d-Allose protects against endotoxemic acute renal injury

Effects of d-allose on anti-brain edema effects and reduction of tumor necrosis factor-alpha and interleukin-6 in the water intoxication model

Rare sugars, which exist only in very small quantities in nature, have recently attracted attention for their various biological functions in medicine. Among them, d-allose is known to have cytoprotective effects by antioxidant effects. In this study, we investigated whether the antioxidant effects of d-allose reduce brain edema in a water intoxication model of cytotoxic brain edema. Methods: Mice were injected intraperitoneally with distilled water (10 % of body weight) to create a model of brain edema. d-allose was administered orally at 400 mg/kg 30 min before the model was created. Two hours later, the degree of brain edema was measured by the dry-weight method to determine whether d-allose reduced brain edema. As an index of antioxidant effects, we measured changes over time in inflammatory cytokines (tumor necrosis factor-alpha, interleukin-6) induced by the water intoxication model, and whether d-allose reduced inflammatory cytokines 4 h after model creation. Results: Administration of d-allose significantly suppressed brain edema formation of the water-intoxication model. And it significantly reduced inflammatory cytokines (tumor necrosis factor-alpha, interleukin-6). These results suggest that the antioxidant effect of d-allose exerts an anti-inflammatory effect and reduces brain edema.

A study of targeted mutation of l-rhamnose isomerase to improve the conversion efficiency of D-allose

D-Allose is a rare cis-caprose with a wide range of physiological functions, which has a wide range of applications in medicine, food, and other industries. L-Rhamnose isomerase (L-Rhi) is the earliest enzyme found to catalyze the production of D-allose from D-psicose. This catalyst has a high conversion rate, but its specificity for substrates is limited; thus, it cannot fulfill the requirements of industrial production of D-allose. In this study, L-Rhi derived from Bacillus subtilis was employed as the research subject, and D-psicose as the conversion substrate. Two mutant libraries were constructed through alanine scanning, saturation mutation, and rational design based on the analysis of the secondary structure, tertiary structure, and interactions with ligands of the enzyme. The yield of D-allose produced by these mutants was assessed; it was found that the conversion rate of mutant D325M to D-allose was increased by 55.73 %, and the D325S improved by 15.34 %, while mutant W184H increased by 10.37 % at 55 °C, respectively. According to modeling analysis, manganese (Mn²⁺) had no significant effect on the production of D-psicose from D-psicose by L-Rhi. The results of molecular dynamics simulation demonstrated that the mutants W184H, D325M, and D325S had more stable protein structures while binding with the substrate D-psicose, as evidenced by its root mean square deviation (RMSD), root mean square fluctuation (RMSF), and binding free energy values. It was more conducive to binding D-psicose and facilitating its conversion to D-allose, providing the basis for the production of D-allose.

Metabolic engineering pathways for rare sugars biosynthesis, physiological functionalities, and applications-a review

Biomolecules like rare sugars and their derivatives are referred to as monosaccharides particularly uncommon in nature. Remarkably, many of them have various known physiological functions and biotechnological applications in cosmetics, nutrition, and pharmaceutical industries. Also, they can be exploited as starting materials for synthesizing fascinating natural bioproducts with significant biological activities. Regrettably, most of the rare sugars are quite expensive, and their synthetic chemical routes are both limited and economically unfeasible due to expensive raw materials. On the other hand, their production by enzymatic means often suffers from low space-time yields and high catalyst costs due to hasty enzyme denaturation/degradation. In this context, biosynthesis of rare sugars with industrial importance is receiving renowned scientific attention, across the globe. Moreover, the utilization of renewable resources as energy sources via microbial fermentation or microbial metabolic engineering has appeared a new tool. This article presents a comprehensive review of physiological functions and biotechnological applications of rare ketohexoses and aldohexoses, including D-psicose, D-tagatose, L-tagatose, D-sorbose, L-fructose, D-allose, L-glucose, D-gulose, L-talose, L-galactose, and L-fucose. Novel in-vivo recombination pathways based on aldolase and phosphatase for the biosynthesis of rare sugars, particularly D-psicose and D-sorbose using robust microbial strains are also deliberated.

Two-step enzymatic synthesis of 6-deoxy-L-psicose

Rare sugars offer a plethora of applications in the pharmaceutical, medicinal, and industries, as well as in synthetic chemistry. However, studies of rare sugars have been hampered by their relative scarcity. In this work, we describe a two-step strategy to efficiently and conveniently prepare 6-deoxy-L-psicose from L-rhamnose. In the first reaction step, the isomerization of L-rhamnose (6-deoxy-L-mannose) to L-rhamnulose (6-deoxy-L-fructose) catalyzed by L-rhamnose isomerase (RhaI), and the epimerization of L-rhamnulose to 6-deoxy-L-psicose catalyzed by D-tagatose 3-epimerase (DTE) were coupled with selective phosphorylation reaction by fructose kinase from human (HK), which selectively phosphorylate 6-deoxy-L-psicose at C-1 position. 6-deoxy-L-psicose 1-phosphate was purified by a silver nitrate precipitation method. In the second step, the phosphate group of the 6-deoxy-L-sorbose 1-phosphate was hydrolyzed with acid phosphatase (AphA) to produce 6-deoxy-L-psicose in 81% yield with respect to L-rhamnose. This method allows that the 6-deoxy-L-psicose to be obtained from readily available starting materials with high purity and without having to undergo isomer separation.

d-Allose Attenuates Overexpression of Inflammatory Cytokines after Cerebral Ischemia/Reperfusion Injury in Gerbil

BACKGROUND

The present study investigates the effects of d-allose, a rare sugar, on the inflammatory response after transient forebrain ischemia in the gerbil and whether it reduces oxidative stress (8-hydroxyl-2'-deoxyguanosine levels) and behavioral deficits.

