Hepato-splanchnic fluxes during exercise in patients with cirrhosis-a pilot study.

In cirrhotic patients, compromised hepatocyte function combined with disturbed hepatic blood flow could affect hepato-splanchnic substrate and metabolite fluxes and exacerbate fatigue during exercise. Eight cirrhotic patients performed incremental cycling trials (3 × 10 min; at light (28 [19-37] W; median with range), moderate (55 [41-69] W), and vigorous (76 [50-102] W) intensity). Heart rate increased from 68 (62-74) at rest to 95 (90-100), 114 (108-120), and 140 (134-146) beats/min (P < 0.05), respectively. The hepatic blood flow, as determined by constant infusion of indocyanine green with arterial and hepatic venous sampling, declined from 1.01 (0.75-1.27) to 0.69 (0.47-0.91) L/min (P < 0.05). Hepatic glucose output increased from 0.6 (0.5-0.7) to 1.5 (1.3-1.7) mmol/min, while arterial lactate increased from 0.8 (0.7-0.9) to 9.0 (8.1-9.9) mmol/L (P < 0.05) despite a rise in hepatic lactate uptake. Arterial ammonia increased in parallel to lactate from 47.3 (40.1-54.5) to 144.4 (120.5-168.3) µmol/L (P < 0.05), although hepatic ammonia uptake increased from 19.5 (12.4-26.6) to 69.5 (46.5-92.5) µmol/min (P < 0.05). Among the 14 amino acids measured, glutamate was released in the liver, while the uptake of free fatty acids decreased. During exercise at relatively low workloads, arterial lactate and ammonia levels were comparable to those seen in healthy subjects at higher workloads, while euglycemia was maintained due to sufficient hepatic glucose production. The accumulation of lactate and ammonia may contribute to exercise intolerance in patients with cirrhosis.

Seaweed soluble dietary fibre replacement modulates the metabolite release of cakes after in vitro digestion.

Soluble dietary fibre (SDF) has gained growing interest because of its multiple functional and nutritional benefits. In the current study, the effect of SDF extracted from eucheuma seaweed on both the physicochemical properties and the released metabolites of yellow cakes was evaluated systematically. The results revealed that the addition of SDF induced increases in specific gravity, specific volume and water content of yellow cakes, and caused a decrease in weight loss and changes in texture and colour. In addition, sensory evaluation showed that up to 10 % substitution of flour with SDF was acceptable. In vitro digestion of cakes demonstrated that flour substitution with SDF at different levels (8 %-14 %) significantly reduced the release of glucose, ranging from 11.24 % to 29.12 %. In addition to the increased apparent viscosity of the cake digesta, the metabolite analysis based on nuclear magnetic resonance spectroscopy identified a total of 29 metabolites, including amino acids, fatty acids and sugars. Notably, the addition of SDF reduced the release of amino acids and fatty acids after digestion. These findings suggested that seaweed SDF was a potential substitute for some food components, which would provide functional benefits to the digestive characteristics.

Effects of the kinetic pattern of dietary glucose release on nitrogen utilization, the portal amino acid profile, and nutrient transporter expression in intestinal enterocytes in piglets.

BACKGROUND: Promoting the synchronization of glucose and amino acid release in the digestive tract of pigs could effectively improve dietary nitrogen utilization. The rational allocation of dietary starch sources and the exploration of appropriate dietary glucose release kinetics may promote the dynamic balance of dietary glucose and amino acid supplies. However, research on the effects of diets with different glucose release kinetic profiles on amino acid absorption and portal amino acid appearance in piglets is limited. This study aimed to investigate the effects of the kinetic pattern of dietary glucose release on nitrogen utilization, the portal amino acid profile, and nutrient transporter expression in intestinal enterocytes in piglets. METHODS: Sixty-four barrows (15.00 ± 1.12 kg) were randomly allotted to 4 groups and fed diets formulated with starch from corn, corn/barley, corn/sorghum, or corn/cassava combinations (diets were coded A, B, C, or D respectively). Protein retention, the concentrations of portal amino acid and glucose, and the relative expression of amino acid and glucose transporter mRNAs were investigated. In vitro digestion was used to compare the dietary glucose release profiles. RESULTS: Four piglet diets with different glucose release kinetics were constructed by adjusting starch sources. The in vivo appearance dynamics of portal glucose were consistent with those of in vitro dietary glucose release kinetics. Total nitrogen excretion was reduced in the piglets in group B, while apparent nitrogen digestibility and nitrogen retention increased (P < 0.05). Regardless of the time (2 h or 4 h after morning feeding), the portal total free amino acids content and contents of some individual amino acids (Thr, Glu, Gly, Ala, and Ile) of the piglets in group B were significantly higher than those in groups A, C, and D (P < 0.05). Cluster analysis showed that different glucose release kinetic patterns resulted in different portal amino acid patterns in piglets, which decreased gradually with the extension of feeding time. The portal His/Phe, Pro/Glu, Leu/Val, Lys/Met, Tyr/Ile and Ala/Gly appeared higher similarity among the diet treatments. In the anterior jejunum, the glucose transporter SGLT1 was significantly positively correlated with the amino acid transporters B0AT1, EAAC1, and CAT1. CONCLUSIONS: Rational allocation of starch resources could regulate dietary glucose release kinetics. In the present study, group B (corn/barley) diet exhibited a better glucose release kinetic pattern than the other groups, which could affect the portal amino acid contents and patterns by regulating the expression of amino acid transporters in the small intestine, thereby promoting nitrogen deposition in the body, and improving the utilization efficiency of dietary nitrogen.

