Kinetics of Gallbladder Emptying During Cholecystokinin Cholescintigraphy as an Indicator of In Vivo Hormonal Sensitivity

Cholecystokinin cholescintigraphy is used clinically to quantify gallbladder ejection fraction as an indicator of functional gallbladder disorder. It can also provide the opportunity to quantify an individual’s responsiveness to the physiologic stimulant of gallbladder contraction, cholecystokinin, which is a major regulator of appetite and postprandial satiety. Methods: In the current work, we use cholecystokinin cholescintigraphy to quantify the kinetics of gallbladder emptying, including average and peak rates, in response to a standard cholecystokinin infusion. Results: We demonstrated that patients with no gallstones or biliary obstruction who empty their gallbladders completely in response to cholecystokinin, having an ejection fraction greater than 80%, exhibit a broad range of sensitivity to this hormone. Three distinct kinetic profiles were observed, with those most sensitive to cholecystokinin achieving the earliest peak and the fastest rate of gallbladder emptying, whereas those least sensitive to cholecystokinin have the latest peak and the slowest rate of emptying. Conclusion: Patients can have abnormal cholecystokinin stimulus–activity coupling as an effect of endogenous negative allosteric modulation by membrane cholesterol. This was predicted in ex vivo studies but has not, to our knowledge, previously been demonstrated in vivo. This type of kinetic analysis provides a tool to quantify cholecystokinin responsiveness in patients and identify patients who might benefit from a drug that would positively modulate cholecystokinin action to improve their appetite regulation and to better control their weight.