Effects of mitiglinide and sulfonylureas in isolated canine coronary arteries and perfused rat hearts

Ischemic Postconditioning Reduces Reperfusion Arrhythmias by Adenosine Receptors and Protein Kinase C Activation but Is Independent of KATP Channels or Connexin 43

Ischemic postconditioning (IPoC) reduces reperfusion arrhythmias but the antiarrhythmic mechanisms remain unknown. The aim of this study was to analyze IPoC electrophysiological effects and the role played by adenosine A₁, A_2A and A₃ receptors, protein kinase C, ATP-dependent potassium (K_ATP) channels, and connexin 43. IPoC reduced reperfusion arrhythmias (mainly sustained ventricular fibrillation) in isolated rat hearts, an effect associated with a transient delay in epicardial electrical activation, and with action potential shortening. Electrical impedance measurements and Lucifer-Yellow diffusion assays agreed with such activation delay. However, this delay persisted during IPoC in isolated mouse hearts in which connexin 43 was replaced by connexin 32 and in mice with conditional deletion of connexin 43. Adenosine A₁, A_2A and A₃ receptor blockade antagonized the antiarrhythmic effect of IPoC and the associated action potential shortening, whereas exogenous adenosine reduced reperfusion arrhythmias and shortened action potential duration. Protein kinase C inhibition by chelerythrine abolished the protective effect of IPoC but did not modify the effects on action potential duration. On the other hand, glibenclamide, a K_ATP inhibitor, antagonized the action potential shortening but did not interfere with the antiarrhythmic effect. The antiarrhythmic mechanisms of IPoC involve adenosine receptor activation and are associated with action potential shortening. However, this action potential shortening is not essential for protection, as it persisted during protein kinase C inhibition, a maneuver that abolished IPoC protection. Furthermore, glibenclamide induced the opposite effects. In addition, IPoC delays electrical activation and electrical impedance recovery during reperfusion, but these effects are independent of connexin 43.

The impact of oral anti-diabetic medications on heart failure: lessons learned from preclinical studies

The prevalence of heart failure (HF) in the diabetic population has rapidly increased over the past 2 decades, triggering research about the impact of oral anti-diabetic medications on it. Unfortunately, not all success at the bench in preclinical experiments has translated to success at the bedside. On the other hand, recent promising clinical data from oral SGLT2 inhibitors mainly lack mechanistic explanation from experimental studies. Hence, it is critical to understand the lessons learned from prior translational studies to gain a better knowledge of the mechanisms of oral anti-diabetic drugs in HF. This review aims to summarize the results from preclinical studies regarding the interaction between oral anti-diabetic medications and heart failure development and/or exacerbation. Although there is a wide spectrum of controversial results, the underlying hope is that the clinical success rate will improve and the adverse events during ineffective targeted therapy will be limited.

Management of hyperglycemia during and in the immediate follow-up of acute coronary syndrome

Diabetes is a serious, frequent, and insidious morbidity and mortality risk factor in patients with coronary artery disease. It has been shown that carbohydrate metabolism disorders are common in acute coronary syndromes (ACSs): 30-40% of patients have diabetes, 25-36% have an intolerance to carbohydrates, and only 30-40% have a normal carbohydrate profile. Hyperglycemia occurring either in diabetic or nondiabetic patients is strongly associated with a poor prognosis. It increases the extent of myocardial necrosis, and the risk of recurrence acute coronary syndrome and hemodynamic complications, particularly heart failure and cardiogenic shock, reflecting the importance of optimal management of glucose metabolism abnormalities. The objective of this article is to suggest a screening and management guide for carbohydrate metabolism disorders during and in the immediate follow-up of ACS in diabetic and nondiabetic patients. Screening must be systematic in any patient admitted for ACS, and based on hemoglobin A1c and oral glucose tolerance testing. Treatment of hyperglycemia in the cardiology intensive care unit is recommended in any patient admitted with hyperglycemia >1.80 g/L or postfeeding blood glucose level >1.40 g/L, and should be based on intravenous insulin with concomitant infusion of glucose solution under strict monitoring. Once the patient is no longer in intensive care, intravenous insulin therapy is no longer recommended, and the passage to a fixed insulin therapy regimen or to oral antidiabetics should be considered in consultation with diabetologists. During the rehabilitation phase, good glycemic control improves both prognosis and survival.

Pharmacokinetic and pharmacodynamic modeling of oral mitiglinide on glucose lowering in healthy Chinese volunteers

Background

Mitiglinide is a widely used agent for diabetic treatment. We established a pharmacokinetic-pharmacodynamic (PK-PD) model to illustrate the relationship between mitiglinide plasma concentration and its glucose lowering effects in healthy volunteers.

