Xylitol vs glucose: effect on the rate of gastric emptying and motilin, insulin, and gastric inhibitory polypeptide release

Physiological functions and potential clinical applications of motilin

Motilin is a gastrointestinal hormone secreted by the duodenum. This peptide regulates a characteristic gastrointestinal contraction pattern, called the migrating motor complex, during the fasting state. Motilin also affects the pressure of the lower esophageal sphincter, gastric motility and gastric accommodation in the gastrointestinal tract. Furthermore, motilin induces bile discharge into the duodenum by promoting gallbladder contraction, pepsin secretion in the stomach, pancreatic juice and insulin secretion from the pancreas. In recent years, it has been shown that motilin is associated with appetite, and clinical applications are expected for diseases affected by food intake, e.g. obesity, by regulating motilin levels. Gastric acid and bile are the two major physiological regulators for motilin release. Caloric foods have varying effects on motilin levels, depending on their composition. Among non-caloric foods, bitter substances reduce motilin levels and are therefore expected to have an appetite-suppressing effect. Various motilin receptor agonists and antagonists have been developed but have yet to reach clinical use.

Effect of the Natural Sweetener Xylitol on Gut Hormone Secretion and Gastric Emptying in Humans: A Pilot Dose-Ranging Study

Sugar consumption is associated with a whole range of negative health effects and should be reduced and the natural sweetener xylitol might be helpful in achieving this goal. The present study was conducted as a randomized, placebo-controlled, double-blind, cross-over trial. Twelve healthy, lean volunteers received intragastric solutions with 7, 17 or 35 g xylitol or tap water on four separate days. We examined effects on: gut hormones, glucose, insulin, glucagon, uric acid, lipid profile, as well as gastric emptying rates, appetite-related sensations and gastrointestinal symptoms. We found: (i) a dose-dependent stimulation of cholecystokinin (CCK), active glucagon-like peptide-1 (aGLP-1), peptide tyrosine tyrosine (PYY)-release, and decelerated gastric emptying rates, (ii) a dose-dependent increase in blood glucose and insulin, (iii) no effect on motilin, glucagon, or glucose-dependent insulinotropic peptide (GIP)-release, (iv) no effect on blood lipids, but a rise in uric acid, and (v) increased bowel sounds as only side effects. In conclusion, low doses of xylitol stimulate the secretion of gut hormones and induce a deceleration in gastric emptying rates. There is no effect on blood lipids and only little effect on plasma glucose and insulin. This combination of properties (low-glycemic sweetener which stimulates satiation hormone release) makes xylitol an attractive candidate for sugar replacement.

Xylitol's Health Benefits beyond Dental Health: A Comprehensive Review

Xylitol has been widely documented to have dental health benefits, such as reducing the risk for dental caries. Here we report on other health benefits that have been investigated for xylitol. In skin, xylitol has been reported to improve barrier function and suppress the growth of potential skin pathogens. As a non-digestible carbohydrate, xylitol enters the colon where it is fermented by members of the colonic microbiota; species of the genus Anaerostipes have been reported to ferment xylitol and produce butyrate. The most common Lactobacillus and Bifidobacterium species do not appear to be able to grow on xylitol. The non-digestible but fermentable nature of xylitol also contributes to a constipation relieving effect and improved bone mineral density. Xylitol also modulates the immune system, which, together with its antimicrobial activity contribute to a reduced respiratory tract infection, sinusitis, and otitis media risk. As a low caloric sweetener, xylitol may contribute to weight management. It has been suggested that xylitol also increases satiety, but these results are not convincing yet. The benefit of xylitol on metabolic health, in addition to the benefit of the mere replacement of sucrose, remains to be determined in humans. Additional health benefits of xylitol have thus been reported and indicate further opportunities but need to be confirmed in human studies.

Acute Effects of Nutritive and Non-Nutritive Sweeteners on Postprandial Blood Pressure

Postprandial hypotension (PPH) is under-recognised, but common, particularly in the elderly, and is of clear clinical importance due to both the independent association between PPH and an increase in mortality and lack of effective management for this condition. Following health concerns surrounding excessive consumption of sugar, there has been a trend in the use of low- or non-nutritive sweeteners as an alternative. Due to the lack of literature in this area, we conducted a systematic search to identify studies relevant to the effects of different types of sweeteners on postprandial blood pressure (BP). The BP response to ingestion of sweeteners is generally unaffected in healthy young subjects, however in elderly subjects, glucose induces the greatest decrease in postprandial BP, while the response to sucrose is less pronounced. The limited studies investigating other nutritive and non-nutritive sweeteners have demonstrated minimal or no effect on postprandial BP. Dietary modification by replacing high nutritive sweeteners (glucose, fructose, and sucrose) with low nutritive (d-xylose, xylitol, erythritol, maltose, maltodextrin, and tagatose) and non-nutritive sweeteners may be a simple and effective management strategy for PPH.

