Can increasing years of schooling reduce type 2 diabetes (T2D)?: Evidence from a Mendelian randomization of T2D and 10 of its risk factors

Associations between epigenetic aging and diabetes mellitus in a Swedish longitudinal study

Diabetes mellitus type 2 (T2D) is associated with accelerated biological aging and the increased risk of onset of other age-related diseases. Epigenetic changes in DNA methylation levels have been found to serve as reliable biomarkers for biological aging. This study explores the relationship between various epigenetic biomarkers of aging and diabetes risk using longitudinal data. Data from the Swedish Adoption/Twin Study of Aging (SATSA) was collected from 1984 to 2014 and included 536 individuals with at least one epigenetic measurement. The following epigenetic biomarkers of aging were employed: DNAm PAI-1, DNAmTL, DunedinPACE, PCHorvath1, PCHorvath2, PCHannum, PCPhenoAge, and PCGrimAge. Firstly, longitudinal analysis of biomarker trajectories was done. Secondly, linear correlations between the biomarkers and time to diabetes were studied within individuals developing diabetes. Thirdly, Cox proportional hazards (PH) models were used to assess the associations between these biomarkers and time of diabetes diagnosis, with adjustments for chronological age, sex, education, smoking, blood glucose, and BMI. The longitudinal trajectories of the biomarkers revealed differences between individuals with and without diabetes. Smoothened average curves for DunedinPACE and DNAm PAI-1 were higher for individuals with diabetes around the age 60-70, compared to controls. Likewise, DunedinPACE and DNAm PAI-1 were higher closer to diabetes onset. However, no significant associations were found between the epigenetic biomarkers of aging and risk of diabetes in Cox PH models. Our findings suggest the potential value of developing epigenetic biomarkers specifically tailored to T2D, should we wish to model and explore the potential for predicting the disease.

A Mendelian randomization study: Years of education and nonalcoholic fatty liver disease

Though years of education have been connected to nonalcoholic fatty liver disease (NAFLD), the exact mechanism underlying this linkage is still unknown. To investigate the causal association between years of education and NAFLD, we will use a 2-sample Mendelian randomization (MR) technique. : Genome-wide association studies data on years of education (n = 766,345) and genome-wide association studies data on nonaffiliated mental illness (n = 778,614) were screened for genetic variations as instrumental variables in the Mr-Base database. MR-Egger regression, weighted median, and inverse variance weighted were used in the MR analysis. Years of education (odds ratio = 0.63; 95% confidence interval: 0.47-0.79; P = 1.28 × 10-8) might be protective against the development of NAFLD. Among the sensitivity analyses were the following: the MR-Egger intercept test revealed P > .05, suggesting that there was no horizontal pleiotropy in the MR analysis and that the inverse variance weighted results were trustworthy; the Cochran Q test revealed P > .05, suggesting that there was no heterogeneity between the 2 samples; Funnel plot results demonstrated that there was no bias in the link between the measure of variability and the impact size. Leave-1-out analysis results demonstrated that no 1 single nucleotide polymorphism had a significant effect on the study's results, showing that the MR results were stable. This study has investigated the connection between years of education and NAFLD, offering novel suggestions for NAFLD treatment and prevention.

Associations of education attainment with gestational diabetes mellitus and the mediating effects of obesity: A Mendelian randomization study

We aim to assess the causal association between educational attainment and gestational diabetes mellitus, and the mediating effect of obesity on this association. We estimated the causal effects of educational attainment on gestational diabetes mellitus using European ancestry genome-wide association study summary data with two-sample univariate Mendelian randomization (UVMR) approach. Two-stage Mendelian randomization analysis was performed to assess the potential mediating role of obesity traits in this association and to calculate the mediating proportion. UVMR analysis demonstrated that higher educational attainment was associated with a reduced risk of GDM (OR 0.76, 95% CI 0.67-0.86; p < 0.01). EA has also been associated with decreased obesity in women. Mediation Mendelian randomization results indicated that body mass index (BMI) was the most significant mediating factor in the relationship between educational attainment and GDM, accounting for 42.52% (95% CI 37.75-55.44%) of the effect, followed by waist-to-hip ratio (WHR) at 34.35% (95% CI 29.82-46.41%), body fat percentage at 28.95% (95% CI 35.99-46.81%), and WHR adjusted for BMI (WHRadjBMI) at 12.51% (95% CI 36.2-58.5%). educational attainment exerts a potential causal protective effect against gestational diabetes mellitus, and obesity-related risk factors play a mediating role. Attention should be paid to the educational attainment of women, and obese women with lower educational attainment may represent a higher risk group for GDM than those with higher educational attainment.

