TDK conference 2016

Butyrate is a short chain fatty acid that is produced by microbial fermentation in the gut as well as applied as a feed additive in poultry nutrition. It was suspected based on previous studies that butyrate acts as an insulin sensitizer in liver and muscle of chicken and that it would enhance the phosphorylation of Akt, a key member of the insulin signalling pathway. In this study the influence of endogenous and exogenous butyrate on Akt phosphorylation and its association with the insulin signalling cascade was investigated. Broiler chickens (Ross-308 strain) were fed with two different basal diets (maize or wheat), supplemented with sodium (n-)butyrate (1.5 g/kg diet) or without butyrate addition. Wheat-based diet, rich in soluble non-starch polysaccharides, was supposed to increase caecal production of short chain fatty acids, primarily that of butyrate. The animals were slaughtered at 21 days of age by decapitation. Liver and muscle (m. gastrocnemius) samples were taken from each individual and thereafter homogenized and diluted to appropriate equal total protein concentrations. Proteins were separated by gel electrophoresis and were blotted to nitrocellulose membranes by turbo-blotting. For protein detection, phospho-Akt was examined in both liver and muscle samples by heterologous antibodies. As housekeeping protein, β-actin was assayed in liver and γ-actin in skeletal muscle.

The results showed an association of butyrate with an increase in body weight gain and a general inhibition of Akt phosphorylation in both liver and muscle samples. In the liver, phosphorylation of Akt was significantly decreased in chicken kept on wheat-based diet compared to the maize-based group, indicating the effect of the endogenously produced butyrate on hepatic Akt phosphorylation. However, in the muscle there was a significant difference concerning the exogenous butyrate, where butyrate as a feed additive diminished the Akt phosphorylation state. These results indicate that the muscle reflects mostly to the effect of exogenously supplemented butyrate, and it might be stated that the origin of butyrate plays critical role in its organ-specific action concerning insulin homeostasis. The present results suggest that butyrate can be considered as a potent effector of insulin signalling, primarily that of Akt phosphorylation in broilers. Further, the mechanism of insulin signalling in chicken might be completely different compared to that of mammals indicating additional trials concerning the role of phospho-Akt in chicken insulin signalling.