Creatine and phosphocreatine in the human red cell

Estimation of mean erythrocyte age using HbA1c or HbA1c/glycated albumin for evaluation of anemia severity

BACKGROUND

Hemoglobin A1c (HbA1c) levels are low in patients with hemolytic anemia, as HbA1c reflects mean erythrocyte age (MRBC ). Erythrocyte creatine (EC) is a hemolytic indicator that also reflects MRBC . We previously reported an equation for estimating MRBC using EC (EC-MRBC ).

AIMS

In this study, EC-MRBC was compared to the HbA1c level expressed in the International Federation of Clinical Chemistry and Laboratory Medicine units (iA1c) and to the iA1c/glycated albumin (GA) ratio to estimate MRBC .

METHODS

This study included 238 subjects, including patients with hemolytic anemia and/or type 2 diabetes mellitus (T2DM).

RESULTS

In non-diabetic individuals, both iA1c and iA1c/GA showed a strong positive correlation with EC-MRBC (p < 0.0001). The equations to estimate iA1c-MRBC and iA1c/GA-MRBC derived from the regression equations between EC-MRBC and iA1c, and EC-MRBC and iA1c/GA in nondiabetic individuals were 1.45 × iA1c and 20.0 × iA1c/GA, respectively. iA1c-MRBC and iA1c/GA-MRBC in non-diabetic individuals without hemolytic anemia were 57.6 ± 4.0 and 57.1 ± 6.4 days, respectively, and iA1c/GA-MRBC in T2DM patients without hemolytic anemia was 56.0 ± 8.8 days.; no significant difference was seen in the comparisons.

CONCLUSIONS

The MRBC can be estimated using iA1c or iA1c/GA in non-diabetic individuals, and iA1c/GA in T2DM patients.

Rapid Identification of New Biomarkers for the Classification of GM1 Type 2 Gangliosidosis Using an Unbiased 1H NMR-Linked Metabolomics Strategy

Biomarkers currently available for the diagnosis, prognosis, and therapeutic monitoring of GM1 gangliosidosis type 2 (GM1T2) disease are mainly limited to those discovered in targeted proteomic-based studies. In order to identify and establish new, predominantly low-molecular-mass biomarkers for this disorder, we employed an untargeted, multi-analyte approach involving high-resolution 1H NMR analysis coupled to a range of multivariate analysis and computational intelligence technique (CIT) strategies to explore biomolecular distinctions between blood plasma samples collected from GM1T2 and healthy control (HC) participants (n = 10 and 28, respectively). The relationship of these differences to metabolic mechanisms underlying the pathogenesis of GM1T2 disorder was also investigated. 1H NMR-linked metabolomics analyses revealed significant GM1T2-mediated dysregulations in ≥13 blood plasma metabolites (corrected p < 0.04), and these included significant upregulations in 7 amino acids, and downregulations in lipoprotein-associated triacylglycerols and alanine. Indeed, results acquired demonstrated a profound distinctiveness between the GM1T2 and HC profiles. Additionally, employment of a genome-scale network model of human metabolism provided evidence that perturbations to propanoate, ethanol, amino-sugar, aspartate, seleno-amino acid, glutathione and alanine metabolism, fatty acid biosynthesis, and most especially branched-chain amino acid degradation (p = 10-12-10-5) were the most important topologically-highlighted dysregulated pathways contributing towards GM1T2 disease pathology. Quantitative metabolite set enrichment analysis revealed that pathological locations associated with these dysfunctions were in the order fibroblasts > Golgi apparatus > mitochondria > spleen ≈ skeletal muscle ≈ muscle in general. In conclusion, results acquired demonstrated marked metabolic imbalances and alterations to energy demand, which are consistent with GM1T2 disease pathogenesis mechanisms.

HbA1c adjusted by erythrocyte creatine is a useful glycemic control indicator in patients with hemolysis

OBJECTIVES

HbA1c shows low in patients with hemolysis, whereas glycated albumin (GA) is not affected by hemolysis. Therefore, the GA/HbA1c ratio reflects hemolysis in diabetic patients with hemolysis. Erythrocyte creatine (EC) is an indicator of hemolysis that reflects the mean erythrocyte age. The aim of this study was to examine whether HbA1c adjusted by EC accurately reflected glycemic control in patients with hemolysis.

MATERIALS AND METHODS

A total of 238 individuals, consisting of 131 diabetic patients and 107 non-diabetic subjects, and consisting of 42 patients with hemolysis, and 196 subjects without hemolysis were selected for the study. HbA1c expressed in the IFCC units (iA1c) as well as in the NGSP units (A1C) were used. From the fact that EC and the GA/iA1c ratio showed a significant positive correlation, a formula for iA1c adjusted by EC (ECadj-iA1c) was created from a regression equation between EC and the GA/iA1c ratio.

