Gastrin-mediated effects of omeprazole on rat colon mucosa

Identifying patients at risk of severe Clostridium difficile-associated disease

Clostridium difficile infection is responsible for a wide spectrum of clinical presentations, ranging from mild diarrhoea to fatal toxic colitis. This article reviews factors which may identify individuals who are at high risk of severe C. difficile-associated disease, and aims to help clinicians predict patients at risk of severe disease.

Long-term safety concerns with proton pump inhibitors

Proton pump inhibitors (PPIs) are among the most widely prescribed medications worldwide. Their use has resulted in dramatic improvements in treatment of peptic ulcer disease and gastroesophageal reflux disease. Despite an acceptable safety profile, mounting data demonstrate concerns about the long-term use of PPIs. To provide a comprehensive review regarding the concerns of long-term PPI use, a literature search was performed to identify pertinent original and review articles. Despite study shortcomings, the collective body of information overwhelmingly suggests an increased risk of infectious complications and nutritional deficiencies. Data regarding any increased risk in gastric or colon malignancy are less convincing. PPIs have revolutionized the management and complications of acid-related disorders with a high margin of safety; however, with the data available, efforts to reduce the dosing of or discontinue the use of PPIs must be reassessed frequently.

Proton pump inhibitors: actions and reactions

Proton pump inhibitors are the second most commonly prescribed drug class in the United States. The increased utilization of PPIs parallels the rising incidence of reflux disease. Owing to their clinical efficacy and relative lack of tachyphylaxis, PPIs have largely displaced H-2 receptor antagonists in the treatment of acid peptic disorders. The elevation of intragastric pH and subsequent alterations of gastric physiology induced by PPIs may yield undesired effects within the upper GI tract. The ubiquity of the various types of H(+), K(+)-ATPase could also contribute to non-gastric effects. PPIs may influence physiology in other ways, such as inducing transepithelial leak.

Comparative role of antibiotic and proton pump inhibitor in experimental Clostridium difficile infection in mice

Clostridium difficile inoculated BALB/c mice were investigated to assess the comparative role of antibiotic and proton pump inhibitor. They were examined for colonization and toxin production by C. difficile as well as myeloperoxidase activity and histopathological changes in the intestinal tract. The C. difficile count, toxin A and B titres and myeloperoxidase activity were significantly higher (P>0.05) in ampicillin and lansoprazole receiving groups as compared to the control and the C. difficile receiving groups. Similarly they showed significant difference (P >0.05) for epithelial damage, oedema and neutrophilic infiltrate in colons. In addition to antibiotic, PPI also acts as an independent risk factor for C. difficile infection in experimental studies.

Chronic proton pump inhibitor therapy and the risk of colorectal cancer

BACKGROUND & AIMS

Chronic acid suppression by proton pump inhibitor therapy can lead to hypergastrinemia. Because existing evidence suggested an association between hypergastrinemia and colorectal cancer, we examined whether long-term proton pump inhibitor use is associated with an increased risk of colorectal cancer in a population-representative cohort.

METHODS

We conducted a nested case-control study among patients 50 years of age and older and with > or =5 years of colorectal cancer-free initial follow-up in the General Practice Research Database (1987-2002) from the United Kingdom. Cases consisted of all patients with an incident diagnosis of colorectal cancer. Using incidence density sampling, up to 10 controls were matched with each case on practice site and both duration and calendar time of follow-up before the index date. The primary exposure of interest was > or =5 years of cumulative proton pump inhibitor therapy. We assessed the presence of duration-response and dose-response effects.

RESULTS

We identified 4432 incident colorectal cancer cases and 44,292 controls. The adjusted odds ratio for > or =5 years of proton pump inhibitor exposure was 1.1 (95% confidence interval, 0.7-1.9). Among high-dose proton pump inhibitor users (ie, > or =1.5 defined daily doses/day), there was a nonstatistically significant trend toward an increased risk with increasing duration of use (test for trend, P = .2). However, patients with pernicious anemia were not at increased risk for colorectal cancer (adjusted odds ratio, 0.9; 95% confidence interval, 0.6-1.3).

CONCLUSIONS

Long-term proton pump inhibitor therapy at a regular dose is not associated with a significantly increased risk of colorectal cancer.

COX-2 selective inhibition reverses the trophic properties of gastrin in colorectal cancer

Gastrin is a gastrointestinal peptide that possesses potent trophic properties on both normal and neoplastic cells of gastrointestinal origin. Previous studies have indicated that chronic hypergastrinaemia increases the risk of colorectal cancer and cancer growth and that interruption of the effects of gastrin could be a potential target in the treatment of colorectal cancer. Here we demonstrate that gastrin leads to a dose-dependent increase in colon cancer cell proliferation and tumour growth in vitro and in vivo, and that this increment is progressively reversed by pretreatment with the cyclo-oxygenase-2 inhibitor NS-398. Gastrin was able to induce cyclo-oxygenase-2 protein expression, as well as the synthesis of prostaglandin E2, the major product of cyclo-oxygenase. Moreover, gastrin leads to approximately a two-fold induction of cyclo-oxygenase-2 promoter activity in transiently transfected cells. The results of these studies demonstrate that cyclo-oxygenase-2 appears to represent one of the downstream targets of gastrin and that selective cyclo-oxygenase-2 inhibition is capable of reversing the trophic properties of gastrin and presumably might prevent the growth of colorectal cancer induced by hypergastrinaemia.

Regulation of glucose-dependent insulinotropic polypeptide release by protein in the rat

Glucose-dependent insulinotropic polypeptide (GIP) release has been demonstrated predominantly after ingestion of carbohydrate and fat. These studies were conducted to determine the effects of protein on GIP expression in the rat. Whereas no significant changes in duodenal mucosal GIP mRNA levels were detected in response to peptone, the duodenal GIP concentration increased from 8.4+/-1.5 to 19.8+/-3.2 ng GIP/mg protein at 120 min (P<0.01). Plasma GIP levels also increased from 95+/-5.2 pg/ml to a peak of 289+/-56.1 pg/ml at 120 min (P<0.01). To determine whether the effects of protein on GIP were due to stimulation of acid secretion, rats were pretreated with 10 mg/kg omeprazole, after which mucosal and plasma GIP concentrations were partially attenuated. To further examine the effects of luminal acid, rats were administered intraduodenal 0.1 M HCl for 120 min, which significantly enhanced GIP expression. These studies indicate that nutrient protein provides a potent stimulus for GIP expression in the rat, an effect that occurs at the posttranslational level and may be mediated in part through the acid-stimulatory properties of protein. The effects of acid on GIP are consistent with a role for GIP as an enterogastrone in the rat.