Mitochondrial Protein Profile in Mice with Low or Excessive Selenium Diets

Supplementation of Micro- and Macronutrients-A Role of Nutritional Status in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a condition in which the pathological cumulation of fat with coexisting inflammation and damage of hepatic cells leads to progressive dysfunctions of the liver. Except for the commonly well-known major causes of NAFLD such as obesity, dyslipidemia, insulin resistance, or diabetes, an unbalanced diet and imbalanced nutritional status should also be taken into consideration. In this narrative review, we summarized the current knowledge regarding the micro- and macronutrient status of patients suffering from NAFLD considering various diets and supplementation of chosen supplements. We aimed to summarize the knowledge indicating which nutritional impairments may be associated with the onset and progression of NAFLD at the same time evaluating the potential therapy targets that could facilitate the healing process. Except for the above-mentioned objectives, one of the most important aspects of this review was to highlight the possible strategies for taking care of NAFLD patients taking into account the challenges and opportunities associated with the micronutrient status of the patients. The current research indicates that a supplementation of chosen vitamins (e.g., vitamin A, B complex, C, or D) as well as chosen elements such as zinc may alleviate the symptoms of NAFLD. However, there is still a lack of sufficient data regarding healthy ranges of dosages; thus, further research is of high importance in this matter.

A genome-wide association study provides insights into the genetic etiology of 57 essential and non-essential trace elements in humans

Trace elements are important for human health but may exert toxic or adverse effects. Mechanisms of uptake, distribution, metabolism, and excretion are partly under genetic control but have not yet been extensively mapped. Here we report a comprehensive multi-element genome-wide association study of 57 essential and non-essential trace elements. We perform genome-wide association meta-analyses of 14 trace elements in up to 6564 Scandinavian whole blood samples, and genome-wide association studies of 43 trace elements in up to 2819 samples measured only in the Trøndelag Health Study (HUNT). We identify 11 novel genetic loci associated with blood concentrations of arsenic, cadmium, manganese, selenium, and zinc in genome-wide association meta-analyses. In HUNT, several genome-wide significant loci are also indicated for other trace elements. Using two-sample Mendelian randomization, we find several indications of weak to moderate effects on health outcomes, the most precise being a weak harmful effect of increased zinc on prostate cancer. However, independent validation is needed. Our current understanding of trace element-associated genetic variants may help establish consequences of trace elements on human health.

Nuclear respiratory factor 1 regulates super enhancer-controlled SPIDR to protect hepatocellular carcinoma cells from oxidative stress

BACKGROUND

Cellular response to oxidative stress plays significant roles in hepatocellular carcinoma (HCC) development, yet the exact mechanism by which HCC cells respond to oxidative stress remains poorly understood. This study aimed to investigate the role and mechanism of super enhancer (SE)-controlled genes in oxidative stress response of HCC cells.

METHODS

The GSE112221 dataset was used to identify SEs by HOMER. Functional enrichment of SE-controlled genes was performed by Metascape. Transcription factors were predicted using HOMER. Prognosis analysis was conducted using the Kaplan-Meier Plotter website. Expression correlation analysis was performed using the Tumor Immune Estimation Resource web server. NRF1 and SPIDR expression in HCC and normal liver tissues was analyzed based on the TCGA-LIHC dataset. ChIP-qPCR was used to detect acetylation of lysine 27 on histone 3 (H3K27ac) levels of SE regions of genes, and the binding of NRF1 to the SE of SPIDR. To mimic oxidative stress, HepG2 and Hep3B cells were stimulated with H2O2. The effects of NRF1 and SPIDR on the oxidative stress response of HCC cells were determined by the functional assays.

RESULTS

A total of 318 HCC-specific SE-controlled genes were identified. The functions of these genes was significant association with oxidative stress response. SPIDR and RHOB were enriched in the "response to oxidative stress" term and were chosen for validation. SE regions of SPIDR and RHOB exhibited strong H3K27ac modification, which was significantly inhibited by JQ1. JQ1 treatment suppressed the expression of SPIDR and RHOB, and increased reactive oxygen species (ROS) levels in HCC cells. TEAD2, TEAD3, NRF1, HINFP and TCFL5 were identified as potential transcription factors for HCC-specific SE-controlled genes related to oxidative stress response. The five transcription factors were positively correlated with SPIDR expression, with the highest correlation coefficient for NRF1. NRF1 and SPIDR expression was up-regulated in HCC tissues and cells. NRF1 activated SPIDR transcription by binding to its SE. Silencing SPIDR or NRF1 significantly promoted ROS accumulation in HCC cells. Under oxidative stress, silencing SPIDR or NRF1 increased ROS, malondialdehyde (MDA) and γH2AX levels, and decreased superoxide dismutase (SOD) levels and cell proliferation of HCC cells. Furthermore, overexpression of SPIDR partially offset the effects of NRF1 silencing on ROS, MDA, SOD, γH2AX levels and cell proliferation of HCC cells.

