Enzymatic erythrocyte creatine determinations as an index for cell age

Creatine kinase in human erythrocytes: A genetic anomaly reveals presence of soluble brain-type isoform

For maintaining energy homeostasis, creatine kinase (CK) is present at elevated levels in tissues with high and/or fluctuating energy requirements such as muscle, brain, and epithelia, while there is very few CK, if any, in peripheral blood cells. However, an ectopic expression of brain-type creatine kinase (BCK) has been reported for platelets and leukocytes in an autosomal dominant inherited anomaly named CKBE. Here we investigated CK in erythrocytes of CKBE individuals from eight unrelated families. The data revealed a varying but significant increase of CK activity in CKBE individuals as compared to controls, reaching an almost 800-fold increase in two CKBE individuals which also had increased erythrocyte creatine. Immunoblotting with highly specific antibodies confirmed that the expressed CK isoform is BCK. Cell fractionation evidenced soluble BCK, suggesting cytosolic and not membrane localization of erythrocyte CK as reported earlier. These results are discussed in the context of putative CK energy buffering and transfer functions in red blood cells.

Diminution of Oxidative Damage to Human Erythrocytes and Lymphocytes by Creatine: Possible Role of Creatine in Blood

Creatine (Cr) is naturally produced in the body and stored in muscles where it is involved in energy generation. It is widely used, especially by athletes, as a staple supplement for improving physical performance. Recent reports have shown that Cr displays antioxidant activity which could explain its beneficial cellular effects. We have evaluated the ability of Cr to protect human erythrocytes and lymphocytes against oxidative damage. Erythrocytes were challenged with model oxidants, 2, 2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and hydrogen peroxide (H₂O₂) in the presence and absence of Cr. Incubation of erythrocytes with oxidant alone increased hemolysis, methemoglobin levels, lipid peroxidation and protein carbonyl content. This was accompanied by decrease in glutathione levels. Antioxidant enzymes and antioxidant power of the cell were compromised while the activity of membrane bound enzyme was lowered. This suggests induction of oxidative stress in erythrocytes by AAPH and H₂O₂. However, Cr protected the erythrocytes by ameliorating the AAPH and H₂O₂ induced changes in these parameters. This protective effect was confirmed by electron microscopic analysis which showed that oxidant-induced cell damage was attenuated by Cr. No cellular alterations were induced by Cr alone even at 20 mM, the highest concentration used. Creatinine, a by-product of Cr metabolism, was also shown to exert protective effects, although it was slightly less effective than Cr. Human lymphocytes were similarly treated with H₂O₂ in absence and presence of different concentrations of Cr. Lymphocytes incubated with oxidant alone had alterations in various biochemical and antioxidant parameters including decrease in cell viability and induction of DNA damage. The presence of Cr attenuated all these H₂O₂-induced changes in lymphocytes. Thus, Cr can function as a blood antioxidant, protecting cells from oxidative damage, genotoxicity and can potentially increase their lifespan.

Kinetics of creatine ingested as a food ingredient

The aim of the present study was to test if the consumption of creatine incorporated in food bars modifies creatine plasma kinetics, erythrocyte retention and loss in urine and in feces when compared with its consumption in the form of an aqueous solution (AS). Seventeen healthy young men ingested 2 g creatine either in the form of AS, or incorporated in a protein (PP)- or in a beta-glucan (BG)-rich food bar. Kinetics of plasma creatine was measured for 8-h duration and urinary excretion for 24 h. Then, the subjects received the same treatment thrice a day for 1 week at the end of which creatine contents were determined in erythrocytes and in feces (n = 4 for feces). The three crossover treatments were interspaced by a 40 +/- 1.2-day wash-out. Absorption of creatine was slowed down by 8-fold in the presence of BG (P < 0.001) and by 4-fold with PP (P < 0.001) whereas the velocity rate constant of elimination and the area under the curve were not modified. Urinary loss of creatine in the first 24 h following ingestion was 15 +/- 1.9% in AS and 14 +/- 2.2% in PP conditions (NS), whereas it was only 8 +/- 1.2% with BG (P = 0.004). Increase in creatine concentration in erythrocyte was similar in whatever form the creatine was ingested. Creatine seems to be totally absorbed since no creatine or creatinine was detectable in feces. No side effects were reported. In conclusion, ingestion of creatine combined with BG facilitates its retention by slowing down its absorption rate and reducing its urinary excretion.

