Increase In Plasma CCK Levels Research Articles

Novel regulation of kidney function by gastrointestinal hormones

The control of whole-body energy metabolism involves intricate crosstalk between multiple organ systems including the gut and the brain that play well-recognized roles in this process. However, the important contributions and mechanisms by other organs are poorly understood. Errors in metabolic regulation can lead to human metabolic diseases including diabetes and obesity that affect 75% of the population and can lead to significant comorbidities. Improving our mechanistic understanding of multi-organ metabolic crosstalk in health and disease is essential for developing highly effcient and new therapeutic approaches. Macula densa (MD) cells in the kidney are chief regulators of renal blood flow and tissue remodeling. We hypothesized that the kidney is a major player in body metabolism via a new mechanism of gut-kidney crosstalk that involves the gut hormones gastrin and cholecystokinine (CCK) activating intrarenal, MD-specific mechanisms to increase blood flow and filtration, progenitor cells and tissue growth factors. High-resolution MD bulk and single-cell transcriptome analysis was performed from freshly isolated, enriched MD cells using MD-GFP mouse kidneys. Single cell MD Ca2+ signaling was analyzed in vivo using intravital multiphoton microscopy (MPM) of Sox2-GT mice that express the ratiometric Ca2+ reporter GCaMP6f/tdTomato in all renal cells. The altered expression of MD specific markers in response to gastrin/CCK8 stimuli was studied using western blot and the novel MDgeo immortalized cell line cultured in vitro. RNA sequencing and transcriptome analysis identified the gastrin/CCK receptor Cckbr as one of the highest expressed genes in MD versus control kidney cells. Intravital multiphoton imaging of Sox2-GCaMP6 reporter mouse kidneys revealed robust and entirely MD cell-specific calcium signaling in response to systemic gastrin/CCK injection. Using the novel MDgeo immortalized cell line cultured in vitro, CCK8 treatment led to 3-fold increases in MD cell synthesis of Prostaglandin E2 (PGE2)-generating COX2 and CCN1 that are established mediators of MD-induced glomerular hyperfiltration and tissue remodeling, respectively. Chronic treatment of Ren1d-Confetti mice with Darunavir, an HIV protease inhibitor significantly increased plasma CCK levels, Ren+ mesenchymal progenitor cell number and clonality, renal cell proliferation and tissue hypertrophy. This study uncovered new regulatory mechanisms of systemic metabolism especially the role of MD cells in the kidney. Repurposing the commonly used HIV drug Darunavir for kidney and metabolic diseases may provide therapeutic benefit for millions of patients worldwide. DK064234, DK123564, DK135290. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PS-BPB08-3: OFF-TARGET EFFECTS OF SLEEVE GASTRECTOMY ON BLOOD PRESSURE INDEPENDENT OF BODY WEIGHT REDUCTION IN DIET-INDUCED OBESITY RATS: ROLE OF CHOLECYSTOKININ

Objective: Sleeve gastrectomy (SG) is currently the most selected surgical bariatric procedure for weight loss by shrinking the stomach. SG has been reported to improve glucose metabolism by altering gastrointestinal hormones, but the details of why blood pressure improves are not known. The purpose of this study is to elucidate the mechanism of why SG lowers blood pressure in diet induced obese rats. Design and method: Male Sprague Dawley (SD) rats were subjected to surgical [sham operation (SO) or SG] and dietary interventions [fed a normal diet or high fat diet (HFD) ad libitum or pair fed (PF)]. Diet induced obese rats fed 60% HFD for 12 weeks. Systolic blood pressure (SBP), urinary sodium excretion, and gastrointestinal hormones and renin angiotensin system in renal tissue were examined 4 weeks after surgery. In addition, cholecystokinin (CCK) was administered intraperitoneally to SD rats and evaluated for changes in blood pressure and renal tissue renin angiotensin system. Results: Both SG and PF treatments reduced body weight compared with SO. SG exhibited a reduction in SBP compared with PF, which was associated with a reduction in renal renin (536 ± 48.5 U/g kidney and 1385 ± 55.1 U/g kidney, p < 0.01), angiotensin II (Ang II) (48.2 ± 5.8 ng/g kidney and 258.7 ± 16.9 ng/g kidney, p < 0.01), and catechol O methyltransferase (COMT) levels (0.68 ± 0.05 /αtub and 1.34 ± 0.13/αtub, p < 0.01). SG increased plasma CCK levels compared with PF (p < 0.01 for each), whereas GLP1 and PYY were not changed in fasting. SD rats after CCK administration showed decreased SBP (107.7 ± 2.3 mmHg and 118.0 ± 1.8 mmHg, p < 0.01), COMT (0.49 ± 0.04 /GAPDH and 1.11 ± 0.19/GAPDH, p = 0.02), renin (967 ± 71.3 U/g kidney and 1394 ± 90.8 U/g kidney, p < 0.01), and Ang II (598 ± 76.7 ng/g kidney and 874 ± 86.6 ng/g kidney, p = 0.02) in the kidney compared to controls. Conclusions: The SG reduced SBP, at least in part, through suppression of the sympathetic nerve action by elevation of CCK which is followed by suppression of the intrarenal renin angiotensin system. Conclusions: CCK may have a blood pressure lowering effect, and further research is needed to determine whether CCK can be used as a new antihypertensive agent in the future.

