Analytical performance of canine acylated and unacylated ghrelin enzyme-linked immunosorbent assays.

OBJECTIVES: Ghrelin is a major appetite-stimulating hormone. It circulates as acylated ghrelin (AG) and unacylated ghrelin (UAG), which could have different metabolic actions in obesity. Our objective was to study the analytical performance of two new canine AG and UAG ELISAs using blood samples from healthy, normal-weight dogs. Additionally, the effect of a protease inhibitor (PI) on short-term sample storage was analyzed. METHODS: The intra- and inter-assay precision for low, intermediate, and high AG and UAG concentrations, accuracy, limits of quantification (LQ), and detection limit (DL) of a blank sample were determined in ten healthy dogs. To study the effects of a PI on ghrelin concentrations, and AG and UAG concentrations were compared in five canine plasma samples stored for 1 month with (PI+), without (PI-), and with PI added at sample thawing (PI+th). RESULTS: The intra- and inter-assay coefficients of variation were 1.8%-5.7% and 2.9%-6.4% for the AG assay, and 0.8%-7.5% and 2.8%-13.4% for the UAG assay, respectively. Accuracy analyses showed nonsignificant deviation from linearity for the AG (R2  = .99; Runs test: P = .37) and UAG (R2  = .99; Runs test: P = .42) assays. For the AG assay, the upper LQ was >1261 pg/mL, the lower LQ was 6.2 pg/mL, and the DL was 0.3 pg/mL. For the UAG assay, the upper LQ was >1785 pg/mL, the lower LQ was 16.3 pg/mL, and the DL was 1.8 pg/mL. No differences in the AG (P = .54) and UAG (P = .95) concentrations were detected in the plasma samples subjected to PI+, PI-, and PI+th. CONCLUSION: The AG and UAG ELISA assays had acceptable precision, accuracy, lower LQ, and DLs, but upper LQ could not be established. An influence of the PI on short-term storage was not detectable. Long-term storage ± PI was not evaluated and should be investigated further.

Gut microbiota composition may relate to weight loss rate in obese pet dogs.

Obese dogs seem to have a different gut microbiome (GM) composition compared to lean dogs, and in humans, GM composition may negatively impact the ability to lose weight in some individuals. The purpose of this study was to investigate the interaction between exercise, weight-loss and the composition of GM in dogs. Eighteen obese pet dogs were recruited for a 12-week weight-loss intervention. All dogs were fed restrictively with a commercial high-protein/high-fibre dry diet, and eight of these dogs were enrolled in an exercise program in addition to the diet intervention. Faecal samples were collected and the dogs were weighed at week 0, week 6 and week 12. GM composition was determined using MiSeq-based tag-encoded 16S rRNA gene high-throughput amplicon sequencing, and concentrations of short chain fatty acids (SCFA) by gas-liquid chromatography. Total weight loss, food allowance and GM were not changed by exercise inclusion. However, Megamonas abundance negatively correlated with weight loss rate and Ruminococcaceae relative abundance was lower at 12 weeks in dogs with a faster weight loss rate (≥1% per week) compared with slower weight loss rate (<1% per week) independent of exercise. Acetic and propionic acid concentrations decreased in the dogs with a faster weight loss rate. Members of Megamonas and Ruminococcaceae produce acetic and propionic acids and we therefore interpret that having a GM that favour SCFA production may negatively affect weight loss rate in dogs. Weight loss rate in dogs may be related to the composition of the GM and its production of metabolites.

Integration of a physical training program in a weight loss plan for overweight pet dogs.

OBJECTIVE: To investigate whether a controlled physical training plan for overweight dogs during a weight loss program would improve cardiorespiratory fitness and better preserve lean body mass, compared with results for dogs undergoing a weight loss program based on caloric restriction alone. DESIGN: Prospective, nonrandomized clinical study. ANIMALS: 19 client-owned overweight or obese dogs. PROCEDURES: All dogs were fed the same calorie-restricted diet rationed to achieve a weight loss rate of 1% to 2%/wk for 12 weeks. The fitness-and-diet (FD) group participated in a training program that included underwater and land-based treadmill exercise 3 times/wk. The diet-only (DO) group had no change in exercise routines. Daily activity before and during the intervention was recorded by accelerometry. Before and after intervention, heart rate during exercise was recorded to assess cardiovascular fitness, and body composition was analyzed by dual-energy x-ray absorptiometry. Differences between groups were evaluated with t tests and multiple regression analysis. RESULTS: Mean weight loss was 13.9% and 12.9% for the FD and DO groups, respectively (n = 8 dogs/group that completed the study). Mean accelerometer counts during intervention were 13% higher than baseline counts for the FD group. Heart rate during exercise declined after intervention in both groups. Lean body mass was preserved in the FD group and lost in the DO group during intervention. CONCLUSIONS AND CLINICAL RELEVANCE: The controlled exercise plan used with a dietary weight loss program prevented loss of lean body mass in dogs. This finding supports inclusion of controlled physical training for obesity management in dogs.

Physical training and weight loss in dogs lead to transcriptional changes in genes involved in the glucose-transport pathway in muscle and adipose tissues.

Obesity is a worldwide problem in humans and domestic animals. Interventions, including a combination of dietary management and exercise, have proven to be effective for inducing weight loss in humans. In companion animals, the role of exercise in the management of obesity has received relatively little attention. The aim of the present study was to investigate changes in the transcriptome of key energy metabolism genes in muscle and adipose tissues in response to diet-induced weight loss alone, or combined with exercise in dogs. Overweight pet dogs were enrolled on a weight loss programme, based on calorie restriction and physical training (FD group, n = 5) or calorie restriction alone (DO group, n = 7). mRNA expression of 12 genes and six microRNAs were investigated using quantitative real-time PCR (qPCR). In the FD group, FOXO1 and RAC1 were expressed at lower levels in adipose tissue, whereas ESRRA and AKT2 were more highly expressed in muscle, when compared with the DO group. Comparing expression before and after the intervention, in the DO group, nine genes and three microRNAs showed significant altered expression in adipose tissue (PPARG, ADIPOQ and FOXO1; P < 0.001) and seven genes and two microRNAs were significantly downregulated (NRF2, RAC1, ESRRA, AKT2, PGC1a and mir-23; P < 0.001) in muscle. Thus, calorie restriction causes regulation of several metabolic genes in both tissues. The mild exercise, incorporated into this study design, was sufficient to elicit transcriptional changes in adipose and muscle tissues, suggesting a positive effect on glucose metabolism. The study findings support inclusion of exercise in management of canine obesity.