The Role of rs713041 Glutathione Peroxidase 4 (GPX4) Single Nucleotide Polymorphism on Disease Susceptibility in Humans: A Systematic Review and Meta-Analysis

Aim: The single-nucleotide polymorphism (SNP) rs713041, located in the regulatory region, is required to incorporate selenium into the selenoprotein glutathione peroxidase 4 (GPX4) and has been found to have functional consequences. This systematic review aimed to conduct a meta-analysis to determine whether there is an association between GPX4 (rs713041) SNP and the risk of diseases in humans and its correlation with selenium status. Material and methods: A systematic search for English-language manuscripts published between January 1990 and November 2022 was carried out using six databases: CINAHL, Cochrane, Medline, PubMed, Scopus and Web of Science. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to assess a relationship between GPX4 (rs713041) SNP and the risk of different diseases based on three genetic models. Review Manager 5.4 and Comprehensive Meta-Analysis 4 software were used to perform the meta-analysis and carry out Egger’s test for publication bias. Results: Data from 21 articles were included in the systematic review. Diseases were clustered according to the physiological system affected to understand better the role of GPX4 (rs713041) SNP in developing different diseases. Carriers of the GPX4 (rs173041) T allele were associated with an increased risk of developing colorectal cancer in additive and dominant models (p = 0.02 and p = 0.004, respectively). In addition, carriers of the T allele were associated with an increased risk of developing stroke and hypertension in the additive, dominant and recessive models (p = 0.002, p = 0.004 and p = 0.01, respectively). On the other hand, the GPX4 (rs713041) T allele was associated with a decreased risk of developing pre-eclampsia in the additive, dominant and recessive models (p < 0.0001, p = 0.002 and p = 0.0005, respectively). Moreover, selenium levels presented lower mean values in cancer patients relative to control groups (SMD = −0.39 µg/L; 95% CI: −0.64, −0.14; p = 0.002, I2 = 85%). Conclusion: GPX4 (rs713041) T allele may influence colorectal cancer risk, stroke, hypertension and pre-eclampsia. In addition, low selenium levels may play a role in the increased risk of cancer.

Effects of astaxanthin in animal models of obesity-associated diseases: A systematic review and meta-analysis

BACKGROUND AND AIM

Obesity is a major risk factor for several diseases, including metabolic syndrome (MetS), non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). The use of natural products, such as astaxanthin (ASX), a potent antioxidant compound produced by the freshwater green microalga Haematococcus pluvialis, has gained particular interest to reduce oxidative stress and inflammation, and to improve redox status, often associated with obesity. A systematic review and meta-analysis was performed to comprehensively examine the effects of ASX in animal models of diet induced obesity-associated diseases in order to inform the design of future human clinical studies for ASX use as supplement or nutraceutical.

METHODS

Cinahl, Cochraine, MEDLINE, Scopus and Web of Science were searched for English-language manuscripts published between January 2000 and April 2020 using the following key words: astaxanthin, obesity, non-alcoholic fatty liver disease, diabetes mellitus type 2, NAFLD and metabolic.

RESULTS

Seventeen eligible articles, corresponding to 21 animal studies, were included in the final quantitative analysis. ASX, at different concentrations and administered for different length of time, induced a significant reduction in adipose tissue weight (P = 0.05) and systolic blood pressure (P < 0.0001) in control animals. In animal models of T2D, ASX significantly reduced serum glucose levels (P = 0.04); whereas it improved several disease biomarkers in the blood (e.g. cholesterol, triglycerides, ALT and AST, P < 0.10), and reduced liver (P = 0.0002) and body weight (P = 0.11), in animal models of NAFLD.

CONCLUSIONS

Supplementation of ASX in the diet has positive effects on symptoms associated with obesity related diseases in animals, by having lipid-lowering, hypo-insulin and hypoglycaemic capacity, protecting organs from oxidative stress and mitigating the immune system, as suggested in this review.

Selenium, as selenite, prevents adipogenesis by modulating selenoproteins gene expression and oxidative stress-related genes

OBJECTIVES

The aim of this study was to assess the effect of the micronutrient selenium, as inorganic selenite, on adipocytes differentiation, and to identify underlying molecular mechanisms to advance the understanding of basic cellular mechanisms associated with adipogenesis.

METHODS

The effect of sodium selenite (Na₂SeO₃) on cell viability (bromide 3-[4,5-dimethylthiazol-2-yl]-2,5-difeniltetrazol [MTT] assay) in preadipocytes, lipid accumulation (oil red O [ORO] assay) and intracellular reactive oxygen species (ROS, [NBT assay]) in mature adipocytes, as well as explore molecular mechanisms via gene expression analyses (real-time quantitative polymerase chain reaction), before and after differentiation, was investigated using 3T3-L1 murine preadipocytes.

RESULTS

Selenite (100, 200, and 400 nM) significantly decreased lipid accumulation during differentiation compared with untreated adipocytes (P < 0.05, 0.001, and 0.01, respectively). Preadipocytes exposure (48 h) to selenite caused an increase in glutathione peroxidase 1 (Gpx1) gene expression in a dose-dependent manner. Adipogenesis significantly increased intracellular reactive oxygen species levels (P < 0.05) while decreasing gene expression of antioxidant enzymes (Gpx1: P < 0.05) and significantly increasing gene expression of regulators of lipid catabolism (type II iodothyronine deiodinase [Dio2], P < 0.01) and markers of differentiation (eg, selenium-binding protein 1 [Selenbp1], peroxisome proliferator activated receptor gamma [Pparg], CCAAT/enhancer binding protein alpha [Cebpa], and fatty acid binding protein 4 [Fab4]) compared with preadipocytes (P < 0.01, 0.01, 0.01, and 0.001, respectively). Selenite exposure (200 nM) caused a significant increase in Gpx1, selenoprotein W (Selenow) and selenoprotein P (Selenop) gene expression, in adipocytes compared with untreated ones (P < 0.01, 0.001, and 0.05, respectively) with a significant decrease in heme oxygenase 1 (Ho-1), cyclooxygenase 2 (Cox2), Dio2, and Fabp4 gene expression (P < 0.001, 0.05, 0.05, and 0.01, respectively).

CONCLUSIONS

Selenium, as selenite, prevented adipogenesis through increasing antioxidant selenoprotein expression, leading to decreased inflammatory markers and, subsequently, to a decrease in differentiation and lipid deposition. These findings, if demonstrated in vivo, could provide valuable data for novel dietary approaches to prevent obesity.

