Increases in Plasma Aβ40 Levels and the Aβ40/42 Ratio in Patients with Diabetes Mellitus and Dementia

Abstract

Aim: The plasma Aβ40/42 ratio is a possible biomarker for the onset of Alzheimer’s disease (AD). We here measured plasma Aβ40 and As42 levels in patients with diabetes mellitus (DM) and dementia in order to clarify the relationship between DM and AD. Methods: Fifty-three patients, including 33 patients with DM and 25 patients with dementia, were assessed using the Mini-mental state examination (MMSE) and brain MRI, plasma Aβ40 and Aβ42, blood sugar levels, and HbA1c % were measured, and the genotype of apolipoprotein E was determined. Plasma Aβ levels and blood sugar levels were measured in 16 out of 53 patients, following fasting and 2 hours after breakfast. Results: Plasma Aβ40 levels and the Aβ40/42 ratio were increased in the DM with dementia group (p<0.01, p<0.001), while HbA1c % correlated with the Aβ40/42 ratio in the non-dementia group. MMSE scores were also associated with the plasma Aβ40/42 ratio and Aβ40 levels in the non-dementia group, independent of the presence of ApoEe4. We did not observed significant direct responses of plasma Aβ protains to an increase in blood sugar levels. Conclusion: These results suggest that plasma Aβ metabolism are closely related chronic hyperglycemia before the onset of dementia. Hirosaki Med.J. 66:110―119,2016