Expression of cholecystokinin2-receptor in rat and human L cells and the stimulation of glucagon-like peptide-1 secretion by gastrin treatment

The critical role of CCK in the regulation of food intake and diet-induced obesity

In 1973, Gibbs, Young, and Smith showed that exogenous cholecystokinin (CCK) administration reduces food intake in rats. This initial report has led to thousands of studies investigating the physiological role of CCK in regulating feeding behavior. CCK is released from enteroendocrine I cells present along the gastrointestinal (GI) tract. CCK binding to its receptor CCK1R leads to vagal afferent activation providing post-ingestive feedback to the hindbrain. Vagal afferent neurons' (VAN) sensitivity to CCK is modulated by energy status while CCK signaling regulates gene expression of other feeding related signals and receptors expressed by VAN. In addition to its satiation effects, CCK acts all along the GI tract to optimize digestion and nutrient absorption. Diet-induced obesity (DIO) is characterized by reduced sensitivity to CCK and every part of the CCK system is negatively affected by chronic intake of energy-dense foods. EEC have recently been shown to adapt to diet, CCK1R is affected by dietary fats consumption, and the VAN phenotypic flexibility is lost in DIO. Altered endocannabinoid tone, changes in gut microbiota composition, and chronic inflammation are currently being explored as potential mechanisms for diet driven loss in CCK signaling. This review discusses our current understanding of how CCK controls food intake in conditions of leanness and how control is lost in chronic energy excess and obesity, potentially perpetuating excessive intake.

CCK-1 and CCK-2 receptor agonism do not stimulate GLP-1 and neurotensin secretion in the isolated perfused rat small intestine or GLP-1 and PYY secretion in the rat colon

Gastrin and cholecystokinin (CCK) are hormones released from endocrine cells in the antral stomach (gastrin), the duodenum, and the jejunum (CCK). Recent reports, based on secretion experiments in an enteroendocrine cell line (NCI-H716) and gastrin receptor expression in proglucagon-expressing cells from the rat colon, suggested that gastrin could be a regulator of glucagon-like peptide-1 (GLP-1) secretion. To investigate these findings, we studied the acute effects of CCK-8 (a CCK1/CCK2 (gastrin) receptor agonist) and gastrin-17 (a CCK2(gastrin) receptor agonist) in robust ex vivo models: the isolated perfused rat small intestine and the isolated perfused rat colon. Small intestines from Wistar rats (n = 6), were perfused intraarterially over 80 min. During the perfusion, CCK (1 nmol/L) and gastrin (1 nmol/L) were infused over 10-min periods separated by washout/baseline periods. Colons from Wistar rats (n = 6) were perfused intraarterially over 100 min. During the perfusion, CCK (1 nmol/L), vasoactive intestinal peptide (VIP) (10 nmol/L), and glucose-dependent insulinotropic polypeptide (GIP) (1 nmol/L) were infused over 10-min periods separated by washout/baseline periods. In the perfused rat small intestines neither CCK nor gastrin stimulated the release of GLP-1 or neurotensin. In the perfused rat colon, neither CCK or VIP stimulated GLP-1 or peptide YY (PYY) release, but GIP stimulated both GLP-1 and PYY release. In both sets of experiments, bombesin, a gastrin-releasing peptide analog, served as a positive control. Our findings do not support the suggestion that gastrin or CCK participate in the acute regulation of intestinal GLP-1 secretion, but that GIP may play a role in the regulation of hormone secretion from the colon.

Gastrin secretion in normal subjects and diabetes patients is inhibited by glucagon-like peptide 1: a role in the gastric side effects of GLP-1-derived drugs?

Background: Randomized and controlled trials of glucagon-like peptide-1 (GLP-1) derived drugs have shown that the most frequent adverse symptoms are gastrointestinal. Some of the side effects such as dyspepsia, nausea and upper abdominal pain may well be of gastric origin. Since the antral hormone gastrin regulates gastric secretion of acid and enzymes and contributes to the regulation of gastric motility, we examined the effect of GLP-1 on the secretion of gastrin in normal subjects and diabetes patients.Method: Plasma was sampled from ten healthy subjects and ten patients with diabetes mellitus type 1 with glucose clamped between 6 and 9 mM. GLP-1 or saline were infused for 4 h during and after a meal. Plasma concentrations of gastrin and GLP-1 were measured using specific radioimmunoassays.Results: Basal plasma concentrations of gastrin were similar in controls and patients. After the meal, the gastrin concentrations rose significantly during saline infusion, whereas the GLP-1 infusion suppressed the secretion of gastrin significantly, most pronounced in the diabetes patients.Conclusions: The results show that GLP-1 infusion suppresses the postprandial secretion of gastrin in normal subjects and even more so in the diabetes patients. The results may therefore shed further light on the upper gastrointestinal side effects of GLP-1-derived drugs in diabetic patients.

