Synthesis of hepatic secretory proteins in normal adults consuming a diet marginally adequate in protein

Albumin and fibrinogen kinetics in sepsis: a prospective observational study

Background

The measurement of circulating substrate concentrations does not provide information about substrate kinetics. It, therefore, remains unclear if a decrease in plasma concentration of albumin, as seen during critical illness, is a consequence of suppressed production in the liver or increased peripheral clearance. In this study, using stable isotope tracer infusions, we measured albumin and fibrinogen kinetics in septic patients and in a control group of non-septic subjects.

Methods

With the approval from the institutional Research Ethics Board and after obtaining written informed consent from patients or their substitute decision maker, mechanically ventilated patients with sepsis and patients scheduled for elective coronary artery bypass grafting were enrolled. Patients in the non-sepsis group were studied on the day before surgery. The stable isotope L-[ring-²H₅]phenylalanine was used to measure absolute synthesis rates (ASR) of albumin and fibrinogen. A priming dose of L-[ring-²H₅]phenylalanine (4 µmol/kg) was given followed by a six-hour infusion at a rate of 0.15 µmol/kg/min. At baseline and hourly thereafter, blood was drawn to measure isotope enrichments by gas chromatography/mass spectrometry. Very low density lipoprotein apolipoprotein-B 100 isotopic enrichment was used to represent the isotopic enrichment of the phenylalanine precursor pool from which the liver synthesizes proteins. Plasma albumin and fibrinogen concentrations were also measured.

Results

Mean plasma albumin in septic patients was decreased when compared to non-septic patients, while synthesis rates were comparable. Mean plasma fibrinogen and ASR in septic patients was increased when compared to non-septic patients. In non-septic patients, no statistically significant correlation between plasma albumin and ASR was observed but plasma fibrinogen significantly correlated with ASR. In septic patients, plasma albumin and fibrinogen significantly correlated with ASR.

Conclusions

While septic patients showed lower plasma albumin levels than non-septic patients, albumin synthesis was similar in the two groups suggesting that hypoalbuminemia during sepsis was not caused by suppressed hepatic production but a result of enhanced clearance from the circulation. Hyperfibrinogenemia in septic patients was a consequence of increased fibrinogen production.

Trial registration: ClinicalTrials.gov: NCT02865408 (registered on August 12, 2016) and ClinicalTrials.gov: NCT02549443 (registered on September 15, 2015).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03860-7.

Metabolic benefits of rivaroxaban in non-valvular atrial fibrillation patients after radiofrequency catheter ablation

BACKGROUND AND OBJECTIVE

Rivaroxaban is a new oral anticoagulant for stroke prevention in patients with non-valvular atrial fibrillation (NVAF), which has less drug-food interaction than warfarin. We conducted this prospective randomized study to evaluate the metabolic benefits as well as the safety and efficacy with rivaroxaban versus warfarin in patients with NVAF following radiofrequency catheter ablation (RFCA).

METHODS

From April to July 2014, 60 patients with NVAF undergoing RFCA were prospectively enrolled in our study. Following RFCA, all patients were randomly assigned to receive rivaroxaban (Group R, n=30) or warfarin (Group W, n=30). Metabolic indices including serum total protein, albumin, globulin, and high-density lipoprotein (HDL) as well as bleeding, stroke, and systemic thromboembolism events were evaluated and compared during follow-up after 15, 30, 60, and 90 d of RFCA procedure.

RESULTS

Serum total protein, albumin, globulin, and HDL levels were all significantly elevated at each follow-up stage in Group R when compared to the baseline (P<0.05 respectively). In Group W, the metabolic indices decreased at first and then had an increasing trend. There were no deaths or thromboembolic complications in each group. The prevalence of total bleeding complications was similar between Group R and Group W (11/30, 36.7% vs. 10/30, 33.3%, P=0.79).

CONCLUSIONS

Patients with NVAF receiving rivaroxaban after RFCA procedures appear to benefit from a metabolic perspective compared with warfarin, providing practical clinical reference for the choice of the anticoagulant. Rivaroxaban seems to be as safe and effective in preventing thromboembolic events as warfarin for these patients.

