Oral oxytocin delivery with proton pump inhibitor pretreatment decreases food intake

Oxytocin (Oxt) is considered as a potential agent to treat multiple neuropsychiatric disorders, obesity and metabolic syndrome. Although the mechanisms underlying these effects remain unclear, nasal administration is considered to be a potential way to deliver Oxt into blood vessels. The development of an easier, more stable and efficient way is expected. A recent study demonstrated that orally administered Oxt can be transmitted into blood if it is prevented from degradation in stomach and reaches the intestinal tract. In this study, we pretreated mice with a proton pump inhibitor (PPI), omeprazole (20 mg/kg), and administered capsulized Oxt (0.25 mg), so that the Oxt can be prevented from degradation by pepsin due to the low pH in stomach and reach the intestinal tract. Functionally, these mice showed a similar decrease in food intake to those who underwent intraperitoneal administration. We also confirmed that this method dramatically increased plasma Oxt levels and the expression of neural activation marker c-Fos protein in the paraventricular and suprachiasmatic nucleus. Our study showed that by pretreating mice with PPI, Oxt in a gelatin-coated capsule can prevent Oxt from degradation by pepsin in stomach, and reach the bloodstream in an effective concentration. These results indicate that our method is a promising oral delivery of Oxt and should be investigated further for other peptide agents based on peripheral injection or nasal administration.