The Evaluation of Postdialysis l-Carnitine Administration and Its Effect on Weekly Requiring Doses of rHuEPO in Hemodialysis Patients

Abstract

Background. In this study, our aim was to evaluate the effect of postdialysis administration of parenteral l-carnitine supplementations on hematological parameters and also on weekly requiring dose of the recombinant human erythropoietine (rHuEPO) in hemodialysis (HD) patients. Material and Methods. The stable 34 patients (17 male, 17 female) were enrolled in the study who were on rHuEPO therapy and a regular maintenance HD program at 5 h, three times a week with bicarbonate dialysate and with biocompatible membranes in HD Center of Medical Faculty Hospital in University of Dicle. rHuEPO was administered subcutanously at 80–120 U/kg/week. The patients were divided into two groups: Group 1, rHuEPO therapy (n = 17) and Group 2, rHuEPO therapy +l-carnitine (n = 17). l-carnitine (l-carnitine ampul, Santa Farma) 1 g was injected postdialysis intravenously via venous route of the dialytic set, three times a week. The patient's hemoglobin (Hgb), hematocrit (Hct), serum iron (Fe^{+ 2}), total iron-binding capacity (TIBC), transferrin saturation index (TSI), and serum ferritin (Fer) levels were followed during the 16-week period. The weekly requiring doses of rHuEPO and hematological parameters of patients were recorded at the beginning of the study, at 8 weeks, and at 16 weeks of the study period. Results. In group 1 (n = 17, 13 female, four male), the mean age was 38.8 ± 12.1 years, mean period time on HD therapy was 18.1 ± 14.9 months, and mean Kt/V value was 1.48 ± 0.28. In group 2 (n = 17, 13 male, four female), the mean age was 48.1 ± 15.4 years, mean period time on HD therapy was 34.4 ± 23.0 months, and mean Kt/V value was 1.29 ± 0.20. The hematological parameters of the groups were found as follows: in group 1, Hgb: 7.9–10.8 g/dl, Hct: 25.3–32.5%; in group 2, Hgb: 10.2–11.8 g/dl, Hct: 30.6–35.4%, respectively (p< 0.05). The target Hgb/Hct values were achieved at the end of the study in both groups. Both groups were the same according to their serum Fe^{+ 2} markers (p > 0.05). But unlike serum Fe^{+ 2} markers, there were significant differences on weekly requiring doses of rHuEPO therapy between groups. While in group 1, the mean weekly requiring dose of rHuEPO was 6529 U/week (120 U/kg/week) at the beginning of the study, and maintenance weekly requiring dose of rHuEPO was 3588 U/week (66 U/kg/week) at the end of the study, in group 2, they were 4882 U/week (80 U/kg/week), and 1705 U/week (28 U/kg/week), respectively. According to these values, the total reduction in weekly requiring dose of rHuEPO was 45% in group 1, and 65% in group 2; the net gain was 20% in group 2 (p< 0.05). Conclusions. If other factors related to anemia are excluded, the postdialysis parenteral l-carnitine therapy can be considered in selected stable patients, which may improve anemia and may reduce the weekly requiring dose of the rHuEPO and also be cost-effective.

• hemodialysis
• rHuEPO
• l-carnitine

Introduction

Anemia is an important problem frequently faced in the hemodialysis (HD) population. The main reason is relative erythropoietine deficiency, in addition to other reasons. Significant improvements were seen on hematological parameters of HD patients after the availability of recombinant human erythropoietine (rHuEPO) in clinical practices. The guidelines have been developed for clinical practice by different study groups for using of rHuEPO.[1] The strategies with proven efficacy to reduce the rHuEPO requirement include iron supplementation, subcutaneous (SC) administration, correction of hyperparathyroidism, treatment of infections, and correction of aluminium intoxication.[2]

Secondary l-carnitine deficiency is another issue that has been studied by many clinicians. Recently, the studies about l-carnitine metabolism and clinical administrations have been summarized by Hörl.[3] l-Carnitine is synthesized primarily in the liver and also in the kidneys. Total carnitine balance depends on the carnitine content and its precursors in the diet, the endogenous synthesis of carnitine, its transport to the tissues, and its excretion. In the human body, 100–200 µmol carnitine is synthesized per day, and a normal diet contains between 300 and 400 µmol/day. Its elimination is mainly via the urinary route, with a small proportion being biliary.[4] l-Carnitine has an important role in cell physiology to provide chemical energy to the tissues by β-oxidation of free fatty acids in mitochondrial matrix,[5] to increase the erythrocyte survival by stabilizing the cellular membrane, and raising red blood cell osmotic resistance,[6] and also to participate in transesterification reactions and prevent organic acids accumulation.[7]

