Albumin kinetics in edematous and nonedematous protein-energy malnourished children

Soy Peptide Supplementation Mitigates Undernutrition through Reprogramming Hepatic Metabolism in a Novel Undernourished Non-Human Primate Model

In spite of recent advances in the field of undernutrition, current dietary therapy relying on the supply of high protein high calorie formulas is still plagued with transient recovery of impaired organs resulting in significant relapse of cases. This is partly attributed to the inadequacy of current research models in recapitulating clinical undernutrition for mechanistic exploration. Using 1636 Macaca fascicularis monkeys, a human-relevant criterion for determining undernutrition weight-for-age z-score (WAZ), with a cutoff point of ≤ -1.83 is established as the benchmark for identifying undernourished nonhuman primates (U-NHPs). In U-NHPs, pathological anomalies in multi-organs are revealed. In particular, severe dysregulation of hepatic lipid metabolism characterized by impaired fatty acid oxidation due to mitochondria dysfunction, but unlikely peroxisome disorder, is identified as the anchor metabolic aberration in U-NHPs. Mitochondria dysfunction is typified by reduced mito-number, accumulated long-chain fatty acids, and disruption of OXPHOS complexes. Soy peptide-treated U-NHPs increase in WAZ scores, in addition to attenuated mitochondria dysfunction and restored OXPHOS complex levels. Herein, innovative criteria for identifying U-NHPs are developed, and unknown molecular mechanisms of undernutrition are revealed hitherto, and it is further proved that soypeptide supplementation reprogramed mitochondrial function to re-establish lipid metabolism balance and mitigated undernutrition.

One-carbon metabolism in children with marasmus and kwashiorkor

BACKGROUND

Kwashiorkor is a childhood syndrome of edematous malnutrition. Its precise nutritional precipitants remain uncertain despite nine decades of study. Remarkably, kwashiorkor's disturbances resemble the effects of experimental diets that are deficient in one-carbon nutrients. This similarity suggests that kwashiorkor may represent a nutritionally mediated syndrome of acute one-carbon metabolism dysfunction. Here we report findings from a cross-sectional exploration of serum one-carbon metabolites in Malawian children.

METHODS

Blood was collected from children aged 12-60 months before nutritional rehabilitation: kwashiorkor (N = 94), marasmic-kwashiorkor (N = 43) marasmus (N = 118), moderate acute malnutrition (N = 56) and controls (N = 46). Serum concentrations of 16 one-carbon metabolites were quantified using LC/MS techniques, and then compared across participant groups.

FINDINGS

Twelve of 16 measured one-carbon metabolites differed significantly between participant groups. Measured outputs of one-carbon metabolism, asymmetric dimethylarginine (ADMA) and cysteine, were lower in marasmic-kwashiorkor (median µmol/L (± SD): 0·549 (± 0·217) P = 0·00045 & 90 (± 40) P < 0·0001, respectively) and kwashiorkor (0·557 (± 0·195) P < 0·0001 & 115 (± 50) P < 0·0001), relative to marasmus (0·698 (± 0·212) & 153 (± 42)). ADMA and cysteine were well correlated with methionine in both kwashiorkor and marasmic-kwashiorkor.

INTERPRETATION

Kwashiorkor and marasmic-kwashiorkor were distinguished by evidence of one-carbon metabolism dysfunction. Correlative observations suggest that methionine deficiency drives this dysfunction, which is implicated in the syndrome's pathogenesis. The hypothesis that kwashiorkor can be prevented by fortifying low quality diets with methionine, along with nutrients that support efficient methionine use, such as choline, requires further investigation.

FUNDING

The Hickey Family Foundation, the American College of Gastroenterology, the NICHD, and the USDA/ARS.

Overview of Albumin Physiology and its Role in Pediatric Diseases

PURPOSE OF REVIEW

Albumin plays a critical role in a wide range of disease processes; however, the role of albumin in pediatric patients has not been well described. This article aims to review albumin physiology and kinetics in children, albumin's impact on pediatric diseases, and the utility of albumin as a predictor of clinical outcome.

RECENT FINDINGS

Hypoalbuminemia is seen in a wide range of conditions, including protein-losing enteropathy, hepatic synthetic failure, malnutrition, inflammatory states, and renal disease. While the impact of hypoalbuminemia has been more extensively studied in adult patients, there is a relative paucity of literature in the pediatric population. Hypoalbuminemia is a marker of poor outcome in critically ill children and those undergoing a wide range of medical interventions. Albumin infusions may be an effective therapy for fluid resuscitation and for patients with severe hypoalbuminemia.

