Human Endogenous Metabolite

Human endogenous metabolites serve critical roles in maintaining cellular and systemic homeostasis through diverse biochemical pathways^[1][2]. These metabolites participate in intercellular communication, modulating signaling cascades such as kinase activation, receptor engagement, and transcriptional regulation^[1][3]. For instance, β-hydroxybutyrate functions not only as an energy substrate during fasting or exercise but also as an epigenetic modifier and agonist for G-protein-coupled receptor GPR109A, influencing inflammatory and neuroprotective pathways^[4]. Similarly, indoxyl 3-sulfate (I3S), a uremic metabolite, selectively activates the human aryl hydrocarbon receptor (AHR), regulating genes including CYP1A1, CYP1A2, and IL6, and contributes to pathophysiology in renal disease^[5][6]. Compared with related isoforms, I3S exhibits approximately 500-fold higher potency in human AHR activation than in mouse, highlighting species-specific isoform distinctions^[5]. Other metabolites, such as shikimic acid, inhibit vascular smooth muscle cell proliferation and migration through modulation of ERK1/2, AKT, and AMPK pathways, illustrating their functional relevance in cardiovascular research models^[2]. Endogenous hydrogen sulfide, generated by CBS and CSE, mediates tissue-specific physiological effects in the genito-urinary system and represents a potential therapeutic target for disorders such as erectile dysfunction and preeclampsia^[7]. These findings collectively support the utility of endogenous metabolites as modulators of signaling, disease biomarkers, and candidates for experimental pharmacological studies^[1][8][3].