SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Disaccharide

165

Trehalose is a non-reducing disaccharide that is used as an osmolyte, transport sugar, carbon reserve and stress protectant in a wide range of organisms. In plants, trehalose 6-phosphate (Tre6P), the intermediate of trehalose biosynthesis, is thought to be a signal of sucrose status. Trehalose itself may play a role in pathogenic and symbiotic plant-microbe interactions, in responses to abiotic stress and in developmental signalling, but its precise functions are unknown. A major obstacle to investigating its function is the technical difficulty of measuring the very low levels of trehalose usually found in plant tissues, as most of the established trehalose assays lack sufficient specificity and/or sensitivity.

Concepts: Bacteria, Glucose, Plant, Carbohydrate, Sugar, Disaccharide, Fructose, Sucrose

147

A number of intravenous immunoglobulin preparations are stabilized with sugar additives that may lead over time to undesirable glycation reactions especially in liquid formulation. This study aims to evaluate the reactivity of sugar excipients on such preparations in condition of temperature, formulation and concentration commonly used for pharmaceutical products. Through an innovative LC-MS method reported to characterize post-translational modifications of IgGs Fc/2 fragments, a stability study of IVIg formulated with reducing and non-reducing sugars has been undertaken. The rate of polyclonal IgGs glycation was investigated during 6 months at 5, 25, 30 and 40°C. High levels of glycation were observed with reducing sugars like glucose and maltose in the first months of the stability study from 25°C. Non-reducing sugars presented a low reactivity even at the highest tested temperature (40°C). Furthermore, a site by site analysis was performed by MS/MS to determine the glycation sites which were mainly identified at Lys246, Lys248 and Lys324. This work points out the high probability of glycation reactions in some commercialized products and describes a useful method to characterize IVIg glycated products issued from reducing sugar excipients.

Concepts: Immune system, Glucose, Posttranslational modification, Carbohydrate, Disaccharide, Fructose, Glycation, Sucrose

87

Obesity is exponentially increasing regardless of its preventable characteristics. The current measures for preventing obesity have failed to address the severity and prevalence of obesity, so alternative approaches based on nutritional and diet changes are attracting attention for the treatment of obesity. Fruit contains large amounts of simple sugars (glucose, fructose, sucrose, etc.), which are well known to induce obesity. Thus, considering the amount of simple sugars found in fruit, it is reasonable to expect that their consumption should contribute to obesity rather than weight reduction. However, epidemiological research has consistently shown that most types of fruit have anti-obesity effects. Thus, due to their anti-obesity effects as well as their vitamin and mineral contents, health organizations are suggesting the consumption of fruit for weight reduction purposes. These contradictory characteristics of fruit with respect to human body weight management motivated us to study previous research to understand the contribution of different types of fruit to weight management. In this review article, we analyze and discuss the relationships between fruit and their anti-obesity effects based on numerous possible underlying mechanisms, and we conclude that each type of fruit has different effects on body weight.

Concepts: Nutrition, Glucose, Carbohydrate, Sugar, Disaccharide, Fructose, Monosaccharide, Sucrose

31

Carbohydrate availability in the form of muscle and liver glycogen is an important determinant of performance during prolonged bouts of moderate- to high-intensity exercise. Therefore, when effective endurance performance is an objective on multiple occasions within a 24-h period, the restoration of endogenous glycogen stores is the principal factor determining recovery. This review considers the role of glucose-fructose co-ingestion on liver and muscle glycogen repletion following prolonged exercise. Glucose and fructose are primarily absorbed by different intestinal transport proteins; by combining the ingestion of glucose with fructose, both transport pathways are utilised, which increases the total capacity for carbohydrate absorption. Moreover, the addition of glucose to fructose ingestion facilitates intestinal fructose absorption via a currently unidentified mechanism. The co-ingestion of glucose and fructose therefore provides faster rates of carbohydrate absorption than the sum of glucose and fructose absorption rates alone. Similar metabolic effects can be achieved via the ingestion of sucrose (a disaccharide of glucose and fructose) because intestinal absorption is unlikely to be limited by sucrose hydrolysis. Carbohydrate ingestion at a rate of ≥1.2 g carbohydrate per kg body mass per hour appears to maximise post-exercise muscle glycogen repletion rates. Providing these carbohydrates in the form of glucose-fructose (sucrose) mixtures does not further enhance muscle glycogen repletion rates over glucose (polymer) ingestion alone. In contrast, liver glycogen repletion rates are approximately doubled with ingestion of glucose-fructose (sucrose) mixtures over isocaloric ingestion of glucose (polymers) alone. Furthermore, glucose plus fructose (sucrose) ingestion alleviates gastrointestinal distress when the ingestion rate approaches or exceeds the capacity for intestinal glucose absorption (~1.2 g/min). Accordingly, when rapid recovery of endogenous glycogen stores is a priority, ingesting glucose-fructose mixtures (or sucrose) at a rate of ≥1.2 g·kg body mass(-1)·h(-1) can enhance glycogen repletion rates whilst also minimising gastrointestinal distress.

