Systemic biochemical changes in pepper (Capsicum annuum L.) against Rhizoctonia solani by kale (Brassica oleracea var. acephala L.) green manure application

BACKGROUND

In the search for new alternatives to avoid the problems associated with the use of synthetic chemical fungicides in agriculture, the use of green manure (GrM) could help combat fungal diseases of crops, such as those produced by the necrotrophic pathogen Rhizoctonia solani. In the case of the use of Brassica tissues as GrM, it could have an elicitor capacity for systemic plant resistance.

RESULTS

We used kale leaves as a GrM and applied it to pepper plants infected with R. solani. The application of freeze-dried kale tissues to the roots of pepper plants produced a systemic activation of foliar defences via the salicylic acid (SA) and ethylene (ET) pathways, significantly reducing pathogen damage. In addition, this systemic response led to the accumulation of secondary defence metabolites, such as pipecolic acid, hydroxycoumarin and gluconic acid, in leaves. Remarkably, pepper plants treated with lyophilised kale GrM accumulated glucosinolates when infected with R. solani. We also confirmed that autoclaving removed part of the glucobrassicin (85%) and sinigrin (19%) content of the kale tissues.

CONCLUSIONS

GrM kale tissues can activate systemic defences in bell pepper against foliar pathogens through SA/ET hormonal pathways, accumulating secondary defence metabolites.

Daytime of leaf wounding determines plant biomass and affect the interplay between growth and defense in Brassica crops

Recent discoveries pointed out the importance of the mutual correlation between timing of environmental stress and plant fitness. However, the internal reshaping of plant growth under daily stress sensing, and their metabolic coordination remain to be investigated. Thus, we aim to study the connection between daytime, growth and defense to understand how plant fitness is affected by diurnal stress inputs. To accomplish that, we examined if simulated herbivory (leaf wounding) in the morning, mid-day or evening differentially influenced plant defensive states vs growth in three different crop species of the Brassica genus, broccoli (Brassica oleraceae), turnip greens (B. rapa) and rapeseed (B. napus). The data presented here revealed that plant's ability to tolerate wounding stress is diurnally regulated in Brassica crops. Trade-offs between plant biomass and investment in glucosinolates (GSL) and phenolics were affected by daytime of leaf stress. Negative correlations between plant biomass and induction of defensive compounds were found for morning and evening treated plants. However, these correlations were positives for mid-day treatment. Interestingly, we revealed new connection between plant growth and changes of aliphatic GSLs and flavonoids in response to wounding. These data suggest that metabolic stress-dependent circadian oscillations of leaves defenses could be one mechanism conferring competitive advantage to plants able to anticipate daily environmental variations by synchronize growth with them. Moreover, this work provides first insights of how secondary metabolites are linked to growth response in a timely manner.

First study on the root endophytic fungus Trichoderma hamatum as an entomopathogen: Development of a fungal bioinsecticide against cotton leafworm (Spodoptera littoralis)

Cotton leaf worm (Spodoptera littoralis) is a pest that produces important losses in horticultural and ornamental crops in greenhouse, being classified as quarantine pest A2 by EPPO. One of the strategies proposed to control agricultural pests in a health and environmentally friendly way is biological control with entomopathogenic fungi. The genus of filamentous fungi Trichoderma includes different species with direct (infection, antibiosis, anti-feeding, etc.) and indirect (systemic activation of plant defenses) insecticidal capacity, however, the species T. hamatum has never been described previously as entomopathogenic. In this work, the entomopathogenic capacity of T. hamatum on S. littoralis L₃ larvae was analyzed by applying spores and fungal filtrates (topically and orally). Infection by spores was compared with the commercial entomopathogenic fungus Beauveria bassiana, obtaining similar results with respect to the production of larval mortality. Oral application of spores reported high mortality and fungal colonization of larvae, however, T. hamatum did not show chitinase activity when grown in the presence of S. littoralis tissues. Therefore, infection of S. littoralis larvae by T. hamatum is through natural openings such as mouth, anus or spiracles. With respect to the application of filtrates, only those obtained from the liquid culture of T. hamatum in contact with S. littoralis tissues reported a significant reduction in larval growth. Metabolomic analysis of the filtrates determined that the filtrate with insecticidal capacity presented the siderophore rhizoferrin in large quantities, which could be responsible for this activity. However, the production of this siderophore had never been previously described in Trichoderma and its insecticidal capacity was unknown. In conclusion, T. hamatum presents entomopathogenic capacity against S. littoralis larvae through the application of spores and filtrates, and both ways could be the basis for the development of efficient bioinsecticides against the pest.

Trichoderma hamatum can act as an inter-plant communicator of foliar pathogen infections by colonizing the roots of nearby plants: A new inter-plant "wired communication"

Trichoderma is a genus of filamentous fungi widely studied and used as a biological control agent in agriculture. However, its ability to form fungal networks for inter-plant communication by means of the so-called inter-plant "wired communication" has not yet been addressed. In our study we used the model plant Arabidopsis thaliana, the fungus Trichoderma hamatum (isolated from Brassicaceae plants) and the pathogens Sclerotinia sclerotiorum and Xanthomonas campestris (necrotrophic fungus and hemibiotrophic bacteria, respectively). We performed different combinations of isolated/neighboring plants and root colonization/non-colonization by T. hamatum, as well as foliar infections with the pathogens. In this way, we were able to determine how, in the absence of T. hamatum, there is an inter-plant communication that induces systemic resistance in neighboring plants of plants infected by the pathogens. On the other hand, the plants colonized by T. hamatum roots show a greater systemic resistance against the pathogens. Regarding the role of T. hamatum as an inter-plant communicator, it is the result of an increase in foliar signaling by jasmonic acid (increased expression of LOX1 and VSP2 genes and decreased expression of ICS1 and PR-1 genes), antagonistically increasing root signaling by salicylic acid (increased expression of ICS1 and PR-1 genes and decreased expression of LOX1 and VSP2). This situation prevents root colonization by T. hamatum of the foliarly infected plant and leads to massive colonization of the neighboring plant, where jasmonic acid-mediated systemic defenses are induced.

Endophytic fungi from kale (Brassica oleracea var. acephala) modify roots-glucosinolate profile and promote plant growth in cultivated Brassica species. First description of Pyrenophora gallaeciana

Endophytic fungi of crops can promote plant growth through various mechanisms of action (i.e., improve nutrient uptake and nutrient use efficiency, and produce and modulate plant hormones). The genus Brassica includes important horticultural crops, which have been little studied in their interaction with endophytic fungi. Previously, four endophytic fungi were isolated from kale roots (Brassica oleracea var. acephala), with different benefits for their host, including plant growth promotion, cold tolerance, and induction of resistance to pathogens (Xanthomonas campestris) and pests (Mamestra brassicae). In the present work, the molecular and morphological identification of the four different isolates were carried out, describing them as the species Acrocalymma vagum, Setophoma terrestris, Fusarium oxysporum, and the new species Pyrenophora gallaeciana. In addition, using a representative crop of each Brassica U’s triangle species and various in vitro biochemical tests, the ability of these fungi to promote plant growth was described. In this sense, the four fungi used promoted the growth of B. rapa, B. napus, B. nigra, B. juncea, and B. carinata, possibly due to the production of auxins, siderophores, P solubilization or cellulase, xylanase or amylase activity. Finally, the differences in root colonization between the four endophytic fungi and two pathogens (Leptosphaeria maculans and Sclerotinia sclerotiorum) and the root glucosinolate profile were studied, at different times. In this way, how the presence of progoitrin in the roots reduces their colonization by endophytic and pathogenic fungi was determined, while the possible hydrolysis of sinigrin to fungicidal products controls the colonization of endophytic fungi, but not of pathogens.

Agronomic and Metabolomic Side-Effects of a Divergent Selection for Indol-3-Ylmethylglucosinolate Content in Kale (Brassica oleracea var. acephala)

Brassica oleracea var. acephala (kale) is a cruciferous vegetable widely cultivated for its leaves and flower buds in Europe and a food of global interest as a “superfood”. Brassica crops accumulate phytochemicals called glucosinolates (GSLs) which play an important role in plant defense against biotic stresses. Studies carried out to date suggest that GSLs may have a role in the adaptation of plants to different environments, but direct evidence is lacking. We grew two kale populations divergently selected for high and low indol-3-ylmethylGSL (IM) content (H-IM and L-IM, respectively) in different environments and analyzed agronomic parameters, GSL profiles and metabolomic profile. We found a significant increase in fresh and dry foliar weight in H-IM kale populations compared to L-IM in addition to a greater accumulation of total GSLs, indole GSLs and, specifically, IM and 1-methoxyindol-3-ylmethylGSL (1MeOIM). Metabolomic analysis revealed a significant different concentration of 44 metabolites in H-IM kale populations compared to L-IM. According to tentative peak identification from MS interpretation, 80% were phenolics, including flavonoids (kaempferol, quercetin and anthocyanin derivates, including acyl flavonoids), chlorogenic acids (esters of hydroxycinnamic acids and quinic acid), hydroxycinnamic acids (ferulic acid and p-coumaric acid) and coumarins. H-IM kale populations could be more tolerant to diverse environmental conditions, possibly due to GSLs and the associated metabolites with predicted antioxidant potential.

