Taking a "good" look at free radicals in the aging process

The mitochondrial free radical theory of aging (MFRTA) proposes that aging is caused by damage to macromolecules by mitochondrial reactive oxygen species (ROS). This is based on the observed association of the rate of aging and the aged phenotype with the generation of ROS and oxidative damage. However, recent findings, in particular in Caenorhabditis elegans but also in rodents, suggest that ROS generation is not the primary or initial cause of aging. Here, we propose that ROS are tightly associated with aging because they play a role in mediating a stress response to age-dependent damage. This could generate the observed correlation between aging and ROS without implying that ROS damage is the earliest trigger or main cause of aging.

When a theory of aging ages badly

According to the widely acknowledged mitochondrial free radical theory of aging (MFRTA), the macromolecular damage that results from the production of toxic reactive oxygen species (ROS) during cellular respiration is the cause of aging. However, although it is clear that oxidative damage increases during aging, the fundamental question regarding whether mitochondrial oxidative stress is in any way causal to the aging process remains unresolved. An increasing number of studies on long-lived vertebrate species, mutants and transgenic animals have seriously challenged the pervasive MFRTA. Here, we describe some of these new results, including those pertaining to the phenotype of the long-lived Mclk1(-/-) mice, which appear irreconcilable with the MFRTA. Thus, we believe that it is reasonable to now consider the MFRTA as refuted and that it is time to use the insight gained by many years of testing this theory to develop new views as to the physiological causes of aging.

Early mitochondrial dysfunction in long-lived Mclk1+/- mice

Reduced activity of CLK-1/MCLK1 (also known as COQ7), a mitochondrial enzyme that is necessary for ubiquinone biosynthesis, prolongs the lifespan of nematodes and mice by a mechanism that is distinct from that of the insulin signaling pathway. Here we show that 2-fold reduction of MCLK1 expression in mice reveals an additional function for the protein, as this level of reduction does not affect ubiquinone levels yet affects mitochondrial function substantially. Indeed, we observe that the phenotype of young Mclk1(+/-) mutants includes a severe reduction of mitochondrial electron transport, ATP synthesis, and total nicotinamide adenine dinucleotide (NAD(tot)) pool size as well as an alteration in the activity of key enzymes of the tricarboxylic acid cycle. Surprisingly, we also find that Mclk1 heterozygosity leads to a dramatic increase in mitochondrial oxidative stress by a variety of measures. Furthermore, we find that the mitochondrial dysfunction is accompanied by a decrease in oxidative damage to cytosolic proteins as well as by a decrease in plasma isoprostanes, a systemic biomarker of oxidative stress and aging. We propose a mechanism for the conjunction of low ATP levels, high mitochondrial oxidative stress, and low non-mitochondrial oxidative damage in a long-lived mutant. Our model helps to clarify the relationship between energy metabolism and the aging process and suggests the need for a reformulation of the mitochondrial oxidative stress theory of aging.

Diversity and relative strength of tandem promoters for the antibiotic-resistance genes of several integrons

The integron is a new type of mobile element containing one or more antibiotic-resistance-encoding genes site-specifically integrated as cassettes. The integrated genes are expressed from a common promoter region located in an adjacent conserved segment. Sequence analysis has revealed the existence of four versions of the integron promoters. In this study, we have determined the relative strength of the different integron promoters and compared their activity with that of the tac promoter. Each version of the promoter was cloned upstream from a promoter-less chloramphenicol acetyltransferase-encoding gene (cat) in plasmid pKK232-8. CAT activity was used to measure transcriptional expression from the promoters of the antibiotic-resistance operon. The strongest promoter is the version (TTGACAN17TAAACT) found in plasmid R388 and in transposon Tn1696. This promoter is six times more efficient than the derepressed tac promoter.

