d-ribose in glycation and protein aggregation

Development of a specific fluorescent probe to detect advanced glycation end products (AGEs)

Advanced glycation end products (AGEs) play a pivotal role in the aging process, regarded as a hallmark of aging. Despite their significance, the absence of adequate monitoring tools has hindered the exploration of the relationship between AGEs and aging. Here, we present a novel AGE-selective probe, AGO, for the first time. AGO exhibited superior sensitivity in detecting AGEs compared to the conventional method of measuring autofluorescence from AGEs. Furthermore, we validated AGO's ability to detect AGEs based on kinetics, demonstrating a preference for ribose-derived AGEs. Lastly, AGO effectively visualized glycation products in a collagen-based mimicking model of glycation. We anticipate that this study will enhance the molecular tool sets available for comprehending the physiological processes of AGEs during aging.

Tai Chi improves non-motor symptoms of Parkinson's disease: One-year randomized controlled study with the investigation of mechanisms

BACKGROUND

Tai Chi was found to improve motor symptoms in Parkinson's disease (PD). Whether long-term Tai Chi training could improve non-motor symptoms (NMS) and the related mechanisms were unknown.

OBJECTIVE

To investigate Tai Chi's impact on non-motor symptoms in PD and related mechanisms.

METHODS

95 early-stage PD patients were recruited and randomly divided into Tai Chi (N = 32), brisk walking (N = 31), and no-exercise groups (N = 32). All subjects were evaluated at baseline, 6 months, and 12 months within one-year intervention. Non-motor symptoms (including cognition, sleep, autonomic symptoms, anxiety/depression, and quality of life) were investigated by rating scales. fMRI, plasma cytokines and metabolomics, and blood Huntingtin interaction protein 2 (HIP2) mRNA levels were detected to observe changes in brain networks and plasma biomarkers.

RESULTS

Sixty-six patients completed the study. Non-motor functions assessed by rating scales, e.g. PD cognitive rating scale (PDCRS) and Epworth Sleepiness scale (ESS), were significantly improved in the Tai Chi group than the control group. Besides, Tai Chi had advantages in improving NMS-Quest and ESS than brisk walking. Improved brain function was seen in the somatomotor network, correlating with improved PDCRS (p = 0.003, respectively). Downregulation of eotaxin and upregulation of BDNF demonstrated a positive correlation with improvement of PDCRS and PDCRS-frontal lobe scores (p ≤ 0.037). Improvement of energy and immune-related metabolomics (p ≤ 0.043), and elevation of HIP2 mRNA levels (p = 0.003) were also found associated with the improvement of PDCRS.

CONCLUSIONS

Tai Chi improved non-motor symptoms in PD, especially in cognition and sleep. Enhanced brain network function, downregulation of inflammation, and enhanced energy metabolism were observed after Tai Chi training.

Non-enzymatic glycation reduces glucose transport in the human cartilage endplate independently of matrix porosity or proteoglycan content

Background

Intervertebral disc degeneration is associated with low back pain, which is a leading cause of disability. While the precise causes of disc degeneration are unknown, inadequate nutrient and metabolite transport through the cartilage endplate (CEP) may be one important factor. Prior work shows that CEP transport properties depend on the porosity of the CEP matrix, but little is known about the role of CEP characteristics that could influence transport properties independently from porosity. Here, we show that CEP transport properties depend on the extent of non-enzymatic glycation of the CEP matrix.

Methods and Results

Using in vitro ribosylation to induce non-enzymatic glycation and promote the formation of advanced glycation end products, we found that ribosylation reduced glucose partition coefficients in human cadaveric lumbar CEP tissues by 10.7%, on average, compared with donor- and site-matched CEP tissues that did not undergo ribosylation (p = 0.04). These reductions in glucose uptake were observed in the absence of differences in CEP porosity (p = 0.89) or in the amounts of sulfated glycosaminoglycans (sGAGs, p = 0.47) or collagen (p = 0.61). To investigate whether ribosylation altered electrostatic interactions between fixed charges on the sGAG molecules and the mobile free ions, we measured the charge density in the CEP matrix using equilibrium partitioning of a cationic contrast agent using micro-computed tomography. After contrast enhancement, mean X-ray attenuation was 11.9% lower in the CEP tissues that had undergone ribosylation (p = 0.02), implying the CEP matrix was less negatively charged.

Conclusions

Taken together, these findings indicate that non-enzymatic glycation negatively impacts glucose transport in the CEP independent of matrix porosity or sGAG content and that the effects may be mediated by alterations to matrix charge density.

Protective effect of thymoquinone on glycation of human myoglobin induced by d-ribose

Nonenzymatic glycation and the subsequent accumulation of advanced glycation end-products (AGEs) in proteins are factors underlying long-term pathogenesis in diabetes. The study of protein glycation is crucial for elucidating their relationship with diabetes mellitus and related disorders. This study explores the interaction between d-ribose and human myoglobin (HMb), as well as the protective effect of thymoquinone (TQ) on glycation. A time-dependent in-vitro glycation study was performed to investigate the mechanism of d-ribose-induced structural interference of HMb in the absence and presence of TQ. Spectroscopic and proteomic analysis indicated that the presence of TQ significantly reduced the total amount of AGEs while maintaining structural characteristics of HMb. 14 glycated sites on HMb were further identified via liquid chromatography-tandem mass spectrometry (LC-MS/MS) after incubation with d-ribose for 12 h, predominantly interacting with lysine residues. TQ was found to disrupt this interaction, reducing the glycated sites from 14 to 12 sites and the percentage of glycated peptides from 26.50 % to 12.97 %. Additionally, there was a significant decrease in the degree of glycation at the same sites. In summary, our findings suggest that TQ has the potential to act as an anti-glycation agent and provide a comprehensive understanding underlying the inhibition mechanism of glycation.

Bushen Tongluo formula ameliorated testosterone propionate-induced benign prostatic hyperplasia in rats

BACKGROUND

Benign prostatic hyperplasia (BPH) is a common disease in older men worldwide. However, there is currently no effective treatment for BPH. Bushen Tongluo Formula (Kidney-supplementing and collaterals-unblocking formula [KCF]) is a traditional Chinese medicine formula commonly used to ameliorate the symptoms of BPH, although the specific molecular mechanisms remain unclear.

PURPOSE

We aimed to discover the effects and potential mechanisms of KCF against BPH.

METHODS

Sixty male SD rats were randomly assigned to one of six group (n = 10): control, low-dosage KCF, medium-dosage KCF, high-dosage KCF, BPH model, and finasteride. A rat model of BPH was established by surgical castration followed by subcutaneous injection of testosterone propionate (TP) for 4 weeks. After treatment, the prostate index, histopathological staining, serum levels of estradiol (E2) and dihydrotestosterone (DHT), protein/mRNA levels of E-cadherin, TGF-β1, caspase-3, Ki67, and vimentin, abundances of serum metabolites, and the proliferation, cell cycle, and apoptosis of BPH-1 cells were documented.

RESULTS

KCF treatment for 4 weeks reduced the prostate volume and prostate index, alleviated histopathological changes to the prostate of rats with TP-induced BPH, decreased serum levels of E2 and DHT, reduced protein/mRNA levels of TGF-β1 and vimentin, and increased E-cadherin levels. Moreover, KCF-spiked serum inhibited proliferation of BPH-1 cells, blocked the cell cycle, and promoted apoptosis. KCF was also found to regulate the contents of three metabolites (D-maltose, citric acid, and fumaric acid).

CONCLUSION

The present study was the first to report that KCF exhibited therapeutic effects against BPH by regulating energy metabolism and inhibiting epithelial-mesenchymal transition in prostate tissues. Hence, KCF presents a viable treatment option for BPH.

