Pathophysiological role of cholecystokinin in humans

Hyperinsulinemia acts via acinar insulin receptors to initiate pancreatic cancer by increasing digestive enzyme production and inflammation

The rising pancreatic cancer incidence due to obesity and type 2 diabetes is closely tied to hyperinsulinemia, an independent cancer risk factor. Previous studies demonstrated reducing insulin production suppressed pancreatic intraepithelial neoplasia (PanIN) pre-cancerous lesions in Kras-mutant mice. However, the pathophysiological and molecular mechanisms remained unknown, and in particular it was unclear whether hyperinsulinemia affected PanIN precursor cells directly or indirectly. Here, we demonstrate that insulin receptors (Insr) in KrasG12D-expressing pancreatic acinar cells are dispensable for glucose homeostasis but necessary for hyperinsulinemia-driven PanIN formation in the context of diet-induced hyperinsulinemia and obesity. Mechanistically, this was attributed to amplified digestive enzyme protein translation, triggering of local inflammation, and PanIN metaplasia in vivo. In vitro, insulin dose-dependently increased acinar-to-ductal metaplasia formation in a trypsin- and Insr-dependent manner. Collectively, our data shed light on the mechanisms connecting obesity-driven hyperinsulinemia and pancreatic cancer development.

The biological functions and metabolic pathways of valine in swine

Valine is an essential amino acid and a type of branched-chain amino acid. Due to the involvement of branched-chain amino acids in various metabolic pathways, there has been a surge of interests in valine nutrition and its role in animal physiology. In pigs, the interactions between valine and other branched-chain amino acids or aromatic amino acids are complex. In this review, we delve into the interaction mechanism, metabolic pathways, and biological functions of valine. Appropriate valine supplementation not only enhances growth and reproductive performances, but also modulates gut microbiota and immune functions. Based on past observations and interpretations, we provide recommended feed levels of valine for weaned piglets, growing pigs, gilts, lactating sows, barrows and entire males. The summarized valine nutrient requirements for pigs at different stages offer valuable insights for future research and practical applications in animal husbandry.

The gut signals to AGRP-expressing cells of the pituitary to control glucose homeostasis

Glucose homeostasis can be improved after bariatric surgery, which alters bile flow and stimulates gut hormone secretion, particularly FGF15/19. FGFR1 expression in AGRP-expressing cells is required for bile acids' ability to improve glucose control. We show that the mouse Agrp gene has 3 promoter/enhancer regions that direct transcription of each of their own AGRP transcripts. One of these Agrp promoters/enhancers, Agrp-B, is regulated by bile acids. We generated an Agrp-B knockin FLP/knockout allele. AGRP-B-expressing cells are found in endocrine cells of the pars tuberalis and coexpress diacylglycerol lipase B - an endocannabinoid biosynthetic enzyme - distinct from pars tuberalis thyrotropes. AGRP-B expression is also found in the folliculostellate cells of the pituitary's anterior lobe. Mice without AGRP-B were protected from glucose intolerance induced by high-fat feeding but not from excess weight gain. Chemogenetic inhibition of AGRP-B cells improved glucose tolerance by enhancing glucose-stimulated insulin secretion. Inhibition of the AGRP-B cells also caused weight loss. The improved glucose tolerance and reduced body weight persisted up to 6 weeks after cessation of the DREADD-mediated inhibition, suggesting the presence of a biological switch for glucose homeostasis that is regulated by long-term stability of food availability.

Odevixibat: an investigational inhibitor of the ileal bile acid transporter (IBAT) for the treatment of biliary atresia

INTRODUCTION

Biliary atresia (BA) is a rare, non-curable cholestasis-causing disease in infancy, due to progressive ascending bile duct sclerosis. Even after restoration of bile flow following Kasai portoenterostomy, about half of these children need a liver transplant by their 2nd birthday, due to progressive fibrosis. Toxicity of bile acids may play a central role in disease progression, but drug therapies are not yet available. With ileal bile acid transporter (IBAT) inhibitors, there is a potential novel drug option that inhibits the absorption of bile acids in the small intestine. As a result of reduced bile acid accumulation in the cholestatic liver, it may be possible to delay hepatic remodeling.

AREAS COVERED

This review summarizes the dataset on bile acids and the potential effects of odevixibat, an IBAT inhibitor, in children with BA.

EXPERT OPINION

Systemic reduction of bile acids with the aim of preventing inflammation, and thus liver remodeling, is a novel, promising, therapeutic concept. In principle, however, the time until diagnosis and surgical treatment of BA should still be kept as short as possible in order to minimize liver remodeling before medical intervention can be initiated. IBAT inhibitors may add to the medical options in limiting disease progression in BA.

Bile Acids: Key Players in Inflammatory Bowel Diseases?

Inflammatory bowel diseases (IBDs) have emerged as a public health problem worldwide with a limited number of efficient therapeutic options despite advances in medical therapy. Although changes in the gut microbiota composition are recognized as key drivers of dysregulated intestinal immunity, alterations in bile acids (BAs) have been shown to influence gut homeostasis and contribute to the pathogenesis of the disease. In this review, we explore the interactions involving BAs and gut microbiota in IBDs, and discuss how the gut microbiota–BA–host axis may influence digestive inflammation.

