The moth and the aspen tree: sodium in early postnatal development

Sodium as a subsidy in the spring: evidence for a phenology of sodium limitation

Understanding the factors that mediate carbon (C) cycling is increasingly important as anthropogenic activities and climate change alter ecosystems. Decomposition rates mediate C cycling and are in part regulated by sodium (Na) where Na is limiting up to some threshold after which Na becomes stressful and reduces decomposition rates (i.e., the Sodium Subsidy-Stress hypothesis). An overlooked pathway by which decomposers encounter increased salts like NaCl is through plants, which often take up Na in proportion to soil concentrations. Here we tested the hypothesis that Na addition through litter (detritus) and water and their interaction would impact detrital processing and leachate chemistry. Laboratory riparian soil mesocosms received either artificial litter (100% cellulose sponges) soaked in 0.05% NaCl (NaCl_L) or just H₂O (H₂O_L: control) and half of each litter treatment received weekly additions of 150 ml of either 0.05% NaCl water (NaCl_W) or just H₂O (H₂O_W: control). After 8 weeks decomposition was higher in NaCl addition treatments (both NaCl_L and NaCl_W and their combo) than controls (H₂O_L + H₂O_W) but reflected a unimodal relationship where the saltiest treatment (NaCl_L + NaCl_W) was only marginally higher than controls indicating a subsidy-stress response. Previous studies in this system found that Na addition in either water or litter decreased decomposition. However, differences may reflect a phenology of Na demand where Na-limitation increases in the spring (this study). These results indicate that our understanding of how Na impacts detrital processes, C cycling, and aquatic-terrestrial linkages necessitates incorporation of temporal dynamics.

Growth failure and metabolic acidosis due to total body sodium depletion in an infant with an ileostomy

Sodium is an essential nutrient and inadequate sodium intake and/or excessive sodium losses can result in suboptimal growth. Infants with ileostomies are at significant risk of developing growth failure as a result of excessive sodium loss in their ileostomy effluent. Chronic sodium depletion can also limit the kidney's ability to excrete hydrogen and potassium ions, mimicking electrolyte abnormalities found in type 4 renal tubular acidosis. This report describes an infant with an ileostomy with severe growth failure, hyperkalaemia and metabolic acidosis-all of which promptly resolved with sodium supplementation.

Dietary reference values for sodium

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) derived dietary reference values (DRVs) for sodium. Evidence from balance studies on sodium and on the relationship between sodium intake and health outcomes, in particular cardiovascular disease (CVD)-related endpoints and bone health, was reviewed. The data were not sufficient to enable an average requirement (AR) or population reference intake (PRI) to be derived. However, by integrating the available evidence and associated uncertainties, the Panel considers that a sodium intake of 2.0 g/day represents a level of sodium for which there is sufficient confidence in a reduced risk of CVD in the general adult population. In addition, a sodium intake of 2.0 g/day is likely to allow most of the general adult population to maintain sodium balance. Therefore, the Panel considers that 2.0 g sodium/day is a safe and adequate intake for the general EU population of adults. The same value applies to pregnant and lactating women. Sodium intakes that are considered safe and adequate for children are extrapolated from the value for adults, adjusting for their respective energy requirement and including a growth factor, and are as follows: 1.1 g/day for children aged 1-3 years, 1.3 g/day for children aged 4-6 years, 1.7 g/day for children aged 7-10 years and 2.0 g/day for children aged 11-17 years, respectively. For infants aged 7-11 months, an Adequate Intake (AI) of 0.2 g/day is proposed based on upwards extrapolation of the estimated sodium intake in exclusively breast-fed infants aged 0-6 months.

Reference ranges and impact of selected confounders on classic serum and urinary renal markers in neonatal period

PURPOSE

Renal injury in term and pre-term neonates may be an antecedent to chronic kidney disease in the child's further life. The aim of the paper was to compile a reference range for selected serum and urinary renal markers in the neonatal period for full-term (FT) and pre-term (PT) newborns.

