Serum levels of soluble receptor for advanced glycation endproducts (sRAGE) in patients with different psychiatric disorders

Soluble receptor of advanced glycation end product as a biomarker in neurocognitive and neuropsychiatric disorders: A meta-analysis of controlled studies

BACKGROUND & OBJECTIVES

Currently, there is a significant focus on the decrease of soluble receptor of advanced glycation end products (sRAGE) in neurocognitive and neuropsychiatric disorders. sRAGE plays a decoy role against the inflammatory response of advanced glycation end products (AGE), which has led to increased interest in its role in these disorders. This meta-analysis aimed to investigate the significant differences in sRAGE levels between neurocognitive and neuropsychiatric disorders compared to control groups.

METHOD

A systematic review was conducted using the PUBMED, Scopus and Embase databases up to October 2023. Two reviewers assessed agreement for selecting papers based on titles and abstracts, with kappa used to measure agreement and finally publications were scanned according to controlled studies. Effect sizes were calculated as weighted mean differences (WMD) and pooled using a random effects model. Heterogeneity was assessed using I2, followed by subgroup analysis and meta-regression tests. Quality assessment was performed using the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

In total, 16 studies were included in the present meta-analysis. Subjects with neurocognitive (n = 1444) and neuropsychiatric (n = 444) disorders had lower sRAGE levels in case-control (WMD: -0.21, 95% CI: -0.33, -0.10; p <.001) and cross-sectional (WMD: -0.29, 95% CI = -0.44, -0.13, p <.001) studies with high heterogeneity and no publication bias. In subgroup analysis, subjects with cognitive impairment (WMD: -0.87, 95% CI: -1.61, -0.13, p =.000), and age >50 years (WMD: -0.39, 95% CI: -0.74, -0.05, p =.000), had lower sRAGE levels in case-control studies. Also, dementia patients (WMD: -0.41, 95% CI: -0.72, -0.10, p =.014) with age >50 years (WMD: -0.33, 95% CI: -0.54, -0.13, p = 0.000) and in Asian countries (WMD: -0.28, 95% CI: -0.42, -0.13, p =.141) had lower sRAGE levels in cross-sectional studies.

CONCLUSION

This meta-analysis revealed a significant reduction in sRAGE in neurocognitive and neuropsychiatric disorders particularly in Asians and moderate age.

Intake of dietary advanced glycation end products may be associated with depression and sleep quality in young adults

BACKGROUND

This study examined the relationship between dietary intake of advanced glycation end products (dAGEs) and depression and sleep quality in young adults.

METHODS

This study, which included 420 university students (F = 80.2 %; M = 19.8 %), is observational and cross-sectional. Dietary AGEs intakes of individuals were taken with a 24-h food consumption record system. Measuring the depression status of the participants was evaluated with the Beck Depression Inventory (BDI), and the assessment of their sleep quality was evaluated with the Pittsburg Sleep Quality Index (PSQI). Individuals' dAGEs intakes were divided into three equal groups (low, medium, and high). The energy was adjusted in all analyzes of dAGEs intake. Study data were analyzed with the SPSS (27.0 version) and GraphPad program (8.0 version).

RESULTS

The BDI and PSQI total score averages of individuals in the high dAGEs intake group were higher than the other groups, and this difference was statistically significant (p < 0.001). There is no significant difference between individuals' dAGEs intakes and energy and macronutrient intakes. Students' dAGEs intake was affected by BDI (β = 0.722, 95 % Cl = 0.639;0.811) and PSQI (β = 0.286, 95 % Cl = 0.179;0.431) scores (p < 0.001). This effect persisted even when various confounding factors were included (age, gender, smoking, body mass index, chronic disease) (p < 0.001).

LIMITATIONS

These data are cross-sectional, which limits the generalizability of results and establishing cause-effect relationships.

CONCLUSION

There may be an association between dAGEs intake and the development of depression and sleep quality in young adults. Clinical intervention studies using objective measurement methods should be conducted on this issue in the future.

Serum levels of high mobility group box-1 protein (HMGB1) and soluble receptors of advanced glycation end-products (RAGE) in depressed patients treated with electroconvulsive therapy

AIMS

High mobility group box-1 (HMGB1) is one of the damage-associated molecular patterns produced by stress and induces inflammatory responses mediated by receptors of advanced glycation end-products (RAGE) on the cell surface. Meanwhile, soluble RAGE (sRAGE) exhibits an anti-inflammatory effect by capturing HMGB1. Animal models have shown upregulation of HMGB1 and RAGE in the brain or blood, suggesting the involvement of these proteins in depression pathophysiology. However, there have been no reports using blood from depressed patients, nor ones focusing on HMGB1 and sRAGE changes associated with treatment and their relationship to depressive symptoms.

METHODS

Serum HMGB1 and sRAGE concentrations were measured by enzyme-linked immunosorbent assay in a group of patients with severe major depressive disorder (MDD) (11 males and 14 females) who required treatment with electroconvulsive therapy (ECT), and also in a group of 25 age- and gender-matched healthy subjects. HMGB1 and sRAGE concentrations were also measured before and after a course of ECT. Depressive symptoms were assessed using the Hamilton Rating Scale for Depression (HAMD).