L-Glutamate stimulates cholecystokinin secretion via the T1R1/T1R3 mediated PLC/TRPM5 transduction pathway.

It is known that cholecystokinin (CCK) plays an essential role in reducing food intake and driving weight loss. Previous studies demonstrated that amino acids were capable of triggering CCK release through G protein-coupled receptors, but the sensing mechanism remains obscure, especially the intracellular signaling pathway. l-Glu, rather than its d-isomer, robustly stimulated CCK secretion in a porcine duodenal model, and the secretory response was augmented by incubation with the allosteric ligand of T1R1, while T1R3 antagonist attenuated it. Upon inhibiting phospholipase C (PLC) or transient receptor potential M5 (TRPM5) activity, l-Glu failed to increase CCK release. Oral administration of monosodium glutamate in rats also suppressed food intake and increased plasma CCK levels, accompanied by elevated expression of T1R1, PLCβ2 and TRPM5 in the duodenum. These data demonstrated that l-Glu stimulated CCK secretion through the activation of T1R1/T1R3 in a PLC/TRPM5-dependent manner. © 2020 Society of Chemical Industry.

Exploring the role of neurogenic pathway-linked cholecystokinin release in remote preconditioning-induced cardioprotection.

Purpose:The current study explored the involvement of neurogenic pathway-linked cholecystokinin (CCK) release in RIP-induced cardioprotection in rats.Methods:Male Wistar rats were subjected to four cycles of alternate episodes of ischemia and reperfusion (five min each) to induce RIP. Thereafter, the hearts were subjected to global ischemia and reperfusion ex vivo. The myocardial damage was assessed by quantifying the levels of heartspecific biochemicals i.e. LDH-1, CK-MB and cTnT. Apoptotic cell injury was assessed by measuring the levels of caspase-3 and Bcl-2. The levels of CCK were measured in the plasma following RIP.Results:Exposure to RIP significantly increased the plasma levels of CCK and attenuated IR-induced myocardial injury. Administration of CCK antagonist, proglumide significantly attenuated RIP-induced cardioprotection. Administration of hexamethonium, a ganglion blocker, abolished RIP-induced increase in plasma CCK levels and cardioprotective effects. Exogenous delivery of CCK-8 restored the effects of RIP in hexamethonium treated animals.Conclusion:RIP activates the neurogenic pathway that may increase the plasma levels of CCK, which may act on the heart-localized CCK receptors to produce cardioprotection against I/R injury.

Cholecystokinin enhances visceral pain-related affective memory via vagal afferent pathway in rats

