Serum neopterin and somatization in women with chemical intolerance, depressives, and normals

Blood concentrations of neopterin and biopterin in subjects with depression: A systematic review and meta-analysis

INTRODUCTION

Pteridines, such as neopterin, biopterin, and tetrahydrobiopterin (BH₄), may be involved in depression pathophysiology owing to their links to immune-inflammatory response, oxidative and nitrosative stress, and monoaminergic transmission. Nonetheless, studies assessing pteridines in depression are inconsistent. We conducted a systematic review and meta-analysis of observational studies comparing blood pteridine concentrations between subjects with depression and healthy controls (HCs).

METHODS

We searched Embase, MEDLINE, and PsycInfo for articles indexed through November 2021. Study quality was appraised, evaluating age and gender comparability between groups, sample representativeness, and methods to assess depression. Random-effects meta-analyses were carried out, generating pooled standardized mean differences (SMDs). Heterogeneity across studies was estimated using the I² statistic.

RESULTS

Twenty-four studies, involving 3075 subjects, were included. Individuals with depression showed blood neopterin concentrations higher than HCs (k = 19; SMD = 0.36; p < 0.001) with moderate heterogeneity across studies (I² = 58.2%). No moderating role of age, gender, or type of blood sample was found. Sensitivity analyses showed no impact of inconsistency and quality of studies on findings. Neopterin concentrations were higher among individuals with major depressive disorder compared to HCs (SMD = 0.44; p < 0.001). This held true also when considering only drug-free subjects (SMD = 0.68; p = 0.003). No differences in biopterin concentrations were found between subjects with depression and HCs (k = 5; SMD = -0.35; p = 0.086), though this result was limited by inconsistency of findings (I² = 77.9%) and quality of studies. Finally, no sufficient data were available for a meta-analysis on BH₄.

CONCLUSIONS

As a whole, our work partly supports the hypothesis of an imbalance of pteridine metabolism in depression.

Multiple Chemical Sensitivity: Review of the State of the Art in Epidemiology, Diagnosis, and Future Perspectives

OBJECTIVE

Systematic bibliography analysis of about the last 17 years on multiple chemical sensitivity (MCS) was carried out in order to detect new diagnostic and epidemiological evidence. The MCS is a complex syndrome that manifests as a result of exposure to a low level of various common contaminants. The etiology, diagnosis, and treatment are still debated among researchers.

METHOD

Querying PubMed, Web of Science, Scopus, Cochrane library, both using some specific MESH terms combined with MESH subheadings and through free search, even by Google.

RESULTS

The studies were analyzed by verifying 1) the typology of study design; 2) criteria for case definition; 3) presence of attendances in the emergency departments and hospital admissions, and 4) analysis of the risk factors.

OUTLOOK

With this review, we give some general considerations and hypothesis for possible future research.

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.

Neurasthenia, subjective health complaints and sensitization

Patients (n=997) visiting general practitioners in an area in Western Norway completed a battery of questionnaires related to subjective health complaints and fatigue. An additional 78 patients were referred directly to the hospital for neurasthenia. After screening the questionnaires and interviews with a selected sample, a total of 73 patients were finally accepted as 'neurasthenia' patients satisfying the ICD-10 diagnosis. These patients were compared with the remaining 1002 patients. Patients with neurasthenia had more prevalent and more severe subjective health complaints, particularly pseudoneurological and musculoskeletal complaints than the reference population of patients. They reported low levels of instrumental coping and poorer physical fitness, in spite of a comparable level of self reported physical activity and exercise. Women were over-represented in this group. This overall higher score on subjective complaints from all organ systems is in accordance with the hypothesis of an overall and general sensitization to the afferent inputs from their psychophysiological systems.

Associations between chemical odor intolerance and sleep disturbances in community-living adults

OBJECTIVE

To investigate associations between sleep disturbances and chemical odor intolerance (COI), which is the subjective report of feeling ill from common odors, such as carpet glue or pesticides.

METHODS

This cross-sectional study consisted of government employees and their family members (n=140; 61% women, mean age=46.3 years) derived from a stratified cluster population living in Pima County, Tucson, AZ. Subjects completed a standard survey that included sleep symptoms, a validated measure of COI, and two questions regarding anxiety and depression. Odds ratios (OR) with 95% confidence intervals (CI) were computed to test the association between COI and sleep symptoms. Stratification according to the Mantel-Haenszel method and logistic regression models were used to test for confounding and/or effect modification.

RESULTS

After adjusting for age and gender, subjects with COI were significantly more likely to report difficulty staying asleep (OR=3.06; CI=1.17-8.03), insufficient sleep (OR=3.93; CI=1.43-10.79), and nightmares (OR=3.17; CI=1.14-8.81) compared to persons without COI. Associations between COI, sleep maintenance problems and insufficient sleep were still significant after adjusting for gender and depression; however, the association between COI and nightmares became borderline.

CONCLUSIONS

Compared to the non-COI, persons with COI are more likely to report sleep maintenance insomnia and insufficient sleep independent of self-reported depression. Nightmares appear to be related more to depression than to COI.

