The Effect of Insulin on Blood Levels of Infused Pentoses in Man

Abstract

In 1931 Wierzuchowski (1) showed an influence of insulin on galactose tolerance of dogs. More recently, Levine, Goldstein, Huddlestun, Klein, and Henry (2, 3) demonstrated that insulin lowers the blood levels of D-galactose, D-xylose, and L-arabinose but not of D-arabinose or D-mannose, following their infusion into the eviscerated nephrectomized dog. The volume of distribution of the responsive sugars was increased from 45 to 70 per cent of body weight as a result of insulin administration. It was suggested that the insulin response represented a facilitation of transport of the sugar across the cell membrane into intracellular fluid. In all the responsive sugars the stereochemical structure of carbon atoms 1 to 3 was like that of D-glucose, and these authors suggested that these structural characteristics determined the insulin responsiveness of a sugar.Confirmatory evidence has appeared that insulin affects transport of D-galactose, D-xylose and L-arabinose across the cell membrane in the rat diaphragm (4-6), eviscerate rat (7), perfused rat heart (8) and intact cat (9). However, slow penetration of a number of sugars into muscle of nephrectomized and eviscerated rats has now also been demonstrated, and this slow penetration is increased by insulin for D-lyxose, D-ribose, D-mannose, D-fructose and D-fucose, as well as for D-xylose, D-galactose and L-arabinose (10, 11). Although these results indicate that the concept of structural specificity in carbon atoms 1 to 3 for insulin responsiveness has proved to be too limited in scope, the lack of an effect of insulin upon intracellular entry of sorbitol, mannitol and raffinose is strong evidence that the action of insulin is not simply an acceleration of a process of physical diffusion (12).

Physiological Disposition and Metabolic Fate of Infused Pentoses in Man

“…The maximum glucose values were consistently recorded 30 to 40 minutes after the end of the pentose infusions, and were followed by gradual declines of blood glucose values to or below the control concentrations. Examples of these rises of blood glucose may be seen in the companion paper by Segal, Wyngaarden, and Foley (13). Similar fusions of L-arabinose (Table I).…”

“…This responsiveness, interpreted by most workers as representing a facilitation of pentose transfer across cell membranes into intracellular fluid, was first thought to be restricted to those pentoses possessing a glucose-like stereochemical constitution of carbon atoms 1 to 3 (12). Recent studies have shown, however, that insulin responsiveness is not restricted to such sugars (13,14).…”

“…This paper presents data on the physiological disposition of infused D-xylose, D-arabinose, L-arabinose, and D-lyxose in man, and observations on the effects of these pentoses on blood levels of glucose, lactate and pyruvate, and inorganic phosphorus. Data on the effects of insulin on blood levels of infused pentoses are presented in a companion paper (13). Studies have also been performed with D-ribose, but because the kinetics of its disposition, and the extent of its utilization, are quite different from the pentoses listed above, these data will be presented in a separate communication.…”

The Metabolic Fate of C14 Labeled Pentoses in Man

“…Previous reports have described the physiological disposition of large quantities of infused pentoses (10), the effect of insulin on blood levels of infused pentoses (11) as well as studies of the metabolism of D-ribose (12). This paper reports some observations on the fate of C14 labeled D-xylOse, D-lyxose, D-arabinose and L-arabinose administered in trace quantities intravenously to normal human subjects.…”

The Metabolism of D-Ribose in Man

“…Preliminary results of these studies have been published (13), as well as a report of the hypoglycemia induced by ribose infusion (14). Previous publications (15,16) from this laboratory have described the physiologic disposition in man of the related pentoses D-Xylose, D-and L-arabinose, and D-lyxose, as well as the effects of insulin on the blood levels of these sugars.…”