Tryptophan depletion increases nausea, headache and photophobia in migraine sufferers

Endogenous pain modulation after sleep restriction in migraine: a blinded crossover study

BACKGROUND

Patients with migraine are vulnerable to insufficient sleep, but the impact of sleep restriction is largely unknown. In addition, the importance of sleep may be different in patients with migraine who mostly have attack onsets during sleep, so called sleep-related migraine, compared to patients with non-sleep-related migraine. In this study we investigate the effect of sleep restriction on endogenous pain modulation in patients with migraine and healthy controls. We also compared the effect of sleep restriction in sleep-related and in non-sleep-related migraine.

METHODS

Measurements were conducted in 39 patients with migraine between attacks and 31 controls, once after habitual sleep and once after two consecutive nights of partial sleep restriction. There were 29 and 10 patients with non-sleep-related and sleep-related migraine respectively. Test stimulus was 2-min tonic noxious heat to the left volar forearm. Temporal summation was calculated as the regression coefficient for rated pain in the late part of this 2-min stimulation. Conditioning stimulus was right hand-immersion in 7 °C water. Conditioned pain modulation was defined as the difference in rated pain with and without the conditioning stimulus and was calculated for temporal summation and mean rated pain for the test stimulus. The effect of sleep restriction on temporal summation and conditioned pain modulation was compared in migraine subjects and controls using two-level models with recordings nested in subjects.

RESULTS

Conditioned pain modulation for temporal summation of heat pain tended to be reduced after sleep restriction in patients with migraine compared to controls (p = 0.060) and, in an exploratory analysis, was reduced more after sleep restriction in sleep-related than in non-sleep-related migraine (p = 0.017). No other differences between groups after sleep restriction were found for temporal summation or conditioned pain modulation.

CONCLUSION

Patients with migraine may have a subtly altered endogenous pain modulation system. Sleep restriction may have an increased pronociceptive effect on this system, suggesting a mechanism for vulnerability to insufficient sleep in migraine. This effect seems to be larger in sleep-related migraine than in non-sleep-related migraine.

Neuroanatomical evidence and a mouse calcitonin gene-related peptide model in line with human functional magnetic resonance imaging data support the involvement of peptidergic Edinger-Westphal nucleus in migraine

ABSTRACT

The urocortin 1 (UCN1)-expressing centrally projecting Edinger-Westphal (EWcp) nucleus is influenced by circadian rhythms, hormones, stress, and pain, all known migraine triggers. Our study investigated EWcp's potential involvement in migraine. Using RNAscope in situ hybridization and immunostaining, we examined the expression of calcitonin gene-related peptide (CGRP) receptor components in both mouse and human EWcp and dorsal raphe nucleus (DRN). Tracing study examined connection between EWcp and the spinal trigeminal nucleus (STN). The intraperitoneal CGRP injection model of migraine was applied and validated by light-dark box, and von Frey assays in mice, in situ hybridization combined with immunostaining, were used to assess the functional-morphological changes. The functional connectivity matrix of EW was examined using functional magnetic resonance imaging in control humans and interictal migraineurs. We proved the expression of CGRP receptor components in both murine and human DRN and EWcp. We identified a direct urocortinergic projection from EWcp to the STN. Photophobic behavior, periorbital hyperalgesia, increased c-fos gene-encoded protein immunoreactivity in the lateral periaqueductal gray matter and trigeminal ganglia, and phosphorylated c-AMP-responsive element binding protein in the STN supported the efficacy of CGRP-induced migraine-like state. Calcitonin gene-related peptide administration also increased c-fos gene-encoded protein expression, Ucn1 mRNA, and peptide content in EWcp/UCN1 neurons while reducing serotonin and tryptophan hydroxylase-2 levels in the DRN. Targeted ablation of EWcp/UCN1 neurons induced hyperalgesia. A positive functional connectivity between EW and STN as well as DRN has been identified by functional magnetic resonance imaging. The presented data strongly suggest the regulatory role of EWcp/UCN1 neurons in migraine through the STN and DRN with high translational value.

Regulation of gut microbiota and serum neurotransmitters in mice by Streptococcus thermophilus GA8- and Lacticaseibacillus rhamnosus HAO9-fermented milk containing high levels of gamma-aminobutyric acid

BACKGROUND

Gamma-aminobutyric acid (GABA) is an important neurotransmitter in the human body, with several negative emotions reported as being associated with GABA dysregulation. This study investigates the safety and modulatory effects of GABA-enriched milk, fermented by Streptococcus thermophilus GA8 and Lacticasebacillus rhamnosus HAO9, on the gut microbiota and neurotransmitter profiles in mice.

RESULTS

Through rigorous culturing and fermentation processes, we achieved consistent GABA production in milk, with concentrations reaching 4.6 and 8.5 g L-1 for GA8-fermented and co-fermented milk, respectively, after 48 h. Using SPF male C57BL/6J mice, we administered either mono-culture or combined-culture milk treatments and monitored physiological impacts. The treatments did not affect mouse body weight but induced significant changes in gut microbiota composition. Beta diversity analysis revealed distinct microbial profiles between treatment groups, highlighting fermentation-specific microbial shifts, such as an increase in Verrucomicrobia for the GA8 group and a modulation in Saccharibacteria_genera_incertae_sedis for the GA8 + HAO9 group. Serum neurotransmitter levels were elevated in both treatment groups, with significant increases in l-glutamine, l-tryptophan and, notably, serotonin hydrochloride in the GA8 + HAO9 group. Correlation analysis identified a positive association between specific bacterial genera and neurotransmitter levels, suggesting a probiotic effect on neuroactive substances.

CONCLUSION

These findings suggest that fermented milk has potential as a probiotic supplement for mood improvement and stress relief, highlighting its role in modulating the gut-brain axis. © 2024 Society of Chemical Industry.

Migraine and the microbiota. Can probiotics be beneficial in its prevention? - a narrative review

Migraine is a recurrent disease of the central nervous system that affects an increasing number of people worldwide causing a continuous increase in the costs of treatment. The mechanisms underlying migraine are still unclear but recent reports show that people with migraine may have an altered composition of the intestinal microbiota. It is well established that the gut-brain axis is involved in many neurological diseases, and probiotic supplementation may be an interesting treatment option for these conditions. This review collects data on the gastrointestinal and oral microbiota in people suffering from migraine and the use of probiotics as a novel therapeutic approach in its treatment.

Tryptophan, an important link in regulating the complex network of skin immunology response in atopic dermatitis

Atopic dermatitis (AD) is a common chronic relapsing inflammatory skin disease, of which the pathogenesis is a complex interplay between genetics and environment. Although the exact mechanisms of the disease pathogenesis remain unclear, the immune dysregulation primarily involving the Th2 inflammatory pathway and accompanied with an imbalance of multiple immune cells is considered as one of the critical etiologies of AD. Tryptophan metabolism has long been firmly established as a key regulator of immune cells and then affect the occurrence and development of many immune and inflammatory diseases. But the relationship between tryptophan metabolism and the pathogenesis of AD has not been profoundly discussed throughout the literatures. Therefore, this review is conducted to discuss the relationship between tryptophan metabolism and the complex network of skin inflammatory response in AD, which is important to elucidate its complex pathophysiological mechanisms, and then lead to the development of new therapeutic strategies and drugs for the treatment of this frequently relapsing disease.

The kynurenine pathway of tryptophan metabolism in abdominal migraine in children - A therapeutic potential?

