Animal models of metabolic syndrome: a review

Metabolic syndrome (MetS) consists of several medical conditions that collectively predict the risk for cardiovascular disease better than the sum of individual conditions. The risk of developing MetS in human depends on synergy of both genetic and environmental factors. Being a multifactorial condition with alarming rate of prevalence nowadays, establishment of appropriate experimental animal models mimicking the disease state in humans is crucial in order to solve the difficulties in evaluating the pathophysiology of MetS in human. This review aims to summarize the underlying mechanisms involved in the pathophysiology of dietary, genetic, and pharmacological models of MetS. Furthermore, we will discuss the usefulness, suitability, pros and cons of these animal models. Even though numerous animal models of MetS have been established, further investigations on the invention of new animal model and clarification of plausible mechanisms are still necessary to confer a better understanding to researchers on the selection of animal models for their studies.

Sugar Transporters in Plants: New Insights and Discoveries

Carbohydrate partitioning is the process of carbon assimilation and distribution from source tissues, such as leaves, to sink tissues, such as stems, roots and seeds. Sucrose, the primary carbohydrate transported long distance in many plant species, is loaded into the phloem and unloaded into distal sink tissues. However, many factors, both genetic and environmental, influence sucrose metabolism and transport. Therefore, understanding the function and regulation of sugar transporters and sucrose metabolic enzymes is key to improving agriculture. In this review, we highlight recent findings that (i) address the path of phloem loading of sucrose in rice and maize leaves; (ii) discuss the phloem unloading pathways in stems and roots and the sugar transporters putatively involved; (iii) describe how heat and drought stress impact carbohydrate partitioning and phloem transport; (iv) shed light on how plant pathogens hijack sugar transporters to obtain carbohydrates for pathogen survival, and how the plant employs sugar transporters to defend against pathogens; and (v) discuss novel roles for sugar transporters in plant biology. These exciting discoveries and insights provide valuable knowledge that will ultimately help mitigate the impending societal challenges due to global climate change and a growing population by improving crop yield and enhancing renewable energy production.

The Evidence for Saturated Fat and for Sugar Related to Coronary Heart Disease

Dietary guidelines continue to recommend restricting intake of saturated fats. This recommendation follows largely from the observation that saturated fats can raise levels of total serum cholesterol (TC), thereby putatively increasing the risk of atherosclerotic coronary heart disease (CHD). However, TC is only modestly associated with CHD, and more important than the total level of cholesterol in the blood may be the number and size of low-density lipoprotein (LDL) particles that contain it. As for saturated fats, these fats are a diverse class of compounds; different fats may have different effects on LDL and on broader CHD risk based on the specific saturated fatty acids (SFAs) they contain. Importantly, though, people eat foods, not isolated fatty acids. Some food sources of SFAs may pose no risk for CHD or possibly even be protective. Advice to reduce saturated fat in the diet without regard to nuances about LDL, SFAs, or dietary sources could actually increase people's risk of CHD. When saturated fats are replaced with refined carbohydrates, and specifically with added sugars (like sucrose or high fructose corn syrup), the end result is not favorable for heart health. Such replacement leads to changes in LDL, high-density lipoprotein (HDL), and triglycerides that may increase the risk of CHD. Additionally, diets high in sugar may induce many other abnormalities associated with elevated CHD risk, including elevated levels of glucose, insulin, and uric acid, impaired glucose tolerance, insulin and leptin resistance, non-alcoholic fatty liver disease, and altered platelet function. A diet high in added sugars has been found to cause a 3-fold increased risk of death due to cardiovascular disease, but sugars, like saturated fats, are a diverse class of compounds. The monosaccharide, fructose, and fructose-containing sweeteners (e.g., sucrose) produce greater degrees of metabolic abnormalities than does glucose (either isolated as a monomer, or in chains as starch) and may present greater risk of CHD. This paper reviews the evidence linking saturated fats and sugars to CHD, and concludes that the latter is more of a problem than the former. Dietary guidelines should shift focus away from reducing saturated fat, and from replacing saturated fat with carbohydrates, specifically when these carbohydrates are refined. To reduce the burden of CHD, guidelines should focus particularly on reducing intake of concentrated sugars, specifically the fructose-containing sugars like sucrose and high-fructose corn syrup in the form of ultra-processed foods and beverages.

