👤 Ai-Guo Xu

The apolipoprotein A5 (APOA5) gene -1131T>C (rs662799) has been suggested to be involved in the pathway of lipid homeostasis and the development of metabolic syndrome (MetS). However, the findings are not consistent. To systematically evaluate the associations between -1131T>C polymorphism and fasting lipid parameters and the risk of MetS, we conducted a case-control study in a Chinese population and a meta-analysis. The findings from 1840 Chinese participants indicated that the C allele carriers had significantly higher fasting total cholesterol (TC), triglycerides (TG) and lower HDL-cholesterol (HDL-C) than the TT homozygotes carriers. The -1131C allele was also found to be significantly associated with increased risk of MetS (OR  =  1.40, 95% confidence interval (CI)  =  1.15, 1.69) compared to the TT homozygotes. In the meta-analysis of 51,868 participants from 46 East Asian studies, 26 European studies and 19 studies of other ethnic groups, the -1131C allele was associated with higher fasting TC (weighted mean difference (WMD)  =  0.08 mmol/L, 95% CI  =  0.05, 0.10, P = 1.74×10(-9)), TG (WMD  =  0.30 mmol/L, 95% CI  =  0.26, 0.33, P =  1.87×10(-55)), LDL-cholesterol (LDL-C) (WMD  =  0.04 mmol/L, 95% CI  =  0.02, 0.07, P = 0.002), and lower HDL-C (WMD  =  -0.05 mmol/L, 95% CI  =  -0.06,-0.04, P = 1.88×10(-21)), respectively. Based on 12 studies with 5,573 MetS cases and 8,290 controls from 5 East Asian studies, 5 European studies and 2 studies of other ethnic groups, the -1131C allele was associated with increased risk of MetS with an OR (95% CI)  =  1.33 (1.16, 1.53) in the overall population, 1.43 (1.29, 1.58) in East Asian and 1.30 (0.94, 1.78) in European populations. In conclusion, the -1131C allele may be associated with elevated levels of fasting TG, TC, LDL-C and decreased HDL-C, and increased risk of MetS, especially in East Asians. Show less

The Apolipoprotein A5 (APO A5) -1131T/C, fibrinogen β (FgB) -455G/A, -148C/T, and cholesteryl ester transfer protein (CETP) TaqIB gene polymorphisms have been indicated to be associated with the coronary artery disease (CAD) risk, but the individual study results are still inconsistent. To explore the relationship between APO A5 -1131T/C, FgB -455G/A, -148C/T, and CETP TaqIB gene polymorphisms and CAD in the Chinese population, the current meta-analysis involving 15,055 subjects from 40 individual studies was conducted. The pooled odds ratio (OR) for the association between APO A5 -1131T/C, FgB -455G/A, -148C/T, and CETP TaqIB gene polymorphisms and CAD and its corresponding 95 % confidence interval (95 % CI) were evaluated by random or fixed effect model. A significant association between APO A5 -1131T/C gene polymorphism and CAD in the Chinese population was found under an allelic (OR: 1.33, 95 % CI: 1.22-1.44, P < 0.00001), recessive (OR: 1.67, 95 % CI: 1.25-2.25, P = 0.0006), dominant (OR: 0.820, 95 % CI: 0.767-0.876, P = 1.0 × 10(-10)), homozygous (OR: 2.36, 95 % CI: 1.55-3.58, P < 0.0001) and heterozygous genetic models (OR: 1.136, 95 % CI:1.075-1.200, P = 1.0 × 10(-10)). A significant association between FgB -455G/A gene polymorphism and CAD was also detected in the Chinese population under an allelic (OR: 1.50, 95 % CI: 1.25-1.81, P < 0.0001), dominant (OR: 0.864, 95 % CI: 0.819-0.912, P = 1.0 × 10(-10)), homozygous (OR: 1.616, 95 % CI: 1.213-2.152, P = 0.001) and heterozygous genetic models (OR: 1.245, 95 % CI:1.138-1.361, P = 1.0 × 10(-10)). No significant association was found between them under a recessive genetic model (OR: 1.124, 95 % CI: 0.844-1.497, P = 0.424). A significant association was also found between FgB -148C/T gene polymorphism and CAD in the Chinese population under an allelic (OR: 1.34, 95 % CI: 1.06-1.71, P = 0.02), recessive (OR: 1. 65, 95 % CI: 1.02-2.69, P = 0.04), dominant (OR: 0.924, 95 % CI: 0.872-0.978, P = 0.007) and homozygous genetic models (OR: 0.968, 95 % CI: 0.942-0.995, P = 0.018). No significant association was found between them under a heterozygous genetic model (OR: 0.979, 95 % CI: 0.937-1.023, P = 0.342). In the whole Chinese population, no significant association between the CETP TaqIB gene polymorphism and CAD was found under an allelic (OR: 1.17, 95 % CI: 0.94-1.45, P = 0.15), dominant (OR: 1.46, 95 % CI: 0.80-2.67, P = 0.22) or recessive genetic models (OR: 0.68, 95 % CI: 0.32-1.44, P = 0.31). However, in the subgroup analysis stratified by ethnicity, there was a significant association between them under an allelic (OR: 1.27, 95 % CI: 1.07-1.52, P = 0.007) and dominant genetic model (OR: 2.04, 95 % CI: 1.49-2.79, P < 0.00001) in the Han subgroup. In the Chinese population, the APO A5 -1131T/C and FgB -455G/A, -148C/T gene polymorphisms were implied to be associated with CAD susceptibility. The APO A5 -1131C, FgB -455A, and -148T alleles might confer susceptibility to CAD. CETP TaqIB gene polymorphism was suggested to be associated with CAD susceptibility in the Chinese Han population. Carriers with B1 allele of CETP TaqIB gene might be predisposed to CAD in the Chinese Han population. Show less

