Rationally Engineered Novel Glycosyltransferase UGT74DD1 from Siraitia grosvenorii Catalyzes the Generation of the Sweetener Mogroside III.

Mogrosides are natural compounds highly valued in the food sector for their exceptional sweetness. Here, we report a novel O-glycosyltransferase (UGT74DD1) from Siraitia grosvenorii that catalyzes the conversion of mogrol to mogroside IIE. Site-directed mutagenesis yielded the UGT74DD1-W351A mutant, which exhibited the new capability to transform mogroside IIE into the valuable sweetener mogroside III, but with low catalytic activity. Subsequently, using structure-guided directed evolution with combinatorial active-site saturation testing, the superior mutant M6 (W351A/Q373 K/E49H/Q335W/S278C/D17F) were obtained, which showed a 46.1-fold increase in catalytic activity compared to UGT74DD1-W351A. Molecular dynamics simulations suggested that the enhanced activity and extended substrate profiles of M6 are due to its enlarged substrate-binding pocket and strengthened enzyme-substrate hydrogen bonding interactions. Overall, we redesigned UGT74DD1, yielding mutants that catalyze the conversion of mogrol into mogroside III. This study thus broadens the toolbox of UGTs capable of catalyzing the formation of valuable polyglycoside compounds.

Tongue-on-a-Chip: Parallel Recording of Sweet and Bitter Receptor Responses to Sequential Injections of Pure and Mixed Sweeteners.

A microfluidic tongue-on-a-chip platform has been evaluated relative to the known sensory properties of various sweeteners. Analogous metrics of typical sensory features reported by human panels such as sweet taste thresholds, onset, and lingering, as well as bitter off-flavor and blocking interactions were deduced from the taste receptor activation curves and then compared. To this end, a flow cell containing a receptor cell array bearing the sweet and six bitter taste receptors was transiently exposed to pure and mixed sweetener samples. The sample concentration gradient across time was separately characterized by the injection of fluorescein dye. Subsequently, cellular calcium responses to different doses of advantame, aspartame, saccharine, and sucrose were overlaid with the concentration gradient. Parameters describing the response kinetics compared to the gradient were quantified. Advantame at 15 µM recorded a significantly faster sweetness onset of 5 ± 2 s and a longer lingering time of 39 s relative to sucrose at 100 mM with an onset of 13 ± 2 s and a lingering time of 6 s. Saccharine was shown to activate the bitter receptors TAS2R8, TAS2R31, and TAS2R43, confirming its known off-flavor, whereas addition of cyclamate reduced or blocked this saccharine bitter response. The potential of using this tongue-on-a-chip to bridge the gap with in vitro assays and taste panels is discussed.

Development of New Multi-Glycosylation Routes to Facilitate the Biosynthesis of Sweetener Mogrosides from Bitter Immature Siraitia Grosvenorii Using Engineered Escherichia coli.

Mogrosides, which have various pharmacological activities, are mainly extracted from Siraitia grosvenorii (Luo Han Guo) and are widely used as natural zero-calorie sweeteners. Unfortunately, the difficult cultivation and long maturation time of Luo Han Guo have contributed to a shortage of mogrosides. To overcome this obstacle, we developed a highly efficient biosynthetic method using engineered Escherichia coli to synthesize sweet mogrosides from bitter mogrosides. Three UDP-glycosyltransferase (UGT) genes with primary/branched glycosylation catalytic activity at the C3/C24 sites of mogrosides were screened and tested. Mutant M3, which could catalyze the glycosylation of nine types of mogrosides, was obtained through enhanced catalytic activity. This improvement in ß-(1,6)-glycosidic bond formation was achieved through single nucleotide polymorphisms and direct evolution, guided by 3D structural analysis. A new multienzyme system combining three UGTs and UDP-glucose (UDPG) regeneration was developed to avoid the use of expensive UDPG. Finally, the content of sweet mogrosides in the immature Luo Han Guo extract increased significantly from 57% to 95%. This study not only established a new multienzyme system for the highly efficient production of sweet mogrosides from immature Luo Han Guo but also provided a guideline for the high-value utilization of rich bitter mogrosides from agricultural waste and residues.

