Objective To explore the relationship between the gut microbiome (GM) and psoriasis using a two-sample two-way Mendelian randomization (MR) approach. Methods The forward analysis uses the gut microbiota as the exposure factor, and its genetic data are derived from the genome-wide association study dataset published by the MiBioGen consortium. Psoriasis was used as the outcome variable, and its genetic data were obtained from the UK Biobank. The reverse MR analysis, on the other hand, took psoriasis as the exposure and the specific gut microbiota taxonomic units identified in the forward analysis as the outcome variable. MR analysis was conducted using maximum likelihood, MR Egger regression, weighted median, inverse variance weighting (IVW), and weighted models to study the causal relationship between the gut microbiota and psoriasis. Then, sensitivity analyses including horizontal pleiotropy test, Cochran’s Q test, and leave-one-out analysis were used to evaluate the reliability of the results. Results A total of 51 single nucleotide polymorphisms from 5 fungi were included in the forward study. The forward IVW analysis results showed that, the class Mollicutes [odds ratio (OR)=1.003, 95% confidence interval (CI) (1.001, 1.006), P=0.004], genus Lachnospiraceae FCS020 group [OR=1.003, 95%CI (1.000, 1.006), P=0.041], and phylum Tenericutes [OR=1.003, 95%CI (1.001, 1.006), P=0.004] were causally associated with an increased risk of psoriasis. The family Victivallaceae [OR=0.998, 95%CI (0.997, 1.000), P=0.005] and order Pasteurellales [OR=0.998, 95%CI (0.996, 1.000), P=0.047] were also linked to a decreased risk of psoriasis. The results of the sensitivity analysis were robust. There was no evidence of a reverse causal relationship from psoriasis to the identified bacterial taxa found in the results of reverse MR analysis results. Conclusions The abundance of three species, class Mollicutes, genus Lachnospiraceae and phylum Tenericutes, may increase the risk of psoriasis. The abundance of two species, family Victivallaceae and order Pasteurellales may reduce the risk of psoriasis. These results provide new directions for the prevention and treatment of psoriasis in the future, but further research is needed to explore how the aforementioned microbiome affects the progression of psoriasis.
Objective To analyze whether there is a causal association between psoriasis and Alzheimer disease (AD) by a two-sample two-way Mendelian randomization (MR) method. Methods In the forward study, the single nucleotide polymorphisms (SNPs) associated with psoriasis were obtained from the comprehensive statistical data of the genome-wide association study database as the instrumental variables, and AD as the outcome; in the reverse study, the SNPs associated with AD were taken as instrumental variables, and psoriasis as the outcome. Using two-sample two-way MR analysis, the odds ratio (OR) value and 95% confidence interval (CI) of regression models, namely inverse variance weighted (IVW) method, MR-Egger regression method, weighted median method, simple pattern method, and weighted pattern method, were used to evaluate the causal relationship between psoriasis and AD. Cochran’s Q test was used to assess the heterogeneity of genetic instrumental variables, MR-Egger intercept method was used to test the horizontal pleiotropy of the assessment, “leave-one-out” method was used to assess the sensitivity of a SNP to the effect of causality, and the symmetry of funnel plot was observed to assess bias. Results A total of 19 SNPs associated with psoriasis were included as instrumental variables in the forward study. The IVW analysis of the forward study showed that there was a causal correlation between psoriasis and AD [OR=1.032, 95%CI (1.014, 1.051), P<0.001], and MR-Egger regression method [OR=1.042, 95%CI (1.012, 1.073), P=0.013], weighted median [OR=1.048, 95%CI (1.023, 1.074), P<0.001], and weighted model [OR=1.046, 95%CI (1.020, 1.073), P=0.002] all supported this result. Heterogeneity test (IVW result: Q=13.752, P=0.745; MR-Egger regression result: Q=13.134, P=0.727), MR-Egger intercept method (Egger intercept=–0.004, P=0.442), the results of “leave-one-out” method and funnel plot showed that the results of MR analysis were reliable. A total of 127 AD-related SNPs were included as instrumental variables in the reverse study. In reverse research, there was no evidence to support the AD could increase the risk of psoriasis (P>0.05). Heterogeneity test (IVW result: Q=232.496, P<0.001; MR-Egger regression result: Q=232.119, P<0.001) suggested heterogeneity, but MR-Egger intercept method (Egger intercept=0.003, P=0.652), the results of “leave-one-out” method and funnel plot showed that the results of MR analysis were reliable. Conclusion There is a causal association between psoriasis and AD, and psoriasis may increase the risk of AD.