Methods

The volunteers participated in the test after the administration of a single dose of 10 mg mitiglinide. The drug concentration in Plasma and the values of glucose levels were determined by LC-MS/MS assay and hexokinase method. A PK-PD model was established with a series of equations to describe the relationship between plasma medicine and glucose, and the equations were solved numerically and fitted to the data with the Phoenix NLME software.

Results

The results of the two-compartment model analysis were based on the maximum likelihood criterion and visual inspection of the fittings. The terminal elimination half-life (t_1/2) was 1.69 ± 0.16 h and the CL/F was 7.80 ± 1.84 L/h. The plasma glucose levels began to decline by 0.2 h, and hit its bottom decreasing values of 2.6 mg/L at 0.5 h after administration. The calculated parameter and fitting curve indicated that the model established in our experiment fitted well.

Conclusions

A PK/PD model illustrates that the relationship between mitiglinide concentration in plasma and glucose lowering effect in healthy volunteers was established. The results of our experiment suggested that the model can be used reasonably to predict the relationship between PK and PD in mitiglinide, which could be used in diabetes mellitus dosage control in clinical trials and other fields.

Variable effects of anti-diabetic drugs in animal models of myocardial ischemia and remodeling: a translational perspective for the cardiologist

Diabetes and heart failure are very prevalent, and affect each other's incidence and severity. Novel therapies to reduce post-myocardial infarction (MI) remodeling that progresses into heart failure are urgently needed, especially in diabetic patients. Clinical studies have suggested that some oral anti-diabetic agents like metformin exert cardiovascular protective effects in heart failure patients with diabetes, whereas other agents may be deleterious. In the current review, we provide an overview of the cardio-specific effects of oral anti-diabetic drugs in animal models of acute MI, post-MI remodeling, and heart failure. Metformin has consistently been shown to ameliorate cardiac remodeling after ischemia/reperfusion (I/R) injury, as well as in several models of heart failure. Sulfonylurea derivatives are controversial with respect to their direct effects on the cardiovascular system. Thiazolidinediones protect against myocardial I/R injury, but their effects on post-MI remodeling are less clear and clinical studies raised concerns about their cardiovascular safety. Glucagon-like peptide-1 analogs have potential beneficial effects on the cardiovascular system that require further confirmation, whereas the results with dipeptidyl peptidase-4 inhibitors are equivocal. Current clinical guidelines, in the absence of prospective clinical trials that evaluated if certain oral anti-diabetic agents are superior over others, only provide generic recommendations, and do not take into account interesting experimental and mechanistic data. The available experimental evidence indicates that some anti-diabetic agents should be preferred over others if cardioprotective effects are warranted. These experimental clues need to be confirmed by clinical trials.

Myocardial blood flow under general anaesthesia with sevoflurane in type 2 diabetic patients: a pilot study

Background

In type 2 diabetic patients, cardiac events in the perioperative period may be associated with diminished myocardial vasomotor function and endothelial dysfunction. The influence of sevoflurane anaesthesia on myocardial endothelial dysfunction in type 2 diabetic mellitus is investigated in this pilot study.

Methods

Six males with type 2 diabetes mellitus and eight healthy controls were included. Using myocardial contrast echocardiography, myocardial blood flow (MBF) was measured at rest, during adenosine-induced hyperaemia (endothelium-independent vasodilation) and after sympathetic stimulation by the cold pressor test (endothelium-dependent vasodilation). Measurements were performed before and after induction of sevoflurane anaesthesia.

Results

Sevoflurane anaesthesia decreased resting MBF in diabetics but not in controls (P = 0.03), while baseline MBF did not differ between diabetics and controls. Without anaesthesia, adenosine-induced hyperaemia increased MBF in both groups compared to resting values. Adenosine combined with sevoflurane resulted in a lower hyperaemic MBF in both groups compared to no anaesthesia. Differences in MBF in response to adenosine before and after sevoflurane administration were larger in diabetic patients, however not statistically significant in this pilot group (P = 0.08). Myocardial blood flow parameters after the cold pressor test were not different between groups.

Conclusion

These pilot data in type 2 diabetic patients show that sevoflurane anaesthesia decreases resting myocardial blood flow compared to healthy controls. Further, we observed a trend towards a lower endothelium-independent vasodilation capacity in diabetic patients under sevoflurane anaesthesia. Endothelium-dependent vasodilation was not affected by sevoflurane in diabetic patients. These data provide preliminary insight into myocardial responses in type 2 diabetic patients under general anaesthesia.

