The relationships between environment, diet, transcriptome and atopic dermatitis in dogs
Updated: Oct 21
DATE: 2018 (Doctoral Dissertation)
AUTHOR: Anturaniemi, Johanna
Canine atopic dermatitis (CAD) is a multifactorial disease including genetic predisposition and other predisposing factors like living environment and diet. There is no known cure for this disease. The right and functional treatment can be hard to find, and more effort should be put into the prevention. The aim of this thesis was to find environmental factors and breeds associated with allergic skin symptoms and atopic dermatitis in pet dogs. In addition, the effect of a raw diet on gene expression, physiology and metabolism was studied with clinical diet intervention trial setup, using client-owned dogs. A population of 8643 dogs from the validated DOGRISK questionnaire was used to analyse the environmental factors and dog characteristics related to CAD. Five breeds with the most owner-reported skin symptoms as a percentage within the breed were found to be i) West Highland white terrier, ii) boxer, iii) English bulldog, iv) Dalmatian, and v) French bulldog. When FCI breed groups were compared to mixed-breed dogs, groups 3 (Terriers) and 6 (Scent hounds and related breeds) had a significantly higher risk for owner-reported skin symptoms. On the other hand, groups 5 (Spitz and primitive types) and 10 (Sighthounds) had a significantly lower risk for owner-reported skin symptoms. The environmental factors found significantly associated with less owner-reported skin symptoms and veterinary-verified CAD were i) being born in the owner family and ii) living with other dogs. In addition, significant association of less owner-reported skin symptoms was found with dogs living in a detached house. Factors that were significantly associated with more owner-reported skin symptoms included extremely clean household and over 50 % of white colour in the coat. In the clinical diet intervention study, 46 client-owned atopic and healthy Staffordshire bull terriers were fed two different kind of diets (raw and dry food). Haematological and clinical chemistry profiles, folate, B12, iron, and transforming growth factor β1 (TGF- β1) concentration were analyzed. In addition, gene expression profiles were determined from the skin samples of eight dogs. Cholesterol was significantly increased in the dry food fed dogs and decresed in the raw food fed dogs. In addition, the raw food significantly decreased, among others, alkaline phosphatase and glucose. Plasma folate and B12 and whole blood iron were significantly decreased, and TGF- β1 significantly increased by the raw food diet. The skin gene expression was also affected by the diet. There were genes related to immune defence, reactive oxygen species and antioxidants upregulated in the dogs fed raw food. Several genes were found differentially expressed between atopic and healthy dogs, some unrelated to diet fed and some differentially affected by the diet in atopic and healthy dogs. These results are preliminary and should be confirmed using more samples. Nevertheless, they give an interesting and novel information about the effect of the diet on the skin gene expression. In conclusion, this thesis presents results from different study designs all concentrating on the same disease, canine atopic dermatitis. Many results presented here are related to immune defense and exposure to microbes. Too clean environment and food might not stimulate the immunity enough and could lead to incorrect development of the immune system in young animals. The incomplete stimulation could result in CAD and hypersensitivities later in life, and should be considered when thinking of the prevention of these diseases.