Reconsidering the reasons for heightened inflammation in major depressive disorder

Genetic predisposition to high BMI increases risk of early life respiratory infections and episodes of severe wheeze and asthma

BACKGROUND

High body mass index (BMI) is an established risk factor for asthma, but the underlying mechanisms remain unclear.

OBJECTIVE

To increase understanding of the BMI-asthma relationship by studying the association between genetic predisposition to higher BMI and asthma, infections and other asthma traits during childhood.

METHODS

Data were obtained from the two ongoing Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts. Polygenic risk scores for adult BMI were calculated for each child. Replication was done in the large-scale register-based Integrative Psychiatric Research (iPSYCH) cohort using data on hospitalisation for asthma and infections.

RESULTS

In the COPSAC cohorts (n=974), the adult BMI polygenic risk score was significantly associated with lower respiratory tract infections (incidence rate ratio (IRR) 1.20, 95% CI 1.08-1.33, false discovery rate p-value (pFDR)=0.005) at age 0-3 years and episodes of severe wheeze (IRR 1.30, 95% CI 1.06-1.60, pFDR=0.04) at age 0-6 years. Lower respiratory tract infections partly mediated the association between the adult BMI polygenic risk score and severe wheeze (proportion mediated: 0.59, 95% CI 0.28-2.24, p-value associated with the average causal mediation effect (pACME)=2e-16). In contrast, these associations were not mediated through the child's current BMI and the polygenic risk score was not associated with an asthma diagnosis or reduced lung function up to age 18 years. The associations were replicated in iPSYCH (n=114 283), where the adult BMI polygenic risk score significantly increased the risk of hospitalisations for lower respiratory tract infections and wheeze or asthma throughout childhood to age 18 years.

CONCLUSION

Children with genetic predisposition to higher BMI had increased risk of lower respiratory tract infections and severe wheeze, independent of the child's current BMI. These results shed further light on the complex relationship between body mass BMI and asthma.

Genetically predicted processed meat, red meat intake, and risk of mental disorders: A multivariable Mendelian randomization analysis

BACKGROUND

Previous observational studies have highlighted potential links between the consumption of processed meat and red meat (such as pork, mutton, and beef intake) and the occurrence of mental disorders. However, it is unclear whether a causal association exists. Therefore, we employed the Mendelian randomization (MR) study to investigate the causal effects of genetically predicted processed meat and red meat on mood disorders (MD), anxiety disorders (AD), and major depressive disorder (MDD).

METHODS

Genetic instruments for processed and red meat were selected from the Genome-Wide Association Study (GWAS) of the UK Biobank Study. Their associations with MD (42,746 cases 254,976), AD (35,385 cases and 254,976 controls), and MDD (38,225 cases and 299,886 controls) were obtained from the FinnGen Consortium. The inverse variance weighted (IVW) method was the primary method for two-sample MR analysis. Additionally, we employed complementary analysis to assess the robustness of our MR findings (eg, MR Egger and weighted median). We also conducted multiple sensitivity analyses to investigate horizontal pleiotropy and heterogeneity. Moreover, we performed a univariate and multivariable MR (MVMR) study to evaluate these associations.

RESULTS

In our univariate MR analysis, we observed that genetically predicted beef intake was associated with a reduced risk of MD [odds ratio (OR) = 0.403, 95 % confidence interval (CI) = 0.246-0.659; PIVW = 4.428 × 10-5], AD (OR = 0.443, 95 % CI = 0.267-0.734; PIVW = 1.563 × 10-3), and MDD (OR = 0.373, 95 % CI = 0.216-0.643; PIVW = 3.878 × 10-4). After adjusting for processed meat, pork, and mutton intake in the MVMR analysis, the protective association of beef intake against MD and MDD remained. However, there was no substantial evidence indicating a significant causal relationship between processed meat, pork, and mutton intake and the occurrence of mental disorders. Furthermore, our sensitivity analysis revealed no significant evidence of horizontal pleiotropy.

CONCLUSION

These findings support a causal relationship between genetically predicted beef intake and reducing the risk of MD and MDD.

