Effects of l-carnitine supplementation on glucolipid metabolism: a systematic review and meta-analysis

Abstract

Background: L-carnitine supplementation has been utilized against glucolipid metabolism disruption. However, to the best of our knowledge, no meta-analysis process has analyzed the effects of L-carnitine supplementation on insulin resistance, fasting blood glucose, lipid metabolism, and liver enzyme levels in adults. Methods: Through the analysis and screening of 12 221 studies, 15 studies were selected from eligible trials for meta-analysis. Meta-analysis was performed in a random effect model with heterogeneity determined by I², and subgroup analyses were used to further identify the source of heterogeneity. Result: The results showed significant effects of L-carnitine on FBG (MD = −4.94 mg dL⁻¹, 95% CI: −7.07 to −2.82), insulin (MD = −0.99 μU mL⁻¹, 95% CI: −1.41 to −0.56), HOMA-IR (MD = −0.58, 95% CI: −0.77 to −0.38), TG (MD = −11.22 mg dL⁻¹, 95% CI: −19.21 to −3.22), TC (MD = −6.45 mg dL⁻¹, 95% CI: −9.95 to −2.95, LDLc (MD = −8.28 mg dL⁻¹, 95% CI: −11.08 to −5.47), and ALT (MD = −19.71 IU L⁻¹, 95% CI: −36.45 to −2.96). However, no significant effect of L-carnitine supplementation was observed in HDLc (MD = −0.77 mg dL⁻¹, 95% CI: −0.10 to −1.63) or AST (MD = −11.05 IU L⁻¹, 95% CI: −23.08 to 0.99). The duration of carnitine supplementation was negatively associated with mean differences in FBG, as assessed by meta-regression. Conclusion: The current meta-analysis revealed that L-carnitine may have favorable effects on glucolipid profile, especially insulin, FBG, HOMA-IR, TG, TC, LDLc, and ALT levels.