Non-glycaemic effects mediated via GLP-1 receptor agonists and the potential for exploiting these for therapeutic benefit: focus on liraglutide

A review of an investigational drug retatrutide, a novel triple agonist agent for the treatment of obesity

BACKGROUND

Obesity is one of the critical public health problems in our society. It leads to various health conditions, such as type 2 diabetes mellitus, cardiovascular disease, hypertension, dyslipidaemia, and non-alcoholic fatty liver disease. With the rising incidence of obesity, there is a growing demand for new therapies which can effectively manage body weight and improve health.

CURRENT EVIDENCE

Currently under development, multi-receptor agonist drugs may offer a promising solution to meet this unmet medical need. Retatrutide is a novel triple receptor agonist peptide that targets the glucagon receptor (GCGR), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon-like peptide-1 receptor (GLP-1R). This novel drug has the potential to treat metabolic abnormalities associated with obesity as well as diseases resulting from it due to its distinct mechanism of action. The Phase III trial of this pipeline drug for treating type 2 diabetes mellitus, non-alcoholic fatty liver disease, and obesity started on August 28, 2023. The results of a Phase II clinical trial have demonstrated significant weight reduction in overweight and obese adults. Specifically, the trial reported an average weight loss of 17.5% and 24.4% at 24 and 48 weeks, respectively.

CONCLUSIONS

These findings hold promise for the development of effective weight loss interventions in this population group. There is a need for more phase III studies to provide sufficient clinical evidence for the effectiveness of retatrutide, as current evidence is limited to phase II studies and has yet to prove its worth in a larger population. Here, we aimed to provide an overview of retatrutide's safety and effectiveness in treating obesity.

Investigating the potential non-authorized use of two different formulations of liraglutide in Europe: A real-world drug utilization study

AIM

To assess the in-market use of Saxenda (liraglutide 3.0 mg) and Victoza (liraglutide 1.2 mg/1.8 mg) according to approved indications and posology.

MATERIALS AND METHODS

This retrospective, non-interventional study was conducted at 41 sites from December 2016 to May 2019. Via medical record review, physicians at each site identified patients who had been prescribed Saxenda (Italy) or Victoza (Italy/Germany) within the 24 months following launch in each country. Pseudonymized data were abstracted on patient and site characteristics, indication for the prescription, posology and duration of usage. Adherence to the approved indications and posology, and to the Saxenda stopping rule, were assessed. No formal statistical analysis was performed.

RESULTS

A total of 440 patients were prescreened and 225 (51.1%) were enrolled (Saxenda: N = 75, all in Italy; Victoza: N = 75 in Italy and N = 75 in Germany). In all, 96% (72/75) of Saxenda prescriptions, and 98.7% (148/150) of Victoza, were in accordance with the approved indications. Among the 40 patients treated with Saxenda for 16 weeks or longer, only two (5.0%) were confirmed as non-adherent to the stopping rule. Adherence could not be assessed in 23 (57.5%) patients because of missing body weight measurements.

CONCLUSIONS

This retrospective, real-world post-authorization safety study provides reassurance that Saxenda and Victoza are primarily used according to the approved European label, thus their real-world utilization did not raise safety concerns.

Sitagliptin attenuates endothelial dysfunction independent of its blood glucose controlling effect

