Development of glucose intolerance in obese (fa/fa) Zucker rats

Development of glucose intolerance in genetically obese (fa/fa) rats was investigated. Comparisons were made with lean (FA/?) control rats. Oral glucose tolerance tests were performed in 7-8 weeks, 9-10 weeks, 12-13 weeks and 16-17 weeks old rats. Irrespectively of age, the obese rats showed impaired glucose tolerance and insulin sensitivity compared with age-matched lean rats. While in FA/? rats only minor changes of glucose-stimulated insulin secretion and glucose tolerance were observed with progression of age, glucose intolerance in obese animals became more pronounced with aging. Obese rats older than 12-13 weeks showed no further progression of glucose intolerance. Glucose-stimulated insulin secretion increased with aging, but basal insulinemia was unaffected. Hence, we conclude that glucose intolerance and insulin resistance in genetically obese (fa/fa) rats is almost completely developed with approximately 12 weeks.