Clinical use of thiazolidinediones: recommendations

A randomized, parallel group, double-blind, multicentre study comparing the efficacy and safety of Avandamet (rosiglitazone/metformin) and metformin on long-term glycaemic control and bone mineral density after 80 weeks of treatment in drug-naïve type 2 diabetes mellitus patients

AIM

The purpose of this study was to evaluate if superior glycaemic control could be achieved with Avandamet® (rosiglitazone/metformin/AVM) compared with metformin (MET) monotherapy, and if glycaemic effects attained with AVM are durable over 18 months of treatment. Bone mineral density (BMD) and bone biomarkers were evaluated in a subgroup of patients.

METHODS

This was a phase IV, randomized, double-blind, multi-centre study in 688, drug naÏve, male and female patients who had an established clinical diagnosis of type 2 diabetes mellitus (T2DM). Patients were randomized in a 1 : 1 ratio either to AVM or MET.

RESULTS

As initial therapy in patients with T2DM, AVM was superior to MET in achieving statistically significant reductions in glycated haemoglobin (HbA1c) (p < 0.0001) and fasting plasma glucose (FPG) (p < 0.001), with more patients reaching recommended HbA1c and FPG targets for intensive glycaemic control. The glycaemic effects attained with AVM compared to MET monotherapy were durable over 18 months of treatment. In the bone substudy, AVM was associated with a significantly lower BMD in comparison with MET at week 80 in the lumbar spine and total hip (p < 0.0012 and p = 0.0005, respectively). Between-treatment differences were not statistically significant for distal one-third of radius BMD, femoral neck BMD or total BMD.

CONCLUSION

Superior glycaemic control was achieved with AVM compared with MET monotherapy. The superior glycaemic effects were shown to be durable over 18 months of treatment. AVM was associated with a significantly reduced BMD in comparison with MET at week 80 in the lumbar spine and total hip.

The risk of coronary heart disease in type 2 diabetic patients exposed to thiazolidinediones compared to metformin and sulfonylurea therapy

PURPOSE

To evaluate whether the risk of coronary heart disease (CHD) differs among adult diabetic patients treated with thiazolidinediones (TZDs) and similar patients treated with combined oral metformin and sulfonylurea (M + S) therapy.

METHODS

We conducted a retrospective cohort study involving 25 140 diabetic patients aged 18 and older who had at least one pharmacy claim for a TZD or combined M + S therapy between 1 January 1999 and 30 June 2002. We used propensity score matching to adjust for observable differences between initiators of combined M + S therapy and TZD initiators. The data were analyzed in two ways: first based on the original matched groups, 'as balanced', without accounting for switching to another medication during follow-up, and second based on actual antidiabetic drug use during follow-up, 'as treated'. Cox proportional hazards regression and multivariable Poisson regression were performed to compare the risk of CHD events.

RESULTS

In the 'as balanced' analysis, the risk for CHD among TZD users relative to combination drug users was close to the null value (adjusted hazard ratio: 1.02, 95% confidence intervals (CI): 0.87-1.20). In the 'as treated' analysis, the risk of CHD was similar for periods of current use of TZDs compared to periods of non-use (incidence rate ratio: 1.10, 95%CI: 0.96-1.25).

CONCLUSIONS

These results do not suggest a cardioprotective or deleterious effects of TZDs compared with combined M + S oral therapy on the short-term CHD event risk in persons with type 2 diabetes after accounting for the greater baseline CHD risk in TZD initiators.

Differential effects of oral hypoglycemic agents on glucose control and cardiovascular risk

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.

Initial treatment with rosiglitazone/metformin fixed-dose combination therapy compared with monotherapy with either rosiglitazone or metformin in patients with uncontrolled type 2 diabetes

AIM

This study assessed the efficacy and safety of rosiglitazone and metformin (RSG/MET) fixed-dose combination (AVANDAMET) as initial therapy in patients with uncontrolled type 2 diabetes compared with monotherapy with either RSG or MET after 32 weeks of treatment.

