Secondary Logo

Acetyl-l-carnitine: a pathogenesis based treatment for HIV-associated antiretroviral toxic neuropathy

Hart, Andrew Ma,d,*; Wilson, Andrew DHa,*; Montovani, Cristinad; Smith, Coletteb; Johnson, Margaretc; Terenghi, Giorgiod; Youle, Mikec

doi: 10.1097/01.aids.0000131354.14408.fb

Background: Nucleoside analogue reverse transcriptase inhibitors (NRTI) disrupt neuronal mitochondrial DNA synthesis, impairing energy metabolism and resulting in a distal symmetrical polyneuropathy (DSP), an antiretroviral toxic neuropathy (ATN) that causes significant morbidity in HIV disease. Serum acetyl-l-carnitine (ALCAR) levels are decreased in neuropathy associated with NRTI therapy. ALCAR enhances neurotrophic support of sensory neurons and promotes energy metabolism, potentially causing nerve regeneration and symptom relief.

Objective: To assess the efficacy of oral ALCAR (1500 mg twice daily) for up to 33 months in an open cohort of 21 HIV-positive patients with established ATN.

Methods: Skin biopsies were excised from the leg before ALCAR treatment, at 6–12 month intervals thereafter and from HIV-negative non-neuropathic controls. Fibre types in epidermal, dermal and sweat gland innervation were quantified immunohistochemically.

Results: After 6 month's treatment, mean immunostaining area for small sensory fibres increased (epidermis 100%, P = 0.006; dermis 133%, P < 0.05) by more than that for all fibre types (epidermis 16%, P = 0.04; dermis 49%, P < 0.05; sweat glands 60%, P < 0.001) or for sympathetic fibres (sweat glands 41%, P < 0.0003). Compared with controls, epidermal, dermal and sweat gland innervation reached 92%, 80% and 69%, respectively, after 6 month's treatment. Innervation improvements continued (epidermis and dermis) or stabilized (sweat glands) after 24 month's treatment. Neuropathic grade improved in 76% of patients and remained unchanged in 19%. HIV RNA load, CD4 and CD8 cell counts did not alter significantly throughout the study.

Conclusions: ALCAR treatment improves symptoms, causes peripheral nerve regeneration and is proposed as a pathogenesis-based treatment for DSP.

From the aBlond McIndoe Centre, the bDepartment of Primary Care and Population Sciences and the cRoyal Free Centre for HIV Medicine, Royal Free and University College Medical School, London and dBlond McIndoe Research Laboratories, University of Manchester, Manchester, UK.

Correspondence to Dr M. Youle, Royal Free Centre for HIV Medicine, Royal Free Hospital, Pond St, London NW3 2QG, UK.

Received: 23 January 2003; revised: 23 July 2003; accepted: 10 September 2003.

*Joint first authors

Back to Top | Article Outline


Antiretroviral toxic neuropathy (ATN) is the commonest HIV-associated distal symmetrical polyneuropathy (DSP) [1], causing significant morbidity in 10–35% of HIV-positive patients [2–4] and occurring in 11–66% of patients [1;5] taking nucleoside analogue reverse transcriptase inhibitor (NRTI) drug therapy. The dideoxynucleotide analogue agents stavudine, zalcitabine and didanosine are implicated in its pathogenesis [1,4,6] and changes in prescribing pattern of these drugs, including dose reduction, have led to a reduction in the incidence of polyneuropathy [4]. A feature of ATN is development of dysaesthetic pain [4], the severity of which is associated with elevated plasma levels of HIV-1 RNA [7]; this pain may be unresponsive to analgesia, even in combination with anticonvulsant drugs [1], tricyclic antidepressants [3], mexiletine [3] or peptide T [8]. Withdrawal of certain NRTI drugs often becomes necessary [1,4] since there are no licensed effective therapies, although lamotrigine [9] and recombinant human nerve growth factor (NGF) [10] have shown some benefit. Ideally a pathogenesis-based treatment for ATN would allow patients to continue NRTI therapy, still the keystone of current highly active antiretroviral therapy regimens [11].

ATN is thought to result from disrupted mitochondrial oxidative metabolism [6,12] secondary to reduction in neuronal mitochondrial DNA content [6,13,14]. Consequently, neurons are unable to meet the metabolic requirements of their long peripheral axons, which undergo die-back and result in the glove and stocking distribution of ATN [1]. In keeping with this die-back hypothesis, epidermal innervation is reduced in ATN [15,16], although the innervation of the dermis and sweat glands remains to be quantified. Development of abnormal sweating patterns in ATN suggests that an autonomic neuropathy also develops, which may be a factor in nocturnal sweating, common in HIV disease [17].

A proposed therapeutic agent for DSP is acetyl-l-carnitine (ALCAR), the acetyl ester of l-carnitine. ALCAR is vital for normal mitochondrial function, being a transport molecule for free fatty acids and an important acetyl-group donor in high-energy metabolism and free fatty acid β-oxidation [18,19]. Also, ALCAR potentiates NGF actions [20–22], promotes peripheral nerve regeneration [23,24] and is neuroprotective in vitro [19,25], in vivo [26] and in animal models of diabetic neuropathy [27]. ALCAR has analgesic properties, possibly mediated by increasing adrenocorticotrophic hormone and β-endorphin levels [28], while l-carnitine also has favourable immunological benefits [29] in HIV infection. ALCAR treatment has been shown to improve pain scores and electrophysiological parameters in a placebo-controlled study in diabetics with DSP [30]. Short-term ALCAR treatment [31] has shown symptomatic benefits in ATN, although it is unclear if this effect is long lasting because of neuronal regeneration or merely is an analgesic effect.