Fine mapping identifies NAD-ME1 as a candidate underlying a major locus controlling temporal variation in primary and specialized metabolism in Arabidopsis

Plant metabolism is modulated by a complex interplay between internal signals and external cues. A major goal of all quantitative metabolomic studies is to clone the underlying genes to understand the mechanistic basis of this variation. Using fine-scale genetic mapping, in this work we report the identification and initial characterization of NAD-DEPENDENT MALIC ENZYME 1 (NAD-ME1) as the candidate gene underlying the pleiotropic network Met.II.15 quantitative trait locus controlling variation in plant metabolism and circadian clock outputs in the Bay × Sha Arabidopsis population. Transcript abundance and promoter analysis in NAD-ME1^Bay-0 and NAD-ME1^Sha alleles confirmed allele-specific expression that appears to be due a polymorphism disrupting a putative circadian cis-element binding site. Analysis of transfer DNA insertion lines and heterogeneous inbred families showed that transcript variation of the NAD-ME1 gene led to temporal shifts of tricarboxylic acid cycle intermediates, glucosinolate (GSL) accumulation, and altered regulation of several GSL biosynthesis pathway genes. Untargeted metabolomic analyses revealed complex regulatory networks of NAD-ME1 dependent upon the daytime. The mutant led to shifts in plant primary metabolites, cell wall components, isoprenoids, fatty acids, and plant immunity phytochemicals, among others. Our findings suggest that NAD-ME1 may act as a key gene to coordinate plant primary and secondary metabolism in a time-dependent manner.

Brain alterations in GABA, glutamate and glutamine markers after chronic atrazine exposure in the male albino rat

Atrazine (ATR; 2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is an herbicide widely used to kill annual grasses and broadleaf weeds in crops such as corn, sorghum, and sugarcane. Studies in rodents have shown that chronic ATR exposure is associated with alterations in the nigrostriatal dopaminergic pathway such as hyperactivity, decreased striatal dopamine levels, and diminished numbers of tyrosine hydroxylase positive cells in substantia nigra pars compacta. However, the effects of ATR on neurotransmitters such as GABA and glutamate have been scarcely studied. To evaluate the impact of ATR on motor and anxiety tasks, tissue levels of GABA, glutamate, glutamine, and extracellular and potassium-evoked release of glutamate in the striatum, we daily exposed Sprague-Dawley male rats to 1 or 10 mg ATR/kg of body weight for 12-14 months. As previously reported, chronic ATR exposure causes hyperactivity in the group exposed to 10 mg ATR/kg and increased anxiety in both groups exposed to ATR. GABA, glutamate, and glutamine levels were differentially altered in brain regions related to nigrostriatal and mesolimbic systems, the amygdala, and the prefrontal cortex. The groups exposed to 10 mg ATR/kg showed increased extracellular levels and release of glutamate in the striatum. These neurochemical alterations could underlie the behavioral changes observed in rats. These results indicate that chronic exposure to the herbicide ATR disrupts the neurochemistry of several brain structures and could be a risk factor for the development of neurodegenerative diseases.

Unraveling the metabolic response of Brassica oleracea exposed to Xanthomonas campestris pv. campestris

BACKGROUND

Brassica crops together with cereals represent the basis of world supplies. Due to their importance, the production losses caused by Xanthomonas campestris pv. campestris (Xcc) infection represent a high economic impact. Understanding molecular and biochemical mechanisms of plants is essential to develop resistant crops with durable protection against diseases. In this regard, metabolomics has emerged as a valuable technology to provide an overview of the biological status of a plant exposed to a disease. This study investigated the dynamic changes in the metabolic profile of Brassica oleracea plants during an Xcc infection from leaves collected at five different days post infection using a mass spectrometry approach.

RESULTS

Results showed that Xcc infection causes dynamic changes in the metabolome of B. oleracea. Moreover, induction/repression pattern of the metabolites implicated in the response follows a complex dynamics during infection progression, indicating a complex temporal response. Specific metabolic pathways such as alkaloids, coumarins or sphingolipids are postulated as promising key role candidates in the infection response.

CONCLUSION

This work tries to decipher the changes produced on Brassica crops metabolome under Xcc infection and represents a step forward in the understanding of B. oleracea-Xcc interaction. © 2018 Society of Chemical Industry.

Effect of Temperature Stress on Antioxidant Defenses in Brassica oleracea

Brassica oleracea crops are exposed to seasonal changes in temperature because of their biennial life cycle. Extreme temperatures (cold and heat) affect the photosynthetic activity and the yield of cabbage (B. oleracea capitata group) and kale (B. oleracea acephala group). We studied the relationship among antioxidant defenses, photosynthesis, and yield under extreme temperatures in both crops. Under these conditions, the plants increase the antioxidant defenses, responding to an increment in reactive oxygen species (ROS). The accumulation of ROS in chloroplasts decreases the chlorophyll content and provokes photoinhibition that leads to a low fixation of CO₂ and loss of dry weight. Low temperatures especially increase the antioxidant defenses and decrease the chlorophyll content compared to the heat conditions. However, dry weight losses are higher when plants are grown under heat than under cold conditions, probably because of the inactivation of Rubisco and/or the associated enzymes. Both crops were more resilient to cold than to heat temperatures, the capitata group being more resistant.

Mating and social exposure induces an opioid-dependent conditioned place preference in male but not in female prairie voles (Microtus ochrogaster)

In rodents, sexual stimulation induces a positive affective state that is evaluated by the conditioned place preference (CPP) test. Opioids are released during sexual behavior and modulate the rewarding properties of this behavior. Prairie voles (Microtus ochrogaster) are a socially monogamous species, in which copulation with cohabitation for 6h induces a pair bond. However, the mating-induced reward state that could contribute to the establishment of the long-term pair bond has not been evaluated in this species. The present study aimed to determine whether one ejaculation or cohabitation with mating for 6h is rewarding for voles. We also evaluated whether this state is opioid dependent. Our results demonstrate that mating with one ejaculation and social cohabitation with mating for 6h induce a CPP in males, while exposure to a sexually receptive female without mating did not induce CPP. In the female vole, mating until one ejaculation, social cohabitation with mating, or exposure to a male without physical interaction for 6h did not induce CPP. To evaluate whether the rewarding state in males is opioid dependent, the antagonist naloxone was injected i.p. The administration of naloxone blocked the rewarding state induced by one ejaculation and by social cohabitation with mating. Our results demonstrate that in the prairie vole, on the basis of the CPP in the testing conditions used here, the stimulation received with one ejaculation and the mating conditions that lead to pair bonding formation may be rewarding for males, and this reward state is opioid dependent.

Defensive changes in maize leaves induced by feeding of Mediterranean corn borer larvae

BACKGROUND

Plants can respond to insect attack via defense mechanisms that reduce insect performance. In this study, we examined the effects of several treatments applied to two maize genotypes (one resistant, one susceptible) on the subsequent growth and survival of Sesamia nonagrioides Lef. (Mediterranean corn borer, MCB) larvae. The treatments were infestation with MCB larvae, application of MCB regurgitant upon wounding, wounding alone, or exposure to methyl jasmonate, and they were applied at the V6-V8 stage of maize development. We also monitored changes in the concentrations of compounds known to be involved in constitutive resistance, such as cell wall-bound hydroxycinnamates and benzoxazinoids.

RESULTS

In both maize genotypes, the leaves of plants pre-infested with MCB larvae were less suitable for larval development than those from untreated plants. Application of MCB regurgitant upon wounding, and wounding itself, resulted in leaf tissues becoming less suitable for larval growth than those of pre-infested plants, suggesting that there could be herbivore-associated effector molecules that suppress some wounding responses. A single application of MCB regurgitant did not seem to mimic feeding by MCB larvae, although the results suggested that regurgitant deposited during feeding may have enhanced ferulates and diferulates synthesis in infested vs. control plants. Jasmonic acid may play a role in mediating the maize response to MCB attack, but it did not trigger hydroxycinnamate accumulation in the leaves to a level comparable to that induced by larval leaf feeding. The EP39 maize genotype showed an increase in leaf cell wall strength by increasing hemicellulose cross-linking in response to MCB attack, while induced defenses in the EP42 plants appeared to reflect a broader array of resistance mechanisms.

