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

Renal impairment with sublethal tubular cell injury in a chronic liver disease mouse model

The pathogenesis of renal impairment in chronic liver diseases (CLDs) has been primarily studied in the advanced stages of hepatic injury. Meanwhile, the pathology of renal impairment in the early phase of CLDs is poorly understood, and animal models to elucidate its mechanisms are needed. Thus, we investigated whether an existing mouse model of CLD induced by 3, 5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC) shows renal impairment in the early phase. Renal injury markers, renal histology (including immunohistochemistry for tubular injury markers and transmission electron microscopy), autophagy, and oxidative stress were studied longitudinally in DDC- and standard diet-fed BALB/c mice. Slight but significant renal dysfunction was evident in DDC-fed mice from the early phase. Meanwhile, histological examinations of the kidneys with routine light microscopy did not show definitive morphological findings, and electron microscopic analyses were required to detect limited injuries such as loss of brush border microvilli and mitochondrial deformities. Limited injuries have been recently designated as sublethal tubular cell injury. As humans with renal impairment, either with or without CLD, often show almost normal tubules, sublethal injury has been of particular interest. In this study, the injuries were associated with mitochondrial aberrations and oxidative stress, a possible mechanism for sublethal injury. Intriguingly, two defense mechanisms were associated with this injury that prevent it from progressing to apparent cell death: autophagy and single-cell extrusion with regeneration. Furthermore, the renal impairment of this model progressed to chronic kidney disease with interstitial fibrosis after long-term DDC feeding. These findings indicated that DDC induces renal impairment with sublethal tubular cell injury from the early phase, leading to chronic kidney disease. Importantly, this CLD mouse model could be useful for studying the pathophysiological mechanisms of sublethal tubular cell injury

Mitochondrial fission in hepatocytes as a potential therapeutic target for nonalcoholic steatohepatitis

[Aim] The mitochondria are highly plastic and dynamic organelles; mitochondrial dysfunction has been reported to play causative roles in diabetes, cardiovascular diseases, and nonalcoholic fatty liver disease (NAFLD). However, the relationship between mitochondrial fission and NAFLD pathogenesis remains unknown. We aimed to investigate whether alterations in mitochondrial fission could play a role in the progression of NAFLD. [Methods] Mice were fed a standard diet or choline-deficient, L-amino acid-defined (CDAA) diet with vehicle or mitochondrial division inhibitor-1. [Results] Substantial enhancement of mitochondrial fission in hepatocytes was triggered by 4 weeks of feeding and was associated with changes reflecting the early stage of human nonalcoholic steatohepatitis (NASH), steatotic change with liver inflammation, and hepatocyte ballooning. Excessive mitochondrial fission inhibition in hepatocytes and lipid metabolism dysregulation in adipose tissue attenuated liver inflammation and fibrogenesis but not steatosis and the systemic pathological changes in the early and chronic fibrotic NASH stages (4- and 12-week CDAA feeding). These beneficial changes due to the suppression of mitochondrial fission against the liver and systemic injuries were associated with decreased autophagic responses and endoplasmic reticulum stress in hepatocytes. Injuries to other liver cells, such as endothelial cells, Kupffer cells, and hepatic stellate cells, were also attenuated by the inhibition of mitochondrial fission in hepatocytes. [Conclusions] Taken together, these findings suggest that excessive mitochondrial fission in hepatocytes could play a causative role in NAFLD progression by liver inflammation and fibrogenesis through altered cell cross-talk. This study provides a potential therapeutic target for NAFLD

The effectiveness and limitations of triphenyltetrazolium chloride to detect acute myocardial infarction at forensic autopsy.

Triphenyltetrazolium chloride (TTC) is one of the most conventional stains to detect infarcted area of the heart in animal experiments. However, its availability and limitations have not been thoroughly discussed in the forensic field. Here, authors stained human hearts with TTC soon after the harvest. Photographs of the samples were analyzed using image analysis software, which evaluated the occupying ratio of the stained area on the surface of each slice. The results showed that the stainability of TTC declines with the length of the postmortem interval (PMI). Specimens reacted well to TTC within 1.5 days after death and then decreased the stainability logarithmically with PMI (y = - 0.294 In (x) + 1.0441; x = PMI, y = TTC-stained areatotal myocardial area, R = 0.5673). Samples with old myocardial infarction produced clear TTC contrast; normal tissue is vivid red, and fibrotic myocardium is white discoloration. In acute myocardial infarction cases where death occurred within 9 hours after the attack, however, the detection of infarcted area was very difficult even when PMI was less than 1.5 days. In summary, the TTC method may be useful within 1.5 days after death, but short suffering period before death disturbs its staining efficiency

Thioredoxin-interacting protein suppresses bladder carcinogenesis.

Thioredoxin-interacting protein (TXNIP), which has a tumor-suppressive function, is underexpressed in some human cancers. The function of TXNIP in vivo in carcinogenesis is not fully understood. Here, we show TXNIP to be downregulated in human bladder cancer according to grade and stage and also that loss of TXNIP expression facilitates bladder carcinogenesis using a mouse bladder cancer model. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced bladder cancer was found in 100% of Txnip knockout (KO) mice at week 8 of 0.025% BBN administration but in only 22% of wild-type (WT) mice at the same point. Among growth stimulators, phospho-extracellular signal-regulated kinase (pERK) expression was stronger during bladder carcinogenesis in Txnip-KO mice than in WT mice. We then evaluated TXNIP's effects on ERK activation through various growth stimulators and their receptors. Overexpression of TXNIP in human bladder cancer cells attenuated pERK expression upon stimulation with stromal cell-derived factor-1 (SDF-1) but not with epidermal growth factor or insulin-like growth factor-1. In Txnip-KO mice, immunohistochemical analysis showed enhanced expression of C-X-C chemokine receptor type 4 (CXCR4), the receptor of SDF-1, and of pERK in urothelial cells during BBN-induced bladder carcinogenesis. Finally, subcutaneous injection of CXCR4 antagonist, TF14016, attenuated pERK in urothelial cells and suppressed bladder carcinogenesis. These data indicate that TXNIP negatively regulates bladder carcinogenesis by attenuating SDF-1-CXCR4-induced ERK activation. This signal transduction pathway can be a potent target in preventing or treating bladder cancer

Graft rejection and hyperacute graft-versus-host disease in stem cell transplantation from non-inherited maternal antigen complementary HLA-mismatched siblings

金沢大学大学院医学系研究科機能再生学Human leukocyte antigen (HLA)-mismatched stem cell transplantation from non-inherited maternal antigen (NIMA)-complementary donors is known to produce stable engraftment without inducing severe graft-versus-host disease (GVHD). We treated two patients with acute myeloid leukemia (AML) and one patient with severe aplastic anemia (SAA) with HLA-mismatched stem cell transplantation (SCT) from NIMA-complementary donors (NIMA-mismatched SCT). The presence of donor and recipient-derived blood cells in the peripheral blood of recipient (donor microchimerism) and donor was documented respectively by amplifying NIMA-derived DNA in two of the three patients. Graft rejection occurred in the SAA patient who was conditioned with a fludarabine-based regimen. Grade III and grade IV acute GVHD developed in patients with AML on day 8 and day 11 respectively, and became a direct cause of death in one patient. The findings suggest that intensive conditioning and immunosuppression after stem cell transplantation are needed in NIMA-mismatched SCT even if donor and recipient microchimerisms is detectable in the donor and recipient before SCT. © 2007 The Authors