Apolipoprotein AIV codon 360 mutation increases with human aging and is not associated with Alzheimer’s disease

Aksam Merched, Yongjing Xia, Anna Papadopoulou, Ge´rard Siest, Sophie Visvikis*

CentredeMe´decinePre´ventiveUPRES,2,rueduDoyenJacquesParisot,F-54501Vandoeuvre-le`s-Nancy,France

Received 8 December 1997; received in revised form 29 December 1997; accepted 29 December 1997

Abstract

In order to evaluate genetic apolipoprotein polymorphisms as risk factors for Alzheimer’s disease (AD), we studied apolipo- protein (apo) AIV after apoE, an apolipoprotein also present in the brain. The allelic distribution of apoAIV codon 360 poly- morphism was no different in AD group (n= 120) compared with elderly healthy individuals (n= 119). Surprisingly, this polymorphism was over-represented (11.40%, vs. 5.7% P, 0.005) in all these aged subjects (74.29 – 8.46 years) and inde- pendently of the clinical and mental status compared with the younger population (39.00 – 9.69 years) of the same regional recruitment. These results suggest that the apoAIV (360:His) allele could be a marker of aging and longevity.  1998 Elsevier Science Ireland Ltd.

Keywords: Longevity; Genetic marker; Alzheimer’s disease; Apolipoprotein E; Apolipoprotein AIV (360:Gln:His); DNA morphism

cell culture and animal models [3,10]. Others suggest that apoAIV may act in the CNS as a factor to control appetite during food intake [8].

Apolipoprotein (apo) AIV is a component of chylomi- crons and high-density lipoproteins which shows a genetic polymorphism in Caucasian populations with two common alleles, ApoAIV-1 and ApoAIV-2. Previously, we identified these alleles to be a result of glutamine (CAG) to histidine (CAT) substitution at codon 360 [1]. Postulated functions of this apolipoprotein include: acting as an activator of the enzyme lecithin:cholesterol acyltransferase (LCAT) [20], promoting removal of cellular cholesterol from extrahepatic tissue [21] and modulating the activation of lipoprotein lipase by apoC-II [9]. Genetic-association studies have demonstrated a relationship between apoAIV polymorph- ism and interindividual variability in plasma cholesterol, triglyceride and glucose levels in supposedly healthy popu- lations, but the results have been somewhat controversial [15–17,25]. Little is known about the function of this apo- lipoprotein at the level of the central nervous system (CNS). Some studies have attributed roles to apoAIV during degen- erative and regenerative processes in the peripheral and central nervous systems, as well as during development in

It was reported that apoAIV was first supposed to cross the blood-brain-barrier [6,14]. However, the recent localiza- tion of apoAIV within the brain [12] and in the CSF [2] increases the potential role of this protein in the CNS. Unchanged apoAIV expression in Alzheimer’s disease (AD) brains compared with controls suggests that qualita- tive rather than quantitative change may be linked to this pathology. Collectively, these data led us to investigate the common apoAIV polymorphism implication in AD. We report our findings as a response to very recent results reporting an association of the apoAIV codon 360 mutation with AD [4].

The population studied included 120 patients (88 females, 32 males) with probable AD established according to the criteria of the NINCDS-ADRDA work group. All patients with AD had a mini-mental state (MMS) score of less than 25. Moreover, we included a population of 119 presumed-healthy elderly subjects (62 females, 57 males) participating in systematic health screening at the Center for Preventive Medicine in Nancy, France. These subjects were

0304-3940/98/$19.00   1998 Elsevier Science Ireland Ltd. All rights reserved PII S0304-3940(98)00025-1

Table 1

ApoE and AIV allelic distributions in AD and control groups

AD patients Elderly control group All elderly General populationa n(M/F%) 120 (27.5/72.5) 119 (51.8/48.2) 239 (60.4/39.6) 264 (50.4/49.6) Age (years – SD) 77.87 – 8.47 70.68 – 6.52 74.29 – 8.46 39.00 – 9.69 AIV allelic frequency (AIV-2) 9.5% 13.27% 11.38%b 5.68% ApoE allelic frequency e4c 27.70% 12.27% – – e3 66.84% 79.55% – – e2 5.46% 8.18% – –

a from our previous results [23]. b P, 0.005 compared with general population. c P, 0.0005 for comparison between AD and elderly control

described here and previously reported revealed similarities in AD patients but also very significant differences in elderly control groups (13.27% here vs. 3.5% in the study of Csazar et al. [4]) despite the same mean age for both groups. The reason for this discrepancy is unclear. Never- theless, it is interesting to note that the control populations in both studies were also different in ApoE genetics. ApoE4 frequency in our group was 12.27% and it was 7% in the study of Csazar et al. [4]. This is relatively low compared with the frequency of this allele in the general population of many European countries (see [19] for review). It is also low compared with what is already reported in larger popula- tions by the same authors [11] who reported a e4-allele frequency of 12.9% in a sample of 202 subjects.

supposed to be free of AD symptoms after clinical exam- inations performed by general clinicians. The results of this study were compared with those previously described from the general population of the same region [23].

Genotyping was performed with DNA isolated from nucleated blood cells [18]. The ApoE genotype was deter- mined as described elsewhere [13]. ApoAIV codon 360 genotyping was performed with a technique using a bispe- cific-allele primer amplification established in our labora- tory [26]. In this technique a simple electrophoresis of PCR products is used for typing the variation at codon 360. When DNA was not available, apoE and apoAIV phenotyping was performed using two-dimensional electrophoresis as described elsewhere [22,23].