Impact of Obesity and Hyperglycemia on Placental Mitochondria

Abstract

A lipotoxic placental environment is recognized in maternal obesity, with increased inflammation and oxidative stress. These changes might alter mitochondrial function, with excessive production of reactive oxygen species, in a vicious cycle leading to placental dysfunction and impaired pregnancy outcomes. Here, we hypothesize that maternal pregestational body mass index (BMI) and glycemic levels can alter placental mitochondria. We measured mitochondrial DNA (mtDNA, real-time PCR) and morphology (electron microscopy) in placentas of forty-seven singleton pregnancies at elective cesarean section. Thirty-seven women were normoglycemic: twenty-one normal-weight women, NW, and sixteen obese women, OB/GDM(-). Ten obese women had gestational diabetes mellitus, OB/GDM(+). OB/GDM(-) presented higher mtDNA levels versus NW, suggesting increased mitochondrial biogenesis in the normoglycemic obese group. These mitochondria showed similar morphology to NW. On the contrary, in OB/GDM(+), mtDNA was not significantly increased versus NW. Nevertheless, mitochondria showed morphological abnormalities, indicating impaired functionality. The metabolic response of the placenta to impairment in obese pregnancies can possibly vary depending on several parameters, resulting in opposite strains acting when insulin resistance of GDM occurs in the obese environment, characterized by inflammation and oxidative stress. Therefore, mitochondrial alterations represent a feature of obese pregnancies with changes in placental energetics that possibly can affect pregnancy outcomes.

Figure 1

Significant correlation between placental efficiency and maternal hemoglobin (p = 0.005, r = 0.412). NW: normal-weight women; OB/GDM(−): obese women without a diagnosis of GDM; OB/GDM(+): obese women with GDM.

Figure 2

Placental mtDNA levels. ^∗p = 0.047 versus NW, Tukey HSD test. NW: normal-weight women; OB/GDM(−): obese women without a diagnosis of GDM; OB/GDM(+): obese women with GDM.

Figure 3

(a) Correlation between placental mtDNA and maternal pregestational BMI. The correlation is significant in patients without a diagnosis of GDM, indicated by the regression line (p = 0.010, r = 0.419). (b). Correlation between placental mtDNA and maternal hemoglobin (p = 0.011, r = −0.373). (c). Correlation between placental mtDNA and umbilical vein hemoglobin (p = 0.019, r = −0.406). NW: normal-weight women; OB/GDM(−): obese women without a diagnosis of GDM; OB/GDM(+): obese women with GDM.

Figure 4

Electron microscopy of term placenta villi showing representative sections of syncytiotrophobast cells from NW (a), OB/GDM(−) (b), and OB/GDM(+) (c) term placentas. M: mitochondria; ER: endoplasmic reticulum; LD: lipid droplet. NW: normal-weight women; OB/GDM(−): obese women without a diagnosis of GDM; OB/GDM(+): obese women with GDM.