Assessment Causality in Associations Between Serum Uric Acid and Risk of Schizophrenia: A Two-Sample Bidirectional Mendelian Randomization Study

Positive Effects of Uric Acid on White Matter Microstructures and Treatment Response in Patients With Schizophrenia

BACKGROUND AND HYPOTHESIS

Schizophrenia involves microstructural changes in white matter (WM) tracts. Oxidative stress is a key factor causing WM damage by hindering oligodendrocyte development and myelin maturation. Uric acid (UA), an endogenous antioxidant, may protect against oxidative stress. We investigated the effect of UA on WM connectivity in antipsychotic-naive or -free patients with early- or chronic-stage schizophrenia.

STUDY DESIGN

A total of 192 patients with schizophrenia (122 recent-onset [ROS] and 70 chronic [CS]) and 107 healthy controls (HCs) participated in this study. Diffusion tensor imaging data and serum UA levels at baseline were obtained.

STUDY RESULTS

Fractional anisotropy was lower in the widespread WM regions across the whole brain, and diffusivity measures were higher in both schizophrenia groups than in HCs. The CS group showed lower diffusivity in some WM tracts than the ROS or HC groups. The linear relationship of serum UA levels with axial and mean diffusivity in the right frontal region was significantly different between schizophrenia stages, which was driven by a negative association in the CS group. WM diffusivity associated with serum UA levels correlated with 8-week treatment responses only in patients with CS, suggesting UA to be protective against long-term schizophrenia.

CONCLUSIONS

UA may protect against the WM damage associated with the progression of schizophrenia by reducing oxidative stress and supporting WM repair against oxidative damage. These results provide insights into the positive role of UA and may facilitate the development of novel disease-modifying therapies.

Bidirectional Mendelian randomization analysis investigating the genetic association between primary breast cancer and colorectal cancer

Purpose

With the advancement in early diagnosis and treatment, the prognosis for individuals diagnosed with breast cancer (BC) has improved significantly. The prognosis of primary breast cancer (PBC) survivors can be significantly influenced by the occurrence of colorectal cancer (CRC) as a secondary primary cancer (SPC). The objective of this study is to explore the possible genetic association between PBC and CRC, aiming to lay a groundwork for the development of preventive strategies against SPC-CRC following BC surgery.

Methods

We employed a bidirectional two-sample Mendelian randomization (MR) approach to thoroughly examine genetic instrumental variables (IVs) derived from genome-wide association studies (GWAS) conducted on PBC and CRC. And applied inverse variance weighted (IVW) and multiple other MR methods (weighted median, simple median, MR-PRESSO and MR-RAPS) to evaluate the association between the two cancers (PBC and CRC) at genetic level. Furthermore, the robustness of the findings was further confirmed through the utilization of the genetic risk score (GRS) method in a secondary analysis.

Results

Forward MR analysis, a total of 179 BC genetic IVs, 25 estrogen receptor-negative (ER-) genetic IVs and 135 ER-positive (ER+) genetic IVs were screened. Reverse MR analysis, 179 genetic IVs of CRC, 25 genetic IVs of colon cancer, 135 genetic IVs of rectal cancer, 25 genetic IVs of left colon cancer and 135 genetic IVs of right colon cancer were screened. IVW and other MR methods found no significant genetic association between PBC and CRC (P > 0.05). Subgroup analysis also showed that ER- BC and ER+ BC were not correlated with the occurrence of CRC (P > 0.05). The findings of the secondary analysis using GRS were consistent with those obtained from the primary analysis, thereby confirming the robustness and reliability of this study.

Conclusions

Our findings do not provide any evidence supporting the association between PBC and CRC at the genetic level. Further large-scale prospective studies are warranted to replicate our findings.

Bidirectional Mendelian randomization analysis of the genetic association between primary lung cancer and colorectal cancer

BACKGROUND

With the development and popularization of low-dose chest CT technology, the diagnosis and survival rates of patients with early lung cancer (LC) have significantly improved. The occurrence of colorectal cancer (CRC) as the second primary cancer (SPC) in primary lung cancer (PLC) survivors has become an essential factor affecting the prognosis of early LC. This study explored the potential association between PLC and CRC genetically, laying a foundation for developing SPC-CRC prevention strategies after primary early LC.