Elevated levels of circulating triglycerides and increased arterial stiffness are associated with cardiovascular disease. Numerous studies have reported an association between levels of circulating triglycerides and arterial stiffness. We used Mendelian randomization to test whether this association is causal. We investigated the association between circulating triglyceride levels, the apolipoprotein A-V (ApoA5) -1131T>C single nucleotide polymorphism and brachial-ankle pulse wave velocity (baPWV) by examining data from 4421 subjects aged 18-74 years who were recruited from the Chinese population. baPWV was significantly associated with the levels of circulating triglycerides after adjusting for age, sex, body mass index (BMI), systolic blood pressure, heart rate, waist-to-hip ratio, antihypertensive treatment and diabetes mellitus status. The -1131C allele was associated with a 5% (95% confidence interval 3-8%) increase in circulating triglycerides (adjusted for age, sex, BMI, waist-to-hip ratio, diabetes mellitus and antihypertensive treatment). Instrumental variable analysis showed that genetically elevated levels of circulating triglycerides were not associated with increased baPWV. These results do not support the hypothesis that levels of circulating triglycerides have a causal role in the development of arterial stiffness. Show less

To investigate AXIN1-related CSRNP1 gene expression and the mechanism of its transcriptional regulation in TGF-β1-induced tumor cells. Human lung carcinoma A549 cells or human prostate cancer PC3 cells were treated with TGF-β1 at different doses (0, 20, 40, and 80 ng/ml) or at 20 ng/ml for 0, 8, 12, or 24 h, and the dose and time effect of TGF-β1 on CSRNP1 mRNA expression in the tumor cells were evaluated with real-time RT-PCR. A549 cells were also treated with TGF-β1 and cycloheximide to clarify whether CSRNP1 expression induced by TGF-β1 required de novo protein synthesis. A549 cells transfected with pcDNA3.1, flag-SMAD3, or flag-SMAD3-mu, after serum starvation, were treated with or without TGF-β1 (20 ng/mL) for 24 h, and the overexpression of wild-type SMAD3 and dominant negative SMAD3-mu mutant were confirmed by Western blotting. The effect of SMAD3 or SMAD3-mu overexpression on CSRNP1 mRNA expression was also measured by real-time RT-PCR. In both A549 and PC3 cells, TGF-β1 dose- and time-dependently stimulated CSRNP1 expression, which required de novo protein synthesis in A549 cells. Overexpression of wild-type SMAD3 significantly increased the expression of CSRNP1 mRNA induced by TGF-β1, while overexpression of dominant negative SMAD3 mutant remarkably reduced CSRNP1 mRNA expression in response to TGF-β1 in A549 cells. TGF-β1 may contribute to CSRNP1 expression through SMAD3 activation and downstream signaling in tumor cells. Show less

We previously reported that Axin1 (Axin) is down-regulated in many cases of lung cancer, and X-ray irradiation increased Axin expression and inhibited lung cancer cells. The mechanisms, however, were not clear. Four lung cancer cell lines were used to detect the methylation status of Axin with or without X-ray treatment. Real-time PCR was used to quantify the expression of Axin, and western blot analysis was applied to measure protein levels of Axin, β-catenin, Cyclin D1, MMP-7, DNMTS, MeCP2 and acetylated histones. Flow cytometric analysis, colony formation assay, transwell assay and xenograft growth experiment were used to study the biological behavior of the cells with hypermethylated or unmethylated Axin gene after X-ray treatment. Hypermethylated Axin gene was detected in 2 of 4 cell lines, and it correlated inversely with Axin expression. X-ray treatment significantly up-regulated Axin expression in H446 and H157 cells, which possess intrinsic hypermethylation of the Axin gene (P<0.01), but did not show up-regulation in LTE and H460 cells, which have unmethylated Axin gene. 2Gy X-ray significantly reduced colony formation (from 71% to 10.5%) in H157 cells, while the reduction was lower in LTE cells (from 71% to 20%). After X-ray irradiation, xenograft growth was significantly decreased in H157 cells (from 1.15 g to 0.28 g) in comparison with LTE cells (from 1.06 g to 0.65 g). Significantly decreased cell invasiveness and increased apoptosis were also observed in H157 cells treated with X-ray irradiation (P<0.01). Down-regulation of DNMTs and MeCP2 and up-regulation of acetylated histones could be detected in lung cancer cells. X-ray-induced inhibition of lung cancer cells may be mediated by enhanced expression of Axin via genomic DNA demethylation and histone acetylation. Lung cancer cells with a different methylation status of the Axin gene showed different radiosensitivity, suggesting that the methylation status of the Axin gene may be one important factor to predict radiosensitivity of the tumor. Show less

