Stomach ulcers are caused by a propeller-shaped bacteria called Helicobacter pylori. In addition to its ability to trigger ulcers and gastric burning sensations, it is in the front line to promote the triggering of stomach cancers. A recent Japanese study that young broccoli shoots, very rich in sulforaphane, can halve the amount of Helicobacter pylori present in the stomach.
Helicobacter pylori is a very particular bacterium which has the characteristic of specifically infecting the stomach of primates, including humans. This infection is made possible by certain properties unique to this bacterium, including its spiral shape which allows it to squeeze through the mucus which covers the stomach wall, its flagella which make it very mobile and its production of ammonia. which allows it to protect itself from the very acid conditions which reign in the stomach (the bacterium secretes an enzyme, urease, which transforms urea into ammonia and thus forms an alkaline shield which neutralizes the acidity on its periphery). A series of highly effective adaptations, as genetic analyzes indicate that this bacterium has cohabited with humans for at least 100,000 years, with still today around half of the world’s population infected with H. pylori.
From stomach ulcer to stomach cancer
The presence of H. pylori in the stomach is problematic, because this bacterium causes the formation of inflammatory lesions (chronic gastritis) which can develop into ulcers or, even worse, into stomach cancer. This discovery, made in 1983 by Australian researchers (Drs. Barry Marshall and Robin Warren), was ridiculed for several years, because the medical dogmatism of the time attributed the responsibility for gastric ulcers to stress. But, truth always triumphs in science, the discovery of Drs Marshall and Warren proved to be a major advance in our understanding of the pathologies of the stomach, which earned them the Nobel Prize for Medicine in 2005.
Helicobacter pylori releases a carcinogenic toxin in the stomach
One of the most serious consequences of H. pylori infection is, of course, the increased risk of stomach cancer, a risk which is about 6 times higher in infected people than in those who are not. . This carcinogenic effect of the bacteria is caused by the secretion of a toxin called CagA (cytotoxin-associated gene A), which enters the cells of the gastric mucosa and changes their structure and functioning.
A recent study has managed to elucidate the mechanism used by H. pylori to inject this carcinogenic toxin into stomach cells and thus promote the development of cancer. This is a very elegant process, which can be separated into two distinct phases:
First, the German scientists observed that the bacterium produces an enzyme (HtrA) which acts as a kind of molecular chisel to decrease the tightness of the mucosa. Under normal conditions, the cells of this lining adhere tightly to each other in order to prevent stomach acid from damaging the stomach. During an infection by H. pylori, the production of the enzyme HtrA leads to the destruction of three proteins involved in the formation of this barrier (occludin, claudin-8 and E-cadherin), which allows the bacterium to sneak between cells.
Once deeper in the mucosa, the bacterium uses surface proteins, a kind of molecular antennae, to bind to a cell protein (integrin) and inject its carcinogenic toxin. The toxin can then disrupt the normal functioning of cells and create an instability that will promote the acquisition of cancerous mutations.
Sulforaphane: broccoli’s secret weapon to reduce the amount of bacteria
In general, H. pylori infection remains asymptomatic for several years before generating clinical signs (stomach pain). It is important to consult quickly if these signs appear, especially for people who have a family history (father, mother, siblings) of stomach cancer (the infection is often transmitted during childhood). Furthermore, it is interesting to note that certain studies have shown that sulforaphane, a molecule contained in broccoli, has antibiotic activity against H. pylori and that regular consumption of this vegetable could exert a protective effect against this bacterium. For example, a clinical study carried out in Japan shows that the consumption of broccoli sprouts, an exceptional source of sulforaphane, makes it possible to halve the quantities of H. pylori present in the mucous membranes of infected people.
Tegtmeyer N et al. “Helicobacter pylori employs a unique basolateral type IV secretion mechanism for CagA delivery”. Cell Host Microbe 2017; 22: 552-560.
Yanaka A et al. “Dietary sulforaphane-rich broccoli sprouts reduce colonization and attenuate gastritis in Helicobacter pylori-infected mice and humans”. Cancer Prev Res. 2009; 2: 353-60.