Increased urinary excretion of aromatic amino acid catabolites by Microtus montanus chronically infected with Trypanosoma brucei gambiense

Microtus montanus infected with Trypanosoma brucei gambiense for 16 and 21 days excreted significantly greater quantities of several aromatic amino acid catabolites when compared to uninfected control animals. Very large quantities of three aromatic alpha-keto acids (alpha-oxocarboxylic acids), phenylpyruvic acid, 4- hydroxyphenylpyruvic acid and indole-3-pyruvic acid, were excreted by infected animals. Increased excretion of indole-3-lactic acid and indole-3-acetic acid was also detected. Gas chromatographic-mass spectral analysis of the trimethylsilyl derivatives of phenylpyruvic acid, 4- hydroxyphenylpyruvic acid and indole-3-pyruvic acid confirms the identity of the aromatic alpha-keto acids elevated during infection. The marked alpha-keto aciduria indicates that a large disturbance exists in aromatic amino acid metabolism in this chronic animal model of African trypanosomiasis. The disturbance may contribute to the pathogenesis of the disease. The increased catabolite concentrations may also prove to be useful diagnostically and prognostically.     

Multiple alpha-keto aciduria in Microtus montanus chronically infected with Trypanosoma brucei gambiense

Microtus montanus chronically infected with a monomorphic strain of Trypanosoma brucei gambiense excreted in urine greatly elevated quantities of not only the aromatic alpha-keto acids, phenylpyruvic and 4-hydroxyphenylpyruvic acids, but also two aliphatic alpha-keto acids, pyruvic and alpha-ketoglutaric acids. Elevated keto acid excretion began approximately midway through infection and quantities remained elevated until death. Daily keto acid excretion did not correlate with daily parasitemia. Thus, a large metabolic disturbance exists in laboratory animals infected with African trypanosomes. The multiple alpha-keto aciduria potentially contributes to the pathogenesis of chronic African trypanosomiasis.     

阿霉素肾病大鼠尿液糖胺聚糖与尿液蛋白含量的相关性

目的探讨阿霉素肾病大鼠疾病进展过程中尿液糖胺聚糖含量的变化及其与尿蛋白的关系。方法采用一次性尾静脉注射阿霉素6mg/kg制作肾病综合征大鼠模型,第1、2、3、4、6周分别收集大鼠24h尿液测定尿糖胺聚糖和尿蛋白含量。43d后结束实验取血及肾脏,检测血生化,观察肾组织病理改变。结果第2、3、4、6周与正常对照组比较,阿霉素肾病大鼠24h尿蛋白排泄量呈进行性明显上升趋势;造模43d后模型组血清白蛋白含量显著下降,总胆固醇和甘油三酯含量显著升高,肾组织病理所见,模型组肾小球系膜区见中度至重度的系膜细胞增殖及基质增生。从第3周开始阿霉素肾病大鼠尿糖胺聚糖浓度显著高于正常组,且与24h尿蛋白排泄量呈正相关关系。第6周尿糖胺聚糖浓度与血清白蛋白浓度负相关,与甘油三酯浓度正相关。结论阿霉素肾病综合征大鼠尿液中糖胺聚糖浓度升高,并与24h尿蛋白排泄、血清白蛋白、甘油三酯浓度显著相关。     

A study of zinc distribution in human serum.

The partition of zinc in human serum between two major zinc-binding proteins, albumin and alpha2-macroglobulin, was studied in 28 control subjects and in 156 hospitalized patients. Albumin-bound zinc was both the major and the more dynamic of the serum zinc components. Over a wide range of values the concentrations of albumin-bound zinc and total serum zinc were highly correlated (r=0.91) with each other, as were concentrations of albumin and albumin-bound zinc (r=0.69). alpha2-Macroglobulin-bound zinc was not strongly correlated either with total serum zinc or with the serum concentration of alpha2-macroglobulin. Twenty-four hour urinary excretion of zinc was not correlated with any of the serum zinc parameters. To a large extent it appears that total serum zinc concentration reflects serum albumin concentration.     