The causal effect of educational attainment on stress urinary incontinence: a two-sample mendelian randomization study

BACKGROUND

Stress urinary incontinence (SUI) is characterized by involuntary urine leakage in response to increased abdominal pressure, such as coughing, laughing, or sneezing. It significantly affects women's quality of life and imposes a substantial disease burden. While pregnancy and childbirth have been previously identified as risk factors for SUI, educational attainment may also play a role. Therefore, this paper investigates the causal relationship between educational attainment and SUI using two-sample Mendelian randomization (TSMR) analysis, years of schooling (YOS), and college or university degree (CUD) as proxies.

METHODS

Summary statistics of YOS, CUD, and SUI were obtained from genome-wide association studies (GWAS), and TSMR analysis was applied to explore potential causal relationships between them. Causal effects were mainly estimated using the standard inverse variance weighting (IVW) method, and complementary and sensitivity analyses were also performed using multiple methods.

RESULTS

The results indicate that both YOS (OR = 0.994, 95% CI: 0.992-0.996; P = 7.764E-10) and CUD (OR = 0.987, 95% CI: 0.983-0.991; P = 1.217E-09) may have a negative causal effect on SUI.

CONCLUSIONS

Improving educational attainment may go some way towards reducing the risk of SUI. Therefore, it is important to increase efforts to improve the imbalance in educational development and safeguard women's health.

Prevalence and Psychosocial Correlates of Diabetes Mellitus in South Africa: Results from the South African National Health and Nutrition Examination Survey (SANHANES-1)

In South Africa, there are a limited number of population estimates of the prevalence of diabetes and its association with psychosocial factors. This study investigates the prevalence of diabetes and its psychosocial correlates in both the general South African population and the Black South African subpopulation using data from the SANHANES-1. Diabetes was defined as a hemoglobin A1c (HbA1c) ≥6.5% or currently on diabetes treatment. Multivariate ordinary least squares and logistic regression models were used to determine factors associated with HbA1c and diabetes, respectively. The prevalence of diabetes was significantly higher among participants who identified as Indian, followed by White and Coloured people, and lowest among Black South Africans. General population models indicated that being Indian, older aged, having a family history of diabetes, and being overweight and obese were associated with HbA1c and diabetes, and crowding was inversely associated with HbA1c and diabetes. HbA1c was inversely associated with being White, having higher education, and residing in areas with higher levels of neighborhood crime and alcohol use. Diabetes was positively associated with psychological distress. The study highlights the importance of addressing the risk factors of psychological distress, as well as traditional risk factors and social determinants of diabetes, in the prevention and control of diabetes at individual and population levels.

A novel "dual-locked" fluorescent probe for ONOO- and viscosity enables serum-based rapid disease screening

Peroxynitrite (ONOO^-) plays important roles in the progression of important disease such as inflammation, cancer, and diabetes, which made it an attractable target for biosensor development. However, to detect ONOO^- solely is highly dependent on the sensitivity of the detection method and may be disturbed by unwillingly false-positive signal. Cellular viscosity is an important microenvironmental parameter and its abnormal changes are closely related to diseases such as diabetes and cancer. In this case, to construct a "dual-locked" molecular tool for both ONOO^- and viscosity sensing and to evaluate the performance of such strategy in disease diagnosis is of great importance. We herein firstly reported the construction of a novel "dual-locked" probe DCI-OV which showed capability for simultaneous measuring ONOO^- concentration and system viscosity with high sensitivity (LOD = 4.7 nM) and high specificity. Moreover, both exogenous and low level of endogenous ONOO^- in living cells could be detected using DCI-OV due to viscosity amplified signal. Furthermore, cancer cells and insulin-resistant cells could be easily distinguished using DCI-OV. By taking advantage of the "dual-locked" sensing strategy, a total of 85 samples of human serum were screened using DCI-OV based rapid disease screening method and it was capable of differentiated and subdivided patients into specific type of disease, indicating the great potential of application of DCI-OV into clinical related disease diagnosis.

Mediators of the association between educational attainment and type 2 diabetes mellitus: a two-step multivariable Mendelian randomisation study

AIMS/HYPOTHESIS

Type 2 diabetes mellitus is a major health burden disproportionately affecting those with lower educational attainment (EA). We aimed to obtain causal estimates of the association between EA and type 2 diabetes and to quantify mediating effects of known modifiable risk factors.

