Abstract
The influence of dietary protein levels on hepatic lipid accumulation and on the activities of lipogenic-related enzymes in the liver were studied in duckling fed isocaloric diets containing corn or barley as the carbohydrate source. The liver triglyceride content, in the corn-soybean diet, was significantly higher in the low protein diet (15%) than in the high protein diet (20%). Aslo, in the low protein diet feeding, the liver triglyceride content was significantly higher in ducklings fed the corn-soybean diet than in those fed barley-soybean diet. Plasma total cholesterol concentration, in the barley-soybean diet, was significantly lower in the high protein diet than in the low protein diet. Plasma phospholipid concentration was not significantly different between the corn-soybean diet and the barley-soybean diet, but it was significantly higher in ducklings fed the low protein diet than in those fed high protein diet.
The activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PDH), NADP-malate dehydrogenase (EC 1.1.1.40; NADP-MDH) and citrate cleavage enzyme (EC 4.1.3. 8; CCE) in the liver, in ducklings fed the corn-soybean diet, were significantly higher in the low protein diet than in the high protein diet. In ducklings fed the low protein diet, NADP-MDH and CCE activities in the liver were significantly higher in the corn-soybean diet than in the barley-soybean diet.
In the present experiment, the activities of hepatic G6PDH was about three times that of NADP-MDH. Furthermore, this value for ducklings was markedly higher compared with that for chickens reported. This may suggest that pentose-phosphate dehydrogenase in the duckling liver, unlike the chicken liver, is probably the major source of reducing equivalent for the support of fatty acid syntheis.
