Aspartic Acid

Elevated aspartic acid may reflect high intake of aspartate- rich foods or use of artificial sweeteners containing aspartic acid (“NutraSweet” or “Equal”).

Elevations may also be due to impaired downstream metabolism from nutritional insufficiencies of enzymatic cofactors such as vitamin B6, magnesium, and ATP.

Because aspartic acid is a major excitatory neurotransmitter, elevations have been noted in epileptic patients.

Decreased Aspartic Acid Levels: Clinical Implications and Updated Perspectives

Low plasma aspartic acid levels may indicate nutritional deficiencies, metabolic disturbances, or organ dysfunction. While aspartic acid is non-essential, its depletion can reflect systemic imbalances requiring clinical attention. Below are evidence-based causes and considerations:

Nutritional Deficiencies

• Protein-energy malnutrition: Insufficient dietary protein reduces precursor availability for aspartic acid synthesis.

• Vitamin B6 deficiency: This condition impairs transamination reactions critical for aspartic acid metabolism.

• Diabetic contexts: Low aspartic acid correlates with the severity of diabetic kidney disease in murine models, with supplementation showing renoprotective effects through oxidative stress reduction.

Metabolic Disorders

• Asparagine synthetase deficiency (ASNSD): ASNSD causes congenital microcephaly and progressive encephalopathy. Interestingly, it can lead to elevated plasma aspartic acid in some patients alongside asparagine deficiency. This condition should be distinguished from aspartate aminotransferase deficiencies, which lack robust clinical documentation.

Organ Dysfunction

• Liver disease: Liver disease typically causes amino acid elevation due to urea cycle impairment. However, specific metabolic defects could theoretically lower aspartic acid in rare scenarios.

• Chronic kidney disease (CKD): D-amino acid dysregulation (e.g., D-serine, D-asparagine) correlates with renal impairment. While aromatic amino acid restriction has been shown to improve renal outcomes, specific data regarding aspartic acid's role in CKD remains limited.

Endocrine and Neurological Considerations

• D-aspartic acid: D-aspartic acid regulates testosterone synthesis and neuroendocrine function. Clinical implications of changes in the D/L ratio require further study.

• Neurological disorders: Altered aspartic acid metabolism has been associated with hyperammonemia and various psychiatric conditions.

Diagnostic and Therapeutic Implications

Emerging Research

• Aspartic acid supplementation shows promise in diabetic nephropathy models.

• D-amino acid chronobiology research reveals circadian influences on renal glucose metabolism.

Aspartic acid is a nonessential amino acid that plays roles in many important metabolic processes, such as energy production (citric acid cycle), hormone metabolism, CNS activation, and the urea cycle. It is found in many protein sources such as oysters, meats, seeds, avocado, asparagus, and beets. It is also an ingredient in artificial sweeteners.

Aspartic acid is a precursor to many amino acids and other molecules like asparagine, arginine, isoleucine, lysine, methionine, isoleucine, threonine, nucleotides, NAD, and pantothenate. Aspartate, like glutamine, can also be considered a neuroexcitatory neurotransmitter since it activates the N-methyl-D-aspartate receptor in the brain.