Acetyl-carnitine deficiency in AIDS patients with neurotoxicity on treatment with antiretroviral nucleoside analogues

Low serum carnitine in HIV-infected children on antiretroviral treatment

OBJECTIVE

HIV-infection and antiretroviral therapies are associated with energy dysfunction and lipid metabolism in adults. Our aim was to detect a possible carnitine deficiency in HIV-infected children on antiretroviral treatments. We analysed the relation among serum carnitine, its amino-acid precursors (methionine and lysine), clinical evaluation and antiretroviral therapy.

DESIGN AND SETTING

Cross-sectional study performed in a tertiary care hospital.

SUBJECTS

A total of 79 HIV-infected children on antiretroviral therapy, monitored prospectively in our hospital.

INTERVENTIONS

Antiretroviral therapy included nucleoside analogues plus protease inhibitors and/or non-nucleoside analogues. Carnitine was analysed by an enzymatic-spectrometric procedure, and amino acids by ion exchange chromatography. Reference values of carnitine and amino acids were established in apparently healthy children who underwent presurgical analysis for minor surgery.

RESULTS

Serum free and total carnitine, acylcarnitines, methionine and lysine were significantly lower in HIV-infected children compared with our reference values for similar ages (P<0.0001; Student's t-test). Low carnitine values were observed in 37% of our HIV-infected children. A significantly positive correlation was observed between serum total carnitine and methionine or lysine (P<0.0001 and P=0.005, respectively; Pearson test). No relation was observed between serum carnitine and clinical stage of HIV infection, immunological or nutritional status or lipodystrophy. Free and total carnitine were significantly lower (P=0.002 and 0.033, respectively) in HIV-infected patients on protease inhibitors (N=56) compared with those on other treatments (N=23).

CONCLUSIONS

Low serum carnitine concentration was observed in 37% of our HIV-infected children on antiretroviral therapy. Malabsorption or defective synthesis may also account for the low serum carnitine values detected in these patients.

Mitochondrial Toxicity in the Era of HAART: Evaluating Venous Lactate and Peripheral Blood Mitochondrial DNA in HIV-Infected Patients Taking Antiretroviral Therapy

Nucleoside analogs can induce mitochondrial toxicity by inhibiting the human DNA polymerase gamma. This can lead to a wide range of clinical toxicities, from asymptomatic hyperlactatemia to death. Despite their technical and physiological variability, we propose that random venous lactate measurements can be useful to monitor the development of nucleoside-related mitochondrial toxicity. Recently, we have developed an assay that can measure changes in mitochondrial DNA levels in peripheral blood cells. Using this assay we have characterized changes in mitochondrial DNA (mtDNA) relative to nuclear DNA (nDNA) in peripheral blood cells of patients with symptomatic nucleoside-induced hyperlactatemia. Our results demonstrate that symptomatic hyperlactatemia was associated with markedly low mtDNA/nDNA ratios, which were on average 69% lower than HIV-uninfected controls and 45% lower than HIV-infected asymptomatic/antiretroviral naive controls. A statistically significant (p = .016) increase in mtDNA/nDNA ratio was observed following discontinuation of antiretroviral therapy. The mtDNA/nDNA ratio remained stable among selected patients who reintroduced antiretroviral therapy with stavudine (d4T)-sparing regimens. Of note, the decline in mtDNA preceded the increase in venous lactate levels. More recently we have evaluated changes in the mtDNA/nDNA ratio in relation to selected antiretroviral drug regimens in a cross-sectional study on a non-random sample of participants within the British Columbia Centre for Excellence in HIV/AIDS Drug Treatment Program. Eligible patients had continuously received saquinavir plus ritonavir with either nevirapine (n = 20), lamivudine (n = 15), d4T (n = 53) or lamivudine + d4T (n = 69), for 4 to 30 months. d4T-sparing regimens were associated with a higher median mtDNA/nDNA ratio than d4T-containing regimens (p = .016), despite the fact that study patients had received d4T-containing regimens for a shorter median time than patients taking d4T-sparing regimens (13 versus 25 months, p = .002). In summary, mtDNA levels are significantly decreased among patients who develop symptomatic, nucleoside-related hyperlactatemia, an effect reversed upon therapy discontinuation. Furthermore, mtDNA/nDNA ratios were statistically significantly lower in patients taking d4T-containing regimens than in those taking selected d4T-sparing regimens in a population setting. These results suggest that measurement of this parameter should be investigated as a potential clinical management tool.

