The effect of l -carnitine supplementation on serum leptin concentrations: a systematic review and meta-analysis of randomized controlled trials

Abstract

Purpose

The actual effects of l-carnitine administration on leptin serum level is inconsistent. In order to assess the efficacy of l-carnitine supplementation on serum leptin we conducted a meta-analysis of randomized controlled trials (RCTs).

Methods

Seven studies with 325 cases and 330 controls were included. The pooled weighted mean difference (WMD) was calculated by random-effects model. The heterogeneity across studies was evaluated by using Cochrane's Q and I² tests. In addition, we carried out the metaninf command to test the effect of each individual study on the overall result.

Results

l-carnitine supplementation seemed to have no significant effect on serum leptin concentrations (WMD: −0.565 ng/mL; 95% CI: −2.417 to 1.287, p = 0.550). However, between-study heterogeneity was higher across all studies (I² = 84.3%, p < 0.0001). Subgroup analysis to find the sources of heterogeneity showed that l-carnitine dosage (g) ( < 2 g: I² = 00.0%, p = 0.408), and study population (diabetes: I² = 46.7%, p = 0.153, and non-diabetes: I² = 15.1%, p = 0.317) were the potential sources of heterogeneity. Besides, a more significant reduction in serum leptin concentration was observed with a daily dose of ≥ 2 mg l-carnitine (WMD: −2.742 ng/mL; 95% CI: −3.039 to −2.444, p < 0.001), in diabetic patients (WMD: −2.946 ng/mL; 95% CI: −3.254 to −2.638, p < 0.001), and with intervention duration <12 weeks (WMD: −2.772 ng/mL; 95% CI: −3.073 to −2.471, p < 0.001).

Conclusion

l-carnitine consumption does not reduce serum leptin significantly. However, a significant effect on leptin was observed in diabetic patients and patients who received doses more than 3 mg per day in the course of <12 weeks.

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