Plasma leptin concentrations in horses have been shown to vary widely. However, many factors may perturb these measurements. Previous research has documented a link between hyperinsulinemia and hyperleptinemia in horses. This condition has been speculated to be associated with components of equine metabolic syndrome, such as insulin resistance and laminitis. However, many of the methods accepted in diagnosing these metabolic abnormalities are expensive and often difficult to perform. Thus, the objectives of the experiments in this thesis were 1) to determine if it is possible to differentiate hyperleptinemic horses from normal ones by hormone manipulation with dexamethasone, a glucocorticoid analog; 2) to evaluate intravenous injection combinations of insulin and glucose to assess insulin sensitivity; and 3) to assess insulin sensitivity in hyperleptinemic and normal horses using two concentrations of exogenous insulin. In the first experiment, it was determined that a single injection of dexamethasone did not enhance the ability to differentiate between hyperleptinemic and normal horses. In the second experiment, the combined intravenous insulin and glucose tests proved to be very simple and inexpensive. However, repeatability among estimates on the same horses was not strong enough to be conclusive or predictive in assessing insulin sensitivity in horses. In the third experiment, a single injection of exogenous insulin at 0.02 IU/kg of body weight proved to be a consistent and efficacious method of differentiating hyperleptinemic from normal horses. Glucose concentrations in hyperleptinemic horses decreased very little (14%) at this insulin dosage compared to those in normal horses that dropped (P < 0.01) 46% from a pre-injection average of 85 to 46 mg/dL 40 min after injection. It was concluded that a low-level insulin injection coupled with routine plasma leptin estimates constitute a simple method of identifying hyperleptinemic horses.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04072009-130600 |
| Date | 07 April 2009 |
| Creators | Caltabilota, Thomas Joseph |
| Contributors | Cathleen C. Williams, L. Lee Southern, Glen T. Gentry, Jr., Donald L. Thompson, Jr. |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04072009-130600/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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