Effect of postnatal high-protein diet on kidney function of rats exposed to intrauterine protein restriction

Early-life exposures and long-term health: adverse gestational environments and the programming of offspring renal and vascular disease

According to the Developmental Origins of Health and Disease hypothesis, exposure to certain environmental influences during early life may be a key determinant of fetal development and short- and long-term offspring health. Indeed, adverse conditions encountered during the fetal, perinatal, and early childhood stages can alter normal development and growth, as well as put the offspring at elevated risk of developing long-term health conditions in adulthood, including chronic kidney disease and cardiovascular diseases. Of relevance in understanding the mechanistic basis of these long-term health conditions are previous findings showing low glomerular number in human intrauterine growth restriction and low birth weight-indicators of a suboptimal intrauterine environment. In different animal models, the main suboptimal intrauterine conditions studied relate to maternal dietary manipulations, poor micronutrient intake, prenatal ethanol exposure, maternal diabetes, glucocorticoid and chemical exposure, hypoxia, and placental insufficiency. These studies have demonstrated changes in kidney structure, glomerular endowment, and expression of key genes and signaling pathways controlling endocrine, excretion, and filtration function of the offspring. This review aims to summarize those studies to uncover the effects and mechanisms by which adverse gestational environments impact offspring renal and vascular health in adulthood. This is important for identifying agents and interventions that can prevent and mitigate the long-term consequences of an adverse intrauterine environment on the subsequent generation.NEW & NOTEWORTHY Human data and experimental animal data show that suboptimal environments during fetal development increase the risk of renal and vascular diseases in adult-life. This is related to permanent changes in kidney structure, function, and expression of genes and signaling pathways controlling filtration, excretion, and endocrine function. Uncovering the mechanisms by which offspring renal development and function is impacted is important for identifying ways to mitigate the development of diseases that strain health care services worldwide.

Protective role of endorepellin in renal developmental programming

Adverse intrauterine and early postnatal environment cause reduced nephron endowment and subsequent hypertension, chronic kidney disease (CKD). Exploring modifiable approaches is particularly important to alleviate the global burden of CKD. Enhanced glomerular progenitor cell apoptosis is a major contributor to renal developmental programming. The differentially expressed protein perlecan, which we previously identified using proteomics, is an important extracellular matrix glycoprotein, and its domain V (endorepellin) can inhibit apoptosis through a paracrine form. In explanted mice embryonic metanephros, we found that endorepellin can rescue glomeruli-deficit phenotype resulting from malnutrition, and this protective effect was also verified in vivo using a renal developmental programming model which was given a low-protein diet during pregnancy. We further demonstrated that endorepellin significantly inhibited glomerular progenitor cell apoptosis which activates ERK1/2 phosphorylation. Our results show that endorepellin rescues the nephron number reduction in renal developmental programming, possibly through the inhibition of progenitor cell apoptosis via the ERK1/2 pathway.

Chorioamnionitis Causes Kidney Inflammation, Podocyte Damage, and Pro-fibrotic Changes in Fetal Lambs

BACKGROUND

Perinatal complications, such as prematurity and intrauterine growth restriction, are associated with increased risk of chronic kidney disease. Although often associated with reduced nephron endowment, there is also evidence of increased susceptibility for sclerotic changes and podocyte alterations. Preterm birth is frequently associated with chorioamnionitis, though studies regarding the effect of chorioamnionitis on the kidney are scarce. In this study, we aim to unravel the consequences of premature birth and/or perinatal inflammation on kidney development using an ovine model.

METHODS

In a preterm sheep model, chorioamnionitis was induced by intra-amniotic injection of lipopolysaccharide (LPS) at either 2, 8, or 15 days prior to delivery. Control animals received intra-amniotic injections of sterile saline. All lambs were surgically delivered at 125 days' gestation (full term is 150 days) and immediately euthanized for necropsy. Kidneys were harvested and processed for staining with myeloperoxidase (MPO), Wilms tumor-1 (WT1) and alpha-smooth muscle actine (aSMA). mRNA expression of tumor necrosis factor alpha (TNFA), Interleukin 10 (IL10), desmin (DES), Platelet derived growth factor beta (PDGFB), Platelet derived growth factor receptor beta (PDGFRB), synaptopodin (SYNPO), and transforming growth factor beta (TGFB) was measured using quantitative PCR.

