Résumé :
|
In mammals, age causes structural and functional changes in the skeletal muscle. In human, muscle changes start during the fourth decade of life and cause progressive disabilities. Besides these changes, associated alterations in body composition favor the onset of many metabolic disorders, such as type 2 diabetes and hypertension. Decrease in the synthesis rate of mitochondrial proteins occurs with age, and is likely to be caused by a reduction in mitochondrial biogenesis and ATP production. Aging is also characterized by an alteration in the hormonal and the nutritional status. During this study, we determined oxidative and metabolic changes occurring in muscle during aging and evaluated the effect of a nutritional supplementation of L-carnitine on these parameters. We observed a decrease in muscle L-carnitine level during aging; a decrease in oxidative capacities in lipolytic muscle was also observed. On the other hand, an increase in markers of the oxidative stress was found. All together these changes lead to a decrease in muscle activity and an increase in fat deposit. We evaluated the effect of a L-carnitine supplementation on several parameters related to muscle physiology and oxidative stress. We described that supplementing old rats with 30 mg/kg b.w. L-carnitine during 12 weeks (i) allowed to restore L-carnitine level in muscle cell, (ii) restored muscle oxidative activity in the soleus, a lipolytic muscle, (iii) induced positive changes in body composition: a decrease in abdominal fat mass and an increase in muscle capabilities without any change in food intake (iv) reduced several parameters linked to the oxidative stress and (v) increased the global antioxidant activity of the plasma. These data suggested that L-carnitine supplementation in old animals may limit the oxidative stress, increase muscle capacities, be beneficial for body composition and could attenuate the progressive decline in some mitochondrial functions that occurs with age.
|