Molecular characterisation of carbohydrate digestion and absorption in equine small intestine

Dyer, Jane; Merediz, E. Fernandez-Castaño; Salmon, Kieron S. H.; Proudman, C. J.; Edwards, Glenn S.; Shirazi-Beechey, Soraya P.

doi:10.2746/042516402776249209

Cited by 84 publications

(87 citation statements)

References 36 publications

(81 reference statements)

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“…Transporter-mediated glucose uptake and V max were significantly higher in duodenum and jejunum compared with ileum (18,24), with K m substantially unchanged. Similar data were obtained for SGLT1 and glucose transport in equine small intestine (15). In steers (33), SGLT1 protein abundance was found to increase from duodenum to ileum, whereas glucose uptake decreased.…”

Section: Mathematical Modelsupporting

confidence: 72%

Intestinal transit of a glucose bolus and incretin kinetics: a mathematical model with application to the oral glucose tolerance test

Salinari

Bertuzzi

Mingrone

2011

American Journal of Physiology-Endocrinology and Metabolism

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The rate of appearance (Ra) of exogenous glucose in plasma after glucose ingestion is presently measured by tracer techniques that cannot be used in standard clinical testing such as the oral glucose tolerance test (OGTT). We propose a mathematical model that represents in a simple way the gastric emptying, the transport of glucose along the intestinal tract, and its absorption from gut lumen into portal blood. The model gives the Ra time course in terms of parameters with a physiological counterpart and provides an expression for the release of incretin hormones as related to glucose transit into gut lumen. Glucose absorption was represented by assuming two components related to a proximal and a distal transporter. Model performance was evaluated by numerical simulations. The model was then validated by fitting OGTT glucose and GLP-1 data in healthy controls and type 2 diabetic patients, and useful information was obtained for the rate of gastric emptying, the rate of glucose absorption, the Ra profile, the insulin sensitivity, and the glucose effectiveness. Model-derived estimates of insulin sensitivity were well correlated (r ϭ 0.929 in controls and 0.886 in diabetic patients) to data obtained from the euglycemic hyperinsulinemic clamp. Although the proposed OGTT analysis requires the measurement of an additional hormone concentration (GLP-1), it appears to be a reasonable choice since it avoids complex and expensive techniques, such as isotopes for glucose Ra measurement and direct assessment of gastric emptying and intestinal transit, and gives additional correlated information, thus largely compensating for the extra expense.glucose intestinal absorption; rate of glucose appearance; insulin sensitivity THE MATHEMATICAL MODEL ANALYSIS of an intravenous glucose tolerance test (IVGTT) is facilitated by the fact the amount of glucose injected is known. In contrast, an oral glucose tolerance test (OGTT) is characterized by uncertainty both in the amount of glucose absorbed and in its absorption rate, which results in the time course of exogenous glucose delivery to plasma. The IVGTT models (3, 7, 31) represent the glucose delivery as a bolus dose of known amount, D, that abruptly raises plasma glucose concentration of an amount D/V G , with V G being the glucose distribution volume. In the OGTT, by contrast, the time course of the rate of appearance (R a ) of exogenous glucose in plasma cannot be specified a priori. Given the ingested dose, indeed, several factors contribute toward affecting the R a : the rate of gastric emptying of ingested glucose, the extent of intestinal absorption during the intestinal transit, and the hepatic uptake of portal glucose. Because of these uncertainties, the R a time course in the OGTT and the meal test has been represented by a piecewise linear function, with the time of break points assigned and values that are estimated from the data (8, 9, 10).Experimental determinations of the R a of ingested glucose in plasma have been obtained using tracer techniques. Ferrannini and col...

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Section: Mathematical Modelsupporting

confidence: 72%

Intestinal transit of a glucose bolus and incretin kinetics: a mathematical model with application to the oral glucose tolerance test

Salinari

Bertuzzi

Mingrone

2011

American Journal of Physiology-Endocrinology and Metabolism

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“…Significantly different from baseline (preexercise) time point for *control and ⌿ electrolyte treatments, P Յ 0.05. supplement. The dextrose concentration (31 mmol/l) of the Perform'N Win supplement serves as a direct source of glucose to provide cellular energy to subserve increased rates of epithelial transport of Na ϩ and water across the small intestine (15,18). Although the amount of dextrose administered with 8 liters of supplement (44 g) was insufficient to result in overall differences in plasma [glucose] compared with control, and significant glycemic responses to feeding occurred in both treatments, plasma [glucose] did increase faster with electrolyte supplementation, peaking at 1 h of recovery in the electrolyte treatment vs. 2 h of recovery in control (see Fig.…”

