Validation of external and internal exposome of the findings associated to cerebral small vessel disease: A Mendelian randomization study

Association of systemic inflammatory markers with white matter hyperintensities and microstructural injury: an analysis of UK Biobank data

BACKGROUND

White matter damage is closely associated with cognitive and psychiatric symptoms and is prevalent in cerebral small vessel disease (CSVD); although the pathophysiological mechanisms involved in CSVD remain elusive, inflammation plays a crucial role. We sought to investigate the relationship between systemic inflammation markers and imaging markers of CVSD, namely white matter hyperintensity (WMH) and microstructural injury.

METHODS

We conducted a study involving both cross-sectional and longitudinal data from the UK Biobank Cohort. We performed multiple linear regression analyses, adjusted for potential confounders, to explore the associations between systemic inflammation markers (e.g., systemic immune-inflammation index [SII], neutrophil-to-lymphocyte ratio [NLR], C-reactive protein [CRP] levels, monocyte count, neutrophil count) and macro- and microstructural white matter injury, as markers of CSVD. We performed Mendelian randomization analysis to investigate the genetically predictive effect of monocytes on WMH, as well as mediation analysis to clarify whether inflammatory markers affected cognitive function via white matter injury.

RESULTS

We included 36 411 participants (mean age 54.8 ± 7.5 yr, 51.9% female) from the UK Biobank Cohort. We found that SII was significantly associated with both WMH and microstructural injury markers (fractional anisotropy, mean diffusivity, intracellular volume fraction, and isotropic compartment volume fraction [ISOVF]), and the neutrophil-to-lymphocyte ratio was significantly associated with WMH and some markers of microstructural injury (mean diffusivity and ISOVF). Our analysis revealed that the CRP level was significantly associated with WMH and WMH progression but not with microstructural injury. We also demonstrated that monocyte count was significantly associated with WMH and ISOVF, and that neutrophil count was significantly associated with WMH, mean diffusivity, and ISOVF. In 2-sample Mendelian randomization analyses, we found positive associations between genetic determinants of monocytes and WMH. The mediating role of WMH suggested that a higher SII value and monocyte count could contribute to cognitive impairment through white matter injury.

LIMITATIONS

Although the study includes both cross-sectional and longitudinal components, the sample size for the longitudinal aspect is limited, and the use of blood biomarkers from a single timepoint is also a limitation of this research.

CONCLUSION

The SII and neutrophil-to-lymphocyte ratio may be early detection markers for white matter damage in patients with CSVD, whereas the CRP level is more closely associated with disease severity and progression. Our findings highlight the clinical relevance of systemic inflammation markers with white matter macro- and microstructural injuries, revealing that systemic inflammation is likely involved in the mechanism of early white matter injury among patients with CSVD.

Discovery and Exploration of Lipid-Modifying Drug Targets for ALS by Mendelian Randomization

Observational studies have faced challenges in identifying replicable causes for amyotrophic lateral sclerosis (ALS). To address this, we employed an unbiased and data-driven approach to discover and explore potential causal exposures using two-sample Mendelian randomization (MR) analyses. In the phenotype discovery stage, we assessed 3948 environmental exposures from the UK Biobank and utilized ALS summary statistics (Europeans, 20,806 cases, 59,804 controls) as the outcome within a phenome-wide MR pipeline. Through a range of sensitivity analyses, two medication traits were identified to be protective for ALS. In the target exploration stage, we further conducted drug target MR analyses using the latest and trans-ethnic summary data on lipid-related traits and ALS (Europeans, 27,205 cases, 110,881 controls; East Asians, 1234 cases, 2850 controls). Our aim was to explore potential causal drug targets through six lipid-modifying effects. These comprehensive analyses revealed significant findings. Specifically, "cholesterol-lowering medication" and "atorvastatin" survived predefined criteria in the phenotype discovery stage and exhibited a protective effect on ALS. Further in the target exploration stage, we demonstrated that the therapeutic effect of APOB through LDL-lowering was associated with reduced ALS liability in Europeans (OR = 0.835, P = 5.61E - 5). Additionally, the therapeutic effect of APOA1 and LDLR through TC-lowering was associated with reduced ALS liability in East Asians (APOA1, OR = 0.859, P = 5.38E - 4; LDLR, OR = 0.910, P = 2.73E - 5). Overall, we propose potential protective effects of cholesterol-lowering drugs or statins on ALS risk from thousands of exposures. Our research also suggests APOB, APOA1, and LDLR as novel therapeutic targets for ALS and supports their potential protective mechanisms may be mediated by LDL-lowering or TC-lowering effects.

