Cardiovascular effects of antidiabetic agents: focus on blood pressure effects of incretin-based therapies. ACTA ACUST UNITED AC. 2012;6:163-168. [PMID: 22433315 DOI: 10.1016/j.jash.2012.02.003]

Structural and Electrical Remodeling of the Sinoatrial Node in Diabetes: New Dimensions and Perspectives

The sinoatrial node (SAN) is composed of highly specialized cells that mandate the spontaneous beating of the heart through self-generation of an action potential (AP). Despite this automaticity, the SAN is under the modulation of the autonomic nervous system (ANS). In diabetes mellitus (DM), heart rate variability (HRV) manifests as a hallmark of diabetic cardiomyopathy. This is paralleled by an impaired regulation of the ANS, and by a pathological remodeling of the pacemaker structure and function. The direct effect of diabetes on the molecular signatures underscoring this pathology remains ill-defined. The recent focus on the electrical currents of the SAN in diabetes revealed a repressed firing rate of the AP and an elongation of its tracing, along with conduction abnormalities and contractile failure. These changes are blamed on the decreased expression of ion transporters and cell-cell communication ports at the SAN (i.e., HCN4, calcium and potassium channels, connexins 40, 45, and 46) which further promotes arrhythmias. Molecular analysis crystallized the RGS4 (regulator of potassium currents), mitochondrial thioredoxin-2 (reactive oxygen species; ROS scavenger), and the calcium-dependent calmodulin kinase II (CaMKII) as metabolic culprits of relaying the pathological remodeling of the SAN cells (SANCs) structure and function. A special attention is given to the oxidation of CaMKII and the generation of ROS that induce cell damage and apoptosis of diabetic SANCs. Consequently, the diabetic SAN contains a reduced number of cells with significant infiltration of fibrotic tissues that further delay the conduction of the AP between the SANCs. Failure of a genuine generation of AP and conduction of their derivative waves to the neighboring atrial myocardium may also occur as a result of the anti-diabetic regiment (both acute and/or chronic treatments). All together, these changes pose a challenge in the field of cardiology and call for further investigations to understand the etiology of the structural/functional remodeling of the SANCs in diabetes. Such an understanding may lead to more adequate therapies that can optimize glycemic control and improve health-related outcomes in patients with diabetes.

Cellular mechanisms and recommended drug-based therapeutic options in diabetic cardiomyopathy

Diabetes mellitus (DM) is associated with a specific cardiac phenotype characterized by structural and functional alterations. This so-called diabetic cardiomyopathy (DM CM) is clinically relevant as patients with DM show high incidence of heart failure. Mechanistically, several parameters interact on the cardiomyocyte level leading to increased inflammation, apoptosis, reactive oxygen species and altered calcium signaling. This in turn provokes functional myocardial changes that might inter alia play into the worsened clinical outcome in DM patients. Therefore, efficient therapeutic options are urgently needed. This review focuses on mechanistic effects of currently recommended antidiabetic treatment and heart failure therapy for DM CM.

An up-to-date evaluation of alogliptin benzoate for the treatment of type 2 diabetes

Introduction: A growth in the market for anti-diabetic drugs, along with an ever-increasing population suffering from type 2 diabetes mellitus (T2DM), requires a critical re-evaluation of anti-diabetic drugs used for a long time, in order to provide up-to-date practical prescribing information for clinicians. Alogliptin benzoate was firstly approved in 2010 in Japan for T2DM, both as a monotherapy or in combination with other anti-diabetic drugs. Areas covered: This article provides a comprehensive review of the latest data on alogliptin benzoate, including hypoglycemic activity and safety. Expert opinion: The cumulative evidence for alogliptin benzoate is robust with regards to glycemic efficacy and safety. Low hypoglycemia risks and weight changes support its consideration as a first-line medication for T2DM, either as a monotherapy or in combination therapy with other anti-diabetic drugs such as metformin. Ongoing trials will look to better analyze and address its safety and efficacy in pediatric patients and expand our clinical knowledge of this medication.