METHODS

Based on a two-sample bidirectional Mendelian randomization (MR) design, this study systematically screened genetic instrumental variables (IVs) based on the genome-wide association studies (GWAS) of PLC and CRC, applied inverse variance weighted (IVW) as the main method to assess the incidence association between the two cancers, and used a variety of other MR methods for supplementary analysis. Finally, the Genetic Risk Scores (GRS) method was used for secondary analysis to verify the results robustness further.

RESULTS

From LC to CRC forward MR analysis, 20 genetic IVs of overall LC, 15 genetic IVs of squamous cell lung carcinoma (LUSC), and 10 genetic IVs of adenocarcinoma of the lung (LUAD) were screened. In the reverse MR analysis from CRC to LC, 47 genetic IVs for overall CRC, 37 for colon cancer, and 25 for rectal cancer were screened. The IVW method and a variety of MR methods all found that overall LC and CRC were significantly associated at the genetic level. Subgroup analysis also showed that LUSC was associated with CRC. And the results of the GRS method were consistent with those of the main analysis, confirming the robustness of the study. Our MR study found an association between LC and CRC, with an increased risk of SPC-CRC following PLC, especially LUSC. Our study provides an essential basis for the precise prevention of SPC-CRC after PLC, suggesting that we should pay more attention to the population with a history of PLC in clinical work, and pay close attention to the incidence of SPC-CRC, and carry out intervention and treatment as soon as possible.

Smoking, alcohol consumption, diabetes, body mass index, and peptic ulcer risk: A two-sample Mendelian randomization study

Background: Observational evidence has shown that smoking, alcohol consumption, type 2 diabetes, and body mass index (BMI) are risk factors for peptic ulcer disease (PUD), including gastric ulcer (GU) and duodenal ulcer (DU). However, the observed associations may be confounding factors. Herein, we use Mendelian randomization (MR) to examine causal associations such as smoking, alcohol, type 2 diabetes, BMI, and risks of PUD. Methods: We used 8,17,41,325,82, 231, and 616 identified genetic variants as proxies for age of smoking initiation (AgeSmk), smoking cessation (SmkCes, current/former), number of cigarettes smoked per day (CigDay), smoking status (SmkIni, ever/never), alcohol consumption, type 2 diabetes, and BMI to obtain unconfounded effect estimates on the GU and DU levels among 452,264 participants from the Gene ATLAS. The causal relationship was estimated by using inverse-variance weighted (IVW) as the main method. Sensitivity analysis includes Cochran's Q test, the MR-Egger test, MR pleiotropy residual sum and outlier (MR-PRESSO), and MR-robust adjusted profile score (MR-RAPS). In addition, secondary MR analysis was conducted within summary data using genetic risk scores (GRSs) as instrumental variables (IVs). Results: In our two-sample MR analyses, genetic predisposition to smoking (SmkInit) and BMI were associated with an increased risk of GU. The beta values were 0.0035 (95% CI, 0.0021, 0.0049, p = 1.56E-06) for smoking (SmkInit) and 0.0021 (95% CI, 0.0009, 0.0033, p = 0.0008) for BMI. Genetic predisposition to smoking (SmkInit) and higher genetically predicted BMI were associated with an increased risk of DU. The beta values of DU were 0.0029 (95% CI, 0.0017, 0.0041, p = 2.43E-06) for smoking (SmkInit) and 0.0018 (95% CI, 0.0007, 0.0029, p = 0.001) for BMI. No other causal association between smoking (AgeSmk, CigDay, and SmkCes), alcohol consumption, type 2 diabetes, and GU or DU was observed. Consistent results were obtained in sensitivity analyses. Furthermore, the GRS approach showed similar results in the several MR methods. Conclusion: These findings do not support a causal role of AgeSmk, CigDay, SmkCes, alcohol consumption, and type 2 diabetes in the development of GU and DU. However, it is confirmed that SmkInit and BMI have a causal part in the development of GU and DU.

Role of uric acid as a biomarker of cognitive function in schizophrenia during maintenance period

Background

Previous studies involving uric acid (UA) in some specialized disease populations have found that high UA is associated with enhanced patient function. The mechanism to explain this association may be that UA, an important antioxidant, exerts neuroprotective effects. Patients with schizophrenia (SCZ) have severe oxidative stress abnormalities, and cognitive impairment is a major obstacle to their rehabilitation. Only few studies have been conducted on UA and cognitive impairment in SCZ. This study aims to clarify the relationship between UA and cognitive impairment and explore whether UA could be used as a potential biological marker of cognition in SCZ during maintenance period.

