Biochemical parameters of renal impairment/injury and surrogate markers of nephron number in intrauterine growth-restricted and preterm neonates at 30-40 days of postnatal corrected age

Blood pressure and kidney function in neonates and young infants with intrauterine growth restriction

BACKGROUND

Intrauterine growth restriction (IUGR) has been associated with changes in kidney anatomy, nephrogenesis and the vascular system, resulting in secondary arterial hypertension and kidney damage in adulthood. Here, we compare routine clinical and metabolic parameters between IUGR and non-IUGR study participants in the neonatal and early infant period.

METHODS

A total of 39 IUGR and 60 non-IUGR neonates were included during an 18-month study period. We compared blood pressure, serum creatinine (SCr), urea nitrogen (BUN), urinary albumin, α-1-microglobulin, transferrin, immunoglobulin G and total protein excretion in spontaneous urine normalized by urine creatinine level during the hospital stay.

RESULTS

There were no significant differences in mean values of blood pressure and urinary protein excretion between cases and controls. SCr and BUN levels were lower in the IUGR group compared to the non-IUGR group.

CONCLUSIONS

The lower levels of SCr and BUN may be attributed to lower liver and muscle mass in IUGR neonates and young infants. Biomarkers currently used in routine clinical care do not allow early postnatal prediction of higher blood pressure or worse kidney function due to IUGR, so further studies are needed. A higher resolution version of the Graphical abstract is available as Supplementary information.

Gene Expression Analysis in gla-Mutant Zebrafish Reveals Enhanced Ca2+ Signaling Similar to Fabry Disease

Fabry disease (FD) is an X-linked inborn metabolic disorder due to partial or complete lysosomal α-galactosidase A deficiency. FD is characterized by progressive renal insufficiency and cardio- and cerebrovascular involvement. Restricted access on Gb3-independent tissue injury experimental models has limited the understanding of FD pathophysiology and delayed the development of new therapies. Accumulating glycosphingolipids, mainly Gb3 and lysoGb3, are Fabry specific markers used in clinical follow up. However, recent studies suggest there is a need for additional markers to monitor FD clinical course or response to treatment. We used a gla-knockout zebrafish (ZF) to investigate alternative biomarkers in Gb3-free-conditions. RNA sequencing was used to identify transcriptomic signatures in kidney tissues discriminating gla-mutant (M) from wild type (WT) ZF. Gene Ontology (GO) and KEGG pathways analysis showed upregulation of immune system activation and downregulation of oxidative phosphorylation pathways in kidneys from M ZF. In addition, upregulation of the Ca2+ signaling pathway was also detectable in M ZF kidneys. Importantly, disruption of mitochondrial and lysosome-related pathways observed in M ZF was validated by immunohistochemistry. Thus, this ZF model expands the pathophysiological understanding of FD, the Gb3-independent effects of gla mutations could be used to explore new therapeutic targets for FD.

Urinary Levels of Cathepsin B in Preterm Newborns

Increased investment in perinatal health in developing countries has improved the survival of preterm newborns, but their significant multiorgan immaturity is associated with short and long-term adverse consequences. Cathepsin B, as a protease with angiogenic properties, may be related to the process of nephrogenesis. A total of 88 neonates (60 premature children, 28 healthy term children) were included in this prospective study. We collected urine samples on the first or second day of life. In order to determine the concentration of cathepsin B in the urine, the commercially available enzyme immunoassay was used. The urinary concentrations of cathepsin B normalized with the urinary concentrations of creatinine (cathepsin B/Cr.) in newborns born at 30-34, 35-36, and 37-41 (the control group) weeks of pregnancy were (median, Q1-Q3) 4.00 (2.82-5.12), 3.07 (1.95-3.90), and 2.51 (2.00-3.48) ng/mg Cr, respectively. Statistically significant differences were found between the group of newborns born at 30-34 weeks of pregnancy and the control group (p < 0.01), and between early and late preterm babies (PTB) (p < 0.05). The group of children born at 35-36 weeks of pregnancy and the control group did not differ significantly. This result suggests that the elevated urinary cathepsin B/Cr. level may be the result of the kidneys' immaturity in preterm newborns.