Highly Efficient Biosynthesis of Rebaudioside M8 through Structure-Guided Engineering of Glycosyltransferase UGT94E13.

Given the low-calorie, high-sweetness characteristics of steviol glycosides (SGs), developing SGs with improved taste profiles is a key focus. Rebaudioside M8 (Reb M8), a novel non-natural SG derivative obtained through glycosylation at the C-13 position of rebaudioside D (Reb D) using glycosyltransferase UGT94E13, holds promise for further development due to its enhanced sweetness. However, the low catalytic activity of UGT94E13 hampers further research and commercialization. This study aimed to improve the enzymatic activity of UGT94E13 through semirational design, and a variant UGT94E13-F169G/I185G was obtained with the catalytic activity improved by 13.90 times. A cascade reaction involving UGT94E13-F169G/I185G and sucrose synthase AtSuSy was established to recycle uridine diphosphate glucose, resulting in an efficient preparation of Reb M8 with a yield of 98%. Moreover, according to the analysis of the distances between the substrate Reb D and enzymes as well as between Reb D and the glucose donor through molecular dynamics simulations, it is found that the positive effect of shortening the distance on glycosylation reaction activity accounts for the improved catalytic activity of UGT94E13-F169G/I185G. Therefore, this study addresses the bottleneck in the efficient production of Reb M8 and provides a foundation for its widespread application in the food industry.

Structural insights into the catalytic selectivity of glycosyltransferase SgUGT94-289-3 towards mogrosides.

Mogrosides constitute a series of natural sweeteners extracted from Siraitia grosvenorii fruits. These mogrosides are glucosylated to different degrees, with mogroside V (M5) and siamenoside I (SIA) being two mogrosides with high intensities of sweetness. SgUGT94-289-3 constitutes a uridine diphosphate (UDP)-dependent glycosyltransferase (UGT) responsible for the biosynthesis of M5 and SIA, by continuously catalyzing glucosylation on mogroside IIe (M2E) and on the subsequent intermediate mogroside products. However, the mechanism of its promiscuous substrate recognition and multiple catalytic modes remains unclear. Here, we report multiple complex structures and the enzymatic characterization of the glycosyltransferase SgUGT94-289-3. We show that SgUGT94-289-3 adopts a dual-pocket organization in its active site, which allows the two structurally distinct reactive ends of mogrosides to be presented from different pockets to the active site for glucosylation reaction, thus enabling both substrate promiscuity and catalytic regioselectivity. We further identified a structural motif that is essential to catalytic activity and regioselectivity, and generated SgUGT94-289-3 mutants with greatly improved M5/SIA production from M2E in an in vitro one-pot setup.

Research progress on biosynthesis of erythritol and multi-dimensional optimization of production strategies.

Erythritol, as a new type of natural sweetener, has been widely used in food, medical, cosmetics, pharmaceutical and other fields due to its unique physical and chemical properties and physiological functions. In recent years, with the continuous development of strategies such as synthetic biology, metabolic engineering, omics-based systems biology and high-throughput screening technology, people's understanding of the erythritol biosynthesis pathway has gradually deepened, and microbial cell factories with independent modification capabilities have been successfully constructed. In this review, the cheap feedstocks for erythritol synthesis are introduced in detail, the environmental factors affecting the synthesis of erythritol and its regulatory mechanism are described, and the tools and strategies of metabolic engineering involved in erythritol synthesis are summarized. In addition, the study of erythritol derivatives is helpful in expanding its application field. Finally, the challenges that hinder the effective production of erythritol are discussed, which lay a foundation for the green, efficient and sustainable production of erythritol in the future and breaking through the bottleneck of production.

A Pharmacological perspective on the temporal properties of sweeteners.

