![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Ross Products Division, Abbott Laboratories, Columbus, OH 43215 and * Chicago Center for Clinical Research, Chicago, IL 60610
2To whom correspondence should be addressed. E-mail: bryan.wolf{at}abbott.com.
 |
ABSTRACT |
|---|
 TOP ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
KEY WORDS: • pullulan • humans • glycemia • breath hydrogen
In light of the increasing incidence of type 2 diabetes mellitus (1 ), there has been a growing interest in the search for therapeutic diets for these individuals. The primary treatment goal is to maintain near-normal blood glucose levels. Of the macronutrients, carbohydrate has the largest effect on postprandial glycemic excursion (2 ). Both the amount and type of dietary carbohydrate are important determinants of postprandial glucose responses to mixed meals (3 –5 ). Differences in glycemic responses to dietary starch are directly related to the rate of starch digestion (6 ). Englyst et al. (7 ) defined slowly digested starch as starch that is likely to be completely digested in the small intestine but at a slower rate.
As a component of our research program, we have been searching for carbohydrate ingredients that are slowly digested and are compatible with liquid enteral formula manufacturing (8 ,9 ). Among slowly digested starches, raw cornstarch is the gold standard (10 –12 ). Unfortunately, raw cornstarch cannot be added to a liquid enteral formula because product retort (i.e., sterilization at high temperature) results in the cooking of the starch. As shown by Chen et al. (13 ) and Collings et al. (14 ), cooking the starch (which allows complete gelatinization) renders the starch rapidly digestible.
Pullulan is a fermentation product of the yeast, Aureobasidium pullulans. It has a starch-like structure in that it is an 
-glucan. It has a relatively simple structure of three -1,4-linked glucose molecules that are repeatedly polymerized by -1,6 linkages on the terminal glucose, resulting in a stair-step structure (15
). Pullulan has been classified as an indigestible carbohydrate (16
–18
). Using an in vitro starch digestion method, we discovered that pullulan hydrolysis occurred slowly over time in both the raw and cooked state. Thus, we sought to evaluate the effects of pullulan ingestion on postprandial blood glucose excursion in humans.
The primary objective of this study was to compare the postprandial glycemic response of healthy nondiabetic adult subjects to pullulan and maltodextrin, which is a rapidly digested starch that normally elicits a high glycemic response. Secondary objectives of this study were as follows: 1) to determine whether malabsorption of carbohydrate from either maltodextrin or pullulan occurred (assessed by the breath hydrogen method); and 2) to evaluate the subjective gastrointestinal intolerance (i.e., nausea, abdominal cramping, distention and flatulence) of nondiabetic healthy adults to a 50-g pullulan challenge.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
The percentage of hydrolyzed carbohydrate was determined as described by Wolf et al. (8
), who used a modification of the in vitro method (-amylase and amyloglucosidase enzyme system) of Muir and O’Dea (19
,20
). This in vitro assay was validated in humans (20
).
The extent of pullulan hydrolysis over time was compared with the extent of hydrolysis of maltodextrin. Both test materials were tested in a raw and cooked state (a simulation of product retort). For cooking, 0.1 g of test material was suspended in 1 mL of water and autoclaved for 30 min at 2.1 kg/cm2 and 121°C. Immediately after autoclave treatment, samples were cooled in a cold-water bath for 10 min and then used in the in vitro procedure as described by Wolf et al. (8 ).
Subjects.
Nondiabetic, healthy subjects (n = 36; 22 men, 14 women) aged 18–75 y (mean ± SEM, 45 ± 2 y) were recruited. Three men and five women withdrew from the study: four requested withdrawal from the study and four were unable to adhere to study protocol. Thus, a total of 28 subjects completed the study. The body weight (mean ± SEM) of the remaining 28 subjects was 73.4 ± 2.2 kg (range = 52.5–104.7 kg). The body mass index (BMI) was 24.8 ± 0.5 kg/m2 (range = 20.3–28.4 kg/m2). Before the study, capillary blood glucose concentration was determined by finger-prick in fasting subjects. The fasting blood glucose concentration of the subjects was 4.4 ± 0.07 mmol/L (range = 3.7–5.0 mmol/L). The self-reported ethnicity of the subjects was as follows: 14 Caucasian, 11 African American, 1 Asian or Pacific Islander, 1 Latino and 1 who reported "mixed race." Potential subjects were excluded from the study during an initial screening process if they had medical conditions or were taking medications (e.g., antibiotics) that would interfere with glucose metabolism or would alter the colonic bacteria. The Schulman Associates Institutional Review Board (Cincinnati, OH) approved the experimental protocol. Informed consent was obtained from all subjects before the start of the study.
