Inflammatory Diseases, Inflammatory Biomarkers, and Alzheimer Disease: An Observational Analysis and Mendelian Randomization

Genome‑wide association study and polygenic risk scores predict psoriasis and its shared phenotypes in Taiwan

Psoriasis is a chronic inflammatory dermatological disease, and there is a lack of understanding of the genetic factors involved in psoriasis in Taiwan. To establish associations between genetic variations and psoriasis, a genome‑wide association study was performed in a cohort of 2,248 individuals with psoriasis and 67,440 individuals without psoriasis. Using the ingenuity pathway analysis software, biological networks were constructed. Human leukocyte antigen (HLA) diplotypes and haplotypes were analyzed using Attribute Bagging (HIBAG)‑R software and chi‑square analysis. The present study aimed to assess the potential risks associated with psoriasis using a polygenic risk score (PRS) analysis. The genetic association between single nucleotide polymorphisms (SNPs) in psoriasis and various human diseases was assessed by phenome‑wide association study. METAL software was used to analyze datasets from China Medical University Hospital (CMUH) and BioBank Japan (BBJ). The results of the present study revealed 8,585 SNPs with a significance threshold of P<5x10‑8, located within 153 genes strongly associated with the psoriasis phenotype, particularly on chromosomes 5 and 6. This specific genomic region has been identified by analyzing the biological networks associated with numerous pathways, including immune responses and inflammatory signaling. HLA genotype analysis indicated a strong association between HLA‑A*02:07 and HLA‑C*06:02 in a Taiwanese population. Based on our PRS analysis, the risk of psoriasis associated with the SNPs identified in the present study was quantified. These SNPs are associated with various dermatological, circulatory, endocrine, metabolic, musculoskeletal, hematopoietic and infectious diseases. The meta‑analysis results indicated successful replication of a study conducted on psoriasis in the BBJ. Several genetic loci are significantly associated with susceptibility to psoriasis in Taiwanese individuals. The present study contributes to our understanding of the genetic determinants that play a role in susceptibility to psoriasis. Furthermore, it provides valuable insights into the underlying etiology of psoriasis in the Taiwanese community.

The association between lipid parameters and erectile dysfunction: a two-sample Mendelian randomization and case-control study

PURPOSE

Lipid parameters have been shown to have significant predictive value for cardiovascular disease, but few studies have evaluated their correlation with erectile dysfunction (ED) in young men.

METHODS

The case-control study encompassed 186 young ED patients (ages 20-40) and 186 healthy controls. Lipid parameters, including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), TC/HDL ratio, TG/HDL ratio, and LDL-C/HDL-C ratio, were assessed in all participants. The International Index of Erectile Function (IIEF-5) scores were collected for all participants to evaluate erectile status. Multivariate logistic regression analysis was utilized to appraise the association of lipid-related parameters with ED. Single-nucleotide polymorphisms (SNPs) significantly correlated with lipid parameters (TC, TG, LDL-C, HDL-C) were selected from genome-wide association studies (GWAS) as instrumental variables (IV) (P < 5.0 × 10-8). Summary data for ED was gathered from a GWAS with a sample size of (n = 17,353 cases/28,210 controls). The inverse variance weighted (IVW) method was employed as the primary mendelian randomization (MR) analysis method to assess causal effects. Causal estimates were represented as odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

Results from the case-control study revealed that, when compared with the control group, levels of LDL-C, TG, UA, LDL-C/HDL-C, TG/HDL-C, and TC/HDL-C in the ED group were significantly elevated (P < 0.01), while HDL-C was significantly decreased (P < 0.01) in the ED group. Multivariate logistic regression analysis indicated LDL-C/HDL-C as a risk factor for both the incidence and severity of ED (P < 0.001). Two-sample MR analysis demonstrated no significant causal correlation between lipid parameters-LDL-C (OR, 0.98, 95% CI, 0.88-1.08, P = 0.616), HDL-C (OR, 1.07, 95% CI: 0.96-1.19, P = 0.249), TC (OR, 1.07, 95% CI, 0.96-1.18, P = 0.208), TG (OR, 0.98, 95% CI, 0.80-1.13, P = 0.579) -and an increased risk of ED (all P > 0.05).

