Impaired glucose regulation is one of the most important risk factors for type 2 diabetes mellitus (T2DM) and cardiovascular diseases, which have become a major public health issue worldwide. Dysregulation of carbohydrate metabolism in liver has been shown to play a critical role in the development of glucose intolerance but the molecular mechanism has not yet been fully understood. In this study, we investigated the role of hepatic LCMT1 in the regulation of glucose homeostasis using a liver-specific LCMT1 knockout mouse model. The hepatocyte-specific deletion of LCMT1 significantly upregulated the hepatic glycogen synthesis and glycogen accumulation in liver. We found that the liver-specific knockout of LCMT1 improved high fat diet-induced glucose intolerance and insulin resistance. Consistently, the high fat diet-induced downregulation of glucokinase (GCK) and other important glycogen synthesis genes were reversed in LCMT1 knockout liver. In addition, the expression of GCK was significantly upregulated in MIHA cells treated with siRNA targeting LCMT1 and improved glycogen synthesis. In this study, we provided evidences to support the role of hepatic LCMT1 in the development of glucose intolerance induced by high fat diet and demonstrated that inhibiting LCMT1 could be a novel therapeutic strategy for the treatment of glucose metabolism disorders.

Background: Non-transfusion-dependent thalassemia (NTDT) characterized by ineffective hematopoiesis and increased intestinal iron absorption, and excessive iron deposits in the bone marrow, heart, and liver, causing progressive organ damage. It has been reported that oxidative stress damage caused by iron overload could induce apoptosis or ferroptosis. However, the related studies and mechanisms are not well unknown in NTDT disorders. Aims: To investigate the effects of iron overload on bone marrow erythropoiesis, heart and liver in NTDT patients and Hbb th3(th3/+) mice. Methods: Patients (19-47 y of age) and 12-month-old Hbb th3(th3/+) mice with NTDT were selected as thalassemia group, healthy human and normal mice were selected as control group. Iron overload related indexes, bone marrow erythropoiesis, oxidative stress, apoptosis and ferroptosis of each sample were detected by Elisa, flow cytometry, RT-PCR and Weston blot methods, respectively. Results: Compared with the control group, Serum ferritin is significantly increased in NTDT group, and there is imbalance of iron metabolism. And in NTDT patients, liver and myocardial iron deposition was assessed by MRI analysis, resonance results suggest that the degree of iron overload in liver is more significant than that in heart. The damage of erythropoiesis in NTDT group was more severe than that in control group, which showed active erythropoiesis, and the differentiation of erythroid precursor cells stagnated in early stage of erythroid precursor cells, and there were maturation disorders. The oxidative stress-related indexes reactive oxygen species (ROS), lipid peroxidation and malondialdehyde (MDA) induced by iron overload were also significantly increased in the NTDT group. However, significant signs of apoptosis were observed in the bone marrow of the NTDT group, including increased proportion of apoptotic cells, signs of apoptosis were mainly observed in the mitochondria of erythroid colony electron microscopy, and the level of GPX4 that is a key indicator of ferroptosis, was increased. But the expression of GPX4, VDAC2 and SLC7A11 of ferroptosis was decreased in the heart and liver with heavy iron deposition, and the signs of ferroptosis were also observed under electron microscopy. Summary/Conclusion: Our study found that there are differences in iron overload and injury performance among different organs in NTDT. Oxidative stress caused by iron overload in the bone marrow impairs erythropoiesis mainly through apoptosis, whereas signs of ferroptosis were observed in the liver and heart of Hbb th3(th3/+) mice.These results suggest that with the gradual accumulation of iron circulation, the damage is a dynamic process, and different organs show different signs of damage, which may be related to the different mechanisms of damage, tolerance and compensation of organs, but further studies are needed to confirm.

