Screening of stimulatory effects of dietary risk factors on mouse intestinal cell kinetics

Abstract

Aim: Although epidemiological and experimental studies validate influence of genetic, environmental and dietary factors in the causation of various types of cancers including colon, results from all these sources are inconclusive. Hypothesizing that high fat diet and obesity are among the major predisposing factors in the incidence of colon cancer, we evaluated the role of diet constituted with food material derived from a tropical plant, Tamarindus indica Linn (TI).

Methods: A two part randomized double-blind study was conducted employing inbred Swiss albino mice from a single generation for the whole investigation. One day-old neonates (n = 12) were subcutaneously administered with monosodium glutamate (MSG) to induce obesity (OB). At weaning these animals were maintained on modified AIN-76 diet supplemented with 10% TI and 10% fat bolus (w/w, TIFB) for 8 wk. Subsequently, in the second part of study, four groups of animals belonging to the same generation, age and gender (n = 12 per group), were maintained on: AIN-76 control diet (CD); AIN-76 mixed with 10% TI extract (TI); and, mixed with 10% TI and 10% FB (TIFB) for 8 wk, to determine intestinal crypt cell proliferation, functionally-specific enzyme activities, fermentation profile, and energy preferences.

Results: We observed a significant increase in the crypt cell production rate in distal colonic segment of experimental animals when compared with the controls. This segment also contained significantly low butyrate levels compared to control and TIFB groups. All the experimental groups showed a gross decrease in the enzyme activities viz., succinate dehydrogenase, acid-galactosidase and dipeptidyl amino peptidase IV demonstrating pathological stress caused by the test regimens, and an altered metabolic flux in the cellular environment.

Conclusion: We have demonstrated a cumulative response to the three dietary factors, one of which (TI) is reported, herein, for the first time to modulate kinetics of large intestinal mucosa, contributing to total risk posed by these test agents.

Figure 1

Linear relationship of metaphase arrest to time used to calculate CCPR.

Figure 2

Crypt cell production rate/Crypt/h in caecum at (A), ascending colon (B) and descending colon (C) tissues isolated from experimental and control groups of animals (mean±SE) at 2, 4 and 8 wk treatment. Significance was seen between CD and the experimental groups TI, TIFB and OB.

Figure 3

Incorporation of [³H] – dThd into the DNA of cecum (A), ascending colon (B) and descending colon (C) tissues at different exposure periods in experimental and control groups (mean±SE). Significance was seen between CD and the experimental groups TI, TIFB and OB.

Figure 4

Mean (%) of acetic, propionic and butyric acids in the mucosal contents of cecum (c), ascending colon (ac) and descending colon (dc) tissue segments isolated from mice of CD, TI, TIFB and OB groups. Results were drawn from the total mean(%) distribution of SCFAs throughout the experimental period (n = 6).

Figure 5

Levels of lactate in mice fed with various dietary factors in CD, TI, TIFB and OB groups for 2, 4 and 8 wk of test periods in the isolated cecum (A), ascending colon (B) and descending colon (C). Values are represented as μmol/g wet mucosal content, mean±SE.