Instrumental variables for MR
We performed a TSMR analysis to explore the causal relationship between diabetes and adhesive capsulitis of shoulder risk. The SNPs were selected from the IEU OpenGWAS database on T1DM (ebi-a-GCST90014023) and T2DM (ebi-a-GCST006867). We selected SNPs strongly associated with diabetes at the genome-wide significance threshold of P < 5e−8. Secondly, clumping was carried out using data from the 1000 Genomes Project (R2 = 0.001, window size = 10000kp) in order to estimate LD between single-nucleotide polymorphisms (SNPs) and to eliminate missing SNPs from the LD reference panel. The outcome information for ACS was extracted from the FinnGen database, and the relationship between the above SNPs and the outcome was obtained from the database. Subsequently, the exposure and outcome datasets were merged, resulting in a total of 89 and 118 IVs, respectively, with both outcome and exposure data. Removing the following SNPs for incompatible alleles:rs3135348 and removing the following SNPs for being palindromic with intermediate allele frequencies: rs2303137, rs7936434, rs13234269, rs1758632, rs2058913, rs6494307. The MR-PRESSO procedure identified and removed a single outlier SNP. The remaining 85 and 114 SNPs constituted the final instrumental variable for the exposure. The selection of IVs meets the above criteria (P < 5e−8, LD r2<0.001, F=R2×(N −2)/(1 − R2), F > 10). It is noteworthy that all of these F values were greater than 10, which signifies that 199 IVs were designated as strong IVs in this study. The forest plot illustrates the causal effects of specific SNPs on the risk of depression in patients with ACS. The specific details of the 199 IVs that have been definitively identified are presented in (Supplementary Tables S1-S2)
Table 1. Results of Mendelian randomization studies
|
Exposure
|
method
|
nSNP
|
OR
|
95% CI
|
pval
|
|
MR Egger
|
|
1.054914
|
1.0213-1.0897
|
0.001768
|
|
Weighted median
|
|
1.063974
|
1.0319-1.0971
|
0.000072
|
T1D
|
Inverse variance weighted
|
85
|
1.048393
|
1.0221-1.0773
|
0.000261
|
|
Simple mode
|
|
1.023035
|
0.9355-1.1188
|
0.619117
|
|
Weighted mode
|
|
1.057028
|
1.0279-1.0870
|
0.000198
|
|
|
|
|
|
|
|
MR Egger
|
|
0.941428
|
0.7659-1.1572
|
0.567683
|
|
Weighted median
|
|
1.049185
|
0.9063-1.2146
|
0.520328
|
T2D
|
Inverse variance weighted
|
114
|
1.036868
|
0.9506-1.1310
|
0.413927
|
|
Simple mode
|
|
0.972990
|
0.7031-1.3465
|
0.869084
|
|
Weighted mode
|
|
1.029270
|
0.8650-1.2247
|
0.745635
|
Causal effects of diabetes and adhesive capsulitis of shoulder
The findings of this study provide genetic evidence supporting the hypothesis that type 1 diabetes is a potential risk factor for adhesive capsulitis of shoulder. However, no causal relationship could be demonstrated between type 2 diabetes and adhesive capsulitis of shoulder. The results of IVW showed a causal relationship between T1DM and an increased risk of ACS IV(β=0.047, SE=0.013, P<0.05, OR=0.97, CI: 0.85–1.11). With the exception of the imputed model, the results from the weighted median, MR-Egger, and weighted mode were consistent with those of the inverse-variance weighted (IVW) method. No evidence was present to support a causal relationship between T2DM and ACS by the IVW random effects model method (β=-0.036, SE=0.044, P=0.414, OR=0.97, CI: 0.95–1.13). The comprehensive results of these analytical modalities are presented in a visual format and summarized (Figure 3 and Table 1).
Heterogeneity refers to the variability observed in the causal estimates obtained for each SNP. The data indicate significant heterogeneity between T1DM and ACS (p=0.045, p < 0.05). However, no heterogeneity was found between T2DM and ACS (p=0.079, p > 0.05). It was acknowledged that heterogeneity may arise from a number of sources, including different analytic platforms, experiments, and population stratification. Random effects modelling was therefore employed to enable MR analysis to be conducted in the presence of heterogeneity. The outcomes demonstrate that the IVs derived from databases did not exert a notable impact on outcomes via pathways other than exposure. As indicated by the Egger-intercept method, this was the case regardless of the specific IVs used (Figure 3). The leave-one-out sensitivity analysis revealed that the omission of a SNP had only a minor impact on the estimated association of diabetes with the risk of ACS (Figure 4). The results of the MR-Egger regression test and funnel plot exhibited favorable symmetry and did not indicate any evidence of horizontal pleiotropy (Table 2 and Figure 5).
Figure 2
The forest plot displays the causal effect of each SNP in diabetes on T1DM(A); T2DM (B)
Figure 3
The slope in the scatter plot represents the causal relationship of diabetes on ACS. An upward tilt indicates a positive correlation between diabetes and ACS, while a downward tilt indicates a negative correlation T1DM(A); T2DM (B).
Figure 4
The leave-one-out plot illustrates the impact of individual SNPs on the robustness of the results, T1DM(A); T2DM (B).