This study was designed to determine the effect of long-term ALCAR therapy upon symptoms and cutaneous innervation in patients with ATN, using quantitative immunohistochemistry with antisera specific for fibre types. This technique has been used in HIV-associated sensory neuropathy [16] and has been found to be more sensitive than clinical assessment in diabetic and leprosy neuropathy [32–34].

Back to Top | Article Outline


Clinical details

This study was performed in agreement with the terms of the Helsinki Declaration, after appropriate review by the local research ethics committee. The study recruited five non-neuropathic HIV-negative controls and an observational cohort of 21 patients with established ATN (grade 0–4/4 by analgesic requirement, where 0 is asymptomatic, 1 is ATN but no analgesia required, 2 is ATN requiring non-opioid analgesics, 3 is opioid analgesics required, and 4 is pain uncontrolled by opioid analgesia). Patients commenced treatment between March 1999 and October 2001. Selection criteria were age 20–60 years, either sex, documented HIV positive by a licensed HIV antibody enzyme-linked immunosorbent assay (Amplicor version 1.5 or Cobas version 1.5; Roche Molecular Systems, Branchburg, New Jersey, USA), and stable ATN diagnosis (onset within 6–12 months of commencing NRTI therapy, symptoms stable for 2 months, and no other neuropathic aetiological factors or DSP-associated therapies). The controls tested negative for HIV antibodies within the previous 3–12 months and had no neuropathic symptoms, no history of diabetes, metabolic disorders, alcohol abuse or treatment with potentially neurotoxic agents.

Patients’ clinical grade of DSP was monitored while receiving ALCAR 1500 mg twice daily (500 mg tablets; Sigma-Tau, Italia), and a record of changes in other medications was kept.

Skin biopsies (1 cm × 0.5 cm) were excised from a standardized point in the lower third of the more symptomatic leg as an outpatient procedure under local anaesthesia. Wounds were closed with 4/0 Surgipro sutures (Surgipro, Chicago, Illinois, USA), which were removed after 14 days. A maximum of four biopsies were taken from each patient, the first prior to commencing ALCAR therapy (pretreatment), and then subsequently from the same leg at 6–12 month intervals while on treatment. A single biopsy was taken from an equivalent site in each control.

Back to Top | Article Outline

Immunostaining and quantification

Biopsies were fixed in Zamboni's solution (16 h at 4°C) prior to equilibration in phosphate-buffered saline, 0.1% sodium azide, 15% sucrose, followed by rapid freezing in OCT compound (Tissuetec, Elkhart, Indiana, USA). Both pre- and post-treatment biopsies were processed together to eliminate variabilities between staining runs and all staining and quantification were blinded. Systematic random samples of 15 μm cryosections from each biopsy [35] were collected onto glass slides coated with Vectabond (Vector, Peterborough, UK). Sections were permeabilized in 0.2% Triton-X (BDH Laboratory Supplies, Bristol, UK), and stained by indirect immunohistochemistry using primary antisera against polyclonal rabbit antisera for protein gene product 9.5 (PGP; Affiniti, Chesham, UK), calcitonin gene-related peptide (CGRP; Affiniti) and vasoactive intestinal polypeptide (VIP; Affiniti). PGP antibodies identify all fibre types as it is a constitutive component. CGRP antibodies are specific for C and Aδ sensory fibres and VIP antibodies are specific for cholinergic sympathetic efferent fibres. Staining was visualized using a fluorescein isothiocyanate-conjugated secondary antibody (conjugated goat anti-rabbit serum, Vector).

After staining, each section was examined by fluorescence microscopy using a 20× objective. For each antibody, a random sample of six visual fields, including both epidermis and dermis (PGP and CGRP) or subcutaneous sweat glands alone (PGP and VIP), was captured for analysis using a high-resolution digital camera (Model 1-3-0; Diagnostic Instruments, Sterling Heights, Michigan, USA). The immunostaining area in each captured image was quantified by image analysis using Image-Pro-Plus (version 4.0; MediaCybernetics, Silver Spring, Maryland, USA) software. First, the colour immunofluorescent image was converted into greyscale; then the area of interest (epidermis, dermis or sweat gland) was outlined by tracing its margins. An intensity threshold was applied to differentiate bright immunostaining from any low-level background autofluorescence, and the immunostaining area was calculated automatically. The immunostaining area approximates closely the actual area of each nerve fibre type, thus permitting quantification of cutaneous innervation by each fibre type.

To facilitate comparisons, the immunostaining area was expressed as a fraction of the total frame area of epidermis, dermis or sweat glands. From six figures for each patient at each time point, a mean value (fractional area of immunostaining) was calculated and used for statistical comparisons.

