Effects of fasting, intermittent feeding or continuous parenteral nutrition on rat liver and brain energy metabolism as assessed by 31P-NMR.

We wanted to determine what happens to brain PCr and ATP relative to that in liver during a series of dietary manipulation consisting of a severe fast, during eating (when nutrients are intermittently supplied), and during and after PN-100, when an excess amount of nutrients are continuously supplied, using 31P-NMR spectroscopy, in rats randomized to a Fast or Fed group in which energy was provided either as chow or as PN-100. Liver ATP concentration, and brain and liver 31P-nuclear magnetic resonance (NMR) spectras were measured serially. Brain energy metabolism was not different between groups and among days. In contrast, Fasted group showed increased liver ATP/Pi ratio and decreased ATP concentration and ATP/phosphomonoester ratio, there being no difference between Fed and PN-100 groups. Data suggest that brain energy metabolism is maintained regardless of whether energy is supplied intermittently or continuously, and during a negative caloric intake period, brain energy metabolism is quantitatively preserved, suggesting that ATP production by liver is subservient to brain ATP state.