Metabolomic changes in severe acute malnutrition suggest hepatic oxidative stress: a secondary analysis

Severe acute malnutrition (SAM), due to poor energy and/or protein intake, is associated with poor growth, depressed immune function, and long-term impacts on metabolic function. As the liver is a major metabolic organ and malnutrition poses metabolic stress, we hypothesize that SAM will be associated with alterations in the hepatic metabolome reflective of oxidative stress, gluconeogenesis, and ketogenesis. Thus, the purpose of this secondary analysis was to understand how SAM alters hepatic metabolism using a piglet model. Weanling piglets were feed either a reference (REF) or protein-energy deficient diet (MAL) for 5 weeks. After dietary treatment MAL piglets were severely underweight (weight-for-age Z-score of -3.29, Welch's t test, P = .0007), moderately wasted (weight-for-length Z-score of-2.49, Welch's t test, P = .003), and tended toward higher hepatic triglyceride content (Welch's t test, P = .07). Hematologic and blood biochemical measurements were assessed at baseline and after dietary treatment. The hepatic metabolome was investigated using ¹H-NMR spectroscopy. Hepatic concentrations of betaine, cysteine, and glutathione tended to be lower in MAL (Welch's t test with FDR correction, P < .1), while inosine, lactate, and methionine sulfoxide concentrations were higher in MAL (inosine: P = .0448, lactate: P = .0258, methionine sulfoxide: P = .0337). These changes suggest that SAM is associated with elevated hepatic oxidative stress, increased gluconeogenesis, and alterations in 1-carbon metabolism.

Nutritional assessment and the role of preexisting inflammation with a bearing on COVID-19

 Although there is consensus in the European, American, Latin-American, and Asiatic nutrition and metabolic scientific societies regarding the definition of malnutrition, this definition has not been operationalized. This means that in different countries, the risk of malnutrition on outcome cannot be adequately determined or predicted. In patients with inflammatory activity, the preexistent nutritional status is an important predictor of outcome. Malnutrition is characterized by three crucial elements: undernutrition, inflammation, and diminished function. Malnutrition in our countries as well as in countries with famine almost always is caused by varying degrees of deficient nutritional intake in combination with disease or other damaging inflammatory causes of varying severity. The female genome appears to be better equipped to survive intercurrent trauma or illness than the male one, which impacts on longevity and the ability to overcome certain infections like COVID-19 at higher ages.

Serum albumin is independently associated with higher mortality in adult sickle cell patients: Results of three independent cohorts

Sickle cell disease (SCD) impacts liver and kidney function as well as skin integrity. These complications, as well as the hyperinflammatory state of SCD, could affect serum albumin. Serum albumin has key roles in antioxidant, anti-inflammatory and antithrombotic pathways and maintains vascular integrity. In SCD, these pathways modulate disease severity and clinical outcomes. We used three independent SCD adult cohorts to assess clinical predictors of serum albumin as well its association with mortality. In 2553 SCD adult participants, the frequency of low (<35 g/L) serum albumin was 5%. Older age and lower hemoglobin (P <0.001) were associated with lower serum albumin in all three cohorts. In age and hemoglobin adjusted analysis, higher liver enzymes (P <0.05) were associated with lower serum albumin. In two of the three cohorts, lower kidney function as measured by Glomerular Filtration Rate (P<0.001) was associated with lower serum albumin. Lower serum albumin predicted higher risk of tricuspid regurgitation velocity ≥ 2.5 m/s (OR = 1.1 per g/L, P ≤0.01). In all three cohorts, patients with low serum albumin had higher mortality (adjusted HR ≥2.9, P ≤0.003). This study confirms the role of serum albumin as a biomarker of disease severity and prognosis in patients with SCD. Albumin as a biomarker and possible mediator of SCD severity should be studied further.

Severe childhood malnutrition

The main forms of childhood malnutrition occur predominantly in children <5 years of age living in low-income and middle-income countries and include stunting, wasting and kwashiorkor, of which severe wasting and kwashiorkor are commonly referred to as severe acute malnutrition. Here, we use the term 'severe malnutrition' to describe these conditions to better reflect the contributions of chronic poverty, poor living conditions with pervasive deficits in sanitation and hygiene, a high prevalence of infectious diseases and environmental insults, food insecurity, poor maternal and fetal nutritional status and suboptimal nutritional intake in infancy and early childhood. Children with severe malnutrition have an increased risk of serious illness and death, primarily from acute infectious diseases. International growth standards are used for the diagnosis of severe malnutrition and provide therapeutic end points. The early detection of severe wasting and kwashiorkor and outpatient therapy for these conditions using ready-to-use therapeutic foods form the cornerstone of modern therapy, and only a small percentage of children require inpatient care. However, the normalization of physiological and metabolic functions in children with malnutrition is challenging, and children remain at high risk of relapse and death. Further research is urgently needed to improve our understanding of the pathophysiology of severe malnutrition, especially the mechanisms causing kwashiorkor, and to develop new interventions for prevention and treatment.

Malnutrition-associated liver steatosis and ATP depletion is caused by peroxisomal and mitochondrial dysfunction

BACKGROUND & AIMS

Severe malnutrition in young children is associated with signs of hepatic dysfunction such as steatosis and hypoalbuminemia, but its etiology is unknown. Peroxisomes and mitochondria play key roles in various hepatic metabolic functions including lipid metabolism and energy production. To investigate the involvement of these organelles in the mechanisms underlying malnutrition-induced hepatic dysfunction we developed a rat model of malnutrition.