BACKGROUND

Abdominal migraine (AM) is a clinical diagnosis specified by Rome IV and ICHD III as a functional gastrointestinal disease (FGID) and a migraine associated syndrome, respectively. Abdominal migraine in childhood and adolescence may continue with migraine headaches in adulthood. This disease is undiagnosed and undertreated, and thus far the FDA has not approved any drug for AM treatment. It was shown that changes in the kynurenine (KYN) pathway of tryptophan (TRP) metabolism played an important role in the pathogenesis and treatment of FIGDs and associated mood disorders. Changes in the KYN pathway were shown in migraine and therefore it may be involved in AM pathogenesis.

FINDINGS

Abdominal migraine reflects an impairment in the communication within the gut-brain axis. Treatment approaches in AM are based on the experience of physicians, presenting personal rather than evidence-based practice, including efficacy of some drugs in adult migraine. Non-pharmacological treatment of AM is aimed at preventing or ameliorating AM triggers and is based on the STRESS mnemonic. Metabolic treatments with riboflavin and coenzyme Q10 were effective in several cases of pediatric migraine, but in general, results on metabolic treatment in migraine in children are scarce and nonconclusive. Modulations within the KYN pathway of TRP metabolism induced by changes in TRP content in the diet, may ameliorate FGIDs and support their pharmacological treatment. Pharmacological manipulations of brain KYNs in animals have brought promising results for clinical applications. Obese children show a higher headache prevalence and may be especially predisposed to AM, and KYN metabolites showed an alternated distribution in obese individuals as compared with their normal-weight counterparts.

CONCLUSIONS

In conclusion, controlled placebo-based clinical trials with dietary manipulation to adjust the amount of the product of the KYN pathway of TRP metabolism are justified in children and adolescents with AM, especially those with coexisting obesity. Further preclinical studies are needed to establish details of these trials.

Making migraine easier to stomach: the role of the gut-brain-immune axis in headache disorders

BACKGROUND AND PURPOSE

Headache disorders place a significant burden on the healthcare system, being the leading cause of disability in those under 50 years. Novel studies have interrogated the relationship between headache disorders and gastrointestinal dysfunction, suggesting a link between the gut-brain-immune (GBI) axis and headache pathogenesis. Although the exact mechanisms driving the complex relationship between the GBI axis and headache disorders remain unclear, there is a growing appreciation that a healthy and diverse microbiome is necessary for optimal brain health.

METHODS

A literature search was performed through multiple reputable databases in search of Q1 journals within the field of headache disorders and gut microbiome research and were critically and appropriately evaluated to investigate and explore the following; the role of the GBI axis in dietary triggers of headache disorders and the evidence indicating that diet can be used to alleviate headache severity and frequency. The relationship between the GBI axis and post-traumatic headache is then synthesized. Finally, the scarcity of literature regarding paediatric headache disorders and the role that the GBI axis plays in mediating the relationship between sex hormones and headache disorders are highlighted.

CONCLUSIONS

There is potential for novel therapeutic targets for headache disorders if understanding of the GBI axis in their aetiology, pathogenesis and recovery is increased.

Excitation-Inhibition Imbalance in Migraine: From Neurotransmitters to Brain Oscillations

Migraine is among the most common and debilitating neurological disorders typically affecting people of working age. It is characterised by a unilateral, pulsating headache often associated with severe pain. Despite the intensive research, there is still little understanding of the pathophysiology of migraine. At the electrophysiological level, altered oscillatory parameters have been reported within the alpha and gamma bands. At the molecular level, altered glutamate and GABA concentrations have been reported. However, there has been little cross-talk between these lines of research. Thus, the relationship between oscillatory activity and neurotransmitter concentrations remains to be empirically traced. Importantly, how these indices link back to altered sensory processing has to be clearly established as yet. Accordingly, pharmacologic treatments have been mostly symptom-based, and yet sometimes proving ineffective in resolving pain or related issues. This review provides an integrative theoretical framework of excitation-inhibition imbalance for the understanding of current evidence and to address outstanding questions concerning the pathophysiology of migraine. We propose the use of computational modelling for the rigorous formulation of testable hypotheses on mechanisms of homeostatic imbalance and for the development of mechanism-based pharmacological treatments and neurostimulation interventions.

Exploring the Tryptophan Metabolic Pathways in Migraine-Related Mechanisms

Migraine is a complex neurovascular disorder, which causes intense socioeconomic problems worldwide. The pathophysiology of disease is enigmatic; accordingly, therapy is not sufficient. In recent years, migraine research focused on tryptophan, which is metabolized via two main pathways, the serotonin and kynurenine pathways, both of which produce neuroactive molecules that influence pain processing and stress response by disturbing neural and brain hypersensitivity and by interacting with molecules that control vascular and inflammatory actions. Serotonin has a role in trigeminal pain processing, and melatonin, which is another product of this pathway, also has a role in these processes. One of the end products of the kynurenine pathway is kynurenic acid (KYNA), which can decrease the overexpression of migraine-related neuropeptides in experimental conditions. However, the ability of KYNA to cross the blood-brain barrier is minimal, necessitating the development of synthetic analogs with potentially better pharmacokinetic properties to exploit its therapeutic potential. This review summarizes the main translational and clinical findings on tryptophan metabolism and certain neuropeptides, as well as therapeutic options that may be useful in the prevention and treatment of migraine.

Citalopram Neuroendocrine Challenge Shows Altered Tryptophan and Kynurenine Metabolism in Migraine

Altered tryptophan (TRP) metabolism may have an important role in migraine susceptibility through its main metabolites, serotonin and kynurenine (KYN). Both affect pain processing and stress response by interfering with neural and brain hypersensitivity and by interacting with chemokines and cytokines that control vascular and inflammatory processes. The involvement of these pathways in migraine has been widely studied, but acute citalopram neuroendocrine challenge on TRP metabolism and cytokine profile has not been investigated yet. In our study, females with episodic migraine without aura and healthy controls were studied before and after acute citalopram or placebo in a double-blind setting. At baseline, increased TRP/large neutral amino acid (LNAA) ratio and decreased RANTES chemokine concentration were detected in migraine patients compared to controls. The challenge induced a significant increase in TRP, KYN, and TRP/LNAA in healthy controls, but not in migraine patients. Furthermore, migraine attack frequency negatively correlated with KYN/TRP ratio and positively correlated with the neuroendocrine-challenge-induced KYN concentration increase. Our results support a decreased breakdown of TRP via KYN pathway and a failure to modulate TRP–KYN pathway during citalopram-induced acute stress together with an increased vascular sensitivity in migraine. These mechanisms may provide useful drug targets for future drug development.

The presence of migraine symptoms was associated with a higher likelihood to present eating disorders symptoms among teenage students

OBJECTIVE

To investigate the association between migraine and signs and symptoms of eating disorders among teenagers. And as secondary objectives: to investigate the prevalence of eating disorders signs and symptoms and to identify the prevalence of migraine among teenagers.

METHODS

Cross-sectional study was carried out in public schools which included adolescents aged 11-18 years, of both sexes. For eating disorders evaluation two self-reported questionnaires were used: Eating Attitudes Test-26 (EAT-26) and The Bulimic Investigatory Test of Edinburg (BITE). The presence and characterization of headache were verified following the International Classification of Headache Disorders (ICHD-II).

RESULTS

607 adolescents (388 females) with mean age of 13.9 years (95% CI: 13.7; 14) were included. The eating disorders symptoms based on EAT-26 (p = 0.041) and the bulimia nervosa symptoms (p = 0.014) evaluation were more prevalent among teenagers with migraine compared with non-migraine. Also, in multivariate analysis, the adjusted odds ratio (OR) to present bulimia nervosa symptoms is 1.85 times higher among females than males. And, the adjusted OR to present bulimia nervosa symptoms among teenagers with migraine is 1.51 times (OR) higher than among non-migraine.