Iron-regulated excretion of alpha-keto acids by Salmonella typhimurium.

Excretion of alpha-keto acids by clinical isolates and laboratory strains of Salmonella typhimurium was determined by high-performance liquid chromatography analysis of culture supernatants. The levels of excretion increased markedly with increasing iron stress imposed by the presence of alpha,alpha'-dipyridyl or conalbumin in the medium. The major product was pyruvic acid, but significant concentrations of alpha-ketoglutaric acid, alpha-ketoisovaleric acid, and alpha-ketoisocaproic acid were also observed. Maximal excretion occurred at iron stress levels that initially inhibited bacterial growth; the concentration of alpha,alpha'-dipyridyl at which this was observed differed between strains depending on their ability to secrete and utilize siderophores, suggesting that the intracellular iron status was important in determining alpha-keto acid excretion. However, prolonged incubation of the siderophore-deficient S. typhimurium strain enb-7 under conditions of high iron stress resulted in significant delayed bacterial growth, promoted by tonB-dependent uptake of iron complexed with the high accumulated levels of pyruvic acid and other alpha-keto acids. Strain RB181, a fur derivative of enb-7, excreted massive amounts of alpha-keto acids into the culture medium even in the absence of any iron chelators (the concentration of pyruvic acid, for example, was >25 mM). Moreover, RB181 was able to grow and excrete alpha-keto acids in the presence of alpha,alpha'-dipyridyl at concentrations threefold greater than that which inhibited the growth of enb-7.     

Effects of gender on kidney function in magnesium-deficient rats

This study investigated the gender differences in the kidney function of magnesium (Mg)-deficient rats. Male and female rats were fed a control diet or a Mg-deficient diet for 21 d. Mg-deficient diet had no significant effect on kidney calcium (Ca) or phosphorus (P) concentration in male rats, while Ca and P concentrations in female rats were significantly higher in Mg-deficient rats than in the control rats. With regard to indicators of kidney function, no significant differences in creatinine clearance and serum urea nitrogen concentration were observed among the groups. Serum albumin concentrations were significantly lower in rats fed the Mg-deficient diet than in rats fed the control diet. In both sexes, urinary albumin excretion was significantly higher in rats fed the Mg-deficient diet than in rats fed the control diet. Gender differences had no significant influence on creatinine clearance, serum urea nitrogen concentration, serum albumin concentration and urinary albumin excretion. These results suggest that gender differences have no effect on kidney function in Mg-deficient rats under the condition used.     

Profile of urinary amino acids and their post-translational modifications (PTM) including advanced glycation end-products (AGEs) of lysine,arginine and cysteine in lean and obese ZSF1 rats