A single glutamyl-tRNA synthetase aminoacylates tRNAGlu and tRNAGln in Bacillus subtilis and efficiently misacylates Escherichia coli tRNAGln1 in vitro

In the presence or absence of its regulatory factor, the monomeric glutamyl-tRNA synthetase from Bacillus subtilis can aminoacylate in vitro with glutamate both tRNAGlu and tRNAGln from B. subtilis and tRNAGln1 but not tRNAGln2 or tRNAGlu from Escherichia coli. The Km and Vmax values of the enzyme for its substrates in these homologous or heterologous aminoacylation reactions are very similar. This enzyme is the only aminoacyl-tRNA synthetase reported to aminoacylate with normal kinetic parameters two tRNA species coding for different amino acids and to misacylate at a high rate a heterologous tRNA under normal aminoacylation conditions. The exceptional lack of specificity of this enzyme for its tRNAGlu and tRNAGln substrates, together with structural and catalytic peculiarities shared with the E. coli glutamyl- and glutaminyl-tRNA synthetases, suggests the existence of a close evolutionary linkage between the aminoacyl-tRNA synthetases specific for glutamate and those specific for glutamine. A comparison of the primary structures of the three tRNAs efficiently charged by the B. subtilis glutamyl-tRNA synthetase with those of E. coli tRNAGlu and tRNAGln2 suggests that this enzyme interacts with the G64-C50 or G64-U50 in the T psi stem of its tRNA substrates.

Effect of modified nucleotides on Escherichia coli tRNAGlu structure and on its aminoacylation by glutamyl-tRNA synthetase. Predominant and distinct roles of the mnm5 and s2 modifications of U34

Overproducing Escherichia coli tRNAGlu in its homologous host results in the presence of several distinctly modified forms of this molecule that we name modivariants. The predominant tRNAGlu modivariant in wild-type E. coli contains five modified nucleosides: Psi13, mnm5s2U34, m2A37, T54 and Psi55. Four other overproduced modivariants differ from it by, respectively, either the presence of an additional Psi, or the presence of s2U34, or the lack of A37 methylation combined with either s2U34 or U34. Chemical probing reveals that the anticodon loop of the predominant modivariant is less reactive to the probes than that of the four others. Furthermore, the modivariant with neither mnm5s2U34 nor m2A37 has additional perturbations in the D- and T-arms and in the variable region. The lack of a 2-thio group in nucleoside 34, which is mnm5s2U in the predominant tRNAGlu modivariant, decreases by 520-fold the specificity of E. coli glutamyl-tRNA synthetase for tRNAGlu in the aminoacylation reaction, showing that this thio group is the identity element in the modified wobble nucleotide of E. coli tRNAGlu. The modified nucleosides content also influences the recognition of ATP and glutamate by this enzyme, and in this case also, the predominant modivariant is the one that allows the best specificity for these two substrates. These structural and kinetic properties of tRNAGlu modivariants indicate that the modification system of tRNAGlu optimizes the stability of tRNAGlu and its action as cofactor of the glutamyl-tRNA synthetase for the recognition of glutamate and ATP.

Recurrent deletion of CHD1 in prostate cancer with relevance to cell invasiveness

Though prostate cancer is often indolent, it is nonetheless a leading cause of cancer death. Defining the underlying molecular genetic alterations may lead to new strategies for prevention or treatment. Towards this goal, we performed array-based comparative genomic hybridization (CGH) on 86 primary prostate tumors. Among the most frequent alterations not associated with a known cancer gene, we identified focal deletions within 5q21 in 15 out of 86 (17%) cases. By high-resolution tiling array CGH, the smallest common deletion targeted just one gene, the chromatin remodeler chromodomain helicase DNA-binding protein 1 (CHD1). Expression of CHD1 was significantly reduced in tumors with deletion (P=0.03), and compared with normal prostate (P=0.04). Exon sequencing analysis also uncovered nonsynonymous mutations in 1 out of 7 (14%) cell lines (LAPC4) and in 1 out of 24 (4%) prostate tumors surveyed. RNA interference-mediated knockdown of CHD1 in two nontumorigenic prostate epithelial cell lines, OPCN2 and RWPE-1, did not alter cell growth, but promoted cell invasiveness, and in OPCN2-enhanced cell clonogenicity. Taken together, our findings suggest that CHD1 deletion may underlie cell invasiveness in a subset of prostate cancers, and indicate a possible novel role of altered chromatin remodeling in prostate tumorigenesis.

