Low plasma BDNF is not a biomarker for cognitive dysfunction in elderly T2DM patients

Type 2 diabetes mellitus (T2DM) is a known cause of cognitive dysfunction, and brain-derived neurotrophic factor (BDNF) is a key protein in promoting memory growth and survival of neurons. However, the relationship between plasma BDNF and diabetic cognitive dysfunction is still elusive. A total of 89 patients over 60 years with T2DM and 40 well-matched health controls were enrolled. All participants received a set of multi-dimensional neuropsychological tests for the cognitive assessment. The subjects were divided into amnesic mild cognitive impairment (aMCI) and non-aMCI groups. An enzyme-linked immunosorbent assay (ELISA) was used to measure plasma BDNF concentrations for all subjects. No significant difference was found between T2DM patients and healthy control in MMSE scores. The T2DM patients performed significantly worse in four cognitive domains (including episodic memory, executive function, visuospatial function, and information processing speed) compared with the controls (all p < 0.05). The prevalence of aMCI in T2DM population was higher [OR = 4.032 (1.536~10.582), 37/89-6/40]. Additionally, the plasma concentration of BDNF in T2DM patients was significantly lower than that in controls (p < 0.01). However, no significant correlation was found between plasma BDNF and cognitive function in T2DM. Our results suggested that T2DM have a higher prevalence of cognitive impairment. The plasma BDNF concentration in T2DM patients was significantly lower than that in controls, but low BDNF was not a biomarker for cognitive dysfunction in T2DM patients.