Effect of Energy Substrates on Protein Degradation in Isolated Small Intestinal Enterocytes From Rats

Abstract

Background: Nutrients affect small intestinal protein mass and metabolism, but studies on the effect of nutrients on small intestinal protein degradation are very limited due to a lack of a proper method. The objectives of this study were to establish a method to directly estimate protein degradation in isolated enterocytes from rats and to test the effect of energy substrates on protein degradation. Methods: Male Sprague-Dawley rats (150–200 g, n ≥ 8 per treatment) were used. Cell viability, tyrosine release as an indicator of protein degradation, and the effect of osmolarity, 50 mmol/L glucose, 20 mmol/L β-hydroxybutyrate, 4.7 mmol/L butyrate, and 30 mmol/L glutamine on protein degradation were measured. Results: The average viability of enterocytes at time 30 minutes was 85.8% (range, 81%–94%). Tyrosine release was linear over the course of experiments, indicating constant protein degradation (R ² = 0.9943; p < .05). Osmolarity, glucose, and glutamine had no effect on protein degradation in isolated enterocytes. β-Hydroxybutyrate significantly decreased it (–16%; p < .05), whereas butyrate slightly increased it (+5%; p < .05). Conclusions: A high viability and constant protein degradation indicate a successful establishment of a method to estimate protein degradation in isolated small intestinal enterocytes from rats. The large effect of β-hydroxybutyrate suggests a potential positive role for ketone bodies to limit the loss of small intestinal protein mass by decreasing protein degradation.

Studies on small intestinal protein degradation are limited due to lack of a method. β-Hydroxybutyrate but not other energy substrates decreases protein degradation. This finding might be significant in catabolic conditions where loss of protein mass is substantial.