Marzena Wojcik

A review of natural and synthetic antioxidants important for health and longevity.

Reactive oxygen species (ROS) generated in the presence of O(2) by mitochondria, phagocytic cells, peroxisomes, and cytochrome P450 enzymes under physiological conditions, may play a dual function in the human organism. On the one hand, they participate in cell signal transduction cascades, leading to the activation of some transcription factors responsible for regulating of the expression of genes relevant for cell growth and differentiation. On the other hand, they cause oxidative damage of cellular DNA, protein and lipids, resulting in the initiation or development of numerous diseases such as cancer, cardiovascular diseases, type 2 diabetes mellitus, cataract, rheumatoid arthritis, or different neurodegenerative diseases. Both endogenous compounds (glutathione, ubiquinol, urate, bilirubin) and enzymes (superoxide dismutase, catalase, glutathione peroxidase) are engaged in the detoxification of ROS. In addition, numerous dietary components such as vitamin C, vitamin E, carotenoids, and polyphenols are thought to be involved in the antioxidant defense system. The present review article is focused on the summary and the assessment of research on the impact of dietary antioxidants in the prevention of chronic diseases, particularly cancer and cardiovascular diseases.

Nicotinamide Riboside Kinase Structures Reveal New Pathways to NAD(

The eukaryotic nicotinamide riboside kinase (Nrk) pathway, which is induced in response to nerve damage and promotes replicative life span in yeast, converts nicotinamide riboside to nicotinamide adenine dinucleotide (NAD+) by phosphorylation and adenylylation. Crystal structures of human Nrk1 bound to nucleoside and nucleotide substrates and products revealed an enzyme structurally similar to Rossmann fold metabolite kinases and allowed the identification of active site residues, which were shown to be essential for human Nrk1 and Nrk2 activity in vivo. Although the structures account for the 500-fold discrimination between nicotinamide riboside and pyrimidine nucleosides, no enzyme feature was identified to recognize the distinctive carboxamide group of nicotinamide riboside. Indeed, nicotinic acid riboside is a specific substrate of human Nrk enzymes and is utilized in yeast in a novel biosynthetic pathway that depends on Nrk and NAD+ synthetase. Additionally, nicotinic acid riboside is utilized in vivo by Urh1, Pnp1, and Preiss-Handler salvage. Thus, crystal structures of Nrk1 led to the identification of new pathways to NAD+.

Structure and physiological functions of the human peroxisome proliferator-activated receptor γ

The peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor superfamily. To date, three different PPAR isotypes, namely PPAR-α, -δ, and -γ, have been identified in vertebrates and have distinct patterns of tissue distribution. Like all nuclear receptors, the human PPAR-γ (hPPAR-γ) is characterized by a modular structure composed of an N-terminal A/B domain, a DNA-binding domain with two zinc fingers (C domain), a D domain, and a C-terminal ligand-binding domain (E/F domain). Human PPAR-γ exists in two protein isoforms, hPPAR-γ1 and -γ2, with different lengths of the N-terminal. The hPPAR-γ2 isoform is predominantly expressed in adipose tissue, whereas hPPAR-γ1 is relatively widely expressed. Human PPAR-γ plays a critical physiological role as a central transcriptional regulator of both adipogenic and lipogenic programs. Its transcriptional activity is induced by the binding of endogenous and synthetic lipophilic ligands, which has led to the determination of many roles for PPAR-γ in pathological states such as type 2 diabetes, atherosclerosis, inflammation, and cancer. Of the synthetic ligands, the thiazolidinedione class of insulin-sensitizing drugs (ciglitazone, pioglitazone, troglitazone, rosiglitazone) is employed clinically in patients with type 2 diabetes.