CONCLUSIONS

The case-control analysis ascertained a significant association between LDL-C, HDL-C, LDL-C/HDL-C, and ED and its severity. However, results from the MR study do not support a causal role of lipid parameters in ED.

Experimental colitis in young Tg2576 mice accelerates the onset of an Alzheimer's-like clinical phenotype

Systemic inflammation and neuroinflammation affect the natural course of the sporadic form of Alzheimer's disease (AD), as supported by epidemiological and preclinical data, and several epidemiological studies indicate a higher prevalence of AD in patients with inflammatory bowel disease. In this study, we explored whether colitis induced by dextran sulfate sodium (DSS) in young, presymptomatic/preplaque mice worsens and/or anticipates age-dependent cognitive impairment in Tg2576, a widely used mouse model of AD. We demonstrated that DSS colitis induced in young Tg2576 mice anticipates the onset age of learning and memory deficit in the Morris water maze test. To explore potential mechanisms behind the acceleration of cognitive decline in Tg2576 mice by DSS colitis, we focused on gut microbiota, systemic inflammation and neuroinflammation markers. We observed a Firmicutes/Bacteroidetes ratio change in Tg2576 DSS animals comparable to that of elderly Tg2576 mice, suggesting accelerated microbiota aging in Tg2576 DSS mice, a change not observed in C57BL6 DSS mice. We also observed substantial differences between Tg2576 and WT mice in several inflammation and neuroinflammation-related parameters as early as 3 months of age, well before plaque deposition, a picture which evolved rapidly (between 3 and 5.5 months of age) in contrast to Tg2576 and WT littermates not treated with DSS. In detail, following induction of DSS colitis, WT and Tg2576 mice exhibited contrasting features in the expression level of inflammation-evoked astrocyte-associated genes in the hippocampus. No changes in microglial features occurred in the hippocampus between the experimental groups, whereas a reduced glial fibrillary acidic protein immunoreactivity was observed in Tg2576 vs. WT mice. This finding may reflect an atrophic, "loss-of-function" profile, further exacerbated by DSS where a decreased of GFAP mRNA expression level was detected. In conclusion, we suggest that as-yet unidentified peripheral mediators evoked by DSS colitis and involving the gut-brain axis emphasize an astrocyte "loss-of-function" profile present in young Tg2576 mice, leading to impaired synaptic morphological and functional integrity as a very early sign of AD.

Exposure to autoimmune disorders increases Alzheimer's disease risk in a multi-site electronic health record analysis

Molecular studies of Alzheimer's disease (AD) implicate potential links between autoimmunity and AD, but the underlying clinical relationships between these conditions remain poorly understood. Electronic health records (EHRs) provide an opportunity to determine the clinical risk relationship between autoimmune disorders and AD and understand whether specific disorders and disorder subtypes affect AD risk at the phenotypic level in human populations. We evaluated relationships between 26 autoimmune disorders and AD across retrospective observational case-control and cohort study designs in the EHR systems at UCSF and Stanford. We quantified overall and sex-specific AD risk effects that these autoimmune disorders confer. We identified significantly increased AD risk in autoimmune disorder patients in both study designs at UCSF and at Stanford. This pattern was driven by specific autoimmunity subtypes including endocrine, gastrointestinal, dermatologic, and musculoskeletal disorders. We also observed increased AD risk from autoimmunity in both women and men, but women with autoimmune disorders continued to have a higher AD prevalence than men, indicating persistent sex-specificity. This study identifies autoimmune disorders as strong risk factors for AD that validate across several study designs and EHR databases. It sets the foundation for exploring how underlying autoimmune mechanisms increase AD risk and contribute to AD pathogenesis.

