Editorial response: hyperlactatemia and hepatic steatosis as features of mitochondrial toxicity of nucleoside analogue reverse transcriptase inhibitors

Acute Response to One Bout of Dynamic Standing Exercise on Blood Glucose and Blood Lactate Among Children and Adolescents With Cerebral Palsy Who are Nonambulant

PURPOSE

To investigate the acute exercise effects of dynamic standing exercise on blood glucose and blood lactate among children and adolescents with cerebral palsy who are nonambulant.

METHODS

Twenty-four participants with cerebral palsy who are nonambulant performed 30 minutes of dynamic standing exercise using a motorized device enabling assisted passive movements in an upright weight-bearing position. Capillary blood samples were taken from the fingertip for measurement of blood glucose and blood lactate at rest and at the end of exercise.

RESULTS

At rest, the participants had hyperlactatemia that was unaffected after exercise, presented as median and interquartile range at rest 1.8 (1.3:2.7) mmol/L, and after exercise 2.0 (1.1:2.5) mmol/L. Children and adolescents with Gross Motor Function Classification System, level V, had higher lactate levels at rest (2.5 [1.8:2.9] vs 1.4 [1.0:2.0]; P = .030) and after exercise (2.3 [2.0:2.6] vs 1.2 [0.9:2.2]; P = .032) compared with children and adolescents with Gross Motor Function Classification System, level IV, respectively. A statistically significant larger decrease in blood lactate levels after exercise was observed in children and adolescents with higher resting blood lactate levels (ρ = .56; P = .004). There were no statistically significant changes in blood glucose.

CONCLUSIONS

Forty percentage of the participants had mild hyperlactatemia at rest and participants with the highest blood lactate levels at rest had the greatest decrease in blood lactate levels after one bout of exercise. Children and adolescents who were classified with the highest level of the Gross Motor Function Classification Scale had higher blood lactate levels. More studies are needed on how to prevent chronically high resting levels of lactate with exercise in children with cerebral palsy who are nonambulant.

Lactic acidosis: an update

Lactate is one of the most crucial intermediates in carbohydrate and nonessential amino acid metabolism. The complexity of cellular interactions and metabolism means that lactate can be considered a waste product for one cell but a useful substrate for another. The presence of elevated lactate levels in critically ill patients has important implications for morbidity and mortality. In this review, we provide a brief outline of the metabolism of lactate, the pathophysiology of lactic acidosis, the clinical significance of D-lactate, the role of lactate measurement in acutely ill patients, the methods used to measure lactate in blood or plasma and some of the methodological issues related to interferences in these assays, especially in the case of ethylene glycol poisoning.

Novel Approaches to Targeting Visceral and Hepatic Adiposities in HIV-Associated Lipodystrophy

Visceral and hepatic adiposities have been associated with both cardiovascular and liver disease and are of concern in HIV-infected persons in the modern era of combination antiretroviral therapy (ART). The development of therapeutic targets to reduce visceral and hepatic adiposities in HIV-infected persons has been slow, because of early reports that attributed the excess adiposity to specific antiretroviral drugs. Visceral adiposity was initially thought to occur as part of a protease inhibitor-induced "HIV-associated lipodystrophy syndrome." Subsequent studies show that visceral adiposity is likely a result of effective ART, recovery of health, and the normal aging process. Visceral adiposity is an established risk factor for hepatic adiposity. Identifying drug targets for non-alcoholic fatty liver disease is under active investigation. The present review summarizes the recent literature on the pathogenesis of visceral and hepatic adiposities in HIV-infected persons, current therapeutic strategies, and novel interventions in HIV-infected and uninfected persons.

Mild to Moderate Symptoms Do Not Correlate with Lactate Levels in HIV-Positive Patients on Nucleoside Reverse Transcriptase Inhibitors

PURPOSE

Nucleoside reverse transcriptase inhibitors (NRTIs) are associated with mitochondrial toxicities ranging from asymptomatic hyperlactatemia to fatal lactic acidosis. It is uncertain whether mild clinical symptoms predict hyperlactatemia and the need to consider changes in antiretroviral therapy. This cross-sectional study evaluated whether an association exists between mild symptoms and lactate levels.

METHOD

HIV-positive patients on NRTIs attending routine clinic visits were surveyed about symptoms associated with hyperlactatemia. Symptom severity was quantified using Likert scales, and the sum was converted into a symptom score ranging from 0 to 30. Tourniquet-free blood specimens were collected simultaneously to measure serum lactate. Symptom scores were compared between patients with normal and elevated lactates.

RESULTS

284 individuals were included. The most common NRTIs used included lamivudine (79%), zidovudine (50%), abacavir (39%), and stavudine (24%). Twenty-two patients (8%) had increased lactates (mean = 2.7 mmol/L; range, 2.1-4.5 mmol/L), while 262 patients (92%) had normal lactates (mean = 1.2 mmol/L, range, 0.1-2.0 mmol/L). Median symptom scores were similar between groups (3 vs. 2, p = .23). Spearman's correlation coefficient for lactate and symptom score was 0.07 (p = .22).

CONCLUSIONS

Mild symptoms did not correlate with lactate levels, and symptoms alone should not trigger clinicians to measure serum lactates and stop NRTIs if the levels are elevated.

Treatment-limiting toxicities associated withnucleoside analogue reverse transcriptase inhibitor therapy: A prospective, observational study

BACKGROUND

The Recover Study is an ongoing, prospective study designed 10 to assess toxicity associated with the use of nucleoside analogue reverse transcriptase inhibitors (NRTIs) (stavudine, zidovudine, lamivudine, didanosine, abacavir) in HIV-1-infected patients receiving highly active antiretroviral therapy (HAART) in routine clinical practice. This project is being conducted at 120 HIV units at teaching hospitals across Spain.

OBJECTIVE

The aim of this study was to identify the most common treatment-limiting 10 moderate to severe clinical and laboratory adverse effects (AEs), and the individual NRTIs involved in the development of these effects, in HIV-1-infected patients receiving HAART who discontinued use of an NRTI in the Recover Study.

METHODS

Patients eligible for participation in the Recover Study are aged10 ≥18 years; have virologically documented HIV-1 infection; have sustained viral suppression (viral load <200 cells/mL or stable, heavily experienced [ie, have received ≥3 antiretroviral regimens] patients with viral load <5000 cells/mL) for ≥6 months; are receiving HAART; are undergoing active follow-up; and have developed 2:1 NRTI-associated AE that, in the opinion of a study investigator and under the conditions of routine clinical practice, justified discontinuation of treatment with the offending drug (principal AE/offending NRTI). The present study included patients recruited for the Recover Study between September 2002 and May 2003.

RESULTS

A total of 1391 patients were enrolled (966 men, 425 women; mean 1 age, 42 years [range, 18-67 years]). Five hundred six patients (36.4%) had been diagnosed with AIDS. The mean duration of treatment with the offending NRTI was 74 months (range, 6-156 months). Seven hundred nine patients (51.0%) were receiving fourth-line (or more) therapy. Eight hundred twenty-one patients (59.0%) were receiving nonnucleoside analogues, and 552 patients (39.7%), protease inhibitors, as components of their HAART regimens. The NRTIs with the highest discontinuation rates were stavudine (914 patients [65.7%]) and zidovudine (177 [12.7%]). The most frequent NRTI-related AEs were lipoatrophy (550 patients [39.5%]) and peripheral neuropathy (170 [12.2%]). Lipoatrophy was most commonly associated with stavudine (480/550 cases [87.3%]); periph eral neuropathy, with stavudine and didanosine (107/170 [62.9%] and 48/170 [28.2%] cases, respectively); and anemia, with zidovudine (70/77 cases [90.9%]).