Heart failure with preserved ejection fraction (HFpEF) is associated with high mortality and has an increasing prevalence associated with the demographic change and limited therapeutic options. Underlying mechanisms are largely elusive and need to be explored to identify specific biomarkers and new targets, which mirror disease progression and intervention success. Obese ZSF1 (O-ZSF1) rats are a useful animal model, as they spontaneously develop hypertension, hyperlipidemia and glucose intolerance and finally HFpEF. The urinary profile of amino acids and their metabolites of post-translational modifications (PTM), including the advanced glycation end-products (AGEs) of lysine, arginine and cysteine, are poorly investigated in HFpEF and ZSF1 rats. The aim of the present study was to characterize the status of free amino acids and their metabolites of PTM and glycation in lean ZSF1 (L-ZSF1) and O-ZSF1 rats in urine aiming to find possible effects of glucose on the excretion of native and modified amino acids. In the urine of twelve L-ZSF1 and twelve O-ZFS1 rats collected at the age of 20 weeks, we measured the concentration of native and modified amino acids by reliable previously validated stable-isotope dilution gas chromatography-mass spectrometry (GC–MS) approaches. Serum glucose was 1.39-fold higher in the O-ZSF1 rats, while urinary creatinine concentration was 2.5-fold lower in the O-ZSF1 rats. We observed many differences in urinary amino acids excretion between L-ZSF1 and O-ZSF1 rats. The creatinine-corrected homoarginine excretion was twofold lower in the O-ZSF1 rats. We also observed distinct associations between the concentrations of serum glucose and urinary amino acids including their PTM and AGE metabolites in the L-ZSF1 and O-ZSF1 rats. Our study shows that PTM metabolites and AGEs are consistently lower in the L-ZSF1 than in the O-ZSF1 rats. Serum malondialdehyde (MDA) concentration was higher in the O-ZSF1 rats. These results suggest that hyperglycemia, hyperlipidemia and elevated oxidative stress in the O-ZSF1 rats favor PTM methylation of arginine and lysine and the glycation of lysine and cysteine. The area under the receiver operation characteristic (ROC) curve values were 0.996 for serum glucose, 0.951 for urinary creatinine, 0.939 for serum MDA, 0.885 for N^ε-carboxyethyl-lysine, 0.830 for carboxyethyl-cysteine, and 0.792 for monomethyl-lysine. Non-invasive measurement of methylation and glycation products of arginine, lysine and cysteine residues in proteins in urine of L-ZSF1 and O-ZSF1 rats may be useful in studying pathophysiology and pharmacology of HFpEF.

     

Microalbuminuria: associations with height and sex in non-diabetic subjects.

OBJECTIVES--To study the association(s) between microalbuminuria and cardiovascular risk factors in non-diabetic subjects. DESIGN--Patients aged 40-75 years were randomly selected from a general practice list and invited to participate. SETTING--Health centre in inner city London. SUBJECTS--Of those invited, 1046 out of 1671 (62.6%) attended. Subjects were excluded for the following reasons: not being white (44); urinary albumin excretion rate > 200 micrograms/min (3); having a urinary infection (5); taking penicillamine or angiotensin converting enzyme inhibitors (7); older than 75 (2); having diabetes (25); missing data on glucose concentration (1). MAIN OUTCOME MEASURES--Glucose tolerance test results, albumin excretion rate from overnight and timed morning collections of urine; blood pressure; height. RESULTS--Mean albumin excretion rate was significantly lower in women than men (mean ratio 0.8, 95% confidence interval (0.69 to 0.91)). Mean albumin excretion rate was significantly associated with age, blood pressure, and blood glucose concentration (fasting, 1 hour, and 2 hour) in men and inversely with height. Men who had microalbuminuria in both samples were significantly shorter (by 5 cm (1.3 to 9.3 cm)) than those who had no microalbuminuria in either sample when age was taken into account. In the case of women only systolic pressure was significantly associated with albumin excretion rate. CONCLUSIONS--Microalbuminuria and short stature in men are associated. Cardiovascular risk has been associated with both of these factors and with lower birth weight. The inverse association of microalbuminuria with height is compatible with the suggestion that factors operating in utero or early childhood are implicated in cardiovascular disease. The higher prevalence of microalbuminuria in men compared with women may indicate that sex differences in cardiovascular risk are reflected in differences in albumin excretion rate.     

Investigation of the content of alpha-fetoprotein and serum albumin in the vitreous body of the eye of human embryos

The content of serum albumin and alpha-fetoprotein in the vitreous body of the eyes of human fetuses from the 16th through the 24th week was investigated. It was detected that albumin and alpha-fetoprotein in the vitreous body of human eyes are presented in equal molar concentrations in the 16th week. There is 1.5-fold increased concentration of alpha-fetoprotein in comparison to albumin during the 17th week. After the 17th week, there was a reduction in the concentration of both proteins. It was reported that cyanine dye, used for detection of albumin, does not interact with alpha-fetoprotein.     

Serum glycoproteins level and urinary glycosaminoglycans excretion in drug induced collagen-like syndrome in guinea pigs.

