1
|
Wasner HK. Metformin's Mechanism of Action Is Stimulation of the Biosynthesis of the Natural Cyclic AMP Antagonist Prostaglandylinositol Cyclic Phosphate (Cyclic PIP). Int J Mol Sci 2022; 23:ijms23042200. [PMID: 35216316 PMCID: PMC8876105 DOI: 10.3390/ijms23042200] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 02/05/2022] [Accepted: 02/10/2022] [Indexed: 11/16/2022] Open
Abstract
Metformin is the leading drug for treating type 2 diabetics, but the mechanism of action of metformin, despite some suggested mechanisms such as the activation of the AMP-kinase, is largely unknown. Among its many positive effects are the reduction of blood glucose levels, the inhibition of cyclic AMP synthesis, gluconeogenesis and an increase in sensitivity to insulin. Recent studies have described the natural antagonist of cyclic AMP, prostaglandylinositol cyclic phosphate. Synthesis of cyclic PIP is stimulated in all organs by hormones such as insulin and also by drugs such as metformin. Its primary action is to trigger the dephosphorylation of proteins/enzymes, phosphorylated on serine/threonine residues. Cyclic PIP triggers many of the regulations requested by insulin. The parallels between the beneficial effects of metformin and the regulations triggered by cyclic PIP suggest that the mechanism of action of this key drug may well be explained by its stimulation of the synthesis of cyclic PIP.
Collapse
Affiliation(s)
- Heinrich K Wasner
- BioReg Biopharm, Technology Innovation Laboratory, University of Illinois at Chicago, 2242 West Harrison St., Ste. 201, Chicago, IL 60612, USA
| |
Collapse
|
2
|
Deng M, Su D, Xu S, Little PJ, Feng X, Tang L, Shen A. Metformin and Vascular Diseases: A Focused Review on Smooth Muscle Cell Function. Front Pharmacol 2020; 11:635. [PMID: 32457625 PMCID: PMC7227439 DOI: 10.3389/fphar.2020.00635] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/21/2020] [Indexed: 12/16/2022] Open
Abstract
Metformin has been used in diabetes for more than 60 years and has excellent safety in the therapy of human type 2 diabetes (T2D). There is growing evidence that the beneficial health effects of metformin are beyond its ability to improve glucose metabolism. Metformin not only reduces the incidence of cardiovascular diseases (CVD) in T2D patients, but also reduces the burden of atherosclerosis (AS) in pre-diabetes patients. Vascular smooth muscle cells (VSMCs) function is an important factor in determining the characteristics of the entire arterial vessel. Its excessive proliferation contributes to the etiology of several types of CVD, including AS, restenosis, and pulmonary hypertension. Current studies show that metformin has a beneficial effect on VSMCs function. Therefore, this review provides a timely overview of the role and molecular mechanisms by which metformin acts through VSMCs to protect CVD.
Collapse
Affiliation(s)
- Mingying Deng
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Dan Su
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Suowen Xu
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Peter J Little
- School of Pharmacy, The University of Queensland, Woolloongabba, QLD, Australia.,Department of Pharmacy, Xinhua College of Sun Yat-sen University, Guangzhou, China
| | - Xiaojun Feng
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Liqin Tang
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Aizong Shen
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| |
Collapse
|
3
|
Liao S, Li D, Hui Z, McLachlan CS, Zhang Y. Metformin added to bosentan therapy in patients with pulmonary arterial hypertension associated with congenital heart defects: a pilot study. ERJ Open Res 2018; 4:00060-2018. [PMID: 30151369 PMCID: PMC6104295 DOI: 10.1183/23120541.00060-2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 07/05/2018] [Indexed: 01/09/2023] Open
Abstract
Pulmonary arterial hypertension (PAH) is a common complication of a congenital heart defect (CHD). Recent studies suggest metformin may be a potential drug to improve cardiac function in PAH. A pilot study was conducted to investigate the efficacy of short-term treatment with a combination regimen consisting of bosentan and metformin in PAH-CHD patients as compared with bosentan monotherapy in a prospective, randomised study. Patients with PAH-CHD were randomised to receive bosentan (initially at 62.5 mg twice daily for 4 weeks and then 125 mg twice daily) for 3 months with or without the combination treatment of metformin (500 mg twice daily). 93 patients were enrolled to bosentan monotherapy (n=48) or bosentan/metformin combination treatment (n=45). After 3 months, both treatments significantly improved World Health Organization functional class, 6-min walking distance (6MWD), N-terminal pro-brain natriuretic peptide and right heart haemodynamic parameters. The improvements in 6MWD and pulmonary vascular resistance index were significantly greater in patients treated with combination therapy than in those who received monotherapy (mean±sd 95±136 versus 48±119 m (p=0.017) and −1.8±1.2 versus −1.2±1.3 Wood units per m2 (p<0.001), respectively). Pulmonary endothelin (EDN)1 was significantly decreased after combination therapy (p=0.006). However, plasma EDN1 levels were not affected. Combination therapy with bosentan and metformin in PAH-CHD patients provides improvements in important outcomes such as exercise capacity and pulmonary haemodynamics, compared with bosentan alone. This study investigated, for the first time, the efficacy of a combination regimen consisting of bosentan and metformin in patients with pulmonary arterial hypertension associated with congenital heart defect as compared with bosentan monotherapyhttp://ow.ly/n4nJ30kT98d
Collapse
Affiliation(s)
- Shutan Liao
- Rural Clinical School, University of New South Wales, Sydney, Australia.,The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Dongsheng Li
- The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Zheng Hui
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Craig S McLachlan
- Rural Clinical School, University of New South Wales, Sydney, Australia
| | - Yang Zhang
- The First Affiliated Hospital of Nanchang University, Nanchang, China
| |
Collapse
|
4
|
Peuler JD, Phelps LE. Sildenafil does not enhance but rather attenuates vasorelaxant effects of antidiabetic agents. J Smooth Muscle Res 2015; 51:22-36. [PMID: 26004378 PMCID: PMC5137313 DOI: 10.1540/jsmr.51.22] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Type 2 diabetic men commonly experience erectile dysfunction for which
phosphodiesterase-5 (PDE5) inhibitors like sildenafil (Viagra) are often recommended. By
preventing degradation of cyclic guanosine monophosphate (cGMP) in vascular smooth muscle,
these inhibitors also enhance arterial vasorelaxant effects of nitric oxide donors (which
stimulate cGMP synthesis). In the present work, we confirmed this enhancing effect after
co-administration of sildenafil with nitroprusside to freshly-isolated rat tail arterial
tissues. However, in the same tissues we also observed that sildenafil does not enhance
but rather attenuates vasorelaxant effects of three commonly-used antidiabetic drugs, i.e.
the biguanide metformin and the thiazolidinediones pioglitazone and rosiglitazone. Indeed,
sildenafil completely blocked vasorelaxant effects of low concentrations of these drugs.
In addition, we found that this same novel anti-vasorelaxant interaction of sildenafil
with these agents was abolished by either 1) omitting extracellular glucose or 2)
inhibiting specific smooth muscle glycolytic pathways; pathways known to preferentially
utilize extracellular glucose to fuel certain adenosine triphosphate (ATP)-dependent ion
transporters: e.g. ATP-sensitive K channels, sarcoplasmic reticulum Ca-ATPase, plasma
membrane Ca-ATPase and Na/K-ATPase. Accordingly, we suspect that altered activity of one
or more of these ion transporters mediates the observed attenuating (anti-vasorelaxant)
interaction of sildenafil with the antidiabetic drugs. The present results are relevant
because hypertension is so common and difficult to control in Type 2 diabetes. The present
data suggest that sildenafil might interfere with the known antihypertensive potential of
metformin and the thiazolidinediones. However, they do not suggest that it will interact
with them to cause life-threatening episodes of severe hypotension, as can occur when it
is co-administered with nitrates.
