Teruki Miyake

Real‐time tissue elastography for evaluation of hepatic fibrosis and portal hypertension in nonalcoholic fatty liver diseases

The aim of this study was to prospectively measure liver stiffness with real‐time tissue elastography in patients with nonalcoholic fatty liver diseases (NAFLD) and to compare the result with the clinical assessment of fibrosis using histological stage. One hundred and eighty‐one prospectively enrolled patients underwent real‐time tissue elastography, with the first 106 being analyzed as the training set and the remaining 75 being evaluated as the validation set. Hepatic and splenic elastic ratios were calculated and compared with stage of histological fibrosis. Portal hypertension (PH) was assessed. Real‐time tissue elastography cut‐off values by stage in the training set were 2.47 for F1, 2.67 for F2, 3.02 for F3, and 3.36 for F4. Using these cut‐off values, the diagnostic accuracy of hepatic fibrosis in the validation set was 82.6%‐96.0% in all stages. Only portal fibrosis correlated with the hepatic elastic ratio by multivariate analysis. The area under the receiver operating characteristic curve of elastic ratio better correlated than serum fibrosis markers in both early and advanced fibrosis stages. Patients with PH, defined by splenic elasticity, had early fibrosis. Patients with severe PH were found only in the group with cirrhosis. Conclusion: Real‐time tissue elastography is useful in evaluating hepatic fibrosis and PH in patients with NAFLD. (HEPATOLOGY 2012)

B Cell-Activating Factor Controls the Production of Adipokines and Induces Insulin Resistance

Visceral adipose tissue (VAT) inflammation has been linked to the pathogenesis of insulin resistance and metabolic syndrome. VAT has recently been established as a new component of the immune system and is involved in the production of various adipokines and cytokines. These molecules contribute to inducing and accelerating systemic insulin resistance. In this report, we investigated the role of B cell‐activating factor (BAFF) in the induction of insulin resistance. We investigated BAFF levels in the sera and VAT of obese mice. In obese mice, the BAFF levels were preferentially increased in VAT and sera compared to these levels in normal control mice. Next, we treated mice with BAFF to analyze its influence on insulin sensitivity. BAFF impaired insulin sensitivity in normal mice. Finally, we investigated the mechanisms underlying insulin resistance induced by BAFF in adipocytes. BAFF also induced alterations in the expression levels of genes related to insulin resistance in adipocytes. In addition, BAFF directly affected the glucose uptake and phosphorylation of insulin receptor substrate‐1 in adipocytes. We propose that autocrine or paracrine BAFF and BAFF‐receptor (BAFF‐R) interaction in VAT leads to impaired insulin sensitivity via inhibition of insulin signaling pathways and alterations in adipokine production.

Impaired dendritic cell functions because of depletion of natural killer cells disrupt antigen-specific immune responses in mice: restoration of adaptive immunity in natural killer-depleted mice by antigen-pulsed dendritic cell

The primary aim of this study was to evaluate the role of natural killer (NK) cells on antigen‐specific adaptive immune responses. After analysing the mechanism of impaired adaptive immune responses of NK‐depleted mice, an immune interventional approach was developed to restore adaptive immunity in NK‐depleted mice. NK cells were depleted from mice by administration of anti‐asialo GM1 antibody (100 μl/mouse), twice, at an interval of 48 h. Hepatitis B surface antigen (HBsAg) was administered intraperitoneally to normal C57BL/6 mice (control mice) and NK‐depleted mice. The levels of antibody to HBsAg (anti‐HBs) in the sera and HBsAg‐specific lymphocytes in the spleen were assessed. The functions of T lymphocytes, B lymphocytes and dendritic cells (DCs) were evaluated in vitro. HBsAg‐pulsed DCs were prepared by culturing spleen DCs with HBsAg for 48 h and administered once to NK‐depleted mice. The levels of anti‐HBs in the sera and HBsAg‐specific lymphocytes were significantly lower in NK‐depleted mice compared with control mice (P < 0·05). The functions of T and B lymphocytes were similar between control mice and NK‐depleted mice. However, the functions of spleen DC and liver DC were significantly lower in NK‐depleted mice compared with control mice (P < 0·05). Administration of HBsAg‐pulsed DCs, but not HBsAg, induced HBsAg‐specific humoral and cellular immune responses in NK‐depleted mice. Our study suggests that cross‐talk between NK cells and DCs regulates the magnitude of adaptive immunity. In addition, antigen‐pulsed immunogenic DCs represent potent immune modulator even if subjects with diminished innate immunity.