Synthetic Lethal and Biochemical Analyses of NAD and NADH Kinases in Saccharomyces cerevisiae Establish Separation of Cellular Functions

Production of NADP and NADPH depends on activity of NAD and NADH kinases. Here we characterized all combinations of mutants in yeast NAD and NADH kinases to determine their physiological roles. We constructed a diploid strain heterozygous for disruption of POS5, encoding mitochondrial NADH kinase, UTR1, cytosolic NAD kinase, and YEF1, a UTR1-homologous gene we characterized as encoding a low specific activity cytosolic NAD kinase. pos5 utr1 is a synthetic lethal combination rescued by plasmid-borne copies of the POS5 or UTR1 genes or by YEF1 driven by the ADH1 promoter. Respiratory-deficient and oxidative damage-sensitive defects in pos5 mutants were not made more deleterious by yef1 deletion, and a quantitative growth phenotype of pos5 and its arginine auxotrophy were repaired by plasmid-borne POS5 but not UTR1 or ADH1-driven YEF1. utr1 haploids have a slow growth phenotype on glucose not exacerbated by yef1 deletion but reversed by either plasmid-borne UTR1 or ADH1-driven YEF1. The defect in fermentative growth of utr1 mutants renders POS5 but not POS5-dependent mitochondrial genome maintenance essential because rho–utr1 derivatives are viable. Purified Yef1 has similar nucleoside triphosphate specificity but substantially lower specific activity and less discrimination in favor of NAD versus NADH phosphorylation than Utr1. Low expression and low intrinsic NAD kinase activity of Yef1 and the lack of phenotype associated with yef1 suggest that Utr1 and Pos5 are responsible for essentially all NAD/NADH kinase activity in vivo. The data are compatible with a model in which there is no exchange of NADP, NADPH, or cytoplasmic NAD/NADH kinase between nucleocytoplasmic and mitochondrial compartments, but the cytoplasm is exposed to mitochondrial NAD/NADH kinase during the transit of the molecule.

Mapping of the functional phosphate groups in the catalytic core of deoxyribozyme 10-23

The RNA phosphodiester bond cleavage activity of a series of 16 thio‐deoxyribozymes 10–23, containing a P‐stereorandom single phosphorothioate linkage in predetermined positions of the catalytic core from P1 to P16, was evaluated under single‐turnover conditions in the presence of either 3 mm Mg2+ or 3 mm Mn2+. A metal‐specificity switch approach permitted the identification of nonbridging phosphate oxygens (proRP or proSP) located at seven positions of the core (P2, P4 and P9–13) involved in direct coordination with a divalent metal ion(s). By contrast, phosphorothioates at positions P3, P6, P7 and P14–16 displayed no functional relevance in the deoxyribozyme‐mediated catalysis. Interestingly, phosphorothioate modifications at positions P1 or P8 enhanced the catalytic efficiency of the enzyme. Among the tested deoxyribozymes, thio‐substitution at position P5 had the largest deleterious effect on the catalytic rate in the presence of Mg2+, and this was reversed in the presence of Mn2+. Further experiments with thio‐deoxyribozymes of stereodefined P‐chirality suggested direct involvement of both oxygens of the P5 phosphate and the proRP oxygen at P9 in the metal ion coordination. In addition, it was found that the oxygen atom at C6 of G6 contributes to metal ion binding and that this interaction is essential for 10–23 deoxyribozyme catalytic activity.

Glutamine-dependent NAD+ Synthetase HOW A TWO-DOMAIN, THREE-SUBSTRATE ENZYME AVOIDS WASTE

Glutamine-dependent NAD+ synthetase, Qns1, utilizes a glutamine aminotransferase domain to supply ammonia for amidation of nicotinic acid adenine dinucleotide (NaAD+) to NAD+. Earlier characterization of Qns1 suggested that glutamine consumption exceeds NAD+ production by 40%. To explore whether Qns1 is systematically wasteful or whether additional features account for this behavior, we performed a careful kinetic and molecular genetic analysis. In fact, Qns1 possesses remarkable properties to reduce waste. The glutaminase active site is stimulated by NaAD+ more than 50-fold such that glutamine is not appreciably consumed in the absence of NaAD+. Glutamine consumption exceeds NAD+ production over the whole range of glutamine and NaAD+ substrate concentrations with greatest efficiency occurring at saturation of both substrates. Kinetic data coupled with site-directed mutagenesis of amino acids in the predicted ammonia channel indicate that NaAD+ stimulates the glutaminase active site in the kcat term by a synergistic mechanism that does not require ammonia utilization by the NaAD+ substrate. Six distinct classes of Qns1 mutants that fall within the glutaminase domain and the synthetase domain selectively inhibit components of the coordinated reaction.

