Neuropeptide Y expression in response to sensory organ-detected fish meal soluble components and orally fed fish meal-based diet in yellowtail Seriola quinqueradiata

• Published in: Aquaculture Vol. 514; p. 734512
• Main Authors: Senzui, Ayaka, Masumoto, Toshiro, Fukada, Haruhisa
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2020
• Subjects: Appetite; Gustation; Neuropeptide Y; Olfaction; Yellowtail; Appetite; Neuropeptide Y; Yellowtail; Gustation; Olfaction
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2019.734512

In aquaculture, the replacement of dietary fish meal (FM) with plant protein is becoming more common because FM resources are limited. However, reducing the dietary FM level often causes low feed intake followed by low fish growth. Improving feed intake (appetite) is important in the use of a low- or non-FM diet. The appetite of fish is intricately regulated by orexigenic and anorexigenic factors in the central and peripheral nervous systems. Neuropeptide Y (NPY), an orexigenic hormone found in fish, is strongly associated with appetite. However, it is still unknown whether appetite is regulated by not only nutrients but also smell and/or taste of FM. In this study, the npy mRNA expression response to the detection of a fish meal soluble fraction (FMS), including smell and/or taste of FM, through the sensory organs (olfaction and gustation) and to feeding with an FM-based diet were investigated in yellowtail Seriola quinqueradiata. In a 7-day feeding test, FMS supplementation to non-FM diet improved feed intake, which showed that FMS works as a feeding stimulant. In both FMS addition (into rearing water) and FM diet feeding tests, expression of npy mRNA in all the regions of the brain increased significantly with fasting; then decreased within only 10 min from smell and/or taste of FM through the sensory organs. A notable npy response was observed in hypothalamus at 180 min, in which npy mRNA recovered to almost the same level as that of 0 min with the addition of FMS, whereas with the FM diet, it did not recover and maintained low expression levels. At 180 min, telencephalic npy mRNA expression showed the opposite response to that in the hypothalamus. This study is probably the first to indicate that smell and/or taste of FM might regulate brain npy mRNA expression in the short term. Moreover, different hypothalamic and telencephalic npy mRNA expression responses between treatments at 180 min suggested that npy is also regulated by absorbed nutrients. These data suggest that smell and/or taste also might regulate appetite through npy in yellowtail. •Response of npy mRNA to a FMS addition and feeding with a FM diet were investigated.•Expression of npy mRNA in the brain regions increased with fasting and decreased within only 10 min after treatment.•Hypothalamus npy mRNA levels at 180 min after treatment recovered in FMS addition but maintained low in FM diet feeding.•Not only nutrients but also smell and/or the taste of fish meal might regulate brain npy mRNA expression in yellowtails.