Methods

A total of 752 cases of SCZ during maintenance period from Baiyun Jingkang Hospital were included. Cognition was measured using the Mini-Mental State Examination scale. UA was measured using the Plus method. The participants were grouped on the basis of UA to evaluate the association of cognition with low-normal (3.50-5.07 mg/dL for men, 2.50-4.19 mg/dL for women), middle-normal (5.07-6.39 mg/dL for men, 4.19-5.18 mg/dL for women), high-normal (6.39-7.00 mg/dL for men, 5.18-6.00 mg/dL for women), and high (>7.00 mg/dL for men, >6.00 mg/dL for women) levels of UA. Multiple logistic regression and linear regression models and restricted cubic spline (RCS) were utilized to evaluate the relationship.

Results

Uric acid was positively associated with cognitive function. Subgroup analyses showed that high UA was associated with enhanced cognition in participants with low anticholinergic cognitive burden (ACB).

Conclusion

Uric acid may be used as a simple objective biological indicator to assess cognition in SCZ during maintenance period.

Serum uric acid is not associated with major depressive disorder in European and South American populations: a meta-analysis and two-sample bidirectional Mendelian Randomization study

OBJECTIVE

Although previous epidemiological studies have demonstrated that serum uric acid (SUA) is associated with major depressive disorder (MDD), these analyses are prone to biases. Here, we applied the Mendelian Randomization approach to determine whether SUA is causally associated with MDD.

METHODS

We conducted a meta-analysis to evaluate the relationship between SUA and MDD, then applied summary data from the Global Urate Genetics Consortium and the Psychiatric Genomics Consortium to estimate their causal effect using a two-sample bidirectional Mendelian Randomization (MR) analysis. Thereafter, the causal effect was further researched using genetic risk scores (GRS) as instrumental variables (IVs).

RESULTS

Results of a meta-analysis of articles comprising 6975 and 13,589 MDD patients and controls, respectively, revealed that SUA was associated with MDD (SMD = -0.690, 95% CI: -0.930 to -0.440, I2 = 97.4%, P < 0.001). In addition, the five MR methods revealed no causal relationship existed between SUA and MDD, which corroborated the results obtained via the GRS approach.

CONCLUSION

This paper found little evidence that this association between SUA and MDD is casual. Genetically, there was no significant causal association between SUA and MDD.

Applications of Mendelian randomization in psychiatry: a comprehensive systematic review

Psychiatric diseases exact a heavy socioeconomic toll, and it is particularly difficult to identify their risk factors and causative mechanisms due to their multifactorial nature, the limited physiopathological insight, the many confounding factors, and the potential reverse causality between the risk factors and psychiatric diseases. These characteristics make Mendelian randomization (MR) a precious tool for studying these disorders. MR is an analytical method that employs genetic variants linked to a certain risk factor, to assess if an observational association between that risk factor and a health outcome is compatible with a causal relationship. We report the first systematic review of all existing applications and findings of MR in psychiatric disorders, aiming at facilitating the identification of risk factors that may be common to different psychiatric diseases, and paving the way to transdiagnostic MR studies in psychiatry, which are currently lacking. We searched Web of Knowledge, Scopus, and Pubmed databases (until 3 May 2022) for articles on MR in psychiatry. The protocol was preregistered in PROSPERO (CRD42021285647). We included methodological details and results from 50 articles, mainly on schizophrenia, major depression, autism spectrum disorders, and bipolar disorder. While this review shows how MR can offer unique opportunities for unraveling causal links in risk factors and etiological elements of specific psychiatric diseases and transdiagnostically, some methodological flaws in the existing literature limit reliability of results and probably underlie their heterogeneity. We highlight perspectives and recommendations for future works on MR in psychiatry.

Inflammatory bowel disease and risk of coronary heart disease : A Mendelian randomization study

BACKGROUND

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), has been reported to be associated with an increased risk of coronary heart disease (CHD); however, the causal link between IBD and CHD is unclear. We performed Mendelian randomization (MR) analysis to investigate the association between genetically predicted IBD and CHD risk.