CONCLUSIONS

The presence of migraine symptoms were associated with a higher likelihood to present eating disorders symptoms among teenagers, especially in females, that was associated with a 1.85-fold increase in the risk to present bulimia nervosa symptoms.

LEVEL OF EVIDENCE

III, Evidence obtained from cross-sectional study.

Migraine signaling pathways: amino acid metabolites that regulate migraine and predispose migraineurs to headache

Migraine is a common, debilitating disorder for which attacks typically result in a throbbing, pulsating headache. Although much is known about migraine, its complexity renders understanding the complete etiology currently out of reach. However, two important facts are clear, the brain and the metabolism of the migraineur differ from that of the non-migraineur. This review centers on the altered amino acid metabolism in migraineurs and how it helps define the pathology of migraine.

The Pharmacological Treatment of Pediatric Vertigo

Vertigo in children is a challenging topic. The lack of dedicated trials, guidelines and papers causes inhomogeneity in the treatment of vertigo in children. Meniere’s disease, migraine equivalents, vestibular neuritis, paroxysmal positional benign vertigo (BPPV), persistent postural-perceptual dizziness (PPPD) and motion sickness may affect children with various degrees of incidence and clinical severity compared to adults. Several drugs are proposed for the management of these conditions, even if their use is subordinated to the child’s age. In this review, we summarize the existing evidence related to the use of drugs for this clinical condition in children as a start point for new trials, stating the urgent need for international guidelines.

Association of plasma tryptophan concentration with periaqueductal gray matter functional connectivity in migraine patients

Altered periaqueductal gray matter (PAG) functional connectivity contributes to brain hyperexcitability in migraine. Although tryptophan modulates neurotransmission in PAG projections through its metabolic pathways, the effect of plasma tryptophan on PAG functional connectivity (PAG-FC) in migraine has not been investigated yet. In this study, using a matched case-control design PAG-FC was measured during a resting-state functional magnetic resonance imaging session in migraine without aura patients (n = 27) and healthy controls (n = 27), and its relationship with plasma tryptophan concentration (TRP) was assessed. In addition, correlations of PAG-FC with age at migraine onset, migraine frequency, trait-anxiety and depressive symptoms were tested and the effect of TRP on these correlations was explored. Our results demonstrated that migraineurs had higher TRP compared to controls. In addition, altered PAG-FC in regions responsible for fear-cascade and pain modulation correlated with TRP only in migraineurs. There was no significant correlation in controls. It suggests increased sensitivity to TRP in migraine patients compared to controls. Trait-anxiety and depressive symptoms correlated with PAG-FC in migraine patients, and these correlations were modulated by TRP in regions responsible for emotional aspects of pain processing, but TRP did not interfere with processes that contribute to migraine attack generation or attack frequency.

Photoaversion in inherited retinal diseases: clinical phenotypes, biological basis, and qualitative and quantitative assessment

Severe light sensitivity is a feature common to a range of ophthalmological and neurological diseases. In inherited retinal diseases (IRDs) particularly, this may be accompanied by significant visual disruption. These symptoms are extremely debilitating for affected individuals and have significant implications in terms of day-to-day activities. Underlying mechanisms remain to be fully elucidated. Currently, there are many assessments of photoaversion (PA), however, all have limitations, with quantitative measurement in particular needing further evaluation. To understand the complexities associated with photoaversion from different pathologies, qualitative and quantitative assessments of the light aversion response must be standardized. There is no treatment to date, and strategies to alleviate symptoms focus on light avoidance. With respect to IRDs, however, gene therapy is currently being investigated in clinical trials and promising and further treatments may be on the horizon. The better characterization of these symptoms is an important end point measure in IRD gene therapy trials.

The Relationship of Psychiatric Comorbidities and Their Impact on Trigger Site Deactivation Surgery for Headaches

BACKGROUND

Patients seeking trigger site deactivation surgery for headaches often have debilitating symptoms that can affect their functional and mental health. Although prior studies have shown a strong correlation between psychiatric variables and chronic headaches, their associations in patients undergoing surgery have not been fully elucidated. This study aims to analyze psychiatric comorbidities and their impact on patients undergoing trigger site deactivation surgery for headaches.

METHODS

One hundred forty-two patients were prospectively enrolled. Patients were asked to complete the Patient Health Questionnaire-2 and Migraine Headache Index surveys preoperatively and at 12 months postoperatively. Data on psychiatric comorbidities were collected by means of both survey and retrospective chart review.

RESULTS

Preoperatively, 38 percent of patients self-reported a diagnosis of depression, and 45 percent of patients met Patient Health Questionnaire-2 criteria for likely major depressive disorder (Patient Health Questionnaire-2 score of ≥3). Twenty-seven percent of patients reported a diagnosis of generalized anxiety disorder. Patients with depression and anxiety reported more severe headache symptoms at baseline. At 1 year postoperatively, patients with these conditions had successful surgical outcomes comparable to those of patients without these conditions. Patients also reported a significant decrease in their Patient Health Questionnaire-2 score, with 22 percent of patients meeting criteria suggestive of depression, compared to 45 percent preoperatively.

CONCLUSIONS

There is a high prevalence of depression and anxiety in patients undergoing trigger site deactivation surgery. Patients with these comorbid conditions achieve successful surgical outcomes comparable to those of the general surgical headache population. Furthermore, trigger site deactivation surgery is associated with a significant decrease in depressive symptoms.

Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders

Migraine, the leading cause of disability in the population aged below 50, is associated with functional gastrointestinal (GI) disorders (FGIDs) such as functional nausea, cyclic vomiting syndrome, and irritable bowel syndrome (IBS). Conversely, changes in intestinal GI transit may cause diarrhea or constipation and are a component of the autonomic symptoms associated with pre- and post-dorsal phases of migraine attack. These mutual relationships provoke a question on a common trigger in migraine and FGIDs. The kynurenine (l-kyn) pathway (KP) is the major route for l-tryptophan (l-Trp) metabolism and transforms l-Trp into several neuroactive compounds. Changes in KP were reported in both migraine and FGIDs. Migraine was largely untreatable, but several drugs approved lately by the FDA, including monoclonal antibodies for calcitonin gene-related peptide (CGRP) and its receptor, create a hope for a breakthrough in migraine treatment. Derivatives of l-kyn were efficient in pain relief with a mechanism including CGRP inhibition. KP products are important ligands to the aryl hydrocarbon receptor (AhR), whose activation is implicated in the pathogenesis of GI and migraine. Toll-like receptors (TLRs) may play a role in migraine and IBS pathogeneses, and KP metabolites detected downstream of TLR activation may be an IBS marker. The TLR4 signaling was observed in initiating and maintaining migraine-like behavior through myeloid differentiation primary response gene 88 (MyD88) in the mouse. The aim of this review is to justify the view that KP modulation may provide common triggers for migraine and FGIDs with the involvement of TLR, AhR, and MyD88 activation.

Clinical relevance of depressed kynurenine pathway in episodic migraine patients: potential prognostic markers in the peripheral plasma during the interictal period

Background

Altered glutamatergic neurotransmission and neuropeptide levels play a central role in migraine pathomechanism. Previously, we confirmed that kynurenic acid, an endogenous glutamatergic antagonist, was able to decrease the expression of pituitary adenylate cyclase-activating polypeptide 1–38, a neuropeptide with known migraine-inducing properties. Hence, our aim was to reveal the role of the peripheral kynurenine pathway (KP) in episodic migraineurs. We focused on the complete tryptophan (Trp) catabolism, which comprises the serotonin and melatonin routes in addition to kynurenine metabolites. We investigated the relationship between metabolic alterations and clinical characteristics of migraine patients.

