2013-09-15 14:48:11
Cancer is still one of the most terrible diseases. A large amount of resources and intelligence have been dedicated to the fight against this ailment, which has enabled some important achievements towards its cure. However, if it is important to cure cancer once it has developed, it is even more important to prevent it from appearing in the first place. Preventing cancer is, without a doubt, a more judicious strategy than trying to cure it once it has appeared.
To prevent the development of a disease, it is important to know its causes. Today it is clearly established that cancer is a genetic disease. It can only occur if mutations are generated in some genes important for the control of cell growth or death. It is known that there are numerous carcinogenic substances or factors, all of which, in one way or another, end up chemically modifying DNA and producing mutations. Avoiding contact with these cancer-promoting factors is, therefore, essential to avoid developing a tumor.
OBESITY AND TUMORS
However, some well-established causes of cancer remain shrouded in mystery from the point of view of the molecular mechanisms involved in tumor development. One of them is obesity. Obese people show a higher incidence of some types of cancer, particularly liver cancer, but it is not known why. How can excess fat in adipose tissue cause damage to the DNA of the liver to the point of inducing a tumor?
Some factors that could explain this phenomenon have recently been discovered. Among them is a higher level of inflammation – associated with obesity – that can also contribute to the development of cancer, as well as changes in the bacteria of the intestinal flora that participate in the development of an abnormal inflammatory response. As we know, the inflammatory response is part of the immune system’s usual fight against microorganisms, and a higher level of inflammation could generate substances that activate not only the immune system but also promote the development of tumors. However, again, it is necessary to understand whether these factors help damage DNA and produce mutations that lead to cancer.
Researchers at several Japanese universities and research centers are tackling this problem in a series of elegant experiments using obese and non-obese strains of laboratory mice, feeding them various high-fat and non-fat diets. What have you found in your studies?
First, the researchers find that if mice are kept in a clean, bacteria-free environment, the development of liver cancer is no different between obese mice fed a high-fat diet and lean mice fed a high-fat diet. those fed a normal diet. Thus, diet and obesity alone do not affect the development of tumors. It is necessary to invoke the existence of other factors, in particular microorganisms that stimulate the immune system and factors that promote tumor development.
MUTATIONS AND DIET
To test this possibility, researchers treat mice shortly after birth with a mutagen – a chemical substance that produces mutations in DNA. In this case, things are very different: all of the mice fed a high-fat diet, but none of those fed a normal diet, developed liver cancer. Clearly, mutagen along with a high-fat diet promotes the development of liver cancer, but again, why? How does the high-fat diet help the mutagen to literally cause an explosion of tumors in mice?
The authors then study whether any substance involved in the metabolism or absorption of fats is involved. It is known that for the correct absorption of fats, bile and the so-called bile acids produced by the liver play an important role. The scientists thus detected a high level of so-called deoxycholic acid, a bile acid, in the blood of mice fed a high-fat diet. Deoxycholic acid was already known to participate in the development of some cancers, such as colorectal cancer, and it is known to be produced by the action of intestinal flora on bile. In fact, the researchers verify that the concentration of deoxycholic acid decreases in the blood of mice treated with an antibiotic that attacks the intestinal flora, and demonstrate that treatment with a cocktail of four antibiotics results in a very marked reduction in liver cancer. in those animals.
These studies, published in the journal Nature, now make the relationship between obesity and cancer much clearer. In fact, it is not obesity that causes cancer, but the high-fat diet that causes and maintains it, and that also generates an increased production of bile, which, in turn, is metabolized by the intestinal flora to produce a chemical derivative, deoxycholic acid, which is returned to the liver by the blood and thus ends up contributing to the generation of liver cancer (and perhaps also to other types of cancer).
Now that we know how all this works, perhaps we will believe with less doubt that being obese and a continued poor diet will destroy our health; Maybe we are more convinced to remedy it. It is one of the advantages of scientific knowledge, which puts us face to face with reality and forces us to make decisions.
WORKS BY JORGE LABORDA.
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