Several non-caloric sweeteners exhibit a delay in sweetness onset and a sweetness linger after sampling. These temporal properties are thought to be the result of non-specific interactions with cell membranes and proteins in the oral cavity. Data and analysis presented in this report also support the potential involvement of receptor affinity and binding kinetics to this phenomenon. In general, affected sweeteners exhibit distinctly higher binding affinity compared to carbohydrate sweeteners, which do not have temporal issues. In addition, binding kinetic simulations illustrate much slower receptor binding association and dissociation kinetics for a set of non-caloric sweeteners presenting temporal issues, in comparison to carbohydrate sweeteners. So, the higher affinity of some non-caloric sweeteners, dictating lower use levels, and affecting binding kinetics, could contribute to their delay and linger in sweetness perception. Simple pharmacology principles could explain, at least in part, some of the temporal issues of sweeteners.

Exploring Bitter and Sweet: The Application of Large Language Models in Molecular Taste Prediction.

The perception of bitter and sweet tastes is a crucial aspect of human sensory experience. Concerns over the long-term use of aspartame, a widely used sweetener suspected of carcinogenic risks, highlight the importance of developing new taste modifiers. This study utilizes Large Language Models (LLMs) such as GPT-3.5 and GPT-4 for predicting molecular taste characteristics, with a focus on the bitter-sweet dichotomy. Employing random and scaffold data splitting strategies, GPT-4 demonstrated superior performance, achieving an impressive 86% accuracy under scaffold partitioning. Additionally, ChatGPT was employed to extract specific molecular features associated with bitter and sweet tastes. Utilizing these insights, novel molecular compounds with distinct taste profiles were successfully generated. These compounds were validated for their bitter and sweet properties through molecular docking and molecular dynamics simulation, and their practicality was further confirmed by ADMET toxicity testing and DeepSA synthesis feasibility. This research highlights the potential of LLMs in predicting molecular properties and their implications in health and chemical science.

Insight into the interaction and binding mechanism of a natural nonnutritive sweetener mogroside V with soybean protein isolates based on multi-spectroscopic techniques and computational simulations.

As a natural low-calorie sweetener, Mogroside V (Mog-V) has gradually become one of the alternatives to sucrose with superior health attributes. However, Mog-V will bring unpleasant aftertastes when exceeding a threshold concentration. To investigate the possibility of soy protein isolates (SPIs), namely ß-conglycinin (7S), and glycinin (11S) as flavor-improving agents of Mog-V, the binding mechanism between Mog-V and SPIs was explored through multi-spectroscopy, particle size, zeta potential, and computational simulation. The results of the multi-spectroscopic experiments indicated that Mog-V enhanced the fluorescence of 7S/11S protein in a static mode. The binding affinity of 7S-Mog-V was greater compared with 11S-Mog-V. Particle size and zeta potential analysis revealed that the interaction could promote aggregation of 7S/11S protein with different stability. Furthermore, computational simulations further confirmed that Mog-V could interact with the 7S/11S protein in different ways. This research provides a theoretical foundation for the development and application of SPI to improve the flavor of Mog-V, opening a new avenue for further expanding the market demand for Mog-V.

Stevioside Ameliorates Palmitic Acid-Induced Abnormal Glucose Uptake via the PDK4/AMPK/TBC1D1 Pathway in C2C12 Myotubes.

