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PubMed1999

Adaptation to a starch environment and regulation of alpha-amylase in Drosophila.

The adaptation to glucose and starch foods in six species, D. melanogaster, D. virilis, D. saltans, D. funebris, D. levanonensis and D. americana, was studied by measuring productivity. D. melanogaster and D. virilis adapted more to the starch environment than to the glucose environment, while D. saltans adapted more to the glucose environment than to the starch environment. D. funebris, D. levanonensis, and D. americana did not distinctly adapt to either environment. In addition, the regulation of amylase in the six species was investigated by measuring the levels of amylase activity with glucose and starch food environments. The levels of amylase activity in D. levanonensis and D. saltans were substantially low, indicating that these species cannot utilize starch as a carbon source. The starch-adapted species, D. melanogaster and D. virilis, showed higher levels of amylase activity with the starch environment and higher inducibility. These results suggest that changing the regulation of amylase is important for the adaptation to a starch environment in Drosophila.

Adaptation, Physiological↗
PubMed2003

Sugar-starch combinations in food and the relationship to dental caries in low-risk adolescents.

The aim of this 2-year prospective cohort study was to determine whether food-level sugar-starch combinations are predictors of dental caries in a low-risk adolescent population. A total of 645 subjects, aged 12-13 yr at baseline, were recruited from 25 secondary colleges in the north-west region of metropolitan Melbourne, Australia. Examinations to record dental caries status were conducted annually. Dental caries was diagnosed according to the criteria of the World Health Organization. Dietary information was collected by four, continuous 4-d records. Demographic data was collected by parental self-administered questionnaire. A total of 504 subjects provided complete information for analysis. Approximately 37% of subjects experienced an increment in caries. In the multivariate model, only the low sugar-high starch food group was a significant predictor of caries increment on all surfaces and pit and fissure surfaces. For both these surfaces, significant interactions with starch at low sugar and across those clusters with a maximum proportion of sugar and/or starch (that is, high sugar-low starch, medium sugar-medium starch and high sugar-low starch) were found. Sugar-starch interactions may be predictive of caries risk in a low-risk adolescent population. Changing patterns of food consumption and the widespread exposure to various fluoride vehicles are possibly altering the diet-dental caries dynamic that once existed.

Adolescent↗
PubMed2000

Production of very-high-amylose potato starch by inhibition of SBE A and B.

High-amylose starch is in great demand by the starch industry for its unique functional properties. However, very few high-amylose crop varieties are commercially available. In this paper we describe the generation of very-high-amylose potato starch by genetic modification. We achieved this by simultaneously inhibiting two isoforms of starch branching enzyme to below 1% of the wild-type activities. Starch granule morphology and composition were noticeably altered. Normal, high-molecular-weight amylopectin was absent, whereas the amylose content was increased to levels comparable to the highest commercially available maize starches. In addition, the phosphorus content of the starch was increased more than fivefold. This unique starch, with its high amylose, low amylopectin, and high phosphorus levels, offers novel properties for food and industrial applications.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2003

Glucoamylase starch-binding domain of Aspergillus niger B1: molecular cloning and functional characterization.

Carbohydrate-binding modules (CBMs) are protein domains located within a carbohydrate-active enzyme, with a discrete fold that can be separated from the catalytic domain. Starch-binding domains (SBDs) are CBMs that are usually found at the C-terminus in many amylolytic enzymes. The SBD from Aspergillus niger B1 (CMI CC 324262) was cloned and expressed in Escherichia coli as an independent domain and the recombinant protein was purified on starch. The A. niger B1 SBD was found to be similar to SBD from A. kawachii, A. niger var. awamori and A. shirusami (95-96% identity) and was classified as a member of the CBM family 20. Characterization of SBD binding to starch indicated that it is essentially irreversible and that its affinity to cationic or anionic starch, as well as to potato or corn starch, does not differ significantly. These observations indicate that the fundamental binding area on these starches is essentially the same. Natural and chemically modified starches are among the most useful biopolymers employed in the industry. Our study demonstrates that SBD binds effectively to both anionic and cationic starch.