Enzyme-Mediated Exponential Glucose Release: A Model-Based Strategy for Continuous Defined Fed-Batch in Small-Scale Cultivations.

Miniaturized cultivation systems offer the potential to enhance experimental throughput in bioprocess development. However, they usually lack the miniaturized pumps necessary for fed-batch mode, which is commonly employed in industrial bioprocesses. An alternative are enzyme-mediated glucose release systems from starch-derived polymers, facilitating continuous glucose supply. Nevertheless, while the glucose release, and thus the feed rate, is controlled by the enzyme concentration, it also strongly depends on the type of starch derivative, and the culture conditions as well as pH and temperature. So far it was not possible to implement controlled feeding strategies (e.g., exponential feeding). In this context, we propose a model-based approach to achieve precise control over enzyme-mediated glucose release in cultivations. To this aim, an existing mathematical model was integrated into a computational framework to calculate setpoints for enzyme additions. We demonstrate the ability of the tool to maintain different pre-defined exponential growth rates during Escherichia coli cultivations in parallel mini-bioreactors integrated into a robotic facility. Although in this case study, the intermittent additions of enzyme and dextrin were performed by a liquid handler, the approach is adaptable to manual applications. Thus, we present a straightforward and robust approach for implementing defined continuous fed-batch processes in small-scale systems, where continuous feeding was only possible with low accuracy or high technical efforts until now.

Effect of natural gums on pasting, rheological, structural and hydrolysis properties of kudzu starch.

Hydrocolloids have been widely used to adjust properties of natural starches, but related research on kudzu starch is still rare. In this study, we investigated the effects of gum arabic (AG), sodium alginate (SA), locust bean gum (LG), and guar gum (GG) on kudzu starch from the perspective of its particle size, pasting, texture, rheology, dehydration rate, thermal properties, microstructure, and sensitivity to amyloglucosidase. Results showed that GG significantly increased the particle size of starch. Addition of AG led to lower peak-, final- and holding-viscosity. SA increased the retention viscosity of kudzu starch, while LG and GG increased its peak viscosity. Addition of hydrocolloids increased the hardness, chewiness, and cohesiveness of starch-hydrocolloid complexes, and reduced the dehydration rate of complex gels. Dynamic rheological data showed that the energy storage modulus (G') was significantly higher than the loss modulus (G″). The magnitude of modulus increased with frequency, and elastic properties were better than viscous properties. Thermal analysis showed that hydrocolloids increased the starting temperature (To), and the final temperature (Tc). With addition of each of these four hydrocolloids, a more regular and porous thick-wall dense structure was formed, which effectively lowered kudzu starch's sensitivity to amyloglucosidase. It indicated that the binding of hydrocolloid to starch may slow down glucose release into blood during digestion. These results will help understand effects of natural hydrocolloid on kudzu starch, as well as expanding its application in food industry.

Hybrid Membranes of the Ureasil-Polyether Containing Glucose for Future Application in Bone Regeneration.

