The mystery of Glucagon/Insulin and CCK

[johnwandering]

I know that Glucagon is stimulated by CCK, and Insulin is inhibited by it...

But I was wondering, what is the reasoning behind this?
CCK means that there is food being digested, which would imply an incoming source of energy. Why would the body want to boost its level of blood glucose if it will have more glucose on the way??


It doesn't seem to make sense to me
=(

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[unhappytnt]

I had no idea that CCK increased Glucagon stimulation. Are you sure about this? A quick search online didn't bring up anything, and in fact suggested that Insulin is stimulated by CCK, not inhibited.

 

[johnwandering]

oh, then is this a misprint?

Kaplan bio says verbatim:

"Glucagon secretion is stimulated by a decrease in blood glucose and by gastrointestinal hormones (e.g., CCK and gastrin) and is inhibited by high plasma glucose levels."



Could anyone also help me understand how Somatostatin is affected by CCK as well??

 

[muhali3]

Somatostatin inhibits both insulin and glucagon secretion. So, according to Kaplan, somatostatin should decrease as a result of CCK. Tbh, I don't think any of this is expected knowledge and you would be given this information in a passage.

All you need to know is that CCK is secreted in response to high fat/protein chyme and stimulates release of bile from the gall bladder into the small intestine and also stimulates release of digestive enzymes from the pancreas.

 

[AlexB]

I'm not sure what CCK is, but I know for a fact that glucagon is secreted when amino acids are consumed. The reasoning is that insulin not only decreases blood glucose levels, but ALSO SHUTTLES AMINO ACIDS INTO CELLS FOR PROTEIN PRODUCTION. So, let's say you eat a large steak after a workout, insulin will fire off to get those AA's in to cells. As a side effect, insulin will also drop blood glucose even lower. To counter this, the body releases glucagon.

 

[muhali3]

I'm not sure what CCK is, but I know for a fact that glucagon is secreted when amino acids are consumed. The reasoning is that insulin not only decreases blood glucose levels, but ALSO SHUTTLES AMINO ACIDS INTO CELLS FOR PROTEIN PRODUCTION. So, let's say you eat a large steak after a workout, insulin will fire off to get those AA's in to cells. As a side effect, insulin will also drop blood glucose even lower. To counter this, the body releases glucagon.

True, I learned this from BR Bio on a question I got wrong. Insulin is used to increase cellular uptake of glucose, AAs, and fatty acids. So when plasma AAs levels rise above normal, insulin will be secreted to normalize AA levels, but plasma glucose levels will be reduced below normal since they were already normal. Hence glucagon will be secreted to counteract the hypoglycemic state caused by insulin.

 

[ModerateMouse]

I know that Glucagon is stimulated by CCK, and Insulin is inhibited by it...

But I was wondering, what is the reasoning behind this?
CCK means that there is food being digested, which would imply an incoming source of energy. Why would the body want to boost its level of blood glucose if it will have more glucose on the way??


It doesn't seem to make sense to me
=(

My class notes say the same thing! CCK leads to increased glucagon secretion. I can't make heads or tails of this. 😱 *wtf*

Here is a textbook that says the same thing (p. 194).

Edit: I am going to email the prof.

 

[kimunji]

If anyone's still interested in how CCK increases glucagon secretion, it is mentioned in this paper that:

"Glucose alone inhibited basal glucagon secretion in a con- centration-dependent manner with a one-half maximal effect (ECso) of 4.6 mM (Fig. 1), Addition of 10 nM CCKs re- versed this glucose effect, i.e, in the presence of 10 nM CCKs glucose increased ghicagon release in a concentration- dependent manner with an ECs0 of 6.9 mM. As shown in Fig. 2 this synergistic effect of CCKs was concentration- dependent at 11.1 mM glucose; in this case its ECs0 was 1.0 nM (Fig. 2)."

E. J. Verspohl and H. P. T. Ammon, Cholecystokinin (CCKs) regulates glucagon, insulin,
and somatostatin secretion from isolated rat pancreatic islets: interaction with glucose, PfltigersArch (1987)410:284-287, 1987

In summary, what this means is that the inhibitory factor on glucagon is due to the increased levels of glucose in the blood. CCK apparently lowers the inhibitory effect glucose has on the release of glucagon, which results in the increase in glucagon secretion. The mechanism of action, however, was not discussed in the paper.

Hope this helps a little 🙂