Browsing by Author "Williams, Lois Esther"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    ATM Expression in peripheral blood mononuclear cells as a biomarker of insulin resistance
    (Stellenbosch : Stellenbosch University, 2019-04) Williams, Lois Esther; Huisamen, Barbara; Stellenbosch University. Faculty of Engineering. Dept. of Biomedical Sciences: Medical Physiology.
    Introduction: The Ataxia Telangiectasia Mutated (ATM) gene codes for the 350 kDa ATM protein kinase. ATM gene mutations cause inactivity/deficiency of the ATM protein, resulting in the autosomal recessive disease Ataxia Telangiectasia (AT). AT patients are predisposed to developing insulin resistance or further progress to type 2 diabetes and are at high risk of developing ischaemic heart disease. Due to the prevalence of insulin resistance in AT patients, we investigated the relationship between ATM protein levels and the degree of insulin resistance and proposed it as a possible early diagnostic technique for insulin resistance. Aim: To determine whether peripheral blood mononuclear cells (PBMCs) can be used to determine ATM levels in insulin resistant subjects and subsequently used as a biomarker of insulin resistance. Objectives: (i) To standardise a protocol for the isolation of PBMCs from rat blood. (ii) To isolate rat PBMCs and determine the ATM levels using Western blotting. (iii) To determine differences between ATM levels in obese rats and compare them to controls. (iv) To analyse PBMCs from a female Black Xhosa population with different degrees of insulin resistance and to determine a relationship with ATM levels. Methods: Male Wistar rats were fed an obesogenic diet (od) for 16 weeks to induce obesity and insulin resistance and compared to age-matched and young controls fed standard rat chow. Body weight and intraperitoneal (IP) fat mass were determined and oral glucose tolerance test (OGTT) was performed. PBMCs were isolated according to the standardised protocol and Western blotted for ATM and P22phox. The Western blotting protocol was repeated with samples collected from patients. Results from the animal model: 1. Effects of obesity/insulin resistance vs. age-matched controls: (i) larger IP fat mass; (ii) increased area under the curve of OGTT’s; (iii) elevated basal glucose levels. (iv) The phospho-(P)/total-(T) ATM ratio was decreased. 2.Effects of age: (i) As expected, older animals weighed more while T-ATM was decreased, P-ATMincreased and the P-/T-ATM ratio increased with age. In PBMC’s from patients, the following were observed: (i) Body mass index (BMI) was significantly higher in obese and pre-diabetic vs. control patients. (ii) The waist-to-hip ratio (WHR) of obese and pre-diabetic women was higher vs. controls. (iii) Trunk-to-limb fat mass (TF/LF) was increased in obese and pre-diabetics vs. controls but (iv) no differences in the lipid profiles were observed except for increased triglyceride levels between young pre-diabetic patients vs. their controls. (v) Fasting blood glucose of obese and pre-diabetic patients was significantly increased vs. controls. (vi) Significantly higher P-ATM levels were seen for obese and pre-diabetic vs. control patients. T-ATM levels increased with the state of insulin resistance. Effects of age: (i) BMI was significantly higher between young (Y) and middle aged (MA) control, obese and pre-diabetic groups vs. their respective controls while (ii) WHR of Y obese and Y pre-diabetic vs. Y controls also increased significantly. (iii) The TF/LF ratio was increased between Y and MA control and Y obese, Y pre-diabetic, MA obese and MA pre-diabetic women vs. their respective controls. Furthermore (iv) the blood glucose levels of Y pre-diabetics were increased vs. Y control. (v) The P-ATM levels was increased in Y pre-diabetic vs. Y control and therefore did not increase with age but the T-ATM levels significantly increased with age. Conclusion: ATM levels can be measured in PBMCs and are affected by the insulin resistant state and age. Unfortunately, due to the variation in ATM levels under different degrees of insulin resistance, it would be difficult to use ATM as a biomarker of insulin resistance.