Evaluation of weight loss and metabolic changes in diabetic patients treated with liraglutide, effect of RS 6923761 gene variant of glucagon-like peptide 1 receptor

Glucagon-Like Peptide 1 (GLP-1) Receptor Variants and Glycemic Response to Liraglutide: A Pharmacogenetics Study in Iranian People with Type 2 Diabetes Mellitus

INTRODUCTION

Pharmacogenetics studies suggest that genetic variants have a possible influence on the inter-individual differences in therapeutic response to glucagon-like peptide 1 receptor agonists (GLP-1 RAs). We aimed to examine the potential role of genetic variability of glucagon-like peptide 1 receptor (GLP-1R) on glycemic response to GLP-1 RAs in a population of Iranian people with type 2 diabetes mellitus (T2DM).

METHODS

In this study, we analyzed the data from participants in a non-inferiority randomized clinical trial between 2019 and 2020. Patients received liraglutide 1.8 mg/day subcutaneously for 24 weeks. They were stratified by the baseline hemoglobin A1c (HbA1c) into four categories: 7-7.99, 8-8.99, 9-9.99, and ≥ 10%. In each category, subjects with HbA1c reduction greater than the median ΔHbA1c value for that group were defined as optimal responders. The pooled number of optimal/suboptimal responders in the four groups was used for the comparison. We evaluated two genetic variants of GLP-1R, rs6923761 and rs10305420, using Sanger sequencing. Logistic regression analyses were performed to examine the associations of the GLP-1R variants with the glycemic response in different genetic models.

RESULTS

Out of 233 participants, 120 individuals were optimal responders. Median HbA1c reduction was - 2.5% in the optimal responder group compared with - 1.0% in the suboptimal responder group (P < 0.001). In genetic models, rs10305420 T allele homozygosity was associated with optimal glycemic response to liraglutide compared with heterozygous and wild-type homozygous states (recessive model: OR 3.28, 95% CI 1.41-7.65, P = 0.006; codominant model: OR 2.52, 95% CI 1.03-6.13, P = 0.04). No significant association was found between rs6923761 variant and HbA1c reduction.

CONCLUSION

GLP-1R rs10305420 polymorphism can explain some of the inter-individual differences in glycemic response to liraglutide in a population of Iranian people with T2DM.

Abolishing β-arrestin recruitment is necessary for the full metabolic benefits of G protein-biased glucagon-like peptide-1 receptor agonists

AIM

Earlier studies have shown that peptide glucagon-like peptide-1 receptor (GLP-1R) agonists with reduced β-arrestin recruitment show enhanced anti-hyperglycaemic efficacy through avoidance of GLP-1R desensitization. However, the ligand modifications needed to decrease β-arrestin recruitment usually also reduces GLP-1R affinity, therefore higher doses are needed. Here we aimed to develop new, long-acting, G protein-biased GLP-1R agonists with acute signalling potency comparable with semaglutide, to provide insights into specific experimental and therapeutic scenarios.

MATERIALS AND METHODS

New GLP-1R agonist peptides were assessed using a variety of in vitro and in vivo assays.

RESULTS

First, we show that very substantial reductions in β-arrestin recruitment efficacy are required to realize fully the benefits of GLP-1R agonism on blood glucose lowering in mice, with more moderate reductions being less effective. Secondly, our lead compound (SRB107) performs substantially better than semaglutide for effects on blood glucose and weight loss, which may be jointly attributable to its biased agonist action and protracted pharmacokinetics. Thirdly, we show that biased agonist-specific GLP-1R internalization profiles occur at clinically relevant pharmacological concentrations. Finally, we show that SRB107 cAMP signalling is differentially modulated by single and double GLP1R coding variants seen in human populations, with implications for GLP-1R agonist pharmacogenomics.

CONCLUSIONS

Completely abolishing β-arrestin recruitment improves the anti-hyperglycaemic effects of GLP-1R agonists in mice.

Precision Medicine in Type 2 Diabetes Mellitus: Utility and Limitations

Type 2 diabetes mellitus (T2DM) is one of the most widespread diseases in Western countries, and its incidence is constantly increasing. Epidemiological studies have shown that in the next 20 years. The number of subjects affected by T2DM will double. In recent years, owing to the development and improvement in methods for studying the genome, several authors have evaluated the association between monogenic or polygenic genetic alterations and the development of metabolic diseases and complications. In addition, sedentary lifestyle and socio-economic and pandemic factors have a great impact on the habits of the population and have significantly contributed to the increase in the incidence of metabolic disorders, obesity, T2DM, metabolic syndrome, and liver steatosis. Moreover, patients with type 2 diabetes appear to respond to antihyperglycemic drugs. Only a minority of patients could be considered true non-responders. Thus, it appears clear that the main aim of precision medicine in T2DM is to identify patients who can benefit most from a specific drug class more than from the others. Precision medicine is a discipline that evaluates the applicability of genetic, lifestyle, and environmental factors to disease development. In particular, it evaluated whether these factors could affect the development of diseases and their complications, response to diet, lifestyle, and use of drugs. Thus, the objective is to find prevention models aimed at reducing the incidence of pathology and mortality and therapeutic personalized approaches, to obtain a greater probability of response and efficacy. This review aims to evaluate the applicability of precision medicine for T2DM, a healthcare burden in many countries.

Precision medicine of obesity as an integral part of type 2 diabetes management - past, present, and future

Obesity is a complex and heterogeneous condition that leads to various metabolic complications, including type 2 diabetes. Unfortunately, for some, treatment options to date for obesity are insufficient, with many people not reaching sustained weight loss or having improvements in metabolic health. In this Review, we discuss advances in the genetics of obesity from the past decade-with emphasis on developments from the past 5 years-with a focus on metabolic consequences, and their potential implications for precision management of the disease. We also provide an overview of the potential role of genetics in guiding weight loss strategies. Finally, we propose a vision for the future of precision obesity management that includes developing an obesity-centred multidisease management algorithm that targets both obesity and its comorbidities. However, further collaborative efforts and research are necessary to fully realise its potential and improve metabolic health outcomes.

Individualised prescription of medications for treatment of obesity in adults

Obesity continues to increase in prevalence globally, driven by changes in environmental factors which have accelerated the development of obesity in individuals with an underlying predisposition to weight gain. The adverse health effects and increased risk for chronic disease associated with obesity are ameliorated by weight loss, with greater benefits from larger amounts of weight reduction. Obesity is a heterogeneous condition, with the drivers, phenotype and complications differing substantially between individuals. This raises the question of whether treatments for obesity, specifically pharmacotherapy, can be targeted based on individual characteristics. This review examines the rationale and the clinical data evaluating this strategy in adults. Individualised prescribing of obesity medication has been successful in rare cases of monogenic obesity where medications have been developed to target dysfunctions in leptin/melanocortin signalling pathways but has been unsuccessful in polygenic obesity due to a lack of understanding of how the gene variants associated with body mass index affect phenotype. At present, the only factor consistently associated with longer-term efficacy of obesity pharmacotherapy is early weight loss outcome, which cannot inform choice of therapy at the time of medication initiation. The concept of matching a therapy for obesity to the characteristics of the individual is appealing but as yet unproven in randomised clinical trials. With increasing technology allowing deeper phenotyping of individuals, increased sophistication in the analysis of big data and the emergence of new treatments, it is possible that precision medicine for obesity will eventuate. For now, a personalised approach that takes into account the person's context, preferences, comorbidities and contraindications is recommended.