Metabolic effects of the natural sweeteners xylitol and erythritol: A comprehensive review

Xylitol and erythritol are widely used in a variety of food and oral care products as sugar substitutes. Although a number of studies have been conducted on the health benefits of xylitol since the 1960s, erythritol only attracted the attention of researchers during the early 1990s. Historically, researchers mainly focused on the effects of xylitol and other sugar alcohols on oral and dental healthcare while the anti-diabetic or antihyperglycemic effects have only been revealed recently. Though a few reviews have been published on the health benefits of sugar alcohols in the last few decades, none of them closely evaluated the antihyperglycemic potential and underlying mechanisms, particularly with a focus on xylitol and erythritol. The current review thoroughly analyzes the anti-diabetic and antihyperglycemic effects as well as other metabolic effects of xylitol and erythritol using articles published in PubMed since the 1960s, containing research done on experimental animals and humans. This review will help researchers ascertain the controversies surrounding sugar alcohols, investigate further beneficial effects of them as well as aid food industries in exploring the possibilities of using sugar alcohols as anti-diabetic supplements in diabetic foods and food products.

Potential for pharmaceutical excipients to impact absorption: A mechanistic review for BCS Class 1 and 3 drugs

The potential for certain excipients to impact drug absorption is the subject of numerous publications. Reflecting this, current Biopharmaceutics Classification System (BCS) guidelines place restrictions on the level of change in excipients to be eligible for a BCS biowaiver. The degree of change permitted between test and reference formulations varies between BCS Class 1 and 3, and also across different regulatory authorities. This article reviews the literature evidence for excipients to impact drug absorption, with a particular focus on identifying effects which may be important for BCS Class 1 and 3 compounds and formulations. Literature examples were categorised according to the mechanism by which the excipient was believed to impact drug absorption, and the relevance of these mechanisms for compounds within BCS Class 1 and 3 was assessed. The likelihood of using the excipient in solid oral immediate release formulations (i.e. formulation types which would be eligible for BCS biowaivers) was also considered. Using this mechanistic and risk-based approach, potential critical excipients for BCS Class 1 and 3 compounds were identified. Based on the literature data, there are only a limited number of mechanisms by which excipients could affect the absorption of a BCS Class 3 drug. For BCS1, absorption is very unlikely to be affected by excipient changes. For many of these excipients, there is no in vivo evidence of such an effect having occurred. The risk can be mitigated to a large extent by applying some compound-specific understanding of the absorption site, rate and mechanism of the particular API under consideration.

Motilin: from gastric motility stimulation to hunger signalling

After the discovery of motilin in 1972, motilin and the motilin receptor were studied intensely for their role in the control of gastrointestinal motility and as targets for treating hypomotility disorders. The genetic revolution - with the use of knockout models - sparked novel insights into the role of multiple peptides but contributed to a decline in interest in motilin, as this peptide and its receptor exist only as pseudogenes in rodents. The past 5 years have seen a major surge in interest in motilin, as a series of studies have shown its relevance in the control of hunger and regulation of food intake in humans in both health and disease. Luminal stimuli, such as bitter tastants, have been identified as modulators of motilin release, with effects on hunger and food intake. The current state of knowledge and potential implications for therapy are summarized in this Review.

Exploring vitamin D metabolism and function in cancer

Vitamin D, traditionally known as an essential nutrient, is a precursor of a potent steroid hormone that regulates a broad spectrum of physiological processes. In addition to its classical roles in bone metabolism, epidemiological, preclinical, and cellular research during the last decades, it revealed that vitamin D may play a key role in the prevention and treatment of many extra-skeletal diseases such as cancer. Vitamin D, as a prohormone, undergoes two-step metabolism in liver and kidney to produce a biologically active metabolite, calcitriol, which binds to the vitamin D receptor (VDR) for the regulation of expression of diverse genes. In addition, recent studies have revealed that vitamin D can also be metabolized and activated through a CYP11A1-driven non-canonical metabolic pathway. Numerous anticancer properties of vitamin D have been proposed, with diverse effects on cancer development and progression. However, accumulating data suggest that the metabolism and functions of vitamin D are dysregulated in many types of cancer, conferring resistance to the antitumorigenic effects of vitamin D and thereby contributing to the development and progression of cancer. Thus, understanding dysregulated vitamin D metabolism and function in cancer will be critical for the development of promising new strategies for successful vitamin D-based cancer therapy.

