Glucagon-Like Peptide-1 (GLP-1)-Based Therapeutics: Current Status and Future Opportunities beyond Type 2 Diabetes

A web-based scoping review assessing the influence of smoking and smoking cessation on antidiabetic drug meabolism: implications for medication efficacy

Currently 1.3 billion individuals globally engage in smoking, leading to significant morbidity and mortality, particularly among diabetic patients. There is urgent need for a better understanding of how smoking influences antidiabetic treatment efficacy. The review underscores the role of cigarette smoke, particularly polycyclic aromatic hydrocarbons (PAHs), in modulating the metabolic pathways of antidiabetic drugs, primarily through the induction of cytochrome P450 (CYP450) enzymes and uridine diphosphate (UDP)-glucuronosyltransferases (UGTs), thus impacting drug pharmacokinetics and therapeutic outcomes. Furthermore, the review addresses the relatively uncharted territory of how smoking cessation influences diabetes treatment, noting that cessation can lead to significant changes in drug metabolism, necessitating dosage adjustments. Special attention is given to the interaction between smoking cessation aids and antidiabetic medications, a critical area for patient safety and effective diabetes management. This scoping review aims to provide healthcare professionals with the knowledge to better support diabetic patients who smoke or are attempting to quit, ensuring tailored and effective treatment strategies. It also identifies gaps in current research, advocating for more studies to fill these voids, thereby enhancing patient care and treatment outcomes for this at-risk population.

The signaling pathways in obesity-related complications

Obesity, a rapidly expanding epidemic worldwide, is known to exacerbate many medical conditions, making it a significant factor in multiple diseases and their associated complications. This threatening epidemic is linked to various harmful conditions such as type 2 diabetes mellitus, hypertension, metabolic dysfunction-associated steatotic liver disease, polycystic ovary syndrome, cardiovascular diseases (CVDs), dyslipidemia, and cancer. The rise in urbanization and sedentary lifestyles creates an environment that fosters obesity, leading to both psychosocial and medical complications. To identify individuals at risk and ensure timely treatment, it is crucial to have a better understanding of the pathophysiology of obesity and its comorbidities. This comprehensive review highlights the relationship between obesity and obesity-associated complications, including type 2 diabetes, hypertension, (CVDs), dyslipidemia, polycystic ovary syndrome, metabolic dysfunction-associated steatotic liver disease, gastrointestinal complications, and obstructive sleep apnea. It also explores the potential mechanisms underlying these associations. A thorough analysis of the interplay between obesity and its associated complications is vital in developing effective therapeutic strategies to combat the exponential increase in global obesity rates and mitigate the deadly consequences of this polygenic condition.

Correlation between intestinal flora and GLP-1 receptor agonist dulaglutide in type 2 diabetes mellitus treatment-A preliminary longitudinal study

GLP-1 receptor agonists (GLP-1 RA) are presently used as the first-line drugs for the clinical treatment of type 2 diabetes mellitus (T2DM). It can regulate blood glucose by stimulating insulin secretion and lowering glucagon levels. We used 16S rRNA amplicon sequencing to detect structural changes in the composition of the intestinal flora of newly diagnosed T2DM after 1 and 48 weeks of dulaglutide administration. Our research found no significant changes in the intestinal flora after the administration of dulaglutide for 1 week to subjects with newly diagnosed T2DM. Nevertheless, after 48 weeks of dulaglutide administration, the composition of the intestinal flora changed significantly, with a significant reduction in the abundance of intestinal flora. Furthermore, we found that fasting glucose levels, fasting c-peptide levels, HbA1c levels, and BMI are also closely associated with intestinal flora. This reveals that intestinal flora may be one of the mechanisms by which dulaglutide treats T2DM.

New insights into nanomedicines for oral delivery of glucagon-like peptide-1 analogs

Type 2 diabetes mellitus (T2DM) is a metabolic disorder that arises when the body cannot respond fully to insulin, leading to impaired glucose tolerance. Currently, the treatment embraces non-pharmacological actions (e.g., diet and exercise) co-associated with the administration of antidiabetic drugs. Metformin is the first-line treatment for T2DM; nevertheless, alternative therapeutic strategies involving glucagon-like peptide-1 (GLP-1) analogs have been explored for managing the disease. GLP-1 analogs trigger insulin secretion and suppress glucagon release in a glucose-dependent manner thereby, reducing the risk of hyperglycemia. Additionally, GLP-1 analogs have an extended plasma half-life compared to the endogenous peptide due to their high resistance to degradation by dipeptidyl peptidase-4. However, GLP-1 analogs are mainly administered via subcutaneous route, which can be inconvenient for the patients. Even considering an oral delivery approach, GLP-1 analogs are exposed to the harsh conditions of the gastrointestinal tract (GIT) and the intestinal barriers (mucus and epithelium). Hereupon, there is an unmet need to develop non-invasive oral transmucosal drug delivery strategies, such as the incorporation of GLP-1 analogs into nanoplatforms, to overcome the GIT barriers. Nanotechnology has the potential to shield antidiabetic peptides against the acidic pH and enzymatic activity of the stomach. In addition, the nanoparticles can be coated and/or surface-conjugated with mucodiffusive polymers and target intestinal ligands to improve their transport through the intestinal mucus and epithelium. This review focuses on the main hurdles associated with the oral administration of GLP-1 and GLP-1 analogs, and the nanosystems developed to improve the oral bioavailability of the antidiabetic peptides. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Dietary impact on fasting and stimulated GLP-1 secretion in different metabolic conditions - a narrative review

Glucagon-like peptide 1 (GLP-1), a gastrointestinal peptide and central mediator of glucose metabolism, is secreted by L cells in the intestine in response to food intake. Postprandial secretion of GLP-1 is triggered by nutrient-sensing via transporters and G-protein-coupled receptors (GPCRs). GLP-1 secretion may be lower in adults with obesity/overweight (OW) or type 2 diabetes mellitus (T2DM) than in those with normal glucose tolerance (NGT), but these findings are inconsistent. Because of the actions of GLP-1 on stimulating insulin secretion and promoting weight loss, GLP-1 and its analogs are used in pharmacologic preparations for the treatment of T2DM. However, physiologically stimulated GLP-1 secretion through the diet might be a preventive or synergistic method for improving glucose metabolism in individuals who are OW, or have impaired glucose tolerance (IGT) or T2DM. This narrative review focuses on fasting and postprandial GLP-1 secretion in individuals with different metabolic conditions and degrees of glucose intolerance. Further, the influence of relevant diet-related factors (e.g., specific diets, meal composition, and size, phytochemical content, and gut microbiome) that could affect fasting and postprandial GLP-1 secretion are discussed. Some studies showed diminished glucose- or meal-stimulated GLP-1 response in participants with T2DM, IGT, or OW compared with those with NGT, whereas other studies have reported an elevated or unchanged GLP-1 response in T2DM or IGT. Meal composition, especially the relationship between macronutrients and interventions targeting the microbiome can impact postprandial GLP-1 secretion, although it is not clear which macronutrients are strong stimulants of GLP-1. Moreover, glucose tolerance, antidiabetic treatment, grade of overweight/obesity, and sex were important factors influencing GLP-1 secretion. The results presented in this review highlight the potential of nutritional and physiologic stimulation of GLP-1 secretion. Further research on fasting and postprandial GLP-1 concentrations and the resulting metabolic consequences under different metabolic conditions is needed.

Effect of Semaglutide on High-Fat-Diet-Induced Liver Cancer in Obese Mice

This study aims to investigate the impact of semaglutide on the expression of liver cancer proteins in obese mice induced by a high-fat diet. Sixteen obese mice were randomly divided into two groups: the high-fat diet group and the semaglutide group, each consisting of eight mice. Additionally, eight normal male mice were included as the control group. Serum samples were collected, and a differential expression analysis of total proteins in adipose tissue was performed using quantitative tandem mass spectrometry (TMT) in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Significant differential proteins were identified and subjected to a bioinformatics analysis. The findings revealed that these differential proteins, namely, integrin αV (ITGAV), laminin γ1 (LAMC1), fatty acid-binding protein 5 (FABP5), and lipoprotein lipase (LPL), regulate the occurrence and development of liver cancer by participating in the extracellular matrix (ECM) signaling pathway and the peroxisome proliferator-activated receptor (PPAR) signaling pathway. Notably, semaglutide can decelerate the progression of liver cancer by inducing the expression of ITGAV, LAMC1, FABP5, and LPL in the adipose tissue of obese mice.