Fenugreek seed extract ameliorates cognitive deficits in streptozotocin-induced diabetic rats

Background Natural medicinal plants have been the focus of current research for developing neuroprotective agents to be used in the diabetes-linked cognitive dysfunction. Trigonella foenum-graecum seeds (known as fenugreek, methi in Hindi), is a well-known traditional medicinal herb and possesses anti-diabetic, anti-oxidant, and anti-inflammatory properties. Purpose This study was undertaken to explore the ameliorative effects of T. foenum-graecum seed extract on diabetes-induced cognitive dysfunction. Methods Experimental diabetes was induced by administering a single dose of streptozotocin (60 mg/kg) through intraperitoneal dose. Cognitive function was assessed using a T-maze and the Morris water maze. Lipid peroxidation levels and oxidative stress in the hippocampus was measured. Quantification of hippocampal CA1 and CA3 regions was done using cresyl violet stain. Results Diabetic rats demonstrated learning and memory impairment, which was evident from poor performance in behavioral tasks, i.e. T-maze and Morris water maze tasks. Learning and memory impairment in diabetic animals is associated with increased blood glucose levels, increased oxidative stress in the hippocampus and decreased number of neurons in the CA1 and CA3 regions of the hippocampus. The diabetic rats administered with T. foenum-graecum showed improved performance in behavioral tasks, and these changes were associated with decreased blood glucose levels, decreased oxidative stress in the hippocampus, and decreased neuronal loss from the CA1 and CA3 regions of the hippocampus. Conclusion In conclusion, administration of T. foenum-graecum seed extract ameliorates diabetes-linked cognitive dysfunction in rats by decreasing blood glucose levels, reducing lipid peroxidation and oxidative stress in the hippocampus, and preventing neuronal loss from the hippocampus.

AMPK is associated with the beneficial effects of antidiabetic agents on cardiovascular diseases

Diabetics have higher morbidity and mortality in cardiovascular disease (CVD). A variety of antidiabetic agents are available for clinical choice. Cardiovascular (CV) safety assessment of these agents is crucial in addition to hypoglycemic effect before clinical prescription. Adenosine 5'-monophosphate-activated protein kinase (AMPK) is an important cell energy sensor, which plays an important role in regulating myocardial energy metabolism, reducing ischemia and ischemia/reperfusion (I/R) injury, improving heart failure (HF) and ventricular remodeling, ameliorating vascular endothelial dysfunction, antichronic inflammation, anti-apoptosis, and regulating autophagy. In this review, we summarized the effects of antidiabetic agents to CVD according to basic and clinical research evidence and put emphasis on whether these agents can play roles in CV system through AMPK-dependent signaling pathways. Metformin has displayed definite CV benefits related to AMPK. Sodium-glucose cotransporter 2 inhibitors also demonstrate sufficient clinical evidence for CV protection, but the mechanisms need further exploration. Glucagon-likepeptide1 analogs, dipeptidyl peptidase-4 inhibitors, α-glucosidase inhibitors and thiazolidinediones also show some AMPK-dependent CV benefits. Sulfonylureas and meglitinides may be unfavorable to CV system. AMPK is becoming a promising target for the treatment of diabetes, metabolic syndrome and CVD. But there are still some questions to be answered.

Long-term effects of sitagliptin in patients with type 2 diabetes mellitus and hypertension: results from the PROLOGUE study

BACKGROUND

The effects of sitagliptin in patients with type 2 diabetes mellitus and hypertension are unclear. Therefore, we evaluated the long-term effects of sitagliptin in those patients.

METHODS

In the PROLOGUE study, 365 patients were diagnosed as type 2 diabetes mellitus and hypertension, and 189 patients in the sitagliptin group, 176 patients in the conventional group. Fasting blood glucose (FBG), HbA1c, systolic pressure (SP), diastolic pressure (DP), serum urea nitrogen (BUN) and serum creatinine (SCR) were measured at the beginning of the study and after 12 and 24 months of treatment.