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

Evaluation of Intravascular Hemolysis With Erythrocyte Creatine in Patients With Cardiac Valve Prostheses

STUDY OBJECTIVES

To detect intravascular hemolysis in patients with cardiac valve prostheses. Erythrocyte creatine, a marker of erythrocyte age that increases with shortening erythrocyte survival, was evaluated with other hemolytic markers and hemodynamic parameters.

DESIGN

Prospective study.

PATIENTS AND MEASUREMENTS

Erythrocyte creatine was enzymatically assayed in 33 patients with prosthetic valves, including 15 patients with aortic valve replacement, 13 patients with mitral valve replacement, and 5 patients with double-valve (aortic and mitral) replacement, and 33 control subjects. Blood flow velocity and valvular regurgitation were determined by Doppler echocardiography. Other hemolytic markers (lactate dehydrogenase [LDH], reticulocyte count, and haptoglobin) and cardiac muscle markers (myoglobin and myosin light chain 1) were also measured.

RESULTS

Erythrocyte creatine and LDH levels were significantly higher (p < 0.0001) and the haptoglobin level was lower (p < 0.0001) in patients with a prosthetic valve as compared with control subjects. However, there were no significant differences in these markers between those with (n = 17) and without (n = 16) regurgitation. Patients with high erythrocyte creatine levels (> 1.8 micro mol/g hemoglobin) exhibited significantly higher total peak flow velocity (sum of peak flow velocities at mitral and aortic valves) than those with normal erythrocyte creatine levels (p = 0.006). Erythrocyte creatine had a significant correlation with total peak flow velocity (r = 0.64, p < 0.0001), but LDH and haptoglobin had no significant correlation with total peak flow velocity. Patients with high LDH levels (> 460 IU/L) showed significantly higher myoglobin (p = 0.008) and myosin light chain 1 (p = 0.02) than those with normal LDH levels, whereas erythrocyte creatine was not related to cardiac muscle markers.

CONCLUSIONS

Erythrocyte creatine is a quantitative and reliable marker for intravascular hemolysis in patients with prosthetic valves. Mild hemolysis is ascribable to valvular flow velocity rather than regurgitation.

Sensitive enzymatic assay for erythrocyte creatine with production of methylene blue

We developed a new, highly sensitive enzymatic method for quantifying creatine in erythrocytes, which comprises creatine amidinohydrolase, sarcosine oxidase, and peroxidase. In the present method, an N-methylcarbamoyl derivative of methylene blue, 10-N-methylcarbamoyl-3,7-bis(dimethylamino)phenothiazine (MCDP), was used as a sensitive chromogenic compound. Potassium ferrocyanide was used to prevent nonspecific oxidation of MCDP. The enzymatic method exhibited good analytical performance: precision, within-run CVs &lt;1.0% and between-day CVs &lt;2.0%; average analytical recovery, 99.3% ± 1.8%; detection limit, 1.0 μmol/L in hemolysate; and linearity, at least up to 500 μmol/L as creatine concentration in hemolysate. Excellent agreement was observed between the present method (y) and HPLC (x), y = 1.029x − 0.002 μmol/g hemoglobin, r = 0.9998, Sy‖x = 0.053 μmol/g hemoglobin (n = 110). No significant interference was produced by various compounds, including guanidino compounds, amino acids, and reducing materials. The reference intervals (mean ± 2 SD) for erythrocyte creatine obtained from 60 males and 60 females were (in μmol/g hemoglobin) 1.18 ± 0.52 (0.66–1.70) for males and 1.35 ± 0.49 (0.86–1.84) for females. Using this method, we documented changes in erythrocyte creatine in patients with various hemolytic conditions, including hemolytic anemia, liver cirrhosis, renal insufficiency, and chronic renal failure treated with hemodialysis with or without the administration of erythropoietin. We conclude that the use of MCDP allows sensitive measurement of erythrocyte creatine and that MCDP with potassium ferrocyanide can improve the sensitivity of assays that use peroxidase for detection of H2O2.

