Insulin may boost breast milk supply

Scientists have found that the hormone insulin may play an important role in breast milk production, a finding that can help explain why many mothers have difficulty making enough milk to breastfeed.
Researchers at Cincinnati Children's Hospital Medical Center and the University of California Davis found insulin to be responsible for lactation success.
The study is the first to describe how the human mammary gland becomes highly sensitive to insulin during lactation. It is also the first study to get an accurate picture of how specific genes are switched on in the human mammary gland during lactation.
The researchers used next generation sequencing technology, RNA sequencing, to reveal "in exquisite detail" the blueprint for making milk in the human mammary gland, according to Laurie Nommsen-Rivers, corresponding author of the study, published in journal PLOS ONE.

For a long time, insulin was not thought to play a direct role in regulating the milk-making cells of the human breast, because insulin is not needed for these cells to take in sugars, such as glucose.
Scientists now, however, appreciate that insulin does more than facilitate uptake of sugars.

"This new study shows a dramatic switching on of the insulin receptor and its downstream signals during the breast's transition to a biofactory that manufactures massive amounts of proteins, fats and carbohydrates for nourishing the newborn baby," said Nommsen-Rivers.
Nommsen-Rivers and her colleagues were able to use a non-invasive method to capture mammary gland RNA - a chain of molecules that are blueprints for making specified proteins - in samples of human breast milk.

They then created the first publicly accessible library of genes expressed in the mammary gland based on RNA-sequencing technology.
This approach revealed a highly sensitive portrait of the genes being expressed in human milk-making cells.
They discovered an orchestrated switching on and off of various genes as the mammary gland transitions from secreting small amounts of immunity-boosting colostrum in the first days after giving birth to the copious production of milk in mature lactation.
In particular, the PTPRF gene, which is known to suppress intracellular signals that are usually triggered by insulin binding to its receptor on the cell surface, may serve as a biomarker linking insulin resistance with insufficient milk supply.

Now that they've demonstrated the significance of insulin signalling in the human mammary gland, scientists are planning a phase I/II clinical trial with a drug used to control blood sugar in type 2 diabetes to determine whether it improves insulin action in the mammary gland, thus improving milk supply.