Dietary treatments.
The two treatments evaluated in this experiment were the control, maltodextrin (Maltrin M100; Grain Processing, Muscatine, IA) and pullulan (Pullulan PF10; Hayashibara, Okayama, Japan). Maltodextrin is a rapidly digested starch (21
). Pullulan had an average molecular weight of 100,000 (Hayashibara). These test materials were incorporated into juice-like beverages (
25 g carbohydrate/237 mL) and flavored to enhance palatability (Table 1
). The beverage vehicle for the test materials did not contain any appreciable energy (<41.84 kJ). Ingredients were made into a solution with water, poured into 237-mL plastic cans (Huhtamaki Plastics, Coleman, MI), and terminally sterilized (Ross Products Division of Abbott Laboratories, Columbus, OH). Both solutions were low in viscosity, 4.2 and 16.1 mPa · s for control and pullulan, respectively. Subjects consumed 50 g of test material in 16 fl oz. (474 mL) for the meal tolerance test.
|
The study was a randomized, double-masked, two-period, two-treatment, crossover design in which subjects participated in two separate 3-h meal tolerance tests. The tolerance tests were spaced 5–13 d apart for each subject. Subjects were randomly assigned to one of two possible treatment sequences. After an overnight fast of 11–15 h, subjects consumed the treatment.
To ensure that subjects had similar glycogen stores on the two test days, they were instructed to consume a high carbohydrate diet (minimum 150 g of carbohydrate/d) for 3 d before each meal tolerance test and were also instructed to avoid exercise for 24 h before the experiment. Adequate carbohydrate intake was verified by 3-d diet records. On the evening before each meal tolerance test, all subjects consumed a low residue dinner consisting of one 237-mL can of Ensure Plus with additional Ensure Nutrition and Energy Bars (Ross Products Division, Abbott Laboratories, Columbus, OH) to provide one third of each subject’s individual daily energy requirement as estimated by the Harris-Benedict equation (22 ) multiplied by an activity factor of 1.3. After their low residue evening meal, subjects were instructed to fast overnight, during which they were allowed to consume only water. Smoking was prohibited. All subjects were recruited and enrolled from one study site.
Blood glucose analysis.
A finger-prick capillary blood sample was obtained from fasting (range 11–15 h) subjects and collected into a capillary tube containing EDTA after 30 min of rest. Subjects then consumed the appropriate test meal within 10 min. Finger-prick capillary blood was obtained at 15, 30, 45, 60, 90, 120, 150 and 180 min postprandially. Capillary blood glucose was measured by the glucose oxidase method using a YSI analyzer (YSI Model 2700 SELECT Biochemistry Analyzer, Yellow Springs Instruments, Yellow Springs, OH).
Calculation of blood glucose area under the curve (AUC) and relative glycemic response (RGR).
The positive incremental AUC, ignoring any areas below the baseline, for the blood glucose values from 0 to 180 min after the meal tolerance test was calculated according to the method of Wolever et al. (23 ). The RGR of pullulan was calculated for each individual subject according to the following formula: [(glucose AUC for pullulan)/(glucose AUC for control)] x 100.
Breath hydrogen analysis.
Subjects were evaluated for carbohydrate malabsorption by measuring their end-alveolar hydrogen and methane concentrations hourly for 8 h after they ingested their meal tolerance test. Samples of end-alveolar air were collected into 10-mL glass vacuum tubes using an EasySampler device (Quintron Instruments, Milwaukee, WI). After the initial 3-h meal tolerance test, subjects were allowed free access to water.
