Influence of gastric inhibitory polypeptide on pentagastrin-stimulated gastric acid secretion in patients with type 2 diabetes and healthy controls

Safety of native glucose-dependent insulinotropic polypeptide in humans

In this systematic review, we assessed the safety and possible safety events of native glucose-dependent insulinotropic polypeptide (GIP)(1-42) in human studies with administration of synthetic human GIP. We searched the PubMed database for all trials investigating synthetic human GIP(1-42) administration. A total of 67 studies were included. Study duration ranged from 30 min to 6 days. In addition to healthy individuals, the studies included individuals with impaired glucose tolerance, type 2 diabetes, type 1 diabetes, chronic pancreatitis and secondary diabetes, latent autoimmune diabetes in adults, diabetes caused by a mutation in the hepatocyte nuclear factor 1-alpha gene, end-stage renal disease, chronic renal insufficiency, critical illness, hypoparathyroidism, or cystic fibrosis-related diabetes. Of the included studies, 78% did not mention safety events, 10% of the studies reported that no safety events were observed in relation to GIP administration, and 15% of the studies reported safety events in relation to GIP administration with most frequently reported event being a moderate and transient increased heart rate. Gastrointestinal safety events, and changes in blood pressure were also reported. Plasma concentration of active GIP(1-42) increased linearly with dose independent of participant phenotype. There was no significant correlation between achieved maximal concentration of GIP(1-42) and reported safety events. Clearance rates of GIP(1-42) were similar between participant groups. In conclusion, the available data indicate that GIP(1-42) in short-term (up to 6 days) infusion studies is generally well-tolerated. The long-term safety of continuous GIP(1-42) administration is unknown.

Effects of Lixisenatide Versus Liraglutide (Short- and Long-Acting GLP-1 Receptor Agonists) on Esophageal and Gastric Function in Patients With Type 2 Diabetes

OBJECTIVE

Short-acting glucagon-like peptide 1 receptor agonists (GLP-1 RAs) decelerate gastric emptying more than long-acting GLP-1 RAs. Delayed gastric emptying is a risk factor for gastroesophageal reflux disease. We aimed to measure esophageal reflux and function as well as gastric emptying and acid secretion during treatment with short-acting (lixisenatide) and long-acting (liraglutide) GLP-1 RAs.

RESEARCH DESIGN AND METHODS

A total of 57 subjects with type 2 diabetes were randomized to a 10-week treatment with lixisenatide or liraglutide. Changes from baseline in the number of reflux episodes during 24-h pH registration in the lower esophagus, lower esophagus sphincter pressure, gastric emptying (¹³C-sodium octanoate acid breath test), and gastric acid secretion (¹³C-calcium carbonate breath test) were analyzed.

RESULTS

Gastric emptying half-time was delayed by 52 min (Δ 95% CI 16, 88) with lixisenatide (P = 0.0065) and by 25 min (3, 46) with liraglutide (P = 0.025). There was no difference in the number of reflux episodes (mean ± SEM 33.7 ± 4.1 vs. 40.1 ± 5.3 for lixisenatide and liraglutide, respectively, P = 0.17) or the extent of gastroesophageal reflux (DeMeester score) (35.1 ± 6.7 vs. 39.7 ± 7.5, P = 0.61), with similar results for the individual GLP-1 RAs. No significant changes from baseline in other parameters of esophageal motility and lower esophageal sphincter function were observed. Gastric acidity decreased significantly by -20.7% (-40.6, -0.8) (P = 0.042) with the GLP-1 RAs.

CONCLUSIONS

Lixisenatide exerted a more pronounced influence on gastric emptying after breakfast than liraglutide. Neither lixisenatide nor liraglutide had significant effects on esophageal reflux or motility. Gastric acid secretion appears to be slightly reduced by GLP-1 RAs.

Reduced GLP-1R expression in gastric glands of patients with type 2 diabetes mellitus

BACKGROUND

The incretin effect is reduced in type 2 diabetes mellitus (T2DM) patients. Whether the impaired function of the enteropancreatic axis in these patients is due to defective GLP-1 receptor (GLP-1R) expression in extrapancreatic target organs is not known.

AIMS AND METHODS

To compare the GLP-1R expression and distribution in gastric mucosa biopsies of patients with (n =22) and without (n =22) T2DM referred for routine esophagogastroduodenoscopies. GLP-1R mRNA levels were estimated by real-time PCR. The intensity of GLP-1R immunostaining, frequency, and types of glandular cells bearing GLP-1R and their glandular distribution in different stomach mucosa regions were evaluated by immunohistochemical morphological semiquantitative and quantitative analysis.

