Miro1 protein may drive insulin resistance in preclinical models

In Oklahoma, Dr John P. Kirwan describes a puzzle that has resisted explanation for years. Muscle stops responding properly to insulin, and the molecular causes of that failure, in his words, have 'remained frustratingly unclear'. His latest study, published in Nature Communications in 2026, points to one protein as a possible part of the answer.

The protein is Miro1, short for mitochondrial Rho GTPase1. It sits on the outer membrane of mitochondria, the structures inside cells that produce energy. The team found it at elevated levels in the skeletal muscle of people with type 2 diabetes. To test whether it was a bystander or a cause, the researchers followed it from cells to preclinical models to patients. In those models, Miro1 accumulation impaired the muscle's response to insulin, and removing the protein restored that response.

The second part of the study involved people. In a randomized controlled trial of participants with obesity and type 2 diabetes, aerobic exercise was compared with standard medical care. Participants who exercised saw their muscle Miro1 levels fall, alongside gains in insulin sensitivity and in the muscles' ability to produce energy. The trial links exercise to lower Miro1 in patients, but it does not show that Miro1 causes insulin resistance in people; that step rests on the preclinical experiments.

For people living with type 2 diabetes, the nearest gain is a clearer explanation of why exercise helps, and a named biological target for researchers to pursue. Any drug that acts on Miro1 would still have to be developed and tested, and the authors say the findings are a foundation for further investigation, not a treatment. Kirwan's team plans to keep connecting laboratory work with studies in people at the Harold Hamm Diabetes Center. 'Ultimately, we are looking for cures,' he said, 'and we hope these recent findings could be part of the solution.'