Liver Of High-fat Diet Research Articles

Etoricoxib treatment prevented body weight gain and ameliorated oxidative stress in the liver of high-fat diet-fed rats.

The main focus of this study was to determine the role of etoricoxib in counterbalancing the oxidative stress, metabolic disturbances, and inflammation in high-fat (HF) diet-induced obese rats. To conduct this study, 28 male Wistar rats (weighing 190-210 g) were distributed randomly into four groups: control, control + etoricoxib, HF, and HF + etoricoxib. After 8 weeks of treatment with etoricoxib (200 mg/kg), all the animals were sacrificed followed by the collection of blood and tissue samples in order to perform biochemical tests along with histological staining on hepatic tissues. According to this study, etoricoxib treatment prevented the body weight gain in HF diet-fed rats. Furthermore, rats of HF + etoricoxib group exhibited better blood glucose tolerance than the rats of HF diet-fed group. In addition, etoricoxib also markedly normalized HF diet-mediated rise of hepatic enzyme activity. Etoricoxib treatment lowered the level of oxidative stress indicators significantly with a parallel augmentation of antioxidant enzyme activities. Furthermore, etoricoxib administration helped in preventing inflammatory cell invasion, collagen accumulation, and fibrotic catastrophe in HF diet-fed rats. The findings of the present work are suggestive of the helpful role of etoricoxib in deterring the metabolic syndrome as well as other deleterious pathological changes afflicting the HF diet-fed rats.

Glucosamine regulation of fibroblast growth factor 21 expression in liver and adipose tissues

Obesity is associated with metabolic disorders. Fibroblast growth factor 21 (FGF21) has been recognized as important in metabolism. Glucosamine (GLN) has been demonstrated to perform diverse beneficial functions. This study aimed to reveal whether and how GLN would modulate FGF21 production in relation to metabolism. With in vivo model of normal diet (ND) and high-fat diet (HFD) mice receiving GLN injection and in vitro model of mouse AML12 liver cells and differentiated 3T3L1 adipocytes challenged with GLN, GLN appeared to improve the glucose metabolism in HFD and ND mice and to elevate FGF21 protein expression in HFD liver and to increase both FGF21 protein and mRNA levels in WAT from HFD and ND mice and it also upregulated FGF21 expression in both AML12 and differentiated 3T3L1 cells. By using inhibitors against various signaling pathways, p38, Akt, NF-κB, and PKA appeared potentially involved in GLN-mediated FGF21 production in AML12 cells; GLN was able to mediate activation of NF-κB, p38 or PKA/CREB signaling. Our accumulated findings suggest that GLN may potentially improve the metabolic performance by inducing FGF21 production in liver and adipose tissues and such induction in liver cells may act in part due to GLN induction of the NF-κB, p38 and PKA pathways.

1845-P: Maternal Overnutrition Causes DNA Alkylation in Fetal Liver, Suppresses FasL, and Upregulates HIF-1 Signaling Pathway in Neonatal Liver in Nonalcoholic Steatohepatitis (NASH)-Based Hepatocellular Carcinoma in Offspring