GWAS of random glucose in 476,326 individuals provide insights into diabetes pathophysiology, complications and treatment stratification

Conventional measurements of fasting and postprandial blood glucose levels investigated in genome-wide association studies (GWAS) cannot capture the effects of DNA variability on 'around the clock' glucoregulatory processes. Here we show that GWAS meta-analysis of glucose measurements under nonstandardized conditions (random glucose (RG)) in 476,326 individuals of diverse ancestries and without diabetes enables locus discovery and innovative pathophysiological observations. We discovered 120 RG loci represented by 150 distinct signals, including 13 with sex-dimorphic effects, two cross-ancestry and seven rare frequency signals. Of these, 44 loci are new for glycemic traits. Regulatory, glycosylation and metagenomic annotations highlight ileum and colon tissues, indicating an underappreciated role of the gastrointestinal tract in controlling blood glucose. Functional follow-up and molecular dynamics simulations of lower frequency coding variants in glucagon-like peptide-1 receptor (GLP1R), a type 2 diabetes treatment target, reveal that optimal selection of GLP-1R agonist therapy will benefit from tailored genetic stratification. We also provide evidence from Mendelian randomization that lung function is modulated by blood glucose and that pulmonary dysfunction is a diabetes complication. Our investigation yields new insights into the biology of glucose regulation, diabetes complications and pathways for treatment stratification.

Potential contributors to variation in weight-loss response to liraglutide

Obesity treatment requires a chronic state of negative energy balance. Obesity medications can help with this, increasing long-term dietary compliance by promoting satiety or reducing hunger. However, efficacy and safety of obesity medications vary for individuals. Early identification of non-responders to obesity medications may limit drug exposure while optimizing benefits for responders. This review summarizes factors that impact weight-loss response to liraglutide. Factors linked to greater weight loss on liraglutide include being female, not having diabetes, having relatively high baseline weight, and losing at least 4% of initial weight after 16 weeks of treatment. Other covariates that may predict treatment response but require further confirmation include central effects, nausea, gastric emptying of solids, and genotype. Baseline body mass index, race, and age seem less relevant for predicting weight-loss response to liraglutide. Lesser known and harder-to-measure factors such as cerebral blood flow, food cue reactivity, gut hormone levels, and dietary adherence possibly impact variability of response to liraglutide. This information should assist healthcare providers with establishing realistic weight-loss probability for individual patients. Future research should improve the ability to identify responders to liraglutide. Importantly, this review may provide a framework to identify responders to other obesity medications.

Pharmacogenetic interactions of medications administered for weight loss in adults: a systematic review and meta-analysis

Aim: To analyze roles of single nucleotide variants (SNVs) on weight loss with US FDA-approved medications. Materials & methods: We searched the literature up until November 2022. Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed. Results: 14 studies were included in qualitative analysis and seven in meta-analysis. SNVs in CNR1, GLP-1R, MC4R, TCF7L2, CTRB1/2, ADIPOQ, SORCS1 and ANKK1 were evaluated relative to weight loss with glucagon-like peptide-1 agonists (13 studies) or naltrexone-bupropion (one study). CNR1 gene (rs1049353), GLP-1R gene (rs6923761, rs10305420), TCF7L2 gene (rs7903146) were associated with weight loss in at least one study involving glucagon-like peptide-1 agonist(s). The meta-analysis did not identify any consistent effect of SNVs. Conclusion: Pharmacogenetic interactions for exenatide, liraglutide, naltrexone-bupropion and weight loss were identified, but the directionality was inconsistent.

Pharmacogenomics of GLP-1 receptor agonists: a genome-wide analysis of observational data and large randomised controlled trials

BACKGROUND

In the treatment of type 2 diabetes, GLP-1 receptor agonists lower blood glucose concentrations, body weight, and have cardiovascular benefits. The efficacy and side effects of GLP-1 receptor agonists vary between people. Human pharmacogenomic studies of this inter-individual variation can provide both biological insight into drug action and provide biomarkers to inform clinical decision making. We therefore aimed to identify genetic variants associated with glycaemic response to GLP-1 receptor agonist treatment.

METHODS

In this genome-wide analysis we included adults (aged ≥18 years) with type 2 diabetes treated with GLP-1 receptor agonists with baseline HbA_1c of 7% or more (53 mmol/mol) from four prospective observational cohorts (DIRECT, PRIBA, PROMASTER, and GoDARTS) and two randomised clinical trials (HARMONY phase 3 and AWARD). The primary endpoint was HbA_1c reduction at 6 months after starting GLP-1 receptor agonists. We evaluated variants in GLP1R, then did a genome-wide association study and gene-based burden tests.

FINDINGS

4571 adults were included in our analysis, of these, 3339 (73%) were White European, 449 (10%) Hispanic, 312 (7%) American Indian or Alaskan Native, and 471 (10%) were other, and around 2140 (47%) of the participants were women. Variation in HbA_1c reduction with GLP-1 receptor agonists treatment was associated with rs6923761G→A (Gly168Ser) in the GLP1R (0·08% [95% CI 0·04-0·12] or 0·9 mmol/mol lower reduction in HbA_1c per serine, p=6·0 × 10^-5) and low frequency variants in ARRB1 (optimal sequence kernel association test p=6·7 × 10^-8), largely driven by rs140226575G→A (Thr370Met; 0·25% [SE 0·06] or 2·7 mmol/mol  [SE 0·7] greater HbA_1c reduction per methionine, p=5·2 × 10^-6). A similar effect size for the ARRB1 Thr370Met was seen in Hispanic and American Indian or Alaska Native populations who have a higher frequency of this variant (6-11%) than in White European populations. Combining these two genes identified 4% of the population who had a 30% greater reduction in HbA_1c than the 9% of the population with the worse response.

INTERPRETATION

This genome-wide pharmacogenomic study of GLP-1 receptor agonists provides novel biological and clinical insights. Clinically, when genotype is routinely available at the point of prescribing, individuals with ARRB1 variants might benefit from earlier initiation of GLP-1 receptor agonists.

FUNDING

Innovative Medicines Initiative and the Wellcome Trust.

Genetic variants of the GLP-1R gene affect the susceptibility and glucose metabolism of gestational diabetes mellitus: a two-center nested case‒control study

BACKGROUND

Gestational diabetes mellitus (GDM) is the most common complication during pregnancy, occurring under the combined action of environmental and genetic factors. Genetic variants of glucagon-like peptide-1 receptor (GLP-1R) have been reported to affect insulin secretion and susceptibility to type 2 diabetes. This study aimed to explore the role of GLP-1R polymorphisms in GDM and glucose metabolism.

