Apolipoprotein E4 Elicits Lysosomal Cathepsin D Release, Decreased Thioredoxin-1 Levels, and Apoptosis.

The major genetic risk factor for Alzheimer's disease (AD), apolipoprotein E4 (ApoE4), has been suggested to have detrimental effects on neurons, including direct toxicity via apoptosis. Thioredoxin-1 (Trx1) is an endogenous antioxidant protein important for redox regulation and participates in the regulation of apoptosis through the inhibition of apoptosis signal-regulating kinase-1 (Ask-1). In this study, we have investigated the effects of ApoE on Trx1 in the brain. Our results showed that the protein levels of Trx1 were reduced in the hippocampus of ApoE4 targeted replacement (TR) mice compared to ApoE3 TR mice. The reduction was also seen in vitro after treatment of both human primary cortical neurons and neuroblastoma cells with human recombinant ApoE4 (rApoE4). Furthermore, ApoE4 caused a disruption of lysosomal integrity and a shift in the localization of Cathepsin D, an enzyme known to degrade Trx1. ApoE4 treatment induced in addition apoptosis through translocation of Death-domain associated protein-6 (Daxx) from the nucleus to the cytosol, suggesting an activation of the Ask-1 pathway. This toxicity was prevented by overexpression of Trx1 and other endogenous Ask-1 inhibitors. Our data suggests that down-regulation of Trx1 is involved in the toxicity caused by ApoE4. An activated ASK-1 pathway might indeed make cells more vulnerable to other insults such as amyloid-ß, which could partially explain the mechanism behind the strongest genetic risk factor for AD.

FTO risk haplotype among early onset and severe obesity cases in a population of western Spain.

Childhood and adult obesity have been widely associated with FTO genetic variability in different populations. This study aimed to investigate the linkage disequilibrium (LD) block structure of a region surrounding the candidate rs9939609 SNP and determine the best single nucleotide polymorphism (SNP) combination that explains the higher proportion of variability observed in children with severe obesity, including obese subjects from families with a very high occurrence of obesity. A sliding window approach pointed to a block containing the rs1477196/rs17817449/rs9939609 haplotype (P value 3.1 × 10(-8)). Carriers of the GGA combination had an increased risk of obesity (odds ratio (OR) 2.07, 95% confidence interval (CI) 1.41-3.04, P = 2.0 × 10(-4)) with respect to those individuals with the reference ATT haplotype. A further SNP, rs9921255, also showed association with obesity (P = 8.3 × 10(-4), OR 1.77; 95% CI 1.15-2.74 and OR 5.78; 95% CI 1.22-27.49 for heterozygotes and homozygotes, respectively) and did not segregate with the previously described risk haplotype. The calculation of risk score based on the GGA haplotype combined with the rs9921255 variant showed a much greater effect of the FTO gene on high BMI. This score yields an attributable risk of 34% for severe obesity, and the increased risk per risk allele was 1.71 (P = 1.0 × 10(-6)). We conclude that the description of this polymorphic combination in the FTO gene could be useful for the early identification of inherited susceptibility to weight-gain since childhood, with a higher sensitivity than considering the effect of a single marker.