Effect of drought stress on sugar metabolism in leaves and roots of soybean seedlings

Sucrose is the main photosynthetic product in plants, and acts as a major energy substrate and signaling regulator of plant growth. Furthermore, sucrose is involved in the responses to various abiotic stresses. However, the role of sucrose in soybean (Glycine max L.) growth and development under drought stress remains largely unknown. In this study, the two soybean cultivars, Shennong8 (CV.SN8) and Shennong12 (CV.SN12), were grown in pot culture and subjected to three water treatments for 15 days: soil moisture contents of 75 ± 5% (CK), 45 ± 5% (MD), and 30 ± 5% (SD) of field capacity. Under drought stress, the reduction in shoot biomass was more pronounced than the reduction of biomass in the root of both soybean cultivars, resulting in higher root/shoot (R/S) ratio. Drought stress increased the contents of soluble sugar and sucrose in the leaves, but decreased starch content; in the roots, all of these parameters were increased. This may be related to the enhanced carbohydrate metabolism activity under drought stress, including notable changes in the activities of sugar metabolism enzymes and expression levels of GmSPS, GmSuSy, GmC-INV, GmA-INV, GmAMY3, and GmBAM1. Furthermore, the expression levels of sucrose transporter genes (GmSUC2, GmSWEET6, and GmSWEET15) in leaves and roots of soybean seedlings were up-regulated under drought stress. In conclusion, our results highlight that the increase in R/S ratio caused by the changes of sugar allocation, metabolism, and transport under drought stress contributes towards drought resistance of soybean.

Simultaneous separation and determination of fructose, sorbitol, glucose and sucrose in fruits by HPLC-ELSD

A high-performance liquid chromatography (HPLC) method with evaporative light scattering detection (ELSD) was optimised for simultaneous determination of fructose, sorbitol, glucose and sucrose in fruits. The analysis was carried out on a Phenomenex Luna 5u NH₂ 100A column (250 mm × 4.60mm, 5 micron) with isocratic elution of acetonitrile:water (82.5:17.5, v/v). Drift tube temperature of the ELSD system was set to 82 °C and nitrogen flow rate was 2.0 L min⁻¹. The regression equation revealed good linear relationship (R = 0.9967-0.9989) within test ranges. The limits of detection (LOD) and quantification (LOQ) for four analytes (peach, apple, watermelon, and cherry fruits) were in the range of 0.07-0.27 and 0.22-0.91 mg L⁻¹, respectively. The proposed HPLC-ELSD method was validated for quantification of sugars in peach, apple, watermelon, and cherry fruits, and the results were satisfactory. The results showed that the contents of the four sugars varied among fruits. While fructose (5.79-104.01 mg g⁻¹) and glucose (9.25-99.62 mg g⁻¹) emerged as common sugars in the four fruits, sorbitol (8.70-19.13 mg g⁻¹) were only found in peach, apple and cherry fruits, and sucrose (15.82-106.39 mg g⁻¹) were in peach, apple and watermelon. There was not detectable sorbitol in watermelon and sucrose in cherry fruits, respectively.

Fructose content in popular beverages made with and without high-fructose corn syrup

OBJECTIVE

Excess fructose consumption is hypothesized to be associated with risk for metabolic disease. Actual fructose consumption levels are difficult to estimate because of the unlabeled quantity of fructose in beverages. The aims of this study were threefold: 1) re-examine the fructose content in previously tested beverages using two additional assay methods capable of detecting other sugars, especially maltose, 2) compare data across all methods to determine the actual free fructose-to-glucose ratio in beverages made either with or without high-fructose corn syrup (HFCS), and 3) expand the analysis to determine fructose content in commonly consumed juice products.

METHODS

Sugar-sweetened beverages (SSBs) and fruit juice drinks that were either made with or without HFCS were analyzed in separate, independent laboratories via three different methods to determine sugar profiles.

RESULTS

For SSBs, the three independent laboratory methods showed consistent and reproducible results. In SSBs made with HFCS, fructose constituted 60.6% ± 2.7% of sugar content. In juices sweetened with HFCS, fructose accounted for 52.1% ± 5.9% of sugar content, although in some juices made from 100% fruit, fructose concentration reached 65.35 g/L accounting for 67% of sugars.

CONCLUSION

Our results provide evidence of higher than expected amounts of free fructose in some beverages. Popular beverages made with HFCS have a fructose-to-glucose ratio of approximately 60:40, and thus contain 50% more fructose than glucose. Some pure fruit juices have twice as much fructose as glucose. These findings suggest that beverages made with HFCS and some juices have a sugar profile very different than sucrose, in which amounts of fructose and glucose are equivalent. Current dietary analyses may underestimate actual fructose consumption.