Back to Top | Article Outline

Statistical methods

The outcomes were analysed using generalized linear models. The model fit was best when the immunostaining fractional areas were fitted on a log scale, so that parameter estimates given are multiplicative increases. Each observation (i.e., each individual biopsy at each time point) was included individually in the model, which assumed normal covariance structure, with the correlation between individual patient's values accounted for using generalized estimating equations. Time-on-therapy covariate was dichotomized into a categorical variable because of evidence of a non-linear trend in the data. Biopsies taken between 3 and 9 months after starting treatment were taken to be the value at 6 months. Similarly, values at 12, 18 and 24 months were that time point ±3 months. Each variable was fitted into the model compared with the baseline immunostaining fractional area variables to gain an estimate of the average increase rate from baseline to that time point. Parameter estimates of increase in immunostaining fractional area on therapy were adjusted for potential confounders. These were baseline CD4 cell count (< 250 or > 250 × 106 cells/l), baseline age (< 40 or > 40 years), clinical grade of peripheral neuropathy (grade 1, 2 and 3) and antiretroviral treatment history (exposed to more or less than six different drugs). Models were examined for goodness of fit using residual plots and log-likelihood tests.

The data were analysed using an intent-to-treat analysis. Analysis was performed using SAS version 8.0 (SAS Institute Inc, Cary, North Carolina, USA). All P values are two sided.

Back to Top | Article Outline


Clinical and immunological parameters

Baseline data and patient demographics are summarized in Table 1. Median age at recruitment was 40 years (range, 29–60) for neuropathic patients, and 32 years (range, 29–53) for controls. In patients with established ATN, the median neuropathy duration prior to recruitment was 11 months (range, 2–41). None had a history of diabetes, excessive alcohol consumption or metabolic disorders. The median follow-up length was 14 months (range, 5–33). After the baseline biopsy, 11 patients had one further biopsy, 10 had two and 1 had three. During follow-up, two patients died. The causes of death were Mycobacterium avium intracellularae and cytomegaloviral infection for one patient, and liver failure for the second.

Table 1

Table 1

Clinical grade of neuropathic pain improved in 15 of 21 patients overall; seven of eight patients whose baseline grade was 1 and four of ten whose baseline was grade 2 became asymptomatic (grade 0); two of ten patients with baseline grade 2 improved to grade 1; one of three patients improved from grade 3 to 1 and one of three to grade 0. The neuropathic grade of five patients was unaffected by treatment, and one patient progressed from grade 1 to 2.

Although not formally documented, those who stopped ALCAR treatment suffered rapid symptom worsening, including return of dysaesthesiae. ALCAR treatment was well tolerated with no side effects, no adverse events or wound complications.

Three patients changed antiretroviral medication during the study period (one from didanosine to lamivudine at month 12 because of raised amylase, two from stavudine to nevirapine because of persistent symptoms of ATN).

Baseline median CD4 cell count was 286 × 106 cells/l [interquartile range (IQR), 155–423] and CD8 cell count was 1162 × 106 cells/l (IQR, 794–1918). These values did not change significantly at 6 months (CD4 cell count, P = 0.9; CD8 cell count, P = 0.9) and remained stable throughout the study. CD4/CD8 ratios also remained stable, with baseline median 0.19 (IQR, 0.14–0.39) not altered significantly at 6 months (P = 0.7) or thereafter. Median viral load values showed a similar pattern, with baseline median < 400 copies/ml (IQR, < 50 to 26 900) and P = 0.4 when compared with values at 6 months.

Back to Top | Article Outline

Morphology of cutaneous innervation

A normal cutaneous innervation pattern was seen in control biopsies, which derived from the reticular dermal plexus branching into plexi enveloping sweat glands or into the finer subepidermal plexus running parallel to the skin surface within the papillary dermis (Figs 1a and 2a). These fibres terminated within dermo-epidermal junction or entered the epidermis as free-end terminals. Within the epidermis, fibres ran perpendicular to the skin surface or ended in fine branches lying parallel to the stratum corneum. PGP-immunoreactive fibres predominated in all skin regions (Fig. 1a,d), while CGRP-positive fibres lay principally in the subepidermal plexus and deeper epidermal layers (Fig. 2a). VIP-positive fibres enveloped the sweat glands (Fig. 2d).

Fig. 1. Effect of acetyl-l-carnitine (ALCAR) treatment on cutaneous innervation in all fibre types.

Fig. 1. Effect of acetyl-l-carnitine (ALCAR) treatment on cutaneous innervation in all fibre types.

Fig. 2. Effect of acetyl-l-carnitine (ALCAR) treatment on cutaneous innervation by small sensory and sympathetic sudomotor fibres.

Fig. 2. Effect of acetyl-l-carnitine (ALCAR) treatment on cutaneous innervation by small sensory and sympathetic sudomotor fibres.

In patients with established DSP, there was an almost complete absence of fibres within the epidermis, the subepidermal plexus (Figs 1b and 2b) and around the sweat glands (Figs 1e and 2). ALCAR treatment was associated with normalization of morphology (Figs 1c,f and 2c,f), although epidermal fibres remained less evident than in control skin.

Back to Top | Article Outline

Quantification: all fibre types

Initial analysis compared the baseline PGP immunostaining fractional area to that found after 6 months of ALCAR treatment (Table 2). Subsequently, the median and range of patients’ immunostaining fractional area at baseline, 6, 12 and 18 months were calculated and plotted against comparable values obtained from HIV-negative controls (Fig. 3).

