Apolipoprotein e variants E 78.0

Lipid metabolic disorder in patients with the epsilon 4 allele of apolipoprotein E and expression of the phenotype E2, E3 or E4 (Huebbe P et al. (2017). This promotes the development of type III hyperlipoproteinaemia (see Fredrickson classification). ApoE2 leads to increased ApoE values and as a consequence to low LDL, ApoB and lipoprotein A values. The ApoE4 variant has the opposite effect: a low ApoE level with consecutively elevated LDL, ApoB and lipoprotein A values. Accordingly, E4 carriers have an increased cardiovascular risk and with increasing age an increased risk of developing Alzheimer's disease (Ferri E et al. 2019). According to more recent study data, the allele also increases the risk of Parkinson's disease (Pal P et al. 2019).

The individual alleles occur with the following frequency in the European population:

• APOE3: 70 to 80%
• APOE4: 10 to 15
• APOE2: 7 to 10

Homozygous for APOE4 are about 2 to 3% of the population.

Allele frequency in M. Alzheimer:

• APOE3: 60 to 70%
• APOE4: 30 to 40
• APOE2: 2 to 5%

It is assumed that the degradation of ApoE leads to increased production of toxic fragments that disturb the cytoskeleton and the energy metabolism in the mitochondria. In this way, ApoE could promote the apoptosis of neurons.

Apolipoprotein E, in short ApoE, is a structural protein in the phospholipid membrane of lipoproteins. Lipoproteins mediate the transport of triglycerides and cholesterol in the blood. Function: In the brain, apolipoprotein E is involved in neurite growth and in the regeneration of axons and myelin.

ApoE is mainly expressed in the liver, brain, kidney and spleen. The protein plays an important role in the catabolism of chylomicrons, IDL (intermediate density lipoproteins), VLDL-remnants (VLDL= very low density lipoproteins) as well as of ApoE-rich HDL. ApoE mediates the cellular uptake of lipoproteins by binding to the Apo E-receptor as well as to the LDL-receptor in the different organs (e.g. liver and small intestine). The frequency of polymorphisms in the APO gene increases with age (Ferri E et al. 2019). They lead to 3 clinically relevant gene variants with the following gene products: ApoE2 ApoE3 and ApoE4. ApoE3 and ApoE4 have a normal binding affinity to the LDL receptor. ApoE2 on the other hand has a significantly lower receptor binding

1. Ferri E et al (2019) Apolipoprotein E gene in physiological and pathological aging. Mech Ageing Dev 178:41-45.
2. Huebbe P et al. (2017) Evolution of human apolipoprotein E (APOE) isoforms: gene structure, protein function and interaction with dietary factors. Ageing Res Rev 37:146-161.
3. Pal P et al. (2019) Role of Apolipoprotein E, Cathepsin D, and Brain-Derived Neurotrophic Factor in Parkinson's Disease: A Study from Eastern India. Neuromolecular Med. 2019 May 28.
4. Xie W et al. (2019) A novel apolipoprotein E mutation caused by a five amino acid deletion in a Chinese family with lipoprotein glomerulopathy: a case report. Diagn Pathol 14:41.