An amino acid found abundantly in watermelon may one day help manage infection rates in trauma patients and cease tumor growth in cancer patients.
Juan Ochoa, MD, UPMC trauma surgeon, University of Pittsburgh associate professor of surgery and critical care medicine, and McGowan Institute researcher knows the science behind nutrition after trauma is complex. Trauma patients are highly susceptible to infection, and feeding a trauma patient the wrong formula can increase its likelihood.
Several years ago, many surgeons began administering an “immune-enhancing diet” to their surgical patients. The diet includes the amino acid arginine. Arginine is a precursor to nitric oxide, which is manufactured by our bodies as part of the immune response. Researchers are currently on the cusp of understanding how the diet works, why it works for some and not others.
Helping him make sense of the science is Juan’s brother, Augusto Ochoa, interim director of Louisiana State University’s Stanley S. Scott Cancer Center. In the early ‘90’s Augusto was working on the cancer research question: Why don’t our immune systems put up a better fight against cancer cells? He learned that cancer patients’ lymphocytes (specifically T cells) are missing a peptide called the “zeta chain.” In 2001, the Ochoa brothers began publishing reports showing that arginine was essential to maintaining the zeta chain. Around the same time, a Japanese scientist showed that trauma patients were missing the zeta chain as well.
Juan Ochoa’s investigations revealed that arginase is present at elevated levels in the tissues of trauma patients. The Ochoa brothers learned that the immune system is dampened the same way in cancer patients. High levels of arginase somehow inhibit the ability of the injured body to keep the needed arginine in store. Arginase robs the arginine necessary to build the zeta chain leaving the T cell unable to proliferate to help fight off intruders and leaves the patient unprotected.
Augusto’s investigations have since injected arginine into the tumor of a mouse. The therapy stopped the tumor from growing further. Juan believes the immune-enhancing diet works similarly: A high concentration of arginine restores the zeta chain, allowing the T cell to do its job to fight off infection.
Juan is anxious to begin refining a diet for precommercial testing in trauma patients. Arginine, however, does not taste great and can have adverse effects. Dr. Ochoa plans to substitute arginine with citrulline—a similar, safer, more palatable amino acid found abundantly in watermelon.
He’s optimistic about the possibilities. “So if we could block the [process that cuts out the zeta chain], we could potentially have a treatment for cancer. We could also have a potential treatment for infection in trauma.”
Illustration: MicroSoft clipart.
Pitt Med (Summer 2007)