An Unreported Congenital Anomaly: Aneurysm of the Lateral Half of the Mitral Valve.

This case draws our attention to a new type of mitral valve anomaly, which seems to be congenital. A 42-year-old man with symptomatic primary severe mitral regurgitation was admitted to our hospital. Echocardiography revealed an aneurysm of the half of the valve, on the anterolateral commissure side, with significant excess tissue. The other half of the valve was normal. The two parts seemed to be separated by a continuous fibrous raphe. The anterolateral papillary muscle was hyperplasic and gave the main part of chordae tendinae.

Prolonged ethanol administration depletes mitochondrial DNA in MnSOD-overexpressing transgenic mice, but not in their wild type littermates.

Alcohol consumption increases reactive oxygen species formation and lipid peroxidation, whose products can damage mitochondrial DNA (mtDNA) and alter mitochondrial function. A possible role of manganese superoxide dismutase (MnSOD) on these effects has not been investigated. To test whether MnSOD overexpression modulates alcohol-induced mitochondrial alterations, we added ethanol to the drinking water of transgenic MnSOD-overexpressing (TgMnSOD) mice and their wild type (WT) littermates for 7 weeks. In TgMnSOD mice, alcohol administration further increased the activity of MnSOD, but decreased cytosolic glutathione as well as cytosolic glutathione peroxidase activity and peroxisomal catalase activity. Whereas ethanol increased cytochrome P-450 2E1 and mitochondrial ROS generation in both WT and TgMnSOD mice, hepatic iron, lipid peroxidation products and respiratory complex I protein carbonyls were only increased in ethanol-treated TgMnSOD mice but not in WT mice. In ethanol-fed TgMnSOD mice, but not ethanol-fed WT mice, mtDNA was depleted, and mtDNA lesions blocked the progress of polymerases. The iron chelator, DFO prevented hepatic iron accumulation, lipid peroxidation, protein carbonyl formation and mtDNA depletion in alcohol-treated TgMnSOD mice. Alcohol markedly decreased the activities of complexes I, IV and V of the respiratory chain in TgMnSOD, with absent or lesser effects in WT mice. There was no inflammation, apoptosis or necrosis, and steatosis was similar in ethanol-treated WT and TgMnSOD mice. In conclusion, prolonged alcohol administration selectively triggers iron accumulation, lipid peroxidation, respiratory complex I protein carbonylation, mtDNA lesions blocking the progress of polymerases, mtDNA depletion and respiratory complex dysfunction in TgMnSOD mice but not in WT mice.

Partial leptin deficiency favors diet-induced obesity and related metabolic disorders in mice.

Partial leptin deficiency is not uncommon in the general population. We hypothesized that leptin insufficiency could favor obesity, nonalcoholic steatohepatitis (NASH), and other metabolic abnormalities, particularly under high calorie intake. Thus, mice partially deficient in leptin (ob/+) and their wild-type (+/+) littermates were fed for 4 mo with a standard-calorie (SC) or a high-calorie (HC) diet. Some ob/+ mice fed the HC diet were also treated weekly with leptin. Our results showed that, when fed the SC diet, ob/+ mice did not present significant metabolic abnormalities except for elevated levels of plasma adiponectin. Under high-fat feeding, increased body fat mass, hepatic steatosis, higher plasma total cholesterol, and glucose intolerance were observed in +/+ mice, and these abnormalities were further enhanced in ob/+ mice. Furthermore, some metabolic disturbances, such as blunted plasma levels of leptin and adiponectin, reduced UCP1 expression in brown adipose tissue, increased plasma liver enzymes, beta-hydroxybutyrate and triglycerides, and slight insulin resistance, were observed only in ob/+ mice fed the HC diet. Whereas de novo fatty acid synthesis in liver was decreased in +/+ mice fed the HC diet, it was disinhibited in ob/+ mice along with the restoration of the expression of several lipogenic genes. Enhanced expression of several genes involved in fatty acid oxidation was also observed only in ob/+ animals. Leptin supplementation alleviated most of the metabolic abnormalities observed in ob/+ fed the HC diet. Hence, leptin insufficiency could increase the risk of obesity, NASH, glucose intolerance, and hyperlipidemia in a context of calorie overconsumption.

Beta-aminoisobutyric acid prevents diet-induced obesity in mice with partial leptin deficiency.

Beta-Aminoisobutyric acid (BAIBA), a thymine catabolite, increases fatty acid oxidation (FAO) in liver and reduces the gain of body fat mass in Swiss (lean) mice fed a standard chow. We determined whether BAIBA could prevent obesity and related metabolic disorders in different murine models. To this end, BAIBA (100 or 500 mg/kg/day) was administered for 4 months in mice totally deficient in leptin (ob/ob). BAIBA (100 mg/kg/day) was also given for 4 months in wild-type (+/+) mice and mice partially deficient in leptin (ob/+) fed a high-calorie (HC) diet. BAIBA did not limit obesity and hepatic steatosis in ob/ob mice, but reduced liver cytolysis and inflammation. In ob/+ mice fed the HC diet, BAIBA fully prevented, or limited, the gain of body fat, steatosis and necroinflammation, glucose intolerance, and hypertriglyceridemia. Plasma beta-hydroxybutyrate was increased, whereas expression of carnitine palmitoyltransferase-1 was augmented in liver and white adipose tissue. Acetyl-CoA carboxylase was more phosphorylated, and de novo lipogenesis was less induced in liver. These favorable effects of BAIBA in ob/+ mice were associated with a restoration of plasma leptin levels. The reduction of body adiposity afforded by BAIBA was less marked in +/+ mice. Finally, BAIBA significantly stimulated the secretion of leptin in isolated ob/+ adipose cells, but not in +/+ cells. Thus, BAIBA could limit triglyceride accretion in tissues through a leptin-dependent stimulation of FAO. As partial leptin deficiency is not uncommon in the general population, supplementation with BAIBA may help to prevent diet-induced obesity and related metabolic disorders in low leptin secretors.

