[NAD(+)] [NADH] REDOX-STATE METABOLITES OF FREEZED-CLAMPED LIVERS OF RATS FED CASEIN OR GELATIN DIETS

Postprandial thermic effects of dietary protein meals have been hypothesized to be related to a diet-mediated increase in amino acid oxidation that may affect the in vivo redox states. The objective of the present study was to determine the effects of isoenergetic isonitrogenous restricted (80% of the ad libitum gross energy intake) diets containing either casein (30%) or gelatin (15% casein, and 12.7% gelatin) for 1, 3, or 28 days to Wistar rats on liver metabolites characterizing cytoplasmic and mitochondrial redox-states. Both casein and gelatin diets produced a progressive decline in the concentrations of lactate and an increase in the concentrations of acetoacetate with the duration of feeding. beta-hydroxybutyrate concentrations were reduced on day 3 in relation to day 1 and were highest on day 28. Pyruvate levels changed moderately or stayed the same. The calculated redox ratios were increased in cytoplasm on day 3 and 28 in relation to day I and were insignificantly higher with the gelatin diet compared with the casein diet. The corresponding redox ratios in mitochondria were increased on day 3 and remained high on day 28 in relation to day 1 and were significantly higher on day 28 in the gelatin diet-fed group in relation to the casein diet-fed group. Adenine nucleotide content and energy charges were only slightly modified by the experimental conditions used. It is suggested that these results are in accordance with a stimulation of amino acid oxidation and reoxidation of reducing equivalents feeding the protein diets.