Reduced Availability of Essential Amino Acids Disrupts Differentiation of Anorexigenic POMC Neurons in the Fetal Rat Hypothalamus.

Abstract

Intrauterine growth restriction (IUGR) is associated with an elevated risk of long-term metabolic disorders, including obesity and type 2 diabetes, aligning with the Developmental Origins of Health and Disease hypothesis. However, the mechanisms underlying metabolic programming remain elusive. This study investigates the impact of gestational protein restriction (PR) on fetal hypothalamic development, focusing on the formation of neuronal populations regulating appetite and energy balance. Using a rat isocaloric PR model (8% protein preconception, 4% during gestation), we examined hypothalamic development at gestational days 15 and 17-critical stages for cell fate determination and differentiation. We measured maternal, fetal, and placental weights, and maternal plasma amino acid concentrations. Then, we performed single-cell RNA-seq to assess the impact on neuronal differentiation and uncover mechanisms, which were further investigated via EdU-labeling, immunohistochemistry, and RNAscope. Additionally, we assessed mTOR signaling and analyzed methylation patterns in the Pomc gene. Gestational PR reduced maternal concentrations of essential amino acids, impaired fetal growth, and selectively disrupted the differentiation of ISL1-precursors into POMC neurons, while sparing NPY precursor differentiation. This correlated with downregulated differentiation genes and disrupted mTOR signaling, linked to decreased maternal branched-chain amino acids and altered expression of the amino acid transporter Lat1. Epigenetic alterations in the Pomc promoter but not its enhancers may contribute to the phenotype. Adequate protein intake is crucial for POMC differentiation in the fetal arcuate nucleus. Further studies should investigate additional developmental windows to optimize dietary recommendations for at-risk pregnancies.