Peripheral inflammatory markers and clinical phenotypes reflecting the impact of diabetes on Parkinson's disease

BackgroundType 2 diabetes mellitus (DM) can influence the phenotype and progression of Parkinson's disease (PD), as both conditions share inflammation as a common pathogenic mechanism.ObjectiveTo explore peripheral inflammatory indices that reflect the impact of DM on PD.MethodsWe analyzed 52 drug-naïve PD patients with DM and 182 without DM, along with age- and sex-matched healthy control (HC) with and without DM in a 1:1 ratio. Clinical features were evaluated, including the Hoehn and Yahr (H&Y) scale and the Unified Parkinson's Disease Rating Scale (UPDRS). Peripheral inflammatory markers included the count of leukocyte subpopulations, high-density lipoprotein-cholesterol (HDL-C), and markers derived from these including neutrophil-to-HDL-C ratio (NHR), monocyte-to-HDL-C ratio (MHR), and lymphocyte-to-HDL-C ratio (LHR).ResultsThere were no significant differences in age, sex, or disease duration between PD with DM and PD without DM group. The PD with DM group showed more symmetric motor features (p = 0.007) compared to the PD without DM group. NHR, MHR, and LHR were elevated in the PD with DM group compared to the other groups. Notably, MHR was highest in the PD with DM group, followed by the HC with DM group and the PD without DM group, and HC without DM group (9.73 vs. 8.30 vs. 7.63 vs. 6.46, p < 0.001). MHR positively correlated with clinical scales, including H&Y and UPDRS, across all PD patients (p < 0.05 for all).ConclusionsOur study suggests that MHR effectively reflects the peripheral inflammatory status related to both PD and diabetes.