RESULTS

Animals with extended (but not acute) LPS exposure had an inflammatory response in the kidney. MPO staining was significantly increased after 8 and 15 days (p = 0.003 and p = 0.008, respectively). Expression of TNFA (p = 0.016) and IL10 (p = 0.026) transcripts was increased, peaking on day 8 after LPS exposure. Glomerular aSMA and expression of TGFB was increased on day 8, suggesting pro-fibrotic mesangial activation, however, this was not confirmed with PDFGB or PDGFRB. The number of WT1 positive nuclei in the glomerulus, as well as expression of synaptopodin, decreased, indicating podocyte injury.

CONCLUSION

We report that, in an ovine model of prematurity, LPS-induced chorioamnionitis leads to inflammation of the immature kidney. In addition, this process was associated with podocyte injury and there are markers to support pro-fibrotic changes to the glomerular mesangium. These data suggest a potential important role for antenatal inflammation in the development of preterm-associated kidney disease, which is frequent.

Elevated blood pressure in high-fat diet-exposed low birthweight rat offspring is most likely caused by elevated glucocorticoid levels due to abnormal pituitary negative feedback

Being delivered as a low birthweight (LBW) infant is a risk factor for elevated blood pressure and future problems with cardiovascular and cerebellar diseases. Although premature babies are reported to have low numbers of nephrons, some unclear questions remain about the mechanisms underlying elevated blood pressure in full-term LBW infants. We previously reported that glucocorticoids increased miR-449a expression, and increased miR-449a expression suppressed Crhr1 expression and caused negative glucocorticoid feedback. Therefore, we conducted this study to clarify the involvement of pituitary miR-449a in the increase in blood pressure caused by higher glucocorticoids in LBW rats. We generated a fetal low-carbohydrate and calorie-restricted model rat (60% of standard chow), and some individuals showed postnatal growth failure caused by growth hormone receptor expression. Using this model, we examined how a high-fat diet (lard-based 45kcal% fat)-induced mismatch between prenatal and postnatal environments could elevate blood pressure after growth. Although LBW rats fed standard chow had slightly higher blood pressure than control rats, their blood pressure was significantly higher than controls when exposed to a high-fat diet. Observation of glomeruli subjected to periodic acid methenamine silver (PAM) staining showed no difference in number or size. Aortic and cardiac angiotensin II receptor expression was altered with compensatory responses. Blood aldosterone levels were not different between control and LBW rats, but blood corticosterone levels were significantly higher in the latter with high-fat diet exposure. Administration of metyrapone, a steroid synthesis inhibitor, reduced blood pressure to levels comparable to controls. We showed that high-fat diet exposure causes impairment of the pituitary glucocorticoid negative feedback via miR-449a. These results clarify that LBW rats have increased blood pressure due to high glucocorticoid levels when they are exposed to a high-fat diet. These findings suggest a new therapeutic target for hypertension of LBW individuals.

Low Birth Weight, Blood Pressure and Renal Susceptibility

PURPOSE OF THE REVIEW

The purpose of this review is to highlight the clinical significance of increased renal risk that has its origins in fetal life. This review will also discuss the critical need to identify therapeutic interventions for use in a pregnancy complicated by placental dysfunction and intrauterine growth restriction that can mitigate the developmental origins of kidney disease without inflicting additional harm on the developing fetus.

RECENT FINDINGS

A reduction in nephron number is a contributory factor in the pathogenesis of hypertension and kidney disease in low birth weight individuals. Reduced nephron number may heighten susceptibility to a secondary renal insult, and recent studies suggest that perinatal history including birth weight should be considered in the assessment of renal risk in kidney donors. This review highlights current findings related to placental dysfunction, intrauterine growth restriction, increased risk for renal injury and disease, and potential therapeutic interventions.

Decreased H3K9ac level of AT2R mediates the developmental origin of glomerulosclerosis induced by prenatal dexamethasone exposure in male offspring rats

