CARNITINE PREVENTS CARB-INDUCED WEIGHT GAIN
Previous studies have found L-carnitine to increase anabolic pathways—such as IGF-1, p-AKT, and mTOR muscle- building pathways—and inhibit the anti-catabolic pathways atrogin, MuRF, and FoxO. Carnitine is a naturally occurring amino acid, which plays a vital role in the metabolism of fat. Carnitine acts as a transporter of fatty acids into the mitochondria, the metabolic furnace of the cell. Researchers from the University of Nottingham in the U.K. investigated the effects and the influence of L-carnitine and carbohydrate feeding on energy metabolism, body fat mass, and muscle expression of fuel metabolism genes. The researchers had 12 males exercise at 50% VO2 max for 30 min once before and once after 12 weeks of twice daily feeding of 80 g carbohydrate or 1.36g L-carnitine + 80g carbohydrate (Vitargo). At the end of the study, the group consuming the carbs twice a day gained weight and fat mass while the carnitine group did not experience weight gain. The “fatty acid shuttle” better known as CPT1 remained similar in both groups over the course of the 12-week study period, however, genes for fat metabolism were up-regulated. The group consuming carnitine had 73 out of 187 genes relating to fuel metabolism to be unregulated. Upon examination of gene analysis, the carnitine group’s upregulated genes were responsible for insulin signaling, PPAR signaling and fatty acid metabolism. The group consuming carnitine increased muscle carnitine stores by 20%, increased the activity of long- chain acyl-CoA, an enzyme that is crucially involved in the mitochondrial oxidation of long-chain fatty acids by +200% and increased whole body energy expenditure by 6%. In conclusion, increasing muscle carnitine in healthy humans can modulate muscle metabolism, energy expenditure, and body composition over a prolonged period.