A comprehensive review on glycation and its potential application to reduce food allergenicity

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

A novel polysaccharide/zein conjugate as an alternative green plastic

The flax seed cake is a waste product from flax oil extraction. Adding value to this wasted material aligns with the concept of circularity. In this study, we explored zein protein conjugation with flax mucilage for packaging material development. Although both flax mucilage and zein have excellent film-forming properties, they lack the required mechanical properties for industrial processing and are sensitive to high humidity. We present a simple and non-toxic one-pot method for developing the novel flax mucilage/zein conjugate. Where the flax mucilage undergoes oxidation to form aldehyde groups, which then react with zein's amino groups in a glycation process. The conjugates were analyzed using different techniques. The flax mucilage conjugate had a water-holding capacity of 87-62%. Increasing the zein content improved the surface smoothness of the films. On the other hand, higher levels of zein led to a significant decrease in film solubility (p < 0.05). The flax mucilage conjugate exhibited thermoplastic and elastic properties; revealing Young's modulus of 1-3 GPa, glass transition temperature between 49 °C and 103 °C and excellent processability with various industrial techniques. Showing its potential as a sustainable alternative to traditional plastics.

Biochemical characterization, and anti-inflammatory and antitumor activities of glycoprotein from lamb abomasum

ETHNOPHARMACOLOGICAL RELEVANCE

Lamb abomasum is used as an edible medicinal source in traditional Chinese medicine for the treatment of gastrointestinal disorders. Lamb abomasum sourced biochemical drug Lamb's trip extract and Vitamin B12 capsule used for the clinical treatment of chronic gastritis, gastric ulcer, and reversal of intestinal metaplasia. Therefore, claimed to have prevention of gastric cancer activity.

AIM OF THE STUDY

In this study, we aim to assess whether the glycoprotein has biological activity in the cure of gastric disorder and conduct a structure-activity relationship.

MATERIALS AND METHODS

Glycoproteins' extraction conditions were optimized by the response surface method and purified with DEAE-cellulose and Sephadex G-50 chromatography. Two homogenous glycoproteins' physiochemical structures were studied with electrophoresis, HPLC analysis, peroxide oxidation, and β-elimination, FT-IR, CD, LC-MS/MS, and EDS analysis. The antiinflammation activity of the glycoprotein was determined against COX-2 and LOX-15 enzyme inhibitory ability in vitro, and antitumor activity against HT-29 and HGC-25, and cytotoxicity on L-02 cells was determined in vivo with the MTT method.

RESULTS

The abomasum was abundant in glycoprotein and the extraction yield of glycoprotein was up to 24.6 ± 2.1% under optimized conditions. Two homogeneous glycoproteins SAGP-I and SAGP-II determined to be ribose-conjugated and sulfated glycoproteins with a molecular weight of 15.6 kDa and 6.4 kDa. And according to the structural analysis, SAGP-I was a mucin-type ribose-conjugated glycoprotein with 14 O-glycosylation and one N- glycosylation site. SAGP-I and SAGP-II have remarkable anti-inflammatory activity against COX-2 enzyme with the IC₅₀ of 17.64 ± 1.25 μg/mL and 16.14 ± 1.11 μg/mL, respectively. Meanwhile, the two glycoproteins showed strong antitumor activity against HT-29 with the EC₅₀ of 19.19 ± 1.46 μg/mL and 184.9 ± 5.6 μg/mL, respectively.

CONCLUSION

The Highly purified glycoprotein SAGP-1 and SAGP-II showed anti-inflammatory activity against the COX-2 enzyme, and antitumor activity against HT-29 human colon cancer cells and noun-inhibitory activity against LOX-15 enzyme and HGC-25. Both glycoproteins are ribose conjugated and sulfated whose characters are related to their anti-inflammatory and anti-tumor activity. Such results suggest the possibility of anti-inflammatory and pre-cancer activity. And in some degree explains the pharmacy of abomasum's traditional use in gastric disorder and clinical use of lamb abomasum APIs drugs' in gastric disorders and gastric cancer development. This study provides a preliminary basis for the further study of the per-cancer mechanism of lamb abomasum glycoprotein. And, would be the material basis of the clinical use of Lamb's trip extract and Vitamin B12 capsule.

Glycated bovine serum albumin for use in feeding trials with animal models - In vitro methodology and characterization of a glycated substrate for modifying feed pellets

This study investigated different methods to produce N^ε-carboxymethyl-lysine (CML)-enriched bovine serum albumin (BSA) as alternatives to the classical approach using glyoxylic acid (GA) and sodium cyanoborohydride (NaBH₃CN) which results in toxic hydrogen cyanide (HCN). The reaction of GA (6 mmol/L) and NaBH₃CN (21 mmol/L) to produce CML remained the most effective with CML yields of 24-35%, followed by 13-24% using 300 mmol/L glyoxal (GO). GA promoted specific modification of lysine to CML, and fewer structural modifications of the BSA molecule compared with GO, as evidenced by fluorescence and proteomic analyses. GO promoted greater arginine modification compared with GA (76 vs 23%). Despite structural changes to BSA with GO, murine fecal clearance of CML was similar to literature values. Hence, BSA glycation with 300 mmol/L glyoxal is a suitable alternative to GA and NaBH₃CN for generating CML-enriched protein free of HCN, but a CML-only fortification model remains to be described.

Untargeted metabolomic analysis reveals the mechanism of Enterococcus faecium agent induced CaCO3 scale inhibition

In this study, a lactic acid bacterium, Enterococcus faecium, was found to prevent CaCO₃ precipitation through its metabolism. On analysis of all stages of E. faecium growth, static jar tests demonstrated that stationary phase E. faecium broth possessed the highest inhibition efficiency of 97.3% at a 0.4% inoculation dosage, followed by the decline and log phases with efficiencies of 90.03% and 76.07%, respectively. Biomineralization experiments indicated that E. faecium fermented the substrate to produce organic acid, which resulted in modulation of the pH and alkalinity of the environment and thus inhibited CaCO₃ precipitation. Surface characterization techniques indicated that the CaCO₃ crystals precipitated by the E. faecium broth tended to be significantly distorted and formed other organogenic calcite crystals. The scale inhibition mechanisms were revealed by untargeted metabolomic analysis on log and stationary phase E. faecium broth. In total, 264 metabolites were detected, 28 of which were differential metabolites (VIP ≥ 1 and p < 0.05). Of these, 15 metabolites were upregulated in stationary phase broth, and 13 metabolites were downregulated in log phase broth. Metabolic pathway analysis suggested that improved glycolysis and the TCA cycle were the main reasons for enhancement of the antiscaling performance of E. faecium broth. These findings have significant implications for microbial metabolism-induced CaCO₃ scale inhibition.

Gut microbiome and serum metabolome analyses identify biomarkers associated with sexual maturity in quails

Increasing evidence indicates that the gut microbiome plays an important role in host aging and sexual maturity. However, the gut microbial taxa associated with sexual maturity in quails are unknown. This study used shotgun metagenomic sequencing to identify bacterial taxa associated with sexual maturity in d 20 and d 70 quails. We found that 17 bacterial species and 67 metagenome-assembled genomes (e.g., Bacteroides spp. and Enterococcus spp.) significantly differed between the d 20 and d 70 groups, including 5 bacterial species (e.g., Enterococcus faecalis) enriched in the d 20 group and 12 bacterial species (e.g., Christensenella massiliensis, Clostridium sp. CAG:217, and Bacteroides neonati) which had high abundances in the d 70 group. The bacterial species enriched in d 20 or d 70 were key biomarkers distinguishing sexual maturity and significantly correlated with the shifts in the functional capacities of the gut microbiome. Untargeted serum metabolome analysis revealed that 5 metabolites (e.g., nicotinamide riboside) were enriched in the d 20 group, and 6 metabolites (e.g., D-ribose, stevioside, and barbituric acid) were enriched in the d 70 group. Furthermore, metabolites with high abundances in the d 20 group were significantly enriched for the KEGG pathways of arginine biosynthesis, nicotinate and nicotinamide metabolism, and lysine degradation. However, glutathione metabolism and valine, leucine and isoleucine biosynthesis were enriched in high-abundance metabolites from the d 70 group. These results provide important insights into the effects of gut microbiome and host metabolism on quail sexual maturity.

