| Objective: At present there are many studies on the pathogenesy of the type 2 diabetes, which pay much attention to the insulin resistance and the disfunction of the islands of pancreas. Researches shows that the insulin resistance has much relation to obesity, hypertention, metabolic disorder of lipid, coronary atherosclerosis as well as type 2 diabetes.In the past the studies on insulin resistance is mostly focus on the impact of obesity and fat factors on the signal conduction pathway of insulin. However, the causes of obesity and the insulin resistance in non-obese person are relatively less seen in the nowadays studies. Recently, researches on the relationship between the catch up growth and the insulin resistance provide new thinking to the pathogenesy of type 2 diabetes. The catch up growth is a phenomenon that appears on the nutrition-restriction individual. In order to catch up the normal people these individuals show off a special growth pattern, such as the height and the weight increase rapidly in a shot time. But the most important influences of the catch up growth on the object organism are the over accumulation of internal organ fatty tissue and the decrease of insulin sensibility. There are two reasons to the catch up growth. One is impact on the foetus,development and give birth to a low birth weight baby, which show off catch up growth when the body obtain adequate nutrition supply. And the other appeared on the individals with mormal birth weight, which suffer growth restriction in the process of growth and development. The second situation is attributed to the increase incidence of type 2 diabetes recently. Studies show that catch up growth individals have high disease incidence of obesity, coronary atherosclerosis and type 2 diabetes, which arouse attention of researchers. In the second situation the restrict interval is the vital factor to determin the individals happen catch up growth or not. But how long time is the shortest interval of the phenomenon? Recently, there are some relative animal experiment , which come to the conclusion that 4-week- diet-restrict rat show off catch up growth after offer adequate food. However, the effect of diet restriction less than 4 weeks is not clear. So we design this experiment to find out the answer.Methods: 55 male-6-week-old wistar rat, clean animal grade, accommodate fed 1week then selected 50 divided into 6 groups at random. The A group contain 10 rats the other groups have 8 rats respectively. The temperature and the humidity of the laboratory were 21±1℃and (60±10)%,made sure 12 hours illumination to the animals everyday. The A group was control group, which gave normal dose food and fed 12 weeks. the B,C,D,E groups were food-limited groups, which gave half dose food of the A group, but the time of limitation were different that were 1,2,3,4weeks respectively. Each food-limited group would feed 8 weeks with mormal dose food after the limitation. The F group was a special group, which fed with normal dose and no food alternately, the interval is one day and fed 12 weeks all together. In the former 4 weeks of the experiment , the measurement of every groups food-intake was took everyday and the weights of every groups was took every week. When the model was done, killed the rats and measured the empty stomach blood glucose, insulin and the blood fat. Separated and weighed the surrounding fatty tissue of the kidney and the testises, then calculated the ratio to the body weight. Made pancreatic pathological sections of each group . Selected 2 rats from every group at random, then put in to the Hyperinsulinemic euglycemic clamp experiment in order to tested the insulin sensibility. The data were analyzed by SPSS13.0 statistical package. One way ANOVA was applied to the group comparison, and the q test was applied to the inter-group comparison.Results:1. The change of food-intake :the intake of the normal control group was to show a downtrend by the fourth week, but there was a slight fluctuation totally. The B,C,D groups had a suddenly increase food-intake at the first week after the limitation but returned normal rapidly. The food-intake of the E group was more than control group after the limitation. The F group,s food-intake was much more than other groups when gave food.2. The change of the weight: the weight of the B,C,D,E groups had no obviously change when the limitation was over and lagged much behind the control group. However the weights increase rapidly when gave the normal dose food, but the final weights of the food-restriction groups did not catch up the control group. The weight of F group increased gradually and had no obviously different with other groups(P=0.51).3. The contents of internal organ: there were no obvious difference of the internal organ contents among these groups except the F group(P=0.834), (P<0.05).4. The blood-fat level: there were no obvious difference in the blood cholesterol level among the groups(P=0.52),the blood triglyceride level was obvious lower than other groups(P<0.05).5. The blood-fasting sugar, insulin level and the HOMA-IR: the E group had the highest blood-fasting sugar and the F group had the lowest level but there were not statistically significant(P=0.08).The E group had the highest insulin level and the difference had statistically significant(P<0.05) .The C,D groups insulin level were higher than the control group and the difference had statistically significant(P<0.05).6. The result of the Hyperinsulinemic euglycemic clamp experiment: the control group had the highest glycose filling rate and the E group had the lowest filling rate. Other groups filling rate were between the two groups.7. The islands of pancreas pathological section: there were no obvious abnormal change in the islands of pancreas of every groups.Conclusion: The harmful effects that come from the transient growth limitation is a chronic accumulative process. The harmful effects include malnutrition during the limitation and the insulin resistance when happen catch up growth even other harmful incident in the long run. We can come to the conclusion through this experiment that the shortest limitation is 2 or 3 weeks in rats, but the genetic factor play a important role in the process of the catch up growth.
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