METHODS

Exposure summary data were obtained from genome-wide association studies (GWAS) with cohorts of IBD (12,882 cases and 21,770 controls), UC (6968 cases and 20,464 controls), and CD (5956 cases and 14,927 controls) of European descent to identify single nucleotide polymorphisms (SNPs) as instrumental variables. Outcome summary data were obtained from a meta-analysis of 22 GWAS including 22,233 cases and 64,762 controls of European descent. To estimate MR, four methods were used, including inverse variance-weighted (IVW), MR-Egger, simple mode, and weighted median methods. Sensitivity analysis was also performed. The Bonferroni method was used to correct the bias of multiple testing.

RESULTS

Three sets of SNPs (69 SNPs of IBD, 40 SNPs of UC, and 58 SNPs of CD) were used to estimate the causal effect between genetically predicted IBD and CHD. Using the IVW method, we found that no causal relationship between genetically predicted IBD and CHD after Bonferroni correction, and there was no causal relationship between UC/CD and the development of CHD. No evidence of significant heterogeneity and pleiotropy was found.

CONCLUSION

The results of this study suggested that genetically predicted IBD may have no causal effect on CHD risk in a population with European ancestry.

Schizophrenia and Alarmins

Schizophrenia, consisting of a group of severe psychiatric disorders with a complex etiology, is a leading cause of disability globally. Due to the lack of objective indicators, accurate diagnosis and selection of effective treatments for schizophrenia remain challenging. The association between schizophrenia and alarmins levels has been proposed for many years, but without solid evidence. Alarmins are prestored molecules that do not require processing and can be released upon cell death or damage, making them an ideal candidate for an early initiator of inflammation. Immunological biomarkers seem to be related to disease progression and treatment effectiveness. Several studies suggest strong associations among the high-mobility group box 1 protein (HMGB1), interleukin-1α, interleukin-33, S100B, heat-shock proteins, and uric acid with schizophrenic disorders. The purpose of this review is to discuss the evidence of central and peripheral immune findings in schizophrenia, their potential causes, and the effects of immunomodulatory therapies on symptoms and outline potential applications of these markers in managing the illness. Although there are currently no effective markers for diagnosing or predicting treatment effects in patients with schizophrenia, we believe that screening immune-inflammatory biomarkers that are closely related to the pathological mechanism of schizophrenia can be used for early clinical identification, diagnosis, and treatment of schizophrenia, which may lead to more effective treatment options for people with schizophrenia.

Childhood maltreatment increases the suicidal risk in Chinese schizophrenia patients

OBJECTIVES

Childhood trauma might be a modifiable risk factor among adults with serious mental illness. However, the correlation of child trauma and suicide is unclear, which were cited most frequently as the biggest challenge to schizophrenia (SCZ) patients in China. We aim to study relationships between child trauma and suicide in SCZ patients of different disease stages.

METHODS

Ninety-one participants were included and divided into two groups, namely, first-episode group (n = 46), relapsed group (n = 45). The Positive and Negative Syndrome Scale was used to evaluate the severity of psychotic symptoms. The Beck's Suicide Intent Scale and The Nurses' Global Assessment of Suicide Risk were conducted by patient self-report to assess suicide symptom. The childhood trauma questionnaire was used to estimate severity of traumatic stress experienced during childhood.

RESULTS

Childhood trauma and different dimensions of suicide were significantly higher in the relapsed group than first-episode group (P < 0.01, respectively). BMI has a significant positive relationship with recent psychosocial stress (β = 0.473, t = 3.521, P < 0.001) in first-episode group. As in relapsed group, BMI has a positive effect between severe mental illness and suicide ideation (β = 0.672, t = 5.949, P < 0.001; β = 0.909, t = 2.463, P < 0.001), Furthermore, emotional neglect presented positively related to the suicide risk and proneness to suicidal behavior (β = 0.618, t = 5.518, P < 0.001; β = 0.809, t = 5.356, P < 0.001).

CONCLUSION

Relapsed group of patients had significantly more severe childhood trauma, recent psychosocial stress, suicidal risk and proneness to suicidal behavior. BMI and emotional neglect are unique predictors for different dimensions of suicide.

