Usefulness of adult medaka fish as a model for the evaluation of alcoholic fatty liver.

Alcohol has long been acknowledged to be one of the main causes of hepatic disorders. In recent years, with the advancements in antiviral therapies, the relative proportion that alcoholic liver disease contributes among liver diseases has increased, necessitating the establishment of a useful model for the elucidation of the mechanism of its development. In this study, we developed a model of alcoholic liver disease using medaka, a small-sized fish known for its usefulness as a model organism. After rearing medaka in water containing ethanol for 2 months, fat deposition was observed in their livers. In addition, on the basis of the metabolomic analysis of the liver to evaluate metabolic changes resulting from ethanol administration, the increases in ethanol metabolites and changes in lipid metabolism were assessed. As minimally invasive evaluation methods, transparent medaka enabled the macroscopic evaluation of the progression of alcoholic fatty liver, while ultrasonography enabled the quantification of the fatty deposition of the liver. Furthermore, intestinal microbiota, the composition of which is important for the development of alcoholic liver disease, was evaluated. Microbiota changes similar to those of humans with alcoholic liver disease were observed. This study demonstrates that the development of liver disease and its amelioration through drugs can be easily evaluated using the present model or modifications thereof. Thus, this study is expected to be useful in the elucidation of liver disease development.

Assessment of high-fat-diet-induced fatty liver in medaka.

Fatty liver, which has been continuously becoming more common in a number of patients, is the most common liver disease. For detailed analysis, a useful model for fatty liver is needed and fish are considered as a potential candidate. We assessed through direct observation of the liver, which is the most conventional method for non-invasive analysis of progression in fatty liver. By using transparent medaka (Oryzias latipes), we were able to observe changes in fat deposition in the liver. An analysis of the progression of fatty liver using ultrasound showed a significant increase in echo intensity, which indicates that this is a useful examination method. In addition, we clarified a metabolite profile in the medaka liver fed a high-fat diet (HFD), which had not previously been shown in detail. This medaka model, allowing non-invasive and repetitive assessment, is a useful model for the analysis of diseases that cause fatty liver in which changes in detailed metabolites are identified.

Evaluating effects of L-carnitine on human bone-marrow-derived mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are multipotent cells showing potential for use in regenerative medicine. Culture techniques that are more stable and methods for the more efficient production of MSCs with therapeutic efficacy are needed. We evaluate the effects of growing bone marrow (Bm)-derived MSCs in the presence of L-carnitine, which is believed to promote lipid metabolism and to suppress apoptosis. The presence of L-carnitine decreased the degree of drug-induced apoptosis and suppressed adipogenic differentiation. Metabolomic analysis by means of the exhaustive investigation of metabolic products showed that, in addition to increased ß-oxidation and the expression of all carnitine derivatives other than deoxycarnitine (an intermediate in carnitine synthesis), polysaturated and polyunsaturated acids were down-regulated. An integrated analysis incorporating both serial analysis of gene expression and metabolomics revealed increases in cell survival, suggesting the utility of carnitine. The addition of carnitine elevated the oxygen consumption rate by BmMSCs that had been cultured for only a few generations and those that had become senescent following repeated replication indicating that mitochondrial activation occurred. Our exhaustive analysis of the effects of various carnitine metabolites thus suggests that the addition of L-carnitine to BmMSCs during expansion enables efficient cell production.

In vitro antimicrobial effects of aztreonam, colistin, and the 3-drug combination of aztreonam, ceftazidime and amikacin on metallo-beta-lactamase-producing Pseudomonas aeruginosa.

BACKGROUND: There are limited choice of antimicrobial agents to treat infection with metallo-beta-lactamase-producing Pseudomonas aeruginosa. We evaluate the antimicrobial effects of aztreonam alone, colistin alone and the 3-drug combination of aztreonam, ceftazidime and amikacin on 23 strains of metallo-beta-lactamase-producing P. aeruginosa by time-killing tests. METHODS: Strains used were from different hospitals in Japan and had different pulse-field gel electrophoresis patterns by restriction with SpeI. The minimum inhibitory concentrations of 11 antimicrobial agents (piperacillin, piperacillin/tazobactam, imipenem, meropenem, aztreonam, ceftazidime, amikacin, tobramycin, arbekacin, ciprofloxacin and colistin) were determined using the agar dilution test. The effects of aztreonam, colistin and the combination of aztreonam, ceftazidime and amikacin were determined by time-killing studies. RESULTS: Bacteriostatic effects after 6 hours of drug exposure were observed in 12 strains (52.2%) of 23 strains of metallo-beta-lactamase-producing P. aeruginosa with 48 mg/l aztreonam, in 19 strains (82.6%) with the 3-drug combination of 16 mg/l aztreonam, 16 mg/l ceftazidime, and 4 mg/l amikacin, and in 23 strains (100%) with 2 mg/l colistin. Bactericidal effects after 6 h drug exposure were observed in 1 strain (4.3%) with 48 mg/l aztreonam, in 8 strains (30.4%) with the 3-drug combination and in all 23 strains (100%) with 2 mg/l colistin. CONCLUSION: Evaluation of in vitro antimicrobial effects on metallo-beta-lactamase-producing P. aeruginosa revealed relatively good effects of the 3-drug combination of aztreonam, ceftazidime and amikacin and marked effects of colistin.