Sex difference in the liver of hepatocyte-specific Pten-deficient mice: A model of nonalcoholic steatohepatitis

Hepatoprotective effects of Xiaoyao San formula on hepatic steatosis and inflammation via regulating the sex hormones metabolism

BACKGROUND

The modified Xiaoyao San (MXS) formula is an adjuvant drug recommended by the National Health Commission of China for the treatment of liver cancer, which has the effect of preventing postoperative recurrence and metastasis of hepatocellular carcinoma and prolonging patient survival. However, the molecular mechanisms underlying that remain unclear.

AIM

To investigate the role and mechanisms of MXS in ameliorating hepatic injury, steatosis and inflammation.

METHODS

A choline-deficient/high-fat diet-induced rat nonalcoholic steatohepatitis (NASH) model was used to examine the effects of MXS on lipid accumulation in primary hepatocytes. Liver tissues were collected for western blotting and immunohistochemistry (IHC) assays. Lipid accumulation and hepatic fibrosis were detected using oil red staining and Sirius red staining. The serum samples were collected for biochemical assays and NMR-based metabonomics analysis. The inflammation/lipid metabolism-related signaling and regulators in liver tissues were also detected to reveal the molecular mechanisms of MXS against NASH.

RESULTS

MXS showed a significant decrease in lipid accumulation and inflammatory response in hepatocytes under metabolic stress. The western blotting and IHC results indicated that MXS activated AMPK pathway but inhibited the expression of key regulators related to lipid accumulation, inflammation and hepatic fibrosis in the pathogenesis of NASH. The metabonomics analysis systemically indicated that the arachidonic acid metabolism and steroid hormone synthesis are the two main target metabolic pathways for MXS to ameliorate liver inflammation and hepatic steatosis. Mechanistically, we found that MXS protected against NASH by attenuating the sex hormone-related metabolism, especially the metabolism of male hormones.

CONCLUSION

MXS ameliorates inflammation and hepatic steatosis of NASH by inhibiting the metabolism of male hormones. Targeting male hormone related metabolic pathways may be the potential therapeutic approach for NASH.

Targeting Protein Phosphatases for the Treatment of Chronic Liver Disease

There exists a huge number of patients suffering from chronic liver disease worldwide. As a disease with high incidence and mortality worldwide, strengthening the research on the pathogenesis of chronic liver disease and the development of novel drugs is an important issue related to the health of all human beings. Phosphorylation modification of proteins plays a crucial role in cellular signal transduction, and phosphatases are involved in the development of liver diseases. Therefore, this article summarized the important role of protein phosphatases in chronic liver disease with the aim of facilitating the development of drugs targeting protein phosphatases for the treatment of chronic liver disease.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

Gender Differences in a Mouse Model of Hepatocellular Carcinoma Revealed Using Multi-Modal Imaging

The worldwide incidence of hepatocellular carcinoma (HCC) continues to rise, in part due to poor diet, limited exercise, and alcohol abuse. Numerous studies have suggested that the loss or mutation of PTEN plays a critical role in HCC tumorigenesis through the activation of the PI3K/Akt signaling axis. The homozygous knockout of PTEN in the livers of mice results in the accumulation of fat (steatosis), inflammation, fibrosis, and eventually progression to HCC. This phenotype bears a striking similarity to non-alcoholic steatohepatitis (NASH) which is thought to occupy an intermediate stage between non-alcoholic fatty liver disease (NAFLD), fibrosis, and HCC. The molecular and physiological phenotypes that manifest during the transition to HCC suggest that molecular imaging could provide a non-invasive screening platform to identify the hallmarks of HCC initiation prior to the presentation of clinical disease. We have carried out longitudinal imaging studies on the liver-specific PTEN knockout mouse model using CT, MRI, and multi-tracer PET to interrogate liver size, steatosis, inflammation, and apoptosis. In male PTEN knockout mice, significant steatosis was observed as early as 3 months using both magnetic resonance spectroscopy (MRS) and computed tomography (CT). Enhanced uptake of the apoptosis tracer 18F-TBD was also observed in the livers of male PTEN homozygous knockout mice between 3 and 4 months of age relative to heterozygous knockout controls. Liver uptake of the inflammation tracer [18F]4FN remained relatively low and constant over 7 months in male PTEN homozygous knockout mice, suggesting the suppression of high-energy ROS/RNS with PTEN deletion relative to heterozygous males where the [18F]4FN liver uptake was elevated at early and late time points. All male PTEN homozygous mice developed HCC lesions by month 10. In contrast to the male cohort, only 20% (2 out of 10) of female PTEN homozygous knockout mice developed HCC lesions by month 10. Steatosis was significantly less pronounced in the female PTEN homozygous knockout mice relative to males and could not accurately predict the eventual occurrence of HCC. As with the males, the [18F]4FN uptake in female PTEN homozygous knockout mice was low and constant throughout the time course. The liver uptake of 18F-TBD at 3 and 4.5 months was higher in the two female PTEN knockout mice that would eventually develop HCC and was the most predictive imaging biomarker for HCC in the female cohort. These studies demonstrate the diagnostic and prognostic role of multi-modal imaging in HCC mouse models and provide compelling evidence that disease progression in the PTEN knockout model is highly dependent on gender.