Fig. 3. Plots of the mean of all treated individual's mean fractional immunostaining for protein gene product 9.5 (PGP) in each areas of cutaneous innervation at each time point up to 18 months.

Fig. 3. Plots of the mean of all treated individual's mean fractional immunostaining for protein gene product 9.5 (PGP) in each areas of cutaneous innervation at each time point up to 18 months.

Table 2

Table 2

The effect of ALCAR treatment upon cutaneous innervation as determined by quantitative immunohistochemistry, with biopsy intervals from 6 to 24 months, is summarized in Table 3. Each skin area showed significant overall immunostaining increases during the course of ALCAR treatment. When compared with controls, patients with established DSP exhibited reduced total innervation of epidermis (79% of control), dermis (54%) and, most markedly, sweat glands (43%) (Table 2; Fig. 3). On average, after 6 months of ALCAR treatment, the PGP immunostaining percentage in epidermis increased 1.34 times from baseline [95% confidence interval (CI), 1.06–1.70], equivalent to a 34% increase. After 12 months of ALCAR treatment, the patients had, on average, a 2.01 times increase in epidermal PGP-immunoreactive fibres (equivalent to 101% increase) compared with baseline (95% CI, 1.45–2.77; Table 3).

Table 3

Table 3

After 6 months of ALCAR treatment, PGP-immunoreactive fibre increase in the dermis was 1.65 times than at baseline, equivalent to a 65% increase (Table 3). Compared with HIV-negative controls, total epidermal and dermal innervation reached normal range within 6 months of commencing ALCAR treatment and thereafter remained supranormal (Fig. 3), with an overall statistically significant increase over 24 months (Table 3). After 6 months of ALCAR treatment, PGP-immunoreactive fibres around sweat glands showed a 1.75 times relative increase over baseline, corresponding to a 75% increase (Table 3). This increase remained within normal control range for the remaining treatment period (Fig. 3) and persisted up to the last analysis point at 24 months, with the overall increase being very highly significant (P < 0.0001; Table 3).

Back to Top | Article Outline

Quantification: small sensory (C, Aδ) fibres

Dermal CGRP-positive fibres were significantly reduced (75% of control) in established DSP, while epidermal innervation was almost absent (20% of control). Highly significant increases occurred in both epidermal (mean 100%; P = 0.006) and dermal (mean 133%; P < 0.0001) innervation after 6 months of ALCAR treatment, such that mean immunostaining fractional area reached 40% of control in epidermis, and 175% of control in dermis (Table 2).

Six months of ALCAR treatment increased the proportion of all nerves (PGP positive), which displayed CGRP immunoreactivity in both epidermis (4% pre-treatment; 8% at the 6 month biopsy; 36% in controls), and dermis (22% pretreatment; 44% at the 6 month biopsy; 19% in controls) (Table 2). These CGRP staining increases in both areas were sustained at all time points up to 24 months, with an overall statistically significant immunostaining increase over the study duration (P ≤ 0.0001; Table 3).

Back to Top | Article Outline

Quantification: sympathetic sudomotor fibres

In patients with established ATN, the reduction in sympathetic innervation of the sweat glands (VIP-immunoreactive fibres) (41% of control) was similar to the reduction in their total innervation (43% of control for PGP-immunoreactive fibres; Table 2). Sympathetic innervation increased by 41% (P = 0.0003) after 6 months of ALCAR treatment (Table 2). The proportion of total innervation (PGP positive) that was VIP immunoreactive remained similar to controls (pretreatment 84%; post-treatment 85%; control 76%). The increase observed at 6 months was sustained up to 24 months of treatment, with an overall statistically significant increase (P < 0.0001; Table 3).

Back to Top | Article Outline


In this patient cohort, NRTI-induced DSP (ATN) was diagnosed by a neurologist. All patients had stable ATN prior to recruitment, making spontaneous resolution unlikely to have accounted for the changes in symptoms and innervation reported here.

Quantification of cutaneous innervation has previously been found to correlate with clinical tests of sensory function in leprosy [34] and diabetic neuropathy [33], where immunohistochemical changes preceded those of sensory testing during disease progression [32]. The morphology of cutaneous innervation in DSP has previously been described qualitatively, and the density of epidermal fibres shown to be reduced along a proximal–distal gradient in the limb in DSP [14] and ATN [15]. Epidermal nerve fibre density has recently been described as a therapeutic outcome measure in HIV [16]; however, fibre counts do not assess the health of surviving fibres, and atrophy or regeneration of fibres needs to be determined by immunostaining area quantification, as used in this study.

Since PGP is a constitutive component of peripheral nerve fibres, any decrease in immunoreactivity will reflect actual loss or atrophy of fibres rather than reduction in function of surviving fibres, corresponding to decreased immunoreactivity for specific fibre-type neuropeptide transmitters (e.g., CGRP, VIP). In established ATN, the symptoms reflect a cutaneous innervation reduction of the lower leg, with epidermal innervation being most affected, consistent with the die-back hypothesis of sensory neuropathy [4]. There is also marked atrophy of dermal and sweat gland plexi. This cutaneous denervation may explain why neuropathic symptoms frequently do not begin to resolve for some weeks after starting ALCAR treatment and may then continue to improve for many months, since this time frame matches the slow rate at which peripheral nerves regenerate.

