Cerebrospinal Fluid Biomarkers of Neuroinflammation and Neuroplasticity in Type 2 Diabetes Mellitus: Association with Cognitive Performance

Background: Type 2 Diabetes Mellitus (T2DM) is associated with cognitive decline, potentially mediated by neuroinflammatory processes and altered neuroplasticity. This study investigated cerebrospinal fluid (CSF) biomarkers of neuroinflammation and neuroplasticity in T2DM individuals versus controls, and their relationship with cognitive performance. Methods: This cross-sectional study included 56 T2DM individuals and 26 controls (aged 37–70 years; 48% male). CSF concentrations of leptin, IL-6, VEGF, BDNF, TNF-α, IGF-1, and IL-1β were measured using ELISA. Cognitive function was assessed using MMSE, the Stroop test, SDMT, RCFT, and TAAV. Group comparisons used Mann–Whitney U or t-tests; Spearman correlations examined variable relationships. Results: No statistically significant differences in CSF biomarkers were observed between groups. However, T2DM patients showed lower word recall (4.66 ± 1.48 vs. 5.81 ± 1.52; p = 0.002), reduced Symbol–Digit performance (17.82 ± 12.16 vs. 24.92 ± 12.10; p = 0.016), and higher Complex Figure Test scores (19.94 ± 9.32 vs. 15.94 ± 5.02; p = 0.009). IL-6 was negatively correlated with MMSE (r = −0.33, p = 0.005). Significant correlations emerged between MMSE and Symbol–Digit scores (r = 0.40, p < 0.001) and among biomarkers. Conclusions: “No statistically significant differences in CSF biomarkers were observed between groups and unadjusted CSF biomarker concentrations did not differ significantly between groups; however, after adjustment for age and BMI, IL-6 was significantly elevated in T2DM patients, indicating that covariate-adjusted analyses may be more sensitive for detecting subtle neuroinflammatory differences in this population.