N-3 fatty acids in glucose metabolism and insulin sensitivity.

Polyunsaturated fatty acids (PUFA) of the n-3 series are essential for normal growth and development. The health effects of these fatty acids include reduction of cardiovascular risk due to antiarrhythmic, antiinflammatory, anti-thrombotic and lipid lowering actions. An increase in unsaturation of the muscle membrane fatty acids is associated with improved insulin sensitivity. Higher proportion of n-3 fatty acids may have beneficial roles, such as antiobesity effects and protection against the metabolic syndrome and type 2 diabetes mellitus through a number of metabolic effects. However, controversy exists on the different effects of n-6 and n-3 polyunsaturated fatty acids as well as on the interacting effect of dietary saturated and monounsaturated fat. In addition, some adverse effects have been described concerning the use of fish oil supplements containing high doses of n-3 fatty acids. Several studies show Eskimos diabetes risk, while results of nutritional interventions on the influence of consuming diets rich in oily fish or other food rich in n-3 fatty acids is very limited. This article reviews the possible mechanisms through which n-3 PUFA are involved in glucose level control and insulin sensitivity. Intervention and epidemiological studies together with recent findings on the nutrigenomic field related with this subject are also briefly reviewed.

N-3 fatty acids in glucose metabolism and insulin sensitivity / Ácidos grasos n-3 en el metabolismo de la glucosa y la sensibilidad a la insulina

Polyunsaturated fatty acids (PUFA) of the n-3 series are essential for normal growth and development. The health effects of these fatty acids include reduction of cardiovascular risk due to antiarrhythmic, antiinflammatory, anti-thrombotic and lipid lowering actions. An increase in unsaturation of the muscle membrane fatty acids is associated with improved insulin sensitivity. Higher proportion of n-3 fatty acids may have beneficial roles, such as antiobesity effects and protection against the metabolic syndrome and type 2 diabetes mellitus through a number of metabolic effects. However, controversy exists on the different effects of n-6 and n-3 polyunsaturated fatty acids as well as on the interacting effect of dietary saturated and monounsaturated fat. In addition, some adverse effects have been described concerning the use of fish oil supplements containing high doses of n-3fatty acids. Several studies show Eskimos diabetes risk, while results of nutritional interventions on the influence of consuming diets rich in oily fish or other food rich in n-3 fatty acids is very limited. This article reviews the possible mechanisms through which n-3 PUFA are involved inglucose level control and insulin sensitivity. Intervention and epidemiological studies together with recent findings on the nutrigenomics field related with this subject are also briefly reviewed (AU)

Los ácidos grasos poliinsaturados (AGP) de la serie n-3son esenciales para el crecimiento normal y el desarrollo. Los efectos de estos ácidos grasos en la salud incluyen reducción del riesgo cardiovascular debido a acciones antiarrítmicas, antiinflamatorias, antitrombóticas ehipolipemiantes. Un aumento en la insaturación de los ácidos grasos de la membrana muscular se asocia con mejora en la sensibilidad a la insulina. Una mayor proporción de ácidos grasos n-3 puede desempeñar papeles beneficios, tales como efectos antiobesidad y protección frente al síndrome metabólico y la diabetes mellitus tipo2. Sin embargo, existe controversia sobre los diferentes efectos de los ácidos grasos n-6 y n-3, así como con la interacción entre la grasa saturada y monoinsaturada. Además, se han descrito algunos efectos adversos en relación al uso de suplementos de aceite de pescado con altas dosis de ácidos grasos n-3. Algunos estudios muestran el riesgo de diabetes en esquimales, mientras que los resultados de intervenciones nutricionales sobre la influencia del consumo de pescado graso u otros alimentos ricos en ácidos grasos n-3 son muy limitados. Este artículo revisa los posibles mecanismos a través de los cuales los AGP n-3intervienen en el control de la glucosa y la sensibilidad a la insulina. Se revisan los estudios epidemiológicos y de intervención junto con los hallazgos más recientes en el campo de la nutrigenómica relacionados con la sensibilidad y resistencia a la insulina (AU)

Overexpression, purification, and characterization of glutaminase-interacting protein, a PDZ-domain protein from human brain.