Non-alcoholic fatty liver disease (NAFLD) is a progressive disorder of liver metabolism and has become the most common chronic liver disease worldwide. Benzo[a]pyrene (BaP) is recognized as a potent carcinogen, but the effect of low-dose BaP on the development of NAFLD has not been well-studied, and its molecular mechanism is still unknown. In this study, we demonstrated that low-dose BaP induced hepatic steatosis in a mouse model with a notable increase in hepatic lipid content. Interestingly, mRNA expression of genes related to fatty acids uptake or synthesis was not significantly altered after BaP exposure. Instead, we found that low-dose BaP promoted lipid deposition in primary mouse hepatocytes by inhibiting autophagy, which was regulated through Leucine carboxyl methyltransferase-1 (LCMT1) mediated Protein Phosphatases 2A subunit C (PP2Ac) methylation. The role of LCMT1 in BaP-induced steatosis was further validated in a liver-specific lcmt1 knockout (L-LCMT1 KO) mouse model. In this study, we provided evidence to support a novel mechanism by which BaP induces the development of hepatic steatosis through PP2Ac mediated autophagy inhibition. These findings provided new insight into the pathogenesis of NAFLD induced by environmental exposure to low-dose BaP.

BACKGROUND:Hepatocellular carcinoma (HCC) is one of the most malignant type of cancers. Leuci carboxyl methyltransferase 1 (LCMT1) is a protein methyltransferase that plays an improtant regulatory role in both normal and cancer cells. The aim of this study is to evaluate the expression pattern and clinical significance of LCMT1 in HCC.METHODS:The expression pattern and clinical relevance of LCMT1 were determined using the Gene Expression Omnibus (GEO) database, the Cancer Genome Atlas (TCGA) program, and our datasets. Gain-of-function and loss-of-function studies were employed to investigate the cellular functions of LCMT1 in vitro and in vivo. Quantitative real-time polymerase chain reaction (RT-PCR) analysis, western blotting, enzymatic assay, and high-performance liquid chromatography were applied to reveal the underlying molecular functions of LCMT1.RESULTS:LCMT1 was upregulated in human HCC tissues, which correlated with a "poor" prognosis. The siRNA-mediated knockdown of LCMT1 inhibited glycolysis, promoted mitochondrial dysfunction, and increased intracellular pyruvate levels by upregulating the expression of alani-neglyoxylate and serine-pyruvate aminotransferase (AGXT). The overexpression of LCMT1 showed the opposite results. Silencing LCMT1 inhibited the proliferation of HCC cells in vitro and reduced the growth of tumor xenografts in mice. Mechanistically, the effect of LCMT1 on the proliferation of HCC cells was partially dependent on PP2A.CONCLUSIONS:Our data revealed a novel role of LCMT1 in the proliferation of HCC cells. In addition, we provided novel insights into the effects of glycolysis-related pathways on the LCMT1regulated progression of HCC, suggesting LCMT1 as a novel therapeutic target for HCC therapy.

目的 探索苯并(a)芘(BaP)对人肝癌细胞株Hep G2细胞脂质含量及脂代谢的影响.方法 0、0.01、1nmol/LBaP作用Hep G2细胞,采用刃天青检测细胞活性,油红O染色、甘油三脂试剂盒检测细胞内甘油三脂含量,实时荧光定量PCR检测脂代谢相关调节因子的mRNA表达.结果 经BaP处理后,Hep G2细胞活性不变,细胞内脂质增加,LXR-α、FANS、MPC1、MPC2、CD36的mRNA表达增加,DAGT1、MPT的mRNA表达下降(P＜0.05),FABP1的mRNA表达没有明显改变.结论 BaP影响Hep G2细胞脂质代谢,促进细胞脂质沉积.

