Topical Area: Maternal, Perinatal and Pediatric Nutrition
Objectives : Nutritional status during intrauterine and/or early postnatal life has substantial influences on adult offspring health. However, evidence on the impact of high fat diet (HFD)-induced maternal obesity on regulation of fetal bone development is sparse. Thus, we investigated the effects of maternal obesity in rodent and human cells on epigenetic regulation of osteoblast differentiation.
Methods : First, female Sprague-Dawley rats were fed either a low-fat AIN-93G control diet or a high fat diet (HFD) (45% fat calories) for 10 wk starting at 6 wk of age. Lean (from control diet) and obese (from HFD) female rats were then time-impregnated (n=6 per group) by control diet fed male rats. At gestational day 18.5 (E18.5), all fetuses were taken and embryonic osteogenic calvarial cells (EOCCs) were isolated. Second, human osteo-progenitors of mesenchymal stem cells were isolated from umbilical cord following delivery from pregnant mothers.
Results : We found epigenetic regulation of polycomb-regulated gene Ezh2 (Enhancer of zeste homolog 2) in embryonic rats from HFD obese rat dams. Increased enrichment of repressive histone mark H3K27me3 on the gene body of SATB2 (ChIP Seq analysis) was associated with aberrant differentiation of EOCCs to mature osteoblasts. Knocking down Ezh2 in EOCCs and ST2 cells increased SATB2 expression; on the other hand, Ezh2 overexpression in EOCCs and ST2 cells decreased SATB2 expression. These data were consistent with ChIP experimental results showing strong association between H3K27me3, Ezh2 and SATB2. Second, human mesenchymal stem cells (MSCs) from umbilical cord (UC) were isolated following delivery from obese/overweight (pre-pregnancy BMI≥25 kg/m2) and control (pre-pregnancy BMI between 19-25 kg/m2) pregnant mothers. We found: 1) UC-MSCs from pregnant obese/overweight mothers showed increased Ezh2 expression and decreased SATB2 mRNA expression, which was concurrent lower osteoblastogenesis potential in EOCCs; 2) ChIP experiments using H3K27me3 IP (immune-precipitation) showed significant association between H3K27me3, Ezh2 and SATB2.
Conclusions : These findings indicate maternal HFD-induced obesity-associated decrease of fetal pre-osteoblastic cell differentiation is under epigenetic control through SATB2 expression.
Funding Sources : Supported by USDA-ARS Project.