BACKGROUND: Stevioside (SV) with minimal calories is widely used as a natural sweetener in beverages due to its high sweetness and safety. However, the effects of SV on glucose uptake and the pyruvate dehydrogenase kinase isoenzyme (PDK4) as an important protein in the regulation of glucose metabolism, remain largely unexplored. In this study, we used C2C12 skeletal muscle cells that was induced by palmitic acid (PA) to assess the effects and mechanisms of SV on glucose uptake and PDK4. METHODS: The glucose uptake of C2C12 cells was determined by 2-NBDG; expression of the Pdk4 gene was measured by quantitative real-time PCR; and expression of the proteins PDK4, p-AMPK, TBC1D1 and GLUT4 was assessed by Western blotting. RESULTS: In PA-induced C2C12 myotubes, SV could significantly promote cellular glucose uptake by decreasing PDK4 levels and increasing p-AMPK and TBC1D1 levels. SV could promote the translocation of GLUT4 from the cytoplasm to the cell membrane in cells. Moreover, in Pdk4-overexpressing C2C12 myotubes, SV decreased the level of PDK4 and increased the levels of p-AMPK and TBC1D1. CONCLUSION: SV was found to ameliorate PA-induced abnormal glucose uptake via the PDK4/AMPK/TBC1D1 pathway in C2C12 myotubes. Although these results warranted further investigation for validation, they may provide some evidence of SV as a safe natural sweetener for its use in sugar-free beverages to prevent and control T2DM.

Recent advancements in mogrosides: A review on biological activities, synthetic biology, and applications in the food industry.

Mogrosides are low-calorie, biologically active sweeteners that face high production costs due to strict cultivation requirements and the low yield of monk fruit. The rapid advancement in synthetic biology holds the potential to overcome this challenge. This review presents mogrosides exhibiting antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, and liver protective activities, with their efficacy in diabetes treatment surpassing that of Xiaoke pills (a Chinese diabetes medication). It also discusses the latest elucidated biosynthesis pathways of mogrosides, highlighting the challenges and research gaps in this field. The critical and most challenging step in this pathway is the transformation of mogrol into a variety of mogrosides by different UDP-glucosyltransferases (UGTs), primarily hindered by the poor substrate selectivity, product specificity, and low catalytic efficiency of current UGTs. Finally, the applications of mogrosides in the current food industry and the challenges they face are discussed.

Development of a tamarind-based functional beverage with partially-hydrolyzed agave syrup and the health effects of its consumption in C57BL/6 mice.

Excess consumption of sweetened beverages is associated with a global rise in metabolic diseases. Tamarind and partially-hydrolyzed agave syrup have potential for developing healthier beverages. Our objective was to develop a functional beverage using these ingredients (PH-AS-B). We also evaluate shelf-life stability (physicochemical, microbiological, and antioxidant properties) and health effects in C57BL/6 mice compared with tamarind beverages sweetened with glucose or fructose. Optimal tamarind extraction conditions were a 1:10 ratio (g pulp/mL water) and boiling for 30 min, and the resulting beverage had a shelf life of two months at 4 °C. Non-volatile metabolites were identified using HPLC/MS. PH-AS-B was associated with decreased blood cholesterol (5%) and triglyceride (20-35%) concentrations in healthy mice as well as lower lipid (82%) concentrations and evidence of protein oxidation (42%) in the liver, compared with glucose- and fructose-sweetened tamarind beverages. In conclusion, PH-AS-B was stable and associated with beneficial metabolic properties in healthy mice.

Effects of common artificial sweeteners at environmentally relevant concentrations on soil springtails and their gut microbiota.

Artificial sweeteners (AS) are extensively utilized as sugar substitutes and have been recognized as emerging environmental contaminants. While the effect of AS on aquatic organisms has garnered recent attention, their effects on soil invertebrates and gut microbial communities remain unclear. To address this knowledge gap, we exposed springtails (Folsomia candida) to both single and combined treatments of four typical AS (sucralose [SUC], saccharin [SAC], cyclamate [CYC], and acesulfame [ACE]) at environmentally relevant concentrations of 0.01, 0.1 and 1 mg kg-1 in soil. Following the first-generational exposure, the reproduction of juveniles showed a significant increase under all the AS treatments of 0.1 mg kg-1. The transcriptomic analysis revealed significant enrichment of several Kyoto Encyclopedia of Gene and Genome pathways (e.g., glycolysis/gluconeogenesis, pentose and glucuronate interconversions, amino sugar, and nucleotide sugar metabolism, ribosome, and lysosome) in springtails under all AS treatments. Analysis of gut bacterial microbiota indicated that three AS (SUC, CYC, and ACE) significantly decreased alpha diversity, and all AS treatments increased the abundance of the genus Achromobacter. After the sixth-generational exposure to CYC, weight increased, but reproduction was inhibited. The pathways that changed significantly (e.g., extracellular matrix-receptor interaction, amino sugar and nucleotide sugar metabolism, lysosome) were generally similar to those altered in first-generational exposure, but with opposite regulation directions. Furthermore, the effect on the alpha diversity of gut microbiota was contrary to that after first-generational exposure, and more noticeable disturbances in microbiota composition were observed. These findings underscore the ecological risk of AS in soils and improve our understanding of the toxicity effects of AS on living organisms.