METHODS

A two-center nested case‒control study was designed, including 200 pregnant women with GDM and 200 pregnant women without GDM genotyped for five tag SNPs of GLP-1R using Sanger sequencing. Logistic regression was used to evaluate the relationship between GLP-1R polymorphisms and GDM risk. Glucose and insulin concentrations were measured based upon the 75 g oral glucose tolerance test (OGTT). Beta cell function of different genotypes was estimated with the 60 min insulinogenic index (IGI₆₀) and OGTT-derived disposition index (DI).

RESULTS

Mutant genotype AG + GG of tag SNP rs6458093 nominally increased GDM risk (p = 0.049), especially among subjects younger than 35 years (p = 0.024) and with BMI no less than 24 (p = 0.041), after adjusting for confounders. Meanwhile, compared with subjects with wild genotype AA, subjects with genotype AG + GG of rs6458093 also showed nominally significantly lower IGI₆₀ (p = 0.032) and DI (p = 0.029), as well as significantly higher 75 g OGTT-based 1 h glucose load plasma glucose levels (p = 0.045). Moreover, the mutant heterozygous genotype GA of tag SNP rs3765467 nominally decreased GDM risk among subjects older than 35 years (p = 0.037) but showed no association with insulin secretion and glucose homeostasis.

CONCLUSIONS

Tag SNP rs6458093 of GLP-1R was nominally associated with increased GDM risk and affected beta cell function and postprandial glucose metabolism, while tag SNP rs3765467 of GLP-1R was nominally associated with decreased GDM risk, providing evidence for molecular markers and etiological study of GDM.

On the Verge of Precision Medicine in Diabetes

The epidemic of type 2 diabetes (T2D) is a significant global public health challenge and a major cause of morbidity and mortality. Despite the recent proliferation of pharmacological agents for the treatment of T2D, current therapies simply treat the symptom, i.e. hyperglycemia, and do not directly address the underlying disease process or modify the disease course. This article summarizes how genomic discovery has contributed to unraveling the heterogeneity in T2D, reviews relevant discoveries in the pharmacogenetics of five commonly prescribed glucose-lowering agents, presents evidence supporting how pharmacogenetics can be leveraged to advance precision medicine, and calls attention to important research gaps to its implementation to guide treatment choices.

Biased Agonism and Polymorphic Variation at the GLP-1 Receptor: Implications for the Development of Personalised Therapeutics

Glucagon-like peptide-1 receptor (GLP-1R) is a well-studied incretin hormone receptor and target of several therapeutic drugs for type 2 diabetes (T2D), obesity and, more recently, cardiovascular disease. Some signalling pathways downstream of GLP-1R may be responsible for drug adverse effects such as nausea, while others mediate therapeutic outcomes of incretin-based T2D therapeutics. Understanding the interplay between different factors that alter signalling, trafficking, and receptor activity, including biased agonism, single nucleotide polymorphisms and structural modifications is key to develop the next-generation of personalised GLP-1R agonists. However, these interactions remain poorly described, especially for novel therapeutics such as dual and tri-agonists that target more than one incretin receptor. Comparison of GLP-1R structures in complex with G proteins and different peptide and non-peptide agonists has revealed novel insights into important agonist-residue interactions and networks crucial for receptor activation, recruitment of G proteins and engagement of specific signalling pathways. Here, we review the latest knowledge on GLP-1R structure and activation, providing structural evidence for biased agonism and delineating important networks associated with this phenomenon. We survey current biased agonists and multi-agonists at different stages of development, highlighting possible challenges in their translational potential. Lastly, we discuss findings related to non-synonymous genomic variants of GLP1R and the functional importance of specific residues involved in GLP-1R function. We propose that studies of GLP-1R polymorphisms, and specifically their effect on receptor dynamics and pharmacology in response to biased agonists, could have a significant impact in delineating precision medicine approaches and development of novel therapeutics.

Effects of liraglutide on gastrointestinal functions and weight in obesity: A randomized clinical and pharmacogenomic trial

OBJECTIVE

This study aimed to determine the effects of a long-acting glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, and placebo subcutaneously over 16 weeks on weight and gastric functions and to evaluate associations of single-nucleotide polymorphisms in GLP1R (rs6923761) and TCF7L2 (rs7903146) with effects of liraglutide.

METHODS

The study conducted a randomized, parallel-group, placebo-controlled, 16-week trial of liraglutide, escalated to 3 mg subcutaneously daily in 136 otherwise healthy adults with obesity. Weight, gastric emptying of solids (GES), gastric volumes, satiation, and body composition measured at baseline and after treatment were compared in two treatment groups using analysis of covariance.

RESULTS

Liraglutide (n = 59) and placebo (n = 65) groups completed treatment. Relative to placebo, liraglutide increased weight loss at 5 and 16 weeks (both p < 0.05), slowed time to half GES (T1/2 ) at 5 and 16 weeks (both p < 0.001), and increased fasting gastric volume (p = 0.01) and satiation (p < 0.01) at 16 weeks. GES T1/2 was positively correlated with weight loss on liraglutide (both p < 0.001). After 16 weeks of liraglutide, GLP1R rs6923761 (AG/AA vs. GG) was associated with reduced percent body fat (p = 0.062), and TCF7L2 rs7903146 (CC vs. CT/TT) was associated with lower body weight (p = 0.015).

CONCLUSIONS

Liraglutide, 3 mg, induces weight loss with delay in GES T1/2 and reduces calorie intake. Slowing GES and variations in GLP1R and TCF7L2 are associated with liraglutide effects in obesity.

Genetic Variability of Incretin Receptors and Alcohol Dependence: A Pilot Study

Alcohol dependence is a chronic mental disorder that leads to decreased quality of life for patients and their relatives and presents a considerable burden to society. Incretin hormones, such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are endogenous gut-brain peptides, which can travel across the blood-brain barrier and access the nervous system. Their respective receptors, GIPR and GLP-1R, are expressed in the reward-related brain areas and are involved in memory formation and neurogenesis, which results in behavioral changes in rodent models. The current study investigated the potential association of genetic variability of incretin receptors with alcohol dependence and alcohol-related psychosymptomatology. Alcohol dependence and comorbid psychosymptomatology were assessed in a cohort of Slovenian male participants, comprised of 89 hospitalized alcohol-dependent patients, 98 abstinent alcohol-dependent patients, and 93 healthy blood donors. All participants were genotyped for GIPR rs1800437 and GLP1R rs10305420 and rs6923761 polymorphisms. For the statistical analysis Kruskal-Wall and Mann-Whitney tests were used in additive and dominant genetic models. Our findings indicated that GIPR rs1800437 genotypes were associated with an increased risk of alcohol dependence. Statistically significant association between GIPR rs1800437 GG genotype and Brief Social Phobia Scale scores were observed in the abstinent alcohol-dependent patients, while GLP1R rs6923761 GG genotype was associated with Zung anxiety scores in healthy controls. Our pilot study indicates that GIPR rs1800437 may play some role in susceptibility to alcohol dependence, as well as in alcohol-related psychosymptomatology symptoms. To our knowledge, this is the first study that indicates the involvement of GIPR in alcohol dependence. However, studies with larger cohorts are needed to confirm these preliminary findings.

