Nutrition for critically ill children and neonates requiring dialysis: Application of clinical practice recommendations

Approximately 30% of all children and neonates admitted to the intensive care unit (ICU) experience acute kidney injury (AKI). Children with AKI are largely poorly fed and experience high rates of malnutrition. Nutrition prescription and provision are exceptionally challenging for critically ill neonates, infants, and children with AKI given the dynamic nature of AKI and its respective treatment modalities. Managing the nutrition prescription of critically ill neonates, infants, and children with AKI requires nutrition support clinicians to have a high-level understanding of the various treatment modalities for AKI, which can affect the patient's protein, fluid, electrolyte, and mineral needs. Accurate and timely nutrition assessment in critically ill neonates and children with AKI can be flawed owing to difficulty obtaining accurate anthropometric parameters. Recently, the Pediatric Renal Nutrition Taskforce introduced clinical practice recommendations for the nutrition management of children with AKI. In this review, we will discuss the practical implications of these recent guidelines and work to bridge the knowledge and practice gaps for pediatric and neonatal nutrition support clinicians providing nutrition therapy for patients with AKI in the ICU. We also appraise special nutrition-related considerations for neonates with AKI given newer available renal replacement treatment modalities.

Documentation of acute kidney injury at discharge from the neonatal intensive care unit and role of nephrology consultation

OBJECTIVE

To investigate whether NICU discharge summaries documented neonatal AKI and estimate if nephrology consultation mediated this association.

STUDY DESIGN

Secondary analysis of AWAKEN multicenter retrospective cohort.

EXPOSURES

AKI severity and diagnostic criteria.

OUTCOME

AKI documentation on NICU discharge summaries using multivariable logistic regression to estimate associations and test for causal mediation.

RESULTS

Among 605 neonates with AKI, 13% had documented AKI. Those with documented AKI were more likely to have severe AKI (70.5% vs. 51%, p < 0.001) and SCr-only AKI (76.9% vs. 50.1%, p = 0.04). Nephrology consultation mediated 78.0% (95% CL 46.5-109.4%) of the total effect of AKI severity and 82.8% (95% CL 70.3-95.3%) of the total effect of AKI diagnostic criteria on documentation.

CONCLUSION

We report a low prevalence of AKI documentation at NICU discharge. AKI severity and SCr-only AKI increased odds of AKI documentation. Nephrology consultation mediated the associations of AKI severity and diagnostic criteria with documentation.

Hyperosmolality, High Blood Pressure, and Decreased Estimated Glomerular Filtration Rate in US Adolescents, National Health and Nutrition Examination Survey 1999-2012

BACKGROUND

Experimental evidence suggests that hyperosmolality may be a causative factor in the development of both salt-sensitive hypertension and chronic kidney disease (CKD). There are no population-wide studies in young persons to assess the relationships among these factors.

OBJECTIVE

To determine the association of serum osmolality and serum sodium with high systolic blood pressure (SBP) and decreased estimated glomerular filtration rate (eGFR) among a nationally representative population of adolescents.

METHOD

Relevant data among participants ages 12-14 were obtained from the National Health and Nutrition Examination Survey cycles 1999-2012. Serum osmolality was calculated using the Worthley equation. eGFR was calculated using the Counahan-Barratt equation, and values < 90 mL/min/1.73 m2 were considered decreased. High SBP was defined as SBP ≥95th percentile for age, height, and sex.

RESULTS

A total of 4,168 adolescents were analyzed (representative population: 10,464,592). Adolescents with serum osmolality ≥290 mOsm/kg and/or serum sodium ≥143 mmol/L had increased odds for both high SBP (serum osmolality ≥290 mOsm/kg: OR 2.04; 95% CI 1.03-4.02; sodium ≥143 mmol/L: OR 4.36; 95% CI 1.58-12.04) and decreased eGFR (serum osmolality ≥290 mOsm/kg: OR 1.61; 95% CI 1.18-2.21; sodium ≥143 mmol/L: OR 3.27; 95% CI 1.77-6.03) when compared to participants with values below these thresholds. These thresholds remained significant even after multivariable adjustment.

