Cholecystokinin-58

Where it comes from

Made in

I cells of the upper small intestine

Sent out by

Fat and protein after a meal

Acts on

• Gallbladder
• Pancreas
• Vagus nerve

What it does

• Reported as the major circulating form in people, but form-specific assays find it a minority, about a tenth, beside CCK-33 and CCK-22 ¹
• Acts longer than the short forms, and in rats it lengthens the gap between meals where CCK-8 only shortens the meal ²
• Does the work the textbooks give to CCK-8

In medicine

• Counted in “total CCK” assays; no medicine copies this form
• Measuring it is a research problem of its own: the long forms stick to plastic and are lost unless the sample is handled for them ¹

Beyond the body’s own use

• Not studied as a treatment, in people or as an analogue
• The interesting claim about it is behavioural and comes from rats: CCK-58 and CCK-8 are not interchangeable, so forty years of satiety work built on the octapeptide may not describe what the gut actually releases ²
• Nobody has infused CCK-58 into a person, so that claim is untested where it matters