1
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Wei CH, Wang ZW, Dai JH, Xiao K, Yu HR, Qu FS, Rong HW, He JG, Ngo HH. Enhanced anaerobic digestion performance and sludge filterability by membrane microaeration for anaerobic membrane bioreactor application. BIORESOURCE TECHNOLOGY 2024; 402:130787. [PMID: 38703955 DOI: 10.1016/j.biortech.2024.130787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 04/30/2024] [Accepted: 05/01/2024] [Indexed: 05/06/2024]
Abstract
Slow dissolution/hydrolysis of insoluble/macromolecular organics and poor sludge filterability restrict the application potential of anaerobic membrane bioreactor (AnMBR). Bubble-free membrane microaeration was firstly proposed to overcome these obstacles in this study. The batch anaerobic digestion tests feeding insoluble starch and soluble peptone with and without microaeration showed that microaeration led to a 65.7-144.8% increase in methane production and increased critical flux of microfiltration membrane via driving the formation of large sludge flocs and the resultant improvement of sludge settleability. The metagenomic and bioinformatic analyses showed that microaeration significantly enriched the functional genes and bacteria for polysaccharide and protein hydrolysis, microaeration showed little negative effects on the functional genes involved in anaerobic metabolisms, and substrate transfer from starch to peptone significantly affected the functional genes and microbial community. This study demonstrates the dual synergism of microaeration to enhance the dissolution/hydrolysis/acidification of insoluble/macromolecular organics and sludge filterability for AnMBR application.
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Affiliation(s)
- Chun-Hai Wei
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China; Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou 510006, China.
| | - Zheng-Wei Wang
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China
| | - Jian-Hua Dai
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China
| | - Kang Xiao
- Beijing Yanshan Earth Critical Zone National Research Station, College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Hua-Rong Yu
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China; Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou 510006, China
| | - Fang-Shu Qu
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China; Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou 510006, China
| | - Hong-Wei Rong
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China; Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou 510006, China
| | - Jun-Guo He
- Department of Municipal Engineering, School of Civil Engineering, Guangzhou University, Guangzhou 510006, China; Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou 510006, China
| | - Huu Hao Ngo
- Centre for Technology in Water and Wastewater, University of Technology, Sydney NSW 2007, Australia
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2
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Wu L, Luo H, Xu J, Yu L, Xiong J, Liu Y, Huang X, Zou X. Vital role of CYP450 in the biodegradation of antidiabetic drugs in the aerobic activated sludge system and the mechanisms. JOURNAL OF HAZARDOUS MATERIALS 2024; 469:134056. [PMID: 38522208 DOI: 10.1016/j.jhazmat.2024.134056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 02/26/2024] [Accepted: 03/14/2024] [Indexed: 03/26/2024]
Abstract
The extensive use of antidiabetic drugs (ADDs) and their detection in high concentrations in the environment have been extensively documented. However, the mechanism of ADDs dissipation in aquatic environments is still not well understood. This study thoroughly investigates the dissipation behavior of ADDs and the underlying mechanisms in the aerobic activated sludge system. The results indicate that the removal efficiencies of ADDs range from 3.98% to 100% within 48 h, largely due to the biodegradation process. Additionally, the gene expression of cytochrome P450 (CYP450) is shown to be significantly upregulated in most ADDs-polluted samples (P < 0.05), indicating the vital role of CYP450 enzymes in the biodegradation of ADDs. Enzyme inhibition experiments validated this hypothesis. Moreover, molecular docking and simulation results indicate that a strong correlation between the biodegradation of ADDs and the interactions between ADDs and CYP450 (Ebinding). The differences in dissipation behavior among the tested ADDs are possibly due to their electrophilic characteristics. Overall, this study makes the initial contribution to a more profound comprehension of the crucial function of CYP450 enzymes in the dissipation behavior of ADDs in a typical aquatic environment.