T cell-mediated skin-brain axis: Bridging the gap between psoriasis and psychiatric comorbidities

Psoriasis, a chronic inflammatory skin condition, is often accompanied by psychiatric comorbidities such as anxiety, depression, suicidal ideation, and other mental disorders. Psychological disorders may also play a role in the development and progression of psoriasis. The intricate interplay between the skin diseases and the psychiatric comorbidities is mediated by the 'skin-brain axis'. Understanding the mechanisms underlying psoriasis and psychiatric comorbidities can help improve the efficacy of treatment by breaking the vicious cycle of diseases. T cells and related cytokines play a key role in the pathogenesis of psoriasis and psychiatric diseases, and are crucial components of the 'skin-brain axis'. Apart from damaging the blood-brain barrier (BBB) directly, T cells and secreted cytokines could interact with the hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS) to exacerbate skin diseases or mental disorders. However, few reviews have systematically summarized the roles and mechanisms of T cells in the interaction between psoriasis and psychiatric comorbidities. In this review, we discussed several key T cells and their roles in the 'skin-brain axis', with a focus on the mechanisms underlying the interplay between psoriasis and mental commodities, to provide data that might help develop effective strategies for the treatment of both psoriasis and psychiatric comorbidities.

Genetic overlap between Alzheimer's disease and immune-mediated diseases: an atlas of shared genetic determinants and biological convergence

The occurrence of immune disease comorbidities in Alzheimer's disease (AD) has been observed in both epidemiological and molecular studies, suggesting a neuroinflammatory basis in AD. However, their shared genetic components have not been systematically studied. Here, we composed an atlas of the shared genetic associations between 11 immune-mediated diseases and AD by analyzing genome-wide association studies (GWAS) summary statistics. Our results unveiled a significant genetic overlap between AD and 11 individual immune-mediated diseases despite negligible genetic correlations, suggesting a complex shared genetic architecture distributed across the genome. The shared loci between AD and immune-mediated diseases implicated several genes, including GRAMD1B, FUT2, ADAMTS4, HBEGF, WNT3, TSPAN14, DHODH, ABCB9, and TNIP1, all of which are protein-coding genes and thus potential drug targets. Top biological pathways enriched with these identified shared genes were related to the immune system and cell adhesion. In addition, in silico single-cell analyses showed enrichment of immune and brain cells, including neurons and microglia. In summary, our results suggest a genetic relationship between AD and the 11 immune-mediated diseases, pinpointing the existence of a shared however non-causal genetic basis. These identified protein-coding genes have the potential to serve as a novel path to therapeutic interventions for both AD and immune-mediated diseases and their comorbidities.

Rheumatoid arthritis is a protective factor against Alzheimer's disease: a bidirectional two-sample Mendelian randomization study

BACKGROUND

Epidemiological evidence suggests that there is an association between rheumatoid arthritis (RA) and Alzheimer's disease (AD). However, the causal relationship between RA and AD remains unclear. Therefore, this study aimed to investigate the causal relationship between RA and AD.

METHODS

Using publicly available genome-wide association study datasets, bidirectional two-sample Mendelian randomization (TSMR) was performed using the inverse-variance weighted (IVW), weighted median, MR‒Egger regression, simple mode, and weighted mode methods.

RESULTS

The results of MR for the causal effect of RA on AD (IVW, odds ratio [OR] = 0.959, 95% confidence interval [CI]: 0.941-0.978, P = 2.752E-05; weighted median, OR = 0.960, 95% CI: 0.937-0.984, P = 0.001) revealed a causal association between genetic susceptibility to RA and an increased risk of AD. The results of MR for the causal effect of AD on RA (IVW, OR = 0.978, 95% CI: 0.906-1.056, P = 0.576; weighted median, OR = 0.966, 95% CI: 0.894-1.043, P = 0.382) indicated that there was no causal association between genetic susceptibility to AD and an increased risk of RA.

CONCLUSIONS

The results of this two-way two-sample Mendelian randomization analysis revealed a causal association between genetic susceptibility to RA and a reduced risk of AD but did not reveal a causal association between genetic susceptibility to AD and an increased or reduced risk of RA.

Association between inflammatory bowel disease and all-cause dementia: A two-sample Mendelian randomization study

BACKGROUND

Numerous observational studies have documented a correlation between inflammatory bowel disease (IBD) and an increased risk of dementia. However, the causality of their associations remains elusive.

AIM

To assess the causal relationship between IBD and the occurrence of all-cause dementia using the two-sample Mendelian randomization (MR) method.

