The effects of fat-induced obesity on bone metabolism in rats

The aim of the current study was to investigate the effects of obesity, induced via a high-fat diet, on bone metabolism in rats.

Two hundred healthy Wistar male rats aged 4 weeks were fed a standard diet and a high-fat diet. At specific time points (week 0, 4, 6, 8, and 10), plasma was collected to determine the levels of glucose and lipid metabolism. Additionally, enzyme-linked immunoassays were performed to determine the plasma levels of adipocyte and bone metabolism factors. Micro-CT imaging was used to determine the parameters of bone metabolism. At 10th week, immunohistochemistry evaluation of femoral bone samples was performed to determine the expression of adipocyte factors.

Receptor activator of nuclear factor kB ligand (RANKL) was positively correlated with levels of triglyceride (TG), free fatty acids (FFA), and tumor necrosis factor alpha (TNF-α) (P<0.05), while receptor activator of the NF-κB (RANK) showed a positive correlation with TG, FFA, TNF-α and leptin (LPT) (P<0.05). CT imaging demonstrated that bone mineral density and trabecular thickness were elevated compared to controls before 6 weeks, but these values were found to be lower in rats fed a high fat diet in the following weeks (P<0.05). Immunohistochemistry showed that the expression of TNF-α, Interleukin- 6 (IL-6) and peroxisome proliferator activated receptor-γ (PPAR-γ) were increased and the expression of adiponectin (APN) were diminished in rats fed a high-fat diet compared to controls at 10 weeks (P<0.05).

With obesity intensifies, the release of FFA cause inflammation factor increase, resulting in bone parameters decreased.