Dysfunction of glucagon-secreting α-cells participates in the progression of diabetes, and glucagon receptor (GCGR) antagonism is regarded as a novel strategy for diabetes therapy. GCGR antagonism upregulates glucagon and glucagon-like peptide-1 (GLP-1) secretion, and notably promotes β-cell regeneration in diabetic mice. Here, we aimed to clarify the role of GLP-1 receptor (GLP-1R) activated by glucagon and/or GLP-1 in the GCGR antagonism-induced β-cell regeneration. We showed that in db/db mice and type 1 diabetic wild-type or Flox/cre mice, GCGR monoclonal antibody (mAb) improved glucose control, upregulated plasma insulin level, and increased β-cell area. Notably, blockage of systemic or pancreatic GLP-1R signaling by exendin 9-39 (Ex9) or Glp1r knockout diminished the above effects of GCGR mAb. Furthermore, glucagon neutralizing antibody (nAb), which prevents activation of GLP-1R by glucagon, also attenuated the GCGR mAb-induced insulinotropic effect and β-cell regeneration. In cultured primary mouse islets isolated from normal mice and db/db mice, GCGR mAb action to increase insulin release, and to upregulate β-cell specific marker expression, was reduced by a glucagon nAb, or by the GLP-1R antagonist Ex9, or by a pancreasspecific Glp1r knockout. These findings suggest that activation of GLP-1R by glucagon participates in β-cell regeneration induced by GCGR antagonism in diabetic mice.

Aims Sodium‐glucose co‐transporter 2 inhibitors, including dapagliflozin, improve ß cell function in type 2 diabetic individuals. Whether dapagliflozin can protect islet microvascular endothelial cells (IMECs) and thus contribute to the improvement of ß cell function remains unknown. Materials and Methods The db/db mice were treated with dapagliflozin or vehicle for 6 weeks. ß cell function, islet capillaries and the levels of inflammatory chemokines in IMECs were detected. The mouse IMEC cell line MS‐1 cells were incubated with palmitate and/or dapagliflozin for 24 h. Angiogenesis and inflammatory chemokine levels were evaluated, and the involved signalling pathways were analysed. The mouse ß cell line MIN6 cells, in the presence or absence of co‐culture with MS‐1 cells, were treated with palmitate and/or dapagliflozin for 24 h. The expression of ß cell specific markers and insulin secretion in MIN6 cells were determined. Results Dapagliflozin significantly improved ß cell function, increased islet capillaries and decreased the levels of inflammatory chemokines of IMECs in db/db mice. In the palmitate‐treated MS‐1 cells, angiogenesis was enhanced and the levels of inflammatory chemokines were downregulated by dapagliflozin. Either a PI3K inhibitor or mTOR inhibitor eliminated the dapagliflozin‐mediated effects. Importantly, dapagliflozin attenuated the palmitate‐induced downregulation of ß cell function‐related gene expression and insulin secretion in MIN6 cells co‐cultured with MS‐1 cells but not in those on mono‐culture. Conclusions Dapagliflozin restores islet vascularisation and attenuates the inflammation of IMECs in type 2 diabetic mice. The dapagliflozin‐induced improvement of ß cell function is at least partially accounted for by its beneficial effects on IMECs in a PI3K/Akt‐mTOR‐dependent manner.

Male diabetic individuals present a marked impairment in fertility; however, knowledge regarding the pathogenic mechanisms and therapeutic strategies is unsatisfactory. The new hypoglycemic drug dapagliflozin has shown certain benefits, such as decreasing the risk of cardiovascular and renal events in patients with diabetes. Even so, until now, the effects and underlying mechanisms of dapagliflozin on diabetic male infertility have awaited clarification. Here, we found that dapagliflozin lowered blood glucose levels, alleviated seminiferous tubule destruction, and increased sperm concentrations and motility in leptin receptor-deficient diabetic db/db mice. Moreover, the glucagon-like peptide-1 receptor (GLP-1R) antagonist exendin (9–39) had no effect on glucose levels but reversed the protective effects of dapagliflozin on testicular structure and sperm quality in db/db mice. We also found that dapagliflozin inhibited the testicular apoptotic process by upregulating the expression of the antiapoptotic protein B-cell lymphoma 2 (BCL2) and X-linked inhibitor of apoptosis protein (XIAP) and inhibiting oxidative stress by enhancing the antioxidant status, including total antioxidant capacity, total superoxide dismutase (SOD) activity, and glutathione peroxidase (GPx) activity, as well as decreasing the level of 4-hydroxynonenal (4-HNE). Exendin (9–39) administration partially reversed these effects. Furthermore, dapagliflozin upregulated the glucagon-like peptide-1 (GLP-1) level in plasma and GLP-1R expression by promoting AKT8 virus oncogene cellular homolog (Akt) phosphorylation in testicular tissue. Exendin (9–39) partially inhibited Akt phosphorylation. These results suggest that dapagliflozin protects against diabetes-induced spermatogenic dysfunction via activation of the GLP-1R/phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Our results indicate the potential effects of dapagliflozin against diabetes-induced spermatogenic dysfunction.