Determination of Indispensable Amino Acid Digestibility of the Red Kidney Bean in Humans Using a Dual Stable Isotope Tracer Method

BACKGROUND

Protein quality of the red kidney bean (RKB), a common source of dietary protein, has been assessed using the protein digestibility-corrected amino acid score (PDCAAS) determined in animal models using mainly oro-fecal digestibility. More recently, the FAO recommended to use digestible indispensable amino acid score (DIAAS) instead of PDCAAS but highlighted insufficient data on true ileal indispensable amino acid (IAA) digestibility of proteins because amino acids are absorbed in the ileum.

OBJECTIVES

Using a recently developed dual stable isotope tracer method, we aimed to measure each IAA digestibility as representation of true ileal digestibility of the RKB, Phaseolus vulgaris, in humans consuming a typical Jamaican meal.

METHODS

RKB-IAAs were intrinsically labeled by adding 2H2O to the plants. Uniformly labeled-[13C]-spirulina (standard protein) was added to a meal prepared with the labeled RKB and fed to 10 healthy adults (5 males, 5 females) in a nonrandomized trial as primed/intermittent doses to achieve a steady state IAA enrichment in plasma. Enrichment of 2H- and 13C-labeled IAA in plasma and the bean was measured by mass spectrometry. Each IAA digestibility (except tryptophan and histidine) was calculated as the ratio of plasma 2H-IAA to meal 2H-IAA divided by the ratio of plasma 13C-IAA to meal 13C-IAA adjusted for loss of 2H-atom during transamination and digestibility of spirulina.

RESULTS

Adequate IAA labeling (>1000 ppm 2H excess) and plasma plateau isotopic enrichment were achieved. Mean RKB-IAA digestibility (%) was 79.4 ± 0.5, ranging from 69.0 ± 1.2 (threonine) to 85.7 ± 1.7 (lysine).

CONCLUSION

The dual stable isotope tracer digestibility data are similar to published oro-fecal digestibility supporting substantial nitrogen exchange in the colon. The individual IAA digestibility is useful to derive DIAAS to replace PDCAAS. Using published RKB-IAA composition, extrapolated DIAAS was 0.63 based on the lowest score for methionine.

CLINICAL TRIAL REGISTRATION

https://register.

CLINICALTRIALS

gov; ID: NCT-04118517.

EXpanding Treatment for Existing Neurological Disease (EXTEND): An Open-Label Phase II Clinical Trial of Hydroxyurea Treatment in Sickle Cell Anemia

BACKGROUND

Cerebral vasculopathy in sickle cell anemia (SCA) begins in childhood and features intracranial arterial stenosis with high risk of ischemic stroke. Stroke risk can be reduced by transcranial doppler (TCD) screening and chronic transfusion therapy; however, this approach is impractical in many developing countries. Accumulating evidence supports the use of hydroxyurea for the prevention and treatment of cerebrovascular disease in children with SCA. Recently we reported that hydroxyurea significantly reduced the conversion from conditional TCD velocities to abnormal velocities; whether hydroxyurea can be used for children with newly diagnosed severe cerebrovascular disease in place of starting transfusion therapy remains unknown.

OBJECTIVE

The primary objective of the EXpanding Treatment for Existing Neurological Disease (EXTEND) trial is to investigate the effect of open label hydroxyurea on the maximum time-averaged mean velocity (TAMV) after 18 months of treatment compared to the pre-treatment value. Secondary objectives include the effects of hydroxyurea on serial TCD velocities, the incidence of neurological and non-neurological events, quality of life (QOL), body composition and metabolism, toxicity and treatment response, changes to brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), genetic and serologic markers of disease severity, and cognitive and pulmonary function.

METHODS

This prospective Phase II trial will enroll children with SCA in Jamaica, between the ages of 2 and 17 years, with either conditional (170-199 cm/sec) or abnormal (≥ 200 cm/sec) TCD velocities. Oral hydroxyurea will be administered daily and escalated to the maximum tolerated dose (MTD). Participants will be seen in the Sickle Cell Unit (SCU) in Kingston, Jamaica monthly until achieving MTD, and then every 3 months. TCD will be performed every 6 months.

