SH2 domain-containing inositol 5-phosphatase (SHIP2) regulates de-novo lipogenesis and secretion of apoB100 containing lipoproteins in HepG2 cells. Biochem Biophys Res Commun. 2015;464:1028-1033. [PMID: 26188518 DOI: 10.1016/j.bbrc.2015.07.059]

High-intensity interval training (HIIT) alleviated NAFLD feature via miR-122 induction in liver of high-fat high-fructose diet induced diabetic rats

Background: Exercise intervention is strongly recommended to manage metabolic diseases. In this study, we investigate, whether HIIT and CET can induce hepatic miR-122 expression, NAFLD rats with diabetes.Methods: 40 Wistar rats divided into 2 groups, non-diabetic (NDC) and diabetic .Type 2 diabetes was induced by high-fat high-fructose diet (HFHFD). Then diabetic rats were subdivided into three groups: diabetic control (HFHFD + DC), CET (HFHFD + CET), and HIIT (HFHFD + HIIT). After eight weeks of exercise on a rodent treadmill, we measured miR-122 and its target genes expression in the liver of rats.Results: HIIT decreased the expression of FAS, ACC, SREBP-1c compared with HFHFD + DC (p = .004, p = .032, p = .043, respectively), and could partially increase miR-122 expression as compared with HFHFD + DC (26.8%, p = .68).Conclusions: Exercise training could be a non-pharmacological intervention for improvement of NAFLD of diabetic rats by induction of miR-122. HIIT had a greater effect on NAFLD amelioration than CET.

High intensity interval training improves diabetic cardiomyopathy via miR-1 dependent suppression of cardiomyocyte apoptosis in diabetic rats

Purpose

Diabetes and its complications such as diabetic cardiomyopathy still account for significant morbidity and mortality. High-quality evidence was shown the importance of exercise in controlling diabetes complications, but the molecular mechanism on diabetic cardiomyopathy is not yet fully understood. This study aimed to compare and investigate the effect of high intensity interval training (HIIT) and continuous endurance training (CET) on the signaling pathway of diabetic cardiomyopathy.

Methods

Hence, 21 Wistar rats with an average weight of 260 ± 10 g, after induction of diabetes (STZ 50 mg/kg BW) were randomly divided into three groups (control, CET and HIIT; n = 7). Training programs were conducted 5 days a week for 5 weeks. CET program was defined as running at 60% vVO₂max for 30 min in each session and the HIIT program was defined as running at 85-90% vVO₂max for 3 min followed by 1 min recovery (30-35% vVO₂max), that was repeated four times in each session. The cardiac performance was analyzed via determination of end systolic and diastolic dimensions and the ejection fraction by echocardiography. To elucidate the responsible molecular mechanism of miR-1, IGF-1 and IGF-1R mRNA and apoptosis marker protein expression were investigated.

Results

Both training programs specifically HIIT, significantly reduced the blood glucose, enhanced heart performance, reduced miR-1 expression, induced IGF-1 and IGF-1R expression and reduced apoptotic protein expression.

Conclusion

We showed that HIIT is more effective than CET for reduction of diabetic cardiomyopathy as a complication of diabetes in animal models through suppressing miR-1 and its downstream apoptosis pathway.

The role of microRNAs in the regulation of insulin signaling pathway with respect to metabolic and mitogenic cascades: A review

Insulin resistance (IR) is a shared pathological condition among type 2 diabetes, obesity, cardiovascular disease, and other metabolic disorders. It is growing significantly all over the world and consequently, a substantial effort is needed for developing the potential novel diagnostics and therapeutics. An insulin signaling pathway is tightly modulated by different mechanisms including the epigenetic modifications. Today, a deal of great attention has been shifted towards the regulatory role of noncoding RNAs on target proteins of the insulin signaling pathway. Noncoding RNAs are a major area of the epigenetics which control gene expression at the posttranscriptional levels and include a large class of microRNAs (miRNAs). With this in view, many studies have implicated the mediatory effects of miRNAs on the downstream metabolic and mitogenic proteins of the insulin signaling pathway. Since providing new biomarkers for the early diagnosis of IR and related metabolic traits are very significant, we intended to review the possible role of miRNAs in the regulation of the insulin signaling pathway, with a primary focus on the downstream target proteins of the metabolic and mitogenic cascades.

