[A role of melatonin in the treatment of low back pain]

The role of melatonergic system in intervertebral disc degeneration and its association with low back pain: a clinical study

Objective

The mechanisms of intervertebral disc degeneration (IVDD) in low back pain (LBP) patients are multiples. In this study, we attempt to investigate whether melatonergic system plays a potential role in IVDD patients with LBP by analyzing their clinical specimens. The fucus will be given to the correlation between the melatonin receptor expression and intervertebral disc tissue apoptosis.

Methods

In this clinical study, 107 lumbar intervertebral disc nucleus pulposus (NP) specimens from patients with LBP were collected with patients' consents. The disc height (DH) discrepancy ratio, range of motion and sagittal parameters of the pathological plane were measured and Pfirrmann grade was used to classified the grades of IVDD level. Discs at grades 1-3 were served as normal control and grades 4-5 were considered as IVDD. The expression levels of melatonin receptor 1A (MT1) and 1B (MT2) were measured by immunohistochemistry. The apoptosis of NP was assessed using TUNEL staining. Their potential associations among MT1/2, DH, apoptosis, sagittal parameters with IVDD and LBP were evaluated with statistical analysis.

Results

The incidence of IVDD was positively associated with age and negatively related to VAS scores for LBP (p < 0.001). Patients with higher degree of IVDD also have higher DH discrepancy ratio (p < 0.001), higher prevalence of lumbar instability (p = 0.003) and higher cell apoptosis compared to the control. Nevertheless, no statistically significant correlation was identified between Pfirrmann grade and lumbar sagittal parameters. MT1 and MT2 both were highly expressed in the NP tissues. Importantly, MT1 expression but not MT2 was significantly increased in the intervertebral disc tissue of patients with IVDD and its level correlated well with cell apoptosis level and the severity of IVDD as well as lower VAS scores for LBP.

Conclusion

The highly elevated MT1 expression was found in NP tissues of patients with IVDD and LBP compared to the control. This phenomenon probably reflects the compensating response of the body to the pathological alteration of the IVDD and LBP. Therefore, these findings provide the novel information to use selective agonists of MT1 to target IVDD and LBP clinically.

Association between single-nucleotide polymorphisms in serotonin receptor 2A and melatonin receptor 1A genes and pain after root canal treatment

AIM

This study aimed to investigate whether single-nucleotide polymorphisms (SNPs) in the genes encoding 5-HTR2A (5-Hydroxytryptamine (serotonin) receptor 2A) and MTNR1A (melatonin receptor 1A) may contribute to postoperative pain perception after root canal treatment. We hypothesised that SNPs in HTR2A and MTNR1A genes were associated with postoperative pain after root canal treatment.

METHODOLOGY

This genetic cohort study enrolled patients with single-rooted teeth diagnosed with pulp necrosis and asymptomatic apical periodontitis before root canal treatment. Root canal treatment was performed in one session using a standardized protocol. Postoperative pain and tenderness were assessed using a visual analogue scale (recorded every day for 7 days and on the 14th and 30th days after root canal treatment). Genomic DNA was extracted from saliva and used to genotype the SNPs in HTR2A (rs4941573 and rs6313) and MTNR1A (rs6553010, rs6847693 and rs13140012) using real-time polymerase chain reaction. Genotypes were compared using univariate and multivariate Poisson regression with generalized estimating equations (p < .05).

RESULTS

In total, 108 patients were enrolled in this study. The SNPs rs6553010 (MTNR1A), rs4941573 and rs6313 (HTR2A) were associated with an increased risk of developing pain after root canal treatment (p < .05).

CONCLUSIONS

This study suggests that SNPs in HTR2A and MTNR1A influence pain response after root canal treatment.

Causal association of sleep disturbances and low back pain: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Previous observational studies have shown that low back pain (LBP) often coexists with sleep disturbances, however, the causal relationship remains unclear. In the present study, the causal relationship between sleep disturbances and LBP was investigated and the importance of sleep improvement in the comprehensive management of LBP was emphasized.

