Acetato de lanreotida e acetato de octreotida de liberação prolongada para o tratamento de pacientes com sintomas associados a tumores endócrinos gastroenteropancreáticos funcionais / Lanreotide acetate and extended-release octreotide acetate for the treatment of patients with symptoms associated with functional gastroenteropancreatic endocrine tumors

INTRODUÇÃO: Os tumores neuroendócrinos (TNE) são neoplasias, com origem mais comum no trato gastrointestinal, que podem cursar com liberação de hormônios associado a sintomas, levando a síndrome carcinoide, com incidência anual estimada em 0,25/1.000.000 na Europa (ano de 2008). As manifestações clínicas mais comuns incluem diarreia secretória e rubor súbito, mas a diarreia é considerada mais debilitante com potencial risco de morte. Quando o tratamento curativo com ressecção completa não é viável pela presença de doença metastática, o tratamento é direcionado para o controle dos sintomas da síndrome carcinoide e os análogos da somatostatina (octreotida ou lanreotida) são considerados terapia de primeira linha na SC. PERGUNTAS DE PESQUISA: O acetato de octreotida de liberação prolongada (octreotida LAR) e o acetato de lanreotida de liberação prolongada (lanreotida LP) são eficazes, seguros e custo-efetivos para o tratamento dos sintomas relacionados à SC associados ao TNE gastroenteropancreático funcional em pacientes adultos? EVIDÊNCIAS CLÍNICAS: Foram selecionados três ensaios clínico

Ligand recognition and G-protein coupling selectivity of cholecystokinin A receptor.

Cholecystokinin A receptor (CCKAR) belongs to family A G-protein-coupled receptors and regulates nutrient homeostasis upon stimulation by cholecystokinin (CCK). It is an attractive drug target for gastrointestinal and metabolic diseases. One distinguishing feature of CCKAR is its ability to interact with a sulfated ligand and to couple with divergent G-protein subtypes, including Gs, Gi and Gq. However, the basis for G-protein coupling promiscuity and ligand recognition by CCKAR remains unknown. Here, we present three cryo-electron microscopy structures of sulfated CCK-8-activated CCKAR in complex with Gs, Gi and Gq heterotrimers, respectively. CCKAR presents a similar conformation in the three structures, whereas conformational differences in the 'wavy hook' of the Gα subunits and ICL3 of the receptor serve as determinants in G-protein coupling selectivity. Our findings provide a framework for understanding G-protein coupling promiscuity by CCKAR and uncover the mechanism of receptor recognition by sulfated CCK-8.

Cholecystokinin system is involved in the anorexigenic effect of peripherally applied palmitoylated prolactin-releasing peptide in fasted mice.

Prolactin-releasing peptide (PrRP) has been proposed to mediate the central satiating effects of cholecystokinin (CCK) through the vagal CCK1 receptor. PrRP acts as an endogenous ligand of G protein-coupled receptor 10 (GPR10), which is expressed at the highest levels in brain areas related to food intake regulation, e.g., the paraventricular hypothalamic nucleus (PVN) and nucleus of the solitary tract (NTS). The NTS and PVN are also significantly activated after peripheral CCK administration. The aim of this study was to determine whether the endogenous PrRP neuronal system in the brain is involved in the central anorexigenic effect of the peripherally administered CCK agonist JMV236 or the CCK1 antagonist devazepide and whether the CCK system is involved in the central anorexigenic effect of the peripherally applied lipidized PrRP analog palm-PrRP31 in fasted lean mice. The effect of devazepide and JMV236 on the anorexigenic effects of palm-PrRP31 as well as devazepide combined with JMV236 and palm-PrRP31 on food intake and Fos cell activation in the PVN and caudal NTS was examined. Our results suggest that the anorexigenic effect of JMV236 is accompanied by activation of PrRP neurons of the NTS in a CCK1 receptor-dependent manner. Moreover, while the anorexigenic effect of palm-PrRP31 was not affected by JMV236, it was partially attenuated by devazepide in fasted mice. The present findings indicate that the exogenously influenced CCK system may be involved in the central anorexigenic effect of peripherally applied palm-PrRP31, which possibly indicates some interaction between the CCK and PrRP neuronal systems.

