Thread: Fructose and muscle glycogen

I'd also be curious if fructokinase really is only found in the liver or could exist in skeletal muscle.

Originally Posted by invain

Anybody read up much on fructose metabolism? People always claim fructose can only be used to refill liver glycogen but I've read a few studies that show fructose can be used to refill muscle glycogen directly. I think the rates were slower than glucose but still comparable.

I'm just curious about the efficiency of refilling glycogen stores with sucrose vs dextrose. Does it really make a big difference?

the rates of muscle glycogen replenishment from glucose based sugars to fructose based are not even close..as you mentioned fructose is metabolized using a non-insulin dependent pathway it is directly metabolized into liver glycogen and it is also slowly absorbed into the intestines. when serum glucose levels drop the liver will only release so much glycogen into the bloodstream at once, while there is no mechanism to regulate the uptake of glucose based sugars into the portal bloodstream

Originally Posted by LAM

the rates of muscle glycogen replenishment from glucose based sugars to fructose based are not even close..as you mentioned fructose is metabolized using a non-insulin dependent pathway it is directly metabolized into liver glycogen and it is also slowly absorbed into the intestines. when serum glucose levels drop the liver will only release so much glycogen into the bloodstream at once, while there is no mechanism to regulate the uptake of glucose based sugars into the portal bloodstream

I'll try to find one of the studies I read. Pretty sure the rates of glycogen replenishment from fructose was something like 50% that of glucose.