Decreased expression of the satiety signal receptor CCKAR is responsible for increased growth and body weight during the domestication of chickens.

Animal domestication has resulted in changes in growth and size. It has been suggested that this may have involved selection for differences in appetite. Divergent growth between chickens selected for egg laying or meat production is one such example. The neurons expressing AGRP and POMC in the basal hypothalamus are important components of appetite regulation, as are the satiety feedback pathways that carry information from the intestine, including CCK and its receptor CCKAR (CCK1 receptor). Using 16 generations of a cross between a fast and a relatively slow growing strain of chicken has identified a region on chromosome 4 downstream of the CCKAR gene, which is responsible for up to a 19% difference in body weight at 12 wk of age. Animals possessing the high-growth haplotype at the locus have lower expression of mRNA and immunoreactive CCKAR in the brain, intestine, and exocrine organs, which is correlated with increased levels of orexigenic AGRP in the hypothalamus. Animals with the high-growth haplotype are resistant to the anorectic effect of exogenously administered CCK, suggesting that their satiety set point has been altered. Comparison with traditional breeds shows that the high-growth haplotype has been present in the founders of modern meat-type strains and may have been selected early in domestication. This is the first dissection of the physiological consequences of a genetic locus for a quantitative trait that alters appetite and gives us an insight into the domestication of animals. This will allow elucidation of how differences in appetite occur in birds and also mammals.

Expression analysis of a cholecystokinin system in human and rat white adipose tissue.

AIM: Cholecystokinin (CCK) participates in the storage of dietary triglycerides in white adipose tissue (WAT). Our goal was to characterize, both in subcutaneous (Sc-WAT) and visceral WAT (Vis-WAT), the functional expression of the two known CCK receptors, CCK-1 (CCK-1R) and CCK-2 (CCK-2R), as well as of CCK. MAIN METHODS: Gene and protein expression was assessed in different cell types of rat and human WAT by means of RT-PCR and western-blot, respectively. The functionality of CCK-Rs was tested by quantifying protein kinase B (Akt) phosphorylation after treatment of pre-adipocytes with the bioactive fragment of CCK, CCK-8. The CCK receptor subtype involved in Akt phosphorylation was investigated by using selective CCK-1R (SR-27,897) and CCK-2R antagonists (L-365,260). KEY FINDINGS: In rats, CCK-1R (Cckar) and CCK-2R (Cckbr) gene expression was detected in the two types of WAT analyzed as well as in isolated adipocytes, mesenchymal stem cells and pre-adipocytes. CCK-1R and CCK-2R proteins were identified in adipocytes and, to a minor extent, in pre-adipocytes. In addition, CCK-2R were detected in subcutaneous mesenchymal stem cells. Gene expression of the CCK precursor preproCCK as well as CCK immunoreactivity were also found in Sc-WAT and Vis-WAT. In human WAT, CCK gene expression as well as CCK-2Rs and CCK were also identified. CCK-8 evoked Akt phosphorylation in rat pre-adipocytes, and this effect was antagonized by SR-27,897 and L-365,260. SIGNIFICANCE: Our data show that both human and rat WAT express a complete CCK system, and suggest that CCK may have an autocrine/paracrine role in regulating adipose tissue biology.

Cholecystokinin (CCK) receptor and CCK gene expression in human pituitary adenomas and in vitro effects of CCK peptides on GH and gonadotrophin secretion.

There is growing evidence that cholecystokinin (CCK) affects growth and differentiation of anterior pituitary cells, via the CCK-B receptor. The possibility of an autocrine / paracrine role for CCK to modulate hormone secretion in human pituitary tumour cells is demonstrated here by RT-PCR and direct sequencing. In support of this conclusion, a neutralising antibody against the CCK peptide exhibited a dose dependent inhibition of hormone secretion by functionless pituitary adenomas. Total RNA was extracted from human pituitary adenomas, reverse transcribed into cDNA and subjected to PCR using primers specific for the gene for CCK, CCK-A and CCK-B receptors. PCR bands of the predicted length were observed in all tumours using human CCK gene and CCK-B receptor primers. Restriction digestion and direct sequence analysis provided further evidence that they represented both the human CCK peptide along with the CCK-A and/B receptor mRNA. CCK-33 and CCK octapeptide sulphate (CCK-8s) both powerfully stimulated phosphatidylinositol hydrolysis, providing evidence for functional activity of the CCK-A and/B receptors. A direct stimulatory effect of CCK peptides on both LH and FSH secretion is reported for the first time, whereas stimulatory effects on GH were blocked by antagonists to CCK. These results may indicate an autocrine role for CCK in the functioning and perhaps development of human pituitary tumours.

