Gluconeogenesis from propionate produced in the colon of the horse.

This research studied the production of propionate in the colon of ponies and its role in glucose synthesis. The results suggested approximately 50-61% of glucose could be synthesized from colon-produced propionate in ponies, varying with their hay or hay and bran diet.

Methodology and Experiment Setup

• The researchers examined the production of propionate, a substance made when bacteria ferment dietary fiber in the large colon of two ponies. The ponies were outfitted with cannulas—tubes inserted into the body to deliver or remove fluid.
• The ponies were fed a standard diet of either hay or hay coupled with wheat bran. This helped them to discern any variance in the production of propionate based on the two different diets.
• A continuous infusion of 14C-labelled sodium propionate was made into a cannula in the right ventral colon of the ponies. This means they continuously introduced radioactively labeled sodium propionate into the ponies, which allowed them to track and measure its presence and progression in the system.
• Meanwhile, samples of the ingesta—the material inside the intestines—were obtained from another cannula near the end of the right dorsal colon.
• A simultaneous intravenous infusion of [2-3H]-labelled glucose was made as a measure of total glucose entry. This indicates they introduced a different radioactive label for glucose into the ponies’ vein, again to track and measure its presence and progression.

Findings

• Colonic propionate production, based on the two diets, varied between 146 mg/h per kg body weight for the hay diet and 195 mg/h per kg body weight for the hay and bran diet. This suggests the diet has a direct influence on the production of propionate in the colon of the ponies. The hay and bran diet resulted in a higher production of colonic propionate compared to the hay diet.
• The total glucose production was somewhat less than the propionate production. For the two diets, it was 120 mg/h per kg body weight (hay diet) and 92 mg/h per kg body weight (hay and bran diet).
• The results revealed that approximately half (50%) of the glucose was synthesized from propionate produced in the colon in ponies on the hay diet. This ratio increased to 61% in ponies on the hay and bran diet. This highlights the role of colon-produced propionate in gluconeogenesis – the synthesis of glucose in organisms.
• Therefore, the study provides evidence that not only does the diet influence propionate production, but the colon-produced propionate significantly contributes to glucose production in ponies.