CONCLUSION

Among adolescents in a nationally representative survey, hypernatremia and hyperosmolality were associated with high SBP and decreased eGFR. These findings may support the hypothesis that an imbalance of salt and water contribute to hypertension and CKD.

Platelet Factor 4 (PF4) Release during Human Platelet Aggregation in Diabetic Patients

The release of platelet factor 4 during platelet aggregation was investigated in diabetic patients. We observed an increased release of platelet factor 4 in diabetic patients.

The authors suggest that the increased release of platelet factor 4 may play an essential role in pathogenesis of thromboembolic complications in diabetes mellitus.

Dietary sodium, dietary potassium, and systolic blood pressure in US adolescents

Both high sodium and low potassium diets are associated with hypertension, but whether these risk factors are distinct or overlapping has not been thoroughly investigated. The authors evaluated the relationship between dietary sodium, potassium, and high systolic blood pressure among 4716 adolescents aged 12 to 14 years who participated in the National Health and Nutrition Examination Survey from 1999 to 2012. There was no association with blood pressure across most values of sodium or potassium intake. However, participants who reported sodium intake ≥7500 mg/d, potassium <700 mg/d, or sodium-potassium ratio ≥2.5 had increased odds for high systolic blood pressure (≥95th percentile for age, sex, and height). Although the high sodium and low potassium groups did not overlap, 49.2% of these adolescents also had a sodium-potassium ratio ≥2.5. In young adolescents, both excessive sodium and limited potassium are associated with high systolic blood pressure, but the balance between sodium and potassium intake may be more useful in explaining blood pressure in this population.

Post-traumatic growth: finding positive meaning in cancer survivorship moderates the impact of intrusive thoughts on adjustment in younger adults

OBJECTIVE

We examined whether post-traumatic growth would moderate the impact of intrusive thoughts on a range of dimensions of well-being in a sample of younger adult survivors of various types of cancer.

METHODS

167 participants completed questionnaires regarding intrusive thoughts, post-traumatic growth, mental and physical health-related quality of life, positive and negative affect, life satisfaction, and spiritual well-being. Multiple regression analyses controlling for relevant background and cancer-related variables tested the interaction effects of post-traumatic growth and intrusive thoughts.

RESULTS

Intrusive thoughts were related to poorer adjustment on all indices except physical health-related quality of life. However, post-traumatic growth moderated the effects of intrusive thoughts on positive and negative affect, life satisfaction, and spiritual well-being in a protective fashion. That is, for those higher in post-traumatic growth, higher levels of intrusive thoughts were related to better adjustment.

CONCLUSIONS

The positive meaning that individuals assign to their cancer experience as reflected in their reports of post-traumatic growth appears to be important in determining the impact of intrusive thoughts on post-cancer adjustment.

Changes in the content of health-promoting compounds and antioxidant activity of broccoli after domestic processing

The effect of water- and steam-cooking on the content of vitamin C, polyphenols, carotenoids, tocopherols and glucosinolates, as well as on the antioxidant activity of broccoli, are reported. Flavonoids, phenolic acids, vitamins C and E, beta-carotene, lutein, and glucosinolates in domestically processed broccoli were quantified using high-performance liquid chromatography (HPLC) methods; total polyphenols were determined with Folin-Ciocalteu reagent. The antioxidant capacities of broccoli extracts were evaluated using the Trolox equivalent antioxidant capacity (TEAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods. The results indicated that steam-cooking of broccoli results in an increase in polyphenols, as well as the main glucosinolates and their total content as compared with fresh broccoli, whereas cooking in water has the opposite effect. Steam-cooking of broccoli has no influence on vitamin C, whereas cooking in water significantly lowers its content. Both, water- and steam-cooking of broccoli results in an increase in beta-carotene, lutein, and alpha- and gamma-tocopherols as compared with fresh broccoli. Similar effects of steaming and water-cooking of broccoli on their antioxidant activity were observed.