Metabolic disturbances associated with antipsychotic drug treatment in patients with schizophrenia: State-of-the-art and future perspectives

Metabolic disturbances and obesity are major cardiovascular risk factors in patients with schizophrenia, resulting in a higher mortality rate and shorter life expectancy compared with those in the general population. Although schizophrenia and metabolic disturbances may share certain genetic or pathobiological risks, antipsychotics, particularly those of second generation, may further increase the risk of weight gain and metabolic disturbances in patients with schizophrenia. This review included articles on weight gain and metabolic disturbances related to antipsychotics and their mechanisms, monitoring guidelines, and interventions. Nearly all antipsychotics are associated with weight gain, but the degree of the weight gain varies considerably. Although certain neurotransmitter receptor-binding affinities and hormones are correlated with weight gain and specific metabolic abnormalities, the precise mechanisms underlying antipsychotic-induced weight gain and metabolic disturbances remain unclear. Emerging evidence indicates the role of genetic polymorphisms associated with antipsychotic-induced weight gain and antipsychotic-induced metabolic disturbances. Although many guidelines for screening and monitoring antipsychotic-induced metabolic disturbances have been developed, they are not routinely implemented in clinical care. Numerous studies have also investigated strategies for managing antipsychotic-induced metabolic disturbances. Thus, patients and their caregivers must be educated and motivated to pursue a healthier life through smoking cessation and dietary and physical activity programs. If lifestyle intervention fails, switching to another antipsychotic drug with a lower metabolic risk or adding adjunctive medication to mitigate weight gain should be considered. Antipsychotic medications are essential for schizophrenia treatment, hence clinicians should monitor and manage the resulting weight gain and metabolic disturbances.

Bile acid-based therapies for non-alcoholic steatohepatitis and alcoholic liver disease

Bile acids are synthesized from cholesterol only in hepatocytes. Bile acids circulating in the enterohepatic system act as physiological detergent molecules to help solubilize biliary cholesterol and emulsify dietary lipids and fat-soluble vitamins in small intestine. Bile acids are signaling molecules that activate nuclear receptor farnesoid X receptor (FXR) and cell surface G protein-coupled receptor TGR5. FXR critically regulates bile acid homeostasis by mediating bile acid feedback inhibition of hepatic bile acid synthesis. In addition, bile acid-activated cellular signaling pathways regulate metabolic homeostasis, immunity, and cell proliferation in various metabolically active organs. In the small and large intestine, gut bacterial enzymes modify primary bile acids to generate secondary bile acids to help shape the bile acid pool composition and subsequent biological effects. In turn, bile acids exhibit anti-microbial properties and modulate gut microbiota to influence host metabolism and immunity. Currently, bile acid-based therapies including systemic and intestine-restricted FXR agonists, TGR5 agonists, fibroblast growth factor 19 analogue, intestine FXR antagonists, and intestine apical sodium-bile acid transporter (ASBT) inhibitors have been developed as promising treatments for non-alcoholic steatohepatitis (NASH). These pharmacological agents improved metabolic and inflammatory disorders via distinct mechanisms of action that are subjects of extensive research interest. More recently, human and experimental alcoholic liver disease (ALD) has been associated with disrupted bile acid homeostasis. In additional, new findings showed that targeting bile acid metabolism and signaling may be promising therapeutic approaches for treating ALD.

Absence of Intestinal Microbiota during Gestation and Lactation Does Not Alter the Metabolic Response to a Western-type Diet in Adulthood

SCOPE

Microbiota composition in early life is implied to affect the risk to develop obesity in adulthood. It is unclear whether this risk is due to long-lasting microbiome-induced changes in host metabolism. This study aims to identify whether the presence or total absence of early-life microbiota affects host metabolism in adulthood.

METHODS AND RESULTS

The effects of a germ-free (Former GF) versus conventional status during gestation and lactation on the metabolic status in adult offspring are compared. Upon conventionalization at weaning, all mice were metabolically challenged with a Western-type diet (WTD) at 10 weeks age. Between age 10 and 30 weeks, a former GF status does not notably affect overall body weight gain, cholesterol metabolism, glucose tolerance or insulin sensitivity at adult age. However, Former GF mice have lower bile flow and bile acid secretion in adulthood, but similar bile acid composition.

CONCLUSIONS

A germ-free status during gestation and lactation does not substantially affect key parameters of the metabolic status before 10 weeks of age on chow diet or in adulthood following a WTD challenge. These data imply that microbiota in early life does not critically affect adult metabolic plasticity.

An update on the pathogenesis of cholesterol gallstone disease

PURPOSE OF REVIEW

Gallstone disease is a major epidemiologic and economic burden worldwide, and the most frequent form is cholesterol gallstone disease.