Preoperative serum ribose concentrations may be associated with postoperative delirium in older patients with a hip fracture

BACKGROUND

Postoperative delirium (POD) is a common postoperative neurocognitive complication, especially in older patients. However, satisfactory biomarkers for predicting individual risks of POD have not been confirmed. D-ribose involvement in protein glycation and aggregation plays a pivotal role in age-related neurodegenerative disorders such as Alzheimer's disease.

OBJECTIVES

This study aimed to determine whether serum D-ribose concentrations contribute to the early diagnosis of POD. We also discuss the probable mechanisms underlying the development of POD.

METHODS

110 older patients with hip fracture who had undergone internal fixation or hip replacement under general anesthesia and had completed our assessments were selected. Preoperative venous blood (4 ml) was collected before the induction of anesthesia. Postoperative venous blood was obtained at 07:00 and 20:00 h on postoperative day 1 and at 20:00 h on postoperative day 2. On the first 2 postoperative days, the patients were assessed twice daily (at 8:00 and 20:00 h on each day) using the Confusion Assessment Method-Chinese Revision.

RESULTS

15 patients were finally diagnosed with POD. We also included 15 patients without POD who were matched with the recruited patients with POD (1:1) on the basis of age, sex, body mass index and the Mini-Mental State Examination score. Serum ribose concentrations were measured by high-performance liquid chromatography. The demographic characteristics of the groups were matched. Preoperative serum ribose concentrations were significantly higher in patients with POD than in those without POD (p < 0.05) and were also an independent risk factor for POD. Moreover, when the preoperative serum ribose concentration doubled, the risk of POD increased by 1.672 times.

CONCLUSIONS

These results indicate that the serum D-ribose concentration may be a potential predictive molecular biomarker for POD, and provide useful information for further pathological mechanism studies.

Synovial tissue metabolomics analysis of the therapeutic effects of stir-fried Xanthii Fructus on rheumatoid arthritis in rats

Rheumatoid arthritis (RA) is a rheumatic disease that easily causes synovial hyperplasia and joint damage. Comprehensive metabolomic profiling of synovial tissue can reveal local pathological changes during RA and identify metabolites as candidate biomarkers. Detecting metabolites in synovial tissue can more directly reflect the pathological state and disease activity associated with it. stir-fried Xanthii Fructus has demonstrated efficacy in treating RA, but its pharmacodynamic property and mechanism of action are unclear. In this study, the molecular composition of the extract of stir-fried Xanthium Fructus was determined through HPLC. The major components that exert anti-inflammatory and analgesic effects were speculated to be phenolic acids. Next, the effect of stir-fried Xanthii Fructus extracts in RA treatment was comprehensively evaluated using rat body weight, foot volume, inflammatory factors, and histopathological sections of the ankle joint as evaluation indicators. The results showed that the extract of stir-fried Xanthii Fructus could significantly reduce the inflammatory response and improve the degree of joint swelling and the imbalance between pro-inflammatory and anti-inflammatory in adjuvant arthritis rats. Finally, non-targeted metabolomics based on UPLC-Q-TOF/MS and multivariate statistical analysis were used to explore the changes of endogenous metabolites in synovium tissues and to search for potential biomarkers and related metabolic pathways in stir-fried Xanthii Fructus extract-treated AA rats. The results showed that stir-fried Xanthii Fructus mainly treated RA by regulating energy metabolism, hormone metabolism, amino acid metabolism and oxidative stress response in adjuvant arthritis rats. This study provides a theoretical basis for the mechanism of action of stir-fried Xanthii Fructus extract in treating RA.

Dietary ribose supplementation improves flesh quality through purine metabolism in gibel carp (Carassius auratus gibelio)

Since the aquaculture industry is currently observing a deterioration in the flesh quality of farmed fish, the use of nutrients as additives to improve the flesh quality of farmed fish species is a viable strategy. The aim of this study was to investigate the effect of dietary D-ribose (RI) on the nutritional value, texture and flavour of gibel carp (Carassius auratus gibelio). Four diets were formulated containing exogenous RI at 4 gradient levels: 0 (Control), 0.15% (0.15RI), 0.30% (0.30RI) and 0.45% (0.45RI). A total of 240 fish (150 ± 0.31 g) were randomly distributed into 12 fibreglass tanks (150 L per tank). Triplicate tanks were randomly assigned to each diet. The feeding trial was carried out in an indoor recirculating aquaculture system for 60 d. After the feeding trial, the muscle and liver of gibel carp were analysed. The results showed that RI supplementation did not result in any negative impact on the growth performance and 0.30RI supplementation significantly increased the whole-body protein content compared to the control group. The contents of collagen and glycogen in muscle were enhanced by RI supplementation. The alterations in the flesh indicated that RI supplementation improved the texture of the flesh in terms of its water-holding capacity and hardness, therefore improving the taste. Dietary RI facilitated the deposition of amino acids and fatty acids in the muscle that contributed to the meaty taste and nutritional value. Furthermore, a combination of metabolomics and expression of key genes in liver and muscle revealed that 0.30RI activated the purine metabolism pathways by supplementing the substrate for nucleotide synthesis and thereby promoting the deposition of flavour substance in flesh. This study offers a new approach for providing healthy, nutritious and flavourful aquatic products.

Ribose Intake as Food Integrator: Is It a Really Convenient Practice?

Reports concerning the beneficial effects of D-ribose administration in cardiovascular and muscle stressful conditions has led to suggestions for the use of ribose as an energizing food supplement for healthy people. However, this practice still presents too many critical issues, suggesting that caution is needed. In fact, there are many possible negative effects of this sugar that we believe are underestimated, if not neglected, by the literature supporting the presentation of the product to the market. Here, the risks deriving from the use of free ribose as ATP source, forcing ribose-5-phosphate to enter into the pentose phosphate pathway, is emphasized. On the basis of the remarkable glycation capacity of ribose, the easily predictable cytotoxic effect of the molecule is also highlighted.

A systematic review and meta-analysis of cognitive and behavioral tests in rodents treated with different doses of D-ribose

BACKGROUND

D-ribose is an aldehyde sugar and a necessary component of all living cells. Numerous reports have focused on D-ribose intervention in animal models to assess the negative effects of D-ribose on cognition. However, the results across these studies are inconsistent and the doses and actual effects of D-ribose on cognition remain unclear. This systematic review aimed to evaluate the effect of D-ribose on cognition in rodents.

METHODS

The articles from PubMed, Embase, Sciverse Scopus, Web of Science, the Chinese National Knowledge Infrastructure, SinoMed, Wanfang, and Cqvip databases were screened. The results from the abstract on cognitive-related behavioral tests and biochemical markers from the included articles were extracted and the reporting quality was assessed.

RESULTS

A total of eight trials involving 289 rodents met the eligibility criteria, and both low- and high-dose groups were included. Meta-analyses of these studies showed that D-ribose could cause a significant decrease in the number of platform crossings (standardized mean difference [SMD]: -0.80; 95% CI: -1.14, -0.46; p < 0.00001), percentage of distance traversed in the target quadrant (SMD: -1.20; 95% CI: -1.47, -0.92; p < 0.00001), percentage of time spent in the target quadrant (SMD: -0.93; 95% CI: -1.18, -0.68; p < 0.00001), and prolonged escape latency (SMD: 0.41; 95% CI: 0.16, 0.65; p = 0.001) in the Morris water maze test. Moreover, D-ribose intervention increased the levels of advanced glycation end products (AGEs) in the brain (SMD: 0.49; 95% CI: 0.34, 0.63; p < 0.00001) and blood (SMD: 0.50; 95% CI: 0.08, 0.92; p = 0.02). Subsequently, subgroup analysis for the dose of D-ribose intervention revealed that high doses injured cognitive function more significantly than low D-ribose doses.