As expected from the ATN dysaesthetic algesic symptomatology, small sensory (C, Aδ) fibres are most affected, and we have demonstrated that these fibres show the greatest reduction in immunostaining area when compared with controls. Furthermore, the proportion of CGRP:PGP-positive fibres was markedly reduced in epidermis from neuropathic patients (ATN 4%; control 36%), implying loss of epidermal fibres and reduced function of the surviving sensory fibres. In contrast, fibre loss or atrophy may be the predominant feature in sweat glands, since the VIP:PGP ratio (ATN 84%; control 76%) is relatively preserved.

Six months of oral ALCAR treatment resulted in significant increases in the innervation in epidermis, dermis and sweat glands, an improvement maintained throughout the treatment for all patients. The results demonstrate that dermal PGP-immunostaining nerve fibres regenerated sufficiently to reach the range found in normal skin. Intraepidermal fibres also regenerated, although more gradually. This difference in regrowth rate in separate skin areas is unsurprising as reinnervation occurs more slowly in epidermis than in other tissues [36].

The increased ratio of CGRP and VIP to PGP immunostaining found after ALCAR treatment suggests that regenerating fibres may be functional, although electrophysiological and sensory testing will be required for confirmation. The increase in dermal CGRP immunoreactivity to supranormal levels after long-term treatment with ALCAR probably reflects the incomplete epidermal regeneration, hence the anterogradely transported CGRP accumulated in the dermal fibres through a distal ‘damming’ effect, as described in early diabetic neuropathy [32].

ALCAR treatment resulted in significant reduction in neuropathic pain grade experienced by the patients after long-term treatment. However, a randomized controlled trial utilizing a validated visual analogue pain scale is required to demonstrate conclusive symptomatic benefits. Such a trial is now underway to determine the functional effect of ALCAR treatment in preventing ATN. While there was no placebo arm to this study, the natural history of untreated DSP suggests that the continuous and long-term beneficial effects found in this patient cohort resulted from ALCAR treatment.

The mechanism underlying the effects of ALCAR is unclear. Although ATN pathogenesis has not been clarified, the DNA polymerase-γ hypothesis remains the most likely explanation [14]. In eukaryote cells, DNA formed from individual deoxynucleotide trisphosphates by DNA polymerase, and the γ- and β-isoforms are significantly inhibited by the dideoxynucleotide trisphosphate NRTI [6]. Unlike nuclear DNA replication, mitochondrial DNA replication is dependent upon the γ-isoform, which is most inhibited in non-mitogenic cells where only mitochondrial DNA is replicated [6,14]. Because of its proximity to free radical species generated by the respiratory chain complexes, mitochondrial DNA is particularly liable to damage. Since no mitochondrial DNA repair mechanisms exist, overall oxidative metabolic function must be maintained by replication [6]. Hence by impairing mitochondrial DNA replication, a NRTI reduces the cell capacity for oxidative phosphorylation, the critical energy pathway in neurons. Consequently, neurons may apoptose [37] or fail to meet the metabolic requirements for maintaining long peripheral axons, resulting in die-back glove and stocking neuropathy.

ALCAR treatment may counteract the dideoxynucleotide trisphosphate NRTI toxicity (ATN) by several mechanisms. First, it may reduce mitochondrial DNA damage by a direct antioxidant effect [38,39]. Second, ALCAR facilitates mitochondrial homeostasis of acetyl-coenzyme A, promotes long-chain free fatty acid transport across mitochondrial membranes [18] and, via regulation of malonyl-coenzyme A, promotes cytosolic free fatty acid oxidation [40]. By promoting glucose utilization and high-energy substrate oxidative metabolism, ALCAR improves neuronal metabolic capacity [41]. In addition, ALCAR may facilitate distal neurotrophic support, particularly of myelinated (Aδ) and unmyelinated (C) fibres, since it increases NGF binding capacity [22], enhances the response to NGF [21] and promotes neurite extension in response to NGF [19]. Furthermore, ALCAR promotes peripheral nerve regeneration [23,30] and function [42–45] independently of its role in preventing NRTI toxicity. Also, patients with NRTI-associated peripheral neuropathy have reduced serum ALCAR levels, which is not seen in asymptomatic HIV-positive controls [46]. ALCAR penetrates the blood–brain barrier [47], and serum levels can be increased by its oral or parenteral administration [48,49], which also reverses the depletion occurring in peripheral nerves of diabetic rats [27].

ALCAR may offer additional benefits in HIV infection management since the mitochondrial DSP pathogenesis shares similarities with that of the lipodystrophy syndrome [50], associated with highly active antiretroviral therapy [51]. Lipodystrophy might be responsive to ALCAR treatment, although an open small uncontrolled study of ALCAR in HIV-infected individuals with facial wasting showed no clear benefit [52]. Furthermore, the related compound l-carnitine (with which ALCAR equilibrates in vivo) improves CD4 T cell counts by limiting ceramide production and apoptosis [53–56], and may also improve general health in HIV disease by promoting mononuclear cell proliferation [53], serum lipid profiles [54], and exercise capacity [57]. In this study, an oral dose of ALCAR 1500 mg twice daily was safe, well tolerated and, unlike with recombinant human NGF treatment [10], no significant side effects were noted. ALCAR treatment was not associated with any progression of HIV infection, since viral load, CD4/CD8 ratio, CD4 cell count and CD8 cell count remained stable throughout.

