Leukocyte telomere length is reduced in patients with abdominal aortic aneurysm

Atturu.G, Brouilette.S, Bown.M.J., Samani.N.J.,Sayers.R.D.,

Vascular surgery group, Department of Cardiovascular Sciences,

University of Leicester, Leicester

Abdominal aorta is the commonest site for aneurysm and the incidence rises sharply after the age of 65. A variety of environmental, haemodynamic and genetic factors has been implicated in the pathogenesis of Abdominal Aortic Aneurysm (AAA) but in particular age is strongly associated with AAA. Telomeres are specialised DNA structures present at the ends of linear chromosome. (Fig 1) In the absence of telomerase the Telomere length shortens with each successive cell division due to ‘end replication problem’ and acts as a mitotic clock which represents cellular biological age. (Fig. 2). Shorter telomere length in white blood cells is associated with vascular aging, Essential hypertension and other vascular risk factors.

The Demographics of the patients were as shown below

The aim of this study was to determine the relationship between Abdominal Aortic Aneurysm (AAA) and white cell telomere length.

Peripheral blood samples were collected from 70 male patients with AAA and 70 age matched male controls. Genomic DNA was extracted from the buffy coat and digested with RsaI and HinfI enzymes. The DNA fragments were seperated by 0.5% agarose gels electrophoresis at 50 V for 18 hours and transferred to a nylon membrane using Southern blotting. The DNA fragments were hybridised with a telomere repeat specific DIG labelled probe and incubated with DIG specific antibody coupled with alkaline phosphatase. The telomere lengths were then measured using chemilumiscence technique with telo-TAGGG telomere length assay kit (Roche-applied science). A sample photograph of the gel is shown in fig. 3. Data was analyzed using Student’s t-test and Pearson correlation (SPSS v14.0).

Patients with abdominal aortic aneurysms have significantly shorter leukocyte telomere lengths than healthy controls and in patients with AAA, aortic size is inversely associated with telomere lengths. This suggests that cellular biological ageing may have a role in the pathogenesis and progression of AAA.

Introduction

Aim

Method

Results

Conclusion

Demographics

  Aorta Control

Total no of patients 70 70

Males 70 70

Mean age 66.3 66.1

Smokers 66 40

HTN 37 25

MI 26 5

Family history of Aneurysm 9 5

Average aneurysm size in cm 4.87 0

Fig. 1 Telomere Complex

The median age of cases and controls was 66 years (range 61 years to 84 years). The mean white cell telomere length was significantly lower in AAA patients compared to controls.(Fig. 4) The mean difference in telomere length between the cases and controls was 283 base pairs (95% confidence interval 480bp to 84bp) (P = 0.005). This difference persisted even after the confounding factors were removed in a regression model. Smoking was significantly associated with telomere length both in cases and controls. There was a significant negative correlation between the size of AAA and telomere length (larger AAA had shorter telomere lengths) (r = -.38, n = 70, P <0.002). (Fig. 5)

Fig. 3 Photograph showing the telomere length bands

MWM MWMControl

Fig. 2 End Replication problem

Fig. 4 Mean telomere lengths of AAA patients and controls

Fig. 5 showing inverse relationship between AAA size and telomere length