The concentrations of carbon dioxide, hydrogen and methane in breath samples were analyzed by gas chromatography (Microlyzer Gas Analyzer, model SC; Quintron Instruments). The observed hydrogen and methane values were corrected for atmospheric contamination of alveolar air by normalizing the concentrations of observed carbon dioxide to 5.26% (5.33 kPa, or 40 torr, the partial pressure of carbon dioxide in alveolar air) (24 ). Samples with a carbon dioxide concentration < 1.3% were considered poor samples, and data were entered as missing. Changes in hydrogen concentrations were calculated by subtracting the lowest hydrogen concentration among the 0, 1 or 2 h samples from the subsequent values. Rather than consistently using the time 0 value, the nadir value was selected as the baseline because some subjects have residual hydrogen accumulation in the colon during sleep that may be excreted over the first few hours of the experiment; thus the time 0 value may not reflect a true basal breath hydrogen level (25 ,26 ). Subjects were classified as having carbohydrate malabsorption (i.e., positive breath hydrogen test) if their breath hydrogen concentrations increased by >10 parts per million (0.9 x 106 g of hydrogen/L of air or 0.45 µmol/L) from their basal nadir value (27 ).
Intolerance symptoms.
Using a questionnaire, subjects were asked to report the frequency and intensity of symptoms of nausea, abdominal cramping, distention, and flatulence for the two 24-h periods (total of 48 h) immediately after consumption of the test material. Intensity and frequency were set to a 100-mm line scale (0 representing "absent" and 100 "severe" and 0 representing "usual" and 100 "more than usual," respectively). Subjects placed a single perpendicular slash mark across the 100-mm horizontal line to indicate their scores for each of these variables of frequency and intensity for each 24-h period.
Statistical analysis.
Using data from a previous study (28 ), a power analysis conducted before this study indicated that 26 subjects would be required to detect a 15% difference in incremental (i.e., baseline-adjusted) peak blood glucose concentration with 80% power, using an expected SD of 1.053 mmol/L.
Data obtained during the two testing days for the blood glucose variables, breath hydrogen concentrations and symptoms of gastrointestinal tolerance were fit to a two-period crossover model. The residuals obtained from fitting the two-period crossover model were examined for evidence of a normal distribution with the Shapiro-Wilk test. The Shapiro-Wilk test for normality was rejected (P < 0.05) for most variables; therefore, a nonparametric model was used. The effects of sequence, period and treatment were examined by a two-sided Wilcoxon rank sum test (SAS version 8.2, SAS Institute, Cary, NC). The binary variable, positive breath hydrogen test, was analyzed using Generalized Estimating Equations (SAS).
|
RESULTS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
|
|
|
|
|
|
DISCUSSION |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
As noted previously, pullulan has been classified as an indigestible carbohydrate (16
–18
). Nakamura (16
) found that <15% of pullulan was hydrolyzed by human salivary amylase and <10% was hydrolyzed by porcine pancreatic amylase during a 22-h in vitro incubation. Similarly, Okada et al. (17
) documented that <10% of pullulan was hydrolyzed by rat intestinal acetone powder, in vitro. Oku et al. (18
) gavaged a 10% pullulan solution into the stomach of rats and determined that 3% of the glycosidic bonds of pullulan were hydrolyzed in the digestive tract within 60 min. Our in vitro and human glycemic response data contradict the results of these studies. If pullulan were an indigestible carbohydrate, it should not give rise to postprandial blood glucose. For example, bolus ingestion of the indigestible oligosaccharides polydextrose (29
) or Fibersol 2 (30
) does not elicit a postprandial rise in blood glucose concentrations.
Optimally, a slowly digested carbohydrate should be completely digested in the small intestine so that it would result in minimal gastrointestinal intolerance. The extent of in vitro hydrolysis of pullulan by -amylase and amyloglucosidase at 5 h was high (95%; Table 2
). However, the postprandial breath hydrogen response was exacerbated by the bolus consumption of 50 g of pullulan (see Fig. 2
). The absolute breath hydrogen concentrations elicited by pullulan were similar to those reported by Lifschitz et al. (31
) who fed 10 subjects 35 g of cooked barley, which contained 5.66 g of ß-glucan. Because the amount of hydrogen in the breath represents only a portion (14%) of the amount produced in the colon (32
), the amount of malabsorbed carbohydrate reaching the colon is difficult to quantify. To conduct a more detailed investigation of the digestion and absorption of pullulan, 13C-labeled pullulan should be used.
The malabsorbed pullulan also increased (P < 0.05) the subjective ranking of flatulence (both intensity and frequency) in the first 24-h postprandial period (0–24 h) after the meal tolerance test (Table 4) . This effect tended to subside in the second 24-h postprandial period (24–48 h). With a smaller dose, fewer gastrointestinal intolerance symptoms might be incurred while still providing the slow digestion necessary to improve postprandial glycemia. For example, a 5-g dose of raw cornstarch was shown to reduce the incidence of nighttime hypoglycemia in campers and counselors at a diabetes camp (10 ).