CONCLUSION

D-ribose treatment caused cognitive impairment, and cognition deteriorated with increasing dose. Furthermore, the increase in AGEs in the blood and brain confirmed that D-ribose may be involved in cognitive impairment through non-enzymatic glycosylation resulting in the generation of AGEs. These findings provide a new research idea for unveiling basic mechanisms and prospective therapeutic targets for the prevention and treatment of patients with cognitive impairment.

d-ribose-mediated glycation of fibrinogen: Role in the induction of adaptive immune response

A nonenzymatic reaction between reducing sugars and amino groups of proteins results in the formation of advanced glycation end products, which are linked to a number of chronic progressive diseases with macro- and microvascular complications. In this research, we sought to ascertain the immunological response to d-ibose-glycated fibrinogen. New Zealand White female rabbits were immunized with native and d-ribose-glycated (Rb-gly-Fb) fibrinogen and used for studying the immunological response. Serum from these rabbits analyzed using direct binding and competitive inhibition ELISA was found to contain a high titer of antibodies against Rb-gly-Fb; Rb-gly-Fb was much more immunogenic than its native form. The IgG against Rb-gly-Fb (Rb-gly-Fb-IgG) was highly specific against the immunogenic protein. Moreover, histopathology and immunofluorescence studies revealed the deposition of the Rb-gly-Fb-IgG immune complex in the glomerular basement membrane of the kidneys of immunized rabbits. Furthermore, immunization with Rb-gly-Fb increased the expression of genes encoding proinflammatory cytokines, tumour necrosis factor α, interleukin-6, interleukin-1β, and interferon-gamma, which is indicative of increased inflammation and the antigenic role of Rb-gly-Fb in provoking an immune response.

Rapid and Selective 19F NMR-Based Sensors for Fingerprint Identification of Ribose

Ribose plays an important role in the process of life. Excessive ribose in the human cerebrospinal fluid or urine can be used as an early diagnostic marker of leukoencephalopathy. Fluorinated phenylboronic acid combined with ¹⁹F NMR spectroscopy was a powerful method for molecular recognition. However, phenylboronic acid-based sensors for selective detection of ribose are rarely reported in the literature. In this study, the rapid and highly selective recognition of ribose was studied by ¹⁹F NMR and 2-fluorophenylboric acid. It was found that 2-fluoro-phenylboric acid was an appropriate ¹⁹F NMR-based sensor molecule for the determination of ribose under physiological conditions with high selectivity and robust anti-interference ability. When 2-fluorophenylboric acid was used for the detection of ribose in human urine without any sample pretreatment, a limit of detection of 78 μM was obtained at room temperature under given ¹⁹F NMR experimental conditions (400 MHz, 512 scans, ca. 12 min), which can well meet the needs of practical application.

Urine D-ribose levels correlate with cognitive function in community-dwelling older adults

Background

D-ribose is involved in the pathogenesis of Alzheimer’s Disease. The study aimed to determine the association between D-ribose and cognitive function in a sample of community-dwelling older adults.

Methods

A cross-sectional study was conducted in Chaoyang District, Beijing in 2019–2020. Eligible participants were community-based older adults aged 60 years and above. D-ribose was analyzed from the morning urine. Cognitive function, subjective cognitive decline, and depressive symptoms were measured by a battery of neuropsychological tests. Linear regressions were performed to determine the relationship between the urine D-ribose levels and cognitive performance.

Results

A sample of 1725 participants (67.1% female) aged 60 to 85 years (69.40 ± 5.87 years, mean ± SD) was enrolled in the analysis. The urine D-ribose concentrations ranged from 1.53 to 208.89 μmol/L (median 38.10 μmol/L; interquartile range 22.52—64.96 μmol/L). Higher levels of D-ribose were associated with worse performance on Mini-Mental State Examination and verbal fluency when age, gender, education, depressive symptoms, and cardiovascular risk factors were included as covariates.

Conclusions

The urine D-ribose was negatively correlated with cognitive function in community-dwelling older adults. The findings suggest that the dysmetabolism of D-ribose may play a role at the early stage of cognitive impairment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03288-w.

Glycation modulates alpha-synuclein fibrillization kinetics: a sweet spot for inhibition

Glycation is a nonenzymatic posttranslational modification (PTM) known to be increased in the brains of hyperglycemic patients. Alpha-synuclein (αSN), a central player in the etiology of Parkinson’s disease, can be glycated at lysine residues, thereby reducing αSN fibril formation in vitro and modulating αSN aggregation in cells. However, the molecular basis for these effects is unclear. To elucidate this, we investigated the aggregation of αSN modified by eight glycating agents, namely the dicarbonyl compound methylglyoxal (MGO) and the sugars ribose, fructose, mannose, glucose, galactose, sucrose, and lactose. We found that MGO and ribose modify αSN to the greatest extent, and these glycation products are the most efficient inhibitors of fibril formation. We show glycation primarily inhibits elongation rather than nucleation of αSN and has only a modest effect on the level of oligomerization. Furthermore, glycated αSN is not significantly incorporated into fibrils. For both MGO and ribose, we discovered that a level of ∼5 modifications per αSN is optimal for inhibition of elongation. The remaining sugars showed a weak but optimal inhibition at ∼2 modifications per αSN. We propose that this optimal level balances the affinity for the growing ends of the fibril (which decreases with the extent of modification) with the ability to block incorporation of subsequent αSN subunits (which increases with modification). Our results are not only relevant for other αSN PTMs but also for understanding PTMs affecting other fibrillogenic proteins and may thus open novel avenues for therapeutic intervention in protein aggregation disorders.

Anti-α-Glucosidase and Antiglycation Activities of α-Mangostin and New Xanthenone Derivatives: Enzymatic Kinetics and Mechanistic Insights through In Vitro Studies

Diabetes mellitus is characterized by chronic hyperglycemia that promotes ROS formation, causing severe oxidative stress. Furthermore, prolonged hyperglycemia leads to glycation reactions with formation of AGEs that contribute to a chronic inflammatory state. This research aims to evaluate the inhibitory activity of α-mangostin and four synthetic xanthenone derivatives against glycation and oxidative processes and on α-glucosidase, an intestinal hydrolase that catalyzes the cleavage of oligosaccharides into glucose molecules, promoting the postprandial glycemic peak. Antiglycation activity was evaluated using the BSA assay, while antioxidant capacity was detected with the ORAC assay. The inhibition of α-glucosidase activity was studied with multispectroscopic methods along with inhibitory kinetic analysis. α-Mangostin and synthetic compounds at 25 µM reduced the production of AGEs, whereas the α-glucosidase activity was inhibited only by the natural compound. α-Mangostin decreased enzymatic activity in a concentration-dependent manner in the micromolar range by a reversible mixed-type antagonism. Circular dichroism revealed a rearrangement of the secondary structure of α-glucosidase with an increase in the contents of α-helix and random coils and a decrease in β-sheet and β-turn components. The data highlighted the anti-α-glucosidase activity of α-mangostin together with its protective effects on protein glycation and oxidation damage.

Comparison of bovine serum albumin glycation by ribose and fructose in vitro and in vivo

Advanced glycation end products (AGEs) play a critical pathogenic role in the development of diabetic complications. Recent studies have shown that diabetes is associated with not only abnormal glucose metabolism but also abnormal ribose and fructose metabolism, although glucose is present at the highest concentration in humans. The glycation ability and contribution of ribose and fructose to diabetic complications remain unclear. Here, the glycation ability of ribose, fructose and glucose under a mimic physiological condition, in which the concentration of ribose or fructose was one-fiftieth that of glucose, was compared. Bovine serum albumin (BSA) was used as the working protein in our experiments. Ribose generated more AGEs and was markedly more cytotoxic to SH-SY5Y cells than fructose. The first-order rate constant of ribose glycation was found to be significantly greater than that of fructose glycation. LC-MS/MS analysis revealed 41 ribose-glycated Lys residues and 12 fructose-glycated residues. Except for the shared Lys residues, ribose reacted selectively with 17 Lys, while no selective Lys was found in fructose-glycated BSA. Protein conformational changes suggested that ribose glycation may induce BSA into amyloid-like monomers compared with fructose glycation. The levels of serum ribose were correlated positively with glycated serum protein (GSP) and diabetic duration in type 2 diabetes mellitus (T2DM), respectively. These results indicate that ribose has a greater glycation ability than fructose, while ribose largely contributes to the production of AGEs and provides a new insight to understand in the occurrence and development of diabetes complications.