CONCLUSIONS

The results of this study in patients with HIV-1 recruited in the10 Recover Study and undergoing HAART suggest that long-term treatment with NRTIs is associated with AEs (lipoatrophy, peripheral neuropathy, and lipodystrophy), with morphologic disorders (lipoatrophy, lipodystrophy) being the most common AEs leading to discontinuation. Minimizing these AEs by switching to an NRTI not associated with these AEs (eg, tenofovir) would contribute to adherence and hence efficacy of long-term HAART.

Antiretroviral and anti-hepatitis C virus direct-acting antiviral-related hepatotoxicity

Antiretroviral-related hepatotoxicity occurs commonly in patients with human immunodeficiency virus (HIV). Liver injury ranges from unconjugated hyperbilirubinemia and nodular regenerative hyperplasia to lactic acidosis and toxic hepatitis. Effective antiretroviral therapy has changed coinfected patients' primary morbidities and mortality to chronic liver disease rather than complications from HIV. Treatment for hepatitis C virus (HCV) is strongly encouraged early in all coinfected patients. However, drug-drug interactions must be considered to ensure safe and tolerable use alone or in combination with antiretroviral therapies. The first-generation and newer HCV direct-acting antivirals are promising in coinfected patients, with minimal side effects and hepatotoxicity.

Hepatic steatosis in HIV-HCV coinfected patients receiving antiretroviral therapy is associated with HCV-related factors but not antiretrovirals

Background

In HIV and hepatitis C virus (HCV) coinfected patients, the role of antiretroviral therapy (ART) on hepatic steatosis (HS) remains controversial.

Methods

HIV/HCV coinfected patients receiving ART and previously untreated for HCV who underwent a liver biopsy were included. Cumulative duration of exposure to each antiretroviral was recorded up to liver biopsy date. Logistic regression analyses evaluated factors associated with steatosis and its severity.

Results

184 patients were included: median age 41years, 84% male, 89% Caucasian, 61% with a past history of intravenous drug use. HCV genotypes were 1 (55%), 2 (6%), 3 (26%), and 4 (13%). Median HCV-RNA was 6.18 log₁₀ IU/ml. HIV-RNA was undetectable (<400 copies/ml) in 67% of patients. Median CD4 count was 321/mm³. All patients had been exposed to nucleoside reverse transcriptase inhibitors (median cumulative exposure 56months); 126 received protease inhibitors (23months), and 79 non-nucleoside reverse transcriptase inhibitors (16months). HS was observed in 102 patients (55%): 41% grade 1; 5% grade 2, and 9% grade 3. In multivariate analysis, HCV genotype 3 and HCV viral load were moderately associated with mild steatosis but strongly with grade 2-3 steatosis. After adjustment for the period of biopsy, no association was detected between HS and exposure to any antiretroviral class or drug, or duration of ART globally or comparing genotype 3 to others.

Conclusions

Among our ART-treated HIV-HCV cohort predominantly infected with genotype 1, 55% of patients had HS which was associated with HCV-related factors, but not ART class or duration of exposure.

The clinical care of the HIV-1-infected infant

Despite well-established strategies to decrease the mother-to-child transmission of HIV-1, new perinatal infections continue to occur globally, reflecting marked disparities in access to health care. Once HIV-1 infection has been established in an infant, the combination of early initiation of antiretroviral therapy and prophylaxis against Pneumocystis jiroveci pneumonia is paramount to reducing disease progression. This article reviews the recommendations and evidence for the treatment of HIV-1-infected infants.

Stavudine-induced hyperlactatemia/lactic acidosis at a tertiary communicable diseases clinic in South Africa

OBJECTIVES

To determine the incidence, presentation, and outcome of hyperlactatemia and lactic acidosis. DESIGN AND METHODS SETTING: Grey's Hospital, a tertiary level referral institution.

STUDY POPULATION

A chart review of 1719 patients commenced on highly active antiretroviral therapy (HAART) between August 1, 2004, and July 31, 2006. A total of 1000 patients (615 females) received stavudine (d4T)/lamivudine (3TC)/efavirenz (EFV), 719 patients (598 females) received d4T/ 3TC/nevirapine (NVP).

RESULTS

Of the 1719 patients, 152 (8.84%) had an elevated plasma venous lactate (>2.2 mmol/L), 45 patients required admission for lactic acidosis. The overall incidence rate was 13.5 cases per 1000 patient years. The most common presenting symptoms were loss of weight (95%), abdominal pain (78.9%), loss of appetite, and paresthesias (63.8%). The median body mass index (BMI) at commencement of HAART and at onset of symptoms was 24.5 and 26, respectively. A median serum lactate level of 6.08 mmol/L (range 2.3-19.7 mmol/L) was observed at the onset of symptoms.

CONCLUSIONS

High BMI at treatment initiation did not always predict hyperlactatemia. All patients who died had a baseline CD4 count <10 cells/mm(3) at HAART initiation.

Mitochondrial oxidative phosphorylation protein levels in peripheral blood mononuclear cells correlate with levels in subcutaneous adipose tissue within samples differing by HIV and lipoatrophy status

Depletion of mitochondrial DNA (mtDNA) and mtDNA-encoded respiratory chain proteins in subcutaneous (SC) fat from patients with HIV lipoatrophy have clearly demonstrated the role of mitochondrial dysfunction in this syndrome. Research in HIV lipoatrophy, however, has been severely hampered by the lack of a suitable surrogate marker in blood or other easily obtained clinical specimens as fat biopsies are invasive and mtDNA levels in peripheral blood mononuclear cells (PBMC) do not consistently correlate with the disease process. We used a simple, rapid, quantitative 2-site dipstick immunoassay to measure OXPHOS enzymes Complex I (CI) and Complex IV (CIV), and rtPCR to measure mtDNA in 26 matched SC fat and PBMC specimens previously banked from individuals on potent antiretroviral (ARV) therapy with HIV lipoatrophy, on similar ARV therapy without lipoatrophy, and in HIV seronegative controls. Significant correlations were found between the respective PBMC and fat levels for both CI (r = 0.442, p = 0.024) and for CIV (r = 0.507, p = 0.008). Both CI and CIV protein levels were also significantly reduced in both PBMCs and fat in lipoatrophic subjects compared to HIV seronegative controls (p < or = 0.05), while a comparative reduction in mtDNA levels in lipoatrophic subjects was observed only in fat. We conclude that CI and CIV levels in PBMCs correlate to their respective levels in fat and may have utility as surrogate markers of mitochondrial dysfunction in lipoatrophy.

Mitochondrial DNA impairment in nucleoside reverse transcriptase inhibitor-associated cardiomyopathy

Acquired immune deficiency syndrome (AIDS) is a global epidemic that continues to escalate. Recent World Health Organization estimates include over 33 million people currently diagnosed with HIV/AIDS. Another 20 million HIV-infected individuals died over the past quarter century. Antiretrovirals are effective treatments that changed the outcome of HIV infection from a fatal disease to a chronic illness. Cardiomyopathy (CM) is a bona fide component of HIV/AIDS with occurrence that is higher in HIV positive individuals. CM may result from individual or combined effects of HIV, immune reactions, or toxicities of prolonged antiretrovirals. Nucleoside reverse transcriptase inhibitors (NRTIs) are the cornerstone of antiretroviral therapy. Despite pharmacological benefits of NRTIs, NRTI side effects include increased risk for CM. Clinical observations and in vitro and in vivo studies support various mechanisms of CM. This perspective highlights some of the hypotheses and focuses on mitochondrial-associated pathways of NRTI- related CM.

