Fixed-dose combination therapy for type 2 diabetes:sitagliptin plus pioglitazone

Type 2 diabetes is typically associated with insulin resistance and dysfunction of insulin-secreting pancreatic beta-cells. Addressing these defects often requires therapy with a combination of differently acting antidiabetic agents. A potential novel combination in development brings together the dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin with the thiazolidinedione pioglitazone into a fixed-dose single-tablet combination. The former component acts mainly to increase prandial insulin secretion; the latter improves insulin sensitivity.

Reduced postprandial proinsulinaemia and 32-33 split proinsulinaemia after a mixed meal in type 2 diabetic patients following sensitization to insulin with pioglitazone

Objective: Reduced insulin sensitivity associated with fasting hyperproinsulinaemia is common in type 2 diabetes. Proinsulinaemia is an established independent cardiovascular risk factor. The objective was to investigate fasting and postprandial release of insulin, proinsulin (PI) and 32-33 split proinsulin (SPI) before and after sensitization to insulin with pioglitazone compared to a group treated with glibenclamide. Design and patients: A randomized double-blind placebo-controlled trial. Twenty-two type 2 diabetic patients were recruited along with 10 normal subjects. After 4 weeks washout, patients received a mixed meal and were assigned to receive pioglitazone or glibenclamide for 20 weeks, after which patients received another identical test meal. The treatment regimes were designed to maintain glycaemic control (HbA1c) at pretreatment levels so that ß-cells received an equivalent glycaemic stimulus for both test meals. Measurements: Plasma insulin, PI, SPI and glucose concentrations were measured over an 8-h postprandial period. The output of PI and SPI was measured as the integrated postprandial response (area under the curve, AUC). Results: Pioglitazone treatment resulted in a significant reduction in fasting levels of PI and SPI compared to those of the controls. Postprandially, pioglitazone treatment had no effect on the insulin AUC response to the meal but significantly reduced the PI and SPI AUCs. Glibenclamide increased fasting insulin and the postprandial insulin AUC but had no effect on the PI and SPI AUCs. Conclusions: Sensitization to insulin with pioglitazone reduces the amount of insulin precursor species present in fasting and postprandially and may reduce cardiovascular risk. © 2007 The Authors.

Pioglitazone

Pioglitazone is a thiazolidinedione (TZD) antihyperglycemic agent introduced in 1999 for the treatment of type 2 (non-insulin dependent) diabetes mellitus. Another TZD, rosiglitazone, is also used in the treatment of type 2 diabetes. Troglitazone has been withdrawn from clinical use, and other TZDs, such as ciglitazone, have not proceeded into clinical use. Pioglitazone, like other TZDs, improves insulin action mainly by activation of the nuclear peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Peroxisome proliferator-activated receptor-gamma is most strongly expressed in adipose tissue and weakly expressed in liver and skeletal muscle, and activation of PPAR-gammain these tissues reinforces the effects of insulin. Pioglitazone may exert effects on other tissues that express PPAR-gamma ..... © 2007 Copyright © 2007 Elsevier Inc. All rights reserved.

Diabetes therapies in renal impairment

Depending on age, duration of diabetes and glycaemic control, 20-40% of patients with type 2 diabetes will incur a moderate or severe deterioration of renal function. This will impact the choice of blood glucose-lowering therapy and require more frequent monitoring of both renal function and glycaemic control. Moderate renal impairment (glomerular filtration rate 30-<60 ml/min) requires consideration of dose reduction or treatment cessation for metformin, glucagon-like peptide-1 receptor agonists, some sulphonylureas and some dipeptidyl peptidase-4 inhibitors. At lower rates of glomerular filtration down to about 15 ml/min it may be appropriate to use a meglitinide, pioglitazone or certain sulphonylureas with careful consideration of dose and co-morbidities. Dipeptidyl peptidase-4 inhibitors can be used at reduced dose in patients with very low rates of glomerular filtration, and linagliptin can be used without dose reduction, and has been used in patients on dialysis. Insulin can be used at any stage of renal impairment, but the regimen and the dose must be suitably adjusted and accompanied by adequate monitoring. © The Author(s), 2012.

New drugs for type 2 diabetes mellitus:what is their place in therapy?

Oral therapy for type 2 diabetes mellitus, when used appropriately, can safely assist patients to achieve glycaemic targets in the short to medium term. However, the progressive nature of type 2 diabetes usually requires a combination of two or more oral agents in the longer term, often as a prelude to insulin therapy. Issues of safety and tolerability, notably weight gain, often limit the optimal application of anti-diabetic drugs such as sulforylureas and thiazolidinediones. Moreover, the impact of different drugs, even within a single class, on the risk of long-term vascular complications has come under scrutiny. For example, recent publication of evidence suggesting potential detrimental effects of rosiglitazone on myocardial events generated a heated debate and led to a reduction in use of this drug. In contrast, current evidence supports the view that pioglitazone has vasculoprotective properties. Both drugs are contraindicated in patients who are at risk of heart failure. An additional recently identified safety concern is an increased risk of fractures, especially in postmenopausal women. Several new drugs with glucose-lowering efficacy that may offer certain advantages have recently become available. These include (i) injectable glucagonlike peptide-1 (GLP-1) receptor agonists and oral dipeptidyl peptidase-4 (DPP-4) inhibitors; (ii) the amylin analogue pramlintide; and (iii) selective cannabinoid receptor-1 (CB1) antagonists. GLP-1 receptor agonists, such as exenatide, stimulate nutrient-induced insulin secretion and reduce inappropriate glucagon secretion while delaying gastric emptying and reducing appetite. These agents offer a low risk of hypoglycaemia combined with sustained weight loss. The DPP-4 inhibitors sitagliptin and vildagliptin are generally weight neutral, with less marked gastrointestinal adverse effects than the GLP-1 receptor agonists. Potential benefits of GLP-1 receptor stimulation on P cell neogenesis are under investigation. Pancreatitis has been reported in exenatide-treated patients. Pramlintide, an injected peptide used in combination with insulin, can reduce insulin dose and bodyweight. The CB1 receptor antagonist rimonabant promotes weight loss and has favourable effects on aspects of the metabolic syndrome, including the hyperglycaemia of type 2 diabetes. However, in 2007 the US FDA declined approval of rimonabant, requiring more data on adverse effects, notably depression. The future of dual peroxisome proliferator-activated receptor-alpha/gamma agonists, or glitazars, is presently uncertain following concerns about their safety. In conclusion, several new classes of drugs have recently become available in some countries that offer new options for treating type 2 diabetes. Beneficial or neutral effects on bodyweight are an attractive feature of the new drugs. However, the higher cost of these agents, coupled with an absence of long-term safety and clinical outcome data, need to be taken into consideration by clinicians and healthcare organizations.

Thiazolidinediones

Thiazolidinediones (TZDs), also termed "glitazones", are used as antidiabetic agents for the treatment of type 2 (non-insulin dependent) diabetes mellitus. They activate the nuclear peroxisome proliferator-activated receptor-gamma (PPAR-gamma). This increases the transcription of various insulin-sensitive genes, improving insulin action and lowering blood glucose concentrations. TZDs currently in clinical use for the treatment of type 2 diabetes are rosiglitazone and pioglitazone. Troglitazone was withdrawn due to hepatotoxicity. Other TZDs (e.g. ciglitazone) have been studied preclinically, but not introduced into clinical use. TZDs do not cause severe hypoglycemia, hence they are regarded as antihyperglycemic (rather than hypoglycemic) agents .... © 2007 Elsevier Inc. All rights reserved..