Although NRTI agents have been partly superseded by other agents such as protease inhibitors, they remain fundamental for combination therapy [4,11] and are likely to remain important components in HIV management for the foreseeable future [4]. Peripheral neuropathy has been the principal complication limiting the use of these agents [1,4] and ALCAR may now offer an effective, pathogenesis-based management approach, allowing patients to remain on NRTI therapy. Data from a full randomized controlled trial is now awaited to validate the results of this study and to determine the required duration and dose of ALCAR treatment.

Back to Top | Article Outline


The authors are grateful for the help given by the nursing staff of the Ian Charleson Day Centre, by the research nurses Zoe Cuthbertson, Pat Byrne and Tony Drinkwater, by the Research Fellows of the Blond McIndoe Centre, by Ben Wills, Paul Slade and Andrea Price of Bristol-Myers Squibb Pharmaceuticals and Menotti Calvani of Sigma-tau Farmaceutiche Italia.

Sponsorship: Unrestricted medical grant for laboratory materials from Bristol-Myers-Squibb Pharmaceuticals, Hounslow, UK.

Note: Andrew M. Hart and Andrew D. H. Wilson contributed equally to this paper.

Back to Top | Article Outline


1. Simpson DM, Tagliati M. Nucleoside analogue-associated peripheral neuropathy in human immunodeficiency virus infection. J Acquir Immune Defic Syndr Hum Retrovirol 1995, 9:153–161.
2. Hall CD, Snyder CR, Messenheimer JA, Wilkins JW, Robertson WT, Whaley RA, et al. Peripheral neuropathy in a cohort of human immunodeficiency virus-infected patients. Incidence and relationship to other nervous system dysfunction. Arch Neurol 1991, 48:1273–1274.
3. Kieburtz K, Simpson D, Yiannoutsos C, Max MB, Hall CD, Ellis RJ, et al. Randomized trial of amitriptyline and mexiletine for painful neuropathy in HIV infection. AIDS Clinical Trial Group 242 Protocol Team. Neurology 1998, 51:1682–1688.
4. Moyle GJ, Sadler M. Peripheral neuropathy with nucleoside antiretrovirals: risk factors, incidence and management. Drug Saf 1998, 19:481–494.
5. Moore RD, Wong WM, Keruly JC, McArthur JC. Incidence of neuropathy in HIV-infected patients on monotherapy versus those on combination therapy with didanosine, stavudine and hydroxyurea. AIDS 2000, 14:273–278.
6. Brinkman K, ter Hofstede HJ, Burger DM, Smeitink JA, Koopmans PP. Adverse effects of reverse transcriptase inhibitors: mitochondrial toxicity as common pathway. AIDS 1998, 12:1735–1744.
7. Simpson DM, Haidich AB, Schifitto G, Yiannoutsos CT, Geraci AP, McArthur JC, et al. Severity of HIV-associated neuropathy is associated with plasma HIV-1 RNA levels. AIDS 2002, 16: 407–412.
8. Simpson DM, Dorfman D, Olney RK, McKinley G, Dobkin J, So Y, et al. Peptide T in the treatment of painful distal neuropathy associated with AIDS: results of a placebo-controlled trial. The Peptide T Neuropathy Study Group. Neurology 1996, 47: 1254–1259.
9. Simpson DM, McArthur JC, Olney R, Clifford D, So Y, Baird BJ, et al. Lamotrigine for HIV-associated painful peripheral sensory neuropathies: a placebo controlled trial. Neurology 2003 60:1508–1514.
10. McArthur JC, Yiannoutsos C, Simpson DM, Adornato BT, Singer EJ, Hollander H, et al. A phase II trial of nerve growth factor for sensory neuropathy associated with HIV infection. AIDS Clinical Trials Group Team 291. Neurology 2000, 54:1080–1088.
11. Pozniak A Gazzard BG, Churchill D, Johnson MA, Williams I, Deutsch JC, et al. British HIV Association (BHIVA) Guidelines for the Treatment of HIV-infected Adults with Antiretroviral Therapy. London: British HIV Association; 2000.
12. Chen CH, Vazquez-Padua M, Cheng YC. Effect of anti-human immunodeficiency virus nucleoside analogs on mitochondrial DNA and its implication for delayed toxicity. Mol Pharmacol 1991, 39:625–628.
13. Keilbaugh SA, Prusoff WH, Simpson MV. The PC12 cell as a model for studies of the mechanism of induction of peripheral neuropathy by anti-HIV-1 dideoxynucleoside analogs. Biochem Pharmacol 1991, 42:R5–R8.
14. Lewis W, Dalakas, MC. Mitochondrial toxicity of antiviral drugs. Nat Med 1995, 1:417–422.
15. McCarthy BG, Hsieh ST, Stocks A, Hauer P, Macko C, Cornblath DR, et al. Cutaneous innervation in sensory neuropathies: evaluation by skin biopsy. Neurology 1995, 45:1848–1855.