Concepts: Nutrition, Glucose, Glycogen, Carbohydrate, Disaccharide, Hydrolysis, Fructose, Sucrose

28

Compared to simple sugars, complex carbohydrates have been assumed invisible to taste. However, two recent studies proposed that there may be a perceivable taste quality elicited by complex carbohydrates independent of sweet taste. There is precedent with behavioural studies demonstrating that rats are very attracted to complex carbohydrates, and that complex carbohydrates are preferred to simple sugars at low concentrations. This suggests that rats may have independent taste sensors for simple sugars and complex carbohydrates. The aim of this paper is to investigate oral sensitivities of two different classes of complex carbohydrates (a soluble digestible and a soluble non-digestible complex carbohydrate), and to compare these to other caloric and non-nutritive sweeteners in addition to the prototypical tastes using two commonly used psychophysical measures. There were strong correlations between the detection thresholds and mean intensity ratings for complex carbohydrates (maltodextrin, oligofructose) (r = 0.94, P < 0.001). There were no significant correlations between the detection thresholds of the complex carbohydrates (maltodextrin, oligofructose) and the sweeteners (glucose, fructose, sucralose, Rebaudioside A, erythritol) (all P > 0.05). However, moderate correlations were observed between perceived intensities of complex carbohydrates and sweeteners (r = 0.48-0.61, P < 0.05). These data provide evidence that complex carbohydrates can be sensed in the oral cavity over a range of concentrations independent of sweet taste sensitivity at low concentrations, but with partial overlap with sweet taste intensity at higher concentrations.

Concepts: Glucose, Carbohydrate, Sugar, Disaccharide, Monosaccharide, Sucrose, Sweeteners, Sugar substitute

28

A triosmium carbonyl cluster-boronic acid conjugate is used as a secondary carbohydrate probe in a SERS-based assay. The assay does not require conjugation of the metal carbonyl probe to a SERS-active species and it utilizes the CO stretching vibrations of the metal carbonyl, which lies in a silent region of the SERS spectrum (1800-2200 cm-1), for quantification. High selectivity for glucose over fructose and galactose is obtained, and a human urine sample doped with glucose is detected accurately.

Concepts: Glucose, Urine, Zinc, Sugar, Disaccharide, Monosaccharide, Sucrose, Iridium

28

The correct labelling of dairy foods as “lactose-free” requires a suitably sensitive and valid analytical method for the quantification of lactose in complex food matrices. Thus, an ion-pair RP-HPLC method for the simultaneous determination of lactose, glucose and galactose in original skim milk was investigated. The samples derived from an enzymatic lactose hydrolysis approach (0.5L) using the commercial β-galactosidase Godo-YNL2. After derivatisation with p-aminobenzoic acid and sodium cyanoborohydride, the samples were injected on a RP-C(18) column. Tetrabutylammonium hydrogen sulphate was used as the ion-pair reagent in the eluent system. The sugars were quantified using photometric- (UV; 303 nm) and fluorescence-detection (λ(ex) 313 nm, λ(em) 358 nm). The overall run time was 27 min. The limits of detection (LOD) were estimated at 2 mgL(-1) (UV detection) and at 0.13 mgL(-1) (fluorescence detection). The limits of quantification were 6 mgL(-1) (UV detection) and 0.45 mgL(-1) (fluorescence detection). Thus, this analytical method is suitable for sensitive lactose quantification in milk systems of less than 10 mgL(-1).