BackgroundPain contains both sensory and affective dimensions. Using a rodent visceral pain assay that combines the colorectal distension (CRD) model with the conditioned place avoidance (CPA) paradigms, we measured a learned behavior that directly reflects the affective component of visceral pain, and showed that perigenual anterior cingulate cortex (pACC) activation is critical for memory processing involved in long-term visceral affective state and prediction of aversive stimuli by contextual cue. Progress has been made and suggested that activation of vagal afferents plays a role in the behavioral control nociception and memory storage processes.In human patients, electrical vagus nerve stimulation enhanced retention of verbal learning performance. Cholecystokinin-octapeptide (CCK), which is a gastrointestinal hormone released during feeding, has been shown to enhance memory retention. Mice access to food immediately after training session enhanced memory retention. It has been well demonstrated that CCK acting on vagal afferent fibers mediates various physiological functions. We hypothesize that CCK activation of vagal afferent enhances visceral pain-related affective memory.ResultsIn the presented study, infusion of CCK-8 at physiological concentration combining with conditional training significantly increased the CRD-induced CPA scores, and enhanced the pain affective memory retention. In contrast, CCK had no effect on CPA induced by non-nociceptive aversive stimulus (U69,593). The physiological implications were further strengthened by the similar effects observed in the rats with duodenal infusion of 5% peptone, which has been shown to induce increases in plasma CCK levels. CCK-8 receptor antagonist CR-1409 or perivagal application of capsaicin abolished the effect of CCK on aversive visceral pain memory, which was consistent with the notion that vagal afferent modulates affective aspects of visceral pain. CCK does not change the nociceptive response (visceral pain sensitivity) and anterior cingulate cortex neuronal responses to CRD.ConclusionCCK activating vagal afferent C fibers enhances memory consolidation and retention involved in long-term visceral negative affective state. Thus, in a number of gastrointestinal disorders, such as irritable bowel syndrome, nutrient content may contribute to painful visceral perception by enhancing visceral aversive memory via acts on vagal afferent pathway.

The G‐protein coupled receptor GPR40 mediates long chain fatty acid induced cholecystokinin secretion

INTRODUCTIONLong chain fatty acid receptors (LCFARs) have been implicated in the chemosensation of dietary fats, however direct studies on native “I” cells have been difficult due to their rare and isolated distribution. The objective of this study was to determine whether dietary fat‐induced cholecystokinin (CCK) secretion is directly mediated by GPR40 expressed on I cells isolated from duodenal mucosa of CCK‐eGFP BAC transgenic mice by fluorescence activated cell sorting.METHODSIsolated CCK‐eGFP cells were evaluated for LCFAR gene expression by Taqman RT‐PCR. GPR40−/− mice were crossed with CCK‐eGFP mice to evaluate the functional relevance of GPR40 on linolenic acid‐stimulated CCK secretion, measured by radioimmunoassay, in isolated CCK‐eGFP cells. Also, plasma CCK secretion in response to olive oil gavage was compared between GPR40+/+ and GPR40−/− mice.RESULTSIsolated CCK‐eGFP cells display a 100‐fold greater expression of GPR40 compared to non‐eGFP cells. In vitro, linolenic acid increased CCK secretion by 53% in GPR40+/+ CCK‐eGFP cells compared to no significant secretion in GPR40−/− CCK‐eGFP cells. In vivo, an olive oil gavage significantly increased plasma CCK levels by 5.7‐fold in GPR40+/+ mice compared to an increase of 3.1‐fold in GPR40−/− mice.CONCLUSIONThis study is the first to demonstrate a direct chemosensory role of GPR40 in dietary fat induced CCK secretion.

Free fatty acids induce cholecystokinin secretion through GPR120

The ingestion of fat induces secretion of the gut peptide hormone cholecystokinin (CCK); however, the mechanism responsible for lipid-induced CCK release remains unknown. Recently, a group of free fatty acid (FFA) receptors, which includes the long-chain FFA receptors GPR120 and GPR40, has been identified. In this study, we examined whether these FFA receptors mediate lipid-induced CCK release in the mouse. We first observed that intra-gastric administration of long-chain FFAs increased plasma CCK levels. Using mouse enteroendocrine STC-1 cells as a model system, we further studied the mechanism of this FFA-induced CCK secretion. Long-chain FFAs promoted CCK secretion from STC-1 cells, which was abolished either by removal of extracellular Ca2+ or by the L-type Ca2+ channel blocker nicardipine. Furthermore, this FFA-induced CCK secretion was specifically inhibited by transfection of GPR120-specific, but not GPR40-specific, short hairpin RNA. These results indicate that long-chain FFAs induce CCK secretion through GPR120-coupled Ca2+ signaling.

Differential mechanism and site of action of CCK on the pancreatic secretion and growth in rats.