Effect of intracerebroventricular administration of two molecular forms of sulfated CCK octapeptide on anxiety-like behavior in the zebrafish danio rerio.

Cholecystokinin octapeptide with sulfate (CCK-8s) regulates feeding behavior and psychomotor activity. In rodents and goldfish, intracerebroventricular (ICV) injection of CCK-8s decreases food intake and also induces anxiety-like behavior. The zebrafish has several merits for investigating the psychophysiological roles of neuropeptides. However, little is known about the brain localization of CCK and the behavioral action of CCK-8s in this species. Here we investigated the brain localization of CCK-like immunoreactivity and found that it was distributed throughout the brain. As CCK-like immunoreactivity was particularly evident in the ventral habenular nucleus, the interpeduncular nucleus and superior raphe, we subsequently examined the effect of zebrafish (zf) CCK-8s on psychomotor control. Since the zebrafish possesses two molecular forms of zfCCK-8s (zfCCKA-8s and zfCCKB-8s), two synthetic peptides were administered intracerebroventricularly at 1, 5 and 10 pmol g-1 body weight (BW). As the zebrafish shows a greater preference for the lower area of a tank than for to the upper area, we used this preference for assessment of anxiety-like behavior. ICV administration of zfCCKA-8 s or zfCCKB-8s at 10 pmol g-1 BW significantly shortened the time spent in the upper area. The actions of these peptides mimicked that of the central-type benzodiazepine receptor inverse agonist FG-7142 (an anxiogenic agent) at 10 pmol g-1 BW. The anxiogenic-like action of the two peptides was attenuated by treatment with the CCK receptor antagonist proglumide at 200 pmol g-1 BW. These results indicate that zfCCKA-8s and zfCCKB-8s potently induce anxiety-like behavior via the CCK receptor-signaling pathway in the zebrafish brain.

Structure-Activity Relationships and Characterization of Highly Selective, Long-Acting, Peptide-Based Cholecystokinin 1 Receptor Agonists.

A group of peptide-based, long-acting, stable, highly selective cholecystokinin 1 receptor (CCK-1R) agonists with the potential to treat obesity has been identified and characterized, based on systematic investigation of synthetic CCK-8 analogues with N-terminal linkage to fatty acids. Sulfated Tyr in such compounds was stable in neutral buffer. CCK-1R selectivity was achieved mostly by introducing d- N-methyl-Asp instead of Asp at the penultimate position of CCK-8. Our compound 9 (NN9056) showed similar in vitro CCK-1R potency and CCK-1R affinity as CCK-8, very high selectivity for CCK-1R over the cholecystokinin 2 receptor (CCK-2R), strong reduction of food intake in lean pigs for up to 48 h after one subcutaneous injection without adverse effects, a plasma half-life of 113 h in minipigs after intravenous injection, and acceptable chemical stability in a neutral liquid formulation. In addition, we found a highly selective CCK-2R agonist by replacing Gly in a CCK-8 derivative with Glu.

Heterogeneous effects of cholecystokinin on neuronal response properties in deep layers of rat barrel cortex.

Cholecystokinin (CCK) is one of the most studied neuropeptides in the brain. In this study, we investigated the effects of CCK-8s and LY225910 (CCK2 receptor antagonist) on properties of neuronal response to natural stimuli (whisker deflection) in deep layers of rat barrel cortex. This study was done on 20 male Wistar rats, weighing 230-260 g. CCK-8s (300 nmol/rat) and LY225910 (1 µmol/rat) were administered intracerebroventricularly (ICV). Neuronal responses to deflection of principal (PW) and adjacent (AW) whiskers were recorded in the barrel cortex using tungsten microelectrodes. Computer controlled mechanical displacement was used to deflect whiskers individually or in combination at 30 ms inter-stimulus intervals. ON and OFF responses for PW and AW deflections were measured. A condition-test ratio (CTR) was computed to quantify neuronal responses to whisker interaction. ICV administration of CCK-8s and LY225910 had heterogeneous effects on neuronal spontaneous activity, ON and OFF responses to PW and/or AW deflections, and CTR for both ON and OFF responses. The results of this study demonstrated that CCK-8s can modulate neuronal response properties in deep layers of rat barrel cortex probably via CCK2 receptors.