Age-dependent sex difference of non-alcoholic fatty liver disease in TSOD and db/db mice

According to previous clinical studies, the prevalence of non-alcoholic fatty liver disease (NAFLD) is higher in men than women only during the reproductive age. Animal models of NAFLD that reflect sex differences in humans have not been established. In this study, we examined sex differences in the hepatic lesions of Tsumura Suzuki obese diabetes (TSOD) and db/db mice, which are representative genetic models of NAFLD. Male and female TSOD and db/db mice were fed with a normal diet and tap water ad libitum. Six male and female mice of each strain were sacrificed at the ages of 3 and 9 months, respectively, and serum biochemical, pathological, and molecular analyses were performed. Serum aspartate aminotransferase (AST) levels were significantly higher in male than female mice of both strains at the age of 3 months; however, at 9 months, significant sex differences were not observed. Similarly, alanine aminotransferase (ALT) levels were significantly higher in male mice than in female TSOD mice at the age of 3 months; however, at 9 months, significant sex differences were not observed. Image analysis of histological slides revealed that the frequency of the steatotic area was significantly higher in male than female db/db mice at the age of 3 months; however, significant sex differences were not observed at 9 months. The frequency of Sirius red-positive fibrotic area was significantly higher in male than female mice in both strains at the age of 3 months; however, significant sex differences were not observed at 9 months. Serum AST and ALT levels and hepatic steatosis and fibrosis in TSOD and db/db mice showed age-dependent sex differences consistent with those observed in human NAFLD. These mice may be suitable for studying sex differences of the disease.

Sex Differences in Nonalcoholic Fatty Liver Disease: State of the Art and Identification of Research Gaps

Despite tremendous research advancements in nonalcoholic fatty liver disease (NAFLD), our understanding of sex differences in NAFLD remains insufficient. This review summarizes the current knowledge on sex differences in NAFLD, identifies gaps, and discusses important considerations for future research. The prevalence and severity of NAFLD are higher in men than in women during the reproductive age. However, after menopause, NAFLD occurs at a higher rate in women, suggesting that estrogen is protective. Sex differences also exist for the major risk factors of NAFLD. In general, animal models of NAFLD recapitulate the sex differences observed in patients, with more severe steatosis and steatohepatitis, more proinflammatory/profibrotic cytokines, and a higher incidence of hepatic tumors in male than female subjects. Based on computer modeling, female and male livers are metabolically distinct with unique regulators modulating sex-specific metabolic outcomes. Analysis of the literature reveals that most published clinical and epidemiological studies fail to examine sex differences appropriately. Considering the paucity of data on sex differences and the knowledge that regulators of pathways relevant to current therapeutic targets for NAFLD differ by sex, clinical trials should be designed to test drug efficacy and safety according to sex, age, reproductive stage (i.e., menopause), and synthetic hormone use. Conclusion: Sex differences do exist in the prevalence, risk factors, fibrosis, and clinical outcomes of NAFLD, suggesting that, while not yet incorporated, sex will probably be considered in future practice guidelines; adequate consideration of sex differences, sex hormones/menopausal status, age, and other reproductive information in clinical investigation and gene association studies of NAFLD are needed to fill current gaps and implement precision medicine for patients with NAFLD.

