A Return to Some Biochemistry: Part 1

Hey, everyone!  I hope you've been keeping busy.  My family is actually at a Lynyrd Skynyrd concert at the moment (my friend's little brother is one of the opening acts, how cool!), so what better way to spend time than writing about biochemistry.  I can't think of anywhere I would rather be at all!

Anyway, I'm going to return to some biochemistry!  I'll actually split this up into two separate posts--this one will be about the function and purpose of certain molecules, and the next one will be about how a low-glucose diet can change them and make them healthier.

This post is going to be about fat oxidation.  Exciting!

But let's review a little first.  Remember that with an excess of glucose, the body produces Malonyl-CoA, which shuts down the oxidation of fat in the mitochondria.

Excess of glucose.

Inhibition of CPT-1, which long chain fatty acids use to get into the mitochondria.

When you don't eat sugar, Malonyl-CoA isn't produced, so the CPT1 gate is opened, which means long chain fatty acids (what's making up triglycerides, for the most part) can be burned as fuel.  Yay!

So, how do the triglycerides get to the mitochondria, anyway?  A healthy person doesn't have any ectopic fat immediately available, so there's no fat in the muscle tissue.  A person on a low-carb diet can't get fat from the liver, either, since they would have burned through all of that already, too.  Well, the obvious answer is from regular fat cells.

From your booty.

Basically, when your body needs to transport fat from one place to another, it produces molecules called lipoproteins.  These lipoproteins act like vacuum cleaners--some suck long chain fatty acids out of fat cells, and some suck these fatty acids into metabolizing cells.

First, let's look at low-density lipoproteins (LDL for short).

As modeled by this fetching vacuum cleaner.

When the body needs to move fat from a fat cell, it sends over some LDL.

This is what Photoshop was made for.

Then the LDL sucks triglycerides from the fat cell,

Fun fact: it actually looks exactly like this.

meaning the LDL is now carrying around long chain fatty acids.

This looks really silly.

The LDL then takes the long chain fatty acids to where they're needed.  Let's say it's a muscle cell.

I'm starting to regret using vacuums.

A different lipoprotein, called high-density lipoprotein (HDL for short) takes over from there.  It takes the long chain fatty acids brought to the cell by LDL and takes it into the cell.

A challenger appears!

What am I doing with my life?

Once the long chain fatty acids are inside the cell, they can enter the mitochondria through the CPT1 gate and be burned for fuel.

We're done with this madness.

And now, with this silly vacuum cleaner nonsense done with, I can end this here for now.  Tune in next time for the thrilling conclusion: what does all this actually mean in terms of health?  Thanks for reading!