Precision Nephrology in Patients with Diabetes and Chronic Kidney Disease

Diabetes is the leading cause of kidney failure and specifically, diabetic kidney disease (DKD) occurs in up to 30% of all diabetic patients. Kidney disease attributed to diabetes is a major contributor to the global burden of the disease in terms of clinical and socio-economic impact, not only because of the risk of progression to End-Stage Kidney Disease (ESKD), but also because of the associated increase in cardiovascular (CV) risk. Despite the introduction of novel treatments that allow us to reduce the risk of future outcomes, a striking residual cardiorenal risk has been reported. This risk is explained by both the heterogeneity of DKD and the individual variability in response to nephroprotective treatments. Strategies that have been proposed to improve DKD patient care are to develop novel biomarkers that classify with greater accuracy patients with respect to their future risk (prognostic) and biomarkers that are able to predict the response to nephroprotective treatment (predictive). In this review, we summarize the principal prognostic biomarkers of type 1 and type 2 diabetes and the novel markers that help clinicians to individualize treatments and the basis of the characteristics that predict an optimal response.

Glucagon-like Peptide-1 Receptor Agonists in the Management of Type 2 Diabetes Mellitus and Obesity: The Impact of Pharmacological Properties and Genetic Factors

Glucagon-like peptide-1 (GLP-1) receptor agonists are a new class of antihyperglycemic drugs that enhance appropriate pancreatic β-cell secretion, pancreatic α-cell (glucagon) suppression, decrease liver glucose production, increase satiety through their action on the central nervous system, slow gastric emptying time, and increase insulin action on peripheral tissue. They are effective in the management of type 2 diabetes mellitus and have a favorable effect on weight loss. Their cardiovascular and renal safety has been extensively investigated and confirmed in many clinical trials. Recently, evidence has shown that in addition to the existing approaches for the treatment of obesity, semaglutide in higher doses promotes weight loss and can be used as a drug to treat obesity. However, some T2DM and obese patients do not achieve a desired therapeutic effect of GLP-1 receptor agonists. This could be due to the multifactorial etiologies of T2DM and obesity, but genetic variability in the GLP-1 receptor or signaling pathways also needs to be considered in non-responders to GLP-1 receptor agonists. This review focuses on the pharmacological, clinical, and genetic factors that may influence the response to GLP-1 receptor agonists in the treatment of type 2 diabetes mellitus and obesity.

Effect of GLP-1R rs2254336 and rs3765467 polymorphisms on gastrointestinal adverse reactions in type 2 diabetes patients treated with liraglutide

PURPOSE

Gastrointestinal adverse reactions (GIARs) to liraglutide exhibit significant individual differences in type 2 diabetes. This study investigated the association between glucagon-like peptide-1 receptor (GLP-1R) single-nucleotide polymorphisms (SNPs) and GIARs.

METHODS

Adverse events of liraglutide were observed in 376 T2DM patients. Seven tag SNPs at GLP-1R were sequenced in 152 participants. The influencing factors of GIARs and the genetic model of tag SNPs were examined by logistic regression analysis. The relationship between the tag SNPs and GIARs was determined by the chi-square test and cochran-armitage trend test. Multifactor dimensionality reduction (MDR) analysis was used to explore interactive analysis in GIARs risk.

RESULTS

Twenty-nine percent of subjects had side effects, mainly GIARs. Nausea was the most common GIARs. Compared with males, females were more likely to develop GIARs (P = 0.043, OR = 1.895, 95% CI: 1.021-3.517). The T allele at GLP-1R rs2254336 (P = 0.028) and the A allele at GLP-1R rs3765467 (P = 0.007) were associated with GIARs of liraglutide. As the number of rs2254336 T alleles (P = 0.014) or rs3765467 A alleles (P = 0.008) increased, the subjects tended to develop GIARs. MDR analysis identified that there were no significant interactions among rs2254336, rs3765467 and sex.

CONCLUSION

Our results suggest that female sex, the T allele at GLP-1R rs2254336 and the A allele at GLP-1R rs3765467 could be predictors of GIARs with liraglutide in T2DM patients.

Association of GLP1R variants rs2268641 and rs6923761 with obesity and other metabolic parameters in a Polish cohort

INTRODUCTION

Obesity is a complex disease associated with excessive fat accumulation and numerous metabolic complications. So far, many factors leading to the development of this disorder have been identified, including genetic susceptibility. Various studies linked GLP1R variants with anthropometric and metabolic parameters, suggesting the role of the variation in this gene in metabolic health.

OBJECTIVE

The aim of this study is to investigate the association of two single nucleotide variants of GLP1R gene, rs2268641 and rs6923761, with excessive weight, metabolic syndrome, anthropometric measurements and selected metabolic parameters.

METHODS

Normal-weight subjects (n= 340, control group) and subjects with excessive body mass (n = 600, study group) participated in this study. For all participants, anthropometric measurements and metabolic parameters were collected, and genotyping of the two single nucleotide variants of GLP1R gene, rs2268641 and rs6923761, was performed using the high-resolution melting curve analysis.

RESULTS

Significant differences in the genotype distribution of rs2268641 were found, where homozygous TT genotype was significantly less frequent in the study group with excessive body mass (OR=0.66; p=0.0298). For rs6923761, A allele and homozygous AA genotype were significantly more frequent in the study group with excessive weight than in the control group (OR=1.27; p=0.0239 and OR=1.69; p=0.0205, respectively). The association of studied variants with metabolic parameters was found for rs6923761. For this variant, AA carriers had higher body mass in comparison to GG carriers (p=0.0246), and AA carriers had higher glucose concentration in comparison to AG carriers (p=0.0498). We did not find an association of rs2268641 and rs6923761 with metabolic syndrome.

CONCLUSION

In our study, AA carriers of rs6923761 had higher risk of excessive body mass, whereas TT carriers of rs2268641 had lower risk of being overweight. Moreover, homozygous carriers of the minor allele of rs6923761 had higher glucose concentration in comparison to heterozygous subjects. None of the studied variants were associated with metabolic syndrome in the studied population.

Molecular and in vivo phenotyping of missense variants of the human glucagon receptor

Naturally occurring missense variants of G protein–coupled receptors with loss of function have been linked to metabolic disease in case studies and in animal experiments. The glucagon receptor, one such G protein–coupled receptor, is involved in maintaining blood glucose and amino acid homeostasis; however, loss-of-function mutations of this receptor have not been systematically characterized. Here, we observed fewer glucagon receptor missense variants than expected, as well as lower allele diversity and fewer variants with trait associations as compared with other class B1 receptors. We performed molecular pharmacological phenotyping of 38 missense variants located in the receptor extracellular domain, at the glucagon interface, or with previously suggested clinical implications. These variants were characterized in terms of cAMP accumulation to assess glucagon-induced Gα_s coupling, and of recruitment of β-arrestin-1/2. Fifteen variants were impaired in at least one of these downstream functions, with six variants affected in both cAMP accumulation and β-arrestin-1/2 recruitment. For the eight variants with decreased Gα_s signaling (D63^ECDN, P86^ECDS, V96^ECDE, G125^ECDC, R225^3.30H, R308^5.40W, V368^6.59M, and R378^7.35C) binding experiments revealed preserved glucagon affinity, although with significantly reduced binding capacity. Finally, using the UK Biobank, we found that variants with wildtype-like Gα_s signaling did not associate with metabolic phenotypes, whereas carriers of cAMP accumulation-impairing variants displayed a tendency toward increased risk of obesity and increased body mass and blood pressure. These observations are in line with the essential role of the glucagon system in metabolism and support that Gα_s is the main signaling pathway effecting the physiological roles of the glucagon receptor.

