Tiam1 mediates Rac1 activation and contraction-induced glucose uptake in skeletal muscle cells.

Contraction-stimulated glucose uptake in skeletal muscle requires Rac1, but the molecular mechanism of its activation is not fully understood. Treadmill running was applied to induce C57BL/6 mouse hind limb skeletal muscle contraction in vivo and electrical pulse stimulation contracted C2C12 myotube cultures in vitro. The protein levels or activities of AMPK or the Rac1-specific GEF, Tiam1, were manipulated by activators, inhibitors, siRNA-mediated knockdown, and adenovirus-mediated expression. Activated Rac1 was detected by a pull-down assay and immunoblotting. Glucose uptake was measured using the 2-NBD-glucose fluorescent analog. Electrical pulse stimulated contraction or treadmill exercise upregulated the expression of Tiam1 in skeletal muscle in an AMPK-dependent manner. Axin1 siRNA-mediated knockdown diminished AMPK activation and upregulation of Tiam1 protein expression by contraction. Tiam1 siRNA-mediated knockdown diminished contraction-induced Rac1 activation, GLUT4 translocation, and glucose uptake. Contraction increased Tiam1 gene expression and serine phosphorylation of Tiam1 protein via AMPK. These findings suggest Tiam1 is part of an AMPK-Tiam1-Rac1 signaling pathway that mediates contraction-stimulated glucose uptake in skeletal muscle cells and tissue.

MiR-448-5p/VEGFA Axis Protects Cardiomyocytes from Hypoxia Through Regulating the FAS/FAS-L Signaling Pathway.

Bioinformatics analysis showed that miR-448-5p expression in the myocardial tissue of rats with myocardial infarction significantly increased, suggesting that it may participate in myocardial cell apoptosis in myocardial infarction. This study aimed to explore the protective effects of miR-448-5p on hypoxic myocardial cells.H9C2 cells were cultured and subjected to anoxia for 2, 4, and 8 hours to establish a hypoxia model. MiR-448-5p mimic and inhibitor were transfected into the cells; then, a dual-luciferase experiment was conducted to verify the targeting relationship between miR-448-5p and VEGFA. Cell viability and apoptosis was detected by cell counting kit-8 and flow cytometry, respectively. The expressions of apoptosis-related proteins, miR-448-5p, FAS, and FAS-L were measured using western blotting and quantitative reverse transcription-polymerase chain reaction (qRT-PCR).Hypoxia-reduced H9C2 cell viability and promoted apoptosis. MiR-448-5p expression was increased after H9C2 cell hypoxia. MiR-448-5p mimic significantly inhibited the viability and promoted the apoptosis of hypoxia-induced model cells. Hypoxia promoted the expression of apoptosis-related protein B-cell lymphoma-2 (Bcl-2) and inhibited the expressions of Bcl-2-associated x protein (Bax), cleaved caspase-3, and caspase-3, whereas the effect of inhibitor on hypoxia-reduced H9C2 cell and apoptotic protein expression were opposite to miR-448-5p mimic. MiR-448-5p targeted VEGFA and regulated its expression. Silenced VEGFA expression significantly inhibited inhibitor effect on increasing cell viability and promoted apoptosis. In addition, miR-448-5p mimic inhibited the effect of hypoxia on promoting the expressions of FAS and FAS-L of H9C2 cells. Inhibitors had the opposite effect on cell hypoxia model.The miR-448-5p/VEGFA axis could protect cardiomyocytes from hypoxia through inhibiting the FAS/FAS-L signaling pathway.

An AMPK/Axin1-Rac1 signaling pathway mediates contraction-regulated glucose uptake in skeletal muscle cells.

Contraction stimulates skeletal muscle glucose uptake predominantly through activation of AMP-activated protein kinase (AMPK) and Rac1. However, the molecular details of how contraction activates these signaling proteins are not clear. Recently, Axin1 has been shown to form a complex with AMPK and liver kinase B1 during glucose starvation-dependent activation of AMPK. Here, we demonstrate that electrical pulse-stimulated (EPS) contraction of C2C12 myotubes or treadmill exercise of C57BL/6 mice enhanced reciprocal coimmunoprecipitation of Axin1 and AMPK from myotube lysates or gastrocnemius muscle tissue. Interestingly, EPS or exercise upregulated total cellular Axin1 levels in an AMPK-dependent manner in C2C12 myotubes and gastrocnemius mouse muscle, respectively. Also, direct activation of AMPK with 5-aminoimidazole-4-carboxamide ribonucleotide treatment of C2C12 myotubes or gastrocnemius muscle elevated Axin1 protein levels. On the other hand, siRNA-mediated Axin1 knockdown lessened activation of AMPK in contracted myotubes. Further, AMPK inhibition with compound C or siRNA-mediated knockdown of AMPK or Axin1 blocked contraction-induced GTP loading of Rac1, p21-activated kinase phosphorylation, and contraction-stimulated glucose uptake. In summary, our results suggest that an AMPK/Axin1-Rac1 signaling pathway mediates contraction-stimulated skeletal muscle glucose uptake.