In recent years, long noncoding RNAs (lncRNAs) have been investigated as a new class of regulators of biological function. A recent study reported that lncRNAs control cell proliferation in hepatocellular carcinoma (HCC). However, the role of lncRNAs in liver regeneration and the overall mechanisms remain largely unknown. To address this issue, we carried out a genome-wide lncRNA microarray analysis during liver regeneration in mice after 2/3 partial hepatectomy (PH) at various timepoints. The results revealed differential expression of a subset of lncRNAs, notably a specific differentially expressed lncRNA associated with Wnt/β-catenin signaling during liver regeneration (an lncRNA associated with liver regeneration, termed lncRNA-LALR1). The functions of lncRNA-LALR1 were assessed by silencing and overexpressing this lncRNA in vitro and in vivo. We found that lncRNA-LALR1 enhanced hepatocyte proliferation by promoting progression of the cell cycle in vitro. Furthermore, we showed that lncRNA-LALR1 accelerated mouse hepatocyte proliferation and cell cycle progression during liver regeneration in vivo. Mechanistically, we discovered that lncRNA-LALR1 facilitated cyclin D1 expression through activation of Wnt/β-catenin signaling by way of suppression of Axin1. In addition, lncRNA-LALR1 inhibited the expression of Axin1 mainly by recruiting CTCF to the AXIN1 promoter region. We also identified a human ortholog RNA of lncRNA-LALR1 (lncRNA-hLALR1) and found that it was expressed in human liver tissues. lncRNA-LALR1 promotes cell cycle progression and accelerates hepatocyte proliferation during liver regeneration by activating Wnt/β-catenin signaling. Pharmacological intervention targeting lncRNA-LALR1 may be therapeutically beneficial in liver failure and liver transplantation by inducing liver regeneration. Show less

Axin is an important negative regulator of Wnt pathway. We have reported that reduced expression of Axin could be detected in lung cancer tissues, but the mechanism is not clear. By analyzing the genomic sequence, we note that Axin gene promoter is rich in CpGs. Little is known about the methylation status of Axin gene in lung cancer. So, nested MSP and RT-PCR were used to study the methylation status and mRNA expression of Axin gene in lung cancer tissues and cell lines. The results showed that hypermethylated Axin gene promoter and reduced mRNA expression level of Axin could be detected in lung cancer tissues but not in their paired autologous normal lung tissues (P < 0.01). The hypermethylated Axin gene promoter significantly correlated with the degree of differentiation (P = 0.03), lymph node metastasis (P = 0.048) and TNM classifications (P = 0.032). Demethylation reagent 5-aza-2-deoxycytidine significantly up-regulate Axin expression in BE1 cells (with hypermethylated Axin gene promoter) but not in H460 cells (with unmethylated Axin gene promoter). MTT (3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and transwell matrigel invasion assay showed that 5-aza-2-deoxycytidine treatment inhibited cell growth and invasion more significantly in BE1 cells than that in H460 cells. Our data indicate that hypermethylated Axin gene significantly correlates with the progression of lung cancer and might serve as a new target of clinical therapy for lung cancer patients in future. Show less

In the postsynaptic density of glutamatergic synapses, the discs large (DLG)-membrane-associated guanylate kinase (MAGUK) family of scaffolding proteins coordinates a multiplicity of signaling pathways to maintain and regulate synaptic transmission. Postsynaptic density-93 (PSD-93) is the most variable paralog in this family; it exists in six different N-terminal isoforms. Probably because of the structural and functional variability of these isoforms, the synaptic role of PSD-93 remains controversial. To accurately characterize the synaptic role of PSD-93, we quantified the expression of all six isoforms in the mouse hippocampus and examined them individually in hippocampal synapses. Using molecular manipulations, including overexpression, gene knockdown, PSD-93 knock-out mice combined with biochemical assays, and slice electrophysiology both in rat and mice, we demonstrate that PSD-93 is required at different developmental synaptic states to maintain the strength of excitatory synaptic transmission. This strength is differentially regulated by the six isoforms of PSD-93, including regulations of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor-active and inactive synapses, and activity-dependent modulations. Collectively, these results demonstrate that alternative combinations of N-terminal PSD-93 isoforms and DLG-MAGUK paralogs can fine-tune signaling scaffolds to adjust synaptic needs to regulate synaptic transmission. Show less

Plasma lipid levels are important risk factors for cardiovascular disease and are influenced by genetic and environmental factors. Recent genome wide association studies (GWAS) have identified several lipid-associated loci, but these loci have been identified primarily in European populations. In order to identify genetic markers for lipid levels in a Chinese population and analyze the heterogeneity between Europeans and Asians, especially Chinese, we performed a meta-analysis of two genome wide association studies on four common lipid traits including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL) in a Han Chinese population totaling 3,451 healthy subjects. Replication was performed in an additional 8,830 subjects of Han Chinese ethnicity. We replicated eight loci associated with lipid levels previously reported in a European population. The loci genome wide significantly associated with TC were near DOCK7, HMGCR and ABO; those genome wide significantly associated with TG were near APOA1/C3/A4/A5 and LPL; those genome wide significantly associated with LDL were near HMGCR, ABO and TOMM40; and those genome wide significantly associated with HDL were near LPL, LIPC and CETP. In addition, an additive genotype score of eight SNPs representing the eight loci that were found to be associated with lipid levels was associated with higher TC, TG and LDL levels (P = 5.52 × 10(-16), 1.38 × 10(-6) and 5.59 × 10(-9), respectively). These findings suggest the cumulative effects of multiple genetic loci on plasma lipid levels. Comparisons with previous GWAS of lipids highlight heterogeneity in allele frequency and in effect size for some loci between Chinese and European populations. The results from our GWAS provided comprehensive and convincing evidence of the genetic determinants of plasma lipid levels in a Chinese population. Show less