RESULTS

Currently, 43 participants have been enrolled out of a projected 50. There was one withdrawal due to immigration, with no permanent screen failures. Of the 43 enrolled, 37 participants have initiated study treatment.

CONCLUSIONS

This trial investigates the effects of hydroxyurea treatment at MTD in children with conditional or abnormal TCD velocities before transfusion therapy and may represent an important advance towards establishing a suitable non-transfusion protocol for stroke prevention in children with SCA. The trial outcomes will have profound significance in developing countries where the disease burden is highest.

CLINICALTRIAL

ClinicalTrials.gov NCT02556099; https://clinicaltrials.gov/ct2/show/NCT02556099 (Archived by WebCite at http://www.webcitation.org/6k1yMAa9G).

Developmental contributions to macronutrient selection: a randomized controlled trial in adult survivors of malnutrition

Background and objectives: Birthweight differences between kwashiorkor and marasmus suggest that intrauterine factors influence the development of these syndromes of malnutrition and may modulate risk of obesity through dietary intake. We tested the hypotheses that the target protein intake in adulthood is associated with birthweight, and that protein leveraging to maintain this target protein intake would influence energy intake (EI) and body weight in adult survivors of malnutrition.

Methodology: Sixty-three adult survivors of marasmus and kwashiorkor could freely compose a diet from foods containing 10, 15 and 25 percentage energy from protein (percentage of energy derived from protein (PEP); Phase 1) for 3 days. Participants were then randomized in Phase 2 (5 days) to diets with PEP fixed at 10%, 15% or 25%.

Results: Self-selected PEP was similar in both groups. In the groups combined, selected PEP was 14.7, which differed significantly (P < 0.0001) from the null expectation (16.7%) of no selection. Self-selected PEP was inversely related to birthweight, the effect disappearing after adjusting for sex and current body weight. In Phase 2, PEP correlated inversely with EI (P = 0.002) and weight change from Phase 1 to 2 (P = 0.002). Protein intake increased with increasing PEP, but to a lesser extent than energy increased with decreasing PEP.

Conclusions and implications: Macronutrient intakes were not independently related to birthweight or diagnosis. In a free-choice situation (Phase 1), subjects selected a dietary PEP significantly lower than random. Lower PEP diets induce increased energy and decreased protein intake, and are associated with weight gain.

Effects of randomized supplementation of methionine or alanine on cysteine and glutathione production during the early phase of treatment of children with edematous malnutrition

BACKGROUND

We have shown that a low glutathione concentration and synthesis rate in erythrocytes are associated with a shortage of protein-derived cysteine in children with edematous severe acute malnutrition (SAM).

OBJECTIVE

We tested the hypothesis that methionine supplementation may increase protein-derived cysteine and upregulate cysteine synthesis, thereby improving glutathione synthesis during the early treatment of edematous SAM.

DESIGN

The cysteine flux, its de novo synthesis and release from protein breakdown, and erythrocyte glutathione synthesis rate were measured in 12 children with edematous SAM in the fed state by using stable isotope tracers at 3 clinical phases as follows: 3 ± 1 d (±SE) [clinical phase 1 (CP1)], 8 ± 1 d [clinical phase 2 (CP2)], and 14 ± 2 d (clinical phase 3) after admission. Subjects were randomly assigned to receive equimolar supplements (0.5 mmol ⋅ kg(-1) ⋅ d(-1)) of methionine or alanine (control) immediately after CP1.

RESULTS

In the methionine compared with the alanine group, cysteine flux derived from protein breakdown was faster at CP2 than CP1 (P < 0.05), and the change in plasma cysteine concentration from CP1 to CP2 was greater (P < 0.05). However, there was no evidence of a difference in cysteine de novo synthesis and its total flux or erythrocyte glutathione synthesis rate and concentration between groups.

CONCLUSIONS

Methionine supplementation increased cysteine flux from body protein but had no significant effect on glutathione synthesis rates. Although cysteine is made from methionine, increased dietary cysteine may be necessary to partially fulfill its demand in edematous SAM because glutathione synthesis rates and concentrations were less than previous values shown at full recovery. This study was registered at clinicaltrials.gov as NCT00473031.

