Century-Old Diabetes Drug Metformin Reduces Insulin Requirements in Type 1 Diabetes Patients
Key Insights
A Garvan Institute clinical trial found that metformin reduces insulin needs by 12% in type 1 diabetes (search) patients, despite not improving insulin resistance (search) as expected.
The INTIMET study randomized 40 adults with long-term type 1 diabetes (search) to receive either metformin or placebo for six months, using sophisticated clamp studies to measure insulin resistance (search).
Researchers are now investigating metformin's mechanism of action through gut microbiome (search) studies, as the drug's century-old therapeutic effects remain unexplained.
A groundbreaking clinical trial has revealed that metformin, a century-old type 2 diabetes (search) medication, can significantly reduce insulin requirements in people with type 1 diabetes (search), offering new hope for improved disease management. The research, led by the Garvan Institute of Medical Research and published in Nature Communications, challenges previous assumptions about how this widely-used drug works in type 1 diabetes.
Unexpected Mechanism Discovered in First Randomized Trial
The world's first randomized controlled trial testing metformin in type 1 diabetes (search) adults, called the Insulin Resistance (search) in Type 1 Diabetes Managed with Metformin (INTIMET) study, produced surprising results. Researchers randomized 40 adults with long-term type 1 diabetes to take either metformin or a placebo for six months, using sophisticated clamp studies to map insulin resistance throughout the body.
"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," explained Professor Jerry Greenfield, who co-led the study with Dr. Jennifer Snaith.
Contrary to expectations, metformin did not improve insulin resistance (search) or change blood sugar levels in type 1 diabetes (search) patients. However, the drug demonstrated a clinically meaningful benefit: participants taking metformin used approximately 12% less insulin than those receiving placebo to maintain stable blood sugar levels.
Addressing Growing Clinical Need
Type 1 diabetes (search) affects over 450,000 people in the UK and more than 130,000 Australians. The autoimmune condition destroys insulin-producing pancreatic cells, requiring lifelong insulin administration. Managing blood sugar levels with insulin presents significant challenges, with patients making an estimated 180 extra daily decisions related to diabetes management.
"Insulin resistance (search) is a growing problem in type 1 diabetes (search). Not only does it make regulating blood sugar levels difficult, but it is an underappreciated risk factor for heart disease (search), which is one of the biggest causes of health complications and deaths in those with type 1 diabetes," said Dr. Jennifer Snaith, an endocrinologist at St Vincent's Hospital Sydney (search).
Long-term insulin use can lead to insulin resistance (search) in some patients, where cells become less responsive to the hormone, necessitating ever-increasing insulin doses for blood sugar control.
Clinical Significance and Patient Impact
The 12% reduction in insulin requirements represents a meaningful improvement for patients struggling with the physical and mental burden of intensive insulin therapy. "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 (search)," Dr. Snaith noted.
The findings are particularly significant given metformin's accessibility and cost-effectiveness. The drug is estimated to be currently used off-label by up to 13,000 Australians with type 1 diabetes (search), though its mechanism of action in this population remained unclear until now.
Investigating Novel Mechanisms
Researchers are now focusing on understanding how metformin achieves its insulin-sparing effects without improving insulin sensitivity. "Metformin has been available in various forms for around 100 years, but its mechanism of action remains unknown," Professor Greenfield explained.
The team is investigating metformin's potential effects on the gut microbiome (search) as a possible explanation for its therapeutic benefits. "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 (search). This has not been studied before in type 1 diabetes," Dr. Snaith said.
Understanding metformin's mechanism could enable more widespread and targeted use of the medication in type 1 diabetes (search) management, potentially improving outcomes for hundreds of thousands of patients worldwide who currently rely solely on insulin therapy.