METHODS

Genetic variants extracted from the large genome-wide association study (GWAS) for IBD (the International IBD Genetics Consortium, n = 34652) were used to identify the causal link between IBD and dementia (FinnGen, n = 306102). The results of the study were validated via another IBD GWAS (United Kingdom Biobank, n = 463372). Moreover, MR egger intercept, MR pleiotropy residual sum and outlier, and Cochran's Q test were employed to evaluate pleiotropy and heterogeneity. Finally, multiple MR methods were performed to estimate the effects of genetically predicted IBD on dementia, with the inverse variance wei-ghted approach adopted as the primary analysis.

RESULTS

The results of the pleiotropy and heterogeneity tests revealed an absence of significant pleiotropic effects or heterogeneity across all genetic variants in outcome GWAS. No evidence of a causal effect between IBD and the risk of dementia was identified in the inverse variance weighted [odds ratio (OR) = 0.980, 95%CI : 0.942-1.020, P value = 0.325], weighted median (OR = 0.964, 95%CI : 0.914-1.017, P value = 0.180), and MR-Egger (OR = 0.963, 95%CI : 0.867-1.070, P value = 0.492) approaches. Consistent results were observed in validation analyses. Reverse MR analysis also showed no effect of dementia on the development of IBD. Furthermore, MR analysis suggested that IBD and its subtypes did not causally affect all-cause dementia and its four subtypes, including dementia in Alzheimer's disease, vascular dementia, dementia in other diseases classified elsewhere, and unspecified dementia.

CONCLUSION

Taken together, our MR study signaled that IBD and its subentities were not genetically associated with all-cause dementia or its subtypes. Further large prospective studies are warranted to elucidate the impact of intestinal inflammation on the development of dementia.

Inflammation, Autoimmunity and Neurodegenerative Diseases, Therapeutics and Beyond

Neurodegenerative disease (ND) incidence has recently increased due to improved life expectancy. Alzheimer's (AD) or Parkinson's disease (PD) are the most prevalent NDs. Both diseases are poly genetic, multifactorial and heterogenous. Preventive medicine, a healthy diet, exercise, and controlling comorbidities may delay the onset. After the diseases are diagnosed, therapy is needed to slow progression. Recent studies show that local, peripheral and age-related inflammation accelerates NDs' onset and progression. Patients with autoimmune disorders like inflammatory bowel disease (IBD) could be at higher risk of developing AD or PD. However, no increase in ND incidence has been reported if the patients are adequately diagnosed and treated. Autoantibodies against abnormal tau, β amyloid and α- synuclein have been encountered in AD and PD and may be protective. This discovery led to the proposal of immune-based therapies for AD and PD involving monoclonal antibodies, immunization/ vaccines, pro-inflammatory cytokine inhibition and anti-inflammatory cytokine addition. All the different approaches have been analysed here. Future perspectives on new therapeutic strategies for both disorders are concisely examined.

Effects of obesity-related anthropometric indices and body composition on erectile dysfunction mediated by coronary artery disease: A Mendelian randomization study

BACKGROUND

The causal relationship between obesity-related anthropometric indicators/body composition and erectile dysfunction has not been established in previous observational studies.

METHOD

We screened single nucleotide polymorphisms significantly associated with exposure from genome-wide association studies as instrumental variables (p < 5.0 × 10-8 ). The summary statistics for erectile dysfunction were collected from a genome-wide association study with a sample size of 223,805. Exposure and outcome populations included are of European ancestry. We used univariate and multivariate Mendelian randomization (i) to investigate the causal relationship between genetically predicted obesity-related anthropometric indicators/body composition and erectile dysfunction and (ii) to examine the mediating role of coronary artery disease. Mendelian randomization analysis was conducted using an inverse variance weighted method. A series of sensitivity analyses validated the results of the Mendelian randomization analysis. Causal estimates are expressed as odds ratios with 95% confidence intervals.

