Scientists at the University of California San Diego have found that high levels of a certain enzyme in the blood could be an early warning sign of Alzheimer’s disease. The enzyme, called PHGDH, plays a role in producing a nutrient known as serine, which is involved in brain function.
In their study, the researchers looked at brain tissue from people with Alzheimer’s, people with early signs of the disease (but no symptoms yet), and healthy individuals. They found that the gene responsible for making PHGDH was more active in people with Alzheimer’s—even in those who had no memory problems yet but whose brains showed early signs of the disease.
The more advanced the disease, the higher the PHGDH levels were. This pattern was also seen in lab mice bred to develop Alzheimer’s, and people with lower memory test scores had higher PHGDH activity in their brains.
This is important because it suggests that PHGDH levels could help doctors detect Alzheimer’s in its earliest stages, before memory problems or confusion begin.
In fact, the research team had already identified PHGDH as a possible blood marker in an earlier study. In this new research, they confirmed that the high levels seen in the blood are also happening inside the brain.
The study included brain samples from four different research groups. Each group had about 40 to 50 people over the age of 50.
These included people diagnosed with Alzheimer’s, people who appeared healthy but whose brains showed Alzheimer’s-related changes after death, and people without any signs of the disease. In all groups, those with Alzheimer’s or early brain changes had consistently higher levels of PHGDH than the healthy controls.
This research also raises a red flag about the use of serine supplements. Serine is an amino acid, a building block of protein, and some people believe it can boost memory or help prevent Alzheimer’s. Some companies even market serine supplements as a brain health booster.
However, because PHGDH is the enzyme that helps make serine in the body, and because PHGDH levels are already higher in people with Alzheimer’s, the researchers suggest that the brain might already be producing more serine than usual in response to the disease.
This means that taking extra serine as a supplement might not help—and could possibly do more harm than good.
Some earlier studies had suggested that PHGDH levels drop in Alzheimer’s, leading to the idea that boosting serine might help. In fact, clinical trials are already underway to test whether serine can slow cognitive decline. But the new findings challenge that idea, showing instead that PHGDH, and possibly serine levels, are increased—not reduced.
The researchers emphasize that more work is needed to fully understand what this means for treatment. But they believe their findings will be helpful in improving how we detect and manage Alzheimer’s disease. Tracking PHGDH levels in the blood could one day become part of routine tests to catch the disease early.
This study was led by Dr. Sheng Zhong and published in Cell Metabolism. It adds to a growing body of research focused on finding better ways to understand, detect, and eventually treat Alzheimer’s disease before it causes lasting damage.
If you care about Alzheimer’s, please read studies about Vitamin D deficiency linked to Alzheimer’s, vascular dementia, and Oral cannabis extract may help reduce Alzheimer’s symptoms.
For more information about brain health, please see recent studies about Vitamin B9 deficiency linked to higher dementia risk, and results showing flavonoid-rich foods could improve survival in Parkinson’s disease.
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