Dietary Oyster (Crassostrea gigas) Extract Increases the Goblet Cell Counts in the Ileum of Mice

抄録

We previously reported that dietary oyster (Crassostrea gigas) extract (OE) promoted fecal mucin excretion in mice fed a normal-fat (NF) diet. However, it remains unclear whether OE increases fecal mucin excretion and ileal goblet cell counts in mice fed a high-fat (HF) diet. This study examined the effect of OE intake on fecal mucin excretion and ileal goblet cell counts in mice fed NF and HF diets. Male C57BL/6 J mice were divided into four groups and fed an AIN-93G diet (NF diet), AIN-93G modified HF diet (HF diet), NF diet containing 5% (w/w) OE (NFOE diet), and HF diet containing 5% (w/w) OE (HFOE diet). After 28 days of experimental diet feeding, feces and distal ileum were collected. Fecal mucin content was quantified using a fluorometric assay kit that discriminates O-linked glycoproteins from N-linked glycoproteins. Goblet cells in the villi of the distal ileum were counted via staining with Alcian blue-periodate Schiff stain. Fecal mucin content and ileal goblet cell count were significantly increased by OE intake (p = 0.013 and 0.007, respectively). OE intake may enhance the intestinal barrier function by increasing the number of goblet cells and mucin secretion in the distal ileum.

We investigated the nutritional and health-promoting functions of oyster extract (OE) prepared by extracting and concentrating the nutritional and functional components of oyster (Crassostrea gigas) meat. We have reported the bioavailability of zinc^{1 ,2)}, hepatoprotective effect³⁾, prevention of colorectal precancerous lesions^{4 ,5)}, and prevention of renal damage⁶⁾ as the nutritional and health-promoting functions of OE intake. Regarding the gut environment, which has been actively studied in relation to health in recent years, OE has proven effective in increasing the proportion of Lactobacillus genus in the feces of rats and mice^{7 ,8)}. In addition, OE attenuates experimental colitis symptoms induced by dextran sulfate sodium, partly owing to improvements in the gut microbiota and short-chain fatty acid composition^{9 ,10)}. Because the gut is exposed to pathogenic bacteria and their toxins, it has a robust barrier function and immune system to protect the body from these factors¹¹⁾. Mucin is a key component of the gut barrier that prevents the entry of pathogenic bacteria and their toxins^{12, 13)}. Dietary OE enhances fecal mucin excretion in mice fed a normal-fat (NF) diet¹⁴⁾. However, it remains unclear whether the addition of OE to a high-fat (HF) diet used to induce obesity and hyperlipidemia in mice enhances fecal mucin excretion. In contrast, mucin is produced and secreted by goblet cells and scattered among absorptive epithelial cells. The number of goblet cells is affected by dietary components¹⁵⁾. However, the effect of OE on the number of ileal goblet cells has not yet been investigated. In this study, we fed mice two experimental diets (NF and HF) supplemented with OE and evaluated the effects of OE on fecal mucin excretion and ileal goblet cell counts.