Adenosine 3',5'-cyclic monophosphate (cAMP)-dependent phosphoregulation of mitochondrial complex I is inhibited by nucleoside reverse transcriptase inhibitors

Nucleoside analog reverse transcriptase inhibitors (NRTIs) are known to directly inhibit mitochondrial complex I activity as well as various mitochondrial kinases. Recent observations that complex I activity and superoxide production are modulated through cAMP-dependent phosphorylation suggests a mechanism through which NRTIs may affect mitochondrial respiration via kinase-dependent protein phosphorylation. In the current study, we examine the potential for NRTIs to inhibit the cAMP-dependent phosphorylation of complex I and the associated NADH:CoQ oxidoreductase activities and rates of superoxide production using HepG2 cells. Phosphoprotein staining of immunocaptured complex I revealed that 3'-azido-3'-deoxythymidine (AZT; 10 and 50 microM), AZT monophosphate (150 microM), and 2',3'-dideoxycytidine (ddC; 1 microM) prevented the phosphorylation of the NDUFB11 subunit of complex I. This was associated with a decrease in complex I activity with AZT and AZT monophosphate only. In the presence of succinate, superoxide production was increased with 2',3'-dideoxyinosine (ddI; 10 microM) and ddC (1 microM). In the presence of succinate+cAMP, AZT showed an inverse dose-dependent effect on superoxide production. None of the NRTIs examined inhibit PKA activity suggesting that the observed effects are due to a direct interaction with complex I. These data demonstrate a direct effect of NRTIs on cAMP-dependent regulation of mitochondrial bioenergetics independent of DNA polymerase-gamma activity; in the case of AZT, these observations may provide a mechanism for the observed long-term toxicity with this drug.

Incidence and Risk Factors for Weight Loss During Dual HIV/Hepatitis C Virus Therapy

BACKGROUND

Clinical observations suggest that patients with HIV/hepatitis C virus (HCV) may lose body weight during dual therapy, but this has not been confirmed analytically.

OBJECTIVES

To determine if the incidence and degree of weight loss among patients with HIV/HCV receiving highly active antiretroviral therapy (HAART) and pegylated (PEG)-interferon plus ribavirin were greater than in (1) HCV-monoinfected patients receiving PEG-interferon plus ribavirin and (2) HIV-monoinfected patients receiving HAART. Risk factors for weight loss among patients with HIV/HCV were also examined.

METHODS

A retrospective cohort study was performed among HIV/HCV-coinfected, HCV-monoinfected, and HIV-monoinfected patients. Body weights were assessed up to 6 months before and up to 12 months after initiation of HCV therapy (HIV/HCV-coinfected and HCV-monoinfected subjects) and over 18 months on HAART (HIV-monoinfected subjects). The primary outcome was clinically significant weight loss (> or =5% of baseline weight).

RESULTS

Of 192 subjects, 63 had HIV/HCV, 64 had HCV alone, and 65 had HIV alone. Clinically significant weight loss occurred in 48 (76%) subjects with HIV/HCV versus 25 (39%) subjects with HCV (P < 0.001) and 2 (3%) subjects with HIV (P < 0.001), yielding adjusted hazard ratios (HRs) of 2.76 (95% confidence interval [CI]: 1.67 to 4.55) and 38.5 (95% CI: 8.5 to 174.7), respectively. Receipt of more than 2 nucleoside reverse transcriptase inhibitors increased the risk of clinically significant weight loss (adjusted HR = 8.17, 95% CI: 2.37 to 28.20).

CONCLUSIONS

The incidence of weight loss is greater in dually treated patients with HIV/HCV than in treated HCV- or HIV-monoinfected patients. Prospective studies should evaluate additional risk factors for weight loss and changes in body composition to elucidate the mechanism for this weight loss.

Liver Triglyceride Content in HIV-1-Infected Patients on Combination Antiretroviral Therapy Studied with 1H-MR Spectroscopy

Objective

To carry out an exploratory evaluation of liver triglyceride content in HIV-1-infected patients receiving highly active antiretroviral therapy (HAART) using proton magnetic resonance spectroscopy and to study how both the treatment itself and the biochemical and physiological variables in which the treatment causes alterations are related to liver fat content.

Methods

Intracellular hepatic triglyceride content was determined in 29 HIV-1-infected patients on their first HAART regime by means of localized water-unsuppressed single voxel proton spectra. Other measurements were body mass index, waist-to-hip ratio, lipodystrophy assessment and a detailed blood biochemical analysis. The relationship between intracellular hepatic triglycerides and relevant descriptive, treatment and biochemical variables was studied by correlation and regression analysis.

Results

Intrahepatic triglycerides were detected in 58.6% of the patients and 13.8% showed a triglyceride content compatible with liver steatosis. Many variables (body mass index, waist-to-hip ratio, cumulative exposure to PIs, lactate, insulin, insulin resistance measured by the homeostasis model assessment method [HOMA-R index], pH, total triglycerides, high density lipoprotein cholesterol and very low density lipoprotein [VLDL] cholesterol) correlated individually with the amount of triglycerides. Stepwise multiple regression analysis showed that the combination of insulin or HOMA-R index and VLDL cholesterol accounted for up to 50.2% of the triglyceride liver variance. A positive relationship was found between the concomitant presence of the metabolic syndrome components (insulin resistance, dyslipidaemia and central obesity) and intrahepatic triglyceride content.

Conclusions

The study showed that intrahepatic triglyceride deposit appears to be a frequent feature of HIV-1-infected patients receiving HAART. A coherent multifactorial combination of biochemical and physiological factors associated with the deposit suggested that cumulative exposure to PIs might be a possible trigger event.

Risk Factors for and Outcome of Hyperlactatemia in HIV-Infected Persons: Is There a Need for Routine Lactate Monitoring?

BACKGROUND

Lactic acidosis is a rare but life-threatening complication of combination antiretroviral therapy (CART). Asymptomatic or mildly symptomatic episodes of hyperlactatemia are more frequent, but their clinical relevance is unknown.

METHODS

The incidences of, risk factors for, and courses of hyperlactatemia and lactic acidosis were prospectively assessed in the following 3 groups at the Zurich center of the Swiss HIV Cohort Study: persons already receiving CART at baseline, treatment-naive persons who initiated CART during the observation period, and persons who received no CART before or during the observation period.

RESULTS

During 4788 person-years of follow-up, a total of 22,678 lactate assessments were performed for 1566 persons; 662 (42.3%) had at least 1 lactate level measurement of > 2.4 mmol/L, and 49 (3.1%) had severe hyperlactatemia (lactate level of > 5.0 mmol/L). The incidence of hyperlactatemia was 227 cases (95% confidence interval [CI], 210-245) and 59 cases (95% CI, 38-93) per 1000 person-years of follow-up among persons with and persons without CART, respectively. During the observation period, the incidence decreased from 459 cases (95% CI, 415-508) to 85 cases (95% CI, 76-107) per 1000 person-years of follow-up, respectively, because of changing CART prescription patterns. Severe hyperlactatemia occurred in treated persons only. In multivariable Cox proportional hazards models, significant risk factors for severe hyperlactatemia were regimens containing stavudine and didanosine (hazard ratio [HR], 6.65; 95% CI, 2.70-16.3) and regimens containing efavirenz (HR, 2.85; 95% CI, 1.31-6.21). Lactic acidosis was diagnosed in 4 of 1566 persons, all of whom were receiving stavudine and didanosine.

