Structural and functional changes in the kidney caused by adverse fetal and neonatal environments

Developmental origins of disease - Effects of iron deficiency in the rat developing kidney and beyond

Iron is an essential cofactor in metabolic and developmental processes. Iron deficiency (ID) is the most common micronutrient deficiency in pregnancy, especially impacting medically underserved populations worldwide. Iron deficiency (ID) in pregnancy predisposes neonates to poor iron status, i.e., congenital ID and associated adverse effects. The role of congenital ID on human kidney development is unstudied, but impaired fetal kidney development is possible. Both vascular and global nutrient restriction rat models report impaired fetal kidney development, as well as induce hypertension, supporting the developmental origins of health and disease (DOHaD) hypothesis. This review compiles findings from 17 published studies in rats examining congenital or early postnatal ID, showing the same. The review compares histological and physiological findings in both congenital and postnatal ID, placing these in the context of recent knowledge describing molecular mechanistic pathways regulating nephrogenesis. Findings in rat early-life ID include lower kidney iron levels, lower glomerular generations and estimated glomerular numbers, larger maculae densa size, interstitial fibrosis, and prolonging active glomerulogenesis past normal temporal cessation. Additionally, several physiological studies in rat congenital ID promote altered renin-angiotensin signaling and hypertension with maturation, especially in males. Key findings of morphological kidney maldevelopment, altered renin-angiotensin signaling, and hypertension in early-life ID underscore the urgent need for future mechanistic data in animals such as rats. The long-term goal would be to leverage understanding from these data into either preventative or early therapeutic strategies in children.

Relationship between apoptosis gene DNA methylation and fetal growth and development

OBJECTIVE

To investigate the relationship between DNA methylation of cord blood apoptosis genes and low birth weight (LBW).

METHODS

A case-control study was conducted on 50 pairs of LBW neonates and normal birth weight. Genome-wide methylation assay was performed using Illumina Human Methylation EPIC microarray to analyze the methylation sites of apoptosis-related genes BCL-2, CASP3, and CASP8. The mRNA level of apoptosis gene was verified by RT-qPCR.

RESULTS

Three CpG sites of BCL-2 and three CpG sites of CASP3 were different between the LBW and NBW groups. Logistic regression showed that higher methylation of BCL-2 CpG sites cg12459502 (OR = 1.208, 95% CI:1.029, 1.418) and cg25059899 (OR = 1.193, 95% CI:1.019, 1.395) increased LBW risk, while cg22152050 was protective (OR = 0.589, 95% CI:0.424, 0.820). Stratified analysis confirmed this. Maternal pre-pregnancy BMI positively correlated with BCL-2 methylation (cg12459502, cg25059899) (b = 0.431, 95% CI: 0.027, 0.835; b = 0.494, 95% CI: 0.141, 0.848), while excessive pregnancy weight gain negatively correlated with cg12459502 methylation (b = -0.269, 95% CI: -0.525, -0.013). The results showed that the mRNA level of BCL-2 in NBW group was significantly higher than that in LBW group (P-value < 0.0001).

CONCLUSION

The DNA methylation levels of BCL-2 and CASP3 genes are associated with fetal growth and development. Additionally, maternal pre-pregnancy BMI and weight gain during pregnancy were found to correlate with BCL-2 methylation, indicating potential epigenetic mechanisms influencing fetal growth.

Maternal periconceptional folic acid supplementation and risk for fetal congenital genitourinary system defects

BACKGROUND

Taking folic acid supplementation could reduce the risk of neural tube defects for offspring in the maternal periconceptional period, but the relationship between folic acid use and other birth defects remains unclear, such as genitourinary system birth defects.

METHODS

The data from a Prenatal Health Care System and Birth Defects Surveillance System in Tongzhou, Beijing, China, were collected from 2013 to 2018. We adjusted for differences in characteristics between comparison groups using propensity score inverse probability weighting and assessed associations with Poisson regression modeling.

RESULTS

A total of 65,418 live births and stillbirths were included, and there were 194 cases with congenital genitourinary defects among them. The prevalence of genitourinary system birth defects was 29.2 (34.9) per 10,000 for FA/MMFA users (nonusers). Compared to nonusers, FA/MMFA users had a lower risk for genitourinary system birth defects (adjusted risk ratio [aRR] 0.81, 95% confidence interval [CI] 0.67, 0.98), and for hypospadias (aRR 0.55, 95% CI 0.40, 0.76).

CONCLUSIONS

FA or MMFA supplementation during the maternal periconceptional period could reduce the risk for genitourinary system birth defects in offspring. More mechanisms should be explored for the protective effect.