Chronic high-sucrose diet increases fibroblast growth factor 21 production and energy expenditure in mice

Excess carbohydrate intake causes obesity in humans. On the other hand, acute administration of fructose, glucose or sucrose in experimental animals has been shown to increase the plasma concentration of anti-obesity hormones such as glucagon-like peptide 1 (GLP-1) and Fibroblast growth factor 21 (FGF21), which contribute to reducing body weight. However, the secretion and action of GLP-1 and FGF21 in mice chronically fed a high-sucrose diet has not been investigated. To address the role of anti-obesity hormones in response to increased sucrose intake, we analyzed mice fed a high-sucrose diet, a high-starch diet or a normal diet for 15 weeks. Mice fed a high-sucrose diet showed resistance to body weight gain, in comparison with mice fed a high-starch diet or control diet, due to increased energy expenditure. Plasma FGF21 levels were highest among the three groups in mice fed a high-sucrose diet, whereas no significant difference in GLP-1 levels was observed. Expression levels of uncoupling protein 1 (UCP-1), FGF receptor 1c (FGFR1c) and β-klotho (KLB) mRNA in brown adipose tissue were significantly increased in high sucrose-fed mice, suggesting increases in FGF21 sensitivity and energy expenditure. Expression of carbohydrate responsive element binding protein (ChREBP) mRNA in liver and brown adipose tissue was also increased in high sucrose-fed mice. These results indicate that FGF21 production in liver and brown adipose tissue is increased in high-sucrose diet and participates in resistance to weight gain.

Gut hormone secretion, gastric emptying, and glycemic responses to erythritol and xylitol in lean and obese subjects

With the increasing prevalence of obesity and a possible association with increasing sucrose consumption, nonnutritive sweeteners are gaining popularity. Given that some studies indicate that artificial sweeteners might have adverse effects, alternative solutions are sought. Xylitol and erythritol have been known for a long time and their beneficial effects on caries prevention and potential health benefits in diabetic patients have been demonstrated in several studies. Glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK) are released from the gut in response to food intake, promote satiation, reduce gastric emptying (GE), and modulate glucose homeostasis. Although glucose ingestion stimulates sweet taste receptors in the gut and leads to incretin and gastrointestinal hormone release, the effects of xylitol and erythritol have not been well studied. Ten lean and 10 obese volunteers were given 75 g of glucose, 50 g of xylitol, or 75 g of erythritol in 300 ml of water or placebo (water) by a nasogastric tube. We examined plasma glucose, insulin, active GLP-1, CCK, and GE with a [(13)C]sodium acetate breath test and assessed subjective feelings of satiation. Xylitol and erythritol led to a marked increase in CCK and GLP-1, whereas insulin and plasma glucose were not (erythritol) or only slightly (xylitol) affected. Both xylitol and erythritol induced a significant retardation in GE. Subjective feelings of appetite were not significantly different after carbohydrate intake compared with placebo. In conclusion, acute ingestion of erythritol and xylitol stimulates gut hormone release and slows down gastric emptying, whereas there is no or only little effect on insulin release.

Effects of xylitol on carbohydrate digesting enzymes activity, intestinal glucose absorption and muscle glucose uptake: a multi-mode study

Some possible mechanisms behind the anti-diabetic effects of xylitol have been understood from the results of this study.

Xylitol improves pancreatic islets morphology to ameliorate type 2 diabetes in rats: a dose response study

Xylitol has been reported as a potential antidiabetic sweetener in a number of recent studies; however, the most effective dietary dose and organ-specific effects are still unclear. Six-week-old male Sprague-Dawley rats were randomly divided into 5 groups: normal control (NC), diabetic control (DBC), diabetic xylitol 2.5% (DXL2.5), diabetic xylitol 5.0% (DXL5), and diabetic xylitol 10.0% (DXL10). Diabetes was induced only in the animals in DBC and DXL groups and considered diabetic when their nonfasting blood glucose level was >300 mg/dL. The DXL groups were fed with 2.5%, 5.0%, and 10% xylitol solution, whereas the NC and DBC groups were supplied with normal drinking water. After 4-wk intervention, body weight, food and fluid intake, blood glucose, serum fructosamine, liver glycogen, serum alanine transaminase, aspartate transaminase, lactate dehydrogenase, creatine kinase, uric acid, creatinine, and most serum lipids were significantly decreased, and serum insulin concentration, glucose tolerance ability, and pancreatic islets morphology were significantly improved in the DXL10 group compared to the DBC group. The data of this study suggest that 10% xylitol has the better antidiabetic effects compared to 2.5% and 5.0% and it can be used as an excellent antidiabetic sweetener and food supplement in antidiabetic foods.