Although the contributions of sitagliptin to endothelial dysfunction in diabetes mellitus were previously reported, the mechanisms still undefined. Autophagy plays an important role in the development of diabetes mellitus, but its role in diabetic macrovascular complications is unclear. This study aims to observe the effect of sitagliptin on macrovascular endothelium in diabetes and explore the role of autophagy in this process. Diabetic rats were induced through administration of high-fat diet and intraperitoneal injection of streptozotocin. Then diabetic rats were treated with or without sitagliptin for 12 weeks. Endothelial damage and autophagy were measured. Human umbilical vein endothelial cells were cultured either in normal glucose or in high glucose medium and intervened with different concentrations of sitagliptin. Rapamycin was used to induce autophagy. Cell viability, apoptosis and autophagy were detected. The expressions of proteins in c-Jun N-terminal kinase (JNK)-Bcl-2-Beclin-1 pathway were measured. Sitagliptin attenuated injuries of endothelium in vivo and in vitro. The expression of microtubuleassociated protein 1 light chain 3 II (LC3II) and beclin-1 were increased in aortas of diabetic rats and cells cultured with high-glucose, while sitagliptin inhibited the over-expression of LC3II and beclin-1. In vitro pre-treatment with sitagliptin decreased rapamycin-induced autophagy. However, after pretreatment with rapamycin, the protective effect of sitagliptin on endothelial cells was abolished. Further studies revealed sitagliptin increased the expression of Bcl-2, while inhibited the expression of JNK in vivo. Sitagliptin attenuates injuries of vascular endothelial cells caused by high glucose through inhibiting over-activated autophagy. JNK-Bcl-2-Beclin-1 pathway may be involved in this process.

Liraglutide-induced structural modulation of the gut microbiota in patients with type 2 diabetes mellitus

Accumulating evidence has suggested the importance of gut microbiota in the development of type 2 diabetes mellitus (T2DM). In the present study, 40 patients with T2DM were treated with liraglutide for 4 months. Feces samples and clinical characteristics were collected from these 40 T2DM patients before and after the liraglutide treatment. The diversity and composition of gut microbiota in the two groups were determined by sequencing the V4 region of bacterial 16S rRNA genes. Meanwhile, blood glucose, insulin, hemoglobin A1c (HbA1c), and lipid metabolism were also measured in the pre- and post-liraglutide-treatment groups. We find that Baseline HbA1c was associated with liraglutide treatment response (R₂ = 0.527, β =  − 0.726, p < 0.0001). After adjusted for baseline HbA1c, blood urea nitrogen was associated with liraglutide treatment response. Besides, our results showed reduced gut microbial alpha diversity, different community structure distribution and altered microbial interaction network in patients treated with liraglutide. The liner discriminant analysis (LDA) effect size (LEfSe) analysis showed that 21 species of bacteria were abundant in the pre-liraglutide-treatment group and 15 species were abundant in the post-liraglutide-treatment group. In addition, we also find that Megamonas were significantly correlated with older age, diabetes duration and diabetic retinopathy, Clostridum were significantly correlated with family history of diabetes and Oscillospira were significantly correlated with both diabetic retinopathy and diabetic peripheral neuropathy. Functional analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) and cluster of orthologous groups (COG) annotations enriched three KEGG metabolic pathways and six functional COG categories in the post-liraglutide-treatment group. In conclusion, our research suggests that baseline HbA1c, blood urea nitrogen and gut microbiota are associated with the liraglutide treatment applied on patients with T2DM. These findings may contribute to the beneficial effects of liraglutide against diabetes.

Effect of Hemoglobin A1c Reduction or Weight Reduction on Blood Pressure in Glucagon-Like Peptide-1 Receptor Agonist and Sodium-Glucose Cotransporter-2 Inhibitor Treatment in Type 2 Diabetes Mellitus: A Meta-Analysis

Background Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2is) have shown their beneficial effects on cardiovascular outcomes and multiple cardiovascular risk factors, including hypertension. However, the mechanism of blood pressure (BP)-lowering effects of these agents has not been elucidated. This study aims to evaluate the effect of hemoglobin A1c reduction or body weight reduction with GLP-1RA treatment and SGLT2i treatment on BP changes in patients with type 2 diabetes mellitus. Methods and Results Studies were identified by a search of MEDLINE, EMBASE, and the Cochrane Central Register until June 2019. Meta-regression analysis was performed to evaluate the association between hemoglobin A1c reduction or body weight reduction and changes of BP. A total of 184 trials were included. Both GLP-1RA and SGLT2i led to significant reductions in systolic BP (weighted mean difference, -2.856 and -4.331 mm Hg, respectively; P<0.001 for both) and diastolic BP (weighted mean difference, -0.898 and -2.279 mm Hg, respectively; P<0.001 for both). For both drug classes, hemoglobin A1c reduction was not independently associated with systolic BP reduction or diastolic BP reduction. In GLP-1RA treatment, weight reduction was positively associated with systolic BP reduction and diastolic BP reduction (β=0.821 and β=0.287, respectively; P<0.001 for both). In SGLT2i treatment, weight loss was significantly associated with systolic BP reduction (β=0.820; P=0.001) but was not associated with diastolic BP reduction. Conclusions Treatment with GLP-1RA and SGLT2i led to significant reductions in BP in patients with type 2 diabetes mellitus. Weight reduction was significantly and independently associated with BP reductions in GLP-1RA treatment and SGLT2i treatment.

