Caloric restriction during pregnancy reduces nephron endowment and impairs adult kidney function by inactivating mTOR and the methionine salvage pathway

עודד וולובלסקי ^1,2 Elad Resnick ² Liad Hinden ³ Joseph Tam ³ Tomer Shlomi ⁵ Raphael Kopan ⁴ Morris Nechama ²

¹Pediatric Nephrology Unit, Hadassah Hebrew University Medical Center, Pediatric Nephrology Unit, Israel
²Pediatric Nephrology Research Lab, Hadassah Hebrew University Medical Center, Pediatric Nephrology Research Lab, Israel
³Obesity and Metabolism Laboratory, School of Pharmacy, the Hebrew University of Jerusalem, Obesity and Metabolism Laboratory, Israel
⁴Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Division of Developmental Biology, USA
⁵Computer Science Department, Technion, Computer Science Department, Israel

Background: Maternal malnutrition during pregnancy correlates with lower nephron numbers and higher risk of chronic kidney disease (CKD) in adulthood, but the underlying molecular mechanisms are still unknown. The nephron progenitor pool exhausts abruptly in third postpartum day in mice with no nephrogenesis at later stages. We used a novel mouse model to study the effects of maternal caloric restriction on nephron progenitor cells (NPCs).

Methods: The caloric intake of pregnant CD1 mice were monitored in was reduced by 30% compared to the average consumption of the control group at the same gestational age. The effect on kidney morphology and function was measured by immunostaining, kidney biomarkers analysis, and nephron count. Six2 GFP NPCs were extracted from Six2 Cre E18.5 embryos and isolated by FACS. mRNA expression and metabolomic activity in sorted NPCs were evaluated by bulk RNAseq and mass spectrometry, respectively. Key findings were validated using western blotting.

Results: Animals exposed to caloric restriction in utero had 50% fewer nephrons after birth and throughout adulthood as well as lower kidney function, as demonstrated by urea levels. Calorically restricted E18.5 Six2 NPCs had decreased expression of mTOR pathway genes, and lower overall mTOR activity, reflected in lower levels of phosphorylated rpS6. Mass spectrometry identified a strong reduction in the methionine salvage pathway in isolated NPCs.

Conclusion: Reduced mTOR signaling and methionine salvage activity in NPCs from fetuses carried by malnourished mothers led to a premature end of nephrogenesis, reduced nephron numbers, and the associated increased risk for CKD in adulthood.