# Type 1 Diabetes Risk Variants Reduce Beta Cell Function

## TL;DR

This study shows that two genetic variants linked to type 1 diabetes harm beta cell function by increasing inflammation and altering key genes.

## Contribution

The study reveals a novel mechanism by which two T1DM risk variants impair beta cell function through HNF1A upregulation and cytokine production.

## Key findings

- Both variants reduce glucose-stimulated insulin secretion and increase pro-inflammatory cytokines in beta cells.
- Silencing HNF1A normalizes gene expression and lncRNA levels altered by the variants.
- The rs10517086 variant is associated with lower C-peptide levels in T1DM but not in T2DM individuals.

## Abstract

Introduction: The variants rs10517086 and rs1534422 are predictive of type 1 diabetes mellitus (T1DM) development and poor residual β cell function within the first year of diagnosis. However, the mechanism by which risk is conferred is unknown. We explored the impact of both variants on β cell function in vitro and assessed their relationship with C-peptide in people with T1DM and type 2 diabetes mellitus (T2DM). Methods: Using CRISPR/Cas9, the variants were introduced into a β cell line (BRIN-BD11) and a T cell line (Jurkat cells) from which the conditioned media was applied to otherwise healthy β cells to model the inflammatory environment associated with these variants. Results: Both variants significantly reduced glucose-stimulated insulin secretion, increased production of pro-inflammatory cytokines and reduced expression of several β cell markers and transcription factors (KCNJ11, KCNQ1, SCL2A2, GCK, NKX6.1, Pdx1 NGN3). However, HNF1A was significantly upregulated in the presence of both variants. We subsequently silenced HNF1A in variant expressing BRIN-BD11 cells using siRNA and found that gene expression profiles were normalised. Induction of each variant significantly increased expression of the lncRNAs they encode, which was normalised upon HNF1A silencing. Analysis of the DARE (Diabetes Alliance for Research in England) study revealed an association of rs10517086_A genotype with C-peptide in 153 individuals with T1DM, but not in 417 people with T2DM. Conclusions: These data suggest that rs1534422 and rs10517086 exert multiple insults on the β cell through excessive upregulation of HNF1A and induction of pro-inflammatory cytokines, and highlight their utility as prognostic markers of β cell function.