Effects of melatonin on the acute inflammatory response associated with endoscopic retrograde cholangiopancreatography: A randomized, double-blind, placebo-controlled trial

Safety of higher doses of melatonin in adults: A systematic review and meta-analysis

Melatonin is commonly used for sleep and jetlag at low doses. However, there is less documentation on the safety of higher doses, which are being increasingly used for a wide variety of conditions, including more recently COVID-19 prevention and treatment. The aim of this review was to investigate the safety of higher doses of melatonin in adults. Medline, Scopus, Embase and PsycINFO databases from inception until December 2019 with convenience searches until October 2020. Randomised controlled trials investigating high-dose melatonin (≥10 mg) in human adults over 30 years of age were included. Two investigators independently abstracted articles using PRISMA guidelines. Risk of bias was assessed by a committee of three investigators. 79 studies were identified with a total of 3861 participants. Studies included a large range of medical conditions. The meta-analysis was pooled data using a random effects model. The outcomes examined were the number of adverse events (AEs), serious adverse events (SAEs) and withdrawals due to AEs. A total of 29 studies (37%) made no mention of the presence or absence of AEs. Overall, only four studies met the pre-specified low risk of bias criteria for meta-analysis. In that small subset, melatonin did not cause a detectable increase in SAEs (Rate Ratio = 0.88 [0.52, 1.50], p = .64) or withdrawals due to AEs (0.93 [0.24, 3.56], p = .92), but did appear to increase the risk of AEs such as drowsiness, headache and dizziness (1.40 [1.15, 1.69], p < .001). Overall, there has been limited AE reporting from high-dose melatonin studies. Based on this limited evidence, melatonin appears to have a good safety profile. Better safety reporting in future long-term trials is needed to confirm this as our confidence limits were very wide due to the paucity of suitable data.

Anti-inflammatory effects of melatonin: A systematic review and meta-analysis of clinical trials

Chronic inflammation contributes to multiple diseases including cardiovascular diseases, autoimmune disorders, metabolic disorders, and psychiatric conditions. Melatonin, a hormone responsible for circadian rhythm, plays a complex role within the immune system, including having an anti-inflammatory effect. While there are numerous animal studies demonstrating this effect, few human clinical trials have been conducted. This systematic review of clinical trials examined whether exogenous melatonin reduces levels of inflammatory markers in humans. We searched PubMed, Embase, Cochrane Library, Scopus, and PsycINFO, and the references of the identified articles for randomized and non-randomized placebo-controlled trials. Data were extracted from the articles and meta-analyses were conducted using a random effects model to calculate standardized mean differences (SMDs, i.e., Cohen's d). From an initial search result of 4548 references, 31 studies met the inclusion criteria and were included involving 1517 participants. Melatonin had significant anti-inflammatory effects on interleukin (IL)-1 (SMD -1.64; 95% confidence interval [CI] -2.86, -0.43; p = 0.008), IL-6 (-3.84; -5.23, -2.46; p < 0.001), IL-8 (-21.06; -27.27, -14.85; p < 0.001), and tumor necrosis factor (TNF) (-1.54; -2.49, -0.58; p = 0.002), but not on C-reactive protein (CRP) (-0.18; -0.91, 0.55; p = 0.62). Trimming outlier studies with large effect sizes eliminated publication bias, and summary effect sizes were significant for IL-1 (SMD -1.11; 95% CI -1.90, -0.32; p = 0.006), IL-6 (-1.91; -2.98, -0.83; p = 0.001), and IL-8 (-13.46; -18.88, -8.04; p < 0.001), but not for TNF (-0.45; -1.13, 0.23; p = 0.19). Exogenous melatonin reduced levels of inflammatory markers and may be useful for prevention and adjuvant treatment of inflammatory disorders. Melatonin is safe with few side effects, which makes it an excellent agent for prevention of inflammatory disorders. Because chronic inflammation increases with aging and inflammation plays a role in the etiology of numerous diseases that affect older populations, melatonin has the potential to be widely used particularly in older adults.

Role of melatonin as an SIRT1 enhancer in chronic obstructive pulmonary disease induced by cigarette smoke

Background

Melatonin has various biological activities that improve the health of an individual. We evaluated the effects of melatonin on inflammatory response in chronic obstructive pulmonary disease (COPD), focusing on the regulation of SIRT1 expression.

Methods

To investigate the effect of melatonin, we used cigarette smoke (CS)‐induced COPD mouse model and CS condensate (CSC)‐stimulated J774 macrophage cells.

Results

CSC‐stimulated J774 macrophages exhibited increased p65 acetylation with a reduction in SIRT1 expression. However, melatonin induced the enhancement of SIRT1 expression, which eventually decreased p65 acetylation in CSC‐stimulated J774 cells. Melatonin‐treated mice exhibited an enhancement in SIRT1 expression with the reduction in p65 acetylation, which decreased the level of inflammatory mediators induced by CS. Additionally, SIRT1 inhibitor treatment increased the level of inflammatory mediators, which was accompanied by an increase in p65 acetylation. However, cotreatment with melatonin and an SIRT1 inhibitor reduced the level of inflammatory mediators compared with that by treatment with the SIRT1 inhibitor alone, which was accompanied by elevation in SIRT1 expression and reduction in p65 acetylation.

Conclusions

Overall, the results indicated that melatonin has therapeutic effects against COPD, owing to its property to enhance SIRT1 expression.