METFORMIN – MORE THAN ‘GOLD STANDARD’ IN THE TREATMENT OF TYPE 2 DIABETES MELLITUS

Key words: diabetes mellitus, metformin, polycystic ovary, nonalcoholic steatohepatitis, HIV lipodystrophy, neoplasms SUMMARY The primary aim of type 2 diabetes mellitus treatment is to

Key words: diabetes mellitus, metformin, polycystic

ovary, nonalcoholic steatohepatitis,

HIV lipodystrophy, neoplasms

SUMMARY

The primary aim of type 2 diabetes mellitus treatment

is to achieve and maintain good glycemic control, and

to minimize the mortality and risk of microvascular

and macrovascular complications Current algorithms

for medical management of type 2 diabetes mellitus

recommend a combination of lifestyle intervention and

metformin as initial therapy and ‘gold standard’

treatment Numerous studies suggest positive

antihyperglycemic and metabolic effects of metformin,

with a wide safety profile There is an increasing

evidence for the potential efficacy of this drug in other

diseases such as polycystic ovary syndrome,

nonalcoholic steatohepatitis, HIV lipodystrophy, and

neoplasms

INTRODUCTION

The prevalence of type 2 diabetes mellitus (DM) is increasing rapidly worldwide, with a prediction of more than 380 million people to be affected by 2025 (1) Insulin resistance in peripheral tissues in combination with relatively impaired insulin secretion

is essential in the pathogenesis of the disease, leading

to hyperglycemia and compensatory hyperinsulinemia (2) The primary goal of type 2 DM treatment is to achieve and maintain good glycemic control, and to reduce the mortality and risk of microvascular and macrovascular complications (3) The current consensus algorithms for medical management of type

2 DM recommend a combination of lifestyle intervention and metformin as initial therapy for type

2 DM (4), followed by other oral hypoglycemic agents and insulin Besides biguanides (metformin), other antidiabetic agents include several groups of drugs, i.e sulfonylureas, glitinides, thiazolidinediones or glitazones, α-glucosidase inhibitors (acarbose), GLP-1 analogues, dipeptidyl peptidase 4 inhibitors, and amylin agonists (pramlintide) Therapeutic profile of metformin has been evaluated for more than five decades Experimental and clinical studies have shed new light on the multiple beneficial effects of this drug, not only in the treatment of diabetes