Dietary Amino Acid Deficiency Reduces the Utilization of Amino Acids for Growth in Growing Pigs after a Period of Poor Health

BACKGROUND

During immune system activation, partitioning of amino acids (AAs) changes between protein gain and use by the immune system.

OBJECTIVE

We determined the effects of health status and dietary AA deficiency on nitrogen retention and AA utilization in pigs.

METHODS

Barrows (55 d of age) were obtained from good health (GH, n = 14) or poor health (PH, n = 14) status farms and allocated to a diet either adequate in essential amino acids (Adq) or 25% deficient in Met + Cys, Thr, and Trp (Def). Nitrogen balance was measured and AA irreversible loss rates (ILRs) were measured after an intravenous bolus of U-(13)C-labeled L-AAs.

RESULTS

On arrival at the experimental facilities, the PH pigs had 14% lower serum albumin and 50% greater serum haptoglobin and blood leukocyte counts than the GH pigs (P < 0.01), but the PH pigs showed signs of recovery during the trial. Total tract nitrogen digestibility was 3 percentage points lower in the PH pigs (P < 0.01). The PH-Adq pigs had compensatory body weight gain after arrival, coinciding with 7% greater nitrogen retention (P < 0.01) in the PH pigs than in the GH pigs. The PH pigs had a 24% greater ILR for Lys. Health status × diet interactions for Lys (P = 0.07), Val (P = 0.03), and Leu (P = 0.10) pool sizes and a greater urea pool size in the PH pigs (P = 0.01) support the observation that the increase in the ILR of Lys in the PH pigs was related to oxidation when feeding the Def diet, but to synthesis when feeding the Adq diet. Feeding Def diets increased monocyte counts by 30% (P < 0.01).

CONCLUSIONS

This study illustrates how the competition for AAs between protein synthesis associated with immune system activation and body protein deposition is greater when the dietary supply of Met + Cys, Thr, and Trp is limited in pigs during and after a period of poor health.

Randomized trial to evaluate nutritional status and absorption of enteral feeding after brain death

CONTEXT

Catecholamines and inflammatory mediators, with elevated levels after brain death, are associated with reduced function and survival of transplanted organs. Enteral nutrition reduces tissue damage and may benefit organs.

OBJECTIVE

To evaluate the effects of immunomodulating enteral nutrition in organ donors.

DESIGN

Prospective, randomized, open-label study.

SETTING

Intensive care unit.

PATIENTS

Thirty-six brain-dead organ donors.

INTERVENTIONS

Donors were randomized to receive enteral nutrition containing omega-3 polyunsaturated fatty acid, antioxidants, and glutamine or standard care (fasting). Donors received hormonal replacement therapy of corticosteroid, levothyroxine, dextrose, and insulin.

MAIN OUTCOME MEASURES

Gastrointestinal assimilation (measured by 13 carbon-labeled uracil breath analysis), quantity of organs recovered, resting energy expenditure, urine level of urea nitrogen, and serum levels of albumin, prealbumin, interleukin 6, tumor necrosis factor-α, and C-reactive protein were evaluated.

RESULTS

Thirteen patients (36%) assimilated 13C-labeled uracil. Resting energy expenditure was significantly higher than predicted between 10 and 14 hours after baseline in 33 donors (P= .007). Other measures were not conclusively different between fed and fasting groups. No adverse events occurred that were related to the enteral feeding.

CONCLUSIONS

About 30% of donors metabolized 13C-labeled uracil, although no difference in oxidation rate was found between fasting and fed donors. Corticosteroid administration lowers plasma levels of interleukin 6 and most likely contributes to greater than predicted resting energy expenditure. Thus energy needs may not be met during fasting if hormones are given. Consequences of this possible energy deficit warrant further study.

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.

