Abstract
Objective: To evaluate the effect of creatine (Cr) supplementation (5 g/day) in Huntington’s disease (HD).
Methods: A 1-year double-blind placebo-controlled study was performed in 41 patients with HD (stage I through III). At baseline and after 6 and 12 months, the functional, neuromuscular, and cognitive status of the patients was assessed by a test battery that consisted of 1) the Unified Huntington’s Disease Rating Scale (UHDRS), 2) an exercise test on an isokinetic dynamometer to assess strength of the elbow flexor muscles, 3) a maximal exercise test on a bicycle ergometer to evaluate cardiorespiratory fitness, and 4) a test to assess bimanual coordination ability. Following the baseline measurements, the subjects were assigned to either a creatine (n = 26) or a placebo group (n = 15).
Results: Scores on the functional checklist of the UHDRS (p < 0.05), maximal static torque (p < 0.05), and peak oxygen uptake (p < 0.05) decreased from the start to the end of the study, independent of the treatment received. Cognitive functioning, bimanual coordination ability, and general motor function (total motor scale, UHDRS) did not change from baseline to 1 year in either group.
Conclusion: One year of Cr intake, at a rate that can improve muscle functional capacity in healthy subjects and patients with neuromuscular disease (5 g/day), did not improve functional, neuromuscular, and cognitive status in patients with stage I to III HD.
Received . Accepted in final form .
Creatine (Cr) is a guanidine compound that plays a pivotal role in the regulation of energy metabolism.1 There is evidence from in vitro and animal experiments that oral Cr supplementation might prevent or slow down Huntington’s disease (HD) neurodegeneration.2 In R6/2 and N171-82Q transgenic mice models of HD, administration of a diet containing 1 to 2% Cr from the age of 3 to 4 weeks to death slowed motor deterioration and delayed onset of weight loss and diabetic symptoms. More importantly, the administration of Cr significantly reduced brain atrophy and the formation of striatal intranuclear inclusions and resulted in an improved survival of 20%.3,4⇓ Furthermore, Cr administration in rats increased brain phosphocreatine (PCr) content, protected against 3-nitroproprionic acid and malonate neurotoxicity, and precluded motor and cognitive deficits.5,6⇓
Cr supplementation may also have a beneficial impact on skeletal musculature functioning of patients with HD. Supplementary Cr intake can enhance muscle functional capacity in young healthy individuals7,8⇓ as well as in patients with various neuromuscular disorders.9-11⇓⇓ This beneficial effect has appeared to be most prominent in individuals with low initial muscle Cr content.12 Interestingly, HD has appeared to be associated with low muscle PCr content.13,14⇓
Therefore, the current pilot study investigated the effects of oral Cr supplementation on muscle strength, cardiorespiratory fitness, motor control, cognitive functioning, and functional ability in HD. The Cr dosage used (5 g/day) is well established to be adequate to enhance muscular performance in young healthy individuals7,8,15⇓⇓ and in patients with neuromuscular disease.10
Methods.
Subjects.
Patients were recruited according to the following inclusion criteria: classification into stages I (symptomatic patients only) to III16 and stable medication intake for a period of at least 3 months. Exclusion criteria were prehistory of renal pathology or existing albuminuria and prior oral Cr supplementation. Forty-two subjects signed the informed consent and were eventually enrolled in the study (table 1, figure). All patients were identified by PCR analysis to be carriers of the huntingtin gene. One subject from the placebo group (PL) was excluded after 6 months because of pregnancy. Furthermore, one PL subject and one subject from the Cr group (CR) withdrew from the study at month 6 of the intervention. One CR subject stopped the intake of tablets early in the study yet continued to participate in all measurements.
Table 1. Baseline characteristics of the subjects from the placebo and the creatine group
Figure. Flow diagram of the progress through the phases of the trial.
Study design.
