Cardiovascular biology of the incretin system

The identification of novel proteins that interact with the GLP-1 receptor and restrain its activity

Glucagon-like peptide 1 receptor (GLP-1R) controls diverse physiological functions in tissues including the pancreatic islets, brain, and heart. To understand the mechanisms that control glucagon-like peptide 1 (GLP-1) signaling better, we sought to identify proteins that interact with the GLP-1R using a membrane-based split ubiquitin yeast two-hybrid (MYTH) assay. A screen of a human fetal brain cDNA prey library with an unliganded human GLP-1R as bait in yeast revealed 38 novel interactor protein candidates. These interactions were confirmed in mammalian Chinese hamster ovarian cells by coimmunoprecipitation. Immunofluorescence was used to show subcellular colocalization of the interactors with GLP-1R. Cluster analysis revealed that the interactors were primarily associated with signal transduction, metabolism, and cell development. When coexpressed with the GLP-1R in Chinese hamster ovarian cells, 15 interactors significantly altered GLP-1-induced cAMP accumulation. Surprisingly, all 15 proteins inhibited GLP-1-activated cAMP. Given GLP-1's prominent role as an incretin, we then focused on 3 novel interactors, SLC15A4, APLP1, and AP2M1, because they are highly expressed and localized to the membrane in mouse insulinoma β-cells. Small interfering RNA-mediated knockdown of each candidate gene significantly enhanced GLP-1-induced insulin secretion. In conclusion, we have generated a novel GLP-1R-protein interactome, identifying several interactors that suppress GLP-1R signaling. We suggest that the inhibition of these interactors may serve as a novel strategy to enhance GLP-1R activity.

Advances in pharmacologic therapies for type 2 diabetes

Type 2 diabetes (T2DM) is a multi-causal, heterogeneous and progressive cardiometabolic condition, with an increasing prevalence worldwide. T2DM is associated with multiple comorbidities that may impact patients' quality of life. Treatment is multifactorial, but pharmacologic treatment of hyperglycemia is still regarded as the mainstay of diabetes management. Current established therapies include metformin, sulfonylurea agents and insulin, the long-term use of which was associated with reduced micro- and macrovascular events in the United Kingdom Prospective Diabetes Study. Despite major recent advances in diabetes care, a large proportion of patients remain in poor glycemic control, necessitating the development of new therapeutic options. The recently published position statement of the American Diabetes Association and European Association for the Study of Diabetes for the management of hyperglycemia in T2DM has accommodated this wider range of therapy choices, as it is less prescriptive and advocates an individualized treatment approach, taking into account many relevant patient- and disease-related factors. This review summarizes the updates on various established agents as well as the recent developments with regard to incretin-based therapies, inhibitors of the renal tubular sodium-glucose-linked-transporter-2 and ultra-long acting basal insulin formulations.

Extra-pancreatic effects of incretin-based therapies: potential benefit for cardiovascular-risk management in type 2 diabetes

Development of cardiovascular disease is one of the major complications of type 2 diabetes mellitus (T2DM). The chronic hyperglycaemic state is often accompanied by dyslipidaemia, hypertension, low-grade systemic inflammation and oxidative stress which collectively result in a high risk of micro- and macrovascular complications. Current glucose-lowering agents do not sufficiently address fore-mentioned macrovascular-risk factors. Recently, new therapeutic agents were introduced, based on the incretin hormone glucagon-like peptide-1 (GLP-1), that is, the GLP-1 receptor agonists (GLP-1RA) and dipeptidyl-peptidase 4 (DPP-4) inhibitors. Beside its effect on pancreatic insulin secretion, GLP-1 exerts several extra-pancreatic effects such as slowing down gastric emptying, promoting satiety and reducing food intake and weight loss. Also, GLP-1 and GLP-1RA were shown to improve cardiovascular-risk profiles, by reducing body fat content, blood pressure, circulating lipids and inflammatory markers in patients with T2DM. This review summarizes the presently known evidence with regard to extra-pancreatic effects of the incretin-based agents, focusing on the actions that improve the cardiovascular-risk profile. We present available data from clinical trials of at least 24 week duration, but also findings from small-sized clinical 'proof of principle' studies. We conclude that GLP-1 RA and to a lesser extent DPP-4 inhibitors are promising agents with regard to their effects on body weight, blood pressure and lipids, which collectively ameliorate the cardiovascular-risk profile and as such may have added value in the treatment of T2DM. However, large-sized long-term outcome studies are warranted to show the true added value of these agents in the treatment of patients with T2DM.

A critical analysis of the clinical use of incretin-based therapies: The benefits by far outweigh the potential risks

There is no question that incretin-based glucose-lowering medications have proven to be effective glucose-lowering agents. Glucagon-like peptide 1 (GLP-1) receptor agonists demonstrate an efficacy comparable to insulin treatment and appear to do so with significant effects to promote weight loss with minimal hypoglycemia. In addition, there are significant data with dipeptidyl peptidase 4 (DPP-4) inhibitors showing efficacy comparable to sulfonylureas but with weight neutral effects and reduced risk for hypoglycemia. However, over the recent past there have been concerns regarding the long-term consequences of using such therapies, and the issues raised are in regard to the potential of both classes to promote acute pancreatitis, to initiate histological changes suggesting chronic pancreatitis including associated preneoplastic lesions, and potentially, in the long run, pancreatic cancer. Other issues relate to an increase in thyroid cancer. There are clearly conflicting data that have been presented in preclinical studies and in epidemiologic studies. To provide an understanding of both sides of the argument, we provide a discussion of this topic as part of this two-part point-counterpoint narrative. In the point narrative preceding the counterpoint narrative below, Dr. Butler and colleagues provide their opinion and review of the data to date and that we need to reconsider use of incretin-based therapies because of the growing concern of potential risk and based on a clearer understanding of the mechanism of action. In the counterpoint narrative provided below, Dr. Nauck provides a defense of incretin-based therapies and that benefits clearly outweigh any concern of risk.

Emerging combinatorial hormone therapies for the treatment of obesity and T2DM

Peptide hormones and proteins control body weight and glucose homeostasis by engaging peripheral and central metabolic signalling pathways responsible for the maintenance of body weight and euglycaemia. The development of obesity, often in association with type 2 diabetes mellitus (T2DM), reflects a dysregulation of metabolic, anorectic and orexigenic pathways in multiple organs. Notably, therapeutic attempts to normalize body weight and glycaemia with single agents alone have generally been disappointing. The success of bariatric surgery, together with emerging data from preclinical studies, illustrates the rationale and feasibility of using two or more agonists, or single co-agonists, for the treatment of obesity and T2DM. Here, we review advances in the science of co-agonist therapy, and highlight promising areas and challenges in co-agonist development. We describe mechanisms of action for combinations of glucagon-like peptide 1, glucagon, gastric inhibitory polypeptide, gastrin, islet amyloid polypeptide and leptin, which enhance weight loss whilst preserving glucoregulatory efficacy in experimental models of obesity and T2DM. Although substantial progress has been achieved in preclinical studies, the putative success and safety of co-agonist therapy for the treatment of patients with obesity and T2DM remains uncertain and requires extensive additional clinical validation.