Nutritional repletion of children with severe acute malnutrition does not affect VLDL apolipoprotein B-100 synthesis rate

VLDL apo B-100 is essential for the secretion of liver fat. It is thought that synthesis of this lipoprotein is impaired in childhood severe acute malnutrition (SAM), especially in the edematous syndromes, and that this contributes to the common occurrence of hepatic steatosis in this condition. However, to our knowledge, it has not been confirmed that VLDL apo B-100 synthesis is slower in edematous compared with nonedematous SAM and that it is impaired in the malnourished compared with the well-nourished state. Therefore, VLDL apo B-100 kinetics were measured in 2 groups of children with SAM (15 edematous and 7 nonedematous), aged 4-20 mo, at 3 stages during treatment. Measurements were done at 4 ± 1 d postadmission, mid- catch-up growth in weight, and at recovery (normal weight-for-length). VLDL apo B-100 synthesis was determined using stable isotope methodology to measure the rate of incorporation of (2)H(3)-leucine into its apoprotein moiety. The fractional and absolute synthesis of VLDL apo B-100 did not differ between the groups or from the initial malnourished stage to the recovery stage. Concentrations of VLDL apo B-100 were greater in the edematous than in the nonedematous group (P < 0.04) and did not differ from the initial stage to recovery. The data indicate that VLDL apo B-100 synthesis is not reduced when children develop either edematous or nonedematous SAM.

Prenatal factors contribute to the emergence of kwashiorkor or marasmus in severe undernutrition: evidence for the predictive adaptation model

Background

Severe acute malnutrition in childhood manifests as oedematous (kwashiorkor, marasmic kwashiorkor) and non-oedematous (marasmus) syndromes with very different prognoses. Kwashiorkor differs from marasmus in the patterns of protein, amino acid and lipid metabolism when patients are acutely ill as well as after rehabilitation to ideal weight for height. Metabolic patterns among marasmic patients define them as metabolically thrifty, while kwashiorkor patients function as metabolically profligate. Such differences might underlie syndromic presentation and prognosis. However, no fundamental explanation exists for these differences in metabolism, nor clinical pictures, given similar exposures to undernutrition. We hypothesized that different developmental trajectories underlie these clinical-metabolic phenotypes: if so this would be strong evidence in support of predictive adaptation model of developmental plasticity.

Methodology/Principal Findings

We reviewed the records of all children admitted with severe acute malnutrition to the Tropical Metabolism Research Unit Ward of the University Hospital of the West Indies, Kingston, Jamaica during 1962–1992. We used Wellcome criteria to establish the diagnoses of kwashiorkor (n = 391), marasmus (n = 383), and marasmic-kwashiorkor (n = 375). We recorded participants' birth weights, as determined from maternal recall at the time of admission. Those who developed kwashiorkor had 333 g (95% confidence interval 217 to 449, p<0.001) higher mean birthweight than those who developed marasmus.

Conclusions/Significance

These data are consistent with a model suggesting that plastic mechanisms operative in utero induce potential marasmics to develop with a metabolic physiology more able to adapt to postnatal undernutrition than those of higher birthweight. Given the different mortality risks of these different syndromes, this observation is supportive of the predictive adaptive response hypothesis and is the first empirical demonstration of the advantageous effects of such a response in humans. The study has implications for understanding pathways to obesity and its cardio-metabolic co-morbidities in poor countries and for famine intervention programs.

Predictors of physical activity energy expenditure in Afro-Caribbean children

BACKGROUND/OBJECTIVES

We hypothesized that maternal size during pregnancy and birth size are determinants of childhood physical activity energy expenditure (PAEE). Also, childhood PAEE is inversely related to adiposity and levels of cardiovascular risk factors.

SUBJECTS/METHODS

The Vulnerable Windows Cohort Study is a longitudinal observational study of 569 Afro-Jamaican mothers recruited from the first trimester and their offspring. Anthropometry, bioelectrical impedance, PAEE (using the Actical monitor) and cardiovascular risk factors (blood pressure, fasting glucose, insulin and lipids) were measured in 124 boys and 160 girls at a mean age of 13.2 years.

