Tissue localization of threonine oxidation in pigs

Area of Science:

• Animal Nutrition
• Biochemistry
• Metabolic Pathways

Background:

• Threonine is an essential amino acid crucial for protein synthesis and metabolic processes in pigs.
• Understanding threonine metabolism, specifically oxidation, is vital for optimizing animal growth and feed efficiency.
• The threonine dehydrogenase (EC 1.1.1.103) pathway is a key route for threonine catabolism.

Purpose of the Study:

• To determine the tissue distribution and activity of threonine oxidation via the threonine dehydrogenase pathway in pigs.
• To compare threonine oxidation between Piétrain x Large White and Large White pig genotypes.
• To investigate the relationship between threonine oxidation and growth performance/nitrogen efficiency.

Main Methods:

• Two experiments involving piglets infused with labeled L-threonine (L-[U-14C]threonine and L-[1-13C]threonine).
• Measurement of threonine dehydrogenase specific activity, and threonine and glycine specific radioactivities/enrichments in various tissues and plasma.
• Analysis of tissue samples from pigs slaughtered at different body weights (5, 12, and 20 kg).

Main Results:

• Threonine dehydrogenase activity was exclusively detected in the liver and pancreas of pigs.
• Specific activities of threonine dehydrogenase were similar in both liver and pancreas.
• Glycine labeling was significantly higher in the pancreas (12-14 fold) compared to the liver, suggesting differential glycine production rates.
• Large White pigs exhibited higher threonine oxidation compared to Piétrain x Large White pigs.

Conclusions:

• The liver and pancreas are the primary sites of threonine oxidation in pigs through the threonine dehydrogenase pathway.
• Differences in glycine metabolism between the liver and pancreas influence the interpretation of threonine oxidation.
• Genotypic variations in threonine oxidation capacity may explain differences in growth performance and nitrogen utilization between pig breeds.