METHODS

Weanling rats were placed on a low protein or control diet (5% or 20% of calories from protein, respectively) for four weeks. Peroxisomal and mitochondrial structural features were characterized using immunofluorescence and electron microscopy. Mitochondrial function was assessed using high-resolution respirometry. A novel targeted quantitative proteomics method was applied to analyze 47 mitochondrial proteins involved in oxidative phosphorylation, tricarboxylic acid cycle and fatty acid β-oxidation pathways.

RESULTS

Low protein diet-fed rats developed hypoalbuminemia and hepatic steatosis, consistent with the human phenotype. Hepatic peroxisome content was decreased and metabolomic analysis indicated peroxisomal dysfunction. This was followed by changes in mitochondrial ultrastructure and increased mitochondrial content. Mitochondrial function was impaired due to multiple defects affecting respiratory chain complex I and IV, pyruvate uptake and several β-oxidation enzymes, leading to strongly reduced hepatic ATP levels. Fenofibrate supplementation restored hepatic peroxisome abundance and increased mitochondrial β-oxidation capacity, resulting in reduced steatosis and normalization of ATP and plasma albumin levels.

CONCLUSIONS

Malnutrition leads to severe impairments in hepatic peroxisomal and mitochondrial function, and hepatic metabolic dysfunction. We discuss the potential future implications of our findings for the clinical management of malnourished children.

LAY SUMMARY

Severe malnutrition in children is associated with metabolic disturbances that are poorly understood. In order to study this further, we developed a malnutrition animal model and found that severe malnutrition leads to an impaired function of liver mitochondria which are essential for energy production and a loss of peroxisomes, which are important for normal liver metabolic function.

The effect of short-term high versus normal protein intake on whole-body protein synthesis and balance in children following cardiac surgery: a randomized double-blind controlled clinical trial

Background

Infants undergoing cardiac surgery are at risk of a negative protein balance, due to increased proteolysis in response to surgery and the cardiopulmonary bypass circuit, and limited intake. The aim of the study was to quantify the effect on protein kinetics of a short-term high-protein (HP) diet in infants following cardiac surgery.

Methods

In a prospective, double-blinded, randomized trial we compared the effects of a HP (5 g · kg⁻¹ · d⁻¹) versus normal protein (NP, 2 g · kg⁻¹ · d⁻¹) enteral diet on protein kinetics in children <24 months, on day 2 following surgical repair of congenital heart disease. Valine kinetics and fractional albumin synthesis rate (FSR_alb) were measured with mass spectrometry using [1-¹³C]valine infusion. The Mann–Whitney U test was used to investigate differences between group medians. Additionally, the Hodges-Lehmann procedure was used to create a confidence interval with a point estimate of median differences between groups.

Results

Twenty-eight children (median age 9 months, median weight 7 kg) participated in the study, of whom in only 20 subjects isotopic data could be used for final calculations. Due to underpowering of our study, we could not draw conclusions on the primary outcome parameters. We observed valine synthesis rate of 2.73 (range: 0.94 to 3.36) and 2.26 (1.85 to 2.73) μmol · kg⁻¹ · min⁻¹ in the HP and NP diet, respectively. The net valine balance was 0.54 (−0.73 to 1.75) and 0.24 (−0.20 to 0.63) μmol · kg⁻¹ · min⁻¹ in the HP and NP group. Between groups, there was no difference in FSR_alb. We observed increased oxidation and BUN in the HP diet, compared to the NP diet, as a plausible explanation of the metabolic fate of surplus protein.

Conclusions

It is plausible that the surplus protein in the HP group has caused the increase of valine oxidation and ureagenesis, compared to the NP group. Because too few patients had completed the study, we were unable to draw conclusions on the effect of a HP diet on protein synthesis and balance. We present our results as new hypothesis generating data.

Trial registration

Dutch Trial Register NTR2334.

Nutritional and other types of oedema, albumin, complex carbohydrates and the interstitium - a response to Malcolm Coulthard's hypothesis: Oedema in kwashiorkor is caused by hypo-albuminaemia

The various types of oedema in man are considered in relation to Starling's hypothesis of fluid movement from capillaries, with the main emphasis on nutritional oedema and the nephrotic syndrome in children. It is concluded that each condition has sufficient anomalous findings to render Starling's hypothesis untenable. The finding that the endothelial glycocalyx is key to control of fluid movement from and into the capillaries calls for complete revision of our understanding of oedema formation. The factors so far known to affect the function of the glycocalyx are reviewed. As these depend upon sulphated proteoglycans and other glycosaminoglycans, the argument is advanced that the same abnormalities will extend to the interstitial space and that kwashiorkor is fundamentally related to a defect in sulphur metabolism which can explain all the clinical features of the condition, including the formation of oedema.

