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

Twenty-four-week effects of liraglutide on body composition, adherence to appetite, and lipid profile in overweight and obese patients with type 2 diabetes mellitus

BACKGROUND

Liraglutide has well-known effects on glucose patterns. However, its several other metabolic properties are still controversial. Given this background, the aims of the present study are to evaluate the effects of 24-week liraglutide treatment on body composition, appetite, and lipid profile in overweight and obese type 2 diabetes mellitus (T2DM) patients.

METHODS

A cohort study was carried out on overweight and obese T2DM patients with glycosylated hemoglobin A1c equal to 6% (42 mmol/mol)-10% (86 mmol/mol), under a 3-month treatment (at least) with maximal dose of metformin as stable regime, by adding liraglutide at doses up to 3 mg/d. Body composition markers were measured by dual-energy X-ray densitometry at baseline and after 24 weeks of liraglutide treatment. Glucose control was monitored by glucose, glycosylated hemoglobin A1c, insulin, and homeostasis model assessment. Finally, the appetite sensation and plasma lipids were also evaluated.

RESULTS

Twenty-eight subjects (male/female: 16/12, mean age: 58.75±9.33 years, body mass index: 34.13±5.46 kg/m(2)) were evaluated. Accounting for the adjustment for age, sex, and duration of diabetes, we noted significant decreases in body mass index (-0.86 kg/m(2), P=0.024), fat mass (-2.01 kg, P=0.015), fat mass index (-0.71 kg/m(2), P=0.014), android fat (-1.72%, P=0.022), trunk fat (-1.52%, P=0.016), and waist circumference (-6.86 cm, P<0.001) from the baseline values. Haber score was increased by 3.82 units (P=0.009), and the number of metabolic syndrome risk factors was decreased (-0.69 units, P=0.012). The glucose control variables and total cholesterol/high-density lipoprotein cholesterol ratio also showed significant decreases from baseline values.

CONCLUSION

The 24-week liraglutide treatment leads to the reduction of fat mass, android fat, trunk fat, and appetite by improving the lipid profile, glucose control, and insulin sensitivity.

The GLP-1 agonist, liraglutide, as a pharmacotherapy for obesity

There is a global obesity epidemic that will continue to be a financial burden on healthcare systems around the world. Tackling obesity through diet and exercise should always be the first intervention, but this has not proved to be effective for a large number of patients. Pharmacotherapeutic options have been limited and many previously available drugs have been withdrawn due to safety concerns. Currently, only bariatric surgery has the capability to induce both substantial and durable weight loss. This article briefly reviews the history of pharmacotherapy for obesity before focusing on the clinical trial evidence for the use of the GLP-1 agonist liraglutide as a weight loss agent and comparing its efficacy with other emerging drug therapies for obesity.

Endogenous GLP-1 mediates postprandial reductions in activation in central reward and satiety areas in patients with type 2 diabetes

AIMS/HYPOTHESIS

The central nervous system (CNS) is a major player in the regulation of food intake. The gut hormone glucagon-like peptide-1 (GLP-1) has been proposed to have an important role in this regulation by relaying information about nutritional status to the CNS. We hypothesised that endogenous GLP-1 has effects on CNS reward and satiety circuits.

METHODS

This was a randomised, crossover, placebo-controlled intervention study, performed in a university medical centre in the Netherlands. We included patients with type 2 diabetes and healthy lean control subjects. Individuals were eligible if they were 40-65 years. Inclusion criteria for the healthy lean individuals included a BMI <25 kg/m(2) and normoglycaemia. Inclusion criteria for the patients with type 2 diabetes included BMI >26 kg/m(2), HbA1c levels between 42 and 69 mmol/mol (6.0-8.5%) and treatment for diabetes with only oral glucose-lowering agents. We assessed CNS activation, defined as blood oxygen level dependent (BOLD) signal, in response to food pictures in obese patients with type 2 diabetes (n = 20) and healthy lean individuals (n = 20) using functional magnetic resonance imaging (fMRI). fMRI was performed in the fasted state and after meal intake on two occasions, once during infusion of the GLP-1 receptor antagonist exendin 9-39, which was administered to block actions of endogenous GLP-1, and on the other occasion during saline (placebo) infusion. Participants were blinded for the type of infusion. The order of infusion was determined by block randomisation. The primary outcome was the difference in BOLD signal, i.e. in CNS activation, in predefined regions in the CNS in response to viewing food pictures.

RESULTS

All patients were included in the analyses. Patients with type 2 diabetes showed increased CNS activation in CNS areas involved in the regulation of feeding (insula, amygdala and orbitofrontal cortex) in response to food pictures compared with lean individuals (p ≤ 0.04). Meal intake reduced activation in the insula in response to food pictures in both groups (p ≤ 0.05), but this was more pronounced in patients with type 2 diabetes. Blocking actions of endogenous GLP-1 significantly prevented meal-induced reductions in bilateral insula activation in response to food pictures in patients with type 2 diabetes (p ≤ 0.03).

CONCLUSIONS/INTERPRETATION

Our findings support the hypothesis that endogenous GLP-1 is involved in postprandial satiating effects in the CNS of obese patients with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT 01363609. Funding The study was funded in part by a grant from Novo Nordisk.

