|MadSci Network: Biochemistry|
To be brief, I would answer your question by saying empahtically YES! Caffeine does affect the type of molecules used for obtaining energy, and in particular, it does increase the ammount of free fatty acids which are available to the mitochondria. When you have alot of fatty acids free, fatty acid synthesis will be down-regulated, and fatty acid metabolism will increase. This will result in increased ATP levels, which will down regulate glycolysis, so you will switch (to a certain extent) from metabolizing glucose to metabolizing fatty-acids.
Of course, since we are on the internet, why be brief when we can be verbose? Lets take a closer look at what is happening, so we can understand a bit more clearly why Caffeine results in an increase in free-fatty acid levels.
Our bodies store chemical energy that cannot immediately be used in the form of fat, and store the fat in specialized fat cells. When the body needs to use those engergy reseves, it signals the fat cells to undergo a process called lipolysis, which converts fat into fatty-acids and glycerol. The fatty-acids are then used for energy. The body signals this using chemical messengers in the blood (aka hormones), which bind to a receptors on the cell surface. When the receptors recognize a hormone, they send another chemical signal into the interior of the cell that tells the cell to undergo lipolysis. This signal is a molecule called cyclic Adenosine Monophosphate or cAMP. Once the signal has been sent into the cell, special enzymes in the cell deactivate the cAMP. The signal can be re-sent if more hormone binds to the receptor, but if there is no more hormone present then the cAMP signal will only last as long as it takes the enzymes to deactivate it. Once the cAMP signal stops, lipolysis will stop.
Caffeine is a molecule that looks alot like Adenine, which is an important part of the cAMP molecule. The chemical name of Caffeine is Trimethylxanthine, meaning that it is a Xanthine molecule with three methyl groups attached. Xanthine is a precursor of Adenine. When Caffeine is present in a fat cell, it interferes with the enzymes that deactivate cAMP ( possibly because it looks like a funny Adenosine molecule), slowing them down. As a result, the cAMP signal lasts longer in the cell, and lipolysis contines for a longer time. So in essense, Caffeine tricks your your fat cells into releasing more fatty-acids than needed by making the hormone signal last longer.
Isn't biochemistry great! I hope this helps!
Try the links in the MadSci Library for more information on Biochemistry.