Rosiglitazone plus metformin: combination therapy for Type 2 diabetes

Peroxisome proliferator-activated receptor activating hypoglycemic effect of Gardenia jasminoides Ellis aqueous extract and improvement of insulin sensitivity in steroid induced insulin resistant rats

Background

The active components of Gardenia (Gardenia jasminoides Ellis, GJ) exhibit a hypoglycemic effect by improving insulin secretion and lowering plasma lipids. In the present study, we fed a water extract of gardenia to steroid-induced insulin-resistant (SIIR) rats and observed changes in signaling proteins in order to elucidate the mechanisms of the insulin-sensitizing effect of GJ and evaluate its possibility as an insulin-sensitizing agent.

Methods

Normal Wistar rats were randomly divided into a control group (i.e., saline) and experimental groups (GJ 100 and 200 mg/kg). Blood samples were taken at 0, 30, and 60 min for plasma glucose assay in order to determine the optimal dose to induce the hypoglycemic effect. SIIR rats were then randomly divided into a control group (i.e., saline) and an experimental group (optimal dose of gardenia extract) to observe the insulin-sensitizing effect of the extract. Finally, western blot analysis was performed to detect intracellular signaling proteins to elucidate the mechanisms of the insulin-sensitization effect of GJ.

Results

The normal Wistar rats in the GJ 200 mg/kg group exhibited significant hypoglycemic activity. Meanwhile, the SIIR rats had higher plasma glucose levels than normal rats. There was no obvious change in insulin level, but the insulin sensitivity index and homeostasis model assessment index were significantly elevated. Meanwhile, a significant hypoglycemic effect was observed with GJ 200 mg/kg. In addition, intracellular signaling proteins including insulin receptor substrate-1 (IRS-1) and peroxisome proliferator-activated receptor (PPARγ) were elevated in muscle cells.

Conclusions

The optimal dose of GJ aqueous extract of 200 mg/kg exerts a PPARγ-activating hypoglycemic effect and improves insulin resistance in SIIR rats. Therefore, it is a potential insulin-sensitizing agent in type 2 diabetes mellitus with insulin resistance.

Assessment of the pharmacokinetics of co-administered metformin and lobeglitazone, a thiazolidinedione antihyperglycemic agent, in healthy subjects

OBJECTIVE

Lobeglitazone as a thiazolidinedione antihyperglycemic agent activates peroxisome proliferator-activated receptor (PPAR) γ and may be suitable as monotherapy or in combination with other antihyperglycemic agents. The primary objective of this study was to investigate potential pharmacokinetic interactions between lobeglitazone and metformin in healthy Korean subjects.

METHODS

A randomized, open-label, multiple-dose, three-treatment, three-period, three-sequence, crossover study was conducted in 24 healthy Korean male volunteers. Serial blood samples were collected after lobeglitazone (0.5 mg/day) and metformin (1000 mg/day) were administered alone or concomitantly for 5 days in each period, and drug concentrations were determined by liquid chromatography-tandem mass spectrometry. CLINICAL TRAIL REGISTRATION NUMBER: NCT01005160.

RESULTS

The steady-state maximum plasma concentrations (C(max, ss); mean ± standard deviation) of lobeglitazone and metformin alone were 29.38 ± 5.25 ng/mL and 1661.84 ± 471.88 ng/mL, respectively; the C(max, ss) during co-administration were 27.15 ± 5.75 ng/mL and 1779.92 ± 405.20 ng/mL, respectively. The steady-state areas under the concentration-time curves during the dose interval (AUC(τ, ss); mean ± standard deviation) of sole administration of lobeglitazone and metformin were 277.53 ± 65.25 ng*h/mL and 9650.27 ± 2089.81 ng*h/mL, respectively. When lobeglitazone and metformin were administered concomitantly, the AUC(τ, ss) were 257.29 ± 60.61 ng*h/mL and 10600.58 ± 1960.40 ng*h/mL, respectively. The geometric mean ratios (90% confidence interval) of co-medication to lobeglitazone alone were 0.92 (0.87-0.97; C(max, ss)) and 0.93 (0.87-0.99; AUC(τ, ss)), and those for co-medication to metformin monotherapy were 1.09 (0.99-1.19; C(max, ss)) and 1.11 (1.04-1.19; AUC(τ, ss)). Both monotherapies and combination therapy were well tolerated; 52 self-resolving, non-serious adverse events were reported from 17 subjects.

