The genetics of dementia

Comparison of the effects of major fatty acids present in the Mediterranean diet (oleic acid, docosahexaenoic acid) and in hydrogenated oils (elaidic acid) on 7-ketocholesterol-induced oxiapoptophagy in microglial BV-2 cells

Increased levels of 7-ketocholesterol (7KC), which results mainly from cholesterol auto-oxidation, are often found in the plasma and/or cerebrospinal fluid of patients with neurodegenerative diseases and might contribute to activation of microglial cells involved in neurodegeneration. As major cellular dysfunctions are induced by 7KC, it is important to identify molecules able to impair its side effects. Since consumption of olive and argan oils, and fish is important in the Mediterranean diet, the aim of the study was to determine the ability of oleic acid (OA), a major compound of olive and argan oil, and docosahexaenoic acid (DHA) present in fatty fishes, such as sardines, to attenuate 7KC-induced cytotoxic effects. Since elaidic acid (EA), the trans isomer of OA, can be found in hydrogenated cooking oils and fried foods, its effects on 7KC-induced cytotoxicity were also determined. In murine microglial BV-2 cells, 7KC induces cell growth inhibition, mitochondrial dysfunctions, reactive oxygen species overproduction and lipid peroxidation, increased plasma membrane permeability and fluidity, nuclei condensation and/or fragmentation and caspase-3 activation, which are apoptotic characteristics, and an increased LC3-II/LC3-I ratio, which is a criterion of autophagy. 7KC is therefore a potent inducer of oxiapoptophagy (OXIdation+APOPTOsis+autoPHAGY) on BV-2 cells. OA and EA, but not DHA, also favor the accumulation of lipid droplets revealed with Masson's trichrome, Oil Red O, and Nile Red staining. The cytotoxicity of 7KC was strongly attenuated by OA and DHA. Protective effects were also observed with EA. However, 7KC-induced caspase-3 activation was less attenuated with EA. Different effects of OA and EA on autophagy were also observed. In addition, EA (but not OA) increased plasma membrane fluidity, and only OA (but not EA) was able to prevent the 7KC-induced increase in plasma membrane fluidity. Thus, in BV-2 microglial cells, the principal fatty acids of the Mediterranean diet (OA, DHA) were able to attenuate the major toxic effects of 7KC, thus reinforcing the interest of natural compounds present in the Mediterranean diet to prevent the development of neurodegenerative diseases.

Associations between APOE polymorphisms and seven diseases with cognitive impairment including Alzheimer's disease, frontotemporal dementia, and dementia with Lewy bodies in southeast China

Supplemental Digital Content is available in the text.

Objective

To explore the effect of APOE polymorphisms on patients with cognitive impairments in The Chinese Han population.

Materials and methods

A total of 1027 cases with Alzheimer’s disease (AD), 40 cases with vascular dementia (VaD), 28 cases with behavioral variant frontotemporal dementia (bvFTD), 54 cases with semantic dementia (SD), 44 cases with dementia with Lewy bodies (DLB), 583 cases with mild cognitive impairment (MCI), and 32 cases with vascular cognitive impairment no dementia (VCIND) were recruited consecutively from memory disorders clinics in Huashan Hospital between January 2010 and December 2014. The 1149 cognitively normal controls were recruited from the community epidemiologic investigations. The APOE genotypes were determined using the TaqMan assay.

Results

The distribution of genotype and allele frequencies of APOE differed significantly between control and AD or MCI, with ε4 increasing the risk of AD and MCI in a dose-dependent pattern and ε2 decreasing the risk of AD, but not the risk of MCI. As for VaD, significant differences in the APOE genotype distribution were found compared with the controls. E4/4 increased the risk of VaD and ε4 increased the risk of VCIND in women. The allele distribution differed between bvFTD and controls, but genotype and allele frequencies of APOE did not affect the risk of bvFTD, SD, and DLB.

Conclusion

In The Chinese Han population, APOE ε4 increased the risk of AD and MCI in a dose-dependent manner and ε2 decreased the risk of AD as reported previously. APOEε4 might increase risk in VaD and female patients with VCIND, but no effects of APOE on bvFTD, DLB, and SD were found.

[Genetics of dementia]

Most psychiatric diseases in adulthood have a multifactorial origin. This also applies for most cases of dementia; however, rare familial forms of Alzheimer's disease and frontotemporal lobar degeneration follow an autosomal dominant (Mendelian) inheritance pattern. Alzheimer's disease that is caused by mutations in the genes for presenilin 1, presenilin 2 and amyloid precursor protein has an onset under the age of 65 years in most cases. Approximately 10 % of frontotemporal lobar degeneration cases display an autosomal dominant inheritance pattern. According to the current S3 guidelines on dementia of the German Association for Psychiatry, Psychotherapy and Psychosomatics and the German Society of Neurology, genetic counseling should be offered if an autosomal dominant disease pattern is suspected. Genetic counseling must conform to the German Genetic Diagnostics Act (Gendiagnostikgesetz).

The neurogenetics of atypical parkinsonian disorders

Although classic Parkinson disease is the disorder most commonly associated with the clinical feature of parkinsonism, there is in fact a broader spectrum of disease represented by a collection of phenotypically similar neurodegenerative conditions that mimic many of its core features. These atypical parkinsonian disorders most commonly include progressive supranuclear palsy and corticobasal degeneration, disorders both associated with frontotemporal dementia, as well as multiple system atrophy and dementia with Lewy bodies. Although the clinical distinction of these disorders still remains a challenge to physicians, recent advances in genetics are poised to tease apart the differences. Insights into the molecular etiologies underlying these conditions will improve diagnosis, yield a better understanding of the underlying disease pathology, and ultimately lend stimulation to the development of potential treatments. At the same time, the wide range of phenotypes observed from mutations in a single gene warrants broad testing facilitated by advances in DNA sequencing. These expanding genomic approaches, ranging from the use of next-generation sequencing to identify causative or risk-associated gene variations to the study of epigenetic modification linking human genetics to environmental factors, are poised to lead the field into a new age of discovery.