Intrauterine growth retarded progeny of pregnant sows fed high protein:low carbohydrate diet is related to metabolic energy deficit

High and low protein diets fed to pregnant adolescent sows led to intrauterine growth retardation (IUGR). To explore underlying mechanisms, sow plasma metabolite and hormone concentrations were analyzed during different pregnancy stages and correlated with litter weight (LW) at birth, sow body weight and back fat thickness. Sows were fed diets with low (6.5%, LP), adequate (12.1%, AP), and high (30%, HP) protein levels, made isoenergetic by adjusted carbohydrate content. At -5, 24, 66, and 108 days post coitum (dpc) fasted blood was collected. At 92 dpc, diurnal metabolic profiles were determined. Fasted serum urea and plasma glucagon were higher due to the HP diet. High density lipoprotein cholesterol (HDLC), %HDLC and cortisol were reduced in HP compared with AP sows. Lowest concentrations were observed for serum urea and protein, plasma insulin-like growth factor-I, low density lipoprotein cholesterol, and progesterone in LP compared with AP and HP sows. Fasted plasma glucose, insulin and leptin concentrations were unchanged. Diurnal metabolic profiles showed lower glucose in HP sows whereas non-esterified fatty acids (NEFA) concentrations were higher in HP compared with AP and LP sows. In HP and LP sows, urea concentrations were 300% and 60% of AP sows, respectively. Plasma total cholesterol was higher in LP than in AP and HP sows. In AP sows, LW correlated positively with insulin and insulin/glucose and negatively with glucagon/insulin at 66 dpc, whereas in HP sows LW associated positively with NEFA. In conclusion, IUGR in sows fed high protein:low carbohydrate diet was probably due to glucose and energy deficit whereas in sows with low protein:high carbohydrate diet it was possibly a response to a deficit of indispensable amino acids which impaired lipoprotein metabolism and favored maternal lipid disposal.

Protein requirement of healthy school-age children determined by the indicator amino acid oxidation method

BACKGROUND

The current Dietary Reference Intake (DRI) recommendations for protein requirements in children are based on a factorial estimate and have not been directly determined.

OBJECTIVE

The objective of the current study was to determine the protein requirement in healthy, school-age children by measuring the oxidation of L-[1-(13)C]-phenylalanine to (13)CO(2) [label tracer oxidation (F(13)CO(2))] in response to graded intakes of protein.

DESIGN

Seven healthy children (6-11 y old) each randomly received a minimum of 7 protein intakes (range: 0.1-2.56 g · kg(-1) · d(-1)) for a total of 56 studies. The diets provided energy at 1.7 times the resting energy expenditure and were made isocaloric by using carbohydrate. Protein was given as an amino acid mixture on the basis of the egg-protein pattern, except for phenylalanine and tyrosine intakes, which were maintained constant across intakes. The mean protein requirement was determined by applying a 2-phase linear regression crossover analysis on F(13)CO(2) data, which identified a breakpoint (requirement) at minimal F(13)CO(2) in response to graded amounts of protein intake.

RESULTS

Mean and population-safe (upper 95% CI) protein requirements were determined to be 1.3 and 1.55 g · kg(-1) · d(-1), respectively. These results are significantly higher than the mean and population-safe protein requirements currently recommended by the DRI 2005 for macronutrients (0.76 and 0.95 g · kg(-1) · d(-1), respectively).

CONCLUSION

To our knowledge, this study was the first to directly estimate protein requirements in children by using stable isotopes and indicated that current recommendations are severely underestimated.

Metabolic and genomic response to dietary isocaloric protein restriction in the rat

