Dysregulation of placental mitochondrial structure dynamics and clearance in maternal obesity and gestational diabetes.

Introduction: The placenta is exposed to an altered metabolic environment in obesity and gestational diabetes (GDM) leading to disruption in placental function. Mitochondria are critical for energy production and cellular adaptation to stress. We previously reported reduced trophoblast mitochondrial respiration in GDM. Here we examine changes in mitochondrial structure dynamics, quality and protein homeostasis as well as clearance in both obese and GDM placentas of male and female fetuses. As obesity significantly increases the risk for GDM, our goal is to determine the distinct effects of each on placental mitochondria. Methods: We collected placental villous tissue following elective cesarean section at term from lean (LN, pre-pregnancy BMI 18.5-24.9), obese (OB, BMI>30) or obese with type A2 GDM women. Expression of proteins involved in mitochondrial biogenesis, structure dynamics, quality control and clearance were assessed by Western blotting. Significant changes between groups were determined in fetal sex-dependent and independent manner. Results: Only placentas from obese women showed increase in proteins regulating mitochondrial biogenesis (PGC-1α and SIRT1). We report fetal sex-specific changes in mitochondrial fusion but an overall decline in fission in OB and GDM placentas. Both maternal obesity and GDM affected proteins involved in maintaining mitochondrial protein quality and genome stability. This was accompanied by a reduction in mitochondrial complexes, suggesting impaired mitochondrial function. Obesity led to partial activation of mitophagy pathways (e.g., increased PINK1 without PARKIN activation), GDM placentas failed to mount this response. Discussion: Obesity and GDM affect placental mitochondria through distinct complex sex-specific mechanisms that may contribute to altered mitochondrial function.