Metformin has been used for the treatment of type II diabetes mellitus for decades due to its safety, low cost, and outstanding hypoglycemic effect clinically. The mechanisms underlying these benefits are complex and still not fully understood. Inhibition of mitochondrial respiratory-chain complex I is the most described downstream mechanism of metformin, leading to reduced ATP production and activation of AMP-activated protein kinase (AMPK). Meanwhile, many novel targets of metformin have been gradually discovered. In recent years, multiple pre-clinical and clinical studies are committed to extend the indications of metformin in addition to diabetes. Herein, we summarized the benefits of metformin in four types of diseases, including metabolic associated diseases, cancer, aging and age-related diseases, neurological disorders. We comprehensively discussed the pharmacokinetic properties and the mechanisms of action, treatment strategies, the clinical application, the potential risk of metformin in various diseases. This review provides a brief summary of the benefits and concerns of metformin, aiming to interest scientists to consider and explore the common and specific mechanisms and guiding for the further research. Although there have been countless studies of metformin, longitudinal research in each field is still much warranted.
Humans ; Metformin/pharmacokinetics* ; Diabetes Mellitus, Type 2/metabolism* ; Hypoglycemic Agents/pharmacology* ; AMP-Activated Protein Kinases/metabolism* ; Aging

OBJECTIVE: To observe whether metformin (MET) inhibits transforming growth factor-β₁ (TGF-β₁)/Smad3 signaling pathway by activating adenosine activated protein kinase (AMPK), so as to alleviate the pulmonary fibrosis caused by paraquat (PQ) poisoning in mice. METHODS: Male C57BL/6J mice were randomly divided into the Control group, PQ poisoning model group (PQ group), MET intervention group (PQ+MET group), AMPK agonist group (PQ+AICAR group), and AMPK inhibitor group (PQ+MET+CC group), according to a random number table method. A mouse model of PQ poisoning was established by one-time peritoneal injection of 1 mL PQ solution (20 mg/kg). The Control group was injected with the same volume of normal saline. After 2 hours of modeling, the PQ+MET group was given 2 mL of 200 mg/kg MET solution by gavage, the PQ+AICAR group was given 2 mL of 200 mg/kg AICAR solution by intraperitoneal injection, the PQ+MET+CC group was given 2 mL of 200 mg/kg MET solution by gavage and then 1 mL complex C (CC) solution (20 mg/kg) was intraperitoneally injected, the Control group and PQ group were given 2 mL of normal saline by gavage. The intervention was given once a day for 21 consecutive days. The 21-day survival rate of ten mice in each group was calculated, and the lung tissues of remaining mice were collected at 21 days after modeling. The pathological changes of lung tissues were observed under light microscope after hematoxylin-eosin (HE) staining and Masson staining, and the degree of pulmonary fibrosis was evaluated by Ashcroft score. The content of hydroxyproline in lung tissue and oxidative stress indicators such as malondialdehyde (MDA) and superoxide dismutase (SOD) were detected. The protein expressions of E-cadherin, α-smooth muscle actin (α-SMA), phosphorylated AMPK (p-AMPK), TGF-β₁ and phosphorylated Smad3 (p-Smad3) in lung tissue were detected by Western blotting. RESULTS: Compared with the Control group, the 21 days survival rate was significantly reduced, lung fibrosis and Ashcroft score were significantly increased in PQ group. In addition, the content of hydroxyproline, MDA and the protein expressions of α-SMA, TGF-β₁ and p-Smad3 in lung tissue were significantly increased, while the activity of SOD and the protein expressions of E-cadherin and p-AMPK were significantly decreased in PQ group. Compared with the PQ group, the 21 days survival rates of mice were significantly improved in the PQ+MET group and PQ+AICAR group (70%, 60% vs. 20%, both P < 0.05). The degree of pulmonary fibrosis and the Ashcroft score were significantly reduced (1.50±0.55, 2.00±0.63 vs. 6.67±0.52, both P < 0.05). The content of hydroxyproline and MDA in lung tissue, as well as α-SMA, TGF-β₁ and p-Smad3 protein expressions were significantly reduced [hydroxyproline (mg/L): 2.03±0.11, 3.00±0.85 vs. 4.92±0.65, MDA (kU/g): 2.06±1.48, 2.10±1.80 vs. 4.06±1.33, α-SMA/GAPDH: 0.23±0.06, 0.16±0.06 vs. 1.00±0.09, TGF-β₁/GAPDH: 0.28±0.03, 0.53±0.05 vs. 0.92±0.06 p-Smad3/GAPDH: 0.52±0.04, 0.69±0.06 vs. 1.11±0.10, all P < 0.05], SOD activity and the protein expressions of E-cadherin and p-AMPK were significantly increased [SOD (μmol/g): 39.76±1.35, 33.03±1.28 vs. 20.08±1.79, E-cadherin/GAPDH: 0.91±0.08, 0.72±0.08 vs. 0.26±0.04, p-AMPK/GAPDH: 0.62±0.04, 0.60±0.01 vs. 0.20±0.04, all P < 0.05]. However, these protective effects of MET were inhibited by the addition of AMPK inhibitor CC solution. CONCLUSIONS MET can effectively alleviate the degree of pulmonary fibrosis in mice poisoned with PQ, and its mechanism may be related to the activation of AMPK and inhibition of TGF-β₁/Smad3 signaling pathway, which can be inhibited by AMPK inhibitor CC.
Mice ; Male ; Animals ; Pulmonary Fibrosis/drug therapy* ; Paraquat ; AMP-Activated Protein Kinases/pharmacology* ; Metformin/pharmacology* ; Hydroxyproline/pharmacology* ; Saline Solution ; Mice, Inbred C57BL ; Lung/metabolism* ; Transforming Growth Factor beta1/pharmacology* ; Cadherins ; Superoxide Dismutase