RESULTS

Obesity-related anthropometric indicators/body composition were associated with an increased risk of erectile dysfunction in univariate Mendelian randomization analyses. For the 1-SD increase in body mass index, the odds ratio was 1.841 (95% confidence interval: 1.049-1.355, p = 0.006). For the 1-SD increase in waist circumference and hip circumference, the odds ratios were 1.275 (95% confidence interval: 1.101-1.478, p = 0.001) and 1.156 (95% confidence interval: 1.015-1.317, p = 0.009), respectively. The odds ratio for the 1-SD increase in whole body fat mass was 1.221 (95% confidence interval: 1.047-1.388, p = 0.002). For the 1-SD increase in leg fat percentage (left and right), the odds ratios were 1.256 (95% confidence interval: 1.006-1.567, p = 0.044) and 1.285 (95% confidence interval: 1.027-1.608, p = 0.028), respectively. For the 1-SD increase in leg fat mass (left and right), the odds ratios were 1.308 (95% confidence interval: 1.108-1.544, p = 0.001) and 1.290 (95% confidence interval: 1.091-1.524, p = 0.003), respectively. For the 1-SD increase in arm fat mass (left and right), the odds ratios were 1.269 (95% confidence interval: 1.113-1.447, p < 0.001) and 1.254, respectively. Multivariate Mendelian randomization analysis showed that after adjusting for coronary artery disease, some genetic predispositions to obesity-related anthropometric indicators and body composition were still associated with an increased risk of erectile dysfunction. Significant associations were found for waist circumference-erectile dysfunction (odds ratio: 1.218, 95% confidence interval: 1.036-1.432), leg fat percentage (left)-erectile dysfunction (odds ratio: 1.245, 95% confidence interval: 1.035-1.497), leg fat mass (left)-erectile dysfunction (odds ratio: 1.264, 95% confidence interval: 1.051-1.521), arm fat mass (right)-erectile dysfunction (odds ratio: 1.186, 95% confidence interval: 1.024-1.373), and arm fat mass (left)-erectile dysfunction (odds ratio: 1.17, 95% confidence interval: 1.018-1.360). Meanwhile, coronary artery disease mediated the effects of fat on erectile dysfunction, and the proportion of coronary artery disease-mediated cases ranged from 10% to 22%.

CONCLUSION

There is a potential causal relationship between obesity-related anthropometric indicators/body composition and erectile dysfunction. Higher waist circumference, leg fat percentage, and arm fat mass may increase the risk of erectile dysfunction, and coronary artery disease partly mediates this overall effect. Understanding the causal relationship between obesity and erectile dysfunction and the mediating role of coronary artery disease may provide more information for erectile dysfunction intervention and prevention strategies.

causalCmprsk: An R package for nonparametric and Cox-based estimation of average treatment effects in competing risks data

BACKGROUND AND OBJECTIVE

Competing risks data arise in both observational and experimental clinical studies with time-to-event outcomes, when each patient might follow one of the multiple mutually exclusive competing paths. Ignoring competing risks in the analysis can result in biased conclusions. In addition, possible confounding bias of the treatment-outcome relationship has to be addressed, when estimating treatment effects from observational data. In order to provide tools for estimation of average treatment effects on time-to-event outcomes in the presence of competing risks, we developed the R package causalCmprsk. We illustrate the package functionality in the estimation of effects of a right heart catheterization procedure on discharge and in-hospital death from observational data.

METHODS

The causalCmprsk package implements an inverse probability weighting estimation approach, aiming to emulate baseline randomization and alleviate possible treatment selection bias. The package allows for different types of weights, representing different target populations. causalCmprsk builds on existing methods from survival analysis and adapts them to the causal analysis in non-parametric and semi-parametric frameworks.

RESULTS

The causalCmprsk package has two main functions: fit.cox assumes a semiparametric structural Cox proportional hazards model for the counterfactual cause-specific hazards, while fit.nonpar does not impose any structural assumptions. In both frameworks, causalCmprsk implements estimators of (i) absolute risks for each treatment arm, e.g., cumulative hazards or cumulative incidence functions, and (ii) relative treatment effects, e.g., hazard ratios, or restricted mean time differences. The latter treatment effect measure translates the treatment effect from probability into more intuitive time domain and allows the user to quantify, for example, by how many days or months the treatment accelerates the recovery or postpones illness or death.