Pharmacotherapy for the management of obesity

In the last 30 years, obesity has rapidly increased and obesity-related comorbidities have surged. Once considered to be a problem only in developed nations, obesity has become a global epidemic. Consequently, the costs associated with managing overweight and obesity worldwide are astronomical. The objective of this mini-review is to provide an overview of current options available for obesity management, with a focus on anti-obesity pharmacotherapies. The impact of weight loss on improving obesity-related comorbidities and risk factors has been well documented. Although established clinical guidelines suggest comprehensive lifestyle modification to induce weight loss, many patients do not respond to lifestyle interventions and may not qualify for bariatric surgery. For these patients, pharmacotherapy may serve as a therapeutic option. Several anti-obesity pharmacotherapies, such as phentermine, are indicated for short-term use and are not required to demonstrate clinically meaningful weight loss (i.e., ≥5%). For long-term weight management, the FDA has approved 5 agents so far-orlistat, lorcaserin, phentermine/topiramate, naltrexone/bupropion, and liraglutide. These drugs have shown efficacy in enabling patients to achieve clinically meaningful weight loss and improving cardiometabolic parameters. Healthcare practitioners can help alleviate the obesity epidemic by tailoring these pharmacotherapies based on individual needs, comorbidities, and associated drug safety concerns.

Exenatide Regulates Cerebral Glucose Metabolism in Brain Areas Associated With Glucose Homeostasis and Reward System

Glucagon-like peptide 1 receptors (GLP-1Rs) have been found in the brain, but whether GLP-1R agonists (GLP-1RAs) influence brain glucose metabolism is currently unknown. The study aim was to evaluate the effects of a single injection of the GLP-1RA exenatide on cerebral and peripheral glucose metabolism in response to a glucose load. In 15 male subjects with HbA1c of 5.7 ± 0.1%, fasting glucose of 114 ± 3 mg/dL, and 2-h glucose of 177 ± 11 mg/dL, exenatide (5 μg) or placebo was injected in double-blind, randomized fashion subcutaneously 30 min before an oral glucose tolerance test (OGTT). The cerebral glucose metabolic rate (CMRglu) was measured by positron emission tomography after an injection of [(18)F]2-fluoro-2-deoxy-d-glucose before the OGTT, and the rate of glucose absorption (RaO) and disposal was assessed using stable isotope tracers. Exenatide reduced RaO0-60 min (4.6 ± 1.4 vs. 13.1 ± 1.7 μmol/min ⋅ kg) and decreased the rise in mean glucose0-60 min (107 ± 6 vs. 138 ± 8 mg/dL) and insulin0-60 min (17.3 ± 3.1 vs. 24.7 ± 3.8 mU/L). Exenatide increased CMRglu in areas of the brain related to glucose homeostasis, appetite, and food reward, despite lower plasma insulin concentrations, but reduced glucose uptake in the hypothalamus. Decreased RaO0-60 min after exenatide was inversely correlated to CMRglu. In conclusion, these results demonstrate, for the first time in man, a major effect of a GLP-1RA on regulation of brain glucose metabolism in the absorptive state.

Emotional eating is associated with increased brain responses to food-cues and reduced sensitivity to GLP-1 receptor activation

OBJECTIVE

The neural correlates and pathophysiology of emotional eating are insufficiently known. Glucagon-like peptide-1 (GLP-1), a postprandial hormone, plays a role in feeding behavior by signaling satiety to the brain. GLP-1 receptor agonists, used for treatment of type 2 diabetes (T2DM), promote weight loss. This study investigated the association between emotional eating and responses to food-cues in brain areas involved in satiety and reward processing, as well as GLP-1 receptor agonist-induced effects on these brain responses.

METHODS

T2DM patients with obesity, normoglycemic individuals with obesity, and lean individuals (n = 48) were studied in a randomized placebo-controlled crossover study. Using functional MRI, we determined the relation between emotional eating and regional brain responses to visual food stimuli and acute effects of intravenous administration of the GLP-1 receptor agonist exenatide on these responses.

RESULTS

Emotional eating scores positively correlated with responses to food-cues in lean subjects in the insula, in normoglycemic subjects with obesity in the insula, and in T2DM patients in the amygdala, orbitofrontal cortex, and insula. Emotional eating scores negatively correlated with exenatide-induced reductions in responses to food-cues in normoglycemic subjects with obesity in the amygdala and in T2DM patients in the insula.

CONCLUSIONS

Our findings indicate that emotional eaters have altered brain responses to food-cues and are less sensitive to the central effects of GLP-1 receptor activation.

Dissociation of GLP-1 and insulin association with food processing in the brain: GLP-1 sensitivity despite insulin resistance in obese humans

Objective

Glucagon-like peptide-1 (GLP-1) is released into the bloodstream after food intake. In addition to stimulating insulin release, it causes satiety and contributes to the termination of food intake. In this study, we investigated whether endogenous GLP-1 affects food-related brain activity and hunger.

Methods

Twenty-four volunteers (12 lean; 12 obese) underwent a 75 g oral glucose tolerance test that promotes GLP-1 secretion. Food cue-induced brain activity was assessed by functional magnetic resonance imaging and GLP-1 concentrations were measured before, 30, and 120 min after glucose intake.

Results

The significant increase in GLP-1 levels negatively correlated with a change in the food cue-induced brain activity in the orbitofrontal cortex, a major reward area. This association was independent of simultaneous alterations in insulin and glucose concentrations. The association was present in lean and overweight participants. By contrast, postprandial insulin changes were associated with orbitofrontal activations in lean individuals only.

Conclusions

The postprandial release of GLP-1 might alter reward processes in the orbitofrontal cortex and might thereby support the termination of food intake and reduce hunger. While obese persons showed brain insulin resistance, no GLP-1 resistance was observed. Our study provides novel insight into the central regulation of food intake by the incretin hormone GLP-1.

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GLP-1 levels associate with food cue-induced brain activity in the orbitofrontal cortex, a major reward area.

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While obese persons are brain insulin-resistant in the orbitofrontal cortex, they still respond to GLP-1.

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Postprandial GLP-1 release may alter reward processes in the orbitofrontal cortex to support the termination of food intake.

