Metabolism of Parenteral Glucose Oligosaccharides in Man

Abstract

Low molecular weight oligosaccharides of glucose may be utilized as a calorie source when given intravenously. Preliminary safety studies included the parenteral infusion of four healthy subjects with a solution of glucose oligosaccharides at a rate of 0.5 mg/kg/min for 1, 2, or 3 hours. Approximately 100% of the oligosaccharides was retained with only trace amounts of the glucose oligosaccharides recovered in the urine. In further studies, 12 healthy males, ages 22-31, were infused with a 10% solution of glucose oligosaccharides containing 25 μCi [U-¹⁴C]glucose oligosaccharides/liter at a rate of 2.5 or 5.0 mg/kg/min for 12 hours with or without insulin (0.12 unit/g oligosaccharides) given subcutaneously in 3 equi-divided doses. Four additional subjects received cold oligosaccharides at a rate of 1.75 mg/kg/min without insulin. Eighty percent of the glucose oligosaccharides consisted of 2 to 8 glucose chain lengths. Blood glucose and oligosaccharide glucose concentrations and ¹⁴CO₂ were measured hourly. Paper chromatography of urine sugars was also performed to determine the sugars excreted. Serum glucose and insulin concentration did not change during the oligosaccharide infusion; insulin injections significantly depressed serum glucose and produced elevations in serum insulin concentration. Plasma FFA decreased in response to oligosaccharide infusion at both 2.5 and 5.0 mg/kg/ min rates, with and without insulin. At the 1.75, 2.5, and 5.0 mg/kg/min rates, 21, 43, and 62% of the infused oligosaccharides, respectively, was excreted into the urine. Only 7-15% of the infused oligosaccharide ¹⁴C was recovered as ¹⁴CO ₂. Insulin did not influence these parameters. Urine chromatography showed that approximately 20, 30, and 40% of excreted sugar was maltotriose, maltose, and higher oligosaccharide chains, respectively. These studies indicate that partial, but significant quantities of glucose oligosaccharides may be metabolized after intravenous infusion, particularly at low infusion rates.