GLP-1 receptor distribution: central and peripheral — one year on

GLP-1 receptor distribution: central and peripheral — one year on — setting out what I have, and where I think it stops being reliable.

An honest uncertainty about GLP-1 receptor distribution rather than a disguised assertion.

I do not know the answer and I have not been able to find one. What I have is the shape of the question, which may be worth more than my guess at the answer.

Central versus peripheral action: GLP-1 agonism works through both central nervous system effects (appetite) and peripheral effects (gastric motility, insulin). The balance is not fully characterised.

The interesting part of this is the exception, and I do not understand the exception.

Picking up post #2: that is the part I would want checked first.

Glucagon receptor agonism: glucagon receptor agonism increases energy expenditure and promotes hepatic fat oxidation. The mechanism is distinct from GLP-1 and GIP agonism and the clinical consequences are still being characterised.

Signalling through cyclic AMP is the canonical pathway and is not the only one. Beta-arrestin recruitment differs between ligands and its clinical significance here is unestablished.

It is one reading of the data and not the only reasonable one.

GLP-1 receptor agonism produces its metabolic effects through more than one route: central satiety signalling, delayed gastric emptying, and glucose-dependent insulin secretion. Attributing everything to one of them is where most simplified accounts go wrong.

That is a description of practice, not a recommendation of it.

Helpful, and easy to find again, which is half of what a good reply is.

Adding the measurement that post #6 says would settle it.

Pharmacological class effects: all GLP-1 agonists slow gastric emptying and suppress appetite. Those are class effects, not unique to one compound. Effects that differ between compounds are usually about potency or receptor selectivity.

The area postrema sits outside the blood-brain barrier and is where a great deal of the nausea signalling in this class originates. That is why the effect is central and not gastric irritation.

Adding a source would improve this post and I do not have one to hand.

Building on post #8 rather than restating it.

Cross-reactivity and selectivity: the compounds are not perfectly selective for their target receptors. Semaglutide has some activity on other receptors; tirzepatide activates both GLP-1 and GIP with different affinities. The off-target effects are part of the overall pharmacology.

In vitro potency and clinical potency are related by a long chain of assumptions. A compound more potent at the receptor is not necessarily more effective at a tolerable dose.

It is worth checking rather than assuming, which costs nothing.