OR12-04 LEAP2 Deletion Does Not Counteract The Effects Of Ghrelin Deletion During Insulin-Induced-Hypoglycemia
Authors: Shankar Kripa , Varshney Salil , Gupta Deepali , Singh Omprakash , Ogden Sean B , Osborne-Lawrence Sherri , Metzger Nathan P , Richard Corine P , Marc Zigman Jeffrey 
Published: October 2023

Abstract
Disclosure: K. Shankar: None. S. Varshney: None. D. Gupta: None. O. Singh: None. S.B. Ogden: None. S. Osborne-Lawrence: None. N.P. Metzger: None. C.P. Richard: None. J.M. Zigman: Grant Recipient; Self; Novo Nordisk.
Objective: The hormones ghrelin and LEAP2 both are endogenous ligands for the growth hormone secretagogue receptor (GHSR). Whereas ghrelin activates GHSR, LEAP2 blocks ghrelin from activating GHSR and also inhibits GHSR constitutive activity. It is via GHSR that the glucoregulatory actions of ghrelin and LEAP2 are mediated. These glucoregulatory actions are highlighted by the findings of severe hypoglycemia in ghrelin-KO mice and LEAP2-overexpressing mice when they are submitted to an acute-on-chronic caloric restriction protocol. Also, recently, our group showed that ghrelin-KO mice require a much higher glucose infusion rate (GIR) and exhibit markedly reduced elevation of counterregulatory hormones when submitted to a hyperinsulinemic-hypoglycemic clamp. In the current study, we investigated the potential of LEAP2 to protect against insulin-induced-hypoglycemia and counteract the effects of ghrelin deletion during the hypoglycemic clamp. Methods: Eight-ten week-old male wild-type (WT), Ghrelin-KO, LEAP2-KO, and LEAP2/Ghrelin-doubleKO (lacking both ghrelin and LEAP2 ) littermates were used for this study (n=7-10 per genotype). Mice were implanted with a right jugular vein catheter. Five days later, hyperinsulinemic-hypoglycemic clamps were performed in conscious, unrestrained mice. A low dose of insulin was infused at 4 mU/kg/min i.v. over 2 hr. A 20% glucose solution was simultaneously infused at a variable rate to achieve hypoglycemia (35–45 mg/dL) during the final 30 min. Blood glucose was measured via tail nicks every 5 min. Results: We were able to achieve the target hypoglycemic range in all four genotypes using this protocol. As compared to WT mice, Ghrelin-KO mice required markedly elevated (∼110% higher) GIRs (10±4 mg/kg/min in WT vs. 22±2 mg/kg/min in Ghrelin-KO mice; p=0.03) by the end of the 2-hr clamp. The GIRs required by LEAP2-KO mice were equivalent to those of WT mice (7±2 mg/kg/min in LEAP2-KO; p=n.s.). Furthermore, although during the first 60 min of the clamp, LEAP2/Ghrelin-doubleKO mice exhibited slightly lower blood glucose levels than the other genotypes and during the middle 60 min of the clamp, they required higher GIRs than the other genotypes, by the end of the 2-hr clamp, their GIRs were similar to Ghrelin-KO mice (25±3 mg/Kg/min in Ghrelin/LEAP2-doubleKO mice, p=n.s.). Conclusions: These data suggest a complex effect of LEAP2 on blood glucose. Alone, LEAP2 deletion does not impact insulin sensitivity. When coupled with ghrelin deletion, LEAP2 deletion lowers fasting blood glucose and causes greater insulin sensitivity early on during the hyperinsulinemic-hypoglycemic clamp. By the end of the clamp, this effect of LEAP2 deletion when coupled to ghrelin deletion is gone. Altogether, these results suggest that LEAP2 deletion does not counteract the effects of ghrelin deletion during insulin-induced hypoglycemia.
Presentation: Friday, June 16, 2023