Effects of Exogenous Interleukin-9 on the Growth, Proliferation and Activity of Interstitial Cells of Cajal Cultured in vitro.

OBJECTIVES: To evaluate the role of exogenous interleukin-9 (IL-9) in the growth, proliferation and activity of interstitial cells of Cajal (ICCs) cultured in vitro, and to assess its role in maintaining the functions of ICCs. METHODS: ICCs of murine gastric antrum were isolated and cultured in vitro. ICCs were identified with c-Kit and ANO1 immunofluorescent antibodies. Both fluorescence microscope and confocal microscopy were used to observe the effects of IL-9 on the growth, proliferation and activity of ICCs in cultured in vitro. ICCs were loaded with fluorescence probe Fluo-3/AM and the fluorescence of intracellular calcium concentration ([Ca2+]i) was measured by confocal microscopy. The effects of exogenous IL-9 on the sulfated cholecystokinin octapeptide (CCK-8S)-evoked [Ca2+]i elevation were observed by confocal microscopy. RESULTS: Immunofluorescence results confirmed the successful separation and culture of ICCs in vitro. IL-9 in concentrations ranging from 0.02 to 1 µg/ml promoted the growth, proliferation and activity of ICCs in culture, and ICCs grew best with 0.5 mg/ml of IL-9. The presence of IL-9 could significantly increase the CCK-8S-evoked [Ca2+]i oscillation, which is probably caused by facilitating the maintenance of the functions of ICCs under suitable conditions for culture. CONCLUSION: IL-9 could promote the growth, proliferation and activity of ICCs, reinforce the CCK-8S-induced [Ca2+]i increment in ICCs, and facilitate the maintenance of the functions of ICCs under suitable culture condition.

A Novel CCK-8/GLP-1 Hybrid Peptide Exhibiting Prominent Insulinotropic, Glucose-Lowering, and Satiety Actions With Significant Therapeutic Potential in High-Fat-Fed Mice.

Glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK) exert important complementary beneficial metabolic effects. This study assessed the biological actions and therapeutic utility of a novel (pGlu-Gln)-CCK-8/exendin-4 hybrid peptide compared with the stable GLP-1 and CCK mimetics exendin-4 and (pGlu-Gln)-CCK-8, respectively. All peptides significantly enhanced in vitro insulin secretion. Administration of the peptides, except (pGlu-Gln)-CCK-8 alone, in combination with glucose significantly lowered plasma glucose and increased plasma insulin in mice. All treatments elicited appetite-suppressive effects. Twice-daily administration of the novel (pGlu-Gln)-CCK-8/exendin-4 hybrid, (pGlu-Gln)-CCK-8 alone, or (pGlu-Gln)-CCK-8 in combination with exendin-4 for 21 days to high-fat-fed mice significantly decreased energy intake, body weight, and circulating plasma glucose. HbA1c was reduced in the (pGlu-Gln)-CCK-8/exendin-4 hybrid and combined parent peptide treatment groups. Glucose tolerance and insulin sensitivity also were improved by all treatment modalities. Interestingly, locomotor activity was decreased in the hybrid peptide group, and these mice also exhibited reductions in circulating triglyceride and cholesterol levels. Pancreatic islet number and area, as well ß-cell area and insulinotropic responsiveness, were dramatically improved by all treatments. These studies highlight the clear potential of dual activation of GLP-1 and CCK1 receptors for the treatment of type 2 diabetes.

Using cholecystokinin to facilitate endoscopic clearance of large common bile duct stones.