As an important enzyme for gluconeogenesis, mitochondrial phosphoenolpyruvate carboxykinase (PCK2) has further complex functions beyond regulation of glucose metabolism. Here, we report that conditional knockout of Pck2 in osteoblasts results in a pathological phenotype manifested as craniofacial malformation, long bone loss, and marrow adipocyte accumulation. Ablation of Pck2 alters the metabolic pathways of developing bone, particularly fatty acid metabolism. However, metformin treatment can mitigate skeletal dysplasia of embryonic and postnatal heterozygous knockout mice, at least partly via the AMPK signaling pathway. Collectively, these data illustrate that PCK2 is pivotal for bone development and metabolic homeostasis, and suggest that regulation of metformin-mediated signaling could provide a novel and practical strategy for treating metabolic skeletal dysfunction.
Mice ; Animals ; Metformin/pharmacology* ; Phosphoenolpyruvate Carboxykinase (ATP)/metabolism* ; Gluconeogenesis/genetics* ; Mice, Knockout

OBJECTIVE: To investigate effects of Jiangtang Sanhuang tablet (JTSHT) for regulating blood glucose and alleviating islet cell damage in db/db mice and its protective effects against endoplasmic reticulum stress (ERS) and autophagy induced by glycolipid toxicity. METHODS: Forty db/db mice were randomized into 4 groups for daily intragastric administration of saline, JTSHT of 2.64 and 1.32 g/kg, and metformin at 0.225g/kg for 8 weeks, using 10 C57BL/6J mice as the normal control. After the treatments, the metabolic indexes of the mice were measured, and morphological changes of the islet cells were observed. A mouse islet cell line (MIN6) was exposed to high glucose (22 mmol/L glucose) and 0.1 mmol/L palmitic acid, followed by treatment with the sera from JTSHT- or saline- treated SD rats, alone or in combination with SP600125, and the changes in cell apoptosis, ERS and autophagy were evaluated using flow cytometry, RT-qPCR and Western blotting. RESULTS: In db/db mice, treatment with JTSHT significantly improved glucose and lipid metabolism (P < 0.05) and suppressed progressive weight gain (P < 0.05) without significant effect on drinking water volume (P > 0.05). JTSHT was also found to promote repair of islet cell injuries. In the cell experiments, high glucose exposure significantly increased apoptosis rate of MIN6 cells (P < 0.05), which was obviously lowered by treatment with JTSHT-treated rat serum (P < 0.05). Western blotting showed that JTSHT significantly reduced the level of ERS and autophagy caused by glycolipid toxicity in MIN6 cells (P < 0.05). Interference with ERS using SP600125 significantly attenuated the protective effect of JTSHT against MIN6 cell injury, apoptosis and autophagy induced by glycolipid toxicity (P < 0.05). CONCLUSION JTSHT has protective effects against glycolipid toxicity in MIN6 cells possibly by inhibiting ERS and autophagy.
Animals ; Anthracenes ; Apoptosis ; Autophagy ; Blood Glucose ; Diabetes Mellitus ; Drinking Water ; Drugs, Chinese Herbal ; Endoplasmic Reticulum Stress ; Glucose/pharmacology* ; Glycolipids/pharmacology* ; Islets of Langerhans ; Metformin ; Mice ; Mice, Inbred C57BL ; Palmitic Acid/pharmacology* ; Tablets/pharmacology*