CONCLUSIONS

The causalCmprsk package provides a convenient and useful tool for causal analysis of competing risks data. It allows the user to distinguish between different causes of the end of follow-up and provides several time-varying measures of treatment effects. The package is accompanied by a vignette that contains more details, examples and code, making the package accessible even for non-expert users.

Neuropathologic evaluation of cerebrovascular disease in patients with rheumatoid arthritis

OBJECTIVES

Active RA has been associated with an increased risk of both cardiovascular and peripheral vascular disease. We aimed to compare cerebrovascular changes in patients with and without RA, both with and without a neuropathologic diagnosis of neurodegenerative disease.

METHODS

Patients with RA (n = 32) who died and underwent autopsy between 1994 and 2021 were matched to non-RA controls (n = 32) on age, sex and level of neurodegenerative proteinopathy. Routine neuropathologic examination was performed at the time of autopsy. Cerebrovascular disease severity was evaluated using modified Kalaria and Strozyk scales. Clinical dementia diagnoses were manually collected from patients' medical records.

RESULTS

Prior to death, 15 (47%) RA patients and 14 (44%) controls were diagnosed with dementia; 9 patients in each group (60% and 64%, respectively) had Alzheimer's disease. The prevalence of cerebral amyloid angiopathy, microinfarcts, infarcts or strokes was found to be similar between groups. Patients with RA were more likely to have more severe vascular changes in the basal ganglia by Kalaria scale (P = 0.04), but not in other brain areas. There were no significant differences in the presence of large infarcts, lacunar infarcts or leukoencephalopathy by Strozyk scale. Among patients with RA and no clinical diagnosis of dementia, the majority had mild-moderate cerebrovascular abnormalities, and a subset of patients had Alzheimer's disease neuropathologic changes.

CONCLUSION

In this small series of autopsies, patients with and without RA had largely similar cerebrovascular pathology when controlling for neurodegenerative proteinopathies, although patients with RA exhibited more pronounced cerebrovascular disease in the basal ganglia.

Genetic overlap between Alzheimer's disease and immune-mediated diseases: An atlas of shared genetic determinants and biological convergence

The occurrence of immune disease comorbidities in Alzheimer's disease (AD) has been observed in both epidemiological and molecular studies, suggesting a neuroinflammatory basis in AD. However, their shared genetic components have not been systematically studied. Here, we composed an atlas of the shared genetic associations between 11 immune-mediated diseases and AD by analyzing genome-wide association studies (GWAS) summary statistics. Our results unveiled a significant genetic overlap between AD and 11 individual immune-mediated diseases despite negligible genetic correlations, suggesting a complex shared genetic architecture distributed across the genome. The shared loci between AD and immune-mediated diseases implicated several genes, including GRAMD1B, FUT2, ADAMTS4, HBEGF, WNT3, TSPAN14, DHODH, ABCB9 and TNIP1, all of which are protein-coding genes and thus potential drug targets. Top biological pathways enriched with these identified shared genes were related to the immune system and cell adhesion. In addition, in silico single-cell analyses showed enrichment of immune and brain cells, including neurons and microglia. In summary, our results suggest a genetic relationship between AD and the 11 immune-mediated diseases, pinpointing the existence of a shared however non-causal genetic basis. These identified protein-coding genes have the potential to serve as a novel path to therapeutic interventions for both AD and immune-mediated diseases and their comorbidities.

Cerebrospinal fluid inflammatory biomarkers for disease progression in Alzheimer's disease and multiple sclerosis: a systematic review