The local ethics committee approved the study protocol. A double-blind placebo-controlled pilot study was performed over a 1-year period. In order to facilitate recruitment of available patients we decided to use an unbalanced study design where two out of three subjects were assigned to CR and only one to PL. Because of the small number of patients expected, together with the need to match the experimental groups for age and severity of the disease, a full random allocation of subjects to the treatment groups was not possible. Subjects were assigned to either CR or PL by an independent investigator, who was otherwise not involved with the study. From the day after the baseline measurements, CR patients ingested 5 g of Cr monohydrate per day (1 g at breakfast, 3 g at lunch, 1 g at dinner). Cr tablets (2.5 g) contained 1 g of Cr monohydrate each and were flavored by the addition of sucrose and natural orange flavor. Placebo tablets were identical in taste and appearance with the Cr tablets and contained starch, sucrose, corn syrup solids, and natural orange flavor. The code was not broken until all patients had completed the 1-year follow-up.
Measurements.
At study entry patients reported to the hospital on the morning of day 1 and first underwent a standard clinical examination. A blood sample (∼10 mL) was taken from an antecubital vein and a 24-hour urine collection was started. The serum samples were immediately transferred to a local routine clinical biochemistry laboratory for determination of hematologic measures and serum urea, creatinine, aspartate aminotransferase (AST), alanine transaminase (ALT), creatine kinase (CK), and lactate dehydrogenase (LDH). Urine samples were analyzed for Cr concentration by a standard enzymatic fluorometric assay17 and creatinine concentrations were assayed on a Hitachi auto-analyzer running on Roche consumables. After the standard clinical examination the patients were scored on the Unified Huntington’s Disease Rating Scale (UHDRS).18 In the afternoon, cardiorespiratory fitness of the patients with HD was evaluated by means of a maximal incremental exercise test (10 Watt + 10 Watt/minute) on an electromagnetically braked bicycle ergometer (Ergoline, model E800s). Tidal volume and oxygen and carbon dioxide concentrations in the inspired and expired air were continuously measured by a breath-by-breath open circuit system and minute ventilation, oxygen uptake, and carbon dioxide output were automatically calculated (Jaeger, Oxycon alpha 4.3). Heart rates were measured from continuous ECG recordings (Marquette, Max Personal Exercise Testing). On day 2 the bimanual coordination ability and strength of the elbow flexor muscles was evaluated. Bimanual coordination skill was evaluated on a test apparatus as previously described in detail.19 The subjects were instructed to produce cyclical, bimanual movements with the forearm in the horizontal plane (40° peak-to-peak displacement), coincident with the beating of an electronic metronome (Korg DTM-12; 1.15 Hz). Bimanual coordination dynamics were quantified through relative phase analyses. Higher scores on the variability and accuracy of relative phasing reflect a less stable movement pattern and a larger absolute deviation from the target score. Finally, maximal voluntary torque and power of the elbow flexor muscles was evaluated on an isokinetic dynamometer as previously described.20 Subjects first generated three maximal isometric elbow flexions (3 s) at an elbow angle of 110° with 1-minute rest pauses in between. After 2 minutes of rest subjects performed a bout of 30 dynamic maximal voluntary arm flexions at a constant velocity of 180° · sec −1. Power was calculated from the registered torque and velocity measurements.
Subjects returned to the hospital for standard clinical examination at 3-month intervals. In addition, all measurements performed at baseline were repeated after 6 and 12 months. At each occasion, the tests were performed on the same day of the week, at the same time of the day, and by the same investigator.
Statistical analyses.
Outcome measures.
Because the potential of oral Cr supplementation to beneficially impact on muscular strength is well documented, static and dynamic force were predefined to be the primary outcome variables. The different sections of the UHDRS, as well as cardiorespiratory fitness and bimanual coordinative ability, were defined as secondary outcome variables.
Sample size.
A post hoc sample size analysis has been performed. The p value of the interaction term was transformed in a z-value using the normal z-distribution (mean = 0, SD = 1). Based on this z-value and the number of observations, the number of participants that would have been required to obtain a significant interaction term in the two-way analysis of covariance at the 5% level of significance was calculated. The analysis showed that sample size would need to be increased by a factor 2 for static force and by 1 for fatigability. The SD of the difference between the scores at 12 and 6 months was 2.7 Nm (PL) and 3.5 Nm (CR) for static force and 10.7% (PL) and 8.2% (CR) for fatigability.
Data processing.
