Comparison of age-related differences in expression of phospholipid hydroperoxide glutathione peroxidase mRNA and activity in various tissues of pigs

The effects of dietary essential fatty acid ratios and energy level on growth performance, lipid metabolism, and inflammation in grow-finish pigs

The objective of this study was to investigate the effects of dietary metabolizable energy (ME) level and the ratio of linoleic acid:α-linolenic acid (LA:ALA) on the growth performance, lipid metabolism, circulatory and joint inflammatory status, and synovial fluid proteome of grow-finish pigs. A total of 224 pigs (BW = 41.5 ± 6.1 kg; PIC Genus 337 × 1050, Hendersonville, TN) were randomly assigned to either a high (3.55 Mcal/kg; HE) or low (3.29 Mcal/kg; LE) ME dietary treatment with a high (23:1) or low (12:1) LA:ALA in a 2 × 2 factorial arrangement. Diets were fed across three 28-d phases. Pigs were housed either four barrows or four gilts per pen. Blood samples were collected on days 0, 21, 42, and 84. Synovial fluid was collected from the hock and carpus joints on days 0 and 84. Liver and adipose tissue samples were collected on day 84. Data were analyzed as repeated measures using PROC MIXED (SAS 9.4) with pen as the experimental unit and energy level, essential fatty acid ratio, sex, phase, and their interactions as fixed effects. Compared to LE, HE increased days 28, 56, and 84 body weight (BW; P = 0.005). For the overall period, HE increased average daily gain (ADG) compared to LE (P < 0.001) and improved feed efficiency (P = 0.001), while LE increased feed intake compared to HE (P < 0.001). Gilts receiving diets with low LA:ALA had similar final BW to barrows receiving a low LA:ALA at days 28, 56, and 84 (P = 0.024), resulting from improved overall days 0-84 ADG compared to gilts receiving the high LA:ALA (P = 0.031). In the liver, HE decreased the mRNA abundance of acetyl CoA carboxylase (ACACA; P = 0.004), cluster of differentiation 36 (P = 0.034), and tended to decrease fatty acid synthase (FASN; P = 0.056). In adipose tissue, HE decreased ACACA (P = 0.001) and FASN (P = 0.017). Plasma inflammatory markers C-reactive protein (CRP) and tumor necrosis factor-α (TNFα) were reduced on day 84 compared to day 0 (P ≤ 0.014). In the hock and carpus synovial fluid, LE tended to reduce CRP and TNFα (P ≤ 0.096). Hock and carpus synovial fluid CRP were also reduced on day 84 compared to day 0 (P = 0.001). Age of the pig impacted serum and hock synovial fluid protein abundance, but not energy level, LA:ALA, or their interactions (P < 0.05). To conclude, the high and low LA:ALA ratios utilized in this study can be fed at varying energy levels without impacting growth. Additionally, LA:ALA ratios can differentially impact the growth of barrows and gilts.

Selenium-enriched foods are more effective at increasing glutathione peroxidase (GPx) activity compared with selenomethionine: a meta-analysis

Selenium may play a beneficial role in multi-factorial illnesses with genetic and environmental linkages via epigenetic regulation in part via glutathione peroxidase (GPx) activity. A meta-analysis was undertaken to quantify the effects of dietary selenium supplementation on the activity of overall GPx activity in different tissues and animal species and to compare the effectiveness of different forms of dietary selenium. GPx activity response was affected by both the dose and form of selenium (p < 0.001). There were differences between tissues on the effects of selenium supplementation on GPx activity (p < 0.001); however, there was no evidence in the data of differences between animal species (p = 0.95). The interactions between dose and tissue, animal species and form were significant (p < 0.001). Tissues particularly sensitive to changes in selenium supply include red blood cells, kidney and muscle. The meta-analysis identified that for animal species selenium-enriched foods were more effective than selenomethionine at increasing GPx activity.

Enhanced water-holding capacity of meat was associated with increased Sepw1 gene expression in pigs fed selenium-enriched yeast

To study the effect of selenium-enriched yeast (SeY) level on selenoprotein genes expression and the relation between gene expression and antioxidant status and meat quality, 30 selenium (Se)-depleted pigs (7-week old, 10.30±0.68 kg) were randomly divided into 3 groups and fed a basal diet plus 0, 0.3 and 3.0 mg Se/kg as SeY for 8 weeks. Results showed that dietary SeY supplementation improved the antioxidant status in muscle. The increased levels of SeY decreased (P<0.05) the drip loss and the concentration of thiobarbituric acid reactive substances in the muscle and meat. However, increased dietary SeY intake quadratically increased (P<0.01) the mRNA level of Sepw1 gene among the 12 selenoprotein genes examined in muscle. Statistical analysis showed drip loss was negatively correlated with the mRNA level of Sepw1 gene. These suggested that the enhanced water-holding capacity of meat was associated with the increased expression of Sepw1 gene.

