Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 2009
Publication Date: March 1, 2010
Citation: Kobayashi, Y., Peterson, B.C., Waldbieser, G.C. 2010. Identification of Two Cholecystokinin mRNA in Channel Catfish: Their Tissue Distribution and Changes in Their Expression After Prolonged Fasting and Refeeding. Aquaculture America Conference.P: 533 Technical Abstract: Food intake in fish is regulated by complex interactions of neural and endocrine factors. Our previous studies showed that channel catfish selected for increased growth consumed more food than those with lower growth. However, mechanisms that resulted in increased food intake of fish selected for increased growth have been largely unknown. Cholecystokinin (CCK) is an enteric anorectic hormone that suppresses food intake in mammals and fish. The gene that encodes CCK has been cloned in various fish species including rainbow trout, Atlantic salmon, winter skate, and flounder. Our objectives were to identify the gene that encodes cholecystokinin in channel catfish, to examine tissue distribution of its mRNA, and to determine whether its mRNA expression was affected by changes in food intake. Comparison of cholecystokinin mRNA sequences of zebrafish and yellowfin tuna with a channel catfish expression tag sequence library revealed two distinct CCK mRNA species (CCKA and CCKB). The DNA and protein sequence analysis revealed that CCKA was similar to trout CCK-L, whereas CCKB was similar to trout CCK-N and CCK-T. Both CCK mRNA transcripts were expressed in various tissues including brain, small intestine, heart, liver, trunk kidney, and muscle. However, expression of both CCK mRNA transcripts was high in the region of small intestine proximal to the stomach (PSI) and brain. We then examined whether changes in feed intake affected expression of CCKA and CCKB mRNA in brain and PSI of channel catfish. Juvenile channel catfish (n=27) were randomly assigned to one of three following groups: fed-control, fasted, or fasted-refed. Fish assigned to fed-control received feed daily for 45 days, whereas fish assigned to fasted group did not receive feed during the experiment. Fish assigned to fasted-refed group did not receive food for the first 30 days of treatment but were fed daily for 15 days thereafter. Expression of CCKA mRNA in brain was similar between fed control and fasted groups, but brain CCKA mRNA expression was greater in the fasted-refed group compared to fed-control (P<0.05). In contrast, expression of CCKB mRNA in brain was similar among the three groups. Changes in feed intake also did not affect expression of both CCK mRNA transcripts in the PSI. The results of our study suggest that changes in feed intake affect expression of CCK mRNA in the brain of channel catfish in a transcript-specific manner. Further studies are required to determine mechanisms that regulate expression of both CCK mRNA in brain and small intestine and whether expression of CCK mRNA is associated with growth rate of channel catfish.