A high-fat diet induces obesity and impairs bone acquisition in young male mice.

The postnatal development of obesity is highly associated with the excessive consumption of a high-calorie, high-fat diet (HFD). However, the correlation between HFD-induced pediatric obesity and skeletal development remains to be elucidated. In the present study, postnatal day 17 (PND17) mice were weaned on a HFD for eight weeks ad libitum to induce obesity. The HFD mice showed a significant increase in the total body weight and gonadal and abdominal fat mass compared with the control animals. Peripheral quantitative (pQ) CT scans of the tibial bone revealed that the bone mineral density (BMD), including the total, trabecular and cortical BMD, was unchanged between the HFD and control diet groups, but that it was inversely associated with body fat. By contrast, the bone mineral content (BMC) and trabecular area were significantly decreased in the HFD group compared with the control. RNA and protein were isolated from the femur. qPCR and western blot analyses showed a significant downregulation in the gene expression of the key canonical Wnt signaling molecule β-catenin, the osteoblastic cell differentiation marker Runt-related transcription factor 2 (Runx2) and also in the β-catenin gene encoded protein levels of the HFD mice when compared with the controls. Consistent with the increased fat mass in the HFD-induced obese animals, the expression of the adipogenic genes and aP2 was increased compared with the controls. Bone marrow cells were aspirated and the ex vivo bone marrow cell cultures showed that the number of colony-forming unit osteoblasts (CFU-OBs) per bone was significantly decreased in the samples from the HFD mice compared with those from the controls. These observations suggested that HFD-induced obesity in growing animals may affect the total available osteoblastic cell differentiation progenitors in the bone, while increasing adipogenesis. This may result in negative consequences for the bone later on in adult life.