An innovative protocol to select the best growth phase for astaxanthin biosynthesis in H. pluvialis

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H. pluvialis non-motile cells produce more astaxanthin.

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H. pluvialis cells could be separated, based on their size, by an electric field.

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H. pluvialis non-motile cells are bigger than motile cells, and it's possible to recovery non-motile cells using this innovative protocol.

H. pluvialis is a green unicellular microalgae and it is the first producer of natural astaxanthin in the world if subjected to stress conditions such as high light, high salinity and nutrient starvation. Astaxanthin is a powerful antioxidant used in many fields, such as aquaculture, pharmaceutical, food supplements and cosmetic. To obtain a large amount of astaxanthin, researcher focused on the optimisation of H. pluvialis growth. H. pluvialis has four different size growth stage (macrozooids, microzooids, palmelloid and “red non-motile astaxanthin accumulated encysted”), and astaxanthin production occur in the last phase. Recent studies shown that non-motile cells can produce more astaxanthin than motile cells if subjected to light stress. For these reasons, the aim of this study is to find a new and innovative methodology to select and recovery H. pluvialis in his last growth phase thanks to an electrophoretic run, and optimize, in this way, astaxanthin production.

Selenium and viral infection: are there lessons for COVID-19?

Se is a micronutrient essential for human health. Sub-optimal Se status is common, occurring in a significant proportion of the population across the world including parts of Europe and China. Human and animal studies have shown that Se status is a key determinant of the host response to viral infections. In this review, we address the question whether Se intake is a factor in determining the severity of response to coronavirus disease 2019 (COVID-19). Emphasis is placed on epidemiological and animal studies which suggest that Se affects host response to RNA viruses and on the molecular mechanisms by which Se and selenoproteins modulate the inter-linked redox homeostasis, stress response and inflammatory response. Together these studies indicate that Se status is an important factor in determining the host response to viral infections. Therefore, we conclude that Se status is likely to influence human response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and that Se status is one (of several) risk factors which may impact on the outcome of SARS-CoV-2 infection, particularly in populations where Se intake is sub-optimal or low. We suggest the use of appropriate markers to assess the Se status of COVID-19 patients and possible supplementation may be beneficial in limiting the severity of symptoms, especially in countries where Se status is regarded as sub-optimal.

A review of lifestyle and environment risk factors for pancreatic cancer

Pancreatic cancer (PaCa) is one of the deadliest cancers known and its incidence is increasing in the developed countries. Because of the lack of biomarkers that allow early detection and the tendency of the disease to be asymptomatic, the diagnosis comes often too late for effective surgical or chemotherapy intervention. Lifestyle factors, that may cause common genetic modifications occurring in the disease, interfere with pancreatic physiology or function, and play a role in PaCa development, have been of concern recently, since a strategy to prevent this severe cancer is needed. This review identifies the latest evidences related to increased risk of developing PaCa due to dietary habits such as high alcohol, fructose and red or processed meat intake, and pathological conditions such as diabetes, obesity and infections in addition to stress and smoking behaviour. It aims to highlight the importance of intervening on modifiable risk factors: the action on these factors could prevent a considerable number of new cases of PaCa.

Impact of rapeseed pomace extract on markers of oxidative stress and DNA damage in human SH-SY5Y cells

With increased longevity and subsequent rise in people with age-related neurodegenerative diseases, protection of neurons from oxidative stress damage has become an important field of study. For the first time, we highlight the neuroprotective properties of rapeseed pomace (RSP) extract in SH-SY5Y human neuroblastoma cells. We used resazurin to determine cell metabolism, 2,7'-dichlorofluorescin diacetate (H₂ DCFDA) to assess the potential of RSP extracts to shield cells from reactive oxygen species (ROS) induced by H₂ O₂ using flow cytometry, HPLC to analyze for malondialdehyde (MDA) as a lipid peroxidation marker and the COMET assay to assess DNA strand breakage. Protein stress arrays were used to investigate the cellular pathways affected by RSP extract. No effect on cell metabolism in SH-SY5Y cells was observed after RSP extract treatment (up to 1.5 mg/ml). Pretreatment (24 hr) with RSP extract (1 mg/ml), before H₂ O₂ -induced stress, alleviated ROS production and DNA strand breakage by 68%, and 38%, respectively. At protein level, the RSP extract increased the levels of FABP-1, HIF-1α, SOD2, and Cytochrome c proteins. Under H₂ O₂ -induced stress, however, it helped to downregulate p38α levels, a protein kinase which is receptive to stress impulse (mitogen-activated). RSP extract shows very promising cell protective properties in relation to oxidative stress. PRACTICAL APPLICATIONS: Oxidative stress has been associated with numerous diseases for example cancer, diabetes, and many neurological disorders including Parkinson's and Alzheimer's diseases. Hence, there is acceptance among the scientific community of antioxidant therapy and the quest for effective, low cost and readily available sources of natural antioxidants is paramount. Rapeseed plantations are abundant around the world due to the use of rapeseed oil in cooking and as a biofuel. The resulting rapeseed pomace (by-product), specifically its extract, contains high levels of phytochemicals that protect cells against oxidative stress. Therefore, RSP extract can potentially be used/developed as functional food and nutraceuticals in the prevention of many complex neurodegenerative diseases.

Adipocytokines and their relationship to endometrial cancer risk: A systematic review and meta-analysis

OBJECTIVE

To investigate the association between circulating levels of adipocytokines (adiponectin, leptin, tumour necrosis factor alpha (TNFα), interleukin 6 (IL-6)) and growth factors (insulin-like growth factor I (IGF-I) and II (IGF-II)), and the risk of endometrial cancer.

METHODS

Cochrane, CINAHL, Embase, Medline and Web of Science were searched for English-language manuscripts published between January 2000 and August 2018 using the following string of words: cancer and endometrial and (obesity or BMI) and (adiponectin or TNF* or IGF-I or IGF-II or IL-6 or leptin).