Nonalcoholic steatohepatitis (NASH), a progressive form of nonalcoholic fatty liver disease (NAFLD), is associated with hepatocellular carcinoma (HCC). The worldwide prevalence of NAFLD in children suggests an early-life origin. To examine the impact of intrauterine nutrition on the development of NASH/HCC, female C57BL/6J mice were fed with either high-fat diet (HFD) or control diet (CD) during gestation. After weaning, the male offspring were fed with CD, generating two groups of male offspring, HFD and CD. HFD remarkably elevated plasma NEFA and ALT. Consistently, HFD had severe form of NASH, presenting the fibrosis, accompanied with HCC. Synchrotron micro-CT showed the architectural remodeling of the parenchyma in HFD at 14.5 days postcoitum (dpc), one week and 15 weeks of age, not in CD. In the liver of HFD at 14.5dpc, gene ontology term enrichment analysis suggested that up-regulated differentially expressed genes (DEGs) significantly enriched in DNA alkylation, bile secretion, and the down-regulated DEGs mainly enriched in neuronal system, cell maturation. KEGG pathway analysis found down-regulated DEGs significantly enriched in five pathways including Graft-versus-host disease (LogP -24.785) such as FasL, and up-regulated HIF-1 signaling pathway in the liver of HFD at one week of age. On the contrary, 15-week-old HFD had increased cytoplasmic pimonidazole staining, but no nuclear staining of HIF-1α in HCC cells, which suggests breakdown of hypoxic response mechanism, concomitantly with up-regulated miR199a-5p, miR-1949, miR214-3p and miR-3090-5p, which target HIF-1α. This study demonstrates that the early exposure to an overnutrition in utero, subsequent neonatal and adult nutritional alternation cause NASH/HCC in offspring, accompanied by multiple changes in gene expressions. This means a “multi-hit theory.” Disclosure T. Takiyama: None. R. Bessho: None. K. Sawamoto: None. Y. Takiyama: Other Relationship; Self; Abbott, Boehringer Ingelheim Pharmaceuticals, Inc., Merck & Co., Inc., Ono Pharmaceutical Co., Ltd., Roche Diagnostics K.K., Taisho Pharmaceutical Co., Ltd.

Niacin increases diet-induced hepatic steatosis in B6129 mice

Nonalcoholic fatty liver disease (NAFLD) is a very common disorder affecting between 20 and 30% of adults in the United States. However, there is no effective pharmacotherapy for treating NAFLD. Niacin, a water-soluble vitamin (B3), at pharmacological doses, decreases hepatic triglyceride (TG) content in NAFLD through inhibition of diacylglycerol acyltransferase 2, a key enzyme that catalyzes the final step in TG synthesis. Alternatively, some studies indicate that niacin induces fatty liver in high-fat diet (HFD)-fed rats. Therefore, in this study we investigated whether niacin is beneficial in treating NAFLD in two strains of mice, C57BL/6J (B6) and B6129SF2/J (B6129) mice, with 20 weeks of HFD feeding. Niacin treatment was started from week 5 until the end of the study. Niacin treatment increased normalized liver weight, hepatic TG content and NAFLD score in HFD-fed B6129 mice but had no impact on B6 mice. Metabolomics analysis revealed that in B6129 mice, 4-hydroxyphenylpyruvic acid (4-HPP), which is associated with fatty acid oxidation, did not change with HFD feeding but significantly decreased with niacin treatment. Lipidomics analysis discovered that the abundance of phosphocholine (PC), which is critical for very low-density lipoprotein (VLDL)–TG production and secretion, was decreased in HFD-fed B6129 with niacin treatment. In conclusion, niacin had no impact on diet-induced NAFLD development in B6 mice but potentiated hepatic steatosis in HFD-fed B6129 mice due to impaired fatty acid oxidation and decreased VLDL-TG production and secretion.

EX-527 Prevents the Progression of High-Fat Diet-Induced Hepatic Steatosis and Fibrosis by Upregulating SIRT4 in Zucker Rats.

Sirtuin (SIRT) is known to prevent nonalcoholic fatty liver disease (NAFLD); however, the role of SIRT4 in the progression of hepatic fibrosis remains unknown. We hypothesize that EX-527, a selective SIRT1 inhibitor, can inhibit the progression of high-fat diet (HFD)-induced hepatic fibrosis. We found that SIRT4 expression in the liver of NAFLD patients is significantly lower than that in normal subjects. In this study, EX-527 (5 µg/kg), administered to HFD rats twice a week for ten weeks, reduced the serum levels of triglyceride (TG), total cholesterol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) and attenuated hepatic fibrosis evidenced by Masson’s trichrome and hepatic fat by oil red-O staining. EX-527 upregulated SIRT2, SIRT3, and SIRT4 expression in the liver of HFD fed rats but downregulated transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) expression. It decreased proinflammatory cytokine production and hydroxyproline levels in the serum and SMAD4 expression and restored apoptotic protein (Bcl-2, Bax, and cleaved caspase-3) expression. These data propose a critical role for the SIRT4/SMAD4 axis in hepatic fibrogenesis. SIRT4 upregulation has the potential to counter HFD-induced lipid accumulation, inflammation, and fibrogenesis. We demonstrate that EX-527 is a promising candidate in inhibiting the progression of HFD-induced liver fibrosis.

