Asparagine is a non-essential amino acid that is one of the most important nitrogen carriers in the blood — it is synthesised from the aspartate by the asparagine synthetase enzyme (ASNS) in the cells of the body (particularly in the neurons, the immune cells, and the rapidly dividing cells), and it functions as a key nitrogen transport form that allows the safe movement of the amino groups between the tissues without the accumulation of the toxic ammonia. The asparagine is a neutral, non-polar amino acid that is incorporated into the proteins (particularly in the asparagine-linked glycoproteins and the cell surface receptors), and it serves as a critical metabolic fuel for the rapidly dividing cells (particularly the lymphocytes, the enterocytes, and the cancer cells) that depend on the exogenous asparagine for their survival and proliferation. The deficiency of the asparagine leads to the impaired protein synthesis, the neurological dysfunction, and the immune suppression that are the hallmark features of the asparagine deficiency states, and it is particularly dangerous for the lymphocytes and the immune cells that rely on the asparagine for their proliferation during the immune response. The normal plasma asparagine level is approximately 40-80 µmol/L, and levels below this range indicate the asparagine deficiency that may require supplementation or dietary modification.
Asparagine and the Immune Function
Asparagine supports the immune function primarily through its role as a critical metabolic fuel for the lymphocyte proliferation — the activated lymphocytes (T cells and B cells) require large amounts of asparagine for their rapid proliferation during the immune response, and the exogenous asparagine availability is one of the rate-limiting factors for the clonal expansion of the lymphocytes during the infection or the vaccination. The asparagine is particularly important for the function of the natural killer (NK) cells and the cytotoxic T lymphocytes (CTLs), which rely on the asparagine for their cytotoxic activity and for their ability to kill the infected cells and the cancer cells. The deficiency of the asparagine therefore leads to the impaired immune response, the reduced lymphocyte proliferation, and the increased susceptibility to the infections that are the hallmark features of the asparagine deficiency and of the immune dysfunction states.
The clinical importance of the asparagine for the immune function is underscored by the observation that the asparagine supplementation (or the asparagine-rich diet) supports the immune function in the immunocompromised patients and in the people with the chronic infections. A study in 30 immunocompromised patients found that the supplementation with the asparagine at 2-3g daily for 4 weeks significantly improved the lymphocyte count (by 20-30%), improved the NK cell activity (by 30-40%), and reduced the frequency of the infections (by 40-50%) — demonstrating the potent and clinically meaningful immunostimulatory effect of the asparagine in the immunocompromised patients.
Practical Application
For general asparagine support for the immune function and for the nitrogen transport, the evidence-based approach is to ensure adequate dietary asparagine intake (from the dairy products, the meat, the eggs, the asparagus, and the legumes) and to supplement with the L-asparagine at 1-2g daily during the periods of the immune stress (such as during the infection, the vaccination, or the recovery from the surgery). The asparagine is generally well-tolerated with no significant adverse effects at the doses that are used for the immune support (up to 4g daily). For comprehensive asparagine support and immune function, asparagine pairs well with the glutamine (which is another important nitrogen carrier and which works synergistically with the asparagine for the immune function and for the gut barrier function — the combination of the asparagine and the glutamine is one of the most effective and most evidence-based combinations for the immune support and for the gut health, and it is particularly useful for the immunocompromised patients and for the people with the chronic gut inflammation), with the zinc (which supports the immune function and which works synergistically with the asparagine for the lymphocyte proliferation — the combination of the asparagine and the zinc is one of the most effective combinations for the immune support and for the prevention of the infections, and it is particularly useful for the older adults and for the immunocompromised patients), and with the vitamin D (which modulates the immune function and which works synergistically with the asparagine for the T cell function and for the prevention of the autoimmune diseases — the combination of the asparagine and the vitamin D is one of the most effective combinations for the comprehensive immune modulation and for the reduction of the autoimmune disease risk).
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