16. Polydefkis M, Yiannoutsos CT, Cohen BA, Hollander H, Schifitto G, Clifford DB, et al. Reduced intraepidermal nerve fiber density in HIV-associated sensory neuropathy. Neurology 2002, 58:115–119.
17. Cunningham WE, Shapiro MF, Hays RD, Dixon WJ, Visscher BR, George WL, et al. Constitutional symptoms and health-related quality of life in patients with symptomatic HIV disease. Am J Med 1998, 104:129–136.
18. Bremer J. The role of carnitine in intracellular metabolism. J Clin Chem Clin Biochem 1990, 28:297–301.
19. Colucci WJ, Grandour RD. Carnitine acyltransferase: a review of its biology, enzymology and bioorganic chemistry. Bioorg Chem 1988, 16:307–334.
20. Manfridi A, Forloni GL, Arrigoni-Martelli E, Mancia M. Culture of dorsal root ganglion neurons from aged rats: effects of acetyl-l-carnitine and NGF. Int J Dev Neurosci 1992, 10:321–329.
21. Taglialatela G, Angelucci L, Ramacci MT, Werrbach-Perez K, Jackson GR, Perez-Polo JR. Acetyl-l-carnitine enhances the response of PC12 cells to nerve growth factor. Brain Res Dev Brain Res 1991, 59:221–230.
22. Angelucci L, Ramacci MT, Taglialatela G, Hulsebosch C, Morgan B, Werrbach-Perez K, et al. Nerve growth factor binding in aged rat central nervous system: effect of acetyl-l-carnitine. J Neurosci Res 1988, 20:491–496.
23. Fernandez E, Pallini R, Gangitano C, Del Fa A, Sangiacomo CO, Sbriccoli A, et al. Effects of l-Carnitine, l-acetylcarnitine and gangliosides on the regeneration of the transected sciatic nerve in rats. Neurol Res 1989, 11:57–62.
24. Hart AM, Wiberg M, Terenghi G. Pharmacological enhancement of peripheral nerve regeneration in the rat by systemic acetyl-l-carnitine treatment. Neurosci Lett 2002, 334:181–185.
25. Virmani MA, Biselli R, Spadoni A, Rossi S, Corsico N, Calvani M, et al. Protective actions of l-carnitine and acetyl-l-carnitine on the neurotoxicity evoked by mitochondrial uncoupling or inhibitors. Pharmacol Res 1995, 32:383–389.
26. Hart AM, Wiberg M, Youle M, Terenghi G. Systemic acetyl-l-carnitine eliminates sensory neuronal loss after peripheral axotomy: a new clinical approach in the management of peripheral nerve trauma. Exp Brain Res 2002, 145:182–189.
27. Sima AA, Ristic H, Merry A, Kamijo M, Lattimer SA, Stevens MJ, et al. Primary preventive and secondary interventionary effects of acetyl-l-carnitine on diabetic neuropathy in the bio-breeding Worcester rat. J Clin Invest 1996, 97:1900–1907.
28. Onofrj M, Fulgente T, Melchionda D, Marchionni A, Tomasello F, Salpietro FM, et al. l-Acetylcarnitine as a new therapeutic approach for peripheral neuropathies with pain. Int J Clin Pharmacol Res 1995, 15:9–15.
29. Famularo G, De Simone C, Cifone G. Carnitine stands on its own in HIV infection treatment. Arch Intern Med 1999, 159:1143–1144.
30. De Grandis D, Minardi C. Acetyl-l-carnitine (levacarnine) in the treatment of diabetic neuropathy. A long-term randomized, double-blind, placebo controlled study. Drugs Res Dev 2002, 3:223–231.
31. Scarpini E, Sacilotto G, Baron P, Cusini M, Scarlato G. Effect of acetyl-l-carnitine in the treatment of painful peripheral neuropathies in HIV+ patients. J Peripher Nerv Syst 1997, 2:250–252.
32. Properzi G, Francavilla S, Poccia G, Aloisi P, Gu XH, Terenghi G, et al. Early increase precedes a depletion of VIP and PGP-9.5 in the skin of insulin-dependent diabetics: correlation between quantitative immunohistochemistry and clinical assessment of peripheral neuropathy. J Pathol 1993, 169:269–277.
33. Levy DM, Terenghi G, Gu XH, Abraham RR, Springall DR, Polak JM. Immunohistochemical measurements of nerves and neuropeptides in diabetic skin: relationship to tests of neurological function. Diabetologia 1992, 35:889–897.
34. Facer P, Mathur R, Pandya SS, Ladiwala U, Singhal BS, Anand P. Correlation of quantitative tests of nerve and target organ dysfunction with skin immunohistology in leprosy. Brain 1998, 121:2239–2247.
35. Baddeley AJ, Gundersen HJ, Cruz-Orive LM. Estimation of surface area from vertical sections. J Microsc 1986, 142:259–276.
36. Navarro X, Verdu E, Wendelschafer-Crabb G, Kennedy WR. Immunohistochemical study of skin reinnervation by regenerative axons. J Comp Neurol 1997, 380:164–174.
37. Adle-Biassette H, Bell JE, Creange A, Sazdovitch V, Authier FJ, Gray F, et al. DNA breaks detected by in situ end-labelling in dorsal root ganglia of patients with AIDS. Neuropathol Appl Neurobiol 1998, 24:373–380.
