3-nitrotyrosine and Cognitive-Dysfunction

Hyperglycemia, inflammation, and oxidative stress are thought to be involved in the pathogenesis of cognitive decline. Dipeptidyl peptidase-4 (DPP4) is a newly identified adipokine related to these risk factors. Hence, we aimed to investigate the association between plasma DPP4 activities and mild cognitive impairment (MCI) in elderly patients with type 2 diabetes.. We evaluated plasma DPP4 activity, inflammatory markers, and oxidative stress parameters in a cross-sectional sample of 1,160 patients with type 2 diabetes aged 60 years or older in China. MCI was diagnosed based on criteria established by the National Institute on Aging-Alzheimer's Association workgroups. Patients in the highest quartile of DPP4 activity had higher HbA1c, interleukin 6 (IL-6), CRP, nitrotyrosine, 8-iso-PGF2a, and lower Montreal Cognitive Assessment (MoCA) scores compared with subjects in the lowest quartile (P < 0.001). In the highest DPP4 quartile, MCI risk was higher (odds ratio 3.49; 95% CI 1.97-4.57) than in the lowest quartile after adjustment for potential confounders. The risk for MCI increased more with higher levels of DPP4 activity, IL-6, CRP, nitrotyrosine, and 8-iso-PGF2a (P < 0.05), but not with higher levels of HbA1c.. This study shows that increased DPP4 activities are independently associated with MCI in elderly patients with type 2 diabetes. The mechanisms might be partly explained by the effect of DPP4 on inflammation and oxidative stress. These observations raise further interest in DPP4 activity for its potential effect on these MCI-related risk factors as a biological marker or even a possible therapeutic target for MCI.

Topics: Aged; Biomarkers; C-Reactive Protein; China; Cognitive Dysfunction; Cross-Sectional Studies; Diabetes Mellitus, Type 2; Dinoprost; Dipeptidyl Peptidase 4; Female; Glycated Hemoglobin; Humans; Inflammation; Interleukin-6; Male; Middle Aged; Odds Ratio; Oxidative Stress; Risk Factors; Tyrosine

Biliverdin reductase-A (BVR-A) is a pleiotropic enzyme and plays pivotal role in the antioxidant defense against free radicals as well as in cell homeostasis. Together with heme oxygenase, BVR-A forms a powerful system involved in the cell stress response during neurodegenerative disorders including Alzheimer's disease (AD), whereas due to the serine/threonine/tyrosine kinase activity the enzyme regulates glucose metabolism and cell proliferation. In this paper, we report results that demonstrate BVR-A undergoes post-translational oxidative and nitrosative modifications in the hippocampus, but not cerebellum, of subjects with AD and amnestic mild cognitive impairment (MCI). A significant increase of nitrated BVR-A was demonstrated only in AD and MCI hippocampi, whereas no significant modifications were found in cerebellar tissue. In addition, a significant reduction in protein carbonyl-derivatives of BVR-A was found in both AD and MCI hippocampi (15% and 18%, respectively). Biliverdin reductase-bound 4-hydroxynonenals were not modified in hippocampi and cerebella from AD and MCI subjects. These results supported the hypothesis of a prevalence of nitrosative stress-induced modifications on BVR-A structure, and this evidence was confirmed by a significant upregulation of inducible nitric oxide synthase in hippocampal tissue of subjects with AD and MCI that was not present in cerebellum. In conclusion, nitrosative stress-induced modifications on hippocampal BVR-A are an early event in the pathogenesis of AD since they appear also in MCI subjects and could contribute to the antioxidant and metabolic derangement characteristic of these neurodegenerative disorders.

Topics: Aged; Aged, 80 and over; Aldehydes; Alzheimer Disease; Blotting, Western; Brain; Cerebellum; Cognitive Dysfunction; Female; Heme Oxygenase (Decyclizing); Hippocampus; Homeostasis; Humans; Immunoprecipitation; Male; Nitric Oxide Synthase Type II; Oxidative Stress; Oxidoreductases Acting on CH-CH Group Donors; Protein Carbonylation; Reactive Nitrogen Species; Tyrosine