Liraglutide modulates gut microbiota and reduces NAFLD in obese mice

Metabolic disorders such as insulin resistance and diabetes are associated with obesity and nonalcoholic fatty liver disease (NAFLD). The aggressive form of a fatty liver disease may progress to cirrhosis and hepatocellular carcinoma. Furthermore, recent studies demonstrated that there is a dysbiosis in the gut microbiota associated with early stages of metabolic disease. Therefore, the identification and repurposing of drugs already used to treat insulin resistance may be an excellent option for other disorders. We evaluated the effect of liraglutide on obesity, NAFLD and gut microbiota modulation in two different animal models of obesity: the ob/ob mice and the high-fat diet (HFD)-fed mice. Liraglutide treatment induced significant weight loss in both obesity models, showed improvements in glycemic parameters and reduced inflammatory cell infiltration in the cecum and the liver. In ob/ob mice, the liraglutide treatment was able to reduce the accumulation of liver fat by 78% and reversed steatosis in the HFD mice. The gut microbiota analysis showed that liraglutide changed the overall composition as well as the relative abundance of weight-relevant phylotypes such as a reduction of Proteobacteria and an increase of Akkermansia muciniphila in the treated HFD group. We show that liraglutide can lead to weight loss and gut microbiota modulations, and is associated with an improvement of NAFLD. Furthermore, by generating a profile of the intestinal microbiota, we compiled a list of potential bacterial targets that may modulate metabolism and induce a metabolic profile that is considered normal or clinically controlled.

Efficacy and safety of liraglutide versus sitagliptin, both in combination with metformin, in Chinese patients with type 2 diabetes: a 26-week, open-label, randomized, active comparator clinical trial

AIMS

To compare the efficacy and safety of liraglutide versus sitagliptin as add-on to metformin after 26 weeks of treatment in Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

This 26-week open-label, active comparator trial (NCT02008682) randomized patients (aged 18-80 years) with T2DM inadequately controlled with metformin [glycated haemoglobin (HbA1c) 7.0-10.0% (53-86 mmol/mol)] 1 : 1 to once-daily subcutaneously administered liraglutide 1.8 mg (n = 184) or once-daily oral sitagliptin 100 mg (n = 184), both as add-on to metformin. The primary endpoint was change in HbA1c from baseline to week 26.

RESULTS

Liraglutide was superior to sitagliptin in reducing HbA1c from baseline [8.1% (65 mmol/mol)] to 26 weeks, as evidenced by estimated mean HbA1c change of -1.65% (-18.07 mmol/mol) versus -0.98% (-10.72 mmol/mol), respectively [estimated treatment difference for liraglutide vs sitagliptin of -0.67% (95% CI -0.86, -0.48) or -7.35 mmol/mol (95% CI -9.43; -5.26); p < 0.0001]. More patients receiving liraglutide (76.5%) than sitagliptin (52.6%) achieved the HbA1c target of <7.0% (53 mmol/mol) at week 26 [odds ratio 3.65 (95% CI 2.18, 6.12); p < 0.0001]. Reductions in fasting plasma glucose, 7-point self-measured plasma glucose and body weight were greater with liraglutide than with sitagliptin (p < 0.0001 for all). More patients experienced nausea (14.8% vs 0.5%), diarrhoea (8.2% vs 2.2%) and decreased appetite (10.9% vs 0.5%) with liraglutide than sitagliptin. Two hypoglycaemic episodes were confirmed for liraglutide and one for sitagliptin; none were severe or nocturnal.

