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Journal of the American College of Nutrition, Vol. 23, No. 5, 414-419 (2004)
Published by the American College of Nutrition

Plasma D-Glucose, D-Fructose and Insulin Responses after Oral Administration of D-Glucose, D-Fructose and Sucrose to Normal Rats

Pablo G. Prieto, MSc, Jesus Cancelas, PhD, Maria L. Villanueva-Peñacarrillo, PhD, Isabel Valverde, MD, PhD and Willy J. Malaisse, MD, PhD, FACN

Fundacíon Jiménez Díaz, Madrid, Spain (J.C., P.G.P., M.L.V., I.V.)
Laboratory of Experimental Hormonology, Brussels Free University, Brussels, Belgium (W.J.M.)

Address reprint requests to: W.J. Malaisse, MD, PhD, FACN, Laboratory of Experimental Hormonology, Brussels Free University (CP 626), 808 Route de Lennik, B-1070 Brussels, BELGIUM. E-mail: malaisse{at}ulb.ac.be

Objective: To assess whether oral D-fructose modifies the plasma D-glucose and insulin responses to oral D-glucose administration in normal rats.

Design: Oral D-glucose (1.7, 3.5, 6.9 or 13.9 µmol/g body weight), D-fructose (6.9 µmol/g), both D-glucose and D-fructose (1.7 or 3.5 µmol/g of each hexose) or sucrose (3.7 µmol/g) were administered intragastrically to overnight fasted rats and the plasma concentration of D-glucose, D-fructose and insulin measured over the ensuing 120 minutes. Control experiments were conducted after oral administration of H2O or saline.

Results: The administration of D-fructose, given as the free hexose or as sucrose, instead of augmenting the plasma D-glucose concentration evoked by the concomitant administration of D-glucose, tended both to improve the insulin response of the pancreatic B-cell and to minimize hyperglycemia, when compared to the results of experiments including the administration of equimolar amounts of D-glucose alone. For instance, the area under the plasma D-glucose curve was comparable in the rats receiving both D-glucose and D-fructose (3.5 µmol/g of each hexose) and the rats receiving only D-glucose (3.5 µmol/g), averaging respectively 836 ± 32 and 850 ± 34 mM · min each. Likewise, the paired ratio between the areas under the plasma insulin and D-glucose curves, when corrected for the threshold concentration for the insulinotropic action of the hexose (2.05 ± 0.10 mM), averaged 44.3 ± 3.0 nmol/mol in the 16 rats receiving D-fructose alone, sucrose alone or both D-glucose and D-fructose, as compared to 37.7 ± 2.9 nmol/mol in the 22 rats receiving increasing amounts of D-glucose alone.

Conclusions: The intake of D-fructose, as the free hexose or as sucrose, favours D-glucose homeostasis. This is likely to be attributable to the reciprocal effects of the aldose and ketose upon their respective phosphorylation by glucokinase in both hepatocytes and insulin-producing pancreatic islet cells.

Key words: D-glucose, D-fructose, sucrose, plasma insulin, normal rats






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