A high-resolution silicon-on-insulator arrayed waveguide grating microspectrometer with sub-micrometer aperture waveguides

We demonstrate a 50-channel high-resolution arrayed waveguide grating microspectrometer with a 0.2 nm channel spacing on a silicon-on-insulator (SOI) platform. The chip size is 8 mm x 8 mm. High channel density and spectral resolution are achieved using high aspect ratio 0.6 mum x 1.5 mum waveguide apertures to inject the light into the input combiner and to intercept different spectral channels at the output combiner focal region. The measured crosstalk is <-10 dB, the 3 dB channel bandwidth is 0.15 nm, and the insertion loss is -17 dB near the central wavelength of lambda = 1.545 mum.

Impact of deoxynivalenol (DON) contaminated feed on intestinal integrity and immune response in swine

This study was performed to characterize the influence of consuming DON naturally contaminated feeds on pig's intestinal immune defenses, antibody response and cellular immunity. Sixteen 4-week-old piglets were randomly allocated to two dietary treatments: control diet or diet contaminated with 3.5 mg DON/kg. At days 7 and 21, animals were immunized with ovalbumin (OVA). On day 42, intestinal samples were collected for measurement of gene expression involved in immune response, oxidative status and barrier function. Primary IgG antibody response to OVA was increased in pigs fed DON diet compared to control animals. In the ileum of pigs fed DON diet, claudin, occludin, and vimentin genes involved in integrity and barrier function were down-regulated compared to controls. Results also revealed that expression of two chemokines (IL-8, CXCL10), interferon-γ, and major antioxidant glutathione peroxidase 2 (GPX-2) were up-regulated whereas expression of genes encoding enzymatic antioxidants including GPX-3, GPX-4 and superoxide dismutase 3 (SOD-3) were down-regulated in pigs fed DON-contaminated diet. These results strongly suggest that ingestion of DON naturally contaminated feed impaired intestinal barrier and immunological functions by modulating expression of genes coding for proteins involved in tight junctions, tissue remodelling, inflammatory reaction, oxidative stress reaction and immune response.

Clinical spectrum of congenital optic nerve hypoplasia: review of 51 patients

Fifty-one patients with congenital optic nerve hypoplasia (CONH) were reviewed. It was found that the risk of having an affected child is higher in an adolescent mother, and that maternal alcohol or drug abuse may be important factors. Frequently the disorder is associated with other neuropsychiatric handicaps, and with neuro-endocrine abnormalities. The findings suggest that CONH probably is not a homogeneous group of disorders; some may be caused by primary failure of differentiation of the retinal ganglion cells, while others may be the product of an acquired transsynaptic degeneration of optic-nerve fibres.

Preoperative coronary artery disease risk stratification based on dipyridamole imaging and a simple three-step, three-segment model for patients undergoing noncardiac vascular surgery or major general surgery

A 3-step, 3-segment scintigraphic model was developed to improve the accuracy of dipyridamole-thallium imaging for preoperative cardiac risk assessment and to simplify the prognostic interpretation of the images. The model was developed in a pilot study of 60 patients and validated in a group of 355 patients referred for vascular and major general surgery. Study end points included myocardial infarction and cardiac death. Step 1: The postoperative cardiac event rate was 1.3% in 225 patients with normal anterior, inferio- and posterolateral segment perfusion and without transient left ventricular dipyridamole-induced cavitary dilation. Step 2: The physiologic rationale for step 2 consists of identifying patients who are most likely to have left main, 3-vessel or high-risk 2-vessel coronary artery disease or a significant amount of jeopardized myocardium in the territory of a critical coronary stenosis. Of 29 patients with either reversible defects of all 3 segments, transient cavitary dilation, or at least 1 severe grade 3/3 reversible defect, 52% (15 of 29) sustained a postoperative cardiac event. Step 3: The remaining 101 patients were stratified according to age greater than 70 years (p = 0.01), presence of diabetes (p = 0.0004) and the number of segments displaying reversible defects (1 or 2) with cardiac event rates ranging from 5 to 36%. The 3-step, 3-segment model is a useful alternative to the conventional interpretation of dipyridamole myocardial perfusion images for the purpose of quick and efficient preoperative risk stratification based on the rationale of correlating surgical risk with the amount of potentially ischemic myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of the mitochondrial phenotype and slow development of oxidative biomarkers of aging in long-lived Mclk1+/- mice

