The Effect of Increased Beta Cell Mass on Glucose Tolerance in Rat

Oh, Eun Sook; Yoon, Kun Ho; Seo, Sun Hee; Lee, Sook Young; Ko, Seung Hyun; Lee, Won Young; Kim, Sung Rae; Kang, Moo Il; Cha, Bong Yon; Lee, Kwang Woo; Son, Ho Young; Kang, Sung Goo

Abstract

BACKGROUND: The aim of the present study is to evaluate the effect of increased beta cell mass by continuous 96-hour 50% glucose infusion on glucose tolerance in insulin resistance state induced by high fat diet in normal Sprague-Dawley rats.
METHODS
The adult Sprague-Dawley rats weighing 200-250 gm were infused with 50% glucose or 0.45% saline via external jugular vein catheter for 96 hours. The both groups of rats were then randomly stratified into the two subgroups, and fed either high fat diet (54% of energy from fat) or normal rat chow (8.6% of energy from fat) for 4 weeks. On day 28, blood was collected for measuring the serum concentration of insulin, and oral glucose tolerance test (2 gm/kg body weight) was performed after overnight fasting. The beta cell mass was counted with the morphometric point-counting technique of Weibel.
RESULTS
After the 96 hour infusion, the percentage of beta cell mass was significantly increased in glucose-infused rats when compared to the saline-infused group (p=0.03) and maintained up to day 28. Body weight gains were significantly greater in glucose infused rats than those of saline infused group (Increased value of weight : 142.9+/-15.2 g in glucose infused rats vs 125.3+/-21.1 g in saline infused rats, p=0.01). In the saline infusion-high fat diet group, the number of rats with impaired glucose tolerance was higher than those of other group (p<0.005). The glucose values at 90 minute and 120 minute were higher in saline infusion-high fat diet group than in glucose infusion-high fat diet group (p< 0.05).
CONCLUSION
Our findings suggest that the increased beta cell mass has a favorable effect on glucose tolerance in insulin resistance state which were evoked by high fat diet.