Collapse
Affiliation(s)
- Jacob D Peuler
- Department of Pharmacology, Midwestern University, Downers Grove, IL, USA
| | | |
Collapse
|
5
|
Maruthini D, Harris SE, Barth JH, Balen AH, Campbell BK, Picton HM. The effect of metformin treatment in vivo on acute and long-term energy metabolism and progesterone production in vitro by granulosa cells from women with polycystic ovary syndrome. Hum Reprod 2014; 29:2302-16. [PMID: 25139174 PMCID: PMC4164147 DOI: 10.1093/humrep/deu187] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
STUDY QUESTION What are the consequences of polycystic ovary syndrome (PCOS) pathology and metformin-pretreatment in vivo in women with PCOS on the metabolism and steroid production of follicular phenotype- and long-term cultured-granulosa cells (GC)? SUMMARY ANSWER PCOS pathology significantly compromised glucose metabolism and the progesterone synthetic capacity of follicular- and long-term cultured-GCs and the metabolic impact of PCOS on GC function was alleviated by metformin-pretreatment in vivo. WHAT IS KNOWN ALREADY Granulosa cells from women with PCOS have been shown to have an impaired insulin-stimulated glucose uptake and lactate production in vitro. However, these results were obtained by placing GCs in unphysiological conditions in culture medium containing high glucose and insulin concentrations. Moreover, existing data on insulin-responsive steroid production in vitro by PCOS GCs vary. STUDY DESIGN, SIZE AND DURATION Case-control experimental research comparing glucose uptake, pyruvate and lactate production and progesterone production in vitro by GCs from three aetiological groups, all undergoing IVF; healthy control women (Control, n = 12), women with PCOS treated with metformin in vivo (Metformin, n = 8) and women with PCOS not exposed to metformin (PCOS, n = 8). The study was conducted over a period of 3 years between 2007 and 2010. PARTICIPANTS/MATERIALS, SETTING, METHODS Rotterdam criteria were used for the diagnosis of PCOS; all subjects were matched for age, BMI and baseline FSH. Individual patient cultures were undertaken with cells incubated in a validated, physiological, serum-free culture medium containing doses of 0–6 mM glucose and 0–100 ng/ml insulin for 6 h and 144 h to quantify the impact of treatments on acute and long-term metabolism, respectively, and progesterone production. The metabolite content of spent media was measured using spectrophotometric plate reader assay. The progesterone content of spent media was measured by enzyme-linked immunosorbent assay. Viable GC number was quantified after 144 h of culture by the vital dye Neutral Red uptake assay. MAIN RESULTS AND THE ROLE OF CHANCE Granulosa cells from women with PCOS pathology revealed reduced pyruvate production and preferential lactate production in addition to their reduced glucose uptake during cultures (P < 0.05). Metformin pretreatment alleviated this metabolic lesion (P < 0.05) and enhanced cell proliferation in vitro (P < 0.05), but cells retained a significantly reduced capacity for progesterone synthesis compared with controls (P < 0.05). LIMITATIONS, REASONS FOR CAUTION Although significant treatment effects were detected in this small cohort, further studies are required to underpin the molecular mechanisms of the effect of metformin on GCs. WIDER IMPLICATIONS OF THE FINDINGS The individual patient culture strategy combined with multifactorial experimental design strengthens the biological interpretation of the data. Collectively, these results support the notion that there is an inherent impairment in progesterone biosynthetic capacity of the GCs from women with PCOS. The positive, acute metabolic effect and the negative long-term steroidogenic effect on GCs following metformin exposure in vivo may have important implications for follicular development and luteinized GC function when the drug is used in clinical practice. STUDY FUNDING/COMPETING INTEREST(S) No competing interests. This work was supported by the UK Medical Research Council Grant Reference number G0800250.
Collapse
Affiliation(s)
- D Maruthini
- The Leeds Centre for Reproductive Medicine, Seacroft Hospital, York Road, Leeds LS14 6UH, UK
| | - S E Harris
- Division of Reproduction and Early Development, Leeds Institute for Genetics, Health and Therapeutics, University of Leeds, Clarendon Way, Leeds LS2 9JT, UK
| | - J H Barth
- Department of Clinical Biochemistry, Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK
| | - A H Balen
- The Leeds Centre for Reproductive Medicine, Seacroft Hospital, York Road, Leeds LS14 6UH, UK
| | - B K Campbell
- Division of Human Development at Nottingham University Hospitals NHS Trust, Department of Obstetrics and Gynaecology, Queen's Medical Centre Campus, Nottingham NG7 2UH, UK
| | - H M Picton
- Division of Reproduction and Early Development, Leeds Institute for Genetics, Health and Therapeutics, University of Leeds, Clarendon Way, Leeds LS2 9JT, UK
| |
Collapse
|
6
|
Nascimento AD, Silva Lara LA, Japur de Sá Rosa-e-Silva AC, Ferriani RA, Reis RM. Effects of metformin on serum insulin and anti-Mullerian hormone levels and on hyperandrogenism in patients with polycystic ovary syndrome. Gynecol Endocrinol 2013. [PMID: 23194004 DOI: 10.3109/09513590.2012.736563] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE To evaluate the relationship between serum anti-Mullerian hormone levels (AMH) and insulin resistance (IR) before and after meformin treatment and to compare AMH levels of polycystic ovary syndrome (PCOS) women in the early follicular phase. METHODS Twenty PCOS women with IR, taking metformin 1500 mg/day for 8 weeks, and 16 non-PCOS controls were enrolled in this longitudinal study. Serum levels of AMH, insulin, glucose, testosterone, and quantitative insulin check index (QUICKI), were assessed before and after treatment in PCOS group. RESULTS AMH levels were higher in untreated PCOS (p < 0.0001), as were luteinizing hormone (LH) (p = 0.0004), testosterone (p = 0.0017) as well as 17-hydroxyprogesterone (p = 0.03). PCOS women show positive correlation between AMH and testosterone (R = 0.83; p < 0.0001) only prior to treatment. Metformin treatment, lead to a significant decrease in serum insulin (p = 0.0132) and testosterone (p = 0.0017) levels. However, no alteration in AMH levels was observed after treatment. CONCLUSION Despite the improvement of metabolic parameters and the reduction of androgen levels, AMH levels did not change after metformin treatment. Maybe, the dose, and possibly the time of use, of metformin are factors associated with the reduction of AMH levels.
Collapse
Affiliation(s)
- Areana Diogo Nascimento
- Sexual Medicine Service, Department of Gynaecology and Obstetrics, Faculty of Medicine of Ribeirão Preto, São Paulo University, Ribeirão Preto, Brazil
| | | | | | | | | |
Collapse
|
7
|
Turban S, Stretton C, Drouin O, Green CJ, Watson ML, Gray A, Ross F, Lantier L, Viollet B, Hardie DG, Marette A, Hundal HS. Defining the contribution of AMP-activated protein kinase (AMPK) and protein kinase C (PKC) in regulation of glucose uptake by metformin in skeletal muscle cells. J Biol Chem 2012; 287:20088-99. [PMID: 22511782 PMCID: PMC3370192 DOI: 10.1074/jbc.m111.330746] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 04/11/2012] [Indexed: 12/25/2022] Open
Abstract
The importance of AMP-activated protein kinase (AMPK) and protein kinase C (PKC) as effectors of metformin (Met) action on glucose uptake (GU) in skeletal muscle cells was investigated. GU in L6 myotubes was stimulated 2-fold following 16 h of Met treatment and acutely enhanced by insulin in an additive fashion. Insulin-stimulated GU was sensitive to PI3K inhibition, whereas that induced by Met was not. Met and its related biguanide, phenformin, stimulated AMPK activation/phosphorylation to a level comparable with that induced by the AMPK activator, 5-amino-1-β-d-ribofuranosyl-imidazole-4-carboxamide (AICAR). However, the increase in GU elicited by AICAR was significantly lower than that induced by either biguanide. Expression of a constitutively active AMPK mimicked the effects of AICAR on GU, whereas a dominant interfering AMPK or shRNA silencing of AMPK prevented AICAR-stimulated GU and Met-induced AMPK signaling but only repressed biguanide-stimulated GU by ∼20%. Consistent with this, analysis of GU in muscle cells from α1(-/-)/α2(-/-) AMPK-deficient mice revealed a significant retention of Met-stimulated GU, being reduced by ∼35% compared with that of wild type cells. Atypical PKCs (aPKCs) have been implicated in Met-stimulated GU, and in line with this, Met and phenformin induced activation/phosphorylation of aPKC in L6 myotubes. However, although cellular depletion of aPKC (>90%) led to loss in biguanide-induced aPKC phosphorylation, it had no effect on Met-stimulated GU, whereas inhibitors targeting novel/conventional PKCs caused a significant reduction in biguanide-induced GU. Our findings indicate that although Met activates AMPK, a significant component of Met-stimulated GU in muscle cells is mediated via an AMPK-independent mechanism that involves novel/conventional PKCs.
