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Dietary and hormonal regulation of pancreatic xanthine dehydrogenase in the chick
Insights
Feeding chicks carbohydrates, particularly glucose, uniquely stimulates pancreatic xanthine dehydrogenase (PXDH) synthesis. This induction is linked to increased plasma glucose and insulin response, suggesting a metabolic pathway for PXDH accumulation.
Area of Science:
- Biochemistry
- Animal Physiology
- Nutritional Science
Background:
- Chick pancreatic xanthine dehydrogenase (PXDH) synthesis is induced by feeding and correlates with growth.
- PXDH induction occurs uniquely with pure glucose feeding in the absence of growth.
Purpose of the Study:
- To elucidate the post-feeding events leading to PXDH synthesis in chicks.
- To investigate the role of dietary macronutrients and insulin in PXDH induction.
Main Methods:
- Chicks were fed diets with varying primary energy sources (carbohydrate, protein, fat) at equal caloric density.
- Plasma glucose levels were monitored after feeding.
- The effect of exogenous insulin injections on PXDH activity was assessed.
Main Results:
- PXDH response was highest with carbohydrate diets, lower with protein, and minimal with fat.
- A transient increase in plasma glucose was observed in carbohydrate-fed chicks.
- Insulin injections (0.001-10.0 IU) elevated PXDH activity by 25-60%.
Conclusions:
- PXDH induction is linked to carbohydrate metabolism, specifically an increase in plasma glucose.
- The sequence of metabolic events likely involves increased plasma glucose, triggering an insulin response that initiates PXDH accumulation.
Abstract:
Chick pancreatic xanthine dehydrogenase (PXDH) is synthesized in response to feeding. Its induction generally correlates with growth; in the absence of growth, induction is observed uniquely when pure glucose is fed. This study attempted to determine what events after feeding lead to PXDH synthesis. When chicks were fed diets providing equal numbers of calories/gram of diet and varying only in the major energy source (carbohydrate, protein, or fat), PXDH response was high in the carbohydrate-fed, low in the protein-fed, and minimal in the fat-fed chicks. A unique, transitory increase in plasma glucose occurred in the carbohydrate-fed chicks within day 2 after feeding. These unique effects of dietary glucose indicated that the induction of PXDH after feeding was linked to carbohydrate metabolism. Effects of injected insulin on PXDH were examined. Insulin doses between 0.001 and 10.0 IU induced PXDH 25-60% above the activity found in carbohydrate-fed chicks. The initiation of PXDH accumulation may be the result of a sequence of metabolic responses to dietary carbohydrate beginning with an increase in plasm glucose, which induces an insulin response.