OBJECTIVETo investigate the association between the expression of turnor necrosis factor alpha (TNF-alpha) mRNA in fat tissue of intrauterine growth retarded (IUGR) rats and insulin resistance, and the long-term effects of early different nutritional diet.

METHODSThe IUGR rat model was established by food restriction of pregnant rats. A total of 32 newborn IUGR rats were randomly divided into 4 groups: IUGR model (S/N) group, IUGR high caloric diet (A) group, IUGR high caloric and high protein diet (B) group, IUGR high protein diet (C) group. Only the mother rats were given those different diets individually, and all IUGR newborn pups were lactated for 3 weeks. From the beginning of the 4(th) week, all IUGR pups were weaned and fed with normal diet till the end of the experiment. Eight normal birth weight newborn rats were used as the control group fed with the normal diet. Weight, perirenal fat weight, fasting glucose and insulin concentration and quantified TNF-alpha mRNA expression in adipose cell were measured at the 48(th) week. The insulin sensitive index (ISI) and the relation index between TNF-alpha mRNA and fat weight, fat weight/body weight (fw/bw) ratio and ISI were calculated.

RESULTSISI of IUGR model group, IUGR A and B groups was lower than normal control group, while perirenal fat weight, fw/bw and the expression of TNF-alpha mRNA in adipose cells were all significantly higher (P < 0.05 or 0.01). There were no significant differences in these indexes between IUGR C group and normal control groups (P > 0.05). A positive correlation was found between TNF-alpha mRNA and fat weight and fw/bw (r(1) = 0.755, r(2) = 0.782, P = 0.000). Significant inverse associations between ISI and TNF-alpha mRNA (r = -0.556, P = 0.000) and fw/bw (r = -0.513, P = 0.02) were also found.

CONCLUSIONThe occurrence of insulin resistance in IUGR rats is possibly associated with central obesity and accumulation of the abdominal fat and adipose cell over-expression of TNF-alpha. The adipose TNF-alpha may be an important pathogenic factor of insulin resistance of IUGR. High protein diet is a reasonable nutritional intervention. Because it promotes the skeleton muscle catch-up growth but not fat catch-up growth, it can avoid the occurrence of central obesity and insulin resistance in IUGR rats.