MD, Eckel-Passow J, Acosta A. Precision Medicine for Obesity

Obesity is a multifactorial disease with a variable and underwhelming weight loss response to current treatment approaches. Precision medicine proposes a new paradigm to improve disease classification based on the premise of human heterogeneity, with the ultimate goal of maximizing treatment effectiveness, tolerability, and safety. Recent advances in high-throughput biochemical assays have contributed to the partial characterization of obesity's pathophysiology, as well as to the understanding of the role that intrinsic and environmental factors, and their interaction, play in its development and progression. These data have led to the development of biological markers that either are being or will be incorporated into strategies to develop personalized lines of treatment for obesity. There are currently many ongoing initiatives aimed at this; however, much needs to be resolved before precision obesity medicine becomes common practice. This review aims to provide a perspective on the currently available data of high-throughput technologies to treat obesity.

The Effect of Exenatide Once Weekly on Carotid Atherosclerosis in Individuals With Type 2 Diabetes: An 18-Month Randomized Placebo-Controlled Study

OBJECTIVE

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) improved multiple proatherogenic risk factors and reduced cardiovascular events in recent clinical trials, suggesting that they may slow progression of atherosclerosis. We tested whether exenatide once weekly reduces carotid plaque progression in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a double-blind, pragmatic trial, 163 participants were randomized (2:1) to exenatide (n = 109) or placebo (n = 54). Changes in carotid plaque volume and composition were measured at 9 and 18 months by multicontrast 3 Tesla MRI. Fasting and post-high-fat meal plasma glucose and lipids, and endothelial function responses, were measured at 3, 9, and 18 months.

RESULTS

Exenatide reduced hemoglobin A_1c (HbA_1c) (estimated difference vs. placebo 0.55%, P = 0.0007) and fasting and postmeal plasma glucose (19 mg/dL, P = 0.0002, and 25 mg/dL, P < 0.0001, respectively). Mean (SD) change in plaque volume in the exenatide group (0.3% [2%]) was not different from that in the placebo group (-2.2% [8%]) (P = 0.4). The change in plaque volume in the exenatide group was associated with changes in HbA_1c (r = 0.38, P = 0.0004), body weight, and overall plasma glucose (r = 0.29, P = 0.007 both). There were no differences in changes in plaque composition, body weight, blood pressure, fasting and postmeal plasma triglycerides, and endothelial function between the groups.

CONCLUSIONS

Exenatide once weekly for up to 18 months improved fasting and postprandial glycemic control but did not modify change in carotid plaque volume or composition. This study raises the possibility that short-term antiatherosclerotic effects may not play a central role in the cardiovascular benefits of GLP-1RAs.

Pharmacogenetics of novel glucose-lowering drugs

The aim of this work was to review studies in which genetic variants were assessed with respect to metabolic response to treatment with novel glucose-lowering drugs: dipeptidyl peptidase-4 inhibitors (DPP-4i), glucagon-like peptide-1 receptor agonists (GLP-1 RA) and sodium-glucose cotransporter 2 inhibitors (SGLT2i). In total, 22 studies were retrieved from the literature (MEDLINE). Variants of the GLP-1 receptor gene (GLP1R) were associated with a smaller reduction in HbA1c in response to DPP-4i. Variants of a number of other genes (KCNQ1, KCNJ11, CTRB1/2, PRKD1, CDKAL1, IL6 promoter region, TCF7L2, DPP4, PNPLA3) have also been related to DPP-4i response, although replication studies are lacking. The GLP1R gene was also reported to play a role in the response to GLP-1 RA, with larger weight reductions being reported in carriers of GLP1R variant alleles. There were variants of a few other genes (CNR1, TCF7L2, SORCS1) described to be related to GLP-1 RA. For SGLT2i, studies have focused on genes affecting renal glucose reabsorption (e.g. SLC5A2) but no relationship between SLC5A2 variants and response to empagliflozin has been found. The relevance of the included studies is limited due to small genetic effects, low sample sizes, limited statistical power, inadequate statistics (lack of gene-drug interactions), inadequate accounting for confounders and effects modifiers, and a lack of replication studies. Most studies have been based on candidate genes. Genome-wide association studies, in that respect, may be a more promising approach to providing novel insights. However, the identification of distinct subgroups of type 2 diabetes might also be necessary before pharmacogenetic studies can be successfully used for a stratified prescription of novel glucose-lowering drugs.

Pharmacogenomics of Medication-Induced Weight Gain and Antiobesity Medications

Obesity is a chronic, multifactorial disease associated with a large number of comorbidities. The clinical management of obesity involves a stepwise integrated approach, beginning with behavioral and lifestyle modification, followed by antiobesity medications, endobariatric procedures, and bariatric surgery. Weight gain and subsequent obesity are common side effects of medications, such as prednisone or antipsychotics. In this era of precision medicine, it is essential to identify patients at the highest risk of weight gain as a result of medication use. Pharmacogenomics could play an important role in obesity management by optimizing use of antiobesity medications as well as minimizing adverse weight gain. This review aims to provide a comprehensive analysis of the current literature on the role of pharmacogenomics in obesity and medication-induced weight gain. In summary, there are more robust studies of medication associated with weight gain and pharmacogenomics, and more studies are needed to understand the role of pharmacogenomics in antiobesity medications.

Association of a glucagon-like peptide-1 receptor gene variant with glucose response to a mixed meal

Dipeptidyl peptidase-4 (DPP-4) inhibitors increase endogenous glucagon-like peptide-1 (GLP-1). We hypothesized that genetic variation in the gene encoding the GLP-1 receptor (GLP1R) could affect the metabolic response to DPP-4 inhibition. To evaluate the relationship between the GLP1R rs6923761 variant (G-to-A nucleic acid substitution) and metabolic responses, we performed mixed meal studies in individuals with type 2 diabetes mellitus and hypertension after 7-day treatment with placebo and the DPP-4 inhibitor sitagliptin. This analysis is a substudy of NCT02130687. The genotype frequency was 13:12:7 GG:GA:AA among individuals of European ancestry. Postprandial glucose excursion was significantly decreased in individuals carrying the rs6923761 variant (GA or AA) as compared with GG individuals during both placebo (P = 0.001) and sitagliptin treatment (P = 0.045), while intact GLP-1 levels were similar among the genotype groups. In contrast, sitagliptin lowered postprandial glucose to a greater degree in GG as compared with GA/AA individuals (P = 0.035). The relationship between GLP1R rs6923761 genotype and therapies that modulate GLP-1 signalling merits study in large populations.

