From Tryptophan to Circadian and Neurochemical Regulators: The Serotonin-Melatonin Pathway

Dear Colleagues,

Recent advances in molecular biology, metabolomics, and systems biology have significantly expanded our understanding of the complexity and regulation of the tryptophan–serotonin–melatonin axis. Beyond their classical roles in mood regulation and sleep–wake cycles, serotonin and melatonin, along with their metabolites, have been implicated in neurodegenerative disorders, psychiatric diseases, metabolic dysfunctions, inflammatory conditions, and cancer. Moreover, emerging evidence highlights the significant influence of the gut microbiota, nutritional factors, and environmental stressors on tryptophan metabolism and indoleamine signaling.

Given the growing recognition of the pleiotropic roles of tryptophan-derived metabolites in maintaining physiological homeostasis and their potential as therapeutic targets, further research is essential to elucidate regulatory mechanisms and pathological alterations within this metabolic network. This Special Issue aims to gather current knowledge and novel insights into the biosynthesis, genetics, metabolism, and biological significance of serotonin and melatonin pathways originating from tryptophan.

Aim: This Special Issue aims to provide a comprehensive overview of advances in understanding tryptophan metabolism, including the biosynthesis of serotonin and melatonin and their downstream metabolic transformations. The Issue will focus on the molecular, biochemical, physiological, and pathological aspects of the tryptophan–serotonin–melatonin axis, highlighting its role in circadian regulation, neurochemical signaling, and systemic homeostasis. Emphasis will be placed on regulatory mechanisms, environmental and nutritional influences, and the involvement of these pathways in human health and disease.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

• Enzymatic and molecular mechanisms of serotonin and melatonin biosynthesis from tryptophan;
• Regulation of tryptophan metabolic pathways, including genetic, epigenetic, and environmental factors;
• Catabolism and metabolic fate of serotonin and melatonin and the biological roles of their metabolites;
• Interactions between tryptophan metabolism and circadian rhythm regulation;
• Neurochemical, endocrine, and immunological functions of serotonin and melatonin;
• The role of gut microbiota in tryptophan and indoleamine metabolism;
• Nutritional and pharmacological modulation of the tryptophan–serotonin–melatonin axis;
• The involvement of these pathways in neurological, psychiatric, metabolic, and inflammatory diseases;
• Emerging analytical approaches and metabolomic profiling of tryptophan-derived indoleamines.

We look forward to receiving your contributions.

Prof. Dr. Anna Cieslinska
Guest Editor

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