Adsorption↗
PubMed1999

Specificity of starch synthase isoforms from potato.

In higher plants several isoforms of starch synthase contribute to the extension of glucan chains in the synthesis of starch. Different isoforms are responsible for the synthesis of essentially linear amylose chains and branched, amylopectin chains. The activity of granule-bound starch synthase I from potato has been compared with that of starch synthase II from potato following expression of both isoforms in Escherichia coli. Significant differences in their activities are apparent which may be important in determining their specificities in vivo. These differences include affinities for ADPglucose and glucan substrates, activation by amylopectin, response to citrate, thermosensitivity and the processivity of glucan chain extension. To define regions of the isoforms determining these characteristic traits, chimeric proteins have been produced by expression in E. coli. These experiments reveal that the C-terminal region of granule-bound starch synthase I confers most of the specific properties of this isoform, except its processive elongation of glucan chains. This region of granule-bound starch synthase I is distinct from the C-terminal region of other starch synthases. The specific properties it confers may be important in defining the specificity of granule-bound starch synthase I in producing amylose in vivo.

Amino Acid Sequence↗
PubMed2002

Starch and natural rubber allergen interaction in the production of latex gloves: a hand-held aerosol.

Starch powders continue to be used as donning agents on natural rubber (NR) gloves. NR aeroallergens are an important aspect of human sensitivity to latex. Asthma, upper airway, and ocular symptoms are associated with these airborne proteins. These bioaerosols feature starch as the carrier. The association of NR allergen and starch is demonstrated in NR glove manufacturing, in laboratory simulation, and as occupational aeroallergens in health care environments. Four aspects of latex allergen affinity for starch powders were examined by using a competitive IgE immunoassay for NR latex. Allergen content was assessed in finished gloves before and after powder process points and related to the allergen content of the raw latex source material. In another manufacturing process, allergen uptake by two different starch powders was quantified. NR allergen affinity for the starches was also determined under laboratory conditions. Finally, NR aeroallergens carried by starch powder in production facilities were measured. This article outlines the sources, mechanisms, and conditions for NR allergens to interact with two different starches. The quantitative airborne allergen data are used to compare and contrast various occupational indices of NR allergen exposure. Powdered NR gloves continue to cause concern; however, the technology used for contemporary glove powder applications may be advanced and improved enough to consistently produce powdered gloves with a low allergen content.

Air Pollutants↗
PubMed2006

A redox-regulated chloroplast protein phosphatase binds to starch diurnally and functions in its accumulation.

Starch is the ultimate storage molecule formed in the photosynthetic fixation of carbon dioxide by chloroplasts. Starch accumulates during the day and is degraded at night to intermediates that are exported to heterotrophic organs. The mechanism by which diurnal cycles control the transitory biosynthesis and degradation of chloroplast starch has long remained a mystery. We now report evidence that a dual-specificity protein phosphatase, DSP4, binds to starch granules during the day and dissociates at night. Disruption of the DSP4 gene resulted in a dramatic increase in the level of starch in mutant Arabidopsis plants. Moreover, although composition was apparently unchanged, the morphology of the starch granule was significantly altered compared to the wild type counterpart. Two regulatory factors linked to light (i.e., pH and redox status) changed both the activity and the starch-binding capacity of DSP4. The results further revealed that DSP4 represents a major fraction of granule-bound phosphatase activity during the day but not at night. Our study suggests that DSP4 acts as a bridge between light-induced redox changes and protein phosphorylation in the regulation of starch accumulation.

Amino Acid Sequence↗
PubMed1995

Replacement of digestible by resistant starch lowers diet-induced thermogenesis in healthy men.