Although there is a consensus that mitochondrial function is somehow linked to the aging process, the exact role played by mitochondria in this process remains unresolved. The discovery that reduced activity of the mitochondrial enzyme CLK-1/MCLK1 (also known as COQ7) extends lifespan in both Caenorhabditis elegans and mice has provided a genetic model to test mitochondrial theories of aging. We have recently shown that the mitochondria of young, long-lived, Mclk1(+/-) mice are dysfunctional, exhibiting reduced energy metabolism and a substantial increase in oxidative stress. Here we demonstrate that this altered mitochondrial condition in young animals paradoxically results in an almost complete protection from the age-dependent loss of mitochondrial function as well as in a significant attenuation of the rate of development of oxidative biomarkers of aging. Moreover, we show that reduction in MCLK1 levels can also gradually prevent the deterioration of mitochondrial function and associated increase of global oxidative stress that is normally observed in Sod2(+/-) mutants. We hypothesize that the mitochondrial dysfunction observed in young Mclk1(+/-) mutants induces a physiological state that ultimately allows for their slow rate of aging. Thus, our study provides for a unique vertebrate model in which an initial alteration in a specific mitochondrial function is linked to long term beneficial effects on biomarkers of aging and, furthermore, provides for new evidence which indicates that mitochondrial oxidative stress is not causal to aging.

Usefulness of the severity and extent of reversible perfusion defects during thallium-dipyridamole imaging for cardiac risk assessment before noncardiac surgery

Thallium-dipyridamole imaging is a very sensitive test for predicting cardiac events after noncardiac surgery, but it lacks specificity. To improve specificity, a semiquantitative scoring system was developed that combined dipyridamole-induced reversible left ventricular dilatation with scintigraphic indexes for severity and extent of reversible perfusion defects. Using this scoring system, patients were classified into low, intermediate and high risk subgroups. Thallium-dipyridamole imaging was performed in 66 patients before major general and vascular surgery. Thirty-nine patients classified as low risk (30 with normal scans and 9 with fixed defects) underwent surgery uneventfully. Surgery was cancelled in 6 patients with extensive thallium redistribution and coronary angiography was performed because of severe coronary artery disease in 5 and idiopathic dilated cardiomyopathy in 1. In the remaining 21 patients with thallium redistribution, a positive statistical correlation (p = 0.001) between scintigraphic indexes of severity and extent, and cardiac events was noted. Using cutoff values for the scintigraphic indexes, patients with reversible defects could be classified into intermediate and high risk subgroups. Only 1 of 11 patients at intermediate risk developed a complication, whereas 8 of 10 patients at high risk had a postoperative event (7 deaths and 1 myocardial infarction). Thus, using scintigraphic indexes for severity and extent, patients with reversible defects can be stratified into an intermediate risk subgroup that can safely undergo surgery and a high risk subgroup that requires coronary angiography.

Folded cavity SOI microring sensors for high sensitivity and real time measurement of biomolecular binding

We demonstrate folded waveguide ring resonators for biomolecular sensing. We show that extending the ring cavity length increases the resonator quality factor, and thereby enhances the sensor resolution and minimum level of detection, while at the same time relaxing the tolerance on the coupling conditions to provide stable and large resonance contrast. The folded spiral path geometry allows a 1.2 mm long ring waveguide to be enclosed in a 150 microm diameter sensor area. The spiral cavity resonator is used to monitor the streptavidin protein binding with a detection limit of approximately 3 pg/mm(2), or a total mass of approximately 5 fg. The real time measurements are used to analyze the kinetics of biotin-streptavidin binding.