RESULTS

There was no significant difference in HMGB1 and sRAGE concentrations in the MDD group compared to healthy subjects. Although ECT significantly improved depressive symptoms, there was no significant change in HMGB1 and sRAGE concentrations before and after treatment. There was also no significant correlation between HMGB1 and sRAGE concentrations and the HAMD total score or subitem scores.

CONCLUSION

There were no changes in HMGB1 and sRAGE in the peripheral blood of severely depressed patients, and concentrations had no relationship with symptoms or ECT.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

RAGE signaling pathway is involved in CUS-induced depression-like behaviors by regulating the expression of NR2A and NR2B in rat hippocampus DG

NMDA receptors play pivotal roles in the neurobiology of chronic stress-induced mood disorders. But the mechanism for chronic stress to disturb the expression of NMDA receptor subunits is still unclear. Recent researches indicated the involvement RAGE signaling pathway in regulation of glutamate system functions. In this study, we hypothesized RAGE signaling pathway mediated chronic stress-induced alteration in the expression of NMDA receptor subunits, leading to depressive-like behaviors. CUS decreased the expression of RAGE, NR2A, and NR2B, inhibited the phosphorylation of transcript factor ERK and CREB in rat hippocampus DG. RAGE knockdown in hippocampus DG by RAGE shRNA lentiviral particles induced depressive-like behaviors, reduced the mRNA and protein expression of NR2A and NR2B, and inhibited the phosphorylation of ERK and CREB. RAGE over-expression in hippocampus DG by RAGE adenovirus particles reversed the effects of CUS on depressive-like behaviors, ERK and CREB phosphorylation, and NR2A and NR2B expression. Our findings suggests that RAGE signaling pathway at least partially participates in the regulation of NR2A and NR2B expression, which mediates the effects of chronic stress on the depressive-like behaviors. These data provide evidence for RAGE signaling as a possible new pathway through which chronic stress results in the maladaptation of NMDA receptors.

The Effects of Dietary Advanced Glycation End-Products on Neurocognitive and Mental Disorders

Advanced glycation end products (AGEs) are glycated proteins or lipids formed endogenously in the human body or consumed through diet. Ultra-processed foods and some culinary techniques, such as dry cooking methods, represent the main sources and drivers of dietary AGEs. Tissue accumulation of AGEs has been associated with cellular aging and implicated in various age-related diseases, including type-2 diabetes and cardiovascular disease. The current review summarizes the literature examining the associations between AGEs and neurocognitive and mental health disorders. Studies indicate that elevated circulating AGEs are cross-sectionally associated with poorer cognitive function and longitudinally increase the risk of developing dementia. Additionally, preliminary studies show that higher skin AGE accumulation may be associated with mental disorders, particularly depression and schizophrenia. Potential mechanisms underpinning the effects of AGEs include elevated oxidative stress and neuroinflammation, which are both key pathogenetic mechanisms underlying neurodegeneration and mental disorders. Decreasing dietary intake of AGEs may improve neurological and mental disorder outcomes. However, more sophisticated prospective studies and analytical approaches are required to verify directionality and the extent to which AGEs represent a mediator linking unhealthy dietary patterns with cognitive and mental disorders.

Intersections between pneumonia, lowered oxygen saturation percentage and immune activation mediate depression, anxiety, and chronic fatigue syndrome-like symptoms due to COVID-19: A nomothetic network approach

BACKGROUND

COVID-19 is associated with neuropsychiatric symptoms including increased depressive, anxiety and chronic fatigue-syndrome (CFS)-like and physiosomatic symptoms.

AIMS

To delineate the associations between affective and CFS-like symptoms in COVID-19 and chest computed tomography scan anomalies (CCTAs), oxygen saturation (SpO₂), interleukin (IL)-6, IL-10, C-Reactive Protein (CRP), albumin, calcium, magnesium, soluble angiotensin converting enzyme (ACE2) and soluble advanced glycation products (sRAGEs).

METHOD

The above biomarkers were assessed in 60 COVID-19 patients and 30 healthy controls who had measurements of the Hamilton Depression (HDRS) and Anxiety (HAM-A) and the Fibromyalgia and Chronic Fatigue (FF) Rating Scales.

RESULTS

Partial Least Squares-SEM analysis showed that reliable latent vectors could be extracted from a) key depressive and anxiety and physiosomatic symptoms (the physio-affective or PA-core), b) IL-6, IL-10, CRP, albumin, calcium, and sRAGEs (the immune response core); and c) different CCTAs (including ground glass opacities, consolidation, and crazy paving) and lowered SpO₂% (lung lesions). PLS showed that 70.0% of the variance in the PA-core was explained by the regression on the immune response and lung lesions latent vectors. One common "infection-immune-inflammatory (III) core" underpins pneumonia-associated CCTAs, lowered SpO₂ and immune activation, and this III core explains 70% of the variance in the PA core, and a relevant part of the variance in melancholia, insomnia, and neurocognitive symptoms.

DISCUSSION

Acute SARS-CoV-2 infection is accompanied by lung lesions and lowered SpO₂ which may cause activated immune-inflammatory pathways, which mediate the effects of the former on the PA-core and other neuropsychiatric symptoms due to SARS-CoV-2 infection.