PRACTICAL APPLICATION

Xylitol is widely used as a potential anticariogenic and sweetening agent in a number of oral care and food products when many of its health benefits are still unknown. Due to its similar sweetening power but lower calorific value (2.5 compared with 4 kcal) and lower glycemic index (13 compared with 65) compared to sucrose, recently it has been widely used as a sugar substitute particularly by overweight, obese, and diabetic patients in order to reduce their calorie intake from sucrose. However, the potential antidiabetic effects of xylitol have been discovered recently. The results of this study confirmed the effective dietary dose of xylitol for diabetics with some of the mechanisms of actions behind its antidiabetic effects.

Xylitol affects the intestinal microbiota and metabolism of daidzein in adult male mice

This study examined the effects of xylitol on mouse intestinal microbiota and urinary isoflavonoids. Xylitol is classified as a sugar alcohol and used as a food additive. The intestinal microbiota seems to play an important role in isoflavone metabolism. Xylitol feeding appears to affect the gut microbiota. We hypothesized that dietary xylitol changes intestinal microbiota and, therefore, the metabolism of isoflavonoids in mice. Male mice were randomly divided into two groups: those fed a 0.05% daidzein with 5% xylitol diet (XD group) and those fed a 0.05% daidzein-containing control diet (CD group) for 28 days. Plasma total cholesterol concentrations were significantly lower in the XD group than in the CD group (p < 0.05). Urinary amounts of equol were significantly higher in the XD group than in the CD group (p < 0.05). The fecal lipid contents (% dry weight) were significantly greater in the XD group than in the CD group (p < 0.01). The cecal microbiota differed between the two dietary groups. The occupation ratios of Bacteroides were significantly greater in the CD than in the XD group (p < 0.05). This study suggests that xylitol has the potential to affect the metabolism of daidzein by altering the metabolic activity of the intestinal microbiota and/or gut environment. Given that equol affects bone health, dietary xylitol plus isoflavonoids may exert a favorable effect on bone health.

Effects of xylitol on blood glucose, glucose tolerance, serum insulin and lipid profile in a type 2 diabetes model of rats

BACKGROUND/AIMS

The present study was conducted to examine the antidiabetic effects of xylitol in a type 2 diabetes rat model.

METHODS

Six-week-old male Sprague-Dawley rats were randomly divided into 3 groups: normal control (NC), diabetic control (DBC) and xylitol (XYL). Diabetes was induced only in the DBC and XYL animal groups by feeding them a 10% fructose solution for 2 weeks followed by an injection (i.p.) of streptozotocin (40 mg/kg body weight). One week after the streptozotocin injection, the animals with a nonfasting blood glucose level of >300 mg/dl were considered to be diabetic. The XYL group was fed further with a 10% xylitol solution, whereas the NC and DBC groups were supplied with normal drinking water.

RESULTS

After 5 weeks of intervention, food and fluid intake, body weight, blood glucose, serum fructosamine and most of the serum lipids were significantly decreased, and serum insulin concentration and glucose tolerance ability was significantly increased in the XYL group compared to the DBC group. Liver weight, liver glycogen and serum triglycerides were not influenced by feeding with xylitol.

CONCLUSION

The data of this study suggest that xylitol can be used not only as a sugar substitute but also as a supplement to antidiabetic food and other food products.

Effect of xylitol gum on the level of oral mutans streptococci of preschoolers: block-randomised trial

OBJECTIVES

To assess the influence of xylitol chewing gum consumption on mutans streptococci level of 3-4 years old Japanese preschoolers.

METHODS

248 participants were examined regarding caries-related factors at baseline and were followed up at 6, 9, and 12 months after the baseline: assessors were blinded, subjects were open labelled and blocked parallel randomised; 142 were selected to use xylitol gum for 3 months (from months 6 to 9) and 106 were controls.