All statistical analyses were done according to the intention-to-treat principle. Missing values were imputed according to the null hypothesis. The therapeutic effect of Cr vs placebo supplementation was evaluated by a two × two [group (creatine, placebo) × time (6 months and 1 year treatment)] two-way analysis of variance, which was covariate adjusted for the baseline values of the variable entered in the analysis, and with repeated measures on the last factor. Such analysis is believed to yield a more powerful test because it takes into account the difference between the treatment groups at baseline to assess the difference between treatment groups at the end of the intervention period. A significant group effect or a significant group × time interaction was considered to identify the therapeutic effects. In addition to this primary analysis, we did a secondary analysis (one-way analysis of variance) to compare within groups the values after 6 months and 1 year of treatment, with the corresponding baseline values (time − effect). However, if the primary two-way analysis of covariance did not show a significant therapeutic effect, subjects from the PL and CR were pooled to perform the secondary analysis. Differences between the experimental groups at baseline were evaluated by unpaired Student t-test. Differences in the frequency distributions between groups were tested by means of χ2 test. A two-sided significance level of p < 0.05 was adopted. All data are expressed as mean ± SEM.
Results.
Patient characteristics and medication intake.
Age, body weight, sex distribution, and the time from onset of the disease were not significantly different between the experimental groups (see table 1). Body weight increased (p < 0.05) by 2% from the start (PL: 65.5 ± 3 kg; CR: 67.7 ± 2 kg) to the end (PL: 66.8 ± 3 kg; CR: 69.2 ± 2 kg) of the study in both groups. At enrollment the proportion of patients taking neuroleptics, alone or in combination with antidepressant medication, was similar between CR and PL. During the study, treatment with neuroleptic medication was started in four patients (CR: n = 2; PL: n = 2), whereas four patients in CR received antidepressants. Furthermore, the dosage of neuroleptics was adapted in a total of 11 patients (higher dose: n = 7; lower dose: n = 4), yet dosage changes were small and equally distributed among the experimental groups.
UHDRS.
Motor function, cognitive function, and functional ability were assessed using the UHDRS (table 2). In the total group of patients (n = 41) functional ability decreased over the 1-year study period. Scores on the functional checklist, independence scale, and total functional capacity scale after 12 months of follow-up were impaired compared with baseline (p < 0.05). However, the deterioration of functional capacity was similar in PL and CR. Scores on the tests aimed to evaluate motor function and cognitive function did not significantly deteriorate within the time window of the study, neither were there any significant differences between PL and CR.
Table 2. Effect of creatine intake on the scores of the UHDRS in Huntington’s disease patients
Cardiorespiratory fitness.
Patients performed an incremental exercise test to volitional exhaustion on a bicycle ergometer (see supplementary table E-1 at www.neurology.org). The finding that peak respiratory exchange ratios (RER) were consistently higher than one is compatible with “near-maximal” exercise at all times of the study. Peak oxygen uptake, peak workload, peak heart rate, and peak RER at baseline were similar between PL and CR. In the total group of subjects peak oxygen uptake decreased by ∼5% from baseline to month 12 (p < 0.05). Accordingly, peak workload decreased to the same degree (p < 0.05) and also peak heart rates were slightly lower at the end of the study (p < 0.05). However, the drop in peak exercise capacity throughout the study, as evidenced by the lower oxygen uptake rate, workload, and heart rate at peak exercise, was similar for PL and CR at all times of the study.
Muscle strength.
Patients performed a strength test that consisted of a series of 30 fast repetitive maximal dynamic contractions subsequent to three maximal static contractions (table 3). At baseline, static and dynamic torque was similar in PL and CR. In the total group of patients static and dynamic torque decreased by 5 to 10% (p < 0.05) within the time window of the study, with no differences between PL and CR. Fatigue, which was expressed as the % force drop from the highest torque measured during contractions 1 to 5 to the last 5 of 30 contractions, did not significantly change in the course of the study and was similar between PL and CR at all times of the study.
Table 3. Effect of creatine intake on strength of the elbow-flexor muscles in Huntington’s disease patients
Bimanual coordination.
Coordination ability was evaluated during bilateral movements with the forearms in the horizontal plane (see supplementary table E-2 at www.neurology.org). At baseline, coordination pattern was better in CR than in PL as evidenced by less variability and greater accuracy of the forearm movements (p < 0.05). In the total group of subjects there were no significant changes across 1 year.
Clinical biochemistry and side effects.