RECENT FINDINGS

Major pathogenetic factors for cholesterol gallstones include a genetic background, hepatic hypersecretion of cholesterol, and supersaturated bile which give life to precipitating cholesterol crystals that accumulate and grow in a sluggish gallbladder. Additional factors include mucin and inflammatory changes in the gallbladder, slow intestinal motility, increased intestinal absorption of cholesterol, and altered gut microbiota. Mechanisms of disease are linked with insulin resistance, obesity, the metabolic syndrome, and type 2 diabetes. The role of nuclear receptors, signaling pathways, gut microbiota, and epigenome are being actively investigated.

SUMMARY

Ongoing research on cholesterol gallstone disease is intensively investigating several pathogenic mechanisms, associated metabolic disorders, new therapeutic approaches, and novel strategies for primary prevention, including lifestyles.

Cholecystokinin (CCK) and related adjunct peptide therapies for the treatment of obesity and type 2 diabetes

Cholecystokinin (CCK) is a hormone secreted from I-cells of the gut, as well as neurons in the enteric and central nervous system, that binds and activates CCK-1 and CCK-2 receptors to mediate its biological actions. To date knowledge relating to the physiological significance of CCK has predominantly focused around induction of short-term satiety. However, CCK has also been highlighted to possess important actions in relation to the regulation of insulin secretion, as well as overall beta-cell function and survival. Consequently, this has led to the development of enzymatically stable, biologically active, CCK peptide analogues with proposed therapeutic promise for both obesity and type 2 diabetes. In addition, several studies have demonstrated metabolic, and therapeutically relevant, complementary biological actions of CCK with those of the incretin hormones GIP and GLP-1, as well as with amylin and leptin. Thus, stable CCK derivatives not only offer promise as potential independent weight-reducing and glucose-lowering drugs, but also as effective adjunctive therapies. This review focuses on the recent and ongoing developments of CCK in the context of new therapies for obesity and type 2 diabetes.

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.

Effect of endogenous cholecystokinin on the course of acute pancreatitis in rats

AIM: To examine the effects of pancreatic rest, stimulation and rest/stimulation on the natural course of recovery after acute pancreatitis.

METHODS: Acute hemorrhagic pancreatitis (AP) was induced in male rats by intraductal infusion of 40 μL/100 g body weight of 3% sodium taurocholate. All rats took food ad libitum. At 24 h after induction of AP, rats were divided into four groups: control (AP-C), pancreas rest (AP-R), stimulation (AP-S), and rest/stimulation (AP-R/S). Rats in the AP-C, AP-R and AP-S groups received oral administration of 2 mL/kg body weight saline, cholecystokinin (CCK)-1 receptor antagonist, and endogenous CCK release stimulant, respectively, twice daily for 10 d, while those in the AP-R/S group received twice daily CCK-1 receptor antagonist for the first 5 d followed by twice daily CCK release stimulant for 5 d. Rats without any treatment were used as control group (Control). Biochemical and histological changes in the pancreas, and secretory function were evaluated on day 12 at 24 h after the last treatment.

RESULTS: Feeding ad libitum (AP-C) delayed biochemical, histological and functional recovery from AP. In AP-C rats, bombesin-stimulated pancreatic secretory function and HOMA-β-cell score were significantly lower than those in other groups of rats. In AP-R rats, protein per DNA ratio and pancreatic exocrine secretory function were significantly low compared with those in Control rats. In AP-S and AP-R/S rats, the above parameters recovered to the Control levels. Bombesin-stimulated pancreatic exocrine response in AP-R/S rats was higher than in AP-S rats and almost returned to control levels. In the pancreas of AP-C rats, destruction of pancreatic acini, marked infiltration of inflammatory cells, and strong expression of α-smooth muscle actin, tumor necrosis factor-α and interleukin-1β were seen. Pancreatic rest reversed these histological alterations, but not atrophy of pancreatic acini and mild infiltration of inflammatory cells. In AP-S and AP-R/S rats, the pancreas showed almost normal architecture.

CONCLUSION: The favorable treatment strategy for AP is to keep the pancreas at rest during an early stage followed by pancreatic stimulation by promoting endogenous CCK release.

Bile Acid Metabolism and Signaling in Cholestasis, Inflammation, and Cancer

Bile acids are synthesized from cholesterol in the liver. Some cytochrome P450 (CYP) enzymes play key roles in bile acid synthesis. Bile acids are physiological detergent molecules, so are highly cytotoxic. They undergo enterohepatic circulation and play important roles in generating bile flow and facilitating biliary secretion of endogenous metabolites and xenobiotics and intestinal absorption of dietary fats and lipid-soluble vitamins. Bile acid synthesis, transport, and pool size are therefore tightly regulated under physiological conditions. In cholestasis, impaired bile flow leads to accumulation of bile acids in the liver, causing hepatocyte and biliary injury and inflammation. Chronic cholestasis is associated with fibrosis, cirrhosis, and eventually liver failure. Chronic cholestasis also increases the risk of developing hepatocellular or cholangiocellular carcinomas. Extensive research in the last two decades has shown that bile acids act as signaling molecules that regulate various cellular processes. The bile acid-activated nuclear receptors are ligand-activated transcriptional factors that play critical roles in the regulation of bile acid, drug, and xenobiotic metabolism. In cholestasis, these bile acid-activated receptors regulate a network of genes involved in bile acid synthesis, conjugation, transport, and metabolism to alleviate bile acid-induced inflammation and injury. Additionally, bile acids are known to regulate cell growth and proliferation, and altered bile acid levels in diseased conditions have been implicated in liver injury/regeneration and tumorigenesis. We will cover the mechanisms that regulate bile acid homeostasis and detoxification during cholestasis, and the roles of bile acids in the initiation and regulation of hepatic inflammation, regeneration, and carcinogenesis.