FK506 is neuroprotective in a model of antiretroviral toxic neuropathy

Antiretroviral toxic neuropathy is the most common neurological complication of human immunodeficiency virus infection. This painful neuropathy not only affects the quality of life of human immunodeficiency virus-infected patients but also severely limits viral suppression strategies. We have developed an in vitro model of this toxic neuropathy to better understand the mechanism of neurotoxicity and to test potential neuroprotective compounds. We show that among the dideoxynucleosides, ddC appears to be the most neurotoxic, followed by ddI and then d4T. This reflects their potency in causing neuropathy. AZT, which does not cause a peripheral neuropathy in patients, does not cause significant neurotoxicity in our model. Furthermore, in this model, we show that the immunophilin ligand FK506 but not cyclosporin A prevents the development of neurotoxicity by ddC, as judged by amelioration of ddC-induced "neuritic pruning," neuronal mitochondrial depolarization, and neuronal necrotic death. This finding suggests a calcineurin-independent mechanism of neuroprotection. As calcineurin inhibition underlies the immunosuppressive properties of these clinically used immunophilin ligands, this holds promise for the neuroprotective efficacy of nonimmunosuppressive analogs of FK506 in the prevention or treatment of antiretroviral toxic neuropathy.

Exposure to dideoxynucleosides is reflected in lowered mitochondrial DNA in subcutaneous fat

OBJECTIVES

Nucleoside reverse transcriptase inhibitors (NRTIs), particularly dideoxynucleoside analogs (ddNs), used in the treatment of HIV, inhibit mitochondrial DNA polymerase gamma in vitro. Mitochondrial DNA (mtDNA) depletion is proposed as the underlying mechanism of many of the in vivo side effects of these agents. A reliable and valid laboratory test to detect this is not yet available. The objective of this study was to correlate tissue mtDNA quantification in HIV-infected patients with exposure to nucleoside analogs.

METHODS

60 HIV-infected adults underwent detailed clinical assessment and blood and tissue sampling. Clinical and antiretroviral treatment details were correlated with results of plasma lactate assays, and real-time polymerase chain reaction quantification of mtDNA in peripheral blood mononuclear cells (PBMCs) and subcutaneous fat from the lower limb.

RESULTS

Forty-nine (82%) subjects were on combination antiretroviral therapy. Of these, 33 (55%) were currently receiving one or more ddNs (stavudine, didanosine, or zalcitabine). mtDNA in subcutaneous fat was lower in subjects currently on ddNs than in those not taking ddNs (mean [log10] 2.47 vs. 2.74, p =.002). Plasma lactate was somewhat higher in subjects currently taking ddNs than those on no antiretroviral treatment (median 1.5 vs. 1.0, p =.03), but was not significantly different in either of these groups compared with subjects on other NRTIs. mtDNA in PBMCs did not vary with treatment status.

CONCLUSIONS

mtDNA in subcutaneous fat was significantly reduced in patients currently taking ddNs. mtDNA in PBMCs was independent of patient exposure to NRTIs.

