The contribution of naturally labelled C fructose to glucose appearance in humans.

Among monosaccharides, fructose has a small hyperglycaemic effect. In order to better explain the mechanisms which cause this metabolic property, we used tracers labelled with stable isotopes (deuterated glucose and naturally C labelled fructose) to quantify the overall glucose appearance, the rate of appearance in plasma of the C glucose synthesized from fructose, and the fructose oxidation in vivo in man during a 6-h period following ingestion of 0.5 and 1 g · kg fructose. Fructose had a very small effect on overall glucose appearance (NS). During the 6 h of the study, it was found that the overall glucose appearance was 0.87±0.06 and 0.89±0.06 g · kg (NS). The amount of glucose synthesized from fructose was 0.27±0.04 and 0.51±0.03 g · kg ( p<0.01) representing 31% and 57% of overall glucose appearance ( p<0.01); the non-fructose glucose production was 0.60±0.02 and 0.38±0.03 g · kg ( p<0.05) after the 0.5 and 1 g · kg load, respectively. Fructose oxidation was 0.28±0.03 and 0.59±0.07 g · kg after the 0.5 and 1 g · kg load respectively ( p<0.01) representing 56% and 59% of the fructose loads (NS). These data show that the low hyperglycaemic effect of fructose is explained by its very small effect on overall glucose appearance and that fructose has a sparing effect on glucose metabolism. [ABSTRACT FROM AUTHOR]