CONCLUSIONS

Liraglutide provided better glycaemic control and greater body weight reduction than sitagliptin when administered as add-on to metformin. More patients had nausea, diarrhoea and decreased appetite with liraglutide versus sitagliptin.

IDegLira Versus Alternative Intensification Strategies in Patients with Type 2 Diabetes Inadequately Controlled on Basal Insulin Therapy

INTRODUCTION

IDegLira is a once-daily combination of insulin degludec (IDeg) and liraglutide. Trials directly comparing IDegLira with alternative strategies for intensifying basal insulin are ongoing. While awaiting results, this analysis compared indirectly how different strategies affected glycated hemoglobin (HbA_1c) and other outcomes.

METHODS

A pooled analysis of five completed Novo Nordisk randomized clinical trials in patients with type 2 diabetes inadequately controlled on basal insulin was used to compare indirectly IDegLira (N = 199) with: addition of liraglutide to basal insulin (N = 225) [glucagon-like peptide-1 receptor agonist (GLP-1RA) add-on strategy]; basal-bolus (BB) insulin [insulin glargine (IGlar) + insulin aspart] (N = 56); or up-titration of IGlar (N = 329). A supplementary analysis was performed with the BB arm including patients who received IGlar or IDeg as basal insulin in the relevant trial (N = 210). All trials had comparable inclusion/exclusion criteria and baseline characteristics. Individual patient-level data were analyzed using multivariable statistical models with potential baseline heterogeneity accounted for using explanatory variables.

RESULTS

At end of study, differences between IDegLira and BB or up-titrated IGlar, respectively, were as follows: reduction in HbA_1c -0.30%, 95% confidence interval (-0.58; -0.01) and -0.65% (-0.83; -0.47); change in body weight -6.89 kg (-7.92; -5.86) and -4.04 kg (-4.69; -3.40) all in favor of IDegLira. Confirmed hypoglycemia rate was 122.8 (90.7; 166.1), 1060.8 (680.2; 1654.4), and 286.1 (231.1; 354.1) events/100 patient-years for IDegLira, BB, and up-titrated IGlar, respectively. Odds ratios for achieving HbA_1c <7.0%, <7.0% without hypoglycemia, and <7.0% without hypoglycemia and no weight gain were greater with IDegLira versus up-titrated IGlar. The supplementary analysis yielded similar results to the main analysis. Results with IDegLira were similar to those for the 'GLP-1RA add-on' arm.

CONCLUSION

These results suggest that IDegLira may be more effective, with lower hypoglycemia rates and less weight gain, than up-titrated basal insulin or BB in patients uncontrolled on basal insulin.

Managing recent-onset diabetes: choosing durable, well-tolerated therapies and understanding the role of incretin-based therapies

Management of recent-onset diabetes offers osteopathic physicians the opportunity to work with patients to set treatment goals and expectations for this progressive yet manageable disease, as well as intervene early to reduce the risk of diabetes-related complications. Starting effective therapy early--and intensifying therapy appropriately--to achieve and maintain glycemic goals has been shown to reduce microvascular risks and produce legacy effects that may have macrovascular benefits. Metformin remains a cornerstone of therapy for those patients who can tolerate it. Early combination therapy that is well tolerated reduces risks of hypoglycemia or unwanted weight gain, improves patient adherence, and addresses the multifactoral pathophysiology of even recent-onset diabetes. Incretin-based therapies have been shown to be effective across the spectrum of type 2 diabetes mellitus, including recent-onset diabetes. The present article reviews the use of incretin-based therapies early in the disease process of type 2 diabetes mellitus.

GLP-1 receptor agonists: Nonglycemic clinical effects in weight loss and beyond

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) receptor agonists are indicated for treatment of type 2 diabetes since they mimic the actions of native GLP-1 on pancreatic islet cells, stimulating insulin release, while inhibiting glucagon release, in a glucose-dependent manner. The observation of weight loss has led to exploration of their potential as antiobesity agents, with liraglutide 3.0 mg day(-1) approved for weight management in the US on December 23, 2014, and in the EU on March 23, 2015. This review examines the potential nonglycemic effects of GLP-1 receptor agonists.

