Effect of increased adiposity on insulin sensitivity and adipokine concentrations in horses and ponies fed a high fat diet, with or without a once daily high glycaemic meal.
BACKGROUND
The relative influences of obesity and adaptation to high glycaemic diets on the development of insulin dysregulation in equids are unclear.


OBJECTIVE
To determine whether increased adiposity per se is responsible for the decreased insulin sensitivity often observed in obese horses or whether a dietary glycaemic response is critically important.


METHODS
Randomised controlled trial.


METHODS
Eighteen horses and ponies were studied over a 20-week period. They received ad libitum hay plus either a high fat (low glycaemic) diet (FAT; n = 6) or a similar (isocaloric) diet containing 1.5 g/kg bwt once daily glucose (GLU; n = 6) to induce obesity. A third group received a control ration (CON; n = 6). Adiposity was monitored using body condition score (BCS) and total body fat mass percentage (TBFM) determined using a deuterium oxide dilution technique. Insulin sensitivity was assessed using a frequently sampled i.v. glucose tolerance test. Plasma concentrations of glucose, insulin, leptin, adiponectin, tumour necrosis factor-α (TNF-α) and serum amyloid A (SAA) were measured.


RESULTS
The FAT and GLU groups became obese (BCS ≥7) whereas the CON group maintained moderate condition (BCS ≤6). Total body fat mass and leptin concentrations were increased in the FAT and GLU groups than in the CON group (P<0.001 and P = 0.003, respectively). Values for both insulin-dependent (SI) and insulin-independent (Sg) glucose disposal were higher in the GLU group compared with the FAT and CON groups (P = 0.006 and P = 0.03, respectively). There were no differences in adiponectin, TNF-α or SAA between groups (all P≥0.4).


CONCLUSIONS
Increased adiposity did not reduce insulin sensitivity in either the FAT or the GLU diet groups, suggesting that obesity per se might not be responsible for the lower SI values reported in previous studies. Contrary to expectations, once daily glucose appeared to increase insulin sensitivity. Further work is required into the dietary causes of insulin resistance in equids.
Faculty of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia.
N J
NJ
Bamford
Faculty of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia.
S J
SJ
Potter
Equine Studies Group, WALTHAM Centre for Pet Nutrition, Melton Mowbray, UK.
P A
PA
Harris
Faculty of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia.
S R
SR
Bailey
D054392:Adipokines / Q000235:genetics / Q000378:metabolism*; D050154:Adiposity / Q000187:drug effects* / Q000502:physiology; D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001786:Blood Glucose; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats / Q000008:administration & dosage* / Q000009:adverse effects; D005786:Gene Expression Regulation / Q000187:drug effects; D038321:Glycemic Index; D006736:Horses / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology*
D054392:Adipokines; D001786:Blood Glucose; D004041:Dietary Fats
glucose; horse; insulin resistance; laminitis; obesity