Impaired Insulin Sensitivity and Secretion in Patients with Alzheimer's Disease: The Relationship with Other Atherosclerosis Risk Factors.

BACKGROUND: The growing body of evidence suggests that atherosclerosis risk factors are important in cognitive decline. OBJECTIVE: To analyse insulin sensitivity, insulin secretion capacity, plasma insulin, adiponectin and lipid levels in normoglycaemic, nonobese patients with Alzheimer's disease (AD) (group A, n=62), mild cognitive impairment (MCI) (group B, n=41), and healthy controls (group C, n=25). METHOD: Insulin sensitivity was determined by euglycemic hyperinsulinaemic clamp (M value) and homeostasis model assessment (HOMA-IR), insulin secretion capacity by first-phase insulin response (FPIR), plasma insulin by RIA, adiponectin by ELISA, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides by enzymatic method. RESULTS: Insulin sensitivity was the lowest in group A (M value: A: 6.2±2.5; B:7.7±2.7; C:8.2±1.5 mg/min/kg, p<0.001; HOMA-IR: A: 4.6±2.2; B: 3.3±1.7; C: 1.5±1.0, p<0.001) as well as FPIR (A:68.9±27.8; B:112.5±47.1; C:147.4±56.0 mU/l, p<0.001). Plasma insulin was higher in group A vs B vs C, while adiponectin was lower in group A vs B vs C. Simultaneously, total and LDL-C were higher and HDL-C levels were lower in groups A and B vs C, with no difference between groups A and B. Triglycerides did not differ between the groups. Binary logistic regression analysis identified only M value, FPIR and plasma insulin as independent predictors of AD and MCI. CONCLUSION: These results imply that in AD and MCI insulin resistance with increased plasma insulin and decreased FPIR may be associated with the development of AD and MCI, accompanied with milder influence of low adiponectin levels and atherogenic lipid profile.

Conformational targeting of intracellular Aß oligomers demonstrates their pathological oligomerization inside the endoplasmic reticulum.

Aß oligomers (AßOs) are crucially involved in Alzheimer's Disease (AD). However, the lack of selective approaches for targeting these polymorphic Aß assemblies represents a major hurdle in understanding their biosynthesis, traffic and actions in living cells. Here, we established a subcellularly localized conformational-selective interference (CSI) approach, based on the expression of a recombinant antibody fragment against AßOs in the endoplasmic reticulum (ER). By CSI, we can control extra- and intracellular pools of AßOs produced in an AD-relevant cell model, without interfering with the maturation and processing of the Aß precursor protein. The anti-AßOs intrabody selectively intercepts critical AßO conformers in the ER, modulating their assembly and controlling their actions in pathways of cellular homeostasis and synaptic signalling. Our results demonstrate that intracellular Aß undergoes pathological oligomerization through critical conformations formed inside the ER. This establishes intracellular AßOs as key targets for AD treatment and presents CSI as a potential targeting strategy.

Characterization of mitochondrial dysfunction in the 7PA2 cell model of Alzheimer's disease.

The 7WD4 and 7PA2 cell lines, widely used as cellular models for Alzheimer's disease (AD), have been used to investigate the effects of amyloid-ß protein precursor overexpression and amyloid-ß (Aß) oligomer accumulation on mitochondrial function. Under standard culture conditions, both cell lines, compared to Chinese hamster ovary (CHO) control cells, displayed an ~5% decrease of O2 respiration as sustained by endogenous substrates. Functional impairment of the respiratory chain was found distributed among the protein complexes, though more evident at the level of complex I and complex IV. Measurements of ATP showed that its synthesis by oxidative phosphorylation is decreased in 7WD4 and 7PA2 cells by ~25%, this loss being partly compensated by glycolysis (Warburg effect). Compensation proved to be more efficient in 7WD4 than in 7PA2 cells, the latter cell line displaying the highest reactive oxygen species production. The strongest deficit was observed in mitochondrial membrane potential that is almost 40% and 60% lower in 7WD4 and 7PA2 cells, respectively, in comparison to CHO controls. All functional parameters point to a severe bioenergetic impairment of the AD cells, with the extent of mitochondrial dysfunction being correlated to the accumulation of Aß peptides and oligomers.