The plasma levels of l-carnitine decrease in end-stage renal disease (ESRD) patients under hemodialysis therapy by impaired biosynthesis and metabolism of l-carnitine and increased loss during hemodialysis through dialytic membranes and by poor content in diet.[8] l-Carnitine supplementation leads to improvement in several complications seen in HD patients, including cardiac complications, impaired exercise and functional capacities, muscle symptoms, increased symptomatic intradialytic hypotension, and anemia requiring large doses of erythropoietin.[9]

In this study, our aim was to evaluate the effect of postdialysis administration of parenteral l-carnitine supplementations on hematological parameters and also on weekly requiring dose of the rHuEPO in HD patients.

Material and Methods

The 48 patients (25 male, 23 female) were enrolled in the study who were on rHuEPO and active vitamin D therapy, and who have no signs of inflammation and infection at the beginning of the study, and undergo a regular maintenance HD program at 5 h intervals, three times a week with bicarbonate dialysate and with biocompatible membranes at the HD center of Medical Faculty Hospital in University of Dicle. The 34 patients (17 male, 17 female) completed the study. The patients who were transferred to another hemodialysis center during the study period (n = 6) or who changed the renal replacement therapy (n = 1) or who had gross blood loss that affects the outcome of the therapy (n = 2) or who got infection/inflammation (n = 2) or who got tertiary hyperparathyroidism (n = 1) and got exitus (n = 2) were excluded from the study.

The patients who were diagnosed for iron deficiency before the study were treated with parenteral iron supplements after determining the total iron requirements. The iron indices were controlled monthly. According to the results, the therapy either stopped or continued with maintenance dose. The rHuEPO was started 80–120 U/kg/week via SC. The patients were divided into two groups: the patients who received only rHuEPO therapy (group 1, n = 17) and the patients who received rHuEPO +l-carnitine (group 2, n = 17). l-Carnitine was injected postdialysis 1 gr (l-carnitine ampul, Santa-Farma) intravenously (IV) via venous route of the dialytic set three times in a week. The basal hemoglobin (Hgb), Hematocrit (Hct), serum iron (Fe^{+ 2}), total iron binding capacity (TIBC), transferrin saturation index (TSI), and serum ferritin (Fer) levels were measured at the beginning of the study in both groups. After 8 weeks and 16 weeks of study, the rHuEPO doses and hematological parameters were recorded.

The statistical analysis was evaluated in 10.0 PC program. Student's t-test, Mann Whitney U test, and Wilcoxon Signed Rank Test were used for the analysis of both group variables. The value of p< 0.05 was accepted as statistically significant. Data were defined as mean ± SD.

Results

In group 1 (n = 17: 13 female, four male), the mean age was 38.8 ± 12.1 years, the mean period time on HD therapy was 18.1 ± 14.9 months, and the mean Kt/V value was 1.48 ± 0.28. In group 2 (n = 17: 13 male, four female), the mean age was 48.1 ± 15.4 years, the mean time on HD therapy was 34.4 ± 23.0 months, and the mean Kt/V value was 1.29 ± 0.20. The patients' characteristics are shown in Table 1. The hematological parameters and the weekly requiring doses of rHuEPO were summarized in Table 2. The increasing levels of Hgb and Hct and decreasing dose of the rHuEPO were demonstrated in Figure 1.

Table 1. The demographic characteristics of the groups

Parameters	Group 1 (n = 17)	Group 2 (n = 17)	p
Male/female	4/13	13/4	< 0.05
Age (years)	38.8 ± 12.1	48.1 ± 15.4	= 0.05
Duration time on HD (months)	18.1 ± 14.9	34.4 ± 23.0	< 0.05
Kt/V	1.48 ± 0.28	1.29 ± 0.20	< 0.05