LINE-1 Methylation in Chronic HBV Infected Patients: Association with HCC, Gender and MTHFR C677T Polymorphism.

BACKGROUND: Polymorphism of methylene tetrahydrofolate reductase (MTHFR) C677T has been reported to be associated with HBV-related hepatocellular carcinoma (HCC) risk. However, the underlying mechanism remains elusive. DNA methylation has been suggested to be associated with HCC onset. MTHFR is the key enzyme in folic acid metabolism, thus, it influences the production of the main donor of methyl groups for DNA methylation. This study aimed to determine the association of global DNA methylation with MTHFR C677T polymorphism in chronic HBV infected patients, as well as its association with HCC and gender. METHODS: In all, 130 chronic hepatitis B (CHB) and 131 HBV-related HCC patients were enrolled in the study. The methylation level of long interspersed nuclear element-1 (LINE-1), the surrogate marker of global DNA methylation, and MTHFR C677T genotypes were determined. RESULTS: The HCC group showed significantly lower LINE-1 methylation than the CHB group (p = 0.016). Females were observed to have a markedly lower LINE-1 methylation level than males in both CHB and HCC groups (p = 0.000, p = 0.014, respectively). A significant relationship between MTHFR C677T polymorphism and LINE-1 methylation was observed in the CHB group (F = 5.985, p = 0.003). CT, TT, and CT + TT genotypes were significantly associated with lower LINE-1 methylation level compared with the CC genotype (p = 0.005, p = 0.018, p = 0.001, respectively). In addition, the association between MTHFR C677T and LINE-1 methylation was more significant in females (F= 5.036, p = 0.011) than in males (F = 3.083, p = 0.051); further, the association was significant in the subjects older than 60 years (F = 3.865, p = 0.028), but not in the subgroup aged less than 60 years (F = 2.496, p = 0.089). CONCLUSIONS: LINE-1 methylation level in chronic HBV infected patients was associated with the occurrence of HBV-related HCC, gender, and MTHFR C677T polymorphism.

Genetic Polymorphism of MTHFR C677T Influences Susceptibility to HBV-Related Hepatocellular Carcinoma in a Chinese Population: a Case-Control Study.

BACKGROUND: Methylene tetrahydrofolate reductase (MTHFR) is the key enzyme of folic acid metabolism and the C677T mutation is associated with decreased enzyme activity. Several studies have shown its regulatory role in carcinogenesis and tumor growth. HBV (hepatitis B virus)-related HCC (hepatocellular carcinoma) is one of the most common liver cancers worldwide. Therefore, the present case-control study aimed to investigate the role of genetic polymorphism of MTHFR C677T in the development and progression of HBV-related HCC in a Chinese population. METHODS: Subjects enrolled included 204 HBV-related HCC patients and 211 HBV infected patients without HCC. MTHFR C677T polymorphism was genotyped via a DNA microarray-based assay. The relationship between the MTHFR C677T polymorphism and HBV-related HCC was analyzed. RESULTS: The genotype frequencies of MTHFR C677T were statistically different between the HCC and control groups (p = 0.025). The TT genotype was associated with elevated risk of HBV-related HCC in a Chinese population under different genetic models after an adjustment for age, gender, HBV infection duration, and HCC family history (T vs. C, OR = 1.462, 95% CI: 1.090 - 1.962, p = 0.011; TT vs. CC, OR = 2.151, 95% CI: 1.143 - 4.049, p = 0.018; TT vs. CC+CT, OR = 1.918, 95% CI: 1.215 - 3.026, p = 0.005). When stratified with the known duration of HBV infection, subjects with HBV infection duration of more than 20 years and carrying the homozygous TT genotype had a higher susceptibility to HCC than those with the C allele (CC/CT) (OR = 2.568, 95% CI: 1.244 - 5.303; p = 0.011). There was no significant association between MTHFR C677T genotypes and HCC stages based on BCLC staging system. CONCLUSIONS: MTHFR C677T polymorphism with TT genotype could be a factor that increases the risk of HBVrelated HCC in a Chinese population, especially those with HBV infection duration of more than 20 years.