RESULTS

161 participants were analysed (xylitol n = 76, control n = 85). Nineteen caries-related variables, including xylitol gum consumption, were analysed for any association with the main outcome, plaque mutans streptococci scores development within the intervention period, by logistic regression. Six showed statistically significant associations by univariate analysis (P < 0.05). However, only xylitol gum consumption remained a significant negative association (P < 0.05) by multiple analyses. Interestingly, over 10% xylitol group children experienced diarrhoea, which was larger than previous investigations.

CONCLUSION

  Xylitol gum is effective in avoiding increased plaque mutans streptococci in young children.

Genetic analysis of D-xylose metabolism by endophytic yeast strains of Rhodotorula graminis and Rhodotorula mucilaginosa

Two novel endophytic yeast strains, WP1 and PTD3, isolated from within the stems of poplar (Populus) trees, were genetically characterized with respect to their xylose metabolism genes. These two strains, belonging to the species Rhodotorula graminis and R. mucilaginosa, respectively, utilize both hexose and pentose sugars, including the common plant pentose sugar, D-xylose. The xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) genes were cloned and characterized. The derived amino acid sequences of xylose reductase (XR) and xylose dehydrogenase (XDH) were 32%∼41% homologous to those of Pichia stipitis and Candida. spp., two species known to utilize xylose. The derived XR and XDH sequences of WP1 and PTD3 had higher homology (73% and 69% identity) with each other. WP1 and PTD3 were grown in single sugar and mixed sugar media to analyze the XYL1 and XYL2 gene regulation mechanisms. Our results revealed that for both strains, the gene expression is induced by D-xylose, and that in PTD3 the expression was not repressed by glucose in the presence of xylose.

Too much of too little: xylitol, an unusual trigger of a chronic metabolic hyperchloremic acidosis

Homeopathic globules are frequently used in children as a first-line treatment. Most of these globules are coated with sugar substitutes like xylitol; these substitutes are known for their laxative effect. Our patient shows that consumption of globules coated with xylitol does not have only laxative effects. It may cause indeed considerable weight loss and life-threatening enteral bicarbonate loss by diarrhea when overdosed in an infant.

The transit of dosage forms through the small intestine

The human small intestine, with its enormous absorptive surface area, is invariably the principal site of drug absorption. Hence, the residence time of a dosage form in this part of the gut can have a great influence on the absorption of the contained drug. Various methods have been employed to monitor the gastrointestinal transit of pharmaceutical dosage forms, but the use of gamma-scintigraphy has superceded all the other methods. However, careful consideration of the time interval for image acquisition and proper analysis of the scintigraphic data are important for obtaining reliable results. Most studies reported the mean small intestinal transit time of various dosage forms to be about 3-4h, being closely similar to that of food and water. The value does not appear to be influenced by their physical state nor the presence of food, but the timing of food intake following administration of the dosage forms can influence the small intestinal transit time. While the mean small intestinal transit time is quite consistent among dosage forms and studies, individual values can vary widely. There are differing opinions regarding the effect of density and size of dosage forms on their small intestinal transit properties. Some common excipients employed in pharmaceutical formulations can affect the small intestinal transit and drug absorption. There is currently a lack of studies regarding the effects of excipients, as well as the timing of food intake on the small intestinal transit of dosage forms and drug absorption.

The effects of polydextrose and xylitol on microbial community and activity in a 4-stage colon simulator

This study focused on the effects of candidate prebiotics polydextrose (PDX) and xylitol on the microbial community and its metabolic activity in a colon simulator. A semicontinuous, anaerobic culture system was used with 4 vessels mimicking the conditions in the human large intestine from proximal to distal colon. Bacterial inocula for the independent simulations were obtained from fecal samples of different donors. Synthetic medium, mimicking the contents of the small intestine, containing either 2% of the prebiotic candidate or no added carbohydrates as a control, was fed to the system. After 48 h of simulation samples were collected and analyzed. A sustained degradation of polydextrose throughout the colon model and a more rapid degradation of xylitol were observed. The fermentation of both compounds was characterized by a significantly increased production of short-chain fatty acids (SCFA). Polydextrose increased the concentrations of all SCFA, especially acetate and propionate, and xylitol especially the concentration of butyrate. Branched-chain fatty acids (BCFA) levels decreased significantly as a result of polydextrose and xylitol supplementation, whereas biogenic amine levels remained mostly unchanged. Thus, a beneficial shift in the metabolic patterns of the colon microbes was measured with both of the tested products. These in vitro studies provide evidence to the prebiotic characteristics of polydextrose; also, further beneficial properties of xylitol were demonstrated in the colon model.

