Metabolic Responses of Chicks during Adaptation to a High Protein, “Carbohydrate-free” Diet

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Abstract
The capacity of chicks to utilize a high protein, “carbohydrate-free” diet (HP-diet) was assessed by the time-course response of several liver and kidney gluconeogenic enzyme activities, growth, and levels of various blood, liver and kidney constituents. These parameters were studied also in chicks subjected to prolonged starvation. Peak activities for liver and kidney glucose-6-phosphatase, glycerol kinase, and fructose-1,6-diphosphatase were observed after chicks had been fed the HP-diet for 24, 48, and 96 hours. Chicks fed the HP-diet exhibited increased liver size, marked kidney hypertrophy, elevated plasma uric acid levels, and essentially unchanged hematocrit and plasma glucose levels as compared with chicks fed the control diet. Plasma glycerol was depressed significantly in chicks fed the HP-diet for 3 days and was preceded by the peak response observed for liver and kidney glycerol kinase activity. These data, in addition to data showing high rates of growth, indicate a marked capacity of chicks to undergo gluconeogenesis from protein and to adapt successfully in short-term studies to high protein diets severely limiting in carbohydrate.