A collagen-like syndrome was produced by a long-term administration of 1-hydrazinophthalazine (hydralazine) to guinea pigs. The results obtained indicate that hydralazine-induced collagen-like syndrome stimulated an increase of the concentration of perchloric acid-soluble proteins, protein-bound hexoses, protein-bound-hexosamines and sialic acids in blood serum as well as urinary excretion of glycosaminoglycans. The increase of serum glycoproteins is not connected with non-specific changes in total protein level. No biochemical differences were found in the parameters studied between subgroups (LE-positive and LE-negative) of hydralazine treated animals.     

Effect of protein restriction in insulin dependent diabetics at risk of nephropathy.

Persistent proteinuria is strongly associated with increased mortality in insulin dependent diabetes, and risk of this condition can be predicted many years in advance by subclinical increases in albumin excretion rate (microalbuminuria). Eight normotensive insulin dependent diabetics with microalbuminuria who had overnight albumin excretion rates of between 15 and 200 micrograms/min underwent a three week randomised crossover study of their normal protein diet (median 92 (range 55-117) g/day) and a low protein diet (47 (38-57) g/day). Both diets were isoenergetic, and the low protein diet was supplemented with calcium and phosphate. Median overnight albumin excretion rate fell from 23.0 (15.0-170.1) micrograms/min during the normal diet to 15.4 (4.1-97.8) micrograms/min during the low protein diet. No consistent change was found in urinary excretion of beta 2 microglobulin during the two diets. The reduction in albumin excretion rate was accompanied by a significant fall in median glomerular filtration rate and fractional renal clearance of albumin. Kidney volume remained unchanged. There were no significant changes in glycaemic control or arterial blood pressure. In these few patients restriction of dietary protein had a beneficial effect on microalbuminuria, independent of changes in glucose concentrations and arterial blood pressure.     

Glucagon auto-immunization fails to stimulate food intake or growth in young rabbits

1. To further investigate the possible role of glucagon in appetite control, weaned rabbits were auto-immunized using a glucagon-bovine serum albumin conjugate (G-BSA). 2. At weekly intervals, the animals were weighed and blood samples collected and subsequently analysed for insulin, glucose and glucagon concentrations. Weekly food consumption was also recorded. 3. At the termination of the experimental period, each animal was subjected to a glucose tolerance test. Following this procedure, the animals were killed and the livers excised and frozen for subsequent glycogen determination. 4. No differences between the controls and auto-immunized group were found at any time for weekly weight gain, food intake, blood glucose or insulin concentrations. 5. Glucagon concentrations in the control group remain stable over the 7 week period; however, after the third week of the experiment, no glucagon could be detected in the blood of any of the auto-immunized animals. 6. The auto-immunized animals had significantly different glucose tolerance profiles and also had significantly more liver glycogen than the control group.     

Trypanosoma congolense. I. Clinical observations of experimentally infected cattle

The course of disease was studied in 8 cattle infected with Trypanosoma congolense. Although the onset of patency was dependent on the numbers of infecting organisms, the duration of the infection was not. High fevers were present on the day of or the day after initial patency. Succeeding peaks of parasitemia, and a progressive weight loss of over 30% occurred. A decrease in packed cell volume (PCV) beginning the first week after infection was observed. Early in the course of the developing anemia, many polychromatophilic erythrocytes and occasional normoblasts were found in the blood. A leucopenia persisted for the duration of the disease. Total serum protein concentrations fell sharply during the first 5 weeks of infection, then gradually increased to low normal levels. Serum albumin levels followed a similar pattern for the first 5 weeks, and remained at a relatively low level. Although gamma globulin levels also declined during the first 5 weeks, their levels gradually surpassed those of preinfection samples. No marked changes in serum glucose were noted. A mild elevation of serum urea nitrogen values occurred early during infection, but subsided. The animals dying early after infection developed elevated total bilirubin levels.     

