In order to find out the effect of diabetic metabolism on plasma cholesterol esterification reaction, the plasma LCAT activities were studied on streptozotocin-treated diabetic rats. The plasma LCAT levels increased as the increase in plasma cholesterol, triglycerides and fasting blood sugar; however, a significant negative correlation was found between LCAT and plasma IRI, suggesting this enzyme reaction is associated with diabetic metabolism.
To investigate further the problems, the plasma cholesterol esterification activities (CEA) were measured in the treated-diabetics and in the non-diabetic subjects. The enzyme levels were not significantly elevated in hyperglycemic diabetics whose plasma TG levels stayed within the normal range. However, they were significantly elevated in hypertriglyceridemics in both groups. These results indicate that the diabetic metabolism per se is not connected to the plasma cholesterol esterification reaction, but it does so through the derangement in plasma TG (VLDL) metabolism.
Our in vitro study revealed net transfer of cholesterol from LDL-Sepharose into rabbit plasma under the presence of active LCAT, however these transfer reaction was not demonstrated when fresh human plasma was incubated with LDL-Sepharose. It seems reasonable to conclude that plasma containing higher CEA relative to cholesterol content can absorb more cholesterol from the insoluble lipoproteins.