Sucrose signaling in higher plants

Sucrose controls various developmental and metabolic processes in plants. In this review, we evaluate whether sucrose could be a preferred signaling molecule that controls processes like carbohydrate metabolism, accumulation of storage proteins, sucrose transport, anthocyanin accumulation, and floral induction. We summarize putative sucrose-dependent signaling pathways. Sucrose, but not other sugars, stimulates the genes that encode ADP-glucose pyrophosphorylase (AGPase), granule-bound starch synthase I, and UDP-glucose pyrophosphorylase in several species. The class-1 patatin promoter is induced under high sucrose conditions in potato (Solanum tuberosum). Exogenous sucrose reduces the loading of sucrose to the phloem by inhibiting the expression of the sucrose transporter and its protein activity in sugar beet (Beta vulgaris). Sucrose also influences a wide range of growth processes, including cell division, ribosome synthesis, cotyledon development, far-red light signaling, and tuber development. Floral induction is promoted by sucrose in several species. The molecular mechanisms by which sucrose functions as a signal are largely unknown. Sucrose enhances the expression of transcription factors such as AtWRKY20 and MYB75, which function upstream of the sucrose-responsive genes. Sucrose controls the expression of AtbZIP11 at the post-transcriptional level by the peptide encoded by uORF2. Sucrose levels affect translation of a group of mRNAs in Arabidopsis. Sucrose increases the activity of AGPase by posttranslational redox-modification. Sucrose interrupts the interaction between sucrose transporter SUT4 and cytochrome b5. In addition, the SNF-related protein kinase-1 appears to be involved in sucrose-dependent pathways by controlling sucrose synthase (SUS4) expression.

A review of recent evidence relating to sugars, insulin resistance and diabetes

The potential impact on health of diets rich in free sugars, and particularly fructose, is of major concern. The focus of this review is the impact of these sugars on insulin resistance and obesity, and the associated risk of developing type 2 diabetes. Much of the concern is focussed on specific metabolic effects of fructose, which are argued to lead to increased fat deposition in the liver and skeletal muscle with subsequent insulin resistance and increased risk of diabetes. However, much of the evidence underpinning these arguments is based on animal studies involving very large intakes of the free sugars. Recent human studies, in the past 5 years, provide a rather different picture, with a clear dose response link between fructose intake and metabolic changes. In particular, the most marked effects are observed when a high sugars intake is accompanied by an excess energy intake. This does not mean that a high intake of free sugars does not have any detrimental impact on health, but rather that such an effect seems more likely to be a result of the high sugars intake increasing the chances of an excessive energy intake rather than it leading to a direct detrimental effect on metabolism.

The rheological properties of tara gum (Caesalpinia spinosa)

The rheological properties of tara gum, as affected by concentration, temperature, pH and the presence of salts and sucrose, were investigated by using steady and dynamic shear measurements and atomic force microscope observation. Tara gum exhibited non-Newtonian, pseudoplastic behaviour without thixotropy at tested concentrations (0.2-1.0%, w/v). Salts (CaCl2 and NaCl) led to a viscosity reduction, which was more sensitive to Ca(2+) than to Na(+). The gum had stable viscosity over a wide pH range (pH 3-11), and the influence of sucrose was concentration dependent. Increasing temperature from 20°C to 80°C decreased the gum viscosity. Frequency sweeps indicated that tara gum (1.0% w/v) behaved as a liquid at low frequency, and acted more like a gel at high frequency. With the decrease of concentration, tara gum may show a viscous property rather than an elastic one. These results are potentially useful for the application of tara gum in food processing.

Pediatric pain treatment and prevention for hospitalized children

Introduction:

Prevention and treatment of pain in pediatric patients compared with adults is often not only inadequate but also less often implemented the younger the children are. Children 0 to 17 years are a vulnerable population.

Objectives:

To address the prevention and treatment of acute and chronic pain in children, including pain caused by needles, with recommended analgesic starting doses.

Methods:

This Clinical Update elaborates on the 2019 IASP Global Year Against Pain in the Vulnerable “Factsheet Pain in Children: Management” and reviews best evidence and practice.

Results:

Multimodal analgesia may include pharmacology (eg, basic analgesics, opioids, and adjuvant analgesia), regional anesthesia, rehabilitation, psychological approaches, spirituality, and integrative modalities, which act synergistically for more effective acute pediatric pain control with fewer side effects than any single analgesic or modality. For chronic pain, an interdisciplinary rehabilitative approach, including physical therapy, psychological treatment, integrative mind–body techniques, and normalizing life, has been shown most effective. For elective needle procedures, such as blood draws, intravenous access, injections, or vaccination, overwhelming evidence now mandates that a bundle of 4 modalities to eliminate or decrease pain should be offered to every child every time: (1) topical anesthesia, eg, lidocaine 4% cream, (2) comfort positioning, eg, skin-to-skin contact for infants, not restraining children, (3) sucrose or breastfeeding for infants, and (4) age-appropriate distraction. A deferral process (Plan B) may include nitrous gas analgesia and sedation.