CONCLUSIONS

The results indicated that leaf feeding by MCB larvae can increase leaf antibiosis against MCB in two maize genotypes with contrasting levels of resistance against this borer. Also, the larval regurgitant played a positive role in eliciting a defense response. We determined the effects of the plant response on larval growth, and detected defense compounds related to borer resistance.

Modification of Leaf Glucosinolate Contents in Brassica oleracea by Divergent Selection and Effect on Expression of Genes Controlling Glucosinolate Pathway

Modification of the content of secondary metabolites opens the possibility of obtaining vegetables enriched in these compounds related to plant defense and human health. We report the first results of a divergent selection for glucosinolate (GSL) content of the three major GSL in leaves: sinigrin (SIN), glucoiberin (GIB), and glucobrassicin (GBS) in order to develop six kale genotypes (Brassica oleracea var. acephala) with high (HSIN, HIGIB, HGBS) and low (LSIN, LGIB, LGBS) content. The aims were to determine if the three divergent selections were successful in leaves, how each divergent selection affected the content of the same GSLs in flower buds and seeds and to determine which genes would be involved in the modification of the content of the three GSL studied. The content of SIN and GIB after three cycles of divergent selection increased 52.5% and 77.68%, and decreased 51.9% and 45.33%, respectively. The divergent selection for GBS content was only successful and significant for decreasing the concentration, with a reduction of 39.04%. Mass selection is an efficient way of modifying the concentration of individual GSLs. Divergent selections realized in leaves had a side effect in the GSL contents of flower buds and seeds due to the novo synthesis in these organs and/or translocation from leaves. The results obtained suggest that modification in the SIN and GIB concentration by selection is related to the GSL-ALK locus. We suggest that this locus could be related with the indirect response found in the GBS concentration. Meantime, variations in the CYP81F2 gene expression could be the responsible of the variations in GBS content. The genotypes obtained in this study can be used as valuable materials for undertaking basic studies about the biological effects of the major GSLs present in kales.

Effect of temperature stress on the early vegetative development of Brassica oleracea L

BACKGROUND

Due to its biennual life cycle Brassica oleracea is especially exposed to seasonal changes in temperature that could limit its growth and fitness. Thermal stress could limit plant growth, leaf development and photosynthesis. We evaluated the performance of two local populations of B. oleracea: one population of cabbage (B. oleracea capitata group) and one population of kale (B. oleracea acephala group) under limiting low and high temperatures.

RESULTS

There were differences between crops and how they responded to high and low temperature stress. Low temperatures especially affect photosynthesis and fresh weight. Stomatal conductance and the leaf water content were dramatically reduced and plants produce smaller and thicker leaves. Under high temperatures there was a reduction of the weight that could be associated to a general impairment of the photosynthetic activity.

CONCLUSIONS

Although high temperatures significantly reduced the dry weight of seedlings, in general terms, low temperature had a higher impact in B. oleracea physiology than high temperature. Interestingly, our results suggest that the capitata population is less sensitive to changes in air temperature than the acephala population.

Identification of metabolic QTLs and candidate genes for glucosinolate synthesis in Brassica oleracea leaves, seeds and flower buds

Glucosinolates are major secondary metabolites found in the Brassicaceae family. These compounds play an essential role in plant defense against biotic and abiotic stresses, but more interestingly they have beneficial effects on human health. We performed a genetic analysis in order to identify the genome regions regulating glucosinolates biosynthesis in a DH mapping population of Brassica oleracea. In order to obtain a general overview of regulation in the whole plant, analyses were performed in the three major organs where glucosinolates are synthesized (leaves, seeds and flower buds). Eighty two significant QTLs were detected, which explained a broad range of variability in terms of individual and total glucosinolate (GSL) content. A meta-analysis rendered eighteen consensus QTLs. Thirteen of them regulated more than one glucosinolate and its content. In spite of the considerable variability of glucosinolate content and profiles across the organ, some of these consensus QTLs were identified in more than one tissue. Consensus QTLs control the GSL content by interacting epistatically in complex networks. Based on in silico analysis within the B. oleracea genome along with synteny with Arabidopsis, we propose seven major candidate loci that regulate GSL biosynthesis in the Brassicaceae family. Three of these loci control the content of aliphatic GSL and four of them control the content of indolic glucosinolates. GSL-ALK plays a central role in determining aliphatic GSL variation directly and by interacting epistatically with other loci, thus suggesting its regulatory effect.

Genetic regulation of cold-induced albinism in the maize inbred line A661

In spite of multiple studies elucidating the regulatory pathways controlling chlorophyll biosynthesis and photosynthetic activity, little is known about the molecular mechanism regulating cold-induced chlorosis in higher plants. Herein the characterization of the maize inbred line A661 which shows a cold-induced albino phenotype is reported. The data show that exposure of seedlings to low temperatures during early leaf biogenesis led to chlorophyll losses in this inbred. A661 shows a high plasticity, recovering resting levels of photosynthesis activity when exposed to optimal temperatures. Biochemical and transcriptome data indicate that at suboptimal temperatures chlorophyll could not be fully accommodated in the photosynthetic antenna in A661, remaining free in the chloroplast. The accumulation of free chlorophyll activates the expression of an early light inducible protein (elip) gene which binds chlorophyll to avoid cross-reactions that could lead to the generation of harmful reactive oxygen species. Higher levels of the elip transcript were observed in plants showing a cold-induced albino phenotype. Forward genetic analysis reveals that a gene located on the short arm of chromosome 2 regulates this protective mechanism.

Thermogenesis is involved in the body-fat lowering effects of resveratrol in rats

The effect of resveratrol on thermogenesis in skeletal muscle and interscapular brown adipose tissue (IBAT) was investigated. Rats were fed an obesogenic diet supplemented with resveratrol (30mg/kg/day) or not supplemented for 6weeks. Resveratrol intake led to increased gene expression of mitochondrial-transcription-factor-A (TFAM), mitochondrial-protein-cytochrome-C-oxidase subunit-2 (COX2), sirtuin-1 (SIRT1), peroxisome-proliferator-activated-receptor-β/δ (PPARβ/δ) and proliferator-activated-receptor-gamma-coactivator1-α (PGC-1α) in IBAT and increased UCP1protein expression; however, peroxisome-proliferator-activated-receptor-α (PPARα) expression remained unchanged. In gastrocnemius muscle, resveratrol increased the gene expression of TFAM and COX2; however, no changes were observed in levels of SIRT1, PGC-1α and PPARβ/δ. Acetylated-PGC-1α was decreased in the resveratrol-treated group, indicating a higher level of activation, and a significant increase of UCP3 protein expression was observed in this group. The increases in UCP protein expression in two important thermogenic tissues after resveratrol treatment may contribute to increased whole-body energy dissipation, which may help to better understand the body-fat lowering effect of this polyphenol.

Hepatic lipid metabolic pathways modified by resveratrol in rats fed an obesogenic diet

OBJECTIVE

The scientific community is on the look-out for safe biomolecules useful in the prevention of obesity and related aberrations such as fatty liver. This study analyzed the influence of resveratrol on hepatic triacylglycerol metabolism.

METHODS

Male Sprague-Dawley rats were divided into control and resveratrol-treated groups (30 mg/kg of body weight per day) and fed a commercial obesogenic diet for 6 wk. Liver triacylglycerol content and the activity of carnitine palmitoyl transferase-Ia (CPT-Ia), acyl-coenzyme A oxydase (ACO), fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME), acetyl-coenzyme A carboxylase (ACC), adenosine monophosphate-activated protein kinase (AMPK), and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) activation were measured. Mitochondrial protein cytochrome C oxidase subunit 2 (COXII), mitochondrial transcription factor A (TFAM), sterol regulatory element-binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor-α (PPAR-α), sirtuin-1 (SIRT1), hepatocyte nuclear factor receptor-4α (HNF-4α), and PGC-1α mRNA levels were also analyzed. Serum insulin was quantified.

