Keto-adapted and triglycerides

From reading my Volek & Phinney I learn that ketones can be used as fuel by tissues and especially the brain.

In the first phase of low carbohydrate eating, ketones rapidly replace glucose as the blood borne energy source.

However in the longer term (the keto-adaptation phase) the tissues adapt their metabolic pathways to store and burn triglycerides for energy and the main use of ketones is for brain fuel.

Reading this, I think that after the initial phase you are triglyceride adapted, not keto adapted.

What I can't determine at the moment is which triglycerides are the main fuel source, and if their concentration goes up once you are fuelled by fat.

http://www.ketogenic-diet-resource.com/metabolic-pathways.html has an interesting take on this.

My main area of confusion is over which bits of cholesterol (LDL, HDL and triglycerides) are the main transports in the blood for fats when your body has switched to being fuelled by fat.

I read that LDL is bad because it is taking lipid to the tissues, and HDL is good because it it scavenging lipids to be processed by the liver. However I then wonder if anything taking fat to the tissues is bad if you are a fat burner.

Further ramblings:

https://en.wikipedia.org/wiki/Triglyceride says:
"
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (tri- + glyceride).[1] Triglycerides are the main constituents of body fat in humans and other animals, as well as vegetable fat.[2] They are also present in the blood to enable the bidirectional transference of adipose fat and blood glucose from the liver, and are a major component of human skin oils.[3]

There are many different types of triglyceride, with the main division between saturated and unsaturated types. Saturated fats are "saturated" with hydrogen – all available places where hydrogen atoms could be bonded to carbon atoms are occupied. These have a higher melting point and are more likely to be solid at room temperature. Unsaturated fats have double bonds between some of the carbon atoms, reducing the number of places where hydrogen atoms can bond to carbon atoms. These have a lower melting point and are more likely to be liquid at room temperature.
"

and also

"
The pancreatic lipase acts at the ester bond, hydrolysing the bond and "releasing" the fatty acid. In triglyceride form, lipids cannot be absorbed by the duodenum. Fatty acids, monoglycerides (one glycerol, one fatty acid), and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down.

In the intestine, following the secretion of lipases and bile, triglycerides are split into monoacylglycerol and free fatty acids in a process called lipolysis. They are subsequently moved to absorptive enterocyte cells lining the intestines. The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with cholesterol and proteins to form chylomicrons. These are excreted from the cells and collected by the lymph system and transported to the large vessels near the heart before being mixed into the blood. Various tissues can capture the chylomicrons, releasing the triglycerides to be used as a source of energy. Liver cells can synthesize and store triglycerides. When the body requires fatty acids as an energy source, the hormone glucagon signals the breakdown of the triglycerides by hormone-sensitive lipase to release free fatty acids. As the brain cannot utilize fatty acids as an energy source (unless converted to a ketone),[citation needed] the glycerol component of triglycerides can be converted into glucose, via gluconeogenesis by conversion into dihydroxyacetone phosphate and then into glyceraldehyde 3-phosphate, for brain fuel when it is broken down. Fat cells may also be broken down for that reason, if the brain's needs ever outweigh the body's.

Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Fatty acids can then be taken up by cells via the fatty acid transporter (FAT).

Triglycerides, as major components of very-low-density lipoprotein (VLDL) and chylomicrons, play an important role in metabolism as energy sources and transporters of dietary fat. They contain more than twice as much energy (approximately 9 kcal/g or 38 kJ/g) as carbohydrates (approximately 4 kcal/g or 17 kJ/g).[7]
"

Read about VLDL and chylomicrons to get even more confused. I was reminded of midi-chlorians for some reason.

Freema said:

the triglycerides are made from carbs aren´t they... when carbs are broken down one of the components are triglycerides

http://antranik.org/the-catabolism-of-fats-and-proteins-for-energy/
http://blog.joslin.org/2011/09/why-does-fat-increase-blood-glucose/

Click to expand...

Ummm......I'm afraid that I think that some of both of those blogs is a load of cobblers. Neither seem to acknowledge the existence of LCHF because they both deny high fat and make some dubious claims about fat metabolism. Little awareness of diabetics who don't inject insulin.
The antranik blog even says "There should never be ketoacids in the urine, just like how there shouldn’t be sugars."
Deity save us all if this is the level of training given to potential nurses and clinical professionals.

Triglycerides; yes they can be made in the body from carbs and this is the normal way that spare carbs are tucked into the fat cells.

However if you aren't eating carbs you can still get triglycerides from your food.
When you eat fat this gets transported into the body then moved around and stored as triglycerides (amongst other things).
Animal fats must, I think, come eventually from carbs if you assume that browsing animals such as cows and sheep eat plants and use those to build fats. However plants also produce fats and oils so some of the animal fats probably come from plant fats.
We can also take in plant fats such as olive oil and these will yet again end up as triglycerides when they move through the blood stream and are stored and used in the tissues.

So triglycerides can come from carbs, but not all triglycerides do!

Contralto said:

Nice links. So, after reading all this, what are your conclusions about what sort of diets we ought pursue? And, besides just VLDL, who do fractionated lipoproteins fit into all this?

Click to expand...

I am a fan of LCHF but I am trying to work out in my head quite what happens once you change over from carbohydrate to fat fuel.

One thing bugging me is that when you are running on triglycerides the cycle is still moderated by insulin and glucagon, just like when you are running on carbs.
Now if your problem is insulin resistance in the tissues, then exercise and LCHF should sort things out and your blood lipids should be nice and low.
If your problem is low insulin production then again LCHF may sort you out because in nutritional ketosis you need to produce far less insulin.
However what if your poor blood glucose control is because the glucagon/insulin alpha/beta cell interaction just ins't working right?
Seems to me that you could end up with too much fat in the blood instead of too much sugar.

Oh! Diversion!!
https://chrismasterjohnphd.com/2012/01/07/we-really-can-make-glucose-from-fatty/
I've read consistently that carbs to fat is a one way street.
This is interesting (if complicated) stuff.
I was thinking that gluconeogenesis was the creation of glucose from protein but I think it means the creation (genesis) of new (neo) glucose from anything.
This says that in difficult times glucose can be created from fats but it is an expensive and difficult pathway.
I take that to mean that this would only happen if there was no easy source of glucose including dietary protein.
Still haven't finished reading it.
Oh, and looks like the glycerol part of triglycerides can be fed back in to produce glucose.

Can't answer about VLDL and f.l.