Methods

Female migraine patients aged between 25 and 50 years (n = 50) and healthy control subjects (n = 34) participated in this study. Blood samples were collected from the cubital veins of subjects (during both the interictal/ictal periods in migraineurs, n = 47/12, respectively). 12 metabolites of Trp pathway were determined by neurochemical measurements (UHPLC-MS/MS).

Results

Plasma concentrations of the most Trp metabolites were remarkably decreased in the interictal period of migraineurs compared to healthy control subjects, especially in the migraine without aura (MWoA) subgroup: Trp (p < 0.025), L-kynurenine (p < 0.001), kynurenic acid (p < 0.016), anthranilic acid (p < 0.007), picolinic acid (p < 0.03), 5-hydroxy-indoleaceticacid (p < 0.025) and melatonin (p < 0.023). Several metabolites showed a tendency to elevate during the ictal phase, but this was significant only in the cases of anthranilic acid, 5-hydroxy-indoleaceticacid and melatonin in MWoA patients. In the same subgroup, higher interictal kynurenic acid levels were identified in patients whose headache was severe and not related to their menstruation cycle. Negative linear correlation was detected between the interictal levels of xanthurenic acid/melatonin and attack frequency. Positive associations were found between the ictal 3-hydroxykynurenine levels and the beginning of attacks, just as between ictal picolinic acid levels and last attack before ictal sampling.

Conclusions

Our results suggest that there is a widespread metabolic imbalance in migraineurs, which manifests in a completely depressed peripheral Trp catabolism during the interictal period. It might act as trigger for the migraine attack, contributing to glutamate excess induced neurotoxicity and generalised hyperexcitability. This data can draw attention to the clinical relevance of KP in migraine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01239-1.

Photophobia in complex regional pain syndrome: visual discomfort is greater on the affected than unaffected side

ABSTRACT

In complex regional pain syndrome (CRPS), hyperalgesia encompasses uninjured sites on the ipsilateral side of the body and may also include the special senses because auditory discomfort often is greater on the CRPS-affected side. To determine whether this hemilateral hyperalgesia involves the visual system, the discomfort threshold to a light-source that increased in intensity at 100 lux/second from 500 to 3600 lux was investigated for each eye, and the nasal and temporal half of each visual field, in 33 patients with CRPS and 21 pain-free controls. Recent headache history was reviewed and, in patients with CRPS, sensitivity to mechanical and thermal stimuli was assessed in all 4 limbs and on each side of the forehead. In addition, the pupils were photographed in dim and bright light. The visual discomfort threshold was lower in patients than controls and was lower on the CRPS-affected than unaffected side (P < 0.001), indicating photophobia. Visual discomfort was unrelated to pupil diameter. Headache frequency was greater in CRPS patients than controls, and unilateral headaches were more likely to be on the CRPS-affected than contralateral side. Similarly, mechanical and thermal hyperalgesia was greater in the CRPS-affected than contralateral limb and was greater ipsilateral than contralateral to CRPS in the forehead and nonsymptomatic limbs. Ipsilateral photophobia was associated with mechanical and thermal hyperalgesia in the ipsilateral forehead but not the CRPS-affected limb. Together, these findings suggest that aberrant processing of nociceptive input in the ipsilateral trigeminal-medullary region of the brainstem contributes to visual discomfort in CRPS.

Use of Nutraceutical Ingredient Combinations in the Management of Tension-Type Headaches with or without Sleep Disorders

Headache is the most common pain complaint in the pediatric population, with tension type headache (TTH) having a prevalence of 10–15% in children. Up to 70% of pediatric patients with chronic headache also experience sleep disruption, with a likely bidirectional relationship between headache and poor sleep. Treatment options include specific pharmacological approaches as well as non-pharmacological alternatives; nutraceuticals have the advantage of a relative lack of side effects. Exogenous melatonin has been shown to be useful and safe in improving sleep-wake cycles and quality of sleep in children, helping to regulate the circadian rhythm, with a secondary positive impact on headache. Supplementation with other nutraceutical ingredients, such as tryptophan, magnesium, and B vitamins, can have significant additional effects in children with primary headache, with or without sleep disorders. Tryptophan may reduce night awakenings and improve the efficiency of sleep. Primary headache has been related to low amounts of magnesium in serum, and integration with magnesium appears to be effective in reducing headache attacks without adverse effects. There are different observational reports and uncontrolled studies suggesting a possible synergistic effect for these nutraceuticals, but there is now a need for high-quality randomized controlled trials in order to confirm these positive preliminary findings.

Social Distancing in Chronic Migraine during the COVID-19 Outbreak: Results from a Multicenter Observational Study

BACKGROUND

The restrictions taken to control the rapid spread of COVID-19 resulted in a sudden, unprecedented change in people's lifestyle, leading to negative consequences on general health. This study aimed to estimate the impact of such changes on migraine severity during 2020 March-May lockdown.

METHODS

Patients affected by migraine with or without aura, diagnosed by expert physicians, completed a detailed interview comprehensive of: assessment of migraine characteristics; measure of physical activity (PA) levels; measure of the intake frequency of main Italian foods; the Insomnia Severity Index (ISI) questionnaire investigating sleep disorders.

RESULTS

We included 261 patients with a mean age of 44.5 ± 12.3 years. During social distancing, 72 patients (28%) reported a headache worsening, 86 (33%) an improvement, and 103 (39%) a stable headache frequency. A significant decrease of the PA levels during COVID-19 quarantine in the whole study sample was observed (median total metabolic equivalent task (METs) decreased from 1170 to 510; p < 0.001). Additionally, a significant difference was reported on median ISI scores (from 7 to 8; p < 0.001), which were increased in patients who presented a stable or worsening headache.

CONCLUSIONS

Our study confirmed that the restrictions taken during the pandemic have affected the practice of PA levels and sleep quality in migraine. Hence, PA and sleep quality should be assessed to find strategies for an improvement in quality of life.

Exploring the Hereditary Nature of Migraine

Migraine is a common neurological disorder which affects 15-20% of the population; it has a high socioeconomic impact through treatment and loss of productivity. Current forms of diagnosis are primarily clinical and can be difficult owing to comorbidity and symptom overlap with other neurological disorders. As such, there is a need for better diagnostic tools in the form of genetic testing. Migraine is a complex disorder, encompassing various subtypes, and has a large genetic component. Genetic studies conducted on rare monogenic subtypes, including familial hemiplegic migraine, have led to insights into its pathogenesis via identification of causal mutations in three genes (CACNA1A, ATP1A2 and SCN1A) that are involved in transport of ions at synapses and glutamatergic transmission. Study of familial migraine with aura pedigrees has also revealed other causal genes for monogenic forms of migraine. With respect to the more common polygenic form of migraine, large genome-wide association studies have increased our understanding of the genes, pathways and mechanisms involved in susceptibility, which are largely involved in neuronal and vascular functions. Given the preponderance of female migraineurs (3:1), there is evidence to suggest that hormonal or X-linked components can also contribute to migraine, and the role of genetic variants in mitochondrial DNA in migraine has been another avenue of exploration. Epigenetic studies of migraine have shown links between hormonal variation and alterations in DNA methylation and gene expression. While there is an abundance of preliminary studies identifying many potentially causative migraine genes and pathways, more comprehensive genomic and functional analysis to better understand mechanisms may aid in better diagnostic and treatment outcomes.

