Glucagon-like peptide-1 (GLP-1) receptor agonists and cardiovascular events in patients with type 2 diabetes mellitus: A meta-analysis of double-blind, randomized, placebo-controlled clinical trials

DOI: https://doi.org/10.21203/rs.2.16671/v3

Abstract

Background: The cardiovascular effects of glucagon-like peptide-1 (GLP-1) receptor agonists are still controversial in the treatment of type 2 diabetes mellitus (T2DM) patients. The purpose of this study was to evaluate the risk of cardiovascular events of GLP-1 (albiglutide, exenatide, liraglutide, semaglutide, lixisenatide and dulaglutide) receptor agonists in T2DM patients.

Methods: PubMed and Embase were searched to find relevant randomized controlled trials (RCTs) from inception to June 2019 that evaluated the effect of GLP-1 receptor agonists on cardiovascular events in patients with T2DM. The T2DM patients of all the eligible trials received either GLP-1 therapy or placebo, and the cardiovascular outcomes included death from cardiovascular causes, fatal or non-fatal myocardial infarction and fatal or non-fatal stroke.

Results: We included 6 multinational double-blind randomized placebo-control trials that included a total of 52821 T2DM patients. The results indicated that GLP-1 receptor agonists reduced the risk of death from cardiovascular causes (RR: 0.90; 95% CI: 0.83–0.97; P = 0.004) and fatal or non-fatal stroke (RR: 0.85; 95% CI: 0.77–0.94; P = 0.001) compared with the placebo controls. But GLP-1 receptor agonists did not significantly alter the fatal or non-fatal myocardial infarction compared with the placebo (RR: 0.91; 95% CI: 0.82 – 1.01; P = 0.06).

Conclusion: We concluded that GLP-1 receptor agonist therapy could reduce the risk of death from cardiovascular causes and fatal or non-fatal stroke compared with the placebo in the treatment of T2DM patients in trials with cardiovascular outcomes.

Background

Type 2 diabetes mellitus patients have a very high risk of cardiovascular events, including death from cardiovascular causes, fatal or non-fatal myocardial infarction and fatal or non-fatal stroke [1]. The rates of cardiovascular death are 2- to 4-fold higher for patients with diabetes compared with the rates for those without diabetes [2]. GLP-1 receptor agonists, which as the glucose-lowering therapeutic agents in the treatment of type 2 diabetes mellitus, have been shown to affect the incidence of cardiovascular outcomes in patients with type 2 diabetes mellitus, although the results regarding GLP-1 receptor agonists remain inconsistent [3–4]. It is well known that GLP-1, as a peptide hormone, stimulates insulin secretion and inhibits glucagon secretion in a glucose-dependent manner [5]. An increasing number of studies have shown that glucagon-like peptide-1 (GLP-1) may improve endothelial functioning and may have direct effects in protecting the vascular system [6]. There are several GLP-1 receptor agonists that are used as therapeutic agents for treating type 2 diabetes mellitus patients in clinical fields. Recently, the GLP-1 receptor was believed to have an effect on individual cardiovascular outcomes in the treatment of diabetes, but not all GLP-1 receptor agonists showed the effect of reducing cardiovascular outcomes because of the varied effectiveness of the different GLP-1 drugs. Just like some multinational randomized controlled trials elaborated that the use of GLP-1 receptor agonists to reduce the rate of cardiovascular events in T2DM patients [7-10]. While other clinical studies concluded that the GLP-1 receptor agonists did not significantly alter the major cardiovascular outcomes in patients with type 2 diabetes [3,4]. Moreover several meta-analysis had concentrated on the cardiovascular effects and the safety in GLP-1-treated T2DM patients [11,12], but the conclusion were inconsistent.

Therefore, we performed a meta-analysis of double-blind randomized placebo-controlled clinical trials to investigate the cardiovascular complications of GLP-1 receptor agonists in T2DM patients. The cardiovascular outcomes included death from cardiovascular causes, fatal or non-fatal myocardial infarction and fatal or non-fatal stroke.

