Star-PAP helps fat cells preserve insulin-receptor production
An RNA-processing enzyme helped maintain the molecular instructions for making insulin receptors in fat cells. Mice lacking its function in adipose tissue lost fat while developing severe metabolic problems. The peer-reviewed study connects RNA stability with insulin responsiveness, combining cell and animal experiments with observations of a rare human variant.
Science··Morning
An RNA enzyme supports insulin responsiveness
Star-PAP, an enzyme involved in processing messenger RNA, helped preserve insulin-receptor production in fat cells. A peer-reviewed Nature Communications study published on October 29 investigated the connection through cell experiments, mice and observations of a rare human genetic variant. Messenger RNA carries instructions for making proteins. Star-PAP adds polyadenylate tails to these molecules and binds directly to an untranslated region of the insulin-receptor transcript, supporting its maturation and stability. When the enzyme was absent, less mature receptor RNA was available and receptor production declined, weakening insulin signaling. A rare variant also reduced RNA maturation in the experimental analysis. Reduced receptor production also limited the ability of the fat cells to store lipids, linking the RNA defect to tissue function.[1], [2]
Fat loss accompanied metabolic damage in mice
Mice without Star-PAP in adipose tissue progressively lost fat and developed severe insulin resistance, high blood glucose and fatty liver. The combination resembled lipodystrophy, a condition in which impaired fat storage brings metabolic complications. Restoring insulin receptors in adipocytes partially improved the abnormalities. That recovery supports an important contribution from receptor loss, while leaving other effects involved. The enzyme’s loss also disturbed acetyl-CoA balance and reduced histone acetylation, a chemical modification associated with regulation of genes involved in fat synthesis. Pyruvate supplementation restored aspects of this process in the experimental system, helping recover gene activity and lipid production.[1], [2]
The rare variant differs from complete enzyme loss
The variant p.D469N was identified in lean participants and was absent from the obese cases studied. It was associated with partial loss of protein function. Its effects in mice were milder than complete loss, including changes in body weight and fat mass under a high-fat diet. These differences matter when interpreting observations in people alongside the animal experiments. The loss of fat seen after eliminating enzyme function occurred with impaired metabolic health, rather than establishing healthy weight reduction. More human variants and clinical observations are needed to establish the connection’s scope in people. The study did not demonstrate a treatment benefit in patients.[1], [2]