Trace Elements, PPARs, and Metabolic Syndrome.

Metabolic syndrome (MetS) is a constellation of metabolic derangements, including central obesity, insulin resistance, hypertension, glucose intolerance, and dyslipidemia. The pathogenesis of MetS has been intensively studied, and now many factors are recognized to contribute to the development of MetS. Among these, trace elements influence the structure of proteins, enzymes, and complex carbohydrates, and thus an imbalance in trace elements is an independent risk factor for MetS. The molecular link between trace elements and metabolic homeostasis has been established, and peroxisome proliferator-activated receptors (PPARs) have appeared as key regulators bridging these two elements. This is because on one hand, PPARs are actively involved in various metabolic processes, such as abdominal adiposity and insulin sensitivity, and on the other hand, PPARs sensitively respond to changes in trace elements. For example, an iron overload attenuates hepatic mRNA expression of Ppar-α; zinc supplementation is considered to recover the DNA-binding activity of PPAR-α, which is impaired in steatotic mouse liver; selenium administration downregulates mRNA expression of Ppar-γ, thereby improving lipid metabolism and oxidative status in the liver of high-fat diet (HFD)-fed mice. More importantly, PPARs’ expression and activity are under the control of the circadian clock and show a robust 24 h rhythmicity, which might be the reasons for the side effects and the clinical limitations of trace elements targeting PPARs. Taken together, understanding the casual relationships among trace elements, PPARs’ actions, and the pathogenesis of MetS is of great importance. Further studies are required to explore the chronopharmacological effects of trace elements on the diurnal oscillation of PPARs and the consequent development of MetS.

In Vitro and In Vivo Nutraceutical Characterization of Two Chickpea Accessions: Differential Effects on Hepatic Lipid Over-Accumulation.

Dietary habits are crucially important to prevent the development of lifestyle-associated diseases. Diets supplemented with chickpeas have numerous benefits and are known to improve body fat composition. The present study was undertaken to characterize two genetically and phenotypically distinct accessions, MG_13 and PI358934, selected from a global chickpea collection. Rat hepatoma FaO cells treated with a mixture of free fatty acids (FFAs) (O/P) were used as an in vitro model of hepatic steatosis. In parallel, a high-fat diet (HFD) animal model was also established. In vitro and in vivo studies revealed that both chickpea accessions showed a significant antioxidant ability. However, only MG_13 reduced the lipid over-accumulation in steatotic FaO cells and in the liver of HFD fed mice. Moreover, mice fed with HFD + MG_13 displayed a lower level of glycemia and aspartate aminotransferase (AST) than HFD mice. Interestingly, exposure to MG_13 prevented the phosphorylation of the inflammatory nuclear factor kappa beta (NF-kB) which is upregulated during HFD and known to be linked to obesity. To conclude, the comparison of the two distinct chickpea accessions revealed a beneficial effect only for the MG_13. These findings highlight the importance of studies addressing the functional characterization of chickpea biodiversity and nutraceutical properties.

Anti-obesity Action of Fermented Barley Extracts with Lactobacillus plantarum dy-1 and Associated MicroRNA Expression in High-fat Diet-induced Obese Rats

ObjectiveTo further explore associated effects of Lactobacillus plantarum dy-1 (LFBE) on obesity and lipid metabolism at the gene expression level, the expression of microRNAs (miRNAs) was investigated in the liver of high-fat diet (HFD) induced obese rats. MethodsThree groups of animal models were established. Changes in miRNA expression in the liver of each group were analyzed by microarray and RT-qPCR, complemented by bioinformatics. Palmitate-induced hepatocellular carcinoma (HepG2) cells were used as a model to validate the test. ResultsLFBE treatment groups and HFD groups were observed to be distinctly different with respect to rates of increase in body weight and body fat percentage and triglyceride (TG) and total cholesterol (TC) levels in serum and liver. In addition, the LFBE group showed upregulation of ten miRNAs and downregulation of five miRNAs in the liver. Downregulation of miR-34a and miR-212 was observed in the livers of the LFBE group. Gene ontology and kyoto encyelopedia of geues and genomes (KEGG) pathway analysis showed that possible target genes of the deregulated miRNAs were significantly enriched in the adrenergic and HIF-1 signaling pathways. ConclusionThese results demonstrate that LFBE might regulate the expression of miRNAs in order to inhibit obesity and fatty liver.