Effect of enprostil on plasma glucose, insulin and lipid metabolism in patients with non-insulin-dependent diabetes mellitus

Measurements of various aspects of glucose, insulin and lipid metabolism were made before and after the administration of enprostil (a synthetic dehydroprostaglandin E2) for one week to ten patients with non-insulin-dependent diabetes mellitus (NIDDM). Both fasting (P less than 0.01) and postprandial (P less than 0.001) plasma glucose concentrations were significantly lower after one week of enprostil, and 24 hour urinary glucose excretion was reduced from (mean +/- SEM) 47 +/- 14 to 25 +/- 9 g/day. There was no change in either fasting or postprandial insulin concentration, but the postprandial GIP response was also significantly reduced (P less than 0.001). In addition, there were significant reductions in postprandial plasma free fatty acid (P less than 0.05) and triglyceride (P less than 0.001) concentrations, associated with a modest fall in fasting plasma triglyceride (P less than 0.05) and cholesterol (P less than 0.07) concentrations when measured after one week of treatment with enprostil. These results raise the possibility that enprostil may be of some benefit in the treatment of patients with non-insulin-dependent diabetes.     

The Brain Response to Peripheral Insulin Declines with Age: A Contribution of the Blood-Brain Barrier?

ObjectivesIt is a matter of debate whether impaired insulin action originates from a defect at the neural level or impaired transport of the hormone into the brain. In this study, we aimed to investigate the effect of aging on insulin concentrations in the periphery and the central nervous system as well as its impact on insulin-dependent brain activity.MethodsInsulin, glucose and albumin concentrations were determined in 160 paired human serum and cerebrospinal fluid (CSF) samples. Additionally, insulin was applied in young and aged mice by subcutaneous injection or intracerebroventricularly to circumvent the blood-brain barrier. Insulin action and cortical activity were assessed by Western blotting and electrocorticography radiotelemetric measurements.ResultsIn humans, CSF glucose and insulin concentrations were tightly correlated with the respective serum/plasma concentrations. The CSF/serum ratio for insulin was reduced in older subjects while the CSF/serum ratio for albumin increased with age like for most other proteins. Western blot analysis in murine whole brain lysates revealed impaired phosphorylation of AKT (P-AKT) in aged mice following peripheral insulin stimulation whereas P-AKT was comparable to levels in young mice after intracerebroventricular insulin application. As readout for insulin action in the brain, insulin-mediated cortical brain activity instantly increased in young mice subcutaneously injected with insulin but was significantly reduced and delayed in aged mice during the treatment period. When insulin was applied intracerebroventricularly into aged animals, brain activity was readily improved.ConclusionsThis study discloses age-dependent changes in insulin CSF/serum ratios in humans. In the elderly, cerebral insulin resistance might be partially attributed to an impaired transport of insulin into the central nervous system.     

Mass spectrometry detection of monomeric renalase in human urine

Renalase is a recently discovered secretory protein, which is suggested to play a role (which still remains elusive) in regulation of blood pressure. Earlier it was purified from urine of healthy volunteers by means of ammonium sulfate fractionation and subsequent affinity chromatography (Xu et al. (2005), J. Clin. Invest., 115, 1275). The resultant purified preparation of renalase contained 2 proteins with molecular masses of 35 and 67?C75 kDa. The authors believed that the latter represents a dimerization (aggregation) product of the 35 kDa protein. In this study we have detected relanase in urinary samples of 2 of 6 volunteers only after immunoaffinity enrichment of urinary samples subjected to ammonium sulfate precipitation. Electrophoresis of the purified preparation also demonstrated the presence of 2 proteins with molecular masses of 35 and 66 kDa, respectively. Mass spectrometry analysis of these proteins identified 35 and 66 kDa proteins as renalase and serum albumin, respectively. Thus, our results do not support suggestion on formation of renalase dimers and they indicate that urinary renalase excretion significantly varies in humans.     