RESULTS

Boys had more fat-free mass (FFM) and expended more energy than girls (12.3±3.3 vs 9.6±2.8 kcal/kg/day; P<0.001). Maternal weight was associated with child's PAEE (r=0.29; P<0.001). PAEE was not significantly associated with birth weight. Maternal weight, after adjusting for child's age and sex, was positively associated with the child's FFM, fat mass and %fat (P-values 0.01). Age- and sex-adjusted PAEE was positively associated with FFM, fat mass and % fat (P-values <0.001), but not after adjusting for current weight. Age- and sex-adjusted PAEE was positively associated with triglycerides, insulin and systolic blood pressure (P-values <0.05), but not after adjusting for weight and height. PAEE was associated with fasting glucose after controlling for age, sex, weight and height (r=-0.12; P=0.02).

CONCLUSIONS

Maternal size, but not birth weight, is a determinant of childhood PAEE. PAEE is not strongly associated with childhood body composition, but is inversely related to fasting glucose concentration.

Polymorphisms in genes involved in folate metabolism as risk factors for oedematous severe childhood malnutrition: a hypothesis-generating study

BACKGROUND

Severe childhood malnutrition (SCM) occurs as both oedematous and non-oedematous syndromes. The reasons why some children develop oedematous SCM (OSCM) have remained elusive but differences in clinical presentation among malnourished children from similar backgrounds suggests that there might be inter-individual variation in susceptibility to OSCM.

AIM

To estimate the strength of the association between variants of three genes involved in folate/methyl group metabolism [methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and cystathionine beta-synthase (CBS)] and risk of OSCM.

METHODS

Patients previously admitted to the Tropical Metabolism Research Unit (TMRU) for treatment of either OSCM (cases, n = 74) or non-oedematous SCM (NOSCM, controls, n = 50) were recruited. Genotypes at four sites within the three genes (MTHFR C677T, MTHFR A1298C, MTR A2756G and CBS 844ins68) were determined using PCR-based assays.

RESULTS

The MTHFR 677T [odds ratio (OR) 0.63, 95% CI 0.2-1.7] and MTR 2756G (OR 0.74, 95% CI 0.4-1.4) alleles were associated with moderate reduction in risk of OSCM whereas the CBS 844ins68 allele (OR 1.4, 0.7-2.4) was associated with an increased risk. None of these risks was significant at the 5% level.

CONCLUSIONS

Genetic variation within folate/methyl group metabolic pathways might have a small but potentially important influence on risk of OSCM. Additional, larger data-sets will be required to test the specific hypotheses (about the putative effect size and direction of association) generated in this preliminary study. Such observations have the potential to improve our understanding of the pathogenesis of clinical heterogeneity in severe malnutrition.

Lipid kinetic differences between children with kwashiorkor and those with marasmus

BACKGROUND

It has been hypothesized that one factor associated with poor prognosis in kwashiorkor, but not in marasmus, is impaired lipid catabolism, which limits the supply of energy that is essential for survival when dietary intake is inadequate. However, this hypothesis has not been tested.

OBJECTIVE

The objective was to measure lipid kinetics in malnourished children with kwashiorkor or marasmus.

DESIGN

Glycerol concentration and flux (index of total lipolysis), palmitate concentration and flux (index of net lipolysis), and palmitate oxidation rate (index of fatty acid oxidation) were measured in 8 children (n = 5 boys and 3 girls) with kwashiorkor and 7 (n = 4 boys and 3 girls) with marasmus, aged 4-20 mo, in the postabsorptive state. The measurements were made approximately 3 d after admission, when the children were malnourished, and after the children attained normal weight-for-length, ie, at recovery.

RESULTS

The glycerol concentration was higher in the malnourished stage than at recovery for the marasmus and kwashiorkor groups combined. Glycerol flux tended to be lower (P = 0.067) and palmitate flux significantly lower (P < 0.05) in the kwashiorkor group than in the marasmus group. Palmitate oxidation was significantly lower in the malnourished stage than at recovery in the kwashiorkor group but not in the marasmus group. In the malnourished stage, palmitate oxidation was slower in the kwashiorkor group than in the marasmus group, but no significant differences between groups were observed at recovery.