Liposomal cargo unloading induced by pH-sensitive peptides

Amphiphilic peptides designed to have a pH-dependent conformational change and membrane activity are described. At physiologic pH, the peptides would exist in a random coil conformation, but at endosomal pH values they would switch to amphiphilic alpha-helices, disrupt membranes, and release liposomal contents. A series of peptides have been investigated that contain a high percentage of Glu residues for the pH-induced conformational switch, and Leu residues for optimal lipid binding. Circular dichroism (CD) results in aqueous and liposomal environments were performed and demonstrate a pH-dependent shift to helicity upon acidification. Liposomal release data at neutral and acidic pH, also document the success of this design strategy.

Probing essential residues for cellular uptake with a cationic nuclear localization signal sequence

The nuclear localization signal sequence (NLS) of the transcription factor NF-kappaB is a cationic peptide with the ability to cross the cytoplasmic membrane and facilitate the delivery of attached cargo, such as DNA and proteins, to cells. Previous research had pointed to the essential role of cationic residues, therefore, the importance of residues within the NLS of NF-kappaB was evaluated for cellular uptake using an alanine replacement strategy. Although it was expected that removal of the cationic groups would have the greatest effect on membrane translocation, the most significant decreases in cellular uptake occurred with the replacement of the hydrophilic Q6 (80%) and the hydrophobic L8 (70%) residues. Replacement of the positively charged residues resulted in 30-40% decrease in cellular uptake, indicating that electrostatic interactions are not the primary driving force for membrane translocation.

Alpha-lactose monohydrate single crystals as hosts for matrix isolation of guest biopolymers

Single crystals of alpha-lactose monohydrate show a remarkable tendency to include biopolymers, such as proteins, oligonucleotides and dextrans, within the growing lattice. Glycosylation increased the amount of protein contained within the crystals. The guest molecules were found only within the (010) growth sector of the hatchet shaped crystals, thereby binding preferentially to one of the seven developed crystal faces. The topographical features of the active surface are described.

DNA binding properties of basic helix-loop-helix fusion proteins of Tal and E47

The basic helix-loop-helix (bHLH) transcription factor Tal has been shown to form heterodimers with the ubiquitously expressed bHLH transcription factor E47 and thereby modulate gene expression. The absence of homodimeric Tal-DNA complexes had been attributed to the inability of Tal to homodimerize, but subsequent studies have shown that the bHLH region of Tal does homodimerize. In order to correlate the contributions of both the basic region and the helix-loop-helix (HLH) domain to the lack of DNA binding by Tal homodimers, mutant and fusion proteins based on Tal and E47 were designed and synthesized. Size-exclusion chromatography established that all mutant and fusion proteins were dimeric. Point mutations were made within the basic region of Tal based on residues within E47 that are essential for DNA binding, but an affinity for DNA was not observed. Even complete replacement of the basic region in Tal with the basic region of E47, in an E47-Tal fusion protein, did not confer DNA binding upon the protein. However, when the dimerization domain in Tal was replaced with its E47 counterpart, in a Tal-E47 fusion protein, sequence specific DNA binding was observed with an apparent dissociation constant of 3.6 x 10(-9) M2. Furthermore, circular dichroism studies showed that the basic region of Tal in the Tal-E47 fusion protein underwent a random coil to helix transition in the presence of a specific DNA probe. These experimental observations indicate that the inability of Tal homodimers to recognize DNA stems from a misalignment of its basic region with respect to the HLH domain, rather than an intrinsic inability of the Tal basic region to bind DNA.

The design of self-replicating helical peptides

The self-assembly of helical peptides and information transfer through autocatalysis and cross-catalysis are the foundation of peptide-based molecular evolution models. Many fundamental properties of living systems, such as environmental sensitivity, chiroselectivity, cross-catalysis, dynamic error correction and conditional selection, are exhibited by various self-replicating peptide systems. Recently, advances have been made in the design of peptide systems with autocatalytic and cross-catalytic properties.

Targeting the dimerization interface for irreversible inhibition of HIV-1 protease

A novel strategy was used to irreversibly inhibit HIV-1 protease. The inhibitor was designed to form a disulfide bond with Cys95, present at the dimerization interface of HIV-1 protease. The inhibitor was shown to be active against HIV-1 protease with K(inact) = 3.7 microM and V(inact) = 0.012 min(-1).

