Adiponectin enhances mouse fetal fat deposition

Abstract

Maternal obesity increases offspring birth weight and susceptibility to obesity. Adiponectin is an adipocyte-secreted hormone with a prominent function in maintaining energy homeostasis. In contrast to adults, neonatal blood adiponectin levels are positively correlated with anthropometric parameters of adiposity. This study was designed to investigate the role of adiponectin in maternal obesityenhanced fetal fat deposition. By using high-fat diet-induced obese mouse models, our study showed that maternal obesity increased fetal fat tissue mass, with a significant elevation in fetal blood adiponectin. However, adiponectin gene knockout (Adipoq(-/-)) attenuated maternal obesity-induced high fetal fat tissue mass. We further studied the effects of fetal adiponectin on fetal fat deposition by using a cross breeding approach to create Adipoq(-/+) and Adipoq(-/-) offspring, whereas maternal adiponectin was null. Adipoq(-/+) offspring had more fat tissue mass at both birth and adulthood. Significantly high levels of lipogenic genes, such as sterol regulatory element-binding protein 1c and fatty acid synthase, were detected in the livers of Adipoq(-/+) fetuses. In addition, expression of genes for placental fatty acid transport was significantly increased in Adipoq(-/+) fetuses. Together, our study indicates that adiponectin enhances fetal fat deposition and plays an important role in maternal obesity-induced high birth weight.

Figures

FIG. 1.

Fetal adiponectin gene expression. A: Anatomical view of C57BL/6 fetuses and newborn mice. Ad, adipose; Br, brain; Em, embryo; H, heart; Li, liver; Lu, lung; M, skeletal muscle; SI, small intestine; Sk, skin; SM, submaxillary gland; Th, thymus; V, vertebrae. B: Adiponectin mRNA was detected by in situ hybridization with labeled adiponectin antisense (as) riboprobe. Gene expression patterns were analyzed by both X-ray file autoradiography and emulsion autoradiography. Cellular level results are shown at low magnification as bright labeling on a dark background. Anatomical data are revealed at high magnification as black labeling by silver grains on hematoxylin-stained background. (A high-quality digital representation of this figure is available in the online issue.)

FIG. 2.

Adiponectin increased fetal fat tissue mass. Two breeding schemes were used for these studies. Adipoq−/− or WT dams were mated with the same genotype sires (scheme 1, Supplementary Fig. 1A), whereas maternal obesity was induced by HF feeding (A–C). Body weights of e17.5-old fetuses from obese and lean dams were compared (A). Body composition of fetuses from WT (B) or Adipoq−/− (C) obese dams were scanned using magnetic resonance imaging and pooled fetal samples; n = 6. Adipoq−/+ and Adipoq−/− offspring were produced by using scheme 2 (Supplementary Fig. 1B), and all dams were Adipoq−/− (D and E). All offspring and dams were fed with regular chow (D–G). Litter size was adjusted to five to six (E–G). Male and female offspring were separated after weaning (p20). Fetal fat and lean tissue mass were compared between Adipoq−/+ and Adipoq−/− fetuses (D, e17.5; n = 6). Body weight and body composition of Adipoq−/+ and Adipoq−/− offspring were monitored from p1–p90 (E–G; n = 21–24). Data of p1 and p15 mice represent both sexes (F). *P < 0.05 vs. Adipoq−/− offspring. F-HFD, fetus from HF diet–fed dams; F-LFD, fetus of LF diet–fed dams.

FIG. 3.

Adiponectin and maternal obesity increased fetal blood FFA. Fetuses were generated using the same breeding scheme 1 (A and B) or 2 (C), as in Supplementary Fig. 1. For the maternal obesity study (A and B), dams were fed with HF or LF diet for 6 weeks before and during gestation. Regular chow was provided to the dams described in C. Fetal blood was collected by heart puncture. Maternal obesity increased blood FFA levels of fetuses from WT dams but not in fetuses from Adipoq−/− dams (A). Maternal HF feeding did not alter fetal TG levels of both WT and Adipoq−/− dams (B). Blood FFA concentrations of Adipoq−/+ fetuses were significantly higher than that of Adipoq−/− fetuses (C). *P < 0.05 vs. F-LF diet or F-HF diet fetuses of WT dams. F-HFD, fetuses from HF diet–fed dams; F-LFD, fetus from LF diet–fed dams. n = 21–24.

FIG. 4.

Adiponectin and maternal obesity enhanced expression of genes that facilitate placental FA transport. Placentas were collected by Cesarean section at e17.5. mRNA levels were determined by real-time PCR. Maternal obesity was induced by HF-diet feeding using WT and Adipoq−/− dams and breeding scheme 1 (A) (see detail in the Research Design and Methods section and Supplementary Fig. 1A). The breeding scheme 2 was used to produce Adipoq−/+ or Adipoq−/− fetuses, whereas maternal adiponectin was null (B) (Supplementary Fig. 1B). These dams were fed with chow (B). Elevated mRNA levels of placental LPL, VLDLr, FABP3, and FABPpm and AdipoR1 were detected in placentas from obese WT dams (A, designated as WT HFD). However, the differences were diminished, except for FABPpm, in placentas of HFD- and LFD-fed Adipoq−/− dams (A, designated as Adipoq−/− HFD and Adipoq−/− LFD). Elevated mRNA levels of LPL, VLDLr, and FABPpm were observed in placentas of Adipoq−/+ fetuses, whereas the dams were Adipoq−/− (B). *P < 0.05 vs. WT LFD (A) or Adipoq−/− fetuses (B); #P < 0.05 vs. WT LFD or WT HFD (A); ▽P < 0.05 vs. Adipoq−/− LFD. HFD, HF diet; LFD, LF diet; n = 12.

FIG. 5.

Adiponectin and maternal obesity increased lipogenic gene expression and activation in fetal livers. WT fetuses were produced by crossing HF diet–induced obese WT dams with WT sires (Scheme 1, Supplementary Fig. 1A) (A). Adipoq−/+ and Adipoq−/− fetuses (B–D) were generated by breeding Adipoq−/− dams with Adipoq−/− or Adipoq+/+ sires, which were fed with chow (Scheme 2, Supplementary Fig. 1B). Liver samples were collected from e17.5-old fetuses, whereas dams were at fed state. The mRNA levels of the main lipogenic genes in fetal livers was measured by real-time PCR (A and D); liver tissue TG levels were compared between Adipoq−/+ and Adipoq−/− fetuses (B). Protein or phospho-protein levels were detected by Western blotting using livers from Adipoq−/+ and Adipoq−/− fetuses (C). Confluent WT and GSK3β−/− MEFs were treated with adiponectin overnight. Increased ACC1, FASN, and SREBP1c were observed in adiponectin-treated WT MEFs, but not in GSK3β−/− MEFs (E). Quantified data are presented in the bottom graph with arbitrary units (C and E). n = 8–12. *P < 0.05 vs. fetuses from lean WT dams (A), or Adipoq−/− fetuses (C and D); #P < 0.05 vs. control MEFs (E). LXR, liver X receptor.