Basal Autophagy Deficiency Causes Thyroid Follicular Epithelial Cell Death in Mice

Autophagy is a catabolic process that involves the degradation of cellular components through the lysosomal machinery, relocating nutrients from unnecessary processes to more pivotal processes required for survival. It has been reported that systemic disruption of the Atg5 or Atg7 gene, a component of autophagy, is lethal and that its tissue-specific disruption causes tissue degeneration in several organs. However, the functional significance of autophagy in the thyroid glands remains unknown. Our preliminary data imply the possible involvement of dysfunctional autophagy in radiation-induced thyroid carcinogenesis. Therefore, we evaluated the effect of Atg5 gene knockout (KO) on thyroid morphology and function. To this end, Atg5flox/flox mice were crossed with TPO-Cre mice, yielding the thyroid follicular epithelial cell (thyrocyte)‒specific ATG5-deficient mice (Atg5thyr-KO/KO). Atg5 gene KO was confirmed by a lack of ATG5 expression, and disruption of autophagy was demonstrated by a decrease in microtubule-associated protein 1 light chain 3-II puncta and an increase in p62. Atg5thyr-KO/KO mice were born normally, and thyroid morphology, thyroid weights, and serum T4 and TSH levels were almost normal at 4 months. However, at 8 and 12 months, a decrease in the number of thyrocytes and an increase in TUNEL+-thyrocytes were observed in Atg5thyr-KO/KO mice even though thyroid function was still normal. The number of irregularly shaped (gourd-shaped) follicles was also increased. Excess oxidative stress was indicated by increased 8-hydroxy-2'-deoxyguanosine and 53BP1 foci in Atg5thyr-KO/KO mice. These data demonstrate that thyrocytes gradually undergo degradation/cell death in the absence of basal levels of autophagy, indicating that autophagy is critical for the quality control of thyrocytes.

Bile acid detoxifying enzymes limit susceptibility to liver fibrosis in female SHRSP5/Dmcr rats fed with a high-fat-cholesterol diet

During middle age, women are less susceptible to nonalcoholic steatohepatitis (NASH) than men. Thus, we investigated the underlying molecular mechanisms behind these sexual differences using an established rat model of NASH. Mature female and male stroke-prone spontaneously hypertensive 5/Dmcr rats were fed control or high-fat-cholesterol (HFC) diets for 2, 8, and 14 weeks. Although HFC-induced hepatic fibrosis was markedly less severe in females than in males, only minor gender differences were observed in expression levels of cytochrome P450 enzymes (CYP)7A1, CYP8B1 CYP27A1, and CYP7B1, and multidrug resistance-associated protein 3, and bile salt export pump, which are involved in fibrosis-related bile acid (BA) kinetics. However, the BA detoxification-related enzymes UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) 2A1, and the nuclear receptors constitutive androstane receptor (CAR) and pregnane X receptor (PXR), were strongly suppressed in HFC-fed males, and were only slightly changed in HFC-diet fed females. Expression levels of the farnesoid X receptor and its small heterodimer partner were similarly regulated in a gender-dependent fashion following HFC feeding. Hence, the pronounced female resistance to HFC-induced liver damage likely reflects sustained expression of the nuclear receptors CAR and PXR and the BA detoxification enzymes UGT and SULT.

Sex hormone affects the severity of non-alcoholic steatohepatitis through the MyD88-dependent IL-6 signaling pathway

Recent research has shown that the occurrence of gender disparity in liver cancer associated with sex differences in MyD88-dependent IL-6 production, but the role of this signaling pathway in sex differences of non-alcoholic steatohepatitis (NASH) remains unknown. To investigate the effects of sex hormone-specific intervention on pathology and progression of NASH, and on the inflammatory TLR-MyD88-IL-6 signaling pathway NASH was modeled in C57/BL6 mice by feeding a methionine and choline-deficient (MCD) diet for 4 weeks. Male mice were subjected to sex hormone-related interventions such as orchidectomy, and orchidectomy combined with administration of either testosterone propionate or estradiol benzoate. Next, the degree of non-alcoholic fatty liver disease activity score (NAS), serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and the expression level of MyD88 and IL-6, were compared between these groups. Males developed more serious inflammatory problems and had a higher NAS than the females. Sex-specific intervention in male mice by orchidectomy reduced NAS, ALT, and AST, and the expression level of MyD88 and IL-6. But administration of exogenous androgen had no influence on either NAS or the expression of ALT, AST, MyD88, and IL-6. On the other hand, exogenous estrogen could alleviate the pathological damage caused by NASH, as well as reduce NAS, ALT and AST, and the expression of MyD88 and IL-6. The result show different sex hormone-related interventions affected the severity of NASH, possibly by modulating the level of sex hormones and regulating the TLR-MyD88-IL-6 signaling pathway.