Uncoiling c-Jun coiled coils: inhibitory effects of truncated Fos peptides on Jun dimerization and DNA binding in vitro

c-Jun is an oncoprotein that comprises a portion of the AP-1 transcription factor and belongs to the basic-leucine zipper (bZIP) DNA binding protein family. Using peptides derived from the leucine zipper region of Fos, we have developed agents that inhibit Jun's DNA binding in the low micromolar range. Fos peptides that were effective inhibitors in the DNA binding assay were also found to inhibit cellular Jun binding to an AP-1 site in a luciferase reporter plasmid in MCF-7 cells. Size exclusion studies confirmed that peptides that inhibit the DNA binding of Jun also inhibit its dimerization. These peptides were found to have a cytotoxic effect on the MCF-7 cell line when delivered with the transfecting agent Tfx-50, possibly due to their role as transcription factor regulators.

A pH-tunable peptide ligase

A chemical ligation system is reported, in which a highly acidic coiled-coil peptide was used to template two basic peptide fragments and catalyze their condensation, in a pH-tunable fashion, to generate a coiled-coil product. This template showed a high catalytic efficiency (with single turnover) under neutral conditions. Under acidic conditions, however, its catalytic efficiency was reduced by approximately 4500-fold.

Helical peptide and protein design

The design of dimeric coiled-coils has ultimately led to novel applications, such as self-replicating peptide systems, whereas the structural features of the less common trimeric coiled-coil continue to be elucidated. Novel topologies have been discovered in designed proteins, as exemplified by the right-handed tetrameric coiled-coil and the inverted U four-helix bundle, and a single switch of two amino acids within a protein has been shown to be sufficient to designate a new protein fold. Conformational switching from helix to sheet has been observed for designed peptides and transcription factors, whereas peptides designed from beta-amino acids have been found to adopt a helical conformation in aqueous solution.

Probing the role of interfacial residues in a dimerization inhibitor of HIV-1 protease

The importance of each side chain of a cross-linked interfacial peptide inhibitor of HIV-1 protease was evaluated using an alanine scanning approach. Whereas the parent inhibitor has an IC50 value of 350 nM, values for the mutations reported here range from 280-9200 nM. The relative importance or each residue was thus assigned and correlated to the solvent accessible surface area (SASA) exposed upon mutation.

Structure-function relationship in a beta-sheet peptide inhibitor of E47 dimerization and DNA binding

A beta-sheet peptide inhibitor, 2H10, has been developed that inhibits the dimerization of the transcription factor E47. Inhibition of E47 dimerization has been demonstrated to also inhibit the DNA binding of this transcription factor. Truncated peptides based on 2H10 have demonstrated that the beta-sheet content of these peptides directly correlates with their inhibitory properties. Individual residues within 2H10 were identified that were responsible for the beta-sheet secondary structure by employing an alanine replacement strategy. The beta-sheet character of the alanine mutants also correlated well with their inhibition of E47 DNA binding. These results provide further evidence that interactions between the interfacial peptide inhibitors of E47 and the transcription factor itself are mediated by a beta-sheet structure.

Selective amplification by auto- and cross-catalysis in a replicating peptide system

Self-replication has been demonstrated in synthetic chemical systems based on oligonucleotides, peptides and complementary molecules without natural analogues. However, within a living cell virtually no molecule catalyses its own formation, and the search for chemical systems in which both auto- and cross-catalysis can occur has therefore attracted wide interest. One such system, consisting of two self-replicating peptides that catalyse each other's production, has been reported. Here we describe a four-component peptide system that is capable of auto- and cross-catalysis and allows for the selective amplification of one or more of the products by changing the reaction conditions. The ability of this system selectively to amplify one or more molecules in response to changes in environmental conditions such as pH or salt concentration supports the suggestions that self-replicating peptides may have played a role in the origin of life.

Restricting the flexibility of crosslinked, interfacial peptide inhibitors of HIV-1 protease

Interfacial peptides of HIV-1 protease were crosslinked with varying length alkyl-chains containing either a single cis or trans double bond, or a triple bond to remove degrees of freedom within the tethers. The synthesis of these compounds and their effects on the activity of HIV-1 protease are described.

