Effect of Folic Acid Supplementation on Renal Phenotype and Epigenotype in Early Weanling Intrauterine Growth Retarded Rats.

BACKGROUND/AIMS: The objective of this study was to examine the responses of p53 promoter methylation involved in kidney structure and function of early weaning intrauterine growth retarded (IUGR) rats to dietary folic acid supplementation. METHOD: Sprague-Dawley rats were fed isocaloric diets containing either 21% protein diet (normal feed) or 10% protein diet throughout pregnancy and normal feed during lactation. After weaning, Offspring were then fed onto normal feed and normal feed supplemented with 5 mg folic acid / kg feed for a month, this produced 4 dietary groups (maternal diet/ weanling diet): Con, Folic, IUGR and IUGR+Folic. Renal function, renal structure, p53 promoter methylation and protein expression of offspring rats were measured at postnatal 2 months and 3 months. RESULTS: Glomerular volume, blood urea nitrogen, 24 hours urine protein were significantly elevated in IUGR rats compared with Con rats but were decreased by dietary folic acid supplementation. p53 protein expression in IUGR rats were significantly higher than that in Con rats, and p53 promoter methylation status in IUGR rats was reduced significantly compared with Con rats. However, the changes in p53 gene expression and DNA methylation status of IUGR rats were reversed by dietary folic acid supplementation. CONCLUSIONS: Our study showed for the first time that folic acid supplementation during early period of life could reverse the abnormality in renal p53 methylation status and protein expression, glomerular volume and renal function of IUGR rats offspring.

Dynamic p53 protein expression and phosphorylation in the kidneys of rats that experienced intrauterine growth restriction.

AIM: This study investigated the mechanisms involved in intrauterine growth restriction (IUGR). METHODS: The IUGR model was established by feeding pregnant SD rats a low-protein diet. Protein expression and phosphorylation were detected using Western blot and/or immunohistochemistry. Cell apoptosis was detected by TUNEL staining. The MDM2 mRNA expression was measured by real-time PCR. RESULTS: Pups from the IUGR group had significantly lower body (7th day, 2 months) and kidney weights (1st day, 7th day, 2 months) compared to pups from the control group (p < 0.01). The glomeruli number in IUGR pups was significantly less than that in the control pups at 2 and 3 months after birth (p < 0.01). p53 protein level and p53 phosphorylation at Ser(15) were time-dependently decreased in the kidney at 1st day, 7th day, 21st day, 2 months and 3 months, but their levels in the kidney of the IUGR pups was significantly higher than that in control pups at each time point (p < 0.05, p < 0.01, or p < 0.001). Significantly more positive p21 staining was observed in IUGR pups than in control pups at each time point. Real-time PCR of MDM2 mRNA expression showed no significant difference between IUGR and control pups (p > 0.05). Significant apoptosis was observed in the kidneys of IUGR pups compared to control pups. CONCLUSION: Malnutrition-induced IUGR may be associated with the activation of p53-p21 signaling in the kidney.

Apoptosis in the kidneys of rats that experienced intrauterine growth restriction.

AIM: Intrauterine growth retardation (IUGR) can affect kidney development, leading to reduction in glomerular number. However, the associated cellular and molecular mechanisms have not been fully elucidated. This study investigated cell apoptosis and Bcl-2 and Bax expression in the kidney of IUGR pups. METHODS: The IUGR model was established in pregnant rats with 10% low-protein diet. Renal cell apoptosis was detected using TUNEL staining. Ki67 protein expression was measured by immunohistochemistry. Bcl-2 and Bax mRNA expression was measured by real-time polymerase chain reaction (PCR). RESULTS: Significant decreases in the number of glomeruli was observed in the kidney of IUGR pups 2 and 3 months after birth (P < 0.01). Obvious apoptosis was observed in the kidney in both groups 1 d, 7 d, and 21 d after birth with a peak at 7 d. Significantly higher apoptosis index was observed in the kidney of IUGR pups compared to control pups (P < 0.01). No significant difference in proliferation was observed between the two groups. Significantly lower Bcl-2 mRNA expression, Bcl-2/Bax ratio, and higher Bax mRNA expression were observed in IUGR pups compared to control pups after birth (P < 0.01). CONCLUSION: The reduction in glomerular number in IUGR pups is associated with increase in renal cell apoptosis. The reduction in Bcl-2/Bax ratio may play a crucial role in renal cell apoptosis in IUGR pups.

[Effects of L-Arg on expression of PI3K and PKB in liver among low-birth-weight newborn rats].

OBJECTIVE: To measure the expression of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB) in liver tissue among low-birth-weight newborn rats treated with L-arginine (L-Arg) in early life, and to investigate the effect of L-Arg on insulin resistance. METHODS: Eighteen pregnant rats were randomly divided into three groups: control, model and intervention (n=6 each). The control group was fed with normal protein feed (protein content=21%) during pregnancy to establish a normal-birth-weight newborn rat model, and the model and intervention groups were fed with low-protein feed (protein content=10%) during pregnancy to establish a low-birth-weight newborn rat model. Newborn rats from the three pregnant rat groups were also assigned to control, model and intervention groups. During 21 days of lactation, maternal rats in the control and model groups were fed with normal protein feed and normal drinking water, while maternal rats in the intervention group were fed with normal protein feed and drinking water rich in L-Arg (200 mg/kg·d). After ablactation, the three groups of newborn rats were fed with normal protein feed and normal drinking water. Liver tissue samples were collected from these newborn rats at 1, 3 and 8 weeks after birth. Protein expression of PI3K and PKB in liver tissue was measured by Western blot. RESULTS: At 1 week after birth, the newborn rats in the intervention group had significantly higher protein expression of PI3K than in the model group (P=0.045), but there was no significant difference when compared with the control group (P=0.503). At 8 weeks after birth, the newborn rats in the intervention group had significantly higher protein expression of PKB than the model group (P=0.039), but there was no significant difference when compared with the control group (P>0.05). CONCLUSIONS: A supplement of L-Arg in early life can boost protein synthesis, increase protein expression of PI3K and PKB in liver tissue, promote insulin signaling and reduce insulin resistance.