The association between air pollutant exposure and cerebral small vessel disease imaging markers with modifying effects of PRS-defined genetic susceptibility

Studies have highlighted a possible link between air pollution and cerebral small vessel disease (CSVD) imaging markers. However, the exact association and effects of polygenic risk score (PRS) defined genetic susceptibility remains unclear. This cross-sectional study used data from the UK Biobank. Participants aged 40-69 years were recruited between the year 2006 and 2010. The annual average concentrations of NOX, NO2, PM2.5, PM2.5-10, PM2.5 absorbance, and PM10, were estimated, and joint exposure to multiple air pollutants was reflected in the air pollution index (APEX). Air pollutant exposure was classified into the low (T1), intermediate (T2), and high (T3) tertiles. Three CSVD markers were used: white matter hyper-intensity (WMH), mean diffusivity (MD), and fractional anisotropy (FA). The first principal components of the MD and FA measures in the 48 white matter tracts were analysed. The sample consisted of 44,470 participants from the UK Biobank. The median (T1-T3) concentrations of pollutants were as follows: NO2, 25.5 (22.4-28.7) μg/m3; NOx, 41.3 (36.2-46.7) μg/m3; PM10, 15.9 (15.4-16.4) μg/m3; PM2.5, 9.9 (9.5-10.3) μg/m3; PM2.5 absorbance, 1.1 (1.0-1.2) per metre; and PM2.5-10, 6.1 (5.9-6.3) μg/m3. Compared with the low group, the high group's APEX, NOX, and PM2.5 levels were associated with increased WMH volumes, and the estimates (95 %CI) were 0.024 (0.003, 0.044), 0.030 (0.010, 0.050), and 0.032 (0.011, 0.053), respectively, after adjusting for potential confounders. APEX, PM10, PM2.5 absorbance, and PM2.5-10 exposure in the high group were associated with increased FA values compared to that in the low group. Sex-specific analyses revealed associations only in females. Regarding the combined associations of air pollutant exposure and PRS-defined genetic susceptibility with CSVD markers, the associations of NO2, NOX, PM2.5, and PM2.5-10 with WMH were more profound in females with low PRS-defined genetic susceptibility, and the associations of PM10, PM2.5, and PM2.5 absorbance with FA were more profound in females with higher PRS-defined genetic susceptibility. Our study demonstrated that air pollutant exposure may be associated with CSVD imaging markers, with females being more susceptible, and that PRS-defined genetic susceptibility may modify the associations of air pollutants.

Development and validation of a diagnostic model for cerebral small vessel disease among rural older adults in China

Objectives

Cerebral small vessel disease (CSVD) visible on MRI can be asymptomatic. We sought to develop and validate a model for detecting CSVD in rural older adults.

Methods

This study included 1,192 participants in the MRI sub-study within the Multidomain Interventions to Delay Dementia and Disability in Rural China. Total sample was randomly divided into training set and validation set. MRI markers of CSVD were assessed following the international criteria, and total CSVD burden was assessed on a scale from 0 to 4. Logistic regression analyses were used to screen risk factors and develop the diagnostic model. A nomogram was used to visualize the model. Model performance was assessed using the area under the receiver-operating characteristic curve (AUC), calibration plot, and decision curve analysis.

Results

The model included age, high blood pressure, white blood cell count, neutrophil-to-lymphocyte ratio (NLR), and history of cerebral infarction. The AUC was 0.71 (95% CI, 0.67-0.76) in the training set and 0.69 (95% CI, 0.63-0.76) in the validation set. The model showed high coherence between predicted and observed probabilities in both the training and validation sets. The model had higher net benefits than the strategy assuming all participants either at high risk or low risk of CSVD for probability thresholds ranging 50-90% in the training set, and 65-98% in the validation set.

Conclusion

A model that integrates routine clinical factors could detect CSVD in older adults, with good discrimination and calibration. The model has implication for clinical decision-making.

Sexual behavior and cardiovascular diseases: univariable and multivariable Mendelian randomization

Background

To assess the relationship of genetically predicted sexual behavior (age at first sex (AFS) and the number of sexual partners (NSP)) on cardiovascular diseases (CVDs).

Methods and results

We performed two-sample Mendelian randomization (MR) with publicly available datasets from the UK Biobank and FinnGen Study, and analyzed genome-wide association results for sexual behaviors and twelve types of CVDs. The univariable MR method provided a total effect of AFS and NSP on CVDs, and showed evidence that early AFS rather than NSP was associated with CVDs, including angina pectoris (AP), atrial fibrillation and flutter (AFF), coronary atherosclerosis (CAS), deep vein thrombosis of the lower extremity (DVT-LE), heart failure (HF), hypertension (HTN), ischaemic stroke (IS), and myocardial infarction (MI). Given sex as a social determinant of CVD risk, we used gender-stratified SNPs to investigate gender differences in the development of CVDs. These results showed a stronger causal relationship of AFS on CVDs in females than in males. Further multivariable MR analyses indicated a direct effect after accounting for insomnia, number of days of vigorous physical activity 10 + minutes (VPA 10 + min), and time spent watching television (TV). Two-step MR demonstrated these three risk factors act as a mediator in AFS associated AP/HTN/HF.

