Effects of streptozotocin-induced diabetes on low density lipoprotein receptor expression in rat adipose tissue

Low density lipoprotein (LDL) receptors are found in most cells, including adipose cells. LDL receptors are primarily regulated by cellular cholesterol content. Insulin and insulin deficiency have been reported to have varying effects on LDL receptors in various tissues. The present study was undertaken to assess the in vivo effects of streptozotocin-induced diabetes on LDL receptor expression and cholesterol content in adipose tissue and liver. Diabetes was induced by a single dose of streptozotocin. After 3 days, some animals were treated with insulin, and all animals were killed 10 days after induction of diabetes. Compared to control rats, 10 days of diabetes caused a decrease in adipose cell size and cellular unesterified cholesterol and cholesteryl esters, and insulin treatment returned these towards normal. No changes were observed in hepatic lipid content with diabetes or insulin treatment. Diabetes was associated with an similar to 50% reduction in immunoreactive LDL receptors in adipose cells (P < 0.01) that was returned to normal with insulin treatment. The levels of LDL receptor mRNA decreased similar to 80% (P < 0.001) in adipose cells isolated from streptozotocin-induced diabetic rats and returned to normal with insulin treatment. Hepatic LDL receptors and mRNA levels were unaffected by diabetes or insulin treatment. In conclusion, diabetes decreased LDL receptor expression in adipose cells while total cellular cholesterol content also declined.