Strong association of serum GSK-3β/BDNF ratio with mild cognitive impairment in elderly type 2 diabetic patients

BACKGROUND: Glycogen synthase kinase (GSK)-3β and brain-derived neurotrophic factor (BDNF) play vital roles in both mild cognitive impairment (MCI) and type 2 diabetes mellitus (T2DM). The underlying mechanisms may involve inflammation and oxidative stress. OBJECTIVES: To investigate the association of the GSK-3β/BDNF ratio with MCI in elderly patients with T2DM, and whether GSK-3β/BDNF ratio can serve as a new diagnostic biomarker for MCI in comorbid with T2DM (MD). METHODS: A total of 326 old Chinese T2DM patients were included and stratified according to cognition and GSK-3β/BDNF ratio quartiles. MCI was diagnosed according to the National Institute on Aging Alzheimer's Association workgroups criteria. In addition to routine hematuria and biochemical examinations, Montreal Cognitive Assessment (MoCA) scale was also used to evaluate the cognitive function, and ELISA method was used to measure GSK-3β activity and the serum levels of BDNF, interleukin 1β (IL-1β), high mobility group box-1 (HMGB1) protein, Malonaldehyde (MDA) and 8-iso-prostaglandinF2α (8-iso-PGF2α). RESULTS: We found that GSK-3β activity was negatively correlated with BDNF (r=-0.270, P=0.008), and patients with higher GSK-3β/BDNF ratio had lower MoCA scores (P=0.001). When compared with T2DM patients without MCI (nMD), MD patients had higher GSK-3β activity and GSK-3β/BDNF ratio, but lower BDNF levels. As for inflammation and oxidative stress, IL-1β was inversely correlated with GSK-3β activity, while 8-isoPGF2α was positively correlated with GSK-3β activity and GSK-3β/BDNF ratio. The odds ratio for MCI increased gradually when GSK-3β/BDNF ratio quartile rose from the lowest to the highest (6.90, 95% CI 3.22-14.78). MoCA score was conversely related to GSK-3β/BDNF ratio, age, and fast blood glucose (FBG), with GSK-3β/BDNF ratio having the most significant influence on cognition (β=-0.199, P<0.001). CONCLUSION: Our data provide evidence for a strong link between GSK-3β/BDNF ratio and MCI. GSK-3β/BDNF ratio may serve as a better diagnostic biomarker for MD than either GSK-3β or BDNF alone, and increased GSK-3β/BDNF ratio indicates a worse cognitive function.