Received: July 22, 2010 Accepted: August 9, 2010

METFORMIN – MORE THAN ‘GOLD STANDARD’ IN THE TREATMENT OF TYPE 2 DIABETES MELLITUS

Andreja Marić

Corresponding author: Andreja Marić, MD, Department of Internal

Medicine, Čakovec County Hospital, Ivana Gorana Kovačića 1E,

HR-40000 Čakovec, Croatia

E-mail: andreja.maric@hi.htnet.hr

DISCOVERY OF METFORMIN

The work of Dr Jean Sterne, a French clinician and

his colleagues led to the discovery of metformin as an

oral antidiabetic agent in the 1950s in Paris (5) The

first synthesis of metformin (dimethyl biguanide) is

attributed to Werner and Bell from Trinity College,

Dublin, Ireland, in 1922 (6), and was a basis for further

experimental and clinical studies on the potential

therapeutic application of biguanides, particularly

metformin The other two biguanide agents,

phenformin and buformin, were soon withdrawn from

widespread clinical use due to their toxicity, especially

lactic acidosis However, five decades were needed to

promote metformin from a minor product to the ‘gold

standard’ in the treatment of type 2 DM, with a wide

safety profile

METFORMIN AND

ANTIHYPERGLYCEMIC ACTION

Metformin reduces blood glucose levels by

inhibiting hepatic glucose production and reducing

insulin resistance, particularly in liver and skeletal

muscle (7) The plasma insulin levels are unchanged or

reduced (8) Metformin decreases intestinal absorption

of glucose, and increases insulin sensitivity by

enhanced glucose uptake and utilization in peripheral

tissues In vitro and in vivo studies have demonstrated

the effects of metformin on membrane-related events,

including plasma membrane fluidity, plasticity of

receptors and transporters (9); suppression of the

mitochondrial respiratory chain (10); increased

insulin-stimulated receptor phosphorylation and

tyrosine kinase activity (7); stimulation of

translocation of GLUT4 transporters to the plasma

membrane (11); and enzymatic effects on metabolic

pathways, e.g., LKB1 activation of AMP-activated

protein kinase – AMPK (12), which inhibits

gluconeogenesis and lipogenesis

Metformin monotherapy will lower HbA1clevels by

approximately 1.5% (13), without causing

hypoglycemia In combination with sulfonylureas,

HbA1c was decreased by 1.25% with glibenclamide,

0.75% with glipizide and 0.7% with glimepiride in

several studies Glitazones added to metformin decreased HbA1c from 8.1% to 6.8% (13-15) When acarbose was added to metformin, HbA1cwas reduced

by 0.8%-1.0% (16) A combination of bedtime insulin and metformin was more effective in controlling glycemia, with a significantly less weight gain compared with bedtime insulin plus glibenclamide, bedtime insulin plus metformin plus glibenclamide, or morning and bedtime insulin (17) Metformin and the GLP-agonists exenatide or liraglutide significantly reduced HbA1ccompared to placebo (18,19)

METFORMIN AND SAFETY PROFILE

Gastrointestinal side effects, i.e diarrhea, nausea, bloating and metallic taste in the palate are not uncommon when treatment with metformin is started, affecting 1%-30% of patients Increasing the dose gradually, most side affects may be diminished There

is clear relationship between the dosage and effect of metformin, so the most effective dosage of metformin observed in studies (20) was 2000 mg/day Increasing the metformin dosage from 2000 to 3000 mg/day only reduced fasting blood glucose levels by further 5%, raising the incidence of gastrointestinal side effects The risk of hypoglycemia was low, almost the same as

in the placebo group (8) Lactic acidosis is the most dangerous side effect, fortunately rare, with an incidence of 0-0.084 cases/1000 patient years (21) To minimize the risk of lactic acidosis, contraindications should be observed, i.e impaired renal function (limit value of creatinine clearance 60 mL/min), severe liver disease, pancreatitis, alcoholism, hypoxic states, respiratory insufficiency, severe cardiac insufficiency (NYHA III/IV), cardiovascular shock, metabolic acidosis, diabetic ketoacidosis, consumptive diseases, low serum level of vitamin B12, preoperative, perioperative and postoperative states, radiological procedures using contrast, advanced age, and calorie

restrictions (<1000 cal per day) (22).

METFORMIN AND BODY WEIGHT

While insulin secretagogues, thiazolidinediones and

insulin itself promote increased body weight in many

patients, treatment with metformin usually results in

no change in body weight or in modest weight loss,

and in combination with other agents it may mitigate

weight gain (8) A meta-analysis of nine trials of at

least 6-week duration found an average difference in

body weight of -4 kg for metformin versus a

sulfonylurea, unaffected by patient age (23) The

ADOPT (A Diabetes Progression Outcomes Trial)

study showed the mean increase in body weight at

study end in the rosiglitazone group relative to

metformin of 6.9 kg (95% CI 6.3 to 7.4%; P<0.001)

(24) A 26-week study in a comparable patient

population showed a reduction in body weight of 2.0

kg with metformin (P<0.05 versus baseline) compared

with an increase of 0.6 kg with rosiglitazone (not

significant versus baseline) (25) A 12-month study

reported a decrease in body weight of 2.5 kg with

metformin compared with an increase of 1.9 kg with

pioglitazone (26) The anorectic effect of metformin

may be at least partly attributable to the inhibiting

effect of DPP-4 (27) Adding metformin in patients

suboptimally controlled on insulin therapy compared

with intensification of the insulin dose by 20%

resulted in lower body weight, lower body mass index,

insulin dose and HbA1c at the end of the study in the

metformin arm (28) Modest weight loss with

metformin has also been observed in subjects with

impaired glucose tolerance enrolled in the Diabetes

Prevention Program (29) and in the Indian Diabetes

Prevention Program (30) Although a meta-analysis of

studies in patients with polycystic ovary syndrome

(PCOS) treated with metformin suggests no

significant effect of metformin on body weight

compared to placebo, some studies have reported a

mean weight loss (1.5-3.6 kg) during 8 months of

treatment with metformin in obese women with PCOS

(31)