Colesevelam improves oral but not intravenous glucose tolerance by a mechanism independent of insulin sensitivity and β-cell function

OBJECTIVE

To determine the mechanism by which the bile acid sequestrant colesevelam improves glycemic control.

RESEARCH DESIGN AND METHODS

We performed a frequently sampled intravenous glucose tolerance test (FSIGT) with minimal model analysis and a meal tolerance test (MTT) in 20 subjects with impaired fasting glucose (11 men, 9 women; mean age 60.7 ± 1.9 years, BMI 29.4 ± 0.9 kg/m(2)) in a single-blind study after 2 weeks of placebo treatment and 8 weeks of colesevelam 3.75 g daily. From these tests, insulin sensitivity, β-cell function, and glucose tolerance were determined, along with gastrointestinal peptide levels during the MTT.

RESULTS

Fasting plasma glucose and HbA(1c) decreased with colesevelam (from 5.9 ± 0.1 to 5.7 ± 0.1 mmol/L, P < 0.05, and from 5.86 ± 0.06 to 5.76 ± 0.06%, P = 0.01, respectively), but fasting insulin did not change. Colesevelam had no effect on any FSIGT measures. In contrast, the MTT incremental area under the curve (iAUC) for both glucose (from 249.3 ± 28.5 to 198.8 ± 23.6 mmol/L · min, P < 0.01) and insulin (from 20,130 [13,542-35,292] to 13,086 [9,804-21,138] pmol/L · min, P < 0.05) decreased with colesevelam. However, the ratio of iAUC insulin to iAUC glucose was not changed. iAUC for cholecystokinin (CCK) increased (from 43.2 [0-130.1] to 127.1 [47.2-295.2] pmol/L · min, P < 0.01), while iAUC for fibroblast growth factor 19 decreased (from 11,185 [1,346-17,661] to 2,093 [673-6,707] pg/mL · min, P < 0.01) with colesevelam. However, iAUC for glucagon, glucose-dependent insulinotropic peptide, and glucagon-like peptide 1 did not change.

CONCLUSIONS

Colesevelam improves oral but not intravenous glucose tolerance without changing insulin sensitivity, β-cell function, or incretins. This effect may be at least partially explained by the colesevelam-induced increase in CCK.

Feasibility and safety of emergency ERCP and small-caliber pancreatic stenting as a bridging procedure in patients with acute biliary pancreatitis but difficult sphincterotomy

BACKGROUND

The aims of the present study were: (1) to assess the feasibility and safety of emergency endoscopic retrograde cholangiopancreatography (ERCP) and pancreatic duct (PD) stenting with small-caliber stents as a bridging procedure in acute biliary pancreatitis (ABP) patients in whom biliary endoscopic sphincterotomy (EST) proved difficult, failed or was contraindicated, and (2) to compare the clinical outcome of those patients having emergency ERCP with and without pancreatic stent.

METHOD

Eighty-seven consecutive patients with ABP were referred for emergency ERCP. In 60 of these ABP patients, ERCP, EST, and stone extraction (if necessary) were performed without PD stenting. In the remaining 27 patients, small-caliber (3-5 F, 4 cm) pancreatic stent insertion was initially applied. All patients were hospitalized for medical therapy and were followed up.

RESULTS

The mean ages, the initial symptom-to-ERCP times, the Glasgow severity scores, and the peak amylase and CRP levels at initial presentation were not significantly different in the ERCP + EST with PD stent group versus the ERCP + EST without PD stent group. More importantly, the complication rate was significantly lower in the ERCP + EST with PD stent group versus the ERCP + EST without PD stent group (7.4% vs. 25%); while the mortality rates (0% vs. 6.7%) were comparable, reasonably low, and demonstrated no statistically significant differences.

CONCLUSIONS

Temporary PD stenting with small-caliber stents is a safe and effective procedure that may afford sufficient PD decompression to reverse the process of ABP and serve as a bridging procedure in severe ABP in patients with failed, complicated, or contraindicated biliary EST.

