Enzymatic Stability and Comparative Effects of Kisspeptin-14, Kisspeptin-13 and Kisspeptin-10 on Beta-Cell Function, Glucose Homeostasis and Appetite Regulation.

Background/

Objective

Kisspeptin peptides are being increasingly recognised as regulators of metabolism, but whether these actions differ depending on peptide isoform remains unclear.

Methods

The current study compared the enzymatic stability and biological effects of kisspeptin-14 (KP-14), kisspeptin-13 (KP-13) and kisspeptin-10 (KP-10) on beta-cell health and function, glucose homeostasis and appetite. Peptide stability was assessed in murine plasma and, following confirmation of KISS1R expression in BRIN-BD11 beta-cells, actions on insulin secretion, beta-cell proliferation and apoptosis were investigated, with additional secretory studies in isolated murine islets. Metabolic effects of KP-14, KP-13 and KP-10 were subsequently evaluated in healthy male and female mice.

Results

KP-14 was resistant to plasma degradation, whereas KP-13 and KP-10 underwent N-terminal proteolysis, with KP-13 degradation generating KP-10 amongst other fragment peptides. The kisspeptin peptides exerted modest direct effects on insulin secretion from BRIN-BD11 cells, with KP-13 being the most efficacious, a bioactivity profile that was confirmed in islets. In addition, KP-13 significantly enhanced beta-cell proliferation and protected against cytokine-induced apoptosis, producing superior beta-cell proliferative effects compared to exenatide. Acute administration of all kisspeptin peptides elevated circulating glucose concentrations, and while KP-14 and KP-10 impaired glucose tolerance, KP-13 did not. Interestingly, KP-14 enhanced glucose-stimulated insulin secretion, with KP-13 and KP-10 being devoid of such actions. All kisspeptin isoforms suppressed food intake, although only KP-13, and especially KP-10 administration, led to an inhibition of feeding.

Conclusions

Taken together, these data identify KP-13 as possessing the most favourable overall metabolic actions, based on a combination of beneficial actions on beta-cell health and function together with inhibition of feeding and lack of prominent glucose-elevating actions, suggesting possible therapeutic application for type 2 diabetes.