RESULTS

FBS and HbA1c levels were not significantly decreased after treatment [12 months: OR: -3.1, 95% CI (-11.3, 5.0); OR: 0.1, 95% CI (0.0, 0.3); 24 months: OR: -0.1, 95% CI (-9.1, 8.8); OR: 0.1, 95% CI (0.0, 0.3), respectively]. BP and DP levels were not significantly decreased after treatment (12 months: OR: 0.9, 95% CI (-2.8, 4.6); OR: 0.6, 95% CI (-2.0, 3.2); 24 months: OR: -0.5, 95% CI (-4.2, 3.1); OR: -1.6, 95% CI (-41, 0.9), respectively]. Furthermore, BUN and SCR levels were not significantly decreased after treatment (12 months: OR: 0.0, 95%CI (-1.2, 1.2); OR: 0.0, 95% CI (-0.1, 0.0); 24 months: OR: 0.4, 95% CI (-1.0, 1.8); OR: -80.8, 95% CI (-201.3, 39.8), respectively]. After adjusting for confounding factors, our results did not change.

CONCLUSIONS

In our study, there was no evidence that treatment with sitagliptin can improve FBS, BP, DP, BUN or SCR in patients with type 2 diabetes mellitus and hypertension.

TRIAL REGISTRATION

University Hospital Medical Information Network Clinical Trials Registry UMIN000004490.

Effects of Vildagliptin and Metformin on Blood Pressure and Heart Rate Responses to Small Intestinal Glucose in Type 2 Diabetes

OBJECTIVE

To evaluate effects of vildagliptin and metformin on blood pressure (BP) and heart rate (HR) responses to intraduodenal (ID) glucose in diet-controlled type 2 diabetes.

RESEARCH DESIGN AND METHODS

Study A compared vildagliptin (50 mg) and placebo, given 60 min before a 120-min ID glucose infusion at 2 or 4 kcal/min (ID2 or ID4) in 16 patients. Study B compared metformin (850 mg) and placebo, given 30 min before ID2 over 120 min in 9 patients.

RESULTS

Systolic (P = 0.002) and diastolic (P < 0.001) BP were lower and HR greater (P = 0.005) after vildagliptin compared with placebo, without interaction between vildagliptin and the glucose infusion rate. In contrast, HR was greater after metformin than placebo (P < 0.001), without any difference in systolic or diastolic BP.

CONCLUSIONS

Vildagliptin reduces BP and increases HR, whereas metformin increases HR without affecting BP during ID glucose infusion in type 2 diabetes. These distinct cardiovascular profiles during enteral nutrient exposure may have implications for postprandial hypotension.

Effects of dipeptidyl peptidase-4 inhibitors on blood pressure in patients with type 2 diabetes: A systematic review and meta-analysis

This review was undertaken to assess the effects of dipeptidyl peptidase-4 (DPP-4) inhibitors on blood pressure (BP) in patients with type 2 diabetes (T2DM). We searched three main databases (PubMed, Web of Science, and Scopus) for relevant articles. Randomized controlled trials which reported BP changes from baseline to study endpoint in patients with T2DM receiving treatment of DPP-4 inhibitors were included for analysis. Random effects models were used to measure the mean differences with 95% confidence intervals (CIs). Fifteen trials involving 5636 participants were identified. When compared with placebo or nontreatment, DPP-4 inhibitors achieved greater reductions for both SBP (mean difference, -3.04  mmHg; 95% CI, -4.37 to -1.72; P < 0.00001) and DBP (mean difference, -1.47  mmHg; 95% CI, -1.79 to -1.15; P < 0.00001). But the BP-lowering effects of sodium-glucose cotransporter 2 inhibitors were more significant than those of DPP-4 inhibitors for both SBP (mean difference, 4.44  mmHg; 95% CI, 2.67-6.22; P < 0.00001) and DBP (mean difference, 2.15  mmHg; 95% CI, 1.08-3.21; P < 0.00001). No significant differences in BP changes were shown between DPP-4 inhibitors with other antidiabetic agents including glucagon-like peptide 1 receptor agonists, pioglitazone, sulphonylureas, metformin, and α-glucosidase inhibitors. DPP-4 inhibitors may exert modest BP-lowering effects compared with placebo or nontreatment for patients with T2DM, but no significant BP improvement was seen with this drug class when compared with other antidiabetic medications.