Collapse
Affiliation(s)
- Sophie Turban
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Clare Stretton
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Olivier Drouin
- the Department of Medicine, Québec Heart and Lung Institute, Université Laval and Metabolism, Vascular, and Renal Health Axis, Laval University Hospital Research Center, Ste-Foy, Québec, G1V 4G2, Canada
| | - Charlotte J. Green
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Maria L. Watson
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Alexander Gray
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Fiona Ross
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Louise Lantier
- INSERM, Institut Cochin, U1016, Paris, France
- CNRS, UMR8104, Paris, France, and
- Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Benoit Viollet
- INSERM, Institut Cochin, U1016, Paris, France
- CNRS, UMR8104, Paris, France, and
- Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - D. Grahame Hardie
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Andre Marette
- the Department of Medicine, Québec Heart and Lung Institute, Université Laval and Metabolism, Vascular, and Renal Health Axis, Laval University Hospital Research Center, Ste-Foy, Québec, G1V 4G2, Canada
| | - Harinder S. Hundal
- From the Division of Cell Signaling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| |
Collapse
|
8
|
Lobato N, Filgueira F, Hagihara G, Akamine E, Pariz J, Tostes R, Carvalho M, Fortes Z. Improvement of metabolic parameters and vascular function by metformin in obese non-diabetic rats. Life Sci 2012; 90:228-35. [DOI: 10.1016/j.lfs.2011.11.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 10/30/2011] [Accepted: 11/14/2011] [Indexed: 01/10/2023]
|
9
|
Sena CM, Matafome P, Louro T, Nunes E, Fernandes R, Seiça RM. Metformin restores endothelial function in aorta of diabetic rats. Br J Pharmacol 2011; 163:424-37. [PMID: 21250975 DOI: 10.1111/j.1476-5381.2011.01230.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The effects of metformin, an antidiabetic agent that improves insulin sensitivity, on endothelial function have not been fully elucidated. This study was designed to assess the effect of metformin on impaired endothelial function, oxidative stress, inflammation and advanced glycation end products formation in type 2 diabetes mellitus. EXPERIMENTAL APPROACH Goto-Kakizaki (GK) rats, an animal model of nonobese type 2 diabetes, fed with normal and high-fat diet during 4 months were treated with metformin for 4 weeks before evaluation. Systemic oxidative stress, endothelial function, insulin resistance, nitric oxide (NO) bioavailability, glycation and vascular oxidative stress were determined in the aortic rings of the different groups. A pro-inflammatory biomarker the chemokine CCL2 (monocyte chemoattractant protein-1) was also evaluated. KEY RESULTS High-fat fed GK rats with hyperlipidaemia showed increased vascular and systemic oxidative stress and impaired endothelial-dependent vasodilatation. Metformin treatment significantly improved glycation, oxidative stress, CCL2 levels, NO bioavailability and insulin resistance and normalized endothelial function in aorta. CONCLUSION AND IMPLICATIONS Metformin restores endothelial function and significantly improves NO bioavailability, glycation and oxidative stress in normal and high-fat fed GK rats. This supports the concept of the central role of metformin as a first-line therapeutic to treat diabetic patients in order to protect against endothelial dysfunction associated with type 2 diabetes mellitus.
Collapse
Affiliation(s)
- Cristina M Sena
- Institute of Physiology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
| | | | | | | | | | | |
Collapse
|
10
|
Klachko D, Whaley-Connell A. Use of Metformin in Patients with Kidney and Cardiovascular Diseases. Cardiorenal Med 2011; 1:87-95. [PMID: 22294985 PMCID: PMC3263972 DOI: 10.1159/000327151] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Metformin is an insulin-sensitizing agent with anti-hyperglycemic properties that is widely used for the treatment of type-2 diabetes. The efficacy of metformin in reducing hyperglycemia is well established, and there is emerging evidence that its chronic use is associated with cancer and cardiovascular disease (CVD) risk reduction. While the hypoglycemic properties of metformin are largely attributed to suppression of hepatic glucose production and increases in peripheral tissue insulin sensitivity, the precise mechanism of the hypoglycemic action of metformin remains unclear. There is evidence that metformin use interrupts mitochondrial oxidative stress in the liver and corrects abnormalities of intracellular calcium metabolism in insulin-sensitive tissues (liver, skeletal muscle, and adipocytes) and cardiovascular tissue. However, the use of metformin in patients with kidney disease, a high-risk CVD state, is confounded by confusion regarding appropriate concerns about the development of lactic acidosis in this population. Thus, we will review current evidence on metformin use for improving CVD outcomes and its therapeutic use in kidney disease.
Collapse
Affiliation(s)
- David Klachko
- Division of Endocrinology, University of Missouri-Columbia School of Medicine, Columbia, Mo., USA
| | - Adam Whaley-Connell
- Division of Nephrology, Department of Internal Medicine, University of Missouri-Columbia School of Medicine, Columbia, Mo., USA
- Division of Harry S. Truman VA Medical Center, Columbia, Mo., USA
| |
Collapse
|
11
|
Hwang YP, Jeong HG. Metformin blocks migration and invasion of tumour cells by inhibition of matrix metalloproteinase-9 activation through a calcium and protein kinase Calpha-dependent pathway: phorbol-12-myristate-13-acetate-induced/extracellular signal-regulated kinase/activator protein-1. Br J Pharmacol 2010; 160:1195-211. [PMID: 20590612 DOI: 10.1111/j.1476-5381.2010.00762.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Population studies have revealed that treatment with the anti-diabetic drug metformin is significantly associated with reduced cancer risk, but the underlying mode of action has not been elucidated. The aim of our study was to determine the effect of metformin on tumour invasion and migration, and the possible mechanisms, using human fibrosarcoma HT-1080 cells. EXPERIMENTAL APPROACH We employed invasion, migration and gelatin zymography assays to characterize the effect of metformin on HT-1080 cells. Transient transfection assays were performed to gene promoter activities, and immunoblot analysis to study its molecular mechanisms of action. KEY RESULTS Metformin inhibited migration and invasion by HT-1080 cells at sub-toxic concentrations. In these cells, metformin also suppressed phorbol-12-myristate-13-acetate (PMA)-enhanced levels of matrix metalloproteinases-9 (MMP-9) protein, mRNA and transcription activity through suppression of activator protein-1 (AP-1) activation. In addition, metformin strongly repressed the PMA-induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and protein kinase C(PKC)alpha, whereas the phosphorylation of p38 mitogen-activated protein kinase was not affected by metformin. Metformin decreased the PMA-induced Ca(2+) influx. Furthermore, treatment with an intracellular Ca(2+) chelator (BAPTA-AM) or a selective calmodulin antagonist (W7) markedly decreased PMA-induced MMP-9 secretion and cell migration, as well as activation of ERK and JNK/AP-1. CONCLUSIONS AND IMPLICATIONS Metformin inhibited PMA-induced invasion and migration of human fibrosarcoma cells via Ca(2+)-dependent PKCalpha/ERK and JNK/AP-1-signalling pathways. Metformin therefore has the potential to be a potent anti-cancer drug in therapeutic strategies for fibrosarcoma metastasis.