Disrupted fat absorption attenuates obesity induced by a high-fat diet in Clock mutant mice.

The Clock gene is a core component of the circadian clock in mammals. We show here that serum levels of triglyceride and free fatty acid were significantly lower in circadian Clock mutant ICR than in wild-type control mice, whereas total cholesterol and glucose levels did not differ. Moreover, an increase in body weight induced by a high-fat diet was attenuated in homozygous Clock mutant mice. We also found that dietary fat absorption was extremely impaired in Clock mutant mice. Circadian expressions of cholecystokinin-A (CCK-A) receptor and lipase mRNAs were damped in the pancreas of Clock mutant mice. We therefore showed that a Clock mutation attenuates obesity induced by a high-fat diet in mice with an ICR background through impaired dietary fat absorption. Our results suggest that circadian clock molecules play an important role in lipid homeostasis in mammals.

Cholecystokinin- and gastrin-induced protein and amylase secretion from the parotid gland of the anaesthetized rat.

I.V. infusion of pentagastrin (20 microg/kg/h) or cholecystokinin (CCK)-8 (1 microg/kg/h) for 10 min caused secretion of salivary proteins from the parotid gland in the anaesthetized rat without any accompanying overt fluid secretion. This "occult" response was revealed by a subsequent wash-out injection of methacholine (5 microg/kg, I.V.) 10 min after the end of the infusion period (aiming at avoiding synergistic interactions). While the fluid response to methacholine was unaffected by the preceding infusion of pentagastrin and CCK-8, the output of protein increased by 147% (pentagastrin) and 74% (CCK-8) and that of amylase by 45% (CCK-8) compared to the responses to methacholine upon saline infusion. Those increases were abolished by the CCK-A receptor blocker (lorglumide), but not by the CCK-B receptor blocker (itriglumide). Evisceration, combined sympathetic and parasympathetic denervation of the glands and assay under adrenoceptor blockade excluded contribution from the gastro-intestinal tract, central or ganglionic mechanisms and circulating catecholamines to the increase in protein/amylase. Furthermore, Western blot demonstrated CCK receptors for both A and B subtypes in normal and chronically denervated glands. In the submandibular gland, both pentagastrin and CCK-8 evoked a trace secretion of saliva but, under the present experimental set-up, no statistically significant increase in protein output. Thus, in addition to the autonomic nervous system, gastrointestinal hormones may, in some types of glands, be involved in the secretion of salivary gland proteins.

Molecular cloning, expression and pharmacological characterization of the canine cholecystokinin 1 receptor.

1 The full-length, canine cholecystokinin 1 (CCK1) receptor was cloned from gallbladder tissue using RT-PCR with a combination of primers designed to interact with conserved regions of the human and rat CCK1 receptor, which also shared homology with the canine genomic sequence. 2 Analysis of the sequence of the canine CCK1 receptor revealed a 1287 base pair product, which encoded a 429 amino-acid protein. This protein was 89% identical to the human and 85% identical to the rat CCK1 receptor. 3 The canine CCK1 receptor was expressed in CHO-K cells for pharmacological characterization. In competition studies, using [(125)I]BH-CCK-8S as radioligand, the affinity values estimated for CCK receptor-selective compounds were not significantly different between the canine and human CCK1 receptors (pK(I)+/-s.e.m. at canine CCK1 receptor; L-364,718=8.82+/-0.08, L-365,260=6.61+/-0.05, YF476=7.91+/-0.15, YM022=8.28+/-0.06 and dexloxiglumide=7.53+/-0.11). Furthermore, the selectivity of these compounds between canine CCK1 and CCK2 receptors was consistent with the selectivity between the human CCK1 and CCK2 receptors. 4 Two additional forms of the canine CCK1 receptor were identified during the cloning procedure. These had three (variant #1) and six (variant #2) amino-acid differences from the wild-type canine CCK1 receptor. Variant #1 bound [(125)I]BH-CCK-8S and displayed an identical pharmacological profile to the wild-type receptor using the ligands described above. No significant binding was measured with variant #2. 5 In conclusion, we have cloned and pharmacologically characterized the canine CCK1 receptor. The data obtained will facilitate the interpretation of numerous pharmacological experiments that have been performed using canine tissue to elucidate the actions of CCK and gastrin.

Immunohistochemical analysis of cholecystokinin A receptor distribution in the rat pancreas.