The thrifty phenotype hypothesis: The association between ultrasound and Doppler studies in fetal growth restriction and the development of adult disease

Barker pioneered the idea that the epidemic of coronary heart disease in Western countries in the 20th century, which paradoxically coincided with improved standards of living and nutrition, has its origin in fetal life. Indeed, there is substantial evidence associating low birthweight because of fetal growth restriction with an increased risk of vascular disease in later adult life. These conclusions led to the second part of the Barker hypothesis, the thrifty phenotype, in which adaptation to undernutrition in fetal life leads to permanent metabolic and endocrine changes. Such changes are beneficial if the undernutrition persists after birth but may predispose the individual to obesity and impaired glucose tolerance if conditions improve. The hypothesis assumes that a poor nutrient supply during a critical period of in utero life may "program" a permanent structural or functional change in the fetus, thereby altering the distribution of cell types, gene expression, or both. The fetus, in response to placental undernutrition and to maintain sufficient vascular supply to the brain, decreases resistance to blood flow in the middle cerebral artery. Simultaneously, because of the limited blood supply to the fetus, the arterial redistribution process is accompanied by increased resistance to flow to other fetal vital organs, such as the heart, kidneys, liver, and pancreas. It may explain why individuals exposed to ischemic changes in utero develop dyslipidemia, lower nephron number, and impaired glucose tolerance, all factors contributing to metabolic syndrome later in life. Nevertheless, support for the hypotheses comes mainly from studies in rodents and retrospective epidemiologic studies. This review focused on ultrasound and Doppler studies of human fetal growth restriction in several fetal organs: the placenta, fetal circulation, brain, heart, kidneys, adrenal glands, liver, and pancreas. Support for the hypothesis was provided by animal studies involving conditions that create fetuses with growth restriction with effects on various fetal organs and by human studies that correlate impaired fetal circulation with the in utero development and function of fetal organs.

3-D Echo Brain Volumes to Predict Neurodevelopmental Outcome in Infants: A Prospective Observational Follow-up Study

Prematurity and intra-uterine growth restriction (IUGR) are risk factors for long-term poor neurodevelopmental outcomes and are associated with reductions in regional brain volumes. In this study, the aim was to determine the possible role of 3-D ultrasonography (3-DUS) volumes of whole brain, thalamus, frontal cortex and cerebellum, measured at postnatal days 30-40, as early predictors of long-term risk for neurobehavioral disorders. To this purpose, a heterogeneous population of full-term, preterm, IUGR and preterm IUGR (pre-IUGR) born individuals (n = 334), characterized by gestational age and birth weight in the ranges 24-41 wk and 860-4000 g, respectively, was followed from postnatal days 30-40 to the second year of life. At enrollment, brain volumes were measured using 3-DUS, whereas neurodevelopment was assessed at 2 y using the Griffiths III test. Cerebral volumes were strictly and significantly lower in infants characterized by a negative outcome and had excellent diagnostic accuracy. The 3-DUS volume of whole brain, thalamus, frontal cortex or cerebellum may be an early predictor of neonates at major risk for neurobehavioral disorders in later life.

Urinary Cystatin-C, a marker to assess and monitor neonatal kidney maturation and function: validation in twins

BACKGROUND

Nephrogenesis is a complex process of nephron formation and maturation that can be compromised by preterm delivery and intrauterine growth restriction. This study aimed to evaluate and compare urinary Cys-C levels with renal volume in a cohort of preterm and term twins, adequate for gestational age or intrauterine growth restricted, to investigate their values in different conditions of nephrogenesis.

METHODS

The study was performed on twins at 30-40 days of postnatal corrected age: renal volumes were measured by 3D ultrasound technology and urine samples were analyzed for Cystatin-C. A follow-up was performed by Cystatin-C.

RESULTS

Renal volumes in preterm and intrauterine growth-restricted twins showed values significantly lower than those observed in term twins and were inversely correlated to urinary Cystatin-C levels. During the follow-up, intrauterine growth-restricted twins showed amplified levels of urinary Cystatin-C; in contrast, invariable or decreased levels were observed in adequate for gestational age twins.

