Apolipoprotein E4 interferes with lipid metabolism to exacerbate depression-like behaviors in 5xFAD mice

Background:Apolipoprotein E4(ApoE4)allele is the strongest genetic risk factor for late-onset Alzheimer's disease,and it can aggravate depressive symptoms in non-AD patients.However,the impact of ApoE4 on AD-associated depression-l ike behaviors and its underlying pathogenic mechanisms remain unclear.Methods:This study developed a 5xFAD mouse model overexpressing human ApoE4(E4FAD).Behavioral assessments and synaptic function tests were conducted to explore the effects of ApoE4 on cognition and depression in 5xFAD mice.Changes in peripheral and central lipid metabolism,as well as the levels of serotonin(5-HT)andγ-aminobutyric acid(GABA)neurotransmitters in the prefrontal cortex,were examined.In addition,the protein levels of 24-dehydrocholesterol reductase/glycogen synthase kinase-3 beta/mammalian target of rapamycin(DHCR24/GSK3β/m TOR)and postsynaptic density protein 95/calmodulin-dependent protein kinase II/brain-derived neurotrophic factor(PSD95/CaMK-II/BDNF)were measured to investigate the molecular mechanism underlying the effects of ApoE4 on AD mice.Results:Compared with 5xFAD mice,E4FAD mice exhibited more severe depressionlike behaviors and cognitive impairments.These mice also exhibited increased amyloid-beta deposition in the hippocampus,increased astrocyte numbers,and decreased expression of depression-related neurotransmitters 5-HT and GABA in the prefrontal cortex.Furthermore,lipid metabolism disorders were observed in E4FAD,manifesting as elevated low-density lipoprotein cholesterol and reduced high-density lipoprotein cholesterol in peripheral blood,decreased cholesterol level in the prefrontal cortex,and reduced expression of key enzymes and proteins related to cholesterol synthesis and homeostasis.Abnormal expression of proteins related to the DHCR24/GSK3β/m TOR and PSD95/CaMK-II/BDNF pathways was also observed.Conclusion:This study found that ApoE4 overexpression exacerbates depressionlike behaviors in 5xFAD mice and confirmed that ApoE4 reduces cognitive function in these mice.The mechanism may involve the induction of central and peripheral lipid metabolism disorders.Therefore,modulating ApoE expression or function to restore cellular lipid homeostasis may be a promising therapeutic target for AD comorbid with depression.This study also provided a better animal model for studying AD comorbid with depression.

The Study of Apolipoprotein E4 Allele Distribution in Parents of Down’s Syndrome Children as a Risk Factor in Khorasan Razavi Province, Iran

Backgrounds: Down syndrome (DS) is the most common chromosomal abnormality. The most important factor in DS is increased maternal age so after the age of 35, the risk of Down syndrome in pregnancy increases. Down syndrome can be diagnosed during pregnancy by prenatal screening. Nondisjunction in cell divisions is the main cause of the DS. Apo lipoprotein E is a 317 amino acid glycoprotein that plays an essential role in metabolism and cholesterol transport. Alzheimer’s disease (AD) is one of the symptoms of adults with DS. The apoE allele e4 has been identified as a risk factor for AD and also, played a main role in nondisjunction. An increased risk of AD in mothers of adults with DS has been reported. We hypothesized that young mothers of DS children (Methods: In this case-control study, 33 DS children and their parents were compared in case of age with 90 families without any history of DS. Genotyping was performed by ARMS-PCR technique. Statistical analysis was performed by SPSS v.21 software. Results: It indicated that there is a significant difference in allele distribution between case and control groups. The C allele for 112 codon of APOE gene and the C allele for 158 codon of APOE gene may associate with nondisjunction. In 112 codon of APOE gene, it seems having T allele reduces the risk of nondisjunction and in contrast C allele may be a risk factor in happening of nondisjunction. (p-value = 0.000006, OR = 2.66, 95% CI = 1.74 - 4.06). In 158 codon of APOE gene, it seems having T allele reduces the risk of nondisjunction and in contrast C allele may be a risk factor in happening of nondisjunction. (p-value = 0.0000, OR = 3.89, 95% CI = 2.38 - 6.34). E4 allele frequency in mothers of DS is about 14% more than those in control group. According to results of this study the C allele in 158 codon of APOE gene and the C allele in 112 codon of APOE gene could be considered as susceptibility genetic factors for nondisjunction in Northeast of Iran.

Genetic predisposition to inflammation:a new risk factor of Alzheimer's disease

Inflammation has been shown to play an important role in the progression of Alzheimer＇s disease （AD）. Recent epidemical study indicates that the incidence of AD in some populations is substantially influenced by the gene polymorphisms of the inflammation mediators. Meanwhile, an ensured risk factor, the ApoE ε4 allele is also reported to directly promote inflammation. Accordingly, it appears that an individual genetic background has partly determined his predisposition for AD by the extent of the inflammation response to the chronic stimulus by β-amyloid peptide （Aβ） deposits and other antigen stressor in the elderly. Hence we present a hypothesis that the inflammation genotypes may contribute to AD susceptibility. This may provide a new orientation both for future identification of individuals at risk and for personalized medication.