Evaluation of the independent and combined effects of xylitol and polydextrose consumed as a snack on hunger and energy intake over 10 d

The study assessed the independent and combined effect of two speciality carbohydrates (polydextrose and xylitol) on appetite. Eight female and seven male lean volunteers were recruited from the University of Leeds campus. Using a repeated measures design, volunteers completed four conditions in a counterbalanced order. Each condition varied according to the yoghurt formulation administered: a control yoghurt (C, yoghurt+25 g sucrose) and three experimental yoghurts (X, yoghurt+25 g xylitol; P, yoghurt+25 g polydextrose; and XP, yoghurt+12·5 g xylitol and 12·5 g polydextrose). Each condition lasted for 10 d during which volunteers consumed 200 g yoghurt on each day. On days 1 and 10, the short- and medium-term effects of yoghurt consumption were assessed by measuringad libitumlunch intake and subjective motivation to eat. The three experimental yoghurts (X, P and XP) induced a slight suppression of energy intake compared with the control (C) yoghurt, but the differences were not statistically significant. However, when the energy content of the yoghurt pre-loads were accounted for, there was a significant suppression of energy intake for P compared with C (P=0·002). The XP yoghurt induced a significantly stronger satiating effect (increase in subjective fullness) compared with C, both with (P=0·003) and without (P<0·001) the differential in energy content of the yoghurt pre-loads accounted for. The study demonstrated that pre-loads of xylitol and polydextrose caused a mild increase in satiety and suppression of energy intake, and that the effects persist after repeated daily administration. The effects exerted by the formulations containing xylitol and polydextrose did not arise from the differences in energy content of the yoghurtper se. Therefore, the usefulness of xylitol and polydextrose as ingredients in functional foods for appetite control are as a result of their lower energy content and suppression of appetite.

Cloning and molecular characterization of a gene coding D-xylulokinase (CmXYL3) from Candida maltosa

AIMS

To clone and identify a gene (CmXYL3) coding D-xylulokinase from Candida maltosa Xu316 and understand its physiological function.

METHODS AND RESULTS

Based on the conserved regions of the known D-xylulokinase-encoding genes, a pair of degenerate primers was designed to clone the CmXYL3 gene from C. maltosa Xu316. The coding region and sequences flanking the CmXYL3 gene were obtained by PCR-based DNA walking method. Southern blotting analysis suggested that there is a single copy of the CmXYL3 gene in the genome. The open reading frame starting from ATG and ending with TAG stop codon encoded 616 amino acids with a calculated molecular mass of 68889.743 Da. The CmXYL3 gene under the control of the GPD1 promoter was heterologously expressed in Saccharomyces cerevisiae deficient in D-xylulokinase (deltaScXKS1::LEU2) activity, and restored growth on D-xylulose. The specific activity of D-xylulokinase varied during xylose fermentation and was correlated with aeration level. After growth on different pentoses and pentitols as sole carbon sources, the highest specific activity of D-xylulokinase was observed on D-xylose.

CONCLUSIONS

The CmXYL3 gene isolated from C. maltosa Xu316 encodes a novel D-xylulokinase that plays a pivotal role in xylulose metabolism.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report that describes the isolation and cloning of D-xylulokinase gene (CmXYL3) from C. maltosa Xu316. D-xylulokinase is pivotal for growth and product formation during xylose metabolism. Better understanding of the biochemical properties and the physiological function of D-xylulokinase will contribute to optimizing fermentation conditions and determining the strategies for metabolic engineering of C. maltosa Xu316 for further improvement of xylitol yield and productivity.

Effect of glucose and lipids on intestinal absorption of sorbitol: role of gastric emptying

The aim of our study was to test the hypothesis that the better absorption of sorbitol when ingested with glucose could be related to a delayed gastric emptying. We tested the effect of the ingestion of glucose and lipids on the gastric emptying and intestinal absorption of sorbitol in six healthy volunteers, using gastric scintigraphy and hydrogen breath test. After an overnight fast, subjects ingested in random order, on 48-h test periods separated by at least one week, the following solutions: (a) 20 g sorbitol alone; (b) 20 g sorbitol and 20 g glucose; (c) 20 g sorbitol and 9 g lipids. Isotopic acquisitions were taken for 3 h following the ingestion of sorbitol labelled with 111Indium. Hydrogen concentration was measured in end-expiratory samples during 5 h, and the areas under the breath hydrogen curve, reflecting the amounts of sorbitol unabsorbed in the small bowel, were compared between periods. Mean area under the curve was 397 +/- 159 when sorbitol was ingested alone, and this was significantly lower when ingested with glucose or lipids (313 +/- 181 and 337 +/- 135, respectively; P < 0.05). The three curves of sorbitol gastric emptying differed significantly from each other, the gastric emptying being the slowest for sorbitol plus lipids, and the fastest for sorbitol taken alone. We found a positive correlation between the half-emptying time and the hydrogen areas under the curve (r = 0.46, P = 0.05). In conclusion, our study demonstrates that adding glucose or lipids to a solution of sorbitol slows the gastric emptying of sorbitol, resulting in a better intestinal absorption of sorbitol.