Gastrin, cholecystokinin and gastrointestinal tract functions in mammals. Nutr Res Rev. 2006;19:254-283. [PMID: 19079889 DOI: 10.1017/S0954422407334082]

The aim of the present review is to synthesise and summarise our recent knowledge on the involvement of cholecystokinin (CCK) and gastrin peptides and their receptors in the control of digestive functions and more generally their role in the field of nutrition in mammals. First, we examined the release of these peptides from the gut, focusing on their molecular forms, the factors regulating their release and the signalling pathways mediating their effects. Second, general physiological effects of CCK and gastrin peptides are described with regard to their specific receptors and the role of CCK on vagal mucosal afferent nerve activities. Local effects of CCK and gastrin in the gut are also reported, including gut development, gastrointestinal motility and control of pancreatic functions through vagal afferent pathways, including NO. Third, some examples of the intervention of the CCK and gastrin peptides are exposed in diseases, taking into account intervention of the classical receptor subtypes (CCK1 and CCK2 receptors) and their heterodimerisation as well as CCK-C receptor subtype. Finally, applications and future challenges are suggested in the nutritional field (performances) and in therapy with regards to the molecular forms or in relation with the type of receptor as well as new techniques to be utilised in detection or in therapy of disease. In conclusion, the present review underlines recent developments in this field: CCK and gastrin peptides and their receptors are the key factor of nutritional aspects; a better understanding of the mechanisms involved may increase the efficiency of the nutritional functions and the treatment of abnormalities under pathological conditions.

Coordinate regulation of gallbladder motor function in the gut-liver axis

Gallstones are one of the most common digestive diseases with an estimated prevalence of 10%-15% in adults living in the western world, where cholesterol-enriched gallstones represent 75%-80% of all gallstones. In cholesterol gallstone disease, the gallbladder becomes the target organ of a complex metabolic disease. Indeed, a fine coordinated hepatobiliary and gastrointestinal function, including gallbladder motility in the fasting and postprandial state, is of crucial importance to prevent crystallization and precipitation of excess cholesterol in gallbladder bile. Also, gallbladder itself plays a physiopathological role in biliary lipid absorption. Here, we present a comprehensive view on the regulation of gallbladder motor function by focusing on recent discoveries in animal and human studies, and we discuss the role of the gallbladder in the pathogenesis of gallstone formation.

Role of CCK and potential utility of CCK1 receptor antagonism in the treatment of pancreatitis induced by biliary tract obstruction. Br J Pharmacol. 2008;153:1650-1658. [PMID: 18297100 DOI: 10.1038/bjp.2008.44]

BACKGROUND AND PURPOSE

Cholecystokinin (CCK) stimulates the release of amylase and lipase from the normal pancreas. However, it is not clear to what extent this occurs in the early stages of pancreatitis induced by biliary tract obstruction in the rat and whether CCK initiates an inflammatory cascade in this condition.

EXPERIMENTAL APPROACH

Selective CCK1 receptor antagonists, JNJ-17156516 ((S)-(3-[5-(3,4-dichloro-phenyl)-1-(4-methoxy-phenyl)-1H-pyrazol-3-yl]-2-m-tolyl-propionic acid) and dexloxiglumide, were used to assess the response of plasma amylase and lipase to a CCK analogue, CCK8S, in normal rats and in rats with bile duct ligation.

KEY RESULTS

Both antagonists suppressed CCK8S-induced elevation of plasma amylase activity in normal rats. JNJ-17156516 was more potent than dexloxiglumide (ED(50)=8.2 vs >30 micromol kg(-1) p.o.) and produced a longer lived inhibition (6 vs 2 h). Plasma amylase and lipase activity were elevated in parallel to CCK plasma concentrations after bile duct ligation and both activities were suppressed in a dose-dependent manner by JNJ-17156516 and dexloxiglumide. JNJ-17156516 was approximately 5- to 10-fold more potent than dexloxiglumide. Infusion of CCK8S to naïve rats to achieve levels similar to those observed after bile duct ligation (20 pM) increased plasma amylase activity and activated nuclear factor-kappaB in the pancreas. These effects were prevented by pretreatment with JNJ-17156516.

CONCLUSIONS AND IMPLICATIONS

The elevation of plasma amylase and lipase activity in the early stages of obstruction-induced pancreatitis is largely driven by elevation of plasma CCK concentration and activation of CCK1 receptors. These data show that CCK is an initiating factor in acute pancreatitis in the rat.

Why does pancreatic overstimulation cause pancreatitis?

Many animal models are available to investigate the pathogenesis of pancreatitis, an inflammatory disorder of the pancreas. However, the secretagogue hyperstimulation model of pancreatitis is the most commonly used. Animals infused with high doses of cholecystokinin (CCK) exhibit hyperamylasemia, pancreatic edema, and acinar cell injury, which closely mimic pancreatitis in humans. Intra-acinar zymogen activation is an essential early event in the pathogenesis of secretagogue-induced pancreatitis. Early in the course of pancreatitis, lysosomal hydrolases colocalize with digestive zymogens and activate them. These activated zymogens then cause acinar cell injury and necrosis, a characteristic of pancreatitis. Besides being the site of initiation of injury in pancreatitis, acinar cells also synthesize and release cytokines and chemokines very early in the course of pancreatitis, which then attract and activate inflammatory cells and initiate the disease's systemic phase.