High doses of stavudine induce fat wasting and mild liver damage without impairing mitochondrial respiration in mice.

OBJECTIVE: Stavudine (d4T), a nucleoside reverse-transcriptase inhibitor (NRTI), can induce lipoatrophy, fatty liver, hyperlactataemia and abnormal liver tests. NRTI toxicity is usually ascribed to mitochondrial DNA (mtDNA) depletion and impaired mitochondrial respiration. However, NRTIs could have effects unrelated to mtDNA. Recently, we reported that 100 mg/kg/day of d4T stimulated fatty acid oxidation (FAO) in mouse liver, and reduced body fatness without depleting white adipose tissue (WAT) mtDNA. We hypothesized that higher d4T doses could further reduce adiposity, while inhibiting hepatic FAO. METHODS: Mice were treated for 2 weeks with d4T (500 mg/kg/day), L-carnitine (200 mg/kg/day) or both drugs concomitantly. Body fatness was assessed by dual energy X-ray absorptiometry, and investigations were performed in plasma, liver, muscle and WAT. RESULTS: D4T reduced the gain of body adiposity, WAT leptin, whole body FAO and plasma ketone bodies, and increased liver triglycerides and plasma aminotransferases with mild ultrastructural abnormalities in hepatocytes. Plasma lactate and respiratory chain activities in tissues were unchanged. Stearoyl-CoA desaturase (SCD-1), an enzyme negatively regulated by leptin, was overexpressed in liver. High doses of beta-aminoisobutyric acid (BAIBA), a d4T catabolite, increased plasma ketone bodies. Although L-carnitine did not correct body adiposity, it prevented d4T-induced impairment of FAO and liver abnormalities. CONCLUSIONS: D4T overdosage triggers fat wasting, leptin insufficiency and mild liver damage, without causing respiratory chain dysfunction. Overexpression of SCD-1 reduces fatty acid oxidation and overcomes the stimulating effect of BAIBA on hepatic FAO. L-carnitine does not correct leptin insufficiency but prevents d4T-induced impairment of FAO and liver damage.

Tamoxifen inhibits topoisomerases, depletes mitochondrial DNA, and triggers steatosis in mouse liver.

Although tamoxifen can trigger steatohepatitis, the mechanism of steatosis is unclear. We hypothesized that this DNA-intercalating, cationic amphiphilic drug could accumulate within mitochondria to impair fatty acid oxidation, respiration, and mitochondrial DNA relaxation and synthesis. We studied the in vitro effects of tamoxifen on topoisomerases and mouse liver mitochondria and its in vivo hepatic effects in mice treated for 1 to 28 days with a daily dose of tamoxifen reproducing the plasma concentrations observed in humans. In vitro, tamoxifen inhibited topoisomerase-mediated plasmid DNA relaxation. It accumulated 40-fold inside mitochondria and inhibited both respiration and fatty acid oxidation. In vivo, a single dose of tamoxifen inhibited palmitic acid oxidation and hepatic lipoprotein secretion. Tamoxifen administration also decreased mitochondrial DNA synthesis and progressively depleted hepatic mitochondrial DNA, down to 40% of control values at 28 days. The decrease in mitochondrial DNA-encoded respiratory complexes sensitized mitochondria to the inhibitory effects of tamoxifen on mitochondrial respiration. Hepatic steatosis was absent at 5 days, mild at 12 days, and moderate at 28 days. The fatty acid synthase protein was normally expressed at 12 days but was decreased by 52% at 28 days. In conclusion, tamoxifen decreases hepatic triglyceride secretion, and it accumulates electrophoretically in mitochondria, where it impairs beta-oxidation and respiration. Tamoxifen also inhibits topoisomerases and mitochondrial DNA synthesis and progressively depletes hepatic mitochondrial DNA in vivo. These combined effects could decrease fat removal from the liver, thus causing hepatic steatosis despite a secondary down-regulation of hepatic fatty acid synthase expression.

[Inflammatory pseudo-tumor of the liver: is pre-operative diagnosis possible?]. / Pseudo-tumeur inflammatoire du foie: le diagnostic pré-opératoire est-il possible?

UNLABELLED: Inflammatory pseudo-tumors of the liver are rare and difficult to diagnose, mimicking malignant tumors. OBJECTIVES: To specify the circumstances of detection and the clinical, biological, radiological and pathological features of inflammatory pseudo-tumors, in order to improve preoperative diagnosis. METHODS: Diagnosis of inflammatory pseudo-tumors of the liver was performed on surgical specimens in 8 patients from January 1987 to January 2001. We retrospectively analyzed the clinical, biological, radiological and pathological features of these 8 inflammatory pseudo-tumors. RESULTS: All the patients (5 females and 3 males) presented a chronic infectious syndrome and/or previous history of chronic inflammatory disease. The correlation between biological, radiological and pathological aspects showed two distinctive types of inflammatory pseudo-tumors: a type revealed by a biological inflammatory syndrome, with a non encapsulated, heterogeneous and hypervascular lesion at imaging, and a dense fibroblastic inflammatory pseudo-tumor with portal endophlebitis on histology (n=5), and a type without inflammatory syndrome, with an encapsulated, homogeneous, hypovascular lesion at imaging and abundant necrosis on histology (n=3). CONCLUSION: The analysis of previous history, of clinical, biological and radiological presentations, specially MRI, could predict the diagnosis of inflammatory lesion which must be confirmed by trans-parietal biopsy to avoid inappropriate radical hepatectomy.