The dynamics of gastritis

Protein acidification and hydrolysis by pepsin ensure efficient trypsin-catalyzed hydrolysis

Enzyme-catalysed hydrolysis is important in protein digestion. Protein hydrolysis is initiated by pepsin at low pH in the stomach. However, pepsin action and acidification happen simultaneously to gastric emptying, especially for liquid meals. Therefore, different extents of exposure to the gastric environment change the composition of the chyme that is emptied from the stomach into the small intestine over time. We assessed the susceptibility of a protein to trypsin-catalysed hydrolysis in the small intestine, depending on its pH and hydrolysis history, simulating chyme at different times after the onset of gastric emptying. Isothermal titration calorimetry was used to study the kinetics of pepsin and trypsin-catalysed hydrolysis. Bovine serum albumin (BSA) that was acidified and hydrolysed with pepsin, showed the highest extent and most efficient hydrolysis by trypsin. BSA in the chyme that would be first emptied from the stomach, virtually bypassing gastric acidity and peptic action, reduced trypsin-catalysed hydrolysis by up to 58% compared to the acidified, intact protein, and 77% less than the acidified, pepsin-hydrolysate. The least efficient substrate for trypsin-catalysed hydrolysis was the acidified, intact protein with a specificity constant (k_cat/K_m) nearly five times lower than that of the acidified, pepsin-hydrolysate. Our results illustrate the synergy between pepsin and trypsin hydrolysis, and indicate that gastric hydrolysis increases the efficiency of the subsequent trypsin-catalysed hydrolysis of a model protein in the small intestine.

The role of the gastrointestinal tract in calcium homeostasis and bone remodeling

While skeletal biology was approached in a rather isolated fashion in the past, an increasing understanding of the interplay between extraskeletal organs and bone remodeling has been obtained in recent years. This review will discuss recent advances in the field that have shed light on how the gastrointestinal tract and bone relate to each other. In particular, the importance of the GI tract in maintaining calcium homeostasis and skeletal integrity will be reviewed as impaired gastric acid production represents a major public health problem with possible implications for sufficient calcium absorption. Osteoporosis, the most prevalent bone disease worldwide, is caused not only by intrinsic defects affecting bone cell differentiation and function but also by a large set of extrinsic factors including hormonal disturbances, malnutrition, and iatrogenic drug application. Given the skeletal requirements of calcium, amino acids, and energy for bone turnover and renewal, it is not surprising that the gastrointestinal (GI) tract is of major importance for skeletal integrity.

Natural history of chronic gastritis in a population-based cohort

OBJECTIVE

To describe and explore the natural history of Helicobacter pylori infection and chronic gastritis in terms of gastric mucosal atrophy and ulcer development over time in a population-based cohort.

MATERIAL AND METHODS

A population-based cohort of 314 volunteers was re-screened (median follow-up interval of 8.4 years) with gastroduodenoscopy with biopsy, assessment of H. pylori status, analysis of pepsinogens, and monitoring of a nonsteroidal anti-inflammatory drug (NSAID) use and alcohol and smoking habits.

RESULTS

The incidence of duodenal or prepyloric ulcer was 0.45 per 100 person years and was associated with weekly NSAID use (odds ratios, OR 27.8), weekly alcohol consumption (OR 19.4) and smoking (OR 31.0), but not with H. pylori status. De novo infection with H. pylori was not observed, and the infection had disappeared in 11 of 113 subjects. Among subjects with chronic gastritis, the incidence of atrophy of the corpus mucosa was 1.4 per 100 person years. Atrophy development was related to age (OR 1.23) and to the severity of chronic inflammation in the corpus mucosa at baseline (OR 8.98). Substituting atrophy for subnormal S-pepsinogen I/S-pepsingen II gave similar results.

CONCLUSIONS

In this cohort, the minimum incidence of ulcer was 0.45 per 100 person years. Smoking, alcohol, and NSAIDs, but not H. pylori infection were significant risk factors. The incidence of atrophy of the corpus mucosa was 1.4 per 100 person years with a positive relation to age and to the degree of chronic inflammation at baseline. Atrophy was stationary in advanced stages.

Helicobacter pylori-related gastric histology classification using support-vector-machine-based feature selection

This study presents a computer-aided diagnosis system using sequential forward floating selection (SFFS) with support vector machine (SVM) to diagnose gastric histology of Helicobacter pylori (H. pylori) from endoscopic images. To achieve this goal, candidate image features associated with clinical symptoms are extracted from endoscopic images. With these candidate features, the SFFS method is applied to select feature subsets, which perform the best classification results under SVM with respect to different histological features. By using the classifiers obtained from the feature subsets, a new diagnosis system is implemented to provide physicians with H. pylori -related histological results from endoscopic images.