METHODS

Genetic variants were extracted as instrumental variables (IVs) from the genome-wide association study (GWAS) of insomnia, sleep duration, short sleep duration, long sleep duration, and daytime sleepiness. Information regarding genetic variants in LBP was selected from a GWAS dataset and included 13,178 cases and 164,682 controls. MR-Egger, weighted median, inverse-variance weighted (IVW), penalized weighted median, and maximum likelihood (ML) were applied to assess the causal effects. Cochran's Q test and MR-Egger intercept were performed to estimate the heterogeneity and horizontal pleiotropy, respectively. Outliers were identified and eliminated based on MR-PRESSO analysis to reduce the effect of horizontal pleiotropy on the results. Removing each genetic variant using the leave-one-out analysis can help evaluate the stability of results. Finally, the reverse causal inference involving five sleep traits was implemented.

RESULTS

A causal relationship was observed between insomnia-LBP (OR = 1.954, 95% CI: 1.119-3.411), LBP-daytime sleepiness (OR = 1.011, 95% CI: 1.004-1.017), and LBP-insomnia (OR = 1.015, 95% CI: 1.004-1.026), however, the results of bidirectional MR analysis between other sleep traits and LBP were negative. The results of most heterogeneity tests were stable and specific evidence was not found to support the disturbance of horizontal multiplicity. Only one outlier was identified based on MR-PRESSO analysis.

CONCLUSION

The main results of our research showed a potential bidirectional causal association of genetically predicted insomnia with LBP. Sleep improvement may be important in comprehensive management of LBP.

Melatonin in Endometriosis: Mechanistic Understanding and Clinical Insight

Endometriosis is defined as the development of endometrial glands and stroma outside the uterine cavity. Pathophysiology of this disease includes abnormal hormone profiles, cell survival, migration, invasion, angiogenesis, oxidative stress, immunology, and inflammation. Melatonin is a neuroendocrine hormone that is synthesized and released primarily at night from the mammalian pineal gland. Increasing evidence has revealed that melatonin can be synthesized and secreted from multiple extra-pineal tissues where it regulates immune response, inflammation, and angiogenesis locally. Melatonin receptors are expressed in the uterus, and the therapeutic effects of melatonin on endometriosis and other reproductive disorders have been reported. In this review, key information related to the metabolism of melatonin and its biological effects is summarized. Furthermore, the latest in vitro and in vivo findings are highlighted to evaluate the pleiotropic functions of melatonin, as well as to summarize its physiological and pathological effects and treatment potential in endometriosis. Moreover, the pharmacological and therapeutic benefits derived from the administration of exogenous melatonin on reproductive system-related disease are discussed to support the potential of melatonin supplements toward the development of endometriosis. More clinical trials are needed to confirm its therapeutic effects and safety.

Safety and Efficacy of Melatonin in Chronic Tension-Type Headache: A Post-Marketing Real-World Surveillance Program

INTRODUCTION

Tension-type headache (TTH) is the most prevalent primary headache. Every year, about 2-3% of patients with TTH progress to chronic TTH with daily or near-daily headache, warranting preventive treatment. The treatment of chronic TTH is complex and very often associated with significant tolerability issues. To date, melatonin has been studied in only a few small uncontrolled trials. The aim of this surveillance program was to evaluate the efficacy of melatonin (Melaxen^®) in patients with TTH and disruption of circadian rhythms in real-world practice.

METHODS

Sixty-one patients with chronic TTH were enrolled. After the 30-day baseline period, patients took 3 mg of melatonin at bedtime for 30 days with a follow-up period of another 30 days. VAS pain intensity assessments, Hamilton Anxiety Rating Scale (HAM-A), Hamilton Depression Rating Scale (HAM-D), HIT-6 and Levin sleep quality scores were obtained at the baseline visit, at month 1, and month 2.