Oral gallic acid improve liver steatosis and metabolism modulating hepatic lipogenic markers in obese mice.

Gallic acid (GA) is a natural endogenous polyphenol found in a variety of fruits, vegetables and wines, with beneficial effects on the energetic homeostasis. The present study aimed to investigate oral gallic acid effects on liver steatosis and hepatic lipogenesis markers in obese mice evaluating new possible molecular related mechanisms. Twenty-four Swiss male mice were divided into four groups and fed for 60days with standard diet (ST), standard diet plus gallic acid (ST+GA), high-fat diet (HFD), and high-fat diet plus gallic acid (HFD+GA). We evaluated the relationship between body weight, food intake and serum levels of total cholesterol, triglycerides, insulin, aspartate and alanine transaminases. Liver histology was analyzed by hematoxylin and eosin staining. These results were accompanied by bioinformatics analyses. The acetyl-CoA carboxylase (ACC), sterol regulatory element binding protein-1 (SREBP-1) and fatty acid synthase (FAS) expression was assessed by quantitative real-time reverse transcriptase PCR (qRT-PCR). The main findings of the present study showed that GA reduced liver steatosis, body weight and plasma insulin levels. Analyzes of hepatic steatosis related genes expression showed that ACC and FAS mRNA were significantly suppressed in liver of HFD+GA mice. These data was corroborated by bioinformatics analysis. These data suggest an important clinical application of GA in the prevention and treatment of liver diseases.

Reference Gene and Protein Expression Levels in Two Different NAFLD Mouse Models.

The expression levels of some reference genes and proteins are used for data normalization and quantification. However, these levels can change in response to experimental conditions or treatments. Aim. The aim of this work was to evaluate reference gene and protein expression in models of nonalcoholic fatty liver disease, using mice fed with a high-fat diet (HFD) and mice that are genetically obese (ob/ob). Main Methods. Histological staining techniques were used to verify the morphology and quantify the amount of lipid droplets present in the liver. Real-time polymerase chain reaction and immunoblotting were employed for monitoring protein expression and gene expression levels, respectively. Key Finding. The results showed that there was a substantial increase in the amount of lipid droplets in the livers of HFD and ob/ob animals when compared to the standard diet (SD) group. There was an observed reduction in the expression of β-actin (10%), α-tubulin (6%), GAPDH (19%), and RPL3 (15%) genes when comparing the ob/ob group to the HFD group. Additionally, the ob/ob mice displayed GAPDH protein levels that were substantially, but not significantly, reduced when compared to SD. Significance. It was concluded that there are slight differences in the expression levels of reference genes and proteins in these two NAFLD animal models, and researchers should consider these alterations when working with these models.

Probiotics improved hyperlipidemia in mice induced by a high cholesterol diet via downregulating FXR.

Probiotics effectively regulated lipid metabolism and improved hyperlipidemia. The purpose of this study was to further evaluate the functions of lipid-lowering strains in vivo and elucidate the mechanism. The hyperlipidemia model was constructed using a high fat diet, and four lipid-lowering strains were selected for intervention. In the four strains, the strains Lactobacillus vaginalis FN3 (FN3) and Bifidobacterium animalis subsp. Lactis F1-7 (F1-7) reduced TG, TC and LDL and increased HDL. These two strains decreased TC and TC in the liver of high fat diet fed mice, and they increased total bile acids (TBA) in feces. F1-7 and FN3 reduced the mRNA levels of Farnesoid X Receptor (FXR), recombinant Fibroblast Growth Factor 15 (FGF 15) and Niemann-Pick C1-Like 1 (NPC1L1), and up-regulated the Liver X Receptor (LXR) mRNA level. They decreased the protein expressions of FXR and NPC1L1. In addition, F1-7 up-regulated the protein expression of cholesterol 7-alpha hydroxylase (CYP7A1). In summary, Bifidobacterium animalis subsp. Lactis F1-7 and Lactobacillus vaginalis FN3 could regulate bile acid metabolism by downregulating the FXR gene and reduce the absorption of exogenous cholesterol by regulating NPC1L1. F1-7 could also participate in the FXR/FGF15 pathway to improve hyperlipidemia, which showed better effects than FN3.