Mitochondrial bioenergetics and D-ribose in HFpEF: a brief narrative review

Objective

In this review article, we briefly describe the status of treatment options for HFpEF and the role of mitochondrial dysfunction in the pathogenesis of HFpEF as an alternative therapeutic target. We also examine the mechanisms of D-ribose in cellular energy production and discuss the potential disadvantages and benefits of supplemental use of D-ribose in patients with HFpEF.

Background

Heart failure is a major cardiovascular disease that impacts over 6 million Americans and is one of the leading causes for morbidity and mortality. Patients with heart failure often experience shortness of breath and fatigue along with impaired physical capacity, all leading to poor quality of life. As a subtype of heart failure, heart failure with preserved ejection fraction (HFpEF) is characterized with impaired diastolic function. Currently, there are no effective treatments specifically for HFpEF, thus clinicians and researchers are searching for therapies to improve cardiac function. Emerging evidence indicate that mitochondrial dysfunction and impaired cardiac bioenergetics are among the underlying mechanisms for HFpEF. There is increased interest in investigating the use of supplements such as D-ribose to enhance mitochondrial function and improve production of adenosine triphosphate (ATP).

Methods

For this narrative review, more than 100 relevant scientific articles were considered from various databases (e.g., PubMed, Web of Science, CINAHL, and Google Scholar) using the keywords “Heart Failure”, “HFpEF”, “D-ribose”, “ATP”, “Mitochondria”, Bioenergetics”, and “Cellular Respiration”.

Conclusions

It is essential to find potential targeted therapeutic treatments for HFpEF. Since there is evidence that the HFpEF is related to impaired myocardial bioenergetics, enhancing mitochondrial function could augment cardiac function. Using a supplement such as D-ribose could improve mitochondrial function by increasing ATP and enhancing cardiac performance for patients with HFpEF. There is a recently completed clinical trial with HFpEF patients that indicates D-ribose increases ATP production and improves cardiac ejection fraction.

Phytochemical thymoquinone prevents hemoglobin glycoxidation and protofibrils formation: A biophysical aspect

d-ribose, a reducing sugar, in diabetic hyperglycemia provokes non-enzymatic glycoxidation of hemoglobin (Hb), an abundant protein of red blood cells (RBCs). Different types of intermediates adduct formation occur during glycoxidation, such as advanced glycation end-products (AGEs) which lead to amyloid formation due to structural and conformational alterations in protein. Therefore, the study of these intermediate adducts plays a pivotal role to discern their relationship with diabetes mellitus and related disorders. Here, we investigated the interaction mechanism of d-ribose with Hb, and Hb prebound phytochemical thymoquinone (TQ). Our investigation reveals that the interaction of TQ with histidine residues of Hb interferes with the interaction of d-ribose with glycine residues at the glycation-site. Based on that, we had performed a time-based (21-days) in-vitro glycoxidation study at 37 °C to investigate the structural perturbation mechanism of Hb at different time-intervals in absence/presence of TQ. We found that prolonged glycoxidation induces amyloid formation in absence of TQ but in its presence, the process was prohibited. In summary, this study examined and characterized biophysically different intermediate-states of protein carrying glycoxidation-modification. Our findings suggested that TQ potentially affects interaction of d-ribose with Hb that prevents glycoxidation and protofibril formation, which establishes TQ as a potential therapeutic agent.

Untargeted metabolomics analysis by gas chromatography/time-of-flight mass spectrometry of human serum from methamphetamine abusers

Methamphetamine (METH) abuse has become a global public health problem. However, the potential mechanisms involving METH-induced metabolic disorders have thus far remained poorly understood. Metabolomics can provide a clue for the cause of apparent changes and consequently be used to investigate the METH-induced dysregulation of metabolite expression and the mechanism of metabolic disorder mechanism. This laboratory investigation included 80 METH abusers and 80 healthy people. The serum metabolites were detected and analysed by gas chromatography/time-of-flight mass spectrometry. Raw data were processed with the software MS DIAL, which includes deconvolution, peak alignment and compound identification. The data matrix was processed by univariate and multivariate analyses for significant metabolite screening with the criteria of variable importance in projection values > 1, fold change > 1.5 and the t test (p value < 0.05). Significant differences in 16 metabolites (deoxycholic acid, cholic acid, hydroxylamine, etc.) in serum were found between the METH abuse group and the control group. Energy metabolic pathways and several amino acid metabolic pathways (alanine, aspartic acid and glutamate metabolism and tryptophan metabolism) were primarily involved. Further analysis indicated that the area under the receiver operating characteristic curve (AUC) was 0.998 for these 16 metabolites. Among the metabolites, three carbohydrates (d-ribose, cellobiose and maltotriose) had an AUC of 0.975, which were determined as potential markers of abuse. We observed metabolic disturbances in METH abusers, particularly perturbation in energy metabolism and amino acid metabolism, which can provide new insights into the search for biomarkers and the mechanisms underlying the adverse effects of METH on human health.

Dietary polyphenols inhibit plasma protein arabinosylation: Biomolecular interaction of genistein and ellagic acid with serum albumins

The mode of interaction of polyphenolic compounds like genistein (GTN) and ellagic acid (EGA) with human and bovine serum albumin (HSA and BSA, respectively) was found to differ significantly. Stern-Volmer (SV) analysis of the fluorescence quenching data revealed that the binding strength of EGA (1.9 ± 0.09 × 10⁵ M^-1) to HSA is about one order of magnitude higher than GTN (2.24 ± 0.06 × 10⁴ M^-1). While the static quenching of HSA fluorescence was found to proceed through simple Stern-Volmer (SV) mechanism, a quenching sphere-of-action model was indispensable for BSA. Temperature dependent fluorescence along with a series of other biophysical experiments and ensemble docking calculation revealed that EGA and GTN bind to the serum proteins primarily through the entropy driven process. The α-helical content and the microenvironment near Trp residue of HSA and BSA did not show any appreciable change due to the binding of either GTN or EGA. Interestingly, both GTN and EGA were found to inhibit the formation of advanced glycated end (AGE) product of serum proteins up to the extent of 70-90% within 12-24 h. Relatively moderate binding propensity along with the anti-glycation ability of the polyphenols confirmed that GTN and EGA can be used either as an alternative or towards development of suitable drugs in the prevention of many diabetic-related complications.

D-ribose: Potential clinical applications in congestive heart failure and diabetes, and its complications (Review)

The quality of life of patients with certain diseases may be improved through the development of technologies and advancements in pharmacology, with the aim of prolonging their life. However, congestive heart failure (CHF), as well their complications, continue to be the leading cause of disease-associated death. The mechanisms underlying the development and progression of diabetes and CHF have been uncovered in a stepwise manner and the understanding of these mechanisms has improved the management of these diseases, resulting in reduced mortality and morbidity rates; however, CHF remains the leading cause of death worldwide, particularly in developed countries. In the past decades, research has indicated that several supplements and naturally occurring compounds may be used to treat muscle weakness, for cardiac failure management, rehabilitation following myocardial ischemia-reperfusion and various complications of diabetes. D-ribose is an essential component of the respiratory, skeletal and nervous systems and is a popular compound, as its supplementation may have beneficial effects. In the present review, the physiological roles, toxic reactions and the potential use of D-ribose in the management of clinical diseases are summarized.

