Comparative study of the gastric emptying of disaccharides and their respective monosaccharides in rats with ontogenic lactase deficiency]

In order to evaluate the gastric emptying of disaccharides and their monosaccharides, 64 male, Wistar rats weighing approximately 180 g, were divided into the following eight groups containing eight animals each: maltose, sucrose, lactose, and lactulose, and their correspondent group of monosaccharides: glucose, fructose plus glucose, galactose plus glucose and galactose plus fructose. Each animal received, after a 20 hours fast, 2 ml/100 g weight of a test meal containing a 10% solution of the correspondent sugar and phenol red (6 mg/dl) as a marker. Gastric retention was determined at 10 minutes after orogastric infusion and expressed as a percentage of the infused volume. The observed values (mean +/- SE) of gastric retention (%) of sucrose (35.0 +/- 1.8), lactose (30.4 +/- 1.5), and lactulose (29.5 +/- 1.6) were significantly lower (t test alpha = 0.05), than those observed with their respective monosaccharides, i.e. glucose plus fructose (46.9 +/- 2.6), glucose plus galactose (48.3 +/- 2.4), galactose plus fructose (43.5 +/- 1.5). No difference was noted between gastric retention of maltose (49.9 +/- 4.7) and that of glucose (53.0 +/- 3.0). As far the disaccharides are concerned, statistical analysis (ANOVA followed by Tukey test alpha = 0.05) revealed no differences among the values of gastric retention of sucrose, lactose and lactulose. Gastric retention of maltose was significantly greater than that of the other disaccharides. No differences were found among the gastric retention of monosaccharides.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of oral and gastric administration of sucrose and maltose on gastric emptying rate and appetite.

OBJECTIVES: To investigate mechanisms by which specific sugars affect feeding behaviour. DESIGN: In an initial study, gastric emptying rate and appetite were measured following ingestion of lemon flavoured solutions of sucrose, maltose (2160 kJ, 575 ml) and water control (67 kJ, 575 ml) given in randomised order on separate days to six male volunteers. In a second study, the effects of intragastric infusions of sucrose and maltose on appetite and gastric emptying were compared in six male volunteers. RESULTS: When given orally, both the sucrose and maltose solutions slowed gastric emptying compared with water, however sucrose emptied at a faster rate than maltose. The sucrose preload increased fullness and decreased prospective consumption during the following 3 h compared with maltose and water. When administered intragastrically, the gastric emptying rate of sucrose was again faster than that of maltose but there was no difference in ratings of hunger, fullness or prospective consumption for 3 h following the infusions. CONCLUSIONS: These results show that gastric emptying of sucrose is faster than that of maltose and suggest that gastric emptying rate and hence period of gastric distension is not the predominant factor regulating appetite by these sugars. The differences observed between oral and gastric delivery suggest that oro-sensory and cognitive factors, possibly stimulated by the sweetness of sucrose, were involved in the induction of satiety.     

Breath hydrogen excretion after lactose and whole milk ingestion. A prospective comparison in lactase deficiency

As the 50 g of lactose in the usual clinical test is unphysiologic both because it is equivalent to 1 L milk and because the usual dietary intake is not the purified sugar, but milk, we undertook a prospective comparison of the absorption of lactose after both lactose and milk ingestion with an equivalent lactose content. We studied 51 healthy volunteers, using the hydrogen breath test technique. All patients received 25 g lactose in aqueous solution. Subjects with an abnormal test had the test repeated with 500 ml whole cow's milk, whereas subjects with a normal test repeated the test after ingesting the unabsorbable sugar lactulose to detect the capacity of their colonic flora to produce the gas. Symptoms of gastrointestinal intolerance were also recorded. Compared to an equivalent lactose amount, milk lactose is better absorbed (8% of the entire population malabsorbed 500 ml whole milk, whereas 33.33% malabsorbed 25 g lactose) and induces intolerance in fewer subjects. We conclude that milk rather than pure lactose must be used in clinical evaluation of lactose malabsorption and intolerance.     

