Researchers studied whether metformin, a widely-used diabetes medication, could help protect the heart in people with diabetes. Using mice with type 2 diabetes, they found that metformin improved how well the heart relaxed between beats—a problem that often develops in diabetic patients. The drug also reduced the thickening of heart muscle cells that typically occurs with diabetes. These findings suggest metformin may offer heart protection beyond just controlling blood sugar levels, which could be important for millions of people taking this medication.

The Quick Take

  • What they studied: Whether metformin, a common diabetes medicine, could improve heart function problems that develop in people with type 2 diabetes
  • Who participated: Male laboratory mice that were given a high-fat diet and a chemical injection to create type 2 diabetes similar to the human disease
  • Key finding: Mice treated with metformin showed significant improvement in how well their hearts relaxed between beats, and their heart muscle cells were less thickened compared to untreated diabetic mice
  • What it means for you: This suggests metformin may protect your heart in ways beyond just lowering blood sugar, though this was tested in mice and human studies are still needed to confirm these benefits

The Research Details

Scientists created type 2 diabetes in mice by feeding them a high-fat diet and giving them a chemical injection that damages insulin-producing cells. After 12.5 weeks, half the mice received metformin in their drinking water while the other half received plain water. The researchers then used ultrasound imaging (similar to what doctors use during pregnancy) to look at how well each mouse’s heart was working. They also examined heart tissue under a microscope to see if the heart muscle cells had changed size.

This type of study is called a preclinical or animal study. Researchers use it to understand how a drug might work before testing it in humans. The mice were chosen because their diabetes develops in ways similar to human type 2 diabetes, making the results more likely to apply to people.

Heart problems in diabetic patients often develop silently without obvious symptoms, making them dangerous. This study focused specifically on diastolic dysfunction—the heart’s inability to relax properly—which is one of the earliest heart problems to appear in diabetic patients. By testing metformin’s effects on this specific problem, researchers could determine if the drug offers protection beyond just controlling blood sugar.

This study was conducted in a controlled laboratory setting with standardized procedures, which is good for reliability. However, because it was done in mice rather than humans, results may not directly apply to people. The study also did not measure certain important factors that might explain how metformin works, which limits our understanding of the mechanism. The specific dose and duration of metformin used in mice may not match what people take.

What the Results Show

Metformin treatment improved the heart’s ability to relax between beats in diabetic mice. Researchers measured this using two different ultrasound measurements: the e’/a’ ratio increased and the E/e’ ratio decreased—both signs of better heart relaxation. These improvements were clear and measurable on the ultrasound images.

When researchers examined the heart tissue under a microscope, they found that metformin reduced the thickening of individual heart muscle cells that normally occurs with diabetes. This is important because enlarged heart muscle cells are a sign of heart damage and can lead to heart failure over time.

As expected, metformin also improved blood sugar control in the diabetic mice. The drug showed a trend toward reducing body fat, though this difference was not as clear-cut as the heart improvements.

Interestingly, the researchers measured a protein called AMPK, which many scientists believed was responsible for metformin’s protective effects. However, metformin did not increase AMPK activity in these mice, even though the heart improvements were still observed. This suggests metformin may protect the heart through a different mechanism than previously thought—a finding that could change how scientists understand this drug.

Previous research has shown that metformin protects the heart in various ways, but most studies focused on how it prevents heart attacks or improves overall heart function. This study is among the first to specifically examine how metformin affects diastolic dysfunction—the relaxation problem—which is particularly important in diabetic patients. The finding that metformin works through a mechanism independent of AMPK is new and contradicts some earlier assumptions about how the drug functions.

The study was conducted only in male mice, so results may not apply equally to females. The researchers used a specific dose of metformin that may not match the doses people take. Because this is an animal study, the results must be confirmed in human clinical trials before doctors can confidently recommend metformin specifically for heart protection. The study did not examine long-term effects or whether benefits persist over extended periods. Additionally, the study did not identify the exact mechanism by which metformin improves heart function, leaving some questions unanswered.

The Bottom Line

If you have type 2 diabetes and are already taking metformin, continue taking it as prescribed by your doctor—this study provides additional evidence that it may benefit your heart. If you have type 2 diabetes but are not on metformin, discuss with your doctor whether it might be appropriate for you, as it remains a first-line treatment. However, do not change your diabetes medications based solely on this mouse study. Confidence level: Moderate for existing metformin users; Low for making new treatment decisions until human studies confirm these findings.

People with type 2 diabetes who take or are considering metformin should find this encouraging. Those with early signs of heart problems related to diabetes may particularly benefit from these findings. This research is less relevant for people with type 1 diabetes or those who cannot take metformin due to kidney problems or other contraindications. People without diabetes should not use these findings to justify taking metformin.

In the mouse study, improvements in heart function were observed after 7.5 weeks of treatment. In humans, benefits might take longer to develop—typically several weeks to months. However, this timeline is speculative based on animal data and should be confirmed in human studies.

Want to Apply This Research?

  • If you have diabetes and take metformin, track your blood sugar readings daily and note any changes in energy levels, shortness of breath, or exercise tolerance. Record these alongside your metformin doses to identify patterns over time.
  • Use the app to set reminders for taking metformin at the same time each day, and log your adherence. Combine this with tracking moderate exercise (like 30-minute walks) and heart-healthy meals to maximize potential benefits. Monitor how you feel during physical activity.
  • Over 3-6 months, track trends in your blood sugar control and any improvements in how you feel during exercise. Share these records with your doctor at regular checkups. If your doctor orders heart imaging or function tests, note the results in the app to monitor long-term changes in heart health.

This research was conducted in laboratory mice and has not yet been tested in humans. While the findings are promising, they should not be used to make changes to your diabetes treatment without consulting your doctor. Metformin is already an FDA-approved medication for type 2 diabetes, and this study provides additional evidence of potential heart benefits, but individual results may vary. If you experience chest pain, shortness of breath, or other heart-related symptoms, seek immediate medical attention. Always discuss any changes to your medications or health regimen with your healthcare provider, as they understand your complete medical history and can provide personalized recommendations.