Evaluating the impact of environmental tobacco smoke on biological age markers: a canine model

This thesis aimed to examine the impact of environmental tobacco smoke on biological markers of ageing in pet dogs. In order to achieve this, community-based dogs and owners were recruited, approximately half of whom lived in smoking homes and half non-smoking homes. Owners were asked to attend 2 appointments, 12 months apart. Questionnaire assessments of dog environmental tobacco smoke exposure were compared to biomarkers in hair of the dogs (Chapter 3). This gave an objective measure of exposure and hair nicotine concentrations reliably reflected information provided by owners. A qPCR technique was optimised to measure telomere lengths (Chapter 4). This was utilised to measure telomere lengths in leukocytes, buccal cells, cremaster muscle, vas deferens and epididymis samples from the study dogs. Owners were offered free-of-charge neutering for their pet, and the spare tissues used for these analyses. A negative relationship in leukocyte telomere length with hair nicotine was observed, among other changes (Chapter 5). mRNA levels of further biomarkers of ageing were measured in testes, as well as leukocyte global DNA methylation percentage (Chapter 6). Again, several significant relationships were found between tobacco smoke exposure markers and the biomarkers of ageing, including a significant negative relationship with CDKN2A expression with increased tobacco smoke exposure. Plasma testosterone and hair cortisol concentrations were measured. In addition, factors which related to weight gain after neutering were examined (Chapter 7). Increased cotinine concentrations in fur were significantly related to increased percentage weight gain. Several avenues for future research were generated, and many areas warrant further investigation