Trial registration

http://www.clinicialtrials.gov, NCT00866801

Postprandial hyperglycemia and endothelial function in type 2 diabetes: focus on mitiglinide

The risk of cardiovascular complication in a diabetes patient is similar to that in a nondiabetic patient with a history of myocardial infarction. Although intensive control of glycemia achieved by conventional antidiabetic agents decreases microvascular complications such as retinopathy and nephropathy, no marked effect has been reported on macrovascular complications or all-cause mortality. Evidence from VADT, ACCORD, and ADVANCE would suggest that glycemic control has little effect on macrovascular outcomes. Moreover, in the case of ACCORD, intensive glycemic control may be associated with an increased risk of mortality. There is sufficient evidence that suggests that postprandial hyperglycemia may be an independent risk factor for cardiovascular disease in diabetes patients. However, there are no prospective clinical trials supporting the recommendation that lowering postprandial blood glucose leads to lower risk of cardiovascular outcomes. Mitiglinide is a short-acting insulinotropic agent used in type 2 diabetes treatment. It has a rapid stimulatory effect on insulin secretion and reduces postprandial plasma glucose level in patients with type 2 diabetes. Because of its short action time, it is unlikely to exert adverse effects related to hypoglycemia early in the morning and between meals. Mitiglinide reduces excess oxidative stress and inflammation, plays a cardioprotective role, and improves postprandial metabolic disorders. Moreover, mitiglinide add-on therapy with pioglitazone favorably affects the vascular endothelial function in type 2 diabetes patients. These data suggest that mitiglinide plays a potentially beneficial role in the improvement of postprandial hyperglycemia in type 2 diabetes patients and can be used to prevent cardiovascular diseases. Although the results of long-term, randomized, placebo-controlled trials for determining the cardiovascular effects of mitiglinide on clinical outcomes are awaited, this review is aimed at summarizing substantial insights into this topic.

Discovery of 1,1-dioxo-1,2,6-thiadiazine-5-carboxamide derivatives as cannabinoid-like molecules with agonist and antagonist activity

A series of new 2-substituted 1,1-dioxo-1,2,6-thiadiazine-5-carboxylate derivatives have been prepared from monosubstituted sulfamides in order to obtain N-substituted 1,1-dioxo-1,2,6-thiadiazine-5-carboxamides as novel cannabinoid derivatives, analogues of Rimonabant (SR141716A). Their potential functional activity on cannabinoid receptors has been evaluated in vitro and in vivo in mice, showing that two compounds (37 and 39) behave as cannabinoid agonists in vitro. Their potency is lower than that of the reference compound, WIN 55,212-2, but their efficacy is similar to that of this cannabinoid agonist, although no in vivo activity is observed. Another derivative (38) behaves as a cannabinoid antagonist both in vitro and in vivo, being its efficacy and potency similar to that of the well-known antagonist SR141716A.

Mitiglinide, a Novel Oral Hypoglycemic Agent, Preserves the Cardioprotective Effect of Ischemic Preconditioning in Isolated Perfused Rat Hearts

Diabetic patients often have manifestation of coronary heart disease. As a consequence, therapeutic strategies for diabetes should pay more attention to hypoglycemic agents which do not have adverse effects on myocardium. Mitiglinide is considered to have little or no impact on the cardioprotective effect of ischemic preconditioning (IP) because of its high selectivity for blocking sulfonylurea receptor1 (SUR1). However, glibenclamide, a nonselective SUR blocker, attenuates this beneficial effect. In the present study, we tested the hypothesis that mitiglinide preserves the protective action of IP evaluated by ischemia/reperfusion ventricular tachyarrhythmia (rVT) in isolated perfused rat hearts. After initial perfusion, the hearts were assigned to one of the following groups: 1) non-IP with control perfusion buffer (non-IP group); 2) IP with control perfusion buffer (IP-C group); 3) IP with perfusion buffer containing glibenclamide (IP-G group); and 4) IP with perfusion buffer containing mitiglinide (IP-M group). The protocol for the non-IP group consisted of 21 minutes of aerobic perfusion before 10 minutes of ischemia. In the other 3 groups (IP groups), there were 3 cycles of 2-minute ischemia followed by 5 minutes of reperfusion before 10 minutes of ischemia. The IP-C group had a significantly shorter rVT duration than the non-IP group (4.4 +/- 1.8 minutes versus 14.3 +/- 2.5 minutes; P < 0.05). rVT duration was the shortest in the IP-M group (3.9 +/- 1.0 minutes), but among the longest in the IP-G group (14.0 +/- 2.6 minutes). In conclusion, mitiglinide preserved the cardioprotective effect of IP, however, glibenclamide abolished this beneficial effect. Therefore, mitiglinide may offer a long-term benefit for myocardial ischemia in diabetic patients.