We have examined hepatic, genomic, and metabolic responses to dietary protein restriction in the non-pregnant Sprague-Dawley rat. Animals were pair-fed either a 6 or 24% casein-based diet for 7-10 days. At the end of the dietary period, a microarray analysis of the liver was performed, followed by validation of the genes of interest. The rates of appearance of phenylalanine, methionine, serine, and glucose and the contribution of pyruvate to serine and glucose were quantified using tracer methods. Plasma and tissue amino acid levels, enzyme activities, and metabolic intermediates were measured. Protein restriction resulted in significant differential expression of a number of genes involved in cell cycle, cell differentiation, transport, transcription, and metabolic processes. RT-PCR showed that the expression of genes involved in serine biosynthesis and fatty acid oxidation was higher, and those involved in fatty acid synthesis and urea synthesis were lower in the liver of protein-restricted animals. Free serine and glycine levels were higher and taurine levels lower in all tissues examined. Tracer isotope studies showed an ∼50% increase in serine de novo synthesis. Pyruvate was the primary (∼90%) source of serine in both groups. Transmethylation of methionine was significantly higher in the protein-restricted group. This was associated with a higher S-adenosylmethionine/S-adenosylhomocysteine ratio and lower cystathione β-synthase and cystathionine γ-lyase activity. Dietary isocaloric protein restriction results in profound changes in hepatic one-carbon metabolism within a short period. These may be related to high methylation demands placed on the organism and caused by possible changes in cellular osmolarity as a result of the efflux of the intracellular taurine.

The effect of total starvation and very low energy diet in lean men on kinetics of whole body protein and five hepatic secretory proteins

It is unclear whether the rate of weight loss, independent of magnitude, affects whole body protein metabolism and the synthesis and plasma concentrations of specific hepatic secretory proteins. We examined 1) whether lean men losing weight rapidly (starvation) show greater changes in whole body protein kinetics, synthesis, and circulating concentrations of selected hepatic secretory proteins than those losing the same amount of weight more slowly [very low energy diet (VLED)]; and 2) whether plasma concentrations and synthetic rates of these proteins are related. Whole body protein kinetics were measured using [1-(13)C]leucine in 11 lean men (6 starvation, 5 VLED). Fractional and absolute synthetic rates of HDL-apolipoprotein A1 (apoA1), retinol binding protein, transthyretin, alpha(1)-antitrypsin (alpha(1)-AT), and transferrin were measured using a prime-constant intravenous infusion of [(13)C(2)]glycine. Compared with VLED group, the starvation group showed greater increases (at a 5% weight loss) in whole body protein oxidation (P < 0.05); fractional synthetic rates of HDL-apoA1 (25.3 vs. -1.52%; P = 0.003) and retinol binding protein (30.6 vs. 7.1%; P = 0.007); absolute synthetic rates of HDL-apoA1 (7.1 vs. -3.8 mg.kg(-1).day(-1); P = 0.003) and alpha(1)-AT (17.8 vs. 3.6 mg.kg(-1).day(-1); P = 0.02); and plasma concentration of alpha(1)-AT (P = 0.025). Relationships between synthetic rates and plasma concentrations varied between the secreted proteins. It is concluded that synthetic rates of hepatic secreted proteins in lean men are more closely related to the rate than the magnitude of weight loss. Changes in concentration of these secreted proteins can occur independently of changes in synthetic rates, and vice versa.

Nutrient ingestion, protein intake, and sex, but not age, affect the albumin synthesis rate in humans

The aim of this study was to assess the effects of nutrient ingestion, dietary protein intake, age, and sex on the fractional synthesis rate (FSR) of albumin. Thirty-six healthy free-living individuals (8 females and 10 males aged 21-43 y and 9 females and 9 males aged 63-79 y) completed three 18-d periods of controlled feeding with protein intakes of 125% (P125, 1.00 g protein x kg(-1) x d(-1)), 94% (P94, 0.75 g protein x kg(-1) x d(-1)), and 63% (P63, 0.50 g protein x kg(-1) x d(-1)) of the recommended dietary allowance. On d 12 of each trial, postabsorptive (PA) serum albumin concentration was determined and PA and postprandial (PP) albumin FSR were estimated from the rate of l-[1- 13C] leucine incorporation into plasma albumin during an 8-h infusion. There were no age-related differences in PA and PP albumin FSR. Albumin FSR was higher PP than PA (P < 0.0001), and the increase in albumin FSR from PA to PP was smaller as dietary protein intake decreased from P125 to P94 and P63 (P < 0.05). Independent of protein intake, males had a higher albumin FSR (P < 0.05) and a greater increase in albumin FSR with feeding (P < 0.05). There was no age or dietary protein effect on serum albumin concentrations, but males had higher albumin concentrations than females (P < 0.0001). These results show that older persons are responsive to nutrient ingestion and dietary protein-related changes in albumin FSR. The greater albumin synthesis rate in males might contribute to a higher albumin concentration set point.