RESULTS

Resveratrol decreased liver fat accumulation, increased CPT-Ia and ACO, and decreased ACC activities. Other lipogenic enzymes, FAS, ME, and G6PDH were not modified. The polyphenol activated AMPK and PGC-1α. The expression of SRBP-1c, PPAR-α, SIRT1, PGC-1α, HNF-4α, TFAM, and COXII was not modified. No changes in serum insulin levels were observed.

CONCLUSION

Resveratrol partly prevents the increase in liver fat accumulation induced by high-fat high-sucrose feeding by increasing fatty acid oxidation and decreasing lipogenesis. These effects are mediated by the activation of the AMPK/SIRT1 axis.

Distribution of resveratrol metabolites in liver, adipose tissue, and skeletal muscle in rats fed different doses of this polyphenol

This study aimed to characterize resveratrol metabolite profiles in liver, skeletal muscle, and adipose tissue in rats treated for 6 weeks with 6, 30, or 60 mg of trans-resveratrol/kg body weight/d. Resveratrol metabolites were quantified by liquid chromatography-tandem mass spectrometry. The greatest number of metabolites was found in liver followed by adipose tissue. A great number of metabolites in muscle was below the limit of detection. The amounts of sulfate conjugates tended to increase when resveratrol dosage was enhanced, while the glucuronide ones increased only between 6 and 30 mg/kg/d. Microbiota metabolites were detected in higher amounts than resveratrol conjugates in liver, while the opposite occurred in adipose tissue and muscle. So, the largest amounts of resveratrol metabolites were found in liver, intermediate amounts in adipose tissue, and the lowest amounts in muscle. Sulfate conjugates, but not glucuronides, showed a dose-response pattern. Microbiota metabolites were predominant in liver.

Inducible maize defense mechanisms against the corn borer Sesamia nonagrioides: a transcriptome and biochemical approach

In spite of multiple studies elucidating individual defense mechanisms against stalk borer feeding, little information is available about the plant response to these members of Lepidoptera. Four maize inbred lines were cultivated in a greenhouse and challenged with larvae of the corn borer Sesamia nonagrioides. Transcriptome and biochemical analyses were performed to elucidate the maize response mechanisms to this insect. General plant defense mechanisms were activated, including the jasmonic acid biosynthetic pathway, proteinase inhibitors, and four defense-related transcription factors. Interestingly, gene ontology analysis shows that maize plants undergo cell-wall reorganization after being attacked. These results were confirmed through biochemical analyses showing that the concentration of some cell-wall-related compounds significantly changed after plant infestation in a genotype-dependent way. In conclusion, maize plants respond to the attack of the corn borer S. nonagrioides through cell-wall fortification, activating genes involved in cell-wall organization, which finally is reflected in a higher concentration of some cell-wall components, especially in resistant genotypes.

Changes in white adipose tissue metabolism induced by resveratrol in rats

Background

A remarkable range of biological functions have been ascribed to resveratrol. Recently, this polyphenol has been shown to have body fat lowering effects. The aim of the present study was to assess some of the potential underlying mechanisms of action which take place in adipose tissue.

Methods

Sixteen male Sprague-Dawley rats were randomly divided into two groups: control and treated with 30 mg resveratrol/kg body weight/d. All rats were fed an obesogenic diet and after six weeks of treatment white adipose tissues were dissected. Lipoprotein lipase activity was assessed by fluorimetry, acetyl-CoA carboxylase by radiometry, and malic enzyme, glucose-6P-dehydrogenase and fatty acid synthase by spectrophotometry. Gene expression levels of acetyl-CoA carboxylase, fatty acid synthase, lipoprotein lipase, hormone-sensitive lipase, adipose triglyceride lipase, PPAR-gamma, SREBP-1c and perilipin were assessed by Real time RT-PCR. The amount of resveratrol metabolites in adipose tissue was measured by chromatography.

Results

There was no difference in the final body weight of the rats; however, adipose tissues were significantly decreased in the resveratrol-treated group. Resveratrol reduced the activity of lipogenic enzymes, as well as that of heparin-releasable lipoprotein lipase. Moreover, a significant reduction was induced by this polyphenol in hormone-sensitive lipase mRNA levels. No significant changes were observed in other genes. Total amount of resveratrol metabolites in adipose tissue was 2.66 ± 0.55 nmol/g tissue.

Conclusions

It can be proposed that the body fat-lowering effect of resveratrol is mediated, at least in part, by a reduction in fatty acid uptake from circulating triacylglycerols and also in de novo lipogenesis.

DNA barcodes for Mexican Cactaceae, plants under pressure from wild collecting

DNA barcodes could be a useful tool for plant conservation. Of particular importance is the ability to identify unknown plant material, such as from customs seizures of illegally collected specimens. Mexican cacti are an example of a threatened group, under pressure because of wild collection for the xeriscaping trade and private collectors. Mexican cacti also provide a taxonomically and geographically coherent group with which to test DNA barcodes. Here, we sample the matK barcode for 528 species of Cactaceae including approximately 75% of Mexican species and test the utility of the matK region for species-level identification. We find that the matK DNA barcode can be used to identify uniquely 77% of species sampled, and 79-87% of species of particular conservation importance. However, this is far below the desired rate of 95% and there are significant issues for PCR amplification because of the variability of primer sites. Additionally, we test the nuclear ITS regions for the cactus subfamily Opuntioideae and for the genus Ariocarpus (subfamily Cactoideae). We observed higher rates of variation for ITS (86% unique for Opuntioideae sampled) but a much lower PCR success, encountering significant intra-individual polymorphism in Ariocarpus precluding the use of this marker in this taxon. We conclude that the matK region should provide useful information as a DNA barcode for Cactaceae if the problems with primers can be addressed, but matK alone is not sufficiently variable to achieve species-level identification. Additional complementary regions should be investigated as ITS is shown to be unsuitable.

Effects of different doses of resveratrol on body fat and serum parameters in rats fed a hypercaloric diet

Recently resveratrol, a compound naturally occurring in various plants, has been proposed as a potential anti-obesity compound. The aim of the present work was to analyse the effects of different doses of resveratrol on body fat and serum parameters in rats. Thirty-two male Sprague-Dawley rats were randomly divided into four groups and fed on a hypercaloric diet for 6 weeks. The doses oftrans-resveratrol used were 6, 30 and 60 mg/kg body weight/d in RSV1, RSV2 and RSV3 groups respectively. The stability of resveratrol when added to the diet was evaluated. Blood samples were collected, and white adipose tissue from different anatomical locations, interscapular brown adipose tissue, gastrocnemious muscles and liver were weighed. Commercial kits were used to measure serum cholesterol, glucose, triacylglycerols and non-esterified fatty acids. While the lowest dose did not have a body fat reducing effect, the intermediate dose reduced all the white adipose depots. The highest dose significantly reduced mesenteric and subcutaneous depots but not epididymal and perirenal tissues. Although the reduction in all the anatomical locations analysed was 19% in the RSV3 group, in the RSV2 group it was 24%. No significant differences among the experimental groups were found in brown adipose tissue, gastrocnemious muscle or liver weights. Serum parameters were not affected by resveratrol intake because no differences among the experimental groups were observed. These results suggest that resveratrol is a molecule with potential anti-obesity effect. The most effective of the three experimental doses was 30 mg/kg body weight/d.

Chloroplastic phosphoadenosine phosphosulfate metabolism regulates basal levels of the prohormone jasmonic acid in Arabidopsis leaves

Levels of the enzymes that produce wound response mediators have to be controlled tightly in unwounded tissues. The Arabidopsis (Arabidopsis thaliana) fatty acid oxygenation up-regulated8 (fou8) mutant catalyzes high rates of alpha -linolenic acid oxygenation and has higher than wild-type levels of the alpha -linolenic acid-derived wound response mediator jasmonic acid (JA) in undamaged leaves. fou8 produces a null allele in the gene SAL1 (also known as FIERY1 or FRY1). Overexpression of the wild-type gene product had the opposite effect of the null allele, suggesting a regulatory role of SAL1 acting in JA synthesis. The biochemical phenotypes in fou8 were complemented when the yeast (Saccharomyces cerevisiae) sulfur metabolism 3'(2'), 5'-bisphosphate nucleotidase MET22 was targeted to chloroplasts in fou8. The data are consistent with a role of SAL1 in the chloroplast-localized dephosphorylation of 3'-phospho-5'-adenosine phosphosulfate to 5'-adenosine phosphosulfate or in a closely related reaction (e.g. 3',5'-bisphosphate dephosphorylation). Furthermore, the fou8 phenotype was genetically suppressed in a triple mutant (fou8 apk1 apk2) affecting chloroplastic 3'-phospho-5'-adenosine phosphosulfate synthesis. These results show that a nucleotide component of the sulfur futile cycle regulates early steps of JA production and basal JA levels.

