Expression of genes relevant to insulin synthesis in intrauterine growth retardation rats at 36 weeks

Abstract

Objective To investigate the expression of genes relevant to insulin synthesis of intrauterine growth retardation(IUGR) rats at 36 weeks. Methods Twenty healthy female SD rats (250-270 g; 8-10 weeks old) were housed in the SPF animal room. After two weeks acclimatization, male and female rats were placed in same cage overnight for mating. Day 1 of pregnancy was defined as the day on which vaginal plugs were found. Female rats were grouped into normal controls (n=10) and model group (n=10) according to random number table. The IUGR rat model was established by maternal nutrition restriction during mid- to late-gestation. Pregnant rats received 50% of their daily food intake beginning from day 11 through day 21 of gestation, compared with their control counterparts who had free access to rat chow. The birth weights of the offsprings born to semistarvation mothers were more than two times of standard deviation below the mean values of the birth weights of the control group with IUGR. The litter size was randomly reduced to eight at birth to assure uniformity of litter size between IUGR and control litters. Two groups of pups were fostered to their mothers until they were weaned at day 21, and then all the pups were fed with standard rat chow until 36 weeks of life. Male offsprings at 36 weeks of age were selected as research subjects. Intraperitoneal glucose tolerance test (IPGTT) and insulin releasing test (IRT) were performed in IUGR and normal groups. RT-PCR was applied to detect the expression of pancreas genes such as Insulin1, Insulin2 and PDX-1. The t test was used in the comparison between two groups. Results At 36 weeks of age, body weight, pancreas weight and pancreas/body weight in IUGR group were much lower than those in normal group ((4971±525) and (5844±398) mg, (0.58±0.05)% and (0.69±0.04)% respectively, t=-2.65 and -3.39, both P 0.05). In IUGR rats, the expressions of Insulin1 mRNA were reduced markedly than those in the controls (0.79±0.17 vs 1.25±0.28, t=-2.78, P 0.05). Conclusions The IUGR rats had deteriorated glucose tolerance at 36 weeks of age with decreased gene expression of Insulin1 in pancreas. Key words: Fetal growth retardation; Genes relevant to insulin synthesis; Rats