Lycopene and apo-10'-lycopenoic acid have differential mechanisms of protection against hepatic steatosis in β-carotene-9',10'-oxygenase knockout male mice

BACKGROUND

Nonalcoholic fatty liver disease is positively associated with obesity and cardiovascular disease risk. Apo-10'-lycopenoic acid (APO10LA), a potential oxidation product of apo-10'-lycopenal that is generated endogenously by β-carotene-9',10'-oxygenase (BCO2) cleavage of lycopene, inhibited hepatic steatosis in BCO2-expressing mice.

OBJECTIVE

The present study evaluated lycopene and APO10LA effects on hepatic steatosis in mice without BCO2 expression.

METHODS

Male and female BCO2-knockout (BCO2-KO) mice were fed a high saturated fat diet (HSFD) with or without APO10LA (10 mg/kg diet) or lycopene (100 mg/kg diet) for 12 wk.

RESULTS

Lycopene or APO10LA supplementation reduced hepatic steatosis incidence (78% and 72%, respectively) and severity in BCO2-KO male mice. Female mice did not develop steatosis, had greater hepatic total cholesterol (3.06 vs. 2.31 mg/g tissue) and cholesteryl ester (1.58 vs. 0.86 mg/g tissue), but had lower plasma triglyceride (TG) (229 vs. 282 mg/dL) and cholesterol (97.1 vs. 119 mg/dL) than male mice. APO10LA-mitigated steatosis in males was associated with reduced hepatic total cholesterol (18%) and activated sirtuin 1 signaling, which resulted in reduced fatty acids (FAs) and TG synthesis markers [stearoyl-coenzyme A (CoA) desaturase protein, 71%; acetyl-CoA carboxylase phosphorylation, 79%; AMP-activated protein kinase phosphorylation, 67%], and elevated cholesterol efflux genes (cytochrome P450 family 7A1, 65%; ATP-binding cassette transporter G5/8, 11%). These APO10LA-mediated effects were not mimicked by lycopene supplementation. Intriguingly, steatosis inhibition by lycopene induced peroxisome proliferator-activated receptor (PPAR)α- and PPARγ-related genes in mesenteric adipose tissue (MAT) that increases mitochondrial uncoupling [cell death-inducing DNA fragmentation factor, α subunit-like effector a, 55%; PR domain-containing 16, 47%; uncoupling protein 3 (Ucp3), 55%], FA β-oxidation (PPARα, 53%; very long chain acyl-CoA dehydrogenase, 38%), and uptake (FA transport protein 4, 29%; lipoprotein lipase 43%). Expressions of 10 MAT PPAR-related genes were inversely correlated with steatosis score, suggesting that lycopene reduced steatosis by increasing MAT FA utilization.

CONCLUSIONS

Our data suggest that lycopene and APO10LA inhibit HSFD-induced steatosis in BCO2-KO male mice through differential mechanisms. Sex disparity of BCO2-KO mice was observed in the outcomes of HSFD-induced liver steatosis and plasma lipids.

Liver immune responses to inflammatory stimuli in a diet-induced obesity model of zebrafish

Obesity- and metabolic syndrome-related diseases are becoming important medical challenges for the western world. Non-alcoholic fatty liver disease (NAFLD) is a manifestation of these altered conditions in the liver, and inflammation appears to be a factor that is tightly connected to its evolution. In this study, we used a diet-induced obesity approach in zebrafish (Danio rerio) based on overfeeding to analyze liver transcriptomic modulation in the disease and to determine how obesity affects the immune response against an acute inflammatory stimulus such as lipopolysaccharide (LPS). Overfed zebrafish developed an obese phenotype, showed signs of liver steatosis, and its modulation profile resembled that observed in humans, with overexpression of tac4, col4a3, col4a5, lysyl oxidases, and genes involved in retinoid metabolism. In response to LPS, healthy fish exhibited a typical host defense reaction comparable to that which occurs in mammals, whereas there was no significant gene modulation when comparing expression in the liver of LPS-stimulated and non-stimulated obese zebrafish at the same statistical level. The stimulation of obese fish represents a double-hit to the already damaged liver and can help understand the evolution of the disease. Finally, a comparison of the differential gene activation between stimulated healthy and obese zebrafish revealed the expected difference in the metabolic state between healthy and diseased liver. The differentially modulated genes are currently being studied as putative new pathological markers in NAFLD-stimulated liver in humans.