Manganese (Mn) exposure leads to autophagy dysfunction and causes neurodegenerative diseases such as Parkinson's syndrome and Alzheimer's disease. However, the mechanism of neurotoxicity of Mn has been less clear. The methylation of the protein phosphatase 2A catalytic subunit determines the dephosphorylation activity of protein phosphatase and plays an important role in autophagy regulation. In this investigation, we established a model of Mn (0-2000 mu mol/L) exposure to N2a cells for 12 h, used the PPME-1 inhibitor ABL-127, and constructed an LCMT1-overexpressing N2a cell line. We also regulated the PP2Ac methylation level and explored the effect of PP2Ac methylation on Mn-induced (0-1000 mu mol/L) N2a cellular autophagy. Our results showed that Mn > 500 mu mol/L induced N2a cell damage and increased oxidative stress. Moreover, Mn modulated autophagy in N2a cells by downregulating PP2Ac methylation, which regulated mTORC1 signaling pathway activation. Both ABL-127 and LCMT1 overexpression can upregulate PP2Ac methylation in parallel with ameliorating N2a cell abnormal autophagy induced by Mn, Briefly, the upregulation of PP2Ac methylation can ameliorate the autophagy disorder of N2a by Mn and effectively alleviate Mn-induced cytotoxicity and oxidative stress, indicating that regulation of autophagy is a protective strategy against Mn-induced neurotoxicity.

The excessive M1 polarization of macrophages drives the occurrence and development of inflammatory diseases. The reprogramming of macrophages from M1 to M2 can be achieved by targeting metabolic events. Taurine promotes for the balance of energy metabolism and the repair of inflammatory injury, preventing chronic diseases and complications. However, little is known about the mechanisms underlying the action of taurine modulating the macrophage polarization phenotype. In this study, we constructed a low-dose LPS/IFN-γ-induced M1 polarization model to simulate a low-grade pro-inflammatory process. Our results indicate that the taurine transporter TauT/SlC6A6 is upregulated at the transcriptional level during M1 macrophage polarization. The nutrient uptake signal on the membrane supports the high abundance of taurine in macrophages after taurine supplementation, which weakens the status of methionine metabolism, resulting in insufficient S-adenosylmethionine (SAM). The low availability of SAM is directly sensed by LCMT-1 and PME-1, hindering PP2Ac methylation. PP2Ac methylation was found to be necessary for M1 polarization, including the positive regulation of VDAC1 and PINK1. Furthermore, its activation was found to promote the elimination of mitochondria by macrophages via the mitophagy pathway for metabolic adaptation. Mechanistically, taurine inhibits SAM-dependent PP2Ac methylation to block PINK1-mediated mitophagy flux, thereby maintaining a high mitochondrial density, which ultimately hinders the conversion of energy metabolism to glycolysis required for M1. Our findings reveal a novel mechanism of taurine-coupled M1 macrophage energy metabolism, providing novel insights into the occurrence and prevention of low-grade inflammation, and propose that the sensing of taurine and SAM availability may allow communication to inflammatory response in macrophages.

The molecular mechanism of Alzheimer-like cognitive impairment induced by manganese (Mn) exposure has not yet been fully clarified, and there are currently no effective interventions to treat neurodegenerative lesions related to manganism. Protein phosphatase 2 A (PP2A) is a major tau phosphatase and was recently identified as a potential therapeutic target molecule for neurodegenerative diseases; its activity is directed by the methylation status of the catalytic C subunit. Methionine is an essential amino acid, and its downstream metabolite S-adenosylmethionine (SAM) participates in transmethylation pathways as a methyl donor. In this study, the neurotoxic mechanism of Mn and the protective effect of methionine were evaluated in Mn-exposed cell and rat models. We show that Mn-induced neurotoxicity is characterized by PP2Ac demethylation accompanied by abnormally decreased LCMT-1 and increased PME-1, which are associated with tau hyperphosphorylation and spatial learning and memory deficits, and that the poor availability of SAM in the hippocampus is likely to determine the loss of PP2Ac methylation. Importantly, maintenance of local SAM levels through continuous supplementation with exogenous methionine, or through specific inhibition of PP2Ac demethylation by ABL127 administration in vitro, can effectively prevent tau hyperphosphorylation to reduce cellular oxidative stress, apoptosis, damage to cell viability, and rat memory deficits in cell or animal Mn exposure models. In conclusion, our data suggest that SAM and PP2Ac methylation may be novel targets for the treatment of Mn poisoning and neurotoxic mechanism-related tauopathies.

