Apoptosis in the kidneys of rats that experienced intrauterine growth restriction

Epigenetic Mechanisms Responsible for the Transgenerational Inheritance of Intrauterine Growth Restriction Phenotypes

A poorly functioning placenta results in impaired exchanges of oxygen, nutrition, wastes and hormones between the mother and her fetus. This can lead to restriction of fetal growth. These growth restricted babies are at increased risk of developing chronic diseases, such as type-2 diabetes, hypertension, and kidney disease, later in life. Animal studies have shown that growth restricted phenotypes are sex-dependent and can be transmitted to subsequent generations through both the paternal and maternal lineages. Altered epigenetic mechanisms, specifically changes in DNA methylation, histone modifications, and non-coding RNAs that regulate expression of genes that are important for fetal development have been shown to be associated with the transmission pattern of growth restricted phenotypes. This review will discuss the subsequent health outcomes in the offspring after growth restriction and the transmission patterns of these diseases. Evidence of altered epigenetic mechanisms in association with fetal growth restriction will also be reviewed.

Effect of fetal growth restriction on urinary podocalyxin levels at birth in preterm neonates

BACKGROUND

Small-for-gestational-age (SGA) neonates are at a higher risk of adult-onset metabolic disorders because of fetal programming in the presence of growth restriction. Nephrogenesis may also be affected in fetal growth restriction. This study hypothesized that urinary podocalyxin levels, a marker of nephrogenesis, would be lower among preterm SGA neonates as compared to appropriate-for-gestational-age (AGA) controls.

METHODS

This cross-sectional study enrolled gestation-matched SGA (n = 90) and AGA (n = 45) neonates born at 26⁰-36⁶ weeks of gestation. The SGA group comprised of 45 neonates with birth weight between 3^rd and 10^th centile and 45 neonates with birth weight <3^rd centile. The primary outcome of the study was the difference in urinary podocalyxin levels between SGA and AGA neonates. Glomerular and tubular functions were also assessed.

RESULTS

Urinary podocalyxin levels were similar in SGA and AGA neonates (ng/mg of creatinine; median [interquartile range]: 28.7 [4.8-70.2] vs. 18.7 [3.1-55.9]), P value 0.14). No correlation was observed between birth weight centile and urinary podocalyxin levels (r: -0.06). Glomerular filtration rate, fractional excretion of sodium, and serum β-2-microglobulin levels were comparable across the study groups.

CONCLUSIONS

Glomerular development as assessed by urinary podocalyxin levels and renal functions are comparable in SGA and AGA preterm neonates.

IMPACT

Neonates born with fetal growth restriction are at a higher risk of adult-onset metabolic disorders because of fetal programming. This cross-sectional study investigated the effect of presence and severity of fetal growth restriction on glomerular development by measuring urinary podocalyxin levels in preterm infants. This study did not observe any effect of the presence or severity of fetal growth restriction on urinary podocalyxin levels and other markers of glomerular and renal tubular functions.

Increased Autophagy and Apoptosis in the Kidneys of Intrauterine Growth Restricted Rats

BACKGROUND

IUGR has been associated with nephron loss and chronic kidney disease (CKD).

MATERIALS AND METHODS

We examined autophagy and apoptosis markers in the kidneys of IUGR Sprague Dawley rats induced by maternal low protein diet (LP), comparing them to controls. The autophagy marker LC3B, the pro-apoptotic protein Bax, and the anti-apoptotic protein Bcl-2 were determined by quantitative immunoblotting. Immunohistochemical expressions of LC3B, Bax, and Bcl-2 were evaluated at 4 weeks age. Glomerular counts (by maceration techniques) were performed at 5 weeks.

RESULTS

The LP diet offspring were lighter (P < 0.05). In IUGR kidneys, LC3B and Bax were increased at birth (p < 0.05, p < 0.001) and at 4 weeks (p < 0.0142, p < 0.0001), Bcl-2 was decreased at birth (p < 0.05), and there were less glomeruli (p < 0.01) at 5 weeks.

CONCLUSIONS

Autophagy and apoptosis may have a role in IUGR associated decreased nephron number in Sprague rats.

Effect of L-arginine supplementation on the hepatic phosphatidylinositol 3-kinase signaling pathway and gluconeogenic enzymes in early intrauterine growth-restricted rats

The present study aimed to investigate the response of the phosphatidylinositol 3-kinase (PI3K) signaling pathway and gluconeogenic enzymes in intrauterine growth-restricted rats to dietary L-arginine (L-Arg) supplementation during the lactation period early in life. Pregnant Sprague-Dawley rats were randomly divided into a control group (CON), an intrauterine growth restriction group (IUGR) and an L-Arg group (LA). The pregnant rats in the CON group were fed a 21% protein diet, and those in the IUGR and LA groups were fed a 10% low protein diet, and all rats were fed a 21% protein diet after delivery. Water was available ad libitum to the pregnant rats during the 21-day lactation period, and the water provided to the LA group included 200 mg/kg/day L-Arg. Blood glucose, serum insulin, homeostasis model of assessment for insulin resistance (HOMA-IR), PI3K and protein kinase B (PKB) protein expression, and phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G-6-Pase) mRNA expression in the offspring rats were measured postnatally at 1, 3 and 8 weeks. No significant difference in blood glucose, serum insulin and HOMA-IR were identified at any time point among the three groups. PI3K and PKB expression was lower in the IUGR group offspring compared with that in the CON group offspring, but both were increased by dietary L-Arg supplementation. PEPCK mRNA and G-6-Pase mRNA expression levels in the offspring of the IUGR group were higher compared with those in the CON group but were downregulated following L-Arg supplementation. These results suggest that dietary L-Arg supplementation during the early lactation period promoted catch-up growth and reversed abnormalities in hepatic insulin signaling and gene expression of gluconeogenic enzymes in IUGR offspring rats.