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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Metformin is regarded as an antihyperglycaemic agent because it lowers blood glucose concentrations in type 2 (non-insulin-dependent) diabetes without causing overt hypoglycaemia. Its clinical efficacy requires the presence of insulin and involves several therapeutic effects. Of these effects, some are mediated via increased insulin action, and some are not directly insulin dependent. Metformin acts on the liver to suppress gluconeogenesis mainly by potentiating the effect of insulin, reducing hepatic extraction of certain substrates (e.g. lactate) and opposing the effects of glucagon. In addition, metformin can reduce the overall rate of glycogenolysis and decrease the activity of hepatic glucose-6-phosphatase. Insulin-stimulated glucose uptake into skeletal muscle is enhanced by metformin. This has been attributed in part to increased movement of insulin-sensitive glucose transporters into the cell membrane. Metformin also appears to increase the functional properties of insulin- and glucose-sensitive transporters. The increased cellular uptake of glucose is associated with increased glycogen synthase activity and glycogen storage. Other effects involved in the blood glucose-lowering effect of metformin include an insulin-independent suppression of fatty acid oxidation and a reduction in hypertriglyceridaemia. These effects reduce the energy supply for gluconeogenesis and serve to balance the glucose-fatty acid (Randle) cycle. Increased glucose turnover, particularly in the splanchnic bed, may also contribute to the blood glucose-lowering capability of metformin. Metformin improves insulin sensitivity by increasing insulin-mediated insulin receptor tyrosine kinase activity, which activates post-receptor insulin signalling pathways. Some other effects of metformin may result from changes in membrane fluidity in hyperglycaemic states. Metformin therefore improves hepatic and peripheral sensitivity to insulin, with both direct and indirect effects on liver and muscle. It also exerts effects that are independent of insulin but cannot substitute for this hormone. These effects collectively reduce insulin resistance and glucotoxicity in type 2 diabetes.
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PMID:The antihyperglycaemic effect of metformin: therapeutic and cellular mechanisms. 1057 23

The UK Prospective Diabetes Study (UKPDS) provides the first conclusive proof for the importance of intensifying diabetes control in individuals with type 2 diabetes mellitus. However, reduction in cardiovascular disease risk with intensive therapy was modest and did not reach statistical significance. Metformin therapy in obese individuals with type 2 diabetes mellitus was associated with reduced cardiovascular death. These observations should be re-evaluated to determine whether various therapeutic agents available for treatment of type 2 diabetes mellitus have different effects on cardiovascular complications of diabetes. The addition of alpha-glucosidase inhibitor, acarbose, improved glycaemic control irrespective of concomitant therapy for diabetes, although compliance with this agent was poor. The tight blood pressure control study embedded in UKPDS reaffirms the importance of lowering the blood pressure below 150/85 to reduce microvascular and macrovascular complications of diabetes.
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PMID:Implications of the UK prospective diabetes study: questions answered and issues remaining. 1080 56

Although metformin is widely used for the treatment of non-insulin-dependent diabetes, its mode of action remains unclear. Here we provide evidence that its primary site of action is through a direct inhibition of complex 1 of the respiratory chain. Metformin(50 microM) inhibited mitochondrial oxidation of glutamate+malate in hepatoma cells by 13 and 30% after 24 and 60 h exposure respectively, but succinate oxidation was unaffected. Metformin also caused time-dependent inhibition of complex 1 in isolated mitochondria, whereas in sub-mitochondrial particles inhibition was immediate but required very high metformin concentrations (K(0.5),79 mM). These data are compatible with the slow membrane-potential-driven accumulation of the positively charged drug within the mitochondrial matrix leading to inhibition of complex 1. Metformin inhibition of gluconeogenesis from L-lactate in isolated rat hepatocytes was also time- and concentration-dependent, and accompanied by changes in metabolite levels similar to those induced by other inhibitors of gluconeogenesis acting on complex 1. Freeze-clamped livers from metformin-treated rats exhibited similar changes in metabolite concentrations. We conclude that the drug's pharmacological effects are mediated, at least in part, through a time-dependent, self-limiting inhibition of the respiratory chain that restrains hepatic gluconeogenesis while increasing glucose utilization in peripheral tissues. Lactic acidosis, an occasional side effect, canal so be explained in this way.
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PMID:Evidence that metformin exerts its anti-diabetic effects through inhibition of complex 1 of the mitochondrial respiratory chain. 1083 93

Hyperglycemia may lead to atherosclerosis by different pathogenic mechanisms. Nonenzymatic glycation and oxidation of LDL may increase its atherogenicity. Glycation may modify some arterial wall structural proteins. Increased blood glucose leads to hypertriglyceridemia which results in decrease of HDL-cholesterol level and in increase of atherogenic dense LDL particles. Hyperglycemia also adversely affects processes of platelet aggregation, hemocoagulation and fibrinolysis. It accelerates the development of diabetic nephropathy--a condition with a high prevalence of macrovascular diseases. Prospective epidemiologic studies have shown that diabetic patients in worse metabolic control had an increased cardiovascular morbidity and mortality. Therapeutic randomized studies in type 1 (DCCT) and type 2 (UKPDS) diabetic patients have shown that better diabetes control had a preventive effect against development of microvascular complications. The incidence of macrovascular complications both in type 1 diabetic patients on intensive insulin or sulfonylurea treatment has been decreased on the level of borderline statistical significance. Metformin lead to a significant decrease in myocardial infarction incidence in the subgroup of obese type 2 diabetic patients. In conclusion, maximal possible metabolic control of diabetes prevents the development of microvascular complication, but more impressive decrease in macrovascular disease incidence probably requires to affect another important risk factors for atherosclerosis, such as dyslipidemia and hypertension.
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PMID:[Hyperglycemia and atherosclerosis. Causal relation or association?]. 1095 84