A beta-sheet peptide inhibitor of E47 dimerization and DNA binding

BACKGROUND

Many transcription factors are active only in their dimeric form, including the basic-helix-loop-helix (bHLH) family of transcription factors. The disruption of the dimer therefore presents a means of inhibiting the biological functions of such transcription factors. E47 is a homodimeric bHLH transcription factor with a four-helix bundle dimerization interface. Here, we investigate the concept of dimerization inhibition using peptides derived from the dimerization domain of E47.

RESULTS

We have synthesized several peptides corresponding to the E47 dimerization interface that inhibit E47 DNA-binding activity with IC50 values in the range of 3.6-120 mM. Interestingly, helix II; a peptide corresponding to the carboxy-terminal helix of the E47 dimerization interface, adopted a beta-sheet structure in solution, as shown using circular dichroism (CD), and inhibited the binding of E47 to DNA at equimolar concentrations. Size-exclusion chromatography, analytical ultracentrifugation and cross-linking experiments verified that this peptide prevented E47 dimerization. Furthermore, CD experiments provided evidence that helix II could induce a beta-sheet secondary structure upon the highly alpha-helical E47 bHLH domain.

CONCLUSIONS

This study is the first demonstration of dissociative inhibition in the bHLH class of transcription factors and also provides an example of beta-sheet induction in an alpha-helical protein. Future experiments will prove the structural determinants of the beta-sheet secondary structure in helix II and investigate the generality of the dissociative strategy in other transcription factor families.

Inhibiting the dimeric restriction endonuclease EcoRI using interfacial helical peptides

BACKGROUND

Many enzymes are active only in a dimeric form, including a variety of type II restriction endonucleases. Disruption of subunit interactions is therefore a potential method for multimeric enzyme inhibition. EcoRI is a homodimeric restriction endonuclease, the dimeric interface of which consists of a four-helix bundle. We set out to design helical peptides to interact with this interface and block dimer formation, thus rendering EcoRI inactive.

RESULTS

Here we describe two synthetic, helical peptides based on the interfacial region of EcoRI. Both peptides inhibit the enzyme, but the peptide derived from the alpha 4 helix of EcoRI had both a higher helical content and better efficacy than a variant peptide, alpha 4(Leu), that has three Ile-->Leu mutations (IC50 values of 27 microM and 90 microM, and helical contents of 29% and 10%, respectively). Size-exclusion chromatography confirmed that the alpha 4 peptide disrupted dimerization of EcoRI, and circular dichroism indicated that EcoRI remained folded upon binding to alpha 4. Inhibition with alpha 4 and alpha 4(Leu) was shown to be specific for EcoRI, as the dimeric restriction enzyme PvuII was not affected by the peptides.

CONCLUSIONS

Interfacial peptide inhibitors of the dimeric EcoRI were obtained that both inhibit dimerization and endonuclease activity. The peptide sequence with a preference for a helical conformation was a more effective inhibitor, presumably because the more preorganized state enhanced interactions with the helical interface of EcoRI. The specific nature of this endonuclease-peptide interaction was also confirmed. The potential of this strategy for inhibiting other enzyme classes is currently being addressed.

Endothiopeptide inhibitors of HIV-1 protease

Endothiopeptide inhibitors of HIV-1 protease were synthesized by chemical and enzymatic methods to individually replace each backbone amide bond in 1 with a thioamide-linkage. Interestingly, agent 7, which contains a thioamide-linkage between the P2' and P3' positions of 1, was the most potent, competitive inhibitor of HIV-1 protease with a Ki of 3.4 microM.

Inhibiting the assembly of protein-protein interfaces

Protein-protein association is found throughout mechanisms of cellular growth and differentiation, and viral replication. Inhibiting the assembly of protein complexes, therefore, presents itself as a novel means of inhibition for a wide variety of cellular and viral events. Peptides and small molecules that modify the overall quaternary structure of a selection of receptor-ligand interactions and oligomeric viral enzymes have been developed recently.

