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Updated: Aug 15, 2026
Assessing Hepatic Metabolic Changes During Progressive Colonization of Germ-free Mouse by 1H NMR Spectroscopy
Published on: December 15, 2011
Mucin secretion in germfree rats fed fiber-free and psyllium diets and bacterial mass and carbohydrate fermentation
L M Cabotaje1, F L Shinnick, J M Lopéz-Guisa
1Department of Nutritional Sciences, University of Wisconsin-Madison 53706-1571.
Abstract:
The effect of psyllium on mucin secretion was determined by comparing water-soluble and -insoluble fractions of excreta from germfree rats fed a fiber-free (FF) diet or a diet containing psyllium seed husk (PS). Excreta from the same rats after colonization with a rat mixed cecal culture were separated into water-soluble, plant, and bacterial fractions to compare the remaining carbohydrate and the mass of bacteria. The sugar composition and water solubility of carbohydrate in excreta from germfree rats fed FF diets indicated that a primary fermentable substrate was mucin. PS increased fecal excretion of mucin-derived sugars almost threefold in germfree rats. Fecal carbohydrate was reduced from 619 to 237 mumol/g of dry feces and mostly in the bacterial fraction when rats fed an FF diet were colonized. The total sugar content and the amount of muramic acid, but not bacterial counts and mass, indicated that PS increased fecal bacteria. Fractionation of excreta from PS-fed rats was complicated by a gel which, based on sugar composition, was PS. Sugar composition of the water-soluble fraction from excreta from PS-fed rats suggested that it contained some bacterial component, possibly exopolysaccharides and some of the PS, but not mucin. PS digestibility ranged from 60 to 80%, depending on what fecal fraction was used for output. Because of the presence of PS-derived sugars in the gel and soluble fraction, it was not possible to determine which, if any, of the PS digestibilities was correct.
Insights
Psyllium seed husk (PS) significantly increased mucin excretion in germfree rats, indicating mucin is a primary fermentable substrate. PS also increased fecal bacteria, though its own digestibility was difficult to determine due to its presence in excreta.
Area of Science:
- Gastroenterology
- Microbiology
- Nutritional Science
Background:
- Mucin is a key component of the gut barrier and a potential energy source for microbes.
- Dietary fiber, such as psyllium seed husk (PS), can influence gut microbial activity and host physiology.
Purpose of the Study:
- To investigate the effect of psyllium seed husk (PS) on mucin secretion and utilization in rats.
- To compare the fermentable substrates in the gut of germfree and conventionally colonized rats.
Main Methods:
- Germfree rats were fed either a fiber-free (FF) diet or a diet containing psyllium seed husk (PS).
- Excreta were analyzed for sugar composition and fractionated into water-soluble, plant, and bacterial components.
- Rats were subsequently colonized with a rat mixed cecal culture, and excreta were re-analyzed.
Main Results:
- In germfree rats, psyllium significantly increased the fecal excretion of mucin-derived sugars, suggesting mucin is a primary fermentable substrate.
- Colonization with gut microbiota reduced overall fecal carbohydrate, with psyllium-fed rats showing increased fecal bacteria.
- The presence of psyllium in the excreta complicated the analysis of its digestibility and the identification of bacterial components.
Conclusions:
- Psyllium seed husk (PS) promotes the utilization of host-derived mucin in the gut.
- PS supplementation appears to increase fecal bacterial populations, although direct quantification is challenging.
- Accurate determination of psyllium digestibility is hindered by its complex interactions within the gut environment.
