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.

Adaptation of in vivo amino acid kinetics facilitates increased amino acid availability for fetal growth in adolescent and adult pregnancies alike.

During pregnancy, adult women with a normal BMI synthesise extra amino acids after an overnight fast by increasing body protein breakdown and decreasing amino acid oxidation. It is not known whether adolescent girls can make these adaptations during pregnancy. The present study aimed to measure and compare the protein, glutamine and alanine kinetics of adult women and adolescent girls at early-, mid- and late-pregnancy. Kinetics were measured in the overnight fasted state using intravenous infusions of 13C-leucine, 15N-glutamine and 15N-alanine in ten adults and twenty adolescents aged 14-17 years in the first and second trimesters (phase 1 study) and infusions of 13C-leucine and 15N2-urea in ten adults and eleven adolescents aged 16-17 years in the first and third trimesters (phase 2 study). In phase 1 study, there were no significant differences between the groups with regard to any of the kinetic parameters measured. In both groups, leucine flux increased (P< 0.05), the percentage of leucine flux oxidised decreased (P< 0.05) and non-oxidative leucine disposal to protein synthesis increased (P< 0.05) from the first to the second trimester. In phase2 study, leucine flux was significantly slower (P< 0.05) in the adult group than in the adolescent group during both trimesters, and whole-body leucine flux and non-oxidative leucine disposal increased significantly in the adolescent group (P< 0.05, respectively) and were higher in the adult group from the first to the third trimester. These results suggest that similar to their adult counterparts after an overnight fast, adolescent girls with a normal BMI provide extra amino acids required for net protein deposition during pregnancy by increasing protein breakdown and decreasing amino acid oxidation.

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.

Glutathione metabolism in type 2 diabetes and its relationship with microvascular complications and glycemia.

AIMS/HYPOTHESES: We hypothesized that there is decreased synthesis of glutathione (GSH) in type 2 diabetes (T2DM) especially in the presence of microvascular complications, and this is dependent on the degree of hyperglycemia. METHODS: In this case-control study, we recruited 16 patients with T2DM (7 without and 9 with microvascular complications), and 8 age- and sex-matched non-diabetic controls. We measured GSH synthesis rate using an infusion of [2H2]-glycine as isotopic tracer and collection of blood samples for liquid chromatography mass spectrometric analysis. RESULTS: Compared to the controls, T2DM patients had lower erythrocyte GSH concentrations (0.90 ± 0.42 vs. 0.35 ± 0.30 mmol/L; P = 0.001) and absolute synthesis rates (1.03 ± 0.55 vs. 0.50 ± 0.69 mmol/L/day; P = 0.01), but not fractional synthesis rates (114 ± 45 vs. 143 ± 82%/day; P = 0.07). The magnitudes of changes in patients with complications were greater for both GSH concentrations and absolute synthesis rates (P-values ≤ 0.01) compared to controls. There were no differences in GSH concentrations and synthesis rates between T2DM patients with and without complications (P-values > 0.1). Fasting glucose and HbA1c did not correlate with GSH concentration or synthesis rates (P-values > 0.17). CONCLUSIONS: Compared to non-diabetic controls, patients with T2DM have glutathione deficiency, especially if they have microvascular complications. This is probably due to reduced synthesis and increased irreversible utilization by non-glycemic mechanisms.

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.

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.

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).

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.

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.

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.

Whole body protein turnover and basal metabolic rate in homozygous sickle cell disease - abstract

Nitrogen balance and isotopic studies have indicated that protein metabolism in HbSS is altered. This is associated with the increased turnover of protein haemoglobin. We have therefore investigated protein matabolism in 6 patients with HbSS and 6 subjects with normal haemoglobin genotype (HbAA) by measuring and comparing whole body protein turnover (WBPT). Basal metabolic rate (BMR) was also measured as there is evidence that WBPT and BMR change in the same direction in various physiological and pathological states. WBPT was measured with an oral primed intermittent infusion of 15N-glycine over 18 hrs on an intake of 0.8-1.2g protein kg(to-1 power) d(-1power) and 187-193kJ kg(to -1 power) d(-1 power). Enrichments in urinary urea and ammonia were used to calculate turnover. BMR was measured by oxygen consumption using a ventilated hood system. Turnover in HbSS subjects was 66-81 percent more than in normal subjects. There were increases in both synthesis and breakdown. BMR was increased by 7 percent in the HbSS subjects compared to normal: the difference was even greater when the results were expressed in terms of body weight (22 percent) and muscle mass (20 percent). Assuming that all the increase in BMR resulted from the increase in turnover, we calculated that as much as 40-44 percent of BMR was consumed by protein turnover in patients with sickle-cell disease compared to 27-32 percent in th normal subjects. The results suggest that patients with Hbss have a hyper-metabolic state in which the demand for energy is greater than normal. Inadequacy of the standard normal diet may therefore be related to the poor growth usually seen in HbSS. Furthermore, the calculated high-energy cost of protien turnover in the patients with sickle-cell disease compared to normal suggest that patients with HbSS are less able to tolerate a reduction in dietary energy. This may help to explain their lowered resistance to stress and trauma, their poor wound healing and their high susceptibility to infection (AU)

