T1D-Related Cataract Risk Amplification: Mendelian Randomisation Confirms a Dual Hit of Immune-Inflammatory Burden and Metabolic Stress.

BACKGROUND/

OBJECTIVE

Observational studies have linked diabetes with cataracts, but they cannot fully elucidate the underlying causes and mechanisms. This investigation aims to evaluate the causal relationship between genetically predicted diabetes and cataract risk utilizing Mendelian randomisation (MR) techniques.

METHODS

We identified single nucleotide polymorphisms (SNPs) with a significant threshold of P < 5×10^-8 as instrumental variables from genome-wide association study datasets pertaining to Type 1 (finn-b-E4_DM1, n=189,113), Type 2 diabetes (finn-b-E4_DM2, n=215,654), and cataract (ukb-b-8329, controls=136,388, cataract=14,254). Various Mendelian randomisation methods were employed, including inverse-variance weighted (IVW), MR-Egger, weighted median, simple mode (SM), and weighted mode analyses. Additionally, sensitivity analyses were conducted to assess the robustness of the findings, encompassing tests for heterogeneity, pleiotropy, and leave-one-out assessments. A multivariable (MVMR) approach was used to account for potential confounders, such as obesity (IEUA-92, controls = 47468, obesity = 2896), smoking (ukba- 16, n = 337030), and alcohol consumption (IEUA-1283, n = 112,117).

RESULTS

The analysis included 12 SNPs, which were derived from loci specifically associated with Type 1 diabetes and known to govern immune-inflammatory and metabolic pathways. The genetically-predicted Type 1 diabetes was found to elevate cataract risk significantly (OR=1.003, 95% CI: 1.001-1.005, P=0.001). The results of the sensitivity analyses corroborated the robustness of these findings, showing no significant heterogeneity (Cochran Q, P value = 0.73) or pleiotropy (MR-Egger intercept, P value = 0.38). Furthermore, multivariable MR demonstrated that the impact of diabetes on cataract risk remained significant after adjustment for multiple lifestyle factors.

DISCUSSION: We provide novel MR evidence that Type 1 diabetes causally increases the risk of cataract through the synergistic activity of immune dysregulation, chronic inflammation, and metabolic disturbance, with immune-metabolic crosstalk as the primary driver.

CONCLUSIONS

T1D causally increases the risk of cataract through the disruption of immuneinflammatory and metabolic pathways. Targeting immune-metabolic interactions may offer novel therapeutic strategies for preventing diabetic cataracts.