Lipoprotein Lipase of Sheep and Rat Adipose Tissues

Abstract

Lipoprotein lipase preparations were obtained by aqueous extraction of various tissues from sheep and rats. Preparations having high activity towards serum-activated triolein emulsions were obtained from actively growing sheep, provided that the tissue was maintained at 37�C throughout the extraction procedure. Activity of lipoprotein lipase from sheep adipose tissue, like that from the rat, was dependent upon the presence of serum in the reaction mixture, and was optimal at pH 8-9. Inhibition of sheep adipose tissue preparations by protamine sulfate (1 mg/ml) and O' 6 M NaCl was similar to that found for rat adipose tissue preparations. The affinity of the lipoprotein lipase preparation for the activated substrate from sheep and rat adipose tissue was, however, markedly different; sheep preparations being activated at much lower substrate concentrations (Km O' 43 mM) than rat preparations (Km > 5 mM). These findings, confirmed with acetone--ether preparations of lipoprotein lipase, indicate that the enzyme from sheep adipose tissue has a greater potential to remove triacylglycerol from the plasma. This could result in a greater deposition of fat in the tissue.

Nutritional status induces divergent variations of GLUT4 protein content, but not lipoprotein lipase activity, between adipose tissues and muscles in adult cattle

“…Our present results on LPL activity (especially in perirenal AT and CM) are in agreement with previous studies (Chilliard et al 1979;DiMarco et al 1981;Tume et al 1983;Bonnet et al 1998Bonnet et al , 2000Faulconnier et al 2001) reporting that ruminant animal AT-LPL activity is down-regulated by underfeeding and up-regulated by refeeding. They also confirm that nutritional status regulates muscle LPL in the same direction as AT-LPL activity, as we first observed in ewes (Bonnet et al 2000;Faulconnier et al 2001).…”

“…This is the case for the lipogenic activities of adipose tissues (AT), which have been mainly studied up to now during fasting and refeeding. It is widely acknowledged that refeeding underfed or fasted ruminant animals increases the level of lipogenesis to values similar to or greater than those in control animals (Pothoven & Beitz, 1975;DiMarco et al 1981;Smith et al 1983;Tume et al 1983;Bocquier et al 1998;Bonnet et al 1998;Faulconnier et al 2001). However, there is less agreement about the fasting effect on the activities of enzymes involved in de novo lipogenesis, since the decreases reported were not always statistically significant (Young et al 1969;Ingle et al 1973;Martin et al 1973;Pothoven & Beitz, 1973, 1975Smith et al 1983).…”