Fatal lactic acidosis and liver steatosis associated with didanosine and stavudine treatment: a respiratory chain dysfunction?

Efficient Elimination of mtDNA from Mammalian Cells with 2',3'-Dideoxycytidine

Mammalian cell lines devoid of mitochondrial DNA (mtDNA) are indispensable in studies aimed at elucidating the contribution of mtDNA to various cellular processes or interactions between nuclear and mitochondrial genomes. However, the repertoire of tools for generating such cells (also known as rho-0 or ρ0 cells) remains limited, and approaches remain time- and labor-intensive, ultimately limiting their availability. Ethidium bromide (EtBr), which is most commonly used to induce mtDNA loss in mammalian cells, is cytostatic and mutagenic as it affects both nuclear and mitochondrial genomes. Therefore, there is growing interest in new tools for generating ρ0 cell lines. Here, we examined the utility of 2',3'-dideoxycytidine (ddC, zalcitabine) alone or in combination with EtBr for generating ρ0 cell lines of mouse and human origin as well as inducing the ρ0 state in mouse/human somatic cell hybrids. We report that ddC is superior to EtBr in both immortalized mouse fibroblasts and human 143B cells. Also, unlike EtBr, ddC exhibits no cytostatic effects at the highest concentration tested (200 μM), making it more suitable for general use. We conclude that ddC is a promising new tool for generating mammalian ρ0 cell lines.

Effect of hydroxy-α-sanshool on lipid metabolism in liver and hepatocytes based on AMPK signaling pathway

BACKGROUND

With the increasing awareness of the safety of traditional Chinese medicine and food, as well as in-depth studies on the pharmacological activity and toxicity of Zanthoxylum armatum DC. (ZADC), it has been found that ZADC is hepatotoxic. However, the toxic substance basis and mechanism of action have not been fully elucidated. Hydroxy-α-sanshool (HAS) belongs to an amide compound in the fruits of ZADC, which may be hepatotoxic. However, the specific effects of HAS, including liver toxicity, are unclear.

PURPOSE

The objectives of this research was to determine how HAS affects hepatic lipid metabolism, identify the mechanism underlying the accumulation of liver lipids by HAS, and offer assurances on the safe administration of HAS.

METHODS

An in vivo experiment was performed by gavaging C57 BL/6 J mice with various dosages of HAS (5, 10, and 20 mg/kg). Biochemical indexes were measured, and histological analysis was performed to evaluate HAS hepatotoxicity. Hepatic lipid levels were determined using lipid indices and oil red O (ORO) staining. Intracellular lipid content were determined by biochemical analyses and ORO staining after treating HepG2 cells with different concentrations of HAS in vitro. Mitochondrial membrane potential, respiratory chain complex enzymes, and ATP levels were assessed by fluorescence labeling of mitochondria. The levels of proteins involved in lipogenesis and catabolism were determined using Western blotting.

RESULTS

Mice in the HAS group had elevated alanine and aspartate aminotransferase blood levels as well as increased liver index compared with the controls. The pathological findings showed hepatocellular necrosis. Serum and liver levels of triglycerides, total cholesterol, and low-density lipoprotein cholesterol levels were increased, whereas high-density lipoprotein cholesterol levels decreased. The ORO staining findings demonstrated elevated liver lipid levels. In vitro experiments demonstrated a notable elevation in triglyceride and total cholesterol levels in the HAS group. ATP, respiratory chain complex enzyme gene expression, mitochondrial membrane potential, and mitochondrial number were reduced in the HAS group. The levels of lipid synthesis-associated proteins (ACC, FASN, and SREBP-1c) were increased, and lipid catabolism-associated protein levels (PPARα and CPT1) and the p-AMPK/AMPK ratio were decreased in vivo and in vitro.

CONCLUSION

HAS has hepatotoxic effects, which can induce fatty acid synthesis and mitochondrial function damage by inhibiting the AMPK signaling pathway, resulting in aberrant lipid increases.

