Type 1 diabetes

The amount of glucose in the blood is normally tightly controlled. But in diabetes blood glucose levels are abnormally high.

The hormone insulin normally reduces blood glucose levels and is produced by cells in the pancreas called ‘beta cells’. However, in type 1 diabetes there is a misdirected ‘autoimmune’ reaction to the insulin-producing beta cells in the pancreas, which leads to insufficient insulin being produced. Without insulin, high levels of glucose accumulate in the blood.

The immune system protects our body from invading microbes. There are normally many safeguards that prevent it from attacking the body’s own tissues. In type 1 diabetes, these safeguards fail, and immune cells specifically destroy beta cells.

Type 1 diabetes is the most common chronic (long-term) childhood illness in Australia. More than 120,000 Australians have type 1 diabetes. The incidence of type 1 diabetes in Australia has increased in the past 30 years.

Most people with type 1 diabetes are diagnosed as children or young adults. Even with a lifetime of the best available care, they are at increased risk of serious complications such as

• Kidney disease (diabetic nephropathy)
• Eye disease and blindness (diabetic retinopathy)
• Nerve damage (diabetic neuropathy)
• Damage to blood vessels, which together with nerve damage can lead to serious problems in the hands and feet
• Heart disease and stroke

Type 1 diabetes is caused by a combination of genetic risk and environmental factors. Our researchers have shown that changes in our environment have contributed to the increase in the incidence of type 1 diabetes in the past few decades.

Many environmental factors have been proposed to trigger or promote type 1 diabetes. These include infections, diet and weight gain.

Known risk factors for type 1 diabetes include:

• Having other autoimmune or inflammatory diseases such as coeliac disease or autoimmune thyroid disease. These conditions all involve aberrant immune responses.
• Having a parent or sibling with type 1 diabetes or other autoimmune diseases. One in five Australians diagnosed with type 1 diabetes have a family history of the condition.
• Living at higher latitudes: the incidence of type 1 diabetes is increased in populations who live furthest from the equator. This may be partly genetic. It may also be related to environmental factors such as vitamin D deficiency and hygiene.

Almost all people with type 1 diabetes rely on insulin injections for their entire lives. They must closely monitor their blood glucose levels. When blood glucose rises, such as after a meal, an appropriate insulin dose is calculated and injected. Insulin is available in ‘slow acting’ and ‘fast acting’ forms. These can aid the smoother control of blood glucose levels.

There is no orally available (tablet) form of insulin. Insulin can only be given by injection, such as with a syringe. Recently, small, attachable insulin pumps have been introduced instead of multiple daily injections. Insulin pumps may control blood glucose better by providing a more steady release of insulin into the body.

The only cure for type 1 diabetes is transplantation or regeneration of insulin-producing cells.

Transplantation of the whole pancreas or the parts of the pancreas containing insulin-secreting beta cells can be performed. It is limited by a shortage of organ donors, and the need for life-long immune suppression to prevent transplant rejection. Thus, transplantation is restricted to people with poorly controlled diabetes and serious complications.

Our researchers have shown that the pancreas contains stem cells that can be transformed into beta cells. Their hope is that it may one day be possible to cure type 1 diabetes by stimulating the regrowth of beta cells. This would depend on stifling the immune cells that originally destroyed the beta cells.

Diabetes Australia has more detailed information about diabetes treatment.