METHODS

A total of 468 drug-naive patients with uncontrolled type 2 diabetes were recruited for this multicentre, double-blind trial if their glycated haemoglobin (A1c) was greater than 7.5%, but less than or equal to 11%, and their fasting plasma glucose (FPG) was less than or equal to 15 mmol/l. Patients were randomized to 32 weeks of blinded treatment with either RSG/MET fixed-dose combination (n = 155), MET (n = 154) or RSG (n = 159). The groups were comparable at baseline, with mean A1c of 8.8% and FPG of 11 mmol/l. RSG/MET was initiated with a total daily dose of 2 mg/500 mg and could be increased up to 8 mg/2000 mg; MET therapy began with a total daily dose of 500 mg and could be increased up to 2000 mg; and RSG treatment began with a total daily dose of 4 mg and could be increased up to 8 mg. Medication was uptitrated during on-therapy visits based on failure to attain glycaemic target of mean daily glucose less than or equal to 6.1 mmol/l (unless at maximum tolerated dose). Patients were assessed for efficacy and safety at nine visits over a 32-week treatment period. This was a trial designed to show greater efficacy of RSG/MET combination therapy compared with MET or RSG monotherapy. The primary end point was change in A1c from baseline to week 32. Secondary end points included the proportion of patients achieving recommended A1c and FPG targets for glycaemic control and change from baseline in FPG, free fatty acid, lipids, insulin, insulin sensitivity, C-reactive protein and adiponectin. Safety evaluations included adverse-event (AE) monitoring, changes in weight and clinical laboratory evaluations.

RESULTS

At week 32, RSG/MET showed significant improvements in A1c from a baseline of 8.9 +/- 1.1% to 6.6 +/- 1.0% at study end, and this 2.3% reduction was significantly greater than the reductions achieved individually with MET (-1.8%; p = 0.0008) and RSG (-1.6%; p < 0.0001). The greatest mean decrease in FPG was seen with RSG/MET (-4.1 mmol/l) and was significant compared with MET (-2.8 mmol/l; p < 0.0001) and RSG (-2.6 mmol/l; p < 0.0001). Target A1c of less than or equal to 6.5% and less than 7% were achieved in more patients in the RSG/MET group (60% and 77%) than with MET (39% and 57%) or RSG (35% and 58%) respectively. Treatment was well tolerated, with nausea, vomiting and diarrhoea as the most commonly reported AEs. Oedema was comparable between RSG/MET (6%) and RSG (7%) and lower in the MET group (3%). No new safety and tolerability issues were observed in the RSG/MET group.

CONCLUSIONS

As first-line therapy in patients with uncontrolled type 2 diabetes, RSG/MET fixed-dose combination therapy achieved significant reductions in A1c and FPG compared with either RSG or MET monotherapy. RSG/MET was generally well tolerated as initial therapy, with no new tolerability issues identified with the fixed-dose combination.

Metabolic syndrome therapy: prevention of vascular injury by antidiabetic agents

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.

Metabolic syndrome and robustness tradeoffs

The metabolic syndrome is a highly complex breakdown of normal physiology characterized by obesity, insulin resistance, hyperlipidemia, and hypertension. Type 2 diabetes is a major manifestation of this syndrome, although increased risk for cardiovascular disease (CVD) often precedes the onset of frank clinical diabetes. Prevention and cure for this disease constellation is of major importance to world health. Because the metabolic syndrome affects multiple interacting organ systems (i.e., it is a systemic disease), a systems-level analysis of disease evolution is essential for both complete elucidation of its pathophysiology and improved approaches to therapy. The goal of this review is to provide a perspective on systems-level approaches to metabolic syndrome, with particular emphasis on type 2 diabetes. We consider that metabolic syndromes take over inherent dynamics of our body that ensure robustness against unstable food supply and pathogenic infections, and lead to chronic inflammation that ultimately results in CVD. This exemplifies how trade-offs between robustness against common perturbations (unstable food and infections) and fragility against unusual perturbations (high-energy content foods and low-energy utilization lifestyle) is exploited to form chronic diseases. Possible therapeutic approaches that target fragility of emergent robustness of the disease state have been discussed. A detailed molecular interaction map for adipocyte, hepatocyte, skeletal muscle cell, and pancreatic beta-cell cross-talk in the metabolic syndrome can be viewed at http://www.systems-biology.org/001/003.html.