Objective: To study the protective effects of metformin on noise-induced hearing loss (NIHL) and its differential protein omics expression profile. Methods: In January 2021, 39 male Wistar rats were randomly divided into control group, noise exposure group and metformin+noise exposure group, with 13 rats in each group. Rats in the noise exposure group and metformin+noise exposure group were continuously exposed to octave noise with sound pressure level of 120 dB (A) and center frequency of 8 kHz for 4 h. Rats in the metformin+noise exposure group were treated with 200 mg/kg/d metformin 3 d before noise exposure for a total of 7 d. Auditory brainstem response (ABR) was used to test the changes of hearing thresholds before noise exposure and 1, 4, 7 d after noise exposure in the right ear of rats in each group. Tandem mass tag (TMT) quantitative proteomics was used to identify and analyze the differentially expressed protein in the inner ear of rats in each group, and it was verified by immunofluorescence staining with frozen sections. Results: The click-ABR thresholds of right ear in the noise exposure group and metformin+noise exposure group were significantly higher than those in the control group 1, 4, 7 d after noise exposure (P<0.05) . The click-ABR threshold of right ear in the metformin+noise exposure group were significantly lower than that in the noise exposure group (P<0.05) . Compared with the noise exposure group, 1035 up-regulated proteins and 1145 down-regulated proteins were differentially expressed in the metformin+noise exposure group. GO enrichment analysis showed that the significantly differentially expressed proteins were mainly involved in binding, molecular function regulation, signal transduction, and other functions. Enrichment analysis of KEGG pathway revealed that the pathways for significant enrichment of differentially expressed proteins included phosphatidylinositol 3-kinase-protein kinase B (PI3K-Akt) signaling pathway, focal adhesion, diabetic cardiomyopathy, mitogen, and mitogen-activated protein kinase (MAPK) signaling pathway. Immunofluorescence experiments showed that compared with the noise exposure group, the fluorescence intensity of insulin-like growth factor 1 receptor (IGF1R) in the metformin+noise exposure group was increased, and the fluorescence intensity of eukaryotic translation initiation factor 4E binding protein 1 (eIF4EBP1) was decreased. Conclusion: Noise exposure can lead to an increase in rat hearing threshold, and metformin can improve noise-induced hearing threshold abnormalities through multiple pathways and biological processes.
Animals ; Auditory Threshold/physiology* ; Cochlea ; Ear, Inner ; Evoked Potentials, Auditory, Brain Stem/physiology* ; Hearing Loss, Noise-Induced/prevention & control* ; Male ; Metformin/pharmacology* ; Phosphatidylinositol 3-Kinases/metabolism* ; Rats ; Rats, Wistar

Polycystic ovary syndrome (PCOS) is a common disease caused by complex endocrine and metabolic abnormalities in women of childbearing age. Metformin is the most widely used oral hypoglycemic drug in clinic. In recent years, metformin has been used in the treatment of PCOS, but its mechanism is not clear. In this study, we aimed to investigate the effect of metformin on PCOS and its mechanism through PCOS mouse model. Female C57BL/6J mice aged 4-5 weeks were intragastrically given letrozole (1 mg/kg daily) combined with a high-fat diet (HFD) for 21 days to establish the PCOS model. After modeling, metformin (200 mg/kg daily) was intragastrically administered. One month later, the body weight and oral glucose tolerance test (OGTT) were measured. Hematoxylin eosin (H&E) staining was used to detect the pathological changes of ovary. The serum levels of anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), E₂ and testosterone (T) were measured by ELISA. The expression of DDX4/MVH was detected by immunohistochemistry. DDX4/MVH and PCNA were co-labeled by immunofluorescence. The protein levels of DDX4/MVH, PCNA, cyclin D2, AMPK and mTOR were detected by Western blot. The results showed that after metformin treatment, the body weights of PCOS mice were gradually returned to normal, glucose tolerance was significantly improved, serum E₂ levels were increased, while AMH, LH, T levels and LH/FSH ratio were decreased. Ovarian polycystic lesions were reduced with reduced atresia follicles. Furthermore, the number of proliferative female germline stem cells (FGSCs) and levels of proliferation related proteins (PCNA, cyclin D2) were significantly increased, and the p-mTOR and p-AMPK levels were markedly up-regulated. These results suggest that metformin treatment not only improves hyperandrogenemia, glucose intolerance and polycystic ovarian lesions in PCOS, but also activates the function of FGSCs. The underlying mechanism may be related to the phosphorylation of AMPK and mTOR. These findings provide new evidence to use metformin in the treatment of PCOS and follicular development disorder.
AMP-Activated Protein Kinases ; Animals ; Cyclin D2 ; Female ; Follicle Stimulating Hormone/therapeutic use* ; Humans ; Luteinizing Hormone/therapeutic use* ; Metformin/pharmacology* ; Mice ; Mice, Inbred C57BL ; Oogonial Stem Cells/metabolism* ; Ovarian Cysts/drug therapy* ; Ovarian Neoplasms ; Polycystic Ovary Syndrome/drug therapy* ; Proliferating Cell Nuclear Antigen/therapeutic use* ; TOR Serine-Threonine Kinases

