Abstract
Obesity in dogs is an increasing problem and better knowledge of the metabolism of overweight dogs is needed. Identification of molecular changes related to overweight may lead to new methods to improve obesity prevention and treatment. The aim of the study was firstly to investigate whether Nuclear Magnetic Resonance (NMR) based metabolomics could be used to differentiate postprandial from fasting urine in dogs, and secondly to investigate whether metabolite profiles differ between lean and overweight dogs in fasting and postprandial urine, respectively. Twenty-eight healthy intact male Labrador Retrievers were included, 12 of which were classified as lean (body condition score (BCS) 4–5 on a 9-point scale) and 16 as overweight (BCS 6–8). After overnight fasting, a voided morning urine sample was collected. Dogs were then fed a high-fat mixed meal and postprandial urine was collected after 3 hours. Metabolic profiles were generated using NMR and 45 metabolites identified from the spectral data were evaluated using multivariate data analysis. The results revealed that fasting and postprandial urine differed in relative metabolite concentration (partial least-squares discriminant analysis (PLS-DA) 1 comp: R2Y = 0.4, Q2Y = 0.32; cross-validated ANOVA: P = 0.00006). Univariate analyses of discriminant metabolites showed that taurine and citrate concentrations were elevated in postprandial urine, while allantoin concentration had decreased. Interestingly, lean and overweight dogs differed in terms of relative metabolite concentrations in postprandial urine (PLS-DA 1 comp: R2Y = 0.5, Q2Y = 0.36, cross-validated ANOVA: P = 0.005) but not in fasting urine. Overweight dogs had lower postprandial taurine and a trend of higher allantoin concentrations compared with lean dogs. These findings demonstrate that metabolomics can differentiate 3-hour postprandial urine from fasting urine in dogs, and that postprandial urine metabolites may be more useful than fasting metabolites for identification of metabolic alterations linked to overweight. The lowered urinary taurine concentration in overweight dogs could indicate alterations in lipid metabolism and merits further investigation.
Highlights
Obesity is an increasing problem in the pet dog population [1, 2], mimicking the human situation worldwide
Vital parameters at physical examination were within the reference range for healthy dogs, but minor health problems were found in 11 dogs, e.g. slightly stiff gait and mild lameness, signs of periodontitis, palpable peri-articular osteophyte formation and skin furunculosis
This study demonstrated that Nuclear Magnetic Resonance (NMR)-based metabolomics can differentiate 3-hour postprandial urine from fasting urine and can be used for evaluation of metabolic events in response to food intake in dogs
Summary
Obesity is an increasing problem in the pet dog population [1, 2], mimicking the human situation worldwide. Overweight dogs have been shown to display metabolic alterations [5,6,7], many of which are found in obese humans [8]. Investigations of the metabolism of obese phenotypes using metabolomics have shown promising results in human and rodent models [12, 13]. A number of studies suggest that urine metabolites can discriminate between lean and overweight subjects [14, 15], revealing metabolites associated with obesity and potentially altered metabolic pathways. To the best of our knowledge, no previous study has reported the use of urine metabolomics to analyse postprandial samples or alterations associated with overweight in dogs
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