Metabolism and the Effect of Animal-Derived Oxysterols in the Diet on the Development of Alzheimer's Disease

Effects silymarin and rosuvastatin on amyloid-carriers level in dyslipidemic Alzheimer's patients: A double-blind placebo-controlled randomized clinical trial

Purpose

The production/excretion rate of Amyloid-β (Aβ) is the basis of the plaque burden in alzheimer's disease (AD), which depends on both central and peripheral clearance. In this study, the effect of silymarin and rosuvastatin on serum markers and clinical outcomes in dyslipidemic AD patients was investigated.

Methods

Participants (n=36) were randomized to silymarin (140 mg), placebo, and rosuvastatin 10 mg orally three times a day for 6 months. Serum collection and clinical outcome tests were performed at baseline and after completion of treatment. Lipid profile markers, oxidative stress markers, Aβ1-42/Aβ1-40 ratio, and Soluble Low-density lipoprotein receptor-Related Protein-1 (sLRP1)/Soluble Receptor for Advanced Glycation End Products (sRAGE) ratio were measured.

Results

There was a statistically significant increase in Δ-high density lipoprotein (ΔHDL) between silymarin and placebo (P<0.000) and also between rosuvastatin and placebo (p=0.044). The level of Δ-triglycerides (ΔTG) in the silymarin group has a significant decrease compared to both the placebo and the rosuvastatin group (p<0.000 and p=0.036, respectively). The Δ-superoxide dismutase (ΔSOD) level in the silymarin group compared to placebo and rosuvastatin had a significant increase (p<0.000 and p=0.008, respectively). The ΔAβ1-42/Aβ1-40 in the silymarin group compared to both the placebo and rosuvastatin groups had a significant increase (p<0.05). There was an inverse relationship between ΔTG and ΔAβ1-42/Aβ1-40 (p=-0.493 and p=0.004). ΔAβ1-42/Aβ1-40 has a direct statistical relationship with ΔSOD marker (p=0.388 and p=0.031). Also, there was a direct correlation between the level of ΔAβ1-42/Aβ1-40 and ΔsLRP1/sRAGE (p=0.491 and p=0.005).

Conclusion

Our study showed the relationship between plasma lipids, especially ΔTG and ΔHDL, with ΔAβ1-42/Aβ1-40 in dyslipidemic AD patients, and modulation of these lipid factors can be used to monitor the response to treatments.

The Chemical Reactivity of Membrane Lipids

It is well-known that aqueous dispersions of phospholipids spontaneously assemble into bilayer structures. These structures have numerous applications across chemistry and materials science and form the fundamental structural unit of the biological membrane. The particular environment of the lipid bilayer, with a water-poor low dielectric core surrounded by a more polar and better hydrated interfacial region, gives the membrane particular biophysical and physicochemical properties and presents a unique environment for chemical reactions to occur. Many different types of molecule spanning a range of sizes, from dissolved gases through small organics to proteins, are able to interact with membranes and promote chemical changes to lipids that subsequently affect the physicochemical properties of the bilayer. This Review describes the chemical reactivity exhibited by lipids in their membrane form, with an emphasis on conditions where the lipids are well hydrated in the form of bilayers. Key topics include the following: lytic reactions of glyceryl esters, including hydrolysis, aminolysis, and transesterification; oxidation reactions of alkenes in unsaturated fatty acids and sterols, including autoxidation and oxidation by singlet oxygen; reactivity of headgroups, particularly with reactive carbonyl species; and E/Z isomerization of alkenes. The consequences of reactivity for biological activity and biophysical properties are also discussed.

Cytoprotective effects of α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol on 7-ketocholesterol - Induced oxiapoptophagy: Major roles of PI3-K / PDK-1 / Akt signaling pathway and glutathione peroxidase activity in cell rescue

On murine N2a cells, 7-ketocholesterol induced an oxiapotophagic mode of cell death characterized by oxidative stress (reactive oxygen species overproduction on whole cells and at the mitochondrial level; lipid peroxidation), apoptosis induction (caspase-9, -3 and -7 cleavage, PARP degradation) and autophagy (increased ratio LC3-II / LC3-I). Oxidative stress was strongly attenuated by diphenyleneiodonium chloride which inhibits NAD(P)H oxidase. Mitochondrial and peroxisomal morphological and functional changes were also observed. Down regulation of PDK1 / Akt signaling pathways as well as of GSK3 / Mcl-1 and Nrf2 pathways were simultaneously observed in 7-ketocholesterol-induced oxiapoptophagy. These events were prevented by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by LY-294002, a PI3-K inhibitor, demonstrated an essential role of PI3-K in cell rescue. The rupture of oxidative stress in 7-ketocholesterol-induced oxiapoptophagy was also associated with important modifications of glutathione peroxidase, superoxide dismutase and catalase activities as well as of glutathione peroxidase-1, superoxide dismutase-1 and catalase level and expression. These events were also counteracted by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by mercaptosuccinic acid, a glutathione peroxidase inhibitor, showed an essential role of this enzyme in cell rescue. Altogether, our data support that the reactivation of PI3-K and glutathione peroxidase activities by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol are essential to prevent 7KC-induced oxiapoptophagy.

Metabolism of hydrogen peroxide by Lactobacillus plantarum NJAU-01: A proteomics study

This study aimed to investigate the time-course effect of Lactobacillus plantarum NJAU-01 in scavenging exogenous hydrogen peroxide (H₂O₂). The results showed that L. plantarum NJAU-01 at 10⁷ CFU/mL was able to eliminate a maximum of 4 mM H₂O₂ within a prolonged lag phase and resume to proliferate during the following culture. Redox state in the start-lag phase (0 h, without the addition of H₂O₂), indicated by glutathione and protein sulfhydryl, was impaired in the lag phase (3 h and 12 h) and then gradually recovered during subsequent growing stages (20 h and 30 h). By using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and proteomics analysis, a total of 163 proteins such as PhoP family transcriptional regulator, glutamine synthetase, peptide methionine sulfoxide reductase, thioredoxin reductase, ribosomal proteins, acetolactate synthase, ATP binding subunit ClpX, phosphoglycerate kinase, UvrABC system protein A and UvrABC system protein B were identified as differential proteins across the entire growth phase. Those proteins were mainly involved in H₂O₂ sensing, protein synthesis, repairing proteins and DNA lesions, amino sugar and nucleotide sugar metabolism. Our data suggest that biomolecules of L. plantarum NJAU-01 are oxidized to passively consume H₂O₂ and are restored by the enhanced protein and/or gene repair systems.