The adrenergic system plays a central role in human physiology. However, it can also affect commensal bacteria via adrenergic hormones. Bacteria use adrenergic hormones as xenosiderophore for iron supply, modulators of biofilm formation, quorum-sensing autoinducers regulating virulence factors and pathogenicity, and for interaction with other commensals influencing the microbiome profiles. Bacteria also produce biogenic amines through aromatic amino acid decarboxylation which is widely expressed in human commensals. These biogenic amines are capable of interacting with adrenergic receptors, leading to a variety of different effects on the human body. Phenylacetyl acid is another compound produced by bacteria found in the gut that acts as a precursor of phenylacetylglutamine, a compound that has been linked to cardiac diseases due to its ability to induce thrombosis by activating adrenergic receptors present in platelets.

The epithelial cells lining the lumen of the tubular system in the kidney are exposed to a highly dynamic microenvironment, owing to the fluid flow of the pro-urine through this system. Renal flow sensing has been linked to various processes in the kidney, including electrolyte reabsorption. An important mediator of renal flow sensing is the primary cilium, which is found on almost all tubular epithelial cells. In this review, we describe the reported effects of fluid flow on electrolyte transport in the different segments of the nephron and whether these effects are dependent on the primary cilium. Collectively, these studies highlight the stimulatory effect of fluid flow on electrolyte reabsorption, with a variable degree of dependency on the primary cilium.