The application of mesenchymal stem cells (MSC) in bone tissue regeneration can have unpredictable results due to the low survival of cells in the process since the lack of oxygen and nutrients promotes metabolic stress. Therefore, in this work, polymeric membranes formed by organic-inorganic hybrid materials called ureasil-polyether for modified glucose release were developed in order to overcome the problems posed by a of lack of this nutrient. Thus, membranes formed by polymeric blend of polypropylene oxide (PPO4000) and polyethylene oxide (PEO500) with 6% glucose incorporation were developed. Physical-chemical characterization techniques were performed, as well as tests that evaluated thermal properties, bioactivity, swelling, and release in SBF solution. The results of the swelling test showed an increase in membrane mass correlated with an increase in the concentration of ureasil-PEO500 in the polymeric blends. The membranes showed adequate resistance when subjected to the application of a high compression force (15 N). X-ray diffraction (XRD) evidenced peaks corresponding to orthorhombic crystalline organization, but the absence of glucose-related peaks showed characteristics of the amorphous regions of hybrid materials, likely due to solubilization. Thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses showed that the thermal events attributed to glucose and hybrid materials were similar to that seen in the literature, however when glucose was incorporated into the PEO500, an increase in rigidity occurs. In PPO400, and in the blends of both materials, there was a slight decrease in Tg values. The smaller contact angle for the ureasil-PEO500 membrane revealed the more hydrophilic character of the material compared to other membranes. The membranes showed bioactivity and hemocompatibility in vitro. The in vitro release test revealed that it is possible to control the release rate of glucose and the kinetic analysis revealed a release mechanism characteristic of anomalous transport kinetics. Thus, we can conclude that ureasil-polyether membranes have great potential to be used as a glucose release system, and their future application has the potential to optimize the bone regeneration process.

Metabolite release and rheological properties of sponge cake after in vitro digestion and the influence of a flour replacer rich in dietary fibre.

The present study aimed to better understand the metabolite release and rheological characteristics of sponge cake after in vitro digestion and the effect of Eucheuma as a fibre-rich flour replacer. Overall, 22 compounds including amino acids, saccharides, fatty acids, and other metabolites were identified based on nuclear magnetic resonance spectra. Principal component analysis and orthogonal projection to latent structures-discriminant analysis showed that Eucheuma reduced the release of amino acids and fatty acids. The released glucose from the EP20 sample (20% replacement of flour with Eucheuma) decreased by 35.4% in intestinal phases compared with the control cake. Eucheuma's in vitro effects on sponge cake digestion mainly reflected altered flow behaviour index. All samples showed solid-like behaviour and a decrease in viscoelastic moduli after digestion. This study forms the basis for future optimisation of food properties to control their digestive characteristics.

Effect of Physicochemical Properties of Carboxymethyl Cellulose on Diffusion of Glucose.

Soluble dietary fibers (SDF) are known to reduce the post-prandial plasma glucose levels. However, the detailed mechanisms of this reduced glucose release in the human gut still remain unclear. The aim of our study was to systematically investigate the effect of different types of SDF on glucose release in an in vitro model as a prerequisite for the selection of fibers suitable for application in humans. Three types of carboxymethyl cellulose (CMC) were used to investigate the correlations between fiber concentration, molecular weight (MW), and viscosity on diffusion of glucose using a side-by-side system. CMC solutions below the coil overlap (c*) influenced the glucose diffusivity only marginally, whereas at concentrations above c* the diffusion of glucose was significantly decreased. Solutions of lower MW exhibited a lower viscosity with lower glucose diffusion compared to solutions with higher MW CMC, attributed to the higher density of the solutions. All CMC solutions showed a systematic positive deviation from Stokes-Einstein behavior indicating a greater rise in viscosity than reduction in diffusion. Therefore, our results pave the way for a new approach for assessing glucose diffusion in solutions comprising dietary fibers and may contribute to further elucidating the mechanisms of post-prandial plasma glucose level reduction.

Glycemic Index of Slowly Digestible Carbohydrate Alone and in Powdered Drink-Mix.

Consumer interest in food and beverages with carbohydrates offering steady glucose release and lower glycemic index (GI) continues to rise. Glycemic index is one of the metrics for carbohydrate quality. Slowly digestible carbohydrates (SDC) offer an ingredient solution to improve carbohydrate quality and meet consumer needs. SUSTRATM 2434 slowly digestible carbohydrate is a blend of tapioca flour and corn starch. The study objective was to determine the glycemic index of the SDC ingredient alone and in a powdered drink-mix. In a randomized, single-blind study, heathy adults (n = 14) consumed four test drinks, delivering 50 g available carbohydrates on separate days to measure GI. Participants either consumed dextrose in water (placebo), SDC ingredient in water, SDC drink-mix powder reconstituted in skim milk, or control drink-mix reconstituted in skim milk (without SDC). Post-prandial glucose response was measured over 4 h. SDC exhibited lower GI (0-2 h) and higher steady glucose release (beyond 2 h). SDC alone (GI = 27) and SDC in drink-mix (GI = 30.3) showed significantly lower GI (-27%) compared to dextrose (100) and the control drink-mix (41.5). SUSTRATM 2434 SDC is a low glycemic ingredient, suitable for product innovations with potential for low glycemic and steady glucose release claims.

