Shared metabolic and neuroimmune mechanisms underlying Type 2 Diabetes Mellitus and Major Depressive Disorder

Effect modification of tumor necrosis factor-α on the kynurenine and serotonin pathways in major depressive disorder on type 2 diabetes mellitus

Major depressive disorder (MDD) is strongly associated with type 2 diabetes mellitus (T2DM). The kynurenine and serotonin pathways, as well as chronic low-grade inflammation, are being considered potential links between them. MDD associated with T2DM is less responsive to treatment than that without T2DM; however, the underlying mechanism remains unknown. We aimed to investigate the effects of inflammatory cytokines on the kynurenine and serotonin pathways in patients with comorbid MDD and T2DM and those with only MDD. We recruited 13 patients with comorbid MDD and T2DM and 27 patients with only MDD. We measured interleukin-6 and tumor necrosis factor-α (TNF-α) levels as inflammatory cytokines and metabolites of the kynurenine pathway and examined the relationship between the two. TNF-α levels were significantly higher in patients with comorbid MDD and T2DM than in those with only MDD in univariate (p = 0.044) and multivariate (adjusted p = 0.036) analyses. TNF-α showed a statistically significant effect modification (interaction) with quinolinic acid/tryptophan and serotonin in patients from both groups (β = 1.029, adjusted p < 0.001; β =  - 1.444, adjusted p = 0.047, respectively). Limitations attributed to the study design and number of samples may be present. All patients were Japanese with mild to moderate MDD; therefore, the generalizability of our findings may be limited. MDD with T2DM has more inflammatory depression components and activations of the kynurenine pathway by inflammatory cytokines than MDD without T2DM. Hence, administering antidepressants and anti-inflammatory drugs in combination may be more effective in patients with comorbid MDD and T2DM.

Puerarin alleviates depressive-like behaviors in high-fat diet-induced diabetic mice via modulating hippocampal GLP-1R/BDNF/TrkB signaling

OBJECTIVE

Depression is one of the most common complications in patients with diabetes. Our previous study demonstrated puerarin, a dietary isoflavone, improved glucose homeostasis and β-cell regeneration in high-fat diet (HFD)-induced diabetic mice. Here, we aim to evaluate the potential effect of puerarin on diabetes-induced depression.

METHODS

The co-occurrence of diabetes and depression with related biochemical alterations were confirmed in HFD mice and db/db mice, respectively using behavioral analysis, ELISA and western blotting assay. Furthermore, impacts of puerarin on depression-related symptoms and pathological changes were investigated in HFD mice.

RESULTS

The results showed that puerarin effectively alleviated the depression-like behaviors of HFD mice, down-regulated serum levels of corticosterone and IL-1β, while up-regulated the content of 5-hydroxytryptamine. Simultaneously, puerarin increased the number of hippocampal neurons in HFD mice, and suppressed the apoptosis of neurons to protect the hippocampal neuroplasticity. GLP-1R expression in hippocampus of HFD mice was enhanced by puerarin, which subsequently activated AMPK, CREB and BDNF/TrkB signaling to improve neuroplasticity. Importantly, our data indicated that puerarin had an advantage over fluoxetine or metformin in treating diabetes-induced depression.

CONCLUSION

Taken together, puerarin exerts anti-depressant-like effects on HFD diabetic mice, specifically by improving hippocampal neuroplasticity via GLP-1R/BDNF/TrkB signaling. Puerarin as a dietary supplement might be a potential candidate in intervention of diabetes with comorbid depression.

Incidence and Factors Associated with Hyperglycemia in Patients with First Hospitalization for Major Depression Disorder: A Large Cross-Sectional Sample

Purpose

Major depressive disorder (MDD) is a mood disorder characterized by persistent spontaneous depression and has a high rate of disability and mortality. There is a complex relationship between MDD and disorders of glucose metabolism, and our study aimed to investigate the prevalence and risk factors for hyperglycemia in patients with MDD who were hospitalized for the first times.

