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Activities of the enzymes of ketone body metabolism in the developing chick
Insights
Developing chicks show higher blood ketone bodies and muscle enzyme activity than adults. This suggests the liver fuels extrahepatic tissues, with ketone bodies powering skeletal muscle post-hatching.
Area of Science:
- Biochemistry
- Developmental Biology
- Avian Metabolism
Background:
- Ketone bodies are crucial energy sources, especially during development.
- Understanding avian metabolic shifts during hatching is vital for developmental studies.
Purpose of the Study:
- To investigate the role of ketone bodies in developing chick metabolism.
- To compare enzyme activities related to ketone body metabolism in pre- and post-hatch chicks versus adults.
Main Methods:
- Measurement of blood ketone body concentrations.
- Assay of key enzymes (3-oxo acid-CoA transferase, acetoacetyl-CoA thiolase, 3-hydroxybutyrate dehydrogenase) in liver and muscle tissues.
- Comparison across developmental stages (pre-hatching, post-hatching) and adult birds.
Main Results:
- Elevated blood ketone body concentrations in developing chicks compared to adults.
- Higher activities of 3-oxo acid-CoA transferase and acetoacetyl-CoA thiolase in chick muscles (heart, leg, pectoral) than adults.
- Consistent increase in 3-hydroxybutyrate dehydrogenase activity during incubation and post-hatching in all muscle tissues.
- Upregulation of ketone body synthesis enzymes in the liver during development.
Conclusions:
- The developing chick's liver likely supplies fuel to extrahepatic tissues.
- Ketone bodies are suggested as a significant fuel source for skeletal muscle oxidation in newly hatched birds.
- Metabolic adaptations involving ketone bodies are critical for avian embryonic and post-hatch development.
Abstract:
The concentration of ketone bodies in the blood of the developing chick prior to and just after hatching were higher than those found in the adult. The activities of 3-oxo acid-CoA transferase and acetoacetyl-CoA thiolase in the heart, leg and pectoral muscle before and after hatching were higher than those of the adult. The activity of 3-hydroxybutyrate dehydrogenase increased constantly during incubation and after hatching in all three muscle tissues. In the liver the activities of the enzymes of ketone body synthesis increased during incubation and after hatching. It is suggested that the liver could provide fuel to the extrahepatic tissues of the developing chick and ketone bodies could contribute as fuel for oxidation in the skeletal muscle of the newly hatched bird.