Cholecystokinin responsiveness varies across the population dependent on metabolic phenotype.

Background: Cholecystokinin (CCK) is an important satiety factor, acting at type 1 receptors (CCK1Rs) on vagal afferent neurons; however, CCK agonists have failed clinical trials for obesity. We postulated that CCK1R function might be defective in such patients due to abnormal membrane composition, such as that observed in cholesterol gallstone disease.Objective: Due to the challenges in directly studying CCK1Rs relevant to appetite control, our goal was to develop and apply a method to determine the impact of a patient's own cellular environment on CCK stimulus-activity coupling and to determine whether CCK sensitivity correlated with the metabolic phenotype of a high-risk population.Design: Wild-type CCK1Rs were expressed on leukocytes from 112 Hispanic patients by using adenoviral transduction and 24-h culture, with quantitation of cholesterol composition and intracellular calcium responses to CCK. Results were correlated with clinical, biochemical, and morphometric characteristics.Results: Broad ranges of cellular cholesterol and CCK responsiveness were observed, with elevated cholesterol correlated with reduced CCK sensitivity. This was prominent with increasing degrees of obesity and the presence of diabetes, particularly when poorly controlled. No single standard clinical metric correlated directly with CCK responsiveness. Reduced CCK sensitivity best correlated with elevated serum triglycerides in normal-weight participants and with low HDL concentrations and elevated glycated hemoglobin in obese and diabetic patients.Conclusions: CCK responsiveness varies widely across the population, with reduced signaling in patients with obesity and diabetes. This could explain the failure of CCK agonists in previous clinical trials and supports the rationale to develop corrective modulators to reverse this defective servomechanism for appetite control. This trial was registered at www.clinicaltrials.gov as NCT03121755.

Does the panic attack activate the hypothalamic-pituitary-adrenal axis?

Realizou-se levantamento bibliográfico no indexadorMEDLINE, através das palavras-chave "cortisol" e "panic", sem limite de tempo, restringindo-se a sereshumanos e à localização das palavras-chave no título e no resumo. Foram excluídos artigos de revisão e relatos de caso, estudos sobre alterações ocorridas entre dois ataques, e os que tratavam de outras doenças psiquiátricas ou de sujeitos sadios, quando não comparados com pacientes de pânico. Os resultados mostraram que ataques de pânico naturais ou provocados pelos agentes panicogênicos seletivos, lactato de sódio e dióxido de carbono, não ativam o eixo hipotálamo-pituitária-adrenal (HPA). Agonistas do receptor de colecistocinina B elevam os hormônios de estresse, quer haja ataque de pânico ou não, parecendo ativar diretamente o eixo HPA. O antagonista benzodiazepínico flumazenil não eleva o nível dos hormônios de estresse, porém não induz ataques de pânico de modo consistente. Agentes farmacológicos que produzem ansiedade em pacientes de pânico e em voluntários saudáveis elevam o nível dos hormônios de estresse, entre estes o antagonista a2-adrenérgico ioimbina, os agentes serotonérgicos 1-(m-clorofenil) piperazina (mCPP) e fenfluramina, bem como o agente psicostimulante cafeína. Portanto, o ataque de pânico não parece ativar o eixo HPA, ao contrário da ansiedade antecipatória.

Effects of secretagogues and bile acids on mitochondrial membrane potential of pancreatic acinar cells: comparison of different modes of evaluating DeltaPsim.

In this study, we investigated the effects of secretagogues and bile acids on the mitochondrial membrane potential of pancreatic acinar cells. We measured the mitochondrial membrane potential using the tetramethylrhodamine-based probes tetramethylrhodamine ethyl ester and tetramethylrhodamine methyl ester. At low levels of loading, these indicators appeared to have a low sensitivity to the uncoupler carbonyl cyanide m-chlorophenylhydrazone, and no response was observed to even high doses of cholecystokinin. When loaded at high concentrations, tetramethylrhodamine methyl ester and tetramethylrhodamine ethyl ester undergo quenching and can be dequenched by mitochondrial depolarization. We found the dequench mode to be 2 orders of magnitude more sensitive than the low concentration mode. Using the dequench mode, we resolved mitochondrial depolarizations produced by supramaximal and by physiological concentrations of cholecystokinin. Other calcium-releasing agonists, acetylcholine, JMV-180, and bombesin, also produced mitochondrial depolarization. Secretin, which employs the cAMP pathway, had no effect on the mitochondrial potential; dibutyryl cAMP was also ineffective. The cholecystokinin-induced mitochondrial depolarizations were abolished by buffering cytosolic calcium. A non-agonist-dependent calcium elevation induced by thapsigargin depolarized the mitochondria. These experiments suggest that a cytosolic calcium concentration rise is sufficient for mitochondrial depolarization and that the depolarizing effect of cholecystokinin is mediated by a cytosolic calcium rise. Bile acids are considered possible triggers of acute pancreatitis. The bile acids taurolithocholic acid 3-sulfate, taurodeoxycholic acid, and taurochenodeoxycholic acid, at low submillimolar concentrations, induced mitochondrial depolarization, resolved by the dequench mode. Our experiments demonstrate that physiological concentrations of secretagogues and pathologically relevant concentrations of bile acids trigger mitochondrial depolarization in pancreatic acinar cells.

Effect of peripheral cholecystokinin receptor agonists on c-Fos expression in brain sites mediating food consumption in rats.

