Regulation of fatty acid biosynthesis in rats by physical training

Physical training in the form of long-term nonexhaustive daily exercise was studied as a means of regulating fatty acid biosynthesis. Male rats were required to swim for periods up to 90 min/day. The exercise was carried out 6 days/wk for approximately 11 wk. Hepatic fatty acid biosynthesis and acetyl-CoA carboxylase [acetyl-CoA: CO2 ligase (EC 6.4.1.2)] activities were compared with nonexercised rats. At the end of the training period the exercised rats had a lower rate of fatty acid biosynthesis activity and a lower rate of acetyl-CoA carboxylase activity. The difference in acetyl-CoA carboxylase activity was due to a change in maximal velocity with no significant change in the Michaelis constant for acetyl-CoA. Untrained rats were subjected to a single bout of exercise. They also exhibited lower rates of fatty acid biosynthesis and acetyl-CoA carboxylase activities compared with nonexercised rats. However, the lower rates of these enzyme activities were sustained longer in the physically trained rats compared with the exercised untrained rats after the cessation of exercise. These results implicate acetyl-CoA carboxylase as a control site in the regulation of hepatic fatty acid biosynthesis by both physical training and acute exercise in rats. Possible inhibitory mechanisms are discussed.