Effects of short- and long-term recombinant equine growth hormone and short-term hydrocortisone administration on tissue sensitivity to insulin in horses.
OBJECTIVE
To determine the effects of short-term IV administration of hydrocortisone or equine growth hormone (eGH) or long-term IM administration of eGH to horses on tissue sensitivity to exogenous insulin.


METHODS
5 Standardbreds and 4 Dutch Warmblood horses.


METHODS
The euglycemic-hyperinsulinemic clamp technique was used to examine sensitivity of peripheral tissues to exogenous insulin 24 hours after administration of a single dose of hydrocortisone (0.06 mg/kg), eGH (20 microg/kg), or saline (0.9% NaCl) solution and after long-term administration (11 to 15 days) of eGH to horses. The amounts of metabolized glucose (M) and plasma insulin concentration (I) were determined.


RESULTS
Values for M and the M-to-I ratio were significantly higher 24 hours after administration of a single dose of hydrocortisone than after single-dose administration of eGH or saline solution. After long-term administration of eGH, basal I concentration was increased and the mean M-to-I ratio was 22% lower, compared with values for horses treated with saline solution.


CONCLUSIONS
Increases in M and the M-to-I ratio after a single dose of hydrocortisone imply that short-term hydrocortisone treatment increases glucose use by, and insulin sensitivity of, peripheral tissues. Assuming a single dose of hydrocortisone improves sensitivity of peripheral tissues to insulin, it may be an interesting candidate for use in reducing insulin resistance in peripheral tissues of horses with several disease states. In contrast, long-term administration of eGH decreased tissue sensitivity to exogenous insulin associated with hyperinsulinemia. Therefore, increased concentrations of growth hormone may contribute to insulin resistance in horses with various disease states.
de Graaf-Roelfsema
Ellen
E
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Tharasanit
Theerawat
T
van Dam
Klien G
KG
Keizer
Hans A
HA
van Breda
Erik
E
Wijnberg
Inge D
ID
Stout
Tom A E
TA
van der Kolk
Johannes H
JH
D020155:3-Hydroxybutyric Acid / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D018592:Cross-Over Studies; D004347:Drug Interactions; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D015309:Glucose Clamp Technique / Q000662:veterinary; D013006:Growth Hormone / Q000494:pharmacology*; D006734:Horse Diseases / Q000097:blood / Q000378:metabolism*; D006736:Horses / Q000097:blood / Q000378:metabolism*; D006854:Hydrocortisone / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007333:Insulin Resistance; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D011897:Random Allocation
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D020155:3-Hydroxybutyric Acid; D006854:Hydrocortisone