L-carnitine reduces lymphocyte apoptosis and oxidant stress in HIV-1-infected subjects treated with zidovudine and didanosine

Apoptosis is critical to the progression of human immunodeficiency virus-1 (HIV-1) infection. It appears reasonable that antiretroviral therapies may not achieve a full control of the infection in the absence of an impact on apoptosis. We assigned 20 asymptomatic HIV-infected subjects with advanced immunodeficiency to receive either zidovudine (AZT), and didanosine (DDI) or the same regimen plus L-carnitine, a known antiapoptotic drug, for 7 months. Immunologic and virologic parameters were measured at baseline and after 15, 60, 120, and 210 days of treatment. We assessed on each time point the following: (a) the frequency of peripheral blood apoptotic CD4 and CD8 lymphocytes, CD4 and CD8 cells with disrupted mitochondrial membrane potential, and CD4 and CD8 cells undergoing oxidant stress; (b) the expression of the molecular markers of apoptosis Fas and caspase-1; and (c) the expression of p35/cdk-5 regulatory subunit that is involved in regulating cell survival and apoptosis. Absolute CD4 and CD8 counts and plasma viremia were also measured. Apoptotic CD4 and CD8 cells, lymphocytes with disrupted mitochondrial membrane potential, and lymphocytes undergoing oxidant stress were greatly reduced in subjects treated with AZT and DDI plus L-carnitine compared with those who did not receive L-carnitine. Fas and caspase-1 were down-expressed and p35 over-expressed in lymphocytes from patients of the L-carnitine group. No difference was found in CD4 and CD8 counts and viremia between the groups. No toxicity of L-carnitine was recognized. The addition of L-carnitine is safe and allows apoptosis and oxidant stress to be greatly reduced in lymphocytes from subjects treated with AZT and DDI.

Mitochondrial dysfunction and antiretroviral nucleoside analog toxicities: what is the evidence?

Mitochondrial dysfunction has been associated with long-term toxicities of human immunodeficiency virus (HIV) therapy, particularly with the nucleoside analog reverse transcriptase inhibitors (NRTIs). Lactic acidosis, hepatic steatosis, myopathies, cardiomyopathies, neuropathies, and lipodystrophy are frequently attributed to mitochondrial toxicity. Since mitochondrial toxicity could pose a major threat to the long-term success of HIV therapy, the scientific evidence underlying an association between mitochondrial toxicity and antiretroviral therapies, must be carefully examined. There is some data to support the association between NRTIs and mitochondria dysfunction. In this review, we examine human, animal, and in vitro data implicating mitochondrial dysfunction as the causal mechanism of NRTI-associated toxicity in HIV-infected patients.

AIDS and AIDS-treatment neuropathies

AIDS and AIDS-treatment neuropathies are common in individuals infected with HIV. As patients live longer due to improved antiretroviral therapies, the impact of painful neuropathy on patients' lives may increase. Several antiretroviral medications are known to cause toxic neuropathy in patients with AIDS, but this may be outweighed by the beneficial effects of viral suppression. Current theories on the pathogenesis of AIDS neuropathies include mitochondrial toxicity secondary to gamma-DNA polymerase inhibition and subsequent abnormal mitochondrial DNA synthesis. Treatment of AIDS neuropathies is directed toward relief of symptoms; however, new evidence suggests that aggressive antiretroviral therapy may also be effective.

Acute liver failure associated with antiretroviral treatment for HIV: a report of six cases

BACKGROUND/AIMS

Severe hepatotoxicity is a rare but potentially fatal side effect of all antiretrovirals. We report a series of six human immunodeficiency virus (HIV)-infected patients admitted with acute liver failure (ALF) over a 25-month period, of whom five died. All had been treated with a range of antiretroviral therapy and only two had had acquired immune deficiency syndrome (AIDS) defining illnesses.

RESULTS

Median duration of antiretroviral therapy was 12.5 months (range 1-23). Median time from the introduction of new antiretroviral therapy to the onset of ALF was 8 weeks (range 2-12). The development of ALF was unrelated to duration of HIV treatment or type of antiretroviral therapy, and was not predicted by close out-patient supervision and monitoring of liver function. Biochemical investigations were variable but revealed a predominantly hepatocellular pattern. Liver biopsy revealed typical features of mitochondrial toxicity in only one case, with confluent hepatocellular necrosis, inflammation and cholestasis seen in the others.

