Disease State, Age, Sex, and Post-Mortem Time-Dependent Expression of Proteins in AD vs. Control Frontal Cortex Brain Samples

Abstract

Human post-mortem brain samples are excellent source material for the analysis of age-related disorders such as Alzheimer's disease (AD). Moreover, data obtained from cell culture- or mouse model-related experiments often need to be validated by using human tissue. In a variety of studies over the last few years, a huge list of genes or proteins with differential expression or abundance between AD-related and control tissue has been reported. However, highly important issues such as changes in post-mortem time, sex, age etc. of the patients have been rarely included in the analysis. In our study we examined human frontal brain samples of 10 AD patients vs. 10 unaffected controls using state-of-the-art two dimensional DIGE proteomics in order to analyze protein expression of up to 10,000 proteins in parallel. Data were analyzed using well established DIGE-software tool as well as an analysis of covariance model including the factor effects of group and sex and the covariable effects of age and post-mortem time. Within this study we report protein expression changes in AD vs. control human frontal brain samples without any influence of other parameters as well as expression changes depending on the parameters mentioned above. In fact, some proteins previously suggested a state of being dysregulated in AD vs. controls revealed age or sex-dependent regulation. Our analysis suggests the necessity of integrating additionally available covariables in comparative proteome studies of two different sets of human tissue.

Brain site-specific proteome changes in aging-related dementia

“…37 Our data are in line with previous studies of ATP5A1, which was downregulated in the Hp whereas ALDOA expression was upregulated. 38 Impairment of brain metabolism has been recognized as a hallmark of AD, and the reduction of glucose utilization is paralleled by a decrease in the expression of glycolytic enzymes. We observed a significant downregulation of ALDOA in the Hp, ENO1 in the Cb and GAPDH in both the Hp and the Cb, thus explaining the impaired glucose metabolic system in AD.…”

“…There are currently a combination of different methods used, such as (1) 2D difference gel electrophoresis (2D-DIGE) combined with MALDI-TOF-MS/MS (matrix-assisted laser desorption/ionization time-of-flight MS/MS) proteomics 17, 37, 38, 116 or (2) 2D-LC-MS/MS-iTRAQ/ICAT (isotope-coded affinity tag); some proteins appear more frequently (for example, 14-3-3 proteins, VDACs, VIM, creatine kinase B, Aldolase, GFAP and HSP70 proteins), whereas others are hardly detected (for example, STAT3, p60TRP, NF-κB, NTRK1 and α-, β- and γ-secretases). 117, 118 Despite improved sensitivity of our 2D-LC-MS/MS analyses, limitations of ‘undersampling' in LC-MS/MS still restrict the number of peptides that can be identified in a specific sample.…”

An update on clinical proteomics in Alzheimer’s research

“…These changes include decreases in the levels of aldolase A in frontal cortex (Korolainen et al. 2006; Muller et al. 2008), heart specific fatty acid binding protein in temporal cortex (Tsuji et al.…”

Insight of brain degenerative protein modifications in the pathology of neurodegeneration and dementia by proteomic profiling

“…However, recent quantitative analyses of brain protein expression in dementia patients have begun to shed light on this phenomenon. In proteomic study of frontal cortex tissues from AD patients, Muller et al observed that disease-associated up-regulation of heat shock 70 kDa protein 1B and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is gender dependent [75]. Similarly, data from our own laboratory have revealed significant modulation of several redox proteins in the temporal lobe of Alzheimer’s disease with cerebrovascular diseases (AD-CVD) patients as well as sex-specific alterations in the white matter and mitochondrial proteome of female patients [55].…”