Recent studies demonstrated that cholecystokinin (CCK) at physiological levels stimulates pancreatic enzyme secretion via a capsaicin-sensitive afferent vagal pathway. This study examined whether chemical ablation of afferent vagal fibers influences pancreatic growth and secretion in rats. Bilateral subdiaphragmatic vagal trunks were exposed, and capsaicin solution was applied. Pancreatic wet weight and pancreatic secretion and growth in response to endogenous and exogenous CCK were examined 7 days after capsaicin treatment. Perivagal application of capsaicin increased plasma CCK levels and significantly increased pancreatic wet weight compared with those in the control rats. Oral administration of CCK-1 receptor antagonist loxiglumide prevented the increase in pancreatic wet weight after capsaicin treatment. In addition, continuous intraduodenal infusion of trypsin prevented the increase in plasma CCK levels and pancreatic wet weight after capsaicin treatment. There were no significant differences in the expression levels of CCK-1 receptor mRNA and protein in the pancreas in capsaicin-treated and control rats. Intraduodenal administration of camostat or intravenous infusion of CCK-8 stimulated pancreatic secretion in control rats but not in capsaicin-treated rats. In contrast, repeated oral administrations of camostat or intraperitoneal injections of CCK-8 significantly increased pancreatic wet weight in both capsaicin-treated and control rats. Present results suggest that perivagal application of capsaicin stimulates pancreatic growth via an increase in endogenous CCK and that exogenous and endogenous CCK stimulate pancreatic growth not via vagal afferent fibers but directly in rats.

Elevated plasma cholecystokinin and appetitive ratings after consumption of a liquid meal in humans

Objective This study had two objectives. The first was to evaluate the possibility that, in a previous study, a soup preload augmented the reduction of food intake in a test meal induced by an exogenous infusion of cholecystokinin (CCK) because the soup also endogenously released CCK. The second was to compare CCK release by soup between men and women to determine whether the increased satiating effectiveness of soup in women as opposed to men could have been partly attributable to differences in CCK release. Methods By using a bioassay that measures all of its known isoforms, we determined plasma CCK levels at baseline and at several times postprandially in eight healthy, non-obese men and women (four of each sex). Each subject ingested 800 g of tomato soup, which was followed 30 min later by 300 g of a yogurt shake. Appetitive ratings were also collected and related to CCK levels. Results Ingestion of tomato soup significantly increased plasma CCK levels by 3.81 pmol/L (± 1.21 standard error, P = 0.016) over baseline within 30 min in all subjects combined. When CCK concentrations at 5 min after soup and 5 min after yogurt were averaged, the women’s mean averaged concentration was 5.58 pmol/L (± 1.994, t = 2.80, P = 0.0073) higher than the men’s. The elevated levels persisted but did not rise further upon consumption of the yogurt shake. Hunger ratings declined and fullness ratings increased after eating, although patterns of ratings did not match exactly patterns of CCK release. Conclusions A large quantity of tomato soup stimulates significant CCK release; therefore, some of the satiating effects of soup preloads could have been mediated by an elevation in endogenous CCK.

Modulation of exocrine pancreatic secretion by leptin through CCK 1-receptors and afferent vagal fibres in the rat

In this report, we determined whether leptin could modify the exocrine pancreatic secretion of anaesthetized rats in vivo. Intravenous injection of recombinant murine leptin resulted in a time- and dose-dependent stimulation of exocrine pancreatic secretion, maximally observed with 30 nmol/kg of leptin. This stimulation of pancreatic water, bicarbonate, and protein output was abolished by atropine, hexamethonium, L364,718 ([3 S(−)- N-(1,3-dihydro-1-methyl-2-oxo-5-phenyl-1 H-1,4-benzodiazepine]), a cholecystokinin CCK 1 receptor antagonist or perivagal capsaicin pretreatment, but unaffected by the CCK 2 receptor antagonist L365,260 ([3 R(+)- N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1 H-1,4-benzodiazepin-3yl)- N′-(3-methylphenyl)urea]). In addition, the physiological dose of 3 nmol/kg leptin, ineffective per se, potentiated the secretory effect of 45 pmol/kg of cholecystokinin octapeptide (CCK-8) on exocrine pancreatic secretion. Furthermore, intraperitoneal leptin induced a rapid increase in plasma CCK levels in vivo in the rat. In conclusion, exogenous leptin can modulate exocrine pancreatic secretion through mechanisms involving CCK 1 receptors and capsaicin-sensitive afferent fibres in the rat. Whether this may have a physiological relevance in the postprandial regulation of exocrine pancreatic secretion and thus in nutrient digestion will require further investigations.