Effect of probiotic supplementation on migraine prophylaxis: a systematic review and meta-analysis of randomized controlled trials

Objective: The prevalence of migraine is higher in patients with gastrointestinal disorders. Possible underlying mechanisms could be increased intestinal permeability and systemic inflammation. Probiotics may reduce gut permeability as well as inflammation, and therefore may improve the clinical features of migraine. This systematic review and meta-analysis aimed to evaluate the impact of probiotic supplementation on the frequency and severity of migraine attacks.Methods: A systematic review of the literature was conducted using ISI Web of Science, PubMed/Medline, Scopus, Cochrane Library, EMBASE, Google Scholar, Magiran.com and Sid.ir to identify eligible studies published up to October 2019. A meta-analysis of eligible trials was performed using the random-effects model to estimate pooled effect size.Results: Three randomized controlled trials with 179 patients (probiotic group = 94, placebo group = 85) were included. Probiotic supplementation had no significant effect on frequency (weighted mean difference (WMD) = -2.54 attacks/month, 95%CI: -5.31-0.22, p = 0.071) and severity of migraine attacks (WMD = -1.23 visual analog scale (VAS) score, 95%CI = -3.37-0.92, p = 0.262) with significant heterogeneity among the studies (I² = 98%, p < 0.001).Conclusions: A pooled analysis of available randomized controlled clinical trials showed that probiotic supplementation had no significant effect on the frequency and severity of episodic migraine attacks.

Development, validation and application of LC-MS/MS method for quantification of amino acids, kynurenine and serotonin in human plasma

Altered serotonergic neurotransmission is a key factor in several neurologic and psychiatric disorders such as migraine. Human and animal studies suggest that chronically low interictal serotonin levels of plasma and brain may facilitate increased activity of the trigeminovascular pathway, and may contribute to development of repeated migraine attacks. However, brain serotonin synthesis is affected by the concentration of tryptophan, its metabolites and a number of amino acids. In this work a simple and robust LC-MS/MS method for the quantitative determination of valine, leucine, isoleucine, phenylalanine, tyrosine, tryptophan, serotonin and kynurenine in human plasma has been developed and validated. Sample preparation was achieved by protein precipitation, using trifluoroacetic acid. Chromatographic separation was carried out on a Supelco Ascentis® Express C18 column (3.0 mm i.d. × 150 mm, 2.7 μm) equipped with an Agilent Zorbax Eclipse XDB C8 guard-column under isocratic conditions at a flow rate of 0.4 mL/min, over a 6.5 min run time. Mobile phase was 0.2% trifluoroacetic acid - acetonitrile (85:15, v/v). The eight analytes and two internal standards were ionized by positive electrospray ionization and detected in multiple reaction monitoring mode. A "fit-for-purpose" validation approach was adopted using surrogate matrix for the preparation of calibration samples. The calibration curves of all analytes showed excellent linearities with a correlation coefficient (r²) of 0.998 or better. Spiked surrogate matrix samples and pooled human plasma were used as quality control samples. Intra-day and inter-day precisions were less than 11.8% and 14.3%, and accuracies were within the ranges of 87.4-114.3% and 87.7-113.3%, respectively. Stability of the components in standard solutions, surrogate matrix, pooled plasma and processed samples were found to be acceptable under all relevant conditions. No significant carryover effect was observed. The surrogate matrix behaved parallel to human plasma when assessed by standard addition method and diluting the authentic matrix with surrogate matrix. The method was successfully applied for analysis of 800 human plasma samples to support a clinical study.

Correlation of 5-HTR6 gene polymorphism with vestibular migraine

Objective

To investigate the correlation of 5‐hydroxy tryptamine receptor 6 (5‐HTR6) gene polymorphism with vestibular migraine (VM).

Methods

A total of 92 VM patients were enrolled as the observation group, and 100 healthy people receiving physical examinations as the control group. Their general clinical information was collected, and the level of 5‐HT in plasma and the vestibular function test indexes were detected. Moreover, the polymorphism of 5‐HTR6 rs770963777 was detected with the TaqMan‐MGB probe.

Results

The observation group had a lower level of 5‐HT than the control group (P < .05), and the abnormality rates of the vestibular function tests, including the caloric test, head‐shaking test, and vestibular autorotation test, were obviously higher than those in the control group (P < .01). The comparisons showed that the distribution frequencies of the genotypes and alleles were different between the two groups (P < .05). According to the analysis of the genetic mode, there were differences in recessive and additive modes between the two groups (P < .05), but the dominant mode was not different between the two groups (P > .05).

Conclusion

The level of 5‐HT and the vestibular function test indexes can serve as the effective indicators for observing VM, and the polymorphism of 5‐HTR6 rs770963777 site is correlated with VM onset.

Probiotics for the Prophylaxis of Migraine: A Systematic Review of Randomized Placebo Controlled Trials

Migraine is a common and disabling neurological condition with a complex etiology. Recent advances in the understanding of the gut microbiome have shown the role of gut micro-organisms in disease outcomes for distant organs—including the brain. Interventions targeting the gut microbiome have been shown to be effective in multiple neurological diagnoses, but there is little research into the role of the microbiome in migraine. This systematic review seeks to assess the current research landscape of randomized placebo controlled trials utilizing probiotic interventions as migraine prophylaxis. Searches were conducted of scientific databases including PubMed, MEDLINE, and the Cochrane Library, following PRISMA guidelines. Of 68 screened studies, 2 were eligible for analysis. Due to methodological differences, meta-analysis was not possible. Qualitative comparison of the studies demonstrated a dichotomy of results—one trial reported no significant change in migraine frequency and intensity, while the second trial reported highly significant improvements. No clear ‘gold standard’ currently exists for microbiome research, let alone for migraine-related microbiome research. The heterogeneity of outcome measures used in the two trials included in this systematic review shows the need for a standardization of outcome measures, therefore a series of recommendations for future probiotic–migraine research are included.

The association between dietary tryptophan intake and migraine

Migraineurs have been identified to have chronically decreased serotonin levels while its concentrations markedly increase during ictal periods. Regarding the importance of adequate tryptophan intake in regulating serotonin homeostasis and subsequent effect on migraine attacks, we designed the current study. The migraine group (n = 514, diagnosed according to the ICHDIII criteria) was recruited from a tertiary headache clinic. The controls consisted of 582 sex-matched healthy volunteers who were randomly selected from general population. After collecting demographic and anthropometric data, a validated 168-item semi-quantitative food frequency questionnaire (FFQ) was used for dietary intake assessments. Multiple regression models were applied to explore the relationship between migraine and tryptophan intake. The mean (SD) of the age of participants in the controls and migraine group was 44.85 (13.84) and 36.20 (9.78) years, respectively. The multiple regression models were adjusted for age (year), sex, body mass index (BMI) (kg/m²), total daily energy intake (kcal/day), dietary intakes of total carbohydrates (g/day), animal-based protein (g/day), plant-based protein (g/day), total fat (g/day), saturated fat (g/day), and cholesterol (mg/day). It was shown that there is a negative association between tryptophan intake and migraine risk ((OR in the 3rd quartile = 0.46; 95% CI = 0.25-0.85) (OR in the 4th quartile = 0.40; 95% CI = 0.16-0.98) compared with the first quartile; P for trend = 0.045). Therefore, our results showed that subjects who had a median intake of 0.84-1.06 g of tryptophan per day had reduced odds of developing migraine by approximately 54-60%, relative to those consumed ≤ 0.56 g/day.

