Effects of dietary wheat bran fiber on rectal epithelial cell proliferation in patients with resection for colorectal cancers.
A preponderance of carcinogenesis studies in rodents and epidemiologic studies in humans suggests a potential role of dietary fiber in the prevention of colorectal cancer. Recently, wheat bran fiber used as a dietary supplement has been shown to decrease the growth of rectal adenomatous polyps in patients with familial polyposis; however, few studies of high-risk human populations have been attempted to determine the effects of dietary fiber supplementation on markers of carcinogenesis in the colon or rectum. We have designed a one-arm study to evaluate the effects of dietary supplementation with wheat bran fiber [i.e., 13.5 g/day for 8 wk; after 1 mo, 2 g/day (compliance evaluation period)] on [3H]thymidine rectal mucosa cell labeling (i.e., percent of epithelial cells incorporating [3H]thymidine into DNA in intact rectal crypt cells over a 90-min exposure as well as in minced rectal biopsy tissue over a 24-hr exposure) in rectal biopsy specimens. The biopsy specimens were obtained at sigmoidoscopy in 17 compliant patients with a history of resected colon or rectal cancer. We categorized patients as having initially low or initially high [3H]thymidine-labeling indices (i.e., percent of mucosa cells that incorporate [3H]thymidine into DNA during 1.5- or 24-hour in vitro incubations) by using the median baseline labeling index as a cutoff between high and low values. On the basis of a chi-square test used to identify patients with a statistically significant (P less than .001) change, six of the eight patients who initially had high 24-hour outgrowth labeling indices showed a significant decrease in the rectal mucosa biopsy specimens obtained after treatment. An overall 22% decrease was observed in rectal mucosa cell biopsy specimens obtained at study termination (P less than .001). Of the eight patients with initially high total [3H]thymidine-labeling indices in crypt organ culture, four had a significant (P less than .001) decrease from baseline values, one had a significant increase, and three showed no change following the fiber intervention. The wheat bran fiber dietary supplement of 13.5 g/day was well tolerated by this group of older (54-70 yr) patients. Although the [3H]-thymidine labeling index data suggest that the wheat bran fiber supplement can inhibit DNA synthesis and rectal mucosa cell proliferation in high-risk patients, the results of this small pilot study should not be overinterpreted vis à vis the potential role of wheat bran fiber as a chemopreventive agent for colorectal cancer.(ABSTRACT TRUNCATED AT 400 WORDS)
Alberts
D S
DS
Department of Medicine, College of Medicine, University of Arizona, Tucson.
Einspahr
J
J
Rees-McGee
S
S
Ramanujam
P
P
Buller
M K
MK
Clark
L
L
Ritenbaugh
C
C
Atwood
J
J
Pethigal
P
P
Earnest
D
D
D000368:Aged; D001706:Biopsy; D002455:Cell Division / Q000187:drug effects; D002986:Clinical Trials as Topic; D003110:Colonic Neoplasms / Q000178:diet therapy* / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000517:prevention & control / Q000601:surgery*; D004247:DNA / Q000378:metabolism; D004043:Dietary Fiber / Q000009:adverse effects / Q000494:pharmacology* / Q000627:therapeutic use; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005069:Evaluation Studies as Topic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009924:Organ Culture Techniques; D012004:Rectal Neoplasms / Q000178:diet therapy* / Q000378:metabolism; D013997:Time Factors; D014908:Triticum; D014316:Tritium; D014407:Tumor Cells, Cultured
D004043:Dietary Fiber; D014316:Tritium; D004247:DNA