Phospholipid profile of developing heart of rats exposed to low-protein diet in pregnancy

Although the myocardial phospholipid and fatty acid content have profound effects on the heart function, very little information is available on the effects of restricted maternal protein intake during pregnancy on the phospholipid profile and fatty acid content of the developing heart. The present study was therefore undertaken to examine the effect of pregnant dams fed diets containing either 180 (normal) or 90 (low) g/kg casein diet for 2 wk before mating and throughout pregnancy on myocardial phospholipid and fatty acid content of male offspring. Whereas no changes in phosphatidylcholine and phosphatidylethanolamine were detected, increases in lysophosphatidylcholine, phosphatidylserine, and sphingomyelin were seen in the hearts of offspring in the low-protein (LP) group. Analysis of cardiac fatty acids revealed that although the saturated fatty acid (myristate, palmitate, and stearate) levels were significantly reduced, the unsaturated fatty acid (linoleate, arachidonate, and decosahexanoate) levels were significantly increased in the developing heart in the LP group. Furthermore, assessment of nuclear transcription factors involved in regulation of cardiac metabolism revealed a decrease in myocyte enhancer factor-2C mRNA levels in the LP group, whereas an increase in the mRNA amount of peroxisome proliferator-activated receptor-alpha was observed in this group. These results demonstrate that maternal LP diet can induce changes in the phospholipid profile and fatty acid content of the developing heart, which may have implications for metabolism of the neonatal heart.

Relation between liver fat content and the rate of VLDL apolipoprotein B-100 synthesis in children with protein-energy malnutrition

BACKGROUND

Fatty infiltration of the liver is associated with an increased morbidity and mortality in children with severe protein-energy malnutrition (PEM), but its pathogenesis remains unclear. Although impaired synthesis of VLDL apolipoprotein B-100 (VLDL-apo B-100) is generally accepted as the pathogenetic mechanism, the rate of it synthesis has not been measured in children with PEM.

OBJECTIVE

The objective of the study was to ascertain the relation between the degree of hepatic steatosis and the rate of VLDL-apo B-100 synthesis in children with PEM.

DESIGN

The fractional and absolute rates of VLDL-apo B-100 synthesis were measured with a prime-constant intravenous infusion of [2H3]leucine in 13 severely malnourished children (8 boys and 5 girls) aged 7-18 mo. Hepatic fat content was estimated by computerized tomography scanning by using the ratio of liver to spleen (L:S) attenuation. The ratio is inversely related to hepatic fat content such that the lower the L:S, the greater the amount of fat in the liver.

RESULTS

There were significant inverse relations between L:S attenuation and VLDL-apo B-100 concentration (P < 0.02), the absolute rate of VLDL-apo B-100 synthesis (P < 0.02), and plasma triacylglycerol (P < 0.02) and serum cholesterol (P < 0.05) concentrations.

CONCLUSIONS

These results suggest that children with PEM synthesize VLDL-apo B-100 at a faster rate as the degree of hepatic fat infiltration increases. Thus, fatty infiltration of the liver in PEM is not due to a reduction in the synthesis of VLDL-apo B-100.

Effects of protein malnutrition on IL-6-mediated signaling in the liver and the systemic acute-phase response in rats