MATERIAL AND METHODS

The prospective study included 23 FT infants (birth weight - BW≥2500g and gestational age - GA≥37Hbd) and 32 PT children (BW<2500g and GA<37Hbd) in good general condition, without acute kidney injury (AKI) or sepsis. Between the 4th and 28th DOL, urinary concentrations of the studied renal markers (uCr, uNa, uOsm) were determined on a daily basis, while serum creatinine (SCr) was assessed minimum every 48-72h.

RESULTS

The mean GA and BW of the FT and PT infants were respectively as follows: 38.5±1.7Hbd; 3433±495.2g and 32.7±2.6Hbd; 1836.7±419.8g. For serum glomerular (SCr, eGFR) and tubular markers (FENa, RFI), the median values with normal ranges were compiled. For urinary renal markers (uCr, uNa, uOsm) and those values standardized for kg of body weight, percentile tables for 4-28DOL were elaborated.

CONCLUSIONS

The study has resulted in determining the normal ranges of serum glomerular and tubular renal markers, as well as percentile tables of selected urinary renal parameters during the neonatal period. The percentile tables may prove to be helpful for further standardization of other urinary parameters per urinary creatinine in neonatal population.

Differential modification of enalapril in the kidneys of lean and 'programmed' obese male young rats

OBJECTIVE

We investigated whether enalapril treatment could have beneficial effects on nutritionally-programmed renal changes in postnatally overfed young rats.

METHODS

Three or 10 male pups per mother were assigned to either the Obese or Lean groups during the first 21 days of life. These pups were treated with enalapril (Obese enalapril, OE; Lean enalapril, LE) or vehicle (Obese control, OC; Lean control, LC) between 15 and 28 days. All pups had their kidneys examined at 29 days.

RESULTS

OC pups weighed more than those in the LC group between 7 and 28 days of age (P<0.05). Enalapril reduced body weights in rats from both the Obese and Lean groups between 22 and 28 days (P<0.05). Renal cell proliferation and apoptosis, glomerulosclerosis, and tubulointerstitial fibrosis were all increased by enalapril (P<0.05). Among the groups, renal cell apoptosis and serum creatinine were the highest in OE pups (P<0.05). Enalapril treatment resulted in contrasting molecular expression profiles involved in renal maturation and repair in the kidneys of the rats from the Lean and Obese groups.

CONCLUSION

Enalapril can differentially modulate renal molecular alterations in lean and postnatally overfed rats and may be not beneficial in obese young male rats.

Anthropogenic changes in sodium affect neural and muscle development in butterflies

The development of organisms is changing drastically because of anthropogenic changes in once-limited nutrients. Although the importance of changing macronutrients, such as nitrogen and phosphorus, is well-established, it is less clear how anthropogenic changes in micronutrients will affect organismal development, potentially changing dynamics of selection. We use butterflies as a study system to test whether changes in sodium availability due to road salt runoff have significant effects on the development of sodium-limited traits, such as neural and muscle tissue. We first document how road salt runoff can elevate sodium concentrations in the tissue of some plant groups by 1.5-30 times. Using monarch butterflies reared on roadside- and prairie-collected milkweed, we then show that road salt runoff can result in increased muscle mass (in males) and neural investment (in females). Finally, we use an artificial diet manipulation in cabbage white butterflies to show that variation in sodium chloride per se positively affects male flight muscle and female brain size. Variation in sodium not only has different effects depending on sex, but also can have opposing effects on the same tissue: across both species, males increase investment in flight muscle with increasing sodium, whereas females show the opposite pattern. Taken together, our results show that anthropogenic changes in sodium availability can affect the development of traits in roadside-feeding herbivores. This research suggests that changing micronutrient availability could alter selection on foraging behavior for some roadside-developing invertebrates.

Evaluation of sodium deficit in infants undergoing intestinal surgery

BACKGROUND

Sodium is a critical growth factor for children. Severe deficits cause growth impairment and cognitive dysfunction. Both the diagnosis and risk of sodium depletion in children undergoing intestinal surgery are poorly understood.

