What Transports Fat Into Cells

[harry1]

My question for the experts out there is we know Insulin is secreted to transport Glucose from Carbohydrates across the Cell Membranes and into the Mitochondria that gives us ATP or energy when eating a high carb diet.

So i was curious is that when we eat a low carb and high fat diet as the fats get absorbed and are in our blood stream what transports them to and/or across the Cell Membranes so they can be incorporated into the Mitochondria's as well.

I'm talking for cellular energy and not fat storage as we know Insulin does that.

I've searched the web and cannot find much help on this.

Thanks harry!

[lisabinil]

Try here http://www.eioba.com/a35257/how_fat_is_burned_turning_fat_into_energy_carbon_dioxide_and_water

[harry1]

Thanks for the article lisabinil....it was a good article of how fat is turned into energy once inside the cell but what transports it into the cell in the first place?

In the case for Glucose there are Insulin Receptors all over the cell and when glucose inters the blood stream Insulin is released from the Pancreas and attaches to the Glucose and it then takes it to the Insulin Receptors to get thru the Cell Membrane to get inside to be burned or stored as fat. But what attaches to Fatty Acids to get them across the Cell Membrane to be burned for energy when we're are on a low carb diet as very little Insulin is released......

[kindke]

interesting question, i often thought about this, but never bothered to really research it.

just a guess but maybe adipose tissue is already receptive to fatty acids in the blood, and dont need some kind of anabolic hormone? i think estrogen is one of them.

[MyJourney]

I may not be understanding your question correctly but wouldnt it be a Chylomicron (A type of Lipoprotein) that would transport the fat to the liver to get broken down?

[MyJourney]

I read your question over again, are you asking how fat is metabolized into energy?

[harry1]

I read your question over again, are you asking how fat is metabolized into energy?
No.... i got that but how does it get from the Blood Stream to INSIDE the Cells.

All Cells have a fatty Membrane that keeps components in and others out. If one eats carbs for energy it becomes Glucose and then Insulin is secreted and attaches the Glucose and carries it ACROSS the Cell Membrane.

We low Carber's eat mainly Protein and Fat. When fat gets absorbed across the Intestines and goes into the Blood Stream what Hormone or Protein etc. is produced that grabs the fatty Acid and Transport it ACROSS the Cell Membrane as we know that its not Insulin.

I don't know how else to explain this....

[MyJourney]

I am still not totally sure what you are asking but I will try and explain what I understand and hopefully it covers it.

Normally, when one is not in ketosis I believe this is what happens. Fat is broken down into triglycerides (3 fatty acid molecules and 1 glycerol molecule) this process I believe this is lipolysis.

The glycerol gets converted into pyruvic acid, then 1 carbon is removed from the pyruvic acid and released as carbon dioxide which exits through the lungs. Hydrogen atoms are removed and you are left with acetic acid that combines with coenzyme A to have Acetyl CoA which then gets converted into ATP. The fatty acids chains break apart and form 2 acetic acid molecules and combines with coenzyme A.

Now, the Acetyl CoA enters the Krebs Cycle. The hydrogen that was removed during both during the conversion to Acetyl CoA and through the Krebs cycle then combine with oxygen and the reaction forms ATP.

Now, when one is in ketosis the fat still get broken down into Acetyl CoA but it does not go through the Krebs Cycle due to (I believe) the low amounts of intermediates like oxaloacetate which is necessary for gluconeogenesis. So then the Acetyl-CoA is then used in biosynthesis of ketone bodies via Acetoacyl-CoA.

[MyJourney]

Hmm... are you asking about digestion?

From Wikipedia - Fatty acids are usually ingested as triglycerides, which cannot be absorbed by the intestine. They are broken down into free fatty acids and monoglycerides by lipases with the help of bile salts. Most are absorbed as free fatty acids and 2-monoglycerides, but a small fraction is absorbed as free glycerol and as diglycerides. Once across the intestinal barrier, they are reformed into triglycerides and packaged into chylomicrons or liposomes, which are released in the lymph system and then into the blood. Eventually, they bind to the membranes of adipose cells or muscle, where they are either stored or oxidized for energy. The liver also acts as a major organ for fatty acid treatment, processing liposomes into the various lipoprotein forms, namely VLDL, LDL, IDL or HDL.

[kindke]

Eventually, they bind to the membranes of adipose cells or muscle, where they are either stored or oxidized for energy.

what are the parameters that decide whether it is stored or burned on the adipose tissue? can adipose tissue burn fat directly? and if so, what activates it?

[harry1]

Thanks guys for trying to answer for me....