RESULTS

Significant correlations were observed between the GA/iA1c ratio and various hemolytic indicators but not between the GA/ECadj-iA1c ratio and those hemolytic indicators. The GA/iA1c ratio in individuals with hemolysis was significantly higher than in individuals without hemolysis, while no significant differences were observed in the GA/ECadj-iA1c ratio between the groups. Further, iA1c concentrations in non-diabetic patients with hemolysis were significantly lower than in the non-diabetic subjects without hemolysis, whereas ECadj-iA1c and GA concentrations showed no significant difference between the two groups.

CONCLUSIONS

These results suggested that ECadj-iA1c accurately reflected glycemic control in patients with hemolysis.

Shortened mean erythrocyte age in female patients with type 2 diabetes mellitus

BACKGROUND

The hyperglycemic state is known to shorten the erythrocyte life span. Erythrocyte creatine (EC) reflects the mean erythrocyte age and is useful as an indicator of hemolysis. Here, we studied the relationship between EC and glycemic control indicators [HbA1c or glycated albumin (GA)] in non-diabetic subjects and diabetic patients.

METHODS

This study included 119 patients with type 2 diabetes mellitus (T2DM) and 76 non-diabetic subjects matched by sex and age. We studied the relationships between EC and HbA1c or GA in patients with T2DM and non-diabetic subjects.

RESULTS

Erythrocyte creatine in T2DM patients was significantly higher than that in non-diabetic subjects, and the ratio of high EC levels (>1.8 μmol/g Hb) in T2DM patients was significantly higher as well. Furthermore, female EC was significantly higher than male EC, and the ratio of high EC levels in females was significantly higher than in the males as well. While male EC had no significant correlation with HbA1c or GA, female EC had significant positive correlations with both. Male EC had no significant difference between T2DM patients and non-diabetic subjects, while the EC in female patients with T2DM was significantly higher than in female non-diabetic subjects.

CONCLUSIONS

The significant positive correlations of EC with HbA1c and GA in female patients with T2DM suggested that the mean erythrocyte age decreased in female diabetic patients with poor glycemic control.

Elevation of Creatine in Red Blood Cells in Vegetarians and Nonvegetarians After Creatine Supplementation

The purpose of this study was to examine the effect of a 5-day creatine (CR) supplementation period on red blood cell (RBC) CR uptake in vegetarian and nonvegetarian young women. Blood samples were collected from lacto-ovo vegetarians (VG, n = 6, age 21.8 ± 1.9 yrs) and nonvegetarians (NV, n = 6, age 21.7 ± 1.9 yrs) before and after a 5-day CR loading period (0. 3 g CR/kg lean body mass/day), and from a control group of nonvegetarians (NV, n = 5, age 22.0 ± 0.7 yrs) who did not supplement with creatine. RBC and plasma samples were analyzed for the presence of creatine. Significant increases (p < .05) in RBC and plasma CR levels were found for vegetarians and nonvegetarians following supplementation. The initial RBC CR content was significantly lower (p < .05) in the vegetarian group. There was no significant difference between vegetarians and nonvegetarians in final RBC CR content, suggesting that a ceiling had been reached. As the uptake into both muscle and RBC is moderated by creatine transporter proteins, analysis of the uptake of CR into RBC may reflect the uptake of CR into muscle, offering an alternative to biopsies. Key words: plasma, erythrocyte, loading

Myocardial density and composition: a basis for calculating intracellular metabolite concentrations

Systems for describing myocardial cellular metabolism with appropriate thermodynamic constraints on reactions have to be on the basis of estimates of intracellular and mitochondrial concentrations of metabolites as driving forces for reactions. This requires that tissue composition itself must be modeled, but there is marked inconsistency in the literature and no full data set on hearts of any species. To formulate a self-consistent set of information on the densities, contents, or concentrations of chemical components and volumes of tissue spaces, we drew on information mostly on rats. From the data on densities, volumes, volume fractions, and mass fractions observed mainly on left ventricular myocardium, cytoplasm, and mitochondria and from morphometric data on cellular components and the vasculature, we constructed a matrix based on conservation laws for density, volume, and constituent composition. The four constituents were water, protein, fat, and solutes (or ash). To take into account the variances in the observed data sets, we used a constrained nonlinear least squares optimization to minimize the differences between the final results and the data sets. The results provide a detailed estimate of cardiac tissue composition, previously unavailable, for the translation of whole tissue concentrations or concentrations per gram protein into estimated local concentrations that are relevant to reaction processes. An example is that the concentrations of phosphocreatine and ATP in cytosolic water space are twice as high as their mean tissue concentrations. This conservation optimization method is applicable to any tissue or organ.