Conclusion:

Failure to implement evidence-based pain prevention and treatment for children in medical facilities is now considered inadmissible and poor standard of care.

Modelling depression in animals: at the interface of reward and stress pathways

RATIONALE

Despite substantial research efforts the aetiology of major depressive disorder (MDD) remains poorly understood, which is due in part to the heterogeneity of the disorder and the complexity of designing appropriate animal models. However, in the last few decades, a focus on the development of novel stress-based paradigms and a focus on using hedonic/anhedonic behaviour have led to renewed optimism in the use of animal models to assess aspects of MDD.

OBJECTIVES

Therefore, in this review article, dedicated to Athina Markou, we summarise the use of stress-based animal models for studying MDD in rodents and how reward-related readouts can be used to validate/assess the model and/or treatment.

RESULTS

We reveal the use and limitations of chronic stress paradigms, which we split into non-social (i.e. chronic mild stress), social (i.e. chronic social defeat) and drug-withdrawal paradigms for studying MDD and detail numerous reward-related readouts that are employed in preclinical research. Finally, we finish with a section regarding important factors to consider when using animal models.

CONCLUSIONS

One of the most consistent findings following chronic stress exposure in rodents is a disruption of the brain reward system, which can be easily assessed using sucrose, social interaction, food, drug of abuse or intracranial self-stimulation as a readout. Probing the underlying causes of such alterations is providing a greater understanding of the potential systems and processes that are disrupted in MDD.

Effects of sucrose amendment on ammonia assimilation during sewage sludge composting

The aim of this study was to evaluate the laboratory-scale composting of sewage sludge and pumice mixtures that were amended with sucrose. The variation in temperature, pH, NH4(+)-N, ammonia emission, bacterial community, ammonia assimilating bacteria (AAB) populations and enzymatic activity related to ammonia assimilation were detected. The addition of sucrose increased the AAB population by 2.5-3.5 times, reduced ammonia emission by 24.7-31.1% compared with the control treatment, and promoted the growth of Bacillus and Wautersiella. The activities of glutamate dehydrogenase (GDH), glutamate synthase (GS) and glutamine synthetase (GOGAT), were enhanced by the addition of sucrose. GDH made a substantial contribution to ammonia assimilation when the ammonia concentration was high (⩾1.5g/kg) in the thermophilic phase. The GS/GOGAT cycle played an important role at low ammonia concentrations (⩽1.1g/kg) in the cooling phase. These results suggested that adding sucrose to sludge compost could promote ammonia assimilation and reduce ammonia emission.

Raffinose oligosaccharide concentrations measured in individual cell and tissue types in Cucumis melo L. leaves: implications for phloem loading

Raffinose, stachyose, and galactinol are synthesized in intermediary cells (specialized companion cells) of the minor-vein phloem of cucurbits. To better understand the role of these carbohydrates and the regulation of their synthesis and transport, we measured the concentrations of each of the components of the raffinose oligosaccharide synthetic pathway in mesophyll and sieve element-intermediary cell complexes (SE-ICCs) in the leaves of melon (Cucumis melo L. cv. Hale's Best Jumbo). These concentrations are consistent with a polymer-trapping mechanism for phloem loading, with sucrose diffusing from mesophyll into intermediary cells and being made into raffinose and stachyose, which are too large to diffuse back to the mesophyll. To determine carbohydrate concentrations, we developed a method involving microdissected tissues. Blind endings of areoles, and mesophyll surrounding these veins, were separately removed from lyophilized leaf tissue. Carbohydrates were quantitated by high-performance liquid chromatography with pulsed amperometric detection. A small amount of mesophyll remained attached to the blind endings; the carbohydrate contribution of these cells to the vein sample was eliminated by subtraction, based on the amount of chlorophyll. Volumes of cells and subcellular compartments were calculated by morphometric analysis and were used to calculate carbohydrate concentrations. Assuming no subcellular compartmentation, the additive concentration of sugars in the SE-ICCs of minor veins is about 600 mM. Stachyose and raffinose concentrations are about 330 mM and 70 mM, respectively, in SE-ICCs; concentrations of these sugars are much lower in mesophyll (0.2 and 0.1 mM). This is consistent with the view that stachyose and raffinose are unable to pass through the plasmodesmata between intermediary cells and bundle-sheath cells. Sucrose levels appear to be higher in the SE-ICC (about 130mM) than in the mesophyll (about 10 mM), but if compartmentation is taken into account the gradient for sucrose is probably downhill from mesophyll to intermediary cells. Flux through plasmodesmata between the bundle sheath and intermediary cells was calculated and was found to be within the range of values of flux through plasmodesmata reported in the literature.