RESULTS

Twenty articles were included in this meta-analysis, which corresponded to 18 studies involving 2921 endometrial carcinoma cases and 5302 controls. Fourteen articles reported circulating levels for adiponectin, seven for leptin, three for TNFα, three for IL-6 and one for IGF-I. No article reported values for IGF-II. Patients with circulating adiponectin levels in the highest tertile had decreased endometrial cancer risk compared to women with levels in the lowest tertile, (summary of odds ratio (SOR) 0.51, 95% confidence interval (CI): 0.38-0.69, p < 0.00001). Women with circulating leptin concentrations in the highest tertile had increased endometrial cancer risk compared to women with concentrations in the lowest tertile (SOR 2.19, 95% CI: 1.45-3.30, p = 0.0002). There was no difference in cancer risk between participants with the highest TNFα and IL-6 levels compared to the lowest levels (SOR 1.27, 95% CI: 0.88-1.83, p = 0.20 and SOR 1.20, 95% CI: 0.89-1.63, p = 0.23, respectively).

CONCLUSIONS

Endometrial cancer risk is inversely affected by adiponectin and leptin levels. There appears to be no relationship between TNFα and IL-6 and the overall risk of endometrial cancer.

mTOR Pathway in Gastroenteropancreatic Neuroendocrine Tumor (GEP-NETs)

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) originate from neuroendocrine cells in the gastrointestinal tract. They are heterogeneous, and though initially considered rare tumors, the incidence of GEP-NENs has increased in the last few decades. Therapeutic approaches for the metastatic disease include surgery, radiological intervention by chemoembolisation, radiofrequency ablation, biological therapy in addition to somatostatin analogs, and PRRT therapy (177Lu-DOTATATE). The PI3K-AKT-mTOR pathway is essential in the regulation of protein translation, cell growth, and metabolism. Evidence suggests that the mTOR pathway is involved in malignant progression and resistance to treatment through over-activation of several mechanisms. PI3K, one of the main downstream of the Akt-mTOR axis, is mainly involved in the neoplastic process. This pathway is frequently deregulated in human tumors, making it a central target in the development of new anti-cancer treatments. Recent molecular studies identify potential targets within the PI3K/Akt/mTOR pathway in GEP-NENs. However, the use of target therapy has been known to lead to resistance due to several mechanisms such as feedback activation of alternative pathways, inactivation of protein kinases, and deregulation of the downstream mTOR components. Therefore, the specific role of targeted drugs for the management of GEP-NENs is yet to be well-defined. The variable clinical presentation of advanced neuroendocrine tumors is a significant challenge for designing studies. This review aims to highlight the role of the PI3K/Akt/mTOR pathway in the development of neuroendocrine tumors and further specify its potential as a therapeutic target in advanced stages.

Seaweed-derived bioactives as potential energy regulators in obesity and type 2 diabetes

There is epidemiological evidence that dietary intake of seaweeds is associated with a lower prevalence of chronic diseases. While seaweeds are of high nutritious value, due to their high content of fiber, polyunsaturated fatty acids and minerals, they also contain an abundance of bioactive compounds. There is a growing body of scientific data that these bioactive moieties exert effects that could correct the metabolic dysregulation that is present in obesity and Type 2 diabetes (T2D). In this review we describe how the molecular mechanisms, specific to different tissues, that underly obesity and T2D are influenced by both seaweed extracts and seaweed-derived bioactive molecules. In obesity, modulation of antioxidant capacity and reduction of intracellular ROS levels within tissues, and regulation of signaling pathways involved in enhancing browning of white adipose tissue, have been highlighted as key mechanism and identified as a potential target for optimal energy metabolism. In T2D, management of post-prandial blood glucose by modulating α-glucosidase or α-amylase activities, modulation of the AMPK signaling pathway, and similarly to obesity, reduction of ROS and NO production with subsequent increased expression of antioxidant enzymes have been shown to play a key role in glucose metabolism and insulin signaling. Future studies aimed at discovering new therapeutic drugs from marine natural products should, therefore, focus on bioactive compounds from seaweed that exert antioxidant activity and regulate the expression of key signaling pathways involved in glucose homeostasis, mechanisms that are common to both obesity and T2D management. In addition, more data is required to provide evidence of clinical benefit.

Meta-analysis demonstrates Gly482Ser variant of PPARGC1A is associated with components of metabolic syndrome within Asian populations

AIM

To determine the association of peroxisome proliferator activated receptor gamma coactivator 1 Gly482Ser variant with components of metabolic syndrome.

MATERIALS AND METHODS

A systematic search was carried out using Web of Science, PubMed, EMBASE and the Cochrane library using the key words: Peroxisome proliferator activator receptor gamma coactivator 1, PPARGC1A, PGC-1, PGC-1alpha, and PGC1alpha alone or with polymorphism, Gly482Ser and rs8192678.

RESULTS

Data from 19 articles generated 28 separate data sets. Under the recessive model fasting plasma glucose was significantly lower in AA genotypes when compared to GG + GA in the total sample group and in non-Asian group (p < .001). The AA genotype showed significantly lower levels of total cholesterol compared to GG + GA genotype using the recessive model with the non-Asian group (p < .05). Under the dominant model, body mass index of the GG genotype was significantly higher in Asian subgroups (p < .05).

CONCLUSION

PPARGC1A Gly482Ser variant impacts differently in Asian population groups.

GST-4-Dependent Suppression of Neurodegeneration in C. elegans Models of Parkinson's and Machado-Joseph Disease by Rapeseed Pomace Extract Supplementation

Genetic mutations and aging-associated oxidative damage underlie the onset and progression of neurodegenerative diseases, like Parkinson’s disease (PD) and Machado-Joseph disease (MJD). Natural products derived from plants have been regarded as important sources of novel bioactive compounds to counteract neurodegeneration. Here, we tested the neuroprotective effect of an ethanolic extract of rapeseed pomace (RSP), a rapeseed (canola) oil production by-product, in C. elegans models of MJD and PD. The extract, containing sinapine and other phenolics, restored motor function of mutant ataxin-3 (ATXN3) animals (MJD) and prevented degeneration of dopaminergic neurons in one toxin-induced and two genetic models of PD. Whole-organism sensors of antioxidant and xenobiotic response activation revealed the induction of phase II detoxification enzymes, including glutathione S- transferase (GST-4) upon RSP extract supplementation. Furthermore in vivo pharmacogenetic studies confirmed gst-4 is required for the therapeutic effect of RSP extract in the two disease models. The results suggest that GST-4-mediated antioxidant pathways may constitute promising therapeutic co-targets for neurodegenerative diseases and confirm the utility of searching for bioactive compounds in novel sources, including food and agricultural waste/by-products, such as RSP.

