Alzheimers Disease (AD) and Mild Cognitive Impairment (MCI) Patients are Characterized by Increased BDNF Serum Levels

Abstract

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline with loss of memory. In the last years there has been a great interest on the early phases of AD, trying to identify the pathogenic mechanisms of AD and define early treatment modalities. In particular, Mild Cognitive Impairment (MCI) is attractive because it represents a transitional state between normal aging and dementia, although not all MCI patients automatically convert to AD. The neurotrophin brain-derived neurotrophic factor (BDNF) is critical for survival and function of neurons that degenerate in AD and represents a potential neuroprotective agent. However, opposite data on serum levels of BDNF have been reported in AD patients, probably reflecting differences in patient recruitment and stage of the disease. Thus, in this study we measured BDNF serum levels in AD patients (with different degree of severity), MCI patients and healthy subjects. We found that serum BNDF levels were significantly increased in MCI and AD patients when compared to healthy subjects and this increase in AD patients was neither dependent on illness severity, nor on treatment with Acetylcholinesterase inhibitors and/or antidepressant medications. Our findings indicate that BDNF serum levels increase in MCI and AD patients, supporting the hypothesis of an upregulation of BDNF in both preclinical phase of dementia (MCI) and clinical stages of AD. Other studies are necessary to establish a direct link between BDNF peripheral levels and AD longitudinal course, as well as the role of other factors, such as blood cell activation, in determining these events.

Depression and Brain-derived Neurotrophic Factor Levels in Alzheimer's Disease

“…Additionally, the sample included MCI patients and control, whereas only AD patients were used in the current study. Although the findings are contradictory to some previous findings on the relationship of BDNF to GDS scores, they are consistent with others showing an increase in BDNF early in Alzheimer's [16] and studies reporting an increase in BDNF in both MCI and Alzheimer's [17]. Our sample consisted of AD patients in the mild stage of dementia and this increased level of BDNF may be a compensatory upregulation to deal with the accumulation of Alzheimer's pathology.…”

Differential Peripheral Inflammatory Factors Associated with Cognitive Function in Patients with Heart Failure

“…As previously noted, there are mixed results in peripheral concentrations of BDNF, some indicating increases and others finding decreases associated with cognitive function [17, 18]. Postmortem brain, cerebrospinal fluid, and blood samples from patients with AD revealed lower BDNF levels than controls [32].…”

“…Although neurotrophin brain-derived neurotrophic factor (BDNF) is suggested to support the survival of neurons and boost the growth and differentiation of new neurons and synapses, research yields mixed findings regarding peripheral assessments. One study found elevated peripheral levels of BDNF in AD and MCI [17], whereas another study found reduced peripheral levels of BDNF in AD, depending on the stage [18]. Meanwhile, there is a relative lack of knowledge relating peripheral neuroinflammation biomarkers and cognitive function specifically in patients with HF.…”

Peripheral leukocyte expression of the potential biomarker proteins Bdnf, Sirt1, and Psen1 is not regulated by promoter methylation in Alzheimer's disease patients

“…Nevertheless, conflicting findings revealed no association or increased serum Bdnf levels in AD and MCI with respect to controls, suggesting that compensatory changes could also take place [5,6].…”