Cytokine-induced sickness behavior: mechanisms and implications

Sickness behavior refers to a coordinated set of behavioral changes that develop in sick individuals during the course of an infection. At the molecular level, these changes are due to the brain effects of proinflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha). Peripherally released cytokines act on the brain via a fast transmission pathway involving primary afferent nerves innervating the bodily site of inflammation and a slow transmission pathway involving cytokines originating from the choroid plexus and circumventricular organs and diffusing into the brain parenchyma by volume transmission. At the behavioral level, sickness behavior appears to be the expression of a central motivational state that reorganizes the organism priorities to cope with infectious pathogens. There is evidence that the sickness motivational state can interact with other motivational states and respond to nonimmune stimuli probably by way of sensitization and/or classical conditioning. However, the mechanisms that are involved in plasticity of the sickness motivational state are not yet understood.

Elevated nitric oxide/peroxynitrite mechanism for the common etiology of multiple chemical sensitivity, chronic fatigue syndrome, and posttraumatic stress disorder

Various types of evidence implicate nitric oxide and an oxidant, possibly peroxynitrite, in MCS and chemical intolerance (CI). The positive feedback loops proposed earlier for CFS may explain the chronic nature of MCS (CI) as well as several of its other reported properties. These observations raise the possibility that this proposed elevated nitric oxide/peroxynitrite mechanism may be the mechanism of a new disease paradigm, answering the question raised by Miller earlier: "Are we on the threshold of a new theory of disease?"

Multiple chemical sensitivity: a review of the theoretical and research literature

Multiple chemical sensitivity (MCS) is a term used to describe a disorder characterized by a vast array of somatic, cognitive, and affective symptoms, the cause of which is attributed to exposure to extremely low levels of a variety of chemicals. Upon examination of the patient with a diagnosis of MCS, objective physical findings and consistent laboratory abnormalities are typically nonexistent. The concept of MCS has ignited considerable controversy in the fields of toxicology, immunology, allergy, psychology, and neuropsychology. Central to the controversy is the disagreement over the extent to which the manifestation of MCS is mediated by psychological factors. Because of the large number of neuropsychological symptoms associated with a diagnosis of MCS, neuropsychologists are increasingly receiving referrats for the assessment of these patients. It is important, therefore, that neuropsychologists become aware of the variety of clinical issues that must be taken into account when assessing an individual with a diagnosis of MCS. The theoretical and research literature on individuals with a diagnosis of MCS is reviewed here.

Neural sensitization model for multiple chemical sensitivity: overview of theory and empirical evidence

This paper summarizes theory and evidence for a neural sensitization model of hyperresponsivity to low-level chemical exposures in multiple chemical sensitivity (MCS). MCS is a chronic polysymptomatic condition in which patients report illness from low levels of many different, structurally unrelated environmental chemicals (chemical intolerance, CI). Neural sensitization is the progressive host amplification of a response over time from repeated, intermittent exposures to a stimulus. Drugs, chemicals, endogenous mediators, and exogenous stressors can all initiate sensitization and can exhibit cross-sensitization between different classes of stimuli. The properties of sensitization overlap much of the clinical phenomenology of MCS. Animal studies have demonstrated sensitization to toluene, formaldehyde, and certain pesticides, as well as cross-sensitization, e.g., formaldehyde and cocaine. Controlled human studies in persons with self-reported CI have shown heightened sensitizability in the laboratory to nonspecific experimental factors and to specific chemical exposures. Useful outcome measures include spectral electroencephalography, blood pressure, heart rate, and plasma beta-endorphin. Findings implicate, in part, dopaminergic mesolimbic pathways and limbic structures. A convergence of evidence suggests that persons with MCS or with low-level CI may share some characteristics with individuals genetically vulnerable to substance abuse: (a) elevated family histories of alcohol or drug problems; (b) heightened capacity for sensitization of autonomic variables in the laboratory; (c) increased amounts of electroencephalographic alpha activity at rest and under challenge conditions over time. Sensitization is compatible with other models for MCS as well. The neural sensitization model provides a direction for further systematic human and animal research on the physiological bases of MCS and CI.

Psychiatric illness in the first-degree relatives of persons reporting multiple chemical sensitivities

The multiple chemical sensitivities (MCS) syndrome is characterized by unexplained physical and psychiatric complaints attributed by patients and some of their physicians to low-level chemical exposures. In this study, we interviewed 15 subjects with MCS and 21 controls about their first-degree relatives using the Family History-Research Diagnostic Criteria (FH-RDC). Subjects with MCS were more likely than controls to report their relatives to have major depression, alcoholism, panic disorder, obsessive-compulsive disorder, and antisocial personality disorder. They were also likely to have past suicide attempts, and to have received some form of psychiatric treatment (hospitalization, medication or electroconvulsive therapy, or counseling). Nearly 30% of the relatives of subjects with MCS were reported to have MCS themselves. Possible reasons for the findings are discussed.