Glutamine depletion induces murine neonatal melena with increased apoptosis of the intestinal epithelium

Figure 1 Macroscopic views of milk-fed mice with colonic hemorrhage. Representative macroscopic views of newborn mice that were fed with glutamine-rich milk (GRM) (A), complete amino acid milk (CAM) (B), and glutamine-deleted milk (GDM) (C) are shown. Compared to the colons of GRM-mice and CAM-mice (asterisks), those of the GDM-mice appeared distended and edematous, with a pool of blood (arrow); D: Close-up views of the resected intestines from a CAM-mouse and a GDM-mouse, shown for comparison; E: Bar chart of the number of mice with melena on each day.

Figure 2 Glutamine depletion induces severe damage of the colonic epithelial structure with reduced epithelial cell growth. A: Representative pictures of H-E staining (left panels) and immunohistochemical staining for BrdU (middle panels) and Ki-67 (right panels). Each colonic epithelium was taken from infant mice fed with glutamine-rich milk (GRM), complete amino acid milk (CAM), or glutamine-deleted milk (GDM). Magnification, × 200. Positive stained epithelial cells with BrdU (B) and Ki-67 (C) were counted and compared with each group in a histogram. ^bP≤ 0.001; ^cP < 0.05.

Figure 3 Apoptotic changes observed in the damaged colonic epithelium. Electron micrographs of colonic epithelia obtained from infant mice with glutamine-rich milk (GRM) (A, D), complete amino acid milk (CAM) (B, E), and glutamine-deleted milk (GDM) (C, F) at low magnification (A-C) and high magnification (D-F). Asterisks (*) represent lipid droplets and the arrow shows an apoptotic cell. G-I: Optical microscopic views (magnification, × 200) of immunohistochemistry for cleaved caspase-3 as a marker of apoptosis using resected tissues from the same mice (G: GRM, H: CAM, I: GDM).

Figure 4 Glutamine depletion suppresses cell proliferation of cultured intestinal epithelial cells. A: IEC6 rat intestinal epithelial cells were treated with media containing different amounts of glutamine (0, 0.4 and 4 mmol/L); Cell morphology and cell number were observed at the indicated time points (B: 24 h, C: 48 h).

Figure 5 Potent antiproliferative effect of glutamine depletion results in increased cleavage of caspase-3. Cell cycle distribution under culture condition with different concentrations of glutamine was analyzed by flow cytometry (A) and cell populations at the sub-G0 phase were compared with each other (B); C: Immunoblotting for caspase-3 and cleaved caspase-3 revealed the induction of apoptosis in IEC6 cells after 24 h of culture without glutamine. Each experiment was independently repeated three times and the representative data among the similar results are shown.