Rosiglitazone regulates anti-inflammation and growth inhibition via PTEN

Peroxisome proliferator-activated receptor gamma (PPARγ) agonist has anti-inflammatory and anticancer properties. However, the mechanisms by which PPARγ agonist rosiglitazone interferes with inflammation and cancer via phosphatase and tensin homolog-(PTEN)-dependent pathway remain unclear. We found that lower doses (<25  μ M) of rosiglitazone significantly inhibited lipopolysaccharide-(LPS)-induced nitric oxide (NO) release (via inducible nitric oxide synthase, iNOS), prostaglandin E2 (PGE2) production (via cyclooxygenase-2, COX-2), and activation of Akt in RAW 264.7 murine macrophages. However, rosiglitazone did not inhibit the production of reactive oxygen species (ROS). In PTEN knockdown (shPTEN) cells exposed to LPS, rosiglitazone did not inhibit NO release, PGE2 production, and activation of Akt. These cells had elevated basal levels of iNOS, COX-2, and ROS. However, higher doses (25-100  μ M) of rosiglitazone, without LPS stimulation, did not block NO release and PGE2 productions, but they inhibited p38 MAPK phosphorylation and blocked ROS generation in shPTEN cells. In addition, rosiglitazone caused G1 arrest and reduced the number of cells in S + G2/M phase, leading to growth inhibition. These results indicate that the anti-inflammatory property of rosiglitazone is related to regulation of PTEN independent of inhibition on ROS production. However, rosiglitazone affected the dependence of PTEN-deficient cell growth on ROS.

Experimental Nonalcoholic Steatohepatitis Induced by Neonatal Streptozotocin Injection and a High-Fat Diet in Rats

Nonalcoholic steatohepatitis (NASH) has become a major concern in clinical hepatology. To elucidate the disease mechanisms and to develop a treatment, the advent of an appropriate experimental model is crucial. Pregnant Sprague-Dawley rats were fed a high-fat diet from gestational day 16. Two days after birth, the neonates were injected subcutaneously with streptozotocin (STZ) (180, 200, or 256 mg/kg). The mothers were fed a high-fat diet during the nursing period. After being weaned (4 weeks of age), the juvenile rats were fed the same high-fat diet. The survival rates at the time of weaning were 25.6% (180 mg/kg STZ), 22.8% (200 mg/kg STZ), and 19.4% (256 mg/kg STZ). The mean body weight of NASH rats was approximately 20% less than that of normal rats. Serum levels of glucose, alanine aminotransferase, and hyaluronic acid increased in NASH rats. Histologically, typical features of steatohepatitis such as ballooning, inflammatory cell infiltration, and perivenular and pericellular fibrosis were observed. In an indocyanine green loading test, the blood half-life was significantly longer in NASH rats (5.04 ± 2.14 vs. 2.72 ± 0.72 min; p < 0.05), which was suggestive of an impaired hepatobiliary transportation function. Concomitantly, biliary ICG concentrations in NASH rats stabilized in a delayed fashion compared with normal rats. In addition, the amount of bile excreted in NASH rats was significantly lower than that in normal rats (4.32 ± 0.83 vs. 7.66 ± 1.05 mg/min; p < 0.01). The rat NASH model presented here mimics the clinical features of the disease and will be a helpful tool for medical and bioscience research.

Blockade of reactive oxygen species and Akt activation is critical for anti-inflammation and growth inhibition of metformin in phosphatase and tensin homolog-deficient RAW264.7 cells

CONTEXT

Metformin is widely used for treatment of type 2 diabetes and has a potential application on the treatment of inflammation and cancer. Phosphatase and tensin homolog (PTEN) plays a critical role in cancer cell growth and inflammation; however, precise mechanisms remain unclear.

OBJECTIVE

We aimed to investigate the possible mechanisms of how PTEN regulates metformin against cell growth and inflammation.

