New application of a traditional method: colorimetric sensor array for reducing sugars based on the in-situ formation of core-shell gold nanorod-coated silver nanoparticles by the traditional Tollens reaction.

An effective and robust colorimetric sensor array for simultaneous detection and discrimination of five reducing sugars (i.e., glyceraldehyde (Gly), fructose (Fru), glucose (Glu), maltose (Mal), and ribose (Rib)) has been proposed. In the sensor array, two negatively charged polydielectrics (sodium polystyrenesulfonate (NaPSS) and sodium polymethacrylate (NaPMAA)), which served as the sensing elements, were individually absorbed on the surface of the cetyltrimethylammonium bromide (CTAB)-coated gold nanorods (AuNR) with positive charges through electrostatic action, forming the designed sensor units (NaPSS-AuNR and NaPMAA-AuNR). In the presence of Tollens reagent (Ag(NH3)2OH), Ag+ was absorbed on the surface of negatively charged NaPSS-AuNR and NaPMAA-AuNRs. When confronted with differential reducing sugars, different reducing sugars exhibited differential levels of deoxidizing abilities toward Ag+, thus Ag+ was reduced to diverse amounts of silver nanoparticles (AgNPs) in situ to form core-shell AuNR@AgNP by the traditional Tollens reaction method, leading to distinct colorimetric response patterns (value of AS/AL (the ratio of absorbance at 360 nm to that at 760 nm in Ag+-NaPMAA-AuNR, and the ratio of absorbance at 360 nm to that at 740 nm in Ag+-NaPSS-AuNR)). These response patterns are characteristic for each reducing sugar, and can be quantitatively distinguished by linear discriminant analysis (LDA) at concentrations as low as 10 nM with relative standard deviation (RSD) of 4.11% (n = 3). The practicability of this sensor array has been validated by recognition of reducing sugars in serum and urine samples. A colorimetric sensor array for reducing sugar discrimination based on the reduction of Ag+ and in situ formation of AuNR@AgNP.

Rapid ultraperformance liquid chromatography-tandem mass spectrometry assay for a characteristic glycogen-derived tetrasaccharide in Pompe disease and other glycogen storage diseases.

BACKGROUND: Urinary excretion of the tetrasaccharide 6-α-D-glucopyranosyl-maltotriose (Glc4) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc4 a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc4 in urine without interference of the Glc4 isomer maltotetraose (M4). METHODS: Urine samples, diluted in 0.1% ammonium hydroxide containing the internal standard acarbose, were filtered, and the filtrate was analyzed by UPLC-MS/MS. RESULTS: We separated and quantified acarbose, M4, and Glc4 using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc4 was linear up to 1500 µmol/L and the limit of quantification was 2.8 µmol/L. Intra- and interassay CVs were 18.0% and 18.4% (10 µmol/L Glc4), and 10.5% and 16.2% (200 µmol/L Glc4). Glc4 in control individuals (n = 116) decreased with increasing age from a mean value of 8.9 mmol/mol to 1.0 mmol/mol creatinine. M4 was present in 5% of urine samples. Mean Glc4 concentrations per age group in untreated patients with Pompe disease (GSD type II) (n = 66) were significantly higher, ranging from 39.4 to 10.3 mmol/mol creatinine (P < 0.001-0.005). The diagnostic sensitivity of Glc4 for GSD-II was 98.5% and the diagnostic specificity 92%. Urine Glc4 was also increased in GSD-III (8 of 9), GSD-IV (2 of 3) and GSD-IX (6 of 10) patients. CONCLUSIONS: The UPLC-MS/MS assay of Glc4 in urine was discriminative between Glc4 and M4 and confirmed the diagnosis in >98% of GSD-II cases.

[Analysis of maltose clearance in plasma and urine of healthy volunteers with high-performance liquid chromatography].

