Written by Marcia J. Egles, MD. L-carnitine supplementation in old rats showed improved muscle function on par with young rats.
It has been said that aging is inevitable, if you just live long enough, that is. At best, its progression may be slowed. Moderate physical exercise has long been identified as a factor favorably influencing aging. L-carnitine may also offer some benefit, as shown by a recent study of young and old rats.
L-carnitine is a molecule that is involved with energy production within cells, especially within highly active cells such as muscle cells. The L-carnitine found in the body can come from food, especially meat (animal muscle) products (1), or the body can make it from other substances. Blood levels of L-carnitine tend to diminish in humans after about the age of seventy, in parallel to declines in muscle mass (2). In mammals, some of the changes of aging include a shrinking of skeletal muscles fibers with a decrease in their performance, and a relative increase in body fat.
As reported in this recent study, supplementation with L-carnitine improved some age-associated declines in rats. Rats at four months old were compared to elderly twenty-four month old rats. The young rats were split into two groups. One young group received L-carnitine at a dose of 30 milligrams per kilogram body weight supplemented through their drinking water. The other young rat group received plain drinking water.
The old rats were divided into four groups. As with the young rats, one group received L-carnitine in water, and a second group only water. A third group of the old rats received no carnitine, but were given extra exercise. A fourth group of old rats received the extra exercise plus the L-carnitine supplement. Running a treadmill for twenty minutes per day three times a week was the extra exercise.
Significant among the findings were the restorative effects of L-carnitine in the elderly rats. Among the young rats, L-carnitine supplementation demonstrated no changes compared to the control group. Compared to the young rats, the unsupplemented rats in the elderly group had concentrations of L-carnitine 34 per cent lower ( p value less than 0.05) in their leg muscles. However, the L-carnitine supplemented old rats were found to have L-carnitine levels in their muscles which equaled the levels found in the young rats. The old rat group which received exercise plus L-carnitine was also found to have similar youthful-like carnitine levels in their muscles. The exercise-only group of old rats showed diminished L-carnitine levels similar to the unsupplemented group of old rats. Moreover, in several biochemical measures of muscle function, the old L-carnitine supplemented rats showed improvements in muscle function on par with the young rats.
All the rats in the experiment had free access to food. This, as expected, produced weight gains in the rats by the end of the twelve weeks. However, the L-carnitine treated rats showed no weight increases. The experimenters considered this lack of weight gain with L-carnitine to be a significant benefit as it might be applicable to elderly humans.
Although not as experimentally controlled as this rat study, several human studies also suggest a benefit of L-carnitine supplementation to elderly persons ( 3,4,5).
Source: Bernard, Arnaud, et al. “L-carnitine supplementation and physical exercise restore age-associated decline in some mitochondrial functions in the rat.” The Journals of Gerontology: Series A 63.10 (2008): 1027-1033.
Copyright 2008 by The Gerontological Society of America
Posted December 5, 2008.
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- Malaguarnera M, Cammalleri L, Gargante MP, Vacante M, Colonna V, Motta M. L-Carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centenarians: a randomized and controlled clinical trial. Am J Clin Nutr. 2007;86:1738-1744.
- Mingrone G, Greco AV, Capristo E, et al. L-carnitine improves glucose disposal in type 2 diabetic patients. J Am Coll Nutr. 1999;18:77-82.
- Pistone G, Marino A, Leotta C, Dell’arte S, Finocchiaro G, Malaguarnera M. Levocarnitine administration in elderly subjects with rapid muscle fatigue. Drugs Aging 2003;20:761–7.