METHODS

We applied two-step, two-sample multivariable Mendelian randomisation (MR) techniques using SNPs as genetic instruments for exposure and mediators, thereby minimising bias due to confounding and reverse causation. We leveraged summary data on genome-wide association studies for EA, proposed mediators (i.e. BMI, blood pressure, smoking, television watching) and type 2 diabetes. The total effect of EA on type 2 diabetes was decomposed into a direct effect and indirect effects through multiple mediators. Additionally, traditional mediation analysis was performed in a subset of the National Health and Nutrition Examination Survey 2013-2014.

RESULTS

EA was inversely associated with type 2 diabetes (OR 0.53 for each 4.2 years of schooling; 95% CI 0.49, 0.56). Individually, the largest contributors were BMI (51.18% mediation; 95% CI 46.39%, 55.98%) and television watching (50.79% mediation; 95% CI 19.42%, 82.15%). Combined, the mediators explained 83.93% (95% CI 70.51%, 96.78%) of the EA-type 2 diabetes association. Traditional analysis yielded smaller effects but showed consistent direction and priority ranking of mediators.

CONCLUSIONS/INTERPRETATION

These results support a potentially causal protective effect of EA against type 2 diabetes, with considerable mediation by a number of modifiable risk factors. Interventions on these factors thus have the potential of substantially reducing the burden of type 2 diabetes attributable to low EA.

Causes and Consequences of Polycystic Ovary Syndrome: Insights From Mendelian Randomization

CONTEXT

Although polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting women of reproductive age, risk factors that may cause the syndrome are poorly understood. Based on epidemiologic studies, PCOS is thought to cause several adverse outcomes such as cardiovascular disease; however, the common presence of comorbidities such as obesity may be responsible for such associations, rather than PCOS in and of itself. To overcome the limitations of observational studies, investigators have employed Mendelian randomization (MR), which uses genetic variants to interrogate causality between exposures and outcomes.

EVIDENCE ACQUISITION

To clarify causes and consequences of PCOS, this review will describe MR studies involving PCOS, both as an exposure and as an outcome. The literature was searched using the terms "Mendelian randomization," "polycystic ovary syndrome," "polycystic ovarian syndrome," and "PCOS" (to May 2021).

EVIDENCE SYNTHESIS

MR studies have suggested that obesity, testosterone levels, fasting insulin, serum sex hormone-binding globulin concentrations, menopause timing, male-pattern balding, and depression may play a causal role in PCOS. In turn, PCOS may increase the risk of estrogen receptor-positive breast cancer, decrease the risk of endometrioid ovarian cancer, and have no direct causal effect on type 2 diabetes, coronary heart disease, or stroke.

CONCLUSIONS

The accumulation of genome-wide association studies in PCOS has enabled multiple MR analyses identifying factors that may cause PCOS or be caused by PCOS. This knowledge will be critical to future development of measures to prevent PCOS in girls at risk as well as prevent complications in those who have PCOS.

Educational level as a cause of type 2 diabetes mellitus: Caution from triangulation of observational and genetic evidence

BACKGROUND AND OBJECTIVE: Education might be causal to type 2 diabetes mellitus (T2DM). We triangulated cohort and genetic evidence to consolidate the causality between education and T2DM.

METHODS

We obtained observational evidence from the English Longitudinal Study of Ageing (ELSA). Self-reporting educational attainment was categorised as high (post-secondary and higher), middle (secondary), and low (below secondary or no academic qualifications) in 6,786 community-dwelling individuals aged ≥ 50 years without diabetes at ELSA wave 2, who were followed until wave 8 for the first diabetes diagnosis. Additionally, we performed two-sample Mendelian randomisation (MR) using an inverse-variance weighted (IVW), MR-Egger, weighted median (WM), and weighted mode-based estimate (WMBE) method. Steiger filtering was further applied to exclude single-nucleotide polymorphisms (SNPs) that were correlated with an outcome (T2DM) stronger than exposure (education attainment).

RESULTS

We observed 598 new diabetes cases after 10.4 years of follow-up. The adjusted hazard ratios (95% CI) of T2DM were 1.20 (0.97-1.49) and 1.58 (1.28-1.96) in the middle- and low-education groups, respectively, compared to the high-education group. Low education was also associated with increased glycated haemoglobin levels. Psychosocial resources, occupation, and health behaviours fully explained these inverse associations. In the MR analysis of 210 SNPs (R² = 0.0161), the odds ratio of having T2DM per standard deviation-decreasing years (4.2 years) of schooling was 1.33 (1.01-1.75; IVW), 1.23 (0.37-4.17; MR-Egger), 1.56 (1.09-2.27; WM), and 2.94 (0.98-9.09; WMBE). However, applying Steiger filtering attenuated most MR results towards the null.