CONCLUSIONS

There is a need to increase awareness of the potential hepatotoxicity of antiretroviral therapy and to develop means of predicting its development. With increasing usage of antiretroviral therapy, severe hepatotoxicity and ALF may arise more frequently, and the outcome is poor despite intensive supportive therapy.

AIDS and AIDS-treatment neuropathies

AIDS and AIDS-treatment neuropathies are common in individuals infected with HIV. As patients live longer due to improved antiretroviral therapies, the impact of painful neuropathy on patients' lives may increase. Several antiretroviral medications are known to cause toxic neuropathy in AIDS patients; but this may be outweighed by the beneficial effects of viral suppression. Current theories on the pathogenesis of AIDS neuropathies include mitochondrial toxicity secondary to gamma-DNA polymerase inhibition and subsequent abnormal mitochondrial DNA synthesis. Treatment of AIDS neuropathies is directed toward relief of symptoms, however, new evidence suggests that aggressive antiretroviral therapy may also be effective.

Mitochondrial toxicity and HIV therapy

Nucleoside reverse transcriptase inhibitors (NRTIs) remain the cornerstone of highly active antiretroviral therapy (HAART) combination regimens. However, it has been known for some time that these agents have the potential to cause varied side effects, many of which are thought to be due to their effects on mitochondria. Mitochondria, the key energy generating organelles in the cell, are unique in having their own DNA, a double stranded circular genome of about 16 000 bases. There is a separate enzyme present inside the cell that replicates mitochondrial DNA, polymerase gamma. NRTIs can affect the function of this enzyme and this may lead to depletion of mitochondrial DNA or qualitative changes. The study of inherited mitochondrial diseases has led to further understanding of the consequences of mutations or depletion in mitochondrial DNA. Key among these is the realisation that there may be substantial heteroplasmy among mitochondria within a given cell, and among cells in a particular tissue. The unpredictable nature of mitochondrial segregation during cellular replication makes it difficult to predict the likelihood of dysfunction in a given tissue. In addition, there is a threshold effect for the expression of mitochondrial dysfunction, both at the mitochondrial and cellular level. Various clinical and in vitro studies have suggested that NRTIs are associated with mitochondrial dysfunction in different tissues, although the weight of evidence is limited in many cases. The heterogeneity in the tissues affected by the different drugs raises interesting questions, and possible explanations include differential distribution or activation of these agents. This article reviews the major recognised toxicities associated with NRTI therapy and evidence for mitochondrial dysfunction in these complications. Data were identified through searching of online databases including Medline and Current Contents for relevant articles, along with abstracts and posters from recent conferences in the HIV and mitochondrial fields.

Peripheral neuropathy during stavudine-didanosine antiretroviral therapy

Peripheral neuropathy (PN) is among the most frequent side effects described with nucleoside reverse transcriptase inhibitors (NRTIs). We investigated the incidence, evolution and predictive factors of PN during stavudine (d4T)-didanosine (ddI) combination therapy in 65 HIV infected patients, previously treated with zidovudine and/or zalcitabine (ddC) for at least 3 months. A subset of 16 patients was referred for systematic electromyographic examination at weeks 0 and 24: six among the 16 exhibited nerve conduction abnormalities at day 0, probably related to previous ddC treatment in four of those and to HIV infection in the other two, with worsening of abnormalities in one patient at week 24. In total, seven of the 59 assessable patients (11.8%) exhibited grade 2-3 neuropathy, with a median time of occurrence of 17 weeks. Distal, symmetrical paraesthesias of the extremities were the first symptoms in all the patients; none had motor symptoms. In all the patients, PN resolved rapidly after stopping d4T. There were no statistically different parameters between the seven cases and the other 52 patients according to CD4 T cells, HIV RNA, Centers for Disease Control and Prevention (CDC) stage C or d4T daily dose. In our study, the d4T-ddI combination did not seem to increase the incidence of PN; risk factors for PN could not be identified, probably in part because of the low number of patients with PN.

Toxicity of antiretroviral nucleoside and nucleotide analogues: is mitochondrial toxicity the only mechanism?

