Switching to normal diet reverses kwashiorkor-induced salivary impairments via increased nitric oxide level and expression of aquaporin 5 in the submandibular glands of male Wistar rats

Abstract

Kwashiorkor, a form of malnutrition, has been shown to cause impaired salivary secretion. However, there is dearth of information on the mechanism that underlies this complication. Also, whether returning to normal diet after kwashiorkor will reverse these complications or not is yet to be discerned. Thus, this study aimed at assessing the mechanisms that underlie kwashiorkor-induced salivary impairments and to evaluate the effects of switching back to normal-diet on kwashiorkor-induced salivary impairments. Weaning rats were randomly divided into 3 groups (control group, kwashiorkor group (KG), re-fed kwashiorkor group (RKG)) of 7 rats each. The control group had standard rat chow while the KG and RKG were fed 2% protein diet for 6 weeks to induce kwashiorkor. The RKG had their diet changed to standard rat-chow for another 6 weeks. Blood and stimulated saliva samples were collected for the analysis of total protein, electrolytes, amylase, immunoglobulin A (IgA) secretion rate, leptin, and ghrelin. Tissue total protein, nitric oxide level, expressions of Na+/K+-ATPase, muscarinic (M3) receptor, and aquaporin 5 in the submandibular glands were also determined. Data were presented as means ± SEM and compared using ANOVA with Tukey’s post hoc test. RKG showed improved salivary function evidenced by reduced salivary lag-time and potassium and increased flow rate, sodium, amylase, IgA secretion rate, leptin, submandibular nitric oxide level, and aquaporin 5 expression compared with KG. This study for the first time demonstrated that kwashiorkor caused significant reduction in salivary secretion through reduction of nitric oxide level and aquaporin 5 expression in submandibular salivary glands. Normal-diet re-feeding after kwashiorkor returned salivary secretion to normal.