Brain uptake pharmacokinetics of albiglutide, dulaglutide, tirzepatide, and DA5-CH in the search for new treatments of Alzheimer's and Parkinson's diseases

BACKGROUND

A number of peptide incretin receptor agonists (IRAs) show promise as therapeutics for Alzheimer's disease (AD) and Parkinson's disease (PD). Transport across the blood-brain barrier (BBB) is one way for IRAs to act directly within the brain. To determine which IRAs are high priority candidates for treating these disorders, we have studied their brain uptake pharmacokinetics.

METHODS

We quantitatively measure the ability of four IRAs to cross the BBB. We injected adult male CD-1 mice intravenously with 125I- or 14C-labeled albiglutide, dulaglutide, DA5-CH, or tirzepatide and used multiple-time regression analyses to measure brain kinetics up to 1 hour. For those IRAs failing to enter the brain 1 h after intravenous injection, we also investigated their ability to enter over a longer time frame (i.e., 6 h).

RESULTS

Albiglutide and dulaglutide had the fastest brain uptake rates within 1 hour. DA5-CH appears to enter the brain rapidly, reaching equilibrium quickly. Tirzepatide does not appear to cross the BBB within 1 h after iv injection but like albumin, did so slowly over 6 h, presumably via the extracellular pathways.

CONCLUSIONS

We find that IRAs can cross the BBB by two separate processes; one that is fast and one that is slow. Three of the four IRAs investigated here have fast rates of transport and should be taken into consideration for testing as AD and PD therapeutics as they would have the ability to act quickly and directly on the brain as a whole.

Cold Exposure and Oral Delivery of GLP-1R Agonists by an Engineered Probiotic Yeast Strain Have Antiobesity Effects in Mice

Advanced microbiome therapeutics (AMTs) holds promise in utilizing engineered microbes such as bacteria or yeasts for innovative therapeutic applications, including the in situ delivery of therapeutic peptides. Glucagon-like peptide-1 receptor agonists, such as Exendin-4, have emerged as potential treatments for type 2 diabetes and obesity. However, current administration methods face challenges with patient adherence and low oral bioavailability. To address these limitations, researchers are exploring improved oral delivery methods for Exendin-4, including utilizing AMTs. This study engineered the probiotic yeast Saccharomyces boulardii to produce Exendin-4 (Sb-Exe4) in the gastrointestinal tract of male C57BL/6 mice to combat diet-induced obesity. The biological efficiency of Exendin-4 secreted by S. boulardii was analyzed ex vivo on isolated pancreatic islets, demonstrating induced insulin secretion. The in vivo characterization of Sb-Exe4 revealed that when combined with cold exposure (8 °C), the Sb-Exe4 yeast strain successfully suppressed appetite by 25% and promoted a 4-fold higher weight loss. This proof of concept highlights the potential of AMTs to genetically modify S. boulardii for delivering active therapeutic peptides in a precise and targeted manner. Although challenges in efficacy and regulatory approval persist, AMTs may provide a transformative platform for personalized medicine. Further research in AMTs, particularly focusing on probiotic yeasts such as S. boulardii, holds great potential for novel therapeutic possibilities and enhancing treatment outcomes in diverse metabolic disorders.

Concept for a Unidirectional Release Mucoadhesive Buccal Tablet for Oral Delivery of Antidiabetic Peptide Drugs Such as Insulin, Glucagon-like Peptide 1 (GLP-1), and their Analogs

Injectable peptides such as insulin, glucagon-like peptide 1 (GLP-1), and their agonists are being increasingly used for the treatment of diabetes. Currently, the most common route of administration is injection, which is linked to patient discomfort as well as being subjected to refrigerated storage and the requirement for efficient supply chain logistics. Buccal and sublingual routes are recognized as valid alternatives due to their high accessibility and easy administration. However, there can be several challenges, such as peptide selection, drug encapsulation, and delivery system design, which are linked to the enhancement of drug efficacy and efficiency. By using hydrophobic polymers that do not dissolve in saliva, and by using neutral or positively charged nanoparticles that show better adhesion to the negative charges generated by the sialic acid in the mucus, researchers have attempted to improve drug efficiency and efficacy in buccal delivery. Furthermore, unidirectional films and tablets seem to show the highest bioavailability as compared to sprays and other buccal delivery vehicles. This advantageous attribute can be attributed to their capability to mitigate the impact of saliva and inadvertent gastrointestinal enzymatic digestion, thereby minimizing drug loss. This is especially pertinent as these formulations ensure a more directed drug delivery trajectory, leading to heightened therapeutic outcomes. This communication describes the current state of the art with respect to the creation of nanoparticles containing peptides such as insulin, glucagon-like peptide 1 (GLP-1), and their agonists, and theorizes the production of mucoadhesive unidirectional release buccal tablets or films. Such an approach is more patient-friendly and can improve the lives of millions of diabetics around the world; in addition, these shelf-stable formulations ena a more environmentally friendly and sustainable supply chain network.

Emerging Role of GLP-1 Agonists in Obesity: A Comprehensive Review of Randomised Controlled Trials

Obesity is a chronic disease with high prevalence and associated comorbidities, making it a growing global concern. These comorbidities include type 2 diabetes, hypertension, ventilatory dysfunction, arthrosis, venous and lymphatic circulation diseases, depression, and others, which have a negative impact on health and increase morbidity and mortality. GLP-1 agonists, used to treat type 2 diabetes, have been shown to be effective in promoting weight loss in preclinical and clinical studies. This review summarizes numerous studies conducted on the main drugs in the GLP-1 agonists class, outlining the maximum achievable weight loss. Our aim is to emphasize the active role and main outcomes of GLP-1 agonists in promoting weight loss, as well as in improving hyperglycemia, insulin sensitivity, blood pressure, cardio-metabolic, and renal protection. We highlight the pleiotropic effects of these medications, along with their indications, contraindications, and precautions for both diabetic and non-diabetic patients, based on long-term follow-up studies.

Comparing the bioequivalence and safety of liraglutide in healthy Chinese subjects: an open, single-dose, randomized, repeated, two-sequence, two-cycle phase I clinical trial

BACKGROUND

Glucagon-like peptide-1 (GLP-1) is an endogenous incretin hormone. Liraglutide, a GLP-1 receptor agonist, can lower blood sugar by increasing insulin production and inhibiting the production of glucagon. This study researched the bioequivalence and safety of the test and reference drugs in healthy Chinese subjects.

RESEARCH DESIGN AND METHODS

Subjects (N = 28) were randomly divided into group A and group B at a ratio of 1:1 for a two-cycle cross-over study. There was single dose per cycle with subcutaneous injection of the test and reference drugs, respectively. The washout was set at 14 days. Plasma drug concentrations were detected by specific liquid chromatography and tandem mass spectrometry (LC-MS/MS) assays. Statistical analysis of major pharmacokinetic (PK) parameters was conducted to assess drug bioequivalence. In addition, we evaluated the safety of the drugs throughout the trial.

RESULTS

The geometric mean ratios (GMRs) of C_max, AUC_0-t, and AUC_0-∞ for the test and reference drugs were 107.11%, 106.56%, 106.09%, respectively. The 90% confidence intervals (CIs) were all within 80%-125%, meeting the bioequivalence standards. In addition, both had good safety in this study.

CONCLUSION

The study shows that the two drugs had similar bioequivalence and safety.

CLINICAL TRIAL REGISTRATION

DCTR: CTR20190914; ClinicalTrials.gov: NCT05029076.

