Comparative study on the modulation of incretin and insulin homeostasis by butyrate in chicken and rabbit

The pancreatic secretion of insulin, a key endocrine regulator of metabolism and growth, can be greatly influenced by the gut-derived incretin hormones, namely by GIP (Glucose-dependent Insulinotropic Peptide) and GLP-1 (Glucagon-like Peptide 1). As insulin is a major stimulator of growth, affecting its producion may be of special importance in food-producing livestock. The aim of the present study was to investigate novel ways of modulating incretin and insulin homeostasis in chickens and rabbits by nutrition, e.g. by oral butyrate application, also studying the mechanisms of incretin action in both species as a comparative approach. Acute oral butyrate challenge significantly decreased plasma GIP levels by approx. 40% in both species: significant interactions of butyrate exposure and incubation time were found in both chickens (P = 0.038 and P = 0.034 at 30 and 60 min following butyrate ingestion [1.25 g/kg BW], respectively) and rabbits (P = 0.036 and P = 0.039 at 30 and 60 min after butyrate ingestion [0.25 g/kg BW], respectively), while plasma GLP-1, insulin and glucose concentrations remained unaffected by butyrate in both species over time. These results are in contrast to butyrate’s stimulating effect on both incretin and insulin secretion in mice, indicating specific, species-dependent differences even among mammalian species. Further, based on the analyzed correlations between the measured endocrine parameters (regardless of the butyrate exposure), it can be assumed that incretins may regulate pancreatic insulin release in rabbits on a partly different way compared to mice, humans and chickens.