Arginine is an essential amino acid that supports protein production, immune function, and other vital processes throughout the body. Although the body makes arginine naturally, it is also found in protein-rich foods such as meat, fish, dairy products, nuts, and legumes. Research has linked unusually low arginine levels to several diseases, including colon cancer and viral infections.
Scientists at The Rockefeller University have been studying the connection between arginine deficiency, cancer, and immune health. In 2023, a team led by Sohail Tavazoie, head of the Elizabeth and Vincent Meyer Laboratory of Systems Cancer Biology, reported that depriving colon cancer cells of arginine caused them to accumulate more mutations.
New research from the team suggests that low arginine levels may also weaken immune surveillance. When arginine is scarce, cells have difficulty producing MHC-1, a protein that helps the immune system identify abnormal cells, cancer-related mutations, and viral infections.
Arginine May Help Restore a Critical Immune Signal
The researchers found that a moderate amount of arginine—roughly equivalent to the amount found in a couple of over-the-counter tablets—could potentially restore activity in genes involved in MHC-1 production. The study was published in Cell.
“Our work reveals how a lack of arginine interferes with the immune system and suggests that increasing arginine intake could prove beneficial,” says first author Qiushuang Wu, a postdoctoral researcher in the lab. “Perhaps it could be used in combination with other therapies to treat cancer and viral infections.”
“Arginine supplementation could be readily tested in patients receiving immunotherapy or provided to high-risk populations exposed to viral pathogens,” Tavazoie says. “Because arginine is inexpensive and widely available, we hope therapeutic and preventive studies can begin soon.”
However, the findings come primarily from laboratory and animal research. Clinical studies are needed to determine whether arginine supplements are safe and effective for preventing or treating cancer and viral disease in humans.
How Codons Control Protein Production
Amino acids are often called the building blocks of proteins. Their production is guided by codons, which are groups of three DNA bases that provide instructions for making specific amino acids. Six different codons encode arginine, underscoring its importance in protein synthesis.
Scientists already know that changes in amino acid availability can influence cell metabolism and signaling. Much less is known about how those changes may directly affect gene expression and the production of specific proteins.
For the new study, Wu examined whether changes in arginine levels caused by diet or disease could alter gene expression. The research was supported in part by the Stavros Niarchos Foundation (SNF) Institute for Global Infectious Disease Research at The Rockefeller University and the Weill Cancer East Hub.
The researchers analyzed several disease models, including colon cancer, influenza, and SARS-CoV-2 infection. Each condition has previously been associated with unusual changes in amino acid levels.
“One of the most dramatic patterns to emerge was that arginine was the most depleted amino acid in all of these diseases,” Wu says.
Arginine Deficiency May Impair Immune Recognition
Using cell cultures, Wu identified genes and proteins affected by declining arginine levels. She found that 414 proteins were present at unusually low levels. Most of those proteins were produced by genes associated with arginine’s known biological functions.
A more unexpected finding involved three HLA genes that help produce MHC-1, or major histocompatibility complex class I, proteins. MHC-1 proteins are displayed on the surface of cells throughout the body. They present foreign or abnormal proteins to T cells, which can then activate other immune cells to respond.
MHC-1 contains multiple sites where arginine must be incorporated during protein production. This led the researchers to suspect that arginine deficiency was disrupting the process. Additional experiments revealed where the breakdown occurred.
When cells lacked arginine, ribosomes—the cellular structures responsible for assembling proteins—stalled while producing MHC-1. Without enough arginine, they could not complete the protein. As a result, cells displayed fewer signals that could alert T cells to cancer-related or viral proteins, potentially allowing dangerous cells to evade immune detection.
“These findings are exciting because they reveal that the availability of a specific amino acid can directly regulate gene expression by increasing production of a protein enriched in that amino acid,” Tavazoie says. “We believe this type of selective translational control through dietary changes may apply to many other proteins and amino acids.”
Arginine-Rich Diets Reduced Colon Tumors in Mice
Wu next tested how different levels of dietary arginine affected mice. Animals fed a low-arginine diet developed more colon cancer tumors, while mice given more dietary arginine developed fewer tumors.
Working with Heinz-Heinrich Hoffman, a research assistant professor in Charles Rice’s Laboratory of Virology and Infectious Disease, Wu repeated the dietary experiments in mouse models of influenza and SARS-CoV-2. The results showed a similar pattern and revealed another unexpected effect.
“Not only did mice on an arginine-rich diet experience milder viral symptoms, but giving arginine to mice after influenza infection also improved their outcomes,” Wu says. “That was very surprising. Our genetic models showed that manipulating arginine levels strongly affected gene expression, but we did not expect dietary changes to have an equally significant impact.”
Potential Links to Aging, Nutrition, and Disease
The findings may help explain why poor nutrition and aging are associated with increased vulnerability to certain cancers and viral infections. Arginine levels naturally decline with age, which could weaken the immune system’s ability to identify abnormal or infected cells.
“Qiushuang’s findings show how poor diet and aging—during which arginine levels naturally decline—could create the perfect conditions for colon cancer to begin. Similarly, age-related arginine loss could contribute to the higher mortality caused by respiratory viruses,” Tavazoie says. “We are also investigating whether changing levels of other amino acids through diet could provide benefits in different disease settings. There are likely many more discoveries ahead.”
Although these results highlight a promising connection between arginine, immune function, colon cancer, and viral disease, people should not begin taking arginine supplements without speaking with a healthcare professional. Human clinical trials are necessary to confirm the potential benefits, determine appropriate doses, and identify possible risks or drug interactions.
Source: www.sciencedaily.com