Patients and Methods

A total of 981 first-time inpatients with MDD were recruited, socio-demographic information, anthropometric data, and biochemical parameters were collected for each participant. The 17-item Hamilton Assessment Scale for Depression (HAMD-17), the 14-item Hamilton Anxiety Scale (HAMA-14), the Positive Syndrome Scale (PSS), and Clinical General Impressions Inventory-Severity of Illness (CGI-SI) scores were used to assess patients' clinical symptoms.

Results

The prevalence of hyperglycemia was 9.28% among patients with MDD who were hospitalized for the first time. Compared to the non-hyperglycemic subgroup, patients in the hyperglycemic subgroup were found to have more extensive and significant demographic and clinical characteristics, higher levels of metabolism-related parameters, and more severe psychological and psycho-pathological symptoms. Age, thyroid stimulating hormone (TSH), triglycerides (TG) were risk factors for hyperglycemia in MDD patients, while course of disease was a protective factor.

Conclusion

The study findings suggest that the prevalence of hyperglycemia is not high in patients with MDD who are hospitalized for the first time. The risk variables for predicting hyperglycemia include age, TSH and TG. The above three factors and course of disease have good combined diagnostic ability for hyperglycemia.

Diabetes mellitus type 2 as an underlying, comorbid or consequent state of mental disorders

Somatic disturbances that occur in parallel with psychiatric diseases are a major challenge in clinical practice. Various factors contribute to the development of mental and somatic disorders. Type 2 diabetes mellitus (T2DM) is a significant health burden worldwide, and the prevalence of diabetes in adults is increasing. The comorbidity of diabetes and mental disorders is very common. By sharing a bidirectional link, both T2DM and mental disorders influence each other in various manners, but the exact mechanisms underlying this link are not yet elucidated. The potential mechanisms of both mental disorders and T2DM are related to immune and inflammatory system dysfunction, oxidative stress, endothelial dysfunction, and metabolic disturbances. Moreover, diabetes is also a risk factor for cognitive dysfunction that can range from subtle diabetes-associated cognitive decline to pre-dementia and dementia. A complex re-lationship between the gut and the brain also represents a new therapeutic approach since gut-brain signalling pathways regulate food intake and hepatic glucose production. The aim of this minireview is to summarize and present the latest data on mutual pathogenic pathways in these disorders, emphasizing their complexity and interweaving. We also focused on the cognitive performances and changes in neurodegenerative disorders. The importance of implementing integrated approaches in treating both of these states is highlighted, along with the need for individual therapeutic strategies.

Risk of type 2 diabetes mellitus between adolescents with antidepressant-resistant and antidepressant-responsive depression: A cohort study of 15,651 adolescents

BACKGROUND

Whether response to antidepressants is related to the risk of developing type 2 diabetes mellitus (T2DM) in adolescents with depression remains unknown.

METHODS

This study used the Taiwan National Health Insurance Research Database to enroll 1739 adolescents with antidepressant-resistant depression, 6956 with antidepressant-responsive depression, and 6956 controls between 2001 and 2010, with an end-of-2011 follow-up. Physician-diagnosed T2DM was identified at follow-up. T2DM-related risk factors, namely hypertension, dyslipidemia, and obesity, were assessed and controlled for as confounding factors.

RESULTS

Adolescents with antidepressant-resistant depression (hazard ratio [HR], 95 % confidence interval [CI]: 4.62, 2.75-7.75) and those with antidepressant-responsive depression (HR, 95 % CI: 3.06, 1.98-4.72) had a higher risk of developing T2DM at follow-up than did the control group. Those with antidepressant-resistant depression were more likely to receive a diagnosis of T2DM (HR, 95 % CI: 1.51, 1.04-2.19) later in life than were those with antidepressant-responsive depression.

DISCUSSION

Clinicians should closely monitor factors related to T2DM, such as fasting blood sugar, in high-risk populations, especially in adolescents with antidepressant-resistant depression.