The effect of linagliptin on microalbuminuria in patients with diabetic nephropathy: a randomized, double blinded clinical trial

The aim of the present study was to investigate the effect of linagliptin on microalbuminuria in patients with diabetic nephropathy (DN). The present double-blind randomized placebo-controlled clinical trial was performed on 92 patients with DN who were divided into two groups. The intervention and control groups received linagliptin 5 mg and placebo for 24 weeks, respectively. Blood pressure, lipid profile, liver enzymes, fasting plasma glucose (FPG), and urine albumin-creatinine ratio (UACR) were assessed and recorded before, 12 weeks, and 24 weeks after the beginning of the intervention. The mean value of UACR decrease was significant over time in both groups, with higher decrease in linagliptin group, however, the differences between two groups were not, statistically significant (P > 0.05). However, the percentage of improvement in microalbuminuria (UACR < 30 mg/g) in the linagliptin group was significantly higher than that of the control group during 24 weeks of intervention (68.3% vs. 25%; P-value < 0.001). There was no statistically significant difference in the mean value of the UACR and other parameters between linagliptin treated and placebo treated patients with diabetic nephropathy. Further studies, with longer periods of follow-up are suggested to examine these patients' renal outcomes.

Sustained release of GLP-1 analog from γ-PGA-PAE copolymers for management of type 2 diabetes

GLP-1 has been clinically exploited for treating type 2 diabetes, while its short circulation half-life requires multiple daily injections to maintain effective glycemic control, thus limiting its widespread application. Here we developed a drug delivery system based on self-assembling polymer-amino acid conjugates (γ-PGA-PAE) to provide sustained release of GLP-1 analog (DLG3312). The DLG3312 loaded γ-PGA based nanoparticles (DLG3312@NPs) exhibited a spherical shape with a good monodispersity under transmission electron microscope (TEM) observation. The DLG3312 encapsulation was optimized, and the loading efficiency was as high as 78.4 ± 2.2 %. The transformation of DLG3312@NPs to network structures was observed upon treatment with the fresh serum, resulting in a sustained drug release. The in vivo long-term hypoglycemic assays indicated that DLG3312@NPs significantly reduced blood glucose and glycosylated hemoglobin level. Furthermore, DLG3312@NPs extended the efficacy of DLG3312, leading to a decrease in the dosing schedule that from once a day to once every other day. This approach combined the molecular and materials engineering strategies that offered a unique solution to maximize the availability of anti-diabetic drug and minimize its burdens to type 2 diabetic patients.

Cardiovascular Protection with a Long-Acting GLP-1 Receptor Agonist Liraglutide: An Experimental Update

Angiotensin II (Ang II), a peptide hormone generated as part of the renin-angiotensin system, has been implicated in the pathophysiology of many cardiovascular diseases such as peripheral artery disease, heart failure, hypertension, coronary artery disease and other conditions. Liraglutide, known as an incretin mimetic, is one of the glucagon-like peptide-1 (GLP-1) receptor agonists, and has been proven to be effective in the treatment of cardiovascular disorders beyond adequate glycemic control. The objective of this review is to compile our recent experimental outcomes-based studies, and provide an overview the cardiovascular protection from liraglutide against Ang II- and pressure overload-mediated deleterious effects on the heart. In particular, the mechanisms of action underlying the inhibition of oxidative stress, vascular endothelial dysfunction, hypertension, cardiac fibrosis, left ventricular hypertrophy and heart failure with liraglutide are addressed. Thus, we support the notion that liraglutide continues to be a useful add-on therapy for the management of cardiovascular diseases.

Prader-Willi Syndrome in Adults: An Update On Nutritional Treatment and Pharmacological Approach

PURPOSE OF REVIEW

Prader-Willi syndrome (PWS) is a rare and complex genetic disorder with multiple effects on the metabolic, endocrine, and neurological systems, as well as behavioral and intellectual difficulties. Despite advances in understanding the genetic basis of obesity in PWS, there are conflicting data on its management. Therefore, the present manuscript aims to provide an update on the nutritional treatment and pharmacological approach in adult patients with PWS.

RECENT FINDINGS

The management of obesity in patients with PWS is challenging and requires the cooperation of an experienced multidisciplinary team, including the nutritionist. An adequate clinical evaluation including nutritional and biochemical parameters should be performed to tailor the best therapeutic strategy. Both lifestyle and pharmacological interventions may represent useful strategies to prevent the high rate of morbidity and mortality related to PWS. The use of bariatric surgery is still controversial. Although it is imperative to adopt an obesity prevention strategy in childhood, there is promising evidence for the treatment of obesity in adulthood with current obesity medications in conjunction with lifestyle interventions.

α/Sulfono-γ-AA peptide hybrids agonist of GLP-1R with prolonged action both in vitro and in vivo

Peptides are increasingly important resources for biological and therapeutic development, however, their intrinsic susceptibility to proteolytic degradation represents a big hurdle. As a natural agonist for GLP-1R, glucagon-like peptide 1 (GLP-1) is of significant clinical interest for the treatment of type-2 diabetes mellitus, but its in vivo instability and short half-life have largely prevented its therapeutic application. Here, we describe the rational design of a series of α/sulfono-γ-AA peptide hybrid analogues of GLP-1 as the GLP-1R agonists. Certain GLP-1 hybrid analogues exhibited enhanced stability (t _1/2 > 14 days) compared to t _1/2 (<1 day) of GLP-1 in the blood plasma and in vivo. These newly developed peptide hybrids may be viable alternative of semaglutide for type-2 diabetes treatment. Additionally, our findings suggest that sulfono-γ-AA residues could be adopted to substitute canonical amino acids residues to improve the pharmacological activity of peptide-based drugs.

Glucagon-like peptide 1 and fibroblast growth factor-21 in non-alcoholic steatohepatitis: An experimental to clinical perspective

Non-alcoholic steatohepatitis (NASH) is a progressive form of Non-alcoholic fatty liver disease (NAFLD), which slowly progresses toward cirrhosis and finally leads to the development of hepatocellular carcinoma. Obesity, insulin resistance, type 2 diabetes mellitus and the metabolic syndrome are major risk factors contributing to NAFLD. Targeting these risk factors is a rational option for inhibiting NASH progression. In addition, NASH could be treated with therapies that target the metabolic abnormalities causing disease pathogenesis (such as de novo lipogenesis and insulin resistance) as well with medications targeting downstream processes such as cellular damage, apoptosis, inflammation, and fibrosis. Glucagon-like peptide (GLP-1), is an incretin hormone dysregulated in both experimental and clinical NASH, which triggers many signaling pathways including fibroblast growth factor (FGF) that augments NASH pathogenesis. Growing evidence indicates that GLP-1 in concert with FGF-21 plays crucial roles in the conservation of glucose and lipid homeostasis in metabolic disorders. In line, GLP-1 stimulation improves hepatic ballooning, steatosis, and fibrosis in NASH. A recent clinical trial on NASH patients showed that the upregulation of FGF-21 decreases liver fibrosis and hepatic steatosis, thus improving the pathogenesis of NASH. Hence, therapeutic targeting of the GLP-1/FGF axis could be therapeutically beneficial for the remission of NASH. This review outlines the significance of the GLP-1/FGF-21 axis in experimental and clinical NASH and highlights the activity of modulators targeting this axis as potential salutary agents for the treatment of NASH.

Oral glucagon-like peptide 1 analogue ameliorates glucose intolerance in db/db mice

OBJECTIVES

We constructed a recombinant oral GLP-1 analogue in Lactococcus lactis (L. lactis) and evaluated its physiological functions.

RESULTS

In silico docking suggested the alanine at position 8 substituted with serine (A8SGLP-1) reduced binding of DPP4, which translated to reduced cleavage by DPP4 with minimal changes in stability. This was further confirmed by an in vitro enzymatic assay which showed that A8SGLP-1 significantly increased half-life upon DPP4 treatment. In addition, recombinant L. lactis (LL-A8SGLP-1) demonstrated reduced fat mass with no changes in body weight, significant improvement of random glycemic control and reduced systemic inflammation compared with WT GLP-1 in db/db mice.

CONCLUSION

LL-A8SGLP-1 adopted in live biotherapeutic products reduce blood glucose in db/db mice without affecting its function.

