Helicobacter pylori induced cognitive dysfunction might be associated with falls and fractures in cirrhosis

Extragastric manifestations of Helicobacter pylori infection: Possible role of bacterium in liver and pancreas diseases

Helicobacter pylori (H. pylori) is an ancient microorganism that has co-evolved with humans for over 60000 years. This bacterium typically colonizes the human stomach and it is currently recognized as the most common infectious pathogen of the gastroduodenal tract. Although its chronic infection is associated with gastritis, peptic ulcer, dysplasia, neoplasia, MALT lymphoma and gastric adenocarcinoma, it has been suggested the possible association of H. pylori infection with several extragastric effects including hepatobiliary and pancreatic diseases. Since a microorganism resembling H. pylori was detected in samples from patients with hepatobiliary disorders, several reports have been discussed the possible role of bacteria in hepatic diseases as hepatocellular carcinoma, cirrhosis and hepatic encephalopathy, nonalcoholic fatty liver disease and fibrosis. Additionally, studies have reported the possible association between H. pylori infection and pancreatic diseases, especially because it has been suggested that this infection could change the pancreatic physiology. Some of them have related a possible association between the microorganism and pancreatic cancer. H. pylori infection has also been suggested to play a role in the acute and chronic pancreatitis pathogenesis, autoimmune pancreatitis, diabetes mellitus and metabolic syndrome. Considering that association of H. pylori to liver and pancreas diseases needs further clarification, our work offers a review about the results of some investigations related to the potential pathogenicity of H. pylori in these extragastric diseases.

Clinical effects of Helicobacter pylori outside the stomach

The discovery of Helicobacter pylori infection in the stomach could be considered as one of the most important events of modern gastroenterology. Understanding of the natural history of many disorders of the upper gastrointestinal tract, including chronic gastritis, peptic ulcer disease, gastric cancer and MALT lymphoma, was altered by this discovery. Interestingly, epidemiological studies have also revealed a correlation between H. pylori infection and some diseases localized outside the stomach, especially those characterized by persistent and low-grade systemic inflammation. Of note, H. pylori has an important role in iron deficiency anaemia, idiopathic thrombocytopenic purpura and vitamin B12 deficiency. Moreover, the association of this bacterial pathogen with many other diseases, including hepatobiliary, pancreatic, cardiovascular and neurodegenerative disorders is currently under investigation. In this Review, we summarize the results of the most important studies performed to date surrounding the association of H. pylori infection with extragastric diseases, as well as the strength of the evidence. We also provide information concerning bacterial-host interactions and the mechanisms implicated in the pathogenesis of each of these extragastric diseases.

A proposed role of human defensins in Helicobacter pylori-related neurodegenerative disorders

Cationic host defence peptides (CHDPs), also known as antimicrobial peptides (AMPs), are essential components of the innate immunity with antimicrobial and pleiotropic immunomodulatory properties. In mammals the two major families of CHDPs are defensins and cathelicidins that comprise an arsenal of innate regulators of principal importance in the host tissues. Research in the last decade has demonstrated that defensins are crucial effectors of both innate and adaptive immunity. Defensins can modulate immune responses, either by stimulation or suppression, thereby controlling inflammatory processes and infections. Currently only few data, mostly hypothetical, focus on the role of defensins in central nervous system (CNS) physiopathology and neurodegeneration. Defensins may function as an initial line of defense within the CNS either as an antimicrobial, immunomodulator, or both. A dysregulation of brain expression of specific defensins might either exacerbate or ameliorate the inflammatory response within the CNS depending upon which extracellular conditions predominate. It is proposed that reduction or abnormal elevation of AMP expression by cerebral microglia, astrocytes or choroid plexus epithelium might contribute to loss of AMP-induced regulation of immune responses, thereby promoting neuronal cell injury and death observed in Alzheimer's disease and possibly in other neurodegenerative disorders. Nevertheless, whether certain AMPs play a crucial role in the onset or promotion of the neuroinflammatory process and neurodegeneration is currently unknown, thereby emphasizing the necessity of further investigation into the regulatory mechanisms that control innate and adaptive immunity within the brain. Recent data indicate that Helicobacter pylori (H. pylori) induces defensins' release associated with chronic inflammatory tissue damage. However, it remains unclear whether and how H. pylori evades the attack by defensins. Moreover, recent evidence indicates that H. pylori infection might contribute to the pathogenesis of neurodegenerative diseases, by releasing several inflammatory mediators that could induce blood-brain barrier breakdown, thereby being involved in the pathogenesis of neurodegeneration. However, currently there are no data regarding the potential impact of human defensins on H. pylori-related neurodegenerative disorders. We herein propose that human defensins might contribute to the pathophysiology of H. pylori-related neurodegenerative disorders by modulating variably innate and adaptive immune system responses. Better understanding of the mechanisms regarding human defensins' possible involvement in H. pylori-induced neurodegeneration might help develop novel therapeutic strategies against H. pylori-related neurodegenerative disorders.