An enzymatic assay for erythrocyte creatine as an index of the erythrocyte life time

OBJECTIVES

To establish and estimate an enzymatic measurement of creatine in erythrocytes as an index of the erythrocyte life time.

DESIGN AND METHOD

The measurement of creatine in erythrocytes was performed using an enzymatic assay kit that was developed for serum and urine creatine. An erythrocyte sample was subjected to creatine measurement after hemolysis and deproteinization. Performance of the method for creatine measurement in erythrocytes was estimated. Effects of age and gender on the creatine content of erythrocytes were also estimated in 305 normal subjects.

RESULTS

The method showed within-run CVs varying from 0.7 to 1.0% (n = 20), and between-day CVs from 1.3 to 1.7% (15 days). Good linearity was observed at least up to 1000 mumol/L as creatine value in hemolyzed sample. The analytical recovery was calculated to be 98.1 +/- 1.3% on average. No considerable interference by various substances, including guanidino compounds and amino acids, with the assay was observed. Excellent correlation was observed between the present method and high performance liquid chromatography. With the unit of mumol/g Hb: slope, 1.034 +/- 0.003 (mean +/- SD); intercept, -0.059 +/- 0.012 (mean +/- SD); correlation coefficient, 0.9996; and Sy.x, 0.069. With the unit of mumol/L RBC: slope, 1.033 +/- 0.003 (mean +/- SD); intercept, -18.23 +/- 3.55 (mean +/- SD); correlation coefficient 0.9996; and Sy.x, 20.40. A significant increase in erythrocyte creatine was observed in females aged 11- to 50 years old as compared with males in the corresponding age bracket, however, a gender difference was not observed in other age bracket. This finding suggests the possibility of a slight decrease in the erythrocyte life time due to menstruation in females.

CONCLUSION

This study showed that the present method is favorable for quantifying erythrocyte creatine, and has analytical characteristics suitable for routine work in clinical laboratories.

Detection of G6PD and pyruvate kinase deficiencies in reticulocytosis by reference to erythrocyte creatine

Erythrocyte activities of G6PD and PK, referenced to creatine content, are presented as a means to detect enzyme deficiencies despite the presence of variable proportions of young erythrocytes in the assayed cell population. Lysate enzyme activities, creatine and hemoglobin concentrations, and whole blood reticulocyte counts were determined on 110 samples from 87 patients with a variety of anemias, including two pyruvate kinase deficient, three G6PD deficient, and four proven G6PD heterozygotes. Highest correlations were obtained between log of G6PD activity/g hemoglobin and lysate creatine, and between PK activity/g hemoglobin and lysate creatine. Ninety-five percent limits for this population are presented for creatine concentrations to 28 mg/dl, corresponding to 20% reticulocyte count. In addition to providing reference intervals appropriate to the suspect patient population, the data afford greater confidence in detecting partial enzyme deficiencies concomitant with other hemolytic processes, such as hemoglobinopathies.

Occurrence of creatine kinase activity in human erythrocyte membrane

Some evidence for creatine kinase activity in normal human erythrocyte membrane were presented. The creatine kinase was indicated to be a constituent of the integral proteins of erythrocyte membrane or to be tightly bound to the membrane, and was contrasted to the results obtained with adenylate kinase. Isoenzyme distribution of the erythrocyte creatine kinase by electrophoresis was identical to MM-creatine kinase from rabbit muscle.

Creatine and creatinine transport in old and young human red blood cells

The time course of creatine influx or efflux as measured in populations of red cells or red cell ghosts with normal age distribution does not follow simple two-compartment kinetics. This suggests that the contributions of individual cells to transport as measured in the populations as a whole are not uniform. In agreement with this inference, fractionation of red cell populations with respect to cell age shows that transport in young cells is considerably faster than in old cells. The dependence of creatine transport on creatine concentration in the medium follows an equation that can be interpreted to represent a super-imposition of a saturable component (apparent Km = 0.02 mM) and another component that cannot be saturated up to a creatine concentration of 5.0 mM. In contrast to the non-saturable component, the saturable component depends on the energy metabolism of the cell and can be inhibited by beta-guanidinopropionic acid and the proteolytic enzyme pronase. This latter finding suggests that the saturable component represents active transport that is mediated by a transport protein. The non-saturable component is little, if at all, dependent on cell age while the saturable component is higher in young cells than in old cells. Phloretin inhibits both components of creatine flux, but the maximal inhibition that can be achieved at high concentration is only 70--80%. Under the experimental conditions used for the study of creatine transport, creatinine equilibration between cells and medium follows the kinetics expected for a steady-state two-compartment system. Creatinine flux is proportional to creatine concentration over the concentration range studied (up to 5 mM). It cannot be inhibited by beta-guanidinopropionic acid or pronase.