Interaction of NKX3.1 and SELENOP genotype with prostate cancer recurrence

BACKGROUND

NKX3.1 is a tumor suppressor frequently lost in prostate cancer. Previous studies by others indicated that the risks associated with reduced NKX3.1 levels can be enhanced by anti-oxidant supplementation. Selenium is an essential component of several proteins with anti-oxidant functions and lower levels of selenium have been associated with greater risk of prostate cancer. In contrast, participants of the select prostate cancer prevention trial were at increased risk of prostate cancer when supplemented with selenium when their baseline selenium levels were high.

METHODS

In order to investigate whether there was an interaction between a functional polymorphism in NKX3.1 that results in less protein and selenium status with prostate cancer grade or outcome, plasma selenium levels and the genotypes of NKX3.1 and the selenium carrier protein SELENOP were determined from a cohort of men who underwent radical protatectomy.

RESULTS

NKX3.1 and SELENOP genotypes were associated with a more aggressive prostate tumor grade at the time of prostatectomy, but there were no significant interactions of NKX3.1 genotype with either selenium status or SELENOP genotype. There was also a significant association between NKX3.1 genotype and prostate cancer recurrence, however this association was modified by SELENOP genotype, but not with plasma selenium levels.

CONCLUSIONS

These data indicate that the impact of selenium status on prostate cancer may be influenced by factors other than the amount of selenium in circulation.

Novel bisnaphthalimidopropyl (BNIPs) derivatives as anticancer compounds targeting DNA in human breast cancer cells

Bisnaphthalimidopropyl (BNIP) derivatives are a family of compounds that exert anti-cancer activities in vitro and, according to previous studies, variations in the linker sequence have increased their DNA binding and cytotoxic activities. By modifying the linker sequence of bisnaphthalimidopropyl diaminodicyclohexylmethane (BNIPDaCHM), a previously synthesised BNIP derivative with anti-cancer properties, three novel BNIP derivatives were designed. Bisnaphthalimidopropyl-piperidylpropane (BNIPPiProp), a structural isomer of BNIPDaCHM, bisnaphthalimidopropyl ethylenedipiperidine dihydrobromide (BNIPPiEth), an isoform of BNIPDaCHM with a shorter linker chain, and (trans(trans))-bisnaphthalimidopropyl diaminodicyclohexylmethane (trans,trans-BNIPDaCHM), a stereoisomer of BNIPDaCHM, were successfully synthesised (72.3-29.5% yield) and characterised by nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). Competitive displacement of ethidium bromide (EtBr) and UV binding studies were used to study the interactions of BNIP derivatives with Calf Thymus DNA. The cytotoxicity of these derivatives was assessed against human breast cancer MDA-MB-231 and SKBR-3 cells by MTT assay. Propidium iodide (PI) flow cytometry was conducted in order to evaluate the cellular DNA content in both breast cancer cell lines before and after treatment with BNIPs. The results showed that all novel BNIPs exhibit strong DNA binding properties in vitro, and strong cytotoxicity, with IC₅₀ values in the range of 0.2-3.3 μM after 24 hours drug treatment. Two of the novel BNIP derivatives, BNIPPiEth and trans,trans-BNIPDaCHM, exhibited greater cytotoxicity against the two breast cancer cell lines studied, compared to BNIPDaCHM. By synthesising enantiopures and reducing the length of the linker sequence, the cytotoxicity of the BNIP derivatives was significantly improved compared to BNIPDaCHM, while maintaining DNA binding and bis-intercalating properties. In addition, cell cycle studies indicated that trans,trans-BNIPDaCHM, the most cytotoxic BNIP derivative, induced sub-G1 cell cycle arrest, indicative of apoptotic cell death. Based on these findings, further investigation is under way to assess the potential efficacy of trans,trans-BNIPDaCHM and BNIPPiEth in treating human breast cancer.

Circulating levels of angiogenesis-related growth factors in breast cancer: A study to profile proteins responsible for tubule formation

The present study exploited a versatile in vitro endothelial cell/fibroblast co-culture cell system to investigate the association between angiogenesis and breast cancer by comparing the capacity of plasma from women with breast cancer and age-matched controls, to influence tubule formation and modulate angiogenesis in vitro, and to identify plasma circulating factors which might be responsible. Plasma from women with breast cancer (n=8) (added on day 7 after co-culture establishment) significantly increased tubule formation by 57% (P<0.01) when compared to cultures grown in culture medium lacking in vascular endothelial growth factor (VEGF) and fetal bovine serum (FBS), whereas plasma from controls (n=8) did not. Higher levels of VEGF, tumour necrosis factor-α (TNFα) and interleukin (IL)-6, but not leptin, were observed in plasma samples of the breast cancer group compared to the control group (n=20 in each group). In independent experiments, the effects of VEGF, TNFα, IL-6 and leptin were assessed and it was found that tubule formation was differentially affected whether these inflammatory cytokines or adipokines were added individually or in combination to the co-culture system. Using Proteome Profiler human angiogenesis array kits, 12 out of 55 angiogenesis-related proteins were differentially expressed in plasma from the breast cancer group compared to the control group. Pro-angiogenic proteins included: amphiregulin, artemin, coagulation factor III, fibroblast growth factor (FGF) acidic, GDNF, IL-8, macrophage inflammatory protein (MIP)-1α, platelet derived growth factor-AB/platelet derived growth factor-BB (PDGF-AB/PDGF-BB) and VEGF, whereas anti-angiogenic proteins were: angiopoietin-2, serpin F1 and serpin B5. In addition, FGF acidic was further identified as differentially expressed, with increased expression, when plasma samples from the normal and cancer groups, which induced an increase in tubule formation, were compared to one another. In conclusion, the present study identified angiogenesis-related proteins circulating in the serum of women with breast cancer that are likely to facilitate the growth and metastasis of breast cancer, in part through their influence on tubule formation, and, therefore, may be potential targets for new cancer therapies.

