Effect of stavudine on mitochondrial genome and fatty acid oxidation in lean and obese mice.

International audienceLike other antihuman immunodeficiency virus dideoxynucleosides, stavudine may occasionally induce lactic acidosis and perhaps lipodystrophy in metabolically or genetically susceptible patients. We studied the effects of stavudine on mitochondrial DNA (mtDNA), fatty acid oxidation, and blood metabolites in lean and genetically obese (ob/ob) mice. In lean mice, mtDNA was depleted in liver and skeletal muscle, but not heart and brain, after 6 weeks of stavudine treatment (500 mg/kg/day). With 100 mg/kg/day, mtDNA transiently decreased in liver, but was unchanged at 6 weeks in all organs, including white adipose tissue (WAT). Despite unchanged mtDNA levels, lack of significant oxidative mtDNA lesions (as assessed by long polymerase chain reaction experiments), and normal blood lactate/pyruvate ratios, lean mice treated with stavudine for 6 weeks had increased fasting blood ketone bodies, due to both increased hepatic fatty acid beta-oxidation and decreased peripheral ketolysis. In obese mice, basal WAT mtDNA was low and was further decreased by stavudine. In conclusion, stavudine can decrease hepatic and muscle mtDNA in lean mice and can also cause ketoacidosis during fasting without altering mtDNA. Stavudine depletes WAT mtDNA only in obese mice. Fasting and ketoacidosis could trigger decompensation in patients with incipient lactic acidosis, whereas WAT mtDNA depletion could cause lipodystrophy in genetically susceptible patients

Effect of stavudine on mitochondrial genome and fatty acid oxidation in lean and obese mice.

International audienceLike other antihuman immunodeficiency virus dideoxynucleosides, stavudine may occasionally induce lactic acidosis and perhaps lipodystrophy in metabolically or genetically susceptible patients. We studied the effects of stavudine on mitochondrial DNA (mtDNA), fatty acid oxidation, and blood metabolites in lean and genetically obese (ob/ob) mice. In lean mice, mtDNA was depleted in liver and skeletal muscle, but not heart and brain, after 6 weeks of stavudine treatment (500 mg/kg/day). With 100 mg/kg/day, mtDNA transiently decreased in liver, but was unchanged at 6 weeks in all organs, including white adipose tissue (WAT). Despite unchanged mtDNA levels, lack of significant oxidative mtDNA lesions (as assessed by long polymerase chain reaction experiments), and normal blood lactate/pyruvate ratios, lean mice treated with stavudine for 6 weeks had increased fasting blood ketone bodies, due to both increased hepatic fatty acid beta-oxidation and decreased peripheral ketolysis. In obese mice, basal WAT mtDNA was low and was further decreased by stavudine. In conclusion, stavudine can decrease hepatic and muscle mtDNA in lean mice and can also cause ketoacidosis during fasting without altering mtDNA. Stavudine depletes WAT mtDNA only in obese mice. Fasting and ketoacidosis could trigger decompensation in patients with incipient lactic acidosis, whereas WAT mtDNA depletion could cause lipodystrophy in genetically susceptible patients

High hepatic glutathione stores alleviate Fas-induced apoptosis in mice.

