Neurochemical Ameliorating of the Hippocampus in Dyslipidemic Alzheimer Patients Following Silymarin; a Double-Blind Placebo-Controlled Randomized Clinical Trial

Background

Amyloid-beta (Aβ) production is a normal physiological process, and an imbalance in Aβ production/excretion rate is the basis of the plaque load increase in AD. LRP1 is involved in both central clearance of Aβ from the CNS and transport of Aβ toward peripheral organs. In this study, the effect of silymarin combination compared to rosuvastatin and placebo on neuro-metabolites and serum levels of LRP1 and Aβ1-42 proteins and oxidative stress enzymes and lipid and cognitive tests of Iranian AD patients.

Methods

In this double-blind placebo-controlled study, thirty-six mild AD patients were divided into groups (n=12) of silymarin 140mg, placebo, and rosuvastatin 10mg. Medications were administered 3 times a day for 6 months. Clinical tests, lipid profile (TG, HDL, TC, and LDL), Aβ1-42, and LRP1 markers were measured at the beginning and end of the intervention. Magnetic resonance spectroscopy (MRS) was used to measure metabolites. Using SPSS software a one-way ANOVA test was used to compare the means of the quantitative variables and Pearson and Spearman's correlations to measure the correlation. GraphPad Prism software was used for drawing graphs. P < 0.05 was considered a significant.

Results

The levels of LRP1 and Aβ1-42 in the silymarin group were significantly increased compared to the other groups (P < 0.05). NAA/mI in the silymarin group had a significant increase compared to both placebo and rosuvastatin groups (P < 0.05). Right and left hippocampal mI/Cr directly correlated with TG (r = 0.603, P = 0.003 and r = 0.595, P = 0.004, respectively). NAA/Cr of the right and left hippocampus was inversely related to TG (r = -0.511, P = 0.0033, and r = -0.532, P = 0.0021, respectively). NAA/Cr and NAA/mI of bilateral hippocampi directly correlated with HDL (P < 0.05). An inverse correlation was observed between the Aβ1-42 and mI/Cr of the right and left hippocampus (r = -0.661, P = 0.000 and r = -0.638, P = 0.000, respectively).

Conclusion

Donepezil and silymarin improved lipid profile associated with increased NAA/Cr, and decreased mI/Cr, in AD patients. Biomarker NAA/mI can be clinically significant in examining AD pathology. Measurement of the lipid factors and neurometabolites can be a suitable method for monitoring this disease.

Effect of amyloid-Β (25-35) in hyperglycemic and hyperinsulinemic rats, effects on phosphorylation and O-GlcNAcylation of tau protein

Aggregation of the amyloid beta (Aβ) peptide and hyperphosphorylation of tau protein, which are markers of Alzheimer's disease (AD), have been reported also in diabetes mellitus (DM). One regulator of tau phosphorylation is O-GlcNAcylation, whereas for hyperphosphorylation it could be GSK3beta, which is activated in hyperglycemic conditions. With this in mind, both O-GlcNAcylation and phosphorylation of tau protein were evaluated in the brain of rats with streptozotocin (STZ)-induced hyperglycemia and hyperinsulinemia and treated with the Aß25-35 peptide in the hippocampal region CA1. Weight, glycated hemoglobin, glucose, and insulin were determined. Male Wistar rats were divided in groups (N=20): a) control, b) treated only with the Aβ25-35 peptide, c) treated with Aβ25-35 and STZ, and d) treated only with STZ. Results showed statistically significant differences in the mean weight, glucose levels, insulin concentration, and HbA1c percentage, between C- and D-treated groups and not STZ-treated A and B (P<0.05). Interestingly, our results showed diminution of O-GlcNAcylation and increase in P-tau-Ser-396 in the hippocampal area of the Aβ25-35- and STZ-treated groups; moreover, enhanced expression of GSK3beta was observed in this last group. Our results suggest that hyperinsulinemia-Aβ25-35-hyperglycemia is relevant for the down regulation of O-GlcNAcylation and up-regulation of the glycogen synthase kinase-3 beta (GSK3beta), favoring Aβ25-35-induced neurotoxicity in the brain of rats.