OBJECTIVE: To analyze the maltose clearance in plasma and urine of healthy volunteers with high-performance liquid chromatography. METHODS: Maltose solution was infused to 12 healthy volunteers during a 4-hour period at an infusion rate of 0.2, 0.3, and 0.5 g/(kg x h), Plasma and urine specimens were collected at different time points before and after infusion, and then analyzed with high-performance liquid chromatography. RESULTS: The coefficients of variation of the precision and accuracy of the analysis method ranged 3.68%-4.58% and 0.44%-4.83% for plasma, respectively, and 2.91%-7.62% and 0.95%-8.27% for urine, respectively. The plasma maltose concentration increased in a dose-dependent manner (r > 0.99). The plasma maltose concentrations returned to the baseline levels 12 hours later. Two hours after injection, the urinary excretion of maltose increased, reached the peak value within 2-4 hours, began to decrease 6 hours later, and became zero 24 hours later. CONCLUSIONS: An infusion rate of 0.2-0.5 g/(kg x h) of maltose will not remarkably increase the blood glucose level in healthy people. The routine infusion rate should below 0.3 g/(kg x h), unless an emergency exists.

Metabolism of circulating disaccharides in man and the rat.

The metabolism of circulating disaccharides was studied in adult humans and rats. After iv infusions of 10 g of either lactose, sucrose, or maltose in four adults, no rise in blood glucose was noted. A mean of 8.7+/-1.89 g of the lactose and 6.3+/-1.39 g of the sucrose was excreted in the 24-hour urine sample. Only 0.11+/-0.03 g of the infused maltose was recovered in the urine, suggesting that the maltose was metabolized.After injection of (14)C-labeled lactose and sucrose in rats, 6.2+/-2.7 and 7.6+/-2.4%, respectively, was oxidized to (14)CO(2) in 24 hours; 62.1+/-13.5 and 68.4+/-10.8% of the respective disaccharides was excreted into the urine. Conversely, after injection of (14)C-labeled maltose 54.6+/-7.0% was oxidized to (14)CO(2) and 4.8+/-3.9% excreted in the urine. The per cent of maltose oxidized to CO(2) was similar to that of glucose. In addition to small intestinal mucosa, homogenates of rat kidney, brain, and liver as well as serum were found to have measurable maltase activities. The role of these tissue maltases in the metabolism of circulating maltose and maltosyloligosaccharides is discussed.

Brush border disaccharidases in dog kidney and their spatial relationship to glucose transport receptors.

The localization of disaccharidases in kidney has been studied by means of the multiple indicator dilution technique. A pulse injection of a solution containing Evans blue dye (plasma marker), creatinine (extracellular marker), and a (14)C-labeled disaccharide (lactose, sucrose, maltose, and alphaalpha-trehalose), is made into the renal artery of an anesthetized dog, and the outflow curves are monitored simultaneously from renal venous and urine effluents. Lactose and sucrose have an extracellular distribution. Trehalose and maltose remain extracellular from the postglomerular circulation. About 75% of filtered tracer maltose or trehalose is extracted by the luminal surface of the nephron. Thin-layer chromatography of urine samples shows that all of the excreted (14)C radiolabel is in the form of the injected disaccharide. Following the administration of phlorizin, all of the filtered radioactivity is recoverable in the urine, but chromatography of the urine samples now reveals that there is a significant excretion of [(14)C]glucose, approximating the amount previously extracted under control conditions (in the absence of phlorizin). It has been verified that no hydrolysis of maltose or trehalose to their constituent glucose subunits occurred during the transit of tracer between the point of injection (renal artery), and the point of filtration (glomerular basement membrane). Similarly, after addition of [(14)C]disaccharides to fresh urine there is no chromatographically recoverable [(14)C]glucose. It is concluded that there exist alpha-glucosidases with maltase and trehalase activity along the brush border of the proximal tubule and that these disaccharidases are located spatially superficial to the glucose transport receptors.

Metabolism of intravenously administered maltose in renal tubules in humans.