Efectos metabólicos del consumo excesivo de fructosa añadida / Metabolic effects of excessive fructose consumption added

El consumo de fructosa ha aumentado en los últimos 50 años por la incorporación a la dieta de jarabe de maíz alto en fructosa (JMAF), presente en productos industrializados, como las bebidas azucaradas. Se puede asociar la ingesta de fructosa en altas concentraciones con el aumento de la obesidad y trastornos metabólicos. La fructosa, un azúcar natural que se encuentra en muchas frutas, se consume en cantidades significativas en las dietas occidentales. En cantidades iguales, es más dulce que la glucosa o la sacarosa y, por lo tanto, se usa comúnmente como edulcorante. Debido al incremento de obesidad entre la población joven y general y a los efectos negativos que puede tener a corto y largo plazo es importante considerar de donde provienen las calorías que se ingieren diariamente. Esta revisión describirá la relación entre el consumo de fructosa en altas concentraciones y el riesgo de desarrollar obesidad, resistencia a la insulina, lipogenesis de novo e inflamación.

The consumption of fructose has increased in the last 50 years due to the incorporation into the diet of high fructose corn syrup (HFCS), present in industrialized products, such as sugary drinks. The intake of fructose in high concentrations can be associated with the increase of obesity and metabolic disorders. Fructose, a natural sugar found in many fruits, is consumed in significant quantities in Western diets. In equal amounts, it is sweeter than glucose or sucrose and, therefore, is commonly used as a sweetener. Due to the increase of obesity among the young and general population and the negative effects that can have in the short and long term it is important to consider where the calories that are ingested daily come from. This review will describe the relationship between fructose consumption in high concentrations and the risk of developing obesity, insulin resistance, de novo lipogenesis, nonalcoholic fatty liver, inflammation and metabolic syndrome.

Postprandial metabolic effects of fructose and glucose in type 1 diabetes patients: a pilot randomized crossover clinical trial

ABSTRACT Objective To test the influence of oral fructose and glucose dose-response solutions in blood glucose (BG), glucagon, triglycerides, uricaemia, and malondialdehyde in postprandial states in type 1 diabetes mellitus (T1DM) patients. Subjects and methods The study had a simple-blind, randomized, two-way crossover design in which T1DM patients were selected to receive fructose and glucose solutions (75g of sugars dissolved in 200 mL of mineral-water) in two separate study days, with 2-7 weeks washout period. In each day, blood samples were drawn after 8h fasting and at 180 min postprandial to obtain glucose, glucagon, triglycerides, uric acid, lactate, and malondialdehyde levels. Results Sixteen T1DM patients (seven men) were evaluated, with a mean age of 25.19 ± 8.8 years, a mean duration of disease of 14.88 ± 4.73 years, and glycated hemoglobin of 8.13 ± 1.84%. Fructose resulted in lower postprandial BG levels than glucose (4.4 ± 5.5 mmol/L; and 12.9 ± 4.1 mmol/L, respectively; p < 0.01). Uric acid levels increased after fructose (26.1 ± 49.9 µmol/L; p < 0.01) and reduced after glucose (-13.6 ± 9.5 µmol/L; p < 0.01). The malondialdehyde increased after fructose (1.4 ± 1.6 µmol/L; p < 0.01) and did not change after glucose solution (-0.2 ± 1.6 µmol/L; p = 0.40). Other variables did not change. Conclusions Fructose and glucose had similar sweetness, flavor and aftertaste characteristics and did not change triglycerides, lactate or glucagon levels. Although fructose resulted in lower postprandial BG than glucose, it increased uric acid and malondialdehyde levels in T1DM patients. Therefore it should be used with caution. ClinicalTrials.gov registration: NCT01713023.

