EFFECTS OF TRIVALENT CHROMIUM ON NORMAL AND INJURED GASTROINTESTINAL TRACT IN LABORATORY RODENTS

Abstract

Trivalent chromium (Cr3+) is an essential mineral required in quantum with reported health benefits. Chromium deficiency has been linked to symptoms associated with onset of adult diabetes and cardiovascular diseases. Its essentiality and presumed functions in the gastrointestinal tract remain poorly understood. Therefore, the effects of Cr3+ on some gastrointestinal functions in normal and injured gut of rats and mice were investigated. Sixty male Wistar rats (90.1±3.5 g) were grouped into three (n=20): Control (distilled water), 10 ppm (Cr3+) and 100 ppm (Cr3+) exposed for twelve weeks. After Cr3+ exposure, rats (n=5 per group) were sacrificed (day 0). Thereafter, experimental gastric ulcer and colitis were induced using acetic acid (50%, 0.2 mL) and (6%, 1 mL), respectively and rats were sacrificed on days 3, 7 and 14. Blood was processed to serum by centrifugation, while processed tissues were homogenized. Blood Cr3+, haematological parameters, gastric acid secretion, ulcer and colitis scores and histology were determined using standard methods. Myeloperoxidase (MPO), Superoxide Dismutase (SOD) and malondialdehyde (MDA) were determined using spectrophotometry. Rats were used for the in vivo intestinal motility study using standard methods. In another experiment, 60 slc:ddY mice (26.2±1.1 g) were grouped and treated according to the previous experiment. Stomach and colon tissues were quantified for selected cytokines mRNA using real-time PCR. In vitro intestinal motility and glucose uptake were determined by Magnus and spectrophotometry methods, respectively. Data were analysed using descriptive statistics and ANOVA at α0.05. Blood Cr3+ in rats was significantly increased in 10 ppm (0.17±0.01 Vs 0.11±0.02 ppm) and 100 ppm (0.19±0.02 Vs 0.11±0.02 ppm). Platelet counts, stomach mucosa width and colon crypt height were significantly increased in normal tissues in 10 ppm (48.92%, 53.43%, 23.41%) and 100 ppm (39.70%, 58.00%, 25.42%) Cr3+ exposed rats compared with control, respectively. Basal gastric acid secretion was significantly reduced in both 10 ppm and 100 ppm compared with control on day 3. Gross ulcer area and histology scores were reduced in both 10 ppm and 100 ppm on day 3 (44.26±1.13 mm2, 27.42±2.49 μm), (37.70±2.04 mm2, 14.54±1.55 μm) and day 7 (3.12±0.22 mm2, 2.16±0.12 μm), (2.94±0.12 mm2, 2.02±0.19 μm) compared with control (50.83±1.90 mm2, 45.33±3.23 μm), (4.01±0.27 mm2, 3.76±0.16 μm), respectively. Colon gross and histology scores after injury decreased in both 10 ppm and 100 ppm on day 3 (42.04%, 46.06%), (47.35%, 52.08%) and day 7 (58.90%, 37.10%), (100.00%, 59.42%) compared with control, respectively. The MPO and MDA in 10 ppm and 100 ppm groups reduced significantly compared with control, while SOD activities increased significantly in Cr3+ groups in both tissues. In mice, total RNA in stomach increased in normal and day 3 post injury of stomach and, colon of 10 ppm, 100 ppm compared with control, respectively. Chromium increased expressions of IL-10, while suppressing TNF-α, IFN-λ mRNA during healing in both tissues. Glucose uptake and motility were significantly reduced in all studies. Chromium promoted healing of gastrointestinal injury by suppressing oxidative stress and inflammation via down regulation of tumor necrotic factor-alpha and up-regulation of interleukin-10 mRNA gene expressions.