THE RELATION BETWEEN THE SERUM UREA CONCENTRATION AND THE PROTEIN CONSUMPTION OF NORMAL INDIVIDUALS

Growth performance and blood profiles of Hanwoo steers at fattening stage fed Korean rice wine residue

The aim of this study was to investigate the effects of Korean rice wine residue (RWR) on the growth performance and blood profiles of Hanwoo steers in the fattening stage. In situ and in vivo experiments were conducted to analyze rumen fermentation characteristics and total tract digestibility, respectively. Three cannulated Hanwoo steers (mean body weight: 448 ± 30 kg) were used in both analyses. The growth performance of 27 experimental animals in the fattening stage (initial body weight: 353.58 ± 9.76 kg) was evaluated after 13 months of feeding. The animals were divided into three treatment groups (n = 9/group). The treatments comprised total mixed ration (TMR) only (CON), TMR + 10% RWR (10% RWR), and TMR + 15% RWR (15% RWR). The diets of equal proportions were fed daily at 08:00 and 18:00 h based on 2% of the body weight. The animals had free access to water and trace mineral salts throughout the experiment. Supplementation of 15% RWR significantly decreased (p < 0.05) the rumen fluid pH compared with the control treatment, but there was no significant difference in the total volatile fatty acid concentration. It also significantly increased (p < 0.05) dry matter digestibility compared with the other treatments. The total weight gain and average daily gain of the animals in the RWR-supplemented groups were significantly higher (p < 0.05) than those in the control group. Furthermore, the feed intake and feed efficiency of the RWR-supplemented groups were higher than those of the control group. Supplementation of RWR did not affect the alcohol, albumin, glucose, total cholesterol, triglyceride, and low-density lipoprotein concentrations, and aspartate aminotransferase and alanine transaminase activities in the blood; these parameters were within the normal range. The high-density lipoprotein and creatinine concentrations were significantly higher in the 15% RWR group, whereas the blood urea nitrogen concentration was significantly higher in the 10% RWR group than in the other groups. These results suggest that TMR with 15% RWR can serve as an alternate feed resource for ruminants.

Prerenal Azotemia: Differentiation of Hyperureagenesis from Renal Hypoperfusion Using Urinary Urea Nitrogen Data

Blood urea nitrogen (BUN) rises disproportionately to serum creatinine in patients with prerenal azotemia whether due to impaired hemodynamics or excessive ureagenesis. To determine whether urinary urea nitrogen excretion rates can distinguish between these causes of hyperuremia we performed a cross-sectional observational study to compare urinary urea nitrogen excretion rates in a highly selected group of patients with prerenal azotemia. Patients who had stable serum creatinine levels, BUN: serum creatinine ratios exceeding 20:1, and progressive azotemia were identified from the hospital laboratory data base. Using conventional clinicolaboratory criteria, 27 patients were diagnosed with either renal hypoperfusion (group I; n = 17) or hyperureagenesis ((group II; n = 10). Random urine sampling for electrolytes, osmolality, creatinine, and urea nitrogen was followed by 24 h collection for creatinine clearance and urinary urea nitrogen. There were no significant differences in age, gender, absolute levels of BUN, or BUN: serum creatinine ratios between the groups. Creatinine clearance (ml/min/1.73 m2) (ml/s/1.73 m2) was lower in group I than in group II (21 ± 16 vs. 36 ± 13; p<0.05) (0.35 ± 0.27 vs. 0.60 ± 0.22; p < 0.05). Twenty-four hour urinary urea nitrogen levels were significantly different (group I, 4.8 ± 2.9 vs. group II, 13.6 ± 3.2 gm; p < 0.001) (group I, 171 ± 300 vs. group II, 486 ± 114 mmol; p < 0.001). Random urine urea excretion indices were less discriminating but nevertheless still capable of separating the groups. Timed as well as random urine urea nitrogen determinations may assist in differentiating prerenal azotemia due to renal hypoperfusion from hyperureagenesis. Differentiation of these causes of prerenal azotemia might prevent iatrogenic overhydration of patients with azotemia incorrectly attributed to hemodynamic disturbances.