This study aimed to demonstrate that prenatal dexamethasone exposure (PDE) can induce kidney dysplasia in utero and adult glomerulosclerosis in male offspring, and to explore the underlying intrauterine programming mechanisms. Pregnant rats were subcutaneously administered dexamethasone 0.2 mg/kg.d from gestational day (GD) 9 to GD20. The male fetus on GD20 and the adult offspring at age of postnatal week 28 were analyzed. The adult offspring kidneys in the PDE group displayed glomerulosclerosis, elevated levels of serum creatinine and urine protein, ultrastructural damage of podocytes, the reduced expression levels of podocyte marker genes, nephrin and podocin. The histone 3 lysine 9 acetylation (H3K9ac) level in the promoter of renal angiotensin II receptor type 2 (AT2R) and its expression were reduced, whereas the angiotensin II receptor type 1a (AT1aR)/AT2R expression ratio was increased. The fetal kidneys in the PDE group displayed an enlarged Bowman's space and a shrunken glomerular tuft, a reduced cortex width and an increase in the nephrogenic zone/cortical zone ratio, reduced the expression level of glial-cell-line derived neurotrophic factor/c-Ret tyrosine kinase receptor (GDNF/c-Ret) signal pathway and podocyte marker genes. Moreover, the H3K9ac and H3K27ac levels of AT2R as well as the gene and protein expression levels of AT2R in fetal kidneys were inhibited by PDE. In vitro, primary metanephric mesenchyme stem cells (MMSCs) were treated with dexamethasone. Overexpression of AT2R reversed the inhibited expression of GDNF/c-Ret and podocin/nephrin induced by dexamethasone, and glucocorticoids receptor antagonist abolished the decreased H3K9ac level and gene expression of AT2R. In conclusion, PDE induced the offspring's kidney dysplasia as well as adult glomerulosclerosis, which was mediated by a sustained decrease in renal AT2R expression via decreasing the H3 K9ac level.

Progression of renal fibrosis in congenital CKD model rats with reduced number of nephrons

A congenital reduction in the number of nephrons is a critical risk factor for both onset of chronic kidney disease (CKD) and its progression to end-stage kidney disease (ESKD). Hypoplastic kidney (HPK) rats have only about 20% of the normal number of nephrons and show progressive CKD. This study used an immunohistological method to assess glomerular and interstitial pathogenesis in male HPK rats aged 35-210days. CD68 positive-macrophages were found to infiltrate into glomeruli in HPK rats aged 35 and 70days and to infiltrate into interstitial tissue in rats aged 140 and 210days. HPK rats aged 35 and 70days showed glomerular hypertrophy, loss of normal linear immunostaining of podocine, and increased expression of PDGFr-β, TGF-β, collagens, and fibronectin, with all of these alterations gradually deteriorating with age. α-SMA-positive myofibroblasts were rarely detected in glomerular tufts, whereas α-SMA-positive glomerular parietal epithelium (GPE) cells were frequently observed along Bowman's capsular walls. The numbers of PDGFr-β-positive fibroblasts in interstitial tissue were increased in rats aged 35days and older, whereas interstitial fibrosis, characterized by the increased expression of tubular PDGF-BB, the appearance of myofibroblasts doubly positive for PDGFr-β and α-SMA, and increased expression of collagens and fibronectin, were observed in rats aged 70 and older. These results clearly indicate that congenital CKD with only 20% of nephrons cause renal fibrosis in rats.

Higher protein intake is associated with increased risk for incident end-stage renal disease among blacks with diabetes in the Southern Community Cohort Study

BACKGROUND AND AIMS

Diabetes, a risk factor for end-stage renal disease (ESRD), is associated with impaired protein metabolism. We investigated whether protein intake is associated with ESRD and whether the risk is higher among blacks with diabetes.

METHODS AND RESULTS

We conducted a nested case-control study of ESRD within the Southern Community Cohort Study, a prospective study of low-income blacks and whites in the southeastern US (2002-2009). Through 2012, 1057 incident ESRD cases were identified by linkage with the United States Renal Data System and matched to 3198 controls by age, sex, and race. Dietary intakes were assessed from a validated food frequency questionnaire at baseline. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed from logistic regression models that included matching variables, BMI, education, income, hypertension, total energy intake, and percent energy from saturated and polyunsaturated fatty acids. Mean (±SD) daily energy intake from protein was higher among ESRD cases than controls (15.7 ± 3.3 vs. 15.1 ± 3.1%, P < 0.0001). For a 1% increase in percent energy intake from protein, the adjusted ORs (95% CIs) for ESRD were 1.06 (1.02-1.10) for blacks with diabetes, 1.02 (0.98-1.06) for blacks without diabetes, 0.99 (0.90-1.09) for whites with diabetes and 0.94 (0.84-1.06) for whites without diabetes. Protein intake in g/kg/day was also associated with ESRD (4th vs. 1st quartile OR = 1.76; 95% CI: 1.17-2.65).

CONCLUSION

Our results raise the possibility that among blacks with diabetes, increased dietary protein is associated with increased incidence of ESRD. Studies on how protein intake and metabolism affect ESRD are needed.