Post-weaning social isolation impairs purinergic signaling in rat brain

Early life stressors, such as social isolation (SI), can disrupt brain development contributing to behavioral and neurochemical alterations in adulthood. Purinergic receptors and ectonucleotidases are key regulators of brain development in embryonic and postnatal periods, and they are involved in several psychiatric disorders, including schizophrenia. The extracellular ATP drives purinergic signaling by activating P2X and P2Y receptors and it is hydrolyzed by ectonucleotidases in adenosine, which activates P1 receptors. The purpose of this study was to investigate if SI, a rodent model used to replicate abnormal behavior relevant to schizophrenia, impacts purinergic signaling. Male Wistar rats were reared from weaning in group-housed or SI conditions for 8 weeks. SI rats exhibited impairment in prepulse inhibition and social interaction. SI presented increased ADP levels in cerebrospinal fluid and ADP hydrolysis in the hippocampus and striatum synaptosomes. Purinergic receptor expressions were upregulated in the prefrontal cortex and downregulated in the hippocampus and striatum. A_2A receptors were differentially expressed in SI prefrontal cortex and the striatum, suggesting distinct roles in these brain structures. SI also presented decreased ADP, adenosine, and guanosine levels in the cerebrospinal fluid in response to D-amphetamine. Like patients with schizophrenia, uric acid levels were prominently increased in SI rats after D-amphetamine challenge. We suggest that the SI-induced deficits in prepulse inhibition might be related to the SI-induced changes in purinergic signaling. We provide new evidence that purinergic signaling is markedly affected in a rat model relevant to schizophrenia, pointing out the importance of purinergic system in psychiatry conditions.

Uric Acid Potential Role in Systemic Inflammation and Negative Symptoms After Acute Antipsychotic Treatment in Schizophrenia

Uric acid (UA) has been shown to have neuroprotective or neurotoxic properties, in relation to specific tissues and diseases that have been studied. Previous studies provided contradictory results on the role of UA in schizophrenia as a neurodegenerative disorder. The aim of this brief report was an additional analysis of UA sera levels in different phases of schizophrenia. Here, 86 patients with first-episode psychosis (FEP) vs. 45 patients with schizophrenia in relapse (SC in relapse) vs. 35 healthy control subjects (HC) were studied before and 1 month after antipsychotic therapy. Further, we aimed to explore the possible correlation of UA with scores presenting clinical features and with serum concentrations of the proinflammatory cytokines interleukin (IL)-6 and IL-17. When comparing the data between all three groups, we did not find significant differences in UA levels, either before or after the applied therapy. Also, comparing sera concentrations of UA in every single group, the analysis did not reveal statistically significant differences between FEP patients, but statistically, a significant difference was found in SC in relapse before and after treatment (334.71 ± 116.84 vs. 289.37 ± 109.15 μmol/L, p = 0.05). Uric acid serum levels correlated with negative sub-score (p = 0.001, r = 0.306), general sub-score (p = 0.015, r = 0.236), and total PANSS score (p = 0.009, r = 0.3) after 1 month of therapy. We have established a statistically significant positive correlation between serum concentrations of UA and IL-6 in exacerbation (p = 0.01, r = 0.220) and with IL-17 after treatment and in the stabilization of psychosis (p = 0.01, r = 0.34), suggesting potential cascades in different phases of schizophrenia that potentiate inflammation.

Effects of Adiponectin on T2DM and Glucose Homeostasis: A Mendelian Randomization Study

PURPOSE

The associations of adiponectin with type 2 diabetes mellitus (T2DM), glucose homeostasis (including β-cell function index (HOMA-β), insulin resistance (HOMA-IR), fasting insulin (FI) and fasting glucose (FG)) have reported in epidemiological studies. However, the previous observational studies are prone to biases, such as reverse causation and residual confounding factors. Herein, a Mendelian Randomization (MR) study was conducted to determine whether causal effects exist among them.

MATERIALS AND AND METHODS

Two-sample MR analyses and multiple sensitivity analyses were performed using the summary data from the ADIPOGen consortium, MAGIC Consortium, and a meta-analysis of GWAS with a considerable sample of T2DM (62,892 cases and 596,424 controls of European ancestry). We got eight valid genetic variants to predict the causal effect among adiponectin and T2DM and glucose homeostasis after excluding the probable invalid or pleiotropic variants.

RESULTS

Adiponectin was not associated with T2DM (odds ratio (OR) = 1.004; 95% confidence interval (CI): 0.740, 1.363) when using MR Egger after removing the invalid SNPs, and the results were consistent when using the other four methods. Similar results existed among adiponectin and HOMA-β, HOMA-IR, FI, FG.

CONCLUSION

Our MR study revealed that adiponectin had no causal effect on T2DM and glucose homeostasis and that the associations among them in observational studies may be due to confounding factors.