Mimicking oxygen delivery and waste removal functions of blood

In addition to immunological and wound healing cell and platelet delivery, ion stasis and nutrient supply, blood delivers oxygen to cells and tissues and removes metabolic wastes. For decades researchers have been trying to develop approaches that mimic these two immediately vital functions of blood. Oxygen is crucial for the long-term survival of tissues and cells in vertebrates. Hypoxia (oxygen deficiency) and even at times anoxia (absence of oxygen) can occur during organ preservation, organ and cell transplantation, wound healing, in tumors and engineering of tissues. Different approaches have been developed to deliver oxygen to tissues and cells, including hyperbaric oxygen therapy (HBOT), normobaric hyperoxia therapy (NBOT), using biochemical reactions and electrolysis, employing liquids with high oxygen solubility, administering hemoglobin, myoglobin and red blood cells (RBCs), introducing oxygen-generating agents, using oxygen-carrying microparticles, persufflation, and peritoneal oxygenation. Metabolic waste accumulation is another issue in biological systems when blood flow is insufficient. Metabolic wastes change the microenvironment of cells and tissues, influence the metabolic activities of cells, and ultimately cause cell death. This review examines advances in blood mimicking systems in the field of biomedical engineering in terms of oxygen delivery and metabolic waste removal.

Short-Term Preoperative Calorie and Protein Restriction Is Feasible in Healthy Kidney Donors and Morbidly Obese Patients Scheduled for Surgery

Introduction. Surgery-induced oxidative stress increases the risk of perioperative complications and delay in postoperative recovery. In mice, short-term preoperative dietary and protein restriction protect against oxidative stress. We investigated the feasibility of a calorie- and protein-restricted diet in two patient populations. Methods. In this pilot study, 30 live kidney donors and 38 morbidly obese patients awaiting surgery were randomized into three groups: a restricted diet group, who received a synthetic liquid diet with 30% fewer calories and 80% less protein for five consecutive days; a group who received a synthetic diet containing the daily energy requirements (DER); and a control group. Feasibility was assessed using self-reported discomfort, body weight changes, and metabolic parameters in blood samples. Results. Twenty patients (71%) complied with the restricted and 13 (65%) with the DER-diet. In total, 68% of the patients reported minor discomfort that resolved after normal eating resumed. The mean weight loss on the restricted diet was significantly greater (2.4 kg) than in the control group (0 kg, p = 0.002), but not in the DER-diet (1.5 kg). The restricted diet significantly reduced levels of serum urea and plasma prealbumin (PAB) and retinol binding protein (RBP). Conclusions. A short-term preoperative calorie- and protein-restricted diet is feasible in kidney donors and morbidly obese patients. Compliance is high and can be objectively measured via changes in urea, PAB, and RBP levels. These results demonstrate that this diet can be used to study the effects of dietary restriction on surgery-induced oxidative stress in a clinical setting.

Rumen fermentation and performance of Hanwoo steers fed total mixed ration with Korean rice wine residue

Background

This study was conducted to evaluate the effects of adding Korean rice wine residue (RWR) in total mixed ration (TMR) on in vitro ruminal fermentation and growth performance of growing Hanwoo steers.

Methods

For in vitro fermentation, the experimental treatments were Control (Con: 0 % RWR + TMR), Treatment 1 (T1: 10 % RWR + TMR), and Treatment 2 (T2: 15 % RWR + TMR). The rumen fluid was collected from three Hanwoo steers and mixed with buffer solution, after which buffered rumen fluid was transferred into serum bottles containing 2 g dry matter (DM) of TMR added with or without RWR. The samples were then incubated for 0 h, 12 h, 24 h, or 48 h at 39 °C and 100 rpm. For the in vivo experiment, 27 Hanwoo steers (6 months old) with an average weight of 196 ± 8.66 kg were subjected to a 24-week feeding trial. The animals were randomly selected and equally distributed into three groups. After which the body weight, feed intake and blood characteristics of each group were investigated.

Results

The pH of the treatments decreased significantly relative to the control during the 12 h of incubation. Total gas production and ammonia nitrogen (NH₃-N) was not affected by RWR addition. The total volatile fatty acid (VFA) was lower after 24 h of incubation but at other incubation times, the concentration was not affected by treatments. Feed cost was 8 % and 15 % lower in T1 and T2 compared to control. Blood alcohol was not detected and a significant increase in total weight gain and average daily gain were observed in Hanwoo steers fed with RWR.

Conclusion

Overall, the results of this study suggest that TMR amended with 15 % RWR can be used as an alternative feed resource for ruminants to reduce feed cost.