METFORMIN AND LIPID PROFILE

A meta-analysis of 41 randomized, controlled evaluations of metformin of at least 6-week duration showed significant reductions in total cholesterol, LDL cholesterol and triglycerides in patients randomized to metformin relative to comparator treatments (32); HDL-cholesterol was rarely improved

by metformin treatment Some non-randomized studies have demonstrated significant reductions in free fatty acids following treatment with metformin (33), while others did not (34) In nondiabetic persons and those with impaired glucose tolerance randomized

in the Diabetes Prevention Program (35), the metformin effect on lipid profile was modest and generally smaller than the effect of the intensive lifestyle intervention included in this trial It suggests that reductions in the risk of macrovascular endpoints with metformin, showed in the UK Prospective Diabetes Study (UKPDS) (8), is associated with other mechanisms, not only the effects on lipids

METFORMIN AND CARDIOVASCULAR EFFECTS

Patients with type 2 DM have a two- to fourfold risk

of heart disease and stroke found in the general population, with a reduction in life expectancy of five

to ten years (36) UKPDS (8) was the first randomized trial demonstrating that metformin treatment was associated with significant reductions compared with diet in the risk of any endpoint related to diabetes (risk

reduction 32%; P=0.0023), myocardial infarction (risk reduction 39%; P=0.01), all-cause mortality (risk reduction 35%; P=0.011), and diabetes-related death (risk reduction 42%; P=0.017) Reductions in the risk

of stroke, peripheral vascular disease and microvascular endpoints did not achieve statistical significance for metformin compared with diet Randomization to sulfonylurea/insulin was not associated with significant reductions in any of the clinical outcomes mentioned above (although significant microvascular benefits were observed with this treatment in a larger analysis of UKPDS 33) (8)

Retrospective and prospective observational studies

showed a strong cardioprotective effect of metformin

in patients with a high prevalence of cardiovascular

disease, including patients with prior coronary heart

disease events, heart failure, or symptomatic angina

pectoris (37,38)

Besides the effects on the classic cardiometabolic

risk factors (dysglycemia, insulin resistance, obesity,

dyslipidemia and high blood pressure) observed in

type 2 DM patients and demonstrated in several

studies, metformin has other potential

anti-atherothrombotic actions Treatment with metformin

improves endothelial function by decreasing

circulating levels of sVCAM-1 and E-selectin, which

are markers of endothelial activation (39); reduces

circulating levels of plasminogen activator inhibitor-1

(40); improves other hemostatic parameters,

decreasing Factor XIII activity and reducing the levels

of Factor VII, a powerful endogenous promoter of

coagulation (41) Metformin reduces circulating

C-reactive protein level (42); inhibits activation of the

pro-inflammatory nuclear transcription factor,

NF-kappaB, secondary to an increase in the activity of the

enzyme AMP-kinase (AMPK), which has been

proposed as a cellular mechanism for the

anti-inflammatory effects of metformin (43) Metformin

also decreases oxidative stress, inhibits lipid

peroxidation of LDL and HDL, and the production of

the superoxide free radical (O2-) in platelets (44)

Metformin may reduce the production of advanced

glycation endproducts (AGE) indirectly, by reduction

of hyperglycemia, and directly by an

insulin-independent mechanism (45) Experimental studies

suggest that metformin may inhibit the binding of

monocytes to cultured vascular cells, and

differentiation of monocytes into macrophages and

their transformation into foam cells (46)

METFORMIN AND POLYCYSTIC OVARY

SYNDROME

Polycystic ovary syndrome (PCOS) is the most

common endocrine disease in women, affecting

5%-10% of those in reproductive age (47) PCOS includes

several cardiometabolic risk factors associated with

insulin resistance, such as abdominal obesity, hypertension, hyperinsulinemia, low HDL cholesterol, hypertriglyceridemia and impaired fibrinolysis, resembling the metabolic syndrome (48-50) A meta-analysis of studies comparing metformin with placebo

or no treatment in women with PCOS showed that metformin significantly reduced fasting plasma glucose, systolic and diastolic blood pressure, LDL cholesterol and fasting insulin, although total cholesterol, HDL cholesterol or triglycerides did not change significantly (51) A Cochrane meta-analysis