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Affiliation(s)
- Ligui Wu
- School of Life Science, Jinggangshan University, Ji'an 343009, China; College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Hao Luo
- School of Life Science, Jinggangshan University, Ji'an 343009, China
| | - Jingcheng Xu
- College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Ling Yu
- School of Life Science, Jinggangshan University, Ji'an 343009, China
| | - Jiangtao Xiong
- School of Life Science, Jinggangshan University, Ji'an 343009, China
| | - Yizhi Liu
- School of Life Science, Jinggangshan University, Ji'an 343009, China
| | - Xiangfeng Huang
- College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
| | - Xiaoming Zou
- School of Life Science, Jinggangshan University, Ji'an 343009, China.
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3
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Dong L, Li S, Huang J, Li WJ, Ali M. Co-occurrence, toxicity, and biotransformation pathways of metformin and its intermediate product guanylurea: Current state and future prospects for enhanced biodegradation strategy. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 921:171108. [PMID: 38395159 DOI: 10.1016/j.scitotenv.2024.171108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 01/29/2024] [Accepted: 02/18/2024] [Indexed: 02/25/2024]
Abstract
Accumulation of metformin and its biotransformation product "guanylurea" are posing an increasing concern due to their low biodegradability under natural attenuated conditions. Therefore, in this study, we reviewed the unavoidable function of metformin in human body and the route of its release in different water ecosystems. In addition, metformin and its biotransformation product guanylurea in aquatic environments caused certain toxic effects on aquatic organisms which include neurotoxicity, endocrine disruption, production of ROS, and acetylcholinesterase disturbance in aquatic organisms. Moreover, microorganisms are the first to expose and deal with the release of these contaminants, therefore, the mechanisms of biodegradation pathways of metformin and guanylurea under aerobic and anaerobic environments were studied. It has been reported that certain microbes, such as Aminobacter sp. and Pseudomonas putida can carry potential enzymatic pathways to degrade the dead-end product "guanylurea", and hence guanylurea is no longer the dead-end product of metformin. However, these microbes can easily be affected by certain geochemical cycles, therefore, we proposed certain strategies that can be helpful in the enhanced biodegradation of metformin and its biotransformation product guanylurea. A better understanding of the biodegradation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of the emerging contaminants of concern, metformin and guanylurea in the near future.
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Affiliation(s)
- Lei Dong
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Shuai Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-sen University, Guangzhou, China; School of Life Science, Jiaying University, Meizhou, China
| | - Jie Huang
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Wen-Jun Li
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-sen University, Guangzhou, China; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China.
| | - Mukhtiar Ali
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-sen University, Guangzhou, China; Advanced Water Technology Laboratory, National University of Singapore (Suzhou) Research Institute, Suzhou, Jiangsu 215123, China..
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4
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Chi B, Li F, Wang X, Pan H, Yi X, Liu Y, Zhan J, Zhang X, Zhou H, Wang W. DMF mineralization and substrate specificity mechanism of Aminobacter ciceronei DMFA1. ENVIRONMENTAL RESEARCH 2024; 245:117980. [PMID: 38142731 DOI: 10.1016/j.envres.2023.117980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 12/04/2023] [Accepted: 12/16/2023] [Indexed: 12/26/2023]
Abstract
N,N-dimethylformamide (DMF) is widely used in various industries, but its direct release into water poses high risks to human beings. Although a lot of DMF-degrading bacteria has been isolated, limited studies focus on the degradation preference among DMF and its analogues. In this study, an efficient DMF mineralization bacterium designated Aminobacter ciceronei DMFA1 was isolated from marine sediment. When exposed to a 0.2% DMF (∼1900 mg/L), strain DMFA1 exhibited a degradation efficiency of 100% within 4 days. The observed growth using formamide as the sole carbon source implied the possible DMF degradation pathway of strain DMFA1. Meanwhile,the strain DMFA1 possesses a broad-spectrum substrate degradation, which could effectively degraded 0.2% N,N-dimethylacetamide (DMAC) and N-methylformamide (NMF). Genomic analysis further confirmed the supposed pathway through annotating the genes encoding N, N-dimethylformamidase (DMFase), formamidase, and formate dehydrogenase. The existence of sole DMFase indicating its substrate specificity controlled the preference of DMAc of strain DMFA1. By integrating multiple sequence alignment, homology modeling and molecular docking, the preference of the DMFase in strain DMFA1 towards DMAc are related to: 1) Mutations in key active site residues; 2) the absence of small subunit; and 3) no energy barrier for substrates entering the active site.
