A fixed-dose combination of pioglitazone and metformin: A promising alternative in metabolic control

Impact of Fixed Combination of Metformin and Pioglitazone on Insulin Resistance of Patients with Type 2 Diabetes: Results of a Randomized Open-Label Study

Aim

To compare the effect of metformin, a fixed combination of metformin and pioglitazone, or dapagliflozin on insulin resistance in patients with newly diagnosed type 2 diabetes.

Methods

In this 6-week randomized open-label trial, 58 patients were randomly assigned to insulin with metformin, a fixed combination of metformin and pioglitazone, or dapagliflozin for 4 weeks. Hyperinsulinemic euglycemic clamp tests and FreeStyle Libre Pro Sensor were used to evaluate the insulin sensitivity represented by glucose-infusion rate (M value) and glycemic control, respectively. The main outcome was changes in insulin resistance compared with baseline.

Results

The baseline characteristics were well matched among the three groups. When compared to baseline, insulin sensitivity after treatment was significantly improved. Further study revealed that the fixed combination of metformin and pioglitazone provided superior M-value improvement compared with metformin, but not different from dapagliflozin. Moreover, a greater reduction in insulin dose was observed in the fixed combination of metformin and pioglitazone group than the metformin or dapagliflozin group. However, there were no significant differences in the parameters of glycemic control within the groups.

Conclusion

In patients with newly diagnosed type 2 diabetes, a fixed combination of metformin and pioglitazone provided greater improvement in insulin resistance than metformin alone and similar changes in insulin resistance to dapagliflozin.

Effect of Human Adenovirus 36 on Response to Metformin Monotherapy in Obese Mexican Patients with Type 2 Diabetes: A Prospective Cohort Study

Human adenovirus 36 (HAdV-36) has been associated with obesity and changes in glucose and lipid metabolism. The virus has been reported to increase insulin sensitivity and paradoxically promote weight gain. Because of its effects on metabolism, infection with the virus could alter the response to several drugs used to treat type 2 diabetes (DM2), such as metformin. The aim of this study was to test whether HAdV-36 affects the response to metformin in a group of obese patients with DM2.

METHODS

In a prospective cohort study, 103 obese patients with newly diagnosed DM2 were divided into two groups based on their HAdV-36 seropositivity (+HAdV-36 and -HAdV-36). Weight, glucose, cholesterol, triglycerides, body mass index, body fat percentage, and waist and hip circumference were measured and compared in both groups at baseline and after 45 days of metformin treatment.

RESULTS

Only glucose was significantly lower in the +HAdV-36 group at baseline, while all other variables were similar between the two study groups. After 45 days of follow-up, it was observed that the effect of metformin did not differ between the groups, but the variables improved significantly after treatment.

CONCLUSIONS

In this study, we did not find that HAdV-36 had an effect on the response to metformin in obese patients with DM2.

AMP-activated protein kinase (AMPK)α2 plays a role in determining the cellular fate of glucose in insulin-resistant mouse skeletal muscle

AIMS/HYPOTHESIS

We determined whether: (1) an acute lipid infusion impairs skeletal muscle AMP-activated protein kinase (AMPK)α2 activity, increases inducible nitric oxide synthase (iNOS) and causes peripheral insulin resistance in conscious, unstressed, lean mice; and (2) restoration of AMPKα2 activity during the lipid infusion attenuates the increase in iNOS and reverses the defect in insulin sensitivity in vivo.

METHODS

Chow-fed, 18-week-old C57BL/6J male mice were surgically catheterised. After 5 days they received: (1) a 5 h infusion of 5 ml kg(-1) h(-1) Intralipid + 6 U/h heparin (Lipid treatment) or saline (Control); (2) Lipid treatment or Control, followed by a 2 h hyperinsulinaemic-euglycaemic clamp (insulin clamp; 4 mU kg(-1) min(-1)); and (3) infusion of the AMPK activator, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) (1 mg kg(-1) min(-1)), or saline during Lipid treatment, followed by a 2 h insulin clamp. In a separate protocol, mice producing a muscle-specific kinase-dead AMPKα2 subunit (α2-KD) underwent an insulin clamp to determine the role of AMPKα2 in insulin-mediated muscle glucose metabolism.

RESULTS

Lipid treatment decreased AMPKα2 activity, increased iNOS abundance/activation and reduced whole-body insulin sensitivity in vivo. AICAR increased AMPKα2 activity twofold; this did not suppress iNOS or improve whole-body or tissue-specific rates of glucose uptake during Lipid treatment. AICAR caused a marked increase in insulin-mediated glycogen synthesis in skeletal muscle. Consistent with this latter result, lean α2-KD mice exhibited impaired insulin-stimulated glycogen synthesis even though muscle glucose uptake was not affected.