CONCLUSION

Lobeglitazone did not significantly affect the pharmacokinetics of metformin or vice versa when both drugs were co-administered. Lobeglitazone can be co-administered with metformin without dose adjustment for either agent. Therefore further patient studies are needed to corroborate these results.

Efficacy and safety of sitagliptin when added to ongoing metformin therapy in patients with type 2 diabetes

AIM

To assess the addition of sitagliptin to ongoing metformin therapy in patients with type 2 diabetes who were inadequately controlled [haemoglobin A(1c) (HbA(1c)) 7-11%] on metformin monotherapy.

METHODS

Patients (n = 273) on metformin (>/=1500 mg/day) were randomized to receive the addition of once-daily placebo, sitagliptin 100 mg or rosiglitazone 8 mg in a 1 : 1 : 1 ratio for 18 weeks. The efficacy analysis was based on the all-patients-treated population using an analysis of co-variance with change in HbA(1c) from baseline as the primary endpoint.

RESULTS

The mean baseline HbA(1c) was 7.7% for the entire cohort. After 18 weeks, both active add-on therapies led to greater improvements in HbA(1c) from baseline: -0.73% for sitagliptin (p < 0.001 vs. placebo) and -0.79% for rosiglitazone compared with -0.22% for placebo. No difference was observed between the sitagliptin and rosiglitazone treatments (0.06% [95% confidence interval (CI): -0.14 to 0.25]). The proportion of patients achieving an HbA(1c) < 7% was greater with sitagliptin (55%) and rosiglitazone (63%) compared with placebo (38%). Body weight increased from baseline with rosiglitazone (1.5 kg) compared with body weight reduction with sitagliptin (-0.4 kg) and placebo (-0.8 kg). The difference in body weight between the sitagliptin and rosiglitazone groups was 1.9 kg (95% CI: 1.3-2.5). In a prespecified analysis, the proportion of patients experiencing a greater than 3-kg increase in body weight was 21% in the rosiglitazone group compared with 2% in both the sitagliptin and placebo groups. Both active treatments were generally well tolerated, with no increased risk of hypoglycaemia or gastrointestinal adverse events compared with placebo.

CONCLUSIONS

In this 18-week study, the addition of sitagliptin was effective and well tolerated in patients with type 2 diabetes inadequately controlled with metformin monotherapy. Treatment with sitagliptin produced similar reductions in HbA(1c) compared with the addition of rosiglitazone.

The significance of compliance and persistence in the treatment of diabetes, hypertension and dyslipidaemia: a review

OBJECTIVES

To review studies of patient compliance/persistence with cardiovascular or antidiabetic medication published since the year 2000; to compare the methods used to measure compliance/persistence across studies; to compare reported compliance/persistence rates across therapeutic classes and to assess whether compliance/persistence correlates with clinical outcomes.

METHODS

English language papers published between January 2000 and November 2005 investigating patient compliance/persistence with cardiovascular or antidiabetic medication were identified through searches of the MEDLINE and EMBASE databases. Definitions and measurements of compliance/persistence were compared across therapeutic areas using contingency tables.

RESULTS

Of the 139 studies analysed, 32% focused on hypertension, 27% on diabetes and 13% on dyslipidaemia. The remainder covered coronary heart disease and cardiovascular disease (CVD) in general. The most frequently reported measure of compliance was the 12-month medication possession ratio (MPR). The overall mean MPR was 72%, and the MPR did not differ significantly between treatment classes (range: 67-76%). The average proportion of patients with an MPR of >80% was 59% overall, 64% for antihypertensives, 58% for oral antidiabetics, 51% for lipid-lowering agents and 69% in studies of multiple treatments, again with no significant difference between treatment classes. The average 12-month persistence rate was 63% and was similar across therapeutic classes. Good compliance had a positive effect on outcome in 73% of the studies examining clinical outcomes.