Effect of placental restriction and neonatal exendin-4 treatment on postnatal growth, adult body composition, and in vivo glucose metabolism in the sheep

Intrauterine growth restriction (IUGR) increases the risk of adult type 2 diabetes (T2D) and obesity. Neonatal exendin-4 treatment can prevent diabetes in the IUGR rat, but whether this will be effective in a species where the pancreas is more mature at birth is unknown. Therefore, we evaluated the effects of neonatal exendin-4 administration after experimental restriction of placental and fetal growth on growth and adult metabolic outcomes in sheep. Body composition, glucose tolerance, and insulin secretion and sensitivity were assessed in singleton-born adult sheep from control (CON; n = 6 females and 4 males) and placentally restricted pregnancies (PR; n = 13 females and 7 males) and in sheep from PR pregnancies that were treated with exendin-4 as neonates (daily sc injections of 1 nmol/kg exendin-4; PR + exendin-4; n = 11 females and 7 males). Placental restriction reduced birth weight (by 29%) and impaired glucose tolerance in the adult but did not affect adult adiposity, insulin secretion, or insulin sensitivity. Neonatal exendin-4 suppressed growth during treatment, followed by delayed catchup growth and unchanged adult adiposity. Neonatal exendin-4 partially restored glucose tolerance in PR progeny but did not affect insulin secretion or sensitivity. Although the effects on glucose tolerance are promising, the lack of effects on adult body composition, insulin secretion, and insulin sensitivity suggest that the neonatal period may be too late to fully reprogram the metabolic consequences of IUGR in species that are more mature at birth than rodents.

Glucagon and GLP-1 exhibit no synergistic enhancement of glucose-stimulated insulin secretion in mice

The combination of glucagon and glucagon-like peptide-1 (GLP-1) has been suggested as an approach to target obesity, since the two hormones have complementary action on body weight. We examined whether complementary action of the two hormones also exist on insulin secretion. Female C57BL/6 mice were injected intravenously with glucose with or without GLP-1, glucagon or the combination of GLP-1 and glucagon at three different dose levels. Furthermore, freshly isolated mouse islets were incubated for 30min in the presence of 2.8, 11.1 or 16.7mmol/l glucose or with 11.1mmol/l glucose in the presence of 100nmol/l glucagon and/or GLP-1. It was found that at 1min after glucose injection alone, insulin rose to a peak level and this peak, as well as the 50min area under the insulin curve (AUC insulin) were dose-dependently augmented by GLP-1 and glucagon. However, peak insulin with the two hormones together (with glucose) was not higher than after either single administration at any of the tested doses, i.e., no additive of synergistic action was observed by the combination on glucose-stimulated insulin secretion. Similar results were observed when calculating insulin for the whole test period. Also in vitro, both glucagon and GLP-1 augmented insulin secretion; however, there was no difference between the combined stimulation of insulin secretion by GLP-1 and glucagon together compared with either hormone alone. Insulin sensitivity did not exhibit significant changes from the glucose only condition. We conclude that the acute combined administration of the strongly insulinotropic GLP-1 and glucagon, both in vivo and in vitro, did not induce any additive or synergistic action on glucose-stimulated insulin secretion. This shows that the risk of a marked insulinotropic action when the two compounds are given together most likely does not result in increased risk of hypoglycemia.

Brain reward-system activation in response to anticipation and consumption of palatable food is altered by glucagon-like peptide-1 receptor activation in humans

AIM

To test the hypothesis that food intake reduction after glucagon-like peptide-1 (GLP-1) receptor activation is mediated through brain areas regulating anticipatory and consummatory food reward.

METHODS

As part of a larger study, we determined the effects of GLP-1 receptor activation on brain responses to anticipation and receipt of chocolate milk versus a tasteless solution, using functional MRI (fMRI). Obese subjects with type 2 diabetes, and obese and lean subjects with normoglycaemia (n = 48) underwent three fMRI sessions at separate visits with intravenous infusion of the GLP-1 receptor agonist exenatide, exenatide with prior GLP-1 receptor blockade by exendin-9-39 or placebo, during somatostatin pituitary-pancreatic clamps.

RESULTS

Body mass index negatively correlated with brain responses to receipt of chocolate milk and positively correlated with anticipation of receipt of chocolate milk in brain areas regulating reward, appetite and motivation. Exenatide increased brain responses to receipt of chocolate milk and decreased anticipation of receipt of chocolate milk compared with placebo, paralleled by reductions in food intake. Exendin-9-39 largely prevented these effects.

CONCLUSIONS

Our findings show that GLP-1 receptor activation decreases anticipatory food reward, which may reduce cravings for food and increases consummatory food reward, which may prevent overeating.

Incretin-based therapies for obesity treatment

Currently, obesity and its associated complications are considered major public health problems worldwide. Because the causes are multifactorial and complex, different treatment methods are used, which include diet and exercise, as well as the use of drugs, although they can have adverse side effects. A new target for the treatment of obesity may be the incretin system, which consists of hormones that seem to contribute to weight loss. In this sense, some studies have shown a relationship between weight loss and drugs related to incretin system, including glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors. The objective of this review is to summarize the association between the incretin system and obesity treatment.

DPP4 in Diabetes

Dipeptidyl-peptidase 4 (DPP4) is a glycoprotein of 110 kDa, which is ubiquitously expressed on the surface of a variety of cells. This exopeptidase selectively cleaves N-terminal dipeptides from a variety of substrates, including cytokines, growth factors, neuropeptides, and the incretin hormones. Expression of DPP4 is substantially dysregulated in a variety of disease states including inflammation, cancer, obesity, and diabetes. Since the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide (GIP), are major regulators of post-prandial insulin secretion, inhibition of DPP4 by the gliptin family of drugs has gained considerable interest for the therapy of type 2 diabetic patients. In this review, we summarize the current knowledge on the DPP4–incretin axis and evaluate most recent findings on DPP4 inhibitors. Furthermore, DPP4 as a type II transmembrane protein is also known to be cleaved from the cell membrane involving different metalloproteases in a cell-type-specific manner. Circulating, soluble DPP4 has been identified as a new adipokine, which exerts both para- and endocrine effects. Recently, a novel receptor for soluble DPP4 has been identified, and data are accumulating that the adipokine-related effects of DPP4 may play an important role in the pathogenesis of cardiovascular disease. Importantly, circulating DPP4 is augmented in obese and type 2 diabetic subjects, and it may represent a molecular link between obesity and vascular dysfunction. A critical evaluation of the impact of circulating DPP4 is presented, and the potential role of DPP4 inhibition at this level is also discussed.

