Growth Hormone and IGF-I Boost Milk Production in Mice During Prolonged Lactation

Prolonged lactation in mammals, including humans, often leads to a decline in milk production, which can negatively impact offspring growth and maternal health. Understanding the mechanisms that regulate mammary gland function during this critical period is essential. This study specifically aimed to investigate if growth hormone (GH) and insulin-like growth factor-I (IGF-I) could enhance lactation performance and how they affect mammary gland signaling and gene expression.

Both mGH and LR3-IGF-I treatments significantly enhanced lactation performance. mGH treatment increased litter weight gain by 20%, while LR3-IGF-I increased it by 25% compared to controls (p<0.05 for both). The combination treatment showed an even greater increase of 30% (p<0.01). Mammary gland weight, DNA, RNA, and protein content were also significantly increased in treated groups. Specifically, mGH enhanced STAT5 phosphorylation by 2.5-fold, a crucial pathway for milk synthesis, whereas LR3-IGF-I significantly increased MAPK and Akt phosphorylation by 1.8-fold and 2.1-fold respectively, indicating enhanced cell growth and survival. Furthermore, both treatments upregulated the expression of milk protein genes like casein and their respective receptor genes (GHR, IGF-1R).