Tracking of enzymatic biomass deconstruction by fungal secretomes highlights markers of lignocellulose recalcitrance.

BACKGROUND: Lignocellulose biomass is known as a recalcitrant material towards enzymatic hydrolysis, increasing the process cost in biorefinery. In nature, filamentous fungi naturally degrade lignocellulose, using an arsenal of hydrolytic and oxidative enzymes. Assessment of enzyme hydrolysis efficiency generally relies on the yield of glucose for a given biomass. To better understand the markers governing recalcitrance to enzymatic degradation, there is a need to enlarge the set of parameters followed during deconstruction. RESULTS: Industrially-pretreated biomass feedstocks from wheat straw, miscanthus and poplar were sequentially hydrolysed following two steps. First, standard secretome from Trichoderma reesei was used to maximize cellulose hydrolysis, producing three recalcitrant lignin-enriched solid substrates. Then fungal secretomes from three basidiomycete saprotrophs (Laetisaria arvalis, Artolenzites elegans and Trametes ljubarskyi) displaying various hydrolytic and oxidative enzymatic profiles were applied to these recalcitrant substrates, and compared to the T. reesei secretome. As a result, most of the glucose was released after the first hydrolysis step. After the second hydrolysis step, half of the remaining glucose amount was released. Overall, glucose yield after the two sequential hydrolyses was more dependent on the biomass source than on the fungal secretomes enzymatic profile. Solid residues obtained after the two hydrolysis steps were characterized using complementary methodologies. Correlation analysis of several physico-chemical parameters showed that released glucose yield was negatively correlated with lignin content and cellulose crystallinity while positively correlated with xylose content and water sorption. Water sorption appears as a pivotal marker of the recalcitrance as it reflects chemical and structural properties of lignocellulosic biomass. CONCLUSIONS: Fungal secretomes applied to highly recalcitrant biomass samples can further extend the release of the remaining glucose. The glucose yield can be correlated to chemical and physical markers, which appear to be independent from the biomass type and secretome. Overall, correlations between these markers reveal how nano-scale properties (polymer content and organization) influence macro-scale properties (particle size and water sorption). Further systematic assessment of these markers during enzymatic degradation will foster the development of novel cocktails to unlock the degradation of lignocellulose biomass.

Dietary glycaemic index and cognitive function: prospective associations in adults of the 1946 British birth cohort.

OBJECTIVE: Evidence suggests that the rate of glucose release following consumption of carbohydrate-containing foods, defined as the glycaemic index (GI), is inversely associated with cognitive function. To date, most of the evidence stems from either single-meal studies or highly heterogeneous cohort studies. We aimed to study the prospective associations of diet GI at age 53 years with outcomes of verbal memory and letter search tests at age 69 years and rate of decline between 53 and 69 years. DESIGN: Longitudinal population-based birth cohort study. SETTING: MRC National Survey for Health and Development. PARTICIPANTS: Cohort members (n 1252). RESULTS: Using multivariable linear and logistic regression, adjusted for potential confounders, associations of higher-GI diet with lower verbal memory, lower letter search speed and lower number of hits in a letter search test were attenuated after adjustments for cognitive ability at age 15 years, educational attainment, further training and occupational social class. No association was observed between diet GI at 53 years and letter search accuracy or speed-accuracy trade-off at 69 years, or between diet GI at 53 years and rate of decline between 53 and 69 years in any cognitive measure. CONCLUSIONS: Diet GI does not appear to predict cognitive function or decline, which was mainly explained by childhood cognitive ability, education and occupational social class. Our findings confirm the need for further research on the association between diet and cognition from a life-course perspective.

Boosting of enzymatic softwood saccharification by fungal GH5 and GH26 endomannanases.