Chronic liver disease in the human immunodeficiency virus patient

There are an estimated 40 million HIV infected individuals worldwide, with chronic liver disease being the 2nd leading cause of mortality in this population. Elevated liver functions are commonly noted in HIV patients and the etiologies are varied. Viral hepatitis B and C, fatty liver and drug induced liver injury are more common. Treatment options for viral hepatitis C are rapidly evolving and are promising, but treatments are limited for the other conditions and is primarily supportive. Opportunistic infections of the liver are now uncommon. Irrespective of etiology, management requires referral to specialized centers and with due diligence mortality can be reduced.

Nonclinical Safety Profile of BMS-986001, a Nucleoside Transcriptase Inhibitor for Combination Retroviral Therapy

Nucleoside reverse transcriptase inhibitors (NRTIs)/nucleotide reverse transcriptase inhibitors are key components of combination antiretroviral therapy for HIV infection. First-generation NRTIs are associated with mitochondrial toxicity in patients, mainly due to inhibition of human DNA polymerase γ (hDNA polγ) that manifests as adverse events such as lipodystrophy, lactic acidosis, myopathy, cardiomyopathy, or nephropathy in patients. In chronic nonclinical studies in rodents and nonrodents, eukaryotic (host) mitochondrial toxicity manifests as some drug-specific toxicities similar to human toxicity. BMS-986001, a novel thymidine analog with minimal hDNA polγ inhibition, has demonstrated antiretroviral activity in early clinical studies. The primary toxicity of BMS-986001 in rats and monkeys is bone marrow dyserythropoiesis with associated decreases in red blood cell mass. Additionally, at high doses, severe platelet reductions accompanied by cutaneous petechiae began during weeks 8 and 11 in 3 of 60 monkeys in chronic toxicity studies. In a 6-month study, platelet reductions required euthanasia of the 2 affected monkeys (300 mg/kg/d) at week 14, but with dose reduction (200 mg/kg/d) remaining monkeys had no platelet changes. One affected monkey (200 mg/kg/d) in a 9-month study completed dosing and its platelet counts recovered during a 1-month recovery. Formation of platelet-bound immunoglobulin in the presence of BMS-986001, together with rapid and complete platelet recovery in the absence of BMS-986001, suggested that platelet decreases in monkeys may be immune mediated. No findings indicative of mitochondrial toxicity were observed in rats or monkeys given BMS-986001, suggesting an improved safety profile compared to marketed NRTI or tenofovir disoproxil fumarate.

Drug-induced steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is currently the most common cause of chronic liver disease in the United States. The term NALFD was first used by Ludwig in 1980 to describe the presence of hepatic steatosis and steatohepatitis in a series of patients with no identifiable cause. Since then, our insight into the pathogenesis of NAFLD has expanded significantly. We now know that NAFLD is closely related to metabolic syndrome and chronic low-grade inflammation. In the following review, the authors summarize the current evidence about drugs that lead to hepatic steatosis and steatohepatitis and pathogenic mechanisms thereof.

Histological features in western patients with idiopathic non-cirrhotic portal hypertension

AIMS

In the western world, idiopathic non-cirrhotic portal hypertension (INCPH) is a rare disease. This study aimed to investigate the histopathological features in western INCPH patients and to assess pathological differences between liver specimens of INCPH with and without HIV.

METHODS AND RESULTS

Biopsies of 70 INCPH patients (of which 15 were HIV-infected) were compared to 23 patients with non-cirrhotic portal vein thrombosis (PVT), which served as a control group for non-cirrhotic portal hypertension. Phlebosclerosis, nodular regeneration (NR), sinusoidal dilatation, paraportal shunting vessels, perisinusoidal fibrosis and portal tract remnants were the most prevalent morphological features of INCPH. There were significant (P < 0.01) morphological differences between INCPH and PVT liver specimens with regard to portal tract remnants (46% versus 0%), phlebosclerosis (95% versus 65%), portal vein dilatation (34% versus 78%) and NR (56% versus 22%). The degree of NR correlated with the severity of phlebosclerosis (P < 0.01). NR was seen more frequently in the HIV-INCPH group, compared to the non-HIV-infected patients (P < 0.001).

