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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Soluble Fiber Viscosity Affects Both Goblet Cell Number and Small Intestine Mucin Secretion in Rats^1–3,

⁴ Graduate School of Science and Technology and ⁵ Department of Applied Biological Chemistry, Faculty of Agriculture, and ⁶ Department of Home Economics, Faculty of Education, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan; ⁷ Division of Applied Bioscience Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589 Japan; and ⁸ Luminacoids Laboratory, Mure 4-1-4, Mitaka, Tokyo 181-0002, Japan

We examined the role of soluble fiber viscosity in small intestinal mucin secretion. Viscosities were defined as the area under the viscosity curve (VAUC). Rats were fed a control diet or diets containing konjac mannan (KM) [low, medium, or high molecular weight (LKM, MKM, HKM), respectively] at 50 g/kg diet for 10 d. Luminal mucin content and goblet cell number increased in proportion to the molecular weight of KM. Such effects with the HKM diet were nullified by the concurrent ingestion of 2 g cellulase/kg diet. Diet containing LKM, MKM, HKM, guar gums (high or low molecular weight; HGG, LGG), psyllium (PS), or pectin (PC) at 50 g/kg was fed to rats. Fibers with higher VAUC (MKM, HKM, HGG, and PS) increased goblet cell numbers, but not those with lower VAUC (LKM, LGG, and PC). Luminal mucins were greater in rats fed HKM, PC, and PS diets. Goblet cell numbers and VAUC were correlated (r = 0.98; P < 0.01). In rats fed the HKM diet, ileal Muc2 gene expression was not affected, but that of Muc3 was lower than in those fed the control diet, indicating that the increase in luminal mucins after ingestion of HKM diet occurred independently of enhanced Muc gene expression. An incorporation study of 5'-bromo-deoxyuridine (BrdU) showed the position of the uppermost-BrdU labeled cell along the villi was higher in rats fed the HKM diet than in those fed the control diet. The results suggest that soluble fibers, except PC, upregulate baseline secretion of luminal mucins by increasing goblet cell numbers in proportion to fiber VAUC.

^* To whom correspondence should be addressed. E-mail: actmori{at}agr.shizuoka.ac.jp.

Manuscript received 15 May 2009. Initial review completed 4 June 2009. Revision accepted 22 June 2009.

Published online 15 July 2009.