Plasma somatostatin response to an oral mixed test meal in cirrhotic patients

Frequency and Causes of False-Positive Elevated Plasma Concentrations of Fasting Gut Hormones in a Specialist Neuroendocrine Tumor Center

INTRODUCTION

In the UK, the fasting plasma concentrations of a panel of gut hormones (comprising vasoactive intestinal peptide (VIP), gastrin, pancreatic polypeptide (PP), glucagon, somatostatin and chromogranin A) are measured to evaluate patients who have or who (due to unexplained and compatible symptoms) are suspected of having neuroendocrine tumors (NETs). False positive elevated hormone concentrations are sometimes found.

OBJECTIVE

To evaluate the frequency and implications of false positive fasting gut hormone results.

METHODS

Retrospective audit of fasting gut hormone profile results at a large UK university teaching hospital over 12 months.

RESULTS

Fasting gut hormone concentrations were measured in 231 patients during 2017. No NETs were found in the 88 patients who had this test performed only to investigate symptoms. 31 false positive gastrin, 8 false positive chromogranin A, two false positive glucagon, three false positive somatostatin, one false positive PP, and one false positive VIP results were found. We extended the audit for glucagon and somatostatin for an additional two years and found seven probable false-positive raised glucagon concentrations and four probable false-positive elevated plasma somatostatin concentrations in total.

CONCLUSIONS

False-positive elevations of plasma gastrin and chromogranin A were common and causes such as proton pump inhibitor use or inadequate fasting accounted for most cases. Elevated plasma concentrations of the other gut hormones were also detected in patients who had no other evidence of NET. Other diagnoses (e.g. cirrhosis and medullary thyroid carcinoma for hypersomatostatinemia and type 2 diabetes mellitus, pancreatitis, liver or renal impairment for hyperglucagonemia) may cause these false positive results.

Gallstones in Patients with Chronic Liver Diseases

With prevalence of 10-20% in adults in developed countries, gallstone disease (GSD) is one of the most prevalent and costly gastrointestinal tract disorders in the world. In addition to gallstone disease, chronic liver disease (CLD) is also an important global public health problem. The reported frequency of gallstone in chronic liver disease tends to be higher. The prevalence of gallstone disease might be related to age, gender, etiology, and severity of liver disease in patients with chronic liver disease. In this review, the aim was to identify the epidemiology, mechanisms, and treatment strategies of gallstone disease in chronic liver disease patients.

Gallbladder hyporesponsiveness to an exogenous nitric oxide donor, glyceryl trinitrate, in patients with advanced liver cirrhosis

OBJECTIVE

An increased production of nitric oxide (NO) in liver cirrhosis has been documented. NO could intervene in regulating gallbladder contraction, as suggested by clinical and experimental studies. Our aim was to investigate the influence of an NO donor on gallbladder motility in cirrhotic patients in relation to the severity of liver cirrhosis.

METHODS

The subjects were six controls and 18 patients with liver cirrhosis (six in each Child class). Gallbladder emptying was monitored by ultrasound for 90 min after a mixed meal (14 g fat, 425 kcal). Fasting gallbladder volume, minimal residual volume, ejection fraction, area under emptying curve, and half contraction time of the gallbladder were assessed at 15-min intervals. The patients were evaluated on two consecutive days, with or without perlingual administration of 0.5 mg glyceryl trinitrate (GTN). Statistical analysis was performed by the two-tailed Student's t test and Pearson's correlation coefficient.

RESULTS

GTN significantly reduced gallbladder motility in controls and compensated cirrhotics (p < 0.02), but had no effect upon gallbladder emptying in Child class B and C cirrhotics.

CONCLUSIONS

Gallbladder hypocontractility in liver cirrhosis is related to the severity of the disease. This study is the first to show that GTN has no effect upon gallbladder motility in advanced liver cirrhosis when administered in doses that induce relaxation in controls and compensated cirrhosis.

Plasma somatostatin response to an oral test meal in liver transplant patients

Ten liver transplant patients were studied in basal conditions and after ingestion of a standard mixed test meal. Control groups included 10 normal subjects, 10 patients with nonalcoholic liver cirrhosis, and seven kidney transplant patients. Plasma somatostatin, blood glucose, and plasma insulin, C-peptide, and glucagon were determined before and 15, 30, 45, 60, 90, 120, and 180 minutes after the start of the meal. In liver transplant patients, basal somatostatin and insulin levels were significantly lower than in cirrhotics and were comparable to those recorded in controls and in kidney transplant patients. The time course of the somatostatin secretory response after the meal was similar in any group, but the increase, evaluated as the incremental area above baseline, was significantly higher in liver transplant patients than in controls and cirrhotics and comparable to that recorded in kidney transplant patients. Insulin incremental areas were also lower than in cirrhotics and comparable to those recorded in controls and kidney transplant patients. The data suggest that in liver transplant patients an increased somatostatin response to a meal may be related to a relative beta-cell secretory defect, which in turn seems consequent to immunosuppressive treatment.