In type II diabetes treated with metformin (Glucophage) lactic acidosis is a rare adverse reaction, fatal in approximately 50 per cent of cases. Metformin is implicated by plasma and intra-erythrocyte levels. An analysis is carried out on available information about this risk for healthcare professionals and for patients. A comparison is made of approved labelling information on Glucophage and its patient leaflets in France and in the USA and an analysis made of the differences. In France, Information given to physicians, pharmacists and patients on the risk of lactic acidosis where Glucophage is implicated must be improved, and on the interest of the metformin plasma level in this case. These are primary points because the issue for the few patients concerned may be fatal. Advice on self-medication may be introduced. The evolution of information provided on these risks depends on the pharmaceutical laboratory, government authorities and healthcare professionals.
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PMID:[Lactic acidosis and metformin implicated: why better information about risk factors?]. 1096 1

Metformin-associated lactic acidosis is not necessarily due to metformin accumulation. It appears that mortality in patients receiving metformin who develop lactic acidosis is mostly linked to underlying disease. It has been suggested that metformin should be the first-line agent for the treatment of obese type 2 diabetic patients since metformin was associated with a significant decrease in macrovascular events and a reduction of all-cause mortality in the United Kingdom Prospective Diabetes Study (UKPDS) in a substudy. However, in this substudy no significant decrease in microvascular complications was observed in obese subjects with intensive metformin therapy. In addition, the use of metformin in combination with sulfonylurea seemed to be associated with excess risk of diabetes-related and all-cause mortality in obese subjects. Due to the discrepant and contradictory nature of the results in the obese patients and a lack of power the UKPDS offered no decision for any drug for initial therapy of type 2 diabetes. The main message of the UKPDS is that lowering of the blood glucose to the normal range is beneficial irrespective of the hypoglycaemic agent used. A rational approach to therapy in a type 2 diabetes patient who fails to sufficiently lower blood sugar with diet and weight loss is to begin therapy with a sulfonylurea or metformin and to add another oral agent if the desired glycaemic control is not achieved.
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PMID:[Current role of metformin in treatment of diabetes mellitus type 2]. 1104 42

Leptin's role in the regulation of food intake, energy expenditure and weight control are widely recognized, especially in rodents. Likewise, the potential regulation of leptin secretion by insulin (and vice versa) has been of particular interest insofar as these nutrient signals may have meaningful, even adverse (inter)actions, in diabetes. We used a freshly isolated rat adipose tissue culture model to examine the effect of insulin, metformin and glibenclamide on basal and steroid-stimulated leptin secretion. This model was selected because of its physiologic rates of leptin formation and preservation of potentially significant cell-cell interactions compared to isolated cells. The basal rate of leptin secretion was 3. 4+/-1.2 ng/100 mg tissue/24 h. The addition of 100 nM dexamethasone or 400 nM hydrocortisone stimulated leptin secretion by 3-4 fold over basal (no steroid). Insulin inhibited both basal and steroid-activated leptin secretion by 35-50%. This inhibition was present with either 1 mM pyruvate or 5 mM glucose as a substrate suggesting that glycolysis was not required. Metformin inhibited basal and dexamethasone-stimulated leptin secretion in a dose dependent manner (50% inhibition occurred at 1 mM metformin) while glibenclamide was ineffective. The effect of insulin on isolated fat cells versus fat tissue was tested in parallel. After 24 h in culture, insulin inhibited leptin secretion similarly in both adipose preparations. The addition of 200 nM (-)N6-(2-phenylisopropyl)-adenosine did not alter the results.
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PMID:Inhibition of leptin secretion by insulin and metformin in cultured rat adipose tissue. 1106 85