Role of CCK/gastrin receptors in gastrointestinal/metabolic diseases and results of human studies using gastrin/CCK receptor agonists/antagonists in these diseases

In this paper, the established and possible roles of CCK1 and CCK2 receptors in gastrointestinal (GI) and metabolic diseases are reviewed and available results from human agonist/antagonist studies are discussed. While there is evidence for the involvement of CCK1R in numerous diseases including pancreatic disorders, motility disorders, tumor growth, regulation of satiety and a number of CCK-deficient states, the role of CCK1R in these conditions is not clearly defined. There are encouraging data from several clinical studies of CCK1R antagonists in some of these conditions, but their role as therapeutic agents remains unclear. The role of CCK2R in physiological (atrophic gastritis, pernicious anemia) and pathological (Zollinger-Ellison syndrome) hypergastrinemic states, its effects on the gastric mucosa (ECL cell hyperplasia, carcinoids, parietal cell mass) and its role in acid-peptic disorders are clearly defined. Furthermore, recent studies point to a possible role for CCK2R in a number of GI malignancies. Current data from human studies of CCK2R antagonists are presented and their potential role in the treatment of these conditions reviewed. Furthermore, the role of CCK2 receptors as targets for medical imaging is discussed.

Gall stones and chronic pancreatitis: the black box in between

The relation between gall stones and chronic pancreatitis is uncertain; there are differing opinions on this issue. Firstly, gall stones are the most common reason for acute pancreatitis, but it cannot cause chronic pancreatitis. Secondly, a connection between gall stones and chronic inflammation of the pancreas might exist. Numerous studies or investigations have shown that changes associated with chronic pancreatitis are common in gallstone patients. Although it seems that gall stones might be a cause of chronic pancreatitis according to these findings, clinical and experimental studies are still needed for confirmation, and further studies are required to determine the mechanisms involved.

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, lovastatin (statin) ameliorates CCK-induced acute pancreatitis in rats

Statin, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has an anti-inflammatory effect. The aim of this study was to investigate the effect of Lovastatin (statin) on the cholecystokinin-octapeptide (CCK)-induced acute pancreatitis in rats. In statin treated group, the pancreas weight/body weight (pw/bw) ratio in CCK-induced acute pancreatitis was significantly lower than DMSO-treated group. Statin also increased the pancreatic level of HSP 60. Additionally, the secretions of IL-1beta, TNF-alpha and IL-6 and the lipase levels were decreased in statin treated group. These results suggest that statin may play an important role in mitigating the progression of the inflammatory reactions during acute pancreatitis.

The role of the pancreatic renin-angiotensin system in acinar digestive enzyme secretion and in acute pancreatitis

The pancreas contains a local renin-angiotensin system (RAS), which is subject to activation by experimental pancreatitis. In the exocrine pancreas, angiotensin II receptor subtypes AT1 and AT2 have been localized in the pancreatic ducts, blood vessels and acinar cells. We hypothesize that local RAS activities may have a potential role in regulating pancreatic acinar digestive enzyme secretion. The present study was designed to elucidate firstly the existence of RAS components in pancreatic acinar cells and their regulation by acute pancreatitis. Secondly, the differential roles of AT1 and AT2 receptors in controlling digestive enzyme secretion from dispersed functional pancreatic acini were also investigated. The mRNA levels of RAS components were assessed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Acinar secretions were assayed by the measurement of alpha-amylase and lipase activities. Induction of acute pancreatitis was achieved by hyperstimulation of two intraperitoneal (i.p.) injections of cerulein (50 microg/kg/h). Results from RT-PCR showed that the mRNA levels of the major RAS components (angiotensinogen, AT1 and AT2 receptors) were expressed in isolated rat pancreatic acinar cells, and they were upregulated during pancreatitis. Exogenous addition of angiotensin II could stimulate a dose-dependent release of digestive enzymes from the acinar cells. Administration of the selective AT1 receptor antagonist losartan significantly inhibited the acinar digestion enzyme secretion in both normal and pancreatitis-induced acini. However, a specific AT2 receptor blocker PD123319 did not exhibit such a suppressive effect. These data indicate the existence of an acinar RAS in the pancreas of potential importance in the physiological regulation of digestive enzyme secretion. The differential actions of AT1 and AT2 receptors and their upregulation may have clinical relevance to the pathogenesis and management of acute pancreatitis.

Smooth muscle function and dysfunction in gallbladder disease

The gallbladder epithelium and smooth muscle layer are exposed to concentrated biliary solutes, including cholesterol and potentially toxic hydrophobic bile salts, which are able to influence muscle contraction. Physiologically, gallbladder tone is regulated by spontaneous muscle activity, hormones, and neurotransmitters released into the muscle from intrinsic neurons and extrinsic sympathetic nerves. Methods to explore gallbladder smooth muscle function in vitro include cholecystokinin (CCK) receptor-binding studies and contractility studies. In human and animal models, studies have focused on cellular and molecular events in health and disease, and in vitro findings mirror in vivo events. The interplay between contraction and relaxation of the gallbladder muscularis leads in vivo to appropriate gallbladder emptying and refilling during fasting and postprandially. Defective smooth muscle contractility and/or relaxation are found in cholesterol stone-containing gallbladders, featuring a type of gallbladder leiomyopathy; defects of CCKA receptors and signal transduction may coexist with abnormal responses to oxidative stress and inflammatory mediators. Abnormal smooth musculature contractility, impaired gallbladder motility, and increased stasis are key factors in the pathogenesis of cholesterol gallstones.