Multiple osteochondromas (MO), an autosomal dominant skeletal disease, is characterized by the presence of multiple cartilage-capped bone tumors (exostoses). Two genes with mutations that are most commonly associated with MO have been identified as EXT1 and EXT2, which are Exostosin-1 and Exostosin-2. In this study, a variety of EXT1 and EXT2 gene mutations were identified in ten Chinese families with MO. We investigated ten unrelated Chinese families involving a total of 46 patients who exhibited typical features of MO. The coding exons of EXT1 and EXT2 were sequenced after PCR amplification in ten probands. Radiological investigation was conducted simultaneously. Nine mutations were identified, five in EXT1 and four in EXT2, of which three were de novo mutations and six were novel mutations. One proband carried mutations in both EXT1 and EXT2 simultaneously, and three probands, including one sporadic case and two familial cases, had no detectable mutations. Our findings are useful for extending the mutational spectrum in EXT1 and EXT2 and understanding the genetic basis of MO in Chinese patients. Show less

Multiple osteochondromas (MO) is an autosomal dominant hereditary disorder caused by heterozygous germline mutations in the exostonsin-1 (EXT1) or exostosin-2 (EXT2) genes. In this study, we screened mutations in the EXT1/EXT2 genes in four Chinese MO kindreds by direct sequencing. Three point mutations were detected, including a nonsense mutation in the EXT2 gene (c.544C > T) and two splice site mutations in the EXT1 and EXT2 genes, respectively (EXT1: c.1883 + 1G > A and EXT2: c.1173 + 1G > T). Although splice site mutations constitute at least 10% of all mutations that cause MO, there has been limited research on their pathogenic effect on RNA processing due to poor availability of patient RNA samples. In this study, ex vivo and in vivo splicing assays were used to investigate the effect of EXT1 and EXT2 mutations on aberrant splicing at the mRNA level. Our results indicate that identified splice site mutations can cause either cryptic splice site usage or exon skipping. Show less

The study of the genetic regulation of metabolism in human serum samples can contribute to a better understanding of the intermediate biological steps that lead from polymorphism to disease. Here, we conducted a genome-wide association study (GWAS) to discover metabolic quantitative trait loci (mQTLs) utilizing samples from a study of prostate cancer in Swedish men, consisting of 402 individuals (214 cases and 188 controls) in a discovery set and 489 case-only samples in a replication set. A global nontargeted metabolite profiling approach was utilized resulting in the detection of 6,138 molecular features followed by targeted identification of associated metabolites. Seven replicating loci were identified (PYROXD2, FADS1, PON1, CYP4F2, UGT1A8, ACADL, and LIPC) with associated sequence variants contributing significantly to trait variance for one or more metabolites (P = 10(-13) -10(-91)). Regional mQTL enrichment analyses implicated two loci that included FADS1 and a novel locus near PDGFC. Biological pathway analysis implicated ACADM, ACADS, ACAD8, ACAD10, ACAD11, and ACOXL, reflecting significant enrichment of genes with acyl-CoA dehydrogenase activity. mQTL SNPs and mQTL-harboring genes were over-represented across GWASs conducted to date, suggesting that these data may have utility in tracing the molecular basis of some complex disease associations. Show less

Variants in the leucine-rich repeat and lg domain containing nogo receptor-interacting protein 1 gene (LINGO1) have been identified to be associated with the increased risk of essential tremor (ET), especially among Caucasians. To explore whether the LINGO1 gene plays a role in ET susceptibility, we performed a systematic genetic analysis of the coding region in the LINGO1 gene. Four nucleotide variants have been genotyped, including three known variants (rs2271398, rs2271397, and rs3743481), and a novel G → C transition (ss491228439). Extended analysis showed no significant difference in genotypic and allelic distributions between 151 patients and 301 control subjects for these four variants (all P > 0.05). However, further sex-stratified analysis revealed that the C allele of rs2271397 and ss491228439 contributed the risk of ET in female (P = 0.017, OR = 2.139, 95 % CI 1.135 ~ 4.030 for rs2271397 and P = 0.038, OR = 1.812, 95 % CI 1.027 ~ 3.194 for ss491228439). Haplotype analysis indicated that A465-C474-C714 haplotype was significantly associated with increased risk of ET in female (P = 0.041, OR = 1.800, 95 % CI 1.020 ~ 3.178). Our results indicate that the LINGO1 variants are associated with ET in Chinese Han female patients. Show less

LINGO-1 is a functional component of the Nogo receptor 1 · p75(NTR) · LINGO-1 and Nogo receptor 1 · TAJ (TNFRSF19/TROY)·LINGO-1 signaling complexes. It has recently been shown that LINGO-1 antagonists significantly improve neuronal survival after neural injury. However, the mechanism by which LINGO-1 signaling influences susceptibility to apoptosis remains unknown. In an effort to better understand how LINGO-1 regulates these signaling pathways, we used an established model of serum deprivation (SD) to induce neuronal apoptosis. We demonstrate that treatment either with a construct containing the intracellular domain of LINGO-1 or with Nogo66, a LINGO-1 receptor complex agonist, resulted in an enhanced rate of apoptosis in primary cultured cortical neurons under SD. Reducing the expression levels of the serine/threonine kinase WNK3 using shRNA or inhibiting its kinase activity had similar effects on the survival of serum-deprived neurons. Consistent with these observations, we found that LINGO-1 and WNK3 co-localized and co-precipitated in cultured cortical neurons and brain tissue. Significantly, this co-association was enhanced by Nogo66 treatment. Binding of WNK3 to the intracellular domain of LINGO-1 led to a reduction in WNK3 kinase activity, as did Nogo66 stimulation. Moreover, in vitro and in vivo evidence indicates that endogenous WNK3 suppresses SD-induced neuronal apoptosis in a kinase-dependent manner, as the expression of either a WNK3 RNAi construct or a kinase-dead N-terminal fragment of WNK3 led to increased apoptosis. Taken together, our results show that LINGO-1 potentiates neuronal apoptosis, likely by inhibiting WNK3 kinase activity. Show less