Low prealbumin is a significant predictor of medical complications in severe anorexia nervosa

OBJECTIVE

Prealbumin levels have been proven to correlate with hospital length of stay, wound healing, infection rates, and mortality in adults hospitalized for medical or surgical purposes, or those who have chronic illnesses. Little is known about the utility of prealbumin evaluation in adults with severe anorexia nervosa (AN).

METHOD

We retrospectively evaluated prealbumin levels, along with numerous other clinical parameters relevant to illness acuity and early refeeding outcomes, in 132 adults with AN admitted for definitive inpatient medical stabilization from October 1, 2008 to December 31, 2012. Per clinical protocol, prealbumin was checked on admission and approximately weekly thereafter until discharge.

RESULTS

Patients had a median age of 28 years old, a mean admission body mass index (BMI) of 12.9 kg/m(2) (S.D. 6.1), and 89% of patients were women. A total of 47% of patients had a low prealbumin at the time of admission. By discharge, 77% of patients had normalized their prealbumin levels. Patients with low admission prealbumin levels had a threefold increased risk of refeeding hypophosphatemia and a twofold increase in hypoglycemia compared with patients who had a normal admission prealbumin, independent of admission BMI.

DISCUSSION

A low serum prealbumin level appeared concurrent with other markers of serious medical compromise, and was associated with two potentially life threatening complications of early refeeding: hypophosphatemia and hypoglycemia. The cause of low prealbumin remains elusive. Prealbumin should be checked in patients with severe AN prior to initiating weight restoration, as low levels may be an important harbinger of early refeeding complications.

Albumin synthesis rates in post-surgical infants and septic adolescents; influence of amino acids, energy, and insulin

BACKGROUND & AIMS

To investigate the effects of glucose, parenteral amino acids, and intravenous insulin on albumin synthesis rates in critically ill children.

METHODS

Two studies were performed in 8 post-surgical infants (age 9.8 ± 1.9 months; weight 9.5 ± 1.1 kg) and 9 septic adolescents (age 15 ± 1 yr; BMI 23 ± 4 kg m(-2)), respectively. All received a primed, constant, tracer infusion with [1-(13)C]Leucine. The infants in study 1 were randomized to receive low (2.5 mg kg(-1) min(-1)) and standard (5.0 mg kg(-1) min(-1)) glucose intake in a cross-over setting of two periods of 4 h each. The adolescents in study 2 were randomized to receive total parenteral nutrition with standard (1.5 g kg(-1) day(-1)) and high (3.0 g kg(-1) day(-1)) amino acid intake in a two day cross-over setting. On both study days, during the last 3 h of the tracer study, they received insulin infused at 80 mU m(-2) min(-1).

RESULTS

The post-surgical infants and the septic adolescents were mildly hypoalbuminemic (∼2.5 g dL(-1)) with high synthesis rates, which were not affected by different intakes of glucose, amino acids, or insulin infusion.

CONCLUSIONS

Albumin synthesis rates in hypoalbuminemic critically ill children are high but were not upregulated through nutrient supply, and in septic adolescents are unaffected by insulin.

The blood level of transforming growth factor-β rises in the early stages of acute protein and energy deficit in the weanling mouse

Plasma transforming growth factor (TGF)-β levels are high in the advanced stages of acute (wasting) pre-pubescent deficits of protein and energy. Consequently, this potently anti-inflammatory cytokine may help to sustain the depression of inflammatory immune competence in acute malnutrition. Our objective was to determine if plasma TGF-β levels rise during the early stages of acute malnutrition and, secondarily, to confirm the elevation reported previously in advanced weight loss. In two experiments, male and female C57BL/6J mice, initially 19 d old, consumedad libituma complete purified diet (group C), or in restricted daily quantities (group R) or had free access to an isoenergetic low-protein diet (group LP). TGF-β bioactivity in platelet-poor plasma was determined via inhibition of Mv1Lu mink lung cell proliferation after 3 d (Expt 1, early stage) or 14 d (Expt 2, advanced stage) of dietary intervention. At 3 d, mean plasma TGF-β bioactivities were 802 (C), 2952 (R) and 4678 (LP) pg/ml, and after 14 d mean bioactivities were 1786 (C), 5360 (R) and 5735 (LP) pg/ml. At both time points, the malnourished groups differed from age-matched controls (P ≤ 0·05). Thus, metabolically distinct weanling systems mimicking paediatric marasmus (group R) and kwashiorkor (group LP) exhibit an early rise in blood TGF-β concentration, and this cytokine joins corticosterone and IL-10 as a third anti-inflammatory hormone temporally positioned to contribute to the initiation (and maintenance) of malnutrition-associated immune depression. This investigation contributes new insight into the active anti-inflammatory form of immune competence that appears to prevail in acute pre-pubescent malnutrition.