Advanced glycation end products measured by skin autofluorescence are associated with melancholic depressive symptoms - Findings from Helsinki Birth Cohort Study

BACKGROUND

Millions of people live with depression and its burden of disease. Depression has an increased comorbidity and mortality that has remained unexplained. Studies have reported connections between advanced glycation end products (AGEs) and various disease processes, including mental health. The present study evaluated associations between AGEs, depressive symptoms, and types of depressive symptoms.

METHODS

From the Helsinki Birth Cohort Study, 815 participants with a mean age of 76 years were recruited for this cross-sectional study. Characteristics regarding self-reported lifestyle and medical history, as well as blood tests were obtained along with responses regarding depressive symptoms according to the Beck Depression Inventory (BDI) and Mental Health Inventory-5. Each participant had their AGE level measured non-invasively with skin autofluorescence (SAF). Statistical analyses looked at relationships between types of depressive symptoms and AGE levels by sex.

RESULTS

Of women, 27% scored ≥10 on the BDI and 18% of men, respectively. Men had higher crude AGE levels (mean [standard deviation], arbitrary units) (2.49 [0.51]) compared to women (2.33 [0.46]) (p < 0.001). The highest crude AGE levels were found in those with melancholic depressive symptoms (2.61 [0.57]), followed by those with non-melancholic depressive symptoms (2.45 [0.45]) and those with no depressive symptoms (2.38 [0.49]) (p = 0.013). These findings remained significant in the fully adjusted model.

CONCLUSIONS

The current study shows an association between depressive symptoms and higher AGE levels. The association is likely part of a multi-factorial effect, and hence no directionality, causality, or effect can be inferred solely based on the results of this study.

MMP9/RAGE pathway overactivation mediates redox dysregulation and neuroinflammation, leading to inhibitory/excitatory imbalance: a reverse translation study in schizophrenia patients

Various mechanisms involved in schizophrenia pathophysiology, such as dopamine dysregulation, glutamate/NMDA receptor dysfunction, neuroinflammation or redox imbalance, all appear to converge towards an oxidative stress "hub" affecting parvalbumine interneurones (PVI) and their perineuronal nets (PNN) (Lancet Psychiatry. 2015;2:258-70); (Nat Rev Neurosci. 2016;17:125-34). We aim to investigate underlying mechanisms linking oxidative stress with neuroinflammatory and their long-lasting harmful consequences. In a transgenic mouse of redox dysregulation carrying a permanent deficit of glutathione synthesis (gclm-/-), the anterior cingulate cortex presented early in the development increased oxidative stress which was prevented by the antioxidant N-acetylcysteine (Eur J Neurosci. 2000;12:3721-8). This oxidative stress induced microglia activation and redox-sensitive matrix metalloproteinase 9 (MMP9) stimulation, leading to the receptor for advanced glycation end-products (RAGE) shedding into soluble and nuclear forms, and subsequently to nuclear factor-kB (NF-kB) activation and secretion of various cytokines. Blocking MMP9 activation prevented this sequence of alterations and rescued the normal maturation of PVI/PNN, even if performed after an additional insult that exacerbated the long term PVI/PNN impairments. MMP9 inhibition thus appears to be able to interrupt the vicious circle that maintains the long-lasting deleterious effects of the reciprocal interaction between oxidative stress and neuroinflammation, impacting on PVI/PNN integrity. Translation of these experimental findings to first episode patients revealed an increase in plasma soluble RAGE relative to healthy controls. This increase was associated with low prefrontal GABA levels, potentially predicting a central inhibitory/excitatory imbalance linked to RAGE shedding. This study paves the way for mechanistically related biomarkers needed for early intervention and MMP9/RAGE pathway modulation may lead to promising drug targets.

The Role of Brain Microvascular Endothelial Cell and Blood-Brain Barrier Dysfunction in Schizophrenia

BACKGROUND

Despite decades of research, little clarity exists regarding pathogenic mechanisms related to schizophrenia. Investigations on the disease biology of schizophrenia have primarily focused on neuronal alterations. However, there is substantial evidence pointing to a significant role for the brain's microvasculature in mediating neuroinflammation in schizophrenia.

SUMMARY

Brain microvascular endothelial cells (BMEC) are a central element of the microvasculature that forms the blood-brain barrier (BBB) and shields the brain against toxins and immune cells via paracellular, transcellular, transporter, and extracellular matrix proteins. While evidence for BBB dysfunction exists in brain disorders, including schizophrenia, it is not known if BMEC themselves are functionally compromised and lead to BBB dysfunction.

KEY MESSAGES

Genome-wide association studies, postmortem investigations, and gene expression analyses have provided some insights into the role of the BBB in schizophrenia pathophysiology. However, there is a significant gap in our understanding of the role that BMEC play in BBB dysfunction. Recent advances differentiating human BMEC from induced pluripotent stem cells (iPSC) provide new avenues to examine the role of BMEC in BBB dysfunction in schizophrenia.