OBJECTIVE: To construct a luciferase reporter gene vector carrying human nuclear factor of activated T cells 2 (NFATc2) gene promoter and examine the effects of metformin and lipopolysaccharide (LPS) on the transcriptional activity of NFATc2 gene. METHODS: The promoter sequence of human NFATc2 gene was acquired from UCSC website for PCR amplification. NFATc2 promoter fragment was inserted into pGL3-basic plasmid double cleaved with Kpn Ⅰ and Hind Ⅲ. The resultant recombinant plasmid pGL3-NFATC2-promoter was co-transfected with the internal reference plasmid pRL-TK in 293F cells, and luciferase activity in the cells was detected. Reporter gene vectors of human NFATc2 gene promoter with different fragment lengths were also constructed and assayed for luciferase activity. The changes in transcription activity of NFATc2 gene were assessed after treatment with different concentrations of metformin and LPS for 24 h. We also examined the effect of mutation in RUNX2-binding site in NFATC2 gene promoter on the regulatory effects of metformin and LPS on NFATc2 transcription. RESULTS: We successfully constructed pGL3-NFATc2-promoter plasmids carrying different lengths (2170 bp, 2077 bp, 1802 bp, 1651 bp, 1083 bp, 323 bp) of NFATc2 promoter sequences as verified by enzymatic digestion and sequencing. Transfection of 293F cells with the plasmid carrying a 1651 bp NFATc2 promoter (pGL3-1651 bp) resulted in the highest transcriptional activity of NFATc2 gene, and the luciferase activity was approximately 3.3 times that of pGL3-2170 bp (1.843 ± 0.146 vs 0.547 ± 0.085). Moderate (5 mmol/L) and high (10 mmol/L) concentrations of metformin significantly upregulated the transcriptional activity of pGL3-1651 bp by up to 2.5 and 3 folds, respectively. LPS at different doses also upregulated the transcriptional activity of pGL3-1651 bp by at least 1.6 folds. The mutation in the RUNX2 binding site on pGL3-1651 bp obviously reduced metformin- and LPS-induced enhancement of pGL3-1651bp transcription by 1.7 and 2 folds, respectively. CONCLUSION pGL3-NFATc2-promoter can be transcribed and activated in 293F cells, and LPS and metformin can activate the transcription of pGL3- NFATc2-promoter in a RUNX2-dependent manner.
Core Binding Factor Alpha 1 Subunit/genetics* ; Humans ; Lipopolysaccharides/pharmacology* ; Luciferases/genetics* ; Metformin/pharmacology* ; NFATC Transcription Factors/genetics* ; Promoter Regions, Genetic ; T-Lymphocytes ; Transcription, Genetic/drug effects* ; Transfection