CONCLUSIONS/INTERPRETATION

Acute induction of insulin resistance via lipid infusion in healthy mice impairs AMPKα2, increases iNOS and causes insulin resistance in vivo. However, these changes do not appear to be interrelated. Rather, a functionally active AMPKα2 subunit is required for insulin-stimulated muscle glycogen synthesis.

Patient adherence to medication requirements for therapy of type 2 diabetes

Type 2 diabetes is a complex, progressive endocrine and metabolical disease that typically requires substantial lifestyle changes and multiple medications to lower blood glucose, reduce cardiovascular risk and address comorbidities. Despite an extensive range of available and effective treatments, < 50% of patients achieve a glycaemical target of HbA(1c) < 7.0% and about two-thirds die of premature cardiovascular disease. Adherence to prescribed therapies is an important factor in the management of type 2 diabetes that is often overlooked. Inadequate adherence to oral antidiabetes agents, defined as collecting < 80% of prescribed medication, is variously estimated to apply to between 36% and 93% of patients. All studies affirm that a significant proportion of type 2 diabetes patients exhibit poor adherence that will contribute to less than desired control. Identified factors that impede adherence include complex dosing regimens, clinical inertia, safety concerns, socioeconomic issues, ethnicity, patient education and beliefs, social support and polypharmacy. This review explores these factors and potential strategies to improve adherence in patients with type 2 diabetes.

Transcriptional upregulation of mitochondrial uncoupling protein 2 protects against oxidative stress-associated neurogenic hypertension

RATIONALE

Mitochondrial uncoupling proteins (UCPs) belong to a superfamily of mitochondrial anion transporters that uncouple ATP synthesis from oxidative phosphorylation and mitigates mitochondrial reactive oxygen species production.

OBJECTIVE

We assessed the hypothesis that UCP2 participates in central cardiovascular regulation by maintaining reactive oxygen species homeostasis in the rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons that maintain vasomotor tone located. We also elucidated the molecular mechanisms that underlie transcriptional upregulation of UCP2 in response to oxidative stress in RVLM.

METHODS AND RESULTS

In Sprague-Dawley rats, transcriptional upregulation of UCP2 in RVLM by rosiglitazone, an activator of its transcription factor peroxisome proliferator-activated receptor (PPAR)gamma, reduced mitochondrial hydrogen peroxide level in RVLM and systemic arterial pressure. Oxidative stress induced by microinjection of angiotensin II into RVLM augmented UCP2 mRNA or protein expression in RVLM, which was antagonized by comicroinjection of NADPH oxidase inhibitor (diphenyleneiodonium chloride), superoxide dismutase mimetic (tempol), or p38 mitogen-activated protein kinase inhibitor (SB203580) but not by extracellular signal-regulated kinase 1/2 inhibitor (U0126). Angiotensin II also induced phosphorylation of the PPARgamma coactivator, PPARgamma coactivator (PGC)-1alpha, and an increase in formation of PGC-1alpha/PPARgamma complexes in a p38 mitogen-activated protein kinase-dependent manner. Intracerebroventricular infusion of angiotensin II promoted an increase in mitochondrial hydrogen peroxide production in RVLM and chronic pressor response, which was potentiated by gene knockdown of UCP2 but blunted by rosiglitazone.

CONCLUSIONS

These results suggest that transcriptional upregulation of mitochondrial UCP2 in response to an elevation in superoxide plays an active role in feedback regulation of reactive oxygen species production in RVLM and neurogenic hypertension associated with chronic oxidative stress.

Fixed-dose single tablet antidiabetic combinations

Combinations of two or more oral agents with different mechanisms of action are often used for the management of hyperglycaemia in type 2 diabetes. While these combinations have customarily been taken as separate tablets, several fixed-dose single tablet combinations are now available. These are based on bioequivalence with the separate tablets, giving similar efficacy to the separate tablets and necessitating the same cautions and contraindications that apply to each active component. Fixed-dose combinations can offer convenience, reduce the pill burden and simplify administration regimens for the patient. They increase patient adherence compared with equivalent combinations of separate tablets, and this is associated with some improvements in glycaemic control. Presently available antidiabetic fixed-dose combinations include metformin combined with a sulphonylurea, thiazolidinedione, dipeptidylpeptidase-4 inhibitor or meglitinide as well as thiazolidinedione-sulphonylurea combinations, each at a range of dosage strengths to facilitate titration. Anticipated future expansion of multiple drug regimens for diabetes management is likely to increase the use of fixed-dose single tablet combinations.

