Evaluating the effect of metabolic traits on oral and oropharyngeal cancer risk using Mendelian randomization

Causal effects of educational attainment on temporomandibular disorders and the mediating pathways: A Mendelian randomization study

BACKGROUND

As one of the most important indicators of socioeconomic status, educational attainment (EA) exhibits a strong association with temporomandibular disorders (TMDs). Despite this link, there is a lack of evidence regarding the causal role of EA in either facilitating or preventing TMDs.

OBJECTIVE

This study aimed to investigate the causal effect of education on TMDs and explore potential mediating pathways.

METHODS

Utilizing summary statistics from genome-wide association studies on years of schooling (N = 766 345) and TMDs (N = 211 023), we conducted Mendelian randomization (MR) to assess the overall effect of education. Additionally, a two-step MR approach was employed to evaluate 30 potential mediators and calculate the mediation proportions in the association. Comprehensive sensitivity analyses were used to verify the robustness, heterogeneity, and pleiotropy.

RESULTS

Univariable MR analyses revealed a causal effect of lower EA on an increased risk of TMDs (OR: 0.53, 95% CI: 0.43-0.66, p < .001). Five out of 30 modifiable factors were identified as causal mediators in the associations of EA with TMDs, including feeling nervous (mediation proportion: 11.6%), feeling tense (10.2%), depression (9.6%), feeling worry (7.6%) and daily smoking (8.9%). Meanwhile, no pleiotropy was detected in the analyses (p > .05).

CONCLUSION

Our findings supported that higher EA has a protective effect on the onset of TMDs, with partial mediation by psychological disorders and daily smoking. Interventions on these factors thus have the potential of substantially reducing the burden of TMDs attributed to low education.

Inflammatory cytokines mediating the effect of oral lichen planus on oral cavity cancer risk: a univariable and multivariable mendelian randomization study

BACKGROUND

While observational studies and experimental data suggest a link between oral lichen planus (OLP) and oral cavity cancer (OCC), the causal relationship and the role of inflammatory cytokines remain unclear.

METHODS

This study employed a univariable and multivariable Mendelian Randomization (MR) analysis to investigate the causal relationship between OLP and the risk of OCC. Additionally, the potential role of inflammatory cytokines in modulating this association was explored. Instrumental variables were derived from genetic variants associated with OLP (n = 377,277) identified in Finngen R9 datasets, with 41 inflammatory cytokines as potential mediators, and OCC (n = 4,151) as the outcome variable. Analytical methods including Inverse Variance Weighted (IVW), Weighted Median, MR-Egger, and MR-PRESSO were utilized to assess the causal links among OLP, inflammatory cytokines, and OCC risk. Multivariable MR (MVMR) was then applied to quantify the mediating effects of these cytokines in the relationship between OLP and increased OCC risk.

RESULTS

MR analysis provided strong evidence of a causal relationship between OLP (OR = 1.417, 95% CI = 1.167-1.721, p < 0.001) and the risk of OCC. Furthermore, two inflammatory cytokines significantly influenced by OLP, IL-13 (OR = 1.088, 95% CI: 1.007-1.175, P = 0.032) and IL-9 (OR = 1.085, 95% CI: 1.005-1.171, P = 0.037), were identified. Subsequent analysis revealed a significant causal association only between IL-13 (OR = 1.408, 95% CI: 1.147-1.727, P = 0.001) and higher OCC risk, establishing it as a potential mediator. Further, MVMR analysis indicated that IL-13 (OR = 1.437, 95% CI = 1.139-1.815, P = 0.002) mediated the relationship between OLP and OCC, accounting for 8.13% of the mediation.

CONCLUSION

This study not only elucidates the potential causal relationship between OLP and the risk of OCC but also highlights the pivotal mediating role of IL-13 in this association.

