Effects of streptozotocin diabetes and insulin treatment on adipose tissue glucose utilization in the rat

[U-14C] glucose utilization by pieces of epididymal fat-pad was studied in streptozotocin-diabetic rats, food-restricted animals, and normal controls. Both CO2 and fatty acids formation were greatly reduced in tissues from the diabetic animals treated or not with insulin and this change was milder in tissues from food-restricted rats. A positive correlation was found between [14C] glucose utilization in vitro and plasma RIA-insulin levels when values from all animals were pooled. The percentual response to high doses of insulin was small in adipose tissue from streptozotocin-diabetic animals for CO2 and total lipids formation, but it was high for fatty acids synthesis; the response in food-restricted animals was high and was greatly augmented in tissues from the streptozotocin-diabetic rats treated with insulin. Results indicate that in adipose tissue from streptozotocin-diabetic animals the alteration of insulin responsiveness occurs distal to the receptor events and that impaired basal glucose metabolism is a direct consequence of their hypoinsulinemia.