of trials that compared metformin with the oral contraceptive pill showed significant improvement in fasting insulin and triglycerides with metformin, but

no overall improvement in fasting glucose (52) Besides, both meta-analyses revealed that metformin significantly reduced serum testosterone, androstenedione and dehydroepiandrostenedione sulfate Many guidelines suggest the use of metformin

as initial pharmacological therapy for most women with PCOS, particularly when overweight or obese (53), or in addition to clomifene in clomifene-resistant anovulatory women (54) Although metformin crosses the placenta, observational studies to date suggest that metformin does not adversely affect fetal or neonatal development (55-57) Metformin used during pregnancy decreased the risk of gestational diabetes in women with PCOS (58,59)

The mechanisms of metformin effects in PCOS pertain to its central and peripheral action At the central level, the possible effect is reduction in serum

LH level At the peripheral level, metformin decreases hepatic gluconeogenesis, increases the synthesis of sex hormone-binding globulin (SHBG), consecutively decreasing free androgen levels Metformin also increases insulin sensitivity in peripheral tissues, reduces free fatty acid oxidation, and reduces ovarian and adrenal secretion of androgens Pleiotropic actions

of metformin are mediated by the AMPK pathway Experimental data show the effect of metformin on the expression of some genes involved in glucose metabolism (60)

METFORMIN AND OTHER POTENTIAL

FUTURE USES

Nonalcoholic fatty liver disease (NAFLD),

nonalcoholic steatohepatitis (NASH) and

lipodystrophy syndrome associated with highly-active

antiretroviral therapy (HAART) for human

immunodeficiency virus (HIV) are associated with

insulin resistance and cardiovascular and metabolic

risk factors

The management of NASH includes lifestyle

intervention with gradual weight loss, fibrates to

control hypertriglyceridemia, gastrointestinal lipase

inhibitor, orlistat, and agents that improve insulin

sensitivity (metformin and thiazolidinedione) (61) In

randomized studies comparing metformin plus diet

versus diet, plasma glucose, body mass index, plasma

insulin and plasma cholesterol improved significantly

in both groups, while plasma C-peptide and insulin

resistance index improved significantly only on

metformin plus diet treatment (62) Another study

compared metformin with vitamin E in patients with

NAFLD and found significant improvement in

metabolic parameters in the metformin group (63)

In patients with HIV-associated lipodystrophy,

metformin significantly reduces hyperinsulinemia,

body weight and diastolic blood pressure (64), and has

superior effects on lipids and endothelial function

compared to diet, placebo and rosiglitazone, although

a combination of treatments is more effective than

metformin alone (65)

METFORMIN AND ITS POTENTIAL FOR

THE TREATMENT OF NEOPLASTIC

DISEASE

Experimental studies suggest a role for the enzyme

AMPK among the important molecular mechanisms

responsible for the beneficial metabolic actions of

metformin Metformin induces tumor suppressor LKB1, which is an upstream regulator of AMPK, supporting the hypothesis on the potential anti-neoplastic effect of metformin Activating AMPK, metformin negatively regulates mTORC1 (mammalian target of rapamycin), which is associated

with a number of human pathologies (66) In vitro

studies in human breast cancer cells showed that metformin inhibited cell proliferation, reduced colony formation, and caused partial cell cycle arrest (67) Metformin was also a potent inhibitor of cell proliferation in endometrial cancer lines (68) A combination of metformin and 2-deoxyglucose induced p53-dependent apoptosis in prostate cancer cells (69) Two large observational studies report on a decreased incidence of neoplastic disease in type 2

DM patients treated with metformin, compared with sulfonylurea and insulin (70,71) UKPDS revealed that metformin treatment reduced the risk of death from cancer by 29% relative to diet Other studies also observed significantly lower cancer mortality rate in

patients treated with metformin versus patients not

receiving metformin (72)

CONCLUSION

Distinctive positive antihyperglycemic and metabolic effects of metformin have been observed and demonstrated in numerous trials and meta-analyses The potential metformin action in other diseases such as PCOS, NASH, HIV lipodystrophy and neoplasms has been suggested in several studies Metformin is not currently indicated for the management of these conditions Thus, additional prospective randomized studies are needed for approval of indications for the treatment and prevention of the mentioned diseases

