The Anti-Diabetic Drug Metformin Suppresses Pathological Retinal Angiogenesis via Blocking the mTORC1 Signaling Pathway in Mice (Metformin Suppresses Pathological Angiogenesis)

Abstract

Purpose

Metformin, a biguanide antihyperglycemic drug, can exert various beneficial effects in addition to its glucose-lowering effect. The effects of metformin are mainly mediated by AMP-activated protein kinase (AMPK)-dependent pathway. AMPK activation interferes with the action of the mammalian target of rapamycin complex 1 (mTORC1), and blockade of mTORC1 pathway suppresses pathological retinal angiogenesis. Therefore, in this study, we examined the effects of metformin on pathological angiogenesis and mTORC1 activity in the retinas of mice with oxygen-induced retinopathy (OIR).

Methods

OIR was induced by exposing the mice to 80% oxygen from postnatal day (P) 7 to P10. The OIR mice were treated with metformin, rapamycin (an inhibitor of mTORC1), or the vehicle from P10 to P12 or P14. The formation of neovascular tufts, revascularization in the central avascular areas, expression of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) 2, and phosphorylated ribosomal protein S6 (pS6), a downstream indicator of mTORC1 activity, were evaluated at P10, P13, or P15.

Results

Neovascular tufts and vascular growth in the central avascular areas were observed in the retinas of P15 OIR mice. The formation of neovascular tufts, but not the revascularization in the central avascular areas, was attenuated by metformin administration from P10 to P14. Metformin had no significant inhibitory effect on the expression of VEGF and VEGFR2, but it reduced the pS6 immunoreactivity in vascular cells at the sites of angiogenesis. Rapamycin completely blocked the phosphorylation of ribosomal protein S6 and markedly reduced the formation of neovascular tufts.

Conclusions

These results suggest that metformin partially suppresses the formation of neovascular tufts on the retinal surface by blocking the mTORC1 signaling pathway. Metformin may exert beneficial effects against the progression of ocular diseases in which abnormal angiogenesis is associated with the pathogenesis.

Keywords:

• Pathologic angiogenesis
• retina
• mammalian target of rapamycin
• ribosomal protein S6
• vascular endothelial growth factor

Acknowledgments

We thank Hiroko Ushikubo for excellent technical assistance.

Authors’ contribution

Tsutomu Nakahara designed research; Rina Yagasaki and Akane Morita performed the experiments; Rina Yagasaki, Akane Morita, Asami Mori, and Tsutomu Nakahara analyzed data; Rina Yagasaki, Kenji Sakamoto, and Tsutomu Nakahara performed statistical analysis; Rina Yagasaki and Tsutomu Nakahara wrote the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author [T. N.], upon reasonable request.

Additional information

Funding

This study was supported by JSPS KAKENHI [Grant Numbers: 26460103 [T.N.] and 21K06604 [T.N.]).