The salt-inducible kinases inhibitor HG-9-91-01 exhibits antidepressant-like actions in mice exposed to chronic unpredictable mild stress

Major depressive disorder is a frequently occurring neuropsychiatric disorder throughout the world. However, the limited and delayed therapeutic efficacy of monoaminergic medications has led to intensive research efforts to develop novel antidepressants. We have previously demonstrated that hippocampal salt-inducible kinase 2 (SIK2) plays a role in the pathogenesis of depression via regulating the downstream CREB-regulated transcription coactivator 1 (CRTC1)-cAMP response element-binding protein (CREB)-brain derived neurotrophic factor (BDNF) pathway. HG-9-91-01 is a potent and selective inhibitor of salt-inducible kinases (SIKs). The present study aims to explore whether HG-9-91-01 has antidepressant-like actions in male C57BL/6J mice. The chronic unpredictable mild stress (CUMS) model of depression, various behavioral tests, western blotting, co-immunoprecipitation, immunofluorescence, stereotactic infusion, and viral-mediated genetic knockdown were used together. It was found that hippocampal infusion of HG-9-91-01 induced significant antidepressant-like effects in the CUMS model, accompanied with preventing the enhancement of CUMS on the hippocampal SIK2 expression and cytoplasmic translocation of CRTC1. HG-9-91-01 treatment also reversed the decreasing effects of CUMS on the BDNF signaling cascade and adult neurogenesis in the hippocampus. Moreover, the antidepressant-like actions of HG-9-91-01 in mice required the hippocampal CRTC1-CREB-BDNF pathway. In conclusion, HG-9-91-01 has potential of being a novel antidepressant candidate.

Clinical pharmacological innovation in the treatment of depression

INTRODUCTION

Deficiencies in standard of care antidepressants are driving novel drug discovery. A new age of antidepressant medications has emerged with the introduction of rapid-acting antidepressants with efficacy in treatment-resistant patients.

AREAS COVERED

The newly approved medicines and those in clinical development for major depressive disorder (MDD) are documented in this scoping review of newly approved and emerging antidepressants. Compounds are evaluated for clinical efficacy, tolerability, and safety and compared to those of standard of care medicines.

EXPERT OPINION

A new age of antidepressant discovery relies heavily on glutamatergic mechanisms. New medicines based upon the model of ketamine have been delivered and are in clinical development. Rapid onset and the ability to impact treatment-resistant depression, raises the question of the best first-line medicines for patients. Drugs with improvements in tolerability are being investigated (e.g. mGlu_2/3 receptor antagonists, AMPA receptor potentiators, and novel NMDA receptor modulators). Multiple companies are working toward the identification of novel psychedelic drugs where the requirement for psychedelic activity is not fully known. Gaps still exist - methods for matching patients with specific medicines are needed, and medicines for the prevention of MDD and its disease progression need research attention.

Shared peripheral blood biomarkers for Alzheimer’s disease, major depressive disorder, and type 2 diabetes and cognitive risk factor analysis

Background

Alzheimer's disease (AD), type 2 diabetes mellitus (T2DM), and Major Depressive Disorder (MDD) have a higher incidence rate in modern society. Although increasing evidence supports close associations between the three, the mechanisms underlying their interrelationships remain elucidated.

Objective

The primary purpose is to explore the shared pathogenesis and the potential peripheral blood biomarkers for AD, MDD, and T2DM.

Methods

We downloaded the microarray data of AD, MDD, and T2DM from the Gene Expression Omnibus database and constructed co-expression networks by Weighted Gene Co-Expression Network Analysis to identify differentially expressed genes. We took the intersection of differentially expressed genes to obtain co-DEGs. Then, we performed GO and KEGG enrichment analysis on the common genes in the AD, MDD, and T2DM-related modules. Next, we utilized the STRING database to find the hub genes in the protein-protein interaction network. ROC curves were constructed for co-DEGs to obtain the most diagnostic valuable genes and to make drug predictions against the target genes. Finally, we conducted a present condition survey to verify the correlation between T2DM, MDD and AD.