Factors Predicting Nutritional Derangements in Patients with Obstructive Jaundice: Multivariate Analysis

Patients with obstructive jaundice (OJ) that requires surgery often have malnutrition associated with increased perioperative morbidity. This study investigated the factors influencing nutritional derangements in these patients. A series of 46 OJ patients were investigated prospectively (28 malignant tumors, 18 benign obstructions). A nutritional risk index of < 83.5 was used to define protein-calorie malnutrition. Liver function, cholecystokinin (CCK), tumor necrosis factor-alpha (TNFalpha), and endotoxin levels were determined. A multivariate analysis was performed, and an obstructive jaundice malnutrition index (OJMI) was obtained. Altogether, 22 (48%) OJ patients had malnutrition (33% with benign obstructions, 57% with malignant disease). Malnourished patients had higher serum bilirubin levels (258 +/- 120 vs. 154 +/- 62 mmol/L; p = 0.005), longer duration of jaundice (16 +/- 9 vs. 9 +/- 5 days; p = 0.03), and higher plasma levels of CCK (4.0 +/- 1.3 vs. 1.7 +/- 1.0 pmol/L; p = 0.005), alanine aminotransferase (ALT) (226 +/- 209 vs. 187 +/- 161 UI/L; p = 0.01), endotoxin (15 +/- 10 vs. 6.5 +/- 7.0 EU/L; p = 0.007), and TNFalpha (69 +/- 82 vs. 23 +/- 15 pg/ml; p = 0.008) than those without malnutrition. However, only serum bilirubin, CCK, ALT, and patient age were predictors for malnutrition by multivariate analysis. Malnutrition might be expected (95% confidence interval) in patients older than 68 years with increased bilirubin (> 290 mmol/L) and ALT (> 210 UI/L) levels that corresponded with an OJMI > 55. It was concluded that nutritional alterations in patients with obstructive jaundice were determined by the intensity of the biliary obstruction correlated with increased plasma CCK levels as well as with liver dysfunction and patient age.

Persistent messles virus (MV) infection of lleal lymphoid tissue in children with lise-colonic lymphoid nodular hyperplasia, entero-colitis and developmental disorder

<h2>Abstract</h2> <b>Background & Aims:</b> It is unclear whether fat digestion is required for the induction of gastrointestinal sensations and whether different fats have different effects. We investigated the effect of fat digestion and of medium-chain triglycerides (MCTs; C < 12) and long-chain triglycerides (LCTs; C > 16) on gastrointestinal sensations. <b>Methods:</b> In a double-blind study, 15 healthy subjects were studied on 5 occasions during which LCT or MCT emulsions (2 kcal/min), with or without 120 mg tetrahydrolipstatin (THL, lipase inhibitor), or sucrose polyester (SPE, nondigestible fat) were infused intraduodenally in randomized order. After 30 minutes, the proximal stomach was distended in 1 mm Hg steps/min. Intensity of gastrointestinal sensations (on a 0–10 visual analog scale), plasma cholecystokinin (CCK) levels, and gastric volumes were assessed throughout. <b>Results:</b> LCT and MCT increased gastric volume at baseline pressure compared with SPE, and LCT more than MCT. THL entirely abolished this effect (volumes [mL]: LCT, 213 ± 19; LCT-THL, 39 ± 3; MCT, 155 ± 12; MCT-THL, 43 ± 5; SPE, 44 ± 5). Only LCT increased plasma CCK levels (pmol/L per 30 minutes: LCT, 21 ± 2; LCT-THL, 9 ± 1; MCT, 9 ± 1; MCT-THL, 11 ± 1; SPE, 9 ± 1). During distentions, intragastric volumes were greater during infusion of LCT and MCT than during the respective THL conditions or SPE, but plasma CCK levels did not change. The intensity of sensations increased (hunger decreased) more with LCT than with MCT. During infusion of THL or SPE, the effects were smaller than during LCT or MCT. <b>Conclusions:</b> Fat digestion is required for the modulation of gastrointestinal sensations during gastric distention. The effects of fat depend on the fatty acid chain length and are not entirely explained by release of CCK. GASTROENTEROLOGY 2001;120:1100-1107

