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Introduction: The study of metabolic profile can be an important tool to better understand, at a systemic level, metabolic alterations caused by different pathological conditions, such as obesity. Furthermore, it allows the discovery of metabolic biomarkers, which may help to diagnose alterations caused by obesity., Objective: To investigate the metabolic profile of blood serum of obese dogs, control dogs, and dogs that were subjected to a weight loss program., Methods: Ten obese adult spayed female dogs were included, and their body composition was determined by the deuterium isotope dilution method. The dogs were subjected to a weight loss program and formed a new experimental group after losing 20% of the initial body weight. A third experimental group was composed of ten lean adult spayed female dogs. The metabolic profile of blood serum was evaluated through nuclear magnetic resonance (NMR). Principal Component Analyses (PCA) and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) models were constructed using Pareto scaling pre-processing. Pathway analysis was also performed using the MetaboAnalist online tool., Results: The PCA shows that the control and after weight loss groups presented a trend to negative PC1, indicating similarities between these two groups. In contrast, obese animals presented a tendency to appear on negative PC2 indicating a different metabolic profile. The OPLS-DA analysis of the serum indicated that healthy groups presented higher content of glucose, while animals that lost weight had higher levels of cholesterol and lactate than the control group. On the other hand, the analysis showed that lipid content, cholesterol, and branched-chain amino acids were highest in obese animals. Variable Influence on Projection (VIP) analysis demonstrated that Lactate is the most important metabolite for the OPLS-DA model and Hierarchical Cluster Analysis (HCA) corroborated the similarity between the control group and the obese after weight loss groups. Moreover, the pathway analysis indicated the most important metabolic pathways related to this dataset., Conclusions: The metabolomic assessment based on NMR of blood serum differed between obese dogs and animals in optimal body condition. Moreover, the weight loss resulted in metabolic profiles similar to those observed in lean animals.

The present study compared the intravenous glucose tolerance test (IVGTT) and the glucose postprandial response (GPPR) test for the evaluation of glucose metabolism in obese dogs. A total of ten owned obese dogs (body condition score (BCS) of 9; fat mass, 45.7 (sem 1.51) %) were used. These dogs had their weight reduced by 20 % (BCS, 8; fat mass, 33.5 (SEM 1.92) %; P < 0.001), designated as weight-reduced (WR) group. A control group of ten Beagle dogs was also included (BCS, 4.5; fat mass, 18.3 (SEM 1.38) %; P < 0.01). Glucose tolerance was measured by two methods: IVGTT (infusion of 0.5 g of glucose/kg body weight) and GPPR (consumption of cooked rice to achieve 6 g of starch/kg body weight). When using the IVGTT, the area under the curve (AUC) for glucose and maximum glycaemia were higher for obese dogs compared with controls (P < 0.05), with intermediate results for the WR group (P>0.05). Basal insulin, insulin response peak, insulinogenic index and the AUC for insulin increment from 0 to 15 min and from 60 to 120 min were higher for the obese group (P < 0.05), while the WR group and control dogs showed similar results (P>0.05). When using the GPPR test, the AUC for insulin increment from 0 to 120 min was higher for the obese group compared with the control group (P < 0.05) and intermediate for the WR group (P>0.05). However, the AUC for insulin increment from 120 to 360 min was similar between the obese and WR groups (P>0.05), while it was lower for the control group (P < 0.05). The IVGTT showed that the loss of 20 % body weight resulted in an improvement of glucose control with reduced insulin secretion, and these same WR dogs showed higher insulin secretion with values similar to those of obese dogs when the GPPR test was used.