Collapse
Affiliation(s)
- Yong P Hwang
- Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon, Korea
| | | |
Collapse
|
12
|
Agard C, Rolli-Derkinderen M, Dumas-de-La-Roque E, Rio M, Sagan C, Savineau JP, Loirand G, Pacaud P. Protective role of the antidiabetic drug metformin against chronic experimental pulmonary hypertension. Br J Pharmacol 2009; 158:1285-94. [PMID: 19814724 DOI: 10.1111/j.1476-5381.2009.00445.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND AND PURPOSE Pulmonary arterial hypertension (PAH) is associated with increased contraction and proliferation of pulmonary vascular smooth muscle cells. The anti-diabetic drug metformin has been shown to have relaxant and anti-proliferation properties. We thus examined the effect of metformin in PAH. EXPERIMENTAL APPROACH Metformin effects were analysed in hypoxia- and monocrotaline-induced PAH in rats. Ex vivo and in vitro analyses were performed in lungs, pulmonary artery rings and cells. KEY RESULTS In hypoxia- and monocrotaline-induced PAH, the changes in mean pulmonary arterial pressure and right heart hypertrophy were nearly normalized by metformin treatment (100 mg.kg(-1).day(-1)). Pulmonary arterial remodelling occurring in both experimental models of PAH was also inhibited by metformin treatment. In rats with monocrotaline-induced PAH, treatment with metformin significantly increased survival. Metformin increased endothelial nitric oxide synthase phosphorylation and decreased Rho kinase activity in pulmonary artery from rats with PAH. These effects are associated with an improvement of carbachol-induced relaxation and reduction of phenylephrine-induced contraction of pulmonary artery. In addition, metformin inhibited mitogen-activated protein kinase activation and strongly reduced pulmonary arterial cell proliferation during PAH. In vitro, metformin directly inhibited pulmonary artery smooth muscle cell growth. CONCLUSIONS AND IMPLICATIONS Metformin protected against PAH, regardless of the initiating stimulus. This protective effect may be related to its anti-remodelling property involving improvement of endothelial function, vasodilatory and anti-proliferative actions. As metformin is currently prescribed to treat diabetic patients, assessment of its use as a therapy against PAH in humans should be easier.
Collapse
Affiliation(s)
- C Agard
- INSERM, U915, Nantes, France
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Palomba S, Falbo A, Zullo F, Orio F. Evidence-based and potential benefits of metformin in the polycystic ovary syndrome: a comprehensive review. Endocr Rev 2009; 30:1-50. [PMID: 19056992 DOI: 10.1210/er.2008-0030] [Citation(s) in RCA: 263] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Metformin is an insulin sensitizer widely used for the treatment of patients affected by type 2 diabetes mellitus. Because many women with polycystic ovary syndrome (PCOS) are insulin resistant, metformin was introduced in clinical practice to treat these patients also. Moreover, metformin's effect has other targets beside its insulin-sensitizing action. The present review was aimed at describing all evidence-based and potential uses of metformin in PCOS patients. In particular, we will analyze the uses of metformin not only for the treatment of all PCOS-related disturbances such as menstrual disorders, anovulatory infertility, increased abortion, or complicated pregnancy risk, hyperandrogenism, endometrial, metabolic and cardiovascular abnormalities, but also for the prevention of the syndrome.
Collapse
Affiliation(s)
- Stefano Palomba
- Department of Gynecology and Obstetrics, University "Magna Graecia" of Catanzaro, Via Pio X, 88100 Catanzaro, Italy.
| | | | | | | |
Collapse
|
14
|
Basu R, Basu A, Chandramouli V, Norby B, Dicke B, Shah P, Cohen O, Landau BR, Rizza RA. Effects of pioglitazone and metformin on NEFA-induced insulin resistance in type 2 diabetes. Diabetologia 2008; 51:2031-40. [PMID: 18769904 PMCID: PMC2701394 DOI: 10.1007/s00125-008-1138-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Accepted: 07/23/2008] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS We sought to determine whether pioglitazone and metformin alter NEFA-induced insulin resistance in type 2 diabetes and, if so, the mechanism whereby this is effected. METHODS Euglycaemic-hyperinsulinaemic clamps (glucose approximately 5.3 mmol/l, insulin approximately 200 pmol/l) were performed in the presence of Intralipid-heparin (IL/H) or glycerol before and after 4 months of treatment with pioglitazone (n = 11) or metformin (n = 9) in diabetic participants. Hormone secretion was inhibited with somatostatin in all participants. RESULTS Pioglitazone increased insulin-stimulated glucose disappearance (p < 0.01) and increased insulin-induced suppression of glucose production (p < 0.01), gluconeogenesis (p < 0.05) and glycogenolysis (p < 0.05) during IL/H. However, glucose disappearance remained lower (p < 0.05) whereas glucose production (p < 0.01), gluconeogenesis (p < 0.05) and glycogenolysis (p < 0.05) were higher on the IL/H study day than on the glycerol study day, indicating persistence of NEFA-induced insulin resistance. Metformin increased (p < 0.001) glucose disappearance during IL/H to rates present during glycerol treatment, indicating protection against NEFA-induced insulin resistance in extrahepatic tissues. However, glucose production and gluconeogenesis (but not glycogenolysis) were higher (p < 0.01) during IL/H than during glycerol treatment with metformin, indicating persistence of NEFA-induced hepatic insulin resistance. CONCLUSIONS/INTERPRETATION We conclude that pioglitazone improves both the hepatic and the extrahepatic action of insulin but does not prevent NEFA-induced insulin resistance. In contrast, whereas metformin prevents NEFA-induced extrahepatic insulin resistance, it does not protect against NEFA-induced hepatic insulin resistance.
Collapse
Affiliation(s)
- R. Basu
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic College of Medicine, 200 1st Street SW, Room 5-194 Joseph, Rochester, MN 55905, USA
| | - A. Basu
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic College of Medicine, 200 1st Street SW, Room 5-194 Joseph, Rochester, MN 55905, USA
| | - V. Chandramouli
- Division of Clinical and Molecular Endocrinology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - B. Norby
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic College of Medicine, 200 1st Street SW, Room 5-194 Joseph, Rochester, MN 55905, USA
| | - B. Dicke
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic College of Medicine, 200 1st Street SW, Room 5-194 Joseph, Rochester, MN 55905, USA
| | - P. Shah
- Department of Endocrine Neoplasia and Hormonal Disorders, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - O. Cohen
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel Hashomer, Israel
| | - B. R. Landau
- Division of Clinical and Molecular Endocrinology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - R. A. Rizza
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic College of Medicine, 200 1st Street SW, Room 5-194 Joseph, Rochester, MN 55905, USA
| |
Collapse
|
15
|
Abstract
Cardiovascular disease (CVD) burden remains the predominant cause of mortality and morbidity in the United States and in most of the developed world. The ongoing twin epidemics of obesity and type 2 diabetes mellitus provide a groundswell source for sustaining this trend for the foreseeable future (increasing the prevalence of CVD by 2-4 times), unless radical changes are made in public health policy. Oral hypoglycemic agents (OHAs) remain a mainstay for management of type 2 diabetes in most practice settings. Although these agents are primarily prescribed to achieve better glycemic control, it is important to evaluate what effects they have on cardiovascular risk and whether there are significant differences in effects among the different OHAs. This review presents the available data on the effects of the various OHAs on cardiovascular risk surrogates and actual events in retrospective and prospective study design settings.