The Prophylactic Activity of Punica granatum L. mesocarp Protects Preadipocytes against Ribosylated BSA-Induced Toxicity

OBJECTIVE

It was aimed at comparing the glycating capacities of glucose and ribose in bovine serum albumin (BSA) and anti-glycation activity of pomegranate mesocarp extract (PME). The protective mechanism of PME against ribosylated BSA (BSA_RIB)-induced toxicity was also investigated.

METHODS

BSA was incubated with glucose or ribose in the presence or absence of PME for 15 days. In preadipocytes pretreated with PME, cell viability, ROS production, lipid peroxidation and mitochondrial membrane potential were investigated following 1, 6, 12, 18 and 24 h exposure to BSA_RIB. Nuclear translocation of NFκB was assessed at 1 h and 24 h of BSA_RIB insult. Accumulation of oxidized proteins, activities of intrinsic antioxidant enzymes and IL-6 secretion were also determined after 24 h exposure to BSA_RIB.

RESULTS

Ribose was a harsher glycating agent as compared to glucose and PME showed strong anti-glycation activity by suppressing (P < 0.05) the increase in levels of fluorescent AGEs, Amadori products, protein carbonyl and advanced oxidation protein products (AOPP). In preadipocytes, BSA_RIB potentiated pro-apoptotic activity by inhibiting the nuclear translocation of NFκB. BSA_RIB induced a time dependent decrease in cell viability, which was significantly suppressed (P < 0.05) by PME. The extract also significantly reduced (P < 0.05) the time dependent increase in ROS level and associated lipid peroxidation as well as loss in mitochondrial membrane potential caused by BSA_RIB. PME also counteracted the BSA_RIB-induced accumulation of oxidized proteins, decrease in intrinsic antioxidant activity and IL-6 over-secretion.

CONCLUSIONS

PME showed anti-glycation activity and afforded protection against BSA_RIB-induced toxicity, oxidative stress and inflammation in preadipocytes.

Protein aggregation as a consequence of non-enzymatic glycation: Therapeutic intervention using aspartic acid and arginine

Non-enzymatic glycation tempted AGEs of proteins are currently at the heart of a number of pathological conditions. Production of chemically stable AGEs can permanently alter the protein structure and function, concomitantly leading to dilapidated situations. Keeping in perspective, present study aims to report the glycation induced structural and functional modification of a cystatin type isolated from rai mustard seeds, using RSC-glucose and RSC-ribose as model system. Among the sugars studied, ribose was found to be most potent glycating agent as evident from different biophysical assays. During the course of incubation, RSC was observed to pass through a series of structural intermediates as revealed by circular dichroism, altered intrinsic fluorescence and high ANS binding. RSC incubation with ribose post day 36 revealed the possible buildup of β structures as observed in CD spectral analysis, hinting towards the generation of aggregated structures in RSC. High thioflavin T fluorescence and increased Congo red absorbance together with enhanced turbidity of the modified form confirmed the aggregation of RSC. The study further revealed anti-glycation and anti-aggregation potential of amino acids; aspartic acid and arginine as they prevented and/or slowed down the process of AGEs and β structure buildup in a concentration dependent manner with arginine proving to be the most effective one.

Ribosylation-Derived Advanced Glycation End Products Induce Tau Hyperphosphorylation Through Brain-Derived Neurotrophic Factor Reduction

Advanced glycation end products (AGEs) have been implicated in the disease process of diabetes mellitus. They have also been found in senile plaques and neurofibrillary tangles in the brains of Alzheimer's disease patients. Furthermore, abnormally high levels of D-ribose and D-glucose were found in the urine of patients with type 2 diabetes mellitus, suggesting that diabetic patients suffer from dysmetabolism of not only D-glucose but also D-ribose. In the present study, intravenous tail injections of ribosylated rat serum albumin (RRSA) were found to impair memory in rats, but they did not markedly impair learning, as measured by the Morris water maze test. Injections of RRSA were found to trigger tau hyperphosphorylation in the rat hippocampus via GSK-3β activation. Tau hyperphosphorylation and GSK-3β activation were also observed in N2a cells in the presence of ribosylation-derived AGEs. Furthermore, the administration of ribosylation-derived AGEs induced the suppression of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB). Both GSK-3β inhibition and BDNF treatment decreased the levels of phosphorylated tau in N2a cells. In particular, the administration of BDNF could rescue memory failure in ribosylated AGE-injected rats. Ribosylation-derived AGEs downregulated the BDNF-TrkB pathway in rat brains and N2a cells, leading to GSK-3β activation-mediated tau hyperphosphorylation, which was involved in the observed rat memory loss. Targeting ribosylation may be a promising therapeutic strategy to prevent Alzheimer's disease and diabetic encephalopathies.

Mechanism of Selenium Nanoparticles Inhibiting Advanced Glycation End Products

Selenium nanoparticles (SeNPs) have been applied in fields of nanobiosensors, environment, nanomedicine, etc. as a result of their excellent characteristics. Early studies had shown that SeNPs have certain inhibition ability against glycation, but the inhibition mechanism, especially for the influence of SeNPs on the reaction activity of glycation sites, remains unclear. The aim of the presented research was to reveal the effects of SeNPs on the β-lactoglobulin (β-Lg)/d-ribose glycation system at the molecular level and explore the possible inhibitory mechanism of SeNPs on the formation of advanced glycation end products (AGEs) by analyzing the glycation sites via high-performance liquid chromatography (HPLC)-Orbitrap-tandem mass spectrometry (MS/MS). Changes in contents of AGE formation and free amino acid contents had indicated that SeNPs could significantly slow the glycation process, thus attenuating the formation of AGEs. HPLC-Orbitrap-MS/MS analysis revealed that, at 6, 12, and 24 h, the number of glycation sites of glycated β-Lg decreased from 7, 7, and 9 to 5, 5, and 6 after the intervention of SeNPs, respectively. The glycation extent of each glycation site was controlled, and the dual-glycation ability of K8, K14, K47, K91, and K101 was changed. All of these results confirmed that SeNPs could indeed slow the process of protein glycation at the molecular level. This may be the reason for SeNPs reducing the formation of AGEs during glycation. Therefore, this study shed light on the insight of how SeNPs reduce the formation of AGEs.

An in vitro approach to unveil the structural alterations in d-ribose induced glycated fibrinogen

Plasma proteins persistently bear non-enzymatic post-translational modifications (NEPTM) that proceeds with nucleophilic addition between free amino groups of proteins, and carbonyl group of reducing sugars. Glycation, a prevalent NEPTM rush by the high availability of reducing sugars results in the generation of advanced glycation end products (AGEs). Plasma proteins are more vulnerable to glycation because of the presence of multiple glycation sites and are widely studied. However, fibrinogen glycation is less studied. Therefore, it was designed as an in vitro study to elucidate d-ribose mediated glycative damage suffered by fibrinogen protein at secondary and tertiary structure level. The glycation induced structural alterations were analyzed by UV-vis, fluorescence, circular dichroism, scanning electron microcopy and Fourier transform infrared spectroscopy. Glycation induced protein aggregation and fibrils formation was confirmed by thioflavin T and congo red assay. Moreover, molecular docking study was performed to further validate physicochemical characterization. Structural alterations, increased ketoamines, protein carbonyls and HMF contents were reported in d-ribose glycated fibrinogen against their native analogues. The results validate structural perturbations, increased glycoxidative stress and AGEs formation, which might influence normal function of fibrinogen especially blood coagulation cascade. Thus, we can conclude that under diabetes induced hyperglycemic state in physiological systems, d-ribose induced fibrinogen glycation might play a crucial role in the onset of micro- and macro-vascular complications, thereby worsen the diabetes associated secondary disorders. Moreover, this in vitro study might pave a path to choose fibrinogen as a future biomarker for the early detection of diabetes mediated vascular complications.Communicated by Ramaswamy H. Sarma.