RESULTS

A significant decrease in the number of headache days per month, VAS pain intensity, HAM-A, HAM-D and HIT-6 scores, and an improvement in sleep quality were observed throughout the study. No treatment-emergent adverse events were reported.

CONCLUSIONS

Melatonin is an effective and safe alternative for the treatment of chronic TTH.

Sleep interventions for osteoarthritis and spinal pain: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

To determine if sleep interventions improve pain and sleep in people with osteoarthritis (OA) and/or spinal pain compared to control/placebo.

DESIGN

Medline, Embase, AMED, PsycINFO, CENTRAL, CINAHL and PEDro were searched from their inception date to July 2017. Keywords relating to "sleep", "OA", "spinal pain", and "randomized controlled trial (RCT)" were combined. Included RCTs investigated the use of sleep interventions for people with OA and/or spinal pain, and measured at least one sleep and health related outcome. Meta-analyses were performed to pool mean differences for pain and sleep quality.

PROSPERO

CRD42016036315.

RESULTS

Of 1445 unique records, 24 studies were included. Sixteen studies included participants with spinal pain, seven with OA, and one included a mixed population. Sleep interventions included established sleep interventions (ESI) [cognitive behavioural therapy (CBT) and pharmacological interventions], and a range of others. Intervention periods ranged from 4 to 10 weeks. Thirteen studies were of moderate to high quality (PEDro ≥ 6/10). Due to high heterogeneity between studies we also performed sub-group and sensitivity analyses. ESI decreased Insomnia Severity Index (ISI) for people with low back pain (LBP) (pooled mean difference: -6.78/28, 95% confidence interval (95% CI): [-9.47, -4.09], I² = 40%) and OA (-2.41, [-4.19, -0.63], 0%). However ESI decreased pain for people with LBP (pooled mean difference: visual analogue scale (VAS) -12.77/100, 95% CI: [-17.57, -7.97], I² = 0%), but not OA (-2.32, [-7.18, 2.54], 27%).

CONCLUSION

ESI appeared to improve sleep and pain for people with LBP, and sleep for people with OA. However more vigorous studies need to be conducted.

Melatonin in Chronic Pain Syndromes

Melatonin is a neurohormone secreted by epiphysis and extrapineal structures. It performs several functions including chronobiotic, antioxidant, oncostatic, immune modulating, normothermal, and anxiolytic functions. Melatonin affects the cardiovascular system and gastrointestinal tract, participates in reproduction and metabolism, and body mass regulation. Moreover, recent studies have demonstrated melatonin efficacy in relation to pain syndromes. The present paper reviews the studies on melatonin use in fibromyalgia, headaches, irritable bowel syndrome, chronic back pain, and rheumatoid arthritis. The paper discusses the possible mechanisms of melatonin analgesic properties. On one hand, circadian rhythms normalization results in sleep improvement, which is inevitably disordered in chronic pain syndromes, and activation of melatonin adaptive capabilities. On the other hand, there is evidence of melatonin-independent analgesic effect involving melatonin receptors and several neurotransmitter systems.

[Melatonin in chronic pain syndromes]

Melatonin, a neurohormone synthesized by the epiphysis and extrapineal structures, has several functions including chronobiotic, antioxidant, oncostatic, immunomodulating, normothymic and anxiolytic ones. It impacts on the cardiovascular system and the gastrointestinal tract and is involved in reproductive functions, metabolism and body mass regulation. Moreover, recent studies have demonstrated the efficacy of melatonin in pain syndromes. The authors present a literature review on the studies of melatonin in treatment of fibromyalgia, headache, irritated bowel syndrome, chronic back pain and rheumatoid arthritis. Possible mechanisms of analgesic properties of melatonin are discussed. On one hand, there is the improvement of sleep and activation of own adaptive potential of melatonin by normalizing circadian rhythms inevitably disturbed in chronic pain syndromes. On the other hand, there are the data on the analgesic effect of melatonin realized through melatonin receptors and several neurotransmitter systems.