RAGE Signaling pathway in hippocampus dentate gyrus involved in GLT-1 decrease induced by chronic unpredictable stress in rats

A pivotal role of glutamatergic neurotransmission in the pathophysiology of major depressive disorder (MDD) has been supported in preclinical and clinical studies. Glutamate transporters are responsible for rapid uptake of glutamate to maintain glutamate homeostasis. Down-regulation of glutamate transporters has been reported in MDD patients and animal models. However, the mechanism for stress-induced modulation of glutamate transporter expression is poorly understood. Receptor for advanced glycosylation end products (RAGE), a member of immunoglobulin family, is found expressed widely in brain and play important roles in neuronal development, neurite growth, neurogenesis and neuroinflammation. Our study showed chronic unpredictable stress (CUS) induced depressive-like behaviors and reduced RAGE expression in hippocampus DG, CA1 and CA3 areas. The protein levels of GLT-1, p-CREB and p-p65 decreased in hippocampus DG as well. Knockdown of RAGE expression in hippocampus DG with RAGE shRNA lentivirus particles induced depressive-like behaviors. Meanwhile, the protein and mRNA levels of GLT-1 were significantly decreased as well as phosphorylation of CREB and p65. Neither CUS nor RAGE knockdown altered GLAST protein and mRNA levels. These findings suggested that RAGE/CREB-NF-κB signaling pathway in hippocampus DG involved in modulation of GLT-1 expression, which possibly contributed to the depressive-like behavior induced by CUS.

Use of skin advanced glycation end product levels measured using a simple noninvasive method as a biological marker for the diagnosis of neuropsychiatric diseases

OBJECTIVES

The accumulation of advanced glycation end products (AGEs) may be involved in the pathophysiology of several neuropsychiatric diseases. In this study, the skin AGEs level of several neuropsychiatric diseases was assessed with a simple noninvasive method. Moreover, whether skin AGE level can be used as a biomarker for the diagnosis of these diseases was evaluated.

METHODS

A total of 27 patients with schizophrenia, 26 with major depressive disorder, and 10 with major neurocognitive disorders (MNDs), such as Alzheimer's disease or dementia with Lewy body, as well as 26 healthy controls were enrolled in this study. The skin AGE levels of the patients were assessed with an AGE scanner, a fluorometric method used to assay skin AGE levels.

RESULTS

One-way analysis of covariance was performed after adjusting for significant covariates, including age. Although the group with MNDs had higher skin AGE levels than the other groups, the main effect of diagnosis did not significantly affect the skin AGE levels of the groups.

CONCLUSIONS

Skin AGE levels in neuropsychiatric diseases with mild symptoms did not significantly differ. Further large-scale studies using a simple noninvasive method for the early detection and treatment of MNDs must be conducted.

Psychological well-being and green tea consumption are associated with lower pentosidine serum levels among elderly female residents in Japan

OBJECTIVE

Pentosidine (PEN), a well-defined advanced glycation end product (AGE), may be affected by psychological status, given the recent findings regarding AGE receptor functions. Because AGEs can be a factor in aging and in the development or worsening of many degenerative diseases, it is important to find a way to reduce the PEN levels in our body. This study aims to investigate novel factors associated with PEN levels.

METHODS

A cross-sectional study involving 106 female participants (aged 59-69) was conducted in a tea-producing district in Japan. The serum concentration of PEN was detected and evaluated in relation to the participants' psychological status, which was assessed using the Japanese version of the 28-item General Health Questionnaire (GHQ) and lifestyle factors. Factors that were significantly associated with PEN were analysed using multiple linear regression analyses. Significance was defined as p < .05.

RESULTS

The serum PEN concentrations were significantly and positively associated with the total GHQ scores and BMI after controlling for covariates (standardised beta coefficient (B) = 0.26, p < .01; B = 0.27, p < .01, respectively). In addition, the PEN levels were significantly lower in participants who consumed seven cups or more of green tea per day than those who consumed six or fewer cups per day (B = 0.19, p < .05).

CONCLUSIONS

Low GHQ scores (i.e. better psychological well-being) and green tea consumption may be helpful in decreasing AGEs.

Advanced glycation end products among patients maintained on antipsychotics

The aim of this study was to measure advanced glycation end products (AGEs) among participants maintained on antipsychotics using the AGE Reader and to compare them with controls from the general population. Participants maintained on antipsychotics for at least 6 months were recruited from the Psychiatry Department at Rumailah Hospital, Doha, Qatar. Healthy controls were recruited from the primary healthcare centers in Doha, Qatar. AGEs of a total of 86 participants (48 patients and 38 controls) were recorded. Among the group maintained on antipsychotics, women, smokers, and Arabs had significantly higher AGEs levels compared with men, nonsmokers, and non-Arabs, respectively (P<0.05). The levels of AGEs were higher among the group of patients maintained on antipsychotics in comparison to controls; however, the difference did not reach statistical significance. This is the first study to examine AGEs in patients maintained on antipsychotics. Our findings showed that such patients do not differ significantly from controls comparing AGEs levels. Future investigations might need to consider recruiting a larger sample size using a prospective design.

High doses of antipsychotic polypharmacy are related to an increase in serum levels of pentosidine in patients with schizophrenia

BACKGROUND

Carbonyl stress in patients with schizophrenia has been reported to be reflected by an increase in peripheral pentosidine levels. This cohort study tested whether the accumulation of pentosidine was related to the disease severity or the treatment (routine administration of high antipsychotic doses).

