The glycemic, cholesterol, and weight effects of L-carnitine in diabetes: A systematic review and meta-analysis of randomized controlled trials

Introduction: L-carnitine possibly impacts insulin sensitivity and glucose metabolism. However, its therapeutic role in diabetes is poorly understood. Methods: A systematic review and meta-analysis were conducted using PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) from inception through June 30, 2021. Included studies evaluated the use of L-carnitine in diabetes on fasting blood glucose (FBG), hemoglobin A1c (HbA1c), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), weight, or body mass index (BMI). Weighted mean difference (WMD) and 95% confidence intervals (CI) were calculated using the DerSimonian and Laird random-effects model. Results: Seventeen studies involving 1622 patients were included. Reductions in FBG (WMD = -0.46 mmol/L, 95% CI = -0.68 to -0.23 mmol/L), HbA1c (WMD = -0.5%, 95% CI = -0.8 to -0.1%), TC (WMD = -0.29 mmol/L, 95% CI = -0.42 to -0.16 mmol/L), and LDL-C (WMD = -0.23 mmol/L, 95% CI = -0.39 to -0.07 mmol/L) were significant. Effects on HDL-C, TG, weight, or BMI were insignificant. Doses between 1001 to 2000 mg showed greatest benefit (p < 0.02 for all). Discussion/Conclusion: L-carnitine plays a potential role as adjunctive therapy in diabetes. Additional research is necessary for patients with higher baseline HbA1c and type 1 diabetes.