Giovanna Bermano

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.

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.

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.

SELENOPROTEIN GENE EXPRESSION DURING SELENIUM-REPLETION OF SELENIUM-DEFICIENT RATS

Selenium repletion of selenium-deficient rats with 20 μg 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.

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.

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.

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.

Synthesis, cytotoxicity and DNA-binding of novel bisnaphthalimidopropyl derivatives in breast cancer MDA-MB-231 cells

New naphthalimidopropyl, bisphthalimidopropyl and bisnaphthalimidopropyl (BNIP) derivatives were synthesised and characterised. Their interactions with Calf Thymus DNA were studied by UV spectrophotometric analysis and a competitive Ethidium bromide displacement assay. Cytotoxicity was determined by MTT assay in a breast cell system (MDA-MB-231 and MCF-10A cells). All BNIPs exhibited strong DNA-binding properties and cytotoxic activity with IC(50) values in the range of 0.83-12.68 microM (24 and 48 h treatment). In addition, the uptake of BNIP derivatives within cancer cells was not via utilisation of the MGBG polyamine transporter. Put together the results confirm that the presence of the bisnaphthalimidopropyl and alkyl linker functionality are crucial for exerting DNA-binding and cytotoxic properties, hence demonstrating promise in their further development as potential anti cancer agents.

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.

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.