METHODS

We followed up our original investigation using a new group of 137 patients with acute schizophrenia and 45 healthy subjects, and then pooled the two cohorts to conduct the following analysis on a total of 274 patients. The associations of serum pentosidine and pyridoxal levels with duration of education, estimated duration of medication, the severity of symptoms, and daily doses of antipsychotics, antiparkinsonian drugs, and anxiolytics were evaluated by multiple linear regression analysis.

RESULTS

The combined cohort of 274 patients exhibited abnormally high serum levels of pentosidine, were associated with a higher daily dose of antipsychotic drugs and a longer estimated duration of medication without statistical significance of diagnosis. This was also observed in the patients treated with antipsychotic polypharmacy, but the serum pentosidine levels of patients treated with first- or second-generation antipsychotic monotherapy showed no relationship with these two variables.

CONCLUSION

High levels of serum pentosidine were associated with high daily doses of antipsychotic drugs and a longer estimated duration of medication in patients treated with antipsychotic polypharmacy.

Association of Polymorphisms of the Receptor for Advanced Glycation Endproducts Gene with Schizophrenia in a Han Chinese Population

Receptor for Advanced Glycation Endproducts (RAGE) is a member of the immunoglobulin superfamily that binds diverse ligands involved in the development of inflammatory damage and diverse chronic diseases including schizophrenia. Here, three single-nucleotide polymorphisms (SNPs) (G82S, -374T/A, and -429T/C) in the RAGE gene were genotyped in 923 patients with schizophrenia and 874 healthy-matched controls in a Han Chinese population using the SNaPshot technique. Additionally, we investigated the association among aforementioned SNPs with the clinical psychotic symptoms of the patients and neurocognitive function. Our study demonstrated that the frequencies of the TC + CC genotypes and the C allele in the -429T/C polymorphism were significantly lower in the patients compared with the controls (p = 0.031 and p = 0.034, resp.). However, the significant effect disappeared when using Bonferroni correction (p = 0.093 and p = 0.102, resp.). And there were no significant differences in the genotype and allele frequencies between the patients and the controls for G82S and -374T/A polymorphisms. Additionally, the -429T/C C allele carriers had marginally higher Symbol coding scores than the subjects with the TT genotypes [p = 0.031 and p (corr) = 0.093]. Our data indicate that the RAGE -429T/C polymorphism may be associated with the susceptibility of schizophrenia.

Microglial Function during Glucose Deprivation: Inflammatory and Neuropsychiatric Implications

Inflammation is increasingly recognized as a contributor to the pathophysiology of neuropsychiatric disorders, including depression, anxiety disorders and autism, though the factors leading to contextually inappropriate or sustained inflammation in pathological conditions are yet to be elucidated. Microglia, as the key mediators of inflammation in the CNS, serve as likely candidates in initiating pathological inflammation and as an ideal point of therapeutic intervention. Glucose deprivation, as a component of the pathophysiology of ischemia or occurring transiently in diabetes, may serve to modify microglial function contributing to inflammatory injury. To this end, primary microglia were cultured from postnatal rat brain and subject to glucose deprivation in vitro. Microglia were characterized for their proliferation, phagocytic function and secretion of inflammatory factors, and tested for their capacity to respond to a potent inflammatory stimulus. In the absence of glucose, microglia remained capable of proliferation, phagocytosis and inflammatory activation and showed increased release of inflammatory factors after presentation of an inflammatory stimulus. Glucose-deprived microglia demonstrated increased phagocytic activity and decreased accumulation of lipids in lipid droplets over a 48-h timecourse, suggesting they may use scavenged lipids as a key alternate energy source during metabolic stress. In the present manuscript, we present novel findings that glucose deprivation may sensitize microglial release of inflammatory mediators and prime microglial functions for both survival and inflammatory roles, which may contribute to psychiatric comorbidities of ischemia, diabetes and/or metabolic disorder.

Advanced Glycation End Product (AGE) Accumulation in the Skin is Associated with Depression: The Maastricht Study

BACKGROUND

Depression is a highly prevalent disease with a high morbidity and mortality risk. Its pathophysiology is not entirely clear. However, type 2 diabetes is an important risk factor for depression. One mechanism that may explain this association may include the formation of advanced glycation end products (AGEs). We therefore investigated the association of AGEs with depressive symptoms and depressive disorder. In addition, we examined whether the potential association was present for somatic and/or cognitive symptoms of depression.

METHODS

Cross-sectional data were used from the Maastricht Study (N = 862, mean age 59.8 ± 8.5 years, 55% men). AGE accumulation was measured with skin autofluorescence (SAF) by use of the AGE Reader. Plasma levels of protein-bound pentosidine were measured with high-performance liquid chromatography and fluorescence detection. Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) were measured with ultraperformance liquid chromatography and tandem mass spectrometry. Depressive symptoms and depressive disorder were assessed by the nine-item Patient Health Questionnaire and the Mini-International Neuropsychiatric Interview.

RESULTS

Higher SAF was associated with depressive symptoms (β = 0.42, 95% CI 0.12-0.73, P = .007) and depressive disorder (OR = 1.42, 95% CI 1.04-1.95, P = .028) after adjustment for age, sex, type 2 diabetes, smoking, BMI, and kidney function. Plasma pentosidine, CML, and CEL were not independently associated with depressive symptoms and depressive disorder.