Gut-brain connection: The neuroprotective effects of the anti-diabetic drug liraglutide

Long-acting glucagon-like peptide-1 (GLP-1) analogues marketed for type 2 diabetes (T2D) treatment have been showing positive and protective effects in several different tissues, including pancreas, heart or even brain. This gut secreted hormone plays a potent insulinotropic activity and an important role in maintaining glucose homeostasis. Furthermore, growing evidences suggest the occurrence of several commonalities between T2D and neurodegenerative diseases, insulin resistance being pointed as a main cause for cognitive decline and increased risk to develop dementia. In this regard, it has also been suggested that stimulation of brain insulin signaling may have a protective role against cognitive deficits. As GLP-1 receptors (GLP-1R) are expressed throughout the central nervous system and GLP-1 may cross the blood-brain-barrier, an emerging hypothesis suggests that they may be promising therapeutic targets against brain dysfunctional insulin signaling-related pathologies. Importantly, GLP-1 actions depend not only on the direct effect mediated by its receptor activation, but also on the gut-brain axis involving an exchange of signals between both tissues via the vagal nerve, thereby regulating numerous physiological functions (e.g., energy homeostasis, glucose-dependent insulin secretion, as well as appetite and weight control). Amongst the incretin/GLP-1 mimetics class of anti-T2D drugs with an increasingly described neuroprotective potential, the already marketed liraglutide emerged as a GLP-1R agonist highly resistant to dipeptidyl peptidase-4 degradation (thereby having an increased half-life) and whose systemic GLP-1R activity is comparable to that of native GLP-1. Importantly, several preclinical studies showed anti-apoptotic, anti-inflammatory, anti-oxidant and neuroprotective effects of liraglutide against T2D, stroke and Alzheimer disease (AD), whereas several clinical trials, demonstrated some surprising benefits of liraglutide on weight loss, microglia inhibition, behavior and cognition, and in AD biomarkers. Herein, we discuss the GLP-1 action through the gut-brain axis, the hormone’s regulation of some autonomic functions and liraglutide’s neuroprotective potential.

Genetic variability in GLP-1 receptor is associated with inter-individual differences in weight lowering potential of liraglutide in obese women with PCOS: a pilot study

PURPOSE

The weight lowering potential of glucagon-like peptide 1 (GLP-1) receptor agonists (RAs) is inter-individually different and clinically unpredictable. The potential role of genetic variability of GLP-1R on body weight response to GLP-1 RAs in obese women with polycystic ovary syndrome (PCOS) has not yet been evaluated.

METHODS

Fifty-seven obese women with PCOS (aged 30.7 ± 7.0, BMI 38.6 ± 5.3 kg/m(2)) were assigned to liraglutide 1.2 mg QD s.c. for 12 weeks and classified as strong responders regarding weight loss if they lost 5% or more of their initial body weight. They were genotyped for common GLP-1R single nucleotide polymorphisms (SNPs) rs6923761 and rs10305420. Changes of measures of obesity were measured before and at the end of the treatment.

RESULTS

Twenty out of 57 subjects were strong responders and lost 7.38 ± 1.74 compared to 2.11 ± 2.17 kg lost in poor responders. Carriers of at least one polymorphic rs10305420 allele had poor treatment response compared to carriers of two wild type alleles (OR = 0.27, 95% CI = 0.09-0.85, P = 0.025). Carriers of at least one polymorphic rs6923761 allele tended to have stronger treatment response compared to carriers of two wild type alleles (OR = 3.06, 95% CI = 0.96-9.74, P = 0.058). Fasting glucose and glucose after oral glucose tolerance test (OGTT) comparably decreased in both groups when compared to baseline, whereas no within treatment differences were found in androgen profile. Gastrointestinal adverse events were transit and balanced between strong and poor responders.

CONCLUSIONS

GLP-1R rs10305420 polymorphism explained some of the inter-individual differences in response to liraglutide regarding weight loss in obese PCOS women.

Weight loss effect of glucagon-like peptide-1 mimetics on obese/overweight adults without diabetes: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) benefit weight maintenance for diabetic patients. We performed a systematic review to evaluate its weight loss effect on obese/overweight patients without diabetes in randomized controlled trials (RCTs).

METHODS

Literature updated to May 5, 2014 from Cochrane Library, MEDLINE, EMBASE and reference lists from relevant articles were identified. RCTs with GLP-1 mimetics treating obese/overweight adults without diabetes for at least 12 weeks were assessed. Studies lacking primary measurements were excluded. Three authors extracted data independently. Either fixed-effect or random-effect models were used to calculate weighted mean differences (WMDs), combined relative risks (RR) and 95% confidence interval (CI) in meta-analyses. Intertrial heterogeneity across studies was examined by I(2) and Q statistics.

RESULTS

A total of 1345 individuals retrieved from eight studies were involved and all included trials were of mild-to-moderate bias risks. Participants in GLP-1RA groups achieved a larger weight loss than those in control groups (-2.85 kg, 95%CI -3.55 to -2.14), and liraglutide may work in a dose-dependent fashion. GLP-1RAs also reduced body mass index (BMI) and waist circumferences (WC) and benefited systolic blood pressure and triglyceride regulation. But GLP-1RAs were associated with increased nausea and vomiting events.

CONCLUSIONS

GLP-1 mimetics induce a weight loss in addition to BMI and WC reduction in obese/overweight adults without diabetes. Further long-term randomized trials and basic studies are required to investigate the mechanisms.

