title: Adaptive response of equine intestinal Na+/glucose co-transporter (SGLT1) to an increase in dietary soluble carbohydrate.
abstract: Experimental and epidemiological evidence suggests that consumption of hydrolyzable carbohydrate, hCHO (grain), by horses is an important risk factor for colic, a common cause of equine mortality. It is unknown whether the small intestinal capacity to digest hCHO and/or to absorb monosaccharides is limiting, or even if horses can adapt to increased carbohydrate load. We investigated changes in the brush-border membrane carbohydrate digestive enzymes and glucose absorptive capacity of horse small intestine in response to increased hCHO. Expression of the Na(+)/glucose co-transporter, SGLT1, was assessed by Western blotting, immunohistochemistry, Northern blotting, QPCR, and Na(+)-dependent D-glucose transport. Glucose transport rates, SGLT1 protein, and mRNA expression were all 2-fold higher in the jejunum and 3- to 5-fold higher in the ileum of horses maintained on a hCHO-enriched diet compared to pasture forage. Activity of the disaccharidases was unaltered by diet. In a well-controlled study, we determined SGLT1 expression in the duodenal and ileal biopsies of horses switched, gradually over a 2-month period, from low (<1.0 g/kg bwt/day) to high hCHO (6.0 g/kg bwt/day) diets of known composition. We show that SGLT1 expression is enhanced, with time, 2-fold in the duodenum and 3.3-fold in the ileum. The study has important implications for dietary management of the horse.
authors.affiliation: Epithelial Function and Development Group, Department of Veterinary Preclinical Sciences, The University of Liverpool, Brownlow Hill and Crown Street, Liverpool L69 7ZJ, UK.
authors.forename: Jane
authors.initials: J
authors.lastname: Dyer
authors.forename: Miran
authors.initials: M
authors.lastname: Al-Rammahi
authors.forename: Louise
authors.initials: L
authors.lastname: Waterfall
authors.forename: Kieron S H
authors.initials: KS
authors.lastname: Salmon
authors.forename: Ray J
authors.initials: RJ
authors.lastname: Geor
authors.forename: Ludovic
authors.initials: L
authors.lastname: Bouré
authors.forename: G Barrie
authors.initials: GB
authors.lastname: Edwards
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Proudman
authors.forename: Soraya P
authors.initials: SP
authors.lastname: Shirazi-Beechey
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D005260:Female; D051273:Glucose Transporter Type 2 / Q000096:biosynthesis; D006736:Horses; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1 / Q000096:biosynthesis / Q000378:metabolism*; D012995:Solubility; D013393:Sucrase / Q000378:metabolism; D000520:alpha-Glucosidases / Q000378:metabolism
chemical_list: D004040:Dietary Carbohydrates; D051273:Glucose Transporter Type 2; D012333:RNA, Messenger; D051269:Sodium-Glucose Transporter 1; D000520:alpha-Glucosidases; D013393:Sucrase