Enhancing β‐cell Sensitivity to Kisspeptin via Linkage to GLP‐1

Abstract

Glucagon Like Peptide‐1 (GLP‐1) and Kisspeptin (KP) receptors are co‐expressed on pancreatic β‐cells, and activation of both receptors potentiate glucose stimulated insulin secretion (GSIS), although they appear to work via different downstream signaling pathways. Unlike GLP‐1, KP has a low affinity for receptor activation (EC50 20 nM vs >1 uM) making it difficult to use as a drug without significant side effects. We developed a bivalent ligand composed of GLP‐17–36 and KP‐10 binding domains linked together, to evaluate if linking KP to a high affinity ligand would promote its activity at low concentrations by presumably increasing its local membrane concentration after GLP‐1 binding. This feature may also provide some specificity for targeting to β‐cells which express both receptors. The effects of KP‐10, GLP‐1 and the KP‐10/GLP‐1 bivalent analog on insulin secretion from the INS 832/3 cell line were investigated. KP‐10 by itself had no effect on insulin secretion in the absence of glucose, but more than doubled GSIS (basal, 0.23 +/− 0.07; GSIS 0.60 +/− 0.02 ng/min) with an EC50 of ~25 μM. At saturating doses, KP‐10 (100 μm) and GLP‐1 (100 nM) had similar effects on GSIS, and together as monomers had an additive effect (0.79 +/− 0.07 (ng/min) consistent with activation of independent downstream signaling pathways. The dimer also did not activate secretion in the absence of glucose, but doubled GSIS much like the individual monomers (0.64 +/− 0.01 ng/min); that is, an additive response was not obvious. This finding suggests that either the KP‐10 moiety is not binding or is not active in the bivalent ligand, or that GLP‐1 activity is diminished in the bivalent construct such that the combined effect of GLP‐1/KP‐10 is diminished when compared to the additive effect or the monomers. We have evidence from previous studies that binding of the GLP‐1 moiety within a bivalent construct is decreased relative to monomeric GLP‐11, suggesting an additive response may be present. Currently, we are determining the ability of GLP‐1/KP‐10 to initiate downstream signaling from both ligands to resolve the question: is KP active in the GLP‐1/KP at concentrations where monomeric KP‐10 is not.Support or Funding InformationFunded by the American Diabetes Association and Juvenile Diabetes Research FoundationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.