1 Metformin The gold standard A scientific

handbook Bailey CJ, Campbell IW, Chan JCN,

Davidson JA, Howlett HCS, Ritz P, editors

England: John Wiley & Sons, Ltd., 2007; pp 1-2

2 LeRoith D Beta-cell dysfunction and insulin

resistance in type 2 diabetes: role of metabolic and

genetic abnormalities Am J Med

2002;113:3S-11S

3 Hemmingsen B, Lund SS, Wetterslev J, Vaag A

Oral hypoglycaemic agents, insulin resistance and

cardiovascular disease in patients with type 2

diabetes Eur J Endocrinol 2009;161:1-9

4 Nathan DM, Buse JB, Davidson MB, Ferrannini E,

Holman RR, Sherwin R, et al Medical

management of hyperglycemia in type 2 diabetes:

a consensus algorithm for the initiation and

adjustment of therapy: a consensus statement of

the American Diabetes Association and the

European Association for the Study of Diabetes

Diabetes Care 2009;32:193-203

5 Sterne J Treatment of diabetes mellitus with

N,N-dimethylguanylguanidine (LA 6023, glucophage)

Therapie 1959;14:625-630

6 Werner A, Bell J CCX1V The preparation of

methylguanidine and of ââ-dimethylguanidine by

the interaction of dicyanodiamide and

methylammonium and dimethylammonium

chlorides respectively J Chem Soc Transact

1922;121:1790-1794

7 Giannarelli R, Aragona M, Coppelli A, Del Prato

S Reducing insulin resistance with metformin: the

evidence today Diabetes Metab

2003;29:6S28-6S35

8 UK Prospective Diabetes study Group Effect of

intensive blood glucose control with metformin on

complications in overweight patients with type 2

diabetes (UKPDS 34) Lancet 1998;352:854-865

9 Muller S, Denet S, Candiloros H, Barrois R, Wiernsperger N, Donner M, et al Action of metformin on erythrocyte membrane fluidity in vitro and in vivo Eur J Pharmacol

1997;337:103-110

10 Detaille D, Guigas B, Leverve X, Wiernsperger N, Devos P Obligatory role of membrane events in the regulatory effect of metformin on the respiratory chain function Biochem Pharmacol 2002;63:1259-1272

11 Matthaei S, Reibold JP, Hamann A, Benecke H, Haring HU, Greten H, et al In vivo metformin treatment ameliorates insulin resistance: evidence for potentiation of insulin-induced translocation and increased functional activity of glucose transporters in obese (fa/fa) Zucker rat adipocytes Endocrinology 1993;133:304-311

12 Musi N, Hirsman MF, Nygren J, Svanfeldt M, Bavenholm P, Rooyackers O, et al Metformin increases AMP-activated protein kinase activity in skeletal muscle of subjects with type 2 diabetes Diabetes 2002;51:2074-2081

13 DeFronzo R, Goodman A Efficacy of metformin

in patients with non-insulin-dependent diabetes mellitus The Multicenter Metformin Study Group

N Engl J Med 1995;333:541-549

14 Blonde L, Rosenstock J, Mooradian AD, Piper BA, Henry D Glyburide/metformin combination product is safe and efficacious in patients with type

2 diabetes failing sulphonylurea therapy Diabetes Obes Metab 2002;4:368-375

15 Goldstein BJ, Pans M, Rubin CJ Muticenter, randomized, double-masked, parallel-group assessment of simultaneous glipizide/metformin as second-line pharmacologic treatment for patients with type 2 diabetes mellitus that is inadequately controlled by a sulfonylurea Clin Ther 2003;25:890-903

