MECHANISMS OF DECREASED LIPOPROTEIN-LIPASE ACTIVITY IN ADIPOCYTES OF STARVED RATS DEPEND ON DURATION OF STARVATION

The aim of this study was to delineate the mechanisms by which varying periods of starvation decrease lipoprotein lipase (LPL) activity in r at adipose tissue. LPL mRNA levels and rates of LPL synthesis, degrada tion and secretion were compared in adipocytes from male rats that had been fed or starved for 1 or 3 d. The decreased LPL activity after 3 d of starvation (-76%) was explained mainly by a 50% decrease in the r elative abundance of LPL mRNA levels (P < 0.05) and a parallel 50% dec rease in relative rates of LPL biosynthesis (P < 0.05). In contrast, s tarvation for 1 d decreased total LPL activity by 47% (P < 0.05) but d id not affect LPL mRNA levels or relative rates of LPL biosynthesis. P ulse-chase studies demonstrated that 1 d of starvation increased the r ate of degradation of newly synthesized LPL (P < 0.05) and markedly de creased its secretion into the medium (P < 0.05), A decrease in overal l protein synthesis also contributed to the decreased LPL activity aft er 1 and 3 d of starvation. We conclude that the relative importance o f pre-and post-translational mechanisms in regulating adipose tissue L PL activity depends on the duration of starvation. During short-term s tarvation, degradation of newly synthesized LPL is an important determ inant to its secretion from the adipocyte and hence its functional act ivity at the capillary endothelium.