METHODS

A literature search was conducted to identify preclinical and clinical evidence on nonglycemic effects of GLP-1 receptor agonists.

RESULTS

GLP-1 receptors are distributed widely in a number of tissues in humans, and their effects are not limited to the well-recognized effects on glycemia. Nonglycemic effects include weight loss, which is perhaps the most widely recognized nonglycemic effect. In addition, effects on the cardiovascular, neurologic, and renal systems and on taste perception may occur independently of weight loss.

CONCLUSIONS

GLP-1 receptor agonists may provide other nonglycemic clinical effects besides weight loss. Understanding these effects is important for prescribers in using GLP-1 receptor agonists for diabetic patients, but also if approved for chronic weight management.

Time course and mechanisms of the anti-hypertensive and renal effects of liraglutide treatment

AIMS

Glucagon-like peptide-1 receptor agonist studies have revealed clinically significant reductions in systolic blood pressure (SBP). The aim was to investigate the time course of the anti-hypertensive effect of liraglutide treatment and potential underlying mechanisms.

METHODS

We used an open-label, single-centre trial; 31 participants with Type 2 diabetes and hypertension completed the study. All participants were treated with liraglutide escalated to a maximum dose of 1.8 mg/day for 7 weeks, followed by a 21-day washout period. The primary outcome was a change in 24-h SBP.

RESULTS

Twenty-four-h SBP increased by 10 mmHg on day 3 (P = 0.008) and 7 mmHg on day 7 (P = 0.033, 0.6 mg/day). On day 29, (1.8 mg/day), 24-h SBP was 7 mmHg lower compared with baseline (P = 0.11). Following the treatment period (day 49) and after washout (day 70), 24-h BP was equivalent to baseline. In addition, extracellular volume (ECV) was reduced by 2.0 l [95% confidence interval (CI) = 1.0-3.1 l, P < 0.001] and midregional-pro-atrial natriuretic peptide (MR-proANP) was reduced by 20% (95% CI = 12-28%, P < 0.001). Also, urinary albumin excretion declined by 30% (95% CI = 12-44%, P = 0.003), GFR by 11 ml/min/1.73 m(2) (95% CI = 7.2-14.4 ml/min/1.73 m(2) , P < 0.001) and fractional albumin excretion by 29% (95% CI = 3-48%, P = 0.032).

CONCLUSIONS

Liraglutide treatment was associated with an initial increase in 24-h SBP, followed by a 7 mmHg reduction after escalation to 1.8 mg/day. This effect subsided after 4 weeks of maximum dose. Reductions in ECV and MR-proANP may explain the anti-hypertensive potential. Liraglutide treatment was associated with reversible reductions in albuminuria and GFR, which has to be confirmed in randomized trials.

Twelve-month treatment with Liraglutide ameliorates Visceral Adiposity Index and common cardiovascular risk factors in type 2 diabetes outpatients

AIM

In addition to the effects on glycemic control and body weight, GLP-1 receptor agonists may favorably affect other major cardiovascular disease (CVD) risk factors, although currently available data are still sparse. In this retrospective study, we evaluated the effects of 12-month treatment with liraglutide on major CVD risk factors in 115 type 2 diabetes outpatients (60 men and 55 women), on stable hypoglycemic, anti-hypertensive and/or lipid-lowering therapy.

METHODS

Clinical and anthropometric data, metabolic and lipid profile, as well as the Visceral Adiposity Index (VAI), an obesity-related CVD risk factor, were measured in all participants at baseline and after 12-month treatment.

