Therapeutic Approaches to Nonalcoholic Fatty Liver Disease: Exercise Intervention and Related Mechanisms

Exercise training ameliorates nonalcoholic fatty liver disease (NAFLD) as well as obesity and metabolic syndrome. Although it is difficult to eliminate the effects of body weight reduction and increased energy expenditure—some pleiotropic effects of exercise training—a number of studies involving either aerobic exercise training or resistance training programs showed ameliorations in NAFLD that are independent of the improvements in obesity and insulin resistance. In vivo studies have identified effects of exercise training on the liver, which may help to explain the “direct” or “independent” effect of exercise training on NAFLD. Exercise training increases peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) expression, improves mitochondrial function and leads to reduced hepatic steatosis, inflammation, fibrosis, and tumor genesis. Crosstalk between the liver and adipose tissue, skeletal muscle and the microbiome is also a possible mechanism for the effect of exercise training on NAFLD. Although numerous studies have reported benefits of exercise training on NAFLD, the optimal duration and intensity of exercise for the prevention or treatment of NAFLD have not been established. Maintaining adherence of patients with NAFLD to exercise training regimes is another issue to be resolved. The use of comprehensive analytical approaches to identify biomarkers such as hepatokines that specifically reflect the effect of exercise training on liver functions might help to monitor the effect of exercise on NAFLD, and thereby improve adherence of these patients to exercise training. Exercise training is a robust approach for alleviating the pathogenesis of NAFLD, although further clinical and experimental studies are required

Influence of muscle fiber type composition on early fat accumulation under high-fat diet challenge

Objective: To investigate whether differences in muscle fiber types affect early-stage fat accumulation, under high fat diet challenge in mice. Methods: Twelve healthy male C57BL/6 mice experienced with short-term (6 weeks) diet treatment for the evaluation of early pattern changes in muscular fat. The mice were randomly divided into two groups: high fat diet (n = 8) and normal control diet (n = 4). Extra- and intra-myocellular lipid (EMCL and IMCL) in lumbar muscles (type I fiber predominant) and tibialis anterior (TA) muscle (type II fiber predominant) were determined using magnetic resonance spectroscopy (MRS). Correlation of EMCL, IMCL and their ratio between TA and lumbar muscles was evaluated. Results: EMCL increased greatly in both muscle types after high fat diet. IMCL in TA and lumbar muscles increased to a much lower extent, with a slightly greater increase in TA muscles. EMCLs in the 2 muscles were positively correlated (r = 0.84, p = 0.01), but IMCLs showed a negative relationship (r = -0.84, p = 0.01). In lumbar muscles, high fat diet significantly decreased type I fiber while it increased type II fiber (all p≤0.001). In TA muscle, there was no significant fiber type shifting (p>0.05). Conclusions: Under short-time high fat diet challenge, lipid tends to initially accumulate extra-cellularly. In addition, compared to type II dominant muscle, Type I dominant muscle was less susceptible to IMCL accumulation but more to fiber type shifting. These phenomena might reflect compensative responses of skeletal muscle to dietary lipid overload in order to regulate metabolic homeostasis

PDCD4 Knockdown Induces Senescence in Hepatoma Cells by Up-Regulating the p21 Expression

While the over-expression of tumor suppressor programmed cell death 4 (PDCD4) induces apoptosis, it was recently shown that PDCD4 knockdown also induced apoptosis. In this study, we examined the cell cycle regulators whose activation is affected by PDCD4 knockdown to investigate the contribution of PDCD4 to cell cycle regulation in three types of hepatoma cells: HepG2, Huh7 (mutant p53 and p16-deficient), and Hep3B (p53- and Rb-deficient). PDCD4 knockdown suppressed cell growth in all three cell lines by inhibiting Rb phosphorylation via down-regulating the expression of Rb itself and CDKs, which phosphorylate Rb, and up-regulating the expression of the CDK inhibitor p21 through a p53-independent pathway. We also found that apoptosis was induced in a p53-dependent manner in PDCD4 knockdown HepG2 cells (p53+), although the mechanism of cell death in PDCD4 knockdown Hep3B cells (p53-) was different. Furthermore, PDCD4 knockdown induced cellular senescence characterized by β-galactosidase staining, and p21 knockdown rescued the senescence and cell death as well as the inhibition of Rb phosphorylation induced by PDCD4 knockdown. Thus, PDCD4 is an important cell cycle regulator of hepatoma cells and may be a promising therapeutic target for the treatment of hepatocellular carcinoma