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Affiliation(s)
- Baihui Chi
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Fei Li
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Xukang Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Haixia Pan
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Xianliang Yi
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Yang Liu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Jingjing Zhan
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Xuwang Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China
| | - Hao Zhou
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Ocean Science and Technology, Panjin Campus, Dalian University of Technology, China.
| | - Wenyuan Wang
- State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China.
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5
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Tassoulas LJ, Rankin JA, Elias MH, Wackett LP. Dinickel enzyme evolved to metabolize the pharmaceutical metformin and its implications for wastewater and human microbiomes. Proc Natl Acad Sci U S A 2024; 121:e2312652121. [PMID: 38408229 DOI: 10.1073/pnas.2312652121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 01/12/2024] [Indexed: 02/28/2024] Open
Abstract
Metformin is the first-line treatment for type II diabetes patients and a pervasive pollutant with more than 180 million kg ingested globally and entering wastewater. The drug's direct mode of action is currently unknown but is linked to effects on gut microbiomes and may involve specific gut microbial reactions to the drug. In wastewater treatment plants, metformin is known to be transformed by microbes to guanylurea, although genes encoding this metabolism had not been elucidated. In the present study, we revealed the function of two genes responsible for metformin decomposition (mfmA and mfmB) found in isolated bacteria from activated sludge. MfmA and MfmB form an active heterocomplex (MfmAB) and are members of the ureohydrolase protein superfamily with binuclear metal-dependent activity. MfmAB is nickel-dependent and catalyzes the hydrolysis of metformin to dimethylamine and guanylurea with a catalytic efficiency (kcat/KM) of 9.6 × 103 M-1s-1 and KM for metformin of 0.82 mM. MfmAB shows preferential activity for metformin, being able to discriminate other close substrates by several orders of magnitude. Crystal structures of MfmAB show coordination of binuclear nickel bound in the active site of the MfmA subunit but not MfmB subunits, indicating that MfmA is the active site for the MfmAB complex. Mutagenesis of residues conserved in the MfmA active site revealed those critical to metformin hydrolase activity and its small substrate binding pocket allowed for modeling of bound metformin. This study characterizes the products of the mfmAB genes identified in wastewater treatment plants on three continents, suggesting that metformin hydrolase is widespread globally in wastewater.
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Affiliation(s)
- Lambros J Tassoulas
- Department of Biochemistry, Biophysics, and Molecular Biology, University of Minnesota, Minneapolis, MN 55455
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108
| | - Joel A Rankin
- Department of Biochemistry, Biophysics, and Molecular Biology, University of Minnesota, Minneapolis, MN 55455
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108
| | - Mikael H Elias
- Department of Biochemistry, Biophysics, and Molecular Biology, University of Minnesota, Minneapolis, MN 55455
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108
| | - Lawrence P Wackett
- Department of Biochemistry, Biophysics, and Molecular Biology, University of Minnesota, Minneapolis, MN 55455
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108
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6
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Lucero RM, Demirer K, Yeh TJ, Stockbridge RB. Transport of metformin metabolites by guanidinium exporters of the small multidrug resistance family. J Gen Physiol 2024; 156:e202313464. [PMID: 38294434 PMCID: PMC10829512 DOI: 10.1085/jgp.202313464] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 12/01/2023] [Accepted: 01/04/2024] [Indexed: 02/01/2024] Open
Abstract
Proteins from the small multidrug resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in the metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMRGdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea. We use solid-supported membrane electrophysiology to evaluate the transport kinetics for guanylurea and native substrate guanidinium by four representative SMRGdx homologs. Using an internal reference to normalize independent electrophysiology experiments, we show that transport rates are comparable for genomic and plasmid-associated SMRGdx homologs, and using a proteoliposome-based transport assay, we show that 2 proton:1 substrate transport stoichiometry is maintained. Additional characterization of guanidinium and guanylurea export properties focuses on the structurally characterized homolog, Gdx-Clo, for which we examined the pH dependence and thermodynamics of substrate binding and solved an x-ray crystal structure with guanylurea bound. Together, these experiments contribute in two main ways. By providing the first detailed kinetic examination of the structurally characterized SMRGdx homolog Gdx-Clo, they provide a functional framework that will inform future mechanistic studies of this model transport protein. Second, this study casts light on a potential role for SMRGdx transporters in microbial handling of metformin and its microbial metabolic byproducts, providing insight into how native transport physiologies are co-opted to contend with new selective pressures.