CONCLUSIONS

Urinary Cystatin-C, evaluated when intrauterine/extrauterine nephrogenesis could be considered completed, concurrently with renal volume assessment can improve the identification of neonates with initial kidney impairment. Its potential value as a useful marker in monitoring physiological/pathological renal conditions could be considered, mainly for neonates at elevated risk of developing long-term renal diseases.

IMPACT

Urinary Cys-C levels are inversely correlated to renal volumes and reflect nephrogenesis conditions. No data in literature are reported regarding: (a) the concurrent assessment of renal volumes and urinary levels of Cystatin-C in preterm and term twins with different conditions of gestational life, i.e., AGA and IUGR and (b) the follow-up of IUGR and preterm neonates using the urinary Cys-C determination. The variations of urinary Cys-C levels, observed in the follow-up of preterm and/or IUGR neonates, support the usefulness of monitoring those neonates with altered nephrogenesis, who are later at risk for renal impairment and for long-term renal diseases.

Urinary Nerve Growth Factor in full-term, preterm and intra uterine growth restriction neonates: Association with brain growth at 30-40 days of postnatal period and with neuro-development outcome at two years. A pilot study

Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF) are crucial for the peripheral and central nervous system development, respectively, and differential brain and blood levels in Intra Uterine Growth Restriction (IUGR) and prematurity have been found. As reduced growth of brain regions, measured at 30-40 days of postnatal period, has been demonstrated in preterm and IUGR neonates who showed impaired neuro-development at two years of age, in this study, the levels of NGF and BDNF were evaluated in the urine samples of 30-40 day-old subjects who were full-term, preterm and IUGR and showed a normal or an abnormal neuro-development at follow up after two years. Neurotrophins were measured concurrently with volumes of whole brain, thalamus, frontal cortex and cerebellum. Values were then correlated with later neuro-developmental outcome. Biochemical parameters and cerebral volumes were assessed using colorimetric ELISA kits and three-dimensional ultra-sonography (3DUS), respectively. Neuro-development was estimated using the Griffiths-II test. Urinary NGF and brain volumes significantly correlated and were lower in preterm and IUGR subjects characterized by poor neuro-development. No differences were seen in the case of BDNF. The present investigation demonstrates, for the first time, the strong and direct association of NGF with brain growth at the initial phase of the postnatal period and with neuro-developmental outcome in later life. Remarkably, urinary NGF may be suggested as an early prognostic indicator of high long-term risk of motor and cognitive impairment in IUGR and preterm neonates.

Programmed Adult Kidney Disease: Importance of Fetal Environment

The Barker hypothesis strongly supported the influence of fetal environment on the development of chronic diseases in later life. Multiple experimental and human studies have identified that the deleterious effect of fetal programming commonly leads to alterations in renal development. The interplay between environmental insults and fetal genome can induce epigenetic changes and lead to alterations in the expression of renal phenotype. In this review, we have explored the renal development and its functions, while focusing on the epigenetic findings and functional aspects of the renin-angiotensin system and its components.

Postnatal serum creatinine is elevated in preterm infants with PPROM-induced anhydramnios

BACKGROUND

The reason for increased serum creatinine levels in preterm infants often remains unclear. We aimed to determine whether postnatal serum creatinine in preterm infants correlates with intake of amniotic fluid, represented by the amount of amniotic fluid after preterm premature rupture of membranes (PPROM).

METHODS

74 preterm infants with PPROM > 48 h duration were retrospectively studied. Postnatal creatinine concentration was determined at day 2-5, 10-17 and 26-33 of life and compared between infants with normal intrauterine amniotic volumes, oligohydramnios and anhydramnios.

RESULTS

Mean gestational age of included patients was 29.7 weeks (range: 24.0-36.1 weeks) and mean birth weight was 1452 g (range: 560-2940 g). Serum creatinine concentration was similar at day 2-5 and day 10-17 of life between the three groups. We observed a significant decrease in creatinine concentration from day 2-5 to day 26-33 in infants with normal amniotic fluid volume and oligohydramnios (p = 0.0001 and p = 0.0071, respectively), but not in anhydramnios. On day 26-33 of life, infants with anhydramnios showed significantly higher creatinine levels compared to infants with normal amniotic fluid volume and oligohydramnios (p = 0.0211).

