Leptin secretion in horses: effects of dexamethasone, gender, and testosterone.
Abstract: Five experiments were performed to evaluate the effects of dexamethasone (DEX), gender, and testosterone on plasma leptin concentrations in horses. In experiment 1, plasma leptin, insulin, glucose, and IGF-1 concentrations were increased (P < 0.01) in stallions following five daily injections of DEX (125 microg/kg BW). In experiment 2, leptin concentrations increased (P < 0.01) in mares, geldings, and stallions following a single injection of DEX, and the response was greater (P < 0.01) in mares and geldings than in stallions. The gender effect was confounded by differences in body condition scores and diet; however, based on stepwise regression analysis, both BCS and gender were significant sources of variation in the best fit model for pre-DEX leptin concentrations (R(2) = 0.65) and for maximum leptin response to DEX (R(2) = 0.75). In experiment 3, in which mares and stallions were pair-matched based on age and body condition and fed similar diets, mares again had higher (P 0.1) in plasma leptin response in mares following four single-injection doses of DEX from 15.6 to 125 microg/kg BW. In experiment 5, treatment of mares with testosterone propionate every other day for 5 days did not alter (P > 0.1) plasma leptin concentrations or the leptin response to DEX. In conclusion, multiple injections of DEX increase leptin concentrations in stallions, as does a single injection in mares (as low as 15.6 microg/kg BW), geldings and stallions. The greater leptin levels observed in mares and geldings relative to stallions were due partially to their greater body condition and partially to the presence of hyperleptinemic individuals; however, even after accounting for body condition and diet, mares still had greater leptin concentrations than stallions after DEX administration. Elevation of testosterone levels in mares for approximately 10 days did not alter leptin concentrations in mares.
Publication Date: 2005-11-08 PubMed ID: 16305819DOI: 10.1016/j.domaniend.2005.10.006Google Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
Summary
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The researchers conducted five experiments to understand the effects of a drug called dexamethasone, along with gender and testosterone levels, on a hormone called leptin in horses. They found that multiple injections of dexamethasone increased leptin levels in male horses and a single injection similarly increased these levels in mares and geldings. Further, they found differences in leptin levels based on the horse’s gender, body condition and diet. Gender differences remained even after controlling for body condition and diet, with females having higher levels of leptin than males after drug administration. Testosterone levels did not significantly affect leptin levels.
Details of the Five Experiments
- In the first experiment, the researchers noted a rise in leptin levels, along with insulin, glucose, and IGF-1 levels in male horses after five consecutive daily injections of dexamethasone.
- The second experiment revealed an increase in leptin levels in female horses, geldings (castrated males), and intact males after a single injection of the drug. The response was greater in females and geldings in comparison to intact males. A further assessment highlighted gender and body condition score (BCS) as significant sources of variation in leptin levels before dexamethasone administration and post its maximum response.
- The third experiment had the horses pair-matched on the basis of age and body condition, consuming similar diets. Despite these matching factors, after dexamethasone treatment, female horses still demonstrated higher amounts of leptin than their male counterparts.
- The fourth experiment applied to female horses. Regardless of the dexamethasone dose administered, ranging from 15.6 to 125 microg/kg body weight, there was no notable difference in the leptin response.
- The final experiment involved treating female horses with testosterone propionate every alternate day for five days. This treatment did not impact the leptin levels or its response to dexamethasone.
Conclusions Drawn from the Experiments
- Dexamethasone injections were found to increase leptin levels in all gender types with the response being more visible in female horses and geldings compared to intact males.
- Gender, along with BCS, significantly determined variations in leptin concentration before and after dexamethasone injection. Despite standardizing factors like diet and body conditions, females consistently showcased higher leptin levels than males post the dexamethasone treatment.
- The leptin response in females remained unchanged regardless of the dexamethasone dose given.
- Testosterone propionate treatment did not modify leptin levels or its response to dexamethasone.
Cite This Article
APA
Cartmill JA, Thompson DL, Del Vecchio RP, Storer WA, Crowley JC.
(2005).
Leptin secretion in horses: effects of dexamethasone, gender, and testosterone.
Domest Anim Endocrinol, 31(2), 197-210.
https://doi.org/10.1016/j.domaniend.2005.10.006 Publication
Researcher Affiliations
- Department of Animal Sciences, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
MeSH Terms
- Adipose Tissue / physiology
- Animals
- Body Weight / physiology
- Dexamethasone / pharmacology
- Female
- Glucocorticoids / pharmacology
- Horses / blood
- Horses / physiology
- Leptin / blood
- Leptin / metabolism
- Male
- Sex Factors
- Testosterone Propionate / pharmacology
Citations
This article has been cited 2 times.- Durham AE, Frank N, McGowan CM, Menzies-Gow NJ, Roelfsema E, Vervuert I, Feige K, Fey K. ECEIM consensus statement on equine metabolic syndrome.. J Vet Intern Med 2019 Mar;33(2):335-349.
- Mohammad-Shahi M, Haidari F, Rashidi B, Saei AA, Mahboob S, Rashidi MR. Comparison of the effects of genistein and daidzein with dexamethasone and soy protein on rheumatoid arthritis in rats.. Bioimpacts 2011;1(3):161-70.
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