METHODS

Transient forebrain ischemia was induced by occlusion of the bilateral common carotid arteries for 5 minutes. d-Allose was intraperitoneally injected immediately after ischemia (400 mg/kg). Inflammatory cytokines and oxidative damage in the hippocampus and behavioral deficits were examined 3 days after ischemia.

RESULTS

d-Allose administration reduced ischemia-induced cytokine production, oxidative stress, and behavioral deficits (motor and memory related).

CONCLUSIONS

The present results suggest that d-allose reduces brain injury after transient global ischemia by suppressing inflammation as well as by inhibiting oxidative stress.

D-allose protects the blood brain barrier through PPARγ-mediated anti-inflammatory pathway in the mice model of ischemia reperfusion injury

Our early experiments confirmed that D-allose was closely involved in the blood brain barrier (BBB) protection from ischemia reperfusion (IR) injury, but the regulatory mechanism is not fully defined. In this study, we aimed to investigate the role of D-allose in the protection of BBB integrity and the relevant mechanisms involved in the mice model of middle cerebral artery occlusion and reperfusion (MCAO/Rep). D-allose was intravenously injected via a tail vein (0.2mg/g and 0.4mg/g, 1h before ischemia), GW9662 was intraperitoneal injected to the mice (4mg/kg) before inducing ischemia 24h. Pretreatment with D-allose ameliorated the neurological deficits, infarct volume and brain edema in brains of MCAO/Rep mice. D-allose inhibited cell apoptosis in the mice model of MCAO/Rep. We observed that D-allose remarkably decreased BBB permeability and prevented the reduction of ZO-1, Occludin and Claudin-5 in mice brains with MCAO/Rep injury. D-allose also repressed the levels of TNF-α, NF-κB, interleukin (IL)-1β and IL-8 in inflammatory responses. The increases of intercellular adhesion molecular-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and CD11b/CD18 were significantly inhibited by D-allose during the MCAO/Rep injury. And D-allose decreased the L-selectin and P-selectin levels after MCAO/Rep. Moreover, D-allose induced up-regulation of peroxisome proliferator-activated receptor γ (PPARγ), and down-regulation of TNF-α and NF-κB after MCAO/Rep, which were abolished by utilization of GW9662. In conclusion, we provided evidences that D-allose may has therapeutic potential against brain IR injury through attenuating BBB disruption and the inflammatory response via PPARγ-dependent regulation of NF-κB.

D-ribose ameliorates cisplatin-induced nephrotoxicity by inhibiting renal inflammation in mice

Cisplatin is one of the most potent chemotherapeutic anticancer drugs, but it can produce side effects such as nephrotoxicity. Inflammatory cytokines, chemokines and adhesion molecules have important roles in the pathogenesis of cisplatin-induced nephrotoxicity. D-Ribose is a naturally occurring five-carbon monosaccharide that is found in all living cells, and has anti-inflammatory effects in renal ischemia/reperfusion injury. The purpose of this study was to determine the protective effects of D-ribose on cisplatin-induced nephrotoxicity. Forty-eight mice were randomly divided into four groups: control, cisplatin, cisplatin + ribose, and ribose. Mice were given cisplatin (20 mg/kg body weight, intraperitoneally) with or without D-ribose (400 mg/kg body weight, intraperitoneally, immediately after cisplatin injection). At 72 h after cisplatin injection, we measured serum and renal tumor necrosis factor (TNF)-α and renal monocyte chemoattractant protein (MCP)-1 concentrations by enzyme-linked immunosorbent assay; renal expression of intercellular adhesion molecule (ICAM)-1 mRNA by real-time polymerase chain reaction; serum blood urea nitrogen and creatinine; and histological changes. Cisplatin increased serum and renal TNF-α concentrations, renal MCP-1 concentration, and renal ICAM-1 mRNA expression. Treatment with D-ribose attenuated the increase in serum and renal TNF-α concentrations, renal MCP-1 concentration, and renal ICAM-1 mRNA expression. Consequently, cisplatin-induced renal dysfunction and renal tubular necrosis were attenuated by D-ribose treatment. This is believed to be the first time that protective effects of D-ribose on cisplatin-induced nephrotoxicity via inhibition of inflammatory reactions have been investigated. Thus, D-ribose may become a new therapeutic candidate for the treatment of cisplatin-induced nephrotoxicity.

Renal angina: an emerging paradigm to identify children at risk for acute kidney injury

Acute kidney injury (AKI) leads to high rates of morbidity and independently increases mortality risk. Therapy for AKI is likely limited by the inability to reliably diagnose AKI in its early stages, and, importantly, small changes in serum creatinine may be associated with poor outcomes and severe AKI. Whereas AKI biomarker research seeks to identify more sensitive and timely indices of kidney dysfunction, AKI lacks physical signs and symptoms to trigger biomarker assessment in at-risk patients, limiting biomarker efficacy. Accurate models of AKI prediction are unavailable. Severity of illness (SOI) scoring systems and organ dysfunction scores (OD), which stratify patients by prediction of mortality risk, are AKI reactive, not predictive. Kidney-specific severity scores do not account for AKI progression, and stratification models of AKI severity are not predictive of AKI. Thus, there is a need for a kidney scoring system that can help predict the development of AKI. This review highlights the concept of renal angina, a combination of patient risk factors and subtle AKI, as a methodology to predict AKI progression. Fulfillment of renal angina criteria will improve the efficiency of AKI prediction by biomarkers, in turn expediting early therapy and assisting in creation of AKI-predictive scoring systems.