Clinical factors associated with the occurrence of nausea and vomiting in type 2 diabetes patients treated with glucagon-like peptide-1 receptor agonists

AIMS/INTRODUCTION

Research has proved a correlation between glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and gastrointestinal adverse events. Predominantly, nausea and vomiting are frequent gastrointestinal adverse events that lead to the discontinuation of GLP-1 RAs treatment. The present study aims to investigate clinical factors related to nausea and vomiting, considering diabetic complications and agents affecting the gastrointestinal tract, such as proton pump inhibitors (PPIs) and histamine-2 receptor antagonists (H2RAs), in patients with type 2 diabetes treated with GLP-1 RAs.

MATERIALS AND METHODS

This retrospective study included Japanese patients with type 2 diabetes who started receiving GLP-1 RAs therapy. We assessed nausea and vomiting up to 48 weeks after treatment with GLP-1 RAs and used Fine-Gray's proportional hazards model to investigate clinical factors related to nausea and vomiting.

RESULTS

A total of 130 patients were included in this study. Patients with PPIs or H2RAs showed a higher incidence of nausea and vomiting at 48 weeks than those without PPIs or H2RAs. The multivariate analysis revealed that female sex, retinopathy and treatment with PPIs or H2RAs were statistically significant risk factors for nausea and vomiting. Analysis of patients without PPIs or H2RAs showed that female sex and retinopathy were also statistically significant risk factors.

CONCLUSIONS

The present study showed a significant correlation of PPIs or H2RAs, female sex, and diabetic retinopathy with nausea and vomiting in patients with type 2 diabetes treated with GLP-1 RAs. Hence, the occurrence of nausea and vomiting in patients with these factors warrants attention.

Cholecystokinin secretion is suppressed by glucagon-like peptide-1: clue to the mechanism of the adverse gallbladder events of GLP-1-derived drugs

OBJECTIVE

Recent randomized and controlled trials of drugs derived from the gut hormone glucagon-like peptide-1 (GLP-1) show that the most frequent adverse symptoms are gastrointestinal, including gallbladder-related side effects such as cholithiasis and cholecystitis. Since the gut hormone cholecystokinin (CCK) stimulates bile secretion and regulates gallbladder motility and emptying, we examined the effect of GLP-1 on the secretion of CCK in normal subjects and patients with type 1 diabetes mellitus.

MATERIALS AND METHODS

Plasma was sampled from 10 healthy subjects and 10 patients with diabetes. With plasma glucose concentrations clamped between 6 and 9 nmol/l, GLP-1 or saline was infused for 240 min during and after a meal. The plasma concentrations of CCK were measured with a highly specific radioimmunoassay.

RESULTS

Basal plasma concentrations of CCK were similar in the normal subjects and in the diabetes patients. During the meal, the CCK concentrations rose significantly during saline infusion, whereas the GLP-1 infusion suppressed the secretion of CCK significantly in both normal subjects and in the diabetes patients.

CONCLUSIONS

The results show that GLP-1 suppresses the secretion of CCK after a meal in normal and diabetic subjects. The suppression attenuates the gallbladder contractility. Our data, therefore, offer an explanation for the increased risk of adverse gallbladder events during treatment with GLP-1-derived drugs.

New Glucose-Lowering Agents for Diabetic Kidney Disease

The prevalence of diabetes mellitus is increasing and is associated with a range of complications including nephropathy. New antidiabetic agents are sought which also have positive effects to diminish diabetic complications. Examples of promising new classes of such agents are glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, and sodium-glucose cotransporter 2 inhibitors. In addition to cardiovascular protective effects such as weight loss and decreased blood pressure of some of these agents, there is evidence for renoprotective effects with these agents. This review elaborates on the main results of renoprotective effects of these 3 treatment classes. In conclusion, currently available trials have demonstrated renoprotective effects for certain glucagon-like peptide-1 receptor agonists, liraglutide and semaglutide, and the sodium-glucose cotransporter 2 inhibitors, empagliflozin and canagliflozin. Dipeptidyl peptidase-4 inhibitors did not show a significant renoprotective effect. Nevertheless, larger studies with respect to renoprotective effects of these 3 drug classes are currently being performed, and thus, no conclusions for all of these agents can yet be made.

