Effect of aging on pancreatic lipolytic enzymes

Pancreatic lipolytic enzyme activities and plasma lipids were measured in three age groups of female Fisher 344 rats (3 months [young], 12 months [adult], and 27 months [old]) in order to evaluate age-related changes and a possible correlation of these parameters. Cholesterol esterase activity was measured in pancreas homogenate, while the lipase activity was further fractionated into heparin-Sepharose unretained (lipase I) and retained (lipase II) fractions. In analogy to the lipolytic enzymes of the human pancreas, lipase I corresponds to pancreatic lipase and lipase II corresponds to pancreatic carboxylesterase. Plasma triglyceride and cholesterol levels were significantly higher in old as compared with adult and young rats. There was no significant correlation between plasma lipid and pancreatic enzyme activity levels. Cholesterol esterase and pancreatic lipase (lipase I) activity did not show any consistent change with age. Pancreatic carboxylesterase (lipase II), on the other hand, was consistently lower in adult and old animals. Although the importance of pancreatic carboxylesterase for triglyceride hydrolysis remains to be established, our results suggest that this enzyme is under long-term metabolic control. We suggest that early in life, high levels of this enzyme may be needed to supplement pancreatic lipase in order to optimize digestion of dietary fat required for optimal growth.