This study examines the effects of malnutrition on IL-6 signaling pathways of rats fed 2% vs. 20% casein diets for 14 days. Effects of malnutrition on the abundance and IL-6-stimulated phosphorylation of signaling proteins in the JAK-STAT and MAP kinase pathways were examined in the liver. Changes of the acute-phase response as reflected by serum α1-acid glycoprotein (AG), TNF-α (TNF), and IL-1β (IL-1) were compared in the two dietary groups at 0, 4, 8, 16, and 24 h after IL-6 administration. Under basal conditions, the abundance of the IL-6 receptor, gp130, JAK1, STAT1, and STAT3 proteins and levels of phosphorylation of ERK1/2 and p38 were significantly increased in the liver in the 2% casein group compared with the 20% casein group. With IL-6 stimulation, the increased phosphorylation per unit of protein of these signaling proteins was not different in the liver between the two groups. Before IL-6 stimulation, serum levels of TNF, IL-1, IL-6, and AG were significantly higher in the 2% casein group than in the 20% casein group. After bolus injection of IL-6, changes in IL-1 and AG were similar in the two dietary groups, although a slight decline in AG level was noted after 8 h of IL-6 administration in the 2% protein group. These data demonstrate that protein malnutrition produces changes in inflammation-related proteins characteristic of a low-grade systemic inflammatory response and, thus, can serve as an inflammatory stimulus. The capacity for response to IL-6 is preserved, suggesting adaptive preservation of acute-phase responsiveness during malnutrition.

Metabolic responses to protein restriction during pregnancy in rat and translation initiation factors in the mother and fetus

A low-protein diet during pregnancy in the rat results in intrauterine growth restricted (IUGR) fetuses. The adaptive responses of the mother to low-protein diet and the mechanisms of IUGR in this model are not understood. In the present study, we report the maternal metabolic responses to protein restriction and their impact on growth, carcass composition, and translation initiation in the fetus. Pregnant Sprague-Dawley rats were pair-fed either a 6% protein (LP, n = 7) or a 24% protein (NP, n = 7) diet from conception until delivery. Plasma amino acids and urea levels and rate of oxygen consumption were measured sequentially through pregnancy. Translation initiation factors eIF2alpha, Ser51 phosphorylated eIF2alpha, eIF4E, phosphorylated eIF4E, and 4E-BP1 were quantified in the maternal and fetal muscle and liver. Protein restriction resulted in higher rate of oxygen consumption (p < 0.01), lower plasma branched chain amino acid (p < 0.05) in the mother, and lower plasma histidine levels (p < 0.05) in the fetus. Plasma urea nitrogen was lower in the LP group throughout gestation. The phosphorylated 4E-BP1 (gamma form) in the maternal liver was 4-fold higher in the LP group. The phosphorylated eIF2alpha was higher in the livers of IUGR fetuses. We speculate that the lower plasma branched chain amino acids in the mother during early pregnancy may be due to a lower rate of protein turnover in the LP group. The mechanism of increased energy consumption due to protein restriction remains unclear. The data on translation initiation factors suggest a higher rate of protein synthesis in the maternal liver and a lower rate in the fetal liver in response to protein restriction.

Response of hepatic proteins to the lowering of habitual dietary protein to the recommended safe level of intake

The plasma concentrations of albumin, HDL apolipoprotein A1 (apoA1), retinol-binding protein (RBP), transthyretin (TTR), haptoglobulin, and fibrinogen were measured, and a stable isotope infusion protocol was used to determine the fractional and absolute synthesis rates of RBP, TTR, and fibrinogen in 12 young adults on three occasions during a reduction of their habitual protein intake from 1.13 to 0.75 g x kg(-1) x day(-1) for 10 days. This study was performed to determine whether healthy adults could maintain the rates of synthesis of selected nutrient transport and positive acute-phase proteins when consuming a protein intake of 0.75 g x kg(-1) x day(-1). During the lower protein intake, the plasma concentration of all the proteins, other than HDL-apoA1, remained unchanged. HDL-apoA1 concentration was significantly reduced (P < 0.05) after 3 days of the lower protein intake, but not at 10 days. The rates of synthesis of RBP and TTR declined significantly (P < 0.05), whereas the rate of synthesis of fibrinogen remained unchanged. The results indicate that, when normal adults consume the recommended safe level of protein, 0.75 g x kg(-1) x day(-1), there is a slower rate of turnover of nutrient transport proteins than on their habitual diet. Hence, healthy individuals consuming this amount of protein may be less able to mount an adequate metabolic response to a stressful stimulus.