Simultaneous determination of glucose, fructose, sucrose and sorbitol in the leaf and fruit peel of different apple cultivars by the HPLC-RI optimized method

A high performance liquid chromatography method with refractive index detection (HPLC-RI), for simultaneous determination of glucose, fructose, sucrose and sorbitol in leaf and/or apple peel samples from nine apple (Malus domestica Borkh.) cultivars and rootstocks, originating from a germplasm collection, has been developed and validated. Box-Behnken design of response surface methodology was applied for the method optimization. The Carbosep Coregel 87H3 column was used under the optimum conditions predicted: mobile phase of H2SO4 0.005 mol L(-1) solution, flow rate of 0.3 mL min(-1) and column temperature of 35°C. The method was validated for linearity (R(2)>0.99), limits of detection (2.67-4.83 μg mL(-1)) and quantification (8.9-16.1 μg mL(-1)), precision (%RSD<5.05) and recovery (93.94-103.06%) and satisfactory results obtained. The sugars content varied across micropropagated plants in vitro, plants regenerated after cryostorage, growing trees in vivo, and fruit peel.

Physicochemical properties and sensory evaluation of fructoligosaccharide enriched cookies

Short dough cookies were enriched with fructoligosaccharide (FOS), a prebiotic soluble fiber and a low calorie sweetener, at levels of 40%, 60%, and 80% sugar replacement basis. Cookies were analyzed for diameter, height, spread ratio, hardness, moisture and acidity of the extracted fat. The mean peak force at 0 month was determined to be 7139 ± 166 g, 7109 ± 75 g, 6970 ± 24 g and 6538 ± 128 g for control (100% sucrose), 40%, 60% and 80% sugar replacement levels cookies respectively. The spread ratio of control cookies was found to be 4.400 and that of FOS based cookies at 40%, 60% and 80% sugar replacement levels was found to be 4.520, 4.983 and 5.205, respectively. Sensory data on a 9 point hedonic scale indicated that the panelists liked FOS cookies (up to 60% sugar replacement) over control cookies because of improved color, texture and appearance. The total fiber content (including oligofructose) of cookies (60% sugar replacement) was 12.1%. As per FDA these cookies can be categorized as 'Good Source' of fiber. Thus, FOS appears to be suitable as a partial replacer of sucrose up to 60% providing increase in the dietary fiber and reduction in the caloric content of cookies.

Leptin modulates nutrient reward via inhibitory galanin action on orexin neurons

Objective

Leptin modulates food reward via central leptin receptor (LepRb) expressing neurons. Food reward requires stimulation of midbrain dopamine neurons and is modulated by central leptin action, but the exact central mechanisms remain unclear. Stimulatory and inhibitory leptin actions on dopamine neurons have been reported, e.g. by indirect actions on orexin neurons or via direct innervation of dopamine neurons in the ventral tegmental area.

Methods

We showed earlier that LepRb neurons in the lateral hypothalamus (LHA) co-express the inhibitory acting neuropeptide galanin (GAL-LepRb neurons). We studied the involvement of GAL-LepRb neurons to regulate nutrient reward in mice with selective LepRb deletion from galanin neurons (GAL-LepRb^KO mice).

Results

We found that the rewarding value and preference for sucrose over fat was increased in GAL-LepRb^KO mice compared to controls. LHA GAL-LepRb neurons innervate orexin neurons, but not the VTA. Further, expression of galanin and its receptor GalR1 are decreased in the LHA of GAL-LepRb^KO mice, resulting in increased activation of orexin neurons.

Conclusion

We suggest galanin as an important mediator of leptin action to modulate nutrient reward by inhibiting orexin neurons.

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GAL-LepRb^KO shows ↓ galanin and ↓ GalR1 mRNA, ↑ body weight gain.

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GAL-LepRb^KO shows ↑ orexin/hypocretin neuronal activation.

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GAL-LepRb neurons innervate local orexin/hypocretin and noradrenergic locus coeruleus neurons.

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Leptin regulates natural reward and body weight via GAL-LepRb neurons.

The minimally effective dose of sucrose for procedural pain relief in neonates: a randomized controlled trial

Background

Orally administered sucrose is effective and safe in reducing pain intensity during single, tissue-damaging procedures in neonates, and is commonly recommended in neonatal pain guidelines. However, there is wide variability in sucrose doses examined in research, and more than a 20-fold variation across neonatal care settings. The aim of this study was to determine the minimally effective dose of 24% sucrose for reducing pain in hospitalized neonates undergoing a single skin-breaking heel lance procedure.