RESULTS

Treatment with liraglutide was associated with a significant reduction from baseline values of fasting blood glucose (-42.1 mg/dl, P < 0.05), HbA1c (-1.5 %, -17 mmol/mol, P < 0.05), body weight (-7.1 kg, P < 0.05), waist circumference (-6.8 cm, P < 0.001), total-cholesterol (-27.4 mg/dl, P < 0.05), LDL-cholesterol (-25.4 mg/dl, P < 0.05), triglycerides (-56.1 mg/dl, P < 0.05), and non-HDL-C (-36.6 mg/dl, P < 0.05) and an increase of HDL-cholesterol concentrations (+9.3 mg/dl, P < 0.001), a significant reduction in both systolic and diastolic blood pressure (-14.7 mmHg, P < 0.001 and -9.0 mmHg, P < 0.05, respectively) and a decrease of VAI values (-1.6, P < 0.001). All these differences were independent of changes in BMI and comparable in men and women.

CONCLUSIONS

In conclusion, 12-month treatment with liraglutide in add-on to on-going hypoglycemic therapy significantly ameliorates all major CVD risk factors and reduces cardiometabolic risk, as estimated by VAI values.

A multiplicity of targets: evaluating composite endpoint studies of the GLP-1 receptor agonists in type 2 diabetes

OBJECTIVE

Current type 2 diabetes (T2D) treatment guidelines include weight maintenance or loss, avoidance of hypoglycemia, and targets for blood pressure and circulating lipids, in addition to glycemic control. Increasingly, clinical trials and meta-analyses employ composite endpoints to capture the net clinical benefit of a given T2D intervention. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) represent a new class of injected antihyperglycemic agents that may be well suited to reaching many of these targets among patients failing on metformin monotherapy.

RESEARCH DESIGNS AND METHODS

Using MEDLINE, Embase and Google Scholar, studies were sought that employed composite endpoints and that reported outcomes with exenatide and/or liraglutide. Bibliographies of relevant review articles were consulted to search for additional reports.

RESULTS

Many trials have used the combination of HbA1c <7%, no weight gain and no hypoglycemic episodes as the composite endpoint in evaluating T2D therapies; however, at least 15 other distinct composite endpoints have been reported. Findings were relatively consistent across studies, regardless of how the composite endpoint was defined. Specifically, the GLP-1 RAs appear to be superior to other agents in their efficacy in providing T2D patients failing on metformin with a net clinical benefit, which can include avoidance of hyperglycemia and maintenance or improvement in body weight.

CONCLUSIONS

Use of composite endpoints represents an important advance in T2D. While no single such endpoint has achieved dominance in the field, widely used composite endpoints capture efficacy in glycemic control as well as safety and effects on markers of cardiovascular risk.

Anti-obesity drugs currently used and new compounds in clinical development

Obesity is a chronic disease which requires treatment. As lifestyle interventions alone hardly ever result in long-term weight loss, pharmacotherapy is an important adjunct to lifestyle measures to improve the induction and maintenance of weight loss. Owing to the limited options currently available for the pharmacological treatment of obesity, it is imperative to develop new safe compounds. This study aims to review the current medications approved by European Medicines Agency and United States Food and Drug Administration (FDA) for the treatment of obesity, focusing essentially on their benefits and risks, as well as on the new drugs which are presently under clinical trials. Moreover, it lists the anti-obesity agents that have been recently withdrawn from the market. A revision of the scientific literature was carried out, through a search on Pubmed for papers published from January 2010 to January 2013. Orlistat (Xenical^®) is currently the only long-term pharmacotherapy for obesity available in the European market, as rimonabant and sibutramine were withdrawn in 2008 and 2010, respectively, due to serious psychiatric and cardiovascular adverse effects. Lorcaserin (Belviq^®) and the association of phentermine and topiramate (Qsymia^TM) were recently approved by FDA. Orlistat suppresses appetite inhibiting gastrointestinal lipase, being its adverse effects mostly gastrointestinal. Lorcaserin activates 5-HT_2C receptors, phentermine is a norepinephrine releasing drug, and topiramate is an anticonvulsivant drug with weight loss properties.