Methods

Data sources and search strategy

We comprehensively searched PubMed and Embase to find relevant randomized controlled trials (RCTs) from inception to June 2019 that evaluated the effect of GLP-1 receptor agonists on cardiovascular events in patients with T2DM. This meta-analysis was conducted and reported in accordance with the 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analysis Statements [13]. We adhere to the PRISMA guidelines in this meta-analysis [13]. The language was confined to English. The search terms were as follows: “incretin” OR “GLP-1” OR “glucagon-like peptide-1 analogue” OR “Liraglutide” OR “exenatide” OR “liraglutide” OR “lixisenatide” OR “albiglutide” OR “dulaglutide” OR “semaglutide” OR “taspoglutide” AND “type 2 diabetes mellitus” OR “T2DM” AND “randomized controlled trials” OR “RCT”. We also comprehensively screened the references of reviews and articles in order to find more eligible articles.

Data selection criteria

The literature search was screened independently by two authors; if there were some inconsistencies, we discussed within the group until a consensus was reached. The research titles and abstracts were initially screened, and then we screened the study design, interventions, control, and outcomes in detail to determine the included trials.

The criteria for including eligible studies were as follows: (1) the studies were double-blind, randomized placebo-controlled trials; (2) the RCTs were evaluating GLP-1 versus placebo in T2DM patients; (3) there was a comparison of cardiovascular risk between GLP-1 receptor agonists and placebo in T2DM patients with or without cardiovascular diseases; and (4) a risk ratio (RR) with corresponding 95% confidence intervals (CIs) or data was reported.

Regarding the exclusion criteria, we excluded studies with the following criteria: (1) the case and control patients; (2) studies with irrelevant data and the small sample size trials which contain less than 3000 T2DM patients; and (3) duplicate publications, animal experimental studies, reviews, conference abstracts, or meta-analyses.

Data extraction and quality assessment

The following data were extracted from the included RCTs by two authors independently: first author’s name; publication year, country, sample size, study design, intervention, glycated haemoglobin, duration of diabetes and the follow-up periods. The quality of the included studies was assessed by the Cochrane Collaboration tool for the risk of bias [14]. Each studies was identified as “low,” “high” or “unclear” risk of bias based on the following items: the statement of randomization, blinding, details of withdrawals and dropouts, generation of random numbers, and concealment of allocation. The quality of each results was assessed according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system which classifies the quality of evidence as high, moderate, low or very low [15].

Data synthesis and statistical analysis

This meta-analysis was performed using Review Manager 5.3 software (RevMan), The Cochrane Collaboration, Copenhagen. For the cardiovascular events in our study, we calculated the risk ratio (RR) with 95% confidence intervals (CIs) to standardize the differences between the GLP-1 receptor agonist and placebo. The forest plots were conducted using a fixed-effect model if there was no obvious heterogeneity or using a random-effect model when heterogeneity of the included studies was obvious [16-17]. Additionally, the chi-squared (χ2) test and the I2 test were used to assess the heterogeneity between studies. When P ≤ 0.10 and I2 > 50%, the heterogeneity between those included studies was defined as obvious heterogeneity [18]. Moreover, if the I2 test value was 25–50%, it was defined as mild heterogeneity, 50–75% as moderate heterogeneity, and 75% as severe heterogeneity. To measure publication bias, we performed a funnel plot and Egger’s tests. A funnel plot was used to qualitatively measure the publication bias [19,20], and P ≤ 0.05 was considered significant publication bias in this meta-analysis.

Results

We obtained 1930 articles after searching PubMed and Embase from 2011 to June 2019. Then, we screened the titles and abstracts and removed the duplicate articles, reviews and conference abstracts, and 11 articles remained for evaluating the details of the full text to determine whether they met the inclusion criteria. Finally, 6 trials were included in this meta-analysis (Fig. 1) [3,4,7,8,9,10]. The Cochrane Collaboration tool was applied to evaluate the quality of the included trials. The results regarding the individual quality of the included trials are shown in Fig. 2.3.4.

