Recently, it was reported that administration of l-arginine enhances the secretion of GLP-1 and peptide YY (PYY), another gut hormone secreted from L-cells, in both rodents and humans 12, 13. Glucose, several types of amino acids, and fatty acids have all been identified as secretagogues of GLP-1 9, 10, 11. Glucagon-like peptide-1 (GLP-1), a gut hormone secreted from enteroendocrine L-cells, plays a role in potentiating glucose-dependent insulin secretion and reducing appetite 7, 8. Furthermore, evidence suggests that this pathway is involved in exocytotic functions through the activation of some targeted proteins, such as phosphodiesterase, protein kinases, or ionic channels NO donors, nitrites, and cGMP analogues potentiate glucose-induced insulin secretion from pancreatic β cells 4, 5, 6. The NO/cGMP signalling pathway is associated with several cell functions, including relaxation of vascular muscles and neurotransmission 3.
SGC is the only conclusively proven receptor for nitric oxide (NO), a signalling molecule produced by the enzyme nitric oxide synthase (NOS) from the amino acid l-arginine 2. Thus, revealing the precise spatiotemporal regulation mechanisms of intracellular cGMP dynamics, particularly its interactions with other signalling molecules such as Ca 2+, is an important research goal. The complexity of intracellular cGMP dynamics depends on the balance of the activation and expression level of these proteins.
Intracellular cGMP concentration is strictly regulated via production by cytosolic/soluble guanylyl cyclase (sGC) or membrane-bound/particulate guanylyl cyclase and through degradation by phosphodiesterase 1. Cyclic guanosine 3′, 5′-monophosphate (cGMP) is an important second messenger involved in a variety of physiological functions such as smooth muscle relaxation and phototransduction 1.
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