Effect of Metformin Treatment in Gestational Diabetes Mellitus on Infant Mesenchymal Stem Cell Metabolism

Abstract

Offspring born to women with gestational diabetes mellitus (GDM) experience long- and short-term health consequences that may be partially mitigated through effective and timely treatment of maternal hyperglycemia. Metformin is an effective anti-diabetic agent that is increasingly prescribed to pregnant women for the treatment of GDM. However, metformin readily crosses the placenta into fetal circulation and concerns regarding the potential impact on fetal development have not been adequately addressed. While investigations conducted in animal models have produced controversial findings, randomized controlled trials in humans have reported altered postnatal growth during infancy and childhood among offspring exposed to metformin in utero. Furthermore, the underlying causal mechanisms by which metformin exerts lasting effects on offspring remain unclear. Nevertheless, the use of human umbilical cord derived mesenchymal stem cells (MCSs) has recently gained recognition as a robust model for studying infant cellular outcomes, and current evidence demonstrates that outcome measures from infant MSCs are tightly correlated with longitudinal measures of infant clinical outcomes, such as adiposity measured from birth to 4-6 years of life; thus, infant MSCs present a unique opportunity to study infant cellular outcomes. To investigate the impact of in utero metformin on infant MSC energy metabolism, we collected infant MSCs from exclusively diet controlled (A1DM-MSCs) or metformin treated (Met-MSCs) GDM pregnancies. In aim one of this dissertation, we investigated the impact of in utero metformin exposure on infant MSC substrate oxidation and insulin action under basal conditions and in response to excess fatty acids using radiolabeled glucose, oleate, and palmitate tracers. Measurements of MSC lipid accumulation and mitochondrial content markers were also conducted, in addition to metformin concentrations in cord blood plasma samples. Met-MSCs displayed lower rates of oleate oxidation under basal conditions, compared to A1DM-MSC, despite no differences in mitochondrial content or lipid availability. Additionally, differences in oleate oxidation were no longer apparent under conditions of excess fatty acids. We also reported a large variability among cord blood plasma metformin concentrations, which did not associate with measures of maternal metformin dosing. In aim two of this dissertation, we examined the impact of in utero metformin exposure on infant MSC mitochondrial capacity and control of respiratory flux across physiologic energy demands in the presence of substrates specific to respiratory complex I (CI), CII, and fatty acid oxidation using cellular respirometry. We also investigated the relationship between metformin exposure measures and MSC mitochondrial outcomes. Met-MSCs exhibited lower mitochondrial maximal capacity and diminished CII-linked respiration and respiratory conductance compared to A1DM-MSCs. We also reported relationships between length of in utero metformin exposure and mitochondrial protein expression of CII and citrate synthase. Collectively, these data demonstrate that infant MSCs adaptively respond to in utero metformin exposure, as evident by the lasting effects observed in infant MSCs in the absence of metformin. These findings are clinically relevant and will help inform clinicians of the potential effects of prescribing metformin to pregnant women diagnosed with GDM on the developing fetus, thus increasing the level of care provided.