Gastric emptying in children. V. Effect of the replacement of glucose by sucrose in a solution for oral rehydration

A study was carried out on 18 children of both sexes aged 3 to 32 months (median 8 months) and weighing 3440 to 9520 grams (median 5120 grams). Each child was submitted to three consecutive gastric emptying tests at 24 hour intervals, using three solutions of different composition. The children were divided into two groups: Group I: twelve children submitted to the gastric emptying test 10 minutes after the administration of the test meal; Group II: six children submitted to the gastric emptying test 30 minutes after the administration of the test meal. The hydrating solutions used in the study consisted of the basic electrolyte composition recommended by the World Health Organization, and only differed in terms of the amount of sugar added. Solution A contained 20 grams of glucose per liter, solution B, 20 grams of sucrose per liter, and solution C, 40 grams of sucrose per liter. Gastric retention, expressed as a percentage of the volume of the test meal, was similar for solutions A and C and significantly higher than for solution B in Group I. In Group II, gastric retention of solution B also tended to be lower than for solutions A and C, although no statistically significant differences were observed between the three solutions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gastric emptying and metabolic acidosis. II. Study, in an experimental model in rats, of gastric retention of a sodium bicarbonate solution]

The gastric emptying of a 0.25 M sodium bicarbonate solution was studied in rats with metabolic acidosis induced by a previous (6 hours) orogastric infusion of a 0.5 M ammonium chloride solution. Two control groups were used: one previously infused with 0.5 M sodium chloride and the other with water, in the same volume that further solutions. Every animal was fed with 2 ml/100 g of its weight of these solutions. The test meal (bicarbonate solution) was utilized containing 6 mg% red fenol as a marker. The gastric retentions were determined 6 hours after those first meals at 5, 10, 20 and 30 minutes. The results demonstrated that the gastric retentions of the bicarbonate solution were significantly lower in the acidotic group than that one of water group (at 20 minutes) and that one of the sodium chloride (at 10, 20 and 30 minutes). The data here presented suggest that metabolic acidosis accelerates the gastric emptying of a sodium bicarbonate solution.     

Glucose and insulin responses to meals containing milk, lactose, glucose or fructose in subjects with non-insulin-dependent diabetes

The postprandial blood glucose and serum insulin responses to liquid test meals containing 40 g carbohydrate from milk, lactose, glucose or fructose and equal amounts of energy were compared in 10 non-insulin-dependent (type 2) diabetic patients. The meals were consumed in random order on consecutive days after an overnight fast. Significant differences (p less than 0.001, ANOVA) were observed between the glucose and insulin responses to the meals. The glucose response was significantly higher after the glucose containing meal and lower after the fructose meal as compared with the other meals. The insulin response was significantly higher after the lactose and glucose meals than after the milk and fructose meals. After the milk and lactose meals the blood glucose responses were similar whereas the insulin response was significantly lower after the milk meal. As lactose apparently was similarly absorbed from the two meals the difference in the insulin response was probably due to different insulinogenic effects of the protein components or to differences in the physical properties of the respective meals.     

Coincidental Malabsorption of Lactose, Fructose, and Sorbitol Ingested at Low Doses Is Not Common in Normal Adults

Normal subjects may incompletely absorb either lactose, fructose, or sorbitol and may therefore have abdominal symptoms. The frequency of coincidental malabsorption of these sugars is not known. This is clinically important, since we often ingest them during the same day and malabsorption may cause abdominal symptoms. To shed light on this issue we studied 32 normal subjects. Volunteers drank in random order the following solutions: 20 g lactulose, 50 g sucrose, 50 and 25 g lactose, 50 and 25 g fructose, 20 and 10 g sorbitol. Semiquantitative carbohydrate malabsorption was estimated with lactulose standards. Frequency of 50-g lactose (69%), 50-g fructose (81%), and 20-g sorbitol (84%) malabsorption was not significantly different (P = 0.3). The estimated median fraction of the ingested high dose malabsorbed was 42, 19, and 68% for lactose, fructose, and sorbitol, respectively. At low challenging doses, 63% of the volunteers absorbed two of three or all three sugars, and 88% were asymptomatic to two or all three sugars. In conclusion, the frequency of coincidental malabsorption of lactose, fructose, and sorbitol and intolerance to these sugars is not common, when normal adults ingest them at low doses.     