Identification of genes related to germination in aged maize seed by screening natural variability

Ageing reduces vigour and viability in maize inbred lines due to non-heritable degenerative changes. Besides non-heritable genetic changes due to chromosome aberrations and damage in the DNA sequence, heritable changes during maize conservation have been reported. Genetic variability among aged seeds of inbred lines could be used for association studies with seed germination. The objective of this study was to identify genes related to germination in aged seeds. The sweet corn inbred line P39 and the field corn inbred line EP44 were used as plant material. Bulks of living and dead seeds after 20 and 22 years of storage were compared by using simple sequence repeats (SSRs) and, when the bulks differed for a marker, the individual grains were genotyped. Differences between dead and living seeds could be explained by residual variability, spontaneous mutation, or ageing. Variability was larger for chromosome 7 than for other chromosomes, and for distal than for proximal markers, suggesting some relationships between position in the genome and viability in aged seed. Polymorphic SSRs between living and dead seeds were found in six known genes, including pathogenesis-related protein 2, superoxide dismutase 4, catalase 3, opaque endosperm 2, and metallothionein1 that were related to germination, along with golden plant 2. In addition, five novel candidate genes have been identified; three of them could be involved in resistance to diseases, one in detoxification of electrophillic compounds, and another in transcription regulation. Therefore, genetic variability among aged seeds of inbreds was useful for preliminary association analysis to identify candidate genes.

Chronic low-level arsenic exposure causes gender-specific alterations in locomotor activity, dopaminergic systems, and thioredoxin expression in mice

Arsenic (As) is a toxic metalloid widely present in the environment. Human exposure to As has been associated with the development of skin and internal organ cancers and cardiovascular disorders, among other diseases. A few studies report decreases in intelligence quotient (IQ), and sensory and motor alterations after chronic As exposure in humans. On the other hand, studies of rodents exposed to high doses of As have found alterations in locomotor activity, brain neurochemistry, behavioral tasks, and oxidative stress. In the present study both male and female C57Bl/6J mice were exposed to environmentally relevant doses of As such as 0.05, 0.5, 5.0, or 50 mg As/L of drinking water for 4 months, and locomotor activity was assessed every month. Male mice presented hyperactivity in the group exposed to 0.5 mg As/L and hypoactivity in the group exposed to 50 mg As/L after 4 months of As exposure, whereas female mice exposed to 0.05, 0.5, and 5.0 mg As/L exhibited hyperactivity in every monthly test during As exposure. Furthermore, striatal and hypothalamic dopamine content was decreased only in female mice. Also decreases in tyrosine hydroxylase (TH) and cytosolic thioredoxin (Trx-1) mRNA expression in striatum and nucleus accumbens were observed in male and female mice, respectively. These results indicate that chronic As exposure leads to gender-dependent alterations in dopaminergic markers and spontaneous locomotor activity, and down-regulation of the antioxidant capacity of the brain.

Adiposity and serum parameters in hamsters fed energy restricted diets supplemented or not with trans-10,cis-12 conjugated linoleic acid

Numerous studies have demonstrated that conjugated linoleic acid (CLA) modulates body composition, reducing body fat accumulation in various mammalian species. However, very few studies have been carried out to assess the effect of CLA on previously stored body fat. The aim of the present work was to analyse the effectiveness of trans-10,cis-12 CLA in improving alterations produced by high-fat feeding in body fat and serum parameters when it was included in an energy-restricted diet. For this purpose male Syrian Golden hamsters were fed on high-fat diet for 7 weeks in order to increase their body fat content, and a further 25% energy-restricted diet supplemented or not with 0.5% trans-10,cis-12 CLA for 3 weeks. Adipose tissues, liver and gastrocnemious muscles were dissected and weighed. Adipocyte diameter and number were assessed in epididymal adipose tissue. Total cholesterol, triacylglycerols, non-esterified fatty acids and glucose were measured in serum. Three weeks of energy restriction resulted in a reduction in body weight and white adipose tissue size in all anatomical locations, without changes in liver and gastrocnemious muscle weights. Epididymal adipocyte size was reduced, but total adipocyte number remained unchanged. Serum cholesterol, triacylglycerols and glucose were significantly reduced. No differences were observed between the restricted groups (control and CLA supplemented). In conclusion, under our experimental conditions, the addition of trans-10,cis-12 CLA to the diet does not increase the benefits produced by energy restriction.

The fou2 gain-of-function allele and the wild-type allele of Two Pore Channel 1 contribute to different extents or by different mechanisms to defense gene expression in Arabidopsis

The fatty acid oxygenation up-regulated 2 (fou2) mutant in Arabidopsis thaliana creates a gain-of-function allele in a non-selective cation channel encoded by the Two Pore Channel 1 (TPC1) gene. This mutant genetically implicates cation fluxes in the control of the positive feedback loop whereby jasmonic acid (JA) stimulates its own synthesis. In this study we observed extensive transcriptome reprogramming in healthy fou2 leaves closely resembling that induced by treatment with methyl jasmonate, biotic stresses and the potassium starvation response. Proteomic analysis of fou2 leaves identified increased levels of seven biotic stress- and JA-inducible proteins. In agreement with these analyses, epistasis studies performed by crossing fou2 with aos indicated that elevated levels of JA in fou2 are the major determinant of the mutant phenotype. In addition, generation of fou2 aba1-5, fou2 etr1-1 and fou2 npr1-1 double mutants showed that the fou2 phenotype was only weakly affected by ABA levels and unaffected by mutations in NPR1 and ETR1. The results now suggest possible mechanisms whereby fou2 could induce JA synthesis/signaling early in the wound response. In contrast to fou2, transcriptome analysis of a loss-of-function allele of TPC1, tpc1-2, revealed no differential expression of JA biosynthesis genes in resting leaves. However, the analysis disclosed reduced mRNA levels of the pathogenesis-related genes PDF1.2a and THI2.1 in healthy and diseased tpc1-2 leaves. The results suggest that wild-type TPC1 contributes to their expression by mechanisms somewhat different from those affecting their expression in fou2.

Effects of trans-10,cis-12 conjugated linoleic acid on cholesterol metabolism in hypercholesterolaemic hamsters

BACKGROUND

Conjugated linoleic acid (CLA) has received great attention in recent years because of its pleiotropic biological activities, but considerably fewer studies have been published addressing its role in serum lipids and atherosclerosis compared to other topics covered.

AIMS OF THE STUDY

The aim of the present study was to assess the effects of the trans-10,cis-12 isomer of CLA on cholesterolaemia and on several metabolic pathways involved in cholesterol metabolism in hamsters.

METHODS

Animals were fed atherogenic diets supplemented with 0.5% linoleic acid, 0.5% trans-10,cis-12 CLA or 1.0% trans-10,cis-12 CLA, for 6 weeks. Serum lipoproteins were separated by FPLC. Cholesterol in serum and liver, as well as triacylglycerols and phospholipids in liver were assessed by spectrophotometry. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoAR), acyl-coenzyme A:cholesterol acyltransferase (ACAT) and cholesteryl ester hydrolase (CEH) activities were measured by radiometry, and LDL receptors were determined by Western blot.

RESULTS

trans-10,cis-12 CLA feeding did not modify food intake nor final body weight. Although serum total cholesterol remained unchanged, when cholesterol fractions were analyzed a significant decrease in VLDL-cholesterol was observed in CLA-fed animals, without changes in HDL-cholesterol or LDL-cholesterol. trans-10,cis-12 CLA decreased cholesterol ester content and increased free cholesterol in liver. The activity of HMGCoAR was not modified. In contrast, ACAT activity was reduced by both CLA doses and CEH was increased by the high CLA dose. LDL receptors were significantly reduced by trans-10,cis-12 feeding when expressed as arbitrary units per mg of protein, however, the total receptor mass remained unchanged.

CONCLUSIONS

These results suggest that, under the present experimental conditions, trans-10,cis-12 CLA feeding reduces cholesterol esterification in liver and decreases the minority serum VLDL-cholesterol fraction, but it does not show a hypocholesterolaemic effect. A dose-response effect was not observed.

