Development of a model for inducing transient insulin resistance in the mare: preliminary implications regarding the estrous cycle

Peripheral insulin resistance is the failure of proper cellular glucose uptake in response to insulin. Insulin resistance and hyperinsulinemia are associated with several disease states in the horse and reproductive function disturbances in humans, including polycystic ovarian syndrome. To test the...

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Bibliographic Details
Published in:Journal of animal science 2004-08, Vol.82 (8), p.2321-2328
Main Authors: Sessions, D.R, Reedy, S.E, Vick, M.M, Murphy, B.A, Fitzgerald, B.P
Format: Article
Language:English
Subjects:
Animal productions
Animals
Biological and medical sciences
blood chemistry
corpus luteum
Disease Models, Animal
estrous cycle
Estrus - drug effects
Estrus - physiology
Fatty Acids, Nonesterified - blood
Female
free fatty acids
Fundamental and applied biological sciences. Psychology
glucose
Glucose - administration & dosage
Glucose Clamp Technique - veterinary
hormonal regulation
hormone secretion
Horse Diseases - physiopathology
Horses - blood
Horses - physiology
hyperinsulinemia
Hyperinsulinism - physiopathology
Hyperinsulinism - veterinary
Infusions, Intravenous - veterinary
insulin
Insulin - blood
Insulin Resistance
lipid metabolism
Lipids - administration & dosage
Lipids - pharmacology
Luteal Phase - drug effects
Luteal Phase - physiology
luteinizing hormone
Luteinizing Hormone - blood
mares
ovarian follicles
ovulation
Ovulation - drug effects
Ovulation - physiology
preovulatory period
progesterone
Progesterone - blood
Terrestrial animal productions
Time Factors
Vertebrates
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Summary:Peripheral insulin resistance is the failure of proper cellular glucose uptake in response to insulin. Insulin resistance and hyperinsulinemia are associated with several disease states in the horse and reproductive function disturbances in humans, including polycystic ovarian syndrome. To test the hypothesis that insulin resistance (IR) and hyperinsulinemia disrupt the estrous cycle in mares, two experiments were conducted to first develop a model to induce IR and to then examine the effect of this model on the duration of the estrous cycle. In Exp. 1, a hyperinsulinemic-eug-lycemic clamp (HEC) procedure was performed on seven mares to determine insulin sensitivity before and immediately following infusion of a heparinized lipid solution. The HEC procedure was repeated 1 wk after lipid infusion. Mares developed IR following the lipid infusion (P < 0.05), and some individuals maintained IR for up to 1 wk. Mares also exhibited increased blood insulin both immediately following treatment and 1 wk later (P < 0.05). In Exp. 2, induction of insulin resistance by lipid solution was not accompanied by changes in circulating concentrations of luteinizing hormone, and duration of the luteal phase, compared with the duration of untreated luteal phases. Nonetheless, lipid infusion and the resultant insulin resistance were associated with an increased interovulatory period (P < 0.05), and peak concentrations of progesterone (P < 0.05) were higher during the treated vs. untreated luteal phases of the estrous cycle. The results from the preliminary study suggest that infusion of a lipid solution may induce transient insulin resistance and hyperinsulinemia. The resulting insulin resistance and hyperinsulinemia may modify characteristics of the estrous cycle, perhaps at the level of the ovary.
ISSN:0021-8812
1525-3163
DOI:10.2527/2004.8282321x