CONCLUSIONS

Children with kwashiorkor break down fat and oxidize fatty acids less efficiently than do children with marasmus; this factor may explain the better survival rate in marasmus.

Relationship between birth weight and urea kinetics in children

OBJECTIVE

To explore the effect of birth weight on urea kinetics in young healthy children.

DESIGN

Observational study.

SETTING

Tertiary center for treatment of malnutrition.

SUBJECTS

A total of 17 male children, 6-24 months old, who had recovered from malnutrition.

INTERVENTIONS

Urea kinetics were measured using stable isotope methodology with [(15)N(15)N]-urea over 36 h.

RESULTS

Birth weight was negatively related to urea hydrolysis after controlling for the intake of protein (adjusted R (2 ) = 0.91, P = 0.001) and separately for energy intake (adjusted R (2) = 0.95, P = 0.001), age (adjusted R (2) = 0.90, P = 0.001) and rate of weight gain (adjusted R (2) = 0.91, P = 0.001). There was a tendency for higher urea production in the children with lower birth weight after controlling for nitrogen intake (adjusted R (2) = 0.93, P = 0.099), and separately for age (adjusted R (2) = 0.94, P = 0.06) and rate of weight gain (adjusted (R (2) = 0.92, P = 0.096). Urea excretion was not significantly related to birth weight.

CONCLUSIONS

The salvaging of urea nitrogen following urea hydrolysis contributed significantly more to the nitrogen economy in children with lower birth weight compared to those with higher birth weight. This may be as a result of reductive adaptation in the children with lower birth weight as a consequence of inappropriate prenatal nutrition and growth.

Maldigestion and malabsorption of dietary lipid during severe childhood malnutrition

BACKGROUND

Diets rich in lipid are used to provide energy density in treating children with severe malnutrition, but the extent to which their digestion and absorption can cope with the load effectively is uncertain.

AIM

To determine the extent of impaired digestion or absorption, in three groups of eight malnourished children (aged 5-23 months) using isotopic probes of the predominant fatty acids in coconut and corn oil used to fortify the diet.

METHODS

Each child received oral doses of one of three (13)C labelled triglycerides (trilaurin, triolein, or trilinolein). The recovery of (13)C label in stool either as triglyceride (TAG) or fatty acid (FA), was used to assess digestion and absorption. In a separate test, the recovery of label in stool following an oral dose of [(13)C]-glycocholate was measured to assess bile salt malabsorption.

RESULTS

The median recovery of label in stool was 9% (range 1-29%) of administered dose. Following treatment there was a reduction in stool (13)C excretion for the labelled TAG (<1%). In half the subjects, label was recovered as TAG in stool (median 0.6%, range 0-44%). Most label in stool was recovered as FA (median 30%, range 0-100%). Following [(13)C]-glycocholate, label was recovered in excess in about one third of studies.

CONCLUSION

Abnormalities in the gastrointestinal handling of lipid were observed in over 50% of children with severe malnutrition, reflecting problems in absorption, although impaired solubilisation or hydrolysis could also be contributory factors. The underlying lesion improves as treatment progresses, leading to concomitant improvement in function.

The effect of splenectomy for hypersplenism on whole body protein turnover, resting metabolic rate and growth in sickle cell disease

OBJECTIVE

To determine whether, in the same individual, an observed fall in whole body protein turnover following splenectomy in children with hypersplenism and homozygous sickle cell (SS) disease is associated with a measurable fall in resting metabolic rate (RMR) and an increase in rate of growth.

SUBJECTS

Six children (5 SS disease, 1 S beta degree thalassaemia), aged 68 to 126 months, were studied before and after splenectomy for hypersplenism.

DESIGN

Protein turnover was measured by the end product method using prime/intermittent oral doses of 15N-glycine and RMR by indirect calorimetry before preoperative transfusion and repeated at least eight weeks after splenectomy. Height and weight velocities were measured over six month periods before and after splenectomy.

SETTING

University Hospital of the West Indies in Jamaica and the Medical Research Laboratories (Jamaica).

RESULTS

After splenectomy protein turnover fell significantly by 30% and RMR by 34 kJ/kg/d. Mean weight velocity which was below normal before surgery, z = -2.3, improved significantly after surgery, z = 0.7, (P = 0.03). Height velocity increased in two children but the mean height velocity did not change following splenectomy. The reduction in protein turnover was estimated to account for 62% of the fall in RMR.