Acute pancreatitis possible initial triggering mechanism and prophylaxis

BACKGROUND AND AIMS

Biliary acute pancreatitis or postendoscopic iatrogenia acute pancreatitis (AP) are likely triggered by autonomous arc reflexes (AAR) initiated in the peri-Vaterian duodenum (PV-D). The bilio-pancreatic duct outlet exclusion closed duodenal loops (BPDOE-CDL) model mimics these circumstances. Our aim was to validate this model and evaluate the role of AAR via their interruption with local anesthetics.

METHODS

Severe AP was induced in Wistar rats with the BPDOE-CDL model: extra-pancreatic insult was provoked in the PV-D by distension with 8% sodium taurocholate and methylene blue for 45 min to show the absence of duodenum pancreatic reflux. Treated experimental groups received a 2% lidocaine chlorhydrate gel instilled into the PV-D prior to triggering the AP, or before and after at the celiac-ganglia complex, or at both sites. The degree of severity was evaluated using biochemical and histopathological analysis.

RESULTS

Induction of AP by BPDOE- CDL was severe, with acinar and fat necrosis and hemorrhage with a greater foci number in the cephalic segment. Groups pretreated with local anesthetic developed mild or moderate AP characterized by edema and leukocyte infiltrate. Serum amylase, lipase and CRP were significantly reduced in all treated groups. Other blood metabolites and pancreatic myeloperoxidase, amylase and lipase, were significantly decreased.

CONCLUSION

The BPDOE-CDL model was validated, emphasizing the importance of AAR as extrapancreatic initiators of AP. The interruption of AAR by lidocaine chlorhydrate prevented excessive pancreatic inflammation and diminished hemorrhage and necrosis and may prove a useful prophylactic procedure to prevent postendoscopic severe AP.

Stability and bioaccessibility of isoflavones from soy bread during in vitro digestion

The impact of simulated digestion on the stability and bioaccessibility of isoflavonoids from soy bread was examined using simulated oral, gastric, and small intestinal digestion. The aqueous (bioaccessible) fraction was isolated from digesta by centrifugation, and samples were analyzed by high-performance liquid chromatography (HPLC). Isoflavonoids were stable during simulated digestion. Partitioning of aglycones, acetylgenistin, and malonylgenistin into the aqueous fraction was significantly (P < 0.01) affected by the concentration of bile present during small intestinal digestion. Omission of bile resulted in nondetectable genistein and <40% of total daidzein, glycitein, and acetylgenistin in the aqueous fraction of digesta. Partitioning of these compounds into the aqueous fraction was increased by physiological concentrations of bile extract. These results suggest that micellarization is required for optimal bioaccessibility of isoflavonoid aglycones. We propose that the bioavailability of isoflavones from foods containing fat and protein may exceed that of supplements due to enhanced bile secretion.

Effects of early decompression and cholecystokinin inhibition in rats with acute pancreatitis induced by bile-pancreatic-duct obstruction

Biologic data related to pancreatic regeneration and acinar-cell homeostasis after ductal decompression would be useful in clinical settings to elucidate the time at which obstructions in human biliary acute pancreatitis (AP) should be removed. Our aim was to evaluate the outcome of AP after early removal of bile-pancreatic-duct obstruction (BPDO) and to ascertain whether cholecystokinin (CCK) blockade accelerates recovery from the disease. We conducted analysis of apoptosis and cell cycle, as well as measurements of enzyme and calcium load, in acinar cells using flow cytometry to ascertain the capability of the pancreas to regain its function after AP. Male Wistar rats were subjected to AP by means of BPDO for 6 hours and 24 hours. In other groups, the BPDO was opened 24 hours after induction; 3 days and 7 days later they were killed. Half of the rats in which the BPDO was opened were administered L364,718, a CCK-receptor antagonist (0.1 mg/kg/12 hours), 30 minutes before the induction of BPDO. Plasma amylase activity, hematocrit, and pancreatic weight returned to control values after BPDO opening. The highest degree of oxidative stress was found in the pancreases of rats subjected to BPDO for 6 hours, as indicated by the decrease in pancreatic glutathione content, but it was not restored 7 days after BPDO opening. Cell-cycle distribution, as measured with propidium iodide DNA staining, showed increases in the proportion of acinar cells in S-phase from 3 days after BPDO opening in L364,718-treated and nontreated rats. Annexin V-fluorescein isothiocyanate labeling revealed deletion of acinar cells by way of apoptosis 3 days after BPDO opening. However, it may be compensated 7 days after BPDO opening because regardless of whether rats were treated with L364,718, significant increases in synthesis and mitosis were detected. Accumulation of digestive enzymes and calcium in acinar cells was found during BPDO, but this appeared to have normalized 3 days after BPDO opening and onward in both L364,718-treated and nontreated rats. In conclusion, early removal of obstruction allowed rapid cell proliferation and prevented the progression of severe alterations within acinar cells induced by BPDO. CCK blockade does not accelerate pancreatic recovery after BPDO opening.