Thetrans-10,cis-12 isomer of conjugated linoleic acid reduces hepatic triacylglycerol content without affecting lipogenic enzymes in hamsters

Conjugated linoleic acid (CLA) refers to the positional and geometric dienoic isomers of linoleic acid. The dietary intake of CLA has been associated with changes in lipid metabolism. The aim of the present work was to assess the effects of the two main isomers of CLA on sterol regulatory element binding protein (SREBP)-1a and SREBP-1c mRNA levels, as well as on mRNA levels and the activities of several lipogenic enzymes in liver. For this purpose hamsters were fed an atherogenic diet supplemented with 5 g linoleic acid,cis-9,trans-11 ortrans-10,cis-12 CLA/kg diet for 6 weeks. Thetrans-10,cis-12 isomer intake produced significantly greater liver weight, but also significantly decreased liver fat accumulation. No changes in mRNA levels of SREBP-1a, SREBP-1c and lipogenic enzymes, or in the activities of these enzymes, were observed. There was no effect of feedingcis-9,trans-11 CLA. These results suggest that increased fat accumulation in liver does not occur on the basis of liver enlargement produced by feeding thetrans-10,cis-12 isomer of CLA in hamsters. The reduction in hepatic triacylglycerol content induced by this isomer was not attributable to changes in lipogenesis.

Dietary fat source regulatesobgene expression in white adipose tissue of rats under hyperphagic feeding

This work was designed to investigate the effect of different lipid sources onobgene expression and serum leptin levels in rats with two different feeding protocols: (1) free access to food; or (2) energy-controlled feeding. Male Wistar rats were fed diets containing 40 % energy as fat (olive oil, sunflower oil or beef tallow), for 4 weeks. In Expt 1 rats had free access to food, and in Expt 2 rats were fed a controlled amount of food (16 g/d, equivalent to 300 kJ/d). Insulin and leptin were determined by ELISA andobmRNA by Northern blot. When rats had free access to food,obmRNA levels were higher in animals fed either olive oil or sunflower oil than in those fed beef tallow. In marked contrast with feedingad libitum, no differences were found among dietary fat groups in rats fed energy-controlled diets. When both feeding protocols were compared, free access to food induced an increased expression ofobmRNA in perirenal and/or epididymal adipose tissues from rats fed either olive oil or sunflower oil, but not from rats fed beef tallow. Dietary lipid type did not induce modifications in serum leptin concentrations. A tendency to higher serum leptin levels was observed more in rats with free access to food than in rats fed energy-controlled feeding. No differences were found in insulin levels. Dietary fat type importantly affectsobmRNA expression in rat white adipose tissue under hyperphagic conditions. Further study is needed in order to elucidate the mechanism underlying this effect.

Effects of trans-10,cis-12 conjugated linoleic acid on body fat and serum lipids in young and adult hamsters

The aim of the present work was to determine whether t-10, c-12 conjugated linoleic acid (CLA) feeding was able to reduce body fat accumulation and improve the serum lipid profile in adult hamsters fed an atherogenic diet, in order to compare these effects with those observed in young growing hamsters. Young and adult hamsters were fed semi-purified atherogenic diets supplemented with 0.5 % linoleic acid or 0.5% t-10, c-12 CLA for 6 weeks. Body weight and food intake were measured every two days. Adipose tissue from different anatomical locations, liver and gastrocnemious muscle were dissected and weighed. Cholesterol, triacylglycerols, non-esterified fatty acids and proteins were determined spectrophotometrically and water content by gravimetry. In young hamsters, no significant differences were found in food intake, final body weight and gastrocnemious muscle weight. White adipose tissue weights were reduced, liver weight was increased and cholesterol and triacyl-glycerols in both serum and liver were reduced. In adult hamsters, CLA feeding decreased food intake and adipose tissue weights. No changes were observed in other parameters. The present study demonstrates that age has an influence in hamster responsiveness to t-10, c-12 CLA because, although when this isomer is added to an atherogenic diet it reduces body fat accumulation in both young and adults hamsters, the lessening of the effects on serum lipids brought about by atherogenic feeding is only observed in young animals. Moreover, it is clear that liver is a target for CLA in young but not in adult hamsters.

Effects of cis-9, trans-11 and trans-10, cis-12 CLA isomers on liver and adipose tissue fatty acid profile in hamsters

The aim of the present study was to investigate the effect of cis-9,trans-11 and trans-10,cis-12 CLA on FA composition of TAG in epididymal adipose tissue and liver, and of hepatic phospholipids PL. Twenty-four Syrian Golden hamsters were randomly divided into three groups of eight animals each and fed semipurified atherogenic diets supplemented with either 0.5 g/100 g diet of linoleic acid or cis-9,trans-11 or trans-12,cis-9 CLA for 6 wk. Total lipids were extracted, and TAG and PL were separated by TLC. FA profile in lipid species from liver and adipose tissue, as well as in feces, was determined by GC. Trans-10,cis-12 CLA feeding significantly reduced linoleic and linolenic acids in TAG from both tissues, leading to reduced total PUFA content. Moreover, in the epididymal adipose tissue docosenoic and arachidonic acids were significantly increased. In liver PL, although no changes in individual FA were observed, total saturated FA (SFA) were decreased. No changes in TAG and PL FA profiles were induced by the cis-9,trans-11 CLA. TAG and PL incorporated cis-9,trans-11 more readily than trans-10,cis-12 CLA. This difference was not due to differential intestinal absorption, as shown by the analysis of feces. We concluded that only trans-10,cis-12 CLA induces changes in FA composition. Whereas increased PUFA content was observed in either liver or adipose tissue TAG, decreased SFA were found in liver PL. Incorporation of cis-9,trans-11 CLA in TAG is greater than that of trans-10,cis-12 CLA, but this is not due to differences in intestinal absorption.

trans-10,cis-12 Conjugated linoleic acid inhibits lipoprotein lipase but increases the activity of lipogenic enzymes in adipose tissue from hamsters fed an atherogenic diet

The aim of the present work was to investigate the effects of trans-10,cis-12 conjugated linoleic acid (CLA) on the activity and expression of lipogenic enzymes and lipoprotein lipase (LPL), as well as on the expression of transcriptional factors controlling these enzymes, in adipose tissue from hamsters, and to evaluate the involvement of these changes in the body fat-reducing effect of this CLA isomer. Thirty male hamsters were divided into three groups and fed atherogenic diets supplemented with 0 (linoleic group), 5 or 10 g trans-10,cis-12 CLA/kg diet, for 6 weeks. Body and adipose tissue weights, food intake and serum insulin were measured. Total and heparin-releasable LPL and lipogenic enzyme activities (acetyl-CoA carboxylase (ACC); fatty acid synthase (FAS); glucose-6-phosphate dehydrogenase (G6PDH); and malic enzyme (ME)) were assessed. ACC, FAS, LPL, sterol regulatory element-binding proteins (SREBP-1a), SREBP-1c and PPARgamma mRNA levels were also determined by real-time PCR. CLA did not modify food intake, body weight and serum insulin level. CLA feeding reduced adipose tissue weight, LPL activity and expression, and increased lipogenic enzyme activities, despite a significant reduction in ACC and FAS mRNA levels. The expression of the three transcriptional factors analysed (SREBP-1a, SREBP-1c and PPARgamma) was also reduced. These results appear to provide a framework for partially understanding the reduction in body fat induced by CLA. Inhibition of LPL activity seems to be an important mechanism underlying body fat reduction in hamsters. Further research is needed to better characterize the effects of CLA on lipogenesis and the role of these effects in CLA action.

Effects of conjugated linoleic acid on skeletal muscle triacylglycerol metabolism in hamsters

OBJECTIVE

The present work evaluated the effects of conjugated linoleic acid (CLA) on various aspects of triacylglycerol metabolism in skeletal muscle to determine the potential involvement of this tissue in the effect of CLA to decrease body fat.

METHODS

Animals were randomized to three groups that were fed atherogenic diets that provided different amounts of trans-10,cis-12 CLA (0%, 0.5%, or 1%) for 6 wk. Muscle triacylglycerol, protein, water, glycogen, and DNA contents and fatty acid profile in triacylglycerols were analyzed. Lipoprotein lipase and carnitine palmitoyltransferase-I (CPT-I) activities were assessed. Triacylglycerol, glucose, and insulin concentrations were evaluated in serum.

RESULTS

The high dose of CLA increased food efficiency and gastrocnemius muscle weight. CLA feeding resulted in decreased muscle triacylglycerol content without changes in protein, water, glycogen, and DNA contents or in cell size (protein/DNA ratio) and produced decreased lipoprotein lipase activity and increased CPT-I activity. No differences were found between CLA doses. CLA feeding led to the saturation of stored triacylglycerols.