The present study describes the effect of replacement of digestible starch by resistant starch (RS) on diet-induced thermogenesis (DIT), postprandial glucose and insulin responses, and colonic fermentation. Ten healthy males consumed three test meals, consisting of diluted, artificially-sweetened fruit syrup and either 50 g raw potato starch (550 g RS/kg), or 50 g pregelatinized potato starch (0 g RS/kg) or 30 g pregelatinized potato starch plus 20 g lactulose (670 g indigestible disaccharide/kg). The meals were served in the morning after an overnight fast. Each volunteer consumed each meal twice on six separate days in random order. Metabolic rate was measured by indirect calorimetry in the fasting state for 15 min and postprandially for 5 h. Shortly before and hourly up to 7 h after consumption of the test meal, end-expiratory breath samples were obtained for H2 and CH4 analysis. Shortly before the meal and 30, 60, 180, and 300 min postprandially, blood samples were taken for glucose and insulin analyses. Postprandial increases in glucose and insulin levels were proportional to the amount of digestible carbohydrate in the meal. Breath H2 and CH4 concentrations indicated that the pregelatinized starch was not fermented and that lactulose was fermented rapidly. Fermentation of the raw starch started only 6 to 7 h after consumption, resulting in a rise in breath H2 but not in CH4. The replacement of 27 g digestible starch by RS in a single meal lowered DIT by on average 90 kJ/5 h, as could also be calculated by assuming that RS does not contribute to DIT. The ingestion of lactulose resulted in a substantial rise in DIT which was most probably caused by its fermentation.

Adult↗
PubMed1995

Abomasal glucose, maize starch and maize dextrin infusions in cattle: small-intestinal disappearance, net portal glucose flux and ileal oligosaccharide flow.

Three castrated male Holstein cattle (423 (SD 19)kg live weight) fitted with elevated carotid artery, portal, and mesenteric venous catheters, and abomasal and ileal cannulas were used to study small-intestinal starch digestion. The cattle were infused abomasally with water (275 ml/h), glucose (66 g/h), maize dextrin (66 g/h) or maize starch (66 g/h) in an incomplete Latin square design, with eight infusion periods. Infusion with carbohydrate resulted in higher arterial glucose concentrations and greater net portal glucose flux than when cattle were infused with water. Arterial glucose concentration and net portal glucose flux were highest when glucose was infused. In the small intestine, 85% of abomasally-infused glucose, 78% of infused dextrin, and 66% of infused starch disappeared. Of the carbohydrate that disappeared in the small intestine, that which could be accounted for as net portal glucose flux was 73% for glucose, 60% for dextrin, and 57% for starch. Ileal digesta contained unpolymerized glucose, and short-chain soluble alpha-glucoside. Of the infused dextrin flowing past the ileum (14 g/h), 0.3 g/h was glucose, 6.2 g/h was soluble alpha-glucoside, and 7.5 g/h was insoluble alpha-glucoside. Of the infused starch flowing at the ileum (22.2 g/h), 0.9 g/h was glucose, 5.3 g/h was soluble alpha-glucoside, and 15.9 g/h was insoluble alpha-glucoside. The average chain lengths of the soluble alpha-glucosides in ileal digesta were 2.07 and 2.36 for dextrin and starch infusions respectively, indicating mostly di- and to a lesser extent trisaccharides. We conclude that (1) when 66 g raw starch is presented to the small intestine per h, about half of the intestinal disappearance appears as glucose in the portal vasculature, and (2) alpha-1,4 glucosidase (EC 3.2.1.20) activity at the brush border is the rate-limiting step to small-intestinal starch digestion in cattle.

Abomasum↗
PubMed1987

Digestion of starch and fibre carbohydrates in peas by adult cockerels.

The digestion of starch and fibre by adult cockerels fed peas which were whole, ground, autoclaved, heated, dehulled, cooked or supplemented with a cellulose degrading enzyme was studied. The starch in ground peas that had been autoclaved, heated or dehulled was slightly, though not significantly, better digested than the starch in peas that had been ground only. Feeding peas whole greatly reduced starch digestibility. Cooking failed to improve starch digestibility as retrograded starch produced in the cooking process was not digested. The more finely ground the foodstuff, the better the in vitro enzymatic hydrolysis of starch. Starch digestibility correlated well (r2 = 0.80) with the true metabolisable energy values obtained for the different pea treatments. In experiment 1 cockerels digested on average 0.22 of the pea fibre from the different forms of peas. A significant decrease in xylose digestion was observed when birds were fed dehulled peas, birds excreting more xylose than they ingested. In experiment 2, cockerels digested on average 0.38 of the pea fibre from different forms of peas. A reduction in fibre digestion was observed when birds were fed cooked peas as a consequence of a decreased digestibility of all monosaccharide residues. A slight increase in fibre digestion was observed when peas were augmented with 'cellulase', entirely because of an increase in xylose digestion.

