Impaired metabolic phenotyping in mice with deletions of GPR10 and NPFFR2 receptors: Implications for lipidized PrRP analog therapy in obesity

Scientific background: Obesity is a growing global health concern with limited treatment options.Prolactin-releasing peptide (PrRP) is a neuropeptide that can reduce food intake when administered centrally but loses this effect when given peripherally.However, lipidization of peptides can enhance their stability and efficacy after peripheral administration.Our previous work showed that lipidized PrRP analogs effectively reduced food intake and body weight in mice 1 .PrRP binds to its GPR10 receptor and with high affinity to neuropeptide FF receptor type 2 (NPFFR2) 2 , both of which are involved in regulating food intake and energy homeostasis.Palmitoylated analog of PrRP31, palm 11 -PrRP31 improved its binding and agonist activity for both receptors 3,6,7 .We have previously shown that deletion of GPR10 resulted in increased food intake, elevated insulin levels, impaired glucose tolerance, and altered lipid metabolism gene expression 4 .NPFFR2 knockout mice showed severe glucose intolerance, which worsened with a high-fat diet (HFD), and developed hypothalamic insulin resistance due to reduced insulin pathway signaling proteins 5 .Deletion of both GPR10 and NPFFR2 caused sex-specific and diet-dependent metabolic changes, including impaired glucose tolerance and hyperglycemia on a high-fat diet. Methods:In this study, we examined the effect of palm 11 -PrRP31 on mice with deletion of either GPR10 or NPFFR2 or both receptors (GPR10/NPFFR2 KO or dKO mice).Male mice were fed a HFD starting at 8 weeks of age for a duration of 5 months.During the final month, they received a 4-week subcutaneous treatment with either saline or palm 11 -PrRP31 (5 mg/kg) administered twice daily.An oral glucose tolerance test (OGTT) was performed in the third week of the interventions, and fasting plasma was collected to measure insulin levels.Finally, the mice were euthanized by decapitation, and organs (brain, liver, adipose tissue) were collected for further analysis. Results and discussion:The palmitoylated palm11-PrRP31 analog demonstrated strong appetite-suppressing and glucose-lowering effects in obese wild-type (WT) mice.Treatment with palm11-PrRP31 led to a significant reduction in body weight and food intake in GPR10 KO mice, whereas in NPFFR2 KO mice, the reduction in body weight was less pronounced and food intake was only slightly reduced.In dKO mice, which lack both GPR10 and NPFFR2 receptors, there was no reduction in body weight or food intake.