Eric Ville

Physiological Study of pH Stability and Sensitivity to Pepsin of Human Gastric Lipase

Background/Aims: The aim of this study was to exactly determine the pH stability of human gastric lipase (HGL) and to investigate the mechanism underlying the inactivation of HGL which occurs in gastric juice. Methods: Samples of human gastric juice and purified HGL were incubated at various pH values ranging from 0.5 to 8.0, and the residual HGL activity was measured as a function of time using the pHstat technique. Samples of purified HGL were also incubated in the presence of human pepsin. Electrophoresis and Western blot analysis were performed on all the samples in which HGL was inactivated. Results: HGL was found to be stable in gastric juice at pH values ranging from 2.0 to 7.0, especially between pH 3.0 and 5.0 (half-inactivation time >24 h). HGL activity decreased rapidly below pH 2.0 and above pH 7.0. The inactivation half times were only 43 ± 9 and 24 ± 18 min at pH 1 and pH 8, respectively. The pH stability of purified HGL was much lower than that of HGL in gastric juice. Acid or alkaline inactivation of HGL could occur without any prior proteolytic degradation, and this inactivation was irreversible. However, proteolytic degradation of HGL by pepsin also occurred at very low pH values, probably because the acid-denatured HGL is more sensitive to proteolytic cleavage by pepsin. An ex vivo study of HGL activity in several gastric juice samples showed that the HGL activity decreased with the pH of the sample, in both basal and pentagastrin-stimulated gastric juice. Conclusion: Although HGL is not as stable as it was previously thought to be under acidic conditions, it is nevertheless the most stable acid lipase and constitutes a good candidate tool for enzyme substitution therapy.

Endoscopic treatment of the main pancreatic duct: correlations among morphology, manometry, and clinical follow-up.

SummaryBackground and Aim. During the course of chronic pancreatitis, the gradual increase in the main pancreatic duct pressure is the main pathophysiological factor responsible for pain, but up to now, the intraductal pressure has never been measured during and after endoscopic stenting and correlated with clinical results. Pressure measurements of this kind could thus provide objective information about the useful duration of stenting period. Methods. Main pancreatic duct pressure was measured by performing endoscopic manometry on 13 chronic pancreatitis symptomatic patients (10 men, 3 women, mean age: 45.1 ± 7.9 yr); clinical follow-up was carried out for a period of 29.0±16.1 mo. Before treatment, the main anatomical alteration present was a localized stenosis of the main pancreatic duct, i.e., one with a diameter of less than 2 mm (chronic pancreatitis alone), 10 cases; chronic pancreatitis associated with pancreas divisum, 3 cases). Stenosis was treated by endoscopic stenting: 7 F stent (7 cases) and 12 F stent (6 cases). The pressure was measured simultaneously in the duodenum (zero level) and within the main pancreatic duct, using an electronic device. The pancreatico-duodenal gradient was taken to be the difference between the pressure in the main pancreatic duct and the duodenum. Results. The endoscopic stenting induced a nonsignificant decrease in the intraductal pressure (p=0.16). Among the 9 patients with a normal pressure at the end of the stenting and a successful anatomical outcome, 6 were painless during the follow-up period whereas 3 presented with recurrent pancreatic-type pain. The remaining 4 patients were symptom-free during the entire follow-up period, although the main pancreatic duct pressure was high at the end of the stenting and the stenosis was not completely cured.Conclusion. The intraductal pressure at the end of the stenting period was perfectly correlated with the anatomical result, whether or not it was successful, but was not an accurate predictor of a favorable clinical outcome in patients with a poor anatomical result.

Lymph node enlargement within the hepatoduodenal ligament in patients with chronic hepatitis C reflects the immunological cellular response of the host

BACKGROUND/AIMS Lymph nodes in the hepatoduodenal ligament seem to be a common ultrasonographic finding in patients with chronic hepatitis C. Lymphadenopathic enlargement is associated with the histological hepatic features reflecting the immunological response of the host, but the correlation between lymphadenopathy, liver histology and the cellular immunoreactivity of the host has never been studied. AIM (1) To specify the prevalence of lymph nodes within the hepatoduodenal ligament; and (2) to investigate whether lymphadenopathies might reflect the immunological response of the host. METHODS One hundred and eleven patients were enrolled in this study. Eleven chronic hepatitis B patients and 34 healthy volunteers served as controls. RESULTS Lymph nodes were detectable in 90 out of the 104 chronic hepatitis C patients studied. After logistic regression, a high CD8 level and the absence of post hepatitis C cirrhosis were associated with lymph node enlargement. The total lymph node volume was correlated with transaminase levels, inflammatory activity, and stage of fibrosis. CONCLUSIONS (1) The prevalence of lymph nodes within the hepatoduodenal ligament is high; (2) lymph node enlargement is correlated with the immunological cellular response of the host; and (3) the total lymph node volume is correlated with hepatic necroinflammatory markers and the stage of fibrosis.