Relationship between molecular structures of sugars and their ability to stimulate the release of glucagon-like peptide-1 from canine ileal loops

The structure-activity relationship of sugars inducing secretion of glucagon-like peptide-1 from the gut was examined using intestinal loops prepared from the terminal portion of the ileum of dogs. The plasma glucagon-like peptide-1 concentration in a mesenteric vein draining only the looped region of the intestine was increased after infusion of 139 mmol/l solutions of D-glucose, D-galactose, D-glucuronic acid, 3-0-methyl-D-glucose, maltose, sucrose or maltitol into the intestinal lumen, but not after infusion of solutions of D-fructose, D-fucose, D-mannose, D-xylose or lactose. The increases in plasma glucagon-like peptide-1 concentration correlated with the corresponding increases in glucagon-like immunoreactivity induced by these sugars. The plasma glucose level of the regional mesenteric vein increased significantly from the basal level after instillation of D-glucose, but not after instillation of other sugars. It is suggested that cells of the gut have a glucose sensor for release of products of the glucagon gene and that this sensor has specific steric requirements. The sugars that induced glucagon-like peptide-1 release share the molecular features of electron density near C(6), an equatorial hydroxyl at C(2), and an axial hydroxyl at C(1), which could account for their recognition by the glucose sensor to initiate the releases of glucagon-like peptide-1 and glucagon-like immunoreactivity.     

Fructose Containing Sugars Do Not Raise Blood Pressure or Uric Acid at Normal Levels of Human Consumption

The impact of fructose, commonly consumed with sugars by humans, on blood pressure and uric acid has yet to be defined. A total of 267 weight‐stable participants drank sugar‐sweetened milk every day for 10 weeks as part of their usual, mixed‐nutrient diet. Groups 1 and 2 had 9% estimated caloric intake from fructose or glucose, respectively, added to milk. Groups 3 and 4 had 18% of estimated caloric intake from high fructose corn syrup or sucrose, respectively, added to the milk. Blood pressure and uric acid were determined prior to and after the 10‐week intervention. There was no effect of sugar type on either blood pressure or uric acid (interaction P>.05), and a significant time effect for blood pressure was noted (P<.05). The authors conclude that 10 weeks of consumption of fructose at the 50th percentile level, whether consumed as pure fructose or with fructose‐glucose–containing sugars, does not promote hyperuricemia or increase blood pressure.     

Interval sampling of breath hydrogen (H2) as an index of lactose malabsorption in lactase-deficient subjects

Interval sampling of breath hydrogen content was used in lactose malabsorbers: (1) to compare hydrogen responses following increasing oral doses of lactose in milk and aqueous solutions; (2) to determine the reproducibility of interval breath sampling, and (3) to compare carbohydrate malabsorption following ingestion of either regular milk or milk containingLactobacillus acidophilus. Significant differences in breath hydrogen responses due to increasing amounts of lactose in milk and aqueous solutions were observed. The individual breath hydrogen responses were reproducible using the same lactose dose on different days. There was no significant difference in breath hydrogen responses or symptoms following administration of either regular milk or milk containingLactobacillus acidophilus. Breath hydrogen sampling at intervals, as performed in these studies, provides a sensitive and reproducible index of lactose malabsorption.Supported by the Oklahoma Agricultural Experiment Station, Stillwater, Oklahoma, and the Veterans Administration.     