AIM: To evaluate the effect of cholecystokinin (CCK) during extracorporeal shockwave lithotripsy (ESWL) in the clearance of common bile duct (CBD) stones in endoscopic retrograde cholangiopancreatography (ERCP). METHODS: Between January 2007 and September 2012, patients with large CBD stones who were treated with ESWL and ERCP were identified retrospectively. Patients were randomized in equal numbers to cholecystokinin (CCK) and no CCK groups. For each CCK case, a dose (3 ng/kg per min for 10 min) of sulfated octapeptide of CCK-8 was administered intravenously near the beginning of ESWL. ERCP was performed 4 h after a session of ESWL. The clearance rate of the CBD was assessed between the two groups. RESULTS: A total of 148 consecutive cases (CCK group: 74, no CCK group: 74) were tallied. Overall there were 234 ESWLs and 228 ERCPs in the 148 cases. The use of CCK showed a significantly higher rate of successful stone removal in the first ESWL/ERCP procedure (71.6% vs 55.4%, P = 0.035), but resulted in similar outcomes in the second (42.8% vs 39.4%) and third (41.7% vs 40.0%) sessions, as well as total stone clearance (90.5% vs 83.8%). The use of mechanical lithotripsy was reduced in the CCK group (6.8% vs 17.6%, P = 0.023), and extremely large stone (≥ 30 mm) removal was higher in the CCK group (72.7% vs 41.7%, P = 0.038). CONCLUSION: CCK during ESWL can aid with the clearance of CBD stones in the first ESWL/ERCP session. Mechanical lithotripsy usage was reduced and the extremely large stone (≥ 30 mm) clearance rate can be raised.

Intraperitoneal CCK and fourth-intraventricular Apo AIV require both peripheral and NTS CCK1R to reduce food intake in male rats.

Apolipoprotein AIV (Apo AIV) and cholecystokinin (CCK) are secreted in response to fat consumption, and both cause satiation via CCK 1 receptor (CCK-1R)-containing vagal afferent nerves to the nucleus of the solitary tract (NTS), where Apo AIV is also synthesized. Fasted male Long-Evans rats received ip CCK-8 or fourth-ventricular (i4vt) Apo AIV alone or in combination. Food intake and c-Fos proteins (a product of the c-Fos immediate-early gene) were assessed. i4vt Apo AIV and/or ip CCK at effective doses reduced food intake and activated c-Fos proteins in the NTS and hypothalamic arcuate nucleus and paraventricular nucleus. Blockade of the CCK-1R by i4vt lorglumide adjacent to the NTS attenuated the satiating and c-Fos-stimulating effects of CCK and Apo AIV, alone or in combination. Maintenance on a high-fat diet (HFD) for 10 weeks resulted in weight gain and attenuation of both the behavioral and c-Fos responses to a greater extent than occurred in low-fat diet-fed and pair-fed HFD animals. These observations suggest that NTS Apo AIV or/and peripheral CCK requires vagal CCK-1R signaling to elicit satiation and that maintenance on a HFD reduces the satiating capacity of these 2 signals.

[Blood serum cholecystokinin and clinical-functional variability of biliary pathology].

RESULTS: Basal and stimulated serum CCK concentrations were not statistically significant differences (p > 0.05) with the control group in patients studied in the whole and in patients subgroups, formed by the diagnosis of biliary pathology and the character of gallbladder emptying. Increased stimulated CCK concentration was found in patients with symptomatic variants. Reduce of serum-cholecystokinin concentration growth (ACCK) after intake of Sorbitol was revealed in subgroup of patients with low-symptom variant. Reduced sensitivity of the gallbladder to CCK was observed in subgroups of patients with gallbladder hypokinetic dyskinesia and one with symptomatic variant of biliary pathology. CONCLUSION: The sensitivity of the gallbladder neuromuscular apparatus to CCK is associated with clinical and functional variability of the biliary pathology.

CCK-8S increases the firing frequency of CCK-positive neurons and facilitates excitatory synaptic transmission in primary rat hippocampal neurons.

The neuropeptide cholecystokinin octapeptide (CCK) is involved in a variety of brain functions. In the hippocampus, most CCK is released from CCK-positive (CCK+) neurons, but the effects of CCK on CCK+ neurons are poorly understood. We employed primary hippocampal cultures to explore the modulatory effect of CCK on CCK+ neurons. CCK-8S (0.2 µM) was added to the culture medium from day in vitro 2 (DIV-2) to DIV-11. An adenovirus integrated with the CCK promoter was used to label CCK+ neurons. Whole-cell patch clamp recording was carried on to record the electrophysiology properties. The results show that: (1) CCK-8S significantly decreased membrane capacity but increased the membrane resistance (Rm) of CCK+ neurons, (2) CCK-8S increased action potential (AP) firing frequency of CCK+ neurons but did not affect the firing pattern, (3) CCK-8S facilitated CCK+ neuron excitatory synaptic transmission but attenuated inhibitory synaptic transmission, and (4) the expression of postsynaptic density-95 (PSD-95) in cultured hippocampal neurons was elevated by CCK-8S treatment. Our results demonstrate that CCK-8S significantly alters the membrane electrophysiological characteristics and synaptic activity of cultured hippocampal CCK+ neurons. These findings may enhance our understanding of the modulatory effect of CCK in the brain.

