Fructose raises the blood glucose threshold at which epiniphrine (adrenaline) will be released. This causes the liver to catabolize glycogen to sugar, and also signals fat cells to release fatty acids. I got that from this study.
/type one/9 .
They explain it like this; 'We hypothesized that this effect was due to the interaction of a "catalytic" dose of fructose with the regulatory protein for glucokinase in glucose-sensing cells that drive counterregulation. '
When a sugar molecule is phosphorylated, it makes it harder for that sugar to leave the cell. Fructose that is absorbed and then finds it's way to the liver, for example, is phosphorylated by fructokinase, and sort of stays put to be converted into glucose or fat or glycerine.
From the discussion;
"In concert with the augmentation of epinephrine release during hypoglycemia, the fructose studies were accompanied by significantly higher rates of EGP during the 3.9- and 3.3-mmol/l glucose steps and corresponding decreases in glucose infusion rates. Moreover, because of this enhanced counterregulatory response in the fructose studies, we were unable to lower the plasma glucose levels below 3.9 mmol/l."