Impaired ferritinophagy induced hepatic insulin resistance via endoplasmic reticulum stress of high fat diet mice

AbstractEmerging evidence has been revealed that high fat diet (HFD) correlate with insulin resistance (IR) which could be induced by endoplasmic reticulum stress (ERS). Recently, obesity or HFD induced nonalcoholic fatty liver disease (NAFLD) could promote alteration of iron metabolism. Disorder of iron metabolism have been linked to unnormal metabolism of glucose and lipid. Herein, we investigated the effect of impaired iron homeostasis on hepatic IR, focusing on ferritinophagy. Male C57/6J mice were administered with HFD (60% energy from fat) or LFD (10% energy from fat) for 10 weeks (n = 10), and Palmitic acid (PA)-insulin treated HepG2 cells were also established. Hepatic IR as evidenced by increased hepatic steatosis and decreased of p-AKT (48%, p < 0.0005), p-GSK-3β (34%, p < 0.05) in the liver of HFD mice. In addition, decreased iron level and expression NCOA4, as well as increased up-regulation of IRE1α and EIF2α were observed in HFD liver. By using desferrioxamine (DFO) and ferric ammonium citrate (FAC), we examined iron level on IRE1α and EIF2α. And glucose uptake assay shown that FAC supplementation, and ERS inhibitors of 4-PBA and STF could improve the glucose uptake of HepG2 cells in the presence of PA. Furthermore, we evaluated the glucose uptake of HepG2 cells incubated with adenovirus which mediated overexpression of NCOA4, FAC, 4-PBA (ERS inhibitor) or STF (IRE1 inhibitor). Taken together, deficiency of iron induced by impaired ferritinophagy induced hepatic IR, partly by aggravating hepatic ERS, especially IRE1 signal pathway in vivo and vitro. These findings provide evidence and new insight for therapeutic strategy of iron deficiency in NAFLD.

Hepatoprotective potential of 7,8-Dihydroxyflavone against alcohol and high-fat diet induced liver toxicity via attenuation of oxido-nitrosative stress and NF-κB activation.

Fatty liver diseases are the most common and major health concern arises from the modern lifestyle and alcohol (ethanol) abuse. The prevalence of non-alcoholic fatty liver diseases (NAFLD) has been observed prominently in obese and diabetic individuals, while alcoholic liver disease is common in alcoholic persons. Fatty liver disease, such as steatohepatitis, leads to fibrosis, cirrhosis and eventually hepatocellular carcinoma. The present study was designed to investigate the effect of 7,8-Dihydroxyflavone (7,8-DHF) against high-fat diet (HFD) and ethanol (EtOH)-induced hepatotoxicity in rats. Male Wistar rats (150-200 g) were fed HFD (58% calories from fat) and EtOH (3-15% in drinking water) for 12 weeks. 7,8-DHF was administered intraperitoneally at the dose of 5 mg/kg/day for the last four weeks. After 12 weeks, biochemical, ELISA, RT-PCR, and histological studies have been carried out. Biochemical analyses revealed the involvement of oxidative stress and inflammation in the liver of HFD and EtOH-fed rats. 7,8-DHF treatment significantly reduced HFD and EtOH-induced oxidative stress as evidenced by the reduction of lipid peroxidation and augmentation of reduced glutathione level. Moreover, IL-1β level was found significantly reduced in 7,8-DHF treated EtOH, HFD and EtOH+HFD groups. The semi-quantitative RT-PCR results indicated down-regulation of Nrf-2 and HO-1 and up-regulation of NF-κB and iNOS mRNA expression level in the liver of HFD and EtOH-fed rats, which was ameliorated by 7,8-DHF treatment. The present study suggested that 7,8-DHF could be an effective pharmacological intervention in combating HFD and EtOH-induced hepatotoxicity.