METHODS

With IRB approval, children undergoing intestinal surgery (2009-2012) who had a urine sodium measurement were retrospectively reviewed. Sodium deficits were defined: urine sodium <30 mmol/L and <10 mmol/L were deficient and severely deficient, respectively. Demographics, weight changes, and intake (sodium, fluid, and nutritional) were tabulated. Data were analyzed using regression analysis and Mann Whitney U tests.

RESULTS

Thirty-nine patients, 51.3% female, with a gestational age of 32.2 weeks and weight of 1.43 kg were identified. The most common diagnoses were NEC (38.5%), intestinal atresia (20.5%), and isolated perforation (10.3%). Sodium deficiency was documented in 36/39 (92%) and 92.9% for those in continuity. Severe deficiency occurred in 64%. Urine sodium was significantly correlated with weight gain (p=0.002). Weight gain in patients with urine sodium <30 mmol/L was significantly decreased vs. those ≥30 mmol/L (+0.58 g/d vs. +21.6 g/d, p=0.016).

CONCLUSION

In this population, sodium depletion is common in children undergoing intestinal surgery, even when the colon is in continuity. Correction of the sodium deficit to achieve urine sodium >30 mmol/L is associated with improved weight gain.

Acute kidney injury post neonatal asphyxia

Acute kidney injury (AKI) is a common consequence of perinatal asphyxia, occurring in up to 56% of these infants. A major difficulty in diagnosing this condition is the lack of a consensus definition of neonatal AKI, largely because of a dearth of specific measurable variables and biochemical markers. This review will discuss the current evidence regarding the epidemiology, investigation, and treatment of AKI in the asphyxiated neonate. Particular emphasis will be given to the investigation of renal function in the neonate and to potential biomarkers that may aid the clinician in the diagnosis of renal injury in this population.

Biobehavior of the human love of salt

We are beginning to understand why humans ingest so much salt. Here we address three issues: The first is whether our salt appetite is similar to that in animals, which we understand well. Our analysis suggests that this is doubtful, because of important differences between human and animal love of salt. The second issue then becomes how our predilection for salt is determined, for which we have a partial description, resting on development, conditioning, habit, and dietary culture. The last issue is the source of individual variation in salt avidity. We have partial answers to that too in the effects of perinatal sodium loss, sodium loss teaching us to seek salt, and gender. Other possibilities are suggested. From animal sodium appetite we humans may retain the lifelong enhancement of salt intake due to perinatal sodium loss, and a predisposition to learn the benefits of salt when in dire need. Nevertheless, human salt intake does not fit the biological model of a regulated sodium appetite. Indeed this archetypal 'wisdom of the body' fails us in all that has to do with behavioral regulation of this most basic need.

Effect of high volume intake of mother's milk with an individualized supplementation of minerals and protein on early growth of preterm infants <28 weeks of gestation

OBJECTIVE

A prospective study was designed to evaluate the effects of high volume intake of mother's milk fortified (FMM) with an individualized supplementation of minerals and protein on tolerance, short-term somatic growth, serum concentrations of calcium, phosphorus, alkaline phosphatase, and total plasma protein in healthy preterm infants below 28 weeks of gestation.

METHODS

Sixty preterm infants were included in the FMM group, for having received >80% or more of the milk volume as their own mother's milk at 3 weeks of postnatal age to 38 weeks of corrected gestational age. This group was compared with 60 preterm infants fed exclusively preterm formula milk (PF). Intended fluid volume of the FMM group was approximately 200 and 150-170 mL/kg/d in the PF group. Mother's milk was supplemented with the goal of a daily protein intake of 3.5-4 g/kg/d. Phosphorus was supplemented from 15.5 to 31 mg per 100mL mother's milk.