Cardiovascular outcome trials in type 2 diabetes and the sulphonylurea controversy: rationale for the active-comparator CAROLINA trial

Sulphonylureas (SUs) are widely used glucose-lowering agents in type 2 diabetes mellitus (T2DM) with apparent declining efficacy over time. Concerns have been raised from observational retrospective studies on the cardiovascular (CV) safety of SUs but there are few long-term data on CV outcomes from randomized controlled trials (RCTs) involving the use of this class of agents. Most of the observational studies and registry data are conflicting and vary with study population and methodology used for analyses. To address the SU controversy, we reviewed the recently published literature (until end of the year 2011) to evaluate the impact of SUs on CV outcomes in modern, longer-term (≥72 weeks) RCTs where they were compared in a head-to-head fashion versus an active comparator or were used as part of a treatment strategy. We identified 15 trials and found no report of an increase in the incidence of CV events with the use of SUs. However, the available data are limited, and, most importantly, there was no adequately powered formal head-to-head CV outcome trial designed to address CV safety. Since SUs are still being advocated as second-line therapy added-on to metformin, as one of several classes, and in certain circumstances first-line therapy in T2DM management, definitive data from a dedicated RCT addressing the CV safety question with SUs would be informative. Cardiovascular Outcome Study of Linagliptin versus Glimepiride in Patients with Type 2 Diabetes (CAROLINA) is such a trial, ongoing since November 2010, and is currently the largest head-to-head CV outcome trial that involves a comparison of a SU (glimepiride) with a dipeptidyl peptidase-4 (DPP-4) inhibitor (linagliptin) and will provide a unique perspective with respect to CV outcomes with these two commonly used agents.

Dipeptidylpeptidase inhibition is associated with improvement in blood pressure and diastolic function in insulin-resistant male Zucker obese rats

Diastolic dysfunction is a prognosticator for future cardiovascular events that demonstrates a strong correlation with obesity. Pharmacological inhibition of dipeptidylpeptidase-4 (DPP-4) to increase the bioavailability of glucagon-like peptide-1 is an emerging therapy for control of glycemia in type 2 diabetes patients. Accumulating evidence suggests that glucagon-like peptide-1 has insulin-independent actions in cardiovascular tissue. However, it is not known whether DPP-4 inhibition improves obesity-related diastolic dysfunction. Eight-week-old Zucker obese (ZO) and Zucker lean rats were fed normal chow diet or diet containing the DPP-4 inhibitor, linagliptin (LGT), for 8 weeks. Plasma DPP-4 activity was 3.3-fold higher in ZO compared with Zucker lean rats and was reduced by 95% with LGT treatment. LGT improved echocardiographic and pressure volume-derived indices of diastolic function that were impaired in ZO control rats, without altering food intake or body weight gain during the study period. LGT also blunted elevated blood pressure progression in ZO rats involving improved skeletal muscle arteriolar function, without reducing left ventricular hypertrophy, fibrosis, or oxidative stress in ZO hearts. Expression of phosphorylated- endothelial nitric oxide synthase (eNOS)(Ser1177), total eNOS, and sarcoplasmic reticulum calcium ATPase 2a protein was elevated in the LGT-treated ZO heart, suggesting improved Ca(2+) handling. The ZO myocardium had an abnormal mitochondrial sarcomeric arrangement and cristae structure that were normalized by LGT. These studies suggest that LGT reduces blood pressure and improves intracellular Cai(2+) mishandling and cardiomyocyte ultrastructure, which collectively result in improvements in diastolic function in the absence of reductions in left ventricular hypertrophy, fibrosis, or oxidative stress in insulin-resistant ZO rats.

GLP-1(28-36) improves β-cell mass and glucose disposal in streptozotocin-induced diabetic mice and activates cAMP/PKA/β-catenin signaling in β-cells in vitro

Recent studies have demonstrated that the COOH-terminal fragment of the incretin hormone glucagon-like peptide-1 (GLP-1), a nonapeptide GLP-1(28-36)amide, attenuates diabetes and hepatic steatosis in diet-induced obese mice. However, the effect of this nonapeptide in pancreatic β-cells remains largely unknown. Here, we show that in a streptozotocin-induced mouse diabetes model, GLP-1(28-36)amide improved glucose disposal and increased pancreatic β-cell mass and β-cell proliferation. An in vitro investigation revealed that GLP-1(28-36)amide stimulates β-catenin (β-cat) Ser(675) phosphorylation in both the clonal INS-1 cell line and rat primary pancreatic islet cells. In INS-1 cells, the stimulation was accompanied by increased nuclear β-cat content. GLP-1(28-36)amide was also shown to increase cellular cAMP levels, PKA enzymatic activity, and cAMP response element-binding protein (CREB) and cyclic AMP-dependent transcription factor-1 (ATF-1) phosphorylation. Furthermore, GLP-1(28-36)amide treatment enhanced islet insulin secretion and increased the growth of INS-1 cells, which was associated with increased cyclin D1 expression. Finally, PKA inhibition attenuated the effect of GLP-1(28-36)amide on β-cat Ser(675) phosphorylation and cyclin D1 expression in the INS-1 cell line. We have thus revealed the beneficial effect of GLP-1(28-36)amide in pancreatic β-cells in vitro and in vivo. Our observations suggest that GLP-1(28-36)amide may exert its effect through the PKA/β-catenin signaling pathway.

Pharmacology, physiology, and mechanisms of incretin hormone action

Incretin peptides, principally GLP-1 and GIP, regulate islet hormone secretion, glucose concentrations, lipid metabolism, gut motility, appetite and body weight, and immune function, providing a scientific basis for utilizing incretin-based therapies in the treatment of type 2 diabetes. Activation of GLP-1 and GIP receptors also leads to nonglycemic effects in multiple tissues, through direct actions on tissues expressing incretin receptors and indirect mechanisms mediated through neuronal and endocrine pathways. Here we contrast the pharmacology and physiology of incretin hormones and review recent advances in mechanisms coupling incretin receptor signaling to pleiotropic metabolic actions in preclinical studies. We discuss whether mechanisms identified in preclinical studies have potential translational relevance for the treatment of human disease and highlight controversies and uncertainties in incretin biology that require resolution in future studies.