International audienceBACKGROUND/AIMS: The agonistic Jo2 anti-Fas antibody reproduces human fulminant hepatitis in mice. We tested the hypothesis that enhancing hepatic glutathione (GSH) stores may prevent Jo2-induced apoptosis. METHODS: We fed mice with a normal diet or a sulfur amino acid-enriched (SAA(+)) diet increasing hepatic GSH by 63%, and challenged these mice with Jo2. RESULTS: The SAA(+) diet markedly attenuated the Jo2-mediated decrease in hepatic GSH and the increase in the oxidized glutathione (GSSG)/GSH ratio in cytosol and mitochondria. The SAA(+) diet prevented protein kinase Czeta (PKCzeta) and p47(phox) phosphorylations, Yes activation, Fas-tyrosine phosphorylation, Bid truncation, Bax, and cytochrome c translocations, the mitochondrial membrane potential collapse, caspase activation, DNA fragmentation, hepatocyte apoptosis, and mouse lethality after Jo2 administration. The protective effect of the SAA(+) diet was abolished by a small dose of phorone decreasing hepatic GSH back to the levels observed in mice fed the normal diet. Conversely, administration of GSH monoethyl ester after Jo2 administration prevented hepatic GSH depletion and attenuated toxicity in mice fed with the normal diet. CONCLUSIONS: The SAA(+) diet preserves GSSG/GSH ratios, and prevents PKCzeta and p47(phox) phosphorylations, Yes activation, Fas-tyrosine phosphorylation, mitochondrial permeabilization, and hepatic apoptosis after Fas stimulation. GSH monoethyl ester is also protective, suggesting possible clinical applications

Modelo experimental de esteatohepatite não-alcoólica com dieta deficiente em metionina e colina Model of experimental nonalcoholic steatohepatitis from use of methionine and choline deficient diet

CONTEXTO: Ainda existem vários aspectos desconhecidos a respeito da esteatohepatite não-alcoólica, principalmente em relação à fisiopatologia e ao seu tratamento medicamentoso. Dessa forma, os modelos experimentais são importante para o melhor entendimento dessa doença, bem como para a avaliação do efeito das drogas. OBJETIVO: Desenvolver um modelo experimental de esteatohepatite não-alcoólica a partir do uso de dieta deficiente em metionina e colina. MÉTODOS: Foram utilizados 50 ratos machos da linhagem Wistar. A dieta deficiente em metionina e colina foi processada de forma artesanal. Um grupo de 40 animais recebeu a dieta durante 90 dias e utilizou-se um grupo controle com 10 ratos que recebeu ração padronizada pelo mesmo período. Após, os animais foram mortos por decapitação e foi realizada laparotomia com hepatectomia total e preparo do material para análise macroscópica e histológica. O nível de significância foi a = 0,05. RESULTADOS: Os ratos que receberam a dieta apresentaram perda significativa de peso, com achados de desnutrição e todos mostraram, pelo menos, algum grau de esteatose macrovesicular. O diagnóstico de esteatohepatite não-alcoólica foi realizado em 27 (70%) dos 39 ratos que receberam a dieta. Nenhum dos 10 ratos que recebeu ração apresentou alterações histológicas. CONCLUSÃO:A dieta com restrição de metionina e colina desenvolvida apresenta índices elevados de indução de esteatose e esteatohepatite em modelo animal com baixo custo.<br>CONTEXT: There are still many unknown aspects about nonalcoholic steatohepatitis, especially regarding its pathophysiology and pharmacological treatment. Thus, experimental models are important for a better understanding of this disease and the evaluation of the effects of drugs. OBJECTIVE: To develop a model of experimental nonalcoholic steatohepatitis from use of methionine and choline deficient diet. METHODS: Fifty Wistar male rats were studied. A methionine and choline deficient diet has been processed in a craft. A group of 40 animals received the deficient diet for 90 days, and a group of 10 rats (control group) received the standardized ration in the same period. After, the animals were killed by decapitation, and laparotomy was performed. Hepatectomy was performed and the liver was studied by macroscopy and microscopy. The level of significance considered was of 0,05. RESULTS: The rats that received the deficient diet showed significant loss of weight with findings from malnutrition and all of them had at least some degree of macrovesicular steatosis. The diagnosis of nonalcoholic steatohepatitis was performed in 27 (70%) of the 39 rats that received this deficient diet (1 rat died during the study). None of the 10 rats that received the standardized diet had histological abnormalities. CONCLUSION: The diet restricted in methionine and choline induced steatosis and steatohepatitis in an animal model with low cost

Mitochondrial involvement in drug-induced liver injury.

International audienceMitochondrial 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