OBJECTIVES/GOALS: Maternal undernutrition, a form of malnutrition, can alter neonatal leptin signaling and result in metabolic dysfunction in adulthood. We developed a mild undernutrition model to relate more to societys nutritional challenges and to test the hypothesis that a shift in the neonatal leptin surge would result in sex-specific metabolic changes. METHODS/STUDY POPULATION: We studied pups from undernourished dams which were calorically restricted by 20% (CR20) from embryonic day 15 until postnatal day (PND) 21. We tested 216 offspring from 11 Fed dams and 13 undernourished dams (CR20), detecting a leptin surge in control fed progeny at PND11. At 3 months of age, offspring from 3 dams per maternal nutrient status were either exposed to a 45% high fat diet (HFD) or control diet (10% fat) for 16 weeks. Anterior pituitary hormones were analyzed in the pituitary and serum of neonates and adults. To determine the mechanism of the phenotype observed in male adult offspring on the HFD, single cell RNA sequencing was used to analyze the pituitary, fat and liver. RESULTS/ANTICIPATED RESULTS: Offspring of CR20 dams had an early leptin surge peaking at PND8 and GH levels at PND1 were higher in CR20 progeny. Weights of both male and female CR20 offspring were lower and body lengths were shorter than controls. As adults, Fed mice from both sexes had increased weight gain with HFD. However, although CR20 females gained weight on the HFD, male progeny from CR20 dams did not gain weight on the HFD and appeared protected from impact. We found sex-specific changes in pituitary Gh, Ghrhr, and Ghsr mRNA levels. Single cell RNA sequencing of pituitary, fat and liver of male offspring showed significant regulation of transcripts in fat of male offspring from Fed dams that was not found in CR20 males when compared to control fed mice. DISCUSSION/SIGNIFICANCE: Mild undernutrition causes a prematurely high leptin surge and sex-specific growth responses to a HFD, including resistance to a HFD in underfed males. Transcript analysis in fat of males resistant to HFD induced obesity may reveal mechanisms that provide protection against HFD induced weight gain.