Antioxidant defenses are modulated in the cow oviduct during the estrous cycle

The balanced presence of reactive oxygen species and antioxidants has a positive impact on sperm functions, oocyte maturation, fertilization, and embryo development in vitro. The mammalian oviduct is likely to provide an optimal environment for final gamete maturation, sperm-egg fusion, and early embryonic development. However, the expression and distribution of antioxidant enzymes in the bovine oviduct are poorly characterized. We analyzed the mRNA expression and enzymatic activities of major antioxidants glutathione peroxidase (GPx), superoxide dismutase (Cu,ZnSOD), and catalase in the bovine oviduct throughout the estrous cycle. The high levels of expression for GPx-3 in the isthmus were in contrast to expression of GPx-1 and GPx-2, which occurred mostly in the ampulla and infundibulum of the oviduct. The highest levels of mRNA expression for GPx-1 were observed toward the end of the estrous cycle before ovulation, whereas GPx-2 was mostly expressed at midcycle. Catalase and Cu,ZnSOD mRNA analyses revealed a homogenous expression along the oviduct. The highest levels of glutathione and enzymatic activities for GPx and catalase occurred at the middle (10-12 days) and end (18-20 days) of the estrous cycle, whereas total SOD activity remained constant throughout the estrous cycle in the oviductal fluids. These findings underscore the importance of hydrogen peroxide and hydroperoxide removal by GPx in the oviduct. The heterogeneous expression of antioxidants such as GPx along the oviduct is a possible indication of their physiological role in the events leading to successful fertilization and implantation in vivo.

Silicon photonic wire biosensor array for multiplexed real-time and label-free molecular detection

We demonstrate a silicon photonic wire waveguide biosensor array chip for the simultaneous monitoring of different molecular binding reactions. The chip is compatible with automated commercial spotting tools and contains a monolithically integrated microfluidic channel for sample delivery. Each array sensor element is a 1.8-mm-long spiral waveguide folded within a 130 microm diameter spot and is incorporated in a balanced Mach-Zehnder interferometer with a near temperature independent response. The sensors are arranged in a 400 microm spacing grid pattern and are addressed through cascaded 1x2 optical power splitters using light from a single input fiber. We demonstrate the real-time monitoring of antibody-antigen reactions using complementary and mismatched immunoglobulin G receptor-analyte pairs and bovine serum albumin. The measured level of detection for each sensor element corresponds to a surface coverage of less than 0.3 pg/mm(2).

Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure

We demonstrate a fully etched, continuously apodized fiber-to-chip surface grating coupler for the first time (to our knowledge). The device is fabricated in a single-etch step and operates with TM-polarized light, achieving a coupling efficiency of 3.7 dB and a 3 dB bandwidth of 60 nm. A subwavelength microstructure is employed to generate an effective medium engineered to vary the strength of the grating and thereby maximize coupling efficiency, while mitigating backreflections at the same time. Minimum feature size is 100 nm for compatibility with deep-UV 193 nm lithography.

Transient left ventricular cavitary dilation during dipyridamole-thallium imaging as an indicator of severe coronary artery disease

Transient left ventricular (LV) cavitary dilation during dipyridamole-thallium imaging was reported in 45 of 510 (9%) consecutive patients referred for dipyridamole-thallium imaging. Clinical and hemodynamic effects observed during dipyridamole infusion were not predictive of transient cavitary dilation on the thallium images. Coronary angiography was performed in 32 of the 45 patients: 75% had either left main, 3-vessel or "high-risk" 2-vessel coronary artery disease. Although 25 of 45 patients (56%) with transient cavitary dilation were either asymptomatic or had only grade 1/4 effort angina, 16 of 25 patients (64%) not referred for coronary revascularization sustained a cardiac event during a mean follow-up of 12 months. Most events were cardiac deaths (75%) and 87% of events occurred within 4 months of the test. Noncardiac surgery was performed in 187 of the 510 patients. The postoperative cardiac event rate was 2% in the 101 patients with normal scans or fixed defects, 19% in 75 patients with reversible perfusion defects and 58% in 12 patients with reversible cavitary dilation (p less than 0.0001). Thus, transient LV dilation during dipyridamole-thallium imaging is a marker of severe underlying coronary artery disease, denotes a poor prognosis and predicts a high risk of postoperative cardiac complications in patients who undergo noncardiac surgery.