Reactive oxygen intermediate-induced pathomechanisms contribute to immunosenescence, chronic inflammation and autoimmunity

Deregulation of reactive oxygen intermediates (ROI) resulting in either too high or too low concentrations are commonly recognized to be at least in part responsible for many changes associated with aging. This article reviews ROI-dependent mechanisms critically contributing to the decline of immune function during physiologic - or premature - aging. While ROI serve important effector functions in cellular metabolism, signalling and host defence, their fine-tuned generation declines over time, and ROI-mediated damage to several cellular components and/or signalling deviations become increasingly prevalent. Although distinct ROI-associated pathomechanisms contribute to immunosenescence of the innate and adaptive immune system, mutual amplification of dysfunctions may often result in hyporesponsiveness and immunodeficiency, or in chronic inflammation with hyperresponsiveness/deregulation, or both. In this context, we point out how imbalanced ROI contribute ambiguously to driving immunosenescence, chronic inflammation and autoimmunity. Although ROI may offer a distinct potential for therapeutic targeting along with the charming opportunity to rescue from deleterious processes of aging and chronic inflammatory diseases, such modifications, owing to the complexity of metabolic interactions, may carry a marked risk of unforeseen side effects.

Comparison of age-related differences in expression of antioxidant enzyme mRNA and activity in various tissues of pigs

Antioxidant enzymes (AOEs), glutathione peroxidase (GPx), superoxide dismutase(SOD) and catalase (CAT) play an important role in protecting tissues from reactive oxygen species (ROS) reactions. The objective of this study was to determine the developmental regulation of AOEs mRNA levels and activity in tissues of different growing phases pigs (Sus scrofa). Nine different tissues were collected from thirty Duroc x Landrace x Yorkshire male pigs with six animals in each age (1, 42, 84, 126 and 168 days) to assay for GPx, CAT and CuZnSOD mRNA expression and activities. Results showed that GPx, CAT, and CuZnSOD mRNA levels in liver increased (P<0.05) at the first stage, and thereafter their levels began to decline (P<0.05), and the maximal mRNA levels of these AOEs were seen at the age of 42, 84, and 126 days, respectively. In Muscle, GPx and CAT mRNA level increased from 1 to 84 days and 1 to 126 days, respectively, and thereafter their levels began to decline, whereas CuZnSOD mRNA level steadily increased (P<0.05) following birth. Activity expression of AOEs in selected tissues was increased as pigs became older (P<0.05) with the exception of CuZnSOD activity in muscle, but changes in AOEs mRNA levels between ages did not fully account for all changes in activity. GPx and CuZnSOD mRNA were most abundantly expressed in muscle, while CAT mRNA were most abundant in brain. AOEs may exert cell and tissue-specific roles in metabolic regulation beyond their mere antioxidant potential. In conclusion, expression of AOEs mRNA and activity exhibit different developmental profiles in various tissues of pigs, and the regulation of AOEs is not tightly coordinated in either tissue.

Enzymatic and immunochemical evaluation of phospholipid hydroperoxide glutathione peroxidase (PHGPx) in testes and epididymal spermatozoa of rats of different ages

Selenium (Se) and selenoproteins such as glutathione peroxidases are necessary for the proper development and fertilizing capacity of sperm cells. Phospholipid hydroperoxide glutathione peroxidase (PHGPx, E.C. 1.11.1.12) is a monomeric seleno-enzyme present in different mammalian tissues in soluble and bound form. Its function, like the other glutathione peroxidases, was originally viewed as a protective role against hydroperoxides, but direct and indirect evidence indicates that it has additional regulatory roles. PHGPx is present in testis cells and sperm cells, and its appearance is hormone regulated. We present here biochemical data, which clearly indicate that the enzyme specific activity in rat is age-dependent during the life-span monitored (from 36 to 365 days), with a maximum at 3 months of age in the testis germ cells and at 6 months of age in the isolated epididymal sperm cells. Western blotting and immunocytochemical analysis by means of anti-PHGPx antibodies show the different distribution and the strong binding of PHGPx in the testes and sperm cell subcellular compartments (nucleus, acrosome, mitochondria and residual bodies) of rats of different age. The presence of the protein exhibits in the testis cells a pattern different from that of the catalytic activity, with a maximum at 6 months of age. The subcellular distribution of PHGPx is qualitatively, but not quantitatively, unchanged during ageing. These different behaviours are compared and discussed.

Discovery of a functional retrotransposon of the murine phospholipid hydroperoxide glutathione peroxidase: chromosomal localization and tissue-specific expression pattern

Phospholipid hydroperoxide glutathione peroxidase (PHGPx), a selenoprotein capable of reducing toxic hydroperoxy ester lipids, has been implicated in antioxidative defense and spermatogenesis. Screening a murine genomic library, we isolated two recombinants (pseudogenes 1 and 2) containing retrotransposons for this enzyme. On comparison with the paralogous cDNA, pseudogene 1 contained only two silent nucleotide exchanges, and the 3'-untranslated region (3'-UTR) carrying the functionally important selenocysteine insertion sequence was free of mutations. This retrotransposon was found in various mouse strains and could be mapped to the region B2-B3 of chromosome 10. In vitro studies indicated significant promoter activity in the 5'-flanking region of pseudogene 1, and we observed a tissuespecific expression of this retrotransposon. In the submandibular gland. Most PHGPx transcripts originated from pseudogene 1. In contrast, pseudogene 2, containing numerous mutations in all parts of the retrotransposon, was not expressed in any tissue. It was mapped to region E3-E4 of chromosome 17, and we did not detect any promoter activity in its 5'-flanking region. These data indicate the existence of two retrotransposed PHGPx pseudogenes, one of which encodes a functional enzyme. This retrotransposon belongs to the rare group of pseudogenes that are tissue-specifically expressed under the control of captured regulatory elements, and it constitutes an example of evolutionarily acquired redundancy in gene expression. The results are important for the design of future knockout strategies aimed at investigating the biological role of this enzyme.