Safety and efficacy of linagliptin in type 2 diabetes patients with common renal and cardiovascular risk factors

Dipeptidyl-peptidase-IV (DPP-4) inhibitors have become an important orally active drug class for the treatment of type 2 diabetes as second-line therapy after metformin failure or as monotherapy or combination therapy with other drugs when metformin is not tolerated or contraindicated. DPP-4 inhibitors act mainly by increasing endogenous incretin hormone concentrations. They stimulate insulin secretion and inhibit glucagon secretion in a glucose-dependent manner with a significantly lower risk for hypoglycaemia than sulfonylureas. Furthermore, DPP-4 inhibitors are weight neutral. Linagliptin is a DPP-4 inhibitor that is eliminated by a hepatobiliary route, whereas the other DPP-4 inhibitors available today show a renal elimination. Therefore, it can be used in normal kidney function as well as in all stages of chronic kidney disease to stage 5 (glomerular filtration rate <15 ml/min/1.73 m(2)) without dose adjustments. Linagliptin was noninferior to metformin and sulfonylureas in clinical studies. In recent studies, it showed a superior safety profile over sulfonylurea treatment regarding hypoglycaemia and weight gain. More patients reached an HbA1c <7% without hypoglycaemia and weight gain with linagliptin compared with glimepiride. The safety profile with respect to a composite cardiovascular endpoint and stroke was also favourable for linagliptin, most likely due to a higher incidence of hypoglycaemia associated with glimepiride therapy and titration. This review gives an overview on the efficacy and safety of linagliptin in comparison with other antidiabetic drugs in type 2 diabetes patients with renal and cardiovascular risk factors as well as an outlook on the perspective for linagliptin in this patient population in the future.

Effect of hypoglycemic agents on ischemic preconditioning in patients with type 2 diabetes and symptomatic coronary artery disease

OBJECTIVE

To assess the effect of two hypoglycemic drugs on ischemic preconditioning (IPC) patients with type 2 diabetes and coronary artery disease (CAD).

RESEARCH DESIGN AND METHODS

We performed a prospective study of 96 consecutive patients allocated into two groups: 42 to group repaglinide (R) and 54 to group vildagliptin (V). All patients underwent two consecutive exercise tests (ET1 and ET2) in phase 1 without drugs. In phase 2, 1 day after ET1 and -2, 2 mg repaglinide three times daily or 50 mg vildagliptin twice daily was given orally to patients in the respective group for 6 days. On the seventh day, 60 min after 6 mg repaglinide or 100 mg vildagliptin, all patients underwent two consecutive exercise tests (ET3 and ET4).

RESULTS

In phase 1, IPC was demonstrated by improvement in the time to 1.0 mm ST-segment depression and rate pressure product (RPP). All patients developed ischemia in ET3; however, 83.3% of patients in group R experienced ischemia earlier in ET4, without significant improvement in RPP, indicating the cessation of IPC (P < 0.0001). In group V, only 28% of patients demonstrated IPC cessation, with 72% still having the protective effect (P < 0.0069).

CONCLUSIONS

Repaglinide eliminated myocardial IPC, probably by its effect on the KATP channel. Vildagliptin did not damage this protective mechanism in a relevant way in patients with type 2 diabetes and CAD, suggesting a good alternative treatment in this population.

CD26/DPP4 levels in peripheral blood and T cells in patients with type 2 diabetes mellitus

CONTEXT

Dipeptidyl peptidase 4 (CD26/DPP4) is expressed on blood T cells and also circulates in a soluble form (sCD26/DPP4).

OBJECTIVE

We aimed to evaluate blood T cell and circulating CD26/DPP4 and its association with metabolic parameters in patients with type 2 diabetes mellitus (T2DM).

DESIGNS

We measured CD26/DPP4 expression (percentage of CD26(+) cells using flow cytometry) on CD4(+) and CD8(+) T cells, serum CD26/DPP4 level and activity, and various metabolic parameters in T2DM patients not on DPP4 inhibitor therapy (n = 148). Nondiabetic subjects (n = 50) were included as a control group.

RESULTS

Compared with the healthy controls, CD26/DPP4 expression on CD4(+) T cells and CD8(+) T cells was higher in T2DM patients. Serum CD26/DPP4 levels and enzymatic activities were also higher in patients with T2DM than in the control group only when metformin and/or thiazolidinedione-treated T2DM patients were excluded; metformin and/or thiazolidinedione-treated T2DM patients had lower values compared with other T2DM patients. Various parameters in T2DM patients were related to CD26/DPP4 expression on the T cells (hemoglobin A1c), serum sCD26/DPP4 (hemoglobin A1c and insulin resistance assessed by updated homeostasis model assessment), and serum CD26/DPP4 activity (insulin resistance assessed by updated homeostasis model assessment, γ-glutamyl transferase, and alanine aminotransferase) by multivariate analyses. After active glucose control for 12 weeks in drug-naive T2DM patients (n = 50), CD26/DPP4 expression on blood T cells was significantly decreased.

CONCLUSIONS

Our results suggest that the CD26/DPP4 level on blood T cells was associated with glucose control status in patients with T2DM.

Recent progress and future options in the development of GLP-1 receptor agonists for the treatment of diabesity

The dramatic rise of the twin epidemics, type 2 diabetes and obesity is associated with increased mortality and morbidity worldwide. Based on this global development there is clinical need for anti-diabetic therapies with accompanied weight reduction. From the approved therapies, the injectable glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are the only class of agents which are associated with a modest weight reduction. Physiological effects of the gastro-intestinal hormone GLP-1 are improvement of glycemic control as well as a reduction in appetite and food intake. Different approaches are currently under clinical evaluation to optimize the therapeutic potential of GLP-1 RAs directed to once-weekly up to once-monthly administration. The next generation of peptidic co-agonists comprises the activity of GLP-1 plus additional gastro-intestinal hormones with the potential for increased therapeutic benefits compared to GLP-1 RAs.

