Endogenous elevation of plasma cholecystokinin does not prevent gallstones

Cholecystokinin and cholecystokinin-A receptor: An attractive treatment strategy for biliary dyskinesia?

Biliary dyskinesia is a relatively common gastrointestinal disease that is increasing in incidence as living standards improve. However, its underlying pathogenesis remains unclear, hindering the development of therapeutic drugs. Recently, "Expression and functional study of cholecystokinin-A receptors on the interstitial Cajal-like cells of the guinea pig common bile duct" demonstrated that cholecystokinin (CCK) regulates the contractile function of the common bile duct through interaction with the CCK-A receptor in interstitial Cajal-like cells, contributing to improving the academic understanding of biliary tract dynamics and providing emerging directions for the pathogenesis and clinical management of biliary dyskinesia. This letter provides a brief overview of the role of CCK and CCK-A receptors in biliary dyskinesia from the perspective of animal experiments and clinical studies, and discusses prospects and challenges for the clinical application of CCK and CCK-A receptors as potential therapeutic targets.

The preference for sugar over sweetener depends on a gut sensor cell

Guided by gut sensory cues, humans and animals prefer nutritive sugars over non-caloric sweeteners, but how the gut steers such preferences remains unknown. In the intestine, neuropod cells synapse with vagal neurons to convey sugar stimuli to the brain within seconds. Here, we found that cholecystokinin (CCK)-labeled duodenal neuropod cells differentiate and transduce luminal stimuli from sweeteners and sugars to the vagus nerve using sweet taste receptors and sodium glucose transporters. The two stimulus types elicited distinct neural pathways: while sweetener stimulated purinergic neurotransmission, sugar stimulated glutamatergic neurotransmission. To probe the contribution of these cells to behavior, we developed optogenetics for the gut lumen by engineering a flexible fiberoptic. We showed that preference for sugar over sweetener in mice depends on neuropod cell glutamatergic signaling. By swiftly discerning the precise identity of nutrient stimuli, gut neuropod cells serve as the entry point to guide nutritive choices.

Buchanan, Rupprecht, Kaelberer and colleagues show that the preference for sugar over sweetener in mice depends on gut neuropod cells. Akin to other sensor cells, neuropod cells swiftly communicate the precise identity of stimuli to drive food choices.

Obesity and Gallstones

BACKGROUND

The prevalence of obesity has been increasing globally and represents the main risk factor for the development of gallstone disease (GD).

SUMMARY

Excess body weight represents the main cause for the development of GD; nevertheless, there have been described multiple risk factors for its development, among them modifiable risk factors as diet, lifestyle, physical inactivity, and non-modifiable risk factors as ethnicity, female sex, advanced age, parity, and genetic mutations. Body mass index, abdominal perimeter, and waist-hip index have been used to determine the degree of adiposity of a person. Hence, central abdominal fat has been mostly associated with insulin resistance with the consequent increase in the hepatic cholesterol secretion; contributing as one of the multiple mechanisms associated with the development of gallstones. This disease has a low mortality; however, it has been associated with multiple diseases such as cardiovascular diseases, carotid atherosclerosis, metabolic associated fatty liver disease, and gallbladder cancer, probably because they share many of the risk factors.

KEY MESSAGES

GD continues to be considered a disease with a high medical burden, in which it is sought to intervene in modifiable risk factors to reduce its development.

Rodent models of cholestatic liver disease: A practical guide for translational research

Cholestatic liver disease denotes any situation associated with impaired bile flow concomitant with a noxious bile acid accumulation in the liver and/or systemic circulation. Cholestatic liver disease can be subdivided into different types according to its clinical phenotype, such as biliary atresia, drug-induced cholestasis, gallstone liver disease, intrahepatic cholestasis of pregnancy, primary biliary cholangitis and primary sclerosing cholangitis. Considerable effort has been devoted to elucidating underlying mechanisms of cholestatic liver injuries and explore novel therapeutic and diagnostic strategies using animal models. Animal models employed according to their appropriate applicability domain herein play a crucial role. This review provides an overview of currently available in vivo animal models, fit-for-purpose in modelling different types of cholestatic liver diseases. Moreover, a practical guide and workflow is provided which can be used for translational research purposes, including all advantages and disadvantages of currently available in vivo animal models.