A comprehensive appraisal on Crocus chrysanthus (Herb.) Herb. flower extracts with HPLC-MS/MS profiles, antioxidant and enzyme inhibitory properties

In the quest for new drugs of herbal origin, the ethyl acetate (EAE), methanol (ME), and water (WE) extracts of Crocus chrysanthus (Herb.) Herb. flowers were analyzed for their polyphenolic composition, antioxidant, and enzyme inhibitory potential. WE showed the highest antioxidant activities in all assays including metal chelating, phosphomolybdenum, FRAP, CUPRAC, ABTS and DPPH. EAE was the most effective enzyme inhibitor, exhibiting the highest inhibition against some enzymes linked to Alzheimer's disease (cholinesterases), diabetes mellitus (α-glucosidase and α-amylase) and hyperpigmentation problems (tyrosinase). The highest total phenolics (34.99 mg GAE/g) and flavonoids content (77.58 mg RE/g) were observed in WE and ME, respectively. Eight compounds were identified in EAE, 24 in ME, and 15 in WE. Kaempferol 3-O glucoside was found in all extracts. In conclusion, C. chrysanthus flowers can be suggested as a source of bioactive components with potential use against chronic disorders caused by oxidative stress. Future in-depth studies are recommended to determine the biological effects of isolated compounds from C. chrysanthus to identify the main compounds modulating the observed activities.

Sleep Disorders and Migraine: Review of Literature and Potential Pathophysiology Mechanisms

Migraine shares a complex and poorly understood relationship with sleep. Patients consistently report poor sleep prior to migraine attacks and during them, identifying poor sleep as a migraine trigger. However, anecdotally, sleep is reported to serve a therapeutic role in terminating headache. Are the associations between migraine and sleep simply the result of various bidirectional relationships? A growing body of evidence suggests there may be a common underlying etiology as well. Our objective was to review studies of sleep and migraine from the last 2 decades utilizing validated subjective and objective measures of sleep and to explore potential mechanisms underlying this complex relationship by incorporating recent advances in neuroscience. We specifically focus on insomnia, obstructive sleep apnea, parasomnias, sleep related movement disorders, and REM sleep related disorders and their relationship to migraine. Parts of brainstem-cortical networks involved in sleep physiology are unintentionally being identified as important factors in the common migraine pathway. Recent discoveries on anatomic localization (the hypothalamus as a key and early mediator in the pathophysiology of migraine), common mediating signaling molecules (such as serotonin and dopamine), and the discovery of a new CNS waste removal system, the glymphatic system, all point to a common pathophysiology manifesting in migraine and sleep problems.

Genetic and biochemical changes of the serotonergic system in migraine pathobiology

Migraine is a brain disorder characterized by a piercing headache which affects one side of the head, located mainly at the temples and in the area around the eye. Migraine imparts substantial suffering to the family in addition to the sufferer, particularly as it affects three times more women than men and is most prevalent between the ages of 25 and 45, the years of child rearing. Migraine typically occurs in individuals with a genetic predisposition and is aggravated by specific environmental triggers. Attempts to study the biochemistry of migraine began as early as the 1960s and were primarily directed at serotonin metabolism after an increase of 5-hydroxyindoleacetic acid (5-HIAA), the main metabolite of serotonin was observed in urine of migraineurs. Genetic and biochemical studies have primarily focused on the neurotransmitter serotonin, considering receptor binding, transport and synthesis of serotonin and have investigated serotonergic mediators including enzymes, receptors as well as intermediary metabolites. These studies have been mainly assayed in blood, CSF and urine as the most accessible fluids. More recently PET imaging technology integrated with a metabolomics and a systems biology platform are being applied to study serotonergic biology. The general trend observed is that migraine patients have alterations of neurotransmitter metabolism detected in biological fluids with different biochemistry from controls, however the interpretation of the biological significance of these peripheral changes is unresolved. In this review we present the biology of the serotonergic system and metabolic routes for serotonin and discuss results of biochemical studies with regard to alterations in serotonin in brain, cerebrospinal fluid, saliva, platelets, plasma and urine of migraine patients.

Serotonin and Migraine: Biology and Clinical Implications

Migraine is the most frequent neurological disorder in the adult population worldwide, affecting up to 12% of the general population and more frequent in women (~25%). It has a high impact on our society due to its disabling nature and, therein, reduced quality of life and increased absenteeism from work. Headache is the primary clinical manifestation and it has been associated with ‘a hereditary or predisposed sensitivity of neurovascular reactions to certain stimuli or to cyclic changes in the central nervous system’ (1). Amongst the many neurotransmitters in the brain, the serotonergic (serotonin, 5-HT) system from the brainstem raphe nucleus has been most convincingly implicated in migraine pathophysiology. The documented changes in 5-HT metabolism and in the processing of central 5-HT-mediated responses during and in between migraine attacks have led to the suggestion that migraine is a consequence of a central neurochemical imbalance that involves a low serotonergic disposition. Although the exact cascade of events that link abnormal serotonergic neurotransmission to the manifestation of head pain and the accompanying symptoms has yet to be fully understood, recent evidence suggests that a low 5-HT state facilitates activation of the trigeminovascular nociceptive pathway, as induced by cortical spreading depression. In this short review, we present and discuss the original and most recent findings that support a role for altered serotonergic neurotransmission in the manifestation of migraine headache.

Fathoming the kynurenine pathway in migraine: why understanding the enzymatic cascades is still critically important

Kynurenine pathway, the quantitatively main branch of tryptophan metabolism, has been long been considered a source of nicotinamide adenine dinucleotide, although several of its products, the so-called kynurenines, are endowed with the capacity to activate glutamate receptors, thus potentially influencing a large group of functions in the central nervous system (CNS). Migraine, a largely unknown pathology, is strictly related to the glutamate system in the CNS pathologic terms. Despite the large number of studies conducted on migraine etio-pathology, the kynurenine pathway has been only recently linked to this disease. Nonetheless, some evidence suggests an intriguing role for some kynurenines, and an exploratory study on the serum kynurenine level might be helpful to better understand possible alterations of the kynurenine pathway in patients suffering from migraine.

A Medical Food Formulation of Griffonia simplicifolia/Magnesium for Childhood Periodic Syndrome Therapy: An Open-Label Study on Motion Sickness

Motion sickness (MS) is a disabling condition dominated by disagreement between visually perceived movement and the vestibular system's sense of movement, with symptoms like dizziness, fatigue, and nausea, and other autonomic disabling symptoms. Preparations of Griffonia simplicifolia, containing high concentrations of 5-HTP, might be effective for serotonin-related disorders, including MS. Therefore, the aim of the present study is to assess the efficacy and safety of the G. simplicifolia/magnesium complex in a pediatric population with MS. The Griffonia/magnesium complex (50 and 200 mg, respectively) was orally administered as a prophylactic therapy for MS twice a day for 3 months to group A, and no therapy for MS was administered to group B. The MS clinical signs were recorded by parents or, where possible, directly from children by a specific module, which included validated questions for the diagnoses that were administered to all subjects and parents of both groups. Two study groups were matched for age (P=.224), sex (P=.801), and z-score body-mass index (P=.173). At T0, all recruited subjects in both groups complained about MS. After 3 months (T1), group A showed an MS prevalence of 36%, significantly lower than MS prevalence in group B (73%) (P<.001). The findings of the present study suggest the role of the Griffonia/magnesium complex as a potential treatment with middle-term efficacy even for MS.