Results

Our findings indicated 127 diff co-DEGs, 19 upregulated co-DEGs, and 25 down-regulated co-DEGs. Functional enrichment analysis showed co-DEGs were mainly enriched in signaling pathways such as metabolic diseases and some neurodegeneration. Protein-protein interaction network construction identified hub genes in AD, MDD and T2DM shared genes. We identified seven hub genes of co-DEGs, namely, SMC4, CDC27, HNF1A, RHOD, CUX1, PDLIM5, and TTR. The current survey results suggest a correlation between T2DM, MDD and dementia. Moreover, logistic regression analysis showed that T2DM and depression increased the risk of dementia.

Conclusion

Our work identified common pathogenesis of AD, T2DM, and MDD. These shared pathways might provide novel ideas for further mechanistic studies and hub genes that may serve as novel therapeutic targets for diagnosing and treating.

Potential therapeutic effect of NK1R antagonist in diabetic non-healing wound and depression

Diabetes is a global disease with huge impacts on patients due to its complications, among which non-healing wounds and depression are common and challenging. The neurokinin 1 receptor (NK1R) inhibitor, aprepitant has been broadly applied for an antidepressant effect in depressive patients. Recent literature has indicated a therapeutic effect of downregulation in NK1R to diabetes-related fracture, cardiomyopathy, gastroparesis, and ocular surface disorders. In this study, differential expression genes in diabetes and depression were analyzed based on several RNA sequencing datasets from the GEO database to confirm NK1R in the overlapping set. Interaction network and gene set enrichment analysis were subsequently conducted. As a result, NK1R-related genes took part in angiogenesis, epithelial-mesenchymal transition (EMT), collagen deposition, and inflammation in diabetes and depression. In vivo, the downregulation of NK1R was proved to promote vascular proliferation and enhance diabetic wound healing, which provides a potential therapeutic target for the management of diabetic non-healing wounds and depression.

Shared genetics and bidirectional causal relationships between type 2 diabetes and attention-deficit/hyperactivity disorder

Background

Type 2 diabetes (T2D) is a chronic metabolic disorder with high comorbidity with mental disorders. The genetic links between attention-deficit/hyperactivity disorder (ADHD) and T2D have yet to be elucidated.

Aims

We aim to assess shared genetics and potential associations between ADHD and T2D.

Methods

We performed genetic correlation, two-sample Mendelian randomisation and polygenic overlap analyses between ADHD and T2D. The genome-wide association study (GWAS) summary results of T2D (80 154 cases and 853 816 controls), ADHD2019 (20 183 cases and 35 191 controls from the 2019 GWAS ADHD dataset) and ADHD2022 (38 691 cases and 275 986 controls from the 2022 GWAS ADHD dataset) were used for the analyses. The T2D dataset was obtained from the DIAGRAM Consortium. The ADHD datasets were obtained from the Psychiatric Genomics Consortium. We compared genome-wide association signals to reveal shared genetic variation between T2D and ADHD using the larger ADHD2022 dataset. Moreover, molecular pathways were constructed based on large-scale literature data to understand the connection between ADHD and T2D.

Results

T2D has positive genetic correlations with ADHD2019 (r_g=0.33) and ADHD2022 (r_g=0.31). Genetic liability to ADHD2019 was associated with an increased risk for T2D (odds ratio (OR): 1.30, p<0.001), while genetic liability to ADHD2022 had a suggestive causal effect on T2D (OR: 1.30, p=0.086). Genetic liability to T2D was associated with a higher risk for ADHD2019 (OR: 1.05, p=0.001) and ADHD2022 (OR: 1.03, p<0.001). The polygenic overlap analysis showed that most causal variants of T2D are shared with ADHD2022. T2D and ADHD2022 have three overlapping loci. Molecular pathway analysis suggests that ADHD and T2D could promote the risk of each other through inflammatory pathways.

Conclusions

Our study demonstrates substantial shared genetics and bidirectional causal associations between ADHD and T2D.