Collapse
Affiliation(s)
- Gabriel I Uwaifo
- Georgetown University College of Medicine, Washington, District of Columbia 20003, USA.
| | | |
Collapse
|
16
|
Tosca L, Chabrolle C, Uzbekova S, Dupont J. Effects of metformin on bovine granulosa cells steroidogenesis: possible involvement of adenosine 5' monophosphate-activated protein kinase (AMPK). Biol Reprod 2006; 76:368-78. [PMID: 17123942 DOI: 10.1095/biolreprod.106.055749] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In mammals, IGFs are important for the proliferation and steroidogenesis of ovarian cells. Metformin is an insulin sensitizer molecule used for the treatment of the infertility of women with polycystic ovary syndrome. It is, however, unclear whether metformin acts on ovarian cells. Adenosine 5' monophosphate-activated protein kinase (AMPK) is involved in metformin action in various cell types. We investigated the effects of metformin on bovine granulosa cell steroidogenesis in response to IGF1 and FSH, and studied AMPK in bovine ovaries. In granulosa cells from small follicles, metformin (10 mM) reduced production of both progesterone and estradiol and decreased the abundance of HSD3B, CYP11A1, and STAR proteins in presence or absence of FSH (10(-8) M) and IGF1 (10(-8) M). In cows, the different subunits of AMPK are expressed in various ovarian cells including granulosa and theca cells, corpus luteum, and oocytes. In bovine granulosa cells from small follicles, metformin, like AICAR (1 mM) a pharmaceutical activator of AMPK, increased phosphorylation of both Thr172 of AMPK alpha and Ser 79 of ACACA (Acetyl-CoA Carboxylase). Both metformin and AICAR treatment reduced progesterone and estradiol secretion in presence or absence of FSH and IGF1. Metformin decreased phosphorylation levels of MAPK3/MAPK1 and MAPK14 in a dose- and time-dependent manner. The adenovirus-mediated production of dominant negative AMPK abolished the effects of metformin on secretion of progesterone and estradiol and on MAPK3/MAPK1 phosphorylation but not on MAPK14 phosphorylation. Thus, in bovine granulosa cells, metformin decreases steroidogenesis and MAPK3/MAPK1 phosphorylation through AMPK activation.
Collapse
Affiliation(s)
- Lucie Tosca
- Unité de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique, 37380 Nouzilly, France
| | | | | | | |
Collapse
|
17
|
Cortizo AM, Sedlinsky C, McCarthy AD, Blanco A, Schurman L. Osteogenic actions of the anti-diabetic drug metformin on osteoblasts in culture. Eur J Pharmacol 2006; 536:38-46. [PMID: 16564524 DOI: 10.1016/j.ejphar.2006.02.030] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Revised: 02/10/2006] [Accepted: 02/17/2006] [Indexed: 12/22/2022]
Abstract
An association has been previously established between uncompensated diabetes mellitus and the loss of bone mineral density and/or quality. In this study, we evaluated the effects of metformin on the growth and differentiation of osteoblasts in culture. Treatment of two osteoblast-like cells (UMR106 and MC3T3E1) with metformin (25-500 microM) for 24 h led to a dose-dependent increase of cell proliferation. Metformin also promoted osteoblastic differentiation: it increased type-I collagen production in both cell lines and stimulated alkaline phosphatase activity in MC3T3E1 osteoblasts. In addition, metformin markedly increased the formation of nodules of mineralization in 3-week MC3T3E1 cultures. Metformin induced activation and redistribution of phosphorylated extracellular signal-regulated kinase (P-ERK) in a transient manner, and dose-dependently stimulated the expression of endothelial and inducible nitric oxide synthases (e/iNOS). These results show for the first time a direct osteogenic effect of metformin on osteoblasts in culture, which could be mediated by activation/redistribution of ERK-1/2 and induction of e/iNOS.
Collapse
Affiliation(s)
- Ana M Cortizo
- Cátedra de Bioquímica Patológica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900 La Plata, and Centro de Endocrinología y Metabolismo, Hospital Francés, Buenos Aires, Argentina.
| | | | | | | | | |
Collapse
|
18
|
Isoda K, Young JL, Zirlik A, MacFarlane LA, Tsuboi N, Gerdes N, Schönbeck U, Libby P. Metformin inhibits proinflammatory responses and nuclear factor-kappaB in human vascular wall cells. Arterioscler Thromb Vasc Biol 2005; 26:611-7. [PMID: 16385087 DOI: 10.1161/01.atv.0000201938.78044.75] [Citation(s) in RCA: 367] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Metformin may benefit the macrovascular complications of diabetes independently of its conventional hypoglycemic effects. Accumulating evidence suggests that inflammatory processes participate in type 2 diabetes and its atherothrombotic manifestations. Therefore, this study examined the potential action of metformin as an inhibitor of pro-inflammatory responses in human vascular smooth muscle cells (SMCs), macrophages (Mphis), and endothelial cells (ECs). METHODS AND RESULTS Metformin dose-dependently inhibited IL-1beta-induced release of the pro-inflammatory cytokines IL-6 and IL-8 in ECs, SMCs, and Mphis. Investigation of potential signaling pathways demonstrated that metformin diminished IL-1beta-induced activation and nuclear translocation of nuclear factor-kappa B (NF-kappaB) in SMCs. Furthermore, metformin suppressed IL-1beta-induced activation of the pro-inflammatory phosphokinases Akt, p38, and Erk, but did not affect PI3 kinase (PI3K) activity. To address the significance of the anti-inflammatory effects of a therapeutically relevant plasma concentration of metformin (20 micromol/L), we conducted experiments in ECs treated with high glucose. Pretreatment with metformin also decreased phosphorylation of Akt and protein kinase C (PKC) in ECs under these conditions. CONCLUSIONS These data suggest that metformin can exert a direct vascular anti-inflammatory effect by inhibiting NF-kappaB through blockade of the PI3K-Akt pathway. The novel anti-inflammatory actions of metformin may explain in part the apparent clinical reduction by metformin of cardiovascular events not fully attributable to its hypoglycemic action.
Collapse
MESH Headings
- Anti-Inflammatory Agents/pharmacology
- Atherosclerosis/drug therapy
- Atherosclerosis/immunology
- Cell Survival/drug effects
- Cells, Cultured
- Diabetes Mellitus, Type 2/drug therapy
- Diabetes Mellitus, Type 2/immunology
- Diabetic Angiopathies/drug therapy
- Diabetic Angiopathies/immunology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/immunology
- Glucose/pharmacology
- Humans
- Hypoglycemic Agents/pharmacology
- Interleukin-1/antagonists & inhibitors
- Interleukin-1/metabolism
- Interleukin-6/metabolism
- Interleukin-8/metabolism
- Macrophages/cytology
- Macrophages/drug effects
- Macrophages/immunology
- Metformin/pharmacology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/immunology
- NF-kappa B/metabolism
- Phosphatidylinositol 3-Kinases/metabolism
- Proto-Oncogene Proteins c-akt/metabolism
- Saphenous Vein/cytology
Collapse
Affiliation(s)
- Kikuo Isoda
- Donald W. Reynolds Cardiovascular Clinical Research Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Dominguez LJ, Sowers JR. Metabolic syndrome therapy: prevention of vascular injury by antidiabetic agents. Curr Hypertens Rep 2005; 7:110-6. [PMID: 15748534 DOI: 10.1007/s11906-005-0083-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
More than 65 million Americans are currently obese. Type 2 diabetes mellitus, frequently seen in obese subjects, affects 17 million adults in the United States, with a continuous and alarmingly increasing rate. To prevent development of diabetes in those who are at high risk, it is recommended to optimize meal planning and enhance physical activity to make sustained weight reduction possible. In addition to lifestyle changes, various oral antidiabetic agents are available, with diverse mechanisms of action. Some target defective insulin secretion (sulphonylureas, benzoic acid derivatives) or glucose absorption (glycosidase inhibitors), whereas others target insulin resistance (metformin, thiazolidinediones). Patients with metabolic syndrome and diabetes have an increased risk for cardiovascular disease linked to a higher prevalence of hypertension, dyslipidemia, microalbuminuria, and altered hemostasis--parameters that may be modified by antidiabetic agents. In this article, we review the oral agents used to treat type 2 diabetes and the metabolic syndrome, and their effects on vascular tissue.
