Determination of cadmium and zinc in Alzheimer's brain tissue using Inductively Coupled Plasma Mass Spectrometry

Abstract

In this work, brain tissue was taken from Alzheimer's Disease (AD) subjects ( n=11), ‘normal’ subjects ( n=10) and from subjects with senile involutive cortical changes (SICC) ( n=6). Concentrations of Cd and Zn were determined in all samples, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The brain tissue was selected and obtained from the Netherlands Brain Bank. Samples were taken in each case, from both hemispheres of the superior frontal gyrus, the superior parietal gyrus, the medial temporal gyrus, the hippocampus and the thalamus of the same brain. Cd which is known to have no essential role in the brain was found to follow, as expected, a lognormal distribution of concentrations in ‘normal’ subjects (Shapiro–Wilk's test (0.98) ( p<0.18)). For the Alzheimer's Disease subjects and SICC subjects, the data tends to follow a lognormal distribution, rather than a normal distribution, but is still significantly different from it (Shapiro–Wilk's test (0.97) ( p<0.03); (0.93) ( p<0.0067), respectively)). In the case of Zn concentrations, the data tends to follow a normal distribution for the ‘normal’ subject group, even though the data is significantly different from it (Shapiro–Wilk's test (0.95) ( p<0.001)). Whereas in the Alzheimer's Disease and SICC subject groups, the data follows a normal distribution (Shapiro–Wilk's test (0.98) ( p<0.21); (0.97) ( p<0.2002), respectively)). When comparing age-matched groups, for all regions and both hemispheres, no significant differences ( p>0.1) for Cd were found between ‘normals’ and Alzheimer's Disease subjects and Alzheimer's Disease subjects and SICC but at a low level of significance, lower concentrations of Cd were found in the SICC group compared to the ‘normals’. For all regions and both hemispheres, Zn was found to be significantly decreased in the Alzheimer's Disease group, compared to the ‘normal’ and SICC groups. Zn concentrations were also found to be significantly decreased in the ‘normals’ compared to the SICC group. It is also of interest that Cd negatively correlates with the scale of tangles in both ‘normals’ ( p<0.001) and Alzheimer's Disease subjects ( p<0.01). In the SICC subjects Cd correlates negatively with the tangles but not significantly so ( p>0.1).