title: The effect of oral metformin on insulin sensitivity in insulin-resistant ponies.
abstract: Metformin may be an effective therapeutic option for insulin-resistant (I-R) horses/ponies because, in humans, it reportedly enhances insulin sensitivity (SI) of peripheral tissues without stimulating insulin secretion. To determine the effect of metformin on insulin and glucose dynamics in I-R ponies, six ponies were studied in a cross-over design by Minimal Model analysis of a frequently-sampled intravenous glucose tolerance test (FSIGT). Metformin was administered at 15 mg/kg bodyweight (BW), orally, twice-daily, for 21 days to the metformin-treated group. The control group received a placebo. A FSIGT was conducted before and after treatment. The Minimal Model of glucose and insulin dynamics rendered indices describing SI, glucose effectiveness (Sg), acute insulin response to glucose (AIRg) and the disposition index (DI). The body condition score (BCS), BW and cresty neck score (CNS) were also assessed. There was no significant change in SI, Sg, AIRg, DI, BW, BCS or CNS in response to metformin, or over time in the control group. There were no measurable benefits of metformin on SI, consistent with recent work showing that the bioavailability of metformin in horses is poor, and chronic dosing may not achieve therapeutic blood concentrations. Alternatively, metformin may only be effective in obese ponies losing weight or with hyperglycaemia.
authors.affiliation: School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW 2650, Australia.
authors.forename: Kellie D
authors.initials: KD
authors.lastname: Tinworth
authors.forename: Ray C
authors.initials: RC
authors.lastname: Boston
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Harris
authors.forename: Martin N
authors.initials: MN
authors.lastname: Sillence
authors.forename: Sharanne L
authors.initials: SL
authors.lastname: Raidal
authors.forename: Glenys K
authors.initials: GK
authors.lastname: Noble
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D018592:Cross-Over Studies; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D007333:Insulin Resistance; D008687:Metformin / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D008687:Metformin