CONCLUSION

This study confirms that there is a significant reduction in energy expenditure following splenectomy for hypersplenism in SS disease. A reduction in protein turnover was a major contributor to the saving in energy, although it is not clear whether it accounted for all. In the present group of children the energy saved was associated with an improvement in the wasting present before splenectomy.

Urea production and salvage during pregnancy in normal Jamaican women

The pattern of aggregate nitrogen demand during pregnancy and the fetal and maternal components are unclear. Excess demand enhances efficiency of nitrogen utilization. Urea salvage contributes to enhanced efficiency. Dietary protein intake, urea production, and salvage of urea nitrogen were measured in eight nonpregnant control subjects, and trimesterly in nine pregnant women. Production was measured after prime-intermittent intravenous doses of [15N 15N]-urea by dilution of label in urinary urea. Dietary protein intake was greater in trimester 1 than in nonpregnant women (167 +/- 36 vs 224 +/- 60 mg N.kg-1.d-1), and increased further in trimester 2 (266 +/- 59 mg N.kg-1.d-1). Urea production was not higher during pregnancy. Despite higher protein intake, urea salvage was higher in pregnancy (40 +/- 24 nonpregnant vs 77 +/- 23, 61 +/- 31, and 51 +/- 12 mg N.kg-1.d-1). Therefore, the demand-supply gap for nitrogen was greatest early in pregnancy when fetoplacental growth is slowest, and implies heightened maternal demand.

Adaptation to a marginal intake of energy in young children

Six male children, aged 8-28 months, were studied for three consecutive periods of 1 week each. They were given diets that provided 1.7 g protein/kg per d and supplements of minerals and vitamins, with a metabolizable energy intake during the 1st, 2nd and 3rd week of 419, 293 and 335 kJ (100, 70 and 80 kcal)/kg per d, diets 1, 2 and 3 respectively. All the food offered was consumed. Each child was weighed at the same time each day on an electronic balance. On the 6th and 7th day of each study period urine and stool were collected for 24 h to assess nitrogen balance. Using linear regression analysis it was shown that all children gained weight on diet 1, 2.3 (SD 1.3) g/kg per d, and five of six children gained weight on diet 3, the mean for the whole group being 2.7 (SD 2.3) g/kg per d, not significantly different. On diet 2 all children lost weight, -5.4 (SD 1.3) g/kg per d, highly significantly different from each of the other dietary periods. Using asymptotic regression analysis it could be shown that the rate of weight loss during the first part of the week on diet 2, -11 g/kg per d, was greater than at the end of the week, -2 g/kg per d, with a tendency towards a steady weight by day 7. Apparent N retention (mg/kg per d) was positive at the end of each of the three dietary periods: diet 1, 112 (SD 25); diet 2, 54 (SD 34); diet 3, 82 (SD 20). In five of the six children there was a marked reduction in stool frequency on diet 2 compared with diet 1, that was maintained to the period on diet 3. The findings suggest that during the period on diet 2 there was a saving of energy of the order of 105 kJ (25 kcal)/kg per d, which lasted through into the period on diet 3.

Urinary excretion of 5-oxoproline (pyroglutamic aciduria) as an index of glycine insufficiency in normal man

1. The evidence is accumulating to suggest that glycine, the simplest amino acid, is conditionally essential in man. Benzoic acid, by conjugation with glycine to form hippuric acid, is known to deplete the free glycine pool of the body. Glycine is one substrate for the enzyme glutathione synthase (EC 6.3.2.3) and in the inborn error of metabolism in which glutathione synthase function is defective, increased quantities of 5-oxoproline are excreted in the urine. 2. An oral dose of 4-10 g sodium benzoate was given to six normal adults to deplete the metabolic pool of glycine, and the urinary excretion of 5-oxoproline was followed for 6 h. In five of the six, a significant increase in the urinary 5-oxoproline was seen within 3 h. 3. These findings show that 5-oxoprolinuria can result from limited glycine availability, and may provide a useful test for assessing glycine sufficiency in a range of physiological and pathological states.