Association of mTORC1‑dependent circulating protein levels with cataract formation: a mendelian randomization study

The mechanistic target of rapamycin (mTOR) signal pathway plays a critical regulating role in the occurrence and development of cataract. However, the role of mTORC1 downstream proteins, including ribosomal protein S6K (RP-S6K), eukaryotic initiation factor 4E-binding protein (EIF4EBP), eukaryotic initiation factor 4G (EIF-4G), eukaryotic initiation factor 4E (EIF-4E), and eukaryotic initiation factor 4A (EIF-4A), in regulating cataract development is still unknown. Herein, we conducted a mendelian randomization (MR) study to understand the function of mTORC1 signaling in the process of cataract development.

The causal estimate was evaluated with inverse-variance weighted (IVW) estimate, weighted median estimator, MR-Egger and MR robust adjusted profile score (MR. RAPS). The single-nucleotide polymorphisms (SNPs), P<5 × 10^- 6 and r²<0.05, were selected to genetically predict the RP-S6K, EIF4EBP, EIF-4E, EIF-4A, and EIF-4G. We included a total of 26,758 cases and 189,604 controls in this MR study. The study revealed causal association between circulating EIF4EBP (OR 1.09, 95% confidence interval 1.03,1.16, P = 0.004), RP-S6K (OR 1.04, 95% confidence interval 1.01, 1.08, P = 0.02) and cataract formation with IVW estimate. Whereas after correcting outliers, MR robust adjusted profile score (MR. RAPS) shows consistent result with IVW for EIF4EBP (OR = 1.08, 95%CI:1.05-1.11, P = 0.007). The observation strengthened the confidence in the true causal associations. However, no association was found for circulating EIF-4E (OR 1.03, 95% confidence interval 0.97, 1.09, P = 0.31), EIF-4A (OR 1.02, 95% confidence interval 0.98, 1.07, P = 0.34), and EIF-4G (OR 1.02, 95% confidence interval 0.94, 1.01, P = 0.64) levels with cataract formation. No evidence of heterogeneity and unbalanced horizontal pleiotropy was detected.

The MR study suggests that EIF4EBP is a high-risk factor for cataract development. There may be a potential causal association between the mTORC1/EIF4EBP axis and cataract. This research highlights the potential mechanism for cataract development and a genetic target to prevent as well as treat cataracts.