Understanding the regulation of islet cell mass has important implications for the discovery of regenerative therapies for diabetes. The liver plays a central role in metabolism and the regulation of endocrine cell number, but liver-derived factors that regulate α-cell and β-cell mass remain unidentified.
Researchers propose a nutrient-sensing circuit between liver and pancreas in which glucagon-dependent control of hepatic amino acid metabolism regulates α-cell mass.
Authors found that glucagon receptor inhibition reduced hepatic amino acid catabolism, increased serum amino acids, and induced α-cell proliferation in an mTOR-dependent manner.
In addition, mTOR inhibition blocked amino-acid-dependent α-cell replication ex vivo and enabled conversion of α-cells into β-like cells in vivo.
Serum amino acids and α-cell proliferation were increased in neonatal mice but fell throughout postnatal development in a glucagon-dependent manner. These data reveal that amino acids act as sensors of glucagon signaling and can function as growth factors that increase α-cell proliferation.