16 Halimi S, Le Berre MA, Grange V Efficacy and

safety of acarbose add-on therapy in the treatment

of overweight patients with type 2 diabetes

inadequately controlled with metformin: a

double-blind, placebo controlled study Diab Res Clin

Pract 2000;50:49-56

17 Yki-Jarvinen H, Ryysy L, Nikkila K, Tulokas T,

Vanamo R, Heikkila M Comparison of bedtime

insulin regimens in patients with type 2 diabetes

mellitus Ann Int Med 1999;130:389-396

18 Fineman MS, Bicsak TA, Shen LZ, Taylor K,

Geines E, Varns A, et al Effect on glycemic

control of exenatide (synthetic exendin-4) additive

to existing metformin and/or sulfonylurea

treatment in patients with type 2 diabetes Diabetes

Care 2003;26:2370-2377

19 Feinglos MN, Saad MF, Pi-Sunyer FX, An B,

Santiago O Effects of liraglutide (NN2211), a

long-acting GLP-2 analogue, on glycaemic control

and body weight in subjects with type 2 diabetes

Diabet Med 2005;22:1016-1023

20 Garber A, Duncan T, Goodman A, Mills D, Rohlf

J Efficacy of metformin in type-II diabetes: results

of a double-blind, placebo controlled,

dose-response trial Am J Med 1997;102:491-497

21 Chan NN, Brain HP, Feher MD

Metformin-associated lactic acidosis: a rare or very rare

clinical entity? Diabetes Care 1998;21:1659-1663

22 Matthaei S, Bierwirth R, Fritsche A, Gallwitz B,

Haring HU, Joost HG Medical

antihyperglycaemic treatment of diabetes mellitus

type 2 Update of the evidence-based guideline of

the German Diabetes Association 2008; pp 1-75

23 Campbell IW, Howlett HC Worldwide experience

of metformin as an effective glucose-lowering

agent: a meta-analysis Diabet Metab Rev

1995;11:S57-S62

24 Kahn SE, Haffner SM, Heise MA, Herman WH,

Holman RR, Kravitz BG, et al Glycemic

durability of rosiglitazone, metformin, or

glyburide monotherapy N Engl J Med

2006;355:2427-2443

25 Hallsten K, Virtanen KA, Lonnqvist F, Sipila H, Oksanen A, Viljanen T, et al Rosiglitazone but not metformin enhances insulin- and exercise-stimulated skeletal muscle glucose uptake in patients with newly diagnosed type 2 diabetes Diabetes 2002;51:3479-3485

26 Schernthaner G, Matthews DR, Charbonnel B, Hanefeld M, Brunetti P Efficacy and safety of pioglitazone versus metformin in patients with type 2 diabetes mellitus: a double-blind, randomized trial J Clin Endocrinol Metab 2004;89:6068-6076

27 Lindsay JR, Duffy NA, McKillop AM, Ardill J, O'Harte FP, Flatt PR, et al Inhibition of dipeptidyl peptidase IV activity by oral metformin in type 2 diabetes Diabet Med 2005;22:654-657

28 Relimpio F, Pumar A, Losada F, Mangas MA, Acosta D, Astorga R Adding metformin versus insulin dose increase in insulin-treated but poorly controlled type 2 diabetes mellitus: an open-label randomized trial Diabet Med 1998;15:997-1002

29 Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, et al Reduction in the incidence of type 2 diabetes with lifestyle intervention of metformin N Engl J Med 2002;346:393-403

30 Ramachandran A, Snehalatha C, Mary S, Mukesh

B, Bhaskar AD, Vijay V, et al The Indian Diabetes Prevention Programme shows that lifestyle modification and metformin prevent type 2 diabetes in Asian Indian subjects with impaired glucose tolerance (IDDP-1) Diabetologia 2006;49:289-297

31 Harborne LR, Sattar N, Norman JE, Fleming R Metformin and weight loss in obese women with polycystic ovary syndrome: comparison of doses J Clin Endocrinol Metab 2005;90:4593-4598

32 Wulffele MG, Kooy A, de Zeeuw D, Stehouwer

CD, Gansevoort RT The effect of metformin on blood pressure, plasma cholesterol and triglycerides in type 2 diabetes mellitus: a systematic review J Int Med 2004;256:1-14