Childhood maltreatment influences adult brain structure through its effects on immune, metabolic, and psychosocial factors

Childhood maltreatment (CM) leads to a lifelong susceptibility to mental ill-health which might be reflected by its effects on adult brain structure, perhaps indirectly mediated by its effects on adult metabolic, immune, and psychosocial systems. Indexing these systemic factors via body mass index (BMI), C-reactive protein (CRP), and rates of adult trauma (AT), respectively, we tested three hypotheses: (H1) CM has direct or indirect effects on adult trauma, BMI, and CRP; (H2) adult trauma, BMI, and CRP are all independently related to adult brain structure; and (H3) childhood maltreatment has indirect effects on adult brain structure mediated in parallel by BMI, CRP, and AT. Using path analysis and data from N = 116,887 participants in UK Biobank, we find that CM is related to greater BMI and AT levels, and that these two variables mediate CM's effects on CRP [H1]. Regression analyses on the UKB MRI subsample (N = 21,738) revealed that greater CRP and BMI were both independently related to a spatially convergent pattern of cortical effects (Spearman's ρ = 0.87) characterized by fronto-occipital increases and temporo-parietal reductions in thickness. Subcortically, BMI was associated with greater volume, AT with lower volume and CPR with effects in both directions [H2]. Finally, path models indicated that CM has indirect effects in a subset of brain regions mediated through its direct effects on BMI and AT and indirect effects on CRP [H3]. Results provide evidence that childhood maltreatment can influence brain structure decades after exposure by increasing individual risk toward adult trauma, obesity, and inflammation.

Limited evidence of a shared genetic relationship between C-reactive protein levels and cognitive function in older UK adults of European ancestry

Introduction

Previous studies have shown associations between cognitive function and C-reactive protein (CRP) levels in older adults. Few studies have considered the extent to which a genetic predisposition for higher CRP levels contributes to this association.

Methods

Data was analyzed from 7,817 UK participants aged >50 years as part of the PROTECT study, within which adults without dementia completed a comprehensive neuropsychological battery. We constructed a polygenic risk score (PRS-CRP) that explained 9.61% of the variance in serum CRP levels (p = 2.362 × 10-7) in an independent cohort. Regressions were used to explore the relationship between PRS-CRP and cognitive outcomes.

Results

We found no significant associations between PRS-CRP and any cognitive measures in the sample overall. In older participants (>62 years), we observed a significant positive association between PRS-CRP and self-ordered search score (i.e., spatial working memory).

Conclusion

Whilst our results indicate a weak positive relationship between PRS-CRP and spatial working memory that is specific to older adults, overall, there appears to be no strong effects of PRS-CRP on cognitive function.

Plasma complement C3 and C3a are increased in major depressive disorder independent of childhood trauma

BACKGROUND

Dysregulated complement system is linked to pathophysiology of major depressive disorder (MDD). Childhood trauma has been associated with an increased incidence of adult depression via a putative mechanism of immune activation. This study aimed to measure and compare peripheral levels of complement C3, C3a, C1q and C-reactive protein (CRP) in MDD patients and healthy controls and explore the relationship between these molecule levels and childhood trauma history in the participants.

METHODS

The participants were 49 medication-free MDD patients and 45 healthy controls. All participants were asked to finish the Childhood Trauma Questionnaire, followed by blood sampling for measurement of plasma complement C3, C3a, C1q and CRP by means of enzyme-linked immunosorbent assay.

RESULTS

Peripheral plasma concentration of C3 and C3a in medication-free MDD group was significantly higher than that in the healthy controls; whereas the concentration of plasma C1q and CRP in depressed patients was comparable to that in healthy controls. All these inflammatory factors were not associated to childhood trauma experience in patients with MDD.

CONCLUSION

Our data suggest that complement C3 and C3a may be implicated in the pathophysiology of MDD, although traumatic childhood experiences were not associated with the circulating levels of complement C3, C3a, C1q and CRP.

The relationship of life-course patterns of adiposity with type 2 diabetes, depression, and their comorbidity in the Northern Finland Birth Cohort 1966

OBJECTIVES

Type 2 diabetes (T2D) and comorbid depression challenges clinical management particularly in individuals with overweight. We aim to explore the shared etiology, via lifecourse adiposity, between T2D and depression.

METHODS

We used data from birth until 46years from Northern Finland Birth Cohort 1966 (n = 6,372; 53.8% females). We conducted multivariate analyses on three outcomes: T2D (4.2%), depression (19.2%) and as comorbidity (1.8%). We conducted (i) Path analysis to clarify time-dependent body mass index (BMI) related pathways, including BMI polygenic risk scores (PRS); and (ii) Cox regression models to assess whether reduction of overweight between 7years and 31years influence T2D, depression and/or comorbidity. The models were tested for covariation with sex, education, smoking, physical activity, and diet score.

