Parkinson’s disease is often described as a disorder of movement, but a new study suggests that the illness may also alter the body’s chemistry in ways shaped by two factors that have not always received equal attention: biological sex and genetic background. Reporting in npj Parkinson’s Disease, Yahyavi, Carrillo, Nuzzo and colleagues examined how circulating amino acids connected to N-methyl-D-aspartate receptors, or NMDARs, are disrupted in people with Parkinson’s disease. Their findings point toward a more individualized biological signature of the condition, one that could eventually influence diagnosis, monitoring and treatment design.
NMDARs are specialized receptors that help nerve cells communicate. They are activated primarily by the neurotransmitter glutamate and require additional molecular signals, including amino-acid-related co-agonists, to function properly. These receptors are central to synaptic plasticity—the ability of neural circuits to strengthen or weaken connections in response to experience. They also participate in learning, memory, sensory processing and the regulation of neuronal survival. When NMDAR signaling becomes excessive or poorly controlled, however, it can contribute to excitotoxicity, a process in which overactivation damages or kills nerve cells.
Parkinson’s disease is classically associated with the gradual loss of dopamine-producing neurons in a region of the brain called the substantia nigra. Dopamine depletion explains many familiar symptoms, including tremor, slowness of movement and muscle rigidity, but it does not capture the full biological complexity of the disease. Non-motor symptoms such as sleep disruption, depression, cognitive changes and pain can emerge years before or alongside motor impairment. Researchers have increasingly turned to systems beyond dopamine to understand why Parkinson’s disease develops differently from one patient to another.
The new work focuses on amino acids circulating in the blood rather than measuring only neurotransmitters inside the brain. This distinction is important. Blood-based molecules provide a comparatively accessible window into metabolism, but they do not offer a simple, one-to-one reading of what is occurring in specific neural circuits. Amino-acid concentrations can reflect dietary intake, liver and kidney function, inflammation, medication, muscle metabolism and the activity of multiple organs. Even so, carefully interpreted blood profiles may reveal biological pathways that are disturbed in disease and may help identify patient subgroups.
The study’s central message is that NMDAR-related amino-acid disruption in Parkinson’s disease is not uniform. Instead, the pattern differs according to sex and genotype. In other words, two people with the same clinical diagnosis may show different biochemical changes depending on whether they are male or female and on the genetic variants they carry. This finding challenges the idea that a single metabolic profile can represent Parkinson’s disease as a whole and reinforces the need to treat sex and genetic variation as essential components of biomedical research rather than secondary details.
Genotype can influence how the body produces, transports, modifies or clears amino acids, as well as how neurons respond to glutamatergic signaling. Genetic differences may affect enzymes involved in metabolism, proteins that regulate synapses or pathways linked to inflammation and mitochondrial function. Sex-related biology can also shape these systems through hormones, chromosomes, immune responses and differences in body composition. The interaction between these variables may help explain why symptoms, disease progression, treatment responses and risks of complications vary across individuals.
The findings are particularly relevant because NMDAR signaling already sits at the intersection of several processes implicated in Parkinson’s disease. Dopamine loss can disturb the balance between neural pathways that promote and suppress movement, while glutamate provides much of the excitatory drive within those circuits. If NMDAR-associated signaling becomes dysregulated, it could amplify abnormal network activity or increase the vulnerability of neurons under stress. Circulating amino acids may therefore serve not as direct substitutes for brain measurements, but as accessible indicators of broader metabolic and signaling changes associated with the disease.
The researchers’ observations may also sharpen the search for biomarkers. A biomarker is a measurable feature that can help detect disease, predict its course or show whether a treatment is working. A single amino acid is unlikely to provide a definitive answer, given the number of factors that influence blood chemistry. More promising could be a composite profile that combines several amino acids with clinical features, genetic information, sex, medication history and other molecular signals. Such a model could help researchers distinguish biologically meaningful subtypes of Parkinson’s disease and design clinical trials that account for those differences.
The study does not mean that a blood test for Parkinson’s disease is ready for routine use, nor does it establish that altered circulating amino acids directly cause neuronal degeneration. Associations must be tested in larger and more diverse populations, followed over time and evaluated alongside brain imaging, cerebrospinal-fluid measurements and detailed clinical data. Future research will need to determine how stable these metabolic signatures are, whether they change as the disease progresses and whether they respond to dopamine therapies or treatments aimed at glutamatergic pathways.
What the research does provide is a compelling reminder that Parkinson’s disease is not one uniform disorder wearing different clinical masks. Its molecular landscape may be partly rewritten by sex and inherited biology, influencing how neural communication and metabolism become disturbed. By bringing NMDAR-related amino acids into that picture, the study adds another layer to the effort to understand—and ultimately personalize—the treatment of Parkinson’s disease. The long-term goal is not merely to identify differences between patients, but to turn those differences into better predictions, more precise therapies and fewer surprises for the millions of people living with the condition.
Subject of Research: Sex- and genotype-related disruption of circulating NMDAR-related amino acids in patients with Parkinson’s disease
Article Title: Sex and genotype influence the disruption of circulating NMDAR-related amino acids in patients with Parkinson’s disease
Article References: Yahyavi, I., Carrillo, F., Nuzzo, T. et al. Sex and genotype influence the disruption of circulating NMDAR-related amino acids in patients with Parkinson’s disease. npj Parkinson’s Disease (2026). https://doi.org/10.1038/s41531-026-01507-4
Image Credits: AI Generated
DOI: 10.1038/s41531-026-01507-4
Keywords: Parkinson’s disease, NMDAR, amino acids, sex differences, genotype, biomarkers, neurodegeneration, glutamatergic signaling, precision medicine
Tags: circulating amino acids in neurodegenerationexcitotoxicity in neurodegenerative diseasesgenetic background and disease progressiongenetic influence on Parkinson’simpact of biological sex on brain chemistryimplications for Parkinson’s diagnosis and treatmentneurotransmitter glutamate in Parkinson’sNMDAR receptor function and dysfunctionNMDAR-related amino acid disruptionsParkinson’s diseasepersonalized biomarkers for Parkinson’ssex differences in neurochemistry