The effect of short-term dietary supplementation with glucose on gastric emptying of glucose and fructose and oral glucose tolerance in normal subjects

Recent observations indicate that gastric emptying may be influenced by patterns of previous nutrient intake. The aims of this study were to determine the effects of a high glucose diet on gastric emptying of glucose and fructose, and the impact of any changes in gastric emptying on plasma concentrations of glucose, insulin and gastric inhibitory polypeptide in response to glucose and fructose loads. Gastric emptying of glucose and fructose (both 75 g dissolved in 350 ml water) were measured in seven normal volunteers on separate days while each was on a "standard' diet and an identical diet supplemented with 440 g/day of glucose for 4-7 days. Venous blood samples for measurement of plasma glucose, insulin and gastric inhibitory polypeptide levels were taken immediately before and for 180 min after ingestion of glucose and fructose loads. Dietary glucose supplementation accelerated gastric emptying of glucose (50% emptying time 82 +/- 8 vs 106 +/- 10 min, p = 0.004) and fructose (73 +/- 9 vs 106 +/- 9 min, p = 0.001). After ingestion of glucose, plasma concentrations of insulin (p < 0.05) and gastric inhibitory polypeptide (p < 0.05) were higher during the glucose-supplemented diet. In contrast, plasma glucose concentrations at 60 min and 75 min were lower (p < 0.05) on the glucose-supplemented diet. We conclude that short-term supplementation of the diet with glucose accelerates gastric emptying of glucose and fructose, presumably as a result of reduced feedback inhibition of gastric emptying from small intestinal luminal receptors. More rapid gastric emptying of glucose has a significant impact on glucose tolerance.

The effects of pharmaceutical excipients on small intestinal transit

1. The effect of three iso-osmotic pharmaceutical excipient solutions on gastrointestinal transit were investigated in eight healthy male volunteers. Each subject received 200 ml radiolabelled purified water, or a 200 ml solution of sodium acid pyrophosphate ((SAPP) 1.1 g/200 ml), mannitol (2.264 g/200 ml) or sucrose (4.08 g/200 ml) in a four way cross over design. On each of the study days the volunteers also received five 6 mm diameter non-disintegrating tablets. Dual isotope gamma scintigraphy was used to assess the transit behaviour of the tablets and solutions. 2. There were no significant differences between the gastric emptying times of the four solution formulations. Rapid gastric emptying was observed in all cases (mean t 50% varied from 11-14 min). 3. Small intestinal transit (SIT) times for the SAPP and mannitol solutions were reduced by 39 and 34%, respectively, when compared with the control solution (purified water = 240 min; SAPP = 147 min; mannitol = 158 min). The 95% confidence limits for the mean differences in SIT time between the control and SAPP solutions was 39-94-149 min, and 40-82-124 min between the mannitol and the control. Intestinal transit for the sucrose solution was similar to that for the control solution (sucrose = 229 min). 4. There were no significant differences in the transit times of the non-disintegrating tablet preparations, when co-administered with each solution.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of different concentrations of mannitol in solution on small intestinal transit: implications for drug absorption

The aim of the present study was to investigate the effect that different concentrations of mannitol have on small intestinal transit, and whether any observed effect was concentration dependent. Eight, healthy male subjects each received 200ml of radiolabelled purified water, or a 200ml solution of mannitol at three different concentrations; 0.755g/200ml, 1.509g/200ml and 2.264g/200ml, in a randomised, four way cross-over study. Transit of the radiolabelled solutions was followed by gamma scintigraphy. The study demonstrated no significant differences between the gastric emptying times of the four solutions. Rapid gastric emptying was observed in most cases. The mean small intestinal transit times for the 0.755g/200ml, 1.509g/200ml and 2.264g/200ml mannitol solutions was reduced by 11%, 23% and 34% respectively, when compared to the control solution. The intestinal transit data of the four solutions demonstrate that mannitol has a concentration dependent effect on small intestinal transit. Small concentrations of mannitol included in a pharmaceutical formulation could therefore lead to reduced uptake with any drug exclusively absorbed from the small intestine.