Low-protein diet fed to crossbred sows during pregnancy and lactation enhances myostatin gene expression through epigenetic regulation in skeletal muscle of weaning piglets

PURPOSE

This study was aimed to investigate the effects of a maternal low-protein diet on transcriptional regulation of the myostatin (MSTN) gene in skeletal muscle of weaning piglets.

METHODS

Sows were fed either a standard-protein (SP, 15 and 18 % crude protein) or a low-protein (LP, 50 % protein level of SP) diet throughout pregnancy and lactation. Longissimus dorsi muscle was sampled from male piglets at 28 days of age. The mRNA was determined by RT-PCR, and protein was measured by Western blot. Chromatin immunoprecipitation assay was used to determine the binding of transcription factors and histone H3 modifications on the MSTN gene promoter.

RESULTS

The maternal LP diet significantly decreased body weight and average daily gain (P < 0.05), which was associated with significantly lower plasma concentration of urea nitrogen and total protein (P < 0.05), as well as decreased muscle RNA content (P < 0.05). MSTN mRNA (P < 0.05) was significantly increased, together with enhanced (P < 0.05) mRNA and protein expression of forkhead box class O family member protein 3 (FoxO3), and a tendency of an increase (P = 0.10) in glucocorticoid receptor (GR) mRNA in the muscle of LP piglets. Furthermore, the binding of both FoxO3 and GR to the MSTN gene promoter was significantly higher (P < 0.05) in muscle of LP piglets, together with significantly enriched (P < 0.05) gene activation markers, H3K9Ac and H3K4me3.

CONCLUSION

These results indicate that MSTN mediates maternal LP diet-induced growth retardation, through epigenetic regulation involving FoxO3 and GR binding to its promoter.

The mean dietary protein intake at different stages of chronic kidney disease is higher than current guidelines

The actual dietary protein intake of adults without and with different stages of chronic kidney disease is not known. To evaluate this we performed cross-sectional analyses of 16,872 adults (20 years of age and older) participating in the National Health and Nutrition Examination Survey 2001-2008 who completed a dietary interview by stage of kidney disease. Dietary protein intake was assessed from 24-h recall systematically collected using the Automated Multiple Pass Method. Complex survey analyses were used to derive population estimates of dietary protein intake at each stage of chronic kidney disease. Using dietary protein intake of adults without chronic kidney disease as the comparator, and after adjusting for age, the mean dietary protein intake was 1.30 g/kg ideal body weight/day (g/kgIBW/d) and was not different from stage 1 or stage 2 (1.28 and 1.25 g/kgIBW/d, respectively), but was significantly different in stage 3 and stage 4 (1.22 and 1.13 g/kgIBW/d, respectively). These mean values appear to be above the Institute of Medicine requirements for healthy adults and the NKF-KDOQI guidelines for stages 3 and 4 chronic kidney disease. Thus, the mean dietary protein intake is higher than current guidelines, even after adjusting for age.

Food protein effect on plasma specific gravity, plasma protein, and hematocrit value

When the protein consumption of normal human individuals is increased from 0.5, to 1.5, to 2.5 gm. of protein per kilo body weight, the specific gravity of the plasma rises and the hematocrit value falls. The analysis of variance demonstrates that the change in protein consumption is a significant but minor factor in determining the total variability of the observations. When albino rats were given diets containing a small, a moderate, and a large amount of protein, there was an increase in serum protein concentration but no change in hematocrit value. During the period over which the most rapid changes in rate of urea excretion and serum urea concentration occurred as normal human individuals passed from a 2.5 to an 0.1 gm. of protein per kilo body weight consumption, there was no change in serum protein concentration. Over a 5 day period during which a diet that was adequate in calories but almost wholly devoid of protein was taken, the serum protein concentration of normal individuals steadily rose. This was associated with a slight increase in hematocrit value but no change in blood or plasma volume. The protein effect is one of the minor factors that contribute to the variability of serum protein and hematocrit measurements in normal individuals. The general conclusion is reached that we shall have to measure the rate at which red cells and protein enter and leave the circulating blood stream before we can hope to comprehend the mechanism of the protein effect.

