Effect of metformin exposure on growth and photosynthetic performance in the unicellular freshwater chlorophyte, Chlorella vulgaris Public Deposited

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  • Many pharmaceuticals have negative effects on biota when released into the environment. For example, recent work has shown that the commonly prescribed antidiabetic drug, metformin (N,N-dimethylbiguanide), has endocrine disrupting effects on fish. However, effects of metformin on aquatic primary producers are poorly known. We exposed cultured isolates of a freshwater chlorophyte, Chlorella vulgaris, to a range of metformin concentrations (0–767.9 mg L⁻¹) to test the hypothesis that exposure negatively affects photosynthesis and growth. A cessation of growth, increase in non-photochemical quenching (NPQ, NPQmax), and reduced electron transport rate (ETR) were observed 24 h after exposure to a metformin concentration of 767.8 mg L⁻¹ (4.6 mM). By 48 h, photosynthetic efficiency of photosystem II (Fv/Fm), α, the initial slope of the ETR-irradiance curve, and Ek (minimum irradiance required to saturate photosynthesis) were reduced. At a lower concentration (76.8 mg L⁻¹), negative effects on photosynthesis (increase in NPQ, decrease in ETR) were delayed, occurring between 72 and 96 h. No negative effects on photosynthesis were observed at an exposure concentration of 1.5 mg L⁻¹. It is likely that metformin impairs photosynthesis either through downstream effects from inhibition of complex I of the electron transport chain or via activation of the enzyme, SnRK1 (sucrose non-fermenting-related kinase 1), which acts as a cellular energy regulator in plants and algae and is an ortholog of the mammalian target of metformin, AMPK (5' adenosine monophosphate-activated protein kinase).
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  • Cummings BM, Needoba JA, Peterson TD (2018) Effect of metformin exposure on growth and photosynthetic performance in the unicellular freshwater chlorophyte, Chlorella vulgaris. PLoS ONE 13(11): e0207041.
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  • 13
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  • 11
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  • This report was prepared by Oregon Sea Grant under award number NA270M-H to TDP and JAN from the National Oceanic and Atmospheric Administration’s National Sea Grant College Program, U.S. Department of Commerce, and by appropriations made by the Oregon State Legislature. The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the views of these funders. The work was also supported through a Robert Malouf Marine Studies Fellowship to BMC. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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