Diminished immune response to vaccinations in obesity: Role of myeloid-derived suppressor and other myeloid cells

Obesity is a chronic inflammatory condition associated with an increased production of cytokines and exacerbated immune response. However, obese subjects are susceptible to infections and respond poorly to vaccines. This study evaluated the immune responses of obese mice and the underlying mechanisms by exploring the roles of myeloid cells. Diet-induced obese (DIO) mice were prepared from C57BL/6J mice fed a high-calorie and high-fat diet for 12 weeks. Humoral and cellular immune responses of DIO mice to a hepatitis B vaccine containing the hepatitis B surface antigen (HBsAg) were assessed in sera and via a lymphoproliferative assay, respectively. The effects of CD11b(+)GR1(+) myeloid-derived suppressor cells (MDSC) and CD11b(+)GR1(-) non-MDSC on T cell proliferation and cytokine production were compared via a cell culture system. The production of cytokines, expression of activation and exhaustion markers, and proportions of apoptotic T cells were estimated with flow cytometry. Increased T and B lymphocyte proliferation and higher interferon-γ and tumor necrosis factor-α levels were detected in spleen cells and liver non-parenchymal cell cultures of DIO mice compared to controls (p<0.05). However, antibody to HBsAg (anti-HBs) levels and HBsAg-specific T cell proliferation were significantly lower in DIO mice compared to controls (p<0.05). The addition of MDSC, but not non-MDSC, induced a decrease in HBsAg-specific T cell proliferation, lower cytokine production, decrease in T cell activation, and increase in T cell exhaustion and apoptosis (p<0.05). MDSC play an important role in mediating impaired antigen-specific immunity.

Blockade of B-cell-activating factor signaling enhances hepatic steatosis induced by a high-fat diet and improves insulin sensitivity

Chronic inflammation is an important contributor to the development and progression of metabolic syndrome. Recent evidence indicates that, in addition to innate immune cells, adaptive immune cells have an important role in this process. We previously showed that the serum level of B-cell-activating factor (BAFF) was increased in patients with nonalcoholic steatohepatitis. However, it is currently unknown whether BAFF and BAFF-R (BAFF-R) have a role in lipid metabolism in the liver. To address this issue, the role played by BAFF and BAFF-R signaling in the development of insulin resistance and hepatic steatosis was examined in BAFF-R−/− mice fed a high-fat diet (HFD). Furthermore, the effect of BAFF on lipid metabolism in hepatocytes was analyzed in vitro. BAFF-R−/− mice showed improvements in HFD-induced obesity and insulin resistance. In addition, the number of B cells, levels of serum IgG, and inflammation of visceral fat were reduced in these mice. However, the expression of steatogenic genes and fatty acid deposition in the liver was higher in these mice than in control mice. BAFF was also found to downregulate the expression of steatogenesis genes and enhance steatosis in hepatocytes through BAFF-R. Collectively, these data indicated that, in addition to its known functions in inflammation and glucose metabolism, BAFF has a protective role in hepatic steatosis by regulating lipid metabolism in the liver.

Non-alcoholic fatty liver disease: factors associated with its presence and onset.

Non‐alcoholic fatty liver disease (NAFLD) may progress to cirrhosis, liver failure, and complicated hepatocellular carcinoma. In addition, NAFLD is a risk factor for the development of other serious diseases, such as diabetes or cardiovascular disease. Therefore, the detection of early‐stage NAFLD is important. Many studies have described the factors that predict the presence of NAFLD and its onset, and several markers have been identified. These markers have enabled the identification of high‐risk patients and have improved routine medical practice. To prevent advanced disease, clinicians need to have simple markers that predict the onset of NAFLD so that interventions can be started at much earlier stages of disease. This review summarizes the current state of knowledge regarding independent factors, as reported in large studies, that predict the presence of NAFLD and its onset, especially markers that can be used in daily medical practice, such as physical measurements and blood tests.