Aberrant cardiomyocyte microtubule growth is a feature of pressure overload induced cardiac hypertrophy believed to contribute to left ventricular (LV) dysfunction. Microtubule Actin Cross-linking Factor 1 (MACF1/Acf7) is a 600 kd spectraplakin that stabilizes and guides microtubule growth along actin filaments. MACF1 is expressed in the heart, but its impact on cardiac microtubules, and how this influences cardiac structure, function, and adaptation to hemodynamic overload is unknown. Here we used inducible cardiac-specific MACF1 knockout mice (MACF1 KO) to determine the impact of MACF1 on cardiac microtubules and adaptation to pressure overload (transverse aortic constriction (TAC).In adult mouse hearts, MACF1 expression was low under basal conditions, but increased significantly in response to TAC. While MACF1 KO had no observable effect on heart size or function under basal conditions, MACF1 KO exacerbated TAC induced LV hypertrophy, LV dilation and contractile dysfunction. Interestingly, subcellular fractionation of ventricular lysates revealed that MACF1 KO altered microtubule distribution in response to TAC, so that more tubulin was associated with the cell membrane fraction. Moreover, TAC induced microtubule redistribution into this cell membrane fraction in both WT and MACF1 KO mice correlated strikingly with the level of contractile dysfunction (r(2) = 0.786, p<.001). MACF1 disruption also resulted in reduction of membrane caveolin 3 levels, and increased levels of membrane PKCα and β1 integrin after TAC, suggesting MACF1 function is important for spatial regulation of several physiologically relevant signaling proteins during hypertrophy. Together, these data identify for the first time, a role for MACF1 in cardiomyocyte microtubule distribution and in adaptation to hemodynamic overload. Show less

The liver is a central organ that controls systemic energy homeostasis and nutrient metabolism. Dietary carbohydrates and lipids, and fatty acids derived from adipose tissue are delivered to the liver, and utilized for gluconeogenesis, lipogenesis, and ketogenesis, which are tightly regulated by hormonal and neural signals. Hepatic lipogenesis is activated primarily by insulin that is secreted from the pancreas after a high-carbohydrate meal. Sterol regulatory element binding protein-1c (SREBP-1c) and carbohydrate-responsive element-binding protein (ChREBP) are major transcriptional regulators that induce key lipogenic enzymes to promote lipogenesis in the liver. Sterol regulatory element binding protein-1c is activated by insulin through complex signaling cascades that control SREBP-1c at both transcriptional and posttranslational levels. Carbohydrate-responsive element-binding protein is activated by glucose independently of insulin. Here, the authors attempt to summarize the current understanding of the molecular mechanism for the transcriptional regulation of hepatic lipogenesis, focusing on recent studies that explore the signaling pathways controlling SREBPs and ChREBP. Show less

Thioredoxin-interacting protein (TXNIP) has emerged as an important factor in pancreatic beta cell biology, and tight regulation of TXNIP levels is necessary for beta cell survival. However, the mechanisms regulating TXNIP expression have only started to be elucidated. The forkhead boxO1 transcription factor (FOXO1) has been reported to up-regulate TXNIP expression in neurons and endothelial cells but to down-regulate TXNIP in liver, and the effects on beta cells have remained unknown. We now have found that FOXO1 binds to the TXNIP promoter in vivo in human islets and INS-1 beta cells and significantly decreases TXNIP expression. TXNIP promoter deletion analyses revealed that an E-box motif conferring carbohydrate response element-binding protein (ChREBP)-mediated, glucose-induced TXNIP expression is necessary and sufficient for this effect, and electromobility shift assays confirmed FOXO1 binding to this site. Moreover, FOXO1 blocked glucose-induced TXNIP expression and reduced glucose-induced ChREBP binding at the TXNIP promoter without affecting ChREBP expression or nuclear localization, suggesting that FOXO1 may compete with ChREBP for binding to the TXNIP promoter. In fact, a FOXO1 DNA-binding mutant (FOXO1-H215R) failed to inhibit TXNIP transcription, and the effects were not restricted to TXNIP as FOXO1 also inhibited transcription of other ChREBP target genes such as liver pyruvate kinase. Together, these results demonstrate that FOXO1 inhibits beta cell TXNIP transcription and suggest that FOXO1 confers this inhibition by interfering with ChREBP DNA binding at target gene promoters. Our findings thereby reveal a novel gene regulatory mechanism and a previously unappreciated cross-talk between FOXO1 and ChREBP, two major metabolic signaling pathways. Show less

Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α. Show less

Liver X receptor α (LXRα) plays a critical role in the transcriptional control of lipid metabolism. LXR activation induces the expression of lipogenic genes, which promote hepatic steatosis and steatohepatitis. However, the regulation of LXR is not fully understood. MicroRNAs (miRs) are regarded as important negative regulators of gene expression. In this study, we found that miR-1/miR-206 repressed LXRα-induced accumulation of lipid droplets in hepatocytes. In addition, bioinformatic analysis predicted a same putative target-site for miR-1/miR-206 located within the 3'-untranslated region (3'-UTR) of LXRα mRNA. The reporter assay revealed that miR-1/miR-206 directly targeted the 3'-UTR of LXRα mRNA. Furthermore, miR-1/miR-206 repressed LXRα expression at both mRNA and protein levels, accompanied with the inhibition of expression of LXRα target genes, such as sterol-regulatory element binding protein 1c, fatty acid synthase, carbohydrate responsive element-binding protein and acetyl-CoA carboxylase 1, which are important effectors of LXRα implicated in lipogenesis. Moreover, ectopic expression of LXRα without the 3'-UTR dramatically attenuated the miR-1/miR-206-induced decrease of lipogenic genes and lipid droplet accumulation. Taken together, we for the first time demonstrated that miR-1/miR-206 attenuated LXRα-induced lipogenesis by targeting the 3'-UTR of LXRα mRNA, suggesting that miR-1/miR-206-LXRα pathway may be a novel target for the treatment of lipogenesis-associated diseases. Show less

The protein, thyroid hormone-responsive SPOT 14 homolog (Thrsp), has been reported to be a lipogenic gene in cultured hepatocytes, implicating an important role of Thrsp in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Thrsp expression is known to be regulated by a variety of transcription factors, including thyroid hormone receptor, pregnane X receptor, and constitutive androstane receptor. Emerging in vitro evidence also points to a critical role of liver X receptor (LXR) in regulating Thrsp transcription in hepatocytes. In the present study, we showed that Thrsp was up-regulated in livers of db/db mice and high-fat-diet-fed mice, two models of murine NAFLD. Hepatic overexpression of Thrsp increased triglyceride accumulation with enhanced lipogenesis in livers of C57Bl/6 mice, whereas hepatic Thrsp gene silencing attenuated the fatty liver phenotype in db/db mice. LXR activator TO901317 induced Thrsp expression in livers of wild-type (WT) and LXR-β gene-deficient mice, but not in LXR-α or LXR-α/β double-knockout mice. TO901317 treatment significantly enhanced hepatic sterol regulatory element-binding protein 1c (SREBP-1c) expression and activity in WT mice, but failed to induce Thrsp expression in SREBP-1c gene-deficient mice. Sequence analysis revealed four LXR response-element-like elements and one sterol regulatory element (SRE)-binding site within a -2,468 ∼+1-base-pair region of the Thrsp promoter. TO901317 treatment and LXR-α overexpression failed to induce, whereas overexpression of SREBP-1c significantly increased Thrsp promoter activity. Moreover, deletion of the SRE site completely abolished SREBP-1c-induced Thrsp transcription. Thrsp is a lipogenic gene in the liver that is induced by the LXR agonist through an LXR-α-mediated, SREBP-1c-dependent mechanism. Therefore, Thrsp may represent a potential therapeutic target for the treatment of NAFLD. Show less

Most of colorectal adenocarcinomas are believed to arise from adenomas, which are premalignant lesions. Sequencing the whole exome of the adenoma will help identifying molecular biomarkers that can predict the occurrence of adenocarcinoma more precisely and help understanding the molecular pathways underlying the initial stage of colorectal tumorigenesis. We performed the exome capture sequencing of the normal mucosa, adenoma and adenocarcinoma tissues from the same patient and sequenced the identified mutations in additional 73 adenomas and 288 adenocarcinomas. Somatic single nucleotide variations (SNVs) were identified in both the adenoma and adenocarcinoma by comparing with the normal control from the same patient. We identified 12 nonsynonymous somatic SNVs in the adenoma and 42 nonsynonymous somatic SNVs in the adenocarcinoma. Most of these mutations including OR6X1, SLC15A3, KRTHB4, RBFOX1, LAMA3, CDH20, BIRC6, NMBR, GLCCI1, EFR3A, and FTHL17 were newly reported in colorectal adenomas. Functional annotation of these mutated genes showed that multiple cellular pathways including Wnt, cell adhesion and ubiquitin mediated proteolysis pathways were altered genetically in the adenoma and that the genetic alterations in the same pathways persist in the adenocarcinoma. CDH20 and LAMA3 were mutated in the adenoma while NRXN3 and COL4A6 were mutated in the adenocarcinoma from the same patient, suggesting for the first time that genetic alterations in the cell adhesion pathway occur as early as in the adenoma. Thus, the comparison of genomic mutations between adenoma and adenocarcinoma provides us a new insight into the molecular events governing the early step of colorectal tumorigenesis. Show less

