McMaster researchers identify immune pathway behind statin muscle side effects

Statins are among the most prescribed medications in the world. Millions of people take them daily to lower cholesterol and reduce their risk of heart attack and stroke. For most, the drugs work as intended. But somewhere between seven and twenty-nine percent of patients who take statins experience a problem the medication was never meant to cause: muscle pain, weakness, and a reduced ability to exercise. Some of these patients stop taking the drug altogether, abandoning a medication that protects their heart because the side effect has become unbearable.

Researchers at McMaster University have now identified why this happens. In a study published in Science Advances, a team led by Jonathan Schertzer, a professor in the Department of Biochemistry and Biomedical Sciences, traced the muscle damage to a specific biological pathway—one that appears to operate independently from the mechanism that makes statins effective at lowering cholesterol. The finding is significant because it suggests that future treatments might one day block the side effect without compromising the drug's cardiovascular benefit.

For decades, scientists knew statins could damage muscle tissue, but the precise mechanism remained a mystery. Schertzer's team, working with first authors Nazli Robin and Nicole Barra, conducted experiments using both isolated muscle cells and mouse models to map out what happens when statins enter the body. They discovered that the drugs disrupt how muscle cells generate energy. This metabolic disruption then triggers an immune response—the body's own defense system attacking the muscle tissue itself. When the researchers blocked this immune response in their experiments, they were able to prevent much of the muscle damage from occurring.

The discovery reveals an unexpected connection between how cells produce energy and how the immune system responds to that disruption. Changes in muscle metabolism, it turns out, can activate inflammation within the cells themselves. This insight into the relationship between metabolism and immunity opens new avenues for understanding not just statin side effects, but how drugs in general can trigger unwanted immune reactions.

What makes this research particularly promising is the separation Schertzer's team identified between two distinct mechanisms. The pathway that causes muscle damage appears to be completely different from the pathway that lowers cholesterol. This means a future drug could theoretically target and block the immune response without interfering with statins' ability to reduce cardiovascular risk. For the millions of patients who currently face a choice between protecting their heart and enduring muscle pain, such a treatment could be transformative.

The work involved an international collaboration spanning France, Australia, and Canada, and was funded by the Natural Sciences and Engineering Research Council of Canada. While the findings are promising, Schertzer emphasized that additional research will be necessary before these discoveries can be translated into actual therapies for patients. The team has identified several potential targets for future drug development, but moving from laboratory findings to clinical treatments typically takes years of further study and testing.

For now, the research provides clarity on a problem that has frustrated both patients and physicians. Schertzer noted that some people reduce their statin dose or abandon the medication entirely because of muscle symptoms, despite knowing the drug protects them from heart disease. Understanding why those symptoms occur is the first step toward preventing them. The next step—developing a way to block the immune response while preserving the cardiovascular benefits—remains ahead, but the path forward is now clearer than it has ever been.