Relationship between insulin resistance and ghrelin level in small for gestational age rats

Objective To observe the change of insulin sensitivity index （ISI） and ghrelin level, to examine their correlation and to explore the role and significance of ghrelin in insulin resistance （IR） in small for gestational age （SGA） rats. Methods The SGA models were established by starvation method in pregnant SD rats. Experimental rats were grouped by body length and/or body weight 4 weeks after birth. Experiment grouping： （ 1 ）SGA group with growth catch-up（Group S1, n=26） ; （2）SGA group without growth catch-up （Group S2, n=31 ） ; （3）Normal control group was composed by male rats whose mothers ate and drank freely during pregnancy （Group C, n=27 ）. Body weight and serum ghrelin level was checked 4 weeks after birth. Body weight, serum ghrelin, fasting blood glucose and fasting insulin were tested when the rats were 12 weeks old, and then ISI was calculated. Correlation of all the indexes was analyzed. Results The ISI of 12-week-old SGA rats was significantly decreased as compared to normal control （Group SI： 2.00＋ 0.58, Group $2：2.23~0.58 vs Group C： 3.17＋0.54, both P〈0.05）. Serum ghrelin level of SGA rats was decreased compared with Group C, but the disparity was not statistically significant [Group SI： （1.357 ± 0.548 ） μg/L, Group S2 ： （ 1.428±0.714） μg/L vs Group C ： （1.843±0.459） μg/L, both P〉0.05 ]. Ghrelin level in 12-week-old rats presented negative correlation with fasting insulin level in blood （r=-0.836, P〈0.01 ）, and positive correlation with ISI （r=0.810, P〈0.01 ）. Conclusion The decrease of serum ghrelin level is correlated with IR in adult SGA rats. Low serum level of ghrelin may be the result oflR. Key words: Infant, small for gestational age;  Insulin;  Insulin resistance;  Ghrelin;  Rats