Researchers at the University of California at San Francisco investigated this potential, comparing PQQ with the beta blocker metoprolol—a standard post-MI clinical treatment. Independently, both treatments reduced the size of the damaged areas and protected against heart muscle dysfunction. When given together, the left ventricle's pumping pressure was enhanced. The combination of PQQ with metoprolol also increased mitochondrial energy-producing functions—but the effect was modest compared with PQQ alone. Only PQQ favorably reduced lipid peroxidation. These results led the researchers to conclude that "PQQ is superior to metoprolol in protecting mitochondria from ischemia/reperfusion oxidative damage."