Revisiting weight reduction and management in the diabetic patient: Novel therapies provide new strategies

Weight gain has been so synonymous with diabetes care that overweight/obesity is considered an intractable aspect of diabetes and its management. A healthy body mass index (BMI) is paramount, however, in preserving the cardiometabolic profile, slowing the course of the disease and extending the life expectancy of patients. It is also key to fostering a healthy and productive society at large. Two trends in care press us to challenge our assumptions about weight control in this population by reconsidering traditional approaches to the management of diabetes. First, new anti-diabetes drug classes have emerged that are more "weight-friendly" than previously available treatments and "gentler" on the faltering β cell. Second, novel anti-obesity agents are proving efficacious in patients with diabetes. This paper presents the composite of newer and older anti-obesity and anti-diabetic drugs. It makes recommendations for anti-diabetic regimens and processes of care that engender weight loss, or neutralize or minimize weight gain, while getting many patients to their glycated hemoglobin (HbA1c) goal. Anti-obesity agents that can be safely and effectively incorporated into these regimens for the patient needing supplemental support are reviewed in detail.

The effects of treatment with liraglutide on atherothrombotic risk in obese young women with polycystic ovary syndrome and controls

BACKGROUND

Polycystic ovary syndrome (PCOS) is associated with obesity and increased cardiovascular (CV) risk markers. In this study our aim was to assess the effects of six months treatment with liraglutide 1.8 mg od on obesity, and CV risk markers, particularly platelet function, in young obese women with PCOS compared to controls of similar age and weight.

METHODS

Carotid intima-media wall thickness (cIMT) was measured by B-mode ultrasonography, platelet function by flow cytometry, clot structure/lysis by turbidimetric assays and endothelial function by ELISA and post-ischaemic reactive hyperemia (RHI). Data presented as mean change (6-month - baseline) ± standard deviation.

RESULTS

Nineteen obese women with PCOS and 17 controls, of similar age and weight, were recruited; baseline atherothrombotic risk markers did not differ between the two groups. Twenty five (69.4%) participants completed the study (13 PCOS, 12 controls). At six months, weight was significantly reduced by 3.0 ± 4.2 and 3.8 ± 3.4 kg in the PCOS and control groups, respectively; with no significant difference between the two groups, P = 0.56. Similarly, HOMA-IR, triglyceride, hsCRP, urinary isoprostanes, serum endothelial adhesion markers (sP-selectin, sICAM and sVCAM), and clot lysis area were equally significantly reduced in both groups compared to baseline. Basal platelet P-selectin expression was significantly reduced at six months in controls -0.17 ± 0.26 but not PCOS -0.12 ± 0.28; between groups difference, 95% confidence interval = -0.14 - 0.26, P = 0.41. No significant changes were noted in cIMT or RHI.

CONCLUSIONS

Six months treatment with liraglutide (1.8 mg od) equally affected young obese women with PCOS and controls. In both groups, liraglutide treatment was associated with 3-4% weight loss and significant reduction in atherothrombosis markers including inflammation, endothelial function and clotting. Our data support the use of liraglutide as weight loss medication in simple obesity and suggest a potential beneficial effect on platelet function and atherothrombotic risk at 6 months of treatment.

TRIAL REGISTRATION

Clinical trial reg. no. ISRCTN48560305. Date of registration 22/05/2012.

Effect of GLP-1 receptor agonists on waist circumference among type 2 diabetes patients: a systematic review and network meta-analysis

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are increasingly used in patients with type 2 diabetes. However, the effect on abdominal obesity has not yet been confirmed. The study aimed to systematically evaluate the effect of GLP-1RAs on waist circumference in patients with type 2 diabetes. MEDLINE, EMBASE, the Cochrane library and www.clinicaltrialgov were searched through October 31, 2013. Randomized controlled trials with available data were selected if they compared GLP-1 RAs with placebo and traditional anti-diabetic drugs with a duration≥8 weeks. Weighted mean difference was estimated using random-effect model. Network meta-analysis was performed to supplement direct comparisons. Seventeen trials with 12 treatments were included. Overall, significant reductions on waist circumference following treatment of liraglutide--1.8 mg once daily (-5.24 cm, 95% CI -7.68, -2.93), liraglutide--1.2 mg once daily (-4.73 cm, 95% CI -6.68, -2.65) and exenatide--10 μg twice daily (-1.34 cm, 95 % CI -2.00, -0.75) were detected versus placebo. The reduction effect was more evident when compared with insulin and thiazolidinediones (range -1.71 to -8.03 cm). Compared with exenatide, liraglutide--0.6 mg once daily, taspoglutide, liraglutide--1.2 mg once daily and liraglutide--1.8 mg once daily significantly decreased waist circumference from -3.32 to -6.01 cm. Besides, liraglutide--1.8 mg once daily significantly decreased waist circumference by -1.73 cm (95 % CI -3.04, -0.55) versus sitagliptin, whereas no significant difference following liraglutide--1.2-mg-once-daily treatment was detected compared with liraglutide--1.8 mg once daily and sitagliptin. Reduction was observed with statistical significance for exenatide--10 μg twice daily compared with exenatide--5 μg twice daily (-1.21 cm, 95% CI -2.43, -0.06). Ranking probability analysis indicated liraglutide--1.8 mg once daily and liraglutide--1.2 mg once daily decreased waist circumference most among all 12 treatments with probability of 98.36% and 91.82%, respectively. Some GLP-1RAs, especially liraglutide--1.8 mg once daily and liraglutide--1.2 mg once daily, were associated with a significant reduction in waist circumference.

