title: Colonic fermentation of ispaghula, wheat bran, glucose, and albumin to short-chain fatty acids and ammonia evaluated in vitro in 50 subjects.
abstract: The production of short-chain fatty acids and ammonia was measured in 16.6% fecal homogenates from 50 subjects incubated at 37 degrees C for 6 and 24 hours. All 50 homogenates produced ammonia and short-chain fatty acids of any chain length (C2-C5). Incubation for 24 hours with dietary fiber (ispaghula husk or wheat bran), albumin, or glucose (10 mg/mL) increased the short-chain fatty acid production (43.6 +/- 2.8, 45.4 +/- 2.0, 60.3 +/- 3.2, and 65.8 +/- 3.1 mmol/L, respectively) compared with controls (21.4 +/- 1.3 mmol/L). The degradation of different substrates was associated with the production of different amounts of ammonia and short-chain fatty acids. Ispaghula, wheat bran, albumin, and glucose were fermented to acetate (> 2 mmol/L; 24-hour incubations) in 86%, 96%, 98%, and 98% of the homogenates, to propionate in 80%, 76%, 100%, and 68%, and to butyrate in 32%, 94%, 88%, and 54% of the homogenates, respectively. Isobutyrate, valerate, and isovalerate were produced from albumin in all (100%) of the homogenates, but only in 2 to 4% of the homogenates incubated with ispaghula or glucose. Ammonia was always (100%) produced after the addition of albumin and always (98%) consumed (assimilated) when glucose was fermented. Surgery (sigmoid or right- or left-sided colonic resection) did not change the pattern of ammonia and short-chain fatty acid production from these substrates. This study suggests that the different colonic flora from a large number of subjects share general biochemical characteristics, which metabolize different substrates to specific patterns of ammonia and short-chain fatty acids.
authors.affiliation: Department of Medicine A, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: P B
authors.initials: PB
authors.lastname: Mortensen
authors.forename: M R
authors.initials: MR
authors.lastname: Clausen
authors.forename: H
authors.initials: H
authors.lastname: Bonnén
authors.forename: H
authors.initials: H
authors.lastname: Hove
authors.forename: K
authors.initials: K
authors.lastname: Holtug
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000418:Albumins / Q000378:metabolism; D000641:Ammonia / Q000032:analysis / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D004043:Dietary Fiber / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D011620:Psyllium / Q000378:metabolism; D014908:Triticum / Q000378:metabolism
chemical_list: D000418:Albumins; D004043:Dietary Fiber; D005227:Fatty Acids; D000641:Ammonia; D011620:Psyllium; D005947:Glucose