Abstract Body (Do not enter title and authors here): BACKGROUND: Atrial natriuretic peptide (ANP) and glucagon-like peptide-1 (GLP-1) are endogenous hormones known for roles in cardiovascular regulation and metabolic homeostasis. ANP mediates its actions via the GC-A receptor, while GLP-1 via the GLP-1 receptor (GLP-1R). Both peptides may stimulate insulin secretion from pancreatic beta cells and augment lipid metabolism in adipocytes, yet potential synergistic effects remain unexplored. To optimize ANP activation of GC-A, we developed a novel 15 amino acid miniaturized GC-A activating peptide CRRL555. CRRL555 possesses greater GC-A binding and activating properties than ANP.
AIMS: We investigated the metabolic properties of CRRL555/GC-A and its interaction with GLP-1/GLP-1R in vitro.
METHODS: Rat pancreatic beta cells (INS-1) were stimulated with high glucose (20mM) and treated with GLP-1 or CRRL555 (10^-10-10^-6M) and together for 1 hr. Supernatant was collected and insulin was measured by ELISA. Human visceral adipocytes were differentiated for 10 days and then treated with GLP-1 or CRRL555 (10^-10-10^-6M) or together for 6 hrs. Supernatant was collected and glycerol and free fatty acid (NEFA), indicators of lipolysis, were measured.
RESULTS: CRRL555 (p<0.05) and GLP-1 (p<0.05), dose dependently, stimulated insulin secretion in INS-1 cells in the presence of high glucose. Importantly, CRRL555 combined with GLP-1, resulted in a greater enhancement (p<0.05) of insulin secretion compared to either peptide alone. While high dose CRRL555 and GLP-1 (10^-6M) stimulated lipolysis in visceral adipocytes with increases in glycerol and NEFA, only CRRL555 at low dose (10^-10M), and not low dose GLP-1 (10^-10M), stimulated glycerol and NEFA production (p<0.05). When low dose GLP-1 (10^-10M) was added to low dose CRRL555(10^-10M), lipolysis was like CRRL555 alone.
CONCLUSION: We report a novel synergy in insulin release from beta cells with combined stimulation of the potent and miniaturized GC-A designer peptide CRRL555 with GLP-1. CRRL555 possesses greater lipolytic properties compared to GLP-1 in visceral adipocytes at low doses advancing novel metabolic actions of CRRL555 alone or combined with GLP-1R activation. These in vitro studies of dual receptor activation of GC-A and GLP-1R highlight the therapeutic potential of combining CRRL555 with GLP-1-based therapies for the treatment of cardiometabolic diseases, thus supporting studies of dual GC-A/GLP-1R activation in experimental cardiometabolic disease states.