The impact of current and novel anti-diabetic therapies on cardiovascular risk

Type 2 diabetes mellitus (T2DM) has become an overwhelming health condition that is no longer just a threat to developed nations, but to undeveloped nations as well. Current therapies for T2DM are relatively effective in controlling hyperglycemia; examples include metformin, thiazolidinediones, sulfonylurea derivatives, α-glucosidase inhibitors, glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors. Despite their efficacy in controlling hyperglycemia, due to recent findings of increased cardiovascular risk following treatment with either rosiglitazone or intensive glucose lowering, new guidelines from the US FDA recommend that new therapies for diabetes not only improve glycemia, but exert no adverse cardiovascular effects. Based on cardiovascular risk profiles, metformin appears to be the superior anti-diabetic therapy, although studies in humans with glucagon-like peptide-1 receptor agonists are encouraging. As patients with T2DM also often have cardiovascular disease, the increased rigor in drug development should ultimately reduce the health burden of both of these conditions.

A multicentre, multinational, randomized, placebo-controlled, double-blind, phase 3 trial to evaluate the efficacy and safety of gemigliptin (LC15-0444) in patients with type 2 diabetes

AIM

This study was designed to assess the efficacy and safety of the dipeptidyl peptidase IV inhibitor gemigliptin (LC15-0444) 50 mg versus placebo in patients with type 2 diabetes.

METHODS

We conducted a 24-week, randomized, double-blind, placebo-controlled phase III trial in 182 patients (74 from Korea and 108 from India) with type 2 diabetes. After an initial 2 weeks of a diet and exercise programme followed by 2 weeks of a single-blind placebo run-in period, eligible patients were randomized to gemigliptin 50 mg or placebo, receiving the assigned treatment for 24 weeks. HbA1c and fasting plasma glucose (FPG) were measured periodically, and oral glucose tolerance test was performed at baseline and weeks 12 and 24.

RESULTS

At week 24, gemigliptin treatment led to significant reductions in HbA1c measurements compared to placebo (adjust mean after subtracting the placebo effect size: -0.71%, 95% confidence interval: -1.04 to -0.37%). A significantly greater proportion of patients achieved an HbA1c <7% with gemigliptin than with placebo. The placebo-subtracted FPG change from baseline at week 24 was -19.80 mg/dl. The overall incidence rates for adverse events were similar in the gemigliptin and placebo groups.

CONCLUSIONS

This study showed the efficacy and safety of gemigliptin 50 mg administered once daily as a monotherapy for type 2 diabetes patients.

Vildagliptin in addition to metformin improves retinal blood flow and erythrocyte deformability in patients with type 2 diabetes mellitus - results from an exploratory study

Numerous rheological and microvascular alterations characterize the vascular pathology in patients with type 2 diabetes mellitus (T2DM). This study investigated effects of vildagliptin in comparison to glimepiride on retinal microvascular blood flow and erythrocyte deformability in T2DM.

Fourty-four patients with T2DM on metformin monotherapy were included in this randomized, exploratory study over 24 weeks. Patients were randomized to receive either vildagliptin (50 mg twice daily) or glimepiride individually titrated up to 4 mg in addition to ongoing metformin treatment. Retinal microvascular blood flow (RBF) and the arteriolar wall to lumen ratio (WLR) were assessed using a laser doppler scanner. In addition, the erythrocyte elongation index (EI) was measured at different shear stresses using laserdiffractoscopy.

Both treatments improved glycaemic control (p < 0.05 vs. baseline; respectively). While only slight changes in RBF and the WLR could be observed during treatment with glimepiride, vildagliptin significantly increased retinal blood flow and decreased the arterial WLR (p < 0.05 vs. baseline respectively). The EI increased during both treatments over a wide range of applied shear stresses (p < 0.05 vs. baseline). An inverse correlation could be observed between improved glycaemic control (HbA1c) and EI (r = −0.524; p < 0.0001) but not with the changes in retinal microvascular measurements.

Our results suggest that vildagliptin might exert beneficial effects on retinal microvascular blood flow beyond glucose control. In contrast, the improvement in erythrocyte deformability observed in both treatment groups, seems to be a correlate of improved glycaemic control.

GLP-1 receptor agonists or DPP-4 inhibitors: how to guide the clinician?

Pharmacological treatment of type 2 diabetes has been enriched during recent years, with the launch of incretin therapies targeting glucagon-like peptide-1 (GLP-1). Such medications comprise either GLP-1 receptor agonists, with short (one or two daily injections: exenatide, liraglutide, lixisenatide) or long duration (one injection once weekly: extended-released exenatide, albiglutide, dulaglutide, taspoglutide); or oral compounds inhibiting dipeptidyl peptidase-4 (DPP-4), the enzyme that inactives GLP-1, also called gliptins (sitagliptin, vildagliptin, saxagliptin, linagliptin, alogliptin). Although both pharmacological approaches target GLP-1, important differences exist concerning the mode of administration (subcutaneous injection versus oral ingestion), the efficacy (better with GLP-1 agonists), the effects on body weight and systolic blood pressure (diminution with agonists versus neutrality with gliptins), the tolerance profile (nausea and possibly vomiting with agonists) and the cost (higher with GLP-1 receptor agonists). Both agents may exert favourable cardiovascular effects. Gliptins may represent a valuable alternative to a sulfonylurea or a glitazone after failure of monotherapy with metformin while GLP-1 receptor agonists may be considered as a good alternative to insulin (especially in obese patients) after failure of a dual oral therapy. However, this scheme is probably too restrictive and modalities of using incretins are numerous, in almost all stages of type 2 diabetes. Physicians may guide the pharmacological choice based on clinical characteristics, therapeutic goals and patient's preference.

GLP-1 receptor activation and Epac2 link atrial natriuretic peptide secretion to control of blood pressure

Glucagon-like peptide-1 receptor (GLP-1R) agonists exert antihypertensive actions through incompletely understood mechanisms. Here we demonstrate that cardiac Glp1r expression is localized to cardiac atria and that GLP-1R activation promotes the secretion of atrial natriuretic peptide (ANP) and a reduction of blood pressure. Consistent with an indirect ANP-dependent mechanism for the antihypertensive effects of GLP-1R activation, the GLP-1R agonist liraglutide did not directly increase the amount of cyclic GMP (cGMP) or relax preconstricted aortic rings; however, conditioned medium from liraglutide-treated hearts relaxed aortic rings in an endothelium-independent, GLP-1R-dependent manner. Liraglutide did not induce ANP secretion, vasorelaxation or lower blood pressure in Glp1r(-/-) or Nppa(-/-) mice. Cardiomyocyte GLP-1R activation promoted the translocation of the Rap guanine nucleotide exchange factor Epac2 (also known as Rapgef4) to the membrane, whereas Epac2 deficiency eliminated GLP-1R-dependent stimulation of ANP secretion. Plasma ANP concentrations were increased after refeeding in wild-type but not Glp1r(-/-) mice, and liraglutide increased urine sodium excretion in wild-type but not Nppa(-/-) mice. These findings define a gut-heart GLP-1R-dependent and ANP-dependent axis that regulates blood pressure.