CONCLUSION

Portal tract remnants, phlebosclerosis and nodular regeneration are typical features of INCPH. Sinusoidal dilatation, paraportal shunting vessels and increased portal and parenchymal vessels might represent pressure-related morphological signs of portal hypertension. Finally, more nodular regeneration was observed in HIV-associated INCPH.

Autophagy inhibition due to thymidine analogues as novel mechanism leading to hepatocyte dysfunction and lipid accumulation

OBJECTIVES

Prolonged nucleoside reverse transcriptase inhibitors (NRTI) exposure can lead to microvesicular steatosis. We hypothesized that thymidine analogues might interfere with autophagy in hepatocytes, a lysosomal degradation pathway implicated in cell survival and regulation of hepatocyte lipid metabolism.

DESIGN

Using HepG2 and HUH7 cell lines and primary human hepatocytes, we performed a comprehensive analysis of NRTI-mediated effects on autophagy.

METHODS

The impact of zidovudine (ZDV), stavudine (d4T) and lamivudine (3TC) on constitutive and induced autophagy was analyzed by fluorescent and electron microscopy, western blotting and flow cytometry. Effects on hepatocyte autophagy were correlated to cellular viability, mitochondrial dysfunction and intracellular lipid accumulation.

RESULTS

ZDV and d4T, but not 3TC, significantly inhibited both constitutive as well as stimulated autophagic activity in a dose-dependent and time-dependent manner. Inhibition of autophagy at therapeutic drug concentrations led to accumulation of dysfunctional mitochondria, increased ROS production, increased apoptosis, decreased proliferation and increased intracellular lipid accumulation. These NRTI effects could be readily resembled by pharmacological and genetic inhibition of hepatocyte autophagy.

CONCLUSION

Our data suggest that thymidine analogues inhibit autophagy in hepatocytes, which in turn leads to increased ROS production, lipid accumulation and hepatic dysfunction. This novel mechanism could contribute to nonalcoholic fatty liver disease in HIV-infected patients.

Central role of mitochondria in drug-induced liver injury

A frequent mechanism for drug-induced liver injury (DILI) is the formation of reactive metabolites that trigger hepatitis through direct toxicity or immune reactions. Both events cause mitochondrial membrane disruption. Genetic or acquired factors predispose to metabolite-mediated hepatitis by increasing the formation of the reactive metabolite, decreasing its detoxification, or by the presence of critical human leukocyte antigen molecule(s). In other instances, the parent drug itself triggers mitochondrial membrane disruption or inhibits mitochondrial function through different mechanisms. Drugs can sequester coenzyme A or can inhibit mitochondrial β-oxidation enzymes, the transfer of electrons along the respiratory chain, or adenosine triphosphate (ATP) synthase. Drugs can also destroy mitochondrial DNA, inhibit its replication, decrease mitochondrial transcripts, or hamper mitochondrial protein synthesis. Quite often, a single drug has many different effects on mitochondrial function. A severe impairment of oxidative phosphorylation decreases hepatic ATP, leading to cell dysfunction or necrosis; it can also secondarily inhibit ß-oxidation, thus causing steatosis, and can also inhibit pyruvate catabolism, leading to lactic acidosis. A severe impairment of β-oxidation can cause a fatty liver; further, decreased gluconeogenesis and increased utilization of glucose to compensate for the inability to oxidize fatty acids, together with the mitochondrial toxicity of accumulated free fatty acids and lipid peroxidation products, may impair energy production, possibly leading to coma and death. Susceptibility to parent drug-mediated mitochondrial dysfunction can be increased by factors impairing the removal of the toxic parent compound or by the presence of other medical condition(s) impairing mitochondrial function. New drug molecules should be screened for possible mitochondrial effects.