Elevated blood interleukin-10 levels and undiminished systemic interleukin-10 production rate prevail throughout acute protein-energy malnutrition in the weanling mouse

The objectives were to determine if blood IL-10 levels rise during the early stages of acute (wasting) pre-pubescent malnutrition in metabolically distinct murine models known to depress inflammatory immune competence and whether systemic IL-10 production is affected in these pathologies. Weanling C57BL/6J mice were assigned to dietary protocols that elicited wasting pathologies mimicking the human diseases of marasmus (restricted-intake group) or incipient kwashiorkor (low-protein group). An age-matched control group also was included. Serum IL-10 bioactivities were assessed in the early (day 3) and advanced (day 14) stages of weight loss, and net systemic IL-10 production was assessed at the same stages of pathology by in vivo cytokine capture. Blood IL-10 levels were elevated in both malnourished groups relative to controls at days 3 and 14 (range of P values: 0.03-0.0001). Further, despite a limited supply of energy and nitrogenous substrates, the systemic IL-10 production rate was at least sustained in the malnourished groups and, in fact, was elevated in the marasmic group (P=0.05) throughout the progression of weight loss. IL-10 emerges as an anti-inflammatory mediator positioned to participate in initiating and upholding the depressed immune competence that accompanies acute pre-pubescent deficits of protein and energy.

A rational approach to nutritional assessment

BACKGROUND & AIMS

Consensus regarding definitions of malnutrition and methods to assess nutritional state is lacking. We propose a definition and its operationalization.

METHODS

A definition was formulated on the basis of the pathophysiology of malnutrition, while reviewing the metabolic and physiological characteristics of different populations, considered to be malnourished. The definition was operationalized to yield measures to perform nutritional assessment.

RESULTS

Malnutrition was defined as "a subacute or chronic state of nutrition in which a combination of varying degrees of over- or undernutrition and inflammatory activity has led to a change in body composition and diminished function". Its operationalization led to four elements that may serve as the basis of nutritional assessment: (1) measurement of nutrient balance, (2) measurement of body composition, (3) measurement of inflammatory activity, and (4) measurement of muscle, immune and cognitive function. Most elements measured should be validated with gold standards; normal values should be obtained in different populations. Values obtained in people considered to be at nutritional risk should be related to outcome.

CONCLUSION

A definition is proposed that reflects the pathophysiology of malnutrition and that, when operationalized, will lead to measures reflecting this pathophysiology. Such an approach may yield comparable and reproducible rates and degrees of malnutrition in populations as well as in individuals.

Albumin synthesis in premature neonates is stimulated by parenterally administered amino acids during the first days of life

BACKGROUND

We recently showed that parenteral administration of amino acids to premature infants immediately after birth is safe and results in a positive nitrogen balance and increased whole-body protein synthesis. However, we did not determine organ-specific effects; albumin, produced by the liver, is an important protein, but its concentration is often low in premature neonates during the first few days after birth.

OBJECTIVE

The objective of the study was to test the hypothesis that the fractional and absolute albumin synthesis rates would increase with the administration of amino acids after birth, even at low nonprotein energy intake.

DESIGN

Premature infants (<1500 g birth weight), who were on ventilation, received from birth onward either glucose only (control group, n = 7) or glucose and 2.4 g amino acid kg(-1) d(-1) (intervention group, n = 8). On postnatal day 2, all infants received a primed continuous infusion of [1-(13)C]leucine, and mass spectrometry techniques were used to determine the incorporation of the leucine into albumin. Results are expressed as medians and 25th and 75th percentiles.

RESULTS

Albumin fractional synthesis rates in the intervention group were significantly higher than those in the control group [22.9% (17.6-28.0%)/d and 12.6% (11.0-19.4%)/d, respectively; P = 0.029]. Likewise, the albumin absolute synthesis rates in the intervention group were significantly higher than those in the control group [228 (187-289) mg kg(-1) d(-1) and 168 (118-203) mg kg(-1) d(-1), respectively; P = 0.030].

CONCLUSION

Amino acid administration increases albumin synthesis rates in premature neonates even at a low energy intake.

Supplementation with aromatic amino acids improves leucine kinetics but not aromatic amino acid kinetics in infants with infection, severe malnutrition, and edema

We investigated whether supplementation with an aromatic amino acid (AAA) cocktail consisting of 0.5 mmol each of phenylalanine, tryptophan, and tyrosine compared with isonitrogenous amounts of alanine (Ala) would improve measures of protein kinetics in 14 (8 with AAA, 6 Ala) children with edematous malnutrition (aged 6-24 mo) during the infected acute malnourished state. Supplementation started immediately after the baseline experiment, 2 d postadmission and continued to the end of the acute phase of treatment. The second (postsupplementation) experiment was done approximately 12 d postadmission. We measured leucine kinetics, phenylalanine and tyrosine fluxes, using an i.g. 8-h prime continuous infusion of (2)H(3)-leucine, and an i.v. 6-h prime continuous infusion of (13)C-leucine, (2)H(2)-tyrosine, and (2)H(5)-phenylalanine in the fed state. Leucine flux tended to be faster (P = 0.06) in the AAA group compared with Ala group after supplementation (mean difference +/- SEM): 22.6 +/- 10.9 micromol/(kg . h). The rate of leucine appearance from protein breakdown [28.1 +/- 9.4 micromol/(kg . h)] and the nonoxidative disposal of leucine [i.e., leucine to protein synthesis; 35.4 +/- 12.9 micromol/(kg . h)] were faster (P < 0.02) in the AAA group than in the Ala group. There was no significant effect of supplementation on leucine splanchnic metabolism, phenylalanine, and tyrosine fluxes. These findings are consistent with the hypothesis that the blunting of the protein catabolic response to infection in children with edematous malnutrition syndrome is due to limited availability of aromatic amino acids.