To investigate how urinary excretion rates (UERs) of maltose and glucose are determined after intravenous maltose infusion, maltose and glucose solutions were infused at various rates and the relationships between UERs of maltose and glucose and their plasma concentrations were examined. Results showed the existence of a threshold plasma maltose concentration for the urinary excretions of maltose and glucose and the existence of a maximum rate of urinary glucose excretion after maltose infusion. Elevation of plasma glucose concentration by simultaneous glucose infusion increased urinary glucose excretion but did not increase urinary maltose excretion; the relationship between plasma total sugar concentration and urinary total sugar excretion was unchanged. Results suggest that maltose administered intravenously is hydrolyzed to glucose by maltase in renal tubules and reabsorbed as glucose competitively with glucose derived from plasma and that the maximum utilization of intravenously infused maltose is determined by the tubular glucose reabsorption capacity.

Glucose-forming amylase in human urine.

This paper describes the isolation and study of glucose-forming amylase existing in human urine as a normal component. After removing alpha-amylase [EC 3.2.1.1] by adsorption onto raw starch, urine was treated with DEAE-cellulose and Bio Gel P-150, and three fractionated proteins (F-1, F-2, and F-3), isolated in a homogeneous state by gel filtration, were shown to display glucose-formine amylase activity. They all hydrolyzed starch and glycogen, releasing glucose as the sole product, and also hydrolyzed maltose. However, their molecular weights, as estimated by gel filtration, isoelectric points, stabilities, and several enzymatic properties were different. The implications of the results are discussed.

Source of the urinary maltose and maltotriose excreted during intravenous infusion of oligosaccharide solutions in young pigs.

Pigs infused with preparations of glucose oligosaccharides excrete sizeable quantities of maltose in urine despite the absence of maltose in the infused solution. Maltose infused without other oligosaccharides is well utilized. Our studies examined possible sources of excreted maltose. We first examined whether simultaneous infusion of larger oligosaccharides with maltose inhibits maltose utilization. Four young pigs were infused for four days with 20 g/d of a maltose-free oligosaccharide preparation to which tracer quantities of U-14C-maltose were added. Urinary excretion of maltose-plus-maltotriose increased significantly (P less than .05) from a mean +/- SD baseline value of .01 +/- .01 g/d to an overall four-day mean value of 1.33 +/- 0.47 g/d. However, only 10.7 +/- 0.78% of infused 14C-maltose was excreted, indicating that simultaneous infusion of larger oligosaccharides did not inhibit maltose utilization. The second study examined whether maltotriose present in the oligosaccharide mixture was the source of excreted maltose. Four young pigs were infused for three days with 20 g/d of a special preparation of oligosaccharides containing only trace quantities of maltose and maltotriose. Urinary maltose plus maltotriose excretion increased significantly (P less than .05) from a mean +/- SD baseline value of .01 +/- .01 g/d to 1.65 +/- 0.41 g/d during oligosaccharide infusion. The data suggest that excreted maltose and maltotriose arise from the catabolism of larger oligosaccharides.

Utilization of intravenous maltose.

Ten healthy male subjects received an infusion of 10% maltose solution at a rate of 0.5 g/kg body weight/h for 345 min. Blood maltose levels rose continuously for the first hours; after 285 min a constant level was maintained. Concomitantly increasing maltosuria occurred; the total renal maltose excretion averaged 30.4% of the administered dose. In addition to maltose losses, considerable glucosuria (up to 16% of total carbohydrate excretion) was found. The glucosuria occurred in spite of normal blood glucose levels. Serum insulin did rise during maltose infusion.

Infusion of maintenance fluids with glucose (Veen 3G) is superior to maltose infusion (Actit) in the rate of energy utilization in rabbits.