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Affiliation(s)
- Rachael M. Lucero
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
| | - Kemal Demirer
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | | | - Randy B. Stockbridge
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Program in Biophysics, University of Michigan, Ann Arbor, MI, USA
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7
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Vijay Pradhap Singh M, Ravi Shankar K. Next-generation hybrid technologies for the treatment of pharmaceutical industry effluents. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 353:120197. [PMID: 38301475 DOI: 10.1016/j.jenvman.2024.120197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 01/03/2024] [Accepted: 01/20/2024] [Indexed: 02/03/2024]
Abstract
Water and industries are intangible units of the globe that are always set to meet the population's demand. The global population depends on one-third of freshwater increasing the demand. The increase in population along with urbanization has polluted the fresh water resources. The pharmaceutical industry is marked as an emerging contaminant of water pollution. The most common type of pharmaceutical drugs that are detected in the environment includes antibiotics, analgesics, NSAIDs, and pain-relieving drugs. These drugs alter the food chain of the organisms causing chaos mainly in the marine ecosystem. Pharmaceutical drugs are found only in shallow amounts (ng/mg) they have a huge impact on the living system. The consumption of water contaminated with pharmaceutical ingredients can disrupt reproduction, hormonal imbalance, cancer, and respiratory problems. Various methods are used to remove these chemicals from the environment. In this review, we mainly focused on the emerging hybrid technologies and their significance in the effective treatment of pharmaceutical wastewater. This review paper primarily elaborates on the merits and demerits of existing conventional technologies helpful in developing integrated technologies for the modern era of pharmaceutical effluent treatment. This review paper further in detail discusses the various strategies of eco-friendly bioremediation techniques namely biostimulation, bioaugmentation, bacterial degradation, mycoremediation, phytoremediation, and others for the ultimate removal of pharmaceutical contaminants in wastewater. The review makes clear that targeted and hybrid solutions are what the world will require in the future to get rid of these pharmacological prints.
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Affiliation(s)
- M Vijay Pradhap Singh
- Department of Biotechnology, Vivekanandha College of Engineering for Women (Autonomous), Namakkal, Elayampalayam, Tiruchengode, Tamil Nadu, 637 205, India.
| | - K Ravi Shankar
- Department of Biotechnology, University College of Engineering, Anna University-BIT Campus, Tiruchirappalli, Tamil Nadu, 620 024, India.
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8
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Tassoulas LJ, Wackett LP. Insights into the action of the pharmaceutical metformin: Targeted inhibition of the gut microbial enzyme agmatinase. iScience 2024; 27:108900. [PMID: 38318350 PMCID: PMC10839685 DOI: 10.1016/j.isci.2024.108900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 12/06/2023] [Accepted: 01/09/2024] [Indexed: 02/07/2024] Open
Abstract
Metformin is the first-line treatment for type 2 diabetes, yet its mechanism of action is not fully understood. Recent studies suggest metformin's interactions with gut microbiota are responsible for exerting therapeutic effects. In this study, we report that metformin targets the gut microbial enzyme agmatinase, as a competitive inhibitor, which may impair gut agmatine catabolism. The metformin inhibition constant (Ki) of E. coli agmatinase is 1 mM and relevant in the gut where the drug concentration is 1-10 mM. Metformin analogs phenformin, buformin, and galegine are even more potent inhibitors of E. coli agmatinase (Ki = 0.6, 0.1, and 0.007 mM, respectively) suggesting a shared mechanism. Agmatine is a known effector of human host metabolism and has been reported to augment metformin's therapeutic effects for type 2 diabetes. This gut-derived inhibition mechanism gives new insights on metformin's action in the gut and may lead to significant discoveries in improving metformin therapy.