In summary, in comparison with maltodextrin, pullulan reduces the glycemic excursion, maintains blood glucose concentrations above baseline over a prolonged period (at least to 180 min), increases carbohydrate malabsorption as measured by breath hydrogen and increases the incidence and frequency of flatulence in healthy nondiabetic humans. Pullulan helps maintain blood glucose levels by reducing the early phase excursion and by appropriately maintaining the later phase excursion. Further investigation of the possible beneficial effects of pullulan in individuals with diabetes mellitus is recommended.
|
FOOTNOTES |
|---|
3 Abbreviations used: AUC, area under the curve; BMI, body mass index; RGR, relative glycemic response.
Manuscript received 31 October 2002. Initial review completed 25 November 2002. Revision accepted 13 January 2003.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1. Mokdad, A. H., Bowman, B. A., Ford, E. S., Vinicor, F., Marks, J. S. & Koplan, J. P. (2001) The continuing epidemics of obesity and diabetes in the United States. J. Am. Med. Assoc. 286:1195-1200.
2. Elliott, R. M., Morgan, L. M., Tredger, J. A., Deacon, S., Wright, J. & Marks, V. (1993) Glucagon-like peptide-1 (7–36)amide and glucose-dependent insulinotropic polypeptide secretion in response to nutrient ingestion in man: acute post-prandial and 24-h secretion patterns. J. Endocrinol. 138:159-166.
3. Wolever, T.M.S. & Bolognesi, C. (1996) Source and amount of carbohydrate affect postprandial glucose and insulin in normal subjects. J. Nutr. 126:2798-2806.
4. Wolever, T.M.S. & Bolognesi, C. (1996) Prediction of glucose and insulin responses of normal subjects after consuming mixed meals varying in energy, protein, fat, carbohydrate and glycemic index. J. Nutr. 126:2807-2812.
5. Wolever, T.M.S. & Jenkins, D.J.A. (1986) The use of the glycemic index in predicting the blood glucose response to mixed meals. Am. J. Clin. Nutr. 43:167-172.
6. O’Dea, K., Snow, P. & Nestel, P. (1981) Rate of starch hydrolysis in vitro as a predictor of metabolic responses to complex carbohydrate in vivo. Am. J. Clin. Nutr. 34:1991-1993.
7. Englyst, H. N., Kingman, S. M. & Cummings, J. H. (1992) Classification and measurement of nutritionally important starch fractions. Eur. J. Clin. Nutr. 46(suppl. 2):S33-S50.
8. Wolf, B. W., Bauer, L. L. & Fahey, G. C., Jr (1999) Effects of chemical modification on in vitro rate and extent of food starch digestion: an attempt to discover a slowly digested starch. J. Agric. Food Chem. 47:4178-4183.[Medline]
9. Wolf, B. W., Wolever, T.M.S., Bolognesi, C., Zinker, B. A., Garleb, K. A. & Firkins, J. L. (2001) Glycemic response to a food starch esterified by 1-octenyl succinic anhydride in humans. J. Agric. Food Chem. 49:2674-2678.[Medline]
10. Kaufman, F. R., Halvorson, M. & Kaufman, N. D. (1995) A randomized, blinded trial of uncooked cornstarch to diminish nocturnal hypoglycemia at diabetes camp. Diabetes Res. Clin. Prac. 30:205-209.[Medline]
11. Wolf, B. W. (2001) Discovery of a Carbohydrate System That Does Not Exacerbate Postprandial Glycemia. Doctoral thesis 2001 The Ohio State University Columbus, OH.
12. Wolfsdorf, J. I. & Crigler, J. F., Jr (1997) Cornstarch regimens for nocturnal treatment of young adults with type I glycogen storage disease. Am. J. Clin. Nutr. 65:1507-1511.
13. Chen, Y.-T., Cornblath, M. & Sidbury, J. B. (1984) Cornstarch therapy in type I glycogen-storage disease. N. Engl. J. Med. 310:171-175.[Medline]
14. Collings, P., Williams, C. & MacDonald, I. (1981) Effects of cooking on serum glucose and insulin responses to starch. Br. Med. J. 282:1032.