Methods

A total of 245 neonates from 4 Canadian tertiary neonatal intensive care units (NICUs), born between 24 and 42 weeks gestational age (GA), were prospectively randomized to receive one of three doses of 24% sucrose, plus non-nutritive sucking/pacifier, 2 min before a routine heel lance: 0.1 ml (Group 1; n = 81), 0.5 ml (Group 2; n = 81), or 1.0 ml (Group 3; n = 83). The primary outcome was pain intensity measured at 30 and 60 s following the heel lance, using the Premature Infant Pain Profile-Revised (PIPP-R). The secondary outcome was the incidence of adverse events. Analysis of covariance models, adjusting for GA and study site examined between group differences in pain intensity across intervention groups.

Results

There was no difference in mean pain intensity PIPP-R scores between treatment groups at 30 s (P = .97) and 60 s (P = .93); however, pain was not fully eliminated during the heel lance procedure. There were 5 reported adverse events among 5/245 (2.0%) neonates, with no significant differences in the proportion of events by sucrose dose (P = .62). All events resolved spontaneously without medical intervention.

Conclusions

The minimally effective dose of 24% sucrose required to treat pain associated with a single heel lance in neonates was 0.1 ml. Further evaluation regarding the sustained effectiveness of this dose in reducing pain intensity in neonates for repeated painful procedures is warranted.

Trial registration

ClinicalTrials.gov: NCT02134873. Date: May 5, 2014 (retrospectively registered).

Correlation between the composition of green Arabica coffee beans and the sensory quality of coffee brews

This research aimed to correlate the composition of green Arabica coffee beans with the sensory quality coffee brews. The chemical composition of green Arabica coffee bean (66 samples) from three coffee quality contests was analyzed by near-infrared spectroscopy. Coffee brews with lower quality scores were correlated with high levels of caffeine, protein, chlorogenic acids and total titratable acidity (TTA) in the green coffee beans. High sucrose/TTA and cafestol/kahweol ratios in the green coffee beans were usually associated with higher scores for the coffee brews. By multivariate analysis techniques, the samples were separated into groups according to production years indicating a strong influence of the environmental conditions on the chemical composition. The profile of the composition of the crude coffee can be indicative of the sensory quality of the coffee brews, relevant information for producers and industry since the green beans are the material used for trading and purchasing coffee.

Mimicking lichens: incorporation of yeast strains together with sucrose-secreting cyanobacteria improves survival, growth, ROS removal, and lipid production in a stable mutualistic co-culture production platform

BACKGROUND

The feasibility of heterotrophic-phototrophic symbioses was tested via pairing of yeast strains Cryptococcus curvatus, Rhodotorula glutinis, or Saccharomyces cerevisiae with a sucrose-secreting cyanobacterium Synechococcus elongatus.

RESULTS

The phototroph S. elongatus showed no growth in standard BG-11 medium with yeast extract, but grew well in BG-11 medium alone or supplemented with yeast nitrogen base without amino acids (YNB w/o aa). Among three yeast species, C. curvatus and R. glutinis adapted well to the BG-11 medium supplemented with YNB w/o aa, sucrose, and various concentrations of NaCl needed to maintain sucrose secretion from S. elongatus, while growth of S. cerevisiae was highly dependent on sucrose levels. R. glutinis and C. curvatus grew efficiently and utilized sucrose produced by the partner in co-culture. Co-cultures of S. elongatus and R. glutinis were sustained over 1 month in both batch and in semi-continuous culture, with the final biomass and overall lipid yields in the batch co-culture 40 to 60% higher compared to batch mono-cultures of S. elongatus. The co-cultures showed enhanced levels of palmitoleic and linoleic acids. Furthermore, cyanobacterial growth in co-culture with R. glutinis was significantly superior to axenic growth, as S. elongatus was unable to grow in the absence of the yeast partner when cultivated at lower densities in liquid medium. Accumulated reactive oxygen species was observed to severely inhibit axenic growth of cyanobacteria, which was efficiently alleviated through catalase supply and even more effectively with co-cultures of R. glutinis.

CONCLUSIONS

The pairing of a cyanobacterium and eukaryotic heterotroph in the artificial lichen of this study demonstrates the importance of mutual interactions between phototrophs and heterotrophs, e.g., phototrophs provide a carbon source to heterotrophs, and heterotrophs assist phototrophic growth and survival by removing/eliminating oxidative stress. Our results establish a potential stable production platform that combines the metabolic capability of photoautotrophs to capture inorganic carbon with the channeling of the resulting organic carbon directly to a robust heterotroph partner for producing biofuel and other chemical precursors.

Further studies on sugar transporter (SWEET) genes in wheat (Triticum aestivum L.)