Fat digestion modulates gastrointestinal sensations induced by gastric distention and duodenal lipid in humans

It is unclear whether fat digestion is required for the induction of gastrointestinal sensations and whether different fats have different effects. We investigated the effect of fat digestion and of medium-chain triglycerides (MCTs; C < 12) and long-chain triglycerides (LCTs; C > 16) on gastrointestinal sensations. In a double-blind study, 15 healthy subjects were studied on 5 occasions during which LCT or MCT emulsions (2 kcal/min), with or without 120 mg tetrahydrolipstatin (THL, lipase inhibitor), or sucrose polyester (SPE, nondigestible fat) were infused intraduodenally in randomized order. After 30 minutes, the proximal stomach was distended in 1 mm Hg steps/min. Intensity of gastrointestinal sensations (on a 0-10 visual analog scale), plasma cholecystokinin (CCK) levels, and gastric volumes were assessed throughout. LCT and MCT increased gastric volume at baseline pressure compared with SPE, and LCT more than MCT. THL entirely abolished this effect (volumes [mL]: LCT, 213 +/- 19; LCT-THL, 39 +/- 3; MCT, 155 +/- 12; MCT-THL, 43 +/- 5; SPE, 44 +/- 5). Only LCT increased plasma CCK levels (pmol/L per 30 minutes: LCT, 21 +/- 2; LCT-THL, 9 +/- 1; MCT, 9 +/- 1; MCT-THL, 11 +/- 1; SPE, 9 +/- 1). During distentions, intragastric volumes were greater during infusion of LCT and MCT than during the respective THL conditions or SPE, but plasma CCK levels did not change. The intensity of sensations increased (hunger decreased) more with LCT than with MCT. During infusion of THL or SPE, the effects were smaller than during LCT or MCT. Fat digestion is required for the modulation of gastrointestinal sensations during gastric distention. The effects of fat depend on the fatty acid chain length and are not entirely explained by release of CCK.

Role of duodenal lipid and cholecystokinin A receptors in the pathophysiology of functional dyspepsia

BACKGROUND/AIMS We aimed to evaluate the role of fat and cholecystokinin (CCK) in the pathophysiology of functional dyspepsia (FD) by investigating symptoms and plasma CCK levels following increasing doses of...

Diazepam-binding inhibitor mediates feedback regulation of pancreatic secretion and postprandial release of cholecystokinin.

Recently, we isolated a trypsin-sensitive cholecystokinin-releasing peptide (CCK-RP) from porcine and rat intestinal mucosa. The amino acid sequence of this peptide was determined to be identical to that of the diazepam-binding inhibitor (DBI). To test the role of DBI in pancreatic secretion and responses to feeding, we used pancreaticobiliary and intestinal cannula to divert bile-pancreatic juice from anesthetized rats. Within 2 hours, this treatment caused a 2-fold increase in pancreatic protein output and a >10-fold increase in plasma CCK. Luminal DBI levels increased 4-fold. At 5 hours after diversion of bile-pancreatic juice, each of these measures returned to basal levels. Intraduodenal infusion of peptone evoked a 5-fold increase in the concentration of luminal DBI. In separate studies, we demonstrated that intraduodenal administration of antiserum to a DBI peptide specifically abolished pancreatic secretion and the increase in plasma CCK levels after diversion of bile-pancreatic juice. To demonstrate that DBI mediates the postprandial rise in plasma CCK levels, we showed that intraduodenal administration of 5% peptone induced dramatic increases in pancreatic secretion and plasma CCK, effects that could be blocked by intraduodenal administration of anti-DBI antiserum. Hence, DBI, a trypsin-sensitive CCK-RP secreted from the proximal small bowel, mediates the feedback regulation of pancreatic secretion and the postprandial release of CCK.

Specific adaptation of gastric emptying to diets with differing protein content in the rat: is endogenous cholecystokinin implicated?

Background—Recent studies indicate that gastric emptying may be influenced by patterns of previous nutrient intake. Endogenous cholecystokinin (CCK), whose synthesis and release can be affected by dietary intake, has a...