CONCLUSIONS

This study shows that AGE accumulation in the skin is independently associated with higher levels of depressive symptoms and depressive disorder. This association is present for both somatic and cognitive symptoms of depression. This might suggest that AGEs are involved in the development of depression.

Blood-based immune-endocrine biomarkers of treatment response in depression

Antidepressant treatment for major depressive disorder remains suboptimal with response rates of just over 50%. Although treatment guidelines, algorithms and clinical keys are available to assist the clinician, the process of finding an effective pharmacotherapy to maximise benefit for the individual patient is largely by "trial and error" and remains challenging. This highlights a clear need to identify biomarkers of treatment response to help guide personalised treatment strategies. We have carried out the largest multiplex immunoassay based longitudinal study to date, examining up to 258 serum markers involved in immune, endocrine and metabolic processes as potential biomarkers associated with treatment response in 332 depression patients recruited from four independent clinical centres. We demonstrated for the first time that circulating Apolipoprotein A-IV, Endoglin, Intercellular Adhesion Molecule 1, Tissue Inhibitor of Metalloproteinases 1, Plasminogen Activator Inhibitor 1, Thrombopoietin, Complement C3, Hepatocyte Growth Factor and Insulin-like Growth Factor-Binding Protein 2 were associated with response to different antidepressants. In addition, we showed that specific sets of immune-endocrine proteins were associated with response to Venlafaxine (serotonin-norepinephrine reuptake inhibitor), Imipramine (tricyclic antidepressant) and other antidepressant drugs. However, we were not able to reproduce the literature findings on BDNF and TNF-α, two of the most commonly reported candidate treatment response markers. Despite the need for extensive validation studies, our preliminary findings suggest that a pre-treatment immune-endocrine profile may help to determine a patient's likelihood to respond to specific antidepressant and/or alternative treatments such as anti-inflammatory drugs, providing hope for future personalised treatment approaches.

The regulation of soluble receptor for AGEs contributes to carbonyl stress in schizophrenia

Our previous study showed that enhanced carbonyl stress is closely related to schizophrenia. The endogenous secretory receptor for advanced glycation end-products (esRAGE) is a splice variant of the AGER gene and is one of the soluble forms of RAGE. esRAGE is considered to be a key molecule for alleviating the burden of carbonyl stress by entrapping advanced glycation end-products (AGEs). In the current study, we conducted genetic association analyses focusing on AGER, in which we compared 212 schizophrenic patients to 214 control subjects. We also compared esRAGE levels among a subgroup of 104 patients and 89 controls and further carried out measurements of total circulating soluble RAGE (sRAGE) in 25 patients and 49 healthy subjects. Although the genetic association study yielded inconclusive results, multiple regression analysis indicated that a specific haplotype composed of rs17846798, rs2071288, and a 63 bp deletion, which were in perfect linkage disequilibrium (r² = 1), and rs2070600 (Gly82Ser) were significantly associated with a marked decrease in serum esRAGE levels. Furthermore, compared to healthy subjects, schizophrenia showed significantly lower esRAGE (p = 0.007) and sRAGE (p = 0.03) levels, respectively. This is the first study to show that serum esRAGE levels are regulated by a newly identified specific haplotype in AGER and that a subpopulation of schizophrenic patients are more vulnerable to carbonyl stress.

Integrating neuroimmune systems in the neurobiology of depression

Data from clinical and preclinical studies indicate that immune dysregulation, specifically of inflammatory processes, is associated with symptoms of major depressive disorder (MDD). In particular, increased levels of circulating pro-inflammatory cytokines and concomitant activation of brain-resident microglia can lead to depressive behavioural symptoms. Repeated exposure to psychological stress has a profound impact on peripheral immune responses and perturbs the function of brain microglia, which may contribute to neurobiological changes underlying MDD. Here, we review these findings and discuss ongoing studies examining neuroimmune mechanisms that influence neuronal activity as well as synaptic plasticity. Interventions targeting immune-related cellular and molecular pathways may benefit subsets of MDD patients with immune dysregulation.

Chronic maternal hyperglycemia induced during mid-pregnancy in rats increases RAGE expression, augments hippocampal excitability, and alters behavior of the offspring

Maternal diabetes during pregnancy may increase the risk of neurodevelopmental disorders in the offspring by increasing inflammation. A major source of inflammatory signaling observed in diabetes is activation of the receptor for advanced glycation end-products (RAGE), and increased RAGE expression has been reported in psychiatric disorders. Thus, we sought to examine whether maternal diabetes creates a proinflammatory state, triggered largely by RAGE signaling, that alters normal brain development and behavior of the offspring. We tested this hypothesis in rats using the streptozotocin (STZ; 50mg/kg; i.p.) model of diabetes induced during mid-pregnancy. Following STZ treatment, we observed a significant increase in RAGE protein expression in the forebrain of the offspring (postnatal day 1). Data obtained from whole-cell patch clamping of hippocampal neurons in cultures from the offspring of STZ-treated dams revealed a striking increase in excitability. When tested in a battery of behavioral tasks in early adulthood, the offspring of STZ-treated dams had significantly lower prepulse inhibition, reduced anxiety-like behavior, and altered object-place preference when compared to control offspring. In an operant-based strategy set-shifting task, STZ offspring did not differ from controls on an initial visual discrimination or reversal learning but took significantly longer to shift to a new strategy (i.e., set-shift). Insulin replacement with an implantable pellet in the dams reversed the effects of maternal diabetes on RAGE expression, hippocampal excitability, prepulse inhibition and object-place memory, but not anxiety-like behavior or set-shifting. Taken together, these results suggest that chronic maternal hyperglycemia alters normal hippocampal development and behavior of the offspring, effects that may be mediated by increased RAGE signaling in the fetal brain.