Section: Discussionmentioning

confidence: 99%

Fluid and electrolyte supplementation after prolonged moderate-intensity exercise enhances muscle glycogen resynthesis in Standardbred horses

Waller¹,

Heigenhauser²,

Geor³

et al. 2009

Journal of Applied Physiology

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Waller AP, Heigenhauser GJ, Geor RJ, Spriet LL, Lindinger MI. Fluid and electrolyte supplementation after prolonged moderateintensity exercise enhances muscle glycogen resynthesis in Standardbred horses. J Appl Physiol 106: 91-100, 2009. First published October 23, 2008 doi:10.1152/japplphysiol.90783.2008.-We hypothesized that postexercise rehydration using a hypotonic electrolyte solution will increase the rate of recovery of whole body hydration, and that this is associated with increased muscle glycogen and electrolyte recovery in horses. Gluteus medius biopsies and jugular venous blood were sampled from six exercise-conditioned Standardbreds on two separate occasions, at rest and for 24 h following a competitive exercise test (CET) designed to simulate the speed and endurance test of a 3-day event. After the CETs, horses were given water ad libitum, and either a hypotonic commercial electrolyte solution (electrolyte) via nasogastric tube, followed by a typical hay/grain meal, or a hay/grain meal alone (control). The CET resulted in decreased total body water and muscle glycogen concentration of 8.4 Ϯ 0.3 liters and 22.6%, respectively, in the control treatment, and 8.2 Ϯ 0.4 liters and 21.9% in the electrolyte treatment. Electrolyte resulted in an enhanced rate of muscle glycogen resynthesis and faster restoration of hydration (as evidenced by faster recovery of plasma protein concentration, maintenance of plasma osmolality, and greater muscle intracellular fluid volume) during the recovery period compared with control. There were no differences in muscle Na, K, Cl, or Mg contents between the two treatments. It is concluded that oral administration of a hypotonic electrolyte solution after prolonged moderate-intensity exercise enhanced the rate of muscle glycogen resynthesis during the recovery period compared with control. It is speculated that postexercise dehydration may be one key contributor to the slow muscle glycogen replenishment in horses. skeletal muscle; rehydration; exercise; instrumental neutron activation analysis IN THE HORSE, BOTH short-term, high-intensity, and prolonged submaximal exercise result in dehydration, loss of water and electrolytes, and depletion of skeletal muscle glycogen (23,30,31,52,53,56). Resynthesis of muscle glycogen stores requires 48 -72 h in horses, compared with 2.5 h in rats (16) and Ͻ24 h in humans (12). Previous studies in horses have altered postexercise nutrition strategies in attempts to enhance muscle glycogen resynthesis. Despite demonstrations that intravenous infusion of large amounts of glucose (3-6 g/kg) modestly accelerated muscle glycogen replenishment (14, 17), conventional feeding strategies have not been successful (23,(53)(54)(55). Initial glycogen resynthesis rates in horses after ingestion of meals with varying soluble carbohydrate (CHO) contents ranged from ϳ8 to ϳ12 mmol⅐kg dry wt Ϫ1 ⅐h Ϫ1 for mixed and high-soluble CHO diets, respectively. In contrast, in humans, initial glycogen storage rates are ϳ40 mmol⅐kg dry wt Ϫ1 ⅐h Ϫ1when at least 5 g/kg...

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“…However, until recently, there was very little information on the mechanism and intestinal site of monosaccharide absorption in the equine small intestine. We showed previously that, in horses maintained on pasture forage, the major site of monosaccharide absorption is in the proximal intestine (duodenum>jejunum), with lower expression of SGLT1 in the ileum [11]. Furthermore, we determined that the disaccharidases, sucrase, lactase, and maltase are expressed in the equine small intestine; maltase having a much higher activity compared to other species [11].…”

Section: Introductionmentioning

confidence: 93%

Adaptive response of equine intestinal Na+/glucose co-transporter (SGLT1) to an increase in dietary soluble carbohydrate

Dyer

Al-Rammahi

Waterfall

et al. 2008

Pflugers Arch - Eur J Physiol

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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.

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Molecular characterisation of carbohydrate digestion and absorption in equine small intestine

Cited by 84 publications

References 36 publications

Intestinal transit of a glucose bolus and incretin kinetics: a mathematical model with application to the oral glucose tolerance test

Intestinal transit of a glucose bolus and incretin kinetics: a mathematical model with application to the oral glucose tolerance test

Fluid and electrolyte supplementation after prolonged moderate-intensity exercise enhances muscle glycogen resynthesis in Standardbred horses

Adaptive response of equine intestinal Na+/glucose co-transporter (SGLT1) to an increase in dietary soluble carbohydrate

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