A narrative review of current trends in liraglutide: insights into the unmet needs in management of type 2 diabetes and obesity

Liraglutide is a long-acting human glucagon-like peptide-1 (GLP-1) analogue and an effective treatment for patients with metabolic diseases including type 2 diabetes mellitus (T2DM) and obesity. This review focuses on the mechanism of action of liraglutide as a well-known glucagon-like peptide-1 receptor agonist (GLP-1 RA) in patients with T2DM and obesity. The lower and the higher doses of GLP-1 RAs are used for glycaemic control in T2DM and in obesity respectively. GLP-1 RAs such as liraglutide enhance insulin secretion and inhibit glucagon release via the stimulation of glucagon-like peptide-1 receptors (GLP-1Rs). Liraglutide decreases hemoglobin A1c (HbA1c) in type 2 diabetes (T2D) patients when prescribes as monotherapy or in combination with one or more antidiabetic drugs. Usually, it is well tolerated with minor hypoglycemia in combination therapy. Liraglutide reduces cardiovascular events and related risk factors including improvement of lipid profile and control of blood pressure. Accordingly, it can be cost-effective and may be a budget neutral medication option by considering its protective effect on the cardiovascular system in long-term use in the health care plan. In the near future, by pharmacogenomics approach, prediction of the highest patient's response with the lowest adverse drug reactions and also rationality of drug development will be possible. Liraglutide can be used as a desirable medicine for glycemic control and obesity. It shows extensive evidence based benefits in diabetes complications. In this narrative review, we have summarized and evaluated studies related to the role of liraglutide in clinical practice.

Pharmacogenomic Studies of Current Antidiabetic Agents and Potential New Drug Targets for Precision Medicine of Diabetes

Diabetes is a major threat to people's health and has become a burden worldwide. Current drugs for diabetes have limitations, such as different drug responses among individuals, failure to achieve glycemic control, and adverse effects. Exploring more effective therapeutic strategies for patients with diabetes is crucial. Currently pharmacogenomics has provided potential for individualized drug therapy based on genetic and genomic information of patients, and has made precision medicine possible. Responses and adverse effects to antidiabetic drugs are significantly associated with gene polymorphisms in patients. Many new targets for diabetes also have been discovered and developed, and even entered clinical trial phases. This review summarizes pharmacogenomic evidence of some current antidiabetic agents applied in clinical settings, and highlights potential drugs with new targets for diabetes, which represent a more effective treatment in the future.

Pharmacogenetics of Type 2 Diabetes-Progress and Prospects

Type 2 diabetes mellitus (T2D) is a chronic metabolic disease resulting from insulin resistance and progressively reduced insulin secretion, which leads to impaired glucose utilization, dyslipidemia and hyperinsulinemia and progressive pancreatic beta cell dysfunction. The incidence of type 2 diabetes mellitus is increasing worldwide and nowadays T2D already became a global epidemic. The well-known interindividual variability of T2D drug actions such as biguanides, sulfonylureas/meglitinides, DPP-4 inhibitors/GLP1R agonists and SGLT-2 inhibitors may be caused, among other things, by genetic factors. Pharmacogenetic findings may aid in identifying new drug targets and obtaining in-depth knowledge of the causes of disease and its physiological processes, thereby, providing an opportunity to elaborate an algorithm for tailor or precision treatment. The aim of this article is to summarize recent progress and discoveries for T2D pharmacogenetics and to discuss the factors which limit the furthering accumulation of genetic variability knowledge in patient response to therapy that will allow improvement the personalized treatment of T2D.

Association of GLP-1 receptor gene polymorphisms with sporadic Parkinson's disease in Chinese Han population

The Glucagon Like Peptide 1 Receptor (GLP1R) plays a critical role in selective death of dopaminergic neurons and development of Parkinson's disease (PD). However, little is known about genetic associations of GLP1R gene polymorphisms with PD susceptibility. Therefore, this study aimed to verify whether GLP1R polymorphisms contribute to PD risk in a Chinese Han population. We recruited 518 individuals comprising 259 sporadic PD patients and 259 healthy controls. All of the participants were genotyped for two possibly functional polymorphisms located in GLP1R (rs3765467 and rs6923761) using the Sequenom MassARRAY platform. The frequency of the rs3765467 GG genotype was significantly higher in the PD group compared with that in the control group (OR = 1.444, 95 % CI: 1.015-2.055, p =  0.041). Subgroup analysis revealed that male patients and late-onset patients with the rs3765467 GG genotype suffered an increased risk of PD compared with healthy controls (p =  0.021 and p =  0.012, respectively). However, the genotype and allele frequencies for rs6923761 were not significantly different between PD and healthy subjects. Our results indicate that the GLP1R rs3765467 GG genotype is a potential risk factor for PD, especially for male and late-onset PD patients in the Chinese Han population.

Genetic variants associated with glycemic response to treatment with dipeptidylpeptidase 4 inhibitors

Aim: We examined associations of eight SNPs in/near seven candidate genes with glycemic response to 6 month treatment with DPP4 inhibitors. Patients & methods: 206 patients with type 2 diabetes (116 men and 90 women) were treated with sitagliptin or vildagliptin (both 100 mg/day) in combination with metformin or metformin/sulphonylurea over 6 months, and the reduction in glycated hemoglobin (HbA1c) was measured. Results: Rs6923761 in GLP1R was significantly associated with a reduction in HbA1c (adjusted p = 0.006). Homozygotes for the minor A allele had smaller reduction in HbA1c by 0.4% (4 mmol/mol) than the G allele carriers (p = 0.016). Conclusion: The missense variant rs6923761 in the GLP1R gene was associated with a smaller glycemic response to 6 month gliptin therapy in diabetic patients of central European origin.

Clinical and genetic predictors of diabetes drug's response

Diabetes is a major health problem worldwide. Glycemic control is the main goal in the management of type 2 diabetes. While many anti-diabetic drugs and guidelines are available, almost half of diabetic patients do not reach their treatment goal and develop complications. The glucose-lowering response to anti-diabetic drug differs significantly between individuals. Relatively little is known about the factors that might underlie this response. The identification of predictors of response to anti-diabetic drugs is essential for treatment personalization. Unfortunately, the evidence on predictors of drugs response in type 2 diabetes is scarce. Only a few trials were designed for specific groups of patients (e.g. patients with renal impairment or older patients), while subgroup analyses of larger trials are frequently unreported. Physicians need help in picking the drug which provides the maximal benefit, with minimal side effects, in the right dose, for a specific patient, using an omics-based approach besides the phenotypic characteristics.