Plasma protein synthesis measurements using a proteomics strategy

The analysis of the synthesis of proteins has been the subject of many studies in animals and humans. Plasma proteins can be used as an easy accessible source of specific proteins. In this paper, an innovative method to study the synthetic rate of plasma proteins is described. This methodology, based on the proteomics approach, enables the direct observation of the effects of posttranslational modifications of protein synthesis and/or degradation. The methodology is based on 1D or 2D electrophoresis and subsequent electrospray ionization liquid chromatography mass spectrometry (ESI-LC-MS). Protein synthesis is measured in isotopically labeled peptides of the identified proteins. This innovative method can be used to assess amino acid adequacy and safety by studying protein synthesis and posttranslational modification of plasma proteins in more detail.

Serum hyaluronic acid as a comprehensive marker to assess severity of liver disease in schistosomiasis

Schistosomiasis mansoni is a non-cirrhotic fibrogenic disease model. The mild form shows normal liver function with slight or no liver fibrosis whereas in the periportal fibrosis form the manifestations of portal hypertension prevail over hepatocellular failure. We assessed serum hyaluronic acid as a marker of the course of the disease. We studied 24 patients presenting with pure chronic forms of schistosomiasis and seven with cirrhosis. In order to measure serum hyaluronic acid we developed a sandwich fluorescent ELISA-like assay. alpha2-Macroglobulin, prothrombin index, gamma-glutamyltransferase, platelets and ultrasound parameters were also assessed. The 20 micro g/l (ROC plot) hyaluronic acid level differentiated patients with the mild form (with no portal hypertension) from those with the severe form of schistosomiasis with 78% diagnostic efficacy. The 80 micro g/l cut-off value differentiated patients with the severe form of schistosomiasis from the cirrhotic group with similar diagnostic efficacy. alpha2-Macroglobulin provided no distinction between the groups studied. The hyaluronic acid serum concentration correlated positively with the splenic vein diameter (P=0.004) and marginally with alpha2-macroglobulin (P=0.059). Serum hyaluronic acid is a good marker for the initial phase of hepatic fibrosis and it was able to assess severity of liver disease in schistosomiasis.

Effects of exercise training on thermoregulatory responses and blood volume in older men

We assessed the effects of aerobic and/or resistance training on thermoregulatory responses in older men and analyzed the results in relation to the changes in peak oxygen consumption rate (VO(2 peak)) and blood volume (BV). Twenty-three older men [age, 64 +/- 1 (SE) yr; VO(2 peak), 32.7 +/- 1.1 ml. kg(-1). min(-1)] were divided into three training regimens for 18 wk: control (C; n = 7), aerobic training (AT; n = 8), and resistance training (RT; n = 8). Subjects in C were allowed to perform walking of ~10,000 steps/day, 6-7 days/wk. Subjects in AT exercised on a cycle ergometer at 50-80% VO(2 peak) for 60 min/day, 3 days/wk, in addition to the walking. Subjects in RT performed a resistance exercise, including knee extension and flexion at 60-80% of one repetition maximum, two to three sets of eight repetitions per day, 3 days/wk, in addition to the walking. After 18 wk of training, VO(2 peak) increased by 5.2 +/- 3.4% in C (P > 0.07), 20.0 +/- 2.5% in AT (P < 0.0001), and 9.7 +/- 5.1% in RT (P < 0.003), but BV remained unchanged in all trials. In addition, the esophageal temperature (T(es)) thresholds for forearm skin vasodilation and sweating, determined during 30-min exercise of 60% VO(2 peak) at 30 degrees C, decreased in AT (P < 0.02) and RT (P < 0.02) but not in C (P > 0.2). In contrast, the slopes of forearm skin vascular conductance/T(es) and sweat rate/T(es) remained unchanged in all trials, but both increased in subjects with increased BV irrespective of trials with significant correlations between the changes in the slopes and BV (P < 0.005 and P < 0.0005, respectively). Thus aerobic and/or resistance training in older men increased VO(2 peak) and lowered T(es) thresholds for forearm skin vasodilation and sweating but did not increase BV. Furthermore, the sensitivity of the increase in skin vasodilation and sweating at a given increase in T(es) was more associated with BV than with VO(2 peak).