Fetal alcohol spectrum disorders (FASD) results from ethanol exposure to the developing fetus and is the leading cause of mental retardation. FASD is associated with a broad range of neurobehavioral deficits which may be mediated by ethanol-induced neurodegeneration in the developing brain. An immature brain is more susceptible to ethanol neurotoxicity. We hypothesize that the enhanced sensitivity of the immature brain to ethanol is due to a limited capacity to alleviate cellular stress. Using a third trimester equivalent mouse model of ethanol exposure, we demonstrated that subcutaneous injection of ethanol induced a wide-spread neuroapoptosis in postnatal day 4 (PD4) C57BL/6 mice, but had little effect on the brain of PD12 mice. We analyzed the expression profile of genes regulating apoptosis, and the pathways of ER stress response (also known as unfolded protein response, UPR) and autophagy during these ethanol-sensitive and resistant periods (PD4 versus PD12) using PCR microarray. The expression of pro-apoptotic genes, such as caspase-3, was much higher on PD4 than PD12; in contrast, the expression of genes that regulate UPR and autophagy, such as atf6, atg4, atg9, atg10, beclin1, bnip3, cebpb, ctsb, ctsd, ctss, grp78, ire1α, lamp, lc3 perk, pik3c3, and sqstm1 was significantly higher on PD12 than PD4. These results suggest that the vulnerability of the immature brain to ethanol could result from high expression of pro-apoptotic proteins and a deficiency in the stress responsive system, such as UPR and autophagy. Show less

Birth weight reflects prenatal metabolic adaption and has been related to later-life obesity risk. This study aimed to evaluate whether birth weight modifies the effect of genetic susceptibility on obesity risk in young Chinese. We recruited 540 young (14-30 years) and obese patients (body mass index, BMI30 kg m(-2)), and 500 age- and sex-matched normal-weight healthy individuals (BMI<23 kg m(-2)). We genotyped 23 BMI-associated genetic variants identified from recent genome-wide association studies (GWAS) in Caucasians with European ancestry with minor allele frequency>0.05 in HapMap Han Chinese in Beijing, China. Six loci, including SEC16B, GNPDA2, BDNF, FTO, MC4R and TMEM160, were significantly associated with obesity risk, with odds ratio from 1.314 to 1.701. The 23 risk loci accounted for 6.38% of the genetic variance in obesity. We created two genetic risk scores (GRSs) by summing the risk alleles of all 23 (GRS1) and 6 obesity-associated (GRS2) genetic variants. Prediction of obesity was significantly improved (P<0.001) when the GRS1 and GRS2 were added to a model with age and gender, with improvement of discrimination for obesity by 0.8% and 2.7%, respectively. In addition, we found that the two GRSs interacted with birth weight in relation to obesity (Pinteraction<0.001). The genetic effect appeared to be more pronounced in individuals with normal range of birth weight (25-75%) than those with either low (<25%) or high (>75%) birth weight. We confirmed the associations of the single-nucleotide polymorphism tagging six loci reported in recent GWAS with obesity in young Chinese. Our data also suggest birth weight may significantly modify genetic susceptibility to obesity risk. Show less

The individuals carrying melanocortin-1 receptor (MC1R) variants, especially those associated with red hair color, fair skin, and poor tanning ability (RHC trait), are more prone to melanoma; however, the underlying mechanism is poorly defined. Here, we report that UVB exposure triggers phosphatase and tensin homolog (PTEN) interaction with wild-type (WT), but not RHC-associated MC1R variants, which protects PTEN from WWP2-mediated degradation, leading to AKT inactivation. Strikingly, the biological consequences of the failure of MC1R variants to suppress PI3K/AKT signaling are highly context dependent. In primary melanocytes, hyperactivation of PI3K/AKT signaling leads to premature senescence; in the presence of BRAF(V600E), MC1R deficiency-induced elevated PI3K/AKT signaling drives oncogenic transformation. These studies establish the MC1R-PTEN axis as a central regulator for melanocytes' response to UVB exposure and reveal the molecular basis underlying the association between MC1R variants and melanomagenesis. Show less

A potent, selective glucagon receptor antagonist 9m, N-[(4-{(1S)-1-[3-(3,5-dichlorophenyl)-5-(6-methoxynaphthalen-2-yl)-1H-pyrazol-1-yl]ethyl}phenyl)carbonyl]-β-alanine, was discovered by optimization of a previously identified lead. Compound 9m is a reversible and competitive antagonist with high binding affinity (IC(50) of 6.6 nM) and functional cAMP activity (IC(50) of 15.7 nM). It is selective for glucagon receptor relative to other family B GPCRs, showing IC(50) values of 1020 nM for GIPR, 9200 nM for PAC1, and >10000 nM for GLP-1R, VPAC1, and VPAC2. Compound 9m blunted glucagon-induced glucose elevation in hGCGR mice and rhesus monkeys. It also lowered ambient glucose levels in both acute and chronic mouse models: in hGCGR ob/ob mice it reduced glucose (AUC 0-6 h) by 32% and 39% at 3 and 10 mpk single doses, respectively. In hGCGR mice on a high fat diet, compound 9m at 3, and 10 mpk po in feed lowered blood glucose levels by 89% and 94% at day 10, respectively, relative to the difference between the vehicle control and lean hGCGR mice. On the basis of its favorable biological and DMPK properties, compound 9m (MK-0893) was selected for further preclinical and clinical evaluations. Show less

Glucose-dependent insulinotropic peptide (GIP) exerts multiple biological effects via the G-protein-coupled receptor GIPR, including glucose-stimulated insulin production and secretion, cell proliferation, and antiapoptosis in pancreatic β-cells. In an obese state, the circulating level of GIP is elevated. GIPR-knockout mice are resistant to high-fat-diet-induced obesity. The rising evidence suggests a potential role of GIP in adipocyte biology and lipid metabolism. In our study, we overexpressed GIPR in 3T3-L1 CAR adipocytes and demonstrated that GIP impaired the physiological functions of adipocytes as a consequence of increased production of inflammatory cytokines and chemokines and phosphorylation of IkB kinase (IKK)-β through activation of the cAMP-PKA pathway. Activation of Jun N-terminal kinase (JNK) pathway was also observed during GIP-induced inflammatory responses in adipocytes. The inhibition of JNK blocked GIP-stimulated secretion of inflammatory cytokines and chemokines, as well as phosphorylation of IKKβ. In addition, GIP-induced inflammatory response increased basal glucose uptake but inhibited insulin-stimulated glucose uptake. Moreover, GIP-induced adipocyte inflammation impaired insulin signaling in adipocytes as demonstrated by a reduction of AKT phosphorylation. Our results suggest that GIP might be one of the stimuli attributable to obesity-induced insulin resistance via the induction of adipocyte inflammation. Show less

