Diffusion MRI in a multiethnic cohort of adults aged 50 and older from the HABS-HD study showed that type 2 diabetes was associated with impaired white matter microstructure in six major tracts, including the corpus callosum body (adjusted Cohen's d 0.28), anterior corona radiata, cingulum, inferior fronto-occipital fasciculus, genu of the corpus callosum and posterior thalamic radiation (d 0.13-0.16). Effects held after false discovery rate correction, appeared even in cognitively unimpaired participants, and trended larger over two years. Statistical mediation analysis attributed up to 15% of the associations to interleukin-6. These findings come from a preprint that has not been peer reviewed, so results may change. The effect sizes are small, and apart from the corpus callosum body they sit near 0.15, so individual-level impact is modest. The design appears largely cross-sectional with short follow-up, which cannot establish that diabetes caused the changes or that IL-6 sits on the causal path; mediation of 15% leaves most of the association unexplained. Still, the signal fits a wider literature linking diabetes to accelerated brain aging, small-vessel injury and dementia risk. The practical takeaway is that brain involvement may begin before symptoms, strengthening the case for early glucose control, blood pressure management, exercise and weight loss in prediabetes and diabetes, though this study tests none of those. Confirmatory rather than paradigm-shifting; the inflammation angle needs longitudinal and interventional data.