Preliminary study characterizing the use of sitagliptin for glycemic control in healthy Beagle dogs with normal gluco-homeostasis

Sitagliptin is a dipeptidyl peptidase-4 inhibitor aimed at treating Type 2 diabetes mellitus (T2DM) and T1DM, by increasing blood levels of Glucagon-like peptide 1 (GLP-1) and insulin. The objective of this preliminary study is to characterize Sitagliptin’s ability for glycemic control, in healthy dogs under an oral glucose tolerance test (OGTT) environment. Overall, Sitagliptin did not result in any significant changes to temporal glucose and insulin concentrations. However, a ~55% increase in median total GLP-1 AUC_0–120min was observed, as compared to baseline control in healthy dogs (n=5), thus indicating a similar mode of action of Sitagliptin between healthy dogs and humans. Future studies to validate the use of Sitagliptin with dogs suffering from insulin independent diabetes are warranted.

Effects of glucagon-like peptide 1 on appetite and body weight: focus on the CNS

The delivery of nutrients to the gastrointestinal tract after food ingestion activates the secretion of several gut-derived mediators, including the incretin hormone glucagon-like peptide 1 (GLP-1). GLP-1 receptor agonists (GLP-1RA), such as exenatide and liraglutide, are currently employed successfully in the treatment of patients with type 2 diabetes mellitus. GLP-1RA improve glycaemic control and stimulate satiety, leading to reductions in food intake and body weight. Besides gastric distension and peripheral vagal nerve activation, GLP-1RA induce satiety by influencing brain regions involved in the regulation of feeding, and several routes of action have been proposed. This review summarises the evidence for a physiological role of GLP-1 in the central regulation of feeding behaviour and the different routes of action involved. Also, we provide an overview of presently available data on pharmacological stimulation of GLP-1 pathways leading to alterations in CNS activity, reductions in food intake and weight loss.

Different prevalence of metabolic control and chronic complication rate according to the time of referral to a diabetes care unit in the elderly

The time of diagnosis is crucial for type 2 diabetes mellitus (T2DM) in terms of disease severity and chronic complications, as initial glycated haemoglobin (HbA1c) predicts 5-year cardiovascular mortality. The Italian health-care system relies on about 650 diabetes care units (DCU) interfacing with a large number of general practitioners (GPs). It may thus reach the goal of preventing complications easier than others by adopting a more comprehensive multifactorial approach. To assess whether the interval between diagnosis and referral to the DCU might influence the course of the disease in terms of HbA1c, associated cardiovascular risk factors, drug utilisation, and chronic complications in the elderly, the electronic records of 313 elderly T2DM patients (74.6 ± 4.9 years) followed by their GPs until referral to our DCU were retrospectively analysed for the above-mentioned parameters and divided into an early referral (ER) group (diagnosed within 12 months, n = 111) and a late referral (LR) group (diagnosed >12 months before, n = 202). A further set of 200 patients routinely taken care by our DCU, matched with the LR group for age, gender, and disease duration, was classified as "long-standing follow-up" (LSF) and compared to the others to rule out any confounding effects of long-standing disease per se on the clinical outcomes investigated in our study. About 35 % of T2DM patients referred to our DCU within 12 months of diagnosis; the rest did so some 5 years after diagnosis. LR patients displayed worse HbA1c levels (10.8 vs. 7.7 %, p < 0.01), used more drugs, and had more than twice as high complication rates as their ER counterparts. Almost all risk factors and complications were lower in the LSF (0.001 < p < 0.05) and ER groups than in the LR group. In both the ER and the LSF groups, we observed a lower burden of diabetes than in the LR group. This rules out the possibility that disease duration might play a major role per se in the burden of the disease in the elderly as opposed to the thoughtful patient care attitude exhibited by the DCU. A better and more efficient organisation has to be developed, including a strong interaction among GPs, diabetes specialists, and elderly people with T2DM allowing the latter to take charge of their own disease management through a sustained empowerment policy.