RESULTS

The odd ratios (OR) of T2D in individuals with depression was 1.68 [95% confidence interval (CI): 1.34-2.11], and no change in estimate was observed when adjusted for covariates. T2D and comorbidity showed similar patterns of relationships in the path analyses (P < 0.001). The genetic risk for obesity (PRS BMI) did not show direct effect on T2D or comorbidity in adulthood but indirectly through measures of adiposity in early childhood and mid-adulthood in the path analysis (P < 0.001). Having early-onset of overweight at 7years and 31years showed highest risk of T2D (OR 3.8, 95%CI 2.4-6.1) and comorbidity (OR 5.0, 95%CI 2.7-9.5), with mild-to-moderate attenuation with adjustments. Depression showed no significant associations.

CONCLUSIONS

We found evidence for overweight since childhood as a risk factor for T2D and co-morbidity between T2D and depression, influenced moderately by lifestyle factors in later life. However, no shared early life adiposity related risk factors were observed between T2D and depression when assessed independently in this Finnish setting.

Proteome-wide Mendelian randomization identifies causal links between blood proteins and severe COVID-19

In November 2021, the COVID-19 pandemic death toll surpassed five million individuals. We applied Mendelian randomization including >3,000 blood proteins as exposures to identify potential biomarkers that may indicate risk for hospitalization or need for respiratory support or death due to COVID-19, respectively. After multiple testing correction, using genetic instruments and under the assumptions of Mendelian Randomization, our results were consistent with higher blood levels of five proteins GCNT4, CD207, RAB14, C1GALT1C1, and ABO being causally associated with an increased risk of hospitalization or respiratory support/death due to COVID-19 (ORs = 1.12-1.35). Higher levels of FAAH2 were solely associated with an increased risk of hospitalization (OR = 1.19). On the contrary, higher levels of SELL, SELE, and PECAM-1 decrease risk of hospitalization or need for respiratory support/death (ORs = 0.80-0.91). Higher levels of LCTL, SFTPD, KEL, and ATP2A3 were solely associated with a decreased risk of hospitalization (ORs = 0.86-0.93), whilst higher levels of ICAM-1 were solely associated with a decreased risk of respiratory support/death of COVID-19 (OR = 0.84). Our findings implicate blood group markers and binding proteins in both hospitalization and need for respiratory support/death. They, additionally, suggest that higher levels of endocannabinoid enzymes may increase the risk of hospitalization. Our research replicates findings of blood markers previously associated with COVID-19 and prioritises additional blood markers for risk prediction of severe forms of COVID-19. Furthermore, we pinpoint druggable targets potentially implicated in disease pathology.

Assessing the Evidence for Causal Associations Between Body Mass Index, C-Reactive Protein, Depression, and Reported Trauma Using Mendelian Randomization

Background

Traumatic experiences are described as the strongest predictors of major depressive disorder (MDD), with inflammation potentially mediating the association between trauma and symptom onset. However, several studies indicate that body mass index (BMI) exerts a large confounding effect on both inflammation and MDD.

Methods

First, we sought to replicate previously reported associations between these traits in a large subset of the UK Biobank, using regression models with C-reactive protein (CRP) and MDD and as the outcome variables in 113,481 and 30,137 individuals, respectively. Second, we ran bidirectional Mendelian randomization analyses between these traits to establish a potential causal framework between BMI, MDD, reported childhood trauma, and inflammation.

Results

Our phenotypic analyses revealed no association between CRP and MDD but did suggest a strong effect of BMI and reported trauma on both CRP (BMI: β = 0.43, 95% CI = 0.43-0.43, p ≤ .001; childhood trauma: β = 0.02, 95% CI = 0.00-0.03, p = .006) and MDD (BMI: odds ratio [OR] = 1.16, 95% CI = 1.14-1.19, p ≤ .001; childhood trauma: OR = 1.99, 95% CI = 1.88-2.11, p ≤ .001). Our Mendelian randomization analyses confirmed a lack of causal relationship between CRP and MDD but showed evidence consistent with a strong causal influence of higher BMI on increased CRP (β = 0.37, 95% CI = 0.36-0.39, p ≤ .001) and a bidirectional influence between reported trauma and MDD (OR trauma-MDD = 1.75, 95% CI = 1.49-2.07, p ≤ .001; OR MDD-trauma = 1.22, 95% CI = 1.18-1.27, p ≤ .001).

Conclusions

Our findings highlight the importance of controlling for both BMI and trauma when studying MDD in the context of inflammation. They also suggest that the experience of traumatic events can increase the risk for MDD and that MDD can increase the experience of traumatic events.

Relationship between CRP and depression: A genetically sensitive study in Sri Lanka

BACKGROUND

Previous studies have shown associations between major depression and C-reactive protein (CRP) levels. Few studies have considered the extent to which shared genetic and environmental factors contribute to this association, nor have they considered the relationship outside of European populations. We examined the association between CRP levels and depression and their aetiology in a Sri Lankan population.