Genetic Polymorphism of Epidermal Growth Factor rs4444903 Influences Susceptibility to HCV-Related Liver Cirrhosis and Hepatocellular Carcinoma in a Chinese Han Population.

BACKGROUND: Genetic polymorphism in the epidermal growth factor (EGF, rs4444903) gene has been demonstrated to be associated with the clinical deterioration in hepatitis C virus (HCV)-related liver cirrhosis (LC) and the development of hepatocellular carcinoma (HCC). Whether this single nucleotide polymorphism (SNP) influences susceptibility to HCV-related LC and HCC in the Chinese Han population is largely unknown. METHODS: In this case-control study, a total of 187 Chinese Han patients with chronic HCV infection were enrolled, including 62 HCV-related LC patients, 46 HCV-related HCC patients, and 79 chronic hepatitis C (CHC) patients without LC and HCC, and the genetic polymorphism was genotyped via a matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) assay. The logistical regression analysis was employed to determine the correlation between the genetic polymorphism and risk of HCV-related LC and HCC. RESULTS: The distribution of EGF rs4444903 genotypes and alleles significantly differed between LC patients and CHC subjects (p = 0.045, p = 0.043, respectively). Under the recessive model, the GG genotype was significantly associated with a two-fold risk of HCV-related LC compared to the AA+AG genotype after an adjustment for age, gender, body mass index (BMI), duration of HCV infection, and HCV RNA level (OR = 2.188; 95% CI = 1.072 - 4.465; p = 0.031). Significant association was observed as well between the GG genotype and increased HCV-related HCC risk (OR = 3.104; 95% CI = 1.319 - 7.307; p = 0.010). CONCLUSIONS: The EGF rs4444903 GG genotype is associated with higher susceptibility to HCV-related LC and HCC in the Chinese Han population. Screening of host genetic polymorphisms might be helpful in designing effective and efficient LC and HCC surveillance programs for chronic HCV-infected patients.

Saturated fatty acids activate caspase-4/5 in human monocytes, triggering IL-1ß and IL-18 release.

Obesity is associated with metabolic tissue infiltration by monocyte-derived macrophages. Saturated fatty acids contribute to proinflammatory gene induction in tissue-embedded immune cells. However, it is unknown how circulating monocytes, the macrophage precursors, react to high-fat environments. In macrophages, saturated fatty acids activate inflammatory pathways and, notably, prime caspase-associated inflammasomes. Inflammasome-activated IL-1ß contributes to type 2 diabetes. We hypothesized that 1) human monocytes from obese patients show caspase activation, and 2) fatty acids trigger this response and consequent release of IL-1ß/IL-18. Human peripheral blood monocytes were sorted by flow cytometry, and caspase activity was measured with a FLICA dye-based assay. Blood monocytes from obese individuals exhibited elevated caspase activity. To explore the nature and consequence of this activity, human THP1 monocytes were exposed to saturated or unsaturated fatty acids. Caspase activity was revealed by isoform-specific cleavage and enzymatic activity; cytokine expression/release was measured by qPCR and ELISA. Palmitate, but not palmitoleate, increased caspase activity in parallel to the release of IL-1ß and IL-18. Palmitate induced eventual monocyte cell death with features of pyroptosis (an inflammation-linked cell death program involving caspase-4/5), scored through LDH release, vital dye influx, cell volume changes, and nuclear morphology. Notably, selective gene silencing or inhibition of caspase-4/5 reduced palmitate-induced release of IL-1ß and IL-18. In summary, monocytes from obese individuals present elevated caspase activity. Mechanistically, palmitate activates a pyroptotic program in monocytes through caspase-4/5, causing inflammatory cytokine release, additional to inflammasomes. These caspases represent potential, novel, therapeutic targets to taper obesity-associated inflammation.

Influential Factors of the Indeterminate Results Tested by QuantiFERON-TB Gold In-Tube (QFT-IT) Assay for Diagnosing TB Infection in HIV-Infected Patients.