CONCLUSION

Postnatal serum creatinine of preterm infants at day 26-33 of life is elevated in infants with PPROM-induced anhydramnios, but not in oligohydramnios.

Deletion of hypoxia-responsive microRNA-210 results in a sex-specific decrease in nephron number

Low nephron number results in an increased risk of developing hypertension and chronic kidney disease. Intrauterine growth restriction is associated with a nephron deficit in humans, and is commonly caused by placental insufficiency, which results in fetal hypoxia. The underlying mechanisms by which hypoxia impacts kidney development are poorly understood. microRNA-210 is the most consistently induced microRNA in hypoxia and is known to promote cell survival in a hypoxic environment. In this study, the role of microRNA-210 in kidney development was evaluated using a global microRNA-210 knockout mouse. A male-specific 35% nephron deficit in microRNA-210 knockout mice was observed. Wnt/β-catenin signaling, a pathway crucial for nephron differentiation, was misregulated in male kidneys with increased expression of the canonical Wnt target lymphoid enhancer binding factor 1. This coincided with increased expression of caspase-8-associated protein 2, a known microRNA-210 target and apoptosis signal transducer. Together, these data are consistent with a sex-specific requirement for microRNA-210 in kidney development.

Length of gestation and birth weight are associated with indices of combined kidney biomarkers in early childhood

Infants born prematurely or with low birth weights are more susceptible to kidney dysfunction throughout their lives. Multiple proteins measured in urine are noninvasive biomarkers of subclinical kidney damage, but few studies have examined the joint effects of multiple biomarkers. We conducted an exploratory study of 103 children in the Programing Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) longitudinal birth cohort, and measured nine proteins selected a priori in banked spot urine samples collected at ages 4-6. The goal of our study was to explore the combined effects of kidney damage biomarkers previously associated with birth outcomes. To do this, we generated kidney biomarker indices using weighted quantile sum regression and assessed associations with length of gestation or birth weight. A decile increase in each kidney biomarker index was associated with 2-day shorter gestations (β = -2.0, 95% CI: -3.2, -0.9) and 59-gram lower birth weights (β = -58.5, 95% CI: -98.3, -18.7), respectively. Weights highlighting the contributions showed neutrophil gelatinase-associated lipocalin (NGAL) (60%) and osteopontin (19%) contributed most to the index derived for gestational age. NGAL (66%) and beta-2-microglobulin (10%) contributed most to the index derived for birth weight. Joint analyses of multiple kidney biomarkers can provide integrated measures of kidney dysfunction and improved statistical assessments compared to biomarkers assessed individually. Additionally, shorter gestations and lower birth weights may contribute to subclinical kidney damage measurable in childhood.

Renal Consequences of Gestational Diabetes Mellitus in Term Neonates: A Multidisciplinary Approach to the DOHaD Perspective in the Prevention and Early Recognition of Neonates of GDM Mothers at Risk of Hypertension and Chronic Renal Diseases in Later Life

Fetal exposure to gestational diabetes mellitus (GDM) seems to stimulate a negative impact on the kidneys. Renal volumes and urinary biomarkers of renal function and tubular impairment and injury were evaluated in 30–40-day old newborns of GDM mothers (n = 139) who needed insulin therapy during pregnancy. We found that neonates of mothers who maintained strict control over normoglycemia (n = 65) during pregnancy and fulfilled the other criteria of the GDM management program showed no differences compared to control (n = 55). Conversely, those (n = 74), whose mothers did not maintain glycemic control and were not compliant to the management program, exhibited significantly lower levels of renal volumes and higher activity of N-acetyl-β-d-glucosaminidase and cathepsin B. Differences due to maternal pre-gestational and gestational body mass index (BMI) as well as to maternal weight gain were demonstrated. Our findings indicate that a multidisciplinary approach, which involves an appropriate management of GDM, prevents the negative effects of GDM on the kidneys at 30–40 days of postnatal age, indicating the fundamental role of glycemic control, as well as of an adequate range of maternal weight gain. Total renal volume, cortical volume, and urinary activity of N-acetyl-β-d-glucosaminidase and cathepsin B may be suggested as indicators for the early recognition of GDM neonates at long-term risk of hypertension and kidney disease.