Protein and amino acid requirements and the composition of complementary foods

In this paper, factorial models of the dietary requirements for protein, nitrogen and individual indispensable amino acids are developed from published information on the relationship between age and protein deposition and between protein (amino acid) intake and nitrogen balance. The results are used to develop recommendations on the protein-energy ratio and the amino acid pattern of the diet. As part of the development of the models, factors affecting dietary protein digestibility, bioavailability and efficiency of utilization are discussed. Over the age range of 6-24 mo the models predict a fall in the weight-specific protein and amino acid requirement that results almost entirely from the changes in the growth rate of the children. It is also concluded that the requirement for the maintenance of body protein equilibrium (so-called maintenance) changes little with age. This contrasts markedly with the relationship between age and energy requirements. The amino acid modeling implies that the optimum pattern of individual essential amino acids also changes only marginally across the age range considered in the report. The calculations of the dietary requirement for whole protein imply that achieving a minimum protein-energy ratio of 6.3% is desirable. The amount of protein needed from complementary foods for breast-fed children is discussed.

The protein metabolic response to HIV infection in young children

BACKGROUND

Growth failure often precedes secondary infections in HIV-infected infants and children, suggesting that inadequate protein deposition may be an early manifestation of infection by the virus. However, the protein metabolic response elicited by the virus in young children is unknown.

OBJECTIVE

We compared children with HIV infection and age-matched children without HIV infection with regard to whole-body and splanchnic protein kinetics and synthesis of acute phase proteins (APPs).

DESIGN

Whole-body and splanchnic leucine kinetics and fractional and absolute synthesis rates of 2 positive and 4 negative APPs were measured in 6 asymptomatic, HIV-infected children (4 males and 2 females) aged 6-17 mo and 4 uninfected children (3 females and 1 male) aged 7-9 mo who were in the fed state.

RESULTS

Compared with the control children, the HIV-infected children had significantly lower dietary energy and protein intakes and leucine balance and significantly faster leucine flux and fractional splanchnic leucine extraction; there was no significant difference between the groups in leucine oxidation rates. The HIV-infected children also had significantly higher plasma concentrations and absolute synthesis rates of the positive APPs and a significantly higher fractional synthesis rate of fibrinogen. The concentrations of 2 of the 4 negative APPs, albumin and HDL apolipoprotein A-I, were significantly lower in the HIV-infected children but were not associated with slower synthesis rates.

CONCLUSIONS

Children with HIV infection but without secondary infection have reduced protein balance because of an inability to down-regulate protein catabolism. Furthermore, the acute phase protein response elicited by HIV infection is characterized by higher concentrations and synthesis rates of positive APPs without lower concentrations of some negative APPs.

New concepts on nutritional management of severe malnutrition: the role of protein

Current guidelines for the management of severe malnutrition are mainly based on new concepts regarding the causes of malnutrition and on advances in our knowledge of the physiological roles of micronutrients. In contrast to the early 'protein dogma', there is a growing body of evidence that severely malnourished children are unable to tolerate large amounts of dietary protein during the initial phase of treatment. Similarly, great caution must be exercised to avoid excessive supply of iron and sodium in the diet, while keeping energy intake at maintenance levels during early treatment. Because severely malnourished children require special micronutrients, a mineral-vitamin mix is added to the milk-based formula diets, which are specially designed for the initial treatment and the rehabilitation phase. To further improve nutritional rehabilitation and reduce cases of relapse, 'ready-to-use therapeutic food' and 'ready-to-eat nutritious supplements' with relatively low protein (10% protein calories) and high fat content (54-59% lipidic calories) have been developed. Although current dietary recommendations do not differentiate between oedematous and nonoedematous forms of malnutrition or between adults and children, there are indications that further clarification is still needed for applying dietary measures for specific target groups.