Mitochondrial involvement in drug-induced liver injury

Mitochondrial dysfunction is a major mechanism of liver injury. A parent drug or its reactive metabolite can trigger outer mitochondrial membrane permeabilization or rupture due to mitochondrial permeability transition. The latter can severely deplete ATP and cause liver cell necrosis, or it can instead lead to apoptosis by releasing cytochrome c, which activates caspases in the cytosol. Necrosis and apoptosis can trigger cytolytic hepatitis resulting in lethal fulminant hepatitis in some patients. Other drugs severely inhibit mitochondrial function and trigger extensive microvesicular steatosis, hypoglycaemia, coma, and death. Milder and more prolonged forms of drug-induced mitochondrial dysfunction can also cause macrovacuolar steatosis. Although this is a benign liver lesion in the short-term, it can progress to steatohepatitis and then to cirrhosis. Patient susceptibility to drug-induced mitochondrial dysfunction and liver injury can sometimes be explained by genetic or acquired variations in drug metabolism and/or elimination that increase the concentration of the toxic species (parent drug or metabolite). Susceptibility may also be increased by the presence of another condition, which also impairs mitochondrial function, such as an inborn mitochondrial cytopathy, beta-oxidation defect, certain viral infections, pregnancy, or the obesity-associated metabolic syndrome. Liver injury due to mitochondrial dysfunction can have important consequences for pharmaceutical companies. It has led to the interruption of clinical trials, the recall of several drugs after marketing, or the introduction of severe black box warnings by drug agencies. Pharmaceutical companies should systematically investigate mitochondrial effects during lead selection or preclinical safety studies.

Mitochondrial Toxicity of Tenofovir, Emtricitabine and Abacavir Alone and in Combination with Additional Nucleoside Reverse Transcriptase Inhibitors

Background

Some nucleoside/nucleotide reverse transcriptase inhibitor (NRTI) combinations cause additive or synergistic interactions in vitro and in vivo.

Methods

We evaluated the mitochondrial toxicity of tenofovir (TFV), emtricitabine (FTC) and abacavir as carbovir (CBV) alone, with each other, and in combination with additional NRTIs. HepG2 human hepatoma cells were incubated with TFV, FTC, CBV, didanosine (ddI), stavudine (d4T), lamivudine (3TC) and zidovudine (AZT) at concentrations equivalent to 1 and 10x clinical steady-state peak plasma levels (Cmax). NRTIs were also used in double and triple combinations. Cell growth, lactate production, intracellular lipids, mtDNA and the mtDNA-encoded respiratory chain subunit II of cytochrome c oxidase (COXII) were monitored for 25 days.

Results

TFV and 3TC had no or minimal toxicity. FTC moderately reduced hepatocyte proliferation independent of effects on mtDNA. ddI and d4T induced a time- and dose-dependent loss of mtDNA and COXII, decreased cell growth and increased levels of lactate and intracellular lipids. CBV and AZT strongly impaired hepatocyte proliferation and increased lactate and lipid production, but did not induce mtDNA depletion. The dual combination of TFV plus 3TC had only minimal toxicity; TFV plus FTC slightly reduced cell proliferation without affecting mitochondrial parameters. All other combinations exhibited more pronounced adverse effects on mitochondrial endpoints. Toxic effects on mitochondrial parameters were observed in all combinations with ddI, d4T, AZT or CBV. TFV and 3TC both attenuated ddI-related cytotoxicity, but worsened the effects of CBV and AZT.

Conclusions

The data demonstrate unpredicted interactions between NRTIs with respect to toxicological endpoints and provide an argument against the liberal use of NRTI cocktails without first obtaining data from clinical trials.

Mitochondrial DNA depletion in liver tissue of patients infected with hepatitis C virus: contributing effect of HIV infection?