Efficacy of pegylated interferon plus ribavirin in combination with corticosteroid for two cases of combined hepatitis C and autoimmune hepatitis

The treatment strategy for cases of combined autoimmune hepatitis (AIH) and chronic hepatitis C (CHC) has not yet been established. A 47-year-old woman and a 53-year-old-woman were hospitalized for treatment of CHC. Ultrasonography and histological findings revealed that their liver was not cirrhotic but did have chronic damage. The histological findings of both patients were suggestive of AIH. The patients were systematically treated with pegylated interferon-alpha 2b plus ribavirin which was preceded by and combined with corticosteroid (CS), and showed sustained virological responses and normal liver function. Although these two patients with combined AIH and CHC were successfully treated with this regimen, careful attention to exacerbation of hepatic inflammation is needed because hepatitis C viral load was increased due to immunosuppression during CS treatment

In vivo monitoring of hydroxyl radical generation caused by x-ray irradiation of rats using the spin trapping/EPR technique

The measurement of hydroxyl radical in living animals irradiated with ionizing radiation should be required to clarify the mechanisms of radiation injury and the in vivo assessment of radiation protectors, because the generation of hydroxyl radical is believed to be one of the major triggers of radiation injury. In this study, hydroxyl radical generation was monitored by spin trapping the secondary methyl radical formed by the reaction of the hydroxyl radical with dimethyl sulfoxide (DMSO). Rats were injected intraperitoneally with a DMSO solution of a-phenyl-N-tert-butylnitrone (PBN). X-ray irradiation of the rats remarkably increased the six-line EPR signal in the bile. The strengthened signal was detectable above 40 Gy. The use of 13C-substituted DMSO revealed that the signal included methyl radical adduct of PBN as a major component. The EPR signal of PBN-methyl radical adduct was completely suppressed by pre-administration of methyl gallate, a scavenger of hydroxyl radical but not of methyl radical. Methyl gallate did not reduce the spin adducts to EPR-silent forms. These observations indicate that what we were measuring was the hydroxyl radical generated in vivo by x-ray irradiation. This is the first report of the in vivo monitoring ofhydroxyl radical generation at a radiation dose close to what people might receive in the case of radiological accident or radiation therapy

Pharmacokinetics of Acyl-Protected Hydrolyalamine Probe, 1-Aceoxy-3-carbamoyl-2,2,5,5-tetramethylpyrrodine, for In Vivo Application of the Probe

Hydroxylamines should be useful probes for in vivo ESR detection of reactive oxygen species (ROS), because they react with superoxide and peroxynitrite to generate nitroxyl radicals giving ESR signals. Acyl-protected hydroxylamine probe, 1-acetoxy-3-carbamoyl-2,2,5,5-tetramethylpyrrolidine (ACP), has been designed to be hydrolyzed to generate hydroxylamine in living body (Itoh et al. 2000, Chem. Lett., Yordanov et al. 2002, J. Med. Chem.). However, the pharmacokinetics of ACP in animal bodies is not understood. Therefore, we investigated the distribution of ACP, its hydroxylamine-form and its nitroxyl radical-form (carbamoyl-PROXYL) in mice after injection of ACP. ACP (140 mM, 200mL) was injected intravenously to male ddY mice (4 weeks old). Organs were removed 3, 10 and 30 min after the injection. Concentration of ACP and carbamoyl-PROXYL in the organ homogenates was measured with HPLC and X-band ESR spectroscopy, respectively. Concentration of hydroxylamine-form was estimated by measurement with X-band ESR after one electron oxidation. ACP was distributed in lung, stomach, heart, spleen, brain, and blood 3 min after intravenous injection. The content in brain was relatively low. The hydroxylamine-form was observed at high content in liver and kidney, whereas the content of ACP was very low in the both organs. Content of hydroxylamine-form decreased with time in liver and kidney, while it increased in other organs. The hydroxylamine-form was equally distributed in the organs except for brain 30 min after injection. Content of carbamoyl-PROXYL was still low at this time. Hydrolysis of ACP occurred remarkably in homogenates of liver and kidney. These observations indicate that ACP is hydrolyzed mainly in liver and kidney to hydroxylamine-form which is then distributed to other organs. These basic data about the pharmacokinetics of ACP are useful for in vivo ESR measurements of reactive oxygen species.The 10th International workshop on Bio-Medical ESR Spectroscopy and Imagin