Cholecystokinin (CCK) plays a major role in the regulation of pancreatic enzyme secretion based on its binding to the CCK-A receptor (CCK-AR). While CCK-AR is known to be expressed in rat islet B cells, the localization of CCK-AR in rat pancreatic A and D cells remains poorly understood. The aim of this study was to identify the localization of CCK-AR in rat pancreatic islets by means of double immunofluorescence straining with antibodies against CCK-AR, glucagon, insulin and somatostatin and with in situ hybridization to detect its transcript. CCK-AR-like immunoreactive cells were found to overlap both with glucagon-like immunoreactive cells and insulin-like immunoreactive cells but not with somatostatin-like immunoreactive cells. An in situ hybridization study using a cRNA probe for CCK-AR revealed that CCK-AR mRNA was expressed in the center and periphery of the pancreatic islets. Further to this, immunofluorecsence staining using anti-glucagon antibody was carried out after in situ hybridization using the CCK-AR cRNA probe in order to identify CCK-AR mRNA expressing cells. CCK-AR mRNA exhibited a distribution pattern almost identical to that of glucagon-like immunoreactive cells. These results show clearly that CCK-AR exists not only in B but also in A cells of the rat pancreas, suggesting that CCK regulates the secretion of insulin and glucagon at least partly via CCK-AR.

Differential expression of cholecystokinin A receptor in gallbladder cancer in the young and elderly suggests two subsets of the same disease?

BACKGROUND: Cholecystokinin type A receptor (CCKAR) is known to be overexpressed in variety of human malignancies but information regarding its expression in gallbladder cancer (GBC) is limited. Attempts were now made to investigate expression pattern of CCKAR mRNA and protein in controls and GBC patients and correlate it with various clinicopathological parameters following surgical resection. MATERIALS AND METHODS: Gallbladder tissue samples from 64 subjects (GBC: 39; control: 25) were studied. Expression of CCKAR mRNA was evaluated by reverse transcriptase-polymerase chain reaction and confirmed using real-time polymerase chain reaction. Protein expression was studied by enzyme-linked immunosorbent assay. RESULTS: Significantly higher expression of CCKAR mRNA (P < 0.0001) and protein (P < 0.0001) was observed in GBC tissues. Overexpression was also observed for stage III and in moderately and poorly differentiated tumors. When the clinicopathological parameters were compared, we found age dependent decrease in CCKAR expression. Relatively higher expression of CCKAR was observed in younger patients (age < 45 years) having more aggressive disease when compared with elderly ones (age ≥ 45 years). CONCLUSIONS: Age related differential expression of CCKAR in GBC may suggest two possible variants of the disease in this endemic belt.

Differential body weight and feeding responses to high-fat diets in rats and mice lacking cholecystokinin 1 receptors.

Prior data demonstrated differential roles for cholecystokinin (CCK)1 receptors in maintaining energy balance in rats and mice. CCK1 receptor deficiency results in hyperphagia and obesity of Otsuka Long-Evans Tokushima Fatty (OLETF) rats but not in mice. To ascertain the role of CCK1 receptors in high-fat-diet (HFD)-induced obesity, we compared alterations in food intake, body weight, fat mass, plasma glucose, and leptin levels, and patterns of hypothalamic gene expression in OLETF rats and mice lacking CCK1 receptors in response to a 10-wk exposure to HFD. Compared with Long-Evans Tokushima Otsuka (LETO) control rats, OLETF rats on HFD had sustained overconsumption over the 10-wk period. High fat feeding resulted in greater increases in body weight and plasma leptin levels in OLETF than in LETO rats. In situ hybridization determinations revealed that, while HFD reduced neuropeptide Y (NPY) mRNA expression in both the arcuate nucleus (Arc) and the dorsomedial hypothalamus (DMH) of LETO rats, HFD resulted in decreased NPY expression in the Arc but not in the DMH of OLETF rats. In contrast to these results in OLETF rats, HFD increased food intake and induced obesity to an equal degree in both wild-type and CCK1 receptor(-/-) mice. NPY gene expression was decreased in the Arc in response to HFD, but was not detectable in the DMH in both wild-type and CCK1 receptor(-/-) mice. Together, these data provide further evidence for differential roles of CCK1 receptors in the controls of food intake and body weight in rats and mice.

Differences in ethanol ingestion between cholecystokinin-A receptor deficient and -B receptor deficient mice.