The selected studies were published between 2015 and 2019. The GLP-1 receptor agonist arms included 26386 patients, and the placebo control arms included 26435 patients. The main characteristics of the included trials are presented in Table 1. The control treatment in the included trials was placebo according to the experimental trial treatment. The cardiovascular outcomes included death from cardiovascular causes, fatal or non-fatal myocardial infarction and fatal or non-fatal stroke.

There was no obvious heterogeneity in the six included studies (I2 = 0%, Cochran Q test P = 0.66) (Fig. 2) regarding the risk of death from cardiovascular causes. Therefore, we used the fixed effect model in the RevMan software. GLP-1 receptor agonists reduced the risk of death from cardiovascular causes compared with the placebo (RR: 0.90; 95% CI: 0.83 – 0.97; P = 0.004) according to the results of the meta-analysis.

There was mild heterogeneity (I2 = 49%, Cochran Q test P = 0.08) (Fig. 3) regarding the risk of fatal or non-fatal myocardial infarction in the included studies. Therefore, we used the random effect model in the RevMan software. No significant effect of GLP-1 receptor agonists identified on the risk of fatal or non-fatal myocardial infarction compared with the placebo controls (RR: 0.91; 95% CI: 0.82 – 1.01; P = 0.06).

There was also no evidence of heterogeneity observed across the included trials regarding fatal or non-fatal stroke (I2 = 4%, Cochran Q test P = 0.39) (see Fig. 4). The fixed effect model was applied in the RevMan software. The results of the meta-analysis indicated that GLP-1 receptor agonists reduced the risk of fatal or non-fatal stroke compared with the placebo (RR: 0.85; 95% CI: 0.77 – 0.94; P = 0.001).

Because only six trials were included, which is less than ten, we have no evidence of publication bias in this meta-analysis by the funnel plot. No individual study had a significant effect on the pooled effect size according to the results of the sensitivity analysis at all end points.

Discussion

The objective of this meta-analysis was to explore the effect of GLP-1 receptor agonists on cardiovascular outcomes in type 2 diabetes mellitus patients. The results of this meta-analysis suggest that GLP-1 therapy has a significant impact on the incidence of death from cardiovascular causes and fatal or non-fatal stroke in T2DM patients. There was no heterogeneity in these six included studies in their assessment of the effect of GLP-1 receptor agonists on the risk of death from cardiovascular causes and fatal or non-fatal stroke; however, there was mild heterogeneity regarding the risk of fatal or non-fatal myocardial infarction in the included studies, and the reasons may be the specific medicine molecule and GLP-1 receptor agonist dose tested, differences in the randomized patients (such as medical history and baseline characteristics), duration of follow-up years and adherence to treatment. As our findings are based on good-quality studies that were all multinational double-blind randomized placebo-control trials and our meta-analysis was based on a mean follow-up of 3.45 years (minimum 1.5 year – maximum 5.4 years), the confounding and attrition bias are controlled, so the risk of unreliable results is diminished.