Effects of Lansoprazole on Human Gastric Lipase Secretion and Intragastric Lipolysis in Healthy Human Volunteers

Background: Lansoprazole is a potent proton-pump inhibitor (PPI) of parietal cells, which reduces the secretion of gastric acid. Although human gastric lipase (HGL) is produced only by the chief cells of the stomach, the possibility that interactions may occur between lansoprazole and HGL has never been addressed so far in humans. The aim of this study was therefore to quantify the effects of lansoprazole on HGL secretion and intragastric lipolysis during the ingestion of test meals by healthy human volunteers. Methods: Six healthy volunteers were intubated twice with a gastric and a duodenal tube, before ingesting a standard liquid test meal alone (–PPI experiments) and after 7 days of lansoprazole treatment (+PPI experiments). The HGL concentration was assessed in gastric and duodenal samples by measuring the lipase activity using a pH-stat, and the lipolysis products were quantified by performing thin layer chromatography. The level of intragastric lipolysis was defined as the percentage acyl chains released from the meal triglycerides. The pyloric outputs of HGL and lipolysis products were calculated, based on the use of a non-absorbable marker added to the meal. Results: The pH of the gastric contents was significantly higher in the +PPI experiments than in the –PPI experiments (p < 0.05), since mean values of 4.3 ± 2.5 and 2.2 ± 1.6, respectively, were recorded at the end of the gastric emptying of the meal. The HGL concentrations recorded during the meal were found to be higher in the experiments with lansoprazole (p < 0.05) than in those without lansopra- zole, but the HGL secretion levels (–PPI: 15.4 ± 8.0 mg; +PPI: 19.0 ± 7.4 mg) and the intragastric lipolysis (–PPI: 24.0 ± 8.0%; +PPI: 23.6 ± 6.8%) were not significantly affected by lansoprazole (p > 0.05 in both cases). Conclusion: Lansoprazole affected neither the HGL secretion nor the intragastric lipolysis levels, although an increase was observed in the intragastric pH at the end of the gastric emptying of the meal. The HGL concentration increased, however, due to the decrease in the acid secretion process, resulting in less diluted gastric contents.

Advantage of Expressing the Variations in Some Digestive Parameters as a Function of Gastric Emptying instead of Time

Background/Aim: Gastric emptying is a major cause of variability when studying gastrointestinal parameters as a function of time. Here, we investigate whether the parametric variability could be reduced by running experiments on a gastric emptying basis rather than on a time basis. Methods: Healthy volunteers were intubated with gastric and duodenal tubes and were given a liquid meal containing polyethylene glycol to monitor gastric emptying. Gastric pH and human gastric lipase (HGL) concentrations were measured. Their variations were plotted as a function of either time or gastric emptying (%). In both cases, mean curves of variation were established by polynomial regression. Results: When time was the variable used, the overall deviation of the experimental values from the values given by the best-fitting curve was high (χ2 = 33 for gastric pH; χ2 = 1,744 for HGL), and the individual deviations increased with time. When gastric emptying was the variable used, the overall deviation of the experimental values from the values given by the best-fitting curve was much lower (χ2 = 10 for gastric pH; χ2 = 642 for HGL). Conclusions: Expressing gastric pH or HGL concentration as a function of gastric emptying instead of time makes it possible to reduce the individual variability. This new type of data analysis may be of a general interest to observe specific variations of gastrointestinal parameters induced by drugs, hormones, and meals, and that might be masked by the large intrinsic variability induced by gastric emptying.

Influence of lansoprazole on the human gastric lipase and the intragastric lipolysis in healthy volunteers

The role of Lewis antigens in the pathogenic process is not well understood. The aim of this study was to determine whether the Lewis antigen expression of H. pylori differed in isolates obtained from symptomatic and asymptomatic individuals. Lewis antigen expression status was determined by ELISA, and confirmation of LPS 0 side chain production in isolates not expressing Lewis antigen phenotype was conducted by SDS-PAGE. Expression of Lewis antigens by H. pylori isolates of symptomatic and asymptomatic individuals differed significantly in three main categories: I) Type I Lewis antigens (Lea and Le) were not expressed at all by isolates from asymptomatic individuals, as compared with low level expression by isolates from symptomatic individuals; 2)incidence of LeX expression was significantly reduced in isolates from asymptomatic individuals; 3) an increased proportion of isolates from asymptomatic individuals did not express any Lewis antigens at all. The identification of differences between H. pylori isolated from symptomatic and asymptomatic individuals is the first step to understanding the potential role Lewis antigens may play in the pathogenicity of this bacteria. The decrease in the LeX expression by isolates from asymptomatic individuals is particularly interesting as this antigen has been noted to be expressed in higher proportions of H. pylori isolated from patients with peptic ulcer disease. The isolation of a high proportion of H. pylori that do not express any Lewis antigens in asymptomatic strains may also indicate a host-mediated cross reaction to the H. pylori Lewis antigens that may cause the pathology seen in some symptomatic patients.