Irisin is a hormone secreted by skeletal muscle following exercise or excess of saturated fatty acids (SFAs) , able to improve metabolic homeostasis and promote energy expenditure. Serum irisin levels are reduced in type 2 diabetes (T2D) , while exogenous irisin administration improves glycemic control in diabetic mice. We have previously demonstrated that irisin protects human and rodent β-cells and pancreatic islets from SFAs-induced apoptosis, increases insulin biosynthesis and glucose-stimulated insulin secretion (GSIS) , and promotes β-cell proliferation, both in vitro and in vivo in healthy wild-type mice. Irisin may also restore the defective GSIS and reduce the high rate of apoptosis that are characteristic of islets from T2D patients. However, the β-cellular effects of irisin administration to diabetic mice are still unknown. 6 weeks-old C57Bl/6 mice (n = 8) were fed a high-fat diet (HFD, 60% of energy deriving from fat) for weeks and then intraperitoneally injected with streptozotocin (STZ, 100 mg/Kg) to induce diabetes. 4 standard diet (SD) -fed mice were used as control. HFD/STZ mice were then treated with 0.5 μg/g irisin (n = 4) or vehicle (n = 4) for 14 days. Glucose tolerance, glycemia, insulinemia, body weight, pancreatic islet architecture and function were assessed throughout the study. As expected, compared to SD mice, HFD/STZ mice showed higher glycemia and body weight, glucose intolerance, and reduced GSIS; in addition, HFD/STZ mice showed reduced islet volume (-78%) , β-cell area (-35%) , and insulin content (-60%) , while increased α-cell area (+54%) . Irisin administration significantly restored glycemia (-31%) , body weight (-13%) , glucose tolerance (-27%, AUC) , GSIS (+23%, AUC) , islet volume (+61%) , β-cell (+34%) and α-cell (-49%) areas, and insulin content (+36%) . Of note, irisin treatment induced a 9-fold increase in β-cell proliferation rate. These results show for the first time that irisin can restore β-cell functional mass when administered in vivo to diabetic mice.
N.Marrano: None. G.Biondi: None. A.Borrelli: None. L.Roberto: None. A.Cignarelli: None. S.Perrini: None. L.Laviola: Advisory Panel; Lilly Diabetes, Novo Nordisk, Roche Diabetes Care, Sanofi, Speaker's Bureau; A. Menarini Diagnostics, Abbott Diabetes, Medtronic, Terumo Corporation. F.Giorgino: Advisory Panel; AstraZeneca, Boehringer Ingelheim International GmbH, Novo Nordisk, Consultant; Lilly Diabetes, Sanofi, Research Support; Lilly Diabetes, Roche Diabetes Care, Takeda Pharmaceutical Company Limited. A.Natalicchio: Consultant; Novo Nordisk, Other Relationship; AstraZeneca, Lilly Diabetes, Sanofi.
EU – ESF PON R&I 2014-20, AIM