Cardioprotective effects of lixisenatide in rat myocardial ischemia-reperfusion injury studies

Background

Lixisenatide is a glucagon-like peptide-1 analog which stimulates insulin secretion and inhibits glucagon secretion and gastric emptying. We investigated cardioprotective effects of lixisenatide in rodent models reflecting the clinical situation.

Methods

The acute cardiac effects of lixisenatide were investigated in isolated rat hearts subjected to brief ischemia and reperfusion. Effects of chronic treatment with lixisenatide on cardiac function were assessed in a modified rat heart failure model after only transient coronary occlusion followed by long-term reperfusion. Freshly isolated cardiomyocytes were used to investigate cell-type specific mechanisms of lixisenatide action.

Results

In the acute setting of ischemia-reperfusion, lixisenatide reduced the infarct-size/area at risk by 36% ratio without changes on coronary flow, left-ventricular pressure and heart rate. Treatment with lixisenatide for 10 weeks, starting after cardiac ischemia and reperfusion, improved left ventricular end-diastolic pressure and relaxation time and prevented lung congestion in comparison to placebo. No anti-fibrotic effect was observed. Gene expression analysis revealed a change in remodeling genes comparable to the ACE inhibitor ramipril. In isolated cardiomyocytes lixisenatide reduced apoptosis and increased fractional shortening. Glucagon-like peptide-1 receptor (GLP1R) mRNA expression could not be detected in rat heart samples or isolated cardiomyocytes. Surprisingly, cardiomyocytes isolated from GLP-1 receptor knockout mice still responded to lixisenatide.

Conclusions

In rodent models, lixisenatide reduced in an acute setting infarct-size and improved cardiac function when administered long-term after ischemia-reperfusion injury. GLP-1 receptor independent mechanisms contribute to the described cardioprotective effect of lixisenatide. Based in part on these preclinical findings patients with cardiac dysfunction are currently being recruited for a randomized, double-blind, placebo-controlled, multicenter study with lixisenatide.

Trial registration

(ELIXA, ClinicalTrials.gov Identifier: NCT01147250)

Alpha cells come of age

The alpha cells that coinhabit the islets with the insulin-producing beta cells have recently captured the attention of diabetes researchers because of new breakthrough findings highlighting the importance of these cells in the maintenance of beta cell health and functions. In normal physiological conditions alpha cells produce glucagon but in conditions of beta cell injury they also produce glucagon-like peptide-1 (GLP-1), a growth and survival factor for beta cells. In this review we consider these new findings on the functions of alpha cells. Alpha cells remain somewhat enigmatic inasmuch as they now appear to be important in the maintenance of the health of beta cells, but their production of glucagon promotes diabetes. This circumstance prompts an examination of approaches to coax alpha cells to produce GLP-1 instead of glucagon.

The efficacy of incretin therapy in patients with type 2 diabetes undergoing hemodialysis

BACKGROUND

Although incretin therapy is clinically available in patients with type 2 diabetes undergoing hemodialysis, no study has yet examined whether incretin therapy is capable of maintaining glycemic control in this group of patients when switched from insulin therapy. In this study, we examined the efficacy of incretin therapy in patients with insulin-treated type 2 diabetes undergoing hemodialysis.

METHODS

Ten type 2 diabetic patients undergoing hemodialysis received daily 0.3 mg liraglutide, 50 mg vildagliptin, and 6.25 mg alogliptin switched from insulin therapy on both the day of hemodialysis and the non-hemodialysis day. Blood glucose level was monitored by continuous glucose monitoring. After blood glucose control by insulin, patients were treated with three types of incretin therapy in a randomized crossover manner, with continuous glucose monitoring performed for each treatment.

RESULTS

During treatment with incretin therapies, severe hyperglycemia and ketosis were not observed in any patients. Maximum blood glucose and mean blood glucose on the day of hemodialysis were significantly lower after treatment with liraglutide compared with treatment with alogliptin (p < 0.05), but not with vildagliptin. The standard deviation value, a marker of glucose fluctuation, on the non-hemodialysis day was significantly lower after treatment with liraglutide compared with treatment with insulin and alogliptin (p < 0.05), but not with vildagliptin. Furthermore, the duration of hyperglycemia was significantly shorter after treatment with liraglutide on both the hemodialysis and non-hemodialysis days compared with treatment with alogliptin (p < 0.05), but not with vildagliptin.

CONCLUSIONS

The data presented here suggest that patients with type 2 diabetes undergoing hemodialysis and insulin therapy could be treated with incretin therapy in some cases.

A patient-centred approach to treatment with incretin-based agents in patients with type 2 diabetes

WHAT IS KNOWN AND OBJECTIVE

The 2012 position statement from the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) recommends a haemoglobin A1c level of <7% for most patients with type 2 diabetes (T2D). Initial therapy consists of lifestyle changes plus metformin, with an emphasis on a patient-centred approach to management. Addition of incretin-based therapy is recommended as an add-on after metformin failure, and later on in combination with basal insulin. Basal insulin is recommended from the onset in patients with A1c ≥10%. The possibility of incorporating incretin-based therapy in the patient-centred approach will be investigated both in the literature and clinical experience.

COMMENT

Incretin-based therapy targets multiple dysfunctional organ systems in T2D and provides sustained glycaemic control, with extraglycaemic benefits and low risk of hypoglycaemia. To initiate an incretin-based therapy that best fits an individual patient's needs, the patient's A1c level, preference and comorbid conditions should be considered along with any drug safety and adherence-related issues.

WHAT IS NEW AND CONCLUSION

There is good evidence to support the patient-centred approach to T2D management. This approach allows patient treatment goals and personal preferences to be matched with the clinical profile(s) of one or more agents to formulate a treatment plan that can best achieve the goals. Incretin-based therapies are an important class of agents to consider after metformin monotherapy failure and later in combination with basal insulin. By matching patient needs with the clinical profiles of the various treatment options, pharmacists can actively engage in the practice of patient-centred care and management.