A human brain cDNA clone coding for a novel PDZ-domain protein of 124 amino acids has been previously isolated in our laboratory. The protein was termed GIP (glutaminase-interacting protein) because it interacts with the C-terminal region of the human brain glutaminase L. Here we report the heterologous expression of GIP as a histidine-tagged fusion protein in Escherichia coli cells. The induction conditions (temperature and isopropyl beta-d-thiogalactopyranoside concentrations) were optimized in such a way that GIP accounted for about 20% of the total E. coli protein. A simple and rapid procedure for purification was developed, which yielded 17 mg of purified GIP per liter of bacterial cell culture. The apparent molecular mass of the protein by SDS-PAGE was 16 kDa, whereas in native form it was determined to be 28 kDa, which suggests dimer formation. The nature and integrity of the recombinant protein were verified by mass spectrometry analysis. The functionality of the GIP protein was tested with an in vitro activity assay: after being pulled down with glutathione S-transferase-glutaminase, GIP was revealed by Western blot using anti-GIP antibodies. Furthermore, the glutaminase activity in crude rat liver extracts was inhibited by the presence of recombinant purified GIP protein.

The C-terminus of human glutaminase L mediates association with PDZ domain-containing proteins.

The enzyme glutaminase in brain is responsible for the synthesis of neurotransmitter glutamate. We used the two-hybrid genetic selection system in yeast to look for interactors of glutaminase in human brain. We have identified two proteins containing PDZ domains, alpha1-syntrophin and a glutaminase-interacting protein, named GIP, that showed association with human glutaminase L, as deduced from specificity test of the two-hybrid system. The complete GIP cDNA clone has 1315 nucleotides with a 372-base open reading frame encoding a 124-amino acids protein. Glutaminase associates with both PDZ proteins through its C-terminal end; mutagenesis of single amino acids revealed the sequence -ESXV as essential for the interaction. These data suggest the possibility that PDZ domain-containing proteins are involved in the regulation of glutaminase in brain.

Identification of two human glutaminase loci and tissue-specific expression of the two related genes.

Glutaminolysis is initiated by either of two isoforms, K- and L-types, of the enzyme phosphate-activated glutaminase. The chromosomal localization, genomic organization, and the tissue-specific expression of the genes have been investigated in the human by using isoform-specific cDNA probes. Results obtained from radiation hybrid mapping experiments assigned the K-glutaminase gene to human Chromosome (Chr) 2, and a second locus for L-glutaminase in Chr 12 was identified. Southern blot analysis with the L-cDNA probe showed hybridization to a single restriction fragment, while four to seven fragments were found to hybridize to the K-cDNA probe. The distribution of human glutaminase expression was also investigated: the L-cDNA probe detected a single band of 2.4 kb in liver, brain, and pancreas, whereas a single transcript of approximately 4.4 kb was detected in kidney, brain, heart, placenta, lung, and pancreas by using the K-cDNA probe. This work provides evidence that the human liver and kidney glutaminase isozymes are encoded by separate genes located on different chromosomes; furthermore, the expression pattern in human tissues revealed for both isoenzymes differs notably from the paradigm based upon the isoenzyme distribution in rats.

Allergy to drugs: antioxidant enzymic activities, lipid peroxidation and protein oxidative damage in human blood.

Reactive oxygen species lead to lipid peroxidation and specific oxidation of some specific enzymes, proteins and other macromolecules, thus affecting many intra- and intercellular systems. Recently, antioxidant functions have been linked to anti-inflammatory properties. Cell defences against toxic oxygen include antioxidant enzymes. We studied the enzymic antioxidant capacity in human blood of both erythrocytes and mononuclear cells from patients suffering from an allergic reaction to different drugs. We determined superoxide dismutases (SODs), glutathione peroxidase (GSHPx) and catalase (CAT) activities in each cell type. We also determined the extent of thiobarbituric acid reactive substances (TBARS) and the oxidative damage to proteins, in order to study the correlation between the cellular enzymic activities, the oxidative status and the allergic reaction. In mononuclear cells from allergic patients, SODs and CAT activities were enhanced compared with controls. Conversely, a decrease in GSHPx activity was found. In erythrocytes, higher values for CAT, GSHPx and SODs activities were found in allergic patients. TBARS were also enhanced in both types of cells, and the carbonyl content of serum was equally increased. The respective enzymic imbalances in mononuclear cells and erythrocytes, namely, GSHPx/SOD and CAT/SOD, and their consequences are discussed. To our knowledge, this is the first global study of antioxidant enzyme determinations, including TBARS level and carbonyl content, in patients suffering from allergies to drugs.

Antioxidant enzymatic activities in human blood cells after an allergic reaction to pollen or house dust mite.