Automated isolation of high-purity plasma albumin for isotope ratio measurements

Measurement of the incorporation of labeled amino acids in plasma albumin, isolated from plasma sampled at different time points after infusion start is a well-known technique to study human albumin synthesis. Unfortunately, no chromatographic method has been described yet, enabling the automated isolation of high-purity albumin from large numbers of plasma samples as is required to study the kinetics of this process. Therefore, we developed a fast protein liquid chromatographic method, capable of processing 200 microliters amounts of plasma in 74 min (injection to injection). The system can run unattended as the FPLC system is connected to a sample processor equipped with a polyether ether ketone (PEEK) sample loop and a cooled sample tray. Albumin isolation was divided into three steps. First, plasma samples were injected onto a 1-ml Blue Sepharose HiTrap affinity column, equilibrated with 50 mmol/l phosphate buffer (pH 7.0). After elution of non-binding protein, switching the solvent to phosphate buffer with 1.5 mol/l sodium chloride eluted albumin. The resulting albumin fraction was desalted on-line by directing it through two consecutive HiTrap 5-ml desalting columns, whereafter it was retained in the system within a 5-ml PTFE loop, connected to a motor value. After switching this valve, thus bypassing the sample loop, the phosphate buffers were changed automatically to Tris buffers. Final purification involved elution of the captured fraction over a 1-ml ion-exchange Resource Q column, using a sodium chloride gradient, ranging from 0 to 0.5 mol/l in Tris buffer (20 mmol/l, pH 7.5). A more than 99% purity of the final albumin fraction was confirmed by capillary electrophoresis.

The acute-phase protein response to human immunodeficiency virus infection in human subjects

Although several studies have shown that asymptomatic human immunodeficiency virus infection elicits an increase in whole body protein turnover, it is not known whether this increased protein turnover includes changes in the kinetics of acute-phase proteins (APPs). To answer this question, we measured 1) the plasma concentrations of four positive (C-reactive protein, alpha1-antitrypsin, haptoglobin, and fibrinogen) and four negative APPs [albumin, high-density lipoprotein (HDL)-apolipoprotein (apo) A1, transthyretin, and retinol-binding protein] and 2) the fractional (FSR) and absolute (ASRs) synthesis rates of three positive and three negative APPs using a constant intravenous infusion of [2H5]phenylalanine in five subjects with symptom-free acquired immunodeficiency syndrome (AIDS) and five noninfected control subjects. Compared with the values of the controls, the plasma concentrations, FSRs, and ASRs of most positive APPs were higher in the AIDS group. The negative APPs had faster FSRs in the AIDS group, there was no difference between the ASRs of the two groups, and only HDL-apoA1 had a lower plasma concentration. These results suggest that symptom-free AIDS elicits an APP response that is different from bacterial infections, as the higher concentrations and faster rates of synthesis of the positive APPs are not accompanied by lower concentrations and slower rates of synthesis of most of the negative APPs.

Chronic protein undernutrition and an acute inflammatory stimulus elicit different protein kinetic responses in plasma but not in muscle of piglets

The changes in protein metabolism of severe childhood malnutrition are generally perceived as a metabolic adaptation to chronic protein undernutrition. However, severe malnutrition is invariably accompanied by infections which also have profound effects on protein metabolism. This study aimed to distinguish the effect of protein undernutrition from that of an inflammatory stimulus on muscle and plasma protein synthesis rates. Two groups of five piglets consumed diets containing either 23% or 3% protein for 4 wk. They then were infused intravenously with 2H3-leucine before and 48 h after subcutaneous injections of turpentine to measure the fractional synthesis rates (FSR) of muscle protein and both the FSR and the absolute synthesis rates (ASR) of albumin and fibrinogen. Prior to turpentine injection, compared to control piglets, protein-deficient piglets had significantly lower muscle FSR and plasma concentrations of both albumin and fibrinogen, although only albumin had lower FSR and ASR. Turpentine injection decreased muscle FSR but increased the FSR, ASR and plasma concentrations of both albumin and fibrinogen in control piglets. In protein-deficient piglets, the inflammatory stress caused a further decrease in muscle protein FSR and in plasma albumin concentration despite marked increases in albumin FSR and ASR. Fibrinogen FSR, ASR and plasma concentration were increased. We conclude that protein undernutrition and inflammation elicit the same kinetic response in muscle protein but different kinetic responses in plasma proteins. Furthermore, whereas protein deficiency reduces the plasma albumin pool via a reduction in albumin synthesis, inflammation reduces it through a stimulation of catabolism and/or loss from the intravascular space.

Of flux and flooding: the advantages and problems of different isotopic methods for quantifying protein turnover in vivo: I. Methods based on the dilution of a tracer

The advantages and problems, both practical and theoretical, of isotope dilution approaches to the determination of whole-body and tissue protein turnover are discussed. It was concluded that: (1) measurements made on the basis of the labelling of plasma and breath are well suited to the measurement of body amino acid oxidation and balance, but because of the problem of inhomogeneity of the body amino acid pools, this approach generally underestimates protein turnover; (2) in investigations of nutritional effects on whole-body amino acid turnover, closer attention should be paid to first-pass splanchnic amino acid metabolism; (3) the trans-organ tracer balance method, particularly if combined with the measurement of tissue amino acid labelling, is a potentially useful approach to the simultaneous and dynamic measurement of both protein synthesis and degradation; (4) leucine may be the most generally useful label for tracer level studies of both whole-body and muscle protein synthesis, as recent studies have shown quite close isotopic equilibrium between muscle-free and tRNA-bound leucine pools.

