The effects of lipoic acid supplementation on blood glucose and insulin concentrations in pony mares1

Lipoic acid has been found to modulate insulin and glucose dynamics in several species; therefore, the objectives of this project were to determine a) blood concentrations of lipoic acid after oral delivery to pony mares and b) whether daily treatments of 10 mg/kg of BW of lipoic acid for 14 d to overweight pony mares would alter insulin and glucose dynamics. In Exp. 1, 3 pony mares were used to determine absorption of lipoic acid into the peripheral blood supply after oral dosing. Jugular catheters were inserted and serial blood samples collected after administration of 10 mg/kg of BW of lipoic acid. Serum concentrations of lipoic acid increased 3,000-fold at 30 min postdosing, providing evidence that orally dosed lipoic acid is absorbed. In Exp. 2, 11 pony mares were blocked by BCS and ovarian status (intact vs. ovariectomized) and randomly assigned to receive daily treatments for 14 d of 10 mg/kg of BW of lipoic acid (LA; n = 6) or to the control group (CON; n = 5). On d 14, CON and LA ponies were fitted with jugular catheters, and i.v. glucose tolerance tests were performed. Insulin area under the curve was greater (P = 0.05) among CON (7,551 ± 1,136) than among LA (4,046 ± 1,037) treated ponies. No differences (P = 0.68) were found in glucose area under the curve between CON (3,961 ± 269) and LA (4,114 ± 246) treated ponies. These data provide evidence that lipoic acid supplementation for 14 d alters insulin dynamics in pony mares.