Sex-Specific Differences in Fat Storage, Development of Non-Alcoholic Fatty Liver Disease and Brain Structure in Juvenile HFD-Induced Obese Ldlr-/-.Leiden Mice.

Background: Sex-specific differences play a role in metabolism, fat storage in adipose tissue, and brain structure. At juvenile age, brain function is susceptible to the effects of obesity; little is known about sex-specific differences in juvenile obesity. Therefore, this study examined sex-specific differences in adipose tissue and liver of high-fat diet (HFD)-induced obese mice, and putative alterations between male and female mice in brain structure in relation to behavioral changes during the development of juvenile obesity. Methods: In six-week-old male and female Ldlr-/-.Leiden mice (n = 48), the impact of 18 weeks of HFD-feeding was examined. Fat distribution, liver pathology and brain structure and function were analyzed imunohisto- and biochemically, in cognitive tasks and with MRI. Results: HFD-fed female mice were characterized by an increased perigonadal fat mass, pronounced macrovesicular hepatic steatosis and liver inflammation. Male mice on HFD displayed an increased mesenteric fat mass, pronounced adipose tissue inflammation and microvesicular hepatic steatosis. Only male HFD-fed mice showed decreased cerebral blood flow and reduced white matter integrity. Conclusions: At young age, male mice are more susceptible to the detrimental effects of HFD than female mice. This study emphasizes the importance of sex-specific differences in obesity, liver pathology, and brain function.

A novel AMPK activator improves hepatic lipid metabolism and leukocyte trafficking in experimental hepatic steatosis

A novel AMP-activated protein kinase (AMPK) activator, IMM-H007 (H007), has been reported to reduce serum lipid levels and inhibit lipid accumulation in the liver in hyperlipidemic animal models. However, how H007 ameliorates hepatic steatosis and inflammation remains unknown. In the present study, H007, at 200 mg/kg, reduced hepatic lipid levels and the levels of collagenous fiber in the liver in high-fat diet (HFD)-fed hamsters compared to those in the HFD group. Meanwhile, compared to the controls, H007 significantly inhibited sterol-regulatory element binding protein (SREBP)-1c and acetyl CoA carboxylase (ACC) expression by upregulating the AMPK activity, suppressing the saturated fatty acid accumulation and increasing polyunsaturated fatty acid synthesis in the liver. Compared to the controls, H007 treatment inhibited the expression of monocyte chemotactic protein (MCP-1) in fatty acid-treated HepG2 cells; suppressed leukocyte adherence and rolling on the liver microvasculature; and suppressed hepatic macrophage infiltration. H007 also suppressed the expression of nuclear factor-κB (NF-κB) p65 in fatty acid- and lipopolysaccharide-treated HepG2 cells compared to that in the controls by activating AMPK. These data suggested that H007 had a beneficial effect by improving the lipid composition in the liver and inhibiting inflammatory cell trafficking in the development of nonalcoholic fatty liver disease.

Protective Effects of Licochalcone A Ameliorates Obesity and Non-Alcoholic Fatty Liver Disease Via Promotion of the Sirt-1/AMPK Pathway in Mice Fed a High-Fat Diet.

Licochalcone A is a chalcone isolated from Glycyrrhiza uralensis. It showed anti-tumor and anti-inflammatory properties in mice with acute lung injuries and regulated lipid metabolism through the activation of AMP-activated protein kinase (AMPK) in hepatocytes. However, the effects of licochalcone A on reducing weight gain and improving nonalcoholic fatty liver disease (NAFLD) are unclear. Thus, the present study investigated whether licochalcone A ameliorated weight loss and lipid metabolism in the liver of high-fat diet (HFD)-induced obese mice. Male C57BL/6 mice were fed an HFD to induce obesity and NAFLD, and then were injected intraperitoneally with licochalcone A. In another experiment, a fatty liver cell model was established by incubating HepG2 hepatocytes with oleic acid and treating the cells with licochalcone A to evaluate lipid metabolism. Our results demonstrated that HFD-induced obese mice treated with licochalcone A had decreased body weight as well as inguinal and epididymal adipose tissue weights compared with HFD-treated mice. Licochalcone A also ameliorated hepatocyte steatosis and decreased liver tissue weight and lipid droplet accumulation in liver tissue. We also found that licochalcone A significantly regulated serum triglycerides, low-density lipoprotein, and free fatty acids, and decreased the fasting blood glucose value. Furthermore, in vivo and in vitro, licochalcone A significantly decreased expression of the transcription factor of lipogenesis and fatty acid synthase. Licochalcone A activated the sirt-1/AMPK pathway to reduce fatty acid chain synthesis and increased lipolysis and β-oxidation in hepatocytes. Licochalcone A can potentially ameliorate obesity and NAFLD in mice via activation of the sirt1/AMPK pathway.

