When does gluconeogenesis kick in during physical activity? - (Dec/13/2013 )
I'm a dietetics student, and my course is really unclear about gluconeogenesis regulation, and exactly WHEN it happens.
What my coursebook teaches me is that glycogenolysis is the main purveyor of energy during physical exercise, and it is triggered by LOW INSULIN, HIGH GLUCAGON and HIGH ADRENALINE, which is exactly what happens when you start working out. So far so good.
But then they tell me that gluconeogenesis is triggered by LOW INSULIN, HIGH GLUCAGON and HIGH ADRENALINE, so: exactly the same conditions as above. And yet they keep saying throughout the chapter that gluconeogenesis SELDOM occurs during physical exertion itself, and that aminoacids are used only as a last resort, even though they specified a few pages before that the main substrate for GNG is alanine (followed by lactate and glycerol).
So there HAS to exist some factor that apparently delays GNG other than the aforementionned hormones, otherwise both metabolisms would start at the same time since they respond to the same hormonal changes. Right? But there is no mention of any such thing in my course.
I'm lost! If anyone could clear that up for me, I'd be really thankful.
PS: apologies for not using the appropriate section, I only realised this after posting and don't know how to move the topic to the "students" section...
Don't worry - you can't move it ... but I can. Moved to the student physiology sub section.
Don't know the answer to your question though, other than to suggest the trigger might well be the lack of glycogen in the blood and absence of stores of readily available glycogen.
I take it you mean glucose since glycogen is not transported in the bloodstream, in which case I agree, but then again if glycogen is depleted by being broken down into glucose molecules, it can't start that process on its own, it only does so because of glucagon release, which itself is a trigger for gluconeogenesis too. So why would GNG not happen at the same time is what I just can't wrap my mind around.
And thanks for moving the thread for me!