The excretion of taurine in severe malnutrition - abstract

Taurine may be a conditionally essential nutrient in man. Diets lacking taurine have resulted in reduced body and urinary taurine and in the development of abnormal retinograms, which were reserved with taurine supplementation. Malnourished children are often fed diets low in taurine and other sulphur amino acids, particularly cow's milk-based diets. It is therefore possible that their taurine body pools and hence excretion are low. Urinary taurine was measured, by spectrophotometry, in 37 malnourished children, aged 3-24 months, on admission to hospital and when recovered. Four normals, aged 60-96 months, were also studied. Taurine in the urine of the normals, expressed as uM/d, was about 6 times that of the malnourished children on admission and on discharge respectively. The difference was even greater when expressed per body weight. The values were also low when compared with published values for normals. The children were rehabilitated on a cow's milk-based diet. Thus, the over-all low levels most likely resulted from low dietary taurine and reduced synthesis. Urinary taurine can serve as a crude index of taurine status, suggesting that the children were at risk of developing abnormal retinograms. The lowest values were from the oedematous children. This observation could be important in terms of new data showing that taurine protects cell membranes by attenuating toxic compounds. Taurine supplementation might beneficial in severe malnutrition (AU)

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 1.7g 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 24h 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, -11g/kg per d, was greater than at the end of the week, -2g/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(SD20). 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

Whole body protein turnover and resting metabolic rate in homozygous sickle cell disease

Whole body protein turnover and resting metabolic rate were measured in six adults with homozyguous sickle cell disease (genotype HbSS) and in six normal adults (genotype HbAA) of similar age. Turnover was measured with prime/intermittent oral doses of [15N]glycine over 18 h and resting energy expenditure was measured by indirect calorimetry. In HbSS, nitrogen flux (0.9 ñ 0.08 g day-1 kg-1), protein synthesis (6.0 ñ 0.5 g day-1 kg-1) and protein degradation (5.6 ñ 0.5 g day-1 kg-1) were significantly increased compared with HbAA nitrogen (flux 0.5 ñ 0.02g day-1 kg-1, protein synthesis 3.2 ñ 0.2 g day-1 kg-1 and protein degradation 2.8 ñ 0.2 g day-1 kg-1). Resting energy expenditure was significantly higher in HbSS compared with HbAA when expressed per unit of body weight (115 ñ 3 and 94 ñ 4 kj day-1 kg-1 respectively) or weight 0.75(317 ñ 6 and 269 ñ 8 kj day-1kg-0.75, respectively). The increase in protein turnover and energy expenditure suggest that patients with HbSS exist in a hypermetabolic state that requires greater dietary energy compared with HbAA. (AU)

Urea kinetics in normal pregnancy - abstract

There is need for an increase in protein deposition during pregnancy. However, the requirement for dietary protein and also the pattern of the increased needs throughout gestation remains unclear. Based on nitrogen balance studies, a single value for the daily allowance throughout pregnancy has been proposed by various expert committees with recognition of the inherent limitations of this recommendation. Urea kinetics which represent a sensitive marker for the adequacy of dietary protein was measured in trimesters 1, 2, and 3 in 13 healthy pregnant women and in 8 healthy non-pregnant women (controls) using the prime/intermittent intravenous presentation of 15N 15N urea. The results are given in a Table. P/I indicates that although more protein was consumed in pregnancy compared to the controls, less was oxidised. Also E/I was significantly less at all stages of pregnancy. T, that portion of P that was salvaged and not excreted, was highest in the 1st trimester. It contributes to the nitrogen available for metabolism and is 20 - 30 per cent of P when protein intake is adequate. T+I, the total nitrogen available for metabolism was highest in the 2nd trimester. The results suggest that the demand for nitrogen is not constant throughout pregnancy and that there is an increased demand in early pregnancy. In particular, this increase was not met by the quantity and/or quality of the deitary intake in the first trimester. These changes in nitrogen metabolism have important implications for making recommendations for dietary protein intake during pregnancy (AU)

Studies of whole body protein turnover within three hours in man using 15 N-glycine as tracer and urinary ammonia as end-product - abstract