The blood and urinary measurements that are most relevant in the context of the current study are summarized in supplementary table E-3 (see www.neurology.org). Plasma creatinine was stable in PL, whereas a minor increase occurred in CR from baseline to month 12 (p < 0.05). Plasma urea, ALT, CK (data at 3 and 9 months of follow-up not shown), AST, LDH, and blood hematology values (data not shown) were all within the normal clinical range throughout the study and were similar in PL and CR at any time.
At baseline urinary Cr excretion was slightly higher in CR (p < 0.05). At 6 and 12 months of follow-up urinary Cr excretion was elevated in CR compared with PL (p < 0.05). None of the patients in PL had urinary Cr excretions out of the normal clinical range. Conversely, in CR the subjects on average exhibited Cr excretions of ∼3 g. Urinary Cr excretion relative to the Cr dosage ingested (5 g) amounted to ∼65% and 60% at 6 and 12 months. Creatinine clearance at baseline was similar between CR (75 ± 3.8 mL/minute) and PL (73 ± 5.1 mL/minute). Although the creatinine clearance at 6 months was slightly lower in PL (67 ± 4.6 mL/minute) compared with CR (76 ± 4.0 mL/minute) (p < 0.05) Cr supplementation had no overall effect on the creatinine clearance. The creatinine clearance in CR (72 ± 4.1) and PL (73 ± 5.4 mL/minute) after 1 year was similar to the values at baseline and after 6 months.
Discussion.
It was hypothesized that Cr supplementation, by enhancing muscular functional capacity7-11⇓⇓⇓⇓ as well as by virtue of its potential neuroprotective effect,3-6⇓⇓⇓ could beneficially impact on neuromuscular and cognitive symptoms in patients with HD and thereby beneficially impact on their functional ability. However, the Cr administration regimen improved neither the functional nor the neuromuscular status of the patients who were included in the study. Within the time window of this study significant regression of cognition did not occur. Therefore, no conclusions can be made with regard to the effect of Cr supplementation on the deterioration of cognitive functioning intrinsic to HD.
The test battery and study power were adequate to demonstrate the anticipated deterioration of the functional status of the patients within the 1-year follow-up period.21,22⇓ The UHDRS showed a significant regression of scores on the functional checklist, as well as on the independence scale and the total functional capacity scale (see table 2). Cognitive measures did not significantly change. However, this may be due to the sensitivity of the cognitive tests being inadequate to detect small changes of cognition.23,24⇓ By analogy, coordinative ability did not significantly change (see supplementary table E-2 at www.neurology.org). However, muscle static and dynamic force dropped by 5 to 10% (see table 3), which represents a substantially greater decrease than would typically occur in healthy persons (∼1 to 2%). A comparison with the muscle strength test data obtained in our laboratory reveals that handgrip strength is ∼20% lower in the patients with HD enrolled in this study than in age- and sex-matched controls (Verbessem et al., unpublished observations). Endurance capacity was reduced in the same order of magnitude (see supplementary table E-1 at www.neurology.org). The above functional measures at any time of the study were independent of the treatment received, which indicates that the Cr supplementation could not significantly enhance the neuromuscular, the cognitive, or the functional profile of the patient group studied. Potential Cr effects were not hidden by the intake of symptomatic medication because neuroleptic and antidepressant medication rates were similar between the treatment groups at any time of the study. The creatine group contained a slightly higher proportion (p > 0.05) of women than the placebo group. However, it is highly unlikely that this would affect the conclusions of the study. First, according to available literature, responsiveness to Cr supplementation is independent of sex and, at least in muscle, there is no difference in cellular Cr content between males and females.7,8⇓ Second, for a given CAG length, disease progression is similar in women and men. However, the small sample size used in conjunction with the short follow-up period may not have yielded sufficient power to detect small treatment effects. Still, it is important to note that, by analogy with HD, Cr administration in G39A transgenic amyotrophic lateral sclerosis (ALS) mice improved motor ability and increased survival.25 Conversely, preliminary findings in patients with ALS did not support a beneficial effect of Cr administration on either the neuromuscular profile or the functional status.26,27⇓
The current observations are in apparent contrast with the recent findings in animal models of HD.3-6⇓⇓⇓ However, the rate of Cr administration used in the aforementioned animal studies (∼1.5 g per kg body weight) exceeds common dosages in humans (0.03 to 0.3 g per kg body weight), including the current study (∼0.07 g per kg body weight), by at least a factor 5. Furthermore, in the animal studies Cr supplementation was started before the onset (or detection) of any symptoms, whereas in the current study patients already were symptomatic at the time the Cr supplementation was started. We thus cannot exclude that Cr supplementation could delay the time of onset of the disease.
