A meta-analysis of differences in IL-6 and IL-10 between people with and without depression: Exploring the causes of heterogeneity.
ABSTRACT Epidemiological evidence for the inflammatory hypothesis of depression is largely cross-sectional; people with depression have elevated levels of circulating pro-inflammatory markers compared to people without depression. The limitation of cross sectional research is the potential for extraneous factors to influence observed effects. The purpose of this meta-analysis of cross-sectional studies of interleukin(IL)-6 and IL-10 in people with and without depression is to provide a targeted analysis of potential moderator factors relating to the diagnosis of depression and to physical and psychiatric comorbidity. Electronic searches of Embase and Medline databases were conducted using subject headings "interleukin-6" or "interleukin-10" and those relating to depression. Studies were included if they measured circulating marker levels in serum or plasma in a group of people with and without depressive symptoms (99 studies for IL-6, 19 studies for IL-10). IL-6 was elevated in depressed compared to non-depressed groups (d=0.46, 99% CI 0.34 to 0.58, I(2)=85.9%). This effect was larger in subgroups where depressive disorders were diagnosed compared to those with only depressive symptoms via standardized inventory, and subgroups where participants were recruited from inpatient or outpatient settings compared to the general community. The effect was also larger in those who were not selected for a particular comorbidity compared to those selected for cardiovascular disease. IL-10 effect size was not significant (d=-0.31, 99% CI -0.95 to 0.32, I(2)=94.1%) which was not accounted for in subgroup analyses or meta-regression, indicating there is not a global elevation in cytokines. These data highlight that comorbidity and behavioral aspects of depression need to be measured and controlled in future prospective and experimental research testing the inflammatory hypothesis of depression.
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ABSTRACT: IL-6 plays a mechanistic role in conditions such as metabolic syndrome, chronic fatigue syndrome and clinical depression and also plays a major role in inflammatory and immune responses to exercise. The purpose of this study was to investigate the levels of resting and post exercise IL-6 when measured in venous plasma, saliva and capillary plasma. Five male and five females completed 2 separate exercise trials, both of which involved standardized exercise sessions on a cycle ergometer. Venous blood and saliva samples were taken immediately before and after Trial A, venous and capillary blood samples were taken immediately before and after Trial B. IL-6 values were obtained using a high-sensitivity enzyme-linked immunosorbent assay (ELISA). In Trial A venous plasma IL-6 increased significantly from 0.4±0.14pg/ml to 0.99±0.29pg/ml (P<0.01) while there was no increase in salivary IL-6. Venous plasma and salivary IL-6 responses were not correlated at rest, post exercise or when expressed as an exercise induced change. In Trial B venous and capillary plasma IL-6 increased significantly (venous: 0.22±0.18 to 0.74±0.28pg/ml (P⩽0.01); capillary: 0.37±0.22 to 1.08±0.30pg/ml (P<0.01). Venous and capillary plasma responses did not correlate at rest (r=0.59, P=0.07) but did correlate post exercise (r=0.79, P⩾0.001) and when expressed as an exercise induced change (r=0.71, P=0.02). Saliva does not appear to reflect systemic IL-6 responses, either at rest or in response to exercise. Conversely, capillary plasma responses are reflective of systemic IL-6 responses to exercise. Copyright © 2014 Elsevier Ltd. All rights reserved.Cytokine 11/2014; 71(2). · 2.87 Impact Factor
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ABSTRACT: Background: Saffron, a spice derived from the flower of Crocus sativus, has now undergone several trials examining its antidepressant effects and, in a recent meta-analysis, was confirmed to be effective for the treatment of major depression. Objective: To provide an expanded systematic analysis of the completed clinical studies on saffron and depression, detailing dosages, extract sources, standardisations, safety profile and treatment duration; and, through a narrative review, to examine its potential antidepressant mechanisms of action. Design: In the systematic review of clinical trials, electronic databases were searched for high-quality, randomised, double-blind studies, with placebo or antidepressant controls. A narrative review of in vivo and in vitro studies was conducted to examine its potential antidepressant mechanisms of action. Results: In the systematic review, six studies were identified. In the placebo-comparison trials, saffron had large treatment effects and, when compared with antidepressant medications, had similar antidepressant efficacy. Saffron's antidepressant effects potentially are due to its serotonergic, antioxidant, anti-inflammatory, neuro-endocrine and neuroprotective effects. Conclusions: Research conducted so far provides initial support for the use of saffron for the treatment of mild-to-moderate depression. Further research is required to expand our understanding of the role and actions of saffron in major depression.Human Psychopharmacology Clinical and Experimental 09/2014; 29(6):517-27. · 1.85 Impact Factor
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ABSTRACT: Major depression is a serious side effect of interferon-α (IFN-α), which is used in the therapy of hepatitis C virus (HCV) infection. Due to the lack of reproducible animal models, the mechanisms underlying IFN-α-related depression are largely unknown. We herein established a mouse model, in which murine IFN-α (250 IU/day) and polyinosinic/polycytidylic acid (poly(I:C); 1 μg/day), a toll-like receptor-3 (TLR3) agonist that mimics the effect of HCV double-strand RNA, were continuously infused into the lateral ventricle via miniosmotic pumps over up to 14 days. The delivery of IFN-α and poly(I:C), but not of IFN-α or poly(I:C) alone, resulted in a reproducible depression-like state that was characterized by reduced exploration behavior in open-field tests, increased immobility in tail suspension and forced swimming tests, and a moderate loss of body weight. In the hippocampus and prefrontal cortex, the pro-inflammatory genes TNF-α, IL-6, tissue inhibitor of metalloproteinases-1 (Timp-1), CXC motif ligand-1 (Cxcl1), Cxcl10, and CC motif ligand-5 (Ccl5) were synergistically induced by IFN-α and poly(I:C), most pronounced after 14-day exposure. In comparison, the interferon-inducible genes of signal transducer and activator of transcription-1 (Stat1), guanylate binding protein-1 (Gbp1), proteasome subunit-β type-9 (Psmb9), ubiquitin-conjugating enzyme E2L-6 (Ube2l6), receptor transporter protein-4 (Rtp4), and GTP cyclohydrolase-1 (Gch1), which had previously been elevated in the blood of IFN-α-treated patients developing depression, in the brains of suicidal individuals, and in primary neurons exposed to IFN-α and poly(I:C), were induced even earlier, reaching maximum levels mostly after 24 hours. We propose that interferon-inducible genes might be useful markers of imminent depression.Molecular Neurobiology 08/2014; · 5.29 Impact Factor