Under strictly Framework Convention on Tobacco Control, novel tobacco products are going to be promising alterations to consumers and manufactures. Even though the novel tobacco products have been considered less harmful than traditional tobaccos, there is a few knowledges about the subsequent substances during consume and their impacts to the consumers due to short introduction into the market. Thus, the present study aims to investigate the adverse effects of novel tobacco products on Caenorhabditis elegans(C. elegans) and to provide relevant references for novel tobacco products toxicity research and assessment. C. elegans individuals at L4 stage were exposed to different kinds of novel tobacco products, including electronic cigarettes liquid (e-liquid), the extract of e-cig aerosol (e-aerosol), mint and black tea flavor snus. After specific exposure time, the multiple toxic endpoints of C. elegans were measured, including acute toxicity, locomotion behavior, body length, and life-span. The oxidative stress was tested too. According to acute toxicity assays, the half lethal dose of four novel tobacco products calculated from theoretical nicotine concentration, ranked as follows e-liquid (0.29 mg/ml) > the extract of e-cig aerosol (0.43 mg/ml) > mint flavor snus (1.20 mg/ml) > black tea flavor snus (1.50 mg/ml). The equivalent lethal rate 5%~20% of four novel tobacco products were applied to following experiments. These novel tobacco products damaged nematode's locomotion including head thrashing and body bending, the damage was most evident in two flavors of snus. The similar trends were found in reproductive performance investigation. At tested concentrations, the retardation development of C. elegans was found throughout all stages with peak blockage at adulthood. Life-span tests showed that novel tobacco products at 5% lethal rate seemed no significant effect on affected the life-span of nematodes, with snus shortened the lifespan of C. elegans at 20% lethal rate. Imaging stress response indicted four types of tobacco productions causing stress response in C. elegans. Exposed to either 5% or 20% lethal levels (5% and 20%), the percentages of worms with DAF-16 redistribution among all groups varied, with higher frequencies in both snus. Summary, novel tobacco products caused multiple adverse impacts to C. elegans, including acute toxicity, locomotion behavior disruption, brood size reduction, development retardation, and life-span reduction. The toxicity was associated with both the feature and concentration of tobacco products, and oxidative stress was the main mechanism.

目的 探讨蛋白磷酸酶2A催化亚基(PP2Ac)去甲基化在苯并(a)芘(benzo[a]pyrene,BaP)诱导人支气管上皮细胞(human bronchial epithelial,HBE)恶性转化中的变化及可能作用.方法 用40 μmol/L BaP处理人支气管上皮细胞,每周一次,共15周,构建BaP诱导的HBE细胞恶性转化模型,采用软琼脂试验和裸鼠成瘤试验鉴定恶性转化是否构建成功,使用蛋白免疫印迹(Western blot)分析比较恶性转化细胞和同期对照组细胞中PP2Ac去甲基化及其调节蛋白表达变化.结果 软琼脂试验和裸鼠成瘤试验结果显示,经BaP处理后的细胞能在软琼脂中形成细胞集落,接种BaP诱导转化细胞的裸鼠可见肿块,说明恶性转化成功.蛋白免疫印迹(Western blot)检测蛋白表达发现,经BaP诱导恶性转化的HBE细胞和经100 μmol/L BaP单次刺激24h的HBE细胞与正常HBE细胞相比,总PP2Ac表达均无差异,亮氨酸羧基甲基转移酶1(LCMT1)表达均明显下降,蛋白磷酸酶甲基酯酶1(PME-1)和PP2Ac去甲基化(Dem-PP2Ac)表达均明显升高,差异有统计学意义(P＜0.05).结论 PP2Ac去甲基化在BaP诱导细胞恶性转化中发挥作用,可能通过增强PP2Ac去甲基化促进BaP致肺癌发生.