Prevention of gallbladder hypomotility via FATP2 inhibition protects from lithogenic diet-induced cholelithiasis

Gallstone disease is a widespread disorder costing billions for annual treatment in the United States. The primary mechanisms underlying gallstone formation are biliary cholesterol supersaturation and gallbladder hypomotility. The relative contribution of these two processes has been difficult to dissect, as experimental lithogenic diets cause both bile supersaturation and alterations in gallbladder motility. Importantly, there is no mechanistic explanation for obesity as a major risk factor for cholelithiasis. We discovered that lithogenic diets induce ectopic triacylglycerol (TAG) accumulation, a major feature of obesity and a known muscle contraction impairing condition. We hypothesized that prevention of TAG accumulation in gallbladder walls may prevent gallbladder contractile dysfunction without impacting biliary cholesterol saturation. We utilized adeno-associated virus-mediated knock down of the long-chain fatty acid transporter 2 (FATP2; Slc27A2), which is highly expressed by gallbladder epithelial cells, to downregulate lithogenic diet-associated TAG accumulation. FATP2-knockdown significantly reduced gallbladder TAG, but did not affect key bile composition parameters. Importantly, measurements with force displacement transducers showed that contractile strength in FATP2-knockdown gallbladders was significantly greater than in control gallbladders following lithogenic diet administration, and the magnitude of this effect was sufficient to prevent the formation of gallstones. FATP2-driven fatty acid uptake and the subsequent TAG accumulation in gallbladder tissue plays a pivotal role in cholelithiasis, and prevention of this process can protect from gallstone formation, even in the context of supersaturated bile cholesterol levels, thus pointing to new treatment approaches and targets.

The cholecystokinin-1 receptor antagonist devazepide increases cholesterol cholelithogenesis in mice

BACKGROUND

A defect in gallbladder contraction function plays a key role in the pathogenesis of gallstones. The cholecystokinin-1 receptor (CCK-1R) antagonists have been extensively investigated for their therapeutic effects on gastrointestinal and metabolic diseases in animal studies and clinical trials. However, it is still unknown whether they have a potential effect on gallstone formation.

DESIGN

To study whether the CCK-1R antagonists enhance cholelithogenesis, we investigated cholesterol crystallization, gallstone formation, hepatic lipid secretion, gallbladder emptying function and intestinal cholesterol absorption in male C57BL/6J mice treated by gavage with devazepide (4 mg/day/kg) or vehicle (as controls) twice per day and fed the lithogenic diet for 21 days.

RESULTS

During 21 days of feeding, oral administration of devazepide significantly accelerated cholesterol crystallization and crystal growth to microlithiasis, with 40% of mice forming gallstones, whereas only agglomerated cholesterol monohydrate crystals were found in mice receiving vehicle. Compared to the vehicle group, fasting and postprandial residual gallbladder volumes in response to the high-fat meal were significantly larger in the devazepide group during cholelithogenesis, showing reduced gallbladder emptying and bile stasis. Moreover, devazepide significantly increased hepatic secretion of biliary cholesterol, but not phospholipids or bile salts. The percentage of intestinal cholesterol absorption was higher in devazepide-treated mice, increasing the bioavailability of chylomicron-derived cholesterol in the liver for biliary hypersecretion into bile. These abnormalities induced supersaturated bile and rapid cholesterol crystallization.

CONCLUSIONS

The potent CCK-1R antagonist devazepide increases susceptibility to gallstone formation by impairing gallbladder emptying function, disrupting biliary cholesterol metabolism and enhancing intestinal cholesterol absorption in mice.