To examine the mechanism by which metformin lowers endogenous glucose production in type 2 diabetic patients, we studied seven type 2 diabetic subjects, with fasting hyperglycemia (15.5 +/- 1.3 mmol/l), before and after 3 months of metformin treatment. Seven healthy subjects, matched for sex, age, and BMI, served as control subjects. Rates of net hepatic glycogenolysis, estimated by 13C nuclear magnetic resonance spectroscopy, were combined with estimates of contributions to glucose production of gluconeogenesis and glycogenolysis, measured by labeling of blood glucose by 2H from ingested 2H2O. Glucose production was measured using [6,6-2H2]glucose. The rate of glucose production was twice as high in the diabetic subjects as in control subjects (0.70 +/- 0.05 vs. 0.36 +/- 0.03 mmol x m(-2) min(-1), P < 0.0001). Metformin reduced that rate by 24% (to 0.53 +/- 0.03 mmol x m(-2) x min(-1), P = 0.0009) and fasting plasma glucose concentration by 30% (to 10.8 +/- 0.9 mmol/l, P = 0.0002). The rate of gluconeogenesis was three times higher in the diabetic subjects than in the control subjects (0.59 +/- 0.03 vs. 0.18 +/- 0.03 mmol x m(-2) min(-1) and metformin reduced that rate by 36% (to 0.38 +/- 0.03 mmol x m(-2) x min(-1), P = 0.01). By the 2H2O method, there was a twofold increase in rates of gluconeogenesis in diabetic subjects (0.42 +/- 0.04 mmol m(-2) x min(-1), which decreased by 33% after metformin treatment (0.28 +/- 0.03 mmol x m(-2) x min(-1), P = 0.0002). There was no glycogen cycling in the control subjects, but in the diabetic subjects, glycogen cycling contributed to 25% of glucose production and explains the differences between the two methods used. In conclusion, patients with poorly controlled type 2 diabetes have increased rates of endogenous glucose production, which can be attributed to increased rates of gluconeogenesis. Metformin lowered the rate of glucose production in these patients through a reduction in gluconeogenesis.
Diabetes 2000 Dec
PMID:Mechanism by which metformin reduces glucose production in type 2 diabetes. 1111 8

Results from the United Kingdom Prospective Diabetes Study showed that intensive treatment of type 2 (non-insulin-dependent) diabetes mellitus, with sulphonylureas or insulin, significantly reduced microvascular complications but did not have a significant effect on macrovascular complications after 10 years. Insulin resistance plays a key role in type 2 diabetes mellitus and is linked to a cluster of cardiovascular risk factors. Optimal treatment for type 2 diabetes mellitus should aim to improve insulin resistance and the associated cardiovascular risk factors in addition to achieving glycaemic control. Treatment with sulphonylureas or exogenous insulin improves glycaemic control by increasing insulin supplies rather than reducing insulin resistance. Metformin and the recently introduced thiazolidinediones have beneficial effects on reducing insulin resistance as well as providing glycaemic control. There is evidence that, like metformin, thiazolidinediones also improve cardiovascular risk factors such as dyslipidaemia and fibrinolysis. Whether these differences will translate into clinical benefit remains to be seen. The thiazolidinediones rosiglitazone and pioglitazone have been available in the US since 1999 (with pioglitazone also being available in Japan). Both products are now available to physicians in Europe.
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PMID:Antidiabetic drugs present and future: will improving insulin resistance benefit cardiovascular risk in type 2 diabetes mellitus? 1112 20

Cardiovascular disease (CVD) risk associated with fat redistribution seen among HIV-infected individuals remains unknown, but may be increased due to hyperlipidemia, hyperinsulinemia, increased visceral adiposity, and a prothrombotic state associated with these metabolic abnormalities. In this study we characterized plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (tPA) antigen levels, markers of fibrinolysis and increased CVD risk, in HIV lipodystrophic patients compared to controls. Furthermore, we investigated the effect of treatment with metformin on PAI-1 and tPA antigen levels in patients with HIV-associated fat redistribution. Eighty-six patients (age 43 +/- 1 yr, BMI 26.1 +/- 0.5 kg/m(2)) with HIV and fat redistribution were compared to 258 age- and BMI-matched subjects from the Framingham Offspring study. In addition, 25 HIV-infected patients with fat redistribution and fasting insulin >15 microU/mL [104 pmol/L] or impaired glucose tolerance, but without diabetes mellitus were enrolled in a placebo-controlled treatment study of metformin 500 mg twice daily. PAI-1 and tPA antigen levels were significantly increased in patients with HIV related fat redistribution compared to Framingham control subjects (46.1 +/- 4 vs 18.9 +/- 0.9 microg/L PAI-1, 16.6 +/- 0.8 vs. 8.0 +/- 0.3 microg/L tPA, P = 0.0001). Among patients with HIV infection, a multivariate regression analysis including age, sex, waist-to-hip ratio, BMI, smoking status, protease inhibitor use and insulin area under the curve (AUC), found gender and insulin AUC were significant predictors of tPA antigen. Twelve weeks of metformin treatment resulted in decreased tPA antigen levels (-1.9 +/- 1.4 vs +1.4 +/- 1.0 microg/L in the placebo-treated group P = 0.02). Similarly, metformin resulted in improvement in PAI-1 levels (-8.7 +/- 2.3 vs +1.7 +/- 2.9 microg/L, P = 0.03). Change in insulin AUC correlated significantly with change in tPA antigen (r = 0.43, P = 0.03). PAI-1 and tPA antigen, markers of impaired fibrinolysis and increased CVD risk, are increased in association with hyperinsulinemia in patients with HIV and fat redistribution. Metformin reduces PAI-1 and tPA antigen concentrations in these patients and may ultimately improve associated CVD risk.
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PMID:Increased PAI-1 and tPA antigen levels are reduced with metformin therapy in HIV-infected patients with fat redistribution and insulin resistance. 1115 71


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