Animals↗
PubMed1995

Influence of starch fermentation on bile acid metabolism by colonic bacteria.

Secondary bile acids (BA) may be involved in the pathogenesis of colorectal cancer. In vivo, starch malabsorption has been shown to reduce fecal excretion of secondary BA. The present in vitro study was performed to investigate the effect of starch fermentation on BA metabolism by colonic bacteria. Fecal samples of healthy volunteers were incubated in anaerobic batch cultures for 48 hours with the primary bile acids cholic (0.6 g/l) and chenodeoxycholic acid (0.4 g/l). Media were starch free or enriched with starch (10 g/l). The pH was controlled and held at 6 or 7. In the starch-free incubations, secondary BA were rapidly formed, and degradation of primary to secondary BA was complete within 24 hours. The formation of secondary BA was partially inhibited by the addition of starch to the media. This effect was stronger at pH 6 than at pH 7. Starch was rapidly and completely fermented. In conclusion, this study showed that formation of secondary BA by fecal bacteria is inhibited when starch is simultaneously fermented, an effect that is mainly, but not completely, explained by reduction of pH.

Bacteria, Anaerobic↗
PubMed1985

The removal of glucose, maltose and different starches from the small intestines of steers.

Four Friesian steers (103-150 kg) each equipped with simple abomasal and re-entrant ileal cannulas were used. Different amounts of glucose, maltose or one of several isolated starches or ground cereal grains, ranging from 80-400 g/8 h, together with polyethylene glycol were infused into the abomasums and absorption up to the ileum examined. The efficiency of removal of glucose remained high at all levels of infusion (greater than 80%) and at the highest level, 26.4 g glucose/kg body weight 0.75/d were calculated to be removed in the small intestines. At low levels of infusions, maltose was removed almost as efficiently as glucose, but the capacity of the small intestines to remove maltose was exceeded with infusions above 15 g/kg body weight 0.75/d. Soluble and isolated wheat starch were removed to similar extents and almost identically to maltose. Isolated maize starch, whilst being removed in the small intestines almost as rapidly as maltose at the lowest level of infusion, was less efficiently removed at higher levels. Rice and potato starches were poorly removed in the small intestines. Intestinal capacities for the removal of related wheat, soluble starch, maize, rice and potato starches were 102, 99, 80, 77 and 55% that of equivalent amounts of maltose. Starch in ground cereal grains (maize and wheat) were removed in the small intestines slightly less efficiently (75-90%) than the corresponding isolated starches.

Animals↗
PubMed1999

Evaluation of the emulsifying properties of some cationic starches.

Different cationic potato, maize, and waxy maize starches were evaluated for their emulsifying properties. Emulsions were prepared using 20% (w/w) arachidic oil and 80% (w/w) water. Emulsions with the cationic starches as emulsifier in a concentration ranging from 1% to 5% (w/w) were prepared and characterized by droplet size and viscosity measurements, and the stability was evaluated visually and by electrical conductance measurements. None of the cationic potato, waxy maize starches, and maize starches with a low degree of substitution (DS) showed adequate emulsifying properties. Emulsions prepared using non-pregelatinized (C [symbol: see text] bond 05914, 2% and 5% w/w; C [symbol: see text] bond 05907, 5% w/w) and pregelatinized (C [symbol: see text] bond 12504, 5% w/w) cationic maize starches with high-DS were visually stable. The initial mean droplet volume diameter of the emulsions prepared with these cationic starches in a 5% (w/w) concentration was similar and ranged from 2.40 to 2.84 microns; however, there was an important difference in droplet size distribution. The droplet size distribution of the emulsions prepared using the non-pregelatinized high-DS cationic starches was markedly narrower than in the case of the emulsions prepared using the pregelatinized high-DS cationic starches. The droplet size of the emulsions remained almost constant during 120 days of storage. Visual inspection and electrical conductance measurements showed that these emulsions were stable for at least 120 days.