MATERIALS AND METHODS

We established PTEN knockdown in RAW264.7 murine macrophages (shPTEN cells) to detect inflammatory mediators using commercial kits, production of reactive oxygen species (ROS) by flow cytometry, cell growth by MTT assay and phosphorylated levels of signal molecules by western blot.

RESULTS

The shPTEN cells had a significant large amount of inflammatory mediators, such as inducible nitric oxide synthase (iNOS)/nitric oxide (NO) and cyclooxygenase-2 (COX-2)/prostaglandin E(2) (PGE(2)); and also elevated the production of ROS and increased cell proliferation. These effects were accompanied with the activation of Akt and p38 mitogen-activated protein kinase (MAPK), and the inactivation of an AMP-activated protein kinase (AMPK) activator and extracellular signal-regulated kinase 1/2. Pretreatment with metformin not only blocked these inflammatory mediators, but also caused growth inhibition induced by significant apoptosis. Furthermore, inactivation of Akt, blockade of ROS generation and independence of activations of AMPK and MAPK by metformin were also observed.

CONCLUSION

Macrophages with PTEN deficiency developed a continuous inflammatory microenvironment, which further aggravated tumor cell growth. Moreover, metformin affected PTEN-deficient cells dependent of inhibition of ROS production and Akt activation against enlarged inflammatory mediators and/or cell growth in shPTEN cells.

Ubiquitous transcription factor YY1 promotes zebrafish liver steatosis and lipotoxicity by inhibiting CHOP-10 expression

The ubiquitous transcription factor Yin Yang 1 (YY1) is known to have diverse and complex cellular functions. Although relevant literature has reported that YY1 expression can induce the down-regulation of C/EBP homologous protein 10 (CHOP-10) and then allow the transactivation of certain transcription factors required for lipogenesis, similar properties of YY1 are poorly understood in animal model systems. In this study, we demonstrate hepatic lipid accumulation in YY1 transgenic zebrafish (GY). Oil-red staining cells were predominantly increased in the livers of both GY larvae and adults, indicating that YY1 functionally promoted lipid accumulation in GY livers. Molecular analysis revealed that YY1 over-expression contributed to the accumulation of hepatic triglycerides (TGs) by inhibiting CHOP-10 expression in the juvenile GY and 3 other fish cell lines; the decreased CHOP-10 expression then induced the transactivation of C/EBP-α and PPAR-γ expression. CHOP-10 morpholino (MO)-injected and rosiglitazone-treated G-liver larvae showed liver steatosis by transactivating PPAR-γ. PPAR-γ MO-injected, and GW9662- and astaxanthin-treated GY larvae showed no liver steatosis by inhibiting PPAR-γ. Moreover, a fatty acid (FA) accumulation and a TG decrease were found in the liver of aged GY, leading to the induction of FA-oxidizing systems that increased hepatic oxidative stress and liver damage. This study is the first to examine YY1 as a potential stimulator for GY liver steatosis and lipotoxicity.

Cannabinoid receptor 1 promotes hepatic lipid accumulation and lipotoxicity through the induction of SREBP-1c expression in zebrafish

The activated cannabinoid receptor 1 (CB1R) is exclusively responsible for food intake and weight gain and regulates several pathological features associated with obesity in mammals. However, the precise role of CB1R in non-mammalian model systems is poorly understood. To investigate the functions of CB1R in zebrafish liver, we conditionally expressed CB1R proteins using a liver-specific Tet(off) transgenic system. In this study, we found hepatic lipid accumulation in CB1R transgenic zebrafish (CB) without doxycycline treatment (-Dox) and a suppression of CB1R expression, resulting in the loss of lipid accumulation in the livers of CB fish that received doxycycline treatment (+Dox). Oil Red O (ORO)-stained hepatocytes were predominant in the liver buds of CB-Dox larvae, indicating that CB1R functionally promotes lipid accumulation during CB hepatogenesis. More than 73 % of CB-Dox adults showed increased lipid content, which leads, in turn, to steatosis. Liver histology and ORO staining of CB-Dox hepatocytes also indicated the accumulation of fatty droplets in the CB liver samples, consistent with the specific pathological features of liver steatosis or steatohepatitis. We also found that hepatic CB1R overexpression accompanies the stimulation of the lipogenic transcription factor SREBP-1c and its target enzymes, acetyl coenzyme-A carboxylase-1 (ACC1) and fatty acid synthase (FAS), and increases de novo fatty acid synthesis. This study is the first to report CB1R as a potential hepatic stimulator for zebrafish liver steatosis.