Nucleoside analogues represent the cornerstones of antiretroviral regimens. A range of drug- or tissue-specific toxicities, such as peripheral neuropathy, myopathy, pancreatitis and lactic acidosis with hepatic steatosis, has been documented with these agents. The fat atrophy seen on long term antiretroviral therapy may also be related to nucleoside analogues. The mechanisms by which nucleoside analogues cause toxicity are not clearly established. In vitro, the triphosphates of these agents are weak to modest substrates for human DNA polymerases, showing the greatest affinity for mitochondrial DNA polymerase gamma. Short term exposure in vitro to some nucleoside analogues has been demonstrated to cause increased lactate production or falls in mitochondrial DNA suggestive of mitochondrial toxicity. However, stavudine and to a lesser extent zidovudine are poor substrates for mitochondrial thymidine kinase type 2, the predominant form in cells that are not actively mitotic such as neurons, myocytes and adipocytes. These are the cell types where the proposed mitochondrial toxicities neuropathy, myopathy and lipoatrophy are observed. Thus, active concentrations of phosphorylated products of stavudine and zidovudine may not be present in mitochondria. The familial mitochondrial diseases do not have identical presentations to nucleoside analogue toxicities. These disorders most commonly involve the CNS, typically with seizures or dementia, and occasionally the kidneys. Although nucleoside analogues are known to penetrate the CNS and are commonly renally excreted unchanged, mitochondrial toxicities at these sites have not been documented. Furthermore, toxicity caused by nucleoside or nucleotide analogues does not always appear to arise through the mitochondrial route. Cidofovir appears to cause renal tubular dysfunction via a toxic intracellular metabolite, and zidovudine-related anaemia appears to be related to decreased globin RNA synthesis. In vitro or animal models suggest that zidovudine myopathy, stavudine-related (but not zalcitabine- or didanosine-related) neuropathy and didanosine-related pancreatitis may all be not related, or not exclusively related, to mitochondrial dysfunction. The integration of nucleoside analogues into nuclear DNA, best documented with zidovudine but likely to occur with other agents, represents an alternative but potentially delayed pathway to cytotoxicity and cell apoptosis. This is the mechanism of cell death during therapy with antineoplastic nucleoside analogues, and may have contributed to the multisystem toxicities observed with the anti-hepatitis B drug fialuridine. New research evaluating the effects of long term exposure of cell lines is required to address the possibility that nuclear genotoxicity plays a role in long term nucleoside analogue toxicity.

Neuropathy in HIV infection

Peripheral nerve complications in patients infected with HIV usually result from the virus itself, or are due to some of the antiretroviral drugs (zalcitabine, didanosine or stavudine). It may be difficult to distinguish between these two aetiologies on clinical or neurophysiological criteria. Since they are a significant cause of morbidity, a number of studies have looked at agents used for symptomatic control. More recently, there has been a focus on treatments that improve nerve function, including recombinant human nerve growth factor and the reduction of HIV viral load with antiretroviral drugs.

Clinical manifestations and management of antiretroviral nucleoside analog-related mitochondrial toxicity

OBJECTIVES

This article reviews the clinical manifestations of mitochondrial toxicity associated with the use of nucleoside analog reverse transcriptase inhibitors (NRTIs) and outlines strategies to manage these sequelae.

BACKGROUND

NRTIs are the key components of the antiretroviral combinations used in the management of patients infected with HIV. The available NRTIs differ in their convenience of administration, frequency of dosing, resistance profiles, and side-effect profiles. NRTIs act as competitive inhibitors of the RNA/DNA polymerase reverse transcriptase of HIV and cause chain termination in the growing viral DNA chain. Many of the important and treatment-limiting side effects of NRTIs may be related to the effect of these agents on human DNA polymerases, in particular, mitochondrial DNA polymerase gamma. Depletion of mitochondrial DNA during chronic NRTI therapy may lead to cellular respiratory dysfunction and generalized and tissue- and drug-specific toxicities, including myopathy, peripheral neuropathy, and lactic acidosis. Recently, it has been proposed that the fat redistribution syndrome, or lipodystrophy, reported during chronic antiretroviral therapy is a manifestation of the differential impact of at least some NRTIs on peripheral and visceral adipocytes. Management of potential mitochondrial toxicity during NRTI therapy remains a challenge. A range of nutritional supplements, both as treatments and prophylaxes, have been proposed, and some have been investigated in vitro; no in vivo studies have yet been conducted.

