Effect of Procyanidin B₂ on Calcium Metabolism and Femur Gene Expression Profile in High-Fat Diet Fed Mice

To investigate the effect of procyanidin B₂ on gene expression in the femur of high-fat diet (HFD)-fed mice with calcium metabolism disorders.

Twenty-seven C57BL/6 male mice were randomly divided into three groups: control, HFD, and HFD plus 0.2% procyanidin B₂. The body mass, plasma lipid levels, calcium homeostasis, calcium absorption capacity, and bone mineral levels of the mice were measured after eight weeks of feeding, and gene expression in the femur of the mice was determined by using eukaryotic transcriptome sequencing. The results showed that procyanidin B₂ significantly reduced plasma lipid and parathyroid hormone levels, significantly increased net calcium absorption and storage capacity (P < 0.05), and ameliorated the reduction in bone mineral, femoral calcium content, and maximum loading capacity in HFD-fed mice. Forty-nine differentially co-expressed genes (DCGs) were identified by high-throughput sequencing, and procyanidin B₂ could improve the expression of 48 of these genes. Gene ontology (GO) enrichment analysis showed that these DCGs belonged to the two branches of biological processes and cell components. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that 13 pathways were significantly enriched (P < 0.05). The expression levels of five DCGs, Cdkn2a, Adrb1, Fcgr4, Aldh1a3, and Calml3, involved in the calcium metabolism-related signal transduction and metabolic pathways were significantly changed (P < 0.05). Compared with the HFD group, procyanidin B₂ supplementation down-regulated the expression of the Cdkn2a, Adrb1, and Fcgr4 genes by 9.19-, 3.68-, and 3.61-fold, and up-regulated the expression of the Aldh1a3 and Calml3 genes by 2.06- and 3.29-fold, respectively.

Procyanidin B₂ ameliorates calcium metabolism disorders in HFD-fed mice, which may be associated with the down-regulated expression of genes related to osteoblast activity and up-regulated expression of genes related to osteoclast activity.