Differential carnitine/acylcarnitine translocase expression defines distinct metabolic signatures in skeletal muscle cells.
Import of acylcarnitine into mitochondrial matrix through carnitine/acylcarnitine-translocase (CACT) is fundamental for lipid catabolism. To probe the effect of CACT down-expression on lipid metabolism in muscle, human myocytes were stably transfected with CACT-antisense construct. In presence of low concentration of palmitate, transfected cells showed decreased palmitate oxidation and acetyl-carnitine content, increased palmitoyl-carnitine level, and reduced insulin-dependent decrease of fatty acylcarnitine-to-fatty acyl-CoA ratio. The augmented palmitoyl-carnitine synthesis, also in the presence of insulin, could be related to an altered regulation of carnitine-palmitoyl-transferase 1 (CPT 1) by malonyl-CoA, whose synthesis is dependent by the availability of cytosolic acetyl-groups. Indeed, all the described effects were completely overcome by CACT neo-expression by recombinant adenovirus vector or by addition of acetyl-carnitine to cultures. Acetyl-carnitine effect was related to an increase of malonyl-CoA and was abolished by down-expression, via antisense RNA strategy, of acetyl-CoA carboxylase-beta, the mitochondrial membrane enzyme involved in the direct CPT 1 inhibition via malonyl-CoA synthesis. Thus, in our experimental model the modulation of CACT expression has consequences for CPT 1 activity, while the biologic effects of acetyl-carnitine are not associated with a generic supply of energy compounds but to the anaplerotic property of the molecule.
Peluso
Gianfranco
G
National Cancer Institute-INT Fondazione G. Pascale, via Mariano Semmola, 80131 Naples, Italy. g.peluso@ibp.cnr.it
Petillo
Orsolina
O
Margarucci
Sabrina
S
Grippo
Pasquale
P
Melone
Mariarosa Anna Beatrice
MA
Tuccillo
Franca
F
Calvani
Menotti
M
D000103:Acetyl-CoA Carboxylase / Q000235:genetics / Q000378:metabolism; D000108:Acetylcarnitine / Q000378:metabolism / Q000494:pharmacology; D000214:Acyl Coenzyme A / Q000378:metabolism; D016375:Antisense Elements (Genetics); D002331:Carnitine / Q000378:metabolism*; D002333:Carnitine Acyltransferases / Q000235:genetics / Q000378:metabolism*; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000378:metabolism; D050356:Lipid Metabolism; D008316:Malonyl Coenzyme A / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology*; D010168:Palmitates / Q000378:metabolism; D016372:RNA, Antisense
D000214:Acyl Coenzyme A; D016375:Antisense Elements (Genetics); D007328:Insulin; D010168:Palmitates; D016372:RNA, Antisense; D008316:Malonyl Coenzyme A; D000108:Acetylcarnitine; D002333:Carnitine Acyltransferases; D002334:Carnitine O-Palmitoyltransferase; D000103:Acetyl-CoA Carboxylase; D002331:Carnitine