The modern pharmacological approach to diabetes: innovative methods of monitoring and insulin treatment

INTRODUCTION

Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterised by a high blood sugar level over a prolonged period of time. In order to maintain this blood glucose value in normal parameters, a careful monitoring of it and insulin administration are necessary.

AREAS COVERED

Thus, to facilitate this procedure, new blood glucose monitoring systems have been studied. The smart lens, the nano tattoo, non-invasive sensors based on reverse ionthophoresis and glucose oxidase - based continuous blood glucose monitoring systems, are the methods described in this study. Of course, not only is blood glucose monitoring important, but also the lifestyle of a drug or the way a drug is administered, especially in the cae of insulin. How insulin is administered is also a topic that we address in this article. In an attempt to promote compliance with the administration, we have discussed about new forms of administering insulin such as: oral, intranasal, administration on the oral mucosa and last but not least, transdermal administration.

EXPERT OPINION

Further, the attention of specialists should be directed to devices based on sensors, with a role in the interruption of insulin administration, in case of detection of hypoglycemia or the additional dose of insulin, if hyperglycemia is detected.

Site-specific N-terminal PEGylation-based controlled release of biotherapeutics: An application for GLP-1 delivery to improve pharmacokinetics and prolong hypoglycemic effects

PEGylation is a well-established technology for half-life extension in drug delivery. In this study, we aimed to develop a site-specific N-terminal PEGylation for biotherapeutics to achieve controlled release, using GLP-1 as a model. An additional threonine was introduced at N-terminal GLP-1. Followed by periodate oxidation, hydrazide-based PEGylation was achieved in a site-selective manner under reductive condition. Two homogenous monovalent mPEG_5k-GLP-1 (peptide 4) and mPEG_20k-GLP-1 (peptide 5) were successfully constructed. After PEGylation, the degradation by DPP-IV and rat plasma was obviously reduced. Their pharmacokinetic performances were enhanced at the expense of impaired GLP-1R stimulating potency, and their hypoglycemic effects were improved in different degrees. Compared with conventional strategies, this approach is devoid of the restriction and alteration of native peptide sequences, and can produce utterly homogenous conjugates with excellent selectivity and efficiency. It provides a practical controlled release approach for peptides by site-specific modification to achieve better pharmacological and therapeutic properties.

Effects of Semaglutide on Glycemic Control and Weight Loss in a Patient with Prader-Willi Syndrome: A Case Report

BACKGROUND

Prader-Willi syndrome is the most frequent genetic cause of obesity and is often complicated by glucose metabolism alterations. Conventional therapies prescribed in type 2 diabetes frequently failed to achieve adequate glycemic control in patients with Prader-Willi syndrome. Beneficial effects of glucagon like peptide-1 receptor agonists exenatide and liraglutide have been reported for the management of type 2 diabetes in Prader-Willi syndrome, but no data are currently available in this population on the use of semaglutide.

CASE PRESENTATION

We report for the first time the use of semaglutide 1 mg per week in a 33-year-old man with Prader-Will syndrome complicated by poor controlled diabetes and severe obesity. After 12 months of semaglutide treatment, we observed an important reduction in glycated hemoglobin levels (11.1% to 7.2%) and body weight (99.5 kg to 94.3 kg), with also a notable decrease in fat mass and insulin requirements. Interestingly, our patient had already tried liraglutide therapy in adjunction to metformin and insulin therapy, reporting no substantial efficacy.

CONCLUSIONS

The beneficial effects of semaglutide on glycemic control and weight reduction provide a promising treatment for diabetes and obesity in Prader-Willi syndrome, even where other glucagons like peptide-1 receptor agonists have failed. Further studies are required to confirm the efficacy and safety of semaglutide in patients with Prader-Willi syndrome.

New Horizons: Next-Generation Insulin Analogues: Structural Principles and Clinical Goals

Design of "first-generation" insulin analogues over the past 3 decades has provided pharmaceutical formulations with tailored pharmacokinetic (PK) and pharmacodynamic (PD) properties. Application of a molecular tool kit-integrating protein sequence, chemical modification, and formulation-has thus led to improved prandial and basal formulations for the treatment of diabetes mellitus. Although PK/PD changes were modest in relation to prior formulations of human and animal insulins, significant clinical advantages in efficacy (mean glycemia) and safety (rates of hypoglycemia) were obtained. Continuing innovation is providing further improvements to achieve ultrarapid and ultrabasal analogue formulations in an effort to reduce glycemic variability and optimize time in range. Beyond such PK/PD metrics, next-generation insulin analogues seek to exploit therapeutic mechanisms: glucose-responsive ("smart") analogues, pathway-specific ("biased") analogues, and organ-targeted analogues. Smart insulin analogues and delivery systems promise to mitigate hypoglycemic risk, a critical barrier to glycemic control, whereas biased and organ-targeted insulin analogues may better recapitulate physiologic hormonal regulation. In each therapeutic class considerations of cost and stability will affect use and global distribution. This review highlights structural principles underlying next-generation design efforts, their respective biological rationale, and potential clinical applications.

Peptide Multimerization as Leads for Therapeutic Development

Multimerization of peptide structures has been a logical evolution in their development as potential therapeutic molecules. The multivalent properties of these assemblies have attracted much attention from researchers in the past and the development of more complex branching dendrimeric structures, with a wide array of biocompatible building blocks is revealing previously unseen properties and activities. These branching multimer and dendrimer structures can induce greater effect on cellular targets than monomeric forms and act as potent antimicrobials, potential vaccine alternatives and promising candidates in biomedical imaging and drug delivery applications. This review aims to outline the chemical synthetic innovations for the development of these highly complex structures and highlight the extensive capabilities of these molecules to rival those of natural biomolecules.

Strategies for the delivery of antidiabetic drugs via intranasal route

Diabetes is a metabolic disorder defined by higher blood glucose levels in the body generally controlled by antidiabetic agents (oral) and insulin (subcutaneous). To avoid the limitations of the conventional routes such as lower bioavailability and pain at the site of injection in case of parenteral route modified delivery systems are proposed like transdermal, pulmonary and inhalation delivery and among the other delivery systems nasal drug delivery system that shows the advantages such as reduced frequency of dose, higher patient compliance, safety, ease of administration, prolonged residence time, improved absorption of drug in the body, higher bioavailability and stability. This review article discusses the strategies adopted for the delivery of antidiabetic drugs by the intranasal delivery system. The insulin and glucagon-like peptides on experimentation show results of improved therapeutic levels and patient compliance. The drugs are transported by the paracellular route and absorbed through the epithelial tight junctions successfully by utilising different strategies. The limitations of the nasal delivery such as irritation or burning on administration, degradation by the enzymes, mucociliary clearance, lesser volume of the nasal cavity and permeation through the nasal mucosa. To overcome the challenges different strategies for the nasal administration are studied such as polymers, particulate delivery systems, complexation with peptides and smart delivery using glucose-responsive systems. A vast scope of intranasal preparations exists for antidiabetic drugs in the future for the management of diabetes and more clinical studies are the requirement for the societal impact to battle against diabetes.

Obesity in Prader-Willi syndrome: physiopathological mechanisms, nutritional and pharmacological approaches

Prader-Willi syndrome (PWS) is a genetic disorder caused by the lack of expression of genes on the paternally inherited chromosome 15q11.2-q13 region. The three main genetic subtypes are represented by paternal 15q11-q13 deletion, maternal uniparental disomy 15, and imprinting defect. Clinical picture of PWS changes across life stages. The main clinical characteristics are represented by short stature, developmental delay, cognitive disability and behavioral diseases. Hypotonia and poor suck resulting in failure to thrive are typical of infancy. As the subjects with PWS age, clinical manifestations such as hyperphagia, temperature instability, high pain threshold, hypersomnia and multiple endocrine abnormalities including growth hormone and thyroid-stimulating hormone deficiencies, hypogonadism and central adrenal insufficiency due to hypothalamic dysfunction occur. Obesity and its complications are the most common causes of morbidity and mortality in PWS. Several mechanisms for the aetiology of obesity in PWS have been hypothesized, which include aberration in hypothalamic pathways of satiety control resulting in hyperphagia, disruption in hormones regulating appetite and satiety and reduced energy expenditure. However, despite the advancement in the research field of the genetic basis of obesity in PWS, there are contradictory data on the management. Although it is mandatory to adopt obesity strategy prevention from infancy, there is promising evidence regarding the management of obesity in adulthood with current obesity drugs along with lifestyle interventions, although the data are limited. Therefore, the current manuscript provides a review of the current evidence on obesity and PWS, covering physiopathological aspects, obesity-related complications and conservative management.