The Effect of a High-Protein Diet and Exercise on Cardiac AQP7 and GLUT4 Gene Expression

High-protein (HP) diets are commonly consumed by athletes despite their potential health hazard, which is postulated to enforce a negative effect on bone and renal health. However, its effects on heart have not been known yet. Aquaporin-7 (AQP7) is an aquaglyceroporin that facilitates glycerol and water transport. Glycerol is an important cardiac energy production substrate, especially during exercise, in conjunction with fatty acids and glucose. Glucose transporter 4 (GLUT4) is an insulin-sensitive glucose transporter in heart. We aimed to investigate the effect of HPD on AQP7 and GLUT4 levels in the rat heart subjected to exercise. Male Sprague-Dawley rats were divided into control (n = 12), exercise (E) training (n = 10), HPD (n = 12), and HPD-E training (n = 9) groups. The HPD groups were fed a 45 % protein-containing diet 5 weeks. The HPD-E and E groups were performed the treadmill exercise during the 5-week study period. Real-time polymerase chain reaction and immunohistochemistry techniques were used to determine the gene expression and localization of AQP7 and GLUT4 in heart tissue. Results of relative gene expression were calculated by the 'Pfaffl' mathematical method using the REST program. Differences in AQP7 and GLUT4 gene expression were expressed as fold change compared to the control group. Heart weight/tibia ratio and ventricular wall thickness were evaluated as markers of cardiac hypertrophy. Further, serum glucose, glycerol, and insulin levels were also measured. AQP7 gene expression was found to be increased in the E (3.47-fold, p < 0.001), HPD (5.59-fold, p < 0.001), and HPD-E (3.87-fold, p < 0.001) groups compared to the control group. AQP7 protein expression was also increased in the HPD and HPD-E groups (p < 0.001). Additionally, cardiac mRNA expression levels of GLUT4 showed a significant increase in the E (2.16-fold, p < 0.003), HPD (7.14-fold, p < 0.001), and HPD-E (3.43-fold, p < 0.001) groups compared to the control group. GLUT4 protein expression was significantly increased in the E, HPD, and HPD-E groups compared to the control group (p = 0.024, p < 0.001, and p < 0.001, respectively). Furthermore, Serum glucose levels were significantly different between groups (p < 0.005). This difference was observed between the HPD groups and normal-protein diet groups (C and E). Serum insulin levels were higher for HPD groups compared with the normal-protein diet groups (p < 0.001), whereas no differences were observed between the exercise and sedentary groups (p = 0.111). Serum glycerol levels were significantly increased in the HPD groups compared with control and E groups (p < 0.05 and p < 0.05, respectively). Consumption of HPD supplementation caused the increased effects on AQP7 and GLUT4 expression in rat heart.

Maternal protein restriction that does not have an influence on the birthweight of the offspring induces morphological changes in kidneys reminiscent of phenotypes exhibited by intrauterine growth retardation rats

Severe restriction of maternal protein intake to 6-8% protein diet results in intrauterine growth retardation (IUGR), low birthweight and high risk of metabolic syndrome in the adult life of the offspring. However, little information is available on the effects of maternal protein restriction on offspring under the conditions that does not have an influence on their birthweight of the offspring,. In the present study, pregnant rats were kept on a diet consisting of either 9% (low-protein, Lp rats) or 18% (normal-protein, Np rats) protein by weight/volume/etc. After birth, both Lp and Np rats were kept on a diet containing 18% protein. Neonatal body weight was significantly lower in Lp rats compared to Np rats from 4 days to 5 weeks after birth. While glomerular number per unit volume (1 mm(3) ) of the kidney (Nv) was comparable between Lp and Np rats 4 weeks after birth, the Nv was significantly decreased in Lp rats at 20 weeks after birth. Four and 20 weeks after birth, glomerular sclerosis index, interstitial fibrosis score, and ratio of ED1-positive cell ratio were all significantly higher in Lp compared to Np rats. Transforming growth factor-β1-positive cells were observed in the distal tubules in the kidney of 4- and 20-week-old Lp rats kidneys, but not in those of age-matched Np rats. Altogether, these findings revealed that maternal protein restriction that does not have an influence on the birthweight of the offspring, induces similar changes as those seen in the kidneys of IUGR neonates.

