Epsilon Open Archive

Abstract

The prevalence of overweight in dogs is increasing. Canine overweight is associated with reduced quality of life, shorter life expectancy and metabolic variations such as insulin resistance and postprandial hyperlipidaemia. Previous metabolic research on overweight dogs has been performed mainly in fasting condition and studies on spontaneously overweight dogs using dynamic metabolic tests are scarce. This thesis therefore evaluated metabolic variations in spontaneously overweight dogs using a feed-challenge test.

Lean and overweight healthy Labrador Retriever dogs underwent a feed-challenge test. Blood and urine samples collected at fasting and after food intake were analysed with serum biochemistry, ELISA and metabolomics techniques. Multivariate and mixed model repeated measurements analyses were used to evaluate responses between body condition groups and/or between time points in the feed-challenge test.

Postprandial serum triglycerides were higher in prominently overweight dogs compared with lean, while no differences between groups were found at fasting. Only one fasted plasma phosphatidylcholine showed higher concentration in prominently overweight compared with lean dogs. Postprandial urine metabolomes, but not fasting metabolomes, distinguished between lean and overweight groups of dogs. Prominently overweight dogs had higher fasting urine cortisol/creatinine ratio than lean dogs, and overweight dogs showed signs of amino acid catabolism in postprandial urine. The acetylcarnitine response in overweight dogs indicated low fatty acid oxidation at fasting and metabolic inflexibility to food intake. Overweight dogs also showed lower carnitine and taurine status than lean dogs, potentially representing an interrelated insufficiency that could theoretically slow down lipid metabolism.

In conclusion, spontaneously overweight Labrador Retriever dogs displayed variations in metabolic parameters compared with lean dogs. Use of a feed-challenge test allowed detection of subtle metabolic variations not noticeable in fasted condition, emphasising the importance of using dynamic tests in metabolic research on canine overweight. Six parameters, all directly or indirectly associated with lipid metabolism, differed between overweight and lean dogs. In this thesis, the complexity of lipid metabolism in canine overweight was revealed by identifying previously known and new metabolic variations in spontaneously overweight Labrador Retriever dogs.