Feeding restriction alters expression of some ATP related genes more sensitively than the RNA/DNA ratio in zebrafish, Danio rerio.

The growth rate of fish shows extensive plasticity in response to various environments. Metabolic responses of fish to excessive nutritional shortages such as starvation have been reported, but the effects of moderate nutrient shortage remain unclear. We examined expression levels of some genes related to ATP metabolism and to myogenesis, the RNA/DNA ratio, and the protein/DNA ratio of fish under different feeding conditions: a diet of 212-432% (frequent feeding, FR) or 32-82% (restricted feeding, RE) of initial body weight per week was supplied. The expression levels of nucleoside diphosphate kinase (NDK)-Z2, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and myogenin genes of RE fish were higher than those of FR fish, although the RNA/DNA ratio and the protein/DNA ratio were unaffected by the feeding amount. Moreover, expression levels of NDK-Z2 and GAPDH were upregulated to a greater extent than those for myogenin and myostatin 1 under restricted feeding. Together, our results show that gene expression is more sensitive to nutrient conditions of fish than traditional indicators such as the RNA/DNA ratio. The ATP metabolic system is more sensitive to moderate nutrient shortages than the myogenic system.