T Nation

A Little Bio-Chem

Just a little refresher here: What is/are the means of amino acids entering the muscle cells in a meal where no carbohydrates are ingested (ie. Massive Eating P+f meal). Am I naive to think that Insulin is not present due to the lack of Carbohydrate? If that’s the case how do the amino acids get uptaken?

Secondly, are there different pathways for amino acids used for energy (out of the bloodstream) versus aminos used for protein synthesis (nirogen retention)?

I’ll get Katch, Katch and McArdle out to clarify, but I thought the T-Men could help.

Thanks in Advance.

There is still a small rise in Insulin after a P+F meal, but the “spike” is not as exaggerated as when carbs are present.

BigRob: Insulin is always, present, even if you are fasting.


What you are attempting to do with modified diets, or “Zone” diets, or Low Carb diets is two-fold:


1)Control the extent, timing and/or degree of the insulin “spikes”.


2)Control you long-term insulin levels. (Chronically high spiking levels have been associated with various disease states).

BigRob: Insulin is always present because glucose is always present in the bloodsteam. It is the primary fuel of the brain. If that fuel is not provided by the diet in some way, the body will “manufacture” and release it from ingested protein AND muscle protein (Gluconeogensis), once all storage forms of glucose have been depleted.

Insulin is also not requisite for AA uptake into the cell, particularly after a workout. It has been proposed that there is an insulin independent transport mechanism that will potentiate AA uptake with carb ingestion, and enable AA uptake in the absence of glucose/insulin elevations.

Thanks Mufasa, appreciate it.

Oh, you had 2 questions. I don’t know if this answers your 2nd question, but there are 2 pathways that aminos can take to end up getting used for energy. The ketogenic type aminos eventually yield ketone bodies, and we all know what happens to those. The glycogenic type aminos eventually participate in forming liver and muscle glycogen.