Lymphocytes telomere length and inflammatory markers in slow and fast progressing Alzheimer’s disease patients

Introduction: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder which is characterized by cognitive impairment,memory loss and characteristic pathological changes in the brain, like senile plaques and neurofibrillary tangles. Although cerebrospinal fluid Amyloid-b, total tau, and phosphorylated tau levels were reported to be strongly associated with AD, patients showing positivity for such biomarkers represent highly heterogeneous clinical cases. Age, lymphocytes telomere shortening and inflammatory processes have been linked to an elevated risk of neurodegenerative disease, in particular AD, and might be concauses of onset and progression of this invaliding pathology. However, the pathogenesis of AD is still unclear. Aim: Aim of this work was to evaluate Telomere Length (TL) in lymphocytes of AD patients and to correlate it with inflammatory markers. Methods: A total of 45 individuals were enrolled in the study: 11 healthy young people (HYP, mean age 21.6 ± 2.1 years); 15 healthy elderly people (HEP, mean age 79.1 ± 8.4 years); 11 patients with slow AD progression (ADS, mean age 80.8 ± 5.7 years) and 8 patients with fast AD progression (ADF, mean age 80.4 ± 4.1 years). AD progression was evaluated by Mini Mental State Examination(MMSE). The patients were categorized as slow progressing if the MMSE decline was less than 3 points after 2 years of follow-up or fast progressing if the MMSE decline was more than 5 points. TL was measured by flow cytometry using telomere PNA/FITC (FL1) kit(Dako).Briefly,lymphocytes from the subjects included in this study and control cells with known telomere length, i.e. 1,301 lymphocyte cell line with TL of about 25 Kb, were mixed in a 1:1 ratio, divided into 4 aliquots (2 negatives and 2 positives) and then stained following manufacturer’s instructions. TL was measured on G0/G1 cells both in lymphocytes and 1,301 cells using the following formula: TL = [(mean FL1 of sample cells with probe-mean FL1 sample cells without probe) x DNA index of 1,301 cells 9 100]/[(mean FL1 1,301 cells with probe-mean FL1 1,301 cells without probe) 9 DNA index of sample cells] 9 25 kb. Inflammatory markers (Interleukin- 10 and Interleukin-6) were measured by ELISA (R&D Systems). Statistical analysis was performed by SPSS version 17. Results: TL (expressed as a mean ±standard error) for HYP, HEP, ADS and ADF was 3.3 ± 0.5, 2.4 ± 0.4, 1.8 ± 0.3 and 2.5 ± 0.4 kb respectively. As expected, HYP had longer telomere compared to the other 3 groups (p\0.005, ANOVA test). Interestingly, ADS had shorter telomere not only compared to HEP but also to ADF(p\0.03), while HEP and ADF had no difference. Considering inflammatory markers, we found only in ADF group a significant correlation between TL and Interleukin-10 (IL-10) levels (r2 = 0.55;p = 0.023). We didn’t found correlations with Interleukin-6 (IL-6) levels. Moreover, considering all subjects, we showed a correlation between IL10 and IL6 levels (r2 = 0.205; p\0.001) that is maintained when we evaluate separately HYP (r2 = 0.426; p\0.001), HEP (r2 = 0.495; p = 0.001) and ADF (r2 = 0.272; p =0.078) groups. This correlation is lost in ADS. Conclusions: A difference in lymphocyte TL exists between ADF and ADS. We speculate that in ADS the telomere shortening is driven by a more accelerated leukocyte biological ageing while in fast progressing higher levels of IL-10 may protect from excessive leukocyte telomere shortening modulating inflammatory response. Further studies are necessary to determine whether TL assessment at AD onset is predictive for a fast or slow progression.This contribution has been awarded as Best Communication.