CONCLUSIONS

Hyperlactatemia was frequently observed in all 3 groups, but severe hyperlactatemia and lactic acidosis were rarely observed among persons who received CART. Lactate monitoring appears to be indicated primarily for persons receiving stavudine and didanosine and for persons who are symptomatic. Long-term follow-up is needed to investigate the risk of novel treatment regimens for hyperlactatemia.

Tratamiento de la hiperlactatemia sintomática y de la acidosis láctica en pacientes con infección por el virus de la inmunodeficiencia humana en tratamiento con inhibidores de la transcriptasa inversa análogos de los nucleósidos

BACKGROUND AND OBJECTIVE

We intended to find out the effectiveness of lactic acidosis therapy for mitochondrial toxicity.

PATIENTS AND METHOD

HIV-patients receiving nucleoside reverse transcriptase inhibitors (NRTIs), hospitalized with lactic acidosis or symptomatic hyperlactatemia. Venous hyperlactatemia was considered at > 2.2 mmol/l. Treatment consisted of a daily vitamin regime of L-carnitine, thiamine, vitamin B6, hydroxicobalamine, and vitamin C; any glucose intake was discontinued. NRTIs treatment was stopped immediately.

RESULTS

Nine patients on current therapy were identified who had symptomatic hyperlactatemia (n = 4) or lactic acidosis (n = 5) from 1/2001 to 9/2002. All were patients with AIDS, receiving NRTIs with a mean duration of 5 years: ddI (n = 7), d4T (n = 5), AZT(n = 3), 3TC (n = 2), abacavir (n = 1). Most common symptoms were tachypnea, slight fever, abdominal pain, nausea, vomiting and diarrhea. All patients had a favourable prognosis after administration of L-carnitine and vitamin complexes, with discontinuation of NRTIs and glucose intake. Clinical features lasted 7 days. After 15 (5) months of follow up, none had a recurrence of the syndrome.

CONCLUSION

The application of this therapy could play a role in the treatment of NRTI - related lactic acidosis.

Muscle and Liver Lactate Metabolism in Haart-Treated and Naive HIV-Infected Patients: The Mitovir Study

Objective

To assess the impact of nucleoside analogue reverse transcriptase inhibitor (NRTI) combination therapy on muscle and liver lactate metabolism in HIV-infected patients.

Methods

This cross-sectional study involved HIV-infected patients who were either antiretroviral-naive (Group 1) or were receiving either a stable triple-drug combination including at least one d-drug (zidovudine, zalcitabine, stavudine, didanosine; Group 2) or a backbone of abacavir and lamivudine (Group 3). Lactataemia was measured at rest. Muscle lactate metabolism was assessed during a standardized exercise test and liver lactate metabolism during intravenous lactate infusion. Mitochondrial DNA was quantified in peripheral blood mononuclear cells.

Results

A total of 65 patients were enrolled (16, 31 and 18 patients in Group 1, Group 2 and Group 3, respectively). None of the patients had symptoms of hyperlactataemia. Patients in Group 3 had received d-drugs for a median of seven years before switching to abacavir and lamivudine. Median baseline lactataemia, although within the normal range, was significantly higher in both treatment groups than in the naive patients (Group 2: 1.4, Group 3: 1.5, and Group 1: 1.0 mmol/l, P=0.005). Muscle lactate clearance was significantly lower in both treatment groups than in naive patients (Group 2: 1.6, Group 3: 1.8, and Group 1: 2.1, P=0.01). Lactate liver metabolism and mitochondrial DNA levels did not differ among the three groups.

Conclusions

In HIV-infected patients without symptomatic hyperlactataemia, all NRTI-containing HAART regimens appear to cause muscle mitochondrial damage but to spare the liver. Absence of difference between Group 2 and Group 3 raises questions about the potential reversibility of muscle mitochondrial dysfunction, and/or the ability of abacavir and lamivudine to induce such mitochondrial damage.

Hyperlactataemia and lactic acidosis in HIV-infected patients receiving antiretroviral therapy

Nucleoside reverse-transcriptase inhibitors (NRTIs) have been associated with functional and structural mitochondrial abnormalities, leading to several adverse events, such as increased serum lactic acid levels and lactic acidosis. Mild-to-moderate, asymptomatic hyperlactataemia has been frequently reported in human immunodeficiency virus (HIV)-infected patients treated with NRTIs, with an estimated prevalence between 15% and 35%. On the contrary, symptomatic, severe hyperlactataemia and lactic acidosis are less common, with an incidence ranging from 1.7 to 25.2 cases per 1000 person-years of antiretroviral treatment, and are associated with a remarkable mortality rate, which varies from 30% to 60% in different studies. The clinical presentation of lactic acid syndrome is non-specific and includes asthenia, malaise, nausea, vomiting, abdominal pain, weight loss, tachypnoea, dyspnoea, liver steatosis and increased transaminase levels, and risk factors include previous or concurrent therapy with stavudine or didanosine. Management of symptomatic lactic acid alterations involves NRTI-therapy interruption and supportive care, while natural history of hyperlactataemia is still unknown, and it is uncertain whether asymptomatic patients with increased lactate concentrations are at increased risk of developing lactic acidosis.

Drug-induced increased mitochondrial biogenesis in a liver biopsy

Oncocytic changes seen in hepatocytes in patients receiving highly active antiretroviral therapy (HAART) are a result of mitochondrial damage. This is the first report that provides the electron microscopy illustration of mitochondrial proliferation as a result of the HAART drug Stavudine (Zerit) hepatotoxicity. The drug's effect on mitochondrial DNA replication leads to depleted mitochondrial-encoded proteins and configurational defects of the mitochondrial inner membrane leading to reduced and abnormal cristae, which house the electron transport chain and elementary bodies. This results in a decrease in the NAD/NADH ratio and reduces oxidative phosphorylation. The shift in the NAD/NADH ratio decreases the rate of fatty acid beta oxidation and oxidation of pyruvate by the Krebs cycle. Decreased oxidation of pyruvate drives it into an alternative pathway to form lactate leading to lactic acidosis. This mitochondrial dysfunction results in a compensatory increase in mitochondrial biogenesis, which results in oncocytic changes of the hepatocytes.

Kinetics of lactate metabolism after submaximal ergometric exercise in HIV-infected patients

OBJECTIVES

It is unknown whether high levels of lactate result from enhanced production or decreased degradation. We therefore investigated differences in the kinetics of plasma lactic acid in HIV-infected patients receiving or not receiving highly active antiretroviral therapy (HAART) and in uninfected controls after submaximal ergometric exercise.

METHODS

Ten healthy controls, 11 HIV-infected therapy-naïve patients, 15 HIV-infected patients on HAART with normal baseline lactate levels, and nine HIV-infected patients on HAART with elevated baseline lactate levels >2 mmol/L performed 10 min of ergometric exercise, with a heart rate of 200 beats/min minus age. Lactate levels were measured at baseline, at the end of exercise and 15, 30, 45, 60 and 120 min thereafter.

