Enhanced transforming growth factor-β signaling and fibrogenesis in ovine fetal skeletal muscle of obese dams at late gestation

Maternal obesity (MO) is increasing at an alarming rate. The objective of this study was to evaluate the effect of MO on fibrogenesis in fetal skeletal muscle during maturation in late gestation. Nonpregnant ewes were assigned to a control diet (Con; fed 100% of NRC nutrient recommendations, n = 6) or obesogenic diet (OB; fed 150% of NRC recommendations, n = 6) from 60 days before conception, and fetal semitendenosus (St) muscle was sampled at 135 days of gestation (term 148 days). Total concentration and area of collagen in cross-sections of muscle increased by 27.0 ± 6.0 (P < 0.05) and 105.1 ± 5.9% (P = 0.05) in OB compared with Con fetuses. The expression of precursor TGF-β was 177.3 ± 47.6% higher, and concentration of phospho-p38 74.7 ± 23.6% was higher (P < 0.05) in OB than in CON fetal muscle. Increases of 327.9 ± 168.0 (P < 0.05) and 188.9 ± 82.1% (P < 0.05), respectively, were observed for mRNA expression of Smad7 and fibronectin in OB compared with Con muscles. In addition, enzymes involved in collagen synthesis, including lysyl oxidase, lysyl hydroxylase 2b, and prolyl 4-hydroxylase-α1, were increased by 350.2 ± 90.0 (P < 0.05), 236.5 ± 25.2 (P < 0.05), and 82.0 ± 36.2% (P = 0.05), respectively, in OB muscle. In conclusion, MO-enhanced fibrogenesis in fetal muscle in late gestation was associated with upregulation of the TGF-β/p38 signaling pathway. Enhanced fibrogenesis at such an early stage of development is expected to negatively affect the properties of offspring muscle because muscle fibrosis is a hallmark of aging.