The effects of 5-hydroxytryptophan in combination with different Fatty acids on gastrointestinal functions: a pilot experiment

Background. Fat affects gastric emptying (GE). 5-Hydroxythryptophan (5-HTP) is involved in central and peripheral satiety mechanisms. Influence of 5-HTP in addition to saturated or monounsaturated fatty acids (FA) on GE and hormone release was investigated. Subjects/Methods. 24 healthy individuals (12f : 12m, 22–29 years, BMI 19–25.7 kg/m²) were tested on 4 days with either 5-HTP + short-chain saturated FA (butter), placebo + butter, 5-HTP + monounsaturated FA (olive oil), or placebo + olive oil in double-blinded randomized order. Two hours after FA/5-HTP or placebo intake, a ¹³C octanoid acid test was conducted. Cortisol, serotonin, cholecystokinin (CCK), and ghrelin were measured, as were mood and GE. Results. GE was delayed with butter and was normal with olive (P < 0.05) but not affected by 5-HTP. 5-HTP supplementation did not affect serotonin levels. Food intake increased plasma CCK (F = 6.136; P < 0.05) irrespective of the FA. Ghrelin levels significantly decreased with oil/5-HTP (F = 9.166; P < 0.001). The diurnal cortisol profile was unaffected by FA or 5-HTP, as were ratings of mood, hunger, and stool urgency. Conclusion. Diverse FAs have different effects on GE and secretion of orexigenic and anorexigenic hormones. Supplementation of 5-HTP had no effect on plasma serotonin and central functions. Further studies are needed to explain the complex interplay.

The relationship between sleep and headache in children: implications for treatment

BACKGROUND

The existence of a correlation and/or comorbidity between sleep disorders and headache, related to common anatomical structures and neurochemical processes, has important implications for the treatment of both conditions.

METHODS

The high prevalence of certain sleep disorders in children with migraine and the fact that sleep is disrupted in these patients highlight the importance of a specific therapy targeted to improve both conditions.

FINDINGS

The treatment of sleep disorders like insomnia, sleep apnea, sleep bruxism and restless legs syndrome, either with behavioral or pharmacological approach, often leads to an improvement of migraine. Drugs like serotoninergic and dopaminergic compounds are commonly used for sleep disorders and for migraine prophylaxis and treatment: Insomnia, sleep-wake transition disorders and migraine have been related to the serotonergic system abnormality; on the other hand prodromal symptoms of migraine (yawning, drowsiness, irritability, mood changes, hyperactivity) support a direct role for the dopaminergic system that is also involved in sleep-related movement disorders.

CONCLUSIONS

Our review of the literature revealed that, beside pharmacological treatment, child education and lifestyle modification including sleep hygiene could play a significant role in overall success of the treatment. Therefore comorbid sleep conditions should be always screened in children with migraine in order to improve patient management and to choose the most appropriate treatment.

Serotonin depletion can enhance the cerebrovascular responses induced by cortical spreading depression via the nitric oxide pathway

Serotonin (5-HT) is an important neurotransmitter involved in the control of neural and vascular responses. 5-HT depletion can induce several neurological disorders, including migraines. Studies on a cortical spreading depression (CSD) migraine animal model showed that the cortical neurons sensitivity, vascular responses, and nitric oxide (NO) production were significantly increased in 5-HT depletion. However, the involvement of NO in the cerebrovascular responses in 5-HT depletion remains unclear. This study aimed to investigate the role of NO in the CSD-induced alterations of cerebral microvessels in 5-HT depletion. Rats were divided into four groups: control, control with L-NAME treatment, 5-HT depleted, and 5-HT depleted with L-NAME treatment. 5-HT depletion was induced by intraperitoneal injection with para-chlorophenylalanine (PCPA) 3 days before the experiment. The CSD was triggered by KCl application. After the second wave of CSD, N-nitro-l-arginine methyl ester (L-NAME) or saline was intravenously injected into the rats with or without L-NAME treatment groups, respectively. The intercellular adhesion molecules-1 (ICAM-1), cell adhesion molecules-1 (VCAM-1), and the ultrastructural changes of the cerebral microvessels were examined. The results showed that 5-HT depletion significantly increased ICAM-1 and VCAM-1 expressions in the cerebral cortex. The number of endothelial pinocytic vesicles and microvilli was higher in the 5-HT depleted group when compared to the control. Interestingly, L-NAME treatment significantly reduced the abnormalities observed in the 5-HT depleted group. The results of this study demonstrated that an increase of NO production is one of the mechanisms involved in the CSD-induced alterations of the cerebrovascular responses in 5-HT depletion.

Biological phenotypes underpin the physio-somatic symptoms of somatization, depression, and chronic fatigue syndrome

OBJECTIVE

Somatization is a symptom cluster characterized by 'psychosomatic' symptoms, that is, medically unexplained symptoms, and is a common component of other conditions, including depression and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This article reviews the data regarding the pathophysiological foundations of 'psychosomatic' symptoms and the implications that this has for conceptualization of what may more appropriately be termed physio-somatic symptoms.

METHOD

This narrative review used papers published in PubMed, Scopus, and Google Scholar electronic databases using the keywords: depression and chronic fatigue, depression and somatization, somatization and chronic fatigue syndrome, each combined with inflammation, inflammatory, tryptophan, and cell-mediated immune (CMI).

RESULTS

The physio-somatic symptoms of depression, ME/CFS, and somatization are associated with specific biomarkers of inflammation and CMI activation, which are correlated with, and causally linked to, changes in the tryptophan catabolite (TRYCAT) pathway. Oxidative and nitrosative stress induces damage that increases neoepitopes and autoimmunity that contribute to the immuno-inflammatory processes. These pathways are all known to cause physio-somatic symptoms, including fatigue, malaise, autonomic symptoms, hyperalgesia, intestinal hypermotility, peripheral neuropathy, etc.

CONCLUSION

Biological underpinnings, such as immune-inflammatory pathways, may explain, at least in part, the occurrence of physio-somatic symptoms in depression, somatization, or myalgic encephalomyelitis/chronic fatigue syndrome and thus the clinical overlap among these disorders.

In myalgic encephalomyelitis/chronic fatigue syndrome, increased autoimmune activity against 5-HT is associated with immuno-inflammatory pathways and bacterial translocation

BACKGROUND

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is accompanied by activation of immuno-inflammatory pathways, increased bacterial translocation and autoimmune responses to serotonin (5-HT). Inflammation is known to damage 5-HT neurons while bacterial translocation may drive autoimmune responses. This study has been carried out to examine the autoimmune responses to 5-HT in ME/CFS in relation to inflammation and bacterial translocation.

METHODS

We examined 5-HT antibodies in 117 patients with ME/CFS (diagnosed according to the centers for disease control and prevention criteria, CDC) as compared with 43 patients suffering from chronic fatigue (CF) but not fulfilling the CDC criteria and 35 normal controls. Plasma interleukin-1 (IL-1), tumor necrosis factor (TNF)α, neopterin and the IgA responses to Gram-negative bacteria were measured. Severity of physio-somatic symptoms was measured using the fibromyalgia and chronic fatigue syndrome rating scale (FF scale).

RESULTS

The incidence of positive autoimmune activity against 5-HT was significantly higher (p<0.001) in ME/CFS (61.5%) than in patients with CF (13.9%) and controls (5.7%). ME/CFS patients with 5-HT autoimmune activity displayed higher TNFα, IL-1 and neopterin and increased IgA responses against LPS of commensal bacteria than those without 5-HT autoimmune activity. Anti-5-HT antibody positivity was significantly associated with increased scores on hyperalgesia, fatigue, neurocognitive and autonomic symptoms, sadness and a flu-like malaise.

DISCUSSION

The results show that, in ME/CFS, increased 5-HT autoimmune activity is associated with activation of immuno-inflammatory pathways and increased bacterial translocation, factors which are known to play a role in the onset of autoimmune reactions. 5-HT autoimmune activity could play a role in the pathophysiology of ME/CFS and the onset of physio-somatic symptoms. These results provide mechanistic support for the notion that ME/CFS is a neuro-immune disorder.