Angiotensin-Converting Enzyme Inhibitor Use and Major Cardiovascular Outcomes in Type 2 Diabetes Mellitus Treated With the Dipeptidyl Peptidase 4 Inhibitor Alogliptin

Activation of the sympathetic nervous system when there is dipeptidyl peptidase 4 inhibition in the presence of high-dose angiotensin-converting enzyme (ACE) inhibition has led to concerns of potential increases in cardiovascular events when the 2 classes of drugs are coadministered. We evaluated cardiovascular outcomes from the EXAMINE (Examination of Cardiovascular Outcomes With Alogliptin versus Standard of Care) trial according to ACE inhibitor use. Patients with type 2 diabetes mellitus and a recent acute coronary syndrome were randomly assigned to receive the dipeptidyl peptidase 4 inhibitor alogliptin or placebo added to existing antihyperglycemic and cardiovascular prophylactic therapies. Risks of adjudicated cardiovascular death, nonfatal myocardial infarction and stroke, and hospitalized heart failure were analyzed using a Cox proportional hazards model in patients according to ACE inhibitor use and dose. There were 3323 (62%) EXAMINE patients treated with an ACE inhibitor (1681 on alogliptin and 1642 on placebo). The composite rates of cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke were comparable for alogliptin and placebo with ACE inhibitor (11.4% versus 11.8%; hazard ratio, 0.97; 95% confidence interval, 0.79–1.19; P =0.76) and without ACE inhibitor use (11.2% versus 11.9%; hazard ratio, 0.94; 95% confidence interval, 0.73–1.21; P =0.62). Composite rates for cardiovascular death and heart failure in patients on ACE inhibitor occurred in 6.8% of patients on alogliptin versus 7.2% on placebo (hazard ratio, 0.93; 95% confidence interval, 0.72–1.2; P =0.57). There were no differences for these end points nor for blood pressure or heart rate in patients on higher doses of ACE inhibitor. Cardiovascular outcomes were similar for alogliptin and placebo in patients with type 2 diabetes mellitus and coronary disease treated with ACE inhibitors.

The dipeptidyl peptidase inhibitor linagliptin and the angiotensin II receptor blocker telmisartan show renal benefit by different pathways in rats with 5/6 nephrectomy

Dipeptidyl peptidase (DPP)-4 inhibitors delay chronic kidney disease (CKD) progression in experimental diabetic nephropathy in a glucose-independent manner. Here we compared the effects of the DPP-4 inhibitor linagliptin versus telmisartan in preventing CKD progression in non-diabetic rats with 5/6 nephrectomy. Animals were allocated to 1 of 4 groups: sham operated plus placebo; 5/6 nephrectomy plus placebo; 5/6 nephrectomy plus linagliptin; and 5/6 nephrectomy plus telmisartan. Interstitial fibrosis was significantly decreased by 48% with linagliptin but a non-significant 24% with telmisartan versus placebo. The urine albumin-to-creatinine ratio was significantly decreased by 66% with linagliptin and 92% with telmisartan versus placebo. Blood pressure was significantly lowered by telmisartan, but it was not affected by linagliptin. As shown by mass spectrometry, the number of altered peptide signals for linagliptin in plasma was 552 and 320 in the kidney. For telmisartan, there were 108 peptide changes in plasma and 363 in the kidney versus placebo. Linagliptin up-regulated peptides derived from collagen type I, apolipoprotein C1, and heterogeneous nuclear ribonucleoproteins A2/B1, a potential downstream target of atrial natriuretic peptide, whereas telmisartan up-regulated angiotensin II. A second study was conducted to confirm these findings in 5/6 nephrectomy wild-type and genetically deficient DPP-4 rats treated with linagliptin or placebo. Linagliptin therapy in wild-type rats was as effective as DPP-4 genetic deficiency in terms of albuminuria reduction. Thus, linagliptin showed comparable efficacy to telmisartan in preventing CKD progression in non-diabetic rats with 5/6 nephrectomy. However, the underlying pathways seem to be different.