Weight loss variability with SGLT2 inhibitors and GLP-1 receptor agonists in type 2 diabetes mellitus and obesity: Mechanistic possibilities

We are facing a global epidemic of obesity and type 2 diabetes. Weight loss, in the context of obesity and type 2 diabetes, may improve glycaemic control and weight-related comorbidities, and in some cases, induce diabetes remission. Although lifestyle-based weight loss strategies may be initially successful, most are not effective long-term. There is an increasing need to consider pharmacological approaches to assist weight loss in diabetes-obesity. Older glucose-lowering agents may cause weight gain, whereas the newer drug classes, sodium-glucose co-transporter 2 inhibitors (SGLT2i) and glucagon-like peptide receptor agonists (GLP-1 RAs), concomitantly target weight loss and glycaemic control. Clinical trial data suggest that both SGLT2i and GLP1 RAs cause a mean weight loss of approximately 2 to 3 kg but real-world evidence and clinical experience suggests a significant heterogeneity in the magnitude of the weight loss (GLP-1 RAs) or the magnitude of the actual weight loss is significantly less than anticipated (SGLT2i). Why do some individuals lose more weight than others in response to these pharmacological treatments? This review will first explore mechanisms by which body weight is regulated through control of energy balance and its dysregulation in obesity, and then consider how these mechanisms may be modulated therapeutically with SGLT2i and GLP1 RAs.

Current Progress in Pharmacogenetics of Second-Line Antidiabetic Medications: Towards Precision Medicine for Type 2 Diabetes

Precision medicine is a scientific and medical practice for personalized therapy based on patients’ individual genetic, environmental, and lifestyle characteristics. Pharmacogenetics and pharmacogenomics are also rapidly developing and expanding as a key element of precision medicine, in which the association between individual genetic variabilities and drug disposition and therapeutic responses are investigated. Type 2 diabetes (T2D) is a chronic metabolic disorder characterized by hyperglycemia mainly associated with insulin resistance, with the risk of clinically important cardiovascular, neurological, and renal complications. The latest consensus report from the American Diabetes Association and European Association for the Study of Diabetes (ADA-EASD) on the management of T2D recommends preferential use of glucagon-like peptide-1 (GLP-1) receptor agonists, sodium-glucose cotransporter-2 (SGLT2) inhibitors, and some dipeptidyl peptidase-4 (DPP-4) inhibitors after initial metformin monotherapy for diabetic patients with established atherosclerotic cardiovascular or chronic kidney disease, and with risk of hypoglycemia or body weight-related problems. In this review article, we summarized current progress on pharmacogenetics of newer second-line antidiabetic medications in clinical practices and discussed their therapeutic implications for precision medicine in T2D management. Several biomarkers associated with drug responses have been identified from extensive clinical pharmacogenetic studies, and functional variations in these genes have been shown to significantly affect drug-related glycemic control, adverse reactions, and risk of diabetic complications. More comprehensive pharmacogenetic research in various clinical settings will clarify the therapeutic implications of these genes, which may be useful tools for precision medicine in the treatment and prevention of T2D and its complications.

GLP1R variant is associated with response to exenatide in overweight Chinese Type 2 diabetes patients

AIM

Exenatide is a glucagon-like peptide 1receptor agonist, having both glycemic and weight loss benefits. Given that previous pharmacogenetic studies reported inconsistent evidence of association between variants in the drug target gene GLP1R and response to exenatide, we set out to examine two common coding variants Chinese population. Materials & methods: Here, we recruited 285 overweight Type 2 diabetes patients from China and investigated the association between two common missense variants and response to exenatide, using multivariate linear model with adjustment for baseline and other covariates. Results: The variant allele T of rs10305420 was associated with a 1.27 kg (p = 0.02) less weight loss and a 0.4% (p = 0.002) lower HbA1c reduction after 6 month of exenatide treatment.

CONCLUSION

The consistent large clinical impact of rs10305420 on glycemic response and weight response to exenatide makes the variant a strong candidate biomarker for precision medicine, particularly among overweight patients with Type 2 diabetes.

Pharmacogenetics of type 2 diabetes mellitus, the route toward tailored medicine

Type 2 diabetes mellitus (T2DM) is a chronic disease that has reached the levels of a global epidemic. In order to achieve optimal glucose control, it is often necessary to rely on combination therapy of multiple drugs or insulin because uncontrolled glucose levels result in T2DM progression and enhanced risk of complications and mortality. Several antihyperglycemic agents have been developed over time, and T2DM pharmacotherapy should be prescribed based on suitability for the individual patient's characteristics. Pharmacogenetics is the branch of genetics that investigates how our genome influences individual responses to drugs, therapeutic outcomes, and incidence of adverse effects. In this review, we evaluated the pharmacogenetic evidences currently available in the literature, and we identified the top informative genetic variants associated with response to the most common anti-diabetic drugs: metformin, DPP-4 inhibitors/GLP1R agonists, thiazolidinediones, and sulfonylureas/meglitinides. Overall, we found 40 polymorphisms for each drug class in a total of 71 loci, and we examined the possibility of encouraging genetic screening of these variants/loci in order to critically implement decision-making about the therapeutic approach through precision medicine strategies. It is possible then to anticipate that when the clinical practice will take advantage of the genetic information of the diabetic patients, this will provide a useful resource for the prevention of T2DM progression, enabling the identification of the precise drug that is most likely to be effective and safe for each patient and the reduction of the economic impact on a global scale.

Determinants of body fat distribution in humans may provide insight about obesity-related health risks

Obesity increases the risks of developing cardiovascular and metabolic diseases and degrades quality of life, ultimately increasing the risk of death. However, not all forms of obesity are equally dangerous: some individuals, despite higher percentages of body fat, are at less risk for certain chronic obesity-related complications. Many open questions remain about why this occurs. Data suggest that the physical location of fat and the overall health of fat dramatically influence disease risk; for example, higher concentrations of visceral relative to subcutaneous adipose tissue are associated with greater metabolic risks. As such, understanding the determinants of the location and health of adipose tissue can provide insight about the pathological consequences of obesity and can begin to outline targets for novel therapeutic approaches to combat the obesity epidemic. Although age and sex hormones clearly play roles in fat distribution and location, much remains unknown about gene regulation at the level of adipose tissue or how genetic variants regulate fat distribution. In this review, we discuss what is known about the determinants of body fat distribution, and we highlight the important roles of sex hormones, aging, and genetic variation in the determination of body fat distribution and its contribution to obesity-related comorbidities.

Glucagon-like peptide-1 acutely affects renal blood flow and urinary flow rate in spontaneously hypertensive rats despite significantly reduced renal expression of GLP-1 receptors

Glucagon‐like peptide‐1 (GLP‐1) is an incretin hormone increasing postprandial insulin release. GLP‐1 also induces diuresis and natriuresis in humans and rodents. The GLP‐1 receptor is extensively expressed in the renal vascular tree in normotensive rats where acute GLP‐1 treatment leads to increased mean arterial pressure (MAP) and increased renal blood flow (RBF). In hypertensive animal models, GLP‐1 has been reported both to increase and decrease MAP. The aim of this study was to examine expression of renal GLP‐1 receptors in spontaneously hypertensive rats (SHR) and to assess the effect of acute intrarenal infusion of GLP‐1. We hypothesized that GLP‐1 would increase diuresis and natriuresis and reduce MAP in SHR. Immunohistochemical staining and in situ hybridization for the GLP‐1 receptor were used to localize GLP‐1 receptors in the kidney. Sevoflurane‐anesthetized normotensive Sprague–Dawley rats and SHR received a 20 min intrarenal infusion of GLP‐1 and changes in MAP, RBF, heart rate, dieresis, and natriuresis were measured. The vasodilatory effect of GLP‐1 was assessed in isolated interlobar arteries from normo‐ and hypertensive rats. We found no expression of GLP‐1 receptors in the kidney from SHR. However, acute intrarenal infusion of GLP‐1 increased MAP, RBF, dieresis, and natriuresis without affecting heart rate in both rat strains. These results suggest that the acute renal effects of GLP‐1 in SHR are caused either by extrarenal GLP‐1 receptors activating other mechanisms (e.g., insulin) to induce the renal changes observed or possibly by an alternative renal GLP‐1 receptor.

