Mechanism for the increased skeletal muscle protein degradation in the obese Zucker rat.

Obese (fa/fa) Zucker rats showed a decreased protein content in skeletal muscle compared with their lean counterparts. This was associated with both a decrease in the fractional rate of protein synthesis and an enhanced fractional rate of protein degradation in skeletal muscle, as studied by pre-loading body proteins with (14)C-bicarbonate. The increased protein degradation could be the result of the clearly enhanced expression for several transcripts of the ubiquitin genes in skeletal muscle. The results suggest that the increased protein degradation in the skeletal muscle of the obese animals may be due to increased activity of the ubiquitin-dependent proteolytic system.