RESULTS

Mean baseline lactate levels were 1.4, 1.5, 1.5 and 2.8 mmol/L in the controls, the therapy-naïve patients, the patients on HAART with normal lactate levels and the patients on HAART with elevated lactate levels, respectively. Maximum lactate levels after exercise were similar in all groups (9.7, 9.4, 9.0 and 10.1 mmol/L, respectively). Significant differences were found in the slope of lactate decline between controls and untreated individuals (P=0.038) and between patients on HAART with normal baseline lactate and patients on HAART with elevated baseline lactate (P=0.028).

CONCLUSIONS

Differences in lactate metabolism do exist between healthy controls and HIV-infected therapy-naïve individuals. Thus, HIV infection in itself may influence lactate levels. Elevated baseline lactate levels are associated with a delayed decline of lactate after exercise. These results could be explained by impaired lactate clearance. Lactate production upon exercise does not seem to be affected by baseline lactate levels.

PENTA guidelines for the use of antiretroviral therapy, 2004

There have been few major advances in paediatric HIV management over the last 2 years. Decisions about starting antiretroviral therapy can now be based on a recent large meta-analysis of the predictive value of CD4 and HIV RNA viral load (VL) in nearly 4000 untreated children, which is discussed in these updated guidelines. Risk estimates for progression to AIDS and death using surrogate markers can now be broken down by age, allowing more accurate discussion with families. In addition, there is increasing recognition of the problems of long-term adherence, drug resistance and cumulative toxicity in adults and children. The controversy over whether to treat asymptomatic infants continues. For older children more data on the efficacy of ritonavir boosted protease inhibitor (PI) regimens suggests that these may be the PI option of first choice. There is still no adult or paediatric trial evidence on which to base decisions about whether to start with PI- or non-nucleoside reverse transcriptase inhibitor (NNRTI)- based regimens, but the PENPACT 1 trial, which is addressing this question, is ongoing. There are increasing moves to provide simpler antiretroviral therapy (ART) regimens, including once daily dosing, but these lag behind adult regimens because of the paucity of pharmacokinetic data. Resistance assays should now be performed in all HIV-infected infants exposed to ART in pregnancy. Therapeutic drug monitoring may be very important in children because of high between- and within-child variability in drug absorption and metabolism. A trial to evaluate this should start shortly in Europe (PENTA 14 trial). The value of resistance tests for choice of second-line and subsequent choices of ART regimens remain unproven (the PERA trial will report late in 2004), but resistance assays are increasingly being used. The issue of when to switch therapy also remains unanswered and is being addressed within the PENPACT 1 trial. Regular formal assessment of adherence is now the standard of care, and routine monitoring in the clinic for lipodystrophy syndrome (LDS) and other ART toxicities is increasingly important. These guidelines will be updated again in 2006.

Lack of Recurrence of Hyperlactatemia in HIV-Infected Patients Switched From Stavudine to Abacavir or Zidovudine

Stavudine (d4T) has been observed in clinical trials and cohort studies to be more often implicated in cases of hyperlactatemia than other nucleoside reverse transcriptase inhibitors, possibly because of its relatively greater propensity to induce mitochondrial toxicity. The ESS40010 study was a 48-week, open-label, switch study that assessed changes in serum lactate levels and signs/symptoms of hyperlactatemia after substitution of abacavir (n = 86) or zidovudine (n = 32) for d4T in 118 virologically suppressed HIV-infected patients (HIV-1 RNA <400 copies/mL) who had developed serum lactate concentrations > or =2.2 mmol/L (n = 16) or had remained normolactatemic (n = 102) after receiving > or =6 months of d4T-based treatment. Median serum lactate decreased significantly below baseline at week 24 (-0.15 mmol/L, P = 0.0002) and week 48 (-0.15 mmol/L, P = 0.0015). In 10 hyperlactatemic patients in whom d4T was discontinued, serum HIV-1 RNA levels rebounded over the ensuing 31 days, but virologic suppression (HIV-1 RNA <400 copies/mL) was regained when treatment using abacavir or zidovudine was subsequently instituted. In the group with elevated lactate at baseline, symptoms of hyperlactatemia improved in 8% to 23% of patients, did not change in 69%, and worsened in 8%. Serum transaminases, which had been elevated while patients received d4T, normalized after d4T discontinuation and remained in the normal range after the switch to abacavir or zidovudine. Overall, in patients with d4T-associated hyperlactatemia, stopping d4T results in normalization of lactate and a rebound in viral load; restarting treatment using abacavir or zidovudine subsequently maintains normal lactate levels and rapidly leads to a return of virologic suppression.

HIV-associated neuromuscular weakness syndrome

OBJECTIVE

To investigate progressive, severe neuromuscular weakness associated with lactic acidosis in some HIV-infected patients after exposure to nucleoside reverse transcriptase inhibitors (NRTI).

METHODS

HIV-associated neuromuscular weakness syndrome (HANWS) was retrospectively identified and classified based on the level of diagnostic certainty: possible (progressive weakness owing to neuromuscular disease), probable (progressive neuromuscular weakness with documented exclusion of confounding causes), or definite (progressive weakness and electrophysiological or pathological evidence of neuromuscular pathology).

RESULTS

Of 69 patients identified with HANWS, 27 had definite HANWS, 19 probable, and 23 possible. In 44 patients with documented follow-up, 16 required intubation and nine died. There was a marginal association between death and hyperlactatemia (P = 0.061). At onset of neurological symptoms, 68 were receiving antiretroviral therapy, including stavudine for 61 (89.7%). Serum lactate level was elevated (> 2.2 mmol/l) in 30/37 (81%), with a trend towards an association between hyperlactatemia and stavudine usage (P = 0.087). In 25, neurological symptoms occurred after antiretroviral therapy discontinuation (median, 14 days). Electrophysiological studies (n = 24) indicated sensorimotor neuropathy in 20 patients and myopathy in three. Nerve biopsy (n = 9) revealed axonal degeneration and inflammation in three, mixed axonal and demyelinating lesions in three, and primary axonal neuropathy in three. Of 15 muscle biopsies, three revealed inflammation and four mitochondrial abnormalities.

CONCLUSIONS

A severe neuromuscular weakness syndrome may occur in HIV-infected individuals. The association with hyperlactatemia and NRTI exposure supports mitochondrial toxicity as a pathogenesis. In some, the onset of neurological symptoms lagged significantly after discontinuation of antiretroviral therapy, suggesting that different etiological mechanisms may underlie these cases.

Prospective evaluation of blood concentration of mitochondrial DNA as a marker of toxicity in 157 consecutively recruited untreated or HAART-treated HIV-positive patients

Highly active antiretroviral therapy (HAART) can cause mitochondrial toxicity. The concentration of mitochondrial DNA (mtDNA) in peripheral blood cells has been reported to be a marker of this toxicity. However, these observations are controversial and were drawn from small series. Thus, we analysed the value of blood mtDNA as a marker of mitochondrial toxicity in a large cohort of human immunodeficiency virus (HIV)-infected out-patients during routine clinical evaluations. Real-time quantitative PCR was used to determine the mtDNA to nuclear DNA (nDNA) ratio in peripheral blood mononuclear cells from 157 consecutive HIV-1-infected patients (13 naive, 144 receiving HAART) and 30 HIV-1-uninfected patients. The mtDNA to nDNA ratio was significantly lower in both groups of HIV-infected patients than in the control group. No significant difference was observed between treated and naive HIV-infected patients. Lactataemia was significantly lower in controls than in the group of HIV-treated patients. None of the treated patients had lactataemia >5 mmol/l or bicarbonates <20 mmol/l. Triglyceride levels were significantly higher in the HAART-treated patients than in the nontreated patients. Clinical symptoms of lipodystrophy were observed in 62 HAART-treated patients. These symptoms were not associated with an abnormal mtDNA to nDNA ratio or plasma triglyceride concentration. The mtDNA to nDNA ratio was lower in DDI/D4T-treated patients than in AZT/3TC-treated patients. In conclusion, there are no obvious links between the mtDNA to nDNA ratio in peripheral mononuclear cells and any clinical symptoms or lactate level. Thus, the mtDNA to nDNA ratio in leukocytes does not seem to be an accurate marker of mild and/or long-term mitochondrial toxicity.