An Azidoribose Probe to Track Ketoamine Adducts in Histone Ribose Glycation

Reactive cellular metabolites can modify macromolecules and form adducts known as nonenzymatic covalent modifications (NECMs). The dissection of the mechanisms, regulation, and consequences of NECMs, such as glycation, has been challenging due to the complex and often ambiguous nature of the adducts formed. Specific chemical tools are required to directly track the formation of these modifications on key targets in order to uncover their underlying physiological importance. Here, we present the novel chemoenzymatic synthesis of an active azido-modified ribose analog, 5-azidoribose (5-AR), as well as the synthesis of an inactive control derivative, 1-azidoribose (1-AR), and their application toward understanding protein ribose-glycation in vitro and in cellulo. With these new probes we found that, similar to methylglyoxal (MGO) glycation, ribose glycation specifically accumulates on histones. In addition to fluorescent labeling, we demonstrate the utility of the probe in enriching modified targets, which were identified by label-free quantitative proteomics and high-resolution MS/MS workflows. Finally, we establish that the known oncoprotein and hexose deglycase, fructosamine 3-kinase (FN3K), recognizes and facilitates the removal of 5-AR glycation adducts in live cells, supporting the dynamic regulation of ribose glycation as well as validating the probe as a new platform to monitor FN3K activity. Altogether, we demonstrate this probe's utilities to uncover ribose-glycation and deglycation events as well as track FN3K activity toward establishing its potential as a new cancer vulnerability.

Microbial and enzymatic strategies for the production of L-ribose

L-Ribose is a non-naturally occurring pentose that recently has become known for its potential application in the pharmaceutical industry, as it is an ideal starting material for use in synthesizing L-nucleosides analogues, an important class of antiviral drugs. In the past few decades, the synthesis of L-ribose has been mainly undertaken through the chemical route. However, chemical synthesis of L-ribose is difficult to achieve on an industrial scale. Therefore, the biotechnological production of L-ribose has gained considerable attention, as it exhibits many merits over the chemical approaches. The present review focuses on various biotechnological strategies for the production of L-ribose through microbial biotransformation and enzymatic catalysis, and in particular on an analysis and comparison of the synthetic methods and different enzymes. The physiological functions and applications of L-ribose are also elucidated. In addition, different sugar isomerases involved in the production of L-ribose from a number of sources are discussed in detail with regard to their biochemical properties. Furthermore, analysis of the separation issues of L-ribose from the reaction solution and different purification methods is presented.Key points • l -Arabinose, l -ribulose and ribitol can be used to produce l -ribose by enzymes. • Five enzymes are systematically introduced for production of l -ribose. • Microbial transformation and enzymatic methods are promising for yielding l -ribose.

The furanosidic scaffold of d-ribose: a milestone for cell life

The recruitment of the furanosidic scaffold of ribose as the crucial step for nucleotides and then for nucleic acids synthesis is presented. Based on the view that the selection of molecules to be used for relevant metabolic purposes must favor structurally well-defined molecules, the inadequacy of ribose as a preferential precursor for nucleotides synthesis is discussed. The low reliability of ribose in its furanosidic hemiacetal form must have played ab initio against the choice of d-ribose for the generation of d-ribose-5-phosphate, the fundamental precursor of the ribose moiety of nucleotides. The latter, which is instead generated through the 'pentose phosphate pathway' is strictly linked to the affordable and reliable pyranosidic structure of d-glucose.

D-ribose and pathogenesis of Alzheimer's disease

It is estimated that the global prevalence of dementia will rise as high as 24 million and predicted to be double in every 20 years which is attributed to the fact that the ageing population is increasing and so more individuals are at risk of developing neurodegenerative diseases like Alzheimer's. Many scientists favored glycation of proteins such as tau, amyloid beta (Aβ) etc. as one of the important risk factor in Alzheimer's disease (AD). Since, D-ribose shows highest glycation ability among other sugars hence, produces advanced glycation end products (AGEs) rapidly. However, there are several other mechanisms suggested by researchers through which D-ribose may cause cognitive impairments. There is a concern related to diabetic patients since they also suffer from D-ribose metabolism, may be more prone to AD risk. Thus, it is imperative that the pathogenesis and the pathways involved in AD progression are explored in the light of ribosylation and AGEs formation for identifying suitable diagnostics marker for early diagnosis or finding promising therapeutic outcomes.

D-Ribose Induces Podocyte NLRP3 Inflammasome Activation and Glomerular Injury via AGEs/RAGE Pathway

D-ribose levels are demonstrated to be increased in type II diabetes mellitus and increased blood D-ribose is involved in the development of diabetic complications such as diabetic encephalopathy and nephropathy. However, the mechanism mediating the pathogenic role of D-ribose in nephropathy remains poorly understood. Given that D-ribose was reported to induce advanced glycation end products (AGEs) formation, the present study tested whether D-ribose induces NLRP3 activation and associated glomerular injury via AGEs/receptor of AGEs (RAGE) signaling pathway. In vivo, C57BL/6J and Asc-/- mice were treated with D-ribose with or without AGEs inhibitor. Administration of D-ribose daily for 30 days was found to induce NLRP3 inflammasome formation in glomerular podocyte, as shown by increased co-localization of NLRP3 with apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) or caspase-1. This D-ribose-induced NLRP3 inflammasome formation was accompanied by its activation as evidenced by increased IL-1β production, a major product of NLRP3 inflammasome. Corresponding to NLRP3 inflammasome activation, D-ribose led to significant glomerular injury in mice. All these D-ribose-induced glomerular inflammasome and associated pathological changes were markedly attenuated by deletion of Asc gene. Furthermore, the accumulation of AGEs and RAGE was found increased in glomeruli of mice receiving D-ribose. In cell studies, we also confirmed that D-ribose induced NLRP3 inflammasome formation and activation in podocytes, which was significantly blocked by caspase-1 inhibitor, YvAD. Mechanically, AGEs formation inhibition and cleavage or silencing of RAGE gene were shown to suppress D-ribose-induced NLRP3 inflammasome formation and activation, as shown by significant reduction of NLRP3 inflammasome molecular aggregation, caspase-1 activity and IL-1β production. These results strongly suggest that relatively long term administration of D-ribose induces NLRP3 inflammasome formation and activation in podocytes via AGEs/RAGE signaling pathway, which may be one of important triggering mechanisms leading to diabetic nephropathy.

D-ribose is elevated in T1DM patients and can be involved in the onset of encephalopathy

Although many mechanisms have been proposed for diabetic encephalopathy in type 2 diabetes mellitus (T2DM), the risk factors for cognitive impairment in type 1 diabetes mellitus (T1DM) are less clear. Here, we show that streptozotocin (STZ)-induced T1DM rats showed cognitive impairment in both Y maze and Morris water maze assays, accompanied with D-ribose was significantly increased in blood and urine, in addition to D-glucose. Furthermore, advanced glycation end products (AGE), Tau hyperphosphorylation and neuronal death in the hippocampal CA4/DG region were detected in T1DM rats. The expression and activity of transketolase (TKT), an important enzyme in the pentose shunt, were decreased in the brain, indicating that TKT may be involved in D-ribose metabolism in T1DM. Support for these change was demonstrated by the activation of TKT with benfotiamine (BTMP) treatment. Decreased D-ribose levels but not D-glucose levels; markedly reduced AGE accumulation, Tau hyperphosphorylation, and neuronal death; and improved cognitive ability in T1DM rats were shown after BTMP administration. In clinical investigation, T1DM patients had high D-ribose levels in both urine and serum. Our work suggests that D-ribose is involved in the cognitive impairment in T1DM and may provide a potentially novel target for treating diabetic encephalopathy.