SWEET proteins represent one of the largest sugar transporter family in the plant kingdom and play crucial roles in plant development and stress responses. In the present study, a total of 108 TaSWEET genes distributed on all the 21 wheat chromosomes were identified using the latest whole genome sequence (as against 59 genes reported in an earlier report). These 108 genes included 14 of the 17 types reported in Arabidopsis and also included three novel types. Tandem duplications (22) and segmental duplications (5) played a significant role in the expansion of TaSWEET family. A number of cis-elements were also identified in the promoter regions of TaSWEET genes, indicating response of TaSWEET genes during development and also during biotic/abiotic stresses. The TaSWEET proteins carried 4-7 trans-membrane helices (TMHs) showing diversity in structure. Phylogenetic analysis using SWEET proteins of wheat and 8 other species gave four well-known clusters. Expression analysis involving both in silico and in planta indicated relatively higher expression of TaSWEET genes in water/heat sensitive and leaf rust resistant genotypes. The results provided insights into the functional role of TaSWEETs in biotic and abiotic stresses, which may further help in planning strategies to develop high yielding wheat varieties tolerant to environmental stresses.

Effect of altitude on biochemical composition and quality of green arabica coffee beans can be affected by shade and postharvest processing method

Although various studies have assessed altitude, shade and postharvest processing effects on biochemical content and quality of coffee beans, data on their interactions are scarce. The individual and interactive effects of these factors on the caffeine, chlorogenic acids (CGA) and sucrose contents as well as physical and sensory qualities of green coffee beans from large plantations in southwestern Ethiopia were evaluated. Caffeine and CGA contents decreased with increasing altitude; they respectively declined 0.12 and 1.23gkg^-1 100m^-1. Sucrose content increased with altitude; however, the altitude effect was significant for wet-processed beans (3.02gkg^-1 100m^-1), but not for dry-processed beans (0.36g kg^-1 100m^-1). Similarly, sucrose content increased with altitude with much stronger effect for coffee grown without shade (2.11gkg^-1 100m^-1) compared to coffee grown under shade (0.93gkg^-1 100m^-1). Acidity increased with altitude when coffee was grown under shade (0.22 points 100m^-1), but no significant altitude effect was observed on coffee grown without shade. Beans grown without shade showed a higher physical quality score for dry (37.2) than for wet processing (29.1). These results generally underline the complex interaction effects between altitude and shade or postharvest processing on biochemical composition and quality of green arabica coffee beans.

Choosing voluntary exercise over sucrose consumption depends upon dopamine transmission: effects of haloperidol in wild type and adenosine A₂AKO mice

RATIONALE

Mesolimbic dopamine (DA) regulates behavioral activation and effort-related decision-making in motivated behaviors. Mesolimbic DA D2 receptors are co-localized with adenosine A2A receptors, and they interact in an antagonistic manner.

OBJECTIVES

A T-maze task was developed to assess dopaminergic involvement in preference between a reinforcer that involves vigorous voluntary activity (running wheel) and a reinforcer that requires minimal behavioral activation (sucrose pellets). Haloperidol (D2 antagonist) was administered to adenosine A2A receptor knockout (A2AKO) and wild-type (WT) littermate controls to assess the involvement of these two receptors in the selection of running wheel activity versus sucrose consumption.

RESULTS

Under control conditions, mice spent more time running and less time eating. In WT mice, haloperidol reduced time running but actually increased time-consuming sucrose. However, A2AKO mice did not show the haloperidol-induced shift from running wheel activity to sucrose intake. Prefeeding reduced sucrose consumption in the T-maze in both strains, indicating that this paradigm is sensitive to motivational devaluation. Haloperidol increased c-Fos immunoreactivity in anterior cingulate cortex (ACg) and nucleus accumbens (Acb) core of WT but not KO mice.

CONCLUSIONS

These results indicate that after DA antagonism, the preference for vigorous physical activity is reduced, while palatable food selection increases. Adenosine A2A receptor deletion provides resistance to these effects of D2 receptor antagonism. These two receptors in Acb core and ACg seem to be involved in the regulation of the intrinsic reinforcing characteristics of voluntary exercise but not in the regulation of the primary reinforcing characteristics of palatable sedentary reinforcers.