Similar to our results, some studies [21,22] also indicated that GLP-1 receptor agonists had a positive effect on the heart and enhanced cardiac function. While some previous studies [23] found a lower incidence of cardiovascular disease (CVD) events when GLP-1 receptor agonists were compared with placebo. Furthermore, a comparison meta-analysis [24-26] indicated that there was no significant reduction in CVD events by GLP-1 receptor agonists. Similarly, Inzucchi et al [27] believed that the evidence of GLP-1 receptor agonist cardiovascular protection was still limited, and the cardiovascular system benefits related to GLP-1 receptor agonists may be independent of its glucose, lipid, or energy metabolism effects. In order to better define the cardiovascular effects of GLP-1 receptor agonist in type 2 diabetes, we perform this meta-analysis. The trials included in the meta-analysis are the EXSCEL study (exenatide), LEADER study (liraglutide), SUSTAIN 6 study (semaglutide) and HARMONY outcomes study (albiglutide), ELIXA study (lixisenatide) and REWIND study (dulaglutide). Not all GLP-1 receptor agonist may have the same effect on cardiovascular events, since the classification of Glucagon-like peptide-1 (GLP-1) receptor agonists included the short acting and long acting. But there were no hand-to-hand cardiovascular outcomes studies focused on GLP-1 receptor agonist class, limiting the investigation of cardiovascular events differences between GLP-1 receptor agonists of different mechanical structure or drug potency.

GLP-1 receptor agonists have had cardiovascular protection effects in cardiovascular trials, the cardiovascular protection mechanisms of GLP-1 RAs contain direct and indirect effects which have been well discussed in preclinical and clinical studies [28]. The cardiovascular indirect effects of GLP-1 receptor agonists might be mediated via improve the common cardiovascular metabolic risk factors such as HbA1c, systolic blood pressure, and body weight, anti-inflammatory pathways, ischaemic conditioning and endothelial function [12,28,29,30]. In addition, the direct effects of GLP-1 RAs to the cardiovascular system included enhancing the endothelial function, cardiac output, and myocardial glucose uptake, since the abundant GLP-1 receptor expressed in cardiac and vascular tissues [28,30].

This meta-analysis has several strengths: (1) Only RCTs were included, so this meta-analysis eliminated the potential control group biases; (2) The large sample size of the 6 included trials allowed us to quantitatively evaluate the GLP-1 receptor agonist effects in T2DM patients; (3) A wide range of patient characteristics was represented, which ensured a comprehensive assessment of the effect of GLP-1 receptor agonists in the treatment of patients with T2DM.

This study has some limitations. First, the publication bias is an inevitable problem in any meta-analysis. Second, T2DM patients who received various GLP-1 receptor agonist drugs, such as albiglutide, exenatide, liraglutide, semaglutide, lixisenatide and dulaglutide might have biased the meta-analysis results. Third, a more detailed analysis was restricted because the meta-analysis used pooled data.

Conclusion

The findings of this study indicated that GLP-1 receptor agonist therapy reduced the incidence of death from cardiovascular causes and fatal or non-fatal stroke in the treatment of T2DM patients. We need additional large RCTs in the future to evaluate the treatment effects of GLP-1 receptor agonists in T2DM.

Declarations

Ethics approval and consent to participate: “Not applicable”

Consent for publication: “Not applicable”

Availability of data and materials: The datasets generated or analyzed during the current study available from the corresponding author on reasonable request.

Competing interests: All authors declare that there are no conflict of interests or special relationships with industry in this meta-analysis.

Funding: “No funding”

Authors' contributions: LS is the corresponding author of this study. She designed this study, collected and analyzed data, wrote the manuscript and made the decision to submit and publish the manuscript. JQ is the first author for the meta-analysis, including collected and analyzed data, and wrote the manuscript.

Acknowledgements: "Not applicable”

Abbreviations

GLP-1 RAs Glucagon-like peptide 1 receptor agonists

T2DM type 2 diabetes mellitus

RCTs randomized controlled trials

GRADE Grading of Recommendations, Assessment, Development, and Evaluation

CVD cardiovascular diseases

RR risk ratio

CIs confidence intervals

HbA1c glycosylated hemoglobin

References

[1] Rawshani A, Rawshani A, Franzén S, et al. Mortality and cardiovascular disease in type 1 and type 2 diabetes.N Engl J Med 2017; 376: 1407–18.

[2] S.J. Haffner, H. Cassells, Hyperglycemia as a cardiovascular risk factor, Am. J. Me. 1013115 (Suppl. 8A) (2003) 6S–11S.