Aerobic interval exercise improves parameters of nonalcoholic fatty liver disease (NAFLD) and other alterations of metabolic syndrome in obese Zucker rats

Metabolic syndrome (MS) is a group of metabolic alterations that increase the susceptibility to cardiovascular disease and type 2 diabetes. Nonalcoholic fatty liver disease has been described as the liver manifestation of MS. We aimed to test the beneficial effects of an aerobic interval training (AIT) protocol on different biochemical, microscopic, and functional liver alterations related to the MS in the experimental model of obese Zucker rat. Two groups of lean and obese animals (6 weeks old) followed a protocol of AIT (4 min at 65%-80% of maximal oxygen uptake, followed by 3 min at 50%-65% of maximal oxygen uptake for 45-60 min, 5 days/week, 8 weeks of experimental period), whereas 2 control groups remained sedentary. Obese rats had higher food intake and body weight (P < 0.0001) and suffered significant alterations in plasma lipid profile, area under the curve after oral glucose overload (P < 0.0001), liver histology and functionality, and antioxidant status. The AIT protocol reduced the severity of alterations related to glucose and lipid metabolism and increased the liver protein expression of PPARγ, as well as the gene expression of glutathione peroxidase 4 (P < 0.001). The training protocol also showed significant effects on the activity of hepatic antioxidant enzymes, although this action was greatly influenced by rat phenotype. The present data suggest that AIT protocol is a feasible strategy to improve some of the plasma and liver alterations featured by the MS.

Leptin inhibits proliferation of breast cancer cells at supraphysiological concentrations by inhibiting mitogen-activated protein kinase signaling

Leptin is a hormone secreted by white fat tissue and signals the amount of overall body fat to the hypothalamus. The circulating concentration of leptin correlates with the level of obesity. Breast cancer risk is higher in obese postmenopausal women compared with postmenopausal women of a normal weight, and high leptin concentrations may contribute to this risk. In the present study, SK-BR-3 and MDA-MB-231 breast cancer cell lines were treated with various concentrations (6.25–1,600 ng/ml) of recombinant leptin and changes in cell proliferation were assessed. The SK-BR-3 breast cancer cells exhibited a concentration-dependent increase in proliferation with physiological leptin concentrations (<100 ng/ml), but no further increase in proliferation at high leptin concentrations (>100 ng/ml) was observed. Cell proliferation was not affected at supraphysiological leptin concentrations (>800 ng/ml) in SK-BR-3 cells, whereas it decreased in MDA-MB-231 cells. Therefore, cell signaling and cell cycle changes were assessed at supraphysiological concentrations (1,600 ng/ml). In the two cell lines, leptin treatment decreased the mitogen-activated protein kinase (MAPK) cell signaling pathway activation. Leptin treatment did not increase Akt phosphorylation or significantly alter the cell population distribution across cell cycle stages. To the best of our knowledge, leptin-induced growth inhibition of breast cancer cells at supraphysiological concentrations has not been reported in the literature to date, and the findings of this study suggest that reduced MAPK activity may be the underlying cause. Thus, the effect of leptin on breast cancer growth warrants further investigation since leptin is considered to be one of the main mediators in the obesity-breast cancer connection.

Cytotoxicity and cell death mechanisms induced by a novel bisnaphthalimidopropyl derivative against the NCI-H460 non-small lung cancer cell line

Some polyamine derivatives, namely the bisnaphthalimidopropyl polyamines (BNIPPs) may have potential as anticancer drugs. Indeed, previous work from some of us had shown that the ability of these molecules to bind to DNA may contribute to their cytotoxicity. However, their precise mode of action has not been fully understood. In the present work, we report for the first time the effect of the previously synthesised compounds, BNIPDaCHM and NPA, together with a new BNIP derivative (BNIP-3,4-DaDPM) in the in vitro growth of a non-small cell lung cancer cell line (NCI-H460). In addition, for the most potent compound (BNIPDaCHM), its activity as sirtuin inhibitor was investigated in vitro and further confirmed in silico. Results in the NCI-H460 cells showed that, from the compounds tested, BNIPDaCHM was the most potent (GI50 of 1.3 μM). In addition, a concentration-dependent alteration in the normal NCI-H460 cell cycle profile was observed following treatment with BNIPDaCHM as well as an increase in the sub-G1 peak (suggestive of apoptotis). This effect was further supported by Annexin V/PI staining and by analysing the expression of proteins related to apoptosis (cleaved PARP and Caspase-3) by Western blot. It was also observed that BNIPDaCHM inhibited the activity of SIRT2 in vitro, but not of SIRT1. Accordingly, this compound also caused a small increase in tubulin acetylation in NCI-H460 cells. To determine the binding potential of BNIPDaCHM on hSIRT2 and to further validate its inhibitory action, in silico docking studies were carried out, which revealed that BNIPDaCHM is composed of an entirely new SIRT2- inhibiting structural scaffold. In conclusion, this study indicates that BNIP derivatives with a novel structural backbone, such as BNIPDaCHM, may have potential as building blocks for novel antitumour agents which might selectively bind to hSIRT-2.

Obesity and its health impact in Africa: a systematic review

Abstract

Obesity and its association with co-morbidities in Africa are on the rise. This systematic review examines evidence of obesity and its association with co-morbidities within the African continent. Comparative studies conducted in Africa on adults 17 years and older with mean body mass index (BMI) ≥ 28 kg/m² were included. Five electronic databases were searched. Surveys, case–control and cohort studies from January 2000 to July 2010 were evaluated. Of 720 potentially relevant articles, 10 met the inclusion criteria. Prevalence of obesity was higher in urban than rural subjects with significant increases in obesity rates among women. Inflammatory marker levels were significantly elevated among Africans compared with Caucasians. The co-relationship between obesity and chronic diseases was also highlighted. This systematic review demonstrates that while obesity remains an area of significant public health importance to Africans, particularly in urban areas, there is little evidence of proper diagnosis, treatment and/or prevention.

The molecular contribution of TNF-α in the link between obesity and breast cancer

Obesity is a growing worldwide medical problem, as it pre-disposes the affected hosts to a number of severe diseases, including postmenopausal breast cancer. Obesity development is characterised, amongst others, by aberrant secretion of adipokines. White fat tissue infiltrating macrophages secrete tumour necrosis factor-α (TNF-α) so that its circulating levels correlate positively with body mass index (BMI). In the study presented here, the effect of TNF-α on cell proliferation, cell signalling pathway activation and cell cycle in two breast cancer cell lines and one breast epithelial cell lines was assessed to determine the contribution of TNF-α on breast cancer progression and aetiology, respectively. TNF-α acted differently on all three cell lines. In MDA-MB-231 breast cancer cells, cell proliferation and PI3-kinase activation were not affected, while MAP-kinase activation and cell cycle progression were decreased, with indications of increased apoptosis. This suggests a growth inhibitory function of TNF-α in these cells. In SK-BR-3 breast cancer cells, cell proliferation and cell signalling pathway activation increased, while cell cycle progression decreased, which contradictorily suggests both growth promoting and growth inhibiting properties of TNF-α on these cells. This makes TNF-α an unlikely candidate for a general contribution to the link between obesity and breast cancer progression, however, individual tumours may be responsive to a proliferative signal of TNF-α. In MCF-10A breast epithelial cells, cell proliferation and MAP-kinase activation increased, while cell cycle progression was unaffected. This suggests a strong proliferative response in these cells, suggesting the possibility that TNF-α may contribute to breast cancer aetiology as a novel link between obesity and increased risk of breast cancer development.