No Association of Proton Pump Inhibitor Use with Fasting or Postload Glycaemia in Patients with Cardiovascular Disease: A Cross-Sectional Retrospective Study

Background: Proton pump inhibitor (PPI) use was reportedly associated with an excess of adverse cardiovascular (CV) events, thus making their systemic effects relevant to public health. PPIs reduce gastric acid secretion, causing increased gastrin release. Gastrin stimulates β-cell neogenesis and enhances insulin release, exerting an incretin-like effect. Our aim was to assess, if PPI usage is associated with altered glycaemia in patients with CV disease. Methods: We retrospectively analyzed medical records of 102 subjects (80 with ischemic heart disease) who underwent a routine oral glucose tolerance test while hospitalized in a cardiology department. Fasting and 2-h postload glucose levels were compared according to PPI use for ≥1 month prior to admission. Results: Compared to 51 subjects without PPIs, those on a PPI were older, more frequently male, had a lower body-mass index and a tendency to a worse renal function. PPI users and non-users exhibited similar glucose levels at baseline (5.6 ± 0.9 vs. 5.5 ± 1.1 mmol/l, P = 0.5) and 2-hrs post glucose intake (9.8 ± 3.0 vs. 9.9 ± 3.4 mmol/l, P = 0.9). This was consistent across subgroups stratified by gender or diabetes status. The results were substantially unchanged after adjustment for different characteristics of subjects with and without PPIs. Conclusions: PPI use does not appear associated with altered glycaemia in subjects with CV disease. Unchanged glucose tolerance despite PPI usage may result from simultaneous activation of pathways that counteract the putative PPI-induced incretin-like effect.

The gastrin-releasing peptide analog bombesin preserves exocrine and endocrine pancreas morphology and function during parenteral nutrition

Stimulation of digestive organs by enteric peptides is lost during total parental nutrition (PN). Here we examine the role of the enteric peptide bombesin (BBS) in stimulation of the exocrine and endocrine pancreas during PN. BBS protects against exocrine pancreas atrophy and dysfunction caused by PN. BBS also augments circulating insulin levels, suggesting an endocrine pancreas phenotype. While no significant changes in gross endocrine pancreas morphology were observed, pancreatic islets isolated from BBS-treated PN mice showed a significantly enhanced insulin secretion response to the glucagon-like peptide-1 (GLP-1) agonist exendin-4, correlating with enhanced GLP-1 receptor expression. BBS itself had no effect on islet function, as reflected in low expression of BBS receptors in islet samples. Intestinal BBS receptor expression was enhanced in PN with BBS, and circulating active GLP-1 levels were significantly enhanced in BBS-treated PN mice. We hypothesized that BBS preserved islet function indirectly, through the enteroendocrine cell-pancreas axis. We confirmed the ability of BBS to directly stimulate intestinal enteroid cells to express the GLP-1 precursor preproglucagon. In conclusion, BBS preserves the exocrine and endocrine pancreas functions during PN; however, the endocrine stimulation is likely indirect, through the enteroendocrine cell-pancreas axis.

Effect of proton pump inhibitors on glycemic control in patients with diabetes

Gastrin is a linear peptide hormone which is secreted mostly in the stomach pyloric antrum G cells. Although the main role of this hormone is the promotion of the secretion of gastric acid from the stomach parietal cells, gastrin can also behave as a growth factor and stimulate gastric cell proliferation. It is also reported that gastrin promotes β cell neogenesis in the pancreatic ductal complex, modest pancreatic β cell replication, and improvement of glucose tolerance in animal models, in which the remodeling of pancreatic tissues is promoted. These findings suggest the possibility that gastrin has the potential to promote an increase of β cell mass in pancreas, and therefore that gastrin may improve glucose tolerance. Proton pump inhibitors (PPIs) are wildly used clinically for the therapy of gastro-esophageal reflex disease, gastritis due to excess stomach acid, and gastric ulcers. PPIs indirectly elevate serum gastrin levels via a negative feedback effect. Recent evidence has revealed the beneficial effect of PPIs on glycemic control especially in patients with type 2 diabetes mellitus (T2DM), probably via the elevation of the levels of serum gastrin, although the detailed mechanism remains unclear. In addition, the beneficial effects of a combination therapy of gastrin or a PPI with a glucagon-like peptide-1 receptor agonist on glycemic control in animal models have been demonstrated. Although PPIs may be possible candidates for a new approach in the therapy of diabetes, a prospective, long-term, randomized, double-blind, placebo-controlled study is needed to establish the effect of PPIs on glycemic control in a large number of patients with T2DM.