CONCLUSION

NRF1 driven SPIDR transcription by occupying its SE, protecting HCC cells from oxidative stress-induced damage. NRF1 and SPIDR are promising biomarkers for targeting oxidative stress in the treatment of HCC.

Differential protein expression due to Se deficiency and Se toxicity in rat liver

There is a U-shaped dose-response between selenium (Se) status and health outcomes, but underlying metabolic processes are unclear. This study aims to identify candidate proteins in liver regulated by dietary Se, ranging from deficiency to toxic. Male rats (n=4) were fed graded Se concentrations as selenite for 28 days. Bulk Se analysis was performed by ICP-MS on both soluble and insoluble fractions. Soluble fraction samples were chromatographically separated for identification of selenocompounds by SEC-ICP-MS and protein quantification by LC-MS/MS. Bioinformatics analysis compared low-Se (0 and 0.08 µg Se g^-1) and high-Se (0.8, 2 and 5 µg Se g^-1) with adequate-Se (0.24 µg Se g^-1) diets. Major breakpoints for Se were seen at 0.8 and 2 µg Se g^-1 in the insoluble and soluble fractions, respectively. Glutathione peroxidase 1 protein abundance reached a plateau at ≥0.08 µg Se g^-1diet; Se bound to selenium binding protein 2 was observed with 2 and 5 µg Se g^-1 Se. The extreme diets presented the highest number of differentially expressed (P value <0.05, FC ≥1.2) proteins in comparison to the adequate-Se diet (0 µg Se g^-1: 45 proteins; 5 µg Se g^-1: 59 proteins); 13 proteins were commonly affected in 0 and 5 µg Se g^-1 treatments. Network analysis revealed that the metabolism of glutathione, xenobiotics and amino acids were enriched in both 0 and 5 µg Se g^-1 diets, indicating a U-shape effect of Se. This similarity is likely due to down-stream effects of lack of essential selenoproteins in Se deficiency and due to toxic effects of Se that exceeds the capacity to cope with excess Se.

Effect of humic acids on lead poisoning in bones and on a subcellular level in mitochondria

Humic acids (HA) are natural substances which exhibit a remarkable spectrum of health benefits, such as their role in chelation. This study aims to supplement the current knowledge on the chelating effects of HA in chronic lead intoxication in rat femurs and in liver, heart and kidney mitochondria in an experiment lasting 10 weeks. Lead acetate trihydrate was administered to rats for 5 weeks at a daily dose of 155.5 mg/kg body weight. At the same time, rats were given three concentrations of HA, with their effect measured over the following 5 weeks. Increased Pb concentrations were detected in the femur after the first week, while HA-administered groups showed a tendency towards inhibiting the increase in Pb deposition. After 5 weeks, Pb concentrations dropped significantly in the HA groups. At the same time, however, other elements were redistributed, with a decrease in Se and Zn being particularly noteworthy. While an increase in Pb concentrations was found after 5 weeks of Pb administration, a concentration of 1% HA resulted in the least significant increase in Pb as well as an increase/decrease in Se/Cu, respectively. In mitochondria, an increase in Pb content was detected after the first and fifth weeks with concomitant redistribution of other elements. At the end of the experiment, again in the 1% HA group, Pb concentrations remained higher only in the liver with the other elements sufficiently normalized, indicating this concentration to be useful in the treatment of Pb intoxication.

Effect of HBx on inflammation and mitochondrial oxidative stress in mouse hepatocytes

Hepatitis B virus × protein (HBx) serves an important role in the pathogenesis of the hepatitis B virus infection. Previous studies have reported that the interaction between HBx and hepatocyte mitochondria is an important factor leading to liver cell injury and apoptosis, ultimately inducing the formation of liver cancer. In the present study, a mouse model expressing HBx was constructed using hydrodynamic in vivo transfection based on the interaction between HBx and cytochrome c oxidase (COX) subunit III. The specific mechanism of HBx-induced oxidative stress in mouse hepatocytes and the subsequent effect on mitochondrial function and inflammatory injury was assessed. The results demonstrated that HBx reduced the activity of COX and the expression of superoxide dismutase and upregulated the expression of malondialdehyde, NF-κB and phospho-AKT, thus increasing oxidative stress. In addition, HBx induced an increase in interleukin (IL)-6, IL-1β and IL-18 expression levels, which created an inflammatory microenvironment in the liver, further promoting hepatocyte inflammatory injury. Therefore, it was proposed that HBx may affect hepatocyte mitochondrial respiration by reducing the activity of cytochrome c oxidase, leading to mitochondrial dysfunction and inducing hepatocyte inflammation and injury.