[3] Pfeffer MA, Claggett B, Diaz R, et al. Lixisenatide in patients with type 2 diabetes and acute coronary syndrome. N Engl J Med 2015; 373: 2247–57.

[4] Holman RR, Bethel MA, Mentz RJ, et al. Effects of once-weekly exenatide on cardiovascular outcomes in type 2 diabetes. N Engl J Med 2017; 377: 1228–39.
[5] Ussher JR, Drucker DJ. Cardiovascular biology of the incretin system. Endocrine Rev 2012; 33:187–215.

[6] A.J. Motta, J. Koska, P. Reaven, R.Q. Migrino, Vascular protective effects of diabetes

medications that mimic or increase glucagon-like peptide-1 activity, Recent Pat. Cardiovasc. Drug Discov. 7 (2012) 2–9.

[7] Marso SP, Daniels GH, Brown-Frandsen K, Kristensen P, Mann JF, Nauck MA, et al. Liraglutide and cardiovascular outcomes in type 2 diabetes. N Engl J Med. 2016; 375:311–22.

 [8] Marso SP, Bain SC, Consoli A, Eliaschewitz FG, Jodar E, Leiter LA, et al. Semaglutide and cardiovascular outcomes in patients with type 2 diabetes. N Engl J Med. 2016;(19):1834–44.

[9] Gerstein HC, Colhoun HM, Dagenais GR, Diaz R, Lakshmanan M, Pais P, Probstfield J, Riesmeyer JS, et al. Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND): a double-blind, randomised placebo-controlled trial. Lancet. 2019 Jul 13;394(10193):121-130.

[10] Hernandez AF, Green JB, Janmohamed S, D'Agostino RB Sr, Granger CB, Jones NP, et al. Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial. Lancet. 2018 Oct 27;392(10157):1519-1529.

[11] M. Monami, I. Dicembrini, C. Nardini, I. Fiordelli, E. Mannucci, Effects of glucagon-like peptide-1 receptor agonists on cardiovascular risk: a meta-analysis of randomized clinical trials, Diabetes Obes. Metab. 16 (2014) 38–47.

[12] Bethel MA, Patel RA, Merrill P, Lokhnygina Y, Buse JB, Mentz RJ, Pagidipati NJ, Chan JC, Gustavson SM, Iqbal N, Maggioni AP, Ohman P, Poulter NR, Ramachandran A, Zinman B, Hernandez AF, Holman RR EXSCEL Study Group. Cardiovascular outcomes with glucagon-like peptide-1 receptor agonists in patients with type 2 diabetes: a meta-analysis. Lancet Diabetes Endocrinol. 2018; 6:105–113.

[13] D. Moher, A. Liberati, J. Tetzlaff, D.G. Altman, PRISMA Group, Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement, PLoS Med. 6 (2009), e1000097.

[14] Higgins, J. P. et al. The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. BMJ 343, d5928 (2011).

[15] Guyatt, G. H. et al. Incorporating considerations of resources use into grading recommendations. BMJ 336, 1170–1173, https://doi.org/10.1136/bmj.39504.506319.80 (2008).

[16] Ades AE, Lu G, Higgins JP. The interpretation of random-effects meta-analysis in decision models. Med Decis Making 2005;25(6):646–54.

[17] DerSimonian R, Laird N. Meta-analysis in clinical trials revisited. Contemp Clin Trials 2015;45(Pt A):139–45.

[18] Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ 2003;327(7414):557–60.

[19] Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ 1997;315(7109):629–34 [PubMed].

[20] Begg CB, Mazumdar M. Operating characteristics of a rank correlation test for publication bias. Biometrics 1994;50(4):1088–101 [PubMed].

[21] A.K. Bose, M.M. Mocanu, R.D. Carr, C.L. Brand, D.M. Yellon, Glucagon-like peptide 1 can directly protect the heart against ischemia/reperfusion injury, Diabetes 54 (2005) 146–151.