Cardiovascular disease and glycemic control in type 2 diabetes: now that the dust is settling from large clinical trials

The relationship between glucose control and cardiovascular outcomes in type 2 diabetes has been a matter of controversy over the years. Although epidemiological evidence exists in favor of an adverse role of poor glucose control on cardiovascular events, intervention trials have been less conclusive. The Action to Control Cardiovascular Risk in Diabetes (ACCORD) study, the Action in Diabetes and Vascular Disease (ADVANCE) study, and the Veterans Affairs Diabetes Trial (VADT) have shown no beneficial effect of intensive glucose control on primary cardiovascular endpoints in type 2 diabetes. However, subgroup analysis has provided evidence suggesting that the potential beneficial effect largely depends on patients’ characteristics, including age, diabetes duration, previous glucose control, presence of cardiovascular disease, and risk of hypoglycemia. The benefit of strict glucose control on cardiovascular outcomes and mortality may be indeed hampered by the extent and frequency of hypoglycemic events and could be enhanced if glucose-lowering medications, capable of exerting favorable effects on the cardiovascular system, were used. This review examines the relationship between intensive glucose control and cardiovascular outcomes in type 2 diabetes, addressing the need for individualization of glucose targets and careful consideration of the benefit/risk profile of antidiabetes medications.

Dipeptidyl peptidase IV inhibition does not adversely affect immune or virological status in HIV infected men and women: a pilot safety study

CONTEXT

People infected with HIV have a higher risk for developing insulin resistance, diabetes, and cardiovascular disease than the general population. Dipeptidyl peptidase IV (DPP4) inhibitors are glucose-lowering medications with pleiotropic actions that may particularly benefit people with HIV, but the immune and virological safety of DPP4 inhibition in HIV is unknown.

OBJECTIVE

DPP4 inhibition will not reduce CD4+ T lymphocyte number or increase HIV viremia in HIV-positive adults.

DESIGN

This was a randomized, placebo-controlled, double-blind safety trial of sitagliptin in HIV-positive adults.

SETTING

The study was conducted at an academic medical center.

PARTICIPANTS

Twenty nondiabetic HIV-positive men and women (9.8 ± 5.5 years of known HIV) taking antiretroviral therapy and with stable immune (625 ± 134 CD4+ T cells per microliter) and virological (<48 copies HIV RNA per milliliter) status.

INTERVENTION

The intervention included sitagliptin (100 mg/d) vs matching placebo for up to 24 weeks.

MAIN OUTCOME MEASURES

CD4+ T cell number and plasma HIV RNA were measured every 4 weeks; fasting serum regulated upon activation normal T-cell expressed and secreted (RANTES), stromal derived factor (SDF)-1α, Soluble TNF receptor II, and oral glucose tolerance were measured at baseline, week 8, and the end of study. ANOVA was used for between-group comparisons; P < .05 was considered significant.

RESULTS

Compared with placebo, sitagliptin did not reduce CD4+ T cell count, plasma HIV RNA remained less than 48 copies/mL, RANTES and soluble TNF receptor II concentrations did not increase. SDF1α concentrations declined (P < .0002) in the sitagliptin group. The oral glucose tolerance levels improved in the sitagliptin group at week 8.

CONCLUSIONS

Despite lowering SDF1α levels, sitagliptin did not adversely affect immune or virological status, or increase immune activation, but did improve glycemia in healthy, nondiabetic HIV-positive adults. These safety data allow future efficacy studies of sitagliptin in HIV-positive people with cardiometabolic complications.

Pleiotropic effects of incretins and antidiabetics with incretine mechanism

Discovery of physiological and pharmacological characteristics of incretins (glucagon-like peptide-1 and glucose-dependent insulinotrop polypeptide), and the introduction of various products of those into the clinical practice has fundamentally changed blood glucose lowering therapy in type 2 diabetes. In addition to the antidiabetic properties more attention is paid to their favourable pleiotropic effects independent from the blood glucose lowering such as cardio-, vaso- and renoprotectiv, blood pressure lowering effects, as well as beneficial changes on blood lipid values and hepatic steatosis. These preferential changes prevail in slightly different way when incretin mimetics applied and dipeptidyl peptidase-4 inhibitors, furthermore, prolonged action of peptides metabolised by this enzyme may serve additional benefits in this latter mentioned group. The article overviews the currently known most important pleiotropic effects of incretins from the point of view of cardiorenal risk accompanying type 2 diabetes. Orv. Hetil., 2013, 154, 248–255.

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.

GLP-1 receptor activation indirectly reduces hepatic lipid accumulation but does not attenuate development of atherosclerosis in diabetic male ApoE(-/-) mice

Glucagon-like peptide-1 receptor (GLP-1R) agonists reduce lipid accumulation in peripheral tissues, attenuating atherosclerosis and hepatic steatosis in preclinical studies. We examined whether GLP-1R activation decreases atherosclerosis progression in high-fat diet-fed male ApoE(-/-) mice after administration of streptozotocin and treatment with the long-acting GLP-1R agonist taspoglutide administered once monthly vs. metformin in the drinking water for 12 wk. Taspoglutide did not reduce plaque area or lipid content in the aortic arch or abdominal aorta, and no significant change in aortic macrophage accumulation was detected after taspoglutide or metformin. In contrast, hepatic triglyceride levels were significantly reduced in livers from taspoglutide-treated mice. Both peripheral and intracerebroventricular administration of exendin-4 rapidly decreased plasma triglyceride levels in fasted mice, and taspoglutide therapy in ApoE(-/-) mice modulated the expression of hepatic genes controlling fatty acid uptake and oxidation. We were unable to detect expression of the entire Glp1r coding sequence in macrophages isolated from ApoE(-/-), C57BL/6, and IL10(-/-) mice. Similarly, Glp1r mRNA transcripts were not detected in RNA from isolated murine hepatocytes. Using Western blotting and tissue extracts from Glp1r(+/+) and Glp1r(-/-) mice, and cells transfected with a tagged murine GLP-1R cDNA, we could not validate the sensitivity and specificity of three different GLP-1R antisera commonly used for the detection of GLP-1R protein. Taken together, these findings illustrate divergent actions of GLP-1R agonists on atherosclerosis progression and accumulation of ectopic lipid in ApoE(-/-) mice and highlight the importance of indirect GLP-1R actions for the control of hepatic lipid accumulation.

Clinical pearls for initiating and utilizing liraglutide in patients with type 2 diabetes

This review presents clinical pearls for initiating liraglutide (Victoza®, Novo Nordisk Inc) therapy for the management of type 2 diabetes and selecting patients who will benefit from liraglutide therapy. Liraglutide, a once-daily glucagon-like peptide 1 receptor agonist, is Food and Drug Administration approved as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes. Liraglutide is effective for reducing hemoglobin A1c levels by 0.8% to 1.5% in patients with type 2 diabetes as monotherapy or in combination with other diabetic medications (such as metformin, sulfonylureas, rosiglitazone, or basal insulin) when compared with placebo and these other diabetic medications, including exenatide. Overweight or obese patients with type 2 diabetes or those with insulin resistance are good candidates for liraglutide therapy because liraglutide use is associated with weight loss (about 2%-4% of initial body weight) and improved β-cell function. The incidence of hypoglycemia with liraglutide is low; therefore, liraglutide would be a safe therapy choice for patients at risk or with a history of symptomatic or severe hypoglycemia. Nausea seems to be the most problematic adverse effect associated with liraglutide therapy, but it is usually transient and is minimized with dose titration.