Long noncoding RNA Mirt2 upregulates USP10 expression to suppress hepatic steatosis by sponging miR-34a-5p

Non-alcoholic fatty liver disease (NAFLD) is always characterized by hepatic steatosis and insulin resistance. Dysregulated long noncoding RNAs regulate pathogenesis of NAFLD. However, the role of Mirt2 (long noncoding RNA myocardial infraction associated transcript 2) in NAFLD remains unclear. This original study aims to investigate the role of Mirt2 in hepatic steatosis and insulin resistance. Mirt2 was decreased in the livers of high-fat diet (HFD) mice, Ob/Ob, Db/Db, and fasting mice. Hepatic Mirt2 restoration attenuated hyperglycemia, insulin resistance and steatosis in the livers of obese mice, and Mirt2 inhibition promoted fasting hyperglycemia and lipid droplets accumulation in normal mouse livers. Furthermore, overexpression of Mirt2 resulted in suppression of miR-34a-5p, whereas knockdown of Mirt2 exerted opposite effects in the livers. Then, miR-34a-5p was a positive regulator of NAFLD by targeting USP10, which serves as a negative regulator of NAFLD. Overexpression of Mirt2 made miR-34a-5p mimic fail to reduce luciferase activity of USP10 3′-UTR, and this regulation was also demonstrated by Western blot. Similarly, overexpression of miR-34a-5p significantly let Mirt2 lost the ability to elevate USP10 protein level. Thus, Mirt2 can function as the sponge of miR-34a-5p. Moreover, Mirt2-mediated upregulation of USP10 protein expression can be reversed by silencing USP10. USP10 inhibition could abolish Mirt2 overexpression-induced suppression of glucose production and lipogenesis in hepatocytes. In conclusion, the decrease of Mirt2 expression contributed to hepatic insulin resistance and steatosis in obese mice, and Mirt2/miR-34a-5p/USP10 was involved in NAFLD development. Overexpression of Mirt2 might be a promising strategy for treatment of NAFLD.

Histone H3K9 demethylase JMJD2B induces hepatic steatosis through upregulation of PPAR\u03b32

Understanding the epigenetic mechanisms underlying the progression of hepatic steatosis is important for identifying new therapeutic targets against nonalcoholic fatty liver disease (NAFLD). We investigated the functional role of histone demethylase JMJD2B in the pathologic regulation of hepatic steatosis. JMJD2B expression was markedly increased in HepG2 cells treated with palmitate and oleate or liver X receptor agonist T09013178 and in the liver of high-fat diet (HFD)-induced obese mice. Overexpression of JMJD2B using adenovirus in HepG2 cells stimulated the expression of peroxisome proliferator-activated receptor γ2 (PPARγ2) and its steatosis target genes associated with fatty acid uptake and lipid droplet formation, resulting in increased intracellular triglyceride (TG) accumulation. Conversely, knocking down JMJD2B using siRNA reversed JMJD2B-mediated effects in HepG2 cells. The JMJD2B-dependent upregulation of PPARγ2 was associated with the removal of di- and trimethylation of histone H3 lysine 9 on the promoter of PPARγ2. Furthermore, exogeneous expression of JMJD2B using adenovirus in mice resulted in hepatic steatosis when fed a HFD, which was accompanied with increased expression of hepatic PPARγ2 and its steatosis target genes. Together, our results provide novel insights into the pivotal role of JMJD2B in the development of hepatic steatosis through upregulation of PPARγ2 and steatosis target genes.