Effect of increasing sucrose concentrations on oral lactic acid production

Oral lactic acid production was studied on 11 healthy dental student volunteers (5 males and 6 females) during clearance of five solutions containing 5, 10, 15, 20 and 30% of sucrose. Oral fluid samples were collected at times zero, immediately before taking the sucrose solutions ('baseline'), and 15 min following intake of the solutions. The samples were analyzed qualitatively and quantitatively for the presence of lactic acid and remaining sugars using high-performance liquid chromatography (HPLC). Results indicate that the amount of lactic acid in oral fluid significantly increased with increasing sucrose concentrations, up to 15% sucrose. With the higher sucrose concentrations (20 and 30%) equivalent or lower amounts of lactic acid were obtained. The threshold level for maximum lactic acid production was found to be between 10 and 15% sucrose. Statistical analysis of the data (Student's t test) indicated a significant difference in lactic acid production between the 5 and 10% sucrose solutions versus the 15, 20 and 30% sucrose solutions tested (p < 0.05). Clinical Significance: Ingestion of solutions with higher sucrose concentrations (>15%) produced similar amounts or less of lactic acid during oral clearance than solutions containing lower sucrose concentrations (<15%).     

Blood glucose and serum insulin responses to breakfast including guar gum and cooked or uncooked milk in Type 2 (non-insulin-dependent) diabetic patients

Summary The post-prandial blood glucose and serum insulin responses to test meals, each including 300 ml fat-free milk taken separately with the meal or premixed before cooking into the meal consisting of oatmeal porridge, were studied in 10 diet-treated Type 2 (non-insulin-dependent) diabetic subjects. The modifying effect of guar gum on the responses was also studied by supplementing both types of test meals with 5 g granulated guar gum taken at the beginning of the meal. The blood glucose response was higher after the meal which contained cooked milk than after the respective meal with milk taken separately. The guar gum supplementation attenuated the blood glucose response after the meals, but the effect was more pronounced after the meal containing cooked milk. Post-prandial serum insulin responses were similar after all test meals. The results suggest that cooking may facilitate the absorption of lactose from milk-containing foods, and that supplementation with guar gum may counteract this response.     

Molecularly defined adult-type hypolactasia in school-aged children with a previous history of cow＇s milk allergy

AIM: To assess the role of lactase non-persistence/persistence in school-aged children and their milk-related symptoms. METHODS: The genotypes for the C/T-13910 variant associated with lactase non-persistence/ persistence were determined using PCR-minisequencing in a group of 172 children with a mean age of 8.6 years (SE = 0.02, 93 boys) participating in a follow-up study for cow's milk allergy. The parents were asked to assess their children's milk consumption and abdominal symptoms. RESULTS: The presence of allergy to cow's milk was not associated with the C/C-13910 genotype related with a decline of lactase enzyme activity during childhood (lactase non-persistence). The frequency of the C/C-13910 genotype (16%) was similar to published figures for the prevalence of adult-type hypolactasia in Finland. The majority of the children (90%) in this series consumed milk but 26% of their families suspected that their children had milk-related symptoms. Forty-eight percent of the children with the C/C-13910 genotype did not drink milk at all or consumed a low lactose containing diet prior to the genotyping (P< 0.004 when compared to the other genotypes). CONCLUSION: Analysis of the C/T-13910 polymorphism is an easy and reliable method for excluding adult-type hypolactasia in children with milk-related symptoms. Genotyping for this variant can be used to advise diets for children with a previous history of cow's milk allergy.     

Nutritional stress affects mosquito survival and vector competence for West Nile virus

Most anautogenous female mosquitoes ingest plant carbohydrates for flight energy and survival, and they imbibe vertebrate blood for egg development. We evaluated the effect of different sucrose meals following a blood meal containing West Nile virus (WNV) on Culex pipiens pipiens survival, nutritional status, and susceptibility to viral infection and transmission. Ten days after blood feeding, no mosquitoes survived on distilled water, 55% survived on 2% sucrose, 61% on 10 and 20% sucrose meals, and over 70% survived on 40% sucrose. There was a positive correlation between sucrose meal concentration and detectable sugars, glycogen, and lipid in whole-body homogenates. Average sugar values increased from 0 microg per starved mosquito (range 0-1.0 microg) to an average of 392 microg per mosquito fed on 40% sucrose (85-1088 microg). Average glycogen values increased from 0 microg (0-5.7 microg) to an average of 620 microg (118-1421 microg). Average lipid values were identical for mosquitoes in the starved and 2% sucrose series (38 microg) and increased to 172 microg per mosquito fed on 40% sucrose (92-266 microg). Mosquitoes in all sucrose series were equally susceptible to WNV infection (p > 0.5), but mosquitoes with lower nutrient reserves as a result of lower sucrose meals were more likely to orally transmit virus (p < 0.05). We discuss how mosquito nutritional status influences probability of daily survival, susceptibility to infection, and vectorial capacity. We conclude that maintaining C. p. pipiens on standard 10% sucrose is justified in light of these results.     