Pleiotropic effects of the dipeptidylpeptidase-4 inhibitors on the cardiovascular system

Dipeptidylpeptidase-4 (DPP-4) is a ubiquitously expressed transmembrane protein that removes NH2-terminal dipeptides from various substrate hormones, chemokines, neuropeptides, and growth factors. Two known substrates of DPP-4 include the incretin hormones glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide, which are secreted by enteroendocrine cells in response to postprandial hyperglycemia and account for 60–70% of postprandial insulin secretion. DPP-4 inhibitors (DPP-4i) block degradation of GLP-1 and gastric inhibitory peptide, extend their insulinotropic effect, and improve glycemia. Since 2006, several DPP-4i have become available for treatment of type 2 diabetes mellitus. Clinical trials confirm that DPP-4i raises GLP-1 levels in plasma and improves glycemia with very low risk for hypoglycemia and other side effects. Recent studies also suggest that DPP-4i confers cardiovascular and kidney protection, beyond glycemic control, which may reduce the risk for further development of the multiple comorbidities associated with obesity/type 2 diabetes mellitus, including hypertension and cardiovascular disease (CVD) and kidney disease. The notion that DPP-4i may improve CVD outcomes by mechanisms beyond glycemic control is due to both GLP-1-dependent and GLP-1-independent effects. The CVD protective effects by DPP-4i result from multiple factors including insulin resistance, oxidative stress, dyslipidemia, adipose tissue dysfunction, dysfunctional immunity, and antiapoptotic properties of these agents in the heart and vasculature. This review focuses on cellular and molecular mechanisms mediating the CVD protective effects of DPP-4i beyond favorable effects on glycemic control.

Comparison of effects of sitagliptin and voglibose on left ventricular diastolic dysfunction in patients with type 2 diabetes: results of the 3D trial

Background

Left ventricular (LV) diastolic dysfunction is frequently observed in patients with type 2 diabetes. Dipeptidyl peptidase-4 inhibitor (DPP-4i) attenuates postprandial hyperglycemia (PPH) and may have cardio-protective effects. It remains unclear whether DPP-4i improves LV diastolic function in patients with type 2 diabetes, and, if so, it is attributable to the attenuation of PPH or to a direct cardiac effect of DPP-4i. We compared the effects of the DPP-4i, sitagliptin, and the alpha-glucosidase inhibitor, voglibose, on LV diastolic function in patients with type 2 diabetes.

Methods

We conducted a prospective, randomized, open-label, multicenter study of 100 diabetic patients with LV diastolic dysfunction. Patients received sitagliptin (50 mg/day) or voglibose (0.6 mg/day). The primary endpoints were changes in the e’ velocity and E/e’ ratio from baseline to 24 weeks later. The secondary efficacy measures included HbA1c, GLP-1, lipid profiles, oxidative stress markers and inflammatory markers.

Results

The study was completed with 40 patients in the sitagliptin group and 40 patients in the voglibose group. There were no significant changes in the e’ velocity and E/e’ ratio from baseline to 24 weeks later in both groups. However, analysis of covariance demonstrated that pioglitazone use is an independent factor associated with changes in the e’ and E/e’ ratio. Among patients not using pioglitazone, e’ increased and the E/e’ ratio decreased in both the sitagliptin and voglibose groups. GLP-1 level increased from baseline to 24 weeks later only in the sitagliptin group (4.8 ± 4.7 vs. 7.3 ± 5.5 pmol/L, p < 0.05). The reductions in HbA1c and body weight were significantly greater in the sitagliptin group than in the voglibose group (−0.7 ± 0.6 % vs. −0.3 ± 0.4, p < 0.005; −1.3 ± 3.2 kg vs. 0.4 ± 2.8 kg, p < 0.05, respectively). There were no changes in lipid profiles and inflammatory markers in both groups.