RESULTS

Both feeding regimes were well tolerated. At the end of the study, nutritional management in both groups resulted in a body weight between the 25th and 50th percentiles of intrauterine growth expectations. Serum values of electrolytes, alkaline phosphatase, plasma protein, blood urea nitrogen, and urinary mineral excretion did not differ significantly between the two groups at study entry as well as at the end of the investigation.

CONCLUSIONS

Mother's milk fed at higher volumes with an individualized fortification of minerals and protein provides sufficient nutrients to allow adequate growth of preterm infants <28 weeks of gestation.

The urinary activity of angiotensin-converting enzyme in preterm, full-term newborns, and children

The urinary activity of the angiotensin-converting enzyme (U(ACE)) is not yet completely documented in human neonates. We measured the U(ACE) in 36 premature neonates on the 1st day and in the 1st, 2nd, 3rd, and 4th weeks of life, in 22 full-term neonates between the 1st and 2nd days, and in 30 nursing and preschool children between 1 month and 6 years of age. The urinary excretion of sodium (U(Na)/U(Cr)) and the potassium/sodium index (U(K)/U(Na)) were analyzed in the neonates. U(ACE) was greater in premature than in full-term neonates and greater in both than in older children (p<0.001). In the premature neonates, U(ACE) peaked at the 2nd week, the U(Na)/U(Cr) index decreased, and the U(K)/U(Na) index increased between the 1st day and the 2nd week (p<0.001). The U(Na)/U(Cr) index on the 1st day and in the 1st and 2nd weeks was greater in premature than in full-term neonates (p<0.001). There was no significant correlation between the U(ACE) and the U(Na)/U(Cr) index. In conclusion, the U(ACE) profile was shown to be age dependent and related to the postnatal renal development. The increase in U(ACE) activity may reflect the high activity of the neonatal intrarenal renin-angiotensin system (RAS).

Renal haemodynamics and function in weanling rats treated with enalapril from birth

1. Inhibition of the renin-angiotensin system (RAS) during kidney development produces chronic alterations in renal morphology and function that have been characterized in detail in adult animals. The aim of the present study was to determine the consequences of neonatal angiotensin-converting enzyme (ACE) inhibition on renal haemodynamics and function in rats at a much earlier age, namely 3-4 weeks. 2. Male Wistar pups received daily intraperitoneal injections of enalapril (10 mg/kg) or isotonic saline from birth until 24-28 days of age, when renal haemodynamics and function were assessed using clearance techniques under pentobarbital anaesthesia. 3. Enalapril-treated rats showed significant reductions in glomerular filtration rate (GFR; -44 +/- 6%; P < 0.05), effective renal plasma flow (ERPF; -33 +/- 6%; P < 0.05) and filtration fraction (-16 +/- 3%; P < 0.05) compared with saline-treated controls. Although mean arterial pressure tended to be lower in enalapril-treated rats, this group demonstrated a significant increase in renal vascular resistance compared with control rats (RVR; 46 +/- 6 vs 32 +/- 3 mmHg/mL per.min per g.kidney weight, respectively; P < 0.05). In enalapril-treated rats, urine osmolality was reduced (-59 +/- 5%; P < 0.05) and urine flow rate and fractional urinary excretion rates of sodium and potassium were markedly elevated compared with controls (P < 0.05). Enalapril-treated rats showed severe renal histological abnormalities, including wall thickening of cortical arterioles, papillary atrophy and tubulointerstitial alterations, mimicking those described previously in similarly treated rats examined in adulthood. 4. In conclusion, neonatal ACE inhibition in rats induces pronounced alterations in renal haemodynamics and function, characterized by reductions in ERPF and GFR, increased RVR and impaired tubular sodium and water reabsorption, which are evident at weaning.

