I do not know how dietary fat gets to the fat cells. i learned that insulin only carries glucose in school, but ive heard weightlifters say the use insulin because it carries amino acids to the muscles. So, now im confused, is insulin just for carrying glucose or does it carry other molecules like fat or amino acids as well. If so, is insulin carrying dietary fat to fat cells a primary reason for fat storage or just a minor factor?
According to my high school Biology class, insulin is a hormone, i.e. a kind of “message” that is sent around the body through the bloodstream. In this case, insulin sends a message to the cells in your liver to take glucose from the bloodstream and convert it into glycogen, a long-term energy storage fat.
Insulin does not “carry” anything anywhere. Blood carries glucose, fat, amino acids, etc throughout the body. Insulin is a hormone, a chemical “flag” that alerts various organs as to the status of blood sugar (among other things).
It’s presence (or absence) triggers a cascade of events which affect how your body processes sugar, fats, and amino acids.
Go here here for a diagram of the insulin signaling pathway
that’s exactly right. My mum has diabetes. There are things called Keytones too, everyone has them. I don’t know too much though and I don’t wish to confuse anyone, including myself.
Ketones are acits produced when the body breaks down fat for energy. This usually happens in diabetics, who, lacking insulin, can’t use blood sugar. It can lead to ketoacidosis, which can be fatal.
(minor nitpick)
two points:
Glycogen is actually a starch consisting of branched chains of glucose. It is a short term storage strategy meant to tide the body over during short periods of fasting (i.e., when you’re sleeping). Your liver contains about a day’s worth of glucose in the form of glycogen. Once that supply is exhausted and there’s no incoming source of glucose, your body starts looking for alternative sources…but that’s another story…
(/minor nitpick)
Insulin inhibits lipolysis, which is the breakdown or “burning” of fat.
Simplistically: Your body prefers to use glucose as fuel, so insulin is released into the blood in response to elevated blood sugar levels after a meal. In insulin-responsive cells it triggers the uptake of glucose. If your body has glucose available for fuel, it dosen’t need to burn fat and so that is inhibited.
That’s it off the top of my head. I’d have to read up on why weightlifters would want to use it and its other actions, which are many. It’s also involved in the regulation of the hormone leptin, which is very involved in the regulation of body fat.
As stated above, it dosen’t transport fat to the adipose (fat) cells, but it affects how those cells metabolize fat.
In addition to preventing the breakdown of fat, insulin also promotes the delivery of dietary fat to fat cells.
Specifically, insulin stimulates the activity of an enzyme called ‘lipoprotein lipase’ (LPL). When LPL is stimulated, it causes circulating fat (i.e. triglyceride) to be taken from the bloodstream and put into fat cells.
More specifically, for those interested in such things, LPL causes lipolysis of dietary triglyceride (carried by chylomicrons)*. The free fatty acids so liberated are taken up by fat cells (with the enzymatic machinery necessary for their re-esterification within the fat cell stimulated by insulin).
[sub][sup]*LPL also stimulates lipolysis of nondietary triglyceride (carried in the so-called Very Low Density Lipoproteins [VLDL]). [/sup][/sub]
Hey Karl Gauss,
I am one one those interested in such things. And you seem like have some expertise–are you an endocrinologist (M.D. or Ph.D.)?
Or just a guy with knowledge (I’m betting on the previous line–you’re a M.D. with training in Endo).
But in this case, I’m less concerned with biochemical feedback pathways than why do bodybuilders think they get some advantage–which relates to the OP.
The OP stated that weightlifters used insulin to “carry amino acids to muscles”.
What is up with that?
Why do body builders think insulin “helps” the building of muscle?
Insulin is an anabolic* hormone. It exists to drive nutrients into cells - not just glucose but fatty acids and amino acids. This thus builds up new tissue.
- builds up tissue