Commonalities in systemic inflammation, oxidative damage and neurocognition predict telomere length in type 2 diabetes mellitus and severe mental disorders

Introduction: Epigenetic mechanisms contribute to the maintenance of both type 2 diabetes mellitus (T2DM) and psychiatric disorders. Emerging evidence suggests that molecular pathways and neurocognitive performance regulate epigenetic dynamics in these disorders. The current prospective and transdiagnostic study investigated whether inflammatory, oxidative stress and adhesion molecule biomarkers and neurocognitive performance are significant predictors of telomere dynamics. Methods: : Peripheral blood inflammatory, oxidative stress and adhesion molecule biomarkers and neurocognitive function were assessed twice over a 1-year period in 80 individuals, including 16 with schizophrenia (SZ), 16 with bipolar disorder (BD), 16 with major depressive disorder (MDD), 15 with T2DM, and 17 healthy controls (HCs). A posteriori, individuals were classified based on their global methylation score (GMS) at baseline into two groups: the below-average methylation (BM) and above-average methylation (AM) groups. Hierarchical and k-means clustering methods, mixed one-way analysis of variance and linear regression analyses were performed. Results: : Overall, the BM group showed a significantly higher leukocyte telomere length (LTL) than the AM group at both time points (p < 0.05; η²p = 0.06). Moreover, the BM group had significantly lower levels of tumor necrosis factor alpha (TNF-α) and C-reactive protein (CRP) than the AM group at the1-year follow-up (p < 0.05; η²p = 0.06). Across all participants, the regression models showed that inflammatory, oxidative stress and adhesion molecule biomarkers, together with neurocognitive performance, were significantly associated with LTL (p < 0.05). Moreover, the model predictive power was increased when tested in both groups separately, explaining 15.8% and 28.1% of the LTL variance at the 1-year follow-up for the AM and BM groups, respectively. Conclusion: Heterogeneous DNA methylation in individuals with T2DM and severe mental disorders seems to support the hypothesis that epigenetic dysregulation occurs in a transdiagnostic manner. Our results elucidated the interplay between epigenetics, molecular processes and neurocognitive function in these disorders. DNA methylation and LTL are potential therapeutic targets for transdiagnostic interventions aimed at decreasing the risk of comorbidities.