A Drosophila gustatory receptor required for the responses to sucrose, glucose, and maltose identified by mRNA tagging

In Drosophila, detection of tastants is thought to be mediated by members of a family of 68 gustatory receptors (Grs). However, only one receptor, Gr5a, has been associated with a sugar, and it appears to be activated specifically by trehalose. It is unclear whether other sugar receptors are activated by single or multiple sugars. Currently, no Grs are known to colocalize with Gr5a. Such Grs would be candidate sugar receptors because Gr5a-expressing cells function in the responses to attractive tastants. Here we use an "mRNA tagging" approach to identify Gr RNAs that are coexpressed with Gr5a. We found that all seven Grs most related to Gr5a (Gr64a-f and Gr61a) were expressed in Gr5a-expressing cells, whereas none of the other Grs examined were enriched in these Gr neurons (GRNs). We characterized the role of one Gr5a-related receptor, Gr64a, and found that it was required for the behavioral responses to glucose, sucrose, and maltose. Gr64a was required for GRN function because action potentials induced by these sugars were dependent on expression of Gr64a in GRNs. These data demonstrate that multiple Grs are coexpressed with Gr5a and that Drosophila Gr64a is required for the responses to multiple sugars.     

The serum insulin and plasma glucose responses to milk and fruit products in Type 2 (non-insulin-dependent) diabetic patients

Summary The plasma glucose and serum insulin responses were determined in untreated Type 2 (non-insulin-dependent) diabetic patients following the ingestion of foods containing sucrose, glucose, fructose or lactose in portions that contained 50 g of carbohydrate. The results were compared to those obtained following the ingestion of pure fructose, sucrose, glucose, +fructose and lactose. The objectives were to determine 1) if the glucose response to naturally occurring foods could be explained by the known carbohydrate content, and 2) whether the insulin response could be explained by the glucose response. The glucose response was essentially the same whether the carbohydrate was given as a pure substance, or in the form of a naturally occurring food. The glucose response to each type of carbohydrate was that expected from the known metabolism of the constituent monosaccharides. The glucose areas following the ingestion of the foods were: Study 1: glucose 11.7, orange juice 7.3, sucrose 5.2, glucose+fructose 6.3, and fructose 0.7 mmol · h/1; Study 2: glucose 14.6, orange juice 7.3, apples 5.5, and apple juice 4.7 mmol · h/1; Study 3 : glucose 12.6, ice cream 8.1, milk 3.7, and lactose 4.1 mmol · h/1. The insulin response was greater than could be explained by the glucose response for all meals except apples. Milk was a particularly potent insulin secretagogue; the observed insulin response was approximately 5-fold greater than would be anticipated from the glucose response. In summary, the plasma glucose response to ingestion of fruits and milk products can be predicted from the constituent carbohydrate present. The serum insulin response cannot.     