Collapse
Affiliation(s)
- Ligia J Dominguez
- Geriatric Unit, Department of Internal Medicine, University of Palermo, viale F. Scaduto 6/c, 90144 Palermo, Italy.
| | | |
Collapse
|
20
|
Gomes MB, Cailleaux S, Tibiriçá E. Metformin prevents the impairment of endothelium-dependent vascular relaxation induced by high glucose challenge in rabbit isolated perfused kidneys. Naunyn Schmiedebergs Arch Pharmacol 2005; 372:24-30. [PMID: 16133490 DOI: 10.1007/s00210-005-1083-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Accepted: 07/04/2005] [Indexed: 10/25/2022]
Abstract
High glucose concentrations are involved in the development of diabetic-associated vascular complications. We have previously reported that acute high glucose challenge, corresponding to post-prandial glycemia levels observed in patients with type 2 diabetes, blunts ACh-induced endothelium-dependent relaxation of the renal circulation of non-diabetic rabbits. Isolated perfused kidneys from non-diabetic rabbits were acutely exposed (3 h) to normal (5.5 mM--control group) or high (15 mM) D-glucose concentrations in the presence or absence of a continuous infusion of metformin (20 or 100 microM). Renal vascular reactivity was evaluated with endothelium-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) vasodilating agents. ACh-induced maximal renal vasodilation was reduced by high glucose infusion (15 mM) in comparison to the control group (25+/-3% and 41+/-3% respectively; P<0.01), being restored to 41+/-4% and 43+/-2% by a simultaneous 3-h infusion of 20 or 100 microM of metformin respectively (P>0.05). Perfusion of the kidneys with the angiotensin II-converting enzyme inhibitor captopril (10 microM) also significantly prevented the deleterious effects of high glucose challenge in the renal circulation. The use of a continuous infusion of N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM) did not affect the protective effect of metformin in the renal circulation (39+/-4%; P>0.05), while tetraethylammonium (TEA, 10 mM) partially blunted this effect (33+/-4, P<0.01). Renal vasodilation induced by SNP was not modified by simultaneous infusion of high glucose and/or metformin. It is concluded that the impairment of ACh-induced endothelium-dependent renal vasodilation observed after acute exposure to high glucose concentrations is abolished by metformin administration. These alterations of renal vascular reactivity can be accounted for, at least in part, by the activation of the renal renin-angiotensin system during hyperglycemia. The protective effects of metformin present some EDHF-dependent component and are not related to metabolic pathways dependent on nitric oxide.
Collapse
Affiliation(s)
- M B Gomes
- Departmento de Medicina, Unidade de Diabetes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
| | | | | |
Collapse
|
21
|
Holland W, Morrison T, Chang Y, Wiernsperger N, Stith BJ. Metformin (Glucophage) inhibits tyrosine phosphatase activity to stimulate the insulin receptor tyrosine kinase. Biochem Pharmacol 2004; 67:2081-91. [PMID: 15135305 DOI: 10.1016/j.bcp.2004.02.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2003] [Accepted: 02/12/2004] [Indexed: 12/25/2022]
Abstract
Metformin is a commonly used anti-diabetic but whether its mechanism involves action on the insulin receptor or on downstream events is still controversial. With a time course that was slow compared with insulin action, metformin increased tyrosine phosphorylation of the regulatory domain of the insulin receptor (specifically, tyrosine residues 1150 and 1151). In a direct action, therapeutic levels of metformin stimulated the tyrosine kinase activity of the soluble intracellular portion of the beta subunit of the human insulin receptor toward a substrate derived from the insulin receptor regulatory domain. However, metformin did not alter the order of substrate phosphorylation by the insulin receptor kinase. Using a Xenopus oocyte preparation, we simultaneously recorded tyrosine kinase and phosphatase activities that regulate the insulin receptor by measuring the tyrosine phosphorylation and dephosphorylation of peptides derived from the regulatory domain of the human insulin receptor. In an indirect stimulation of the insulin receptor, metformin inhibited endogenous tyrosine phosphatases and purified human protein tyrosine phosphatase 1B that dephosphorylate and inhibit the insulin receptor kinase. Thus, there was evidence that metformin acted directly upon the insulin receptor and indirectly through inhibition of tyrosine phosphatases.
Collapse
Affiliation(s)
- William Holland
- Department of Biology, University of Colorado-Denver, Denver, CO 80217, USA
| | | | | | | | | |
Collapse
|
22
|
Abstract
Metformin, a biguanide, has been available in the US for the treatment of type 2 diabetes mellitus for nearly 8 years. Over this period of time, it has become the most widely prescribed antihyperglycaemic agent. Its mechanism of action involves the suppression of endogenous glucose production, primarily by the liver. Whether the drug actually has an insulin sensitising effect in peripheral tissues, such as muscle and fat, remains somewhat controversial. Nonetheless, because insulin levels decline with metformin use, it has been termed an 'insulin sensitiser'. Metformin has also been shown to have several beneficial effects on cardiovascular risk factors and it is the only oral antihyperglycaemic agent thus far associated with decreased macrovascular outcomes in patients with diabetes. Cardiovascular disease, impaired glucose tolerance and the polycystic ovary syndrome are now recognised as complications of the insulin resistance syndrome, and there is growing interest in the management of this extraordinarily common metabolic disorder. While diet and exercise remain the cornerstone of therapy for insulin resistance, pharmacological intervention is becoming an increasingly viable option. We review the role of metformin in the treatment of patients with type 2 diabetes and describe the additional benefits it provides over and above its effect on glucose levels alone. We also discuss its potential role for a variety of insulin resistant and prediabetic states, including impaired glucose tolerance, obesity, polycystic ovary syndrome and the metabolic abnormalities associated with HIV disease.
Collapse
Affiliation(s)
- Ripudaman S Hundal
- Diabetes & Metabolic Disease Center, Christiana Care, Wilmington, Delaware, USA
| | | |
Collapse
|
23
|
Sasaoka T, Kikuchi K, Wada T, Sato A, Hori H, Murakami S, Fukui K, Ishihara H, Aota R, Kimura I, Kobayashi M. Dual role of SRC homology domain 2-containing inositol phosphatase 2 in the regulation of platelet-derived growth factor and insulin-like growth factor I signaling in rat vascular smooth muscle cells. Endocrinology 2003; 144:4204-14. [PMID: 12933696 DOI: 10.1210/en.2003-0190] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Src homology domain 2 (SH2)-containing inositol phosphatase 2 (SHIP2) possesses 5-phosphatase activity and an SH2 domain. The role of SHIP2 in platelet-derived growth factor (PDGF) and IGF-I signaling was studied by expressing wild-type (WT-) and a catalytically defective (Delta IP-) SHIP2 into rat aortic smooth muscle cells by adenovirus-mediated gene transfer. PDGF- and IGF-I-induced tyrosine phosphorylation of their respective receptors and phosphatidylinositol 3-kinase (PI3-kinase) activity were not affected by the expression of either WT- or Delta IP-SHIP2. SHIP2 possessed 5'-phosphatase activity to hydrolyze the PI3-kinase product phosphatidylinositol 3,4,5-trisphosphate in vivo. Akt and glycogen synthase kinase 3beta are known to be downstream molecules of PI3-kinase, leading to the antiapoptotic effect. Overexpression of WT-SHIP2 inhibited PDGF- and IGF-I-induced phosphorylation of these molecules and the protective effect of poly(ADP-ribose) polymerase degradation, whereas these phosphorylations and the protective effect were enhanced by the expression of Delta IP-SHIP2, which functions in a dominant negative fashion. Regarding the Ras-MAPK pathway, PDGF- and IGF-I-induced tyrosine phosphorylation of Shc was not affected by the expression of either WT- or Delta IP-SHIP2, whereas both expressed SHIP2 associated with Shc. Importantly, PDGF and IGF-I stimulation of Shc/Grb2 binding, MAPK activation, and 5-bromo-2'-deoxyuridine incorporation were all decreased in both WT- and Delta IP-SHIP2 expression. These results indicate that SHIP2 plays a negative regulatory role in PDGF and IGF-I signaling in vascular smooth muscle cells. As the bifunctional role, our results suggest that SHIP2 regulates PDGF- and IGF-I-mediated signaling downstream of PI3-kinase, leading to the antiapoptotic effect via 5-phosphatase activity, and that SHIP2 regulates the growth factor-induced Ras-MAPK pathway mainly via the SH2 domain.