Adiposity and cancer: meta-analysis, mechanisms, and future perspectives

Obesity is a recognised risk factor for many cancers and with rising global prevalence, has become a leading cause of cancer. Here we summarise the current evidence from both population-based epidemiologic investigations and experimental studies on the role of obesity in cancer development. This review presents a new meta-analysis using data from 40 million individuals and reports positive associations with 19 cancer types. Utilising major new data from East Asia, the meta-analysis also shows that the strength of obesity and cancer associations varies regionally, with stronger relative risks for several cancers in East Asia. This review also presents current evidence on the mechanisms linking obesity and cancer and identifies promising future research directions. These include the use of new imaging data to circumvent the methodological issues involved with body mass index and the use of omics technologies to resolve biologic mechanisms with greater precision and clarity.

Association between human blood metabolome and the risk of hypertension

Hypertension, commonly referred to as high blood pressure, is a chronic medical condition characterized by persistently elevated blood pressure levels. It is a prevalent global health issue, affecting a significant portion of the population worldwide. Hypertension is often asymptomatic, making it a silent but potentially dangerous condition if left untreated. Genetic instruments for 1,091 were from a recent comprehensive metabolome genome-wide association study (GWAS). Summary statistics of diastolic blood pressure (DBP) and systolic blood pressure (SBP) involving 757,601 sample size were analyzed. Two-sample Mendelian Randomization (MR) was conducted to assess causal effect of metabolites on DBP and SBP risk, and reverse MR analysis was performed to identify the DBP/SBP causal effect on blood metabolites. Twelve and twenty-two metabolites were identified to be associated with DBP and SBP, respectively. Sensitive analysis showed four metabolites had robustness association on BP. Reverse MR demonstrated DBP and SBP could decrease the tricosanoyl sphingomyelin (d18:1/23:0)* level and increase the 2-hydroxyhippurate (salicylurate) level in blood, respectively. Our findings reveal an association between blood metabolites and blood pressure (DBP and SBP), suggesting potential therapeutic targets for hypertension intervention.

Obesity and head and neck cancer risk: a mendelian randomization study

BACKGROUND

Observational studies have reported controversial results on the association between obesity and head and neck cancer risk. This study aimed to perform a two-sample Mendelian randomization (MR) analysis to assess the causal association between obesity and head and neck cancer risk using publicly available genome-wide association studies (GWAS) summary statistics.

METHODS

Single-nucleotide polymorphisms (SNPs) for obesity [body mass index (BMI), waist-to-hip ratio (WHR), whole body fat mass, lean body mass, and trunk fat mass] and head and neck cancer (total head and neck cancer, oral cavity cancer, oropharyngeal cancer, and oral cavity and oropharyngeal cancer) were retrieved from published GWASs and used as genetic instrumental variables. Five methods including inverse-variance-weighted (IVW), weighted-median, MR-Egger, weighted mode, and MR-PRESSO were used to obtain reliable results, and odds ratio with 95% confidence interval (CI) were calculated. Tests for horizontal pleiotropy, heterogeneity, and sensitivity were performed separately.

RESULTS

Genetically predicted BMI was negatively associated with the risk of total head and neck cancer, which was significant in the IVW [OR (95%CI), 0.990 (0.984-0.996), P = 0.0005], weighted-median [OR (95%CI), 0.984 (0.975-0.993), P = 0.0009], and MR-PRESSO [OR (95%CI), 0.990 (0.984-0.995), P = 0.0004] analyses, but suggestive significant in the MR-Egger [OR (95%CI), 0.9980 (0.9968-0.9991), P < 0.001] and weighted mode [OR (95%CI), 0.9980 (0.9968-0.9991), P < 0.001] analyses. Similar, genetically predicted BMI adjust for smoking may also be negatively associated with the risk of total head and neck cancer (P < 0.05). Genetically predicted BMI may be negatively related to the risk of oral cavity cancer, oropharyngeal cancer, and oral cavity and oropharyngeal cancer (P < 0.05), but no causal association was observed for BMI adjust for smoking (P > 0.05). In addition, no causal associations were observed for other exposures and outcomes (all P > 0.05).

CONCLUSION

This MR analysis supported the causal association of BMI-related obesity with decreased risk of total head and neck cancer. However, the effect estimates from the MR analysis were close to 1, suggesting a slight protective effect of BMI-related obesity on head and neck cancer risk.