RESULTS

Mean mRNA GLP-1R levels were significantly reduced in patients with T2DM compared with nondiabetic patients (P < .02). Immunohistochemical analysis revealed that the reduced GLP-1R expression in T2DM patients was due to a decreased intensity of immunostaining (P < .01). The number of glandular GLP-1R-bearing cells in both body and antrum mucosa was decreased in T2DM patients. Most notably, the frequency of GLP-1R immunoreactive acid-secreting parietal cells was reduced in the neck area of the gastric principal glands of T2DM patients (P < .01). No correlation was found between the reduced GLP-1R expression and clinical parameters including body mass index, age, glycosylated hemoglobin, and disease duration.

CONCLUSION

This is the first evidence of reduced GLP-1R expression in gastric glands of T2DM patients. These data demonstrate that the defective function of the incretin axis in T2DM may also result from decreased GLP-1R expression in its extrapancreatic target organs.

Differences in intragastric pH in diabetic vs. idiopathic gastroparesis: relation to degree of gastric retention

Evidence suggests that distinct mechanisms underlie diabetic and idiopathic gastroparesis. Differences in gastric acid in gastroparesis of different etiologies and varying degrees of gastric stasis are uninvestigated. We tested the hypotheses that 1) gastric pH profiles show differential alteration in diabetic vs. idiopathic gastroparesis and 2) abnormal pH profiles relate to the severity of gastric stasis. Sixty-four healthy control subjects and 44 gastroparesis patients (20 diabetic, 24 idiopathic) swallowed wireless transmitting capsules and then consumed (99m)Tc-sulfur colloid-labeled meals for gastric scintigraphy. Gastric pH from the capsule was recorded every 5 s. Basal pH was higher in diabetic (3.64 +/- 0.41) vs. control subjects (1.90 +/- 0.18) and idiopathic subjects (2.41 +/- 0.42; P < 0.05). Meals evoked initial pH increases that were greater in diabetic (4.98 +/- 0.32) than idiopathic patients (3.89 +/- 0.39; P = 0.03) but not control subjects (4.48 +/- 0.14). pH nadirs prior to gastric capsule evacuation were higher in diabetic patients (1.50 +/- 0.23) than control subjects (0.58 +/- 0.11; P = 0.003). Four-hour gastric retention was similar in diabetic (18.3 +/- 0.5%) and idiopathic (19.4 +/- 0.5%) patients but higher than control subjects (2.2 +/- 0.5%; P < 0.001). Compared with control subjects, those with moderate-severe stasis (>20% retention at 4 h) had higher basal (3.91 +/- 0.55) and nadir pH (2.23 +/- 0.42) values (P < 0.05). In subgroup analyses, both diabetic and idiopathic patients with moderate-severe gastroparesis exhibited increased pH parameters vs. those with mild gastroparesis. In conclusion, diabetic patients with gastroparesis exhibit reduced gastric acid, an effect more pronounced in those with severely delayed gastric emptying. Idiopathic gastroparetic subjects exhibit nearly normal acid profiles, although those with severely delayed emptying show reduced acid vs. those with mild delays. Thus both etiology and degree of gastric stasis determine gastric acidity in gastroparesis.

Glucagon-like peptide 2 inhibits ghrelin secretion in humans

INTRODUCTION

The growth hormone secretagogue receptor ligand ghrelin is known to play a pivotal role in the central nervous control of energy homeostasis. Circulating ghrelin levels are high under fasting conditions and decline after meal ingestion, but the mechanisms underlying the postprandial drop in ghrelin levels are poorly understood. In the present study we addressed, whether (1) exogenous GLP-2 administration decreases ghrelin levels and (2) what other endogenous factors are related to ghrelin secretion under fasting conditions.

PATIENTS AND METHODS

Fifteen healthy male volunteers were studied with the intravenous infusion of GLP-2 (2 pmol l(-1) min(-1)) or placebo over 120 min in the fasting state. Plasma concentrations of glucose, insulin, C-peptide, glucagon, intact GLP-2 and ghrelin were determined.

RESULTS

During the infusion of GLP-2, plasma concentrations of intact GLP-2 increased from 10.0+/-1.5 pmol/l to steady-state levels of 207.7+/-8.3 pmol/l (p < 0.0001). Administration of GLP-2 led to an approximately 10% reduction in ghrelin concentrations, whereas placebo administration was without an effect (p < 0.001). After cessation of the GLP-2 infusion, ghrelin levels returned to baseline values, and were no longer different from those in the placebo experiments. There was a strong inverse linear relationship between the fasting concentrations of ghrelin and the respective levels of glucose, insulin and C-peptide (r = 0.49, p < 0.01; r = 0.55, p < 0.01 and r = 0.59, p < 0.001, respectively). In contrast, there was no detectable association between fasting ghrelin levels and the ambient concentrations of glucagon or intact GLP-2.

CONCLUSIONS

GLP-2 inhibits ghrelin secretion in humans at plasma levels of approximately 200 pmol/l. However, the physiological importance of this effect appears to be minor compared to the actions of insulin and glucose.