The PTEN and Myotubularin phosphoinositide 3-phosphatases: linking lipid signalling to human disease

Two classes of lipid phosphatases selectively dephosphorylate the 3 position of the inositol ring of phosphoinositide signaling molecules: the PTEN and the Myotubularin families. PTEN dephosphorylates PtdIns(3,4,5)P(3), acting in direct opposition to the Class I PI3K enzymes in the regulation of cell growth, proliferation and polarity and is an important tumor suppressor. Although there are several PTEN-related proteins encoded by the human genome, none of these appear to fulfill the same functions. In contrast, the Myotubularins dephosphorylate both PtdIns(3)P and PtdIns(3,5)P(2), making them antagonists of the Class II and Class III PI 3-kinases and regulators of membrane traffic. Both phosphatase groups were originally identified through their causal mutation in human disease. Mutations in specific myotubularins result in myotubular myopathy and Charcot-Marie-Tooth peripheral neuropathy; and loss of PTEN function through mutation and other mechanisms is evident in as many as a third of all human tumors. This chapter will discuss these two classes of phosphatases, covering what is known about their biochemistry, their functions at the cellular and whole body level and their influence on human health.

Clinical characteristics of obese boys and girls in a high school: focused on abdominal fat indices, fatty liver and carotid intima-media thickness

Purpose

Our study aimed to evaluated sex differences in clinical features of obese high school students.

Methods

One hundred three obese high school students (body mass index [BMI]≥85th percentile) and 51 control students (BMI<85th percentile) were enrolled in this study. Anthropometric measurements were performed. Fasting serum glucose, insulin, aspartate aminotransferase, alanine aminotransferase, total cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and high-sensitive C-reactive protein were measured. Abdominal fat thickness, degree of fatty liver, and carotid intima-media thickness were measured by ultrasound.

Results

In control and obese groups, waist circumference was significantly longer in boys but body fat mass was significantly higher in girls. In the control group, total cholesterol and LDL-C were higher in girls. In the obese group, however, aspartate aminotransferase, alanine aminotransferase and triglyceride were higher and HDL-C was lower in boys. Preperitoneal fat thickness was significantly higher in obese girls. In obese group, the degree of fatty liver was significantly higher in boys. Carotid intima-media thickness was not significantly different between boys and girls.

Conclusion

Obese adolescents had distinguishable sex differences in body measurements, metabolic abnormalities, abdominal fat thickness and fatty liver. We can infer that these characteristics may extend into adult obesity.

Overexpression of gankyrin induces liver steatosis in zebrafish (Danio rerio)

Gankyrin is a small ankyrin-repeat protein that previous research has confirmed to be overexpressed in hepatocellular carcinoma (HCC). Although relevant literature has reported on gankyrin functions in cellular proliferation and tumorigenesis, the exact role of gankyrin is poorly understood in animal model systems. This study analyzed hepatic lipid accumulation in gankyrin transgenic (GK) zebrafish. Bromodeoxyuridine (BrdU)-positive cells were predominantly increased in the liver bud of GK larvae, indicating that gankyrin functionally promoted cell proliferation at the larval stage in GK fish. However, over 90% of the viable GK adults showed an increased lipid content, leading in turn to liver steatosis. Liver histology and oil red O staining also indicated the accumulation of fatty droplets in GK fish, consistent with the specific pathological features of severe steatosis. Molecular analysis revealed that gankyrin overexpression induced hepatic steatosis and modulated the expression profiles of four hepatic microRNAs, miR-16, miR-27b, miR-122, and miR-126, and 22 genes involved in lipid metabolism. Moreover, significantly increased hepatic cell apoptosis resulted in liver damage in GK adults, leading to liver failure and death after approximately 10months. This study is the first to report gankyrin as a potential link between microRNAs and liver steatosis in zebrafish.

Impact of cigarette smoking on onset of nonalcoholic fatty liver disease over a 10-year period

BACKGROUND

Metabolic syndrome, which includes obesity, hyperglycemia, dyslipidemia, and hypertension, is a major risk factor for the development of nonalcoholic fatty liver disease (NAFLD). Cigarette smoking is a well-known risk factor for metabolic syndrome, but the epidemiological impact of cigarette smoking on development of NAFLD is unclear.