Fixed combination of insulin and a glucagon-like peptide-1 analog for the treatment of type 2 diabetes, exemplified by insulin degludec and liraglutide

Insulin therapy in the management of Type 2 diabetes is often postponed and/or not adequately intensified to maintain glycemic control because of the risk of weight gain and hypoglycemia. A fixed combination of the long-acting insulin degludec and liraglutide has recently been accepted by the EMA for the management of Type 2 diabetes. The incentive for this combination is to exploit the advantages of each of the drugs while counterbalancing the side effects. Insulin degludec effectively reduces fasting plasma glucose, but carries the risk of hypoglycemia and body weight gain. Liraglutide, on the other hand, exerts glycemic control with a minimal risk of hypoglycemia and, at the same time, reduces appetite and body weight.

Liraglutide and obesity: a review of the data so far

The prevalence of obesity worldwide has nearly doubled since 1980 with current estimates of 2.1 billion in 2013. Overweight and obesity lead to numerous adverse conditions including type 2 diabetes, cardiovascular disease, stroke, and certain cancers. The worldwide spread of obesity and associated comorbidities not only threatens quality of life but also presents a significant economic burden. While bariatric surgery has proven to be a viable treatment option for the morbidly obese, there is clearly a need for less invasive alternatives. Recent research has suggested that long-acting analogs of the gut hormone, glucagon-like peptide 1 (GLP-1), may have potential as an antiobesity treatment. The GLP-1 receptor agonist, liraglutide (trade name Saxenda), was recently approved by the US Food and Drug Administration as an obesity treatment option and shown in clinical trials to be effective in reducing and sustaining body weight loss. This review presents the basis for GLP-1-based therapies with a specific focus on animal and human studies examining liraglutide's effects on food intake and body weight.

Therapeutic stimulation of GLP-1 and GIP protein with DPP-4 inhibitors for type-2 diabetes treatment

Dipeptidyl peptidase-4 (DPP-4) inhibition is a new treatment for type-2 diabetes. DPP-4 inhibition increases levels of active GLP-1. GLP-1 enhances insulin secretion and diminishes glucagon secretion, in this manner reducing glucose concentrations in blood. A number of DPP-4 inhibitors are under clinical development. However, the durability and long-term safety of DPP-4 inhibition remain to be established. These synthetic DPP-4 inhibitors are showing some side effects. Herbal medicines are alternative medicine over synthetic drugs that can relieve the patients. Various research studies have been carried all over the world to evaluate the efficacy of herbs in the treatment of Type II diabetes mellitus. For a long time type II diabetes mellitus has been treated orally with herbal medicines, because plant products are frequently prescribed due to their less toxicity than conventional medicines.

Effect of liraglutide on proliferation and differentiation of human adipose stem cells

Glucagon-Like Peptide-1 (GLP-1) receptor agonists, used as glucose-lowering drugs, also induce weight loss by inhibiting food intake. The present study was aimed at the assessment of the in vitro effects of the GLP-1 receptor agonist liraglutide on proliferation and differentiation of human adipose stem cells (ASC) obtained from subcutaneous adipose tissue of morbidly obese subjects undergoing bariatric surgery. Liraglutide (10-100 nM) significantly inhibited ASC proliferation and viability, with a maximum effect at 6 days of culture (45% and 50%, for liraglutide 10 and 100 nM, respectively); the effect was reverted by exendin 9-39. Glucose uptake was significantly reduced by liraglutide in a dose dependent manner. Treatment with liraglutide reduced intracellular lipid accumulation in differentiating ASC, together with FABP-4 mRNA expression (-18%, -23%, -46%, for 1 nM, 10 nM and 100 nM, respectively), whereas it stimulated adiponectin (APN) expression (1.86-, 2.64-, 2.28-fold increase, for 1 nM, 10 nM and 100 nM, respectively). Liraglutide exerts effects on human adipose cell precursors, inhibiting proliferation and differentiation, while stimulating the expression of the insulin-sensitizing adipokine APN. These effects could contribute to the actions of GLP-1 receptor agonists on body weight and insulin sensitivity.

Stabilization of postprandial blood glucose fluctuations by addition of glucagon like polypeptide-analog administration to intensive insulin therapy

Aims/Introduction

The nature of the action of concomitant liraglutide to stabilize postprandial blood glucose level (PBG) in patients on intensive insulin therapy with unstable PBG remains unclear. The aim was to identify the nature of liraglutide's actions to stabilize PBGs.

Materials and Methods

The study participants consisted of 20 diabetes patients showing unstable PBGs after dinner despite undergoing intensive insulin therapy. The dose of bolus insulin was reduced by three units for each meal, and 0.9 mg/day of liraglutide was added and used in combination. We evaluated the participants' data after the first evaluation (immediately before using liraglutide in combination) and the second evaluation (16 weeks after starting concomitant therapy). PBGs after dinner were measured every day for a period of 28 days immediately before carrying out both evaluations. The mean value of the 28 sets of blood glucose data and their standard deviation (SD) values were established as PBGs after dinner, as well as the SD for each participant. The changes in the mean values of the 20 participants, as well as their SD between before and after concomitant therapy, were evaluated.

Results

The mean value of PBGs (12.0 ± 1.0 to 10.1 ± 0.9 mmol/L) and SD values (5.1 ± 0.7–3.5 ± 0.8) after dinner both declined. A multiple regression analysis showed that the combined use of liraglutide was a significant independent variable of the SD values of PBGs after dinner.

Conclusion

The treatment of reducing the dose of insulin and using liraglutide in combination not only suppresses PBGs, but also stabilizes their blood glucose fluctuations.

Differential hypoglycaemic, anorectic, autonomic and emetic effects of the glucagon-like peptide receptor agonist, exendin-4, in the conscious telemetered ferret

Background

Rodents are incapable of emesis and consequently the emetic potential of glucagon-like peptide-1 receptor (GLP-1R) agonists in studies designed to assess a potential blood glucose lowering action of the compound was missed. Therefore, we investigated if the ferret, a carnivore with demonstrated translation capability in emesis research, would identify the emetic potential of the GLP-1R agonist, exendin-4, and any associated effects on gastric motor function, appetite and cardiovascular homeostasis.