Gallbladder emptying, plasma levels of estradiol and progesterone, and cholecystokinin secretion in liver cirrhosis

Defective gallbladder emptying has been proposed as a possible accessory pathogenetic factor to explain the increased prevalence of gallstones in liver cirrhosis. In this study we have evaluated the fasting volume and the meal-stimulated emptying of the gallbladder, the plasma levels of estradiol and progesterone, and the basal and postprandial secretion of cholecystokinin in Child A cirrhotic patients compared to normal subjects. Basal (42.2 +/- 27 vs 22.8 +/- 8.4 ml) (P < 0.002) and residual (8.4 +/- 8.7 vs 4.6 +/- 3.8 ml) (P < 0.05) gallbladder volumes were higher in cirrhotics but neither the integrated gallbladder response to meal nor the maximal percentage of emptying was significantly different. Circulating estradiol and progesterone was slightly increased in only 1/13 and 5/13 cirrhotics, respectively. In eight cirrhotics and seven normals taken from the overall populations, the secretion of cholecystokinin was also measured. The fasting plasma level of cholecystokinin was higher in the cirrhotics (6.71 +/- 5.08 vs 2.02 +/- 0.46 pmol/liter) (P < 0.01). The meal-stimulated integrated plasma cholecystokinin response also was greater in cirrhotics (438.5 +/- 615 pmol/liter/270 min) than in normals (153 +/- 170.4 pmol/liter/270 min), but this difference was not significant because of the small study population. In spite of a normal kinetics of postprandial emptying, cirrhotic patients show increased fasting gallbladder volume and increased plasma levels of basal and postprandial cholecystokinin. Circulating estradiol and progesterone do not seem to be responsible for the large gallbladder volume found in liver cirrhosis.

An experimental study on somatostatin receptors in the brains of hepatic encephalopathy rats

The present study was undertaken to evaluate the effect of somatostatin (SS) receptor, a brain-gut peptide receptor which is capable of inhibiting central neurons, on the pathogenesis of hepatic encephalopathy (HE). By means of radioligand binding assay, SS receptors in crude synaptosomal membrane of rat brains were investigated in a rat model of HE induced by partial hepatectomy following carbon tetrachloride intoxication and in controls. Binding to SS receptor was studied using 125 I-SS as radioligand. Scatchard analysis of binding data was linear, yielding a dissociation constant (Kd) of 3.99 +/- 0.22 nmol/L and a maximal binding capacity (Bmax) of 238 +/- 14.2 fmol/mg of protein in HE rats. Only increased Bmax values were observed (P < 0.005), while the Kd values were statistically unchanged (P > 0.50), in HE rats as compared with those in controls. The results suggest that the changes of SS receptors in brains play a significant role in the pathogenesis of HE. The mechanism of HE induced by the alterations of SS receptors in the brains was discussed in this paper.

Intestinal fat does not inhibit gastric function through a hormonal somatostatin mechanism in dogs

In awake dogs with chronic gastric, duodenal, and jejunal fistulas, F(ab)1 fragments of somatostatin monoclonal antibody (mAb S607) were administered intravenously (IV) to test the hypothesis that intraintestinal lipid inhibits peptone-stimulated gastric acid secretion and emptying by a hormonal somatostatin mechanism. Plasma somatostatin was increased significantly by duodenal and jejunal perfusion with 20% lipid. Somatostatin administered IV caused dose-dependent inhibition of meal-stimulated gastric acid secretion and gastric emptying similar to that seen after intestinal perfusion with lipid. Administration of mAb S607 F(ab)1 fragments significantly reversed somatostatin (400 pmol.kg-1.h-1, IV)-induced inhibition of peptone-stimulated acid output and gastric emptying. Acid output inhibited by intraduodenal lipid was reversed partially after F(ab)1 administration, but the inhibitory effect of intrajejunal lipid was not altered. Inhibition of acid secretion by IV somatostatin and by intraintestinal fat was not caused by a decrease in circulating gastrin concentrations. Gastric emptying delayed by intraintestinal lipid was unaffected by antibody administration. Somatostatin does not appear to be a major hormonal mediator of intestinal fat-induced inhibition of gastric acid secretion or delayed gastric emptying in dogs.