Allelic variant in the glucagon-like peptide 1 receptor gene associated with greater effect of liraglutide and exenatide on gastric emptying: A pilot pharmacogenetics study

BACKGROUND

Weight loss in response to the long-acting GLP-1 receptor (GLP1R) analog, liraglutide, is correlated with delay in gastric-emptying (GE). The aim of this pilot study was to assess whether specific genetic variants in GLP1R or TCF7L2 are associated with delayed GE and weight loss in obese patients treated with liraglutide or the short-acting GLP-1 agonist, exenatide.

METHODS

We evaluated in obese individuals the associations of genetic variations of GLP1R (rs6923761) and TCF7L2 (rs7903146) on GE T1/2 and weight from two trials that evaluated separately exenatide, 5 μg BID for 30 days, or liraglutide, 3 mg daily for 5 weeks. Data were analyzed using the dominant genetic model and intention-to-treat analysis.

KEY RESULTS

There was a significant correlation between changes in weight and GE T1/2 (rs  = -.382, P = .004). GLP1R rs6923761 minor allele A (AA_AG) carriers who received either exenatide or liraglutide had greater delay in GE T1/2 relative to baseline (117.9 ± 27.5 [SEM] minutes and 128.9 ± 38.32 minutes) compared to GG genotype (95.8 ± 30.4 minutes and 61.4 ± 21.4 minutes, respectively; P = .11). There was a non-significant difference in weight loss based on GLP1R rs6923761 genotype after 5 weeks of treatment. There were no significant correlations with TCF7L2 (rs7903146) genotype.

CONCLUSIONS & INFERENCES

The minor A allele of GLP1R (rs6923761) is associated with greater delay in GE T1/2 in response to liraglutide and exenatide. These studies provide data to plan pharmacogenetics testing of the hypothesis that GLP1R (rs6923761) influences weight loss in response to GLP1R agonists.

rs6923761 gene variant in glucagon-like peptide 1 receptor: Allelic frequencies and influence on cardiovascular risk factors in a multicenter study of Castilla-Leon

BACKGROUND

Some GLP-1 receptor studies have identified polymorphisms in the GLP-1 receptor gene that might be related to different cardiovascular risk factors.

OBJECTIVE

Our aim was to investigate the allelic distribution of rs6923761 GLP-1 receptor polymorphism in a geographic area of Spain (Community of Castilla y Leon) and to evaluate the influence of this polymorphism on obesity anthropometric parameters and cardiovascular risk factors in the fasted state in obese patients.

DESIGN

A sample of 341 obese subjects (body mass index ≥ 30 kg/m²) was analyzed. Fasting blood glucose, C-reactive protein (CRP), plasma insulin, insulin resistance (HOMA-IR), and lipid profile were determined. Anthropometric parameters, dietary intake and blood pressure were recorded.

RESULTS

One hundred and forty three patients (42.0%) had the genotype GG (wild-type group) and one hundred and ninety eight (58.0%) patients were A carriers: GA (164 patients, 48.1%) or AA (34 patients, 9.9%) (mutant-type group). Valladolid and Segovia health areas had the lowest percentage of wild type genotype and G allelic (than other Health Areas). Burgos Health Area had a higher percentage of wild-type genotype. In wild-type group (GG genotype), BMI (0.9 ± 1.3 kg/m²; p < 0.05), weight (3.3 ± 1.1 kg; p < 0.05), fat mass (2.5 ± 1.1 kg; p < 0.05), waist to hip ratio (0.02 ± 0.005 cm; p < 0.05), waist circumference (2.8 ± 1.1 cm; p < 0.05), triglycerides (14.4 ± 3.3 mg/dl; p < 0.05) insulin (3.1 ± 1.0 mg/dl; p < 0.05) and HOMA-IR (1.2 ± 0.9 mg/dl; p < 0.05) were higher than A allele carriers. In non A allele carriers, lower HDL cholesterol levels than A allele carriers (6.4 ± 2.3 mg/dl; p < 0.05) were found.

CONCLUSION

Data from our study revealed different allelic distribution in this geographic area, with better parameters (Body mass index, weight, fat mass, waist circumference, triglycerides, insulin, HOMA-IR and HDL cholesterol) in A allele carriers than in non A allele carriers.

A missense variant in GLP1R gene is associated with the glycaemic response to treatment with gliptins

Gliptins act by increasing endogenous incretin levels. Glucagon-like peptide-1 receptor (GLP1R) and glucose-dependent insulinotropic peptide receptor (GIPR) are their indirect drug targets. Variants of GLP1R and GIPR have previously been associated with the incretin effect. The aim of the present pilot study was to examine associations of the GLP1R and GIPR gene variants with the glycaemic response to gliptins. A total of 140 consecutive patients with type 2 diabetes were followed-up 6 months after initiation of gliptin treatment. GLP1R rs6923761 (Gly168Ser) and GIPR rs10423928 genotyping was performed using real-time PCR, with subsequent high-resolution melting analysis. The main study outcome was reduction in glycated haemoglobin (HbA1c) after treatment. GLP1R Gly168Ser variant was significantly associated with reduction in HbA1c in an additive model (β = -0.33, p = 0.011). The mean reduction in HbA1c in Ser/Ser homozygotes was significantly lower compared with Gly-allele carriers [0.12 ± 0.23% vs. 0.80 ± 0.09% (1.3 ± 2.5 mmol/mol vs. 8.7 ± 1.0 mmol/mol); p = 0.008]. In conclusion, GLP1R missense variant was associated with a reduced response to gliptin treatment. The genotype-related effect size of ∼0.7% (8 mmol/mol) is equal to an average effect of gliptin treatment and makes this variant a candidate for use in precision medicine.

Pharmacogenetic aspects of the treatment of Type 2 diabetes with the incretin effect enhancers

Incretin effect enhancers are drugs used in the treatment of Type 2 diabetes and include GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors (gliptins). Variants in several genes were shown to be involved in the physiology of incretin secretion. Only two gene variants have evidence also from pharmacogenetic studies. TCF7L2 rs7903146 C>T and CTRB1/2 rs7202877 T>G minor allele carriers were both associated with a smaller reduction in HbA1c after gliptin treatment when compared with major allele carriers. After replication in further studies, these observations could be of clinical significance in helping to identify patients with potentially lower or higher response to gliptin treatment.