High-fructose corn syrup-55 consumption alters hepatic lipid metabolism and promotes triglyceride accumulation

High-fructose corn syrup-55 (HFCS-55) has been suggested to be more lipogenic than sucrose, which increases the risk for nonalcoholic fatty liver disease (NAFLD) and dyslipidemia. The study objectives were to determine the effects of drinking different sugar-sweetened solutions on hepatic gene expression in relation to liver fatty acid composition and risk of NAFLD. Female rats were randomly assigned (n=7 rats/group) to drink water or water sweetened with 13% (w/v) HFCS-55, sucrose or fructose for 8 weeks. Rats drinking HFCS-55 solution had the highest (P=.03) hepatic total lipid and triglyceride content and histological evidence of fat infiltration. Rats drinking HFCS-55 solution had the highest hepatic de novo lipogenesis indicated by the up-regulation of stearoyl-CoA desaturase-1 and the highest (P<.001) oleic acid (18:1n-9) content. This was accompanied by reduced β-oxidation indicated by down-regulation of hepatic peroxisome proliferator-activated receptor α. Disposal of excess lipids by export of triglyceride-rich lipoprotein from the liver was increased as shown by up-regulation of gene expression of microsomal triglyceride transfer protein in rats drinking sucrose, but not HFCS-55 solution. The observed lipogenic effects were attributed to the slightly higher fructose content of HFCS-55 solution in the absence of differences in macronutrient and total caloric intake between rats drinking HFCS-55 and sucrose solution. Results from gene expression and fatty acid composition analysis showed that, in a hypercaloric state, some types of sugars are more detrimental to the liver. Based on these preclinical study results, excess consumption of caloric sweetened beverage, particularly HFCS-sweetened beverages, should be limited.

The highly selective orexin/hypocretin 1 receptor antagonist GSK1059865 potently reduces ethanol drinking in ethanol dependent mice

The orexin/hypocretin (ORX) system plays a major role in motivation for natural and drug rewards. In particular, a number of studies have shown that ORX signaling through the orexin 1 receptor (OX1R) regulates alcohol seeking and consumption. Despite the association between ORX signaling and motivation for alcohol, no study to date has investigated what role the ORX system plays in alcohol dependence, an understanding of which would have significant clinical relevance. This study was designed to evaluate the effect of the highly selective OX1R antagonist GSK1059865 on voluntary ethanol intake in ethanol-dependent and control non-dependent mice. Mice were subjected to a protocol in which they were evaluated for baseline ethanol intake and then exposed to intermittent ethanol or air exposure in inhalation chambers. Each cycle of chronic intermittent ethanol (CIE), or air, exposure was followed by a test of ethanol intake. Once the expected effect of increased voluntary ethanol intake was obtained in ethanol dependent mice, mice were tested for the effect of GSK1059865 on ethanol and sucrose intake. Treatment with GSK1059865 significantly decreased ethanol drinking in a dose-dependent manner in CIE-exposed mice. In contrast GSK1059865 decreased drinking in air-exposed mice only at the highest dose used. There was no effect of GSK1059865 on sucrose intake. Thus, ORX signaling through the OX1R, using a highly-selective antagonist, has a profound influence on high levels of alcohol drinking induced in a dependence paradigm, but limited or no influence on moderate alcohol drinking or sucrose drinking. These results indicate that the ORX system may be an important target system for treating disorders of compulsive reward seeking such as alcoholism and other addictions in which motivation is strongly elevated.

Response of sugar metabolism in apple leaves subjected to short-term drought stress

For a comprehensive understanding of gene expression, enzyme activity and sugar concentrations in response to short-term water deficit in apple (Greensleeves), sugar-modulated gene expression and enzyme activities were analyzed. Water stress resulted in the accumulation of sorbitol, glucose, fructose, galactose and starch, accompanied by a significant reduction in photosynthesis and sucrose concentration. In response to short-term water deficits, the activities of aldose-6-phosphate reductase (A6PR; EC 1.1.1.200), sorbitol dehydrogenase (SDH; EC 1.1.1.14), neutral invertase (NINV; EC 3.2.1.26), sucrose synthase (SUSY; EC 2.4.1.13), and fructokinase (FK; EC 2.7.1.4) were higher, whereas cell wall invertase (CWINV; EC 3.2.1.26) and hexokinase (HK; EC 2.7.1.1) activities were lower. In addition, sucrose phosphate synthase (SPS; EC 2.4.1.14) activity increased during the initial stages of dehydration and then decreased as the drought strengthened. Transcript levels of MdA6PR, MdSDH1/2, MdNINV1/2, MdSUSY3, MdFK1/2/4, MdSOT1/2, MdSUC1-3, MdTMT2/3, MdvGT1, MdpGlcT1-4 were upregulated, whereas transcript levels of MdCWINV1/2, MdHK1/2/3/5, and MdTMT1 were downregulated after 6 days of water stress. These findings suggest that the sorbitol metabolism pathway is induced and high levels of hexose derived from photosynthetic products are transported into vacuoles for adjustment to the water deficit. Our results provide insights into the relationships between sugar levels and sugar-modulated gene and enzyme activity in response to the imposition of short-term water stress.