Advanced glycation end products and schizophrenia: A systematic review

Oxidative stress has become an exciting area of research on schizophrenia, which is a highly prevalent condition that affects approximately 1% of the worldwide population. Advanced glycation end products (AGEs), which are considered metabolic biomarkers of increased oxidative stress, have a pathogenic role in the development and progression of different oxidative stress-based diseases including atherosclerosis, diabetes, neurodegenerative disorders and schizophrenia. AGE formation and accumulation as well as the activation of its receptor (RAGE) can lead to signaling through several inflammatory signaling pathways and further damaging effects. This systematic review is based on a search conducted in July 2014 in which 6 studies were identified that met our criteria. In this work, we describe how recent methodological advances regarding the role of AGEs may contribute to a better understanding of the pathophysiology of schizophrenia and provide a different approach in the comprehension of the relationship between cardiovascular disease and schizophrenia. These latest findings may lead to new directions for future research on novel diagnostic and treatment strategies.

Altered serum glyceraldehyde-derived advanced glycation end product (AGE) and soluble AGE receptor levels indicate carbonyl stress in patients with schizophrenia

Recent cross-sectional and longitudinal studies indicate that measurements of peripheral blood carbonyl stress markers such as the advanced glycation end product (AGE) pentosidine and the reactive carbonyl-detoxifying B6 vitamin pyridoxal could be used as therapeutic biological markers in subpopulations of schizophrenia patients. Glyceraldehyde-derived AGEs (Glycer-AGE) have strong neurotoxicity, and soluble receptors for AGEs (sRAGE) may ameliorate the effects of AGEs. In the present study, we measured Glycer-AGEs and sRAGE levels to determine their potential as diagnostic, therapeutic, or clinical biological markers in patients with schizophrenia. After enrollment of 61 admitted Japanese patients with acute schizophrenia and 39 healthy volunteers, 54 patients were followed up from the acute stage to remission. Serum biomarkers were measured in blood samples taken before breakfast using competitive enzyme-linked immunosorbent assays, and Glycer-AGEs were significantly higher and sRAGE levels were significantly lower in patients with acute schizophrenia than in healthy controls. Glycer-AGEs/sRAGE ratios were also higher in schizophrenia patients and were stable during the clinical course. Furthermore, discriminant analyses confirmed that Glycer-AGEs and Glycer-AGEs/sRAGE ratios are significant diagnostic markers for schizophrenia, and distinguished between patients and healthy controls in 70.0% of cases. However, these markers of carbonyl stress were not correlated with clinical features, including disease severity, or with daily chlorpromazine doses. These data indicate the potential of Glycer-AGEs, RAGEs, and their relative ratios as diagnostic markers for patients with schizophrenia.

Common biological mechanisms between bipolar disorder and type 2 diabetes: Focus on inflammation

INTRODUCTION

Bipolar disorder (BD) patients present a 3-5 fold greater risk of developing type 2 diabetes (T2D) compared to general population. The underlying mechanisms for the increased prevalence of T2D in BD population are poorly understood.

OBJECTIVES

The purpose of this review is to critically review evidence suggesting that inflammation may have an important role in the development of both BD and T2D.

RESULTS

The literature covered in this review suggests that inflammatory dysregulation take place among many BD patients. Such dysregulated and low grade chronic inflammatory process may also increase the prevalence of T2D in BD population. Current evidence supports the hypothesis of dysregulated inflammatory processes as a critical upstream event in BD as well as in T2D.

CONCLUSIONS

Inflammation may be a factor for the development of T2D in BD population. The identification of inflammatory markers common to these two medical conditions will enable researchers and clinicians to better understand the etiology of BD and develop treatments that simultaneously target all aspects of this multi-system condition.

Nutritional psychiatry research: an emerging discipline and its intersection with global urbanization, environmental challenges and the evolutionary mismatch

In 21st-century public health, rapid urbanization and mental health disorders are a growing global concern. The relationship between diet, brain function and the risk of mental disorders has been the subject of intense research in recent years. In this review, we examine some of the potential socioeconomic and environmental challenges detracting from the traditional dietary patterns that might otherwise support positive mental health. In the context of urban expansion, climate change, cultural and technological changes and the global industrialization and ultraprocessing of food, findings related to nutrition and mental health are connected to some of the most pressing issues of our time. The research is also of relevance to matters of biophysiological anthropology. We explore some aspects of a potential evolutionary mismatch between our ancestral past (Paleolithic, Neolithic) and the contemporary nutritional environment. Changes related to dietary acid load, advanced glycation end products and microbiota (via dietary choices and cooking practices) may be of relevance to depression, anxiety and other mental disorders. In particular, the results of emerging studies demonstrate the importance of prenatal and early childhood dietary practices within the developmental origins of health and disease concept. There is still much work to be done before these population studies and their mirrored advances in bench research can provide translation to clinical medicine and public health policy. However, the clear message is that in the midst of a looming global epidemic, we ignore nutrition at our peril.