Methods

The biological activity of the GLP-1R ligands was investigated in vivo using a glucose tolerance test in pentobarbitone-anesthetised ferrets and in vitro using organ bath studies. Radiotelemetry was used to investigate the effect of exendin-4 on gastric myoelectric activity (GMA) and cardiovascular function in conscious ferrets; behaviour was also simultaneously assessed. Western blot was used to characterize GLP-1R distribution in the gastrointestinal and brain tissues.

Results

In anesthetised ferrets, exendin-4 (30 nmol/kg, s.c.) reduced experimentally elevated blood glucose levels by 36.3%, whereas the GLP-1R antagonist, exendin (9–39) (300 nmol/kg, s.c.) antagonised the effect and increased AUC_0–120 by 31.0% when injected alone (P < 0.05). In animals with radiotelemetry devices, exendin-4 (100 nmol/kg, s.c.) induced emesis in 1/9 ferrets, but inhibited food intake and decreased heart rate variability (HRV) in all animals (P < 0.05). In the animals not exhibiting emesis, there was no effect on GMA, mean arterial blood pressure, heart rate, or core body temperature. In the ferret exhibiting emesis, there was a shift in the GMA towards bradygastria with a decrease in power, and a concomitant decrease in HRV. Western blot revealed GLP-1R throughout the gastrointestinal tract but exendin-4 (up to 300 nM) and exendin (9–39), failed to contract or relax isolated ferret gut tissues. GLP-1R were found in all major brain regions and the levels were comparable those in the vagus nerve.

Conclusions

Peripherally administered exendin-4 reduced blood glucose and inhibited feeding with a low emetic potential similar to that in humans (11% vs 12.8%). A disrupted GMA only occurred in the animal exhibiting emesis raising the possibility that disruption of the GMA may influence the probability of emesis occurring in response to treatment with GLP-1R agonists.

Fat sensing and metabolic syndrome

Overconsumption of dietary fat contributes to the development of obesity and metabolic syndrome. Recent evidence suggests that high dietary fat may promote these metabolic states not only by providing calories but also by inducing impaired control of energy balance. In normal metabolic states, fat interacts with various organs or receptors to generate signals for the regulation of energy balance. Many of these interactions are impaired by high-fat diets or in obesity, contributing to the development or maintenance of obesity. These impairments may arise largely from fundamental alterations in the hypothalamus where all peripheral signals are integrated to regulate energy balance. This review focuses on various mechanisms by which fat is sensed at different stages of ingestion, circulation, storage, and utilization to regulate food intake, and how these individual mechanisms are altered by high-fat diets or in obesity.

GLP-1: benefits beyond pancreas

INTRODUCTION

Glucagon-like peptide 1 (GLP-1) is an intestinal hormone secreted after the ingestion of various nutrients. The main role of GLP-1 is to stimulate insulin secretion in a glucose-dependent manner. However, the expression of GLP-1 receptor was found to be expressed in a variety of tissues beyond pancreas such as lung, stomach, intestine, kidney, heart and brain. Beyond pancreas, a beneficial effect of GLP-1 on body weight reduction has been shown, suggesting its role for the treatment of obesity. In addition, GLP-1 has been demonstrated to reduce cardiovascular risk factors and to have a direct cardioprotective effect, fostering heart recovery after ischemic injury. Further, data from both experimental animal models and human studies have shown beneficial effect of GLP-1 on bone metabolism, either directly or indirectly on bone cells.

MATERIALS AND METHODS

We review here the recent findings of the extra-pancreatic effects of GLP-1 focusing on both basic and clinical studies, thus opening future perspectives to the use of GLP-1 analogs for the treatment of disease beyond type 2 diabetes.

CONCLUSION

Finally, the GLP-1 has been demonstrated to have a beneficial effect on both vascular, degenerative diseases of central nervous system and psoriasis.

Efficacy and tolerability of GLP-1 agonists in patients with type 2 diabetes mellitus: an Indian perspective

Glucagon like peptide-1 (GLP-1) agonists have been able to address the unmet needs of type 2 diabetes patients across the world. Indian patients with type 2 diabetes have also been able to benefit from effects of GLP-1 analogues to a more or less similar extent compared with patients from other parts of the world. As there is no nationwide data on use of GLP-1 agonists in India, we used the clinical data from different studies and compared them with the global data on GLP-1 analogues. The review is limited to only two approved GLP-1 analogues in India: exenatide and liraglutide. The efficacy of GLP-1 analogues, in terms of glycated haemoglobin (HbA1c), fasting plasma glucose (FPG) and postprandial glucose (PPG), is found to be similar in Indian patients compared with the global data. The other beneficial effects such as weight loss, incidence of hypoglycaemia were found to be on similar lines in the Indian setting. In a single-centre study, liraglutide reduced the dose of antihypertensive medications due to its effect on blood pressure. The gastrointestinal adverse effects such as nausea and vomiting were major adverse events, but these were transient and varied from one particular agent to another. Liraglutide is found to be superior in terms of compliance compared with exenatide in the Indian setting. Overall, the GLP-1 analogues have presented a treatment option that gives patient a benefit of glycaemic control, weight loss and very low incidence of hypoglycaemia, but the cost of the therapy presents a major barrier.

