The highest prevalence of type 1 diabetes occurs in Northern Europe, particularly in Scandinavia.
There is still a great deal of uncertainty about the causes of type 1 diabetes (T1D), but now scientists have managed to shed new light on the disease.
They have discovered that a mutation in a certain gene may be essential for the development of T1D.
“Scientists have known for years that type 1 diabetes has a strong genetic component. But this is probably the first time that a mutation has been discovered in a single gene that causes type 1 diabetes,” says Professor Flemming Pociot, MD, a research group leader at Glostrup Hospital, Denmark, who took part in the international study.
How do scientists determine that gene mutations can cause a disease?
It is normally very difficult to locate the right places in the genome as there are some 20,000 different genes in the human body to go through.
”For this reason, scientists often search for defective genes in families where many members are affected by the same disease. That way we can see whether the affected family members share any specific gene mutations,” explains Pociot.
In the new study, the researchers examined an Israeli family in which four members suffered from T1D. Having searched through the family’s genome, they located a mutation in a gene known as SIRT1.
”This gene is incredibly interesting because other studies indicate that it could play a part in prolonging life, and that it can for instance prevent cancer and cardiovascular disease.”
In most T1D patients, the disease is autoimmune, i.e. the patient’s immune defence attacks the body’s own cells.
This was also the case with the Israeli patients, and it soon became clear that the defective sirtuin protein was partly responsible for these faults in the immune system.
“We compared the cell behaviour in the patients to that of the healthy family members. It turned out that the patients were far more sensitive to some of the factors we know are central in autoimmune diseases,” says the researcher.
They also carried out a series of experiments on mice to see if they could identify the detailed mechanisms behind the defective sirtuin protein.
They noted that the sirtuin proteins appeared to affect the so-called cytokines – a type of protein that plays a key role in the regulation of the immune system.
The researchers’ theory is, simply stated, that the mutated sirtuin proteins cause the cytokines in the immune system to kill the wrong cells, including those that produce the body’s vital hormone insulin.
The lack of insulin, which helps regulate the blood sugar, is one of the hallmarks of T1D.
Type 1 diabetes is a chronic disease in which there are high levels of sugar in the blood.
Incidence of type 1 diabetes varies from 8 to 17 per 100,000 in Northern Europe and the US, with a high of about 35 per 100,000 in Scandinavia to a low of 1 per 100,000 in Japan and China.
“We also carried out some mice trials, which helped confirm that sirtuin plays a part in diabetes. We gave the mice diabetes, and in some of them we knocked out the SIRT gene entirely, leaving the mice with no sirtuin protein,” he explains.
“Compared to the normal mice, these mice developed the disease much quicker and it was much severer too. This is another strong indication that it’s not good to lack sirtuin.”
Professor Torben Hansen of the Steno Diabetes Center in Copenhagen also sees great potential in the new study:
”When I look at the diabetes patients in our clinic, there are clear differences in their disease. So it’s great to see a study that explains these differences, and that gives us a better opportunity to advise them properly,” he says.
”Ultimately, this could lead to improved treatment and perhaps even prevention of diabetes when as we learn more about the genetics behind the individual patients’ disease.”