High protein intake in neonatal period induces glomerular hypertrophy and sclerosis in adulthood in rats born with IUGR

BACKGROUND

Intrauterine growth restriction (IUGR) and postnatal nutrition are risk factors for cardiovascular and renal diseases in both humans and animals. The long-term renal effects of protein intake early in life remain unknown. The objective was to evaluate the effects of a neonatal feeding with high protein (HP) milk on renal functions and structure in IUGR male rats.

METHODS

Maternal gestational low protein diet was used to produce IUGR. At day 5, IUGR pups were gastrostomized in the "pup-in-the cup" model and received either normal protein (NP) milk or HP (+50% protein content) milk until day 21. After weaning, the animals were fed the same standard diet. Renal functions and structure were assessed at postnatal day 18 (D18) and in adult offspring.

RESULTS

During the preweaning period, the postnatal weight gain between the two groups was unaffected. On D18, kidneys from HP offspring were heavier with significant glomerular hypertrophy (+40%, P < 0.05). HP diet was associated with significant proteinuria and glomerulosclerosis (+49%, P < 0.05). Glomerular number was unaltered.

CONCLUSION

Neonatal HP feeding following IUGR affects renal functions and structure at adulthood. These alterations may result from a single nephron glomerular hyperfiltration.

Postnatal high-protein diet improves learning and memory in premature rats via activation of mTOR signaling

PURPOSE

The present study investigated whether a high-protein diet affects spatial learning and memory in premature rats via modulation of mammalian target of rapamycin (mTOR) signaling.

METHODS

Pre- and full-term Sprague-Dawley pups were fed a normal (18% protein) or high-protein (30% protein) diet (HPD) for 6 or 8 weeks after weaning. Spatial learning and memory were tested in the Morris water maze at week 6 and 8. The activation of mTOR signaling pathway components was evaluated by western blotting.

RESULTS

Spatial memory performance of premature rats consuming a normal and HPD was lower than that of full-term rats on the same diet at 6 weeks, and was associated with lower levels of ribosomal protein S6 kinase p70 subtype (p70S6K) and initiation factor 4E-binding protein 1 (4EBP1) phosphorylation in the hippocampus. Spatial memory was improved in 8-week-old premature rats on an HPD as compared to those on a normal diet. Premature rats on an HPD had p70S6K and 4EBP1 phosphorylation levels in the hippocampus that were comparable to those of full-term rats on an HPD.

CONCLUSION

Long-term consumption of a protein-rich diet can restore the impairment in learning and memory in pre-term rats via upregulation of mTOR/p70S6K signaling.

Dietary restriction in moderately obese rats improves body size and glucose handling without the renal and hepatic alterations observed with a high-protein diet

Obesity is increasing worldwide, and high-protein (HP) diets are widely used for weight loss. However, the overall safety of HP diets is not well established in obese individuals, who make up a significant proportion of the population. To evaluate the health effects of an HP diet in obesity, obesity-prone (OP) Sprague-Dawley rats were given high-fat diets for 12 weeks to induce obesity. Following this, for 8 more weeks, these rats were given either a normal-protein (NP) (15% of energy) or an HP (35% of energy) diet ad libitum, or the NP diet at a restricted level to achieve body weights similar to those of the HP group (pair-weighted (PW) group). Obesity-resistant (OR) control rats were also given the NP diet throughout the feeding period. The HP-OP group had higher food intake but lower body weight, improved glucose handling, and lowered serum haptoglobin compared with the NP-OP group. These benefits were also observed in PW-OP rats. In addition, PW-OP rats had less fat accumulation when compared with NP-OP rats, and an improved Lee index, lower liver size, and lower serum alanine aminotransferase when compared with HP-OP rats. On the other hand, kidney size, proteinuria, and serum homocysteine were increased in HP-OP rats compared with NP-OP rats, whereas PW-OP rats did not experience these effects. These results indicate that in obese rats, more benefits are obtained via dietary restriction with an NP diet and without some of the potentially detrimental effects of an HP diet.