Tumor necrosis factor α decreases glucagon-like peptide-2 expression by up-regulating G-protein-coupled receptor 120 in Crohn disease

Glucagon-like peptide (GLP)-2, secreted by L cells in the small intestine, has anti-inflammatory effects in the gastrointestinal tract. A GLP-2 analogue has been an effective treatment for Crohn disease (CD). G-protein-coupled receptor (GPR) 40 and GPR120 are probably involved in GLP-2 production, the mechanisms of which remain unclear. In our experiments, normal ileal mucosa expressed GPR40, but rarely expressed GPR120. However, both GPRs were overexpressed in the L cells of the inflamed ileal mucosa of CD patients. Mucosal inflammation induced the overexpression of GPR40, GPR120, and several inflammatory cytokines, with correlations between ileal concentrations of tumor necrosis factor (TNF)-α and GPR expression levels; however, inflammation did not induce the expression of proglucagon, a precursor of GLP-2 in CD patients. In rat L cells and GLUTag cells, TNF-α treatment increased GPR120 mRNA expression without affecting GPR40 mRNA expression. Dual agonists of GPR40 and GPR120, GW9508 and linoleic acid, respectively, increased GLP-2 production from L cells, but these agonists decreased it in the presence of TNF-α. The GPR40 antagonist, GW1100, inhibited the GW9508-induced increase in GLP-2 production, and silencing GPR120 resulted in further elevation of GLP-2 production. Thus, GPR120-dependent signaling inhibited the stimulatory effects of GPR40 on GLP-2 expression, and TNF-α treatment decreased GLP-2 expression by up-regulating GPR120 expression in L cells.

Treatment of type 2 diabetes, lifestyle, GLP1 agonists and DPP4 inhibitors

In recent years the treatment focus for type 2 diabetes has shifted to prevention by lifestyle change and to more aggressive reduction of blood sugars during the early stage of treatment. Weight reduction is an important goal for many people with type 2 diabetes. Bariatric surgery is no longer considered a last resort treatment. Glucagon-like peptide-1 agonists given by injection are emerging as a useful treatment since they not only lower blood sugar but are associated with a modest weight reduction. The role of the oral dipeptidyl peptidase 4 inhibitors is emerging as second line treatment ahead of sulphonylureas due to a possible beneficial effect on the beta cell and weight neutrality. Drugs which inhibit glucose re-absorption in the kidney, sodium/glucose co-transport 2 inhibitors, may have a role in the treatment of diabetes. Insulin treatment still remains the cornerstone of treatment in many patients with type 2 diabetes.

Effects of GLP-1 on appetite and weight

Glucagon-like peptide 1 (GLP-1) is a cleavage product of the pre-proglucagon gene which is expressed in the α-cells of the pancreas, the L-cells of the intestine, and neurons located in the caudal brainstem and hypothalamus. GLP-1 is of relevance to appetite and weight maintenance because it has actions on the gastrointestinal tract as well as the direct regulation of appetite. It delays gastric emptying and gut motility in humans. In addition, interventricular injections of GLP-1 inhibit food intake, independent of the presence of food in the stomach or gastric emptying. Peripherally administered GLP-1 also affects the central regulation of feeding. It is therefore the synergistic actions of GLP-1 in the gut and brain, acting on both central and peripheral receptors that seem responsible for the effects of the hormone on satiety.

Lixisenatide, a drug developed to treat type 2 diabetes, shows neuroprotective effects in a mouse model of Alzheimer's disease

Type 2 diabetes is a risk factor for developing Alzheimer's disease (AD). In the brains of AD patients, insulin signalling is desensitised. The incretin hormone Glucagon-like peptide-1 (GLP-1) facilitates insulin signalling, and analogues such as liraglutide are on the market as treatments for type 2 diabetes. We have previously shown that liraglutide showed neuroprotective effects in the APPswe/PS1ΔE9 mouse model of AD. Here, we test the GLP-1 receptor agonist lixisenatide in the same mouse model and compare the effects to liraglutide. After ten weeks of daily i.p. injections with liraglutide (2.5 or 25 nmol/kg) or lixisenatide (1 or 10 nmol/kg) or saline of APP/PS1 mice at an age when amyloid plaques had already formed, performance in an object recognition task was improved in APP/PS1 mice by both drugs at all doses tested. When analysing synaptic plasticity in the hippocampus, LTP was strongly increased in APP/PS1 mice by either drug. Lixisenatide (1 nmol/kg) was most effective. The reduction of synapse numbers seen in APP/PS1 mice was prevented by the drugs. The amyloid plaque load and dense-core Congo red positive plaque load in the cortex was reduced by both drugs at all doses. The chronic inflammation response (microglial activation) was also reduced by all treatments. The results demonstrate that the GLP-1 receptor agonists liraglutide and lixisenatide which are on the market as treatments for type 2 diabetes show promise as potential drug treatments of AD. Lixisenatide was equally effective at a lower dose compared to liraglutide in some of the parameters measured.

Systems-Level G Protein-Coupled Receptor Therapy Across a Neurodegenerative Continuum by the GLP-1 Receptor System

With our increasing appreciation of the true complexity of diseases and pathophysiologies, it is clear that this knowledge needs to inform the future development of pharmacotherapeutics. For many disorders, the disease mechanism itself is a complex process spanning multiple signaling networks, tissues, and organ systems. Identifying the precise nature and locations of the pathophysiology is crucial for the creation of systemically effective drugs. Diseases once considered constrained to a limited range of organ systems, e.g., central neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington' disease (HD), the role of multiple central and peripheral organ systems in the etiology of such diseases is now widely accepted. With this knowledge, it is increasingly clear that these seemingly distinct neurodegenerative disorders (AD, PD, and HD) possess multiple pathophysiological similarities thereby demonstrating an inter-related continuum of disease-related molecular alterations. With this systems-level appreciation of neurodegenerative diseases, it is now imperative to consider that pharmacotherapeutics should be developed specifically to address the systemic imbalances that create the disorders. Identification of potential systems-level signaling axes may facilitate the generation of therapeutic agents with synergistic remedial activity across multiple tissues, organ systems, and even diseases. Here, we discuss the potentially therapeutic systems-level interaction of the glucagon-like peptide 1 (GLP-1) ligand-receptor axis with multiple aspects of the AD, PD, and HD neurodegenerative continuum.