Characterization of the use of liraglutide for glycemic control in healthy and Type 1 diabetes mellitus suffering dogs

Glucagon-like peptide 1 (GLP-1) is a glucose-lowering, intestinal-derived factor with multiple physiological effects, making it attractive for diabetes therapy. However, the therapeutic potential of endogenous GLP-1 is limited, because of rapid inactivation by dipeptidyl peptidase-4. Recently, enhanced incretin preparations, such as liraglutide, have emerged, which are more resistant to degradation and longer lasting. Liraglutide is a long-acting acylated human GLP-1 receptor agonist, with a 97% amino acid sequence identity to endogenous human GLP-1, and 100% amino acid sequence homology with canine GLP-1. Since liraglutide has yet to be examined for use in dogs, and the incretin effect has been reported to exist in dogs, we sought to initially characterize liraglutide's ability for glycemic control in healthy dogs, under an oral glucose tolerance test (OGTT) environment initially. This was followed up a more realistic scenario involving food with insulin injection +/- liraglutide injection resulting in a glucose curve based study involving dogs suffering from Type 1 diabetes mellitus (T1DM). Overall, liraglutide had a stabilizing effect on glucose levels, maintaining circulating levels between 77.0 and 137.0mg/ml throughout the OGTT test period, resulting in a significant reduction of 13.8% in glucose AUC0-120 min (total area under the curve for 0-120 min) as compared to baseline control in healthy dogs (n=5). Interestingly, the liraglutide associated reduction in circulating glucose was not accompanied by any significant increase in insulin. Moreover, T1DM dogs (n=4) responded favorably to liraglutide treatment, which lead to a significant reduction of 46.0% in glucose AUC0-12h (total area under the curve for 0-12h), and a significant reduction of 66.5% in serum glucose as compared to baseline controls (insulin treatment only). Therefore, liraglutide's prandial glucagon suppressive ability appears to play a key role in its glucose-lowering capability, and offers great potential for use with dogs suffering from T1DM.

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)

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.

Experience with the high-intensity sweetener saccharin impairs glucose homeostasis and GLP-1 release in rats

Previous work from our lab has demonstrated that experience with high-intensity sweeteners in rats leads to increased food intake, body weight gain and adiposity, along with diminished caloric compensation and decreased thermic effect of food. These changes may occur as a result of interfering with learned relations between the sweet taste of food and the caloric or nutritive consequences of consuming those foods. The present experiments determined whether experience with the high-intensity sweetener saccharin versus the caloric sweetener glucose affected blood glucose homeostasis. The results demonstrated that during oral glucose tolerance tests, blood glucose levels were more elevated in animals that had previously consumed the saccharin-sweetened supplements. In contrast, during glucose tolerance tests when a glucose solution was delivered directly into the stomach, no differences in blood glucose levels between the groups were observed. Differences in oral glucose tolerance responses were not accompanied by differences in insulin release; insulin release was similar in animals previously exposed to saccharin and those previously exposed to glucose. However, release of GLP-1 in response to an oral glucose tolerance test, but not to glucose tolerance tests delivered by gavage, was significantly lower in saccharin-exposed animals compared to glucose-exposed animals. Differences in both blood glucose and GLP-1 release in saccharin animals were rapid and transient, and suggest that one mechanism by which exposure to high-intensity sweeteners that interfere with a predictive relation between sweet tastes and calories may impair energy balance is by suppressing GLP-1 release, which could alter glucose homeostasis and reduce satiety.

Liraglutide in oral antidiabetic drug combination therapy

The glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide is indicated as an add-on to oral antidiabetic drug regimens in subjects with type 2 diabetes. Herein, the results of clinical trials assessing the efficacy, safety and tolerability of liraglutide when used in combination with either one or two oral antidiabetic therapies are summarised, then contrasted with the effects of exenatide and dipeptidyl peptidase (DPP-4) inhibitors. GLP-1 receptor agonists lead to effective glycaemic control when used as combination therapy with either one or two oral antidiabetic agents, and may confer overall benefits in weight loss and blood pressure in some subjects. These agents are well tolerated; the most commonly reported adverse effect is mild-to-moderate gastrointestinal symptoms, which are usually transient. Rates of hypoglycaemia in these trials were low, although higher rates were noted when combined with a sulphonylurea. While further study will be required, GLP-1 receptor agonists may offer important advantages over other diabetic therapies, including DPP-4 inhibitors.