CONCLUSIONS

Decreased fatty acid uptake and increased fatty acid oxidation can contribute to the decreased muscle triacylglycerol content observed in hamsters fed the CLA diets. The increase in muscle fatty acid beta-oxidation might ultimately prevent storage of triacylglycerols in adipose tissue. Nevertheless, the lack of matching of lipoprotein lipase and CPT-I modifications makes it difficult to ensure that skeletal muscle is responsible, at least in part, for the effect of CLA on decreasing body fat; thus, further research is needed.

Body fat-lowering effect of conjugated linoleic acid is not due to increased lipolysis

The ability of conjugated linoleic acid (CLA) to reduce adiposity may be due to changes in energy expenditure and/or direct effects on adipocyte lipid metabolism. The aim of the present work was to analyse if CLA supplementation modifies lipolytic activity in adipose tissue from hamsters fed on high-fat diet. Hamsters were divided into two groups and fed on diets supplemented with either 0.5% linoleic acid (control) or 0.5% trans-10,cis-12 CLA. After 6 weeks, animals were fasted overnight and adipose tissues were dissected and weighed. Adipocytes were isolated by collagenase digestion and incubated in Krebs-Ringer bicarbonate buffer with or without several agents acting at different levels of the lipolytic cascade. Adipocyte diameters were measured by microscopy. Adipose tissue DNA content was assessed by spectrophotometry. Animals fed on CLA diet showed significantly reduced adipose tissue mass. No differences between both groups was found for basal lipolysis, lipolytic effects of isoproterenol, forskolin, dibutyryl-cAMP and isobutylmethylxanthine, and pD2 for isoproterenol. A similar total DNA amount was found in adipose tissue of both groups, showing that CLA diet had no effect on total cell number per fat pad. Although DNA content per gram tissue, an indirect reverse index of cell size, was significantly increased in CLA fed hamsters, microscopy did not reveal differences in medium mature adipocyte diameter, nor in cell size distribution between both groups. These results suggest that adipose tissue size reduction induced by trans-10,cis-12 CLA intake is not due to changes in lipolysis. Reduced preadipocyte differentiation into mature adipocytes may account for this fat-lowering effect.

Effects of conjugated linoleic acid on liver composition and fatty acid oxidation are isomer-dependent in hamster

OBJECTIVE

The present work was designed to study the effects of the two main isomers of conjugated linoleic acid (CLA), cis-9,trans-11 and trans-10,cis-12, on liver composition and hepatic fatty acid oxidation in hamsters.

METHODS

Animals were divided into three groups that were fed atherogenic diets supplemented with 0.5% linoleic acid, cis-9,trans-11 CLA, or trans-10,cis-12 CLA for 6 wk. Liver lipids, protein, water and DNA contents, and histologic structure were analyzed. Hepatic carnitine palmitoyltransferase-I and acyl coenzyme A oxidase activities were assessed. Triacylglycerol concentration, and aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, and alkaline phosphatase activities were evaluated in serum. CLA isomer contents were analyzed by gas chromatography in hepatic triacylglycerols. Peroxisome proliferator-activated receptor-alpha mRNA was determined by reverse transcriptase polymerase chain reaction.

RESULTS

Trans-10,cis-12 CLA led to significantly greater weight, lower levels of triacylglycerol, cholesterol, and phospholipid, and larger total cell number in liver. Carnitine palmitoyltransferase-I and acyl coenzyme A oxidase activities were significantly increased by this isomer. No changes were induced by cis-9,trans-11 CLA. Trans-10,cis-12 CLA was recovered in significantly lower proportions than cis-9,trans-11 in liver triacylglycerols. Histopathologic analysis showed no abnormalities. No significant differences in serum aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, and alkaline phosphatase activities or in hepatic mRNA peroxisome proliferator-activated receptor-alpha expression were found among the three experimental groups.

CONCLUSIONS

These results suggest that the addition of 0.5% of these CLA isomers to the diet do not induce toxic effects in liver after 6 wk of feeding. Intake of trans-10,cis-12 isomer but not of cis-9,trans-11 CLA increases liver fatty acid oxidation. This effect leads to decreased hepatic and serum triacylglycerols.

[Conjugated linoleic acid lowers hypercholesterolemia but increases the risk for biliary lithiasis]

The term conjugated linoleic acid (CLA) refers to a series of linoleic acid isomers present in meat and diary products from ruminants that have their double bonds in a conjugated position. The aim of the present work was to study the effects of a CLA isomer, trans-10,cis-12, on cholesterolemia and biliary lithiasis risk in an animal model of diet-induced hypercholesterolemia. For that, two groups of hamsters were fed with a hypercholesterolemic diet supplemented with 0.5% linoleic acid or with the trans-10,cis-12 CLA isomer, respectively. Daily food intake and weight were determined and, 6 weeks later, serum and bile samples were obtained, and livers and spleens were dissected and weighted. Cholesterolemia, hepatic and splenic cholesterol content, and biliary cholesterol phosnolipid and bileacid concentrations were determined; Biliary Lithogenic Index was calculated, and presence of gallstones was assessed. CLA did not modify energetic intake or final body weight, spleen size or spleen cholesterol content, but it did significantly reduce total serum cholesterol (-18%) at the expense of c-LDL (-66%), and it also significantly reduced hepatic content of free cholesterol (-26%), without changes in esterified cholesterol. Besides, CLA produced a 32% increase in biliary cholesterol concentration, a 28% increase in Lithogenic Index, and a higher incidence of biliary lithiasis. Therefore, the present study shows that the CLA trans-10,cis-12 isomer is hypercholesterolemic since it increases, at least in part, cholesterol secretion to the bile. As a consequence, this effect increases the risk for biliary lithiasis.

Glutathione Reductase Inhibition and Methylated Arsenic Distribution in Cd1 Mice Brain and Liver

Inorganic arsenic exposure via drinking water has been associated with cancer and serious injury in various internal organs, as well as with peripheral neuropathy and diverse effects in the nervous system. Alterations in memory and attention processes have been reported in exposed children, whereas adults acutely exposed to high amounts of inorganic arsenic showed impairments in learning, memory, and concentration. Glutathione (GSH) is extensively involved in the metabolism of inorganic arsenic, and both arsenite and its methylated metabolites have been shown to be potent inhibitors of glutathione reductase (GR) in vitro. Brain would be more susceptible to GR inhibition because of the decreased activities of superoxide dismutase (SOD) and catalase reported in this tissue. To investigate whether GR inhibition could be documented in vivo, we determined the activity and levels of GR in brain as well as in liver, the main organ of arsenic metabolism in mice exposed to 2.5, 5, or 10 mg/kg/day of sodium arsenite over a period of 9 days. In contrast to what has been observed in vitro, significant inhibition of the expression and activity of GR was observed only at the highest concentration used (10 mg/kg/day) in both organs. Although the disposition of arsenicals was higher in liver, significant amounts of inorganic and methylated arsenic forms were determined in the brain of exposed animals. The formation of monomethylarsenic (MMA) and dimethylarsenic (DMA) metabolites in the brain was confirmed by incubating brain slices for 24, 48, and 72 h with sodium arsenite.

The effects of arsenic exposure on the nervous system

Arsenic (As) is a common environmental contaminant widely distributed around the world. Human exposure to this metalloid comes from well water and contaminated soil, from fish and other sea organisms rich in methylated arsenic species, and from occupational exposure. It has been reported that human arsenic exposure causes several health problems such as cancer, liver damage, dermatosis, and nervous system disturbances such as polyneuropathy, EEG abnormalities and, in extreme cases, hallucinations, disorientation and agitation. Although there is evidence that arsenic exposure has a toxic effect on the nervous system there are few studies that address this issue. The purpose of this review is to describe what is presently known about the effects of arsenic compounds on the nervous system in humans and rodents and to discuss its possible mechanisms of action.

Effects of conjugated linoleic acid on body fat accumulation and serum lipids in hamsters fed an atherogenic diet

Conjugated linoleic acid (CLA) refers to a mixture of naturally occurring positional and geometric isomers of linoleic acid that exist in dairy products and meat. The aim of the present work was to study the effects of c-9,t-11 and t-10,c-12 CLA isomers on body fat accumulation and serum lipids in hamsters fed an atherogenic diet. Hamsters were divided in four groups: one group was fed a chow diet (control) and the other three groups were given semi-purified atherogenic diets with 0.5% linoleic acid (LA), c-9,t-11 or t-10,c-12 CLA. Body weight and food intake were measured daily. After 6 weeks, adipose tissues from different anatomical locations and liver were dissected and weighed. Serum glucose, total cholesterol, HDL-c, LDL-c and triacylglycerol levels, as well as total and free cholesterol, triacylglycerol and phospholipid content in liver were determined by enzymatic methods. No differences in either energy intake or final body weight were found. The addition of t-10,c-12 CLA reduced fat accumulation and led to lower serum cholesterol, as compared with LA group. Nevertheless the level remained higher than in the control animals. The reduction in serum cholesterol was limited to LDL-c. This isomer also reduced triacylglycerol content in liver but did not modify serum triacylglycerol level. In summary, the present study demonstrates that t-10,c-12 CLA is the biologically active agent when anti-obesity and hypocholesterolaemic properties of CLA are considered. In contrast, the isomer c-9,t-11 has no effect on lipid metabolism in hamsters.