Involvement of cholecystokinin/gastrin-related peptides and their receptors in clinical gastrointestinal disorders

In this paper the possible roles of cholecystokinin (CCK), gastrin, or gastrin-related peptides and their receptors in human gastrointestinal diseases are reviewed. For CCK/CCK(A) receptors (CCK(A)-R), the evidence for their proposed involvement in diseases caused by impaired CCK release or CCK(A)-R mutations, pancreatic disorders (acute/chronic pancreatitis), gastrointestinal motility disorders (gallbladder disease, irritable bowel syndrome), pancreatic tumor growth and satiety disorders, is briefly reviewed. The evidence that has established the involvement of gastrin/CCK(B)-R in mediating the action of hypergastrinaemic disorders, mediating hypergastrinaemic effects on the gastric mucosa (ECL hyperplasia, carcinoids, parietal cell mass), and acid-peptic diseases, is reviewed. The evidence for their possible involvement in mediating growth of gastric and pancreatic tumours and possible involvement of gastrin-related peptides in colon cancers, is reviewed briefly.

Low enzyme content in the pancreas does not reduce the severity of acute pancreatitis induced by bile-pancreatic duct obstruction

Enzyme load in pancreas has been considered a risk factor in the development of acute pancreatitis. In order to confirm this hypothesis our aim was to analyze the development and evolution of acute pancreatitis (AP) induced by bile-pancreatic duct obstruction (BPDO) after reducing the pancreatic enzyme content. L-364,718 - a potent CCK-receptor antagonist - was administered (0.1 mg/kg/day) for 7 days before inducing AP by BPDO. The course of AP was evaluated at different times from 1.5-48 h after BPDO. Amylase and trypsinogen contents and cytosolic calcium levels were measured by flow cytometry using specific antisera against pancreatic enzymes labelled with isothiocyanate of fluorescein and Fluo 3, respectively. The severity of the disease at the different stages was evaluated by measurements of amylase activity in ascites and plasma, percentage of pancreatic fluid and haematocrit. Electron microscopy study of the pancreas showed an increased number of zymogen granules spread through the acinar cells of control rats treated with L-364,718 for 7 days, however, total enzyme content in individual acinar cells was significantly (p < 0.01) diminished. AP significantly increased intracellular amylase and trypsinogen load from 3-12 h after BPDO, and prior L-364,718 treatment enhanced the blockade of enzyme secretion. As a result, acinar enzyme content was significantly increased from earlier stages (1.5 h after BPDO). In parallel, increased cytosolic calcium levels observed up to 24 h after BPDO appeared earlier in L-364,718-treated rats than in those not treated. The severity of AP seems to have been higher in rats previously treated with the CCK-receptor antagonist as indicated by the significantly higher pancreatic fluid and amylase activity in ascites and plasma observed at different times after BPDO. Our results indicate that there is no correlation between the severity of pancreatitis and the amount of enzymes accumulated in the pancreas before the disease is induced.

Impaired pancreatic secretion in severely malnourished patients is a consequence of primary pancreatic dysfunction

Severe undernutrition has been associated with reduced secretions of gastric acid and pancreatic enzymes. This may be the result of an impaired gut mucosal response to food and primary gastric parietal and pancreatic acinar cell secretory dysfunction as a consequence of the poor nutritional state. To investigate the relative contributions of these factors, severely undernourished patients underwent enteral-meal-stimulated (ES; n = 7) or intravenous hormone (pentagastrin and cholecystokinin-8)-stimulated (HS; n = 12) gastric acid and pancreatic enzyme secretion before and after a period of nutritional support. Results were evaluated in comparison with normal healthy control subjects (ES = 7, HS = 10). In the control subjects, enteral-meal and cholecystokinin-8 stimulation resulted in similar outputs of the pancreatic enzymes amylase (2213 versus 2305 U/h), lipase (84.93 versus 118.6 U/h), and trypsin (498.9 versus 341.4 U/h), whereas acid output was significantly lower in the ES group (10.90 versus 25.53 mEq/h; P < 0.01). Compared with controls, malnourished groups had significantly reduced secretions of amylase (ES = 870.1 U/h, HS = 686.5 U/h; P < 0.02), lipase (ES = 30.68 U/h, HS = 25.96 U/h; P < 0.02), and trypsin (ES = 175.6 U/h, HS = 109.3 U/h; P < 0.01). The response to enteral-meal or CCK-8 stimulation was comparable. Gastric acid was similarly reduced in the undernourished patients (ES = 4.39 mEq/h, HS = 5.04 mEq/h; P < 0.01). After refeeding, secretion of amylase (ES = 2351 U/h, HS = 2228 U/h) and lipase (ES = 58.83 U/h, HS = 84.91 U/h) improved to levels not significantly different from controls, whereas trypsin (ES = 226.4 U/h, HS = 213.1 U/h; P < 0.03) and acid secretion (ES = 3.52 mEq/h, HS = 11.85 mEq/h; P < 0.01) remained significantly impaired. Severe undernutrition was associated with primary gastric parietal and pancreatic acinar cell dysfunction, which, at least in the case of pancreatic enzymes, appeared to be the determining factor controlling secretion in these patients.