Relationship between oral glucose tolerance and gastric emptying in normal healthy subjects

The relationships between gastric emptying and intragastric distribution of glucose and oral glucose tolerance were evaluated in 16 healthy volunteers. While sitting in front of a gamma camera the subjects drank 350 ml water containing 75 g glucose and 20 MBq 99mTc-sulphur colloid. Venous blood samples for measurement of plasma glucose, insulin and gastric inhibitory polypeptide were obtained at--2, 2,5,10,15,30,45,60,75,90,105,120 and 150 min. Gastric emptying approximated a linear pattern after a short lag phase (3.3 +/- 0.8 min). The 50% emptying time was inversely related to the proximal stomach 50% emptying time (r = -0.55, p < 0.05) and directly related to the retention in the distal stomach at 120 min (r = 0.72, p < 0.01). Peak plasma glucose was related to the amount emptied at 5 min (r = 0.58, p < 0.05) and the area under the blood glucose curve between 0 and 30 min was related to the amount emptied at 30 min (r = 0.58, p < 0.05). In contrast, plasma glucose at 120 min was inversely related to gastric emptying (r = -0.56, p < 0.05) and plasma insulin at 30 min (r = -0.53, p < 0.05). Plasma insulin at 120 min was inversely related (r = -0.65, p < 0.01) to gastric emptying. The increase in plasma gastric inhibitory polypeptide at 5 min was related directly to gastric emptying (r = 0.53, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Modulating effect of dietary carbohydrate supplementation on Candida albicans colonization and invasion in a neutropenic mouse model

We studied the effect of dietary carbohydrate supplementation on Candida albicans colonization and invasion of the gastrointestinal tract in a neutropenic mouse model. Mice inoculated with C. albicans were allowed free access to standard chow and drinking water supplemented with either glucose or xylitol or no carbohydrates (control). On days 33 through 36 postinoculation, the mean +/- standard error log10 CFU of C. albicans per gram on the mucosal surface, determined by quantitating CFU dislodged in the first wash of the gastric wall, was significantly higher in mice given the glucose supplement: 7.20 +/- 0.09 (glucose) versus 5.38 +/- 0.28 (xylitol) and 5.11 +/- 0.33 (control) CFU/g (P < or = 0.05 for each comparison by Fisher's protected least-significant-difference test). Fecal cultures also yielded the highest quantities of C. albicans in the glucose group. Invasion of the gastric wall by C. albicans correlated well with surface colonization in glucose-supplemented animals. Eight of 10 mice in this group, all with > 10(6) CFU/g, showed extensive invasive growth, as compared with only 2 of 26 mice in the remaining groups (P = 0.00006 by Fisher's exact test). These results indicate that dietary glucose intake is a key determinant of C. albicans growth in the gastrointestinal tract. The data provide an experimental rationale for clinical trials to decrease the intake of glucose or its utilization by C. albicans in immunocompromised patients.

Adaptive changes in the pyloric motor response to intraduodenal dextrose in normal subjects

Gastric emptying of glucose is faster after dietary supplementation of glucose, suggesting specific adaptation to changes in nutrient intake. In the present study, the effects of a continuous long-term (0-120-minute) and two short-term (0-20- and 80-100-minute) intraduodenal infusions of dextrose (2.4 kcal/min) on antropyloroduodenal motility and blood glucose, plasma gastric inhibitory polypeptide, and insulin concentrations were evaluated in nine volunteers. In four volunteers, an intraduodenal infusion of triglyceride (2.4 kcal/min) was administered immediately after the long-term dextrose infusion. The long-term dextrose infusion initially increased isolated pyloric pressure waves (IPPWs) and basal pyloric pressure (P < 0.05 for both), but after about 30 minutes IPPWs and basal pyloric pressure decreased and returned to baseline within 80 minutes. Each short-term infusion increased IPPWs and basal pyloric pressure (P < 0.05 for both). Antral pressure waves remained suppressed during the long-term dextrose infusion. Intraduodenal triglyceride increased IPPWs and basal pyloric pressure (P < 0.05 for both). The long-term dextrose infusion was associated with a sustained increase, and both short-term dextrose infusions were associated with peaks in glucose, insulin, and gastric inhibitory polypeptide levels. There was no significant relationship between biochemical measurements and antropyloroduodenal motility. It is concluded that specific adaptive changes occur rapidly in the phasic and tonic pyloric motor response, but not the antral motor response, to intraduodenal dextrose.