Developmental changes in lipogenic enzymes in muscle compared to liver and extramuscular adipose tissues in the...

The developmental changes in the activities of acetyl-CoA-carboxylase, malic enzyme and glucose-6-phosphate dehydrogenase were compared in longissimus muscle, liver and adipose tissues in growing rabbits. Activities of lipogenic enzymes were low in muscle, as compared to the other tissues studied. The lipogenic activities in longissimus muscle increased with age. This increase was well correlated with the age-related increase in intramuscular lipid content, suggesting that intramuscular adipose tissue results from in situ lipid synthesis. During growth, each tissue displayed a specific developmental pattern for lipogenic enzyme activities. In liver and adipose tissues, the three lipogenic enzyme activities first increased and subsequently decreased, during the postweaning period. In the muscle, no such decrease was observed, suggesting that intramuscular adipose tissue develops later than the other tissues tested. Throughout postnatal period, the ratio of malic enzyme to glucose-6-phosphate dehydrogenase was reversed in muscle compared to other fat sites (5 vs 0.04). Further studies are necessary to determine the role of malic enzyme in rabbit intramuscular lipid metabolism.