Metabolic Effects of L-carnitine on Type 2 Diabetes Mellitus: Systematic Review and Meta-analysis

Introduction: Carnitine is an endogenous metabolite and exogenous nutrient with a pivotal role in lipid metabolism. Plasma levels of carnitine are reduced in type 2 Diabetes Mellitus (T2DM). The aim was to evaluate the metabolic effects of the administration of L-carnitine in T2DM. Method: A systematic review was performed. Relevant randomized, controlled-trials trials were searched in Pubmed, Trip Database and Cochrane Library, and selected when they had enough methodological quality assessed with the Jadad scale. Article search strategy included Carnitine OR L-carnitine AND Diabetes Mellitus OR Diabetes mellitus, type 2 OR Noninsulindependent-diabetes mellitus. Meta-analysis was performed, and the difference of means calculated with a 95 % confidence interval. Heterogeneity was evaluated with the Q statistic. Results: The systematic review included 4 trials with 284 patients. Oral L-carnitine lowered fasting plasma glucose [-14.3 mg/dl (CI95% -23.2 to -5.4); p = 0,002], total cholesterol [-7.8 mg/dL (95%CI -15.5 to -0.1); p = 0.09], low density lipoprotein [-8.8 mg/dl (CI95% -12.2 to -8.5), p < 0.0001], apolipoprotein-B100 [-7.6 mg/dl (CI95% -13.6 to -1.6); p = 0.013] and apolipoprotein-A1 [-6.0 mg/dl (CI95% -10.5 a -1.5); p = 0.523]. There was no significant heterogeneity. The changes in triglycerides, lipoprotein (a) or HbA(1c) were not significant. Conclusion: The administration of L-carnitine in type 2 diabetes mellitus is associated with an improvement in glycaemia and plasma lipids.