Available online 26 April 2022, 101353

Data on the genetic background of patients with early-onset type 2 diabetes are scarce and inconclusive.

Our data show that rare and possibly deleterious variants in monogenic diabetes genes are associated with early diabetes onset.

Common variants known to affect susceptibility to type 2 diabetes are also associated with anticipation of the disease. This effect is significantly higher in individuals carrying rare and deleterious variants in monogenic diabetes genes.

Our findings suggest that the genetic background of early-onset type 2 diabetes is based on a synergic effect of both rare and common variants.

This study investigated whether rare, deleterious variants in monogenic diabetes-genes are associated with early-onset type 2 diabetes (T2D).

A nested case-control study was designed from 9,712 Italian patients with T2D. Individuals with age at diabetes onset ≤35 yrs (n=300; cases) or ≥65 yrs (n=300; controls) were selected and screened for variants in 27 monogenic diabetes-genes by targeted resequencing. Rare (minor allele frequency-MAF <1%) and possibly deleterious variants were collectively tested for association with early-onset T2D. The association of a genetic risk score (GRS) based on 17 GWAS-SNPs for T2D was also tested.

When all rare variants were considered together, each increased the risk of early-onset T2D by 65% (allelic OR =1.64, 95% CI: 1.08-2.48, p=0.02). Effects were similar when the 600 study participants were stratified according to their place of recruitment (Central-Southern Italy, 182 cases vs. 142 controls, or Rome urban area, 118 vs. 158, p for heterogeneity=0.53). Progressively less frequent variants showed increasingly stronger effects in the risk of early-onset T2D for those with MAF <0.001% (OR=6.34, 95% CI: 1.87-22.43, p=0.003). One unit of T2D-GRS significantly increased the risk of early-onset T2D (OR 1.09, 95% CI: 1.01-1.18; p=0.02). This association was stronger among rare variants carriers as compared to non-carriers (p=0.02).

Rare variants in monogenic-diabetes genes are associated with an increased risk of early-onset T2D, and interact with common T2D susceptibility variants in shaping it. These findings might help develop prediction tools to identify individuals at high risk of developing T2D in early adulthood.

type 2 Diabetes

early-onset type 2 diabetes

rare variants

monogenic diabetes, genetic risk score

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