Conclusions

Our trial showed that sitagliptin reduces HbA1c levels more greatly than voglibose does, but that neither was associated with improvement in the echocardiographic parameters of LV diastolic function in patients with diabetes.

Trial registration

Registered at http://www.umin.ac.jp under UMIN000003784

Implications of incretin-based therapies on cardiovascular disease

BACKGROUND

Incretin-based therapies offer another treatment option for patients with type 2 diabetes. Agents that provide glycaemic control in addition to attenuating cardiovascular disease (CVD) risk factors are important for diabetes management. This review will focus on the off-target effects of incretin-based therapies on CVD risk factors [body weight, blood pressure (BP), lipid profile and albuminuria], major adverse cardiovascular events (MACE), heart failure (HF) and beta-cell preservation.

METHODS

A literature search was conducted to identify English-language publications for incretin-based therapies evaluating the following off-target end-points: body weight, BP, lipid profile, albuminuria, MACE, HF and beta-cell function. Randomised controlled trials (RCTs) were prioritised as the primary source of information.

RESULTS

Overall, incretin-based therapies have shown beneficial effects on CVD risk factors, and glucagon-like peptide 1 (GLP-1) receptor agonists appear to have a more pronounced effect compared with dipeptidyl peptidase-4 inhibitors. RCTs are being conducted to determine if these positive effects on CVD risk factors translate to a reduction in MACE. To date, these studies have not shown an increase in MACE. A signal of increased hospitalisations for HF was observed with saxagliptin, warranting continued evaluation and vigilance in high-risk patients. In addition, incretin-based therapies have shown positive effects on measures of beta-cell function supporting their durability in the management of diabetes.

CONCLUSIONS

Incretin-based therapies are an important treatment option for patients with type 2 diabetes, offering beneficial effects on CVD risk factors without increasing MACE.

Effects of sodium-glucose co-transporter 2 inhibitors on blood pressure: a systematic review and meta-analysis

Sodium-glucose co-transporter 2 (SGLT2) inhibitors represent a new class of antihyperglycemic agents that block renal sodium and glucose reabsorption and may reduce blood pressure (BP). We assessed the BP lowering ability of these agents using meta-analytic techniques. PubMed, SCOPUS, and Cochrane Central were searched through October 2013. We included fully published randomized controlled trials (RCTs) that evaluated SGLT2 inhibitors in patients with type-2 diabetes mellitus and reported change in systolic and/or diastolic BP. Subgroup analyses were performed for placebo-controlled trials and those with active controls. We also conducted meta-regression to assess for a dose-response effect, and whether baseline BP, changes in body weight, heart rate, and hematocrit were associated with the BP effects. Twenty-seven RCTs (n = 12,960 participants) were included. SGLT2 inhibitors significantly reduced both systolic BP (weighted mean difference, -4.0 mm Hg; 95% confidence interval, -4.4 to -3.5) and diastolic BP (weighted mean difference, -1.6 mm Hg; 95% confidence interval, -1.9 to -1.3) from baseline. Only canagliflozin had a significant dose-response relationship with SBP (P = .008). Significant reductions in body weight and hematocrit were seen with the SGLTs. SGLTs had no significant effect on the incidence of orthostatic hypotension (P > .05). SGLT2 inhibitors significantly reduce BP in patients with type 2 diabetes.

Cardiovascular effects of dipeptidyl peptidase-4 inhibitors: from risk factors to clinical outcomes

Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) are oral incretin-based glucose-lowering agents with proven efficacy and safety in the management of type 2 diabetes mellitus (T2DM). In addition, preclinical data and mechanistic studies suggest a possible additional non-glycemic beneficial action on blood vessels and the heart, via both glucagon-like peptide-1-dependent and glucagon-like peptide-1-independent effects. As a matter of fact, DPP-4 inhibitors improve several cardiovascular risk factors: they improve glucose control (mainly by reducing the risk of postprandial hyperglycemia) and are weight neutral; may lower blood pressure somewhat; improve postprandial (and even fasting) lipemia; reduce inflammatory markers; diminish oxidative stress; improve endothelial function; and reduce platelet aggregation in patients with T2DM. In addition, positive effects on the myocardium have been described in patients with ischemic heart disease. Results of post hoc analyses of phase 2/3 controlled trials suggest a possible cardioprotective effect with a trend (sometimes significant) toward lower incidence of major cardiovascular events with sitagliptin, vildagliptin, saxagliptin, linagliptin, or alogliptin compared with placebo or other active glucose-lowering agents. However, the definite relationship between DPP-4 inhibition and better cardiovascular outcomes remains to be proven. Major prospective clinical trials involving various DPP-4 inhibitors with predefined cardiovascular outcomes are under way in patients with T2DM and a high-risk cardiovascular profile: the Sitagliptin Cardiovascular Outcome Study (TECOS) on sitagliptin, the Saxagliptin Assessment of Vascular Outcomes Recorded in Patients With Diabetes Mellitus-Thrombolysis in Myocardial Infarction (SAVOR-TIMI) 53 trial on saxagliptin, the Cardiovascular Outcomes Study of Alogliptin in Subjects With Type 2 Diabetes and Acute Coronary Syndrome (EXAMINE) trial on alogliptin, and the Cardiovascular Outcome Study of Linagliptin Versus Glimepiride in Patients With Type 2 Diabetes (CAROLINA) on linagliptin. If these trials confirm that a DPP-4 inhibitor can reduce the cardiovascular burden of T2DM, it would be major progress that would dramatically influence the management of the disease.

Cardiovascular safety of the dipetidyl peptidase-4 inhibitor alogliptin in type 2 diabetes mellitus

AIM

As there have been concerns that some classes or agents for the treatment of type 2 diabetes may increase CV risk, we evaluated the cardiovascular profile of the dipeptidyl peptidase-4 inhibitor alogliptin.

METHODS

We evaluated the incidence of CV events in patients treated with alogliptin, placebo or comparator antihyperglycaemic drugs in the clinical trial database for alogliptin using the composite major adverse cardiovascular event (MACE) endpoints of CV death, non-fatal myocardial infarction and non-fatal stroke.

RESULTS

The pooled analysis included 4168 patients exposed to alogliptin 12.5 and 25 mg daily for 2023 patient-years compared to 691 patients treated with placebo for 263 patient-years and 1169 patients treated with other antidiabetic agents (metformin, sulfonylureas and thiazolidinediones) for 703 patient-years. CV events were adjudicated by an expert endpoint committee blinded to treatment allocation. The incidence rates of the combined MACE were not significantly different between patients treated with alogliptin and comparator therapies (hazard ratio=0.635, 95% confidence interval, 0.0, 1.41). Additionally, other types of serious CV events were not significantly different between patients treated with alogliptin and comparator therapies.

CONCLUSION

These analyses have not shown a signal of increased CV risk with alogliptin in patients with type 2 diabetes. Future results from the adequately powered EXAMINE trial will definitively assess the CV safety profile of aloglipin in patients with type 2 diabetes mellitus.

Cardiovascular effects of gliptins

Dipeptidyl peptidase 4 (DPP-4) inhibitors (commonly referred to as gliptins) are a novel class of oral antihyperglycaemic agents with demonstrated efficacy in the treatment of type 2 diabetes mellitus (T2DM). Preclinical data and mechanistic studies have indicated a possible beneficial action on blood vessels and the heart, via both glucagon-like peptide 1 (GLP-1)-dependent and GLP-1-independent effects. DPP-4 inhibition increases the concentration of many peptides with potential vasoactive and cardioprotective effects. Clinically, DPP-4 inhibitors improve several risk factors in patients with T2DM. They improve blood glucose control (mainly by reducing postprandial glycaemia), are weight neutral (or even induce modest weight loss), lower blood pressure, improve postprandial lipaemia, reduce inflammatory markers, diminish oxidative stress, and improve endothelial function. Some positive effects on the heart have also been described in patients with ischaemic heart disease or congestive heart failure, although their clinical relevance requires further investigation. Post-hoc analyses of phase II-III, controlled trials suggest a possible cardioprotective effect with a trend for a lower incidence of major cardiovascular events with gliptins than with placebo or active agents. However, the actual relationship between DPP-4 inhibition and cardiovascular outcomes remains to be proven. Major prospective clinical trials with predefined cardiovascular outcomes and involving various DPP-4 inhibitors are now underway in patients with T2DM and a high-risk cardiovascular profile.