Serum l-lactate and pyruvate in HIV-infected patients with and without presumed NRTI-related adverse events compared to healthy volunteers

BACKGROUND

Nucleoside reverse transcriptase inhibitors (NRTIs) used in antiretroviral therapy may cause mitochondrial toxicity. Mitochondrial dysfunction leads to disturbance of the glucose metabolism, resulting in an accumulation of L-lactate (L) and pyruvate (P), with an enhanced L/P ratio.

OBJECTIVES

We analysed lactate and pyruvate blood samples of patients of our outpatient department. Aim of the analysis was to detect preliminary mitochondrial toxicity in patients on antiretroviral nucleoside analogues, which might result in disturbances of L, P, L/P ratio, bicarbonate (Bic) or beta-hydroxybutyrate/aceto-acetate (beta-HB/AA) ratios.

STUDY DESIGN

Blood samples of L, P, Bic, beta-HB and AA were analysed in four groups of subjects. The first group (A) consisted of patients with presumed NRTI-related adverse events (n=21), the second group (B) consisted of patients without adverse events (n=28), the third group (C) were HIV-infected patients without antiretroviral therapy (n=6) and the last group (D) were healthy controls (n=12). The mean duration of NRTI-treatment was 18 months (range 0-78 months).

RESULTS

The mean lactate level in group A was 2319 micromol/l (S.D. +/-1231, median 1741 micromol/l), in group B 1257 micromol/l (S.D. +/-607, median 1087), Group C 1285 (S.D. +/-451, median 1245 micromol/l) and 951 micromol/l (S.D. +/-270, median 979) in the healthy controls. No significant differences in pyruvate, L/P, Bic and beta-HB/AA were seen in the four groups. The mean lactate level in patients on stavudine was 1980 micromol/l (S.D. +/-1197) versus 1051 micromol/l (S.D. +/-395, P=0.01) in patients on zidovudine. All patients with lactate values above 2700 micromol/l (eight) experienced adverse events.

CONCLUSION

Lactate levels were higher in patients with presumed NRTI-related adverse events. Furthermore, HIV patients receiving a stavudine containing antiretroviral therapy had higher lactate values than patients without stavudine. Although routine lactate measurement in all patients on antiretroviral therapy is not recommended, lactate measurement might be useful for follow up of patients with presumed NRTI-related adverse events and in patients with lactate levels above 2500 micromol/l. These patients require extra surveillance to evaluate if discontinuation of the current antiretroviral therapy is needed.

[Adverse effects of antiretroviral therapy. Aspects of pathogenesis]

Highly active antiretroviral therapy has resulted in remarkable reduction of morbidity and mortality of HIV infection. With increasing duration of therapy metabolic alterations such as hyperlipidemia, diabetes mellitus type 2 and lipodystrophy are encountered which considerably reduced quality of life for the patients. These adverse events are most likely due to protease inhibitors and nucleoside analogues with synergistic effects. The pathogenesis is related to metabolic alterations of the adipocytes with cellular insulin resistance and enhanced apoptosis of these cells caused by adipocytic cytokines such as adiponectin, leptin, TNF-alpha and interleukin 2. Switch of therapy regimens with elimination of the most suspicious substances and certain protease inhibitors can lead to improvement of deranged metabolism. Also symptomatic therapy is possible to cope with hyperlipidemia and diabetes, although no effective treatment is available to reverse already existing lipodystrophy. Our knowledge about the pathogenesis of these alterations might lead to new concepts and causal therapy in the future.

Lactic acidemia in human immunodeficiency virus-uninfected infants exposed to perinatal antiretroviral therapy

OBJECTIVE

To investigate potential mitochondrial toxicity in HIV-uninfected infants exposed to highly active antiretroviral therapy (HAART) in utero and/or neonatal zidovudine.

DESIGN

A prospective observational study performed in a tertiary referral center for HIV-infected women and their infants and children.

METHODS

Plasma lactate was measured repeatedly during the first 6 months of life in a consecutive cohort of infants exposed to HAART in utero and/or neonatal zidovudine. Maternal CD4, HIV RNA concentration, antiretroviral and substance use histories, mode of delivery, infant gender, cord pH, Apgar score and birth weight were collected.

RESULTS

The plasma lactate was above normal on at least 1 occasion in 35 of 38 (92%) infants and reached levels > or =5 mmol/l in 10 (26%) infants. Overall 78 of 117 (68%) lactate measurements were elevated, with 11 (10%) in the serious (> or =5 mmol/l) range. None of the infants received antiretrovirals beyond 6 weeks, yet elevated lactates persisted up to age 6 months. Two infants had reversible symptoms consistent with those of lactic acidemia. No association was found between the infant peak lactate and the type of therapy during pregnancy, its duration or maternal substance use.

CONCLUSION

Transient lactic acidemia was observed in the majority of HIV uninfected infants exposed to HAART in utero and/or zidovudine neonatally. We hypothesize that the hyperlactatemia is a consequence of persistent, primarily subclinical, mitochondrial toxicity from the transplacental and neonatal exposure to antiretrovirals and of impaired hepatic lactate clearance. Although the clinical relevance of our findings is unknown, we recommend lactate monitoring in these infants, considering discontinuation of neonatal zidovudine in symptomatic infants with lactate > or =5 mmol/l and careful long term follow up of these children.

Lactic acidosis related to nucleoside therapy in HIV-infected patients

The incidence of nucleoside analogue-related lactic acidosis has been estimated in 0.57 - 8.5 cases/1000 person years of antiretroviral therapy. The onset of lactic acidosis is usually insidious and patients complain of nausea, vomiting, abdominal pain, fatigue and weight loss. When lactate levels are high enough, a catastropic clinical situation develops, resulting in multiorgan failure. The mortality rate of patients with lactic acidosis related to nucleoside therapy is very high, 33 - 60%. Although all nucleoside analogues have been implicated in lactic acidosis, most cases are associated with stavudine. At present, there are no controlled trials to evaluate the treatment of nucleoside-induced lactic acidosis. Therapy is based on supportive measures and discontinuation of all antiretroviral drugs. Administration of essential vitamin coenzymes, electron acceptors and L-carnitine may be useful in some cases.