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing
- Adenoviridae/genetics
- Animals
- Antimetabolites/pharmacokinetics
- Aorta, Thoracic/cytology
- Bromodeoxyuridine/pharmacokinetics
- Cells, Cultured
- GRB2 Adaptor Protein
- Gene Expression Regulation, Enzymologic/drug effects
- Gene Expression Regulation, Enzymologic/physiology
- Glycogen Synthase Kinase 3/metabolism
- Glycogen Synthase Kinase 3 beta
- Hypoglycemic Agents/pharmacology
- Insulin/pharmacology
- Insulin-Like Growth Factor I/pharmacology
- Mitogen-Activated Protein Kinases/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/enzymology
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphatidylinositol Phosphates/metabolism
- Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
- Phosphoric Monoester Hydrolases/genetics
- Phosphoric Monoester Hydrolases/metabolism
- Phosphorylation
- Platelet-Derived Growth Factor/pharmacology
- Poly(ADP-ribose) Polymerases/metabolism
- Protein Serine-Threonine Kinases
- Proteins/metabolism
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-akt
- Rats
- Signal Transduction/drug effects
- Signal Transduction/physiology
- src Homology Domains/physiology
Collapse
Affiliation(s)
- Toshiyasu Sasaoka
- Department of Clinical Pharmacology, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Abstract
OBJECTIVES This study was designed to assess the effect of metformin on impaired endothelial function in type 2 diabetes mellitus. BACKGROUND Abnormalities in vascular endothelial function are well recognized among patients with type 2 (insulin-resistant) diabetes mellitus. Insulin resistance itself may be central to the pathogenesis of endothelial dysfunction. The effects of metformin, an antidiabetic agent that improves insulin sensitivity, on endothelial function have not been reported. METHODS Subjects with diet-treated type 2 diabetes but without the confounding collection of cardiovascular risk factors seen in the metabolic syndrome were treated with metformin 500 mg twice daily (n = 29) or placebo (n = 15) for 12 weeks. Before and after treatment, blood flow responses to intraarterial administration of endothelium-dependent (acetylcholine), endothelium-independent (sodium nitroprusside) and nitrate-independent (verapamil) vasodilators were measured using forearm plethysmography. Whole-body insulin resistance was assessed on both occasions using the homeostasis model (HOMA-IR). RESULTS Subjects who received metformin demonstrated statistically significant improvement in acetylcholine-stimulated flows compared with those treated with placebo (p = 0.0027 by 2-way analysis of variance), whereas no significant effect was seen on nitroprusside-stimulated (p = 0.27) or verapamil-stimulated (p = 0.40) flows. There was a significant improvement in insulin resistance with metformin (32.5% reduction in HOMA-IR, p = 0.01), and by stepwise multivariate analysis insulin resistance was the sole predictor of endothelium-dependent blood flow following treatment (r = -0.659, p = 0.0012). CONCLUSIONS Metformin treatment improved both insulin resistance and endothelial function, with a strong statistical link between these variables. This supports the concept of the central role of insulin resistance in the pathogenesis of endothelial dysfunction in type 2 diabetes mellitus. This has important implications for the investigation and treatment of vascular disease in patients with type 2 diabetes mellitus.
Collapse
Affiliation(s)
- K J Mather
- Division of Endocrinology and Metabolism, Indiana University, Indianapolis, USA
| | | | | |
Collapse
|
25
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide inhibits cell respiration via an indirect effect targeted on the respiratory chain complex I. J Biol Chem 2000; 275:223-8. [PMID: 10617608 DOI: 10.1074/jbc.275.1.223] [Citation(s) in RCA: 1056] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We report here a new mitochondrial regulation occurring only in intact cells. We have investigated the effects of dimethylbiguanide on isolated rat hepatocytes, permeabilized hepatocytes, and isolated liver mitochondria. Addition of dimethylbiguanide decreased oxygen consumption and mitochondrial membrane potential only in intact cells but not in permeabilized hepatocytes or isolated mitochondria. Permeabilized hepatocytes after dimethylbiguanide exposure and mitochondria isolated from dimethylbiguanide pretreated livers or animals were characterized by a significant inhibition of oxygen consumption with complex I substrates (glutamate and malate) but not with complex II (succinate) or complex IV (N,N,N',N'-tetramethyl-1, 4-phenylenediamine dihydrochloride (TMPD)/ascorbate) substrates. Studies using functionally isolated complex I obtained from mitochondria isolated from dimethylbiguanide-pretreated livers or rats further confirmed that dimethylbiguanide action was located on the respiratory chain complex I. The dimethylbiguanide effect was temperature-dependent, oxygen consumption decreasing by 50, 20, and 0% at 37, 25, and 15 degrees C, respectively. This effect was not affected by insulin-signaling pathway inhibitors, nitric oxide precursor or inhibitors, oxygen radical scavengers, ceramide synthesis inhibitors, or chelation of intra- or extracellular Ca(2+). Because it is established that dimethylbiguanide is not metabolized, these results suggest the existence of a new cell-signaling pathway targeted to the respiratory chain complex I with a persistent effect after cessation of the signaling process.
Collapse
Affiliation(s)
- M Y El-Mir
- Laboratoire de Bioénergétique Fondamentale et Appliquée, Université Joseph Fourier, F-38041 Grenoble-Cedex 09, France
| | | | | | | | | | | |
Collapse
|
26
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 order by 1-- #] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
27
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 order by 8029-- awyx] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
28
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 order by 8029-- -] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
29
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 and 1880=1880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
30
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 order by 1-- -] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
31
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 order by 8029-- #] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
32
|
El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide Inhibits Cell Respiration via an Indirect Effect Targeted on the Respiratory Chain Complex I. J Biol Chem 2000. [DOI: 10.1074/jbc.275.1.223 order by 1-- gadu] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
|
33
|
Detaille D, Wiernsperger N, Devos P. Cellular and molecular mechanisms involved in insulin's potentiation of glycogen synthase activity by metformin. Biochem Pharmacol 1999; 58:1475-86. [PMID: 10513991 DOI: 10.1016/s0006-2952(99)00222-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
By taking advantage of the Xenopus oocyte model, we recently confirmed the in vitro enhancing effect of metformin (MET) on glycogen synthase (GS) activity when induced by insulin (INS). We now investigated some mechanistic aspects of its modulatory role upon the hormonal regulation of this rate-limiting enzyme. The action of 20 microM MET (approximately 3.3 microg/mL) was measurable at early steps in the intracellular metabolic pathway: the amount of adenosine 3',5'-cyclic monophosphate (cAMP) was markedly decreased in the presence of the biguanide plus 50 nM INS (to about 60% of control vs 25% with INS alone). The injection of tyrphostin B46, a potent inhibitor of insulin receptor (IR)-associated tyrosine kinase activity, led to a drastic reduction in MET-stimulated GS activity in the presence of INS. MET failed to increase the activity of type 2 protein phosphatases whether INS was present or not. However, a specific inhibitor of type 1 phosphatases, when microinjected, blocked both the hormonal effect on GS and its potentiation by MET. The salient feature of this study was that there was almost no accumulation of radiolabeled MET in oocytes: less than 0.1% was found in the cytosol of cells which had been exposed to MET at a therapeutic dose (10 microM) for up to 16 hr. Moreover, a lack of detectable intracellular MET after a 60-min incubation nevertheless correlated with its sustained action on INS-regulated GS activity. From these results, it could be inferred that the major site of MET action may reside within some membrane components of a signaling complex most likely linked to the IR, but in any case located upstream of the branching of reactions which tightly control GS activity.