CCK-8S increased the filopodia and spines density in cultured hippocampal neurons of APP/PS1 and wild-type mice.

Cholecystokinin (CCK), a neuropeptide, is widely distributed in the brain. The function of CCK is involved in many brain functions including learning and memory, but the cellular mechanism is poorly understood. In the present study, we investigated the effect of CCK on dendritic filopodia and spines of cultured hippocampal neurons from wild-type and APP/PS1 mice. The cultured hippocampal neurons were infected with CMV-GFP (CMV promoter with green fluorescent protein) adenovirus 24h before image acquisition to display the subtle structure of dendrites. Cholecystokinin octapeptide sulfated (CCK-8S, 0.2µM) was added into the cultured solution from divided in vitro day 2 (DIV 2). A decrease of filopodia and spines density was observed in APP/PS1 mice compared with that of wild type mice. CCK-8S increased the density of filopodia and spines at DIV 7, DIV 14 and DIV 21 in hippocampal neurons of both wild-type and APP/PS1 mice. In addition, this effect was inhibited by CI988, an antagonist of CCK-2 receptor. Those results indicate that CCK-8S can influence the dendritic development and spine genesis of cultured hippocampal neurons derived from both wild-type and APP/PS1 mice. These data suggest that CCK may play an important role in learning and memory.

(pGlu-Gln)-CCK-8[mPEG]: a novel, long-acting, mini-PEGylated cholecystokinin (CCK) agonist that improves metabolic status in dietary-induced diabetes.

BACKGROUND: Cholecystokinin (CCK) is a gastrointestinal hormone that has been proposed as a potential therapeutic option for obesity-diabetes. As such, (pGlu-Gln)-CCK-8 is an N-terminally modified CCK-8 analogue with improved biological effectiveness over the native peptide. METHODS: The current study has examined the in vitro stability, biological activity and in vivo therapeutic applicability of a novel second generation mini-PEGylated form of (pGlu-Gln)-CCK-8, (pGlu-Gln)-CCK-8[mPEG]. RESULTS: (pGlu-Gln)-CCK-8[mPEG] was completely resistant to enzymatic degradation and in addition displayed similar insulinotropic (p<0.05 to p<0.001) and satiating effects (p<0.01 to p<0.001) as (pGlu-Gln)-CCK-8. This confirmed the capability of (pGlu-Gln)-CCK-8[mPEG] to bind to and activate the CCK receptor. Sub-chronic twice daily injection of (pGlu-Gln)-CCK-8[mPEG] in high fat fed mice for 35days significantly decreased body weight gain (p<0.05), food intake (p<0.01 to p<0.001) and triacylglycerol deposition in liver (p<0.001) and muscle (p<0.001). Furthermore, (pGlu-Gln)-CCK-8[mPEG] markedly improved intraperitoneal glucose tolerance (p<0.05) and insulin sensitivity (p<0.001). Despite this therapeutic profile, once daily injection of (pGlu-Gln)-CCK-8[mPEG] in high fat fed mice for 33days, at the same dose, was not associated with alterations in food intake and body weight. In addition, metabolic responses to exogenous glucose and insulin injection were similar to saline treated controls. CONCLUSION: These studies emphasise the therapeutic potential of (pGlu-Gln)-CCK-8[mPEG] and similar molecules. GENERAL SIGNIFICANCE: A more detailed analysis of the dose and administration schedule employed for (pGlu-Gln)-CCK-8[mPEG] could provide a novel and effective compound to treat obesity-diabetes.

Comparison of independent and combined metabolic effects of chronic treatment with (pGlu-Gln)-CCK-8 and long-acting GLP-1 and GIP mimetics in high fat-fed mice.