Structural principles of insulin formulation and analog design: A century of innovation

BACKGROUND

The discovery of insulin in 1921 and its near-immediate clinical use initiated a century of innovation. Advances extended across a broad front, from the stabilization of animal insulin formulations to the frontiers of synthetic peptide chemistry, and in turn, from the advent of recombinant DNA manufacturing to structure-based protein analog design. In each case, a creative interplay was observed between pharmaceutical applications and then-emerging principles of protein science; indeed, translational objectives contributed to a growing molecular understanding of protein structure, aggregation and misfolding.

SCOPE OF REVIEW

Pioneering crystallographic analyses-beginning with Hodgkin's solving of the 2-Zn insulin hexamer-elucidated general features of protein self-assembly, including zinc coordination and the allosteric transmission of conformational change. Crystallization of insulin was exploited both as a step in manufacturing and as a means of obtaining protracted action. Forty years ago, the confluence of recombinant human insulin with techniques for site-directed mutagenesis initiated the present era of insulin analogs. Variant or modified insulins were developed that exhibit improved prandial or basal pharmacokinetic (PK) properties. Encouraged by clinical trials demonstrating the long-term importance of glycemic control, regimens based on such analogs sought to resemble daily patterns of endogenous β-cell secretion more closely, ideally with reduced risk of hypoglycemia.

MAJOR CONCLUSIONS

Next-generation insulin analog design seeks to explore new frontiers, including glucose-responsive insulins, organ-selective analogs and biased agonists tailored to address yet-unmet clinical needs. In the coming decade, we envision ever more powerful scientific synergies at the interface of structural biology, molecular physiology and therapeutics.

Research Progress on Dipeptidyl Peptidase Family: Structure, Function and Xenobiotic Metabolism

Prolyl-specific peptidases or proteases, including Dipeptidyl Peptidase 2, 4, 6, 8, 9, 10, Fibroblast Activation Protein, prolyl endopeptidase and prolyl carboxypeptidase, belong to the dipeptidyl peptidase family. In human physiology and anatomy, they have homology amino acid sequences, similarities in structure, but play distinct functions and roles. Some of them also play important roles in the metabolism of drugs containing endogenous peptides, xenobiotics containing peptides, and exogenous peptides. The major functions of these peptidases in both the metabolism of human health and bioactive peptides are of significant importance in the development of effective inhibitors to control the metabolism of endogenous bioactive peptides. The structural characteristics, distribution of tissue, endogenous substrates, and biological functions were summarized in this review. Furthermore, the xenobiotics metabolism of the dipeptidyl peptidase family is illustrated. All the evidence and information summarized in this review would be very useful for researchers to extend the understanding of the proteins of these families and offer advice and assistance in physiology and pathology studies.

Central GLP-1 contributes to improved cognitive function and brain glucose uptake after duodenum-jejunum bypass on obese and diabetic rats

The improvement of cognitive function following bariatric surgery has been highlighted, yet its underlying mechanisms remain elusive. Finding the improved brain glucose uptake of patients after Roux-en-Y gastric bypass (RYGB), duodenum-jejunum bypass (DJB), and sham surgery (Sham) were performed on obese and diabetic Wistar rats, and intracerebroventricular (ICV) injection of glucagon-like peptide-1 (GLP-1) analog liraglutide (Lira), antagonist exendin-(9-39) (Exe-9), and the viral-mediated GLP-1 receptor (Glp-1r) knockdown (KD) were applied on both groups to elucidate the role of GLP-1 in mediating cognitive function and brain glucose uptake assessed with the Morris water maze (MWM) and positron emission tomography (PET). Insulin and GLP-1 in serum and cerebral spinal fluid (CSF) were measured, and the expression of glucose uptake-related proteins including glucose transporter 1 (GLUT-1), GLUT-4, phospho-Akt substrate of 160kDa (pAS160), AS160, Rab10, Myosin-Va as well as the c-fos marker in the brain were examined. Along with augmented glucose homeostasis following DJB, central GLP-1 was correlated with the improved cognitive function and ameliorated brain glucose uptake, which was further confirmed by the enhancive role of Lira on both groups whereas the Exe-9 and Glp-1r KD were opposite. Known to activate insulin-signaling pathways, central GLP-1 contributes to improved cognitive function and brain glucose uptake after DJB.NEW & NOTEWORTHY The improvement of cognitive function following bariatric surgery has been highlighted while its mechanisms remain elusive. The brain glucose uptake of patients was improved after RYGB, and the DJB and sham surgery performed on obese and diabetic Wistar rats revealed that the elevated central GLP-1 contributes to the dramatic improvement of cognitive function, brain glucose uptake, transport, glucose sensing, and neuronal activation.

A quinoxaline-based compound ameliorates bone loss in ovariectomized mice

DMB (6,7-dichloro-2-methylsulfonyl-3-Ntert-butylaminoquinoxaline) is a quinoxaline-based compound that has been investigated as a glucagon-like peptide-1 receptor (GLP-1R) agonist. To clarify anti-osteoporosis effect of DMB, an osteoporotic mice model was established by ovariectomy (OVX) operation. The OVX mice were given intraperitoneally DMB, exendin-4 (EX-4), or 17β-estradiol (E₂) for two months. Then bone mass and structure, and bone morphometric parameters were examined by micro-CT. Weight gain and food consumption, bone turnover markers, and biomechanical strength of the femur were tested, and bone histomorphometry was analyzed. The food intake and weight gain was obviously reduced by E₂ or EX-4, but not DMB. However, DMB or EX-4 treatment obviously inhibited skeletal deterioration and enhanced bone strength. The improvement involved in the increased osteoblast number and level of bone formation markers, and reduced osteoclasts number and level of bone resorption markers. In addition, DMB was found to stimulate osteoblastogenesis-related marker gene expression. These results demonstrated that DMB ameliorated bone loss mainly via induction of bone formation, which suggests that the small molecule compound might be applied to the management of postmenopausal osteoporosis.

The Present and Future Role of Microfluidics for Protein and Peptide-Based Therapeutics and Diagnostics

The implementation of peptide-based molecules within the medical field has vast potential, owing to their unique nature and predictable physicochemical profiles. However, peptide therapeutic usage is hindered by delivery-related challenges, meaning that their formulations must be altered to overcome these limitations. This process could be propelled by applying microfluidics (MFs) due to its highly controllable and adaptable attributes; however, therapeutic research within this field is extremely limited. Peptides possess multifunctional roles within therapeutic formulations, ranging from enhancing target specificity to acting as the active component of the medicine. Diagnostically, MFs are well explored in the field of peptides, as MFs provide an unsullied platform to provide fast yet accurate examinations. The capacity to add attributes, such as integrated sensors and microwells, to the MF chip, only enhances the attractiveness of MFs as a diagnostic platform. The structural individuality of peptides makes them prime candidates for diagnostic purposes, for example, antigen detection and isolation. Therefore, this review provides a useful insight into the current applications of MFs for peptide-based therapy and diagnostics and highlights potential gaps in the field that are yet to be explored or optimized.