Androgens down-regulate bcl-2 protooncogene expression in ZR-75-1 human breast cancer cells

Although a large proportion of primary human breast cancers express the androgen receptor, and treatment with androgens exerts beneficial effects in women with breast cancer, the role and especially the mechanism of action of androgens in breast cancer development and growth are not well understood. The potential effect of androgens on bcl-2 protooncogene expression was investigated in a human breast cancer cell line whose proliferation is known to be inhibited by androgens. The estrogen-responsive ZR-75-1 cells were grown in the presence or absence of 5alpha-dihydrotestosterone (DHT), alone or in combination with 17beta-estradiol. DHT caused a marked down-regulation of Bcl-2 protein and messenger RNA levels in both the presence and absence of 17beta-estradiol. The inhibitory effect of DHT was completely prevented by coincubation with the pure antiandrogen hydroxyflutamide. The present data indicate that androgens can down-regulate bcl-2 protooncogene levels via an androgen receptor-mediated mechanism, thus providing a novel mechanism for their known inhibitory effect on breast cancer cell growth.

Major identity determinants in the "augmented D helix" of tRNA(Glu) from Escherichia coli

By a kinetic analysis of 59 variant transcripts of Escherichia coli tRNA(Glu) with glutamyl-tRNA synthetase (GluRS), the U11.A24 base-pair, the U13.G22..A46 base-triple, and the lack of residue 47 (delta47) were found to serve as major determinants for tRNA(Glu) identity. This is the first system for which major identity determinants are reported to be clustered in the "augmented D helix", consisting of the D stem with some neighboring residues and the variable loop. Other identity determinants are U34, U35, C36 and A37 in the anticodon loop, and G1.C72 and U2.A71 in the acceptor stem. Phosphate-group protection by GluRS from ethylnitrosourea was observed most strongly for the minor groove side of D-stem helix, indicating that GluRs tightly binds to the D stem for recognition, on the minor groove side, of the potent identity-determinant groups of the U11.A24 and U13.G22 base-pairs. A46 is not involved in direct recognition by GluRS; the U13.G22..A46 base-triple is required probably for formation of the structural features that are recognized by GluRS. In this context, the essential role of characteristic delta47 in tRNA(Glu) identity may be to maintain the U13.G22..A46 base-triple.

Widespread use of the glu-tRNAGln transamidation pathway among bacteria. A member of the alpha purple bacteria lacks glutaminyl-trna synthetase

The expression of the Rhizobium meliloti glutamyl-tRNA synthetase gene in Escherichia coli under the control of a trc promoter results in a toxic effect upon isopropyl-beta-D-thiogalactopyranoside induction, which is probably caused by a misacylation activity. To further investigate this unexpected result, we looked at the pathway of Gln-tRNAGln formation in R. meliloti. No glutaminyl-tRNA synthetase activity has been found in R. meliloti crude extract, but we detected a specific aminotransferase activity that changes Glu-tRNAGln to Gln-tRNAGln. Our results show that R. meliloti, a member of the alpha-subdivision of the purple bacteria, is the first Gram-negative bacteria reported to use a transamidation pathway for Gln-tRNAGln synthesis. A phylogenetic analysis of the contemporary glutamyl-tRNA synthetase and glutaminyl-tRNA synthetase amino acid sequences reveals that a close evolutionary relationship exists between R. meliloti and yeast mitochondrial glutamyl-tRNA synthetases, which is consistent with an origin of mitochondria in the alpha-subdivision of Gram-negative purple bacteria. A 256-amino acid open reading frame closely related to bacterial glutamyl-tRNA synthetases, which probably originates from a glutamyl-tRNA synthetase gene duplication, was found in the 4-min region of the E. coli chromosome. We suggest that this open reading frame is a relic of an ancient transamidation pathway that occurred in an E. coli ancestor before the horizontal transfer of a eukaryotic glutaminyl-tRNA synthetase (Lamour, V., Quevillon, S., Diriong, S., N'Guyen, V. C., Lipinski, M., and Mirande, M.(1994) Proc. Natl. Acad. Sci. U. S. A. 91, 8670-8674) and that it favored its stable acquisition. From these observations, a revisited model for the evolution of the contemporary glutamyl-tRNA synthetases and glutaminyl-tRNA synthetases that differs from the generally accepted model for the evolution of aminoacyl-tRNA synthetases is proposed.