33 Manzella D, Grella R, Esposito K, Giugliano D,

Barbagallo M, Paliosso G Blood pressure and

cardiac autonomic nervous system in obese type 2

diabetic patients: effect of metformin

administration Am J Hypert 2004;17:223-227

34 Jung HS, Youn BS, Cho YM, Yu KY, Park HJ, Shin

CS, et al The effects of rosiglitazone and

metformin on the plasma concentrations of resistin

in patients with type 2 diabetes mellitus

Metabolism 2005;6:8-15

35 Diabetes Prevention Program Research Group

Reduction in the incidence of type 2 diabetes with

lifestyle intervention of metformin N Engl J Med

2002;346:393-403

36 Holman R Cardiovascular benefits In:

Metformin The gold standard A scientific

handbook Bailey CJ, Campbell IW, Chan JCN,

Davidson JA, Howlett HCS, Ritz P, editors

England: John Wiley & Sons, Ltd., 2007; p 115

37 Eurich DT, Majumdar SR, McAlister FA, Tsuyuki

RT, Johnson JA Improved clinical outcomes

associated with metformin in patients with

diabetes and heart failure Diabetes Care

2005;28:2345-2351

38 Montaguti U, Celin D, Ceredi C, Descovitch GC

Efficacy of the long-term administration of

metformin in hyperlipidaemic patients Res Clin

Forums 1979;1:95-103

39 De Jager J, Kooy A, Lehert P, Bets D, Wulffele

MG, Teerlink T, et al Effects of short-term

treatment with metformin on markers of

endothelial function and inflammatory activity in

type 2 diabetes mellitus: a randomized,

placebo-controlled trial J Int Med 2005;257:100-109

40 Gin H, Roudat MF, Vergnot V, Baillet L, Rigalleau

V Effect of metformin on fibrinolytic parameters

in insulin-treated, type 2 diabetic patients

Diabetes Metab 2003;29:505-508

41 Grant PJ Beneficial effects of metformin on

haemostasis and vascular function in man

Diabetes Metab 2003;29:6S44-6S52

42 Carter AM, Bennett CE, Bostock JA, Grant PJ Metformin reduces C-reactive protein but not complement factor C3 in overweight patients with type 2 diabetes mellitus Diabetes Med 2005;22:1282-1284

43 Hattori Y, Suzuki K, Hattori S, Kasai K Metformin inhibits cytokine-induced nuclear factor kappaB activation via AMP-activated protein kinase activation in vascular endothelial cells Hypertension 2006;47:1813-1822

44 Gargiulo P, Caccese D, Pignatelli P, Brufani C, De Vito F, Marino R, et al Metformin decreases platelet superoxide anion production in diabetic patients Diabetes Metab Res Rev

2002;18:156-159

45 Beisswenger P, Ruggiero-Lopez, D Metformin inhibition of glycation processes Diabetes Metab 2003;29:6S95-6S103

46 Mamputu JC, Wiernsperger NF, Reiner G Antiatherogenic properties of metformin: the experimental evidence Diabetes Metab 2003;29:6S71-6S76

47 Azziz R, Woods KS, Reyna R, Key TJ, Knochenhauer ES, Yildiz BO The prevalence and features of the polycystic ovary syndrome in an unselected population J Clin Endocrin Metab 2004;89:2745-2749

48 Dunaif A, Segal KR, Futterweit W, Dobrjansky A Profound peripheral insulin resistance, independent of obesity, in polycystic ovary syndrome Diabetes 1989;38:1165-1174

49 Dokras A, Bochner M, Hollinrake E, Markham S, Vanvoorhis B, Jagasia DH Screening women with polycystic ovary syndrome for metabolic syndrome Obstet Gynecol 2005;106:131-137

50 Rotterdam ESHRE/ASRM Sponsored PCOS Consensus Workshop Group Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome Fertil Steril 2004;81:19-25

