Plasma lactate, insulin concentration and intestinal glycogen deposition responses to fructose infusion in male dogs

Ingested carbohydrates digested to monosaccharides are absorbed directly into the bloodstream by the intestinal epithelial cells; recent research has shown intravenous infusion of fructose causes increase intestinal glucose uptake (IGU) and increase in blood glucose, however the fate of glucose has not been reported if it was metabolized or oxidized in the process. Ten fasted male anaesthetized adult dogs (Mongrel) were used for his experiment; the animals were divided into two groups (5 dogs per group). Control group received normal saline while the treatment group were infused with fructose (0.73 mg/kg/min). Through a midline laparotomy, the upper jejunum was cannulated for blood flow measurement and blood samples were obtained for measurement of glucose content of the arterial blood and venous blood from the upper jejunal segment. Mean intestinal glucose uptake (IGU) increased significantly from 38.86±2.44 (mg/dl) to 162.78±7.31 (mg/dl) in 30 min which was at peak uptake. Mean lactate concentration increased significantly from 66.45±2.02 (mg/dl) to 98.00±7.93 (mg/dl). However, there was a marginal increase in insulin concentration from 25.00±1.77 (mg/dl) to 27.25 (mg/dl) and no evidence of glycogen deposition in the small intestine. This study showed that intestinal glucose uptake increased in response to fructose infusion and probably the absorbed glucose after the infusion was converted to lactate with no trace of intestinal glycogen deposition.