Cardiovascular protective properties of incretin-based therapies in type 2 diabetes

PURPOSE OF REVIEW

Type 2 diabetes mellitus is a chronic dysmetabolic condition characterized by hyperglycemia and accompanied by dyslipidemia (low HDL, high triglycerides), and hypertension associated with insulin resistance in obesity. In addition to the glucose-reducing effects, incretin-based therapies have been found to have cardiovascular protective properties. This review summarizes the best available evidence favoring these positive pleiotropic effects of incretin mimetics as well as incretin enhancers.

RECENT FINDINGS

Studies in animals and humans are accumulating showing the direct as well as indirect actions of the glucagon-like peptide 1 analogues and dipeptidyl peptidase 4 inhibitors on the cardiovascular system. This class of agents appear to have effects on the cardiomyocytes, blood vessels, adipose tissue, regulation of blood pressure, and postprandial intestinal lipoprotein metabolism.

SUMMARY

Long-term hard outcome trials are under way that investigate the effects of incretin-based treatments on elevated cardiovascular risks in patients with type 2 diabetes.

What the future holds for gliptins

Gliptins have revolutionised the treatment of Type 2 Diabetes Mellitus, addressing the hyperglycemia through its effects on the alpha and beta cells of the pancreas. In this article,we review the extra-glycemic effects of gliptins on central nervous system, cardiovascular biology and the bone health and concerns regarding pancreatitis and pancreatic cancer.

New antidiabetic therapies: innovative strategies for an old problem

PURPOSE OF REVIEW

Over the last few years, a variety of new antidiabetic drugs have been approved for clinical use and novel agents are currently under development. All of these are facing new regulations created by the demand to not only lower HbA1c but also provide long-term clinical benefit and cardiovascular safety.

RECENT FINDINGS

The present review will discuss the following novel therapeutic options: GLP-1 mimetics and DPP-4 inhibitors are new antidiabetic drugs which favourably affect glucose metabolism without a significant risk for hypoglycaemic events and preliminary clinical data suggesting potential beneficial effects with respect to cardiovascular risk reduction. In addition, new antidiabetic concepts include SGLT2 inhibition, dual peroxisome proliferator-activated receptor agonists and G-protein receptor agonists, all of which provide beneficial cardiometabolic characteristics.

SUMMARY

The development of novel antidiabetic strategies currently does not only focus on potent glucose-lowering properties but also on safety aspects and potential cardiovascular benefits.

Inflammation and incretins

Nutrient excess results in systemic inflammation in diabetes contributing to insulin resistance, dyslipidaemia and increased cardiovascular risk. GLP-1 agonists and DPP-4 inhibitors, which are now well accepted therapies for diabetes may play a unique role in modulating this inflammatory process. Incretin based therapies have shown beneficial anti-inflammatory effects on surrogate markers but cardiovascular outcome data is still lacking.

The dipeptidyl peptidase-4 inhibitors in type 2 diabetes mellitus: cardiovascular safety

The dipeptidyl peptidase-4 (DPP-4) inhibitors are a relatively new class of oral antidiabetic agents that improve glycemic control in patients with type 2 diabetes mellitus. These agents differ in structure, but all act by inhibiting the DPP-4 enzyme. Dipeptidyl peptidase-4 inhibition increases levels of the incretin hormones glucagon-like peptide-1 and glucose-dependent insulinotropic peptide, which in turn stimulate insulin secretion in a glucose-dependent fashion. Clinical trials have shown that DPP-4 inhibitors provide significant reductions in glycated hemoglobin levels, with a low risk of hypoglycemia. Animal model experiments and proof-of-concept studies suggest that the incretins favorably affect the cardiovascular system; it is possible that these same effects may be conveyed by DPP-4 inhibitor therapy. Pooled and meta-analyses of DPP-4 inhibitor clinical trial data have shown no increase in major adverse cardiovascular events, and, in fact, suggest a potential cardiovascular benefit to such therapy. Long-term cardiovascular safety trials are currently underway to more fully define and understand the cardiovascular impact of DPP-4 therapy in patients with type 2 diabetes mellitus.

New insight into the mechanisms underlying the function of the incretin hormone glucagon-like peptide-1 in pancreatic β-cells: the involvement of the Wnt signaling pathway effector β-catenin

During the past two decades, the exploration of function of two incretin hormones, namely glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide (GIP), has led to the development of two categories of novel therapeutic agents for diabetes and its complications, known as GLP-1 receptor (GLP-1R) agonists and DPP-IV inhibitors. Mechanisms underlying the function of GLP-1, however, still need to be further explored. GLP-1 not only functions as an incretin hormone in stimulating insulin secretion in response to nutritional, hormonal and neuronal stimulations, but also acts as an "insulin-like" factor in β-cell and extra-pancreatic organs. In addition to these insulinotropic and insulinomimetic effects, GLP-1 was shown to exert its protective effect in β-cell by repressing the expression of TxNIP, a mediator of glucolipotoxicity. A number of recent studies have shown that the Wnt signaling pathway effector, the bipartite transcription factor β-catenin/TCF, controls not only the production of GLP-1, but also the function of GLP-1. Furthermore, previously assumed "degradation" products of GLP-1(7-36)amide, including GLP-1(9-36)amide and GLP-1(28-36)amide, have been shown to exert beneficial effect in pancreas and extra-pancreatic tissues or cell lineages. Here we summarized our current knowledge on the metabolic, proliferative and protective effects of GLP-1(7-36)amide and its cleavage fragments, mainly focusing on pancreatic β-cells and the involvement of the Wnt signaling pathway effector β-catenin.