Collapse
Affiliation(s)
- D Detaille
- Laboratory of Comparative Biochemistry and Psysiology, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium.
| | | | | |
Collapse
|
34
|
Poretsky L, Cataldo NA, Rosenwaks Z, Giudice LC. The insulin-related ovarian regulatory system in health and disease. Endocr Rev 1999; 20:535-82. [PMID: 10453357 DOI: 10.1210/edrv.20.4.0374] [Citation(s) in RCA: 402] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- L Poretsky
- Department of Medicine, New York Presbyterian Hospital and Weill Medical College of Cornell University, New York, New York 10021, USA
| | | | | | | |
Collapse
|
35
|
Abstract
Metformin has been used for over 40 years as an effective glucose-lowering agent in type 2 (noninsulin-dependent) diabetes mellitus. Typically it reduces basal and postprandial hyperglycaemia by about 25% in more than 90% of patients when either given alone or coadministered with other therapies including insulin during a programme of managed care. Metformin counters insulin resistance and offers benefits against many features of the insulin resistance syndrome (Syndrome X) by preventing bodyweight gain, reducing hyperinsulinaemia and improving the lipid profile. In contrast to sulphonylureas, metformin does not increase insulin secretion or cause serious hypoglycaemia. Treatment of type 2 diabetes mellitus with metformin from diagnosis also offers greater protection against the chronic vascular complications of type 2 diabetes mellitus. The most serious complication associated with metformin is lactic acidosis which has an incidence of about 0.03 cases per 1000 patients years of treatment and a mortality risk of about 0.015 per 1000 patient-years. Most cases occur in patients who are wrongly prescribed the drug, particularly patients with impaired renal function (e.g. serum creatinine level > 130 micromol/L or > 1.5 g/L). Other major contraindications include congestive heart failure, hypoxic states and advanced liver disease. Serious adverse events with metformin are predictable rather than spontaneous and are potentially preventable if the prescribing guidelines are respected. Gastrointestinal adverse effects, notably diarrhoea, occur in less than 20% of patients and remit when the dosage is reduced. The life-threatening risks associated with metformin are rare and could mostly be avoided by strict adherence to the prescribing guidelines. Given the 4 decades of clinical experience with metformin, its antihyperglycaemic efficacy and benefits against Syndrome X, metformin offers a very favourable risk-benefit assessment when compared with the chronic morbidity and premature mortality among patients with type 2 diabetes mellitus.
Collapse
Affiliation(s)
- H C Howlett
- Clinical Research, Merck Lipha, West Drayton, England.
| | | |
Collapse
|
36
|
Goalstone ML, Natarajan R, Standley PR, Walsh MF, Leitner JW, Carel K, Scott S, Nadler J, Sowers JR, Draznin B. Insulin potentiates platelet-derived growth factor action in vascular smooth muscle cells. Endocrinology 1998; 139:4067-72. [PMID: 9751484 DOI: 10.1210/endo.139.10.6270] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Correlative studies have indicated that hyperinsulinemia is present in many individuals with atherosclerosis. Insulin resistance has also been linked to cardiovascular disease. It has proved to be difficult to decipher whether hyperinsulinemia or insulin resistance plays the most important role in the pathogenesis of atherosclerosis and coronary artery disease. In this study, we demonstrate that insulin increases the amount of farnesylated p21Ras in vascular smooth muscle cells (VSMC), thereby augmenting the pool of cellular Ras available for activation by platelet-derived growth factor (PDGF). In VSMC incubated with insulin for 24 h, PDGF's influence on GTP-loading of Ras was significantly increased. Furthermore, in cells preincubated with insulin, PDGF increased thymidine incorporation by 96% as compared with a 44% increase in control cells (a 2-fold increment). Similarly, preincubation of VSMC with insulin increased the ability of PDGF to stimulate gene expression of vascular endothelial growth factor 5- to 8-fold. The potentiating influence of insulin on PDGF action was abrogated in the presence of a farnesyltransferase inhibitor. Thus, the detrimental influence of hyperinsulinemia on the arterial wall may be related to the ability of insulin to augment farnesyltransferase activity and provide greater amounts of farnesylated p21Ras for stimulation by various growth promoting agents.
Collapse
Affiliation(s)
- M L Goalstone
- Research Service, Denver VA Medical Center and Department of Medicine University of Colorado Health Sciences Center, 80220, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Abstract
Although low-density lipoprotein (LDL) cholesterol is a critically important factor in the development of atherosclerosis, nearly half the patients with coronary artery disease have LDL cholesterol levels within the National Cholesterol Education Program (NCEP) guidelines. Therefore, attention has focused on other modifiable risk factors that could strongly impact the development of coronary artery disease. Type 2 diabetics have a 3-fold increased risk of coronary artery disease; prediabetics, without chronic hyperglycemia, have a 2-fold increased risk compared with normal subjects. Insulin resistance has also been implicated as the cause of atherosclerosis. Insulin resistance is associated with hyperinsulinemia and a constellation of other factors, some of which are themselves independent risk factors for coronary artery disease. These include reduced levels of high-density lipoprotein (HDL) cholesterol, hypertriglyceridemia, increased small dense LDL particles, hypertension, visceral obesity, and increased levels of plasminogen activator inhibitor-1 (PAI-1). Hyperinsulinemia and insulin resistance at the vascular level also may contribute to vascular injury and the atherosclerotic process. Current studies suggest that controlling hyperglycemia, LDL cholesterol, and blood pressure are important to protect the diabetic from atherosclerosis. A key question, particularly in type 2 diabetes, is to define the best regimen for glucose control that will protect the vasculature. Sulfonylureas, metformin, and troglitazone have direct vascular actions. Metformin lowers LDL cholesterol and triglycerides, while troglitazone reverses many of the components associated with the insulin resistance syndrome. Clinical trials focusing on coronary artery disease outcomes are now warranted to prevent coronary artery disease, the major vascular complication and cause of mortality in diabetes.
Collapse
Affiliation(s)
- W A Hsueh
- Department of Medicine, University of California/Los Angeles, School of Medicine, USA
| | | |
Collapse
|
38
|
Stith BJ, Woronoff K, Wiernsperger N. Stimulation of the intracellular portion of the human insulin receptor by the antidiabetic drug metformin. Biochem Pharmacol 1998; 55:533-6. [PMID: 9514089 DOI: 10.1016/s0006-2952(97)00540-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Our prior work suggested that the antidiabetic metformin must enter the cell to act and that the drug stimulates tyrosine kinase activity. We now report that therapeutic concentrations (approximately 1 microg/mL) of metformin stimulated the tyrosine kinase activity of the intracellular portion of the beta-subunit of the human insulin receptor (IPbetaIRK), the intracellular portion of the epidermal growth factor receptor and pp60-src, but not cAMP-dependent protein kinase. A derivative of metformin unable to lower glucose was ineffective in stimulating IPbetaIRK. Two derivatives more effective than metformin in patients were also more effective than metformin in stimulating IPbetaIRK. Higher levels (10-100 microg/mL) of metformin or methylglyoxyl bis(guanylhydrazone) inhibited the tyrosine kinases, and this inhibition may be responsible for the ability of these two drugs to block cell proliferation.
Collapse
Affiliation(s)
- B J Stith
- Department of Biology, University of Colorado-Denver, 80217, USA
| | | | | |
Collapse
|