Modelos celulares hepáticos para el estudio del metabolismo de los lípidos. Revisión de literatura

Introducción. El hígado juega un papel importante en la homeostasis lipídica, especialmente en la síntesis de ácidos grasos y triglicéridos. Una amplia variedad de modelos celulares ha sido utilizada para investigar el metabolismo lipídico hepático y para elucidar detalles específicos de los mecanismos bioquímicos del desarrollo y progresión de enfermedades relacionadas, brindando información para tratamientos que reduzcan su impacto. Los modelos celulares hepáticos poseen un alto potencial en la investigación del metabolismo de lípidos y de agentes farmacológicos o principios activos que permiten la reducción de la acumulación de lípidos.Objetivo. Comparar algunos modelos celulares hepáticos utilizados para el estudio del metabolismo lipídico, sus características y los resultados más relevantes de investigación en ellos.Materiales y métodos. Se realizó una búsqueda sistemática en bases de datos sobre los modelos celulares hepáticos de mayor uso para el estudio del metabolismo de lípidos.Resultados. Se exponen los cinco modelos celulares más utilizados para este tipo de investigaciones, destacando su origen, aplicación, ventajas y desventajas al momento de estimular el metabolismo lipídico.Conclusión. Para seleccionar el modelo celular, el investigador debe tener en cuenta cuáles son los requerimientos y el proceso que desea evidenciar, sin olvidar que los resultados obtenidos solo serán aproximaciones de lo que en realidad podría suceder a nivel del hígado como órgano.

Theacrine protects against nonalcoholic fatty liver disease by regulating acylcarnitine metabolism

OBJECTIVE

Acylcarnitine metabolism disorder contributes significantly to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). There are, however, few ideal medications for NAFLD, which work by targeting acylcarnitine metabolism. The aim of this study was to investigate the protective effects of theacrine, a rare purine alkaloid isolated from Camellia assamica var. kucha, against acylcarnitine metabolism disorder in NAFLD.

METHODS

The pharmacological activities of theacrine were studied using high-fat diet (HFD)-fed ApoE-/- and C57BL/6J mice models. Oleate-treated HepG2 and L-02 cells were used to investigate the molecular mechanism of theacrine on acylcarnitine metabolism. The target of theacrine was confirmed in vitro as the blockade of sirtuin 3 (SIRT3) and protein kinase A.

RESULTS

Theacrine inhibits hepatic steatosis and liver inflammation and improves energy expenditure in HFD-fed mice. Theacrine ameliorates acylcarnitine metabolism disorder in HFD-fed mice and oleate-treated hepatocytes by improving fatty acid oxidation. The underlying mechanism involves theacrine's activation of the mitochondrial deacetylase SIRT3 and consequently, the increased activity of long-chain acyl coenzyme A dehydrogenase (LCAD) through deacetylation.

CONCLUSION

Theacrine promotes acylcarnitine metabolism in NAFLD through the SIRT3/LCAD signaling pathway. The target of theacrine's activities on NAFLD is identified as SIRT3.

Aerobic endurance training improves nonalcoholic fatty liver disease (NAFLD) features via miR-33 dependent autophagy induction in high fat diet fed mice

Due to changes in life style, obesity and obesity related complication such as insulin resistance, type 2 diabetes and non-alcoholic fatty liver disease caused worldwide health problems. Regular exercise has been frequently prescribed to combat metabolic complication of obesity but its molecular mechanism has not been fully illustrated. We investigated molecular mechanism of lipid lowering effect of exercise training in high fat diet fed mice by focusing on miR-33 expression and autophagy pathway. 24 mice were assigned to normal chow (NC) (n=8), high-fat diet (HFD) (n=16) group and subjected to NC and HFD for 13-weeks. HFD groups were divided to sedentary (HFD n=8) or continuous endurance training (HFD+CET, n=8) subgroups. The HFD+CET mice were subjected to treadmill running for 10-weeks in 23-week HFD course. HFD increased body weight, fasting blood sugar, triglyceride, cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT), liver lipogenic genes expression and reduced miR-33 mRNA expression and autopahgy pathway while training program reversed them. Exogenous miR-33 mimic sequence induced autophagy and reduced lipogenesis in HepG2 cells. Autophagy induction by rapamycin reduced lipogenesis and autophagy inhibition by chloroquine, enhanced lipogenesis in HepG2 cells. These findings suggest that aerobic exercise training as a non-pharmacological therapy exerts its lipid lowering effects by miR-33 dependent autophagy induction.

