Diabetes exacerbates loss of gray matter, cognitive function in Parkinson’s patients

Diabetes seems to hasten the loss of gray matter in the brains of Parkinson’s patients, and the effect is readily observable in the frontal lobes, where higher mental processes such as decision-making take place, according to a small study published online Feb. 10 in Academic Radiology.

Myria Petrou, MD, University of Michigan, and colleagues looked at 36 Parkinson’s patients, mean age 66, 12 of whom had diabetes and 24 of whom did not.

In their study report, the authors detail how, along with clinical and cognitive assessments, the subjects underwent high-resolution T1-weighted brain MRI and [11C]dihydrotetrabenazine (11C-DTBZ) PET to quantify loss of nerve supply in the nigrostriatal bundle, one of the brain’s major dopamine pathways.

Petrou and team found that the impact of diabetes on total gray matter volume was significant (P  = 0.02), while subsequent analyses showed that diabetes was more selectively associated with lower gray matter volumes in the frontal regions (P = 0.01).

In the functional analyses, the combination of total gray matter volume and diabetes status was notably associated with composite (P = 0.007), executive (P = 0.02), and visuospatial domain cognitive z-scores (P = 0.005).

These associations were also significant for the frontal cortical gray matter.

The researchers relied on subjects to accurately self-report their diabetes status, which the authors list among their study’s several limitations.

In their discussion, Petrou et al. note that cognitive decline in the elderly places a great burden on patients, caregivers and the healthcare system as a whole.

“Treatments to attenuate cognitive decline in these patients are highly sought after to improve patient outcomes,” they write. “Our results may have clinical relevance because of the correlations between total and frontal gray matter volumes and cognitive scores, especially in the executive and visuospatial domains.”

Intervening in possible diabetes-related brain pathologies, they add, “may be a strategy to preserve cognition in Parkinson’s disease with comorbid glucose intolerance.”