METHODS

The information in this review was compiled using MEDLINE and AIDSLINE searches of the literature, including conference abstracts.

CONCLUSIONS

At present, interruption of NRTI therapy or substitution of the probable causative agent with alternative NRTIs that appear to be better tolerated represents the mainstay of management for mitochondrial toxicity and its clinical manifestations.

HIV-associated peripheral neuropathy: epidemiology, pathophysiology and treatment

Peripheral neuropathy is the most frequent neurological complication associated with human immunodeficiency virus type 1 (HIV) infection and advanced acquired immunodeficiency syndrome (AIDS). There are at least 6 patterns of HIV-associated peripheral neuropathy, although these diagnoses are often overlooked or misdiagnosed. Distal symmetrical polyneuropathy (DSP) is the most common form of peripheral neuropathy in HIV infection. DSP occurs mainly in patients with advanced immunosuppression and may also be secondary to the neurotoxicity of several antiretroviral agents. Treatment of painful DSP is primarily symptomatic, while pathogenesis-based therapies are under investigation. Reduction or discontinuation of neurotoxic agents should be considered if possible. Inflammatory demyelinating polyneuropathy (IDP) can present in an acute or chronic form. The acute form may occur at the time of primary HIV infection or seroconversion. Cerebrospinal fluid lymphocytic pleocytosis (10 to 50 cells/mm3) is helpful in the diagnosis of HIV-associated IDP. Treatment consists of immunomodulatory therapy. Progressive polyradiculopathy (PP) most commonly occurs in advanced immunosuppression and usually is caused by cytomegalovirus (CMV) infection. Rapidly progressive flaccid paraparesis, radiating pain and paresthesias, areflexia and sphincter dysfunction are the cardinal clinical features. Rapid diagnosis and treatment with anti-CMV therapy are necessary to prevent irreversible neurological deficits resulting from nerve root necrosis. Mononeuropathy multiplex (MM) that occurs in early HIV infection is characterised by self-limited sensory and motor deficits in the distribution of individual peripheral nerves. In advanced HIV infection, multiple nerves in two or more extremities or cranial nerves are affected. Treatment includes immunomodulation or anti-CMV therapy. Autonomic neuropathy may be caused by central or peripheral nervous system abnormalities. Treatment is supportive with correction of metabolic or toxic causes. Diffuse infiltrative lymphocytosis syndrome (DILS) presents as a Sjögren's-like disorder with CD8 T cell infiltration of multiple organs. Antiretroviral therapy and steroids may be effective treatments.

Incidence of neuropathy in HIV-infected patients on monotherapy versus those on combination therapy with didanosine, stavudine and hydroxyurea

BACKGROUND

Sensory neuropathy is a common adverse effect of the nucleoside analogue anti-retroviral drugs didanosine (ddl) and stauvudine (d4T). These drugs are increasingly being used in combination, and it is not currently known whether the incidence of neuropathy is higher with combination compared to individual drug use. It is also not known if hydroxyurea, used to potentiate the antiviral efficacy of these drugs, may also increase the risk of neuropathy. The purpose of this analysis is to investigate if the combination of ddl and d4T, with or without hydroxyurea, has a higher incidence of neuropathy than a single drug regimen.

METHODS

Data were obtained from patients followed longitudinally by the Johns Hopkins AIDS Services. Incidence rates of development of neuropathy were calculated for each of five regimens: ddl (+/- hydroxyurea), ddl + d4T (+/- hydroxyurea), and d4T. Cox proportional hazard regression was used to compare the relative risk of neuropathy for each regimen adjusting for CD4 cell count, other drugs received, and time on therapy.

