Nutrient status modulates the expression of nesfatin-1 encoding nucleobindin 2A and 2B mRNAs in zebrafish gut, liver and brain

• In zebrafish, NUCB2A and NUCB2B encode the highly conserved satiety peptide, nesfatin-1.
• Both NUCB2A and NUCB2B mRNAs are ubiquitously expressed in zebrafish.
• NUCB2/nesfatin-1-like immunoreactivity is present in zebrafish gut and it co-localizes with ghrelin.
• Food deprivation causes a decrease in NUCB2A and NUCB2B mRNA expression in zebrafish brain and gut.
• Food deprivation causes an increase in NUCB2B mRNA in the liver of zebrafish.

Nesfatin-1 is a naturally occurring, 82-amino acid peptide processed from the precursor nucleobindin 2 (NUCB2), a highly conserved protein among vertebrates. In fish, two isoforms of NUCB2 (NUCB2A and NUCB2B) exist, and nesfatin-1 has been identified in goldfish and Ya fish. We recently reported the presence and appetite suppressing effects of nesfatin-1 in goldfish. The main objectives of this study were to characterize NUCB2 in zebrafish, and determine whether NUCB2 mRNAs are affected by food availability. Tissue distribution of NUCB2A and NUCB2B mRNAs, and NUCB2/nesfatin-1-like immunoreactivity (ir) in the gut of zebrafish were also investigated. In zebrafish, nesfatin-1 region (1–82 amino acids) in NUCB2A is 78% identical to NUCB2B. Both NUCB2A and NUCB2 mRNAs were most abundant in the liver, while less expression was found in other tissues including the brain and gut. NUCB2/nesfatin-1-like immunoreactivity was detected in the mucosal layer cells of zebrafish anterior gastrointestinal tract. NUCB2A and NUCB2B mRNA expression were decreased in the brain of zebrafish 3 h after feeding, and after a 7-day food deprivation. Both NUCB2A and NUCB2B mRNAs in the gut were also decreased following 7 days of food deprivation, while NUCB2B mRNA was increased in the liver. Our results provide molecular and functional evidences to support potential anorectic and metabolic roles for endogenous nesfatin-1 in zebrafish. To our knowledge, this is the first report on NUCB2B characterization in vertebrates.