climacteric mood, sleep, and vasomotor symptoms. The aims of this study were to compare the serum concentrations of melatonin in perimenopausal and postmenopausal women and to evaluate melatonin's influence on mood, sleep, vasomotor symptoms, and quality of life.

METHODS

We analyzed the data of 17 healthy perimenopausal women (aged 43-51 y) and 18 healthy postmenopausal women (aged 58-71 y) who participated in a prospective study. On study night (9:00 pm-9:00 am), serum melatonin was sampled at 20-minute (9:00 pm-12:00 midnight; 6:00-9:00 am) and 1-hour (12:00 midnight-6:00 am) intervals. Questionnaires were used to assess depression (Beck Depression Inventory), anxiety (State-Trait Anxiety Inventory), insomnia and sleepiness (Basic Nordic Sleep Questionnaire [BNSQ]), subjective sleep quality, vasomotor symptoms, and quality of life (EuroQoL).

RESULTS

Postmenopausal women had lower nighttime serum melatonin concentrations than perimenopausal women. The duration of melatonin secretion tended to be shorter in postmenopause, whereas melatonin peak time did not differ. Mean melatonin concentrations and exposure levels did not correlate with follicle-stimulating hormone level, estradiol level, body mass index, Beck Depression Inventory score, State-Trait Anxiety Inventory score, BNSQ insomnia score, BNSQ sleepiness score, subjective sleep score, climacteric vasomotor score, or quality of life. In perimenopause, the later is the melatonin peak, the higher is the level of anxiety (P = 0.022), and the longer is the melatonin secretion, the better is the quality of life (P < 0.001).

CONCLUSIONS

Longitudinal research is needed to better understand the possible contributory role of menopause in lower melatonin levels.