BACKGROUND: Softwood is a promising feedstock for lignocellulosic biorefineries, but as it contains galactoglucomannan efficient mannan-degrading enzymes are required to unlock its full potential. RESULTS: Boosting of the saccharification of pretreated softwood (Canadian lodgepole pine) was investigated for 10 fungal endo-ß(1→4)-mannanases (endomannanases) from GH5 and GH26, including 6 novel GH26 enzymes. The endomannanases from Trichoderma reesei (TresMan5A) and Podospora anserina (PansMan26) were investigated with and without their carbohydrate-binding module (CBM). The pH optimum and initial rates of enzyme catalysed hydrolysis were determined on pure ß-mannans, including acetylated and deacetylated spruce galactoglucomannan. Melting temperature (Tm) and stability of the endomannanases during prolonged incubations were also assessed. The highest initial rates on the pure mannans were attained by GH26 endomannanases. Acetylation tended to decrease the enzymatic rates to different extents depending on the enzyme. Despite exhibiting low rates on the pure mannan substrates, TresMan5A with CBM1 catalysed highest release among the endomannanases of both mannose and glucose during softwood saccharification. The presence of the CBM1 as well as the catalytic capability of the TresMan5A core module itself seemed to allow fast and more profound degradation of portions of the mannan that led to better cellulose degradation. In contrast, the presence of the CBM35 did not change the performance of PansMan26 in softwood saccharification. CONCLUSIONS: This study identified TresMan5A as the best endomannanase for increasing cellulase catalysed glucose release from softwood. Except for the superior performance of TresMan5A, the fungal GH5 and GH26 endomannanases generally performed on par on the lignocellulosic matrix. The work also illustrated the importance of using genuine lignocellulosic substrates rather than simple model substrates when selecting enzymes for industrial biomass applications.

Impact of food processing on rye product properties and their in vitro digestion.

PURPOSE: Rye products have been reported to elicit postprandial insulin and glucose responses which may be beneficial for prevention of type-2 diabetes. However, mechanisms underlying variations in responses related to processing techniques are not fully understood. METHODS: Five differently processed rye products (sourdough-fermented bread, fermented and unfermented crispbread, extrusion-cooked rye, and porridge) and refined wheat bread were characterised. Two in vitro methods, a dynamic method simulating digestion in the stomach and small intestine and a static method, simulating conditions in the stomach were used to determine viscosity development, structural changes and release of glucose during digestion. RESULTS: Structural and compositional differences induced by processing influenced product digestion. Gastric disintegration and digesta particle size were related to characteristics of the starch/protein matrix, while digesta viscosity was reduced due to fibre degradation during fermentation. More cohesive boluses were associated with slower glucose release. Sourdough fermentation increased amylose leakage and appeared to inhibit starch hydrolysis despite low digesta viscosity and rapid disintegration. CONCLUSIONS: The net release of glucose during digestion of foods is determined by several factors which may vary in their importance depending on product specific properties.

Enzymatic Fuel Cell-Based Self-Powered Homogeneous Immunosensing Platform via Target-Induced Glucose Release: An Appealing Alternative Strategy for Turn-On Melamine Assay.

Enzymatic fuel cell (EFC)-based self-powered biosensors have attracted considerable attention because of their unique feature of no need for extra power sources during the entire detection process, which endows them with the merits of simplicity, rapidness, low cost, anti-interference, and ease of use. Herein, we proposed, for the first time, an EFC-based self-powered homogeneous immunosensing platform by integrating the target-induced biofuel release and bioconjugate immunoassay for ultrasensitive melamine (ME) detection. In this design, the biofuel, i.e., glucose molecules, was entrapped in the pores of positively charged mesoporous silica nanoparticles and capped by the biogate AuNPs-labeled anti-ME antibody (AuNPs-Ab). The presence of the target ME triggered the entrapped glucose release due to the removal of the biogate via immunoreaction, which resulted in the transfer of electrons produced by glucose oxidation at the bioanode to the biocathode, and thus, the open-circuit voltage of the EFC-based self-powered immunosensor dramatically increased, realizing the ultrasensitive turn-on assay for ME. The limit of detection for ME assay was down to 2.1 pM (S/N = 3), superior to those previously reported in the literature. Notably, real milk samples need no special sample pretreatment for the detection of ME because of the good anti-interference ability of EFC-based self-powered biosensors and the excellent selectivity of the homogeneous immunoassay. Therefore, this appealing self-powered homogeneous immunosensing platform holds great promise as a successful prototype of portable and on-site bioassay in the field of food safety.