Monosialyl Ganglioside GM3 Decreases Apolipoprotein B-100 Secretion in Liver Cells

Some sialic acid-containing glycolipids are known to regulate development of atherosclerosis with accumulated plasma apolipoprotein B-100 (Apo-B)-containing lipoproteins, because Apo-B as an atherogenic apolipoprotein is assembled mainly in VLDL and LDL. Previously, we have elucidated that disialyl GD3 promotes the microsomal triglyceride transfer protein (MTP) gene expression and secretion of triglyceride (TG)-assembled ApoB, claiming the GD3 role in ApoB lipoprotein secretion in liver cells. In the synthetic pathway of gangliosides, GD3 is synthesized by addition of a sialic acid residue to GM3. Thus, there should be some regulatory links between GM3 and GD3. In this study, exogenous and endogenous monosialyl GM3 has been examined how GM3 plays a role in ApoB secretion in Chang liver cells in a view point of MTP and ApoB degradation in the same cells. The level of GM3 ganglioside in the GM3 synthase gene-transfected cells was increased in the cell extract, but not in the medium. In addition, GM3 synthase gene-transfected cells showed a diminished secretion of TG-enriched ApoB with a lower content of TG in the medium. Exogenous GM3 treatment for 24 h exerted a dose dependent inhibitory effect on ApoB secretion together with TG, while a liver-specific albumin was unchanged, indicating that GM3 effect is limited to ApoB secretion. GM3 decreased the mRNA level of MTP gene, too. ApoB protein assembly dysregulated by GM3 indicates the impaired ApoB secretion is caused by a proteasome-dependent pathway. Treatment with small interfering RNAs (siRNAs) decreased ApoB secretion, but GM3-specific antibody did not. These results indicate that plasma membrane associated GM3 inhibits ApoB secretion, lowers development of atherosclerosis by decreasing the secretion of TG-enriched ApoB containing lipoproteins, suggesting that GM3 is an inhibitor of ApoB and TG secretion in liver cells. J. Cell. Biochem. 118: 2168-2181, 2017. © 2017 Wiley Periodicals, Inc.

PI3K/SHIP2/PTEN pathway in cell polarity and hepatitis C virus pathogenesis

Hepatitis C virus (HCV) infects hepatocytes, polarized cells in the liver. Chronic HCV infection often leads to steatosis, fibrosis, cirrhosis and hepatocellular carcinoma, and it has been identified as the leading cause of liver transplantation worldwide. The HCV replication cycle is dependent on lipid metabolism and particularly an accumulation of lipid droplets in host cells. Phosphoinositides (PIs) are minor phospholipids enriched in different membranes and their levels are tightly regulated by specific PI kinases and phosphatases. PIs are implicated in a vast array of cellular responses that are central to morphogenesis, such as cytoskeletal changes, cytokinesis and the recruitment of downstream effectors to govern mechanisms involved in polarization and lumen formation. Important reviews of the literature identified phosphatidylinositol (PtdIns) 4-kinases, and their lipid products PtdIns(4)P, as critical regulators of the HCV life cycle. SH2-containing inositol polyphosphate 5-phosphatase (SHIP2), phosphoinositide 3-kinase (PI3K) and their lipid products PtdIns(3,4)P2 and PtdIns(3,4,5)P3, respectively, play an important role in the cell membrane and are key to the establishment of apicobasal polarity and lumen formation. In this review, we will focus on these new functions of PI3K and SHIP2, and their deregulation by HCV, causing a disruption of apicobasal polarity, actin organization and extracellular matrix assembly. Finally we will highlight the involvement of this pathway in the event of insulin resistance and nonalcoholic fatty liver disease related to HCV infection.

Inhibition of SH2-domain-containing inositol 5-phosphatase (SHIP2) ameliorates palmitate induced-apoptosis through regulating Akt/FOXO1 pathway and ROS production in HepG2 cells

The serine-threonine kinase Akt regulates proliferation and survival by phosphorylating a network of protein substrates; however, the role of a negative regulator of the Akt pathway, the SH2-domain-containing inositol 5-phosphatase (SHIP2) in apoptosis of the hepatocytes, remains unknown. In the present study, we studied the molecular mechanisms linking SHIP2 expression to apoptosis using overexpression or suppression of SHIP2 gene in HepG2 cells exposed to palmitate (0.5 mM). Overexpression of the dominant negative mutant SHIP2 (SHIP2-DN) significantly reduced palmitate-induced apoptosis in HepG2 cells, as these cells had increased cell viability, decreased apoptotic cell death and reduced the activity of caspase-3, cytochrome c and poly (ADP-ribose) polymerase. Overexpression of the wild-type SHIP2 gene led to a massive apoptosis in HepG2 cells. The protection from palmitate-induced apoptosis by SHIP2 inhibition was accompanied by a decrease in the generation of reactive oxygen species (ROS). In addition, SHIP2 inhibition was accompanied by an increased Akt and FOXO-1 phosphorylation, whereas overexpression of the wild-type SHIP2 gene had the opposite effects. Taken together, these findings suggest that SHIP2 expression level is an important determinant of hepatic lipoapotosis and its inhibition can potentially be a target in treatment of hepatic lipoapoptosis in diabetic patients.