Impaired expression of glutathione peroxidase-4 gene in peripheral blood mononuclear cells: a biomarker of increased breast cancer risk

Breast cancer aetiology is unclear despite comprising approximately 28% of female cancers. Several risk factors are known. Not all women exhibiting established risk factors will develop breast cancer but many without recognised risk factors will, indicating involvement of unknown risk factors. Impaired basal or oxidation-stimulated gene expression of redox enzymes, particularly Glutathione Peroxidase 1 and 4 (GPX1 and 4), resulting in increased oxidative stress, could be an "unknown" risk factor in breast cancer. We determined whether basal expression of GPX1 and 4, two major redox enzymes, in Peripheral Blood Mononuclear Cells (PBMNC) and/or their stimulated expression (oxidative stress) was impaired in women with breast cancer who have no known markers of risk compared with control women without breast cancer. A significant 30% impairment (p< 0.01) in basal PBMNC GPX4, but not GPX1, gene expression was observed in cancer patients. Oxidative stress stimulation in vitro did not increase GPX4 expression significantly in cancer patients or control women whereas GPX1 expression was significantly increased (30%, p<0.05) only in the cancer group. Attenuation of GPX4 mRNA expression in PBMNC suggests this could be a simple,early biomarker for future breast cancer risk in the high proportion of women without known risk factors who eventually contract the disease.

Evidence that a polymorphism within the 3'UTR of glutathione peroxidase 4 is functional and is associated with susceptibility to colorectal cancer

Low selenium (Se) status has been associated with increased risk of colorectal cancer (CRC). Se is present as the amino acid selenocysteine in selenoproteins, such as the glutathione peroxidases. Se incorporation requires specific RNA structures in the 3' untranslated region (3'UTR) of the selenoprotein mRNAs. A single nucleotide polymorphism (SNP) occurs at nucleotide 718 (within the 3'UTR) in the glutathione peroxidase 4 gene. In the present study, Caco-2 cells were transfected with constructs in which type 1 iodothyronine deiodinase coding region was linked to the GPx4 3'UTR with either C or T variant at position 718. Higher reporter activity was observed in cells expressing the C variant compared to those expressing the T variant, under either Se-adequate or Se-deficient conditions. In addition, a disease association study was carried out in cohorts of patients with either adenomatous polyps, colorectal adenocarcinomas and in healthy controls. A higher proportion of individuals with CC genotype at the GPx4 T/C 718 SNP was present in the cancer group, but not in the polyp group, compared with the control group (P < 0.05). The present data demonstrate the functionality of the GPx4 T/C 718 SNP and suggest that T genotype is associated with lower risk of CRC.

Glucagon-like peptide-1 stimulates human insulin promoter activity in part through cAMP-responsive elements that lie upstream and downstream of the transcription start site

Glucagon-like peptide-1 (GLP-1) is a peptide hormone secreted from the enteroendocrine L-cells of the gut and which acts primarily to potentiate the effects of glucose on insulin secretion from pancreatic beta-cells. It also stimulates insulin gene expression, proinsulin biosynthesis and affects the growth and differentiation of the islets of Langerhans. Previous studies on the mechanisms whereby GLP-1 regulates insulin gene transcription have focused on the rat insulin promoter. The aim of this study was to determine whether the human insulin promoter was also responsive to GLP-1, and if so to investigate the possible role of cAMP-responsive elements (CREs) that lie upstream (CRE1 and CRE2) and downstream (CRE3 and CRE4) of the transcription start site. INS-1 pancreatic beta-cells were transfected with promoter constructs containing fragments of the insulin gene promoter placed upstream of the firefly luciferase reporter gene. GLP-1 was found to stimulate the human insulin promoter, albeit to a lesser degree than the rat insulin promoter. Mutagenesis of CRE2, CRE3 and CRE4 blocked the stimulatory effect of GLP-1 while mutagenesis of CRE1 had no effect. Analysis of nuclear protein binding to the four CREs showed that, while they share some proteins, each CRE site is unique. Stimulation of transcription by GLP-1 through CRE2, CRE3 and CRE4 resulted in altered protein binding that was different for each of the CRE sites involved. Collectively, these data show that the four human CREs are not simply multiple copies of the rat CRE site and further emphasise that the human insulin promoter is distinct from the rodent promoter.

Effects of Se-depletion on glutathione peroxidase and selenoprotein W gene expression in the colon

Selenium (Se)-containing proteins have important roles in protecting cells from oxidative damage. This work investigated the effects of Se-depletion on the expression of the genes encoding selenoproteins in colonic mucosa from rats fed diets of different Se content and in human intestinal Caco-2 cells grown in Se-adequate or Se-depleted culture medium. Se-depletion produced statistically significant (P<0.05) falls in glutathione peroxidase (GPX) 1 mRNA (60-83%) and selenoprotein W mRNA (73%) levels, a small but significant fall in GPX4 mRNA (17-25%) but no significant change in GPX2. The data show that SelW expression in the colon is highly sensitive to Se-depletion.