The renin-angiotensin system in kidney development: role of COX-2 and adrenal steroids

Recent data from studies in rodents with targeted gene disruption and pharmacological antagonists have shown that the renin-angiotensin-aldosterone system (RAAS) and cyclooxygenase type-2 (COX-2) are necessary for late stages of kidney development. The present review summarizes data on the developmental changes of RAAS and COX-2 and the pathways by which they are activated; their possible interplay and the mechanisms by which they affect kidney development. Intrarenal and circulating renin and angiotensin II (ANG II) are stimulated at birth in most mammals. In rats, renin and ANG II stay significantly elevated in the suckling period while aldosterone stabilizes at an adult level. COX-2 is stimulated in thick ascending limb of Henle's loop in the suckling period at a time when urine concentrating ability is not developed. Data suggest that this induction is mediated by combined low plasma glucocorticoid concentration and by a low NaCl intake. Studies with selective inhibitors of COX-2 and COX-2 null mice show that COX-2 activity stimulates renin secretion from JG-cells during postnatal kidney development and that lack of COX-2 activity leads to pathological change in cortical architecture and eventually to renal failure. In the postnatal period, ANG II initiates and maintains pelvic and ureteric contractions necessary for urine flow. Lack of ANG II in the neonatal period is thought to cause injury by a chronic increase of renal pelvic pressure. Aldosterone is crucial for survival and growth in the neonatal period through its effects on sodium reabsorption and the intrarenal sensitivity to aldosterone is increased in the postnatal period. Final maturation of the kidney occurs through an intimate interplay between a low dietary sodium intake and a non-responsive HPA-axis which stimulates cortical COX-2 activity. COX-2 supports increased activity of the RAAS and may contribute to a low concentrating ability.

Qualitative urinalyses in puppies 0 to 24 weeks of age

Suggestions for interpreting qualitative urinalyses from puppies have been based on limited results obtained in the laboratory setting. Proteinuria, glucosuria, and decreased concentration of urine have been considered normal in puppies <8 weeks of age due to immature renal function. In this study, the authors reviewed 149 voided urine samples from 118 different, apparently healthy, random-source puppies. The primary finding was that mean urine specific gravity (USG) was significantly lower in 0- to 3-week-old puppies when compared to puppies 4 to 24 weeks old. Mean USG in all other age groups was >1.030. There was no difference in the frequency of positive protein or occult blood dipstick results among age groups, and there were no positive glucose, ketone, bilirubin, or urobilinogen reactions in any samples analyzed. Urine sediment results are reported for 41 samples. Epithelial cells and white blood cells were the most common sediment findings in these 41 voided samples, observed in 34 (83%) and 18 (44%) samples, respectively. Crystals were observed in 15 (37%) samples, whereas casts, bacteria, and red blood cells were observed less commonly.

Renal aspects of the term and preterm infant: a selective update

This review discusses new aspects of normal and abnormal renal development that expand insight into the adaptation of the neonatal kidneys to the stress of extrauterine life. Highlighted are some pitfalls in measuring glomerular filtration rate in the neonate mainly caused by postnatal fluctuations in serum creatinine levels. Serum creatinine levels are correlated with the authors' recent finding of tubular reabsorption of creatinine in the immature neonatal kidney. Renal maldevelopment in premature and small-for-date babies has been shown related to serious medical problems in adult life, including hypertension. This finding presents the pediatrician with a new role in the time-honored vocation of preventing disease. Mutations in several genes may be responsible for most cases of congenital or hereditary renal aberrations. Two renal disorders, congenital nephrotic syndrome and neonatal acute renal failure, and one form of treatment modality of newborn infants, renal replacement therapy, are discussed in detail. These conditions are rare in general pediatric practice, but they illustrate some of the new developments in the renal care of the newborn. A word of caution is offered about the use of nonsteroidal anti-inflammatory drugs during pregnancy and the newborn period. All nonsteroidal anti-inflammatory drugs administered indirectly to the unborn fetus and directly to the young newborn impair renal structure (fetus) and function (both fetus and newborn). The new data have been obtained with genetic and molecular biology techniques and with established methods of developmental renal physiology. A better understanding of the pathogenesis of neonatal renal disorders will result in new diagnostic procedures and improved preventive and therapeutic possibilities relevant to the neonate with a renal disorder.