A century-old, affordable medication could offer new hope for individuals living with type 1 diabetes, according to recent findings from Australia. The study highlights that metformin, a drug commonly used for type 2 diabetes, may lower the need for insulin in individuals with type 1 diabetes.

This discovery could revolutionize the management of type 1 diabetes, researchers state. This condition, impacting around 450,000 people in the UK, occurs when the immune system erroneously targets insulin-producing cells in the pancreas.

Because of this, individuals with type 1 diabetes must rely on insulin administration throughout their lives to keep blood sugar levels in check. Over time, some patients develop insulin resistance, where the cells become less responsive to insulin, necessitating ever-increasing doses to maintain normal blood sugar levels.

Metformin has been prescribed by doctors for insulin resistance in type 1 diabetes based on observational evidence. However, the recent clinical trial shows that while metformin doesn’t directly address insulin resistance, it does help reduce the insulin needed to keep blood sugar levels stable.

Published in the journal Nature Communications, these unexpected results may lead to improved treatment strategies for type 1 diabetes, potentially reducing the challenges faced by patients relying solely on insulin.

Dr. Jennifer Snaith, co-leader of the study from the Garvan Institute of Medical Research, remarked, “Insulin resistance is an escalating issue in type 1 diabetes. It complicates blood sugar management and poses an often-overlooked threat for heart disease, a leading cause of complications and fatalities among those with type 1 diabetes.”

A Garvan team led by Dr Snaith and Professor Jerry Greenfield conducted the world’s first randomised controlled trial in adults examining whether metformin – typically used to combat insulin resistance in type 2 diabetes – could achieve the same results in type 1 diabetes.

Prof Greenfield said: “We randomised 40 adults with long-term type 1 diabetes to take either metformin or a placebo for six months. We examined whether their insulin resistance changed over that time through a sophisticated and comprehensive research technique, called a clamp study, that allowed us to map insulin resistance in different parts of the body.”

The team were astonished to discover that metformin use did not result in improvements to insulin resistance or alterations to blood sugar levels. They said this indicates that, unlike for type 2 diabetes, metformin fails to work against insulin resistance in type 1 diabetes. Nevertheless, metformin did reduce the quantity of insulin people required to maintain stable blood sugar levels.

Dr Snaith said: “Although we didn’t find changes to insulin resistance from the use of metformin, we did show that people taking it used around 12% less insulin than those on placebo. This is an important result. Insulin is a relatively old treatment which, while lifesaving, comes with significant mental and physical burden.

“This means that lowering the amount of insulin used is a priority for many people living with type 1 diabetes. We have shown that a very cheap, accessible, medication may serve this purpose and this is very exciting.”

The team is now delving into how metformin might work to reduce the amount of insulin required by those with type 1 diabetes.

Professor Greenfield added: “Metformin has been available in various forms for around 100 years, but its mechanism of action remains unknown. We would have expected that the observed reductions in insulin dose induced by metformin in our study would be due to the body becoming more sensitive to insulin, that is, becoming less insulin resistant.

“But we have shown that is not the case. Our priority is now working out how metformin is achieving this effect.”

Dr Snaith said: “There is increasing evidence suggesting that metformin may act on the gut. This is why we are now investigating how metformin changes gut flora, also known as the microbiome, in people with type 1 diabetes. This has not been studied before in type 1 diabetes. We’re hoping this will provide clues on metformin’s mechanism of action, so that it can be more widely used in the management of type 1 diabetes.”