RESULTS

A total of 1116 patients received at least one of the five regimens. There were 117 cases of neuropathy. The crude incidence rate of neuropathy ranged from 6.8 cases per 100 person-years for ddl to 28.6 cases per 100 person-years for ddl + d4T + hydroxyurea. Compared with ddl alone, and adjusting for CD4 cell counts and other variables, the relative risk of neuropathy was 1.39 [95% confidence interval (CI): 0.84-2.32] for d4T alone, 2.35 (95% CI: 0.69-8.07) for ddl + hydroxyurea, 3.50 (95% CI: 1.81-6.77) for ddl + d4T, and 7.80 (95% CI: 3.92-15.5) for ddl + d4T + hydroxyurea.

CONCLUSIONS

Based on the data, the risk of neuropathy is additive or even synergistic for ddl + d4T + hydroxyurea compared with ddl or d4T alone. The combination of ddl + d4T also increases the risk of neuropathy but less than when hydroxyurea is included.

Mitochondrial toxicity of nucleoside analogue reverse transcriptase inhibitors: a looming obstacle for long-term antiretroviral therapy?

Nucleoside reverse transcriptase inhibitors suppress HIV replication by blocking reverse transcriptase, an RNA-dependent DNA polymerase. These drugs can also affect cellular and mitochondrial DNA polymerases. Mitochondrial DNA polymerase gamma is particularly sensitive to nucleoside reverse transcriptase inhibitors, and the majority of adverse effects caused by nucleoside reverse transcriptase inhibitors are most likely caused by mitochondrial dysfunction. This article reviews the recent clinical implications of nucleoside reverse transcriptase inhibitor-induced mitochondrial toxicity and discusses options for management.

Acetyl-L-carnitine administration increases insulin-like growth factor 1 levels in asymptomatic HIV-1-infected subjects: correlation with its suppressive effect on lymphocyte apoptosis and ceramide generation

The aim of this study was to investigate the impact of long-term acetyl-L-carnitine administration on CD4 and CD8 absolute counts, apoptosis, and insulin-like growth factor-1 (IGF-1) serum levels in HIV-1-infected subjects. The generation of cell-associated ceramide and HIV-1 viremia were also investigated. Eleven asymptomatic, HIV-1-infected subjects were treated daily with acetyl-L-carnitine (3 g) for 5 months. Immunologic and virologic measures and safety were monitored at the start of the treatment and then on days 90 and 150. Altogether our findings suggest that acetyl-L-carnitine administration has a substantial impact on the main immunologic abnormality associated with HIV infection, the loss of CD4 cells, by reducing the rate of apoptotic lymphocyte death. The reduction of ceramide generation and the increase of the serum levels of IGF-1, a major survival factor able to protect cells from apoptosis by different stimuli and conditions, could represent two important mechanisms underlying the observed anti-apoptotic effects of acetyl-L-carnitine.

Neuromuscular Complications of HIV-1 Infection

Neuromuscular disorders are the most frequent neurologic complications that occur in patients with HIV infection. The distinction among the different forms of peripheral neuropathy (ie, distal symmetrical polyneuropathy, polyradiculopathy, mononeuritis multiplex) is crucial in determining their potential etiology and treatment. Distal symmetrical polyneuropathy is most common in HIV-infected patients with advanced immunosuppression and may also result from neurotoxicity of several antiretroviral agents. Myopathy may occur at any stage of HIV disease, and has also been described as a toxic side effect of zidovudine. This paper reviews current knowledge of pathogenesis, clinical manifestations, and treatment of HIV-associated neuromuscular disorders.