Efficacy and safety of exenatide once weekly: an overview of the DURATION trials

Diabetes management involves controlling glycemia and cardiometabolic risk factors. In the DURATION trials, the efficacy and safety of exenatide (EX) once weekly (q.w.), a new long-acting glucagon-like-peptide-1 receptor agonist, was studied as monotherapy or as add-on to metformin with or without sulfonylurea, and compared with oral (metformin, pioglitazone or sitagliptin) and injectable antidiabetic drugs (EX twice daily [EX b.i.d.], liraglutide and insulin glargine). EX q.w. reduced HbA_1c by 1.3-1.9% and showed better overall glycemic control compared with EX b.i.d., sitagliptin, pioglitazone and insulin glargine, but not liraglutide. Fasting plasma glucose was reduced more by EX q.w. than by EX b.i.d. or sitagliptin, whereas postprandial glycemia was better controlled by EX b.i.d. Weight loss was achieved by EX q.w. and EX b.i.d., in contrast to pioglitazone and insulin glargine. EX q.w. improved systolic blood pressure, lipids and cardiovascular risk markers. EX q.w. was well tolerated without safety issues. The most common adverse events were nausea, vomiting and constipation. Injection-site reactions were present in 5-13%. The risk of hypoglycemia of EX q.w. was similar to EX b.i.d., sitagliptin and pioglitazone. Hypoglycemia risk was not increased when EX q.w. was not combined with sulfonylurea.

Potential role of glucagon-like peptide-1 (GLP-1) in neuroprotection

The current understanding of neurodegenerative processes in sporadic diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) or multiple sclerosis is very limited. Several risk factors have been identified that may shed light on the underlying mechanisms that initiate the neurodegeneration. Type 2 diabetes mellitus has been identified as a risk factor for AD and PD. In AD patients, desensitization of insulin receptors in the brain has been shown, even in non-diabetic patients. Insulin acts as a growth factor in the brain and supports neuronal repair, dendritic sprouting and synaptogenesis, and protection from oxidative stress. Importantly, several drugs have been developed to treat type 2 diabetes that re-sensitize insulin receptors and may be of use to prevent neurodegenerative processes. Glucagon-like peptide-1 (GLP-1) is a hormone that facilitates insulin release under high blood sugar conditions. Interestingly, GLP-1 also has very similar growth factor-like properties to insulin, and has been shown to reduce a range of degenerative processes. In pre-clinical studies, GLP-1 and longer-lasting protease-resistant analogues cross the blood-brain barrier, protect memory formation (AD) or motor activity (PD), protect synapses and synaptic functions, enhance neurogenesis, reduce apoptosis, protect neurons from oxidative stress, and reduce plaque formation and the chronic inflammation response in the brains of mouse models of AD, PD, amyotrophic lateral sclerosis, stroke and other degenerative diseases. GLP-1 signalling does not affect blood sugar levels in non-diabetic people and therapies that affect GLP-1 signalling have a good safety profile as shown by the chronic application of drugs currently on the market (liraglutide, Victoza(®); NovoNordisk, Copenhagen, Denmark, and exendin-4, Byetta(®); Amylin, San Diego, CA, USA). Based on the extensive evidence, several clinical trials are currently underway, testing liraglutide and exendin-4 in AD and PD patients. Therefore, GLP-1 analogues show great promise as a novel treatment for AD or other neurodegenerative conditions.

Adipose tissue, hormones, and treatment of type 1 diabetes

Type 1 diabetes (T1D) is a serious disease with increasing incidence worldwide, with fatal consequences if untreated. Traditional therapies require direct or indirect insulin replacement, which involves numerous limitations and complications. While insulin is the major regulator of blood glucose, recent reports demonstrate the ability of several extra-pancreatic hormones to decrease blood glucose and improve metabolic homeostasis. Such hormones mainly include adipokines originating from adipose tissue (AT), while specific factors from the gut and liver also contribute to glucose homeostasis. Correction of T1D with adipokines is progressively becoming a realistic option, with the potential to overcome many problems associated with insulin replacement. Several recent studies demonstrate insulin-independent reversal or amelioration of T1D through administration of specific adipokines. Our recent work demonstrates the ability of healthy AT to compensate for the function of endocrine pancreas in long-term correction of T1D. This review discusses the potential of AT-related therapies for T1D as viable alternatives to insulin replacement.

Glucagon-like peptide 1 and cardiac cell survival

During myocardial infarction (MI), a variety of mechanisms contribute to activation of cell death processes in cardiomyocytes, which determines the final MI size, subsequent mortality, and post-MI remodeling. The deleterious mechanisms activated during the ischemia and reperfusion phases in MI include oxygen deprival, decreased availability of nutrients and survival factors, accumulation of waste products, generation of oxygen free radicals, calcium overload, neutrophil infiltration in the ischemic area, depletion of energy stores, and opening of the mitochondrial permeability transition pore, all of them contributing to activation of apoptosis and necrosis in cardiomyocytes. Glucagon-like peptide-1 [GLP-1 (7-36) amide] has gained relevance in recent years for metabolic treatment of patients with type 2 diabetes mellitus. Cytoprotection of different cell types, including cardiomyocytes, is among the pleiotropic actions reported for GLP-1. This paper reviews the most relevant experimental studies that have contributed to a better understanding of the molecular mechanisms and intracellular pathways involved in cardioprotection induced by GLP-1 and analyzes in depth its potential role as a therapeutic target both in the ischemic and reperfused myocardium and in other conditions that are associated with myocardial remodeling and heart failure.

Pleiotropic effects of sitagliptin in the treatment of type 2 diabetes mellitus patients

BACKGROUND

Sitagliptin is a DPP-4 inhibitor that became available for use in Japan three years ago. This study was conducted to identify the pleiotropic effects of sitagliptin other than blood glucose lowering in Japanese type 2 diabetes mellitus patients.

METHODS

A retrospective, observational study of 940 type 2 diabetes mellitus patients was conducted. The primary outcome measures were HbA1c, blood pressure, and lipid profiles measured at 0, 4, and 12 weeks of sitagliptin therapy.

RESULTS

After 12 weeks of sitagliptin treatment, compared with baseline, HbA1c decreased 0.64% ± 0.86%; systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreased significantly; and serum creatinine (Cr) and uric acid (UA) levels were mildly but significantly elevated. A correlation analysis of the changes in systolic blood pressure, diastolic blood pressure, creatinine, and uric acid (ΔSBP, ΔDBP, ΔCr, ΔUA) from baseline to 12 weeks showed significant negative correlations between ΔSBP and ΔCr, ΔSBP and ΔUA, and ΔDBP and ΔCr. Total cholesterol and postprandial triglycerides were significantly decreased at both 4 and 12 weeks. Alkaline phosphatase (ALP) decreased significantly, and there was a significant positive correlation between changes in ALP and HbA1c.

CONCLUSIONS

Sitagliptin seems to be effective not only in lowering blood glucose but also in lowering blood pressure, lipid, and ALP levels. Sitagliptin appears to contribute to a Na-diuretic action due to GLP-1.