Beneficial long-term antidiabetic actions of N- and C-terminally modified analogues of apelin-13 in diet-induced obese diabetic mice.

AimsThis study investigated the chronic effects of twice daily administration of stable apelin analogues, apelin-13 amide and (pGlu)apelin-13 amide, on metabolic parameters in glucose intolerant and insulin resistant diet-induced obese (DIO) mice fed a high-fat diet for 150 days.Study Design & MethodsGroups of mice received twice daily (09:00 and 17:00 h) injections of saline vehicle, apelin-13 amide, (pGlu)apelin-13 amide or exendin-4(1–39) for 28 days (all at 25 nmol/kg). Energy intake, body weight, non-fasting blood glucose, plasma insulin, glucose tolerance, metabolic response to feeding and insulin sensitivity together with pancreatic hormone content and biochemical parameters such as lipids and total GLP-1 were monitored. Dual-energy X-ray absorptiometry (DXA) analysis and indirect calorimetry were also performed.ResultsAdministration of apelin-13 amide, (pGlu)apelin-13 amide or exendin-4 significantly decreased bodyweight, food intake, blood glucose and increased plasma insulin compared with high-fat fed saline treated controls (P < 0.05 and P < 0.001), Additionally, all peptide treated groups exhibited improved glucose tolerance (oral and ip), metabolic responses to feeding and associated insulin secretion. (pGlu)apelin-13 amide also significantly improved HbA1c and insulin sensitivity after 28 days. Both (pGlu)apelin-13 amide and exendin-4 increased bone mineral content and decreased respiratory exchange ratio (RER), whereas only (pGlu)apelin-13 amide increased energy expenditure. All treatment groups displayed reduced circulating triglycerides and increased GLP-1 concentrations, although only (pGlu)apelin-13 amide significantly reduced LDL-cholesterol, total body fat, and increased pancreatic insulin content.ConclusionThese data indicate the therapeutic potential of stable apelin-13 analogues with effects equivalent to or better than exendin-4.