Objective To analyze the potential causal relationship between sunscreen/ultraviolet protection and the risk of non-Hodgkin lymphoma using a two sample Mendelian randomization (MR) study method. Methods The summary data of genome-wide association study was used to select three types of non-Hodgkin lymphoma, namely diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, T/NK cell lymphoma, and sunscreen/ultraviolet protection highly correlated genetic loci, namely single nucleotide polymorphism (SNP), as instrumental variables. The reverse variance weighting method was used as the main method for MR analysis, MR Egger and MR-PRESO were used to detect level pleiotropy, and leave-one-out method was used for sensitivity analysis to ensure the robustness of the results. Results A total of 132 SNPs were included in the analysis. The results of the inverse variance weighted analysis showed that sunscreen/ultraviolet protection increased the incidence of DLBCL [odds ratio=2.439, 95% confidence interval (1.109, 5.362), P=0.027]. The heterogeneity test results showed that there was no heterogeneity in the causal relationship between sunscreen/ultraviolet protection and DLBCL (P>0.05). The results of the horizontal pleiotropy test showed that SNP did not exhibit horizontal pleiotropy (P>0.05). The leave-one-out method showed that no SNP with a significant impact on the results was found. There was no causal relationship between sunscreen/ultraviolet protection and follicular lymphoma and T/NK cell lymphoma. Conclusion There is a positive causal relationship between sunscreen/ultraviolet protection and the incidence of DLBCL.
Objective To explore the causal relationship between DNA copy number and the risk of Alzheimer disease (AD) using Mendelian randomization (MR) methods, as well as to investigate the potential mediating effects of immune cells. Methods The data related to 731 immune cell types, DNA copy number and AD from the Genome-Wide Association Study database were collected. A bidirectional MR analysis was conducted to explore the causal relationship between DNA copy number and AD, primarily using the inverse-variance weighted method and MR-Egger method. Additionally, a two-step mediation analysis was performed to identify potential mediating immune cells. Results A total of 134 single-nucleotide polymorphisms were included for bidirectional MR analysis. The MR methods results showed a negative causal relationship between DNA copy number and the risk of AD (P<0.05), while the reverse analysis showed no statistical significance. Sensitivity analysis confirmed the robustness of these results. The mediation analysis indicated that the immune cell phenotype (HVEM on CD45RA-CD4+) partially mediated the causal relationship between DNA copy numbers and the risk of AD, with a mediation effect proportion of 4.6%. Conclusion An increase in DNA copy numbers may reduce the risk of AD, and immune cells partially mediate this causal relationship.
ObjectiveA two-sample Mendelian randomization analysis was used to explore the causal associations between four basic body indices (basal metabolic rate, body fat percentage, BMI and hip circumference) and myasthenia gravis (MG). MethodsPooled gene-wide association study (GWAS) data were obtained from large publicly searchable databases, and four basic body indices were selected as the exposure factors and myasthenia gravis as the outcome factors, and single nucleotide polymorphisms (SNPs), which were strongly correlated with the phenotype of the exposure factors, were screened as the instrumental variables, and two-sample Mendelian randomization analyses were performed in order to assess the potential causal relationship between the exposure and the disease. ResultsInverse variance weighting (IVW) analysis showed that increased basal metabolic rate (OR=1.39, 95%CI 1.00 to 1.93, P=0.047), body fat percentage (OR=1.61, 95%CI 1.06 to 2.44, P=0.024), and hip circumference (OR=1.67, 95%CI 1.29 to 2.17, P<0.001) increased the risk of MG. But there was no significant causal relationship between BMI and MG. ConclusionBasal metabolic rate, body fat percentage and hip circumference have a positive causal relationship with MG, while BMI does not have a significant causal relationship with MG.
Lung cancer is a major cause of cancer mortality worldwide, but the risk factors contributing to its development are not yet fully elucidated. Deepening the understanding of the risk factors and potential complications associated with lung cancer is of significant importance for the prevention and treatment of this disease. Traditional observational clinical studies and randomized controlled trials, due to the influence of various factors, render the process of causal inference more complex and may introduce biases into the results. Compared to the traditional methods, Mendelian randomization (MR) has attracted an increasing amount of attention in lung cancer research, due to its simplicity of operation and effective control of confounding factors and reverse causality biases. This paper employs bibliometric methods to analyze the published MR studies related to lung cancer, and further summarizes and discusses the content of these studies. The findings indicate that traditional risk factors, such as lifestyle habits, nutrition, obesity, socioeconomic factors, environmental pollution, and inflammatory biomarkers, have been substantiated within the context of MR studies. Additionally, MR studies support the existence of causal relationships between lung cancer and certain gut microbiota, medications, and other systemic diseases. Despite the inherent limitations of MR studies, they nonetheless hold significant value in enhancing our comprehension of the etiology of lung cancer and in identifying potential therapeutic interventions.
