Effect of diabetes and insulin therapy on human mononuclear leukocyte lysosomal acid lipase activity

Acid lipase activity was measured in mononuclear leukocytes obtained from 18 newly diagnosed type-I diabetics and from six newly diagnosed type-II diabetics before and five to ten days after the initiation of insulin therapy. Using either 4-methylumbelliferyl oleate or cholesteryl[1-14C]oleate as substrate for the enzyme assays, acid lipase activity in the diabetics was not found to be significantly different from that in the controls, significantly less (P less than 0.05) after insulin therapy in type-I diabetics, and unchanged following treatment in the type-II patients. These results differ from those found in previous studies of acid lipase activity in type-II diabetics, in whom insulin therapy evoked a doubling of enzyme activity. The effect of insulin treatment on the activity of lysosomal acid lipase requires further evaluation.