AIM: The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK) are gastrointestinal peptides with important physiological effects. However, rapid enzymatic degradation results in short-lived biological actions. METHODS: This study has examined metabolic actions of exendin-4, GIP[mPEG] and a novel CCK-8 analogue, (pGlu-Gln)-CCK-8 as enzymatically stable forms of GLP-1, GIP and CCK, respectively. RESULTS: All peptides significantly (p < 0.01-p < 0.001) stimulated insulin secretion from BRIN BD11 cells, and acute in vivo experiments confirmed prominent antihyperglycaemic and insulinotropic responses to GLP-1 or GIP receptor activation in normal mice. Twice daily injection of (pGlu-Gln)-CCK-8 alone and in combination with exendin-4 or GIP[mPEG] in high fat-fed mice significantly decreased accumulated food intake (p < 0.05-p < 0.01), body weight gain (p < 0.05-p < 0.01) and improved (p < 0.05) insulin sensitivity in high fat-fed mice. However, there was no evidence for superior effects compared to (pGlu-Gln)-CCK-8 alone. Combined treatment of (pGlu-Gln)-CCK-8 and exendin-4 resulted in significantly (p < 0.05) lowered circulating glucose levels and improved (p < 0.05) intraperitoneal glucose tolerance. These effects were superior to either treatment regime alone but not associated with altered insulin concentrations. A single injection of (pGlu-Gln)-CCK-8, or combined with exendin-4, significantly (p < 0.05) lowered blood glucose levels 24 h post injection in untreated high fat-fed mice. CONCLUSION: This study highlights the potential of (pGlu-Gln)-CCK-8 alone and in combination with incretin hormones for the treatment of type 2 diabetes.

Role of the vagus in the reduced pancreatic exocrine function in copper-deficient rats.

Copper plays an essential role in the function and development of the central nervous system and exocrine pancreas. Dietary copper limitation is known to result in noninflammatory atrophy of pancreatic acinar tissue. Our recent studies have suggested that vagal motoneurons regulate pancreatic exocrine secretion (PES) by activating selective subpopulations of neurons within vagovagal reflexive neurocircuits. We used a combination of in vivo, in vitro, and immunohistochemistry techniques in a rat model of copper deficiency to investigate the effects of a copper-deficient diet on the neural pathways controlling PES. Duodenal infusions of Ensure or casein, as well as microinjections of sulfated CCK-8, into the dorsal vagal complex resulted in an attenuated stimulation of PES in copper-deficient animals compared with controls. Immunohistochemistry of brain stem slices revealed that copper deficiency reduced the number of tyrosine hydroxylase-immunoreactive, but not neuronal nitric oxide synthase- or choline acetyltransferase-immunoreactive, neurons in the dorsal motor nucleus of the vagus (DMV). Moreover, a copper-deficient diet reduced the number of large (>11 neurons), but not small, intrapancreatic ganglia. Electrophysiological recordings showed that DMV neurons from copper-deficient rats are less responsive to CCK-8 or pancreatic polypeptide than are DMV neurons from control rats. Our results demonstrate that copper deficiency decreases efferent vagal outflow to the exocrine pancreas. These data indicate that the combined selective loss of acinar pancreatic tissue and the decreased excitability of efferent vagal neurons induce a deficit in the vagal modulation of PES.

Chemical cholecystokinin receptor activation protects against obesity-diabetes in high fat fed mice and has sustainable beneficial effects in genetic ob/ob mice.

The current study has determined the ability of (pGlu-Gln)-CCK-8 to counter the development of diet-induced obesity-diabetes and examined persistence of beneficial metabolic effects in high fat and ob/ob mice, respectively. Twice daily injection of (pGlu-Gln)-CCK-8 in normal mice transferred to a high fat diet reduced energy intake (p < 0.001), body weight (p < 0.01), circulating insulin and LDL-cholesterol (p < 0.001) and improved insulin sensitivity (p < 0.001) as well as oral and intraperitoneal (p < 0.001) glucose tolerance. Energy intake, body weight, circulating insulin and glucose tolerance of (pGlu-Gln)-CCK-8 mice were similar to lean controls. In addition, (pGlu-Gln)-CCK-8 prevented the effect of high fat feeding on triacylglycerol accumulation in liver and muscle. Interestingly, (pGlu-Gln)-CCK-8 significantly (p < 0.001) elevated pancreatic glucagon content. Histological examination of the pancreata of (pGlu-Gln)-CCK-8 mice revealed no changes in islet number or size, but there was increased turnover of beta-cells with significantly (p < 0.001) increased numbers of peripherally located alpha-cells, co-expressing both glucagon and GLP-1. Beneficial metabolic effects were observed similarly in ob/ob mice treated twice daily with (pGlu-Gln)-CCK-8 for 18 days, including significantly reduced energy intake (p < 0.05), body weight (p < 0.05 to p < 0.01), circulating glucose (p < 0.05 to p < 0.01) and insulin (p < 0.05 to p < 0.001) and improved glucose tolerance (p < 0.05) and insulin sensitivity (p < 0.001). Notably, these beneficial effects were still evident 18 days following cessation of treatment. These studies emphasize the potential of (pGlu-Gln)-CCK-8 for the treatment of obesity-diabetes.

