Partial Physiologic Differences between High-fat Diet Induced Obesity-prone and Obesity-resistant Rats

Objective: To observe the differences of partial physiologic indexes including weight, food intake, Lee's index, the wet weight of fat pad, plasma lipids and the genetic expression of LPL mRNA in adipose tissue between obesity-prone rats (OP) and obesity-resistant rats (OR) on a high-fat diet. Methods: After 1 week of free access to a high-fat diet (HFD), 48 rats were separated on the basis of 1 week body weight percentage gained in OP (OP≥P75) or OR (OR≤P25) groups. Rats were continuously fed on the HFD for another 4 weeks. The body weight and food intake were recorded in the course of model-making. And the Lee's index, the plasma lipid and lipoproteins, the wet weight of both epididymal and retroperitoneal fat pad were measured after the rat was killed. And the level of LPL mRNA expression in adipose tissue was detected by Northern Blot technique. Results: ① In OP rats, the speed of body weight gain, the cumulative energy intake, the Lee's index, and the wet weight of fat pad at both epididymal and retroperitoneal sites were significantly higher than those in OR rats, but there was no significant difference in the level of plasma lipid and lipoproteins between these two groups. ②After 1 week and 5 weeks on the high-fat diet, the gain of body weight in OP rats were about 6.45 and 4.25 times of those in OR rats. Meanwhile, the cumulative energy intake in OP rats was only about 1.13 and 1.15 times of those in OR rats. ③Despite the depressive effect of the high-fat diet on the level of LPL mRNA expression in adipose tissue, there was a significant level of LPL mRNA in adipose tissue of OP rats compared with that in OR rats-Conclusion: The physiologic differences exist between OP and OR rats. Besides a higher level of energy intake, the higher energy efficiency associated with LPL mRNA expression in adipose tissue may also contribute to the enhancement of susceptibility to obesity in OP rats.