Effects of a panel of dietary lectins on cholecystokinin release in rats.

We previously showed that soybean lectin (SBL) releases cholecystokinin (CCK) and have now asked whether other dietary lectins have this effect and if extracellular calcium is involved. Lectins and vehicle were first infused into the duodenum of anesthetized rats. The CCK response to vehicle was 3.1 +/- 0.6 pmol/l (P < 0.05 vs. basal). SBL and peanut lectin (PNL) (84 microg/ml) significantly increased plasma CCK concentrations from 2.0 +/- 0.4 pmol/l to a maximum of 8.4 +/- 0.5 pmol/l (P < 0.01 vs. vehicle, mean +/- SE) and from 1.9 +/- 0.5 to 7.0 +/- 0.6 pmol/l (P < 0.05 vs. vehicle, mean +/- SE), respectively. Wheat germ lectin (WGL) (840 microg) also increased plasma CCK levels from 1.5 +/- 0.3 pmol/l to a maximum of 9.7 +/- 1.3 pmol/l (P < 0.05 vs. vehicle, mean +/- SE). Corresponding increases in pancreatic protein output occurred. Broad bean lectin (BBL) had no effect on either parameter. Dose-dependent responses were seen with SBL, PNL, and WGL (1, 10, and 100 microg/ml) in perifused rat intestinal cells. These responses were abolished in calcium-free medium and in the presence of the competing sugars of the lectins. Therefore, SBL, PNL, and WGL, which bind to motifs including N-acetyl-D-galactosamine, galactose, and N-acetylglucosamine, respectively, released CCK, but BBL, which binds to mannose and glucose, did not. Ingestion of lectins may have major CCK-mediated effects on gastrointestinal function and growth.

Mechanisms for the Pancreatic Oncogenic Effects of the Peroxisome Proliferator Wyeth-14,643

Several peroxisome proliferators have been shown to produce pancreatic acinar cell hyperplasia/adenocarcinomas in 2-year bioassays with rats: ammonium perfluorooctanoate (C8), clofibrate, methylclofenapate, HCFC-123, and Wyeth-14,643 (WY). We have usedin vitro(C8, WY) andin vivo(WY) approaches to examine several possible mechanisms of pancreatic tumorigenesis by peroxisome proliferating compounds. These mechanisms include cholecystokinin receptor agonism (CCKA), trypsin inhibition, alterations in gut fat content, cholestasis, and altered bile flow/composition. All of these mechanisms enhance pancreatic growth either by binding to the CCKAreceptor or by increasing plasma CCK levels.In vitroexperiments using a receptor competition binding assay demonstrated that WY and C8 do not bind directly to the CCKAreceptor. In a continuous spectrophotometric assay, WY and C8 also failed to inhibit trypsin, a common mechanism for increasing plasma CCK levels. Thesein vitroresults suggested that WY was not acting via the two most common mechanisms for modulation of pancreas growth. Two types ofin vivoexperiments were conducted. The subchronic study (2-month duration) was designed primarily to detect early changes in pancreatic growth such as those mediated by compounds that inhibit trypsin or act as CCKAreceptor agonists. The chronic study (6 months) was designed primarily to evaluate whether the pancreatic lesions were secondary to hepatic changes such as cholestasis and/or altered bile flow/composition. In thein vivoexperiments, male Crl:CDBR rats were fed diets containing 0 or 100 ppm WY. In the subchronic study WY-treated rats had a twofold increase in mean relative liver weights, an eightfold increase in hepatic peroxisomal proliferation, and a fourfold increase in hepatocyte cell proliferation after 1 week which remained elevated throughout the 2 months of treatment. In contrast, no pancreatic weight effects, increases in plasma CCK, or acinar cell proliferation was seen through 2 months in the WY group when compared to the control group. Fecal fat concentrations were also measured at 2 months and demonstrated no difference between control and WY-treated animals. The absence of any early pancreas changes in the subchronic study is consistent with thein vitrodata which demonstrated that WY is not a CCKAagonist or a trypsin inhibitor. The chronic study demonstrated increases in pancreatic weights at 3 months (6% above control) and 6 months (17% above control), as well as increased CCK plasma levels in the WY-treated group. Liver effects in the chronic study paralleled those of the subchronic time points. Clinical pathology endpoints including increased serum concentrations of bile acids, alkaline phosphatase, and bilirubin were indicative of cholestasis in the chronic WY-treated group. The cholestasis may be responsible for the downward trend in total bile acid output, both of which may contribute to the modest increases in plasma CCK levels. These results indicate that chronic exposure to WY causes liver alterations such as cholestasis, which may increase plasma concentrations of CCK. Hence, WY may induce pancreatic acinar cell adenomas/adenocarcinomas via a mild but sustained increase in CCK levels secondary to hepatic cholestasis.