[Role of uncoupling proteins in obesity]

The discovery of a protein of the internal mitochondrial membrane of the brown adipocytes, the UCP1, marked an important advance in the understanding of the thermogenic process, as well as of the working of the brown adipose tissue. This protein is only of importance in the newly born and small animals, however the later discovery of proteins that were analogues of UCP1 (UCP2, widely distributed, and UCP3, mainly present in the muscle) with a similar functioning and also present in human tissue, created new perspectives and scientific goals. These proteins uncouple the respiratory chain of the oxidative phosphorylation, thus dissipating energy in the form of heat without producing ATP, by means of a mechanism that is still the subject of debate. From the studies of regulation that have been made, it emerges that their activity is modified when facing different physiological and nutritional stimuli, with greater activity observed in situations where an increase of energy expenditure is required. The studies carried on humans seem to corroborate the results obtained in experiments on animals, and action can thus be proposed on the activity, or the quantity, of these proteins in humans, as a means for fighting overweightedness and obesity. However, there is still an evident need to complete and improve the existing information on the importance of these proton transporting proteins in humans.

Lipolysis induced by leptin in rat adipose tissue from different anatomical locations

The aim of the present work is to compare the lipolytic response of three fat depots (subcutaneous, epididymal and perirenal) to leptin under in vitro conditions in rats. Moreover an assessment of the potential differences between young and mature rats in terms of the response of these tissues to leptin is made. Adipocytes from 6- and 20-wk-old rats were isolated by collagenase digestion and incubated in vitro both in the absence and the presence of either leptin (10(-12)-10(-6) M) or isoproterenol (10(-6) M). Lipolysis was measured by the release of glycerol into the incubation medium over 2 hours of incubation. Adipocytes responded in a dose-dependent manner to leptin concentrations ranging from 10(-12) M to 10(-6) M. The lowest leptin concentration inducing a significant lipolytic effect was 10(-9) M in all tissues. No significant differences in the effect of the maximal concentration of leptin (10(-6) M) were observed among tissues for either age. The lipolytic effect of isoproterenol (10(-6) M) was significantly reduced in adipose tissues from mature rats; in contrast no significant differences in the effect of leptin (10(-6) M) were observed between young and mature rats. In summary, no anatomical-specific differences exist in the response of rat adipose tissue to lipid mobilization induced by leptin. Furthermore, this leptin action is not decreased in mature rats compared with young ones.

Sibutramine decreases body weight gain and increases energy expenditure in obese Zucker rats without changes in NPY and orexins

The aim of the present work was to describe the effects of sibutramine on body weight and adiposity and to establish the potential involvement of neuropeptide Y (NPY) and orexins in the anorectic action of this drug. Male obese Zucker rats were daily administered with sibutramine (10 mg/kg, intraperitoneal) for two weeks. Carcass composition was assessed using the official methods of the Association of Official Analytical Chemists. Total body oxygen consumption was measured daily for 60 min before sibutramine or saline injection and for 30 min (from 60 to 90 min) after drug or saline injection. Hypothalamic arcuate and paraventricular nuclei, and the lateral hypothalamic area were immunostained for NPY, orexin A and orexin B. Commercial kits were used for serum determinations. Reductions in body weight and adipose tissue weights were observed after sibutramine treatment in obese Zucker rats. No changes in NPY immunostaining in the arcuate and paraventricular nuclei were found. Orexin A and orexin B immunostaining was not modified in the lateral hypothalamic area in treated rats. The reduction in body weight and adiposity induced by sibutramine was achieved by both a reduction in food intake and an increase in energy expenditure. NPY and orexins do not seem to be involved in the anorectic effect of sibutramine.

Effects of sodium arsenite exposure on development and behavior in the rat

Arsenic is an environmental contaminant found in soil, water and air in some zones of the world. It has been widely studied for its effects as a human carcinogenic agent, but few studies have dealt with neurobehavioral effects. In addition, studies of arsenic effects on development have only addressed its effects on embryotoxicity and teratogenicity after a single oral, gavage or intraperitoneal exposure. Among the behavioral alterations reported after intoxication with arsenic are both increased and decreased locomotor activity and learning deficits in a delayed alternation task [Toxicol. Lett. 54 (1990) 345; Bull. Environ. Contam. Toxicol. 50 (1993) 100; Brain Res. Bull. 55 (2001) 301]. To further characterize developmental and behavioral alterations induced by arsenic exposure, Sprague-Dawley rats were exposed to arsenite (36.70 mg arsenic/l in drinking water) from gestation day 15 (GD 15) or postnatal day 1 (PND 1), until approximately 4 months old. The pregnant or lactating dams received either the arsenic solution or regular drinking water and once pups were weaned, they continued receiving the same solution as drinking water. Animals exposed from GD 15 showed increased spontaneous locomotor activity and both exposed groups showed increased number of errors in a delayed alternation task in comparison to the control group. Total arsenic (TA) content in brain was similar for both exposed groups and significantly different from the control group. These results indicate that rats exposed to arsenic during development present deficits in spontaneous locomotor activity and alterations in a spatial learning task.

Nefazodone alters NPY immunostaining in rat arcuate-paraventricular projection without changes in food intake and body weight

Nefazodone is an antidepressant drug that inhibits serotonin and noradrenaline reuptake. The aim of the present work was to study the effects of nefazodone on food intake, body weight, adiposity and hypothalamic NPY immunostaining in rats. For this purpose, male Sprague-Dawley rats (3-month-old) were administered with nefazodone (20 mg/kg; i.p) daily for two weeks. The control group was given 0.9% NaCl solution. Hypothalamic arcuate, paraventricular, periventricular, supraoptic and suprachiasmatic nuclei and the lateral hypothalamic area were immunostained for NPY. Chronic nefazodone administration in rats did not modify food intake, body weight and adipose depot size (subcutaneous, perirenal and epididymal white adipose tissues, and interscapular brown adipose tissue). However, a significant decrease in paraventricular NPY immunostaining was found in the nefazodone group compared with the control group. No changes in other hypothalamic regions such as arcuate, periventricular, supraoptic and suprachiasmatic nuclei, and lateral and medial preoptic areas were observed. Because nefazodone is an alpha1-adrenoceptor antagonist, it can be proposed that the expected decrease in food intake after nefazodone administration, due to its effects on NPY arcuate-paraventricular projection, could be masked by the opposite orexigenic effect of alpha1-adrenoceptor blockade.

Dietary fat source regulates ob gene expression in white adipose tissue of rats under hyperphagic feeding

This work was designed to investigate the effect of different lipid sources on ob gene expression and serum leptin levels in rats with two different feeding protocols: (1) free access to food; or (2) energy-controlled feeding. Male Wistar rats were fed diets containing 40 % energy as fat (olive oil, sunflower oil or beef tallow), for 4 weeks. In Expt 1 rats had free access to food, and in Expt 2 rats were fed a controlled amount of food (16 g/d, equivalent to 300 kJ/d). Insulin and leptin were determined by ELISA and ob mRNA by Northern blot. When rats had free access to food, ob mRNA levels were higher in animals fed either olive oil or sunflower oil than in those fed beef tallow. In marked contrast with feeding ad libitum, no differences were found among dietary fat groups in rats fed energy-controlled diets. When both feeding protocols were compared, free access to food induced an increased expression of ob mRNA in perirenal and/or epididymal adipose tissues from rats fed either olive oil or sunflower oil, but not from rats fed beef tallow. Dietary lipid type did not induce modifications in serum leptin concentrations. A tendency to higher serum leptin levels was observed more in rats with free access to food than in rats fed energy-controlled feeding. No differences were found in insulin levels. Dietary fat type importantly affects ob mRNA expression in rat white adipose tissue under hyperphagic conditions. Further study is needed in order to elucidate the mechanism underlying this effect.