Growth kinetic models of five species of Lactobacilli and lactose consumption in batch submerged culture

Abstract Kinetic behaviors of five Lactobacillus strains were investigated with Contois and Exponential models. Awareness of kinetic behavior of microorganisms is essential for their industrial process design and scale up. The consistency of experimental data was evaluated using Excel software. L. bulgaricus was introduced as the most efficient strain with the highest biomass and lactic acid yield of 0.119 and 0.602 g g-1 consumed lactose, respectively. The biomass and carbohydrate yield of L. fermentum and L. lactis were slightly less and close to L. bulgaricus. Biomass and lactic acid production yield of 0.117 and 0.358 for L. fermentum and 0.114 and 0.437 g g-1 for L.actobacillus lactis were obtained. L. casei and L. delbrueckii had the less biomass yield, nearly 11.8 and 22.7% less than L. bulgaricus, respectively. L. bulgaricus (R 2 = 0.9500 and 0.9156) and L. casei (R 2 = 0.9552 and 0.8401) showed acceptable consistency with both models. The investigation revealed that the above mentioned models are not suitable to describe the kinetic behavior of L. fermentum (R 2 = 0.9367 and 0.6991), L. delbrueckii (R 2 = 0.9493 and 0.7724) and L. lactis (R 2 = 0.8730 and 0.6451). Contois rate equation is a suitable model to describe the kinetic of Lactobacilli. Specific cell growth rate for L. bulgaricus, L. casei, L. fermentum, L. delbrueckii and L. lactis with Contois model in order 3.2, 3.9, 67.6, 10.4 and 9.8-fold of Exponential model.

Fructose and NAFLD: metabolic implications and models of induction in rats / Frutose e NAFLD: implicações metabólicas e modelos de indução em ratos

PURPOSE: The increase in fructose consumption is paralleled by a higher incidence of obesity worldwide. This monosaccharide is linked to metabolic syndrome, being associated with hypertriglyceridemia, hypertension, insulin resistance and diabetes mellitus. It is metabolized principally in the liver, where it can be converted into fatty acids, which are stored in the form of triglycerides leading to NAFLD. Several models of NAFLD use diets high in simple carbohydrates. Thus, this study aimed to describe the major metabolic changes caused by excessive consumption of fructose in humans and animals and to present liver abnormalities resulting from high intakes of fructose in different periods of consumption and experimental designs in Wistar rats. METHODS: Two groups of rats were fasted for 48 hours and reefed for 24 or 48 hours with a diet containing 63 percent fructose. Another group of rats was fed an diet with 63 percent fructose for 90 days. RESULTS: Refeeding for 24 hours caused accumulation of large amounts of fat, compromising 100 percent of the hepatocytes. The amount of liver fat in animals refed for 48 hours decreased, remaining mostly in zone 2 (medium-zonal). In liver plates of Wistar rats fed 63 percent fructose for 45, 60 and 90 days it's possible to see that there is an increase in hepatocytes with fat accumulation according to the increased time; hepatic steatosis, however, is mild, compromising about 20 percent of the hepatocytes. CONCLUSIONS: Fructose is highly lipogenic, however the induction of chronic models in NAFLD requires long periods of treatment. The acute supply for 24 or 48 hours, fasted rats can cause big changes, liver steatosis with macrovesicular in all lobular zones.

