Radioprotective effect of the anti-diabetic drug metformin
Silvia Siteni, Summer Barron, Krishna Luitel, Jerry W. Shay
Abstract
Metformin is a biguanide currently used in the treatment of diabetes mellitus type 2. Besides its anti-glycemic effects, metformin has been reported to induce different cellular pleiotropic effects, depending on concentration and time of treatment. Here we report one administration of metformin (0.5 mM) has radioprotective effects in vitro on BJ human fibroblasts, increasing DNA damage repair and increasing SOD1 expression in the nucleus. Importantly, metformin (200 mg/kg) pre-administration for only 3 days in wild type 129/sv mice, decreases the formation of micronuclei in bone marrow cells and DNA damage in colon and lung tissues compared to control irradiated mice at sub-lethal and lethal doses, increasing the overall survival fraction by 37% after 10Gy total body irradiation.
Introduction
Ionizing radiation (IR) induces direct damage on cellular DNA, lipids and proteins as well as indirectly through the radiolysis processes [1]. The radiolysis of water molecules generates reactive oxygen species (ROS), hydroxyl radicals (•OH), ionized water (H2O+), and hydrogen radicals (H•), whereas superoxide (O2•−) and hydrogen peroxide (H2O2) are formed as secondary ROS products of IR [2]. Low-dose radiation is an important diagnostic tool (e.g., computed tomography scanning) while high-dose radiation is a well-known approach for the treatment of many tumor types.
Materials and method
Cell lines
BJ human foreskin fibroblasts were obtained from the ATCC (Manassas, VA) and grown in Medium X (DMEM:199, 4:1, Hyclone, Logan, UT) supplemented with 10% cosmic calf serum (Hyclone, Logan, UT) without antibiotics and incubated in a humidified atmosphere with 5% CO2 at 37°C. Only BJs with a population doubling between 5 and 15 were used. BJ cells are very stable in vitro maintaining a normal karyotype for over 50 population doubles. Thus, the BJ cells used in the present studies would still be considered young or middle aged and not old.
Results
Metformin 0.5mM does not affect long-term growth in normal human BJ fibroblasts, induces AMPK phosphorylation and activates a detoxification mechanism through expression of SOD1
We first performed a Cell Titer Glo (CTG) analysis to study the short-term effects of metformin on human BJs fibroblasts and observed an IC50 value of 25 mM (S1A Fig). We then evaluated the expression of the superoxide dismutase SOD1 at the concentration of 0.05, 0.1, 0.5, 1mM after 72 hours. We found 0.5 mM and 1 mM metformin showing the highest expression of SOD1 (S1B Fig). To determine the impact of metformin on long-term survival, we performed a clonogenic assay with normal human BJ fibroblasts.
Discussion
Metformin remains the preferred first-line pharmacologic treatment for type 2 diabetes. However, metformin has been reported to have additional applications, including as a radioprotective compound [33]. One of the main issues about metformin is the usage of the correct concentration that is safe. Supra-pharmacological concentrations of metformin are not translatable in human beings, and, importantly pharmacological or supra-pharmacological concentrations lead to different cellular effects [34].
Acknowledgments
This work would not have been possible without support from Dr. Adam Rusek and Peter Guida and other members of the BNL and NSRL team.
Citation: Siteni S, Barron S, Luitel K, Shay JW (2024) Radioprotective effect of the anti-diabetic drug metformin. PLoS ONE 19(7): e0307598. https://doi.org/10.1371/journal.pone.0307598
Editor: Hanbing Li, Zhejiang University of Technology, CHINA
Received: April 1, 2024; Accepted: July 8, 2024; Published: July 23, 2024
Copyright: © 2024 Siteni et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: https://doi.org/10.18738/T8/JPAKKV.
Funding: This work was supported by NASA Grants # NNX16AE08G to JWS and NNX15AI21G to J.W.S and Albert Fornace. K.L. was supported by Cancer Training Grant T32CA124334. This work was performed in laboratories constructed with support from NIH grant C06 RR30414. We also acknowledge the Harold Simmons NCI Designated Comprehensive Cancer Center Support Grant (CA142543).
Competing interests: J.W.S. holds the distinguished Southland Financial Corporation chair in Geriatrics Research. J.W.S is a SAB member of Reata Pharmaceutical, Inc. (Irving, TX). S.S, S.B and K.L. declare no competing interests.