METHODS

Data were collected from 2577 twins and 899 singletons in Colombo, Sri Lanka. Depression symptoms were assessed using the revised Beck Depression Inventory (BDI-II). High-sensitive CRP blood levels were assessed using immunoturbidimetry. Linear regressions were performed to test the association between CRP and depression. The heritability of CRP levels was estimated using Structural Equation Modelling.

RESULTS

CRP was significantly associated with BMI (p < 0.01) but not depression (p > 0.05). In males, variance in CRP levels was explained by shared environment (51% 95%CIs: 13-62) and non-shared environment (45% 95%CIs: 36-54). In contrast, in females, CRP variance was explained by genetic (41% 95%CIs: 10-52) and non-shared environment (56% 95%CIs: 47-67). A genetic correlation between CRP and BMI was observed in females only.

LIMITATIONS

CRP level was based on a single data collection point, longer term data collection would give a more accurate picture of an individual's state of inflammation.

CONCLUSIONS

The lack of association between depression and CRP strengthens the hypothesis that inflammation might contribute to the development of some, but not all types of depression. CRP levels were moderated by the environment, suggesting interventions aimed at reducing CRP levels and risk for inflammatory conditions, particularly in males.

Pathomechanisms of Vascular Depression in Older Adults

Depression in older individuals is a common complex mood disorder with high comorbidity of both psychiatric and physical diseases, associated with high disability, cognitive decline, and increased mortality The factors predicting the risk of late-life depression (LLD) are incompletely understood. The reciprocal relationship of depressive disorder and age- and disease-related processes has generated pathogenic hypotheses and provided various treatment options. The heterogeneity of depression complicates research into the underlying pathogenic cascade, and factors involved in LLD considerably differ from those involved in early life depression. Evidence suggests that a variety of vascular mechanisms, in particular cerebral small vessel disease, generalized microvascular, and endothelial dysfunction, as well as metabolic risk factors, including diabetes, and inflammation that may induce subcortical white and gray matter lesions by compromising fronto-limbic and other important neuronal networks, may contribute to the development of LLD. The "vascular depression" hypothesis postulates that cerebrovascular disease or vascular risk factors can predispose, precipitate, and perpetuate geriatric depression syndromes, based on their comorbidity with cerebrovascular lesions and the frequent development of depression after stroke. Vascular burden is associated with cognitive deficits and a specific form of LLD, vascular depression, which is marked by decreased white matter integrity, executive dysfunction, functional disability, and poorer response to antidepressive therapy than major depressive disorder without vascular risk factors. Other pathogenic factors of LLD, such as neurodegeneration or neuroimmune regulatory dysmechanisms, are briefly discussed. Treatment planning should consider a modest response of LLD to antidepressants, while vascular and metabolic factors may provide promising targets for its successful prevention and treatment. However, their effectiveness needs further investigation, and intervention studies are needed to assess which interventions are appropriate and effective in clinical practice.

Genetic risk for severe COVID-19 correlates with lower inflammatory marker levels in a SARS-CoV-2-negative cohort

Objectives

It remains unknown how inflammatory marker levels differ amongst individuals susceptible to coronavirus disease 2019 (COVID-19), prior to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the onset of the cytokine storm. We used genetic risk scores to model how susceptibility to severe COVID-19 correlates with baseline levels of 35 inflammatory markers, by testing their impact in a SARS-CoV-2-negative population cohort. Because of the established effects of age and body mass index on severe COVID-19 risk, we further considered how these variables interacted with genetic risk to affect inflammatory marker levels.

Methods

We accessed data on 406 SARS-CoV-2-negative individuals as part of a UK population study. Multiplex electrochemiluminescence methods were applied to blood serum, and 35 inflammatory markers were assayed. Corresponding genotype data, alongside results from a large genome-wide association study of severe COVID-19, allowed us to construct genetic risk scores and to test their impact on inflammatory protein levels.

Results

Our results revealed that a higher genetic risk for severe COVID-19 was associated with lower blood levels of interferon gamma (IFN-γ), vascular endothelial growth factor D (VEGF-D) and tumor necrosis factor alpha (TNF-α). Inflammatory profiles of those with high genetic risk increasingly diverge from the norm in association with age and obesity.

Conclusion

Our results support the theory that individuals at risk of severe COVID-19 have a deficient innate immunity marked by reduced levels of inflammatory markers at baseline, including IFN-γ, VEGF-D and TNF-α. We hypothesise that a secondary overactive adaptive immune response may subsequently explain the high levels of cytokines observed in SARS-CoV-2-positive COVID-19 patients.