Cations↗
PubMed2005

Insulin-sensitizing effects of dietary resistant starch and effects on skeletal muscle and adipose tissue metabolism.

BACKGROUND: Resistant starch may modulate insulin sensitivity, although the precise mechanism of this action is unknown. OBJECTIVE: We studied the effects of resistant starch on insulin sensitivity and tissue metabolism. DESIGN: We used a 4-wk supplementation period with 30 g resistant starch/d, compared with placebo, in 10 healthy subjects and assessed the results by using arteriovenous difference methods. RESULTS: When assessed by euglycemic-hyperinsulinemic clamp, insulin sensitivity was higher after resistant starch supplementation than after placebo treatment (9.7 and 8.5 x 10(-2) mg glucose x kg(-1) x min(-1) x (mU insulin/L)(-1), respectively; P = 0.03); insulin sensitivity during the meal tolerance test (MTT) was 33% higher (P = 0.05). Forearm muscle glucose clearance during the MTT was also higher after resistant starch supplementation (P = 0.03) despite lower insulin concentrations (P = 0.02); glucose clearance adjusted for insulin was 44% higher. Subcutaneous abdominal adipose tissue nonesterified fatty acid (NEFA; P = 0.02) and glycerol (P = 0.05) release were lower with resistant starch supplementation, although systemic NEFA concentrations were not significantly altered. Short-chain fatty acid concentrations (acetate and propionate) were higher during the MTT (P = 0.05 and 0.01, respectively), as was acetate uptake by adipose tissue (P = 0.03). Fasting plasma ghrelin concentrations were higher with resistant starch supplementation (2769 compared with 2062 pg/mL; P = 0.03), although postprandial suppression (40-44%) did not differ significantly. Measurements of gene expression in adipose tissue and muscle were uninformative, which suggests effects at a metabolic level. The resistant starch supplement was well tolerated. CONCLUSION: These results suggest that dietary supplementation with resistant starch has the potential to improve insulin sensitivity. Further studies in insulin-resistant persons are needed.

Adipose Tissue↗
PubMed1981

Rate of starch hydrolysis in vitro as a predictor of metabolic responses to complex carbohydrate in vivo.

This study was designed to determine whether the rate of hydrolysis of different starches by pancreatic amylase in vitro was proportional to the postprandial glucose and insulin response to those starches after oral ingestion. Lean young men consumed four test meals of rice containing 75 g starch: white rice, unpolished (brown) rice, ground white rice, and ground brown rice. Postprandial glucose and insulin responses were measured over 4 h and showed the following pattern: ground white rice congruent to ground brown rice greater than white rice greater than brown rice. The maximum increases in blood glucose after the four meals were brown rice 0.9 mM, white rice 1.5 mM, ground brown rice 3.3 mM, and ground white rice 3.6 mM. Samples of the cooked rices were incubated in vitro with pancreatic amylase for 30 min and the percentage starch hydrolysis determine. The relative rates of starch hydrolysis correlated very closely with the peak glucose responses: brown rice 17.6%, white rice 30.8%, ground brown rice 68.2% and ground white rice 71.8%. These results indicated that the rate of intestinal hydrolysis of starch is an extremely important determinant of the metabolic responses to a particular starch. The rate of starch hydrolysis can be determine simply by an in vitro method and should assist the design of diets for the treatment of diabetes.

Amylases↗
PubMed2000

Digestion of so-called resistant starch sources in the human small intestine.

