Abstract
This study is the first to evaluate oxidative stress biomarkers in saliva/blood of patients with varying degrees of dementia progression. The study included 50 healthy controls and 50 dementia patients divided into two groups: those with mild and moderate dementia (MMSE 11–23) and patients suffering from severe dementia (MMSE 0–10). Cognitive functions of the subjects were assessed using the Mini Mental State Examination (MMSE). Enzymatic and non-enzymatic antioxidants, oxidative damage products and protein glycoxidative modifications were determined in non-stimulated (NWS) and stimulated (SWS) saliva as well as erythrocyte/plasma samples. Generally, in dementia patients, we observed the depletion of antioxidant defences leading to oxidative and glycoxidative damage in NWS, SWS and blood samples. Both salivary and blood oxidative stress increased with the severity of the disease, and correlated with a decrease of cognitive functions. Interestingly, in dementia patients, reduced glutathione (GSH) in NWS correlated not only with the severity of dementia, but also with GSH concentration in the plasma. In receiver operating characteristic (ROC) analysis, we have demonstrated that salivary GSH clearly distinguishes patients with severe dementia from those suffering from mild or moderate dementia (area under the curve (AUC) = 1). Therefore, salivary GSH can be used as a non-invasive biomarker of cognitive impairment.
Highlights
Dementia is a syndrome of gradual deterioration of cognitive functions, accompanied by behavioural disorders and difficulties in everyday functioning
No significant differences in either biochemical parameters or blood morphology were found between the groups
Cognitive functions in the Mini Mental State Examination (MMSE) and formal education in years were statistically different between patients with dementia as compared to the controls
Summary
Dementia is a syndrome of gradual deterioration of cognitive functions, accompanied by behavioural disorders and difficulties in everyday functioning. AD is a degenerative brain disease caused by the accumulation of pathological proteins (amyloid β, Tau protein and α-synuclein) in this organ, resulting in the loss of neurons and the connections between them [4]. Different types of dementia have different clinical pictures, it is believed that they are based on similar mechanisms, leading to neurodegeneration. This state is undoubtedly related to oxidative stress (OS) caused by the imbalance between the formation of reactive oxygen species (ROS) as well as reactive nitrogen species (RNS) and the antioxidant balance of the body [4,5]. Protein oxidation products are more and more often used in laboratory diagnostics in psychiatry [7,10,11]
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