Hyperlactataemia syndromes associated with HIV therapy

Hyperlactataemia is seen in 8-18.3% of HIV-infected patients taking nucleoside-analogue reverse transcriptase inhibitors (NRTIs). Recent epidemiological studies suggest that most episodes are transient and subclinical. However, symptomatic and occasionally life-threatening cases accompanied by metabolic acidosis and hepatic steatosis (ie, lactic acidosis syndrome) have also been described. Though yet to be fully elucidated, the proposed mechanism is NRTI-induced inhibition of mitochondrial DNA polymerase culminating in derangements in oxidative phosphorylation and lactate homeostasis. Signs and symptoms range from mild hyperlactataemia accompanied by nausea, abdominal discomfort, and weight loss to severe, intractable lactic acidosis complicated by coma and multi-organ failure. Significant progress has recently been made with regard to the natural history of NRTI-related hyperlactataemia. However, other important aspects of the disorder, such as its pathogenesis, predisposing conditions, and management, remain poorly understood. This article reviews the current published work on these issues, identifies areas of controversy, and addresses directions for future research.

Bench-to-bedside review: severe lactic acidosis in HIV patients treated with nucleoside analogue reverse transcriptase inhibitors

Nucleoside reverse transcriptase inhibitors (NRTIs) are effective antiretroviral therapy for the treatment of HIV-infected patients. NRTIs can induce mitochondrial impairment that leads to a number of adverse events, including symptomatic lactic acidosis. In the present review, we describe the underlying mechanism of NRTI-induced toxicity and the main clinical features of this infrequent, but severe, emerging complication. We also summarise experimental data and clinical observations that support the use of L-carnitine supplementation to reverse NRTI-induced mitochondrial impairment.

Natural history of hyperlactataemia in human immunodeficiency virus-1-infected patients during highly active antiretroviral therapy

A study on the course of hyperlactataemia during highly active antiretroviral therapy (HAART) and the association between hyperlactataemia and antiretroviral drugs was conducted at the outpatient department, Rigshopitalet, Copenhagen. Lactate levels were monitored in 848 patients during a study period of 1 y. Longitudinal analysis was performed on all human immunodeficiency virus-1-infected patients who had plasma lactate > 2.1 mM. Hyperlactataemia was found in 178 patients (21%), of whom 7 patients needed treatment modification, owing to symptomatic hyperlactataemia in 3 and neuropathy in 4 patients, while 171 remained on unchanged therapy. Lactate levels increased in 20 patients during the study period, but the increases were modest with a mean of 0.6 mM (range 0.1-1.7 mM). The association between antiretroviral drugs and hyperlactataemia was studied using logistic regression in 263 patients with data on their treatment regimen available in electronic form. Only stavudine and ritonavir were significantly associated with hyperlactataemia, with odds ratios of 5.1 and 2.6, respectively. In conclusion, symptomatic hyperlactataemia is uncommon, while asymptomatic hyperlactataemia is a frequent and apparently benign condition unlikely to progress to lactic acidosis. A significant association between stavudine and hyperlactataemia was confirmed. The unexpected association between ritonavir and hyperlactataemia will need confirmation in future studies.

Antiretroviral-associated liver injury

ART-related hepatotoxicity can manifest in a variety of ways. Although benign, asymptomatic LEEs predominate, liver injury occurring in the context of either hypersensitivity or hyperlactatemia, represents a medical emergency and mandates immediate cessation of ART. Underpinning this broad spectrum of presentations are several, as yet poorly understood, mechanisms of liver damage that reflect contributions by constituents of HAART and host factors. Thus far, the most significant predisposing condition to emerge from clinical studies is chronic viral hepatitis. A more precise understanding, however, of the processes and factors that underlie ART-related hepatotoxicity is critical not only to the management of liver injury from current antiretroviral drugs but also to the design of safer drugs in the future.

HIV viral suppression in the era of antiretroviral therapy

Altogether 42 million people worldwide have been infected with HIV, and 12 million have died over the last 20 years. Effective antiretroviral therapy has lead to sustained HIV viral suppression and immunological recovery in patients who have been infected with the virus. The incidence of AIDS has declined in the Western world with the introduction of effective antiretroviral therapy. Questions on When to start treatment?, What to start with?, How to monitor patients?, remain heavily debated. Adherence to antiretroviral treatment remains the cornerstone of effective treatment, and failure to adhere is the strongest predictor of virological failure. Long term therapy can lead to metabolic complications. Resource poor countries are dealing with difficult issues such as mother to child prevention of HIV transmission. Other treatment options are now available, with the recent introduction of fusion inhibitors, second generation non-nucleoside reverse transcriptase inhibitors, and nucleotide reverse transcriptase inhibitors to clinical practice.

Mitochondrial DNA replication, nucleoside reverse-transcriptase inhibitors, and AIDS cardiomyopathy

Nucleoside reverse-transcriptase inhibitors (NRTIs) in combination with other antiretrovirals (HAART) are the cornerstones of current AIDS therapy, but extensive use brought mitochondrial side effects to light. Clinical experience, pharmacological, cell, and molecular biological evidence links altered mitochondrial (mt-) DNA replication to the toxicity of NRTIs in many tissues, and conversely, mtDNA replication defects and mtDNA depletion in target tissues are observed. Organ-specific pathological changes or diverse systemic effects result from and are frequently attributed to HAART in which NRTIs are included. The shared features of mtDNA depletion and energy depletion became key observations and related the clinical and in vivo experimental findings to inhibition of mtDNA replication by NRTI triphosphates in vitro. Subsequent to those findings, other observations suggested that mitochondrial energy deprivation is concomitant with or the result of mitochondrial oxidative stress in AIDS (from HIV, for example) or from NRTI therapy itself.

Increased fat accumulation in the liver in HIV-infected patients with antiretroviral therapy-associated lipodystrophy

OBJECTIVE

To determine liver fat content in patients with highly active antiretroviral therapy (HAART)-associated lipodystrophy.

BACKGROUND

Lipodystrophy in several animal models is associated with fat accumulation in insulin-sensitive tissues, such as the liver. This causes hyperinsulinaemia, dyslipidaemia and other features of insulin resistance.

DESIGN

A cross-sectional study.

SUBJECTS AND METHODS

Three age- and weight-matched groups were compared: 25 HIV-positive men with HAART-associated lipodystrophy (HAART+LD+), nine HIV-positive men receiving HAART, but without lipodystrophy (HAART+LD-), and 35 HIV-negative healthy men (HIV-). Liver fat content was measured using proton spectroscopy. Intra-abdominal and subcutaneous fat were determined using magnetic resonance imaging.

RESULTS

Liver fat content was significantly higher in the HAART+LD+ (8 +/- 10%) than the HIV- (5 +/- 7%; P < 0.05) or the HAART+LD- (3 +/- 5%; P < 0.01) group. Liver fat content correlated with serum fasting insulin in the HAART+LD+ (r = 0.47; P < 0.05) and HIV- groups (r = 0.65; < 0.001), but not with the amount of intra-abdominal fat. Within the HAART+LD+ group, serum insulin did not correlate with the amount of intra-abdominal fat. The HAART+LD+ group had a lower serum leptin concentration when compared to the two other groups. Features of insulin resistance, including hepatic fat accumulation, were not found in HAART+LD-group.

CONCLUSIONS

The severity of the insulin resistance syndrome in patients with HAART-associated lipodystrophy is related to the extent of fat accumulation in the liver rather than in the intra-abdominal region. Fat accumulation in the liver may therefore play a causative role in the development of insulin resistance in these patients.

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.

