Timing determines programming of energy homeostasis by maternal PM_2.5 exposure in mouse models

Maternal exposure to particulate matter with an aerodynamic diameter ≤2.5 μm (PM_2.5) is believed to be a risk factor of developmental origins of health and disease (DOHaD), but its effect on offspring's susceptibility to obesity, a common target disease of DOHaD, remains controversial. To pinpoint the effect of maternal PM_2.5 exposure on offspring's energy homeostasis, female C57BL/6J mice were exposed to filtered air (FA) or concentrated ambient PM_2.5 (CAP) for 12 weeks and mated with normal male mice to produce offspring. After parturition, a cross-fostering strategy was exploited to determine whether prenatal and/or postnatal mothering by CAP-exposed dams program offspring's energy homeostasis and susceptibility to obesity. Moreover, oocytes were collected from FA- or CAP-exposed mice and subjected to in vitro fertilization (IVF) to determine whether maternal pre-conceptional exposure to PM_2.5 programs energy homeostasis. Results showed that prenatal mothering by CAP-exposed dams increased suckling's milk intake and weight gain, decreased normal diet (ND)-fed offspring's adulthood food intake and body weight, and did not influence offspring's diet-induced obesity (DIO). Postnatal mothering by CAP-exposed dams did not influence suckling's milk intake and weight gain, increased ND-fed offspring's adulthood food intake and body weight and did not influence offspring's DIO. Prenatal plus postnatal mothering by CAP-exposed dams increased suckling's milk intake and weight gain, increased ND-fed offspring's adulthood food intake and body weight, and aggravated offspring's DIO. IVF study revealed that male offspring derived from CAP-exposed mice versus controls had significantly decreased adulthood food intake and body weight. RNA sequencing showed that CAP exposure influenced oocyte estrogen signaling and histone methylation. This study thus clearly reveals that timing determines programming of energy homeostasis by maternal PM_2.5 exposure.