RESUMEN
BACKGROUND: In Korea, the prevalence of type 2 diabetes has been rapidly increased in parallel with the westernization of eating behavior, which can be potential contributors for insulin resistance. We determined whether Western diet (WD), Korean diet (KD), Western-Korean exchange diet (WDK), Korean-Western exchange diet (KDW) and control diet (CD) altered insulin secretion and insulin resistance in weaning male Sprague Dawley rats. METHODS: Weaning rats were provided by KD (77 En% of starch, 5 En% of corn oil and 13 En% of gluten plus 5 En% of casein), WD (42 En% of starch, 40 En% of butter and 18% of casein) or CD (62 En% of starch, 20 En% of corn oil and 18% of casein) for 21 weeks. At the 13th week, rats in the WDK and KDW groups exchanged the diets from WD to KD and KD to WD, respectively, and they continued on the exchanged diets for 9 weeks. RESULTS: Fasting serum glucose levels were lower in KD and WDK than any other groups. Insulin secretion was higher by 2.2+/-0.4 folds in WD and 1.9+/-0.3 folds in KDW than KD at baseline. In hyperglycemic clamp, insulin secretion to maintain 11.1 mmol/L of serum glucose levels showed the same results as the baseline. Whole body glucose disposal rates were highest in KD among all groups. Glycogen deposits in soleus and quadriceps muscles were highest in KD among all groups, and their triglyceride contents were lowest. GLUT4 contents and fraction velocity of glycogen synthase were highest in KD in soleus muscles. CONCLUSION: Westernized high fat diets increased insulin resistance, and insulin secretion increased to overcome insulin resistance. Increased insulin resistance was due to increased triglyceride and decreased glycogen, GLUT4 and glycogen synthase contents in muscles.