Zinc-fortification restores gut nitric oxide without expression of inducible nitric oxide synthase gene in enterotoxigenic E. coli-induced diarrhea in zinc-deficient rats

Abstract

Nitric oxide maintains the integrity of the gastric epithelium and is also elevated in diarrheal disease condition. Nitric oxide synthase isoforms (NOS) are responsible for production of nitric oxide (NO) in physiological and pathophysiological circumstances. Zinc supplementation has been used as part of treatment of infants and children with diarrheal illnesses in most developing nations. The aim of this study was to establish the effect of zinc-fortification on fecal nitric oxide and colonal inducible nitric oxide synthase gene in enterotoxigenic E. coli (ETEC) induced zinc-deficient diarrhea. Albino rats were grouped into normal fed (NF), zinc deficient (ZD) and zinc fortified (ZF) groups with control, LT-ETEC induced and ST-ETEC induced diarrheal sub-groups. Nitric oxide concentrations were determined in feces using griess reaction system while reverse transcription polymerase chain reaction with GAPDH gene as internal reference was used to monitor the presence of colonal inducible NOS gene. The amount of stool output was significantly (p ˂ 0.05) increased in normal fed and zinc deficient LT [661 ± 2.00], [760 ± 2.22] and ST-induced [772 ± 2.00], [886 ± 2.12] groups when compared with the control [555 ± 3.03], [600 ± 3.11] groups, respectively. Fecal nitric oxide significantly increased in LT [82.09 ± 1.30], [132.24 ± 2.24] and ST-ETEC [68.81 ± 2.30], [88.21 ± 1.14] induced groups in NF and ZD rats when compared with controls [54.27 ± 1.23], [66.86 ± 2.01], respectively. When compared with both NF and ZD rats, fecal NO decreased significantly in ZF rats in both LT [48.06 ± 0.96] and ST-induced [45.48 ± 0.60] groups. The colonal inducible nitric oxide synthase gene was not detected in NF, ZD and ZF rats. Zinc deficiency increased both stool output and fecal nitric oxide in ETEC induced diarrhea, while zinc-fortification reduced stool output and restores fecal nitric oxide. This suggests that zinc and nitric oxide play a role in mediating pathological conditions in ETEC-induced diarrhea of which inducible nitric oxide synthase may not be involved.