Altered hepatic glucose homeostasis in AnxA6-KO mice fed a high-fat diet.

Annexin A6 (AnxA6) controls cholesterol and membrane transport in endo- and exocytosis, and modulates triglyceride accumulation and storage. In addition, AnxA6 acts as a scaffolding protein for negative regulators of growth factor receptors and their effector pathways in many different cell types. Here we investigated the role of AnxA6 in the regulation of whole body lipid metabolism and insulin-regulated glucose homeostasis. Therefore, wildtype (WT) and AnxA6-knockout (KO) mice were fed a high-fat diet (HFD) for 17 weeks. During the course of HFD feeding, AnxA6-KO mice gained less weight compared to controls, which correlated with reduced adiposity. Systemic triglyceride and cholesterol levels of HFD-fed control and AnxA6-KO mice were comparable, with slightly elevated high density lipoprotein (HDL) and reduced triglyceride-rich lipoprotein (TRL) levels in AnxA6-KO mice. AnxA6-KO mice displayed a trend towards improved insulin sensitivity in oral glucose and insulin tolerance tests (OGTT, ITT), which correlated with increased insulin-inducible phosphorylation of protein kinase B (Akt) and ribosomal protein S6 kinase (S6) in liver extracts. However, HFD-fed AnxA6-KO mice failed to downregulate hepatic gluconeogenesis, despite similar insulin levels and insulin signaling activity, as well as expression profiles of insulin-sensitive transcription factors to controls. In addition, increased glycogen storage in livers of HFD- and chow-fed AnxA6-KO animals was observed. Together with an inability to reduce glucose production upon insulin exposure in AnxA6-depleted HuH7 hepatocytes, this implicates AnxA6 contributing to the fine-tuning of hepatic glucose metabolism with potential consequences for the systemic control of glucose in health and disease.

Glutathione Deficiency Induces Epigenetic Alterations of Vitamin D Metabolism Genes in the Liver of High-Fat Diet–Induced Type 2 Diabetic Mice

Vitamin D (VD) deficiency is an epidemic health problem. Over a billion people worldwide are VD-deficient or insufficient. VD-regulates the functions of over 200 genes and is essential for growth and development. VD-deficiency can result in diabetes, hypertension, heart disease and stroke. VD levels correlate positively with GSH and negatively with insulin resistance in type 2 diabetic patients. HFD-fed mice exhibited elevated blood glucose, and decreased blood GSH and 25(OH)VD with reduced GSH and increased oxidative stress in the liver. We investigated whether GSH deficiency induces epigenetic alterations in VD-metabolism genes in the high-fat diet (HFD) fed mice. The levels of VD-metabolism genes (CYP2R1, CYP27A1, CYP27B1, and VDR) and GSH biosynthesis pathway genes (GCLC, GCLM, GSS, and GSR) were significantly (p<0.005) down-regulated in the liver of HFD-fed mice. Conversely, CYP24A1 which metabolizes the active VD was significantly (p<0.005) increased. In vitro mouse hepatocyte GCLC knockdown decreases GSH and alters VD-regulatory genes in the similar pattern of HFD-fed mice. Further, significant increased DNMTs (1, 3a and 3b) and global DNA methylation levels with decreased TET1 (p<0.005) but not TET2/3 were observed in the cultured hepatocytes and liver. Notably, significant (p<0.005) gene-specific hypermethylation of CYP2R1 (1.71, 2.55; Control vs. HFD), CYP27A1 (7.58, 8.68), CYP27B1 (0.11, 0.77), VDR (0.16, 0.46) and hypomethylation of CYP24A1 (0.59, 0.33) was observed in the liver of HFD-fed (16 weeks) mice compared with control (normal diet) group. GSH deficiency-induced epigenetic alterations (methylation status) of VD-metabolism enzyme genes and the VDR gene appear to play a significant role in the circulating VD. These findings indicate that GSH epigenetically regulates VD-metabolism genes in obesity/T2DM and a novel adjuvant therapeutic target for restoring VD-deficiency in susceptible populations. Disclosure R. Parsanathan: None. S.K. Jain: None.