Neonatal Morbidities of Fetal Growth Restriction: Pathophysiology and Impact

Being born small lays the foundation for short-term and long-term implications for life. Intrauterine or fetal growth restriction describes the pregnancy complication of pathological reduced fetal growth, leading to significant perinatal mortality and morbidity, and subsequent long-term deficits. Placental insufficiency is the principal cause of FGR, which in turn underlies a chronic undersupply of oxygen and nutrients to the fetus. The neonatal morbidities associated with FGR depend on the timing of onset of placental dysfunction and growth restriction, its severity, and the gestation at birth of the infant. In this review, we explore the pathophysiological mechanisms involved in the development of major neonatal morbidities in FGR, and their impact on the health of the infant. Fetal cardiovascular adaptation and altered organ development during gestation are principal contributors to postnatal consequences of FGR. Clinical presentation, diagnostic tools and management strategies of neonatal morbidities are presented. We also present information on the current status of targeted therapies. A better understanding of neonatal morbidities associated with FGR will enable early neonatal detection, monitoring and management of potential adverse outcomes in the newborn period and beyond.

The Multifaceted Role of the Lysosomal Protease Cathepsins in Kidney Disease

Kidney disease is worldwide the 12th leading cause of death affecting 8–16% of the entire population. Kidney disease encompasses acute (short-lasting episode) and chronic (developing over years) pathologies both leading to renal failure. Since specific treatments for acute or chronic kidney disease are limited, more than 2 million people a year require dialysis or kidney transplantation. Several recent evidences identified lysosomal proteases cathepsins as key players in kidney pathophysiology. Cathepsins, originally found in the lysosomes, exert important functions also in the cytosol and nucleus of cells as well as in the extracellular space, thus participating in a wide range of physiological and pathological processes. Based on their catalytic active site residue, the 15 human cathepsins identified up to now are classified in three different families: serine (cathepsins A and G), aspartate (cathepsins D and E), or cysteine (cathepsins B, C, F, H, K, L, O, S, V, X, and W) proteases. Specifically in the kidney, cathepsins B, D, L and S have been shown to regulate extracellular matrix homeostasis, autophagy, apoptosis, glomerular permeability, endothelial function, and inflammation. Dysregulation of their expression/activity has been associated to the onset and progression of kidney disease. This review summarizes most of the recent findings that highlight the critical role of cathepsins in kidney disease development and progression. A better understanding of the signaling pathways governed by cathepsins in kidney physiopathology may yield novel selective biomarkers or therapeutic targets for developing specific treatments against kidney disease.

Renal consequences of preterm birth

Background

The developmental origin of health and disease concept identifies the brain, cardiovascular, liver, and kidney systems as targets of fetal adverse programming with adult consequences. As the limits of viability in premature infants have been pushed to lower gestational ages, the long-term impact of prematurity on kidneys still remains a significant burden during hospital stay and beyond.

Objectives

The purpose of this study is to summarize available evidence, mechanisms, and short- and long-term renal consequences of prematurity and identify nephroprotective strategies and areas of uncertainty.

Results

Kidney size and nephron number are known to be reduced in surviving premature infants due to disruption of organogenesis at a crucial developmental time point. Inflammation, hyperoxia, and antiangiogenic factors play a role in epigenetic conditioning with potential life-long consequences. Additional kidney injury from hypoperfusion and nephrotoxicity results in structural and functional changes over time which are often unnoticed. Nephropathy of prematurity and acute kidney injury confound glomerular and tubular maturation of preterm kidneys. Kidney protective strategies may ameliorate growth failure and suboptimal neurodevelopmental outcomes in the short term. In later life, subclinical chronic renal disease may progress, even in asymptomatic survivors.

Conclusion

Awareness of renal implications of therapeutic interventions and renal conservation efforts may lead to a variety of short and long-term benefits. Adequate monitoring and supplementation of microelement losses, gathering improved data on renal handling, and exploration of new avenues such as reliable markers of injury and new therapeutic strategies in contemporary populations, as well as long-term follow-up of renal function, is warranted.