Dietary fructose may increase risk of laminitis via exacerbation of insulin resistance and hyperinsulinemia in horses with an insulin resistant phenotype.
Introduction
Dietary carbohydrate intake may modify risk of laminitis via alterations in insulin resistance and/or insulin dynamics. Serum insulin concentration was increased in insulin resistant ponies fed a hay diet supplemented with inulin (3 g/kg/d), while high glycemic diets have been associated with decreased insulin sensitivity in healthy horses. In this study, the relative effects of dietary glucose, fructose and fructan (inulin) on glucose and insulin dynamics were assessed in overweight/obese, insulin resistant (IR) and healthy (Con) Thoroughbred mares.
Methods
In a balanced crossover design, IR and Con (n = 6/group) mares were fed each of four isocaloric diets: timothy hay only or hay supplemented with inulin (IN), fructose (F) or glucose (G) at 3 g/kg/d (divided into 3 meals). Diets were fed for 2 weeks with a 3-week washout between treatments. Glucose and insulin dynamics were assessed before and after each treatment by intravenous glucose tolerance testing and minimal model analysis. Data were analyzed by repeated measures ANOVA.
Results
Diet did not affect resting serum insulin concentration or minimal model insulin sensitivity (SI) and acute insulin response to glucose (AIRg) in Con. In IR mares, however, SI was decreased by 54% and AIRg increased by 93% in F (both P < 0.05), while mean (± SEM) resting insulin increased (P < 0.05) from 20.9 ± 7.9 to 45.9 ± 11.5 mU/L. There was a statistical trend (P = 0.09) for increased SI in IR mares after IN.
Conclusions and Clinical Relevance
Two weeks of dietary fructose supplementation (3 g/kg/d) resulted in decreased SI and increased insulin concentration in IR but not Con mares. Dietary fructose, but not glucose or inulin, appears to alter glucose and insulin dynamics in overweight/obese, insulin resistant mares.
1Middleburg Agricultural Research and Extension Center, Virginia Tech and Equine Studies Group, WALTHAM Centre for Pet Nutrition
2Present address for Dr. Geor: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University
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