CONCLUSIONS

Non-compliance with cardiovascular and antidiabetic medication is a significant problem, with around 30% of days 'on therapy' not covered by medication and only 59% of patients taking medication for more than 80% of their days 'on therapy' in a year. Good compliance has a positive effect on clinical outcome, suggesting that the management of CVD may be improved by improving patient compliance.

Effect of metformin plus roziglitazone compared with metformin alone on glycaemic control in well-controlled Type 2 diabetes

AIMS

To investigate the effect of metformin plus roziglitazione (RSGMET) compared with metformin alone (MET) on glycaemic control in well-controlled Type 2 diabetes.

METHODS

Subjects (drug naïve or those on glucose-lowering monotherapy) were randomized (n = 526), following a 4-week placebo run-in period, to RSGMET [4 mg rosiglitazone (RSG)/500 mg MET] or MET 500 mg. From weeks 2-18, medication was escalated every 4 weeks (based on gastrointestinal tolerability), then remained at RSGMET 8 mg/2 g or MET 3 g for 14 weeks.

RESULTS

RSGMET reduced HbA(1c) from 7.2 +/- 0.6 to 6.7 +/- 0.8% at week 32, compared with a reduction from 7.2 +/- 0.6 to 6.8 +/- 0.9% with MET (treatment difference -0.13%; P = 0.0357). More subjects achieved an HbA(1c) value of </= 6.5% at week 32 with RSGMET (51.6 vs. 43.7%), but the treatment difference was not significant (odds ratio 1.37, P = 0.0949). RSGMET produced larger reductions from baseline in mean fasting plasma glucose (adjusted difference -0.62 mmol/l, P < 0.0001), with the odds ratio of achieving a target of < 7.0 mmol/l being 2.33 (P < 0.0001). Statistically significant differences in favour of RSGMET relative to MET were seen for homeostatic model assessment (HOMA)-derived estimates of insulin sensitivity and pancreatic B-cell function, C-reactive protein (CRP), and systolic blood pressure. Overall rates of gastrointestinal adverse events (relevant to the known profile of MET) were comparable, but with a lower incidence of diarrhoea (8 vs. 18%) with RSGMET. Hypoglycaemia was reported in </= 7% subjects per group.

CONCLUSIONS

RSGMET provided similar short-term glycaemic control to MET with greater improvements in estimates of insulin sensitivity, B-cell function and CRP, with less diarrhoea and low risk of biochemical hypoglycaemia, suggesting that early use of combination therapy may be appropriate.

Acute pulmonary edema due to rosiglitazone use in a patient with diabetes mellitus

Rosiglitazone is a peroxisome proliferator active receptor. gamma agonist, which increases insulin sensitivity in adipose tissue, muscle, and liver. Rosiglitazone is a member of the thiazolidinedione group, and because of its significantly positive effect on glycemic control, it is especially preferred in type 2 diabetic patients with a high cardiovascular disease risk. This drug, because of its decreasing effect on insulin resistance, is used alone or combined with type 2 diabetic drugs. A 73-year-old female patient was admitted to the emergency department with dyspnea, pink frothing phlegm, cyanosis, and tiredness. She was lethargic, uncooperative, and had no orientation. In arterial blood gases, hypoxemia and hypercapnia were found. She was taken to the general intensive care unit, and oxygen was applied via mask. The patient had a history of 10 years of diabetes mellitus, hypertension, and atherosclerotic cardiac disease, and she was using rosiglitazone for the past 6 weeks. Her chest x-ray was taken, and acute pulmonary edema was diagnosed. In her last echocardiography, which was performed 1 year before, no signs indicating cardiac failure and pleural effusion could be found. Therefore, it was concluded that pulmonary edema occurred as a complication of rosiglitazone use. After stabilizing the patient's vital signs, blood glucose levels, and lactate levels, medical treatment of diabetes mellitus was rearranged, and she was discharged on the seventh day after her admittance. In a patient with diabetes mellitus who has been admitted to the intensive care unit because of acute pulmonary edema, for differential diagnosis, use of rosiglitazone should be kept in mind during the determination of treatment. Therefore, the authors aim to discuss the effect of rosiglitazone on creating acute pulmonary edema with a case report presentation.