OBJECTIVES

It has been suggested that chronic hepatitis C virus (HCV) infection depletes mitochondrial DNA (mtDNA) in the liver. Because decreased mtDNA levels were also found in humans infected with HIV, we investigated whether HIV may have aggravated hepatic mtDNA depletion in individuals with HCV infection.

METHODS

In this cross-sectional study, liver biopsies were performed in a total of 40 individuals prior to any antiviral therapy. The individuals were recruited from the Hospital Clinic, Barcelona and the HIV Centre, Dusseldorf. Seventeen patients were negative for HIV and HCV and were biopsied for liver enzyme elevation of unknown cause (controls), 14 individuals had chronic HCV but no HIV infection, and nine subjects were coinfected with both viruses. mtDNA and liver histology were centrally assessed.

RESULTS

The groups did not differ with respect to age, gender, liver function tests and HCV viral load, where applicable. mtDNA levels were decreased by 19% in the HCV-monoinfected group (P=0.03) and by 27% in the HIV/HCV-coinfected subjects (P=0.02) compared to controls. The mtDNA content, however, did not differ between individuals with HCV monoinfection and HCV/HIV coinfection (P=0.75). The degrees of liver fibrosis, inflammatory activity or steatosis did not correlate with mtDNA content.

CONCLUSIONS

Liver mtDNA content is reduced in both HCV-monoinfected and HIV/HCV-coinfected patients. Under the limitations of our study, we could demonstrate only a slight trend towards more pronounced mtDNA depletion in HIV/HCV-coinfected subjects.

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.

Metabolic complications associated with the use of highly active antiretroviral therapy in HIV-1-infected adults

The availability of highly active antiretroviral therapy (HAART) has resulted in dramatic declines in morbidity and mortality in patients infected with human immunodeficiency virus-1 (HIV-1). However, the success of HAART has been tempered by the recognition of adverse metabolic effects clearly associated with its use. These "metabolic complications" include dyslipidemia, changes in body fat distribution, insulin resistance and glucose intolerance, metabolic bone disease, and lactic acidosis. Guidelines to assist clinicians in the management of these complications have been put forth by various organizations, including the International AIDS Society, the HIV Medicine Association of the Infectious Disease Society of America, and the Adult AIDS Clinical Trials Group.

Mitochondrial and metabolic effects of nucleoside reverse transcriptase inhibitors (NRTIs) in mice receiving one of five single- and three dual-NRTI treatments

Although treatments with nucleoside reverse transcriptase inhibitors (NRTIs) can modify fat metabolism and fat distribution in humans, the mechanisms of these modifications and the roles of diverse NRTIs are unknown. We studied the mitochondrial and metabolic effects of stavudine (d4T), zidovudine (AZT), didanosine (ddI), lamivudine (3TC), zalcitabine (ddC), and three combinations (AZT-3TC, d4T-3TC, and d4T-ddI) in mice treated for 2 weeks with daily doses equivalent to the human dose per body area. Concentrations of AZT and d4T in plasma were lower when these drugs were administered with 3TC or ddI. Whatever the treatment, mitochondrial DNA was not significantly decreased in muscle, heart, brain, or white adipose tissue but was moderately decreased in liver tissue after the administration of AZT, 3TC, or d4T alone. Blood lactate was unchanged, even when NRTIs were administered at supratherapeutic doses. In contrast, the level of plasma ketone bodies increased with the administration of AZT or high doses of d4T but not with ddC, 3TC, or ddI, suggesting that the thymine moiety could be involved. Indeed, the levels of plasma ketone bodies increased in mice treated with beta-aminoisobutyric acid, a thymine catabolite. Treatment with AZT, d4T, or beta-aminoisobutyric acid increased hepatic carnitine palmitoyltransferase I (CPT-I) mRNA expression and the mitochondrial generation of ketone bodies from palmitate. In conclusion, therapeutic doses of NRTIs have no or moderate effects on mitochondrial DNA and no effects on plasma lactate in mice. However, AZT and high doses of d4T increase the levels of hepatic CPT-I, mitochondrial fatty acid beta-oxidation, and ketone bodies, and these catabolic effects are reproduced by beta-aminoisobutyric acid, a thymine metabolite.