Efficacy and safety of therapy with metformin plus pioglitazone in the treatment of patients with type 2 diabetes: a double-blind, placebo-controlled, clinical trial

OBJECTIVE

To assess the efficacy and safety of combination therapy with pioglitazone and metformin in Japanese patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

During a 12-week observation period 236 patients were treated with metformin 500 or 750 mg/day. 169 patients with a confirmed HbA(1c) level >or= 6.5% were randomized (stratified according to metformin dosage) to receive pioglitazone 15 mg/day for 12 weeks then increased to 30 mg/day for a further 16 weeks (n = 83), or placebo (n = 86). Outcome measures included HbA(1c), fasting blood glucose (FBG), percentage of patients achieving HbA(1c) < 6.5%, lipid profile, and other metabolic parameters.

RESULTS

Mean HbA(1c) was reduced by 0.67% in patients receiving pioglitazone plus metformin versus an increase of 0.25% in those receiving metformin alone (p < 0.0001). After 8 weeks' treatment and until the end of the study, HbA(1c) was significantly lower with pioglitazone plus metformin and more patients in this group achieved an HbA(1c) < 6.5% (38.6% vs. 8.1%; p < 0.0001). FBG was also reduced by a significantly greater amount in patients receiving pioglitazone plus metformin compared with metformin monotherapy (-20.5 vs. 1.9 mg/dl; p < 0.0001). Combination therapy was associated with significantly increased HDL-cholesterol, total cholesterol, and adiponectin, and significantly decreased levels of fasting insulin, free fatty acids, and homeostasis model assessment insulin resistance (HOMA-R) compared with metformin monotherapy. Overall, combination therapy and monotherapy were equally well tolerated and the incidence of adverse effects 'possibly' related to therapy was 15.7% and 11.6% (p = 0.505), respectively. Edema occurred slightly more often in the combination group (6.0 vs. 1.2%).

CONCLUSION

Pioglitazone plus metformin significantly improved glycemic control (HbA(1c) and FBG), and markers associated with increased insulin resistance and cardiovascular risk compared with metformin monotherapy.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN 000001110.

Redefining the role of thiazolidinediones in the management of type 2 diabetes

There is a need to evaluate oral glucose-lowering agents not only for their value in achieving glycemic control but also for their impact on cardiac risk factor modification. This article reviews the evidence base for the two thiazolinediones currently available, pioglitazone and rosiglitazone. These drugs exert their effects through actions affecting metabolic control, lipid profiles, and the vascular wall. They have been shown to be as efficacious in establishing glycemic control, in both monotherapy and combination therapy regimens, as more traditional oral agents, and may be able to sustain that control in the long term. Both thiazolidinediones have demonstrated favorable effects on markers of cardiovascular disease. Evidence from the large PROactive outcomes study suggests that pioglitazone may exert protective effects in patients with type 2 diabetes and macrovascular disease. Thiazolidinediones are generally well tolerated but they can cause weight gain, induce fluid retention, and may contribute to bone loss in postmenopausal women. The place of thiazolidinediones in the management of type 2 diabetes is well established. The potential for additional benefits in reducing macrovascular risk encourages further long-term study of these agents.

Adipokines regulate systemic insulin sensitivity in accordance to existing energy reserves

Adipocyte-derived hormones, including adiponectin and leptin, regulate systemic insulin sensitivity in accordance to existing triglyceride reserves. Leptin levels reflect existing fat mass and the adipokine negatively regulates insulin action in adipose tissue. Adiponectin, on the other hand, preserves insulin sensitivity via transient increments of AMPK activity and its circulating levels seem to reflect the adipogenic capacity of adipose tissue. Because adiponectin and insulin synergize in their postprandial actions, it seems evident that inadequate adiponectin production causes systemic insulin resistance. As a consequence, compounds that either increase adiponectin production or mimic its actions can be considered as an efficient strategy for improving insulin sensitivity in type 2 diabetics. We have previously shown that troglitazone and metformin exert opposing actions on adiponectin production, indicating that combined use of troglitazone and metformin is a more efficient strategy as compared to metformin treatment. Here, we will provide additional arguments which stress the need for a fixed dose of troglitazone and metformin in order to preserve endogenous adiponectin production. Finally, after delineating critical nodes of insulin and adipokine crosstalk, putative pathways are proposed by which adiponectin and leptin cooperatively regulate systemic insulin sensitivity in accordance to existing fat mass. By amplifying insulin action downstream of PI3K, leptin exerts negative feedback on insulin signaling via mTOR-dependent pathways that target IRS-1 for serine phosphorylation and protein degradation. Adiponectin-mediated increments of AMPK activity, on the other hand, may attenuate mTOR signaling, leading to the preservation of insulin sensitivity in periods of increased nutrient availability. Considering that leptin and adiponectin are inversely associated with BMI, the proposed model provides a plausible explanation for the observation that leptin exerts strong negative feedback on systemic insulin sensitivity, while increasing PIP3 availability.