Obesity and gastrointestinal liver disorders in Japan

In Japan, the prevalence of obesity in adult men has increased since the 1970s, while that in adult women has not changed. The prevalence of obesity in 5‐, 8‐, 11‐, and 14‐year‐old boys and girls increased from the late 1980s to late 1990s and has decreased since 2000, while that in 17‐year‐old girls increased in 2002, similar to that for boys, but has since decreased. In 2009, 33.3% of adult men and 25.0% of adult women were obese, and 8–10% of children (age, 5–17 years) were obese. The prevalence of visceral obesity in adults was 50.8% of men and 18.0% of women. Obesity, especially visceral obesity, affects insulin resistance and increases metabolic diseases (diabetes mellitus, dyslipidemia, hypertension, cardiovascular disease, and non‐alcoholic fatty liver disease [NAFLD]) and various cancers. In Japan, with a body mass index (BMI) of 23–25 as the reference category, the hazard ratio of total mortality is 1.36 for a BMI of 30–40 in men and 1.37 with a BMI of 30–40 in women. The frequency of patients with NAFLD has gradually increased in proportion to the increase in the population with obesity. From recent studies in Japan, the number of NAFLD patients is estimated to be 10 million, and around 2 million are considered to have non‐alcoholic steatohepatitis. Dietary and behavioral modification is effective for body weight loss and for improvement of obesity‐related gastrointestinal liver diseases. If necessary, bariatric surgery is useful for obesity treatment.

A relationship between motilin and growth hormone secretagogue receptors

The motilin receptor (MR) belongs to a family of Class I G protein-coupled receptors that also includes growth hormone secretagogue receptor (GHSR). Their potentially unique structure and the molecular basis of their binding and activation are not yet clear. We previously reported that the perimembranous residues in the predicted extracellular loops and amino-terminal tail of the MR were important for responses to the natural peptide ligand, motilin, and the transmembrane domains of the MR were important for a non-peptidyl ligand, erythromycin. We also reported that the perimembranous residues in the second extracellular loop of the GHSR were critical for natural ligand ghrelin binding and activity. The MR is 52% identical to GHSR, with 86% sequence identity in the transmembrane domains. In the current work, to gain insight into a relationship between MR and GHSR, we studied functional responses to motilin, erythromycin and ghrelin of expression cells of chimeric constructs of MR and GHSR and co-expression cells of both MR and GHSR. We also generated human MR transgenic mice, and clarified a relationship between motilin and ghrelin. MR(1-62)/GHSR(68-366) construct responded only to ghrelin, MR(1-102)/GHSR(108-366) responded to ghrelin and erythromycin, and MR(1-129)/GHSR(135-366) and MR(1-178)/GHSR(184-366) responded to erythromycin, while GHSR(1-183)/MR(179-412) responded to neither motilin, erythromycin nor ghrelin. MR and GHSR co-expression cells have no additional responses to these ligands. Motilin or erythromycin administration to human MR transgenic mice resulted in a decrease of serum acyl-ghrelin levels, while MR and GHSR mRNA expression in the gastrointestinal tracts were not changed. These data suggested that in species expressing both motilin-MR and ghrelin-GHSR, there is a compensatory relationship in vivo.

Regulatory natural killer cells in murine liver and their immunosuppressive capacity

Background: Abundant amounts of natural killer (NK) cells are present in the liver, most of which are endowed with direct cytotoxic and inflammatory cytokine production capacities. However, the control of compromised immunity in the liver may be accomplished by a population of regulatory NK cells possessing suppressive or tolerogenic functions.

Nocturia and prevalence of erectile dysfunction in Japanese patients with type 2 diabetes mellitus: The Dogo Study

Several epidemiological studies have reported a positive association between nocturia and erectile dysfunction (ED). Yet only limited evidence exists regarding the association between nocturia and ED among patients with type 2 diabetes mellitus, although nocturia and ED are common among type 2 diabetes mellitus patients.