Developing GLP-1 Conjugated Self-Assembling Nanofibers Using Copper-Catalyzed Alkyne-Azide Cycloaddition and Evaluation of Their Biological Activity

Glucagon-like peptide-1 GLP-1 is a gut-derived peptide secreted from pancreatic β-cells that reduces blood glucose levels and body weight; however, native GLP-1 (GLP-1(7-36)-NH₂ and GLP-1(7-37)) have short in vivo circulation half-lives (∼2 min) due to proteolytic degradation and rapid renal clearance due to its low molecular weight (MW; 3297.7 Da). This study aimed to improve the proteolytic stability and delivery properties of glucagon-like peptide-1 (GLP-1) through modifications that form nanostructures. For this purpose, N- (NtG) and C-terminal (CtG), and Lys26 side chain (K26G) alkyne-modified GLP-1 analogues were conjugated to an azide-modified lipidic peptide (L) to give N-L, C-L, and K-26-L, respectively; or CtG was conjugated with a fibrilizing self-assembling peptide (SAP) (AEAEAKAK)₃ to yield C-S, using copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). N-L demonstrated the best serum stability (t_1/2 > 48 h) compared to K-26-L (44 h), C-L (20 h), C-S (27 h), and the parental GLP-1(7-36;A8G)-NH₂ (A8G) (19 h) peptides. Each conjugate demonstrated subnanomolar hGLP-1RA potency, and none demonstrated toxicity toward PC-3 cells at concentrations up to 1 μM. Each analogue was observed by transmission electron microscopy to form fibrils in solution. K-26-L demonstrated among the best human serum stability (t_1/2 = 44 h) and similar hGLP-1RA potency (EC₅₀ 48 pM) to C-S. In conclusion, this study provided an alternative to lipid modification, i.e., fibrillizing peptides, that could improve pharmacokinetic parameters of GLP-1.

Efficacy and safety of glucagon-like peptide-1/glucagon receptor co-agonist JNJ-64565111 in individuals with type 2 diabetes mellitus and obesity: A randomized dose-ranging study

Weight loss has been shown to improve metabolic parameters and cardiovascular risk in people with type 2 diabetes mellitus (T2DM). This phase 2 study evaluated the safety and efficacy of JNJ-64565111, a dual agonist of GLP-1 and glucagon receptors, in individuals with T2DM and class II/III obesity. In this randomized, double-blind study, participants with T2DM (HbA1c 6.5%-9.5%), body mass index of 35 to 50 kg/m² and stable weight were randomly assigned (1:1:1:1) to placebo or JNJ-64565111 (5.0 mg, 7.4 mg or 10.0 mg). The primary endpoint was percent change from baseline in body weight at week 12. Of 195 dosed participants, 144 (73.8%) completed treatment. At week 12, placebo-subtracted body weight changes were -4.6%, -5.9% and -7.2% with JNJ-64565111 5.0 mg, 7.4 mg and 10.0 mg, respectively. All JNJ-64565111 doses were associated with no change in HbA1c and slight numerical elevation of fasting insulin. Numerical increases in fasting plasma glucose were observed with JNJ-64565111 5.0 mg and 7.4 mg. Incidence of treatment-emergent adverse events, especially nausea and vomiting, was higher with JNJ-64565111 vs placebo. Overall, JNJ-64565111 significantly reduced body weight in a dose-dependent manner vs placebo but was associated with greater incidence of treatment-emergent adverse events, no HbA1c reductions, and increased fasting plasma glucose and fasting insulin.

Matrine, as a CaSR agonist promotes intestinal GLP-1 secretion and improves insulin resistance in diabetes mellitus

BACKGROUND

Matrine (Mat), a bitter tastes compounds of derived from leguminosae such as Sophora flavescens and S. subprostrata, commonly used to improve obesity and diabetes.

PURPOSE

Our study to demonstrate bitter substances can stimulate the Bitter taste receptors (TAS2Rs) or Calcium-sensing receptor (CaSR) to stimulate the secretion of GLP-1 to promote blood glucose regulation.

METHODS

The diabetic mice and intestinal secretory cell model were established to evaluate the Mat on glucose metabolism, intestinal insulin secretion and GLP-1 secretion related substances. To clarify the mechanism of Mat in regulating GLP-1 secretion by immunofluorescence, calcium labeling, siRNA, and molecular docking.

RESULTS

The results showed that Mat could significantly improve glucose metabolism and increased insulin and GLP-1 secretion in diabetic mice and increased trisphosphate inositol (IP3) levels by affecting the expression of phospholipase C β2 (PLCβ2) and promote an increase in intracellular Ca2+ levels in STC-1 cells to subsequently stimulate the secretion of GLP-1. Knockdown of the bitter taste receptors mTas2r108, mTas2r137, and mTas2r138 in STC-1 cells by siRNA did could not affect the role of Mat in regulating GLP-1. However, the secretion of GLP-1 by Mat could be significantly inhibited by administration of a CaSR inhibitor or siRNA CaSR. Molecular docking analysis showed that Mat could embed CaSR protein and bind to the original ligand of the egg white at the same amino acid site to play the role of an agonist.

CONCLUSION

Matrine is a typical bitter alkaloid could be used as an agonist of CaSR to stimulate the secretion of GLP-1 in the intestine, and it may be used as a potential drug for diabetes treatment.

ACTUALITIES IN ENDOCRINE PHARMACOLOGY: ADVANCES IN THE DEVELOPMENT OF ORAL FORMULATIONS FOR CALCITONIN AND SEMAGLUTIDE

As the medical utility of injectable therapeutic peptides is expanding, so is the challenge of developing technologies that allow the administration of such molecules via alternative routes, considering that chronic patients requiring treatment with parenteral formulations are less adherent and compliant to the therapeutic regimens. Hence, substantial efforts have been made to develop technologies that allow the oral formulation of peptides. Due to their importance in the field of pharmaceutical technology, we describe the latest advancements made in the development of oral salmon calcitonin and oral semaglutide, in co-formulation with absorption enhancers such as 8-[(5-chloro-2-hydroxybenzoyl) amino] octanoic acid (or 5-CNAC) and N-[8-(2-hydroxybenzoyl) amino] caprylate (or SNAC). Oral semaglutide is considered to be a landmark for oral peptide delivery technology, as it is one of the very few successful examples of peptides that can be administered orally. Unlike semaglutide, oral calcitonin is still not approved by the regulatory authorities because it failed to demonstrate the anticipated effects in phase III clinical trials conducted so far. However, the efforts for obtaining an oral form of calcitonin have significantly contributed to the development of technologies that facilitate the absorption of peptide-structure macromolecules.

Progress in research of gastrointestinal motility regulation

Gastrointestinal motility is an important part of the physiological function of the digestive tract, and its dysfunction is one of the key factors that cause different gastrointestinal motility disorders. These diseases seriously affect patients' normal life. With the development of scientific research and technology, well-designed research studies have been conducted on the regulatory mechanisms of gastrointestinal motility, which mainly include the regulation of gastrointestinal hormones, intestinal microflora, neurotransmitters, brain-gut peptides, interstitial cells of Cajal, and gastrointestinal electrical activities. In addition, current studies have proved that bitter taste receptors have certain regulatory effects on gastrointestinal motility. This paper primarily discusses the relevant pathways controlling gastrointestinal motility.

Glucagon and Glucagon-like Peptide-1 Receptors: Promising Therapeutic Targets for an Effective Management of Diabetes Mellitus

G-protein-coupled receptors (GPCRs) are membrane-bound proteins, which are responsible for the detection of extracellular stimuli and the origination of intracellular responses. Both glucagon and glucagon-like peptide-1 (GLP-1) receptors belong to G protein-coupled receptor (GPCR) superfamily. Along with insulin, glucagon and GLP-1 are critical hormones for maintaining normal serum glucose within the human body. Glucagon generally plays its role in the liver through cyclic adenosine monophosphate (cAMP), where it compensates for the action of insulin. GLP-1 is secreted by the L-cells of the small intestine to stimulate insulin secretion and inhibit glucagon action. Despite extensive research efforts and the multiple approaches adopted, the glycemic control in the case of type-2 diabetes mellitus remains a major challenge. Therefore, a deep understanding of the structure-function relationship of these receptors will have great implications for future therapies in order to maintain a normal glucose level for an extended period of time. The antagonists of glucagon receptors that can effectively block the hepatic glucose production, as a result of glucagon action, are highly desirable for the tuning of the hyperglycemic state in type 2 diabetes mellitus. In the same manner, GLP-1R agonists act as important treatment modalities, thanks to their multiple anti-diabetic actions to attain normal glucose levels. In this review article, the structural diversity of glucagon and GLP-1 receptors along with their signaling pathways, site-directed mutations and significance in drug discovery against type-2 diabetes are illustrated. Moreover, the promising non-peptide antagonists of glucagon receptor and agonists of GLP-1 receptor, for the management of diabetes are presented with elaboration on the structure-activity relationship (SAR).