Table 2. The hematological parameters of the groups

Parameters	Week	Group 1 (n = 17)	Group 2 (n = 17)	p
Hct-1	0	25.3 ± 4.3	30.7 ± 4.1	< 0.05
Hct-2	8	29.5 ± 3.0	33.2 ± 4.2	< 0.05
Hct-3	16	32.5 ± 2.9	35.4 ± 2.2	< 0.05
%TSI	0	28 ± 16	35 ± 21	> 0.05
%TSI	8	48 ± 21	45 ± 18	> 0.05
%TSI	16	48 ± 19	43 ± 18	> 0.05
Ferritine	0	510 ± 272	600 ± 274	> 0.05
Ferritine	8	647 ± 340	743 ± 212	> 0.05
Ferritine	16	734 ± 214	763 ± 201	> 0.05
EPO-1	0	6529 ± 1419	4882 ± 1453	< 0.05
EPO-2	8	5353 ± 931	2235 ± 1091	< 0.05
EPO-3	16	3588 ± 1228	1705 ± 1213	< 0.05

Figure 1 The modifications in dose of rHuEPO according to the hematocrit levels in both groups.

The hematological parameters of groups were found as follows: in group 1, Hgb: 7.9–10.8 g/dl, Hct: 25.3–32.5%; in group 2: Hgb: 10.2–11.8 g/dl, Hct: 30.6–35.4%, respectively (p< 0.05). The target Hgb/Hct values were achieved at the end of the study in both groups. The serum Fe^{+ 2} markers were established as in group 1: TSI: 28–48%, serum Fer: 510–734 ng/ml, and in group 2: TSI: 35–43% serum Fer: 600–763 ng/ml, respectively. Both groups were the same according to their serum iron markers, so there were no statistically significant differences between groups (p > 0.05).

There was significant difference between groups concerning the weekly requiring doses of rHuEPO compared to the increasing Hct levels. In group 1, the weekly requiring dose of the rHuEPO was 6529 U/week (120 U/kg/week) at the beginning of the study (0. week), and at the end of the study, the maintenance dose was 3588 U/week (66 U/kg/week). The total decrease in rHuEPO dose was 2941 U/week. In the same study period, these values were 4882 U/week (80 U/kg/week) and 1705 U/week (28 U/kg/week) in group 2, respectively. The total decrease in doses of rHuEPO was 3177 U/week. According to these values, the total decrease in rHuEPO dose was 45% in group 1 and 65% in group 2, respectively (p< 0.05).

There was a significant difference in the weekly requiring doses of rHuEPO between groups when comparing therapy and maintenance doses (p< 0.05).

Discussion

Recently, the secondary l-carnitine deficiency was thought to be the possible cause of anemia, requiring large doses of rHuEPO, or unresponsiveness to the rHuEPO was suggested in some reports.[2] According to all of the evidence in the reports, the etiological factors of secondary l-carnitine deficiency in uremia may be classified intrinsic and extrinsic, as discussed below:

1. Intrinsic factors: the impairment of biosynthesis and metabolism of l-carnitine; the utilization of carnitine by a new RBC population that increased erythropoiesis by stimulation of rHuEPO;[10] the impaired influx of the acyl-groups in the erythrocyte membranes; the decreased activity of carnitine palmitoil transferase (CPT) and gliserofosfolipid acyl transferase (GAT); the reduced ratio of long-chain acyl Co A/free Co A; the increased ratio of long-chain acyl carnitine/free carnitine;[4-11] the increased deformability of erythrocytes that affect the survival of the erythrocytes, their microcirculation, and tissue oxygen delivery;[12] the inhibition of the Na–K pump in the erythrocyte's membranes by uremic plasma;[13] the impaired erythrocyte's membrane stability.[14&15]

2. Extrinsic factors: poor content of l-carnitine in diet; a 75% decrease in plasma concentration during the dialysis sessions;[16] dialytic membrane materials; time on HD; weekly HD time.[17]

Some clinical observations and experimental studies have shown that l-carnitine acts on some enzymes and metabolic functions in the erythrocytes, such as increased activity of CPT and GAT,[4], [11], [18] improved acyl fluxes in the erythrocytes membranes, increased ratio of long-chain acyl Co A/free Co A, decreased ratio of long-chain acyl carnitine/free carnitine.[11-18]

Mingardi et al. reported that after administration of IV carnitine, the plasma concentration of free carnitine did not change, but the total plasma concentration of carnitine increased, so the ratio of free l-carnitine/total carnitine[19&20] was reduced. Nikolaos et al.[12] addressed that following l-carnitine supplementation, there was a significant reduction of erythrocyte's deformability, a significant increase in the hematocrit, and a substantial reduction in rHuEPO dose.

