Obesity is the most common nutritional disorder in small animals. To establish a computed tomographic (CT) method for assessment of visceral and subcutaneous fat content in the dog, CT analysis was performed in normal and obese beagles. Fat area was measured by the level detection method at varied attenuation ranges and compared with body fat content estimated by the deuterium oxide dilution method. Fat area measured at L3 using the attenuation range of -135/-105 Hounsfield unit had the best correlation with body fat content (r = 0.98). Regional fat distribution was almost the same between normal and obese dogs, with more fat accumulation at L1-S1 than T10-T13. Moreover, visceral and subcutaneous fat area could be estimated separately. This CT method may contribute to both the clinical diagnosis and the study of canine obesity, especially for studies in the relationship between body fat distribution and obesity-associated diseases.

The positive relationship between plasma leptin concentration and body fat content in dogs was similar to correlations reported for humans and rodents, suggesting that plasma leptin is a quantitative marker of adiposity in dogs.

ABSTRACT. Leptin is a protein synthesized and secreted primarily by adipocytes, and the circulating leptin concentration is elevated in obese humans and rodents. Recently, we have established a sandwich enzyme-linked immunosorbent assay for canine leptin. In the present study, plasma leptin concentrations were measured in experimentally developed obese beagles and in clinically obese dogs. When 5 male beagles were given a high-energy diet for 3 months, all of them became obese and the plasma leptin concentration significantly increased from 2.4 ± 1.2 to 4.9 ± 0.9 ng/ml, positively correlating with body fat content estimated by the deuterium oxide dilution method (r=0.87). The leptin concentrations of plasma samples collected from 59 dogs in veterinary practices were compared with their body condition scores (BCS). The plasma leptin concentrations of obese dogs were 9.7 ± 0.7 and 12.3 ± 1.5 ng/ml at BCS=4 and BCS=5, respectively, which were significantly higher than those of optimal (BCS=3) dogs (2.7 ± 0.3 ng/ml). There was no significant effect of sex and breed. A weak positive correlation (r=0.37) was found between the plasma leptin concentration and age, probably due to the lesser content of visceral fat in puppies younger than 1 year old. These results indicate that plasma leptin is a good index of adiposity in dogs regardless of breed, age and sex, and may be useful for quantitative assessment of obesity in small animal practice.

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