Air pollution, genetic factors and the risk of depression

Both genetics and ambient air pollutants contribute to depression, but the degree to which genetic susceptibility modifies the effect of air pollution on depression remains unknown. We aimed to investigate the effect of the modification of genetic susceptibility on depression. Notably, 490,780 participants who were free of depression at baseline in the UK Biobank study were recruited from 2006 to 2010. A land use regression (LUR) model was performed to estimate the concentrations of particulate matter with diameters ranging from ≤2.5-≤10 μm (PM_2.5, PM_2.5-10 and PM₁₀), nitrogen dioxide (NO₂), and nitrogen oxides (NO_x). The International Classification of Diseases 10th Revision (ICD-10) code was used to identify depression cases. Cox proportional hazard models adjusted for covariates were used to investigate the association between ambient air pollutants and depression. Moreover, the polygenic risk score (PRS) was calculated to evaluate cumulative genetic effects, and additive interaction models were established to explore whether genetic susceptibility modified the effects of air pollutants on depression. PM_2.5, PM₁₀, NO₂ and NO_x exposure were significantly positively associated with the risk of depression, and the hazard ratios and 95 % confidence intervals for a 10-μg/m³ increase in PM_2.5, PM₁₀, NO₂ and NO_x concentrations were 2.12 (1.82, 2.47), 1.12 (1.03, 1.23), 1.07 (1.05, 1.10) and 1.04 (1.03, 1.05), respectively. Air pollutants and genetic variants exerted significant additive effects on the risk of depression (relative excess risk due to the interaction [RERI]: 0.15 for PM_2.5, 0.12 for PM₁₀, 0.10 for NO₂, and 0.12 for NO_x; attributable proportion due to the interaction [AP]: 0.12 for PM_2.5, 0.10 for PM₁₀, 0.08 for NO₂, and 0.09 for NO_x). Air pollution exposure was significantly associated with the risk of depression, and participants with a higher genetic risk were more likely to develop depression when exposed to high levels of air pollution.

The role of metformin as a treatment for neuropsychiatric illness

Advances in psychopharmacology have been significantly slower to evolve than in other disciplines of medicine and therefore investigation into novel therapeutic approaches is required. Additionally, concurrent metabolic conditions are prevalent among people with mental disorders. Metformin is a widely used hypoglycaemic agent that is now being studied for use beyond diabetes management. Evidence is emerging that metformin has multiple effects on diverse neurobiological pathways and consequently may be repurposed for treating mental illness. Metformin may have beneficial neuroimmunological, neuroplastic, neuro-oxidative and neuro-nitrosative effects across a range of psychiatric and neurodegenerative illnesses. Mechanisms include glucose lowering effects and effects on AMP-activated protein kinase (AMPK) signalling, however the best evidence for clinical benefit is through the glucose lowering effects, with other mechanisms less supported by the current evidence base. This narrative review aims to draw together the existing evidence for use of metformin as a psychopharmaceutical and present the role of metformin in the context of physical and psychiatric ill health, including metabolic, endocrinological and cancer domains. It not only has therapeutic potential in medical comorbidity but may have potential in core illness domains.

The molecular pathophysiology of depression and the new therapeutics

Major depressive disorder (MDD) is a highly prevalent and disabling disorder. Despite the many hypotheses proposed to understand the molecular pathophysiology of depression, it is still unclear. Current treatments for depression are inadequate for many individuals, because of limited effectiveness, delayed efficacy (usually two weeks), and side effects. Consequently, novel drugs with increased speed of action and effectiveness are required. Ketamine has shown to have rapid, reliable, and long-lasting antidepressant effects in treatment-resistant MDD patients and represent a breakthrough therapy for patients with MDD; however, concerns regarding its efficacy, potential misuse, and side effects remain. In this review, we aimed to summarize molecular mechanisms and pharmacological treatments for depression. We focused on the fast antidepressant treatment and clarified the safety, tolerability, and efficacy of ketamine and its metabolites for the MDD treatment, along with a review of the potential pharmacological mechanisms, research challenges, and future clinical prospects.