Diagnostic classifications in depression and somatization should include biomarkers, such as disorders in the tryptophan catabolite (TRYCAT) pathway

The tryptophan catabolite (TRYCAT) pathway is induced by indoleamine 2,3-dioxygenase (IDO), which upon activation depletes plasma tryptophan (TRP) and increases the synthesis of TRYCATs. Both phenomena are associated with somatization and depression. The aims of this study are to examine whether disorders in the TRYCAT pathway are specific to depression or somatization and whether the diagnoses somatization, depression, and comorbid depression+somatization reflect qualitatively distinct clinical and biological categories. Plasma TRP, the kynurenine (KY)/TRP and KY/kynurenic acid (KA) ratios were measured in 36 patients with somatization, 35 depressed and 38 depressed+somatization patients and 22 controls. Using pattern recognition methods, the diagnosis comorbid depression+somatization could not be validated, while there was an important overlap between depression and somatization, which form one continuum. Cluster analysis detected a) a control cluster; b) a cluster with lower tryptophan, and higher KY/TRP and KY/KA ratios and somatization scores; and c) a cluster with increased depression but lower KY/TRP values. The differences between both patient clusters were quantitative and not qualitative. Within the patient group, cluster analysis has generated a "pathway phenotype", i.e. aberrations in the TRYCAT pathway, which are associated with somatization rather than with depression.

Pathophysiology of medication-overuse headache: implications from animal studies

Recent animal experiments have shown that chronic medication exposure profoundly affects the function of several areas in the nervous system related to headache pathogenesis. These changes include upregulation of calcitonin gene-related peptide, substance P, and nitric oxide synthase in trigeminal ganglia; expansion of receptive field and decreased nociceptive threshold of central trigeminal neurons; decrease in diffuse noxious inhibitory control; and increased susceptibility to develop cortical spreading depression (CSD). These changes indicate an increase in excitability of cortical and trigeminal neurons. The neuronal hyperexcitability may be the result of derangement of a central, possibly serotonin (5-HT)-dependent, modulating control system. Experiments with animals with low 5-HT showed that the processes of CSD and trigeminal nociception are enhanced in this condition. Derangement in the central 5-HT-dependent modulating system as a result of chronic medication use may underlie the chronification of headache as observed in patients with medication-overuse headache.

Brainstem changes in 5-HT1A receptor availability during migraine attack

BACKGROUND

Among serotonin receptors, 5-HT(1A) receptors are implicated in the regulation of central serotoninergic tone and could be involved in the abnormal brain 5-HT turnover suspected in migraineurs. The aim of this study was to investigate 5-HT(1A) receptors' availability during migraine attacks.

METHODS

Ten patients suffering from odor-triggered migraine attacks and 10 control subjects were investigated using positron emission tomography (PET) and [(18)F]MPPF PET tracer, a selective 5-HT(1A) antagonist. All subjects underwent calibrated olfactory stimulations prior to the PET study.

RESULTS

Four patients developed a migraine attack during the PET study. In these patients, statistical parametrical mapping and region of interest analyses showed an increased [(18)F]MPPF binding potential (BP(ND)) in the pontine raphe when compared to headache-free migraineurs and control subjects. This ictal change was confirmed at the individual level in each of the four affected patients. In comparison with the headache-free migraineurs, patients with a migraine attack also showed significantly increased [(18)F]MPPF BP(ND) in the left orbitofrontal cortex, precentral gyrus and temporal pole. No significant change in [(18)F]MPPF BP(ND) was observed between headache-free migraineurs and controls.

CONCLUSIONS

Our results emphasize the role of 5HT(1A) receptors in the pontine raphe nuclei during the early stage of migraine attacks.

Acute tryptophan depletion increases experimental nausea but also induces hunger in healthy female subjects

BACKGROUND

Acute tryptophan depletion (ATD) is an experimental model to reduce central serotonin levels.

METHODS

Thirty-eight healthy female subjects were randomly assigned to two groups (ATD and control) in a randomized, double-blinded parallel-group design. Following a standardized and balanced amino acid diet (including 1.21 g tryptophan) on the first day, they received either a protein drink without tryptophan (but substituted by other amino acids) (ATD condition) or the balanced protein drink with tryptophan (control condition) 24 h later. Four hours after its consumption, they were exposed to a standard rotation procedure. Symptom ratings (SR), ratings of hunger and mood scores were taken prior to rotation, at each break, and 15 and 30 min thereafter, together with saliva cortisol samples.

KEY RESULTS

Five subjects could not tolerate the entire rotation procedure and were excluded from analysis. For the remaining n = 33, SR and hunger ratings were higher during ATD than during control conditions, but mood was unaffected. Cortisol levels rose significantly with rotation but were unaffected by ATD. High baseline cortisol levels were associated with lower SR during rotation. The protective effects of morning cortisol were pronounced during the menstrual and follicular phase of the cycle and not present during ovulation and the luteal phase.

CONCLUSIONS & INFERENCES

Acute tryptophan depletion is associated with increased symptoms of nausea in healthy female subjects when exposed to body rotation. Acute tryptophan depletion also increases hunger rating. These opposite effects may indicate independent actions of the serotonin on central and peripheral functions.

Functional gene variants of the serotonin-synthesizing enzyme tryptophan hydroxylase 2 in migraine

Serotonin (5-HT) plays an important role in the pathophysiology of migraine. Tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme in the biosynthesis of 5-HT in the brain and is therefore a major factor in the availability of 5-HT and its rate of production. We hypothesized that functional TPH2 gene variants are associated with migraine. In a case-control study approach, two proven functional and two putatively functional variants of the TPH2 gene were investigated in 266 migraine patients and 153 controls. Genotype, allele, and haplotype frequencies did not differ between healthy subjects and migraineurs. A subgroup analysis for the occurrence of aura or clinical characteristics, including the number of attacks, did not reveal a positive association for the investigated polymorphisms. Our data argue against a major influence of the TPH2 gene promoter region in migraine.

Serotonin depletion increases nociception-evoked trigeminal NMDA receptor phosphorylation

OBJECTIVE

To investigate the effect of serotonin depletion on phosphorylation and expression of NR1 subunit of N-methyl-D-aspartate (NMDA) receptor in trigeminal nucleus caudalis (TNC), and on trigeminal nociception evoked by dural inflammation.

BACKGROUND

Migraine is associated with low serotonin condition and an increased neuronal excitability. NMDA receptor is implicated in central plasticity change that leads to neural sensitization. Alteration in NMDA receptor phosphorylation or expression in TNC may be responsible for increased trigeminal nociception in serotonin-depleted state.

METHODS

Adult male Wistar rats were separated into normal and low serotonin groups. Serotonin was depleted by intraperitoneal injection with para-chlorophenylalanine 3 days before the experiment. Trigeminal nociception was induced by applying inflammatory soup on exposed dura. Two hours after induction, phosphorylated NR1, NR1, and Fos expressions were studied in TNC by immunohistochemistry.

RESULTS

Dural application of inflammatory soup led to the activation of trigeminal nociceptive system as well as the phosphorylation of NR1, which were further enhanced in the low serotonin condition. There was a strong relationship between NR1 phosphorylation and trigeminal nociception. However, neither meningeal inflammation nor serotonin depletion altered NR1 expression.

CONCLUSIONS

Low serotonin condition facilitates dural inflammation-induced NR1 phosphorylation and trigeminal nociception. It is suggested that the mechanism of nociceptive facilitation in serotonin-depleted state may involve the increase in NR1 phosphorylation rather than the upregulation of NR1 subunit of NMDA receptor.