Subtilisin-catalyzed religation of proteolyzed hen egg-white lysozyme: investigation of the role of disulfides

BACKGROUND

The use of proteases to form, instead of break, peptide bonds has expanded the repertoire of techniques available for protein semisynthesis. Several groups have previously reported the use of proteases in aqueous-organic solvents to form single amide bonds within proteins, but low yields and lengthy reaction times make this an impractical approach to protein synthesis. We recently found that proteolyzed triose phosphate isomerase can be re-ligated rapidly and efficiently by subtilisin, in mixed aqueous-organic solvent systems.

RESULTS

We now report the use of subtilisin to resynthesize hen egg-white lysozyme from a mixture of its proteolyzed fragments in high yield and with rapid reaction times. This enzymatic religation can also be achieved after reduction of the four disulfide bonds present in lysozyme, with the same efficiency as that observed for the disulfide-containing proteolysis mixture.

CONCLUSIONS

For egg-white lysozyme, the subtilisin religation reaction can be used to re-synthesize a proteolyzed protein even after reduction of disulfide bonds. The utility of this reaction in more generalized protein semisynthesis reactions is currently being explored.

Synthesis of the basic-helix-loop-helix region of the immunoglobulin enhancer binding protein E47 and evaluation of its structural and DNA binding properties

The basic-helix-loop-helix (bHLH) region of the immunoglobulin enhancer binding protein E47 (IEB E47) was prepared in high yield by a solid-phase peptide synthesis methodology. Size-exclusion chromatography, sedimentation equilibrium and cross-linking data showed that the synthetic bHLH protein, 1, was dimeric, and higher-order aggregates of trimer and tetramer were also observed. The circular dichroism spectrum of 1 showed a high helical content, which increased upon addition of DNA containing the kappa E2 sequence. Gel mobility shift experiments showed that protein 1 bound sequence specifically to the kappa E2 sequence with a binding constant of 10(-10) M2, and had an affinity for other E box sequences as well. Comparisons between the co-crystal structure of IEB E47 with DNA and structural studies in solution showed lower helical contents in solution as would have been predicted from the crystal structure.

The rational design of highly stable, amphiphilic helical peptides

A computer algorithm was devised for the evaluation of helical stability of potentially amphiphilic peptide sequences of specified length containing a set number of leucines in the hydrophobic region. All possible combinations of Glu, Lys and Gln in the hydrophilic region are rated using a set of empirical rules for salt bridge formation in alpha-helices, and the sequences which rate the highest are displayed. The rules for salt bridge formation were largely derived from published studies on the effects of salt bridges on helical stability. The algorithm was tested by redesigning a known amphiphilic alpha-helical peptide, alpha 1B or 1, which has been shown to aggregate into four-helix bundles. Comparison of the circular dichroism spectra of two peptides, 2 and 3, to 1 demonstrated that the redesigned peptide with the highest priority score from the algorithm, 2, was more helical when aggregated and slightly more helical as a monomer, whereas the peptide with the low priority score, 3, was somewhat less helical when aggregated and much less helical when monomeric. These results support the design of the algorithm, although conclusions based on aggregation data are complicated by the importance of interhelix contacts in the bundle. Further studies are underway to examine the reliability of the algorithm's predictions regarding the design of other helical peptides.

Chromosome numbers of goldenrods, Euthamia and Solidago (Compositae-Astereae)

Chromosome number determinations were made from 227 populations of 43 taxa of Euthamia and Solidago. Nearly all were confirmations of previous reports. The majority of the populations sampled were from Ontario. First report: Solidago hispida Muhl. var. tonsa Fern., 2n = 18.

[Supraventricular subarachnoid cysts]

Five patients with supraventricular subarachnoid cysts are described. In most patients epilepsy was the presenting sign. Cerebral angiography showed in all cases only an avascular lesion and and the correct diagnosis was established only during the operation. In only one case recurrent filling of the cyst was observed.

[Case of Hakim's syndrome]

The authors report a case of Hakim's syndrome developing in a 53-year-old man. Manifestations of parkinsonian syndrome prevailed. After implantation of a Pudenz-type valve significant improvement was obtained which confirms the clinical diagnosis.