51 Lord JM, Flight IH, Norman RJ

Insulin-sensitising drugs (metformin, troglitazone,

rosiglitazone, pioglitazone, D-chiro-inositol) for

polycystic ovary syndrome Cochrane Database

Syst Rev 2003;(3):CD003053

52 Costello MF, Shrestha B, Eden J, Johnson NP,

Sjoblom P Metformin versus oral contraceptive

pill in polycystic ovary syndrome: a Cochrane

review Hum Reprod 2007;22:1200-1209

53 American Association of Clinical

Endocrino-logists Position statement on metabolic and

cardiovascular consequences of polycystic ovary

syndrome Available from: http://www.aace.com/

pub/pdf/guidelines/PCOSpositionstatement.pdf

54 National Institute for Health and Clinical

Excellence Guideline CG11 Fertility Available

from: http://www.nice.org.uk/guidance/CG11/

guidance/pdf/English

55 Glueck CJ, Wang P, Goldenberg N, Sieve-Smith L

Pregnancy outcomes among women with

polycystic ovary syndrome treated with

metformin Hum Reprod 2002;17:2858-2864

56 Glueck CJ, Goldenberg N, Pranikoff J, Loftspring

M, Sieve L, Wang P Height, weight, and

motor-social development during the first 18 months of

life in 126 infants born to 109 mothers with

polycystic ovary syndrome who conceived on and

continued metformin through pregnancy Hum

Reprod 2004;19:1323-1330

57 Gilbert C, Valois M, Koren G Pregnancy outcome

after first-trimester exposure to metformin: a

meta-analysis Fertil Steril 2006;86:658-663

58 Norman RJ, Wang JX, Hague W Should we

continue or stop insulin sensitising drugs during

pregnancy? Curr Opin Obstet Gynecol

2004;16:245-250

59 Glueck CJ, Goldenberg N, Wang P, Loftspring M, Sherman A Metformin during pregnancy reduces insulin, insulin resistance, insulin secretion, weight, testosterone and development of gestational diabetes: prospective longitudinal assessment of women with polycystic ovary syndrome from preconception throughout pregnancy Hum Reprod 2004;19:510-521

60 Palomba S, Falbo A, Zullo F, Orio F Jr Evidence-based and potential benefits of metformin in the polycystic ovary syndrome: a comprehensive review Endocr Rev 2009;30(1):1-50

61 Medina J, Fernandez-Salazar LI, Garcia-Buey L, Moreno-Otero R Approach to the pathogenesis and treatment of nonalcoholic steatohepatitis Diabetes Care 2004;27:2057-2066

62 Uygun A, Kadayifci A, Isik AT, Ozgurtas T, Deveci

S, Tuzun A, et al Metformin in the treatment of patients with non-alcoholic steatohepatitis Aliment Pharmacol Ther 2004;19:537-544

63 Bugianesi E, Gentilcore E, Manini R, Natale S, Vanni E, Villanova N, et al A randomized controlled trial of metformin versus vitamin E or prescriptive diet in nonalcoholic fatty liver disease

Am J Gastroenterol 2005;100:1082-1090

64 Hadigan C, Corcoran C, Basgoz N, Davis B, Sax P, Grinspoon S Metformin in the treatment of HIV lipodystrophy syndrome: a randomized controlled trial JAMA 2000;284:472-477

65 Van Wijk JP, de Koning EJ, Cabezas MC, op't Roodt J, Joven J, Rabelink TJ, et al Comparison of rosiglitazone and metformin for treating HIV lipodystrophy: a randomized trial Ann Intern Med 2005;143:337-346

66 Kalender A, Selvaraj A, Kim SY, Gulati P, Brule S, Viollet B, et al Metformin, independent of AMPK, inhibits mTORC1 in a rag GTPase-dependent manner Cell Metab 2010;11(5):390-401

67 Alimova IN, Liu B, Fan Z, Edgerton SM, Dillon T, Lind SE, et al Metformin inhibits breast cancer cell growth, colony formation and induces cell cycle arrest in vitro Cell Cycle 2009;8:909-915

68 Cantrell LA, Zhou C, Mendivil A, Malloy KM,

Gehrig PA, Bae-Jump VL Metformin is a potent

inhibitor of endometrial cancer cell proliferation –

implications for a novel treatment strategy

Gynecol Oncol 2010;116(1):92-98

69 Ben Sahra I, Laureni K, Giuliano S, Larbret F,

Ponzio G, Guonon P, et al Targeting cancer cell

metabolism: the combination of metformin and

2-deoxyglucose induces p53-dependent apoptosis in

prostate cancer cells Cancer Res

2010;70(6):2465-2475

70 Evans JM, Donnelly LA, Emslie-Smith AM, Alessi DR, Morris AD Metformin and reduced risk of cancer in diabetic patients BMJ 2005;330:1304-1305

71 Bowker SL, Majumdar SR, Veugelers P, Johnson

JA Increased cancer-related mortality for patients with type 2 diabetes who use sulfonylureas or insulin Diabetes Care 2006;29:254-258

72 Landman GW, Kleefstra N, van Hateren KJ, Groenier KH, Gans RO, Bilo HJ Metformin associated with lower cancer mortality in type 2 diabetes ZODIAC-16