Several diseases have been related to oxidative stress. Recently, antioxidant functions have also been linked to anti-inflammatory properties. Cell defenses against reactive oxygen species include antioxidant enzymes. We studied the enzymatic antioxidant capacity in human blood of both red blood and mononuclear cells from patients suffering from an allergic reaction to pollen or house dust mite. We determined superoxide dismutases (SODs), glutathione peroxidase (GSHPx) and catalase (CAT) activities in each cell type. We also determined the extent of thiobarbituric acid reactive substances (TBARS), in order to study the correlation between the cellular enzymatic activities, the redox status and the disease. In mononuclear cells from allergic patients, SODs and CAT activities were enhanced compared to controls. Conversely, a decrease in GSHPx activity was found. In erythrocytes, higher values for GSHPx and SODs and similar CAT activities were found in allergic patients and controls. Interestingly, CuZnSOD and MnSOD activities were enhanced in the same proportion for both, erythrocytes and mononuclear cells. TBARS were also enhanced in both types of cells. The respective enzymatic imbalances in mononuclear cells and erythrocytes, namely, GSHPx/SOD and CAT/SOD, and their consequences are discussed. To our knowledge, this is the first global study of antioxidant enzymes, including TBARS level determinations, in allergy.

First Report of Powdery Mildew of Tomato Caused by an Erysiphe sp. in Spain.

A new powdery mildew disease of tomato (Lycopersicum esculentum Mill.) was observed for the first time in several greenhouses in Almería (Spain) in March through June 1997. Fungal growth appeared as typical, white, powdery mildew colonies that were restricted to upper leaf surfaces. Initially, individual colonies were small and nearly circular in shape but later enlarged and coalesced to cover the whole leaf surface. Conidia were produced singly on unbranched, 3-cell conidiophores, and were cylindrical to ovate, ranging in size from 27.6 to 43.5 µm (mean = 35.3, SD = 3.8) in length and from 14.1 to 23.2 µm (mean = 19.0, SD = 2.2, n = 95) in width. No fibrosin bodies were observed. Germ tubes were formed from the ends of conidia. Appressoria from mycelia were single and moderately lobed. Conidiophores measured from 56.6 to 108.8 µm (mean = 84.8, SD = 14.2) with straight foot cells 24.7 to 55.1 µm (mean = 38.6, SD = 7.5) in length, and from 7.3 to 10.2 µm (mean = 8.0, SD = 1) in width. Morphological characteristics of this powdery mildew are similar to those previously given for the Erysiphe sp. described in the United Kingdom (1) and Greece (2). Cleistothecia were not found, so species identification was not made. Conidia from infected tomato leaves were shaken onto leaves of melon (Cucumis melo L. 'Rochet'), cucumber (Cucumis sativus L. 'Bellpuig'), summer squash (Cucurbita pepo L. 'Black Beauty'), watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai 'Sugar Baby') and tomato cvs. Roma, Daniela, and Marmande. After 7 days the disease was observed on summer squashes, melons, and all tomato cultivars, but not on watermelons or cucumbers. References: (1) J. T. Fletcher et al. Plant Pathol. 37:594, 1988. (2) D. J. Vakalounakis and A. Papadakis. Plant Pathol. 41:372, 1992.

Bacterial Apical Necrosis of Mango in Southern Spain: A Disease Caused by Pseudomonas syringae pv. syringae.

ABSTRACT A necrotic bacterial disease of mango trees (Mangifera indica) in Spain affecting buds, leaves, and stems is described for the first time. Necrosis of flower and vegetative buds on commercial trees during winter dormancy was the most destructive symptom of the disease. The apical necrosis is caused by Pseudomonas syringae, which was always isolated from mango trees with disease symptoms. Of 95 bacterial strains isolated from symptomatic tissues and characterized from 1992 to 1997, over 90% were identified as P. syringae pv. syringae. Additional strains were isolated from healthy mango trees, and they were identical to the isolates from diseased tissues. Pathogenicity tests on mango plants showed that P. syringae pv. syringae incited the apical necrosis, but that climatic conditions determined the onset of disease development. Populations of total bacteria and of P. syringae and the number of active ice nuclei were monitored over a 3-year period. The largest populations of P. syringae were associated with cool, wet periods that coincided with the highest disease severity, whereas P. syringae was only occasionally detected on healthy trees. The median effective dose was estimated from infectivity titration assays.