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.

Exercise, training and red blood cell turnover

Endurance training can lead to what has been termed 'sports anaemia'. Although under normal conditions, red blood cells (RBCs) have a lifespan of about 120 days, the rate of aging may increase during intensive training. However, RBC deficiency is rare in athletes, and sports anaemia is probably due to an expanded plasma volume. Cycling, running and swimming have been shown to cause RBC damage. While most investigators measure indices of haemolysis (for example, plasma haemoglobin or haptoglobin), RBC removal is normally an extravascular process that does not involve haemolysis. Attention is now turning to cellular indices (such as antioxidant depletion, or protein or lipid damage) that may be more indicative of exercise-induced damage. RBCs are vulnerable to oxidative damage because of their continuous exposure to oxygen and their high concentrations of polyunsaturated fatty acids and haem iron. As oxidative stress may be proportional to oxygen uptake, it is not surprising that antioxidants in muscle, liver and RBCs can be depleted during exercise. Oxidative damage to RBCs can also perturb ionic homeostasis and facilitate cellular dehydration. These changes impair RBC deformability which can, in turn, impede the passage of RBCs through the microcirculation. This may lead to hypoxia in working muscle during single episodes of exercise and possibly an increased rate of RBC destruction with long term exercise. Providing RBC destruction does not exceed the rate of RBC production, no detrimental effect to athletic performance should occur. An increased rate of RBC turnover may be advantageous because young cells are more efficient in transporting oxygen. Because most techniques examine the RBC population as a whole, more sophisticated methods which analyse cells individually are required to determine the mechanisms involved in exercise-induced damage of RBCs.

Glomerular filtration rate and creatinine production in adult icteric patients

Various methods for serum creatinine determination were compared and validity of the Cockroft-Gault algorithm for calculating creatinine clearance was tested in adult icteric patients. Using conventional Jaffé assays, negative interference is proportional to the serum bilirubin content. Pretreatment of the serum with bilirubin oxidase was more efficient in eliminating bilirubin than pretreatment with potassium ferricyanide. Due to a continued creatine-poor diet and liver dysfunction, erythrocyte creatine levels and creatinine output rate were decreased. Median effect (creatinine equivalent) of non-specific chromogens in the unmodified Jaffé assay was 21 mumol/l (range: 1-108 mumol/l), vs. 19 mumol/l (range: 16-26 mumol/l) for the reference population. In the absence of multi-organ failure, the Cockroft-Gault algorithm could be used for estimating glomerular filtration rate. In patients with multiple organ failure however, we recommend correction for both bilirubin and non-specific chromogens for measuring the serum creatinine concentration.

Effects of the recombinant human erythropoietin (rHuEPO) administration on hematologic parameters, red cell creatine and 2,3-diphosphoglycerate contents, in patients affected by end-stage renal disease

Twenty patients with renal failure and severe anemia (hemoglobin range 6.6-8.7 g/dl) on thrice-weekly maintenance hemodialysis were treated with recombinant human erythropoietin (rHuEPO). After three months of intravenous (iv) therapy the hemoglobin increase averaged 2 g/dl, and was steadily maintained even after two months of subcutaneous (sc) therapy. The significant increase of macrocyte counts, determined by an automated red blood cell counter after both steps of therapy, suggested the release of young red cells (large cells) into blood circulation. This assumption may be supported by the significant increase of the red cell creatine contents. 2,3-diphosphoglycerate (2,3-DPG) levels of the erythrocytes did not significantly change after rHuEPO administration.