SOME QUESTIONS AND ANSWERS

Can diabetes be cured?

Because diabetes involves damage to the cells that produce insulin, and these cells do not readily regenerate, there is no non-surgical cure for either type 1 or type 2 diabetes.

In type 1 diabetes, beta cell destruction is caused by an autoimmune process, and the damage is not reversible. Hence, those with type 1 diabetes have to continue taking insulin, unless they are given a transplanted pancreas or islet cells. However, in this case, immunosuppressive medicines must be taken for the rest of the person's life to prevent rejection, which occurs in about half of all cases. Islet cell transplantation, developed over the past five years, is still a highly experimental procedure that is not yet generally available.

Beta cell destruction occurs through different mechanisms in type 2 diabetes and tends to be preceded by increasing insulin resistance. Studies have shown that it is possible to slow or prevent the onset of diabetes and to prevent or slow the emergence of later complications by a combination of medicines and lifestyle changes. As insulin resistance is generally the dominant feature of type 2 diabetes, transplantation is generally not considered appropriate.

Is diabetes inherited?

In both type 1 and type 2 diabetes, susceptibility to developing the disease has an inherited component. However, in both cases, many genes are involved. In addition, non-inherited factors are also important in determining whether someone actually develops the disease or not.

In type 1 diabetes, over two dozen regions on 14 of the 23 human chromosomes, and more than 100 individual genes, have been found to have an influence (either positive or negative) on the likelihood of developing the condition.

The link with the HLA (Human Leukocyte Antigen) genes on chromosome 6 has been found to have the most direct effect. More than 95 per cent of Caucasian people with type 1 diabetes carry HLADR3 and/or HLA-DR4 antigens, as compared with 50 per cent of people without diabetes. Siblings of Caucasian children with type 1 diabetes have a 20 per cent risk of also developing the disease if they share the same HLA antigens. However, the great majority of people who have the HLA-DR3 and HLA-DR4 antigens do not develop diabetes, and so many other factors must be required for its development.

In type 2 diabetes, a great many genes have also been implicated in disease susceptibility, although lifestyle-related factors such as obesity clearly seem to be the dominant triggers of diabetes. Fifteen to 25 per cent of first-degree relatives of a person with type 2 diabetes develop impaired glucose tolerance or diabetes, and the lifetime risk of developing type 2 diabetes by the age of 80 has been calculated to be 38 per cent if one parent had the disease. The risk is 60 per cent by age 60 if both parents were affected.

A recent study has reported that even healthy, normal-weight men with normal blood glucose values may have impaired function of their small blood vessels if they have a strong family history of type 2 diabetes (at least two second-degree relatives, or at least one first-degree relative). Hence, extra attention to minimising risk factors such as poor diet and/or lack of exercise may be advised in those with a pre-disposing family history, to avoid the risk of disease.

Can you catch diabetes from someone else?

Type 2 diabetes is not thought to be linked to an infectious disease.

The situation is less clear for type 1 diabetes, where as many as 14 different viruses have been suggested to be a possible cause of the disease.

Congenital rubella (German measles) infection is one such suspected culprit, but the enterovirus Coxsackie virus type B is most often cited as a possible trigger for disease onset in those with an inherited susceptibility.

Infection with the type 4B strain that has been shown to cause persistent infection in human pancreatic islet cells has been reported to be more common in children with newly-diagnosed type 1 diabetes. However, there is evidence that makes a causative link between infection and disease unlikely. At present, the possibility of an infectious trigger for type 1 diabetes remains unproven. It also seems likely that there are many other factors that may be involved in the development of the disease in those with an inherited susceptibility.