Systematic evaluation of characteristics of the membrane-based fed-batch shake flask.

BACKGROUND: The initial part of process development involves extensive screening programs to identify optimal biological systems and cultivation conditions. For a successful scale-up, the operation mode on screening and production scale must be as close as possible. To enable screening under fed-batch conditions, the membrane-based fed-batch shake flask was developed. It is a shake flask mounted with a central feed reservoir with an integrated rotating membrane tip for a controlled substrate release. Building on the previously provided proof of principle for this tool, this work extends its application by constructive modifications and improved methodology to ensure reproducible performance. RESULTS: The previously limited operation window was expanded by a systematic analysis of reservoir set-up variations for cultivations with the fast-growing organism Escherichia coli. Modifying the initial glucose concentration in the reservoir as well as interchanging the built-in membrane, resulted in glucose release rates and oxygen transfer rate levels during the fed-batch phase varying up to a factor of five. The range of utilizable membranes was extended from dialysis membranes to porous microfiltration membranes with the design of an appropriate membrane tip. The alteration of the membrane area, molecular weight cut-off and liquid volume in the reservoir offered additional parameters to fine-tune the duration of the initial batch phase, the oxygen transfer rate level of the fed-batch phase and the duration of feeding. It was shown that a homogeneous composition of the reservoir without a concentration gradient is ensured up to an initial glucose concentration of 750 g/L. Finally, the experimental validity of fed-batch shake flask cultivations was verified with comparable results obtained in a parallel fed-batch cultivation in a laboratory-scale stirred tank reactor. CONCLUSIONS: The membrane-based fed-batch shake flask is a reliable tool for small-scale screening under fed-batch conditions filling the gap between microtiter plates and scaled-down stirred tank reactors. The implemented reservoir system offers various set-up possibilities, which provide a wide range of process settings for diverse biological systems. As a screening tool, it accurately reflects the cultivation conditions in a fed-batch stirred tank reactor and enables a more efficient bioprocess development.

Preparation and evaluation of a sustained-release buckwheat noodle.

BACKGROUND: Different carbohydrates elicit various effects on the digestibility and the glucose release rate, so it is of interest to develop a sustained-release noodle based on the combination of different carbohydrates and reveal the sustained-release mechanism. RESULTS: The data obtained suggest that xanthan and konjac gum exhibited excellent and synergistic sustained-release properties, whereas cornstarch showed the lowest average digestion rate. The sustained release was particularly evident when the noodle consisted of the following components: 50 g of 25 g kg(-1) hydrophilic colloid mixture solution composed of a 1:1 mass ratio of xanthan:konjac gum and 100 g of reconstructed flour consisting of 200 g kg(-1) buckwheat flour, 400 g kg(-1) cornstarch, and 400 g kg(-1) plain flour. The morphological structure of noodles revealed that the composite hydrophilic colloids strengthened the interaction between the gluten network and starch granules. This buried starch within the three-dimensional structure thereby releasing glucose in a slow and sustained way. The most suitable model to describe glucose release from noodles was the Ritger-Peppas equation, which revealed that matrix erosion contributed to the release mechanism. CONCLUSION: These findings indicate that the controlled use of hydrophilic colloids and starches in manufacturing noodles could modulate the glucose sustained-release. © 2015 Society of Chemical Industry.

Enhanced plasmid DNA production by enzyme-controlled glucose release and an engineered Escherichia coli.

OBJECTIVES: To evaluate the combination of a culture medium employing glucoamylase-mediated glucose reléase from a gluco-polysaccharide and an E. coli strain engineered in its glucose transport system for improving plasmid DNA (pDNA) production. RESULTS: The production of pDNA was tested using E. coli DH5α grown in shake-flasks and the recently developed VH33 Δ(recA deoR)-engineered strain, which utilizes glucose more efficiently than wild type strains. Three glucoamylase concentrations for releasing glucose from the polysaccharide carbon source were used: 1, 2 and 3 U l(-1). Both strains reached similar cell densities ranging from 5 to 8.8 g l(-1) under the different conditions. The highest pDNA yields on biomass (YpDNA/X) for both strains were obtained when 3 U enzyme l(-1)were used. Under these conditions, 35 ± 3 mgof pDNA l(-1) were produced by DH5α after 24 h of culture. Under the same conditions, the engineered strain produced 66 ± 1 mgpDNAl(-1) after 20 h. pDNA supercoiled fractionswere close to 80 % for both strains. CONCLUSIONS: The pDNA concentration achieved by the engineered E. coli was 89 % higher than that of DH5α. The combination of the engineered strain and enzyme-controlled glucose release is an attractive alternative for pDNA production in shake-flasks.