Rosiglitazone/Metformin

The thiazolidinedione rosiglitazone and the biguanide metformin are effective antihyperglycaemic agents with different modes of action; rosiglitazone primarily increases insulin sensitivity, whereas metformin primarily reduces hepatic glucose output. Antihyperglycaemic combination therapy is often required to achieve effective glycaemic control. A fixed-dose formulation of rosiglitazone/metformin was recently approved in the EU and the US for the treatment of type 2 diabetes mellitus in patients inadequately controlled on metformin monotherapy. Bioequivalence between the fixed-dose combination tablet and coadministration of rosiglitazone with metformin at the same dosage has been established in a pharmacokinetic study. Fixed-dose rosiglitazone/metformin 8 mg/2g per day reduced glycosylated haemoglobin (HbA1c) and fasting plasma glucose (FPG) levels to a significantly greater extent than metformin 3 g/day in patients with type 2 diabetes in a 24-week, randomised, double-blind study. Rosiglitazone plus metformin was significantly more effective than metformin alone at reducing HbA1c and FPG levels in patients with type 2 diabetes in three 26-week, randomised, double-blind, placebo-controlled studies. Rosiglitazone plus metformin was generally well tolerated in all studies and had a tolerability profile similar to that of metformin monotherapy. Mild or moderate symptomatic hypoglycaemia was reported in <or=4.4% of rosiglitazone plus metformin recipients.

Multiple weak hits confuse complex systems: a transcriptional regulatory network as an example

Robust systems, like the molecular networks of living cells, are often resistant to single hits such as those caused by high-specificity drugs. Here we show that partial weakening of the Escherichia coli and Saccharomyces cerevisiae transcriptional regulatory networks at a small number (3-5) of selected nodes can have a greater impact than the complete elimination of a single selected node. In both cases, the targeted nodes have the greatest possible impact; still, the results suggest that in some cases broader specificity compounds or multitarget drug therapies may be more effective than individual high-affinity, high-specificity ones. Multiple but partial attacks mimic well a number of in vivo scenarios and may be useful in the efficient modification of other complex systems.

Increased potency and efficacy of combined phosphorylase inactivation and glucokinase activation in control of hepatocyte glycogen metabolism

Glucokinase and phosphorylase both have a high control strength over hepatocyte glycogen metabolism and are potential therapeutic targets for type 2 diabetes. We tested whether combined phosphorylase inactivation and glucokinase activation is a more effective strategy for controlling hepatic glycogen metabolism than single-site targeting. Activation of glucokinase by enzyme overexpression combined with selective dephosphorylation of phosphorylase-a by an indole carboxamide that favors the T conformation of phosphorylase caused a greater stimulation of glycogen synthesis than the sum of either treatment alone. This result is explained by the complementary roles of elevated glucose-6-phosphate (G6P; a positive modulator) and depleted phosphorylase-a (a negative modulator) in activating glycogen synthase and also by synergistic inactivation of phosphorylase-a by glucokinase activation and the indole carboxamide. Inactivation of phosphorylase-a by the indole carboxamide was counteracted by 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside, which is metabolized to an AMP analog; this effect was reversed by G6P. Our findings provide further evidence for the inverse roles of G6P and AMP in regulating the activation state of hepatic phosphorylase. It is proposed that dual targeting of glucokinase and phosphorylase-a enables improved potency and efficacy in controlling hepatic glucose metabolism.