IMPACT

Folic acid (FA) or multiple micronutrients containing folic acid (MMFA) supplementation during the maternal periconceptional period could reduce the risk for genitourinary system birth defects in offspring. Maternal FA/MMFA supplementation during the periconceptional period may reduce the risk for hypospadias.

Renal deficit and associated factors in children born with low birth weight

INTRODUCTION

Kidney problems may be due to low birth weight alone or may occur in association with other conditions. The objective this study was to evaluate the association between maternal and birth characteristics, anthropometric measurements, and kidney function deficit in low birth weight infants.

METHODS

Cross-sectional study with children who were born weighing < 2500 grams and were under outpatient follow-up. Maternal factors investigated were prenatal care and presence of hypertension, diabetes, and infection during pregnancy. The children's variables were sex, gestational age, birth weight, Apgar score, use of nephrotoxic medications, age, body weight at the time of evaluation, height, and serum creatinine and cystatin C dosages. The glomerular filtration rate (GFR) was estimated with the combined Zapittelli equation. Multivariate logistic regression model was used for identification of associated factors, with renal function deficit (GFR < 60 mL/min/1.73 m2) as the dependent variable.

RESULTS

Of the 154 children evaluated, 34.42% had kidney function deficit. Most of them had a gestational age > 32 weeks (56.6%), a mean birth weight of 1439.7 grams, and mean estimated GFR of 46.9 ± 9.3 mL/min/1.73 m2. There was a significant association of GFR < 60 mL/min/1.73 m2 with children's current weight and use of nephrotoxic drugs.

DISCUSSION

Children born with low birth weight had a high prevalence of kidney function deficit and current normal weight was a protective factor while the use of nephrotoxic drugs during perinatal period increased the chance of kidney deficit. These findings reinforce the need to evaluate the kidney function in these children, especially those who use nephrotoxic drugs.

Insulin-like growth factor-1 replacement therapy after extremely premature birth: An opportunity to optimize lifelong lung health by preserving the natural sequence of lung development

The past decades have seen markedly improved survival of increasingly immature preterm infants, yet major health complications persist. This is particularly true for bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, which has become the most common sequelae of prematurity and a significant predictor of respiratory morbidity throughout childhood as well as adult life, neurodevelopmental disability, cardiovascular disease, and even death. The need for novel approaches to reduce BPD and related complications of prematurity has never been more critical. Thus, despite major advances in the use of antenatal steroids, surfactant therapy, and improvements in respiratory support, there is a persistent need for developing therapeutic strategies that more specifically reflect our growing understanding of BPD in the post-surfactant age, or the "new BPD." In contrast with the severe lung injury leading to marked fibroproliferative disease from the past, the "new BPD" is primarily characterized by an arrest of lung development as related to more extreme prematurity. This distinction and the continued high incidence of BPD and related sequelae suggest the need to identify therapies that target critical mechanisms that support lung growth and maturation in conjunction with treatments to improve respiratory outcomes across the lifespan. As the prevention of BPD and its severity remains a primary goal, we highlight the concept from preclinical and early clinical observations that insulin-like growth factor 1 (IGF-1) can potentially support the natural sequence of lung growth as a replacement therapy after preterm birth. Data supporting this hypothesis are robust and include observations that low IGF-1 levels persist after extremely preterm birth in human infants and strong preclinical data from experimental models of BPD highlight the therapeutic benefit of IGF-1 in reducing disease. Importantly, phase 2a clinical data in extremely premature infants where replacement of IGF-1 with a human recombinant human IGF-1 complexed with its main IGF-1 binding protein 3, significantly reduced the most severe form of BPD, which is strongly associated with multiple morbidities that have lifelong consequences. As physiologic replacement therapy of surfactant heralded the success of reducing acute respiratory distress syndrome in preterm infants, the paradigm has the potential to become the platform for discovering the next generation of therapies like IGF-1, which becomes deficient after extremely premature birth where endogenous production by the infant is not sufficient to maintain the physiologic levels adequate to support normal organ development and maturation.