Glucagon-Like Peptide-1 Analog Liraglutide Attenuates Pressure-Overload Induced Cardiac Hypertrophy and Apoptosis through Activating ATP Sensitive Potassium Channels

PURPOSE

This study aimed to investigate whether inhibition of glucagon-like peptide-1 (GLP-1) on pressure overload induced cardiac hypertrophy and apoptosis is related to activation of ATP sensitive potassium (KATP) channels.

METHODS

Male SD rats were randomly divided into five groups: sham, control (abdominal aortic constriction), GLP-1 analog liraglutide (0.3 mg/kg/twice day), KATP channel blocker glibenclamide (5 mg/kg/day), and liraglutide plus glibenclamide.

RESULTS

Relative to the control on week 16, liraglutide upregulated protein and mRNA levels of KATP channel subunits Kir6.2/SUR2 and their expression in the myocardium, vascular smooth muscle, aortic endothelium, and cardiac microvasculature. Consistent with a reduction in aortic wall thickness (61.4 ± 7.6 vs. 75.0 ± 7.6 μm, p < 0.05), liraglutide enhanced maximal aortic endothelium-dependent relaxation in response to acetylcholine (71.9 ± 8.7 vs. 38.6 ± 4.8%, p < 0.05). Along with a reduction in heart to body weight ratio (2.6 ± 0.1 vs. 3.4 ± 0.4, mg/g, p < 0.05) by liraglutide, hypertrophied cardiomyocytes (371.0 ± 34.4 vs. 933.6 ± 156.6 μm², p < 0.05) and apoptotic cells (17.5 ± 8.2 vs. 44.7 ± 7.9%, p < 0.05) were reduced. Expression of anti-apoptotic protein BCL-2 and contents of myocardial ATP were augmented, and expression of cleaved-caspase 3 and levels of serum Tn-I/-T were reduced. Echocardiography and hemodynamic measurement showed that cardiac systolic function was enhanced as evidenced by increased ejection fraction (88.4 ± 4.8 vs. 73.8 ± 5.1%, p < 0.05) and left ventricular systolic pressure (105.2 ± 10.8 vs. 82.7 ± 7.9 mmHg, p < 0.05), and diastolic function was preserved as shown by a reduction of ventricular end-diastolic pressure (-3.1 ± 2.9 vs. 6.7 ± 2.8 mmHg, p < 0.05). Furthermore, left ventricular internal diameter at end-diastole (5.8 ± 0.5 vs. 7.7 ± 0.6 mm, p < 0.05) and left ventricular internal diameter at end-systole (3.0 ± 0.6 vs. 4.7 ± 0.4 mm, p < 0.05) were improved. Dietary administration of glibenclamide alone did not alter all the parameters measured but significantly blocked liraglutide-exerted cardioprotection.

CONCLUSION

Liraglutide ameliorates cardiac hypertrophy and apoptosis, potentially via activating KATP channel-mediated signaling pathway. These data suggest that liraglutide might be considered as an adjuvant therapy to treat patients with heart failure.

Structural optimization of pyrazolo[1,5-a]pyrimidine derivatives as potent and highly selective DPP-4 inhibitors

Our previous discovery of pyrazolo [1,5-a]pyrimidin-7(4H)-one scaffold-based DPP-4 inhibitors yielded two potent compounds b2 (IC₅₀ = 79 nM) and d1 (IC₅₀ = 49 nM) but characterized by cytotoxicity. Herein, with scaffold hopping and fragment-based drug design strategies, highly potent and selective pyrazolo [1,5-a]pyrimidine DPP-4 inhibitors were found featured by reduced or diminished cytotoxicity. Specifically, c24 (IC₅₀ = 2 nM) exhibits a 25 to 40-fold increase of inhibitory activity respect to those of b2 and d1, respectively, 2-fold from Alogliptin (IC₅₀ = 4 nM), and remarkable selectivity over DPP-8 and DPP-9 (>2000 fold). Further docking studies confirmed that the pyrazolo [1,5-a]pyrimidine core interacts with the S1 pocket whereas its substituted aromatic ring interacts with the sub-S1 pocket. The interactive mode in this case resembles that of Alogliptin and Trelagliptin. Further in vivo IPGTT assays in diabetic mice demonstrated that c24 effectively reduces glucose excursion by 48% at the dose of 10 mg/kg, suggesting that c24 is worthy of further development as a potent anti-diabetes agent.

Is there a role for glucagon-like peptide-1 receptor agonists in the management of diabetic nephropathy?

Chronic kidney disease constitutes a major microvascular complication of diabetes mellitus. Accumulating data suggest that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) might have a role in the management of diabetic kidney disease (DKD). GLP-1 RAs appear to reduce the incidence of persistent macro-albuminuria in patients with type 2 diabetes mellitus. This beneficial effect appears to be mediated not only by the glucose-lowering action of these agents but also on their blood pressure lowering, anti-inflammatory and antioxidant effects. On the other hand, GLP-1 RAs do not appear to affect the rate of decline of glomerular filtration rate. However, this might be due to the relatively short duration of the trials that evaluated their effects on DKD. Moreover, these trials were not designed nor powered to assess renal outcomes. Given than macrolbuminuria is a strong risk factor for the progression of DKD, it might be expected that GLP-1 RAs will prevent the deterioration in renal function in the long term. Nevertheless, this remains to be shown in appropriately designed randomized controlled trials in patients with DKD.

The Cascade System of Osmotic Homeostasis Regulation

The human and animal osmoregulation system is aimed at stabilizing serum osmolality in order to maintain cell volume. It has been shown that the introduction of 5 mL water per 100 g of body weight into the stomach of rats decreases serum osmolality and the concentration of Na and Ca, but not K and Mg. The cascade system of osmotic homeostasis increases secretion of glucagon-like peptide-1 (GLP-1) and oxytocin, and decreases secretion of vasopressin, which reduces the osmotic permeability of collecting duct. After water loading and the injection of 0.015 nM exenatide (GLP-1 mimetic), the time of excretion of 50% of water was halved from 112 ± 4 to 57 ± 5 min (p < 0.01), and after the injection of 0.015 nM oxytocin, it decreased to 83 ± 6 min (p < 0.01). The physiological mechanism of renal effect of the aforementioned hormones which accelerate the recovery of osmotic homeostasis has been found.

The Race to Bash NASH: Emerging Targets and Drug Development in a Complex Liver Disease

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD) characterized by liver steatosis, inflammation, and hepatocellular damage. NASH is a serious condition that can progress to cirrhosis, liver failure, and hepatocellular carcinoma. The association of NASH with obesity, type 2 diabetes mellitus, and dyslipidemia has led to an emerging picture of NASH as the liver manifestation of metabolic syndrome. Although diet and exercise can dramatically improve NASH outcomes, significant lifestyle changes can be challenging to sustain. Pharmaceutical therapies could be an important addition to care, but currently none are approved for NASH. Here, we review the most promising targets for NASH treatment, along with the most advanced therapeutics in development. These include targets involved in metabolism (e.g., sugar, lipid, and cholesterol metabolism), inflammation, and fibrosis. Ultimately, combination therapies addressing multiple aspects of NASH pathogenesis are expected to provide benefit for patients.

