L-arginine: its role in human physiology, in some diseases and mainly in viral multiplication as a narrative literature review

Abstract

Abstract Background L-arginine (Arg) is an amino acid that contributes to several aspects of human biochemistry. Individuals with malnutrition and certain physical conditions could benefit from arginine intake. However, as Arg is required by certain viruses, it is advised to avoid it in one's diet and supplementation during viral illnesses. New studies have emerged during the COVID-19 pandemic, and pioneering research has been reviewed. Main body of the abstract The purpose of this review is to determine when and why Arg depletion, supplementation, or avoidance is advisable, considering the divergent results. A narrative review was conducted by surveying scientific publications indexed in electronic databases. Studies published from 1960 up to 2024, with no language restrictions, were included. Arg comes from proteins in the human diet. The kidney is the main site of endogenous Arg synthesis and also responsible for the overall metabolism of this amino acid, participating in synthesis, degradation and reabsorption. The liver can synthesize Arg, but since this is completely recycled in the urea cycle, it contributes little or no to the Arg plasma flux. Arg present in diet is passively absorbed in the small intestine and also transformed into urea and ornithine via urea cycle in hepatocytes. It is associated with macrophage metabolism, vasomotor control, intracellular signaling, memory formation, immune response, and an important messenger of the bronchopulmonary, cardiovascular and neural systems. Thus, excessive or decreased Arg concentration could impair health condition. High Arg concentrations stimulated rapid reactivation and resumption of protein synthesis in some viruses. Conclusion According to research, caution should be exercised when supplementing or depleting the amino acid arginine. Individuals who are carriers of latent viruses, such as herpesviruses, and/or who have been exposed to other viruses studied, should avoid arginine supplements and the consumption of foods rich in arginine. However, as prophylaxis or antiviral therapy, control of arginine intake as well as the use of lysine supplements, its antagonist, is recommended for short periods starting after a possible viral exposure, or in face of stimuli that can remove viruses from their latent state and/or at the very beginning of the viral manifestation, in order to avoid a large viral multiplication and consequently control the infection. Long-term arginine depletion can significantly affect cellular metabolism and its use as supplemental therapy needs case-by-case evaluation. Graphical abstract