Severe nucleoside-associated lactic acidosis in human immunodeficiency virus-infected patients: report of 12 cases and review of the literature

Lactic acidosis is a rare but often fatal complication reported in some human immunodeficiency virus (HIV)-infected patients treated with nucleoside-analogue reverse-transcriptase inhibitors. We report a series of 12 patients with HIV infection treated with nucleoside analogues who developed unexplained metabolic acidosis. We have also reviewed 60 additional published cases. The aim of the present study is to describe the clinical picture, prognostic factors, and final outcome for nucleoside-associated lactic acidosis. The mortality rate is high: 33% for our patients, and 57% for the patients described in the literature. In the multivariate analysis, a lactate serum level of >10 mM (odds ratio [OR], 13.23; 95% confidence interval [CI], 2.96-59.25) was the only factor associated with higher mortality. The administration of specific therapy with cofactors against acidosis was associated with a lower mortality (OR, 0.17; 95% CI, 0.04-0.73). We conclude that specific therapy with cofactors may improve the outcome for patients with this syndrome.

Hyperlactatemia syndromes in people with HIV infection

Hyperlactatemia associated with use of nucleoside analogue reverse transcriptase inhibitors (NRTIs) is not a single entity but a spectrum of abnormalities. The spectrum reflects varying degrees of derangement in systemic homeostasis in the face of primary drug effects on lactate load. Lactic acidosis, characterized by metabolic acidosis, blood lactate above 5 mmol/l, hepatic steatosis and high mortality, represents the extreme end of this spectrum where there is complete decompensation. Partially compensated states of lactate excess have now been described, ranging from less fulminant symptomatic hyperlactatemia with hepatic steatosis to chronic or intermittent low-grade hyperlactatemia without acidosis, steatosis or any symptoms. At a population level, average venous lactate concentrations do rise following treatment with NRTIs but stabilize long term in the majority of cases. The average increase in systemic lactate turnover that is required to maintain such compensated blood levels is not known and research into this may provide insights into the extent of incipient mitochondrial toxicity associated with chronic NRTI use. At a tissue-specific level, it is not known which tissues or organs (liver, fat, other) are the predominant contributors to an increase in systemic lactate load, nor whether the primary defect is one of increased production, decreased elimination or both.

Combined antiretroviral therapy causes cardiomyopathy and elevates plasma lactate in transgenic AIDS mice

Highly active antiretroviral therapy (HAART) is implicated in cardiomyopathy (CM) and in elevated plasma lactate (LA) in AIDS through mechanisms of mitochondrial dysfunction. To determine mitochondrial events from HAART in vivo, 8-week-old hemizygous transgenic AIDS mice (NL4-3Delta gag/pol; TG) and wild-type FVB/n littermates were treated with the HAART combination of zidovudine, lamivudine, and indinavir or vehicle control for 10 days or 35 days. At termination of the experiments, mice underwent echocardiography, quantitation of abundance of molecular markers of CM (ventricular mRNA encoding atrial natriuretic factor [ANF] and sarcoplasmic calcium ATPase [SERCA2]), and determination of plasma LA. Myocardial histologic features were analyzed semiquantitatively and results were confirmed by transmission electron microscopy. After 35 days in the TG + HAART cohort, left ventricular mass increased 160% by echocardiography. Molecularly, ANF mRNA increased 250% and SERCA2 mRNA decreased 57%. Biochemically, LA was elevated (8.5 +/- 2.0 mM). Pathologically, granular cytoplasmic changes were found in cardiac myocytes, indicating enlarged, damaged mitochondria. Findings were confirmed ultrastructurally. No changes were found in other cohorts. After 10 days, only ANF was elevated, and only in the TG + HAART cohort. Results show that cumulative HAART caused mitochondrial CM with elevated LA in AIDS transgenic mice.

Hyperlactataemia in HIV-Infected Patients: The Role of NRTI-Treatment

Background

Long-term treatment with nucleoside reverse transcriptase inhibitors (NRTIs) can induce mitochondrial dysfunction, most severely represented by lactic acidosis. Diagnostic tests for mitochondrial dysfunction are lacking, although persistently elevated serum lactate might be a surrogate marker.

Objectives

To determine the occurrence of hyperlactataemia in HIV-infected patients on NRTI-treatment and to evaluate the possible risk factors.

Methods

Cross-sectional analysis of lactic-acid levels in asymptomatic HIV-infected patients. Hyperlactactaemia was considered mild if between 2.0–5 mmol/l, serious if >5 mmol/l and lactic acidosis was defined as lactic acid levels >5 mmol/l with bicarbonate <20 mmol/l. Possible risk factors, such as current and preceding NRTI-treatment as well as treatment with non-nucleoside reverse transcriptase inhibitors or protease inhibitors and concurrent liver disease, were analysed.

Results

Two hundred and twenty three asymptomatic HIV-infected patients were studied, including 174 patients (78%) on NRTI treatment, 12 patients (5%) treated without NRTIs and 37 patients (17%) not treated. Mild hyperlactataemia was found in 42 patients (19%), from whom 38/42 (90%) were NRTI-treated and the remaining patients (4/42, 10%) received no treatment (χ2, P<0.05). The significant risk factors for hyperlactataemia in the univariate analysis were NRTI-treatment as a group ( P=0.03) and elevated ALT ( P=0.008). In multivariate analysis NRTI use ( P=0.05) and ALT level ( P=0.03) remained a significant determinant of hyperlactataemia. Among the different individual NRTIs, a stavudine-containing ( P=0.004) and a zalcitabine-containing ( P=0.07) regimen were most notably associated with the development of hyperlactataemia, whereas for the combinations of NRTIs, such association was only found for stavudine/lamivudine ( P=0.05).

Conclusions

A correlation between hyperlactataemia and NRTI treatment was found, but the value of routine lactate measurement for individual treatment monitoring remains uncertain.

Chronic hyperlactatemia in HIV-infected patients taking antiretroviral therapy

OBJECTIVE

To determine the prevalence, course and risk factors for hyperlactatemia in HIV-infected patients.

DESIGN

A prospective, longitudinal study of venous lactate concentrations over an 18-month period in 349 participants of the Western Australian HIV Cohort Study.

RESULTS

In 516 patient-years of observation, two patients experienced severe fulminant lactic acidosis (lactate > 5 mmol/l) and hepatic steatosis attributable to nucleoside analogue reverse transcriptase inhibitors (NRTI). A further five patients with lesser elevations of lactate (2.8-4.1 mmol/l) but with symptoms of nausea or abdominal discomfort and evidence of hepatic steatosis had NRTI therapy revised, with relief of symptoms and a fall in lactate levels. Most remaining patients on highly active antiretroviral therapy (HAART) had mild, chronic, asymptomatic hyperlactatemia, with mean lactate level between 1.5 mmol/l and 3.5 mmol/l most commonly. Longitudinal data was analysed in a non-linear mixed effects growth model which indicated that average lactate levels rose after the start of HAART but tended to stabilise at low-grade elevation, with an average 0.23 mmol/l greater long term level in stavudine users compared with zidovudine users (p < 0.01). A multiple linear regression model showed that the association between stavudine and higher lactate level was not confounded by longer duration of total NRTI exposure. Risk of hyperlactatemia was not significantly associated with use of other NRTIs, protease inhibitors, non-nucleoside analogue reverse transcriptase inhibitors or multiple immunological and virological factors in multivariate analyses.

CONCLUSIONS

Chronic, compensated, asymptomatic hyperlactatemia is common in patients taking HAART. Decompensated, life-threatening lactic acidosis/hepatic steatosis is rare. Treatment with stavudine appears to be the predominant risk factor for development of chronic hyperlactatemia.