Recent Advances in Half-life Extension Strategies for Therapeutic Peptides and Proteins

Peptides and proteins are two classes of molecules with attractive possibilities for therapeutic applications. However, the bottleneck for the therapeutic application of many peptides and proteins is their short halflives in vivo, typically just a few minutes to hours. Half-life extension strategies have been extensively studied and many of them have been proven to be effective in the generation of long-acting therapeutics with improved pharmacokinetic and pharmacodynamic properties. In this review, we summarize the recent advances in half-life extension strategies, illustrate their potential applications and give some examples, highlighting the strategies that have been used in approved drugs and for drugs in clinical trials. Meanwhile, several novel strategies that are still in the process of discovery or at a preclinical stage are also introduced. In these strategies, the two most frequently used half-life extension methods are the reduction in the rate of renal clearance or the exploitation of the recycling mechanism of FcRn by binding to the albumin or IgG-Fc. Here, we discuss half-life extension strategies of recombinant therapeutic protein via genetic fusion, rather than chemical conjugation such as PEGylation. With the rapid development of genetic engineering and protein engineering, novel strategies for half-life extension have been emerged consistently. Some of these will be evaluated in clinical trials and may become viable alternatives to current strategies for making next-generation biodrugs.

Ureidopeptide GLP-1 analogues with prolonged activity in vivo via signal bias and altered receptor trafficking

The high demand of the pharmaceutical industry for new modalities to address the diversification of biological targets with large surfaces of interaction led us to investigate the replacement of α-amino acid residues with ureido units at selected positions in peptides to improve potency and generate effective incretin mimics. Based on molecular dynamics simulations, N-terminally modified GLP-1 analogues with a ureido residue replacement at position 2 were synthesized and showed preservation of agonist activity while exhibiting a substantial increase in stability. This enabling platform was applied to exenatide and lixisenatide analogues to generate two new ureidopeptides with antidiabetic properties and longer duration of action. Further analyses demonstrated that the improvement was due mainly to differences in signal bias and trafficking of the GLP-1 receptor. This study demonstrates the efficacy of single α-amino acid substitution with ureido residues to design long lasting peptides.

A free-energy landscape for the glucagon-like peptide 1 receptor GLP1R

G-protein-coupled receptors (GPCRs) are among the most important receptors in human physiology and pathology. They serve as master regulators of numerous key processes and are involved in as well as cause debilitating diseases. Consequently, GPCRs are among the most attractive targets for drug design and pharmaceutical interventions (>30% of drugs on the market). The glucagon-like peptide 1 (GLP-1) hormone receptor GLP1R is closely involved in insulin secretion by pancreatic β-cells and constitutes a major druggable target for the development of anti-diabetes and obesity agents. GLP1R structure was recently solved, with ligands, allosteric modulators and as part of a complex with its cognate G protein. However, the translation of this structural data into structure/function understanding remains limited. The current study functionally characterizes GLP1R with special emphasis on ligand and cellular partner binding interactions and presents a free-energy landscape as well as a functional model of the activation cycle of GLP1R. Our results should facilitate a deeper understanding of the molecular mechanism underlying GLP1R activation, forming a basis for improved development of targeted therapeutics for diabetes and related disorders.

Liraglutide protects high-glucose-stimulated fibroblasts by activating the CD36-JNK-AP1 pathway to downregulate P4HA1

BACKGROUND

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes mellitus. It's known that glucagon-like peptide-1 (GLP-1) and prolyl 4-hydroxylase subunit alpha-1 (P4HA1) have significant effect on cardiovascular function, but their interaction in cardiac fibroblasts (CFs) is still being unraveled.

METHODS AND RESULTS

The present study demonstrated that glucose promotes CFs proliferation and cardiac fibrosis. Using qRT-PCR, Western blot, CCK-8, EdU, flow cytometry, wound healing and Transwell assays to explore the functions of liraglutide and P4HA1 in high-glucose (HG)-induced CFs, we proved that liraglutide as well as silencing of P4HA1 inhibited cell proliferation, migration and invasion, and promoted cell cycle arrest and apoptosis in HG-induced CFs. In addition, liraglutide downregulated P4HA1 expression, upregulated CD36 and P-JNK expression levels, and enhanced the DNA binding activity of AP-1 on P4HA1. Inhibition of CD36 or p--JNK promoted P4HA1 expression.

CONCLUSIONS

Liraglutide may down-regulate P4HA1 expression at least partly though CD36-JNK-AP1 pathway, thereby reducing myocardial fibrosis. Therefore, our study provides novel insight into the molecular mechanism and function of liraglutide in HG-mediated CFs.

Glucagon-Like Peptide-1 Receptor Agonists and Strategies To Improve Their Efficiency

Type 2 diabetes mellitus (T2DM) is increasing in global prevalence and is associated with serious health problems (e.g., cardiovascular disease). Various treatment options are available for T2DM, including the incretin hormone glucagon-like peptide-1 (GLP-1). GLP-1 is a therapeutic peptide secreted from the intestines following food intake, which stimulates the secretion of insulin from the pancreas. The native GLP-1 has a very short plasma half-life, owning to renal clearance and degradation by the enzyme dipeptidyl peptidase-4. To overcome this issue, various GLP-1 agonists with increased resistance to proteolytic degradation and reduced renal clearance have been developed, with several currently marketed. Strategies, such as controlled release delivery systems, methods to reduce renal clearance (e.g., PEGylation and conjugation to antibodies), and methods to improve proteolytic stability (e.g., stapling, cyclization, and glycosylation) provide means to further improve the ability of GLP-1 analogs. These will be discussed in this literature review.

Glucagon-like peptide-1 receptor activation alleviates lipopolysaccharide-induced acute lung injury in mice via maintenance of endothelial barrier function

Glucagon-like peptide-1 (GLP-1), which is well known for regulating glucose homeostasis, exhibits multiple actions in cardiovascular disorders and renal injury. However, little is known about the effect of GLP-1 receptor (GLP-1R) activation on acute lung injury (ALI). In this study, we investigated the effect of GLP-1R on ALI and the potential underlying mechanisms with the selective agonist liraglutide. Our results show that GLP-1 levels decreased in serum, though they increased in bronchoalveolar lavage fluid (BALF) and lung tissue in a mouse model of lipopolysaccharide (LPS)-induced ALI. Liraglutide prevented LPS-induced polymorphonuclear neutrophil (PMN) extravasation, lung injury, and alveolar-capillary barrier dysfunction. In cultured human pulmonary microvascular endothelial cells (HPMECs), liraglutide protected against LPS-induced endothelial barrier injury by restoring intercellular tight junctions and adherens junctions. Moreover, liraglutide prevented PMN-endothelial adhesion by inhibiting the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), and thereafter suppressed PMN transendothelial migration. Furthermore, liraglutide suppressed LPS-induced activation of Rho/NF-κB signaling in HPMECs. In conclusion, our results show that GLP-1R activation protects mice from LPS-induced ALI by maintaining functional endothelial barrier and inhibiting PMN extravasation. These results also suggest that GLP-1R may be a potential therapeutic target for the treatment of ALI.

C-Peptide Area Under the Curve at Glucagon Stimulation Test Predicts Glucose Improvements by GLP-1 Receptor Analogue: A Retrospective Observational Study

INTRODUCTION

Despite the widespread use of glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1ras) to improve glycemic regulation, with a low risk of hypoglycemia and weight reduction, their effectiveness varies among individuals. This study aimed to identify predictors of the efficacy of GLP-1ra on Hemoglobin A1c (HbA1c) in patients with insulin-independent diabetes.

METHODS

In total, 58 patients with insulin-independent diabetes were included. Patients were included if their β-cell function was evaluated via a glucagon stimulation test (GST) before the introduction of GLP-1ra therapy. β-Cell function-related indices, such as the C-peptide index (CPI), increments in C-peptide immunoreactivity (CPR) after glucagon stimulation (ΔCPR), and the area under the CPR curve (CPR-AUC) during the GST, were evaluated. HbA1c and body weight (BW) were measured at 6 and 12 months after the initiation of GLP-1ra.

RESULTS

A univariate regression analysis revealed a significant correlation between CPR-AUC and changes in HbA1c at 6 months and with changes in BW at 6 and 12 months. A multivariate regression analysis revealed that CPR-AUC was significantly correlated with changes in HbA1c at 6 months. A receiver-operating characteristic analysis revealed that 21.9 ng/ml·min CPR-AUC was the optimal cut-off value to predict an HbA1c level < 7%, i.e., 53 mmol/mol.

CONCLUSION

Residual β-cell function, as assessed via CPR-AUC in the GST, is an effective predictor of the efficacy of GLP-1ras.