Minoru Kihara

Fermentation of dietary carbohydrates to short-chain fatty acids by gut microbes and its influence on intestinal morphology of a detritivorous teleost tilapia (Oreochromis niloticus)

Fermentability of dietary cellulose, sodium alginate, chitin, α-starch and kaolin (non-fermentable control) by gut microbes was compared in a tilapia, Oreochromis niloticus, fed a diet containing one of the above supplements (150 g · kg−1) for 14 days. The thickness of the tunica muscularis was also compared among fish fed these diets. The concentration of short-chain fatty acids (SCFA) in gut contents was higher in fish fed the α-starch than in fish fed the sodium alginate, chitin, or kaolin diets. Intestinal contents from fish fed the kaolin (control) diet were incubated in batch culture with each of the other supplements. The volume of released gas and production of SCFA for 24 hr was greater with a α-starch as a substrate than in those with the other substrates. The thickness of the tunica muscularis differed among dietary groups but villus height did not. Fish fed chitin or α-starch had a thicker tunica muscularis than those fed cellulose or sodium alginate. These results suggest that this detritivorous fish digests α-starch to produce SCFA in the intestine by microbial fermentation.

Trophic effect of dietary lactosucrose on intestinal tunica muscularis and utilization of this sugar by gut microbes in red seabream Pagrus major, a marine carnivorous teleost, under artificial rearing

Abstract We examined the effects of dietary lactosucrose (20 mg · kg body mass −1 · day −1 ) on body mass gain and the thickness of intestinal tunica muscularis in artificially reared red seabream fed a commercial diet. Lactosucrose did not affect body mass gain. Fish fed lactosucrose had thicker and tougher intestinal tunica muscularis than control fish. In vitro batch culture of intestinal contents of these fish showed that gut fermentation exists in this marine carnivorous teleost. The fermentation can utilize lactosucrose as a substrate, at least in vitro .

Stimulative effect of skipjack tuna soluble extract on pepsin-like protease in the stomach of rockfish (Sebastes schlegelii) using an in vitro perfusion method.

The effect of intra-gastric infusion of skipjack tuna (Katsuwonus pelamis) muscle soluble extract and of carnosine, anserine and histidine, on pepsin-like protease activity was studied in the isolated, externally batch-cultured stomach of the rockfish (Sebastes schlegelii). Stomach was isolated from the fish, then intragastrically infused with the above solutions or with a balanced saline solution (control solution) as the stimulant at 0.1 mL/min for 6h. Intra-gastric efflux was collected for measurement of pepsin-like protease activity. Skipjack tuna soluble extract, but not carnosine, anserine or histidine alone caused significant enhancement of pepsin-like protease activity during the infusion. Pepsin-like protease activity from skipjack tuna soluble extract responded immediately after infusion and was kept for 150 min after infusion. Stomach motility at the end of infusion was also observed. These results suggest that isolated stomach can receive mucosal side stimulants in vitro. It is likely that some effective components for stomach digestion in fish exist in skipjack tuna soluble extract.

Protective Effect of Dietary Ghrelin‐Containing Salmon Stomach Extract on Mortality and Cardiotoxicity in Doxorubicin‐Induced Mouse Model of Heart Failure

Ghrelin exhibits a cardioprotective effect. We examined whether orally administered ghrelin-containing salmon stomach extract (sSE) instead of chemically synthesized ghrelin protects against doxorubicin (DOX)-induced cardiotoxicity in mice. Mice were divided into four groups: (i) the control, (ii) DOX groups were fed a control diet (AIN-93G), (iii) the sSE, and (iv) DOX + sSE groups were fed a 10% sSE diet (AIN-93G + 10% sSE). After a 4-week pretreatment of sSE, DOX or saline was administered to the corresponding groups by intraperitoneal injection. The groups fed the 10% sSE diet consumed significantly more food than the groups fed the control diet before the DOX injection. No mortality was observed in the DOX + sSE group, whereas 40% (2 of 5) mortality was observed in the DOX group. Compared with the DOX group, levels of ascites and plasma cardiac troponin I improved in the DOX + sSE group. Significantly lesser DOX-induced collagen accumulation was observed in the left heart ventricle of the DOX group than in that of the DOX + sSE group. These results suggest that the dietary ghrelin contained in sSE mimics synthetic ghrelin in cardioprotective effect. Ghrelin in sSE (45 pmol/g) and the food intake-stimulating effect of sSE may explain, at least in part, the protective effect of orally administered teleost ghrelin.