Developmental origins of chronic renal disease: an integrative hypothesis

Cardiovascular diseases are one of the leading causes of mortality. Hypertension (HT) is one of the principal risk factors associated with death. Chronic kidney disease (CKD), which is probably underestimated, increases the risk and the severity of adverse cardiovascular events. It is now recognized that low birth weight is a risk factor for these diseases, and this relationship is amplified by a rapid catch-up growth or overfeeding during infancy or childhood. The pathophysiological and molecular mechanisms involved in the “early programming” of CKD are multiple and partially understood. It has been proposed that the developmental programming of arterial hypertension and chronic kidney disease is related to a reduced nephron endowment. However, this mechanism is still discussed. This review discusses the complex relationship between birth weight and nephron endowment and how early growth and nutrition influence long term HT and CKD. We hypothesize that fetal environment reduces moderately the nephron number which appears insufficient by itself to induce long term diseases. Reduced nephron number constitutes a “factor of vulnerability” when additional factors, in particular a rapid postnatal growth or overfeeding, promote the early onset of diseases through a complex combination of various pathophysiological pathways.

The fetal origins of hypertension: a systematic review and meta-analysis of the evidence from animal experiments of maternal undernutrition

OBJECTIVE

Numerous experiments in animals have been performed to investigate the effect of prenatal undernutrition on the development of hypertension in later life, with inconclusive results. We systematically reviewed animal studies examining the effects of maternal undernutrition on SBP, DBP, and mean arterial blood pressure (BP) in offspring.

METHODS

A search was performed in Medline and Embase to identify articles that reported on maternal undernutrition and hypertension in experimental animal studies. Summary estimates of the effect of undernutrition on SBP, DBP, and mean arterial BP were obtained through meta-analysis.

RESULTS

Of the 6151 articles identified, 194 were considered eligible after screening titles and abstracts. After detailed evaluation, 101 met the inclusion criteria and were included in the review. Both maternal general and protein undernutrition increased SBP [general undernutrition: 14.5 mmHg, 95% confidence interval (CI) 10.8-18.3; protein undernutrition: 18.9 mmHg, 95% CI 16.1-21.8] and mean arterial BP (general undernutrition: 5.0 mmHg, 95% CI 1.4-8.6; protein undernutrition: 10.5 mmHg, 95% CI 6.7-14.2). There was substantial heterogeneity in the results. DBP was increased by protein undernutrition (9.5 mmHg, 95% CI 2.6-16.3), whereas general undernutrition had no significant effect.

CONCLUSION

The results of this meta-analysis generally support the view that in animals, maternal undernutrition--both general and protein--results in increased SBP and mean arterial BP. DBP was only increased after protein undernutrition. The results depended strongly on the applied measurement technique and animal model.

Physiopathology of intrauterine growth retardation: from classic data to metabolomics

It is well known that adverse conditions during intrauterine life, such as intrauterine growth restriction (IUGR), can result in permanent changes in the physiology and metabolism of the newborn, which in turn leads to an increased risk of disease in adulthood (fetal origin of adult disease hypothesis). In the first part of this review the epidemiological studies in which a correlation between low birth weight and chronic pathologies in adulthood was observed are reported. The second part of the review is focused on metabolomics studies that have revealed an altered metabolism in IUGR patients compared to controls. Together with more classic biomarkers of IUGR, such as endothelin-1, leptin, protein S100B and visfatin, the new holistic metabolomics approach has assumed a crescent role in the identification of disorders in the neonatal metabolic profile, determined by the interconnection of the different processes.

Urinary metabolomics in newborns and infants

Metabolomics is a new approach based on the systematic study of the full complement of metabolites in a biological sample. This technology consists of two sequential steps: (1) an experimental technique, based on nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry, designed to profile low-molecular-weight compounds, and (2) multivariate data analysis. The metabolomic analysis of biofluids or tissues has been successfully used in the fields of physiology, diagnostics, functional genomics, pharmacology, toxicology, and nutrition. Recent studies have evaluated how physiological variables or pathological conditions can affect metabolomic profiles of different biofluids in pediatric populations. The overall metabolic status of the neonate is little known. If more information on perinatal/neonatal maturational processes and their metabolic background were available, the management of sick or preterm newborns might be improved. Currently, the use of metabolomics in neonatology is still in the pioneering phase. Meaningful diagnostic information and simple, noninvasive collection techniques make urine a particularly suitable biofluid for metabolomic approach in neonatal medicine, although blood has also been investigated. Different fields of neonatology such as postnatal maturation, asphyxia/hypoxia, inborn errors of metabolism, nutrition, nephrouropathies, nephrotoxicity, cardiovascular diseases, and other conditions have been investigated using a metabolomic approach. Together with genomics and proteomics, metabolomics appears to be a promising tool in neonatology for the monitoring of postnatal metabolic maturation, the identification of biomarkers as early predictors of outcome, the diagnosis and monitoring of various diseases, and the "tailored" management of neonatal disorders.