METHODS

In this retrospective study, 2,029 subjects underwent a complete medical health checkup in 1998 and again in 2008. Those who were positive for hepatitis B surface antigen or hepatitis C virus antibody, or had an alcohol intake of > 20 g/day as assessed by questionnaire, were excluded. Fatty liver was diagnosed by abdominal ultrasonography. Independent risk factors associated with the development of NAFLD were determined by multiple logistic regression analysis. Smoking status was expressed using the Brinkman index (BI), which was calculated as the number of cigarettes smoked per day multiplied by the number of years of smoking.

RESULTS

Of 1,560 subjects without NAFLD in 1998, 266 (17.1%) were newly diagnosed with NAFLD in 2008. Multiple logistic analysis identified age [adjusted odds ratio (AOR) 0.95, 95% confidence interval (95% CI) 0.94-0.97], male sex (AOR 1.46, 95% CI 1.01-2.10), body mass index ≥ 25 (AOR 3.08, 95% CI 2.20-4.32), dyslipidemia (AOR 1.79, 95% CI 1.25-2.58) and cigarette smoking (AOR 1.91, 95% CI 1.34-2.72) as risk factors associated with the development of NAFLD. Smoking status at baseline was also associated with the development of NAFLD (BI 1-399: AOR 1.77, 95% CI 1.02-3.07, BI ≥ 400: AOR 2.04, 95% CI 1.37-3.03).

CONCLUSION

Cigarette smoking is an independent risk factor for onset of NAFLD.

Steatosis induced by the accumulation of apolipoprotein A-I and elevated ROS levels in H-ras12V transgenic mice contributes to hepatic lesions

Hepatic steatosis is considered to have an important impact on liver tumorigenesis, despite a lack of clear experimental evidence. Histopathological analysis of H-ras12V transgenic mice showed liver lesions on a steatosis background had significantly higher incidence than on a non-steatosis background. Further investigation showed that apolipoprotein A-I was elevated and accumulated around fatty vacuoles. This elevated level of apolipoprotein A-I was coupled with an elevated level of H-ras12V protein and ROS. In conclusion, our results suggest that the expression of H-ras12V oncogene leads to elevated levels of ROS and apolipoprotein A-I that contribute to steatosis. The steatosis, in turn, promotes the development of hepatic lesions induced by H-ras12V oncogene.

Obese boys at increased risk for nonalcoholic liver disease: evaluation of 16,390 overweight or obese children and adolescents

OBJECTIVE

Comorbidities of childhood obesity challenge health-care systems in Europe. Further, there is a lack of population-specific prevalence data and diagnostic strategies available, especially for obesity-related disturbances of liver function. Therefore, the prevalence of elevated liver enzymes and their relationship to biological parameters were studied in a large pediatric obesity cohort.

METHODS

In 111 specialized pediatric obesity centers in Germany, Austria and Switzerland, 16,390 children and adolescents (age 12.4±2.6 years, 58% boys) were categorized as overweight (body mass index (BMI) >90th percentile) and obese (>97th percentile) and studied for related comorbidities, especially nonalcoholic fatty liver disease (NAFLD; as defined by aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) >50 U l(-1)). Data were collected using a standardized software program (APV) for longitudinal multicenter documentation. Pseudonymized data were transmitted for central statistical analysis.

RESULTS

In this pediatric cohort, 16% of the study population was overweight, 46% obese and 35% extremely obese (>99.5th percentile extreme obesity (Xob)). NAFLD was present in 11% of the study population, but predominantly in boys (boys vs girls; 14.4:7.4%; P<0.001), in Xob (obese vs Xob; 9.5:17.0%; P<0.001) and in older age (< 12 vs ≥12 years; 8:12%; P<0.001; adjusted for BMI). ALT >50 U l(-1) was significantly associated with fasting insulin and BMI-SDS. In multiple logistic regression models, Xob and male gender were strongly associated with NAFLD (odds ratio Xob vs normal weight=3.2; boys vs girls OR=2.3).

CONCLUSION

In a large cohort of overweight and obese European children and adolescents, markers of nonalcoholic liver disease, especially ALT, are frequent and predicted by Xob and male gender. The results underline the epidemiological dimension of this obesity-related morbidity even in childhood. Therefore, at least ALT is recommended as a screening parameter in basic care.