Amounts of artificial food colors in commonly consumed beverages and potential behavioral implications for consumption in children

Artificial food colors (AFCs) are widely used to color foods and beverages. The amount of AFCs the Food and Drug Administration has certified over the years has increased more than 5-fold since 1950 (12 mg/capita/day) to 2012 (68 mg/capita/day). In the past 38 years, there have been studies of adverse behavioral reactions such as hyperactivity in children to double-blind challenges with AFCs. Studies that used 50 mg or more of AFCs as the challenge showed a greater negative effect on more children than those which used less. The study reported here is the first to quantify the amounts of AFCs in foods (specifically in beverages) commonly consumed by children in the United States. Consumption data for all foods would be helpful in the design of more challenge studies. The data summarized here should help clinicians advise parents about AFCs and beverage consumption.

Increased advanced glycation end-products (AGEs) assessed by skin autofluorescence in schizophrenia

BACKGROUND

Oxidative stress has been intensively studied as a key biochemical system in the pathophysiology of schizophrenia. However, little is known about the implication of oxidative stress in the development of physical illnesses in schizophrenia patients, who are characterized by high cardiovascular risk and decreased life expectancy. Advanced glycation end-products (AGEs) are considered to be markers of oxidative stress and are linked to the development of atherosclerosis.

METHODS

We investigated AGE levels determined by a noninvasive skin autofluorescence (skin AF) method (AGE-Reader™) in schizophrenia patients. Skin AF was assessed in 55 schizophrenia patients without diabetes or renal disease and 55 healthy controls matched for age, gender and smoking status. Nineteen of the 55 schizophrenia patients had a severe form of the disease (Kraepelinian schizophrenia).

RESULTS

Skin AF was significantly higher in schizophrenia patients compared to controls (2.46 ± 0.52 and 1.90 ± 0.21, respectively, p < 0.0001). Kraepelinian schizophrenia patients had significantly higher skin AF than non-Kraepelinian schizophrenia patients (p = 0.05).

CONCLUSIONS

This is the first study to demonstrate high AGE levels assessed by a noninvasive method in schizophrenia patients.

Association between serum endogenous secretory receptor for advanced glycation end products and risk of type 2 diabetes mellitus with combined depression in the Chinese population

OBJECTIVE

The role of the endogenous secretory receptor for advanced glycation end products (esRAGE) in depression of diabetes patients and its clinical significance are unclear. This study investigated the role of serum esRAGE in patients with type 2 diabetes mellitus with depression in the Chinese population.

PATIENTS AND METHODS

One hundred nineteen hospitalized patients with type 2 diabetes were recruited at Fujian Provincial Hospital (Fuzhou, China) from February 2010 to January 2011. All selected subjects were assessed with the Hamilton Rating Scale for Depression (HAMD). Among them, 71 patients with both type 2 diabetes and depression were included. All selected subjects were examined for the following: esRAGE concentration, glycosylated hemoglobin (HbA1c), blood lipids, C-reactive protein, trace of albumin in urine, and carotid artery intima-media thickness (IMT). Association between serum esRAGE levels and risk of type 2 diabetes mellitus with depression was also analyzed.

RESULTS

There were statistically significant differences in gender, age, body mass index, waist circumference, and treatment methods between the group with depression and the group without depression (P<0.05). Multiple linear regression analysis showed that HAMD scores were negatively correlated with esRAGE levels (standard regression coefficient -0.270, P<0.01). HAMD-17 scores were positively correlated with IMT (standard regression coefficient 0.183, P<0.05) and with HbA1c (standard regression coefficient 0.314, P<0.01).

CONCLUSIONS

Female gender, younger age, obesity, poor glycemic control, complications, and insulin therapy are all risk factors of type 2 diabetes mellitus with combined depression in the Chinese population. Inflammation and atherosclerosis play an important role in the pathogenesis of depression. esRAGE is a protective factor of depression among patients who have type 2 diabetes.

Cerebrospinal fluid S100B levels reflect symptoms of depression in patients with non-inflammatory neurological disorders

Recent findings document numerous interactions between neuronal and glial systems that likely play a role in the pathophysiology of depression. These findings suggest that glia-derived neurotrophic protein S100B may play a significant role in developing depression. To test the relationship between S100B and depressive symptoms we designed cross-sectional clinical study including S100B serum and CSF levels in neurological patients with non-inflammatory disorders (NIND), who undergone cerebrospinal fluid assessment for diagnostic purposes. The present study was focused on psychometric testing of depression (BDI-II), anxiety (SAS) and alexithymia (TAS-20), and neurochemical measure of cerebrospinal fluid (CSF) and serum levels of S100B in 40 NIND inpatients [mean age 41.67]. The main result shows that S100B in CSF is significantly negatively correlated with BDI-II (Spearman R=-0.51, p<0.0009) but not with SAS and TAS-20. The finding indicates that decreased level of S100B in CSF is related to increased symptoms of depression in the NIND patients.