We have been investigating ways in which to simplfy the method for measuring proteing turnover, by shortening the time required for reliable measurements. It has been possible, using 15N-Glycine and urinary ammonia as the end-product, to measure turnover in two to three hours in normal man. Turnover was calculated following either oral or continuous infusion of 15N-Glycine (0.005 15N/kg/h) in 8 adult men. Plataeu was reached within 120 minutes and was maintained for at least 4 to 6 hours. The results were as follows: AMMONIA ENRICHMENT: Oral dose - turnover (mgN/kg/D) 960ñ128 (SD), synthesis (gPr/kg/D) 4.7ñ0.7, breakdown (gPr/kg/D) 4.9ñ0.8; AMMONIA ENRICHMENT: I.V. dose turnover - (mgN/kg/D) 608ñ128, synthesis (gPr/kg/D) 3.1ñ0.8, breakdown (gPr/kg/D) 2.8ñ0.8. There was a significant linear relationship between ammonia enrichment (oral) and ammonia enrichment (I.V.) (R=0.82; p<0.05). In the same group, turnover measured from ammonia enrichment over 18 hours was 450 ñ 30mg N/kg/D. Turnover measured over 3 hours thus gave higher values than measurements over 18 hours; this is probably because more proteins with shorter half-lives are included in the 3 hour measurements. This would imply that previously reported measurements which used the longer measurement period underestimated turnover by at least 50 percent, and hence significantly underestimated the contribution of protein turnover to basal energy expenditure. The (3 hr) oral measurement appears to measure flux through a pool not included in the measurement intravenously. As this is of a similar magnitude to the pool into which hydrolysed urea nitrogen passess (Jackson et al, Hum. Nutr. Clin. Nutr., 38C, 339, 1984) it may represent a distinct enterohepatic pool of metabolic nitrogen (AU)

Whole-body protein turnover before and after splenectomy in children with homozygous sickle cell disease - abstract

Splenomegaly in sickle-cell disease is associated with excessive red cell destruction. We previously found whole body protein turnover and energy expenditure to be significantly higher in adults patients with sickle-cell disease compared to normals. The increase could be largely due to the increased turnover of the red cell, in particular the protein haemoglobin, in this disease state. We therefore measured whole body protein turnover in four children with sickle-cell disease, before and after splenectomy, to find out if the reduction in haemolysis that follows splenectomy would be reflected in a reduction in protein turnover. Protein turnover was measured with an oral primed intermittent infusion of 15N-glycine over 12-16 hours on the standard hospital diet. Isotopic excretion in urinary urea and ammonia were used to calculate protein turnover. (Table Included) Protein turnover was reduced by 23-47 percent after splenectomy. This reduction is presumably due to the fall in the excessive haemolysis that is associated with enlarged spleen. From a regression of protein turnover against energy expenditure in our previous study, it is estimated that the reduction in turnover after splenectomy could result in a theoretical saving of energy after splenectomy could be associated with the growth spurt that generally follow operation (AU)

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

The evidence is accumulating to suggest that glycine, the simplest amino 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. 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. 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 (AU)

Urea production and salvage during pregnancy in normal Jamaica women

The pattern of aggregated 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 [15N15N]-urea by dilution of label in urinary urea. Dietary protein intake was greater in trimester 1 than in nonpregnant women (167 ñ 36 vs 224 ñ 60 mg N.kg-1.d-1), and increased further in trimester 2 (266 ñ 59 mg N.kg-1.d-1). Urea production was not higher during pregnancy. Despite higher protein intake urea salvage was higer in pregnancy (40 ñ 24 nonpregnant vs 77 ñ 23, 61 ñ 31, and 51 ñ 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 (AU)

Whole-body protein turnover in man determined in three hours with oral or intravenous 15N-glycine and enrichment in urinary ammonia

Studies were carried out in eight normal adults to simplify the continuous infusion-end product method for measuring whole-body protein turnover using 15 N-glycine. When a priming dose of label suitable for the urea pool was followed by intermittent oral doses of label, plateau enrichment was maintained in urinary urea and ammonia from 9 to 18 h, giving values for nitrogen flux. (18h) of 0.69ñ0.05 g N/kg/d with urea and 0.46ñ0.01 g N/kg/d with ammonia. With a priming dose appropriate for the ammonia pool, plateau was reached in urinary ammonia in less than 120 min an maintained for up to 6h. Nitrogen flux (3h) with oral 15N-glycine was 0.96ñ0.12 g N/kg/d, and with intravenous label was 0.61ñ0.13 g N/kg/d. There was a significant linear relationship between flux measured with oral and intravenous isotope. It is suggested that different components of protein turnover are measured with the different approaches, and that the short method in particular measures rapidly turning over proteins associated with the gastrointestinal tract.(AU)