ObjectiveTo investigate the causal relationship between gastroesophageal reflux disease (GERD) and obstructive sleep apnea (OSA) with its typical symptoms (snoring and daytime sleepiness) by using Mendelian randomization (MR). MethodsThe inverse-variance weighted method was used as the main analysis method to assess the causal effect. Sensitivity and pleiotropy analyses were carried out using leave-one-out and MR-Egger analysis, and then heterogeneity tests were conducted. ResultsIn the MR analysis, genetically predicted GERD was associated with a greater risk of OSA (IVW: OR=1.528, 95%CI 1.374 to 1.699, P=5.315E?15). Additional MR results were consistent with the IVW results, and no pleiotropy or heterogeneity was found. We also discovered a significant causal relationship between GRED and snoring (IVW: OR=0.959, 95%CI 0.949 to 0.969, P=1.507E?15), and daytime sleepiness (IVW: OR=1.024, 95%CI 1.021 to 1.036, P=4.580E?5), with no evidence of pleiotropy. ConclusionThe MR study supports a causal effect between GERD and OSA with its typical symptoms (daytime sleepiness and snoring).
Objective To explore the causal relationship between breast cancer and rotator cuff injury using bidirectional two-sample Mendelian randomization. Methods Instrumental variables for breast cancer and rotator cuff injury were extracted from published genome-wide association study data. The positive study used breast cancer as the exposure and rotator cuff injury as the outcome, with single nucleotide polymorphisms (SNPs) closely associated with both breast cancer and rotator cuff injury as genetic instrumental variables. The reverse study used rotator cuff injury as the exposure and breast cancer as the outcome, with SNPs closely associated with both breast cancer and rotator cuff injury as genetic instrumental variables. Bidirectional MR analysis was conducted using five models: inverse variance weighted (IVW), simple model, weighted median, weighted model, and MR-Egger to assess the causal relationship between breast cancer and rotator cuff injury. Cochran Q test was used to detect heterogeneity, MR-Egger to detect horizontal pleiotropy, and leave-one-out method for sensitivity analysis to ensure the robustness of the results. Results A total of 51 SNPs closely associated with breast cancer were included in the forward study. The results indicated a positive causal association between breast cancer and an increased risk of rotator cuff injury [IVW: odds ratio=1.08, 95% confidence interval (1.02, 1.12), P=0.014], with no evidence of heterogeneity in the causal relationship between breast cancer and rotator cuff injury (P>0.05). Horizontal pleiotropy test results showed no horizontal pleiotropy in the SNPs (P>0.05). Leave-one-out test results did not detect any SNP with a large impact on the results. In the reverse study, a total of 3 SNPs related to rotator cuff injury were included as instrumental variables. There was no strong evidence that rotator cuff injury had a causal effect on breast cancer incidence [IVW: odds ratio=0.95, 95% confidence interval (0.86, 1.05), P=0.334]. Conclusions There is a potential causal association between breast cancer and rotator cuff injury. Therefore, it is suggested to increase the screening for rotator cuff injury in breast cancer patients.
ObjectiveThyroid nodules are an exceptionally common thyroid disorder. Past studies suggested a possible link between thyroid diseases and breast neoplasms. However, few studies have delved into the causal relationship between thyroid nodules and breast neoplasms. This study conducted a Mendelian randomization (MR) analysis to further investigate the causal relationship between them. MethodsThis study was conducted using data sourced from genome-wide association study (GWAS) summary datasets. The study focused on thyroid nodules, benign breast tumors, and malignant breast cancers as the research objects, and relevant single nucleotide polymorphisms (SNPs) were selected as instrumental variables (IVs). The inverse-variance weighted (IVW) was primarily used to assess the causal relationship between thyroid nodules and breast neoplasms. Cochran’s Q test was employed to detect heterogeneity, while MR-Egger intercept and MR-PRESSO were used to test for pleiotropy. Sensitivity analysis was conducted using the leave-one-out method. ResultsThere was a significant causal relationship between thyroid nodules and malignant neoplasm of breast (OR=0.88, 95%CI 0.83 to 0.95, P<0.01), with no evidence of reverse causality between them (OR=1.01, 95%CI 0.99 to 1.03, P=0.16). No causal relationship was found between thyroid nodules and benign neoplasm of breast, as indicated by both forward MR analysis (OR=0.97, 95%CI 0.89 to 1.06, P=0.51) and reverse MR analysis (OR=0.97, 95%CI 0.92 to 1.04, P=0.40). Sensitivity analyses suggested that the study findings were accurate and reliable. ConclusionThe present study identifies thyroid nodules as a potential protective factor for malignant neoplasm of breast.
Randomization was the basis for the design and conduct of clinical trials. However, the traditional randomized controlled trials (RCTs) were often randomized in a fixed manner with unbalanced potential covariates, which spured researchers to develop a more flexible and practical randomization method. Thus, the adaptive randomization emerged as the time needed. In this paper, the application of adaptive randomization in clinical trials was introduced, and its key points of implementation, advantages and disadvantages were summarized. The development space of the adaptive randomization in clinical applications was also discussed, and it provided evidence for the development of the drug clinical trials in China.