Acute-phase protein response to infection in severe malnutrition

It is not known whether malnourished infants can mount a comprehensive acute-phase protein (APP) response and, if so, whether this is achieved by increasing APP synthesis rates. To address these issues, we measured 1) the plasma concentrations of five APPs (C-reactive protein, alpha1-acid glycoprotein, alpha1-antitrypsin, haptoglobin, and fibrinogen) and 2) the synthesis rates of three APPs (alpha1-antitrypsin, haptoglobin, and fibrinogen) using a constant intragastric infusion of [2H3]leucine in nine infected marasmic children at approximately 2 days postadmission (study 1), approximately 9 days postadmission when infections had cleared (study 2), and approximately 59 days postadmission at recovery (study 3). Except for fibrinogen, the plasma concentrations of all APPs were higher in study 1 than in studies 2 and 3. Although the rate of synthesis of haptoglobin was significantly greater in study 1 than study 2, the rates of fibrinogen and alpha1-antitrypsin synthesis were similar in all three studies. These results show that 1) severely malnourished children can mount an APP response to infection which does not include fibrinogen and 2) the APP response is accomplished through different mechanisms.

[Protein and energy needs of the infant with severe malnutrition. Application in a hospital environment for the treatment of malnutrition caused by deficient intake]

Severe malnutrition is defined by a weight for height below 70% of international standards or by presence of oedema in a clinically undernourished child. Severe malnutrition associated with oedema is called kwashiorkor. The origin of oedemas of kwashiorkor is still debated, but its relation with protein deficiency is strongly questioned. The same dietary management is now recommended for malnutrition with or without oedema. Present recommendations are based, as for well nourished children, on the separate estimation of nutritional requirements for maintenance and growth. Total requirements vary between 0.7 g/kg/day in the first few days of treatment to 5 g/kg/day or more when weight gain is maximum. As a result of high energy requirement during catch-up growth, protein requirements never exceed 10 to 12% of total energy needs.

Repletion of the plasma pool of nutrient transport proteins occurs at different rates during the nutritional rehabilitation of severely malnourished children

Increased morbidity and mortality are associated with lower plasma protein concentrations in children with severe protein-energy malnutrition. However, the kinetic changes responsible for repletion of the plasma pools of nutrient transport proteins and the rapidity of their replenishment in these children have not been determined. This study was undertaken to determine whether an increased rate of synthesis is the mechanism responsible for repletion of the plasma retinol-binding protein, transthyretin and high density lipoprotein-apolipoprotein A1 concentrations of children with severe malnutrition during nutritional rehabilitation. The plasma concentrations and synthesis rates of retinol-binding protein, transthyretin and high density lipoprotein-apolipoprotein A1 were measured using a constant intragastric infusion of 2H3-leucine in 22 children with severe protein-energy malnutrition, at approximately 2 d postadmission (study 1), approximately 8 d post-admission when infections were under control (study 2) and approximately 59 d postadmission at recovery (study 3). In study 1 the plasma concentrations and rates of synthesis of all the proteins were lower compared with values at recovery. In study 2, retinol-binding protein and transthyretin concentrations and absolute synthesis rates increased to the recovered values seen in study 3, but the high density lipoprotein-apolipoprotein A1 concentration and synthesis rate remained significantly lower. These results suggest that repletion of the plasma pool of these three nutrient transport proteins occurs at different rates, through an increase in the rate of synthesis.

Transferrin kinetics are altered in children with severe protein-energy malnutrition

This study was undertaken to determine the following: 1) the kinetic changes responsible for the depletion and repletion of plasma transferrin (Tr) concentration in children with protein-energy malnutrition (PEM); 2) the role of infection in mediating these changes; and 3) whether plasma Tr concentration is related to body protein status. We measured plasma Tr concentration, and fractional (FSR) and absolute (ASR) Tr synthesis rates with the use of a constant intragastric infusion of 2H3-leucine in 14 children with PEM, at 2 d postadmission (study 1), 8 d postadmission when infections were under control (study 2), and at recovery (study 3). In studies 1 and 2, the children synthesized less Tr and had lower Tr concentrations compared with values at recovery. When infections were controlled, plasma Tr concentration rose, but Tr synthesis was unchanged. There were only fair correlations (P < 0. 05) between plasma Tr concentrations and indices of wasting. Concerning malnourished children, we reached the following conclusions: 1) changes in the Tr pool size are achieved mainly through changes in synthesis rate; 2) infections play a minor role in reducing the Tr pool through either changes in the rate of catabolism or loss from the intravascular space; and 3) Tr concentration is not a very good indicator of protein nutritional status.

Protein-energy interactions in the management of severemalnutrition

The three syndromes of childhood malnutrition are contrasted with respect to protein. It is concluded that stunting and wasting are the outcomes of protein deficiency, and that kwashiorkor is not due to protein deficiency, rather it is related to unopposed oxidant stress. Formula for the energy and protein requirements are derived and contour plots of the amounts needed to sustain high rates of weight gain at different body compositions generated. It is suggested that all nutrients be expressed with energy as the denominator. No more than 12.5% of protein energy is required to sustain maximum likely rates of weight gain. Using this approach to design a diet, high rates of weight gain are achieved under field conditions in refugee camps.