4-bromocrotonic-acid and 2-bromopalmitate

Two inhibitors of fatty acid oxidation, 2-bromopalmitic acid (Br-C16) and 4-bromocrotonic acid (Br-C4) were examined for their effect on lipolysis in 3T3-L1 adipocytes. Both agents inhibited in a dose-dependent manner the rate of oxidation of exogenously added [1-14C]palmitate with similar time-courses, reaching a plateau at 3-9 h. While Br-C16 at 50 microM and 100 microM inhibited palmitate oxidation by approximately 40% and 60%, respectively, pretreatment with both concentrations inhibited lipolysis in washed cells in an almost identical manner. The magnitude of inhibition increased with time of pretreatment. On the other hand, like inhibition of fatty acid oxidation, inhibition of lipolysis by Br-C4 pretreatment was dose-dependent with maximal inhibition reached after 3 h pretreatment. The finding that isoproterenol- and dibutyryl cAMP-stimulated lipolysis were similarly suppressed by either Br-C4 or Br-C16 pretreatment, suggesting that a step distal to cAMP formation was involved. In addition, while the inhibitory effect of Br-C16 was not significantly influenced, the inhibition of lipolysis caused by Br-C4 was attenuated by pretreating cells with crotonic acid, octanoate, or palmitate. The longer chain-length of the fatty acids the cells were exposed, the stronger attenuation of the inhibition caused by Br-C4 was observed. Moreover, whereas pretreatment with Br-C16 was without effect, pretreatment with Br-C4 significantly decreased hormone-sensitive lipase (HSL) activity in cell extracts, albeit to an extent much smaller than its inhibitory effect on lipolysis. In conclusion, these results indicate that irreversible inhibition of lipolysis by Br-C16 or Br-C4 cannot be attributed to their effect on fatty acid oxidation. Some factor capable of modulating HSL activity seems to be involved.

Topics: 3T3 Cells; Adipocytes; Animals; Bucladesine; Crotonates; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fatty Acids; Isoproterenol; Lipolysis; Mice; Palmitates; Sterol Esterase

The effects of 4-bromocrotonic acid, 2-bromopalmitic acid, 3-mercaptopropionic acid, 4-pentenoic acid, and 2-tetradecylglycidic acid on the oxidations of palmitate, octanoate, and pyruvate in adult rat myocytes were studied. Since all of these compounds inhibit the oxidation of palmitate but not of pyruvate, they are specific inhibitors of fatty acid oxidation. Fifty percent inhibition of palmitate oxidation was obtained when myocytes were preincubated for 10 min with one of the following: 0.1 microM 2-tetradecylglycidic acid, 60 microM 4-bromocrotonic acid, 60 microM 2-bromopalmitic acid, 100 microM 3-mercaptoproprionic acid, or 100 microM 4-pentenoic acid. Removal of the inhibitors from the medium after preincubation relieved the inhibition caused by 3-mercaptopropionic acid but did not reverse the effects of the other inhibitors. This study leads to the conclusion that 2-tetradecylglycidic acid is the compound of choice for inhibiting the mitochondrial uptake of fatty acids and thereby their oxidation, whereas 4-bromocrotonic acid is the best irreversible inhibitor of the mitochondrial beta-oxidation cycle.

Topics: 3-Mercaptopropionic Acid; Animals; Cells, Cultured; Crotonates; Epoxy Compounds; Fatty Acids; Fatty Acids, Monounsaturated; Myocardium; Oxidation-Reduction; Palmitates; Rats