Activated Immune System and Inflammation in Healthy Ageing: Relevance for Tryptophan and Neopterin Metabolism
Immune activation not only accompanies inflammation in various disorders including infections, autoimmune syndromes and
cancer, but it also represents a characteristic feature of ageing. Immune deviations which are most widely expressed in the elderly include
increased neopterin production and tryptophan breakdown. These biochemical events result from the activation of the immune system
and are preferentially triggered by pro-inflammatory stimuli, such as the Th1-type cytokine interferon-γ. They seem to play a role in the
development of several age-related disorders and might be involved in the pathogenesis of common symptoms, including neurobehavioral
disorders (e.g., cognitive and mood disturbances), anemia, cachexia, weight-loss but also immunodeficiency. Concentrations of the
biomarkers neopterin and Kyn/Trp were found to be predictive of overall disease specific mortality in coronary artery disease, infections
and various types of cancer. Immune activation and inflammation are also accompanied by high output of reactive oxygen species and
thereby may lead to the development of oxidative stress and contribute to the vitamin deficiency which is often observed in the elderly.
Accordingly, increases in neopterin were found to correlate with a substantial decline in key vitamins, including folate and vitamin-B6, -
B12, -C, -D and -E.
Keywords: Aging, neopterin, tryptophan breakdown, inflammation, antioxidants, vitamins.
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