Plasma leptin concentration in donkeys.

BACKGROUND

Donkeys appear to be more predisposed than large breed horses to suffer from hyperlipemia. The reason for that predisposition is unknown but anorexia is a consistent feature of the disease. Leptin, a protein synthesized in fat tissue, is one of the major inhibitors of appetite in mammals.

OBJECTIVE

We hypothesized that donkeys could have elevated plasma leptin concentrations compared to horses.

ANIMALS AND METHODS

Blood samples were obtained from 50 donkeys for measurement of leptin, triglycerides (TGs), glucose, and insulin. Glucose/insulin ratio, modified insulin to glucose ratio, and reciprocal of the square root of insulin were calculated. Based on their body condition score (BCS), donkeys were classified as lean (n = 18), normal (n = 16), or overweight (n = 16). The results were compared with reference values from our laboratory and with a group of horses (n = 25) used as an internal control.

RESULTS

Values of both leptin and TGs in donkeys were above the horse reference range and also significantly higher than those of the control horses: leptin (11.2 ± 1.7 versus 5.8 ± 0.5 µg/L, p < 0.05) and TGs (0.93 ± 0.1 versus 0.54 ± 0.1 mmol/L, p < 0.01). Overweight donkeys had leptin (19.3 ± 2.9 µg/L) and TG (1.3 ± 0.2 mmol/L) concentrations that were significantly (p < 0.01) higher than normal (9.4 ± 3.3 µg/L and 0.85 ± 0.1 mmol/L, respectively) and lean (5.5 ± 1.0 µg/L and 0.66 ± 0.1 mmol/L, respectively) donkeys. A significant positive correlation (p < 0.01) was found between BCS and leptin (r = 0.43), TGs (r = 0.46), glucose (r = 0.41), and insulin (r = 0.40).

CONCLUSION

Donkeys have higher plasma leptin concentrations than horses and leptin is correlated with BCS.