Effect of L-Carnitine on Human Immunodeficiency Virus-1 Infection-Associated Apoptosis: A Pilot Study

The Fas/Fas ligand system is involved in uncontrolled apoptosis, which ultimately leads to the loss of T lymphocytes in human immunodeficiency virus (HIV)-infected individuals. The signal transduced by Fas receptor involves the activation of an acidic sphingomyelinase, sphingomyelin breakdown, and ceramide production. Our recent reports have shown that L-carnitine inhibits Fas-induced apoptosis and ceramide production both in vitro and in vivo. The aim of this study was to study, in a preliminary fashion, the impact of long-term L-carnitine administration on CD4 and CD8 absolute counts, rate, and apoptosis in HIV-1–infected subjects. The generation of cell-associated ceramide and HIV-1 viremia was also investigated. Eleven, asymptomatic, HIV-1–infected subjects, who refused any antiretroviral treatment despite experiencing a progressive decline of CD4 counts, were treated with daily infusions of L-carnitine (6 g) for 4 months. Immunologic and virologic measures and safety were monitored at the start of the treatment and then on days 15, 30, 90, and 150. L-carnitine therapy resulted in an increase of absolute CD4 counts, which was statistically significant on day 90 and 150 (P = .010 and P = .019, respectively). A positive, not significant trend was also observed even in the change in absolute counts of CD8 lymphocytes. L-carnitine therapy also led to a drop in the frequency of apoptotic CD4 and CD8 lymphocytes. This reduction occurred gradually, but changes in actual values between each time point and baseline were strongly significant (P = .001 at the end of the study compared with the baseline). A strong reduction (P = .001) in cell-associated ceramide levels was found at the end of the study. In general, HIV-1 viremia increased slightly. No toxicity related to L-carnitine therapy was observed and dose reductions were not necessary. In HIV-1–infected subjects, long-term infusions of L-carnitine produced substantial increases in the rate and absolute counts of CD4 and, to a lesser degree, of CD8 lymphocytes. This was paralleled by a reduced frequency of apoptotic cells of both subgroups and a decline in the levels of ceramide. No clinically relevant change of HIV-1 viremia was observed.

Effect of L-Carnitine on Human Immunodeficiency Virus-1 Infection-Associated Apoptosis: A Pilot Study

The Fas/Fas ligand system is involved in uncontrolled apoptosis, which ultimately leads to the loss of T lymphocytes in human immunodeficiency virus (HIV)-infected individuals. The signal transduced by Fas receptor involves the activation of an acidic sphingomyelinase, sphingomyelin breakdown, and ceramide production. Our recent reports have shown that L-carnitine inhibits Fas-induced apoptosis and ceramide production both in vitro and in vivo. The aim of this study was to study, in a preliminary fashion, the impact of long-term L-carnitine administration on CD4 and CD8 absolute counts, rate, and apoptosis in HIV-1–infected subjects. The generation of cell-associated ceramide and HIV-1 viremia was also investigated. Eleven, asymptomatic, HIV-1–infected subjects, who refused any antiretroviral treatment despite experiencing a progressive decline of CD4 counts, were treated with daily infusions of L-carnitine (6 g) for 4 months. Immunologic and virologic measures and safety were monitored at the start of the treatment and then on days 15, 30, 90, and 150. L-carnitine therapy resulted in an increase of absolute CD4 counts, which was statistically significant on day 90 and 150 (P = .010 and P = .019, respectively). A positive, not significant trend was also observed even in the change in absolute counts of CD8 lymphocytes. L-carnitine therapy also led to a drop in the frequency of apoptotic CD4 and CD8 lymphocytes. This reduction occurred gradually, but changes in actual values between each time point and baseline were strongly significant (P = .001 at the end of the study compared with the baseline). A strong reduction (P = .001) in cell-associated ceramide levels was found at the end of the study. In general, HIV-1 viremia increased slightly. No toxicity related to L-carnitine therapy was observed and dose reductions were not necessary. In HIV-1–infected subjects, long-term infusions of L-carnitine produced substantial increases in the rate and absolute counts of CD4 and, to a lesser degree, of CD8 lymphocytes. This was paralleled by a reduced frequency of apoptotic cells of both subgroups and a decline in the levels of ceramide. No clinically relevant change of HIV-1 viremia was observed.