That quote is exactly what i'm looking for '' Eventually they BIND to the membrane of adipose cells or muscle'' . The key word is BIND.......How do they BIND..... Glucose (carbs) and Amino Acids (protein) BIND by Insulin to the Membrane so how does triglycerides (fat) BIND to the Membranes. Thats what i've been asking. They can't BIND by themselves and its not Insulin so what is it.....

Thanks again.....

[MyJourney]

I found this online. I am not sure how much it helps. I am looking for you.

Here we are sitting inside a capillary that is in a bed of adipose tissue and we have these chylomicrons that float down. Here you see the chylomicrons, a bunch of triglycerides, a little bit of phospholipids and some cholesterol, but mainly triglycerides, packaged together in this ball which is held together by an apoprotein, that for chylomicrons is usually apoprotein B48 or sometimes B100. There are some other apoproteins C2 and these little green guys, which are lipoprotein lipase and are on these proteoglycan chains in order to act on this chylomicron and liberate the free fatty acids. In adipose tissue, the primary activator of lipoprotein lipase is insulin. That activates these guys and it frees up these free fatty acids to enter the adipose tissue where they reassemble back into triglycerides and are used for storage. Again, a lot of this transport is about using these triglycerides back and forth; triglycerides to free fatty acids, back and forth, and allowing them to travel where they need to go. Here we have our adipose tissue and that is what happens when insulin levels are higher, like after a meal, which creates these in the first place.

What happens in the fasting state, insulin levels drop. That activates hormone-sensitive lipase, an enzyme in adipose tissue. What does that do? Well, it breaks apart these triglycerides back into the free fatty acids, and the free fatty acids, we said they're hydrophobic, they don't like to travel in an aqueous environment like the blood, so they have to ride on albumin as one of their vehicles, and it's three to a car, and they float through the bloodstream and then they are shunted to the tissues that need them once again, like skeletal muscle, that can oxidize them and use them for energy. The other place they can go to, though, is to the liver, where the liver can repackage them into triglycerides and put them into another form of lipid protein, called VLDL, very low density lipoprotein. VLDL can then circulate through the body just like we saw with the chylomicron and drop off its triglyceride load and cholesterol to the tissues that seem to want it or to need it, whose membranes are activated to bind to it. And then as it goes, VLDL, as it loses more triglyceride and essentially gains more cholesterol, relative cholesterol content, it becomes an LDL, and then part of its metabolism to HDL. That's a whole lecture unto itself. So, I'm not going to go any further there.

[Mallory08]

wow interesting... i have a question... when low carbing to lose weight you need to be burning stored fat correct? well is there a process in which you go from using eatten fat to stored fat or is that still called ketosis?

[Nancy LC]

Ketosis can come from either dietary or stored fat.

[harry1]

I am looking for you. THANKYOU !! MyJourney.... for looking and i believe you found it what i was looking for...

APOPROTEIN........

I googled that and if i read some of these sites correctly thats what BINDS to the Fatty Acids and takes them to the Fat Receptors on the Cell Membranes which are then transfered inside the cells to be used to build new Membranes and also for energy in the Krebs Cycle (in Ketosis)

So in conclusion...Glucose and Amino Acids need Insulin to be attached to the Cell Receptors and Fatty Acids need Apoprotein to be attached to the cell receptors.....

Thankyou again MyJourney and everyone else who researched and participated as we all learned something interesting if i'm correct on the Apoproteins.......

[MyJourney]

I am glad you found what you were looking for. I was hoping that's what you were looking for. :-)

Yes, this was very informative. Thank you for asking.

wow interesting... i have a question... when low carbing to lose weight you need to be burning stored fat correct? well is there a process in which you go from using eatten fat to stored fat or is that still called ketosis?

To lose weight whether you are high carbing or low carbing you need to burn fat (well, you can lose water weight or muscle but the kind of weight we all want to lose is fat).

I believe ketosis is considered to be the state where ketogenesis is happening at high levels. Everyone creates ketone bodies at modest levels but are not actually in ketosis until these levels are really above that like in many low carb plans. Whatever we eat is always going to be used as energy before we start using stored energy like body fat. Many feel that there is a metabolic advantage to low carbing and the theories range from low carbing speeds up the metabolism so that one burns through stored energy faster to the process of metabolizing fat as energy is more energy intensive than carbohydrate.

[scthgharpy]

Wow. You know, Im just stunned at all this incredible medical information. Makes my head spin.

But you know? If the medical profession knows this much about how fat does what it does...you think they would be able to get it to do what we WANT it to do. Why cant drs help us lose weight?

[dane]

Fatty Acid Metabolism
(http://www.ngeeann.edu.sg/lsct/biochemistry/aab/topics/aab_lipid.htm) :thup: