CEREBRAL VASCULAR HEALTH AND ACCELERATED LEUKOCYTE TELOMERE SHORTENING IN TYPE II DIABETES

Author: Samira Tajbakhsh

Tajbakhsh, Samira, 2017 CEREBRAL VASCULAR HEALTH AND ACCELERATED LEUKOCYTE TELOMERE SHORTENING IN TYPE II DIABETES, Flinders University, School of Health Sciences

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Abstract

Background: Hyperglycaemia and insulin resistance are the main causes of type 2 diabetes (T2D). The prevalence of T2D is rapidly growing with 257 million people worldwide having the disease in 2010. T2D increases the risk of emergent cardiovascular disease in patients. Within the vasculature, the endothelium becomes dysfunctional and the cells develop a senescence-like phenotype. Senescent cells can no longer replicate and, more importantly, release destructive factors that promote other diseases such as cardiovascular disease. Preventing cellular senescence could therefore curtail the onset of T2D-related diseases. Cells can become senescent through disruption of their telomeres; protective DNA-protein caps at the end of the chromosome. Damaged telomeres predisposes the cell to chromosomal instability, DNA damage and disease risk. Despite the profound effects of inflammation and oxidative stress (key events in T2D) on telomeres, there is virtually nothing known regarding telomere integrity in the T2D vasculature. Therefore the objective of this project is to assess DNA telomeric length in an established animal model of T2D. We will test the hypothesis that T2D causes both vascular cell and leukocyte telomere shortening. Methods: Male Hooded Wistar rats were split into two groups, control and T2D and were fed either a normal diet or high-fat diet, followed by an injection of a low dose of vehicle or streptozotocin. Blood parameters were measured and SIRT1, eNOS, and immunoblotting in cerebral artery lysates was used to assess the markers of oxidative stress including manganese superoxide dismutase (MnSOD), p66Shc, 3-nitrotyrosine (3-NT) and Nox2. DNA was extracted from whole blood DNA and femoral artery and telomere length (T/S ratio) measured using qPCR. Results: Fasting blood glucose, free fatty acids and C-reactive protein were significantly higher in T2D rats in comparison with control rats. Plasma insulin and leptin were significantly lower in T2D rats. Cerebral artery protein expression of SIRT1, eNOS, MnSOD and p66Shc were significantly reduced in T2D rats compared with control rats. However, 3 NT and Nox2 protein expression were comparable between groups. Arterial telomere length was comparable while leukocyte telomere length was significantly shorter in T2D rats compared with their control counterparts. Conclusions: Our results suggest that telomere length was shortened in leukocytes but not in arteries, in T2D compared with control rats. T2D was associated with reduced vascular SIRT1, eNOS and MnSOD protein expression. We have demonstrated that hyperglycaemia and down regulation of vascular SIRT1 are not sufficient to prematurely shorten vascular telomeres.

Keywords: Type II Diabetes, Teleomere Shortening, Cerebral Vasculature, Leukocyte Telomere, Rats, artery telomere length, leukocyte telomere length, SIRT1, eNOS, MnSOD, T2D.
Subject: Health Sciences thesis

Thesis type: Masters
Completed: 2017
School: School of Health Sciences
Supervisor: Dr. Elke Sokoya