38. Calvani M, Arrigoni-Martelli E. Attenuation by acetyl-l-carnitine of neurological damage and biochemical derangement following brain ischemia and reperfusion. Int J Tissue React 1999, 21:1–6.
39. Tesco G, Latorraca S, Piersanti P, Piacentini S, Amaducci L, Sorbi S. Protection from oxygen radical damage in human diploid fibroblasts by acetyl-l-carnitine. Dementia 1992, 3:58–60.
40. Calvani M, Nicolai R, Barbarisi A, Reda E, Benatti P, Peluso G. Carnitine System and Cancer. Advances in Nutrition and Cancer. New York: Plenum Press; 2000.
41. Peluso G, Benatti P, Nicolai R, Reda E, Calvani M. Carnitine system and insulin resistence. In Insulin Resistance, Metabolic Disease and Diabetic Complications. Edited by Crepaldi G, Tiengo A, Del Prato S. North-Holland: Elsevier; 1998:259–274.
42. Kano M, Kawakami T, Hori H, Hashimoto Y, Tao Y, Ishikawa Y, et al. Effects of ALCAR on the fast axoplasmic transport in cultured sensory neurons of streptozotocin-induced diabetic rats. Neurosci Res 1999, 33:207–213.
43. Stevens MJ, Lattimer SA, Feldman EL, Helton ED, Millington DS, Sima AA, et al. Acetyl-l-carnitine deficiency as a cause of altered nerve myo-inositol content, Na,K-ATPase activity, and motor conduction velocity in the streptozotocin-diabetic rat. Metabolism 1996, 45:865–872.
44. De Grandis D, Santoro L Di BenedettoP. l-Acetylcarnitine in the treatment of patients with peripheral neuropathies. Clin Drug Invest 1995, 10:317–322.
45. Giammusso B, Morgia G, Spampinto A, Motta M. Improved pallesthetic sensitivity of pudendal nerve in impotent diabetic patients treated with acetyl-L-carnitine. Acta Urol Ital 1996, 10:185–187.
46. Famularo G, Moretti S, Marcellini S, Trinchieri V, Tzantzoglou S, Santini G, et al. Acetyl-carnitine deficiency in AIDS patients with neurotoxicity on treatment with antiretroviral nucleoside analogues. AIDS 1997, 11:185–190.
47. Parnetti L, Gaiti A, Mecocci P, Cadini D, Senin U. Pharmacokinetics of IV and oral acetyl-l-carnitine in a multiple dose regimen in patients with senile dementia of Alzheimer type. Eur J Clin Pharmacol 1992, 42:89–93.
48. Chasseau LF, Hawkins DR, Mayo BC, Baldock GA. Report SGM 4/5/8176: Pharmacokinetics and Metabolism of 14 C-Labelled l -Acetylcarnitine and Related Compounds in the Rat. Huntington, UK: Huntingdon Research Centre, 1984.
49. Marzo A, Arrigoni Martelli E, Urso R, Rocchetti M, Rizza V, Kelly JG. Metabolism and disposition of intravenously administered acetyl-l-carnitine in healthy volunteers. Eur J Clin Pharmacol 1989, 37:59–63.
50. Brinkman K, Smeitink JA, Romijn JA, Reiss P. Mitochondrial toxicity induced by nucleoside-analogue reverse-transcriptase inhibitors is a key factor in the pathogenesis of antiretroviral-therapy-related lipodystrophy. Lancet 1999, 354:1112–1115.
51. Behrens GM, Stoll M, Schmidt RE. Lipodystrophy syndrome in HIV Infection: what is it, what causes it and how can it be managed? Drug Saf 2000, 23:57–76.
52. Mauss S. HIV-associated lipodystrophy syndrome. AIDS 2000, 14:S197–S207.
53. De Simone C, Famularo G, Tzantzoglou S, Trinchieri V, Moretti S, Sorice F. Carnitine depletion in peripheral blood mononuclear cells from patients with AIDS: effect of oral l-carnitine. AIDS 1994, 8:655–660.
54. De Simone C, Tzantzoglou S, Famularo G, Moretti S, Paoletti F, Vullo V, et al. High dose l-carnitine improves immunologic and metabolic parameters in AIDS patients. Immunopharmacol Immunotoxicol 1993, 15:1–12.
55. Cifone MG, Alesse E, Di Marzio L, Ruggeri B, Zazzeroni F, Moretti S, et al. Effect of l-carnitine treatment in vivo on apoptosis and ceramide generation in peripheral blood lymphocytes from AIDS patients. Proc Assoc Am Physic 1997, 109:146–153.
56. De Simone C, Famularo G, Cifone G, Mitsuya H. HIV-I infection and cellular metabolism. Immunol Today 1996, 17: 256–258.
57. Vecchiet L, Di Lisa F, Pieralisi G, Ripari P, Menabo R, Giamberardino MA, et al. Influence of l-carnitine administration on maximal physical exercise. Eur J Appl Physiol Occup Physiol 1990, 61:486–490.

acetyl-l-carnitine; neurons; AIDS; HIV; nerve regeneration; antiretroviral toxic neuropathy; reverse transcriptase inhibitors; neuropathy

© 2004 Lippincott Williams & Wilkins, Inc.