Background: Glucagon-like peptide-1 (GLP-1) receptor agonists are a new class of hypoglycemic drugs, including exenatide, liraglutide, albiglutide, lixisenatide, and taspoglutide. Insulin glargine is a standard agent used to supplement basal insulin in type 2 diabetes mellitus (T2DM).
Objective: The aim of this study was to review the efficacy and safety profiles of GLP-1 receptor agonists versus insulin glargine in type 2 diabetic patients who have not achieved treatment goals with oral hypoglycemic agents.
Methods: The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and the database of ongoing trials were searched from inception through April 2010. Additional data were sought from relevant Web sites, the American Diabetes Association, reference lists of included trials and related (systematic) reviews, and industry. Randomized controlled trials (RCTs) were selected if they were ≥3 months in duration, compared GLP-1 receptor agonists with insulin glargine in patients with T2DM, and included ≥1 of the following outcomes: mortality, complications of T2DM, glycemie control, weight, lipids, blood pressure, adverse effects, and health-related quality of life. Quasirandomized controlled trials were excluded. The quality of the eligible studies was assessed on the basis of the following aspects: randomization procedure, allocation concealment, blinding, incomplete outcome data (intent-to-treat [ITT] analysis), selective outcome reporting, and publication bias.
Results: A total of 410 citations were retrieved; 5 multicenter RCTs that met the inclusion criteria were identified. They were all open-label designs with an insulin glargine arm, predefined outcomes reported, and ITT analysis. One trial had an unclear randomization procedure and allocation concealment. Publication bias was not able to be determined. No data wete found with regard to mortality or diabetes-associated complications, and few data were found on quality of life. The results of the metaanalysis suggest that insulin glargine was significantly better in reducing the fasting blood glucose (mean difference [MD] [95% CI], 1.31 [1.04 to 1.58]; P < 0.001), but exhibits greater incidence of nocturnal hypoglycemia (risk ratio [RR] [95% CI], 0.40 [0.23 to 0.71]; P = 0.002) and influenza (RR [95% CI], 0.56 [0.32 to 0.98]; P = 0.04). GLP-1 receptor agonists are more conducive to reducing weight (MD [95% CI], -3.96 [-5.14 to -2.77]; P < 0.001), postprandial blood glucose (after breakfast, P < 0.001; after dinner, P < 0.001), and LDL-C (MD [95% CI], -0.18 [-0.28 to -0.08]; P < 0.001), but have significantly more gastrointestinal adverse effects (eg, nausea/ vomiting, P < 0.001). There were no significant differences between GLP-1 receptor agonists and insulin glargine in reducing glycosylated hemoglobin (HbA1c) levels (MD [95% CI], -0.03 [-0.13 to 0.08]) and the overall incidence of hypoglycemia (RR [95% CI], 0.69 [0.42 to 1.14]).
Conclusions: Compared with insulin glargine, GLP-1 receptor agonists did not have a significant difference in regard to reducing HbA1c levels and they were significantly associated with decreased weight but increased gastrointestinal adverse events. It remains unclear whether GLP-1 receptor agonists influence mortality or diabetes-associated complications in patients with T2DM. More trials with longer follow-up are needed to determine the exact long-term efficacy and safety profiles of this new class of hypoglycemic drugs.
Keywords: GLP-1; diabetes mellitus; glucagon-like peptide-1; insulin detemir; insulin glargine; meta-analysis; type 2 diabetes.