Bacterial and nonbacterial expression of wild-type and mutant human phospholipid hydroperoxide glutathione peroxidase and purification of the mutant enzyme in the milligram scale

15-Lipoxygenases and phospholipid hydroperoxide glutathione peroxidases are counterparts in the metabolism of hydroperoxy lipids and a balanced regulation of both enzymes is essential for normal cell function. Glutathione peroxidases contain selenocysteine as catalytically active amino acid and this selenocysteine is encoded by a TGA stop codon. Detailed protein chemical investigations on phospholipid hydroperoxide glutathione peroxidases and crystal trials have been hampered in the past by limited protein supply. There is no efficient natural source for large-scale enzyme preparation and overexpression of the functional protein in recombinant systems has not been reported so far. To avoid problems with recognition of the selenocysteine stop codon we mutated the selenocysteine to a cysteine and expressed the Sec46Cys mutant in milligram amounts in the baculovirus/insect cell system and as His-tag fusion protein in Escherichia coli. The recombinant enzyme species were purified by conventional fast protein liquid chromatography (nonfusion protein) or by affinity chromatography on a nickel matrix (His-tag protein). Surprisingly, we found that both protein variants were functional although their specific activities were reduced when compared with the wild-type enzyme. Basic protein chemical and enzymatic properties of the purified enzyme species were determined and monoclonal antibodies which recognize the native phospholipid hydroperoxide glutathione peroxidases were raised using our enzyme preparations as antigen. The described strategies for overexpression of mutant phospholipid hydroperoxide glutathione peroxidase species and their purification from recombinant sources provide sufficient amounts of enzyme for future protein chemical investigations and detailed crystal trials.

Cloning of the mouse phospholipid hydroperoxide glutathione peroxidase gene

15-Lipoxygenases and phospholipid hydroperoxide glutathione peroxidases (PH-GPx) are counterparts in the metabolism of hydroperoxy lipids and a balanced regulation of both enzymes appears to be important for the cellular peroxide tone regulating the expression of redox sensitive genes. In contrast to lipoxygenases the molecular biology of PH-GPx is less well investigated. In this study we cloned the PH-GPx cDNA from a mouse fibroblast cDNA library and the PH-GPx gene from a mouse genomic library. The gene spans approximately 4 kb which includes 1 kb of 5'-flanking region and consists of seven exons and six introns. The immediate promoter region does not contain a TATA box but there are binding sites for several transcription factors which also occur in the porcine gene. Our investigations provide useful tools for future targeted gene disruption studies.

Knockout of cellular glutathione peroxidase affects selenium-dependent parameters similarly in mice fed adequate and excessive dietary selenium

This study was to determine whether or not effects of the cellular glutathione peroxidase (GPX1) knockout on several Se-dependent parameters in mice were tissue, dietary Se concentration, and selenoprotein specific. A 2 x 3 factorial experiment was conducted with 18 GPX1 knockout mice [GPX1(-)] and 18 controls (3 weeks old, half males and females). These mice were fed a torula yeast diet supplemented with all-rac-alpha-tocopheryl acetate (50 mg/kg of feed) and Se (sodium selenite) at 0, 0.5, or 3.0 mg/kg of feed for 6 weeks. Both kidney GPX1 mRNA levels and liver, kidney, lung, and testis total GPX activities, assayed using hydrogen peroxide, were affected (p < 0.001) by the GPX1 knockout and dietary Se concentrations, whereas kidney extracellular or plasma GPX (GPX3) mRNA levels and phospholipid hydroperoxide GPX (GPX4) activities in the four tissues were affected (p < 0.001) by only dietary Se concentrations. Total GPX activity in testis was reduced approximately 90% (p < 0.01) by the GPX1 knockout. Neither the GPX1 knockout nor the dietary Se concentrations affected mRNA levels of GPX4 in testis or selenoprotein P in kidney. Total liver Se concentrations were not different between the GPX1(-) and control mice at 0 mg Se/kg of feed, but were reduced (p < 0.01) by 61 and 64% in the GPX1(-) mice at 0.5 and 3.0 mg Se/kg of feed, respectively. These results not only confirm the independent expression of GPX3, GPX4, and selenoprotein P from that of GPX1, but also show similar effects of the GPX1 knockout on Se-dependent parameters in mice between different dietary Se concentrations, tissues, and selenoproteins.