Objective  To evaluate intestine-moistening and constipation-relieving effects of walnut (Juglans regia) oligopeptides in mice and to provide evidences for application of walnut oligopeptides in treatment of constipation.

  Methods  Mice constipation model was established with gastric gavage of loperamide hydrochloride at dosages of 5 and 10 mg/kg body weight. Totally 120 ICR adult male mice were randomly assigned into two subgroups for observations of ink propulsion in small intestine and defecation after experiment and then the mice of each subgroup were randomly divided into a control group (with saline), a model group (with saline), a whey protein group (440 mg/kg bw), and 3 walnut oligopeptides groups (220, 440, and 880 mg/kg bw). All the treatments were performed by gastric gavage once a day continuously for 7 days. Sixteen hours after the last treatment, all the mice were gavaged with loperamide hydrochloride except for those of the control group and 30 minutes later with ink. The propulsion rate of ink in small intestine and the time for the first black fences granule discharge, the number, weight and water content of black feces granules were determined; the serum concentrations of substance P, vasoactive intestinal peptide, endothelin (ET), somatostatin (SS), motilin (MLT), gastrin were detected; and the length of small intestinal villus was measured.

  Results  Compared with those of the whey protein group, the propulsion rate of ink in small intestine was significantly increased (0.92 ± 0.14 vs. 0.69 ± 0.10); the time for the first black feaces discharge was shortened (241.50 ± 29.88 vs. 272.60 ± 24.83 minutes); and the number and weight of feces granules were increased (number: 6.80 + 1.75 vs. 5.00 + 1.41; weight: 0.12 + 0.03 vs. 0.06 + 0.02 gram) in high dose walnut oligopeptides group. Futhermore, the serum concentration of ET and MTL were significantly increased, while the level of SS was significantly decreased in comparison with those of the whey protein group.

  Conclusion  Walnut oligopeptides could promote intestine-moistening and constipation-relieving in mice and the mechanism of the effect may be related to up-regulated serum expression of endotoxin, motilin and down-regulated expression of somatostatin.