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.

Depletion of mitochondrial DNA in liver under antiretroviral therapy with didanosine, stavudine, or zalcitabine

The "D drug" HIV reverse-transcriptase inhibitors zalcitabine, didanosine, and stavudine are relatively strong inhibitors of polymerase-gamma compared with the "non-D drugs" zidovudine, lamivudine, and abacavir. D drugs deplete mitochondrial DNA (mtDNA) in cultured hepatocytes. This mtDNA depletion is associated with an increased in vitro production of lactate. To investigate the origin of hyperlactatemia in HIV-infected patients and the effects of antiretroviral therapy on liver mtDNA, we biopsied liver tissue from 94 individuals with chronic hepatitis C virus (HCV) infection. Eighty subjects were coinfected with HIV. Serum lactate was measured at the time of biopsy. Hepatic mtDNA and liver histology were centrally assessed. Liver mtDNA content of HIV-infected patients receiving D drugs at the time of biopsy (n = 34) was decreased by 47% (P<.0001) compared with those without D drugs (n = 35). Aside from a possible association between HCV genotype I status and mtDNA depletion in multivariate analysis, there were no other virologic, immunologic, histologic, demographic or treatment-related variables that could explain the mtDNA depletion. Lactate was above the upper limit of normal in only three patients, all of whom were treated with D drugs. The mtDNA in each of them was lower than in any non-D drug patient and significantly (P =.017) depleted compared with D drug patients with normal lactate. In conclusion, D drug treatment is associated with decreased hepatic mtDNA in HIV-infected patients with chronic HCV infection. Moderate mtDNA depletion in liver does not necessarily lead to hyperlactatemia, but more pronounced decreases in hepatic mtDNA may be an important contributor to lactate elevation.

Mitochondrial Effects of Antiretroviral Therapies in Asymptomatic Patients

Background

A decrease in the mitochondrial (mt) DNA to nuclear DNA ratio has gained acceptance as a marker of mitochondrial toxicity in treated HIV-infected patients, but the functional meaning of this alteration is unclear.

Methods

We assessed mtDNA content, mitochondrial content and function in peripheral blood mononuclear cells (PBMCs) of consecutive asymptomatic HIV-infected patients. Patients selected had been receiving a first-line highly active antiretroviral therapy (HAART) regimen for at least 6 months, consisting of zidovudine plus lamivudine or stavudine plus didanosine plus either nelfinavir or nevirapine, or were antiretroviral-naive. The mtDNA content was assessed by quantitative real-time PCR, mitochondrial content by citrate synthase activity, enzyme activity of complexes III and IV (both partially encoded by mtDNA) of the electron transport chain by spectrophotometry, oxygen consumption by polarography, and oxidative damage in cell membranes by monitoring cis-parinaric acid fluorescence.

Results

Mitochondrial content was significantly lower in all treated groups. Patients receiving stavudine plus didanosine had mtDNA depletion and a decrease in complex IV activity. However, oxygen consumption capacity and lipid peroxidation were unaffected in all groups.

Conclusion

Long-term HAART may induce mitochondrial abnormalities in PBMC mitochondria, which do not necessarily translate into functional abnormalities, at least in asymptomatic patients. This study was presented in the 4th International Workshop on Adverse Drug Reactions & Lipodystrophy in HIV (San Diego, Calif., USA, September 2002) and in ‘Late Breakers & Hot Topics’ session in the 6th International Congress on Drug Therapy in HIV Infection (Glasgow, UK, November 2002).

