PROJECT SUMMARY Global health agencies have reported their concern on the increasing trend in women entering pregnancy as either overweight or obese and having excessive gestational weight gain (GWG). Follow-up studies of mother- offspring dyads have shown the association between maternal prepregnancy body mass index (BMI) and GWG as significant contributors to offspring development. The increasing prevalence in childhood obesity is a public health matter since obese children are likely to stay obese in adulthood and develop diseases associated with the metabolic syndrome earlier in life. Clinical studies have demonstrated the associations of pregravid maternal obesity with infant adiposity and cardiometabolic risk, suggesting a possible mechanistic link between in utero overnutrition with fetal overgrowth and high risk of obesity, type-2 diabetes and cardiovascular disease in the offspring. Therefore, prevention of childhood obesity begins with interventions on maternal BMI before gestation. The research project proposed for this fellowship is an ancillary study of the randomized controlled trial “Lifestyle Interventions in Preparation for Pregnancy” (LIPP). The goal of the intervention (Mediterranean diet and guided exercise) is to promote a 5-7% weight loss before a planned pregnancy in overweight/obese women to improve maternal metabolism and reduce neonatal adiposity. Evidence from clinical research has reported the benefits of 5-10% weight loss on improving adipose tissue (AT) insulin sensitivity, however the molecular changes in AT driving enhanced insulin sensitivity in this range of weight loss need to be determined. The proposed ancillary study seeks to provide empirical data on the longitudinal effects of the intervention on maternal adipocyte glucose and lipid metabolism as well as the inflammatory state. The analysis will be done utilizing gluteal AT biopsies obtained at study enrollment (baseline), 6 months after randomization, and in early pregnancy. The molecular longitudinal changes will be associated with clinical metabolic parameters of body composition, resting energy expenditure, and serum markers of inflammation and insulin resistance. In addition to the maternal studies, I will investigate if the intervention beneficially impacts the metabolic programming of umbilical cord mesenchymal stem cells (ucMSC). I will utilize the novel technique of ucMSC adipogenic differentiation (ad-ucMSC) as an index of neonatal adipocyte function and determine if lifestyle interventions prior to a planned pregnancy enhance insulin sensitivity and improve lipid metabolism of ad-ucMSC. The proposed research is a unique opportunity to investigate the longitudinal effects of pregravid lifestyle interventions on maternal AT metabolic function and neonatal adiposity. The findings obtained will examine potential early biomarkers and mechanisms as predictors of long-term metabolic outcomes in the offspring.