Conclusions

We provide evidence that early AFS increased the risk of CVDs. These associations may be partly caused by VPA 10 + min, insomnia, and the time spent on TV. The causality of AFS on CVDs in females was stronger than in males. Conversely, genetically predicted NSP was not associated with CVDs.

Implication of heart rate variability on cerebral small vessel disease: A potential therapeutic target

OBJECTIVE

This study aimed to investigate the relationships of heart rate variability (HRV) with the presence, severity, and individual neuroimaging markers of cerebral small vessel disease (CSVD).

METHOD

A total of 4676 participants from the Third China National Stroke Registry (CNSR-III) study were included in this cross-sectional analysis. CSVD and its markers, including white matter hyperintensity (WMH), lacunes, enlarged perivascular spaces (EPVS), cerebral microbleeds (CMBs), and brain atrophy (BA), were evaluated. Two common HRV parameters, including the square root of the mean of the sum of the squares of differences between adjacent N-N intervals (RMSSD) and the standard deviation of all N-N intervals (SDNN), were used to evaluate the function of the autonomic nervous system (ANS). Binary or ordinal logistic regression analyses were performed to investigate the association between HRV and CSVD. In addition, two-sample mendelian randomization (MR) analyses were performed to investigate the causality of HRV with CSVD.

RESULTS

RMSSD was significantly associated with total burden of CSVD (Wardlaw's scale, common odds ratio [cOR] 0.80, 95% confidence interval [CI] 0.67-0.96, p = 0.02; Rothwell's scale, cOR 0.75, 95% CI 0.60-0.93, p = 0.008) and the presence of CSVD (Rothwell, OR 0.75, 95% CI 0.60-0.93, p = 0.008). However, no significant associations between SDNN and the presence or total burden of CSVD were observed. Moreover, RMSSD was related to WMH burden (OR 0.80, 95% CI 0.66-0.96, p = 0.02), modified WMH burden (cOR 0.82, 95% CI 0.69-0.97, p = 0.02), and Deep-WMH (OR 0.75, 95% CI 0.62-0.91, p = 0.003), while SDNN was related to Deep-WMH (OR 0.80, 95% CI 0.66-0.96, p = 0.02) and BA (cOR 0.80, 95% CI 0.68-0.95, p = 0.009). Furthermore, adding HRV to the conventional model based on vascualr risk factors enhanced the predictive performance for CSVD, as validated by the integrated discrimination index (p < 0.05). In addition, no causality between HRV and CSVD was observed in two-sample MR analyses.

CONCLUSION

Decreased HRV may be a potential risk factor of CSVD, implying the possible role of the ANS in the pathogenesis of CSVD.

Women's reproductive traits and ischemic stroke: a two-sample Mendelian randomization study

OBJECTIVE

We conducted a Mendelian randomization (MR) study to disentangle causal associations between women's reproductive behaviors and ischemic stroke (IS) and investigate the roles of two modifiable risk factors (body mass index (BMI) and educational attainment (EA)) in these associations.

METHODS

Using summary-level data from large-scale genome-wide association studies, we performed univariable MR to examine whether there is genetic evidence that women's reproductive traits are causally associated with IS and its subtypes. Multivariable MR and MR mediation analysis were used to investigate whether BMI and EA are common mechanisms or mediators for these associations. A set of sensitivity analyses were conducted to test valid MR assumptions.

RESULTS

We observed consistent and statistically significant associations across female and sex-combined analyses for earlier age at first birth (AFB) and age at first sexual intercourse (AFS) with a higher risk of IS and large-artery atherosclerotic stroke (LAS) risk in the primary analysis. The odds ratios of IS per 1 SD increase in genetically predicted early AFB and AFS were 0.93 (95% CI, 0.86-0.99; p = 0.046) and 0.83 (95% CI, 0.70-0.97, p = 0.020), respectively. Further analyses indicated that BMI played a shared role in AFS and IS/LAS while EA played a shared role in AFS/AFB and IS/LAS as well as a mediator in the path from AFS to IS/LAS.

INTERPRETATION

These findings may inform prevention strategies and interventions directed toward relative women's reproductive behaviors and IS. Future studies are warranted to explore other factors related to EA which are responsible for these causalities.