The submitochondrial distribution of ubiquinone affects respiration in long-lived Mclk1+/- mice

MCLK1 and COQ3 are mitochondrial enzymes necessary for ubiquinone biosynthesis, but only MCLK1 also regulates the partitioning of ubiquinone between mitochondrial membranes and affects longevity in mice.

Mclk1 (also known as Coq7) and Coq3 code for mitochondrial enzymes implicated in the biosynthetic pathway of ubiquinone (coenzyme Q or UQ). Mclk1^+/− mice are long-lived but have dysfunctional mitochondria. This phenotype remains unexplained, as no changes in UQ content were observed in these mutants. By producing highly purified submitochondrial fractions, we report here that Mclk1^+/− mice present a unique mitochondrial UQ profile that was characterized by decreased UQ levels in the inner membrane coupled with increased UQ in the outer membrane. Dietary-supplemented UQ₁₀ was actively incorporated in both mitochondrial membranes, and this was sufficient to reverse mutant mitochondrial phenotypes. Further, although homozygous Coq3 mutants die as embryos like Mclk1 homozygous null mice, Coq3^+/− mice had a normal lifespan and were free of detectable defects in mitochondrial function or ubiquinone distribution. These findings indicate that MCLK1 regulates both UQ synthesis and distribution within mitochondrial membranes.

The potential effects of antioxidant feed additives in mitigating the adverse effects of corn naturally contaminated with Fusarium mycotoxins on antioxidant systems in the intestinal mucosa, plasma, and liver in weaned pigs

Seventy-two piglets (6.0 kg BW) were randomly distributed within six different dietary treatments to evaluate the effect of deoxynivalenol (DON) and the potential of four antioxidant feed additives in mitigating the adverse effects of DON on growth performances and oxidative status. Dietary treatments were as follows: control diet 0.8 mg/kg DON; contaminated diet (DON-contaminated diet) 3.1 mg/kg DON; and four contaminated diets, each supplemented with a different antioxidant feed additive, DON + vitamins, DON + organic selenium (Se)/glutathione (GSH), DON + quercetin, and DON + COMB (vitamins + Se/GSH + quercetin from the other treatments). Although DON was the main mycotoxin in the contaminated diet, this diet also contained 1.8 mg/kg of zearalenone (ZEN). The "mycotoxin" effects therefore included the combined effect of these two mycotoxins, DON, and ZEN. The DON-ZEN ingestion did not affect growth performances, average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (G:F ratio), but partially induced oxidative stress in weaned pigs as shown by increased malondialdehyde (MDA) content in the plasma and superoxide dismutase (SOD) activity in liver (P < 0.05). However, no change in the activity of other antioxidant enzymes or GSH concentrations was observed in plasma and liver of piglets fed the DON-contaminated diet (P > 0.05). Supplementation with individual antioxidant feed additive had a limited effect in weaned pigs fed DON-ZEN-contaminated diets. Combination of antioxidants (vitamins A, C, and E, quercetin, and organic Se/GSH) reduced plasma and liver MDA content and SOD activity in liver (P < 0.05) of piglets fed DON-ZEN-contaminated diets. Furthermore, this combination also reduced MDA content in the ileum (P < 0.05), although activity of glutathione peroxidases (GPx), SOD or catalase (CAT) in the ileum was not affected by DON-ZEN contamination or antioxidant supplements. In conclusion, DON-ZEN contamination induced oxidative stress in weaned pigs and combination of antioxidant feed additives restored partially the oxidative status. Further studies will be necessary to assess whether the effects of antioxidant feed additives on oxidative status are specific when feed is contaminated with DON-ZEN.