title: Effects of metformin hydrochloride on blood glucose and insulin responses to oral dextrose in horses.
abstract: BACKGROUND
  Metformin is a potential therapeutic agent for the treatment of insulin resistance (IR). In laboratory animals, orally administered metformin reduces intestinal glucose absorption and may therefore affect insulinaemic responses to oral carbohydrate ingestion.
  
  
  OBJECTIVE
  To determine whether pretreatment with metformin reduces plasma glucose concentration and insulin responses following consumption of dextrose in horses.
  
  
  METHODS
  Therapeutic cross-over study.
  
  
  METHODS
  Seven healthy Standardbred and Thoroughbred geldings were subjected to an oral dextrose challenge test on 4 occasions: with and without metformin, before and after induction of IR with dexamethasone. Metformin was administered by nasogastric tube at 30 mg/kg bwt 1 h before administration of dextrose. Glucose and insulin concentrations in plasma/serum were measured at regular intervals during each test. Linear mixed models were specified for each predetermined outcome variable, and for each model the 'treatment' was included as a fixed effect with 4 categorical levels (none, metformin, dexamethasone and dexamethasone with metformin) and horse accounted for as a random effect.
  
  
  RESULTS
  In healthy horses, the administration of metformin resulted in a statistically significant reduction in peak glucose concentration (P = 0.002), area under the glucose curve (P<0.001) and insulin concentration 120 min after dextrose administration (P = 0.011). Following the induction of IR, administration of metformin was associated with significant differences in peak glucose concentration (P<0.001), the percentage increase in glucose concentration (P = 0.010), the area under the glucose curve (P<0.001) and insulin concentration at 120 min (P = 0.034) and 150 min after dextrose administration (P = 0.014).
  
  
  CONCLUSIONS
  Metformin resulted in reduced glycaemic and insulinaemic responses both in healthy horses and in horses with experimentally induced IR.
  
  
  CONCLUSIONS
  Metformin may benefit horses with naturally acquired IR by reducing glycaemic and insulinaemic responses to dietary nonstructural carbohydrates. Further investigations into the mechanisms of action of metformin in horses and controlled clinical trials are warranted.
authors.affiliation: The Liphook Equine Hospital, Liphook, UK.
authors.forename: D I
authors.initials: DI
authors.lastname: Rendle
authors.forename: F
authors.initials: F
authors.lastname: Rutledge
authors.forename: K J
authors.initials: KJ
authors.lastname: Hughes
authors.forename: J
authors.initials: J
authors.lastname: Heller
authors.forename: A E
authors.initials: AE
authors.lastname: Durham
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects*; D018592:Cross-Over Studies; D003907:Dexamethasone / Q000494:pharmacology; D005938:Glucocorticoids / Q000494:pharmacology; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D006736:Horses; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D008297:Male; D008687:Metformin / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D005938:Glucocorticoids; D007004:Hypoglycemic Agents; D007328:Insulin; D003907:Dexamethasone; D008687:Metformin; D005947:Glucose
keywords: equine metabolic syndrome; horse; hyperinsulinaemia; insulin resistance; laminitis; obesity