Age-dependent alterations in mitochondrial enzymes in cortex, striatum and hippocampus of rat brain: potential role of L-Carnitine

Mitochondria link the energy -- releasing activities of electron transport and proton pumping with the energy conserving process of oxidative phosphorylation to form ATP. A declined mitochondrial performance has been generally observed during aging. In the present investigation, the activities of tricarboxylic acid cycle enzymes such as isocitrate, alpha-ketoglutarate, succinate and malate dehydrogenases and electron transport complexes I-IV were measured in mitochondria isolated from brain regions like cortex, striatum and hippocampus of young and aged rats before and after L-Carnitine supplementation. All the three brain regions of aged rats showed decreased activities of isocitrate, alpha-ketoglutarate and succinate dehydrogenases, complexes I and IV when compared to control young rats. Striatum seems to be the most susceptible region when compared to hippocampus and cortex. L-Carnitine supplementation to aged rats reversed the activities of these enzymes to near normal whereas treatment to young rats did not show any significant alterations. These results confirm that L-Carnitine can alleviate the age-associated decline in the metabolic efficiency of mitochondria in all three brain regions under investigation.