The Effects of Cinnamomum Cassia on Blood Glucose Values are Greater than those of Dietary Changes Alone

Eighteen type II diabetics (9 women and 9 men) participated in a 12-week trial that consisted of 2 parts, a 3-week control phase followed by a 9-week experimental phase where half of the subjects received 1000 mg of Cinnamomum cassia while the other half received 1000 mg of a placebo pill. All of the subjects that were in the cinnamon group had a statistically significant decrease in their blood sugar levels with a P-value of 3.915 × 10⁻¹⁰. The subjects in the cinnamon group had an average overall decrease in their blood sugar levels of about 30 mg/dL, which is comparable to oral medications available for diabetes. All subjects were educated on appropriate diabetic diets and maintained that diet for the entire 12 week study. Greater decreases in blood glucose values were observed in patients using the cinnamon compared to those using the dietary changes alone.

Diabetes-related alterations in the enteric nervous system and its microenvironment

Gastric intestinal symptoms common among diabetic patients are often caused by intestinal motility abnormalities related to enteric neuropathy. It has recently been demonstrated that the nitrergic subpopulation of myenteric neurons are especially susceptible to the development of diabetic neuropathy. Additionally, different susceptibility of nitrergic neurons located in different intestinal segments to diabetic damage and their different levels of responsiveness to insulin treatment have been revealed. These findings indicate the importance of the neuronal microenvironment in the pathogenesis of diabetic nitrergic neuropathy. The main focus of this review therefore was to summarize recent advances related to the diabetes-related selective nitrergic neuropathy and associated motility disturbances. Special attention was given to the findings on capillary endothelium and enteric glial cells. Growing evidence indicates that capillary endothelium adjacent to the myenteric ganglia and enteric glial cells surrounding them are determinative in establishing the ganglionic microenvironment. Additionally, recent advances in the development of new strategies to improve glycemic control in type 1 and type 2 diabetes mellitus are also considered in this review. Finally, looking to the future, the recent and promising results of metagenomics for the characterization of the gut microbiome in health and disease such as diabetes are highlighted.

Incretin hormones as immunomodulators of atherosclerosis

Atherosclerosis results from endothelial cell dysfunction and inflammatory processes affecting both macro- and microvasculature which are involved in vascular diabetic complications. Glucagon-like peptide-1 (GLP-1) is an incretin hormone responsible for amplification of insulin secretion when nutrients are given orally as opposed to intravenously and it retains its insulinotropic activity in patients with type 2 diabetes mellitus (T2D). GLP-1 based therapies, such as GLP-1 receptor (GLP-1R) agonists and inhibitors of dipeptidyl peptidase-4, an enzyme that degrades endogenous GLP-1 are routinely used to treat patients with T2D. Recent experimental model studies have established that GLP-1R mRNA is widely expressed in several immune cells. Moreover, its activation contributes to the regulation of both thymocyte and peripheral T cells proliferation and is involved in the maintenance of peripheral regulatory T cells. GLP-1R is also expressed in endothelial and smooth muscle cells. The effect of incretin hormones on atherosclerogenesis have recently been studied in animal models of apolipoprotein E-deficient mice (apoE(-/-)). These studies have demonstrated that treatment with incretin hormones or related compounds suppresses the progression of atherosclerosis and macrophage infiltration in the arterial wall as well as a marked anti-oxidative and anti-inflammatory effect on endothelial cells. This effect may have a major impact on the attenuation of atherosclerosis and may help in the design of new therapies for cardiovascular disease in patients with type 2 diabetes.