Insulin promoter factor-1 mutations and diabetes in Trinidad: identification of a novel diabetes-associated mutation (E224K) in an Indo-Trinidadian family

This study investigated the prevalence of insulin promoter factor-1(IPF-1) mutations in familial early-onset diabetes mellitus in Trinidad. We screened 264 unrelated subjects with type 2 diabetes diagnosed before 40 yr of age and a family history of diabetes for mutations in the minimal promoter and coding region of the IPF-1 gene (IPF1). This study population included 169 patients of East Indian descent (Indo-Trinidadians), 66 of African descent (Afro-Trinidadians), and 29 of mixed ancestry. We identified five IPF1 variants, including one new missense mutation E224K, the previously described diabetes-associated duplication P242 P243dupP, two silent mutations in the codons for Leu54 (c.162G>A) and Ala256 (c.768C>A), and a substitution in the 5'-untranslated region (c.-18C>T). The E224K mutation was found in two unrelated diabetic Indo-Trinidadians and 0 of 60 controls. It was present on the same haplotype in both patients suggesting a founder effect. The E224K mutation cosegregated with early-onset diabetes or impaired glucose tolerance in a large family, suggestive of the type 4 form of maturity-onset diabetes of the young rather than type 2 diabetes. Functional studies of E224K showed reduced transactivation activity. IPF1 mutations leading to synthesis of a mutant protein may contribute to the development of familial early-onset diabetes/maturity-onset diabetes of the young in Indo-Trinidadians.

Perinuclear mRNA localisation by vimentin 3'-untranslated region requires a 100 nucleotide sequence and intermediate filaments

The role of the vimentin 3'-untranslated region (3'-UTR) in mRNA localisation was studied in cells transfected with a reporter sequence linked to subregions of the 3'-UTR. In situ hybridisation showed that nucleotides 37-137, including a previously identified protein-binding domain, were sufficient to localise transcripts to perinuclear cytoplasm. Transfection of two SW13 cell lines that do and do not express vimentin showed that perinuclear localisation due to either the vimentin or c-myc 3'-UTR requires intermediate filaments. The data suggest that both a specific protein-binding region of the vimentin 3'-UTR and intermediate filaments themselves are required to determine the site of vimentin synthesis.

Glucose regulates islet amyloid polypeptide gene transcription in a PDX1- and calcium-dependent manner

Islet amyloid polypeptide (IAPP) and insulin are expressed in the beta-cells of the islets of Langerhans. They are co-secreted in response to changes in glucose concentration, and their mRNA levels are also regulated by glucose. The promoters of both genes share similar cis-acting sequence elements, and both bind the homeodomain transcription factor PDX1, which plays an important role in the regulation of the insulin promoter and insulin mRNA levels by glucose. Here we examine the role of PDX1 in the regulation of the human IAPP promoter by glucose. The experiments were facilitated by the availability of a human beta-cell line (NES2Y) that lacks PDX1. NES2Y cells also lack operational K(ATP) channels, resulting in a loss of control of calcium signaling. We have previously used these cells to show that glucose regulation of the insulin gene is dependent on PDX1, but not calcium. In the mouse beta-cell line Min6, glucose (16 mm) stimulated a 3.5-4-fold increase in the activity of a -222 to +450 IAPP promoter construct compared with values observed in 0.5 mm glucose. In NES2Y cells, glucose failed to stimulate transcriptional activation of the IAPP promoter. Overexpression of PDX1 in NES2Y cells failed to reinstate glucose-responsive control of the IAPP promoter. Glucose effects on the IAPP promoter were observed only in the presence of PDX1 when normal calcium signaling was restored by overexpression of the two K(ATP) channel subunits SUR1 and Kir6.2. The importance of calcium was further emphasized by an experiment in which glucose-stimulated IAPP promoter activity was inhibited by the calcium channel blocker verapamil (50 microm). Verapamil was further shown to inhibit the stimulatory effect of glucose on IAPP mRNA levels. These results demonstrate that like the insulin promoter, glucose regulation of the IAPP promoter is dependent on the activity of PDX1, but unlike the insulin promoter, it additionally requires the activity of another, as yet uncharacterized factor(s), the activity of which is calcium-dependent.

Thyroid stimulating hormone and selenium supply interact to regulate selenoenzyme gene expression in thyroid cells (FRTL-5) in culture

In the absence of a sodium selenite supplement, FRTL-5 cells showed a reduced activity of cytosolic glutathione peroxidase (cGSH-Px), a marker of selenium status, indicating the cells were Se-deficient. Se-deficient cells showed a 65% reduction in cGSH-Px mRNA abundance but little change in abundance of either phospholipid hydroperoxide glutathione peroxidase or type 1 deiodinase (IDI) mRNA. In Se-replete cells increased thyroid stimulating hormone (TSH) caused a small decrease in IDI abundance but in Se-deficient cells TSH caused a large increase. The results indicate an interaction between TSH and Se status in the regulation of thyroid selenoenzyme synthesis.

Regulatory signals in messenger RNA: determinants of nutrient-gene interaction and metabolic compartmentation

Nutrition has marked influences on gene expression and an understanding of the interaction between nutrients and gene expression is important in order to provide a basis for determining the nutritional requirements on an individual basis. The effects of nutrition can be exerted at many stages between transcription of the genetic sequence and production of a functional protein. This review focuses on the role of post-transcriptional control, particularly mRNA stability, translation and localization, in the interactions of nutrients with gene expression. The effects of both macronutrients and micronutrients on regulation of gene expression by post-transcriptional mechanisms are presented and the post-transcriptional regulation of specific genes of nutritional relevance (glucose transporters, transferrin, selenoenzymes, metallothionein, lipoproteins) is described in detail. The function of the regulatory signals in the untranslated regions of the mRNA is highlighted in relation to control of mRNA stability, translation and localization and the importance of these mRNA regions to regulation by nutrients is illustrated by reference to specific examples. The localization of mRNA by signals in the untranslated regions and its function in the spatial organization of protein synthesis is described; the potential of such mechanisms to play a key part in nutrient channelling and metabolic compartmentation is discussed. It is concluded that nutrients can influence gene expression through control of the regulatory signals in these untranslated regions and that the post-transcriptional regulation of gene expression by these mechanisms may influence nutritional requirements. It is emphasized that in studies of nutritional control of gene expression it is important not to focus only on regulation through gene promoters but also to consider the possibility of post-transcriptional control.