Regulation of gastric emptying by ileal nutrients in humans

Studies were carried out in 25 healthy male volunteers to investigate the effect of ileal infusion of solutions of different nutrient composition and osmolality on the profiles of a radiolabeled solid meal emptying from the stomach. Ileal infusion of a 50% corn oil emulsion or a 20% oleic acid emulsion slowed the rate of gastric emptying compared with ileal infusion of isotonic saline (0.9%). In contrast, infusion of either hypertonic saline (430 mosmol), distilled water, or isotonic solutions containing protein hydrolysate (8 g%) or glucose (50 mM) had no effect on the gastric emptying profile. These experiments support the hypothesis that the presence of unabsorbed lipid or fatty acids in the distal small intestine may delay gastric emptying, but suggest that sugars and proteins are ineffective. As infusion of both protein hydrolysates and lipid into the ileum can delay small bowel transit in humans, the data suggest that ileal regulation of gastric emptying and small bowel transit may be mediated by different mechanisms.     

Gastric emptying of lactose and milk in subjects with lactose malabsorption

Six lactose absorbers (LA) and 5 lactose malabsorbers (LM) had tests of gastric emptying with 750-ml meals of glucose in water, lactose in water, plain milk, and chocolate milk. The glucose and lactose meals emptied in a similar fashion in LA and LM subjects with a significant decrease in gastric emptying as the osmolarity of the meals was doubled. If the data are normalized by dividing lactose emptying by the emptying of glucose meals of twice the osmolality in each individual, the lactose malabsorbers empty significantly more lactose. Both LA and LM subjects emptied comparable amounts of milk meals having similar osmolarity. Chocolate milk, which had a higher osmolality than plain milk, emptied more slowly than plain milk in both groups, and this difference was significant in the LM group.     

Effect of dietary and infused lactose on rat intestinal lymph lipids

Twenty-four male, 6- to 8-week-old Sprague-Dawley rats were fed one of two skim-milk-based diets or stock laboratory diet for 100-120 days to assess the effect of dietary and infused lactose on intestinal lymph lipids. One skim-milk-based diet had its lactose enzymatically hydrolyzed by commercial beta-galactosidase to its constituent monosaccharides galactose and glucose, while the second skim milk diet was unaltered. Serum triglycerides, but not serum cholesterol, were higher in the lactose- versus the glucose-/galactose-adapted rats at 90 days. There was no diet-associated qualitative difference in serum lipoproteins as analyzed by agarose gel electrophoresis. After the rats had consumed the diets for 100-120 days, 0.9% saline and 20% solutions of lactose, and equimolar mixtures of glucose/galactose, glucose and maltose were infused sequentially via a duodenal cannula, then intestinal lymph was collected via a mesenteric lymph duct cannula, the only significant difference was a 134% increase in lymph cholesterol, but not lymph triglyceride output, when lactose was infused into lactose-adapted rats.     

Effects of graded α-glucosidase inhibition on sugar absorptionin vivo

The effect of inhibition of disaccharidases on the degree of absorption of glucose, lactose, and sucrose was examined utilizing an in vivo model in the rat. Acarbose, a competitive alpha-glucosidase inhibitor was utilized to selectively inhibit small intestinal mucosal enzymes. Adult rats (250-350 g body weight) were the subjects of intraduodenal bolus infusion experiments with either sugar alone or sugar plus acarbose. All sugars were infused at a dose of 0.5 g/kg body weight. Portal venous blood glucose was determined at 30-min intervals from 0 to 150 min. Glucose (monosaccharide) and lactose (beta-galactoside) absorption were not altered by the presence of acarbose. In contrast, sucrose (alpha-glucosidase) absorption was significantly diminished in the presence of acarbose. Sucrose absorption in the presence of increasing acarbose doses (0.7-5.6 mg/kg body weight) was depressed in a dose-dependent fashion. Linear regression analysis revealed a high degree of correlation between residual sucrase activity and area under blood glucose curve (r = 0.9837). Similar degrees of correlation were found between acarbose dose and area under blood glucose curve (r = -0.9322), and between residual sucrase activity and acarbose dose (r = -0.9695). These data confirm that acarbose is a selective alpha-glucosidase inhibitor that does not affect monosaccharidase transport. In the presence of acarbose, alpha-glucosidase absorption is diminished in a dose-dependent fashion. Postprandial glucose rise following an alpha-glucosidase meal seems to be determined, in the presence of graded acarbose inhibition, by residual mucosal alpha-glucosidase activity.