Peripheral cholecystokinin (CCK) elicits satiety by acting on hypothalamic nuclei. The anoretic effect of CCK is mediated by the vagus nerve and involves brainstem areas receiving vagal inputs, such as the nucleus tractus solitarius (NTS) and the area postrema (AP). This work aims to analyze, by measuring c-Fos expression, the effect of selective CCK receptor agonists on brain areas involved in food-intake/satiety process. We observed that SR-146,131, a CCK(1)R agonist, increased c-Fos expression in NTS and AP as well as in some hypothalamic nuclei. CCK-4, a CCK(2)R agonist which does not cross the blood-brain barrier (BBB), only was effective in the hypothalamus. Our data show that the activation of the brainstem is not a requisite to obtain a hypothalamic effect of peripheral CCK and suggest that CCK-4 may indirectly stimulate hypothalamic areas endowed with BBB, without previous activation of neither NTS nor AP.

Inhibition by CCK of ascending contraction elicited by mucosal stimulation in the duodenum of the rat.

CCK released by intraluminal stimuli modifies duodenal activity contributing to a decrease in gastric emptying. However, the neural mechanisms by which CCK controls motility are not well known. The aim of this study was to investigate the interaction between CCK and the enteric nervous system through the study of the effects of CCK-8 on ascending excitation. Anaesthetized Sprague-Dawley rats were prepared with a strain-gauge sutured to the duodenum wall. An electrode holder was placed in the duodenum lumen to elicit ascending contraction. Electrical field stimulation of the duodenal mucosa (4 Hz, 0.6 ms, 30 V) induced an ascending excitation which was blocked by hexamethonium (10 mg kg-1; n=5) and atropine (0.3 mg kg-1; n=5), but enlarged by L-NNA (10(-5) mol kg-1; n=5). CCK-8 (3 ¿ 10(-9) mol kg-1 10 min-1) blocked ascending excitation and an inhibition of the induced phasic activity was observed instead (n=18). Individually, none of the CCK receptor antagonists (L-364 718 and L-365 260) (3 ¿ 10(-7) mol kg-1; n=6 each) blocked the inhibition of ascending excitation induced by CCK-8. However, simultaneous infusion of both antagonists abolished CCK-8 effect on electrical stimulation (n=5). Similarly, none of the CCK-8 agonists (A-71623, A-71378, gastrin) modified the ascending excitation. In contrast, the simultaneous infusion of A-71623 and CCK-4 (n=4) induced an effect similar to CCK-8. In conclusion, CCK-8 blocked ascending contraction elicited by electrical field stimulation of duodenal mucosa by means of simultaneous activation of CCK-A and CCK-B receptors.

Cholecystokinin modulates mucosal immunoglobulin A function.

BACKGROUND: We have established that mucosal immunoglobulin A (IgA) production is highly dependent on cholecystokinin release and is markedly suppressed by glucocorticoids. The purpose of the present study was to examine the role of cholecystokinin on the functional responsiveness of the mucosal IgA system in glucocorticoid treated rats. METHODS: A total of 24 Fischer rats were assigned to three groups of 8 animals each. Animals were injected with vehicle (CON), dexamethasone (DEX) (0.08 mg/150 g), or DEX (0.08 mg/150 gm) and ARL1294KF (500 ng twice daily), a novel and potent long-acting cholecystokinin agonist (DEX+CCK). Animals were treated for 48 hours and killed. Duodenum was harvested, and the total mucosal concentration of cholecystokinin was measured by radioimmunoassay. Mucosal IgA was assayed by quantitation of immunoreactive cells in the ileum. Bacterial adherence was evaluated by quantitative culture of vigorously washed stripped cecal mucosa. Transepithelial electrical resistance, a measure of tight junction permeability, was assessed by mounting strips of adjacent cecal mucosa in Ussing chambers. RESULTS: Glucocorticoid administration resulted in a statistically significant (p < 0.001) decrease in duodenal cholecystokinin, decreased IgA, and impaired mucosal immunity (increased bacterial adherence and decreased tissue resistance). Cholecystokinin administration preserved mucosal immune function in DEX-treated rats. CONCLUSIONS: Cholecystokinin may play an important role in maintaining the functional responsiveness of mucosal immunity during catabolic stress.

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 used in vitro (C8, WY) and in vivo (WY) approaches to examine several possible mechanisms of pancreatic tumorigenesis by peroxisome proliferating compounds. These mechanisms include cholecystokinin receptor agonism (CCK(A)), 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 CCK(A) receptor or by increasing plasma CCK levels. In vitro experiments using a receptor competition binding assay demonstrated that WY and C8 do not bind directly to the CCK(A) receptor. In a continuous spectrophotometric assay, WY and C8 also failed to inhibit trypsin, a common mechanism for increasing plasma CCK levels. These in vitro results suggested that WY was not acting via the two most common mechanisms for modulation of pancreas growth. Two types of in vivo experiments 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 CCK(A) receptor 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 the in vivo experiments, 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 the in vitro data which demonstrated that WY is not a CCK(A) agonist 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.

Comparative 3H-CCK-8S binding studies on CCKB-type receptors in guinea-pig cortex and continuous cell lines.

The present study was undertaken to compare binding characteristics of CCKB-type receptors in guinea-pig cortex, Jurkat T-cells, GH3 cells and C6 cells. The rank order of potency of a variety of CCK agonists and antagonists in inhibiting specific [3H]CCK-8S binding was highly correlated for the 4 CCKB receptor models as demonstrated by a computer-assisted statistical analysis. Taking the ligand binding profiles as the criterion it is concluded that CCKB receptors in guinea-pig cortex, Jurkat T-cells, pituitary GH3 cells and rat glioma C6 cells share identical pharmacological properties.