CONCLUSIONS

Our inconsistent findings between cohort and genetic evidence did not support the causality between education and T2DM.

Estimating causal effects of atherogenic lipid-related traits on COVID-19 susceptibility and severity using a two-sample Mendelian randomization approach

BACKGROUND

As the number of COVID-19 deaths continues to rise worldwide, the identification of risk factors for the disease is an urgent issue, and it remains controversial whether atherogenic lipid-related traits including serum apolipoprotein B, low-density lipoprotein (LDL)-cholesterol, and triglyceride levels, are risk factors. The aim of this study was to estimate causal effects of lipid-related traits on COVID-19 risk in the European population using a two-sample Mendelian randomization (MR) approach.

METHODS

We used summary statistics from a genome-wide association study (GWAS) that included 441,016 participants from the UK Biobank as the exposure dataset of lipid-related traits and from COVID-19 Host Genetics Initiative GWAS meta-analyses of European ancestry as the outcome dataset for COVID-19 susceptibility (32,494 cases and 1,316,207 controls), hospitalization (8316 cases and 1,549,095 controls), and severity (4792 cases and 1,054,664 controls). We performed two-sample MR analyses using the inverse variance weighted (IVW) method. As sensitivity analyses, the MR-Egger regression, weighted median, and weighted mode methods were conducted as were leave-one-out sensitivity analysis, the MR-PRESSO global test, PhenoScanner searches, and IVW multivariable MR analyses. A P value below 0.0055 with Bonferroni correction was considered statistically significant.

RESULTS

This MR study suggested that serum apolipoprotein B or LDL-cholesterol levels were not significantly associated with COVID-19 risk. On the other hand, we inferred that higher serum triglyceride levels were suggestively associated with higher risks of COVID-19 susceptibility (odds ratio [OR] per standard deviation increase in lifelong triglyceride levels, 1.065; 95% confidence interval [CI], 1.001-1.13; P = 0.045) and hospitalization (OR, 1.174; 95% CI, 1.04-1.33; P = 0.012), and were significantly associated with COVID-19 severity (OR, 1.274; 95% CI, 1.08-1.50; P = 0.004). Sensitivity and bidirectional MR analyses suggested that horizontal pleiotropy and reverse causation were unlikely.

CONCLUSIONS

Our MR study indicates a causal effect of higher serum triglyceride levels on a greater risk of COVID-19 severity in the European population using the latest and largest GWAS datasets to date. However, as the underlying mechanisms remain unclear and our study might be still biased due to possible horizontal pleiotropy, further studies are warranted to validate our findings and investigate underlying mechanisms.

Educational Attainment Decreases the Risk of COVID-19 Severity in the European Population: A Two-Sample Mendelian Randomization Study

Observational studies have reported that the severity of COVID-19 depends not only on physical conditions but also on socioeconomic status, including educational level. Because educational attainment (EA), which measures the number of years of schooling, is moderately heritable, we investigated the causal association of EA on the risk of COVID-19 severity using the Mendelian randomization (MR) approach. A two-sample MR analysis was performed using publicly available summary-level data sets of genome-wide association studies (GWASs). A total of 235 single-nucleotide polymorphisms (SNPs) were extracted as instrumental variables for the exposure of EA from the Social Science Genetic Association Consortium GWAS summary data of 766,345 participants of European ancestry. The effect of each SNP on the outcome of COVID-19 severity risk was obtained from the GWAS summary data of 1,059,456 participants of European ancestry gathered from the COVID-19 Host Genetics Initiative. Using inverse variance weighted method, our MR study shows that EA was significantly associated with a lower risk of COVID-19 severity (odds ratio per one standard deviation increase in years of schooling, 0.540; 95% confidence interval, 0.376–0.777, P = 0.0009). A series of sensitivity analyses showed little evidence of bias. In conclusion, we show for the first time using a two-sample MR approach the associations between higher EA and the lower risk of COVID-19 severity in the European population. However, the genetic or epidemiological mechanisms underlying the association between EA and the risk of COVID-19 severity remain unknown, and further studies are warranted to validate the MR findings and investigate underlying mechanisms.