An important argument to do this study was the assumption that oral Cr supplementation could increase neuronal Cr content and thereby suppress neuronal deterioration. There is no evidence that neuronal Cr deficiency is implicated in the pathogenesis of HD. However, there is clear evidence from H+-NMR studies in healthy subjects that oral Cr supplementation, even in the absence of a Cr deficiency, can substantially increase brain Cr content.28 We did not measure brain Cr content. However, if it were increased by the Cr therapy, then it did not result in a detectable improvement of the functional status of the patients.
It is well established that in healthy subjects muscular functional capacity is enhanced by Cr supplementation, yet only in individuals exhibiting a substantial increase of total muscle Cr content.7,8⇓ We did not measure muscle Cr content and thus cannot exclude that the Cr supplementation protocol used (5 g/day) did not increase muscle Cr content and thus failed to enhance muscle force. Nonetheless, our findings clearly indicate that a Cr intake regimen, which has been proven to effectively increase muscle Cr content and muscle force in young healthy subjects7,8,15⇓⇓ as well as in patients with neuromuscular disease,10 did not enhance muscle strength in patients with HD. There are a number of possible explanations for this apparent discrepancy. First, the bulk of literature data refer to short-term Cr supplementation (1 week to 1 month). However, during long-term Cr supplementation muscle cells may not be able to maintain the high Cr content established by acute or short-term Cr intake.29,30⇓ Because we did not assess muscle strength after a short term of Cr supplementation, we cannot exclude that patients may have exhibited a temporary improvement of their muscular status within the initial weeks of Cr supplementation. However, this effect had vanished by 6 months of Cr intake. Second, it is well established from studies in young healthy subjects that low initial muscle Cr content predisposes to significant functional improvement with oral Cr supplementation. There is some evidence from NMR studies to indicate that muscle PCr content might be reduced in HD.13,14⇓ However, the mechanism underlying low muscle Cr content in HD may be different from a normal healthy condition. In healthy muscle, low muscle Cr content probably represents a metabolic property intrinsic to the muscle cells. In addition, because Cr content is lower in type I than in type II fibers, low Cr content in mixed muscle also reflects the proportion of type I to type II fibers. Conversely, in patients with HD, low muscle Cr content might simply reflect a higher proportion of type I fibers resulting from selective denervation of type II motor units.
The current findings should only be extrapolated to patients with HD with a similar clinical status, treated with the same dose of Cr (5 g/day) and for the same period of time (1 year). Further studies are needed to elucidate whether other Cr administration regimens, for either shorter or longer periods of time, could result in different findings.
Acknowledgments
Supported by the “Onderzoeksraad K.U. Leuven” (grant OT99/38), the “Fonds voor Wetenschappelijke Onderzoek Vlaanderen” (grants G.03331.98 and G.0255.01), and the “Nationale Vereniging tot Steun aan Gehandicapte Personen” (P.V.), which are independent research grant organizations. The creatine (Neotine) and placebo supplements used in this clinical trial were donated by the Avicena Group (Boston, MA), who also sponsored the study in part.
Acknowledgment
The authors thank the patients and their families; Wim Emmelkamp, Mia Lemmens, Kathleen Porke, Filip Raes, Dirk Schepers, and Petra Weckx for assistance with the data collection; Monique Ramaekers for laboratory work; the Center of Human Genetics and the Flemish Huntington’s Disease Organization for assistance with patient recruitment; and Rima Kaddurah-Daouk for valuable discussions in the different stages of the study.
Footnotes
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Presented in part at the 54th annual meeting of the American Academy of Neurology; Denver, CO; April 2002.
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Additional material related to this article can be found on the Neurology Web site. Go to www.neurology.org and scroll down the Table of Contents for the October 14 issue to find the title link for this article.
References
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