Interpretive Summary: Interactions of amino acids and hormones regulate the balance between growth and milk protein synthesis in lactating rats fed diets differing in protein content
By Anne ZInn
A recent study published in the Journal of Animal Science aimed to explore the correlations among circulating amino acids and insulin-like growth factor-I, growth hormone, and prolactin concentrations in plasma and producing tissue of lactating rats fed diets with varying protein content. The team hypothesized that concentrations of these hormones were affected by dietary protein content, and that the effects were associated with blood concentrations of one or more amino acids. Insulin-like growth factor-I, growth hormone, and prolactin play important roles in milk protein synthesis, and previous research has suggested that their plasma concentrations were affected by dietary protein intake, but the details of the relationships among circulating amino acid concentrations and hormonal responses during lactation still needs to be further investigated.
To investigate this relationship, 18 Wistar rats were assigned to a low standard or high-protein diet from parturition through day 15 of lactation. The results of the present study showed that varying dietary protein content had different effects on concentrations of insulin-like growth factor-I, growth hormone, and prolactin in plasma and producing tissue. Correlation and regression analysis suggested that the hormone changes were strongly associated with several circulating amino acid concentrations. Additionally, variations in the hormone receptor and amino acid transporter gene expression indicated that whole-body nutrients distribution may be affected by hormonal concentrations and tissue responsiveness to those hormones.
Overall, it was concluded that variations in concentrations of some of the circulating amino acids are likely mediators of the effects of dietary protein on concentrations of insulin-like growth factor-I, growth hormone, and prolactin in lactating rats, which may partially mediate the effects of dietary protein on peripheral tissue metabolism.
The full paper can be found on the Journal of Animal Science website.