d-Ribose contributes to the glycation of serum protein

d-Ribose is active in glycation and rapidly produces advanced glycation end products, leading to cell death and to cognitive impairment in mice. Glycated serum protein (GSP) is a relatively short-term biomarker for glycemic control in diabetes mellitus. However, whether d-ribose is related to GSP is unclear. The aim of this work was to identify the contribution of d-ribose to GSP compared to d-glucose. Here, we showed that the yield of glycated human serum albumin with d-ribose was at least two-fold higher than that with d-glucose in a 2-week incubation. The glycation of human serum albumin (HSA) with d-ribose was much faster than that with d-glucose, as determined by monitoring changes in the fluorescent intensity of glycation products with time. Liquid chromatography-mass spectrometry/mass spectrometry revealed that 17 and 7 lysine residues on HSA were glycated in the presence of d-ribose and d-glucose, respectively, even when the concentration ratio [d-ribose]/[d-glucose] was 1/50. The intraperitoneal injection of d-ribose significantly increased the GSP levels in Sprague Dawley rats, but the injection of d-glucose did not. The level of d-ribose was more positively associated with GSP than the level of d-glucose in streptozotocin-treated rats. In diabetic patients, the levels of both d-ribose and d-glucose were closely related to the level of GSP. Together, these in vitro and in vivo findings indicated that d-ribose is an important contributor to the glycation of serum protein, compared to d-glucose. To assess GSP levels in diabetes mellitus, we should consider the contribution from d-ribose, which plays a nonnegligible role.

Changes in the phenolic compositions of Elaeagnus umbellata and Sambucus lanceolata after in vitro gastrointestinal digestion and evaluation of their potential anti-diabetic properties

In this work, the phenolic composition of E. umbellata leaves and berries is reported. Berries were rich in flavonols, whereas leaves presented abundant flavonols and ellagitannins. Then, the enzyme-inhibitory properties, anti-glycation and antioxidant activities of E. umbellata and Sambucus lanceolata (its phenolic profile has been already established in a previous work) were tested by several in vitro assays and compared. The simulated gastrointestinal digestion resulted in a decrease on their phenolic composition. Nevertheless, both species still had the ability to inhibit aldose reductase activity and protein glycation and scavenge free radicals at the end of the process. Thus, the potential beneficial effects of E. umbellata and S. lanceolata seems to be kept to some extent after passage throughout the digestive system. Altogether, this study provides further insight into investigation of these species as dietary sources of bioactive compounds to lower the risk of type-2 diabetes and obesity.

Protective Effects of Kaempferol on D-Ribose-Induced Mesangial Cell Injury

Recently, it has been found that the level of urinary D-ribose in type 2 diabetes is notably higher than that in age-matched normal control, and D-ribose is more reactive in the glycation than D-glucose and induces oxidative stress. Kaempferol is one of the main bioactive components in Astragalus membranaceus, with numerous physiological actives, such as antioxidant. The present study investigated the protective effects of kaempferol on D-ribose-treated mesangial cells. CCK-8 and LDH assay were used to test cell viability and cell toxicity. Immunofluorescence and flow cytometry were used to detect the AGE formation and ROS accumulation. GSH level was measured to reflect oxidation resistance. Cell apoptosis was evaluated by Hoechst 33258 staining, AO/EB staining, and western blot. Mitochondrial membrane integrity was detected by JC-1 staining, western blot, and RT-PCR. The change of autophagy level was tested by western blot. The results indicated that D-ribose induced not only cell damage and increased AGE formation and ROS accumulation but also GSH depletion. Further studies demonstrated that D-ribose induced mitochondrial depolarization and the activation of caspase-9/3. But kaempferol could partly block these damages. Subsequently, it was confirmed that kaempferol repaired the autophagy disturbance induced by D-ribose, and 3-MA could reverse the protective effect of kaempferol under D-ribose condition. Our study demonstrated that D-ribose induced AGE accumulation and ROS production in mesangial cell and caused mitochondrial apoptosis, but kaempferol could attenuate these changes and its protective effect might be related to the repair of autophagy.

Glycated Insulin Exacerbates the Cytotoxicity of Human Islet Amyloid Polypeptides: a Vicious Cycle in Type 2 Diabetes

The aggregation of human islet amyloid polypeptide (hIAPP) is one of the triggering factors of type 2 diabetes mellitus (T2DM). hIAPP is cosynthesized, costored, and cosecreted with insulin in pancreatic β-cells, and insulin inhibits hIAPP aggregation. In T2DM patients, long-term hyperglycemia causes glycation of near 10% of total insulin. The glycation not only modifies insulin but also cross-links insulin into oligomers. However, the effect of glycated human insulin on hIAPP aggregation is unknown. In this study, four physiologically relevant monosaccharides, methylglyoxal, glucose, fructose, and ribose were used to glycate human insulin and two C-terminus truncated insulin analogues. Glycated insulin monomers or low molecular weight oligomers such as dimers significantly exacerbated the cytotoxicity of hIAPP. Notably, glycation-induced cross-linking of insulin inhibited the aggregation, membrane disruption, and cytotoxicity of hIAPP, which was corroborated by a control study using EGS-induced cross-linking of insulin or lysozyme. Removal of B29^Lys on the C terminus of the insulin B chain not only abolished glycation-induced cross-linking but also attenuated the aggravation effect of glycated insulin on hIAPP cytotoxicity. Taken together, this study reveals a vicious cycle in T2DM, that hyperglycemia-driven insulin glycation exacerbates the cytotoxicity of hIAPP, which accelerates β-cells death and further deteriorates T2DM.

Interaction of chlorpropamide with serum albumin: Effect on advanced glycated end (AGE) product fluorescence

Carrier proteins like bovine or human serum albumin (BSA and HSA, respectively) are prone to glycation as compared to the other available proteins. In this study, reducing sugars such as l-arabinose (ara), d-(-) galactose (gal) and d-(-) fructose (fru) were used to create model glycated serum albumins and binding ability of these with well-known antidiabetic drug chlorpropamide (CPM) was monitored. Fluorescence quenching experiment revealed that interaction of CPM with native as well as glycated albumins undergoes through a ground state complex formation. CPM binds strongly to glycated HSA with arabinose (gHSA_ara) as compared to other glycated systems and to the native proteins. CPM interacts through Van der Waals and hydrogen bonding interaction to glycated BSA by d-(-) fructose (gBSA_fru) and also with native HSA; whereas, it's interaction with BSA and others glycated systems like gBSA_ara, gBSA_gal and gHSA_ara occurs primarily through hydrophobic interaction. CPM showed an enhancement in the production of the advanced glycated end products (AGE) in all the glycated proteins. The difference in the binding capability of CPM to differently glycated albumins could be a major model to understand the drug carrying capacity of the glycated serum albumins.

Current Status of Proteomic Technologies for Discovering and Identifying Gingival Crevicular Fluid Biomarkers for Periodontal Disease

Periodontal disease is caused by bacteria in dental biofilms. To eliminate the bacteria, immune system cells release substances that inflame and damage the gums, periodontal ligament, or alveolar bone, leading to swollen bleeding gums, which is a sign of gingivitis. Damage from periodontal disease can cause teeth to loosen also. Studies have demonstrated the proteomic approach to be a promising tool for the discovery and identification of biochemical markers of periodontal diseases. Recently, many studies have applied expression proteomics to identify proteins whose expression levels are altered by disease. As a fluid lying in close proximity to the periodontal tissue, the gingival crevicular fluid (GCF) is the principal target in the search for periodontal disease biomarkers because its protein composition may reflect the disease pathophysiology. Biochemical marker analysis of GCF is effective for objective diagnosis in the early and advanced stages of periodontal disease. Periodontal diseases are also promising targets for proteomics, and several groups, including ours, have applied proteomics in the search for GCF biomarkers of periodontal diseases. This search is of continuing interest in the field of experimental and clinical periodontal disease research. In this article, we summarize the current situation of proteomic technologies to discover and identify GCF biomarkers for periodontal diseases.