15. Kimoto, T., Shibuya, T. & Shiobara, S. (1997) Safety studies of a novel starch, pullulan: chronic toxicity in rats and bacterial mutagenicity. Food Chem. Toxicol. 35:323-329.[Medline]
16. Nakamura, S. (1984) Pullulan. J. Synth. Org. Chem., Jpn. (in Japanese) 42:584-588.
17. Okada, K., Yoneyuama, M., Mandai, T., Aga, H., Sakai, S. & Ichikawa, T. (1990) Digestion and fermentation of pullulan. J. Jpn. Soc. Nutr. Food Sci. (in Japanese) 43:23-29.
18. Oku, T., Yamada, K. & Hosoya, N. (1979) Effect of pullulan and cellulose on the gastrointestinal tract of rats. Nutr. Diets (in Japanese) 32:235-241.
19. Muir, J. G. & O’Dea, K. (1992) Measurement of resistant starch: factors affecting the amount of starch escaping digestion in vitro. Am. J. Clin. Nutr. 56:123-127.
20. Muir, J. G. & O’Dea, K. (1993) Validation of an in vitro assay for predicting the amount of starch that escapes digestion in the small intestine of humans. Am. J. Clin. Nutr. 57:540-546.
21. Philipson, E. H., Rossi, K. Q., Isaac, R. M. & Kahlan, S. C. (1992) Glucose, insulin, gastric inhibitory polypeptide, and pancreatic polypeptide responses to polycose during pregnancy. Obstet. Gynecol. 79:592-596.[Medline]
22. Harris, J. A. & Benedict, F. G. (1919) A Biometric Study of Basal Metabolism in Man 1919:227 Carnegie Institute Washington, DC. Publication no. 279.
23. Wolever, T., Jenkins, D., Jenkins, A. L. & Josse, R. G. (1991) The glycemic index: methodology and clinical implications. Am. J. Clin. Nutr. 54:846-854.
24. Holum, J. R. (1982) Fundamentals of General, Organic, and Biological Chemistry 1982:111 Wiley and Sons New York, NY.
25. Read, N. W., Al-Janabi, M. N., Bates, T. E., Holgate, A. M., Cann, P. A., Kinsman, R. I., McFarlane, A. & Brown, C. (1985) Interpretation of the breath hydrogen profile obtained after ingesting a solid meal containing unabsorbable carbohydrate. Gut 26:834-842.
26. Hertzler, S. R., Huynh, B.-C.L. & Savaiano, D. A. (1996) How much lactose is low lactose?. J. Am. Diet. Assoc. 96:243-246.[Medline]
27. Strocchi, A., Corazza, G., Ellis, C. J., Gasbarrini, G. & Levitt, M. D. (1993) Detection of malabsorption of low doses of carbohydrate: accuracy of various breath H2 criteria. Gastroenterology 105:1404-1410.[Medline]
28. Wolf, B. W., Wolever, T.M.S., Bolognesi, C., Zinker, B. A. & Garleb, K. A. (2001) Glycemic response to a rapidly digested starch is not affected by the addition of an indigestible dextrin in humans. Nutr. Res. 21:1099-1106.
29. Pfizer Inc. (1978) Polydextrose Food Additive Petition (FDA petition 9A3441) 1978 Pfizer Inc. New York, NY.
30. Tsuji, K. & Gordon, D. T. (1998) Energy value of a mixed glycosidic linked dextrin determined in rats. J. Agric. Food Chem. 46:2253-2259.
31. Lifschitz, C. H., Grusak, M. A. & Butte, N. F. (2002) Carbohydrate digestion in humans from a ß-glucan-enriched barely is reduced. J. Nutr. 132:2593-2596.
32. Levitt, M. D. (1969) Production and excretion of hydrogen gas in man. N. Engl. J. Med. 281:122-127.
This article has been cited by other articles:
|
|
 |
|
  M. L. Asp, S. R. Hertzler, J. Chow, and B. W. Wolf Gamma-Cyclodextrin Lowers Postprandial Glycemia and Insulinemia without Carbohydrate Malabsorption in Healthy Adults. J. Am. Coll. Nutr., February 1, 2006; 25(1): 49 - 55. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. K. Spears, L. K. Karr-Lilienthal, C. M. Grieshop, E. A. Flickinger, B. W. Wolf, and G. C. Fahey Jr Pullulans and {gamma}-Cyclodextrin Affect Apparent Digestibility and Metabolism in Healthy Adult Ileal Cannulated Dogs J. Nutr., August 1, 2005; 135(8): 1946 - 1952. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
