From the Journals

‘Emerging’ biomarker may predict mild cognitive impairment years before symptoms



Measuring levels of the synaptic protein NPTX2 in cerebrospinal fluid (CSF) may serve as an early predictor of mild cognitive impairment (MCI) years before symptoms appear, new research indicates.

“Our study shows that low NPTX2 levels are predictive of MCI symptom onset more than 7 years in advance, including among individuals who are in late middle age,” said study investigator Anja Soldan, PhD, associate professor of neurology, Johns Hopkins University School of Medicine, Baltimore.

NPTX2 is still considered an “emerging biomarker” because knowledge about this protein is limited, Dr. Soldan noted.

Prior studies have shown that levels of NPTX2 are lower in people with MCI and dementia than in those with normal cognition and that low levels of this protein in people with MCI are associated with an increased risk of developing dementia.

“Our study extends these prior findings by showing that low protein levels are also associated with the onset of MCI symptoms,” Dr. Soldan said.

The study was published online in Annals of Neurology.

New therapeutic target?

The researchers measured NPTX2, as well as amyloid beta 42/40, phosphorylated (p)-tau181, and total (t)-tau in CSF collected longitudinally from 269 cognitively normal adults from the BIOCARD study.

The average age at baseline was 57.7 years. Nearly all were White, 59% were women, most were college educated, and three-quarters had a close relative with Alzheimer’s disease.

During a mean follow-up average of 16 years, 77 participants progressed to MCI or dementia within or after 7 years of baseline measurements.

In Cox regression models, lower baseline NPTX2 levels were associated with an earlier time to MCI symptom onset (hazard ratio, 0.76; P = .023). This association was significant for progression within 7 years (P = .036) and after 7 years from baseline (P = .001), the investigators reported.

Adults who progressed to MCI had, on average, about 15% lower levels of NPTX2 at baseline, compared with adults who remained cognitively normal.

Baseline NPTX2 levels improved prediction of time to MCI symptom onset after accounting for baseline Alzheimer’s disease biomarker levels (P < .01), and NPTX2 did not interact with the CSF Alzheimer’s disease biomarkers or APOE-ε4 genetic status.

Higher baseline levels of p-tau181 and t-tau were associated with higher baseline NPTX2 levels (both P < .001) and with greater declines in NPTX2 over time, suggesting that NPTX2 may decline in response to tau pathology, the investigators suggested.

Dr. Soldan said NPTX2 may be “a novel target” for developing new therapeutics for Alzheimer’s disease and other dementing and neurodegenerative disorders, as it is not an Alzheimer’s disease–specific protein.

“Efforts are underway for developing a sensitive way to measure NPTX2 brain levels in blood, which could then help clinicians identify individuals at greatest risk for cognitive decline,” she explained.

“Other next steps are to examine how changes in NPTX2 over time relate to changes in brain structure and function and to identify factors that alter levels of NPTX2, including genetic factors and potentially modifiable lifestyle factors,” Dr. Soldan said.

“If having higher levels of NPTX2 in the brain provides some resilience against developing symptoms of Alzheimer’s disease, it would be great if we could somehow increase levels of the protein,” she noted.


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