TINY IN SIZE, BIG IN IMPACT: EXTRACELLULAR VESICLES AS MODULATORS OF MOOD, ANXIETY AND NEURODEVELOPMENTAL DISORDERS

Extracellular Vesicles (EVs) are tiny vesicles used by cells as means of cellular communication, through which the function and state of a given cell can be changed. A body of evidence has suggested that EVs could be culprits in the development and progression of various types of diseases, including neurodegenerative diseases such as Multiple Sclerosis (MS) and Alzheimer's Disease (AD). Unsurprisingly, EVs have also been implicate in mood, anxiety and neurodevelopmental disorders, such as Major Depressive Disorder (MDD), anxiety disorder and Autism-Spectrum Disorder (ASD), respectively. Here, we review the state-of-art regarding the roles of EVs in the aforementioned diseases and focus on the mechanisms by which they can cause and worsen disease. Harnessing the knowledge of EVs is not only important to deliver different cargos to cells in a specific manner to treat these diseases, but also to establish reliable disease biomarkers, which will aid in the early disease diagnosis and treatment, increasing the chance of successful treatment.

How Microbes Affect Depression: Underlying Mechanisms via the Gut-Brain Axis and the Modulating Role of Probiotics

Accumulating evidence suggests that the gut microbiome influences the brain functions and psychological state of its host via the gut-brain axis, and gut dysbiosis has been linked to several mental illnesses, including major depressive disorder (MDD). Animal experiments have shown that a depletion of the gut microbiota leads to behavioral changes, and is associated with pathological changes, including abnormal stress response and impaired adult neurogenesis. Short-chain fatty acids such as butyrate are known to contribute to the up-regulation of brain-derived neurotrophic factor (BDNF), and gut dysbiosis causes decreased levels of BDNF, which could affect neuronal development and synaptic plasticity. Increased gut permeability causes an influx of gut microbial components such as lipopolysaccharides, and the resultant systemic inflammation may lead to neuroinflammation in the central nervous system. In light of the fact that gut microbial factors contribute to the initiation and exacerbation of depressive symptoms, this review summarizes the current understanding of the molecular mechanisms involved in MDD onset, and discusses the therapeutic potential of probiotics, including butyrate-producing bacteria, which can mediate the microbiota-gut-brain axis.

Intersections between Copper, β-Arrestin-1, Calcium, FBXW7, CD17, Insulin Resistance and Atherogenicity Mediate Depression and Anxiety Due to Type 2 Diabetes Mellitus: A Nomothetic Network Approach

Type 2 diabetes mellitus (T2DM) is frequently accompanied by affective disorders with a prevalence of comorbid depression of around 25%. Nevertheless, the biomarkers of affective symptoms including depression and anxiety due to T2DM are not well established. The present study delineated the effects of serum levels of copper, zinc, β-arrestin-1, FBXW7, lactosylceramide (LacCer), serotonin, calcium, magnesium on severity of depression and anxiety in 58 men with T2DM and 30 healthy male controls beyond the effects of insulin resistance (IR) and atherogenicity. Severity of affective symptoms was assessed using the Hamilton Depression and Anxiety rating scales. We found that 61.7% of the variance in affective symptoms was explained by the multivariate regression on copper, β-arrestin-1, calcium, and IR coupled with atherogenicity. Copper and LacCer (positive) and calcium and BXW7 (inverse) had significant specific indirect effects on affective symptoms, which were mediated by IR and atherogenicity. Copper, β-arrestin-1, and calcium were associated with affective symptoms above and beyond the effects of IR and atherogenicity. T2DM and affective symptoms share common pathways, namely increased atherogenicity, IR, copper, and β-arrestin-1, and lowered calcium, whereas copper, β-arrestin-1, calcium, LacCer, and FBXW7 may modulate depression and anxiety symptoms by affecting T2DM.