Analysis of the quantitative relationship between anemia and chronic renal failure

The authors analyzed data from 106 adults with chronic renal failure [(CRF), serum creatinine (Scr) greater than 132.6 mumol/l (1.5 mg/dl)], to define the precision of, and effects of covariables on, the relationship between anemia and CRF. We excluded dialyzed or patients who had received transplants and those with obvious potential nonrenal causes of anemia. Hct was a linear function of BUN and Scr (r = -0.48, and r = -0.67, respectively), and a curvilinear function of creatinine clearance (r = 0.68), all p less than .0001. Confidence interval analysis revealed a +/- 10 volume percent variation in Hct at any level of renal function. Sex was the only covariable that affected Hct independently of CRF. This study suggests that CRF may have a different effect on Hct in males and females and indicates that the range of Hct possible at a given level of CRF precludes attributing anemia to CRF with assurance.

An evaluation of the diurnal rhythm of urea excretion in healthy young adults

A diurnal variation in urine urea excretion has been documented to exist in healthy young adults. Its persistence when dietary nitrogen intake approaches zero suggests that influences other than diet may in part generate the rhythm. These may include variations in the efficiency of rates of endogenous protein turnover of perhaps changes in renal tubular handling of urea especially in states of dietary nitrogen inadequacy. Recognition of these effects in the normal state are important before ascribing importance to changes in the disease state, particularly as we gain the ability to intervene nutritionally in the hospital setting.

The effect of age, sex and other factors on blood chemistry in health

Quantitative data is presented concerning the influence that age, sex, the menopause, oral contraception, blood group and time of blood collection have on 19 commonly-determined blood chemistry values. The data were derived from 1000 healthy blood donors in whom blood sampling conditions were standardised to conform with those applying to hospital out-patients. Statistical techniques were used to allow for the effects of analytical variation and to enable the effects of the various factors and their interactions to be expressed in a practically useful manner. Age and sex effects are shown to be the rule and to interact in many instances. Creatinine, urea, glucose, cholesterol, potassium and globulin show a tendency to increase in concentration with age, while total protein, albumin, calcium, inorganic phosphate and iron levels tend to fall progressively. Evidence is given to suggest that many of the changes occurring in women at about 50 years should be attributed to hormonal changes. In all instances when the menopause has a significant influence there is a rise in the concentration of the constituent concerned. It is proposed that other laboratories should assemble age and sex stratified reference ranges from (a) figures given for the mean values for defined age and sex groups, adjusted if necessary to allow for different analytical bias, (b) figures given for nonsystematic biological variation, and (c) their own measurements of analytical precision. Details of the necessary procedure are given, allowance being made for logarithmic transformation of the results where necessary.

Protein absorption and ammonia production: the effects of dietary protein and removal of the colon

1. The effect of increasing dietary protein content on the amount of faecal nitrogen was measured in six normal subjects and five subjects without functioning colons (three with ileostomy and two with ileo-rectal anastomosis). 2. There was a significant inontent in the subjects without functioning colons. 3. In normal subjects with intact colons, faceal N content was found to be lower than that in subjects without colons, and furthermore there was no significant variation with diet. 4. The source of the increase in faecal N with increased dietary protein content in subjects without functioning colons is discussed and the significance of these findings in relation to the efficiency of protein absorption is considered.

Urea metabolism in an azotaemic woman with normal renal function

The blood-urea of a 43-year-old woman with normal renal function was 150 mg. per 100 ml. because she regularly consumed about 400 g. of protein daily. She had no symptoms of uraemia and her haemoglobin concentration was normal. Although she had a very large body-urea pool she degraded no more urea than healthy individuals on a normal diet. The failure of endogenous urea hydrolysis to increase in proportion to the blood-urea in renal failure has tentatively been ascribed to toxic effects of compounds retained with urea in renal failure; the findings in this azotaemic patient, who had neither signs nor symptoms of uraemia, cast doubt upon that explanation.

The relationship between serum urea levels and dietary nitrogen ultilization in young men

1. Results from metabolic balance studies in young adult men were examined for the relationships between the concentration of serum urea (SUN) and the efficiency of dietary nitrogen utilization. A total of 231 separate balance periods were included in the analysis. Net protein utilization (NPU) was used as an index of dietary protein quality.

2. Protein intake ranged from 0·27–0·73 g/kg body-weight per d in the various experiments. There was a highly significant negative correlation between NPU and urea levels. The relationship was: NPU = 1·23–0·029 × SUN (mmol/l) (r = −0·89).

3. These results are considered in relation to the evaluation of protein quality in adult humans.