BACKGROUND: QuantiFERON-TB Gold In-Tube test (QFT-IT) is a recommended method for diagnosing TB in HIV-infected patients. However, the rate of indeterminate results is higher than that in HIV-uninfected patients. Our previous study showed that the CD4 cell count was an important influential factor for the indeterminate results of QFT-IT. Whether other influential factors affect the QFT-IT results was unclear. METHODS: In this paper, 98 HIV-infected patients with suspected TB infection were enrolled and the plasma of peripheral blood was collected for QFT-IT. The relationship between the CD4 T-cell count, lymphocyte count, lymphocyte percentage, and the results of QFT-IT were analyzed. RESULTS: All patients who have the clinical symptoms of TB including fever and productive cough and were later confirmed by other assays including the sputum culture and chest radiography (n = 8) tested as QFT-positive (positive rate 100%). The other 90 patients without clinical symptoms tested as negative (n = 51), indeterminate (n = 33), and positive (n = 6). The lymphocyte count and the lymphocyte percentage as well as the CD4 T-cell count were significant higher in the positive group and negative group than in the indeterminate group (p < 0.05, for all). CONCLUSIONS: The QFT-IT could be a potential, simple, and feasible method for diagnosing and screening TB in HIV-infected patients. In addition, the CD4 T-cell count, the lymphocyte count, and the lymphocyte percentage were influential factors of the indeterminate results of QFT-IT.

Inhibitory Effect of Paeonol on Apoptosis, Oxidative Stress, and Inflammatory Response in Human Umbilical Vein Endothelial Cells Induced by High Glucose and Palmitic Acid Induced Through Regulating SIRT1/FOXO3a/NF-κB Pathway.

Reactive oxygen species (ROS) induced by high glucose and high fat of diabetes mellitus (DM) finally caused the occurrence and progression of atherosclerosis and other macrovascular complications. Paeonol (Pae) exhibits anti-inflammation, antioxidation, and antiatherosclerosis activities. However, the role of Pae in diabetic cardiopathy has not been fully understood. Therefore, we aimed to investigate the role of Pae in diabetic cardiovascular diseases. Human umbilical vein endothelial cells (HUVECs) were exposed to high glucose and palmitic acid (HG/HP), a model DM environment and different doses of Pae. The viability and apoptotic rate of HUVECs were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometry assay, respectively. Oxidative indicators (ROS, malondiadehyde [MDA], superoxide dismutase [SOD]), and inflammatory cytokines (tumor necrosis factor-α, interleukin-1ß, and interleukin-6) were detected by 2,7-dichlorodihydrofluorescein diacetate, colorimetry, and enzyme-linked immunosorbent assay. The protein levels of Sirtuin type 1 (SIRT1), Bcl-2, Bax, Cleaved caspase-3, p-p65, and p-65 were detected by Western blot. The mRNA levels of Bcl-2 and Bax were detected by quantitative real-time polymerase chain reaction. The acetylation and protein levels of forkhead box O3a (FOXO3a) were detected by immunoprecipitation assay. SIRT1 silencing was used to confirm the role of Pae in the resistance to apoptosis, oxidative stress, and inflammatory response. Pae increased SIRT1 expression, cell viability, and SOD activity and suppressed apoptosis, the levels of p-p65/p-65, ROS, MDA, and inflammatory cytokines, and the expression of acetylated-FOXO3a induced by HG/HP in HUVECs. SIRT1 silencing abrogated the effect of Pae on HG/HP-mediated HUVECs. Inhibitory effect of Pae on apoptosis, oxidative stress, and inflammatory response in HUVECs induced by HG/HP induced through regulating SIRT1/FOXO3a/NF-κB pathway.

The role of AMPKα2 in the HFD-induced nonalcoholic steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD) is associated with hepatic steatosis, inflammation and liver fibrosis and has become one of the leading causes of hepatocellular carcinoma and liver failure. However, the underlying molecular mechanism of hepatic steatosis and the progression to nonalcoholic steatohepatitis (NASH) are not fully understood. Herein, we discovered that AMPKα2 catalytic subunit showed reduced expression in the liver following high fat diet (HFD) feeding to mice. Importantly, knockout of AMPKα2 in mice aggravated NAFLD, hepatic steatosis, inflammation and fibrosis. On the other hand, hepatocyte-targeted overexpression of AMPKα2 prevented or reversed NAFLD indications. In vivo mechanistic studies revealed that increased phosphorylation of IKKα/ß and NF-κB in HFD-fed AMPKα2-/- mice compared to WT mice, and treatment of these mouse cohorts with an inhibitor of NF-κB signaling for 4 weeks, effectively attenuated the progression of steatohepatitis and metabolic disorder features. In summary, AMPKα2 provides a protective role in the process of hepatic steatosis to NASH progression through suppression of liver NF-κB signaling.