Antiretroviral Therapy-associated Serious and Life-threatening Toxicities

In the late 1980s and early 1990s, when HIV/AIDS had become the leading cause of death in 25- to 44-year-old persons in the United States, it was acceptable to prescribe newer antiretroviral therapy such as zidovudine, which has significant bone marrow toxicities but can potentially improve patient survival. Although current antiretroviral therapy is not likely to eradicate HIV-1 infection, the advances in the use of combination antiretroviral therapy (including protease inhibitors and non-nucleoside reverse transcriptase inhibitors) have dramatically improved the overall survival, immune status, and productivity of HIV-infected individuals in developed countries. Instead of prevention and treatment of HIV-associated complications, many of the patients" clinic visits are focused on finding strategies to manage and prevent antiretroviral therapy-associated complications. Because only a few HIV-infected persons fulfilling stringent inclusion criteria were included in premarketing clinical trials and because the US Food and Drug Administration"s (FDA) accelerated approval process for antiretroviral therapy requires only 24-week safety and efficacy data, newly emerging and previously unrecognized adverse effects of antiretroviral therapy continue to surface when these drugs are administered to a larger patient population for a longer duration. Unfortunately, some of these adverse effects can be unpredictable and serious, and, if not recognized early and managed aggressively, can lead to fatality. This article reviews four of the most serious, life-threatening toxicities associated with antiretroviral therapy.

Lactic acidemia in infection with human immunodeficiency virus

Lactic acidosis in patients infected with the human immunodeficiency virus was initially identified as a rare complication of therapy with nucleoside analog reverse transcriptase inhibitors (NRTIs). The only patient group that appears to be at greater risk is pregnant women. More recently, milder elevations in lactate (i.e., lactic acidemia or hyperlactatemia) have been found to be more common and to be associated with numerous illnesses. Mild asymptomatic lactic acidemia is common, but it appears to lead to more severe illness only rarely. This suggests that routine measurement of plasma lactate should be limited to patients with previous acidemia who reinitiate NRTI therapy and to pregnant women. For symptomatic lactic acidemia (generally >5 mmol/L), NRTIs and other antiretroviral therapy should be ceased. Currently, asymptomatic lactic acidemia should not be treated and should not lead to a change in antiretroviral therapy.

Metabolic acidosis and hepatic steatosis in two HIV-infected patients on stavudine (d4T) treatment

Nucleoside analog reverse transcriptase inhibitors (NRTI) have been used to treat HIV-infected patients for >10 years. Some severe adverse events have been attributed to mitochondrial dysfunction. Since 1991, cases of severe lactic acidosis have been reported in association with nucleoside therapy. Our objective was to report two cases of metabolic acidosis and hepatic steatosis in patients receiving stavudine (d4T) and to review the literature. A male and a female, 47 and 45 years of age, respectively, presented with abdominal pain, nausea, vomiting, and weakness after 9 and 6 months, respectively, of treatment with stavudine. At presentation, both patients had severe metabolic acidosis and liver failure. Ultrasonography showed hepatic steatosis (confirmed by biopsy in one case). All antiretroviral drugs were withdrawn and patients were treated with bicarbonate. Both patients developed fulminant liver dysfunction and multiple organ failure. We reviewed the literature and found 75 cases of lactic acidosis and hepatic steatosis associated with use of NRTI; 57 of these patients received d4T (76%). Of all cases reported in association with nucleoside therapy, 63% were females and mortality was 47%. General weakness, hepatic enzyme elevation, and liver steatosis are data that should alert physicians to this serious adverse event and to respond with prompt interruption of antiretroviral drugs and measurement of lactic acid in plasma. It is important to report serious adverse events in commercially released drugs to know prevalence in an exposed population. Physicians should be aware of risk and early signs of this serious adverse event.

Management of metabolic complications associated with antiretroviral therapy for HIV-1 infection: recommendations of an International AIDS Society-USA panel

OBJECTIVE

Alterations in glucose and lipid metabolism, lactic acidemia, bone disorders, and abnormal body fat distribution have been recognized recently as frequent complications associated with HIV-1 infection and potent antiretroviral therapy, but limited data are available regarding the appropriate management of these disorders. These recommendations were developed to guide physicians actively involved in HIV care in the management of metabolic complications that occur primarily within the context of potent antiretroviral therapy.