Inflammatory processes are involved in the pathophysiology of both Alzheimer's disease (AD) and multiple sclerosis (MS) but their exact contribution to disease progression remains to be deciphered. Biomarkers are needed to define pathophysiological processes of these disorders, who may increasingly co-exist in the elderly generations of the future, due to the rising prevalence in both and ameliorated treatment options with improved life expectancy in MS. The purpose of this review was to provide a systematic overview of inflammatory biomarkers, as measured in the cerebrospinal fluid (CSF), that are associated with clinical disease progression. International peer-reviewed literature was screened using the PubMed and Web of Science databases. Disease progression had to be measured using clinically validated tests representing baseline functional and/or cognitive status, the evolution of such clinical scores over time and/or the transitioning from one disease stage to a more severe stage. The quality of included studies was systematically evaluated using a set of questions for clinical, neurochemical and statistical characteristics of the study. A total of 84 papers were included (twenty-five for AD and 59 for MS). Elevated CSF levels of chitinase-3-like protein 1 (YKL-40) were associated with disease progression in both AD and MS. Osteopontin and monocyte chemoattractant protein-1 were more specifically related to disease progression in AD, whereas the same was true for interleukin-1 beta, tumor necrosis factor alpha, C-X-C motif ligand 13, glial fibrillary acidic protein and IgG oligoclonal bands in MS. We observed a broad heterogeneity of studies with varying cohort characterization, non-disclosure of quality measures for neurochemical analyses and a lack of adequate longitudinal designs. Most of the retrieved biomarkers are related to innate immune system activity, which seems to be an important mediator of clinical disease progression in AD and MS. Overall study quality was limited and we have framed some recommendations for future biomarker research in this field.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42021264741.

The gut-lung axis: Mendelian randomization identifies a causal association between inflammatory bowel disease and interstitial lung disease

BACKGROUND

Previous studies have suggested the association between interstitial lung disease (ILD) and inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC).

OBJECTIVES

To examine the potential bidirectional causal relationship between IBD and ILD using the Mendelian randomization (MR) method.

METHODS

We obtained the data from the genome-wide association studies (GWASs) in European individuals for IBD (25,042 cases and 34,915 controls) and ILD (21,806 cases and 196,986 controls) from the IEU GWAS database. We screened for instrumental variables based on the three assumptions of MR. The two-sample bidirectional MR analysis was performed using the inverse-variance weighted method and multiple sensitivity analyses.

RESULTS

Genetic liability to IBD was significantly associated with an increased ILD risk (odds ratio (OR) = 1.20, 95% confidence interval (CI) = 1.17-1.24, p = 3.67E-33). When considering the IBD subtypes, ILD risk was associated with genetic liability to both CD (OR = 1.14, 95% CI = 1.10-1.17, p = 1.91E-17) and UC (OR = 1.16, 95% CI = 1.12-1.21, p = 3.51E-13). There was weak evidence for the effect of genetic liability to ILD on IBD (OR = 1.32, 95% CI = 0.99-1.76, p = 0.062), CD (OR = 1.25, 95% CI = 1.00-1.55, p = 0.046), and UC (OR = 1.47, 95%CI = 1.01-2.14, p = 0.046).

CONCLUSION

The results indicate a strong causal effect of IBD (including CD and UC) on ILD.

Mental Illnesses in Inflammatory Bowel Diseases: mens sana in corpore sano

Background and aims: Inflammatory bowel diseases (IBD) are chronic disorders associated with a reduced quality of life, and patients often also suffer from psychiatric comorbidities. Overall, both mood and cognitive disorders are prevalent in chronic organic diseases, especially in the case of a strong immune component, such as rheumatoid arthritis, multiple sclerosis, and cancer. Divergent data regarding the true incidence and prevalence of mental disorders in patients with IBD are available. We aimed to review the current evidence on the topic and the burden of mental illness in IBD patients, the role of the brain-gut axis in their co-existence, and its implication in an integrated clinical management. Methods: PubMed was searched to identify relevant studies investigating the gut-brain interactions and the incidence and prevalence of psychiatric disorders, especially of depression, anxiety, and cognitive dysfunction in the IBD population. Results: Among IBD patients, there is a high prevalence of psychiatric comorbidities, especially of anxiety and depression. Approximately 20-30% of IBD patients are affected by mood disorders and/or present with anxiety symptoms. Furthermore, it has been observed that the prevalence of mental illnesses increases in patients with active intestinal disease. Psychiatric comorbidities continue to be under-diagnosed in IBD patients and remain an unresolved issue in the management of these patients. Conclusions: Psychiatric illnesses co-occurring in IBD patients deserve acknowledgment from IBD specialists. These comorbidities highly impact the management of IBD patients and should be studied as an adjunctive therapeutic target.