Role of the 3' untranslated region in the regulation of cytosolic glutathione peroxidase and phospholipid-hydroperoxide glutathione peroxidase gene expression by selenium supply

Selenium is an essential nutrient and synthesis of selenoproteins is affected by limited selenium supply. During selenium deficiency there is a differential regulation of selenoprotein synthesis and gene expression; for example, there is a decrease in abundance of mRNA for cytosolic glutathione peroxidase (cGSH-Px) and a preservation of mRNA for phospholipid-hydroperoxide glutathione peroxidase (PHGSH-Px). This difference is not due to an alteration in the rate of transcription but might reflect differences in translation. The aim of the present work was to assess the role of cGSH-Px and PHGSH-Px 3' untranslated regions (UTRs) in the regulation of selenoprotein mRNA stability and translation by using H4-II-E-C3 cells transfected with different constructs containing a type I iodothyronine deiodinase-coding region linked to different selenoprotein mRNA 3' UTRs. Translational efficiency results showed that the efficiency of the 3' UTRs in permitting selenocysteine incorporation is similar in selenium-replete conditions but, when selenium is limiting, the 3' UTR of cGSH-Px is less efficient than the 3' UTR of PHGSH-Px. The results suggest that the 3' UTR of these selenoprotein mRNA species influences their extent of translation when selenium levels are low. The different sensitivity of the 3' UTRs to selenium deficiency can explain the differential effect that selenium deficiency has on cGSH-Px and PHGSH-Px activity and mRNA levels, stability and translation. This might be partly responsible for channelling selenium for synthesis of PHGSH-Px rather than cGSH-Px.

Selective control of cytosolic glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase mRNA stability by selenium supply

Selenium depletion of H4 hepatoma cells reduced cytosolic glutathione peroxidase (cGSH-Px) mRNA abundance but had no effect on phospholipid hydroperoxide glutathione peroxidase (PHGSH-Px) mRNA abundance. Actinomycin D chase experiments showed that selenium depletion had no effect on the stability of PHGSH-Px mRNA but decreased the stability of cGSH-Px mRNA. In Se-replete cells puromycin decreased the stability of both cGSH-Px and PHGSH-Px mRNAs. The results suggest that when selenium supply is limiting PHGSH-Px mRNA translation is maintained more than that of cGSH-Px mRNA, and thus more cGSH-Px mRNA is released from polysomes and degraded.

Selenoprotein gene expression during selenium-repletion of selenium-deficient rats

Selenium repletion of selenium-deficient rats with 20 micrograms selenium / kg body weight as Na2SeO3 was used as a model to investigate the mechanisms that control the distribution of the trace element to specific selenoproteins in liver and thyroid. Cytosolic glutathione peroxidase (cGSHPx), phospholipid hydroperoxide glutathione peroxidase (PHGSHPx), and iodothyronine 5'-deiodinase (IDI) activities were all transiently increased in liver 16 to 32 h after ip injection with selenium. However, only cGSHPx and PHGSHPx activities increased in the thyroid where IDI activity was already increased by selenium deficiency. These responses were owing to synthesis of the seleoproteins on newly synthesised and/or existing mRNAs. The selenoprotein mRNAs in the thyroid gland were increased two- and threefold after the transitory increases in selenoprotein activity. In contrast, there were parallel changes in selenoprotein mRNAs and enzyme activities in the liver, with no prolonged rises in mRNA levels. The organ differences suggest that increased thryotrophin (TSH) concentrations, which are known to induce thyrodial IDI and mRNA, may control the mRNAs for all the thyroidal selenoproteins investigated and be a major mechanism for the preservation of thyroidal selenoproteins when selenium supplies are limited.

Influence of organic acids on aluminium absorption and storage in rat tissues

Six groups of 16 rats each were fed a standard diet for 8 weeks. Aluminium (Al) complexed with organic anions (citrate, lactate, malate, or tartrate) was added to the diet of four of the groups and aluminium hydroxide to the diet of one group (control 'Al +'). Aluminium concentrations in the diets were 1500-2000 mg/kg. The sixth group (control 'Al -') served as control. Plasma, bone (femur), kidneys, cerebral cortex and cerebellum levels of aluminium were determined at 4 and 8 weeks. All the complexing agents increased tissue accumulations, compared with values in the two control groups, especially citrate in bone and kidneys and lactate in cerebral cortex. There were no significant differences (P < 0.05) in aluminium levels in the tissues considered between the 'Al +' and 'Al -' control groups. Our results show the ability of dietary organic acids to increase aluminium absorption and tissue accumulation and indicate that concurrent intake of aluminium and dietary organic acids is not appropriate.

Dietary selenium intake and selenoproteins in rat plasma

Selenium (Se) is vital for animals and humans, as it is an essential component of Se-dependent glutathione peroxidase (GPx), an enzyme that reduces peroxides and protects cells against the damaging effects of oxidation. Se has, however, been found in rat plasma even when the enzymatic activity of GPx is very low, supporting the hypothesis that Se is also bound to other proteic structures. The purpose of this work was partially to purify the selenium-containing proteins in plasma, without denaturation, by isoelectrofocusing. We observed two pH intervals in the plasma where Se-containing proteins concentrated upon focusing: the first, at pH 6.0 +/- 0.2 and with GPx activity, and the second, between pH 4.6 and 5.4, with no enzymatic activity. We can infer therefore that other Se-containing proteins are present at a lower pH than 6, and in particular between 4.6 and 5.4

Tissue-specific regulation of selenoenzyme gene expression during selenium deficiency in rats

Regulation of synthesis of the selenoenzymes cytosolic glutathione peroxidase (GSH-Px), phospholipid hydroperoxide glutathione peroxidase (PHGSH-Px) and type-1 iodothyronine 5'-deiodinase (5'IDI) was investigated in liver, thyroid and heart of rats fed on diets containing 0.405, 0.104 (Se-adequate), 0.052, 0.024 or 0.003 mg of Se/kg. Severe Se deficiency (0.003 mg of Se/kg) caused almost total loss of GSH-Px activity and mRNA in liver and heart. 5'IDI activity decreased by 95% in liver and its mRNA by 50%; in the thyroid, activity increased by 15% and mRNA by 95%. PHGSH-Px activity was reduced by 75% in the liver and 60% in the heart but mRNA levels were unchanged; in the thyroid, PHGSH-Px activity was unaffected by Se depletion but its mRNA increased by 52%. Thus there is differential regulation of the three mRNAs and subsequent protein synthesis within and between organs, suggesting both that mechanisms exist to channel Se for synthesis of a particular enzyme and that there is tissue-specific regulation of selenoenzyme mRNAs. During Se depletion, the levels of selenoenzyme mRNA did not necessarily parallel the changes in enzyme activity, suggesting a distinct mechanism for regulating mRNA levels. Nuclear run-off assays with isolated liver nuclei showed severe Se deficiency to have no effect on transcription of the three genes, suggesting that there is post-transcriptional control of the three selenoenzymes, probably involving regulation of mRNA stability.