Multiple genetic loci associated with obesity or body mass index (BMI) have been identified through genome-wide association studies conducted predominantly in populations of European ancestry. We performed a meta-analysis of associations between BMI and approximately 2.4 million SNPs in 27,715 east Asians, which was followed by in silico and de novo replication studies in 37,691 and 17,642 additional east Asians, respectively. We identified ten BMI-associated loci at genome-wide significance (P < 5.0 × 10(-8)), including seven previously identified loci (FTO, SEC16B, MC4R, GIPR-QPCTL, ADCY3-DNAJC27, BDNF and MAP2K5) and three novel loci in or near the CDKAL1, PCSK1 and GP2 genes. Three additional loci nearly reached the genome-wide significance threshold, including two previously identified loci in the GNPDA2 and TFAP2B genes and a newly identified signal near PAX6, all of which were associated with BMI with P < 5.0 × 10(-7). Findings from this study may shed light on new pathways involved in obesity and demonstrate the value of conducting genetic studies in non-European populations. Show less

Clinically, elevated cancer antigen 125 (CA-125) in blood predicts tumor burden in a woman's body, especially in the ovary, but cannot differentiate between malignant or benign. We here used intensive modern proteomic approaches to identify predictive proteins in the serum of women with elevated CA-125 to differentiate malignant from benign ovarian tumors. We identified differentially expressed proteins in serum samples of ovarian cancer (OC) patients, benign ovarian tumor (BT) patients, and healthy control women using mass spectrometry-based quantitative proteomics. Both the OC and BT patients had elevated CA-125. Quantitation was achieved using isobaric tags for relative and absolute quantitation. We obtained 124 quantified differential serum proteins in OC compared with BT. Two proteins, apolipoprotein A-4 (APOA4) and natural resistance-associated macrophage 1, were verified using Western blotting. Proteome profiling applied to OC cases identified several differential serum proteins in the serum of women with elevated CA-125. A novel protein, APOA4, has the potential to be a marker for malignant tumor differentiation in the serum of women with elevated CA-125. Show less

The APOA5 -1131 T/C polymorphism (rs662799) exhibits a very strong association with elevated TG levels in different racial groups. High resolution melting (HRM) analysis with the use of unlabeled probes has shown to be a convenient and reliable tool to genotyping, but not yet been used for detecting rs662799 polymorphism. We applied the unlabeled probe HRM analysis and direct DNA sequencing to assay the -1131T>C SNP in 130 cases DNA samples blindly. This HRM analysis can be completed in <3 min for each sample. The two melting peaks were displayed at 66.1±0.4°C for CC homozygote and 68.7±0.2°C for TT homozygote; TC heterozygote showed the both melting peaks. The genotyping results by HRM method were completely concordant with direct DNA sequencing. The distribution of CC, TC, and TT genotypes for the -1131T>C SNP was 9.2, 49.2, and 41.5%, respectively. This assay was sensitive enough to detect C allele down to 20% and 10% for T allele. The limit of detection for C and T allele was 6.2 and 2.5 ng/μL DNA, respectively. The developed unlabeled probe HRM method provides an alternative mean to detect ApoA5 -1131T>C SNP rapidly and accurately. Show less

Triglyceride (TG) is a complex phenotype influenced by both genetic and environmental factors. Recent genome-wide association studies (GWAS) have identified genes or loci affecting lipid levels; however, such studies in Chinese populations are limited. A two-stage GWAS were conducted to identify genetic variants that were associated with TG in a Chinese population of 3495 men. Gene-environment interactions on serum TG levels were further investigated for the seven single nucleotide polymorphisms (SNPs) that were studied in both stages. Two previously reported SNPs (rs651821 in APOA5, rs328 in LPL) were replicated in the second stage, and the combined P-values were 9.19 × 10(-26) and 1.41 × 10(-9) for rs651821 and rs328, respectively. More importantly, a significant interaction between aldehyde dehydrogenase 2 (ALDH2) rs671 and alcohol consumption on serum TG levels were observed (P = 3.34 × 10(-5)). Rs671 was significantly associated with serum TG levels in drinkers (P = 1.90 × 10(-10)), while no association was observed in non-drinkers (P > 0.05). For drinkers, men carrying the AA/AG genotype have significantly lower serum TG levels, compared with men carrying the GG genotype. For men with the GG genotype, the serum TG levels increased with the quantity of alcohol intake (P = 1.28 × 10(-8) for trend test). We identified a novel, significant interaction effect between alcohol consumption and the ALDH2 rs671 polymorphism on TG levels, which suggests that the effect of alcohol intake on TG occurs in a two-faceted manner. Just one drink can increase TG level in susceptible individuals who carry the GG genotype, while individuals carrying AA/AG genotypes may actually benefit from moderate drinking. Show less