Physiological and Pathophysiological Functions of SIRT1

The human SIRT1 is a nuclear enzyme from the class III histone deacetylases (HDACs) which is widely distributed in mammalian tissues. A variety of SIRT1 substrates hints that this protein is involved in the regulation of diverse biological processes, including cell survival, apoptosis, gluconeogenesis, adipogenesis, lipolysis, stress resistance, muscle differentiation, and insulin secretion. This review emphasizes catalytic properties of SIRT1 and its role in apoptosis, insulin pathway, and neuron survival.

The relationship between adipose tissue-derived hormones and gestational diabetes mellitus (GDM)

Gestational diabetes mellitus (GDM) is defined as a glucose intolerance of varying severity with onset or first recognition during pregnancy. The prevalence of GDM is growing rapidly worldwide, resulting in numerous and serious complications for both mother and foetus. Two major metabolic disorders, insulin resistance and β cells dysfunction, are currently linked to the pathogenesis of GDM, although the cellular mechanisms involved in the development of GDM are not yet completely understood. Increasing evidence from clinical and experimental studies indicates that adipose tissue dysfunction, characterised by abnormal production of adipokines, is an essential factor linked to insulin resistance and GDM. To date, several adipose tissue-derived hormones have been identified, including leptin, adiponectin, resistin, visfatin, apelin, retinol-binding protein 4 (RBP-4), vaspin, and omentin. The relationship of leptin and adiponectin to insulin resistance in GDM is relatively well documented, but the molecular mechanisms by which these hormones affect insulin resistance are not yet fully known. The other aforementioned adipokines appear to be also important players in the pathophysiology of GDM, although their precise function in this complex process remains to be established. The aim of this article is to review the literature concerning the relationship between the above-mentioned adipokines and GDM, and to clarify their role in the pathophysiology of GDM.

GROWTH AND NUTRITION OF M.26 EMLA APPLE ROOTSTOCK AS INFLUENCED BY TITANIUM FERTILIZATION

The objective of this study was to examine the effect of different mode of titanium (Ti) fertilization on growth and nutrition by M.26 EMLA apple rootstock (Malus spp.) grown in three soils with diverse physical and chemical properties. Soils were taken from Warszawa, Grojec and Brzezna regions (fruit growing regions) of Poland. The experiment was carried out during 120 days in a greenhouse. The following treatments were applied: soil Ti fertilization at a rate of 2 and 4 mg Ti per plant and four- and eight-times Ti sprays at a rate of 0.5 mg Ti per plant in each spray. Titanium was applied as TiCl4. Plants unfertilized with Ti served as control. Titanium sprays increased levels of this element in leaf and stem tissues. Soil Ti applications had no effect on Ti concentrations in plant tissues except plants grown in Warszawa soil where root tissue had higher Ti status compared to those of control plants. Foliar Ti applications enhanced plant dry matter and levels of phosphorus (P), iron (Fe), manganese (Mn), and zinc (Zn) in leaf tissues only in Brzezna soil. Leaves of plants sprayed with Ti grown in Brzezna soil were greener and had higher concentrations of Fe2+ and chlorophyll than those of control plants. These results suggest that the primary reason for higher biomass in plants sprayed with Ti was higher leaf Fe2+ level, which enhanced chlorophyll synthesis and uptake of P, Fe, Mn, and Zn.

The elevated gene expression level of the A2B adenosine receptor is associated with hyperglycemia in women with gestational diabetes mellitus

Adenosine receptors denoted by A1, A2A, A2B, and A3 and encoded by ADORA1, ADORA2A, ADORA2B, and ADORA3 genes, respectively, are adenosine‐activated G‐protein‐coupled receptors that play an important role in obesity and type 2 diabetes mellitus. However, little is known about their significance in gestational diabetes mellitus (GDM). The purpose of this study was to investigate whether there are changes in leukocyte AR expression in GDM patients and whether these alterations are linked to well‐known diabetic genes.