OBJETIVO: O aumento do consumo de frutose é concomitante a maior incidência mundial de obesidade. Este monossacarídeo está relacionado à Síndrome Metabólica, sendo vinculado à hipertrigliceridemia, hipertensão arterial, resistência à insulina e diabetes mellitus. É metabolizada principalmente no fígado, onde pode ser convertida em ácidos graxos, os quais serão estocados na forma de trigligérides ocasionando a esteatose hepática não alcoólica (NAFLD). Vários modelos de NAFLD utilizam dietas ricas em carboidratos simples. Desta forma, este trabalho teve como objetivos descrever as principais alterações metabólicas causadas pelo consumo excessivo de frutose em humanos e em animais e apresentar as alterações hepáticas decorrentes da alta ingestão de frutose em diferentes períodos de consumo e desenhos experimentais em ratos Wistar. MÉTODOS: Dois grupos de ratos Wistar foram mantidos em jejum durante 48 horas e realimentados por 24 ou 48 horas com dieta contendo 63 por cento de frutose. Outro grupo de ratos Wistar foi alimentado com 63 por cento de frutose durante 90 dias. RESULTADOS: A realimentação por 24 horas provocou acúmulo de grande quantidade de gordura. A quantidade de gordura hepática nos animais realimentados por 48 horas diminuiu, mantendo-se principalmente nas zona 2 (medio-zonal). Em fígados de ratos Wistar alimentados com 63 por cento de frutose até 90 dias foi possível observar que há aumento de hepatócitos com acúmulo de gordura consequente ao aumento do tempo, no entanto a esteatose hepática é leve (20 por cento). CONCLUSÕES: A frutose é altamente lipogênica, no entanto a indução de NAFLD em modelos crônicos necessita de longos períodos de tratamento. A oferta aguda, por 24 ou 48 horas, a ratos mantidos em jejum é capaz de ocasionar grandes mudanças hepáticas, com presença de esteatose macrovesicular em todas as zonas lobulares.

S. mutans biofilm model to evaluate antimicrobial substances and enamel demineralization

The aim of this study was to validate a model of S. mutans biofilm formation, which simulated 'feast-famine' episodes of exposure to sucrose that occur in the oral cavity, showed dose-response susceptibility to antimicrobials and allowed the evaluation of substances with anticaries potential. S. mutans UA159 biofilms were grown for 5 days on bovine enamel slabs at 37°C, 10 percent CO2. To validate the model, the biofilms were treated 2x/day with chlorhexidine digluconate (CHX) at 0.012, 0.024 and 0.12 percent (concentration with recognized anti-plaque effect) and 0.05 percent NaF (concentration with recognized anti-caries effect). CHX showed dose-response effect decreasing biomass, bacterial viability and enamel demineralization (p < 0.05). Whereas, 0.05 percent NaF did not show antimicrobial effect but had similar effect to that of 0.12 percent CHX decreasing enamel demineralization (p < 0.05). The model developed has potential to evaluate the effect of substances on biofilm growth and on enamel demineralization.

Fructose and cardiometabolic disorders: the controversy will, and must, continue: [review]

The present review updates the current knowledge on the question of whether high fructose consumption is harmful or not and details new findings which further pushes this old debate. Due to large differences in its metabolic handling when compared to glucose, fructose was indeed suggested to be beneficial for the diet of diabetic patients. However its growing industrial use as a sweetener, especially in soft drinks, has focused attention on its potential harmfulness, possibly leading to dyslipidemia, obesity, insulin resistance/metabolic syndrome and even diabetes. Many new data have been generated over the last years, confirming the lipogenic effect of fructose as well as risks of vascular dysfunction and hypertension. Fructose exerts various direct effects in the liver, affecting both hepatocytes and Kupffer cells and resulting in non-alcoholic steatotic hepatitis, a well known precursor of the metabolic syndrome. Hepatic metabolic abnormalities underlie indirect peripheral metabolic and vascular disturbances, for which uric acid is possibly the culprit. Nevertheless major caveats exist (species, gender, source of fructose, study protocols) which are detailed in this review and presently prevent any firm conclusion. New studies taking into account these confounding factors should be undertaken in order to ascertain whether or not high fructose diet is harmful.