AIMS: Cholecystokinin (CCK) modulates dopamine release in the nucleus accumbens through the CCK-A receptor (CCK-AR). The dopaminergic neurotransmission between the ventral tegmental area and the limbic forebrain is a critical neurobiological component of alcohol and drug self-administration. Based on the evidence of interaction between CCK and dopamine, we had found previously that the CCK-AR gene -81A/G polymorphism was associated with alcohol dependence. Since the precise mechanism underlying this association has not been elucidated, the role of CCK-AR in ethanol ingestion was examined using CCK-AR gene deficient (-/-) mice and compared with those of CCK-BR(-/-) and wild-type mice. METHODS: The two-bottle choice protocol was conducted and the righting reflex was examined in these three genotypes. Furthermore, the protein level of dopamine 2 receptor (D2R) in the nucleus accumbens was determined by western blotting. RESULTS: CCK-AR(-/-) mice consumed more ethanol than CCK-BR(-/-) and wild-type mice, and showed no aversion to high concentrations of ethanol solution. However, the difference was actually in the total fluid consumption and alcohol preference remained unchanged, indicating that the differences were not specific to alcohol. Behavioral sensitivity to ethanol, examined using the righting reflex, did not differ significantly between the groups. D2R expression in the nucleus accumbens was significantly lower in the CCK-BR(-/-) mice and was significantly higher in CCK-AR(-/-) mice than in wild-type mice. CONCLUSIONS: Voluntary ingestion of ethanol differed between CCK-AR(-/-) and CCK-BR(-/-) mice. The difference might be attributable in part to the different levels of D2R expression in the nucleus accumbens.

CCK-A receptor induction and P38 and NF-kappaB activation in acute pancreatitis.

Bile-pancreatic duct ligation in rats excludes bile-pancreatic juice from the gut and induces acute pancreatitis. Bile-pancreatic juice exclusion from the gut results in increased plasma cholecystokinin (CCK) levels. CCK-A receptor-mediated exocrine pancreatic hyperstimulation is implicated in disease pathogenesis. In the present study, we show for the first time a progressive rise in CCK-A receptor protein expression in ligation-induced acute pancreatitis in rats. As CCK-A receptor induction could amplify CCK-mediated acinar hyperstimulation and exacerbate acinar cell stress with activation of the p38(MAPK) stress kinase pathway, we studied CCK-A receptor protein expression and p38(MAPK) activation in duct ligation-induced acute pancreatitis in rats. Compared to sham-operated controls, acute pancreatitis induced by bile-pancreatic duct ligation associates with a temporal increase in pancreatic CCK-A receptor protein expression, p38(MAPK) expression and activation, and NF-kappaB activation. These findings may have significance in the mechanism of disease pathogenesis in this experimental model.

Effect of lipopolysaccharide on expression and characterization of cholecystokinin receptors in rat pulmonary interstitial macrophages.

AIM: To investigate the effect of lipopolysaccharide (LPS) on the expression and the binding characteristics of cholecystokinin receptors (CCK-R) in rat pulmonary interstitial macrophages (PIMs). METHODS: The PIMs isolated from rat lung tissues were purified by the collagenase digestion method combined with alveolar lavage and pulmonary vessel perfusion. The expression of CCK-R mRNA was detected by RT-PCR and Southern blot analysis and the binding experiments were performed by radioligand binding assay (RBA). RESULTS: CCK-A receptor (CCK-AR) and CCK-B receptor (CCK-BR) mRNA were detected in rat PIMs and their RT-PCR amplified products had a size of approximately 1.37 kb and 480 bp, respectively. The relative expression of CCK-BR mRNA was higher than that of CCK-AR mRNA after incubation with LPS for 0.5, 2, and 6 h. The expression of CCK-R mRNA could be upregulated obviously by LPS. Southern blot analysis of RT-PCR amplified CCK-AR and CCK-BR mRNA products using [gamma-32P]ATP 5'-end-labelled probe showed specific hybridization bands. The specific binding of [3H]CCK-8S to rat PIM membranes was detected in the rats administered with LPS for 48 h, but not in normal rats. Scatchard analysis of the saturation curves suggested the presence of CCK-R with a high affinity (Kd = 0.68 +/- 0.28 nmol/L) and a low binding capacity (Bmax = 32.5 +/- 2.7 fmol/g protein) in rat PIMs. The specific binding of [3H]CCK-8S to rat PIM membranes was inhibited by unlabelled CCK-8S (IC50 = 2.3 +/- 0.8 nmol/L), CCK-AR specific antagonist CR1409 (IC50 = 0.19 +/- 0.06 micromol/L) and CCK-BR specific antagonist CR2945 (IC50 = 3.2 +/- 0.1 nmol/L). CONCLUSION: Two types of functional CCK-AR and CCK-BR existed in rat PIMs and their expression could be upregulated by LPS.