In the present study, we examined the rates of urinary excretion of glucose and maltose after an infusion of maintenance fluid with glucose or maltose in adult rabbits. Three maintenance fluids (sugar-free, 5% glucose [Veen 3G] and 5% maltose [Actit]), which contained different sugars but were identical in electrolyte and acetate compositions and concentrations (Na: 45, K: 17, Mg: 5, Cl: 37, H2PO4: 10 and CH3COO: 20 mEq/l), were used in this study. In addition, the optimum infusion speed for maintenance therapy (10 ml/kg/h) was used. Animals were not given food or water during the 10-day period of administration. The body weights of the animals were measured every day. The concentrations of total protein, albumin, free fatty acids and glucose in the serum were measured. Urine samples for determination of glucose and maltose concentrations were collected from the 1st to 10th administrations. After infusion with 5% maltose, urinary maltose excretion decreased time-dependently, while that of glucose increased. This suggests that maltase activity time-dependently increases after infusion with maltose. In addition, total sugar was only minimally excreted into urine in the 5% glucose group compared with the 5% maltose group. Thus, the glucose infusion was superior to the maltose infusion in the rate of energy utilization. However, neither the loss of body weight nor the increase in concentration of free fatty acids in serum differed significantly among the 3 groups. In conclusion, infusion of maintenance fluid with 5% maltose results in the excretion of maltose and glucose into urine, since enzymatic hydrolysis of maltose to glucose is limited to that by maltase.

[The catabolism of infused maltose in man]. / Uber den Abbau von infundierter Maltose beim Menschen

The use of intravenously administered maltose was tested in 9 healthy human subjects and 3 insulin-dependent diabetic patients. The concentration of the blood sugar has not been influenced by the administered maltose. The concentration of maltose in the blood increases up to 170 mg/100 ml blood depending on the rate of the maltose infusion. The excretion of maltose in the urinis correlated with the applied dosis and with the blood maltose concentration. Under our experimental conditions 20 to 30% of the administered maltose have been excreted and 7.5 to 23.4% have been oxidized within 8 hours. The highest rate of degradation was about 40 mg maltose/min/human subject and is reached 2 hours later than the peak concentration of maltose in the blood. The metabolism of maltose is reduced in insulin-dependent diabetic patients. In these patients only 3% of the applied maltose have been oxidized and 51% excreted in the urin within 8 hours. Therefore, this disaccharide cannot be recommended as carbohydrate source of parenteral nutrition in insulin-dependent diabetic patients. The balance of intravenously administered maltose is not satisfactory in healthy adult humans, too. Infusion of maltose solutions have no real advantages over the infusions of oligosaccharide solutions.

Utilization of intravenously administered glycogen by young pigs.

Previous studies evaluated solutions of small oligosaccharides as potential sources of carbohydrate-derived energy for patients fed intravenously. Although results with these solutions were disappointing, the data suggested that very large oligosaccharides were potential sources of intravenous carbohydrate. To test this hypothesis, four young pigs (3.6 +/- 0.2 kg; mean +/- SD) were infused with sterile solutions for a 6-d period. On days 1 and 6, a balanced isotonic electrolyte solution was infused. On days 2-5 a 9% solution of glycogen was infused at a rate providing 17.7 +/- 0.77 g/d. For each study day the remaining portion of the energy, protein, essential fatty acids and micronutrients was supplied enterally. No adverse reactions were noted during glycogen infusion, and the animals continued to grow. Glycogen utilization was 66.4 +/- 4.3%. Of the total carbohydrate excreted, 85.4% was composed of oligosaccharides of maltotetraose size or larger. Free glucose accounted for 3.5% of the total excreted, while maltose plus maltotriose accounted for 11.1%. Plasma concentrations of oligosaccharide-bound glucose increased during glycogen infusion, rising from a base-line value of 11.0 +/- 14 mg/dL to an overall mean value for the 4-d period of 100.3 +/- 31.6 mg/dL.

Quantitative determination of lactose, maltose, and sucrose in urine.

A simple method for determination of lactose, maltose and sucrose in urine is described. The principle of the method consists of enzymatic splitting of these disaccharides and specific measurement the resulting glucose by the Beckman Glucose-Analyzer. The precision and accuracy of the method have been evaluated and its clinical application is briefly discussed.