Acetylcarnitine

Acetyl- L -carnitine or ALCAR, is an acetylated form of L -carnitine. It is naturally produced by the body, although it is often taken as a dietary supplement. Acetylcarnitine is broken down in the blood by plasma esterases to carnitine which is used by the body to transport fatty acids into the mitochondria for breakdown.

Biochemical production and action
ALCAR is an acetylated derivative of L -carnitine. During strenuous exercise, a large portion of L -carnitine and unused acetyl-CoA are converted to ALCAR and CoA inside mitochondria by carnitine O-acetyltransferase. The ALCAR is transported outside the mitochondria where it converts back to the two constituents. The L -carnitine is cycled back into the mitochondria with acyl groups to facilitate fatty acid utilization, but excess acetyl-CoA may block it. Excess acetyl-CoA causes more carbohydrates to be used for energy at the expense of fatty acids. This occurs by different mechanisms inside and outside the mitochondria. ALCAR transport decreases acetyl-CoA inside the mitochondria, but increases it outside. Glucose metabolism in diabetics improves with administration of either ALCAR or L -carnitine. ALCAR decreases glucose consumption in favor of fat oxidation in non-diabetics. A portion of L -carnitine is converted to ALCAR after ingestion in humans.

Absorption compared to L -carnitine
It has been claimed ALCAR is superior to L -carnitine in terms of bioavailability. Both use the same mechanism for intestinal absorption that improves with sodium. One study shows ALCAR has a lower blood concentration in humans after ingestion possibly because ALCAR is hydrolyzed more in blood.

Health effects
ALCAR has the ability to cross the blood–brain barrier and enter the brain, where it acts as an antioxidant. Its supplementation has been shown to be neuroprotective in instances of cerebral ischaemia in rats and may be useful in treating peripheral nerve injury as well as spinal cord injury. It has been shown to be of benefit to Alzheimer's patients. It may have some neuroprotective benefit in the treatment of Parkinson's disease, but further research is required. ALCAR is also known to increase sperm motility, which describes the ability of sperm to move vigorously. Since motility is among the most important factors that help in the determination of sperm’s fertilization capability, acetyl- L -carnitine can help sperm cells move more actively, which consequently leads to the improved male fertility.

ALCAR has been shown to be more effective than tamoxifen in improving the curvature and reducing the pain and plaque sizes for men who sought treatment for their Peyronie's disease early and having low curvature deformities. ALCAR has also been shown to improve insulin response. It may induce epigenetic changes that may, in turn, give it utility as a therapeutic agent in neuropathic pain and depression. These findings are in line with recent studies in humans that have demonstrated the efficacy of acetylcarnitine in the treatment of these conditions.

In animal models of alcohol abuse, ALCAR has been shown to inhibit gastric mucosal injury, neuronal injury and general oxidative stress, and has been proposed as a method of protecting from both negative short term and negative long-term effects of alcohol.

Other reviews

 * Carnitine (L-carnitine), University of Maryland Medical Center
 * Carnitine (L-carnitine), University of Maryland Medical Center

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