Labonia et al.[13] noticed an increase of Na–K pump activity of the erythrocyte membrane in uremic patients after supplementation of l-carnitine. Donatelli et al.[21] also reported a rational explanation of this subject. Arduini et al.[14] suggested that l-carnitine increased the stability of the erythrocyte membranes under high shear stress and preserved the erythrocytes for free radical toxicity. All of these mechanisms remove the molecules that trigger the oxidative reactions and provide some possibilities for improvement of cell integration. Also, it is suggested that l-carnitine is a component of the secondary antioxidant repairing system.[18]

Vlassopoulos et al.[17] reported that low erythrocyte osmotic resistance (EOR) is related to dialysis membranes and is aggravated by time on hemodialysis, and for this reason, low EOR aggravates anemia and increases EPO needs in dialysis patients. The biocompatible membranes, 5 h/three times/week HD program and HD adequacy (Kt/V ≥ 1.2) were the main factors in all patients achieving target Hct/Hgb levels at the end of our study in both groups. But in group 2, the weekly requiring dose of rHuEPO was much less than that in group 1. Furthermore, the other factors, except dialytic membranes and time on HD, must be considered, such as high/low flux membranes, the blood pump rate, surface areas of the membranes, etc.

The studies about the alterations of plasma l-carnitine concentrations during the dialysis sessions and after the dialysis sessions reported different findings. Rodriguez-Segade et al.[16] suggested that the small water-soluble carnitine molecule is dialyzable, and a 75% decrease in plasma concentration has been noted during dialysis sessions.[24] Several hours after dialysis, however, l-carnitine concentrations return to predialytic values as a consequence of reequilibration, i.e., the return of l-carnitine from tissue stores to the extracellular space.

Differing from this opinion, some authors[20], [22] reported that in patients who have been dialysed for many years, the postdialytic rebound of free l-carnitine serum concentration is attenuated, and even a gradual decrease of predialytic free or total l-carnitine is observed.

The studies of l-carnitine as an adjuvant therapy to rHuEPO in the treatment of anemia in HD patients yield significant data.[23] Hurot et al.[25] established that l-carnitine improves anemia in uremic patients before routine administration of the rHuEPO in the treatment of the anemia. After then, they demonstrated that l-carnitine therapy reduced the resistance and dose of rHuEPO in HD patients who routinely get rHuEPO.

Vesela et al.[26] demonstrated that the erythropoietin dose could be reduced from an average value of 5500 to 3500 U/week in regularly dialyzed patients. Likewise, we established a 3200 U/week reduction in dose of weekly requiring rHuEPO in group 2. Labonia[27] found that the administration of l-carnitine reduced the weekly requiring dose of rHuEPO approximately 38.1% in HD patients. We observed a 65% reduction in weekly requiring dose of the rHuEPO in group 2, and a 45% in group 1 at the end of the study period. We could say that l-carnitine has a 20% contribution to reducing the weekly requiring dose of the rHuEPO in group 2.

However, there was a reduction in weekly requiring dose of the rHuEPO, as the Hct level was 35.4% at the end of the study, while it was 30.7 at the beginning of the study in group 2. These results resembled the results from the studies by Matsumoto,[28] Takeda,[29] and Albertazzi et al.[30] When we compared the groups in achievement of the target Hct levels, we found that the percent of increase in Hct level was much higher (7.2% versus 4.7%) in group 1 than in group 2. However, there was a striking elevation in the Hct level in group 1, and there was a controlled elevation in group 2. The latter is very important in our opinion because of the prevention of potential complications of rHuEPO in this population.

We believed that the administration of l-carnitine as adjuvant therapy to rHuEPO may provide some modifications in weekly requiring dose of the rHuEPO. Our serum iron markers, including serum iron, TSI, and serum Fer, were the same as those in the Trovato et al.[31] results. In addition, the administration of l-carnitine has a significant effect on the hematological profile of the uremic patients mentioned above[32-34] and an important feature in that it reduces the cost-effectiveness of the weekly requiring dose of the rHuEPO.[35]

The National Kidney Foundation (NKF)[36] and other consensus study groups[37] have not developed any accepted guideline for administration of l-carnitine as a adjuvant therapy, in spite of its benefits.

In conclusion, when serum iron deficiency, HD inadequacy, elevation of PTH, signs of infection/inflammation, presence of aluminium intoxication, and malnutrition are excluded, the postdialysis parenteral l-carnitine therapy can be considered in select stable patients and may improve anemia and reduce the weekly requiring dose of the rHuEPO, and also providing a cost-effective solution.