Déficit renal e fatores associados em crianças nascidas com baixo peso

RESUMO Introdução: Problemas renais podem ser devido apenas ao baixo peso ao nascer ou podem ocorrer em associação com outras condições. O objetivo deste estudo foi avaliar a associação entre características maternas e de nascimento, medidas antropométricas e déficit da função renal em bebês de baixo peso ao nascer. Métodos: Estudo transversal com crianças que nasceram com peso < 2500 gramas e estavam sob acompanhamento ambulatorial. Os fatores maternos investigados foram cuidados pré-natal e presença de hipertensão, diabetes e infecção durante a gravidez. As variáveis das crianças foram sexo, idade gestacional, peso ao nascer, índice Apgar, uso de medicamentos nefrotóxicos, idade, peso corporal no momento da avaliação, altura e dosagens séricas de creatinina e cistatina C. A taxa de filtração glomerular (TFG) foi estimada com a equação combinada de Zapittelli. Utilizou-se um modelo de regressão logística multivariada para identificação de fatores associados, com déficit da função renal (TFG < 60 mL/min/1,73 m2) como variável dependente. Resultados: Das 154 crianças avaliadas, 34,42% apresentaram déficit da função renal. A maioria tinha idade gestacional > 32 semanas (56,6%), peso médio ao nascer de 1439,7 gramas, e TFG média estimada de 46,9 ± 9,3 mL/min/1,73 m2. Houve uma associação significativa da TFG < 60 mL/min/1,73 m2 com o peso atual das crianças e o uso de medicamentos nefrotóxicos. Discussão: Crianças nascidas com baixo peso apresentaram alta prevalência de déficit da função renal e o peso atual normal foi um fator de proteção, enquanto o uso de medicamentos nefrotóxicos durante o período perinatal aumentou a chance de déficit renal. Estes achados reforçam a necessidade de avaliar a função renal destas crianças, especialmente aquelas que usam medicamentos nefrotóxicos.

Bronchopulmonary Dysplasia and Impaired Neurodevelopment-What May Be the Missing Link?

Bronchopulmonary dysplasia (BPD) and poor neurodevelopmental outcome after preterm birth are closely associated. However, mechanistic links are uncertain. We are exploring the hypothesis that decreased circulating insulin-like growth factor (IGF)-1 after preterm birth due to the abrupt end of supply by the placenta impairs growth during critical windows of development in most organs, including the lung and brain. Throughout gestation, the fetus uses glycolysis as its main source of energy. Metabolism is mainly stopped at pyruvate, which serves as a "metabolic crossroad", allowing for the production of amino acids and other "building blocks" for new cells. Metabolic pathways are differentially regulated in the nucleus and the cytoplasm. The ratio between pyruvate dehydrogenase (PDH) and pyruvate dehydrogenase kinase (PDK) determines the biochemical activity which irreversibly metabolizes pyruvate to acetyl-co-A. Metabolites in the nucleus modulate epigenetic remodeling, an essential mechanism of normal growth and maturation during development. IGF-1 has been shown to contribute significantly to the development of virtually all organs, especially related to the regulation of microvascular growth, based on extensive studies of the brain, retina, lung, and intestine. With a preterm birth, the abrupt withdrawal of the placental supply of IGF-1 and its local production directly affects metabolism and microvascular development, which may contribute to a high risk for organ maldevelopment and injury after birth. We speculate that reduced bioavailability of IGF-1 is a possible link between lung and brain development disruption and increases susceptibility for major pulmonary and neurocognitive morbidities in preterm babies. KEY POINTS: · Metabolic changes inherent to prterm birth may cause epigenetic changes which cause "dysmaturational" development.. · IGF-1 may be the potential link between BPD and brain development.. · The ratio between pyruvate dehydrogenase and pyruvate dehydrogenase kinase determines the biochemical activity..

Recent findings on the role of microRNAs in genetic kidney diseases

BACKGROUND

MicroRNAs (miRNAs) are non-coding, endogenous, single-stranded, small (21-25 nucleotides) RNAs. Various target genes at the post-transcriptional stage are modulated by miRNAs that are involved in the regulation of a variety of biological processes such as embryonic development, differentiation, proliferation, apoptosis, inflammation, and metabolic homeostasis. Abnormal miRNA expression is strongly associated with the pathogenesis of multiple common human diseases including cardiovascular diseases, cancer, hepatitis, and metabolic diseases.

METHODS AND RESULTS

Various signaling pathways including transforming growth factor-β, apoptosis, and Wnt signaling pathways have also been characterized to play an essential role in kidney diseases. Most importantly, miRNA-targeted pharmaceutical manipulation has represented a promising new therapeutic approach against kidney diseases. Furthermore, miRNAs such as miR-30e-5p, miR-98-5p, miR-30d-5p, miR-30a-5p, miR-194-5p, and miR-192-5p may be potentially employed as biomarkers for various human kidney diseases.

CONCLUSIONS

A significant correlation has also been found between some miRNAs and the clinical markers of renal function like baseline estimated glomerular filtration rate (eGFR). Classification of miRNAs in different genetic renal disorders may promote discoveries in developing innovative therapeutic interventions and treatment tools. Herein, the recent advances in miRNAs associated with renal pathogenesis, emphasizing genetic kidney diseases and development, have been summarized.