PARTICIPANTS

A 12-member panel representing international expertise in HIV-1 patient care, antiretroviral therapy, and endocrine and metabolic disorders was selected in the spring of 2000 by the International AIDS Society-USA, a not-for-profit physician education organization. Panel members met in closed meetings beginning in May 2000. All work was funded by the International AIDS Society-USA; the panel members are not compensated for their participation.

EVIDENCE

The panel reviewed published results of clinical, epidemiologic, and basic science studies and data and abstracts presented at research conferences, primarily from 1997 to 2002. The panel also considered studies of the pathophysiology and treatment of similar metabolic abnormalities in noninfected persons. Emphasis was placed on results from prospective, randomized, controlled clinical trials when available.

PROCESS

For each metabolic complication, 1 or more member(s) reviewed and presented all available evidence to the panel, and then wrote a summary of the evidence and preliminary recommendations. Final recommendations were determined by full group consensus. The summaries were combined into a single working document and all panel members edited and approved all subsequent drafts.

CONCLUSIONS

Carefully controlled studies to determine the incidence, etiology, risk factors, and most appropriate treatments for metabolic complications in HIV-1 infection are urgently needed. In the absence of these data, and to prevent acute illness and mitigate long-term risks, the panel recommends routine assessment and monitoring of glucose and lipid levels and assessment and monitoring of lactic acidemia and bone abnormalities if clinical signs or symptoms are detected. With the exception of body fat distribution abnormalities, specific treatments for these complications are also recommended. Successful long-term antiretroviral therapy will require diligent monitoring and preemptive treatment of metabolic complications to optimize the risk-benefit ratio of antiretroviral therapies.

Induction therapy with consensus interferon (CIFN) does not improve sustained virologic response in chronic hepatitis C

In patients infected with hepatitis C virus (HCV) genotype 1, sustained viral response (SVR) averages 10-40% depending on treatment regime. It has been proposed that high dose daily interferon (IFN) therapy early in therapy (induction dosing) may enhance SVR. In the present study we examined this issue and also assessed whether one could predict SVR and non-SVR, based on viral kinetics during the first month of induction therapy. End of treatment response and SVR was determined in 173 HCV infected patients who were treated with different induction doses of consensus interferon (CIFN) for one month followed by 11 months of standard 9 microg of CIFN thrice weekly (TIW). The second phase decline slope was calculated by log-linear regression on weekly measurements of serum HCV RNA during the first 7-28 days of treatment; rapid viral response (RVR) during the first month of induction dosing was defined as a decline of > 0.3 log copies/mL/week. Overall, SVR occurred in 11% of genotype 1 infected patients and 41% of patients with nongenotype 1. High dose induction therapy did not increase the rate of SVR, in either genotype 1 or genotype 2/3 infected patients. No patient without a RVR during the first month had SVR, while SVR occurred in 55% of the patients with RVR. RVR was the best predictor of SVR using multivariate analysis. These results indicate that induction dosing with CIFN does not improve SVR rates. They also suggest that early viral kinetics during the first month of therapy can predict non-SVR and thus save a patient a year long treatment which is fraught with side-effects and significant cost.

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.

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.

Fatal portal hypertension, liver failure, and mitochondrial dysfunction after HIV-1 nucleoside analogue-induced hepatitis and lactic acidaemia

Acute hepatitis with lactic acidosis is a life-threatening but reversible toxic effect on mitochondria of HIV-1 nucleoside-analogue treatment. We report fatal portal hypertension, liver failure, and persistent mitochondrial dysfunction in a man aged 65 years with HIV-1 infection who had recovered from nucleoside-analogue-induced acute hepatitis and lactic acidaemia more than 18 months previously. We believe that symptom free patients who receive nucleoside-analogue therapy should have hepatic function constantly monitored, especially those with past or present lactic acidaemia.

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.