Concepts: Enzyme, Glucose, Milk, Carbohydrate, Disaccharide, Fructose, Galactose, Lactose

28

Changes in cold hardiness, carbohydrate content and β-amylase gene expression were monitored in the shoots of the highbush blueberry (Vaccinium corymbosum L.) cultivars ‘Sharpblue’ and ‘Jersey’ during cold acclimation (CA) and deacclimation (DA). The seasonal patterns were similar in both cultivars, but the levels of cold hardiness determined by electrolyte leakage analysis were significantly different; ‘Jersey’ was hardier than ‘Sharpblue’. Cold hardiness was closely related to total soluble sugar content (r = -0.98** and -0.99** for ‘Sharpblue’ and ‘Jersey’, respectively). In ‘Jersey’, more soluble sugars accumulated during CA. Of the detected soluble sugars, glucose, fructose and raffinose contents were significantly associated with cold hardiness in both cultivars. Sucrose was abundant in both cultivars, and stachyose content changed significantly during CA and DA. However, they were not associated with cold hardiness. A sharp decrease in starch contents in the middle of CA coincided with β-amylase gene (VcBMY) expression, indicating the conversion of starch into soluble sugars. During CA, VcBMY was expressed up to twofold higher in ‘Jersey’ than in ‘Sharpblue’. These results suggest that intraspecies differences in the cold hardiness of highbush blueberries are associated with total soluble sugar content, which is driven partly by differential expression of VcBMY.

Concepts: Glucose, Carbohydrate, Sugar, Disaccharide, Fructose, Sucrose, Blueberry, Northern highbush blueberry

27

Peak exogenous carbohydrate oxidation rates typically reach ~1 g∙min-1 during exercise when ample glucose or glucose polymers are ingested. Fructose co-ingestion has been shown to further increase exogenous carbohydrate oxidation rates. The purpose of this study was to assess the impact of fructose co-ingestion provided either as a monosaccharide or as part of the disaccharide sucrose on exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists. Ten trained male cyclists (VO2peak: 65 ± 2 mL∙kg-1∙min-1) cycled on four different occasions for 180 min at 50% Wmax during which they consumed a carbohydrate solution providing 1.8 g∙min-1 of glucose (GLU), 1.2 g∙min-1 glucose + 0.6 g∙min-1 fructose (GLU + FRU), 0.6 g∙min-1 glucose + 1.2 g∙min-1 sucrose (GLU + SUC), or water (WAT). Peak exogenous carbohydrate oxidation rates did not differ between GLU + FRU and GLU + SUC (1.40 ± 0.06 vs. 1.29 ± 0.07 g∙min-1, respectively, p = 0.999), but were 46% ± 8% higher when compared to GLU (0.96 ± 0.06 g∙min-1: p < 0.05). In line, exogenous carbohydrate oxidation rates during the latter 120 min of exercise were 46% ± 8% higher in GLU + FRU or GLU + SUC compared with GLU (1.19 ± 0.12, 1.13 ± 0.21, and 0.82 ± 0.16 g∙min-1, respectively, p < 0.05). We conclude that fructose co-ingestion (0.6 g∙min-1) with glucose (1.2 g∙min-1) provided either as a monosaccharide or as sucrose strongly increases exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists.

Concepts: Glucose, Carbohydrate, Sugar, Disaccharide, Hydrolysis, Fructose, Monosaccharide, Sucrose

27

The liver is an important integrator of nutrient metabolism, yet no liver-derived factors regulating nutrient preference or carbohydrate appetite have been identified. Here we show that the liver regulates carbohydrate intake through production of the hepatokine fibroblast growth factor 21 (FGF21), which markedly suppresses consumption of simple sugars, but not complex carbohydrates, proteins, or lipids. Genetic loss of FGF21 in mice increases sucrose consumption, whereas acute administration or overexpression of FGF21 suppresses the intake of both sugar and non-caloric sweeteners. FGF21 does not affect chorda tympani nerve responses to sweet tastants, instead reducing sweet-seeking behavior and meal size via neurons in the hypothalamus. This liver-to-brain hormonal axis likely represents a negative feedback loop as hepatic FGF21 production is elevated by sucrose ingestion. We conclude that the liver functions to regulate macronutrient-specific intake by producing an endocrine satiety signal that acts centrally to suppress the intake of “sweets.”

Concepts: Metabolism, Nutrition, Glucose, Carbohydrate, Sugar, Disaccharide, Monosaccharide, Sucrose