[22] T. Zhao, P. Parikh, S. Bhashyam, et al., Direct effects of glucagon-like peptide-1 on myocardial contractility and glucose uptake in normal and postischemic isolated rat hearts, J. Pharmacol. Exp. Ther. 317 (2006) 1106–1113.

 [23] F. Sun, K. Yu, S. Wu, et al., Cardiovascular safety and glycemic control of glucagon- like peptide-1 receptor agonists for type 2 diabetes mellitus: a pairwise and network meta-analysis, Diabetes Res. Clin. Pract. 98 (2012) 386–395.

[24] M. Monami, F. Cremasco, C. Lamanna, et al., Glucagon-like peptide-1 receptor agonists and cardiovascular events: a meta-analysis of randomized clinical trials,Exp. Diabetes Res. 2011 (2011) 215764.

[25] R.Ratner,J.Han,D.Nicewarner,I.Yushmanova,B.J.Hoogwerf,L.Shen,Cardiovascu- lar safety of exenatide BID: an integrated analysis from controlled clinical trials in participants with type 2 diabetes, Cardiovasc. Diabetol. 10 (2011) 22.

[26] S.P. Marso, J.B. Lindsey, J.M. Stolker, et al., Cardiovascular safety of liraglutide assessed in a patient-level pooled analysis of phase 2:3 liraglutide clinical development studies, Diab. Vasc. Dis. Res. 8 (2011) 237–240.

[27] S.E. Inzucchi, D.K. McGuire, New drugs for the treatment of diabetes: part II: Incretin-based therapy and beyond, Circulation 117 (2008) 574–584.

[28] Nauck MA, Meier JJ, Cavender MA, Abd El Aziz M, Drucker DJ. Cardiovascular actions and clinical outcomes with glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors. Circulation. 2017;136: 849–870.

 [29] Alvarez-Villalobos NA, Trevino-Alvarez AM, Gonzalez-Gonzalez JG. Liraglutide and cardiovascular outcomes in type 2 diabetes. N Engl J Med. 2016; 375:1797–1798.

[30] Kang YM, Jung CH. Cardiovascular effects of glucagon-like peptide-1 receptor agonists. Endocrinol Metab (Seoul) 2016; 31:258–274.

Tables

   

Table 1. The characteristics of included trials

 

 

Study

Country of publication

Country of patients

Experimental Sample size

Control Sample Size

Age

Duration of diabetes

Intensive

Therapy

Control therapy

Follow-up

Adrian F Hernandez 2018

USA

Western Europe

Eastern and central Europe

North America

Latin America 

Asia Pacific 

4731

4732

64.2/

64.2

4.1/

4.2

Albiglutide

(30-50mg)  once a week

Placebo once a week

1.5 years

Rury R. Holman 2017

United Kingdom

Europe
Latin America
 Europen subcategories

Asia-pacific

Eastern Europe

Western Europe North America

7356

7396

<65y 

8813

≥65y

5939

12.0

(7.0-18.0)

 exenatide at a dose of 2 mg once weekly

Placebo once a week

2.3 years

Steven P2016

USA

North AmericaEurope Asia

Rest of the world 

4668

4672

<60y 2321

 

≥60y       

7019

12.8 years

liraglutide 1.8 mg (or the maximum tolerated dose) once daily 

placebo once daily 

3.8 years

Steven P. Marso2016 

United Kingdom 

 230 sites in 20 countries.

1648

1649

64.6±

7.4

13.9±

8.1 

semaglutide (0.5mg    or

1.0mg) once a week

Placebo once a week

109 weeks

Preffer MA 2015

Thailand

49 countrirs

3034

3034

60.3

9.3

lixisenatide

placebo

2.1 years

Gerstein HC 2019

UK

371 sites

24 countries

4949

4952

66.2

10.5/

9.5

dulaglutide 1.5mg

placebo

5.4 years