Plasma cholecystokinin levels in acute pancreatitis.

Recent studies have shown that cholecystokinin (CCK) is involved in the induction and development of acute pancreatitis in experimental animals. In the present study we determined basal plasma CCK concentrations by a specific and sensitive radioimmunoassay using antiserum OAL656 in 17 patients with acute pancreatitis due to gallstone in the common bile duct (n = 7), alcoholic (n = 4), post endoscopic retrograde pancreatography (n = 1), and unknown causes (n = 4), and 37 patients with cholelithiasis (n = 18) and choledocholithiasis (n = 19). Plasma CCK concentrations in patients with gallstone pancreatitis on hospital day 1 (mean +/- SEM, 6.78 +/- 1.39 pM) were significantly higher than those in patients with other causes (1.33 +/- 0.16 pM) or in 20 healthy control subjects (1.55 +/- 0.11 pM). There was no relationship between plasma CCK and serum pancreatic enzyme levels, the severity of acute pancreatitis, or serum bilirubin concentrations. Plasma CCK levels in patients with acute symptomatic cholelithiasis (n = 7; 4.35 +/- 0.90 pM) and choledocholithiasis (n = 8; 4.52 +/- 1.17 pM) were significantly higher than those in patients without symptoms (cholelithiasis, n = 11, 1.40 +/- 0.17 pM; choledocholithiasis, n = 11, 1.88 +/- 0.49 pM) but tended to be lower than those in patients with gallstone pancreatitis. These present observations suggest that the increase in plasma CCK levels in gallstone pancreatitis appears not to be the cause but to be the result of gallstone pancreatitis probably due to a transient disturbance of bile flow into the duodenum by stones or edema of the bile duct. Our present results provide some evidence for the usefulness of CCK receptor antagonists for the treatment of biliary colics and acute pancreatitis.

Effects of 5-HT agonists, selective for different receptor subtypes, on oxytocin, CCK, gastrin and somatostatin plasma levels in the rat

Adult male Sprague–Dawley rats were administered the 5-HT subtype selective receptor agonists 8-OH-DPAT (0.5–2.0mg/kg) (5-HT1B), buspirone (2–8mg/kg) (5-HT1A), TFMPP (0.125–2.0mg/kg), DOI (0.125–2.0mg/kg) (5-HT2A) and m-CPBG (1.25–20.0mg/kg) (5-HT3), subcutaneously. Oxytocin, cholecystokinin (CCK), somatostatin and gastrin plasma levels were determined by standard RIA techniques 30 and 120min after injection of the respective 5-HT receptor agonist. It was found that the 5-HT1A and the 5-HT2A/C, but not the 5-HT2B or the 5-HT3 receptor agonists produced an increase in plasma oxytocin levels and these effects were, at least partially, antagonized by the corresponding subtype selective antagonists (−)pindolol (2mg/kg) and ritanserin (2mg/kg), respectively, administered 10min before 8-OH-DPAT (0.5mg/kg) or DOI (0.5mg/kg). The maximal response to the 5-HT1A receptor agonists (approx. 120nmol/l) was from 8 to 5 times the maximal response to the 5-HT2A/C receptor agonist. In addition, 8-OH-DPAT and DOI caused a decrease in plasma CCK levels, whereas the 5-HT1B receptor agonist TFMPP gave rise to an increase in plasma CCK levels. There were no statistically significant effects by any of the 5-HT receptor agonists on plasma somatostatin or gastrin levels under the present conditions. It is suggested that the clinical effects of new anxiolytic 5-HT1A receptor agonists, such as buspirone, to an extent may be mediated via an increased release of oxytocin.