Effects of diet-induced weight gain on insulin sensitivity and plasma hormone and lipid concentrations in horses.
OBJECTIVE
To determine the effects of diet-induced weight gain on glucose and insulin dynamics and plasma hormone and lipid concentrations in horses.


METHODS
13 adult geldings.


METHODS
Horses were fed 200% of their digestible energy requirements for maintenance for 16 weeks to induce weight gain. Frequently sampled IV glucose tolerance tests were performed before and after weight gain to evaluate glucose and insulin dynamics. Adiposity (assessed via condition scoring, morphometric measurements, and subcutaneous fat depth) and plasma concentrations of insulin, glucose, nonesterified fatty acids, triglycerides, and leptin were measured on a weekly or biweekly basis.


RESULTS
Mean + or - SD body weight increased by 20% from 440 + or - 44 kg to 526 + or - 53 kg, and body condition score (scale, 1 to 9) increased from 6 + or - 1 to 8 + or - 1. Plasma glucose, triglyceride, and nonesterified fatty acid concentrations were similar before and after weight gain. Leptin and insulin concentrations increased with weight gain. Mean + or - SD insulin sensitivity decreased by 71 + or - 28%, accompanied by a 408 + or - 201% increase in acute insulin response to glucose, which resulted in similar disposition index before and after weight gain.


CONCLUSIONS
Diet-induced weight gain in horses occurred concurrently with decreased insulin sensitivity that was effectively compensated for by an increase in insulin secretory response. Obesity resulted in hyperinsulinemia and hyperleptinemia, compared with baseline values, but no changes in lipid concentrations were apparent. Preventing obesity is a potential strategy to help avoid insulin resistance, hyperinsulinemia, and hyperleptinemia in horses.
Department of Animal and Poultry Sciences, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. Carterre@vet.upenn.edu
Rebecca A
RA
Carter
L Jill
LJ
McCutcheon
Lindsey A
LA
George
Tracy L
TL
Smith
Nicholas
N
Frank
Raymond J
RJ
Geor
D050154:Adiposity; D000821:Animal Feed; D000818:Animals; D001786:Blood Glucose; D004032:Diet / Q000662:veterinary*; D004435:Eating; D006736:Horses / Q000502:physiology*; D007333:Insulin Resistance / Q000502:physiology*; D008055:Lipids / Q000097:blood*; D008297:Male; D013997:Time Factors; D015430:Weight Gain / Q000502:physiology*
D001786:Blood Glucose; D008055:Lipids