Serum Fructosamine Levels in Dairy Cows Related to Metabolic Status in Early Lactation

Serum levels of fructosamine were assayed in 57 samples from 23 Norwegian Red Cattle dairy cows in early lactation. The animals were assigned to a 22 factorial feeding experiment. The groups differed in energy and protein supply. All samples were collected before morning feeding. The relationship between fructosamine levels and the plasma concentrations of glucose, acetoacetate, free fatty acids, total cholesterol, lipoproteins, triglycerides, total proteins, progesterone and to weight and energy balance was studied. The overall mean fructosamine level was 1.41 ± 0.20 mmol/1 ranging from 0.92–1.92 mmol/1. Significant relationships were recorded between fructosamine and the concentrations of glucose, acetoacetate, free fatty acids, triglyceride, total cholesterol and energy and weight balance. Free fatty acids and cholesterol showed the best correlation with fructosamine (rs =–0.67 and 0.70, respectively, p < 0.001). The levels of fructosamine increased significantly between 2 and 4 weeks and between 4 and 8 weeks after calving. Animals with a weight gain during 3 weeks prior to fructosamine measurement had higher fructosamine levels than those showing a weight loss (<–7 kg/week) (p < 0.05). The results indicate that serum fructosamine levels in cows may be of interest as an indicator of metabolic status in the early stages of lactation.     

Serum fructosamine concentrations in patients with type II (non-insulin-dependent) diabetes mellitus during changes in management.

The serum fructosamine concentration was examined as a new means to monitor metabolic control in non-insulin-dependent diabetes during changes in management. Weekly fructosamine estimations were compared with glycosylated haemoglobin (HbA1c), 24 hour urinary glucose, and fasting plasma glucose concentrations in a 17 week study entailing withdrawal and reinstitution of oral treatment. The serum fructosamine concentration was more sensitive than the other measurements in detecting a deterioration in diabetic control after stopping oral hypoglycaemic drugs. The response to reinstitution of treatment was not significant in the first three weeks (p = 0.266), despite a highly significant reduction in fasting plasma glucose (p = 0.001) and 24 hour urinary glucose concentrations (p = 0.012). Compared with HbA1c, concentrations of fructosamine appeared more useful in monitoring short term (three to six weeks) changes after alterations in management of diabetes. Additional advantages were lower cost and technical simplicity of measurement.     

Carbohydrate, protein and glycoprotein metabolism by the guinea-pig liver in chronic metribuzin poisoning

Male guinea-pigs weighing 400-600 g, 8 months old, were given metribuzin directly into the gastric lumen over a period of 30 days (20 animals) or 90 days (20 animals) 6 times a week. In the liver of the poisoned animals, the glycogen level and the AspAT and AlAT activities, while in the serum the total protein and the fractions albumin, alpha 1-globulin and gamma-globulin significantly decreased; serum glucose and the serum fractions alpha 2-globulin and beta-globulin, each showed an increase. The glycogen level in the liver, total protein, glucose as well as the alpha 1 and alpha 2 globulin fractions in the serum showed not appreciable difference between 30 and 90 days of intoxication. After 90 days of metribuzin treatment AspAT and AlAT dropped in the liver and rose in the serum, in comparison to the 30-day values. As to the parameters of glycoprotein metabolism, the intoxicated animals showed a significant decrease and increase in concentration of hexosamines and sialic acids in the liver and serum, respectively. Metribuzin intoxication also cause a significant decrease in activity of glucosamine phosphate isomerase and significant increase in activity of glycosidases in the liver. The results suggest that metribuzin disturbs the metabolism of carbohydrates, proteins and glycoproteins in the guinea-pig liver.     

Effects of ornithine or arginine administration on serum amino acid levels

In healthy humans after overnight fasting, an oral administration of ornithine induced a new steady state: an accumulation of serum alanine and proline, a decrease in serum valine concentration, transient reductions in serum urea and urinary urea contents, and then an increased urea excretion. On the other hand, an oral administration of arginine resulted in an anabolic state: decreases in serum leucine and isoleucine concentrations, reductions in serum glucose and free fatty acid contents and a rapid increase in serum insulin level. It was assumed that the effect of ornithine administration may be exerted through an activation of hepatic System A transport and that of arginine is an insulin-mediated action.