Comparison of the independent and combined metabolic effects of subchronic modulation of CCK and GIP receptor action in obesity-related diabetes.

OBJECTIVE: Compromise of gastric inhibitory polypeptide (GIP) receptor action and activation of cholecystokinin (CCK) receptors represent mechanistically different approaches to the possible treatment of obesity-related diabetes. In the present study, we have compared the individual and combined effects of (Pro(3))GIP[mPEG] and (pGlu-Gln)-CCK-8 as an enzymatically stable GIP receptor antagonist and CCK receptor agonist molecule, respectively. RESULTS: Twice-daily injections of (pGlu-Gln)-CCK-8 alone and in combination with (Pro(3))GIP[mPEG] in high-fat-fed mice for 34 days significantly decreased the energy intake throughout the entire study (P<0.05 to P<0.01). Body weights were significantly depressed (P<0.05 to P<0.01) in all treatment groups from day 18 onwards. Administration of (pGlu-Gln)-CCK-8, (Pro(3))GIP[mPEG] or a combination of both peptides significantly (P<0.01 to P<0.001) decreased the overall glycaemic excursion in response to both oral and intraperitoneal glucose challenge when compared with the controls. Furthermore, oral glucose tolerance returned to lean control levels in all treatment groups. The beneficial effects on glucose homeostasis were not associated with altered insulin levels in any of the treatment groups. In keeping with this, the estimated insulin sensitivity was restored to control levels by twice-daily treatment with (pGlu-Gln)-CCK-8, (Pro(3))GIP[mPEG] or a combination of both peptides. The blood lipid profile on day 34 was not significantly different between the high-fat controls and all treated mice. CONCLUSION: These studies highlight the potential of (pGlu-Gln)-CCK-8 and (Pro(3))GIP[mPEG] in the treatment of obesity-related diabetes, but there was no evidence of a synergistic effect of the combined treatment.

Metabolic effects of activation of CCK receptor signaling pathways by twice-daily administration of the enzyme-resistant CCK-8 analog, (pGlu-Gln)-CCK-8, in normal mice.

Cholecystokinin (CCK) is a hormone that has important physiological effects on energy balance. This study has used a stable CCK(1) receptor agonist, (pGlu-Gln)-CCK-8, to evaluate the metabolic effects of prolonged administration in normal mice. Twice-daily injection of (pGlu-Gln)-CCK-8 for 28 days resulted in significantly lowered body weights (P<0.05) on days 24 and 28, which was associated with decreased accumulated calorie intake (P<0.01) from day 12 onward. Nonfasting plasma glucose was significantly reduced (P<0.05) on day 28, while plasma insulin concentrations were increased (P<0.05). After 28 days, glucose tolerance and glucose-mediated insulin secretion were not significantly different in (pGlu-Gln)-CCK-8-treated mice. However, following a 15-min refeeding period in 18-h fasted mice, glucose levels were significantly (P<0.05) decreased by (pGlu-Gln)-CCK-8 despite similar food intake and nutrient-induced insulin levels. Insulin sensitivity in (pGlu-Gln)-CCK-8-treated mice was significantly (P<0.01) improved compared with controls. Accumulation of triacylglycerol in liver was reduced (P<0.01) but there were no differences in circulating cholesterol and triacylglycerol concentrations, as well as triacylglycerol content of pancreatic, muscle, and adipose tissue in (pGlu-Gln)-CCK-8 mice. These data highlight the beneficial metabolic effects of prolonged (pGlu-Gln)-CCK-8 administration and confirm a lack of detrimental effects.