OBJECTIVE: To investigate the effect of metformin on the proliferation and apoptosis of HER-2-positive breast cancer cell line SKBR3 and explore the possible mechanism of its action. METHODS: SKBR3 cells were treated with different concentrations (20-120 μmol/L) of metformin, and the changes in cell proliferation and colony formation ability were assessed using CCK-8 assay and crystal violet staining, respectively. Flow cytometry was performed to analyze cell apoptosis and cell cycle changes. Real-time fluorescent quantitative PCR (qRT-PCR) was used to detect mRNA expressions of YAP, TAZ, EGFR, CTGF, CYR61, E-cadherin, N-cadherin, vimentin and fibronectin in the treated cells, and the protein expressions of YAP and TAZ were detected using Western blotting; immunofluorescence assay was used to observe YAP/TAZ nuclear translocation in the cells. RESULTS: Metformin treatment significantly inhibited the proliferation of SKBR3 cells (P < 0.05) in a concentration- and time-dependent manner. The results of flow cytometry showed that metformin significantly promoted apoptosis and caused cell cycle arrest at G1 phase in SKBR3 cells. Metformin treatment significantly down-regulated the mRNA expressions of YAP, TAZ, EGFR, CTGF and CYR61, N-cadherin, vimentin and fibronectin (P < 0.05) and up-regulated the expression of E-cadherin (P < 0.05); Western blotting results showed that YAP and TAZ protein expressions were significantly down-regulated in the cells after metformin treatment (P < 0.05). Immunofluorescence assay revealed that metformin treatment caused the concentration of YAP and TAZ in the cytoplasm, and significantly reduced their amount in the cell nucleus. CONCLUSION Metformin can inhibit proliferation and promote apoptosis and epithelal-mesenchymal transition of HER-2 positive breast cancer cells possibly by that inhibing YAP and TAZ expression and their nuclear localization.
Apoptosis ; Cadherins ; Cell Proliferation ; ErbB Receptors ; Fibronectins ; Metformin/pharmacology* ; Neoplasms ; Protein Serine-Threonine Kinases ; RNA, Messenger ; Transcription Factors/metabolism* ; Vimentin

OBJECTIVE: To investigate the protective effect of fucoxanthin (FX) against diabetic cardiomyopathy and explore the underlying mechanism. METHODS: Rat models of diabetes mellitus (DM) induced by intraperitoneal injection of streptozotocin (60 mg/kg) were randomized into DM model group, fucoxanthin treatment (DM+FX) group and metformin treatment (DM+ Met) group, and normal rats with normal feeding served as the control group. In the two treatment groups, fucoxanthin and metformin were administered after modeling by gavage at the daily dose of 200 mg/kg and 230 mg/kg, respectively for 12 weeks, and the rats in the DM model group were given saline only. HE staining was used to examine the area of cardiac myocyte hypertrophy in each group. The expression levels of fibrotic proteins TGF-β1 and FN proteins in rat hearts were detected with Western blotting. In the cell experiment, the effect of 1 μmol/L FX on H9C2 cell hypertrophy induced by exposure to high glucose (HG, 45 mmol/L) was evaluated using FITC-labeled phalloidin. The mRNA expression levels of the hypertrophic factors ANP, BNP and β-MHC in H9C2 cells were detected using qRT-PCR. The protein expressions of Nrf2, Keap1, HO-1 and SOD1 proteins in rat heart tissues and H9C2 cells were determined using Western blotting. The DCFH-DA probe was used to detect the intracellular production of reactive oxygen species (ROS). RESULTS: In the diabetic rats, fucoxanthin treatment obviously alleviated cardiomyocyte hypertrophy and myocardial fibrosis, increased the protein expressions of Nrf2 and HO-1, and decreased the protein expressions of Keap1 in the heart tissue (P < 0.05). In H9C2 cells with HG exposure, fucoxanthin significantly inhibited the enlargement of cell surface area, lowered the mRNA expression levels of ANP, BNP and β-MHC (P < 0.05), promoted Nrf2 translocation from the cytoplasm to the nucleus, and up-regulated the protein expressions its downstream targets SOD1 and HO-1 (P < 0.05) to enhance cellular antioxidant capacity and reduce intracellular ROS production. CONCLUSION Fucoxanthin possesses strong inhibitory activities against diabetic cardiomyocyte hypertrophy and myocardial fibrosis and is capable of up-regulating Nrf2 signaling to promote the expression of its downstream antioxidant proteins SOD1 and HO-1 to reduce the level of ROS.
Animals ; Antioxidants/metabolism* ; Atrial Natriuretic Factor/pharmacology* ; Cardiomegaly ; Diabetes Mellitus, Experimental/metabolism* ; Fibrosis ; Kelch-Like ECH-Associated Protein 1/metabolism* ; Metformin ; NF-E2-Related Factor 2/metabolism* ; Oxidative Stress ; RNA, Messenger/metabolism* ; Rats ; Reactive Oxygen Species/metabolism* ; Superoxide Dismutase-1/pharmacology* ; Xanthophylls

Animals ; Blood Glucose ; Diabetes Mellitus, Type 2/drug therapy* ; Insulin ; Insulin Resistance ; Islets of Langerhans ; Metformin/pharmacology* ; Mice ; Prediabetic State ; Sitagliptin Phosphate/pharmacology*