Adiponectin supplementation in pregnant mice prevents the adverse effects of maternal obesity on placental function and fetal growth

Abstract

Mothers with obesity or gestational diabetes mellitus have low circulating levels of adiponectin (ADN) and frequently deliver large babies with increased fat mass, who are susceptible to perinatal complications and to development of metabolic syndrome later in life. It is currently unknown if the inverse correlation between maternal ADN and fetal growth reflects a cause-and-effect relationship. We tested the hypothesis that ADN supplementation in obese pregnant dams improves maternal insulin sensitivity, restores normal placental insulin/mechanistic target of rapamycin complex 1 (mTORC1) signaling and nutrient transport, and prevents fetal overgrowth. Compared with dams on a control diet, female C57BL/6J mice fed an obesogenic diet before mating and throughout gestation had increased fasting serum leptin, insulin, and C-peptide, and reduced high-molecular-weight ADN at embryonic day (E) 18.5. Placental insulin and mTORC1 signaling was activated, peroxisome proliferator-activated receptor-α (PPARα) phosphorylation was reduced, placental transport of glucose and amino acids in vivo was increased, and fetal weights were 29% higher in obese dams. Maternal ADN infusion in obese dams from E14.5 to E18.5 normalized maternal insulin sensitivity, placental insulin/mTORC1 and PPARα signaling, nutrient transport, and fetal growth without affecting maternal fat mass. Using a mouse model with striking similarities to obese pregnant women, we demonstrate that ADN functions as an endocrine link between maternal adipose tissue and fetal growth by regulating placental function. Importantly, maternal ADN supplementation reversed the adverse effects of maternal obesity on placental function and fetal growth. Improving maternal ADN levels may serve as an effective intervention strategy to prevent fetal overgrowth caused by maternal obesity.

Keywords: adipokines; amino acids; glucose; insulin resistance; maternal-fetal exchange.

Fig. S1.

Flow chart illustrating the allocation of mice to different diets, treatments, and experimental analyses. All animals were maintained on their respective diets throughout the experimental protocol. Gray shading indicates animals on a high-fat and high-sugar (OB) diet. WB, Western blot.

Fig. S2.

Daily caloric intake in pregnant mice at different gestational intervals. Total caloric intake (A), carbohydrate (B), protein (C), and fat (D) were calculated from the weight of the remaining pelleted food at the end of the gestational interval indicated. In addition, the amount of sugar consumed was determined at regular periods. Data are mean + SEM [n = 7 (C/PBS), n = 10 (OB/PBS), and n = 9 (OB/ADN)]. Statistical significance was determined using one-way ANOVA followed by Tukey’s post hoc test. *P < 0.05; ***P < 0.001.

Fig. S3.

DsbA-L protein expression in s.c. adipose tissues collected from flank adipose of pregnant dams at E18.5. Expression of DsbA-L was significantly increased in OB/ADN dams compared with OB/PBS dams. Data are mean + SEM [n = 7 (C/PBS), n = 10 (OB/PBS), and n = 9 (OB/ADN)]. Statistical significance was determined using one-way ANOVA followed by Tukey’s post hoc test. **P < 0.01.

Fig. 1.

ADN infusion in OB pregnant mice decreases placental nutrient transporter expression and function. Placental nutrient transport capacity in vivo was measured at E18.5. Unidirectional maternal-fetal clearances for MeG (A) and MeAIB (B) were measured in anesthetized dams. Protein expression of glucose (C) and system A amino acid (D) transporter isoforms was determined in isolated TPMs. Data are mean + SEM (n = 5 per group). Statistical significance was determined using one-way ANOVA followed by Tukey’s post hoc test. *P < 0.05; **P < 0.01; ***P < 0.001.

Fig. 2.

Impact of maternal obesity and ADN infusion on placental insulin and mTORC1 signaling. Placental insulin signaling as determined by the expression and/or phosphorylation of IR-β and IRS-1 (A) and downstream activation of the PI3K/Akt (B) and Grb/Erk (C) pathways. (D) mTORC1 signaling was determined by the expression and phosphorylation of 4EBP1, S6K1, and rpS6. Data are mean + SEM [n = 7 (C/PBS), n = 10 (OB/PBS), and n = 9 (OB/ADN)]. Statistical significance was determined using one-way ANOVA followed by Tukey’s post hoc test. *P < 0.05; **P < 0.01; ***P < 0.001. S, Ser 307; Y, Tyr 608.

Fig. 3.

Regulation of placental PPARα, p38 MAPK, and AMPK activity by maternal obesity and ADN treatment. Activation of placental PPARα, p38 MAPK, and AMPK was determined by the phosphorylation and expression of these proteins. Data are mean + SEM [n = 7 (C/PBS), n = 10 (OB/PBS), and n = 9 (OB/ADN)]. Statistical significance was determined using one-way ANOVA followed by Tukey’s post hoc test. *P < 0.05; **P < 0.01; ***P < 0.001.

Fig. S4.

Time course studies of MeG and MeAIB in maternal serum, placenta, and fetus in C/PBS animals at E18.5. The placental clearance rate was linear over 5 min; therefore, 3.5 min was used in subsequent studies. Each time point represents a different C/PBS animal.

Fig. S5.

Alkaline phosphatase enrichment ratio in TPMs isolated from C/PBS, OB/PBS, and OB/ADN mice. TPM enrichment was determined by alkaline phosphatase activity of TPM/homogenate. NS, not significant.