Acetyl-L-Carnitine: The Memory Amino
Acetyl-L-carnitine (ALC) occurs naturally in the body.
Carnitines (amino acids) produced in the body exist as a "carnitine pool"
consisting of L-carnitine and several acetyl-carnitine esters. Intracellular
enzymes and cell membrane transporters can rapidly interconvert the carnitines
to the needed form and transport them between the tissues and extracellular
space. ALC, the most important carnitine ester, is converted to L-carnitine.[1] [2]
The distribution of inside the cell was found to be 60% as free l-carnitine,
which was to be expected, and 40% as ALC, which underscores the importance of
this unique substance in the body.[3]
Role with
Acetylcholine & Memory
ALC is structurally related to acetylcholine. It also serves
as a precursor to acetyl coenzyme A (a component of energy metabolism) and contributes
acetyl groups to acetylcholine.1 In doing so, it seems to promote
acetylcholine release[4],
which is considered to be the "memory neurotransmitter". This is consistent
with other ALC related memory research.
ALC supplementation has been shown to improve some measures
of cognitive function and memory in elderly people with age-related mental
impairment.[5] [6] [7]
Futhermore, ALC slowed the rate of disease progression, improved memory, and
improved some measures of cognitive function and behavioral performance in some
patients with Alzheimer's disease.[8]
[9]
[10]
[11]
In addition, ALC supplementation improved memory and visuospatial capacity in
30-60 year-old chronic alcoholics with cognitive impairment.[12]
Perhaps one reason
why ALC is so effective for memory is a function of the blood-brain barrier.
The blood-brain barrier is a selectively permeable protective membrane that
controls whether substances in the blood can pass through into the brain
tissue. ALC is able to cross the blood-brain barrier more effectively than
L-carnitine, which makes it especially appropriate for promoting brain
function.[13]
Promotes Fatty Acid Metabolism
Carnitines play an important role in lipid metabolism and
energy production. They are essential for normal mitochondrial function, acting
as a transporter of long-chain fatty acids into the mitochondria for where they
are burned as an energy fuel (i.e. beta-oxidation).[14] [15] [16] [17]
Decrease Age-Related Testosterone Deficiency
ALC supplementation for 6 months, in combination with
propionyl-L-carnitine, improved symptoms of androgen decline in older men
sexual dysfunction, depression, and fatigue.[18]
Improve Diabetic Neuropathy
Patients with diabetic neuropathy had improved symptoms
after taking 1500-3000 mg ALC daily in divided doses for a year.
Acetyl-L-carnitine seems to increase nerve fibers, regenerate nerve fiber
clusters, and improve vibratory sensations.[19] [20] [21] [22]
Increase Sperm Motility
Supplementing with ALC and L-carnitine for 6 months increased
sperm motility in men with infertility.[23]
References
[1] Pettegrew JW, Levine J, McClure RJ.
Acetyl-L-carnitine physical-chemical, metabolic, and therapeutic properties:
relevance for its mode of action in Alzheimer's disease and geriatric
depression. Mol Psychiatry 2000;5:616-32.
[2] Rebouche CJ. Kinetics, pharmacokinetics, and
regulation of L-carnitine and acetyl-L-carnitine metabolism. Ann N Y Acad Sci
2004;1033:30-41.
[3] Frenkel, R., et al (eds). Carnitine Biosynthesis, Metabolism, and Functions (1980) New York: Academic Press; 1980:73-89.
[4] Mayeux R, Sano M. Treatment of Alzheimer's Disease. N
Engl J Med 1999;341:1670-9.
[5] Cucinotta D, Passeri M, Ventura S, et al. Multicenter clinical placebo-controlled study with
acetyl-L-carnitine (ALC) in the treatment of mildly demented elderly patients
Drug Development Res 1988;14:213-6.
[6] Salvioli G, Neri M. L-acetylcarnitine treatment of
mental decline in the elderly. Drugs Exp Clin Res 1994;20:169-76.
[7] Passeri M, Cucinotta D, Bonati PA, et al.
Acetyl-L-carnitine in the treatment of mildly demented elderly patients. Int J
Clin Pharmacol Res 1990;10:75-9.
[8] Pettegrew JW, Klunk WE, Panchalingam K, et al.
Clinical and neurochemical effects of acetyl-L-carnitine in Alzheimer's
disease. Neurobiol Aging 1995;16:1-4.
[9] Rai G, Wright G, Scott L, et al. Double-blind,
placebo controlled study of acetyl-l-carnitine in patients with Alzheimer's
dementia. Curr Med Res Opin 1990;11:638-47.
[10] SanoM, Bell K, Cote L, et al. Double-blind parallel
design pilot study of acetyl levocarnitine in patients with Alzheimer's
disease. Arch Neurol 1992;49:1137-41.
[11] Bonavita E. Study of the efficacy and tolerability of
L-acetylcarnitine therapy in the senile brain. Int J Clin Pharmacol Ther
Toxicol 1986;24:511-6.
[12] Tempesta E, Troncon R, Janiri L, et al. Role of
acetyl-L-carnitine in the treatment of cognitive deficit in chronic alcoholism.
Int J Clin Pharmacol Res 1990;10:101-7.
[13] Tweed V. Basic Health Publications User's Guide to
Carnitine and Acetyl-L-Carnitine. Laguna Beach, CA: Basic Health Publications; 2006.
[14] Hart AM, Wilson AD, Montovani C, et al. Acetyl-l-carnitine: a
pathogenesis based treatment for HIV-associated antiretroviral toxic
neuropathy. AIDS 2004;18:1549-60.
[15] Stanley CA. Carnitine deficiency disorders in
children. Ann N Y Acad Sci 2004;1033:42-51.
[16] Evans AM, Fornasini G. Pharmacokinetics of
L-carnitine. Clin Pharmacokinet 2003;42:941-67.
[17] Sima AAF, Calvani M, Mehra M, et al.
Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception
in patients with chronic diabetic neuropathy: An analysis of two randomized,
placebo-controlled trials. Diabetes Care 2005;28:89-94.
[18] Cavallini G, Caracciolo S, Vitali G, et al. Carnitine
versus androgen administration in the treatment of sexual dysfunction,
depressed mood, and fatigue associated with male aging. Urology 2004;63:641-6.
[19] Sima AAF, Calvani M, Mehra M, et al.
Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception
in patients with chronic diabetic neuropathy: An analysis of two randomized,
placebo-controlled trials. Diabetes Care 2005;28:89-94.
[20] Onofrj M, Fulgente T, Melchionda D, et al.
L-acetylcarnitine as a new therapeutic approach for peripheral neuropathies
with pain. Int J Clin Pharmacol Res 1995;15:9-15.
[21] De Grandis D, Minardi C. Acetyl-L-carnitine
(levacecarnine) in the treatment of diabetic neuropathy. A long-term,
randomised, double-blind, placebo-controlled study. Drugs R D 2002;3:223-31.
[22] Quatraro A, Roca P, Donzella C, et al.
Acetyl-L-carnitine for symptomatic diabetic neuropathy. Diabetologia
1995;38:123.
[23] Lenzi A, Sgro P, Salacone P, et al. A
placebo-controlled double-blind randomized trial of the use of combined
l-carnitine and l-acetyl-carnitine treatment in men with asthenozoospermia.
Fertil Steril 2004;81:1578-84.