BACKGROUND: Resistant starch sources, which are only partially digested in the small intestine, can be used to increase colonic availability of short-chain fatty acids. OBJECTIVE: To study the characteristics of the fermentation of resistant starch, the digestion of resistant starch in the small intestine has to be quantified. We compared the metabolic fates of highly digestible cornstarch (DCS), Hylon VII (type 2 resistant starch), and Novelose 330 (type 3 resistant starch), which are of corn origin and, therefore, naturally enriched in (13)C. DESIGN: After administration of 40 g starch or glucose to 7 healthy volunteers, glucose and exogenous glucose concentrations in serum and (13)CO(2) excretion in breath were analyzed for 6 h. (13)C abundance in carbon dioxide was analyzed by isotope ratio mass spectrometry (IRMS) and (13)C abundance in glucose by gas chromatography-combustion IRMS. RESULTS: By comparing the area under the curve (2 h) of exogenous glucose concentration in serum ((13)C glycemic index) after intake of starch or glucose, (13)C glycemic indexes for DCS, Hylon VII, and Novelose 330 were calculated to be 82 +/- 23%, 44 +/- 16%, and 43 +/- 15%, respectively. Comparison of 6-h cumulative percentage dose recovery in breath showed that 119 +/- 28% of DCS, 55 +/- 23% of Hylon VII, and 50 +/- 26% of Novelose 330 was digested in the small intestine. CONCLUSION: The exogenous glucose response in serum and the (13)CO(2) excretion in breath can be used to estimate small intestinal digestion of resistant starch, which amounts to approximately 50%.

Adult↗
PubMed2002

Enhancement of sucrose sweetness with soluble starch in humans.

The effect of soluble starch (acid-modified starch) on taste intensity was investigated in human subjects. Different concentrations of sucrose (Suc), six sweeteners, NaCl, quinine-HCl (QHCl) and citric acid (Cit) were dissolved in either distilled water (DW; standard) or starch solution (test solution). The solutions were presented to naive subjects and each subject was requested to taste and compare the sweetness intensity between the standard and test solutions based on a scale ranging from +3 (enhanced) to -3 (inhibited). A greater sweetness intensity occurred with Suc at different concentration (0.1-1.0 M) dissolved in soluble starch (0.125% to 4.0%) than with Suc in DW. Similarly, five other different products of soluble starch at 0.25 and 4.0% resulted in enhancement of sweetness for 0.3 and 1.0 M Suc. With the sole exception of the taste of 0.3 M Suc, sweet enhancement did not occur with 0.43 M fructose, 0.82 M glucose, 0.82 M sorbitol, 0.0037 M aspartame, 0.0042 M saccharin-Na or 0.016 M cyclamate. Neither the saltiness of NaCl (0.01-0.3 M), the bitterness of QHCl (0.00003-0.001 M) nor the sourness of Cit (0.0003-0.01 M) were affected by the soluble starch. These results suggest that the taste enhancing effects of soluble starch on Suc sweetness might depend not only on the taste transduction mechanism, but also on the molecular interaction between Suc and soluble starch.

Adult↗
PubMed2001

Changes in starch content in oat (Avena sativa) shoot pulvini during the gravitropic response.

In order to determine if components of the signal transduction pathway are involved in starch metabolism during the gravitropic response, the effects of inhibitors of phosphoprotein phosphatases and protein kinases (OA), and calcium channel blockers (LaCl3), on gravitropic bending and starch levels in gravisensitive node/pulvini of oat shoots were examined. Among the compounds tested, okadaic acid (OA) and lanthanum chloride (LaCl3) showed the strongest inhibitory effects on the negative gravitropic curvature response in oat shoot node/pulvini. At the same time, they caused a rapid loss of starch in graviresponding pulvini based on a quantitative analysis of starch levels in the bending tissues over 48 h periods. These two compounds act initially to block the net increase in starch content that occurs during the early stages (0-9 h) in graviresponding oat shoot pulvini. As a result, starch levels drop precipitously in shoots treated with OA and LaCl3, starting at time zero of gravistimulation by reorientation. These findings suggest that protein dephosphorylation and calcium play a role in starch metabolism in oat shoot pulvini in response to a gravistimulation signal. They also indicate that the amount of starch present in the chloroplast gravisensors in oat shoot pulvini may determine the rate of upward bending in graviresponding pulvini.

Avena↗