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Affiliation(s)
- Lambros J. Tassoulas
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, MN 55455, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA
| | - Lawrence P. Wackett
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, MN 55455, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA
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9
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Lucero RM, Demirer K, Yeh TJ, Stockbridge RB. Transport of metformin metabolites by guanidinium exporters of the Small Multidrug Resistance family. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.552832. [PMID: 37645731 PMCID: PMC10461911 DOI: 10.1101/2023.08.10.552832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Proteins from the Small Multidrug Resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMRGdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea. We use solid supported membrane electrophysiology to evaluate the transport kinetics for guanylurea and native substrate guanidinium by four representative SMRGdx homologues. Using an internal reference to normalize independent electrophysiology experiments, we show that transport rates are comparable for genomic and plasmid-associated SMRGdx homologues, and using a proteoliposome-based transport assay, we show that 2 proton:1 substrate transport stoichiometry is maintained. Additional characterization of guanidinium and guanylurea export properties focuses on the structurally characterized homologue, Gdx-Clo, for which we examined the pH dependence and thermodynamics of substrate binding and solved an x-ray crystal structure with guanylurea bound. Together, these experiments contribute in two main ways. By providing the first detailed kinetic examination of the structurally characterized SMRGdx homologue Gdx-Clo, they provide a functional framework that will inform future mechanistic studies of this model transport protein. Second, this study casts light on a potential role for SMRGdx transporters in microbial handling of metformin and its microbial metabolic byproducts, providing insight into how native transport physiologies are co-opted to contend with new selective pressures.
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Affiliation(s)
| | - Kemal Demirer
- Department of Molecular, Cellular, and Developmental Biology
| | - Trevor Justin Yeh
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Randy B Stockbridge
- Program in Chemical Biology
- Department of Molecular, Cellular, and Developmental Biology
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
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10
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Foretz M, Guigas B, Viollet B. Metformin: update on mechanisms of action and repurposing potential. Nat Rev Endocrinol 2023:10.1038/s41574-023-00833-4. [PMID: 37130947 PMCID: PMC10153049 DOI: 10.1038/s41574-023-00833-4] [Citation(s) in RCA: 82] [Impact Index Per Article: 82.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/24/2023] [Indexed: 05/04/2023]
Abstract
Currently, metformin is the first-line medication to treat type 2 diabetes mellitus (T2DM) in most guidelines and is used daily by >200 million patients. Surprisingly, the mechanisms underlying its therapeutic action are complex and are still not fully understood. Early evidence highlighted the liver as the major organ involved in the effect of metformin on reducing blood levels of glucose. However, increasing evidence points towards other sites of action that might also have an important role, including the gastrointestinal tract, the gut microbial communities and the tissue-resident immune cells. At the molecular level, it seems that the mechanisms of action vary depending on the dose of metformin used and duration of treatment. Initial studies have shown that metformin targets hepatic mitochondria; however, the identification of a novel target at low concentrations of metformin at the lysosome surface might reveal a new mechanism of action. Based on the efficacy and safety records in T2DM, attention has been given to the repurposing of metformin as part of adjunct therapy for the treatment of cancer, age-related diseases, inflammatory diseases and COVID-19. In this Review, we highlight the latest advances in our understanding of the mechanisms of action of metformin and discuss potential emerging novel therapeutic uses.
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Affiliation(s)
- Marc Foretz
- Université Paris Cité, CNRS, Inserm, Institut Cochin, Paris, France
| | - Bruno Guigas
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - Benoit Viollet
- Université Paris Cité, CNRS, Inserm, Institut Cochin, Paris, France.
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