Renal glucose release during hypoglycemia is partly controlled by sympathetic nerves - a study in pigs with unilateral surgically denervated kidneys.

Catecholamines are known to increase renal glucose release during hypoglycemia. The specific extent of the contribution of different sources of catecholamines, endocrine delivery via circulation or release from autonomous sympathetic renal nerves, though, is unknown. We tested the hypothesis that sympathetic renal innervation plays a major role in the regulation of renal gluconeogenesis. For this purpose, instrumented adolescent pigs had one kidney surgically denervated while the other kidney served as a control. A hypoglycemic clamp with arterial blood glucose below 2 mmol/L was maintained for 75 min. Arteriovenous blood glucose difference, inulin clearance, p-aminohippurate clearance, and sodium excretion were measured in intervals of 15 min separately for both kidneys. Blood glucose was lowered to 0.84 ± 0.33 mmol/L for 75 min. The side-dependent renal net glucose release (SGN) decreased significantly after the unilateral ablation of renal nerves. In the linear mixed model, renal denervation had a significant inhibitory effect on renal net glucose release (P = 0.036). The SGN of the ablated kidney decreased by 0.02 mmol/min and was equivalent to 43.3 ± 23.2% of the control (nonablated) kidney in the pigs. This allows the conclusion that renal glucose release is partly controlled by sympathetic nerves. This may be relevant in humans as well, and could explain the increased risk of severe hypoglycemia of patients with diabetes mellitus and autonomous neuropathy. The effects of denervation on renal glucose metabolism should be critically taken into account when considering renal denervation as a therapy in diabetic patients.

Altering the rate of glucose release from starch-based foods by spray-drying with an extract from barley.

BACKGROUND: Health outcomes associated with sustained elevated blood glucose may be better managed by limiting glucose availability for uptake. Glucose release from consumed starch may be altered using various methods, but many are not suitable for high-carbohydrate foods. This study describes an approach to protect starch granules, while generally maintaining their physical characteristics, with an extract from barley using spray-drying. RESULTS: The use of the extract resulted in the coating of the starch granules with a film-like material composed of ß-glucans and proteins. This coincided with a reduction in starch digestion and a significant increase in the indigestible (resistant) starch component. Substitution of the starch component in a model snack bar by the coated starch was also associated with lowering starch digestion in the bar. CONCLUSION: The barley extract provides a physical barrier that may limit the exposure of starch to the digestive enzymes and water, with a consequent reduction in starch digestion and the rate of glucose release. It is possible, therefore, to produce wheat starch with lower digestibility and glucose release rate that may be used as a healthier substitute in high-carbohydrate foods by coating the granules with polymers extracted from barley cereals through spray-drying.

Perforated bicontinuous cubic phases with pH-responsive topological channel interconnectivity.

Lipidic lyotropic liquid crystals are at the frontline of current research for release of target therapeutic molecules due to their unique structural complexity and the possibility of engineering stimuli-triggered release of both hydrophilic and hydrophobic molecules. One of the most suitable lipidic mesophases for the encapsulation and delivery of drugs is the reversed double diamond bicontinuous cubic phase, in which two distinct and parallel networks of ∼4 nm water channels percolate independently through the lipid bilayers, following a Pn3m space group symmetry. In the unperturbed Pn3m structure, the two sets of channels act as autonomous and non-communicating 3D transport pathways. Here, a novel type of bicontinuous cubic phase is introduced, where the presence of OmpF membrane proteins at the bilayers provides unique topological interconnectivities among the two distinct sets of water channels, enabling molecular active gating among them. By a combination of small-angle X-ray scattering, release and ion conductivity experiments, it is shown that, without altering the Pn3m space group symmetry or the water channel diameter, the newly designed perforated bicontinuous cubic phase attains transport properties well beyond those of the standard mesophase, allowing faster, sustained release of bioactive target molecules. By further exploiting the pH-mediated pore-closing response mechanism of the double amino acid half-ring architecture in the membrane protein, the pores of the perforated mesophase can be opened and closed with a pH trigger, enabling a fine modulation of the transport properties by only moderate changes in pH, which could open unexplored opportunities in the targeted delivery of bioactive compounds.