Association Between Dietary Selenium Intake and the Prevalence of Nonalcoholic Fatty Liver Disease: A Cross-Sectional Study

Objective: The aim was to examine the association between dietary selenium intake and nonalcoholic fatty liver disease (NAFLD) in a large group of middle-aged and elderly Chinese persons.Method: The data included in this analysis were from a population-based study, the Xiangya Hospital Health Management Center Study. NAFLD was diagnosed by (1) imaging or histological evidence of hepatic steatosis; (2) absence of specific etiologies of NAFLD; and (3) no heavy consumption of alcohol. Dietary selenium intake was assessed using a validated semi-quantitative food frequency questionnaire. The association between dietary selenium intake and the prevalence of NAFLD was evaluated using logistic and spline regression in a cross-sectional study of 5436 subjects.Results: The prevalence of NAFLD was 36.8%. Compared with the lowest quintile, the energy-adjusted odds ratios for NAFLD were 1.27 (95% confidence interval [CI], 1.07-1.52), 1.30 (95% CI, 1.09-1.55), and 1.58 (95% CI, 1.33-1.89) for the third, fourth, and fifth quintiles of selenium intake, respectively, and there was a positive dose-response relationship (r = 0.88, p for trend = 0.008). Similar results were observed for men and women separately. The findings were not materially altered by adjustment for potential confounders (i.e., age, gender, body mass index, smoking status, diabetes, hypertension, activity level, nutritional supplements, energy intake, fat intake, fiber intake, cholesterol and saturated fatty acid intake).Conclusions: In this middle-aged and elderly population, subjects with higher dietary selenium intake, even below the recommended nutrient intake in China, had higher prevalence of NAFLD in a dose-response relationship manner.

Selenium Supplementation Alters Hepatic Energy and Fatty Acid Metabolism in Mice

Background

Human and animal studies have raised concerns that supplemental selenium can increase the risk of metabolic disorders, but underlying mechanisms are unclear.

Objective

We used an integrated transcriptome and metabolome analysis of liver to test for functional pathway and network responses to supplemental selenium in mice.

Methods

Male mice (8-wk-old, C57BL/6J) fed a standard diet (0.41 ppm Se) were given selenium (Na2SeO4, 20 μmol/L) or vehicle (drinking water) for 16 wk. Livers were analyzed for selenium concentration, activity of selenoproteins, reduced glutathione (GSH) redox state, gene expression, and high-resolution metabolomics. Transcriptomic and nontargeted metabolomic data were analyzed with biostatistics, bioinformatics, pathway enrichment analysis, and combined transcriptome-metabolome-wide association study (TMWAS).

Results

Mice supplemented with selenium had greater body mass gain from baseline to 16 wk (55% ± 5%) compared with controls (40% ± 3%) (P < 0.05); however, no difference was observed in liver selenium content, selenoenzyme transcripts, or enzyme activity. Selenium was higher in the heart, kidney, and urine of mice supplemented with selenium. Gene enrichment analysis showed that supplemental selenium altered pathways of lipid and energy metabolism. Integrated transcriptome and metabolome network analysis showed 2 major gene-metabolite clusters, 1 centered on the transcript for the bidirectional glucose transporter 2 (Glut2) and the other centered on the transcripts for carnitine-palmitoyl transferase 2 (Cpt2) and acetyl-CoA acyltransferase (Acaa1). Pathway analysis showed that highly associated metabolites (P < 0.05) were enriched in fatty acid metabolism and bile acid biosynthesis, including acylcarnitines, triglycerides and glycerophospholipids, long-chain acyl-coenzyme As, phosphatidylcholines, and sterols. TMWAS of body weight gain confirmed changes in the same pathways.

Conclusions

Supplemental selenium in mice alters hepatic fatty acid and energy metabolism and causes increases in body mass. A lack of effect on hepatic selenium content suggests that signaling involves an extrahepatic mechanism.