Knowing the triggers of this autoimmune disease will help prevent it.A new study provides evidence of the influence of the elements that act on the expression of genes.

Various environmental factors have been described that protect or promote autoimmunity against beta cells or diabetes progression.In green, those who tell with greater evidence.(The Lancet)

Incidence of type 1 diabetes in Spain

The incidence of type 1 diabetes has increased considerably in the last 30 years.Knowing the causes of this trend can be very useful for prevention.There are still many unknown elements, but other issues are clarified.For example, that this increase in the appearance of new cases is driven by changes in the environment or in the lifestyle, since genetic factors have not varied.

As in the rest of the diseases with a strong genetic component, it has been appreciated that environmental factors - such as exposure to certain viruses or diet - can induce alterations in the expression of genes through the so -called epigenetic mechanisms.A study that has just been published in Nature Communications, which has had Spanish participation, provides new evidence that this interaction with genes, in this case with those related to the immune system, is key in the appearance of pathology.

After all, it is an autoimmune disease that occurs in genetically susceptible individuals and that results in destruction - mediated by T -lymphocytes of pancreatic beta cells, which are responsible for synthesizing and segregating insulin.

Study in twin brothers

An international team of researchers, among which is IVO GUT, director of the National Center for Genomic Analysis (CNAG), in Barcelona, ​​has evaluated the contribution of epigenetic signals in 52 pairs of identical twins, with the particularity that only oneOf the two brothers had developed type 1 diabetes.

The epigenetic study was carried out taking blood samples, but for the analysis three cell types were separated: T cells, B cells and monocytes."With this information we could see the differences between the three types and within each type," says Gut.

Specifically, methylation was analyzed, which is the main epigenetic mechanism.The genomics specialist exposes the main findings: "We have seen genomic regions where the sick showed methylation and the twins did not. This was seen in the three cell types."Therefore, he concludes, this study feels the foundations of a possible way to identify biomarkers that help in the diagnosis and the search for possible treatments.

Some of the observed epigenetic changes were related to the regulation of the function of the immune system cells.GUT clarifies that this does not represent "a big surprise", being an autoimmune disease, although it can provide new details about the development of the disease.

cause-effect relationship

In the expert's opinion, the most novelty of the work that has just been published, which has been coordinated by David Leslie, of the University of London, is that it is the first time "that is done with such a broad resolution, of 450,000 positions ofmethylation, and with twins. "The effect of environmental factors on disease development is very difficult to measure.However, "now we have genome points with differential methylation that can be useful to carry out studies with environmental parameters to establish cause-effect relationships."

There are many studiesOn the influence of various environmental factors in the development of type 1 diabetes, but there is still no definitive clue that allows preventive actions.As Lluís Forga, head of the Endocrinology Service of the Hospital Complex of Navarra (Pamplona) points out, in general terms "the passage of the most depressed countries at a higher standard of living is not only accompanied by an increase in type 2 diabetes, butalso of type 1 ".He has studied the evolution of the incidence of this disease in Navarra, where "it has quadrupled in the last 40 years."However, it has not been a linear increase and seems to have stabilized in 20 cases per 100,000 inhabitants a year.

As for the causes of this increase, there are only theories for now.One of them is related to socioeconomic development: the one known as hygiene hypothesis, which would also be behind the growth of allergies.In a nutshell, the greatest control of infections would lead to an alteration of the immune system that, not having to face bacteria and viruses, would dedicate itself to attacking other structures that are not harmful.

Another hypothesis would be that of certain viruses as triggers, because type 1 diabetes "usually debut in cold months", according to Forga, who adds that this theory does not have "conclusive results."Nor has it been possible to demonstrate the influence of the vitamin D deficit in pregnancy or as soon as they are born.

The risk factors that have been revealed as more determinants in type 2 diabetes, such as obesity and sedentary lifestyle, do not play such an important role in this case."They influence not so much on the appearance, as at the time it occurs," says the specialist in endocrinology.Thus, overweight and more sedentary children would develop the pathology before.

Finland, the country with more cases

"The incidence of type 1 diabetes varies up to 576 times among the different countries of the world and reaches a 2/1 ratio between autonomous communities."This was stated by Luis Forga in a review published in 2014 in advances in Diabetology.The country with the highest incidence in children under 14 is Finland, with 57.6 cases per 100,000 inhabitants a year.

At the opposite end is Papua New Guinea, with 0.1 cases.There are several hypotheses about the reasons for this great heterogeneity in terms of incidence.In a study published this year in Diabetological Act, a team of Italian researchers analyze the possible causes of the high incidence of pathology on the Island of Sardinia, which records 45 cases per 100,000 inhabitants.

Various epidemiological studies have shown that exposure to recognized environmental factors (nutritional elements, pollution, toxins, chemicals, infections in the first stage of life) has changed over time.One of the peculiarities that stand out is the possible link between Mycobacterium Avium paratuberculosis infection and the increase in the incidence of type 1 diabetes in Sardinia.

They also refer to the impact that, according to other studies, could exercise the great density of heavy metals on the island, without losing sight of the importance of genetic factors.